JP2008122664A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which is capable of suppressing occurrence of hollow character and scratch of a photoreceptor. <P>SOLUTION: The image forming apparatus successively transferring images formed on a plurality of photoreceptors to a transfer body to form a color image has at least one set of the combinations of the photoreceptors which has such a relationship between two photoreceptors that the surface friction coefficient of the photoreceptor forming the image on the downstream side is smaller than that of the photoreceptor forming the image on the upstream side in order of transferring the image to the transfer body. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  In a tandem type color image forming apparatus, toners of at least four colors (for example, yellow (Y), magenta (M), cyan (C), and black (Bk)) formed on a photoreceptor are sequentially transferred to a transfer body. As a result, a color image is formed.

  In the process in which yellow (Y), magenta (M), cyan (C), and black (Bk) toners are sequentially transferred to the transfer body, magenta toner is placed on the first transferred yellow toner. The cyan toner and the black toner are finally transferred to form a color image. However, a phenomenon occurs in which the toner once transferred to the transfer body is reversely transferred to the photoreceptor.

  When the toner is reversely transferred to the photoconductor, characters and lines are lost and the photoconductor is scratched, resulting in an image defect.

  In a conventional tandem type full-color image forming apparatus, it is known to mount four photoconductors having the same shape and performance.

Further, each photoconductor in the image forming unit for each color has two or more different properties using a photoconductor in which a photoconductive layer having a charge generation layer and a charge transport layer is provided on a conductive support. A tandem-type color image forming apparatus that has a configuration and is excellent in reproducibility of output images over a long period of time by making the variation in charging characteristics and sensitivity characteristics of a plurality of photoconductors uniform has been studied (for example, Patent Document 1). reference.).
JP 2003-215882 A

  However, the proposed photoconductor has the effect of uniforming the variation in charging characteristics and sensitivity characteristics. However, when color printing is performed in a high temperature and high humidity (for example, 30 ° C., 85% RH) environment, characters are lost. And the photoconductor was damaged.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of suppressing the occurrence of missing characters and photoconductor scratches.

  The present invention is achieved by adopting the following configuration.

1.
In an image forming apparatus that sequentially transfers images formed on a plurality of photosensitive members to a transfer member to form a color image,
The surface friction coefficient of the photoreceptor that forms the downstream image in the order in which the relationship between the two photoreceptors is transferred to the transfer body is lower than the surface friction coefficient of the photoreceptor that forms the upstream image. An image forming apparatus having at least one combination of photosensitive members.

2.
2. The image forming apparatus as described in 1 above, wherein the surface friction coefficient of the plurality of photoconductors sequentially decreases from the upstream side to the downstream side.

3.
In an image forming apparatus that sequentially transfers images formed on a plurality of photosensitive members to a transfer member to form a color image,
The relationship between the pure water contact angle of the photoconductor that forms the downstream image in the order in which the relationship between the two photoconductors is transferred to the transfer body is lower than the pure water contact angle of the photoconductor that forms the upstream image. An image forming apparatus comprising at least one combination of photoconductors having the above.

4).
4. The image forming apparatus as described in 3 above, wherein the pure water contact angle of the plurality of photosensitive members sequentially decreases from the upstream side to the downstream side.

5.
In an image forming apparatus that sequentially transfers images formed on a plurality of photosensitive members to a transfer member to form a color image,
A photosensitive member having a relationship in which the surface roughness of the photosensitive member forming the downstream image in the order in which the relationship between the two photosensitive members is transferred to the transfer member is smaller than the surface roughness of the photosensitive member forming the upstream image. An image forming apparatus having at least one body combination.

6).
6. The image forming apparatus as described in 5 above, wherein the surface roughness of the plurality of photoconductors decreases in order from the upstream side to the downstream side.

  The image forming apparatus of the present invention has an excellent effect capable of suppressing the occurrence of missing characters and photoconductor scratches.

  As a result of studying the cause of missing characters and scratches on the photoconductor, the present inventors made an image on the upstream photoconductor in the order of transfer to the transfer body, and transferred the toner image onto the transfer body. However, it was found that reverse transfer development occurred from the transfer member to the photosensitive member at the downstream transfer portion of the photosensitive member, and voids occurred in characters and lines.

  The present inventors arrange a reverse transfer development of toner at the transfer portion from the photoconductor to the transfer body by arranging a photoconductor excellent in releasability on the downstream side from the upstream side in the order of transfer to the transfer body. It has been found that a high-quality toner image can be formed with less occurrence of missing letters and scratches on the photoreceptor.

  A photoconductor excellent in releasability has good releasability from the toner on the surface of the photoconductor, so that the toner once transferred to the transfer body is less likely to adhere to the photoconductor, and the reverse transfer phenomenon is less likely to occur. I guess.

  However, a photoreceptor excellent in releasability has a soft surface, and is easily scratched during printing of a large number of sheets, and image defects due to scratches are likely to occur.

  In particular, in a color image, there are many halftone images, and image defects due to scratches are easily noticeable, and the occurrence of scratches is a serious problem in a photoconductor that forms a color image. On the other hand, a black image is mainly a line image, and the occurrence of scratches is not a problem with a photoconductor that forms a black image.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus in which even when a large number of sheets are printed, image defects do not occur due to missing characters or scratches on a photoreceptor, and scratches are not noticeable.

  In order to solve the above-described problem, in the present invention, the releasability of the photosensitive member that forms the downstream image in the order in which the relationship between the two photosensitive members is transferred to the transfer member is the photosensitive member that forms the upstream image. At least one combination of photoreceptors having a relationship lower than the releasability of the body is provided.

  Examples of the properties showing releasability include friction coefficient, pure water contact angle, and surface roughness.

  Hereinafter, the present invention will be described in detail.

  FIG. 1 is a structural cross-sectional view showing an example of a color image forming apparatus for forming an image using a photoreceptor according to the present invention.

  In FIG. 1, 1Y, 1M, 1C and 1K are photosensitive members, 4Y, 4M, 4C and 4K are developing means, 5Y, 5M, 5C and 5K are primary transfer rolls as primary transfer means, and 5A is a secondary transfer. Secondary transfer rolls as means, 6Y, 6M, 6C and 6K are cleaning means, 7 is an intermediate transfer member unit, 24 is a heat roll type fixing device, and 70 is an intermediate transfer member.

  This image forming apparatus is called a tandem color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an endless belt-shaped intermediate transfer body unit 7 as a transfer unit, and a recording member P. An endless belt-shaped sheet feeding / conveying means 21 and a heat roll type fixing device 24 as a fixing means. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus.

  As one of the different color toner images formed on each photoconductor, an image forming unit 10Y that forms a yellow image includes a drum-shaped photoconductor 1Y as a first photoconductor, and a periphery of the photoconductor 1Y. A charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, a primary transfer roll 5Y as a primary transfer unit, and a cleaning unit 6Y. An image forming unit 10M that forms a magenta image as another different color toner image is disposed around a drum-shaped photoconductor 1M as a first photoconductor, and the photoconductor 1M. A charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roll 5M as a primary transfer unit, and a cleaning unit 6M. In addition, an image forming unit 10C that forms a cyan image as one of other different color toner images is disposed around the photoconductor 1C as a drum-type photoconductor 1C as a first photoconductor. The charging unit 2C, the exposure unit 3C, the developing unit 4C, the primary transfer roll 5C as the primary transfer unit, and the cleaning unit 6C are provided. Further, an image forming unit 10K that forms a black image as one of other different color toner images is disposed around a drum-shaped photosensitive member 1K as a first photosensitive member, and the photosensitive member 1K. It has a charging means 2K, an exposure means 3K, a developing means 4K, a primary transfer roll 5K as a primary transfer means, and a cleaning means 6K.

  The endless belt-like intermediate transfer body unit 7 has an endless belt-like intermediate transfer body 70 as an intermediate transfer endless belt-like second image carrier that is wound around a plurality of rolls and is rotatably supported.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred onto the rotating endless belt-shaped intermediate transfer body 70 by the primary transfer rolls 5Y, 5M, 5C, and 5K, and is combined. A colored image is formed. A recording member P such as a sheet as a transfer material accommodated in the sheet feeding cassette 20 is fed by the sheet feeding / conveying means 21, passes through a plurality of intermediate rolls 22 A, 22 B, 22 C, 22 D, and a registration roll 23, and is secondary. A color image is transferred onto the recording member P at a time by being conveyed to a secondary transfer roll 5A as a transfer means. The recording member P to which the color image has been transferred is fixed by the heat roll type fixing device 24, is sandwiched by the paper discharge roll 25, and is placed on the paper discharge tray 26 outside the apparatus.

  On the other hand, after the color image is transferred to the recording member P by the secondary transfer roll 5A, the residual toner is removed from the endless belt-shaped intermediate transfer body 70 from which the recording member P is separated by the curvature by the cleaning means 6A.

  During the image forming process, the primary transfer roll 5K is always in pressure contact with the photoreceptor 1K. The other primary transfer rolls 5Y, 5M, and 5C are in pressure contact with the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roll 5A is pressed against the endless belt-shaped intermediate transfer body 70 only when the recording member P passes through the secondary transfer roll 5A and the secondary transfer is performed.

  Further, the housing 8 can be pulled out from the apparatus main body A through the support rails 82L and 82R.

  The housing 8 includes image forming units 10Y, 10M, 10C, and 10K, and an endless belt-shaped intermediate transfer body unit 7.

  The image forming units 10Y, 10M, 10C, and 10K are arranged in tandem in the vertical direction. An endless belt-shaped intermediate transfer body unit 7 is arranged on the left side of the photoreceptors 1Y, 1M, 1C, and 1K in the figure. The endless belt-shaped intermediate transfer body unit 7 includes an endless belt-shaped intermediate transfer body 70 that can be rotated by winding rolls 71, 72, 73, 74, and 76, primary transfer rolls 5Y, 5M, 5C, and 5K, and a cleaning unit. 6A.

  The image forming units 10Y, 10M, 10C, and 10K and the endless belt-shaped intermediate transfer body unit 7 are integrally pulled out from the main body A by the drawer operation of the housing 8.

  In this way, toner images are formed on the photoreceptors 1Y, 1M, 1C, and 1K by charging, exposure, and development, and the toner images of the respective colors are superimposed on the endless belt-shaped intermediate transfer body 70, and are collectively applied to the recording member P. The image is transferred, and fixed by pressing and heating with a heat roll type fixing device 24 and fixed. The photoreceptors 1Y, 1M, 1C, and 1K after transferring the toner image to the recording member P are cleaned with the cleaning device 6A to remove the toner remaining on the photoreceptor, and then the above-described charging, exposure, and development cycle. The next image formation is performed.

  In the present invention, “upstream” and “downstream” refer to the first side of the transfer sequence in the process of sequentially transferring the toner images formed on the photosensitive member to the transfer member, and the subsequent transfer side is referred to as the downstream.

  In FIG. 1, 1Y is an upstream photoconductor, and 1M, 1C, and 1Bk are downstream photoconductors.

(Transfer material)
The transfer material used in the present invention is a support for holding a toner image, and is usually called an image support, a transfer material or a transfer paper. Specifically, various transfer materials such as plain paper and fine paper from thin paper to thick paper, coated printing paper such as art paper and coated paper, commercially available Japanese paper and postcard paper, plastic film for OHP, cloth, etc. However, it is not limited to these.

  The photoreceptor according to the present invention has a photosensitive layer on a conductive substrate. If necessary, an intermediate layer can be provided between the conductive substrate and the photosensitive layer, and a protective layer can be provided on the photosensitive layer.

  When the photoconductor according to the present invention is mounted on the image forming apparatus, a photoconductor excellent in releasability is arranged on the downstream side of the upstream side in the order of transfer to the transfer body.

(Photoreceptor layer structure)
Examples of the layer structure of the photoreceptor include the following structures.

1) A structure in which a charge generation layer, a charge transport layer, and a protective layer are sequentially laminated on a conductive support;
2) A structure in which a single layer including a charge transport material and a charge generation material and a protective layer are formed as a photosensitive layer on a conductive support;
3) A structure in which an intermediate layer, a charge transport layer, a charge generation layer, and a protective layer are sequentially laminated on a conductive support;
The photoreceptor used in the present invention may have any of the above-mentioned structures, but among these, those prepared by providing an intermediate layer, a charge generation layer, a charge transport layer, and a protective layer on a conductive substrate are preferable. .

  FIG. 2 is a schematic diagram showing an example of the layer structure of the photoreceptor used in the present invention.

  In FIG. 2, 1 is a photoreceptor, 11 is a conductive substrate, 12 is an intermediate layer, 13 is a photosensitive layer, 14 is a charge generation layer, 15 is a charge transport layer, 16 is a protective layer, and 17 is a surface layer.

  FIG. 2A shows the photoreceptor 1 manufactured by providing the intermediate layer 12 and the photosensitive layer 13 on the conductive substrate 11. (B) shows the photoreceptor 1 produced by providing a photosensitive layer 13 comprising an intermediate layer 12, a charge generation layer 14 and a charge transport layer 15 on a conductive substrate 11. (C) shows the photoreceptor 1 produced by providing an intermediate layer 12, a photosensitive layer 13 composed of a charge generation layer 14 and a charge transport layer 15, and a protective layer 16 on a conductive substrate 11.

Next, members and layers constituting the photoreceptor according to the present invention will be described (conductive substrate).
The conductive substrate (conductive support) used in the present invention is preferably cylindrical and has a specific resistance of 10 ³ Ωcm or less. As a specific example, cylindrical aluminum whose surface has been cleaned after cutting can be mentioned.

(Middle layer)
The intermediate layer is formed by applying and drying an intermediate layer coating liquid composed of a binder, a dispersion solvent, and the like on a conductive substrate.

  Examples of the binder for the intermediate layer include polyamide resins, vinyl chloride resins, vinyl acetate resins, and copolymer resins containing two or more of these resin repeating units. Among these resins, a polyamide resin is preferable because it can reduce a residual potential increase due to repeated use.

  As the solvent for preparing the coating solution for the intermediate layer, a solvent in which the inorganic particles added as needed are well dispersed and the polyamide resin is dissolved is preferable. Specifically, alcohols having 2 to 4 carbon atoms such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol and the like are excellent in solubility and coating performance of the polyamide resin. 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 is preferably 0.2 to 40 μm, and more preferably 0.3 to 20 μm.

(Photosensitive layer)
The photosensitive layer may have a single layer structure in which a charge generation function and a charge transport function are provided in one layer, but more preferably the function of the photosensitive layer is separated into a charge generation layer (CGL) and a charge transport layer (CTL). It is more preferable to take a layer structure. By adopting a configuration in which the functions are separated, it is possible to control the increase in residual potential with repeated use, and to easily control other electrophotographic characteristics according to the purpose. In the negatively charged photoreceptor, 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 opposite to that in the negatively charged photoconductor. A preferred layer structure of the photosensitive layer is a negatively charged photoreceptor having the function separation structure.

  Hereinafter, each layer of the photosensitive layer of the function-separated negatively charged photoreceptor will be described.

<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.

  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 from 0.01 to 2 μm.

<Charge transport layer>
When the charge transport layer is a surface layer, the charge transport layer is formed from the particles according to the present invention, a charge transport material (CTM), and a binder resin. Other substances may be formed by adding additives such as antioxidants as necessary. The thickness of the charge transport layer is preferably 5 to 40 μm, and more preferably 10 to 30 μm.

  When the charge transport layer forms the surface layer, the amount of the particles according to the present invention in the charge transport layer is preferably 5 to 80% by mass, and more preferably 10 to 50% by mass.

  A known charge transport material (CTM) can be used as the charge transport material (CTM). For example, a triphenylamine derivative, a hydrazone compound, a styryl compound, a benzidine compound, a butadiene compound, or the like can be used.

  Examples of the resin used for the charge transport layer (CTL) include polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, and polycarbonate. Resin, silicone resin, melamine resin, and copolymer resin containing two or more of the repeating units of these resins. In addition to these insulating resins, polymer organic semiconductors such as poly-N-vinylcarbazole can be used.

  Most preferred as a binder for these CTLs is a polycarbonate resin. The polycarbonate resin is most preferable in improving the dispersibility and electrophotographic characteristics of CTM. The ratio of the binder resin to the charge transport material is preferably 10 to 200 parts by mass with respect to 100 parts by mass of the binder resin. The thickness of the charge transport layer is preferably 10 to 40 μm.

  As the antioxidant, a known compound can be used, and specifically, “Irganox 1010” (manufactured by Ciba Geigy Japan) can be mentioned.

(Protective layer)
The protective layer is formed by mixing a charge transport material, a resin, and a material that controls releasability.

  As the charge transport material for the protective layer, the same compound as that used for the charge transport layer can be used.

  As the resin for the protective layer, for example, a polycarbonate resin, an acrylic resin, a phenol resin, an epoxy resin, a urethane resin, and a siloxane resin are used, and the same resin as that used for the charge transport layer may be used.

  Examples of methods for controlling the releasability (surface friction coefficient, pure water contact angle, surface roughness) of the protective layer include the following methods.

1. Control of surface friction coefficient Control of surface friction coefficient includes a method of using a resin having excellent releasability as a resin for forming a protective layer, and a method of dispersing resin particles having excellent releasability in a protective layer. A method of dispersing resin particles having excellent releasability in the protective layer is preferable because a stable film can be easily formed.

  Examples of the resin excellent in releasability include a fluororesin and a silicone resin.

  Examples of the resin particles excellent in releasability include fluorine resin particles and silicone resin particles.

  The surface friction coefficient of the photoreceptor of the present invention is preferably 0.40 to 0.70, and more preferably 0.42 to 0.62. Within this range, the surface friction coefficient of the downstream photoconductor is adjusted from the upstream photoconductor.

  The difference in surface friction coefficient between the upstream photoreceptor and the downstream photoreceptor is preferably 0.10 or more, and more preferably 0.20 or more.

2. Control of pure water contact angle Control of pure water contact angle is a method of using a resin having a large pure water contact angle as a resin for forming a protective layer, and a method of dispersing resin particles having a large pure water contact angle in the protective layer. However, a method of dispersing resin particles having a large pure water contact angle in the protective layer is preferable because a stable film is easily formed.

  Examples of the resin having a large pure water contact angle include fluororesin particles and silicone resin.

  Examples of the resin particles having a large pure water contact angle include fluorine resin particles and silicone resin particles.

  The pure water contact angle of the photoreceptor of the present invention is preferably 80 to 105 °, more preferably 90 to 104 °. Within this range, the pure water contact angle of the downstream photoconductor is adjusted from the upstream photoconductor.

  The difference between the upstream and downstream pure water contact angles is preferably 2 ° or more, and more preferably 3 ° or more.

3. Control of surface roughness The method of controlling the surface roughness is preferably a method of dispersing roughness particles in the protective layer.

  Examples of the coarse particles include tetrafluoroethylene resin, crosslinked polyester resin particles, and crosslinked acrylic resin particles.

  The surface roughness of the photoreceptor of the present invention is preferably 0.05 to 1.0, more preferably 0.08 to 0.9. Within this range, the surface roughness of the downstream photoconductor is adjusted from the upstream photoconductor.

  The difference between the upstream and downstream surface roughness is preferably 0.1 or more, and more preferably 0.2 or more.

  Evaluation (measurement) of the releasability (surface friction coefficient, pure water contact angle, surface roughness) of the photoreceptor surface is performed by the following method.

<Measurement of surface friction coefficient>
The surface friction coefficient on the surface of the photoreceptor is measured using a surface property test apparatus “HEIDON-14” (manufactured by Shinto Kagaku Co., Ltd.) under the following conditions.

Blade hardness: 70 °
Rebound resilience: 55%
Free length: 8mm
Blade length: 20mm
Thickness: 2mm
Contact angle: 20 °
Line speed: 10mm / sec
Weight range: 5 g / cm to 30 g / cm
Measurement environment: High temperature and high humidity (30 ° C, 85% RH)
In the measurement, the tensile speed is 10 mm / sec, the load is continuously increased from 5 g, and the stress until reaching 30 g is measured. The data is taken into a digital recorder, the slope of the plot with respect to the load is obtained by the least square method, and this slope is obtained as the surface friction coefficient.

  FIG. 3 is a schematic diagram showing an example of measurement conditions when measuring the surface friction coefficient.

<Measurement of pure water contact angle>
The contact angle on the surface of the photoreceptor is measured in an environment of 23 ° C. and 50% RH using a fully automatic contact angle meter “CA-W type roll special model” (manufactured by Kyowa Interface Science Co., Ltd.). . In order to achieve both the change in the measured value due to the evaporation of pure water and the stability of the measurement, the measurement is completed within 5 to 30 seconds after the dropping of the pure water. The measurement is based on the θ / 2 method. The contact angle value does not change within the normal pure water droplet amount range, but in the case of a photosensitive drum, the measurement is from a direction perpendicular to the axial direction, and the deviation from the drum curvature is ignored. Is set to 70 μl.

  Measurement points were measured at four locations at 90 ° in the circumferential direction at three locations at the center of the cylindrical photoconductor and 5 cm from the left and right ends, for a total of 12 locations, and this average value was used as the pure water contact angle. .

<Measurement of surface roughness>
The surface roughness of the photoreceptor surface is determined by measuring the ten-point average roughness Rz with a surface roughness meter (Surfcoder SE-30H manufactured by Kosaka Laboratory Ltd.).

Measurement conditions Measurement speed: 0.1 mm / sec
Measuring distance: 8mm
Stylus tip radius: 2 μm
Cut-off value: 0.8mm
Cut-off type: Gaussian Cut-off ratio: 300

  The present invention will be specifically described below with reference to examples, but the embodiments of the present invention are not limited to these examples.

<< Production of photoconductor >>
A photoreceptor was prepared by the following method.

<Preparation of Photoreceptor 11>
(Conductive substrate)
The surface of the cylindrical aluminum support was cut to prepare a conductive substrate.

(Middle layer)
The following intermediate layer dispersion was diluted twice with methanol, allowed to stand overnight, and then filtered (filter; rigesh mesh 5 μm filter manufactured by Nippon Pole Co., Ltd.) to prepare an intermediate layer coating solution.

Polyamide resin “CM8000” (manufactured by Toray Industries Inc.) 1 part by weight Inorganic particles: titanium oxide (number average primary particle size 35 nm: titanium oxide treated with silica / alumina and methylhydrogenpolysiloxane) 3 parts by weight Methanol 10 parts by weight are mixed Then, a sand mill was used as a disperser, and dispersion was carried out for 10 hours in a batch manner to prepare an intermediate layer dispersion.

  An “intermediate layer” having a dry film thickness of 1.0 μm was formed on the conductive support by the dip coating method using the coating solution.

(Charge generation layer (CGL))
Titanyl phthalocyanine pigment (a titanyl phthalocyanine pigment having a maximum diffraction peak at 27.3 ° at the Bragg angle (2θ ± 0.2 °) of the characteristic X-ray diffraction spectrum of Cu-Kα) 24 parts by mass Polyvinyl butyral resin “ESREC BL -1 "(manufactured by Sekisui Chemical Co., Ltd.) 12 parts by mass 2-butanone / cyclohexanone (mass ratio 4/1) 300 parts by mass The above composition was mixed and dispersed using a sand mill to prepare a coating solution for a charge generation layer. . This coating solution was applied onto the intermediate layer by a dip coating method to form a “charge generation layer” having a dry film thickness of 0.5 μm.

(Charge transport layer (CTL))
A liquid in which the following components are mixed is dispersed for 10 hours using a batch-type sand mill disperser, and then filtered (filter; rigesh mesh filter manufactured by Nippon Pole Co., Ltd., nominal filtration accuracy: 5 μm, pressure: 50 kPa) for the charge transport layer. A coating solution was prepared.

Coating solution for charge transport layer 4-methoxy-4 '-(4-methyl-α-phenylstyryl) triphenylamine
70 parts by mass Bisphenol Z-type polycarbonate “Iupilon-Z300” (Mitsubishi Gas Chemical Co., Ltd.) 100 parts by mass Antioxidant (Compound 1) 8 parts by mass Tetrahydrofuran / toluene (mass ratio 8/2) 750 parts by mass The penetration depth of the dip coating was adjusted, and the charge transport layer coating film was formed by coating and drying from the upper end of the conductive substrate provided with the charge generation layer to 10 mm.

  Thereafter, the charge transport layer coating film from the lower end of the conductive substrate to 10 mm is removed with a tape impregnated with a solvent (tetrahydrofuran / toluene (mass ratio 8/2)) to expose the lower end of the substrate. Layer "was formed. The film thickness is a value measured using an eddy current type film thickness measuring device “EDDY560C” (manufactured by HELMUT FISCHER GMBTE CO).

(Protective layer)
A liquid containing the following components is dispersed for 10 hours using a batch type sand mill disperser, and then filtered (filter; rigesh mesh filter manufactured by Nihon Pall Co., Ltd., nominal filtration accuracy: 5 μm, pressure: 50 kPa) and applied for a protective layer. A liquid was prepared.

4-methoxy-4 '-(4-methyl-α-phenylstyryl) triphenylamine
120 parts by mass Bisphenol Z-type polycarbonate “Iupilon-Z300” (Mitsubishi Gas Chemical Co., Ltd.) 300 parts by mass Fluorine type comb-type graft polymer “GF300 (Toagosei Co., Ltd.)” 6 parts by mass Inorganic particles “Titanium dioxide” (number average) Primary particle diameter 33 nm) 50 parts by weight Organic particles A (* 1) 75 parts by weight Antioxidant (Compound 1) 12 parts by weight Silicone oil (viscosity, 0.4 Pa · s) 0.1 part by weight Tetrahydrofuran 1200 parts by weight Charge transport On the surface of the layer, the above-mentioned protective layer coating solution was applied with a circular amount-regulating coating device and dried to form a “protective layer” having a film thickness of 6 μm, thereby producing “Photoreceptor 11”.

* 1: Organic particle A “tetrafluoroethylene resin” (number average primary particle size 98 nm)
<Preparation of Photoreceptor 12>
A “photoreceptor 12” was prepared in the same manner except that 75 parts by mass of the organic particles A used in the photoreceptor 11 was changed to 40 parts by mass.

<Preparation of Photoreceptor 13>
In the same manner, except that 75 parts by mass of the organic particles A used in the photoreceptor 11 were changed to 20 parts by mass and a coating solution for a protective layer to which 45 parts by mass of organic particles B (* 2) was newly added was used. Body 13 "was produced.

* 2: Organic particle B “crosslinked polyester resin” (number average primary particle size 120 nm)
<Preparation of Photoreceptor 14>
A “photoreceptor 14” was produced in the same manner except that the organic particles A used in the photoreceptor 11 were not added.

<Preparation of Photoreceptor 21>
(Conductive substrate)
The surface of the cylindrical aluminum support was cut to prepare a conductive substrate.

(Middle layer)
The following intermediate layer dispersion was diluted twice with methanol, allowed to stand overnight, and then filtered (filter; rigesh mesh 5 μm filter manufactured by Nippon Pole Co., Ltd.) to prepare an intermediate layer coating solution.

Polyamide resin “CM8000” (manufactured by Toray Industries Inc.) 1 part by weight Inorganic particles: titanium oxide (number average primary particle size 35 nm: titanium oxide treated with silica / alumina and methylhydrogenpolysiloxane) 3 parts by weight Methanol 10 parts by weight are mixed Then, a sand mill was used as a disperser, and dispersion was carried out for 10 hours in a batch manner to prepare an intermediate layer dispersion.

  An “intermediate layer” having a dry film thickness of 1.0 μm was formed on the conductive substrate by dip coating using the coating solution.

(Charge generation layer (CGL))
Titanyl phthalocyanine pigment (a titanyl phthalocyanine pigment having a maximum diffraction peak at 27.3 ° at the Bragg angle (2θ ± 0.2 °) of the characteristic X-ray diffraction spectrum of Cu-Kα) 24 parts by mass Polyvinyl butyral resin “ESREC BL -1 "(manufactured by Sekisui Chemical Co., Ltd.) 12 parts by mass 2-butanone / cyclohexanone (mass ratio 4/1) 300 parts by mass The above composition was mixed and dispersed using a sand mill to prepare a coating solution for a charge generation layer. . This coating solution was applied onto the intermediate layer by a dip coating method to form a “charge generation layer” having a dry film thickness of 0.5 μm.

(Charge transport layer (CTL))
A liquid in which the following components are mixed is dispersed for 10 hours using a batch-type sand mill disperser, and then filtered (filter; rigesh mesh filter manufactured by Nippon Pole Co., Ltd., nominal filtration accuracy: 5 μm, pressure: 50 kPa) for the charge transport layer. A coating solution was prepared.

Coating solution for charge transport layer 4-Methoxy-4 '-(4-methyl-α-phenylstyryl) triphenylamine 70 parts by mass Bisphenol Z-type polycarbonate “Iupilon-Z300” (Mitsubishi Gas Chemical Co., Ltd.) 100 parts by mass Antioxidation Agent (Compound 1) 8 parts by mass Tetrahydrofuran / toluene (mass ratio 8/2) 750 parts by mass Adjusting the penetration depth of the dip coating, 10 mm from the upper end of the conductive substrate provided with the charge generation layer The charge transport layer was formed by coating and drying.

  Thereafter, the charge transport layer coating film from the lower end of the substrate to 10 mm is removed with a tape impregnated with a solvent (tetrahydrofuran / toluene (mass ratio 8/2)) to expose the lower end of the conductive substrate. Layer "was formed. The film thickness is a value measured using an eddy current type film thickness measuring device “EDDY560C” (manufactured by HELMUT FISCHER GMBTE CO).

(Protective layer)
A liquid containing the following components is dispersed for 10 hours using a batch type sand mill disperser, and then filtered (filter; rigesh mesh filter manufactured by Nihon Pall Co., Ltd., nominal filtration accuracy: 5 μm, pressure: 50 kPa) and applied for a protective layer. A liquid was prepared.

4-methoxy-4 '-(4-methyl-α-phenylstyryl) triphenylamine
120 parts by mass Bisphenol Z-type polycarbonate “Iupilon-Z300” (Mitsubishi Gas Chemical Co., Ltd.) 300 parts by mass Cross-linked acrylic resin (* 3) 60 parts by mass Antioxidant (Compound 1) 12 parts by mass Silicone oil (viscosity, 0.4 Pa -S) 0.1 part by mass Tetrahydrofuran 1200 parts by mass The above protective layer coating solution is applied to the surface of the charge transport layer with a circular amount-regulating coating device and dried to form a "protective layer" having a thickness of 6 μm. “Photosensitive member 21” was produced.

* 3: Cross-linked acrylic resin “MP1450 (number average primary particle size: 0.25 μm), manufactured by Soken Chemical Co., Ltd.”
<Preparation of Photoconductor 22>
“Photoconductor 22” was prepared in the same manner except that 60 parts by mass of the crosslinked acrylic resin used in the production of photoconductor 21 was changed to 30 parts by mass.

<Preparation of Photoconductor 23>
“Photoconductor 23” was prepared in the same manner except that 60 parts by mass of the crosslinked acrylic resin used in the production of photoconductor 21 was changed to 15 parts by mass.

<Preparation of Photoconductor 24>
A “photosensitive member 24” was prepared in the same manner except that 60 parts by mass of the crosslinked acrylic resin used in the production of the photosensitive member 21 was not added.

  Table 1 shows the measurement results of the surface friction coefficient, pure water contact angle, and surface roughness of the prepared photoreceptor.

  In addition, the measurement of a surface friction coefficient, a pure water contact angle, and surface roughness is the value calculated | required and measured by the said measuring method.

<Evaluation>
A commercially available full-color MFP “8050” (manufactured by Konica Minolta Business Technologies, Inc.) having the configuration shown in FIG. 2 was set under the following conditions and used as an evaluation apparatus.

Photoconductor: mounted with the photoconductor prepared above Developing means: loaded with a two-component developer (both Y, M, C, and Bk) containing carrier and toner Transfer means: using an intermediate transfer belt Photoconductor cleaning means: rubber An elastic cleaning blade is used under a contact condition of a linear load of 18 (N / m). Cleaning means for the intermediate transfer member: a rubber elastic cleaning blade is used. For image formation, the above-prepared photosensitive member is attached to this image forming apparatus. I went there.

<Image evaluation>
Printed manuscripts for image evaluation include character images with a pixel rate of 7% (3-point, 5-point characters), human face photographs (dot images including halftones), 1 cm squares with a line width of 0.3 mm, solid An original image in which the black images are divided into ¼ equal parts was used. A4 size fine paper (64 g / m ² ) was used as the image forming medium (transfer material).

  Printing was performed 100,000 sheets in an environment of high temperature and high humidity (30 ° C., 85% RH).

  The image evaluation was performed for the following items at the start and every 1000 prints. The evaluation criteria are ◎, ○, and Δ are acceptable and × is unacceptable.

(Cut out of text image)
The three-point and five-point characters of the printed image were enlarged with a loupe, and the occurrence of missing characters in the character image was visually evaluated.

◎: Up to 100,000 prints, 3 point and 5 point characters are good with no voids. ○: 3 point characters are slightly broken with 3 point characters. No problem △: Occurrence of missing characters in 3 point characters on the 100,000th print, but no problem for practical use ×: Omitted in 3 points and 5 points on the 50,000th print There is a problem in practical use.

(Line image missing)
A line having a line width of 0.3 mm in the grid image was enlarged with a loupe both vertically and horizontally, and the occurrence of a void in the line having a line width of 0.3 mm was visually evaluated.

◎: The line image is good with no occurrence of voids until the 100,000th print. ○: The line image shows some occurrence of voids, but there is no practical problem. △: 100,000th image In this print, there is a problem in the line image, but there is no problem in practical use. X: In the print of the 50,000th sheet, there is a problem in the line image because the line image is generated.

(Photoconductor scratches)
The photoreceptor damage was evaluated by how many white stripes having a width of 0.4 mm or more per A4 size in the solid image portion. The width of the white stripe was measured with a microscope with a video printer.

Evaluation criteria A: Good when white stripes of 0.4 mm or more are printed at 2 lines / A4 or less at the time of printing 100,000 sheets ○: White stripes of 0.4 mm or more are printed at 5 lines / A4 or less at the time of printing 100,000 sheets No problem in practical use △: White streaks of 0.4 mm or more occurred at 50,000 sheets when printing was 5 lines / A4 or less No problem in practical use ×: White streaks of 0.4 mm or more were printed at 50,000 sheets There are practical problems with over 5 lines / A4.

  Table 2 shows the evaluation results.

  From the results of Table 2, Examples 1-4 of the present invention were good in any evaluation item, but Comparative Examples 1-5 had a problem in any of the evaluation items and achieved the object of the present invention. It turns out that there is no.

1 is a cross-sectional view illustrating an example of a color image forming apparatus that performs image formation using a photoreceptor according to the present invention. It is a schematic diagram showing an example of a layer structure of a photoreceptor used in the present invention. It is the schematic which shows an example of the measurement conditions when measuring a surface friction coefficient.

Explanation of symbols

1Y, 1M, 1C, 1K Photoconductor 4Y, 4M, 4C, 4K Developing means 5Y, 5M, 5C, 5K Primary transfer roll 5A Secondary transfer roll 6Y, 6M, 6C, 6K Cleaning means 7 Intermediate transfer body unit 24 Heat Roll type fixing device 70 Intermediate transfer member

Claims (6)

In an image forming apparatus that sequentially transfers images formed on a plurality of photosensitive members to a transfer member to form a color image,
The surface friction coefficient of the photoreceptor that forms the downstream image in the order in which the relationship between the two photoreceptors is transferred to the transfer body is lower than the surface friction coefficient of the photoreceptor that forms the upstream image. An image forming apparatus having at least one combination of photosensitive members. 2. The image forming apparatus according to claim 1, wherein the surface friction coefficient of the plurality of photoconductors decreases sequentially from the upstream side to the downstream side. In an image forming apparatus that sequentially transfers images formed on a plurality of photosensitive members to a transfer member to form a color image,
The relationship between the pure water contact angle of the photoconductor that forms the downstream image in the order in which the relationship between the two photoconductors is transferred to the transfer body is lower than the pure water contact angle of the photoconductor that forms the upstream image. An image forming apparatus comprising at least one combination of photoconductors having the above. 4. The image forming apparatus according to claim 3, wherein the contact angle of pure water of the plurality of photoconductors decreases sequentially from the upstream side to the downstream side. In an image forming apparatus that sequentially transfers images formed on a plurality of photosensitive members to a transfer member to form a color image,
A photosensitive member having a relationship in which the surface roughness of the photosensitive member forming the downstream image in the order in which the relationship between the two photosensitive members is transferred to the transfer member is smaller than the surface roughness of the photosensitive member forming the upstream image. An image forming apparatus having at least one body combination. 6. The image forming apparatus according to claim 5, wherein the surface roughness of the plurality of photoconductors decreases in order from the upstream side to the downstream side.

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