JP2020166034A - Resin substrate for electrophotographic photosensitive drum and electrophotographic photosensitive drum - Google Patents

Abstract

To provide a resin substrate for electrophotographic photosensitive drum which is small in deflection by a contact pressure of a peripheral member.SOLUTION: There is provided a cylindrical resin substrate for electrophotographic photoreceptor, in which the resin substrate contains a polyester resin, the resin substrate has a central region having a predetermined width toward both ends of the resin substrate with a center in a direction perpendicular to the circumferential direction as a starting point and two end regions having predetermined widths toward the center from both of the ends of the resin substrate, and when a degree of crystallization of the central region is represented by A (%) and degrees of crystallization of the end regions are represented by B (%), relationships of A≥40 and 0.50≤B/A≤0.84 are satisfied.SELECTED DRAWING: Figure 5

Description

The present disclosure is directed to a cylindrical resin substrate used in an electrophotographic apparatus or an electrostatic recording apparatus, and an electrophotographic photosensitive drum using the resin substrate.

An electrophotographic image forming apparatus such as a copier or a printer forms an electrostatic image on the peripheral surface of a rotating electrophotographic photosensitive drum, develops the electrostatic image, and transfers the electrostatic image to a recording sheet to form an image. This electrophotographic photosensitive drum is basically composed of a photosensitive layer that forms a latent image by charging and exposure using light, and a substrate on which the photosensitive layer is provided.
Conventionally, as a substrate used for an electrophotographic photosensitive drum, a substrate obtained by processing aluminum into a cylindrical shape has generally been used. Then, it is generally used in a state where a photosensitive layer is formed on the surface of this aluminum, and driving members such as gears and flanges made of a resin material are attached to both ends by adhesion or crimping. It has been done.
On the other hand, from the viewpoint of cost reduction, the development of a resin-made cylindrical substrate as an alternative to aluminum is being actively promoted. When resin is used as the substrate material, its rigidity is lower than that of aluminum. Therefore, due to the contact pressure received from peripheral members adjacent to the electrophotographic photosensitive drum, such as charging rollers and toner cleaning blades, the electrophotographic photosensitive drum Deflection / deformation may occur. Furthermore, the deflection and deformation of the electrophotographic photosensitive drum makes the rotation unstable during driving, and image defects due to uneven charging and uneven toner transfer are likely to occur. Therefore, the electrophotographic photosensitive drum due to this contact pressure It is necessary to devise ways to suppress deflection and deformation.
Further, as the speed of the electrophotographic image forming apparatus increases, the contact pressure from peripheral members such as the charging roller and the toner cleaning blade applied to the photosensitive drum tends to increase, and the shape change can be further suppressed for the electrophotographic photosensitive drum. A resin substrate is needed.
Patent Document 1 makes an attempt to increase the strength by blending an inorganic filler with a resin. Specifically, as a resin-made electrophotographic photosensitive drum substrate capable of reducing a decrease in mechanical strength, the weight relative to the volume of the entire cylindrical substrate including the hollow portion is 0.2 g / cm ³ or more, and 0. A resin substrate has been proposed, characterized in that it is less than 65 g / cm ³ .

JP-A-2002-174917

However, according to the study by the present inventors, in the resin substrate according to Patent Document 1, image defects may occur due to the deformation due to the contact pressure. Then, when an electrophotographic image was formed using a resin substrate that was greatly bent under the contact pressure, an image defect was observed at a position corresponding to the bent portion of the electrophotographic image. In the flexible portion, the amount of gap between the surface of the electrophotographic photosensitive drum and the charging roller becomes large, and insufficient charging occurs because the voltage for normal charging is not applied. It is considered that the cause of the image defect is that the electrostatic latent image for forming the target image cannot be formed in the portion where the charge is insufficient, and the toner transfer amount at the time of development is insufficient.
One aspect of the present invention is to provide a resin substrate for an electrophotographic photosensitive drum, which is excellent in cost and has a small deflection due to contact pressure of peripheral members. Another aspect of the present invention is to provide an electrophotographic photosensitive drum using the resin substrate.

According to one aspect of the present invention, in a cylindrical resin substrate for an electrophotographic photosensitive member containing a polyester resin, a predetermined width is formed from the center in the direction orthogonal to the circumferential direction toward both ends of the resin substrate. It has a central region having a central region and two end regions having a predetermined width from both ends of the resin substrate toward the center.
When the crystallinity of the central region is A% and the crystallinity of the end region is B%, A and B are the following relational expressions (1) and (2):
A ≧ 40 (1)
0.50 ≤ B / A ≤ 0.84 (2)
A resin substrate that satisfies the above conditions is provided.
Further, according to another embodiment of the present invention, there is provided an electrophotographic photosensitive drum having the resin substrate and a photosensitive layer provided on the outer peripheral surface of the resin substrate.

According to one aspect of the present invention, a resin substrate for an electrophotographic photosensitive drum capable of stabilizing charging and developing and forming a high-quality electrophotographic image by suppressing deflection due to contact pressure received from peripheral members can be obtained. Can be provided. Further, according to another aspect of the present invention, it is possible to provide an electrophotographic photosensitive drum capable of stabilizing charging and developing and forming a high-quality electrophotographic image.

It is sectional drawing which shows an example of the electrophotographic drawing apparatus using the electrophotographic photosensitive drum which concerns on this aspect. This is an analysis example in which the resin substrate according to this embodiment is measured by X-ray diffraction. It is the schematic sectional drawing of the injection molding apparatus. It is the schematic sectional drawing of the primary blow molding apparatus. It is a perspective view of the resin substrate which concerns on this aspect.

<Cylindrical resin substrate>
The cylindrical resin substrate contains a crystalline thermoplastic resin, and the crystalline thermoplastic resin contains a polyester resin. The resin substrate has a central region having a predetermined width toward both ends of the resin substrate starting from the center in a direction orthogonal to the circumferential direction, and a predetermined width from both ends of the resin substrate toward the center. It has two end regions. Then, the crystallinity of the central region and the crystallinity of the end region have a predetermined relationship described later.
As a specific configuration of the resin substrate, for example, a resin substrate obtained by blending a polyester resin with a conductive agent and processing it into a cylindrical shape can be exemplified. Further, a resin substrate in which a resin layer, a metal layer, or both layers are provided on an outer peripheral surface or an inner peripheral surface or both peripheral surfaces of a polyester resin processed into a cylindrical shape, and a resin in which a conductive agent is blended in the resin layer. Examples include a substrate. Further, a resin substrate processed into a cylindrical shape, in which gears, flanges and the like are integrally molded on one side end portion or both side end portions, can also be used. By integrally molding gears, flanges, etc., it is possible to reduce the area where an image cannot be formed and reduce the size of the electrophotographic photosensitive drum.

<Polyester resin>
The polyester resin can be obtained as a thermoplastic polyester resin by polycondensation of a dicarboxylic acid and a diol, polycondensation of an oxycarboxylic acid or a lactone, or polycondensation using a plurality of these components. Further, a polyfunctional monomer may be used in combination. The polyester resin may be a homopolyester containing one type of ester bond or a copolyester (copolymer) containing a plurality of ester bonds.
As the polyester resin used in the present invention, at least one selected from the group consisting of polyalkylene terephthalate and polyalkylene naphthalate having high crystallinity and exhibiting excellent heat resistance can be mentioned as a preferable example.
The form of the copolymer at this time may be a block copolymer or a random copolymer. The carbon number of the alkylene in the polyalkylene terephthalate and the polyalkylene naphthalate is preferably 2 or more and 16 or less from the viewpoint of high crystallinity and heat resistance. More specifically, as the polyester resin according to the present invention, polyethylene terephthalate and polyethylene naphthalate are preferable.

<Additives blended in polyester resin>
Other components may be added to the polyester resin as long as the effects of the present invention are not impaired. Examples of other components include conductive polymers, conductive monomers, antioxidants, UV absorbers, organic pigments, inorganic pigments, pH regulators, cross-linking agents, compatibilizers, mold release agents, cross-linking agents, coupling agents, etc. Includes lubricants, insulating fillers, conductive fillers and the like. One type of these additives may be used alone, or two or more types may be used in combination. The amount of the additive used can be appropriately set and is not particularly limited.
The polyester resin containing the above additives can be obtained by heat melt kneading. The heat-melt kneading means that the polyester resin is heated and kneaded in a molten state, and the polyester resin can be kneaded at a temperature equal to or higher than the melting point of the resin so that the polyester resin is sufficiently kneaded. The kneading method is not particularly limited, and a single-screw extruder, a twin-screw kneading extruder, a Banbury mixer, a roll, a lavender, a plast graph, a kneader, or the like can be used.

Hereinafter, the resin substrate according to this embodiment will be described with reference to FIG.
<Crystallinity>
Methods for measuring the crystallinity of the resin substrate include differential scanning calorimetry (DSC), wide-angle X-ray diffraction method, small-angle X-ray scattering method, infrared absorption method, density method, and the like. The degree is calculated by the peak multiplex separation method using the wide-angle X-ray diffraction method.
In FIG. 5, the cylindrical resin substrate 200 according to the present invention contains a polyester resin and has a central region 201 having a predetermined width toward both ends of the resin substrate starting from the center in a direction orthogonal to the circumferential direction thereof. Have. Further, the resin substrate 200 has two end regions 202 having a predetermined width from both ends of the resin substrate toward the center. The crystallinity A of the central region is 40% or more. When the crystallinity A of the central portion of the resin substrate is 40% or more, the entire resin substrate can be suppressed from bending, and the formation of a gap with the peripheral member can be effectively suppressed. The crystallinity A is more preferably 50% or more.
Further, when the crystallinity of the end region is B (%), the B / A is 0.5 or more and 0.84 or less. When the B / A is 0.5 or more, the deformation difference due to the contact pressure can be reduced between the end portion and the center portion of the resin substrate, and the generation of a gap between the peripheral member and the peripheral portion at the boundary portion can be prevented. When the B / A is 0.84 or less, it is possible to prevent the resin substrate from flexing uniformly and forming a large gap in the central portion, and it is possible to prevent the occurrence of image defects due to poor charging in the central portion. It should be noted that the B / A shall satisfy the relationship of 0.58 or more and 0.75 or less in particular in order to suppress the occurrence of deflection and stably output a high-quality image even after long-term use. Is preferable.

The present inventors consider the reason why image defects occur in the electrophotographic photosensitive drum according to Patent Document 1 as follows.
That is, the diameter of the toner is reduced in order to improve the image quality, and the blade contact pressure for cleaning the residual toner on the electrophotographic photosensitive drum is larger than that in the conventional case. Along with this, the amount of deflection of the resin substrate increases, so that a gap is generated between the electrophotographic photosensitive drum and the charging roller, and charging is not performed normally (hereinafter referred to as "charging failure"), resulting in image failure. I think that will occur.
Further, in order to cope with the recent miniaturization and power consumption of the electrophotographic apparatus, the electrophotographic photosensitive drum has a smaller diameter and a thinner wall, and the deflection tends to be larger than before.
In response to such poor charging of the electrophotographic photosensitive drum, the present inventors have investigated a mechanism by which the resin substrate can be normally charged by suppressing bending even when it receives the contact pressure of the cleaning blade. As a result, it was obtained that the deflection of the electrophotographic photosensitive drum was suppressed by making a difference in the crystallinity between both ends and the center of the resin substrate.
Specifically, the resin substrate is made of a polyester resin, and has a central region having a predetermined width toward both ends of the resin substrate starting from the center in a direction orthogonal to the circumferential direction thereof, and from both ends of the resin substrate. It has two end regions having a predetermined width towards the center. Then, when the crystallinity of the central region is A (%) and the crystallinity of the end region is B (%), A and B satisfy the following relational expressions (1) and (2). We found that deflection was suppressed.

A ≧ 40 (1)
0.50 ≤ B / A ≤ 0.84 (2)

This is because the crystallinity of both ends of the resin substrate is lower than that of the central part, and when the contact pressure is applied from the peripheral members, the amorphous part of the resin is preferentially distorted to absorb the contact pressure and crystallize. It is considered that this is because the deflection of the central portion of the substrate having a high degree of crystallinity can be suppressed.
Further, it is more preferable that the A and the B satisfy the following relational expression (3).
0.58 ≤ B / A ≤ 0.75 (3)

<Thickness of cylindrical resin substrate>
The thickness (thickness) of the cylindrical resin substrate according to the present invention is preferably 0.50 mm or more and 2.00 mm or less. When the thickness is 0.50 mm or more, it is easy to secure the mechanical strength, and the deformation of the resin substrate due to long-term use can be effectively suppressed. Further, when the thickness is 2.00 mm or less, the time required for shape correction by holding at a high temperature in the mold and adjustment of the crystallinity can be shortened.

<Central area of cylindrical resin substrate>
The width of the central region of the resin substrate is preferably 82% or more and 98% or less with respect to the sum of the width of the central region and the width of the two end regions. When the width of the central region is 82% or more, it is possible to avoid the occurrence of poor charging due to the deformed end region overlapping the image output region and the resulting image defects. Further, when the width of the central region is 98% or less, it is possible to secure a region that positively absorbs the contact pressure of the peripheral members, and it is possible to more reliably suppress the occurrence of deflection in the image region.

<End area of cylindrical resin substrate>
The widths of the two end regions of the cylindrical resin substrate according to the present invention are preferably 5 mm or more and 20 mm or less, respectively. When the width of the end region is 5 mm or more, it is possible to secure a region that positively absorbs the contact pressure of the peripheral member, and it is possible to more reliably suppress the occurrence of deflection in the image region. Further, when the width of the end region is 20 mm or less, it is possible to avoid the occurrence of poor charging due to the deformed end region overlapping the image output region and the resulting image defect.

In addition to blending a conductive agent with the polyester resin in order to impart conductivity to the resin substrate, an energy-curable resin or the like containing a conductive agent on the outer peripheral surface, the inner peripheral surface, or both surfaces of the resin substrate. May be provided by applying and curing the conductive layer. Alternatively, a conductive layer may be provided on the metal material by a method such as sputtering.
Further, in order to improve the adhesion to the photosensitive layer described later, the surface of the resin substrate may be subjected to an electrochemical treatment such as anodization, a blast treatment, a cutting treatment or the like.
The use of the cylindrical resin substrate according to the present invention is not particularly limited, but is preferably used for, for example, a substrate for a photosensitive drum, a substrate for a charging roller, a substrate for a drive roller, and the like. In particular, it can be suitably used as a substrate for a photosensitive drum.
In the case of using a cylindrical shaped resin substrate as a base for the photosensitive drum preferably has a surface resistivity of cylindrical resin substrate is 1 × 10 ⁷ Ω / □ or less. If the surface resistivity is 1 × 10 ⁷ Ω / □ or less, that such charge potential between the electrophotographic photosensitive drum and the charging roller can be easily obtained, to effectively prevent the development failure due to charging insufficiency it can.

<Flange of resin substrate>
The cylindrical resin substrate of the present invention may have a gear portion (flange or coupling mechanism) having an outer diameter larger than that of the resin substrate integrally formed at at least one end thereof. The flange may have a gear shape such as a spiral tooth gear or a spur tooth gear, and the shape is not limited as long as the electrophotographic photosensitive drum can be driven. Further, by integrally molding the cylindrical portion by injection molding or the like, the strength of the connecting portion is increased, and the rotational drive of the electrophotographic photosensitive drum can be stably performed even over a long period of use.

<Manufacturing method of resin substrate>
The above-mentioned cylindrical resin substrate can be obtained by using a known molding method such as a continuous melt extrusion molding method, an injection molding method, a stretch blow molding method, and an inflation molding method. A stretch blow molding method is more preferable as a method for molding the cylindrical resin substrate. The method for producing a cylindrical resin substrate by the stretch blow molding method includes the following steps. That is, the step of molding the preform of the cylindrical resin substrate, the step of heating the preform, and the heated preform are mounted on a mold for molding the cylindrical resin substrate, and then the mold is used. This is a process in which a gas is flowed into the inside to perform stretching molding. Further, it includes a step of heating and holding the mold to promote shape correction and crystallization.
A specific manufacturing method will be described with reference to FIGS. 3 and 4, but the resin substrate of the present invention is not limited to the following description.
In FIG. 3, the dried pellet-shaped polyester resin is charged into the hopper 48 of the injection molding apparatus. Then, the cylinder temperature is raised, melted in the screws 42 and 42A, and injection molded into the mold through the nozzle 41A to prepare a preform. Next, the crystallinity of each part can be controlled by heating the lower end, the central part, and the upper end of the preform at different temperatures by using a plurality of heaters installed in the height direction with respect to the preform. ..
After that, the preform 104 is put into the blow molding apparatus shown in FIG. 4, and blow molded by the stretching rod 109 and the force of air (blow air injection portion 110) in the blow mold to form a test tube-shaped cylindrical substrate 112. obtain. Next, high-temperature oil is circulated in the flow path formed inside the blow mold, and a predetermined air pressure is applied for a predetermined time in the blow mold maintained at a constant temperature. After that, the oil is circulated and cooled to room temperature to release the pressure applied to the cylindrical substrate, and the dimensions are improved by annealing to obtain a highly crystallized cylindrical resin substrate.

<Electrophotophotosensitive drum>
The electrophotographic photosensitive drum according to the present invention has, for example, a conductive layer, an undercoat layer, a charge generating layer as a photosensitive layer, a charge transport layer, a protective layer, and the like on the outer surface of the cylindrical resin substrate. Examples of the method for producing the electrophotographic photosensitive drum according to the present invention include a method in which a coating liquid for each layer described later is prepared, applied in the order of desired layers, and dried. At this time, examples of the coating method of the coating liquid include immersion coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, and ring coating. Among these, dip coating is preferable from the viewpoint of efficiency and productivity.

<Conductive layer>
In the present invention, by providing the conductive layer on the cylindrical resin substrate, not only the conductivity is imparted, but also the scratches and irregularities on the surface of the support are concealed, and the reflection of light on the surface of the support is controlled. can do. The conductive layer preferably contains conductive particles and a resin.
Examples of the material of the conductive particles include metal oxides, metals, and carbon black.
Examples of the metal oxide include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, and bismuth oxide. Examples of the metal include aluminum, nickel, iron, nichrome, copper, zinc, silver and the like.
Examples of the resin include, but are not limited to, polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, and alkyd resin.
The conductive layer can be formed by preparing a coating liquid for a conductive layer containing each of the above-mentioned materials and a solvent, forming this coating film, and drying it. Examples of the solvent used for the coating liquid include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, aromatic hydrocarbon solvents and the like. Examples of the dispersion method for dispersing the conductive particles in the coating liquid for the conductive layer include a method using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

<Underlay layer>
In the present invention, the undercoat layer may be provided on the cylindrical resin substrate or the conductive layer. By providing the undercoat layer, the adhesive function between the layers is enhanced, and the charge injection blocking function can be imparted.
The undercoat layer preferably contains a resin. Further, an undercoat layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group.
Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinylphenol resin, and alkyd resin. Examples of other resins include polyvinyl alcohol resin, polyethylene oxide resin, polypropylene oxide resin, polyamide resin, polyamic acid resin, polyimide resin, polyamideimide resin, and cellulose resin.
Examples of the polymerizable functional group contained in the monomer having a polymerizable functional group include an isocyanate group, a blocked isocyanate group, a methylol group, an alkylated methylol group, an epoxy group and a metal alkoxide group. Other examples of the polymerizable functional group of the monomer having a polymerizable functional group include a hydroxyl group, an amino group, a carboxyl group, a thiol group, a carboxylic acid anhydride group, a carbon-carbon double bond group and the like.
Further, the undercoat layer may further contain an electron transporting substance, a metal oxide, a metal, a conductive polymer, or the like for the purpose of enhancing the electrical characteristics. Among these, it is preferable to use an electron transporting substance and a metal oxide.
Examples of the electron transporting substance include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienilidene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, and cyanovinyl compounds. In addition, examples of other electron transporting substances include aryl halide compounds, silol compounds, and boron-containing compounds. An undercoat layer may be formed as a cured film by using an electron transporting substance having a polymerizable functional group as the electron transporting substance and copolymerizing it with the above-mentioned monomer having a polymerizable functional group.
Examples of the metal oxide include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, silicon dioxide and the like. Examples of the metal include gold, silver and aluminum.
Further, the undercoat layer may further contain an additive.
The undercoat layer can be formed by preparing a coating liquid for an undercoat layer containing each of the above-mentioned materials and solvents, forming this coating film, and drying or curing it, or by drying and curing it. .. Examples of the solvent used for the coating liquid include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, aromatic hydrocarbon-based solvents, and the like.

<Photosensitive layer>
The photosensitive layer of the electrophotographic photosensitive drum is mainly classified into (1) a laminated photosensitive layer and (2) a single-layer photosensitive layer. (1) The laminated photosensitive layer has a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance. (2) The single-layer type photosensitive layer has a photosensitive layer containing both a charge generating substance and a charge transporting substance.

(1) Laminated Photosensitive Layer The laminated photosensitive layer has a charge generation layer and a charge transport layer.
(1-1) Charge generating layer The charge generating layer preferably contains a charge generating substance and a resin.
Examples of the charge generating substance include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, phthalocyanine pigments and the like. Among these, azo pigments and phthalocyanine pigments are preferable. Among the phthalocyanine pigments, oxytitanium phthalocyanine pigments, chlorogallium phthalocyanine pigments, and hydroxygallium phthalocyanine pigments are preferable.
The content of the charge generating substance in the charge generating layer is preferably 40% by mass or more and 85% by mass or less, and more preferably 60% by mass or more and 80% by mass or less with respect to the total mass of the charge generating layer. preferable.
Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, polyvinyl butyral resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin and the like. Examples of other resins include polyvinyl alcohol resin, cellulose resin, polystyrene resin, polyvinyl acetate resin, and polyvinyl chloride resin. Among these, polyvinyl butyral resin is more preferable.
Further, the charge generation layer may further contain additives such as an antioxidant and an ultraviolet absorber. Specific examples thereof include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.
The charge generation layer can be formed by preparing a coating liquid for a charge generation layer containing each of the above-mentioned materials and a solvent, forming the coating film, and drying the coating film. Examples of the solvent used for the coating liquid include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, aromatic hydrocarbon solvents and the like.

(1-2) Charge Transport Layer The charge transport layer preferably contains a charge transport substance and a resin.
Examples of the charge transporting substance include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these substances. Be done. Among these, triarylamine compounds and benzidine compounds are preferable.
The content of the charge transporting substance in the charge transport layer is preferably 25% by mass or more and 70% by mass or less, and more preferably 30% by mass or more and 55% by mass or less, based on the total mass of the charge transport layer. preferable.
Examples of the resin include polyester resin, polycarbonate resin, acrylic resin, polystyrene resin and the like. Among these, polycarbonate resin and polyester resin are preferable. As the polyester resin, a polyarylate resin is particularly preferable.
The content ratio (mass ratio) of the charge transporting substance and the resin is preferably 4: 10 to 20:10, more preferably 5: 10 to 12:10.
Further, the charge transport layer may contain additives such as an antioxidant, an ultraviolet absorber, a plasticizer, a leveling agent, a slipperiness imparting agent, and an abrasion resistance improving agent. Specific examples of the additive include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, and the like. Examples of other additives include polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, boron nitride particles and the like.
The charge transport layer can be formed by preparing a coating liquid for a charge transport layer containing each of the above-mentioned materials and a solvent, forming the coating film, and drying the coating film. Examples of the solvent used for the coating liquid include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Among these solvents, ether-based solvents or aromatic hydrocarbon-based solvents are preferable.

(2) Single-layer type photosensitive layer The single-layer type photosensitive layer is formed by preparing a coating liquid for a photosensitive layer containing a charge generating substance, a charge transporting substance, a resin and a solvent, forming this coating film, and drying the coating film. can do. The charge generating substance, the charge transporting substance, and the resin are the same as the examples of the materials in the above "(1) Laminated photosensitive layer".

<Protective layer>
In the present invention, a protective layer may be provided on the photosensitive layer. Durability can be improved by providing a protective layer.
The protective layer preferably contains conductive particles, / or both, and a resin.
Examples of the conductive particles include particles of metal oxides such as titanium oxide, zinc oxide, tin oxide, and indium oxide.
Examples of the charge transporting substance include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these substances. Among these, triarylamine compounds and benzidine compounds are preferable.
Examples of the resin include polyester resin, acrylic resin, phenoxy resin, polycarbonate resin, polystyrene resin, phenol resin, melamine resin, epoxy resin and the like. Of these, polycarbonate resin, polyester resin, and acrylic resin are preferable.
Further, the protective layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. Examples of the reaction at that time include a thermal polymerization reaction, a photopolymerization reaction, and a radiation polymerization reaction. Examples of the polymerizable functional group contained in the monomer having a polymerizable functional group include an acrylic group and a methacrylic group. As the monomer having a polymerizable functional group, a material having a charge transporting ability may be used.
The protective layer may contain additives such as an antioxidant, an ultraviolet absorber, a plasticizer, a leveling agent, a slipper-imparting agent, and an abrasion resistance improver. Specific examples of the additive include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, and the like. Examples of other additives include polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, boron nitride particles and the like.
The protective layer can be formed by preparing a coating liquid for a protective layer containing each of the above-mentioned materials and solvents, forming this coating film, and drying or curing it, or by drying and curing it. Examples of the solvent used for the coating liquid include alcohol-based solvents, ketone-based solvents, ether-based solvents, sulfoxide-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

<Electrophotograph image forming apparatus>
An example of an electrophotographic image forming apparatus using an electrophotographic photosensitive drum according to this embodiment will be described below. As shown in FIG. 1, in the electrophotographic photosensitive drum according to the present invention, an electrophotographic station of a plurality of colors is referred to as an electrophotographic belt according to the present invention (hereinafter referred to as an intermediate transfer belt) in an electrophotographic image forming apparatus. It has a so-called tandem type configuration in which they are arranged side by side in the direction of rotation. In the following description, the symbols of the configurations for each color of yellow, magenta, cyan, and black are subscripted with Y, M, C, and k, respectively, but the subscripts are omitted for the same configuration. In some cases.
In FIG. 1, around the photosensitive drums 1Y, 1M, 1C, and 1k, a charging device 2Y, 2M, 2C, 2k, an exposure device 3Y, 3M, 3C, a developing device 4Y, 4M, 4C, 4k, and an intermediate transfer belt ( Intermediate transcript) 6 is arranged. The photosensitive drum 1 is rotationally driven at a predetermined peripheral speed (process speed) in the direction of arrow F. The charging device 2 charges the peripheral surface of the photosensitive drum 1 to a predetermined polarity and potential (primary charging). The laser beam scanner as the exposure apparatus 3 outputs laser light that has been on / off-modulated in response to image information input from an external device such as an image scanner (not shown) or a computer, and charges the photosensitive drum 1. The surface is scanned and exposed. By this scanning exposure, an electrostatic latent image corresponding to the target image information is formed on one surface of the photosensitive drum.
The developing devices 4Y, 4M, 4C, and 4k contain toners of yellow (Y), magenta (M), cyan (C), and black (k), respectively. Then, the developing device 4 to be used is selected based on the image information, the developing agent (toner) is developed on one surface of the photosensitive drum, and the electrostatic latent image is visualized as a toner image. In the present embodiment, a reverse development method is used in which toner is adhered to the exposed portion of the electrostatic latent image to develop the image. Further, such a charging device, an exposure device, and a developing device constitute an electrophotographic means.
Further, the intermediate transfer belt 6 is an endless belt, which is arranged so as to be in contact with the surface of the photosensitive drum 1, and is stretched on a plurality of tension rollers 20, 21 and 22. Then, it rotates in the direction of the arrow G. In the present embodiment, the tension roller 20 is a tension roller for controlling the tension of the intermediate transfer belt 6 to be constant, the tension roller 22 is a drive roller for the intermediate transfer belt 6, and the tension roller 21 is for secondary transfer. Opposing rollers. Further, primary transfer rollers 5Y, 5M, 5C, and 5k are arranged at the primary transfer positions facing the photosensitive drum 1 with the intermediate transfer belt 6 interposed therebetween.

Each color unfixed toner image formed on the photosensitive drum 1 is an intermediate transfer belt by applying a primary transfer bias having a polarity opposite to the charging polarity of the toner to the primary transfer roller 5 by a constant voltage source or a constant current source. The primary transfer is sequentially electrostatically performed on the 6. Then, a full-color image in which four colors of unfixed toner images are superimposed on the intermediate transfer belt 6 is obtained. The intermediate transfer belt 6 rotates while carrying the toner image transferred from the photosensitive drum 1 in this way. After each rotation of the photosensitive drum 1 after the primary transfer, the surface of the photosensitive drum 1 is cleaned with the transfer residual toner by the cleaning device 11 and repeatedly enters the image forming process.
Further, at the secondary transfer position of the intermediate transfer belt 6 facing the transport path of the recording material 7, a secondary transfer roller (transfer portion) 9 is pressure-welded on the toner image supporting surface side of the intermediate transfer belt 6. Further, on the back surface side of the intermediate transfer belt 6 at the secondary transfer position, an opposing roller 21 that serves as an opposing electrode of the secondary transfer roller 9 and to which a bias is applied is arranged. When the toner image on the intermediate transfer belt 6 is transferred to the recording material 7, a bias having the same polarity as the toner is applied to the opposing roller 21 by the transfer bias applying means 28, for example, −1000 to −3000V is applied to −10. A current of ~ -50 μA flows. The transfer voltage at this time is detected by the transfer high voltage detecting means 29. Further, on the downstream side of the secondary transfer position, a cleaning device (belt cleaner) 12 for removing the toner remaining on the intermediate transfer belt 6 after the secondary transfer is provided.
The recording material 7 introduced at the secondary transfer position was held and conveyed at the secondary transfer position, and at that time, it was controlled to a predetermined value by the secondary transfer bias applying means 28 to the opposing roller 21 of the secondary transfer roller 9. A constant voltage bias (transfer bias) is applied. By applying a transfer bias having the same polarity as the toner to the opposing roller 21, a four-color full-color image (toner image) superimposed on the intermediate transfer belt 6 at the transfer site is collectively transferred to the recording material 7 and transferred to the recording material 7. A full-color unfixed toner image is formed on the top. The recording material 7 to which the toner image has been transferred is introduced into a fixing device (not shown) and fixed by heating.

Examples and comparative examples will be shown below, and the resin substrate according to this embodiment and the electrophotographic photosensitive drum according to this embodiment will be specifically described.

(Measurement method and evaluation method of characteristic value)
First, the evaluation methods (1) to (3) of the cylindrical resin substrate and the electrophotographic photosensitive drum according to Examples and Comparative Examples described later will be described. In the following evaluation, the transfer medium used for image formation was left in an environment with a temperature of 23 ° C. and a relative humidity of 45% for one day, with Ra (arithmetic mean roughness) of 4, Rzjis (ten-point average roughness). A4 size paper with a value of 15 was used.

(1) Crystallinity Two samples of about 5 × 5 mm were cut out at 180 ° intervals in each portion divided into four parts with respect to the width of each region from the central region and the end region of the resin substrate. Using a sample horizontal multipurpose X-ray diffractometer (trade name: Ultima IV, manufactured by Rigaku), CuKα ray was used as a radiation source, and the diffraction intensity was measured with a scanning angle of 2θ = 10 to 40 °. FIG. 2 shows an example in which the produced resin substrate was measured by wide-angle X-ray diffraction measurement. This spectrum was fitted by a Voigt function and divided by crystal-derived peaks, meso-phase-derived peaks, and amorphous halo scattering. After that, the ratio of the crystal scattering intensity to the total scattering intensity in the measurement range was calculated as the crystallinity, and the average value of the total of 8 samples obtained in each region was the crystallinity A (%) in the central region and the end portion, respectively. The crystallinity of the region was B (%).
In this embodiment, a portion having a length of 5% with respect to the total length of the resin substrate from both ends of the resin substrate is set as the end region, and the other portion is set as the central region. The length obtained by dividing the total length of the resin substrate from the length of the central region is defined as the ratio (%) of the width of the central region to the total length, and this ratio is 90%.

(2) Evaluation of image quality
The produced electrophotographic photosensitive drum was mounted on a drum cartridge of a full-color electrophotographic apparatus (trade name: LBP-5200, manufactured by Canon Inc.). The diameter of the charging roller in the cartridge is 8.5 mmΦ and the length is 232 mm. Using this full-color electrophotographic apparatus, a halftone image of magenta toner was formed on a transfer medium. The images formed on the 10000th transfer medium were visually evaluated based on the following criteria.
Rank A: Solid image defects due to toner transfer due to poor charging cannot be confirmed.
Rank B: Solid image defects due to toner transfer caused by poor charging can be slightly confirmed.
Rank C: Solid image defects due to toner transfer caused by poor charging can be clearly confirmed in one place.
Rank D: Solid image defects due to toner transfer caused by poor charging can be clearly confirmed in two or more places.

(3) Evaluation of the amount of gap between the electrophotographic photosensitive drum and the rubber blade The gap when a rubber blade 20 mm shorter than the manufactured electrophotographic photosensitive drum is brought into contact with the electrophotographic photosensitive drum in parallel and an evenly distributed load of 70 N / m is applied. The amount was measured using a high-precision dimension measuring instrument (trade name: LS-9030, manufactured by Keyence). The measured value at the center of the electrophotographic photosensitive drum was taken as the gap amount.
First, the materials shown in Table 1 below were prepared as materials used for producing the cylindrical substrates according to Examples and Comparative Examples.

[Examples 1 to 14]
The pelletized polyester resin shown in Table 1 was dried at a temperature of 140 ° C. for 6 hours. Next, a dried pellet-shaped polyester resin was put into a hopper 48 of an injection molding apparatus (trade name: SE180D, manufactured by Sumitomo Heavy Industries, Ltd.) having the configuration shown in FIG.
Then, the cylinder set temperature was set to 290 ° C., the mixture was melted in the screws 42 and 42A, and injection molded into a mold through the nozzle 41A to prepare a preform 104 having an average diameter of about 23 mm and an average height of about 100 mm. The temperature of the injection molding die at this time was 30 ° C.
Next, five heaters of the same type (maximum output 1000 J / s) were installed at a horizontal distance of 100 mm from the preform, and the preform was heated for 1 minute at the output shown in Table 2. Specifically, the heaters 1 to 5 were installed at heights of 100 mm, 75 mm, 50 mm, 25 mm, and 0 mm (same as the lower end of the preform) from the lower end of the preform, respectively. Here, the average heating temperature at a height of 25 to 75 mm from the lower end of the preform (the central portion of the preform) and the average heating temperature at heights of 0 mm and 100 mm (the upper and lower ends of the preform) from the lower end of the preform. Table 2 also shows the measurements of and.
After that, the preform 104 was put into the blow molding apparatus shown in FIG. Then, in the blow mold, blow molding was performed with the stretching rod 109 and the force of air (blow air injection portion 110) at an air pressure of 1.2 MPa and a stretching rod speed of 500 mm / s to obtain a test tube-shaped cylindrical substrate 112. ..
Next, high-temperature oil circulated in the flow path formed inside the blow mold, and the inner surface of the blow mold was held at 200 ° C. for 30 seconds at an air pressure of 2.0 MPa. Then, the oil at 20 ° C. was circulated and cooled to room temperature to release the pressure applied to the cylindrical substrate, and the dimensions were improved by annealing to obtain a highly crystallized cylindrical resin substrate.
Then, a conductive layer, a charge generating layer as a photosensitive layer, a charge transporting layer, and a protective layer were applied to the outer surface of the cylindrical resin substrate in this order by a spray method and dried. Then, by cutting both ends, a photosensitive drum for an electrophotographic image forming apparatus having a diameter of 24 mmΦ and a length of 257 mm was obtained. Table 3 shows the results of the evaluations (1) to (3) above for this photosensitive drum.

As shown in Table 3, under the production conditions of Examples 1 to 14, only a small gap was observed in the central portion of the resin substrate for the electrophotographic photosensitive drum, and the image quality was all B rank or higher and very very high. It was good. Considering the results of preform heating in Table 2, the average heating temperature of the central part of the preform should be 150 ° C or higher and the average heating temperature of both ends should be lower than the average heating temperature of the central region during heating. Therefore, a desired resin substrate or photosensitive drum can be obtained. That is, the crystallinity of the central region of the resin substrate is 40% or more, and the crystallinity (B / A) of the end region with respect to the central region of the resin substrate is 0.50 or more and 0.84 or less. It can be seen that good image quality can be obtained by adjusting.

[Comparative Examples 1 to 7]
A resin substrate for an electrophotographic photosensitive drum was obtained in the same manner as in Examples 1 to 14, except that the preform was heated under the heating conditions shown in Table 4. The evaluation results are shown in Table 5.

[Comparative Example 8]
The pellet-shaped polyamide resin shown in Table 1 was dried at a temperature of 80 ° C. for 6 hours. Next, the dried pellet-shaped polyamide resin was put into the hopper 48 of the injection molding apparatus (trade name: SE180D, manufactured by Sumitomo Heavy Industries, Ltd.) having the configuration shown in FIG.
Then, the cylinder set temperature was set to 290 ° C., the mixture was melted in the screws 42 and 42A, and injection molded into the mold through the nozzle 41A to directly prepare a cylindrical resin substrate. The temperature of the injection molding die at this time was 30 ° C.

In Comparative Example 1, the temperature of the central portion during preform heating was as low as 140 ° C., and the crystallinity of the resin substrate was lower than 40%, so that the entire substrate was greatly bent and the central portion of the substrate was poorly charged. A solid image defect that seems to be the cause was confirmed. In Comparative Examples 2 to 5, the difference in average heating temperature between the central portion and both ends during preform heating was excessively small, so that the B / A of the resin substrate was larger than 0.84. As a result, the contact pressure was not sufficiently absorbed at the end of the substrate, a large gap was formed in the center of the substrate, and a solid image defect which was considered to be caused by the charging defect occurred. In Comparative Examples 6 and 7, the B / A of the resin substrate was smaller than 0.50 because the difference in the average heating temperature between the central portion and both ends during preform heating was excessively large. As a result, a large difference was generated in the deformation with respect to the contact pressure between the end portion and the center portion of the substrate, and a gap with the peripheral member was generated at the boundary portion. Corresponding to the gap at the boundary, a solid image defect, which is considered to be caused by a poor charging, occurred. In Comparative Example 8, the crystallinity of the central region of the substrate is lower than 40%, the B / A is larger than 0.84, the entire resin substrate is uniformly greatly bent, and a large gap is generated in the entire substrate. A solid image defect, which is thought to be caused by poor charging, occurred.

1 Photosensitive drum 6 Intermediate transfer belt 11 Cleaning device 22 Drive roller 41 Nozzle 42 Screw 48 Hopper 104 Preform 107 Heating device 108 Blow mold 109 Stretching rod 110 Air injection part 112 Cylindrical base 200 Resin base 201 Central area 202 End area

Claims (10)

A cylindrical resin substrate for an electrophotographic photosensitive drum, wherein the resin substrate contains a crystalline thermoplastic resin, and the crystalline thermoplastic resin contains a polyester resin.
The resin substrate has a central region having a predetermined width toward both ends of the resin substrate starting from the center in a direction orthogonal to the circumferential direction, and a predetermined width from both ends of the resin substrate toward the center. Has two end regions and
When the crystallinity of the central region is A (%) and the crystallinity of the end region is B (%),
A and B are the following relational expressions (1) and (2)
A ≧ 40 (1)
0.50 ≤ B / A ≤ 0.84 (2)
A resin substrate characterized by satisfying. The resin substrate according to claim 1, wherein the crystallinity A in the central region is 50% or more. The A and B are the following relational expressions (3)
0.58 ≤ B / A ≤ 0.75 (3)
The resin substrate according to claim 1 or 2, which satisfies the above conditions. The resin substrate according to any one of claims 1 to 3, wherein the polyester resin contains at least one selected from the group consisting of polyalkylene terephthalate and polyalkylene naphthalate. The resin substrate according to any one of claims 1 to 4, wherein the thickness of the resin substrate is 0.50 mm or more and 2.00 mm or less. Claims 1 to 1, wherein the predetermined width of the central region is 82% or more and 98% or less with respect to the sum of the predetermined width of the central region and the predetermined width of the two end regions. 5. The resin substrate according to any one of 5. The resin substrate according to any one of claims 1 to 6, wherein the predetermined widths of the two end regions are independently 5 mm or more and 20 mm or less, respectively. The resin substrate according to any one of claims 1 to 7, wherein a gear portion having an outer diameter larger than that of the resin substrate is integrally molded on at least one of the end portions of the resin substrate. An electrophotographic photosensitive drum that is placed in contact with a charging roller in an electrophotographic image forming apparatus, and the length of the electrophotographic photosensitive drum in a direction orthogonal to the circumferential direction is the circumferential direction of the charging roller. Longer than the length in the orthogonal direction, the electrophotographic photosensitive drum has a cylindrical resin substrate and a photosensitive layer provided on the outer peripheral surface of the resin substrate.
The resin substrate contains a polyester resin, and the first position and the second position corresponding to the positions of the resin substrate that abut on both ends of the charging roller in the direction orthogonal to the circumferential direction of the electrophotographic photosensitive drum. Two ends having a predetermined width toward the end of the resin substrate on the side closer to each position, starting from each of the central region between the positions and the first position and the second position. When the crystallinity of the central region is A (%) and the crystallinity of the end region is B (%), A and B are the following relational expressions (1) and (2). )
A ≧ 40 (1)
0.50 ≤ B / A ≤ 0.84 (2)
An electrophotographic photosensitive drum characterized by satisfying. An electrophotographic photosensitive drum comprising the resin substrate according to any one of claims 1 to 8 and a photosensitive layer provided on an outer peripheral surface of the resin substrate.

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