Patent Publication Number: US-2022228036-A1

Title: Pressure sensitive adhesive particle, adhesive material, apparatus for producing printed material, method for producing printed material, printed material, sheet for producing printed material, and method for producing sheet for producing printed material

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2021-006585 filed Jan. 19, 2021. 
     BACKGROUND 
     (i) Technical Field 
     The present disclosure relates to a pressure sensitive adhesive particle, an adhesive material, an apparatus for producing a printed material, a method for producing a printed material, a printed material, a sheet for producing a printed material, and a method for producing a sheet for producing a printed material. 
     (ii) Related Art 
     Japanese Unexamined Patent Application Publication No. 2007-229993 discloses a pressure-bonded postcard paper that includes an adhesive layer obtained by applying an adhesive layer composition containing a pressure-sensitive adhesive that does not exhibit tackiness or adhesiveness when in a normal state but can be released under pressure, a fine particle filler, a binder, and a hydrophobic polymer, in which the adhesive layer contains an acrylic acid⋅alkyl methacrylate copolymer. 
     Japanese Unexamined Patent Application Publication No. 2018-002889 discloses an adhesive material that satisfies formula 1 below: 
       20° C.≤ T (1 MPa)− T (10 MPa)  Formula 1:
 
     where T(1 MPa) represents a temperature at which the viscosity is 10 4  Pa·s at an applied pressure of 1 MPa as measured with a flow tester, and T(10 MPa) represents a temperature at which the viscosity is 10 4  Pa·s at an applied pressure of 10 MPa as measured with a flow tester. 
     SUMMARY 
     Aspects of non-limiting embodiments of the present disclosure relate to a pressure sensitive adhesive particle that exhibits a higher releasing force in the obtained pressure-bonded material compared to when the sea-island structure of the particle includes islands solely constituted by one resin. 
     Aspects of certain non-limiting embodiments of the present disclosure overcome the above disadvantages and/or other disadvantages not described above. However, aspects of the non-limiting embodiments are not required to overcome the disadvantages described above, and aspects of the non-limiting embodiments of the present disclosure may not overcome any of the disadvantages described above. 
     According to an aspect of the present disclosure, there is provided a pressure sensitive adhesive particle that includes a sea-island structure constituted by a sea containing a resin A and islands containing a resin B1 and a resin B2, in which a viscosity of the resin B1 at 100° C. is smaller than a viscosity of the resin B2 at 100° C. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present disclosure will be described in detail based on the following figures, wherein: 
         FIG. 1  is a schematic diagram illustrating one example of an apparatus for producing a printed material according to an exemplary embodiment; 
         FIG. 2  is a schematic diagram illustrating another example of the apparatus for producing a printed material according to an exemplary embodiment; and 
         FIG. 3  is a schematic diagram of yet another example of the apparatus for producing a printed material according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments will now be described. These descriptions and examples are merely illustrative exemplary embodiments and do not limit the scope of the exemplary embodiments. 
     In the exemplary embodiments, a numerical range that uses “to” indicates a range that includes a figure that precedes “to” and a figure that follows “to” as the minimum value and the maximum value, respectively. 
     In numerical ranges described stepwise in the exemplary embodiments, the upper limit or the lower limit of one numerical range may be substituted with an upper limit or a lower limit of a different numerical range also described stepwise. In addition, in any numerical range described in the exemplary embodiments, the upper limit or the lower limit of the numerical range may be substituted with a value indicated in Examples. 
     In the exemplary embodiments, the term “step” indicates not only an independent step but also any feature that achieves the intended purpose of a certain step although such a feature may not be clearly distinguishable from other steps. 
     When exemplary embodiments are described by referring to the drawings, the features of the exemplary embodiments are not limited to those illustrated in the drawings. Furthermore, the size of components illustrated in the drawings is schematic, and the relative size relationship between the components it not limited to what is illustrated in the drawings. 
     In the exemplary embodiments, each component may contain more than one corresponding substances. In the exemplary embodiments, when the amount of a component in a composition is referred and when there are two or more substances that correspond to that component in the composition, the amount is the total amount of the two or more substances in the composition unless otherwise noted. 
     In the exemplary embodiments, particles corresponding to each component may contain more than one types of particles. When there are more than one types of particles corresponding to one component in the composition, the particle diameter of each component is a particle diameter of a mixture of the more than one types of particles present in the composition unless otherwise noted. 
     In the exemplary embodiments, the notation “(meth)acryl” means “acryl” or “methacryl”. 
     In the exemplary embodiments, the “toner for developing an electrostatic charge image” may also be simply referred to as the “toner”, and the “electrostatic charge image developer” may also be simply referred to as the “developer”. 
     In the exemplary embodiments, a printed material formed by folding a recording medium and bonding the opposing surfaces thereof or a printed material formed by stacking two or more recording media on top of each other and bonding the opposing surfaces thereof is referred to as a “pressure-bonded printed material”. 
     Pressure Sensitive Adhesive Particle 
     The pressure sensitive adhesive particle according to an exemplary embodiment has a sea-island structure constituted by a sea containing a resin A and islands containing a resin B1 and a resin B2, and the viscosity of the resin B1 at 100° C. is smaller than the viscosity of the resin B2 at 100° C. 
     In recent years, pressure-bonded materials, such as pressure-bonded postcards, that are pressure-bonded with pressure sensitive adhesive resin particles are expected to achieve an improved adhesive force. 
     When a pressure sensitive adhesive resin particle that has islands that contain the resin A and the resin B, in which the viscosity of the resin A at 100° C. is smaller than the viscosity of the resin B at 100° C., is used, the resin A having a low viscosity satisfactorily wet-spreads, and tacking properties (tackiness) improve the adhesiveness. Moreover, since the aggregation force of the resin B having a high viscosity is high, the strength is improved, and the adhesion force is concertedly improved. Presumably thus, a pressure sensitive adhesive particle having a high releasing force in the obtained pressure-bonded material is obtained. 
     The components, structure, and properties of the pressure sensitive adhesive particle according to this exemplary embodiment will now be described in detail. In the description below, unless otherwise noted, a “styrene resin” refers to a “styrene resin that contains, as polymerization components, 50 mass % or more of a styrene monomer and a vinyl monomer other than the styrene monomer”, and a “(meth)acryl resin” refers to a “(meth)acryl resin that contains, as a polymerization component, 50 mass % or more of a (meth)acryl compound”. 
     The (meth)acryl compound may be any compound that has a (meth)acryl group, and examples thereof include (meth)acrylate compounds, (meth)acrylamide compounds, (meth)acrylic acid, and (meth)acrylonitrile. 
     In the pressure sensitive adhesive particle according to the exemplary embodiment, the viscosity of the resin B1 at 100° C. is smaller than the viscosity of the resin B2 at 100° C. 
     From the viewpoint of improving the releasing force, the value obtained by viscosity of resin B2 at 100° C.−viscosity of resin B1 at 100° C. is preferably 5,000 Pa·s or more, more preferably 8,000 Pa·s or more, and yet more preferably 10,000 Pa·s or more and 20,000 Pa·s or less. 
     The viscosity of the resin at 100° C. in the exemplary embodiment is measured as follows. 
     The viscosity is measured with a flow tester (Flowtester CFT-500 produced by Shimadzu Corporation). The resin is compressed and solidified to prepare a pellet-shaped sample. The sample is placed in the flow tester and is gradually heated (at a temperature elevation rate of +1° C./min) from 50° C. within the measurement temperature range of 50° C. or more and 150° C. or less, and the viscosity of the sample is measured at 100° C. while applying an extrusion pressure of 1 MPa. 
     In the pressure sensitive adhesive particle according to the exemplary embodiment, from the viewpoint of improving the releasing force, the weight average molecular weight (Mw) of the resin B1 may be smaller than the weight average molecular weight (Mw) of the resin B2. 
     From the viewpoint of improving the releasing force, the weight average molecular weight of the resin B2 is preferably 1.2 times the weight average molecular weight of the resin B1 or more and 10 times the weight average molecular weight of the resin B1 or less, more preferably 1.5 times the weight average molecular weight of the resin B1 or more and 7 times the weight average molecular weight of the resin B1 or less, and particularly preferably 2 times the weight average molecular weight of the resin B1 or more and 4 times the weight average molecular weight of the resin B1 or less. 
     From the viewpoint of improving the releasing force, the value obtained by weight average molecular weight of resin B2−weight average molecular weight of resin B1 is preferably 10,000 or more, more preferably 30,000 or more, more preferably 30,000 or more and 300,000 or less, and particularly preferably 50,000 or more and 200,000 or less. 
     From the viewpoints of the storage stability, the application property, and the improvement of the releasing force, the weight average molecular weight of the resin B1 is preferably 5,000 to 200,000, more preferably 10,000 to 100,000, yet more preferably 15,000 to 80,000, and particularly preferably 20,000 to 60,000. 
     From the viewpoints of the storage stability, the application property, and the improvement of the releasing force, the weight average molecular weight of the resin B2 is preferably 50,000 to 300,000, more preferably 100,000 to 300,000, yet more preferably 120,000 to 280,000, and particularly preferably 150,000 to 250,000. 
     From the viewpoint of improving the releasing force, in the pressure sensitive adhesive particle of the exemplary embodiment, the resin B1 and the resin B2 preferably each include a resin having a wide (for example, 3 or more) molecular weight distribution (Mw/Mn) and are more preferably each composed of a resin having a wide molecular weight distribution. 
     From the viewpoint of improving the releasing force, the resin B1 and the resin B2 each contain a resin preferably having a molecular weight distribution of 5 or more, more preferably having a molecular weight distribution of 10 or more, and yet more preferably having a molecular weight distribution of 10 or more and 20 or less. 
     In the exemplary embodiment, the weight-average molecular weight (Mw), the number-average molecular weight (Mn), and the molecular weight distribution (Mw/Mn) of the resin is measured by gel permeation chromatography (GPC). The molecular weight measurement by GPC is conducted by using HLC-8120GPC produced by TOSOH CORPORATION as a GPC instrument with columns, TSKgel Super HM-M (15 cm) produced by TOSOH CORPORATION, and tetrahydrofuran as a solvent. The weight-average molecular weight and the number-average molecular weight of a resin are calculated by using molecular weight calibration curves prepared by using monodisperse polystyrene standard samples. 
     From the viewpoint of improving the releasing force, the value obtained by SP value (solubility parameter) of resin A−SP value of resin B1 is preferably 0.7 MPa 1/2  or more, more preferably 1 MPa 1/2  or more, and particularly preferably 1 MPa 1/2  or more and 10 MPa 1/2  or less. 
     Furthermore, from the viewpoint of improving the releasing force, the value obtained by SP value of resin A−SP value of resin B2 is preferably 0.7 MPa 1/2  or more, more preferably 1 MPa 1/2  or more, and yet more preferably 1 MPa 1/2  or more and 10 MPa 1/2  or less. 
     From the viewpoint of improving the releasing force, the value obtained by SP value of resin B1−SP value of resin B2 is preferably 0.7 MPa 1/2  or less, more preferably 0.5 MPa 1/2  or less, and particularly preferably −0.5 MPa 1/2  or more and 0.5 MPa 1/2  or less. The lower limit is preferably −1 MPa 1/2  or more, more preferably −0.7 MPa 1/2  or more, and particularly preferably −0.5 MPa 1/2  or more. 
     From the viewpoint of improving the releasing force, the SP value of the resin A is preferably 20 MPa 1/2  or more and 30 MPa 1/2  or less, more preferably 20 MPa 1/2  or more and 28 MPa 1/2  or less, and particularly preferably 20 MPa 1/2  or more and 27 MPa 1/2  or less. 
     Furthermore, from the viewpoint of improving the releasing force, the SP value of the resin B1 is preferably 10 MPa 1/2  or more and 20 MPa 1/2  or less, more preferably 15 MPa 1/2  or more and 20 MPa 1/2  or less, and particularly preferably 17 MPa 1/2  or more and 20 MPa 1/2  or less. 
     From the viewpoint of improving the releasing force, the SP value of the resin B2 is preferably 10 MPa 1/2  or more and 20 MPa 1/2  or less, more preferably 15 MPa 1/2  or more and 20 MPa 1/2  or less, and particularly preferably 17 MPa 1/2  or more and 20 MPa 1/2  or less. 
     The solubility parameter (SP value) of a resin in the exemplary embodiment is a value calculated by the Fedors method (Polym. Eng. Sci., 14, 147 (1974)). 
     As for the solubility parameter (SP value) of the resin, for example, when the resin is a polyester resin and an ethylene oxide adduct of bisphenol A is used as the alcohol component, the SP value of the polyester resin to be obtained can be decreased by changing the ethylene oxide adduct to a propylene oxide adduct. When the resin is a polyester resin and an aliphatic dicarboxylic acid, such as sebacic acid, is used as the dicarboxylic acid used as the acid component, the SP value can be increased by changing the aliphatic dicarboxylic acid to an aromatic dicarboxylic acid, such as terephthalic acid. 
     The SP value of the resin can be actually measured by examining the solubility in known solvents. However, the actual compatibilizing phenomenon between resins are not solely dependent on the magnitude of the SP value since the interaction between the resins and the like are also involved. In this exemplary embodiment, the aforementioned method (the Fedors method) is employed to calculate the SP value. 
     From the viewpoint of improving the releasing force, the resin A content in the sea may be larger than the total content of the resin B1 and the resin B2 in the islands. 
     Furthermore, from the viewpoint of improving the releasing force, the resin A content in the sea relative to the total content of the resin A, the resin B1, and the resin B2 is preferably 55 mass % or more and 80 mass % or less, is more preferably 60 mass % or more and 75 mass % or less, and is yet more preferably 65 mass % or more and 70 mass % or less. 
     From the viewpoint of improving the releasing force, the value of the mass ratio M B1 /M B2  of the resin B1 content M B1  in the islands to the resin B2 content M B2  in the islands is preferably 0.1 or more and 10 or less, more preferably 0.2 or more and 5 or less, yet more preferably 0.5 or more and 2 or less, and particularly preferably 0.8 or more and 1.2 or less. 
     Examples of the resin A include styrene resins and (meth)acryl resins; however, from the viewpoint of improving the releasing force, the resin A preferably contains a styrene resin and is more preferably composed of a styrene resin. 
     Examples of the resin B1 include styrene resins and (meth)acryl resins; however, from the viewpoint of improving the releasing force, the resin B1 preferably contains a (meth)acryl resin and is more preferably composed of a (meth)acryl resin. 
     Examples of the resin B2 include styrene resins and (meth)acryl resins; however, from the viewpoint of improving the releasing force, the resin B2 preferably contains a (meth)acryl resin and is more preferably composed of a (meth)acryl resin. 
     The resin B1 and the resin B2 may contain different constituting units or the same constituting units. When the constituting units contained are the same, the resins may be resins between which the mass ratios of the constituting units are different and may be resins between which the mass ratios of the constituting units are the same but the weight average molecular weights are different. 
     The pressure sensitive adhesive particle of the exemplary embodiment may further contain a coloring agent, a releasing agent, and other additives. 
     Hereinafter, the styrene resin and the (meth)acryl resin that are suitable for use as the resin A, the resin B1, and the resin B2 are described. 
     Styrene Resin 
     The pressure sensitive adhesive particle according to the exemplary embodiment preferably contains a styrene resin that contains, as polymerization components, a styrene monomer and a vinyl monomer other than the styrene monomer, and more preferably contains a styrene resin as the resin A. 
     From the viewpoint of suppressing fluidization of the pressure sensitive adhesive particles in an unpressured state, the mass ratio of styrene relative to the total of the polymerization components of the styrene resin is preferably 60 mass % or more, more preferably 70 mass % or more, and yet more preferably 75 mass % or more. From the viewpoint of forming pressure sensitive adhesive particles that easily undergo pressure-induced phase transition, the mass ratio is preferably 95 mass % or less, more preferably 90 mass % or less, and yet more preferably 85 mass % or less. 
     Examples of the vinyl monomer other than styrene constituting the styrene resin include styrene monomers other than styrene and acryl monomers. 
     Examples of the styrene monomers other than styrene include vinyl naphthalene; alkyl-substituted styrenes such as α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, and p-n-dodecylstyrene; aryl-substituted styrenes such as p-phenylstyrene; alkoxy-substituted styrenes such as p-methoxystyrene; halogen-substituted styrenes such as p-chlorostyrene, 3,4-dichlorostyrene, p-fluorostyrene, and 2,5-difluorostyrene; and nitro-substituted styrenes such as m-nitrostyrene, o-nitrostyrene, and p-nitrostyrene. These styrene monomers may be used alone or in combination. 
     The acryl monomer may be at least one acryl monomer selected from the group consisting of (meth)acrylic acid and (meth)acrylates. Examples of the (meth)acrylates include alkyl (meth)acrylates, carboxy-substituted alkyl (meth)acrylates, hydroxy-substituted alkyl (meth)acrylates, alkoxy-substituted alkyl (meth)acrylates, and di(meth)acrylates. These acryl monomers may be used alone or in combination. 
     Examples of the alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and isobornyl (meth)acrylate. 
     An example of the carboxy-substituted alkyl (meth)acrylates is 2-carboxylethyl (meth)acrylate. 
     Examples of the hydroxy-substituted alkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. 
     An example of the alkoxy-substituted alkyl (meth)acrylates is 2-methoxyethyl (meth)acrylate. 
     Examples of the di(meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, pentanediol di(meth)acrylate, hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, and decanediol di(meth)acrylate. 
     Examples of the (meth)acrylates also include 2-(diethylamino)ethyl (meth)acrylate, benzyl (meth)acrylate, and methoxypolyethylene glycol (meth)acrylate. 
     Examples of other vinyl monomer constituting the styrene resin include, in addition to the styrene monomers and acryl monomers, (meth)acrylonitrile; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and vinyl isopropenyl ketone; and olefines such as isoprene, butene, and butadiene. 
     From the viewpoint of forming pressure sensitive adhesive particles that easily undergo pressure-induced phase transition, the styrene resin preferably contains, as a polymerization component, a (meth)acrylate, more preferably an alkyl (meth)acrylate, yet more preferably an alkyl (meth)acrylate in which the alkyl group contains 2 to 10 carbon atoms, still more preferably an alkyl (meth)acrylate in which the alkyl group contains 4 to 8 carbon atoms, and particularly preferably at least one of n-butyl acrylate and 2-ethylhexyl acrylate. From the viewpoint of forming a pressure sensitive adhesive particle that easily undergoes pressure-induced phase transition, the styrene resin and the (meth)acryl resin may contain the same (meth)acrylate as a polymerization component. 
     From the viewpoint of suppressing fluidization of the pressure sensitive adhesive particle in an unpressured state, the mass ratio of the (meth)acrylate relative to the total of the polymerization components of the styrene resin is preferably 40 mass % or less, more preferably 30 mass % or less, and yet more preferably 25 mass % or less. From the viewpoint of forming a pressure sensitive adhesive particle that easily undergoes pressure-induced phase transition, the mass ratio is preferably 5 mass % or more, more preferably 10 mass % or more, and yet more preferably 15 mass % or more. The (meth)acrylate here is preferably an alkyl (meth)acrylate, yet more preferably an alkyl (meth)acrylate in which the alkyl group contains 2 to 10 carbon atoms, and still more preferably an alkyl (meth)acrylate in which the alkyl group contains 4 to 8 carbon atoms. 
     The styrene resin particularly preferably contains, as a polymerization component, at least one of n-butyl acrylate and 2-ethylhexyl acrylate, and the total amount of n-butyl acrylate and 2-ethylhexyl acrylate relative to the total of polymerization components of the styrene resin is preferably 40 mass % or less, more preferably 30 mass % or less, and yet more preferably 25 mass % or less from the viewpoint of suppressing fluidization of the pressure sensitive adhesive particle in an unpressured state. From the viewpoint of forming a pressure sensitive adhesive particle that easily undergoes pressure-induced phase transition, the total amount is preferably 5 mass % or more, more preferably 10 mass % or more, and yet more preferably 15 mass % or more. 
     From the viewpoint of suppressing fluidization of the pressure sensitive adhesive particle in an unpressured state, the weight-average molecular weight of the styrene resin is preferably 3000 or more, more preferably 4000 or more, and yet more preferably 5000 or more. From the viewpoint of forming a pressure sensitive adhesive particle that easily undergoes pressure-induced phase transition, the weight-average molecular weight is preferably 60000 or less, more preferably 55000 or less, and yet more preferably 50000 or less. 
     From the viewpoint of suppressing fluidization of the pressure sensitive adhesive particle in an unpressured state, the glass transition temperature of the styrene resin is preferably 30° C. or more, more preferably 40° C. or more, and yet more preferably 50° C. or more. From the viewpoint of forming a pressure sensitive adhesive particle that easily undergoes pressure-induced phase transition, the glass transition temperature is preferably 110° C. or less, more preferably 100° C. or less, yet more preferably 90° C. or less, and particularly preferably 80° C. or less. 
     In the exemplary embodiment, the glass transition temperature of a resin is determined from a differential scanning calorimetry curve (DSC curve) obtained by performing differential scanning calorimetry (DSC). More specifically, the glass transition temperature is determined from the “extrapolated glass transition onset temperature” described in the method for determining the glass transition temperature in JIS K 7121:1987 “Testing Methods for Transition Temperatures of Plastics”. 
     The glass transition temperature of a resin can be controlled by the types of polymerization components and the polymerization ratios. The glass transition temperature has a tendency to decrease as the density of flexible units, such as a methylene group, an ethylene group, and an oxyethylene group, contained in the main chain increases, and has a tendency to increase as the density of rigid units, such as aromatic rings and cyclohexane rings, contained in the main chain increases. Moreover, the glass transition temperature has a tendency to decrease as the density of aliphatic groups in side chains increases. 
     From the viewpoint of suppressing fluidization of the pressure sensitive adhesive particle in an unpressured state, the mass ratio of the styrene resin relative to the entire pressure sensitive adhesive particle in this exemplary embodiment is preferably 55 mass % or more, more preferably 60 mass % or more, and yet more preferably 65 mass % or more. From the viewpoint of forming a pressure sensitive adhesive particle that easily undergoes pressure-induced phase transition, the mass ratio is preferably 80 mass % or less, more preferably 75 mass % or less, and yet more preferably 70 mass % or less. 
     (Meth)Acryl Resin 
     The pressure sensitive adhesive particle of this exemplary embodiment may contain a (meth)acryl resin from the viewpoint of improving the releasing force. 
     From the viewpoint of improving the releasing force, the (meth)acryl resin is preferably a (meth)acrylate resin, more preferably a (meth)acrylate resin that contains, as polymerization components, at least two (meth)acrylates, and particularly preferably a (meth)acrylate resin that contains, as polymerization components, at least two (meth)acrylates that account for 90 mass % or more of all polymerization components of the (meth)acrylate resin. 
     The (meth)acrylates preferably account for 90 mass % or more, preferably 95 mass % or more, more preferably 98 mass % or more, and yet more preferably 100 mass % of all polymerization components of the (meth)acryl resin. 
     Examples of the (meth)acrylates include alkyl (meth)acrylates, carboxy-substituted alkyl (meth)acrylates, hydroxy-substituted alkyl (meth)acrylates, alkoxy-substituted alkyl (meth)acrylates, and di(meth)acrylates. 
     Examples of the alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and isobornyl (meth)acrylate. 
     An example of the carboxy-substituted alkyl (meth)acrylates is 2-carboxylethyl (meth)acrylate. 
     Examples of the hydroxy-substituted alkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. 
     An example of the alkoxy-substituted alkyl (meth)acrylates is 2-methoxyethyl (meth)acrylate. 
     Examples of the di(meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, pentanediol di(meth)acrylate, hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, and decanediol di(meth)acrylate. 
     Examples of the (meth)acrylates also include 2-(diethylamino)ethyl (meth)acrylate, benzyl (meth)acrylate, and methoxypolyethylene glycol (meth)acrylate. 
     These (meth)acrylates may be used alone or in combination. 
     From the viewpoint of forming a pressure sensitive adhesive particle that easily undergoes pressure-induced phase transition and has excellent adhesiveness, the (meth)acrylates are preferably alkyl (meth)acrylates, yet more preferably alkyl (meth)acrylates in which the alkyl group contains 2 to 10 carbon atoms, still more preferably alkyl (meth)acrylates in which the alkyl group contains 3 to 8 carbon atoms, and particularly preferably n-butyl acrylate and 2-ethylhexyl acrylate. From the viewpoint of forming a pressure sensitive adhesive particle that easily undergoes pressure-induced phase transition, the styrene resin and the (meth)acryl resin may contain the same (meth)acrylate as a polymerization component. 
     From the viewpoint of forming a pressure sensitive adhesive particle that easily undergoes pressure-induced phase transition and has excellent adhesiveness, the alkyl (meth)acrylates preferably account for 90 mass % or more, more preferably 95 mass % or more, yet more preferably 98 mass % or more, and still more preferably 100 mass % of all polymerization components of the (meth)acryl resin. The alkyl (meth)acrylates here preferably each have an alkyl group having 2 to 10 carbon atoms and more preferably each have an alkyl group containing 3 to 8 carbon atoms. 
     From the viewpoint of forming a pressure sensitive adhesive particle that easily undergoes pressure-induced phase transition and has excellent adhesiveness, the mass ratio between two (meth)acrylates having the largest and second-largest mass ratios among the at least two (meth)acrylates contained as the polymerization components in the (meth)acryl resin is preferably 80:20 to 20:80, more preferably 70:30 to 30:70, and yet more preferably 60:40 to 40:60. 
     The two (meth)acrylates having the largest and second-largest mass ratios among the at least two (meth)acrylates contained as the polymerization components in the (meth)acryl resin are preferably alkyl (meth)acrylates. The alkyl (meth)acrylates here preferably each have an alkyl group having 2 to 10 carbon atoms and more preferably each have an alkyl group containing 4 to 8 carbon atoms. 
     When the two (meth)acrylates having the largest and second-largest mass ratios among the at least two (meth)acrylates contained as polymerization components in the (meth)acryl resin are alkyl (meth)acrylates, from the viewpoint of forming a pressure sensitive adhesive particle that easily undergoes pressure-induced phase transition and has excellent adhesiveness, the difference in the number of carbon atoms in the alkyl group between the two alkyl (meth)acrylates is preferably 1 to 4, more preferably 2 to 4, and yet more preferably 3 or 4. 
     From the viewpoint of forming a pressure sensitive adhesive particle that easily undergoes pressure-induced phase transition and has excellent adhesiveness, the (meth)acryl resin preferably contains, as polymerization components, n-butyl acrylate and 2-ethylhexyl acrylate. In particular, the two (meth)acrylates having the largest and second-largest mass ratios among the at least two (meth)acrylates contained as polymerization components in the (meth)acrylate resin are preferably n-butyl acrylate and 2-ethylhexyl acrylate. The total amount of n-butyl acrylate and 2-ethylhexyl acrylate relative to all polymerization components of the (meth)acryl resin is preferably 90 mass % or more, more preferably 95 mass % or more, yet more preferably 98 mass % or more, and still more preferably 100 mass %. 
     In particular, from the viewpoint of improving the releasing force, the (meth)acryl resin is preferably a copolymer of two or more alkyl (meth)acrylates each having an alkyl group having 3 or more and 8 or less carbon atoms, is more preferably a copolymer of two or three alkyl (meth)acrylates each having an alkyl group having 3 or more and 8 or less carbon atoms, and is particularly preferably a copolymer of n-butyl acrylate and 2-ethylhexyl acrylate or a copolymer of hexyl acrylate and propyl acrylate. 
     The (meth)acryl resin may further contain, as polymerization components, vinyl monomers other than (meth)acrylates. Examples of the vinyl monomers other than the (meth)acrylates include (meth)acrylic acid; styrene; styrene monomers other than styrene; (meth)acrylonitrile; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and vinyl isopropenyl ketone; and olefines such as isoprene, butene, and butadiene. These vinyl monomers may be used alone or in combination. 
     When the (meth)acryl resin contains a vinyl monomer other than (meth)acrylates as polymerization components, the vinyl monomer other than the (meth)acrylates is preferably at least one of acrylic acid and methacrylic acid and is more preferably acrylic acid. 
     From the viewpoint of suppressing fluidization of the pressure sensitive adhesive particle in an unpressured state, the weight-average molecular weight of the (meth)acryl resin is preferably 50,000 or more, more preferably 100,000 or more, yet more preferably 120,000 or more, and particularly preferably 150,000 or more. From the viewpoint of forming a pressure sensitive adhesive particle that easily undergoes pressure-induced phase transition, the weight-average molecular weight is preferably 250,000 or less, more preferably 220,000 or less, and yet more preferably 200,000 or less. 
     From the viewpoint of forming a pressure sensitive adhesive particle that easily undergoes pressure-induced phase transition, the glass transition temperature of the (meth)acryl resin is preferably 10° C. or less, more preferably 0° C. or less, and yet more preferably −10° C. or less. From the viewpoint of suppressing fluidization of the pressure sensitive adhesive particle in an unpressured state, the glass transition temperature is preferably −90° C. or more, more preferably −80° C. or more, and yet more preferably −70° C. or more. 
     In this exemplary embodiment, from the viewpoint of forming a pressure sensitive adhesive particle that easily undergoes pressure-induced phase transition, the mass ratio of the (meth)acryl resin relative to the entire pressure sensitive adhesive base particle is preferably 20 mass % or more, more preferably 25 mass % or more, and yet more preferably 30 mass % or more. From the viewpoint of suppressing fluidization of the pressure sensitive adhesive particle in an unpressured state, the mass ratio is preferably 45 mass % or less, more preferably 40 mass % or less, and yet more preferably 35 mass % or less. 
     From the viewpoint of improving the releasing force, examples of the combination of the resin B1 and the resin B2 include: 
     a combination of a copolymer of n-butyl acrylate and 2-ethylhexyl acrylate as the resin B1 and a copolymer of hexyl acrylate and propyl acrylate as the resin B2; 
     a combination of a copolymer of hexyl acrylate and propyl acrylate as the resin B1 and a copolymer of n-butyl acrylate and 2-ethylhexyl acrylate as the resin B2; 
     a combination of copolymers of n-butyl acrylate and 2-ethylhexyl acrylate as the resin B1 and the resin B2, the copolymers having different copolymerization ratios; and 
     a combination of copolymers of n-butyl acrylate and 2-ethylhexyl acrylate as the resin B1 and the resin B2, the copolymers having a molecular weight distribution of 10 or more. 
     In this exemplary embodiment, the total amount of the styrene resin and the (meth)acryl resin contained in the pressure sensitive adhesive base particle relative to the entire pressure sensitive adhesive base particle is preferably 70 mass % or more, more preferably 80 mass % or more, yet more preferably 90 mass % or more, still preferably 95 mass % or more, and most preferably 100 mass %. 
     Other Resins 
     The pressure sensitive adhesive particle may contain, for example, polystyrene, and a non-vinyl resin such as an epoxy resin, a polyester resin, a polyurethane resin, a polyamide resin, a cellulose resin, a polyether resin, or modified rosin. These resins may be used alone or in combination. 
     Various Additives 
     The pressure sensitive adhesive particle may contain, if needed, a coloring agent (for example, a pigment or a dye), a releasing agent (for example, hydrocarbon wax, natural wax such as carnauba wax, rice wax, or candelilla wax, a synthetic or mineral or petroleum wax such as montan wax; or ester wax such as fatty acid ester or montanic acid ester), a charge controlling agent, and the like. 
     When the pressure sensitive adhesive particle of this exemplary embodiment is transparent, the amount of the coloring agent in the pressure sensitive adhesive particle relative to the entire pressure sensitive adhesive base particle may be 1.0 mass % or less, and, from the viewpoint of increasing the transparency of the pressure sensitive adhesive particle, is preferably as small as possible. 
     Structure of Pressure Sensitive Adhesive Base Particle 
     The inner structure of the pressure sensitive adhesive particle has a sea-island structure constituted by a sea containing a resin A and islands containing a resin B1 and a resin B2. 
     The sea-island structure preferably includes a sea containing the resin A and islands dispersed in the sea and containing the resin B1 and the resin B2, and more preferably includes a sea containing a styrene resin as the resin A and islands dispersed in the sea and containing, as the resin B1 and the resin B2, (meth)acryl resins. 
     The islands may include a domain (one independent island) that contains the resin B1 and the resin B2, a domain that contains the resin B1 but not the resin B2, a domain that contains the resin B2 but not the resin B1, etc.; however, the islands may contain at least a domain that contains the resin B1 and the resin B2. 
     The islands may contain a domain that does not contain the resin B1 or the resin B2. 
     When the pressure sensitive adhesive particle has a sea-island structure, the average diameter of the islands may be 200 nm or more and 500 nm or less. When the average diameter of the islands is 500 nm or less, the pressure sensitive adhesive base particle easily undergoes pressure-induced phase transition. When the average diameter of the islands is 200 nm or more, excellent mechanical strength suitable for the pressure sensitive adhesive base particle (for example, the strength that withstands deformation during stirring in a developing device) is exhibited. From these viewpoints, the average diameter of the islands is more preferably 220 nm or more and 450 nm or less and yet more preferably 250 nm or more and 400 nm or less. 
     Examples of the method for controlling the average diameter of the islands in the sea-island structure to be within the aforementioned range include increasing or decreasing the amount of the (meth)acryl resin relative to the amount of the styrene resin and increasing or decreasing the length of time of maintaining a high temperature in the step of fusing and coalescing aggregated resin particles in the method for producing pressure sensitive adhesive particles described below. 
     The sea-island structure is confirmed and the average diameter of the islands is measured as follows. 
     Pressure sensitive adhesive particles are embedded in an epoxy resin, a cross section is prepared by using a diamond knife or the like, and the prepared cross section is stained with osmium tetroxide or ruthenium tetroxide in a desiccator. The stained section is observed with a scanning electron microscope (SEM). The sea and the islands of the sea-island structure are distinguished by the shade created by the degree of staining with osmium tetroxide or ruthenium tetroxide, and the presence or absence of the sea-island structure is identified by the shade. From an SEM image, one hundred islands are selected at random, a long diameter of each island is measured, and the average of one hundred long diameters is used as the average diameter. 
     The pressure sensitive adhesive particle may have a single layer structure or may have a core-shell structure including a core and a shell layer that covers the core. From the viewpoint of suppressing fluidization of the pressure sensitive adhesive particle in an unpressured state, the pressure sensitive adhesive particle may have a core-shell structure. 
     From the viewpoint of facilitating the pressure-induced phase transition, when the pressure sensitive adhesive particle has a core-shell structure, the core may contain a styrene resin and a (meth)acryl resin. From the viewpoint of suppressing fluidization of the pressure sensitive adhesive particle in an unpressured state, the shell layer may contain a styrene resin. The specific examples of the styrene resin are as described above. The specific examples of the (meth)acryl resin are as described above. 
     When the pressure sensitive adhesive particle has a core-shell structure, the core may have a sea that contains a styrene resin, and islands that are dispersed in the sea and contain a (meth)acryl resin. The average diameter of the islands may be within the aforementioned range. In addition to the core having the above-described structure, the shell layer may contain a styrene resin. In such a case, the sea of the core and the shell layer form a continuous structure, and the pressure sensitive adhesive base particle easily undergoes pressure-induced phase transition. The specific examples of the styrene resin contained in the sea of the core and the shell layer are as described above. The specific examples of the (meth)acryl resin contained in the islands of the core are as described above. 
     Examples of the resin contained in the shell layer also include polystyrene, and non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins polyether resins, and modified rosin. These resins may be used alone or in combination. 
     From the viewpoint of suppressing deformation of the pressure sensitive adhesive particle, the average thickness of the shell layer is preferably 120 nm or more, more preferably 130 nm or more, and yet more preferably 140 nm or more. From the viewpoint of facilitating the pressure-induced phase transition of the pressure sensitive adhesive base particle, the average thickness is preferably 550 nm or less, more preferably 500 nm or less, and yet more preferably 400 nm or less. 
     The average thickness of the shell layer is measured by the following method. 
     The pressure sensitive adhesive particles are embedded in an epoxy resin, a section is prepared by using a diamond knife or the like, and the prepared section is stained with osmium tetroxide or ruthenium tetroxide in a desiccator. The stained section is observed with a scanning electron microscope (SEM). From an SEM image, sections of ten pressure sensitive adhesive base particles are selected at random, the thickness of the shell layer is measured at twenty positions for each of the pressure sensitive adhesive base particles, and the average thickness is calculated. The average value of ten pressure sensitive adhesive base particles is used as the average thickness. 
     From the viewpoint of handling ease of the pressure sensitive adhesive base particle, the volume-average particle diameter (D50v) of the pressure sensitive adhesive particle is preferably 4 μm or more, more preferably 5 μm or more, and yet more preferably 6 μm or more, and from the viewpoint of facilitating the pressure-induced phase transition of the entire pressure sensitive adhesive base particle, the volume-average particle diameter (D50v) is preferably 12 μm or less, more preferably 10 μm or less, and yet more preferably 9 μm or less. 
     The volume-average particle diameter (D50v) of the pressure sensitive adhesive particle is determined by using Coulter MULTISIZER II (produced by Beckman Coulter Inc.) with an aperture having a diameter of 100 μm. Into 2 mL of a 5 mass % aqueous sodium alkyl benzenesulfonate solution, 0.5 mg or more and 50 mg or less of the pressure sensitive adhesive base particles are added and dispersed, and then the resulting dispersion is mixed with 100 mL or more and 150 mL or less of an electrolyte (ISOTON-II produced by Beckman Coulter Inc.). The resulting mixture is dispersed for 1 minute in an ultrasonic disperser, and the obtained dispersion is used as a sample. The particle diameters of 50000 particles having a particle diameter of 2 μm or more and 60 μm or less in the sample are measured. The particle diameter at 50% accumulation in a volume-based particle size distribution calculated from the small diameter side is used as the volume-average particle diameter (D50v). 
     The pressure sensitive adhesive particle of the exemplary embodiment may be a particle that does not contain an external additive, or a particle that contains an external additive and a pressure sensitive adhesive base particle that has a sea-island structure constituted by a sea containing a resin A and islands containing a resin B1 and a resin B2. 
     External Additive 
     An example of the external additive is inorganic particles. Examples of the inorganic particles include SiO 2 , TiO 2 , Al 2 O 3 , CuO, ZnO, SnO 2 , CeO 2 , Fe 2 O 3 , MgO, BaO, CaO, K 2 O, Na 2 O, ZrO 2 , CaO.SiO 2 , K 2 O.(TiO 2 )n, Al 2 O 3 .2SiO 2 , CaCO 3 , MgCO 3 , BaSO 4 , and MgSO 4 . 
     The surfaces of the inorganic particles serving as an external additive may be hydrophobized. Hydrophobizing involves, for example, immersing inorganic particles in a hydrophobizing agent. The hydrophobizing agent may be any, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. These may be used alone or in combination. The amount of the hydrophobizing agent is, for example, 1 part by mass or more and 10 parts by mass or less relative to 100 parts by mass of the inorganic particles. 
     Other examples of the external additive include resin particles (resin particles of polystyrene, polymethyl methacrylate, melamine resin, etc.), and cleaning activating agents (for example, particles of metal salts of higher aliphatic acids such as zinc stearate and fluorine high-molecular-weight materials). 
     The externally added amount of the external additive relative to the pressure sensitive adhesive base particle is preferably 0.01 mass % or more and 5 mass % or less and is more preferably 0.01 mass % or more and 2.0 mass % or less. 
     Properties of Pressure Sensitive Adhesive Particle 
     The pressure sensitive adhesive particle of the exemplary embodiment has at least two glass transition temperatures, one of which is presumed to be that of the resin A and the other one of which is presumed to be that of the resin B1 and the resin B2. 
     Furthermore, the pressure sensitive adhesive particle of the exemplary embodiment may have at least three glass transition temperatures, one of which is presumed to be that of the styrene resin, another one of which is presumed to be that of the resin B1, and another one of which is presumed to be that of the resin B2. 
     From the viewpoint of facilitating the pressure-induced phase transition of the pressure sensitive adhesive particle, the pressure sensitive adhesive particle of this exemplary embodiment may have at least two glass transition temperatures, and the difference between the lowest glass transition temperature and the highest glass transition temperature may be 30° C. or more. From the viewpoint of facilitating the pressure-induced phase transition of the pressure sensitive adhesive particle, the difference between the lowest glass transition temperature and the highest glass transition temperature is preferably 40° C. or more, yet more preferably 50° C. or more, and still more preferably 60° C. or more. The upper limit of the difference between the highest glass transition temperature and the lowest glass transition temperature is, for example, 140° C. or less, and may be 130° C. or less or 120° C. or less. 
     From the viewpoint of facilitating the pressure-induced phase transition of the pressure sensitive adhesive particle, the lowest glass transition temperature of the pressure sensitive adhesive particle of this exemplary embodiment is preferably 10° C. or less, more preferably 0° C. or less, and yet more preferably −10° C. or less. From the viewpoint of suppressing fluidization of the pressure sensitive adhesive particle in an unpressured state, the lowest glass transition temperature is preferably −90° C. or more, more preferably −80° C. or more, and yet more preferably −70° C. or more. 
     From the viewpoint of suppressing fluidization of the pressure sensitive adhesive particle in an unpressured state, the highest glass transition temperature of the pressure sensitive adhesive particle of this exemplary embodiment is preferably 30° C. or more, more preferably 40° C. or more, and yet more preferably 50° C. or more. From the viewpoint of facilitating the pressure-induced phase transition of the pressure sensitive adhesive particle, the highest glass transition temperature is preferably 70° C. or less, more preferably 65° C. or less, and yet more preferably 60° C. or less. 
     In the exemplary embodiment, the glass transition temperature of the pressure sensitive adhesive particle is determined from a differential scanning calorimetry curve (DSC curve) obtained by performing differential scanning calorimetry (DSC). More specifically, the glass transition temperature is determined from the “extrapolated glass transition onset temperature” described in the method for determining the glass transition temperature in JIS K 7121:1987 “Testing Methods for Transition Temperatures of Plastics”. 
     The pressure sensitive adhesive particle of the exemplary embodiment undergoes pressure-induced phase transition, and may satisfy formula 1 below: 
       10° C.≤ T 1− T 2  Formula 1:
 
     In formula 1, T1 represents a temperature at which the viscosity is 10,000 Pa·s at a pressure of 1 MPa, and T2 represents a temperature at which the viscosity is 10,000 Pa·s at a pressure of 10 MPa. 
     From the viewpoint of facilitating the pressure-induced phase transition of the pressure sensitive adhesive particle, the temperature difference (T1−T2) is preferably 10° C. or more, more preferably 15° C. or more, and yet more preferably 20° C. or more. From the viewpoint of suppressing fluidization of the pressure sensitive adhesive particle in an unpressured state, the temperature difference (T1−T2) is preferably 120° C. or less, more preferably 100° C. or less, and yet more preferably 80° C. or less. 
     The value of the temperature T1 is preferably 140° C. or less, more preferably 130° C. or less, yet more preferably 120° C. or less, and still more preferably 115° C. or less. The lower limit of the temperature T1 is preferably 80° C. or more and more preferably 85° C. or more. 
     The value of the temperature T2 is preferably 40° C. or more, more preferably 50° C. or more, and yet more preferably 60° C. or more. The upper limit of the temperature T2 may be 85° C. or less. 
     One indicator of how easily the pressure sensitive adhesive particle undergoes pressure-induced phase transition is the temperature difference (T1−T3) between the temperature T1 at which the viscosity is 10,000 Pa·s at a pressure of 1 MPa and the temperature T3 at which the viscosity is 10,000 Pa·s at a pressure of 4 MPa. The temperature difference (T1−T3) may be 5° C. or more. From the viewpoint of facilitating the pressure-induced phase transition, the temperature difference (T1−T3) of the pressure sensitive adhesive particle is preferably 5° C. or more and more preferably 10° C. or more. 
     The temperature difference (T1−T3) is typically 25° C. or less. 
     From the viewpoint of adjusting the temperature difference (T1−T3) to 5° C. or more, the temperature T3 of the pressure sensitive adhesive particle of the exemplary embodiment at which the viscosity is 10,000 Pa·s at a pressure of 4 MPa is preferably 90° C. or less, more preferably 85° C. or less, and yet more preferably 80° C. or less. The lower limit of the temperature T3 may be 60° C. or more. 
     The method for determining the temperature T1, the temperature T2, and the temperature T3 is as follows. 
     Pressure sensitive adhesive particles are compressed into a pellet-shaped sample. The pellet-shaped sample is placed in a Flowtester (CFT-500 produced by Shimadzu Corporation), the applied pressure is fixed at 1 MPa, and the viscosity at 1 MPa relative to the temperature is measured. From the obtained viscosity graph, the temperature T1 at which the viscosity is 10 4  Pa·s at an applied pressure of 1 MPa is determined. The temperature T2 is determined by the same method for determining the temperature T1 except that the applied pressure is changed from 1 MPa to 10 MPa. The temperature T3 is determined by the same method for determining the temperature T1 except that the applied pressure is changed from 1 MPa to 4 MPa. The temperature difference (T1−T2) is calculated from the temperature T1 and the temperature T2. The temperature difference (T1−T3) is calculated from the temperature T1 and the temperature T3. 
     Method for Producing Pressure Sensitive Adhesive Particle 
     The pressure sensitive adhesive particle of the exemplary embodiment is obtained by first producing a pressure sensitive adhesive base particle and then externally adding an external additive to the pressure sensitive adhesive base particle. 
     The pressure sensitive adhesive base particle may be produced by a dry method (for example, a kneading and pulverizing method) or a wet method (for example, an aggregation and coalescence method, a suspension polymerization method, or a dissolution suspension method). There is no limitation on these methods, and any known method may be employed. Among these methods, the aggregation and coalescence method may be employed to produce the pressure sensitive adhesive base particle. 
     When the pressure sensitive adhesive base particle is to be produced by the aggregation and coalescence method, the pressure sensitive adhesive base particle is produced through, for example, the following steps: 
     a step of preparing a styrene resin particle dispersion in which styrene resin particles containing a styrene resin are dispersed (styrene resin particle dispersion preparation step); 
     a step of polymerizing a (meth)acryl resin in the styrene resin particle dispersion so as to form composite resin particles containing the styrene resin and the (meth)acryl resin (composite resin particle forming step); 
     a step aggregating the composite resin particles in the composite resin particle dispersion in which the composite resin particles are dispersed so as to form aggregated particles (aggregated particle forming step); and 
     a step of heating the aggregated particle dispersion in which the aggregated particles are dispersed so as to fuse and coalesce the aggregated particles and thereby form pressure sensitive adhesive base particles (fusing and coalescing step). 
     These steps will now be described in detail. 
     In the description below, a method for obtaining a pressure sensitive adhesive base particle not containing a coloring agent or a releasing agent is described. A coloring agent, a releasing agent, and other additives may be used as needed. When the pressure sensitive adhesive base particle is to contain a coloring agent and a releasing agent, the fusing and coalescing step is performed after the composite resin particle dispersion, a coloring agent particle dispersion, and a releasing agent particle dispersion are mixed. The coloring agent particle dispersion and the releasing agent particle dispersion can be, for example, prepared by mixing raw materials and then dispersing the particles in a known disperser machine. 
     Styrene Resin Particle Dispersion Preparation Step 
     The styrene resin particle dispersion is, for example, prepared by dispersing styrene resin particles in a dispersion medium by using a surfactant. 
     Examples of the dispersion medium include aqueous media such as water and alcohols. These may be used alone or in combination. 
     Examples of the surfactant include anionic surfactants such as sulfate esters, sulfonates, phosphate esters, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycol, alkyl phenol-ethylene oxide adducts, and polyhydric alcohols. A nonionic surfactant may be used in combination with an anionic surfactant or a cationic surfactant. Among these, an anionic surfactant may be used. The surfactants may be used alone or in combination. 
     Examples of the method for dispersing the styrene resin particles in a dispersion medium include methods that involve mixing a styrene resin and a dispersion medium and then dispersing the resin by stirring in a rotational shear-type homogenizer, or a mill that uses media such as a ball mill, a sand mill, or a dyno mill. 
     Another example of the method for dispersing styrene resin particles in a dispersion medium is an emulsion polymerization method. Specifically, after polymerization components of a styrene resin, and a chain transfer agent or a polymerization initiator are mixed, an aqueous medium containing a surfactant is added to the resulting mixture, the resulting mixture is stirred to prepare an emulsion, and the styrene resin is polymerized in the emulsion. Here, the chain transfer agent may be dodecanethiol. 
     The volume-average particle diameter of the styrene resin particles dispersed in the styrene resin particle dispersion is preferably 100 nm or more and 250 nm or less, more preferably 120 nm or more and 220 nm or less, and yet more preferably 150 nm or more and 200 nm or less. 
     The volume-average particle diameter (D50v) of the resin particles contained in the resin particle dispersion is determined by measuring the particle diameter with a laser diffraction scattering particle size distribution meter (for example, LA-700 produced by Horiba Ltd.) and determining the particle diameter at 50% accumulation in a volume-based particle size distribution calculated from the small diameter side. 
     The styrene resin particle content in the styrene resin particle dispersion is preferably 30 mass % or more and 60 mass % or less and is more preferably 40 mass % or more and 50 mass % or less. 
     Composite Resin Particle Forming Step 
     The styrene resin particle dispersion and the polymerization components of a (meth)acryl resin are mixed, and the (meth)acryl resin is polymerized in the styrene resin particle dispersion so as to form composite resin particles containing the styrene resin and the (meth)acryl resin. 
     The composite resin particles may be resin particles containing a styrene resin and a (meth)acryl resin that are in a microphase-separated state. Such resin particles can be produced by, for example, the following method. 
     To a styrene resin particle dispersion, polymerization components (a group of monomers including at least two (meth)acrylates) of the (meth)acryl resin are added, and, if needed, an aqueous medium is added thereto. Next, while slowly stirring the dispersion, the temperature of the dispersion is elevated to a temperature higher than or equal to the glass transition temperature of the styrene resin (for example, a temperature 10° C. to 30° C. higher than the glass transition temperature of the styrene resin). Next, while maintaining the temperature, an aqueous medium containing a polymerization initiator is slowly added dropwise, and then stirring is continued for a long time within the range of 1 to 15 hours. Here, the polymerization initiator may be ammonium persulfate. 
     The detailed mechanism is not clear; however, it is presumed that when the aforementioned method is employed, the monomers and the polymerization initiator penetrate into the styrene resin particles, and the (meth)acrylates become polymerized inside the styrene-based resin particles. It is presumed that because of this mechanism, composite resin particles in which the (meth)acryl resin is contained inside the styrene resin particles and in which the styrene resin and the (meth)acryl resin are in a microphase-separated state inside the particles are obtained. 
     During or after production of the composite resin particles described above, polymerization components (in other words, a styrene monomer and a vinyl monomer other than the styrene monomer) of the styrene resin may be added to the dispersion containing the dispersed composite resin particles, and the polymerization reaction may be continued. Presumably as a result, composite resin particles in which the styrene resin and the (meth)acryl resin form a microphase-separated state inside the particles and in which the styrene resin is attached to the particle surfaces are obtained. A pressure sensitive adhesive particle produced by using a composite resin particle having a styrene resin attached to a particle surface thereof generates relatively fewer coarse particles. 
     The vinyl monomer, which is a polymerization component of the styrene resin to be attached to the surface of the composite resin particle, may contain the same monomer as at least one of the monomers constituting the styrene resin or the (meth)acryl resin inside the composite resin particle, and, specifically, may contain at least one of n-butyl acrylate and 2-ethylhexyl acrylate. 
     The volume-average particle diameter of the composite resin particles dispersed in the composite resin particle dispersion is preferably 140 nm or more and 300 nm or less, more preferably 150 nm or more and 280 nm or less, and yet more preferably 160 nm or more and 250 nm or less. 
     The composite resin particle content in the composite resin particle dispersion is preferably 20 mass % or more and 50 mass % or less and is more preferably 30 mass % or more and 40 mass % or less. 
     Aggregated Particle Forming Step 
     The composite resin particles are aggregated in the composite resin particle dispersion so as to form aggregated particles having diameters close to the target diameter of the pressure sensitive adhesive base particle. 
     For example, in the aggregated particle forming step, two or more types of composite resin particle dispersions may be used and aggregated so as to introduce a component having a different composition into the pressure sensitive adhesive base particle. 
     Specifically, for example, an aggregating agent is added to the composite resin particle dispersion while the pH of the composite resin particle dispersion is adjusted to acidic (for example, a pH of 2 or more and 5 or less), and after a dispersion stabilizer is added as needed, the dispersion is heated to a temperature close to the glass transition temperature of the styrene resin (specifically, for example, a temperature −10° C. to −30° C. lower than the glass transition temperature of the styrene resin) so as to aggregate the composite resin particles and form aggregated particles. 
     In the aggregated particle forming step, heating may be performed after an aggregating agent is added to the composite resin particle dispersion being stirred in a rotational shear-type homogenizer at room temperature (for example, 25° C.), the pH of the composite resin particle dispersion is adjusted to acidic (for example, a pH2 or more and 5 or less), and a dispersion stabilizer is added as needed. 
     Examples of the aggregating agent include a surfactant having an opposite polarity to the surfactant contained in the composite resin particle dispersion, an inorganic metal salt, and a divalent or higher valent metal complex. When a metal complex is used as the aggregating agent, the amount of the surfactant used is reduced, and the charge properties are improved. 
     An additive that forms a complex with a metal ion in the aggregating agent or that forms a similar bond therewith may be used in combination with the aggregating agent as needed. An example of such an additive is a chelating agent. 
     Examples of the inorganic metal salt include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate; and inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. 
     A water-soluble chelating agent may be used as the chelating agent. Examples of the chelating agent include oxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid; and aminocarboxylic acids such as iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA). 
     The amount of the chelating agent added is preferably 0.01 parts by mass or more and 5.0 parts by mass or less and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass relative to 100 parts by mass of the resin particles. 
     Fusing and Coalescing Step 
     Next, the aggregated particle dispersion containing dispersed aggregated particles is heated to, for example, a temperature equal to or higher than the glass transition temperature of the styrene resin (for example, a temperature 10° C. to 30° C. higher than the glass transition temperature of the styrene resin) to fuse and coalesce the aggregated particles and form pressure sensitive adhesive base particles. 
     The pressure sensitive adhesive base particle obtained through the above-described steps usually has a sea-island structure that has a sea containing a styrene resin and islands containing a (meth)acryl resin and being dispersed in the sea. It is presumed that although the styrene resin and the (meth)acryl resin are in a microphase-separated state in the composite resin particles, the styrene resin has gathered to form a sea, and the (meth)acryl resin has gathered to form islands in the fusing and coalescence step. 
     The average diameter of the islands of the sea-island structure can be controlled by, for example, increasing or decreasing the amount of the styrene resin particle dispersion or the amount of the at least two (meth)acrylates used in the composite resin particle forming step, or by increasing or decreasing the length of time of maintaining a high temperature in the fusing and coalescing step. 
     The pressure sensitive adhesive base particles having a core-shell structure are produced through the following steps, for example: 
     after an aggregated particle dispersion is obtained, a step of mixing the aggregated particle dispersion and a styrene resin particle dispersion so that the styrene resin particles further attach to the surfaces of the aggregated particles and form second aggregated particles; and 
     a step of heating the second aggregated particle dispersion in which the second aggregated particles are dispersed so as to fuse and coalesce the second aggregated particles and thereby form pressure sensitive adhesive base particles having a core-shell structure. 
     The pressure sensitive adhesive base particle having a core-shell structure obtained through the aforementioned steps has a shell layer containing a styrene resin. Instead of the styrene resin particle dispersion, a resin particle dispersion in which a different type of resin particles are dispersed may be used to form a shell layer that contains the different type of resin. 
     After completion of the fusing and coalescing step, the pressure sensitive adhesive base particles formed in the solution are subjected to a washing step, a solid-liquid separation step, and a drying step known in the art so as to obtain dry pressure sensitive adhesive base particles. From the viewpoint of chargeability, the washing step may involve thorough displacement washing with ion exchange water. From the viewpoint of productivity, the solid-liquid separation step may involve suction filtration, pressure filtration, or the like. From the viewpoint of productivity, the drying step may involve freeze-drying, flash-drying, fluid-drying, vibration-type fluid-drying, or the like. 
     The pressure sensitive adhesive particle of this exemplary embodiment is formed by, for example, adding an external additive to the obtained dry pressure sensitive adhesive base particle, and mixing the resulting mixture. Mixing may be performed by using a V blender, a HENSCHEL mixer, a Lodige mixer, or the like. Furthermore, if needed, a vibrating screen, an air screen, or the like may be used to remove coarse particles of the pressure sensitive adhesive particle. 
     Adhesive Material 
     An adhesive material according to an exemplary embodiment contains the pressure sensitive adhesive particle of the exemplary embodiment. 
     Alternatively, the adhesive material according to the exemplary embodiment may contain the pressure sensitive adhesive particle of the exemplary embodiment. 
     When the adhesive material according to the exemplary embodiment is a liquid composition, the adhesive material of the exemplary embodiment may contain a dispersion medium. 
     Examples of the dispersion medium include water; and aqueous media such as propylene glycol, 1,3-propanediol, and diethylene glycol. These may be used alone or in combination. 
     When the adhesive material of the exemplary embodiment is a liquid composition, the pressure sensitive adhesive resin particle content is not particularly limited and may be 10 mass % or more and 80 mass % or less relative to the entire adhesive material. 
     The adhesive material of the exemplary embodiment may also contain additives such as a surfactant, a dispersion stabilizer, a viscosity adjustor, a pH adjustor, an antioxidant, a UV absorber, a preservative, and a fungicide. 
     Cartridge A cartridge according to an exemplary embodiment stores the pressure sensitive adhesive particle of the exemplary embodiment or the adhesive material of the exemplary embodiment, and is detachably attachable to a printed material producing apparatus. When the cartridge is attached to a printed material producing apparatus, the cartridge connects, via a supply pipe, to an applying unit that constitutes a part of the printed material producing apparatus and that applies the pressure sensitive adhesive particle to a recording medium. 
     When the pressure sensitive adhesive particle is supplied from the cartridge to the applying unit and the pressure sensitive adhesive particle level in the cartridge has run low, the cartridge is replaced. 
     Apparatus and Method for Producing Printed Material, and Printed Material 
     An apparatus for producing a printed material according to an exemplary embodiment includes an applying unit that stores the pressure sensitive adhesive particle of the exemplary embodiment or the adhesive material of the exemplary embodiment and applies the pressure sensitive adhesive particle to a recording medium; and a pressure bonding unit that folds and pressure-bonds the recording medium or pressure-bonds the recording medium and another recording medium placed on top of each other. 
     A printed material according to an exemplary embodiment may be bonded with the pressure sensitive adhesive particle of the exemplary embodiment or the adhesive material of the exemplary embodiment. 
     Examples of the printed material of the exemplary embodiment includes a printed material formed of a folded recording medium having opposing surfaces bonded with the pressure sensitive adhesive particles contained in the adhesive material of the exemplary embodiment, and a printed material formed of more than one recording media stacked on top of each other and having opposing surfaces bonded with the pressure sensitive adhesive particles contained in the adhesive material of the exemplary embodiment. 
     The applying unit is equipped with, for example, a placing device that places the pressure sensitive adhesive particle on a recording medium, and a fixing device that fixes the pressure sensitive adhesive particle placed on the recording medium onto the recording medium. 
     For example, the pressure bonding unit is equipped with: a folding device that folds a recording medium having the pressure sensitive adhesive particle applied thereto or a stacking device that stacks another recording medium on top of the recording medium having the pressure sensitive adhesive particle applied thereto; and a pressurizing device that pressurizes the folded recording medium or the recording media stacked on top of each other. 
     The pressurizing device in the pressure bonding unit applies a pressure to a recording medium having pressure sensitive adhesive particle applied thereto. In this manner, the pressure sensitive adhesive particle is fluidized and exhibits adhesiveness on the recording medium. 
     A method for producing a printed material of this exemplary embodiment is performed by using the apparatus for producing a printed material of this exemplary embodiment. The method for producing a printed material according to the exemplary embodiment includes an applying step of using the pressure sensitive adhesive particle of the exemplary embodiment or the adhesive material of the exemplary embodiment, and applying the pressure sensitive adhesive particle to a recording medium; and a pressure bonding step of folding the recording medium and pressure-bonding the folded recording medium, or pressure-bonding the recording medium and another recording medium stacked on top of each other. 
     The applying step includes, for example, a step of placing a pressure sensitive adhesive particle onto a recording medium, and may further include a step of fixing the pressure sensitive adhesive particle placed on the recording medium onto the recording medium. 
     The pressure bonding step includes, for example, a folding step of folding the recording medium or a stacking step of stacking another recording medium on the recording medium; and a pressurizing step of pressurizing the folded recording medium or the stacked recording media. 
     The pressure sensitive adhesive particle may be applied to the entire surface of the recording medium or one part of the recording medium. One layer or two or more layers of the pressure sensitive adhesive particle are applied to the recording medium. The layer of the pressure sensitive adhesive particle may be a layer continuous in the surface direction of the recording medium or a layer discontinuous in the surface direction of the recording medium. The layer of the pressure sensitive adhesive particle may be a layer in which the pressure sensitive adhesive particles are aligned as particles or a layer in which adjacent pressure sensitive adhesive particles are fused and aligned with each other. 
     The amount of the pressure sensitive adhesive particles (preferably, transparent pressure sensitive adhesive particles) on the recording medium and applied in the region is, for example, 0.5 g/m 2  or more and 50 g/m 2  or less, 1 g/m 2  or more and 40 g/m 2  or less, or 1.5 g/m 2  or more and 30 g/m 2  or less. The thickness of the layer of the pressure sensitive adhesive particles (preferably, transparent pressure sensitive adhesive particles) on the recording medium is, for example, 0.2 μm or more and 25 μm or less, 0.4 μm or more and 20 μm or less, or 0.6 μm or more and 15 μm or less. 
     Examples of the recording medium used in the apparatus for producing a printed material according to this exemplary embodiment include paper, coated paper obtained by coating the surface of paper with a resin or the like, cloths, nonwoven cloths, resin films, and resin sheets. The recording medium may have an image on one surface or both surfaces. 
     Although some examples of the apparatus for producing a printed material according to the exemplary embodiment are described below, the exemplary embodiments are not limited to these. 
       FIG. 1  is a schematic diagram of an example of an apparatus for producing a printed material according to this exemplary embodiment. The apparatus for producing a printed material illustrated in  FIG. 1  is equipped with an applying unit  100  and a pressure bonding unit  200  downstream of the applying unit  100 . The arrow indicates the direction in which the recording medium is conveyed. 
     The applying unit  100  is a device that applies the pressure sensitive adhesive particles of the exemplary embodiment to a recording medium P. The recording medium P has an image formed on one or both surfaces in advance. 
     The applying unit  100  is equipped with a placing device  110  and a fixing device  120  disposed downstream of the placing device  110 . 
     The providing device  110  provides pressure sensitive adhesive particles M onto a recording medium P. Examples of the placing method employed by the placing device  110  include a spraying method, a bar coating method, a die coating method, a knife coating method, a roll coating method, a reverse roll coating method, a gravure coating method, a screen printing method, an ink jet method, a lamination method, and an electrophotographic method. Depending on the placing method, the pressure sensitive adhesive particles M may be dispersed in a dispersion medium to prepare a liquid composition, and this liquid composition may be used by the placing device  110 . 
     The recording medium P having the pressure sensitive adhesive particles M placed thereon by the placing device  110  is conveyed to the fixing device  120 . 
     Examples of the fixing device  120  include a heating device that has a heating source and heats the pressure sensitive adhesive particles M on the recording medium P passing therethrough to fix the pressure sensitive adhesive particles M onto the recording medium P; a pressurizing device that has a pair of pressurizing members (roll/roll or belt/roll) and pressurizes the recording medium P passing therethrough to fix the pressure sensitive adhesive particles M onto the recording medium P; and a pressurizing and heating device that has a pair of pressurizing members (roll/roll or belt/roll) equipped with heating sources inside and pressurizes and heats the recording medium P passing therethrough to fix the pressure sensitive adhesive particles M onto the recording medium P. 
     When the fixing device  120  has a heating source, the surface temperature of the recording medium P heated by the fixing device  120  is preferably 10° C. or more and 80° C. or less, more preferably 20° C. or more and 60° C. or less, and yet more preferably 30° C. or more and 50° C. or less. 
     When the fixing device  120  has a pressurizing member, the pressure applied to the recording medium P from the pressurizing member may be lower than the pressure applied to the recording medium P 2  from the pressurizing device  230 . The recording medium P that has passed the applying unit  100  turns into a recording medium P 1  having pressure sensitive adhesive particles M applied on the image. The recording medium P 1  is conveyed toward the pressure bonding unit  200 . 
     In the apparatus for producing a printed material according to this exemplary embodiment, the applying unit  100  and the pressure bonding unit  200  may be close to each other or distant from each other. When the applying unit  100  and the pressure bonding unit  200  are distant from each other, the applying unit  100  and the pressure bonding unit  200  are, for example, linked via a conveying unit (for example, a belt conveyor) that conveys the recording medium P 1 . 
     The pressure bonding unit  200  is equipped with a folding device  220  and a pressurizing device  230 , and folds and pressure-bonds the recording medium P 1 . 
     The folding device  220  folds the recording medium P 1  passing therethrough to prepare a folded recording medium P 2 . The recording medium P 2  may be folded in two, in three, or in four, and may be folded only partly. The pressure sensitive adhesive particles M are applied to at least part of at least one of the opposing surface of the recording medium P 2 . 
     The folding device  220  may have a pair of pressurizing members (for example, roll/roll or belt/roll) that apply a pressure to the recording medium P 2 . The pressure which the pressurizing members of the folding device  220  apply to the recording medium P 2  may be lower than the pressure which the pressurizing device  230  applies to the recording medium P 2 . 
     The pressure bonding unit  200  may be equipped with a stacking device that stacks another recording medium on top of the recording medium P 1  instead of the folding device  220 . Examples of the way in which the recording medium P 1  and the additional recording medium are stacked on top of each other include stacking one recording medium on the recording medium P 1 , and stacking one recording medium on each of multiple regions in the recording medium P 1 . This additional recording medium may have an image formed on one or both surfaces in advance, may be free of any image, or may be a pressure-bonded printed material prepared in advance. 
     The recording medium P 2  exits the folding device  220  (or stacking device) and is conveyed toward the pressurizing device  230 . 
     The pressurizing device  230  is equipped with a pair of pressurizing members (in other words, pressurizing rolls  231  and  232 ). The pressurizing roll  231  and the pressurizing roll  232  contact and push each other at their outer peripheral surfaces to apply a pressure onto the passing recording medium P 2 . The pair of pressurizing members in the pressurizing device  230  is not limited to the combination of pressurizing rolls, and may be a combination of a pressurizing roll and a pressurizing belt or a combination of a pressurizing belt and a pressurizing belt. 
     When a pressure is applied to the recording medium P 2  passing the pressurizing device  230 , the pressure sensitive adhesive particles M on the recording medium P 2  are fluidized under pressure and exhibit adhesiveness. 
     The pressurizing device  230  may have a heating source (for example, a halogen heater) inside for heating the recording medium P 2 , but this is optional. The pressurizing device  230  may have no heating source inside, and this does not exclude that the temperature inside the pressurizing device  230  increases to a temperature equal to or more than the environment temperature due to heat from a motor in the pressurizing device  230  or the like. 
     As the recording medium P 2  passes the pressurizing device  230 , the opposing folded surfaces bond with each other with the fluidized pressure sensitive adhesive particles M, and a pressure-bonded printed material P 3  is obtained. Two opposing surfaces of the pressure-bonded printed material P 3  are bonded to each other partly or entirely. 
     The finished pressure-bonded printed material P 3  is discharged from the pressurizing device  230 . 
     A first form of the pressure-bonded printed material P 3  is formed of a folded recording medium having opposing surfaces bonded with the pressure sensitive adhesive particles M. The pressure-bonded printed material P 3  of this form is produced by the apparatus for producing a printed material equipped with a folding device  220 . 
     A second form of the pressure-bonded printed material P 3  is formed of multiple recording media stacked on top of each other and having opposing surfaces bonded with the pressure sensitive adhesive particles M. The pressure-bonded printed material P 3  of this form is produced by the pressure-bonded printed material producing apparatus equipped with a stacking device. 
     The apparatus for producing a printed material according to this exemplary embodiment is not limited to a type that continuously conveys the recording medium P 2  from the folding device  220  (or stacking device) to the pressurizing device  230 . The apparatus for producing a printed material according to this exemplary embodiment may be of a type that stocks the recording media P 2  discharged from the folding device  220  (or stacking device) and conveys the recording media P 2  to the pressurizing device  230  after a predetermined amount of the recording media P 2  are stored. 
     In the apparatus for producing a printed material according to this exemplary embodiment, the folding device  220  (or stacking device) and the pressurizing device  230  may be close to each other or distant from each other. When the folding device  220  (or stacking device) and the pressurizing device  230  are distant from each other, the folding device  220  (or stacking device) and the pressurizing device  230  are, for example, linked via a conveying unit (for example, a belt conveyor) that conveys the recording medium P 2 . 
     The apparatus for producing a printed material according to this exemplary embodiment may be equipped with a cutting unit that cuts the recording medium into a predetermined size. Examples of the cutting unit include a cutting unit that is disposed between the applying unit  100  and the pressure bonding unit  200  and cuts off a part of the recording medium P 1 , the part being a region where no pressure sensitive adhesive particles M are applied; a cutting unit that is disposed between the folding device  220  and the pressurizing device  230  and cuts off a part of the recording medium P 2 , the part being a region where no pressure sensitive adhesive particles M are applied; and a cutting unit that is disposed downstream of the pressure bonding unit  200  and cuts off a part of the pressure-bonded printed material P 3 , the part being a region not bonded with the pressure sensitive adhesive particles M. 
     The apparatus for producing a printed material according to this exemplary embodiment is not limited to a single-sheet type. The apparatus for producing a printed material according to this exemplary embodiment may be of a type that performs an applying step and a pressure bonding step on a long recording medium to form a long pressure-bonded printed material, and then cuts the long pressure-bonded printed material into a predetermined size. 
     The apparatus for producing a printed material (image forming apparatus) according to this exemplary embodiment may further include a color image forming unit that forms a color image on a recording medium by using a coloring material. Examples of the color image forming unit include a unit that forms a color ink image on a recording medium by an inkjet method using a color ink as a coloring material, and a unit that electrophotographically forms a color image on a recording medium by using a color electrostatic charge image developer. 
     The above-described production apparatus is used to implement the method for producing a printed material of the exemplary embodiment, the method further including a color image forming step of forming a color image on the recording medium by using a coloring material. Examples of the color image forming step include a step of forming a color ink image on a recording medium by an inkjet method using a color ink as a coloring material, and a step of electrophotographically forming a color image on a recording medium by using a color electrostatic charge image developer. 
     Sheet for producing printed material and method for producing sheet for producing printed material A sheet for producing a printed material according to an exemplary embodiment includes a substrate and pressure sensitive adhesive particles of the exemplary embodiment applied to the substrate, and may include a substrate and an adhesive material of the exemplary embodiment applied to the substrate. 
     The sheet for producing a printed material according to this exemplary embodiment is produced by using the pressure sensitive adhesive particles of the exemplary embodiment. The pressure sensitive adhesive particles on the substrate may or may not keep the particle shape from before being applied to the substrate. 
     The sheet for producing a printed material according to this exemplary embodiment serves as, for example, a masking sheet to be placed on and bonded to a recording medium to conceal information recorded on the recording medium, or as a releasing sheet used to form an adhesive layer on a recording medium when recording media placed on top of each other are to be bonded. 
     Examples of the substrate that serves as the sheet for producing a printed material according to the exemplary embodiment include paper, coated paper obtained by coating the surface of paper with a resin or the like, cloths, nonwoven cloths, resin films, and resin sheets. The substrate may have an image formed on one or both surfaces. 
     In the sheet for producing a printed material according to this exemplary embodiment, the pressure sensitive adhesive particles may be applied to the entire surface of or one part of the substrate. One layer or two or more layers of the pressure sensitive adhesive particles are applied to the substrate. The layer of the pressure sensitive adhesive particles may be a layer continuous in the surface direction of the substrate or a layer discontinuous in the surface direction of the substrate. The layer of the pressure sensitive adhesive particles may be a layer in which the pressure sensitive adhesive particles are aligned as particles or a layer in which adjacent pressure sensitive adhesive particles are fused and aligned with each other. 
     The amount of the pressure sensitive adhesive particles on the substrate applied in the region is, for example, 0.5 g/m 2  or more and 50 g/m 2  or less, 1 g/m 2  or more and 40 g/m 2  or less, or 1.5 g/m 2  or more and 30 g/m 2  or less. The thickness of the layer of the pressure sensitive adhesive particles on the substrate is, for example, 0.2 μm or more and 25 μm or less, 0.4 μm or more and 20 μm or less, or 0.6 μm or more and 15 μm or less. 
     The sheet for producing a printed material according to the exemplary embodiment is produced by, for example, a production method that includes an applying step of using the pressure sensitive adhesive particles of the exemplary embodiment and applying the pressure sensitive adhesive particles to a substrate. 
     The applying step includes, for example, a placing step of placing the pressure sensitive adhesive particles onto a substrate and, furthermore, a fixing step of fixing the pressure sensitive adhesive particles on the substrate onto the substrate. 
     The placing step is performed by a placing method such as a spraying method, a bar coating method, a die coating method, a knife coating method, a roll coating method, a reverse roll coating method, a gravure coating method, a screen printing method, an ink jet method, a lamination method, or an electrophotographic method, for example. Depending on the placing method employed in the placing step, the pressure sensitive adhesive particles may be dispersed in a dispersion medium to prepare a liquid composition, and the liquid composition may be used the placing step. 
     The fixing step is, for example, a heating step of heating pressure sensitive adhesive particles on the substrate with a heating source to fix the pressure sensitive adhesive particles onto the substrate; a pressurizing step of pressurizing the substrate having the pressure sensitive adhesive particles placed thereon with a pair of pressurizing members (roll/roll or belt/roll) to fix the pressure sensitive adhesive particles onto the substrate; or a pressurizing and heating step of pressurizing and heating a substrate having the pressure sensitive adhesive particles placed thereon with a pair of pressurizing members (roll/roll or belt/roll) equipped with heating sources inside to fix the pressure sensitive adhesive particles onto the substrate. 
     Producing Printed Material by Electrophotographic Method 
     An exemplary embodiment in which the pressure sensitive adhesive particles of the exemplary embodiment are used in the electrophotographic method will now be described. In the electrophotographic method, the pressure sensitive adhesive particles are used as a toner. 
     Electrostatic Charge Image Developer 
     An electrostatic charge image developer of this exemplary embodiment contains at least the pressure sensitive adhesive particles of the exemplary embodiment. The electrostatic charge image developer of the exemplary embodiment may be a one-component developer that contains only the pressure sensitive adhesive particles of the exemplary embodiment or a two-component developer that is a mixture of the pressure sensitive adhesive particles of the exemplary embodiment and a carrier. 
     The carrier is not particularly limited and may be any known carrier. Examples of the carrier include a coated carrier prepared by covering the surface of a magnetic powder core with a resin, a magnetic powder-dispersed carrier prepared by dispersing and blending magnetic powder in a matrix resin, and a resin-impregnated carrier prepared by impregnating porous magnetic powder with a resin. The magnetic powder-dispersed carrier and the resin-impregnated carrier may each be a carrier that has a core being composed of the particles constituting the carrier and having a resin-coated surface. 
     Examples of the magnetic powder include magnetic metals such as iron, nickel, and cobalt, and magnetic oxides such as ferrite and magnetite. 
     Examples of the resin for coating and the matrix resin include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, a vinyl chloride-vinyl acetate copolymer, a styrene-acrylate copolymer, a straight silicone resin containing an organosiloxane bond and modified products thereof, fluororesin, polyester, polycarbonate, phenolic resin, and epoxy resin. The resin for coating and the matrix resin may contain other additives, such as conductive particles. Examples of the conductive particles include particles of metals such as gold, silver, and copper, and particles of carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate. 
     An example of the method for covering the surface of the core with the resin is a method that involves coating the surface of the core with a coating layer-forming solution prepared by dissolving the resin for coating and various additives (used as needed) in an appropriate solvent. The solvent is not particularly limited and may be selected by considering the type of the resin to be used, suitability of application, etc. 
     Specific examples of the resin coating method include a dipping method involving dipping cores in the coating-layer-forming solution, a spraying method involving spraying the coating-layer-forming solution onto core surfaces, a fluid bed method involving spraying a coating-layer-forming solution while having the cores float on a bed of air, and a kneader coater method involving mixing cores serving as carriers and a coating-layer-forming solution in a kneader coater and then removing the solvent. 
     In a two-component developer, the pressure sensitive adhesive particle-to-carrier mixing ratio (mass ratio) is preferably 1:100 to 30:100 and is more preferably 3:100 to 20:100. 
     Apparatus and Method for Producing Printed Material 
     An apparatus for producing a printed material according to an exemplary embodiment that employs an electrophotographic method includes an applying unit that stores a developer that contains the pressure sensitive adhesive particles of the exemplary embodiment or the adhesive material of the exemplary embodiment, and electrophotographically applies the pressure sensitive adhesive particles to a recording medium; and a pressure bonding unit that folds and pressure-bonds the recording medium or pressure-bonds the recording medium and another recording medium stacked on top of each other. 
     The method for producing a printed material of this exemplary embodiment by an electrophotographic method is performed by using the apparatus for producing a printed material of this exemplary embodiment. The method for producing a printed material according to an exemplary embodiment includes an applying step of electrophotographically applying pressure sensitive adhesive particles of the exemplary embodiment to a recording medium by using a developer that contains the pressure sensitive adhesive particles; and a pressure bonding step of folding and pressure-bonding the recording medium or pressure-bonding the recording medium and another recording medium stacked on top of each other. 
     The applying unit included in the apparatus for producing a printed material according to this exemplary embodiment includes, for example, a photoreceptor, a charging unit that charges a surface of the photoreceptor, an electrostatic charge image forming unit that forms an electrostatic charge image on the charged surface of the photoreceptor, a developing unit that stores the electrostatic charge image developer of the exemplary embodiment and develops the electrostatic charge image on the surface of the photoreceptor into a pressure sensitive adhesive particle portion by using the electrostatic charge image developer, and a transfer unit that transfers the pressure sensitive adhesive particle portion on the surface of the photoreceptor onto a surface of a recording medium. 
     The applying unit may further include a fixing unit that fixes the pressure sensitive adhesive particle portion which has been transferred onto the surface of the recording medium. 
     The applying step included in the method for producing a printed material according to this exemplary embodiment includes, for example, a charging step of charging a surface of the photoreceptor, an electrostatic charge image forming step of forming an electrostatic charge image on the charged surface of the photoreceptor, a developing step of developing the electrostatic charge image on the surface of the photoreceptor into a pressure sensitive adhesive particle portion by using the electrostatic charge image developer of the exemplary embodiment, and a transfer step of transferring the pressure sensitive adhesive particle portion on the surface of the photoreceptor onto a surface of a recording medium. 
     The applying step may further include a fixing step of fixing the pressure sensitive adhesive particle portion which has been transferred onto the surface of the recording medium. 
     The applying unit is, for example, a direct transfer type device with which a pressure sensitive adhesive particle portion on the surface of the photoreceptor is directly transferred onto a recording medium; an intermediate transfer type device with which a pressure sensitive adhesive particle portion on the surface of the photoreceptor is first transferred onto a surface of an intermediate transfer body and then the pressure sensitive adhesive particle portion on the intermediate transfer body is transferred onto a surface of a recording medium; a device equipped with a cleaning unit that cleans the surface of the photoreceptor before charging and after the transfer of the pressure sensitive adhesive particle portion; and a device equipped with a charge erasing unit that erases charges on the surface of the photoreceptor by applying charge erasing light after the transfer of the pressure sensitive adhesive particle portion and before charging. When the applying unit is of an intermediate transfer type, the transfer unit includes, for example, an intermediate transfer body having a surface onto which a pressure sensitive adhesive particle portion is transferred, a first transfer unit that transfers the pressure sensitive adhesive particle portion on the surface of the photoreceptor onto the surface of the intermediate transfer body, and a second transfer unit that transfers the pressure sensitive adhesive particle portion on the surface of the intermediate transfer body onto a surface of a recording medium. 
     A portion of the applying unit that includes the developing unit may be configurated as a cartridge structure (process cartridge) that is detachably attachable to the applying unit. A process cartridge that stores the electrostatic charge image developer of the exemplary embodiment and is equipped with a developing unit, for example, is suitable as this process cartridge. 
     The pressure bonding unit included in the apparatus for producing a printed material according to this exemplary embodiment applies a pressure to a recording medium to which the pressure sensitive adhesive particles of the exemplary embodiment have been applied. In this manner, the pressure sensitive adhesive particles of the exemplary embodiment become fluidized and exhibit adhesiveness on the recording medium. The pressure that the pressure bonding unit applies to the recording medium to fluidize the pressure sensitive adhesive particles of the exemplary embodiment is preferably 3 MPa or more and 300 MPa or less, more preferably 10 MPa or more and 200 MPa or less, and yet more preferably 30 MPa or more and 150 MPa or less. 
     The pressure sensitive adhesive particles of the exemplary embodiment may be applied to the entire surface of the recording medium or one part of the recording medium. One layer or two or more layers of the pressure sensitive adhesive particles of the exemplary embodiment are applied to the recording medium. The layer of the pressure sensitive adhesive particles of the exemplary embodiment may be a layer continuous in the surface direction of the recording medium or a layer discontinuous in the surface direction of the recording medium. The layer of the pressure sensitive adhesive particles according to the exemplary embodiment may be a layer in which the pressure sensitive adhesive particles are aligned as particles or a layer in which adjacent pressure sensitive adhesive particles are fused and aligned with each other. 
     The amount of the pressure sensitive adhesive particles (preferably, transparent pressure sensitive adhesive particles) of the exemplary embodiment on the recording medium and applied in the region is, for example, 0.5 g/m 2  or more and 50 g/m 2  or less, 1 g/m 2  or more and 40 g/m 2  or less, or 1.5 g/m 2  or more and 30 g/m 2  or less. The thickness of the layer of the pressure sensitive adhesive particles (preferably, transparent pressure sensitive adhesive particles) of the exemplary embodiment on the recording medium is, for example, 0.2 μm or more and 25 μm or less, 0.4 μm or more and 20 μm or less, or 0.6 μm or more and 15 μm or less. 
     Examples of the recording medium used in the apparatus for producing a printed material according to this exemplary embodiment include paper, coated paper obtained by coating the surface of paper with a resin or the like, cloths, nonwoven cloths, resin films, and resin sheets. The recording medium may have an image on one surface or both surfaces. 
     Although some examples of the apparatus for producing a printed material according to the exemplary embodiment employing an electrophotographic system are described below, the exemplary embodiments are not limited to these. 
       FIG. 2  is a schematic diagram of an example of an apparatus for producing a printed material according to this exemplary embodiment. The apparatus for producing a printed material illustrated in  FIG. 2  is equipped with an applying unit  100  and a pressure bonding unit  200  downstream of the applying unit  100 . The arrow indicates the direction in which the photoreceptor rotates or the recording medium is conveyed. 
     The applying unit  100  is of a direct transfer type and uses a developer containing the pressure sensitive adhesive particles of the exemplary embodiment to electrophotographically apply the pressure sensitive adhesive particles of the exemplary embodiment to a recording medium P. The recording medium P has an image formed on one or both surfaces in advance. 
     The applying unit  100  includes a photoreceptor  101 . A charging roll (one example of the charging unit)  102  that charges the surface of the photoreceptor  101 , an exposing device (one example of the electrostatic charge image forming unit)  103  that forms an electrostatic charge image by exposing the charged surface of the photoreceptor  101  with a laser beam, a developing device (one example of the developing unit)  104  that develops the electrostatic charge image by supplying pressure sensitive adhesive particles to the electrostatic charge image, a transfer roll (one example of the transfer unit)  105  that transfers the developed pressure sensitive adhesive particle portion onto the recording medium P, and a photoreceptor cleaning device (one example of the cleaning unit)  106  that removes the pressure sensitive adhesive particles remaining on the surface of the photoreceptor  101  after the transfer are disposed around the photoreceptor  101 . 
     The operation of the applying unit  100  applying the pressure sensitive adhesive particles of the exemplary embodiment to the recording medium P will now be described. 
     First, the surface of the photoreceptor  101  is charged by the charging roll  102 . The exposing device  103  applies a laser beam onto the charged surface of the photoreceptor  101  in accordance to image data sent from a controller (not illustrated). As a result, an electrostatic charge image of an application pattern of the pressure sensitive adhesive particles of this exemplary embodiment is formed on the surface of the photoreceptor  101 . 
     The electrostatic charge image formed on the photoreceptor  101  is rotated to a developing position as the photoreceptor  101  is run. The electrostatic charge image on the photoreceptor  101  is developed by the developing device  104  at this developing position so as to form a pressure sensitive adhesive particle portion. 
     A developer that contains at least the pressure sensitive adhesive particles of this exemplary embodiment and a carrier is stored in the developing device  104 . The pressure sensitive adhesive particles of this exemplary embodiment are frictionally charged as they are stirred with the carrier in the developing device  104 , and are carried on the developer roll. As the surface of the photoreceptor  101  passes the developing device  104 , the pressure sensitive adhesive particles electrostatically adhere to the electrostatic charge image on the surface of the photoreceptor  101 , and the electrostatic charge image is thereby developed with the pressure sensitive adhesive particles. The photoreceptor  101  on which the pressure sensitive adhesive particle portion has been formed is continuously run, and the pressure sensitive adhesive particle portion on the photoreceptor  101  is conveyed to a transfer position. 
     After the pressure sensitive adhesive particle portion on the photoreceptor  101  is conveyed to the transfer position, a transfer bias is applied to the transfer roll  105 . An electrostatic force working from the photoreceptor  101  toward the transfer roll  105  also acts on the pressure sensitive adhesive particle portion, and, thus, the pressure sensitive adhesive particle portion on the photoreceptor  101  is transferred onto the recording medium P. 
     The pressure sensitive adhesive particles remaining on the photoreceptor  101  are removed by the photoreceptor cleaning device  106  and recovered. The photoreceptor cleaning device  106  is, for example, a cleaning blade or a cleaning brush. From the viewpoint of suppressing the phenomenon in which the pressure sensitive adhesive particles of the exemplary embodiment remaining on the surface of the photoreceptor fluidize under a pressure and attach to the surface of the photoreceptor while forming a film, the photoreceptor cleaning device  106  may be a cleaning brush. 
     The recording medium P onto which the pressure sensitive adhesive particle portion has been transferred is conveyed to a fixing device (one example of the fixing unit)  107 . The fixing device  107  is, for example, a pair of fixing members (roll/roll or belt/roll). The applying unit  100  need not be equipped with a fixing device  107 ; however, from the viewpoint of suppressing detachment of the pressure sensitive adhesive particles of the exemplary embodiment from the recording medium P, the applying unit  100  is preferably equipped with a fixing device  107 . The pressure which the fixing device  107  applies to the recording medium P may be lower than the pressure which the pressurizing device  230  applies to the recording medium P 2 , and may specifically be 0.2 MPa or more and 1 MPa or less. 
     The fixing device  107  may have a heating source (for example, a halogen heater) for heating the recording medium P inside, but this is optional. When the fixing device  107  has a heating source inside, the surface temperature of the recording medium P heated by the heating source is preferably 150° C. or more and 220° C. or less, more preferably 155° C. or more and 210° C. or less, and yet more preferably 160° C. or more and 200° C. or less. The fixing device  107  may have no heating source inside, and this does not exclude that the temperature inside the fixing device  107  increases to a temperature equal to or more than the environment temperature due to heat from a motor in the applying unit  100  or the like. 
     The recording medium P that has passed the applying unit  100  turns into a recording medium P 1  having pressure sensitive adhesive particles of the exemplary embodiment applied on the image. The recording medium P 1  is conveyed toward the pressure bonding unit  200 . 
     In the apparatus for producing a printed material according to this exemplary embodiment, the applying unit  100  and the pressure bonding unit  200  may be close to each other or distant from each other. When the applying unit  100  and the pressure bonding unit  200  are distant from each other, the applying unit  100  and the pressure bonding unit  200  are, for example, linked via a conveying unit (for example, a belt conveyor) that conveys the recording medium P 1 . 
     The pressure bonding unit  200  is equipped with a folding device  220  and a pressurizing device  230 , and folds and pressure-bonds the recording medium P 1 . 
     The folding device  220  folds the recording medium P 1  passing therethrough to prepare a folded recording medium P 2 . The recording medium P 2  may be folded in two, in three, or in four, and may be folded only partly. The pressure sensitive adhesive particles of the exemplary embodiment are applied to at least part of at least one of the opposing surfaces of the recording medium P 2 . 
     The folding device  220  may have a pair of pressurizing members (for example, roll/roll or belt/roll) that apply a pressure to the recording medium P 2 . The pressure which the pressurizing members of the folding device  220  apply to the recording medium P may be lower than the pressure which the pressurizing device  230  applies to the recording medium P 2 , and may specifically be 1 MPa or more and 10 MPa or less. 
     The pressure bonding unit  200  may be equipped with a stacking device that stacks another recording medium on top of the recording medium P 1  instead of the folding device  220 . Examples of the way in which the recording medium P 1  and the additional recording medium are stacked on top of each other include stacking one recording medium on the recording medium P 1 , and stacking one recording medium on each of multiple regions in the recording medium P 1 . This additional recording medium may have an image formed on one or both surfaces in advance, may be free of any image, or may be a pressure-bonded printed material prepared in advance. 
     The recording medium P 2  exits the folding device  220  (or stacking device) and is conveyed toward the pressurizing device  230 . 
     The pressurizing device  230  is equipped with a pair of pressurizing members (in other words, pressurizing rolls  231  and  232 ). The pressurizing roll  231  and the pressurizing roll  232  contact and push each other at their outer peripheral surfaces to apply a pressure onto the passing recording medium P 2 . The pair of pressurizing members in the pressurizing device  230  is not limited to the combination of pressurizing rolls, and may be a combination of a pressurizing roll and a pressurizing belt or a combination of a pressurizing belt and a pressurizing belt. 
     When a pressure is applied to the recording medium P 2  passing the pressurizing device  230 , the pressure sensitive adhesive particles of the exemplary embodiment on the recording medium P 2  are fluidized under pressure and exhibit adhesiveness. The pressure that the pressurizing device  230  applies to the recording medium P 2  is preferably 3 MPa or more and 300 MPa or less, more preferably 10 MPa or more and 200 MPa or less, and yet more preferably 30 MPa or more and 150 MPa or less. 
     The pressurizing device  230  may have a heating source (for example, a halogen heater) inside for heating the recording medium P 2 , but this is optional. When the pressurizing device  230  has a heating source inside, the surface temperature of the recording medium P 2  heated by the heating source is preferably 30° C. or more and 120° C. or less, more preferably 40° C. or more and 100° C. or less, and yet more preferably 50° C. or more and 90° C. or less. The pressurizing device  230  may have no heating source inside, and this does not exclude that the temperature inside the pressurizing device  230  increases to a temperature equal to or more than the environment temperature due to heat from a motor in the pressurizing device  230  or the like. 
     As the recording medium P 2  passes the pressurizing device  230 , the opposing folded surfaces bond with each other with the fluidized pressure sensitive adhesive particles of the exemplary embodiment, and a pressure-bonded printed material P 3  is obtained. The opposing surfaces of the pressure-bonded printed material P 3  are partly or entirely bonded to each other. 
     The finished pressure-bonded printed material P 3  is discharged from the pressurizing device  230 . 
     A first form of the pressure-bonded printed material P 3  is formed of a folded recording medium having opposing surfaces bonded with the pressure sensitive adhesive particles of the exemplary embodiment. The pressure-bonded printed material P 3  of this form is produced by the apparatus for producing a printed material equipped with a folding device  220 . 
     A second form of the pressure-bonded printed material P 3  is formed of multiple recording media stacked on top of each other and having opposing surfaces bonded with the pressure sensitive adhesive particles of the exemplary embodiment. The pressure-bonded printed material P 3  of this form is produced by the pressure-bonded printed material producing apparatus equipped with a stacking device. 
     The apparatus for producing a printed material according to this exemplary embodiment is not limited to a type that continuously conveys the recording medium P 2  from the folding device  220  (or stacking device) to the pressurizing device  230 . The apparatus for producing a printed material according to this exemplary embodiment may be of a type that stocks the recording media P 2  discharged from the folding device  220  (or stacking device) and conveys the recording media P 2  to the pressurizing device  230  after a predetermined amount of the recording media P 2  are stored. 
     In the apparatus for producing a printed material according to this exemplary embodiment, the folding device  220  (or stacking device) and the pressurizing device  230  may be close to each other or distant from each other. When the folding device  220  (or stacking device) and the pressurizing device  230  are distant from each other, the folding device  220  (or stacking device) and the pressurizing device  230  are, for example, linked via a conveying unit (for example, a belt conveyor) that conveys the recording medium P 2 . 
     The apparatus for producing a printed material according to this exemplary embodiment may be equipped with a cutting unit that cuts the recording medium into a predetermined size. Examples of the cutting unit include a cutting unit that is disposed between the applying unit  100  and the pressure bonding unit  200  and cuts off a part of the recording medium P 1 , the part being a region where no pressure sensitive adhesive particles of the exemplary embodiment are applied; a cutting unit that is disposed between the folding device  220  and the pressurizing device  230  and cuts off a part of the recording medium P 2 , the part being a region where no pressure sensitive adhesive particles of the exemplary embodiment are applied; and a cutting unit that is disposed downstream of the pressure bonding unit  200  and cuts off a part of the pressure-bonded printed material P 3 , the part being a region not bonded with the pressure sensitive adhesive particles of the exemplary embodiment. 
     The apparatus for producing a printed material according to this exemplary embodiment is not limited to a single-sheet type. The apparatus for producing a printed material according to this exemplary embodiment may be of a type that performs an applying step and a pressure bonding step on a long recording medium to form a long pressure-bonded printed material, and then cuts the long pressure-bonded printed material into a predetermined size. 
     The apparatus for producing a printed material according to this exemplary embodiment may further include a color image forming unit that forms a color image on a recording medium by an electrophotographic method by using a color electrostatic charge image developer. The color image forming unit is equipped with, for example, a photoreceptor, a charging unit that charges a surface of the photoreceptor, an electrostatic charge image forming unit that forms an electrostatic charge image on the charged surface of the photoreceptor, a developing unit that stores a color electrostatic charge image developer and develops the electrostatic charge image on the surface of the photoreceptor into a color toner image by using the color electrostatic charge image developer, a transfer unit that transfers the color toner image on the surface of the photoreceptor onto a surface of a recording medium, and a thermal fixing unit that thermally fixes the color toner image transferred onto the surface of the recording medium. 
     The above-described production apparatus is used to implement the method for producing a printed material of the exemplary embodiment, the method further including a color image forming step of forming a color image on the recording medium by an electrophotographic method using a color electrostatic charge image developer. The color image forming step includes, specifically, a charging step of charging a surface of a photoreceptor, an electrostatic charge image forming step of forming an electrostatic charge image on the charged surface of the photoreceptor, a developing step of developing the electrostatic charge image on the surface of the photoreceptor into a color toner image by using a color electrostatic charge image developer, a transfer step of transferring the color toner image on the surface of the photoreceptor onto a surface of a recording medium, and a thermal fixing step of thermally fixing the color toner image transferred onto the surface of the recording medium. 
     Examples of the color image forming unit included in the apparatus for producing a printed material according to the exemplary embodiment include: a direct transfer type device with which a color toner image on the surface of the photoreceptor is directly transferred onto a recording medium; an intermediate transfer type device with which a color toner image on the surface of the photoreceptor is first transferred onto a surface of an intermediate transfer body and then the color toner image on the intermediate transfer body is transferred onto a surface of a recording medium; a device equipped with a cleaning unit that cleans the surface of the photoreceptor before charging and after the transfer of the color toner image; and a device equipped with a charge erasing unit that erases charges on the surface of the photoreceptor by applying charge erasing light after the transfer of the color toner image and before charging. When the color image forming unit is an intermediate transfer type device, the transfer unit has, for example, an intermediate transfer body having a surface to which a color toner image is transferred, a first transfer unit that transfers (first transfer) the color toner image on the surface of the photoreceptor onto a surface of the intermediate transfer body, and a second transfer unit that transfers (second transfer) the color toner image on the surface of the intermediate transfer body onto a surface of a recording medium. 
     In the apparatus for producing a printed material according to this exemplary embodiment, when the applying unit for applying a developer containing the pressure sensitive adhesive particles of the exemplary embodiment and a color image forming unit both employ an intermediate transfer method, the applying unit and the color image forming unit may share the intermediate transfer body and the second transfer unit. 
     In the apparatus for producing a printed material according to this exemplary embodiment, the applying unit that applies an image developer containing the pressure sensitive adhesive particles of the exemplary embodiment and the color image forming unit may share the thermal fixing unit. 
     Other examples of the apparatus for producing a printed material according to the exemplary embodiment equipped with a color image forming unit are described below, but these examples are not limiting. Only relevant parts illustrated in the drawing are described in the description below, and descriptions of other parts are omitted. 
       FIG. 3  is a schematic diagram of an example of an apparatus for producing a printed material according to this exemplary embodiment employing an electrophotographic system. The apparatus for producing a printed material illustrated in  FIG. 3  is equipped with a printing unit  300  that applies the pressure sensitive adhesive particles of the exemplary embodiment to a recording medium and forms a color image on the recording medium, and a pressure bonding unit  200  disposed downstream of the printing unit  300 . 
     The printing unit  300  is a five-stand-tandem intermediate transfer-type printing unit. The printing unit  300  is equipped with a unit  10 T that applies the pressure sensitive adhesive particles (T) of the exemplary embodiment, and units  10 Y,  10 M,  10 C, and  10 K that respectively form yellow (Y), magenta (M), cyan (C) black (K) images. The unit  10 T is the applying unit that applies the pressure sensitive adhesive particles of the exemplary embodiment to the recording medium P by using a developer that contains the pressure sensitive adhesive particles of the exemplary embodiment. Each of the units  10 Y,  10 M,  10 C, and  10 K is a unit that forms a color image on the recording medium P by using a developer that contains a color toner. The units  10 T,  10 Y,  10 M,  10 C, and  10 K employ an electrophotographic system. 
     The units  10 T,  10 Y,  10 M,  10 C, and  10 K are disposed side by side with spaces therebetween in the horizontal direction. The units  10 T,  10 Y,  10 M,  10 C, and  10 K may each be a process cartridge detachably attachable to the printing unit  300 . 
     An intermediate transfer belt (one example of the intermediate transfer body)  20  extends below and throughout the units  10 T,  10 Y,  10 M,  10 C, and  10 K. The intermediate transfer belt  20  is wound around a driving roll  22 , a supporting roll  23 , and a counter roll  24  that are in contact with the inner surface of the intermediate transfer belt  20 , and runs in a direction from the unit  10 T to the unit  10 K. An intermediate transfer body cleaning device  21  is installed on the image carrying surface side of the intermediate transfer belt  20  so as to face the driving roll  22 . 
     The units  10 T,  10 Y,  10 M,  10 C, and  10 K are respectively equipped with developing devices (examples of the developing unit)  4 T,  4 Y,  4 M,  4 C, and  4 K. The pressure sensitive adhesive particles of the exemplary embodiment stored in the pressure sensitive adhesive particle cartridge  8 T, and, a yellow toner, a magenta toner, a cyan toner, and a black toner stored in the toner cartridges  8 Y,  8 M,  8 C, and  8 K are respectively supplied to the developing devices  4 T,  4 Y,  4 M,  4 C, and  4 K. 
     Since the units  10 T,  10 Y,  10 M,  10 C and  10 K are identical in structure and in operation, the unit  10 T that applies the pressure sensitive adhesive particles of this exemplary embodiment to the recording medium is described as a representative example. 
     The unit  10 T has a photoreceptor  1 T. A charging roll (one example of the charging unit)  2 T that charges the surface of the photoreceptor  1 T, an exposing device (one example of the electrostatic charge image forming unit)  3 T that forms an electrostatic charge image by exposing the charged surface of the photoreceptor  1 T with a laser beam, a developing device (one example of the developing unit)  4 T that develops the electrostatic charge image by supplying pressure sensitive adhesive particles to the electrostatic charge image, a first transfer roll (one example of the first transfer unit)  5 T that transfers the developed pressure sensitive adhesive particle portion onto the intermediate transfer belt  20 , and a photoreceptor cleaning device (one example of the cleaning unit)  6 T that removes the pressure sensitive adhesive particles remaining on the surface of the photoreceptor  1 T after the first transfer are provided in that order around the photoreceptor  1 T. The first transfer roll  5 T is disposed on the inner side of the intermediate transfer belt  20  and is positioned to face the photoreceptor  1 T. 
     In the description below, operation of applying the pressure sensitive adhesive particles of the exemplary embodiment and formation of a color image on the recording medium P is described by using the operation of the unit  10 T as an example. 
     First, the surface of the photoreceptor  1 T is charged by the charging roll  2 T. The developing device  3 T applies a laser beam onto the charged surface of the photoreceptor  1 T in accordance to image data sent from a controller (not illustrated). As a result, an electrostatic charge image of an application pattern of the pressure sensitive adhesive particles of this exemplary embodiment is formed on the surface of the photoreceptor  1 T. 
     The electrostatic charge image formed on the photoreceptor  1 T is rotated to a developing position as the photoreceptor  1 T is run. The electrostatic charge image on the photoreceptor  1 T is developed by the developing device  4 T at this developing position so as to form a pressure sensitive adhesive particle portion. 
     A developer that contains at least the pressure sensitive adhesive particles of this exemplary embodiment and a carrier is stored in the developing device  4 T. The pressure sensitive adhesive particles of this exemplary embodiment are frictionally charged as they are stirred with the carrier in the developing device  4 T, and are carried on the developer roll. As the surface of the photoreceptor  1 T passes the developing device  4 T, the pressure sensitive adhesive particles electrostatically adhere to the electrostatic charge image on the surface of the photoreceptor  1 T, and the electrostatic charge image is thereby developed with the pressure sensitive adhesive particles. The photoreceptor  1 T on which the pressure sensitive adhesive particle portion has been formed is continuously run, and the pressure sensitive adhesive particle portion on the photoreceptor  1 T is conveyed to a first transfer position. 
     After the pressure sensitive adhesive particle portion on the photoreceptor  1 T is conveyed to the first transfer position, a first transfer bias is applied to the first transfer roll  5 T. An electrostatic force working from the photoreceptor  1 T toward the first transfer roll  5 T also acts on the pressure sensitive adhesive particle portion, and, thus, the pressure sensitive adhesive particle portion on the photoreceptor  1 T is transferred onto the intermediate transfer belt  20 . The pressure sensitive adhesive particles remaining on the photoreceptor  1 T are removed by the photoreceptor cleaning device  6 T and recovered. The photoreceptor cleaning device  6 T is, for example, a cleaning blade or a cleaning brush, and is preferably a cleaning brush. 
     An operation similar to that performed in the unit  10 T is also performed in the units  10 Y,  10 M,  10 C, and  10 K by using developers that contain color toners. The intermediate transfer belt  20  onto which the pressure sensitive adhesive particle portion has been transferred in the unit  10 T sequentially passes the units  10 Y,  10 M,  10 C, and  10 K, and toner images of respective colors are transferred (multi-layer transfer) onto the intermediate transfer belt  20 . 
     The intermediate transfer belt  20  onto which the pressure sensitive adhesive particle portion and the toner images are transferred and superposed as the intermediate transfer belt  20  passes the units  10 T,  10 Y,  10 M,  10 C, and  10 K reaches a second transfer portion constituted by the intermediate transfer belt  20 , the counter roll  24  in contact with the inner surface of the intermediate transfer belt  20 , and a second transfer roll (one example of the second transfer unit)  26  disposed on the image carrying surface side of the intermediate transfer belt  20 . Meanwhile, a recording medium P is supplied to a gap where the second transfer roll  26  and the intermediate transfer belt  20  contact each other via a supplying mechanism, and a second transfer bias is applied to the counter roll  24 . During this process, an electrostatic force working from the intermediate transfer belt  20  toward the recording medium P and the toner images acts on the pressure sensitive adhesive particle portion, and the pressure sensitive adhesive particle portion and the toner images on the intermediate transfer belt  20  are transferred onto the recording medium P. 
     The recording medium P onto which the pressure sensitive adhesive particle portion and the toner images have been transferred is conveyed to a thermal fixing device (one example of the thermal fixing unit)  28 . The thermal fixing device  28  is equipped with a heating source such as a halogen heater, and heats the recording medium P. The surface temperature of the recording medium P when heated by the thermal fixing device  28  is preferably 150° C. or more and 220° C. or less, more preferably 155° C. or more and 210° C. or less, and yet more preferably 160° C. or more and 200° C. or less. As the recording medium P passes the thermal fixing device  28 , the color toner images are thermally fixed to the recording medium P. 
     From the viewpoints of suppressing detachment of the pressure sensitive adhesive particles of the exemplary embodiment from the recording medium P and improving the fixability of the color image to the recording medium P, the thermal fixing device  28  may be a device that applies heat and pressure, for example, a pair of fixing members (roll/roll or belt/roll) equipped with heating sources inside. When the thermal fixing device  28  is to apply pressure, the pressure which the thermal fixing device  28  applies to the recording medium P may be lower than the pressure which the pressurizing device  230  applies to the recording medium P 2 , and may specifically be 0.2 MPa or more and 1 MPa or less. 
     The recording medium P passes the printing unit  300  and turns into a recording medium P 1  on which color images and the pressure sensitive adhesive particles of the exemplary embodiment are placed. The recording medium P 1  is conveyed toward the pressure bonding unit  200 . 
     The structure of the pressure bonding unit  200  illustrated in  FIG. 3  may be the same as that of the pressure bonding unit  200  illustrated in  FIG. 2 , and the detailed descriptions of the structure and the operation of the pressure bonding unit  200  are omitted. 
     In the apparatus for producing a printed material according to this exemplary embodiment, the printing unit  300  and the pressure bonding unit  200  may be close to each other or distant from each other. When the printing unit  300  and the pressure bonding unit  200  are distant from each other, the printing unit  300  and the pressure bonding unit  200  are, for example, linked via a conveying unit (for example, a belt conveyor) that conveys the recording medium P 1 . 
     The apparatus for producing a printed material according to this exemplary embodiment may be equipped with a cutting unit that cuts the recording medium into a predetermined size. Examples of the cutting unit include a cutting unit that is disposed between the printing unit  300  and the pressure bonding unit  200  and cuts off a part of the recording medium P 1 , the part being a region where no pressure sensitive adhesive particles of the exemplary embodiment are applied; a cutting unit that is disposed between the folding device  220  and the pressurizing device  230  and cuts off a part of the recording medium P 2 , the part being a region where no pressure sensitive adhesive particles of the exemplary embodiment are applied; and a cutting unit that is disposed downstream of the pressure bonding unit  200  and cuts off a part of the pressure-bonded printed material P 3 , the part being a region not bonded with the pressure sensitive adhesive particles of the exemplary embodiment. 
     The apparatus for producing a printed material according to this exemplary embodiment is not limited to a single-sheet type. The apparatus for producing a printed material according to this exemplary embodiment may be of a type that performs a color image forming step, an applying step, and a pressure bonding step on a long recording medium to form a long pressure-bonded printed material, and then cuts the long pressure-bonded printed material into a predetermined size. 
     Process Cartridge 
     A process cartridge used in an apparatus for producing a printed material by an electrophotographic method will now be described. 
     A process cartridge according to an exemplary embodiment is equipped with a developing unit that stores the electrostatic charge image developer of the exemplary embodiment and develops an electrostatic charge image on the surface of a photoreceptor into a pressure sensitive adhesive particle portion by using the electrostatic charge image developer, and is detachably attached to the apparatus for producing a printed material. 
     The process cartridge of this exemplary embodiment may be configured to include a developing unit and, if needed, at least one selected from a photoreceptor, a charging unit, an electrostatic charge image forming unit, a transfer unit, and other units. 
     An example of the process cartridge is a cartridge in which a photoreceptor, and a charging roll (one example of the charging unit), a developing device (one example of the developing unit), and a photoreceptor cleaning device (one example of the cleaning unit) disposed around the photoreceptor are integrated by a casing. The casing has an opening to allow exposure. The casing has an installation rail, and the process cartridge is installed to the apparatus for producing a printed material by using the installation rail. 
     The image forming apparatus illustrated in  FIG. 1  has a structure to which toner cartridges  8 Y,  8 M,  8 C, and  8 K are detachably attached, and developing devices  4 Y,  4 M,  4 C, and  4 K are respectively connected to the corresponding toner cartridges of the respective colors via toner supply tubes not illustrated in the drawings. When the toner in the toner cartridge has run low, the toner cartridge is replaced. 
     EXAMPLES 
     The exemplary embodiments will now be described in further detail through examples and comparative examples, but the exemplary embodiments are not limited by these examples. The “parts” and “%” that indicate the amounts are on a mass basis unless otherwise noted. 
     Examples 1 to 8 and Comparative Examples 1 to 3 
     Preparation of Dispersion Containing Styrene Resin Particles 
     Preparation of Styrene Resin Particle Dispersion (St1) 
     
         
         
           
             Styrene: 390 parts 
             n-Butyl acrylate: 100 parts 
             Acrylic acid: 10 parts 
             Dodecanethiol: 7.5 parts 
           
         
       
    
     The above-described materials are mixed and dissolved to prepare a monomer solution. 
     In 205 parts of ion exchange water, 8 parts of an anionic surfactant (DOWFAX 2A1 produced by The Dow Chemical Company) is dissolved, and is dispersed and emulsified by adding the aforementioned monomer solution to obtain an emulsion. 
     In 462 parts of ion exchange water, 2.2 part of an anionic surfactant (DOWFAX 2A1 produced by The Dow Chemical Company) is dissolved. The resulting solution is charged into a polymerization flask equipped with a stirrer, a thermometer, a reflux cooling tube, and a nitrogen inlet tube and is heated to 73° C. under stirring, and the temperature is retained thereat. 
     In 21 parts of ion exchange water, 3 parts of ammonium persulfate is dissolved, and the resulting solution is added dropwise to the aforementioned polymerization flask over a period of 15 minutes via a metering pump. Then, the aforementioned emulsion is added dropwise thereto over a period of 160 minutes via a metering pump. 
     Subsequently, while slow stirring is continued, the polymerization flask is retained at 75° C. for 3 hours, and then the temperature is returned to room temperature. 
     As a result, a styrene resin particle dispersion (St1) that contains styrene resin particles, that has a volume-average resin particle diameter (D50v) of 174 nm, a weight-average molecular weight of 49,000 as determined by GPC (UV detection), and a glass transition temperature of 54° C., and that has a solid content of 42% is obtained. 
     The styrene resin particle dispersion (St1) is dried to obtain styrene resin particles, and the thermal behavior in the temperature range of −100° C. to 100° C. is analyzed with a differential scanning calorimeter (DSC-60A produced by Shimadzu Corporation). One glass transition temperature is observed. Table 1 indicates the glass transition temperatures. 
     Preparation of Styrene Resin Particle Dispersions (St2) to (St14) 
     Styrene resin particle dispersions (St2) to (St14) are prepared as with the preparation of the styrene resin particle dispersion (St1) except that the monomers are changed as indicated in Table 1. 
     The compositions and the physical properties of the styrene resin particle dispersion (St1) etc., are indicated in Table 1. In Table 1, the monomers are abbreviated as follows. 
     Styrene: St, n-butyl acrylate: BA, 2-ethylhexyl acrylate: 2EHA, ethyl acrylate: EA, 4-hydroxybutyl acrylate: 4HBA, acrylic acid: AA, methacrylic acid: MAA, 2-carboxyethyl acrylate: CEA 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Resin A: Styrene resin particle dispersion 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 D50v of 
                   
                   
               
               
                   
                   
                 resin 
                 Mw 
               
               
                   
                 Polymerization components (mass ratio) 
                 particles 
                 (k) 
                 Tg 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 No. 
                 St 
                 BA 
                 2EHA 
                 EA 
                 4HBA 
                 AA 
                 MAA 
                 CEA 
                 nm 
                 — 
                 ° C. 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 St1 
                 78 
                 20 
                 0 
                 0 
                 0 
                 2 
                 0 
                 0 
                 174 
                 49 
                 54 
               
               
                 St2 
                 88 
                 10 
                 0 
                 0 
                 0 
                 2 
                 0 
                 0 
                 170 
                 50 
                 76 
               
               
                 St3 
                 83 
                 15 
                 0 
                 0 
                 0 
                 2 
                 0 
                 0 
                 172 
                 52 
                 65 
               
               
                 St4 
                 78 
                 20 
                 0 
                 0 
                 0 
                 0 
                 2 
                 0 
                 177 
                 48 
                 57 
               
               
                 St5 
                 80 
                 15 
                 0 
                 0 
                 5 
                 0 
                 0 
                 0 
                 172 
                 46 
                 55 
               
               
                 St6 
                 80 
                 15 
                 5 
                 0 
                 0 
                 0 
                 0 
                 0 
                 174 
                 51 
                 54 
               
               
                 St7 
                 80 
                 20 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 169 
                 50 
                 54 
               
               
                 St8 
                 77 
                 20 
                 0 
                 0 
                 0 
                 0 
                 0 
                 3 
                 168 
                 48 
                 54 
               
               
                 St9 
                 72 
                 26 
                 0 
                 0 
                 0 
                 2 
                 0 
                 0 
                 172 
                 55 
                 43 
               
               
                 St10 
                 68 
                 30 
                 0 
                 0 
                 0 
                 2 
                 0 
                 0 
                 173 
                 53 
                 35 
               
               
                 St11 
                 80 
                 0 
                 20 
                 0 
                 0 
                 0 
                 0 
                 0 
                 171 
                 52 
                 56 
               
               
                 St12 
                 78 
                 0 
                 20 
                 0 
                 0 
                 2 
                 0 
                 0 
                 167 
                 49 
                 56 
               
               
                 St13 
                 63 
                 0 
                 0 
                 35 
                 0 
                 2 
                 0 
                 0 
                 169 
                 51 
                 54 
               
               
                 St14 
                 60 
                 20 
                 20 
                 0 
                 0 
                 0 
                 0 
                 0 
                 169 
                 51 
                 54 
               
               
                   
               
            
           
         
       
     
     Preparation of Dispersion Containing Composite Resin Particles 
     Preparation of Composite Resin Particle Dispersion (M1) 
     
         
         
           
             Styrene resin particle dispersion (St1): 1190 parts (solid content: 500 parts) 
             2-Ethylhexyl acrylate: 250 parts 
             n-Butyl acrylate: 250 parts 
             Ion exchange water: 982 parts 
           
         
       
    
     The above-described materials are charged into a polymerization flask, stirred at 25° C. for 1 hour, and heated to 70° C. 
     In 75 parts of ion exchange water, 2.5 parts of ammonium persulfate is dissolved, and the resulting solution is added dropwise to the aforementioned polymerization flask over a period of 60 minutes via a metering pump. 
     Subsequently, while slow stirring is continued, the polymerization flask is retained at 70° C. for 3 hours, and then the temperature is returned to room temperature. 
     As a result, a composite resin particle dispersion (M1) that contains composite resin particles, that has a volume-average resin particle diameter (D50v) of 219 nm and a weight-average molecular weight of 219,000 as determined by GPC (UV detection), and that has a solid content of 32% is obtained. 
     The composite resin particle dispersion (M1) is dried to obtain composite resin particles, and the thermal behavior in the temperature range of −150° C. to 100° C. is analyzed with a differential scanning calorimeter (DSC-60A produced by Shimadzu Corporation). Two glass transition temperatures are observed. Table 2 indicates the glass transition temperatures. 
     Preparation of Composite Resin Particle Dispersions (M2) to (M13) 
     Composite resin particle dispersions and (M2) to (M13) are prepared as with the preparation of the composite resin particle dispersion (M1) except that the styrene resin particle dispersion (St1) is changed as described in Table 3 or that the polymerization components of the (meth)acryl resin are changed as described in Table 2. 
     The compositions and the physical properties of the polyester resin and the like contained in the composite resin particle dispersion (M1) etc., are indicated in Table 2. In Table 2, the monomers are abbreviated as follows. 
     Styrene: St, n-butyl acrylate: BA, 2-ethylhexyl acrylate: 2EHA, ethyl acrylate: EA, 4-hydroxybutyl acrylate: 4HBA, acrylic acid: AA, methacrylic acid: MAA, 2-carboxyethyl acrylate: CEA, hexyl acrylate: HA, propyl acrylate: PA 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Resin B1 and resin B2: (Meth)acrylic resin particle dispersion 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                 D50v of 
                   
                 Molecular 
                 Viscosity at 
                   
               
               
                   
                 Polymerization 
                 resin 
                 Mw 
                 weight 
                 100° C. 
               
               
                   
                 components (mass ratio) 
                 particles 
                 (k) 
                 distribution 
                 (Pa · s) 
                 Tg 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 No. 
                 BA 
                 2EHA 
                 HA 
                 PA 
                 nm 
                 — 
                 — 
                 Pa · s 
                 ° C. 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 Ac1 
                 50 
                 50 
                 0 
                 0 
                 219 
                 79 
                 7.5 
                 5,990 
                 −52 
               
               
                 Ac2 
                 70 
                 30 
                 0 
                 0 
                 235 
                 74 
                 5.5 
                 7,620 
                 −54 
               
               
                 Ac3 
                 100 
                 0 
                 0 
                 0 
                 235 
                 98 
                 6.9 
                 8,670 
                 −55 
               
               
                 Ac4 
                 0 
                 100 
                 0 
                 0 
                 222 
                 88 
                 7.9 
                 4,130 
                 −51 
               
               
                 Ac5 
                 50 
                 0 
                 50 
                 0 
                 250 
                 90 
                 8.1 
                 3,630 
                 −57 
               
               
                 Ac6 
                 50 
                 0 
                 0 
                 50 
                 242 
                 81 
                 7.8 
                 3,370 
                 −47 
               
               
                 Ac7 
                 50 
                 50 
                 0 
                 0 
                 235 
                 166 
                 13 
                 17,720 
                 −52 
               
               
                 Ac8 
                 70 
                 30 
                 0 
                 0 
                 238 
                 146 
                 8.6 
                 11,350 
                 −54 
               
               
                 Ac9 
                 100 
                 0 
                 0 
                 0 
                 212 
                 141 
                 8.3 
                 14,480 
                 −55 
               
               
                 Ac10 
                 0 
                 100 
                 0 
                 0 
                 230 
                 144 
                 8.7 
                 18,550 
                 −51 
               
               
                 Ac11 
                 50 
                 0 
                 50 
                 0 
                 160 
                 162 
                 11 
                 15,480 
                 −57 
               
               
                 Ac12 
                 50 
                 0 
                 0 
                 50 
                 150 
                 164 
                 13 
                 11,650 
                 −47 
               
               
                 Ac13 
                 50 
                 50 
                 0 
                 0 
                 257 
                 189 
                 15 
                 18,600 
                 −52 
               
               
                   
               
            
           
         
       
     
     Preparation of Pressure Sensitive Adhesive Particle 
     Preparation of Pressure Sensitive Adhesive Particle (1) 
     
         
         
           
             Composite resin particle dispersion (M1 (component of Ac)): 252 parts 
             Composite resin particle dispersion (M7 (component of Ac7)): 252 parts 
             Ion exchange water: 710 parts 
             Anionic surfactant (DOWFAX 2A1 produced by The Dow Chemical Company): 1 part 
           
         
       
    
     The above-described materials are placed in a reactor equipped with a thermometer and a pH meter, and the pH is adjusted to 3.0 by adding a 1.0% aqueous nitric acid solution at a temperature of 25° C. Then, while the resulting mixture is dispersed in a homogenizer (ULTRA-TURRAX T50 produced by IKA Japan) at a rotation rate of 5,000 rpm, 23 parts of a 2.0% aqueous aluminum sulfate solution is added. Subsequently, a stirrer and a heating mantle are attached to the reactor. The temperature is elevated at a temperature elevation rate of 0.2° C./minute up to a temperature of 40° C. and then at 0.05° C./minute beyond 40° C. The particle diameter is measured every 10 minutes with MULTISIZER II (aperture diameter: 50 μm, produced by Beckman Coulter Inc.). The temperature is retained when the volume-average particle diameter reached 5.0 μm, and 170 parts of the styrene resin particle dispersion (St1) is added thereto over a period of 5 minutes. After completion of addition, a temperature of 50° C. is held for 30 minutes, a 1.0% aqueous sodium hydroxide solution is added thereto, and the pH of the slurry is adjusted to 6.0. Subsequently, while the pH is adjusted to 6.0 every 5° C., the temperature is elevated at a temperature elevation rate of 1° C./minute up to 90° C., and the temperature is retained at 90° C. The particle shape and the surface property are observed with an optical microscope and a field emission-type scanning electron microscope (FE-SEM), and coalescence of particles is confirmed at the 10th hour. The reactor is then cooled with cooling water over a period of 5 minutes to 30° C. 
     The cooled slurry is passed through a nylon mesh having 15 μm opening to remove coarse particles, and the slurry that has passed through the mesh is filtered at a reduced pressure by using an aspirator. The solid matter remaining on the paper filter is manually pulverized as finely as possible and is added to ion exchange water (temperature: 30° C.) in an amount ten times the amount of the solid matter. The resulting mixture is stirred for 30 minutes. Subsequently, the solid matter remaining on the paper filter after filtration at a reduced pressure in an aspirator is pulverized manually as finely as possible and is added to ion exchange water (temperature: 30° C.) in an amount ten times the amount of the solid matter. The resulting mixture is stirred for 30 minutes and is again filtered at a reduced pressure with an aspirator. The electrical conductivity of the filtrate is measured. This operation is repeated until the electrical conductivity of the filtrate is 10 μS/cm or less so as to wash the solid matter. 
     The washed solid matter is finely pulverized in a wet-dry-type particle sizer (Comil) and then vacuum-dried in an oven at 25° C. for 36 hours. As a result, pressure sensitive adhesive base particles (1) is obtained. The volume-average particle diameter of the pressure sensitive adhesive base particles (1) is 8.0 μm. 
     One hundred parts of the pressure sensitive adhesive base particles (1) and 1.5 parts of hydrophobic silica (RY50 produced by Nippon Aerosil Co., Ltd.) are mixed, and the resulting mixture is mixed in a sample mill at 13,000 rpm for 30 seconds. The mixture is then screened through a vibrating screen having 45 μm openings. As a result, pressure sensitive adhesive particles (1) are obtained. 
     Using the pressure sensitive adhesive particle (1) as a sample, the thermal behavior in the temperature range of −150° C. to 100° C. is analyzed with a differential scanning calorimeter (DSC-60A produced by Shimadzu Corporation). Two glass transition temperatures are observed. Table 3 indicates the glass transition temperatures. 
     A cross section of the pressure sensitive adhesive particle (1) is observed with a scanning electron microscope (SEM). A sea-island structure is observed. The pressure sensitive adhesive particle (1) has a core in which islands are present, and a shell layer in which no islands are present. The sea contains a styrene resin, and the islands contain a (meth)acryl resin. The average diameter of the islands is determined by the aforementioned measuring method. The average diameter of the islands is indicated in Table 3. 
     Preparation of Pressure Sensitive Adhesive Particles (2) to (8) 
     The pressure sensitive adhesive particles (2) to (8) are prepared as with the preparation of the pressure sensitive adhesive particle (1) except that the composite resin particle dispersion and the styrene resin particle dispersion are changed as indicated in Table 3. 
     Preparation of Pressure Sensitive Adhesive Particles (c1) to (c3) for Comparison 
     The pressure sensitive adhesive particles (c1) to (c3) are prepared as with the preparation of the pressure sensitive adhesive particle (1) except that the composite resin particle dispersion and the styrene resin particle dispersion are changed as indicated in Table 3. 
     Evaluation of releasing force Postcard paper V424 produced by Fuji Xerox Co., Ltd. is prepared as a recording medium. By using an image forming apparatus DocuCentre C7550I produced by Fuji Xerox Co., Ltd., and commercially available yellow toner, magenta toner, cyan toner, and black toner products available from Fuji Xerox Co., Ltd., an image having an area density of 30% and including both black characters and a full-color photographic image is formed on one surface of a postcard sheet and is fixed. 
     Next, the pressure sensitive adhesive particles are sprayed onto the entire image-formed surface of the postcard sheet so that the amount of the pressure sensitive adhesive particles applied is 3 g/m 2 , and the postcard sheet is passed through a belt roll-type fixing machine so as to fix the pressure sensitive adhesive particles onto the image-formed surface of the postcard sheet and form a layer of the pressure sensitive adhesive particles. 
     The postcard sheet having a layer of the pressure sensitive adhesive particles on the image-formed surface is folded in two with the image-formed surface facing inward by using a sealer, PRESSLE multi II produced by Toppan Forms Co., Ltd., and a pressure is applied to the bi-folded recording medium so as to bond the inner image-formed surfaces to each other at a pressure of 90 MPa. 
     Ten postcards are continuously formed by using the above-described apparatus under the above-described conditions by folding a postcard sheet in two with the image-formed surfaces facing inward and then bonding the image-formed surfaces of the postcard sheet. 
     The tenth postcard is cut in the long side direction at a width of 15 mm to prepare a rectangular test piece, and the test piece is subjected to the 90 degrees peel test. The peeling speed of the 90 degrees peel test is set to 20 mm/minute, the load (N) from 10 mm to 50 mm is sampled at 0.4 mm intervals after start of the measurement, the average of the results is calculated, and the loads (N) observed from three test pieces are averaged. The releasing force (N) required for peeling is categorized as follows. The results are indicated in Table 3. 
     A: 0.8 N or more 
     B: 0.6 N or more but less than 0.8 N 
     C: 0.4 N or more but less than 0.6 N 
     D: 0.2 N or more but less than 0.4 N 
     E: Less than 0.2 N 
     
       
         
           
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
             
            
               
                   
                 Core (sea-island structure) 
               
            
           
           
               
               
               
            
               
                   
                 Sea 
                 Islands 
               
               
                   
                 Resin A 
                 Resin B1 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                 Content 
                   
                 Viscosity 
                   
                   
                   
                   
                 Content 
               
               
                   
                   
                 (parts 
                   
                 at 
                   
                 Molecular 
                   
                   
                 (parts 
               
               
                   
                   
                 by 
                   
                 100° C. 
                 Mw 
                 weight 
                 SP value 
                 Tg 
                 by 
               
               
                   
                 Type 
                 mass) 
                 Type 
                 (Pa · s) 
                 (k) 
                 distribution 
                 (MPa 1/2 ) 
                 (° C.) 
                 mass) 
               
               
                   
               
               
                 Example 1 
                 St1 
                 60 
                 Ac1 
                 5,990 
                 79 
                 7.5 
                 18.6 
                 −52 
                 20 
               
               
                 Example 2 
                 St1 
                 60 
                 Ac1 
                 5,990 
                 79 
                 7.5 
                 18.6 
                 −52 
                 20 
               
               
                 Example 3 
                 St1 
                 60 
                 Ac6 
                 3,370 
                 81 
                 7.8 
                 19.4 
                 −47 
                 20 
               
               
                 Example 4 
                 St1 
                 60 
                 Ac1 
                 5,990 
                 79 
                 7.5 
                 18.6 
                 −52 
                 15 
               
               
                 Example 5 
                 St1 
                 60 
                 Ac1 
                 5,990 
                 79 
                 7.5 
                 18.6 
                 −52 
                 25 
               
               
                 Example 6 
                 St1 
                 60 
                 Ac13 
                 18,600 
                 189 
                 15 
                 18.6 
                 −52 
                 40 
               
               
                 Example 7 
                 St1 
                 60 
                 Ac1 
                 5,990 
                 79 
                 7.5 
                 18.6 
                 −52 
                 20 
               
               
                 Example 8 
                 St1 
                 60 
                 Ac1 
                 5,990 
                 79 
                 7.5 
                 18.6 
                 −52 
                 20 
               
               
                 Comparative 
                 St1 
                 60 
                 Ac2 
                 7,620 
                 74 
                 5.5 
                 18.8 
                 −54 
                 40 
               
               
                 Example 1 
               
               
                 Comparative 
                 St1 
                 60 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 Example 2 
               
               
                 Comparative 
                 St14 
                 100 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 Example 3 
               
               
                   
               
            
           
           
               
               
            
               
                   
                 Core (sea-island structure) 
               
               
                   
                 Islands 
               
            
           
           
               
               
               
            
               
                   
                 Resin B2 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                 Viscosity 
                   
                   
                   
                   
                 Content 
                   
               
               
                   
                   
                 at 
                   
                 Molecular 
                   
                   
                 (parts 
               
               
                   
                   
                 100° C. 
                 Mw 
                 weight 
                 SP value 
                 Tg 
                 by 
               
               
                   
                 Type 
                 (Pa · s) 
                 (k) 
                 distribution 
                 (MPa 1/2 ) 
                 (° C.) 
                 mass) 
                 M B1 /M B2   
               
               
                   
               
               
                 Example 1 
                 Ac7 
                 17,720 
                 166 
                 13 
                 18.6 
                 −52 
                 20 
                 1.0 
               
               
                 Example 2 
                 Ac8 
                 11,350 
                 146 
                 8.6 
                 18.8 
                 −54 
                 20 
                 1.0 
               
               
                 Example 3 
                 Ac7 
                 17,720 
                 166 
                 13 
                 18.6 
                 −52 
                 20 
                 1.0 
               
               
                 Example 4 
                 Ac7 
                 17,720 
                 166 
                 13 
                 18.6 
                 −52 
                 25 
                 0.6 
               
               
                 Example 5 
                 Ac7 
                 17,720 
                 166 
                 13 
                 18.6 
                 −52 
                 15 
                 1.7 
               
            
           
           
               
               
               
            
               
                 Example 6 
                 Included in the resin 
                 — 
               
               
                   
                 described in Resin B1 having a wide 
               
               
                   
                 molecular weight distribution 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Example 7 
                 Ac7 
                 17,720 
                 166 
                 13 
                 18.6 
                 −52 
                 20 
                 1.0 
               
               
                 Example 8 
                 Ac7 
                 17,720 
                 166 
                 13 
                 18.6 
                 −52 
                 20 
                 1.0 
               
               
                 Comparative 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 1.0 
               
               
                 Example 1 
               
               
                 Comparative 
                 Ac12 
                 11,650 
                 164 
                 13 
                 19.4 
                 −47 
                 40 
                 1.0 
               
               
                 Example 2 
               
               
                 Comparative 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
                 — 
               
               
                 Example 3 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Mass 
                 Pressure sensitive adhesive particles 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 ratio 
                   
                 Average 
                   
                   
                   
                   
               
               
                   
                   
                   
                 of 
                   
                 domain 
                   
                   
                 Pressure- 
               
               
                   
                   
                   
                 core 
                   
                 diameter 
                   
                   
                 induced 
               
               
                   
                   
                 Shell 
                 to 
                   
                 of 
                   
                   
                 phase 
               
               
                   
                   
                 layer 
                 shell 
                 D50v 
                 islands 
                 T1 
                 T3 
                 transition 
                 Releasing 
               
               
                   
                   
                 Type 
                 layer 
                 (μm) 
                 (nm) 
                 (° C.) 
                 (° C.) 
                 (T1 − T3) 
                 force 
               
               
                   
                   
               
               
                   
                 Example 1 
                 St1 
                 85/15 
                 8.0 
                 320 
                 110 
                 95 
                 15 
                 A 
               
               
                   
                 Example 2 
                 St1 
                 85/15 
                 10 
                 270 
                 107 
                 93 
                 14 
                 B 
               
               
                   
                 Example 3 
                 St1 
                 85/15 
                 11 
                 280 
                 97 
                 85 
                 12 
                 A 
               
               
                   
                 Example 4 
                 St1 
                 85/15 
                 11 
                 360 
                 111 
                 96 
                 15 
                 A 
               
               
                   
                 Example 5 
                 St1 
                 85/15 
                 9.5 
                 400 
                 91 
                 76 
                 15 
                 A 
               
               
                   
                 Example 6 
                 St1 
                 85/15 
                 9.5 
                 420 
                 110 
                 98 
                 12 
                 A 
               
               
                   
                 Example 7 
                 St2 
                 85/15 
                 10 
                 270 
                 107 
                 93 
                 14 
                 A 
               
               
                   
                 Example 8 
                 St3 
                 85/15 
                 11 
                 280 
                 97 
                 85 
                 12 
                 A 
               
               
                   
                 Comparative 
                 St1 
                 85/15 
                 9.5 
                 320 
                 115 
                 83 
                 32 
                 C 
               
               
                   
                 Example 1 
               
               
                   
                 Comparative 
                 St1 
                 85/15 
                 9.5 
                 280 
                 128 
                 95 
                 33 
                 C 
               
               
                   
                 Example 2 
               
               
                   
                 Comparative 
                 St1 
                 85/15 
                 10 
                 — 
                 — 
                 — 
                 — 
                 E 
               
               
                   
                 Example 3 
               
               
                   
                   
               
            
           
         
       
     
     The results indicate that the releasing force for the obtained pressure bonded matter is high in Example compared to Comparative Examples. 
     Examples 101 to 110 and Comparative Examples 101 to 104 
     Producing Printed Material by Electrophotographic Method 
     Into a V-type blender, 10 parts of any one of the pressure sensitive adhesive particles (1) to (8) and (c1) to (c3), and 100 parts of the following resin-coated carrier (1) are placed, and the resulting mixture is stirred for 20 minutes. Then the mixture is screened through a vibrating screen having 212 μm openings to obtain a developers (1) to (8) and (c1) to (c3). 
     Resin-Coated Carrier (1) 
     
         
         
           
             Mn—Mg—Sr ferrite particles (average particle diameter: 40 μm): 100 parts 
             Toluene: 14 parts 
             Polymethyl methacrylate: 2 parts 
             Carbon black (VXC72 produced by Cabot Corporation): 0.12 parts 
           
         
       
    
     Glass beads (diameter: 1 mm, in an amount equal to the amount of toluene) and the above-described materials other than the ferrite particles are mixed, and the resulting mixture is stirred in a sand mill produced by KANSAI PAINT CO., LTD., at a rotation rate of 1200 rpm for 30 minutes. As a result, a dispersion is obtained. This dispersion and the ferrite particles are placed in a vacuum deaerator-type kneader, and the resulting mixture is dried at a reduced pressure under stirring to obtain a resin-coated carrier (1). 
     An apparatus of a type illustrated in  FIG. 3  is prepared as the apparatus for producing a printed material. In other words, an apparatus for producing a printed material, the apparatus being equipped with a five-stand-tandem intermediate transfer-type printing unit that performs application of the pressure sensitive adhesive particles of the exemplary embodiment and formation of color images on a recording medium, and a pressure bonding unit that has a folding device and a pressurizing device is prepared. 
     The developer (or comparative developer) of this exemplary embodiment, a yellow developer, a magenta developer, a cyan developer, and a black developer are respectively placed in five developing devices in the printing unit. Commercially available products produced by Fuji Xerox Co., Ltd., are used as the developers of respective colors such as yellow. 
     Postcard paper V424 produced by Fuji Xerox Co., Ltd. is prepared as a recording medium. 
     The image to be formed on the postcard paper is an image having an area density of 30% and including both black characters and a full-color photographic image. The image is formed on one surface of the postcard sheet. 
     The amount of the pressure sensitive adhesive particles of the exemplary embodiment (or comparative pressure sensitive adhesive particles) applied is what is described in Table 4 (1 g/m 2  to 3 g/m 2 ) in an image-formed region of an image-formed surface of the postcard sheet. 
     The folding device is a device that folds the postcard sheet in two such that the surface on which the image is formed is arranged on the inner side. 
     The pressurizing device is to apply a pressure of 90 MPa. 
     Ten postcards are continuously formed by using the above-described apparatus under the above-described conditions by folding a postcard sheet in two with the image-formed surface facing inward and then bonding the image-formed surfaces of the flaps of the postcard sheet. 
     The tenth postcard is cut in the long side direction at a width of 15 mm to prepare a rectangular test piece, and the test piece is subjected to the 90 degrees peel test. The peeling speed of the 90 degrees peel test is set to 20 mm/minute, the load (N) from 10 mm to 50 mm is sampled at 0.4 mm intervals after start of the measurement, the average of the results is calculated, and the loads (N) observed from three test pieces are averaged. The releasing force (N) required for peeling is categorized as follows. The results are indicated in Table 4. 
     A: 0.8 N or more 
     B: 0.6 N or more but less than 0.8 N 
     C: 0.4 N or more but less than 0.6 N 
     D: 0.2 N or more but less than 0.4 N 
     E: Less than 0.2 N 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                   
                 Application 
                   
               
               
                   
                 Pressure sensitive 
                 amount 
                 Releasing 
               
               
                   
                 adhesive particles 
                 (g/m 2 ) 
                 force 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Example 101 
                 Pressure sensitive 
                 3 
                 A 
               
               
                   
                 adhesive particles of 
               
               
                   
                 Example 1 
               
               
                 Example 102 
                 Pressure sensitive 
                 3 
                 B 
               
               
                   
                 adhesive particles of 
               
               
                   
                 Example 2 
               
               
                 Example 103 
                 Pressure sensitive 
                 3 
                 A 
               
               
                   
                 adhesive particles of 
               
               
                   
                 Example 3 
               
               
                 Example 104 
                 Pressure sensitive 
                 3 
                 A 
               
               
                   
                 adhesive particles of 
               
               
                   
                 Example 4 
               
               
                 Example 105 
                 Pressure sensitive 
                 3 
                 A 
               
               
                   
                 adhesive particles of 
               
               
                   
                 Example 5 
               
               
                 Example 106 
                 Pressure sensitive 
                 3 
                 A 
               
               
                   
                 adhesive particles of 
               
               
                   
                 Example 6 
               
               
                 Example 107 
                 Pressure sensitive 
                 3 
                 A 
               
               
                   
                 adhesive particles of 
               
               
                   
                 Example 7 
               
               
                 Example 108 
                 Pressure sensitive 
                 3 
                 A 
               
               
                   
                 adhesive particles of 
               
               
                   
                 Example 8 
               
               
                 Example 109 
                 Pressure sensitive 
                 1 
                 B 
               
               
                   
                 adhesive particles of 
               
               
                   
                 Example 1 
               
               
                 Example 110 
                 Pressure sensitive 
                 1 
                 B 
               
               
                   
                 adhesive particles of 
               
               
                   
                 Example 2 
               
               
                 Comparative 
                 Pressure sensitive 
                 3 
                 C 
               
               
                 Example 101 
                 adhesive particles of 
               
               
                   
                 Comparative Example 1 
               
               
                 Comparative 
                 Pressure sensitive 
                 3 
                 C 
               
               
                 Example 102 
                 adhesive particles of 
               
               
                   
                 Comparative Example 2 
               
               
                 Comparative 
                 Pressure sensitive 
                 3 
                 E 
               
               
                 Example 103 
                 adhesive particles of 
               
               
                   
                 Comparative Example 3 
               
               
                 Comparative 
                 Pressure sensitive 
                 2 
                 D 
               
               
                 Example 104 
                 adhesive particles of 
               
               
                   
                 Comparative Example 1 
               
               
                   
               
            
           
         
       
     
     The results indicate that the releasing force for the obtained printed material is high in Example compared to Comparative Examples. In particular, the results indicate that excellent releasing force is exhibited even when the amount applied is small. 
     The foregoing description of the exemplary embodiments of the present disclosure has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the disclosure and its practical applications, thereby enabling others skilled in the art to understand the disclosure for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the following claims and their equivalents.