JP2015212837A - Electrophotographic photoreceptor, method for manufacturing the same, and electrophotographic device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor having high sensitivity and high durability, which is applied to a high-resolution and high-speed electrophotographic device employing a positive charging system, and which exhibits excellent operational stability, prevents an image memory phenomenon or image defects due to cracks induced by a contact member or by contamination with fat and oil or sebum, and stably gives high picture qualities, a method for manufacturing the electrophotographic photoreceptor, and an electrophotographic photoreceptor using the electrophotographic photoreceptor.SOLUTION: The electrophotographic photoreceptor includes a charge transporting layer 2 comprising a hole transporting material and a binder resin, and a charge generating layer 3 comprising a charge generating material, a hole transporting material, an electron transporting material and a binder resin, successively layered on a conductive support body 1. A total amount of residual solvents included in the charge generating layer and the charge transporting layer is 50 μg/cmor less; a mass ratio of the electron transporting material to the hole transporting material included in the charge generating layer is 5:1 to 4:2; the charge transporting layer has a film thickness of 3 to 40 μm; the charge generating layer has a film thickness of 3 to 40 μm; and a moisture content percentage of the charge generating layer and the charge transporting layer as a whole is 0.05 to 1.5 mass%.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor (hereinafter also simply referred to as “photoreceptor”), a method for producing the same, and an electrophotographic apparatus using the same, and more specifically, used for electrophotographic printers, copying machines, facsimiles, and the like. The present invention relates to an electrophotographic photoreceptor, a method for producing the same, and an electrophotographic apparatus using the same.

  In general, an image forming apparatus using an electrophotographic method such as a printer, a copying machine, a facsimile, or the like has a photosensitive member as an image carrier, a charging device that uniformly charges the surface of the photosensitive member, and an image on the surface of the photosensitive member. An exposure device for writing an electrical image (electrostatic latent image) corresponding thereto, a developing device for developing the electrostatic latent image with toner to form a toner image, and a transfer device for transferring the toner image to transfer paper, Is provided. A fixing device for fusing the toner on the transfer paper to the transfer paper is also provided.

  In such an image forming apparatus, the photoconductor used differs depending on the apparatus concept, but at present, excluding inorganic photoconductors such as Se and a-Si in large machines and high speed machines, its excellent stability, From the viewpoint of cost and ease of use, an organic photoconductor (OPC) in which an organic pigment is dispersed in a resin is widely used. The organic photoreceptor is generally negatively charged, as opposed to the positively charged inorganic photoreceptor. The reason for this is that while negatively charged organic photoreceptors have been developed for a long time with hole transport materials having a good hole transport function, positively charged organic photoreceptors have good electron transport capability. It is in the point that the electron transport material with has not been developed.

  On the other hand, in this negative charging process for negatively charged organic photoconductors, the amount of ozone generated by negative corona discharge is overwhelmingly about 10 times that of positive polarity, which adversely affects the photoconductor and the usage environment. The negative impact on is a problem. Therefore, in this negative charging process, the amount of ozone generation is suppressed by employing a contact charging method such as roller charging or brush charging. However, this contact charging method is disadvantageous in cost compared to the positive non-contact charging method, and contamination of the charging member is unavoidable, and is insufficient in terms of reliability, It also has a disadvantage in terms of high image quality, such as it is difficult to equalize the surface potential of the body.

  In order to solve these problems, it is effective to apply a positively charged organic photoreceptor, and a high-performance positively charged organic photoreceptor is required. In addition to the merits inherent in the positive charging system as described above, the positively charged organic photoreceptor generally has a carrier generation position near the surface of the photosensitive layer, so that the carrier is more lateral than the negatively charged organic photoreceptor. It has the advantage of less directional diffusion and excellent dot reproducibility (resolution and gradation). For this reason, positively charged organic photoreceptors are being studied in various fields where resolution is increasing.

  The positively charged organic photoconductors are roughly classified into four types of layers as described below, and various types have been conventionally proposed. The first is a function separation type photoreceptor having a two-layer structure in which a charge transport layer and a charge generation layer are sequentially laminated on a conductive support (see, for example, Patent Document 1 and Patent Document 2). The second is a function separation type photoreceptor having a three-layer structure in which a surface protective layer is laminated on the two-layer structure (see, for example, Patent Document 3, Patent Document 4, and Patent Document 5). The third type is a function-separated type photoconductor having a two-layer structure in which a charge generation layer and a charge (electron) transport layer are sequentially stacked, contrary to the first one (for example, Patent Document 6 and Patent Document). 7). The fourth is a single-layer type photoreceptor in which a charge generation material, a hole transport material, and an electron transport material are dispersed in the same layer (see, for example, Patent Document 6 and Patent Document 8). In the above four types of classification, the presence or absence of the undercoat layer is not considered.

  Of these, the fourth single-layer type photoconductor has been studied in detail, and is in widespread use in general. The main reason for this is thought to be that the hole transport material complements the electron transport function of the electron transport material that is inferior in transport ability compared to the hole transport function of the hole transport material. . Since this single-layer type photoreceptor is a dispersion type, carrier generation occurs inside the film, but the closer to the surface of the photosensitive layer, the larger the carrier generation amount, and the electron transport compared to the hole transport distance. Since the distance is small, it is considered that the electron transport ability does not need to be as high as the hole transport ability. This achieves practically sufficient environmental stability and fatigue characteristics as compared to the other three types.

  However, in a single-layer type photoreceptor, since a single film has both functions of carrier generation and carrier transport, it is possible to simplify the coating process and easily obtain a high yield rate and process capability. On the other hand, there is a problem that the content of the binder resin is reduced by containing both the hole transport material and the electron transport material in a single layer in order to increase the sensitivity, and the durability is lowered. was there. Therefore, there has been a limit to achieving both high sensitivity and high durability in the single layer type photoreceptor.

  Further, when the ratio of the binder resin in the single-layer type photoreceptor is lowered, the glass transition point is lowered, and there is a problem that the stain resistance against the contact member is deteriorated. Further, as disclosed in Patent Document 9, Patent Document 10 and Patent Document 11, when a phenylene compound is added as a plasticizer in a single-layer type photosensitive layer as a countermeasure against oil and sebum contamination, the glass transition point is lowered. Will be promoted more. For this reason, in a device having a high contact pressure such as a roller that contacts the organic photoconductor, there is a problem that creep deformation becomes remarkable and printing defects become apparent.

  For this reason, it is difficult to use conventional single-layer positively charged organic photoconductors in order to achieve both sensitivity, durability, and contamination resistance corresponding to recent downsizing, high speed, high resolution, and colorization of devices. A multilayer positively charged photoreceptor in which a charge transport layer and a charge generation layer are sequentially laminated has also been proposed (see, for example, Patent Document 12 and Patent Document 13). The layer structure of this laminated positively charged photoreceptor is similar to the first layer structure described above, but the charge generation material contained in the charge generation layer is reduced and the electron transport material is contained, so that The film can be made thicker than the charge transport layer, and the amount of hole transport material in the charge generation layer can be reduced, so the resin ratio in the charge generation layer can be set higher than the conventional single layer type, resulting in higher sensitivity. And high durability.

  The multilayer positively charged organic photoconductor is manufactured by a dip coating method when mass-produced, like the single-layer photoconductor. Therefore, when the charge generation layer is applied on the charge transport layer, it is important that the charge generation layer has good material solubility, dispersibility, and dispersion stability. It is necessary to select a solvent that does not easily elute the charge transport layer material. As such a solvent, those having a high boiling point are generally preferred, and specifically those having a boiling point of 60 ° C. or higher, particularly 80 ° C. or higher are desirable. Among them, when titanyl phthalocyanine having a high quantum efficiency is used as a charge generation material for increasing sensitivity, dichloroethane having a large specific gravity and a boiling point of 80 ° C. or higher is preferable. As an improved technique related to the solvent, for example, Patent Document 14 discloses a technique related to a photoreceptor in which the amount of residual solvent in the photosensitive layer is defined within a predetermined range.

Japanese Patent Publication No. 05-30262 Japanese Patent Laid-Open No. 04-242259 Japanese Patent Publication No. 05-47822 Japanese Patent Publication No. 05-12702 Japanese Patent Laid-Open No. 04-241359 JP 05-45915 A Japanese Patent Laid-Open No. 07-160017 Japanese Patent Laid-Open No. 03-256050 Japanese Patent Laid-Open No. 2007-163523 JP 2007-256768 A JP 2007-121733 A JP 2009-288568 A International Publication No. 2009/104571 Pamphlet Japanese Patent Laid-Open No. 9-43887

  However, the laminated positively charged organic photoconductors disclosed in Patent Documents 12 and 13 can achieve both high sensitivity, high durability, and resistance to contamination by oils such as grease. It was not possible to completely prevent contamination to sebum from the origin, that is, generation of cracks.

  Accordingly, an object of the present invention is to solve the above-mentioned problems and to be applied to a high-resolution and high-speed positively charged electrophotographic apparatus, which has excellent operational stability and is contaminated by image memory, contact members, oils or sebum. The present invention provides a highly sensitive and highly durable photoconductor for electrophotography, a method for producing the same, and an electrophotographic apparatus using the same, which are free from image defects caused by cracks and can stably obtain high image quality. There is.

  The inventors of the present invention can reduce the amount of charge transport material contained in the surface layer of the photoreceptor compared with a single-layer type organic photoreceptor, and increase the ratio of the binder resin. As a result of intensive studies on the cause of the occurrence of cracks due to sebum in the photoreceptor, it has been found that the influence of the amount of the residual solvent and the amount of the charge transport material is large.

  FIG. 3 is a graph showing the relationship between the standing time at room temperature and the amount of residual solvent for a laminated positively charged organic photoreceptor in which the charge generation layer was dried at 90 ° C. for 1 hour, and FIG. It is a graph which shows the crack generation rate after making sebum adhere on the surface of a charged organic photoreceptor for 10 days. Here, the sebum of the cracked part is often discolored, and it is considered that the charge transport material dissolved by the oil from the sebum is easily moved in the sebum direction on the surface. Is presumed to have the following mechanism.

  That is, when a residual solvent is present in the film of the photosensitive layer, the charge transport material dissolved by the oil that has permeated from the sebum easily moves in the direction of the sebum on the film surface. After that, the movement of the electron transport material makes the voids in the film larger, and it is considered that cracks occur due to stress concentration in the enlarged voids, and as a trigger for this series of phenomena, It is considered that the residual solvent contributes greatly.

  Here, in order to reduce the amount of residual solvent in the photosensitive layer, it is considered effective to perform a drying process at a high temperature and to increase the processing time in the manufacturing process. However, these methods tend to cause deterioration of the functional material due to the influence of heat, tend to deteriorate the electrical characteristics of the photoreceptor, that is, sensitivity characteristics and residual potential characteristics, and easily deteriorate performance.

  From such a viewpoint, as a result of further studies, the inventors have been able to reduce the amount of residual solvent at the lowest possible temperature and in the shortest possible time, and it is effective to perform drying under reduced pressure as a method that does not impair productivity. It has been found that this makes it possible to stably produce highly durable multilayer positively charged organic photoconductors with excellent sensitivity and stain resistance that prevent the occurrence of cracks due to sebum adhesion without impairing electrical properties. As a result, the present invention has been completed.

That is, the electrophotographic photoreceptor of the present invention comprises, on a conductive support, a charge transport layer containing at least a hole transport material and a binder resin, and at least a charge generating material, a hole transport material, an electron transport material and a binder. In a laminate type positively charged electrophotographic photoreceptor in which a charge generation layer containing a resin is sequentially laminated,
The total amount of residual solvent contained in the charge generation layer and the charge transport layer is 50 μg / cm ² or less, and the mass ratio of the electron transport material to the hole transport material in the charge generation layer is 5: 1 to 4 2 in the range, the film thickness of the charge transport layer is in the range of 3 μm to 40 μm, the film thickness of the charge generation layer is in the range of 3 μm to 40 μm, and the charge generation layer and the charge transport layer The moisture content of the entire layer is in the range of 0.05% by mass to 1.5% by mass.

In the present invention, the total amount of residual solvents contained in the charge generation layer and the charge transport layer is preferably 5 μg / cm ² or more and 50 μg / cm ² or less. The charge generation material contains titanyl phthalocyanine, the content of the charge generation material is 1 to 2.5% by mass in the charge generation layer, and the solvent is used when forming the charge generation layer. Is preferably dichloroethane. Furthermore, the binder resin contained in the charge transport layer is a polycarbonate resin, and the mass ratio of the hole transport material and the binder resin in the charge transport layer is 25:75 to 75:25. It is preferable.

Further, the production method of the electrophotographic photoreceptor of the present invention, in producing the electrophotographic photoreceptor of the present invention,
The charge transport layer and the charge generation layer are sequentially formed on the conductive support by a dip coating method, and the formed charge transport layer and the charge generation layer are dried under reduced pressure. It is what.
In the present invention, the solvent used for the dip coating of the charge generation layer is preferably a halogenated hydrocarbon having a boiling point of 60 ° C. or higher. In addition, after the charge transport layer is formed by a dip coating method, the charge transport layer is dried with hot air in a range of 90 to 120 ° C., and the charge generation layer is formed by a dip coating method, and then the formed charge is formed. Prior to drying the transport layer and the charge generation layer under reduced pressure, the charge generation layer is preferably dried with hot air in the range of 90 to 120 ° C. Furthermore, it is preferable that the charge transport layer and the charge generation layer are dried under reduced pressure at a vacuum degree of 500 Pa or less under conditions of 80 to 100 ° C. and 30 to 60 minutes.

  Furthermore, an electrophotographic apparatus of the present invention is equipped with the electrophotographic photoreceptor of the present invention.

  According to the present invention, because of the above configuration, it is applied to a high-resolution and high-speed positively-charged electrophotographic apparatus, has excellent operational stability, and is caused by contamination with an image memory, a contact member, oil or fat or sebum. It is possible to realize a highly sensitive and highly durable electrophotographic photoreceptor, a method for producing the same, and an electrophotographic apparatus using the same, in which there is no occurrence of image defects due to cracks and stable high image quality can be obtained. It has become possible.

FIG. 2 is a schematic cross-sectional view showing a configuration example of a laminated positively charged electrophotographic photoreceptor of the present invention. FIG. 6 is a schematic cross-sectional view showing another example of the configuration of the laminated positively charged electrophotographic photoreceptor of the present invention. 3 is a graph showing the relationship between the standing time at room temperature of a laminated positively charged organic photoreceptor and the amount of residual solvent. It is a graph which shows the crack generation rate after attaching sebum on the surface of a lamination type positively charged organic photoreceptor for 10 days. 1 is a schematic configuration diagram illustrating a configuration example of an electrophotographic apparatus of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited by the following description.

  FIG. 1 and FIG. 2 are schematic cross-sectional views showing an example of the configuration of the laminated positively charged electrophotographic photoreceptor of the present invention. As shown in FIG. 1, the electrophotographic photoreceptor of the present invention is a positively charged multi-layer electrophotographic apparatus in which at least a charge transport layer 2 and a charge generation layer 3 are sequentially laminated on a conductive support 1. It is a photoreceptor. Further, as shown in FIG. 2, the electrophotographic photoreceptor of the present invention may include an undercoat layer 4 as a countermeasure against interference fringes.

In the present invention, the charge transport layer 2 includes at least a hole transport material and a binder resin, and the charge generation layer 3 includes at least a charge generation material, a hole transport material, an electron transport material, and a binder resin. It is important that the total amount of residual solvent contained in the layer 3 and the charge transport layer 2 is 50 μg / cm ² or less. As described above, in order to suppress the occurrence of cracks due to sebum contamination, it is considered to be important to suppress the amount of residual solvent and the amount of charge transport material. It is related to basic characteristics and cannot be adjusted alone. Therefore, in the present invention, the amount of residual solvent is kept within the above range, thereby improving the resistance to oil and fat contamination. The total amount of the residual solvent needs to be 50 μg / cm ² or less, preferably 25 μg / cm ² or less.

  In the present invention, the total amount of residual solvent contained in the charge generation layer and the charge transport layer may be any as long as the above conditions are satisfied, and thereby the intended effect of the present invention can be obtained. It is. In the present invention, conditions such as a specific configuration of each of the other layers can be appropriately determined as desired, and are not particularly limited.

[Conductive support]
The conductive support 1 serves as one electrode of the photoconductor, and at the same time serves as a support for each layer constituting the photoconductor. The conductive support 1 may have any shape such as a cylindrical shape, a plate shape, or a film shape. In terms of material, a conductive treatment is applied to the surface of glass, resin, or the like in addition to metals such as aluminum, stainless steel, and nickel. It may be given.

[Underlayer]
The undercoat layer 4 is basically unnecessary in the present invention, but can be provided as necessary. The undercoat layer 4 is composed of a resin-based layer or a metal oxide film such as alumite, for the purpose of improving the adhesion between the conductive support and the charge transport layer, and the charge injection property to the photosensitive layer. It is provided for the purpose of controlling. Examples of the resin material used for the undercoat layer include insulating polymers such as casein, polyvinyl alcohol, polyamide, melamine, and cellulose, and conductive polymers such as polythiophene, polypyrrole, and polyaniline. Alternatively, they can be used in combination as appropriate. These resins can also contain metal oxides such as titanium dioxide and zinc oxide.

[Charge transport layer]
The charge transport layer 2 is mainly composed of a hole transport material and a binder resin.

(Hole transport material)
As the hole transport material used for the charge transport layer 2, various hydrazone compounds, styryl compounds, diamine compounds, butadiene compounds, indole compounds and the like can be used alone or in appropriate combination, but include a triphenylamine skeleton. Styryl compounds are preferred in terms of cost and performance. The charge transport layer 2 is inside the charge generation layer 3 and is less affected by member contamination, that is, the contact pressure of the transfer roller and the developing roller. In the charge transport layer 2, it is possible to use a low molecular weight triphenylamine as a plasticizer for preventing cracks while suppressing side effects.

(Binder resin)
Examples of the binder resin for the charge transport layer 2 include polycarbonate resins such as bisphenol A type, bisphenol Z type, bisphenol A type-biphenyl copolymer, polyester resins, polystyrene resins, polyphenylene resins, and the like. Or they can be used in appropriate combinations. Among these, as will be described later, the binder resin for the charge transport layer 2 is preferably the same as the binder resin for the charge generation layer 3 and has a molecular weight of 30,000 or more from the viewpoint of difficulty in elution. In particular, a polycarbonate resin having a molecular weight of 50,000 or more is optimal.

(solvent)
Examples of the solvent for the charge transport layer include halogenated hydrocarbons such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, and chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, dioxane, dioxolane, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether; acetone, Examples include ketones such as methyl ethyl ketone and cyclohexanone. The solvent used for the charge transporting layer is selected in consideration of the solubility, coating property and storage stability of the hole transporting material and the binder resin.

(composition)
The mass ratio of the hole transport material and the binder resin in the charge transport layer 2 can be in the range of 1: 3 to 3: 1 (25:75 to 75:25), preferably 1: 1. The range is from 5 to 1.5: 1 (40:60 to 60:40). If the content of the hole transport material is less than 25% by mass in the charge transport layer 2, generally the transport function is insufficient, the residual potential becomes high, and the environmental dependence of the exposed portion potential in the apparatus becomes large, Since the environmental stability of image quality deteriorates, it may not be suitable for use. On the other hand, when the content of the hole transport material is more than 75% by mass in the charge transport layer 2, that is, when the binder resin is less than 25% by mass in the charge transport layer 2, the charge generation layer 2 is applied. There is a risk of adverse effects of elution.

(Film thickness)
The film thickness of the charge transport layer 2 is determined in consideration of the charge generation layer 3 described later, but from the viewpoint of ensuring practically effective performance, the range of 3 μm to 40 μm is preferable, and more preferably 5 μm to It is 30 μm, more preferably 10 μm to 20 μm.

[Charge generation layer]
As described above, the charge generation layer 3 is formed by a method of applying a coating liquid in which particles of a charge generation material are dispersed in a binder resin in which a hole transport material and an electron transport material are dissolved. The charge generation layer 3 has a function of receiving light to generate carriers, and a function of transporting generated electrons to the surface of the photoreceptor and transporting holes to the charge transport layer 2. The charge generation layer 3 has high carrier generation efficiency, and at the same time, the injection property of the generated holes into the charge transport layer 2 is important, has little electric field dependency, and preferably has good injection even at a low electric field.

(Charge generation material)
As the charge generation material, X-type metal-free phthalocyanine alone, or α-type titanyl phthalocyanine, β-type titanyl phthalocyanine, Y-type titanyl phthalocyanine, γ-type titanyl phthalocyanine, and amorphous-type titanyl phthalocyanine can be used alone or in appropriate combination. A suitable substance can be selected according to the light wavelength region of the exposure light source used for image formation. From the viewpoint of increasing sensitivity, titanyl phthalocyanine having high quantum efficiency is optimal.

  Here, when titanyl phthalocyanine is used as the charge generation material, the moisture content of the charge generation layer 3 and the charge transport layer 2 as a whole is 0.05 mass% to 1.5 mass%, particularly 0.1 mass% to The range is preferably 1.0% by mass. By increasing the water content, the sensitivity of titanyl phthalocyanine can be improved, and in particular, it is possible to easily ensure the print density in a low temperature and low humidity environment. On the other hand, if the water content is too high, the chargeability tends to be insufficient particularly in a high-temperature and high-humidity environment, and depending on the device to be mounted, the charging performance may be insufficient and the resolution may be lowered.

(Charge transport material (hole transport material))
The hole transport material preferably has a small difference in ionization potential from the charge transport material of the charge transport layer, specifically, within 0.5 ev because it is necessary to inject holes into the charge transport layer. In particular, in the present invention, since the charge generation layer 3 is formed on the charge transport layer 2, the influence of elution of the charge transport layer 2 into the coating solution is suppressed when the charge generation layer 3 is applied. 3, it is preferable that the hole transport material contained in the charge transport layer 2 is also contained in the charge generation layer 3, more preferably the charge transport layer 2 and the charge generation layer 3. The same material is used as the hole transport material used in the above.

(Charge transport material (electron transport material))
The electron transport material is preferably a material having a high mobility, and quinone materials such as benzoquinone, stilbenequinone, naphthoquinone, diphenoquinone, phenanthrenequinone, and azoquinone are preferable. These can be used alone or in combination with a binder resin to increase the content of the electron transporting material while suppressing precipitation, because of its injectability into the charge transporting layer and compatibility with the binder resin. preferable.

(Binder resin)
As the binder resin for the charge generation layer, polycarbonate resins such as bisphenol A type, bisphenol Z type, bisphenol A type-biphenyl copolymer, polyester resins, polystyrene resins, polyphenylene resins, etc. may be used alone or It can be used by mixing in an appropriate combination. Among these, polycarbonate resins are preferable from the viewpoint of dispersion stability of the charge generation material, compatibility with the hole transport material and the electron transport material, mechanical stability, chemical stability, and thermal stability. In particular, as in the case of the hole transport material, in order to stabilize the liquid state of the charge generation layer 3 by suppressing the influence of elution into the coating liquid of the charge transport layer 2 when the charge generation layer 3 is applied, It is preferable that the binder resin contained in the transport layer 2 is also contained in the charge generation layer 3, and more preferably, the same resin is used as the binder resin used in the charge transport layer 2 and the charge generation layer 3.

(solvent)
As the solvent for the charge generation layer, halogenated hydrocarbons such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, dioxane, dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether; acetone, Examples include ketones such as methyl ethyl ketone and cyclohexanone. Of these, those having a high boiling point are generally preferred. Specifically, those having a boiling point of 60 ° C. or higher, particularly those having a boiling point of 80 ° C. or higher are preferably used. In particular, when titanyl phthalocyanine with high quantum efficiency is used as a charge generation material for high sensitivity, dichloroethane having a heavy specific gravity and a boiling point of 80 ° C. or higher is used as a solvent for forming the charge generation layer. It is preferable to use as the point of dispersion stability and difficulty in elution of the charge transport layer.

(composition)
The distribution amount of each functional material (charge generation material, electron transport material and hole transport material) in the charge generation layer 3 is set as follows. First, in the present invention, the content of the charge generation material in the charge generation layer 3 is 1 to 2.5 mass%, particularly 1.3 to 2.0 mass% in the charge generation layer 3. preferable. The mass ratio of the sum of the functional materials (charge generation material, electron transport material and hole transport material) and the binder resin in the charge generation layer 3 is 35:65 to 65:35 in order to obtain desired characteristics. Although it is set in a range, it is preferable to increase the amount of the binder resin by setting the mass ratio to 50 or less: 50 or more from the viewpoint of suppressing member contamination, oil contamination and sebum contamination while ensuring durability. .

  When the mass ratio of the functional material is greater than 65 mass% in the charge generation layer 3, that is, when the amount of the binder resin is less than 35 mass%, the amount of film reduction increases and durability decreases. Decrease in the glass transition point leads to insufficient creep strength, which tends to cause toner filming, external additives, and filming of paper powder, and more likely to cause contact member contamination (creep deformation). Contamination and sebum contamination are also worsened. Further, when the mass ratio of the functional material is less than 35 mass% in the charge generation layer 3, that is, when the amount of the binder resin is more than 65 mass%, it is difficult to obtain desired sensitivity characteristics. May not be suitable.

  The mass ratio of the electron transport material and the hole transport material can be changed in the range of 1: 5 to 5: 1. In the present invention, the charge transport having a hole transport function is provided in the lower layer of the charge generation layer 3. Contrary to the composition of the hole transport material rich of 1: 5 to 2: 4, which is a general range of the above mass ratio in the single layer type organic photoreceptor, 5: 1 to 4: The range of 2 is suitable, and in particular, the range of 4: 1 to 3: 2 is more preferable in terms of overall characteristics. Thus, in the multilayer photoconductor according to the present invention, a large amount of a hole transport material can be blended in the charge transport layer 2 which is the lower layer, so that the charge generation layer 3 which is the upper layer is different from the single layer photoconductor. , The content of the hole transporting material, which is one factor in the generation of cracks due to sebum adhesion, can be kept low.

(Other additives)
In the present invention, the charge generation layer and the charge transport layer contain, as desired, a deterioration inhibitor such as an antioxidant or a light stabilizer for the purpose of improving environmental resistance and stability against harmful light. Can be made. Compounds used for this purpose include chromanol derivatives such as tocopherol and esterified compounds, polyarylalkane compounds, hydroquinone derivatives, etherified compounds, dietherified compounds, benzophenone derivatives, benzotriazole derivatives, thioether compounds, phenylenediamine derivatives. Phosphonic acid ester, phosphorous acid ester, phenol compound, hindered phenol compound, linear amine compound, cyclic amine compound, hindered amine compound and the like.

  In addition, the charge generation layer and the charge transport layer may contain a leveling agent such as silicone oil or fluorine-based oil for the purpose of improving the leveling property of the formed film and imparting lubricity. Furthermore, metal oxides such as silicon oxide (silica), titanium oxide, zinc oxide, calcium oxide, aluminum oxide (alumina), zirconium oxide, etc. for the purpose of adjusting film hardness, reducing friction coefficient, and imparting lubricity Contains metal sulfate such as barium sulfate and calcium sulfate, fine particles of metal nitride such as silicon nitride and aluminum nitride, fluorine resin particles such as tetrafluoroethylene resin, fluorine comb-type graft polymerization resin, etc. May be. Furthermore, if necessary, other known additives can be contained as long as the electrophotographic characteristics are not significantly impaired.

(Film thickness)
The film thickness of the charge generation layer 3 is determined in view of the balance with the charge transport layer 2, but from the viewpoint of ensuring practically effective performance, a range of 3 μm to 40 μm is preferable, preferably 5 μm to 30 μm. More preferably, it is 10 micrometers-20 micrometers.

  In the photoreceptor of the present invention, the charge transport layer 2 and the charge generation layer 3 are sequentially formed on the conductive support 1 by a dip coating method according to a conventional method, and then the charge transport layer 2 and the charge generation layer formed. 3 can be produced by drying under reduced pressure. Specifically, first, according to a conventional method, the charge transport layer 2 is formed on the conductive support 1 by a dip coating method and dried by hot air drying or the like. Next, the charge generation layer 3 is formed on the formed charge transport layer 2 by a dip coating method according to a conventional method, and dried by hot air drying or the like. In order not to impair the performance of the functional material contained in each layer, the hot air drying after the formation of each layer is usually performed in the range of 90 to 120 ° C. Next, the formed charge transport layer 2 and charge generation layer 3 are further dried under reduced pressure to effectively reduce the amount of the solvent remaining in the charge transport layer 2 and the charge generation layer 3. In addition, it is possible to obtain the photoconductor of the present invention having good productivity and excellent stain resistance without impairing the electrical characteristics of the photoconductor.

  Here, the reduced-pressure drying in the present invention can be performed under conditions of 30 to 60 minutes with hot air at a temperature of about 80 to 100 ° C. in a vacuum degree of 500 Pa or less, particularly 100 Pa or less, for example. If the pressure reduction is insufficient, the temperature is too low, or the time is too short, the amount of residual solvent is not sufficiently reduced, and there is a possibility that the contamination resistance is insufficient. Also, if the temperature is too high or the time is too long, the electrical characteristics of the photoreceptor may be impaired.

  In addition, since the moisture content contained in the charge transport layer 2 and the charge generation layer 3 is reduced by the reduced pressure drying, in the present invention, after the reduced pressure drying, the photosensitive member is kept at a predetermined high temperature and high humidity for a predetermined time. It is preferable to place under conditions. Thereby, the moisture content in the charge transport layer 2 and the charge generation layer 3 can be adjusted within the preferred range.

(Electrophotographic equipment)
The electrophotographic photoreceptor of the present invention can achieve the desired effects when applied to various machine processes. Specifically, systems with and without a paper dust removal process using sponge rollers, brushes, etc., and contact development and non-development using development systems such as non-magnetic one component, magnetic one component, and two components. A sufficient effect can be obtained even in a development process such as a contact development system.

  As an example, FIG. 5 shows a schematic configuration diagram showing a configuration example of the electrophotographic apparatus of the present invention. The electrophotographic apparatus 60 of the present invention mounts the electrophotographic photoreceptor 7 of the present invention including the conductive support 1, the undercoat layer 4 and the photosensitive layer 300 coated on the outer peripheral surface thereof. Further, the electrophotographic apparatus 60 includes a charger (scorotron) 21, a high-voltage power source 22 that supplies an applied voltage to the scorotron 21, an image exposure member 23, and a developer, which are disposed on the outer peripheral edge of the photoreceptor 7. A developing device 24 having a roller 241, a paper feeding member 25 having a paper feeding roller 251 and a paper feeding guide 252, a transfer pole (transfer roller) 26, a paper dust removing member (paper dust removing sponge roller) 27, Consists of The electrophotographic apparatus 60 of the present invention can be a color printer.

  Hereinafter, specific embodiments of the present invention will be described in more detail using examples. The present invention is not limited by the following examples unless it exceeds the gist.

<Example of production of electrophotographic photoreceptor>
<Example 1>
As the conductive support, an aluminum 0.75 mm thick tube cut to a surface roughness (Rmax) of 0.2 μm and having a shape of φ30 mm × length 244.5 mm was used.

(Preparation of charge transport layer coating solution)
Polycarbonate resin composed of a styryl compound (CTM-A) represented by the following structural formula 1 as a hole transport material and a repeating unit represented by the following structural formula 2 as a binder resin (TS2050, manufactured by Teijin Chemicals Ltd.) (CTB-A) was dissolved in tetrahydrofuran as a solvent in an amount of 100 parts by mass to prepare a charge transport layer coating solution.

(Preparation of charge generation layer coating solution)
For 100 parts by mass of the same polycarbonate resin (CTB-A) used in the charge transport layer as the binder resin, 3 parts by mass of Y-type titanyl phthalocyanine represented by the following structural formula 3 as a charge generation material, and a hole transport material 11 parts by mass of the same compound (CTM-A) as used in the charge transporting layer and 44 parts by mass of the compound (ETM-A) shown in the following structural formula 4 as an electron transporting material are added to 1,2-dichloroethane. The mixture was mixed and dispersed by a dyno mill (MULTILAB of Shinmaru Enterprise Co., Ltd.) to obtain a charge generation layer coating solution.

(Production of photoconductor)
On the conductive support, the charge transport layer coating solution prepared above is applied by a dip coating method, and then dried in a drying furnace at 110 ° C. for 1 hour, and the dried charge transport layer having a thickness of 15 μm is formed. Formed. Next, the charge generation layer coating solution prepared above is applied on the formed charge transport layer by a dip coating method, then dried at 115 ° C. for 1 hour, and the charge generation layer having a thickness of 15 μm after drying. To form a photoreceptor.

With respect to the obtained photoreceptor, the amount of residual solvent in the film was measured by gas chromatograph analysis and the water content in the film was measured by Karl Fischer analysis under the following conditions. As a result, the total amount of residual solvent contained in the charge generation layer and the charge transport layer was 24 μg / cm ² and the water content was 0.10%. The measurement method is the same in the following.

(Residual solvent amount measurement)
i) Thermal desorption thermal desorption apparatus: Curie-point pyrolyzer (HS-100A) manufactured by Nippon Analytical Industries, Ltd.
Trap temperature: 150 ° C / 20min heating → -50 ° C cold trap,
ii) Gas chromatographic analysis (GC-MS) measurement GC-MS measuring apparatus: GC-MS QP5000 manufactured by Shimadzu Corporation
Inlet temperature: 280 ° C,
Split: 1/10,
Column: J & W manufactured capillary column DB-5 (slight polarity) φ0.25 × 30 m,
Column temperature: 40 ° C. (3 minutes hold) → 280 ° C. (10 ° C./min)→3 minutes hold at 280 ° C. (measurement time 30 minutes),
Carrier gas: Helium 1mL / min

(Moisture content measurement)
Karl Fischer (KF) moisture measuring device: KF-100, manufactured by Mitsubishi Chemical
Fixed mode: volumetric titration method,
KF reagent: Aquamicron SS (Mitsubishi Chemical Corporation),
Dehydrated solvent: Aquamicron PE (Mitsubishi Chemical Corporation),
Sample preparation: An OPC drum cut piece is placed in a 50 cc screw tube and dissolved in about 35 g of dichloromethane (DCM) to obtain a KF analysis sample.
Calculation method: The moisture content in the film and the moisture content in the photosensitive film peeling element tube are subtracted as background from the measured moisture content value in the analysis sample, and the moisture content in the film is calculated based on the following formula. The membrane weight is DCM dissolved.
“Calculation formula of moisture content in membrane”:
(OPC drum solution moisture content × OPC drum weight−element tube solution moisture amount × element tube weight−DCM moisture amount × DCM amount) / membrane weight

<Example 2>
The charge generation layer is formed in the same manner as in Example 1 except that the drying condition after application of the charge generation layer is 100 ° C. for 1 hour, and then dried at a pressure of 200 Pa and 100 ° C. for 30 minutes in a vacuum drying furnace. The photoreceptor of Example 2 was obtained. In this photoreceptor, the total amount of residual solvent contained in the charge generation layer and the charge transport layer was 25 μg / cm ² and the moisture content in the film was 0.05%.

<Example 3>
The photoreceptor of Example 2 was further allowed to stand for 4 hours in a high-temperature and high-humidity environment at 60 ° C. and 90% RH to obtain the photoreceptor of Example 3. In this photoreceptor, the total amount of residual solvent contained in the charge generation layer and the charge transport layer was the same as in Example 2, and the moisture content in the film was 0.33%.

<Example 4>
The photoreceptor of Example 2 was further allowed to stand for 24 hours in a high-temperature and high-humidity environment at 70 ° C. and 90% RH to obtain a photoreceptor of Example 4. In this photoreceptor, the total amount of residual solvent contained in the charge generation layer and the charge transport layer was the same as in Example 2, and the moisture content in the film was 1.45%.

<Example 5>
A photoconductor was produced in the same manner as in Example 3 except that the total amount of residual solvent was adjusted to 15 μg / cm ² by changing the drying conditions in the vacuum drying furnace. The moisture content in the film was 0.42%.

<Example 6>
A photoconductor was produced in the same manner as in Example 3 except that the total amount of residual solvent was adjusted to 5 μg / cm ² by changing the drying conditions in the vacuum drying furnace. The moisture content in the film was 0.56%.

<Example 7>
A photoconductor was prepared in the same manner as in Example 1 except that the ratio of the electron transport material to the hole transport material in the charge generation layer was 3: 1 (41.25 parts by mass: 13.75 parts by mass). .

<Example 8>
A photoconductor was prepared in the same manner as in Example 1 except that the ratio of the electron transport material to the hole transport material in the charge generation layer was 2: 3 (22 parts by mass: 33 parts by mass).

<Example 9>
In the same manner as in Example 1, except that the compound (CTM-B) represented by the following structural formula 5 was used in place of the compound (CTM-A) as the hole transport material for the charge generation layer and the charge transport layer. The body was made.

<Example 10>
In the same manner as in Example 8, except that the compound (CTM-B) represented by the above structural formula 5 was used in place of the compound (CTM-A) as the hole transport material for the charge generation layer and the charge transport layer. The body was made.

<Example 11>
In the same manner as in Example 1 except that the compound (CTM-C) represented by the following structural formula 6 was used in place of the compound (CTM-A) as the hole transport material for the charge generation layer and the charge transport layer. The body was made.

<Example 12>
In the same manner as in Example 8, except that the compound (CTM-C) represented by the above structural formula 6 was used in place of the compound (CTM-A) as the hole transport material for the charge generation layer and the charge transport layer. The body was made.

<Example 13>
Except that 10% by mass of the compound (CTM-A) was replaced with the compound (CTM-D) represented by the following structural formula 7 as the hole transport material for the charge generation layer and the charge transport layer, the same as in Example 1. Thus, a photoreceptor was produced.

<Example 14>
As in Example 8, except that 10% by mass of the compound (CTM-A) was replaced with the compound (CTM-D) shown in the structural formula 7 as a hole transport material for the charge generation layer and the charge transport layer. Thus, a photoreceptor was produced.

<Example 15>
A photoconductor was prepared in the same manner as in Example 1 except that instead of the compound (ETM-A), the compound (ETM-B) represented by the following structural formula 8 was used as the electron transport material for the charge generation layer.

<Example 16>
A photoconductor was prepared in the same manner as in Example 8 except that instead of the compound (ETM-A), the compound (ETM-B) represented by the structural formula 8 was used as the electron transport material for the charge generation layer.

<Example 17>
Example 1 except that a polycarbonate resin (CTB-B) composed of a repeating unit represented by the following structural formula 9 was used instead of the polycarbonate resin (CTB-A) as a binder resin for the charge generation layer and the charge transport layer. Similarly, a photoreceptor was produced.

<Example 18>
Example 8 except that the polycarbonate resin (CTB-B) composed of the repeating unit shown in the structural formula 9 was used as the binder resin for the charge generation layer and the charge transport layer instead of the polycarbonate resin (CTB-A). Similarly, a photoreceptor was produced.

<Example 19>
Example 1 except that a polycarbonate resin (CTB-C) composed of repeating units represented by the following structural formula 10 was used as the binder resin for the charge generation layer and the charge transport layer instead of the polycarbonate resin (CTB-A). Similarly, a photoreceptor was produced.

<Example 20>
Example 8 was used except that the polycarbonate resin (CTB-C) composed of the repeating unit represented by the structural formula 10 was used as the binder resin for the charge generation layer and the charge transport layer instead of the polycarbonate resin (CTB-A). Similarly, a photoreceptor was produced.

<Example 21>
The photoreceptor of Example 2 was further allowed to stand for 48 hours in a high-temperature and high-humidity environment at 70 ° C. and 90% RH to obtain the photoreceptor of Example 21. In this photoreceptor, the total amount of residual solvent contained in the charge generation layer and the charge transport layer was the same as in Example 2, and the moisture content in the film was 1.61%.

<Example 22>
A photoconductor was produced in the same manner as in Example 2 except that drying in a vacuum drying furnace was performed at 85 ° C. for 40 minutes, so that the total amount of residual solvent was 38 μg / cm ² .

<Example 23>
A photoconductor was produced in the same manner as in Example 2 except that drying in a vacuum drying oven was performed at 85 ° C. for 30 minutes, so that the total amount of residual solvent was 45 μg / cm ² .

<Comparative Example 1>
By performing drying in a vacuum drying furnace at 85 ° C. for 20 minutes, a photoconductor was produced in the same manner as in Example 2 except that the total amount of residual solvent was changed to 55 μg / cm ² .

(Photoreceptor evaluation)
The performance of the photoconductor was evaluated in each of the following items (1) to (4) in four stages of ◎, ○, Δ, and ×. In each case, ◎ is a very good level, ◯ is a good level, Δ is a level that does not cause a problem in actual use, and × is an unusable level. The obtained results are shown in the following table.

(1) Durability of actual machine Using a commercially available monochrome laser printer HL-6050 manufactured by Brother Industries, Ltd., low temperature and low humidity (10 ° C., 20% RH), normal temperature and normal humidity (24 ° C., 45% RH), and high temperature and high humidity (35 Endurance test up to 30000 sheets under an environment of 90 ° C), print density (surface density), resolution (reproducibility of white lines and isolated dots), fog, image memory (halftone image) Ghost images) and the level of point defects due to filming.

(2) Contamination of the member With the photosensitive drum and toner cartridge mounted on the drum cartridge of the above apparatus, it was left in an environment of 50 ° C. and 90% RH for 5 days to check whether the surface of the photosensitive drum had changed.

(3) Oil and grease resistance The grease used in the above apparatus was adhered to the surface of the photoconductor, and the presence or absence of a change in the surface of the photoconductor after being allowed to stand for 5 days was investigated.

(4) Sebum Contamination Property Human-derived sebum was adhered to the surface of the photoconductor, and the presence or absence of cracks in the adhered portion after leaving for 10 days was investigated.

  From the results in the above table, in the photoconductors of each Example in which the amount of residual solvent was reduced, there was no occurrence of cracks due to the adhesion of sebum, the contamination resistance was improved, and the moisture content in the film was set to a predetermined value. It was confirmed that stable high image quality can be secured by setting the value within the range. On the other hand, in the photoconductor of the comparative example having a large amount of residual solvent, the contamination resistance against sebum was insufficient and cracks occurred on the surface of the photoconductor.

  As a result of the above, according to the present invention, it is applied to a high-resolution and high-speed positively chargeable electrophotographic apparatus, and has excellent operational stability, and is caused by cracks caused by contamination due to image memory, contact members, oils or sebum. Thus, there can be obtained a highly sensitive and highly durable electrophotographic photoreceptor, a method for producing the same, and an electrophotographic apparatus using the same, in which no image defects are generated and high image quality can be stably obtained.

DESCRIPTION OF SYMBOLS 1 Conductive support body 2 Charge transport layer 3 Charge generation layer 4 Undercoat layer 7 Electrophotographic photoreceptor 21 Charger (Scorotron)
22 High-voltage power supply 241 Developing roller 24 Developing device 251 Paper feeding roller 252 Paper feeding guide 25 Paper feeding member 26 Transfer pole (transfer roller)
27 Paper dust removing member (sponge roller)
60 Electrophotographic apparatus 300 Photosensitive layer

Claims (9)

A charge transport layer including at least a hole transport material and a binder resin, and a charge generation layer including at least a charge generation material, a hole transport material, an electron transport material and a binder resin are sequentially stacked on the conductive support. In the laminated positively charged electrophotographic photoreceptor,
The total amount of residual solvent contained in the charge generation layer and the charge transport layer is 50 μg / cm ² or less, and the mass ratio of the electron transport material to the hole transport material in the charge generation layer is 5: 1 to 4 2 in the range, the film thickness of the charge transport layer is in the range of 3 μm to 40 μm, the film thickness of the charge generation layer is in the range of 3 μm to 40 μm, and the charge generation layer and the charge transport layer An electrophotographic photoreceptor, wherein the moisture content of the entire layer is in the range of 0.05% by mass to 1.5% by mass. The electrophotographic photoreceptor according to claim 1, wherein the total amount of residual solvent contained in the charge generation layer and the charge transport layer is 5 μg / cm ² or more and 50 μg / cm ² or less.   The charge generation material contains titanyl phthalocyanine, the content of the charge generation material is 1 to 2.5% by mass in the charge generation layer, and the solvent used for forming the charge generation layer is dichloroethane The photoconductor for electrophotography according to claim 1.   The binder resin contained in the charge transport layer is a polycarbonate-based resin, and a mass ratio of the hole transport material and the binder resin in the charge transport layer is 25:75 to 75:25. The electrophotographic photoreceptor according to 1. In producing the electrophotographic photoreceptor according to claim 1,
The charge transport layer and the charge generation layer are sequentially formed on the conductive support by a dip coating method, and the formed charge transport layer and the charge generation layer are dried under reduced pressure. A method for producing an electrophotographic photoreceptor.   The method for producing an electrophotographic photoreceptor according to claim 5, wherein the solvent used for the dip coating of the charge generation layer is a halogenated hydrocarbon having a boiling point of 60 ° C. or higher.   After the charge transport layer is formed by a dip coating method, the charge transport layer is dried with hot air in a range of 90 to 120 ° C., and the charge generation layer is formed by a dip coating method. The method for producing an electrophotographic photoreceptor according to claim 6, wherein the charge generation layer is dried with hot air in the range of 90 to 120 ° C. prior to drying the charge generation layer under reduced pressure.   The method for producing an electrophotographic photoreceptor according to claim 7, wherein the charge transport layer and the charge generation layer are dried under reduced pressure at a vacuum degree of 500 Pa or less under conditions of 80 to 100 ° C. and 30 to 60 minutes. .   An electrophotographic apparatus comprising the electrophotographic photosensitive member according to claim 1.

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