JP2005115356A - Organophotoreceptor, process cartridge, image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organophotoreceptor which prevents deterioration of broadening or contrast latent dot image and can form a high gradation and high definition electrophotographic image, even if reduction in the thickness of the organophotoreceptor proceeds after long-term use. <P>SOLUTION: The organophotoreceptor has at least an intermediate layer, a charge generation layer and a charge transport layer on a conductive substrate, wherein thickness of the intermediate layer is 6-15 μm, thickness of the charge transport layer is 5-15 μm, and work function of the intermediate layer satisfies α≤0.8 when the relation between the work function ψ<SB>UL</SB>of the intermediate layer and the work function ψ<SB>M</SB>of a sample side electrode is linearly approximated by the expression: ψ<SB>UL</SB>=α ψ<SB>M</SB>+β wherein α and β are each a constant and both function are obtained by measuring a contact potential difference for the sample side electrode when the sample side electrode is changed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an organic photoreceptor (hereinafter also simply referred to as a photoreceptor) used in the field of copying machines and printers, and a process cartridge, an image forming apparatus, and an image forming method using the organic photoreceptor.

In order to improve the image quality of an electrophotographic image, a technique for forming a fine dot image by forming a fine latent image on an organic photoreceptor using an exposure light source having a small spot diameter has been developed. For example, a method of forming a high-definition latent image on an organic photoreceptor using a light source having a spot diameter of 4000 μm ² or less is known (Patent Document 1). In order to form an accurate latent image by such a small diameter spot exposure method, it is important to reduce the diffusion of charge carriers generated by exposure when forming a latent image by image exposure on an organic photoreceptor. That is, in order to faithfully reproduce the image information as an electrostatic latent image, it is necessary to ensure a sufficient potential contrast in the exposed / unexposed area. This is because the generated carriers reach the surface charge. It is important to suppress diffusion. For example, the latent image deterioration of a high-density image such as 1200 dpi (dpi is the number of pixel dots per 2.54 cm) has a ratio D / μ between the diffusion constant (D) and the drift mobility (μ) of the charge transport layer. It is described that the effect of diffusion at the time of forming the electrostatic latent image cannot be ignored when the thickness is increased, and that the latent image deterioration is increased as the thickness of the charge transport layer is increased (Non-Patent Document 1). Furthermore, it has been reported from the analysis result of the latent image of 1 dot that the diffusion of the latent image increases as the drift mobility (μ) of the charge transport layer increases. (Non-patent document 2) For this reason, in a high-resolution process, an organic photoreceptor has already been proposed in which a charge transport layer is thinned to prevent diffusion of an electrostatic latent image (patent document 2).

  However, these proposed organic photoreceptors cannot be a sufficient solution in terms of durability of the photoreceptor. That is, the organic photoreceptor generally has a large film thickness dependency such as charging ability and sensitivity, and the film thickness wear due to repeated use tends to cause an increase in image defects such as fogging and black spots. In particular, in an organic photoreceptor having a thin photosensitive layer, the load condition of the charging potential at the time of forming the electrostatic latent image tends to increase the electric field strength per unit film thickness. Problems such as potential rise are likely to occur.

  In addition, recent electrophotographic devices such as digital copying machines and printers have been pursuing higher image quality, and have become smaller and faster, with higher sensitivity corresponding to higher speed as photoconductor characteristics and longer life due to improved wear resistance. Both are required.

  In order to satisfy the above-described demands for higher image quality, smaller size, and higher speed, it is required to increase the time response of the sensitivity of the photoreceptor. In order to meet these requirements, efforts have been made to develop charge-sensitive materials with high sensitivity. As a result, phthalocyanine pigments such as Y-type phthalocyanine (a titanyl phthalocyanine pigment having a maximum peak at a Bragg angle 2θ of 27.3 ° in a Cu-Kα characteristic X-ray spectrum) as a typical highly sensitive charge generation material. An electrophotographic photoreceptor using the pigment has been developed and put into practical use (Non-patent Document 3). However, these electrophotographic photoreceptors have a high line speed of the photoreceptor, a high-speed image forming process in which the charging time and the movement time from the exposure process to the development process are short, the charging potential is not stable, and the dot image is deteriorated. Or residual potential increases, fogging is likely to occur, and image density is likely to decrease.

That is, in an organic photoreceptor that requires high image quality and high-speed characteristics, the change in the thickness of the photoreceptor due to repeated use affects the size of the electrostatic latent image of the dot image and the formation of the potential contrast. Deterioration and increase in residual potential occur, fogging is likely to occur, and image density is likely to decrease. In particular, when a dot image of 1200 dpi or more is required and a printed image of a photographic image in which gradation reproducibility is important, the deterioration of the dot image caused by the decrease in the film thickness of the photoreceptor is likely to occur, and it is necessary to prevent this. is there.
JP-A-8-272197 JP-A-5-119503 Journal of the Imaging Society of Japan Vol. 38, No. 4, 296 Fuji Jiho Vol.75, No.3, p.194 Journal of Electrophotographic Society, 29 (3), 250 (1990)

  The present invention solves the problems of the prior art as described above, and in an organic photoreceptor used in an image forming apparatus for forming a high-resolution electrophotographic image of 1200 dpi or more, the organic photoreceptor is used for a long time, To provide an organic photoreceptor capable of preventing formation of a latent image of a dot image and deterioration of the contrast even when the thickness wears down, forming a high gradation, high-definition electrophotographic image with little decrease in image density. And a process cartridge, an image forming apparatus, and an image forming method using the organic photoreceptor.

In order to improve the reproducibility of the above-described problems of the present invention, that is, high-quality dot images and obtain high-definition electrophotographic images, the thickness of the photosensitive layer of the organic photoreceptor is reduced, Even if the photoconductor is used for a long time and the film thickness wears down, the intermediate layer is thickened so that the electric field intensity per unit thickness of the photoconductive layer is difficult to change, and it exists between the conductive support and the charge generation layer. The present invention has been completed by finding that the intermediate layer has a specific work function characteristic.
(Claim 1)
In an organic photoreceptor used in an electrophotographic image forming apparatus for writing a digital image with a resolution of 1200 dpi or more and forming an electrostatic latent image, at least an intermediate layer, a charge generation layer, and a charge transport layer on a conductive support. The intermediate layer has a thickness of 6 to 15 μm, the charge transport layer has a thickness of 5 to 15 μm, and the work function of the intermediate layer is changed by changing the sample-side conductive electrode by contact potential difference measurement. An organic photoreceptor characterized in that α ≦ 0.8 when the relationship between the work function φ _UL of the obtained intermediate layer and the work function φ _M of the sample-side conductive electrode is linearly approximated by the following formula (a).

Formula (a) φ _UL = α · φ _M + β (where α and β are constants)
(Claim 2)
The organophotoreceptor according to claim 1, wherein the intermediate layer contains N-type semiconductor particles.
(Claim 3)
The organophotoreceptor according to claim 2, wherein the N-type semiconductor particles are anatase-type titanium oxide.
(Claim 4)
The organic photoreceptor according to any one of claims 1 to 3, wherein the intermediate layer contains a curable resin having an organic segment component and an inorganic segment component.
(Claim 5)
The organophotoreceptor according to claim 1, wherein α is 0.3 ≦ α ≦ 0.8.
(Claim 6)
In a process cartridge that can be detachably attached to an electrophotographic image forming apparatus main body for writing a digital image on an organic photoreceptor with a resolution of 1200 dpi or more and forming an electrostatic latent image, a charging unit, a developing unit, a transfer unit, At least one of the cleaning means and the conductive support have at least an intermediate layer, a charge generation layer, and a charge transport layer. The intermediate layer has a thickness of 6 to 15 μm, and the charge transport layer has a thickness of 5 to 15 μm. The relationship between the work function φ _{UL of the} intermediate layer and the work function φ _M of the sample-side conductive electrode obtained by changing the sample-side conductive electrode in the contact potential difference measurement of the work function of the intermediate layer is expressed by the above formula (a). And an electrophotographic photosensitive member satisfying α ≦ 0.8 when linearly approximated by a process cartridge.
(Claim 7)
In an electrophotographic image forming apparatus that has at least an organic photoreceptor, charging means, exposure means, and developing means, writes a digital image on the organic photoreceptor with a resolution of 1200 dpi or more, and forms an electrostatic latent image. The organic photoreceptor has at least an intermediate layer, a charge generation layer, and a charge transport layer on a conductive support, the thickness of the intermediate layer is 6 to 15 μm, the thickness of the charge transport layer is 5 to 15 μm, The relationship between the work function φ _{UL of the} intermediate layer and the work function φ _M of the sample-side conductive electrode obtained by changing the sample-side conductive electrode in the contact potential difference measurement using the contact potential difference measurement is expressed by the above formula (a). An image forming apparatus characterized in that α ≦ 0.8 when linear approximation is performed.
(Claim 8)
8. The image forming apparatus according to claim 7, wherein a charging potential of the organic photoreceptor by the charging unit is 200 to 400V.
(Claim 9)
At least an organic photoreceptor, charging means and exposure means for writing a digital image on the organic photoreceptor with a resolution of 1200 dpi or more to form an electrostatic latent image, and developing the electrostatic latent image into a toner image A plurality of image forming units each having a developing unit that converts the toner image formed on the organic photoreceptor and a transfer unit that transfers the toner image onto a recording material, and each image forming unit is formed using a differently colored toner. In the image forming apparatus in which each toner image is sequentially transferred to a recording material to form a color image, the organic photoreceptor has at least an intermediate layer, a charge generation layer, and a charge transport layer on a conductive support, and the intermediate layer The film thickness of the intermediate layer is 5 to 15 μm, the charge transport layer is 5 to 15 μm, and the work function of the intermediate layer is obtained by changing the sample-side conductive electrode by contact potential difference measurement. _UL and sample When linear approximation relation between the work function phi _M conductive electrode by the formula (a), the image forming apparatus, characterized in that the alpha ≦ 0.8.
(Claim 10)
An image forming method, comprising: forming an electrophotographic image using the image forming apparatus according to claim 7.
(Claim 11)
In an organic photoreceptor used in an electrophotographic image forming apparatus for writing a digital image and forming an electrostatic latent image of a digital image under a charging potential of 200 to 400 V, at least an intermediate is provided on a conductive support. A layer, a charge generation layer and a charge transport layer, the intermediate layer has a thickness of 6 to 15 μm, the charge transport layer has a thickness of 5 to 15 μm, and the work function of the intermediate layer is a contact potential difference measurement, When the relationship between the work function φ _{UL of the} intermediate layer obtained by changing the sample-side conductive electrode and the work function φ _M of the sample-side conductive electrode is linearly approximated by the above equation (a), α ≦ 0.8. An organic photoreceptor characterized by the following.

  By using the organic photoreceptor of the present invention, a high-quality dot image of 1200 dpi or more can be formed, and an electrophotographic image with good sharpness and gradation can be provided without image defects. A process cartridge, an image forming apparatus, and an image forming method using the body can be provided.

  Hereinafter, the present invention will be described in detail.

The organophotoreceptor of the present invention has at least an intermediate layer, a charge generation layer and a charge transport layer on a conductive support. The intermediate layer has a thickness of 6 to 15 μm, and the charge transport layer has a thickness of 5 to 15 μm. , and the and the the middle layer work function contact potential difference measurements, following the relationship between the work function phi _M work function phi _UL and sample side conductive electrode of the intermediate layer obtained by changing the sample-side conductive electrode type ( When linear approximation is performed in a), α ≦ 0.8.

Formula (a) φ _UL = α · φ _M + β (where α and β are constants)
The organic photoconductor has the above structure, so that a latent image of a dot image of 1200 dpi or more can be formed. Even if the organic photoconductor is used for a long period of time and the film thickness is reduced, the resolution is 1200 dpi or higher. Variations in the quality of the electrophotographic image can be reduced, and fine line reproducibility, gradation, sharpness, and quality deterioration of color images can be prevented.

  Hereinafter, the organic photoreceptor of the present invention will be described in detail.

  In the present invention, the organic photoconductor means an electrophotographic photoconductor constituted by providing an organic compound with at least one of a charge generation function and a charge transport function essential to the configuration of the electrophotographic photoconductor. All known organic photoreceptors such as a photoreceptor composed of the above organic charge generating substance or organic charge transporting substance, a photoreceptor composed of a polymer complex with a charge generating function and a charge transporting function are contained.

  The charge transport layer of the present invention means a layer having a function of transporting charge carriers generated in the charge generation layer by light exposure to the surface of the organic photoreceptor, and the specific detection of the charge transport function is charge generation. It can be confirmed by laminating a layer and a charge transport layer on a conductive support and detecting the optical conductivity.

  The layer structure of the organic photoreceptor of the present invention basically comprises a photosensitive layer in which an intermediate layer is formed on a conductive support, and a charge generation layer and a charge transport layer are laminated thereon.

  Hereinafter, a specific configuration of the photoreceptor used in the present invention will be described.

Conductive Support As the conductive support used in the photoreceptor of the present invention, a sheet-like or cylindrical conductive support is used.

  The cylindrical conductive support of the present invention means a cylindrical support necessary for forming an endless image by rotating, and the straightness is in the range of 0.1 mm or less and the deflection is 0.1 mm or less. Certain conductive supports are preferred. Exceeding the range of straightness and shake makes it difficult to form a good image.

As a material for the conductive support, 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. In particular, the conductive support of the present invention is preferably an aluminum-based material (the main component is aluminum and contains a few percent or less physical property adjusting metal such as manganese or zinc), and the specific resistance at room temperature is 10 ³ Ωcm or less. preferable.

  As the conductive support used in the present invention, one having an alumite film that has been sealed on the surface thereof may be used. The alumite treatment is usually performed in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, sulfamic acid, etc., but anodizing treatment in sulfuric acid gives the most preferable result. In the case of anodizing in sulfuric acid, the sulfuric acid concentration is preferably 100 to 200 g / l, the aluminum ion concentration is 1 to 10 g / l, the liquid temperature is about 20 ° C., and the applied voltage is preferably about 20 V. It is not limited. The average film thickness of the anodized film is usually 20 μm or less, particularly preferably 10 μm or less.

Intermediate Layer The intermediate layer of the present invention has a film thickness of 6 to 15 μm between the conductive support and the charge generation layer, and α in the formula (a) is 0.8 or less as measured by the work function of the intermediate layer. It is characterized by becoming.
By using such an intermediate layer for the organophotoreceptor of the present invention, it is possible to satisfactorily prevent injection of charges from the conductive support and to have an intermediate layer thickness of 6 to 15 μm, comparable to the charge transport layer. Even if the thickness of the charge transport layer is increased, the deterioration of the residual potential and the charging potential is small. By providing such a thick intermediate layer, even if the thickness of the charge transport layer is as thin as 5 to 15 μm, image formation is possible. The required charging potential can be applied to the photoreceptor.

  The formula (a) of the work function of the intermediate layer will be described.

  It is obtained by changing the sample-side conductive electrode in the above formula (a) contact potential difference measurement of the work function of the intermediate layer of the present invention. A method called the Kelvin method is generally used for measuring the work function. The Kelvin method and the work function determination method are described in detail in "New Experimental Chemistry Course 18 -Interface and Colloid-" (Edited by Chemical Society of Japan, P181 to 192).

  When determining the work function of the intermediate layer, an intermediate layer is provided on the sample-side conductive electrode as a sample, and the potential difference between the intermediate layer surface and the gold electrode (counter electrode) surface is measured using the gold electrode as a counter electrode. . The intermediate layer is in contact with the gold electrode via the sample-side electrode, but in the case of sufficient electron transfer from the high Fermi level to the low side through the contact interface, Regardless of the intervening metal, the contact potential difference between the intermediate layer and the gold electrode should be constant, and therefore the work function of the intermediate layer should also be constant. However, in the actual measurement result, the work function value of the intermediate layer changes depending on the work function of the sample-side conductive electrode. This indicates that the contact equilibrium between the intermediate layer and the sample-side electrode is different from that due to ideal electron transfer, and is noted as a behavior reflecting the electronic characteristics of the intermediate layer.

The gradient α of the linear relationship between φ _UL and φ _M of the intermediate layer of the present invention is characterized in that α ≦ 0.8. By setting the slope of the work function of the intermediate layer to the formula (a) of 0.8 or less, the characteristics of injecting electrons generated in the charge generation layer into the intermediate layer are improved. It has been found that even if the thickness is made as thick as 6 to 15 μm, a characteristic with a small increase in the residual potential can be obtained, and a rectifying characteristic that effectively suppresses the injection of charges from the conductive support can be obtained.

  The lower limit of the α value is α = 0, but is preferably 0.3 or more, and most preferably 0.5 or more. When α is less than 0.3, injection of thermally excited carriers from the charge generation layer tends to increase, and the dark decay of the charged potential tends to increase.

  Next, the structure of the intermediate layer of the present invention having the above characteristics will be described below.

  In order to obtain the characteristics of the intermediate layer as described above, the intermediate layer is preferably formed of a resin layer in which N-type semiconductor particles are dispersed.

  N-type semiconductive particles refer to fine particles having the property of using conductive carriers as electrons. That is, since it has the property of using conductive carriers as electrons, the intermediate layer containing the N-type semiconductor particles in an insulating binder effectively blocks hole injection from the substrate. It has the property of having little blocking property against electrons from. For example, zinc oxide, titanium oxide and the like can be mentioned, and among them, anatase type titanium oxide is preferable.

  The anatase-type titanium oxide particles are preferably fine particles having a number average primary particle diameter in the range of 5 to 400 nm. In particular, 10 nm to 200 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.

  In the present invention, anatase-type titanium oxide pigment containing niobium element in the intermediate layer in an amount of 100 ppm to 2.0 mass% is preferable. By including niobium element in the above range in the anatase-type titanium oxide pigment, the rectification characteristics of the anatase-type titanium oxide pigment are stably exhibited even during long-term use of the photoreceptor, and dielectric breakdown and black spots are generated. Even if the environmental conditions of temperature and humidity change, the change in charging characteristics and sensitivity characteristics is small.

  The content of niobium element in the anatase titanium oxide pigment is more preferably 300 ppm to 1.8% by mass.

  The concentration of niobium element in the whole anatase-type titanium oxide particles of the present invention can be analyzed by quantitative analysis by ICP (inductively coupled plasma emission spectrometry).

  The anatase-type titanium oxide pigment of the present invention can be produced by a known sulfuric acid method. That is, it is obtained by heating and hydrolyzing a solution containing titanium sulfate and titanyl sulfate to produce a hydrous titanium dioxide slurry, and dehydrating and firing the titanium dioxide slurry. Hereinafter, the manufacturing method of the anatase type titanium oxide pigment containing a niobium element is described.

  First, niobium sulfate (water-soluble niobium compound) is added to a hydrous titanium dioxide slurry obtained by hydrolyzing a titanyl sulfate aqueous solution. The addition amount is suitably 0.15 to 5 mass% niobium sulfate as niobium ions with respect to the amount of titanium in the slurry (in terms of titanium dioxide). Specifically, (i) hydrous titanium dioxide slurry obtained by hydrolyzing 0.15 to 5% by mass of niobium sulfate as niobium ion to titanyl sulfate aqueous solution, or (ii) hydrolyzing titanyl sulfate aqueous solution A slurry obtained by adding 0.15 to 5% by mass of niobium sulfate as niobium ions to the hydrous titanium dioxide slurry obtained as described above can be used.

  The hydrous titanium dioxide slurry containing the niobium ions and the like is dehydrated and fired. In general, the firing temperature is suitably 850 to 1100 ° C. When the firing temperature is less than 850 ° C., firing is not sufficiently performed. On the other hand, if the temperature exceeds 1100 ° C., the particles are sintered and the dispersibility of the pigment is significantly impaired. Niobium ions added to the slurry are segregated on the particle surface during firing, and are contained in the surface layer in a large amount as niobium oxide. By this production method, an anatase-type titanium oxide pigment having an average primary particle diameter of 0.01 to 10 μm and containing 100 ppm to 2 mass% of niobium element can be obtained.

  There is also a method of forming a titanium oxide pigment by gas sintering using titanium tetrachloride. In this case, unless other metal halogen components are brought into the raw gas component, other metal elements such as niobium are used. An anatase titanium oxide pigment having a content of zero (substantially not contained) can also be produced.

  The anatase-type titanium oxide of the present invention preferably has an anatase degree of 90 to 100%. By the above method, anatase-type titanium oxide having an anatase degree of almost 100% can be produced. Further, the intermediate layer of the present invention containing the anatase-type titanium oxide containing niobium element in this range has a good rectifying property and is stably achieved, and the above-described effects of the present invention are well achieved.

Here, the degree of anatase is measured by measuring the intensity IA of the strongest interference line of anatase (surface index 101) and the intensity IR of the strongest interference line of rutile (surface index 110) in powder X-ray diffraction of titanium oxide, It is a value obtained by the following formula.
Degree of anataseization (%) = 100 / (1 + 1.265 × IR / IA)
In order to produce the anatase degree in the range of 90 to 100%, in the production of titanium oxide, an anatase degree of almost 100% is obtained by heating and hydrolyzing a solution containing titanium sulfate and titanyl sulfate as a titanium compound. A shaped titanium oxide is obtained. Further, when an aqueous solution of titanium tetrachloride is neutralized with an alkali, anatase-type titanium oxide having a high degree of anatase formation can be obtained.

  The coefficient α of the formula (a) of the work function of the intermediate layer of the present invention can be adjusted by changing the particle size, surface treatment, or addition amount of N-type semiconductive particles such as anatase titanium oxide pigment. . Originally, anatase-type titanium oxide pigments have strong N-type characteristics, but by applying a surface treatment, the N-type characteristics can be suppressed, and as a result, the coefficient α in the formula (a) tends to increase. Become.

  The anatase-type titanium oxide pigment can change the N-type characteristics by performing a surface treatment with a reactive organosilicon compound. The surface treatment of the anatase titanium oxide pigment with the reactive organosilicon compound can be performed by the following wet method. The surface treatment of the reactive organosilicon compound means that a reactive organosilicon compound is used for the treatment liquid.

  That is, the anatase-type titanium oxide pigment is added to a solution obtained by dissolving or suspending the reactive organosilicon compound in an organic solvent or water, and this mixed solution is dispersed in a medium for several minutes to one day. And depending on the case, after heat-processing a liquid mixture, it passes through processes, such as filtration, It dries, and the anatase type titanium oxide pigment which coat | covered the surface with the organosilicon compound is obtained. Note that the reactive organosilicon compound may be added to a suspension in which titanium oxide is dispersed in an organic solvent or water.

  The amount of the reactive organosilicon compound used for the surface treatment is 0.1 to 10 parts by mass of the reactive organosilicon compound with respect to 100 parts by mass of the anatase-type titanium oxide pigment in the amount charged in the surface treatment. More preferably, 0.1 to 5 parts by mass is used. When the surface treatment amount is less than the above range, the surface treatment effect is not sufficiently imparted and the dispersibility of the titanium oxide particles in the intermediate layer is deteriorated. Further, when the surface treatment amount exceeds the above range, the electrophotographic characteristics are deteriorated, and as a result, the residual potential is increased and the charged potential is decreased.

  Examples of the reactive organosilicon compound used in the present invention include an organosilicon compound represented by the following general formula (2), but if it is a compound that undergoes a condensation reaction with a reactive group such as a hydroxyl group on the titanium oxide surface, It is not limited to the following compounds.

General formula (2)
(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 (2), 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 (2) may be individual, and may be used in combination of 2 or more types.

  Moreover, when it is a specific compound of the organosilicon compound represented by General formula (2) and n is two or more, several R may be 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 (2), R and X may be the same between each compound, and may differ.

  Moreover, a polysiloxane compound is mentioned as a preferable reactive organosilicon compound. In particular, methyl hydrogen polysiloxane is preferred. The polysiloxane compound having a molecular weight of 1000 to 20000 is generally easily available, and has a good function to prevent occurrence of black spots.

  Another surface treatment of the titanium oxide of the present invention is titanium oxide particles that have been surface treated with an organosilicon compound having a fluorine atom. It is preferable to perform the surface treatment with the organosilicon compound having a fluorine atom and the wet method described above.

  In the present invention, the surface of the titanium oxide particles is coated with a reactive organosilicon compound because photoelectron spectroscopy (ESCA), Auger electron spectroscopy (Auger), secondary ion mass spectrometry (SIMS), and diffuse reflection. This is confirmed by combining surface analysis techniques such as FI-IR.

  Another one of the surface treatments of the anatase-type titanium oxide pigment includes at least one kind of surface treatment selected from alumina, silica, and zirconia.

  The alumina treatment, silica treatment, and zirconia treatment are treatments for precipitating alumina, silica, or zirconia on the surface of anatase-type titanium oxide. Japanese products are also included.

  The treatment of alumina and silica may be performed simultaneously, but it is particularly 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 anatase titanium oxide with a metal oxide such as alumina, silica, and zirconia can be performed by a wet method. For example, anatase-type titanium oxide subjected to surface treatment of silica or alumina can be produced as follows.

  When anatase type titanium oxide is used, 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 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.

  In addition, the amount of the metal oxide used for the surface treatment is 0.1 to 50 parts by mass, more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the titanium oxide particles in the amount charged in the surface treatment. These metal oxides are used. In the case of using alumina and silica as described above, for example, in the case of anatase-type titanium oxide particles, it is preferable to use 1 to 10 parts by mass with respect to 100 parts by mass of titanium oxide particles, and the amount of silica is larger than that of alumina. Is preferred.

Moreover, it is preferable that the intermediate layer of the present invention 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%
When 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 electrophotographic photosensitive member 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.

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

  The intermediate layer of the present invention preferably contains N-type semiconductive particles in an amount of 10 to 10,000 parts by mass, preferably 50 to 1,000 parts by mass with respect to 100 parts by mass of the binder resin. By using the N-type semiconductor particles in this range, the dispersibility of the N-type semiconductor particles can be kept good, dielectric breakdown and black spots do not occur, and a good intermediate where the potential fluctuation is small. A layer can be formed.

  On the other hand, as the binder resin for dispersing these particles and forming the layer structure of the intermediate layer, a polyamide resin or the like can be used in order to obtain good dispersibility of the particles. A curable resin having an inorganic segment component is preferred.

  The intermediate layer of the organic photoreceptor of the present invention preferably contains a binder resin having an organic segment component and an inorganic segment component. Furthermore, the binder resin preferably contains an antioxidant structure component.

  Here, the organic segment component refers to a component having a repeating unit structure in which a chain structure forming a resin is formed of an organic substance (including a carbon atom in the chain structure).

  For example, it refers to a chain structure component constituting a vinyl resin, a polyester resin, a polycarbonate resin, or the like. The resin of the intermediate layer of the present invention contains this organic segment component as a partial structure of the resin structure together with the inorganic segment component.

  The organic segment component of the present invention is preferably a segment component polymerized from a chain polymerizable monomer. Especially, the vinyl-type resin component formed using acrylic acid ester or methacrylic acid ester as a chain-polymerizable monomer is preferable.

  On the other hand, the inorganic segment component refers to a component having a repeating unit in which a resin chain structure is formed of an inorganic substance. A preferable inorganic segment component includes a siloxane condensate component having a chain structure of silicon and oxygen.

  Hereinafter, a resin in which a siloxane condensate component as an inorganic segment component is bonded to an organic segment component composed of a vinyl resin component will be described.

  In order to connect the siloxane condensate component to the organic segment component by a chemical bond, a polymerizable silane compound of the following general formula (1) having a polymerizable unsaturated group of a carbon-carbon unsaturated bond is formed at the time of forming the organic segment. By coexisting and reacting these polymerizable silane compounds with the progress of polymerization of the chain polymerizable monomer (chain polymerizable monomer of the organic segment component) during the formation of the organic segment component, A silyl-modified organic segment component into which a group has been introduced is formed, and then a siloxane condensate (siloxane resin component) is formed on this silyl group, or an already formed siloxane condensate is bonded.

In the general formula (1), R ³ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aralkyl group having 1 to 10 carbon atoms, R ⁴ is an organic group having a polymerizable double bond, X is a halogen atom, alkoxy A group, an acyloxy group, an aminoxy group, and a phenoxy group, and n is an integer of 1 to 3.

The polymerizable silane compound represented by the general formula (1) is not particularly limited as long as it is a compound having a silyl group, particularly a hydrolyzable silyl group, and capable of polymerizing with various chain polymerizable monomers described below. For example, CH ₂ = CHSi (CH ₃ ) (OCH ₃ ) ₂ , CH ₂ = CHSi (OCH ₃ ) ₃ , CH ₂ = CHSi (CH ₃ ) Cl ₂ , CH ₂ = CHSiCl ₃ , CH ₂ = CHCOO (CH ₂ ) ₂ Si (CH ₃ ) (OCH ₃ ) ₂ , CH ₂ = CHCOO (CH ₂ ) ₂ Si (OCH ₃ ) ₃ , CH ₂ = CHCOO (CH ₂ ) ₃ Si (CH ₃ ) (OCH ₃ ) ₂ , CH ₂ = CHCOO (CH ₂ ) ₃ Si (OCH ₃ ) ₃ , CH ₂ = CHCOO (CH ₂ ) ₂ Si (CH ₃ ) Cl ₂ , CH ₂ = CHCOO (CH ₂ ) ₂ SiCl ₃ , CH ₂ = CHCOO ( _{CH 2) 3 Si (CH 3} ) Cl 2 _{CH 2 = CHCOO (CH 2)} 3 SiCl 3, CH 2 = C (CH 3) COO (CH 2) 2 Si (CH 3) (OCH 3) 2, CH 2 = C (CH 3) COO (CH 2) ₂ Si (OCH ₃ ) ₃ , CH ₂ ═C (CH ₃ ) COO (CH ₂ ) ₃ Si (CH ₃ ) (OCH ₃ ) ₂ , CH ₂ ═C (CH ₃ ) COO (CH ₂ ) ₃ Si (OCH _{3) 3, CH 2 = C} (CH 3) COO (CH 2) 2 Si (CH 3) Cl 2, CH 2 = C (CH 3) COO (CH 2) 2 SiCl 3, CH 2 = C (CH 3 ) COO (CH ₂ ) ₃ Si (CH ₃ ) _{Cl 2} , CH ₂ ═C (CH ₃ ) COO (CH ₂ ) ₃ SiCl ₃ ,

Etc. These polymerizable silane compounds can be used alone or in admixture of two or more.

  Examples of the chain polymerizable monomer forming the organic segment component include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and cyclohexyl (meth). (Meth) acrylic acid esters such as acrylates; carboxylic acids such as (meth) acrylic acid, itaconic acid and fumaric acid and acid anhydrides such as maleic anhydride; epoxy compounds such as glycidyl (meth) acrylate; diethylaminoethyl (meth) Amino compounds such as acrylate and aminoethyl vinyl ether; Amide compounds such as (meth) acrylamide, itaconic acid diamide, α-ethylacrylamide, crotonamide, fumaric acid diamide, maleic acid diamide, N-butoxymethyl (meth) acrylamide; Nitrile, styrene, alpha-methyl styrene, vinyl chloride, vinyl acetate, be used one or more of the vinyl chain-polymerizable monomer selected from the group consisting of vinyl propionate preferred. In addition, a vinyl chain polymerizable monomer (monomer) containing a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxyvinyl ether, N-methylol acrylamide, etc. may be used. Can do.

  In the photoreceptor of the present invention, the intermediate layer preferably contains a binder resin having an organic segment component, an inorganic segment component, and an antioxidant structure component.

Here, the antioxidant structural component refers to a group having ozone, active gas such as NO _x, or oxidation or reduction resistance caused by light irradiation such as ultraviolet rays.

  The phrase “resin has an antioxidant structure component” means that the resin structure has an antioxidant structure component such as a hindered amine or a hindered phenol as a partial structure. The antioxidant structure component can introduce an antioxidant structure component such as hindered amine or hindered phenol as a partial structure into the organic segment component.

  That is, a resin having an organic segment component, an inorganic segment component, and an antioxidant structure component includes a chain polymerizable monomer that forms an organic segment component, a polymerizable monomer that forms an antioxidant structure component, and a polymerizable silane compound. It can be achieved by conducting a polymerization reaction to form an organic segment component having an antioxidant structure component and a silyl group, and then forming a siloxane condensate on the silyl group of the organic segment component.

  Here, the hindered amine group refers to a group having steric hindrance in the vicinity of the N atom of the amino group of the amine compound and a derivative thereof. As the steric hindrance group, a branched alkyl group, a group having 3 or more carbon atoms, and the like are preferable.

  The hindered phenol group refers to a group having a steric hindrance at the ortho position with respect to the hydroxyl group of phenol and a derivative thereof. (However, the hydroxyl group may be converted to alkoxy). The sterically hindering group is preferably a branched alkyl group or a group having 3 or more carbon atoms.

  In order to introduce a hindered amine group or a hindered phenol group into the organic segment component as a partial structure, a hindered amine compound (monomer) or hinder having a polymerizable unsaturated group of a carbon-carbon unsaturated bond at the time of forming the organic segment component Dophenol compounds (monomers) are allowed to coexist, and these compounds are reacted with the progress of polymerization of the chain polymerizable monomer during the formation of the organic segment component, whereby a hindered amine group or a hindered phenol group is contained in the organic segment component. Can be introduced.

  As such a hindered amine compound having a polymerizable unsaturated group, a sterically hindered amine compound containing a polymerizable unsaturated group is preferable, and among them, a sterically hindered piperidine compound containing a polymerizable unsaturated group (hereinafter referred to as “piperidine-based compound”). "Monomer") is particularly preferred. Typical examples of the piperidine compounds include compounds represented by the following general formula (A).

In the general formula (A), R ⁵ represents a hydrogen atom or a cyano group, R ⁶ and R ⁷ may be the same or different from each other, represent a hydrogen atom, a methyl group or an ethyl group, and X represents an oxygen atom or an imino group. Y represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or a polymerizable unsaturated group represented by the following general formula (B).

In the general formula (B), R ⁸ and R ⁹ may be the same as or different from each other, and represent a hydrogen atom, a methyl group, or an ethyl group.

  The hydrogen atom in the imino group of X in the general formula (A) may be substituted or unsubstituted. Examples of the alkyl group having 1 to 18 carbon atoms in Y in the general formula (A) include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl. Group, t-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group And linear or branched alkyl groups such as a group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group and n-octadecyl group.

  Among the piperidine compounds of the general formula (A), preferred compounds are 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloylamino-2,2, 6,6-tetramethylpiperidine, 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloylamino-1,2,2,6,6-pentamethyl Piperidine, 4-cyano-4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4-cyano-4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4-cyano-4- (meth) acryloylamino-1,2 2,6,6-pentamethylpiperidine, 1- (meth) acryloyl-4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4- (meth) acryloyl Amino-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4-cyano-4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 1- (meth) Acryloyl-4-cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 4-crotonoylamino- 2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-1,2,2,6,6-pentamethylpiperidine, 4-crotonoyl Mino-1,2,2,6,6-pentamethylpiperidine, 4-cyano-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 4-cyano-4-crotonoylamino-2, 2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoylamino-2,2,6,6- Tetramethylpiperidine, 1-crotonoyl-4-cyano-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-cyano-4-crotonoylamino-2,2,6 6-tetramethylpiperidine, among others 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloyl Oxy-1,2,2,6,6-pentamethylpiperidine is particularly preferred.

  Moreover, as a hindered phenol compound which has a polymerizable unsaturated group, the hindered phenol compound which contains a polymerizable unsaturated group is preferable, for example, the following compounds can be mentioned. That is, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2- (3,5-di-t-butyl-4-hydroxyphenyl) ) Ethyl acrylate, 2- (3,5-di-s-propyl-4-hydroxyphenyl) ethyl acrylate, 2- (3,5-di-t-octyl-4-hydroxyphenyl) ethyl acrylate, 2- (3 -T-butyl-5- (3-t-butyl-2-hydroxy-5-methylbenzyl) 4-hydroxyphenyl) ethyl acrylate, 2-t-butyl-6- (3-t-butyl-2-hydroxy- 5-methylbenzyl) -4-methylphenyl (meth) acrylate, 2- (3,5-di-t-butyl-4-hydroxyphenyl) ethyl (meth) acrylate, 2- 3,5-di-s-propyl-4-hydroxyphenyl) ethyl (meth) acrylate, 2- (3,5-di-t-octyl-4-hydroxyphenyl) ethyl (meth) acrylate, 2- (3- t-butyl-5- (3-t-butyl-2-hydroxy-5-methylbenzyl) 4-hydroxyphenyl) ethyl (meth) acrylate, vinyl 3,5-di-t-butyl-4-hydroxyphenylpropionate Ester, 3,5-di-t-octyl-4-hydroxyphenylpropionic acid vinyl ester, 3,5-di-t-butyl-4-hydroxyphenylpropionic acid-isopropenyl ester, 3,5-di-t- And octyl-4-hydroxyphenylpropionic acid-isopropenyl ester.

  The compounds having the antioxidant structure component can be used alone or in admixture of two or more. Further, “having a hindered amine group or hindered phenol group” means having at least one of a hindered amine group or a hindered phenol group, and may have both groups.

  Here, a synthesis example of an organic segment component having a hindered amine group or a hindered phenol group and silyl-modified (having a silyl group) will be described.

(Synthesis example of organic segment component A solution: hindered amine group-containing silyl-modified vinyl polymer A solution)
In a reaction vessel equipped with a reflux condenser and a stirrer, 25 parts of γ-methacryloyloxypropyltrimethoxysilane, 1 part of 4-methacryloyloxy-1,2,2,6,6, -pentamethylpiperidine as monomers, methacrylic acid After adding 80 parts of methyl, 15 parts of 2-ethylhexyl methacrylate, 29 parts of n-butyl acrylate, 150 parts of 2-propanol, 50 parts of 2-butanone and 25 parts of methanol, the mixture was heated to 80 ° C. with stirring. A solution of 4 parts of azobisisovaleronitrile dissolved in 10 parts of xylene was added dropwise to this mixture over 30 minutes, and then reacted at 80 ° C. for 5 hours to have a hindered amine group in the side chain with a solid content concentration of 40%. In addition, a vinyl polymer A solution having a silyl group was obtained.

(Synthesis example of organic segment component B solution: vinyl polymer B solution having a hindered phenol group and silyl-modified)
In a reaction vessel equipped with a reflux condenser and a stirrer, 20 parts of γ-methacryloyloxypropyltrimethoxysilane as a monomer, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl)- 2-methylphenyl acrylate 2 parts, methyl methacrylate 70 parts, n-butyl acrylate 40 parts, acrylic acid 5 parts, 2-hydroxyethyl methacrylate 13 parts, 1,1,1-trimethylamine methacrylamide 1 part, 2-propanol 150 1 part, 50 parts of 2-butanone and 25 parts of methanol were added and mixed, and then heated to 80 ° C. with stirring, and a solution of 4 parts of azobisisovaleronitrile in 10 parts of xylene was added to this mixture over 30 minutes. After adding dropwise, the reaction is carried out at 80 ° C. for 5 hours to form a hindered phenol on the side chain with a solid content of 40%. To obtain a vinyl polymer B solution and having a silyl group having a group.

  As shown in the above synthesis examples A and B, a hindered amine compound having a polymerizable unsaturated group, a hindered phenol compound, a polymerizable silane compound, and a vinyl chain polymerizable monomer are allowed to coexist and polymerize on the side chain. An organic segment component (vinyl polymer component) having a hindered amine group or a hindered phenol group and having a silyl group can be synthesized.

  The degree of polymerization of the organic segment component having a silyl group is not particularly limited, but is preferably 100 to 500.

  Next, the intermediate layer having the resin structure of the present invention can be formed by forming a siloxane condensate component on the vinyl polymers A and B having the silyl group. That is, a siloxane condensate component is formed on a silyl group of a vinyl polymer having a silyl group using the vinyl polymer having the silyl group and an organosilicon compound as described below. The formation of the siloxane condensate component may be performed simultaneously with the formation of the intermediate layer, or the intermediate layer may be formed by previously forming the siloxane condensate component at the silyl group terminal in the intermediate layer solution.

  The siloxane condensate component has a structure in which a plurality of siloxane bonds are three-dimensionally connected and has a resin structure obtained by polycondensation of an organosilicon compound represented by the general formula (2). .

  Further, when two or more organosilicon compounds represented by the general formula (2) are used in producing the siloxane condensate component of the present invention, the R of each organosilicon compound may be the same or different. .

  The organosilicon compound used as a raw material for the siloxane condensate component having a cross-linked structure is generally an organosilicon compound when n of the number of hydrolyzable groups (4-n) bonded to silicon atoms is 3. Polymerization reaction is suppressed. When n is 0, 1 or 2, a polymerizing reaction is likely to occur. In particular, when 1 or 0, the crosslinking reaction can be advanced to a high degree. Therefore, by controlling these, the storage stability of the coating layer solution obtained, the hardness of the coating film, and the like can be controlled.

  The intermediate layer of the present invention contains a resin having an organic segment component, an inorganic segment component, and an antioxidant structure component, but these components are bonded to each other by chemical bonds in the resin, and the entire intermediate layer is crosslinked. It is formed of a resin layer having a structure.

  The mass ratio of the organic segment component, the inorganic segment component, and the antioxidant structure component of the resin constituting the intermediate layer is relative to the organic segment component 1, the inorganic segment component 0.25-4, the antioxidant structure component 0.01-1 It is preferable that it is comprised by mass ratio. When the mass ratio of the inorganic segment component is small, the residual potential is likely to increase during repeated image formation, and the image density is likely to decrease during reversal development. When there are too many inorganic segment components, the applicability of the charge generation layer placed on the intermediate layer deteriorates, and a uniform film cannot be formed. Further, even if the mass ratio of the antioxidant structure component is large or small, the electrophotographic characteristics (charging, sensitivity, residual potential characteristics, etc.) during repeated use are likely to deteriorate.

Photosensitive layer 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.

  In the organic photoreceptor of the present invention, a phthalocyanine pigment, an azo pigment, a perylene pigment, an azulenium pigment, or the like can be used alone or in combination as a charge generating material. Among these pigments, titanyl phthalocyanine pigments, gallium phthalocyanine pigments, perylene pigments, and the like that are highly sensitive and have good potential stability are preferably used. For example, titanyl phthalocyanine having a maximum peak at a Bragg angle 2θ of 27.2 ° with respect to Cu—Kα rays, benzimidazole perylene having a maximum peak at 12.4 of 2θ, and the Bragg angle of a characteristic X-ray diffraction spectrum of Cu—Kα ( 2θ ± 0.2 °) chlorgallium phthalocyanine pigment having diffraction peaks at positions of at least 7.4 °, 16.6 °, 25.5 °, 28.3 °, or at least 7.5 °, 9. Changes in charging performance and sensitivity due to repeated use of hydroxygallium phthalocyanine pigments having diffraction peaks at 9 °, 12.5 °, 16.3 °, 18.6 °, 25.1 ° and 28.1 ° There is almost no and it is used well.

  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 0.1 μm to 2 μm.

Charge transport layer A charge transport layer having a film thickness of 5 to 15 μm is used for the charge transport layer of the present invention. If the film thickness is less than 5 μm, the charging potential is insufficient, the potential contrast of the electrostatic latent image is not sufficiently obtained, image blurring is likely to occur, and periodic image defects such as black spots are likely to occur. . On the other hand, if the film thickness exceeds 15 μm, diffusion of the electrostatic latent image tends to be large, and the image is easily blurred and sharpness is likely to deteriorate.

  The charge transport layer of the present invention is basically composed of a charge transport material (CTM) and a binder resin having a film forming function in which the CTM is dispersed.

  Examples of charge transport materials include triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine compounds, butadiene compounds, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazoline derivatives, Bisimidazolidine derivatives, styryl compounds, hydrazone compounds, benzidine compounds, pyrazoline derivatives, stilbene compounds, oxazolone derivatives, benzothiazole derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, poly-N -Vinylcarbazole, poly-1-vinylpyrene, poly-9-vinylanthracene alone, There can be used in combination. Among these charge transport materials, in order to obtain stable electrophotographic characteristics (charging ability, sensitivity, etc.) in combination with the above-described charge generation materials, the charge transport materials are triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine. It is preferable to select from a compound and a butadiene compound. These charge transport materials are usually dissolved in a suitable binder resin to form a layer.

  As the binder resin for the charge transport layer, a binder resin having a low dielectric constant is preferably used, and examples thereof include polystyrene resins and styrene butadiene copolymers.

  If necessary, the charge transport layer may contain an additive such as an antioxidant.

  The binder resin used in the charge transport layer (CTL) is not limited to either a thermoplastic resin or a thermosetting resin, but a binder resin having a low dielectric constant is preferably used, and a particularly preferable binder resin is polystyrene. It is preferable to use a resin, a styrene butadiene copolymer, a polycarbonate or the like alone or in a blend.

  The ratio of the binder resin to the charge transport material is preferably 50 to 200 parts by mass with respect to 100 parts by mass of the binder resin.

  The charge transport layer may be composed of a plurality of charge transport layers. The film thickness of the plurality of charge transport layers may be within the range of 5 to 15 μm.

  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.

  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, etc. is used. In order to prevent dissolution as much as possible, and in order to achieve uniform coating processing, it is preferable to use a coating processing method such as spray coating or circular amount regulation type (circular slide hopper type is a typical example). 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.

  FIG. 1 is a cross-sectional configuration diagram illustrating an example of a tandem intermediate transfer type image forming apparatus.

  This example is an apparatus having a drum-type intermediate transfer unit. After a color image is formed on the transfer unit 10 by superimposing color toner as a developer, a recording material (support on the final image: plain paper, In this mode, transfer is performed on a recording sheet P which is a transparent sheet or the like.

The transfer unit 10 includes yellow (Y), magenta (M), cyan (C), and black (K) toners formed by four sets of image forming units 20Y, 20M, 20C, and 20K arranged around the transfer unit 10. The images are sequentially superposed and carried. The transfer means 10 is a drum-shaped transfer body 10 on an aluminum substrate 11 which is a cylindrical metal substrate, and a conductive rubber layer 12 (thickness 500 to 5000 μm, electric resistance 10 ⁸ to 10 as an elastic layer). ¹⁴ Ω · cm urethane rubber layer) and a release film 13 (Teflon (registered trademark) layer having a thickness of 20 to 200 μm and an electric resistance of 10 ¹⁰ to 10 ¹⁶ Ω · cm for separation) thereon. Is provided. Around the transfer body 10, four sets of image forming units 20Y, 20M, 20C, and 20K, a recording paper transfer unit 30, and a cleaning unit 16 are provided. The transfer body 10 is rotatably supported by the color image forming apparatus 100 by a shaft 101.

  The four sets of image forming units 20Y, 20M, 20C, and 20K are provided in the frame bodies 26Y, 26M, 26C, and 26K, respectively, and the frame bodies 26Y, 26M, 26C, and 26K are provided in the color image forming apparatus 100. Movable members 27Y, 27M, and 27C for moving each image forming unit to the image transfer position or the non-image transfer position with respect to the drum-shaped transfer body 10 according to the color used. , 27K are provided in contact with the frame bodies 26Y, 26M, 26C, 26K, respectively.

  The four sets of image forming units 20Y, 20M, 20C, and 20K include charging means 22Y, 22M, 22C, and 22K that rotate around the photosensitive drums 21Y, 21M, 21C, and 21K, and image exposure means 23Y, 23M, 23C, 23K, rotating developing means 24Y, 24M, 24C, 24K, and cleaning means 25Y, 25M, 25C, 25K for cleaning the photosensitive drums 21Y, 21M, 21C, 21K.

  The image forming units 20Y, 20M, 20C, and 20K have the same configuration except that the color of the toner image formed on the transfer body 10 is different, and FIG. 2 (a cross section of the image forming unit used in the image forming apparatus of the present invention). The image forming unit 20Y will be described in detail with reference to the configuration diagram).

  An image forming unit 20Y provided in the frame 26Y has an image forming body charging unit 22Y (hereinafter simply referred to as a charging unit 22Y or a charger 22Y), an exposure unit around a photosensitive drum 21Y as an image forming unit. 23Y, a developing unit 24Y, and an image forming body cleaning unit 25Y (hereinafter simply referred to as a cleaning unit 25Y or a cleaning blade 25Y) are arranged to form a yellow (Y) toner image on the photosensitive drum 21Y. . In the present embodiment, in the image forming unit 20Y, at least the photosensitive drum 21Y, the charging unit 22Y, the developing unit 24Y, and the cleaning unit 25Y are provided so as to be integrated.

The charging means 22Y is a means for applying a uniform potential to the photosensitive drum 21Y. In the present embodiment, a roller-shaped charger 22Y that rotates while being in contact with the photosensitive drum 21Y is used. It has been.
The charging potential of the organic photoreceptor of the present invention can be applied with a charging potential having an upper limit of about 1000 V. However, in an image forming apparatus that writes a digital image with a resolution of 1200 dpi or more, the charging potential is 800 V or less. Most preferably, the range is 200 to 400V. That is, by forming a latent image with a low charging potential, an electrostatic latent image of a dot image faithful to image exposure can be formed.

  The image exposure means 23Y performs exposure based on the image signal (yellow) on the photosensitive drum 21Y given a uniform potential by the roller-shaped charger 22Y, and an electrostatic latent image corresponding to the yellow image. The exposure means 23Y is composed of an LED in which light emitting elements are arranged in an array in the axial direction of the photosensitive drum 21Y and an imaging element (trade name; Selfoc lens). Alternatively, a laser optical system or the like is used.

The organic photoreceptor of the present invention is premised on forming an electrostatic latent image by writing a digital image at a resolution of 1200 dpi or higher. In order to form such an electrostatic latent image of a high-resolution dot image on the photoreceptor, image exposure is performed using an exposure beam having a spot area of 5.00 × 10 ⁻¹⁰ m ² (500 μm ² ) or less. Is preferred.

  Even if such small-diameter beam exposure is performed, the organophotoreceptor of the present invention can faithfully form an electrostatic image corresponding to the spot area, has a dot image of 1200 dpi or more, and has excellent sharpness. Thus, an electrophotographic image with a rich gradation can be achieved. The number of dot images formed on the organic photoreceptor of the present invention is 1200 dpi or more, preferably 1200 to 3000 dpi, more preferably 1200 to 2500 dpi. In order to increase the number of dot images, it is necessary to reduce the spot area of the exposure beam and expose the photosensitive member.

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 the light intensity is 1 / e ² or more of the maximum peak intensity. It means the area corresponding to the region.

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 developing unit 24Y is a unit that stores yellow toner as a developer, and reversely develops the electrostatic latent image formed on the photosensitive drum 21Y to form a yellow toner image. In the developing unit 24Y of the present embodiment, the yellow toner contained in the developing unit 24Y is stirred by the stirring member 241Y, and then the toner rotating roller 242Y whose surface rotates in the direction of the arrow is elastic (sponge). To supply the developing sleeve 243Y. At this time, the yellow toner on the developing sleeve 243Y is made into a uniform thin layer by the thin layer forming member 244Y. During the developing action of the developing means 24Y, a developing bias applied with direct current or further alternating current is applied to the developing sleeve 243Y rotating in the direction of the arrow, and jumping development with one component contained in the developing means 24Y is performed. A non-contact reversal development is performed by applying a bias in which a DC component and an AC component having the same polarity as the toner are applied to the grounded photosensitive drum 21Y. Note that the abutting rollers provided at both ends outside the image area of the developing sleeve 243Y are in contact with the photosensitive drum 21Y, so that the developing sleeve 243Y and the photosensitive drum 21Y are kept in non-contact. In addition, contact development can be used instead of non-contact development.

  The yellow toner image formed on the photosensitive drum 21Y rotates while the abutting roller is in contact with the positioning portion of the transfer body 10, and the transfer body 10 to which a bias voltage having a polarity opposite to that of the toner is applied sequentially. And transferred onto the transfer body 10.

  The cleaning unit 25Y is a unit for removing the yellow toner remaining on the photosensitive drum 21Y after the yellow toner image is transferred to the transfer body 10, from the photosensitive drum 10, and in the present embodiment. The residual toner is removed by the cleaning means 25Y being in sliding contact with the photosensitive drum 21Y.

  In this manner, the yellow toner image corresponding to the image signal (yellow) formed by the charging, exposure, and development steps is transferred onto the transfer body 10 by the image forming unit 20Y.

  As shown in FIG. 1, the other image forming units 20M, 20C, and 20K similarly have magenta toner images and image signals (image signals (magenta) corresponding to the image signals (magenta)) on the photosensitive drums 21M, 21C, and 21K, respectively. A cyan toner image corresponding to cyan) and a black toner image corresponding to the image signal (K) are formed in parallel processing while being synchronized. By such an operation, the toner images formed on the photosensitive drums 21Y, 21M, 21C, and 21K of the image forming units 20Y, 20M, 20C, and 20K are sequentially transferred with a transfer bias of 1 to 2 kV applied thereto. It is transferred onto the body 10 and the toner images are superimposed. When all the toner images are superimposed, a color toner image is formed on the transfer body 10.

  On the other hand, a sheet feeding cassette CA which is a recording material storage means is provided below the transfer body 10, and the recording sheet P which is a recording material stored in the sheet feeding cassette CA is operated by the operation of the sheet feeding roller r1. The sheet is unloaded from the sheet feeding cassette CA and sent to the timing roller pair r2. The timing roller pair r2 feeds the recording paper P so as to synchronize with the color toner image formed on the transfer body 10.

  The fed recording paper P is transferred with the color toner image formed on the transfer body 10 by the recording paper transfer means 30 at the transfer position. The recording paper transfer means 30 includes a grounded roller 31, a transfer belt 32, a paper charger 33, a transfer electrode 34, and a paper separation AC static eliminator 35.

The fed recording paper P is stretched around the roller 31 and conveyed to the transfer position by the transfer belt 32 that rotates in the direction of the arrow in synchronization with the peripheral speed of the transfer body 10. The transfer belt 32 is a belt having a high resistance of 10 ⁶ to 10 ¹⁰ Ω · cm. At this time, the recording paper P is charged to the same polarity as the toner by a paper charger 33 as a recording material charging means, and is attracted to the transfer belt 32 and fed to the transfer position. By charging the paper with the same polarity as that of the toner, it is prevented from attracting the color toner image on the transfer body 10 and the color toner image is prevented from being disturbed. Further, as the recording material charging means, an energizing roller that can contact and separate from the transfer belt 32, a brush charger, or the like can be used.

  At the transfer position, the color toner image on the transfer body 10 is transferred onto the recording paper P by the transfer electrode 34. By the transfer electrode 34, corona discharge is performed on the back surface of the recording paper P so as to have a potential of 1.5 to 3 kV, which is a voltage having a polarity opposite to that of the toner higher than the bias of the transfer body 10.

  The recording paper P that has received the transfer of the color toner image is further conveyed by the transfer belt 32, neutralized by the paper separation AC neutralizer 35 for separating the recording material, separated from the transfer belt 32, and conveyed to the fixing unit 40. Is done. In the fixing unit 40, the color toner image is applied and fixed on the recording paper P by being heated and pressed by the heating roller 41 and the pressure roller 42, and then the recording paper P is discharged to the color image forming apparatus by the discharge roller pair r 3. It is discharged on a tray provided on the top of the tray.

  On the other hand, the transfer body 10 on which the color toner image has been transferred to the recording paper P is rubbed on the transfer body 10 by a cleaning blade 161 which is a transfer body cleaning means 16, and residual toner remaining on the transfer body 10 is removed.・ Cleaned. Further, a blade is in sliding contact with the transfer belt 32 as the transfer belt cleaning means 36, and the transfer belt 32 after paper separation is cleaned.

  In the image forming unit shown in FIG. 2, the developing unit and the photosensitive drum are process cartridges that can be detached from the image forming unit. However, in the present invention, the process cartridge is not limited thereto, and the photosensitive member, Any process cartridge having at least one of charging means, image exposure means, developing means, transfer means, separation means, and cleaning means may be used.

  FIG. 3 is a cross-sectional configuration diagram showing another example of an image forming unit used in the image forming apparatus of the present invention. FIG. 3 is a cross-sectional view of the image forming unit having a slightly different configuration from that of FIG. 2 in which the developing unit and the photosensitive drum are detachable process cartridges from the image forming unit.

  This embodiment will be described by taking the configuration of the image forming unit 20C as an example.

  The frame body 26C constituting the image forming unit 20C is provided on a guide member 111 provided in the color image forming apparatus, and a cam-structured moving member 27C is provided so as to contact a part of the frame body 26C. The image forming unit 20C is stopped at a predetermined image forming position together with the frame 26C against the spring SC. In the frame 26C, a charging unit 22C and an exposure unit 23C are provided around the photosensitive drum 21C as an image forming body. The second frame is a process cartridge which is detachably provided on the frame 26C and can be replaced. In the body 261C, a developing unit 24C, a developer supplying unit 241C, and a developer stirring unit 242C are provided, and the developing unit 24C is disposed so as to face the periphery of the photosensitive drum 21C.

  Further, cyan (C) toner made of the one-component developer T is built in the second frame 261C, and a developer remaining amount detecting means A for detecting the remaining amount of the one-component developer T is provided. It is provided in the developing means 24C.

  A cyan (C) toner image is formed on the photosensitive drum 21C by the image forming process, and the cyan (C) toner image is transferred from the photosensitive drum 21C to the transfer body 10 in the same manner as described above. It arrange | positions so that the circumference | surroundings of the body drum 21C may be cleaned with the cleaning means 25C.

  FIG. 4 is a cross-sectional configuration diagram of another image forming apparatus of the present invention. FIG. 4 shows an image forming apparatus that directly transfers to a recording material on a transfer belt. The image forming procedure in FIG. 4 is almost the same as that in FIGS. 1 to 3 except that the image is directly transferred to the recording material instead of the intermediate transfer member.

  An image forming apparatus that directly transfers to a recording material on the transfer belt in FIG. 4 will be described. A color image by a tandem color image forming apparatus in which four photoconductors are arranged in parallel and toner images of four colors of yellow (Y), magenta (M), cyan (C), and black (K) are sequentially transferred. It is a formation example.

  According to FIG. 4, a photosensitive drum 21Y (21M, 21C, 21K), a scorotron charger (charging means) 22Y (22M, 22C, 22K), an exposure optical system (exposure means), a developing device (developing means) 24Y ( 24M, 24C, 24K) and a cleaning device (cleaning means) 25Y (25M, 25C, 25K), Y, M, C, and K image forming units 20Y (20M, 20C, 20K) are provided, and Y, M, C The toner images formed by the toner image forming units of K and K are supplied with a recording material (recording paper P) at the same timing, and sequentially transferred by a transfer device 34Y (34M, 34C, 34K) as a transfer unit, A superimposed color toner image is formed.

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

  Further, after passing through the transport unit 160, it is transported to a fixing device (fixing means) 40 constituted by the heating roller 41 and the pressure roller 42, and a nip portion formed by the additional fixing roller 41 and the pressure roller 42. The recording paper P is sandwiched by T, and the superimposed toner image on the recording paper P is fixed by applying heat and pressure, and then discharged outside the apparatus.

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

Example 1
Production of 1 photoconductor group (4 photoconductors with the same prescription for tandem)
<Intermediate layer (UCL)>
The following intermediate layer coating solution was prepared and applied onto a washed cylindrical aluminum substrate having a diameter of 30 mm by a dip coating method to form an intermediate layer.

(Preparation of intermediate layer coating solution A)
Organic segment component A solution (hindered amine group-containing vinyl-based polymer A solution) 100 parts Methyltrimethoxysilane 70 parts Dimethyldimethoxysilane 30 parts Fine particles: The following anatase-type titanium oxide A1 (number average primary particle size: 35 nm, surface treatment is methylhydrogenpolysiloxane treatment) 100 parts i-butyl alcohol 100 parts butyl cellosolve 75 parts di-i-propoxyethyl acetoacetate aluminum 10 parts are mixed and stirred well. A portion was added dropwise and reacted at 60 ° C. for 4 hours. Next, the mixture was cooled to room temperature, 10 parts of an i-propyl alcohol solution of dioctyltin dimaleate ester (solid content 15%) was added and stirred to prepare an intermediate layer coating solution A.

This intermediate layer coating solution A is applied onto the cylindrical aluminum substrate by a circular amount-regulating coating apparatus, and is heated and cured at 120 ° C. for 1 hour, and the organic segment component of the present invention having a dry film thickness of 6.5 μm, inorganic An intermediate layer of a resin layer having a segment component and an antioxidant structure component was formed. The volume resistance of the intermediate layer after drying was 3 × 10 ¹³ Ω · cm under the above measurement conditions.

<Charge generation layer (CGL)>
Oxytitanyl phthalocyanine (G-1: Maximum peak angle of X-ray diffraction by Cu-Kα characteristic X-ray is 27.3 in Bragg 2θ) 20 parts Polyvinyl butyral (# 6000-C, manufactured by Denki Kagaku Kogyo) 10 parts 2- 700 parts of butanone 300 parts of 4-methoxy-4-methyl-2-pentanone The above composition was mixed and dispersed using a sand mill 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.

<Charge transport layer (CTL)>
Charge transport material (T-1: [4- (2,2-diphenylvinyl) phenyl] -di-p-tolylamine) 75 parts Polycarbonate resin (Iupilon Z300: manufactured by Mitsubishi Gas Chemical Company) 100 parts Irganox 1010 (manufactured by Ciba Geigy Japan) ) 6 parts methylene chloride 750 parts The above composition was mixed and dissolved to prepare a charge transport layer coating solution. This coating solution is applied onto the charge generation layer with a circular amount-regulating coating machine, dried at 105 ° C. for 70 minutes to form a charge transport layer having a dry film thickness of 12 μm, and a group of photoreceptors (identical for tandem) Four photoconductors having a prescription were prepared.

Production of two photoreceptors (four photoreceptors with the same formulation for tandem)
In the production of the photoreceptor 1 group, the photoreceptor 2 group was produced in the same manner except that the dry film thickness of the intermediate layer was changed from 10 μm to 6.5 μm.

Production of 3 groups of photoconductors (4 photoconductors with the same formulation for tandem)
In the production of the photosensitive member 1 group, the intermediate layer coating solution A for the intermediate layer was changed to the following intermediate layer coating solution B, and the dry film thickness of the intermediate layer was changed from 10 μm to 15 μm. Was made.

(Preparation of intermediate layer coating solution B)
Organic segment component B solution (vinyl polymer B solution having a hindered phenol group and modified with silyl) 100 parts Methyltrimethoxysilane 70 parts Dimethyldimethoxysilane 30 parts Fine particles: The following anatase-type titanium oxide A1 (number average primary particles) Diameter: 35 nm, surface treatment is methyl hydrogen polysiloxane treatment) 150 parts i-butyl alcohol 100 parts butyl cellosolve 75 parts di-i-propoxyethyl acetoacetate aluminum 10 parts are mixed and stirred well. 30 parts of water was added dropwise and reacted at 60 ° C. for 4 hours. Subsequently, it cooled to room temperature, 10 parts of i-propyl alcohol solutions (solid content 15%) of dioctyltin dimaleate ester were added, and it stirred, and the intermediate | middle layer coating liquid B was prepared.

Production of Photoreceptor Group 4 to Photoreceptor Group 12 In production of photoreceptor group 1, the surface roughness of the aluminum substrate, the type of fine particles in intermediate layer coating solution A: anatase-type titanium oxide A1, and the dry film thickness of intermediate layer: Photoconductor 4 group to Photoconductor 12 group were prepared in the same manner except that 10 μm, the dry thickness of the charge transport layer: 12 μm, and the charge generation material: G-1 were changed as shown in Table 1.

Preparation of anatase-type titanium oxide A1 100 parts by mass of anatase-type titanium oxide pigment (primary particle size 35 nm) was mixed with a solution obtained by dissolving 4 parts by mass of methylhydrogenpolysiloxane in 100 parts by mass of an alcohol / water (10/1) solvent. And media distribution. After the media dispersion was performed all day and night, the anatase-type titanium oxide pigment was taken out of the media dispersion and dried to obtain titanium oxide A1 (degree of anataseization: 100%) surface-treated with methylhydrogenpolysiloxane.

Production of anatase type titanium oxide A2 Anatase type titanium oxide A2 was produced in the same manner as the production of anatase type titanium oxide A1, except that the amount of methyl hydrogen polysiloxane was changed from 4 parts by mass to 5 parts by mass.

Production of anatase type titanium oxide A3 Anatase type titanium oxide A3 was produced in the same manner as the production of anatase type titanium oxide A1, except that the amount of methyl hydrogen polysiloxane was changed from 4 parts by mass to 6 parts by mass.

<Evaluation 1: Measurement of Coefficient α of Intermediate Layer of Photoreceptor 1 Group to Photoreceptor 12 Group>
Contact potential difference measurement and work function plot of intermediate layer of photoreceptor 1 group to photoreceptor 12 group In contact potential difference measurement, the intermediate layer coating solution was palladium (Pd), indium tin oxide (ITO), nickel-chromium alloy (Ni- Cr), titanium (Ti), aluminum (Al), aluminum-chromium alloy (Al-Cr), etc., spin-coated on the electrode, then dried to prepare a measurement sample, and in the atmosphere using the Kelvin method I went there. The work function φ _UL of the intermediate layer thus obtained is expressed as a work function plot with respect to the work function φ _M of the corresponding electrode metal (measured without applying the intermediate layer), and the coefficient α of the equation (a) is obtained. It was. A work function plot of the intermediate layer of the photoreceptor 1 group is shown in FIG. Table 1 shows the measurement results of the coefficient α in the formula (a) together with the surface roughness, intermediate layer, charge generation layer, and charge transport layer of the aluminum bases of the photoconductor 1 group to photoconductor 12 group.

In the table,
G-1 is a titanyl phthalocyanine pigment having a maximum peak at 27.2 ° at a Bragg angle (2θ ± 0.2 °) of the characteristic X-ray diffraction spectrum of Cu-Kα. G-2 is a characteristic X-ray diffraction of Cu-Kα. 17. at least 7.5 °, 9.9 °, 12.5 °, 16.3 °, 18. at the Bragg angle of the spectrum (2θ ± 0.2 °).
Hydroxygallium phthalocyanine pigment having diffraction peaks at 6 °, 25.1 °, and 28.1 ° <Evaluation 2: Image evaluation>
Each photoconductor group is combined with a 1200 dpi digital color printer (exposure wavelength: 650 nm) based on the image forming apparatus shown in FIG. 1 as shown in Table 2, and pixels are obtained at room temperature and normal humidity (20 ° C., 50% RH). Monochrome images and color images with 8% character and halftone mixed were continuously printed on A4 paper. The ratio between the monochrome image and the color image was printed at a ratio of 9 monochrome images and 1 color image, that is, a ratio of 9: 1, considering the monochrome and color print ratio of the tandem color image forming apparatus. However, printing was paused when necessary for the following evaluation. Evaluation items and evaluation criteria are shown below. The evaluation results are shown in Table 2. Incidentally, the amount of film thickness loss of the monochrome photoconductor after the above-mentioned 150,000 prints of the monochrome photoconductor was approximately 6.5 μm for each photoconductor.

Evaluation items and evaluation criteria "Dot reproducibility of monochrome images"
The dot reproducibility constituting the black image was evaluated by looking through a 100 × magnifier. Evaluation was made with black images at the start of printing (S), after 50,000 sheets (50,000), and after 150,000 sheets (150,000).

A: Dot images are produced with an increase / decrease of less than 30% of the exposure spot area, and are reproduced independently (good)
◯: Dot images are produced with an increase / decrease of 30 to 60% with respect to the exposure spot area, and each is reproduced independently (practical level)
X: The dot image is produced with an increase / decrease exceeding 60% with respect to the exposure spot area, and the dot image is partially lost or connected (practical problem level).
"Color image dot reproducibility"
The dot reproducibility constituting the image was evaluated by looking through a 100 × magnifier. Evaluation was made with color images at the start of printing (S), after 50,000 sheets (50,000), and after 150,000 sheets (150,000).

A: Reproduced with little variation between K, Y, M, and C dots in color image (maximum and minimum difference of each dot is less than 30% in dot area difference), and color image has good color balance (Good)
○: The variation between the K, Y, M, and C dots of the color image is reproduced with the maximum and minimum difference of each dot being 30 to 60% of the dot area difference, and the color balance of the color image is Maintained (practical level)
X: The color image has a large variation between the K, Y, M, and C dots (the maximum and minimum difference of each dot is greater than 60% in terms of dot area), and the color balance of the color image is reproduced. Is lost. (Practical problem level)
"Periodic image defects"
The occurrence of image defects (generated as black spots (including color spots), white spots, or linear image defects) that coincided with the period of the photoreceptor was evaluated. Evaluation was performed with monochrome and color images after 150,000 sheets.

Evaluation criteria: A: Occurrence of clear periodic image defects is hardly observed (in the case of black spots, 3 / A4 or less, in the case of linear, the density is within 0.02: good)
○: Occurrence of clear periodic image defects is within the range of practicality (in the case of black spots, 4 to 10 / A4 or less, in the case of linear, the concentration is 0.03 to 0.04: practical) level)
Δ: A clear periodic image defect occurs, and the practicality needs to be reexamined (in the case of black spots, 11 to 20 pieces / A4 or less, in the case of linear, the density is 0.05 to 0.06) : Level of practicality review required)
X: Occurrence of clear periodic image defects frequently (21 in the case of black spots / A4 or more, in the case of linear, the density is 0.07 or more: practically problematic level)
"Sharpness"
The sharpness of the image was evaluated by the resolution of the line image. Evaluation was made according to the following criteria. Evaluation was performed with monochrome and color images after 150,000 sheets.

A: The resolution of the line image has achieved 16 lines / mm or more (good).
○: The resolution of the line image has achieved 10-15 lines / mm (no problem in practical use)
×: Resolution of line image is 9 lines / mm or less (unsuitable as a high resolution image)
"Gradation"
The evaluation condition was changed to a room temperature and normal humidity (20 ° C., 60% RH) environment, and an original image having 60 gradation steps from a white image to a solid black image was copied, and the gradation property was evaluated. The evaluation was performed by visually evaluating an image of gradation steps under sufficient daylight conditions, and evaluating the total number of gradation steps with significance.

A: The gradation step is 41 steps or more (good)
○: gradation step is 21 to 40 (no problem in practical use)
Δ: gradation step of 11 to 20 (re-examination of practicality required: practicality for image quality where gradation is not important)
X: The gradation step is 10 steps or less (there is a practical problem)
Potential Characteristics of Photoreceptor As potential characteristics of the photoreceptor, the residual potential (Vr) from the start to 150,000 prints was measured, and the fluctuation range (ΔVr) was calculated.

Other Evaluation Conditions Photoconductor charging conditions: The potential of the non-image area was detected by a potential sensor so that feedback control was possible, and the target potential was set to -800V.

Image exposure: Semiconductor laser (wavelength: 650 nm)
Image exposure conditions: semiconductor laser, exposure spot area: 3.54 × 10 ⁻¹⁰ m ² , 1200 dpi
Neutralizing Condition The neutralizing condition before charging was irradiating LED light of 680 nm (light quantity value more than 3 times the quantity of light necessary to reach the exposure part potential). The value of the surface potential after static elimination was measured as the residual potential.

  Development conditions: The developer was a reversal development using the following developer.

  Developer 1K: 0.5 parts by mass of hydrophobic silica (hydrophobic degree = 75 / number average primary particle size = 12 nm) on 100 parts by mass of colored particles having a volume average of 5.2 μm using carbon black as a color pigment, and A toner added with 0.25 part by mass of 0.05 μm titanium oxide and a resin-coated 45 μm ferrite carrier (mixing ratio of toner and carrier is 1/10 by mass) were used.

  Developer 1Y: The color pigment of the toner of developer 1K is replaced by C.I. I. A developer prepared in the same manner except that CI Pigment Yellow 185 was used was used.

  Developer 1M: The color pigment of the toner of developer 1K is replaced by C.I. I. A developer prepared in the same manner except that CI Pigment Red 122 was used was used.

  Developer 1C: The color pigment of the toner of Developer 1K is replaced with C.I. I. A developer prepared in the same manner except that CI Pigment Blue 15: 3 was used was used.

As is apparent from Table 2, the conductive support has at least an intermediate layer, a charge generation layer, and a charge transport layer. The intermediate layer has a thickness of 6 to 15 μm, and the charge transport layer has a thickness of 5 to 15 μm. And the work function of the intermediate layer is a contact potential difference measurement, and the relationship between the work function φ _{UL of the} intermediate layer obtained by changing the sample side conductive electrode and the work function φ _M of the sample side conductive electrode is represented by the above formula ( When linear approximation is performed in a), the photoreceptors 1 to 6 and 11 that satisfy the condition of α ≦ 0.8 have good dot reproducibility of monochrome and color images. And the occurrence of periodic image defects and the increase in residual potential are small. On the other hand, the photoreceptor 7 having an intermediate layer thickness of 17 μm has a large deterioration in dot reproducibility of monochrome and color images, and an increase in residual potential and a decrease in color sharpness. Further, the photosensitive member 8 having an intermediate layer thickness of 5 μm also has a deterioration in dot reproducibility of monochrome and color images, and periodic image defects are also generated. Photoreceptor 9 having a charge transport layer thickness of 17 μm shows deterioration in dot reproducibility and sharpness of monochrome and color images, and photoconductor 10 having a charge transport layer thickness of 4 μm is monochrome and color. Deterioration of image dot reproducibility, occurrence of periodic image defects, and deterioration of gradation are observed. On the other hand, the photosensitive member 12 having α larger than 0.8 has an increased residual potential, and the dot reproducibility of monochrome and color images is gradually lowered and the sharpness is also deteriorated.

<Evaluation 3: Image evaluation>
Using the photoconductors 1 to 6 and 11 in the present invention, the image exposure conditions in Evaluation 2 were changed as follows.

Image exposure conditions: Exposure spot area: 9.00 × 10 ⁻¹¹ m ² , 2400 dpi
Evaluation Results Under the exposure conditions of 2400 dpi, the photoreceptors 1 to 6 and 11 of the present invention obtained almost the same evaluation results as in the 1200 dpi exposure conditions for each evaluation item.

<Evaluation 4: Image evaluation>
Evaluation was performed in the same manner as in Evaluation 2 except that the photosensitive members 1 to 6 and 11 in the present invention were used and the charging conditions of the photosensitive member in Evaluation 2 were changed as follows. The evaluation results are shown in Table 3.

  Photoconductor charging conditions: The potential of the non-image area was detected by a potential sensor, and feedback control was possible. The target potential was set to -400V.

  When the charging condition is a target potential of −400 V, the photoconductors 1 to 6 and 11 of the present invention have periodic image defects, sharpness, and gradation as compared with the case where the target potential of evaluation 2 is −800 V. It is found that the effect of improving the tonality is improved.

<Evaluation 5: Image evaluation>
Evaluation was performed in the same manner as in Evaluation 4 except that the photosensitive members 1 to 6 and 11 in the present invention were used and the charging conditions of the photosensitive member in Evaluation 4 were changed as follows.

  Photoconductor charging conditions: The potential of the non-image area was detected by a potential sensor, and feedback control was possible, and the target potential was evaluated at two levels of -200V and -300V.

Evaluation Results When the charging conditions were set to the target potentials of −200 V and −300 V, the photoreceptors 1 to 6 and 11 of the present invention obtained substantially the same effect as when the target potential of the evaluation 4 was −400 V. .

1 is a cross-sectional configuration diagram illustrating an example of a tandem intermediate transfer type image forming apparatus. 1 is a cross-sectional configuration diagram of an image forming unit used in an image forming apparatus of the present invention. It is a cross-sectional block diagram which shows the other example of the image forming unit used for the image forming apparatus of this invention. It is a cross-sectional block diagram of the other image forming apparatus of this invention. It is a work function plot figure of the intermediate | middle layer of a photoreceptor 1 group.

Explanation of symbols

10 Transfer body (transfer means)
20Y, 20M, 20C, 20K Image forming unit 21Y, 21M, 21C, 21K Photosensitive drum (image forming body)
22Y, 22M, 22C, 22K Charging unit 23Y, 23M, 23C, 23K Exposure unit 24Y, 24M, 24C, 24K Developing unit 25Y, 25M, 25C, 25K Cleaning unit 26Y, 26M, 26C, 26K Frame 27Y, 27M, 27C , 27K Moving member

Claims (11)

In an organic photoreceptor used in an electrophotographic image forming apparatus for writing a digital image with a resolution of 1200 dpi or more and forming an electrostatic latent image, at least an intermediate layer, a charge generation layer, and a charge transport layer on a conductive support. The intermediate layer has a thickness of 6 to 15 μm, the charge transport layer has a thickness of 5 to 15 μm, and the work function of the intermediate layer is changed by changing the sample-side conductive electrode by contact potential difference measurement. An organic photoreceptor characterized in that α ≦ 0.8 when the relationship between the work function φ _UL of the obtained intermediate layer and the work function φ _M of the sample-side conductive electrode is linearly approximated by the following formula (a).
Formula (a) φ _UL = α · φ _M + β (where α and β are constants) The organophotoreceptor according to claim 1, wherein the intermediate layer contains N-type semiconductor particles. The organophotoreceptor according to claim 2, wherein the N-type semiconductor particles are anatase titanium oxide. The organic photoreceptor according to claim 1, wherein the intermediate layer contains a curable resin having an organic segment component and an inorganic segment component. The organophotoreceptor according to claim 1, wherein α is 0.3 ≦ α ≦ 0.8. In a process cartridge that can be detachably attached to an electrophotographic image forming apparatus main body for writing a digital image on an organic photoreceptor with a resolution of 1200 dpi or more and forming an electrostatic latent image, a charging unit, a developing unit, a transfer unit, At least one of the cleaning means and the conductive support have at least an intermediate layer, a charge generation layer, and a charge transport layer. The intermediate layer has a thickness of 6 to 15 μm, and the charge transport layer has a thickness of 5 to 15 μm. The relationship between the work function φ _{UL of the} intermediate layer and the work function φ _M of the sample-side conductive electrode obtained by changing the sample-side conductive electrode in the contact potential difference measurement of the work function of the intermediate layer is expressed by the above formula (a). And an electrophotographic photosensitive member satisfying α ≦ 0.8 when linearly approximated by a process cartridge. In an electrophotographic image forming apparatus that has at least an organic photoreceptor, charging means, exposure means, and developing means, writes a digital image on the organic photoreceptor with a resolution of 1200 dpi or more, and forms an electrostatic latent image. The organic photoreceptor has at least an intermediate layer, a charge generation layer, and a charge transport layer on a conductive support, the thickness of the intermediate layer is 6 to 15 μm, the thickness of the charge transport layer is 5 to 15 μm, The relationship between the work function φ _{UL of the} intermediate layer and the work function φ _M of the sample-side conductive electrode obtained by changing the sample-side conductive electrode in the contact potential difference measurement using the contact potential difference measurement is expressed by the above formula (a). An image forming apparatus characterized in that α ≦ 0.8 when linear approximation is performed. 8. The image forming apparatus according to claim 7, wherein a charging potential of the organic photoreceptor by the charging unit is 200 to 400V. At least an organic photoreceptor, charging means and exposure means for writing a digital image on the organic photoreceptor with a resolution of 1200 dpi or more to form an electrostatic latent image, and developing the electrostatic latent image into a toner image A plurality of image forming units each having a developing unit that converts the toner image formed on the organic photoreceptor and a transfer unit that transfers the toner image onto a recording material, and each image forming unit is formed using a differently colored toner. In the image forming apparatus in which each toner image is sequentially transferred to a recording material to form a color image, the organic photoreceptor has at least an intermediate layer, a charge generation layer, and a charge transport layer on a conductive support, and the intermediate layer The film thickness of the intermediate layer is 5 to 15 μm, the charge transport layer is 5 to 15 μm, and the work function of the intermediate layer is obtained by changing the sample-side conductive electrode by contact potential difference measurement. _UL and sample When linear approximation relation between the work function phi _M conductive electrode by the formula (a), the image forming apparatus, characterized in that the alpha ≦ 0.8. An image forming method, comprising: forming an electrophotographic image using the image forming apparatus according to claim 7. In an organic photoreceptor used in an electrophotographic image forming apparatus for writing a digital image and forming an electrostatic latent image of a digital image under a charging potential of 200 to 400 V, at least an intermediate is provided on a conductive support. A layer, a charge generation layer and a charge transport layer, the intermediate layer has a thickness of 6 to 15 μm, the charge transport layer has a thickness of 5 to 15 μm, and the work function of the intermediate layer is a contact potential difference measurement, When the relationship between the work function φ _{UL of the} intermediate layer obtained by changing the sample-side conductive electrode and the work function φ _M of the sample-side conductive electrode is linearly approximated by the above equation (a), α ≦ 0.8. An organic photoreceptor characterized by the following.

Images