JP2001117245A - Method for manufacturing electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dry a coating film by preventing the expansion of the liquid pool produced in a coating application stage. SOLUTION: In the coating application stage, a conductive substrate is immersed into a coating application vessel 1 filled with a coating liquid for a photosensitive layer containing a solvent and is then pulled up, by which a coating liquid film is formed on its surface. In the next preheating stage, the substrate is placed onto a pallet previously heated to a prescribed temperature by passing a drying furnace 3 or by a heating controller that the pallet itself possesses, by which the bottom end in at least its coating application direction is heated. In the next drying stage, the substrate kept placed on the pallet is transported in this state to the drying furnace 3 where the coating liquid film is heated and dried. The preheating temperature is set at a temperature lower by 5 to 25 deg.C than the boiling point of the solvent, a temperature at which the saturated vapor pressure of the solvent attains 300 to 600 mmHg or at a temperature lower by 35 to 60 deg.C than the drying temperature. The bottom of the pallet is provided with a heat storage member. The coating liquid contains the solvent having the boiling point of >=50 deg.C or a non-halogen-base solvent. The thickness of the photosensitive layer film is >=20 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrophotographic photosensitive member.

[0002]

2. Description of the Related Art Among electrophotographic photosensitive members (hereinafter, also referred to as "photosensitive members") used in image forming apparatuses such as copying machines and laser printers, photosensitive members using an organic photoconductive material are inorganic. Sensitivity, durability and environmental stability are slightly inferior to photoconductors using photoconductive materials, but toxicity, cost,
Due to the excellent degree of freedom in material design, it has been widely used in recent years, and various sensitization methods have been proposed. In particular, a photosensitive layer comprising a charge generating layer containing a charge generating substance that generates charge carriers by light irradiation and a charge transporting layer mainly composed of a charge transporting substance that receives and transports the charge carriers generated in the charge generating layer. Laminated photoreceptors with layers exhibit excellent sensitization and account for the majority of photoreceptors currently in practical use,
It is also expected to be the mainstream of photoconductors in the future. Also,
An undercoat layer is provided between the conductive substrate and the photosensitive layer to improve chargeability, prevent unnecessary charge injection from the conductive substrate,
The durability is improved by covering defects on the conductive substrate, preventing the generation of pinholes, and improving the adhesiveness of the photosensitive layer. The photosensitive layer is prepared by dissolving or dispersing a photoconductive material in a solvent together with a binder resin to prepare a coating solution for the photosensitive layer, and generally applying the coating solution on a conductive substrate by an immersion method, followed by drying. It is formed.

In the immersion method, a liquid pool is formed at the lower end of the photosensitive member in the coating direction due to dripping of the coating liquid in the coating step. When a photosensitive member having a liquid pool is used in an image forming apparatus, the distance between the photosensitive member and the developing roller becomes uneven, which adversely affects image formation. For this reason, in the past, the liquid pool was wiped off, but now, by controlling the distance between the flange of the photoreceptor and the color of the developing tank, the adverse effect on image formation has been reduced. Therefore, the liquid pool was not wiped off. However, there is a disadvantage that the liquid pool expands due to heating in the subsequent drying step.

When a halogen-based solvent such as dichloromethane or trichloroethane is used, most of the solvent in the coating film evaporates before entering the drying oven, and only the residual solvent evaporates in the drying oven. Expansion is unlikely to occur. However, halogen-based solvents tend not to be used in consideration of the effect on the environment. Non-halogenated solvents used in place of halogenated solvents have a higher boiling point than halogenated solvents and are less likely to evaporate at room temperature, resulting in larger liquid pools and higher temperature drying. When a non-halogen solvent is used, the amount of solvent that evaporates before entering the drying oven is small, and in the drying oven, the liquid pool is rapidly exposed to high temperatures, the solvent evaporates rapidly, and the coating liquid film surface dries. Harden. In this state, heating is further performed, so that the gas evaporated inside the coating liquid film expands, and the liquid pool expands like a balloon. In recent years, it has been desired to improve the durability of the photoreceptor from the viewpoint of extending the life of the photoreceptor, and the film quality is improved by the material of the photosensitive layer, and the thickness of the photosensitive layer tends to be increased. By increasing the film thickness, the pool becomes even larger,
Expansion is more likely to occur.

[0005] When a photoreceptor in which the liquid reservoir expands is used in an image forming apparatus, the distance between the photoreceptor and the developing roller becomes uneven, which adversely affects image formation. For this reason, a drying condition in which a rapid temperature rise in a drying furnace is suppressed is required so that the expansion phenomenon does not occur. The time required from immediately after the coating step to the drying step is usually about 10 to 15 minutes. When a halogen-based solvent is used, most of the solvent evaporates during this period, but when a non-halogen-based solvent is used, the amount of the solvent remaining in the coating liquid film increases. In order to reduce the amount of residual solvent, there is a method in which the above-mentioned time is lengthened to promote the evaporation of the solvent. However, the manufacturing time per photoreceptor is lengthened and the manufacturing cost is increased. The likelihood of a rate drop is increased. As another method, there is a method in which drying is carried out by increasing the temperature stepwise. However, a modification of the drying furnace is required, and the production cost increases in terms of equipment.

[0006] Japanese Patent Application Laid-Open No. 8-44089 discloses that
As a drying method to prevent defects that occur from after the coating process to completion of the photoreceptor after drying, after the temperature of the substrate reaches the minimum boiling point in the coating liquid, the temperature is raised based on a predetermined relational expression. A method of drying at a speed has been proposed. JP-A-63-254461 discloses a technique of spray-coating a coating solution, pre-drying, and then heating and drying a protective layer provided between a conductive substrate and a photosensitive layer. I have.

[0007]

However, Japanese Unexamined Patent Publication No. Hei 8-4
In the drying method described in Japanese Patent No. 4089, the drying conditions for reaching the minimum boiling point in the coating liquid are not specified. Therefore, if the temperature is rapidly increased during this time, the liquid pool generated in the coating process will expand. Also, JP-A-63-
Japanese Patent No. 254461 relates to a protective layer, and even if this technique is applied to a photosensitive layer, the expansion of a liquid pool cannot be prevented.

It is an object of the present invention to provide a method of manufacturing an electrophotographic photoreceptor capable of drying a coating liquid film while preventing expansion of a liquid pool generated in a coating step.

[0009]

According to the present invention, there is provided a method for producing an electrophotographic photosensitive member having a photosensitive layer on a conductive substrate.
Dipping and pulling up a conductive substrate in a coating solution for a photosensitive layer containing a solvent, and applying a coating liquid film on the surface thereof; preheating at least a lower end portion of the substrate in a coating direction; And heating and drying the coating liquid film of (1).

According to the present invention, in the preheating step provided after the coating step and before the drying step, the solvent in the coating liquid film applied on the conductive substrate evaporates and decreases. In particular, the solvent efficiently evaporates in the liquid pool generated at the lower end in the coating direction of the photoconductor in the coating process. Therefore, the expansion of the liquid pool in the drying step can be prevented.

Further, the present invention is characterized in that in the preheating step, the preheating is performed at a temperature lower by 5 ° C. to 25 ° C. than the boiling point of the solvent.

According to the present invention, in the preheating step, it is preferable to heat at a temperature lower by 5 ° C. to 25 ° C. than the boiling point of the solvent contained in the coating liquid. If the preheating temperature is lower than the boiling point of the solvent, the solvent in the liquid pool will not evaporate. If the boiling point of the solvent is higher than the boiling point, the solvent in the liquid pool rapidly evaporates and the liquid pool expands. By setting the preheating temperature in the above-mentioned optimum temperature range which is not too low or not higher than the boiling point of the solvent, the solvent can be sufficiently evaporated while preventing the expansion of the liquid pool.

Further, the present invention is characterized in that in the preheating step, the preheating is performed at a temperature at which the saturated vapor pressure of the solvent is in the range of 300 mmHg to 600 mmHg.

According to the present invention, in the preheating step, the saturated vapor pressure of the solvent contained in the coating liquid is not less than 300 mmHg and not more than 60 mmHg.
It is preferable to heat at a temperature within the range of 0 mmHg or less. When the solvent in the liquid pool generated in the coating process evaporates rapidly, the liquid pool expands. If the vapor pressure is relatively high, evaporation occurs rapidly, and the higher the vapor pressure, the higher the evaporation rate. Also, if the vapor pressure is relatively low, no evaporation occurs. By setting the preheating temperature to a temperature within the above-described optimum range where the saturated vapor pressure of the solvent is not too low or too high, the solvent can be sufficiently evaporated while preventing the expansion of the liquid pool.

Further, the present invention is characterized in that in the preheating step, the preheating is performed at a temperature lower by 35 ° C. to 60 ° C. than the drying temperature in the drying step.

According to the present invention, in the preheating step, it is preferable to heat at a temperature lower by 35 ° C. to 60 ° C. than the drying temperature in the drying step. The drying temperature is set to an optimum temperature at which excellent electrical characteristics and image characteristics are obtained in the manufactured photoreceptor. If the preheating temperature for preventing the expansion of the liquid pool is lower than the drying temperature but too close to the drying temperature, the liquid pool expands. If the temperature is lower than the drying temperature but too far from the drying temperature, the solvent in the liquid pool does not evaporate. By setting the preheating temperature to a temperature lower than the drying temperature and in the above-described optimum temperature range that is not too close or too far, it is possible to sufficiently evaporate the solvent while preventing the expansion of the liquid pool. it can.

The present invention also relates to a method of manufacturing an electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, wherein the conductive substrate is immersed in a coating solution for a photosensitive layer containing a solvent, pulled up, and coated on the surface. A step of applying a liquid film, and a step of heating and drying the coating liquid film on the conductive substrate, wherein the conductive substrate is transported from the application step to the drying step using a pallet heated to a predetermined temperature in advance. A method for manufacturing an electrophotographic photoreceptor.

According to the present invention, the conductive substrate coated with the coating liquid film in the coating step is placed on a pallet and transported to the drying step. Since the pallet used is preheated to a predetermined temperature, the coating liquid film is preheated during transportation, and the solvent in the coating liquid film evaporates and decreases. In particular, the solvent efficiently evaporates in the liquid pool generated at the lower end of the photoconductor in the coating process. Therefore, the expansion of the liquid pool in the drying step can be prevented.

Further, the present invention is characterized in that the pallet is passed through a drying oven in advance and heated to a predetermined temperature.

According to the invention, the heating of the pallet is effected by passing through a drying oven. If the pallet is used by circulating between the coating process and the drying process, the temperature and time of the drying process, the time from when the drying process is completed to when the conductive substrate after the coating process is mounted, and the material of the pallet , It is possible to always heat the pallet to a predetermined temperature. Therefore, the pallet is always heated to a predetermined temperature by passing through the drying furnace, so that the expansion of the liquid pool can be easily prevented and the solvent can be evaporated.

Further, the present invention is characterized in that the pallet is provided with heating control means therein, and the pallet is heated to a predetermined temperature by the heating control means.

According to the present invention, the pallet is heated by heating control means of the pallet itself. Therefore, by using the same pallet in the coating step and the drying step, it is possible to always heat to a stable predetermined temperature without being affected by environmental conditions such as air temperature during manufacturing, and to easily prevent the expansion of the liquid pool and prevent the solvent from being expanded. Can evaporate.

Further, the present invention is characterized in that the pallet is provided with a heat storage member at its bottom.

According to the present invention, the temperature change of the pallet is different depending on the material, and the temperature change is large especially when the pallet is used by circulating between the coating step and the drying step. By doing so, heat can be prevented from being released. For example, it is preferable to provide a heat storage member made of oil or sand at the bottom of the pallet. Therefore, it is possible to easily prevent the liquid pool from expanding and evaporate the solvent.

Further, the present invention is characterized in that the pallet is heated to a temperature lower by 5 ° C. to 25 ° C. than the boiling point of the solvent.

According to the present invention, it is preferable to heat the pallet to a temperature lower by 5 ° C. to 25 ° C. than the boiling point of the solvent contained in the coating liquid. Thus, the solvent can be sufficiently evaporated while preventing expansion of the liquid pool in an optimum temperature range that is not too low and not higher than the boiling point of the solvent.

Further, the present invention is characterized in that the pallet is heated to a temperature at which the saturated vapor pressure of the solvent is in the range of 300 mmHg to 600 mmHg.

According to the present invention, the saturated vapor pressure of the solvent contained in the pallet is 300 mmHg or more and 600 mm
It is preferable to heat to a temperature within the range of Hg or less.
This makes it possible to sufficiently evaporate the solvent while preventing the expansion of the liquid pool at an optimum temperature at which the saturated vapor pressure of the solvent is not too low or too high.

Further, the present invention is characterized in that the pallet is heated to a temperature lower by 35 ° C. to 60 ° C. than a drying temperature in the drying step.

According to the present invention, it is preferable to heat the pallet to a temperature lower by 35 ° C. to 60 ° C. than the drying temperature in the drying step. This allows the optimal temperature range below the drying temperature and not too close or too far away,
The solvent can be sufficiently evaporated while preventing the expansion of the liquid pool.

In the present invention, the coating solution for the photosensitive layer may be at 50 ° C.
It is characterized by containing a solvent having the above boiling point.

According to the present invention, when the boiling point of the solvent in the coating liquid for the photosensitive layer is less than 50 ° C., the amount of the solvent in the coating liquid film applied to the conductive substrate is reduced during the transportation from the coating step to the drying step. Is reduced by natural drying without preheating, and the liquid pool does not expand in the coating process in the drying process. Therefore, there is no need for preheating. However, when the boiling point of the solvent is 50 ° C. or higher, the amount of the solvent that evaporates during natural drying during transport is small, and the amount of the solvent remaining in the coating liquid film, particularly the liquid pool, is large, and the liquid pool expands in the drying step. Cheap. For this reason, it is necessary to carry out the preheating step as described above or to carry by a pallet heated to a predetermined temperature. Thus, the solvent can be sufficiently evaporated while preventing the liquid pool from expanding.

The present invention is also characterized in that the coating solution for a photosensitive layer contains a non-halogen solvent.

According to the present invention, a halogen-based solvent tends not to be used in consideration of environmental issues. Instead, a non-halogen-based solvent having a higher boiling point than the halogen-based solvent and hardly evaporating at room temperature is used. In the immersion method using the non-halogen solvent, the liquid pool becomes large, the amount of the solvent that evaporates during the period from the application step to the drying step is small, and the liquid pool expands in the drying step. Therefore, when a non-halogen solvent is used, it is necessary to carry out the preheating step as described above or to carry by a pallet heated to a predetermined temperature. Thus, the solvent can be sufficiently evaporated while preventing the liquid pool from expanding.

In the present invention, the photosensitive layer preferably has a thickness of 20 μm.
m or more.

According to the present invention, the amount of the solvent in the coating liquid film varies depending on the thickness of the photosensitive layer, and the expansion and size of the liquid pool due to rapid evaporation of the solvent differ. Since the amount of the solvent in the liquid film increases, the liquid pool becomes large and the liquid film easily expands. Therefore, when the film thickness is relatively large, particularly when the film thickness is 20 μm or more, it is necessary to carry out the preheating step as described above or transfer the pallet heated to a predetermined temperature. Thus, the solvent can be sufficiently evaporated while preventing the liquid pool from expanding. In particular, when a non-halogen solvent having a high boiling point is used and the thickness of the photosensitive layer is set to 20 μm or more, the amount of the solvent in the coating liquid film increases, the liquid pool increases, and the liquid easily expands. Transport by pallets heated to temperature is essential.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, an electrophotographic photoreceptor is formed by forming a photosensitive layer on a conductive substrate. When the photosensitive layer is a stacked type (separated type), the photosensitive layer is formed by stacking a charge generation layer and a charge transport layer. An undercoat layer (barrier layer) may be formed between the conductive substrate and the charge generation layer or the charge transport layer, or between the charge generation layer and the charge transport layer so as not to impair the photosensitive characteristics. Alternatively, a protective layer may be formed on the photosensitive layer.

As the conductive substrate, various types of conventionally known substrates can be used. For example, metal substrates such as aluminum and stainless steel, phenol resin, polyamide,
A substrate formed of a polymer material such as polyethylene terephthalate and polystyrene can be used.

Various known resins can be used for the undercoat layer. For example, polyamide, copolymerized nylon, polyvinyl alcohol, polyurethane, polyester, epoxy, phenolic resin, casein, cellulose and gelatin can be used. Particularly, alcohol-soluble copolymerized nylon is preferable.

The undercoat layer is formed using an undercoat layer coating solution in which the above resin is dissolved in water or various non-halogen solvents. Specific examples of the above resin include water, methanol, ethanol, butanol, 1,3-dioxolane and a glycol-based single solvent, a water / alcohol-based mixed solvent, two or more alcohol-based mixed solvents, and two or more glycols. And a mixed solvent of 1,3-dioxolane and an alcohol. The undercoat layer coating liquid is applied to the surface of the conductive substrate by an application method or the like. The thickness of the undercoat layer is preferably about 0.1 μm to 5 μm.

The undercoat layer may be provided with zinc oxide, titanium oxide, titanium oxide, or the like, if necessary, particularly for setting the volume resistivity of the undercoat layer and improving the repeated aging characteristics in a low-temperature / low-humidity environment. Inorganic pigments such as tin, indium oxide, silica and antimony oxide may be dispersed and contained. The inorganic pigment was prepared by adding the inorganic pigment / resin = 20 /
It is used by being dispersed at a ratio of 80 to 95/5 (weight ratio).

The charge generation layer is composed mainly of a charge generation substance which generates charges by light irradiation, and may contain a known binder resin, a plasticizer and a sensitizer as required. Examples of the charge generating substance include perylene-based pigments such as perylene imide and perylene anhydride, polycyclic quinone-based pigments such as quinacridone and anthraquinone, phthalocyanine-based pigments such as metal phthalocyanine, metal-free phthalocyanine and halogen-free metal phthalocyanine, and squaraine. Azo having a carbazole skeleton, a styrylstilbene skeleton, a triphenylamine skeleton, a dibenzothiophene skeleton, an oxadiazole skeleton, a fluorenone skeleton, a bisstilbene skeleton, a distyryloxadiazole skeleton, and a distyrylcarbazole skeleton. Pigments. In particular, as a charge-generating substance having high charge-generating ability and high sensitivity, metal-free phthalocyanine pigments, oxotitanyl phthalocyanine pigments, bisazo pigments containing a fluorene ring or a fluorenone ring, bisazo pigments composed of an aromatic amine and trisazo Pigments.

The charge transport layer contains a charge transport material capable of accepting and transporting the charge generated in the charge generation layer and a binder resin as essential components. If necessary, a known silicone leveling agent, a plasticizer, and It comprises a sensitizer and the like. Examples of the charge transport material include poly-N-vinylcarbazole and its derivatives, poly-γ-carbazolylethylglutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylvillene,
Polyvinyl phenanthrene, oxazole derivative, oxodiazole derivative, imidazole derivative, 9- (p-
Electron donation of diethylaminostyryl) anthracene, 1,1-bis (4-dibenzylaminophenyl) propane, styrylanthracene, styrylvirazoline, phenylhydrazones, hydrazone derivatives, and azine compounds having a 3-methyl-2-benzothiarizone ring. Substances. In addition, fluorenone derivatives, dibenzothiophene derivatives, intenothiophene derivatives, phenanthrenequinone derivatives, intenopyridine derivatives, thioxanthone derivatives, benzo [C] cinnoline derivatives, phenazine oxide derivatives, tetracyanoethylene, tetracyanoquinodimethane, bromanyl , Chloranil and benzoquinone. The charge transport materials may be used alone or in combination of two or more. In the case where a charge transporting substance having a film-forming property such as polyvinyl carbazole is used, a binder resin is not necessarily required.

Various resins can be used as a binder resin which is used as needed for the charge generation layer and essential for the charge transport layer. Examples of the binder resin include styrene polymers, acrylic polymers, and styrene. -Acrylic copolymer, polyethylene,
Ethylene-vinyl acetate copolymer, chlorinated polyethylene,
Olefin polymers such as polypropylene and ionomer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, epoxy resin, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, silicone resin, ketone Resin, polyvinyl butyral resin,
Examples thereof include photocurable resins such as polyether resins, phenol resins, urethane acrylates, and epoxy acrylates. The binder resin may be used alone or in combination of two or more. In particular, polystyrene, polycarbonate, and polyarylate are preferable because they have a volume resistivity of 10 ¹³ Ω or more and have excellent film-forming properties and electrical characteristics.

Incidentally, an antioxidant such as a hydroquinone compound, a tocopherol compound and a phenol compound, and a leveling agent such as polysiloxane may be added to the charge transport layer, if necessary.

A non-halogen solvent is used for forming the charge generation layer and the charge transport layer. Examples of the solvent include alcohols such as methanol, ethanol, isopropanol and butanol, aliphatic hydrocarbons such as n-hexane, octane and cyclohexane, aromatic hydrocarbons such as benzene, toluene and xylene, dimethyl ether, diethyl ether and tetrahydrofuran. , 1,3-
Dioxolan, ethylene glycol dimethyl ether,
Ethers such as ethylene glycol dieleether and diethylene glycol dimethyl ether, ketones such as acetone, methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate and methyl acetate,
Various solvents such as dimethylformamide and dimethylsulfoxide. The solvent may be used alone or in combination of two or more.

When a binder resin is used in the charge generation layer, the charge generation substance and the binder resin can be used in various ratios, but 5 parts by weight of the charge generation substance is used with respect to 100 parts by weight of the binder resin. Parts to 1000 parts by weight, especially 20 parts by weight
500 parts by weight are preferred. The charge generation layer may have an appropriate thickness, but preferably has a thickness of 0.01 μm to 5 μm, particularly preferably about 0.1 μm to 3 μm.

The charge transport material and the binder resin in the charge transport layer can be used in various ratios as long as the charge transport is not inhibited. However, the charge generated in the charge generation layer by light irradiation can be easily transported. , Based on 100 parts by weight of the binder resin, 10 parts by weight to 500 parts by weight of the charge transport material,
5 parts by weight to 200 parts by weight is preferred. Further, the thickness of the charge transport layer is preferably from 2 μm to 100 μm, particularly preferably from about 5 μm to 30 μm.

The charge-generating layer and the charge-transporting layer are formed by appropriately using the above-mentioned materials and applying a coating liquid for the charge-generating layer by a conventionally known method such as a roll mill, a ball mill, an attritor, a paint shaker, a sand mill and an ultrasonic disperser. The coating liquid for the charge transport layer is prepared, the coating liquid is applied on a conductive substrate in a coating step using a conventionally known coating apparatus, and the applied coating liquid film is dried and formed in a subsequent drying step. Is done. Examples of the method of applying the coating liquid include a dip coating method, a spray type coating method, and a nozzle type coating method. The dip coating method is the most common, and the apparatus is simple.

In the present invention, in particular, a preheating step of the coating liquid film is provided after the coating step until the drying step. Specifically, the conductive substrate that has undergone the application step is transported to the drying step using a pallet heated to a predetermined temperature, thereby preheating the coating film. In the preheating, at least the lower end of the substrate in the application direction is preheated, whereby the amount of the solvent in the coating liquid film is reduced, and particularly, the solvent in the liquid pool generated at the lower end of the conductive substrate is effectively evaporated. For this reason, the expansion of the liquid pool in the drying step can be prevented.

When the boiling point of the solvent in the coating liquid is less than 50 ° C.,
The solvent in the coating liquid film evaporates by natural drying up to the drying step, and the amount of the remaining solvent is sufficiently reduced. Therefore, in the drying step, the liquid pool does not expand, and preheating is unnecessary. However, when the boiling point of the solvent in the coating liquid is 50 ° C. or higher, the amount of evaporation of the solvent is small and the amount of the remaining solvent is large in natural drying until the drying step. Therefore, in the drying step, the liquid pool easily expands, and preheating is required.
By the preheating, the solvent in the coating liquid film, particularly the liquid pool, evaporates and the amount of the remaining solvent is sufficiently reduced, so that the expansion of the liquid pool in the drying step can be prevented. In the drying step after the preheating, a drying oven is used. Examples of the type of the drying oven include an air convection hot air oven and an infrared drying oven.

In view of environmental problems, halogen-based solvents tend not to be used, and non-halogen-based solvents are used instead. When dip coating is performed using a non-halogen solvent that has a higher boiling point than that of a halogen solvent and does not easily evaporate at room temperature, the liquid pool becomes large and the liquid pool easily expands. Therefore, preheating as described above is necessary. By the preheating, the solvent in the coating liquid film, particularly the liquid pool, evaporates and the amount of the remaining solvent is sufficiently reduced, so that the expansion of the liquid pool in the drying step can be prevented.

In performing the preheating as described above,
If the preheating temperature is too low below the boiling point of the solvent in the coating liquid,
The solvent in the coating liquid film, especially in the liquid pool, does not sufficiently evaporate before the drying step. On the other hand, if the preheating temperature is higher than the boiling point of the solvent in the coating liquid, the coating liquid film, particularly the solvent in the liquid pool, rapidly evaporates before the drying step, and the liquid pool easily expands. Therefore, the optimal preheating temperature is preferably a temperature that is neither too low nor too high of the boiling point of the solvent in the coating liquid, that is, a range of 5 to 25 ° C lower than the boiling point of the solvent.

The preheating temperature must be lower than the boiling point of the solvent, that is, the temperature at which the solvent reaches a saturated vapor pressure. Therefore, the optimal preheating temperature is set so that the solvent in the coating liquid film evaporates gradually, not suddenly, and the saturated vapor pressure becomes 30%.
The temperature is preferably from 0 mmHg to 600 mmHg. In particular, 320 mmHg or more and 570 mmH
g or less.

The drying temperature is set to a temperature at which excellent electrical characteristics and image characteristics are obtained in the photosensitive member to be manufactured, and the preheating temperature is set to a temperature more than necessary to prevent the liquid pool from expanding. It is not necessary to do so, but rather a temperature that is 35 ° C to 60 ° C below the drying temperature is preferred.

Further, the amount of the solvent remaining in the coating liquid film varies depending on the thickness of the charge generation layer and the charge transport layer, and the expansion and size of the liquid pool differ. When the film thickness is large, the amount of the solvent remaining in the coating liquid film increases, so that the liquid pool becomes large, and the film easily expands. Therefore, the above-described preheating is required. When a non-halogen solvent having a high boiling point is used as the solvent in the coating liquid, the thickness of the charge generation layer and the charge transport layer is 20 μm.
In this case, preheating is required.

As a method of preheating, various methods can be adopted depending on the circulation path of the pallet used for transporting the conductive substrate, the method of heating the pallet, and the shape and material of the pallet. An example will be described below.

FIG. 1 is a view showing a moving path of a pallet for explaining a method of manufacturing an electrophotographic photosensitive member according to an embodiment of the present invention. In the coating step, a conductive liquid substrate is immersed in the coating tank 1 and pulled up to apply a coating liquid film on the substrate. Here, the coating liquid in the coating tank 1 is a coating liquid for a charge generation layer or a coating liquid for a charge transport layer. In the next preheating step, the substrate after the application step at the drying pallet transfer point 2 is placed on a pallet of a predetermined temperature and conveyed to the drying step while being preheated. In the next drying step, the substrate placed on the pallet passes through the drying furnace 3 at a predetermined temperature.
The substrate that has passed through the drying furnace 3 is taken out at the finished product take-out port 4, and the pallet from which the substrate has been taken out passes through the pallet circulation path 5 and is then heated to a predetermined temperature by passing through the drying furnace 3 and again. Returning to the drying pallet transfer point 2, the substrate after the application step is mounted again and transported to the preheating step and the drying step.

Here, the heating furnace for heating the pallet to a predetermined temperature and the drying furnace for drying the substrate are the same drying furnace 3, but a separate drying furnace may be provided. Further, the path of the pallet is not limited to that shown in FIG. 1 as long as the pallet is heated to a predetermined temperature in advance.
As a material of a pallet used for transporting such a substrate, a material having high thermal conductivity such as stainless steel and aluminum is preferable, but a material provided with a heat storage member made of oil, pebbles, etc. at the bottom of the pallet is preferable. Particularly preferred.

FIG. 2 is a diagram showing a moving path of a pallet for explaining a method of manufacturing an electrophotographic photosensitive member according to another embodiment of the present invention. In FIG. 1, preheating is performed using a pallet that has been heated to a predetermined temperature in advance by passing through a drying furnace 3, but in FIG. 2, preheating is performed by a heating control device of the pallet itself. In the coating step, as described above, the conductive liquid substrate is dipped in the coating tank 6 and pulled up, so that the coating liquid film is coated on the substrate. Here, the coating liquid in the coating tank 6 is a coating liquid for a charge generation layer or a coating liquid for a charge transport layer. The substrate coated with the coating liquid film is placed on a pallet and transported to a preheating step. In the next preheating step, the timing at which the pallet or the base passes the predetermined position on the conveyor is detected by the sensor 7, and in response to this, the heating control device of the pallet is operated, and the pallet is placed on the pallet at the predetermined temperature. Through the pallet heating space 8. In the next drying step, the sheet passes through a drying furnace 9 at a predetermined temperature. Thereafter, the substrate is taken out at the finished product take-out port 10. After the substrate is taken out, the pallet is circulated through the pallet circulation path 11 by the conveyor, and returns to the application step again. In this case, the material of the pallet
The material is not limited to stainless steel and aluminum, but may be ceramic or a heat-resistant solvent-resistant resin.

[0061]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1 50 parts by weight of methanol, 50 parts by weight of 1,3-dioxolane, 3 parts by weight of titanium oxide, and a nylon copolymer resin (CM4000 manufactured by Toray Industries, Inc.) The resulting mixture was dispersed with a paint shaker for 10 hours to prepare a coating liquid for an undercoat layer.

As a charge generating layer coating liquid, methyl isobutyl ketone (97 parts by weight), a bisazo pigment (chlorodiane blue) of the following structural formula (I): 1.5 parts by weight, and butyral resin (manufactured by Union Carbide Co., Ltd.) The mixture with 1.5 parts by weight was dispersed with a paint shaker for 10 hours to prepare a coating liquid for a charge generation layer.

Further, a hydrazone compound (4, -diethylaminobenzaldehyde-) of the following structural formula (II) was added to 8 parts by weight of tetrahydrofuran as a coating solution for the charge transport layer.
A mixture of 1 part by weight of N, N-diphenylhydrazone) and 1 part by weight of a polycarbonate resin (Iupilon, manufactured by Mitsubishi Gas Chemical Company) was stirred and dissolved with a magnetic stirrer to prepare a coating liquid for a charge transport layer. . In addition,
The boiling point of tetrahydrofuran is 66 ° C.

[0065]

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[0066]

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As the conductive substrate, a thickness of 1 mm and a diameter of 65
An aluminum cylindrical substrate having a length of 348 mm and a length of 348 mm was used.
An undercoat layer was formed so as to have a thickness of 5 μm. Next, a charge generation layer was formed on the undercoat layer by a dipping method so that the thickness after drying was 0.8 μm. Finally, a charge transport layer was formed on the charge generation layer by a dipping method so that the thickness after drying was 25 μm. Thus, an electrophotographic photosensitive member was manufactured.

In the production of the charge generation layer, the pallet movement path shown in FIG. 1 was adopted, and preheating and drying were performed. At this time, the substrate was placed on a pallet preheated to 55 ° C. and transported to a drying step. The saturated vapor pressure of tetrahydrofuran at 55 ° C. is 550 mmHg. In the drying step of the drying furnace 3, the substrate was heated at 100 ° C./1.
Heated and dried over time. In the completed photoreceptor, the liquid pool at the lower end did not expand. Table 1 shows various conditions and results.

Comparative Example 1 Various coating solutions were prepared in the same manner as in Example 1 to form an undercoat layer, a charge generation layer and a charge transport layer. In the manufacture of the charge transport layer, the pallet movement path shown in FIG. 1 was employed, and preheating and drying were performed. At this time, the substrate was placed on a pallet preheated to 35 ° C. and transported to a drying step. In the drying step of the drying furnace 3, the substrate was heated and dried at 100 ° C. for 1 hour. The saturated vapor pressure of tetrahydrofuran at 35 ° C. is 26
3 mmHg. In the completed photoreceptor, the liquid pool at the lower end was expanded, and was at a level of a defective product. Although preheating was performed, the temperature was insufficient to sufficiently evaporate the solvent in the coating liquid film, and it is considered that the liquid pool expanded. Table 1 shows various conditions and results.

Comparative Example 2 Various coating solutions were prepared in the same manner as in Example 1 to form an undercoat layer, a charge generation layer and a charge transport layer. In the manufacture of the charge transport layer, the pallet movement path shown in FIG. 1 was employed, and preheating and drying were performed. At this time, the substrate was placed on a pallet preheated to 70 ° C. and transported to a drying step. In the drying step of the drying furnace 3, the substrate was heated and dried at 100 ° C. for 1 hour. The saturated vapor pressure of tetrahydrofuran at 70 ° C. is 76
0 mmHg. During the preheating step up to the heating and drying step, the liquid pool at the lower end of the photoreceptor had expanded, and was at a level of a defective product. It is considered that because the preheating temperature was too high, the liquid pool was rapidly heated and the film surface evaporated and dried before the solvent inside evaporated, and the liquid pool expanded. Table 1 shows various conditions and results.

Comparative Example 3 Various coating solutions were prepared in the same manner as in Example 1 to form an undercoat layer, a charge generation layer and a charge transport layer. In the production of the charge transport layer, the substrate was transported to the drying step without going through the preheating step. In the drying step of the drying furnace 3, the substrate was heated and dried at 100 ° C./1 hour. The temperature up to the drying step was 20 ° C. In the completed photoreceptor, the liquid pool at the lower end was expanded, and was at a level of a defective product. Table 1 shows various conditions and results.

Comparative Example 4 Various coating solutions were prepared in the same manner as in Example 1 to form an undercoat layer having a thickness of 1.5 μm after drying, and a thickness of 0.8 μm after drying. Was formed, and a charge transport layer having a thickness after drying of 18 μm was formed. In the production of the charge generation layer, the substrate was transported to the drying step without passing through the preheating step. In the drying step of the drying furnace 3, the substrate was heated and dried at 100 ° C./1 hour. In addition,
The temperature up to the drying step was 20 ° C. In the completed photoreceptor, there was no liquid pool at the lower end and no expansion. Since the film thickness was so thin that no liquid pool was formed at the lower end, it is considered that the liquid pool did not expand even if the temperature of the substrate rapidly increased, so that the preheating step is unnecessary. Table 1 shows various conditions and results.

Comparative Example 5 The coating liquid for the undercoat layer and the charge generating layer was the same as in Example 1, except that dichloromethane was used as the solvent as the coating liquid for the charge transporting layer. The coating liquid was adjusted. The boiling point of dichloromethane is 40 ° C. An undercoat layer, a charge generation layer and a charge transport layer were formed in the same manner as in Example 1. In the production of the charge transport layer, the substrate was transported to the drying step without going through the preheating step. In the drying step of the drying furnace 3, the substrate was heated and dried at 80 ° C./1 hour. The temperature up to the drying step is 20
° C. The saturated vapor pressure of dichloromethane at 20 ° C. is 349 mmHg. In the completed photoreceptor, there was no expansion of the liquid pool at the lower end. It is considered that when dichloromethane was used as the solvent, most of the solvent in the coating liquid film was evaporated before the drying step, and the liquid pool did not expand even if the temperature of the substrate rapidly increased. Table 1 shows various conditions and results.

(Example 2) The coating liquid for the undercoat layer and the charge generation layer was the same as that in Example 1, except that 1,4-dioxane was used as the solvent as the coating liquid for the charge transport layer. Various coating solutions were prepared. The boiling point of 1,4-dioxane is 101 ° C. An undercoat layer, a charge generation layer and a charge transport layer were formed in the same manner as in Example 1. In the manufacture of the charge transport layer, the substrate was transported to the preliminary heating step and the drying step using the pallet moving path shown in FIG. 1 using a pallet heated to 82 ° C. In the drying step of the drying furnace 3, the substrate was heated and dried at 130 ° C./1 hour. The saturated vapor pressure of 1,4-dioxane at 82 ° C. is 40
0 mmHg. In the completed photoreceptor, there was no expansion of the liquid pool at the lower end. Table 1 shows various conditions and results.

[0075]

[Table 1]

In Examples 1 and 2 and Comparative Examples 1 and 2, a heat storage member made of oil was mounted on the bottom of a pallet used when the substrate was moved to the drying step. Even when preheating was performed, the result of expansion of the liquid pool was the same as in Table 1. In addition, even when preheating was performed using the pallet movement path shown in FIG. 2, the result of the expansion of the liquid pool was the same as in Table 1. Here, a 500 W electric heater was provided inside the pallet as a heating control device.

[0077]

As described above, according to the present invention, since the preheating step is provided after the coating step and before the drying step, the coating liquid applied to the conductive substrate in the preheating step is provided. The solvent in the membrane, especially in the pool, evaporates and diminishes efficiently.
Therefore, the expansion of the liquid pool in the drying step can be prevented.

Further, according to the present invention, in the preheating step, by preheating at a temperature lower by 5 ° C. to 25 ° C. than the boiling point of the solvent in the coating liquid, the solvent can be sufficiently prevented while preventing the expansion of the liquid pool. Can evaporate.

According to the present invention, in the preheating step, the solvent is sufficiently evaporated while preventing the expansion of the liquid pool by preheating at a temperature at which the saturated vapor pressure of the solvent is in the range of 300 mmHg to 600 mmHg. be able to.

According to the present invention, in the preheating step, by preheating at a temperature lower by 35 ° C. to 60 ° C. than the drying temperature in the drying step, the solvent is sufficiently evaporated while preventing the expansion of the liquid pool. can do.

According to the present invention, the conductive substrate on which the coating liquid film has been applied in the application step is placed on a pallet heated to a predetermined temperature and transported to the drying step. During this transfer,
The coating liquid film is pre-heated, and the solvent in the coating liquid film, particularly in the liquid pool, is efficiently evaporated and reduced. Therefore, the expansion of the liquid pool in the drying step can be prevented.

According to the present invention, since the pallet is heated to a predetermined temperature after passing through the drying path in advance, the pallet is always heated to the predetermined temperature to easily prevent the liquid pool from expanding and evaporate the solvent. be able to.

According to the present invention, the pallet is heated to a predetermined temperature by the heating control means provided inside the pallet. Therefore, it is possible to always stably heat to a predetermined temperature without being influenced by environmental conditions, and it is possible to easily prevent expansion of the liquid pool and evaporate the solvent.

Further, according to the present invention, since the heat storage member is provided at the bottom of the pallet, it is possible to easily prevent the expansion of the liquid pool and evaporate the solvent by preventing heat from being released.

According to the present invention, the pallet is heated to a temperature lower by 5 ° C. to 25 ° C. than the boiling point of the solvent.
The solvent can be sufficiently evaporated while preventing the expansion of the liquid pool.

Further, according to the present invention, since the pallet is heated to a temperature at which the saturated vapor pressure of the solvent is in the range of 300 mmHg to 600 mmHg, the solvent can be sufficiently evaporated while preventing the expansion of the liquid pool. .

According to the present invention, since the pallet is heated to a temperature lower by 35 ° C. to 60 ° C. than the drying temperature in the drying step, it is possible to sufficiently evaporate the solvent while preventing the expansion of the liquid pool. it can.

According to the present invention, the coating solution for the photosensitive layer is 50
Because it contains a solvent with a boiling point of ℃ or more, by carrying out a preheating step or pallet heated to a predetermined temperature,
The solvent can be sufficiently evaporated while preventing the expansion of the liquid pool.

Further, according to the present invention, since the coating liquid for the photosensitive layer contains a non-halogen solvent, it is possible to prevent the expansion of the liquid pool by performing a preheating step or transporting by a pallet heated to a predetermined temperature. The solvent can be sufficiently evaporated while doing so.

According to the present invention, the photosensitive layer has a thickness of 20
Since the thickness is not less than μm, the solvent can be sufficiently evaporated while preventing the expansion of the liquid pool by carrying out the preheating step or the conveyance by the pallet heated to a predetermined temperature.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a moving path of a pallet for describing a method of manufacturing an electrophotographic photosensitive member according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a moving path of a pallet for describing a method of manufacturing an electrophotographic photosensitive member according to another embodiment of the present invention.

[Explanation of symbols]

 1,6 Coating tank 2 Dry pallet transfer point 3,9 Drying furnace 4,10 Finished product take-out port 5,11 Pallet circulation path 7 Sensor 8 Pallet heating section

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayuki Sakamoto 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Inside Sharp Corporation (72) Inventor Makoto Kurokawa 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Inside Sharp Corporation (72) Inventor Tatsuhiro Morita 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Prefecture Inside Sharp Corporation (72) Inventor Sayaka 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Sharp Corporation F term (reference) 2H068 AA21 BA01 BA02 BA03 BA12 EA14 EA16 EA19 FA00

Claims (14)

[Claims] 1. A method for producing an electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, wherein the conductive substrate is immersed in a coating solution for a photosensitive layer containing a solvent, pulled up, and a coating liquid film is formed on the surface thereof. A method for producing an electrophotographic photoreceptor, comprising: a step of applying; a step of preheating at least a lower end portion in a coating direction of a substrate; and a step of heating and drying a coating liquid film on a conductive substrate. 2. The method according to claim 1, wherein in the preheating step, the preheating is performed at a temperature lower by 5 ° C. to 25 ° C. than the boiling point of the solvent. 3. The method according to claim 1, wherein in the preheating step, the preheating is performed at a temperature at which a saturated vapor pressure of the solvent is in a range of 300 mmHg to 600 mmHg. 4. The method according to claim 1, wherein in the preheating step, the preheating is performed at a temperature lower by 35 ° C. to 60 ° C. than a drying temperature in the drying step. 5. A method for producing an electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, wherein the conductive substrate is immersed in a coating solution for a photosensitive layer containing a solvent, pulled up, and a coating liquid film is formed on the surface thereof. A coating step; and a step of heating and drying the coating liquid film on the conductive substrate, wherein the conductive substrate is transferred from the coating step to the drying step using a pallet heated to a predetermined temperature in advance. A method for producing an electrophotographic photoreceptor. 6. The method according to claim 5, wherein said pallet is heated to a predetermined temperature by passing through a drying furnace in advance. 7. The method according to claim 5, wherein the pallet is provided with a heating control means therein, and the pallet is heated to a predetermined temperature by the heating control means. 8. The method according to claim 5, wherein the pallet includes a heat storage member at a bottom thereof. 9. The method according to claim 1, wherein the pallet has a temperature of 5 ° C. or lower than the boiling point of the solvent.
6. The method for producing an electrophotographic photosensitive member according to claim 5, wherein the photosensitive member is heated to a temperature lower by 25 [deg.] C. 10. The pallet having a saturated vapor pressure of a solvent of 3
6. The method for producing an electrophotographic photoreceptor according to claim 5, wherein the heating is performed to a temperature within a range from 00 mmHg to 600 mmHg. 11. The method according to claim 5, wherein the pallet is heated to a temperature lower by 35 ° C. to 60 ° C. than a drying temperature in the drying step. 12. The method according to claim 1, wherein the coating solution for a photosensitive layer contains a solvent having a boiling point of 50 ° C. or higher. 13. The method according to claim 1, wherein the coating solution for a photosensitive layer contains a non-halogen solvent. 14. The method according to claim 1, wherein the thickness of the photosensitive layer is 20 μm or more.