Patent Description:
An electrophotographic method is an image forming method to form a visible image by developing an electrostatic latent image with a developer. Specifically, an electrostatic latent image is formed on an electrostatic latent image bearer (also referred to as "photoconductor") containing a photoconductive substance, then the electrostatic latent image is developed with a developer containing toner to form a toner image, and the toner image is transferred onto a recording medium such as a paper sheet and fixed thereon by heat and pressure to form a fixed image.

To form a full-color image by the electrophotographic method, a toner set containing black toner in combination with cyan, magenta, and yellow toners, which are toners of three process colors, is generally used.

In recent years, as electrophotographic color image forming apparatuses have become widespread, the uses of the printed products thereof have been diversified. Particularly in the field of custom-designed general consumer goods, there is an increasing need for an electrophotographic printing method that makes it possible to make print on materials which have been unable to make print with conventional electrophotographic toners that are designed to be printed on paper media. For example, there is a need for printing on recording media made of cloth ("cloth media") such as uniforms, shoes, and bags for athletics teams.

To be fixed on such cloth media, toner is required to be fixable on cloth fibers having a high degree of irregularity. The fixed toner layer is required to be able to follow deformation of the cloth with an appropriate flexibility. Toner is thus required to have properties that have not been required when fixed on conventional paper media. <CIT> proposes to make a print on a film, which is a readily-deformable recording medium, with a toner containing a pigment and a polyester-based plasticizer having a glass transition temperature of -<NUM> degrees C or lower. However, the proposed toner does not meet the requirements for being printed on the cloth. None of the conventional toners has met such requirements.

An object of the present invention is to provide a toner that forms a fixed image having no image unevenness, excellent blocking resistance, and high washing fastness.

<CIT> discloses a white toner prepared by uniformly dispersing a white pigment and a polyester plasticizer having a glass transition temperature of -<NUM> ° C or less, and the white pressure-sensitive adhesive composition obtained by mixing the white toner and the pressure-sensitive adhesive is used for a decorative pressure-sensitive adhesive sheet.

In accordance with some embodiments of the present invention, a toner is provided that forms a fixed image having no image unevenness, excellent blocking resistance, and high washing fastness.

It will be further understood that the terms "includes" and/or "including", when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Embodiments of the present invention are described in detail below with reference to accompanying drawings. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.

For the sake of simplicity, the same reference number will be given to identical constituent elements such as parts and materials having the same functions and redundant descriptions thereof omitted unless otherwise stated.

The toner according to an embodiment of the present invention contains a binder resin, and preferably further contains an adhesive agent as claimed.

The toner may further optionally contain other components as necessary.

The glass transition temperature (Tg) of the toner is -<NUM> degrees C or higher and <NUM> degrees C or lower.

The binder resin is not particularly limited, and any of conventionally known resins can be used. Examples of the binder resin include, but are not limited to, styrene-based resins such as styrene, α-methylstyrene, chlorostyrene, styrene-propylene copolymer, styrenebutadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylate copolymer, styrene-methacrylate copolymer, and styrene-acrylonitrile-acrylate copolymer, polyester resins, vinyl chloride resins, rosin-modified maleic acid resins, phenol resins, epoxy resins, polyethylene resins, polypropylene resins, ionomer resins, polyurethane resins, silicone resins, ketone resins, xylene resins, petroleum resins, and hydrogenated petroleum resins. Each of these can be used alone or in combination with others. Among these, styrene-based resins containing aromatic compounds as constitutional units and polyester resins are preferred, and polyester resins are more preferred.

The polyester resin may be obtained by a polycondensation reaction between commonly known alcohols and acids.

Specific examples of the alcohols include, but are not limited to: diols such as polyethylene glycol, diethylene glycol, triethylene glycol, <NUM>,<NUM>-propylene glycol, <NUM>,<NUM>-propylene glycol, <NUM>,<NUM>-propylene glycol, neopentyl glycol, and <NUM>,<NUM>-butenediol; etherified bisphenols such as <NUM>,<NUM>-bis(hydroxymethyl)cyclohexane, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, and polyoxypropylenated bisphenol A; divalent alcohol monomers obtained by substituting the above compounds with a saturated or unsaturated hydrocarbon group having <NUM> to <NUM> carbon atoms; other divalent alcohol monomers; and trivalent or higher alcohol monomers such as sorbitol, <NUM>,<NUM>,<NUM>,<NUM>-hexanetetraol, <NUM>,<NUM>-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose, <NUM>,<NUM>,<NUM>-butanetriol, <NUM>,<NUM>,<NUM>-pentanetriol, glycerol, <NUM>-methylpropanetriol, <NUM>-methyl-<NUM>,<NUM>,<NUM>-butanetriol, trimethylolethane, trimethylolpropane, and <NUM>,<NUM>,<NUM>-trihydroxymethylbenzene. Each of these can be used alone or in combination with others.

The acids are not particularly limited and can be suitably selected to suit to a particular application, but carboxylic acids are preferred.

Specific examples of the carboxylic acids include, but are not limited to: monocarboxylic acids such as palmitic acid, stearic acid, and oleic acid; maleic acid, fumaric acid, mesaconic acid, citraconic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, and malonic acid, and divalent organic acid monomers obtained by substituting these acids with a saturated or unsaturated hydrocarbon group having <NUM> to <NUM> carbon atoms; anhydrides of these acids; dimers of lower alkyl esters and linolenic acid; <NUM>,<NUM>,<NUM>-benzenetricarboxylic acid, <NUM>,<NUM>,<NUM>-benzenetricarboxylic acid, <NUM>,<NUM>,<NUM>-naphthalenetricarboxylic acid, <NUM>,<NUM>,<NUM>-naphthalenetricarboxylic acid, <NUM>,<NUM>,<NUM>-butanetricarboxylic acid, <NUM>,<NUM>,<NUM>-hexanetricarboxylic acid, <NUM>,<NUM>-dicarboxyl-<NUM>-methyl-<NUM>-methylenecarboxypropane, tetra(methylenecarboxyl)methane, <NUM>,<NUM>,<NUM>,<NUM>-octanetetracarboxylic acid, and enpol trimer acid; and trivalent or higher polyvalent carboxylic acid monomers such as anhydrides of the above acids. Each of these can be used alone or in combination with others.

The method for producing the binder resin is not particularly limited and can be suitably selected to suit to a particular application. Examples of thereof include, but are not limited to, bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization.

The inventors of the present invention have found that a toner containing an adhesive agent is remarkably improved in fixability on cloth recording media and the fixed toner layer is imparted with appropriate flexibility.

The toner contains at least one adhesive agent selected from polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, and polybutylene isophthalate. Each of these can be used alone or in combination with others. Preferably, the toner contains at least one of polyethylene terephthalate and polybutylene terephthalate as a main component, for imparting flexibility.

The adhesive agent may be either a synthesized product or a commercially available product. Examples of the commercially available product include, but are not limited to, hot melt adhesives PES-<NUM>, PES-<NUM>, PES-111EE, and PES-126EH (all manufactured by Toagosei Co.

The glass transition temperature of the adhesive agent is preferably -<NUM> degrees C or higher and <NUM> degrees C or lower. When the glass transition temperature is -<NUM> degrees C or higher, the toner is prevented from undergoing a significant deterioration of heat-resistant storability. When the glass transition temperature is +<NUM> degrees C or lower, the fixed toner layer is prevented from lacking flexibility.

A <NUM>/<NUM> outflow temperature of the adhesive agent is preferably <NUM> degrees C or higher and <NUM> degrees C or lower. When the <NUM>/<NUM> outflow temperature is <NUM> degrees C or higher, the fixed toner image is prevented from melting out when ironed. When the <NUM>/<NUM> outflow temperature is <NUM> degrees C or lower, it does not become difficult to melt-knead toner components and the adhesive agent in the process of producing the toner.

The <NUM>/<NUM> outflow temperature is measured using a flowtester (CFT-500D manufactured by Shimadzu Corporation) as follows. First, <NUM> of a sample is applied with a load of <NUM> MPa by a plunger while being heated at a temperature rising rate of <NUM> degrees C/min and extruded from a nozzle having a diameter of <NUM> and a length of <NUM>. The amount of decent of the plunger of the flowtester is plotted against the temperature, and the temperature at which the half of the sample has flowed out is taken as the <NUM>/<NUM> outflow temperature.

The weight average molecular weight of the adhesive agent is preferably from <NUM>,<NUM> to <NUM>,<NUM>. When the weight average molecular weight is <NUM>,<NUM> or higher, the fixed toner image is prevented from melting out when ironed. When the weight average molecular weight is <NUM>,<NUM> or lower, it does not become difficult to melt-knead toner components and the adhesive agent in the process of producing the toner.

The weight average molecular weight of the adhesive agent is determined from a molecular weight distribution of THF-soluble matter as measured with a GPC (gel permeation chromatography) measuring instrument GPC-150C (manufactured by Waters Corporation).

The measurement is conducted using columns (SHODEX KF <NUM> to <NUM> manufactured by Showa Denko K. ) as follows. The columns are stabilized in a heat chamber at <NUM> degrees C. Tetrahydrofuran (THF) as a solvent is let to flow in the columns at that temperature at a flow rate of <NUM> per minute. Next, <NUM> of a sample is thoroughly dissolved in <NUM> of THF and filtered with a pretreatment filter (e.g., a chromatographic disk having a pore size of <NUM>, manufactured by KURABO INDUSTRIES LTD. ) to prepare a THF solution of the sample having a sample concentration of from <NUM>% to <NUM>% by weight, and <NUM> to <NUM>µL thereof is injected in the measuring instrument.

The weight average molecular weight Mw of the sample is determined by comparing the molecular weight distribution of the sample with a calibration curve created with several types of monodisperse polystyrene standard samples that shows the relation between the logarithmic values of molecular weights and the number of counts.

The polystyrene standard samples for creating the calibration curve may be those having molecular weights of <NUM> × <NUM><NUM>, <NUM> × <NUM><NUM>, <NUM> × <NUM><NUM>, <NUM> × <NUM><NUM>, <NUM> × <NUM><NUM>, <NUM> × <NUM><NUM>, <NUM> × <NUM><NUM>, <NUM> × <NUM><NUM>, <NUM> × <NUM><NUM>, and <NUM> × <NUM><NUM> , respectively, manufactured by Pressure Chemical Co. or Toyo Soda Manufacturing Co. , Ltd (now Tosoh Corporation). Preferably, about <NUM> standard polystyrene samples are used.

As the detector, a refractive index (RI) detector is used.

The structure of the adhesive agent in the toner can be specified in the following manner.

The toner is dispersed in chloroform and stirred overnight. Subsequently, the resultant dispersion liquid is centrifuged, and only the supernatant is collected. The collected supernatant is evaporated to dryness, thus preparing a sample to be subjected to a composition analysis by GC-MS.

About <NUM>µL of a methylating agent (<NUM>% methanol solution of tetramethylammonium hydroxide (TMAH)) is dropped into about <NUM> of the sample, thus preparing a specimen.

The structure of the adhesive agent in the toner can also be specified in the following manner.

The toner is dispersed in chloroform and stirred overnight. Subsequently, the resultant dispersion liquid is centrifuged, and only the supernatant is collected. The collected supernatant is evaporated to dryness, thus preparing a sample to be subjected to a composition analysis by NMR (nuclear magnetic resonance).

NMR equipment: ECX-<NUM> manufactured by JEOL Ltd.

The proportion of the adhesive agent in the toner is preferably <NUM>% by mass or more and <NUM>% by mass or less. When the proportion is <NUM>% by mass or more, the fixability of the toner on cloth media is sufficient. When the proportion is <NUM>% by mass or less, the toner is prevented from deteriorating in heat-resistant storability, and the occurrence of aggregation of the toner particles is prevented.

The toner may further contain other components which are not particularly limited and can be suitably selected to suit to a particular application, as long as they are usable for ordinary toners. Examples thereof include, but are not limited to, a colorant, a wax, a charge controlling agent, and an external additive. Each of these may be used alone or two or more of these may be used in combination.

The colorant is not particularly limited and may be selected to suit to a particular application as long as it is usable for ordinary toners. Examples of the colorant include, but are not limited to, black colorants, cyan colorants, magenta colorants, yellow colorants, green colorants, blue colorants, and white pigments. Each of these can be used alone or in combination with others.

Examples of the black colorants include, but are not limited to, carbon black alone, and a mixture of carbon black as a main component with copper phthalocyanine, whose hue and lightness have been adjusted.

Examples of the cyan colorants include, but are not limited to, copper phthalocyanine (Pigment Blue <NUM>:<NUM>) and a mixture of the copper phthalocyanine with aluminum phthalocyanine.

Examples of the magenta colorants include, but are not limited to, Pigment Red <NUM>:<NUM>, Pigment Red <NUM>, Pigment Red <NUM>, and Pigment Red <NUM>.

Examples of the yellow colorants include, but are not limited to, Pigment Yellow <NUM>, Pigment Yellow <NUM>, Pigment Yellow <NUM>, and Pigment Yellow <NUM>. Among these, Pigment Yellow <NUM> alone and a mixture of Pigment Yellow <NUM> and Pigment Yellow <NUM> are preferred for saturation and storability.

Examples of the green colorants include, but are not limited to, Pigment Green <NUM>.

Examples of the blue colorants include, but are not limited to, Pigment Blue <NUM>:<NUM> and Pigment Violet <NUM>.

Examples of the white pigments include, but are not limited to, titanium dioxide which is surface-treated with silicon, zirconia, aluminum, or polyol.

The wax is not particularly limited and can be suitably selected to suit to a particular application. Examples thereof include, but are not limited to, aliphatic hydrocarbons such as liquid paraffin, micro-crystalline wax, natural paraffin, synthetic paraffin, and polyolefin wax, and partial oxides, fluorides, and chlorides thereof; animal oils such as beef tallow and fish oil; vegetable oils such as coconut oil, soybean oil, rapeseed oil, rice bran wax, and carnauba wax; higher aliphatic alcohols and higher fatty acids such as montan wax; fatty acid amides and fatty acid bisamides; metal soaps such as zinc stearate, calcium stearate, magnesium stearate, aluminum stearate, zinc oleate, zinc palmitate, magnesium palmitate, zinc myristate, zinc laurate, and zinc behenate; fatty acid esters; and polyvinylidene fluoride. Each of these can be used alone or in combination with others. In particular, the wax preferably comprises at least an ester wax such as a fatty acid ester.

The proportion of the wax in the toner is preferably <NUM>% by mass or more and <NUM>% by mass or less. When the proportion is <NUM>% by mass or more, the occurrence of waste sheet jam, caused when the toner and the fixing roller (or fixing belt) cannot be separated from each other at the time of fixing the toner, is prevented. When the proportion is <NUM>% by mass or more, the fixability of the toner on cloth media is sufficient.

The charge controlling agent is not particularly limited and can be suitably selected to suit to a particular application as long as it is usable for ordinary toners. Examples of the charge controlling agent include, but are not limited to: nigrosine and modified products with fatty acid metal salts; onium salts such as phosphonium salt and lake pigments thereof; triphenylmethane dyes and lake pigments thereof; metal salts of higher fatty acids; diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, and dicyclohexyltin oxide; diorganotin borates such as dibutyltin borate, dioctyltin borate, and dicyclohexyltin borate; organometallic complexes, chelate compounds, monoazo metal complexes, acetylacetone metal complexes, aromatic hydroxycarboxylic acids, metal complexes of aromatic dicarboxylic acids, and quaternary ammonium salts.

Examples of the charge controlling agent further include aromatic hydroxycarboxylic acids, aromatic mono- and poly- carboxylic acids and metal salts, anhydrides, and esters thereof, and phenol derivatives such as bisphenol. Each of these can be used alone or in combination with others.

The amount of the charge controlling agent is preferably from <NUM> to <NUM> parts by mass with respect to the entire binder resin. To prevent undesirable coloring of the toner, a colorless material is preferably selected for the charge controlling agent except for the case of black toner.

Preferred examples of the external additive include inorganic particles. Specific examples of the inorganic particles include, but are not limited to, silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand, clay, mica, wollastonite, diatomaceous earth, chromium oxide, cerium oxide, red iron oxide, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride. Among these, silica, alumina, and titanium oxide are preferred.

The inorganic particles may be those treated with a surface treatment agent such as a hydrophobizing agent. Examples of the hydrophobizing agent include, but are not limited to, silane coupling agents, silylation agents, silane coupling agents having a fluorinated alkyl group, organic titanate coupling agents, and aluminum coupling agents. Also, silicone oils are also effective as the hydrophobizing agent.

The primary particles of the inorganic particles preferably have an average particle diameter of from <NUM> to <NUM>, more preferably from <NUM> to <NUM>. When the average particle diameter is <NUM> or more, the occurrence of aggregation of the inorganic particles is prevented to prevent the inorganic particles from being non-uniformly dispersed in the toner. When the average particle diameter is <NUM> or less, heat-resistant storage stability does not deteriorate due to a filler effect. Here, the average particle diameter is directly determined from a photograph of particles obtained with a transmission electron microscope. Preferably, the average particle diameter is the average value of long diameters of at least <NUM> or more particles observed.

The glass transition temperature (Tg) of the toner is -<NUM> degrees C or higher and <NUM> degrees C or lower, more preferably -<NUM> degree C or higher and <NUM> degree C or lower. When the glass transition temperature is lower than -<NUM> degrees C, the toner may undergo a significant deterioration of heat-resistant storability. When the glass transition temperature is higher than <NUM> degrees C, the fixed toner layer may lack flexibility.

When the glass transition temperature of the toner is -<NUM> degrees C or higher and <NUM> degrees C or lower, the toner is prevented from undergoing a significant deterioration of heat-resistant storability and from lacking flexibility.

The glass transition temperature (Tg) is measured using a differential scanning calorimeter (DSC210 manufactured by Seiko Instruments & Electronics Ltd. ) by weighing <NUM> to <NUM> of a sample in an aluminum pan at room temperature, then cooling the sample to -<NUM> degrees C at a temperature falling rate of <NUM> degrees C/min, and heating the sample to <NUM> degrees C at a temperature rising rate of <NUM> degrees C/min. The glass transition temperature (Tg) is determined as a temperature at the intersection of an extended line of a base line of the resulted endothermic curve, and a tangent line of the endothermic curve which indicates the maximum slope between the peak rising portion and the peak top.

Preferably, the number-based particle diameter distribution of the toner has at least two peaks.

More preferably, the at least two peaks include a peak in a number-based particle diameter range of from <NUM> to <NUM> and another peak in a number-based particle diameter range of from <NUM> to <NUM>.

As the particle diameter of the toner increases, the pile height of the toner layer (i.e., the thickness of the toner layer in which toners of several colors are superposed) increases, making it easy to level irregularities on the cloth surface. To balance the easiness in leveling irregularities on the cloth surface and the transferability of the toner, which are in a trade-off relationship, the toner preferably comprises large-particle-diameter toner particles and small-particle-diameter toner particles. The peak on the larger particle side among the two peaks, which is derived from the large-particle-diameter toner particles, preferably have a number-based particle diameter in the range of from <NUM> to <NUM>.

The small-particle-diameter toner particles have a number-based particle diameter in the range of from <NUM> to <NUM>, and are used to broaden the particle diameter distribution of the toner. This makes it possible to increase the transferability of the large-particle-diameter toner particles that have poor transferability. It is also possible to fill the gap between the large-particle-diameter toner particles with the small-particle-diameter toner particles, thereby smoothening the surface of the toner layer while ensuring the pile height.

The small-particle-diameter toner particles and the large-particle-diameter toner particles may have the same or different compositions. Preferably, toner particles having a peak in the number-based particle diameter range of from <NUM> to <NUM> have a glass transition temperature in the range of from -<NUM> to +<NUM> degrees C and are colorless, for securing good fixability of the toner on cloth media and flexibility of the fixed layer of the toner.

The number-based particle diameter distribution is measured using a particle size analyzer (MULTISIZER III manufactured by Beckman Coulter, Inc. ) with setting the aperture diameter to <NUM> and analyzed with an analysis software program (Beckman Colter Multisizer <NUM> Version <NUM>). Specifically, <NUM> of a <NUM>% by weight aqueous solution of a surfactant (an alkylbenzene sulfonate, NEOGEN SC-A manufactured by DKS Co. ) is put in a <NUM>-mL glass beaker, then <NUM> of the toner is added thereto and mixed using a micro spatula, and <NUM> of ion-exchange water is further added thereto. The resulting dispersion liquid is subjected to a dispersion treatment using an ultrasonic disperser (W-113MK-II manufactured by HONDA ELECTRONICS CO. ) for <NUM> minutes. The dispersion liquid is measured using the MULTISIZER III and ISOTON III (manufactured by Beckman Coulter, Inc. ) as a solution for measurement. In the measurement, the toner sample dispersion liquid is dropped so that the concentration indicated by the apparatus becomes <NUM>±<NUM>%. In this measurement, the concentration is adjusted to <NUM>±<NUM>% for the measurement reproducibility of particle diameter. Within this concentration range, no error occurs in the measurement of the particle diameter.

When the toner of the present disclosure is used to form a base layer (i.e., a layer closest to the recording medium) and an upper layer is formed thereon with the conventional toner, the conventional toner can also be satisfactorily fixed on cloth media having a high level of irregularity due to fibers. When used in this manner, the toner of the present disclosure preferably comprises white toner particles, colorless toner particles (free of colorant), or a mixture thereof, so as not to impair the color of the toner superposed thereon.

Further, it is preferable that toner particles having a function of fixing on a cloth medium and having a peak in the range of from <NUM> to <NUM> are colorless toner particles.

The method for manufacturing the toner according to an embodiment of the present invention is not particularly limited and can be suitably selected to suit to a particular application, and may include the following procedures. First, a binder resin, a colorant, and a release agent, optionally together with a charge controlling agent, are well mixed by a mixer such as HENSCHEL MIXER and SUPER MIXER.

The mixture is then melt-kneaded by a heat melt kneader such as a heat roll, a kneader, and an extruder, so that the materials are thoroughly mixed. The kneaded mixture is cooled to solidify, then pulverized into fine particles, and the fine particles are classified by size to obtain a toner.

The pulverizing process may be of a jet mill process in which a high-speed airflow incorporates toner particles to let the toner particles collide with a collision plate and be pulverized by the collision energy, an inter-particle collision process which lets toner particles collide with each other in an airflow, or a mechanical pulverizing process in which toner particles are supplied to a narrow gap formed with a rotor rotating at a high speed to be pulverized.

The toner according to an embodiment of the present invention may also be prepared by a dissolution suspension method. In this method, an oil phase is dispersed in an aqueous medium. Here, the oil phase comprises an organic solvent and toner materials dissolved or dispersed therein. After a reaction for forming a resin is conducted, removal of the solvent, filtration, washing, and drying are conducted, thus obtaining toner base particles.

The toner of the present disclosure may be mixed with a carrier to provide a two-component developer, which is used for an electrophotographic image forming method employing a two-component developing system.

When a two-component developing system is employed, fine particles of a magnetic material can be used as a magnetic carrier. Specific examples of the magnetic materials include, but are not limited to: magnetites; spinel ferrites containing gamma iron oxide; spinel ferrites containing at least one metal (e.g., Mn, Ni, Zn, Mg, and Cu) other than iron; magnetoplumbite-type ferrites such as barium ferrite; and particulate iron or alloy having an oxidized layer on its surface.

The magnetic material may be in any of granular, spherical, or needle-like shape.

When high magnetization is required, ferromagnetic fine particles, such as iron, are preferably used.

For chemical stability, magnetites, spinel ferrites containing gamma iron oxide, and magnetoplumbite-type ferrites such as barium ferrite are preferred. Specific preferred examples thereof include, but are not limited to, commercially available products such as MFL-<NUM> and MFL-35HS (manufactured by Powdertech Co. ); and DFC-<NUM>, DFC-<NUM>, and SM-350NV (manufactured by Dowa IP Creation Co.

A resin carrier may also be used which has a desired magnetization by containing an appropriate type of magnetic fine particles in an appropriate amount. Such a resin carrier preferably has a magnetization strength of from <NUM> to <NUM> emu/g at <NUM>,<NUM> oersted. Such a resin carrier may be produced by spraying a melt-kneaded product of magnetic fine particles with an insulating binder resin by a spray dryer, or dispersing magnetic fine particles in a condensation-type binder resin by reacting/curing its monomer or prepolymer in an aqueous medium in the presence of magnetic fine particles. Chargeability of the magnetic carrier may be controlled by fixedly adhering positively-chargeable or negatively-chargeable fine particles or conductive fine particles to the surface of the magnetic carrier, or coating the magnetic carrier with a resin.

Examples of the surface coating resin include silicone resin, acrylic resin, epoxy resin, and fluorine-based resin. These resins may contain positively-chargeable or negatively-chargeable fine particles or conductive fine particles. Among these resins, silicone resin and acrylic resin are preferred.

The proportion of the carrier in the developer is preferably from <NUM>% to <NUM>% by mass. When the proportion is <NUM>% by mass or higher, the toner is prevented from scattering from the developing device, thereby preventing the occurrence of defective images. When the proportion is <NUM>% by mass or less, an excessive increase of the charge amount of the toner and shortage of the toner to be supplied can be prevented, thereby effectively preventing a decrease of image density and the occurrence of defective images.

The toner set according to an embodiment of the present invention contains a base toner and a color toner.

The base toner is the above-described toner according to an embodiment of the present invention. The base toner preferably comprises colorless toner particles, white toner particles, or a mixture of white toner particles and colorless toner particles.

The color toner comprises a binder resin and a colorant.

The binder resin and the colorant may be the same as those used for the base toner as described above.

A toner accommodating unit according to an embodiment of the present invention is a unit accommodating the toner in a container having a function of accommodating toner. The toner accommodating unit may be in the form of, for example, a toner accommodating container, a developing device, or a process cartridge.

The toner accommodating container refers to a container accommodating the toner.

The developing device refers to a device accommodating the toner and having a developing unit configured to develop an electrostatic latent image into a toner image with the toner.

The process cartridge refers to a combined body of an image bearer with a developing unit accommodating the toner, detachably mountable on an image forming apparatus. The process cartridge may further include at least one of a charger, an irradiator, and a cleaner.

An image forming apparatus according to an embodiment of the present invention includes: an electrostatic latent image bearer; a charger configured to charge the electrostatic latent image bearer; an irradiator configured to irradiate the charged electrostatic latent image bearer with light to form an electrostatic latent image; a developing device containing a developer containing a toner, configured to develop the electrostatic latent image with the developer to form a toner image; a transfer device configured to transfer the toner image formed on the electrostatic latent image bearer onto a recording medium; and a fixing device configured to fix the toner image on the recording medium. The image forming apparatus may further include other devices appropriately selected as necessary.

The image forming method according to an embodiment of the present invention can be suitably performed by the image forming apparatus according to an embodiment of the present invention.

The toner may comprise the toner according to an embodiment of the present invention or the toner set according to an embodiment of the present invention.

On the recording medium, it is preferable that the base toner image is transferred closer to the recording medium than the color toner image is. The base toner image may be formed closer to the recording medium as follows: transferring the color toner image onto a release paper sheet, then transferring the base toner image over the color toner image, placing the recording medium on the base toner image, applying a pressure from above the release paper sheet toward the recording medium (and raising the temperature) to fix the toner images on the recording medium, and removing the release paper sheet.

The recording medium is not particularly limited and may be appropriately selected to suit to a particular application. Specific examples of the recording medium include, but are not limited to, paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, and composite materials thereof. Examples of the cloth include, but are not limited to, uniforms, shoes, and bags.

<FIG> is a schematic diagram illustrating an image forming apparatus according to an embodiment of the present invention. The image forming apparatus illustrated in <FIG> includes five toner image forming units 20Y, 20C, <NUM>, <NUM>, and 20A accommodating yellow, cyan, magenta, black, and white toners, respectively, arranged in parallel. This image forming apparatus is a tandem image forming apparatus in which toner images of yellow (Y), cyan (C), magenta (M), black (K), and white (A) respectively formed in the five toner image forming units are superimposed to form a full-color image. There is no particular limitation on the arrangement order of the toner image forming units for each color.

The toner image forming units 20Y, 20C, <NUM>, <NUM>, and 20A respectively include photoconductor drums 4Y, 4C, <NUM>, <NUM>, and 4A as image bearers that are driven to rotate. The image forming apparatus further includes an irradiator <NUM> configured to irradiate the photoconductor drums 4Y, 4C, <NUM>, <NUM>, and 4A with laser light or LED (light emitting diode) light based on image information of each color to form latent images thereon.

An intermediate transfer belt <NUM> as an intermediate transferor, the surface of which is movable, is disposed so as to face the toner image forming units 20Y, 20C, <NUM>, <NUM>, and 20A. Primary transfer rollers 61Y, 61C, <NUM>, <NUM> and 61A are disposed facing the respective photoconductor drums 4Y, 4C, <NUM>, <NUM>, and 4A via the intermediate transfer belt <NUM> to transfer the toner images formed on the respective photoconductor drums 4Y, 4C, <NUM>, <NUM>, and 4A onto the intermediate transfer belt <NUM>.

The primary transfer rollers 61Y, 61C, <NUM>, <NUM>, and 61A sequentially transfer the toner images formed in the toner image forming units 20Y, 20C, <NUM>, <NUM>, and 20A, described in detail later, onto the intermediate transfer belt <NUM> to form a full-color image by superimposition.

A secondary transfer device <NUM> that collectively transfers the toner images on the intermediate transfer belt <NUM> onto a transfer sheet is disposed downstream of the primary transfer rollers 61Y, 61C, <NUM>, <NUM>, and 61A in the direction of surface movement of the intermediate transfer belt <NUM>. Further, a belt cleaner <NUM> that removes toner remaining on the surface of the intermediate transfer belt <NUM> is disposed downstream of the secondary transfer device <NUM>.

A sheet feeder <NUM> including a sheet tray <NUM> and a feed roller <NUM> is disposed on a lower part of the image forming apparatus. The sheet feeder <NUM> sends out a transfer sheet toward a registration roller pair <NUM>. The registration roller pair <NUM> sends out the transfer sheet toward the position where the intermediate transfer belt <NUM> and the secondary transfer device <NUM> are facing in synchronization with an entry of the toner image to that position. The full-color toner image on the intermediate transfer belt <NUM> is transferred onto the transfer sheet by the secondary transfer device <NUM>, fixed on the transfer sheet by a fixing device <NUM>, and ejected outside the image forming apparatus.

Next, each of the toner image forming units 20Y, 20C, <NUM>, <NUM>, and 20A is described in detail below. Each of the toner image forming units 20Y, 20C, <NUM>, <NUM>, and 20A has almost the same configuration and operates in the same manner except for accommodating different color toners. Hereinafter, the configuration and operation of each toner image forming unit are described referring to a toner image forming unit <NUM> from which the suffix Y, C, M, K, or A has been omitted. <FIG> is a schematic diagram illustrating a main part of the image forming apparatus.

In the toner image forming unit <NUM>, various devices for performing an electrophotographic process are disposed around a photoconductor drum <NUM>, such as a charger <NUM>, a developing device <NUM>, and a cleaner <NUM>. The toner image forming unit <NUM> forms a toner image on the photoconductor drum <NUM> by a conventional operation. The toner image forming unit <NUM> may be in the form of a process cartridge that is detachably mounted on the image forming apparatus main body.

<FIG> is a schematic diagram illustrating a main part of an image forming apparatus according to an embodiment of the present invention, including five developing devices. The description of the same parts as those of the above-described image forming apparatus is omitted.

This image forming apparatus includes photoconductors <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, around which respective chargers <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respective developing devices <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respective transfer devices <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, and respective cleaners <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are disposed. The photoconductors <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are irradiated with exposure light <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively.

A developing unit for each color includes the corresponding photoconductor, charger, developing device, and cleaner. Developing units <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> respectively form images with white toner, black toner, cyan toner, magenta toner, and yellow toner, and the images are transferred onto an intermediate transfer belt <NUM>. The images formed on the intermediate transfer belt <NUM> are transferred onto a recording medium by a transfer device <NUM> and fixed thereon by a fixing device <NUM>.

Having generally described this invention, further understanding can be obtained by reference to certain specific examples which are provided herein for the purpose of illustration only and are not intended to be limiting. In the following descriptions, "parts" represents "parts by mass" unless otherwise specified.

The toner raw materials listed above were preliminarily mixed using a HENSCHEL MIXER (FM20B manufactured by NIPPON COKE & ENGINEERING CO. ) and melt-kneaded using a single-shaft kneader (BUSS CO-KNEADER manufactured by Buss AG) at a temperature of from <NUM> to <NUM> degrees C. The kneaded product was cooled to room temperature and coarsely pulverized using a ROTOPLEX to have a diameter of from <NUM> to <NUM>. The resulted particles were further finely pulverized using a COUNTER JET MILL (100AFG manufactured by Hosokawa Micron Corporation) to have a predetermined number average particle diameter while appropriately adjusting the pulverization air pressure. The resulted particles were classified by size using an air classifier (EJ-LABO manufactured by MATSUBO Corporation) to have a predetermined number average particle diameter distribution while appropriately adjusting the opening of the louver. Thus, toner base particles were prepared. Next, <NUM> parts of the toner base particles were stir-mixed with additives including <NUM> part of HDK-<NUM> and <NUM> part of H05TD, both manufactured by Clariant, using a HENSCHEL MIXER. Thus, a toner <NUM> was prepared.

A toner of Example <NUM> was prepared in the same manner as in Example <NUM> except that the toner raw materials were replaced with the following materials.

Toners of Examples <NUM> to <NUM> were prepared in the same manner as in Example <NUM> except that the pulverization/classification conditions were changed such that the peaks in the particle size distribution were as presented in Tables <NUM>-<NUM> and <NUM>-<NUM>.

A toner of Comparative Example <NUM> was prepared in the same manner as in Example <NUM> except that the toner raw materials were replaced with the following materials.

A color toner was prepared in the same manner as in Example <NUM> except that the toner raw materials were replaced with the following materials.

The glass transition temperatures of the toners prepared in Examples <NUM>-<NUM> and Comparative Examples <NUM>-<NUM> were measured using a differential scanning calorimeter (DSC210 manufactured by Seiko Instruments & Electronics Ltd. ) in the following manner. The measurement results are presented in Tables <NUM>-<NUM> and <NUM>-<NUM>.

First, <NUM> to <NUM> of each toner was weighed in an aluminum pan at room temperature, then cooled to -<NUM> degrees C at a temperature falling rate of <NUM> degrees C/min, and heated to <NUM> degrees C at a temperature rising rate of <NUM> degrees C/min. The glass transition temperature (Tg) was determined as a temperature at the intersection of an extended line of a base line of the resulted endothermic curve, and a tangent line of the endothermic curve which indicated the maximum slope between the peak rising portion and the peak top.

The number-based particle diameter distributions of the toners prepared in Examples <NUM>-<NUM> and Comparative Examples <NUM>-<NUM> were measured using a particle size analyzer (MULTISIZER III manufactured by Beckman Coulter, Inc. The measurement results are presented in Tables <NUM>-<NUM> and <NUM>-<NUM>.

The measurement was performed by setting the aperture diameter to <NUM> and the analysis was performed using an analysis software program (Beckman Colter Multisizer <NUM> Version <NUM>). Specifically, <NUM> of a <NUM>% by mass aqueous solution of a surfactant (an alkylbenzene sulfonate, NEOGEN SC-A manufactured by DKS Co. ) was put in a <NUM>-mL glass beaker, then <NUM> of the toner was added thereto and mixed using a micro spatula, and <NUM> of ion-exchange water was further added thereto. The resulting dispersion liquid was subjected to a dispersion treatment using an ultrasonic disperser (W-113MK-II manufactured by HONDA ELECTRONICS CO. ) for <NUM> minutes. The dispersion liquid was measured using the MULTISIZER III and ISOTON III (manufactured by Beckman Coulter, Inc. ) as a solution for measurement. In the measurement, the toner sample dispersion liquid was dropped so that the concentration indicated by the apparatus became <NUM>±<NUM>%.

The above materials were dispersed by a homomixer for <NUM> minutes to prepare a coating layer forming liquid. Manganese (Mn) ferrite particles having a weight average particle diameter of <NUM> as core materials were coated with the coating layer forming liquid using a fluidized bed coating device while controlling the temperature inside the fluidized bed to <NUM> degrees C, followed by drying, so that the coating layer was formed on the surface of the core materials with an average film thickness of <NUM>. The core materials having the coating layer were burnt in an electric furnace at <NUM> degrees C for <NUM> hours. Thus, a carrier A was prepared.

Each of the toners prepared in Examples <NUM>-<NUM> and Comparative Examples <NUM>-<NUM> (white toners) and the color toner was uniformly mixed with the carrier A using a TURBULA MIXER (manufactured by Willy A. Bachofen AG (WAB)) at a revolution of <NUM> rpm for <NUM> minutes to be charged. Thus, each two-component developer was prepared. The mixing ratio of the toner to the carrier was <NUM>% by mass, which was equal to the initial toner concentration in the developer in the test machine.

An image was produced using an image forming apparatus (RICOH Pro C7200S manufactured by Ricoh Co. ) by the following procedure. Each of the toners prepared in Examples <NUM>-<NUM> and Comparative Examples <NUM>-<NUM> was set in the 5th station of the image forming apparatus.

First, a magenta unfixed solid image was output on a release paper sheet under the development and transfer conditions adjusted by the process controller such that the toner deposition amount became <NUM>/cm<NUM>.

Next, an unfixed solid image of each of the toners of Examples <NUM>-<NUM> and Comparative Examples <NUM>-<NUM> was output superimposed on the magenta unfixed solid image on the release paper sheet, under the development and transfer conditions adjusted by the process controller such that the toner deposition amount became <NUM>/cm<NUM>.

A cloth material made of <NUM>% polyester was superimposed on each toner image of Examples <NUM>-<NUM> and Comparative Examples <NUM>-<NUM>, and an iron at <NUM> degrees C was applied thereto for <NUM> seconds to thermally transfer the toner to the cloth material. Thus, a fixed image was obtained.

The obtained fixed image was visually observed to evaluate the degree of image unevenness according to the following evaluation criteria. The evaluation results are presented in Tables <NUM>-<NUM> and <NUM>-<NUM>.

The fixed image obtained for evaluating image unevenness was subjected to a washing fastness test based on the test method according to JIS (Japanese Industrial Standards) <NUM>:<NUM> ("Test methods for colour fastness to washing and laundering"), and washing fastness was evaluated based on the following evaluation criteria. The evaluation results are presented in Tables <NUM>-<NUM> and <NUM>-<NUM>.

The fixed images obtained for evaluating image unevenness were superimposed on one another so that the image portions, or the image portion and the non-image portion, came to face each other. The superimposed portion was applied with a pressure of <NUM>/cm<NUM> by a weight placed whereon, then left to stand for one day in a high-temperature high-humidity tank at <NUM> degrees C and a relative humidity of <NUM>%. After being left to stand, each of the two superimposed fixed images was visually observed to judge the degree of image defects, and blocking resistance was evaluated based on the following evaluation criteria. The evaluation results are presented in Tables <NUM>-<NUM> and <NUM>-<NUM>.

Claim 1:
A toner comprising a binder resin and an adhesive agent,
wherein the toner has a glass transition temperature of -<NUM> degrees C or higher and <NUM> degrees C or lower;
wherein the toner contains at least one adhesive agent selected from polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, and polybutylene isophthalate; and
wherein the glass transition temperature (Tg) is measured according to the description.