JP2006047695A - Method for manufacturing electrophotographic photoreceptor, electrophotographic photoreceptor manufactured by the method, and image forming apparatus equipped with the electrophotographic photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor in which a coating is efficiently formed without producing a coating defect and no image defect is induced when the photoreceptor is used for forming an image. <P>SOLUTION: The electrophotographic photoreceptor comprises a support base 2 made of a conductive material and a plurality of layers on the support base 2, wherein in at least two layers soluble with the same solvent and formed adjacent to each other, the layer farther from the support base is formed by coating in a coating apparatus 1 employing a roll coating method. The support base 2 attached to the coating apparatus 1 is brought into contact while rotating with a coating roll 4 which is also rotating, and a coating film of a coating liquid 3 supplied to the coating roll 4 from a coating liquid supply means 5 is transferred to form the layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing an electrophotographic photosensitive member, an electrophotographic photosensitive member produced by the method, and an image forming apparatus including the electrophotographic photosensitive member.

  An electrophotographic photosensitive member used for electrophotographic image formation, in which an electrostatic latent image is formed by exposure with light according to image information, is mounted on an image forming apparatus. An image forming apparatus equipped with this electrophotographic photosensitive member is widely used in addition to a copying machine and a printer as output means such as a computer whose demand has been increasing in recent years.

  In general, an electrophotographic photosensitive member is formed by coating an organic photosensitive layer on the outer peripheral surface of a hollow cylindrical support made of a conductive material. Recently, many electrophotographic photoreceptors have a laminated structure in which an undercoat layer, a charge generation layer, and a charge transport layer are sequentially applied and laminated in order to develop higher performance.

  Since the environment in which an image forming apparatus on which an electrophotographic photosensitive member is mounted is used varies, it is important for the performance of the electrophotographic photosensitive member to be less dependent on temperature and humidity, but in an extremely humid or low humidity environment. However, it is reported that image defects occur due to a change in performance of the electrophotographic photosensitive member. This is because the water content in the photosensitive layer containing the charge generating material and the charge transport material of the electrophotographic photosensitive member varies greatly depending on the surrounding environment, so that the electrical characteristics of the electrophotographic photosensitive member change greatly and image defects are reduced. It is thought to invite.

  For example, as described above, in the case of an electrophotographic photosensitive member having a photosensitive layer formed on an undercoat layer, the photosensitive layer is composed of a hydrophobic resin having a low water absorption rate such as a polycarbonate resin, and the undercoat layer is a polyamide. It is often composed of a resin having a high water absorption rate such as a resin. When such a layer containing a resin having a high water absorption rate is present in the electrophotographic photosensitive member, the amount of water contained in the layer varies greatly depending on the environmental humidity, and the charging ability changes depending on the amount of moisture. , Image defects and image density changes occur.

  As a conventional technique for solving such a problem, it has been proposed to use a hydrophobic binder (see Patent Document 1). When a hydrophobic binder is used for the undercoat layer and the dip coating method commonly used in the manufacture of electrophotographic photosensitive members is used for coating the upper layer in contact with the undercoat layer, the upper layer solvent dissolves the undercoat layer. Therefore, even if the undercoat layer peels off or does not peel off, a part of the coating film dissolves and becomes non-uniform, and when an image is formed using the electrophotographic photoreceptor thus formed, an image is formed. Cause defects. Therefore, Patent Document 1 proposes manufacturing a uniform electrophotographic photosensitive member by performing a charge generation layer, which is an upper layer of the undercoat layer, by a spray coating method.

  However, in the spray coating method, the coating liquid is ejected from the spray nozzle as small droplets, and the coating is performed. Thus, although the appearance after coating is good, the layer thickness that can be formed by one spray coating is small. Since it is thin, in order to form a layer having a necessary thickness, it is necessary to repeat the coating several times, and there is a problem that productivity is low.

  In addition, when a large amount of coating liquid is spray-applied at once, there is a problem that the applied coating liquid drips and a layer having a non-uniform layer thickness is formed. Furthermore, since the coating liquid is ejected and coating is performed, easily volatile components in the coating liquid are volatilized, the viscosity of the coating liquid increases, and an orange peel (an orange skin-like surface on the surface) is formed. There is a problem that undulation occurs.

  In addition, when a coating solution containing a solvent that dissolves the coating film is spray applied onto the coating film that is a pre-formed layer, spherical particles that are droplets formed by spraying collide with the coating film. When the particles are dried after dissolving a part of the coating film, the concentration of the components contained in the layer becomes non-uniform, and the electrophotographic photosensitive member in which the component concentrations in the layer are formed non-uniformly. When the body is used for image formation, there is also a problem that an image defect occurs. In particular, when the pre-formed layer is a thin layer such as the undercoat layer, in an electrophotographic photoreceptor in which a photosensitive layer is formed by spray coating on the undercoat layer coating film, Such image defects are prominent.

  In addition, the electrophotographic photosensitive member is repeatedly subjected to processes such as charging, exposure, development, transfer, cleaning, and static elimination, so that electrical and mechanical external forces are directly applied thereto. Durability is required. Particularly recently, in order to realize cost reduction and maintenance free of an image forming apparatus using an electrophotographic system, extremely high durability has been demanded.

  As a means for improving the durability of the electrophotographic photosensitive member, it is easiest to increase the ratio of the binder resin contained in the outermost layer among the layers formed on the electrophotographic photosensitive member. However, when the outermost layer is a photosensitive layer, for example, the charge transport material is diluted as the binder resin content is increased. Therefore, if the binder resin content is too high, the responsiveness decreases. If the responsiveness is poor, the residual potential rises, and the surface potential of the electrophotographic photosensitive member is repeatedly used in a state where it is not sufficiently attenuated. There is a problem that the image quality is deteriorated at an early stage without being erased. In addition, the viscosity of the coating liquid increases with an increase in the binder resin content, and there is a problem that the coating cannot be applied by the dip coating method.

  As a conventional technique for solving such a problem, at least two charge transport layers are provided, and the arrangement of each layer is such that the concentration of the charge transport material decreases sequentially toward the surface of the electrophotographic photosensitive member, in other words, the binder resin. Constructed so that the density gradually increases toward the surface of the electrophotographic photosensitive member, and a plurality of charge transport layers are formed by at least two spray coatings or dip coating and at least one spray coating. It has been proposed (see Patent Document 2).

  However, as described above, the spray coating method has various problems and is not practical because of low productivity. In particular, in the case of a coating liquid having a high binder resin content as in Patent Document 2, it is necessary to considerably dilute the solid content concentration because of its high viscosity, and a coating film having a desired composition can be obtained by using a large amount of a diluent solvent. Since the number of spray coatings required for the production increases, the productivity further decreases, and the coating film in the lower layer is melted and peeled off by a large amount of the dilution solvent. Thus, the electrophotographic photoreceptor produced in this way Then, there is a high risk of image defects.

  Furthermore, the electrophotographic photoreceptor is also required to have durability against deterioration of the surface layer due to adhesion of active substances such as ozone and NOx generated during charging. In general, such problems are prevented by selecting an appropriate charge transport material and adding an additive. However, there is no compound that has both responsiveness and resistance to active substances as a charge transport material, and if additives are added in a large amount to prevent deterioration, the electrical characteristics of the electrophotographic photoreceptor are adversely affected. End up. Therefore, to improve the durability against active substances, it is conceivable to use a plurality of charge transport layers and assign functions to each charge transport layer. However, as described above, it is necessary to efficiently apply while maintaining the soundness of each layer. There is a problem that can not be.

Japanese Patent Laid-Open No. 6-123988 JP-A-5-72759

  An object of the present invention is to provide a method for producing an electrophotographic photosensitive member that can be efficiently applied and formed without causing application defects and that does not generate image defects when used for image formation.

  Another object of the present invention is to provide an image forming apparatus comprising the electrophotographic photosensitive member produced by the production method and capable of stably forming an image having excellent image quality for a long period of time. is there.

The present invention includes an electrophotographic image having a support made of a conductive material and a plurality of layers formed on the support, and an electrostatic latent image is formed by exposure with light according to image information. In the method for producing an electrophotographic photoreceptor for producing a photoreceptor,
The plurality of layers are formed by laminating, and the upper layer that is the layer farther from the support among the at least two layers that are soluble in the same solvent and are in contact with each other is applied by a roll coating method. An electrophotographic photosensitive member manufacturing method characterized in that the electrophotographic photosensitive member is formed.

According to the present invention, at least two layers which are soluble in the same solvent and are in contact with each other are formed between a photosensitive layer formed by including a charge generation material and a charge transport material, and the photosensitive layer and the support. And is a subbing layer
The undercoat layer comprises a hydrophobic binder soluble in the solvent,
When the photosensitive layer is composed of one layer, the photosensitive layer is formed by applying a roll coating method, and when the photosensitive layer is formed by laminating the charge generation layer and the charge transport layer, at least the layer on the side in contact with the undercoat layer is It is formed by being applied by a roll coating method.

In the present invention, the plurality of layers formed on the support includes a photosensitive layer on which an electrostatic latent image is formed,
The photosensitive layer has a laminated structure in which a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material are laminated,
The charge transport layer further comprises a plurality of layers, and at least the uppermost charge transport layer that is the farthest from the support among the plurality of charge transport layers is formed by being applied by a roll coating method. To do.

In the present invention, at least one of the plurality of charge transport layers is
The composition is different from that of the remaining charge transport layer.

  In addition, the present invention is an electrophotographic photoreceptor produced by any one of the above-described production methods.

Further, the present invention is an electrophotographic photoreceptor produced by a production method in which the plurality of charge transport layers are formed,
The ratio (B / A) of the weight (B) of the binder resin to the weight (A) of the charge transport material in the uppermost charge transport layer which is the layer farthest from the support among the plurality of charge transport layers is 2 An electrophotographic photosensitive member having a viscosity of 0.0 to 6.0.

Further, in the present invention, the plurality of charge transport layers contain at least one of an antioxidant and a light stabilizer,
The amount of antioxidant and / or light stabilizer contained in the uppermost charge transport layer is
It is characterized by being larger than the amount of the antioxidant and / or the light stabilizer contained in the charge transport layer located below the uppermost charge transport layer.

  In the present invention, the ionization potential of the charge transport material in the uppermost charge transport layer is 5.65 eV or more.

In the present invention, the mobility of the entire plurality of charge transport layers is
It is characterized by being 1.0 × 10 ⁻⁶ cm ² / Vs or more at an environmental temperature of 5 ° C. and an electric field strength of 2.5 × 10 ⁵ V / cm.

  According to another aspect of the present invention, there is provided an image forming apparatus comprising any one of the electrophotographic photosensitive members.

  According to the present invention, the plurality of layers of the electrophotographic photosensitive member are formed by being laminated, and are layers far from the support among at least two layers that are soluble in the same solvent and are in contact with each other. Since the upper layer is formed by being applied by a roll coating method, it can be easily applied without application defects.

  When two adjacent layers soluble in the same solvent are applied by the dip coating method, after the lower layer close to the support is applied, the coating solution for the upper layer far from the support is stored. When the support on which the lower layer is applied is immersed, the lower layer coating film dissolves in the coating liquid, so that the dissolution of the lower part of the coating tank that is immersed in the coating liquid for a long time proceeds, and the lower layer is in the vertical direction. Becomes uneven. In addition, since the lower layer components are mixed into the upper layer coating solution, the components of the coating solution change as the number of coatings increases, and the characteristics of the electrophotographic photoreceptor to be produced are different for each production batch. Change. Moreover, even if it applies with a spray application method, an image defect will arise and productivity will fall.

  On the other hand, in the roll coating method of the present invention, since the coating film previously applied to the coating roll is only transferred onto the lower layer, dissolution of the lower layer by the upper layer solvent is uniform. Further, in the roll coating method, the coating roll is applied at a peripheral speed of several tens m / min to several hundreds m / min. Therefore, since the flow velocity of air relative to the peripheral speed of the coating roll is increased, the coating liquid on the surface layer of the coating roll is considerably dried, and this drying proceeds and the surface with less solvent is transferred and applied to the lower layer. , Underlayer dissolution is minimized. This makes it possible to produce an electrophotographic photosensitive member free from coating defects with extremely high efficiency.

  According to the present invention, at least two layers that are soluble in the same solvent and are in contact with each other include a photosensitive layer that includes a charge generation material and a charge transport material, and a space between the photosensitive layer and the support. And an undercoat layer. Further, the undercoat layer contains a hydrophobic binder soluble in the solvent. When the photosensitive layer is composed of one layer, one photosensitive layer is applied by a roll coating method, and the photosensitive layer is transported with the charge generation layer and the charge transport layer. When the layers are laminated, at least the layer in contact with the undercoat layer is applied by a roll coating method.

  In this way, by using a hydrophobic binder with a low water absorption rate for the undercoat layer provided between the support and the photosensitive layer, the electrical characteristics do not change due to humidity, and electrophotography with high environmental stability. A photoreceptor is realized. In general, a hydrophobic binder dissolves in the solvent of the photosensitive layer coating solution, so that coating defects are likely to occur, but roll coating is applied to the photosensitive layer or a layer on the side of the photosensitive layer that contacts the undercoat layer. By using the method, it is possible to easily apply without causing a coating defect in the undercoat layer.

  Furthermore, since an undercoat layer is provided between the support and the photosensitive layer, injection of charges from the support to the photosensitive layer can be prevented, so that a decrease in chargeability of the photosensitive layer can be prevented. Further, it is possible to prevent the occurrence of defects such as fogging in the image by suppressing the decrease of the surface charge other than the portion to be erased by the exposure. Further, the undercoat layer can cover the defects on the surface of the support to obtain a uniform surface, so that the film formability of the photosensitive layer can be improved. Further, peeling of the photosensitive layer from the support can be suppressed, and adhesion between the support and the photosensitive layer can be improved.

  According to the invention, the photosensitive layer has a laminated structure of a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material, and the charge transport layer comprises a plurality of layers, and a plurality of charge transport layers. The uppermost charge transport layer, which is at least the layer farthest from the support, is applied and formed by a roll coating method.

  In this way, the photosensitive layer has a laminated structure of a charge generation layer and a charge transport layer, and the charge generation function and the charge transport function are assigned to different layers, so that the most suitable materials for the charge generation function and the charge transport function can be obtained. Therefore, it is possible to obtain an electrophotographic photoreceptor having high sensitivity, excellent stability during repeated use, and high durability.

  Furthermore, since the charge transport layer has a multilayer structure of at least two or more layers, it becomes possible to laminate charge transport layers having specific functions as separate layers, and preferably at least the uppermost layer is coated. By applying each layer by a roll coating method, it becomes possible to apply and form a charge transport layer without worrying about dissolution of the lower layer, so that it is possible to produce a high-performance and high-performance electrophotographic photosensitive member. it can.

  Further, according to the present invention, at least one of the plurality of charge transport layers is formed so as to have a composition different from that of the remaining charge transport layer. Therefore, the types and composition ratios of the charge transport material, the binder resin, the additive, and the like. By changing the above, it is possible to produce a high-performance and high-performance electrophotographic photosensitive member by imparting a specific function to each charge transport layer.

  Further, according to the present invention, two layers formed in contact with each other that are soluble in the same solvent can be applied without causing coating defects, so that an electrophotographic photoreceptor having various functions, for example, environmental stability Thus, an electrophotographic photoreceptor excellent in durability and the like is realized.

  According to the invention, in the electrophotographic photosensitive member having a plurality of charge transport layers, the ratio of the weight of the binder resin to the weight of the charge transport material in the uppermost charge transport layer, which is the layer farthest from the support, is Therefore, an electrophotographic photoreceptor excellent in durability against surface abrasion and scratches due to rubbing is realized. Furthermore, if the ratio of the binder contained in the charge transport layer is increased, the viscosity of the coating liquid increases and it becomes difficult to apply by the dip coating method and the spray coating method. Since a coating liquid having a viscosity of 10 to several tens of thousands mPa · s can be easily applied, the binder content ratio can be increased to the limit on electrical characteristics.

  According to the invention, the amount of the antioxidant and / or light stabilizer contained in the outermost charge transport layer is the same as the amount of the antioxidant and / or light stabilizer contained in the lower charge transport layer. Therefore, durability against deterioration of the surface layer due to adhesion of active substances such as ozone and NOx generated during charging can be efficiently improved. That is, if a large amount of an antioxidant and / or a light stabilizer is added to prevent deterioration of the electrophotographic photosensitive member, the electrical characteristics of the electrophotographic photosensitive member are adversely affected, but a large amount is added only to the outermost charge transport layer. As a result, the adverse effects on the electrical characteristics of the electrophotographic photosensitive member can be minimized, and the deterioration of the outermost layer, which is the most deteriorated, can be minimized, thereby realizing a highly durable electrophotographic photosensitive member. The

  Further, according to the present invention, the ionization potential of the charge transport material in the outermost charge transport layer is set to 5.65 eV or more, thereby reducing the surface resistance due to adhesion of active materials such as ozone and NOx generated during charging. It is possible to prevent occurrence of image defects such as whitening when an image is formed using the electrophotographic photosensitive member.

  In addition, according to the present invention, since the mobility of the plurality of charge transport layers as a whole is sufficiently high, an electrophotographic photoreceptor capable of exhibiting sufficient responsiveness even in a low temperature environment is realized.

  Further, according to the present invention, since the electrophotographic photosensitive member having high functionality and high performance, for example, excellent environmental stability and durability, is provided, it is possible to form a high quality image under various environments. A high image forming apparatus can be obtained.

  FIG. 1 is a schematic diagram showing the configuration of a roll coating type coating apparatus 1 that is preferably used in the practice of the present invention. A coating apparatus 1 shown in FIG. 1 is a natural roll coating type apparatus.

  The coating apparatus 1 has a support 2 made of a conductive material as an object to be coated, and a plurality of layers formed on the support 2, and is statically exposed by light according to image information. In the production of an electrophotographic photosensitive member on which an electrostatic latent image is formed, the plurality of layers are formed by being laminated, and at least two layers that are soluble in the same solvent and are in contact with each other, whichever is farther from the support The upper layer, which is the above layer, is used for coating and forming by a roll coating method.

  Of the at least two layers that are soluble in the same solvent and are in contact with each other, the lower layer, which is the layer closer to the support, is formed by dip coating, spray coating, ink jet, or the like. It may also be formed by applying the same roll coating method.

  The coating apparatus 1 is in contact with a support 2 that is rotatably supported by an apparatus main body (not shown) so that its axis is parallel to the axis of the support 2 and through the coating liquid 3. Arrangement, that is, an application roll (also referred to as an applicator roll) 4 arranged to have a specific nip pressure with the support 2, and a coating liquid 3 on the application roll 4 so as to have a constant film thickness The coating liquid supply means 5 to be supplied, the axis of the coating roll 4 and the axis of the coating roll 4 are parallel and arranged so as to contact the coating roll 4, and the excess coating liquid that has not been applied to the support 2 is scraped off. This configuration includes a scraping roll 6 and a cleaning blade 7 that cleans the surface of the scraping roll 6.

  The coating apparatus 1 includes an attachment / detachment apparatus that attaches and detaches the support 2 that is an object to be applied to the apparatus main body, a support drive apparatus that rotationally drives the support 2, and a support separation that separates the support 2 from the application roll 4. Responding to the detection output of each detection means, each detecting means for detecting the operating state of the apparatus, the chock for mounting the application roll 4 on the apparatus main body, the application roll driving device for rotating the application roll 4, each driving device and the separating device Thus, although control means for controlling the operation of each drive device and separation device are included, the illustration is omitted in order to avoid complication of the drawing.

  In the case of the natural roll coating method, it is preferable that at least the surface layer of the coating roll 4 is made of an elastic material. Examples of elastic materials include silicone rubber, organic polysulfide rubber, nitrile butadiene rubber, nitrosulfonated polyethylene, styrene butadiene rubber, silicone resin, fluororesin resin, etc. A coated one is mentioned.

  As the coating liquid supply means 5, a known means can be used. Here, means for supplying a coating film having a constant film thickness to the coating roll 4 from the nozzle 5a is used. In the case of the natural roll coating method, the scraping roll 6 is provided to prevent the coating roll 4 from being damaged because at least the surface layer portion of the coating roll 4 is made of an elastic material. The cleaning blade 7 is made of an elastic metal plate or resin plate, and is provided so that its free end is in contact with the surface of the scraping roll 6. The cleaning liquid 7 is applied to the surface of the scraping roll 6. Remove.

  FIG. 2 is a schematic diagram showing the configuration of another roll coating type coating apparatus 10 that is preferably used in the practice of the present invention. Another roll coating type coating apparatus 10 is similar to the above-described coating apparatus 1, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.

  Another feature of the roll coating type coating apparatus 10 is that the coating liquid supply means 11 includes a pan 12 for storing the coating liquid 3 and two first and second metering rolls 13 and 14. It is composed of. The first metering roll 13 adheres the coating liquid 3 accommodated in the pan 12 and forms a predetermined uniform coating film by the gap between the first metering roll 13 and the second metering roll 14. Supply to roll 4.

  1 and 2 show a natural roll coating method, but the present invention is not limited to this, and a reverse roll coating method in which the coating roll and the support body have the same rotational direction. There may be. In the reverse roll coating method, most of the application rolls are composed of metal rolls, and are arranged in parallel with a support that is an object to be coated with a specific gap. The film thickness also depends on the size of the gap. Can be controlled. In the case of a reverse roll coating type coating apparatus, the cleaning blade may be provided so as to directly contact the coating roll.

  Hereinafter, for example, a coating method when the coating liquid 3 is applied to the support 2 using the coating apparatus 10 shown in FIG. 2 will be described.

  First, in a state where the support 2 is separated from the coating roll 4, the support 2 is rotated at a predetermined peripheral speed in the direction of the arrow 15 in the figure by the support driving device. Next, the coating liquid 3 having a constant film thickness generated by the coating liquid supply means 11 is transferred to the coating roll 4 and rotated several times to apply the coating liquid 3 having a uniform thickness on the surface of the coating roll 4. A film is formed. Thereafter, the coating 2 is transferred to the support 2 by bringing the support 2 rotating at a predetermined peripheral speed into contact with the coating roll 4.

  After the start of coating, that is, after the support 2 is brought into contact with the coating roll 4, the support 2 has a number of rotations (number of coatings) of 1 or more, Rotated to be in the range of less than The number of rotations is preferably 1.5 to 10 times, more preferably 2 to 5 times. If the number of rotations of the support 2 is less than 1, an uncoated outer peripheral surface remains, so that a coating film having a uniform thickness cannot be obtained. If the number of rotations of the support 2 exceeds 20, the work time will be long and the production efficiency will be reduced. Therefore, the number of rotations was set to 1 to 20 times.

  Excess coating film on the application roll 3 that has not been transferred to the support 2 at the time of application is transferred to the scraping roll 6 and further discharged out of the apparatus by the cleaning blade 7. In addition, the film thickness of the coating liquid 3 transferred to the support 2 is adjusted by the coating liquid supply means 11 described above, the peripheral speed of the coating roll 4 and the support 2, and the coating on the support 2. It can be controlled by adjusting the number of times, the physical properties of the coating liquid 3, the material of the surface of the support 2 and the coating roll 4, the nip width between the support 2 and the coating roll 4, the size of the gap, and the like.

  After the start of application, when the number of times of application of the support 2 reaches a predetermined number, the support 2 is separated from the application roll 4 by a support separating apparatus. At this time, the peripheral speed V1 of the support 2 is set to be faster than the peripheral speed V2 of the coating roll 4 (V1> V2). In particular, the ratio R (= V1 / V2) between the peripheral speed V1 of the support 2 and the peripheral speed V2 of the coating roll 4 is preferably 1.2 to 15.0. By this operation, the cut (seam) of the coating on the surface of the support 2 at the time of separation disappears, and a coating having a uniform thickness can be formed on the support 2.

  For example, if the peripheral speed V1 of the support 2 and the peripheral speed V2 of the coating roll 4 are the same when the coating roll 4 and the support 2 are separated from each other, the support 2 is separated even though they are separated from each other. Since the upper coating film and the coating film on the coating roll 4 extend to each other, a connecting portion of the coating liquid is formed between the support 2 and the coating roll 4. Since the connecting portion of the coating liquid is formed as if a bridge is formed between the support 2 and the coating roll 4, this is referred to as a bridge structure for convenience.

  In general, when the film thickness is thin, the solvent concentration in that portion decreases quickly, so that the surface tension is higher in the thin film portion than in the other thick film portions. Since the bridge structure portion described above has a small film thickness, the coating liquid flows from the coating film on the surfaces of the support 2 and the coating roll 4 toward the bridge structure portion. Further, when the support 2 and the coating roll 4 are further separated from each other and the bridge structure is cut, an edge is formed at the cut portion of the bridge structure, and the coating liquid flows toward the edge portion as described above, and the edge is formed. The amount of coating liquid in the part increases. The edge portion in which the amount of the coating liquid is increased in this way is not sufficiently uniform even when leveling is performed by rotating the support 2, and a thick seam is formed.

  On the other hand, when the peripheral speed V1 of the support 2 at the time of separation between the support 2 and the coating roll 4 is made faster than the peripheral speed V2 of the coating roll 4, the coating liquid for forming the coating film has tension in the separation direction. Since a shearing force is applied abruptly in the rotational direction, the coating solution is cut without forming a bridge structure. As a result, since the seam of the coating film as described above is not formed, a coating film having a uniform thickness is formed on the surface of the support 2. In particular, the ratio R (= V1 / V2) of the peripheral speed between the support 2 and the coating roll 4 when being separated is set in the range of 1.2 to 15.0, thereby reliably preventing the occurrence of seams. can do. The range of the ratio R is preferably 1.2 to 8.0. If the peripheral speed ratio R is less than 1.2, the shear force is insufficient, so that the generation of seams cannot be sufficiently prevented, and a coating film having a uniform thickness cannot be obtained. When the ratio R of the peripheral speed exceeds 15.0, the degree of speed increase before and after the separation of the support 2 becomes too large, so that the coating film undulates due to acceleration, and the coating film has a uniform thickness. You will not be able to get. Therefore, the peripheral speed ratio R is set to 1.2 to 15.0.

  The separation speed between the coating roll 4 and the support 2 is not particularly limited, but is preferably set in the range of 5 mm / sec to 350 mm / sec. If the separation speed is less than 5 mm / sec, there is a possibility that sufficient tension to act on the coating film cannot be obtained. If it exceeds 350 mm / sec, the tension applied to the coating film is sufficient, but the coating film on the surface of the support 2 may wave due to the acceleration during separation, making it impossible to obtain a coating film with a uniform thickness. . Further, by separating the coating roll 4 and the support 2 from each other, the shearing force and the tension are applied to each other to cut the coating film without forming a bridge structure, and then the rotation of the support 2 is performed for a predetermined time. It is preferable to continue and dry the coating film on the surface of the support 2 to some extent. For example, when the solvent of the coating liquid applied to the support 2 has a high boiling point, after the coating liquid 4 is applied to the support 2 and the coating roll 4 and the support 2 are separated from each other, the coating constituting the coating film is formed. Since the working fluid has fluidity, the coating film may sag downward due to the action of gravity, making it impossible to form a coating film having a uniform thickness. When a relatively volatile solvent is used as the solvent, a cover member that covers the coating roll 4 and the support 2 or the entire coating apparatus 10 is provided in order to prevent drying due to volatilization of the solvent. A substantially sealed state is also effective for forming a coating film having a uniform thickness.

  When the upper layer of the two layers that are soluble in the same solvent and are in contact with each other is applied on the support 2 by such a roll coating type coating apparatus, the coating film previously applied to the coating roll 4 is applied. Since it can be applied only by transferring onto the lower layer, dissolution of the lower layer substrate by the upper solvent can be made uniform, and contamination of the coating liquid can be minimized. Furthermore, in the roll coating method, the coating roll 4 is applied at a peripheral speed of several tens of m / min to several hundreds of m / min. Therefore, the surface of the coating roll 4 is coated by the air flow relative to the peripheral speed of the coating roll 4. Drying is greatly accelerated, and this drying transfers the solvent-depleted surface to the lower layer, thus minimizing dissolution of the lower layer. Therefore, it is possible to produce an electrophotographic photosensitive member free from coating defects with extremely high efficiency.

  The case where an electrophotographic photoreceptor is produced in more detail is described below. The type of the electrophotographic photosensitive member applied and formed by the production method of the present invention is not particularly limited, and various modifications are allowed. For example, the photosensitive layer alone may be formed on the support, the undercoat layer may be formed on the support, and the photosensitive layer may be formed thereon. A surface protective layer may be formed on the layer.

  The photosensitive layer may be a single layer type in which the charge generation material and the charge transport material are contained in the same layer, or the charge generation layer containing the charge generation material and the charge containing the charge transport material. A laminated type in which a transport layer is laminated may be used. Further, in the case of a laminated type, the charge generation layer and the charge transport layer do not need to be composed of only one layer, and may be formed by laminating two or more layers having different configurations in order to exhibit required characteristics. Good.

  The above-described form in which the undercoat layer is provided between the support and the photosensitive layer is preferable as an electrophotographic photosensitive member. By forming the undercoat layer, it is possible to prevent injection of charges from the support to the photosensitive layer, and thus it is possible to prevent a decrease in chargeability of the electrophotographic photosensitive member. According to the electrophotographic photosensitive member in which the undercoat layer is formed, a decrease in surface charge other than the portion to be erased by exposure is suppressed, so that it is possible to prevent the occurrence of defects such as fogging on the image. In addition, since the undercoat layer covers defects on the surface of the support, a uniform surface can be obtained, so that the film formability of the photosensitive layer can be improved. Further, peeling of the photosensitive layer from the support can be suppressed, and adhesion to the support can be improved.

  In the production of an electrophotographic photoreceptor, various coating liquids are applied on a support. The coating liquid includes a photosensitive layer forming coating liquid for forming a photosensitive layer, an undercoat layer forming coating liquid for forming an undercoat layer according to design specifications, and a surface protective layer forming for forming a surface protective layer. Coating liquid is used. When the photosensitive layer is a laminate type, the photosensitive layer forming coating solution is further divided into a charge generation layer forming coating solution and a charge transport layer forming coating solution.

Hereinafter, the support, each layer, and each layer forming coating solution will be described.
As a material of the support (electrophotographic photosensitive member tube), for example, a metal material such as aluminum, aluminum alloy, copper, zinc, stainless steel, titanium, or the like can be used. Also, without being limited to these metal materials, polymer materials such as polyethylene terephthalate, polyester, polyoxymethylene, and polystyrene, those obtained by laminating metal foil on the surface of hard paper or glass, and those obtained by vapor deposition of metal materials Alternatively, a conductive polymer, tin oxide, indium oxide, carbon particles, metal particles, or a conductive compound layer deposited or applied may be used. The surface of the support is optionally subjected to irregular reflection treatment such as anodizing film treatment, surface treatment with chemicals or hot water, coloring treatment, or roughening the surface within a range that does not affect the image quality. You may give it. In the electrophotographic process using a laser as an exposure light source, the wavelengths of the laser light are uniform, so that the incident laser light and the light reflected in the electrophotographic photosensitive member cause interference, and interference fringes due to this interference appear on the image. May appear and cause image defects. By subjecting the surface of the support to the irregular reflection treatment as described above, it is possible to prevent image defects due to the interference of laser light having the same wavelength.

  The charge generation layer contains, as a main component, a charge generation material that generates charges by absorbing light. Substances effective as a charge generating substance include azo pigments such as monoazo pigments, bisazo pigments, trisazo pigments, indigo pigments such as indigo or thioindigo, perylene pigments such as peryleneimide or perylene anhydride, anthraquinone or Polycyclic quinone pigments such as pyrenequinone, phthalocyanine pigments such as metal phthalocyanine or metal-free phthalocyanine, triphenylmethane dyes represented by methyl violet, crystal violet, knight blue, victoria blue, erythrosine, rhodamine B, rhodamine 3R Acridine dyes typified by acridine orange, frappeosin, thiazine dyes typified by methylene blue, methylene green, capri blue or meldra blue Oxazine dyes, squarylium dyes, pyrylium salts and thiopyrylium salts, thioindigo dyes, bisbenzimidazole dyes, quinacridone dyes, quinoline dyes, lake dyes, azo lake dyes, dioxazine dyes, azurenium dyes, Various organic pigments and dyes such as triallylmethane dyes, xanthene dyes, cyanine dyes, and inorganic such as amorphous silicon, amorphous selenium, tellurium, selenium-tellurium alloys, cadmium sulfide, antimony sulfide, zinc oxide, zinc sulfide Materials can be mentioned. These charge generation materials are used alone or in combination of two or more.

  The charge generation layer is usually a charge generation layer forming coating solution obtained by dispersing a charge generation material in a solvent, and in particular, a binder resin solution obtained by mixing a binder resin as a binder in a solvent. It is formed by applying a coating liquid obtained by dispersing a charge generating material by a known method on a support or an undercoat layer. When the undercoat layer is formed on the support and the undercoat layer is soluble in the same solvent used for the charge generating layer forming coating solution, the charge generating layer forming coating solution is It is applied on the undercoat layer by a roll coating method which is a manufacturing method of the invention.

  Examples of the binder resin used in the charge generation layer forming coating solution include polyester resin, polystyrene resin, polyurethane resin, phenol resin, alkyd resin, melamine resin, epoxy resin, silicone resin, acrylic resin, methacrylic resin, polycarbonate resin, One kind selected from the group consisting of a resin such as a polyarylate resin, a phenoxy resin, a polyvinyl butyral resin, a polyvinyl formal resin, and a copolymer resin containing two or more repeating units constituting these resins. Or a mixture of two or more. Specific examples of the copolymer resin include insulating resins such as vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, and acrylonitrile-styrene copolymer resin. be able to. The binder resin is not limited to those described above, and a commonly used known resin can be used as the binder resin.

  Solvents include, for example, halogenated hydrocarbons such as tetrachloropropane or dichloroethane, ketones such as isophorone, methyl ethyl ketone, acetophenone, cyclohexanone, esters such as ethyl acetate, methyl benzoate, butyl acetate, tetrahydrofuran (THF), dioxane, dioxane. Ethers such as benzyl ether, 1,2-dimethoxyethane or dioxane, aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, tetralin, diphenylmethane, dimethoxybenzene and dichlorobenzene, sulfur-containing solvents such as diphenyl sulfide, Fluorine solvents such as hexafluoroisopropanol, aprotic polar solvents such as N, N-dimethylformamide or N, N-dimethylacetamide, etc. are used.Moreover, the mixed solvent which mixed 2 or more types of these solvents can also be used.

  The mixing ratio of the charge generation material and the binder resin is preferably such that the charge generation material is in the range of 10 wt% to 99 wt% when the weight of the entire charge generation layer is 100%. If the charge generation material is less than 10% by weight, the sensitivity is lowered. When the charge generation material exceeds 99% by weight, not only the film strength of the charge generation layer decreases, but also the dispersibility of the charge generation material decreases and coarse particles increase, and the surface other than the portion to be erased by exposure. Since the charge decreases, image defects, particularly image fogging called black spots, in which toner adheres to a white background and minute black spots are formed, are generated.

  As a pretreatment for dispersing the charge generation material in the binder resin solution, the charge generation material may be pulverized in advance by a pulverizer. Examples of the pulverizer used for the pulverization treatment include a ball mill, a sand mill, an attritor, a vibration mill, and an ultrasonic disperser.

  When the charge generating material is dispersed in the binder resin solution, examples of the disperser used include a paint shaker, a ball mill, and a sand mill. As the dispersion condition at this time, it is desirable to select an appropriate condition so that impurities are not mixed due to wear of the container used and the members constituting the disperser.

  Furthermore, you may add various additives, such as a hole transport material, an electron transport material, antioxidant, a dispersion stabilizer, and a sensitizer, to a charge generation layer as needed. As a result, potential characteristics are improved, stability as a coating liquid is increased, fatigue deterioration when an electrophotographic photosensitive member is repeatedly used can be reduced, and durability can be improved.

  Examples of the method for applying the charge generation layer forming coating liquid include a roll coating method, a spray method, a blade method, a ring method, and a dip coating method. Among these coating methods, the roll coating method, as described above, can coat two layers formed in contact with each other with the same solvent without causing defects, etc. Is soluble in the same solvent used in the charge generation layer forming coating solution, and is used as an essential coating method when the charge generation layer is formed on the undercoat layer.

  The thickness of the charge generation layer is preferably 0.05 μm or more and 5 μm or less, more preferably 0.1 μm or more and 1 μm or less. If the thickness of the charge generation layer is less than 0.05 μm, the light absorption efficiency is lowered, and the sensitivity is lowered. If the film thickness of the charge generation layer exceeds 5 μm, the charge transfer inside the charge generation layer becomes the rate-determining step in the process of erasing the charge on the surface of the electrophotographic photoreceptor, and the sensitivity is lowered.

  Next, the charge transport layer is obtained by including in the binder resin a charge transport material having the ability to accept and transport charges generated by the charge generation material. As the charge transport material, a hole transport material and an electron transport material can be used. Examples of hole transport materials include carbazole derivatives, pyrene derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, Polycyclic aromatic compounds, indole derivatives, pyrazoline derivatives, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, triarylmethane derivatives, phenylenediamine derivatives, stilbene Derivatives, enamine derivatives, benzidine derivatives and the like can be mentioned. Polymers having groups derived from these compounds in the main chain or side chain, such as poly-N-vinylcarbazole, poly-1-vinylpyrene, ethylcarbazole-formaldehyde resin, triphenylmethane polymer, poly-9-vinylanthracene, etc. Or polysilane etc. are mentioned.

  Examples of the electron transport material include benzoquinone derivatives, tetracyanoethylene derivatives, tetracyanoquinodimethane derivatives, fluorenone derivatives, xanthone derivatives, phenanthraquinone derivatives, phthalic anhydride derivatives, diphenoquinone derivatives and other organic compounds, amorphous silicon, Examples include inorganic materials such as amorphous selenium, tellurium, selenium-tellurium alloy, cadmium sulfide, antimony sulfide, zinc oxide, and zinc sulfide. The charge transport materials are not limited to those listed here, and can be used alone or in admixture of two or more.

As the binder resin for the charge transport layer, a resin having excellent compatibility with the charge transport material is selected. Specific examples include vinyl polymer resins such as polymethyl methacrylate resin, polystyrene resin, and polyvinyl chloride resin, and copolymer resins thereof, as well as polycarbonate resin, polyester resin, polyester carbonate resin, polysulfone resin, phenoxy resin, and epoxy. Examples thereof include resins such as resins, silicone resins, polyarylate resins, polyamide resins, methacrylic resins, acrylic resins, polyether resins, polyurethane resins, polyacrylamide resins, and phenol resins. Moreover, you may use the thermosetting resin which bridge | crosslinked these resin partially. These resins may be used alone or in combination of two or more. Among the resins described above, polystyrene resin, polycarbonate resin, polyarylate resin, or polyphenylene oxide has a volume resistance value of 10 ¹³ Ω or more, excellent electrical insulation, and excellent film formability and potential characteristics. Therefore, it is particularly preferable to use these for the binder resin.

  As a means for realizing high durability, it is conceivable to increase the binder resin content in the charge transport layer. However, if the binder resin content is too high, the charge transport material in the charge transport layer is diluted as the content increases, so that the photoresponsiveness decreases and sufficient sensitivity cannot be obtained. Further, when the photoresponsiveness is lowered, the residual potential is increased, and the surface potential of the electrophotographic photosensitive member is repeatedly used in a state where the surface potential is not sufficiently attenuated. It is not erased sufficiently, and the image quality is deteriorated at an early stage.

  The content of the binder resin in the charge transport layer is the ratio (B / A) of the weight (B) of the binder resin to the weight (A) of the charge transport material in the case of an electrophotographic photoreceptor produced by a dip coating method. Is about 12/10 to 20/10 (= 1.2 to 2.0), and can be increased to about 25/10 (= 2.5) only in a special case. However, since the hole mobility of the charge transport material must be high in order to ensure responsiveness, the charge transport materials that can be used are limited. Further, when the ratio (B / A) exceeds 20/10 (= 2.0) and the binder resin content is increased, the viscosity of the coating liquid for forming a charge transport layer generally increases and the coating speed decreases. And the productivity is remarkably deteriorated. Further, when the amount of the solvent in the charge transport layer forming coating solution is increased in order to suppress the increase in the viscosity, a brushing phenomenon occurs and white turbidity is generated in the formed charge transport layer. Further, when the ratio (B / A) is less than 12/10 (= 1.2) and the binder resin ratio is low, the printing durability is lowered and the charge transport is lower than when the binder resin ratio is high. As the amount of wear of the layer increases, the endurance life is shortened and deviated from the specifications. That is, in the dip coating method, the content ratio of the ratio (B / A) as described above is required because the content of the binder resin that satisfies the conflicting specifications between the responsiveness and the printing durability must be satisfied by only one layer. The maximum is about 20/10 (= 2.0) in a general electrophotographic photosensitive member.

  On the other hand, when the charge transport layer has a layer structure of two or more layers, it is possible to relatively easily achieve both photoresponsiveness and printing durability. For example, among the plurality of charge transport layers, the ratio (B / A) in the uppermost charge transport layer is made higher than the aforementioned 20/10 (= 2.0) to increase the content ratio of the binder resin, Further, when the ratio (B / A) in the charge transport layer of the inner layer is lowered to reduce the content ratio of the binder resin, both durability and responsiveness can be achieved.

  That is, the uppermost layer of the charge transport layer is formed with a thickness equal to or greater than the thickness that is worn over the life of the electrophotographic photosensitive member, the content of the binder resin in the charge transport layer is extremely increased, and the wear resistance is increased. In order to ensure the responsiveness, the responsiveness of the entire charge transporting layer is also ensured by increasing the content ratio of the charge transporting material in the lower layer than the uppermost layer to increase the hole mobility.

  The ratio (B / A) in the uppermost charge transport layer for expressing a suitable wear resistance life is 20/10 to 60/10 (= 2.0 to 6.0) by weight. If the ratio (B / A) exceeds 6.0 and the binder resin ratio becomes high, the concentration of the charge transport material becomes too low, so that hopping conduction hardly occurs and the hole mobility becomes extremely poor. On the other hand, when the ratio (B / A) is less than 2.0, the printing durability becomes lower than when the binder resin ratio is high, and the wear amount of the charge transport layer increases. Therefore, the ratio (B / A) is set to 2.0 or more and 6.0 or less.

  Moreover, the suitable range of the said ratio (B / A) of a lower layer part is 8 / 10-20 / 10 (= 0.8-2.0) by weight ratio. When the ratio (B / A) exceeds 2.0 and the binder resin ratio increases, the hole mobility becomes slow, and the responsiveness of the entire charge transport layer becomes too low. If the ratio (B / A) is less than 0.8, the concentration of the charge transport material is high, so that the crystallization of the charge transport material occurs during repeated use, and the image quality is extremely deteriorated.

Furthermore, the mobility of all of the uppermost layer and the lower layer portion, that is, the entire charge transport layer is 1.0 × 10 ⁻⁶ cm ^{2 at} an environmental temperature of 5 ° C. and an electric field strength of 2.5 × 10 ⁵ V / cm. By setting it to / Vs or more, the responsiveness of the electrophotographic photoreceptor required for the current image formation can be sufficiently ensured.

  The mobility of the entire charge transport layer can be controlled by adjusting the binder resin content in the upper and lower charge transport layers, adjusting the film thickness of the upper and lower layers, or the material structure of the upper and lower charge transport materials. It can be realized by optimizing. That is, since the mobility is proportional to the concentration of the charge transport material, the mobility is high when the content of the charge transport material in the charge transport layer is high, and the mobility is low when the content is low. When the charge transport layer is composed of two or more layers and the mobility of each layer is different, if the layer with low mobility is thickened, the mobility of the entire charge transport layer becomes low, and conversely the layer with high mobility If the thickness is increased, the mobility of the entire charge transport layer increases. Furthermore, the mobility of the charge transport layer can be increased by using a charge transport material having a high mobility. In reality, by optimizing the above conditions according to the specifications required for the electrophotographic photoreceptor, an electrophotographic photoreceptor having sufficiently high mobility of the charge transport layer and satisfying the necessary specifications can be obtained. Can be created.

In the case where the charge transport layer is composed of two layers, the mobility of the entire charge transport layer can be obtained by the following equation (1). Therefore, the above conditions are selected and set based on the equation (1). Thus, the desired mobility is controlled.
Mobility of entire charge transport layer = (d ₁ η ₁ c ₁ + d ₂ η ₂ c ₂ ) / (d ₁ + d ₂ ) (1)
Where d _{1 is} the thickness of the lower layer
η ₁ : mobility of the charge transport material in the lower layer
c ₁ : Concentration of charge transport material in the lower layer
d ₂ : film thickness of the upper layer
η ₂ : mobility of the charge transport material in the upper layer
c ₂ : concentration of the charge transport material in the upper layer

  The concentration c of the charge transport material is a value obtained by dividing the amount of the charge transport material by (amount of charge transport material + amount of binder resin).

  In order to improve the film formability, flexibility and surface smoothness, an additive such as a plasticizer or a surface modifier may be added to the charge transport layer as necessary. Examples of the plasticizer include biphenyl, biphenyl chloride, benzophenone, o-terphenyl, dibasic acid ester, fatty acid ester, phosphoric acid ester, phthalic acid ester, various fluorohydrocarbons, chlorinated paraffin, and epoxy type plasticizer. be able to. Examples of the surface modifier include silicone oil and fluororesin.

  The charge transport layer may be added with fine particles of an inorganic compound or an organic compound in order to enhance mechanical strength and improve electrical characteristics. Further, various additives such as an antioxidant and / or a light stabilizer may be added as necessary. As a result, deterioration of the surface layer due to adhesion of active substances such as ozone and NOx generated during charging is reduced, and durability when the electrophotographic photosensitive member is repeatedly used can be improved. Further, the stability as a coating liquid for forming a charge transport layer is increased, the life of the liquid is extended, and the electrophotographic photosensitive member produced with the coating liquid is also improved in durability because impurities are reduced.

  As the antioxidant and the light stabilizer, hindered phenol derivatives or hindered amine derivatives are preferably used. The hindered phenol derivative is preferably used in a weight ratio in the range of 0.001 to 0.10 with respect to the weight of the charge transport material. The hindered amine derivative is preferably used in a weight ratio in the range of 0.001 to 0.10 with respect to the weight of the charge transport material. A hindered phenol derivative and a hindered amine derivative may be mixed and used. In this case, the total amount of hindered phenol derivative and hindered amine derivative used is preferably a weight ratio in the range of 0.001 to 0.10 with respect to the weight of the charge transport material.

  Charge transport layer formation when the amount of hindered phenol derivative used or the amount of hindered amine derivative used or the total amount of hindered phenol derivative and hindered amine derivative used is less than 0.001 by weight with respect to the weight of the charge transport material. It is not possible to exhibit a sufficient effect for improving the stability of the coating liquid for coating and improving the durability of the electrophotographic photosensitive member. On the other hand, if the weight ratio exceeds 0.10, the electrophotographic photoreceptor characteristics are adversely affected.

  When the charge transport layer is composed of a plurality of layers, the total amount of the antioxidant and / or light stabilizer contained in the outermost charge transport layer among the plurality of layers is contained in the charge transport layer in the lower layer portion. By adding the antioxidant and / or the light stabilizer so as to exceed the amount, the durability against deterioration of the surface layer due to adhesion of active substances such as ozone and NOx generated during charging can be improved efficiently. . That is, by adding a large amount of an antioxidant and / or a light stabilizer only to the outermost charge transport layer exposed to active substances such as ozone and NOx, the outermost layer efficiently captures the active substance. Since it can be activated, the electrophotographic photosensitive member can be effectively prevented from being deteriorated, and the total amount of antioxidants and / or light stabilizers can be suppressed as the entire charge transporting layer, which adversely affects the electrical characteristics of the electrophotographic photosensitive member. Don't give. Therefore, it is possible to provide a highly durable electrophotographic photosensitive member.

  Further, ozone and NOx cause an interaction with the charge transport material, lower the surface resistance of the electrophotographic photosensitive member surface, and cause image defects such as white spots. This occurs because ozone and NOx interact with the charge transport material on the surface layer of the charge transport layer, so select a charge transport material with an ionization potential of 5.65 eV or more that does not easily interact with ozone and NOx. It can be suppressed by using the uppermost charge transport layer.

  The charge transport layer is prepared by dissolving or dispersing the charge transport material, the binder resin, and, if necessary, the aforementioned additives in a suitable solvent to prepare a charge transport layer forming coating solution. It is formed by applying the forming coating solution onto the charge generation layer, preferably by a roll coating method. When the charge generation layer and the charge transport layer are composed of two layers that are soluble and in contact with each other, the charge transport layer is composed of a plurality of layers, and the plurality of charge transport layers are composed of the same solvent. When two layers formed in contact with each other are formed, the upper layer of the two layers is always formed by a roll coating method.

  The roll coating method is particularly useful when two or more charge transport layers are applied because two layers formed in contact with each other in the same solvent can be applied without causing application defects. It is. Furthermore, since it is possible to apply a high-viscosity coating solution that is difficult to apply by other manufacturing methods, for example, a coating film having a high printing durability with an increased binder resin content can be easily obtained. Can be created.

  Solvents used for the charge transport layer forming coating solution include aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, tetralin, diphenylmethane, dimethoxybenzene, dichlorobenzene, halogenated hydrocarbons such as dichloromethane or dichloroethane, Ethers such as THF, dioxane, dibenzyl ether and dimethoxymethyl ether, ketones such as cyclohexanone, acetophenone and isophorone, esters such as methyl benzoate and ethyl acetate, sulfur-containing solvents such as diphenyl sulfide, hexafluoroisopropanol, etc. Are selected from the group consisting of aprotic polar solvents such as N, N-dimethylformamide, or a mixture of two or more of them. Further, a solvent such as alcohols, acetonitrile or methyl ethyl ketone can be further added to the above-described solvent as necessary.

  The thickness of the charge transport layer is preferably 5 μm or more and 50 μm or less, more preferably 10 μm or more and 40 μm or less. When the thickness of the charge transport layer is less than 5 μm, the charge holding ability on the surface of the electrophotographic photosensitive member is lowered. When the film thickness of the charge transport layer exceeds 50 μm, the resolution of the electrophotographic photosensitive member decreases. Accordingly, the thickness is set to 5 μm or more and 50 μm or less.

  In the case of a laminated type photoreceptor, a charge transport layer may be laminated on the charge generation layer, and conversely, a charge generation layer may be laminated on the charge transport layer. In the case of a single layer type photoreceptor, the layer containing the charge generation material and the charge transport material is formed by the same method as that for forming the charge transport layer. For example, a photosensitive layer forming coating solution is prepared by dissolving or dispersing a charge generation material, a hole transport material and electron transport material, which are charge transport materials, and a binder resin in the appropriate solvent described above. It is formed by applying the layer forming coating solution by a roll coating method. The film thickness of the photosensitive layer of the single layer type photoreceptor is preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 50 μm or less. When the film thickness of the photosensitive layer is less than 5 μm, the charge holding ability of the surface of the electrophotographic photoreceptor is lowered. When the film thickness of the photosensitive layer exceeds 100 μm, productivity decreases.

  The electrophotographic photosensitive member may be provided with an undercoat layer between the support and the photosensitive layer as described above. By providing the undercoat layer, injection of electric charge from the support to the photosensitive layer is prevented, and the surface of the support is smoothed to improve the coating film adhesion of the photosensitive layer.

  If there is no subbing layer between the conductive support and the photosensitive layer, charge is injected from the support to the photosensitive layer, the chargeability is lowered, and surface charge other than the portion to be erased by exposure is reduced. Defects such as fogging may occur in the image. In particular, when an image is formed using a reversal development process, a toner image is formed in a portion where the surface charge has decreased due to exposure. Therefore, if the surface charge decreases due to a factor other than exposure, the toner adheres to a white background and becomes minute. There is a possibility that fogging of an image called a black spot where black spots are formed may cause deterioration of image quality. That is, due to defects in the support or the photosensitive layer, the chargeability in a minute region is reduced, and image fogging such as black spots occurs, resulting in an image defect.

  By providing the undercoat layer, it is possible to prevent the charge from being injected from the support to the photosensitive layer as described above. Therefore, it is possible to prevent the chargeability of the photosensitive layer from being lowered, and other than the portion that should be erased by exposure. It is possible to suppress the reduction of the surface charge and prevent the occurrence of defects such as fogging on the image. In addition, since a uniform surface can be obtained by covering defects on the support surface, the film-forming property of the photosensitive layer can be improved, and the adhesion of the photosensitive layer to the support can be suppressed by suppressing the peeling of the photosensitive layer from the support. Can be improved.

  Examples of the undercoat layer include resin layers or alumite layers made of various resin materials. The resin material that forms the resin layer is polyethylene resin, polypropylene resin, polystyrene resin, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyurethane resin, epoxy resin, polyester resin, melamine resin, polycarbonate resin, polyester carbonate resin, polysulfone. Resins, phenoxy resins, polyarylate resins, silicone resins, polyvinyl butyral resins, polyamide resins and the like, copolymer resins containing two or more repeating units constituting these resins, casein, gelatin, polyvinyl alcohol, Examples thereof include ethyl cellulose.

  Among these, in particular, hydrophobic binders such as polycarbonate resin, polyarylate resin, polymethyl methacrylate resin, polystyrene resin, aromatic polyester resin, polyester carbonate resin, phenoxy resin, polyethylene resin, ABS resin, and polyvinyl chloride resin are used. By using it as an undercoat layer, it is possible to provide an undercoat layer that has a low water absorption rate and hardly changes in electrical characteristics due to humidity. Therefore, an electrophotographic photoreceptor having high environmental stability can be provided.

  The undercoat layer may contain particles such as a metal oxide. By containing these particles, the volume resistance value of the undercoat layer can be adjusted, and the injection of charges from the support to the photosensitive layer can be further suppressed, and the electrical characteristics of the electrophotographic photosensitive member can be improved in various environments. Can be maintained. Examples of the metal oxide particles include titanium oxide, aluminum oxide, aluminum hydroxide, and tin oxide particles. When particles such as metal oxide are contained in the undercoat layer, for example, a coating solution for forming the undercoat layer is prepared by dispersing these particles in a resin solution in which the above resin is dissolved. An undercoat layer can be formed by applying the liquid on a support.

  As the solvent for the resin solution, in addition to the organic solvent, alcohols such as water, methanol, ethanol and butanol, and glyme series such as methyl carbitol and butyl carbitol can be used. Moreover, the mixed solvent which mixed 2 or more types of these solvents can also be used.

  As a method for dispersing the metal oxide particles in the resin solution, a general method using a ball mill, a sand mill, an attritor, a vibration mill, an ultrasonic disperser, or the like can be used.

  When the weight of the total content of the resin and the metal oxide in the coating solution for forming the undercoat layer is C and the weight of the content of the solvent in the coating solution for forming the undercoat layer is D, The ratio (C / D) is preferably 1/99 to 40/60 (= 0.01 to 0.67), more preferably 2/98 to 30/70 (= 0.02 to 0.43). ).

  The ratio (E / F) of the resin content (weight E) and the metal oxide content (weight F) in the coating solution for forming the undercoat layer is 1/99 to 90/10 (= 0.01). To 9.0), more preferably 5/95 to 70/30 (= 0.05 to 2.33).

  The thickness of the undercoat layer is preferably 0.01 μm or more and 20 μm or less, more preferably 0.1 μm or more and 10 μm or less. If the thickness of the undercoat layer is less than 0.01 μm, the undercoat layer substantially does not function as an undercoat layer, and a uniform surface cannot be obtained by covering defects of the support, and from the support to the photosensitive layer. Since charge injection cannot be prevented, the chargeability of the photosensitive layer is reduced. If the thickness of the undercoat layer is larger than 20 μm, it is difficult to form the undercoat layer uniformly, and the sensitivity of the electrophotographic photosensitive member is lowered, which is not preferable.

  A surface protective layer may be provided on the outer periphery of the photosensitive layer. By providing the surface protective layer, the wear resistance life of the electrophotographic photosensitive member can be improved, and chemicals for the photosensitive layer such as ozone and NOx generated by corona discharge when charging the surface of the electrophotographic photosensitive member. Adverse effects can be prevented.

  As the surface protective layer, for example, a layer made of a curable resin, an inorganic filler-containing resin, an inorganic oxide, or the like is used. When the surface protective layer is formed on the outer periphery of the photosensitive layer, the antioxidant and / or the light stabilizer may be contained in either the photosensitive layer or the protective layer, or may be contained in both layers. Good. When the surface protective layer forming material and the photosensitive layer forming material are soluble in the same solvent, the surface protective layer formed as a layer farther from the support is applied and formed on the photosensitive layer by a roll coating method. .

  Next, FIG. 3 is a side arrangement diagram showing a simplified configuration of an image forming apparatus 20 according to another embodiment of the present invention. The image forming apparatus 20 includes an electrophotographic photosensitive member 21 manufactured by the manufacturing method of the present invention described above. With reference to FIG. 3, an image forming apparatus 20 according to another embodiment of the present invention will be described. Note that the image forming apparatus of the present invention is not limited to the following description.

  The image forming apparatus 20 is an electrophotographic photosensitive member 21 manufactured by the manufacturing method of the present invention, and is an electrophotographic photosensitive member 21 rotatably supported by an apparatus main body (not shown), a charger 24, and an exposure unit. 28, a developing unit 25, a transfer unit 26, a cleaner 27, and a fixing unit 30.

  The electrophotographic photosensitive member 21 is rotationally driven around the rotation axis 22 in the direction of the arrow 23 by a driving unit (not shown). The drive means includes, for example, an electric motor and a reduction gear, and rotates the electrophotographic photosensitive member 21 at a predetermined peripheral speed by transmitting the driving force to a support that forms the core of the electrophotographic photosensitive member 21. Drive. The charger 24, the exposure unit 28, the developing unit 25, the transfer unit 26, and the cleaner 27 are arranged along the outer peripheral surface of the electrophotographic photosensitive member 21 from the upstream side in the rotation direction of the electrophotographic photosensitive member 21 indicated by an arrow 23. They are provided in this order toward the downstream side.

  The charger 24 is a charging unit that charges the outer peripheral surface of the electrophotographic photosensitive member 21 to a predetermined potential. In the present embodiment, the charger 24 is realized by a contact-type charging roller 24a and a bias power source 24a that applies a voltage to the charging roller 24a.

  The exposure unit 28 includes, for example, a semiconductor laser as a light source, and is charged by irradiating light 28 a such as a laser beam output from the light source between the charger 24 and the developing unit 25 of the electrophotographic photosensitive member 21. The outer peripheral surface of the electrophotographic photosensitive member 21 is exposed according to image information. The light 28a is repeatedly scanned in the main scanning direction in the direction in which the rotation axis 22 of the electrophotographic photosensitive member 21 extends, and accordingly, electrostatic latent images are sequentially formed on the surface of the electrophotographic photosensitive member 21.

  The developing unit 25 is a developing unit that develops an electrostatic latent image formed on the surface of the electrophotographic photosensitive member 21 by exposure with a developer, and is provided facing the electrophotographic photosensitive member 21. A developing roller 25a that supplies toner to the outer peripheral surface of the electrophotographic photosensitive member, and the developing roller 25a is rotatably supported around a rotation axis parallel to the rotation axis 22 of the electrophotographic photosensitive member 21, and a developer containing toner is accommodated in the internal space. Casing 25b.

  The transfer unit 26 transfers a toner image, which is a visible image formed on the outer peripheral surface of the electrophotographic photosensitive member 21 by development, between the electrophotographic photosensitive member 21 and the transfer unit 26 from the direction of the arrow 29 by a conveying unit (not shown). Transfer means for transferring onto a transfer paper 30 as a recording medium supplied to the printer. The transfer device 26 is, for example, a non-contact type transfer unit that includes a charging unit and transfers a toner image onto the transfer paper 30 by applying a charge having a polarity opposite to that of the toner to the transfer paper 30.

  The cleaner 27 is a cleaning unit that removes and collects toner remaining on the outer peripheral surface of the electrophotographic photosensitive member 21 after the transfer operation by the transfer device 26, and removes the toner remaining on the outer peripheral surface of the electrophotographic photosensitive member 21. 27a and a recovery casing 27b for storing the toner separated by the cleaning blade 27a. The cleaner 27 is provided together with a charge eliminating lamp (not shown).

  Further, the image forming apparatus 20 includes a fixing device 31 as fixing means for fixing the transferred image on the downstream side where the transfer paper 30 that has passed between the electrophotographic photosensitive member 21 and the transfer device 26 is conveyed. Provided. The fixing device 31 includes a heating roller 31a having a heating unit (not shown), and a pressure roller 31b that is provided to face the heating roller 31a and is pressed by the heating roller 31a to form a contact portion.

  The image forming operation by the image forming apparatus 20 is performed as follows. First, when the electrophotographic photosensitive member 21 is rotationally driven in the direction of the arrow 23 by the driving unit, the charger 24 provided on the upstream side in the rotational direction of the electrophotographic photosensitive member 21 with respect to the imaging point of the light 28a by the exposure unit 28. As a result, the surface of the electrophotographic photosensitive member 21 is uniformly charged to a predetermined positive or negative potential.

  Next, light 28 a corresponding to image information is irradiated from the exposure unit 28 to the surface of the electrophotographic photosensitive member 21. By this exposure, the surface charge of the part irradiated with the light 28a is removed from the electrophotographic photosensitive member 21, and the surface potential of the part irradiated with the light 28a is different from the surface potential of the part not irradiated with the light 28a. And an electrostatic latent image is formed.

  Toner is supplied to the surface of the electrophotographic photosensitive member 21 on which the electrostatic latent image is formed from a developing unit 25 provided downstream of the image forming point of the light 28a by the exposure means 28 in the rotation direction of the electrophotographic photosensitive member 21. The electrostatic latent image is developed to form a toner image.

  In synchronization with the exposure of the electrophotographic photosensitive member 21, the transfer paper 30 is supplied between the electrophotographic photosensitive member 21 and the transfer unit 26. The transfer device 26 applies a charge having a polarity opposite to that of the toner to the supplied transfer paper 30, and the toner image formed on the surface of the electrophotographic photosensitive member 21 is transferred onto the transfer paper 30.

  The transfer paper 30 onto which the toner image has been transferred is conveyed to a fixing device 31 by a conveying means, and is heated and pressurized when passing through a contact portion between a heating roller 31a and a pressure roller 31b of the fixing device 31, and toner The image is fixed on the transfer paper 30 and becomes a robust image. The transfer paper 30 on which the image is formed in this way is discharged to the outside of the image forming apparatus 20 by the conveying means.

  On the other hand, the toner remaining on the surface of the electrophotographic photosensitive member 21 even after the transfer of the toner image by the transfer device 26 is separated from the surface of the electrophotographic photosensitive member 21 by the cleaner 27 and collected. The charge on the surface of the electrophotographic photosensitive member 21 from which the toner has been removed in this manner is removed by the light from the static elimination lamp, and the electrostatic latent image on the surface of the electrophotographic photosensitive member 21 disappears. Thereafter, the electrophotographic photosensitive member 21 is further rotationally driven, and a series of operations starting from charging is repeated to continuously form images.

  Examples of the present invention will be described below. The present invention is not limited to these examples.

(Test 1)
In Test 1, the electrophotographic photoreceptors of Examples 1 and 2 of the present invention and the electrophotographic photoreceptors of Comparative Examples 1 to 3 deviating from the present invention were produced, and the film formability during the production of the electrophotographic photoreceptor, The produced electrophotographic photosensitive member was evaluated for the environmental stability of the electrical characteristics and the quality of the image formed by being mounted on the image forming apparatus.

Example 1
An aluminum cylindrical conductive support having a diameter of 30 mm and a total length of 340 mm was prepared, and each coating solution was applied on the support using the coating apparatus shown in FIG. 2 to form each layer.

a: Undercoating layer Dendritic titanium oxide (Ishihara Sangyo Co., Ltd .: TTO-D-1) 10 wt. surface treated with aluminum oxide (chemical formula: Al ₂ O ₃ ) and zirconium dioxide (chemical formula: ZrO ₂ ) Part, 10 parts by weight of polycardate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z200) and 90 parts by weight of cyclohexanone are dispersed for 12 hours using a paint shaker, and are used for forming an undercoat layer. Was prepared.
This undercoat layer forming coating solution was applied onto a support by a roll coating method. The application conditions were as follows. Each roll has a peripheral speed of 6 m / min, and the peripheral speed of the support when separating the coating roll and the support is 9 m / min (that is, the peripheral speed during separation and after separation / peripheral speed before separation = 1) 5), and the separation speed of the support with respect to the coating roll was adjusted to 50 mm / sec. The gap between the metering rolls was 80 μm.
First, while rotating all the rolls of the coating apparatus, the coating liquid for forming the undercoat layer contained in the pan was supplied to the metering roll to form a coating film having a uniform thickness on the outer peripheral surface thereof. Thereafter, the coating roll was transferred by bringing the metering roll into contact with the rotating coating roll. Next, coating was started by contacting the coating roll while rotating the support. The application was performed until the support was rotated twice, and when the support was rotated twice, the coating roll and the support were separated. In the separated state, the rotation of the support was continued for 2 minutes to form an undercoat layer coating film.

b: Charge generation layer As an oxotitanium phthalocyanine which is a charge generation material, at least a Bragg angle (2θ ± 0.2 °) of 27.2 ° in an X-ray diffraction spectrum by Cu-Kα characteristic X-ray (wavelength: 1.54Å) 4 parts by weight of oxotitanium phthalocyanine having a crystal structure showing a clear diffraction peak, 4 parts by weight of polyvinyl butyral resin (Sekisui Chemical Co., Ltd .: ESREC BM-S), and 92 parts by weight of cyclohexanone are mixed and painted A coating solution for forming a charge generation layer was prepared by dispersing for 10 hours with a shaker.
This charge generation layer coating solution was applied onto the previously formed undercoat layer by a roll coating method. Each roll has a peripheral speed of 4 m / min, and the peripheral speed of the support when separating the coating roll and the support is 6 m / min (peripheral speed during and after separation / peripheral speed before separation = 1.5). And the separation speed of the support relative to the coating roll was adjusted to 50 mm / sec. The gap between the metering rolls was 30 μm.
The application was performed in the same manner as in the case of forming the undercoat layer, and after transferring twice to the support, the coating roll and the support were separated. In the separated state, the rotation of the support was continued for 1 minute to form a charge generation layer coating film.

c: Charge transport layer A triphenylamine dimer represented by the following structural formula (I) which is a charge transport material (
Triphenylamine dimer (abbreviation: TPD) 10 parts by weight, polycarbonate resin as a binder resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z200) 18 parts by weight, 2,6-di-t-butyl-4-methylphenol ( BHT) 0.1 part by weight was dissolved in 100 parts by weight of cyclohexanone to prepare a charge transport layer forming coating solution. The obtained charge transport layer forming coating solution was applied onto the previously formed charge generation layer by a roll coating method.
Each roll has a peripheral speed of 20 m / min, and the peripheral speed of the support when separating the coating roll and the support is 34 m / min (peripheral speed during and after separation / peripheral speed before separation = 1.7). And the separation speed of the support relative to the coating roll was adjusted to 50 mm / sec. The gap between the metering rolls was 300 μm.
The coating was performed in the same manner as in the case of forming the undercoat layer and the charge generation layer. After three transfer onto the support, the coating roll and the support were separated. In the separated state, the rotation of the support was continued for 2 minutes and then dried at 130 ° C. for 1 hour to form a charge transport layer having a thickness of 20 μm.
As described above, the electrophotographic photosensitive member of Example 1 was produced.

(Example 2)
An electrophotographic photoreceptor of Example 2 was produced in the same manner as in Example 1 except that the polycarbonate resin in the undercoat layer forming coating solution was replaced with a polyphenylene oxide resin (Union Carbide, PKHH). .

(Comparative Example 1)
The undercoat layer is composed of 21 parts by weight of titanium oxide (Ishihara Sangyo Co., Ltd .: TTO55A) and 39 parts by weight of a copolymer nylon resin (Toray Industries, Inc .: Amilan CM8000), 329 parts by weight of methanol and 1,4-dioxolane 611. In addition to the mixed solvent with parts by weight, a coating solution for forming an undercoat layer that was dispersed for 8 hours using a paint shaker was used, and the same as in Example 1 except that it was formed by a dip coating method. An electrophotographic photosensitive member was produced.

(Comparative Example 2)
a: Undercoat layer An undercoat layer was formed on the support in the same manner as in Example 1.

b: Charge generation layer As a charge generation layer forming coating solution, at least a Bragg angle 2θ (error: 2θ ± 0.2 °) in an X-ray diffraction spectrum for Cu-Kα characteristic X-rays (wavelength: 1.54 mm) 2 parts by weight of oxotitanium phthalocyanine having a crystal structure showing a clear diffraction peak at 2 °, 1 part by weight of polyvinyl butyral resin (manufactured by Sekisui Chemical Co., Ltd .: ESREC BM-S), and 97 parts by weight of THF are mixed, A charge generating layer forming coating solution was prepared by dispersing with a paint shaker.
Using this charge generation layer forming coating solution, an attempt was made to apply and form a charge generation layer on a support on which an undercoat layer was formed by a dip coating method. However, when the support is immersed in the charge generation layer forming coating solution and pulled up, the subbing layer is eluted with the solvent of the charge generation layer formation coating solution, and the substrate of the support is exposed to a considerable extent. An electrophotographic photosensitive member could not be prepared due to a coating defect.

(Comparative Example 3)
a: Undercoat layer An undercoat layer was formed on the support in the same manner as in Example 1.

b: Charge generation layer A charge generation layer forming coating solution having the same composition as in Example 1 was prepared, and the charge generation layer forming coating solution was applied by spray coating on the support on which the undercoat layer was formed. Applied. The support was attached to a spray coating apparatus, and the charge generation layer was formed by spray coating a coating solution for forming a charge generation layer on the rotated support.

c: Charge transport layer On the charge generation layer, a charge transport layer forming coating solution having the same composition as in Example 1 was applied by a roll coating method to form a charge transport layer. Produced.

(Evaluation 1)
For each of the electrophotographic photosensitive members of Examples 1 and 2 and Comparative Examples 1 and 3, the following three conditions differing in environmental temperature and humidity: Temperature / humidity: 5 ° C./20%, 25 ° C./50%, Light having a wavelength of 780 nm (1.0 μJ) obtained by corona discharge at −6.5 kV by a scorotron method using a test apparatus CYNTHIA56SN manufactured by Gentec Co., Ltd. at 35 ° C./80%, and by spectroscopy with a monochromator. / Cm ² ), the surface potential VL of the electrophotographic photosensitive member after 80 msec was measured. The charge retention rate was measured by measuring the surface potential V _0.5 when the electrophotographic photosensitive member was charged by a scorotron method so that the surface potential at the time of non-exposure was −600 V, and held for 0.5 seconds in a dark place, It calculated by the following formula (2).
Charge retention (%) = V _0.5 / (− 600) × 100 (2)

  Each electrophotographic photosensitive member is mounted on a laser printer (manufactured by Sharp Corporation: DM-4501), and a halftone image is formed on A3-size plain paper defined in Japanese Industrial Standard (JIS) P0138. did. Here, the halftone image is an image in which gradation of the image is expressed by gradation using black and white dots. The obtained images were visually observed, and image defects and image quality were evaluated as the presence or absence of image unevenness. The evaluation results are shown in Table 1.

  Focusing on the undercoat layer and the charge generation layer as two layers formed in contact with each other that are soluble in the same solvent, the charge generation layer, which is the upper layer, was applied and formed by roll coating. Although the film formability of the electrophotographic photosensitive member was good, in Comparative Example 2 in which the charge generation layer was formed by dip coating, the undercoat layer, which is the lower layer, was dissolved, and two layers were formed. In Comparative Example 3 in which the charge generation layer was applied and formed by the spray coating method, coating defects were generated in the undercoat layer, and uneven coating was observed. Therefore, although the image quality of the halftone image formed by mounting the electrophotographic photosensitive member of Examples 1 and 2 on a laser printer was good, the image formed by mounting the electrophotographic photosensitive member of Comparative Example 3 Image unevenness was observed.

  In the electrophotographic photoreceptors of Examples 1 and 2 in which the undercoat layer containing a hydrophobic binder was formed, three environmental conditions of 5 ° C./20%, 25 ° C./50%, and 35 ° C./80% were used. In contrast, in the electrophotographic photoreceptor of Comparative Example 1 in which the undercoat layer containing a hydrophilic binder was formed, the VL and the charge retention were both substantially the same, but the environmental condition of 25 ° C./50% However, under the environmental conditions of 5 ° C./20% and 35 ° C./80%, both VL and the charge retention rate are poor, and the temperature and humidity dependency. Therefore, it was confirmed that the environmental stability is increased by using a hydrophobic binder for the undercoat layer.

(Test 2)
In Test 2, the electrophotographic photoreceptors of Examples 3 and 4 of the present invention and the electrophotographic photoreceptors of Comparative Examples 4 to 6 that deviate from the present invention were prepared. The produced electrophotographic photosensitive member was evaluated for electric characteristics and quality of an image formed by being mounted on an image forming apparatus.

(Example 3)
A cylindrical conductive support made of aluminum having a diameter of 40 mm and a total length of 340 mm was prepared, and each layer was applied and formed as follows.

a: Undercoat layer Titanium oxide (Ishihara Sangyo Co., Ltd .: TTO55A) 21 parts by weight and copolymer nylon resin (Toray Industries, Inc .: Amilan CM8000) 39 parts by weight, methanol 329 parts by weight and 1,4-dioxolane 611 In addition to the mixed solvent with parts by weight, an undercoat layer-forming coating solution was prepared by dispersing for 8 hours using a paint shaker. An undercoat layer having a thickness of 1.0 μm was formed by a dip coating method in which the coating liquid for forming the undercoat layer was filled in a coating tank and the support was immersed in the coating tank and then pulled up.

b: Charge generation layer As oxotitanium phthalocyanine, a clear diffraction peak is shown at least at a Bragg angle (2θ ± 0.2 °) of 27.2 ° in an X-ray diffraction spectrum by Cu-Kα characteristic X-ray (wavelength: 1.54Å) 2 parts by weight of oxotitanium phthalocyanine having a crystal structure, 1 part by weight of polyvinyl butyral resin (manufactured by Sekisui Chemical Co., Ltd .: ESREC BM-S) and 97 parts by weight of methyl ethyl ketone are mixed and dispersed with a paint shaker. Thus, a charge generation layer forming coating solution was prepared. By applying this coating solution for forming a charge generation layer on the undercoat layer by the same dip coating method as that for the undercoat layer, a charge generation layer having a thickness of 0.4 μm was formed on the undercoat layer. .

c1: First charge transport layer 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and 10 parts by weight of polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) as a binder resin 0.1 parts by weight of 2,6-di-t-butyl-4-methylphenol (BHT) was dissolved in 60 parts by weight of cyclohexanone to prepare a coating solution for forming a first charge transport layer. The obtained coating solution for forming the first charge transport layer was applied on the charge generation layer by a roll coating method.
Each roll has a peripheral speed of 20 m / min, and the peripheral speed of the support when separating the coating roll and the support is 34 m / min (peripheral speed during and after separation / peripheral speed before separation = 1.7). And the separation speed of the support relative to the coating roll was adjusted to 50 mm / sec. The gap between the metering rolls was 200 μm.
The coating was transferred twice to the support, and then the coating roll and the support were separated. In the separated state, the rotation of the support was continued for 2 minutes and then dried at 130 ° C. for 1 hour to form a first charge transport layer having a thickness of 15 μm.

c2: Second charge transport layer 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and 30 parts by weight of a polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) as a binder resin A second charge transport layer forming coating solution was prepared by dissolving 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol (BHT) in 160 parts by weight of cyclohexanone. The obtained coating liquid for forming a second charge transport layer was applied on the first charge transport layer by a roll coating method.
Each roll has a peripheral speed of 20 m / min, and the peripheral speed of the support when separating the coating roll and the support is 34 m / min (peripheral speed during and after separation / peripheral speed before separation = 1.7). And the separation speed of the support relative to the coating roll was adjusted to 50 mm / sec. The gap between the metering rolls was 150 μm.
The coating was transferred twice to the support, and then the coating roll and the support were separated. In the separated state, the rotation of the support was continued for 2 minutes, and then dried at 130 ° C. for 1 hour to form a second charge transport layer having a thickness of 10 μm. Therefore, the film thickness of the entire charge transport layer, which is the sum of the film thickness of the first charge transport layer and the film thickness of the second charge transport layer, was 25 μm.
As described above, the electrophotographic photosensitive member of Example 3 was produced.

Example 4
In coating and forming the second charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 40 as a binder resin are used. A coating solution for forming a second charge transport layer in which 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol (BHT) was dissolved in 210 parts by weight of cyclohexanone was used. An electrophotographic photosensitive member of Example 4 was produced in the same manner as Example 3 except for the above.

(Comparative Example 4)
In the same manner as in Example 3, an undercoat layer, a charge generation layer, and a first charge transport layer were formed.

c2: Second charge transport layer 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and 30 parts by weight of a polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) as a binder resin 2,6-di-t-butyl-4-methylphenol (BHT) 0.1 part by weight and dimethylpolysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd .: KF-96) 0.006 part by weight, THF 200 weight A coating solution for forming a second charge transport layer dissolved in the part was prepared.
It tried to apply | coat this coating liquid for 2nd charge transport layer formation on a 1st charge transport layer by the dip coating method. However, when the film thickness of the entire charge transport layer was measured after drying, only a very thin coating film of 12 μm was obtained. This is because when the support formed up to the first charge transport layer was immersed in the second charge transport layer forming coating solution, the first charge transport layer was eluted with the solvent of the second charge transport layer forming coating solution. It is thought that. Therefore, after dissolving the entire charge transport layer with acetone, the soluble part is concentrated, and the weight composition ratio (B / A) of the binder resin (B) and the charge transport material (A) is measured by ¹ H-NMR. As a result, the ratio (B / A) was 29/10 (= 2.9), and it was confirmed that most of the first charge transport layer was dissolved. From this, it is impossible to apply and form the second charge transport layer, which is the upper layer, of the first and second charge transport layers that are soluble in the same solvent and in contact with each other by the dip coating method. I found out that

(Comparative Example 5)
In the same manner as in Example 3, an undercoat layer, a charge generation layer, and a first charge transport layer were formed.
c2: Second charge transport layer 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and 30 parts by weight of a polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) as a binder resin A coating solution for forming a second charge transport layer was prepared by dissolving 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol (BHT) in 500 parts by weight of cyclohexanone and 200 parts by weight of THF. did. Using this second charge transport layer forming coating solution, an attempt was made to coat and form the second charge transport layer on the first charge transport layer by spray coating.
The support formed up to the first charge transport layer is attached to a spray coating apparatus, the second charge transport layer forming coating solution is spray coated while rotating the support, and dried at 130 ° C. for 2 hours after coating. Thus, an electrophotographic photosensitive member having a thickness of the entire charge transport layer of 25 μm was obtained.
As described above, an electrophotographic photosensitive member of Comparative Example 5 was produced.

(Comparative Example 6)
In the same manner as in Example 3, an undercoat layer and a charge generation layer were formed.
c: Charge transport layer 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material, 16 parts by weight of polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) as a binder resin, 2 , 6-di-t-butyl-4-methylphenol (BHT) 0.1 part by weight and dimethylpolysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd .: KF-96) 0.006 part by weight in THF 95 parts by weight A dissolved charge transport layer forming coating solution was prepared. A charge transport layer having a film thickness of 25 μm is formed by a dip coating method in which the coating liquid for forming the charge transport layer is filled in a coating tank and the support formed up to the charge generation layer is immersed in the coating liquid for forming the charge transport layer. An electrophotographic photosensitive member of Comparative Example 6 consisting of 1 layer was prepared.

(Evaluation 2)
For each of the electrophotographic photosensitive members of Examples 3 and 4 and Comparative Examples 4 to 6 described above, using a test apparatus CYNTHIA56SN manufactured by Gentec Co., Ltd. under the environment of temperature / humidity: 5 ° C./20%, by scorotron method The surface potential VL of the electrophotographic photosensitive member after 80 msec was measured after exposure with light having a wavelength of 780 nm (1.0 μJ / cm ² ) obtained by corona discharge at −6.5 kV and spectroscopy with a monochromator. . Further, the surface of the charged electrophotographic photosensitive member is exposed, and the energy (half exposure amount E _1/2) required to halve the surface potential from the surface potential V _{0 of the} electrophotographic photosensitive member at this time. (ΜJ / cm ² )) was also measured.

  Each electrophotographic photosensitive member was mounted on a laser printer (manufactured by Sharp Corporation: DM-4501), and a halftone image was formed on A3-size plain paper defined in JIS-P0138. The obtained halftone image was visually observed, and image defects and image quality were evaluated as the presence or absence of image unevenness. The evaluation results are shown in Table 2.

  Focusing on the first charge transport layer and the second charge transport layer as two layers formed in contact with each other that are soluble in the same solvent, the second charge transport layer, which is the upper layer, was formed by coating by a roll coating method. In the electrophotographic photoreceptors of Examples 3 and 4, the film formability was good, and the image formed by being mounted on the laser printer was good with no image unevenness.

  On the other hand, in Comparative Example 4 in which the second charge transporting layer, which is the upper layer, was applied and formed by a dip coating method, two layers could not be formed. Further, in Comparative Example 5 in which the second charge transport layer was formed by spray coating, dissolution peeling or the like occurred in the first charge transport layer, which is the lower layer, resulting in uneven coating in the two-layer formation, and laser Image unevenness was observed in the image formed on the printer.

Further, from the comparison of VL and E1 _{/ 2} in Example 4 and Comparative Example 6, even if two charge transport layers are applied by the roll coating method, one layer is used by the dip coating method currently most widely used. It was confirmed that almost the same electrical characteristics as those obtained when the charge transport layer was applied were obtained.

(Test 3)
In Test 3, the electrophotographic photosensitive members of Examples 3 to 6 of the present invention (Examples 3 and 4 were prepared in the previous Test 2) and the electrophotographic photosensitive members of Comparative Examples 6 to 9 that deviate from the present invention. (Comparative Example 6 was produced in the previous test 2), and the electrophotographic photoreceptor thus produced had electrical characteristics, mobility, and film loss when the image was formed on an image forming apparatus. Evaluated.

(Example 5)
In coating and forming the second charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 60 as a binder resin are used. A coating solution for forming a second charge transport layer in which 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol (BHT) was dissolved in 260 parts by weight of cyclohexanone was used. An electrophotographic photoreceptor of Example 5 was produced in the same manner as Example 3 except for the above.

(Example 6)
In coating and forming the second charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 20 as a binder resin are used. A coating solution for forming a second charge transport layer in which 110 parts by weight of cyclohexanone and 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol (BHT) were dissolved was used. An electrophotographic photoreceptor of Example 6 was produced in the same manner as Example 3 except for the above.

(Comparative Example 7)
In coating and forming the second charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 65 as a binder resin are used. A coating solution for forming a second charge transport layer in which 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol (BHT) was dissolved in 280 parts by weight of cyclohexanone was used. An electrophotographic photoreceptor of Comparative Example 7 was produced in the same manner as Example 3 except for the above.

(Comparative Example 8)
When coating and forming the first charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin as a binder resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 10 Using a coating solution for forming a first charge transport layer in which 60 parts by weight of cyclohexanone and 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol (BHT) are dissolved, In coating and forming the second charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and a polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 18 as a binder resin are used. Parts by weight and 0.1 part by weight of 2,6-di-tert-butyl-4-methylphenol (BHT) Except for using a second charge transport layer coating solution obtained by dissolving the emissions 115 parts by weight, an electrophotographic photoreceptor was prepared in Comparative Example 8 in the same manner as in Example 3.

(Comparative Example 9)
In coating and forming the first charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin as a binder resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 16 Using a coating solution for forming a first charge transport layer in which parts by weight and 0.1 parts by weight of 2,6-di-t-butyl-4-methylphenol (BHT) are dissolved in 85 parts by weight of cyclohexanone, In coating and forming the second charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 60 as a binder resin are used. Parts by weight and 0.1 part by weight of 2,6-di-tert-butyl-4-methylphenol (BHT) Except for using a second charge transport layer coating solution obtained by dissolving the emissions 260 parts by weight, an electrophotographic photoreceptor was prepared in Comparative Example 9 in the same manner as in Example 3.

(Evaluation 3)
For each of the electrophotographic photoreceptors of Examples 3 to 6 and Comparative Examples 6 to 9, using the X-TOF measurement mode of the test apparatus CYNTHIA56SN manufactured by Gentec Corporation, the environmental temperature is 5 ° C., and the electric field strength is 2 The hole mobility of the entire charge transport layer at 5 × 10 ⁵ V / cm was measured.

  Each electrophotographic photosensitive member is mounted on a laser printer (manufactured by Sharp Corporation: DM-4501), and after 10,000 images are formed, an undercoat layer and a photosensitive layer formed on the support. The difference between the film thickness d0 and the film thickness d0 before the image formation by forming the electrophotographic photosensitive member and mounting it on the laser printer is defined as a film reduction amount Δd (= d0−d1). The printing durability was evaluated. The smaller the film reduction amount Δd, the better the printing durability.

Furthermore, a surface potential meter (Gentec Corporation: CATE751) is provided inside the body of the laser printer so as to measure the surface potential of the photoconductor in the image forming process, and 35 ° C / 80% RH, 5 ° C / 20% RH. In this environment, a charging potential V ₀ (V), which is a surface potential immediately after charging, and a surface potential VL (V) immediately after exposure by laser light were measured. The surface of the electrophotographic photosensitive member was charged by a negative charging process. The evaluation results are shown in Table 3.

As shown in Table 3, the charge transport layer is composed of two layers, the content ratio of the binder resin in the second charge transport layer, which is the upper layer, is increased, and the content of the charge generation material in the entire charge transport layer is within an appropriate range. As a result, it was found that the responsiveness in a low temperature environment can be secured and the amount of film loss can be greatly suppressed. However, when the B / A of the lower first charge transport layer is 1.6 and the concentration of the charge transport material is too low, the mobility of the entire charge transport layer is relatively 1.0 × 10 ⁻⁶ cm ^2. / Vs, and as a result, the VL increased at a low temperature, and it was at a level that could produce an image.

  Furthermore, when the weight ratio (B / A) of the charge transport material (A) to the binder resin (B) in the second charge transport layer was less than 2.0, the amount of film reduction increased. On the other hand, when the weight ratio (B / A) exceeded 6.0, the mobility rapidly decreased. This is thought to be because the charge transport material concentration in the charge transport layer became too low, and the intermolecular distance of the charge transport material was increased, making it difficult for hopping conduction of holes to occur.

(Test 4)
In Test 4, the electrophotographic photoreceptors of Examples 7 to 10 of the present invention and the electrophotographic photoreceptors of Comparative Examples 10 and 11 deviating from the present invention were produced, and the durability of the produced electrophotographic photoreceptors was evaluated. .

(Example 7)
In coating and forming the first charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin as a binder resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 16 Using a coating solution for forming a first charge transport layer in which parts by weight and 0.01 parts by weight of 2,6-di-t-butyl-4-methylphenol (BHT) are dissolved in 85 parts by weight of cyclohexanone, In coating and forming the second charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 30 as a binder resin are used. Parts by weight of cyclohexanone with 0.5 parts by weight of 2,6-di-tert-butyl-4-methylphenol (BHT). It excepts for using a second charge transport layer coating solution obtained by dissolving the non-160 parts by weight, the produced electrophotographic photosensitive member of Example 7 in the same manner as in Example 3. In addition, the density | concentration of antioxidant with respect to the whole charge transport layer in Example 7 was 0.52 weight%.

(Example 8)
When coating and forming the first charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin as a binder resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 10 The first charge transport layer forming coating solution in which 60 parts by weight of cyclohexanone is dissolved in the weight part is used to form the second charge transport layer and is represented by the structural formula (I) as a charge transport material. 10 parts by weight of TPD, 30 parts by weight of polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) as binder resin, 0.5 of 2,6-di-t-butyl-4-methylphenol (BHT) Except for using the coating solution for forming the second charge transport layer in which 160 parts by weight of cyclohexanone was dissolved in parts by weight, In the same manner as in Example 3, an electrophotographic photoreceptor of Example 8 was produced. In addition, the density | concentration of the antioxidant with respect to the whole charge transport layer in Example 8 was 0.52 weight%.

Example 9
In coating and forming the first charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin as a binder resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 16 Using a coating solution for forming a first charge transport layer in which parts by weight and 0.01 parts by weight of 2,6-di-t-butyl-4-methylphenol (BHT) are dissolved in 85 parts by weight of cyclohexanone, In coating and forming the second charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 30 as a binder resin are used. 160 parts by weight of cyclohexanone and 0.2 parts by weight of SANOL LS-2626 (manufactured by Sankyo Corporation) An electrophotographic photosensitive member of Example 9 was produced in the same manner as in Example 3 except that the coating solution for forming the second charge transport layer dissolved in an amount was used. The concentration of the antioxidant with respect to the entire charge transport layer in Example 9 was 0.22% by weight.

(Example 10)
In coating and forming the first charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin as a binder resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 16 Using a coating solution for forming a first charge transport layer in which parts by weight and 0.01 parts by weight of 2,6-di-t-butyl-4-methylphenol (BHT) are dissolved in 85 parts by weight of cyclohexanone, In coating and forming the second charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 30 as a binder resin are used. Parts by weight, 0.2 parts by weight of Sumilizer MDP-S (manufactured by Sumitomo Chemical Co., Ltd.), and Sanol LS-77 Example 10 was carried out in the same manner as Example 3 except that 0.1 parts by weight of 0 (manufactured by Sankyo Co., Ltd.) and a coating solution for forming a second charge transport layer dissolved in 160 parts by weight of cyclohexanone were used. An electrophotographic photosensitive member was produced. In addition, the density | concentration of the antioxidant with respect to the whole charge transport layer in Example 10 was 0.32 weight%.

(Comparative Example 10)
In coating and forming the first charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin as a binder resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 16 Using the first charge transport layer forming coating solution prepared by dissolving parts by weight and 0.16 parts by weight of 2,6-di-t-butyl-4-methylphenol (BHT) in 85 parts by weight of cyclohexanone, In coating and forming the second charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 30 as a binder resin are used. Parts by weight and 0.16 parts by weight of 2,6-di-tert-butyl-4-methylphenol (BHT) Except for using a second charge transport layer coating solution prepared by dissolving Sanon 160 parts by weight, an electrophotographic photoreceptor was prepared in Comparative Example 10 in the same manner as in Example 3. In addition, the density | concentration of the antioxidant with respect to the whole charge transport layer in the comparative example 10 was 0.53 weight%.

(Comparative Example 11)
In coating and forming the first charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin as a binder resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 16 Using a coating solution for forming a first charge transport layer in which parts by weight and 0.23 parts by weight of 2,6-di-t-butyl-4-methylphenol (BHT) are dissolved in 85 parts by weight of cyclohexanone, In coating and forming the second charge transport layer, 10 parts by weight of TPD represented by the structural formula (I) as a charge transport material and polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) 30 as a binder resin are used. Parts by weight and 0.01 parts by weight of 2,6-di-tert-butyl-4-methylphenol (BHT) Except for using a second charge transport layer coating solution prepared by dissolving Sanon 160 parts by weight, an electrophotographic photoreceptor was prepared in Comparative Example 11 in the same manner as in Example 3. In addition, the density | concentration of antioxidant with respect to the whole charge transport layer in the comparative example 11 was 0.54 weight%.

(Evaluation 4)
Each of the electrophotographic photosensitive members of Examples 7 to 10 and Comparative Examples 10 and 11 is mounted on a laser printer (manufactured by Sharp Corporation: DM-4501), and the electron in the image forming process is mounted inside the laser printer body. A surface potential meter (Gentec Corporation: CATE751) is provided so that the surface potential of the photographic photosensitive member can be measured, and the surface potential immediately after charging in an environment of 35 ° C./80% RH and 5 ° C./20% RH. The charging potential V ₀ (V) and the surface potential VL (V) immediately after exposure by laser light were measured. This potential measurement was performed both at the initial stage before the image formation and after the image formation of 10,000 sheets, and the stability of the electrical characteristics after the fatigue was evaluated. The surface of the electrophotographic photosensitive member was charged by a negative charging process.

  Further, a halftone image for image quality evaluation was formed at the initial stage and after the image formation of 10,000 sheets, and image defects and image quality were evaluated. The obtained halftone image was visually observed, and the image quality was evaluated according to the degree of image defects such as white spots, black bands, and image blur. The evaluation criteria for image quality were as follows.

A: Good. No image defects.
B: Somewhat bad. There are image defects that can be ignored.
C: Defect. There is an obvious image defect.
The evaluation results are shown in Table 4.

  As shown in Table 4, the charge transport layer is divided into two layers, and the amount of the antioxidant contained in the second charge transport layer as the upper layer is determined by the amount of the antioxidant contained in the first charge transport layer as the lower layer. By increasing the amount, the adverse effect on the electrical characteristics of the electrophotographic photosensitive member can be suppressed to a minimum, and the deterioration of the second charge transport layer, which is the outermost layer with the highest deterioration, can be suppressed to a minimum. Therefore, an electrophotographic photosensitive member having an excellent durability life has been realized.

(Test 5)
In Test 5, the electrophotographic photoreceptors of Examples 11 and 12 of the present invention and the electrophotographic photoreceptors of Comparative Examples 12 and 13 that deviate from the present invention were prepared, and the NO ₂ gas exposure test was conducted to endure the active substance. Performance was evaluated.

(Example 11)
When coating and forming the second charge transport layer, 10 parts by weight of a charge transport material represented by the following structural formula (II) and 30 parts by weight of a polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) as a binder resin; Except for using a coating solution for forming a second charge transport layer in which 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol (BHT) was dissolved in 160 parts by weight of cyclohexanone, In the same manner as in Example 3, an electrophotographic photoreceptor of Example 11 was produced.

(Example 12)
When coating and forming the second charge transport layer, 10 parts by weight of a charge transport material represented by the following structural formula (III) and 16 parts by weight of a polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) as a binder resin; Except for using 0.16 parts by weight of 2,6-di-t-butyl-4-methylphenol (BHT) in 85 parts by weight of cyclohexanone, the second charge transport layer forming coating solution was used. In the same manner as in Example 3, an electrophotographic photoreceptor of Example 12 was produced.

(Comparative Example 12)
When coating and forming the second charge transport layer, 10 parts by weight of a charge transport material represented by the following structural formula (IV) and 30 parts by weight of a polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) as a binder resin; Except for using a coating solution for forming a second charge transport layer in which 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol (BHT) was dissolved in 160 parts by weight of cyclohexanone, The electrophotographic photosensitive member of Comparative Example 12 was produced in the same manner as Example 3.

(Comparative Example 13)
When coating and forming the second charge transport layer, 10 parts by weight of a charge transport material represented by the following structural formula (V) and 16 parts by weight of a polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd .: Iupilon Z300) as a binder resin; Except for using 0.16 parts by weight of 2,6-di-t-butyl-4-methylphenol (BHT) in 85 parts by weight of cyclohexanone, the second charge transport layer forming coating solution was used. The electrophotographic photosensitive member of Comparative Example 13 was produced in the same manner as Example 3.

(Evaluation 5)
For each of the electrophotographic photoreceptors of Examples 11 and 12 and Comparative Examples 12 to 14, the ionization potential of the second charge transport layer was measured by AC-1: manufactured by Riken Keiki Co., Ltd.

Each electrophotographic photoreceptor was subjected to a NO ₂ gas exposure test. Although details of the apparatus are omitted, each electrophotographic photoreceptor was held in an exposure tester and exposed to 100 ppm of NO ₂ gas for 1 hour. Each electrophotographic photosensitive member before and after the exposure test was mounted on a laser printer (manufactured by Sharp Corporation: DM-4501) to form a halftone image. The image obtained after the exposure and the image before the exposure were visually observed to compare the image density.

  Table 5 shows the measured ionization potential value and the image quality evaluation result based on the halftone image. In the electrophotographic photoreceptors of Example 11 and Example 12 in which the ionization potential of the charge transport material is 5.65 eV or more, good images were obtained. On the other hand, in the electrophotographic photoreceptors of Comparative Examples 12 and 13 in which the ionization potential of the charge transport material is less than 5.65 eV, the image density after exposure is lower than the image before exposure. An image defect called “.” That causes the image density to become thin occurs over the entire surface.

  As described above, it was found that by setting the ionization potential of the charge transport material in the charge transport layer to 5.65 eV or more, image defects caused by active materials such as ozone and NOx generated during charging can be effectively prevented. .

It is a schematic diagram which shows the structure of the coating apparatus 1 of the roll coating system used suitably for implementation of this invention. It is a schematic diagram which shows the structure of the coating apparatus 10 of another roll coating system used suitably for implementation of this invention. FIG. 6 is a side view schematically showing a configuration of an image forming apparatus 20 according to another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,10 Coating apparatus 2 Support body 3 Coating liquid 4 Coating roll 5,11 Coating liquid supply means 6 Scraping roll 7 Cleaning blade 12 Pan 13 1st metering roll 14 2nd metering roll 20 Image forming apparatus 21 Electron Photoconductor

Claims (10)

Manufactures an electrophotographic photosensitive member having a support made of a conductive material and a plurality of layers formed on the support, and forming an electrostatic latent image when exposed to light according to image information. In the method for producing an electrophotographic photoreceptor,
The plurality of layers are formed by laminating, and the upper layer that is the layer farther from the support among the at least two layers that are soluble in the same solvent and are in contact with each other is applied by a roll coating method. A method for producing an electrophotographic photosensitive member, wherein At least two layers that are soluble in the same solvent and are in contact with each other include a photosensitive layer that includes a charge generation material and a charge transport material, and an undercoat layer that is formed between the photosensitive layer and the support. And
The undercoat layer comprises a hydrophobic binder soluble in the solvent,
When the photosensitive layer is composed of one layer, the photosensitive layer is formed by applying a roll coating method, and when the photosensitive layer is formed by laminating the charge generation layer and the charge transport layer, at least the layer on the side in contact with the undercoat layer is A method for producing an electrophotographic photoreceptor, wherein the electrophotographic photoreceptor is formed by being applied by a roll coating method. The plurality of layers formed on the support includes a photosensitive layer on which an electrostatic latent image is formed,
The photosensitive layer has a laminated structure in which a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material are laminated,
The charge transport layer further comprises a plurality of layers, and at least the uppermost charge transport layer that is the farthest from the support among the plurality of charge transport layers is formed by being applied by a roll coating method. The method for producing an electrophotographic photosensitive member according to claim 1. At least one of the plurality of charge transport layers is
4. The method for producing an electrophotographic photosensitive member according to claim 3, wherein the composition differs from that of the remaining charge transport layer.   An electrophotographic photoreceptor produced by the production method according to claim 1. An electrophotographic photoreceptor produced by the production method according to claim 3 or 4,
The ratio (B / A) of the weight (B) of the binder resin to the weight (A) of the charge transport material in the uppermost charge transport layer which is the layer farthest from the support among the plurality of charge transport layers is 2 An electrophotographic photosensitive member having a viscosity of 0.0 to 6.0. The plurality of charge transport layers contains at least one of an antioxidant and a light stabilizer;
The amount of antioxidant and / or light stabilizer contained in the uppermost charge transport layer is
7. The electrophotographic photosensitive member according to claim 6, wherein the amount of the antioxidant and / or the light stabilizer contained in the charge transport layer located below the uppermost charge transport layer is larger. The ionization potential of the charge transport material in the uppermost charge transport layer is
The electrophotographic photosensitive member according to claim 6 or 7, wherein the electrophotographic photosensitive member is 5.65 eV or more. Mobility across multiple charge transport layers is
It is 1.0 * 10 < ^-6 > cm < ² > / Vs or more in environmental temperature: 5 degreeC and electric field strength: 2.5 * 10 < ⁵ > V / cm, It is any one of Claims 6-8 characterized by the above-mentioned. The electrophotographic photosensitive member described.   An image forming apparatus comprising the electrophotographic photosensitive member according to claim 5.

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