JP4825691B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having high durability and capable of forming high-definition images. <P>SOLUTION: The image forming apparatus includes: an electrostatic latent image carrier; a means of charging the electrostatic latent image carrier; a writing means of forming an electrostatic latent image by photoirradiation; a developing means of developing the electrostatic latent image with a toner to form a visible image; a transfer means of transferring the visible image onto a recording medium; a fixing means of fixing the transferred image on the recording medium; and a discharge means of removing residual charges on the electrostatic latent image carrier with light. The electrostatic latent image carrier includes a support, and an intermediate layer and a photosensitive layer consisting of a charge generating layer and a charge transport layer on the support, wherein the intermediate layer includes a metal oxide and the charge generating layer comprises an organic charge generating material. The writing means irradiates writing light having a wavelength shorter than 450 nm, which is absorbed in the metal oxide in the intermediate layer to generate a carrier. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus, an image forming method, and a process cartridge.

  In recent years, there has been a remarkable development of information processing system machines using electrophotography. In particular, an optical printer that converts information into a digital signal and records information by light is markedly improved in print quality and reliability. This digital recording technique is applied not only to printers but also to ordinary copying machines, and so-called digital copying machines have been developed. In addition, since a variety of information processing functions are added to a conventional copying machine equipped with this digital recording technology for analog copying, the demand is expected to increase further in the future. Furthermore, with the spread of personal computers and the improvement in performance, the progress of digital color printers for performing color output of images and documents is rapidly progressing.

  The electrophotographic photoreceptors currently used in these systems generally have a so-called function in which a charge generation layer is formed directly or via an intermediate layer on a conductive support and a charge transport layer is provided thereon. Separable laminated photoconductors are the mainstream. Furthermore, a surface protective layer is formed on the outermost surface of the photoreceptor as necessary for improving mechanical or chemical durability. In this function-separated laminated photoconductor, when a photoconductor whose surface is charged is exposed, light passes through the charge transport layer and is absorbed by the charge generation material in the charge generation layer. The charge generating material absorbs this light and generates charge carriers. The generated charge carriers are injected into the charge transport layer and move along the electric field generated by charging to neutralize the surface charge of the photoreceptor. As a result, an electrostatic latent image is formed on the surface of the photoreceptor. Therefore, the function-separated type multilayer photosensitive member mainly has a charge generation material having absorption from the near infrared part to the visible part, and does not prevent transmission of absorbed light of the charge generation material, that is, from the visible part (yellow light region) to the ultraviolet part. Many combinations with charge transport materials having absorption are used.

  As a light source adapted to such a digital recording method, for example, a small and inexpensive semiconductor laser (LD) or light emitting diode (LED) with high reliability is often used. The oscillation wavelength region of the LD that is most often used at present is in the near infrared light region near 780 to 800 nm. The emission wavelength of a typical LED is 740 nm.

On the other hand, recently, a purple to blue short wavelength LD and LED having an oscillation wavelength shorter than 450 nm (375 to 450 nm) as a writing light source corresponding to the digital recording system such as DVD have been developed and listed. It is. For example, when a short wavelength LD whose oscillation wavelength is nearly half that of a conventional near infrared region LD is used as a writing light source, the formula (a)
d∝ (π / 4) (λf / D) (a)
(Where d is the spot diameter on the photoconductor, λ is the wavelength of the laser beam, f is the focal length of the fθ lens, and D is the lens diameter), and the spot of the laser beam on the photoconductor It is possible to theoretically reduce the diameter considerably. Therefore, they are very advantageous for increasing the writing density or resolution of the latent image.

  In this way, by using a light source having a wavelength shorter than 450 nm as writing light, a beam spot system having a dot diameter of about 30 μm equivalent to 1200 dpi or a dot diameter of about 15 μm equivalent to 2400 dpi is maintained in a state where the sharpness of the outline is maintained. Irradiation on the photoconductor becomes possible.

  The printers and copiers are required to have higher image quality and higher durability, including colorization. There are two problems in improving the image quality in a digital machine. One is how to uniformly form an electrostatic latent image with minute dots, and the other is how to reduce various abnormal images. As for the former, as mentioned above, the writing light source can be considerably solved by shortening the wavelength, but the latter has not been solved yet.

  In terms of increasing durability, extending the life of the photoreceptor is the most effective method.

  There are various approaches to solve these problems, but what can be said in common with both is how to reduce the deterioration due to electrostatic fatigue of the photoreceptor used in these image forming apparatuses. It can be said. Specifically, it is how to suppress an increase in the potential of the exposed portion during repeated use.

  As a countermeasure for increasing the potential of the exposed area, the development so far has been performed by devising the design (prescription, configuration, etc.) of the photoreceptor. However, the electrostatic fatigue of the photoreceptor varies greatly depending on the photoreceptor formulation or process conditions, and when considered from the development side of the photoreceptor, it is necessary to cope with each process condition. Under such circumstances, from the viewpoint of a photoreceptor prescription suitable for a short wavelength light source, little study has been made on electrostatic fatigue of the photoreceptor.

  On the other hand, Patent Document 1 discloses a photoreceptor comprising a short wavelength absorption layer, a photosensitive layer, and a surface protective layer on a conductive support. The short wavelength absorption layer is a layer that contains an N-type organic pigment and absorbs writing light of 400 to 450 nm. This prevents the occurrence of moire. According to this method, the reflection from the support or the short wavelength absorption layer does not occur, and moire can be prevented.

However, the only drawback is the use of organic pigments. The short wavelength writing light source has large energy, and has energy of the second absorption band depending on the material. The photocarrier generation mechanism of the organic material is represented by a scheme as shown in FIG. The photocarrier generation mechanisms of organic materials known so far are mostly based on a reaction consisting of two steps (photoexcitation → intermediate generation → free carrier generation) as shown in FIG. At this time, the charge generation material absorbs light and is excited to a higher excited state, but the formation of the intermediate occurs from a certain energy level. This constant energy level is the lowest excited singlet state (S ₁ ). When an energy (light having a long wavelength) smaller than that between the ground state (S ₀ ) and the lowest excited singlet state (S ₁ ) is irradiated, optical carriers are hardly generated.

On the other hand, when irradiated with energy (short wavelength light) larger than between the ground state (S ₀ ) and the lowest excited singlet state (S ₁ ), the energy level (S ^* ) higher than S _1. And is immediately relaxed to the S ₁ state, and an intermediate is formed from S ₁ . At this time, the energy corresponding to the energy difference between S ^* and S ₁ is thermally relaxed (shown as surplus energy in the figure).

  When this surplus energy is very large, another reaction may occur directly from the excited state of the charge generation layer, just by thermal relaxation alone. For example, the oxidation or decomposition of the material corresponds to this. In particular, when an organic pigment is used for the short wavelength absorption layer, the organic pigment is used at a higher concentration than the charge generation layer so that there is almost no reflection of writing light, so that the influence is great. . For this reason, even with the technique described in Patent Document 1, even if the moire prevention can be achieved, the suppression of the exposure portion potential rise cannot be continuously achieved.

Therefore, in order to form a highly durable and high-definition image, it is possible to obtain an image forming apparatus and an image forming method capable of suppressing a rise in the potential of the exposed portion during repeated use of the photoreceptor and forming a highly durable and high-definition image. It is desired.
JP 2002-268255 A

  One object of the present invention is to provide an image forming apparatus, an image forming method, and a process cartridge that have high durability and can form a high-definition image.

  According to a first aspect of the present invention, there is provided an electrostatic latent image carrier, means for charging the electrostatic latent image carrier, writing means for forming an electrostatic latent image by light irradiation, and the electrostatic latent image. Developing means for developing a visible image by developing with toner, transfer means for transferring the visible image to a recording medium, fixing means for fixing the transferred image transferred to the recording medium, and electrostatic latent image carrying An image forming apparatus having at least a static elimination unit for static neutralizing residual charges of a body, wherein the electrostatic latent image carrier is a support, and at least an intermediate layer, a charge generation layer, and a charge transport layer on the support The intermediate layer contains at least a metal oxide, and the charge generation layer contains an organic charge generation material, and the writing means has a wavelength shorter than 450 nm and the intermediate layer The metal oxide contained in the film absorbs writing light and generates carriers. An image forming apparatus which is a writing means for irradiating light of wavelength is possible Rukoto.

  In the image forming apparatus according to the first aspect of the present invention, preferably, the metal oxide is a metal oxide that has not been surface-treated.

  In the image forming apparatus according to the first aspect of the present invention, the transmittance of the charge generation layer with respect to the writing light is preferably 10% or more and 25% or less.

  In the image forming apparatus according to the first aspect of the present invention, preferably, the organic charge generating material is an azo pigment represented by the following formula (I).

In the formula, Cp ₁ and Cp ₂ represent coupler residues. R ₂₀₁ and R ₂₀₂ each represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, or a cyano group, and may be the same or different. Cp ₁ and Cp ₂ are represented by the following formula (II):

In the formula, R ₂₀₃ represents a hydrogen atom, an alkyl group, or an aryl group. R ₂₀₄ , R ₂₀₅ , R ₂₀₆ , R ₂₀₇ and R ₂₀₈ each represent a hydrogen atom, a nitro group, a cyano group, a halogen atom, a halogenated alkyl group, an alkyl group, an alkoxy group, a dialkylamino group or a hydroxyl group, and Z is A group of atoms necessary for constituting a substituted or unsubstituted aromatic carbocyclic ring or a substituted or unsubstituted aromatic heterocyclic ring.

In the image forming apparatus according to the first aspect of the present invention, preferably, Cp ₁ and Cp ₂ are different substituents.

  In the image forming apparatus according to the first aspect of the present invention, preferably, the organic charge generating material is at least as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to a characteristic X-ray (wavelength 1.542 mm) of CuKα. It has a maximum diffraction peak at 27.2 °, and further has main peaks at 9.4 °, 9.6 °, and 24.0 °, and the peak at 7.3 ° as the lowest diffraction peak It is a titanyl phthalocyanine crystal having no peak between the peak at 7.3 ° and the peak at 9.4 °, and further having no peak at 26.3 °.

  In the image forming apparatus according to the first aspect of the present invention, the transmittance of the charge transport layer with respect to the writing light is preferably 30% or more.

  The image forming apparatus according to the first aspect of the present invention preferably has a protective layer on the photosensitive layer.

  In the image forming apparatus according to the first aspect of the present invention, preferably, the protective layer transmits writing light by 30% or more.

In the image forming apparatus according to the first aspect of the present invention, the protective layer preferably contains at least one selected from inorganic pigments and metal oxides having a specific resistance of 10 ¹⁰ Ω · cm or more.

  In the image forming apparatus according to the first aspect of the present invention, preferably, the protective layer has at least a trifunctional or higher functional radical polymerizable monomer having no charge transporting structure and a radical polymerization having a monofunctional charge transporting structure. It is formed by curing a functional compound.

  In the image forming apparatus according to the first aspect of the present invention, preferably, the radical polymerizable compound having a monofunctional charge transporting structure used in the protective layer is at least one of the following general formula (1) or (2): One or more.

{In the formula, R ₁ represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, an aryl group which may have a substituent, a cyano group, a nitro group, Group, alkoxy group, —COOR ₇ (R ₇ is a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent or an aryl group which may have a substituent), halogen Carbonyl group or CONR ₈ R ₉ (R ₈ and R ₉ may have a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. Represents a good aryl group, which may be the same or different from each other, and Ar ₁ and Ar ₂ represent a substituted or unsubstituted arylene group, which may be the same or different. Ar ₃ and Ar ₄ represent a substituted or unsubstituted aryl group, and may be the same or different. X represents a single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted cycloalkylene group, a substituted or unsubstituted alkylene ether group, an oxygen atom, a sulfur atom, or a vinylene group. Z represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylene ether divalent group, or an alkyleneoxycarbonyl divalent group. m and n represent an integer of 0 to 3. }
In the image forming apparatus according to the first aspect of the present invention, preferably, the radical polymerizable compound having a monofunctional charge transporting structure used in the protective layer is at least one of the following general formula (3). .

(Wherein, o, p and q are each an integer of 0 or 1, Ra represents a hydrogen atom or a methyl group, Rb and Rc represent a substituent other than a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, And s and t each represents an integer of 0 to 3. Za is a single bond, a methylene group, an ethylene group,

Represents. )
In the image forming apparatus according to the first aspect of the present invention, preferably, the protective layer curing means is heating or light energy irradiation means.

  In the image forming apparatus according to the first aspect of the present invention, preferably, the intermediate layer includes a charge blocking layer and a moire preventing layer, and a metal oxide is contained in the moire preventing layer.

  In the image forming apparatus according to the first aspect of the present invention, preferably, the charge blocking layer is made of an insulating material, and the thickness of the charge blocking layer is 0.1 μm or more and less than 2.0 μm.

  In the image forming apparatus according to the first aspect of the present invention, preferably, the insulator material includes N-methoxymethylated nylon.

  In the image forming apparatus according to the first aspect of the present invention, preferably, the moire prevention layer further includes a binder resin, and a ratio of the volume of the metal oxide to the volume of the binder resin is 1 or more and 3 or less. is there.

  In the image forming apparatus according to the first aspect of the present invention, preferably, the light source wavelength used in the charge eliminating unit is shorter than 450 nm and the metal oxide contained in the intermediate layer absorbs the writing light, It is a light source having a wavelength capable of generating carriers.

  The image forming apparatus according to the first aspect of the present invention preferably includes a plurality of the photoconductors, a plurality of the charging units, and a plurality of the writing units.

  In the image forming apparatus according to the first aspect of the present invention, preferably, at least the photosensitive member, the charging unit, and the writing unit are detachably attached as a unit.

  The second aspect of the present invention comprises a charging step for charging on an electrostatic latent image carrier, a writing step for forming an electrostatic latent image by light irradiation, and developing the electrostatic latent image with toner. A developing process for forming a visible image, a transferring process for transferring the visible image to a recording medium, a fixing process for fixing the transferred image transferred to the recording medium, and a residual charge on the electrostatic latent image carrier are subjected to photostatic discharge. The electrostatic latent image carrier has a support and a photosensitive layer comprising at least an intermediate layer, a charge generation layer and a charge transport layer on the support. The intermediate layer contains at least a metal oxide, and the charge generation layer contains an organic charge generation material, and the writing step has a wavelength shorter than 450 nm and is contained in the intermediate layer. Can absorb writing light and generate carriers The image forming method which is a write step of irradiating the light of a certain wavelength.

  In the image forming method according to the second aspect of the present invention, preferably, the light source wavelength used in the static elimination step is shorter than 450 nm and the metal oxide contained in the intermediate layer absorbs the writing light, It is a light source having a wavelength capable of generating carriers.

  The image forming method according to the second aspect of the present invention preferably includes a plurality of the charging steps and a plurality of the writing steps.

  According to a third aspect of the present invention, there is provided a photosensitive member comprising at least a photosensitive layer, a support for supporting the photosensitive layer, and an intermediate layer provided between the photosensitive layer and the support, and charging the photosensitive member. And a process cartridge that integrally includes a charging means for irradiating and a writing means for irradiating the charged photosensitive member with light to form an electrostatic latent image on the photosensitive member, and detachably attached to the main body of the image forming apparatus The intermediate layer contains a metal oxide, and the writing means is capable of generating carriers with a wavelength shorter than 450 nm and the metal oxide contained in the intermediate layer absorbing the writing light. A process cartridge is a means for irradiating a photosensitive member with light of a certain wavelength.

  According to the first aspect of the present invention, it is possible to provide an image forming apparatus that has high durability and can form a high-definition image.

  According to the second aspect of the present invention, it is possible to provide an image forming method capable of forming a high-definition image while having high durability.

  According to the third aspect of the present invention, it is possible to provide a process cartridge that has high durability and can form a high-definition image.

  Next, embodiments of the present invention will be described with reference to the drawings.

  In an embodiment of the present invention, an electrostatic latent image carrier (hereinafter, also referred to as “electrophotographic photosensitive member”, “photosensitive member”, or “photoconductive insulator”) used in an image forming apparatus is used. The present invention relates to an image forming apparatus, an image forming method, and a process cartridge having a photosensitive layer composed of at least a charge generation layer and a charge transport layer and containing an organic charge generation material in the charge generation layer.

  The inventors of the present invention have studied the electrostatic fatigue of the photoreceptor during repeated use in an image forming apparatus, particularly the increase in the potential of the exposed area during intense exposure such as laser light.

Regarding the fatigue phenomenon in the repeated use of the photoconductor, the residual potential of the photoconductor has generally been discussed in the examination so far. In this measurement, evaluation has been performed by irradiating a charged photoconductor with not so strong light (at most, about several μW / cm ² ) for about several tens of seconds, and calling a potential at which the surface potential does not decrease any more as a residual potential. It was. This method is an effective evaluation method in an apparatus that forms an image using an analog light source such as a fluorescent lamp. When the residual potential after the repeated use of the photoreceptor is analyzed by such a method, a result that the residual potential is generated by the trap generated in the bulk of the charge transport layer is obtained. For this reason, in order to suppress this increase in the residual potential, it is concluded that it is necessary to design (improve) the charge transport layer.

  However, in the image forming apparatus using the digital light source targeted in the embodiment of the present invention, the exposure amount per unit time and unit area is overwhelmingly different from the above measurement (at least several hundreds in the case of LD writing). And the light attenuation characteristics of the photoconductor are significantly different from those of an analog light source. In particular, this effect is significant when a light source having a wavelength shorter than 450 nm is used, the beam diameter is reduced, and writing is performed at a high density.

  Under such circumstances, the exposed portion potential rises when a photoreceptor in which an intermediate layer, a charge generation layer, and a charge transport layer are laminated in this order on a conductive support is used repeatedly. As a result of analyzing this phenomenon, it was found that the response of the photosensitive member (movement of positive and negative carriers) to writing for a very short time is the key. In recent electrophotographic photoreceptors, development of a charge transport material contained in the charge transport layer has greatly progressed along with the downsizing and speeding up of the image forming apparatus, and the writing-development time is 0.1 seconds or less. It has become possible to cope with high-speed processes. Therefore, among the photocarriers generated in the charge generation layer, carriers crossing the charge transport layer (in most cases, holes) are not controlled by movement, and are unlikely to cause an increase in potential of the exposed portion in repeated use. .

  On the other hand, carriers having the opposite polarity to the carriers injected into the charge transport layer (in most cases, electrons) are injected from the charge generation layer into the intermediate layer and carried to the conductive support. A plurality of functions are given to an intermediate layer of a photoreceptor used in a recent image forming apparatus. For example, (i) transport of the photocarrier generated in the charge generation layer to the support, (ii) concealment of defects (scratches, dirt, unevenness, etc.) of the conductive support, (iii) prevention of moire (by coherent light writing) Various functions such as suppression of interference fringes), (iv) prevention of charge injection from the support (prevention of charge injection opposite to the charge polarity of the photoreceptor), and (v) improvement of adhesion between the photosensitive layer and the support. Can be mentioned.

  Of these, it is generally very difficult to achieve both the function (i) and the function (iv). In so-called OPC using an organic charge generation material for the charge generation layer, the surface is operated with a negative charge. For this reason, the intermediate layer needs to transport electrons among the carriers generated in the charge generation layer. At the same time, the injection of holes from the conductive support must be prevented. Here, a material having a rectifying property that transports only electrons, which is generally called N-type, is used for the intermediate layer. However, as an actual material, there is almost no material showing complete N-type characteristics. In many cases, the design is made with priority given to either of the functions.

  In the negative / positive development used in recent years, most of the writing ratio of the monochrome original is about 10% or less, and most of the output image area corresponds to the background portion. Therefore, when the above functions (i) and (iv) have a trade-off relationship, the function (iv), that is, hole injection prevention, is mainly designed. This is because, in a monochrome manuscript, the area of the background is almost the same, and if a hole injection cannot be prevented, an image defect called background contamination (background contamination) occurs. In addition, there are few originals that require halftone output or full-color output, and even if the electron transport function of (i) is slightly deteriorated, the decrease in image density is not noticeable.

  On the other hand, the high-quality image forming apparatus targeted in the embodiment of the present invention takes full advantage of its features and exhibits its true value. Therefore, it is necessary to design suitable for full-color image formation. Unlike a monochrome image, a full-color image has a relatively high writing rate of an original, and in some cases, even full-surface writing (100%) exists. In addition, halftone writing becomes very large, and items such as color balance and color reproducibility are given priority over background stains. However, since the image forming apparatus is designed to output monochrome images at the same time, it is not possible to ignore the background dirt.

  In view of this point, the present inventors considered the behavior of electrons generated in the charge generation layer. Due to the structure of the photoreceptor, the intermediate layer is given a hole injection preventing function from the support, but it was estimated that the electron injection from the charge generation layer was also deteriorated. Although it cannot be said that the electron transport property of the intermediate layer is so high, it was considered that the poor injection property from the charge generation layer caused an increase in the potential of the exposed portion during high-density writing.

  Generally, writing light is not 100% absorbed by the charge generation layer, and 10 to several tens of percent is transmitted through the charge generation layer (thus, a moire image is generated). The present inventors considered using this transmitted light to generate optical carriers in the intermediate layer. As a result, the idea was to make up for the shortage of electrons injected from the charge generation layer.

  That is, in the embodiment of the present invention, the intermediate layer disposed between the conductive support and the photosensitive layer (charge generation layer) contains a metal oxide that absorbs writing light, and the intermediate layer generates photocarriers. By doing so, an increase in the potential of the exposed portion in high-density writing is suppressed.

  In FIG. 2, the schematic diagram of the optical carrier generation | occurrence | production mechanism of an inorganic material is shown. In general, in the case of inorganic materials, a band model is applied, so a model composed of a valence band and a conduction band as shown in FIG. 2 is submitted. Electrons that have obtained energy corresponding to the band gap by photoexcitation can move freely in the valence band and exist as free carriers. At this time, it is a characteristic that it becomes a free carrier directly in the region of the conduction band. Accordingly, when energy larger than the energy gap is obtained as shown in FIG. 1, carrier generation efficiency (ion dissociation efficiency) is improved, but no surplus energy is generated. This point is greatly different from the photocarrier generation mechanism of the organic photoreceptor. That is, the present invention is a technique having a completely different idea from the technique described in Japanese Patent Laid-Open No. 2002-268255, and the stability to writing is also completely different. In this way, the present invention has been completed.

  This invention is based on the said knowledge of this inventor, and following (1)-(22) etc. are mentioned as embodiment of this invention.

  (1) An electrostatic latent image carrier, means for charging the electrostatic latent image carrier, writing means for forming an electrostatic latent image by light irradiation, and developing the electrostatic latent image with toner Development means for forming a visible image, transfer means for transferring the visible image to a recording medium, fixing means for fixing the transferred image transferred to the recording medium, and residual charge of the electrostatic latent image carrier. An image forming apparatus having at least a charge eliminating unit for discharging, wherein the electrostatic latent image carrier has a support and a photosensitive layer comprising at least an intermediate layer, a charge generation layer and a charge transport layer on the support. And the intermediate layer contains at least a metal oxide, and the charge generation layer contains an organic charge generation material, and the writing means has a wavelength shorter than 450 nm and the metal oxidation contained in the intermediate layer. Objects can absorb writing light and generate carriers Image forming apparatus which is a writing means for irradiating light of that wavelength.

  (2) The image forming apparatus according to (1), wherein the metal oxide is a metal oxide that has not been surface-treated.

  (3) The image forming apparatus according to item (1) or (2), wherein the charge generation layer has a transmittance for writing light of 10% to 25%.

  (4) The image forming apparatus according to any one of (1) to (3), wherein the organic charge generating substance is an azo pigment represented by the following formula (I):

In the formula, Cp ₁ and Cp ₂ represent coupler residues. R ₂₀₁ and R ₂₀₂ each represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, or a cyano group, and may be the same or different. Cp ₁ and Cp ₂ are represented by the following formula (II):

In the formula, R ₂₀₃ represents a hydrogen atom, an alkyl group, or an aryl group. R ₂₀₄ , R ₂₀₅ , R ₂₀₆ , R ₂₀₇ and R ₂₀₈ each represent a hydrogen atom, a nitro group, a cyano group, a halogen atom, a halogenated alkyl group, an alkyl group, an alkoxy group, a dialkylamino group or a hydroxyl group, and Z is A group of atoms necessary for constituting a substituted or unsubstituted aromatic carbocyclic ring or a substituted or unsubstituted aromatic heterocyclic ring.

(5) The image forming apparatus according to (4), wherein Cp ₁ and Cp ₂ are different from each other.

  (6) The organic charge generation material has a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to CuKα characteristic X-rays (wavelength 1.542 mm), and further 9 It has major peaks at .4 °, 9.6 °, and 24.0 °, and has a peak at 7.3 ° as the lowest diffraction peak, and the peak at 7.3 ° and 9.4 °. Any one of the above items (1) to (3), wherein the crystal is a titanyl phthalocyanine crystal having no peak between the peaks of ° and no peak at 26.3 °. Image forming apparatus.

  (7) The image forming apparatus according to any one of (1) to (6), wherein the charge transport layer has a transmittance for writing light of 30% or more.

  (8) The image forming apparatus according to any one of (1) to (7), wherein a protective layer is provided on the photosensitive layer.

  (9) The image forming apparatus according to item (8), wherein the protective layer transmits writing light by 30% or more.

(10) The image forming apparatus according to (8) or (9), wherein the protective layer includes at least one selected from inorganic pigments and metal oxides having a specific resistance of 10 ¹⁰ Ω · cm or more.

  (11) The protective layer is formed by curing at least a trifunctional or higher radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. The image forming apparatus according to (8) or (9).

  (12) The above-mentioned (11), wherein the radical polymerizable compound having a monofunctional charge transporting structure used in the protective layer is at least one of the following general formula (1) or (2): The image forming apparatus described in the item.

{In the formula, R ₁ represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, an aryl group which may have a substituent, a cyano group, a nitro group, Group, alkoxy group, —COOR ₇ (R ₇ is a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent or an aryl group which may have a substituent), halogen Carbonyl group or CONR ₈ R ₉ (R ₈ and R ₉ may have a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. Represents a good aryl group, which may be the same or different from each other, and Ar ₁ and Ar ₂ represent a substituted or unsubstituted arylene group, which may be the same or different. Ar ₃ and Ar ₄ represent a substituted or unsubstituted aryl group, and may be the same or different. X represents a single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted cycloalkylene group, a substituted or unsubstituted alkylene ether group, an oxygen atom, a sulfur atom, or a vinylene group. Z represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylene ether divalent group, or an alkyleneoxycarbonyl divalent group. m and n represent an integer of 0 to 3. }
(13) The above-mentioned item (11) or ((1), wherein the radical polymerizable compound having a monofunctional charge transporting structure used in the protective layer is at least one of the following general formula (3). The image forming apparatus according to item 12).

(Wherein, o, p and q are each an integer of 0 or 1, Ra represents a hydrogen atom or a methyl group, Rb and Rc represent a substituent other than a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, And s and t each represents an integer of 0 to 3. Za is a single bond, a methylene group, an ethylene group,

Represents. )
(14) The image forming apparatus according to any one of (11) to (13), wherein the protective layer curing means is heating or light energy irradiation means.

  (15) Any one of (1) to (14) above, wherein the intermediate layer includes a charge blocking layer and a moire preventing layer, and the metal oxide is contained in the moire preventing layer. The image forming apparatus described.

  (16) The image forming apparatus according to (15), wherein the charge blocking layer is made of an insulating material, and the thickness of the charge blocking layer is not less than 0.1 μm and less than 2.0 μm. .

  (17) The image forming apparatus according to (16), wherein the insulating material includes N-methoxymethylated nylon.

  (18) The moiré prevention layer further includes a binder resin, and the ratio of the volume of the metal oxide to the volume of the binder resin is 1 or more and 3 or less, wherein (17) The image forming apparatus according to any one of items.

  (19) The light source wavelength used for the static elimination means is a light source having a wavelength shorter than 450 nm and capable of absorbing the write light and generating carriers by the metal oxide contained in the intermediate layer. The image forming apparatus according to any one of (1) to (18), wherein:

  (20) The image forming apparatus according to any one of (1) to (19), including a plurality of the photosensitive members, a plurality of charging units, and a plurality of writing units.

  (21) The image forming apparatus according to any one of (1) to (20), wherein at least the photosensitive member, the charging unit, and the writing unit are detachably attached as a unit. apparatus.

  (22) A charging step for charging the electrostatic latent image carrier, a writing step for forming an electrostatic latent image by light irradiation, and developing the electrostatic latent image with toner to form a visible image. At least a development step, a transfer step for transferring the visible image to a recording medium, a fixing step for fixing the transferred image transferred to the recording medium, and a static elimination step for photo-staticizing residual charges on the electrostatic latent image carrier. The latent electrostatic image bearing member has a support and a photosensitive layer comprising at least an intermediate layer, a charge generation layer and a charge transport layer on the support, and the intermediate layer includes the photosensitive layer. The metal oxide contains at least a metal oxide and an organic charge generation material in the charge generation layer, and the writing process has a wavelength shorter than 450 nm and the metal oxide contained in the intermediate layer absorbs the writing light. Light of a wavelength that is capable of generating carriers Image forming method which is a write step of irradiating.

  (23) The light source wavelength used in the static elimination step is a light source having a wavelength shorter than 450 nm, and the metal oxide contained in the intermediate layer can absorb static elimination light and generate carriers. The image forming method according to item (22), wherein:

  (24) The image forming method according to (22) or (23), which includes a plurality of charging steps and a plurality of writing steps.

  (25) At least a photosensitive layer, a support that supports the photosensitive layer, and a photoreceptor including an intermediate layer provided between the photosensitive layer and the support, a charging unit that charges the photoreceptor, and A process cartridge that integrally includes writing means for irradiating the charged photosensitive member with light to form an electrostatic latent image on the photosensitive member, and is detachably attached to the main body of the image forming apparatus, The layer includes a metal oxide, and the writing means is sensitive to light having a wavelength shorter than 450 nm and a wavelength that allows the metal oxide contained in the intermediate layer to absorb the writing light and generate carriers. A process cartridge which is means for irradiating a body.

  Note that as the writing light in the embodiment of the present invention, the wavelength at which the metal oxide can absorb the writing light and generate carriers is the width of the band gap of the metal oxide (conduction band and valence band). Defined as a wavelength (short wavelength) having an energy larger than the energy corresponding to the energy gap or band gap. For example, in the case of titanium oxide (rutile type), the energy gap is 3.0 eV, which is about 410 nm in terms of wavelength. This is the wavelength on the longest wavelength side where titanium oxide (rutile type) can be absorbed, and light having a wavelength shorter than 410 nm can be absorbed by titanium oxide, and carriers can be generated. To say.

  As described above, the wavelength at which the metal oxide can absorb writing light and generate carriers is defined as a wavelength having energy larger than the energy gap. A method for measuring this energy gap will be described. In general, three methods are conceivable.

  One is a method of measuring the spectral reflection spectrum of the intermediate layer and obtaining the absorption edge on the long wavelength side. This can be easily measured with a commercially available spectral absorption spectrum apparatus. This measurement is used in the embodiments of the present invention. The wavelength that can be absorbed by the intermediate layer is obtained as light having a shorter wavelength than the absorption edge obtained by this method.

  The second is a method of obtaining the spectral absorption spectrum and emission spectrum of the intermediate layer, describing them in the same graph, and obtaining the wavelength at the intersection of the two. These can be measured with a commercially available spectrophotometer and fluorometer. The wavelength that can be absorbed by the intermediate layer is determined as light having a shorter wavelength than the wavelength (intersection) determined by this method.

  Third, the energy level of the conduction band and the valence band is measured, and the difference between the two is obtained as the energy gap. These require dedicated measurement equipment and are not very common. The wavelength that can be absorbed by the intermediate layer is obtained as light on the shorter wavelength side than the wavelength by converting the energy gap (unit is energy) into a wavelength unit.

  In addition, the writing light having a wavelength shorter than 450 nm as the writing light in the embodiment of the present invention does not completely include or substantially does not include light on the long wavelength side of 450 nm or more (included to a negligible level). It indicates that it is light (hereinafter, it may be referred to as writing light of less than 450 nm). Similarly, the neutralization light having a wavelength shorter than 450 nm as the neutralization light in the embodiment of the present invention does not completely include or substantially does not include light on the long wavelength side of 450 nm or more (including negligible). It indicates that it is light (hereinafter, it may be referred to as static elimination light of less than 450 nm).

  By using writing light having a wavelength that can be absorbed by the metal oxide, a detailed mechanism that can suppress an increase in residual potential in repeated use of the photoreceptor has not been clarified. At present, the mechanism is considered as follows.

  In repeated use of the photoconductor, when writing is performed with light having a wavelength longer than the wavelength that the metal oxide can absorb, all the photocarriers generated by the photoconductor are generated in the charge generation layer. At this time, holes are injected into the charge transport layer and electrons are injected into the intermediate layer, and are transported to the surface of the photoreceptor or the conductive support, respectively, and surface charges or induced charges (charges induced on the support side during main charging). Cancel. In the high-speed process which is the object of the embodiment of the present invention, the electron transport in the intermediate layer is slower than the hole transport in the charge transport layer, so that electrons are accumulated in the intermediate layer with repeated use. In addition, since the electron injection property from the charge generation layer to the intermediate layer is not sufficient, electrons are accumulated at the charge generation layer / intermediate layer interface.

  On the other hand, when writing is performed with light having a wavelength that can be absorbed by the metal oxide, photocarriers are also generated in the charge generation layer, but the charge generation layer does not absorb 100% of the writing light, and the intermediate layer Even the writing light reaches. When the writing light is light having a wavelength shorter than the wavelength that can be absorbed by the metal oxide, the metal oxide contained in the intermediate layer absorbs light and generates a photocarrier via a photoexcited state. . In this case, it is formed of an intermediate layer and is efficient because there is no injection process from the charge generation layer. In this way, the photocarrier generated in the intermediate layer can suppress the residual potential increase by canceling the residual charge (electrons) accumulated until the previous image formation.

  In general, organic charge generation materials used in the charge generation layer have absorption in the visible region, so that the writing light of less than 450 nm is transmitted at a certain rate, and the intermediate layer reaches the amount of light necessary for carrier generation. To do. However, organic charge generating materials cannot be said to have no absorption at less than 450 nm due to their structure, and photocarriers can be sufficiently generated even with writing light of less than 450 nm. For this reason, in the charge generation layer, it is possible to secure the same amount of photocarrier generation as that of writing by normal writing light (exposure of 450 nm or more), and it does not adversely affect the optical writing itself.

  In order to sufficiently exhibit such an effect, it is necessary that the writing light sufficiently reaches at least the intermediate layer of the photoreceptor. For this purpose, the charge generation layer and the charge transport layer installed on the upper layer of the intermediate layer need to sufficiently transmit writing light of less than 450 nm.

  In the charge generation layer, if the transmittance for writing light is too large, the amount of generated carriers is insufficient, and if it is too small, the writing light does not reach the intermediate layer. Therefore, there is a proper range. In general, the lower limit is 10% and the upper limit is 25%. Setting within this range provides a well-balanced design.

  In the charge transport layer, various side effects occur when the writing light is absorbed. For example, not only the writing light does not reach the lower charge generation layer and intermediate layer, but also the deterioration of the charge transport material is promoted. For this reason, it is preferable that the transmittance | permeability with respect to the write light of a charge transport layer is 30% or more. More preferably, it is 50% or more, and more desirably 85% or more.

  Among materials that have been usefully used as charge transport materials for electrophotographic photoreceptors so far, materials that absorb light of less than 450 nm are also included. For this reason, when such a material is used, it may be difficult to obtain the effect of the embodiment of the present invention sufficiently. Even if the material sufficiently transmits light of less than 450 nm, it may be difficult to ensure the stability of the electrostatic characteristics of the photoreceptor in repeated use unless the ability as a charge transport material is sufficient. is there.

  For this reason, the characteristics required for the charge transport material used in the embodiment of the present invention are as follows: (1) a sufficient transmission of writing light of less than 450 nm with the charge transport layer formed; Specifically, it is desirable to transmit at least 30% of the writing light. (2) Good matching with the organic charge generation material, specifically, good energy matching, and photocarriers generated in the charge generation layer. (3) It shows the stability as a material in the repeated use of the photoreceptor, specifically, it has resistance to oxidizing gas generated by the charging means, etc., against long-term energization However, it is stable.

  By adopting a configuration that satisfies the above-described conditions, the effect of the embodiment of the present invention becomes more remarkable.

  One embodiment of the present invention is an image forming apparatus that can solve various problems in the prior art and can perform image formation with high durability and high image quality, and includes an intermediate layer containing at least a metal oxide, a charge In the electrostatic latent image carrier having a laminated photosensitive layer comprising a generation layer and a charge transport layer, the charge generation layer contains an organic charge generation material, the writing light source has a wavelength shorter than 450 nm, and the metal oxide is written An image forming apparatus using a light source having a wavelength capable of absorbing light and generating carriers. Accordingly, it is possible to provide an image forming apparatus, an image forming method, and a process cartridge that can output a stable image with high durability and few abnormal images.

(Image forming apparatus and image forming method)
An image forming apparatus according to an embodiment of the present invention has a laminated photosensitive layer comprising an intermediate layer containing a metal oxide, a charge generation layer containing an organic charge generation material, and a charge transport layer on at least a conductive support. An electrostatic latent image carrier, a charging unit, a writing unit having a light source with a wavelength shorter than 450 nm and capable of absorbing carriers and generating carriers, and a developing unit. The image forming apparatus includes at least a transfer unit, a fixing unit, and a charge removal unit, and further includes other units selected as necessary, for example, a cleaning unit, a recycling unit, and a control unit.

  An image forming method according to an embodiment of the present invention includes a charging step and a writing step having a light source with a wavelength shorter than 450 nm and a wavelength at which the metal oxide can absorb writing light and generate carriers. The image forming apparatus includes at least a developing process, a transfer process, a charge eliminating process, and a fixing process, and further includes other processes appropriately selected as necessary, for example, a cleaning process, a recycling process, a control process, and the like.

  The image forming method according to the embodiment of the present invention can be suitably performed by the image forming apparatus according to the embodiment of the present invention, the charging step can be performed by the charging unit, and the writing step is the writing The developing step can be performed by the developing unit, the transferring step can be performed by the transferring unit, the discharging step can be performed by the discharging unit, and the fixing step can be performed. It can be performed by the fixing means, and the other steps can be performed by the other means.

  An image forming apparatus according to an embodiment of the present invention includes an electrostatic latent image carrier, charging means for forming an electrostatic latent image on the electrostatic latent image carrier, and an electrostatic latent image. Writing means; developing means for developing the electrostatic latent image with toner to form a visible image; transfer means for transferring the visible image to a recording medium; and the electrostatic latent image carrier. It has at least static elimination means for removing residual charges and fixing means for fixing the transferred image transferred to the recording medium. The writing means has a wavelength shorter than at least 450 nm, and the metal oxide emits writing light. The electrostatic latent image carrier is irradiated with writing light by a light source having a wavelength capable of absorbing and generating carriers.

-Electrostatic latent image carrier-
As the electrostatic latent image carrier, the material, shape, structure, size, except that the intermediate layer contains a metal oxide and the charge generation layer contains an organic charge generation material. There is no restriction | limiting in particular about etc., It can select suitably from well-known things. As the support, a conductive support having conductivity is preferable.

  Next, the electrophotographic photosensitive member used in the embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 3 is a cross-sectional view showing a structural example of the electrophotographic photosensitive member used in the embodiment of the present invention. On the support (31), an intermediate layer (39) containing a metal oxide, and charge generation A charge generation layer (35) having at least an organic charge generation material as a main component as a substance and a charge transport layer (37) having a charge transfer substance as a main component are stacked.

  FIG. 4 is a cross-sectional view showing another structural example of the electrophotographic photosensitive member used in the embodiment of the present invention, in which the intermediate layer (39) contains a charge blocking layer (43) and a metal oxide to prevent moire. A charge generation layer (35) mainly composed of at least an organic charge generation material as a charge generation material and a charge transport layer (37) mainly composed of a charge transport material on the intermediate layer. It has a stacked configuration.

  FIG. 5 is a cross-sectional view showing still another structural example of the electrophotographic photosensitive member used in the embodiment of the present invention, and an intermediate layer (39) containing a metal oxide on the support (31). ) And a charge generation layer (35) mainly composed of at least an organic charge generation material as a charge generation material, and a charge transport layer (37) mainly composed of a charge transport material, and a charge transport layer (photosensitive layer). ) Is provided with a protective layer (41).

Examples of the conductive support 31 include those having a volume resistance of 10 ¹⁰ Ω · cm or less, for example, metals such as aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum, tin oxide, indium oxide, etc. The metal oxide of the above is coated with film or cylindrical plastic or paper by vapor deposition or sputtering, or a plate made of aluminum, aluminum alloy, nickel, stainless steel or the like and extruded by drawing or drawing. After pipe formation, surface treatment pipes such as cutting, superfinishing, and polishing can be used. Endless nickel belts and endless stainless steel belts can also be used as the conductive support.

  In addition, a material obtained by dispersing and coating conductive powder in an appropriate binder resin on the support can be used as the conductive support in the embodiment of the present invention. Examples of the conductive powder include carbon black, acetylene black, metal powder such as aluminum, nickel, iron, nichrome, copper, zinc and silver, or metal oxide powder such as conductive tin oxide and ITO. It is done. The binder resin used at the same time is polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer. , Polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxy resin, Examples thereof include thermoplastic, thermosetting resins, and photocurable resins such as melamine resin, urethane resin, phenol resin, and alkyd resin. Such a conductive layer can be provided by dispersing and coating these conductive powder and binder resin in a suitable solvent such as tetrahydrofuran, dichloromethane, methyl ethyl ketone, and toluene.

  Furthermore, it is electrically conductive by a heat shrinkable tube in which the conductive powder is contained in a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, Teflon (registered trademark) on a suitable cylindrical substrate. Those provided with a conductive layer can also be favorably used as a conductive support in the embodiment of the present invention.

  Of these, a cylindrical support made of aluminum, which can be easily subjected to the anodic oxide film treatment, can be most preferably used. As used herein, aluminum includes both pure aluminum and aluminum alloys. Specifically, JIS 1000, 3000, and 6000 series aluminum or aluminum alloy is most suitable. The anodized film is obtained by anodizing various metals and various alloys in an electrolyte solution. Among them, a film called anodized aluminum or an aluminum alloy that has been anodized in an electrolyte solution is an embodiment of the present invention. It is most suitable for the photoreceptor used in the above. In particular, it is excellent in preventing point defects (black spots, background stains) that occur when used in reversal development (negative and positive development).

The anodizing treatment is performed in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, sulfamic acid. Of these, treatment with a sulfuric acid bath is most suitable. For example, sulfuric acid concentration: 10 to 20%, bath temperature: 5 to 25 ° C., current density: 1 to 4 A / dm ² , electrolytic voltage: 5 to 30 V, treatment time: treatment in the range of about 5 to 60 minutes However, the present invention is not limited to this. Since the anodic oxide film produced in this way is porous and has high insulation, the surface is very unstable. For this reason, there is a change with time after fabrication, and the physical property value of the anodized film is likely to change. In order to avoid this, it is preferable to further seal the anodized film. Examples of the sealing treatment include a method of immersing the anodized film in an aqueous solution containing nickel fluoride and nickel acetate, a method of immersing the anodized film in boiling water, and a method of treating with pressurized steam. Among these, the method of immersing in the aqueous solution containing nickel acetate is the most preferable. Subsequent to the sealing treatment, the anodic oxide film is washed. The main purpose of this is to remove excess metal salts and the like attached by the sealing treatment. If this remains excessively on the surface of the support (anodized film), it not only adversely affects the quality of the coating film formed on this surface, but also generally low resistance components remain, resulting in the occurrence of soiling. It can also be a cause. Cleaning may be performed with pure water only once, but usually, multistage cleaning is performed. At this time, it is preferable that the final cleaning liquid is as clean (deionized) as possible. Moreover, it is preferable to perform physical rubbing cleaning with a contact member in one of the multi-stage cleaning processes. The thickness of the anodized film formed as described above is preferably about 5 to 15 μm. If it is too thin, the barrier effect as an anodic oxide film is not sufficient, and if it is too thick, the time constant as an electrode becomes too large, resulting in the generation of residual potential and the response of the photoreceptor. There is a case.

  Next, the intermediate layer 39 will be described. It is essential that the intermediate layer used in the embodiment of the present invention contains a metal oxide. The intermediate layer generally contains a resin as a main component, but these resins are preferably resins having a high solvent resistance with respect to a general organic solvent in consideration of applying a photosensitive layer thereon with a solvent. . Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine resin, phenol resin, alkyd-melamine resin, and epoxy. Examples thereof include a curable resin that forms a three-dimensional network structure such as a resin.

Further, the intermediate layer contains a metal oxide for the purpose of reducing the residual potential, etc., but this also has the effect of preventing moire. The absorption wavelength range of the metal oxide varies depending on the impurities contained therein. Therefore, the energy gap of the material to be used or the intermediate layer using the same is actually measured by the method described above. As the metal oxide, titanium oxide, acid zirconium, tin oxide, indium oxide. Among these, titanium oxide and tin oxide are effectively used. Among the titanium oxides, rutile type titanium oxide is preferable. Anatase-type titanium oxide can also be used, but considering the generation of optical carriers (light absorption), the anatase type has an absorption wavelength region on the shorter wavelength side than the rutile type, and the writing light needs to be on the shorter wavelength side accordingly. Comes out. In this case, when the spectral transmittance of the charge transport layer is taken into consideration, when the anatase type is used, restrictions on the charge transport material that can be used may occur as compared with the case where the rutile type is used. For this reason, the rutile type is more advantageous.

  Moreover, the metal oxide to be used is advantageously one that has not been subjected to surface treatment. This is because the surface treatment reduces the surface area of the unmodified metal oxide and acts in a disadvantageous direction when transporting the carriers generated from the metal oxide. Thereby, the effect of embodiment of this invention may be reduced. If surface treatment is desired for reasons such as dispersion stability, the minimum amount should be used.

  These intermediate layers can be formed using an appropriate solvent and coating method as in the photosensitive layer described later. The thickness of the intermediate layer is suitably from 0.1 to 5 μm.

  The intermediate layer 39 has a function of preventing the injection of reverse polarity charges induced on the electrode side when the photosensitive member is charged into the photosensitive layer, in addition to the generation of optical carriers during writing, and writing with coherent light such as laser light. It has at least two functions of preventing moiré that sometimes occurs. A function separation type intermediate layer in which this function is separated into two or more layers is an effective means for the photoreceptor used in the embodiment of the present invention. Hereinafter, the function separation type intermediate layer of the charge blocking layer 43 and the moire preventing layer 45 will be described.

  The charge blocking layer 43 is a layer having a function of preventing the reverse polarity charge induced in the electrode (conductive support 31) during charging of the photosensitive member from being injected into the photosensitive layer from the support. In the case of negative charging, it has a function of preventing hole injection, and in the case of positive charging, it has a function of preventing electron injection. The charge blocking layer includes an anodized film typified by an aluminum oxide layer, an inorganic insulating layer typified by SiO, a layer formed from a glassy network of metal oxide, a layer made of polyphosphazene, an aminosilane reaction A layer made of a product, a layer made of an insulating binder resin, a layer made of a curable binder resin, and the like can be given. Among them, a layer composed of an insulating binder resin or a curable binder resin that can be formed by a wet coating method can be used favorably. Since the charge blocking layer is formed by laminating a moiré preventing layer and a photosensitive layer thereon, when these are provided by a wet coating method, the charge blocking layer must be composed of a material or a structure that does not attack the coating film by these coating solvents. Is essential.

Examples of binder resins that can be used include thermoplastic resins such as polyamide, polyester, vinyl chloride-vinyl acetate copolymer, and thermosetting resins such as active hydrogen (—OH group, —NH ₂ group, —NH group, etc.). A thermosetting resin obtained by thermally polymerizing a compound containing a plurality of (hydrogen) and a compound containing a plurality of isocyanate groups and / or a compound containing a plurality of epoxy groups can also be used. In this case, examples of the compound containing a plurality of active hydrogens include acrylic resins containing active hydrogen such as polyvinyl butyral, phenoxy resin, phenol resin, polyamide, polyester, polyethylene glycol, polypropylene glycol, polybutylene glycol, and hydroxyethyl methacrylate groups. System resin and the like. Examples of the compound containing a plurality of isocyanate groups include tolylene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate and the like, and prepolymers thereof. Examples of the compound having a plurality of epoxy groups include bisphenol A type epoxy resin. can give. Among these, polyamide is most preferably used from the viewpoint of film formability, environmental stability, solvent resistance, and the like. Among polyamides, N-methoxymethylated nylon is most suitable. N-methoxymethylated nylon is a polyamide containing polyamide 6 as a constituent, for example, T.I. L. It can be obtained by modification by the method proposed by Cairns (J. Am. Chem. Soc. 71. P651 (1949)). N-methoxymethylated nylon is obtained by replacing the amide bond hydrogen of the original polyamide with a methoxymethyl group. This substitution rate can be selected in a wide range depending on the modification conditions, but it is preferably 15 mol% or more from the viewpoint of environmental stability, suppressing the hygroscopicity of the intermediate layer to some extent, excellent alcohol affinity. More preferably, the substitution rate is 35 mol% or more. In addition, as the degree of amide substitution (N—N-methoxymethylation) increases, the alcoholic solvent affinity increases, but the influence of the bulk side chain group around the main chain becomes stronger, and the main chain is in a relaxed state or main chain. Because the coordination state between the chain and the main chain changes, the hygroscopicity also increases, the crystallinity decreases, the melting point decreases, and the mechanical strength and elastic modulus decrease. % Or less is preferable. More preferably, the substitution rate is 70 mol% or less. Further, according to the examination results, nylon 6 is most preferable as nylon, then nylon 66 is preferable, and conversely, a copolymer nylon such as nylon 6/66/610 is disclosed in JP-A-9-265202. Contrary to the contents, it was not very preferable.

  In addition, a thermosetting resin obtained by thermally polymerizing an oil-free alkyd resin and an amino resin such as a butylated melamine resin, a polyurethane having an unsaturated bond, a resin having an unsaturated bond such as an unsaturated polyester, and thioxanthone A photocurable resin such as a combination with a photopolymerization initiator such as a compound based on methylbenzyl formate can also be used as the binder resin.

  In addition, a conductive polymer having a rectifying property or an acceptor (donor) resin / compound may be added in accordance with the charging polarity to provide a function of suppressing charge injection from the substrate.

  The film thickness of the charge blocking layer is 0.1 μm or more and less than 2.0 μm, preferably about 0.3 μm or more and less than 2.0 μm. When the charge blocking layer becomes thick, the residual potential increases remarkably at low temperature and low humidity due to repeated charging and exposure, and when the film thickness is too thin, the blocking effect is reduced. Further, the charge blocking layer 5 is added with a chemical, a solvent, an additive, a curing accelerator and the like necessary for curing (crosslinking) as necessary, and blade coating, dip coating, spray coating, It is formed on the substrate by coating, nozzle coating or the like. After the coating, it is dried or cured by a curing process such as drying, heating, or light.

  The moiré prevention layer 45 is a layer having a function of preventing the generation of a moiré image due to light interference inside the photosensitive layer when writing with coherent light such as laser light. In the case where the intermediate layer has a function separation type structure, a metal oxide is included in the moire prevention layer, and the moire prevention layer has a function of generating a photocarrier during writing. Basically, it has a function of causing light scattering of the writing light. In order to exhibit such a function, it is effective that the anti-moire layer has a material having a large refractive index.

  In the case where the intermediate layer is composed of a charge blocking layer and a moiré preventing layer, the effect is further enhanced by making the moiré preventing layer in contact with the charge generation layer, and the most effective photosensitive layer. Body composition.

  Further, in the photoreceptor having the function separation type intermediate layer, the charge injection from the support 31 is prevented by the charge blocking layer. Therefore, in the moiré preventing layer, at least the charge charged on the photoreceptor surface has the same polarity. From the viewpoint of preventing residual potential, it is preferable to have a function of transferring the electric charge. For this reason, for example, in the case of a negatively charged type photoreceptor, it is desirable to impart electronic conductivity to the moire prevention layer, and the metal oxide to be used is one that has electronic conductivity, or one that is conductive. It is desirable to do. Alternatively, the use of an electron conductive material (for example, an acceptor) or the like for the moire preventing layer makes the effect of the embodiment of the present invention more remarkable.

  As the binder resin, the same resin as the charge blocking layer can be used. However, in consideration of laminating a photosensitive layer (charge generation layer 35, charge transport layer 37) on the moire prevention layer, the photosensitive layer (charge generation layer, It is important not to be affected by the coating solvent for the charge transport layer.

  A thermosetting resin is preferably used as the binder resin. In particular, alkyd / melamine resin mixtures are best used. At this time, the mixing ratio of the alkyd / melamine resin is an important factor that determines the structure and characteristics of the moire prevention layer. A range in which the ratio (weight ratio) between the two is 5/5 to 8/2 can be cited as a good mixing ratio range. When the melamine resin is richer than 5/5, volume shrinkage is increased during thermosetting, and coating film defects are likely to occur, or the residual potential of the photoreceptor is increased. If the alkyd resin is richer than 8/2, it is effective in reducing the residual potential of the photoconductor, but it is not desirable because the bulk resistance becomes too low and the soiling becomes worse.

  In the moiré prevention layer, the volume ratio between the metal oxide and the binder resin determines an important characteristic. For this reason, it is important that the volume ratio of the metal oxide and the binder resin is in the range of 1/1 to 3/1. When the volume ratio of the two is less than 1/1, not only the moire prevention ability is lowered, but there is a case where the increase of the residual potential in repeated use becomes large. On the other hand, in the region where the volume ratio exceeds 3/1, not only the binding ability of the binder resin is inferior, but also the surface property of the coating film is deteriorated, which may adversely affect the film forming property of the upper photosensitive layer. This effect can be a serious problem when the photosensitive layer is a laminated type and a thin layer such as a charge generation layer is formed. When the volume ratio exceeds 3/1, there are cases where the binder resin cannot cover the metal oxide surface, and the direct contact with the charge generating material increases the probability of heat carrier generation, resulting in soil contamination. May be adversely affected.

  Furthermore, by using two kinds of metal oxides having different average particle diameters for the moire prevention layer, it is possible to improve the hiding power on the conductive substrate and suppress moire and cause abnormal images. Pinholes can be eliminated. For this purpose, it is important that the ratio of the average particle diameters of the two types of metal oxides used is within a certain range (0.2 <D2 / D1 ≦ 0.5). In the case of the particle size ratio outside the range specified in the embodiment of the present invention, that is, the ratio of the average particle size of the other metal oxide (T2) to the average particle size of the metal oxide (T1) having a large average particle size is When it is too small (0.2 ≧ D2 / D1), the activity on the surface of the metal oxide is increased, and the electrostatic stability of the electrophotographic photosensitive member is significantly impaired. Further, when the ratio of the average particle diameter of the other metal oxide (T2) to the average particle diameter of one metal oxide (T1) is too large (D2 / D1> 0.5), the hiding power to the conductive substrate Decreases, and the suppression of moiré and abnormal images decreases. The average particle size mentioned here is obtained from a particle size distribution measurement obtained when strong dispersion is performed in an aqueous system.

  The average particle size (D2) of the metal oxide (T2) having a smaller particle size is an important factor, and it is important that 0.05 μm <D2 <0.20 μm. When the thickness is 0.05 μm or less, the hiding power is reduced, and moire may be generated. On the other hand, in the case of 0.20 μm or more, the metal oxide filling rate of the moire prevention layer is lowered, and the background stain suppressing effect cannot be sufficiently exhibited.

  The mixing ratio (weight ratio) of the two metal oxides is also an important factor. When T2 / (T1 + T2) is smaller than 0.2, the filling rate of the metal oxide is not so large and the effect of suppressing soiling cannot be sufficiently exhibited. On the other hand, when it is larger than 0.8, the concealing power is reduced, and moire may be generated. Therefore, it is important that 0.2 ≦ T2 / (T1 + T2) ≦ 0.8.

  The thickness of the moire preventing layer is 1 to 10 μm, preferably 2 to 5 μm. If the film thickness is less than 1 μm, the effect is small, and if it exceeds 10 μm, residual potential is accumulated, which is not desirable.

  The metal oxide is dispersed together with a solvent and a binder resin by a conventional method, for example, a ball mill, a sand mill, an attrier, etc., and a chemical, a solvent, an additive, a curing accelerator, etc. necessary for curing (crosslinking) are added as necessary. In general, it is formed on the substrate by blade coating, dip coating, spray coating, beat coating, nozzle coating, or the like. After the coating, it is dried or cured by a curing process such as drying, heating, or light.

  Next, the photosensitive layer will be described. The photosensitive layer has a laminated structure of a charge generation layer 35 containing an organic charge generation material as a charge generation material and a charge transport layer 37 containing a charge transport material as a main component.

  The charge generation layer 35 is a layer mainly composed of an organic charge generation material as a charge generation material. The organic charge generating material is formed by dispersing the organic charge generating material in a suitable solvent together with a binder resin, if necessary, using a ball mill, attritor, sand mill, ultrasonic wave, etc., applying this onto the intermediate layer, and drying.

  The binder resin used in the charge generation layer as necessary includes polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polysulfone, and poly-N-vinyl. Examples include carbazole, polyacrylamide, polyvinyl benzal, polyester, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyphenylene oxide, polyamide, polyvinyl pyridine, cellulose resin, casein, polyvinyl alcohol, polyvinyl pyrrolidone, and the like. . The amount of the binder resin is suitably 0 to 500 parts by weight, preferably 10 to 300 parts by weight with respect to 100 parts by weight of the charge generating material.

  Examples of the solvent used here include isopropanol, acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethyl cellosolve, ethyl acetate, methyl acetate, dichloromethane, dichloroethane, monochlorobenzene, cyclohexane, toluene, xylene, ligroin and the like. As a coating method for the coating solution, a dip coating method, spray coating, beat coating, nozzle coating, spinner coating, ring coating, or the like can be used. The film thickness of the charge generation layer is suitably about 0.01 to 5 μm, preferably 0.1 to 2 μm.

  Further, the transmittance of the charge generation layer at the wavelength of the writing light is desirably 10% or more and 25% or less. If it does not show transparency to the writing light, sufficient writing light does not reach the intermediate layer, and if it does not show sufficient light absorption, it does not show sufficient light attenuation when forming the electrostatic latent image. Therefore, the above range is an appropriate range.

  An organic charge generation material can be used as the charge generation material.

  A known material can be used as the organic charge generating substance. For example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, azulenium salt pigments, squaric acid methine pigments, azo pigments having carbazole skeleton, azo pigments having triphenylamine skeleton, azo pigments having diphenylamine skeleton, dibenzothiophene skeleton Azo pigments having a fluorenone skeleton, azo pigments having an oxadiazole skeleton, azo pigments having a bis-stilbene skeleton, azo pigments having a distyryl oxadiazole skeleton, azo pigments having a distyrylcarbazole skeleton, perylene Pigments, anthraquinone or polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, Goido based pigments, and bisbenzimidazole pigments. These charge generation materials can be used alone or as a mixture of two or more.

Among these, azo pigments represented by the following formula (I) are effectively used. In particular, an asymmetric azo pigment in which Cp ₁ and Cp ₂ of the azo pigment are different from each other has high carrier generation efficiency, and can be effectively used as a charge generation material in the embodiment of the present invention.

In the formula, Cp ₁ and Cp ₂ represent coupler residues.

R ₂₀₁ and R ₂₀₂ each represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, or a cyano group, and may be the same or different. Cp ₁ and Cp ₂ are represented by the following formula (II):

In the formula, R ₂₀₃ represents a hydrogen atom, an alkyl group such as a methyl group or an ethyl group, or an aryl group such as a phenyl group. R ₂₀₄ , R ₂₀₅ , R ₂₀₆ , R ₂₀₇ and R ₂₀₈ are each a hydrogen atom, a nitro group, a cyano group, a halogen atom such as fluorine, chlorine, bromine or iodine, a halogenated alkyl group such as a trifluoromethyl group, methyl Represents an alkyl group such as an ethyl group, an alkoxy group such as a methoxy group or an ethoxy group, a dialkylamino group or a hydroxyl group, and Z constitutes a substituted or unsubstituted aromatic carbocyclic ring or a substituted or unsubstituted aromatic heterocyclic ring Represents the atomic group necessary to

  Moreover, titanyl phthalocyanine can also be used effectively as a charge generating material in the embodiment of the present invention. Among them, titanyl having a maximum diffraction peak at 27.2 ° (± 0.2 °) as a diffraction peak (± 0.2 °) twice as large as the Bragg angle with respect to the characteristic X-ray (wavelength 1.542 mm) of CuKα. Phthalocyanine crystals, of which the maximum diffraction peak is at 27.2 ° (± 0.2 °), and 9.4 ° (± 0.2 °), 9.6 ° (± 0.2 °), 24 It has a major peak at 0.0 ° (± 0.2 °), and has a peak at 7.3 ° (± 0.2 °) as the diffraction peak at the lowest angle, and this 7.3 ° peak The titanyl phthalocyanine crystal, which has no peak between 1 and 9.4 ° and no peak at 26.3 °, has a large carrier generation efficiency and is effective as a charge generating material in the embodiment of the present invention. Can be used for The Bragg angle θ (°) is half of the angle 2θ formed by the X-ray incident on the crystal and the X-ray diffracted by the crystal.

  In the organic charge generating material contained in the electrophotographic photosensitive member in the embodiment of the present invention, the effect is expressed by making the particle size of the charge generating material finer, and the average particle size is 0. .25 μm or less is preferable, and 0.2 μm or less is more preferable. The manufacturing method is shown below. A method for controlling the particle size of the charge generating material contained in the photosensitive layer is a method of removing coarse particles larger than 0.25 μm after dispersing the charge generating material.

  The average particle size referred to here is a volume average particle size, and is determined by an ultracentrifugal automatic particle size distribution analyzer: CAPA-700 (manufactured by Horiba, Ltd.). At this time, the particle diameter (Median diameter) corresponding to 50% of the cumulative distribution was calculated. However, this method may not be able to detect a very small amount of coarse particles. Therefore, in order to obtain more details, it is important to observe the charge generation material powder or dispersion directly with an electron microscope and determine the size. It is.

  As a result of further observation of the dispersion and examination of micro defects, the above phenomenon was understood as follows. Usually, in the method of measuring the average particle size, when an extremely large particle is present in several% or more, the presence can be detected, but it is about 1% or less of the whole. When the amount is too small, the measurement is below the detection limit. As a result, the presence of coarse particles is not detected only by measuring the average particle size, making it difficult to interpret the above minute defects.

  6 and 7 show photographs observing the state of two types of dispersions in which only the dispersion time is changed while fixing the dispersion conditions. A photograph of the dispersion liquid having a short dispersion time under the same conditions is shown in FIG. 6. Compared with FIG. 7 having a long dispersion time, it is observed that coarse particles remain. The black particles in FIG. 6 are coarse particles.

  The average particle size and particle size distribution of these two types of dispersions were measured according to a known method using a commercially available particle size distribution measuring device (manufactured by Horiba: ultracentrifugal automatic particle size distribution measuring device, CAPA700). The result is shown in FIG. “A” in FIG. 8 corresponds to the dispersion shown in FIG. 6, and “B” corresponds to the dispersion shown in FIG. When both are compared, there is almost no difference in the particle size distribution. In addition, the average particle diameter values of the two are “A” of 0.29 μm and “B” of 0.28 μm, and taking into account measurement errors, there is no difference between the two.

  Therefore, it is understood that the remaining of a minute amount of coarse particles cannot be detected only by the definition of the known average particle size (particle size), and it cannot be applied to the recent high-resolution negative / positive development. The presence of such a minute amount of coarse particles can be recognized for the first time by observing the coating solution at the microscope level.

  Next, a method of removing coarse particles after dispersing the organic charge generating material will be described.

  That is, it is a method in which a dispersion liquid with as fine a particle as possible is prepared and then filtered through an appropriate filter. For the preparation of the dispersion, a general method is used. By dispersing the organic charge generating substance in a suitable solvent together with a binder resin as necessary, using a ball mill, an attritor, a sand mill, a bead mill, an ultrasonic wave, or the like. It is obtained. At this time, the binder resin may be selected depending on the electrostatic characteristics of the photoreceptor, and the solvent may be selected depending on the wettability to the pigment, the dispersibility of the pigment, and the like.

  This method is a very effective means in that it can remove a minute amount of coarse particles that cannot be visually observed (or cannot be detected by particle size measurement), and that the particle size distribution is uniform. Specifically, the dispersion prepared as described above is filtered through a filter having an effective pore size of 5 μm or less, more preferably 3 μm or less, thereby completing the dispersion. Also by this method, a dispersion liquid containing only an organic charge generating substance having a small particle size (0.25 μm or less, preferably 0.2 μm or less) can be produced, and a photoconductor using the dispersion is mounted on an image forming apparatus. By using it, the effect of the present application is made more remarkable.

  At this time, when the particle size of the dispersion to be filtered is too large or the particle size distribution is too wide, the loss due to filtration becomes large or the filtration becomes clogged and filtration becomes impossible. There is a case. For this reason, in the dispersion before filtration, it is desirable to perform dispersion until the average particle size reaches 0.3 μm or less and the standard deviation reaches 0.2 μm or less. When the average particle size is 0.3 μm or more, the loss due to filtration increases, and when the standard deviation is 0.2 μm or more, there may be a problem that the filtration time becomes very long.

  The charge generation material used in the embodiment of the present invention has an extremely strong intermolecular hydrogen bonding force, which is a feature of the charge generation material exhibiting highly sensitive characteristics. For this reason, the interaction between the dispersed pigment particles is very strong. As a result, there is a great possibility that the charge generation material particles dispersed by a disperser etc. are re-aggregated by dilution or the like. Such agglomerates can be removed. At this time, since the dispersion is in a thixotropic state, particles having a size smaller than the effective pore size of the filter to be used are removed. Or the liquid which shows structural viscosity can also be changed into the state close | similar to Newton property by a filter process. Thus, the effect of the embodiment of the present invention is remarkably improved by removing the coarse particles of the charge generation material.

  The filter for filtering the dispersion varies depending on the size of coarse particles to be removed, but according to the study by the present inventors, as a photoreceptor used in an electrophotographic apparatus that requires a resolution of about 600 dpi. The presence of coarse particles of at least 3 μm affects the image. Therefore, a filter with an effective pore size of 5 μm or less should be used. More preferably, a filter having an effective pore size of 3 μm or less is used. As for the effective pore size, the finer the particle, the more effective the removal of coarse particles. However, if the particle size is too fine, the necessary pigment particles themselves are also filtered, and therefore there is an appropriate size. In addition, if it is too fine, it takes time for filtration, clogging of the filter, and excessive load is applied when liquid is sent using a pump or the like. As a matter of course, a material having resistance to the solvent used in the dispersion to be filtered is used as the material of the filter used here.

  The charge transport layer 37 is a layer mainly composed of a charge transport material, and can be formed by dissolving or dispersing the charge transport material and a binder resin in an appropriate solvent, and applying and drying the solution on the charge generation layer. Moreover, a plasticizer, a leveling agent, antioxidant, etc. can also be added as needed.

  Charge transport materials include hole transport materials and electron transport materials. Examples of the hole transport material include poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, pyrene-formaldehyde condensates and derivatives thereof, polyvinylpyrene, polyvinylphenanthrene, polysilane, oxazole derivatives, Oxadiazole derivatives, imidazole derivatives, monoarylamine derivatives, diarylamine derivatives, triarylamine derivatives, stilbene derivatives, α-phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9-styrylanthracene derivatives, pyrazolines Derivatives, divinylbenzene derivatives, hydrazone derivatives, indene derivatives, butadiene derivatives, pyrene derivatives, etc., bisstilbene derivatives, enamine derivatives, etc. Other known materials may be mentioned. These charge transport materials may be used alone or in combination of two or more.

  Examples of the electron transporting material include chloroanil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4 , 5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophen-4-one, 1,3,7-tri Examples thereof include electron-accepting substances such as nitrodibenzothiophene-5,5-dioxide and benzoquinone derivatives.

  The binder resin is polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polychlorinated. Vinylidene, polyarate, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol resin, Examples thereof include thermoplastic or thermosetting resins such as alkyd resins.

  The amount of the charge transport material is 20 to 300 parts by weight, preferably 40 to 150 parts by weight, based on 100 parts by weight of the binder resin. The thickness of the charge transport layer is preferably about 5 to 100 μm.

  As the solvent used here, tetrahydrofuran, dioxane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexanone, methyl ethyl ketone, acetone and the like are used. Among them, the use of a non-halogen solvent is desirable for the purpose of reducing the environmental load. Specifically, cyclic ethers such as tetrahydrofuran, dioxolane and dioxane, aromatic hydrocarbons such as toluene and xylene, and derivatives thereof are preferably used.

  In the embodiment of the present invention, a charge generation layer and a charge transport layer are formed on the intermediate layer. For this reason, unless an appropriate charge transport material is selected, there is a case where the writing light does not sufficiently reach the intermediate layer and the generation of photocarriers in the intermediate layer does not work clearly. In addition, there is a case where the charge transport material is easily deteriorated by absorbing the writing light, and conversely, a residual potential rise is generated. Therefore, in the case of the above configuration, it is desirable that the transmittance of the charge transport layer with respect to writing light is 30% or more, preferably 50% or more, and more desirably 85% or more.

  In order to set the charge transport layer to such a condition, it is important to select a charge transport material appropriate for the static elimination light and form the charge transport layer. Among the charge transport materials described above, a charge transport material having a triarylamine skeleton is easy to transmit static elimination light of less than 450 nm and has a high mobility. Therefore, the charge transport material used for the photoconductor in the embodiment of the present invention. It is suitable as a substance.

  In the embodiment of the present invention, a plasticizer or a leveling agent may be added to the charge transport layer. As the plasticizer, those used as general plasticizers such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount used is suitably about 0 to 30% by weight based on the binder resin. As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, polymers or oligomers having a perfluoroalkyl group in the side chain are used, and the amount used is 0 to 0 with respect to the binder resin. 1% by weight is suitable.

  In the electrophotographic photosensitive member in the embodiment of the present invention, a protective layer may be provided on the photosensitive layer for the purpose of protecting the photosensitive layer. In recent years, computers have been used on a daily basis, and there has been a demand for miniaturization of devices as well as high-speed output by printers. Therefore, by providing the protective layer and improving the durability, it is possible to effectively use the photoconductor with high sensitivity and no abnormal defect in the embodiment of the present invention.

  The effective protective layer used in the embodiment of the present invention can be roughly classified into two types. One is a configuration in which a filler is added to the binder resin. The other one uses a cross-linking binder.

  First, a configuration in which a filler is added to the protective layer will be described.

  Materials used for the protective layer include ABS resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallylsulfone, polybutylene, Polybutylene terephthalate, polycarbonate, polyarylate, polyethersulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic resin, polymethylbenten, polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS resin, butadiene-styrene copolymer, polyurethane, polychlorinated Examples thereof include resins such as vinyl, polyvinylidene chloride, and epoxy resin. Of these, polycarbonate or polyarylate can be most preferably used.

  Other protective layers include fluorine resins such as polytetrafluoroethylene, silicone resins, and inorganic fillers such as titanium oxide, tin oxide, potassium titanate, and silica for the purpose of improving wear resistance. What disperse | distributed the filler etc. can be added.

  Among the filler materials used for the protective layer of the photoreceptor, examples of the organic filler material include fluororesin powder such as polytetrafluoroethylene, silicone resin powder, a-carbon powder, and the like. Metals such as copper, tin, aluminum, indium, etc., metals such as silica, tin oxide, zinc oxide, titanium oxide, indium oxide, antimony oxide, bismuth oxide, antimony-doped tin oxide, tin-doped indium oxide Inorganic materials such as oxide and potassium titanate can be mentioned. In particular, it is advantageous to use an inorganic material among them from the viewpoint of the hardness of the filler. In particular, inorganic pigments and metal oxides are preferable, and silica, titanium oxide, and alumina can be used effectively.

  The filler concentration in the protective layer varies depending on the type of filler used and also on the electrophotographic process conditions using the photoconductor, but the ratio of filler to the total solid content on the outermost layer side of the protective layer is preferably 5% by weight or more, preferably It is 10% by weight or more and 50% by weight or less, preferably about 30% by weight or less. Moreover, the volume average particle diameter of the filler to be used is preferably in the range of 0.1 μm to 2 μm, and preferably in the range of 0.3 μm to 1 μm. In this case, if the average particle size is too small, the wear resistance is not sufficiently exhibited, and if it is too large, the surface property of the coating film is deteriorated or the coating film itself cannot be formed.

  In addition, the average particle diameter of the filler in the embodiment of the present invention is a volume average particle diameter unless otherwise specified, and was determined by an ultracentrifugal automatic particle size distribution analyzer: CAPA-700 (manufactured by Horiba). Is. At this time, the particle diameter (Median diameter) corresponding to 50% of the cumulative distribution was calculated. In addition, it is important that the standard deviation of each particle measured simultaneously is 1 μm or less. If the standard deviation is larger than this, the particle size distribution may be too wide, and the effects of the embodiment of the present invention may not be obtained remarkably.

  Further, the pH of the filler used in the embodiment of the present invention greatly affects the resolution and the dispersibility of the filler. One possible reason is that hydrochloric acid or the like remains in the filler, particularly the metal oxide, during production. When the remaining amount is large, the occurrence of image blur is unavoidable, and depending on the remaining amount, the dispersibility of the filler may be affected.

  Another reason is due to the difference in chargeability on the surface of the filler, particularly the metal oxide. Usually, particles dispersed in a liquid are charged positively or negatively, and ions having opposite charges gather to try to keep it electrically neutral, and an electric double layer is formed there. The dispersed state of the particles is stabilized. The potential (zeta potential) gradually decreases with increasing distance from the particle, and the potential in a region that is sufficiently away from the particle and electrically neutral is zero. Therefore, the stability increases as the repulsive force of the particles increases due to an increase in the absolute value of the zeta potential, and the particles tend to aggregate and become unstable as they approach zero. On the other hand, the zeta potential varies greatly depending on the pH value of the system, and at a certain pH value, the potential becomes zero and has an isoelectric point. Therefore, the dispersion system is stabilized by increasing the absolute value of the zeta potential as far as possible from the isoelectric point of the system.

  In the configuration of the embodiment of the present invention, the filler having a pH at the isoelectric point of at least 5 is preferably from the viewpoint of suppressing image blur, and the more basic the filler, the more effective the filler. It was confirmed that there was a tendency to increase. The filler having a high basic pH at the isoelectric point has a higher zeta potential when the system is acidic, so that dispersibility and stability thereof are improved.

  Here, the pH of the filler in the embodiment of the present invention is the pH value at the isoelectric point from the zeta potential. At this time, the zeta potential was measured with a laser zeta potentiometer manufactured by Otsuka Electronics Co., Ltd.

Further, as the filler that is less likely to cause image blur, a filler having high electrical insulation (specific resistance is 10 ¹⁰ Ω · cm or more) is preferable, and the filler having a pH of 5 or more or the filler having a dielectric constant of 5 or more. The ones shown can be used particularly effectively. In addition, a filler having a pH of 5 or more or a filler having a dielectric constant of 5 or more can be used alone, or two or more fillers having a pH of 5 or less and a filler having a pH of 5 or more can be mixed. It is also possible to use a mixture of two or more fillers having a dielectric constant of 5 or less and a filler having a dielectric constant of 5 or more. Among these fillers, α-type alumina, which has high insulation properties, high thermal stability, and high wear resistance, is a hexagonal close-packed structure, from the viewpoint of suppressing image blur and improving wear resistance. It is particularly useful.

The specific resistance of the filler used in the embodiment of the present invention is defined as follows. Since the specific resistance value of a powder such as a filler varies depending on the filling rate, it is necessary to measure under certain conditions. In the embodiment of the present invention, the specific resistance value of the filler was measured using an apparatus having the same configuration as that of the measuring apparatus disclosed in Japanese Patent Laid-Open No. 5-113688 (FIG. 1), and this value was used. . In the measuring device, the electrode area is 4.0 cm ² . Prior to the measurement, a load of 4 kg is applied to the electrode on one side for 1 minute, and the sample amount is adjusted so that the distance between the electrodes is 4 mm. At the time of measurement, the measurement is performed with the upper electrode weight (1 kg) loaded, and the applied voltage is measured at 100V. The area of 10 ⁶ Ω · cm or higher was measured with a HIGH RESISTER METER (Yokogawa Hewlett Packard), and the area below it was measured with a digital multimeter (Fluk). The specific resistance value obtained in this way is defined as the specific resistance value in the embodiment of the present invention.

  The dielectric constant of the filler was measured as follows. Using a cell similar to the measurement of the specific resistance as described above, after applying a load, the capacitance was measured, and the dielectric constant was determined from this. For the measurement of the capacitance, a dielectric loss measuring device (Ando Electric) was used.

Furthermore, these fillers can be surface-treated with at least one kind of surface treatment agent, which is preferable from the viewpoint of the dispersibility of the filler. Decreasing the dispersibility of the filler not only increases the residual potential, but also decreases the transparency of the coating, causes defects in the coating, and decreases the wear resistance. It can develop into a big problem. As the surface treatment agent, all conventionally used surface treatment agents can be used, but a surface treatment agent capable of maintaining the insulating properties of the filler is preferable. For example, a titanate coupling agent, an aluminum coupling agent, a zircoaluminate coupling agent, a higher fatty acid, etc., or a mixing treatment of these with a silane coupling agent, Al ₂ O ₃ , TiO ₂ , ZrO ₂ , Silicone, aluminum stearate, or the like, or a mixture thereof is more preferable from the viewpoint of filler dispersibility and image blur. The treatment with the silane coupling agent is strongly influenced by image blur, but the influence may be suppressed by performing a mixing treatment of the surface treatment agent and the silane coupling agent. The surface treatment amount varies depending on the average primary particle size of the filler used, but is preferably 3 to 30 wt%, more preferably 5 to 20 wt%. If the surface treatment amount is less than this, the filler dispersion effect cannot be obtained, and if it is too much, the residual potential is significantly increased. These filler materials may be used alone or in combination of two or more. The surface treatment amount of the filler is defined by the weight ratio of the surface treatment agent to be used with respect to the filler amount as described above.

  These filler materials can be dispersed by using an appropriate disperser. Further, from the viewpoint of the transmittance of the protective layer, it is preferable that the filler used is dispersed to the primary particle level and has less aggregates.

  Further, the protective layer may contain a charge transport material for reducing residual potential and improving responsiveness. As the charge transport material, the materials described in the description of the charge transport layer and known charge transport materials can be used. When a low molecular charge transport material is used as the charge transport material, a concentration gradient in the protective layer may be provided. In order to improve wear resistance, it is an effective means to reduce the concentration of the surface side. The concentration here refers to the ratio of the weight of the low molecular charge transporting material to the total weight of all the materials constituting the protective layer, and the concentration gradient is a gradient that lowers the concentration on the surface side in the above weight ratio. It shows that. The use of a polymer charge transport material is very advantageous in terms of enhancing the durability of the photoreceptor.

  In addition, a known polymer charge transport material can also be used as the binder resin for the protective layer. As an effect when this is used, an improvement in wear resistance and an effect of high-speed charge transport can be obtained.

  As a method for forming such a protective layer, a normal coating method is employed. In addition, about 0.1-10 micrometers is suitable for the thickness of the protective layer mentioned above.

  Next, a protective layer having a crosslinked structure will be described as a binder structure of the protective layer (hereinafter referred to as a crosslinked protective layer).

  Regarding the formation of a cross-linked structure, a reactive monomer having a plurality of cross-linkable functional groups in one molecule is used to cause a cross-linking reaction using light or thermal energy to form a three-dimensional network structure. is there. This network structure functions as a binder resin and exhibits high wear resistance.

  Moreover, it is a very effective means to use a monomer having a charge transporting ability in whole or in part as the reactive monomer. By using such a monomer, a charge transporting site is formed in the network structure, and the function as a protective layer can be sufficiently expressed. A reactive monomer having a triarylamine structure is effectively used as the monomer having charge transporting ability.

  The protective layer having such a network structure has high wear resistance, but has a large volume shrinkage during the crosslinking reaction, and if it is too thick, it may cause cracks. In such a case, the protective layer may be a laminated structure, a low molecular dispersion polymer protective layer may be used for the lower layer (photosensitive layer side), and a protective layer having a crosslinked structure may be formed on the upper layer (surface side). good.

  Among the crosslinked protective layers, a protective layer having the following specific structure is particularly effectively used.

  The specific crosslinkable protective layer is a protective layer formed by curing at least a trifunctional or higher functional radical polymerizable monomer having no charge transporting structure and a radical polymerizable compound having a monofunctional charge transporting structure. It is. Since it has a cross-linked structure obtained by curing a tri- or higher-functional radically polymerizable monomer, a three-dimensional network structure is developed, and a high hardness and high elasticity surface layer having a very high crosslink density is obtained, and it is uniform and highly smooth. High wear resistance and scratch resistance are achieved. In this way, it is important to increase the crosslink density on the surface of the photoreceptor, that is, the number of crosslink bonds per unit volume. However, since a large number of bonds are instantaneously formed in the curing reaction, internal stress due to volume shrinkage occurs. This internal stress increases as the thickness of the crosslinkable protective layer increases. Therefore, when the entire protective layer is cured, cracks and film peeling tend to occur. Even if this phenomenon does not appear initially, it may be likely to occur over time due to repeated use in the electrophotographic process and the influence of charging, development, transfer, cleaning hazards and thermal fluctuations.

  As a method for solving this problem, (1) a polymer component is introduced into the crosslinked layer and the crosslinked structure, (2) a large amount of monofunctional and bifunctional radically polymerizable monomers are used, and (3) a flexible group is introduced. Although the directionality which makes a cured resin layer soft, such as using the polyfunctional monomer which has, is mentioned, the crosslink density of a bridge | crosslinking layer becomes thin in any case, and remarkable wear resistance is not achieved. On the other hand, in the photoconductor in the embodiment of the present invention, a crosslinkable protective layer having a high crosslink density in which a three-dimensional network structure is developed on the charge transport layer is preferably provided with a film thickness of 1 μm or more and 10 μm or less. Therefore, the above-mentioned cracks and film peeling do not occur, and very high wear resistance is achieved. By making the film thickness of the crosslinkable protective layer 2 μm or more and 8 μm or less, in addition to further improving the margin for the above problem, it is possible to select a material for increasing the crosslink density that leads to further improvement in wear resistance. It becomes possible.

  The reason why the photoconductor in the embodiment of the present invention can suppress cracking and film peeling is that the cross-linkable protective layer can be made thin, so that the internal stress does not increase, and since the lower layer has a photosensitive layer or charge transport layer, This is because the internal stress of the crosslinkable protective layer can be relaxed. For this reason, it is not necessary to contain a large amount of polymer material in the crosslinkable protective layer, and the polymer material and radical polymerizable composition (radically polymerizable monomer or radical polymerizable compound having a charge transporting structure) generated at this time are generated. Scratches and toner filming due to incompatibility with the cured product resulting from the reaction are less likely to occur. Further, when the thick film over the entire protective layer is cured by irradiation with light energy, the light transmission from the absorption by the charge transporting structure is limited, and the curing reaction may not sufficiently proceed. In the cross-linked protective layer in the embodiment of the present invention, preferably a thin film having a thickness of 10 μm or less allows the curing reaction to progress uniformly to the inside, and high wear resistance is maintained inside as well as the surface. In addition, in the formation of the crosslinkable protective layer in the embodiment of the present invention, in addition to the trifunctional radical polymerizable monomer, a radical polymerizable compound having a monofunctional charge transporting structure is further contained. Incorporated into the cross-linking bond at the time of curing the above trifunctional or higher radical polymerizable monomer. On the other hand, when a low molecular charge transport material having no functional group is contained in the cross-linked surface layer, precipitation of the low molecular charge transport material and white turbidity occur due to its low compatibility, and the cross-linked surface layer The mechanical strength also decreases. On the other hand, when a bifunctional or higher-functional charge transporting compound is used as the main component, the crosslink structure is fixed by a plurality of bonds and the crosslink density is further increased. However, the charge transporting structure is very bulky, so that the cured resin structure is distorted. Becomes very large, which increases the internal stress of the crosslinked protective layer.

  Furthermore, the photoconductor in the embodiment of the present invention has good electrical characteristics, and is therefore excellent in repeated stability, realizing high durability and high stability. This is because a radical polymerizable compound having a monofunctional charge transporting structure is used as a constituent material of the crosslinkable protective layer and is immobilized in a pendant shape between the crosslinks. As described above, the charge transport material having no functional group causes precipitation and clouding phenomenon, and the electrical characteristics are remarkably deteriorated in repeated use such as reduction in sensitivity and increase in residual potential. When a bifunctional or higher-functional charge transporting compound is used as the main component, it is fixed in the crosslinked structure with a plurality of bonds, so the intermediate structure (cation radical) during charge transport cannot be kept stable, Sensitivity decreases due to traps and residual potential increases. Such deterioration of the electric characteristics appears as an image such as a decrease in image density and thinning of characters. Furthermore, in the photoconductor in the embodiment of the present invention, a high mobility design with less charge trapping of the conventional photoconductor can be applied as the lower charge transport layer, and the electrical side effects of the crosslinked protective layer can be minimized. Can be suppressed.

  Furthermore, in the formation of the above-mentioned crosslinkable protective layer in the embodiment of the present invention, the drastic wear resistance is exhibited particularly by making the crosslinkable protective layer insoluble in the organic solvent. The cross-linkable protective layer in the embodiment of the present invention is formed by curing a tri- or higher functional radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. As a whole, a three-dimensional network structure is developed and has a high crosslinking density, but it contains additives other than the above components (for example, additives such as mono- or bifunctional monomers, polymer binders, antioxidants, leveling agents, plasticizers, etc.) In some cases, the cross-linking density is locally dilute or is formed as an aggregate of minute hardened products cross-linked with high density depending on the curing conditions. Such a crosslinkable protective layer has a low bonding strength between cured products and is soluble in organic solvents, and is repeatedly used in the electrophotographic process. Detachment easily occurs. By making the crosslinkable protective layer insoluble in the organic solvent as in the embodiment of the present invention, the original three-dimensional network structure is developed and has a high degree of crosslinking, and the chain reaction proceeds in a wide range. Since the cured product has a high molecular weight, a dramatic improvement in wear resistance is achieved.

  Next, the constituent material of the crosslinking-type protective layer coating solution in the embodiment of the present invention will be described.

  The trifunctional or higher functional radical polymerizable monomer having no charge transporting structure used in the embodiment of the present invention is, for example, a hole transporting structure such as triarylamine, hydrazone, pyrazoline, carbazole, such as condensed polycyclic quinone. , A monomer having no electron transport structure such as diphenoquinone, an electron-withdrawing aromatic ring having a cyano group or a nitro group, and having three or more radically polymerizable functional groups. The radical polymerizable functional group may be any group as long as it has a carbon-carbon double bond and is capable of radical polymerization. Examples of these radical polymerizable functional groups include 1-substituted ethylene functional groups and 1,1-substituted ethylene functional groups shown below.

  (1) Examples of the 1-substituted ethylene functional group include functional groups represented by the following formulas.

CH ₂ = CH-X _1-( Formula 10)
(In the formula 10, X ₁ represents an arylene group such as a phenylene group and a naphthylene group which may have a substituent, an alkenylene group which may have a substituent, a —CO— group, a —COO— group, -CON _{(R 10)} - group _{(R 10} is hydrogen, alkyl group such as a methyl group, an ethyl group, a benzyl group, naphthylmethyl group, an aralkyl group such as a phenethyl group, a phenyl group, an aryl group such as phenyl or naphthyl Represents a -S- group.)
Specific examples of these functional groups include vinyl group, styryl group, 2-methyl-1,3-butadienyl group, vinylcarbonyl group, acryloyloxy group, acryloylamide group, vinylthioether group and the like.

  (2) Examples of the 1,1-substituted ethylene functional group include functional groups represented by the following formulas.

_{CH 2 = C (Y) -X} 2 - ····· Formula 11
(However, in Formula 11, Y is an alkyl group which may have a substituent, an aralkyl group which may have a substituent, a phenyl group which may have a substituent, a naphthyl group, etc. An aryl group, a halogen atom, a cyano group, a nitro group, an alkoxy group such as a methoxy group or an ethoxy group, a -COOR ₁₁ group (R ₁₁ is a hydrogen atom, an optionally substituted methyl group, an ethyl group, etc. An alkyl group, an aralkyl group such as an optionally substituted benzyl or phenethyl group, an aryl group such as an optionally substituted phenyl group or naphthyl group, or -CONR ₁₂ R ₁₃ (R ₁₂ and R ₁₃ is a hydrogen atom, which may have a substituent an alkyl group such as methyl group and ethyl group, which may have a substituent group benzyl group, naphthylmethyl group or a phenethyl group, Aralkyl group or substituent a phenyl group which may have a represents an aryl group such as phenyl or naphthyl, which may be the same or different from each other.) Further, X ₂ is the same as X ₁ in the formula 10 substituents and a single bond, an alkylene group. However, Y, at least one oxycarbonyl group in X _2, a cyano group, an alkenylene group, and an aromatic ring.)
Specific examples of these functional groups include an α-acryloyloxy chloride group, a methacryloyloxy group, an α-cyanoethylene group, an α-cyanoacryloyloxy group, an α-cyanophenylene group, and a methacryloylamino group.

In addition, examples of the substituent further substituted with the substituent for X ₁ , X ₂ , and Y include, for example, a halogen atom, a nitro group, a cyano group, a methyl group, an alkyl group such as an ethyl group, a methoxy group, an ethoxy group, and the like And an aryloxy group such as a phenoxy group, an aryl group such as a phenyl group and a naphthyl group, and an aralkyl group such as a benzyl group and a phenethyl group.

  Among these radical polymerizable functional groups, acryloyloxy group and methacryloyloxy group are particularly useful, and a compound having three or more acryloyloxy groups is, for example, a compound having three or more hydroxyl groups in the molecule and an acrylic group. It can be obtained by using an acid (salt), an acrylic acid halide, or an acrylic ester to cause an ester reaction or a transesterification reaction. A compound having three or more methacryloyloxy groups can be obtained in the same manner. Further, the radical polymerizable functional groups in the monomer having three or more radical polymerizable functional groups may be the same or different.

  Specific examples of the trifunctional or higher functional radical polymerizable monomer having no charge transporting structure include the following, but are not limited to these compounds.

  That is, examples of the radical polymerizable monomer used in the embodiment of the present invention include trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate, trimethylolpropane alkylene-modified triacrylate, and trimethylolpropane ethyleneoxy-modified. (Hereinafter EO modified) triacrylate, trimethylolpropane propyleneoxy modified (hereinafter PO modified) triacrylate, trimethylolpropane caprolactone modified triacrylate, trimethylolpropane alkylene modified trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate (PETTA) Glycerol triacrylate, glycerol epichlorohydrin modified (hereinafter referred to as E H-modified) triacrylate, glycerol EO-modified triacrylate, glycerol PO-modified triacrylate, tris (acryloxyethyl) isocyanurate, dipentaerythritol hexaacrylate (DPHA), dipentaerythritol caprolactone-modified hexaacrylate, dipentaerythritol hydroxypentaacrylate , Alkylated dipentaerythritol pentaacrylate, alkylated dipentaerythritol tetraacrylate, alkylated dipentaerythritol triacrylate, dimethylolpropane tetraacrylate (DTMPTA), pentaerythritol ethoxytetraacrylate, EO-modified triacrylate phosphate, 2,2 , 5,5, -Tetrahydroxymethylcyclopentanone tet Acrylate and the like, which may be used in combination either alone or in combination.

  Further, the trifunctional or higher functional radical polymerizable monomer having no charge transporting structure used in the embodiment of the present invention includes a functional group in the monomer in order to form a dense crosslink in the crosslinkable protective layer. The ratio of molecular weight to the number of groups (molecular weight / number of functional groups) is preferably 250 or less. On the other hand, if this ratio is larger than 250, the crosslinked protective layer tends to be soft and wear resistance tends to decrease somewhat. Therefore, among the monomers exemplified above, monomers having modifying groups such as EO, PO, caprolactone, etc. In the method, it is not preferable to use a compound having an extremely long modifying group alone. In addition, the proportion of the trifunctional or higher functional radical polymerizable monomer having no charge transporting structure used in the crosslinkable protective layer is 20 to 80% by weight, preferably 30 to 70% by weight, based on the total amount of the crosslinkable protective layer. is there. When the monomer component is less than 20% by weight, the three-dimensional crosslink density of the crosslinkable protective layer is small, and it is difficult to achieve a dramatic improvement in wear resistance as compared with the case of using a conventional thermoplastic binder resin. On the other hand, when it exceeds 80% by weight, the content of the charge transporting compound is lowered, and the electrical characteristics tend to be deteriorated. The electrical characteristics and abrasion resistance required vary depending on the process used, and the thickness of the cross-linked protective layer of the photoconductor also varies accordingly. A weight percent range is most preferred.

  The radical polymerizable compound having a monofunctional charge transporting structure used in the crosslinked protective layer in the embodiment of the present invention is a hole transporting structure such as triarylamine, hydrazone, pyrazoline, carbazole, etc. It refers to a compound having an electron transport structure such as polycyclic quinone, diphenoquinone, an electron-withdrawing aromatic ring having a cyano group or a nitro group, and having one radical polymerizable functional group. Examples of the radical polymerizable functional group include those shown in the above radical polymerizable monomer, and acryloyloxy group and methacryloyloxy group are particularly useful. In addition, a triarylamine structure has a high effect as a charge transporting structure, and in particular, when a compound represented by the structure of the following general formula (1) or (2) is used, electrical characteristics such as sensitivity and residual potential Is well maintained.

{In the formula, R ₁ represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, an aryl group which may have a substituent, a cyano group, a nitro group, Group, alkoxy group, —COOR ₇ (R ₇ is a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent or an aryl group which may have a substituent), halogen Carbonyl group or CONR ₈ R ₉ (R ₈ and R ₉ may have a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. Represents a good aryl group, which may be the same or different from each other, and Ar ₁ and Ar ₂ represent a substituted or unsubstituted arylene group, which may be the same or different. Ar ₃ and Ar ₄ represent a substituted or unsubstituted aryl group, and may be the same or different. X represents a single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted cycloalkylene group, a substituted or unsubstituted alkylene ether group, an oxygen atom, a sulfur atom, or a vinylene group. Z represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylene ether divalent group, or an alkyleneoxycarbonyl divalent group. m and n represent an integer of 0 to 3. }
Specific examples of general formulas (1) and (2) are shown below.

In the general formulas (1) and (2), in the substituent of R ₁ , examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group, and examples of the aryl group include a phenyl group and a naphthyl group. The aralkyl group includes a benzyl group, a phenethyl group, and a naphthylmethyl group, and the alkoxy group includes a methoxy group, an ethoxy group, a propoxy group, and the like. These include a halogen atom, a nitro group, a cyano group, and a methyl group. Substituted with an alkyl group such as an ethyl group, an alkoxy group such as a methoxy group or an ethoxy group, an aryloxy group such as a phenoxy group, an aryl group such as a phenyl group or a naphthyl group, an aralkyl group such as a benzyl group or a phenethyl group, etc. May be.

Of the substituents for R ₁ , particularly preferred are a hydrogen atom and a methyl group.

Ar ₃ and Ar ₄ are substituted or unsubstituted aryl groups. In the embodiment of the present invention, the aryl group includes a condensed polycyclic hydrocarbon group, a non-condensed cyclic hydrocarbon group, and a heterocyclic group, and includes the following groups.

  The condensed polycyclic hydrocarbon group preferably has 18 or less carbon atoms forming a ring, for example, a pentanyl group, an indenyl group, a naphthyl group, an azulenyl group, a heptaenyl group, a biphenylenyl group, an as-indacenyl group. , S-indacenyl group, fluorenyl group, acenaphthylenyl group, preadenyl group, acenaphthenyl group, phenalenyl group, phenanthryl group, anthryl group, fluoranthenyl group, acephenanthrenyl group, aceanthrylenyl group, triphenylyl group, pyrenyl group , A chrycenyl group, a naphthacenyl group, and the like.

  Examples of the non-fused cyclic hydrocarbon group include monovalent groups of monocyclic hydrocarbon compounds such as benzene, diphenyl ether, polyethylene diphenyl ether, diphenyl thioether and diphenyl sulfone, or biphenyl, polyphenyl, diphenylalkane, diphenylalkene, diphenylalkyne, Monovalent groups of non-condensed polycyclic hydrocarbon compounds such as triphenylmethane, distyrylbenzene, 1,1-diphenylcycloalkane, polyphenylalkane, and polyphenylalkene, or ring assemblies such as 9,9-diphenylfluorene And monovalent groups of hydrocarbon compounds.

  Examples of the heterocyclic group include monovalent groups such as carbazole, dibenzofuran, dibenzothiophene, oxadiazole, and thiadiazole.

The aryl group represented by Ar ₃ or Ar ₄ may have a substituent as shown below, for example.

  (1) Halogen atom, cyano group, nitro group and the like.

(2) Alkyl groups, preferably C ₁ -C _12, especially C ₁ -C ₈ , more preferably C ₁ -C ₄ linear or branched alkyl groups, further including fluorine atoms , a hydroxyl group, a cyano _group, an alkoxy group of C 1 -C _4, a phenyl group or a halogen _atom, which may have a phenyl group substituted by an alkoxy group C 1 -C ₄ alkyl or _C 1 -C ₄ Good. Specifically, methyl group, ethyl group, n-butyl group, i-propyl group, t-butyl group, s-butyl group, n-propyl group, trifluoromethyl group, 2-hydroxyethyl group, 2-ethoxyethyl Group, 2-cyanoethyl group, 2-methoxyethyl group, benzyl group, 4-chlorobenzyl group, 4-methylbenzyl group, 4-phenylbenzyl group and the like.

(3) An alkoxy group (—OR ₂ ), and R ₂ represents the alkyl group defined in (2). Specifically, methoxy group, ethoxy group, n-propoxy group, i-propoxy group, t-butoxy group, n-butoxy group, s-butoxy group, i-butoxy group, 2-hydroxyethoxy group, benzyloxy group And a trifluoromethoxy group.

(4) An aryloxy group, and examples of the aryl group include a phenyl group and a naphthyl group. It _may contain an alkoxy group having C 1 -C _4, alkyl group, or a halogen atom C 1 -C ₄ as a substituent. Specific examples include a phenoxy group, a 1-naphthyloxy group, a 2-naphthyloxy group, a 4-methoxyphenoxy group, and a 4-methylphenoxy group.

  (5) Alkyl mercapto group or aryl mercapto group, and specific examples include methylthio group, ethylthio group, phenylthio group, p-methylphenylthio group and the like.

  (6)

(In the formula, R ₃ and R ₄ each independently represent a hydrogen atom, an alkyl group defined in (2) above, or an aryl group. Examples of the aryl group include a phenyl group, a biphenyl group, and a naphthyl group. these may form a ring _C 1 -C ₄ alkoxy _groups, C 1 -C a alkyl group or a halogen atom ₄ which may contain as substituents .R ₃ and _{R 4} jointly)
Specifically, amino group, diethylamino group, N-methyl-N-phenylamino group, N, N-diphenylamino group, N, N-di (tolyl) amino group, dibenzylamino group, piperidino group, morpholino group And pyrrolidino group.

  (7) An alkylenedioxy group or an alkylenedithio group such as a methylenedioxy group or a methylenedithio group.

  (8) A substituted or unsubstituted styryl group, a substituted or unsubstituted β-phenylstyryl group, a diphenylaminophenyl group, a ditolylaminophenyl group, and the like.

The arylene group represented by Ar ₁ and Ar ₂ is a divalent group derived from the aryl group represented by Ar ₃ and Ar ₄ .

  X represents a single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted cycloalkylene group, a substituted or unsubstituted alkylene ether group, an oxygen atom, a sulfur atom, or a vinylene group.

The substituted or unsubstituted alkylene group is a C ₁ -C ₁₂ , preferably C ₁ -C ₈ , more preferably C ₁ -C ₄ linear or branched alkylene group, and these alkylene groups include a fluorine atom, a hydroxyl group, a cyano _group, an alkoxy group of C 1 -C _4, a phenyl group or a halogen _atom, a phenyl group substituted with an alkyl group or a _C 1 -C ₄ alkoxy group C 1 -C ₄ It may be. Specifically, methylene group, ethylene group, n-butylene group, i-propylene group, t-butylene group, s-butylene group, n-propylene group, trifluoromethylene group, 2-hydroxyethylene group, 2-ethoxyethylene Group, 2-cyanoethylene group, 2-methoxyethylene group, benzylidene group, phenylethylene group, 4-chlorophenylethylene group, 4-methylphenylethylene group, 4-biphenylethylene group and the like.

The substituted or unsubstituted cycloalkylene _group, a cyclic alkylene group of C 5 -C _7, these are the cyclic alkylene group fluorine atom, a hydroxyl _group, an alkyl group of C 1 -C _4, a C 1 -C ₄ It may have an alkoxy group. Specific examples include a cyclohexylidene group, a cyclohexylene group, and a 3,3-dimethylcyclohexylidene group.

  The substituted or unsubstituted alkylene ether group represents ethyleneoxy, propyleneoxy, ethylene glycol, propylene glycol, diethylene glycol, tetraethylene glycol, tripropylene glycol, alkylene ether group alkylene group is hydroxyl group, methyl group, ethyl group, etc. You may have the substituent of.

  The vinylene group is

R ₅ is hydrogen, an alkyl group (same as the alkyl group defined in (2) above), an aryl group (same as the aryl group represented by Ar ₃ or Ar ₄ above), a is 1 or 2 , B represents 1-3.

  Z represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylene ether divalent group, or an alkyleneoxycarbonyl divalent group.

  Examples of the substituted or unsubstituted alkylene group include the same alkylene groups as those described above for X.

  Examples of the substituted or unsubstituted alkylene ether divalent group include the alkylene ether divalent group of X.

  Examples of the alkyleneoxycarbonyl divalent group include a caprolactone divalent modifying group.

  Further, the radical polymerizable compound having a monofunctional charge transport structure in the embodiment of the present invention is more preferably a compound having a structure of the following general formula (3).

(Wherein, o, p and q are each an integer of 0 or 1, Ra represents a hydrogen atom or a methyl group, Rb and Rc represent a substituent other than a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, And s and t each represent an integer of 0 to 3. Za represents a single bond, a methylene group or an ethylene group.)

As the compound represented by the above general formula, compounds having a methyl group or an ethyl group as substituents for Rb and Rc are particularly preferable.

  The radically polymerizable compound having a monofunctional charge transporting structure represented by the general formulas (1) and (2), particularly (3) used in the embodiment of the present invention has carbon-carbon double bonds on both sides. In the polymer that is released and polymerized, it does not become a terminal structure, but is incorporated into a chain polymer and crosslinked by polymerization with a trifunctional or higher radical polymerizable monomer. Exists in the cross-linked chain between the main chain and the main chain (in this cross-linked chain, an intermolecular cross-linked chain between one polymer and another polymer and a folded state in one polymer) There is an intramolecular cross-linked chain in which a site with a main chain and another site derived from a polymerized monomer are cross-linked at a position away from this in the main chain), but even if it exists in the main chain Even if it is present in the crosslinked chain, the triarylamine structure suspended from the chain portion. Has at least three aryl groups arranged radially from the nitrogen atom and is bulky, but is not directly bonded to the chain part and is suspended from the chain part via a carbonyl group or the like. Since these triarylamine structures are fixed in a flexible manner in the positioning, they can be arranged adjacent to each other in the polymer, so that there is little structural distortion in the molecule, and electrophotography In the case of the surface layer of the photoreceptor, it is presumed that an intramolecular structure that is relatively free from interruption of the charge transport path can be adopted.

  Specific examples of the radical polymerizable compound having a monofunctional charge transporting structure in the embodiment of the present invention are shown below, but are not limited to the compounds having these structures.

Further, the radical polymerizable compound having a monofunctional charge transporting structure used in the embodiment of the present invention is important for imparting the charge transporting performance of the crosslinkable protective layer, and this component is added to the crosslinkable protective layer. It is 20 to 80% by weight, preferably 30 to 70% by weight. If this component is less than 20% by weight, the charge transport performance of the cross-linked protective layer cannot be sufficiently maintained, and repeated use tends to cause deterioration of electrical characteristics such as sensitivity reduction and residual potential increase. On the other hand, if it exceeds 80% by weight, the content of the trifunctional monomer having no charge transporting structure is lowered, and the crosslink density is lowered, so that high wear resistance tends to be hardly exhibited. The electrical properties and abrasion resistance required vary depending on the process used, and the thickness of the crosslinked protective layer of the photoconductor in the embodiment of the present invention varies accordingly. In view of the above, the range of 30 to 70% by weight is most preferable.

  The crosslinkable protective layer constituting the electrophotographic photosensitive member in the embodiment of the present invention includes at least a trifunctional or higher radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. In addition to this, monofunctional and bifunctional radical polymerizability for the purpose of imparting functions such as viscosity adjustment during coating, stress relaxation of the cross-linked protective layer, lower surface energy and reduced friction coefficient, etc. A monomer, a functional monomer, and a radical polymerizable oligomer can be used in combination. Known radical polymerizable monomers and oligomers can be used.

  Examples of the monofunctional radical monomer include 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, tetrahydrofurfuryl acrylate, 2-ethylhexyl carbitol acrylate, 3-methoxybutyl acrylate, benzyl acrylate, and cyclohexyl acrylate. , Isoamyl acrylate, isobutyl acrylate, methoxytriethylene glycol acrylate, phenoxytetraethylene glycol acrylate, cetyl acrylate, isostearyl acrylate, stearyl acrylate, styrene monomer, and the like.

  Examples of the bifunctional radical polymerizable monomer include 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol diacrylate, 1, Examples include 6-hexanediol dimethacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, bisphenol A-EO modified diacrylate, bisphenol F-EO modified diacrylate, and neopentyl glycol diacrylate.

  Examples of the functional monomer include those substituted with a fluorine atom such as octafluoropentyl acrylate, 2-perfluorooctylethyl acrylate, 2-perfluorooctylethyl methacrylate, 2-perfluoroisononylethyl acrylate, No. 60503, JP-B-6-45770, siloxane repeating units: 20-70 acryloyl polydimethylsiloxane ethyl, methacryloyl polydimethylsiloxane ethyl, acryloyl polydimethylsiloxane propyl, acryloyl polydimethylsiloxane butyl, diacryloyl polydimethylsiloxane Examples include vinyl monomers having a polysiloxane group such as diethyl, acrylates and methacrylates.

  Examples of the radical polymerizable oligomer include epoxy acrylate, urethane acrylate, and polyester acrylate oligomers.

  However, when a large amount of monofunctional and bifunctional radically polymerizable monomers and radically polymerizable oligomers are contained, the three-dimensional crosslink density of the crosslinkable protective layer is substantially reduced, resulting in a decrease in wear resistance. Therefore, the content of these monomers and oligomers is more preferably 50 parts by weight or less, preferably 30 parts by weight or less, with respect to 100 parts by weight of the tri- or higher functional radical polymerizable monomer.

  In addition, the crosslinkable protective layer in the embodiment of the present invention is obtained by curing at least a trifunctional or higher radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. However, a polymerization initiator may be contained in the crosslinkable protective layer coating solution in order to efficiently advance the curing reaction as necessary.

  Examples of the thermal polymerization initiator include 2,5-dimethylhexane-2,5-dihydroperoxide, dicumyl peroxide, benzoyl peroxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di ( Peroxybenzoyl) hexyne-3, di-t-butyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, lauroyl peroxide, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) B) Peroxide-based initiators such as propane, azo-based compounds such as azobisisobutylnitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate, azobisisobutylamidine hydrochloride, 4,4′-azobis-4-cyanovaleric acid Initiators are mentioned.

  Examples of the photopolymerization initiator include diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 4- (2-hydroxyethoxy) phenyl- (2 -Hydroxy-2-propyl) ketone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2- Acetophenone-based or ketal-based photopolymerization initiators such as methyl-2-morpholino (4-methylthiophenyl) propan-1-one, 1-phenyl-1,2-propanedione-2- (o-ethoxycarbonyl) oxime, Benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl ether Benzoin ether photopolymerization initiators such as benzoin isopropyl ether, benzophenone, 4-hydroxybenzophenone, methyl o-benzoylbenzoate, 2-benzoylnaphthalene, 4-benzoylbiphenyl, 4-benzoylphenyl ether, acrylated benzophenone, Benzophenone photopolymerization initiators such as 1,4-benzoylbenzene, thioxanthones such as 2-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone Examples of photopolymerization initiators and other photopolymerization initiators include ethyl anthraquinone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoic acid. Phenylethoxyphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, bis (2,4-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, methylphenylglyoxyester, 9,10 -Phenanthrene, an acridine type compound, a triazine type compound, an imidazole type compound is mentioned. Moreover, what has a photopolymerization acceleration effect can also be used individually or in combination with the said photoinitiator. Examples thereof include triethanolamine, methyldiethanolamine, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, (2-dimethylamino) ethyl benzoate, 4,4′-dimethylaminobenzophenone, and the like.

  These polymerization initiators may be used alone or in combination of two or more. The content of the polymerization initiator is 0.5 to 40 parts by weight, preferably 1 to 20 parts by weight with respect to 100 parts by weight of the total content having radical polymerizability.

  Furthermore, the coating liquid for forming a crosslinkable protective layer according to the embodiment of the present invention may contain various plasticizers (for the purpose of stress relaxation and adhesion improvement), leveling agents, and low molecular charge transport that does not have radical reactivity as necessary. Additives such as substances can be included. As these additives, known additives can be used, and as plasticizers, those used in general resins such as dibutyl phthalate and dioctyl phthalate can be used, and the amount used is the total solid content of the coating liquid. To 20 wt% or less, preferably 10 wt% or less. As leveling agents, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, polymers or oligomers having a perfluoroalkyl group in the side chain can be used, and the amount used is based on the total solid content of the coating liquid. 3% by weight or less is appropriate.

  The crosslinkable protective layer in an embodiment of the present invention includes a coating containing at least a trifunctional or higher functional radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. It is formed by applying and curing a liquid on the aforementioned charge transport layer. When the radically polymerizable monomer is a liquid, such a coating liquid can be applied by dissolving other components in the liquid, but if necessary, it is diluted with a solvent and applied. Solvents used at this time include alcohols such as methanol, ethanol, propanol and butanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, esters such as ethyl acetate and butyl acetate, tetrahydrofuran, dioxane and propyl ether. Ethers such as dichloromethane, halogens such as dichloromethane, dichloroethane, trichloroethane, and chlorobenzene, aromatics such as benzene, toluene, and xylene, and cellosolves such as methyl cellosolve, ethyl cellosolve, and cellosolve acetate. These solvents may be used alone or in combination of two or more. The dilution ratio with the solvent varies depending on the solubility of the composition, the coating method, and the target film thickness, and is arbitrary. The application can be performed by dip coating, spray coating, bead coating, ring coating, or the like.

In the embodiment of the present invention, after applying such a crosslinkable protective layer coating liquid, energy is applied from the outside and cured to form a crosslinkable protective layer. The external energy used at this time is heat. There is light and radiation. The heat energy is applied by heating from the coating surface side or the support side using a gas such as air or nitrogen, steam, various heat media, infrared rays or electromagnetic waves. The heating temperature is preferably 100 ° C. or higher and 170 ° C. or lower. If the heating temperature is lower than 100 ° C., the reaction rate is slow and the curing reaction tends not to be completed completely. At a high temperature exceeding 170 ° C., the curing reaction proceeds non-uniformly, and large strains, a large number of unreacted residues, and reaction termination terminals are generated in the crosslinked protective layer. In order to advance the curing reaction uniformly, it is also effective to complete the reaction by heating at a relatively low temperature of less than 100 ° C. and then heating to 100 ° C. or more. As light energy, UV irradiation light sources such as high-pressure mercury lamps and metal halide lamps that have an emission wavelength mainly in the ultraviolet region can be used, but a visible light source can be selected according to the absorption wavelength of radically polymerizable substances and photopolymerization initiators. Is also possible. Irradiation light amount is 50 mW / cm ² or more, preferably 1000 mW / cm ² or less, it takes time for the curing reaction is less than 50 mW / cm ^2. If it is higher than 1000 mW / cm ^2, the progress of the reaction becomes non-uniform, and local wrinkles are generated on the surface of the cross-linked protective layer, and many unreacted residues and reaction termination ends are generated. In addition, internal stress increases due to rapid crosslinking, which causes cracks and film peeling. Examples of radiation energy include those using electron beams. Among these energies, those using heat and light energy are useful because of the ease of reaction rate control and the simplicity of the apparatus.

  The film thickness of the crosslinked protective layer in the embodiment of the present invention is preferably 1 μm or more and 10 μm or less, more preferably 2 μm or more and 8 μm or less. If it is thicker than 10 μm, cracks and film peeling are likely to occur as described above, and if it is 8 μm or less, the margin is further improved, so that the crosslink density can be increased, and material selection and curing that further increases wear resistance. Conditions can be set. On the other hand, the radical polymerization reaction is prone to oxygen inhibition, that is, the surface in contact with the air is not easily cross-linked or non-uniform due to the influence of radical trapping by oxygen. This effect appears remarkably when the surface layer is less than 1 μm, and a crosslinked protective layer having a thickness less than this thickness is likely to have a reduced wear resistance or uneven wear. In addition, when the crosslinkable protective layer is applied, the lower charge transport layer component is mixed.In particular, if the coating thickness of the crosslinkable protective layer is thin, the contaminants spread throughout the layer, inhibiting the curing reaction and reducing the crosslink density. Bring about a decline. For these reasons, the cross-linkable protective layer in the embodiment of the present invention has a good wear resistance and scratch resistance at a film thickness of 1 μm or more, but was locally scraped to the lower charge transport layer in repeated use. If the portion is formed, the wear of the portion increases, and the density unevenness of the halftone image tends to occur due to the charging property and sensitivity fluctuation. Therefore, it is desirable that the thickness of the cross-linking protective layer is 2 μm or more for a longer life and higher image quality.

  In the configuration in which the intermediate layer (charge blocking layer, moire prevention layer), photosensitive layer (charge generation layer, charge transport layer), and crosslinkable protective layer of the electrophotographic photosensitive member in the embodiment of the present invention are sequentially laminated, When the crosslinkable protective layer is insoluble in an organic solvent, it is characterized in that dramatic wear resistance and scratch resistance are achieved. As a method for testing the solubility in an organic solvent, a drop of an organic solvent having high solubility in a polymer substance, for example, tetrahydrofuran, dichloromethane, or the like, is dropped on the surface layer of the photoconductor, and the surface shape of the photoconductor is dried after natural drying. It can be determined by observing the change with a stereomicroscope. Highly soluble photoconductors have a phenomenon that the central part of the droplet becomes concave and the surroundings swell up, the charge transport material precipitates and becomes cloudy or cloudy due to crystallization, and the surface swells and then shrinks, causing wrinkles Changes such as the phenomenon to be seen. In contrast, an insoluble photoconductor does not exhibit the above-described phenomenon, and does not change at all as before dropping.

  In the configuration of the embodiment of the present invention, in order to make the crosslinkable protective layer insoluble in an organic solvent, (1) composition of the crosslinkable protective layer coating solution, adjustment of the content ratio thereof, and (2) crosslinkage Adjustment of dilution solvent and solid content concentration of mold protective layer coating solution, (3) Selection of coating method of crosslinkable protective layer, (4) Control of curing condition of crosslinkable protective layer, (5) Charge transport in lower layer It is important to control these, such as making the layer difficult to dissolve, but it is not achieved by a single factor.

  The composition of the crosslinkable protective layer coating solution may be a radical polymerizable compound in addition to the above-described trifunctional or higher functional radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. When a large amount of additives such as a binder resin having no functional group, an antioxidant, and a plasticizer is contained, the crosslinking density is reduced, and the cured product resulting from the reaction and phase separation between the additive and the organic solvent are caused. It tends to be soluble. Specifically, it is important to suppress the total content to 20% by weight or less with respect to the total solid content of the coating liquid. Further, in order not to dilute the crosslinking density, the total content of monofunctional or bifunctional radical polymerizable monomers, reactive oligomers, and reactive polymers is 20% by weight or less based on the trifunctional radical polymerizable monomers. It is desirable. Further, when a large amount of a radical polymerizable compound having a bifunctional or higher functional charge transporting structure is contained, a bulky structure is fixed in the crosslinked structure by a plurality of bonds, so that distortion is likely to occur. It is easy to become an aggregate. This can cause solubility in organic solvents. Although different depending on the compound structure, the content of the radical polymerizable compound having a bifunctional or higher functional charge transporting structure is preferably 10% by weight or less based on the radical polymerizable compound having a monofunctional charge transporting structure.

  As for the diluting solvent of the crosslinkable protective layer coating solution, if a solvent with a slow evaporation rate is used, the remaining solvent may hinder the curing, or increase the amount of the lower layer component mixed. Reduces the cured density. For this reason, it tends to be soluble in organic solvents. Specifically, tetrahydrofuran, a mixed solvent of tetrahydrofuran and methanol, ethyl acetate, methyl ethyl ketone, ethyl cellosolve and the like are useful, but are selected according to the coating method. Moreover, regarding the solid content concentration, if it is too low for the same reason, it tends to be soluble in an organic solvent. Conversely, the upper limit concentration is constrained by the limitations of film thickness and coating solution viscosity. Specifically, it is desirable to use in the range of 10 to 50% by weight. As a coating method for the cross-linked protective layer, for the same reason, the solvent content at the time of forming the coating film, a method of reducing the contact time with the solvent is preferable, specifically, the spray coating method, the amount of coating liquid A regulated ring coat method is preferred. Also, in order to suppress the amount of the lower layer component mixed in, a polymer charge transport material is used as the charge transport layer, and a crosslinkable protective layer is applied between the photosensitive layer (or charge transport layer) and the crosslinkable protective layer. It is also effective to provide an intermediate layer insoluble in the solvent.

As the curing conditions for the cross-linkable protective layer, if the energy of heating or light irradiation is low, the curing is not completely completed and the solubility in the organic solvent is increased. On the other hand, when cured with very high energy, the curing reaction becomes non-uniform, and it tends to increase the number of uncrosslinked parts and radical stopping parts and to form an aggregate of minute cured products. For this reason, it may become soluble in an organic solvent. In order to insolubilize in an organic solvent, the heat curing conditions are preferably 100 to 170 ° C. and 10 minutes to 3 hours, and the curing conditions by UV light irradiation are 50 to 1000 mW / cm ² and 5 seconds to 5 minutes. In addition, it is desirable to control the temperature rise to 50 ° C. or less to suppress non-uniform curing reaction.

  An example of a method for making the cross-linkable protective layer constituting the electrophotographic photoreceptor in the embodiment of the present invention insoluble in an organic solvent is, for example, as an application liquid, an acrylate monomer having three acryloyloxy groups, and one When using a triarylamine compound having one acryloyloxy group, these use ratios are 7: 3 to 3: 7, and a polymerization initiator is added in an amount of 3 to 20% by weight based on the total amount of these acrylate compounds. Further, a solvent is added to prepare a coating solution. For example, in the case where the charge transport layer which is the lower layer of the crosslinkable protective layer uses a triarylamine donor as the charge transport material and polycarbonate as the binder resin and the surface layer is formed by spray coating, the above coating liquid As the solvent, tetrahydrofuran, 2-butanone, ethyl acetate and the like are preferable, and the use ratio thereof is 3 to 10 times the total amount of the acrylate compound.

  Next, for example, the prepared coating solution is applied by spraying or the like onto a photoreceptor in which an intermediate layer, a charge generation layer, and the charge transport layer are sequentially laminated on a support such as an aluminum cylinder. Thereafter, it is naturally dried or dried at a relatively low temperature for a short time (25 to 80 ° C., 1 to 10 minutes) and cured by UV irradiation or heating.

For UV irradiation, uses a metal halide lamp, illuminance 50 mW / cm ² or more, 1000 mW / cm ² or less, preferably about 5 minutes 5 seconds as the time, the drum temperature is controlled so as not to exceed 50 ° C. .

  In the case of thermosetting, the heating temperature is preferably 100 to 170 ° C. For example, when a blowing oven is used as a heating means and the heating temperature is set to 150 ° C, the heating time is 20 minutes to 3 hours.

  After the curing is completed, the photosensitive member in the embodiment of the present invention is obtained by further heating at 100 to 150 ° C. for 10 to 30 minutes to reduce the residual solvent.

  In addition to the protective layer containing the filler and the crosslinked protective layer described above, a known material such as a-C or a-SiC formed by a vacuum thin film forming method can be used as the protective layer. .

  As described above, when a protective layer is formed on the photosensitive layer, the writing light and / or the static elimination light does not reach the photosensitive layer sufficiently unless the appropriate protective layer is selected, and the writing and / or static elimination action is clear. May not work. In addition, the protective layer may be easily deteriorated by absorbing the writing light and / or the neutralizing light, and on the contrary, there may be a case where a residual potential rise is generated. Therefore, in any of the above-described protective layers, it is desirable that the transmittance with respect to writing light and / or static elimination light is 30% or more, preferably 50% or more, and more desirably 85% or more.

  The transmittance of the protective layer is measured by the same method as that for the charge transport layer. That is, the protective layer used for the photoconductor is formed alone, and the spectral absorption spectrum is measured with a commercially available spectrophotometer. It is obtained by obtaining the transmittance at the wavelength of the static elimination light used in the image forming apparatus from the spectrum.

  In addition, when a protective layer is provided on the photosensitive layer configured in the order of the charge generation layer and the charge transport layer, and the charge removal light is irradiated from the surface side of the photoreceptor, the charge removal light passes through the protection layer and the charge transport layer. The charge generation layer is irradiated. Accordingly, the transmittance in a form in which the charge transport layer and the protective layer are laminated is important. In this case, in the state where the charge transport layer and the protective layer are laminated, it is desirable that the transmittance with respect to the static elimination light is 30% or more, preferably 50% or more, and more desirably 85% or more.

  In such a case, the transmittance can be obtained by measuring the spectral absorption spectrum of the coating film in a state where the charge transport layer and the protective layer are laminated as described above.

  As described above, providing a protective layer on the surface of the photoconductor not only enhances the durability (wear resistance) of each photoconductor, but is also used in a tandem type full-color image forming apparatus as described below. In such a case, a new effect that does not exist in the monochrome image forming apparatus is also produced.

  In the embodiment of the present invention, a protective layer, a charge transport layer, a charge generation layer, a charge blocking layer, and a moire prevention layer are provided for the purpose of preventing a decrease in sensitivity and an increase in residual potential, in order to improve environmental resistance. An antioxidant can be added to each layer.

(Phenolic compounds)
2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearyl-β- (3,5-di-t-butyl-4 -Hydroxyphenyl) propionate, 2,2'-methylene-bis- (4-methyl-6-tert-butylphenol), 2,2'-methylene-bis- (4-ethyl-6-tert-butylphenol), 4, 4'-thiobis- (3-methyl-6-tert-butylphenol), 4,4'-butylidenebis- (3-methyl-6-tert-butylphenol), 1,1,3-tris- (2-methyl-4 -Hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene- -(3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, bis [3,3'-bis (4'-hydroxy-3'-t-butylphenyl) butyric acid] Crycol esters, tocopherols, etc.

(Paraphenylenediamines)
N-phenyl-N'-isopropyl-p-phenylenediamine, N, N'-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl-p-phenylenediamine, N, N'- Di-isopropyl-p-phenylenediamine, N, N′-dimethyl-N, N′-di-t-butyl-p-phenylenediamine and the like.

(Hydroquinones)
2,5-di-t-octylhydroquinone, 2,6-didodecylhydroquinone, 2-dodecylhydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t-octyl-5-methylhydroquinone, 2- (2-octadecenyl) ) -5-methylhydroquinone and the like.

(Organic sulfur compounds)
Dilauryl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, ditetradecyl-3,3′-thiodipropionate, and the like.

(Organic phosphorus compounds)
Triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine, and the like.

  These compounds are known as antioxidants such as rubbers, plastics and fats and oils, and commercially available products can be easily obtained. The addition amount of the antioxidant in the embodiment of the present invention is 0.01 to 10% by weight with respect to the total weight of the layer to be added.

  In the case of a full-color image, various types of images are input, but on the contrary, a typical image may also be input. For example, the presence of a seal in a Japanese document or the like. Something like indicia is usually located towards the edge of the image area, and the colors used are also limited. In a state in which a random image is always written, image writing, development, and transfer are performed on the photoconductor in the image forming element on average. When many image formations are repeated or only a specific image forming element is used, the durability balance is lost. When a photoconductor having a low surface durability (physical / chemical / mechanical) is used in such a state, this difference becomes prominent and easily causes an image problem. On the other hand, when the photoconductor is made highly durable, the amount of such local change is small, and as a result, it becomes difficult to appear as a defect on the image, so that high durability is achieved and the stability of the output image is improved. This is very effective.

-Electrostatic latent image formation-
The electrostatic latent image can be formed, for example, by uniformly charging the surface of the electrostatic latent image carrier and then exposing (writing) imagewise. It can be done by means.

  The electrostatic latent image forming means includes, for example, at least a charger that uniformly charges the surface of the electrostatic latent image carrier and an exposure device that exposes the surface of the electrostatic latent image carrier imagewise. Prepare.

-Charging means-
The charger is not particularly limited and may be appropriately selected depending on the purpose. For example, a known contact charging device including a conductive or semiconductive roll, brush, film, rubber blade, etc. And non-contact chargers using corona discharge such as corotron and scorotron (including proximity-type non-contact chargers having a gap of 100 μm or less between the surface of the photoreceptor and the charger).

  The electric field strength applied to the electrostatic latent image carrier by the charger is preferably 20 to 60 V / μm, and more preferably 30 to 50 V / μm. The higher the electric field strength applied to the photoconductor, the better the dot reproducibility. However, if the electric field strength is too high, problems such as dielectric breakdown of the photoconductor and carrier adhesion during development may occur.

  The electric field strength is expressed by the following mathematical formula (1).

Electric field strength (V / μm) = SV / G (1)
In Equation (1), SV represents the absolute value of the surface potential (V) at the unexposed portion of the electrostatic latent image carrier at the development position. G represents the film thickness (μm) of the photosensitive layer including at least the photosensitive layer (charge generation layer and charge transport layer).

-Writing means-
The writing can be performed, for example, by exposing the surface of the latent electrostatic image bearing member imagewise using the exposure device. The type of the exposure device is not particularly limited as long as it emits light having a wavelength shorter than 450 nm and can be appropriately selected according to the purpose. For example, a copying optical system, a rod lens array system, Various exposure devices such as a laser optical system and a liquid crystal shutter optical system may be mentioned. In the embodiment of the present invention, an optical backside system that performs imagewise exposure from the backside of the electrostatic latent image carrier may be adopted. As the light source, a light source capable of ensuring high luminance such as a light emitting diode (LED), a semiconductor laser (LD), or electroluminescence (EL) is used.

  There are several techniques for causing laser oscillation in such a wavelength range. One is to use a non-linear optical material and to halve the wavelength of the laser beam using second harmonic generation (SHG) (for example, Japanese Patent Laid-Open Nos. 9-275242 and 9). No. 189930, JP-A-5-313033, etc.). Since this system can use a GaAs-based LD or YAG laser that has already established technology and can output high power as a primary light source, it is possible to extend the life and output. The other uses a wide-gap semiconductor, and the size of the apparatus can be reduced as compared with a device using SHG.

  LD using a ZnSe-based semiconductor (see JP-A-7-321409, JP-A-6-334272, etc.) or a GaN-based semiconductor (see JP-A-8-88441, JP-A-7-335975, etc.) However, because of its high luminous efficiency, it has been the subject of many studies. As a relatively recent technology, LD (405 nm oscillation) using a GaN-based semiconductor has been put into practical use by Nichia Corporation, and a writing system has been developed that is much more advanced than the above technology. It can also be used beneficially in this form. In addition, LED lamps using the above materials are on the market, and these can also be used effectively.

  On the other hand, at the present time, the lower limit is determined by the following problem. That is, as a material constituting the photoconductor (the charge transport layer or the protective layer existing on the writing light incident side), a charge transport material can be mentioned. Among charge transport materials having high mobility and usable at a practical level. In other words, there is no material that is sufficiently transparent with respect to light having a component shorter than about 350 nm. This is because most of the charge transport materials currently developed have a triarylamine structure, and the absorption edge on the long wavelength side of this material is approximately 300 to 350 nm. Therefore, if further shortening of the wavelength of the static elimination light source and further transparency of the charge transport material (shortening of absorption wavelength) are realized, the oscillation wavelength of the light source that can be used in the embodiment of the present invention can be further increased or decreased. It extends to the short wavelength side.

  Depending on the resolution of the light source (write light) to be used, the resolution of the electrostatic latent image and thus the toner image to be formed is determined, and the higher the resolution, the clearer the image. However, if writing is performed at a higher resolution, writing takes longer, so writing with one writing light source is limited by the drum linear speed (process speed). Therefore, when there is one writing light source, a resolution of about 2400 dpi is the upper limit. If there are a plurality of writing light sources, each of them only has to bear the writing area, and the upper limit is substantially “2400 dpi × number of writing light sources”. Among these light sources, light emitting diodes and semiconductor lasers have high irradiation energy and are used favorably.

-Development means-
The development can be performed by developing the electrostatic latent image with toner to form a visible image. As the toner, toner having the same polarity as the charged polarity of the photoreceptor is used, and the electrostatic latent image is developed by reversal development (negative / positive development). There are two methods, a one-component method in which development is performed with toner alone and a two-component method in which a two-component developer comprising a toner and a carrier is used. Either method can be used favorably.

-Transfer means-
The transfer means is a means for transferring the visible image onto a recording medium. The transfer means can be transferred onto the intermediate transfer body using a method of directly transferring the visible image from the surface of the photoreceptor to the recording medium and an intermediate transfer body. There is a method in which a visual image is primarily transferred and then the visible image is secondarily transferred onto the recording medium. Either aspect can be used satisfactorily, but the former (direct transfer) method with a small number of transfers is preferred when the adverse effect of the transfer is great when the image quality is improved.

  The transfer can be performed, for example, by charging the latent electrostatic image bearing member (photoconductor) of the visible image using a transfer charger, and can be performed by the transfer unit. The transfer unit is not particularly limited, and can be appropriately selected from known transfer units according to the purpose. For example, a transfer conveyance belt that can simultaneously convey a recording medium can be preferably cited. It is done.

  The transfer means (the primary transfer means and the secondary transfer means) is a transfer for peeling and charging the visible image formed on the electrostatic latent image carrier (photoconductor) to the recording medium side. It is preferable to have at least a charger. There may be one transfer means or two or more transfer means. Examples of the transfer charger include a corona transfer device using corona discharge, a transfer belt, a transfer roller, a pressure transfer roller, and an adhesive transfer device. The recording medium is not particularly limited and can be appropriately selected from known recording media (recording paper).

  The transfer charger may be a transfer belt or a transfer roller, but it is desirable to use a contact type such as a transfer belt or transfer roller that generates less ozone. As a voltage / current application method at the time of transfer, either a constant voltage method or a constant current method can be used, but the transfer charge amount can be kept constant, and a constant voltage with excellent stability can be used. The current method is more desirable. As such a transfer member, a known member can be used as long as it can satisfy the configuration of the embodiment of the present invention.

  Depending on the surface potential of the photoreceptor after transfer (the surface potential of the difference entering the charge eliminating portion), the amount of charge passing through the photoreceptor per cycle of image formation varies greatly. The larger this is, the greater the influence on the electrostatic fatigue of the photoreceptor in repeated use.

  This passing charge amount corresponds to the amount of charge flowing in the film thickness direction of the photoreceptor. As an operation in the image forming apparatus of the photoconductor, the main charger is charged to a desired charging potential (in most cases, negatively charged), and optical writing is performed based on an input signal corresponding to the original. At this time, photocarriers are generated in the portion where writing is performed, and the surface charge is neutralized (potential decay). At this time, the amount of charge depending on the amount of generated photocarriers flows in the direction of the photoreceptor film thickness. On the other hand, the region where the optical writing is not performed (non-writing portion) proceeds to the static elimination process through the development process and the transfer process (a cleaning process is performed before that if necessary). Here, when the surface potential of the photoconductor is close to the potential applied by main charging (excluding dark decay), the amount of charge is almost the same as that in the area where optical writing is performed. Will flow into. Generally, since current writing is low in writing, when this method is used, the amount of charge passing through the photoreceptor in repeated use is almost the current that flows in the static elimination process (the writing rate is 10%). Then, the current flowing in the static elimination process occupies 90% of the total).

  This passing charge greatly affects the electrostatic characteristics of the photoconductor, for example, causing deterioration of the material constituting the photoconductor. As a result, the residual potential of the photosensitive member is raised, depending on the amount of passing charge. When the residual potential of the photosensitive member increases, the image density decreases in the negative and positive development used in the embodiment of the present invention, which is a serious problem. Therefore, there is a problem of how to reduce the passing charge amount of the photoconductor in order to increase the lifetime (high durability) of the photoconductor in the image forming apparatus.

  On the other hand, there is a way of thinking that the photostatic discharge is not performed, but if the main charger is not sufficiently charged, the charging cannot be stabilized and a problem such as an afterimage may occur. The passing charge of the photoconductor is generated by the movement of the generated optical carrier by light irradiation by the electric potential (the electric field generated thereby) charged on the surface of the photoconductor. Accordingly, if the surface potential of the photosensitive member can be attenuated by means other than light, the amount of passing charge per one rotation of the photosensitive member (one cycle of image formation) can be reduced.

For this purpose, it is effective to adjust the charge passing through the photosensitive member by adjusting the transfer bias in the transfer process. That is, a non-writing portion that is charged by main charging and does not perform writing enters the transfer process in a state close to the charged potential except for the dark attenuation amount. At this time, the absolute value on the polarity side charged by the main charger is reduced to 100 V or less, so that almost no photocarrier is generated even if the subsequent charge removal process is entered, and no passing charge is generated. This value is preferably closer to 0V.
Furthermore, by adjusting the transfer bias, by applying a transfer bias so that the surface potential of the photosensitive member is charged to a polarity opposite to the charging polarity applied by the main charging, it is more preferable because no optical carrier is generated. . However, under transfer conditions that charge to a reverse polarity, there may be cases where a large amount of transfer dust occurs or the main charge of the next image forming process (cycle) cannot catch up. In that case, since a problem such as an afterimage may occur, the absolute value of the reverse polarity is preferably 100 V or less.
Adding the control as described above can be effectively used with the effects in the embodiment of the present invention being remarkable.

-Fixing means-
The fixing is a means for fixing the visible image transferred to the recording medium using a fixing device. However, the fixing may be performed each time the toner of each color is transferred to the recording medium, or the toner of each color may be applied. On the other hand, it may be carried out simultaneously at the same time in a state of being laminated.

  There is no restriction | limiting in particular as said fixing device, Although it can select suitably according to the objective, A well-known heating-pressing means is suitable. Examples of the heating and pressing means include a combination of a heating roller and a pressure roller, a combination of a heating roller, a pressure roller, and an endless belt. The heating in the heating and pressing means is usually preferably 80 ° C to 200 ° C. In the embodiment of the present invention, for example, a known optical fixing device may be used together with or in place of the fixing step and the fixing unit depending on the purpose.

-Static elimination means-
The neutralization means is not limited as long as it can neutralize the electrostatic latent image carrier, and can be appropriately selected from known neutralization devices. For example, a semiconductor laser (LD), a light emitting diode (LED) ), Electroluminescence (EL) and the like. Further, the effect of the embodiment of the present invention becomes more remarkable by setting the charge eliminating light to a wavelength of less than 450 nm (however, the wavelength that can be absorbed by the metal oxide contained in the intermediate layer of the photoreceptor). Become.

  As a light source for obtaining static elimination light having such a wavelength, a semiconductor laser (LD) having an oscillation wavelength of less than 450 nm, electroluminescence (EL), or the like, or a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, A xenon lamp or the like combined with an appropriate optical filter that can limit light emission to less than 450 nm can be used. The optical filter includes various types such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter in order to irradiate only light in a desired wavelength range (less than 450 nm). A filter can also be used.

-Others-
The cleaning means is not particularly limited as long as it can remove the electrophotographic toner remaining on the electrostatic latent image carrier, and can be appropriately selected from known cleaners. Suitable examples include brush cleaners, electrostatic brush cleaners, magnetic roller cleaners, blade cleaners, brush cleaners, web cleaners, and the like.

  The recycling unit is a step of recycling the electrophotographic color toner removed by the cleaning unit to the developing unit, and examples thereof include a known conveyance unit.

  The control means is a process for controlling the respective steps, and can be suitably performed by the control means.

  The control means is not particularly limited as long as the movement of each means can be controlled, and can be appropriately selected according to the purpose. Examples thereof include devices such as a sequencer and a computer.

  Here, one aspect of the image forming apparatus according to the embodiment of the present invention will be described with reference to FIG.

  FIG. 9 is a schematic diagram for explaining an image forming apparatus according to an embodiment of the present invention, and a modified example as described later also belongs to the category of the embodiment of the present invention.

  In FIG. 9, a photoreceptor (1) as an electrostatic latent image bearing member contains an intermediate layer containing at least a metal oxide, a charge generation layer containing an organic charge generation material, and a charge transport material on a support. A laminated photosensitive layer comprising a charge transport layer is provided. The photosensitive member (1) has a drum shape, but may be a sheet or an endless belt.

  As the charger (3), a wire type charger or a roller-type charger is used. When high-speed charging is required, a scorotron charger is preferably used. In a compact or tandem image forming apparatus that uses a plurality of photoconductors described later, acid gas (NOx, SOx, etc.) A roller-shaped charger that generates less ozone is effectively used. Although the photosensitive member is charged by this charger, the higher the electric field strength applied to the photosensitive member, the better the dot reproducibility. Therefore, it is desirable to apply an electric field strength of 20 V / μm or more. . However, there is a possibility that problems such as dielectric breakdown of the photosensitive member and carrier adhesion during development occur, and the upper limit is approximately 60 V / μm or less, more preferably 50 V / μm or less.

  In addition, the image exposure part (5) can ensure high luminance such as light emitting diode (LED), semiconductor laser (LD), electroluminescence (EL), etc., and has a wavelength shorter than 450 nm (however, the metal contained in the intermediate layer) A light source that can be written at a wavelength that the oxide can absorb) is used. Depending on the resolution of the light source (writing light), the resolution of the formed electrostatic latent image, and thus the toner image, is determined. The higher the resolution, the clearer the image. However, if writing is performed at a higher resolution, writing takes longer, so writing with one writing light source is limited by the drum linear speed (process speed). Therefore, when there is one writing light source, a resolution of about 1200 dpi is the upper limit. When there are a plurality of write light sources, each of them only has to bear a write area, and the upper limit is substantially “1200 dpi × number of write light sources”. Among these light sources, light emitting diodes and semiconductor lasers have high irradiation energy and are used favorably.

  The developing unit (6) which is a developing means has at least one developing sleeve.

  In the developing unit (6), toner having the same polarity as the charged polarity of the photoreceptor is used, and the electrostatic latent image is developed by reversal development (negative / positive development). Depending on the light source used in the previous image exposure unit, in the case of a digital light source used in recent years, there is generally a reversal development method in which toner development is performed on the writing portion in response to a low image area ratio. This is advantageous in view of the life of the light source. There are two methods, a one-component method in which development is performed with toner alone and a two-component method in which a two-component developer comprising a toner and a carrier is used. Either method can be used favorably.

  The transfer charger (10) may be a transfer belt or a transfer roller, but it is desirable to use a contact type such as a transfer belt or transfer roller that generates less ozone. As a voltage / current application method at the time of transfer, either a constant voltage method or a constant current method can be used, but the transfer charge amount can be kept constant, and a constant voltage with excellent stability can be used. The current method is more desirable. In particular, by subtracting the current that flows from the power supply member (high-voltage power supply) that supplies electric charge to the transfer member and does not flow into the photosensitive member, the current to the photosensitive member is subtracted. A method of controlling the value is preferred.

  The transfer current is a current based on the amount of charge required to peel off the toner electrostatically attached to the photosensitive member and transfer it to a transfer target (transfer paper or intermediate transfer member). In order to avoid transfer defects such as transfer residue, it is only necessary to increase the transfer current. However, in the case of using negative and positive development, charging with a polarity opposite to the charging polarity of the photosensitive member is given. As a result, the electrostatic fatigue of the photoconductor becomes remarkable. The larger the transfer current, the more advantageous it is because a charge amount exceeding the electrostatic adhesion force between the photoconductor and the toner can be given. However, if a certain threshold value is exceeded, a discharge phenomenon occurs between the transfer member and the photoconductor, and it becomes fine. As a result, the developed toner image is scattered. For this reason, the upper limit is a range in which this discharge phenomenon does not occur. This threshold varies depending on the gap (distance) between the transfer member and the photoconductor, the material constituting the both, and the like, but the discharge phenomenon can be avoided by using it at about 200 μA or less. Therefore, the upper limit value of the transfer current is about 200 μA.

  Further, the toner image formed on the photoconductor is transferred onto the transfer paper to become an image on the transfer paper. At this time, there are two methods. One is a method for directly transferring the toner image developed on the surface of the photosensitive member as shown in FIG. 9 and the other is a method in which the toner image is once transferred from the photosensitive member to the intermediate transfer member, and this is transferred to the transfer paper. It is the method of transferring to. Either case can be used in the embodiment of the present invention.

  As such a transfer member, a known member can be used as long as it can satisfy the configuration of the embodiment of the present invention.

  Further, by controlling the transfer current as described above, reducing the photoreceptor surface potential after transfer (the unexposed portion of the writing light) reduces the amount of charge passing through the photoreceptor per one cycle of image formation. It can be used effectively in the embodiment of the present invention.

  The light source such as the static elimination lamp (2) is only required to neutralize the electrostatic latent image carrier, and can be appropriately selected from known static elimination devices. For example, a semiconductor laser (LD) , Electroluminescence (EL) and the like are preferable. In particular, the use of a light source having a wavelength of less than 450 nm (however, a wavelength that can be absorbed by the metal oxide contained in the intermediate layer of the photoreceptor) makes the effect of the embodiment of the present invention more remarkable. And can be used beneficially.

  For light sources such as semiconductor lasers (LD) and electroluminescence (EL), semiconductor lasers (LD) and electroluminescence (EL) having an oscillation wavelength of less than 450 nm, or fluorescent lamps, tungsten lamps, halogen lamps, mercury lamps, sodium A combination of a lamp, a xenon lamp, or the like with an appropriate optical filter that can limit light emission to less than 450 nm can be used. The optical filter includes various types such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter in order to irradiate only light in a desired wavelength range (less than 450 nm). A filter can also be used.

  In FIG. 9, 8 is a registration roller, 11 is a separation charger, and 12 is a separation claw.

  In addition, the toner developed on the photoreceptor (1) by the developing unit (6) is transferred to the transfer paper (9), but when toner remaining on the photoreceptor (1) is generated, a fur brush ( 14) and the blade (15). Cleaning may be performed only with a cleaning brush, and a known brush such as a fur brush or a mag fur brush is used as the cleaning brush.

  Next, FIG. 10 is a schematic diagram for explaining a tandem type full-color image forming apparatus according to an embodiment of the present invention, and the following modifications also belong to the category of the embodiment of the present invention. is there.

  In FIG. 10, reference numerals (16Y), (16M), (16C), and (16K) denote drum-shaped photoconductors. The photoconductors are intermediate layers containing at least a metal oxide on the support, and organic charge generation. A laminated photosensitive layer comprising a charge generation layer containing a substance and a charge transport layer containing a charge transport substance is provided.

  The photoconductors (16Y), (16M), (16C), and (16K) can rotate in the direction of the arrow in FIG. 10, and the chargers (17Y), (17M), (17C) at least in the order of rotation therearound. , (17K), developing means (19Y), (19M), (19C), (19K) having at least one developing sleeve, cleaning member (20Y), (20M), (20C), (20K), static elimination means (27Y), (27M), (27C), and (27K) are arranged. The chargers (17Y), (17M), (17C), and (17K) are chargers that constitute a charging device for uniformly charging the surface of the photoreceptor. From the surface of the photoreceptor between the chargers (17Y), (17M), (17C), (17K) and the developing means (19Y), (19M), (19C), (19K), an exposure unit (18Y) , (18M), (18C), and (18K) are irradiated with laser light having a wavelength shorter than 450 nm, and electrostatic latent images are formed on the photoconductors (16Y), (16M), (16C), and (16K). It has come to be. Then, the four image forming elements (25Y), (25M), (25C), and (25K) centering on such photoconductors (16Y), (16M), (16C), and (16K) serve as transfer materials. They are juxtaposed along the transfer conveyance belt (22) which is a conveyance means. The transfer / conveying belt (22) includes developing means (19Y), (19M), (19C), (19K) and a cleaning member (20Y) of the image forming units (25Y), (25M), (25C), (25K). , (20M), (20C), and (20K) are in contact with the photosensitive member (16Y), (16M), (16C), and (16K), and contact the back side of the photosensitive member side of the transfer conveyance belt (22). Transfer brushes (21Y), (21M), (21C), and (21K) for applying a transfer bias are arranged on the surface (back surface). Each of the image forming elements (25Y), (25M), (25C), and (25K) is different in the color of the toner inside the developing device, and the others are the same in configuration.

  In the full-color image forming apparatus having the configuration shown in FIG. 10, the image forming operation is performed as follows. First, in each of the image forming elements (25Y), (25M), (25C), and (25K), an electrostatic latent image is formed on the photoconductors (16Y), (16M), (16C), and (16K). It has become. Then, the photoreceptors (16Y), (16M), (16C), and (16K) rotate, and the photoreceptors are charged by the chargers (17Y), (17M), (17C), and (17K). The At this time, in order to form a high-definition latent image, charging is performed so that the electric field strength of the photosensitive member is 20 V / μm or more (60 V μm or less, preferably 50 V / μm or less).

  Next, in the exposed portions (18Y), (18M), (18C), and (18K) arranged outside the photoconductor, the wavelength is shorter than 450 nm (however, the wavelength that can be absorbed by the metal oxide contained in the intermediate layer) ) Is written at a resolution of 1200 dpi or higher (preferably 2400 dpi or higher), and an electrostatic latent image corresponding to each color image to be created is formed. As the writing light source, as described above, a light source suitable for an arbitrary photoconductor is used. In this case as well, 2400 dpi writing is generally the upper limit for one writing light source.

  Next, the latent image is developed by the developing means (19Y), (19M), (19C), and (19K) to form a toner image. Developing means (19Y), (19M), (19C), and (19K) are developing means for developing with toners of Y (yellow), M (magenta), C (cyan), and K (black), respectively. The toner images of the respective colors formed on the two photoconductors (16Y), (16M), (16C), and (16K) are superimposed on the transfer paper. The transfer paper (26) is fed out from the tray by a paper feeding roller (not shown), temporarily stopped by a pair of registration rollers (23), and transferred and conveyed (22) in synchronization with the image formation on the photosensitive member. ). The transfer paper (26) held on the transfer conveyance belt (22) is conveyed, and each color is in contact with each photoconductor (16Y), (16M), (16C), (16K) (transfer section). The toner image is transferred.

  The toner image on the photoconductor includes transfer bias applied to the transfer brushes (21Y), (21M), (21C), and (21K) and the photoconductors (16Y), (16M), (16C), and (16K). The image is transferred onto the transfer paper (26) by an electric field formed from the potential difference. Then, the recording paper (26) on which the four color toner images are passed through the four transfer sections is conveyed to the fixing device (24), where the toner is fixed, and is discharged to a paper discharge section (not shown).

  Further, residual toner remaining on each of the photoconductors (16Y), (16M), (16C), and (16K) without being transferred by the transfer unit is removed from the cleaning devices (20Y), (20M), (20C), ( 20K).

  Subsequently, excess residual charges on the photosensitive member are removed by the charge eliminating members (27Y), (27M), (27C), and (27K). Thereafter, charging is performed uniformly by the charger, and the next image formation is performed.

  In the example of FIG. 10, the image forming elements are arranged in the order of Y (yellow), M (magenta), C (cyan), and K (black) from the upstream side to the downstream side in the transfer paper conveyance direction. However, it is not limited to this order, and the color order is arbitrarily set. In addition, when creating a black-only document, a mechanism for stopping image forming elements other than black ((25Y), (25M), (25C)) is particularly provided in the embodiment of the present invention. It can be used effectively.

  Further, as described above, the surface of the photoreceptor after transfer is preferably charged to 100 V or less on the polarity side charged by the main charger, more preferably charged to the reverse polarity side, and to the reverse polarity side. It is particularly preferable to charge to 100 V or less. As a result, an increase in residual potential due to repeated use of the photoreceptor can be reduced.

  The image forming means as described above may be fixedly incorporated in a copying apparatus, a facsimile, or a printer, but may be incorporated in these apparatuses in the form of a process cartridge. The process cartridge is a single device (part) that contains a photosensitive member, and further includes an electrostatic latent image forming unit, a developing unit, a transfer unit, a cleaning unit, a charge eliminating unit, and the like. There are many shapes and the like of the process cartridge, but a general example is the one shown in FIG. The photoreceptor (101) is provided with a laminated photosensitive layer comprising an intermediate layer containing at least a metal oxide, a charge generation layer containing an organic charge generation material, and a charge transport layer containing a charge transport material on a support. It becomes.

  As described above, the image exposure unit (103) uses a light source that can be written with light having a wavelength shorter than 450 nm (however, the wavelength that can be absorbed by the metal oxide contained in the intermediate layer). An arbitrary charger is used for the charger (102). In FIG. 11, 104 is a developing means having at least one developing sleeve, 105 is a transfer member, 106 is a transfer means, 107 is a cleaning means, and 108 is a charge eliminating member.

[Example]
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to the following Example at all. All parts are parts by mass.

  First, a method for synthesizing the azo pigment and titanyl phthalocyanine crystal used in the present invention will be described. The azo pigments used in the following examples were prepared according to the methods described in Japanese Patent Publication No. 60-29109 and Japanese Patent No. 3026645. Moreover, the titanyl phthalocyanine crystal | crystallization was produced according to Unexamined-Japanese-Patent No. 2001-19871 and Unexamined-Japanese-Patent No. 2004-83859.

-Synthesis of titanyl phthalocyanine crystals-
(Synthesis Example 1)
A pigment was prepared according to Japanese Patent Application Laid-Open No. 2001-19871, Synthesis Example 1. That is, 29.2 g of 1,3-diiminoisoindoline and 200 ml of sulfolane are mixed, and 20.4 g of titanium tetrabutoxide is added dropwise under a nitrogen stream. After completion of the dropwise addition, the temperature was gradually raised to 180 ° C., and the reaction was carried out by stirring for 5 hours while maintaining the reaction temperature between 170 ° C. and 180 ° C. After the reaction is complete, the mixture is allowed to cool, and then the precipitate is filtered, washed with chloroform until the powder turns blue, then washed several times with methanol, then washed several times with hot water at 80 ° C. and dried. Crude titanyl phthalocyanine was obtained. Crude titanyl phthalocyanine is dissolved in 20 times the amount of concentrated sulfuric acid, added dropwise to 100 times the amount of ice water with stirring, the precipitated crystals are filtered, and then ion-exchanged water (pH: 7.) until the washing solution becomes neutral. 0, specific conductivity: 1.0 μS / cm) Repeated washing with water (pH value of ion-exchanged water after washing was 6.8, specific conductivity was 2.6 μS / cm), wet of titanyl phthalocyanine pigment A cake (water paste) was obtained. 40 g of the obtained wet cake (water paste) was put into 200 g of tetrahydrofuran, stirred for 4 hours, filtered and dried to obtain titanyl phthalocyanine powder. This is designated as Pigment 1.

  The solid content concentration of the wet cake was 15% by mass. The crystal conversion solvent was used in a mass ratio of 33 times that of the wet cake. In addition, the halogen-containing compound is not used for the raw material of the synthesis example 1.

  The obtained titanyl phthalocyanine powder was measured for the X-ray diffraction spectrum under the following conditions using a commercially available X-ray diffractometer (Rigaku Denki: RINT 1100). The Bragg angle of the Cu-Kα ray (wavelength: 1.542Å) Double 2θ has a maximum peak at 27.2 ± 0.2 ° and a peak at a minimum angle of 7.3 ± 0.2 °, and 9.4 ± 0.2 ° and 9.6 ± 0.2 °. , With a major peak at 24.0 ± 0.2 ° and no peak between the 7.3 ° and 9.4 ° peaks and a further peak at 26.3 ° No titanyl phthalocyanine powder was obtained. The result is shown in FIG.

  A part of the water paste obtained in Synthesis Example 1 was dried at 80 ° C. under reduced pressure (5 mmHg) for 2 days to obtain a low crystalline titanyl phthalocyanine powder. An X-ray diffraction spectrum of the dry powder of the water paste is shown in FIG.

<X-ray diffraction spectrum measurement conditions>
X-ray tube: Cu
Voltage: 50kV
Current: 30mA
Scanning speed: 2 ° / min Scanning range: 3 ° -40 °
Time constant: 2 seconds (Synthesis example 2)
-Synthesis of titanyl phthalocyanine crystals-
According to the method of JP 2004-83859 A, Example 1, an aqueous paste of titanyl phthalocyanine pigment was synthesized, and crystal conversion was performed as follows to obtain a phthalocyanine crystal having smaller primary particles than the previous synthesis example 1. .

  400 parts by mass of tetrahydrofuran was added to 60 parts by mass of the water paste before crystal conversion obtained in Synthesis Example 1 above, and the mixture was vigorously stirred (2000 rpm) with a homomixer (Kennis, MARKIIf model) at room temperature, and the dark blue color of the paste When the color changed to light blue (20 minutes after the start of stirring), stirring was stopped and filtration under reduced pressure was immediately performed. The crystals obtained on the filtration device were washed with tetrahydrofuran to obtain a wet cake of pigment. This was dried under reduced pressure (5 mmHg) at 70 ° C. for 2 days to obtain 8.5 parts by mass of titanyl phthalocyanine crystals. This is designated as Pigment 2. The raw material of Synthesis Example 2 does not use a halogen-containing compound. The solid content concentration of the wet cake was 15% by mass. The crystal conversion solvent was used in a mass ratio of 44 times that of the wet cake.

  Part of the pre-crystallized titanyl phthalocyanine (water paste) prepared in Synthesis Example 1 was diluted with ion-exchanged water to approximately 1% by mass, and the surface was scooped with a copper net that was conductively treated. Were observed with a transmission electron microscope (TEM, Hitachi: H-9000NAR) at a magnification of 75000 times. The average particle size was determined as follows.

  The TEM image observed as described above is taken as a TEM photograph, and 30 titanyl phthalocyanine particles (a shape close to a needle shape) projected are arbitrarily selected, and the size of each major axis is measured. An arithmetic average of the major diameters of the measured 30 individuals was determined and used as the average particle diameter. The average particle diameter in the water paste (wet cake) in Synthesis Example 1 determined by the above method was 0.06 μm.

  In addition, the titanyl phthalocyanine crystal after crystal conversion just before filtration in Synthesis Example 1 and Synthesis Example 2 was diluted with tetrahydrofuran so as to be about 1% by mass, and observed in the same manner as the above method. The average particle diameter determined as described above is shown in Table 1. In addition, the titanyl phthalocyanine crystal produced in Synthesis Example 1 and Synthesis Example 2 did not necessarily have the same shape of all crystals (a shape close to a triangle, a shape close to a square, etc.). For this reason, the calculation was carried out with the length of the largest diagonal line of the crystal as the major axis.

The pigment 2 produced in Synthesis Example 2 was measured for the X-ray diffraction spectrum by the same method as described above. As a result, the X-ray diffraction spectrum of Pigment 2 prepared in Synthesis Example 2 matched the spectrum of Pigment 1 prepared in Synthesis Example 1.

(Dispersion Preparation Example 1)
Pigment 1 prepared in Synthesis Example 1 was dispersed under the following composition under the following conditions to prepare a dispersion as a charge generation layer coating solution.

Titanyl phthalocyanine pigment (Pigment 1) 15 parts Polyvinyl butyral (manufactured by Sekisui Chemical: BX-1) 10 parts 2-butanone 280 parts A commercially available bead mill disperser (DISPERMAT: SL-05C1-EX) with a PSZ ball having a diameter of 0.5 mm All the 2-butanone and pigment dissolved with polyvinyl butyral were used and the rotor rotation speed was 1200 r. p. m. For 30 minutes to prepare a dispersion. This was designated as Dispersion Liquid 1.

(Dispersion preparation example 2)
A dispersion was prepared under the same conditions as in Dispersion Preparation Example 1, using Pigment 2 prepared in Synthesis Example 2 instead of Pigment 1 used in Dispersion Preparation Example 1. This was designated as Dispersion Liquid 2.

(Dispersion preparation example 3)
The dispersion 1 prepared in Dispersion Preparation Example 1 was filtered using a cotton wind cartridge filter, TCW-1-CS (effective pore size 1 μm) manufactured by Advantech. During filtration, a pump was used and filtration was performed in a pressurized state. This was designated as Dispersion Liquid 3.

(Dispersion preparation example 4)
Dispersion was performed by pressure filtration in the same manner as in Dispersion Preparation Example 3, except that the filter used in Dispersion Preparation Example 3 was changed to Advantech's Cotton Wind Cartridge Filter and TCW-3-CS (effective pore size 3 μm). A liquid was prepared. This was designated as Dispersion Liquid 4.

(Dispersion preparation example 5)
Dispersion was carried out under the conditions shown below with a formulation having the following composition to prepare a dispersion as a charge generation layer coating solution.

    5 parts of azo pigment with the following structure

Polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd .: BX-1) 2 parts Cyclohexanone 250 parts 2-butanone 100 parts Using a PSZ ball having a diameter of 10 mm in a ball mill disperser, all of the solvent and azo pigment in which polyvinyl butyral was dissolved were added, and the rotational speed was 85 r. . p. m. For 7 days to prepare a dispersion (referred to as dispersion 5).

(Dispersion Preparation Example 6)
A dispersion was prepared in the same manner as Dispersion Preparation Example 5 except that the azo pigment used in Dispersion Preparation Example 5 was changed to one having the following structure (referred to as Dispersion 6).

The particle size distribution of the pigment particles in the dispersion prepared as described above was measured by HORIBA, Ltd .: CAPA-700. The results are shown in Table 2.

(Photoreceptor Preparation Example 1)
On a φ30 mm aluminum drum (JIS 1050), an intermediate layer coating solution, a charge generation layer coating solution, and a charge transport layer coating solution having the following composition were sequentially applied and dried to form a 3.5 μm intermediate layer, a charge. A generation layer and a charge transport layer having a thickness of 25 μm were formed to produce a laminated photoreceptor (referred to as electrophotographic photoreceptor 1).

  The film thickness of the charge generation layer was adjusted as follows. A support in which a polyethylene terephthalate film was wound around a φ30 aluminum drum was prepared in advance, and the charge generation layer was coated in the same manner as in the preparation of the photoreceptor. Using this, the transmittance | permeability of light with a wavelength of 407 nm was calculated | required with the commercially available spectrophotometer (Shimadzu: UV-3100) (a comparison object is an uncoated polyethylene terephthalate film). As a result, the transmittance of the charge generation layer was adjusted to 20%.

  Similarly, the transmittance of the charge transport layer was also evaluated. As a result, the transmittance at a wavelength of 407 nm of the charge transport layer having the following composition was 98%.

◎ Intermediate layer coating liquid Untreated surface rutile type titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average particle size: 0.25 μm) 112 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%),
Dainippon Ink & Chemicals, Inc.] 33.6 parts Melamine resin [Super Becamine L-121-60 (solid content 60%),
Manufactured by Dainippon Ink & Chemicals, Inc.] 18.7 parts 2-butanone 260 parts ◎ Charge generation layer coating liquid Dispersion 1 prepared above was used.

◎ Charge transport layer coating solution Polycarbonate (TS2050: manufactured by Teijin Chemicals Ltd.) 10 parts Charge transport material of the following structural formula 7 parts

80 parts of methylene chloride An intermediate layer was formed in the same manner as the photoreceptor 1 on an aluminum plate having a thickness of 1 mm using the intermediate layer coating solution. The spectral reflection spectrum of the intermediate layer was measured using a commercially available spectrophotometer (Shimadzu: UV-3100). From the spectral reflection spectrum, the absorption edge of the intermediate layer (upper limit wavelength on the long wavelength side that can be absorbed) was determined, and the absorption edge of titanium oxide was determined to be about 410 nm.

(Photoreceptor preparation example 2)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 1 except that the intermediate layer coating solution used in Photoconductor Preparation Example 1 was changed to one having the following composition (referred to as electrophotographic photoconductor 2).

◎ Intermediate layer coating liquid Surface Si-treated rutile type titanium oxide (manufactured by Ishihara Sangyo Co., Ltd., average particle size: 0.25 μm) 112 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%),
Dainippon Ink & Chemicals, Inc.] 33.6 parts Melamine resin [Super Becamine L-121-60 (solid content 60%),
Dainippon Ink & Chemicals, Inc.] 18.7 parts 2-butanone 260 parts The above-mentioned surface Si-treated rutile type titanium oxide is 2% by weight based on the weight of the surface untreated rutile type titanium oxide used in Photoconductor Preparation Example 1. The surface treatment was performed using this siloxane.

  An intermediate layer was formed in the same manner as the photoreceptor 1 on an aluminum plate having a thickness of 1 mm using the intermediate layer coating solution. The spectral reflection spectrum of the intermediate layer was measured using a commercially available spectrophotometer (Shimadzu: UV-3100). From the spectral reflection spectrum, the absorption edge of the intermediate layer (upper limit wavelength on the long wavelength side that can be absorbed) was determined, and the absorption edge of titanium oxide was determined to be about 410 nm.

(Photoreceptor Preparation Example 3)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 1 except that the intermediate layer coating solution used in Photoconductor Preparation Example 1 was changed to one having the following composition (referred to as electrophotographic photoconductor 3).

◎ Intermediate layer coating solution Surface untreated zinc oxide:
(SAZEX # 2000: Sakai Chemical Industry Co., Ltd., average particle size: 0.60 μm) 112 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%),
Dainippon Ink & Chemicals, Inc.] 33.6 parts Melamine resin [Super Becamine L-121-60 (solid content 60%),
Dainippon Ink & Chemicals, Inc.] 18.7 parts 2-butanone 260 parts Using the above intermediate layer coating solution, an intermediate layer was formed on the 1 mm thick aluminum plate in the same manner as the photoreceptor 3. As in the case of the photoreceptor 1, the spectral reflection spectrum of the intermediate layer was measured using a commercially available spectrophotometer (Shimadzu: UV-3100). From the spectral reflection spectrum, the absorption edge of the intermediate layer (upper limit wavelength on the long wavelength side that can be absorbed) was determined, and the absorption edge of zinc oxide was determined to be approximately 388 nm.

(Photosensitive member production example 4)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 1 except that the thickness of the charge generation layer in Photoconductor Preparation Example 1 was changed and the transmittance at a wavelength of 407 nm was changed to 12% (electrophotographic photosensitive member). Body 4).

(Photoreceptor Preparation Example 5)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 1 except that the thickness of the charge generation layer in Photoconductor Preparation Example 1 was changed and the transmittance at a wavelength of 407 nm was changed to 8% (electrophotographic photosensitive member). Body 5).

(Photosensitive member preparation example 6)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 2 except that the thickness of the charge generation layer in Photoconductor Preparation Example 2 was changed and the transmittance at a wavelength of 407 nm was changed to 12% (electrophotographic photosensitive member). Body 6).

(Photoreceptor Preparation Example 7)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 2 except that the thickness of the charge generation layer in Photoconductor Preparation Example 2 was changed and the transmittance at a wavelength of 407 nm was changed to 8% (electrophotographic photosensitive member). Body 7).

(Photoreceptor Preparation Example 8)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 1 except that the charge transport material in Photoconductor Preparation Example 1 was changed to one having the following structure (referred to as electrophotographic photoconductor 8).

As a result of evaluating the transmittance at a wavelength of 407 nm of the charge transport layer in the photoreceptor preparation example 8 in the same manner as described above, it was 40%.

(Photoreceptor Preparation Example 9)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 8 except that the charge transport layer coating solution in Photoconductor Preparation Example 8 was changed to the following composition (referred to as electrophotographic photoconductor 9).

◎ Charge transport layer coating solution Polycarbonate (TS2050: manufactured by Teijin Chemicals Ltd.) 10 parts Charge transport material of the following structural formula 10 parts

Methylene chloride 80 parts The transmittance of the charge transport layer at a wavelength of 407 nm in Photoconductor Preparation Example 9 was evaluated in the same manner as described above, and was found to be 25%.

Example 1
The electrophotographic photosensitive member 1 produced as described above is mounted on an image forming apparatus as shown in FIG. 9, the image exposure light source is a 407 nm semiconductor laser (image writing by a polygon mirror), a scorotron charger as a charging member, a transfer member A transfer belt was used as a member, and a 380 nm LED (manufactured by Nichia Chemical) was used as a static elimination light source. Process conditions before the test are set as follows, and a chart with a writing rate of 6% (characters equivalent to 6% as an image area are written on the entire A4 surface) is continuously 50,000. Sheet printing was performed.

Photoconductor charging potential (unexposed portion potential): −900 V
Development bias: -650V (negative / positive development)
Exposed portion surface potential: -120V
Evaluation was made by measuring the photosensitive member charging potential and the exposed portion potential before and after printing 50,000 sheets of images. Even after printing 50,000 sheets, the writing conditions (exposure amount) were fixed to the values in the initial state, and the potential measurement was performed.

  As a measuring method, a surface potential meter is mounted at the developing portion position shown in FIG. 9, and after charging the photosensitive member to −900 V, solid writing is performed with the semiconductor laser, and the surface potential of the unexposed portion and the exposure at the developing portion are measured. The partial potential was measured. The results are shown in Table 3.

( Reference Example 2)
Evaluation was performed in the same manner as in Example 1 except that the neutralization light source in Example 1 was changed to 502 nm LED (manufactured by Seiwa Denki: full width at half maximum of 15 nm). The results are shown in Table 3.

(Comparative Example 1)
Evaluation was performed in the same manner as in Reference Example 2 except that the writing light source in Reference Example 2 was changed to 440 nm LD (image writing by a polygon mirror). The results are shown in Table 3. The transmittance of the charge generation layer at a wavelength of 440 nm was 38%, and the transmittance of the charge transport layer was 98%.

(Example 3)
In Example 1, evaluation was performed in the same manner as in Example 1 except that the electrophotographic photosensitive member 2 was used instead of the electrophotographic photosensitive member 1 used. The results are shown in Table 3.

Example 4
Evaluation was performed in the same manner as in Example 1 except that the writing light source in Example 1 was changed to 375 nm LD (image writing by a polygon mirror) and the electrophotographic photosensitive member 3 was used instead of the used electrophotographic photosensitive member 1. Went. The results are shown in Table 3. The transmittance of the charge generation layer at a wavelength of 375 nm was 17%, and the transmittance of the charge transport layer was 77%.

(Comparative Example 2)
In Example 1, evaluation was performed in the same manner as in Example 1 except that the electrophotographic photosensitive member 3 was used instead of the electrophotographic photosensitive member 1 used. The results are shown in Table 3.

(Comparative Example 3)
In Comparative Example 1, evaluation was performed in the same manner as in Comparative Example 1 except that the electrophotographic photosensitive member 3 was used instead of the used electrophotographic photosensitive member 1. The results are shown in Table 3.

(Example 5)
In Example 1, evaluation was performed in the same manner as in Example 1 except that the electrophotographic photosensitive member 4 was used instead of the used electrophotographic photosensitive member 1. The results are shown in Table 3.

(Example 6)
In Example 1, evaluation was performed in the same manner as in Example 1 except that the electrophotographic photosensitive member 5 was used instead of the electrophotographic photosensitive member 1 used. The results are shown in Table 3.

(Example 7)
In Example 1, evaluation was performed in the same manner as in Example 1 except that the electrophotographic photosensitive member 8 was used instead of the electrophotographic photosensitive member 1 used. The results are shown in Table 3. Note that the amount of writing light was set so that the exposure portion potential was the same as in Example 1 in the initial state.

(Example 8)
In Example 1, evaluation was performed in the same manner as in Example 3 except that the electrophotographic photosensitive member 9 was used instead of the used electrophotographic photosensitive member 1. The results are shown in Table 3. Note that the amount of writing light was set so that the exposure portion potential was the same as in Example 1 in the initial state.

Example 9
In Example 3, evaluation was performed in the same manner as in Example 3 except that the electrophotographic photosensitive member 6 was used instead of the used electrophotographic photosensitive member 2. The results are shown in Table 3.

(Example 10)
In Example 3, evaluation was performed in the same manner as in Example 3 except that the electrophotographic photosensitive member 7 was used instead of the used electrophotographic photosensitive member 2. The results are shown in Table 3.

From Table 3, when the writing light wavelength is shorter than 450 nm and light is absorbed by the metal oxide (titanium oxide) contained in the intermediate layer (Example 1), when not absorbed (Comparative Example 1) In comparison, it can be seen that the increase in the exposed portion potential after repeated use is small. This effect is greater when the neutralizing light is absorbed by the intermediate layer (Example 1) than when it is not absorbed ( Reference Example 2).

  Further, it can be seen that the effect of reducing the residual potential is small when the titanium oxide used for the intermediate layer is subjected to surface treatment (Example 3) and when it is not treated (Example 1).

  Compared to the case where the writing light wavelength is shorter than 450 nm and the metal oxide (zinc oxide) contained in the intermediate layer absorbs light (Example 4), and the light is not absorbed (Comparative Examples 2 and 3). Thus, it can be seen that the increase in the potential of the exposed portion after repeated use is small.

  Further, when the transmittance of the charge generation layer with respect to the writing light wavelength is less than 10% (Examples 6 and 10), it is used repeatedly more than the case of 10% or more (Examples 1, 5, and Examples 3 and 9). It can be seen that the subsequent exposure area potential increase is large.

  Furthermore, when the transmittance of the charge transport layer with respect to the charge elimination light wavelength is less than 30% (Example 8), compared to the case where it is 30% or more (Examples 1 and 7), the amount of increase in potential of the exposed portion after repeated use Can be seen to be large.

(Example 11)
In Example 1, the chart used for the test was tested using the chart in which the solid white portion and the black solid portion as shown in FIG. Went. At this time, the exposed portion potentials of the white solid portion and the black solid portion after 50,000 sheets were measured. The results are shown in Table 4.

(Example 12)
In Reference Example 2, the chart used for the test was tested using the chart in which the white solid portion and the black solid portion as shown in FIG. Went. At this time, the exposed portion potentials of the white solid portion and the black solid portion after 50,000 sheets were measured. The results are shown in Table 4.

From Table 4, when the light is absorbed by the metal oxide (titanium oxide) contained in the intermediate layer as static elimination light (Example 11), a document having an extremely different image density as shown in FIG. 14 is printed. However, there is no significant difference in the exposed portion potential, but when it is not absorbed (Example 12), a difference occurs in the exposed portion potential between the white solid portion and the black solid portion.

(Photoreceptor Preparation Example 10)
In Photoconductor Preparation Example 1, a photoconductor was prepared in the same manner as in Photoconductor Preparation Example 1 except that Dispersion 2 prepared previously was used as the charge generation layer coating solution (referred to as electrophotographic photoconductor 10). . The film thickness of the charge generation layer was adjusted to 20% as the transmittance of the writing light wavelength.

(Photoreceptor Preparation Example 11)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 1 except that the charge generation layer coating liquid (dispersion 1) in Photoconductor Preparation Example 1 was changed to Dispersion 3 (referred to as electrophotographic photoconductor 11). . The film thickness of the charge generation layer was adjusted to 20% as the transmittance of the writing light wavelength.

(Photoconductor Preparation Example 12)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 1 except that the charge generation layer coating solution (Dispersion 1) in Photoconductor Preparation Example 1 was changed to Dispersion 4 (referred to as electrophotographic photoconductor 12). . The film thickness of the charge generation layer was adjusted to 20% as the transmittance of the writing light wavelength.

(Example 13)
Evaluation was performed using the electrophotographic photosensitive member 10 instead of the electrophotographic photosensitive member 1 under the same conditions as in Example 1. In addition, after outputting 50,000 images, a solid white image was output to evaluate the background stain. Table 5 shows the results together with the results of Example 1.

(Example 14)
Evaluation was performed using the electrophotographic photosensitive member 11 instead of the electrophotographic photosensitive member 1 under the same conditions as in Example 1. In addition, after outputting 50,000 images, a solid white image was output to evaluate the background stain. The results are shown in Table 5.

(Example 15)
Evaluation was performed using the electrophotographic photosensitive member 12 instead of the electrophotographic photosensitive member 1 under the same conditions as in Example 1. In addition, after outputting 50,000 images, a solid white image was output to evaluate the background stain. The results are shown in Table 5.

  For the background dirt evaluation, a rank evaluation was performed from the number and size of sunspots generated on the background. The ranking was performed in four stages, and very good ones were indicated by ◎, good ones by ○, slightly inferior by Δ, and very bad by x.

From Table 5, when the average particle diameter of the coating liquid used for the charge generation layer is 0.25 μm or less (Examples 13 to 15), the surface potential of the exposed portion in the initial state of the photoreceptor can be lowered and repeatedly used. Later, it can be seen that the occurrence of background contamination can be suppressed without affecting the increase in potential of the exposed portion.

(Photoreceptor Preparation Example 13)
Same as Photoconductor Preparation Example 1 except that the thickness of the charge transport layer in Photoconductor Preparation Example 1 was 23 μm, a protective layer coating solution having the following composition was applied and dried on the charge transport layer, and a 2 μm protective layer was provided. A photoconductor was prepared (referred to as electrophotographic photoconductor 13). Apart from the photoreceptor, only a protective layer was formed on a polyethylene terephthalate film, and the transmittance at 407 nm was evaluated with a spectrophotometer. As a result, the transmittance was 98%. The transmittance of the charge transport layer was 98%.

◎ Protective layer coating solution Polycarbonate (TS2050: manufactured by Teijin Chemicals Ltd.) 10 parts Charge transport material of the following structural formula: 7 parts

4 parts of alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.4 μm)
Cyclohexanone 500 parts Tetrahydrofuran 150 parts (Photoconductor Preparation Example 14)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 13 except that the alumina fine particles in the protective layer coating solution in Photoconductor Preparation Example 13 were changed to the following (referred to as electrophotographic photoconductor 14). The transmittance of the protective layer at a wavelength of 407 nm was 95%.

4 parts of titanium oxide fine particles (specific resistance: 1.5 × 10 ¹⁰ Ω · cm, average primary particle size: 0.5 μm)
(Photoreceptor Preparation Example 15)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 13 except that the alumina fine particles in the protective layer coating solution in Photoconductor Preparation Example 13 were changed to the following (referred to as electrophotographic photoconductor 15). The transmittance of the protective layer at a wavelength of 407 nm was 93%.

4 parts of tin oxide-antimony oxide powder (specific resistance: 10 ⁶ Ω · cm, average primary particle size 0.4 μm)
(Photoreceptor Preparation Example 16)
An electrophotographic photosensitive member was prepared in the same manner as in the photosensitive member preparation example 13 except that the protective layer coating solution in the photosensitive member preparation example 13 was changed to one having the following composition (referred to as an electrophotographic photosensitive member 16). The transmittance of the protective layer at a wavelength of 407 nm was 90%.

◎ Protective layer coating solution 17 parts of polymer charge transport material of the following structural formula (weight average molecular weight: about 140000)

4 parts of alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.4 μm)
Cyclohexanone 500 parts Tetrahydrofuran 150 parts (Photoconductor Preparation Example 17)
An electrophotographic photosensitive member was prepared in the same manner as in the photosensitive member preparation example 13 except that the protective layer coating solution in the photosensitive member preparation example 13 was changed to one having the following composition (referred to as an electrophotographic photosensitive member 17). The transmittance of the protective layer at a wavelength of 407 nm was 38%.

◎ Protective layer coating solution Methyltrimethoxysilane 100 parts 3% acetic acid 20 parts Charge transporting compound with the following structure 35 parts

Antioxidant (Sanol LS2626: Sankyo Chemical Co., Ltd.) 1 part Curing agent (dibutyltin acetate) 1 part 2-propanol 200 parts (Photoconductor Preparation Example 18)
An electrophotographic photosensitive member was prepared in the same manner as in the photosensitive member preparation example 13 except that the protective layer coating solution in the photosensitive member preparation example 13 was changed to one having the following composition (referred to as an electrophotographic photosensitive member 18). The transmittance of the protective layer at a wavelength of 407 nm was 32%.

◎ Protective layer coating solution Methyltrimethoxysilane 100 parts 3% acetic acid 20 parts Charge transporting compound with the following structure 35 parts

15 parts of alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.4 μm)
Antioxidant (Sanol LS2626: Sankyo Chemical Co., Ltd.) 1 part Polycarboxylic acid compound BYK P104: BYK Chemie 0.4 part Curing agent (dibutyltin acetate) 1 part 2-propanol 200 parts (Photoconductor Preparation Example 19)
An electrophotographic photosensitive member was prepared in the same manner as in the photosensitive member preparation example 13 except that the protective layer coating solution in the photosensitive member preparation example 13 was changed to the one having the following composition (referred to as an electrophotographic photosensitive member 19). The transmittance of the protective layer at a wavelength of 407 nm was 74%.

◎ Protective layer coating solution Trifunctional or higher functional radical polymerizable monomer having no charge transporting structure 10 parts {Trimethylolpropane triacrylate (KAYARAD TMPTA, Nippon Kayaku)
Molecular weight: 296, number of functional groups: trifunctional, molecular weight / number of functional groups = 99}
10 parts of radically polymerizable compound having a monofunctional charge transporting structure having the following structure (Exemplary Compound No. 54)

Photoinitiator 1 part 1-Hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
Tetrahydrofuran 100 parts Protective layer is spray-coated and air-dried for 20 minutes, followed by light irradiation under conditions of metal halide lamp: 160 W / cm, irradiation intensity: 500 mW / cm ² , irradiation time: 60 seconds The film was cured.

(Photoreceptor Preparation Example 20)
In Photoconductor Preparation Example 19, all the examples except for changing the tri- or higher functional radical polymerizable monomer having no charge transporting structure contained in the protective layer coating solution to the following radical polymerizable monomer An electrophotographic photoreceptor was prepared in the same manner as in 19 (referred to as an electrophotographic photoreceptor 20). The transmittance of the protective layer at a wavelength of 407 nm was 73%.

10 parts of tri- or higher functional radical polymerizable monomer having no charge transport structure (pentaerythritol tetraacrylate (SR-295, manufactured by Kayaku Sartomer)
(Molecular weight: 352, number of functional groups: tetrafunctional, molecular weight / number of functional groups = 88)
(Photoconductor Preparation Example 21)
A trifunctional or higher functional radical polymerizable monomer having no charge transport structure contained in the protective layer coating solution of Photosensitive Member Preparation Example 19 is converted into a bifunctional radical polymerizable monomer having no charge transport structure as described below. Except for changing to 10 parts, an electrophotographic photosensitive member was manufactured in the same manner as in the photosensitive member manufacturing example 19 (referred to as an electrophotographic photosensitive member 21). The transmittance of the protective layer at a wavelength of 407 nm was 74%.

10 parts of a bifunctional radically polymerizable monomer having no charge transporting structure (1,6-hexanediol diacrylate (manufactured by Wako Pure Chemical Industries, Ltd.))
Molecular weight: 226, number of functional groups: bifunctional, molecular weight / number of functional groups = 113)
(Photoconductor Preparation Example 22)
In Photoconductor Preparation Example 19, photoconductor preparation was performed except that the trivalent or higher functional radical polymerizable monomer having no charge transporting structure contained in the protective layer coating solution was replaced with the following radical polymerizable monomer. An electrophotographic photoreceptor was produced in the same manner as in Example 19 (referred to as electrophotographic photoreceptor 22). The transmittance of the protective layer at a wavelength of 407 nm was 71%.

Trifunctional or higher functional radical polymerizable monomer having no charge transport structure 10 parts (Caprolactone-modified dipentaerythritol hexaacrylate (KAYARAD DPCA-120, manufactured by Nippon Kayaku)
(Molecular weight: 1947, number of functional groups: 6 functions, molecular weight / number of functional groups = 325)
(Photoconductor Preparation Example 23)
The radical polymerizable compound 10 having a bifunctional charge transporting structure represented by the following structural formula is used as the radical polymerizable compound having a monofunctional charge transporting structure contained in the protective layer coating solution of Photoconductor Preparation Example 19. An electrophotographic photosensitive member was produced in the same manner as in Photoreceptor Preparation Example 19 (except for the electrophotographic photosensitive member 23), except that the parts were changed. The transmittance of the protective layer at a wavelength of 407 nm was 3%.

(Photoconductor Preparation Example 24)
In Photoconductor Preparation Example 19, an electrophotographic photoconductor was prepared in the same manner as Photoconductor Preparation Example 19 except that the protective layer coating solution was changed to the following composition (referred to as electrophotographic photoconductor 24). The transmittance of the protective layer at a wavelength of 407 nm was 72%.

◎ Protective layer coating liquid Trifunctional or higher functional radical polymerizable monomer having no charge transport structure 6 parts {Trimethylolpropane triacrylate (KAYARAD TMPTA, Nippon Kayaku)
Molecular weight: 296, number of functional groups: trifunctional, molecular weight / number of functional groups = 99}
14 parts of radically polymerizable compound having a monofunctional charge transporting structure having the following structure (Exemplary Compound No. 54)

Photoinitiator 1 part 1-Hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
Tetrahydrofuran 100 parts (Photoconductor Preparation Example 25)
In Photoconductor Preparation Example 19, an electrophotographic photoconductor was prepared in the same manner as Photoconductor Preparation Example 19 except that the protective layer coating solution was changed to the following composition (referred to as electrophotographic photoconductor 25). The transmittance of the protective layer at a wavelength of 407 nm was 74%.

◎ Protective layer coating solution Trifunctional or higher functional radical polymerizable monomer having no charge transport structure 14 parts {Trimethylolpropane triacrylate (KAYARAD TMPTA, Nippon Kayaku)
Molecular weight: 296, number of functional groups: trifunctional, molecular weight / number of functional groups = 99}
6 parts of a radical polymerizable compound having a monofunctional charge transport structure having the following structure (Exemplary Compound No. 54)

Photoinitiator 1 part 1-Hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
Tetrahydrofuran 100 parts (Photoconductor Preparation Example 26)
In Photoconductor Preparation Example 19, an electrophotographic photoconductor was prepared in the same manner as Photoconductor Preparation Example 19 except that the protective layer coating solution was changed to the following composition (referred to as electrophotographic photoconductor 26). The transmittance of the protective layer at a wavelength of 407 nm was 74%.

◎ Protective layer coating solution Trifunctional or higher functional radical polymerizable monomer having no charge transport structure 2 parts {Trimethylolpropane triacrylate (KAYARAD TMPTA, Nippon Kayaku)
Molecular weight: 296, number of functional groups: trifunctional, molecular weight / number of functional groups = 99}
18 parts of radically polymerizable compound having a monofunctional charge transport structure having the following structure (Exemplary Compound No. 54)

Photoinitiator 1 part 1-Hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
Tetrahydrofuran 100 parts (Photoconductor Preparation Example 27)
In Photoconductor Preparation Example 19, an electrophotographic photoconductor was prepared in the same manner as Photoconductor Preparation Example 19 except that the protective layer coating solution was changed to the following composition (referred to as electrophotographic photoconductor 27). The transmittance of the protective layer at a wavelength of 407 nm was 73%.

◎ Protective layer coating solution Trifunctional or higher functional radical polymerizable monomer having no charge transporting structure 18 parts {Trimethylolpropane triacrylate (KAYARAD TMPTA, Nippon Kayaku)
Molecular weight: 296, number of functional groups: trifunctional, molecular weight / number of functional groups = 99}
2 parts of radically polymerizable compound having a monofunctional charge transporting structure having the following structure (Exemplary Compound No. 54)

Photoinitiator 1 part 1-Hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184, manufactured by Ciba Specialty Chemicals)
Tetrahydrofuran 100 parts (Example 16)
The electrophotographic photosensitive member 1 produced as described above is mounted on an image forming apparatus as shown in FIG. 9, the image exposure light source is a 407 nm semiconductor laser (image writing by a polygon mirror), a scorotron charger as a charging member, a transfer member A transfer belt was used as a member, and the following was used as a static elimination light source. The process conditions before the test were set to be as follows, and continuous 70,000 sheets were printed using a chart with a writing rate of 6%.

Photoconductor charging potential (unexposed portion potential): −900 V
Development bias: -650V (negative / positive development)
Exposed portion surface potential: -120V
Static elimination light source:
A xenon lamp and a spectroscope were combined to produce a monochromatic light of 405 nm, which was guided to an image forming apparatus by an optical fiber, and a slit-shaped light was irradiated to the surface of the photoreceptor by a charge eliminating portion.

<Evaluation items>
(1) Measurement of surface potential Evaluation was made by measuring the potential of the photosensitive member exposed area before and after printing 70,000 images. Even after printing 70,000 sheets, the writing conditions (exposure amount) were fixed to the values in the initial state, and the potential measurement was performed.

  As a measuring method, a surface potential meter was mounted at the position of the developing portion shown in FIG. 9, and the photosensitive member was charged to −900 V, and then solid writing was performed with the semiconductor laser, and the exposed portion potential at the developing portion was measured. The results are shown in Table 6.

(2) Soil evaluation Further, after outputting 70,000 images (after completion of the surface potential measurement), a solid white image was output to evaluate the soil (22 ° C.-50% RH). The background dirt evaluation was performed by the above-described four-level rank evaluation. The results are shown in Table 6.

(3) Evaluation of cleaning property Further, after evaluation of soiling, under a low temperature and low humidity environment (10 ° C., 15% RH), using a test chart as shown in FIG. The image was output in the direction from solid to white, 50 sheets were continuously printed, and the cleaning property was evaluated. At this time, the image of the 50th white solid portion was visually evaluated. Evaluation is performed in 4 stages, ◎ for very good (no cleaning failure at all), ◯ for good (level with slight black streaks, 1 to 2 in the longitudinal direction), slightly inferior (slightly) A black streak level (3-4 places in the longitudinal direction) was represented by Δ, and a very bad one (level where black streaks clearly entered) was represented by x. The results are shown in Table 6.

(4) Dot reproducibility evaluation Subsequent to the previous cleaning test, a further sheet passing test (used with the previous 6% char) was conducted in a high temperature and high humidity environment (30 ° C.-90% RH). A one-dot image evaluation (outputting an image in which independent dots were written) was performed after passing the sheet. A one-dot image was observed with an optical microscope, and the clarity of the dot outline was ranked. The rank evaluation was performed in four stages, and very good ones were indicated by ◎, good ones by ○, slightly inferior by Δ, and very bad by x. The results are shown in Table 6.

(5) Wear amount evaluation The initial film thickness of the photoconductor was measured, and the film thickness was measured again after completing the above tests (1) to (4). The difference in film thickness (amount of wear) before and after all tests was evaluated. The film thickness was measured at intervals of 1 cm, excluding 5 cm at both ends in the longitudinal direction of the photoreceptor, and the average value was taken as the film thickness.

(Examples 17 to 31)
Under the same conditions as in Example 16, the electrophotographic photoreceptors 13 to 27 produced as described above were evaluated. The results are shown in Table 6. Table 6 also shows the used electrophotographic photosensitive member numbers corresponding to the example numbers.

Table 6 shows the following.

  Even when the protective layer is provided, the wavelength of the writing light is set to 407 nm, and the effect of preventing the residual potential from rising is recognized by absorbing the light in the titanium oxide contained in the intermediate layer.

  By providing the protective layer (Examples 17 to 31), the wear resistance is improved as compared with the case where the protective layer is not provided (Example 16).

In the case where a protective layer containing an inorganic pigment (metal oxide) is provided (Examples 17 to 19), the inorganic pigment (metal oxide) having a specific resistance of 10 ¹⁰ Ω · cm or higher contains a high temperature. The dot reproducibility does not decrease so much even under high humidity (Examples 18 and 19).

  By having the crosslinked structure in the protective layer, the wear resistance is improved as compared with the case where it is not present. Furthermore, in the case of using a protective layer formed by curing a radically polymerizable monomer having three or more functional groups having no charge transporting structure and a radically polymerizable compound having a monofunctional charge transporting structure, High wear resistance is obtained (Examples 20, 23, 26, 28-31).

  In addition, when a protective layer formed by curing a radically polymerizable monomer having three or more functional groups having no charge transporting structure and a radically polymerizable compound having a monofunctional charge transporting structure is used, cleaning is performed. The property is also good.

  It can be seen that when the transmittance of the protective layer with respect to writing light is less than 30% (Example 27), the dot reproducibility is lower than when the transmittance is 30% or more.

( Reference Example 32)
Exposed portion potential was measured and evaluated in the same manner as in Example 26, except that the neutralization light source in Example 26 was changed to a 502 nm LED (manufactured by Seiwa Electric Co., Ltd .: full width at half maximum of 15 nm). The amount of charge removed was adjusted so that the surface potential of the photoreceptor after charge removal would be the same as in Example 26. The results are shown in Table 7 together with the results of Example 26. The transmittance of the charge generation layer at the writing light wavelength (407 nm) of the used photoreceptor was 20%, and the transmittance of the charge transport layer was 98%.

(Comparative Example 4)
Evaluation was performed in the same manner as in Reference Example 32, except that the writing light source in Reference Example 32 was changed to 440 nm LD (image writing by a polygon mirror). The amount of writing light was adjusted so that the surface potential of the exposed area in the initial state was equal to that in Reference Example 32. The results are shown in Table 7. The transmittance of the charge generation layer at the writing light wavelength (407 nm) of the used photoreceptor was 38%, and the transmittance of the charge transport layer was 98%.

From Table 7, even when the protective layer is provided, when the writing light wavelength is shorter than 450 nm and the metal oxide (titanium oxide) contained in the intermediate layer absorbs light (Example 26), absorption is achieved. It can be seen that the increase in the potential of the exposed area after repeated use is small compared to the case where it is not used (Comparative Example 4). This effect is greater when the neutralizing light is absorbed in the intermediate layer (Example 26) than when it is not absorbed ( Reference Example 32).

(Photoreceptor Preparation Example 28)
An electrophotographic photosensitive member was prepared in the same manner as the photosensitive member preparation example 22 except that the protective layer thickness in the photosensitive member preparation example 22 was changed to 2.2 μm (referred to as an electrophotographic photosensitive member 28).

(Photoconductor Preparation Example 29)
An electrophotographic photosensitive member was prepared in the same manner as the photosensitive member preparation example 22 except that the protective layer thickness in the photosensitive member preparation example 22 was changed to 4.1 μm (referred to as an electrophotographic photosensitive member 29).

(Example 33)
The electrophotographic photosensitive member 22 produced as described above is mounted on an image forming apparatus as shown in FIG. 9, and an image exposure light source is a 407 nm semiconductor laser (image writing by a polygon mirror), a scorotron charger as a charging member, a transfer member A transfer belt was used as a member, and the following was used as a static elimination light source. The process conditions before the test were set to be as follows, and continuous 70,000 sheets were printed using a chart with a writing rate of 6%.

Photoconductor charging potential (unexposed portion potential): −900 V
Development bias: -650V (negative / positive development)
Exposed portion surface potential: -130V
Static elimination light source:
A xenon lamp and a spectroscope were combined to produce a monochromatic light of 409 nm, which was guided to an image forming apparatus by an optical fiber, and a slit-shaped light was irradiated to the surface of the photoreceptor by a charge eliminating portion.

  Evaluation was made by measuring the potential of the photosensitive member exposed area before and after printing 70,000 images. Even after printing 70,000 sheets, the writing conditions (exposure amount) were fixed to the values in the initial state, and the potential measurement was performed.

  As a measuring method, a surface potential meter is mounted at the developing portion position shown in FIG. 9, and after charging the photosensitive member to −900 V, solid writing is performed with the semiconductor laser, and the surface potential of the unexposed portion and the exposure at the developing portion are measured. The partial potential was measured. The results are shown in Table 8.

  Further, after the potential measurement was performed after 70,000 sheets were output, a chart as shown in FIG. 16 (the front half was a stripe and the rear half was a halftone) was output, and image unevenness in the halftone portion was observed.

  In order to measure the transmittance of the protective layer, only the protective layer in the electrophotographic photosensitive members 28 and 29 is formed on a φ30 mm aluminum drum wound with a polyethylene terephthalate film under the same conditions as in the electrophotographic photosensitive members 22 and 23. did. Using a commercially available spectrophotometer (Shimadzu: UV-3100) with a polyethylene terephthalate film without a protective layer cut out to an appropriate size, a spectral transmittance in the range of 500 to 300 nm is obtained. It was measured. The transmittance of the charge generation layer at the writing light wavelength (407 nm) of the used photoreceptor was 20%, and the transmittance of the charge transport layer was 98%.

(Example 34)
In Example 33, evaluation was performed in the same manner as in Example 33 except that the electrophotographic photosensitive member 29 was used instead of the used electrophotographic photosensitive member 28. The results are shown in Table 8. The transmittance of the charge generation layer at the writing light wavelength (407 nm) of the used photoreceptor was 20%, and the transmittance of the charge transport layer was 98%.

(Example 35)
In Example 33, the evaluation was performed in the same manner as in Example 33 except that the writing light source was changed to a semiconductor laser of 380 nm (image writing by a polygon mirror). The amount of light was adjusted to be equal to that in Example 33 (initial state). The results are shown in Table 8. The transmittance of the charge generation layer at the writing light wavelength (380 nm) of the used photoreceptor was 20%, and the transmittance of the charge transport layer was 98%.

(Example 36)
In Example 34, evaluation was performed in the same manner as in Example 34 except that the writing light source was changed to a 380 nm semiconductor laser (image writing by a polygon mirror). The results are shown in Table 8. The transmittance of the charge generation layer at the writing light wavelength (380 nm) of the used photoreceptor was 20%, and the transmittance of the charge transport layer was 98%.

As can be seen from Table 8, when the transmittance of the protective layer against static elimination light is less than 30%, the effect is slightly reduced.

  In the chart output of FIG. 16, the halftone portions of Examples 33 to 34 formed completely normal images. However, in Examples 35 and 36, the level was not a problem, but the halftone portions were striped. A slight afterimage corresponding to was observed. This degree was worse in Example 36 than in Example 35.

  From the above results, it is possible to suppress an increase in the potential of the exposed portion after repeated use by irradiating writing light of less than 410 nm and absorbing the titanium oxide contained in the intermediate layer. It can be seen that a side effect slightly occurs when the transmittance with respect to is less than 30%.

(Photoreceptor Preparation Example 30)
The intermediate layer in the photoreceptor preparation example 1 has a laminated structure of a charge blocking layer and a moire preventing layer. Photoconductor Preparation Example 1 except that the charge blocking layer coating solution and the moire prevention layer coating solution having the following composition were applied and dried to obtain a 1.0 μm charge blocking layer and a 3.5 μm moire prevention layer. Similarly, a photoconductor was prepared (referred to as electrophotographic photoconductor 30).

◎ Charge blocking layer coating solution N-methoxymethylated nylon (Lead City: Fine Resin FR-101) 4 parts Methanol 70 parts n-Butanol 30 parts ◎ Moire prevention layer coating solution Titanium oxide (CR-EL: Ishihara Sangyo Co., Ltd.) Manufactured, average particle size: 0.25 μm) 126 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%),
Dainippon Ink & Chemicals, Inc.] 33.6 parts Melamine resin [Super Becamine L-121-60 (solid content 60%),
Dainippon Ink & Chemicals, Inc.] 18.7 parts 2-butanone 100 parts In the above composition, the volume ratio of the inorganic pigment to the binder resin is 1.5 / 1.

  The ratio of alkyd resin to melamine resin is a 6/4 weight ratio.

(Photoreceptor Preparation Example 31)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 30 except that the thickness of the charge blocking layer was 0.3 μm in Photoconductor Preparation Example 30 (referred to as electrophotographic photoconductor 31).

(Photoconductor Preparation Example 32)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 30 except that the thickness of the charge blocking layer was 1.8 μm in Photoconductor Preparation Example 30 (referred to as electrophotographic photoconductor 32).

(Photoconductor Preparation Example 33)
In Photoconductor Preparation Example 30, a photoconductor was prepared in the same manner as Photoconductor Preparation Example 30 except that the charge blocking layer coating solution was changed to one having the following composition (referred to as electrophotographic photoconductor 33).

Charge blocking layer coating solution Alcohol-soluble nylon (Toray: Amilan CM8000) 4 parts Methanol 70 parts n-Butanol 30 parts (Photoconductor Preparation Example 34)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 30 except that the moire-preventing layer coating solution was changed to one having the following composition in Photoconductor Preparation Example 30 (referred to as electrophotographic photoconductor 34).

◎ Moire prevention layer coating solution Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average particle size: 0.25 μm) 252 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%),
Dainippon Ink & Chemicals, Inc.] 33.6 parts Melamine resin [Super Becamine L-121-60 (solid content 60%),
Dai Nippon Ink Chemical Co., Ltd.] 18.7 parts 2-butanone 100 parts In the above composition, the volume ratio of the inorganic pigment to the binder resin is 3/1.

  The ratio of alkyd resin to melamine resin is a 6/4 weight ratio.

(Photoconductor Preparation Example 35)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 30 except that the moire-preventing layer coating solution was changed to one having the following composition in Photoconductor Preparation Example 30 (referred to as electrophotographic photoconductor 35).

◎ Moire prevention layer coating solution Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd., average particle size: 0.25 μm, 84 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%),
Dainippon Ink & Chemicals, Inc.] 33.6 parts Melamine resin [Super Becamine L-121-60 (solid content 60%),
Dai Nippon Ink Chemical Co., Ltd.] 18.7 parts 2-butanone 100 parts In the above composition, the volume ratio of the inorganic pigment to the binder resin is 1/1.

  The ratio of alkyd resin to melamine resin is a 6/4 weight ratio.

(Examples 37 to 42)
The electrophotographic photoreceptors 30 to 35 produced as described above were subjected to 70,000 running tests under the same conditions as in Example 16 (the same evaluation method and items). The results are shown in Table 9 in comparison with the case of Example 16. In any case, the transmittance of the charge generation layer at the writing light wavelength (407 nm) of the photosensitive member used was 20%, and the transmittance of the charge transport layer was 98%.

From the results of Table 9, it can be seen that the durability against soiling is improved by configuring the intermediate layer as a charge blocking layer and a moire prevention layer.

(Photoconductor Preparation Example 36)
An electrophotographic photosensitive member was prepared in the same manner as in the photosensitive member preparation example 1 except that the charge generation layer coating liquid (dispersion liquid 1) in the photosensitive member preparation example 1 was changed to the dispersion liquid 5 (referred to as an electrophotographic photosensitive member 36). ). The film thickness of the charge generation layer was adjusted so that the transmittance at 407 nm was 20%.

(Photoreceptor Preparation Example 37)
An electrophotographic photosensitive member was prepared in the same manner as in the photosensitive member preparation example 1 except that the charge generation layer coating liquid (dispersion liquid 1) in the photosensitive member preparation example 1 was changed to the dispersion liquid 6 (referred to as an electrophotographic photosensitive member 37). ). The film thickness of the charge generation layer was adjusted so that the transmittance at 407 nm was 20%.

(Photoconductor Preparation Example 38)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 36 except that the intermediate layer coating solution used in Photoconductor Preparation Example 36 was changed to one having the following composition (referred to as electrophotographic photoconductor 38).

◎ Intermediate layer coating liquid Surface Si-treated rutile type titanium oxide (manufactured by Ishihara Sangyo Co., Ltd., average particle size: 0.25 μm) 112 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%),
Dainippon Ink & Chemicals, Inc.] 33.6 parts Melamine resin [Super Becamine L-121-60 (solid content 60%),
Dainippon Ink & Chemicals, Inc.] 18.7 parts 2-butanone 260 parts The above-mentioned surface Si-treated rutile type titanium oxide is 2% by weight based on the weight of the surface untreated rutile type titanium oxide used in the photoreceptor preparation example 36. The surface treatment was performed using this siloxane.

(Photoconductor Preparation Example 39)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 36 except that the intermediate layer coating solution used in Photoconductor Preparation Example 36 was changed to one having the following composition (referred to as electrophotographic photoconductor 39).

◎ Intermediate layer coating solution Surface untreated zinc oxide:
(SAZEX # 2000: manufactured by Sakai Chemical Industry Co., Ltd., average particle size: 0.60 μm) 112 parts Alkyd resin [Beckolite M6401-50-S (solid content 50%),
Dainippon Ink & Chemicals, Inc.] 33.6 parts Melamine resin [Super Becamine L-121-60 (solid content 60%),
Dainippon Ink & Chemicals, Inc.] 18.7 parts 2-butanone 260 parts Using the above intermediate layer coating solution, an intermediate layer was formed on a 1 mm thick aluminum plate in the same manner as the photoreceptor 39. As in the case of the photoreceptor 1, the spectral reflection spectrum of the intermediate layer was measured using a commercially available spectrophotometer (Shimadzu: UV-3100). From the spectral reflection spectrum, the absorption edge of the intermediate layer (upper limit wavelength on the long wavelength side that can be absorbed) was determined, and the absorption edge of titanium oxide was determined to be approximately 388 nm.

(Example 43)
The previously produced electrophotographic photosensitive member 36 is mounted on a process cartridge as shown in FIG. 11, mounted in an image forming apparatus as shown in FIG. 10, and an image exposure light source is a 407 nm semiconductor laser (image writing by a polygon mirror). ), A contact roller charger as the charging member, a transfer belt as the transfer member, and a 380 nm LED (manufactured by Nichia Chemical) as the static elimination light source. Process conditions before the test are set as follows, and a chart with a writing rate of 6% (characters equivalent to 6% as an image area are written on the entire A4 surface) is continuously 50,000. Sheet printing was performed. The transmittance of the charge generation layer at the writing light wavelength (407 nm) of the used photoreceptor was 20%, and the transmittance of the charge transport layer was 98%.

Photoconductor charging potential (unexposed portion potential): −900 V
Development bias: -650V (negative / positive development)
Exposed portion surface potential: -60V
In the evaluation, the photosensitive member exposed portion potential was measured before and after printing 50,000 images (black station). Even after printing 50,000 sheets, the writing conditions (exposure amount) were fixed to the values in the initial state, and the potential measurement was performed. As a measuring method, a surface potential meter is mounted at the position of the developing portion shown in FIG. 10, and after charging the photosensitive member to −900 V, solid writing is performed with the semiconductor laser, and the surface potential of the unexposed portion and the exposure at the developing portion are measured. The partial potential was measured. The results are shown in Table 10.

  Further, before and after printing 50,000 sheets, an ISO / JIS-SCID image N1 (portrait) was output to evaluate the color color reproducibility.

( Reference Example 44)
Evaluation was performed in the same manner as in Example 43 except that the static elimination light source in Example 43 was changed to 502 nm LED (manufactured by Seiwa Denki: full width at half maximum of 15 nm). The results are shown in Table 10.

(Comparative Example 5)
Evaluation was performed in the same manner as in Reference Example 44, except that the writing light source in Reference Example 44 was changed to 440 nm LD (image writing by a polygon mirror). The amount of light was adjusted to be equal to the exposed portion surface potential in Reference Example 44 (initial state). The results are shown in Table 10. The transmittance of the charge generation layer at the writing light wavelength (440 nm) of the used photoreceptor was 17%, and the transmittance of the charge transport layer was 98%.

(Example 45)
Evaluation was performed in the same manner as in Example 43 except that the electrophotographic photosensitive member 37 was used instead of the electrophotographic photosensitive member 36 used in Example 43. The results are shown in Table 10. The transmittance of the charge generation layer at the writing light wavelength (407 nm) of the used photoreceptor was 18%, and the transmittance of the charge transport layer was 98%.

(Example 46)
Evaluation was performed in the same manner as in Example 43 except that the electrophotographic photosensitive member 38 was used instead of the electrophotographic photosensitive member 36 used in Example 43. The results are shown in Table 10. The transmittance of the charge generation layer at the writing light wavelength (407 nm) of the used photoreceptor was 17%, and the transmittance of the charge transport layer was 98%.

(Example 47)
Evaluation was made in the same manner as in Example 43 except that the writing light source in Example 43 was changed to 375 nm LD (image writing by a polygon mirror) and the electrophotographic photosensitive member 39 was used instead of the used electrophotographic photosensitive member 36. Went. The amount of light was adjusted to be equal to the exposed portion surface potential of Example 43 (initial state). The results are shown in Table 10. The transmittance of the charge generation layer at the writing light wavelength (375 nm) of the used photoreceptor was 26%, and the transmittance of the charge transport layer was 77%.

(Comparative Example 6)
In Example 43, evaluation was performed in the same manner as in Example 43 except that the electrophotographic photosensitive member 39 was used instead of the electrophotographic photosensitive member 36 used. The results are shown in Table 10. The transmittance of the charge generation layer at the writing light wavelength (407 nm) of the used photoreceptor was 20%, and the transmittance of the charge transport layer was 98%.

(Comparative Example 7)
In Comparative Example 5, evaluation was performed in the same manner as Comparative Example 5 except that the electrophotographic photosensitive member 39 was used instead of the used electrophotographic photosensitive member 36. The results are shown in Table 10. The transmittance of the charge generation layer at the writing light wavelength (440 nm) of the used photoreceptor was 20%, and the transmittance of the charge transport layer was 98%.

From Table 10, when the wavelength of the writing light is set to 407 nm and light is absorbed by titanium oxide contained in the intermediate layer (Example 43), a longer wavelength is used and light is not absorbed by titanium oxide. Compared with (Comparative Example 5), it can be seen that the increase in the exposed portion potential after repeated use is small. This effect is greater when the neutralizing light is absorbed by the intermediate layer (Example 43) than when it is not absorbed ( Reference Example 44).

  From the results of the test chart, in Example 43, an image almost the same as the initial image was output even after printing 50,000 sheets, but in Comparative Example 5, the color balance was improved after printing 50,000 sheets. The image was a bit crumbled.

  Further, from the comparison of the exposed portion potentials of Example 43 and Example 45, the exposed portion surface potential in Example 43 is lower. This shows that the asymmetry of the coupler component of the azo pigment used in Example 43 contributes to high sensitivity.

  It can also be seen that the effect of reducing the residual potential is small when the titanium oxide used for the intermediate layer is subjected to surface treatment (Example 46) and when it is not treated (Example 43).

  When the writing light wavelength is 375 nm and the metal oxide (zinc oxide) contained in the intermediate layer is light-absorbed (Example 47) and not absorbed (Comparative Examples 6 and 7), after repeated use It can be seen that the increase in the exposed portion potential is small.

  Although the embodiments and examples of the present invention have been specifically described above, the present invention is not limited to these embodiments and examples, and these embodiments and examples of the present invention are not limited thereto. Can be changed or modified without departing from the spirit and scope of the present invention.

It is a conceptual diagram of the optical carrier generation | occurrence | production mechanism of an organic material. It is a conceptual diagram of the optical carrier generation | occurrence | production mechanism of an inorganic material. It is a figure showing the layer structure of the electrophotographic photosensitive member used for embodiment of this invention. It is a figure showing another layer structure of the electrophotographic photosensitive member used for embodiment of this invention. It is a figure showing another layer structure of the electrophotographic photosensitive member used for embodiment of this invention. It is a figure which shows the state of the dispersion liquid when dispersion time is short. It is a figure which shows the state of the dispersion liquid when dispersion time is long. It is a figure which shows an average particle diameter and a particle size distribution about the dispersion liquid of FIG. 1 is a schematic diagram for explaining an electrophotographic process and an image forming apparatus according to an embodiment of the present invention. 1 is a schematic diagram for explaining a tandem-type full-color image forming apparatus according to an embodiment of the present invention. FIG. FIG. 3 is a diagram for explaining a process cartridge for an image forming apparatus according to an embodiment of the present invention. 4 is a diagram illustrating an XD spectrum of titanyl phthalocyanine synthesized in Synthesis Example 1. FIG. It is a figure showing the XD spectrum of the dry powder of the water paste (wet cake). 10 is a test chart used in Example 11. FIG. 18 is a test chart used in Example 16. FIG. 42 is a test chart used in Example 33. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Static elimination lamp 3 Charging member 5 Image exposure part 6 Development unit 8 Registration roller 9 Transfer paper 10 Transfer charger 11 Separation charger 12 Separation claw 14 Fur brush 15 Cleaning blade 16Y, 16M, 16C, 16K Photoconductor 17Y, 17M, 17C, 17K Charging member 18Y, 18M, 18C, 18K Exposure unit 19Y, 19M, 19C, 19K Developing member 20Y, 20M, 20C, 20K Cleaning member 21Y, 21M, 21C, 21K Transfer brush 22 Transfer conveyance belt 23 Registration roller 24 Fixing Device 25Y, 25M, 25C, 25K Image forming element 26 Transfer paper 27Y, 27M, 27C, 27K Static elimination member 31 Conductive support 35 Charge generation layer 37 Charge transport layer 39 Intermediate layer 41 Protective layer 43 Charge blocking 45 moiré preventing layer 101 photosensitive member 102 charging unit 103 writing light 104 developing means 105 transfer member 106 transfer means 107 cleaning means 108 discharging means

Claims (20)

An electrostatic latent image carrier, means for charging the electrostatic latent image carrier, writing means for forming an electrostatic latent image by light irradiation, and developing the electrostatic latent image with toner to make it visible light neutralizing a developing unit for forming an image, a transfer unit that transfers the visible image onto a recording medium, the residual charge of the fixing means and said electrostatic latent image bearing member configured to fix the transferred image on the recording medium An electrostatic latent image carrier having a support and a photosensitive layer comprising at least an intermediate layer, a charge generation layer, and a charge transport layer on the support. In addition, the intermediate layer contains at least titanium oxide and / or zinc oxide , and the charge generation layer contains an organic charge generation material, and the writing means has emission intensity only in a wavelength region shorter than 450 nm. and, and titanium oxide contained in the intermediate layer and / Absorb the zinc oxide writing light, Ri writing means der for irradiating light of wavelength can be carriers generated, light source wavelength to be used in the charge-eliminating unit is only the short wavelength region than 450nm emission intensity the a, and the intermediate titanium oxide and / or zinc oxide is contained in the layer absorbs the discharging light, the image forming apparatus according to claim source der Rukoto wavelength can be carriers generated. The titanium oxide and / or zinc oxide, an image forming apparatus according to claim 1, characterized in that the titanium oxide and / or zinc oxide which is not surface-treated.   The image forming apparatus according to claim 1, wherein the charge generation layer has a transmittance of 10% to 25% for writing light. 4. The image forming apparatus according to claim 1, wherein the organic charge generating substance is an azo pigment represented by the following formula (I).
In the formula, Cp ₁ and Cp ₂ represent coupler residues. R ₂₀₁ and R ₂₀₂ each represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, or a cyano group, and may be the same or different. Cp ₁ and Cp ₂ are represented by the following formula (II):
In the formula, R ₂₀₃ represents a hydrogen atom, an alkyl group, or an aryl group. R ₂₀₄ , R ₂₀₅ , R ₂₀₆ , R ₂₀₇ and R ₂₀₈ each represent a hydrogen atom, a nitro group, a cyano group, a halogen atom, a halogenated alkyl group, an alkyl group, an alkoxy group, a dialkylamino group or a hydroxyl group, and Z is A group of atoms necessary for constituting a substituted or unsubstituted aromatic carbocyclic ring or a substituted or unsubstituted aromatic heterocyclic ring. The image forming apparatus according to claim 4, wherein Cp ₁ and Cp ₂ are different from each other.   The organic charge generating material has a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.542 mm) of CuKα, and further 9.4 °. , 9.6 °, 24.0 °, and the lowest angle diffraction peak at 7.3 °, the 7.3 ° peak and the 9.4 ° peak 4. The image forming apparatus according to claim 1, wherein the image forming apparatus is a titanyl phthalocyanine crystal that does not have a peak between them and further has no peak at 26.3 °.   The image forming apparatus according to claim 1, wherein the charge transport layer has a transmittance for writing light of 30% or more.   The image forming apparatus according to claim 1, further comprising a protective layer on the photosensitive layer.   The image forming apparatus according to claim 8, wherein the protective layer transmits 30% or more of the writing light. The image forming apparatus according to claim 8, wherein the protective layer includes at least one selected from inorganic pigments and metal oxides having a specific resistance of 10 ¹⁰ Ω · cm or more.   The protective layer is formed by curing at least a trifunctional or higher functional radical polymerizable monomer having no charge transport structure and a radical polymerizable compound having a monofunctional charge transport structure. Item 10. The image forming apparatus according to Item 8 or 9. 12. The image formation according to claim 11, wherein the radical polymerizable compound having a monofunctional charge transporting structure used in the protective layer is at least one of the following general formula (1) or (2). apparatus.
{In the formula, R ₁ represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, an aryl group which may have a substituent, a cyano group, a nitro group, Group, alkoxy group, —COOR ₇ (R ₇ is a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent or an aryl group which may have a substituent), halogen Carbonyl group or CONR ₈ R ₉ (R ₈ and R ₉ may have a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an aralkyl group which may have a substituent, or a substituent. Represents a good aryl group, which may be the same or different from each other, and Ar ₁ and Ar ₂ represent a substituted or unsubstituted arylene group, which may be the same or different. Ar ₃ and Ar ₄ represent a substituted or unsubstituted aryl group, and may be the same or different. X represents a single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted cycloalkylene group, a substituted or unsubstituted alkylene ether group, an oxygen atom, a sulfur atom, or a vinylene group. Z represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylene ether divalent group, or an alkyleneoxycarbonyl divalent group. m and n represent an integer of 0 to 3. } 13. The image forming apparatus according to claim 11, wherein the radical polymerizable compound having a monofunctional charge transporting structure used in the protective layer is at least one of the following general formula (3).
(Wherein, o, p and q are each an integer of 0 or 1, Ra represents a hydrogen atom or a methyl group, Rb and Rc represent a substituent other than a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, And s and t each represents an integer of 0 to 3. Za is a single bond, a methylene group, an ethylene group,
Represents. )   The image forming apparatus according to claim 11, wherein the protective layer curing means is heating or light energy irradiation means. 15. The image forming apparatus according to claim 1, wherein the intermediate layer includes a charge blocking layer and a moire preventing layer, and titanium oxide and / or zinc oxide is contained in the moire preventing layer. The charge blocking layer is made of an insulator material,
The image forming apparatus according to claim 15, wherein the charge blocking layer has a thickness of 0.1 μm or more and less than 2.0 μm.   The image forming apparatus according to claim 16, wherein the insulator material includes N-methoxymethylated nylon. The moire prevention layer further includes a binder resin,
18. The image forming apparatus according to claim 15, wherein a ratio of a volume of the titanium oxide and / or zinc oxide to a volume of the binder resin is 1 or more and 3 or less.   The image forming apparatus according to claim 1, comprising a plurality of the photoconductors, a plurality of the charging units, and a plurality of the writing units. At least said photosensitive member, said charging means and said writing means, the image forming apparatus according to any one of claims 1 to 19, characterized in that it is removably attached as a unit.