JP5534796B2 - Method for producing electrophotographic photosensitive member - Google Patents

Description

  The present invention relates to a method for producing an electrophotographic photoreceptor.

  In the production of an electrophotographic photoreceptor, examples of methods for forming a coating film such as an intermediate layer, a photosensitive layer, and a protective layer on a support include a roll coater method, a spray method, an electrostatic coating method, and a dip coating method. Among these, the dip coating method is widely used because it is an advantageous method for producing an electrophotographic photosensitive member having a three-dimensional shape such as a cylindrical shape or a seamless belt shape. This method uses a coating tank containing a coating liquid and a device for holding and lifting the coated body, immersing the coated body in the coating liquid in the coating tank, and then pulling it up at an appropriate speed. A coating film is formed on an object to be coated.

  In this dip coating method, a coating film having a desired film thickness can be obtained by appropriately setting coating conditions such as the viscosity, solid content, and lifting speed of the coating solution according to the object to be coated. However, simply immersing the substrate to be coated in the coating solution in the coating tank and pulling it up lowers the liquid level of the coating solution due to the excluded volume of the substrate to be coated. May decrease. In addition, since the liquid surface of the coating liquid is in contact with air, the coating liquid adheres as a film inside the upper part of the coating tank, and eventually the coating liquid is contaminated by peeling off and re-mixing in the coating liquid. Sometimes it ends up. Furthermore, in the vicinity of the liquid surface of the coating liquid in the coating tank, the concentration change of the coating liquid due to the volatilization of the solvent in the coating liquid is remarkable, and a concentration gradient of the coating liquid occurs in the vertical direction of the coating tank, resulting in unevenness of the coating film. In some cases. As described above, in the dip coating method using a stationary coating solution, the above-described disadvantage may occur, and this disadvantage may appear more remarkably in mass production.

  Therefore, a method of performing dip coating in a state where the coating liquid is continuously circulated between a recovery tank provided separately from the coating tank has been devised and used (see Patent Document 1). In this method, as shown in FIG. 1, the coating liquid is fed from the recovery tank 102 to the lower part of the coating tank 101 using the liquid feeding means 103, and the coating liquid exceeding the capacity of the coating tank overflows into the recovery tank. It is a mechanism to return. As a result, the level of the coating liquid in the coating tank is kept constant, and the concentration of the coating liquid in the coating tank becomes uniform. As the liquid feeding means, in order to maintain a stable flow rate of the coating liquid without being affected by the pressure resistance by the filter 104, a pump 105 having a high liquid feeding pressure such as a diaphragm pump is usually used. A diaphragm pump is a pump having a diaphragm valve.

  The film thickness of the coating film formed by dip coating is determined by the viscosity of the coating solution and the lifting speed of the substrate to be coated with respect to the coating solution. In recent electrophotographic apparatuses, low running cost, high speed, and high image quality are demanded from the market, and a coating film (especially using a thermoplastic resin) such as a photosensitive layer of an electrophotographic photoreceptor used therefor. With respect to the surface layer (such as a charge transport layer), the resin used has been increased in strength and thickness. For this reason, the coating liquid for coatings has been increasing in viscosity. In addition, with the increase in image quality of electrophotographic apparatuses, slight coating defects are likely to appear as image defects in the output image.

  As described above, conventionally, in order to form a coating film with a desired film thickness, the pumping speed of an object to be coated is determined, and a pump having a discharge capacity capable of always overflowing the coating liquid in the coating tank is selected. The dip coating was performed while circulating.

  However, in recent years when the image quality of an electrophotographic apparatus has been improved, a slight image defect caused by a small number of bubbles entrained in a coating solution has been regarded as a problem. In particular, when a diaphragm pump capable of quantitative liquid feeding is used as the pump, there is a problem that cavitation at the diaphragm valve is likely to occur due to its mechanism. Further, when a coating solution having a high viscosity is used, there is a problem in that bubbles once entering the coating solution do not escape and cause image defects. Further, when production is continued for a long time, the incidence of defects that cause image defects tends to increase.

  In order to avoid these problems, if the pump is stopped and the coating solution is allowed to stand, the productivity cannot be denied.

  In order to solve these problems, a method has been devised in which a pump is not used for liquid feeding to a coating tank. Since it is not necessary to use a fixed-quantity pump as long as the pump is not used for liquid feeding to the coating tank, it is not necessary to use a diaphragm pump.

  In Patent Document 2, as shown in FIG. 5, a storage tank 508 that is a third tank is provided at a position higher than the coating tank 501, and the coating liquid is prevented so that the pulsation by the liquid feeding means does not propagate into the coating tank. A method of releasing the pressurized state once by releasing it to atmospheric pressure when being sent into the storage tank 508 is disclosed. In this method, the liquid feeding method from the storage tank 508 to the coating tank 501 does not use a pump, but is a liquid feeding method that uses only the gravity of the coating liquid based on the principle of siphon. The pulsation is suppressed. This method has the advantage that the pulsation by the pump 503 does not reach the inside of the coating tank 501, but has the following disadvantages. First, it is difficult to keep the flow rate of the coating solution in the coating tank 501 constant. That is, the flow rate of the coating liquid in the coating tank 501 is affected by the difference in liquid level between the coating tank 501 and the storage tank 508. Therefore, when the coating liquid in the coating tank 501 always overflows and the liquid level 506 of the coating liquid is constant, the liquid surface height 507 of the coating liquid in the storage tank 508 can be stabilized. This is a necessary condition for stabilizing the flow rate of the coating liquid. However, in the case of the method disclosed in Patent Document 2, the application liquid of the excluded volume by the object to be coated 505 when the object to be coated 505 is immersed is sent to the collection tank 502 at a time. Therefore, immediately after the object to be coated 505 is pulled up, the liquid level 507 of the coating liquid in the storage tank 508 becomes lower than before the object to be coated is immersed. In addition, when continuous dip coating is performed, the height of the liquid surface 507 of the storage tank 508 is also increased or decreased due to consumption or replenishment of the coating solution, or supplementation of a dilution solvent for adjusting the viscosity of the coating solution. It becomes a factor which makes it unstable. Therefore, it is substantially difficult to keep the flow rate of the coating liquid in the coating tank 501 constant by maintaining the height of the liquid surface 507 of the storage tank 508 constant during continuous coating. When the electrophotographic photosensitive member is produced by continuously dip coating, the film thickness value of the formed coating film tends to fluctuate, so the method disclosed in Patent Document 2 is unsuitable. .

  As a second disadvantage of the method disclosed in Patent Document 2, since the coating liquid is released from the pressurized state to the atmospheric pressure before entering the storage tank 508, the coating liquid is air in this portion. The air bubbles are easily generated in the coating solution. Bubbles in the coating liquid may be sent to the coating tank 501 and adhere to the coated body 505, which causes a coating defect.

  In addition, unlike the method disclosed in Patent Document 2, in Patent Document 3, the storage tank is positioned higher than the coating tank, unlike the method disclosed in Patent Document 2, but the coating liquid is sent to the storage tank. A method is disclosed that uses an apparatus that does not open to atmospheric pressure when being used. In this method as well as the method disclosed in Patent Document 2, it is difficult to keep the liquid level of the storage tank constant, so from the viewpoint of the stability of the flow rate of the coating liquid in the coating tank. Not enough.

  Patent Document 4 discloses a method of circulating a coating liquid using a height difference. In this method, when the flow rate of the coating liquid having a high viscosity is increased, it is necessary to make the difference in height extremely large. When using a coating liquid having a high viscosity, this method is not an effective method.

JP 59-90667 A Japanese Unexamined Patent Publication No. 09-122551 Japanese Patent Laid-Open No. 02-140751 Japanese Patent Laid-Open No. 2006-320791

An object of the present invention is to use a diaphragm pump having a diaphragm valve and dip-apply the coating liquid on the substrate while continuously circulating the coating liquid between the coating tank and the recovery tank. In the method for producing an electrophotographic photoreceptor having a step of forming,
An object of the present invention is to provide a method for producing an electrophotographic photosensitive member in which generation of bubbles is suppressed and generation of image defects due to bubbles is suppressed.

The present invention relates to a method of manufacturing an electrophotographic photosensitive member using an immersion coating apparatus having a diaphragm pump having a diaphragm valve, a coating tank, and a recovery tank.
The manufacturing method uses the diaphragm pump to dip coat the coating solution on the substrate while continuously circulating the coating solution between the coating tank and the recovery tank. Having a process of forming,
The coating solution contains a solvent having a boiling point of 70 ° C. or less,
The pump stroke of the diaphragm valve is 80 to 100% of 14.7 mm;
A method for producing an electrophotographic photosensitive member, wherein the maximum acceleration of the diaphragm valve is controlled to 30 mm / s ² or less.

  According to the present invention, it is possible to provide a method for producing an electrophotographic photosensitive member in which the generation of bubbles is suppressed and the generation of image defects due to bubbles is suppressed.

It is the schematic which shows an example of the coating liquid circulation type immersion coating apparatus which used the pump for the liquid feeding to a coating tank. It is the schematic which shows an example of the diaphragm pump used for this invention. It is the schematic which shows an example of the coating liquid circulation type immersion coating apparatus which used the pump for the liquid feeding to a coating tank. It is the schematic which shows an example of the coating liquid circulation type immersion coating apparatus which used the pump for the liquid feeding to a coating tank. It is the schematic which shows an example of the coating liquid circulation type dip coating apparatus using the method which does not use a pump for the liquid feeding from a storage tank to a coating tank.

  An example of a coating solution circulation type dip coating apparatus that can be used in the present invention is shown in FIG. Reference numeral 305 denotes an object to be coated, and an upper portion thereof is connected by a lifting device when not shown. Reference numeral 301 denotes a coating tank for dip-coating a coating solution on an object to be coated to form a coating film. The coating liquid that always overflows the coating tank 301 moves to the recovery tank 302 via the pipe. The movement of the coating liquid to the collection tank 302 is performed by the weight of the coating liquid by inclining the piping and arranging the coating liquid level in the collection tank 302 to be lower than that of the coating tank 301. It is like that. If the connection position of the pipe to the recovery tank 302 is set above the liquid level of the coating liquid in the recovery tank 302, the coating liquid may involve air bubbles.

  From the lower part of the collection tank 302, a pipe is arranged so as to send the coating liquid to the coating tank 301 through the filter 304 using a diaphragm pump 303 having a diaphragm valve.

  The volume of the recovery tank 302 is preferably 100 to 300 liters, and the inner diameter of the pipe is preferably 20 to 80 mm.

  The recovery tank 302 can have a pressurizing mechanism. As the pressurizing mechanism, a means for introducing gas is preferable. As the gas, an inert gas such as nitrogen gas or argon gas is preferable. FIG. 3 shows a gas inlet 306 and an inert gas tank 307 as a pressurizing mechanism.

  The filter 304 may or may not be disposed, but it is preferable to dispose the filter 304 in order to remove dust mixed in the coating liquid.

In the present invention, the reason why the generation of bubbles is suppressed by controlling the maximum acceleration of the diaphragm valve to 30 mm / sec ² or less is presumed as follows.

  An example of a diaphragm pump having a diaphragm valve is shown in FIG. When the diaphragm valve 201 expands, the coating liquid enters the diaphragm pump from the liquid inlet 202. Then, when the diaphragm valve 201 is narrowed, the coating liquid is discharged from the liquid outlet 203. Since the volume into which the coating liquid enters can be controlled to be constant, the diaphragm pump functions as a quantitative pump.

  The diaphragm valve of the diaphragm pump normally operates so as to be phased in the shape of a sine wave with respect to the time axis.

  However, when feeding a coating liquid having a high viscosity, a negative pressure may be generated between the diaphragm valve and the coating liquid without being able to follow the instantaneous movement of the diaphragm valve. When the coating liquid boils due to this negative pressure, bubbles are generated in the coating liquid. For this reason, the present inventors considered that the generation of bubbles is suppressed by improving the followability of the diaphragm valve, that is, by suppressing the acceleration of the diaphragm valve from zero speed.

  As a method for suppressing the acceleration of the diaphragm valve, there is a method of simply lowering the pump stroke. However, if the pump stroke is lowered, the maximum acceleration of the diaphragm valve can be suppressed, but the number of pistons per unit time increases, so that the opportunity for bubble generation increases. Further, if the pump stroke is lowered, it is necessary to increase the number of diaphragm pumps in order to obtain a necessary flow rate. Therefore, it is preferable to suppress the acceleration of the diaphragm valve without reducing the pump stroke.

  In addition, the effect of the present invention is exhibited even when applied to any viscosity coating solution, but when applied to a coating solution (high viscosity coating solution) having a viscosity of 200 to 1500 mPas, particularly 800 mPas or more. Is particularly effective. This viscosity is a viscosity under conditions (temperature, etc.) when the coating liquid is continuously circulated between the coating tank and the recovery tank and dip coating is actually performed.

  Further, it is considered that increasing the flowability of the coating liquid to the diaphragm pump improves the followability to the diaphragm valve. For this reason, it is considered that an increase in the flowability of the coating liquid into the diaphragm pump by feeding the coating liquid under pressure to the liquid inlet of the diaphragm pump produces a greater effect.

  Next, the structure of the electrophotographic photoreceptor to which the production method of the present invention is applied will be described.

  An electrophotographic photoreceptor generally has a support and a photosensitive layer formed on the support.

  The photosensitive layer has a single layer type photosensitive layer containing a charge generation material and a charge transport material in a single layer, and a laminate type having a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material Broadly divided into photosensitive layers. The laminated photosensitive layer includes a normal layer type photosensitive layer laminated in the order of the charge generation layer and the charge transport layer from the support side, and a reverse layer type photosensitive layer laminated in the order of the charge transport layer and the charge generation layer from the support side. There is. Among these, a normal layer type photosensitive layer is preferable from the viewpoint of electrophotographic characteristics.

  As the support, a cylindrical support having conductivity is preferable. For example, a cylindrical support made of metal such as aluminum, aluminum alloy, or stainless steel can be used. In the case of aluminum or aluminum alloy, ED tube, EI tube, or these are cut, electrolytic composite polishing (electrolysis with electrode having electrolytic action and polishing with grinding stone having polishing action), wet or dry honing treatment Can also be used. In addition, a metal cylindrical support or a resin cylindrical support (polyethylene terephthalate, polybutylene terephthalate, phenol resin, polypropylene, polystyrene, having a film formed by vacuum deposition of aluminum, an aluminum alloy, or an indium oxide-tin oxide alloy. Etc.) can also be used. In addition, a cylindrical support obtained by impregnating resin or paper with conductive particles such as carbon black, tin oxide particles, titanium oxide particles, or silver particles, or a cylindrical support made of conductive binder resin can also be used. .

  On the support, a conductive layer for the purpose of covering scratches on the surface of the support may be provided. The conductive layer can be formed by applying a conductive layer coating solution in which conductive particles and a binder resin are dispersed or dissolved in a solvent.

Examples of the conductive particles used in the conductive layer include carbon black, acetylene black, aluminum, nickel, iron, nichrome, copper, zinc, silver and other metal powders, conductive tin oxide, and metal oxides such as ITO. Examples of the binder resin used for the conductive layer include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polychlorinated resin. Vinyl, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic Examples thereof include thermoplastic resins such as resins, silicone resins, epoxy resins, melamine resins, urethane resins, phenol resins, and alkyd resins, thermosetting resins, and photocurable resins.

  Examples of the solvent used in the conductive layer coating solution include ether solvents such as tetrahydrofuran and ethylene glycol dimethyl ether, alcohol solvents such as methanol, ketone solvents such as methyl ethyl ketone, and methylbenzene. Such aromatic hydrocarbon solvents.

  The thickness of the conductive layer is preferably 5 μm or more and 40 μm or less, and more preferably 10 μm or more and 30 μm or less.

  An intermediate layer having an electrical barrier function may be provided on the support or the conductive layer.

  The intermediate layer can be formed by applying an intermediate layer coating solution containing a binder resin and drying it.

  Examples of the binder resin used in the intermediate layer include water-soluble resins such as polyvinyl alcohol, polyvinyl methyl ether, polyacrylic acids, methyl cellulose, ethyl cellulose, polyglutamic acid, and casein, polyamide, polyimide, polyamideimide, polyamic acid, and melamine. Resins, epoxy resins, polyurethane, polyglutamic acid esters and the like can be mentioned. In order to effectively express the electric barrier function of the intermediate layer, and from the viewpoints of coatability, adhesion, solvent resistance, and resistance, the binder resin of the intermediate layer is preferably a thermoplastic resin. Specifically, thermoplastic polyamide is preferable. As the polyamide, low-crystalline or non-crystalline copolymer nylon that can be applied in a solution state is preferable.

  The thickness of the intermediate layer is preferably 0.1 μm or more and 2.0 μm or less.

  Also, in order to prevent the flow of electric charges (carriers) in the intermediate layer, semiconductive particles are dispersed in the intermediate layer, or an electron transport material (electron-accepting material such as an acceptor) is included. May be.

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

  Examples of the charge generation material include azo pigments such as monoazo, disazo, and trisazo, phthalocyanine pigments such as metal phthalocyanine and nonmetal phthalocyanine, indigo pigments such as indigo and thioindigo, perylene acid anhydride, and perylene acid. Perylene pigments such as imides, polycyclic quinone pigments such as anthraquinone and pyrenequinone, squarylium dyes, pyrylium salts and thiapyrylium salts, triphenylmethane dyes, inorganic substances such as selenium, selenium-tellurium and amorphous silicon Quinacridone pigments, azulenium salt pigments, cyanine dyes, xanthene dyes, quinoneimine dyes, styryl dyes, and the like. These charge generation materials may be used alone or in combination of two or more. Among these, metal phthalocyanines such as oxytitanium phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine are particularly preferable because of their high sensitivity.

  When the photosensitive layer is a laminated photosensitive layer, examples of the binder resin used for the charge generation layer include polycarbonate, polyester, polyarylate, butyral resin, polystyrene, polyvinyl acetal, diallyl phthalate resin, acrylic resin, methacrylic resin, Examples thereof include vinyl acetate resin, phenol resin, silicone resin, polysulfone, styrene-butadiene copolymer resin, alkyd resin, epoxy resin, urea resin, vinyl chloride-vinyl acetate copolymer resin. Among these, a butyral resin is preferable. These can be used singly or in combination of two or more as a mixture or copolymer.

  The charge generation layer can be formed by applying a charge generation layer coating solution obtained by dispersing a charge generation material together with a binder resin and a solvent and drying the coating solution. Examples of the dispersion method include a method using a homogenizer, an ultrasonic wave, a ball mill, a sand mill, an attritor, a roll mill, and the like. The ratio between the charge generating material and the binder resin is preferably in the range of 10: 1 to 1:10 (mass ratio), and more preferably in the range of 3: 1 to 1: 1 (mass ratio).

  Examples of the solvent used in the charge generation layer coating solution include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. These solvents may be used alone or in combination.

  The thickness of the charge generation 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, plasticizers, and the like can be added to the charge generation layer as necessary. In order to prevent the flow of charges (carriers) in the charge generation layer from stagnation, the charge generation layer may contain an electron transport material (an electron accepting material such as an acceptor).

  Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, benzidine compounds, triarylamine compounds, triphenylamine, or groups composed of these compounds. Examples thereof include a polymer having a chain or a side chain.

  Examples of the binder resin used for the charge transport layer include polyester, polycarbonate, polymethacrylic acid ester, polyarylate, polysulfone, polystyrene, and the like. Among these, polycarbonate and polyarylate are preferable. Moreover, the thing whose molecular weight measured using the gel permeation chromatography (GPC) is 10,000-300,000 as a weight average molecular weight (Mw) is preferable.

  The charge transport layer can be formed by applying a charge transport layer coating solution obtained by dissolving a charge transport material and a binder resin in a solvent and drying it. The ratio of the charge transport material and the binder resin is preferably in the range of 10: 5 to 5:10 (mass ratio), and more preferably in the range of 10: 8 to 6:10 (mass ratio).

  Solvents used in the charge transport layer coating solution include, for example, ketones such as acetone and methyl ethyl ketone, esters such as methyl acetate and ethyl acetate, ethers such as dimethoxymethane, tetrahydrofuran and dioxane, toluene and xylene. And aromatic hydrocarbons such as chlorobenzene, dichloromethane, chloroform and carbon tetrachloride, and the like. These solvents may be used alone or in combination. In particular, in order to improve coating sagging, it is preferable to use a mixture of a low boiling point solvent and a high boiling point solvent. In addition, when a low boiling point solvent having a boiling point of 70 ° C. or less is used, although the effect of improving the sag of the coating film is large, cavitation is likely to occur in the diaphragm valve, so that the present invention works more effectively.

  The film thickness of the charge transport layer is preferably 5 μm or more and 40 μm or less, and more preferably 10 μm or more and 40 μm or less.

  In addition, various antioxidants, ultraviolet absorbers, plasticizers, and the like can be added to the charge transport layer as necessary.

  Further, a protective layer may be formed on the photosensitive layer. The protective layer is preferably a layer in which conductive resin or a charge transport material is contained in a binder resin. Further, the protective layer may contain an additive such as a lubricant. Further, the protective layer may be formed of the binder resin itself having conductivity and charge transportability. The resin used for the protective layer may be a curable resin that is cured by heat, light, radiation (such as an electron beam), or may be a non-curable thermoplastic resin.

  The thickness of the protective layer is preferably 0.5 μm or more and 10 μm or less, and more preferably 1 μm or more and 5 μm or less.

  In the following examples and comparative examples, the following were employed unless otherwise specified. That is, a diaphragm pump (trade name: 3AXBW-K150S4S-22) manufactured by Iwaki Co., Ltd. was employed as the diaphragm pump having a diaphragm valve. The inner diameters of the liquid inlet and the liquid outlet of this diaphragm pump are both 30.0 mm. Further, the stroke distance of the diaphragm valve of this diaphragm pump is 14.7 mm, and the number of strokes is 72 s / min. Further, the time for one stroke is 0.83 s when the motor is operated at 50 Hz. Moreover, the diaphragm valve of this diaphragm pump operates as described above. In addition, an inverter was attached to the motor of this diaphragm pump, and the operating frequency of the motor was changed, so that the acceleration (frequency) of the diaphragm valve was modified.

  The following examples and comparative examples are examples in which the present invention is applied to a charge transport layer coating solution (an example in which the coating film is a charge transport layer), but the present invention is a coating solution for other coating films. It can also be applied to.

[Example 1]
The dip coating apparatus used in this example is a coating liquid circulation type dip coating apparatus having a configuration shown in FIG. In this dip coating apparatus, three diaphragm pumps are arranged in parallel, and operate with a phase difference in order to suppress pulsation. In this embodiment, 15 coating tanks (only four are shown in FIG. 3) are attached, and the inner diameter of the coating tank is 110 mm. Moreover, all piping was 40 A (inner diameter: 41.2 mm).

  The charge transport layer coating solution used in this example was prepared as follows.

  That is, 100 parts of polyarylate having a repeating structural unit represented by the following structural formula (1) and a repeating structural unit represented by the following structural formula (2) (copolymerization ratio is 7: 3),

72 parts of an amine compound (charge transport material) represented by the following structural formula (3), and

8 parts of an amine compound (charge transport material) represented by the following structural formula (4)

  Was dissolved in a mixed solvent of chlorobenzene / dimethoxymethane (methylal) = 3/2 (mass ratio) to prepare a charge transport layer coating solution. The mixed solvent of chlorobenzene / dimethoxymethane was used in such an amount that the viscosity of the charge transport layer coating solution was 900 mPa · s.

  The prepared charge transport layer coating solution is put into the coating solution circulation type dip coating device, the charge transport layer coating solution is circulated for 10 minutes, and the charge transport layer coating solution is spread over the entire dip coating device. And left for 24 hours. This is because the bubbles generated when the charge transport layer coating solution is introduced into the dip coating apparatus are completely removed once. The bubbles were confirmed by visually observing the coating tank and the collection tank. Thereafter, circulation of the coating solution for the charge transport layer was started under the operating conditions shown in Table 1.

  An electrophotographic photoreceptor used for evaluation was prepared as follows.

  A conductive layer coating solution composed of the following materials is dip-coated on an aluminum cylinder (support) having a diameter of 62 mm, a length of 370 mm, and a wall thickness of 1.7 mm, and this is heated and cured at 140 ° C. for 30 minutes. As a result, a conductive layer having a thickness of 15 μm was formed.

Conductive particles: SnO2-coated barium sulfate 10 mass parts Resistance adjusting particles: titanium oxide 2 mass parts Binder resin: phenol resin 6 mass parts Leveling material: silicone oil 0.001 mass parts Solvent: methanol / methoxypropanol = 2 / 8 (mass ratio) 20 parts by mass Next, for intermediate layer, 3 parts by mass of N-methoxymethylated nylon and 3 parts by mass of copolymer nylon are dissolved in a mixed solvent of 65 parts by mass of methanol and 30 parts by mass of n-butanol. A coating solution was prepared.

  This intermediate layer coating solution was dip-coated on the conductive layer and dried to form an intermediate layer having a thickness of 0.5 μm.

  Next, 4 parts by mass of an azo compound represented by the following structural formula (5),

Disperse 2 parts by weight of polyvinyl butyral (trade name: ESREC BLS, manufactured by Sekisui Chemical Co., Ltd.) and 35 parts by weight of cyclohexanone with a sand mill using glass beads having a diameter of 1 mm for 12 hours, and then add 60 parts of methyl ethyl ketone. Thus, a charge generation layer coating solution was prepared.

  The charge generation layer coating solution was dip-coated on the intermediate layer and dried to form a charge generation layer having a thickness of 0.3 μm.

  Next, a charge transport layer having a thickness of 30 μm was formed by dip-coating the charge transport layer coating liquid after being circulated for 24 hours with the coating liquid circulation type dip coating apparatus on the charge generation layer. .

  In this manner, 20,000 electrophotographic photoreceptors having a charge transport layer as a surface layer were produced.

Evaluation As an evaluation, first, the presence or absence of bubbles in the coating tank and the collection tank of the dip coating apparatus after producing 20,000 electrophotographic photosensitive members was visually confirmed. The produced electrophotographic photosensitive member is mounted on an electrophotographic apparatus (trade name: iRC3100) manufactured by Canon Inc., which adopts an AC / DC charging method as a charging method of the electrophotographic photosensitive member, and a halftone image is output. Then, image defects (pochi) caused by bubbles were confirmed (image defect evaluation 1).

  The produced electrophotographic photosensitive member is mounted on a modified iRC3100 in which the charging method of the electrophotographic photosensitive member is modified to a DC charging method, and a halftone image is output under the conditions of a charging bias of −500 V and a developing bias of −350 V. Then, image defects (pochi) caused by bubbles were confirmed (image defect evaluation 2). Next, the development bias of this modified machine was changed to -450 V, and a solid black image was output to check for image defects (pots) caused by bubbles (image defect evaluation 3).

  In the DC charging method in which the voltage applied to the charging member is only a DC voltage, minute defects of the electrophotographic photosensitive member tend to appear as potential unevenness of the dark portion potential. Further, when the developing bias is brought close to the charging bias, the potential unevenness can be directly observed as an output image.

  The image defect evaluations 1 to 3 were performed using 1000 electrophotographic photoreceptors each produced, and the evaluation result was obtained by dividing the number of electrophotographic photoreceptors in which image defects occurred by 1000 and obtaining a percentage of 100. (Image defect occurrence rate (%)).

[Examples 2-8, Comparative Examples 1-4]
In Example 1, the electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that the viscosity of the charge transport layer coating solution and the operating conditions during circulation of the charge transport layer coating solution were changed as shown in Table 1. Were made and evaluated.

  In Examples 1 and 2, a sealing lid is attached to the recovery tank, the coating liquid is pressurized by flowing nitrogen gas, and the coating liquid is fed to the liquid inlet of the diaphragm pump by pressurization ( Pressure mechanism). In Examples 1 and 2, a coating liquid circulation type dip coating apparatus having the configuration shown in FIG. 3 is used. In Examples 3 to 8 and Comparative Examples 1 to 4, the coating liquid circulation type having the configuration shown in FIG. 4 is used. A dip coating apparatus was used. The coating liquid circulation type dip coating apparatus having the configuration shown in FIG. 4 is the same as the coating liquid circulation type dip coating apparatus having the configuration shown in FIG. 3 except that the gas inlet 306 and the inert gas tank 307 are not provided. It is the same. In FIG. 4, 401 is a coating tank, 402 is a collection tank, 403 is a diaphragm pump, 404 is a filter, and 405 is an object to be coated.

  Further, the maximum acceleration in the examples was obtained as follows.

  The pump operation frequency of 60 Hz and the time required for one stroke when the pump stroke is 100% can be found from the pump catalog value. Further, since the diaphragm valve uses a general motor, the diaphragm valve operates to take a phase in the shape of a sine wave.

That is, when the phase position Y of the diaphragm valve is time t, one cycle is T, and the distance when the pump stroke is 100% is A,
Y = Asin (2π / T) t
It can be expressed.

  Therefore, the acceleration of the diaphragm valve is obtained as -A (2π / T) 2sin (2π / T) t. From this equation, the maximum acceleration of the diaphragm valve was calculated.

  The evaluation results of Examples 1 to 8 and Comparative Examples 1 to 4 are shown in Table 2.

As described above, even when the coating liquid has a very high viscosity such as 1500 mPa · s, the image defect (potential) caused by bubbles is controlled by controlling the maximum acceleration of the diaphragm valve to 30 mm / s ² or less. ) Can be suppressed to 1% or less.

  In addition, generation of bubbles is further suppressed by applying pressure to the liquid inlet of the diaphragm pump and feeding the coating liquid.

301 Coating tank 302 Recovery tank 303 Diaphragm pump 304 Filter 305 Object to be coated 306 Gas inlet 307 Inert gas tank

Claims (4)

In a method for producing an electrophotographic photosensitive member using a diaphragm pump having a diaphragm valve, a dip coating apparatus having a coating tank and a recovery tank, the manufacturing method uses the diaphragm pump, While continuously circulating the coating liquid between the coating tank and the recovery tank, the method has a step of forming a coating film by dip-coating the coating liquid on an object to be coated,
The coating solution contains a solvent having a boiling point of 70 ° C. or less,
The pump stroke of the diaphragm valve is 80 to 100% of 14.7 mm;
A method for producing an electrophotographic photosensitive member, wherein the maximum acceleration of the diaphragm valve is controlled to 30 mm / s ² or less.   The method for producing an electrophotographic photosensitive member according to claim 1, wherein in the step of forming the coating film, the coating liquid is fed under pressure to a liquid inlet of the diaphragm pump.   The method for producing an electrophotographic photosensitive member according to claim 1, wherein the coating solution has a viscosity of 200 mPa · s to 1500 mPa · s.   The method for producing an electrophotographic photosensitive member according to claim 3, wherein the coating solution has a viscosity of 800 mPa · s to 1500 mPa · s.

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