JP5499580B2 - Method for producing coating liquid for forming undercoat layer of electrophotographic photosensitive member, and electrophotographic photosensitive member - Google Patents

Description

The present invention resides in a method for producing a coating solution for forming an undercoat layer of an electrophotographic photoreceptor and an electrophotographic photoreceptor having at least an undercoat layer and a photosensitive layer formed from the coating solution for forming an undercoat layer.
More specifically, in a method for producing a coating solution for forming an undercoat layer containing at least inorganic particles, the dispersibility is good, the dispersion can be efficiently performed, and further, there is no contamination such as bead fragments or wear powder. A coating solution for forming an undercoat layer of a photographic photoreceptor can be obtained.

  Conventionally, inorganic photoconductive materials such as selenium, selenium-tellurium alloys, arsenic selenide, and cadmium sulfide have been widely used for electrophotographic photoreceptors. On the other hand, in recent years, an organic electrophotographic photosensitive member (OPC) that uses a low-pollution, easy-to-manufacture organic photoconductive material for a photosensitive layer has surpassed an inorganic electrophotographic photosensitive member, and absorbs light. Laminated photoconductors comprising a charge generation layer and a charge transport layer, which separate the function of generating charge and the function of transporting the generated charge, are the mainstream.

An electrophotographic photosensitive member has a basic structure in which a photosensitive layer is formed on a conductive substrate. An undercoat layer is provided between the photosensitive layer and the conductive substrate in order to eliminate image defects caused by charge injection from the conductive substrate and defects in the conductive substrate, improve adhesion to the photosensitive layer, and improve charging properties. Things have been done.
As the undercoat layer, for example, polyvinyl methyl ether, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, ethylene-acrylic acid copolymer, polyamide, casein, gelatin, polyethylene, polyester, phenol resin, vinyl chloride- It is known to use resin materials such as vinyl acetate copolymer, epoxy resin, polyvinyl pyrrolidone, polyvinyl pyridine, polyurethane, polyglutamic acid, and polyacrylic acid. Of these resin materials, an alcohol-soluble nylon resin is particularly preferable.

Furthermore, in order to improve electrical characteristics and image characteristics in a wide range of environments ranging from low temperature and low humidity to high temperature and high humidity, subbing in which inorganic particles such as alumina particles, titania particles, or zinc oxide particles are dispersed in the binder resin. The layers are known. (Patent Documents 1 and 2)
These undercoat layers are mainly formed in the state of a coating solution on a conductive substrate by a coating process such as dip coating, ring coating or spray coating.

Recently, with the trend toward higher performance of the undercoat layer, when inorganic particles are added, it has become desirable to be well dispersed. Furthermore, there is a demand for a method for producing a coating liquid for forming an undercoat layer that is free from bead fragments and wear powder and has excellent productivity and manageability.
A bead mill is generally known as a means for dispersing particles. Certainly, the bead mill is good at improving dispersibility, but it is unavoidable that bead fragments and wear powder are mixed because the beads and the material to be dispersed are dispersed by shearing. In particular, the beads are zirconia (Mohs hardness: 8-8.5) and the object to be dispersed is alumina (Mohs hardness: 9) or silicon carbide (modified Mohs hardness: 13). If the hardness is high, the amount of mixed beads and wear powder increases, which affects the image formed on the electrophotographic photosensitive member. In the case of a bead mill, since the beads are worn out, it is difficult to manage the beads.

In the case of using ultrasonic dispersion, there is no problem with mixing of wear particles of beads as in a bead mill, but the dispersion force is not as strong as the bead mill, and dispersion for a long time is required, resulting in poor productivity. Furthermore, ultrasonic transducers are easily degraded and difficult to manage.
On the other hand, high-pressure liquid collision is also known as a method for dispersing particles (Patent Documents 3 and 4). However, these are all intended to disperse organic particles such as fluorine atom-containing resin particles in the outermost surface layer of the photosensitive layer to prevent aggregation. However, it was not originally intended to disperse inorganic particles having a small particle diameter.

Japanese Patent Laid-Open No. 10-90930 JP-A-10-69116 JP 2005-62734 A JP 2005-157117 A

  The present invention has been made in view of the above-mentioned background art, and its problem is that in the method for producing a coating liquid for forming an undercoat layer containing inorganic particles, bead fragments and wear powder are not mixed, The object is to provide a method that is easy to manage and sufficiently dispersed.

As a result of intensive studies to solve the above-mentioned problems, the present inventor used a coating liquid for forming the undercoat layer in which inorganic particles were dispersed by high-pressure liquid collision, thereby allowing the fragments of beads and wear powder to be dispersed. The present inventors have found that the dispersibility can be improved without being mixed in, and the above problems can be solved, and the following invention has been completed.
The present invention relates to a method for producing a coating solution for forming an undercoat layer containing inorganic particles, which is used for an electrophotographic photosensitive member, and an inorganic particle dispersion obtained by high-pressure liquid collision between the inorganic particles and an organic solvent, and a binder resin The present invention resides in a method for producing a coating solution for forming an undercoat layer for an electrophotographic photosensitive member, which comprises mixing a solution .

The inorganic particles are preferably metal oxide particles, and by containing the metal oxide particles, electrical characteristics and image characteristics in a wide range of environments ranging from low temperature and low humidity to high temperature and high humidity can be improved.
In the present invention, the inorganic particles preferably have a volume average primary particle size of 100 nm or less. When the volume average particle size is within the above range, the effect of the stability of the coating solution is remarkably exhibited.

  Furthermore, the present invention resides in an electrophotographic photoreceptor having an undercoat layer and a photosensitive layer formed from the above undercoat layer forming coating solution on a conductive substrate.

  According to the method of the present invention, a coating solution for forming an undercoat layer is obtained that has excellent dispersibility of inorganic particles, is free of bead fragments and wear powder, is excellent in productivity, is stable, and is easy to manage. It is done. The electrophotographic photosensitive member having the undercoat layer formed from the undercoat layer forming coating solution of the present invention can provide a good image.

Embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is an example of embodiments of the present invention, and is not limited to these contents.
The electrophotographic photoreceptor of the present invention is characterized by having an undercoat layer and a photosensitive layer on a conductive substrate. In the case where the photosensitive layer of the electrophotographic photoreceptor is a laminated type described later, it has a charge generation layer and a charge transport layer on the undercoat layer. In addition, when the photosensitive layer of the electrophotographic photosensitive member is a single layer type, which will be described later, in addition to the components used for the charge generating layer and the charge transporting layer of the laminated photosensitive member, an electron is formed on the undercoat layer. It is common to use a transport material.

[Underlayer]
In the electrophotographic photoreceptor of the present invention, an undercoat layer is provided.
The undercoat layer is a layer that is located between the conductive substrate and the photosensitive layer closest to the conductive substrate, has substantially no charge generation capability, has insulating properties, and has a charge transport capability. .
The undercoat layer of the present invention is formed by applying an undercoat layer forming coating solution, and the coating solution contains an organic solvent, inorganic particles, and a binder resin.

-Binder resin The undercoat layer contains a binder resin. As the binder resin, any of a thermoplastic resin, a thermosetting resin, and a photocurable resin can be used, but an alcohol-soluble polyamide resin is preferable in terms of good image characteristics and environmental characteristics. Here, the “alcohol-soluble polyamide resin” means, in the present invention, a polyamide that dissolves in methanol at a temperature of any one of a temperature range from 20 ° C. to the boiling point of methanol at a concentration of at least 3% by mass. Refers to resin.

  Such alcohol-soluble polyamide resins include a modified type and a copolymer type, both of which can be preferably used in the present invention. Examples of the modified type include Nylon 6 N-methyl modified, Nylon 6 methoxymethyl modified, Nylon 8 N-ethyl modified, Nylon 8 ethoxymethyl modified, etc. Among them, nylon 6 methoxymethyl Modified products are preferred.

  Examples of the copolymer type include copolymers such as 6 nylon, 8 nylon, 11 nylon, 12 nylon, 66 nylon, 610 nylon, 612 nylon, and 620 nylon. Among these, 6/66/11 copolymer nylon, 6 Ternary or quaternary copolymer nylons such as / 66/12 copolymer nylon, 6/66/610 copolymer nylon, and 6/66/610/12 copolymer nylon are preferable.

Furthermore, an alcohol-soluble polyamide resin which is a copolymer nylon as described above and has a diamine ring having a cyclohexyl ring which may have a substituent as a repeating unit is particularly preferable in terms of image characteristics and coating solution stability. preferable.
Along with the diamine compound having a cyclohexyl ring which may have a substituent, the following may be mentioned as preferred examples of what is included in the copolymerized polyamide resin as a repeating unit. That is, examples of the diamine component include alkylene diamines such as hexamethylene diamine, and examples of the dicarboxylic acid component include succinic acid, adipic acid, hexamethylene dicarboxylic acid, octamethylene dicarboxylic acid, decamethylene dicarboxylic acid, and octadecamethylene. Examples include alkylene dicarboxylic acids such as dicarboxylic acids. Examples of the component containing an amino group and a carboxyl group in one molecule include amino acids, and examples of the cyclic amide component include lactams such as γ-butyrolactam, δ-valerolactam, and ε-caprolactam.

  The number average molecular weight of the polyamide resin is not particularly limited, but is preferably in the range of 5,000 to 50,000, and more preferably in the range of 10,000 to 30,000. If the number average molecular weight is too large, the solubility in the coating solution for forming the undercoat layer may decrease, or the time required for coating formation of the undercoat layer may be increased. Since formation of the undercoat layer having strength may be difficult, it is not preferable.

Inorganic particles In the present invention, inorganic particles are contained in the undercoat layer, but as inorganic particles,
Metal oxide particles are preferable, and examples include silicon oxide, aluminum oxide, titanium oxide, tin oxide, zinc oxide, iron oxide, nickel oxide, antimony oxide, strontium titanate, calcium titanate, and barium titanate. Particularly preferred are titanium oxide and zinc oxide.

As for the particle diameter of the inorganic particles, the volume average primary particle diameter is preferably 100 nm or less, preferably 80 nm or less, particularly preferably 50 nm or less, from the viewpoint of the stability of the coating liquid, electrical characteristics and the like. When the particle diameter of the metal oxide particles is too large, the stability of the coating solution may be deteriorated. On the other hand, if it is too small, it is difficult to handle.
The ratio of the inorganic particles to the binder resin can be arbitrarily selected, but from the viewpoint of the stability of the coating liquid, electrical characteristics and image characteristics, 0.5 to 6 parts by mass with respect to 1 part by mass of the total resin. The range of is preferable. Especially preferably, it is the range of 0.8 mass part to 4 mass parts. When there are too many inorganic particles, the image characteristics and the stability of the coating solution may be deteriorated, and when they are too few, the electric characteristics may be deteriorated.

-Organic solvent As an organic solvent used for the coating liquid for undercoat layer formation, alcohols, such as methanol, a propanol, and butanol, toluene, and these mixtures are used suitably.
-Other components In addition to the undercoat layer of the electrophotographic photosensitive member of the present invention, additives such as an antioxidant and a leveling agent, a conductive agent, and other resins may be added as necessary.

-Manufacturing method of undercoat layer The coating liquid for undercoat layer formation contains an inorganic particle, and is obtained by disperse | distributing an inorganic particle by a high pressure liquid collision. At this time, the coating solution may be prepared by mixing an organic solvent and a binder resin, and then dispersing inorganic particles by high-pressure liquid collision, or dispersing inorganic particles by high-pressure liquid collision of inorganic particles and organic solvent. After preparing the liquid, the binder resin may be mixed and adjusted. At this time, the binder resin is preferably prepared in advance as a binder resin solution dissolved in an organic solvent. In consideration of thermal aggregation of inorganic particles or cleaning of a machine after work, it is preferable to mix an inorganic particle dispersion obtained by high-pressure liquid collision of inorganic particles and an organic solvent and a binder resin solution.

In addition, it is preferable from the viewpoint of dispersibility that the inorganic particles and the solvent are preliminarily mixed with an ultrasonic wave, a ball mill or the like before colliding with the high pressure liquid.
The pressure of the high-pressure liquid collision is 10 Mpa or more, preferably 20 Mpa or more and 100 MPa or less, preferably 80 Mpa or less. When the pressure is 10 MPa or less, the dispersion force is not sufficient, and when it exceeds 100 MPa, an apparatus that can output 100 MPa or more becomes expensive, which is not preferable in terms of cost.

The number of collision passes may be one, but in order to disperse more sufficiently, it is preferably a plurality of times, and more preferably 5 times or more. Moreover, since the heat | fever which arises at the time of a liquid collision accumulates when too much, it is 20 times or less, Preferably 15 times or less is desirable.
The thickness of the undercoat layer is usually about 0.1 μm to 30 μm, preferably 0.3 μm to 15 μm, and more preferably 0.5 μm to 10 μm. If the film thickness is too large, the electrical characteristics may deteriorate, and if it is too small, the image characteristics may deteriorate.

As long as the coating solution for forming the undercoat layer can be applied to a certain degree of uniformity, any coating method may be used, but a dip coating method, a spray coating method, a nozzle coating method, a blade coating, etc. are usually used. It is preferable to apply according to the method, and among them, the dip coating method is preferable in terms of excellent production efficiency.
As an example of the dip coating method, a binder resin, metal oxide particles, and other components as required are added to the solvent / dispersion medium, and the total solid content is preferably 1 to 50 with respect to the entire coating solution. % By mass, particularly preferably 5 to 35% by mass. The viscosity of the coating solution is preferably 1.0 mPa · s or more, particularly preferably 3.0 mPa · s or more, and the upper limit is preferably adjusted to 100 mPa · s or less, particularly preferably 50 mPa · s or less. The coating liquid for layer formation is adjusted.

[Conductive substrate]
As the conductive substrate used in the electrophotographic photoreceptor of the present invention, for example, a metal material such as aluminum, aluminum alloy, stainless steel, copper, or nickel, or conductive powder such as metal, carbon, or tin oxide is added. Mainly used are a resin material imparted with conductivity, or a resin, glass, paper, or the like obtained by depositing or coating a conductive material such as aluminum, nickel, or ITO (indium tin oxide) on its surface. As a form, a drum shape, a sheet shape, a belt shape or the like is used. A conductive material having an appropriate resistance value may be applied to a conductive substrate made of a metal material in order to control conductivity, surface properties, etc. or to cover defects.

When a metal material such as an aluminum alloy is used as the conductive substrate, it may be used after an anodized film is applied. When an anodized film is applied, it is desirable to perform a sealing treatment by a known method. For example, an anodic oxidation film is formed by anodizing in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, boric acid, sulfamic acid, etc. give. In the case of anodic oxidation in sulfuric acid, sulfuric acid concentration is 100 g / L or more and 300 g / L or less, dissolved aluminum concentration is 2 g / L or more and 15 g / L or less, liquid temperature is 15 ° C. or more and 30 ° C. or less, and electrolysis voltage is 10 V or more and 20 V. Hereinafter, the current density is preferably set in the range of 0.5 A / dm ² or more and 2 A / dm ² or less, but is not limited to the above conditions.

It is preferable to perform a sealing treatment on the anodic oxide film thus formed. The sealing treatment may be performed by a known method, for example, a low-temperature sealing treatment in which the sealing material is immersed in an aqueous solution containing nickel fluoride as a main component, or a high temperature that is immersed in an aqueous solution containing a sealing agent. A sealing treatment is preferably performed.
The concentration of the nickel fluoride aqueous solution used in the case of the low-temperature sealing treatment can be selected as appropriate, but more preferable results are obtained when it is used in the range of 3 g / L to 6 g / L. In order to smoothly proceed with the sealing treatment, the treatment temperature is 25 ° C. or more and 40 ° C. or less, preferably 30 ° C. or more and 35 ° C. or less, and the nickel fluoride aqueous solution pH is 4.5 or more and 6.5. Hereinafter, the treatment is preferably performed in the range of 5.5 to 6.0. As the pH adjuster, oxalic acid, boric acid, formic acid, acetic acid, sodium hydroxide, sodium acetate, aqueous ammonia and the like can be used. The treatment time is preferably in the range of 1 minute to 3 minutes per 1 μm of film thickness. In order to further improve the physical properties of the film, cobalt fluoride, cobalt acetate, nickel sulfate, a surfactant or the like may be added to the nickel fluoride aqueous solution. Subsequently, it is washed with water and dried to finish the low temperature sealing treatment.

  As the sealing agent in the case of the above high-temperature sealing treatment, an aqueous metal salt solution such as nickel acetate, cobalt acetate, lead acetate, nickel acetate-cobalt, barium nitrate can be used, and it is particularly preferable to use nickel acetate. . The concentration in the case of using an aqueous nickel acetate solution is preferably 5 g / L or more and 20 g / L or less. The treatment temperature is 80 ° C. or higher and 100 ° C. or lower, preferably 90 ° C. or higher and 98 ° C. or lower. The pH of the nickel acetate aqueous solution is preferably 5.0 or higher and 6.0 or lower.

Here, aqueous ammonia, sodium acetate, or the like can be used as the pH adjuster. The treatment time is 10 minutes or longer, preferably 20 minutes or longer. In this case as well, sodium acetate, organic carboxylic acid, anionic and nonionic surfactants may be added to the nickel acetate aqueous solution in order to improve the film properties. Subsequently, it is washed with water and dried to finish the high temperature sealing treatment. When the average film thickness is thick, stronger sealing conditions are required due to the higher concentration of the sealing liquid and high temperature / long-time treatment. Accordingly, productivity is deteriorated and surface defects such as spots, dirt, and dusting are likely to occur on the coating surface. From such a point, it is preferable that the average film thickness of the anodic oxide coating is usually 20 μm or less, particularly 7 μm or less.

  The surface of the conductive substrate may be smooth, or may be roughened by using a special cutting method or polishing treatment. Further, it may be roughened by mixing particles having an appropriate particle diameter with the material constituting the conductive substrate. In order to reduce the cost, it is possible to use the drawing tube as it is without cutting. Especially when using non-cutting aluminum supports such as drawing, impact processing, ironing, etc., the process eliminates dirt, foreign matter, etc. on the surface, small scratches, etc., and a uniform and clean support can be obtained. Therefore, it is preferable.

[Photosensitive layer]
As a type of the photosensitive layer, a charge generation material and a charge transport material are present in the same layer and are dispersed in a binder resin, a charge generation layer in which a charge generation material is dispersed in a binder resin, and a charge. A functional separation type (laminated type) composed of two layers of a charge transport layer in which a transport material is dispersed in a binder resin can be mentioned, but any type may be used.

In addition, as the laminated photosensitive layer, a charge generation layer and a charge transport layer are laminated in this order from the conductive substrate side, and conversely, a charge transport layer and a charge generation layer are laminated in that order. There are reverse laminated type photosensitive layers, and any of them can be adopted, but a forward laminated type photosensitive layer capable of exhibiting the most balanced photoconductivity is preferable.
-Charge generation layer in the multilayer type In the case of the multilayer type in which the photosensitive layer is functionally separated, a charge generation layer is provided on the conductive substrate via an undercoat layer, and the charge generation layer contains a charge generation material. .

As the charge generating substance, a phthalocyanine pigment, a bisazo pigment, and a trisazo pigment are preferable in terms of sensitivity.
In the present invention, the “phthalocyanine pigment” refers to a compound having a phthalocyanine skeleton. Specific examples include metal-free phthalocyanines; phthalocyanines having a planar molecular structure such as copper phthalocyanine, zinc phthalocyanine, lead phthalocyanine; oxytitanium phthalocyanine, oxyvanadium phthalocyanine, chloroaluminum phthalocyanine, chlorogallium phthalocyanine, chloroindium phthalocyanine, hydroxygallium Phthalocyanines whose molecules have a shuttlecock structure; phthalocyanines whose molecules have a top structure such as dichlorotin phthalocyanine, dichlorosilicon phthalocyanine, dihydroxytin phthalocyanine, dihydroxysilicon phthalocyanine; and the like.

  When the phthalocyanine pigment according to the present invention is composed of a single type of phthalocyanine compound, a phthalocyanine compound having a shuttlecock structure is desirable in view of the characteristics as an electrophotographic photoreceptor. Further, among phthalocyanine compounds having a shuttlecock structure, since the characteristics as an electrophotographic photoreceptor are generally good, the central metal of the phthalocyanine compound molecule takes the form of an oxide, chloride or hydroxide. In view of the ease of the structure of the phthalocyanine crystal, the central metal is more preferably in the form of an oxide. As a specific example, oxytitanium phthalocyanine or oxyvanadium phthalocyanine is preferable, and oxytitanium phthalocyanine is more preferable.

Examples of such oxytitanium phthalocyanine include, but are not limited to, those having a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) of 27.3 ° in X-ray diffraction by CuKα rays. is not. The crystal type of oxytitanium phthalocyanine is generally called Y type or D type. For example, FIG. 2 of Japanese Patent Laid-Open No. 62-067094 (referred to as type II in the same publication) ), FIG. 1 of Japanese Patent Laid-Open No. 2-008256, FIG. 1 of Japanese Patent Laid-Open No. 64-082045, Journal of Electrophotographic Society Vol. 92 (issued in 1990), No. 3, pages 250-258 (published) It is shown as Y-type). This crystalline oxytitanium phthalocyanine is characterized by having a maximum diffraction peak at 27.3 °, but normally has peaks at 7.4 °, 9.7 °, and 24.2 °.

  The intensity of the diffraction peak may vary depending on the crystallinity, the orientation of the sample, and the measurement method. However, in the measurement by the Bragg-Brentano concentration method usually used for X-ray diffraction of powder crystals, Type oxytitanium phthalocyanine has a maximum diffraction peak at 27.3 °. In addition, when measured by a thin film optical system (generally called thin film method or parallel method), 27.3 ° may not be the maximum diffraction peak depending on the state of the sample. This is probably because it is oriented in the direction.

  A phthalocyanine pigment may use only a single compound, and may be used in a some mixed state. As a method of forming a mixed state in the phthalocyanine pigment or the crystalline state here, the respective constituent elements may be used after mixing, or the production / treatment process of the phthalocyanine pigment such as synthesis, pigmentation, crystallization, etc. A mixed state may be generated in. As such treatment, acid paste treatment, grinding treatment, solvent treatment and the like are used. Moreover, the said other pigment may be used together with the phthalocyanine pigment.

  The charge generation material is used alone or in combination with a binder resin to form the charge generation layer. Binder resins for the charge generation layer include polymers or copolymers of vinyl compounds such as styrene, vinyl acetate, vinyl chloride, acrylic acid ester, methacrylic acid ester, vinyl alcohol, ethyl vinyl ether, polyvinyl acetal, polycarbonate, polyester, polyamide , Polyurethane, cellulose ether, phenoxy resin, silicon resin, epoxy resin, and the like. Polyvinyl acetal is preferable in terms of dispersibility of the phthalocyanine pigment.

  The ratio between the charge generation material and the binder resin is not particularly limited, but generally, 5 to 500 parts by mass, preferably 20 to 300 parts by mass of the binder polymer is used with respect to 100 parts by mass of the charge generation material. The charge generation layer may be a vapor deposition film of the charge generation material. In addition, the charge generation layer may contain various additives such as a leveling agent, an antioxidant, and a sensitizer for improving coating properties as necessary.

  When forming the charge generation layer, the charge generation material is dispersed or dissolved in an appropriate dispersion medium using a ball mill, ultrasonic disperser, paint shaker, attritor, sand grinder, bead mill, etc., and a binder resin is added as necessary. Then, the charge generation layer forming coating solution is prepared, and this coating solution is applied and formed. When the charge generating material is used alone, the coating solution may be prepared and applied without adding a binder to the dispersion, or may be formed by a method such as vapor deposition or sputtering. The film thickness of the charge generation layer is usually 0.05 to 5 μm, preferably 0.1 to 2 μm.

-Charge transport layer in stacked type In the forward stacked type photosensitive layer, a charge transport layer is provided on the charge generation layer. Examples of the charge transport material in the charge transport layer include polymer compounds such as polyvinylcarbazole, polyvinylpyrene, and polyacenaphthylene; diphenoquinone derivatives, aromatic nitro compounds such as 2,4,7-trinitrofluorenone, carbazole derivatives, and indoles. Derivatives, imidazole derivatives, oxazole derivatives, pyrazole derivatives, oxadiazole derivatives, pyrazoline derivatives, thiadiazole derivatives and other heterocyclic compounds, aniline derivatives, hydrazone derivatives, arylamine derivatives, stilbene derivatives, butadiene derivatives, enamine compounds, these compounds A polymer having a plurality of bonded groups or a group composed of these compounds in the main chain or side chain can be used. In addition, you may use the said charge transport material in mixture of 2 or more types.

  As the binder resin for the charge transport layer, a resin having good compatibility with the above charge transport material and that does not crystallize or phase separate after formation of the coating film is preferable. Examples thereof include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, vinyl chloride, acrylic acid ester, methacrylic acid ester, vinyl alcohol, ethyl vinyl ether, polyvinyl acetal, polycarbonate, polyarylate, polyester, polysulfone. , Polyphenylene oxide, polyurethane, cellulose ester, cellulose ether, phenoxy resin, silicon resin, epoxy resin and the like, and polyester or polycarbonate is preferable.

    The content ratio of the charge transport material and the binder resin is preferably 10 parts by mass or more, and particularly preferably 30 parts by mass or more with respect to 100 parts by mass of the binder resin. Moreover, 200 mass parts or less are preferable, and 150 mass parts or less are especially preferable. If the content ratio of the binder resin is too large, the electrical characteristics may be deteriorated. In addition, the charge transport material is usually compatible with the binder resin and has a high influence on the mechanical properties of the charge transport layer. Therefore, if the content ratio of the charge transport material becomes too large, the mechanical strength of the photosensitive layer decreases. There is a case.

  In order to improve the film forming property, flexibility, coating property, stain resistance, gas resistance, light resistance, etc. in the charge transport layer, or to further improve the mechanical strength of the photosensitive layer, a well-known plasticizer, It is also preferable to add additives such as a lubricant, a dispersion aid, an antioxidant, an ultraviolet absorber, an electron-withdrawing compound, a dye, a pigment, a sensitizer, a leveling agent, a stabilizer, a fluidity-imparting agent, and a crosslinking agent. . Examples of the antioxidant include hindered phenol compounds and hindered amine compounds. Examples of dyes and pigments include various pigment compounds and azo compounds. Examples of leveling agents include silicone oil and fluorine-based surfactants.

  Electron-withdrawing compounds include tetracyanoquinodimethane, dicyanoquinomethane, cyano compounds such as aromatic esters having a dicyanoquinovinyl group, nitro compounds such as 2,4,6-trinitrofluorenone, and condensation of perylene. Polycyclic aromatic compounds, diphenoquinone derivatives, quinones, aldehydes, ketones, esters, acid anhydrides, phthalides, metal complexes of substituted and unsubstituted salicylic acid, metal salts of substituted and unsubstituted salicylic acid, aromatic carboxylic acids And metal salts of aromatic carboxylic acids. Preferably, cyanide compounds, nitro compounds, condensed polycyclic aromatic compounds, diphenoquinone derivatives, metal complexes of substituted and unsubstituted salicylic acid, metal salts of substituted and unsubstituted salicylic acid, metal complexes of aromatic carboxylic acid, aromatic carboxylic acid Metal salts are used.

Although the formation method of a charge transport layer is mentioned later, the film thickness of a charge transport layer is 10 micrometers-50 micrometers normally, Preferably it is 13 micrometers-35 micrometers.
-Photosensitive layer in a single layer type When the photosensitive layer is a single layer type, a single photosensitive layer is provided on a conductive substrate via an undercoat layer. The charge transport material or the electron withdrawing material may be included. In addition, there may be a plurality of electron transport materials such as perylene pigments and charge generation materials.
At this time, the particle size of the charge generating material needs to be sufficiently small, and is preferably 1 μm or less, more preferably 0.5 μm or less. The amount of the charge generating material dispersed or dissolved in the single-layer type photosensitive layer is, for example, in the range of 0.5 to 50% by mass with respect to the entire photosensitive layer. If the amount is too small, sufficient sensitivity cannot be obtained. If the amount is too large, there are problems such as a decrease in chargeability and a decrease in sensitivity. Particularly preferably, it is used in the range of 1 to 20% by mass. The content ratio of the charge transport material and the binder resin is preferably 30 parts by mass or more, and particularly preferably 40 parts by mass or more with respect to 100 parts by mass of the binder resin. Moreover, 80 mass parts or less are preferable, and 60 mass parts or less are especially preferable.

  As in the case of the charge transport layer in the multilayer photosensitive layer, if the content ratio of the binder resin is too large, the electrical characteristics may be deteriorated. In addition, since the charge transport material is usually compatible with the binder resin, if the content ratio of the charge transport material is too large, the mechanical strength of the photosensitive layer may be lowered. Furthermore, the same additive as that which can be blended in the charge transport layer in the multilayer photosensitive layer can be used in the single-layer photosensitive layer.

The coating solution obtained by blending the predetermined components is applied on the undercoat layer and dried to form a single-layer type photosensitive layer. The film thickness is usually 2 μm to 70 μm, preferably 10 μm to 45 μm, Especially preferably, it is 20 micrometers-35 micrometers.
[Method for producing photosensitive layer]
Solvents and dispersion media used when applying the above layers include butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, acetone, methyl ethyl ketone, cyclohexanone, benzene, toluene, Xylene, chloroform, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethane, dichloromethane, tetrahydrofuran, dioxane, methyl alcohol , Ethyl alcohol, isopropyl alcohol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cellosolve, and the like. These solvents may be used alone or in combination of two or more.

  As a method for coating and forming a photosensitive layer, a spray coating method, a bar coater method, a blade method, a roll coater method, a wire bar coating method, a knife coater coating method, which are usually used for coating and forming a photosensitive layer of an electrophotographic photosensitive member. Any coating method such as a spiral coating method, a ring coating method, a dip coating method, or a spinner coating method can be used. A photosensitive layer is obtained by applying and then drying the coating solution.

  Spray coating methods include air spray, airless spray, electrostatic air spray, electrostatic airless spray, rotary atomizing electrostatic spray, hot spray, and hot airless spray. Considering the degree of conversion, adhesion efficiency, etc., in the rotary atomizing electrostatic spray, the conveying method disclosed in the republished Japanese Patent Publication No. 1-805198, that is, the cylindrical workpiece is rotated while the axial direction is spaced. By using a continuous conveyance method, it is possible to obtain an electrophotographic photoreceptor excellent in film thickness uniformity with high overall deposition efficiency.

Examples of the spiral coating method include a method using a liquid injection coating machine or a curtain coating machine disclosed in Japanese Patent Laid-Open No. 52-119651, and paint from a minute opening disclosed in Japanese Patent Laid-Open No. 1-2231966. A method of flying continuously in a streak shape, a method using a multi-nozzle body disclosed in JP-A-3-193161, and the like are used.
As an example of the dip coating method, the following charge transport layer coating formation procedure may be mentioned. Using a charge transport material, a binder resin, a solvent, etc., the total solid concentration is preferably 15% by mass or more, particularly preferably 40% by mass or less, and the viscosity is preferably 50 mPa · s or more, particularly preferably 100 mPa · s. A coating solution for forming a charge transport layer is prepared at s or more, preferably 700 mPa · s or less, particularly preferably 500 mPa · s or less. Here, the viscosity of the coating solution is substantially determined by the molecular weight of the binder resin, but as described above, when the molecular weight is too low, the mechanical strength of the photosensitive layer is lowered, so that the binder has a molecular weight that does not impair this. It is preferable to use a resin. A photosensitive layer such as a charge transport layer is formed by a dip coating method using the coating solution thus prepared.

Thereafter, the coating film is dried, and the drying temperature and drying time are adjusted so that necessary and sufficient drying is performed. A drying temperature is 100-250 degreeC normally, Preferably it is 110-170 degreeC, More preferably, it is the range of 115-140 degreeC. Examples of the drying method include a method using a hot air dryer, a steam dryer, an infrared dryer, a far infrared dryer and the like.
Further, the photosensitive layer of the electrophotographic photoreceptor of the present invention may be a single-layer type or a functionally separated laminated type, and is a known plasticizer for improving the film formability, flexibility, coatability, and mechanical strength. , An antioxidant, an ultraviolet absorber, and a leveling agent may be contained.

Other functional layers An overcoat layer may be used on the photosensitive layer in order to improve mechanical properties and gas resistant properties such as ozone and NOx. Furthermore, it goes without saying that an adhesive layer, an intermediate layer, a transparent insulating layer, and the like may be provided as necessary.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention still in detail, this invention is not limited to these, unless the summary is exceeded. In addition, "part" used in an Example shows a mass part, when there is no notice.
[Example 1]
[Preparation of undercoat layer forming coating solution P]
Alumina particles (trade name: Aluminum Oxide C, manufactured by Nippon Aerosil Co., Ltd., particle size: 13
nm) 8 parts by mass was mixed with 92 parts by mass of a mixed solvent of methanol / 1-propanol = 7/3, and preliminarily dispersed with an ultrasonic wave for 5 minutes. Next, this premixed slurry was subjected to collision of 30 Mpa 10 times with a nano maker (manufactured by Tokai Co., Ltd.), whereby 300 L of inorganic particle dispersion was obtained in 10 minutes. When this dispersion was evaluated for the amount of Zr mixed by fluorescent X-ray analysis, Zr was below the detection limit (0.004%: alumina).

Further, the inorganic particle dispersion is divided by the absorption at the absorption of 400 cm ^-1 at 1000 cm ^-1, is 6.1%, were well dispersed dispersed.
A binder resin solution obtained by dissolving 8 parts by mass of a random copolymer polyamide resin represented by the following structural formula in 92 parts by mass of methanol / 1-propanol = 7/3 mixed solvent, and an inorganic particle dispersion prepared as described above And an undercoat layer forming coating solution (coating solution P) was prepared by applying ultrasonic waves for 1 hour.

[Comparative Example 1]
A slurry in which 8 parts by mass of alumina particles used in Example 1 were mixed with 92 parts by mass of a mixed solvent of methanol / 1-propanol = 7/3 was mixed with a small bead mill UAM015 (manufactured by Kotobuki Kogyo Co., Ltd.) and 0.05 mmΦ zirconia. An inorganic particle dispersion was obtained by performing 5 passes with beads. When the amount of Zr mixed in this inorganic particle dispersion was evaluated by fluorescent X-ray analysis in the same manner as in Example 1, a considerable amount of 1.5 wt% (with respect to alumina) was detected.

[Comparative Example 2]
32 kg of a mixed slurry of 8 parts by mass of alumina particles and 92 parts by mass of a mixed solvent of methanol / 1-propanol = 7/3 used in Example 1 was dispersed for 5 hours with an ultrasonic cleaner to obtain an inorganic particle dispersion. The value obtained by dividing the absorption at 1000 cm ⁻¹ by the absorption at 400 cm ⁻¹ of this inorganic particle dispersion was 7.6%.

[Example 2]
<Preparation of coating solution for charge generation layer formation>
10 parts by mass of a charge generation material represented by the following formula, 5 parts by mass of polyvinyl butyral (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name # 6000-C), 5 parts by mass of phenoxy resin, 400 parts by mass of 1,2-dimethoxyethane A coating solution for forming a charge generation layer (coating solution Q) was prepared by pulverizing and dispersing with a sand grind mill.

<Preparation of charge transport layer forming coating solution>
100 parts by mass of a polycarbonate resin having two repeating structural units shown below (monomer molar ratio = 1: 1),

  95 parts by mass of the hydrazone compound shown below,

And 1.5 parts by mass of the cyanide compound shown below

Were mixed with stirring to produce a charge transport layer forming coating solution (coating solution R).
<Creation of electrophotographic photoreceptor>
A cylinder obtained by anodizing a surface of aluminum having a length of 354.3 mm and an outer diameter of 30 mm was dip coated on the coating liquid P, and an undercoat layer was provided so that the dry film thickness was 1.0 μm. Next, an aluminum cylinder provided with an undercoat layer was dip-coated in the coating liquid Q, and a charge generation layer was provided so that the dry film thickness was 0.325 μm. Next, an aluminum cylinder provided with the charge generation layer was dip-coated in the coating solution R, and a charge transport layer was provided so that the dry film thickness was 19.5 μm, thereby producing an electrophotographic photoreceptor.

  When this photoconductor was mounted on a Z-810 manufactured by Sharp Corporation, a black solid image and a halftone image were printed, and a fine white spot was evaluated, the fine white spot was not seen at all and was good.

Claims (4)

A method for producing a coating solution for forming an undercoat layer containing inorganic particles used in an electrophotographic photosensitive member, wherein an inorganic particle dispersion obtained by high-pressure liquid collision of the inorganic particles and an organic solvent is mixed with a binder resin solution A method for producing a coating solution for forming an undercoat layer of an electrophotographic photosensitive member.   2. The method for producing a coating solution for forming an undercoat layer of an electrophotographic photosensitive member according to claim 1, wherein the inorganic particles are metal oxide particles.   The method for producing a coating solution for forming an undercoat layer of an electrophotographic photosensitive member according to claim 1 or 2, wherein the inorganic particles have a volume average primary particle size of 100 nm or less.   An electrophotographic photoreceptor comprising an undercoat layer formed from the coating solution for forming an undercoat layer according to any one of claims 1 to 3 and a photosensitive layer on a conductive substrate.