JP2006010917A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tandem system image forming apparatus and image forming method by which occurrence of a dash mark liable to occur in formation of a large number of color images is suppressed and lowering of image density and occurrence of image defects such as color difference are prevented, whereby color images having good sharpness and bright hue are reproduced. <P>SOLUTION: In the image forming apparatus in which color toner images formed on an organophotoreceptor with different color toners in a plurality of respective image forming units are sequentially transferred in piles onto a recording material to form a color toner image and this color toner image is fused to form a color image, a surface layer of the organophotoreceptor contains a polycarbonate having a structural unit represented by a general formula (1) and an antioxidant. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus used as a color copying machine or a color printer, and an image forming method using the image forming apparatus.

  Conventionally, as one of color image forming methods, a color toner image is formed on a separate electrophotographic photosensitive member (hereinafter also simply referred to as a photosensitive member) for each color, which is referred to as a tandem method, and these color toner images are recorded. An image forming apparatus that overlaps a material is known (Patent Document 1).

  However, this tandem method forms an electrostatic latent image on a separate photoconductor based on color-separated image information, that is, image information corresponding to each color of yellow, magenta, cyan, and black. Yellow, magenta, cyan, and black color toner images corresponding to the respective colors are formed on the electrostatic latent image, and these toner images are superimposed on a recording material to form a color image. This tandem color image forming apparatus forms a color image by superimposing toner images of different hues formed by a plurality of image forming units on a recording material, so that an electrophotographic system capable of forming a high-speed color image is used. An image forming apparatus can be developed.

  However, since this tandem system uses a separate photoconductor for each color toner image, image defects and color misregistration are likely to occur if the performance of each photoconductor is not stable.

On the other hand, a technique for forming a fine dot image by forming a fine latent image on an electrophotographic photosensitive member using an exposure light source such as a laser with a small spot diameter has been developed to improve the color image quality. Yes. For example, a method of forming a high-definition latent image on an electrophotographic photosensitive member using a light source having a spot diameter of 4000 μm ² or less is known (Patent Document 2). When such a small-diameter spot exposure method is used for the above-described tandem color image formation, it is important that the performance of the photoreceptor corresponding to the four colors described above is stable.

  In recent years, organic photoconductors are widely used as electrophotographic photoconductors in recent years because of the ease of color sensitivity to image exposure light sources and the variety of responses to environmental problems.

  When an organic photoreceptor (hereinafter simply referred to as a photoreceptor) is applied to the tandem image forming apparatus, the following problems occur.

  In other words, organic photoreceptors are subject to wear deterioration and repeated adhesion of foreign matter to the surface (adhesion of toner components and paper dust components), resulting in changes in toner developability and transferability, resulting in low image density and color misregistration. Image defects such as (a large change in chromaticity) are likely to occur.

  In particular, in a tandem type image forming apparatus, the difference in film thickness wear and the amount of foreign matter adhered between the photoconductors of each image forming unit is large, and there is a large difference in toner developability, transferability, etc. between the photoconductors. And the problem that the chromaticity of the color image is not stable has occurred.

  In order to reduce the difference in film thickness wear of the organic photoreceptor, a polycarbonate resin having a high wear resistance for the binder of the charge transport layer, that is, a polycarbonate resin having a central carbon atom as a cyclohexylene group (polycarbonate Z (also simply referred to as BPZ). Has been proposed (Patent Document 3).

  However, when the wear resistance of the organic photoreceptor is improved by using the binder, the wear resistance is improved, but the surface of the photoreceptor is easily contaminated with the external additive component of the toner. Small streak images), toner image transfer also changes, and color misregistration easily occurs.

  As a technique for improving the same wear resistance, a photoconductor using an ether-bonded polycarbonate resin in which the central carbon atom of bisphenol A is replaced with an oxygen atom has been proposed (Patent Document 4).

  However, the photoconductor using the ether-bonded polycarbonate resin cannot solve the problem of dash mark generation and color misregistration during repeated use.

Also, in recent electrophotographic image forming apparatuses, there is a tendency to be used as information equipment for printing out image information produced by a computer, and there are copying machines and printers capable of forming high-quality digital images. It has been demanded. Therefore, there is a need for developing means for faithfully developing the electrostatic latent image formed on the organic photoreceptor, and as one of the means, developing means is used for developing polymerized toner having a uniform shape factor and particle size distribution. (Patent Document 5). However, such a polymerized toner has strong adhesion to the above-mentioned organic photoreceptor and cleaning properties are likely to deteriorate. Therefore, in order to improve this, an inorganic external additive such as silica is added to the toner for practical use. . Therefore, these silica and the like are attached to the organic photoconductor to increase the occurrence of the above-mentioned dash marks and color shifts, and the characteristics of the polymerized toner improved by the shape factor and the particle size distribution are not sufficiently exhibited. The problem was found.
JP 2001-222129 A JP-A-8-272197 Japanese Patent Application Laid-Open No. 60-172044 JP-A-6-51544 JP 2000-214629 A

  The object of the present invention is to solve the above problems. That is, an object of the present invention is to provide a good color electrophotographic image using a tandem type image forming apparatus, and particularly to improve the generation of a dash mark that has occurred in the formation of a large number of color images. Another object of the present invention is to provide a tandem type image forming apparatus and an image forming method for preventing the occurrence of image defects such as a decrease in image density and color misregistration, and reproducing a color image with good sharpness and a vivid hue.

  As a result of detailed studies on the above problems, the present inventors have found that in a tandem image forming apparatus, the difference in film thickness wear and the amount of foreign matter adhered between the photoreceptors of each image forming unit is reduced, and toner development is performed. In order to reduce the difference in the transferability, transferability, etc., it is important to reduce the change in toner developability and transferability between the initial use of the photoconductor and after repeated use. The present invention has found that it is important to use a resin that improves wear resistance for the charge transport layer that forms the surface layer of the body, and to make it difficult for toner components and fat powder to adhere to the surface of the photoreceptor. completed. That is, by using a photoconductor having a charge transport layer in which a binder resin having an ether bond and an antioxidant coexist as a surface layer, it is possible to simultaneously solve wear resistance and adhesion of foreign matter, and uniform shape factor, particle size distribution, etc. It has been found that even when an electrophotographic image is formed using a toner that has been converted into a toner, the occurrence of a dash mark and the change in transferability of toner from a photoreceptor to a recording material can be reduced, and the present invention has been completed.

That is, the object of the present invention is achieved by adopting one of the following configurations.
(Claim 1)
A plurality of image forming units having at least an organic photosensitive member, a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit are arranged and arranged on the organic photosensitive unit using toner having a different color for each of the plurality of image forming units. In the image forming apparatus for forming the color toner image by fixing each color toner image formed on the recording material in sequence on the recording material to form a color toner image and fixing the color toner image, the surface of the organic photoreceptor An image forming apparatus, wherein the layer contains a polycarbonate having a structural unit represented by the following general formula (1) and an antioxidant.

(In the formula, X represents an oxygen atom or a sulfur atom, and R _{1 to} R ₈ represent a hydrogen atom, a halogen atom, a hydroxyl group, or an alkyl group having 1 to 4 carbon atoms.)
(Claim 2)
An image forming unit having at least an organic photoreceptor, a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit is arranged in four sets for black, yellow, magenta, and cyan, and the four sets of image formation are provided. Each color toner image formed on the organic photoconductor using toner having different colors for each unit is sequentially superimposed on the recording material and transferred to form a color toner image, and the color toner image is fixed to form a color image. The image forming apparatus according to claim 1, wherein the surface layer of the organic photoreceptor contains a polycarbonate having a structural unit represented by the general formula (1) and an antioxidant.
(Claim 3)
The image forming apparatus according to claim 1, wherein the polycarbonate contains a copolymer polycarbonate having a structural unit represented by the general formula (1) and the following general formula (2).

(In the formula, A represents a linear, branched or cyclic alkylidene group, aryl-substituted alkylidene group and arylene group having 1 to 10 carbon atoms, and R _{9 to} R ₁₆ represent a hydrogen atom, a halogen atom, a hydroxyl group or a carbon atom. Represents an alkyl group of formulas 1 to 4.)
(Claim 4)
The image forming apparatus according to claim 1, wherein the antioxidant is a compound having a hindered phenol group.
(Claim 5)
The image forming apparatus according to claim 1, wherein the antioxidant is a compound having a hindered amine group.
(Claim 6)
6. The organic photoreceptor has a structure in which a charge transport layer is laminated on at least a charge generation layer on a conductive support, and the charge transport layer constitutes a surface layer. The image forming apparatus according to any one of the above.
(Claim 7)
The image forming apparatus according to claim 6, wherein the organic photoreceptor has an intermediate layer containing N-type semiconductive particles between the conductive support and the charge generation layer.
(Claim 8)
The image forming apparatus according to claim 7, wherein the N-type semiconductor particles are a metal oxide.
(Claim 9)
The image forming apparatus according to claim 8, wherein the N-type semiconductor particles are titanium oxide or zinc oxide.
(Claim 10)
The image forming apparatus according to claim 9, wherein the N-type semiconductor particles are titanium oxide.
(Claim 11)
The image forming apparatus according to claim 10, wherein the titanium oxide is anatase titanium oxide or rutile titanium oxide.
(Claim 12)
The image forming apparatus according to claim 7, wherein the N-type semiconductor particles are subjected to a surface treatment.
(Claim 13)
The image forming apparatus according to claim 7, wherein the intermediate layer contains a binder of polyamide resin.
(Claim 14)
The image forming apparatus according to claim 13, wherein the polyamide resin is a polyamide resin having a heat of fusion of 0 to 40 J / g and a water absorption of 5% by mass or less.
(Claim 15)
A plurality of image forming units having at least an organic photosensitive member, a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit are arranged and arranged on the organic photosensitive unit using toner having a different color for each of the plurality of image forming units. In the image forming apparatus for forming a color image by fixing the color toner image by sequentially superimposing and transferring the color toner images formed on the recording material to form a color toner image, the organic photoreceptor comprises: The toner having a surface layer containing a polycarbonate having a structural unit represented by the general formula (1) and an antioxidant, wherein the developing means has a shape factor of 1.2 to 1.6. An image forming apparatus comprising a toner of a number% or more.
(Claim 16)
A plurality of image forming units having at least an organic photosensitive member, a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit are arranged and arranged on the organic photosensitive unit using toner having a different color for each of the plurality of image forming units. In the image forming apparatus for forming a color image by fixing the color toner image by sequentially superimposing and transferring the color toner images formed on the recording material to form a color toner image, the organic photoreceptor comprises: It has a surface layer containing an antioxidant and a polycarbonate having the structural unit represented by the general formula (1), and the developing means contains a toner having 50% by number or more of toner particles without corners. An image forming apparatus.
(Claim 17)
A plurality of image forming units having at least an organic photosensitive member, a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit are arranged and arranged on the organic photosensitive unit using toner having a different color for each of the plurality of image forming units. In the image forming apparatus for forming a color image by fixing the color toner image by sequentially superimposing and transferring the color toner images formed on the recording material to form a color toner image, the organic photoreceptor comprises: Natural logarithm lnD, having a surface layer containing a polycarbonate having the structural unit represented by the general formula (1) and an antioxidant, and the developing means having a particle size of toner particles as D (μm) the horizontal axis, relative frequency of toner particles included in the most frequent class in the histogram showing a particle size distribution of number-based divided the horizontal axis into a plurality of classes at 0.23 intervals (m ₁₎ An image forming apparatus, wherein the sum of the relative frequency of toner particles included in the next higher frequency of class modal class (m ₂₎ (M) contains a toner is 70% or more.
(Claim 18)
A plurality of image forming units having at least an organic photosensitive member, a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit are arranged and arranged on the organic photosensitive unit using toner having a different color for each of the plurality of image forming units. In the image forming apparatus for forming a color image by fixing the color toner image by sequentially superimposing and transferring the color toner images formed on the recording material to form a color toner image, the organic photoreceptor comprises: A surface layer containing a polycarbonate having a structural unit represented by the general formula (1) and an antioxidant, wherein the developing means has a variation coefficient of a shape factor of toner particles of 16% or less, An image forming apparatus comprising a toner having a number variation coefficient of 27% or less.
(Claim 19)
An image forming method comprising forming an electrophotographic image using at least the image forming apparatus according to claim 1.

  By using the present invention, when forming a color image with a tandem type image forming apparatus, the difference in film thickness wear and the amount of foreign matter adhered between the photoconductors is reduced to reduce image density and color misregistration. It is an object of the present invention to provide an electrophotographic image forming apparatus and an image forming method that prevent the occurrence of image defects such as the above and reproduce a color image having a good sharpness and a vivid hue.

  The image forming apparatus of the present invention is provided with a plurality of image forming units having at least an organic photosensitive member, a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit, and the plurality of image forming units have different colors. An image forming apparatus for forming a color toner image by fixing each color toner image formed on an organic photoreceptor using toner in sequence on a recording material to form a color toner image and fixing the color toner image The surface layer of the organic photoreceptor contains a polycarbonate having a structural unit represented by the general formula (1) and an antioxidant.

  Further, the image forming apparatus of the present invention has an image forming unit having at least an organic photoreceptor, a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit, arranged in four groups for black, yellow, magenta, and cyan. Each color image formed on the organic photoreceptor using toner having different colors for each of the four image forming units is sequentially superimposed on the recording material and transferred to form a color toner image. In the image forming apparatus for fixing the color toner image to form a color image, the surface layer of the organophotoreceptor contains a polycarbonate having a structural unit represented by the general formula (1) and an antioxidant. Features.

  Since the image forming apparatus of the present invention has the above-described configuration, the difference in toner developability, transferability, etc. generated between the photoreceptors of each image forming unit used in the tandem image forming apparatus is reduced, and the image is formed. The occurrence of image defects such as density reduction and color misregistration can be prevented, and a color image having a clear and vivid hue can be provided.

  The configuration of the image forming apparatus of the present invention will be described below.

  The surface layer of the organophotoreceptor of the present invention contains a polycarbonate having a structural unit represented by the general formula (1) and an antioxidant.

  The polycarbonate having the structural unit represented by the general formula (1) may be a polycarbonate having a chemical structure with the same repeating unit structure, but more preferably the structures of the general formula (1) and the general formula (2). More preferred are copolymer polycarbonates having units. Hereinafter, polycarbonates preferably used in the present invention are exemplified, but the present invention is not limited to polycarbonates having these exemplified structures.

  Among the copolymer polycarbonates having the structural units of the general formula (1) and the general formula (2), a copolymer polycarbonate containing 30 to 70 mol% of the structural unit of the general formula (1) in the entire structure is preferable. More preferred is a copolymer polycarbonate containing 50 to 70 mol%.

  The polycarbonate resin used in the present invention can be obtained by a general polycarbonate synthesis method such as a phosgene method using a diol compound having each structural unit.

  The molecular weight of the polycarbonate of the present invention is preferably a viscosity average molecular weight (Mv) in the range of 10,000 to 150,000, particularly 15 in consideration of the dash mark resistance and abrasion resistance. , Preferably in the range of 100,000 to 100,000.

  The antioxidant of the present invention is a substance having the property of preventing or suppressing the action of oxygen under conditions of light, heat, discharge, etc., against an auto-oxidizing substance present in the photoreceptor or on the photoreceptor surface. However, when used in combination with the polycarbonate having the structural unit represented by the general formula (1) of the present invention, it is possible to prevent the occurrence of the dash mark described above, and to reduce the change in transfer of toner from the photoreceptor to the recording material. Has the effect of

  In the present invention, as an antioxidant that is particularly preferably used, a hindered phenol-based or hindered amine-based antioxidant is preferable. Two or more of these may be used in combination, and the molecule may contain the above structural unit, for example, a hindered phenol structural unit and a hindered amine structural unit.

  When these antioxidants and the polycarbonate having the structural unit represented by the general formula (1) are used in combination to form a surface layer, the adhesion of toner components such as silica to the surface layer is reduced. It seems that the occurrence and the change in transfer of toner from the photoreceptor to the recording material are reduced.

  The content of the hindered phenol-based or hindered amine-based antioxidant in the surface layer is preferably 0.01 to 20% by mass. If it is less than 0.01% by mass, the effect of preventing the generation of dash marks and color shift is small, and if the content is more than 20% by mass, the charge transporting ability in the surface layer is lowered, and the residual potential is likely to increase. Concentration tends to decrease.

  Here, hindered phenol refers to compounds having a branched alkyl group at the ortho position relative to the hydroxyl group of the phenol compound and derivatives thereof (however, the hydroxyl group may be converted to alkoxy).

  The hindered amine system is a compound having a bulky organic group near the N atom. The bulky organic group includes a branched alkyl group, for example, a t-butyl group is preferable. For example, compounds having an organic group represented by the following structural formula are preferred.

In the formula, R ₁₃ represents a hydrogen atom or a monovalent organic group, R ₁₄ , R ₁₅ , R ₁₆ and R ₁₇ represent an alkyl group, and R ₁₈ represents a hydrogen atom, a hydroxyl group or a monovalent organic group.

  Examples of the antioxidant having a hindered phenol partial structure include compounds described in JP-A-1-118137 (P7 to P14), but the present invention is not limited thereto.

  Examples of the antioxidant having a hindered amine partial structure include compounds described in JP-A-1-118138 (P7 to P9), but the present invention is not limited thereto.

  As an organic phosphorus compound, there exist the following as a typical thing with the compound represented by general formula: RO-P (OR) -OR, for example. Here, R represents a hydrogen atom, each substituted or unsubstituted alkyl group, alkenyl group or aryl group.

  As an organic sulfur type compound, there exist the following as a typical thing with the compound represented by general formula: R-S-R, for example. Here, R represents a hydrogen atom, each substituted or unsubstituted alkyl group, alkenyl group or aryl group.

  The following are examples of typical antioxidant compounds.

  Next, a structure in which the surface layer of the photosensitive layer is a charge transport layer and the polycarbonate and the antioxidant of the present invention are used for the charge transport layer will be described.

  When using the said polycarbonate resin for a charge transport layer, the ratio of the said binder resin which occupies in a charge transport layer is 20-80 mass%, Preferably it is 30-60 mass%. In the charge transport layer, in addition to the above polycarbonate copolymer, for example, polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate A resin, a silicone resin, a melamine resin, and a copolymer resin containing two or more of the repeating unit structures of these resins may be used in combination.

  In the charge transport layer, a compound represented by the following general formula (3) is preferably used as a carrier transport material as a charge transport material.

[Wherein Ar ₅ , Ar ₆ and Ar ₇ represent a substituted or unsubstituted aromatic hydrocarbon or heterocyclic group, and R ₃ represents a hydrogen atom or a substituted or unsubstituted aromatic hydrocarbon group or heterocyclic group. Represents. n is 2 or 3. ]
The charge transport material of the general formula (3) has good compatibility with the polycarbonate having the structural unit of the general formula (1) described above. By using these charge transport material and the polycarbonate together, micro phase separation is achieved. Forms a charge transport layer that is uniform and difficult to adhere to foreign matter, prevents the occurrence of dashes and scratches, prevents transferability of toner to the recording material, and forms stable and good color images be able to.

  Specific examples of the compound of the general formula (3) are listed below, but the present invention is not limited to the specific examples.

Among the general formula (3), Ar ₅ is preferably a phenyl group having a methyl group as a substituent, Ar ₆ is preferably an unsubstituted phenylene group, Ar ₇ is a substituted or unsubstituted phenyl group, R ₃ is preferably a phenyl group, particularly a phenyl group having a methyl group as a substituent.

  Further, among the compounds of the general formula (3), the compound having n = 2 is particularly excellent in compatibility with the polycarbonate of the present invention, and the effects of the present invention can be achieved remarkably.

  In addition to the charge transport material represented by the general formula (3), the charge transport layer may include other charge transport materials (CTM) such as triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine compounds, and butadiene compounds. Can be used. In the combined use of these charge transport materials, the main charge transport material is preferably represented by the general formula (3).

  The mass ratio of the binder resin using the polycarbonate in the charge transport layer and the charge transport material is preferably 30 to 200 parts by mass, more preferably 50 to 150 parts by mass with respect to 100 parts by mass of the binder.

  The thickness of the charge transport layer is preferably 10 to 40 μm. If the film thickness is less than 10 μm, deterioration of the halftone image tends to appear, and if it exceeds 40 μm, the residual power rises easily and sharpness tends to deteriorate.

  Further, the charge transport layer may be composed of two layers, and the polycarbonate of the present invention may be used for the charge transport layer serving as the surface layer.

  Next, the layer structure of the organic photoreceptor having the above surface layer will be described.

  The organic photoconductor of the present invention means an electrophotographic photoconductor constituted by giving an organic compound at least one of a charge generation function and a charge transport function indispensable for the constitution of the electrophotographic photoconductor. It contains all known organic electrophotographic photoreceptors such as a photoreceptor composed of an organic charge generating material or an organic charge transport material, a photoreceptor composed of a polymer complex with a charge generating function and a charge transport function.

  The constitution of the organic photoreceptor used in the present invention is described below.

Conductive Support The conductive support used for the photoreceptor may be either a sheet or a cylinder, but a cylindrical conductive support is preferred for designing an image forming apparatus compactly. .

  Cylindrical conductive support means a cylindrical support necessary for forming an endless image by rotating. Conductivity is within a range of 0.1 mm or less in straightness and 0.1 mm or less in deflection. A support is preferred. Exceeding the range of straightness and shake makes it difficult to form a good image.

As the conductive material, a metal drum such as aluminum or nickel, a plastic drum deposited with aluminum, tin oxide, indium oxide or the like, or a paper / plastic drum coated with a conductive substance can be used. The conductive support preferably has a specific resistance of 10 ³ Ωcm or less at room temperature. The conductive support of the present invention is most preferably an aluminum support. As the aluminum support, one in which components such as manganese, zinc, magnesium and the like are mixed in addition to the main component aluminum is also used.

Intermediate layer In the present invention, an intermediate layer is preferably provided between the conductive support and the photosensitive layer.

  The intermediate layer used in the present invention preferably contains N-type semiconductor particles. The N-type semiconductive particle means a particle whose main charge carrier is an electron. That is, since the main charge carriers are electrons, the intermediate layer containing the N-type semiconductive particles in the insulating binder effectively blocks hole injection from the substrate, and the electrons from the photosensitive layer. In contrast, it has a property of low blocking.

  Here, a method for discriminating N-type semiconductor particles will be described.

  An intermediate layer having a thickness of 5 μm is formed on the conductive support (the intermediate layer is formed using a dispersion in which 50% by mass of particles are dispersed in the binder resin constituting the intermediate layer). The intermediate layer is negatively charged and the light attenuation characteristics are evaluated. In addition, the light attenuation characteristics are similarly evaluated by charging to positive polarity.

  N-type semiconductive particles are particles that are dispersed in the intermediate layer in the above evaluation when the light attenuation when charged negatively is greater than the light attenuation when charged positively. It is called semiconductive particle.

As the N-type semiconductor particles, metal oxides such as titanium oxide (TiO ₂ ) and zinc oxide (ZnO) are preferable, and titanium oxide is particularly preferably used.

  The N-type semiconductor particles are preferably fine particles having a number average primary particle size in the range of 3.0 to 200 nm. Particularly, 5 nm to 100 nm is preferable. The number average primary particle diameter is a measured value as the average diameter in the ferret direction by image analysis by magnifying fine particles 10,000 times by transmission electron microscope observation, randomly observing 100 particles as primary particles. N-type semiconducting particles having a number average primary particle size of less than 3.0 nm are difficult to uniformly disperse in the intermediate layer binder, and tend to form aggregated particles. It's easy to do. On the other hand, N-type semiconducting particles having a number average primary particle size larger than 200 nm tend to make large irregularities on the surface of the intermediate layer, and these large irregularities cause a difference in transferability of the toner to the recording material. A color shift is likely to occur in a tone image or the like. Further, the N-type semiconducting particles having a number average primary particle size of more than 200 nm are likely to precipitate in the dispersion, and aggregates are likely to be generated, which also tends to cause color shift in the halftone image.

  The titanium oxide particles include anatase, rutile, brookite, and amorphous forms as crystal forms. Among them, the anatase form titanium oxide pigment or the rutile form titanium oxide pigment has a rectifying property of charge passing through the intermediate layer. In other words, the electron mobility is increased, the charging potential is stabilized, the residual potential is prevented from increasing, and the occurrence of spots is prevented.

  N-type semiconductive particles are preferably surface-treated with a polymer containing methylhydrogensiloxane units. The molecular weight of the polymer containing the methyl hydrogen siloxane unit is 1000 to 20000, and the surface treatment effect is high. As a result, the rectifying property of the N-type semiconductor particles is improved, and the N-type semiconductor particles are contained. By using the intermediate layer, the occurrence of black spots is prevented and there is an effect in producing a good halftone image.

The polymer containing a methylhydrogensiloxane unit is preferably a copolymer of a structural unit of-(HSi (CH ₃ ) O)-and a structural unit other than this (other siloxane unit). As other siloxane units, dimethylsiloxane units, methylethylsiloxane units, methylphenylsiloxane units, diethylsiloxane units, and the like are preferable, and dimethylsiloxane is particularly preferable. The proportion of methylhydrogensiloxane units in the copolymer is 10 to 99 mol%, preferably 20 to 90 mol%.

  The methylhydrogensiloxane copolymer may be any of a random copolymer, a block copolymer, a graft copolymer, etc., but a random copolymer and a block copolymer are preferred. In addition to methylhydrogensiloxane, the copolymerization component may be one component or two or more components.

  The N-type semiconductive particles may be those that have been surface-treated with a reactive organosilicon compound represented by the following general formula (4).

General formula (4)
(R) _n -Si- (X) _4-n
(In the formula, Si represents a silicon atom, R represents an organic group in which carbon is directly bonded to the silicon atom, X represents a hydrolyzable group, and n represents an integer of 0 to 3.)
In the organosilicon compound represented by the general formula (4), the organic group in which carbon is directly bonded to the silicon represented by R includes alkyl such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl and dodecyl. Group, aryl group such as phenyl, tolyl, naphthyl, biphenyl, epoxy-containing group such as γ-glycidoxypropyl, β- (3,4-epoxycyclohexyl) ethyl, γ-acryloxypropyl, γ-methacryloxypropyl (Meth) acryloyl group, hydroxyl group such as γ-hydroxypropyl and 2,3-dihydroxypropyloxypropyl, vinyl group such as vinyl and propenyl, mercapto group such as γ-mercaptopropyl, γ-aminopropyl, Amino-containing groups such as N-β (aminoethyl) -γ-aminopropyl, γ-chloropropyl, , 1,1-tri fluoroalkyl propyl, nonafluorohexyl, halogen-containing groups such as perfluorooctylethyl, other nitro, and cyano-substituted alkyl group. Examples of the hydrolyzable group for X include alkoxy groups such as methoxy and ethoxy, halogen groups, and acyloxy groups.

  Moreover, the organosilicon compound represented by General formula (4) may be individual, and may be used in combination of 2 or more type.

  Moreover, in the specific compound of the organosilicon compound represented by the general formula (4), when n is 2 or more, a plurality of R may be the same or different. Similarly, when n is 2 or less, the plurality of Xs may be the same or different. Moreover, when using 2 or more types of organosilicon compounds represented by General formula (4), R and X may be the same between each compound, and may differ.

  Further, prior to the surface treatment of the methylhydrogensiloxane copolymer or the reactive organosilicon compound, the N-type semiconductive particles may be subjected to an inorganic surface treatment such as alumina or silica.

  In addition, although the above-mentioned treatment of alumina and silica may be performed simultaneously, it is preferable to perform the alumina treatment first and then the silica treatment. Further, the amount of treatment of alumina and silica when treating alumina and silica is preferably higher than that of alumina.

  The surface treatment of the N-type semiconductive fine particles such as titanium oxide with a metal oxide such as alumina, silica or zirconia can be performed by a wet method. For example, N-type semiconductive particles subjected to silica or alumina surface treatment can be prepared as follows.

  When titanium oxide particles are used as the N-type semiconductive particles, titanium oxide particles (number average primary particle size: 50 nm) are dispersed in water at a concentration of 50 to 350 g / L to form an aqueous slurry. Add acid salt or water-soluble aluminum compound. Thereafter, alkali or acid is added for neutralization, and silica or alumina is precipitated on the surface of the titanium oxide particles. Subsequently, filtration, washing, and drying are performed to obtain the target surface-treated titanium oxide. When sodium silicate is used as the water-soluble silicate, it can be neutralized with an acid such as sulfuric acid, nitric acid or hydrochloric acid. On the other hand, when aluminum sulfate is used as the water-soluble aluminum compound, it can be neutralized with an alkali such as sodium hydroxide or potassium hydroxide.

  The intermediate layer coating solution prepared for forming the intermediate layer used in the present invention is composed of a binder resin, a dispersion solvent and the like in addition to the N-type semiconductive particles such as the surface-treated titanium oxide.

  The ratio of the N-type semiconductive particles in the intermediate layer is preferably 0.5 to 2.0 times in terms of the volume ratio of the intermediate layer to the binder resin (when the volume of the binder resin is 1). By using the N-type semiconductor particles of the present invention at such a high density in the intermediate layer, the rectifying property of the intermediate layer is increased, and even if the film thickness is increased, no increase in residual potential and no occurrence of spots occur. An organic photoreceptor that can effectively prevent black spots and can produce a good halftone image with small potential fluctuations can be formed. Further, such an intermediate layer preferably uses 50 to 200 parts by volume of N-type semiconductive particles with respect to 100 parts by volume of the binder resin.

  On the other hand, the binder resin in which these particles are dispersed to form the layer structure of the intermediate layer is preferably a polyamide resin in order to obtain good dispersibility of the particles, but the polyamide resin shown below is particularly preferable.

  That is, a polyamide resin having a heat of fusion of 0 to 40 J / g and a water absorption of 5% by mass or less is preferable for the intermediate layer. The heat of fusion is more preferably 0 to 30 J / g, and most preferably 0 to 20 J / g. On the other hand, when the water absorption exceeds 5% by mass, the moisture content in the intermediate layer increases, the rectification property of the intermediate layer decreases, black spots tend to occur, and the halftone image tends to deteriorate. The water absorption is more preferably 4% by mass or less.

  The heat of fusion of the resin is measured by DSC (Differential Scanning Calorimetry). However, if the same measurement value as the DSC measurement value is obtained, the DSC measurement method is not particular. The heat of fusion is determined from the endothermic peak area when the DSC temperature rises.

  On the other hand, the water absorption rate of the resin is determined by mass change by the water immersion method or by the Karl Fischer method.

  The binder resin for the intermediate layer is preferably an alcohol-soluble polyamide resin. As the binder resin for the intermediate layer of the organic photoreceptor, a resin having excellent solvent solubility is required in order to form the intermediate layer with a uniform film thickness. As such an alcohol-soluble polyamide resin, a copolymerized polyamide resin or a methoxymethylated polyamide resin composed of a chemical structure with few carbon chains between amide bonds such as 6-nylon described above is known. This resin has a high water absorption rate, and the intermediate layer using such a polyamide tends to be highly environment-dependent. As a result, for example, charging characteristics and sensitivity under high temperature and high humidity and low temperature and low humidity are likely to change. Black spots are likely to occur and halftone images are likely to deteriorate.

  Alcohol-soluble polyamide resin improves the above-mentioned drawbacks and improves the disadvantages of conventional alcohol-soluble polyamide resins by giving the characteristics of heat of fusion 0-40 J / g and water absorption of 5% by mass or less. Even if the external environment changes or even if the organic photoreceptor is used continuously for a long time, a good electrophotographic image can be obtained.

  Hereinafter, the alcohol-soluble polyamide resin having a heat of fusion of 0 to 40 J / g and a water absorption of 5% by mass or less will be described.

  The alcohol-soluble polyamide resin is preferably a polyamide resin containing a repeating unit structure having 7 to 30 carbon atoms between amide bonds in an amount of 40 to 100 mol% of the entire repeating unit structure.

  Here, a repeating unit structure having 7 to 30 carbon atoms between amide bonds will be described. The repeating unit structure means an amide bond unit forming a polyamide resin. This is because a polyamide resin (type A) formed by condensation of a compound having a repeating unit structure having both an amino group and a carboxylic acid group, and a polyamide resin (type B) formed by condensation of a diamino compound and a dicarboxylic acid compound. ) In both examples.

  That is, the repeating unit structure of type A is represented by the general formula (5), and the carbon number contained in X is the carbon number of the amide bond unit in the repeating unit structure. On the other hand, the repeating unit structure of type B is represented by the general formula (6), and the number of carbon atoms contained in Y and the number of carbon atoms contained in Z are the number of carbon atoms of the amide bond unit in the repeating unit structure.

In general formula (5), R ₁ is a hydrogen atom, a substituted or unsubstituted alkyl group, X is a substituted or unsubstituted alkylene group, a group containing a divalent cycloalkane, a divalent aromatic group, and these A mixed structure is shown, and l is a natural number.

In general formula (6), R ₂ and R ₃ are each hydrogen atom, a substituted or unsubstituted alkyl group, Y and Z are each substituted or unsubstituted alkylene group, a group containing a divalent cycloalkane, divalent And m and n are natural numbers.

  As described above, the repeating unit structure having 7 to 30 carbon atoms includes a substituted or unsubstituted alkylene group, a group containing a divalent cycloalkane, a divalent aromatic group, and a chemical structure having a mixed structure thereof. Among them, a chemical structure having a group containing a divalent cycloalkane is preferable.

  The polyamide resin has 7 to 30 carbon atoms between amide bonds in the repeating unit structure, preferably 9 to 25, more preferably 11 to 20. The proportion of the repeating unit structure having 7 to 30 carbon atoms between amide bonds in the entire repeating unit structure is 40 to 100 mol%, preferably 60 to 100 mol%, more preferably 80 to 100 mol%.

  When the carbon number is less than 7, the hygroscopicity of the polyamide resin is large, the electrophotographic characteristics, particularly the humidity dependency of the potential during repeated use is large, and image defects such as black spots are likely to occur, and the halftone image is Easy to deteriorate. If it is larger than 30, the dissolution of the polyamide resin in the coating solvent becomes worse, and it is not suitable for forming a coating film of the intermediate layer.

  Further, when the ratio of the repeating unit structure having 7 to 30 carbon atoms between amide bonds to the entire repeating unit structure is smaller than 40 mol%, the above effect is reduced.

  Preferred polyamide resins of the present invention include polyamides having a repeating unit structure represented by the following general formula (7).

In General Formula (7), Y ₁ represents a group containing a divalent alkyl-substituted cycloalkane, Z ₁ represents a methylene group, m represents 1 to 3, and n represents 3 to 20.

In the general formula (7), the group containing a divalent alkyl-substituted cycloalkane of Y ₁ preferably has the following chemical structure. That is, the polyamide resin of the present invention in which Y ₁ has the following chemical structure shows an improvement effect of preventing deterioration of a halftone image due to black spots or scratches.

In the above chemical structure, A represents a single bond and an alkylene group having 1 to 4 carbon atoms, R ₄ represents a substituent, represents an alkyl group, and p represents a natural number of 1 to 5. However, the plurality of R ₄ may be the same or different.

  Specific examples of the polyamide resin include the following examples.

  In the above specific examples, “%” in parentheses indicates the ratio (mol%) of the repeating unit structure having 7 or more carbon atoms between amide bonds in the repeating unit structure.

  Among the above specific examples, N-1 to N-4 polyamide resins having a repeating unit structure of the general formula (7) are particularly preferable.

  The molecular weight of the polyamide resin is preferably 5,000 to 80,000, more preferably 10,000 to 60,000 in terms of number average molecular weight. When the number average molecular weight is 5,000 or less, the uniformity of the film thickness of the intermediate layer is deteriorated, and the effects of the present invention are not sufficiently exhibited. On the other hand, if it is larger than 80,000, the solvent solubility of the resin tends to be lowered, and an agglomerated resin is likely to be generated in the intermediate layer, so that black spots and halftone images are likely to be deteriorated.

  A part of the polyamide resin is already available on the market. For example, the polyamide resin is sold under the trade names such as Vestamelt X1010 and X4685 manufactured by Daicel Degussa Co., Ltd., and can be produced by a general synthesis method of polyamide. However, an example of a synthesis example is given below.

Synthesis of exemplified polyamide resin (N-1) 215 parts by mass of lauryl lactam, 3-aminomethyl-3,5,5-trimethylcyclohexylamine in a polymerization kettle equipped with a stirrer, nitrogen, nitrogen introduction tube, thermometer, dehydration tube, etc. 112 parts by mass, 153 parts by mass of 1,12-dodecanedicarboxylic acid and 2 parts by mass of water were mixed and reacted for 9 hours while distilling water under heating and pressure. When the polymer was taken out and the copolymer composition was determined by C ¹³ -NMR, it coincided with the composition of N-1. The melt flow index (MFI) of the synthesized copolymer was 5 g / 10 min under the condition of (230 ° C./2.16 kg).

As the solvent for dissolving the polyamide resin and preparing the coating solution, alcohols having 2 to 4 carbon atoms such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol are preferable, It is excellent in the solubility of polyamide and the coating property of the prepared coating solution. These solvents are 30 to 100% by mass, preferably 40 to 100% by mass, and more preferably 50 to 100% by mass in the total solvent. Examples of co-solvents that can be used in combination with the above-mentioned solvent to obtain preferable effects include methanol, benzyl alcohol, toluene, methylene chloride, cyclohexanone, and tetrahydrofuran.
The thickness of the intermediate layer of the present invention is preferably 0.3 to 10 μm. If the thickness of the intermediate layer is less than 0.5 μm, black spots and halftone images are likely to be deteriorated. If the thickness exceeds 10 μm, the residual potential is likely to increase and the spots are likely to be sharp and sharpness is likely to be deteriorated. As for the film thickness of an intermediate | middle layer, 0.5-5 micrometers is more preferable.

Moreover, it is preferable that the said intermediate | middle layer is an insulating layer substantially. Here, the insulating layer has a volume resistance of 1 × 10 ⁸ or more. The volume resistance of the intermediate layer and the protective layer of the present invention is preferably 1 × 10 ⁸ to 10 ¹⁵ Ω · cm, more preferably 1 × 10 ⁹ to 10 ¹⁴ Ω · cm, and further preferably 2 × 10 ⁹ to 1 ×. 10 ¹³ Ω · cm. The volume resistance can be measured as follows.

  Measurement conditions: According to JIS: C2318-1975.

Measuring instrument: Hiresta IP manufactured by Mitsubishi Yuka
Measurement conditions: Measurement probe HRS
Applied voltage: 500V
Measurement environment: 30 ± 2 ℃, 80 ± 5RH%
If the volume resistance is less than 1 × 10 ⁸ , the charge blocking property of the intermediate layer decreases, the occurrence of black spots increases, the potential holding property of the organic photoreceptor deteriorates, and good image quality cannot be obtained. On the other hand, if it is greater than 10 ¹⁵ Ω · cm, the residual potential tends to increase in repeated image formation, and good image quality cannot be obtained.

Photosensitive layer The photosensitive layer configuration of the photoreceptor of the present invention may be a single-layer photosensitive layer configuration in which the intermediate layer has a charge generation function and a charge transport function in one layer, but more preferably the function of the photosensitive layer. The charge generation layer (CGL) and the charge transport layer (CTL) may be separated from each other. By adopting a configuration in which the functions are separated, an increase in the residual potential due to repeated use can be controlled to be small, and other electrophotographic characteristics can be easily controlled according to the purpose. In the negatively charged photoconductor, it is preferable that a charge generation layer (CGL) is formed on the intermediate layer, and a charge transport layer (CTL) is formed thereon. In the positively charged photoconductor, the order of the layer configuration is the reverse of that in the negatively charged photoconductor. The most preferred photosensitive layer structure of the present invention is a negatively charged photoreceptor structure having the function separation structure.

  The structure of the photosensitive layer of the function-separated negatively charged photoreceptor will be described below.

Charge generation layer The charge generation layer contains a charge generation material (CGM). Other substances may contain a binder resin and other additives as necessary.

  A known charge generation material (CGM) can be used as the charge generation material (CGM). For example, a phthalocyanine pigment, an azo pigment, a perylene pigment, an azulenium pigment, or the like can be used. Among these, CGM which can minimize the increase in residual potential due to repeated use has a crystal structure capable of taking a stable aggregate structure among a plurality of molecules, specifically, a phthalocyanine pigment having a specific crystal structure, CGM of a perylene pigment is mentioned. For example, titanyl phthalocyanine having a maximum peak at a Bragg angle 2θ of 27.2 ° with respect to Cu—Kα rays, titanyl phthalocyanine having a remarkable diffraction peak at 7.5 ° and 28.7 ° of the same 2θ, and 12.2 of the same 2θ. CGM such as bisbenzimidazole perylene having a maximum peak at 4 is hardly deteriorated by repeated use, and the residual potential can be increased and decreased.

  When a binder is used as the CGM dispersion medium in the charge generation layer, a known resin can be used as the binder, but the most preferred resins include formal resin, butyral resin, silicone resin, silicone-modified butyral resin, phenoxy resin, and the like. Can be mentioned. The ratio of the binder resin to the charge generating material is preferably 20 to 600 parts by mass with respect to 100 parts by mass of the binder resin. By using these resins, the increase in residual potential associated with repeated use can be minimized. The thickness of the charge generation layer is preferably 0.01 μm to 1 μm. If the thickness is less than 0.01 μm, sufficient sensitivity characteristics cannot be obtained, and the residual potential tends to increase. On the other hand, even if it exceeds 1 μm, the sensitivity tends to decrease.

Charge Transport Layer The charge transport layer of the present invention is used as the charge transport layer of the present invention.

  Solvents or dispersion media used to form layers such as intermediate layers, charge generation layers, and charge transport layers include n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, acetone , Methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, dichloromethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, trichloroethylene, Tetrachloroethane, tetrahydrofuran, dioxolane, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cello Lube, and the like. Although this invention is not limited to these, Dichloromethane, 1, 2- dichloroethane, methyl ethyl ketone, etc. are used preferably. These solvents may be used alone or as a mixed solvent of two or more.

  Further, the coating solution for each layer is preferably filtered with a metal filter, a membrane filter or the like in order to remove foreign matters and aggregates in the coating solution before entering the coating step. For example, it is preferable to select a pleat type (HDC), a depth type (profile), a semi-depth type (profile star), etc., manufactured by Nippon Pole Co., Ltd. according to the characteristics of the coating solution and perform filtration.

  Next, as a coating processing method for manufacturing the organic photoreceptor, a coating processing method such as dip coating, spray coating, circular amount regulation type coating or the like is used. It is most preferable to use the circular amount regulation type coating method for the protective layer. The circular amount regulation type coating is described in detail in, for example, Japanese Patent Application Laid-Open No. 58-189061.

  In addition, the present invention employs an image forming apparatus that uses the organic photoreceptor and a toner having a uniform shape factor and a sharp particle size distribution as described below, thereby reducing the halftone image due to dash marks and scratches. It is possible to prevent the occurrence of spots and to produce a good electrophotographic image.

(1) Toner containing 65% by number or more of toner particles having a shape factor in the range of 1.2 to 1.6 The toner having such characteristics is the shape of toner particles (the toner particles mean individual particles). Is close to a true sphere and has a similar shape, the toner has uniform charging characteristics and has a property of faithfully developing a latent image on the photoreceptor. For this reason, there is a large tendency to more clearly reproduce the occurrence of dash marks due to external additives adhering to the photoreceptor, or the occurrence of spots, but toner particles having a shape factor in the range of 1.2 to 1.6 By using the toner containing 65% by number or more in combination with the above-described organic photoreceptor of the present invention, it is possible to prevent dash marks and spots, and it is possible to produce a good electrophotographic image with no noticeable color shift.

  On the other hand, when the number of toner particles having a shape factor in the range of 1.2 to 1.6 is less than 65% by number, the toner charge amount distribution becomes large, and as a result, overcharged toner particles are likely to be generated. These adhere firmly to the surface of the photoconductor and easily generate dash marks.

(2) Toner containing 50% by number or more of toner particles having no corners Toner particles having no corners are toner particles that substantially do not have protrusions that concentrate charges or that tend to be crushed by stress. When the ratio of toner particles without corners is 50% by number or more, more preferably 70% by number or more, generation of fine particles is less likely to occur due to stress with the developer conveying member and the like. Occurrence of a dash mark due to adhesion of toner to the photoreceptor can be prevented. That is, when used in combination with the photoreceptor of the present invention, it is possible to form a good electrophotographic image in which a dash mark is hardly generated and color misregistration is not noticeable over a long period of time. For this purpose, the proportion of toner particles without corners is preferably 50% by number or more, more preferably 70% by number or more.

(3) When the particle diameter of toner particles is D (μm), the horizontal axis represents the natural logarithm lnD, and the horizontal axis represents a number-based particle size distribution divided into a plurality of classes at intervals of 0.23. The sum (M) of the relative frequency (m ₁ ) of the toner particles contained in the most frequent class and the relative frequency (m ₂ ) of the toner particles contained in the next most frequent class is 70% or more. The toner contained The toner having a relative frequency (m ₁ ) and a sum (M) of the relative frequency (m ₂ ) of 70% or more makes the particle size distribution of the toner particles constituting the toner sharp, and the charging property is improved. As a result, it is possible to form a stable toner image, and as a result, by using it together with the photoconductor of the present invention, it is possible to prevent scratches, dashes and spots, and to produce a good electrophotographic image with no noticeable color shift. I can do it.

(4) Toner in which the number variation coefficient in the number particle size distribution of the toner particles is 27% or less and the variation coefficient of the toner particle shape factor is 16% or less The variation coefficient of the toner shape factor is 16% or less, and By using a toner having a number variation coefficient of 27% or less in the number particle size distribution, stable charging characteristics can be imparted to the toner. By using such a toner in combination with the above-described photoreceptor of the present invention, scratches, dash marks, and spots can be prevented, and a good electrophotographic image with no noticeable color shift can be produced. The number variation coefficient of the toner is 27% or less, preferably 25% or less. The variation coefficient of the shape factor of the toner particles is 16% or less, more preferably 14% or less.

  The toner of the present invention can be used in combination with the organic photoreceptor of the present invention as long as it satisfies at least one of the above conditions (1), (2), (3), and (4). In addition, scratches, dashes and spots can be prevented, and a good electrophotographic image can be produced. Further, among the conditions (1), (2), (3) and (4), (2) The toner satisfying at least one of the above condition (1) or (3) is more preferable, and the toner satisfying all the above conditions (1), (2), (3), and (4) is most preferable.

  The toner preferably has a number average primary particle size of 3 to 8 μm. When the toner particles are formed by a polymerization method, the particle size can be controlled by the concentration of the aggregating agent, the amount of the organic solvent added, the fusing time, and further the composition of the polymer itself.

  When the number average particle diameter is 3 to 8 μm, it is possible to reduce the presence of excessively adhering toner or low adhering toner on the developer conveying member in the fixing step, and developability over a long period of time. And the transfer efficiency is increased, the image quality of halftone is improved, and the image quality of fine lines and dots is improved.

  The shape factor of the toner is expressed by the following formula and indicates the degree of roundness of the toner particles.

Shape factor = ((maximum diameter / 2) ² × π) / projection area Here, the maximum diameter is the distance between the parallel lines when the projected image of toner particles on a plane is sandwiched between two parallel lines. The maximum particle width. The projected area refers to the area of the projected image of the toner particles on the plane.

  This shape factor is obtained by taking a photograph in which toner particles are magnified 2000 times with a scanning electron microscope, and then analyzing a photographic image using “SCANNING IMAGE ANALYZER” (manufactured by JEOL Ltd.) based on this photograph. Was measured. At this time, the shape factor of the present invention was measured by the above formula using 100 toner particles.

  In the toner of the present invention, the number of toner particles having a shape factor in the range of 1.2 to 1.6 is 65% by number or more, preferably 70% by number or more.

  The method for controlling the shape factor is not particularly limited. For example, a method in which toner particles are sprayed into a hot air stream, a method in which toner particles are repeatedly applied with mechanical energy due to impact force in a gas phase, or a method in which a toner is not dissolved in a solvent to add a swirl flow However, in the present invention, it is preferable to produce a shape factor and the like within the scope of the present invention using a polymerized toner produced by a polymerization method.

  The variation coefficient of the toner shape factor is calculated from the following equation.

Coefficient of variation = [S / K] x 100 (%)
[In the formula, S represents the standard deviation of the shape factor of 100 toner particles, and K represents the average value of the shape factor. ]
In order to control the shape factor of the toner and the coefficient of variation of the shape factor uniformly without any lot variation, the production process of the polymerized toner, that is, the step of polymerizing, fusing and controlling the shape of the resin particles (polymer particles) The proper process end time may be determined while monitoring the characteristics of the toner particles (colored particles) being formed.

  Monitoring means that a measuring device is incorporated in-line, and process conditions are controlled based on the measurement result. In other words, in the case of a polymerization method toner that is formed by incorporating measurement such as shape in-line, for example, by associating or fusing resin particles in an aqueous medium, the shape and particle size are measured while performing sequential sampling in the fusing step. The reaction is stopped when the desired shape is obtained.

  Although it does not specifically limit as a monitoring method, The flow type particle image analyzer FPIA-2000 (made by Toa Medical Electronics Co., Ltd.) can be used. This apparatus is suitable because the shape can be monitored by performing image processing in real time while passing the sample liquid. That is, a pump or the like is used from the reaction field and is constantly monitored to measure the shape and the like, and the reaction is stopped when the desired shape is obtained.

  The number particle size distribution and the number variation coefficient of the toner are measured by a Coulter Counter TA-II or Coulter Multisizer (manufactured by Coulter Inc.). In the present invention, a Coulter Multisizer is used, and an interface (manufactured by Nikkaki Co., Ltd.) that outputs a particle size distribution and a personal computer are connected. The aperture used in the Coulter Multisizer was 100 μm, and the volume and number of toners of 2 μm or more were measured to calculate the particle size distribution and average particle size. The number particle size distribution represents the relative frequency of the toner particles with respect to the particle size, and the number average particle size represents the median diameter in the number particle size distribution.

  The number variation coefficient in the toner number particle size distribution is calculated from the following equation.

Number variation coefficient = [S / Dn] × 100 (%)
[In the formula, S represents the standard deviation in the number particle size distribution, and Dn represents the number average particle size (μm). ]
The method for controlling the number variation coefficient is not particularly limited. For example, a method of classifying toner particles by wind force can be used, but classification in a liquid is effective for reducing the number variation coefficient. As a method of classifying in this liquid, there is a method of separating and collecting toner particles according to a difference in sedimentation speed caused by a difference in toner particle diameter by using a centrifuge and controlling the rotation speed.

  In particular, when a toner is produced by a suspension polymerization method, a classification operation is indispensable in order to make the number variation coefficient in the number particle size distribution 27% or less. In the suspension polymerization method, it is necessary to disperse a polymerizable monomer in an oil droplet having a desired size as a toner in an aqueous medium before polymerization. That is, mechanical shearing with a homomixer or homogenizer is repeated for large oil droplets of a polymerizable monomer to reduce the oil droplets to the size of toner particles. In the method using shearing, the number particle size distribution of the obtained oil droplets is wide, and therefore the particle size distribution of the toner obtained by polymerizing the oil droplets is also wide. For this reason, classification operation is essential.

  The toner particles having no corners are toner particles that substantially do not have protrusions that concentrate charges or protrusions that easily wear due to stress. That is, as shown in FIG. When the major axis of the particle T is L, a circle C having a radius (L / 10) is rolled into the toner T when the inner side is rolled in contact with the peripheral line of the toner particle T at one point. The case where the toner particles do not substantially protrude outside is referred to as “toner particles having no corners”. “A case where the protrusion does not substantially protrude” refers to a case where the protrusion having the protruding circle is one or less. The “major diameter of toner particles” refers to the width of a particle that maximizes the interval between the parallel lines when the projected image of the toner particles on a plane is sandwiched between two parallel lines. 2B and 2C show projection images of toner particles having corners, respectively.

  The measurement of toner without corners was performed as follows. First, an enlarged photograph of the toner particles is taken with a scanning electron microscope, and further enlarged to obtain a 15,000 times photographic image. The photographic image is then measured for the presence or absence of the corners. This measurement was performed on 100 toner particles.

  A method for obtaining toner having no corners is not particularly limited. For example, as described above as a method for controlling the shape factor, a method in which toner particles are sprayed into a hot air stream, a method in which toner particles are repeatedly applied with mechanical energy by impact force in a gas phase, or a toner is dissolved. It can be obtained by adding in a solvent that does not, and applying a swirling flow. However, in consideration of production cost and energy cost, a polymerized toner by a polymerization method is preferable.

  For example, in a polymerization toner formed by associating or fusing resin particles, the fusing particle surface has many irregularities at the fusing stop stage, and the surface is not smooth, but the temperature in the shape control step, By making the conditions such as the number of revolutions of the stirring blade and the stirring time appropriate, a toner having no corners can be obtained. These conditions vary depending on the physical properties of the resin particles. For example, by setting the rotational speed to be higher than the glass transition temperature of the resin particles, the toner can be formed with a smooth surface and no corners.

  The toner of the present invention preferably has a number average particle diameter of 3 to 8 μm. When the toner particles are formed by a polymerization method, the particle size can be controlled by the concentration of the aggregating agent, the amount of the organic solvent added, the fusing time, and further the composition of the polymer itself.

As the polymerized toner preferably used in the present invention, when the particle diameter of the toner particle is D (μm), the natural logarithm lnD is taken on the horizontal axis, and the horizontal axis is divided into a plurality of classes at intervals of 0.23. In the histogram showing the particle size distribution, the relative frequency (m ₁ ) of the toner particles included in the most frequent class and the relative frequency (m ₂ ) of the toner particles included in the most frequent class after the most frequent class. A toner having a sum (M) of 70% or more is preferable.

When the sum (M) of the relative frequency (m ₁ ) and the relative frequency (m ₂ ) is 70% or more, the dispersion of the particle size distribution of the toner particles is narrowed, so that the toner is used in the image forming process. The occurrence of selective development can be reliably suppressed.

  In the present invention, the histogram showing the particle size distribution based on the number is a natural logarithm lnD (D: particle size of individual toner particles) having a plurality of classes (0 to 0.23: 0.23) at intervals of 0.23. 0.46: 0.46-0.69: 0.69-0.92: 0.92-1.15: 1.15-1.38: 1.38-1.61: 1.61-1. 84: 1.84 to 2.07: 2.07 to 2.30: 2.30 to 2.53: 2.53 to 2.76, and so on). This histogram is prepared by transferring the particle size data of a sample measured by a Coulter Multisizer to a computer via an I / O unit according to the following conditions and using the particle size distribution analysis program in the computer. is there.

〔Measurement condition〕
(1) Aperture: 100 μm
(2) Sample preparation method: Electrolyte [ISOTON R-11 (manufactured by Coulter Scientific Japan)] 50-100 ml, an appropriate amount of a surfactant (neutral detergent) was added and stirred, and a measurement sample 10-20 mg was added thereto. Add This system is prepared by dispersing for 1 minute with an ultrasonic disperser.

The method for controlling the shape factor and the like of the present invention is preferable in that the polymerized toner is simple as a production method and the characteristics are easily controlled as compared with the pulverized toner.
The term “polymerized toner” means a toner in which a toner binder resin is formed and the toner shape is formed by polymerization of a raw material monomer of the binder resin and, if necessary, subsequent chemical treatment. More specifically, it means a toner formed through a polymerization reaction such as suspension polymerization or emulsion polymerization, and if necessary, a step of fusing particles between them.
Since the polymerized toner is produced by uniformly dispersing the raw material monomers in an aqueous system and then producing the toner, a toner having a uniform toner particle size distribution and shape can be obtained.

  The polymerized toner is produced by emulsion polymerization of monomers in a suspension polymerization method or in a solution to which an emulsion of necessary additives is added to produce fine polymer particles, and then an organic solvent, an aggregating agent, etc. It can manufacture by the method of adding and associating. A method of preparing by mixing with a dispersion liquid such as a release agent or a colorant necessary for the composition of the toner at the time of association, or a toner component such as a release agent or a colorant is dispersed in the monomer And a method of emulsion polymerization. Here, the association means that a plurality of resin particles and colorant particles are fused.

  That is, various constituent materials such as a colorant and, if necessary, a release agent, a charge control agent, and a polymerization initiator are added to the polymerizable monomer, and a homogenizer, a sand mill, a sand grinder, an ultrasonic disperser, etc. Various constituent materials are dissolved or dispersed in the polymerizable monomer. The polymerizable monomer in which these various constituent materials are dissolved or dispersed is dispersed in oil droplets having a desired size as a toner in an aqueous medium containing a dispersion stabilizer using a homomixer or a homogenizer. Thereafter, the stirring mechanism is transferred to a reaction apparatus which is a stirring blade described later, and the polymerization reaction is advanced by heating. After completion of the reaction, the dispersion stabilizer is removed, filtered, washed, and dried to prepare a toner.

  Further, as a method for producing the toner of the present invention, a method of preparing by associating or fusing resin particles in an aqueous medium can also be mentioned. The method is not particularly limited, and examples thereof include methods disclosed in JP-A-5-265252, JP-A-6-329947, and JP-A-9-15904. That is, a method of associating a plurality of fine particles composed of resin particles and colorants, etc., or particles composed of resin and colorant, in particular, after dispersing them in water using an emulsifier, the critical aggregation concentration The above flocculant is added for salting out, and at the same time, the formed polymer itself is heated and fused at a temperature higher than the glass transition temperature to gradually grow the particle size while forming fused particles. Then, a large amount of water is added to stop the particle size growth, and the shape is controlled by smoothing the particle surface while heating and stirring, and the particles are heated and dried in a fluidized state while containing water, whereby toner Can be formed. Here, an organic solvent that is infinitely soluble in water may be added simultaneously with the flocculant.

Note that materials and manufacturing methods for producing a uniform toner such as a shape factor used in the present invention, a polymerization toner reaction device, and the like are described in detail in JP-A-2000-214629.
<Developer>
The toner used in the present invention may be a one-component developer or a two-component developer, but is preferably a two-component developer.

  When used as a one-component developer, there is a method in which the toner is used as it is as a non-magnetic one-component developer. Usually, however, the toner particles contain about 0.1 to 5 μm of magnetic particles as a magnetic one-component developer. Use. As a method for its inclusion, it is usually contained in non-spherical particles in the same manner as the colorant.

  Further, it can be mixed with a carrier and used as a two-component developer. In this case, conventionally known materials such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead are used as the magnetic particles of the carrier. Ferrite particles are particularly preferable. The magnetic particles preferably have a volume average particle size of 15 to 100 μm, more preferably 25 to 60 μm.

  The volume average particle diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

  The carrier is preferably a carrier in which magnetic particles are further coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. The resin composition for coating is not particularly limited, and for example, olefin resin, styrene resin, styrene / acrylic resin, silicone resin, ester resin, or fluorine-containing polymer resin is used. The resin for constituting the resin-dispersed carrier is not particularly limited, and known resins can be used. For example, a styrene acrylic resin, a polyester resin, a fluorine resin, a phenol resin, or the like can be used. it can.

  FIG. 1 is a cross-sectional configuration diagram of an image forming apparatus capable of producing a color image according to an embodiment of the present invention.

  In the image forming apparatus of FIG. 1, four sets of image forming units 20Y, 20M, 20C, and 20Bk are provided along a transfer belt (recording material conveyance belt) 115.

  Each image forming unit includes a photosensitive drum 21Y (21M, 21C, 21Bk), a scorotron charger (charging means) 22Y (22M, 22C, 22Bk), an exposure optical system (exposure means) 23Y (23M, 23C, 23Bk), The developing unit (developing unit) 24Y (24M, 24C, 24Bk) and the cleaning device (cleaning unit) 25Y (25M, 25C, 25Bk) are configured, and the photosensitive drum (21Y, 21M, 21C, 21Bk) of each image forming unit. Each toner image formed above is sequentially transferred to a recording material (recording paper such as plain paper or transparent sheet) P that is conveyed in time by a transfer unit 34Y (34M, 34C, 34Bk) as a transfer unit. Transfer to form a superimposed color toner image.

In the image forming method of the present invention, when an electrostatic latent image is formed on a photoreceptor, it is preferable to perform image exposure using an exposure beam having a spot area of 2000 μm ² or less. Even when such small-diameter beam exposure is performed, the organic photoreceptor of the present invention can faithfully form an image corresponding to the spot area. A more preferable spot area is 100 to 1000 μm ² . As a result, an electrophotographic image having a gradation of not less than 800 dpi (dpi is the number of dots per 2.54 cm) can be achieved.

The spot area of the exposure beam is a light intensity distribution plane appearing on the cut surface when the exposure beam is cut along a plane perpendicular to the beam, and in a region where the light intensity is 1 / e ² or more of the maximum peak intensity. It means the corresponding area.

Examples of the light beam used include a scanning optical system using a semiconductor laser, and a solid state scanner such as an LED or a liquid crystal shutter. The light intensity distribution includes a Gaussian distribution and a Lorentz distribution, but 1 / e of each peak intensity. ^The area up to ² is the spot area.

  The recording material P is transported on the transfer belt 115 and is discharged by a paper separation AC static eliminator 161 as a recording material separating means, and a separation claw 210 which is a separation member provided in the transport unit 160 at a predetermined interval. And separated from the conveyor belt.

  Next, the recording material P passes through the transport unit 160, and is then transported to a fixing device (fixing unit) 40 including a heating roller 41 and a pressure roller 42, and is heated by the heating roller 41 and the pressure roller 42. The recording material P is sandwiched by the formed nip portion T, and the superimposed toner image on the recording material P is fixed by applying heat and pressure, and then discharged outside the apparatus.

  As the image exposure light source, a scanning optical system using a semiconductor laser, a solid state scanner such as an LED or a liquid crystal shutter, and the like can be used as the exposure means.

  The transfer belt 115 that conveys the recording material includes a polymer film such as polyimide, polycarbonate, and PVdF, and a conductive rubber that is made by adding a conductive filler such as carbon black to a synthetic rubber such as silicone rubber or fluorine rubber. Either a drum shape or a belt shape may be used, but a belt shape is preferable from the viewpoint of freedom in device design.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this. However, “part” in the following text indicates “part by mass”.

  A photoreceptor used for evaluation was produced as follows.

Preparation of photoreceptor 1 Intermediate layer The following intermediate layer coating solution is applied by a dip coating method onto a cleaned cylindrical aluminum substrate (10-point surface roughness Rz defined by JISB-0601 by cutting): 0.81 μm) And dried at 120 ° C. for 30 minutes to form an intermediate layer having a dry film thickness of 3.0 μm.

  The following intermediate layer dispersion is diluted twice with the same mixed solvent, and is allowed to stand overnight and then filtered (filter; rigesh mesh filter made by Nippon Pole Co., Ltd., nominal filtration accuracy: 5 microns, pressure: 50 kPa). Produced.

(Preparation of intermediate layer dispersion)
Binder resin: (Exemplary polyamide N-1) 1 part (1.00 volume part)
2. Rutile-type titanium oxide A1 (primary particle size 35 nm; a surface treatment using a copolymer of methylhydrogensiloxane and dimethylsiloxane (molar ratio 1: 1) in an amount of 5% by mass of the total mass of titanium oxide) 5 parts (1.0 part by volume)
Ethanol / n-propyl alcohol / THF (= 45/20/30 mass ratio) 10 parts The above components were mixed and dispersed in a batch system for 10 hours using a sand mill disperser to prepare an intermediate layer dispersion. .

Charge generation layer The following components were mixed and dispersed using a sand mill disperser to prepare a charge generation layer coating solution. This coating solution was applied by a dip coating method to form a charge generation layer having a dry film thickness of 0.3 μm on the intermediate layer.

Y-form oxytitanyl phthalocyanine (a titanyl phthalosine pigment having a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) of 27.3 ° in an X-ray diffraction spectrum by Cu-Kα characteristic X-ray) 20 parts Silicone-modified polyvinyl Butyral 10 parts 4-Methoxy-4-methyl-2-pentanone 700 parts t-butyl acetate 300 parts Charge transport layer The following components were mixed and dissolved to prepare a charge transport layer coating solution. This coating solution was applied onto the charge generation layer by a dip coating method to form a charge transport layer having a dry film thickness of 25 μm.

Charge transport material (Exemplary compound CTM-129) 70 parts Binder resin (Exemplary compound PC-1 (Mv: 30000)) 100 parts Antioxidant (Exemplary compound 1-1) 8 parts Tetrahydrofuran / toluene (volume ratio 8/2) 750 parts Preparation of photoreceptors 2 to 14 Table 1 shows the N-type semiconductive particles of the intermediate layer, the binder resin, the dry film thickness, the binder resin of the charge transport layer, the charge transport material, the antioxidant, the film thickness, etc. Photoconductors 2 to 14 were produced in the same manner as Photoconductor 1 except for the changes. However, the volume ratio of the interlayer in Table 1 is the same as the volume of the binder resin and the volume of the binder resin after the total volume of the binder resin in all the interlayers of the photoreceptors 1 to 14 and the volume of the N-type semiconductor particles are made constant. An intermediate layer dispersion was prepared by changing the volume ratio (Vn / Vb) of the type semiconductive particles to form an intermediate layer.

At the same time as the production of the photoconductors 1 to 14, each intermediate layer coating solution was applied onto an aluminum-deposited polyethylene terephthalate support using the intermediate layer coating solution of each photoconductor. An intermediate layer having a dry film thickness of 10 μm was formed under the same conditions to prepare a volume resistance measurement sample, and the volume resistance of each intermediate layer was measured. As a result, the volume resistances of the intermediate layers of the photoreceptors 1 to 14 were all 1 × 10 ⁸ Ω · cm or more. The structural formula of the binder resin PC-Z used for the photoreceptor 13 is shown below.

In the table,
A1 is rutile titanium oxide A2 is anatase titanium oxide Z is zinc oxide * 1 is a copolymer of methylhydrogensiloxane and dimethylsiloxane (molar ratio 1: 1)
* 2 is a copolymer of methylhydrogensiloxane and dimethylsiloxane (molar ratio 9: 1)
* 3 is a copolymer of methylhydrogensiloxane and dimethylsiloxane (molar ratio 2: 8)
* 4 is a copolymer of methylhydrogensiloxane and diethylsiloxane (molar ratio 1: 1)
* 5: Copolymer of methylhydrogensiloxane and methylethylsiloxane (molar ratio 1: 1)
* 6 is methylhydrogenpolysiloxane * 7 is primary treatment: silica / alumina, secondary treatment methyltrimethoxysilane In the table, surface treatment refers to the substance used for the surface treatment applied to the surface of the particles (however, The silica / alumina of the primary treatment means silica / alumina deposited on the particle surface).

  The heat of fusion and water absorption in the table were measured as follows.

Measurement conditions of heat of fusion Measuring machine: Measured using Shimadzu Corporation “Shimadzu heat flow rate differential scanning calorimeter DSC-50”.

  Measurement conditions: The measurement sample is set in the above-mentioned measuring machine, measurement is started from room temperature (24 ° C.), the temperature is raised to 200 ° C. at 5 ° C./min, and then cooled to room temperature at 5 ° C./min. This is repeated twice, and the heat of fusion is calculated from the endothermic peak area due to melting during the second temperature increase.

Measurement condition of water absorption rate The sample to be measured is sufficiently dried at 70 to 80 ° C. for 3 to 4 hours, and its mass is accurately weighed. Next, the sample is put into ion-exchanged water maintained at 20 ° C., and after a certain period of time, the sample surface is pulled up and wiped off with a clean cloth, and the mass is measured. The above operation was repeated until the increase in mass was saturated, and the value obtained by dividing the increased mass (increase) of the resulting sample by the initial mass was taken as the water absorption rate.

  In the table, the ratio of the unit structure having 7 or more carbon atoms refers to the ratio (mol%) of the repeating unit structure having 7 or more carbon atoms between amide bonds in the repeating unit structure.

<< Evaluation 1 >>
Basically, evaluation was performed using a tandem digital copying machine having image forming units of Y (yellow), M (magenta), C (cyan), and Bk (black) shown in FIG.

Process conditions for digital copying machines Line speed for image formation L / S: 180 mm / s
Charging condition of the photoconductor (40 mmφ): The potential of the non-image part is detected by a potential sensor and can be feedback-controlled, and a charged potential of −750 V is applied to each organic photoconductor, and the photoconductor when fully exposed The surface potential was set in the range of −50 to 0V.

Image exposure conditions: semiconductor laser, exposure spot area: 7.5 × 10 ⁻¹⁰ m ² , 800 dpi
Development: Yellow toner, magenta toner, cyan toner, and black toner used in each developing means (4Y, 4M, 4C, 4Br) have a physical property value such as a shape factor shown in Table 2, Group 1, Group 2, Groups of polymerized toner groups were used. The yellow toner, magenta toner, cyan toner and black toner in each group contain an external additive of 0.3 μm hydrophobic titanium oxide and 15 nm hydrophobic silica, respectively. A two-component developer made of a ferrite carrier was used. Reverse development method

Transfer conditions Transfer belt: A urethane rubber dispersed with carbon was used at an elongation rate of 3% when used.

Transfer electrode: Corona discharger Transfer current power supply voltage: +3.5 kV to +7.5 kV
Photoconductor cleaning conditions Cleaning blade: A urethane rubber blade was brought into contact with the rotating direction of the photoconductor in a counter manner.

  Fixing is a thermal fixing method using a fixing roller in which a heater is disposed inside the roller.

Evaluation Items and Evaluation Criteria Image density Measured using Macbeth RD-918. The relative reflection density was measured with the paper reflection density set to “0”. When the residual potential increases in printing a large number of sheets, the image density decreases. Measurement was performed on solid image portions of each color after printing 10,000 sheets.

A: Each density of a solid (solid) image portion of Bk and Y, M, and C is 1.2 or more (good)
○: Each density of Bk and Y, M, C solid (solid) image part is 0.8 or more (no problem in practical use)
X: The density of at least one of the solid (solid) image portions of Bk and Y, M, and C is less than 0.8 (practical problem)
The fog density was measured by reflection density of a solid white image using RD-918 manufactured by Macbeth. The reflection density was evaluated by a relative density (the density of A4 paper not printed is 0.000). The measurement was performed on the solid white image portion after 10,000 copies each.

A: Concentration is less than 0.010 (good)
○: Concentration of 0.010 or more and 0.020 or less (a level causing no practical problem)
X: Concentration is higher than 0.020 (a level that causes practical problems)
Dash Mark The state of occurrence of a dash mark (small comet-like streak image) whose periodicity coincides with the period of the photoreceptor on the halftone image was determined according to the following criteria.

A: Frequency of dash marks of 0.4 mm or more: All printed images are 5 / A4 or less (good)
O: Frequency of dash marks of 0.4 mm or more: 1 or more of 6 / A4 or more and 10 / A4 or less (no problem in practical use)
X: Frequency of dash mark image defects of 0.4 mm or more: 11 or more A4 or more occurred (practical problem)
Color difference (color shift)
Continuous printing running was performed under an environment of 20 ° C. and 60% RH, and the color of the solid image portion (solid image portion) of the secondary color (red, green, blue) in the image after initial printing and 10,000 printing was “ It was measured by “Macbeth Color-Eye 7000”, and the color difference was calculated using the CMC (2: 1) color difference formula. The secondary color having the largest color difference was selected, and the color difference determined by the CMC (2: 1) color difference formula was 5 or less within the allowable range, and evaluated according to the following criteria.

A: Color difference is less than 3 (good)
○: Color difference of 3 or more and less than 5 (no problem in practical use)
×: Color difference of 5 or more (practical problem)
Sharpness ◎; solid image density is high (density 1.2 or higher), color shift is inconspicuous, and halftone images are reproduced with clean images (good)
○: The density of the solid image is sufficient (density 0.8 or more), the color shift is not noticeable, and the halftone image is reproduced with a clean image (no problem in practical use)
X: The density of the solid image is low (density is less than 0.8), the color shift is conspicuous, or the halftone image is rough. (There are practical problems)
The results are shown in Table 3.

  From Table 3, the image forming apparatus of the tandem system contains the photosensitive member of the present invention, that is, the polycarbonate whose surface layer (= charge transport layer) has a structural unit represented by the following general formula (1) and an antioxidant. Organic photoconductors 1 to 12 have a sufficiently high image density, no fogging, improved dash marks, small color difference (color shift) after 10,000 printing, and 10,000 printing from the beginning. Until then, a color image with good sharpness has been obtained. On the other hand, the photoconductor 13 using the polycarbonate PC-Z outside the present invention for the surface layer has many dash marks, the image density is lowered, the color difference after 10,000 printing is large, and the sharpness is deteriorated. Further, the photoreceptor 14 which does not contain an antioxidant in the surface layer has a decrease in image density, occurrence of fogging, large color difference after 10,000 printing, and sharpness is also deteriorated.

1 is a cross-sectional configuration diagram of an image forming apparatus capable of producing a color image showing an embodiment of the present invention. (A) is explanatory drawing which shows the projection image of a toner particle without an angle | corner, (b) and (c) are explanatory drawings which show the projection image of a toner particle with an angle | corner, respectively.

Explanation of symbols

20Y, 20M, 20C, 20Bk Image forming unit 21Y, 21M, 21C, 21Bk Photosensitive drum (image forming body)
22Y, 22M, 22C, 22Bk Charging means 23Y, 23M, 23C, 23Bk Exposure means 24Y, 24M, 24C, 24Bk Developing means 25Y, 25M, 25C, 25Bk Cleaning means

Claims (19)

A plurality of image forming units having at least an organic photosensitive member, a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit are arranged and arranged on the organic photosensitive unit using toner having a different color for each of the plurality of image forming units. In the image forming apparatus for forming the color toner image by fixing each color toner image formed on the recording material in sequence on the recording material to form a color toner image and fixing the color toner image, the surface of the organic photoreceptor An image forming apparatus, wherein the layer contains a polycarbonate having a structural unit represented by the following general formula (1) and an antioxidant.

(In the formula, X represents an oxygen atom or a sulfur atom, and R _{1 to} R ₈ represent a hydrogen atom, a halogen atom, a hydroxyl group, or an alkyl group having 1 to 4 carbon atoms.) An image forming unit having at least an organic photoreceptor, a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit is arranged in four sets for black, yellow, magenta, and cyan, and the four sets of image formation are provided. Each color toner image formed on the organic photoconductor using toner having different colors for each unit is sequentially superimposed on the recording material and transferred to form a color toner image, and the color toner image is fixed to form a color image. The image forming apparatus according to claim 1, wherein the surface layer of the organic photoreceptor contains a polycarbonate having a structural unit represented by the general formula (1) and an antioxidant. The image forming apparatus according to claim 1, wherein the polycarbonate contains a copolymer polycarbonate having a structural unit represented by the general formula (1) and the following general formula (2).

(In the formula, A represents a linear, branched or cyclic alkylidene group, aryl-substituted alkylidene group and arylene group having 1 to 10 carbon atoms, and R _{9 to} R ₁₆ represent a hydrogen atom, a halogen atom, a hydroxyl group or a carbon atom. Represents an alkyl group of formulas 1 to 4.) The image forming apparatus according to claim 1, wherein the antioxidant is a compound having a hindered phenol group. The image forming apparatus according to claim 1, wherein the antioxidant is a compound having a hindered amine group. 6. The organic photoreceptor has a structure in which a charge transport layer is laminated on at least a charge generation layer on a conductive support, and the charge transport layer constitutes a surface layer. The image forming apparatus according to any one of the above. The image forming apparatus according to claim 6, wherein the organic photoreceptor has an intermediate layer containing N-type semiconductive particles between the conductive support and the charge generation layer. The image forming apparatus according to claim 7, wherein the N-type semiconductor particles are a metal oxide. The image forming apparatus according to claim 8, wherein the N-type semiconductor particles are titanium oxide or zinc oxide. The image forming apparatus according to claim 9, wherein the N-type semiconductor particles are titanium oxide. The image forming apparatus according to claim 10, wherein the titanium oxide is anatase titanium oxide or rutile titanium oxide. The image forming apparatus according to claim 7, wherein the N-type semiconductor particles are subjected to a surface treatment. The image forming apparatus according to claim 7, wherein the intermediate layer contains a binder of polyamide resin. The image forming apparatus according to claim 13, wherein the polyamide resin is a polyamide resin having a heat of fusion of 0 to 40 J / g and a water absorption of 5% by mass or less. A plurality of image forming units having at least an organic photoconductor, a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit are arranged and arranged on the organic photoconductor using toner having a different color for each of the plurality of image forming units. In the image forming apparatus for forming a color image by fixing the color toner image by sequentially superimposing and transferring the color toner images formed on the recording material to form a color toner image, the organic photoreceptor comprises: The toner having a surface layer containing a polycarbonate having a structural unit represented by the general formula (1) and an antioxidant, wherein the developing means has a shape factor in the range of 1.2 to 1.6 is 65. An image forming apparatus comprising a toner of a number% or more. A plurality of image forming units having at least an organic photosensitive member, a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit are arranged and arranged on the organic photosensitive unit using toner having a different color for each of the plurality of image forming units. In the image forming apparatus for forming a color image by fixing the color toner image by sequentially superimposing and transferring the color toner images formed on the recording material to form a color toner image, the organic photoreceptor comprises: It has a surface layer containing an antioxidant and a polycarbonate having the structural unit represented by the general formula (1), and the developing means contains a toner having 50% by number or more of toner particles without corners. An image forming apparatus. A plurality of image forming units having at least an organic photosensitive member, a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit are arranged and arranged on the organic photosensitive unit using toner having a different color for each of the plurality of image forming units. In the image forming apparatus for forming a color image by fixing the color toner image by sequentially superimposing and transferring the color toner images formed on the recording material to form a color toner image, the organic photoreceptor comprises: Natural logarithm lnD, having a surface layer containing a polycarbonate having the structural unit represented by the general formula (1) and an antioxidant, and the developing means having a particle size of toner particles as D (μm) the horizontal axis, relative frequency of toner particles included in the most frequent class in the histogram showing a particle size distribution of number-based divided the horizontal axis into a plurality of classes at 0.23 intervals (m ₁₎ An image forming apparatus, wherein the sum of the relative frequency of toner particles included in the next higher frequency of class modal class (m ₂₎ (M) contains a toner is 70% or more. A plurality of image forming units having at least an organic photosensitive member, a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit are arranged and arranged on the organic photosensitive unit using toner having a different color for each of the plurality of image forming units. In the image forming apparatus for forming a color image by fixing the color toner image by sequentially superimposing and transferring the color toner images formed on the recording material to form a color toner image, the organic photoreceptor comprises: A surface layer containing a polycarbonate having a structural unit represented by the general formula (1) and an antioxidant, wherein the developing means has a variation coefficient of a shape factor of toner particles of 16% or less, An image forming apparatus comprising a toner having a number variation coefficient of 27% or less. An image forming method comprising forming an electrophotographic image using at least the image forming apparatus according to claim 1.

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