JP4485294B2 - Method for producing electrophotographic photosensitive member - Google Patents

Description

The present invention relates to the production how the electrophotographic photosensitive member.

Organic photoreceptors are widely used as photoreceptors used in electrophotography. The organic photoreceptor includes a functionally separated laminated photoreceptor in which a charge generation material and a charge transport material are laminated as separate layers, and a single-layer photoreceptor in which the charge generation material and the charge transport material are provided as a single layer. There is.
In these photoreceptors, a charge generation material and / or a charge transport material is dissolved or dispersed in a solvent together with a binder resin, and the formed coating solution is placed on a conductive support such as aluminum or a conductive support. It is manufactured by applying and drying on an intermediate layer formed on the body by dipping, spraying, blade coater method or the like. For drying the coating layer, heat drying at about 100 ° C. to about 150 ° C. with a hot-air dryer or the like is used.
The coating liquid is formed through a process of dispersing a pigment such as a charge generating material or a circulation process of the coating liquid. For this reason, the opportunity to embed air in the coating liquid increases. The air entrapped in the coating liquid is united over time and defoamed from the surface of the coating liquid, but all fine bubbles remain in the coating liquid without being defoamed. In particular, when the viscosity of the coating solution is relatively high (50 to 400 mPa · s), bubbles are not sufficiently degassed during drying after coating.
Further, as the solvent used as the coating solution for the photosensitive layer, a solvent having a relatively low boiling point is used. On the other hand, the heating for drying is performed at a temperature higher than the boiling point of the solvent. Inside, bubbles are generated due to bumping of the solvent. In particular, coating solutions that use non-halogen solvents such as cyclic ether compounds, ketone compounds, and aromatic hydrocarbon compounds are environmentally friendly because the boiling point of the solvent used is higher than the boiling point of the halogen solvent. The amount of residual solvent in the initial stage increases, and bubbles are likely to be generated due to bumping of the solvent during drying.

Conventionally, an intermediate layer is generally provided between the support and the photosensitive layer in order to improve the chargeability, improve the adhesion between the photosensitive layer and the support, and conceal defects on the support surface. One of the characteristics required for such an intermediate layer is that the characteristics of the photoreceptor are not adversely affected even when used repeatedly. However, such characteristics are difficult to achieve by using only an intermediate layer made of a single resin. For this reason, a material in which conductive powder is dispersed in a resin in the intermediate layer has been proposed. In addition, in the case of a photoconductor used in a laser printer or the like that writes an image with coherent light such as laser light, a white pigment having a high refractive index is dispersed in the resin in the intermediate layer in order to prevent the occurrence of moire. It has also been proposed.
In such a pigment dispersion layer, the thicker the film thickness, the more severe the surface unevenness. As a result, when a photosensitive layer is applied on the surface, bubbles remain at the interface with the intermediate layer, and bubbles are generated during drying. It tends to occur.

Furthermore, the corona charging method has been conventionally used as the charging method, but the ozone concentration increases when the electrophotographic process by corona charging is repeated and the safety of the use environment is significantly hindered. The charging method has been used. Compared with the corona charging method, the contact charging method generates significantly less ozone, which improves the environmental safety problem. However, on the other hand, a problem peculiar to the contact charging method is the occurrence of breakdown of the photoreceptor due to the high voltage directly applied to the photoreceptor. When this discharge breakdown occurs, a large black spot is obtained in the reverse development. Further, when a coating film defect such as blistering due to bubbles or a crack due to bursting of bubbles occurs in the photosensitive layer, in the case of the contact charging method, breakdown of the photosensitive member is likely to occur.
Thus, in the case of the contact charging method, generation of bubbles in the photosensitive layer must be suppressed.
Furthermore, as a method of preventing discharge breakdown, the electric field applied to the electrophotographic photosensitive member is increased by thickening the intermediate layer to sufficiently cover defects such as scratches and irregularities on the surface of the conductive support, or by increasing the thickness of the photosensitive layer. It is also an effective method to reduce the size. Increasing the thickness of the intermediate layer and photosensitive layer not only prevents discharge breakdown in the contact charging method described above, but also prevents the occurrence of black spots and background stains due to repeated use in the case of a photoreceptor used for reversal development. It becomes a highly reliable photoconductor.
However, when the intermediate layer is thickened, the irregularities on the surface of the intermediate layer become severe accordingly, and as a result, bubbles tend to remain at the interface with the photosensitive layer coated thereon.
Further, by increasing the thickness of the photosensitive layer, the amount of residual solvent in the photosensitive layer increases, and bubbles are likely to be generated during drying.
As a result, black spots and white spots are generated in the generated image, the image quality is deteriorated, and further, the photosensitive member is liable to be poorly cleaned. Further, in the contact charging method, discharge breakdown occurs.

Thus, methods as described in Patent Documents 1 to 5 have been proposed as methods for preventing blisters and cracks that occur during coating and drying.
However, although any technique is effective in the case of no intermediate layer or in the case of a resin-only intermediate layer, an inorganic pigment-dispersed intermediate layer is provided, and a cyclic ether compound, a ketone compound, and an aromatic compound are provided for the environment. In the case where a photosensitive layer coating solution using a non-halogen solvent such as a hydrocarbon compound is used, the generation of bubbles cannot be completely suppressed.

JP-A-6-301224 JP-A-7-160014 JP-A-8-44089 JP-A-11-311871 Japanese Patent Laid-Open No. 11-352704

Halogen-based solvent is a low boiling point solvent and has a high evaporation rate, so even if the intermediate layer is an inorganic pigment dispersion film, even if it is dried without worrying about the drying conditions immediately after coating, the generation of bubbles should be prevented. I was able to. However, for environmental protection, a photosensitive layer coating solution using a non-halogen solvent such as a cyclic ether compound, a ketone compound, or an aromatic hydrocarbon compound is applied onto the inorganic pigment-dispersed intermediate layer and dried. In this case, air bubbles are generated when dried in the same manner as in the case of using a halogen-based solvent.
Therefore, the object of the present invention is to suppress the generation of bubbles in the photosensitive layer and to have no film defects such as blisters and cracks in the photosensitive layer, and as a result, to form a high-quality image without black spots or white spots. is to provide a manufacturing how the electrophotographic photosensitive member as possible.

  Accordingly, as a result of intensive studies, the present inventors have determined that the drying step of the coated photosensitive layer is not less than two steps, and the maximum heating rate and the average heating rate of the conductive support are controlled. Thus, it was found that the generation of bubbles in the photosensitive layer during drying can be effectively prevented, and the present invention has been completed.

The invention of claim 1 comprises at least an intermediate layer having a thickness of 3.0 to 5.0 μm in which an inorganic pigment is dispersed on a conductive support, a cyclic ether compound, a ketone compound and an aromatic hydrocarbon compound. One or more types selected from a charge generation layer coated with a coating solution for a charge generation layer containing one or more selected solvents, and cyclic ether compounds, ketone compounds, and aromatic hydrocarbon compounds In the method for producing an electrophotographic photosensitive member having a charge transport layer having a thickness of 20 to 30 μm applied and formed in this order using a charge transport layer coating solution containing the above solvent, the applied and formed charge transport layer is dried. drying steps are over 2 steps, a first drying maximum heating rate of the conductive support in step 1 ℃ / sec~ 5 ℃ / se c drying the charge transport layer immediately after coating formation, and the average rate of temperature increase is 0.005 ℃ / sec A process for producing an electrophotographic photosensitive member, which is a 0.05 ℃ / se c.
According to this configuration, there is no coating film defect such as blistering caused by bubbles or cracks caused by bursting bubbles in the photosensitive layer, and a method for producing an electrophotographic photosensitive member capable of forming a high-quality image without black spots or white spots. Can provide.
As described above, a photosensitive layer coating solution using a non-halogen solvent such as a cyclic ether compound, a ketone compound, or an aromatic hydrocarbon compound has a low boiling point of the solvent used and remains in the photosensitive layer. Easy to grow into bubbles in the drying process. When the intermediate layer is an inorganic pigment dispersion film, fine nuclei of bubbles are likely to be generated at the interface between the intermediate layer and the photosensitive layer. Further, fine bubble nuclei exist in the photosensitive layer from the state of the coating solution. These bubble nuclei also tend to grow into bubbles in the drying process. Therefore, in the present invention, it is possible to suppress the generation of bubbles in the final drying process by defining the conditions of the first drying process immediately after the formation of the photosensitive layer as described above by setting the drying process to two or more processes. . That is, by defining the conditions of the first drying step immediately after the formation of the photosensitive layer as described above, it is possible to promote the drying and solidification of the surrounding photosensitive layer rather than the growth of bubble nuclei. Suppress the growth of. In addition, when a large amount of non-halogen solvent remains in the photosensitive layer, the growth of bubble nuclei is generally promoted in the drying process, but by using the production method of the present invention, the generation of bubbles can be suppressed. .

According to the invention of claim 2, the final ultimate temperature of the conductive support in the first drying step is 20 ° C. or higher and 80 ° C. or lower, and the final ultimate temperature of the conductive support in the final drying step is 120 ° C. or higher. The method for producing an electrophotographic photosensitive member according to claim 1, wherein the temperature is 160 ° C. or lower.
According to this configuration, the occurrence of coating film defects such as blisters due to bubbles and cracks due to bursting of bubbles is further suppressed, and a high-quality image without black spots or white spots can be formed. Furthermore, it is possible to suppress sensitivity deterioration and increase in residual potential due to repeated use. By setting the final reached temperature in the first drying step to 20 ° C. or higher and 80 ° C. or lower, it is possible to further promote the drying and solidification of the photosensitive layer around the bubble nuclei, and the subsequent growth of the bubble nuclei. Suppress. Further, by setting the final temperature of the conductive support in the final drying step to 120 ° C. or higher, it is possible to suppress sensitivity deterioration and residual potential increase due to the residual solvent. In addition, by setting the final temperature of the conductive support in the final drying step to 160 ° C. or less, it is possible to suppress sensitivity deterioration and residual potential increase due to thermal deterioration of the photosensitive layer.

According to the present invention, generation of bubbles in the photosensitive layer is suppressed, and there are no coating film defects such as blisters and cracks in the photosensitive layer, and as a result, a high-quality image without black spots or white spots can be formed. producing how the electrophotographic photosensitive member is provided.

Hereinafter, the present invention will be described in more detail.
Examples of the conductive support used in the present invention include metals such as aluminum, nickel, and stainless steel; plastic in which conductive pigments such as carbon are dispersed; metal is deposited on an insulating support (such as plastic or plastic film). Or those coated with a conductive paint.

Next, the intermediate layer provided on the conductive support will be described.
The inorganic pigment used in the intermediate layer may be a commonly used pigment, but white or a pigment with almost no absorption in visible light and near infrared light is desirable when considering higher sensitivity of the photoreceptor. Examples thereof include white pigments such as titanium oxide, zinc white, zinc sulfate, lead white, and lithopone, and extender pigments such as aluminum oxide, silica, calcium carbonate, and barium sulfate.
Of these, titanium oxide is preferable because it has a higher refractive index than other white pigments, is chemically and physically stable, has a large hiding power, and has a high degree of whiteness.
Further, as the intermediate layer binder resin used in the present invention, an appropriate one can be used. For example, water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, curable resins that form a three-dimensional network structure such as polyurethane, melamine resin, and epoxy resin Etc.
The intermediate layer coating solution is prepared by dissolving the binder resin in a solvent and dispersing it together with an inorganic pigment by a ball mill, roll mill, sand mill, attritor or the like. An intermediate layer is formed by coating and drying this dispersion on a conductive support using a coating method such as blade coating, knife coating, spray coating, or dip coating.
The mass ratio range of the binder resin / inorganic pigment in the intermediate layer is preferably in the range of 1/15 to 2/1.
The thickness of the intermediate layer is preferably 0.5 μm or more and 20.0 μm or less. However, in order to obtain a highly durable photoreceptor that is less likely to be stained due to repeated use, the thicker the intermediate layer, the more advantageous. An intermediate layer of 5.0 μm or more is desirable. Further, when the charging means is a contact charging means, it is more desirable to use an intermediate layer of 5.0 μm or more in order to prevent discharge breakdown.

The photosensitive layer provided on the intermediate layer may be a single layer type or a laminated type. However, in either case, the solvent used in the photosensitive layer coating solution is at least one solvent selected from cyclic ether compounds, ketone compounds, and aromatic hydrocarbon compounds.
Furthermore, the film thickness of the photosensitive layer is desirably 28 μm or more so as not to generate an abnormal image even when used repeatedly. Preferably, it is 28-50 micrometers.
The photoreceptor is worn by the contact member due to repeated use, and the film thickness decreases. As a result, the electric field strength applied to the photosensitive member increases, and abnormal images such as background stains are generated by charge injection from the conductive support. Therefore, by increasing the film thickness of the photosensitive layer, it is possible to continue to provide high-quality images even after repeated use.
The film thickness of the photosensitive layer here is the total film thickness of the charge generation layer and the charge transport layer when the photosensitive layer is composed of a stack of a charge generation layer and a charge transport layer. In the case of a single layer, it is the film thickness of the photosensitive layer itself.
As described above, the solvent used for the photosensitive layer coating solution is a solvent selected from cyclic ether compounds, ketone compounds, and aromatic hydrocarbon compounds.
Examples of cyclic ether compounds include tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane and the like.
Examples of ketone compounds include methyl ethyl ketone, acetone, and cyclohexanone.
In addition, examples of the aromatic hydrocarbon compound include toluene, xylene, benzene, and the like.

First, the case where the photosensitive layer is composed of a charge generation layer and a charge transport layer will be described. The charge generation layer is a layer mainly composed of a charge generation material. As the charge generation material, inorganic and organic materials are used, and representative examples include monoazo pigments, disazo pigments, trisazo pigments, perylene pigments, perinone pigments, quinacridone pigments, quinone condensed polycyclic compounds, squalic acid dyes, Examples include phthalocyanine pigments, naphthalocyanine pigments, azurenium salt dyes, selenium, selenium-tellurium, selenium-arsenic alloys, and amorphous silicon. The charge generation material may be used alone or in combination of two or more.
For the charge generation layer, the charge generation material is dispersed with a binder resin and a cyclic ether compound, ketone compound, and / or aromatic hydrocarbon compound using a ball mill, attritor, sand mill, etc., and a dispersion is applied. To form. The coating can be performed using a dip coating method, a spray coating method, a bead coating method, or the like. Examples of the binder resin that is appropriately used include polyurethane, polyester, epoxy resin, polycarbonate, acrylic resin, polyvinyl butyral, polyvinyl formal, polystyrene, and polyacrylamide that are soluble in the organic solvent. The thickness of the charge generation layer is suitably about 0.01 to 5 μm, preferably 0.1 to 2 μm. The amount of the charge generating material is suitably 10 to 10000 parts by mass, preferably 20 to 5000 parts by mass with respect to 100 parts by mass of the binder resin.

The charge transport layer is obtained by dissolving or dispersing a charge transport material and a binder resin in a cyclic ether compound, a ketone compound, and / or an aromatic hydrocarbon compound, and applying and drying the solution on the charge generation layer. Can be formed. Moreover, a plasticizer, a leveling agent, etc. can also be added as needed.
Charge transport materials include hole transport materials and electron transport materials. Examples of the electron transporting material include chloroanil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4 , 5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophen-4-one, 1,3,7-tri Examples thereof include electron-accepting substances such as nitrodibenzothiophene-5,5-dioxide and benzoquinone derivatives.
Examples of hole transport materials include poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutarate and derivatives thereof, pyrene-formaldehyde condensates and derivatives thereof, polyvinylpyrene, polyvinylphenanthrene, polysilane, and oxal derivatives. Oxadiar derivative, imidazole derivative, monoaramine derivative, diaramine derivative, triaramine derivative, stilbene derivative, α-phenylstilbene derivative, benzidine derivative, diarylmethane derivative, triarylmethane derivative, 9-styrylanthracene derivative, pyrazoline derivative, divinyl Benzene derivatives, hydrazine derivatives, indene derivatives, butadiene derivatives, pyrene derivatives, bisstilbene derivatives, enamine derivatives, other polymerisations The hole transport material such as a known material and the like.
Examples of the binder resin used for the charge transport layer include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer. Coalescence, polyvinyl acetate, polyvinylidene chloride, polyarylate, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxy resin, There are thermoplastic or thermosetting resins such as melamine resin, urethane resin, phenol resin, alkyd resin, and various polycarbonate copolymers described in JP-A-5-158250 and JP-A-6-51544. It is.
The amount of the charge transport material is appropriately 20 to 300 parts by mass, preferably 40 to 150 parts by mass with respect to 100 parts by mass of the binder resin. The amount of the hole transport material is appropriately 20 to 300 parts by mass, preferably 40 to 150 parts by mass with respect to 100 parts by mass of the binder resin.
In the present invention, a leveling agent and an antioxidant may be added to the charge transport layer. As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, polymers or oligomers having a perfluoroalkyl group in the side chain can be used, and the amount used is 100 parts by mass of the binder resin. 0 to 1 part by mass is appropriate.
Antioxidants such as hindered phenol compounds, sulfur compounds, phosphorus compounds, hindered amine compounds, pyridine derivatives, piperidine derivatives, morpholine derivatives can be used as the antioxidant, and the amount used is binder resin 100. About 0-5 mass parts is suitable with respect to mass parts.

  Next, the case where the photosensitive layer has a single layer structure will be described. In this case, at least the charge generation material and the charge transport material are used as a binder resin, a phenol compound, and an organic sulfur compound as one or more solvents selected from cyclic ether compounds, ketone compounds, and aromatic hydrocarbon compounds. It can be formed by dissolving or dispersing, coating and drying. Moreover, a plasticizer etc. can also be added as needed. As the binder resin, the binder resin mentioned above in the charge transport layer can be used as it is, and the binder resin mentioned in the charge generation layer may be mixed.

In the photoreceptor of the present invention, a protective layer may be provided on the photosensitive layer for the purpose of protecting the photosensitive layer. Materials used for the protective layer include ABS resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether, allyl resin, phenolic resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallylsulfone, polybutylene. , Polybutylene terephthalate, polycarbonate, polyethersulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic resin, polymethylpentene, polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS resin, butadiene-styrene copolymer, polyurethane, polyvinyl chloride, Examples of the resin include polyvinylidene chloride and epoxy resin.
In addition to the protective layer, fluorine resins such as polytetrafluoroethylene, silicone resins, and inorganic materials such as titanium oxide, alumina, silica, tin oxide, and potassium titanate are used for the purpose of improving wear resistance. A dispersed product or the like can be added. Among inorganic materials, metal oxides are effectively used. In particular, titanium oxide, alumina, and silica are effectively used. In addition, it is an effective means to use a charge transport material in combination with the protective layer. As the charge transport material, a low molecular charge transport material and a polymer charge transport material can be used, and the materials described in the description of the charge transport layer can be used effectively. As a method for forming the protective layer, a normal coating method (spray coating, beat coating, nozzle coating, spinner coating, ring coating, etc.) is employed. The thickness of the protective layer is suitably about 0.1 to 10 [μm]. In addition to the above, a known material such as a-C or a-SiC formed by a vacuum thin film forming method can be used as the protective layer.

Next, the drying of the photosensitive layer will be described.
As the dryer, a hot air dryer, a steam dryer, an infrared dryer, a far infrared dryer, or the like can be used.
Since the dryer used in the present invention requires two or more steps, the dryer is prepared for each step, or a method of sequentially changing to the required drying conditions using one dryer is adopted. Can do.
The rate of temperature increase and final temperature of the conductive support can be easily achieved by changing the wind speed and set temperature in the dryer to be used.
In order to perform necessary and sufficient drying while suppressing the generation of bubbles which are a serious defect, the conductive support in the first drying step in which the drying step is performed in two or more steps and the photosensitive layer immediately after coating formation is dried. The maximum temperature rising rate may be 5 ° C./sec or less and the average temperature rising rate may be 0.05 ° C./sec or less. By doing so, there is no coating film defect such as blistering due to bubbles or cracks due to bursting of bubbles in the photosensitive layer, and a method for producing an electrophotographic photoreceptor capable of forming a high-quality image without black spots or white spots. Can be provided.
In addition, by adding the conditions that the final ultimate temperature of the conductive support in the first drying step is 20 ° C. or higher and 80 ° C. or lower, and the final ultimate temperature of the conductive support in the final drying step is 120 ° C. or higher and 160 ° C. or lower. Furthermore, not only the generation of bubbles in the photosensitive layer can be suppressed, but also the amount of residual solvent in the photosensitive layer can be reduced, so that deterioration of the photoreceptor sensitivity and increase in residual potential due to repeated use can be suppressed.
The drying time in the first drying step is suitably 1 minute to 1 hour, and the drying time in the final drying step is suitably 5 minutes to 1 hour. In addition, the drying step is 2 steps or more, preferably 2 to 5 steps. When another drying step is included between the first drying step and the final drying step, the maximum temperature of the final drying step (160 ° C. ) Should not be exceeded.

Next, the electrophotographic apparatus and the electrophotographic process of the present invention will be described.
The electrophotographic apparatus of the present invention comprises at least a charging means, an image exposure means, a reversal developing means, a transfer means, a cleaning means, and an electrophotographic photosensitive member, and the electrophotographic photosensitive member is at least on a conductive support. A photosensitive layer coated with a coating solution for a photosensitive layer containing an intermediate layer in which an inorganic pigment is dispersed, and at least one solvent selected from a cyclic ether compound, a ketone compound and an aromatic hydrocarbon compound It is characterized by having dried by applying the said drying method.
The outer peripheral surface of the rotating drum-shaped photoconductor is charged to a predetermined positive or negative voltage by a charging unit. A positive or negative DC voltage is applied to the charging means. The DC voltage applied to the charging means is preferably −2000V to + 2000V. Recently, as a charging method for an electrophotographic apparatus, an apparatus using contact charging instead of general corona charging has been put into practical use. This method has advantages such as simplification of the apparatus and reduction of ozone generated by corona discharge.
The contact charging unit is disposed in contact with the surface of the photoconductor, and applies an external voltage directly and uniformly to the photoconductor to charge the surface of the photoconductor to a predetermined potential. Examples of such contact charging means include metals such as aluminum, iron, and copper, conductive polymer materials such as polyacetylene, polypyrrole, and polythiophene, and conductive particles such as carbon black and metal to insulating resins such as polycarbonate and polyethylene. For example, rubber or artificial fiber that is dispersed and conductively treated, or a surface of an insulating resin coated with a conductive substance can be used. Further, these shapes may take any shape such as a roller, a brush, a blade, and a belt.
The applied voltage to the contact charging means may be any of direct current, alternating current or direct current + alternating current. Also, the application method may be applied instantaneously, or the applied voltage may be increased stepwise.
The charged photoreceptor is then subjected to optical image exposure (such as slit exposure or laser beam scanning exposure) by image exposure means. During this exposure scanning, exposure is interrupted for the non-image portion of the document surface, and reversal development is performed by applying a developing bias slightly lower than the surface potential to the image portion that has become low potential due to exposure, thereby An electrostatic latent image corresponding to the original image including the non-image portion described above is sequentially formed.
The electrostatic latent image is then developed with toner by the developing means, and the toner developed image is fed by the transfer means from the paper feed unit in synchronization with the rotation of the photoconductor between the photoconductor and the transfer means. Sequentially transferred onto the surface of the material. The recording material that has undergone image transfer is separated from the surface of the photosensitive member, introduced into image fixing means, subjected to image fixing, and output to the outside as a copy (copy).

As described above, the toner image is transferred onto a transfer material such as paper by the transfer unit, but not all the toner is transferred, and a part of the toner image remains on the photosensitive member. If this residual toner is not removed, a high-quality image free from dirt or the like cannot be obtained in the repeated process. Therefore, it is necessary to clean the residual toner. The cleaning means typically uses a fur brush, a magnetic brush, a blade, or the like, but blade cleaning is mainly used in terms of cleaning accuracy, apparatus configuration, and the like.
In order to increase the cleaning accuracy of the toner, it is preferable that the surface of the photoconductor is not uneven due to bubbles. If blisters due to bubbles or cracks due to bursting of bubbles occur, a cleaning failure will occur, resulting in an abnormal image. However, since the photoconductor produced by the production method of the present invention does not generate bubbles, an electrophotographic apparatus having a cleaning means using a blade does not cause poor cleaning, and black streaks and background stains are generated even after repeated use. An electrophotographic apparatus that continues to provide good images without lowering the rank.

The image density output by the electrophotographic apparatus provided with the reversal developing means greatly depends on the sensitivity and the residual potential of the electrophotographic photoreceptor to be mounted. Therefore, in an electrophotographic apparatus equipped with a photoconductor in which the sensitivity and residual potential of the electrophotographic photoconductor are greatly changed by repeated use, the image density is changed by repeated use.
However, in the electrophotographic apparatus of the present invention, the sensitivity and residual potential of the mounted electrophotographic photosensitive member do not change even if it is repeatedly used. As a result, the exposed portion potential becomes constant over time, and the image density is uniform and high. Quality image.
The contact charging method tends to cause discharge breakdown of the photoreceptor, and as a result, a large black spot is formed in the reversal development process, resulting in an abnormal image.
However, in the photoreceptor of the present invention, even if the intermediate layer and / or the charge transport layer is thickened, the photosensitive layer does not have coating film defects such as blisters due to bubbles or cracks due to bursting of bubbles, and as a result, contact charging means is used. Even if it is mounted on an electrophotographic apparatus, it does not cause discharge breakdown, and even if it is used repeatedly, it becomes an electrophotographic apparatus that continues to provide a high-quality image with a uniform image density over time.

The electrophotographic process of the present invention performs at least charging, image exposure, development, transfer and cleaning on an electrophotographic photosensitive member, and the electrophotographic photosensitive member has at least an inorganic pigment dispersed on a conductive support. An intermediate layer, and a photosensitive layer coated and formed using a coating solution for a photosensitive layer containing at least one solvent selected from a cyclic ether compound, a ketone compound, and an aromatic hydrocarbon compound, The image is dried by applying a drying method, wherein an electrostatic latent image is formed on the surface of the electrophotographic photosensitive member, and the formed electrostatic latent image is reversely developed.
In the reversal development process, if there is a crack due to the burst of bubbles in the photoconductor, it becomes a black spot and becomes a very noticeable abnormal image. The output image density greatly depends on the exposure potential. The exposure potential greatly depends on the sensitivity and residual potential of the electrophotographic photoreceptor to be mounted. For this reason, in the reversal development process using the electrophotographic photosensitive member in which the sensitivity and the residual potential of the electrophotographic photosensitive member are greatly changed by repeated use, the exposure potential varies with time, so that the image density fluctuates.
However, in the electrophotographic process of the present invention, since there is no crack due to bursting of bubbles in the electrophotographic photosensitive member to be mounted, there is no occurrence of abnormal images due to bubbles, and the sensitivity and residual potential do not change even when used repeatedly. The exposure potential is uniform over time, and a high-quality image with a uniform image density can be provided.
Further, in the reversal development process, if a sufficient potential difference between the dark part potential and the bright part potential is obtained, there is a margin with respect to potential fluctuation due to fluctuations in the environment and the like, and a good image can be provided. As one of the means, there is a method of increasing the charging potential of the photoconductor. On the contrary, the discharge breakdown becomes higher as the charging potential on the surface of the photoconductor is higher. However, by using the process of the present invention, there is no problem even if the charging potential is charged to 600 V or more in absolute value, and a good image can always be provided even if it is used repeatedly. That is, it is possible to always provide a good image by an electrophotographic process in which an electrostatic latent image having a dark portion potential of 600 V or more in absolute value is formed on the surface of the photosensitive member, and the formed electrostatic latent image is reversely developed.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not restrict | limited to the following example.

Example 1
Alkyd resin beccosol 1307-60EL (solid content 60% by mass) (Dainippon Ink Chemical) 80 parts by mass, butylated benzoguanamine resin Super Becamine TD-126 (solid content 60% by mass) (Dainippon Ink Chemical) 55 mass A part was dissolved in 350 parts by mass of methyl ethyl ketone, and 350 parts by mass of titanium oxide powder CR-EL (manufactured by Ishihara Sangyo Co., Ltd.) was ball milled for 48 hours using alumina balls to prepare an intermediate layer coating solution.
This was dip-coated on an aluminum drum of φ100 mm × L360 mm and dried at 130 ° C. for 20 minutes to form an intermediate layer having a thickness of 3.5 μm.
Next, 20 parts by mass of titanyl phthalocyanine pigment was placed in a glass pot together with zirconia beads having a diameter of 2 mm, 350 parts by mass of tetrahydrofuran was further added, and ball milling was performed at room temperature of 25 ° C. for 20 hours. Thereafter, a resin solution prepared by dissolving 10 parts by mass of polyvinyl butyral resin ESREC BX-1 (manufactured by Sekisui Chemical Co., Ltd.) in 600 parts by mass of methyl ethyl ketone is added, and ball milling is further performed for 2 hours, thereby applying a coating solution for the charge generation layer. It was created. The charge generation layer coating solution thus obtained was dip-coated on the intermediate layer and dried at 65 ° C. for 20 minutes to form a charge generation layer having a thickness of 0.1 μm.
Next, 770 parts by mass of 70 parts by mass of the charge transport material of the following structural formula (1), 100 parts by mass of the polycarbonate resin Iupilon Z-200 (manufactured by Mitsubishi Gas Chemical), 0.002 parts by mass of silicon oil KF-50 (manufactured by Shin-Etsu Chemical) In tetrahydrofuran. The charge transport layer coating solution thus obtained is dip coated on the charge generation layer and dried by the following drying method using a hot air drier to form a charge transport layer with a thickness of 25 μm, An electrophotographic photoreceptor was prepared.

  The electrophotographic photoreceptor obtained above was subjected to a drying process under the following conditions using a hot air drier.

Examples 2-3 and Comparative Examples 1-2
In Example 1, Example 1 was repeated except that the drying conditions of the electrophotographic photosensitive member were changed as follows. The drying conditions were changed by changing the air volume and set temperature of the hot air dryer.

Example 4
Example 1 was repeated except that the solvent used in preparing the charge transport layer coating solution in Example 1 was 1,3-dioxolane.

Example 5
Example 1 was repeated except that xylene was used as the solvent used in preparing the charge transport layer coating solution in Example 1.

Example 6
Example 1 was repeated except that toluene was used as the solvent used in preparing the charge transport layer coating solution in Example 1.

Comparative Example 3
In Example 1, a photoconductor was prepared in exactly the same manner except that the solvent used for preparing the charge transport layer coating solution was changed to dichloromethane.

  Next, the obtained electrophotographic photosensitive member was visually counted for the number of bubbles, and then mounted on Imagio MF-7070 (manufactured by Ricoh) to evaluate the initial image. IMAGIO MF-7070 is equipped with non-contact charging means, image exposure means, reversal developing means, transfer means, and cleaning means using a cleaning blade.

Examples 7 to 10, Comparative Example 4
In Example 1, the aluminum drum was changed to φ60 mm × L334 mm, and an intermediate layer coating solution was prepared as follows.
30 parts by mass of methoxymethylated nylon fine resin FR-102 (methoxymethylation rate 30%) (manufactured by Lead City) and butylated melamine resin Superbecamine G-821-60 (nonvolatile content 60%) (Dainippon) Ink Chemical Co., Ltd.) 50 parts by mass was dissolved in a mixed solvent of 200 parts by mass of methanol, 50 parts by mass of n-butanol and 250 parts by mass of methyl ethyl ketone, and CR-60 (manufactured by Ishihara Sangyo Co., Ltd.) 300 parts by mass was added and dispersed for 100 hours by a ball mill. Thereafter, 30.0 parts by mass of hypophosphorous acid (solid content 10%) dissolved in methanol was added to prepare an intermediate layer coating solution.
A photoconductor was prepared in the same manner as in Example 1 except that the thickness of the intermediate layer, the thickness of the charge transport layer, and the drying conditions were changed as follows.

(By changing the air volume and set temperature of the hot air dryer, the maximum temperature rise rate, the average temperature rise rate, and the final temperature reached were changed. The unit of the average temperature rise rate is (° C./sec).)

  The surface of the obtained photoreceptor was visually observed, and the number of bubbles was counted.

  Next, the obtained electrophotographic photoreceptor was mounted on imagio NEO450 (manufactured by Ricoh), and the initial image and the image after 100K (A4 horizontal) running were evaluated. The imagio NEO450 is equipped with contact charging means using a charging roller, image exposure means, reversal developing means, transfer means, and cleaning means using a cleaning blade.

Examples 11-14, Comparative Examples 5-8
In Example 1, the aluminum drum was changed to φ30 mm × L340 mm, and an intermediate layer coating solution was prepared as follows.
150 parts by weight of alkyd resin Beccosol 1307-60EL (solid content 60% by mass) (Dainippon Ink Chemical), 100 parts by weight of melamine resin Super Becamine G-821-60 (solid content 60% by mass) (Dainippon Ink Chemical) Parts were dissolved in 500 parts by mass of methyl ethyl ketone. 500 parts by mass of titanium oxide TA-300 (manufactured by Fuji Titanium Industry Co., Ltd.) was added thereto, and dispersed for 35 hours by a ball mill using alumina balls as a medium to prepare an intermediate layer coating solution.
In addition, the charge generation layer was changed as follows.
60.0 parts by mass of an azo pigment of the following structural formula (2) was dispersed in 330 parts by mass of methyl ethyl ketone for 200 hours using a ball mill. After the dispersion is completed, a resin solution prepared by dissolving 10 parts by mass of polyvinyl butyral (ESREC BL-1: manufactured by Sekisui Chemical Co., Ltd.) in 400 parts by mass of methyl ethyl ketone and 1850 parts by mass of cyclohexanone is added and dispersed for 5 hours. A liquid was created.

A photoconductor was prepared in the same manner as in Example 1 except that the thickness of the intermediate layer, the thickness of the charge transport layer, and the drying conditions were changed as follows.
For Comparative Examples 5, 6, 7, and 8, photoconductors were prepared in the same manner as described above, except that the solvent used for preparing the charge transport layer coating solution was changed to dichloromethane.

  The photosensitive layer was visually observed and the number of bubbles was counted. The photoreceptor thus obtained was mounted on a digital copier IMAGEIO MF2200 (manufactured by Ricoh) and adjusted to a dark portion charging potential of −600 V and a reversal developing bias of −350 V, and then an initial image was evaluated. The IMAGEIO MF2200 is an electrophotographic apparatus including a contact contact charging unit using a charging roller, an image exposing unit using a laser, a reverse developing unit, a transfer unit, and a cleaning unit using a blade.

  Regarding Examples 11 to 14, images after 50K (A4 horizontal) continuous run after initial image evaluation were also evaluated.

  From the examples and comparative examples described above, the drying process of the coated photosensitive layer is made to be two or more processes, and the maximum temperature increase rate and the average temperature increase rate of the conductive support are controlled, so that the photosensitivity during drying is controlled. It can be seen that the generation of bubbles in the layer can be effectively prevented, and a high-quality image can be formed.

According to the present invention, generation of bubbles in the photosensitive layer is suppressed, and there are no coating film defects such as blisters and cracks in the photosensitive layer, and as a result, a high-quality image without black spots or white spots can be formed. producing how the electrophotographic photosensitive member is provided.

Claims (2)

An intermediate layer having a thickness of 3.0 to 5.0 μm in which an inorganic pigment is dispersed on a conductive support, and at least one kind selected from a cyclic ether compound, a ketone compound and an aromatic hydrocarbon compound A charge generation layer formed by coating using a coating solution for a charge generation layer containing a solvent, and a charge transport layer containing one or more types of solvents selected from cyclic ether compounds, ketone compounds and aromatic hydrocarbon compounds In the method for producing an electrophotographic photosensitive member having a charge transport layer having a thickness of 20 to 30 μm applied and formed using a coating liquid in this order, the drying step for drying the applied and formed charge transport layer is performed in two or more steps. There is a first dryer maximum heating rate of the conductive support in step 1 ℃ / sec~ 5 ℃ / se c drying the charge transport layer immediately after coating formation, and the average heating rate is 0.005 ℃ / sec~ 0.05 ℃ / se c Process for producing an electrophotographic photoreceptor, characterized in that.   The final reached temperature of the conductive support in the first drying step is 20 ° C. or higher and 80 ° C. or lower, and the final reached temperature of the conductive support in the final drying step is 120 ° C. or higher and 160 ° C. or lower. The method for producing an electrophotographic photosensitive member according to claim 1, wherein