Methods for producing electrophotographic photosensitive member and organic device each having charge transporting layer

The present invention relates to a method for producing an electrophotographic photosensitive member and a method for producing an organic device.

Organic devices having a charge transporting layer in a part thereof are studied, developed, and produced in many fields such as organic electroluminescent elements, organic EL elements, solar cells, actuators, organic sensors, electronic paper, touch panels and electrophotographic photosensitive members. Organic devices having a charge transporting layer are often provided with a thin film formed by coating a substrate with a coating solution with a charge transporting substance dissolved in an organic solvent. Also for a method for producing an electrophotographic photosensitive member that is one of organic devices, a method is generally used in which a coating liquid with a charge transporting substance dissolved in an organic solvent is made and applied onto a support. A charge transporting layer is often demanded for having durability, among the respective layers of a laminate type electrophotographic photosensitive member, and a coat of the layer has a thicker film thickness than other layers. Therefore, the amount of a coating liquid used is larger, thereby resulting in a charge transporting layer in which a large amount of an organic solvent is used. In order to reduce the amount of an organic solvent in producing an electrophotographic photosensitive member, it is desirable to reduce the amount of an organic solvent for use in a coating liquid for a charge transporting layer. However, in order to make the coating liquid for a charge transporting layer, a halogen solvent and an aromatic organic solvent are required to be used because of highly dissolving a charge transporting substance and a resin, and thus the amount of an organic solvent is reduced with difficulty.

PTL 1 relates to a coating material for forming a charge transporting layer and reports an approach for the purpose of reducing the amount of an organic solvent for reducing a volatile substance and carbon dioxide. This Literature discloses making of an emulsion for a charge transporting layer by charging into water an organic solution with substances contained in a charge transporting layer dissolved in an organic solvent and forming oil drops in this water.

Patent Literature

PTL 1: Japanese Patent Application Laid-Open No. 2011-128213

Technical Problem

However, the present inventors have reviewed and as a result, have found that in the method for producing an electrophotographic photosensitive member disclosed in PTL 1, in which the emulsion is prepared, although a uniform emulsion state is achieved just after preparing the emulsion, deterioration in liquid properties of the emulsion is observed after the emulsion is left to stand for a long time. It has also been found that a film obtained by leaving the emulsion to stand for a long time, thereafter applying the emulsion and then drying the resultant is insufficient in terms of uniformity.

The reason for this is considered that the organic solution with substances contained in a charge transporting layer dissolved in an organic solvent coalesces in water over time to hardly form a stable emulsified state, thereby causing aggregation and precipitation. A further improvement is demanded in terms of reducing the amount of an organic solvent and at the same time securing the stability of the coating liquid for a charge transporting layer.

Solution to Problem

An object of the present invention is to provide a method for producing an electrophotographic photosensitive member, in particular, a method for producing an electrophotographic photosensitive member, that reduces the amount of an organic solvent for use in a coating liquid for a charge transporting layer and at the same time enhances the stability of the coating liquid after storage for a long time, thereby enabling forming a charge transporting layer having a high film uniformity, in a method for forming a charge transporting layer.

Another object of the present invention is to provide a method for producing an organic device, in particular, a method for producing an organic device, that reduces the amount of an organic solvent for use in a coating liquid for a charge transporting layer and at the same time enhances the stability of the coating liquid after storage for a long time, thereby enabling forming a charge transporting layer having a high film uniformity, in a method for forming a charge transporting layer.

Advantageous Effects of Invention

The above objects are achieved by the following present invention.

The present invention relates to a method for producing an electrophotographic photosensitive member which has a support and a charge transporting layer formed thereon, the production method including the steps of; preparing a first solution containing; a first liquid having a solubility in water at 25° C. and 1 atm of 1.0 mass % or less, a charge transporting substance, and a binder resin, preparing a second solution containing; a second liquid having a solubility in water at 25° C. and 1 atm of 5.0 mass % or more and a solubility in the first liquid at 25° C. and 1 atm of 5.0 mass % or more, and water, dispersing the first solution in the second solution to prepare an emulsion, forming a coat of the emulsion, and heating the coat to form the charge transporting layer.

The present invention also relates to a method for producing an organic device which has a charge transporting layer, the production method including the steps of; preparing a first solution containing; a first liquid having a solubility in water at 25° C. and 1 atm of 1.0 mass % or less, a charge transporting substance, and a binder resin preparing a second solution containing; a second liquid having a solubility in water at 25° C. and 1 atm of 5.0 mass % or more and a solubility in the first liquid at 25° C. and 1 atm of 5.0 mass % or more, and water, dispersing the first solution in the second solution to prepare an emulsion, forming a coat of the emulsion, and heating the coat to form the charge transporting layer.

The present invention also relates to a method for producing an electrophotographic photosensitive member which has a support and a charge transporting layer formed thereon, the production method including the steps of; preparing a first solution containing; a first liquid, a charge transporting substance, and a binder resin, preparing a second solution containing; a second liquid, and water, dispersing the first solution in the second solution to prepare an emulsion, forming a coat of the emulsion, and heating the coat to form the charge transporting layer, and wherein the first liquid is at least one selected from the group consisting of toluene, chloroform, dichlorobenzene, chlorobenzene, xylene, ethylbenzene and phenetole, and the second liquid is at least one selected from the group consisting of tetrahydrofuran, dimethoxymethane, 1,2-dioxane, 1,3-dioxane, 1,4-dioxane, 1,3,5-trioxane, methanol, 2-pentanone, ethanol, tetrahydropyran, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, propylene glycol n-butyl ether, propylene glycol monopropyl ether, ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol monoallyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, propylene glycol diacetate, methyl acetate, ethyl acetate, n-propyl alcohol, 3-methoxybutanol, 3-methoxybutyl acetate, and ethylene glycol monomethyl ether acetate.

According to the present invention, the methods for producing an electrophotographic photosensitive member and an organic device each having a charge transporting layer having a high film uniformity, the methods enhancing the stability of the coating liquid for a charge transporting layer (emulsion) after storage for a long time, in methods for producing an electrophotographic photosensitive member and an organic device, can be provided.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawing.

FIG. 1 is a view illustrating one example of a schematic configuration of an electrophotographic apparatus provided with a process cartridge having an electrophotographic photosensitive member of the present invention.

Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawing.

The method for producing an electrophotographic photosensitive member of the present invention is a method for producing an electrophotographic photosensitive member which has a charge transporting layer, as described above, the production method including the steps of; preparing a first solution containing; a first liquid having a solubility in water at 25° C. and 1 atm of 1.0 mass % or less, a charge transporting substance, and a binder resin, preparing a second solution containing; a second liquid having a solubility in water at 25° C. and 1 atm of 5.0 mass % or more and a solubility in the first liquid at 25° C. and 1 atm of 5.0 mass % or more, and water, dispersing the first solution in the second solution to prepare an emulsion, forming a coat of the emulsion, and heating the coat to form the charge transporting layer.

The method for producing an organic device of the present invention is a method for producing an organic device which has a charge transporting layer, as described above, the production method including the steps of; preparing a first solution containing; a first liquid having a solubility in water at 25° C. and 1 atm of 1.0 mass % or less, a charge transporting substance, a binder resin preparing a second solution containing; a second liquid having a solubility in water at 25° C. and 1 atm of 5.0 mass % or more and a solubility in the first liquid at 25° C. and 1 atm of 5.0 mass % or more, and water, preparing an emulsion from the first solution and the second solution, forming a coat of the emulsion, and heating the coat to form the charge transporting layer.

Hereinafter, the method for producing an electrophotographic photosensitive member which has a charge transporting layer of the present invention will be described.

First, the first solution containing a first liquid, a charge transporting substance and a binder resin will be described.

The charge transporting substance for use in the charge transporting layer can be a substance having hole transporting ability (hole transporting substance), and examples of the hole transporting substance include a triarylamine compound or a hydrazone compound. In particular, the hole transporting substance can be a triarylamine compound from the viewpoints of electrophotographic characteristics of an electrophotographic photosensitive member and high hole transporting ability (hole transferring ability) of an organic device.

Hereinafter, specific examples of the charge transporting substance will be represented, but are not limited to the following.

The binder resin as a component of the charge transporting layer includes a styrene resin, an acrylic resin, a polycarbonate resin, a polyester resin, and the like. The binder resin can also be a resin soluble in the first liquid. In particular, the binder resin can be a polycarbonate resin or a polyester resin. Furthermore, the binder resin can be a polycarbonate resin having a repeating structural unit represented by the following formula (2), or a polyester resin having a repeating structural unit represented by the following formula (3).

(In the formula (2), R 21 to R 24 each independently represent a hydrogen atom or a methyl group. X 1 represents a single bond, a methylene group, an ethylidene group, a propylidene group, a phenylethylidene group, a cyclohexylidene group, or an oxygen atom.)

(In the formula (3), R 31 to R 34 each independently represent a hydrogen atom or a methyl group. X 2 represents a single bond, a methylene group, an ethylidene group, a propylidene group, a cyclohexylidene group, or an oxygen atom. Y represents a m-phenylene group, a p-phenylene group, or a divalent group where two p-phenylene groups are bound with an oxygen atom.)

Specific examples of the polycarbonate resin and the polyester resin include the following.

The weight average molecular weight of each resin described in the present invention corresponds to a weight average molecular weight on the polystyrene equivalent basis, measured according to an ordinary method, specifically the method described in Japanese Patent Application Laid-Open No. 2007-79555.

The charge transporting layer of an electrophotographic photosensitive member may contain an additive in addition to the charge transporting substance and the binder resin. Examples of the additive as a component of the charge transporting layer include antidegradation agents such as an antioxidant, an ultraviolet absorber and a light stabilizer, and a releasability-imparting resin. Examples of the antidegradation agent include a hindered phenol-based antioxidant, a hindered amine-based light stabilizer, a sulfur atom-containing antioxidant, and a phosphorous atom-containing antioxidant. Examples of the releasability-imparting resin include a fluorine atom-containing resin and a resin containing a siloxane structure.

In the method for producing an electrophotographic photosensitive member of the present invention, the charge transporting substance and the binder resin are dissolved in the first liquid to prepare the first solution. The first liquid has a solubility in water at 25° C. and 1 atm of 1.0 mass % or less. The first liquid having the above characteristics exhibits hydrophobicity. Specific examples of the first liquid are shown in Table 1, but are not limited to the examples in Table 1. Each solubility in water in Table 1 corresponds to the solubility in water at 25° C. and 1 atm (atmospheric pressure) of the first liquid, represented by mass %.

Among the above first liquids, a solvent having an aromatic ring structure is preferable from the viewpoint of the solubilities of the charge transporting substance and the binder resin, in particular, at least one selected from the group consisting of toluene, chloroform, dichlorobenzene, chlorobenzene, xylene, ethylbenzene and phenetole is preferable, and further, at least one of toluene and xylene is more preferable from the viewpoint of enhancement in stability of the emulsion. In addition, xylene can be o-xylene. Two or more of the above first liquids can be mixed and used.

The total mass of the charge transporting substance and the binder resin contained in the first solution can be 10 to 50 mass % based on the mass of the first solution in view of production because the viscosity of the first solution is appropriate. The ratio of the charge transporting substance to the binder resin in the first solution preferably ranges from 4:10 to 20:10 (mass ratio), and more preferably ranges from 5:10 to 12:10 (mass ratio). In order to achieve the above mixing ratio, the ratio of the charge transporting substance and the binder resin contained in the first solution is adjusted. In the case where the first solution contains the above additive, the proportion of such an additive is preferably 50 mass % or less and more preferably 30 mass % or less, based on the total solid content ratio of the charge transporting substance to the binder resin. The first solution may also contain a surfactant.

Then, the second solution will be described. The second solution contains a second liquid having a solubility in water at 25° C. and 1 atm of 5.0 mass % or more and a solubility in the first liquid at 25° C. and 1 atm of 5.0 mass % or more, and water. The second liquid is shown in Table 2. In Table 2, each solubility in water corresponds to the solubility in water at 25° C. and 1 atm (atmospheric pressure) of the second liquid represented by mass %, and each solubility in first liquid corresponds to the solubility in the first liquid at 25° C. and 1 atm (atmospheric pressure) of the second liquid represented by mass %.

It is to be noted that each value of “Solubility in first liquid” in Table 2 corresponds to each value of solubility in the first liquid described in Table 1.

Among the above second liquids, a liquid having a solubility in water at 25° C. and 1 atm of 20.0 mass % or more can be used. Among the above second liquids, a solvent having an ether bond is preferable, in particular, at least one selected from the group consisting of tetrahydrofuran, dimethoxymethane, 1,2-dioxane, 1,3-dioxane, 1,4-dioxane, 1,3,5-trioxane, methanol, 2-pentanone, ethanol, tetrahydropyran, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, propylene glycol n-butyl ether, propylene glycol monopropyl ether, ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol monoallyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, propylene glycol diacetate, methyl acetate, ethyl acetate, n-propyl alcohol, 3-methoxybutanol, 3-methoxybutyl acetate, and ethylene glycol monomethyl ether acetate is preferable, and further, tetrahydrofuran, propylene glycol monopropyl ether, and dimethoxymethane are more preferable from the viewpoint of stabilizing the emulsion. Two or more of the second liquids may also be mixed and used.

The ratio of the second liquid to water in the second solution can be as follows: mass of second liquid:mass of water=3/97 to 40/60.

The second solution may also contain a surfactant.

Then, the emulsion prepared from the first solution and the second solution will be described.

As an emulsifying method for preparing the emulsion, any existing emulsifying method can be used. The emulsion contains at least the charge transporting substance and the binder resin at least partially dissolved in emulsified particles. Hereinafter, a stirring method and a high pressure impingement method will be described as specific emulsifying methods, but the production method of the present invention is not limited to the methods.

The stirring method is described. The first solution is gradually added while the second solution being stirred by a stirring machine without being foamed. Water contained in the second solution can be ion exchange water from which a metal ion and the like have been removed by an ion exchange resin and the like, from the viewpoints of characteristics of an electrophotographic photosensitive member and an organic device thin film. The conductivity of ion exchange water can be 5 μS/cm or less. The stirring machine can be a stirring machine capable of stirring at a high speed from the viewpoint of capable of uniformly dispersing in a short time. The stirring machine includes a homogenizer (Physcotron) manufactured by Microtec Co., Ltd., and a circulation homogenizer (Clearmix) manufactured by M Technique Co., Ltd., and the like.

The emulsion can also be dispersed by an apparatus that allows a mixed liquid to impinge at a high pressure. Such a dispersing apparatus includes Microfluidizer M-110EH manufactured by Microfluidics Corporation, Nanomizer YSNM-2000AR manufactured by Yoshida Kikai Co., Ltd., and the like.

The emulsion may also be subjected to the above dispersing method at a high pressure after being treated by the above stirring method.

The mixing ratio of the first solution containing the first liquid, the charge transporting substance and the binder resin to the second solution containing the second liquid and water is as follows: mass of first solution/mass of second solution=5/5 to 2/8. The mixing ratio can be 5/5 to 3/7 from the viewpoint of maintaining the stability of the emulsion and at the same time obtaining an emulsion having a high solid content concentration.

The ratio (w/(a+c)) of the mass (w) of water to the total mass (a+c) of the first liquid and the second liquid in the emulsion can be 5/5 to 7/3 from the viewpoints of making the emulsified particles smaller in the case of being emulsified and enhancing the stability of the emulsion.

The ratio (a/c) of the mass (a) of the first liquid to the mass (c) of the second liquid in the emulsion can be 97/3 to 30/70. The above ratios are adjusted so that the charge transporting substance and the binder resin are dissolved in the first liquid, and thus can be adjusted within a proper range so that the particle size of the emulsified particles and the desired solid content concentration are achieved. The ratio of the charge transporting substance to the binder resin in the first solution can be within such a range that the charge transporting substance and the binder resin are dissolved and an appropriate viscosity is achieved at the time of emulsifying, from the viewpoint of preparing a stable emulsion. Specifically, the total contents of the charge transporting substance and the binder resin dissolved in the first solution can be within a range of 10 mass % or more and 50 mass % or less. The viscosity of the first solution with the charge transporting substance and the binder resin dissolved can be within a range of 50 mPa·s or more and 500 mPa·s or less.

The emulsion of the present invention may also contain a surfactant for the purpose of further stabilizing emulsifying. The surfactant can be a non-ionic surfactant from the viewpoint of suppressing deterioration of charge transport characteristics. The non-ionic surfactant is a surfactant whose hydrophilic site is non-electrolyte, namely, a surfactant having a hydrophilic portion not to be ionized. Examples of the non-ionic surfactant include the following:

Naroacty series, Emulmin series, Sannonic series and Newpol series manufactured by Sanyo Chemical Industries Ltd.;

Emulgen series, Rheodol series and Emanon series manufactured by Kao Corporation;

Adekatol series, Adekaestol series and Adekanol series manufactured by ADEKA Corporation; and

non-ionic surfactant series among Newcol series manufactured by Nippon Nyukazai Co., Ltd.

One, or two or more of the above surfactants can be used singly, or can be used in combination. In addition, a surfactant having an HLB value (hydrophilic-lipophilic balance value) ranging from 8 to 15 can be selected for stabilizing the emulsion.

The amount of the surfactant added can be as small as possible from the viewpoint of not deteriorating charge transport characteristics, and the content of the surfactant in the emulsion preferably ranges from 0 mass % to 1.5 mass % and more preferably ranges from 0 mass % to 0.8 mass %. The surfactant may be contained in the second solution, or may be contained in the first solution. The surfactant may also be contained in both of the first solution and the second solution. The emulsion of the present invention may also contain additives such as a leveling agent, antifoaming agent, and a viscoelastic modifier as long as the effects of the present invention are not impaired. The additives are more effective when being soluble in water. The leveling agent is not limited irrespective of a structure as long as the leveling agent is a material that can give a leveling effect. Particularly, the leveling agent can be silicone-based or acrylic-based. The silicone-based leveling agent includes LS-430 manufactured by Kusunoki Chemicals Ltd., BYK-345, BYK-347 and BYK-348 manufactured by BYK Japan KK, and the like. The acrylic-based leveling agent includes AQ-7120 manufactured by Kusumoto Chemicals Ltd., BYK-340 manufactured by BYK Japan KK, and the like.

The average particle size of the emulsified particles in the emulsion preferably ranges from 0.1 to 20.0 μm and more preferably ranges from 0.1 to 5.0 μm, from the viewpoint of the stability of the emulsion.

Then, a method for forming a coat of the emulsion on the support will be described. For a method for applying the emulsion to form a coat, any existing method of a dip coating method, a ring coating method, a spray coating method, a spinner coating method, a roller coating method, a Mayer bar coating method, a blade coating method, and the like can be applied, and a dip coating method can be applied from the viewpoint of productivity. By any of the above methods, the emulsion of the present invention can be applied to form a coat on the support.

Then, a step of heating the coat to thereby form the charge transporting layer will be described. The formed coat is heated to thereby form the charge transporting layer on the support.

Since the emulsion at least containing the charge transporting substance and the binder resin is applied to form the coat in the present invention, the coat can be heated to remove a dispersing medium, and at the same time to allow the emulsified particles to adhere to one another and to allow a film to be more uniformly formed, from the viewpoint of forming a coat having a high uniformity. From the viewpoint of the uniformity of the film thickness, the particle size of the emulsified particles can be made smaller because the uniformity of the film thickness is rapidly made higher after the dispersing medium is removed. The heating temperature can be 100° C. or higher. The heating temperature can also be a temperature equal to or higher than the melting point of a charge transporting substance whose melting point is the lowest among charge transporting substances as components of the charge transporting layer, from the viewpoint of making the adhesiveness of the emulsified particles higher. The charge transporting substance is melted by heating at a temperature equal to or higher than the melting point of the charge transporting substance and thus the binder resin is dissolved in the melted charge transporting substance, thereby enabling forming a coat having a high uniformity. The heating temperature can also be a temperature higher than the melting point of a charge transporting substance whose melting point is the lowest among charge transporting substances as components of the charge transporting layer, by 5° C. or higher. If the heating temperature is too high, the charge transporting substance is caused to be modified and the like, and thus the heating temperature can be 200° C. or lower.

The film thickness of the charge transporting layer is preferably 5 μm or more and 50 μm or less, and more preferably 8 μm or more and 35 μm or less.

In the present invention, the second liquid soluble in the first liquid contained in the first solution is present in the second solution, thereby making the emulsified particles smaller. It is considered that the second liquid soluble in the first liquid is present in the second solution, thereby allowing the first liquid to be eluted from the first solution to the second solution during emulsifying, and that the volume of the emulsified particles containing the first solution is reduced, thereby making the emulsified particles smaller. It is considered that the emulsified particles are made smaller, thereby enabling the emulsified particles to be stably present in the emulsion, and preventing the emulsified particles from aggregating (coalescing). Therefore, the emulsion can be kept in the dispersion state even after being stored for a long period. In addition, if the emulsion in which the emulsified particles are made smaller is used as the coating liquid, a uniform charge transporting layer can be formed after film formation.

It is also considered that in the case where the boiling point of the second liquid is higher than the heating temperature, an effect as a film-forming aid for making the adhesiveness of the emulsified particles higher is also exerted.

Then, the method for producing an organic device which has a charge transporting layer according to the present invention will be described.

In the method for producing an organic device according to the present invention, the charge transporting substance is dissolved in the first liquid to prepare the first solution. The first liquid has a solubility in water at 25° C. and 1 atm of 1.0 mass % or less. The first liquid having such characteristics exhibits hydrophobicity. Specific examples of the first liquid are shown in Table 1, but are not limited to the examples in Table 1.

Among the above first liquids, a solvent having an aromatic ring structure is preferable from the viewpoint of the solubility of the charge transporting substance, and in particular, toluene and o-xylene are more preferable from the viewpoint of enhancement in stability of the emulsion. Two or more of the first liquids can be mixed and used.

The mass of the charge transporting substance contained in the first solution can be 10 to 50 mass % based on the mass of the first solution in view of production because the viscosity of the first solution is appropriate. The first solution may also contain a surfactant.

Then, the second solution in the method for producing an organic device which has a charge transporting layer according to the present invention will be described.

The second solution contains a second liquid having a solubility in water at 25° C. and 1 atm of 5.0 mass % or more and a solubility in the first liquid at 25° C. and 1 atm of 5.0 mass % or more, and water. The second liquid is shown in Table 2. Among the above second liquids, an ether-based solvent is preferable, and in particular, tetrahydrofuran and propylene glycol monopropyl ether are more preferable from the viewpoint of stabilizing the emulsion. Two or more of the second liquids may also be mixed and used. The ratio of the second liquid to water in the second solution can be as follows: mass of second liquid/mass of water=3/97 to 40/60. The second solution may also contain a surfactant.

Then, the emulsion prepared from the first solution and the second solution in the method for producing an organic device which has a charge transporting layer of the present invention will be described.

An emulsifying method for preparing the emulsion of the present invention is as described above.

The mixing ratio of the first solution containing the first liquid and the charge transporting substance to the second solution containing the second liquid and water is as follows: mass of first solution/mass of second solution=5/5 to 2/8. The mixing ratio can be 5/5 to 3/7 from the viewpoint of obtaining an emulsion having a high solid content concentration while the stability of the emulsion being maintained.

The ratio (w/(a+c)) of the mass (w) of water to the total mass (a+c) of the first liquid and the second liquid in the emulsion can be 5/5 to 7/3 from the viewpoints of making the size of oil drops smaller in the case of being emulsified and stabilizing the emulsion.

The ratio (a/c) of the mass (a) of the first liquid to the mass (c) of the second liquid in the emulsion can be 97/3 to 30/70. The above ratios are adjusted so that the charge transporting substance is dissolved in the first liquid, and thus can be adjusted within a proper range so that the desired particle size of the emulsified particles and the desired solid content concentration are achieved.

The emulsion of the present invention may also contain a surfactant for the purpose of further stabilizing emulsifying. The surfactant is as described above.

The amount of the surfactant added can be as small as possible from the viewpoint of not deteriorating charge transport characteristics, and the content of the surfactant in the emulsion preferably ranges from 0 mass % to 1.5 mass % and more preferably ranges from 0 mass % to 0.8 mass %. The surfactant may be contained in the second solution, or may be contained in the first solution. The surfactant may also be contained in both of the first solution and the second solution. The emulsion of the present invention may also contain additives such as a leveling agent, antifoaming agent, and a viscoelastic modifier as long as the effects of the present invention are not impaired.

The average particle size of the emulsified particles in the emulsion preferably ranges from 0.1 to 20.0 μm and more preferably ranges from 0.1 to 5.0 μm, from the viewpoint of the stability of the emulsion.

Then, a method for forming the coat of the emulsion on the support in the method for producing an organic device which has a charge transporting layer of the present invention will be described.

For a method for coating the emulsion to form the coat, any existing method of a spinner coating method, a roller coating method, a Mayer bar coating method, a blade coating method, and the like can be applied. By any of the above methods, the emulsion of the present invention can be applied to form the coat on the support.

Then, a step of heating the coat to thereby form the charge transporting layer will be described. The formed coat is heated to thereby form the charge transporting layer on the support.

Since the emulsion at least containing the charge transporting substance is applied to form the coat in the present invention, the coat can be heated to remove a dispersing medium, and at the same time to allow the emulsified particles to adhere to one another and to allow a film to be more uniformly formed, from the viewpoint of forming a coat having a high uniformity. From the viewpoint of the uniformity of the film thickness, the particle size of the emulsified particles can be made smaller because the uniformity of the film thickness is rapidly made higher after the dispersing medium is removed. The heating temperature can be 100° C. or higher.

Then, a configuration of an electrophotographic photosensitive member produced by the method for producing an electrophotographic photosensitive member according to the present invention will be described.

The method for producing an electrophotographic photosensitive member of the present invention is a method for producing an electrophotographic photosensitive member which has a support, and a charge generating layer and a charge transporting layer on the support.

While the electrophotographic photosensitive member generally widely used is a cylindrical electrophotographic photosensitive member with a photosensitive layer on a cylindrical support, the electrophotographic photosensitive member can also be a belt-shaped or sheet-shaped.

The support can be a support having conductivity (conductive support), and a support made of a metal such as aluminum, an aluminum alloy, or stainless can be used. In the case where the support is a support made of aluminum or an aluminum alloy, an ED tube, an EI tube, or a support obtained by subjecting such a tube to cutting, electrolytic composite polishing, or wet or dry honing treatment can also be used. In addition, a support made of a metal, having a layer in which a cover is formed by vacuum deposition of aluminum, an aluminum alloy or an indium oxide-tin oxide alloy, or a support made of a resin can also be used. In addition, a support in which a resin is impregnated with conductive particles such as carbon black, tin oxide particles, titanium oxide particles, or silver particles, or a plastic having a conductive resin can also be used.

The surface of the support may be subjected to a cutting treatment, a surface-roughening treatment, an alumite treatment, or the like.

A conductive layer may also be provided between the support and an intermediate layer or a charge generating layer described later. The conductive layer is a layer formed by using a coating liquid for a conductive layer, in which conductive particles are dispersed in a resin. Examples of the conductive particles include carbon black, acetylene black, powders of metals such as aluminum, nickel, iron, nichrome, copper, zinc and silver, and powders of metal oxides such as conductive tin oxide and ITO.

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

Examples of a solvent for the coating liquid for a conductive layer include an ether-based solvent, an alcohol-based solvent, a ketone-based solvent and an aromatic hydrocarbon solvent.

The film 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 further more preferably 5 μm or more and 30 μm or less.

An intermediate layer may also be provided between the support or the conductive layer and the charge generating layer.

The intermediate layer can be formed by coating the conductive layer with a coating liquid for an intermediate layer, containing a resin, and drying or curing the resultant.

Examples of the resin of the intermediate layer include polyacrylic acids, methylcellulose, ethylcellulose, a polyamide resin, a polyimide resin, a polyamide-imide resin, a polyamide acid resin, a melamine resin, an epoxy resin, a polyurethane resin and a polyolefin resin. The resin of the intermediate layer can be a thermoplastic resin. Specifically, the resin can be a thermoplastic polyamide resin or a polyolefin resin. The polyamide resin can be low crystalline or non-crystalline copolymerized nylon that can be applied in the state of a solution. The polyolefin resin can be usable as a particle dispersion. Furthermore, the polyolefin resin can be dispersed in an aqueous medium.

The film thickness of the intermediate layer is preferably 0.05 μm or more and 7 μm or less, and more preferably 0.1 μm or more and 2 μm or less.

The intermediate layer may also contain semiconductive particles, an electron transporting substance, or an electron acceptable substance.

A charge generating layer is provided on the support, the conductive layer or the intermediate layer.

Examples of a charge generating substance for use in the electrophotographic photosensitive member of the present invention include an azo pigment, a phthalocyanine pigment, an indigo pigment and a perylene pigment. One, or two or more of the charge generating substances may be used alone, or may be used in combination. Among the charge generating substances, in particular, the charge generating substance can be metal phthalocyanine such as oxytitanium phthalocyanine, hydroxygallium phthalocyanine or chlorogallium phthalocyanine because of having a high sensitivity.

Examples of a resin for use in the charge generating layer include a polycarbonate resin, a polyester resin, a butyral resin, a polyvinyl acetal resin, an acrylic resin, a vinyl acetate resin and a urea resin. Among the resins, in particular, the resin can be a butyral resin. One, or two or more of the resins can be used singly, or can be used as a mixture or a copolymer.

The charge generating layer can be formed by applying a coating liquid for a charge generating layer, obtained by dispersing the charge generating substance together with the resin and the solvent, and drying the resultant. The charge generating layer may also be a film with the charge generating substance deposited.

Examples of a dispersing method include a method using a homogenizer, an ultrasonic wave, a ball mill, a sand mill, an attritor or a roll mill.

The ratio of the charge generating substance to the resin preferably ranges from 1:10 to 10:1 (mass ratio), and particularly more preferably ranges from 1:1 to 3:1 (mass ratio).

A solvent for use in the coating liquid for a charge generating layer is selected depending on the solubilities and dispersing stabilities of the resin and the charge generating substance used. Examples of an organic solvent include an alcohol-based solvent, a sulfoxide-based solvent, a ketone-based solvent, an ether-based solvent, an ester-based solvent or an aromatic hydrocarbon solvent.

The film thickness of the charge generating layer is preferably 5 μm or less, and more preferably 0.1 μm or more and 2 μm or less.

In addition, various sensitizers, antioxidants, ultraviolet absorbers and plasticizers can also be added to the charge generating layer, if necessary. In order to allow the flow of charge not to interrupt in the charge generating layer, the charge generating layer may also contain an electron transporting substance or an electron acceptable substance.

The charge transporting layer is provided on the charge generating layer.

The charge transporting layer of the present invention is produced by the method described above.

Various additives can be added to the respective layers of the electrophotographic photosensitive member of the present invention. Examples of the additive include antidegradation agents such as an antioxidant, an ultraviolet absorber and a light stabilizer, and fine particles such as organic fine particles and inorganic fine particles. Examples of the antidegradation agent include a hindered phenol-based antioxidant, a hindered amine-based light stabilizer, a sulfur atom-containing antioxidant and a phosphorous atom-containing antioxidant. Examples of the organic fine particles include fluorine atom-containing resin particles, and polymer resin particles such as polystyrene fine particles and polyethylene resin particles. Examples of the inorganic fine particles include metal oxides such as silica and alumina.

In coating the respective coating liquids for the respective layers, any coating method such as a dip coating method, a spray coating method, a spinner coating method, a roller coating method, a Mayer bar coating method or a blade coating method can be used.

In addition, an unevenness shape (depressing shape, protruding shape) may also be formed on the surface of the surface layer of the electrophotographic photosensitive member. For a method for forming an unevenness shape, a known method can be employed. The forming method includes a method for forming a depressing shape by blowing abrasive particles on the surface, a method for forming an unevenness shape by bringing a mold having an asperity shape into contact with the surface under pressure, a method for forming a depressing shape by irradiating the surface with laser light, and the like. In particular, the forming method can be a method for forming an unevenness shape by bringing a mold having an unevenness shape into contact with the surface of the surface layer of the electrophotographic photosensitive member under pressure.

FIG. 1 illustrates one example of a schematic configuration of an electrophotographic apparatus provided with a process cartridge having an electrophotographic photosensitive member of the present invention.

In FIG. 1 , reference number 1 denotes a cylindrical electrophotographic photosensitive member, and is rotatably driven around an axis 2 in an arrow direction at a predetermined peripheral velocity. The surface of the electrophotographic photosensitive member 1 to be rotatably driven is uniformly charged by a charging unit (primary charging unit: charge roller or the like) 3 at a predetermined positive or negative potential. Then, the surface receives exposing light (image exposing light) 4 output from an exposing unit (not illustrated) such as a slit exposing unit or a laser beam scanning exposing unit. Thus, an electrostatic latent image corresponding to the intended image is sequentially formed on the surface of the electrophotographic photosensitive member 1 .

The electrostatic latent image formed on the surface of the electrophotographic photosensitive member 1 is developed by a toner contained in a developer of a developing unit 5 , thereby being turned into a toner image. Then, the toner image formed and supported on the surface of the electrophotographic photosensitive member 1 is sequentially transferred to a transfer material (paper or the like) P by a transfer bias from a transferring unit (transfer roller or the like) 6 . It is to be noted that the transfer material P is ejected in synchronization with the rotation of the electrophotographic photosensitive member 1 and fed from a transfer material-feeding unit (not illustrated) to a place (abutting portion) between the electrophotographic photosensitive member 1 and the transferring unit 6 .

The transfer material P on which the toner image is transferred is separated from the surface of the electrophotographic photosensitive member 1 , introduced into a fitting unit 8 , subjected to image fixing, and thus printed out as an image-formed article (print, copy) to the outside of an apparatus.

The remaining developer (toner) is removed from the surface of the electrophotographic photosensitive member 1 after the toner image is transferred and the surface is cleaned by a cleaning unit (cleaning blade or the like) 7 . Then, the surface is subjected to a neutralization treatment with pre-exposing light (not illustrated) from a pre-exposing unit (not illustrated), and then repeatedly used for forming an image. It is to be noted that as in illustrated in FIG. 1 , in the case where the charging unit 3 is a contact charging unit using a charge roller or the like, pre-exposing is not necessarily needed.

A plurality of components among the electrophotographic photosensitive member 1 , the charging unit 3 , the developing unit 5 , the transferring unit 6 , the cleaning unit 7 and the like are accommodated in a container and configured to be bound integratedly with a process cartridge, and the process cartridge may also be configured to be mountable to or detachable from the main body of an electrophotographic apparatus such as a copier or a laser beam printer. In FIG. 1 , the electrophotographic photosensitive member 1 , the charging unit 3 , the developing unit 5 and the cleaning unit 7 are integratedly supported to be formed into a cartridge, and a guiding unit 10 such as a rail of the main body of the electrophotographic apparatus is used to form a process cartridge 9 mountable to or detachable from the main body of the electrophotographic apparatus.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following Examples at all. It is to be noted that “part(s)” in the Examples means “part(s) by mass”.