JP4302648B2 - Electrophotographic photosensitive member, method for producing the same, and image forming apparatus including the electrophotographic photosensitive member - Google Patents

Description

The present invention relates to a method for manufacturing an electrophotographic photosensitive member used in an image forming apparatus such as a copying machine, a printer, and a facsimile machine.

  2. Description of the Related Art An electrophotographic image forming apparatus (hereinafter referred to as an electrophotographic apparatus) that forms an image using electrophotographic technology is widely used as a copying machine, a printer, a facsimile apparatus, and the like. In an electrophotographic apparatus, an image is formed through the following electrophotographic process. First, a photosensitive layer of an electrophotographic photosensitive member (hereinafter also simply referred to as a photosensitive member) provided in the apparatus is uniformly charged to a predetermined potential by a charging unit, exposed according to image information by an exposure unit, and electrostatically charged. A latent image is formed. The formed electrostatic latent image is developed with a developer to form a toner image. The formed toner image is transferred from the surface of the photosensitive member to the transfer paper by the transfer unit and fixed by the fixing unit. As a result, an image is formed on the transfer paper. On the other hand, the photoconductor after the transfer of the toner image is cleaned by a cleaning means including a cleaning blade, and the toner remaining on the surface of the photoconductor without being transferred onto the transfer material during the transfer operation is removed. Thereafter, the surface of the photosensitive layer is neutralized by a static eliminator or the like, and the electrostatic latent image disappears.

  An electrophotographic photoreceptor used in an electrophotographic apparatus has a configuration in which a photosensitive layer containing a photoconductive material is laminated on the outer peripheral surface of a cylindrical or columnar conductive substrate. In recent years, the development of photoconductive materials for use in electrophotographic photoreceptors has progressed, replacing organic photoconductive materials such as zinc oxide, cadmium sulfide, amorphous selenium, and amorphous silicon that have been used in the past with organic materials. A photoconductive material, that is, an organic photoconductor (Organic Photoconductor; OPC) is frequently used. An electrophotographic photosensitive member using an organic photoconductive material has some problems in sensitivity, durability and stability to the environment, but is inorganic in terms of toxicity, manufacturing cost, and freedom of material design. Compared to a photoreceptor using a photoconductive material of the system, it has many advantages.

  In particular, a charge generation layer containing a charge generating substance (hereinafter referred to as a charge generation substance) and a charge transport layer mainly composed of a charge transporting substance (hereinafter referred to as a charge transport substance) are laminated. Laminated type separation-type photoreceptors having a photoconductive layer as a photosensitive layer are excellent in electrophotographic characteristics such as sensitivity, chargeability, and repetitive stability, and most of the electrophotographic photoreceptors currently in practical use. is occupying.

  In recent years, image forming apparatuses such as copying machines and printers have been required to have high image quality, high durability, low cost, full color, and so on. Functionalization is desired. For example, in order to realize high durability of the image forming apparatus, high durability of the electrophotographic photosensitive member is required. The photosensitive layer, which is the surface layer of the photoreceptor, is exposed to various loads (stresses) during the electrophotographic process. For example, in the charging process, a load such as adsorption of ozone and nitrogen oxides by corona discharge or rubbing by contact charging means is applied. Further, the developing process and the transfer process receive a rubbing with a developer or transfer paper, and the cleaning process receives a rubbing with a cleaning blade or a brush. These loads cause the photosensitive layer to wear and reduce the film thickness.

  The change in film thickness accompanying the abrasion of the photosensitive layer causes deterioration in image quality such as a decrease in chargeability and photosensitivity of the photosensitive member, a corresponding decrease in image density, and ground fog. For this reason, various methods for improving the abrasion resistance of the photosensitive layer have been studied in order to achieve high durability of the photoreceptor.

  As a method for improving the abrasion resistance of the photosensitive layer, it has been proposed to provide a protective layer on the surface of the photoconductive layer (see, for example, Patent Documents 1 and 2). As the binder resin for the protective layer, a curable resin such as a thermosetting resin obtained by reacting a crosslinkable resin or the like with a main resin and a curing agent is used because of excellent abrasion strength. For example, Patent Document 1 discloses a photoreceptor provided with a protective layer containing a thermosetting silicone resin. Patent Document 2 discloses a photoconductor using a mixture of a curable resin and an acrylic resin as a binder resin for a protective layer.

  The protective layer is formed by applying a coating liquid for forming a protective layer on the surface of the photoconductive layer. As described above, when a curable resin is used as the binder resin for the protective layer, there is a problem in the storage stability of the coating liquid for forming the protective layer. That is, the coating solution for forming a protective layer for forming a protective layer using a curable resin is prepared by mixing the main resin and the curing agent, so that the main resin can be stored during storage or during production of the photoreceptor. The reaction between the resin and the curing agent proceeds, the main resin is cured, and the coating liquid for forming the protective layer is gelled. For this reason, it is difficult to maintain a coating solution that can stably produce a high-quality photoreceptor, and a problem arises that a homogeneous protective layer cannot be stably formed. In order to form a uniform protective layer, it is necessary to discard the gelled coating solution, which causes a problem of an increase in manufacturing cost due to loss of the coating solution.

  There are also various problems in applying the coating solution. Known coating methods for the coating liquid include dip coating, roll coating, bar coating, blade coating, ring coating, and spray coating. For example, in the dip coating method, after the substrate is immersed in a coating solution stored in a coating tank, the coating solution is applied to the surface of the substrate by pulling it up from the coating solution at a constant speed or a speed that changes sequentially.

  FIG. 5 is a system diagram showing an example of the configuration of a dip coating apparatus used in the dip coating method. In the dip coating apparatus 1, the coating tank 4 contains a coating solution 5 containing a photosensitive material. A conductive substrate (hereinafter simply referred to as a substrate) 11 held by the chucking device 8 is immersed in the coating solution 5 in the coating tank 4. When dipping, the chucking device 8 is lowered by the elevator 2 including the motor 3. As a result, the substrate 11 is immersed in the coating solution 5. After sufficient immersion, the chucking device 8 is raised by the elevator 2. By adjusting the rotation amount of the motor 3 of the elevator 2, the base body 11 can be immersed to a desired depth in the coating tank 4. The coating liquid 5 overflowing (overflowing) from the coating tank 4 when the substrate 11 is immersed flows in the direction of the arrow 13 and is collected in the auxiliary tank 7. In the auxiliary tank 7, the recovered coating liquid 5 is adjusted by the viscosity measuring device 16 and the solvent adding device 10 so as to have a predetermined viscosity while being stirred by the stirring device 12. Thereafter, the coating liquid 5 is returned to the coating tank 4 by the pump 6 while filtering foreign substances in the liquid through the filter 9. In the coating tank 4 filled with the coating solution 5 again in this way, the next dip coating is performed.

  As described above, the dip coating method is relatively simple and excellent in productivity, so that it is frequently used in the production of an electrophotographic photosensitive member. However, in the dip coating method, it is necessary to store a coating liquid in an amount exceeding the amount consumed as a coating film so that the entire substrate is immersed, so that the usage efficiency of the coating liquid is poor. There's a problem. Since the coating solution cannot be used due to changes in viscosity, etc. over time, most of the prepared coating solution is not consumed and is discarded after the end of its life. Incurs an increase. In particular, the coating solution for forming the protective layer contains the main resin and the curing agent as described above, and the reaction proceeds while being stored in the coating tank. Improvement in efficiency is required. In addition, in order to accommodate a large amount of coating liquid in the coating tank as described above, it is necessary to take explosion-proof measures in order to satisfy the restrictions on the specified quantity related to the Fire Service Act, which increases the capital investment cost. Also occurs.

  In the dip coating method, it is necessary to replace the coating tank to be used and clean the coating tank according to the dimensions of the substrate, for example, the outer diameter of the cylindrical substrate and the length in the longitudinal direction. For example, since the dimensions of the photoconductor differ depending on the model of the electrophotographic apparatus to be mounted, it is necessary to remove the coating liquid and clean the coating tank each time the so-called model switching is performed. The number of work processes increases, leading to an increase in manufacturing costs. Also, in the dip coating method, the cylindrical substrate is moved in the longitudinal direction and immersed in the coating solution, so the influence of the solvent vapor in the coating solution and the immersion time in the coating solution are different at various locations in the longitudinal direction of the substrate. Uneven coating is likely to occur. Further, at the end portion on the lower end side of the substrate that is immersed in the coating solution for a long time, there is a problem that the previously formed lower layer is eluted in the coating solution.

  In contrast, the roll coating method, the bar coating method, the blade coating method, the ring coating method, and the spray coating method do not cause problems such as poor use efficiency of the coating liquid and elution of the lower layer, which are problems in the dip coating method. For example, in the roll coating method, the bar coating method, the blade coating method, and the ring coating method, since the coating solution is applied to the substrate via a coating member such as a roll, the base coating solution required for production is smaller than that in the dip coating method. The amount is small and the usage efficiency of the coating solution is good. However, when the coating member is pulled away from the substrate, the surface tension of the coating solution causes a phenomenon in which excess coating solution adheres to the substrate, a phenomenon in which a part of the coating film applied to the substrate swells, and the film thickness is reduced. There is a problem that it becomes uniform.

  In addition, the spray coating method is a method of spraying only the amount of coating liquid necessary for the formation of a coating film, and does not require a large amount of coating liquid exceeding the necessary amount. Liquid use efficiency can be realized. FIG. 6 is a system diagram showing an example of the configuration of a spray coating apparatus used in the spray coating method. In the spray coating device 20, the storage tank 22 contains the coating solution 5 containing a photosensitive material. A clean atomizing gas is fed to the spray nozzle 21 via a compressor 23 and an air filter 24. The coating liquid 5 is fed to the spray nozzle 21 by the pump 6 while filtering foreign substances in the liquid through the filter 9 and sprayed onto the conductive substrate 11 by the spraying gas. At the time of spraying, the conductive substrate 11 is rotationally driven in the direction of the arrow 25 around the axis, and the spray nozzle 21 is an arrow that is in a direction parallel to the axial direction of the conductive substrate 11, that is, in the vertical direction toward the paper surface of FIG. It is reciprocated in the direction of the mark 26. As a result, the coating liquid 5 is applied to the entire outer peripheral surface of the cylindrical conductive substrate 11. In the spray coating apparatus 20, the film thickness of the coating film to be formed can be controlled by adjusting the rotation speed of the substrate 11, the moving speed of the spray nozzle 21, the number of reciprocating movements of the spray nozzle 21, and the like.

  In such a spray application device, when switching the production model, it is only necessary to replace the storage tank and clean the spray nozzle, so the number of work steps is smaller than the dip coating method and the cost is relatively low. It is. In addition, since coating can be performed in the same manner over the entire length of the substrate, uneven coating in the length direction of the substrate can also be reduced.

  However, since the coating liquid sprayed from the spray nozzle spreads and spreads over a wider range than the diameter of the opening of the spray nozzle, it is applied to the periphery of the portion to be coated. In order to further improve the use efficiency of the coating solution, a coating method is required in which the coating solution is not applied to such unnecessary portions. In addition, since the droplets of the coating liquid sprayed from the spray nozzle have a relatively large diameter and are non-uniform, the spray coating method is used when forming a thin layer having a thickness of 10 μm or less like a protective layer. The film quality becomes coarse. When such a protective layer is formed as a surface layer of the photosensitive layer, there arises a problem that the image quality is deteriorated.

  As a method other than the above, there is a so-called ink jet method (hereinafter also referred to as an ink jet method) (for example, see Patent Document 3). In the ink jet method, the coating liquid is ejected as droplets from the ejection nozzle and adhered to the coating object while relatively moving the object to be coated and the discharge nozzle.

  As a method of discharging the coating liquid from the discharge nozzle, a piezo method in which the coating liquid is extruded by the vibration pressure of a piezoelectric element (hereinafter also referred to as a piezo element), a heater is energized to heat the coating liquid, and thereby the coating liquid is The bubble jet (registered trademark) system that generates bubbles in the bubble and extrudes the coating liquid by the expansion pressure of the generated bubbles, energizes the heater to generate bubbles in the coating liquid, and ruptures the bubbles. There are thermal methods to extrude. For example, in the technique disclosed in Patent Document 3 described above, pressure is applied to the coating solution to continuously fly in a streak form from a plurality of minute nozzles, and the coating is applied to the object to be coated.

  FIG. 7 is a system diagram showing an example of the configuration of an inkjet coating apparatus used in the inkjet method. In the ink jet coating apparatus 30, an ink jet type nozzle head 31 incorporating a piezoelectric element or a heater is provided instead of the spray nozzle 21 provided in the spray coating apparatus 20 shown in FIG. The coating liquid 5 stored in the storage tank 22 is supplied to the nozzle head 31 by the pump 6 through the filter 9 and is discharged as droplets from the discharge nozzle (not shown) in the nozzle head 31 toward the substrate 11.

  In the ink jet method, ejected droplets can be ejected linearly with very high accuracy, and the operations of a plurality of ejection nozzles provided in the nozzle head 31 can be individually controlled. The spread of the coating liquid can be suppressed. For this reason, there is an advantage that the use efficiency of the coating liquid is good, masking is unnecessary, and the coating efficiency is very high. In addition, since the nozzle head 31 itself has a built-in mechanism for discharging the coating liquid, there is an advantage that it is not necessary to provide a device for supplying the spraying gas such as the compressor 23 and the air filter 24 of the spray coating device 20. is there. In addition, the coating liquid can be easily replaced by simply replacing the storage tank for storing the coating liquid, and the coating liquid can be used up, so that the production efficiency is very high. In addition, since the droplets ejected by the ink jet method have a diameter as small as several tens of μm and are uniform, there is an advantage that even a thin layer having a thickness of 10 μm or less can be formed smoothly. .

  However, the inkjet method has a problem that the discharge nozzle is easily clogged and it is difficult to stably discharge the coating liquid for a long period of time. In particular, when a solvent having a low boiling point such as tetrahydrofuran is used as the solvent for the coating liquid as in the technique disclosed in Patent Document 3 described above, since the solvent volatilizes quickly, the coating liquid is easily dried at the discharge nozzle portion, and the discharge liquid is discharged. Nozzle clogging is likely to occur. In addition, since the coating liquid using only such a low-boiling solvent as a solvent is quick to dry after coating, there is a problem that leveling properties are not sufficient and it is difficult to form a layer having a uniform thickness. is there.

Japanese Patent Laid-Open No. 3-155558 JP-A-60-3639 Japanese Patent Laid-Open No. 11-19554

An object of the present invention is to provide a manufacturing how the electrophotographic photosensitive member that can be manufactured uniform quality and a high quality electrophotographic photosensitive member having a layer thickness stably efficiently and inexpensively .

The present invention is a method for producing an electrophotographic photoreceptor in which a photosensitive layer including a photoconductive layer and a protective layer, which are sequentially laminated on a conductive substrate, is laminated,
The step of forming the protective layer includes
Two or more kinds of coating liquids including a main resin-containing coating liquid containing a main resin and a curing agent-containing coating liquid containing a curing agent are each ejected in droplet form from an ejection nozzle toward the conductive substrate by an inkjet method . A coating step of coating so that the coating liquids are in a mixed state at least on the conductive substrate;
Look including a drying step of the two or more coating liquid drying the applied conductive substrate,
Each of the two or more coating liquids contains a high boiling point solvent having a boiling point of 120 ° C. or higher and 260 ° C. or lower in an amount of 5% by weight to 40% by weight of the total amount of the coating liquid,
The protective layer is formed by a layer containing a thermosetting resin obtained by a reaction between the main resin and the curing agent .

Further, the invention is characterized in that the volume of one drop of the coating liquid discharged from the discharge nozzle is 30 pL .

  In the present invention, the high boiling point solvent is one or more selected from cyclohexanone, 2-pyrrolidone, N-methyl-2-pyrrolidone and p-xylene.

  In the invention, it is preferable that the at least one layer is formed to have a thickness of 1 μm to 10 μm.

Further, the present invention provides the application step,
The coating liquid is discharged from a discharge nozzle by vibration of a piezoelectric element.

Further, the present invention provides the application step,
The conductive substrate and the discharge nozzle are relatively moved, and the coating liquid is discharged from the discharge nozzle.

According to the present invention , the protective layer, which is a layer constituting the photosensitive layer of the electrophotographic photosensitive member, ejects two or more kinds of coating liquids from the ejection nozzles in the form of droplets by an inkjet method, and at least on the conductive substrate. It forms through the application | coating process apply | coated so that it may be in the mixed state, and the drying process which dries the electroconductive base | substrate with which 2 or more types of coating liquids were apply | coated. Here, the photosensitive layer is composed of a single photoconductive layer containing a charge generation material and a charge transport material, a charge generation layer containing a charge generation material, and a charge transport layer containing a charge transport material. And those formed by further laminating a protective layer on these photoconductive layers.

By thus dividing the protective layer coating liquid for forming the two or more kinds, it is possible to apply the components constituting the protective layer as a separate coating solution, the protective layer gelation is likely to occur Gelling of the coating liquid for forming (hereinafter referred to as a coating liquid for forming a protective layer) , sedimentation, aggregation, and alteration of components contained in the coating liquid can be prevented , and storage stability can be improved. The Thereby, a homogeneous layer can be formed stably. Moreover, the loss of coating liquid can be suppressed and manufacturing cost can be reduced. In addition, since each inkjet liquid is applied by an ink jet method in which droplets are discharged from the discharge nozzle and applied, the flight path of the discharged droplets can be easily controlled. Thereby, since the coating liquids can be mixed uniformly, a uniform layer can be formed over the entire conductive substrate in the portion where the coating liquid is to be applied. Further, when forming the layer, it is only necessary to discharge a necessary amount of the coating liquid, and it is not necessary to store a large amount of the coating liquid, so that the usage efficiency of the coating liquid is high and the manufacturing cost can be reduced. . Furthermore, since coating can be performed on conductive substrates of various dimensions, it is possible to easily switch between models and achieve high productivity. Therefore, in the method for producing an electrophotographic photoreceptor of the present invention, a high-quality electrophotographic photoreceptor having a homogeneous layer can be produced stably, efficiently, and inexpensively.
The protective layer contains a thermosetting resin. Since the thermosetting resin is excellent in abrasion resistance, a protective layer having excellent durability can be formed by using the thermosetting resin.
Thus, when using a thermosetting resin, the coating liquid for protective layer formation of a thermosetting resin is apply | coated separately at least to the main resin containing coating liquid and the hardening | curing agent containing coating liquid. This prevents the main resin and the curing agent from being touched until they are applied to the conductive substrate, thereby suppressing the reaction between the main resin and the curing agent in the coating liquid for forming the protective layer, and the protective layer. Gelation of the forming coating liquid, sedimentation and aggregation of components can be prevented more reliably. Therefore, the durability of the protective layer can be improved using the thermosetting resin without impairing the life of the coating solution.
Further, the coating solution preferably contains a high boiling point solvent having a boiling point of 120 ° C. or higher and 260 ° C. or lower (hereinafter simply referred to as a high boiling point solvent) of 5% by weight to 40% by weight of the total amount of the coating solution. . Accordingly, drying of the coating liquid at the discharge nozzle portion can be suppressed, so that the discharge stability of the coating liquid can be improved and clogging of the discharge nozzle can be prevented. Moreover, since the sedimentation and aggregation of the components in the coating solution due to the decrease in the solvent can be suppressed, the storage stability of the coating solution can be improved. Moreover, since the leveling property after application | coating can be improved, the layer which has uniform thickness can be formed.
According to the invention, the volume of one drop of the coating liquid discharged from the discharge nozzle is 30 pL.

  According to the invention, the high boiling point solvent is preferably one or more selected from cyclohexanone, 2-pyrrolidone, N-methyl-2-pyrrolidone and p-xylene. Since these solvents have an appropriate boiling point, the use of these solvents further improves the ejection stability of the coating liquid and the leveling properties after coating. Therefore, a layer having a uniform thickness can be formed more stably.

  Moreover, according to this invention, the layer formed through the above-mentioned application | coating process and a drying process is formed so that layer thickness may be 1 micrometer or more and 10 micrometers or less. A layer having such a layer thickness is suitable for formation by an ink jet method because the number of times of overcoating is small. Further, since drying after application can be completed in a relatively short time, the above-mentioned high boiling point solvent can be used, and clogging of the discharge nozzle and leveling failure due to drying and solidification of the application liquid can be prevented. That is, the method for producing an electrophotographic photosensitive member of the present invention is suitable for forming a layer having a layer thickness in the range of 1 μm to 10 μm.

  According to the invention, the application liquid is applied using a piezo method in which the application liquid is discharged from the discharge nozzle by the vibration of the piezoelectric element. As a result, discharge failure due to kogation can be prevented, and the coating liquid can be discharged stably. Therefore, a uniform layer can be formed more stably.

  Here, kogation is a substance generated by thermal decomposition of a resin component in a coating liquid in a discharge system using a heat source such as a heater such as a bubble jet (registered trademark) system or a thermal jet system, and is included in the coating liquid. This is a phenomenon in which a minute amount of impurities, aggregates, and the like are deposited and deposited on the heat source, and as a result, the coating liquid cannot be sufficiently heated by the heat source and the coating liquid cannot be discharged.

  Further, according to the present invention, when applying the coating liquid by discharging it, it is preferable to discharge the coating liquid while relatively moving the conductive substrate and the discharge nozzle. As a result, uniform coating can be performed over the entire conductive substrate where the coating liquid is to be applied, so that uneven coating can be prevented and a more uniform layer can be formed.

  The method for producing an electrophotographic photoreceptor, which is an embodiment of the present invention, is a method for producing an electrophotographic photoreceptor in which a photosensitive layer composed of one or more layers is laminated on a conductive substrate. In the method for producing an electrophotographic photoreceptor of this embodiment, at least one of the layers constituting the photosensitive layer uses an inkjet method, and two or more kinds of coating liquids are respectively discharged from the discharge nozzle toward the conductive substrate. By discharging in the form of droplets, a coating process for coating so that the coating liquids are mixed on at least the conductive substrate, and the conductive substrate coated with the two or more coating liquids are dried. It is formed through a drying process.

  In this way, the coating liquid for forming the layer constituting the photosensitive layer is divided into two or more kinds of coating liquids, so that the components for forming the layers are contained in the different coating liquids and applied. be able to. This prevents each component from being touched until it is mixed on the conductive substrate, thus preventing gelation of the coating solution, sedimentation, aggregation, and alteration of components contained in the coating solution, and a uniform layer. Can be formed stably. Moreover, the loss of coating liquid can be suppressed and manufacturing cost can be reduced.

  FIG. 1 is a system diagram showing a simplified configuration of an ink jet coating apparatus 40 that is preferably used in the method of manufacturing an electrophotographic photosensitive member of the present embodiment. The ink jet coating apparatus 40 shown in FIG. 1 is preferably used when two types of coating liquids are used in the above coating process. The inkjet coating apparatus 40 includes a nozzle head 41, a guide rail portion 42 on which the nozzle head 41 is movably mounted, a coating liquid supply unit 43 that supplies a coating liquid to the nozzle head 41, a filter 44, and a pump 45. The transport tube 46 that connects the nozzle head 41 and the coating liquid supply unit 43, the base support means 47 that supports the conductive base 61, and the arrow 48 around the axis of the conductive base 61 via the base support means 47. And rotational drive means (not shown) that rotationally drives in the direction. As the conductive substrate 61, a cylindrical or columnar thing can be used. A conduit (not shown) is formed inside the transport tube 46 and functions as a transport channel for the coating liquid. In the present embodiment, the nozzle head 41 includes a first discharge nozzle 49 and a second discharge nozzle 50.

  The coating liquid supply unit 43 includes a storage tank that stores the coating liquid. In the present embodiment, the coating liquid supply unit 43 includes a first storage tank 53 and a second storage tank 54 that store two types of coating liquids, that is, the first coating liquid 51 and the second coating liquid 52, respectively. Two conduits (not shown) are formed inside the transport tube 46 connected to the coating liquid supply unit 43, and the first storage tank 53 and the first discharge nozzle 49 are connected via these conduits, The second storage tank 54 and the second discharge nozzle 50 are connected. The nozzle head 41 discharges the first coating liquid 51 supplied from the first storage tank 53 of the coating liquid supply unit 43 from the first discharge nozzle 49 toward the conductive substrate 61 as the first droplet 51a, and the second The second coating liquid 52 supplied from the storage tank 54 is discharged as a second droplet 52a from the second discharge nozzle 50 toward the conductive substrate 61.

  In the present embodiment, the first discharge nozzle 49 and the second discharge nozzle 50 are each in a direction orthogonal to the axis of the conductive substrate 61 such that the center lines of the openings intersect each other on the surface of the conductive substrate 61. In contrast, it is inclined. As a result, the first droplet 51a and the second droplet 52a can be landed on substantially the same position on the surface of the conductive substrate 61, so that the first droplet 51a and the second coating solution 52, which are the first coating solution 51. The second droplet 52a can be uniformly mixed on the conductive substrate 61. Therefore, a layer having a uniform property can be formed over the portion of the conductive substrate 61 where the first coating liquid 51 and the second coating liquid 52 are to be applied.

  Thus, in the inkjet coating apparatus 40, the flight paths of the first droplet 51a and the second droplet 52a can be easily controlled, and the first droplet 51a and the second droplet 52a are uniformly mixed. Since a homogeneous layer can be formed, it is suitable for the method for producing an electrophotographic photoreceptor according to this embodiment. Further, in the ink jet coating apparatus 40, since it is not necessary to store a large amount of coating liquid that greatly exceeds the required amount as in the dip coating apparatus 1 shown in FIG. 5 described above, the usage efficiency of the coating liquid is high. Compared with the case where the dip coating apparatus 1 is used, the manufacturing cost can be reduced. Furthermore, in the ink jet coating apparatus 40, when changing the dimension of the conductive substrate 61, for example, the length in the axial direction, it is only necessary to change the movement range of the ink head 41 in the direction parallel to the axial line of the conductive substrate 61. Good. That is, in the ink jet coating apparatus 40, since the model to be produced can be easily switched, high productivity can be realized. In this embodiment, since the coating is performed by the inkjet coating method using the inkjet coating apparatus 40 shown in FIG. 1 having such advantages, a high-quality electrophotographic photosensitive member having a layer of uniform quality and thickness is obtained. It can be manufactured stably, efficiently and inexpensively.

  In the present embodiment, the first discharge nozzle 49 includes a piezoelectric element and an electrode (not shown), and discharges the first coating liquid 51a by the vibration of the piezoelectric element due to distortion when a voltage is applied to the piezoelectric element. Nozzle. Similarly, the second discharge nozzle 50 includes a piezoelectric element and an electrode (not shown), and is a piezo-type discharge nozzle that discharges the second droplet 52a by vibration of the piezoelectric element.

  In addition to the piezo method, there are a bubble jet (registered trademark) method, a thermal method, and the like as droplet discharge methods in the inkjet method. In these methods, heat is locally applied to the coating liquid using a heating element such as a heater to generate bubbles, which may cause ejection failure due to kogation. On the other hand, the piezo method is preferable because the coating liquid can be stably discharged without causing kogation.

  The guide rail portion 42 is, for example, a metal rod-like member, and is attached to rail support means (not shown) so that its axis is parallel to the axis of the conductive base 61. Accordingly, the nozzle head 41 attached to the guide rail portion 42 is guided by the guide rail portion 42 so as to maintain a certain distance from the conductive base 61 and is parallel to the axis of the conductive base 61. Can move in the direction. The movement of the nozzle head 41 can be realized, for example, by forming the guide rail portion 42 as a rack, providing an electric motor in the nozzle head 41, and providing a pinion on the output shaft of the electric motor.

  The ink jet coating apparatus 40 rotates and drives the conductive substrate 61 around the axis, and discharges the coating liquid in the form of droplets while moving the nozzle head 41 in a direction parallel to the axis of the conductive substrate 61. A coating solution is applied to the conductive substrate 61. The first discharge nozzle 49 and the second discharge nozzle 50 provided in the nozzle head 41 move in a direction parallel to the axis of the conductive substrate 61 as the nozzle head 41 moves. In this way, by applying the coating liquid while moving the conductive substrate 61 and the discharge nozzles 49 and 50 relatively, the coating liquid is uniformly applied over the entire portion of the conductive substrate 61 to which the coating liquid is to be applied. Therefore, the occurrence of uneven coating can be prevented, and a layer such as a protective layer can be formed more uniformly.

  During the coating operation by the inkjet coating device 40, the nozzle head 41 is guided by the guide rail portion 42 and is repeatedly moved back and forth in a direction parallel to the axis of the conductive substrate 61. In the ink jet coating apparatus 40, the rotational speed of the conductive substrate 61 when the coating liquids 51 and 52 are coated, the moving speed at which the nozzle head 41 moves while being guided by the guide rail portion 42, the number of reciprocating movements of the nozzle head 41, and the discharge It is formed by adjusting the discharge speed of the droplets 51a and 52a from the nozzles 49 and 50, the discharge amount of the droplets 51a and 52a from the discharge nozzles 49 and 50, that is, the volume of the discharged droplets 51a and 52a. It is possible to control the thickness of the coating film, and thus the thickness of the protective layer obtained by drying the coating film.

  In the case where the coating liquids 51 and 52 are applied to the surface of the layer formed on the surface of the conductive substrate 61 using the inkjet coating apparatus 40 shown in FIG. 1, the conductive substrate 61 on which the layer is formed. Is held by the substrate support means, and the coating liquids 51 and 52 are applied.

  In the ink jet coating apparatus 40 shown in FIG. 1, the first discharge nozzle 49 and the second discharge nozzle 50 are formed so as to be inclined so that the center line of the opening intersects the surface of the conductive substrate 61. Without being limited thereto, the opening may be formed so as to be inclined so that the center line of the opening intersects the space closer to the opening than the surface of the conductive substrate 61. Accordingly, the first droplet 51a and the second droplet 52a can collide and mix in the air before landing on the conductive substrate 61, and can land on the conductive substrate 61 as a unit. Therefore, the first coating liquid 51 and the second coating liquid 52 can be mixed more uniformly, and the uniformity of the formed layer can be improved.

  The first discharge nozzle 49 and the second discharge nozzle 50 may be formed such that the center line of the opening is orthogonal to the axis of the conductive substrate 61 and does not cross each other. In this case, the ink jet coating apparatus 40 sequentially discharges the first droplet 51 a and the second droplet 52 a from the first discharge nozzle 49 and the second discharge nozzle 50, and the nozzle head 41 is connected to the first conductive substrate 61. The second droplet 52a is moved in a direction parallel to the axis of the conductive substrate 61 so that the second droplet 52a is landed at the position where the droplet 51a has landed. Thus, the first droplet 51a and the second droplet 52a can be mixed on the surface of the conductive substrate 61.

  Moreover, although the inkjet coating apparatus 40 shown in FIG. 1 is provided with the two storage tanks 53 and 54 and the two discharge nozzles 49 and 50, you may be provided with three or more storage tanks and discharge nozzles, respectively. By using such an ink jet coating apparatus, the coating solution for forming the layer constituting the photosensitive layer can be applied in three or more parts.

  FIG. 2 is a partial cross-sectional view showing a simplified configuration of an electrophotographic photoreceptor 60 that is an example of an electrophotographic photoreceptor produced by the method for producing an electrophotographic photoreceptor of this embodiment. An electrophotographic photoreceptor 60 shown in FIG. 2 is a laminated photoreceptor, and has a cylindrical conductive substrate 61, an undercoat layer 62, a charge generation layer 63, and a charge transport layer 64 that are sequentially stacked on the conductive substrate 61. And a protective layer 65. The charge generation layer 63 and the charge transport layer 64 constitute a photoconductive layer 66, and the undercoat layer 62, the photoconductive layer 66 and the protective layer 65 constitute a photosensitive layer 67. Among the layers constituting the photosensitive layer 67, at least the protective layer 65 is formed through the above-described coating process and drying process.

  Hereinafter, the layer configuration and constituent materials of the electrophotographic photoreceptor 60 will be described. The photosensitive material according to the present invention is not limited to the following description.

  Examples of the conductive material constituting the conductive base 61 include metal materials such as aluminum, copper, zinc, nickel, chromium, molybdenum, vanadium, indium, titanium, gold, platinum and other simple metals, and alloys such as brass and stainless steel. Can be used. Without being limited to these metal materials, metal materials such as aluminum, aluminum alloys and gold or conductive compounds such as tin oxide and indium oxide are deposited or coated on the surface of plastic films such as polyester or paper. It is also possible to use a plastic or paper containing conductive particles, a plastic containing a conductive polymer, or the like. These conductive materials are used after being processed into a predetermined shape such as a cylindrical shape, a columnar shape, or a thin film sheet shape. In the present embodiment, at least the protective layer 65 among the layers constituting the photosensitive layer 67 is formed using the ink jet apparatus 40 shown in FIG. 1 described above, so that the conductive substrate 61 is cylindrical or columnar. It is preferable.

  As shown in FIG. 2, an undercoat layer 62 is provided between the conductive substrate 61 and the photoconductive layer 66. By providing the undercoat layer 62 between the conductive substrate 61 and the photoconductive layer 66, the injection of charges from the conductive substrate 61 to the photoconductive layer 66 is prevented, and the chargeability of the photoreceptor 60 is reduced due to repeated use. Can be prevented. In addition, the chargeability of the photoreceptor 60 in a low temperature and low humidity environment can be improved. Furthermore, since scratches, irregularities, and the like on the surface of the conductive substrate 61 can be covered with the undercoat layer 62, the film formability of the photoconductive layer 66 can be improved.

  The undercoat layer 62 is formed of a resin material such as polyamide, copolymer nylon, polyvinyl alcohol, polyurethane, polyester, epoxy resin, phenol resin, casein, cellulose, or gelatin. Among these, alcohol-soluble copolymer nylon is preferably used.

  For the undercoat layer 62, inorganic pigments such as zinc oxide, titanium oxide, tin oxide, indium oxide, silica, and antimony oxide are used for the purpose of adjusting the volume resistivity and improving the repeated aging characteristics in a low temperature and low humidity environment. It may be added. The content of the inorganic pigment in the undercoat layer 62 is preferably 30% by weight or more and 95% by weight or less.

  The undercoat layer 62 is, for example, added with the above-described resin material and, if necessary, an additive such as the above-mentioned inorganic pigment in an appropriate solvent, and dispersed using a dispersing machine such as a ball mill, a dyno mill, or an ultrasonic oscillator. Then, a coating solution for forming the undercoat layer is prepared, and this coating solution can be applied to the surface of the conductive substrate 61.

  As the solvent for the coating solution for forming the undercoat layer, water, various organic solvents, and the like are used. One of these solvents may be used alone, or two or more thereof may be mixed and used as a mixed solvent. As the single solvent, alcohols such as water, methanol, ethanol and butanol are preferably used. As the mixed solvent, a mixed solvent of water and alcohols, a mixed solvent of two or more alcohols, a mixed solvent of ketones and alcohols such as acetone, a mixed solvent of ethers and alcohols such as dioxolane, A mixed solvent of a chlorinated solvent such as dichloroethane, chloroform or trichloroethane and alcohols is preferably used. Among these, in consideration of the influence on the global environment and the safety of workers, it is preferable to use a non-halogen, especially non-chlorine organic solvent.

  As a method for forming the coating liquid for forming the undercoat layer, an inkjet method, a dip coating method, or the like is preferably used. However, when the coating liquid for forming the undercoat layer contains an inorganic pigment such as the above-mentioned titanium oxide, these inorganic pigments have a high specific gravity and are likely to settle. Therefore, inkjet coating using the inkjet coating apparatus 40 shown in FIG. When applied by the method, the pigment is liable to settle and agglomerate at the nozzle portion, which may cause ejection failure. Further, inorganic pigments such as titanium oxide are very robust and easily wear the nozzle, so that the durability of the ink jet coating apparatus is lowered. Therefore, the dip coating method using the above-described dip coating apparatus shown in FIG. 5 is preferably used for coating the coating liquid for forming the undercoat layer containing the inorganic pigment.

  When using the dip coating method, after immersing the conductive substrate 61 in a coating tank filled with a coating solution, the subbing layer 62 is formed on the surface of the conductive substrate 61 by pulling it up at a constant speed or a speed that changes sequentially. Can be formed. The film thickness of the coating film formed by the dip coating method can be controlled by the speed at which the conductive substrate 61 is pulled up (hereinafter referred to as the pulling speed), the viscosity of the coating liquid, and the like. For example, when the film thickness is reduced, the pulling speed of the conductive substrate 61 is increased to decrease the coating speed, or the viscosity of the coating solution is decreased to increase the film thickness, and the conductive substrate 61 is increased. The pulling speed of 61 is decreased to increase the coating speed, or the viscosity of the coating liquid is increased. The viscosity of a coating liquid can be adjusted with the density | concentration of the solid content in a coating liquid.

  The thickness of the undercoat layer 62 is preferably 0.1 μm or more and 5 μm or less. If the thickness of the undercoat layer 62 is less than 0.1 μm, the undercoat layer 62 does not substantially function as the undercoat layer 62 and charge injection from the conductive substrate 61 to the photoconductive layer 66 cannot be prevented. In addition, the chargeability of the photoconductor 60 may be reduced. In addition, since it becomes difficult to cover the defects of the conductive substrate 61 to obtain a uniform surface property, the film formability of the photoconductive layer 66 may be lowered. If the thickness of the undercoat layer 62 is greater than 5 μm, the inflow of charges from the photoconductive layer 66 to the conductive substrate 61 is hindered, and the sensitivity of the photoreceptor 60 may be reduced.

  The charge generation layer 63 formed on the surface of the undercoat layer 62 is mainly composed of a charge generation material that generates charges by light irradiation, and additives such as a binder resin, a plasticizer, and a sensitizer are added as necessary. contains. Examples of charge generating materials include perylene pigments such as peryleneimide and perylene anhydride, polycyclic quinone pigments such as quinacridone and anthraquinone, phthalocyanine pigments such as metal or metal-free phthalocyanine, metal halide and metal-free phthalocyanine, and square. A carbazole skeleton, a styryl stilbene skeleton, a triphenylamine skeleton, a dibenzothiophene skeleton, an oxadiazole skeleton, a fluorenone skeleton, a bis stilbene skeleton, a distyryl oxadiazole skeleton or a distyryl carbazole skeleton. And azo pigments. Among these charge generation materials, those having a particularly high charge generation ability include metal-free phthalocyanine pigments, oxotitanium phthalocyanine pigments, gallium phthalocyanine pigments, chlorogallium phthalocyanine pigments, mixed crystals of metal phthalocyanine and metal-free phthalocyanine, and fluorene. Examples thereof include a bisazo pigment having a ring and / or a fluorenone ring, a bisazo pigment made of an aromatic amine, and a trisazo pigment. By using these, a photoconductor having high sensitivity can be realized.

  The content of the charge generation material in the charge generation layer 63 is preferably 30% by weight or more and 90% by weight or less. If the content of the charge generation material is less than 30% by weight, the sensitivity of the photoreceptor 60 may not be sufficiently obtained. If the content of the charge generation material exceeds 90% by weight, the film strength of the charge generation layer 63 may decrease. In addition, the dispersibility of the charge generation material in the charge generation layer 63 decreases, coarse particles increase, surface charges other than the portions to be erased decrease by exposure, and image fogging such as black spots may occur. There is. Here, black spots are a phenomenon in which minute black spots are formed due to toner adhering to a portion to be white background.

  As the binder resin for the charge generation layer 63, melamine resin, epoxy resin, silicone resin, polyurethane resin, acrylic resin, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, vinyl chloride -Vinyl acetate-polyvinyl alcohol copolymer resin, polycarbonate resin, phenoxy resin, phenol resin, polyvinyl butyral resin, polyarylate resin, polyamide resin, polyester resin and the like.

  As a method for forming the charge generation layer 63, a vacuum deposition method in which the aforementioned charge generation material is directly deposited on the surface of the undercoat layer 62 by vacuum deposition, a coating solution for forming a charge generation layer is prepared as described below, An application method of applying this to the surface of the undercoat layer 62 is exemplified. Among these, the latter coating method is preferably used.

  Solvents for the coating solution for forming the charge generation layer include ketones such as acetone, methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate and butyl acetate, ethers such as tetrahydrofuran, dioxane, dioxolane and dimethoxyethane, benzene, toluene and xylene. And aprotic polar solvents such as N, N-dimethylformamide and dimethyl sulfoxide. The solvent of the coating solution for forming the charge generation layer is not limited to these, but in consideration of the impact on the global environment and the safety of workers, non-halogen, especially non-chlorine organic solvents are used. It is preferable to do.

  The charge generation layer forming coating solution is the same as the case of adding the above-described charge generation material and, if necessary, the above-mentioned binder resin in an appropriate solvent, and dispersing the inorganic pigment in the above-described undercoat layer forming coating solution. It can be prepared by dispersing by the method. Examples of the coating method of the charge generation layer forming coating solution include a dip coating method, a roll coating method, and an inkjet coating method.

  The layer thickness of the charge generation layer 63 is preferably 0.05 μm or more and 5 μm or less, more preferably 0.1 μm or more and 2.5 μm or less. If the layer thickness of the charge generation layer 63 is less than 0.05 μm, the light absorption efficiency is lowered, and the sensitivity of the photoreceptor 60 may be lowered. If the layer thickness of the charge generation layer 63 exceeds 5 μm, the charge transfer inside the charge generation layer 63 becomes a rate-determining step in the process of erasing the charge on the surface of the photosensitive layer 67, and the sensitivity of the photoreceptor 60 may be reduced.

  The charge transport layer 64 provided on the surface of the charge generation layer 63 receives a charge generated by the charge generation material and transports the charge transport material, a binder resin for binding the charge transport material, It contains additives such as known plasticizers and sensitizers as necessary. As the charge transport material, a hole transport material or an electron transport material is used.

  The hole transport materials include poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, condensates and derivatives of pyrene and formaldehyde, polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, oxalate derivatives. Diazole derivatives, imidazole derivatives, 9- (p-diethylaminostyryl) anthracene, 1,1-bis (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazoline, pyrazoline derivatives, phenylhydrazones, hydrazone derivatives, tri Examples thereof include electron donating substances such as phenylamine compounds, triphenylmethane compounds, stilbene compounds, and azine compounds having a 3-methyl-2-benzothiazoline ring. Examples of electron transport materials include fluorenone derivatives, dibenzothiophene derivatives, indenothiophene derivatives, phenanthrenequinone derivatives, indenopyridine derivatives, thioxanthone derivatives, benzo [c] cinnoline derivatives, phenazine oxide derivatives, tetracyanoethylene, tetracyanoquino. Examples include electron accepting substances such as dimethane, promanyl, chloranil, and benzoquinone. One of these charge transport materials may be used alone, or two or more thereof may be used in combination.

The binder resin constituting the charge transport layer 64 may be any resin having compatibility with the charge transport material, such as polycarbonate and copolymer polycarbonate, polyarylate, polyvinyl butyral, polyamide, polyester, epoxy resin, polyurethane, Examples include polyketone, polyvinyl ketone, polystyrene, polyacrylamide, phenol resin, phenoxy resin, polysulfone resin, and copolymer resins thereof. Among these, polystyrene, polycarbonate, copolymer polycarbonate, polyarylate, and polyester are preferably used because they have a volume resistivity of 10 ¹³ Ω or more, excellent insulation properties, and excellent film formability and potential characteristics. It is done. Binder resin may be used individually by 1 type, and 2 or more types may be used together.

  In the charge transport layer 64, the content of the charge transport material is preferably 30% by weight or more and 80% by weight or less. When the content of the charge transport material is less than 30% by weight, the charge transport capability of the charge transport layer 64 is insufficient, and the sensitivity of the photoreceptor 60 may be reduced. If the content of the charge transport material exceeds 80% by weight, the ratio of the binder resin is lowered, and the film formability of the charge transport layer 64 may be lowered.

  The charge transport layer 64 is formed by dissolving or dispersing the above-described charge transport material and binder resin and, if necessary, known additives such as a plasticizer and a sensitizer in an appropriate solvent, thereby forming a charge transport layer forming coating solution. Can be formed by coating the charge generation layer 63. Examples of the solvent for the coating solution for forming the charge transport layer include alcohols such as methanol and ethanol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, ethers such as ethyl ether, tetrahydrofuran, dioxane and dioxolane, chloroform, dichloromethane and dichloroethane. Halogenated aliphatic hydrocarbons, aromatic hydrocarbons such as benzene, chlorobenzene, and toluene can be used. Among these, in consideration of the influence on the global environment and the safety of workers, it is preferable to use a non-halogen, especially non-chlorine organic solvent.

  As a coating method of the coating liquid for forming the charge transport layer, a dip coating method, a roll coating method, an ink jet method, or the like can be used. However, when the ink-jet coating method is used to form the charge transport layer 64 having a layer thickness exceeding 10 μm, the number of times of overcoating of the coating solution becomes very large and the coating time becomes very long. In addition, it is necessary to use a highly volatile solvent in order to ensure the drying property, and there is a concern about clogging of the nozzle due to drying and solidification in the vicinity of the discharge nozzle, leveling failure after application, and the like. Therefore, when the charge transport layer 64 having a layer thickness exceeding 10 μm is formed, it is preferable to use a dip coating method, a roll coating method or the like.

  The layer thickness of the charge transport layer 64 is preferably 10 μm or more and 50 μm or less, more preferably 15 μm or more and 40 μm or less. If the layer thickness of the charge transport layer 64 is less than 10 μm, the charge holding ability of the surface of the photoreceptor 60 may be lowered. If the layer thickness of the charge transport layer 64 exceeds 50 μm, the resolution of the photoreceptor 60 may be lowered.

  As described above, the photoconductive layer 66 including the charge generation layer 63 and the charge transport layer 64 is formed. In the photoreceptor 60 shown in FIG. 2, the charge generation layer 63 and the charge transport layer 64 are laminated on the undercoat layer 62 in this order. However, the present invention is not limited to this, and the charge transport layer 64 and the charge generation layer 63 are arranged in this order. It may be laminated on the pulling layer 62.

  In each layer of the photoconductive layer 66, that is, the charge generation layer 63 and the charge transport layer 64, in order to improve sensitivity and suppress an increase in residual potential and fatigue deterioration during repeated use, One or more sensitizers such as sensitizers may be added. Examples of chemical sensitizers include succinic anhydride, maleic anhydride, phthalic anhydride, acid anhydrides such as 4-chloronaphthalic anhydride, cyano compounds such as tetracyanoethylene and terephthalmalondinitrile, and 4-nitrobenzaldehyde. Such as aldehydes such as anthraquinone, anthraquinones such as 1-nitroanthraquinone, polycyclic or heterocyclic nitro compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitrofluorenone Substances can be used. Examples of the optical sensitizer include dyes such as xanthene dyes, thiazine dyes, triphenylmethane dyes, quinoline pigments, and organic photoconductive compounds such as copper phthalocyanine.

  In addition, a plasticizer may be added to each layer of the photoconductive layer 66 in order to improve moldability, flexibility, mechanical strength, and the like. Examples of the plasticizer include dibasic acid esters, fatty acid esters, phosphate esters, phthalate esters, chlorinated paraffins, and epoxy type plasticizers. In addition, leveling agents such as polysiloxane may be added to prevent itching, and phenolic compounds, hindered amine compounds, hydroquinone compounds, tocopherol compounds, paraphenylenediamines are used to improve durability. , Arylalkanes and their derivatives, amine compounds, organic sulfur compounds, organic phosphorus compounds, and other antioxidants or ultraviolet absorbers may be added. Here, the yuzu skin is a phenomenon in which the surface of each layer has small and gentle irregularities like the surface of the yuzu skin.

  A protective layer 65 is provided on the surface of the photoconductive layer 66 formed as described above. By providing the protective layer 65, the printing durability of the photosensitive layer 67 can be improved, and the durability of the photoreceptor 60 can be improved. Further, it is possible to prevent a chemical adverse effect on the photoconductive layer 66 such as ozone and active gas such as nitrogen oxide generated by corona discharge when charging the surface of the photoreceptor 60.

  The protective layer 65 is formed of a layer containing at least a binder resin. As the binder resin for forming the protective layer 65, it is preferable to use a curable resin such as a thermosetting resin or an ultraviolet curable resin, and it is more preferable to use a thermosetting resin. A well-known thing can be used as a thermosetting resin, Among these, the thermosetting resin obtained by mixing and heating and reacting main resin and a hardening | curing agent is used suitably. Thermosetting resins, particularly thermosetting resins obtained by the reaction between the main resin and the curing agent, are excellent in wear resistance. By using these thermosetting resins, the protective layer 65 having excellent durability is formed. In addition, the printing durability of the photoreceptor 60 can be improved.

  Main resins include urea resin, melamine resin, phenol resin, epoxy resin, unsaturated polyester resin, alkyd resin, polyurethane resin, polyamide resin, polyester resin, polyether resin, acrylic resin, polyvinyl alcohol resin, polyvinyl acetal resin, etc. Examples of the resin that can react with the curing agent. As for main resin, 1 type may be used independently and 2 or more types may be used together. Examples of the curing agent include isocyanate, organic peroxide, amine, acid anhydride and the like. A hardening | curing agent is suitably selected and used according to the kind of main resin. The curing agent is preferably used in a state of being blocked with a blocking agent so that reaction with the main resin does not occur before heating. The blocked curing agent can be mixed with the main resin and heated to dissociate the blocking agent and react with the main resin.

  As the thermosetting resin, a resin obtained by a reaction between a main resin containing at least a polyvinyl acetal resin and a curing agent is particularly preferably used. Examples of the polyvinyl acetal resin include polyvinyl butyral resin. Isocyanate etc. are mentioned as a hardening | curing agent of polyvinyl acetal resin.

  The protective layer 65 preferably contains a filler. By containing the filler in the protective layer 65, the wear resistance of the protective layer 65 can be improved, and the printing durability of the photosensitive layer 67 can be further improved. The average particle diameter of the filler is preferably 0.02 μm or more and 1 μm or less. If the average particle size of the filler is less than 0.02 μm, the effect of improving the wear resistance may not be sufficiently obtained. When the average particle diameter of the filler exceeds 1 μm, the light irradiated to the photoreceptor 60 during exposure is scattered by the filler in the protective layer 65, and the resolution may be lowered.

  As the filler, for example, metal oxide particles such as silica, alumina, titanium oxide, zirconium oxide, tin oxide, and indium oxide are preferably used. Among these, titanium oxide is preferable. One type of filler may be used alone, or two or more types may be mixed and used.

  These fillers are preferably surface-treated. By performing the surface treatment, the dispersibility of the filler can be improved and the wear resistance of the protective layer 65 can be improved. As the filler surface treatment agent, inorganic substances such as silica, alumina and zirconium oxide are preferably used. In particular, titanium oxide surface-treated with silica, alumina, or zirconium oxide is particularly preferably used because it has good dispersibility and can significantly improve the wear resistance when the protective layer 65 is formed.

  The amount of filler used in the protective layer 65 is preferably 10 to 50 parts by weight with respect to 100 parts by weight of the binder resin. If the amount of filler used is less than 10 parts by weight with respect to 100 parts by weight of the binder resin, sufficient wear resistance may not be obtained. On the other hand, when the amount exceeds 50 parts by weight, the volume resistance of the protective layer 65 decreases, and the electrostatic charge on the surface of the protective layer 65 cannot be retained, and image defects such as image flow and image blur may occur. Here, the image flow is a phenomenon in which the toner image is formed so as to be shifted from the position where the image forming surface of the transfer material should be originally formed.

  The protective layer 65 preferably contains a charge transport material. By containing the charge transport material in the protective layer 65, it is possible to suppress an increase in the residual potential during repeated use and the accompanying image defects. As such a charge transport material, the charge transport material used for the charge transport layer 64 mentioned above can be used. When the charge transport material is contained, the binder resin is preferably selected in consideration of compatibility with the charge transport material used for the protective layer 65. Among the thermosetting resins described above, the thermosetting resin formed from the main resin including at least one of thermosetting acrylic resin, melamine resin, and polyvinyl acetal resin is very compatible with the charge transport material. It is preferable because the protective layer 65 having high transparency can be formed.

  In the protective layer 65, the ratio (A / B) of the weight (A) of the charge transport material to the weight (B) of the binder resin is 1/3 (1/3) from the viewpoint of wear resistance and electrical characteristics. The range of 3 (3/1) or less is preferable. If the ratio A / B exceeds 3 (3/1), the ratio of the binder resin is lowered, and the printing durability of the protective layer 65 may not be sufficiently ensured. If the ratio A / B is less than 1/3, the sensitivity of the photoreceptor 60 may be reduced.

  In addition to the filler and the charge transport material, the protective layer 65 may be added with known additives such as a plasticizer, a leveling agent, an antioxidant, and an ultraviolet absorber for the purpose of improving adhesiveness, smoothness, and chemical stability. An agent may be added. Examples of the plasticizer include dibasic acid esters, fatty acid esters, phosphate esters, phthalate esters, chlorinated paraffins, and epoxy type plasticizers. Examples of the leveling agent include silicone oils such as polydimethylsiloxane. Antioxidants or ultraviolet absorbers include phenolic compounds, hindered amine compounds, hydroquinone compounds, tocopherol compounds, paraphenylenediamine, arylalkanes and their derivatives, amine compounds, organic sulfur compounds, and organic phosphorus compounds. Can be mentioned.

  The protective layer 65 can be formed by applying a coating liquid for forming a protective layer, prepared as described later, onto the photoconductive layer 66, heating, drying and curing. The coating liquid for forming the protective layer contains the above-described binder resin and, if necessary, fillers such as metal oxide particles, various additives such as a charge transport material and a plasticizer.

  In this embodiment, the coating liquid for forming the protective layer includes two or more coating liquids, preferably two kinds including a main resin-containing coating liquid containing a main resin and a curing agent-containing coating liquid containing a curing agent. It is divided into the above coating solutions. The two or more kinds of coating liquids thus formed are respectively discharged from the discharge nozzles toward the conductive substrate 61 on which the photoconductive layer 66 is formed using the inkjet coating apparatus 40 shown in FIG. It is ejected in the form of droplets, applied at least on the conductive substrate 61, specifically on the photoconductive layer 66 formed on the conductive substrate 61, so that the coating liquid is mixed, and then dried. Thus, the protective layer 65 is formed.

  In this way, the coating solution for forming the protective layer is applied to at least the main resin-containing coating solution and the curing agent-containing coating solution, so that the main resin and the curing agent are touched until they are applied onto the photoconductive layer 66. Therefore, the reaction between the main resin and the curing agent in the coating solution can be suppressed, gelation of the coating solution, sedimentation and aggregation of components can be prevented, and storage stability can be improved. Therefore, the uniform protective layer 65 can be stably formed. Moreover, the loss of coating liquid can be suppressed and manufacturing cost can be reduced.

  Since the photoreceptor 60 according to this embodiment includes the uniform protective layer 65 formed as described above as the outermost layer, it is possible to form a high-quality image. In this embodiment, even when a thermosetting resin is used as the binder resin, the uniform protective layer 65 can be formed, so that an image with good image quality can be formed and It is possible to realize a photoreceptor 60 that is excellent in printability.

  It is preferable that the coating liquid applied by the inkjet coating method like the coating liquid for forming a protective layer according to this embodiment contains a high boiling point solvent having a boiling point of 120 ° C. or higher and 260 ° C. or lower. Accordingly, drying of the coating liquid at the discharge nozzle portion can be suppressed, so that the discharge stability of the coating liquid can be improved and clogging of the discharge nozzle can be prevented. Moreover, since the drying of the solvent during storage can be suppressed and the sedimentation and aggregation of components in the coating solution due to the decrease in the amount of the solvent can be suppressed, the storage stability of the coating solution can be improved. Moreover, since the leveling property after application | coating can be improved, the protective layer 65 which has uniform thickness can be formed.

  If only a solvent having a boiling point of less than 120 ° C. is used as the solvent for the coating solution, the coating solution is likely to dry, and the discharge nozzle may be clogged. Further, the solvent is volatilized and reduced, and there is a possibility that the components in the coating solution may settle and aggregate. Moreover, the leveling property after application | coating becomes inadequate, and the layer thickness of the protective layer 65 may become non-uniform | heterogenous. On the other hand, if a solvent having a boiling point exceeding 260 ° C. is contained in the coating solution, the discharge stability and the storage stability are good, but the coating solution is difficult to dry, and the coating film hangs down in the weight direction and formed protection. The surface of the layer 65 may become non-uniform. If an image is formed using such a photoreceptor having a non-uniform protective layer 65 formed as the outermost layer, image defects such as blurring and blurring occur, and the reproducibility of the image deteriorates.

  The content of the high boiling point solvent in the coating solution is preferably 5% by weight or more and 40% by weight or less of the total amount of the coating solution. If the content of the high-boiling solvent is less than 5% by weight, the effect of containing the high-boiling solvent is not sufficiently exerted, so that the discharge stability cannot be sufficiently secured and the discharge nozzle may be clogged. . Moreover, leveling property may fall and the surface of the protective layer 65 may become non-uniform | heterogenous. On the other hand, when the content of the high-boiling solvent exceeds 40% by weight, the ejection stability and the storage stability are good, but the coating film is difficult to dry and drips in the direction of gravity, and the surface of the protective layer 65 is uneven. There is a possibility.

  Among the high-boiling solvents, those having a boiling point of 130 ° C. or higher and 250 ° C. or lower are particularly preferable. Specific examples of the high-boiling solvent include known ones, among which cyclohexanone (boiling point 155 ° C.), 2-pyrrolidone (boiling point 245 ° C.), N-methyl-2-pyrrolidone (boiling point 200 ° C.), p- Xylene (boiling point 138 ° C.) is preferred. One high boiling point solvent may be used alone, or two or more high boiling point solvents may be used in combination. In addition, the coating liquid apply | coated by inkjet methods, such as a coating liquid for protective layer formation, may contain solvents other than a high boiling point solvent within the range which does not impair the preferable effect of this invention.

  The thickness of the protective layer 65 is preferably 1 μm or more and 10 μm or less, and more preferably 3 μm or more and 5 μm or less. If the thickness of the protective layer 65 is less than 1 μm, there is a possibility that all of the protective layer 65 may disappear due to wear before the lifetime of the photoconductor 60, that is, before the photoconductor 60 becomes unusable due to a decrease in sensitivity due to repeated use. is there. Further, when an external force from a contact member such as a charging roller is received in the image forming apparatus, the protective layer 65 may be peeled off from the interface with the lower photoconductive layer 66 due to the external force. When the thickness of the protective layer 65 exceeds 10 μm, there is a possibility that the sensitivity decreases and the residual potential increases due to repeated use. In addition, the charges transported toward the surface of the photoreceptor 60 may be diffused in the process of moving in the protective layer 65, and the resolution may be lowered.

  Thus, since the protective layer 65 has a small thickness of 1 μm or more and 10 μm or less, the protective layer 65 can be formed with a small number of times of overcoating even when an inkjet coating method is used. Therefore, it is suitable for formation by an ink jet coating method. In addition, when the film thickness is as small as 1 μm or more and 10 μm or less as described above, even if a high boiling point solvent is used as the solvent of the coating solution as described above, it can be dried in a relatively short time, thus reducing productivity. Without using the high boiling point solvent, it is possible to prevent clogging of the discharge nozzle and leveling failure due to drying and solidification of the coating liquid.

  Each layer constituting the photosensitive layer 67, that is, the undercoat layer 62, the charge generation layer 63, the charge transport layer 64 and the protective layer 65 is naturally applied after being sequentially applied and formed by the above-described method or every time each layer is applied and formed. Drying or drying is performed using a dryer using hot air, far infrared rays, or the like as a heat source. The drying temperature and the drying time are not particularly limited and can be appropriately selected according to various conditions such as the solvent used in the coating solution and the thickness of each layer. Preferably, the temperature is 40 to 130 ° C. for 10 minutes to 2 hours. Degree.

  FIG. 3 is a partial cross-sectional view showing a simplified configuration of an electrophotographic photosensitive member 70 that is another example of the electrophotographic photosensitive member manufactured by the method of manufacturing an electrophotographic photosensitive member according to this embodiment. The photoconductor 70 shown in FIG. 3 is similar to the photoconductor 60 shown in FIG. 2, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. It should be noted in the electrophotographic photoreceptor 70 that the photoconductive layer 71 has a single layer structure composed of a single layer. That is, the photoconductor 70 is a single layer type photoconductor.

  The single-layer type photoreceptor 70 shown in FIG. 3 is suitable as a photoreceptor for a positively charged image forming apparatus that generates less ozone, and has only one photoconductive layer 71 to be applied. The yield is superior to the multilayer photoreceptor 60 shown in FIG. In the single layer type photoreceptor 70 shown in FIG. 3, the photosensitive layer 72 includes an undercoat layer 62, a single layer type photoconductive layer 71, and a protective layer 65.

  As the single-layer photoconductive layer 72, a material in which a charge generating substance is dispersed in a binder resin is used. As the charge generation material, the same material as the charge generation material used for the charge generation layer 63 shown in FIG. 2 can be used. These charge generating materials are preferably used in the form of particles. As the binder resin, the binder resin used for the charge generation layer 63 shown in FIG. 2 can be used.

  The content of the charge generating material in the photoconductive layer 72 is preferably 0.5 wt% or more and 50 wt% or less, more preferably 1 wt% or more and 20 wt% or less. If the content of the charge generation material is less than 0.5% by weight, the sensitivity of the photoreceptor 70 may not be sufficiently obtained. When the content of the charge generation material exceeds 50% by weight, the dispersibility of the charge generation material in the photoconductive layer 71 is reduced and coarse particles are increased, and the surface charge other than the portion to be erased is reduced by exposure. There is a risk of fogging of images such as black spots.

  The photoconductive layer 72 preferably contains a charge transport material together with the charge generation material. By including the charge transport material, the responsiveness of the photoreceptor 70 can be improved, and the increase in the residual potential during repeated use and the accompanying image defects can be prevented.

  In addition, the photoconductive layer 72 includes a plasticizer for improving film formability, flexibility, mechanical strength, an antioxidant or an ultraviolet absorber for suppressing an increase in residual potential, and improved dispersion stability. A known additive such as a dispersion aid for the coating, a leveling agent for improving the coating property, and a surfactant may be added.

  The single-layer photoconductive layer 72 has the same amount of the above-described charge generation material and binder resin, and if necessary, the appropriate amount of the charge transport material and various additives in the same manner as in the above-described charge generation layer forming coating solution. A photoconductive layer-forming coating solution can be prepared by dissolving or dispersing in a suitable solvent, and this photoconductive layer-forming coating solution can be applied to the surface of the undercoat layer 62.

  As a coating method of the photoconductive layer forming coating solution, a dip coating method, a roll coating method, an ink jet coating method, or the like can be used. However, when the photoconductive layer 72 having a layer thickness exceeding 10 μm is formed, if the ink jet method is used, the number of overcoating times becomes very large and the productivity is deteriorated. Therefore, a dip coating method, a roll coating method, or the like is used. Is preferred.

  The layer thickness of the photoconductive layer 72 is preferably 5 μm or more and 50 μm or less, and more preferably 10 μm or more and 40 μm or less. If the layer thickness of the photoconductive layer 72 is less than 5 μm, the charge holding ability of the surface of the photoreceptor 70 may be lowered. If the layer thickness of the photoconductive layer 72 exceeds 50 μm, the resolution of the photoreceptor 70 may be lowered.

  FIG. 4 is a side view showing a simplified configuration of an image forming apparatus 80 according to another embodiment of the present invention. The image forming apparatus 80 includes an electrophotographic photoreceptor 81 manufactured by the electrophotographic photoreceptor manufacturing method of the present invention. The electrophotographic photoreceptor 81 is manufactured, for example, in the same manner as the multilayer photoreceptor 60 shown in FIG. 2 or the single-layer photoreceptor 70 shown in FIG. An image forming apparatus 80 exemplified as the present embodiment is a laser printer 80 including a semiconductor laser element as a light source of an exposure unit.

  The laser printer 80 includes the above-described photoreceptor 81, charger 82, exposure means 82, developing device 84, transfer paper cassette 90, paper feed roller 91, registration roller 92, transfer charger 93, separation charger 94, and conveyance belt 95. The image forming apparatus includes a fixing device 96, a paper discharge tray 97, and a cleaner 98. The exposure unit 83 includes a semiconductor laser element 84, a rotary polygon mirror 85, an imaging lens 86 and a mirror 87. The cleaner 98 is provided together with a static elimination lamp (not shown).

  The photoconductor 81 has a cylindrical shape, for example, and is mounted on the laser printer 80 so as to be rotatable around the axis in the direction of the arrow 99 by a driving unit (not shown). The photoconductor 81 may be cylindrical. The semiconductor laser element 84 emits a laser beam 85 toward the rotary polygonal mirror 86 in accordance with an instruction from a control unit (not shown). The laser beam 85 emitted from the semiconductor laser element 84 is repeatedly scanned by the rotary polygon mirror 86 in the longitudinal direction of the photoconductor 81 that is the main scanning direction with respect to the surface of the photoconductor 81. The imaging lens 87 has f-θ characteristics, and the laser beam 85 is reflected by the mirror 88 to form an image on the surface of the photoconductor 81 to expose the surface of the photoconductor 81. The surface of the photoconductor 81 is exposed in accordance with image information by rotating the photoconductor 81 and forming an image by scanning the laser beam 85 as described above.

  The charger 82 is provided upstream of the image forming point of the laser beam 85 in the rotation direction of the photoconductor 81, and uniformly charges the surface of the photoconductor 81. By exposing the surface of the charged photoconductor 81 by the exposure means 83 as described above, an electrostatic latent image corresponding to the image information is formed on the surface of the photoconductor 81. As the charger 82, for example, a corona charger is used. The charger 82 is not limited to this, and may be a corotron charger, a scorotron charger, a sawtooth charger, a roller charger, or the like. The developing device 89 is provided on the downstream side of the image forming point of the laser beam 85 in the rotation direction of the photoconductor 81, and supplies toner to the surface of the photoconductor 81 on which the electrostatic latent image is formed. Is developed as a toner image. As the developing unit 89, for example, a contact-type developing unit is used. The developing device 89 is not limited to this, and may be a non-contact type developing unit, or may be a combination of a contact type developing unit and a non-contact type developing unit.

  The transfer paper accommodated in the transfer paper cassette 90 is taken out one by one by the paper feed roller 91, and in synchronization with the exposure of the photoconductor 81 by the registration roller 92, the rotation direction of the photoconductor 81 is further increased than the developing unit 89. A transfer charger 93 provided on the downstream side is provided. The transfer charger 93 transfers the toner image to the transfer paper by applying a charge having a polarity opposite to that of the toner image. The transfer charger 93 is a non-contact type transfer unit in the present embodiment, and is realized by, for example, a corona charger. The transfer charger 93 is not limited to this, and may be a contact-type transfer unit. As the contact type transfer means, for example, a transfer roller is provided, and a toner image is transferred to the transfer paper by applying a voltage to the transfer roller while the transfer roller is pressed against the photosensitive member 81 via the transfer paper. Can be used. The separation charger 94 is further provided downstream of the transfer charger 95 in the rotation direction of the photoconductor 81 and in the vicinity of the transfer charger 95. The separation charger 94 discharges the transfer paper onto which the toner image has been transferred from the photoconductor 81. To separate.

  The transfer paper separated from the photosensitive member 81 is fed to the conveyance belt 95 and conveyed to the fixing device 44 by the conveyance belt 95. The fixing device 44 fixes the toner image on the transfer paper by heating or heating and pressurizing the transfer paper on which the toner image is transferred. The cleaner 98 is provided further on the downstream side in the rotation direction of the photoconductor 81 than the separation charger 94 and on the upstream side in the rotation direction of the photoconductor 81 relative to the charger 82, and removes toner remaining on the surface of the photoconductor 81 after the transfer. to clean up. The cleaner 98 is realized by, for example, a blade cleaner that includes a blade as a cleaning member that contacts the photoreceptor surface 81 and cleans the photoreceptor surface 81. The cleaner 98 is not limited to this, and may be a brush cleaner including a brush as a cleaning member. A neutralizing lamp (not shown) provided together with the cleaner 98 neutralizes the surface of the photoreceptor 81 after cleaning, and the electrostatic latent image disappears.

  In the laser printer 80 shown in FIG. 4, an image is formed as follows. First, in accordance with an instruction from a control unit (not shown), the photoconductor 81 is rotationally driven in the direction of the arrow 99 by the driving means, and the surface of the photoconductor 81 is charged by the charger 82. Next, in accordance with an instruction from the control unit, the photoconductor 81 is exposed by the exposure unit 83, and an electrostatic latent image is formed on the surface of the photoconductor 81. In synchronization with the exposure of the photosensitive member 81, the transfer paper is supplied to the transfer position between the transfer transfer unit 93 and the photosensitive member 81 by the registration roller 92.

  Next, the electrostatic latent image is developed by the developing device 89 and a toner image is formed on the surface of the photoreceptor 81. The formed toner image is transferred onto a transfer sheet by a transfer charger 93. The transfer paper onto which the toner image has been transferred is conveyed to a fixing device 96 by a conveying belt 95, and is heated and pressurized. As a result, the toner image is fixed on the transfer paper to form an image. The transfer paper on which the image is formed in this manner is discharged to the paper discharge tray 97. On the other hand, after the toner image is transferred to the transfer paper, the surface of the photoconductor 81 rotating further in the direction of the arrow 99 is cleaned by the cleaner 98 and further unloaded by the charge eliminating lamp. As a result, the electrostatic latent image on the surface of the photoreceptor 81 disappears. Thereafter, the photoconductor 81 is further rotated and a series of operations starting from charging of the photoconductor 81 is repeated. As described above, images are continuously formed.

  As described above, the photoconductor 81 provided in the laser printer 80 which is the image forming apparatus of the present embodiment is produced by the method for producing an electrophotographic photoconductor of the present invention. Therefore, at least of the layers constituting the photoconductive layer. One layer, specifically the outermost protective layer, has uniform properties and thickness. Therefore, according to the laser printer 80, it is possible to stably form an image with excellent image quality without blurring or fogging.

  The image forming apparatus according to the present invention is not limited to the configuration of the laser printer 80 shown in FIG. 4 described above, and other different configurations as long as the photoconductor according to the present invention can be used. It may be.

  For example, when a photoconductor 81 having a small outer diameter of 40 mm or less is used, the separation charger 94 may not be provided. Further, by devising the timing of applying a high voltage such as a developing bias voltage to the photoconductor 81, a configuration in which no static elimination lamp is provided can be used. In particular, in the case of an image forming apparatus using a small diameter outer diameter of 40 mm or less as the photosensitive member 81, a low-speed low-end printer, etc. It is preferable that the lamp is not provided.

  In addition, the photosensitive member 81 may be integrated with at least one of the charger 82, the developing unit 89, and the cleaner 98 to be a process cartridge that can be attached to and detached from the laser printer 80. For example, a process cartridge incorporating all of the photosensitive member 81, the charger 82, the developing device 89, and the cleaner 98, a process cartridge incorporating the photosensitive member 81, the charger 82, and the developing device 89, the photosensitive member 81, and the cleaner 98. Can be constructed, a process cartridge incorporating the photosensitive member 81 and the developing device 89, and the like. When the process cartridge integrally formed in this way is used, it is not necessary to individually mount or remove each member such as the photosensitive member 81 with respect to the laser printer 80. Therefore, the photosensitive member in the image forming apparatus such as the laser printer 80 can be used. Replacement of members such as the body 81 is facilitated.

  EXAMPLES Hereinafter, although a manufacture example, an Example, and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited to the following description content.

Example 1
4 parts by weight of titanium oxide (TiO ₂ , trade name: STR-60N, manufactured by Sakai Chemical Co., Ltd.) and 6 parts by weight of copolymer nylon resin (trade name: CM8000, manufactured by Toray Industries, Inc.) as a binder resin, 35 weights of methanol The resulting mixture was dispersed for 8 hours with a paint shaker to prepare an undercoat layer coating solution. This coating solution was applied to the surface of the conductive substrate by a dip coating method and naturally dried to form an undercoat layer having a thickness of about 1.0 μm. As the conductive substrate, an aluminum non-cutting cylindrical tube formed by an Expand Draw (abbreviation ED) method having a diameter of 30 mm and a length in the longitudinal direction of 360 mm was used.

  Next, after adding 1 part by weight of titanyl phthalocyanine pigment and 1 part by weight of polyvinyl butyral resin (trade name: # 6000-C, manufactured by Denki Kagaku Kogyo Co., Ltd.) to a mixed solvent of 83 parts by weight of tetrahydrofuran and 15 parts by weight of cyclohexanone. The obtained mixed solution was dispersed with a paint shaker for 12 hours to prepare a charge generation layer coating solution. This coating solution was applied onto the surface of the previously formed undercoat layer by a dip coating method and naturally dried to form a charge generation layer having a thickness of about 0.2 μm.

  Subsequently, 10 parts by weight of 4-dibenzylamino-2-methylbenzaldehyde-1,1-diphenylhydrazone, which is a hydrazone-based charge transport material, is used as a charge transport material, a polycarbonate resin of bisphenol Z type (trade name: Z-400, Mitsubishi 14 parts by weight of Gas Chemical Co., Ltd.) and 0.02 parts by weight of a silicone-based leveling agent (trade name: KF-96, manufactured by Shin-Etsu Chemical Co., Ltd.) are added to 76 parts by weight of tetrahydrofuran and mixed to form a charge. A transport layer coating solution was prepared. The obtained coating solution is applied to the surface of the charge generation layer formed earlier by dip coating and naturally dried, and further heated and dried at 120 ° C. for 1 hour to obtain a charge having a thickness of about 25 μm. A transport layer was formed. As described above, a photoconductive layer formed by laminating the charge generation layer and the charge transport layer was formed.

  Next, protective layer-forming coating solutions A1 and B1 were prepared as protective layer-forming coating solutions according to this example as follows.

[Protective layer forming coating solution A1]
Curing agent (blocked isocyanate, trade name: Sumidur 3175, manufactured by Sumitomo Bayern Urethane Co., Ltd.) 10 parts by mass, polydimethylsiloxane-silicone oil (trade name: KF-96, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.06 parts by weight Then, 80 parts by weight of tetrahydrofuran (boiling point: 66 ° C.) and 10 parts by weight of cyclohexanone (boiling point: 155 ° C.) were mixed and dissolved to prepare a coating liquid A1 for forming a protective layer.

[Protective layer forming coating solution B1]
Polyvinyl butyral resin (trade name: BM-1, manufactured by Sekisui Chemical Co., Ltd.) 10 parts by mass, polydimethylsiloxane-silicone oil (trade name: KF-96, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.06 parts by weight, tetrahydrofuran 80 parts by weight (boiling point: 66 ° C.) and 10 parts by weight of cyclohexanone (boiling point: 155 ° C.) were mixed and dissolved to prepare a coating liquid B1 for forming a protective layer.

  Subsequently, the prepared coating liquids A1 and B1 for forming a protective layer were filled in coating liquid storage tanks of a remodeling machine of a commercially available inkjet printing apparatus (product name: AR-2000, manufactured by Sharp Corporation). The discharge method of the discharge nozzle provided in the inkjet printing apparatus AR-2000 is a piezo method. A protective layer is formed from each discharge nozzle of the modified machine on the surface of the charge transport layer while rotating the conductive substrate on which the charge transport layer is formed as described above at a rotation speed of 60 revolutions per minute (60 rpm). The coating liquids A1 and B1 were applied in the form of droplets so that the volume of one drop (dot) was 30 pL. Then, it heated and dried at 130 degreeC for 1 hour, and formed the protective layer about 3 micrometers in thickness. An electrophotographic photosensitive member was produced as described above.

(Example 2)
In preparing the protective layer-forming coating solutions A1 and B1, protective layer-forming coating solutions A2 and B2 were prepared using 2-pyrrolidone (boiling point: 245 ° C.) instead of cyclohexanone, respectively. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that was formed.

(Example 3)
In the preparation of the protective layer forming coating solutions A1 and B1, protective layer forming coating solutions A3 and B3 were prepared using N-methyl-2-pyrrolidone (boiling point: 200 ° C.) instead of cyclohexanone, respectively. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the protective layer was formed using the same.

(Example 4)
In preparing the protective layer forming coating solutions A1 and B1, protective layer forming coating solutions A4 and B4 were prepared using p-xylene (boiling point: 138.4 ° C.) instead of cyclohexanone, respectively. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that a protective layer was formed.

(Example 5)
In preparing the protective layer forming coating solutions A1 and B1, the amount of tetrahydrofuran used was changed to 70 parts by weight, the amount of cyclohexanone used was changed to 20 parts by weight, and the protective layer forming coating solutions A5 and B5 were used. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the protective layer was formed using these.

(Example 6)
In preparing the protective layer forming coating solutions A1 and B1, the amount of tetrahydrofuran used was changed to 60 parts by weight, the amount of cyclohexanone used was changed to 30 parts by weight, and the protective layer forming coating solutions A6 and B6 were used. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the protective layer was formed using these.

(Example 7)
In preparing the protective layer forming coating solutions A1 and B1, the amount of tetrahydrofuran used was changed to 50 parts by weight, the amount of cyclohexanone used was changed to 40 parts by weight, and the protective layer forming coating solutions A7 and B7 were used. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the protective layer was formed using these.

(Example 8)
In the formation of the protective layer, an electrophotographic process was carried out in the same manner as in Example 1, except that the protective layer forming coating solutions C and D prepared as follows were used instead of the protective layer forming coating solutions A1 and B1. A photoconductor was prepared.

[Coating liquid C for forming protective layer]
4-dibenzylamino-2-methylbenzaldehyde-1,1-diphenylhydrazone 1 part by weight, curing agent (blocked isocyanate, trade name: Sumidur 3175, manufactured by Sumitomo Bayern Urethane) 9 parts by weight, polydimethylsiloxane-silicone 0.06 part by weight of oil (trade name: KF-96, manufactured by Shin-Etsu Chemical Co., Ltd.), 80 parts by weight of tetrahydrofuran and 10 parts by weight of cyclohexanone were mixed and dissolved to prepare a coating solution C for forming a protective layer.

[Protective layer forming coating solution D]
4-dibenzylamino-2-methylbenzaldehyde-1,1-diphenylhydrazone 1 part by weight, polyvinyl butyral resin (trade name: BM-1, manufactured by Sekisui Chemical Co., Ltd.) 9 parts by weight, polydimethylsiloxane-silicone oil ( (Product name: KF-96, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.06 parts by weight, 80 parts by weight of tetrahydrofuran and 10 parts by weight of cyclohexanone were mixed and dissolved to prepare a coating solution D for forming a protective layer.

(Comparative Example 1)
In the formation of the protective layer, an electrophotographic photosensitive film was prepared in the same manner as in Example 1 except that only the protective layer forming coating solution E prepared as follows was used instead of the protective layer forming coating solutions A1 and B1. The body was made.

[Coating liquid E for protective layer]
Curing agent (blocked isocyanate, trade name: Sumidur 3175, manufactured by Sumitomo Bayern Urethane Co., Ltd.) 5 parts by mass, polyvinyl butyral resin (trade name: BM-1, manufactured by Sekisui Chemical Co., Ltd.) 5 parts by weight, polydimethylsiloxane Silicone oil (trade name: KF-96, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.06 parts by weight, 80 parts by weight of tetrahydrofuran and 10 parts by weight of cyclohexanone were mixed and dissolved to prepare coating solution E for protective layer.

(Comparative Example 2)
In preparing the protective layer forming coating solutions A1 and B1, respectively, the protective layer forming coating solutions A8 and B8 were prepared by changing the amount of tetrahydrofuran used to 90 parts by weight without using cyclohexanone. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that a protective layer was formed.

(Comparative Example 3)
In preparing the protective layer-forming coating solutions A1 and B1, protective layer-forming coating solutions A9 and B9 were prepared using tripropylene glycol (boiling point: 271 ° C.) instead of cyclohexanone, respectively, and the protective layer was used. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that was formed.

(Comparative Example 4)
In preparing the protective layer forming coating solutions A1 and B1, the amount of tetrahydrofuran used was changed to 95 parts by weight, the amount of cyclohexanone used was changed to 5 parts by weight, and the protective layer forming coating solutions A10 and B10 were used. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the protective layer was formed using these.

(Comparative Example 5)
In preparing the protective layer forming coating liquids A1 and B1, the amount of tetrahydrofuran used was changed to 45 parts by weight, the amount of cyclohexanone used was changed to 45 parts by weight, and the protective layer forming coating liquids A11 and B11 were used. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the protective layer was formed using these.

(Comparative Example 6)
In the same manner as in Example 1, an undercoat layer, a charge generation layer, and a charge transport layer were formed, and protective layer forming coating solutions A1 and B1 were prepared.

  Next, using the modified machine of the above-described inkjet printing apparatus AR-2000, the discharge amount per dot is 30 pL with respect to the surface of the charge transport layer of the conductive substrate rotating at 60 revolutions per minute (60 rpm). The coating liquid A1 for forming the protective layer was discharged and applied so that it was naturally dried at room temperature for 30 minutes. Thereafter, the protective layer forming coating solution B1 is discharged and applied to the surface of the charge transport layer coated with the protective layer forming coating solution A1 and dried in the same manner as the protective layer coating solution A1, and the temperature is 130 ° C. And dried for 1 hour to form a protective layer having a thickness of about 3 μm. An electrophotographic photosensitive member was produced as described above.

  For Examples 1 to 8 and Comparative Examples 1 to 6 described above, (a) ejection stability of the protective layer forming coating solution, (b) storage stability of the protective layer forming coating solution, (c) The appearance of the protective layer and (d) the durability of the electrophotographic photosensitive member were evaluated.

(A) Discharge stability of the coating liquid for forming the protective layer In Examples 1 to 8 and Comparative Examples 1 to 6, the inkjet printing apparatus used for coating the coating liquid for forming the protective layer after the production of the electrophotographic photosensitive member The nozzle was visually observed to determine whether or not the discharge nozzle was clogged, and the discharge stability was evaluated based on the following criteria.
○: Good. The discharge nozzle is not clogged.
X: Practical difficulty. The discharge nozzle is clogged.

(B) Storage stability of protective layer-forming coating solution The protective layer-forming coating solutions used in Examples 1 to 8 and Comparative Examples 1 to 6 were respectively packed in sample bottles, and the sample bottles were kept at a temperature of 50 ° C. After standing for 1 week, it was visually observed to determine whether sedimentation, aggregation or gelation occurred. In addition, about the thing which sedimentation generate | occur | produced, each coating liquid was shaken and it was judged whether it could re-disperse easily. From these results, storage stability was evaluated based on the following criteria.
○: Good. No sedimentation, aggregation or gelation.
Δ: Practical. Although sedimentation occurs, it can be easily redispersed and does not aggregate and gel.
X: Practical difficulty. Sedimentation, aggregation or gelation occurs and does not redisperse upon shaking.

  However, for Examples 1 to 7 and Comparative Examples 1 to 6 using the two types of protective layer forming coating liquids, the evaluation results of the protective layer forming coating liquids with lower evaluations are shown in the examples or comparative examples. It was set as the evaluation result of the storage stability of the coating liquid for protective layer formation in.

(C) Appearance of protective layer In Examples 1 to 8 and Comparative Examples 1 to 6, the protective layers of the produced electrophotographic photoreceptors were visually observed, and the appearance was evaluated based on the following criteria.
○: Good. The surface of the protective layer is uniform.
X: Practical difficulty. The surface of the protective layer is uneven.

(D) Image reproducibility The produced electrophotographic photosensitive member is mounted on a commercially available full-color copying machine (product name: AR-C260, manufactured by Sharp Corporation), and is at room temperature and normal humidity with a temperature of 25 ° C. and a relative humidity of 50%. Below, a continuous copying test was performed in which a predetermined test image was continuously formed on 10,000 recording sheets. Each image formed in the continuous copying test was visually observed to determine whether image defects such as blurring and blurring occurred, and the image reproducibility of the electrophotographic photosensitive member was evaluated based on the following criteria.
○: Good. Through a continuous copying test of 10,000 sheets, a clear image free from image defects such as blurring and blurring can be obtained.
X: Practical difficulty. Before the number of copies reaches 10,000, image defects such as blurring and blurring occur in the formed image.

  The above evaluation results are shown in Table 1. In addition, content shown in Table 1 is content of the solvent whose boiling point in each coating liquid for protective layer formation is 120 degreeC or more. Moreover, the boiling point shown in Table 1 is a boiling point of a solvent with a higher boiling point among the solvents contained in each coating liquid for protective layer formation. Also, items that were not evaluated are described as “-”.

  From Table 1, the coating liquid for forming the protective layer was applied separately into two types of coating liquids, specifically, a curing agent-containing coating liquid containing a curing agent and a main resin-containing coating liquid containing a main resin. In Examples 1-8, it turns out that the discharge stability and storage stability of the coating liquid for protective layer formation are favorable, and it can form stably the protective layer which has a uniform surface. In addition, it can be seen that the electrophotographic photoreceptors formed in Examples 1 to 8 are excellent in image reproducibility and can stably form images having no image defects over a long period of time.

  On the other hand, in Comparative Example 1 in which the protective layer forming coating solution E containing the main resin and the curing agent was used as the protective layer forming coating solution, the storage stability of the protective layer forming coating solution E was poor, and photosensitivity. Although the protective layer having a uniform film quality could be formed at the beginning of the production of the body, the gelation of the coating liquid E for forming the protective layer gradually progressed while producing a large number of photoreceptors over a long period of time. Only a protective layer having a non-uniform film quality can be formed. For this reason, the entire amount of the protective layer forming coating solution E prepared for the production of the photoreceptor cannot be used up, resulting in an increase in cost. The evaluation of image reproducibility was performed only for the electrophotographic photosensitive member on which a protective layer having a uniform film quality was formed, and not on the electrophotographic photosensitive member having a protective layer having a non-uniform film quality.

  Further, in Comparative Example 2 using the protective layer forming coating solutions A8 and B8 that do not contain a high boiling point solvent as the protective layer forming coating solution, although the storage stability of the protective layer forming coating solution was good, The discharge stability of the coating liquid for forming the protective layer was poor, and the discharge nozzle was clogged. Further, coating failure occurred when forming the protective layer, and it was impossible to form a protective layer having a uniform film quality even in the first electrophotographic photosensitive member. This is considered to be because the coating liquids A8 and B8 for forming the protective layer contain only a low-boiling solvent having a boiling point of less than 120 ° C. as a solvent and no high-boiling solvent. In Comparative Example 2, since a uniform protective layer could not be formed, the image reproducibility was not evaluated.

  Further, in Comparative Example 3 using the protective layer forming coating solutions A9 and B9 containing a solvent having a boiling point higher than 260 ° C., the protective layer forming coating solution had good storage stability. When the coating solution is applied, the protective layer does not sufficiently dry naturally, and a part of the surface of the lower charge transport layer elutes and droops in the direction of gravity, so-called dripping occurs, resulting in the desired electrophotography. The photoconductor could not be manufactured. For this reason, image reproducibility was not evaluated.

  Further, in Comparative Example 4 using the protective layer-forming medical coating solutions A10 and B10 in which the content of the high-boiling solvent is less than 5% by weight, the storage stability of the protective layer-forming coating solution is good, and the high boiling point is high. Although the discharge stability of the protective layer-forming coating liquid was improved as compared with Comparative Example 2 using the protective layer-forming coating liquids A8 and B8 that did not contain a solvent, it was still inadequate and the production of an electrophotographic photosensitive member was not sufficient. Over time, the surface of the protective layer became non-uniform. This is presumably because the coating film is too easy to dry because the content of the high boiling point solvent is less than 5% by weight. In addition, the electrophotographic photosensitive member produced in Comparative Example 4 had low image reproducibility, and the formed image had image defects.

  Conversely, in Comparative Example 5 using the protective layer forming coating liquids A11 and B11 in which the content of the high-boiling solvent exceeds 40% by weight, although the ejection stability and the storage stability were good, the surface of the protective layer Became non-uniform. This is because the coating liquids A11 and B11 for forming the protective layer contain a large amount of high-boiling solvent exceeding 40% by weight, so that the coating film applied to the surface of the charge transport layer is difficult to dry and droops. It is guessed that. In addition, the electrophotographic photosensitive member produced in Comparative Example 5 had low image reproducibility, and the formed image had image defects.

  In the electrophotographic photosensitive member produced in Comparative Example 6, the image quality deteriorated before reaching the target number of copies in the continuous copying test. In Comparative Example 6, since the protective layer was formed by applying and drying the protective layer forming coating solution A1, and then drying the protective layer forming coating solution B1, the protective layer forming coating was performed. It is thought that the curing agent in the liquid A1 and the main resin in the coating liquid B1 for forming the protective layer were not sufficiently mixed, the curing reaction was insufficient, and the printing durability of the protective layer was insufficient. It is done.

It is a systematic diagram which simplifies and shows the structure of the inkjet coating apparatus 40 used suitably for the manufacturing method of the electrophotographic photoreceptor of this embodiment. It is a fragmentary sectional view which simplifies and shows the structure of the electrophotographic photosensitive member 60 which is an example of the electrophotographic photosensitive member produced by the manufacturing method of the electrophotographic photosensitive member of this embodiment. It is a fragmentary sectional view which simplifies and shows the structure of the electrophotographic photosensitive member 70 which is another example of the electrophotographic photosensitive member produced by the manufacturing method of the electrophotographic photosensitive member of this embodiment. It is a side view which simplifies and shows the structure of the image forming apparatus 80 which is other embodiment of this invention. It is a systematic diagram which shows an example of a structure of the dip coating apparatus used for the dip coating method. It is a systematic diagram which shows an example of a structure of the spray coating apparatus used for the spray coating method. It is a systematic diagram which shows an example of a structure of the inkjet coating apparatus used for the inkjet method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 40 Inkjet coating device 41 Ink head 42 Guide rail part 43 Coating liquid supply part 44 Filter 45 Pump 46 Conveying tube 47 Substrate support means 49 1st discharge nozzle 50 2nd discharge nozzle 51 1st coating liquid 51a 1st droplet 52 2nd Coating liquid 52a Second droplet 53 First storage tank 54 Second storage tank 60, 70, 81 Electrophotographic photosensitive member 61 Conductive substrate

Claims (6)

A method for producing an electrophotographic photosensitive member in which a photosensitive layer including a photoconductive layer and a protective layer that are sequentially laminated on a conductive substrate is laminated,
The step of forming the protective layer includes
Two or more kinds of coating liquids including a main resin-containing coating liquid containing a main resin and a curing agent-containing coating liquid containing a curing agent are each ejected in droplet form from an ejection nozzle toward the conductive substrate by an inkjet method . A coating step of coating so that the coating liquids are in a mixed state at least on the conductive substrate;
Look including a drying step of the two or more coating liquid drying the applied conductive substrate,
Each of the two or more coating liquids contains a high boiling point solvent having a boiling point of 120 ° C. or higher and 260 ° C. or lower in an amount of 5% by weight to 40% by weight of the total amount of the coating liquid,
The protective layer is formed by a layer containing a thermosetting resin obtained by a reaction between the main resin and the curing agent . 2. The method for producing an electrophotographic photosensitive member according to claim 1, wherein the volume of one droplet of the coating liquid ejected from the ejection nozzle is 30 pL . 3. The electrophotographic photosensitive member according to claim 1, wherein the high boiling point solvent is one or more selected from cyclohexanone, 2-pyrrolidone, N-methyl-2-pyrrolidone and p-xylene. Manufacturing method. Protective layer, the manufacturing method of the electrophotographic photosensitive member according to any one of claims 1-3, characterized in that the layer thickness is formed so as to 1μm or 10μm or less. In the application step,
The method for producing an electrophotographic photosensitive member according to any one of claims 1-4, characterized in that ejected from the ejection nozzle by vibration of the piezoelectric element of the coating liquid. In the application step,
The conductive substrate and a discharge nozzle with relatively moving, producing an electrophotographic photosensitive member according to any one of claims 1-5, characterized in that discharging the coating liquid from the discharge nozzle Method.

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