JP2008009139A - Multilayer electrophotographic photoreceptor and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress generation of residual charges in a charge generating layer in a negative charge type multilayer electrophotographic photoreceptor by efficiently transferring holes generated in the charge generating layer to the outside of the charge generating layer, and to effectively suppress exposure memory due to such residual charges. <P>SOLUTION: There are provided a negative charge type multilayer electrophotographic photoreceptor having a charge generating layer and a charge transport layer formed on a substrate directly or by way of an intermediate layer and an image forming apparatus using the same. The charge generating layer contains oxotitanyl phthalocyanine crystals as a charge generating agent and also contains at least one hole transport agent selected from the group consisting of charge transport agents represented by formula (1), etc., in an amount of 4-200 pts.wt. based on 100 pts.wt. of a binder resin in the charge generating layer. In the formula (1), R<SP>1</SP>and R<SP>2</SP>are each independently a substituent such as a 1-12C substituted or unsubstituted alkyl group; a plurality of symbols Ra and Rb are each independently a substituent such as a 1-12C substituted or unsubstituted alkyl group; the number of repetitions, m is an integer of 0-5; the number of repetitions, n is an integer of 0-4; Ar<SP>1</SP>and Ar<SP>2</SP>are each independently a substituent such as a 6-30C substituted or unsubstituted aryl group; and the numbers of repetitions, o and p are each an integer of 0-1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multilayer electrophotographic photosensitive member and an image forming apparatus. In particular, the present invention relates to a multilayer electrophotographic photosensitive member capable of effectively suppressing exposure memory and a static elimination-less type image forming apparatus including the same.

Conventionally, as an electrophotographic photoreceptor such as an image forming apparatus, a charge generation layer containing a charge generation agent and a binder resin and a charge transport layer containing a charge transfer agent and a binder resin are provided on a substrate. A multilayer electrophotographic photosensitive member is known. Such a multilayer electrophotographic photosensitive member is easier to manufacture than conventional inorganic photosensitive members, and there are various options for photosensitive materials such as a charge generating agent and a charge transporting agent. There is an advantage that the degree is high.
However, the multilayer electrophotographic photosensitive member has a problem that exposure memory is easily generated. As a cause of such an exposure memory, it is considered that residual charges generated in the charge generation layer are affected.

Therefore, in order to solve such a problem, in the positively chargeable laminated electrophotographic photosensitive member, a compound having a hole transporting ability is contained in the charge generation layer, so that the residual in the charge generation layer. Methods for removing charges have been proposed (for example, Patent Documents 1 and 2).
JP-A-5-113669 (Claims) JP-A-9-230612 (Claims)

However, the multilayer electrophotographic photosensitive members described in Patent Documents 1 and 2 are positively charged, and the negatively charged multilayered electrophotographic photosensitive member has not yet solved the problem of the exposure memory. There was a problem.
That is, in a negatively chargeable laminated electrophotographic photosensitive member, a preferred compound as a charge transport agent contained in the charge generation layer, a preferred content thereof, and suitable charge transport agents and charge generators used. No such combination has been found yet. Therefore, in the negatively charged multilayer electrophotographic photosensitive member, there has been a problem that the residual charge in the charge generation layer can be efficiently removed and the exposure memory cannot be effectively suppressed.
Therefore, as a method for erasing such an exposure memory, a static elimination process using a static elimination means such as a static elimination lamp is performed. However, since the potential decay also occurs in such a static elimination step, there is a problem that residual charges are generated inside the multilayer electrophotographic photosensitive member, and the repetitive characteristics in charging potential and sensitivity are unstable.
In addition, the provision of such a charge eliminating means increases the number of parts of the image forming apparatus, which makes it difficult to reduce the size and simplify the apparatus.

Therefore, as a result of intensive studies, the present inventors have used a specific compound as a charge generating agent and a hole transporting agent having a specific structure in the charge generating layer of the negatively charged multilayer electrophotographic photosensitive member. The inventors have found that the exposure memory can be effectively suppressed by containing within a predetermined range, and have completed the present invention.
That is, according to the present invention, in a negatively charged multilayer electrophotographic photosensitive member, residual charges are generated in the charge generation layer by efficiently transporting holes generated in the charge generation layer to the outside of the charge generation layer. It is an object of the present invention to effectively suppress the occurrence of exposure memory due to such residual charges.

  According to the present invention, there is provided a negatively charged multilayer electrophotographic photosensitive member in which a charge generation layer and a charge transport layer are formed directly or via an intermediate layer on a substrate, the charge generation layer comprising: It contains an oxo titanyl phthalocyanine crystal as a charge generating agent, and contains at least one hole transporting agent selected from the group consisting of hole transporting agents represented by the following general formulas (1) to (6) In addition, there is provided a multilayer electrophotographic photosensitive member characterized in that the content thereof is set to a value within the range of 4 to 200 parts by weight with respect to 100 parts by weight of the binder resin in the charge generation layer. The problem can be solved.

(In General Formula (1), R ¹ and R ² are each an independent substituent, and are a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted group having 6 to 30 carbon atoms. A plurality of Ra and Rb are each an independent substituent, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a carbon number A substituted or unsubstituted alkenyl group having 6 to 30; or —OR ³ (R ³ is an alkyl group having 1 to 10 carbon atoms, a perfluoroalkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 30 carbon atoms. The repeating number m is an integer of 0 to 5, the repeating number n is an integer of 0 to 4, Ar ¹ and Ar ² are each an independent substituent, Substitution of 6 to 30 carbon atoms or (It is an unsubstituted aryl group, and the repeating numbers o and p are integers of 0 to 1.)

(In the general formula (2), R ^{4 to} R ¹² are each an independent substituent, and are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted group having 1 to 12 carbon atoms, or An unsubstituted alkoxy group, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted alkenyl group having 6 to 30 carbon atoms, or —OR ¹³ (R ¹³ is an alkyl group having 1 to 10 carbon atoms) , A perfluoroalkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 30 carbon atoms), and R ^{4 to} R ⁸ , R ⁹ and R ¹⁰ , R ¹¹ and R ^12. May be linked to each other to form a saturated / unsaturated hydrocarbon ring, R ⁶ and R ¹⁰ may be a substituent represented by the following general formula (2 ′), , X ¹ is a substituted or unsubstituted arylene group having 6 to 30 carbon atoms, carbon An unsaturated hydrocarbon group having an aryl group having 6 to 30 prime numbers or a condensed polycyclic hydrocarbon group having 10 to 30 carbon atoms.)

(In the general formula (2 ′), Ar ³ and Ar ⁴ are each an independent substituent, and are a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, or a substituted or non-substituted group having 6 to 30 carbon atoms. (It is a substituted aryl group, and the repeating number c is an integer of 0 to 2.)

(In the general formula (3), R ^{14 to} R ²⁴ are each an independent substituent, and are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted group having 1 to 12 carbon atoms, or An unsubstituted alkoxy group, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted alkenyl group having 6 to 30 carbon atoms, or —OR ²⁵ (R ²⁵ is an alkyl group having 1 to 10 carbon atoms) , A perfluoroalkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 30 carbon atoms), and R ^{14 to} R ¹⁸ , R ¹⁹ and R ²⁰ , R ²¹ and R ^24. R ²² and R ²³ may be linked to each other to form a saturated / unsaturated hydrocarbon ring, and R ¹⁶ may be a substituent represented by the following general formula (3 ′). In addition, X ² is a substituted or unsubstituted aryl having 6 to 30 carbon atoms. A ren group, an unsaturated hydrocarbon group having an aryl group having 6 to 30 carbon atoms, or a condensed polycyclic hydrocarbon group having 10 to 30 carbon atoms.)

(In the general formula (3 ′), Ar ⁵ and Ar ⁶ are each an independent substituent, and are a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, or a substituted or non-substituted group having 6 to 30 carbon atoms. (It is a substituted aryl group, and the repeating number d is an integer of 0 to 2.)

(In the general formula (4), R ^{26 to} R ³⁴ are each an independent substituent, and are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted group having 1 to 12 carbon atoms, or An unsubstituted alkoxy group, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted alkenyl group having 6 to 30 carbon atoms, or —OR ³⁵ (R ³⁵ is an alkyl group having 1 to 10 carbon atoms) , A perfluoroalkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 30 carbon atoms), and R ^{26 to} R ³⁰ , R ³¹ and R ³² , R ³³ and R ^34. May be linked to each other to form a saturated / unsaturated hydrocarbon ring, and Ar ⁷ and Ar ⁸ are each an independent substituent and are a hydrogen atom, a C 1-12 substituent or Unsubstituted alkyl group or 6 to 3 carbon atoms An aryl group, the repetition number e is an integer of 0 to 2.)

(In the general formula (5), a plurality of Rc to Re are each an independent substituent, and are a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted group having 6 to 30 carbon atoms. An aryl group, or a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, the repeating number q is an integer of 0 to 4, r to s are integers of 0 to 5, Ar ⁹ and Ar ¹⁰ are And a substituted or unsubstituted aryl group having 6 to 30 carbon atoms.)

(In the general formula (6), R ³⁶ and R ³⁷ are each an independent substituent, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms. R ³⁶ may combine with Rg to form a saturated hydrocarbon ring, and a plurality of Rf to Ri are each an independent substituent, and a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms. Group, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, and repeating numbers t, u, and w are integers of 0 to 5 and repeating The number v is an integer from 0 to 4.)

  That is, in the charge generation layer of the negatively charged multilayer electrophotographic photosensitive member, an oxotitanyl phthalocyanine crystal is used as the charge generation agent, and the hole transport agent represented by the general formulas (1) to (6) By containing within the range, holes generated from the charge generating agent by exposure can be efficiently transported out of the charge generating layer. Therefore, it is possible to suppress the generation of residual charges in the charge generation layer and to effectively suppress the generation of exposure memory due to such residual charges.

In constructing the laminated electrophotographic photosensitive member of the present invention, a value obtained by subtracting the ionization potential of oxotitanylphthalocyanine as a charge generating agent from the ionization potential of the hole transport agent is a value within the range of 0 to 0.4 eV. It is preferable that
By comprising in this way, the hole transport between the charge generation agent and the hole transport agent in the charge generation layer can be carried out more efficiently.

In constituting the multilayer electrophotographic photoreceptor of the present invention, the thickness of the charge generation layer is preferably set to a value in the range of 0.05 to 1.0 μm.
By comprising in this way, while the charge generation amount by exposure can be improved, the charge generation layer contains a specific charge generation agent and a hole transport agent having a specific structure. Generation of residual charges can be effectively suppressed.

Further, in constituting the multilayer electrophotographic photosensitive member of the present invention, the oxotitanyl phthalocyanine crystal as a charge generator has a maximum peak at a Bragg angle 2θ ± 0.2 = 27.2 ° and has a differential. In scanning calorimetry, it is preferable to have one peak in the range of 270 to 400 ° C. other than the peak accompanying vaporization of adsorbed water.
By comprising in this way, it can suppress that the crystal form of this oxo titanyl phthalocyanine crystal | crystallization changes from Y type to alpha type and beta type in an organic solvent, and can improve charge generation efficiency.

In constituting the multilayer electrophotographic photoreceptor of the present invention, the charge transport layer preferably contains the same hole transport agent as the hole transport agent contained in the charge generation layer.
With this configuration, the efficiency of transporting holes to the outside of the charge generation layer can be further improved.

Another embodiment of the present invention includes any of the above-described laminated electrophotographic photosensitive members, and a charging unit, an exposing unit, a developing unit, and a transferring unit around the laminated electrophotographic photosensitive member. The image forming apparatus is characterized by being a static elimination-less type that is arranged and does not have a static elimination means.
That is, since any one of the laminated electrophotographic photosensitive members described above is provided, the generation of residual charges in the charge generation layer can be suppressed, and the exposure memory caused by the residual charges can be effectively suppressed. Therefore, it is possible to form a high-quality image even if the charge eliminating unit is omitted, and to reduce the size and simplify the image forming apparatus.

In constituting the image forming apparatus of the present invention, the charging means is preferably a charging roller.
With this configuration, it is possible to obtain an image forming apparatus that has a simple overall configuration as compared to the case where the non-contact charging method is employed, and that is excellent in environmental characteristics without generation of harmful substances such as ozone.

[First Embodiment]
A first embodiment of the present invention is a negatively charged multilayer electrophotographic photosensitive member in which a charge generation layer and a charge transport layer are formed directly or via an intermediate layer on a substrate, The generation layer contains oxo titanyl phthalocyanine crystal as a charge generation agent, and at least one kind of holes selected from the group consisting of the hole transport agents represented by the general formulas (1) to (6) described above. A multilayer electrophotographic photosensitive member containing a transport agent and having a content within a range of 4 to 200 parts by weight with respect to 100 parts by weight of a binder resin in a charge generation layer. .
Hereinafter, the multilayer electrophotographic photosensitive member according to the first embodiment of the present invention will be described in detail.

1. Basic Configuration As shown in FIG. 1A, a laminated electrophotographic photosensitive member 20 according to the present invention has a specific charge generating agent and a specific structure on a substrate 12 by means of vapor deposition or coating. A charge generation layer 24 containing a hole transport agent is formed, and then a charge transport layer coating solution containing a hole transport agent and a binder resin is applied onto the charge generation layer 24 and dried. Thus, the charge transport layer 22 can be formed.
In contrast to the above structure, as shown in FIG. 1, the charge transport layer 22 may be formed on the substrate 12 and the charge generation layer 24 may be formed thereon. In this case, an electron transporting agent is used as the charge transporting agent used in the charge transporting layer.
However, since the charge generation layer 24 is much thinner than the charge transport layer 22, the charge transport layer 22 is formed on the charge generation layer 24 as shown in FIG. It is more preferable. In any case, by configuring in this way, a negatively charged multilayer electrophotographic photosensitive member that negatively charges the surface and forms an electrostatic latent image on the surface by transport of holes generated by exposure is obtained. Obtainable.

2. Substrate As the substrate on which the laminated photosensitive layer is formed, various conductive materials can be used. For example, substrates formed of metals such as iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass, and the above-described metals are vapor-deposited Alternatively, a substrate made of a laminated plastic material, a glass substrate coated with aluminum iodide, alumite, tin oxide, indium oxide, or the like is exemplified.
That is, it is only necessary that the substrate itself has conductivity or the surface of the substrate has conductivity. Further, it is preferable that the substrate has sufficient mechanical strength when used.
The shape of the substrate may be any of a sheet shape and a drum shape according to the structure of the image forming apparatus to be used.

3. Intermediate layer It is also preferable that an intermediate layer is interposed between the above-described substrate and a charge generation layer described later.
This is because the charge on the substrate side can be prevented from being easily injected into the photosensitive layer, and the photosensitive layer can be firmly bound on the substrate to cover and smooth the defects on the substrate surface. is there.

(1) Basic Configuration As shown in FIG. 1C, in the multilayer electrophotographic photosensitive member 20 ″ in such an embodiment, first, an intermediate layer 25 is formed on a substrate. Then, a charge generation layer 24 containing a specific charge generation agent and a hole transport agent having a specific structure is formed on the intermediate layer 25 by means such as vapor deposition or coating. Further, the charge transport layer and the binder resin containing the charge transport layer coating solution can be applied and dried to form the charge transport layer 22.

(2) Binder resin Also, as the binder resin, for example, at least selected from the group consisting of polyamide resin, polyvinyl alcohol resin, polyvinyl butyral resin, polyvinyl formal resin, vinyl acetate resin, phenoxy resin, polyester resin, acrylic resin It is preferable to use one resin.

(3) Additives In addition, in the range where sedimentation at the time of manufacture does not become a problem, for the purpose of preventing the generation of interference fringes by causing light scattering and improving dispersibility, etc. It is also preferable to add a small amount of an additive (organic fine powder or inorganic fine powder).
In particular, white pigments such as titanium oxide, zinc oxide, zinc white, zinc sulfide, lead white, lithopone, inorganic pigments such as alumina, calcium carbonate, barium sulfate, etc., fluorine resin particles, benzoguanamine resin particles, styrene resins Particles and the like are preferred additives.
Moreover, when adding additives, such as a fine powder, it is preferable to make the particle size into the value within the range of 0.01-3 micrometers. This is because if the particle size is too large, the unevenness of the intermediate layer may increase, an electrically non-uniform portion may occur, and image quality defects may easily occur. On the other hand, if the particle size is too small, a sufficient light scattering effect may not be obtained.
In addition, when adding additives, such as a fine powder, 10 to 90 weight% is preferable at the weight ratio with respect to solid content of an intermediate | middle layer, and 20 to 80 weight% is further more preferable.

(4) Thickness Moreover, since the concealability of the unevenness in the base material is increased by increasing the film thickness of the intermediate layer, spot-like image quality defects tend to be reduced. There is a tendency for electrical characteristics such as potential increase to decrease.
Accordingly, the thickness of the intermediate layer is preferably set to a value within the range of 0.1 to 50 μm, and more preferably set to a value within the range of 1 to 30 μm.

4). Charge generation layer (1) Charge generation agent (1) -1 type The laminated electrophotographic photosensitive member of the present invention is characterized in that oxo titanyl phthalocyanine crystal is used as the charge generation agent.
This is because, by using oxotitanyl phthalocyanine crystal as a charge generating agent, it is possible to generate charges efficiently by exposure, while by combining with a hole transporting agent having a specific structure described later, by exposure. This is because holes generated from the charge generating agent can be efficiently transported out of the charge generating layer. Therefore, it is possible to suppress the generation of residual charges in the charge generation layer and to effectively suppress the occurrence of exposure memory due to such residual charges.

Moreover, it is preferable to use the compound represented by following General formula (7) as an oxo titanyl phthalocyanine compound.
This is because the use of the oxotitanyl phthalocyanine compound having such a structure makes it easy to adjust the ionization potential, the optical characteristics and thermal characteristics of the crystal, and the like within a suitable range, as will be described later. . And, by adjusting these characteristics, it is possible to improve the hole transport efficiency between the hole transport agent having a specific structure and the stability of the oxotitanyl phthalocyanine crystal itself. is there.

(1) -2 Ionization potential Moreover, it is preferable to make the ionization potential in oxo titanyl phthalocyanine into the value within the range of 5.2-5.3 eV.
The reason for this is that, as will be described later, the value obtained by subtracting the ionization potential of oxotitanylphthalocyanine from the ionization potential of the hole transport agent having a specific structure can be easily set to a value within a predetermined range. This is because the hole can be transported more efficiently with the hole transport agent having the structure.
The measurement method and details will be described in the section of hole transport agent.

(1) -3 Optical Properties The oxo titanyl phthalocyanine crystal preferably has a maximum peak at a Bragg angle 2θ ± 0.2 ° = 27.2 ° in the CuKα characteristic X-ray diffraction spectrum as an optical property ( First optical characteristic).
In the CuKα characteristic X-ray diffraction spectrum, it is preferable that there is no peak at the Bragg angle 2θ ± 0.2 ° = 26.2 ° (second optical characteristic).
Furthermore, in the CuKα characteristic X-ray diffraction spectrum, it is preferable that there is no peak at a Bragg angle 2θ ± 0.2 ° = 7.4 ° (third optical characteristic).
The reason for this is that by providing the first optical characteristic, the crystal form of the oxotitanylphthalocyanine crystal is prevented from changing from Y-type to α-type or β-type in an organic solvent, thereby improving the charge generation efficiency. It is because it can be made.
That is, when the first optical characteristic is not provided, the stability in the organic solvent tends to be significantly reduced as compared with the oxotitanyl phthalocyanine crystal having such an optical characteristic. In other words, the storage stability in the organic solvent can be improved by providing the first optical characteristic, more preferably the second optical characteristic and the third optical characteristic. As a result, the charge generation ability of the oxotitanyl phthalocyanine crystal is effectively exhibited, so that even when image formation is continuously performed, generation of image memory can be effectively suppressed and excellent sensitivity can be obtained. Obtainable.
In addition, the oxotitanyl phthalocyanine crystal collected after being immersed in an organic solvent for 7 days has a maximum peak at least at a Bragg angle 2θ ± 0.2 ° = 27.2 ° in a CuKα characteristic X-ray diffraction spectrum, and 26. It is preferable that there is no peak at 2 °.
The reason for this is that, even when immersed in an organic solvent for 7 days, the crystal transition of the oxotitanyl phthalocyanine crystal in the organic solvent is more reliably controlled by maintaining the above-mentioned characteristics. Because it can.
In addition, the immersion experiment evaluation in the organic solvent used as the reference | standard which evaluates the storage stability of an oxo titanyl phthalocyanine crystal | crystallization is the coating liquid (henceforth a charge generation layer hereafter) for producing the electrophotographic photoreceptor, for example. It is preferable to carry out under the same conditions as the conditions for actually storing the coating liquid for coating. Therefore, for example, it is preferable to evaluate the storage stability of oxotitanyl phthalocyanine crystals in a closed system under conditions of a temperature of 23 ± 1 ° C. and a relative humidity of 50 to 60% RH.

The organic solvent for evaluating the storage stability of the oxotitanyl phthalocyanine crystal is at least one selected from the group consisting of tetrahydrofuran, dichloromethane, toluene, 1,4-dioxane, and 1-methoxy-2-propanol. It is preferable that
The reason for this is that when such an organic solvent is used as the organic solvent in the coating solution for the charge generation layer, the stability of the oxotitanyl phthalocyanine crystal can be more reliably determined, and the oxotitanyl phthalocyanine crystal can be used in a specific manner described later. This is because the compatibility of the hole transport agent having a structure, the binder resin, and the like is improved. Therefore, it is possible to form a charge generation layer that exhibits the characteristics of the oxotitanyl phthalocyanine crystal and the hole transporting agent having a specific structure more effectively, so that the laminated electrophotography further excellent in electrical characteristics and image characteristics This is because the photoreceptor can be manufactured stably.

(1) -4 Thermal Characteristics In addition to the above-described optical characteristics, oxotitanyl phthalocyanine crystal as a charge generator has a thermal characteristic of 270 in addition to the peak accompanying vaporization of adsorbed water in differential scanning calorimetry. It is preferable to have one peak in the range of ˜400 ° C.
The reason for this is that if the oxotitanyl phthalocyanine crystal having such optical characteristics and thermal characteristics is added to an organic solvent and left for a long time, the crystal structure becomes an α-type crystal and a β-type crystal. This is because crystal transition can be effectively suppressed. Therefore, by using such a titanyl phthalocyanine crystal, it is possible to obtain a coating solution for a charge generation layer excellent in storage stability, and as a result, the charge generation ability of the oxo titanyl phthalocyanine crystal is more effectively exhibited. Therefore, even when image formation is continuously performed, generation of an image memory can be more effectively suppressed and more excellent sensitivity can be obtained.
In addition, it is more preferable that one peak appearing in the range of 270 to 400 ° C. other than the peak accompanying vaporization of the adsorbed water appears in the range of 290 to 400 ° C., and the range of 300 to 400 ° C. More preferably, it appears within.
A specific method for measuring the Bragg angle in the CuKα characteristic X-ray diffraction spectrum and a specific method for differential scanning calorimetry will be described in detail in Example 1 described later.

(1) -5 Content Further, the content of the charge generating agent is preferably set to a value within the range of 5 to 1000 parts by weight with respect to 100 parts by weight of the binder resin constituting the charge generating layer.
The reason for this is that when the content is less than 5 parts by weight with respect to 100 parts by weight of the binder resin, the charge generation amount becomes insufficient and it becomes difficult to form a clear electrostatic latent image. This is because there are cases. On the other hand, when the content exceeds 1000 parts by weight with respect to 100 parts by weight of the binder resin, it may be difficult to form a uniform charge generation layer.
Therefore, the content of the charge generating agent with respect to 100 parts by weight of the binder resin constituting the charge generating layer is more preferably set to a value within the range of 30 to 500 parts by weight.

(2) Hole Transfer Agent (2) -1 Type The charge generation layer of the multilayer electrophotographic photosensitive member according to the present invention is selected from the group of hole transfer agents represented by the general formulas (1) to (6). It contains at least one kind of hole transporting agent.
The reason for this is that the positive charge generated from the charge generating agent by exposure by containing the specific charge generating agent described above and the hole transporting agents represented by the general formulas (1) to (6) in the charge generating layer. This is because the holes can be efficiently transported out of the charge generation layer. Therefore, it is possible to suppress the generation of residual charges in the charge generation layer and to effectively suppress the occurrence of exposure memory due to such residual charges.
That is, between the hole transporting agent having such a specific structure and the specific charge generating agent, the difference in their ionization potential can be adjusted to a value within a predetermined range as will be described in detail in the next section. It becomes easy. Therefore, holes generated from the charge generation agent can be efficiently transported out of the charge generation layer, and generation of residual charges in the charge generation layer can be suppressed.

  Specific examples of the hole transporting agent represented by the general formulas (1) to (6) include compounds (HTM-1 to 6) represented by the following formulas (8) to (13). it can.

(2) -2 Ionization potential Further, a value obtained by subtracting the ionization potential of oxo titanyl phthalocyanine as a charge generating agent from the ionization potential of a hole transport agent having a specific structure is set to a value within a range of 0 to 0.4 eV. It is preferable.
This is because the hole can be transported more efficiently between the charge generating agent and the hole transporting agent in the charge generating layer in this manner.
That is, when the value obtained by subtracting the ionization potential of the charge generating agent from the ionization potential of the hole transporting agent is less than 0 eV, the difference between the ionization potential of the hole transporting agent and the ionization potential of the charge generating agent is excessively small. This is because the charging characteristics of the electrophotographic photosensitive member may be deteriorated.

On the other hand, when the value obtained by subtracting the ionization potential of the charge generating agent from the ionization potential of the hole transporting agent exceeds 0.4 eV, efficient charge transport becomes difficult, and the sensitivity is lowered or the exposure is reduced. This is because memory may be generated.
Therefore, it is more preferable to set the difference between the ionization potential of the hole transport agent and the ionization potential of the charge generation agent to a value within the range of 0.05 to 0.3 eV, preferably 0.1 to 0.2 eV. More preferably, the value is within the range.
In addition, each ionization potential in the hole transport agent having a specific structure with oxophthalocyanine can be measured using, for example, an atmospheric-type ultraviolet photoelectron analyzer (manufactured by Riken Keiki Co., Ltd., AC-1). it can.

In addition, the ionization potential of the hole transport agent is preferably set to a value in the range of 5.2 to 5.7 eV.
This is because it is practically easy to adjust the value obtained by subtracting the ionization potential of the charge generating agent from the ionization potential of the hole transport agent to a value within the range of 0 to 0.4 eV.
Therefore, the ionization potential of the hole transport agent is more preferably set to a value within the range of 5.25 to 5.65 eV, and further preferably set to a value within the range of 5.3 to 5.6 eV.

(2) -3 Content The content of the hole transport agent having a specific structure is set to a value within the range of 4 to 200 parts by weight with respect to 100 parts by weight of the binder resin in the charge generation layer. Features.
This is because in the charge generation layer, the content of the hole transport agent having a specific structure is set to a value within the range of 4 to 200 parts by weight with respect to 100 parts by weight of the binder resin in the charge generation layer. This is because the generated holes can be more efficiently transported out of the charge generation layer.
That is, when the content is less than 4 parts by weight with respect to 100 parts by weight of the binder resin in the charge generation layer, it is difficult to sufficiently transport holes generated in the charge generation layer to the outside of the charge generation layer. This is because there may be cases. On the other hand, when the content exceeds 200 parts by weight with respect to 100 parts by weight of the binder resin in the charge generation layer, the hole transport agent is easily crystallized in the charge generation layer or a uniform charge generation layer. This is because it may be difficult to form.
Therefore, the content of the hole transport agent having a specific structure is more preferably set to a value within the range of 10 to 180 parts by weight with respect to 100 parts by weight of the binder resin in the charge generation layer. More preferably, the value is within the range of parts.

Here, the relationship between the content of the hole transport agent having a specific structure in the charge generation layer and the exposure memory potential in the negatively charged multilayer electrophotographic photosensitive member provided with the charge generation layer is shown in FIG. Will be described.
In FIG. 2, the content (parts by weight) of the hole transport agent having a specific structure with respect to 100 parts by weight of the binder resin of the charge generation layer on the horizontal axis and the negative charge type having the charge generation layer on the vertical axis. 2 shows characteristic curves obtained by taking the exposure memory potential (V) of each of the laminated electrophotographic photoreceptors. In addition, as a hole transport agent which has a specific structure, the hole transport agent (HTM-1) represented by Formula (8) is used.
As can be understood from the characteristic curve, as the content of the hole transport agent having a specific structure is increased, the exposure memory potential changes critically, and the characteristic curve is a downward convex curve. It has become.
More specifically, when the content of the hole transport agent having a specific structure is increased from 0 to 4 parts by weight, the exposure memory potential is increased from about 35 V to about 30 V accordingly. , It can be seen that it has dropped rapidly. When the content of the hole transport agent having a specific structure is in the range of 4 parts by weight to 200 parts by weight, the exposure memory potential is stably maintained at about 25V. On the other hand, when the content of the hole transport agent having a specific structure is increased over 200 parts by weight, the exposure memory potential starts to increase rapidly. When the content is 300 parts by weight, the exposure memory potential is It turns out that it will increase to about 50V.
Therefore, by setting the content of the hole transporting agent having a specific structure within the range of 4 to 200 parts by weight with respect to 100 parts by weight of the binder resin in the charge generation layer, the exposure memory potential is reduced to about 25V. It is understood that the value can be suppressed.
A method for measuring the exposure memory potential will be described in a later example.

(3) Binder resin The binder resin used for the charge generation layer is polycarbonate resin such as bisphenol A type, bisphenol Z type or bisphenol C type, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polystyrene. Resin, polyvinyl acetate resin, styrene-butadiene copolymer resin, vinylidene chloride-acrylonitrile copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd Examples thereof include a single type of resin, N-vinylcarbazole, or a combination of two or more types.

(4) Solvent Examples of the solvent used for forming the charge generation layer include aromatic hydrocarbons such as benzene, toluene and chlorobenzene, ketones such as acetone and 2-butanone, methylene chloride, chloroform, Examples thereof include halogenated aliphatic hydrocarbons such as ethylene chloride, cyclic or linear ethers such as tetrahydrofuran, dioxane, ethylene glycol and diethyl ether, and mixed solvents thereof.

(5) Thickness The thickness of the charge generation layer is preferably set to a value in the range of 0.05 to 1.0 μm.
This is because the charge generation amount by exposure can be improved by setting the thickness of the charge generation layer to a value within this range, while the charge generation layer has a specific charge generation agent and a specific structure. This is because the generation of residual charges can be effectively suppressed because the hole transporting agent is contained.
That is, with the conventional general charge generation layer, increasing the thickness can improve the amount of charge generation while increasing the generation of residual charges. It was.
However, since the charge generation layer in the present invention contains a hole transport agent having a specific charge generation layer and a specific structure, even if the thickness is increased, the residual charge is effectively reduced. The generation of the exposure memory can be suppressed by suppressing the generation.
Further, the thickness will be described in more detail. When the thickness of the charge generation layer is less than 0.05 μm, it may be difficult to form a charge generation layer having sufficient charge generation capability. On the other hand, if the thickness of the charge generation layer exceeds 1.0 μm, it may be difficult to suppress the generation of residual charges or it may be difficult to form a uniform charge generation layer.
Therefore, the thickness of the charge generation layer is more preferably set to a value within the range of 0.07 to 0.7 μm, and further preferably set to a value within the range of 0.1 to 0.5 μm.

5. Charge transport layer (1) Charge transport agent The charge transport agent (hole transport agent and electron transport agent) used in the charge transport layer is 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadi Oxadiazole derivatives such as azole, pyrazolines such as 1,3,5-triphenyl-pyrazoline, 1- [pyridyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminostyryl) pyrazoline Derivatives, aromatic tertiary amino compounds such as triphenylamine, tri (p-methyl) phenylamine, N, N-bis (3,4-dimethylphenyl) biphenyl-4-amine, dibenzylaniline, N, N Aromatic tertiary diamino compounds such as' -diphenyl-N, N'-bis (3-methylphenyl)-[1,1-biphenyl] -4,4'-diamine, 3- (4 1,2,4-triazine derivatives such as' -dimethylaminophenyl) -5,6-di- (4'-methoxyphenyl) -1,2,4-triazine, 4-diethylaminobenzaldehyde-1,1-diphenylhydrazone Hydrazone derivatives such as 2-phenyl-4-styryl-quinazoline, benzofuran derivatives such as 6-hydroxy-2,3-di (p-methoxyphenyl) -benzofuran, p- (2,2-diphenylvinyl ) Hole transport materials such as α-stilbene derivatives such as —N, N-diphenylaniline, enamine derivatives, carbazole derivatives such as N-ethylcarbazole, poly-N-vinylcarbazole and derivatives thereof; chloranil, bromoanil, anthraquinone, etc. Quinone compounds, tetracyanoquinodimethane compounds, 2, , 7-trinitrofluorenone, 2,4,5,7-tetranitro-9-fluorenone and other fluorenone compounds, xanthone compounds, thiophene compounds, diphenoquinone compounds and other electron transport materials; Alternatively, one or a combination of two or more polymers such as polymers in the side chain may be mentioned.

When a hole transport agent is used as the charge transport agent in the charge transport layer, a hole transport agent similar to the hole transport agent contained in the charge generation layer described above is used as a particularly preferable hole transport agent. Is preferred.
The reason for this is that the hole transporting agent similar to the hole transporting agent used in the charge generation layer can be used to further improve the hole transport efficiency from the charge generation layer to the charge transport layer. .
That is, if the hole transport agent is the same as the hole transport agent used in the charge generation layer, even when receiving holes directly from the charge generation agent at the interface between the charge generation layer and the charge transport layer, Further, even when holes are received via a hole transport agent in the charge generation layer, holes can be efficiently transported. Such efficient hole transport results from the respective ionization potentials of the charge generating agent and the hole transporting agent, as described in the charge generation layer section.

  The amount of the charge transport agent added is preferably 20 to 500 parts by weight, preferably 30 to 200 parts by weight with respect to 100 parts by weight of the binder resin. More preferred.

(2) Binder Resin As the binder resin used for the charge transport layer, specifically, polycarbonate resin such as acrylic resin, polyarylate, polyester resin, bisphenol A type, bisphenol Z type or bisphenol C type, polystyrene , Acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, chlorinated rubber and other organic photoconductive materials such as polyvinyl carbazole, polyvinyl anthracene, polyvinyl pyrene And a copolymer resin thereof.

(3) Solvent The charge transport layer can be formed by applying a solution obtained by dissolving the charge transport agent and the binder resin in an appropriate solvent and then drying.
Examples of the solvent used when forming the charge transport layer in this manner include aromatic hydrocarbons such as benzene, toluene, and chlorobenzene, ketones such as acetone and 2-butanone, methylene chloride, chloroform, and ethylene chloride. And halogenated aliphatic hydrocarbons, cyclic or linear ethers such as tetrahydrofuran, dioxane, ethylene glycol and diethyl ether, or mixed solvents thereof.

(4) Additive In addition, for the purpose of preventing deterioration of the electrophotographic photosensitive member due to ozone, oxidizing gas, light, or heat generated in the electrophotographic apparatus, an antioxidant, a light stabilizer, It is preferable to add a heat stabilizer or the like.
For example, as the antioxidant, hindered phenol, hindered amine, paraphenylenediamine, arylalkane, hydroquinone, spirochroman, spiroidanone and derivatives thereof, organic sulfur compounds, organic phosphorus compounds, and the like are used. Examples of the light stabilizer include derivatives such as benzophenone, benzotriazole, dithiocarbamate, and tetramethylpiperidine.

(5) Thickness The film thickness of the charge transport layer is generally preferably in the range of 5 to 50 μm. This is because when the thickness of the charge transport layer is less than 5 μm, it may be difficult to apply uniformly. On the other hand, when the thickness of the charge transport layer exceeds 50 μm, the mechanical strength may decrease. Therefore, it is more preferable to set the value within the range of 10 to 40 μm.

6). Manufacturing Method (1) Preparation of Substrate In order to prevent the occurrence of interference fringes, the surface of the supporting substrate is formed using methods such as etching, anodizing, wet blasting, sand blasting, rough cutting, and centerless cutting. It is preferable to perform a roughening treatment.

(2) Formation of intermediate layer It is also preferable that an intermediate layer is interposed between the substrate described above and a charge generation layer described later.
The reason for this is that, as already described above, the charge on the substrate side is prevented from being easily injected into the photosensitive layer, and the photosensitive layer is firmly bonded onto the substrate to cover and smooth the defects on the substrate surface. Because it can.

(2) -1 Preparation of coating solution for intermediate layer In forming the intermediate layer, it is preferable to add a titanium oxide or the like to the solution in which the resin component is dissolved and perform a dispersion treatment to produce a coating solution.
The method for carrying out the dispersion treatment is not particularly limited, but generally known roll mills, ball mills, vibration ball mills, attritors, sand mills, colloid mills, paint shakers and the like are preferably used.

(2) -2 Application of Intermediate Layer Coating Solution Further, the application method of the intermediate layer application solution is not particularly limited, but includes a dip coating method, a spray coating method, a bead coating method, a blade coating method, A coating method such as a roller coating method can be used.
In order to form the intermediate layer and the photosensitive layer thereon more stably, it is possible to carry out a heat drying treatment at 30 to 200 ° C. for 5 minutes to 2 hours after application of the intermediate layer coating solution. desirable.

(3) Formation of charge generation layer (3) -1 Preparation of coating solution for charge generation layer In forming the charge generation layer, a specific charge generation agent and a specific structure are added to the solution in which the resin component is dissolved. A hole transport agent or the like is added and subjected to a dispersion treatment to produce a coating solution.
Further, the method for performing the dispersion treatment is not particularly limited, but it is generally possible to disperse and mix using a known roll mill, ball mill, attritor, paint shaker, ultrasonic disperser, etc. to obtain a coating solution. preferable.

(3) -2 Application of Coating Solution for Charge Generation Layer Further, the coating method of the coating solution for charge generation layer is not particularly limited. For example, spin coater, applicator, spray coater, bar coater, dip It is preferable to use a coater, a doctor blade or the like.
Moreover, after an application | coating process, it is preferable to make it dry at the drying temperature of 60 degreeC-150 degreeC, for example using a high temperature dryer, a vacuum dryer, etc. in a drying process.

(4) Formation of charge transport layer The charge transport layer is preferably formed by adding a charge transport agent or the like to a solution in which a resin component is dissolved to produce a coating solution. The dispersion treatment, coating method, and drying method are omitted because they overlap with the charge generation layer.

[Second Embodiment]
The second embodiment of the present invention includes the multilayer electrophotographic photosensitive member described in the first embodiment, and a charging unit, an exposing unit, a developing unit, and a transfer around the multilayer electrophotographic photosensitive member. The image forming apparatus is characterized by being a static elimination-less type in which the respective means are arranged and the static elimination means is not provided.
Hereinafter, a specific description will be given focusing on differences from the description of the first embodiment.

The basic configuration and operation of the image forming apparatus according to the present invention will be described with reference to FIG.
First, the multilayer electrophotographic photosensitive member 111 of the image forming apparatus 100 is rotated at a predetermined process speed (circumferential speed) in the direction indicated by the arrow A, and then the surface thereof is set to a predetermined potential (negative polarity) by the charging unit 112. Charge. In FIG. 3, a charging roll is used as the charging unit 112.
Next, the exposure unit 113 exposes the surface of the electrophotographic photosensitive member 111 through a reflection mirror or the like while being light-modulated according to image information. By this exposure, an electrostatic latent image is formed on the surface of the electrophotographic photosensitive member 111.
Next, based on the electrostatic latent image, latent image development is performed by the developing unit 114. The developing means 114 stores toner, and the toner adheres corresponding to the electrostatic latent image on the surface of the electrophotographic photosensitive member 111 to form a toner image.
The recording paper 120 is conveyed to the lower part of the electrophotographic photosensitive member along a predetermined transfer conveyance path. At this time, the toner image can be transferred onto the recording material 120 by applying a predetermined transfer bias between the electrophotographic photoreceptor 111 and the transfer means 115.

Next, the recording paper 120 to which the toner image has been transferred is separated from the surface of the electrophotographic photosensitive member 111 by a separating means (not shown) and conveyed to a fixing device by a conveying belt. Next, the toner image is fixed on the surface by being heated and pressed by the fixing device, and then discharged to the outside of the image forming apparatus 100 by a discharge roller.
On the other hand, the electrophotographic photosensitive member 111 after the toner image is transferred continues to rotate, and residual toner (adhered matter) that has not been transferred to the recording paper 120 at the time of transfer is removed from the surface of the electrophotographic photosensitive member 111 by the cleaning device 117. The
As described above, the electrophotographic photosensitive member 111 includes the predetermined charge generation layer described above. Therefore, the generation of residual charges in the charge generation layer can be suppressed, and the exposure memory resulting from such residual charges can be effectively suppressed. Therefore, it is possible to form a high-quality image even if the charge eliminating unit is omitted, and to reduce the size and simplify the image forming apparatus.

In constituting the image forming apparatus of the present invention, the charging means is preferably a charging roller.
This is because the overall configuration is easier than in the case where the non-contact charging method is adopted, and an image forming apparatus having excellent environmental characteristics without generation of harmful substances such as ozone can be obtained.
Further, since air is not passed between the charging means and the electrophotographic photosensitive member as in the non-contact charging method, the dependency on the environment such as temperature and humidity can be reduced.

[Example 1]
1. Production of multilayer electrophotographic photoreceptor (1) Preparation of intermediate layer In a container, titanium oxide surface-treated with alumina and silica and then surface-treated with methylhydrogenpolysiloxane (Taika, SMT-02, number average) 150 parts by weight of primary particle size (10 nm), 100 parts by weight of titanium oxide (Taika, MT-05, number average primary particle size: 10 nm) surface-treated with alumina and silica, 600 parts by weight of methanol, and 150 parts by weight of butanol And 50 parts by weight of Amilan CM8000 (manufactured by Toray Industries, Inc., quaternary copolymer polyamide resin) previously dissolved in a ratio of 200 parts by weight of methanol and 50 parts by weight of butanol, and then added a bead mill (media: The mixture was mixed for 1 hour using a zirconia ball having a diameter of 0.5 mm to obtain a primary dispersion solution.
Next, 200 parts by weight of methanol and 50 parts by weight of CM8000 dissolved in a ratio of 50 parts by weight of butanol were added, and then mixed for 1 hour using a paint shaker to obtain an intermediate layer coating solution.
Next, the obtained intermediate layer coating solution is filtered through a 5 micron filter, and then the intermediate layer coating is obtained with one end of an aluminum substrate (supporting substrate) having a diameter of 30 mm and a length of 238.5 mm facing upward. It was immersed in the liquid at a speed of 5 mm / sec and applied. Then, the hardening process was performed on 130 degreeC and the conditions for 30 minutes, and the intermediate layer with a film thickness of 2 micrometers was formed.
In addition, regarding the addition amount of each constituent material in the above-described intermediate layer coating solution, the total amount of Amilan CM8000 added to the intermediate layer coating solution is used as a reference amount (100 parts by weight).

(2) Preparation of charge generation layer Next, 100 parts by weight of an oxotitanyl phthalocyanine crystal produced by the procedure described later, 4 parts by weight of a hole transport agent (HTM-1) represented by formula (8), and a binder resin As a dispersion, 100 parts by weight of polyvinyl acetal resin (Sekisui Chemical Co., Ltd., ESREC KS-5), 2000 parts by weight of propylene glycol monomethyl ether as a dispersion medium, and 6000 parts by weight of tetrahydrofuran are mixed and dispersed for 48 hours using a ball mill. A coating solution for the generation layer was prepared.
The obtained coating solution for charge generation layer is filtered through a 3 micron filter, and then applied onto the intermediate layer by dip coating, dried at 80 ° C. for 5 minutes, and a film thickness of 0.3 μm. The charge generation layer was formed.

(3) Preparation of charge transport layer Next, 70 parts by weight of a hole transport agent (HTM-1) represented by the formula (8) as a hole transport agent and 100 parts by weight of a polycarbonate resin (Teijin as a binder resin) Kasei TS2020) and 460 parts by weight of tetrahydrofuran as a solvent were mixed and dissolved to prepare a coating solution for a charge transport layer.
Next, the resulting charge transport layer coating solution was applied onto the charge generation layer in the same manner as the charge generation layer coating solution, dried under conditions of 130 ° C. for 30 minutes, and then charge transport having a thickness of 20 μm. A layer was formed to obtain a laminated electrophotographic photoreceptor.

The titanyl phthalocyanine crystal used was synthesized by the following procedure.
First, 22 g (0.17 mol) of o-phthalonitrile, 25 g (0.073 mol) of titanium tetrabutoxide, 2.28 g (0.038 mol) of urea and 300 g of quinoline were added to a flask purged with argon. The temperature was raised to 150 ° C. while stirring. Next, after evaporating the steam generated from the reaction system, the temperature was raised to 215 ° C. while the reaction temperature was maintained, and the reaction was further continued for 2 hours while maintaining the reaction temperature.
After completion of the reaction, when the reaction mixture is cooled to 150 ° C., the reaction mixture is taken out from the flask, filtered through a glass filter, and the resulting solid is washed successively with N, N-dimethylformamide and methanol and then vacuum-dried. 24 g of a purple solid was obtained. (Pigmentation pretreatment)

  Next, 10 g of the obtained blue-purple solid was added to 100 ml of N, N-dimethylformamide, heated to 130 ° C. with stirring, and stirred for 2 hours. Next, heating was stopped at the time when 2 hours had elapsed, and after cooling to 23 ± 1 ° C., stirring was stopped, and the liquid was allowed to stand in this state for 12 hours for stabilization treatment. Subsequently, the stabilized liquid was filtered off with a glass filter, and the obtained solid was washed with methanol and then vacuum-dried to obtain 9.83 g of a crude crystal of a titanyl phthalocyanine compound. (Pre-acid treatment)

Next, 5 g of the crude crystal of titanyl phthalocyanine obtained in the above-mentioned pre-acid treatment step was added to 100 ml of concentrated sulfuric acid and dissolved. Next, this solution was added dropwise to ice-cooled water, stirred for 15 minutes at room temperature, and then allowed to stand at about 23 ± 1 ° C. for 30 minutes for recrystallization. Next, the liquid described above was filtered off with a glass filter, and the obtained solid was washed with water until the washing liquid became neutral, and then dispersed in 200 ml of chlorobenzene in the presence of water without drying. The mixture was heated to 0 ° C. and stirred for 10 hours. Next, the liquid was filtered off with a glass filter, and the obtained solid was vacuum-dried at 50 ° C. for 5 hours to obtain 4.1 g of unsubstituted titanyl phthalocyanine crystals (blue powder) represented by the formula (7). Got. (Acid treatment process)
The obtained titanyl phthalocyanine was immersed in the initial and 1,3-dioxolane or tetrahydrofuran for 7 days, and the Bragg angle 2θ ± 0.2 ° = 7.4 ° and 26 ° in the CuKα characteristic X-ray diffraction spectrum was obtained. No peak was generated at 2 °, and one peak was confirmed at 296 ° C. in addition to the peak near 90 ° C. accompanying vaporization of adsorbed water in the differential scanning calorimetry.

In addition, the CuKα characteristic X-ray diffraction spectrum in the titanyl phthalocyanine crystal was measured by the following measuring method.
First, 0.3 g of titanyl phthalocyanine crystal was dispersed in 5 g of tetrahydrofuran and stored in a closed system for 24 hours under conditions of a temperature of 23 ± 1 ° C. and a relative humidity of 50-60% RH. A sample holder of RINT1100 (manufactured by Co., Ltd.) was filled for measurement.
Measurement conditions were as follows.
X-ray tube: Cu
Tube voltage: 40 kV
Tube current: 30 mA
Start angle: 3.0 °
Stop angle: 40.0 °
Scanning speed: 10 ° / min

Moreover, DSC (differential scanning calorimetry) of the titanyl phthalocyanine crystal was performed using a differential scanning calorimeter (TAS-200 type, DSC8230D manufactured by Rigaku Corporation). The measurement conditions are as follows.
Sample pan: Aluminum heating rate: 20 ° C / min

2. Evaluation (1) Evaluation of Exposure Memory Potential Using the obtained multilayer electrophotographic photosensitive member, the exposure memory potential was evaluated.
In other words, the stacked electrophotographic photosensitive member is mounted on a printer (Microline 22 Oki Data Co., Ltd.) that does not have static elimination means, and the surface potential of the unexposed part and the surface potential of the exposed part after the charging process is measured. The difference was measured as an exposure memory. The obtained results are shown in Table 1.

(2) Evaluation of exposure memory image Moreover, the exposure memory image was evaluated using the obtained multilayer electrophotographic photosensitive member.
That is, the obtained multilayer electrophotographic photosensitive member is mounted on a printer (Microline 22 Oki Data Co., Ltd.), and subjected to high temperature and high humidity (temperature: 35 ° C., humidity: 85%) and low temperature and low humidity (temperature: 10). After copying 10,000 sheets each at a temperature of 20 ° C and a humidity of 20%, a halftone image was continuously copied after the character image, and the character image as an afterimage was observed on the halftone image. And evaluated. The obtained results are shown in Table 1.
◎: No character is recognized in the halftone image portion ○: Character shape is not recognized in the halftone image portion, but a slight shadow is recognized Δ: A part of the character is present in the halftone image portion Recognized ×: Characters are clearly recognized in the halftone image area

(3) Evaluation of sensitivity Moreover, the sensitivity was evaluated using the obtained multilayer electrophotographic photosensitive member.
That is, the produced electrophotographic photosensitive member was charged to a surface potential of −700 V using a drum sensitivity tester at room temperature and normal humidity (temperature: 20 ° C., humidity: 60%).
Next, light having a light intensity of 0.6 μJ / cm ² monochromatized to a wavelength of 780 nm and a half width of 20 nm using a bandpass filter was exposed to the surface of the electrophotographic photosensitive member for 40 milliseconds, and then 0. The surface potential after 5 seconds was measured as a bright potential. The obtained results are shown in Table 1. In Table 1, the absolute value of the bright potential is shown.

(4) Evaluation of crystallization Moreover, crystallization was evaluated using the obtained multilayer electrophotographic photosensitive member.
That is, the presence or absence of crystals in the photosensitive layer was visually confirmed and evaluated according to the following criteria.
A: No crystals are observed
X: Crystal is observed

[Examples 2 to 7]
In Examples 2 to 7, a laminated electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the content of the hole transport agent in the charge generation layer was changed as shown in Table 1. evaluated. The obtained results are shown in Table 1.

[Examples 8 to 12]
Moreover, in Examples 8-12, while making the kind of hole transport agent in a charge generation layer into the hole transport agent (HTM-2-6) represented by Formula (9)-(13), respectively, A laminated electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 1 except that the content was 30 parts by weight with respect to 100 parts by weight of the binder resin of the charge generation layer. The obtained results are shown in Table 1.

[Comparative Examples 1-4]
In Comparative Examples 1 to 4, a laminated electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the content of the hole transport agent in the charge generation layer was changed as shown in Table 1. evaluated. The obtained results are shown in Table 1.

According to the multilayer electrophotographic photosensitive member and the image forming apparatus using the same according to the present invention, a specific compound is used as a charge generating agent in the charge generation layer of the negatively charged multilayer electrophotographic photosensitive member. The exposure memory can be effectively suppressed by containing a hole transporting agent having the structure in a predetermined range.
Therefore, the multilayer electrophotographic photosensitive member and the image forming apparatus using the same of the present invention not only improve electrical characteristics and image characteristics in various image forming apparatuses such as copying machines and printers, but also a simple configuration with a reduced number of parts. It is expected to contribute significantly to the provision of an image forming apparatus having a structure.

(A)-(c) is a figure provided in order to demonstrate the structure of a laminated type electrophotographic photoreceptor. It is a figure provided in order to demonstrate the relationship between content of the hole transport agent which has a specific structure, and exposure memory potential. It is a figure provided in order to demonstrate the image forming apparatus provided with the lamination type electrophotographic photosensitive member.

Explanation of symbols

20: Laminated photoreceptor 20 ′: Laminated photoreceptor 20 ″: Laminated photoreceptor 22: Charge transport layer 24: Charge generation layer 25: Intermediate layer 100: Image forming apparatus 111: Laminated electrophotographic photoreceptor 112: Charging means 113: exposure means 114: developing means 115: transfer means 117: cleaning device 120: recording paper

Claims (7)

A negatively charged type laminated electrophotographic photosensitive member in which a charge generation layer and a charge transport layer are formed directly or via an intermediate layer on a substrate,
The charge generation layer contains an oxotitanyl phthalocyanine crystal as the charge generation agent, and at least one selected from the group consisting of hole transport agents represented by the following general formulas (1) to (6) A laminate type electrophotographic photosensitive material containing a hole transport agent and having a content in the range of 4 to 200 parts by weight with respect to 100 parts by weight of the binder resin in the charge generation layer body.

(In General Formula (1), R ¹ and R ² are each an independent substituent, and are a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted group having 6 to 30 carbon atoms. A plurality of Ra and Rb are each an independent substituent, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a carbon number A substituted or unsubstituted alkenyl group having 6 to 30; or —OR ³ (R ³ is an alkyl group having 1 to 10 carbon atoms, a perfluoroalkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 30 carbon atoms. The repeating number m is an integer of 0 to 5, the repeating number n is an integer of 0 to 4, Ar ¹ and Ar ² are each an independent substituent, Substitution of 6 to 30 carbon atoms or (It is an unsubstituted aryl group, and the repeating numbers o and p are integers of 0 to 1.)

(In the general formula (2), R ^{4 to} R ¹² are each an independent substituent, and are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted group having 1 to 12 carbon atoms, or An unsubstituted alkoxy group, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted alkenyl group having 6 to 30 carbon atoms, or —OR ¹³ (R ¹³ is an alkyl group having 1 to 10 carbon atoms) , A perfluoroalkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 30 carbon atoms), and R ^{4 to} R ⁸ , R ⁹ and R ¹⁰ , R ¹¹ and R ^12. May be linked to each other to form a saturated / unsaturated hydrocarbon ring, R ⁶ and R ¹⁰ may be a substituent represented by the following general formula (2 ′), , X ¹ is a substituted or unsubstituted arylene group having 6 to 30 carbon atoms, carbon An unsaturated hydrocarbon group having an aryl group having 6 to 30 prime numbers or a condensed polycyclic hydrocarbon group having 10 to 30 carbon atoms.)

(In the general formula (2 ′), Ar ³ and Ar ⁴ are each an independent substituent, and are a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, or a substituted or non-substituted group having 6 to 30 carbon atoms. (It is a substituted aryl group, and the repeating number c is an integer of 0 to 2.)

(In the general formula (3), R ^{14 to} R ²⁴ are each an independent substituent, and are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted group having 1 to 12 carbon atoms, or An unsubstituted alkoxy group, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted alkenyl group having 6 to 30 carbon atoms, or —OR ²⁵ (R ²⁵ is an alkyl group having 1 to 10 carbon atoms) , A perfluoroalkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 30 carbon atoms), and R ^{14 to} R ¹⁸ , R ¹⁹ and R ²⁰ , R ²¹ and R ^24. R ²² and R ²³ may be linked to each other to form a saturated / unsaturated hydrocarbon ring, and R ¹⁶ may be a substituent represented by the following general formula (3 ′). In addition, X ² is a substituted or unsubstituted aryl having 6 to 30 carbon atoms. A ren group, an unsaturated hydrocarbon group having an aryl group having 6 to 30 carbon atoms, or a condensed polycyclic hydrocarbon group having 10 to 30 carbon atoms.)

(In the general formula (3 ′), Ar ⁵ and Ar ⁶ are each an independent substituent, and are a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, or a substituted or non-substituted group having 6 to 30 carbon atoms. (It is a substituted aryl group, and the repeating number d is an integer of 0 to 2.)

(In the general formula (4), R ^{26 to} R ³⁴ are each an independent substituent, and are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted group having 1 to 12 carbon atoms, or An unsubstituted alkoxy group, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted alkenyl group having 6 to 30 carbon atoms, or —OR ³⁵ (R ³⁵ is an alkyl group having 1 to 10 carbon atoms) , A perfluoroalkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 30 carbon atoms), and R ^{26 to} R ³⁰ , R ³¹ and R ³² , R ³³ and R ^34. May be linked to each other to form a saturated / unsaturated hydrocarbon ring, and Ar ⁷ and Ar ⁸ are each an independent substituent and are a hydrogen atom, a C 1-12 substituent or Unsubstituted alkyl group or 6 to 3 carbon atoms An aryl group, the repetition number e is an integer of 0 to 2.)

(In the general formula (5), a plurality of Rc to Re are each an independent substituent, and are a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted group having 6 to 30 carbon atoms. An aryl group, or a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, the repeating number q is an integer of 0 to 4, r to s are integers of 0 to 5, Ar ⁹ and Ar ¹⁰ are And a substituted or unsubstituted aryl group having 6 to 30 carbon atoms.)

(In the general formula (6), R ³⁶ and R ³⁷ are each an independent substituent, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms. R ³⁶ may combine with Rg to form a saturated hydrocarbon ring, and a plurality of Rf to Ri are each an independent substituent, and a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms. Group, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, and repeating numbers t, u, and w are integers of 0 to 5 and repeating The number v is an integer from 0 to 4.)   2. The laminate according to claim 1, wherein a value obtained by subtracting an ionization potential of oxotitanylphthalocyanine as the charge generation agent from an ionization potential of the hole transport agent is set to a value within a range of 0 to 0.4 eV. Type electrophotographic photoreceptor.   3. The multilayer electrophotographic photosensitive member according to claim 1, wherein the thickness of the charge generation layer is set to a value within a range of 0.05 to 1.0 [mu] m.   The oxo titanyl phthalocyanine crystal as the charge generating agent has a maximum peak at a Bragg angle of 2θ ± 0.2 ° = 27.2 °, and a peak accompanying vaporization of adsorbed water in differential scanning calorimetry. The multilayer electrophotographic photoreceptor according to any one of claims 1 to 3, which has one peak in a range of 270 to 400 ° C.   The stacked electron according to any one of claims 1 to 4, wherein the charge transport layer contains a hole transport agent similar to the hole transport agent contained in the charge generation layer. Photoconductor.   A multilayer electrophotographic photosensitive member according to any one of claims 1 to 5 is provided, and a charging unit, an exposure unit, a developing unit, and a transfer unit are disposed around the multilayer electrophotographic photosensitive member. In addition, an image forming apparatus characterized by being a static elimination-less type that does not have a static elimination means.   The image forming apparatus according to claim 6, wherein the charging unit is a charging roller.

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