Source: http://patents.com/us-7391994.html
Timestamp: 2018-12-12 02:44:55
Document Index: 778376538

Matched Legal Cases: ['in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine']

US Patent # 7,391,994. Image forming apparatus, image forming process, and process cartridge for image forming apparatus - Patents.com
United States Patent 7,391,994
Takada , et al. June 24, 2008
Disclosed is an image forming apparatus for lowering friction coefficient and lowering surface energy of photoconductor surface in particular, which comprises an electrophotographic photoconductor, charging unit, light exposure unit, developing unit, transferring unit, and fixing unit, the electrophotographic photoconductor comprises a photosensitive layer on a conductive support and fluoropolymer fine particles at the outermost layer, a part of the fluoropolymer fine particles are exposed above the surface of the outermost layer in configurations of primary particles and secondary particles formed by flocculation of plural primary particles, and sum of area ratios of particles in the configurations of the primary particles and the secondary particles, each particles having an average diameter D of 0.15 .mu.m.ltoreq.D.ltoreq.3.0 .mu.m as respective projected figures of exposed portion above the surface of the outermost layer, is 10% to 60% based on the entire surface area of the outermost layer, and wherein the binder resin in the outermost layer comprises a polyalylate copolymer resin having a structural unit of alkylene-aryldicarboxylate.
Inventors: Takada; Takeshi (Yokohama, JP), Ikegami; Takaaki (Susono, JP), Sugino; Akihiro (Numazu, JP)
Appl. No.: 11/006,643
Dec 09, 2003 [JP] 2003-409713
Current U.S. Class: 399/159 ; 430/66
Current International Class: G03G 15/00 (20060101); G03G 15/04 (20060101)
Field of Search: 430/66 399/159
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1. An image forming apparatus comprising: an electrophotographic photoconductor, a charging unit configured to charge the electrophotographic photoconductor, a light exposure unit configured to expose light onto the charged electrophotographic photoconductor to form a latent electrostatic image, a developing unit loaded with a toner and configured to visualize the latent electrostatic image by depositing the toner to form a visual image, a transferring unit configured to transfer the visual image onto a recording medium, and a fixing unit configured to fix the visual image transferred onto the recording medium, wherein the electrophotographic photoconductor comprises a photosensitive layer on a conductive support wherein an outermost surface of the photosensitive layer comprises: fluoropolymer fine particles; and a binder resin; wherein the fluoropolymer fine particles comprise primary particles, and secondary particles, the secondary particles are formed by flocculation of plural primary particles, and a part of the fluoropolymer fine particles comprising the primary particles and the secondary particles are exposed above the surface of the outermost layer, and each fluoropolymer fine particle as an average diameter, D, of exposed portion above the surface of the outermost surface of 0.15 .mu.m.ltoreq.D.ltoreq.3.0 .mu.m and a total area ratio of the fluoropolymer fine particles comprising the primary particles and the secondary particles is 10% to 60% based on the entire surface area of the outermost layer, and the binder resin in the outermost layer comprises a polyalylate copolymer resin having a structural unit of alkylene-aryldicarboxylate.
2. The image forming apparatus according to claim 1, wherein the polyalylate copolymer resin having a structural unit of alkylene-aryldicarboxylate is the polyalylate copolymer resin expressed by the general formula (I): ##STR00011## wherein Ar.sub.1, Ar.sub.2, and Ar.sub.3 are each independently a substituted or unsubstituted aryl group, X is an alkylene group, said substituent group is a halogen atom or alkyl group; 1 and m are each a mole ratio in relation of 0.05.ltoreq.1<0.6, 0.4.ltoreq.m<0.95,1+m=1; n is a positive integer that satisfies the copolymer to have a weight-averaged molecular weight of 1.times.10.sup.3 to 1.times.10.sup.6 in terms of polystyrene.
3. The image forming apparatus according to claim 1, wherein the polyalylate copolymer resin having a structural unit of alkylene-aryldicarboxylate is the polyalylate copolymer resin expressed by the general formula (II): ##STR00012## wherein Ar.sub.1 and Ar.sub.2 are each independently a substituted or unsubstituted aryl group, X is a divalent alkylene group, said substituent group is a halogen atom or alkyl group; R.sub.1 and R.sub.2 are each independently a hydrogen atom, alkyl group, or aryl group, and may be cyclic; R.sub.3 and R.sub.4 are each independently a hydrogen atom, halogen atom, or alkyl group; o and p are each an integer of 1 to 4, and may identical or different in case of 2 or more; 1 and m are each a mole ratio in relation of 0.05.ltoreq.1<0.6,0.4.ltoreq.m<0.95, and 1+m =1; n is a positive integer that satisfies the copolymer to have a weight-averaged molecular weight of 1.times.10.sup.3 to 1.times.10.sup.6 in terms of polystyrene.
4. The image forming apparatus according to claim 2, wherein Ar.sub.1 and Ar.sub.2 of the polyalylate copolymer resin expressed by the general formula (I) are each a phenylene group.
5. The image forming apparatus according to claim 3, wherein Ar.sub.1 and Ar.sub.2 of the polyalylate copolymer resin expressed by the general formula (II) are each a phenylene group.
8. The image forming apparatus according to claim 1, wherein a sum of area ratios of exposed portions of the fluorochemical fine particles above the surface of the outermost layer, is 10% to 60% based on the entire surface area of the outermost layer, and each of the primary and secondary particles has an average diameter of 0.2 to 1.5 .mu.m.
11. The image forming apparatus according to claim 1, wherein the electrophotographic photoconductor comprises a protective layer on the photosensitive layer, the photosensitive layer comprises a charge generating substance and a charge transporting substance, the protective layer is laminated on the photosensitive layer, and the protective layer comprises a binder resin and fluoropolymer fine particles.
16. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises an intermediate transferring unit configured to transfer primarily a toner image developed on the electrophotographic photoconductor to an intermediate transferring body, then to transfer secondarily the toner image on the intermediate transferring body onto a recording medium, and wherein a color image is formed through overlapping plural toner images each having individual color in turn on the intermediate transferring body, and the color image is secondarily transferred at the same time on the recording medium.
17. A process cartridge for an image forming apparatus, comprising: an electrophotographic photoconductor, and a developing unit loaded with a toner and configured to visualize the latent electrostatic image by depositing the toner to form a visual image, wherein the electrophotographic photoconductor comprises a photosensitive layer on a conductive support wherein an outermost surface of the photosensitive layer comprises: fluoropolymer fine particles; and a binder resin; wherein the fluoropolymer fine particles comprise primary particles, and secondary particles, the secondary particles are formed by flocculation of plural primary particles, and a part of the fluoropolymer fine particles comprising the primary particles and the secondary particles are exposed above the surface of the outermost layer, and each fluoropolymer fine particle has an average diameter, D, of exposed portion above the surface of the outermost surface of 0.15 .mu.m .ltoreq.D.ltoreq.3.0 .mu.m and a total area ratio of the fluoropolymer fine particles comprising the primary particles and the secondary particles is 10% to 60% based on the entire surface area of the outermost layer, the binder resin in the outermost layer comprises a polyalylate copolymer resin having a structural unit of alkylene-aryldicarboxylate, and the process cartridge is attachable and detachable to a main body of the image forming apparatus.
Examples of the lubricants include fluorine-containing resin (hereinafter "fluoropolymer") such as polytetrafluoroethylene, spherical particles of acrylic resin, polyethylene resin powder, metal oxide powders such as silicon oxide and aluminum oxide, and liquid of silicone oil. Fluoropolymers with higher content of fluorine may provide a remarkable effect as lubricant due to their lower surface energy. The fluoropolymers are employed as crystalline fine particles, and formed into a surface layer or protective layer of photoconductors, after being dispersed into a binder resin such as acrylic resins, polyester resins, polyurethane resins, and polycarbonate resins.
wherein the toner bears two or more types of resin fine particles on the toner surface, the two or more types of resin fine particles comprise resin fine particle (A) of which the glass transition temperature T.sub.A is highest and resin fine particle (B) of which the glass transition temperature T.sub.B is lowest among the two or more types of resin fine particles, and T.sub.A minus T.sub.B is 20.degree. C. to 150.degree. C.,
wherein the electrophotographic photoconductor comprises a photosensitive layer on a conductive support and fluoropolymer fine particles at the outermost layer, a part of the fluoropolymer fine particles are exposed above the surface of the outermost layer in configurations of primary particles and secondary particles formed by flocculation of plural primary particles, and sum of area ratios of particles in the configurations of the primary particles and the secondary particles, each particles having an average diameter D of 0.15 .mu.m.ltoreq.D.ltoreq.3.0 .mu.m as respective projected figures of exposed portion above the surface of the outermost layer, is 10% to 60% based on the entire surface area of the outermost layer, and
in the above formula (I), Ar.sub.1, Ar.sub.2, and Ar.sub.3 are each a substituted or unsubstituted aryl group, X is an alkylene group, said substituent group is a halogen atom or alkyl group; l and m are each a mole ratio in relation of 0.05.ltoreq.1<0.6, 0.4.ltoreq.m<0.95, l+m=1; n is a positive integer that satisfies the copolymer to have a weight-averaged molecular weight of 1.times.10.sup.3 to 1.times.10.sup.6 in terms of polystyrene.
in the formula (II), Ar.sub.1 and Ar.sub.2 are each a substituted or unsubstituted aryl group, X is a divalent alkylene group, said substituent group is a halogen atom or alkyl group; R.sub.1 and R.sub.2 are each a hydrogen atom, alkyl group, or aryl group; R.sub.3 and R.sub.4 are each a hydrogen atom, alkyl group, or aryl group; o and p are each an integer of 1 to 4, and may identical or different in case of 2 or more; 1 and m are each mole ratio in relation of 0.05.ltoreq.1<0.6, 0.4.ltoreq.m<0.95, l+m=1; n is a positive integer that satisfies the copolymer to have a weight-averaged molecular weight of 1.times.10.sup.3 to 1.times.10.sup.6 in terms of polystyrene.
in the formula (III), Ar.sub.2 and Ar.sub.3 are each an aryl group; n is a positive integer that satisfies the copolymer to have a weight-averaged molecular weight of 1.times.10.sup.3 to 1.times.10.sup.6 in terms of polystyrene.
in the formula (IV), n is a positive integer that satisfies the copolymer to have a weight-averaged molecular weight of 1.times.10.sup.3 to 1.times.10.sup.6 in terms of polystyrene.
in the formula (V), Ar.sub.1 is a substituted or unsubstituted aryl group, X is a divalent alkyl group, said substituent group is a halogen atom or alkyl group.
The aromatic dicarboxylic acid compounds for producing the structural unit of alkyl-aryldicarboxylate may be derived from aromatic carboxylic acid compounds such as isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, diphenyl-4,4'-dicarboxylic acid, diphenyl-3,3'-dicarboxylic acid, diphenylmethane-4,4'-dicarboxylic acid, diphenylethane-4,4'-dicarboxylic acid, diphenylpropane-4,4'-dicarboxylic acid, benzophenone-4,4'-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, diphenylether-4,4'-dicarboxylic acid, diphenylthioether-4,4'-dicarboxylic acid, and diphenylsulfide-4,4'-dicarboxylic acid.
The aromatic diol component that constitutes the alylate structure may be derived from such compounds as 1,3-benzenediol, 1,4-benzenediol, 1,3-naphthalenediol, 1,2-naphthalenediol, 1,4-naphthalenediol, 1,7-naphthalenediol, 1,6-naphthalenediol, 1,5-naphthalenediol, 1,8-naphthalenediol, 2,3-naphthalenediol, 2,6-naphthalenediol, 2,7-naphthalenediol, 4,4'-dihydroxydiphenyl, 2,2'-dihydroxydiphenyl, 3,3'-dipropyl-4,4'-dihydroxydiphenyl, bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)phenylmethane, bis(4-hydroxyphenyl)diphenylmethane, 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, bisphenol A [2,2-bis(4-hydroxyphenyl)propane], 2,2-bis(3-methyl-4-hydroxyphenyl)propane, 2,2-bis(3-chloro-4-hydroxyphenyl)propane, 2,2-bis(3-bromo-4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)cyclopentane, 2,2-bis(3-phenyl-4-hydroxyphenyl)propane, 2,2-bis(3-isopropyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, 4,4'-dihydroxy diphenylsulfone, 4,4'-dihydroxy diphenylsulfoxide, 4,4'-dihydroxy diphenylsulfide, 3,3'-dimethyl-4,4'-dihydroxy diphenylsulfide, 4,4'-dihydroxy diphenyloxide, 2,2-bis(4-hydroxyphenyl)hexafluoropropane, 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxyphenyl)xanthene, and 1,3-bis(4-hydroxyphenyl)tetramethyldisiloxane.
in the formula (II), Ar.sub.1 and Ar.sub.2 are each a substituted or unsubstituted aryl group, X is a divalent alkylene group, said substituent group is a halogen atom or alkyl group; R.sub.1 and R.sub.2 are each a hydrogen atom, halogen atom, or alkyl group, and may be cyclic; R.sub.3 and R.sub.4 are each a hydrogen atom, alkyl group, or aryl group; o and p are each an integer of 1 to 4, and may identical or different in case of 2 or more; 1 and m are each mole ratio in relation of 0.05.ltoreq.1<0.6, 0.4.ltoreq.m<0.95, l+m=1.
In the structure expressed by formula (II), preferably, Ar.sub.1 and Ar.sub.2 are each an divalent phenyl group; preferably, the divalent alkylene group X is an ethylene group.
Preferably, the glass transition temperature of the polyalylate copolymer resin adapted to the present invention is 120.degree. C. or more and 170.degree. C. or less; n is a positive integer that satisfies the copolymer to have a weight-averaged molecular weight of 1.times.10.sup.3 to 1.times.10.sup.6, preferably 1.times.10.sup.4 to 1.times.10.sup.5 in terms of polystyrene. The weight-averaged molecular weight of less than 1.times.10.sup.3 often leads to insufficient mechanical strength of the resin itself, and decrease of abrasion resistance in continuous usages; on the other hand, the weight-averaged molecular weight of more than 1.times.10.sup.6 often leads to lower solubility of the resin in coating solvent, resulting in insufficient layer thickness.
The conductive supports, utilized for electrophotographic conductors, adapted to the present invention may be formed of electric conductors such as metal or alloy e.g. Al, Ni, Fe, Cu; conductive-treated electric insulators i.e. composite material of insulating material such as polyester, polycarbonate, polyimide, and glass and thin film of conductive materials, formed on the insulating material, such as Al, Ag, Au, In.sub.2O.sub.3, SnO.sub.2; composite material of resin and electric conductive material, dispersed into the resin to impart conductivity to the resin, such as carbon black, graphite, Al, Cu, Ni, conductive glass powder; and conductive-treated paper. The shape of the conductive supports is not particularly limited, and may be plate-like, drum-like, or belt-like. The supports of belt-like construction typically require an inside driving roller and related rollers, therefore, often lead to complicated and enlarged apparatuses, while the layout may be advantageously and freely designed. However, when a protective layer is introduced, the surface may be damaged to cracks due to insufficient flexibility, resulting possibly background smear of particulate shape. As such, drum-shape supports are preferred owing to the higher rigidity.
In addition, a metal oxide layer which is formed, for example, by a sol-gel method using a silane coupling agent, titanium coupling agent, or chromium coupling agent may be used as the undercoat layer. Further, a layer of aluminum oxide which is formed by an anodic oxidation method, and a layer of an organic compound such as polyparaxylylene or an inorganic compound such as SiO, SnO.sub.2, TiO.sub.2, ITO or CeO.sub.2, which is formed by a vacuum evaporation method, may be used as the undercoat layer. The thickness of the undercoat layer is preferably from 0.1 to 5 .mu.m.
The thickness of the charge generating layer is preferably about 0.01 to 5 .mu.m, and more preferably is about 0.05 to 2 .mu.m.
In order to satisfy such requirements, the charge transporting layer is mainly constituted of a charge transporting substance together with a binder resin (polycarbonate resin). The charge transporting layer is typically prepared as follows: (1) a charge transporting substance, a binder resin and an additive are dissolved or dispersed in a solvent such as tetrahydrofuran to prepare a coating liquid; and (2) coating the coating liquid, for example, on the charge generating layer and then drying the coated liquid, resulting in formation of a charge transporting layer.
The charge transporting layer may include an additive such as plasticizer, antioxidant, leveling agent etc., in an amount such that these agents do not deteriorate the characteristics of the charge transporting layer.
The film thickness of the charge transporting layer is preferably about 5 to 100 .mu.m, more preferably is about 5 to 30 .mu.m to achieve higher image density of 1200 dpi or more since lower film thickness of charge transporting layers is desired in connection with demands for higher image density in recent years.
Preferably, the primary particle size of the fine particles of the fluoropolymer is not too large as well as not too small, in order to satisfy the preferable average diameter of primary particles and secondary particles. Preferably, the average particle diameter of the primary particles is 0.1 to 0.3 .mu.m.
Inorganic filler materials typically exhibit higher hardness than those of organic filler materials, therefore, may provide more efficient improvement in wear resistance in general. By the way, it has been experienced that improvement of latent image bearing member in the wear resistance result in that the surface of the latent image bearing member hardly wears; however, reactive gas such as ozone and NO.sub.x, generated at charging, tends to decrease the surface resistance; consequently, the electrostatic charge at the surface gradually comes to be difficult to maintain and the electrostatic charge is likely to move toward the surface.
As a result, the electrostatic latent images tend to bleed, and extraordinary images such as image blur and image flow are often induced when the electrostatic latent images are developed by means of toner. As such, the filler adapted to the present invention has preferably higher resistance such as more than 10 ohmcm. Such filler may prevent the resistance decrease at outermost surface of photoconductors, and may suppress the occurrences of extraordinary images.
These filler materials may be dispersed by means of an appropriate dispersing device along with charge transporting substance, binder resin, solvent and the like. The average primary diameter of filler is preferably 0.05 to 1.0 .mu.m, more preferably is 0.1 to 0.3 .mu.m.
The average primary diameter of filler of less than 0.05 .mu.m possibly results in insufficient abrasion resistance. On the other hand, the average primary diameter of filler of more than 1.0 .mu.m possibly results in image blur and/or thicker letters, since the transmittance is decreased due to scattering of writing light by the filler.
Preferably, the layer thickness of the photosensitive layer of mono-layer photoconductor is about 5 to 100 .mu.m.
Preferably, the film thickness of the resulting protective layer is 0.1 to 15 .mu.m, more preferably is 1 to 10 .mu.m.
As for the glass transition temperature of the resin fine particles adapted to the present invention, preferably, the glass transition temperature of resin fine particles (A) is 55 to 150.degree. C., and that of resin fine particles (B) is 25 to 100.degree. C. Preferably, the difference between the two glass transition temperatures of the respective resin fine particles is no less than 20.degree. C., more preferably is 25 to 70.degree. C. When the temperature difference is less than the range, the superior properties of resin fine particles (A) and resin fine particles (B) are suppressed to display, possibly resulting in one or more insufficient properties of fixing ability at lower temperatures, offset resistance, and preservation resistance at higher temperatures.
The glass transition temperatures are measured by means of Differential Scanning Calorimeter DSC-60 (Shimadzu Co.); specifically, the temperature is raised from room temperature to 200.degree. C. at a rate of 10.degree. C./min, and is lowered to room temperature at a rate of 10.degree. C./min, then measurements are conducted at a heating rate of 10.degree. C./min, wherein the glass transition temperature is determined from the point where the baseline under the glass transition temperature and the height of baseline (h) of over the glass transition temperature correspond to 1/2.
The distribution of the components of resin fine particles may be determined by means of GPC as follows. The column is stabilized in a heating chamber at 40.degree. C., tetrahydrofuran is flowed at a velocity of 1 ml/min as the column solvent at the temperature, the sample solution is prepared at a concentration of 0.05 to 0.6 weight % using tetrahydrofuran as the solvent, then the sample solution is injected at an amount of 50 to 200 .mu.L and procedures for measuring are carried out.
In determining the molecular weight of a sample, the molecular weight distribution of the sample is calculated from logarithmic values of analytical curves prepared from plural kinds of monodisperse-polystyrene standard samples and the count values. As for the standard polystyrene samples for preparing the analytical curve, those having molecular weight of 6.times.10.sup.2, 2.1.times.10.sup.2, 4.times.10.sup.2, 1.75.times.10.sup.4, 1.1.times.10.sup.5, 3.9.times.10.sup.5, 8.6.times.10.sup.5, 2.times.10.sup.6, 4.48.times.10.sup.6, are utilized, and at least about ten standard polystyrene samples are employed. As for the detector, RI (refractive index) is employed.
The resin fine particles in the toner are added when producing the toner in order to control the toner configuration such as circularity and particle size distribution. Preferably, the average particle diameter of the resin fine particles is 20 to 400 nm, the BET specific surface area of the resin fine particles is 0.5 to 6.0 m.sup.2/g. When the average particle diameter is less than 20 nm, or the BET specific surface area is less than 0.5 m.sup.2/g, the organic components of the resin fine particles, remaining on the toner surface, tend to cover the entire surface of the toner, thereby the resin fine particles inhibit the adhesion between the binder resin and the fixing medium, and the lower limit of fixing temperature is likely to rise. Moreover, since the resin fine particles tend to inhibit the bleeding of waxes, the waxes do not display releasing effect and offset often occurs. Further, when the average particle diameter is no less than 400 nm, or the BET specific surface area is no less than 6.0 m.sup.2/g, the resin fine particles remaining on the toner surface may protrude considerably as convex portions, alternatively the resin fine particles may remain as multiple layers in rough condition, thereby the resin fine particles also inhibit the adhesion between the binder resin and the fixing medium, and the lower limit of fixing temperature is likely to rise. Moreover, since the resin fine particles tend to inhibit the bleeding of waxes, the waxes do not display sufficiently releasing effect and offset often occurs.
The ratio of the polyol (1) to the polycarboxylic acid (2) in terms of the equivalence ratio [OH]/[COOH] of the hydroxyl groups [OH] to the carboxyl groups [COOH] is generally from 2/1 to 1/1, preferably from 1.5/1 to 1/1, and more preferably from 1.3/1 to 1.02/1. The polyisocyanate (3) includes, but is not limited to, aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and 2,6-diisocyanatomethyl caproate; alicyclic polyisocyanates such as isophorone diisocyanate, and cyclohexylmethane diisocyanate; aromatic diisocyanates such as tolylene diisocyanate, and diphenylmethane diisocyanate; aromatic-aliphatic diisocyanates such as .alpha.,.alpha.,.alpha.',.alpha.'-tetramethylxylylene diisocyanate; isocyanurates; blocked products of the polyisocyanates with, for example, phenol derivatives, oximes, or caprolactams; and mixtures of these compounds. The amount of the polyisocyanate (3) in terms of the equivalence ratio [NCO]/[OH] of isocyanate groups [NCO] to hydroxyl groups [OH] of the polyester is generally from 5/1 to 1/1, preferably from 4/1 to 1.2/1, and more preferably from 2.5/1 to 1.5/1. If the ratio [NCO]/[OH] is more than 5, image-fixing properties at low temperatures may deteriorate. If the ratio [NCO/[OH] is less than 1, a urea content in the modified polyester decreases, and the toner may have deteriorated hot offset resistance. The content of the polyisocyanate (3) in the prepolymer (A) having an isocyanate group is generally from 0.5% by weight to 40% by weight, preferably from 1% by weight to 30% by weight, and more preferably from 2% by weight to 20% by weight. If the content is less than 0.5% by weight, the hot off-set resistance may deteriorate, and satisfactory storage stability at high temperatures and image-fixing properties at low temperatures may not be obtained concurrently. If the content is more than 40% by weight, the image-fixing properties at low temperatures may deteriorate. The prepolymer (A) generally has, in average, 1 or more, preferably 1.5 to 3, and more preferably 1.8 to 2.5 isocyanate groups per molecule. If the number of the isocyanate group per molecule is less than 1, the urea-modified polyester may have a low molecular weight and the hot off-set resistance may deteriorate.
The amine (B) includes, for example, diamines (B1), trivalent or more polyamines (B2), amine alcohols (B3), aminomercaptans (B4), amino acids (B5), and amino-blocked products (B6) of the amines (B1) to (B5). The diamines (B1) include, but are not limited to, aromatic diamines such as phenylenediamine, diethyltoluenediamine, and 4,4'-diaminodiphenylmethane; alicyclic diamines such as 4,4'-diamino-3,3'-dimethyldicyclohexylmethane, diaminocyclohexanes, and isophoronediamine; and aliphatic diamines such as ethylenediamine, tetramethylenediamine, and hexamethylenediamine. The trivalent or more polyamines (B2) include, for example, diethylenetriamine, and triethylenetetramine.
A colorant for use in the present invention may be a master batch prepared by mixing and kneading a pigment with a resin. Examples of binder resins for use in the production of the master batch or in kneading with the master batch are, in addition to the aforementioned modified and unmodified polyester resins, polystyrenes, poly-p-chlorostyrenes, polyvinyltoluenes, and other polymers of styrene and substituted styrenes; styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers, styrene-vinylnaphthalene copolymers, styrene-methyl acrylate copolymers, styrene-ethyl acrylate copolymers, styrene-butyl acrylate copolymers, styrene-octyl acrylate copolymers, styrene-methyl methacrylate copolymers, styrene-ethyl methacrylate copolymers, styrene-butyl methacrylate copolymers, styrene-methyl .alpha.-chloromethacrylate copolymers, styrene-acrylonitrile copolymers, styrene-vinyl methyl ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers, styrene-maleic acid copolymers, styrene-maleic ester copolymers, and other styrenic copolymers; poly(methyl methacrylate), poly(butyl methacrylate), poly(vinyl chloride), poly(vinyl acetate), polyethylenes, polypropylenes, polyesters, epoxy resins, epoxy polyol resins, polyurethanes, polyamides, poly(vinyl butyral), poly(acrylic acid) resins, rosin, modified rosin, terpene resins, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, and paraffin waxes. Each of these resins can be used alone or in combination.
The charge controlling agent, incorporated into the toner utilized optionally in the present invention, may be one or combination of conventional charge controlling agents such as metal chelates, metal salts of organic acids, metal-containing dyes, Nigrosine dies, amide-containing compounds, phenol compounds, naphthol compounds and metal salts thereof, urethane-bond-containing compounds, and acidic or electron-absorbing organic substances. Further, metal salts or complexes of salicylic acid or alkyl salicylic acid with chromium, zinc, and aluminum; metal salts or metal complexes of benzilic acid; amide compounds, phenol compounds, naphthol compounds, phenolamide compounds, hydroxynaphthalene compounds such as 4,4'-methylene bis [2-[N-(4-chlorophenyl)amide]-3-hydroxynaphthalene are preferable for negative charging ability form the view point of color toner compatibility i.e. no interference for toner color owing to colorless or pale color of the charge controlling agent itself. The content of charge controlling agent may be dependent on the desired charging amount of toner; usually is 0.01 to 10 parts by weight based on 100 parts by weight of toner, preferably is 0.1 to 10 parts by weight.
Inorganic fine particles can be preferably used as the external additive to improve or enhance the fluidity, developing properties, and charging ability of the toner particles. Among them, hydrophobic silica and/or hydrophobic titanium oxide is typically preferred. The inorganic fine particles have a primary particle diameter of preferably from 5 nm to 2 .mu.m, and more preferably from 5 nm to 500 nm and have a specific surface area as determined by the BET method of preferably from 20 m.sup.2/g to 500 m.sup.2/g. The amount of the inorganic fine particles is preferably from 0.01% by weight to 5% by weight, and more preferably from 0.01% by weight to 2.0% by weight based on the toner.
A cleaning agent or cleaning improver may also be added in order to remove the developer remained on a photoconductor or on a primary transfer member after transfer. Suitable cleaning agents are, for example, metal salts of stearic acid and other fatty acids such as zinc stearate, and calcium stearate; and poly(methyl methacrylate) fine particles, polystyrene fine particles, and other fine polymer particles prepared by, for example, soap-free emulsion polymerization. Such fine polymer particles preferably have a relatively narrow particle distribution and a volume-average particle diameter of 0.01 .mu.m to 1 .mu.m.
When toners that have a weight-averaged particle diameter Dw of 4 to 8 .mu.m, and a ratio (Dw/Dn) of 1.25 or less, preferably 1.10 to 1.25, wherein Dn is a number-average particle diameter Dn, are utilized as dry toners, image gloss is superior in full-color copiers. Further, when the toner is used in a double-component developer, variation of the toner particle diameter is minimized even after repeating cycles of consumption and addition of the toner with respect to carrier. As the toner keeps a narrow average particle diameter without being affected by stirring in a developing device for a long period, the toner can keep stable and excellent developing properties. When the toner is used as a single-component developer, the variation of the toner particle diameter is minimized as in the double-component developer. In addition, toner filming to development rollers, and toner fusion of members such as a toner blade which control the toner thickness on the development roller are also prevented. Hence, even if the toner is used or stirred in the image developer for a long period of time, the toner can keep stable and excellent developing properties to form high-quality images stably.
The toner of the present invention can be used as a two-component developer after mixed with a magnetic carrier. The content of the toner in the developer is preferably 1 to 10 parts by weight based on 100 parts by weight of the carrier. Any conventionally-known magnetic carrier, such as iron powder, ferrite powder, magnetite powder, magnetic resin carrier, can be used. Examples of resins for covering the surface of the carrier include amino resin, urea-formaldehyde resin, melamine resin, benzoguanamine resin, urea resin, polyamide resin and epoxy resin. Also usable for covering a carrier are polyvinyl or polyvinylidene resins; polystyrene resins such as acrylic resin, polymethyl methacrylate resin, polyacrylonitrile resin, polyvinyl acetate resin, polyvinyl alcohol resin, polyvinyl butyral resin, polystyrene resin and styrene-acrylic copolymer; halogenated olefin resins such as polyvinyl chloride resin; polyester resins such as polyethylene terephthalate resin and polybutylene terephthalate resin; polycarbonate resins; polyethylene resins; polyvinyl fluoride resins; polyvinylidene fluoride resins; polytrifluoroethylene resins; polyhesafluoropropylene resins; copolymers of vinylidene fluoride and an acrylic monomer; copolymers of vinylidene fluoride and vinyl fluoride; terpolymers of tetrafluoroethylene, vinylidene fluoride and a fluorine-free monomer; and silicone resins. The resin coating for the carrier may contain conductive powder such as metal powder, carbon black, titanium oxide, tin oxide or zinc oxide. The conductive powder preferably has an average particle size of 1 .mu.m or less for reasons of easy control of the electric resistance. The toner utilized in the present invention may be used as a one-component magnetic or nonmagnetic toner requiring no carrier.
The dispersing procedure is not specifically limited and includes known procedures such as low-speed shearing, high-speed shearing, dispersing by function, high-pressure jetting, and ultrasonic dispersion. To allow the dispersion to have an average particle diameter of from 2 to 20 .mu.m, the high-speed shearing procedure is preferred. When a high-speed shearing dispersing machine is used, the number of rotation is not specifically limited and is generally from 1,000 to 30,000 rpm and preferably from 5,000 to 20,000 rpm. The dispersion time is not specifically limited and is generally from 0.1 to 20 minutes in batch systems. The temperature at dispersing is usually 0 to 150.degree. C. under application of pressure, preferably 10 to 98.degree. C.
As for the organic solvent utilized in the present invention, conventional solvents that may dissolve the active-hydrogen-containing compounds, compounds having a site reactive with active-hydrogen-containing compounds, and binder resins. Preferably, the solvent is volatile and the boiling point is less than 100.degree. C., since the solvent can be removed easily. Examples of the solvent include ethyl acetate, acetone, methylethylketone, and THF. The amount of the organic solvent is usually 10 parts by weight based on 100 parts by weight of dispersion, preferably is 20 to 400 parts by weight, and more preferably is 50 to 300 parts by weight. The way to remove the organic solvent from raw toner particles dispersed in the aqueous medium may be conventional removing way by means of heating and optional evacuating. During removing the organic solvent, the crosslinking reaction occurs between the compound having a site reactive with active-hydrogen-containing compounds and crosslinking or extension agent (i.e. an active-hydrogen-containing compound). The liquid containing raw toner particles is subjected to solid-liquid separation by means of centrifugal separator, Spacra filter, or filter press, then the resulting powder is dried, thereby the toner utilized in the present invention may be obtained. Examples of apparatuses for drying the powder include the apparatuses of air current, vibration and fluidization, fluidizing bed, evacuation, and circulated air types. These apparatuses may be used alone or in combination. Classification may be combined such as air classification in order to obtain an intended particle distribution.
When the fluorine-contained resin is covered by means of a cleaning blade, the following conditions of cleaning blade will be appropriate such as 10 to 30.degree. of contacting angle, 0.3 to 4 g/mm of contacting pressure, 60 to 70 degrees of urethane rubber hardness for the blade, 30 to 70% of impact resilience, 30 to 60 kgf/cm.sup.2 of modulus of elasticity, 1.5 to 3.0 mm of thickness, 7 to 12 mm of free length, 0.2 to 2 mm of blade edge interlocking into the photoconductor. In FIG. 5, (4) indicates an eraser, (8) indicates a resist roller, and (12) indicates a separating claw.
As for full-color image forming apparatuses, to which the present invention is applied, an aspect of printer of electrophotographic type (hereinafter, referring to "printer") will be discussed.
An intermediate transferring unit is disposed at the downstream from the developing site in the revolution direction of the photoconductor drum (56). The intermediate transferring unit is activated by rotating endlessly in clockwise direction the intermediate transferring belt (58), tensioned on tension roller (59a), intermediate transferring bias roller (57) as transferring unit, secondary transferring backup roller (59b), and belt driving roller (59c), by the rotating force of the belt driving roller (59c). The yellow toner image, magenta toner image, cyan toner image, and black toner image developed on the photoconductor drum (56) progress into the intermediate nip where photoconductor drum (56) and intermediate transferring belt make contact. Then the color image formed of overlapped four colors is produced by overlapping on intermediate transferring belt (58) under the effect of the bias from the intermediate transferring bias roller (57).
The present invention will be illustrated in further detail with reference to several examples and comparative examples below, which are never intended to limit the scope of the present invention. In the followings, "parts" written in below refers to "parts by weight".
Into a reactor equipped with a stirring rod and a thermometer were poured 683 parts of water, 6 parts of sodium sulfate of ethylene oxide adduct of methacrylic acid (ELEMINOL RS-30, by Sanyo Chemical Industries, Ltd.), 85 parts of styrene, 85 parts of methacrylic acid, 111 parts of butyl acrylate, and 1 part of ammonium persulfate, and the mixture was stirred at 400 rpm for 15 minutes to yield a white emulsion. The emulsion was heated to an inner temperature of 75.degree. C., followed by allowing to react for 5 hours. The reaction mixture was further treated with 30 parts of 1% aqueous solution of ammonium sulfate, and was aged at 75.degree. C. for 5 hours, thereby yielding an aqueous dispersion of Fine Particle Dispersion 1 of a vinyl resin (copolymer of styrene-methacrylic acid-butyl acrylate-sodium sulfate of ethylene oxide adduct of methacrylic acid). Fine Particle Dispersion 1 had a weight-averaged particle diameter of 300 nm when measured with a laser diffraction-scattering size distribution analyzer LA-920 (trade name, available from Horiba, Ltd., Japan). Part of Fine Particle Dispersion 1 was dried to isolate the resin component. The resin component had a glass transfer temperature Tg of 78.degree. C., number-averaged molecular weight of 2100, and weight-average molecular weight of 9900.
Into a reactor equipped with a stirring rod and a thermometer were poured 683 parts of water, 5 parts of sodium sulfate of ethylene oxide adduct of methacrylic acid (ELEMINOL RS-30, by Sanyo Chemical Industries, Ltd.), 81 parts of styrene, 81 parts of methacrylic acid, 107 parts of butyl acrylate, 13 parts of 1,6-hexanediol diacrylate and 1 part of ammonium persulfate, and the mixture was stirred at 400 rpm for 15 minutes to yield a white emulsion. The emulsion was heated to an inner temperature of 75.degree. C., followed by allowing to react for 5 hours. The reaction mixture was further treated with 30 parts of 1% aqueous solution of ammonium sulfate, and was aged at 75.degree. C. for 5 hours, thereby yielding an aqueous dispersion of Fine Particle Dispersion 2 of a vinyl resin (copolymer of styrene-methacrylic acid-butyl acrylate-sodium sulfate of ethylene oxide adduct of methacrylic acid). Fine Particle Dispersion 2 had a weight-averaged particle diameter of 295 nm when measured with a laser diffraction-scattering size distribution analyzer LA-920 (by Horiba, Ltd.). Part of Fine Particle Dispersion 2 was dried to isolate the resin component. The resin component had a glass transfer temperature Tg of 105.degree. C., number-averaged molecular weight of 10,000, and weight-average molecular weight of 1,000,000.
Into a reactor equipped with a condenser, stirrer, and nitrogen gas inlet were poured 220 parts of ethylene oxide (2 mole) adduct of bisphenol A, 561 parts of propylene oxide (3 mole) adduct of bisphenol A, 208 parts of terephthalic acid, 46 parts of adipic acid, and 2 parts of dibutyltin oxide. The mixture was reacted at 230.degree. C. at ambient pressure for 8 hours and was further reacted at reduced pressure of 10 to 15 mmHg for 5 hours. The reaction mixture was further treated with 44 parts of trimellitic anhydride at 180.degree. C. at ambient pressure for 1.8 hours, thereby yielding Low-Molecular Weight Polyester 1.
Into a reactor equipped with a condenser, stirrer, and nitrogen gas inlet were poured 682 parts of ethylene oxide (2 mole) adduct of bisphenol A, 81 parts of a propylene oxide (2 mole) adduct of bisphenol A, 283 parts of terephthalic acid, 22 parts of trimellitic anhydride, and 2 parts of dibutyltin oxide. The mixture was reacted at 230.degree. C. at ambient pressure for 8 hours, was further reacted under a reduced pressure of 10 to 15 mmHg for 5 hours, thereby yielding Intermediate Polyester 1 having a number-average molecular weight of 2100, weight-average molecular weight of 9500, Tg of 55.degree. C., acid value of 0.5, and hydroxyl value of 49.
Into a reactor equipped with a condenser, stirrer, and nitrogen gas inlet were poured 411 parts of Intermediate Polyester 1, 89 parts of isophorone diisocyanate, and 500 parts of ethyl acetate, followed by allowing to react at 100.degree. C. for 5 hours to yield Prepolymer 1.
Into a reactor equipped with a stirring rod and a thermometer were poured 170 parts of isophoronediamine and 75 parts of methylethylketone, followed by allowing to react at 50.degree. C. for 5 hours to yield Ketimine Compound 1.
Into a reactor equipped with a stirring rod and a thermometer were poured 628 parts of Low-molecular Weight Polyester 1, 110 parts of carnauba wax, 22 parts of CCA (metal complex of salicylic acid E-84, by Orient Chemical Industries Ltd.), and 947 parts of ethyl acetate. The mixture was heated at 80.degree. C. for 5 hours with stirring and was then cooled to 30.degree. C. over 1 hour. Then, 250 parts of carbon black (Regal 400R, Cabot Co.) and 500 parts of ethyl acetate were poured into the reactor and mixed for one hour to prepare Raw Material Solution 1.
Into a vessel equipped with a stirrer and a thermometer was poured Emulsified Slurry 1 and was heated at 30.degree. C. for 8 hours to remove the solvent therefrom. The slurry was aged at 45.degree. C. for 4 hours and thereby yielded Dispersed Slurry 1. The Dispersed Slurry 1 exhibited a weight-averaged particle diameter of 4.95 .mu.m and a number-averaged particle diameter of 4.45 .mu.m (measured by Multi-Sizer II).
(2) The Filtered Cake prepared in (1) was dried at 45.degree. C. for 48 hours in a circulating air dryer, was sieved with a 75 .mu.m mesh sieve thereby to yielded a toner. To the resulting toner of 100 parts, 0.7 part of hydrophobic silica and 0.3 part of hydrophobic titanium oxide were blended by means of Henschel mixer to prepare Toner 1.
Fine Particle Dispersion 3 had a weight-averaged particle diameter of 42 nm when measured with a size distribution analyzer LA-920 (Horiba, Ltd.). Part of Fine Particle Dispersion 3 was dried to isolate the resin component. The resin component had a glass transfer temperature Tg of 107.degree. C., number-averaged molecular weight of 320,000, and weight-average molecular weight of 2,100,000.
Fine Particle Dispersion 4 had a weight-averaged particle diameter of 40 nm when measured with a size distribution analyzer LA-920 (Horiba, Ltd.). Part of Fine Particle Dispersion 4 was dried to isolate the resin component. The resin component had a glass transfer temperature Tg of 79.degree. C., number-averaged molecular weight of 300,000, and weight-average molecular weight of 3,000,000.
The coating liquid was coated on an aluminum substrate of 90 mm in diameter by 392 mm in length, and dried at 130.degree. C. for 120 minutes, to form an undercoat layer in 3.5 .mu.m thick.
Then, 10 parts of bisazo pigment was added to the silution, and was subjected to dispersion by means of a ball moll; then 210 parts of cyclohexane was added and further subjected to dispersion for 3 hours. The liquid was recovered in a vessel and diluted by cyclohexane to a solid content of 1.5% by weight. The resulting coating liquid for charge generating layer was coated on the intermediate layer, and dried at 130.degree. C. for 20 minutes to form a charge generating layer of 0.2 .mu.m thick.
Then, 10 parts of bisphenol Z type polycarbonate resin and 0.002 part of silicone oil (KF-50, by Shin-Etsu Chemical Co. Ltd.) were dissolved into 100 parts of tetrahydrofuran, then 10 parts of charge transporting substance, having formula (2) shown below, was added to the solution to prepare a coating liquid for charge transporting layer. The resulting coating liquid for charge transporting layer was coated on the charge generating layer by dip coating, and was dried at 110.degree. C. for 20 minutes to form a charge transporting layer of 20 .mu.m thick.
The coating liquid for protective layer was coated 3 times on the charge transporting layer through spray coating by means of a spray gun (Peacecon PC308, by Olinpos Co., 2 kg/cm.sup.2 of air pressure) and drying at 30.degree. C. for 60 minutes to form a protective layer of about 5 .mu.m thick, thereby Photoconductor 1 was prepared.
Using a developer formed from 5% by weight of above noted Toner and 95% by weight of Cu--Zn ferrite carrier coated with silicone resin and having an average particle size of 40 .mu.m, and adjusting the charger voltage such that voltage at non-exposed portions (VD) was -700V, then running tests were respectively carried out such that 50000 sheets of A4 size were printed by writing in 600 dpi and 5% of image area ratio at 35.degree. C. and 90% relative humidity; after and before the respective running test, a test pattern for evaluating abnormal was outputted, then abnormal images such as decrease of resolution, voids of halftone, and thickening of narrow lines were evaluated. Further, the decrease of film thickness was determined after the running test.
(b) Similar evaluations with (a) were conducted at the condition of 25.degree. C. and 45% relative humidity. The results were shown in Table 1
TABLE-US-00001 TABLE 1 Running Evaluation of Abration Toner Photoconductor Condition Abnormal Images Wear (.mu.m) Ex. 1 Toner 1 Photoconductor 1 35.degree. C. 90% Good, no problem 2.0 Ex. 2 Toner 1 Photoconductor 2 35.degree. C. 90% Good, no problem 2.2 Ex. 3 Toner 1 Photoconductor 1 25.degree. C. 45% Good, no problem 1.8 Ex. 4 Toner 1 Photoconductor 2 25.degree. C. 45% Good, no problem 1.8 Ex. 5 Toner 2 Photoconductor 1 35.degree. C. 90% Good, no problem 2.1 Ex. 6 Toner 2 Photoconductor 2 35.degree. C. 90% Good, no problem 1.9 Ex. 7 Toner 2 Photoconductor 1 25.degree. C. 45% Good, no problem 1.8 Ex. 8 Toner 2 Photoconductor 2 25.degree. C. 45% Good, no problem 1.9 Comp. Toner 1 Comp. 35.degree. C. 90% Decrease of resolution 3.1 Ex. 1 Photoconductor 1 Thickening of narrow lines Comp. Toner 1 Comp. 25.degree. C. 45% Decrease of resolution 2.9 Ex. 2 Photoconductor 1 Thickening of narrow lines Voids of halftone Comp. Toner 2 Comp. 35.degree. C. 90% Some decrease of resolution 1.8 Ex. 3 Photoconductor 2 Slight thickening of narrow lines Comp. Toner 2 Comp. 25.degree. C. 45% Some decrease of resolution 1.6 Ex. 4 Photoconductor 2 Slight thickening of narrow lines Comp. Comp. Photoconductor 1 35.degree. C. 90% Filming 1.4 Ex. 5 Toner 1 Deposition of contaminant Comp. Comp. Photoconductor 1 25.degree. C. 45% Filming 1.6 Ex. 6 Toner 1 Deposition of contaminant
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