JP2016153854A - Method for producing coating liquid for undercoat layer of electrophotographic photoreceptor, and method for producing electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a coating liquid for an undercoat layer of an electrophotographic photoreceptor which has excellent dispersibility of inorganic particles.SOLUTION: A method for producing a coating liquid for an undercoat layer of an electrophotographic photoreceptor which contains a resin, inorganic particles and an organic solvent includes: a step of mixing a resin and an organic solvent to prepare a solution; and a step of adding slurry of inorganic particles to the solution to prepare a coating liquid for an undercoat layer. The viscosity of the solution is 100 mPa s or less.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing an undercoat layer coating solution for an electrophotographic photoreceptor, and a method for producing an electrophotographic photoreceptor.

  Among electrophotographic photosensitive members, an electrophotographic photosensitive member using an organic photoconductive substance (charge generating substance) has good film forming properties and can be produced by coating. Therefore, an electrophotographic photosensitive member having high productivity can be provided. Has advantages.

  An electrophotographic photoreceptor generally has a support and a photosensitive layer formed on the support. In many cases, an undercoat layer is provided between the support and the photosensitive layer for the purpose of improving the adhesion between the support and the photosensitive layer, and suppressing charge injection from the support to the photosensitive layer. .

  The properties of the undercoat layer are required to be low in resistance so that a current flows from the photosensitive layer to the support, and to have a blocking property so that charges are not injected from the support to the photosensitive layer.

  In order to establish the above characteristics, an undercoat layer is known in which inorganic particles such as inorganic oxides such as alumina particles, titania particles, zinc oxide particles, and silica particles are dispersed in the undercoat layer. Patent Document 1 describes a technique for suppressing charge injection suppression by including metal oxide particles having a small particle diameter in an undercoat layer.

JP 2006-268011 A

  An undercoat layer containing inorganic particles is generally prepared by dispersing inorganic particles in a solution containing a binder resin and an organic solvent to prepare an undercoat layer coating solution. It is formed by forming and drying the coating film. However, as a result of the study by the present inventors, when the dispersibility of the inorganic particles is poor, the coating liquid for the undercoat layer is not uniformly applied, resulting in a coating film defect or an increase in surface roughness. Contrast reduction and black spots and fogging may occur on a white background.

  An object of the present invention is to provide a method for producing a coating solution for an undercoat layer of an electrophotographic photosensitive member having good dispersibility of inorganic particles. Another object of the present invention is to provide a method for producing an electrophotographic photoreceptor having an undercoat layer using the undercoat layer coating solution.

The present invention is a method for producing a coating solution for an undercoat layer of an electrophotographic photoreceptor containing a resin, inorganic particles and an organic solvent,
A step of preparing a solution by mixing a resin and an organic solvent, and a step of preparing a coating solution for an undercoat layer by adding a slurry of inorganic particles to the solution,
Have
The present invention relates to a method for producing an undercoat layer coating solution for an electrophotographic photosensitive member, wherein the solution has a viscosity of 100 mPa · s or less.

Further, the present invention is a method for producing an electrophotographic photoreceptor having a support, an undercoat layer formed on the support, and a photosensitive layer formed on the undercoat layer,
A method of preparing a coating solution for an undercoat layer by the method for producing a coating solution for an undercoat layer of the electrophotographic photoreceptor, and forming a coating film of the coating solution for the undercoat layer, and drying the coating film. Forming an undercoat layer;
The present invention relates to a method for producing an electrophotographic photosensitive member.

  ADVANTAGE OF THE INVENTION According to this invention, the method of manufacturing the coating liquid for undercoat layers of the electrophotographic photoreceptor with the favorable dispersibility of an inorganic particle can be provided. Further, it is possible to provide a method for producing an electrophotographic photoreceptor having an undercoat layer using the undercoat layer coating solution.

It is a figure explaining an example of a layer structure of an electrophotographic photosensitive member.

  The electrophotographic photoreceptor of the present invention has a support, an undercoat layer formed on the support, and a photosensitive layer formed on the undercoat layer. The photosensitive layer is formed by laminating a single layer type photosensitive layer containing a charge generation material and a charge transport material in a single layer, a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material. And a laminated photosensitive layer. A laminated photosensitive layer is preferred.

  FIG. 1 shows an example of the layer structure of the electrophotographic photosensitive member of the present invention. In FIG. 1, 101 is a support, 102 is an undercoat layer, 103 is a charge generation layer, and 104 is a charge transport layer.

[Support]
As a support body, what has electroconductivity (conductive support body) is preferable. For example, a support made of a metal or alloy such as aluminum, nickel, copper, gold, or iron can be used. A support in which a thin film of metal such as aluminum, silver, or gold is formed on an insulating support such as polyester resin, polycarbonate resin, polyimide resin, or glass, or a thin film of conductive material such as indium oxide or tin oxide is formed. A support is mentioned.

  The surface of the support may be subjected to electrochemical treatment such as anodic oxidation, wet honing treatment, blast treatment, cutting treatment, etc. in order to improve electrical characteristics and suppress interference fringes.

[Conductive layer]
A conductive layer may be provided between the support and the undercoat layer. The conductive layer is obtained by forming a coating film of a coating solution for conductive layer in which conductive particles are dispersed in a resin on a support and drying the coating film. Examples of the conductive particles include carbon black, acetylene black, metal powder such as aluminum, nickel, iron, nichrome, copper, zinc, and silver, and metal oxide powder such as conductive tin oxide and ITO. Can be mentioned.

  Examples of the resin include polyester resin, polycarbonate resin, polyvinyl butyral resin, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol resin, and alkyd resin.

  Examples of the solvent for the conductive layer coating solution include ether solvents, alcohol solvents, ketone solvents, and aromatic hydrocarbon solvents. The thickness of the conductive layer is preferably 0.2 μm or more and 40 μm or less, more preferably 1 μm or more and 35 μm or less, and even more preferably 5 μm or more and 30 μm or less.

[Undercoat layer]
An undercoat layer is formed between the support or conductive layer and the photosensitive layer.

  The undercoat layer 102 contains a resin and inorganic particles. Or the polymer of the composition containing resin and an inorganic particle are contained. The undercoat layer may further contain an electron transport material. In the present invention, the undercoat layer preferably contains a polymer of a composition containing a resin, an electron transport material, and a crosslinking agent. Moreover, you may add additives, such as a leveling agent, antioxidant, a dispersion | distribution adjuvant, a electrically conductive agent, etc. as needed.

  Another layer such as a second undercoat layer may be provided between the support and the undercoat layer or between the undercoat layer and the photoreceptor.

  The undercoat layer coating solution is produced as follows. First, the first step is characterized in that a solution is prepared by mixing a resin and an organic solvent, and the viscosity of the solution is 100 mPa · s or less. And it has the process of adding the slurry of an inorganic particle to this solution, and preparing the coating liquid for undercoat. This solution may further contain an electron transport material, a crosslinking agent, and a catalyst.

  Examples of the electron transport material include a quinone compound, an imide compound, a benzomidazole compound, and a cyclopentadienylidene compound. The electron transport material preferably has a polymerizable functional group such as a hydroxy group, a thiol group, an amino group, a carboxyl group, or a methoxy group. The polar group may be directly bonded to the skeleton structure responsible for electron transport or may be present in the side chain.

  Below, the compound shown by either of following formula (A-1)-(A-11) is shown as a specific example of an electron transport substance.

In formulas (A1) to (A11), R ^{11 to} R ¹⁶ , R ^{21 to} R ³⁰ , R ^{31 to} R ³⁸ , R ^{41 to} R ⁴⁸ , R ^{51 to} R ⁶⁰ , R ^{61 to} R ⁶⁶ , R ^{71 to} R ^{78, R 81 ~R 90, R} 91 ~R 98 ^is R 101 ^{to R 110 is} R 111 ^{to R 120} each independently represents a monovalent group represented by the following formula (alpha), a hydrogen atom, a cyano A group, a nitro group, a halogen atom, an alkoxycarbonyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic ring; One of the carbon atoms in the main chain of the alkyl group may be replaced with O, S, NH, or NR ¹²¹ (R ¹²¹ is an alkyl group). At least one of R ^{11 to} R ¹⁶ , at least one of R ^{21 to} R ³⁰ , at least one of R ^{31 to} R ³⁸ , at least one of R ^{41 to} R ⁴⁸ , at least one of R ^{51 to} R ⁶⁰ , At least one of R ^{61 to} R ⁶⁶ , at least one of R ^{71 to} R ⁷⁸ , at least one of R ^{81 to} R ⁹⁰ , at least one of R ^{91 to} R ⁹⁸ , at least one of R ^{101 to} R ¹¹⁰ , At least one of R ^{111 to} R ¹²⁰ has a monovalent group represented by the formula (α).

The substituent of the substituted alkyl group is an alkyl group, an aryl group, a halogen atom, or an alkoxycarbonyl group. The substituent of the substituted aryl group and the substituent of the substituted heterocyclic group are a halogen atom, a nitro group, a cyano group, an alkyl group, a halogen-substituted alkyl group, and an alkoxy group. Z ²¹ , Z ³¹ , Z ⁴¹ and Z ⁵¹ each independently represent a carbon atom, a nitrogen atom or an oxygen atom. When Z ²¹ is an oxygen atom, R ²⁹ and R ³⁰ do not exist, and when Z ²¹ is a nitrogen atom, R ³⁰ does not exist. When Z ³¹ is an oxygen atom, R ³⁷ and R ³⁸ do not exist, and when Z ³¹ is a nitrogen atom, R ³⁸ does not exist. If Z ⁴¹ is an oxygen atom ^{R 47} and ^{R 48} are ^absent, when ^{Z 41} is a nitrogen atom ^{R 48} is absent. When Z ⁵¹ is an oxygen atom, R ⁵⁹ and R ⁶⁰ do not exist, and when Z ⁵¹ is a nitrogen atom, R ⁶⁰ does not exist.

  In the formula (α), at least one of α, β, and γ is a group having a polymerizable functional group, and the polymerizable function is selected from the group consisting of a hydroxy group, a thiol group, an amino group, a carboxyl group, and a methoxy group. At least one group selected. l and m are each independently 0 or 1, and the sum of l and m is 0 or more and 2 or less.

α is an alkylene group having 1-6 atoms in the main chain, an alkylene group having 1-6 atoms in the main chain substituted with an alkyl group having 1-6 carbon atoms, or a main chain substituted with a benzyl group. An alkylene group having 1 to 6 atoms, an alkylene group having 1 to 6 atoms in the main chain substituted with an alkoxycarbonyl group, or an alkylene group having 1 to 6 atoms in the main chain substituted with a phenyl group . These groups may have a polymerizable functional group. One of the carbon atoms in the main chain of the alkylene group may be replaced with O, S, NR ¹²² (wherein R ¹²² represents a hydrogen atom or an alkyl group).

  β represents a phenylene group, an alkyl-substituted phenylene group having 1 to 6 carbon atoms, a nitro-substituted phenylene group, a halogen-substituted phenylene group, or an alkoxy-substituted phenylene group. These groups may have a polymerizable functional group.

γ represents a hydrogen atom, an alkyl group having 1 to 6 atoms in the main chain, or an alkyl group having 1 to 6 atoms in the main chain substituted with an alkyl group having 1 to 6 carbon atoms. These groups may have a polymerizable functional group. One of the carbon atoms in the main chain of the alkyl group may be replaced with O, S, or NR ¹²³ (wherein R ¹²³ represents a hydrogen atom or an alkyl group).

  Derivatives having any one of the structures (A2) to (A6) and (A9) (electron transport material derivatives) are available from Tokyo Chemical Industry Co., Ltd., Sigma Aldrich Japan Co., Ltd., and Johnson Matthey Japan Incorporated. Can be purchased from The derivative having the structure of (A1) can be synthesized by reaction of naphthalene tetracarboxylic dianhydride, which can be purchased from Tokyo Chemical Industry Co., Ltd. or Johnson Matthey Japan Incorporated, and a monoamine derivative. The derivative having the structure (A7) can be synthesized using a phenol derivative that can be purchased from Tokyo Chemical Industry Co., Ltd. or Sigma-Aldrich Japan Co., Ltd. as a raw material. The derivative having the structure of (A8) can be synthesized by reaction of perylenetetracarboxylic dianhydride that can be purchased from Tokyo Chemical Industry Co., Ltd. or Sigma Aldrich Japan Co., Ltd. and a monoamine derivative. The derivative having the structure (A10) is obtained by oxidizing a phenol derivative having a hydrazone structure with an appropriate oxidizing agent such as potassium permanganate in an organic solvent using a known synthesis method described in Japanese Patent No. 3717320, for example. Can be synthesized. Derivatives having the structure of (A11) are naphthalenetetracarboxylic dianhydride, monoamine derivative and hydrazine, which can be purchased from Tokyo Chemical Industry Co., Ltd., Sigma-Aldrich Japan Co., Ltd. or Johnson Matthey Japan Incorporated. It can be synthesized by the reaction of

The compound represented by any of (A1) to (A11) may have a polymerizable functional group (hydroxy group, thiol group, amino group, carboxyl group, and methoxy group) that can be polymerized with a crosslinking agent. As a method for synthesizing a compound represented by any of (A1) to (A11) by introducing a polymerizable functional group into a derivative having any one of the structures (A1) to (A11), the following method is used. Is mentioned. For example, there is a method of directly introducing a polymerizable functional group after synthesizing a derivative having any one of the structures (A1) to (A11). There is also a method of introducing a structure having a polymerizable functional group or a functional group that can be a precursor of the polymerizable functional group. As a method to be described later, based on the halide of the derivative having any one of the structures (A1) to (A11), for example, a cross-coupling reaction using a palladium catalyst and a base is used to form an aryl group having a functional group. There is a way to introduce. Further, there is a method of introducing an alkyl group having a functional group using a cross-coupling reaction using a FeCl ₃ catalyst and a base based on a halide of a derivative having any one of the structures (A1) to (A11). is there. Further, there is a method of introducing a hydroxyalkyl group or a carboxyl group by allowing an epoxy compound or CO ₂ to act after lithiation based on a halide of a derivative having any one of the structures (A1) to (A11). .

  Next, the crosslinking agent will be described.

  As the crosslinking agent, an electron transport material having a polymerizable functional group and a compound that polymerizes or crosslinks with a resin (a resin having a polymerizable functional group) can be used. Specifically, compounds described in Shinzo Yamashita and Tosuke Kaneko “Crosslinking Agent Handbook” published by Taiseisha (1981) and the like can be used.

  The crosslinking agent used for the undercoat layer is preferably an isocyanate compound or an amine compound. An isocyanate compound having 2 to 6 isocyanate groups or blocked isocyanate groups is preferred. For example, triisocyanatebenzene, triisocyanatemethylbenzene, triphenylmethane triisocyanate, lysine triisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, naphthalene diisocyanate diphenylmethane diisocyanate, isophorone diisocyanate, xylylene diisocyanate, 2,2 , 4-trimethylhexamethylene diisocyanate, methyl-2,6-diisocyanate hexanoate, norisocyanurate modified products such as norbornane diisocyanate, biuret modified products, allophanate modified products, adduct modified products with trimethylolpropane and pentaerythritol, etc. Is mentioned. Among these, an isocyanurate modified body and an adduct modified body are more preferable.

The blocked isocyanate group is a group having a structure of —NHCOX ¹ (X ¹ is a protecting group). X ¹ may be any protecting group that can be introduced into an isocyanate group, but groups represented by the following formulas (H1) to (H6) are more preferable.

  Below, the specific example of an isocyanate compound is shown.

  As the amine compound, for example, an amine compound having a plurality (two or more) of N-methylol groups or alkyl etherified N-methylol groups is preferable. Examples of amine compounds include melamine compounds, guanamine compounds, and urea compounds. Specifically, a compound represented by any of the following formulas (C1) to (C5) or an oligomer of a compound represented by any of the following formulas (C1) to (C5) is preferable.

In formulas (C1) to (C5), R ^{11 to} R ¹⁶ , R ^{22 to} R ²⁵ , R ^{31 to} R ³⁴ , R ^{41 to} R ⁴⁴ , and R ^{51 to} R ⁵⁴ are each independently a hydrogen atom, hydroxy A monovalent group represented by a group, an acyl group, or —CH ₂ —OR ¹ ; At least one of R ^{11 to} R ¹⁶ , at least one of R ^{22 to} R ²⁵ , at least one of R ^{31 to} R ³⁴ , at least one of R ^{41 to} R ⁴⁴ , and at least one of R ^{51 to} R ⁵⁴ Is a monovalent group represented by —CH ₂ —OR ¹ . R ¹ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group (n-propyl group, iso-propyl group), a butyl group (n-butyl group, iso-butyl group, tert-butyl group), and the like from the viewpoint of polymerizability. preferable. R ²¹ represents an aryl group, an alkyl group-substituted aryl group, a cycloalkyl group, or an alkyl group-substituted cycloalkyl group.

  Examples of generally commercially available compounds of the above formula (C1) include Super Melami No. 90 (manufactured by NOF Corporation), Super Becamine (R) TD-139-60, L-105-60, L127-60, L110-60, J-820-60, G-821-60 (manufactured by DIC) , Uban 2020 (Mitsui Chemicals), Sumitex Resin M-3 (Sumitomo Chemical Industries), Nicalak MW-30, MW-390, MX-750LM (manufactured by Nippon Carbide), and the like. Examples of generally commercially available compounds represented by the above formula (C2) include, for example, “Superbecamine (R) L-148-55, 13-535, L-145-60, TD-126. (Manufactured by DIC), Nicarak BL-60, BX-4000 (manufactured by Nippon Carbide), etc. Examples of generally commercially available compounds represented by the above formula (C3) include Nicarak MX. -280 (manufactured by Nippon Carbide Co., Ltd.), etc. Examples of generally commercially available compounds represented by the above formula (C4) include Nicalac MX-270 (manufactured by Nippon Carbide Co., Ltd.). Examples of generally commercially available compounds represented by the above formula (C5) include Nicalac MX-290 (manufactured by Nippon Carbide).

  Next, the resin will be described. Examples of the resin include acetal resin, polyolefin resin, polyester resin, polyether resin, polyamide resin, polycarbonate resin, and polyarylate resin. From the viewpoint of the undercoat layer forming the polymer, a resin having a structural unit represented by the following formula (D) is preferable.

In the formula (D), R ⁶¹ represents a hydrogen atom or an alkyl group. Y ¹ represents a single bond, an alkylene group or a phenylene group. W ¹ represents a hydroxy group, a thiol group, an amino group, a carboxyl group, or a methoxy group.

  Examples of the resin having the structural unit represented by the formula (D) include an acetal resin, a polyolefin resin, a polyester resin, a polyether resin, and a polyamide resin. The structural unit represented by the above formula (D) may be included in the following characteristic structure, or may be included other than the characteristic structure. Characteristic structures are shown in the following (E-1) to (E-6). (E-1) is a structural unit of an acetal resin. (E-2) is a structural unit of polyolefin resin. (E-3) is a structural unit of a polyester resin. (E-4) is a structural unit of a polyether resin. (E-5) is a structural unit of polyamide resin.

In the above ^formula, R 201 ^{to R 205} each independently represent a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. R ^{206 to} R ²¹⁰ each independently represent a substituted or unsubstituted alkylene group or a substituted or unsubstituted arylene group. When R ²⁰¹ is C ₃ H _7, it is represented as butyral.

  Resin having a structural unit represented by formula (D) (hereinafter also referred to as resin D) is a polymerized monomer having a polymerizable functional group, which can be purchased from, for example, Sigma-Aldrich Japan Co., Ltd. or Tokyo Chemical Industry Co., Ltd. Can be obtained.

  Examples of the resin that can be purchased as the resin having the structural unit represented by the above formula (D) include the following. Polyether polyol resins such as AQD-457 and AQD-473 manufactured by Nippon Polyurethane Industry Co., Ltd., Sannics GP-400 and GP-700 manufactured by Sanyo Chemical Industry Co., Ltd., Phthalkid W2343 manufactured by Hitachi Chemical Co., Ltd., DIC Polyester polyol resins such as Watersol S-118 and CD-520 manufactured by Harima Chemical Co., Ltd., and Haripip WH-1188 manufactured by Harima Kasei Co., Ltd. Polyacrylic polyols such as Burnock WE-300 and WE-304 manufactured by DIC Corporation Resins, polyvinyl alcohol resins such as Kuraray Kuraraypoval PVA-203, Sekisui Chemical Co., Ltd. KW-1 and KW-3, BX-1, BM-1, KS-1, KS -3, KS-5Z and other polyvinyl acetal resins, Toraysin F manufactured by Nagase ChemteX Corporation -350 and other polyamide compound resins, Nippon Shokubai Co., Ltd. Aquaric, Lead City Co., Ltd. Finelex SG2000 and other carboxyl group-containing resins, DIC Co., Ltd. racamide and other polyamines, Toray Industries, Inc. QE Polythiols such as -340M.

  The weight average molecular weight (Mw) of the resin D is more preferably in the range of 5000 to 400,000.

  When using resin with a crosslinking agent, you may contain a catalyst in order to accelerate | stimulate superposition | polymerization. Examples of the catalyst include dibutyltin dilaurate, amine catalyst, and metal soap.

  Examples of the organic solvent used in the coating solution for the undercoat layer include alcohol solvents such as methanol and butanol, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents.

  In the present invention, from the viewpoint of coatability, the dispersibility after adding the slurry of inorganic particles is improved by setting the viscosity to 100 mPa · s or less. This is considered to be because, by setting the liquid viscosity within the above range, it becomes easy to mix even different solvent types and viscosities. Also, if the viscosity of the above solution is too higher than 100 mPa · s, it takes a long time for coating when a slurry of inorganic particles is added to prepare an undercoat layer coating solution to form a thin film of 1 μm or less. Another reason is that it is not preferable.

  The viscosity was measured at 60 rpm using a Bismetron viscometer (VDA-L type) manufactured by Shibaura System. In the case of a liquid having a viscosity of 50 mPa · s or less, a TVB-10M type low viscosity rotor manufactured by Toki Sangyo Co., Ltd. was used.

  In the solution of the present invention, the solid content concentration of the solution is preferably 60% by mass or less from the viewpoint of suppressing the viscosity change from becoming too large. More preferably, it is 20 mass% or less.

  Next, the inorganic particle slurry will be described. In order to improve the dispersibility of the slurry, the inorganic particle slurry of the present invention may further contain a resin.

  As the inorganic particles, inorganic oxide particles are preferable. Specific examples include silicon oxide particles, titanium oxide particles, zinc oxide particles, tin oxide particles, zirconium oxide particles, and aluminum oxide particles. These inorganic oxide particles may be subjected to a surface treatment in terms of dispersibility of the coating solution for the undercoat layer and electrical characteristics of the electrophotographic photosensitive member. In addition, the inorganic particles can be used in a mixture of two or more types such as those having different material types, different surface treatments, or different specific surface areas, and various composite oxidations such as silica particles and alumina particles. Physical particles may be used.

  Further, a dispersant may be added to the slurry for the purpose of enhancing the dispersibility and stability of the inorganic particle slurry. Examples of the dispersant include polymeric dispersants having a main chain such as alkyl esters and polyethers.

  As a method for obtaining a slurry of inorganic particles, there is a method of dispersing powdery inorganic particles in an organic solvent in addition to using a commercially available inorganic particle slurry. Examples of the dispersion method include a method using a homogenizer, an ultrasonic disperser, a ball mill, a sand mill, a roll mill, and a vibration mill.

  The average primary particle size of the inorganic particles in the inorganic particle slurry is preferably 300 nm or less from the viewpoint of liquid stability. More preferably, it is 10 nm or more and 100 nm or less. When the particle diameter is too large, the dispersion stability is deteriorated. On the other hand, when the particle diameter is too small, the particles are aggregated and the dispersibility may be deteriorated.

  The inorganic particle slurry may contain ionic impurities such as sulfate ions, alkali metal / alkaline earth metal ions, and organic acids such as formic acid and citric acid.

  In particular, in the case of using hydrophilic inorganic particles or inorganic particles in which a hydroxyl group remains to some extent even if the surface is modified, the undercoat layer coating solution may contain moisture. As will be described later, when the undercoat layer coating solution is prepared by mixing with a resin or the like, water may be contained as long as there is no problem with the amount of water.

  The inorganic particle slurry contains an organic solvent. Examples of the organic solvent include alcohol solvents such as methanol and butanol, ketone solvents, sulfoxide solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents.

  In the slurry of inorganic particles, the solid content concentration of the inorganic particles is preferably about 5 to 60% by mass. More preferably, it is 20 mass% or less. If the solid content is higher than 60%, aggregation tends to occur and a good dispersion state cannot be obtained.

  The viscosity of the inorganic particle slurry is preferably 200 mPa · s or less, more preferably 50 mPa · s or less. If it is this range, the dispersibility at the time of mixing with the said solution will be favorable.

  In the slurry of inorganic particles, solidified solids may be generated near the wall surface or lid of the storage container due to the volatilization of the solvent during storage. For the purpose of removing such large aggregated particles, when adding to the above solution, it is added through a mesh (such as a synthetic fiber network such as polyester or nylon) or filter paper appropriately selected according to the target particle size. May be.

  After adding the slurry of inorganic particles, the mixed solution is preferably stirred for about 1 hour. Further, when adding the slurry of inorganic particles, the efficiency of dispersion becomes higher if the solution is added with stirring.

  Depending on the storage environment of the inorganic particle slurry, the undercoat layer coating solution may contain moisture. The amount of water in the coating solution for the undercoat layer may include about 0.1 to 10% by mass on the basis of a moisture content based on the moisture vaporization Karl Fischer method. From the viewpoint of film formation and electrical characteristics, the content is preferably less than 10% by mass.

  The solid content concentration of the solution and the solid content concentration of the inorganic particles in the inorganic particle slurry are measured by a heat-dry weight method. Specifically, 1 to 2 g of a measurement liquid (solution, inorganic particle slurry) is dropped into a weighed aluminum cake cup and weighed. The mass of the measurement liquid (solution, inorganic particle slurry) is R1 (g). The solid content obtained by heating and drying at a temperature at which only the solid content remains for a certain period of time and weighing the solid content remaining in the aluminum cake cup is defined as R2 (g). From the values of R1 and R2, the solid content concentration of the solution and the solid content concentration of the inorganic particle slurry are obtained by the following equation (1).

Solid content (%) = R2 / R1 × 100 (1)
As a measuring instrument for measuring the amount of water in the undercoat layer coating solution, a moisture measuring device (product name: AQ-2100) manufactured by Hiranuma Sangyo Co., Ltd. is used. Using this measuring instrument, as a reagent, Hydranal Coulomat AG (electrolytic solution) manufactured by Hayashi Pure Chemical Co., Ltd. and Hydranal Coulomat CG (Counter Electrode Solution) manufactured by Hayashi Pure Chemical Co., Ltd. are used, and a minimum count of 5 μg is used as a carrier gas. Measurement was performed at 120 ° C. while flowing nitrogen at about 150 mL / min.

  Because the solvent volatilization may cause solids to dry on the wall of the container for preparing the coating solution for the undercoat layer, when using the coating solution for the undercoat layer, filtration is performed for the purpose of removing the solid matter. It is preferable to carry out.

  The solid matter may be provided with a prefilter for shortening the filtration time and preventing clogging, or may be subjected to circulation filtration for the purpose of further increasing the cleanliness. As the filter at the time of filtration, a Teflon filter having solvent resistance is particularly preferable. Moreover, the eyes of a filter should just be a grade which the target particle diameter passes.

  The undercoat layer can be formed by applying the coating solution for the undercoat layer prepared as described above to form a coating film and drying the coating film.

  Examples of the method for applying the coating solution for the undercoat layer include a dip coating method (dip coating method), a spray coating method, a curtain coating method, and a spin coating method. Among these, the dip coating method is preferable from the viewpoints of efficiency and productivity.

  At the time of dip coating, the concentration change due to the volatilization of the solvent is significant on the liquid level of the coating tank in which the object to be coated is immersed, and a concentration gradient occurs in the vertical direction of the coating tank, resulting in uneven coating of the photoreceptor. In the dip coating method using the coating solution that has been allowed to stand in this way, the above-mentioned disadvantages occur, and this disadvantage appears more prominently during mass production. For the purpose of improving the non-uniformity of the liquid concentration, a method of applying in a state where the coating liquid is continuously circulated between a recovery tank provided separately from the coating tank may be used. A diaphragm pump or the like is used as a pump built in the circulator. However, the flow rate in the coating tank is unstable due to the pulsation of the liquid, resulting in defects such as film unevenness formed on the surface of the coated body. It may be a cause. As a method of improving this drawback, without using a power source such as a pump for liquid feeding from the storage tank to the coating tank, by using a liquid feeding method using only the gravity of the coating liquid based on the principle of siphon, A method for preventing pulsation of the coating solution in the coating tank is effective. Specifically, a storage tank that is a third tank is provided at a position higher than the application tank, the recovery tank, and the application tank, and the coating liquid is sent into the storage tank so that the pulsation by the liquid feeding means is not propagated to the application tank. In this case, it is once released under atmospheric pressure to release the pressurized state. Further, for the purpose of keeping the liquid level in the storage tank constant, the pulsation of the coating liquid is stored by overflowing the coating liquid in the storage tank, as described in JP-A-2006-320791. It is even better to have a mechanism for absorption on the overflow side of the tank.

  Furthermore, a filter may be provided in the flow path of the circulator for the purpose of removing dust, dust and the like mixed in the undercoat layer coating solution.

  Moreover, since the coating liquid for undercoat obtained by this invention is excellent in a dispersibility, it shows the coating property outstanding also at the time of simultaneous application | coating of two or more.

  The heating temperature when the coating film of the undercoat layer coating solution is dried by heating is preferably 50 to 200 ° C.

  The thickness of the undercoat layer is preferably from 0.5 μm to 15 μm, and more preferably from 0.5 μm to 5 μm.

  For measurement of the dry film thickness of the undercoat layer, the film thickness can be obtained through analysis by the peak valley method using a film thickness measurement system (product name: F20) by reflection spectroscopy manufactured by Filmetrics.

(Charge generation layer)
A charge generation layer is provided immediately above the undercoat layer.

  Charge generation materials include azo pigments, perylene pigments, anthraquinone derivatives, anthanthrone derivatives, dibenzpyrenequinone derivatives, pyranthrone derivatives, violanthrone derivatives, isoviolanthrone derivatives, indigo derivatives, thioindigo derivatives, metal phthalocyanines, metal-free phthalocyanines, etc. Phthalocyanine pigments and bisbenzimidazole derivatives. Among these, at least one of an azo pigment and a phthalocyanine pigment is preferable. Among the phthalocyanine pigments, oxytitanium phthalocyanine, chlorogallium phthalocyanine, and hydroxygallium phthalocyanine are preferable.

  As oxytitanium phthalocyanine, those having the following crystal forms are preferable. Crystal form oxytitanium phthalocyanine crystals having peaks at 9.0 °, 14.2 °, 23.9 ° and 27.1 ° of the Bragg angle (2θ ± 0.2 °) in CuKα characteristic X-ray diffraction. Bragg angles (2θ ± 0.2 °) of 9.5 °, 9.7 °, 11.7 °, 15.0 °, 23.5 °, 24.1 ° and 27.3 in CuKα characteristic X-ray diffraction Crystalline oxytitanium phthalocyanine crystal with strong peak at °.

  As hydroxygallium phthalocyanine, those having the following crystal forms are preferred. A hydroxygallium phthalocyanine crystal having a crystal form having peaks at 7.3 °, 24.9 °, and 28.1 ° of the Bragg angle (2θ ± 0.2 °) in CuKα characteristic X-ray diffraction. Bragg angles (2θ ± 0.2 °) of 7.5 °, 9.9 °, 12.5 °, 16.3 °, 18.6 °, 25.1 ° and 28.3 in CuKα characteristic X-ray diffraction Crystalline hydroxygallium phthalocyanine crystal having a peak at °.

  Examples of the binder resin used for the charge generation layer include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, vinyl chloride, acrylic acid ester, methacrylic acid ester, vinylidene fluoride, and trifluoroethylene, Examples include polyvinyl alcohol resin, polyvinyl acetal resin, polycarbonate resin, polyester resin, polysulfone resin, polyphenylene oxide resin, polyurethane resin, cellulose resin, phenol resin, melamine resin, silicon resin, and epoxy resin. Among these, polyester resin, polycarbonate resin, and polyvinyl acetal resin are preferable, and polyvinyl acetal is more preferable.

  In the charge generation layer, the mass ratio of the charge generation material to the binder resin (charge generation material / binder resin) is preferably in the range of 10/1 to 1/10, and is preferably 5/1 to 1/5. A range is more preferable. Examples of the solvent used in the charge generation layer coating liquid include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. The thickness of the charge generation layer is preferably 0.05 μm or more and 5 μm or less.

(Charge transport layer)
A charge transport layer is formed on the charge generation layer.

  Examples of the charge transport material include a polycyclic aromatic compound, a heterocyclic compound, a hydrazone compound, a styryl compound, a benzidine compound, a triarylamine compound, triphenylamine, or a group derived from these compounds as a main chain or The polymer which has in a side chain is mentioned. Among these, a triarylamine compound, a benzidine compound, or a styryl compound is preferable.

  Examples of the binder resin used for the hole transport layer include a polyester resin, a polycarbonate resin, a polymethacrylate resin, a polyarylate resin, a polysulfone resin, and a polystyrene resin. Among these, polycarbonate resin and polyarylate resin are preferable. Moreover, as these molecular weight, the range of a weight average molecular weight (Mw) = 10,000-300,000 is preferable.

  In the charge transport layer, the mass ratio of the charge transport material and the binder resin (charge transport material / binder resin) is preferably 10/5 to 5/10, and more preferably 10/8 to 6/10.

  The thickness of the charge transport layer is preferably 3 μm or more and 40 μm or less. From the viewpoint of the film thickness with the undercoat layer, it is more preferably 5 μm or more and 16 μm or less. Examples of the solvent used in the charge transport layer coating solution include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents.

  A protective layer may be formed on the charge transport layer. The protective layer contains conductive particles or a charge transport material and a binder resin. The surface protective layer may further contain an additive such as a lubricant. Further, the binder resin itself of the protective layer may have conductivity and charge transport property. In that case, the protective layer may not contain conductive particles other than the resin or a charge transport material. Further, the binder resin of the protective layer may be a thermoplastic resin or a curable resin that is polymerized by heat, light, radiation (electron beam, etc.), or the like.

  As a method of forming each layer constituting the electrophotographic photosensitive member such as a conductive layer, a charge generation layer, and a charge transport layer, a coating solution obtained by dissolving and / or dispersing materials constituting each layer in a solvent is applied. A method of forming the obtained coating film by drying and / or curing is preferable. Examples of the method for applying the coating liquid include a dip coating method (dip coating method), a spray coating method, a curtain coating method, and a spin coating method. Among these, the dip coating method is preferable from the viewpoints of efficiency and productivity.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to the following. In the examples, “part” means “part by mass”.

  The structure of the electron transport material used in the following examples is shown below.

Example 1
An aluminum cylinder (JIS-A3003, aluminum alloy) having a length of 260.5 mm and a diameter of 30 mm was used as a support (conductive support).

[Conductive layer]
Next, 214 parts of titanium oxide (TiO ₂ ) particles coated with oxygen-deficient tin oxide (SnO ₂ ) as conductive particles,
132 parts of phenol resin (monomer / oligomer of phenol resin) as a binding material (trade name: Priorofen J-325, manufactured by Dainippon Ink & Chemicals, Inc., resin solid content: 60% by mass), and
98 parts of 1-methoxy-2-propanol as solvent
Place in a sand mill using 450 parts of glass beads with a diameter of 0.8 mm, perform dispersion treatment under the conditions of rotation speed: 2000 rpm, dispersion treatment time: 4.5 hours, cooling water set temperature: 18 ° C. to obtain a dispersion. It was.

  Glass beads were removed from this dispersion with a mesh (aperture: 150 μm). Silicone resin particles (trade name: Tospearl 120, as a surface roughening agent) so as to be 10% by mass with respect to the total mass of the metal oxide particles and the binder material in the dispersion after removing the glass beads. Momentive Performance Materials, Inc., average particle size 2 μm) was added to the dispersion. In addition, silicone oil as a leveling agent (trade name: SH28PA, manufactured by Toray Dow Corning Co., Ltd.) so as to be 0.01% by mass with respect to the total mass of the metal oxide particles and the binder material in the dispersion. ) Was added to the dispersion and stirred to prepare a conductive layer coating solution. This conductive layer coating solution was dip-coated on a support, and the resulting coating film was dried and thermally cured at 150 ° C. for 30 minutes to form a conductive layer 1 having a thickness of 30 μm.

[Undercoat layer]
(Preparation of undercoat layer coating solution)
4.6 parts of an electron transport material represented by the following formula (A1),

8.6 parts of blocked isocyanate compound (trade name: SBN-70D, manufactured by Asahi Kasei Chemicals Corporation), and 0.6 part of polyvinyl acetal resin (trade name: KS-5Z, manufactured by Sekisui Chemical Co., Ltd.), Is dissolved in a mixed solvent of 50 parts of 1-methoxy-2-propanol and 50 parts of tetrahydrofuran and zinc hexanoate (II) (trade name: zinc hexanoate (II), manufactured by Mitsuwa Chemicals Co., Ltd.) as a catalyst is used. .15 parts was added to prepare a solution having a solid content concentration of 12% by mass. When the viscosity was measured after confirming the dissolution of the above materials, the water content in the solution was 0.16% at 3.5 mPa · s. The blocked isocyanate compound has a skeleton represented by (B1) and has (H1) as a blocking group.

  Silica slurry (product name: IPA-ST-UP, manufactured by Nissan Chemical Industries, Ltd., solid content concentration: 15 mass%, viscosity: 9 mPa · s) dispersed in isopropyl alcohol and having an average primary particle size of 9-15 nm. s) was passed through a nylon screen mesh sheet (product name: N-No. 150T) manufactured by Tokyo Screen Co., Ltd., and 1.8 parts were added, followed by stirring for 1 hour. Then, it filtered under pressure using the filter (product name: PF020) made from Teflon by ADVANTEC Co., Ltd., and prepared the coating liquid for undercoat layers.

  The particle size of the inorganic particle slurry was measured using a particle size measuring device (product name: Zetasizer Nano Nano-ZS) manufactured by Spectris Co., Ltd. using a dynamic light scattering method. At the time of measurement, a slurry (stock solution) of inorganic particles was diluted 70 times with THF / methoxypropanol to prepare a sample, and the number average particle diameter was measured.

[Dispersibility of inorganic particles]
Evaluation of the dispersibility of the inorganic particles was carried out by measuring the number average particle diameter of the inorganic particles in the slurry of inorganic particles and the number average particle diameter of the inorganic particles in the coating liquid for the undercoat layer as described above. The number average particle diameter of the inorganic particles was compared and used as an index of dispersibility.

  As a result, the number average particle size of the inorganic particles in the inorganic particle slurry was 37 nm, and the number average particle size of the inorganic particles in the coating solution for the undercoat layer was 39 nm. Therefore, the difference in the number average particle diameter of the inorganic particles is 2 nm.

  Using this coating solution for the undercoat layer, a coating film was formed on the conductive layer at a coating speed of 300 mm / sec by dip coating with a circulator having the structure shown in FIG. 4 of JP-A-2006-320791. . This coating film was heated at 170 ° C. for 20 minutes and cured (polymerized) to form a 0.7 μm undercoat layer. In the measurement of the dry film thickness of the undercoat layer, a paint was directly applied on an aluminum cylinder, and a film thickness measurement system (product name: F20) by reflection spectroscopy manufactured by Filmetrics was used.

(Charge generation layer)
Next, Bragg angles (2θ ± 0.2 °) in CuKα characteristic X-ray diffraction of 7.5 °, 9.9 °, 12.5 °, 16.3 °, 18.6 °, 25.1 ° and A crystalline hydroxygallium phthalocyanine crystal (charge generation material) having a peak at 28.3 ° was prepared. 10 parts of this hydroxygallium phthalocyanine crystal, 5 parts of polyvinyl butyral (trade name: ESREC BX-1, manufactured by Sekisui Chemical Co., Ltd.) and 250 parts of cyclohexanone are placed in a sand mill using glass beads having a diameter of 1 mm and dispersed for 2 hours. Processed. Next, 250 parts of ethyl acetate was added thereto to prepare a charge generation layer coating solution.

  This charge generation layer coating solution was dip coated on the undercoat layer, and the resulting coating film was dried at 95 ° C. for 10 minutes to form a charge generation layer having a thickness of 0.17 μm.

(Charge transport layer)
Next, 7 parts of an amine compound (hole transport material) represented by the following formula (1), 1 part of an amine compound represented by the following formula (2),

And a polyester resin (P1) having a repeating structural unit represented by the following formulas (C-1) and (C-2) at a molar ratio of 5/5 and having a weight average molecular weight (Mw) of 100,000. ) 10 parts

A charge transport layer coating solution was prepared by dissolving in a mixed solvent of 40 parts of dimethoxymethane and 60 parts of o-xylene.

  The charge transport layer coating solution was dip-coated on the charge generation layer, and the resulting coating film was dried at 120 ° C. for 40 minutes to form a charge transport layer having a thickness of 15 μm.

(Black spot evaluation)
The manufactured electrophotographic photosensitive member for evaluation was mounted on a laser beam printer (trade name: LBP-2510) manufactured by Canon Inc. for evaluation. Specifically, it is as follows.

  The charging conditions and the laser exposure amount were set so that the surface potential of the electrophotographic photosensitive member was an initial dark portion potential of −550 V and an exposed portion potential of −150 V. For surface potential measurement, the cartridge was remodeled, and a potential probe (trade name: model6000B-8, manufactured by Trek Japan Co., Ltd.) was attached to the development position. And the electric potential of the electrophotographic photosensitive member central part was measured using the surface potentiometer (Brand name: model344, manufactured by Trek Japan KK).

For the evaluation of black spots, A4 size gloss paper was used and a solid white image was output. The output image is included in the area of one circumference of the electrophotographic photosensitive member (a rectangular region having a vertical length of 297 mm which is the long side length of A4 paper and a horizontal length of 94.2 mm which is one circumference of the electrophotographic photosensitive member). The number of black spots was visually evaluated. The evaluation results are shown in Table 3. Ranks A and B (up to 3 black spots) were defined as levels where the effects of the present invention were obtained.
Rank A: No black spots found Rank B: 1-3 black spots larger than 0.3 mm in diameter Rank C: 4-5 black spots larger than 0.3 mm in diameter Rank D: Diameter 6-7 black spots with a diameter greater than 0.3 mm can be seen Rank E: Eight or more black spots with a diameter greater than 0.3 mm can be seen

(Examples 2 to 19)
An undercoat layer coating solution and an electrophotographic photosensitive member were prepared in the same manner as in Example 1 with the material configurations shown in Table 2, and the dispersibility and black spot evaluation of the inorganic particles were similarly performed. The results are shown in Table 3.

(Example 20)
An undercoat layer was formed in the same manner as in Example 1 except that an undercoat layer coating solution was prepared as described below to prepare an electrophotographic photoreceptor.

  5.0 parts of methoxymethylated nylon resin (trade name: Toresin EF30T, manufactured by Nagase ChemteX Corporation) is dissolved in a mixed solution of 33 parts of methanol and 67 parts of butanol, and a solution having a solid content of 4.8% by mass is dissolved. Prepared. The viscosity of this solution was measured and found to be 8.0 mPa · s.

  In this solution, a silica slurry (product name: IPA-ST-UP, manufactured by Nissan Chemical Industries, solid content concentration: 15 mass%, viscosity: 9 mPa · s) dispersed in isopropyl alcohol and having an average primary particle size of 9 to 15 nm. 0.7 part was added and stirred for 1 hour. In this way, an undercoat layer coating solution was prepared. The results are shown in Table 3.

(Examples 21 and 22)
An undercoat layer coating solution and an electrophotographic photosensitive member were produced in the same manner as in Example 16 with the material configurations shown in Table 2, and the dispersibility and black spots of the inorganic particles were similarly evaluated. The results are shown in Table 3.

(Examples 23 and 24)
An undercoat layer coating solution and an electrophotographic photosensitive member were prepared in the same manner as in Example 1 with the material configurations shown in Table 2, and the dispersibility and black spot evaluation of the inorganic particles were similarly performed. The results are shown in Table 3.

(Comparative Examples 1-4)
An undercoat layer coating solution and an electrophotographic photosensitive member were produced in the same manner as in Example 1 with the material configurations shown in Table 13, and the dispersibility and black spot evaluation of the inorganic particles were similarly performed. The results are shown in Table 3.

  In Table 2, the electron transport materials A2 to A5 are compounds represented by the following formulae.

  In Table 2, the crosslinking agent (B1: H1) is BL-3175 (manufactured by Sumika Bayer Co., Ltd.). BL-3175 is a blocked isocyanate compound having a skeleton represented by (B1) and having (H1) as a blocking group.

  In Table 2, resin KS-5 is a polyvinyl butyral resin having a structure represented by (E-1) and is KS-5Z (manufactured by Sekisui Chemical Co., Ltd.). BM-1 is a polyvinyl butyral resin having a structure represented by (E-1) and is BM-1 (manufactured by Sekisui Chemical Co., Ltd.). EF30T is a polyamide resin having a structure represented by (E-5) and represents Toresin EF30T (manufactured by Nagase ChemteX Corporation).

  In Table 2, the solvent THF represents tetrahydrofuran. MP is 1-methoxy-2-propanol. MeOH is methanol. MEK is methyl ethyl ketone. 1-BuOH represents 1-butanol.

  In Table 2, the inorganic particles P1 are silica slurry (trade name: IPA-ST-UP, manufactured by Nissan Chemical Industries, Ltd., solid content concentration: 15% by mass, average primary particle size: 9 to 15 nm). The inorganic particles P2 are titanium oxide slurry (trade name: TDK-701, manufactured by Teika Co., Ltd., solid content concentration: 17% by mass, average primary particle size: 6 nm). The inorganic particles P3 are silica slurry (trade name: PL-1-TOL, manufactured by Fuso Chemical Industry Co., Ltd., solid content concentration: 38% by mass, average primary particle size: 10 to 15 nm). The inorganic particles P4 are silica slurry (trade name: PL-10L-MEK, manufactured by Fuso Chemical Industry Co., Ltd., solid content concentration: 20% by mass, average primary particle size: 100 nm).

Claims (7)

A method of producing a coating solution for an undercoat layer of an electrophotographic photoreceptor containing a resin, inorganic particles, and an organic solvent,
A step of preparing a solution by mixing a resin and an organic solvent, and a step of preparing a coating solution for an undercoat layer by adding a slurry of inorganic particles to the solution,
Have
A method for producing a coating solution for an undercoat layer of an electrophotographic photosensitive member, wherein the viscosity of the solution is 100 mPa · s or less.   The method for producing a coating solution for an undercoat layer of an electrophotographic photosensitive member according to claim 1, wherein the solid content concentration of the solution is 60% by mass or less.   The method for producing a coating solution for an undercoat layer of an electrophotographic photosensitive member according to claim 1, wherein the inorganic particle slurry has a solid content concentration of 20% by mass or less.   The method for producing a coating solution for an undercoat layer of an electrophotographic photosensitive member according to any one of claims 1 to 3, wherein the inorganic particles are inorganic oxide particles.   The method for producing a coating liquid for an undercoat layer according to claim 4, wherein the inorganic oxide particles are silica particles or titanium oxide particles.   The method for producing a coating solution for an undercoat layer according to any one of claims 1 to 5, wherein the solution further contains an electron transport material having a polymerizable functional group and a crosslinking agent. A method for producing an electrophotographic photosensitive member having a support, an undercoat layer formed on the support, and a photosensitive layer formed on the undercoat layer,
A step of preparing a coating solution for an undercoat layer by the method for producing a coating solution for an undercoat layer of the electrophotographic photosensitive member according to any one of claims 1 to 6, and coating of the coating solution for the undercoat layer Forming a film and drying the coating film to form an undercoat layer;
A process for producing an electrophotographic photosensitive member, comprising:

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