JP2005250079A - Electrophotographic photoreceptor, process cartridge and electrophotographic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor using a hydrazone-based compound as a charge transporting agent, which is relatively easily manufactured at a low production cost so as to prevent problems of deterioration due to exposure to light, fog or increase in the residual potential due to photomemory and transfer memory, in an electrophotographic photoreceptor using a cylinder of a small diameter and having a charge transporting layer as a thin film, and also to provide a small-size high picture quality electrophotographic apparatus and a process cartridge free from the above problems by using the above electrophotographic photoreceptor. <P>SOLUTION: The electrophotographic photoreceptor has a photosensitive layer produced by layering at least a charge generating layer and a charge transporting layer containing a charge transporting agent and a binder resin, in this order on a cylindrical conductive substrate having 8 to 25 mm outer diameter, with the charge transporting layer having 5 to 15 μm film thickness. In the photoreceptor, the charge transporting layer contains at least a specified charge transporting agent and a binder resin having a specified repeating structural unit. The photoreceptor is used for the process cartridge and the electrophotographic apparatus. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrophotographic photosensitive member used in an electrophotographic apparatus provided with at least a charging unit, an exposure unit, a developing unit, and a transfer unit in this order. The present invention also relates to a process cartridge and an electrophotographic apparatus having the electrophotographic photosensitive member.

  An electrophotographic photoreceptor using an organic photoconductive material (organic electrophotographic photoreceptor) contains a charge generating material on a support as a photosensitive layer in order to satisfy both electrical characteristics and mechanical characteristics. In many cases, a laminated photosensitive layer in which a charge generating layer and a charge transporting layer containing a charge transporting material are laminated is employed. In most cases, the charge transport layer is a surface layer of an electrophotographic photosensitive member.

  The charge transport layer is usually composed of a charge transport agent and a binder resin, and may contain an antioxidant, a lubricant and the like.

  As the charge transfer agent, hydrazone compounds, triarylamine compounds, styryl compounds, butadiene compounds, and the like are used. Among them, hydrazone compounds can be manufactured relatively easily, and are preferably used because of low manufacturing costs.

  However, when a hydrazone compound is used as a charge transport agent, there have been problems of deterioration due to exposure to light, increased fog remaining due to photo memory, and transfer memory.

  As the binder resin, polycarbonate resins and polyarylate resins having relatively high mechanical strength are often used (Japanese Patent Laid-Open Nos. 61-137157, 57-74748, etc.).

  Although the thickness of the charge transport layer depends on the use conditions of the electrophotographic photosensitive member, it is generally said that when the thickness is less than 5 μm, toner fogging occurs and this is a practical problem. In other words, the minimum required film thickness for the charge transport layer is 5 μm.

  However, reducing the thickness of the charge transport layer is a means for sharpening the potential distribution of the electrostatic latent image. For example, in the case of a laminated electrophotographic photoreceptor, the charge generated in the charge generation layer is injected into the charge transport layer and moves to the surface along the electric field, neutralizing the surface potential of the electrophotographic photoreceptor and forming an electrostatic latent image. However, by reducing the film thickness of the charge transport layer, the electric field strength is increased and the diffusion distance is reduced, thereby suppressing the diffusion of charges in the direction perpendicular to the electric field, and faithful to digital light such as laser light. It is possible to form a sharp electrostatic latent image. Further, when the electrophotographic photosensitive member is considered as a kind of dielectric, the electrostatic capacity of the electrophotographic photosensitive member is increased by reducing the thickness of the charge transport layer, and therefore, an electrophotographic method for obtaining a predetermined surface potential. As a result, the charge density on the surface of the photoreceptor increases, and as a result, the development electric field is increased, and the potential of the electrostatic latent image becomes deeper in the potential direction, thereby realizing high resolution.

In recent years, the demand for downsizing has increased, and the size of the electrophotographic photosensitive member itself, particularly in the case of a cylindrical electrophotographic photosensitive member, tends to have a smaller cylinder diameter.
JP 61-137157 A JP-A-57-74748

  Since the hydrazone compound can be produced relatively easily, the production cost is low, and it is preferably used as a charge transport agent. However, when a hydrazone compound is used as a charge transport agent, there has been a problem of deterioration due to light exposure, that is, a fog remaining power increase due to a photo memory and a transfer memory. This problem tended to become prominent at low temperatures or high humidity.

  Here, the following can be said with respect to the diameter of the electrophotographic photoreceptor and the film thickness of the charge transport layer of the electrophotographic photoreceptor.

  In recent years, the demand for downsizing has increased, and the size of the electrophotographic photosensitive member itself, particularly in the case of a cylindrical electrophotographic photosensitive member, tends to have a smaller cylinder diameter. The reduction in diameter (8 to 25 mmφ) not only reduces the size of the apparatus, but also reduces the cost of the electrophotographic photosensitive member.

  Further, by reducing the film thickness of the charge transport layer of the electrophotographic photosensitive member, it becomes possible to form a sharp electrostatic latent image faithful to digital light such as laser light. Further, when the electrophotographic photosensitive member is considered as a kind of dielectric, the electrostatic capacity of the electrophotographic photosensitive member is increased by reducing the film thickness. Therefore, the surface of the electrophotographic photosensitive member for obtaining a predetermined surface potential is increased. As a result, the charge density increases, and as a result, the development electric field is increased, and the potential of the electrostatic latent image becomes deeper in the potential direction, and high resolution is realized. In other words, the charge transport layer is generally the thickest among the functionally separated organic photosensitive layers, and the ratio of the material cost to the photosensitive layer is large, but the charge transport layer should be brought close to the minimum necessary thickness. Leads to a reduction in cost as well as the amount of solvent used in preparing the photosensitive layer. In recent years, high image quality has been demanded, but it is advantageous for high image quality by making the charge transport layer a thin film (5 to 15 μm).

  However, problems caused by the electrophotographic photosensitive member using these hydrazone compounds become conspicuous by reducing the diameter of the cylinder and reducing the thickness of the charge transport layer.

  That is, by reducing the diameter of the electrophotographic photosensitive member and the cylinder diameter, the number of rotations of the cylinder for obtaining an electrophotographic image per unit area is increased, so that the electrophotographic process means (charging, This is because light and electrical damage from exposure and transfer increase, and deterioration due to light exposure, that is, fog remaining power increase due to photo memory, and problems of transfer memory become remarkable. That is, when the diameter of the electrophotographic photosensitive member is small, specifically, 25 mmφ or less, the phenomenon becomes particularly prominent, which is disadvantageous compared to the electrophotographic photosensitive member of the conventional size.

  On the other hand, as the film thickness of the charge transport layer decreases, the capacitance increases, so that the amount of current necessary for charging to a constant dark portion potential increases. In addition, as the thickness of the charge transport layer decreases, the capacitance increases and the number of charges increases. Therefore, the amount of exposure necessary to obtain a constant bright portion potential when a latent image is formed on the electrophotographic photoreceptor is also increased. The charge transport layer increases as the thickness of the charge transport layer decreases. That is, the light and electrical damage from the electrophotographic process means (charging, exposure, transfer) to the electrophotographic photosensitive member are increased, so that deterioration due to light exposure, that is, the fog remaining power increase due to the photo memory, the problem of the transfer memory Becomes prominent. Therefore, when the thickness of the charge transport layer of the electrophotographic photosensitive member is thin, specifically, when the thickness is 15 μm or less, the phenomenon becomes more prominent, so the thickness of the conventional charge transport layer (generally 20 ˜30 μm), which is disadvantageous.

  An object of the present invention is to use a hydrazone-based compound that can be produced relatively easily and at a low production cost in an electrophotographic photoreceptor using a small diameter cylinder of 8 to 25 mmφ and a charge transport layer of 5 to 15 μm. It is intended to provide an electrophotographic photosensitive member that does not suffer from the problems of deterioration due to light exposure, increase in fog remaining due to photo memory, and transfer memory.

  Another object of the present invention is to use the above-described electrophotographic photosensitive member, which does not cause the problem of deterioration due to light exposure, i.e., the occurrence of a fog remaining power increase due to a photomemory, and a transfer memory, and is small and high-quality electrophotographic apparatus and process cartridge. Is to provide.

  The present invention has a photosensitive layer that is cylindrical and has a charge transport layer containing at least a charge generation layer, a charge transport agent, and a binder resin in this order on a conductive substrate having an outer diameter of 8 to 25 mmφ. In the electrophotographic photosensitive member having a charge transport layer thickness of 5 to 15 μm, the charge transport layer is represented by at least the charge transport agent (CTM-1) represented by the following formula (1) and the following formula (2). A binder resin having a repeating structural unit,

(Wherein, Ar ₁ and Ar ₂ .Ar ₁ and Ar ₂ represents an aryl group which may have a substituent group may be the same or different.)

(In the formula (2), R ^{11 to} R ¹⁸ are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted monovalent aliphatic hydrocarbon group, a substituted or unsubstituted monovalent alicyclic carbonization. A hydrogen group or a substituted or unsubstituted monovalent aromatic hydrocarbon group, R ¹⁹ represents a divalent linking group, and Ar ¹¹ represents a substituted or unsubstituted divalent aromatic hydrocarbon group. K is 0 or 1.)
Among the resin molecules constituting the binder resin contained in the charge transport layer, the resin molecules having a molecular weight in the range of 1500 to 5500 include a chain resin molecule having a structure represented by the following formula (21) and the following formula: The electrophotographic photosensitive member is characterized in that both of the cyclic resin molecules having the structure represented by (22) exist.

(Equation (21), in ^{(22), R 11 ~R 18} , R 19, Ar 11, k have the same meanings as ^{R 11 ~R 18, R 19,} Ar 11, k in Equation (2). E ¹¹ and E ¹² each independently represent a monovalent end group, and m and n are each independently a positive integer.)
The present invention also provides a process cartridge and an electrophotographic apparatus having the electrophotographic photosensitive member.

  According to the present invention, a hydrazone compound having a specific structure and a binder resin having a specific structure are used for the charge transport layer of the electrophotographic photosensitive member, so that the diameter of the charge transport layer is smaller than that of the conventional one. Also, an electrophotographic photosensitive member having a thin film (5 to 15 μm), a process cartridge and an electrophotographic apparatus using the same can be provided. That is, (1) the small diameter can contribute to the miniaturization of the apparatus and can provide an inexpensive electrophotographic photosensitive member, process cartridge, and electrophotographic apparatus. (2) Since the film thickness of the charge transport layer is a thinner film (5 to 15 μm) than the conventional one, it is possible to provide a high-quality image in addition to being inexpensive. (3) An inexpensive electrophotographic photosensitive member can be provided by using a hydrazone-based compound that can be manufactured relatively easily and has a low manufacturing cost as a charge transporting agent. In addition, problems caused by electrophotographic photoreceptors using hydrazone compounds that become conspicuous when the diameter of the cylinder is reduced or the thickness of the charge transport layer is reduced by combining with a specific binder resin (deterioration due to light exposure, that is, photo memory Therefore, it is possible to provide an electrophotographic photosensitive member that does not cause a fog remaining power increase and a transfer memory problem, and a process cartridge and an electrophotographic apparatus using the same.

  Hereinafter, the present invention will be described in detail.

  The present invention has a photosensitive layer that is cylindrical and has a charge transport layer containing at least a charge generation layer, a charge transport agent, and a binder resin in this order on a conductive substrate having an outer diameter of 8 to 25 mmφ. An electrophotographic photoreceptor having a charge transport layer thickness of 5 to 15 μm, wherein the charge transport layer contains at least a specific charge transport agent and a binder resin having a specific repeating structural unit, A process cartridge and an electrophotographic apparatus using First, the charge transport layer of the electrophotographic photoreceptor of the present invention will be described.

  As the charge transport agent used in the charge transport layer of the present invention, at least the charge transport agent (CTM-1) represented by the following formula (1) is used.

(Wherein, Ar ₁ and Ar ₂ .Ar ₁ and Ar ₂ represents an aryl group which may have a substituent group may be the same or different.)
Table 1 gives specific examples of the charge transfer agent (CTM-1) represented by the above formula (1). However, the present invention is not limited to these specific examples.

  In general, hydrazone compounds have a trans structure, but the charge transfer agent (CTM-1) represented by the above formula (1) is isomerized by an electrical action during charging or exposure to change into a cis structure. The molecular orientation is expected to change. When it cannot be combined with the binder resin described later, CTM-1 has a cis structure, and due to the localization of electrons, charges are trapped in the charge transport layer and are difficult to hop. The smoothness becomes worse, and deterioration due to light exposure, that is, the problem of the fog remaining power increase due to the photo memory and the transfer memory become more remarkable.

  However, the combination with the binder resin described later results in a molecular orientation in which the charges are less likely to stay, and the electrons are delocalized, so that the charges can move smoothly in the charge transport layer, It is expected that deterioration due to light exposure, i.e., a fog remaining power increase due to photo memory, and a problem of transfer memory will not occur.

  In order to obtain the effect, it is more preferable that the charge transport layer contains at least a compound (CTM-2) represented by the following formula (6) in addition to the CTM-1 as a charge transport agent. The preferable value of the mass ratio of CTM-1 and CTM-2 is that CTM-2 is 1 to 3 with respect to CTM-1 and 100.

(In the formula, Ar ₃ represents a condensed polycycle which may have a substituent.)
Table 2 gives specific examples of the charge transfer agent (CTM-2) represented by the above formula (5). However, the present invention is not limited to these specific examples.

  Moreover, a favorable effect is acquired similarly by containing the compound (CTM-3) shown by following formula (6) at least other than said CTM-1 as a charge transport agent in a charge transport layer. The preferable value of the mass ratio of CTM-1 and CTM-3 is 5 to 15 for CTM-3 to 100.

  A molecule in which the charge transport layer contains both CTM-1 and CTM-2 or CTM-3, and the charge is less likely to stay in combination with the binder resin described later than when CTM-2 or CTM-3 is not contained. It becomes oriented and charges can move more smoothly in the charge transport layer, and there is no problem of deterioration due to light exposure, that is, fog remaining power up due to photo memory, transfer memory problem, and a greater effect Expected to be obtained.

  The mass ratio of CTM-1 and CTM-2, or the mass ratio of CTM-1 and CTM-3 is preferably within the range of the values shown above, but if it is smaller than this range, CTM-2 or The effect of the combination is not the same as when CTM-3 is not provided. Moreover, when larger than this range, the effect of CTM-1 will be inhibited.

  On the other hand, the binder resin used for the charge transport layer of the electrophotographic photosensitive member of the present invention is a resin having a repeating structural unit represented by the following formula (2).

(In the formula (2), R ^{11 to} R ¹⁸ are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted monovalent aliphatic hydrocarbon group, a substituted or unsubstituted monovalent alicyclic carbonization. A hydrogen group or a substituted or unsubstituted monovalent aromatic hydrocarbon group, R ¹⁹ represents a divalent linking group, and Ar ¹¹ represents a substituted or unsubstituted divalent aromatic hydrocarbon group. K is 0 or 1.)
Among the resin molecules constituting the binder resin contained in the charge transport layer, the resin molecules having a molecular weight in the range of 1500 to 5500 include a chain resin molecule having a structure represented by the following formula (21) and the following formula: The electrophotographic photosensitive member is characterized in that both of the cyclic resin molecules having the structure represented by (22) exist.

(Equation (21), in ^{(22), R 11 ~R 18} , R 19, Ar 11, k have the same meanings as ^{R 11 ~R 18, R 19,} Ar 11, k in Equation (2). E ¹¹ and E ¹² each independently represent a monovalent end group, and m and n are each independently a positive integer.)
In the above formula (2), when k is 0, the resin having a repeating structural unit represented by the formula is a polycarbonate resin, and when k is 1, the resin having a repeating structural unit represented by the formula is polyarylate. Resin. Of the resin molecules constituting the binder resin, resin molecules having a molecular weight in the range of 1500 to 5500 include chain resin molecules having the structure represented by the above formula (21) and the above formula (22). There are both cyclic resin molecules having the structure shown.

  In addition, about the phthalic acid structure in the repeating structural unit which polyarylate resin has, it is that the molar ratio (terephthalic acid structure: isophthalic acid structure) of a terephthalic acid structure and an isophthalic acid structure is 30: 70-70: 30. preferable.

  Some substances having a cyclic structure have inclusion properties, and when a low molecular weight component as a guest compound is included, they are firmly fixed. By forming the clathrate compound, the original properties of the low molecular weight component that is the guest compound are less likely to appear in the table.

  The polycarbonate resin and polyarylate resin used as the binder resin for the charge transport layer, which is the surface layer of the electrophotographic photoreceptor of the present invention, have relatively high carbonate bonds and ester bonds. If it is a substance having a carbonate bond or an ester bond and having a cyclic structure, the low molecular weight component can be firmly included. Polycarbonate resin and polyarylate resin can cause a head to tail cyclization reaction, and the cyclic structure can be produced in various sizes. It is possible to tightly include the components.

  As an example, a reaction formula for synthesizing a polycarbonate resin using bisphenol A is shown.

  In the above reaction formula, x is a positive integer.

  In addition, the polycarbonate resin and the polyarylate resin, which are thermoplastic resins, are relatively three-dimensionally crosslinked with respect to the curable resin, so that the conformation is relatively easily changed. The polycarbonate resin or polyarylate resin having a specific structure according to the present invention can be used in combination with the above-described charge transporting agent, and the charge transporting agent changed to a cis structure is not localized in the charge transporting layer. It seems that there is a function to orient it at a position where it can move. As a result, it is expected that the deterioration due to light exposure, that is, the problem of the fog remaining power increase due to the photo memory and the transfer memory will not occur, and a greater effect can be obtained.

  The present inventors have included the above cyclic resin molecule as a resin molecule constituting the polycarbonate resin or polyarylate resin which is the binder resin of the charge transport layer, whereby the cyclic resin molecule has changed to a cis structure. It has been found that the charge transport agent has a function of orienting the charge transport agent at a position where the charge can be smoothly moved without being localized in the charge transport layer.

  In particular, it was more effective if the molecular weight of the cyclic resin molecule was 1000 or more.

  Even if the weight average molecular weight (Mw) of the binder resin itself is increased, the cyclic resin molecules in the binder resin itself are not so large, and the molecular weight is often in the range of 1500 to 5500. And it became clear that the cyclic resin molecule having a molecular weight in the range of 1500 to 5500 greatly contributes to the expression of the effect obtained by including the cyclic resin molecule.

  However, the cyclic resin molecule tends to have steric strain energy as compared with the chain resin molecule, and in particular, the low molecular weight cyclic resin molecule having a low degree of freedom tends to increase the strain energy. Therefore, if the content of the cyclic resin molecule is small, the effect obtained by including the cyclic resin molecule is small, while if the content of the cyclic resin molecule is large, the cyclic structure is immediately formed by the energy of discharge during charging. Since the cyclic resin molecule is not present, the effect of the present invention cannot be obtained.

  Therefore, in order to obtain the effect of the present invention, among the resin molecules constituting the binder resin contained in the charge transport layer, the chain resin molecules and the above-mentioned resin molecules having a molecular weight in the range of 1500 to 5500 are added. Both of the cyclic resin molecules must be present.

  Specific preferred ranges for the ratio of chain resin molecules to cyclic resin molecules in the binder resin of the charge transport layer and the weight average molecular weight (Mw) of the binder resin itself are as follows.

  That is, when the binder resin contained in the charge transport layer is a polycarbonate resin, the weight average molecular weight (Mw) is preferably 40000 or more and 250,000 or less, and the molecular weight is in the range of 1500 or more and 5500 or less. When the number of chain resin molecules having the structure represented by 21) is ΣLm and the number of cyclic resin molecules having the structure represented by the above formula (22) in the molecular weight range of 1500 to 5500 is ΣCn, ΣLm and It is preferable that ΣCn satisfies the following relational expression (3).

  When the binder resin contained in the charge transport layer is a polyarylate resin, the weight average molecular weight (Mw) is preferably 40,000 or more and 200,000 or less, and the above formula in the range of molecular weight of 1500 or more and 5500 or less. When the number of chain resin molecules having the structure represented by (21) is ΣLm, and the number of cyclic resin molecules having the structure represented by the above formula (22) in the molecular weight range of 1500 to 5500 is ΣCn, ΣLm And ΣCn preferably satisfy the following relational expression (4).

  Further, as described above, the charge transport layer which is the surface layer of the electrophotographic photosensitive member of the present invention is a thin film, and specifically, the film thickness is 5 μm or more and 15 μm or less.

  These samples analyze a sample in which a charge transport layer is dissolved with a matrix-assisted laser detachable ionization-time-flight-mass spectrometer (MALDI-TOF MS), and are chain-like among peaks in a molecular weight range of 1500 to 5500. It can be derived from the sum of peak intensities of resin molecules and the sum of peak intensities of cyclic resin molecules. The peak of the chain resin molecule and the peak of the cyclic resin molecule are the same in the repeating structural unit, so the peak interval itself is the same, but the position where the peak appears differs depending on the presence or absence of the terminal group. It is possible to analyze.

  This analysis method has a feature that analysis can be performed directly from the charge transport layer of the electrophotographic photoreceptor after fabrication.

  Specifically, the charge transport layer which is the surface layer of the electrophotographic photoreceptor is scraped, dissolved in tetrahydrofuran or chloroform, and then dissolved in a solution in which matrix molecules such as 1,8-dihydroxyanthracene and 9-nitroanthracene are dissolved. Mix to make a measurement sample. At this time, the ratio of the matrix molecule to the charge transport layer (matrix molecule: charge transport layer) is preferably 100: 1 to 1000: 1 by mass ratio. If the ratio of the charge transport layer is too low, the amount of detection decreases, and if the ratio of the charge transport layer is too high, desorption and ionization of the substance to be measured may be hindered.

  Further, there is no particular limitation on the wavelength of the laser beam irradiated at the time of measurement. For example, a nitrogen laser (wavelength: 337 nm) has strong absorption in the matrix, whereas the binder resin of the charge transport layer has almost absorption. Therefore, it is preferable because the measurement can be performed without causing the destruction of the binder resin.

  In addition, a metal salt such as silver trifluoroacetate may be added for the purpose of promoting ionization during measurement sample preparation. The measurement is preferably performed in a positive ion detection mode. In particular, when a metal salt is not added as an ionization accelerator, a measurement target substance is detected as a proton adduct (molecular weight is increased by 1), and a metal salt is added. In some cases, it is detected as an adduct of the metal ion (mass increases by the atomic weight of the metal).

  The method for adjusting the ratio of the cyclic resin molecules to the resin molecules constituting the binder resin is, for example, a method of adding a desired amount of cyclic resin molecules that have been prepared in advance, or a temperature during the polymerization reaction is appropriately controlled. Or appropriately controlling the polymerization termination reaction during the synthesis of chain resin molecules, adjusting the concentration of various monomers and polymerization initiators in the polymerization reaction system, and adjusting the rigidity of various monomer molecules as appropriate. Thus, a method of making both a chain resin molecule and a cyclic resin molecule can be mentioned. As a method of increasing the ratio of the cyclic resin molecule, methods disclosed in JP-A-61-238823, JP-A-2-133425, JP-A-3-199231 and the like can be referred to. As methods for reducing the ratio of the resin molecules, methods disclosed in JP-A-7-179996, JP-A-7-102056, JP-A-2003-40997 and the like can be referred to.

  Polycarbonate resins and polyarylate resins are synthesized using bisphenol as a starting material. Specific examples of bisphenol are given below. However, the present invention is not limited to these specific examples.

  Further, specific examples of polycarbonate resins starting from these bisphenols are shown in Table 3, and specific examples of polyarylate resins are shown in Table 4. However, the present invention is not limited to these specific examples.

  The ratio of the charge transport agent to the binder resin in the charge transport layer is preferably 2 or more and less than 5 with respect to the binder resin 10. Since it is not sufficient, an appropriate bright part potential cannot be obtained, and when the ratio of the charge transport agent is too large, the molecular orientation of the charge transport agent is disturbed and starts to localize, so that a sufficient effect cannot be obtained.

  Hereinafter, other than the charge transport layer of the electrophotographic photoreceptor of the present invention will be described.

  As the conductive support, one having conductivity itself, for example, aluminum, aluminum alloy, or stainless steel can be used, and aluminum, aluminum alloy, indium oxide-tin oxide alloy, or the like can be used by vacuum deposition. The support having a film-formed layer, plastic, a support in which plastic or paper is impregnated with a suitable binder resin with conductive fine particles (for example, carbon black, tin oxide, titanium oxide and silver particles), conductive A plastic having a binder resin can be used. In addition, the shape is a sheet or a cylinder, but the cylinder rotation speed for obtaining an electrophotographic image per unit area is particularly reduced by reducing the outer diameter of the cylinder, that is, the diameter of the electrophotographic photosensitive member. This is because the increase in light and electrical damage from the electrophotographic process means (charging, exposure, transfer) to the electrophotographic photosensitive member is caused by light exposure when a conventional electrophotographic photosensitive member is used. Deterioration, that is, the problem of increased fog remaining due to photo memory and transfer memory becomes significant. That is, when the diameter of the electrophotographic photosensitive member is small, specifically, 25 mmφ or less, the phenomenon becomes particularly prominent. However, by using the electrophotographic photosensitive member of the present invention, the effect is conspicuous. Become.

  Further, a binder layer (adhesive layer) having a barrier function and an adhesive function can be provided between the support and the photosensitive layer. The binder layer is used to improve the adhesion of the photosensitive layer, improve the coatability, protect the support, cover defects on the support, improve the charge injection from the support, and protect against electrical breakdown of the photosensitive layer. It is formed. The binder layer can be formed of casein, polyvinyl alcohol, ethyl cellulose, ethylene-acrylic acid copolymer, polyamide, modified polyamide, polyurethane, gelatin, aluminum oxide, or the like. The film thickness of the binder layer is preferably 5 μm or less, and particularly preferably 0.1 to 3 μm.

  Examples of the charge generating substance used in the present invention include (1) azo pigments such as monoazo, disazo and trisazo, (2) phthalocyanine pigments such as metal phthalocyanine and nonmetal phthalocyanine, and (3) indigo compounds such as indigo and thioindigo. Pigments, (4) perylene pigments such as perylene anhydride and perylene imide, (5) polycyclic quinone pigments such as anthraquinone and pyrenequinone, (6) squarylium dyes, (7) pyrylium salts and thiapyrylium salts ( 8) Triphenylmethane dyes, (9) inorganic substances such as selenium, selenium-tellurium and amorphous silicon, (10) quinacridone pigments, (11) azulenium salt pigments, (12) cyanine dyes, (13) xanthene dyes, 14) Quinone imine dye, (15) Su Lil dyes, and (16) cadmium sulfide and (17) zinc oxide.

  Examples of the binder resin used for the charge generation layer include polycarbonate resin, polyester resin, polyarylate resin, butyral resin, polystyrene resin, polyvinyl acetal resin, diallyl phthalate resin, acrylic resin, methacrylic resin, vinyl acetate resin, phenol resin, Examples include, but are not limited to, silicone resins, polysulfone resins, styrene-butadiene copolymer resins, alkyd resins, epoxy resins, urea resins, and vinyl chloride-vinyl acetate copolymer resins. These can be used alone or as a mixture or as a copolymer polymer.

  The solvent used for the charge generation layer coating is selected from the solubility and dispersion stability of the resin used and the charge generation material, but examples of the organic solvent include alcohols, sulfoxides, ketones, ethers, esters, Aliphatic halogenated hydrocarbons or aromatic compounds can be used.

  The charge generation layer is well dispersed by a method such as a homogenizer, ultrasonic wave, ball mill, sand mill, attritor or roll mill, together with a binder resin and a solvent in an amount of 0.3 to 4 times the mass of the charge generation material, It is formed by coating and drying. The thickness is preferably 5 μm or less, and particularly preferably in the range of 0.01 to 1 μm.

  In addition, various sensitizers, antioxidants, ultraviolet absorbers, plasticizers, and known charge generating substances can be added to the charge generation layer as necessary.

  As the charge generating material in the present invention, those generally known can be used, such as selenium-tellurium, pyrylium, metal phthalocyanine, metal-free phthalocyanine, anthanthrone, dibenzpyrenequinone, trisazo, cyanine, disazo, monoazo. , Each pigment such as indigo and quinacdrine. These pigments were well dispersed using a homogenizer, ultrasonic dispersion, ball mill, vibration mill, sand mill attritor, roll mill, liquid collision type high-speed disperser, etc. together with binder resin and solvent having a weight of 0.3 to 4 times. A dispersion is obtained. In the case of a multilayer electrophotographic photoreceptor, a charge generation layer is obtained by applying this solution and drying. The film thickness is preferably 5 μm or less, and particularly preferably 0.1 to 2 μm.

  Hereinafter, the present invention will be described in more detail with reference to specific examples. However, embodiments of the present invention are not limited to these. In the examples, “part” means “part by mass”.

(Example 1)
A 5 mass% methanol solution of polyamide resin (trade name: Amilan CM8000, manufactured by Toray Industries, Inc.) is applied on this by using an aluminum cylinder of φ24 mm × 246 mm as a support, and an undercoat layer having a film thickness of 0.5 μm is applied. Provided.

  Next, 3.5 parts of hydroxygallium phthalocyanine crystals having strong peaks at 7.4 ° and 28.2 ° of the Bragg angle (2θ ± 0.2 °) in the characteristic X-ray diffraction of CuKα and polyvinyl butyral resin (trade name) : ESREC BX-1, Sekisui Chemical Co., Ltd.) 1 part is added to 120 parts of cyclohexanone, dispersed in a sand mill using 1 mmφ glass beads for 3 hours, and diluted with 120 parts of ethyl acetate. A coating solution was prepared. On the undercoat layer, this charge generation layer coating solution was applied by dip coating and dried at 100 ° C. for 10 minutes to form a charge generation layer having a thickness of 0.15 μm.

  Subsequently, compound example No. of Table 1 was shown. No. 1 charge transport agent 4.00 parts and Table 3 Compound Example No. 10.00 parts of the polycarbonate resin represented by 1 was dissolved in 100.00 parts of monochlorobenzene. This coating solution was applied onto the charge generation layer and dried with hot air at 105 ° C. over 1 hour to form a charge transport layer having a thickness of 12 μm, whereby an electrophotographic photoreceptor was obtained.

  This electrophotographic photosensitive member was evaluated using a modified machine of HP LaserJet 1300. The HP LaserJet 1300 remodeling machine is equipped with a volume that changes the voltage of the primary charging high-voltage power supply and laser exposure so that the initial dark part potential and light part potential become appropriate, even when paper is not passed And a switch B for applying a transfer voltage without printing. This switch A was changed over when the paper was passed / not passed. Further, the switch B was appropriately operated in order to evaluate the transfer memory. When the switch B is OFF, the transfer voltage is turned ON / OFF according to the operation of the HP LaserJet 1300, and the transfer voltage is forcibly applied only when the switch B is ON.

  On the other hand, a modified version of the HP LaserJet 1300 process cartridge was also prepared. The modification was made by removing the cleaning blade, removing the developing unit, and attaching a potential probe so that the potential of the electrophotographic photosensitive member could be measured at the place where the developing unit was located. Hereinafter, this process cartridge is referred to as a potential cartridge. A modified version of the HP LaserJet 1300 process cartridge was prepared as follows. The content of the modification is that the electrophotographic photosensitive member can be replaced so that the image of the electrophotographic photosensitive member of the present invention can be evaluated, and this modified process cartridge is hereinafter referred to as an image cartridge. One image cartridge was prepared for each evaluation environment for each sample.

  First, the electrophotographic photosensitive member, the potential process cartridge, the image cartridge, and the modified HP LaserJet 1300 are left overnight at 20.0 ° C., 6.5% RH, or 38.0 ° C., 82% RH, respectively. The electrophotographic photosensitive member was incorporated into a potential process cartridge. The potential process cartridge was attached to a modified machine of HP LaserJet 1300, and a white solid image was printed for one A4 size sheet without passing paper, and the dark part potential at that time was measured. When the dark portion potential was not −690 V, the primary charging voltage was adjusted, and a white solid image was printed again for A4 size with no paper passing, and the dark portion potential at that time was measured. When the dark part potential was -690 V, three white solid images were printed in A4 size without passing paper, and the dark part potential was reconfirmed. Next, one black solid image was printed in A4 size, and the bright part potential at that time was measured. When the bright part potential was not −170 V, the laser exposure amount was adjusted, and one black solid image was printed again in A4 size with no paper passing, and the bright part potential at that time was measured. When the light portion potential was −170 V, three black solid images were printed in A4 size without passing paper, and the light portion potential was reconfirmed. Next, remove the electrophotographic photosensitive member from the potential cartridge, replace it with an image cartridge, and print two white solid images in A4 size, two text images, and two white solid images in A4 size. The initial image was used. Thereafter, 2000 continuous text images were printed, and after printing, two white solid images were printed in A4 size, two text images were printed, and two white solid images were printed in A4 size. Further, the switch B is turned on for 1 minute so that a transfer voltage is applied to a part of the electrophotographic photosensitive member. After the switch B is turned off, two white solid images are printed in A4 size and two character images are printed. Two solid white images were printed in A4 size, and used as transfer memory evaluation images. Next, the electrophotographic photosensitive member is replaced with a potential cartridge, and three white solid images are printed in A4 size without paper passing, and then three white solid images are printed in A4 size without paper passing. Then, the dark part potential and the light part potential were measured. These potentials were evaluated as potentials at portions other than forcibly applying the transfer voltage for transfer memory evaluation. These results are shown in Table 5. Image ranks were ranked by ◎, ○, ○ △, and ×. ◎ indicates the best and X indicates the worst. There is no practical problem until △△. ◎, ○, ○ △ rank the initial image, the post-endurance image after continuous printing of 2000 sheets, and the transfer memory evaluation image by fog, transfer memory and the like. The bright portion potential after endurance correlates with the fog (photo memory fog) on the image, and the fog on the image is worse as the bright portion potential after endurance is larger on the minus side.

(Example 2)
The charge transport agent for the charge transport layer of the electrophotographic photosensitive member is represented by the compound example No. 1 in Table 1. 1 from the charge transporting agent shown in Table 1. An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that the charge transfer agent shown in FIG. The results are shown in Table 5.

(Example 3)
The charge transport agent for the charge transport layer of the electrophotographic photosensitive member is represented by the compound example No. 1 in Table 1. 1 from 4.00 parts of the charge transfer agent shown in Table 1. 1.92 parts of the charge transport agent shown in Table 1 and Compound Example No. An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that 0.08 part of the charge transfer agent represented by 1 was used. The results are shown in Table 5.

Example 4
The charge transport agent for the charge transport layer of the electrophotographic photosensitive member is represented by the compound example No. 1 in Table 1. 1 from 4.00 parts of the charge transfer agent shown in Table 1. An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that 3.64 parts of the charge transfer agent represented by 1 and 0.36 parts of the compound represented by formula (6) were used. The results are shown in Table 5.

(Examples 5-6)
Compound Example Nos. The charge transfer agent represented by No. 1 is compound No. 1 of Table 1. An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 3 or 4 except that the charge transporting agent represented by 8 was used. The results are shown in Table 5.

(Example 7)
The charge transport agent for the charge transport layer of the electrophotographic photosensitive member is represented by the compound example No. 1 in Table 1. 1 from 4.00 parts of the charge transfer agent shown in Table 1. 3.64 parts of the charge transfer agent represented by 1 and the following formula (7)

An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 1 except that 0.36 part of the compound represented by the formula (1) was used. The results are shown in Table 5.

(Examples 8 to 9)
The charge transport agent for the charge transport layer of the electrophotographic photosensitive member is represented by the compound example No. 1 in Table 1. An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that the charge transfer agent represented by 1 was changed from 4.00 parts to 2.00 parts and 5.00 parts, respectively. The results are shown in Table 5.

(Examples 10 to 11)
The charge transport agent for the charge transport layer of the electrophotographic photosensitive member is represented by the compound example No. 1 in Table 1. 1 to 3.96 parts and 3.89 parts, respectively, from 3.92 parts to the charge transfer agent represented by Compound No. 1 in Table 1. An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 3 except that the charge transfer agent represented by 3 was changed from 0.08 parts to 0.04 parts and 0.11 parts, respectively. The results are shown in Table 5.

(Examples 12 to 13)
The charge transport agent for the charge transport layer of the electrophotographic photosensitive member is represented by the compound example No. 1 in Table 1. 8 to 3.80 parts and 3.48 parts, respectively, and from 0.36 parts of the compound represented by formula (6) to 0.20 parts and 0.52 parts, respectively. An electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 4 except for the change. The results are shown in Table 5.

(Examples 14 to 17)
The binder resin of the charge transport layer of the electrophotographic photosensitive member is compound No. in Table 3. Compound Example No. 1 in Table 3 from the polycarbonate resin shown in FIG. An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that the polycarbonate resin was changed to 3, 4, 5, or 6. The results are shown in Table 5.

(Examples 18 to 20)
An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that the thickness of the charge transport layer of the electrophotographic photosensitive member was changed to 5, 8, and 15 μm. The results are shown in Table 5.

(Examples 21 to 33)
The binder resin of the charge transport layer of the electrophotographic photosensitive member is compound No. in Table 3. From the polycarbonate resin shown in FIG. An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Examples 1 to 13 except that the polyarylate resin represented by 3 was used. The results are shown in Table 5.

(Examples 34 to 35)
The binder resin of the charge transport layer of the electrophotographic photosensitive member is represented by the compound No. in Table 4. Compound Example No. 1 in Table 4 from the polyarylate resin shown in FIG. An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 21 except that the polycarbonate resin shown in 2 was used. The results are shown in Table 5.

(Examples 36 to 38)
An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 21 except that the thickness of the charge transport layer of the electrophotographic photosensitive member was changed to 5, 8, and 15 μm. The results are shown in Table 5.

(Comparative Examples 1-2)
Compound Example Nos. In place of the polycarbonate resin shown in FIG. Evaluation was performed in the same manner as in Example 1 except that a charge transport layer was formed using resins having a cyclic resin molecular ratio of 1.00 and 0.00, respectively, of the polycarbonate resin represented by 1 to produce an electrophotographic photosensitive member. The results are shown in Table 5.

(Comparative Examples 3-4)
Compound Example Nos. In place of the polyarylate resin shown in FIG. Evaluation was conducted in the same manner as in Example 21 except that the charge transport layer was formed using resins having a cyclic resin molecular ratio of 1.00 and 0.00, respectively, of the polyarylate resin represented by 3 to produce an electrophotographic photosensitive member. . The results are shown in Table 5.

Claims (12)

A charge transport layer having a photosensitive layer in which a charge transport layer containing at least a charge generation layer, a charge transport agent, and a binder resin is sequentially laminated on a conductive substrate having a cylindrical shape and an outer diameter of 8 to 25 mmφ In the electrophotographic photosensitive member having a film thickness of 5 to 15 μm, the charge transport layer is at least a charge transport agent (CTM-1) represented by the following formula (1) and a repeating structural unit represented by the following formula (2): A binder resin having

(Wherein, Ar ₁ and Ar ₂ .Ar ₁ and Ar ₂ represents an aryl group which may have a substituent group may be the same or different.)

(In the formula (2), R ^{11 to} R ¹⁸ are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted monovalent aliphatic hydrocarbon group, a substituted or unsubstituted monovalent alicyclic carbonization. A hydrogen group or a substituted or unsubstituted monovalent aromatic hydrocarbon group, R ¹⁹ represents a divalent linking group, and Ar ¹¹ represents a substituted or unsubstituted divalent aromatic hydrocarbon group. K is 0 or 1.)
Among the resin molecules constituting the binder resin contained in the charge transport layer, the resin molecules having a molecular weight in the range of 1500 to 5500 include a chain resin molecule having a structure represented by the following formula (21) and the following formula: An electrophotographic photoreceptor characterized in that both of the cyclic resin molecules having the structure represented by (22) are present.

(Equation (21), in ^{(22), R 11 ~R 18} , R 19, Ar 11, k have the same meanings as ^{R 11 ~R 18, R 19,} Ar 11, k in Equation (2). E ¹¹ and E ¹² each independently represent a monovalent end group, and m and n are each independently a positive integer.)   The electrophotographic photosensitive member according to claim 1, wherein the binder resin contained in the charge transport layer is a polycarbonate resin in which k in the formulas (2), (21), and (22) is 0.   The electrophotographic photosensitive member according to claim 2, wherein the polycarbonate resin has a weight average molecular weight (Mw) of 40000 to 250,000. The number of the chain resin molecules having the structure represented by the formula (21) in the molecular weight range of 1500 to 5500 is ΣLm, and the molecular weight is in the range of 1500 to 5500 in the formula (22). The electrophotographic photosensitive member according to claim 3, wherein ΣLm and ΣCn satisfy the following relational expression (3), where ΣCn is the number of cyclic resin molecules.

  The electrophotographic photosensitive member according to claim 1, wherein the binder resin contained in the charge transport layer is a polyarylate resin in which k in the formulas (2), (21), and (22) is 1.   The electrophotographic photosensitive member according to claim 5, wherein the polyarylate resin has a weight average molecular weight (Mw) of 40000 to 200000. The number of the chain resin molecules having the structure represented by the formula (21) in the molecular weight range of 1500 to 5500 is ΣLm, and the molecular weight is in the range of 1500 to 5500 in the formula (22). The electrophotographic photosensitive member according to claim 6, wherein ΣLm and ΣCn satisfy the following relational expression (4), where ΣCn is the number of cyclic resin molecules.

  The electrophotographic photosensitive member according to claim 1, wherein the charge transport agent and the binder resin in the charge transport layer have a mass ratio of 2 or more and less than 5 to the binder resin 10. The charge transport layer contains at least a compound (CTM-2) represented by the following formula (5) in addition to the CTM-1 as a charge transport agent, and the mass ratio of CTM-1 to CTM-2 is CTM-1,100. The electrophotographic photosensitive member according to any one of claims 1 to 8, wherein CTM-2 is 1 to 3.

(In the formula, Ar ₃ represents a condensed polycycle which may have a substituent.) In addition to CTM-1, the charge transport layer contains at least a compound (CTM-3) represented by the following formula (6) as a charge transport agent, and the mass ratio of CTM-1 to CTM-3 is CTM-1,100. The electrophotographic photosensitive member according to any one of claims 1 to 8, wherein CTM-3 is 5 to 15.

  An electrophotographic apparatus comprising at least a charging unit, an exposure unit, a developing unit, and a transfer unit in this order, wherein the electrophotographic photosensitive member used in the electrophotographic apparatus is the electrophotographic photosensitive member according to claim 1. An electrophotographic device.   11. The electrophotographic photosensitive member according to claim 1, and at least one unit from the group consisting of a charging unit, a developing unit, and a cleaning unit is integrally supported, and is detachable from the main body of the electrophotographic apparatus. Electrophotographic process cartridge.