JP2020079915A - Electrophotographic photoreceptor - Google Patents

Abstract

To provide an electrophotographic photoreceptor that is excellent in sensitivity and wear resistance and can prevent LSU light reflection stripes.SOLUTION: An electrophotographic photoreceptor comprises: a conductive substrate; and a photosensitive layer directly or indirectly provided on the conductive substrate. The photosensitive layer has a charge generating layer and a charge transport layer provided sequentially from the conductive substrate. The charge transport layer contains a binder resin, a hole transport agent, and titanyl phthalocyanine. The binder resin contains a polyarylate resin having a repeating unit represented by a general formula (1) and a general formula (2), and a terminal group represented by a general formula (3). The titanyl phthalocyanine has a main peak at a Bragg angle of (2θ±0.2°) at 27.2°. A content of titanyl phthalocyanine in the charge transport layer is 0.1 parts by mass or more and 0.5 parts by mass or less based on 100 parts by mass of the binder resin.SELECTED DRAWING: None

Description

  The present invention relates to an electrophotographic photoreceptor.

  The electrophotographic photosensitive member is used in an electrophotographic image forming apparatus. As the electrophotographic photoreceptor, for example, a laminated electrophotographic photoreceptor or a single-layer electrophotographic photoreceptor is used. The laminated electrophotographic photoreceptor includes a photosensitive layer including a charge generating layer having a charge generating function and a charge transporting layer having a charge transporting function. The single-layer type electrophotographic photoreceptor includes a single-layer photosensitive layer having a charge generating function and a charge transporting function.

  Patent Document 1 describes a polyarylate resin effective for improving the abrasion resistance of the photosensitive layer.

JP, 2018-141071, A

  However, the electrophotographic photosensitive member using the polyarylate resin described in Patent Document 1 is excellent in abrasion resistance, but is compatible with both improvement in sensitivity and suppression of reflection of exposure light (especially light having a wavelength of 780 nm). The inventors of the present invention have found that there is room for improvement.

  The present invention has been made in view of the above problems, and an object thereof is to provide an electrophotographic photosensitive member that is excellent in sensitivity and abrasion resistance and can suppress reflection of exposure light.

  The electrophotographic photoreceptor of the present invention comprises a conductive substrate and a photosensitive layer provided directly or indirectly on the conductive substrate. The photosensitive layer includes a charge generation layer and a charge transport layer sequentially provided from the side of the conductive substrate. The charge transport layer contains a binder resin, a hole transport material, and titanyl phthalocyanine. The binder resin includes a first repeating unit represented by the following general formula (1), a second repeating unit represented by the following general formula (2), and an end group represented by the following general formula (3). A polyarylate resin having The titanyl phthalocyanine has a main peak at 27.2° of Bragg angle (2θ±0.2°) in the CuKα characteristic X-ray diffraction spectrum. The content of the titanyl phthalocyanine in the charge transport layer is 0.1 parts by mass or more and 0.8 parts by mass or less with respect to 100 parts by mass of the binder resin.

In the general formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or a methyl group. R ⁵ and R ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R ⁵ and R ⁶ may be bonded to each other to represent a divalent group represented by the following general formula (X). In the general formula (2), X ¹ represents a divalent group represented by the following chemical formula (2A), (2B), (2C) or (2D). In the general formula (3), R ^f represents a chain aliphatic group having 1 to 20 carbon atoms, which is substituted with one or more fluorine atoms.

  In the general formula (X), t represents an integer of 1 or more and 3 or less. * Represents a bond.

  The electrophotographic photoreceptor of the present invention has excellent sensitivity and abrasion resistance, and can suppress the reflection of exposure light.

FIG. 3 is a cross-sectional view showing an example of an electrophotographic photosensitive member according to the exemplary embodiment of the present invention. FIG. 3 is a cross-sectional view showing an example of the electrophotographic photosensitive member according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments described below. The present invention can be implemented with appropriate modifications within the scope of the object of the present invention. It should be noted that although the description may be omitted as appropriate for the overlapping description, the gist of the invention is not limited.

  Hereinafter, the compound and the derivative thereof may be generically referred to by adding "system" after the compound name. When a "system" is added after the compound name to represent the polymer name, it means that the repeating unit of the polymer is derived from the compound or its derivative.

  Hereinafter, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an alkyl group having 1 to 6 carbon atoms, an alkyl group having 1 to 4 carbon atoms, an alkyl group having 3 to 5 carbon atoms, carbon An alkoxy group having 1 to 8 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, and 6 to 14 carbon atoms The aryl group, the cycloalkyl group having 3 to 10 carbon atoms, the cycloalkyl group having 5 to 8 carbon atoms, the aralkyl group having 7 to 20 carbon atoms, and the heterocyclic group must not be specified. , Respectively, have the following meanings.

  Examples of the halogen atom (halogen group) include a fluorine atom (fluoro group), a chlorine atom (chloro group), a bromine atom (bromo group) and an iodine atom (iodo group).

  The alkyl group having 1 to 8 carbon atoms, the alkyl group having 1 to 6 carbon atoms, the alkyl group having 1 to 4 carbon atoms, and the alkyl group having 3 to 5 carbon atoms are each a straight chain. In the form of a branched or branched chain and is unsubstituted. Examples of the alkyl group having 1 to 8 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group. Group, neopentyl group, 1,2-dimethylpropyl group, linear or branched hexyl group, linear or branched heptyl group, and linear or branched octyl group Can be mentioned. Examples of the alkyl group having 1 to 6 carbon atoms, the alkyl group having 1 to 4 carbon atoms or the alkyl group having 3 to 5 carbon atoms are described as examples of the alkyl group having 1 to 8 carbon atoms. Among these groups, each is a group having 1 to 6 carbon atoms, a group having 1 to 4 carbon atoms, or a group having 3 to 5 carbon atoms.

  The alkoxy group having 1 to 8 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, the alkoxy group having 1 to 4 carbon atoms, and the alkoxy group having 1 to 3 carbon atoms are each a straight chain. In the form of a branched or branched chain and is unsubstituted. Examples of the alkoxy group having 1 to 8 carbon atoms include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, n-pentoxy group, Examples thereof include an isopentoxy group, a neopentoxy group, a linear or branched hexyloxy group, a linear or branched heptyloxy group, and a linear or branched octyloxy group. Examples of the alkoxy group having 1 to 6 carbon atoms, the alkoxy group having 1 to 4 carbon atoms, or the alkoxy group having 1 to 3 carbon atoms are as examples of the alkoxy group having 1 to 8 carbon atoms. Of the above-mentioned groups, each is a group having 1 to 6 carbon atoms, a group having 1 to 4 carbon atoms, or a group having 1 to 3 carbon atoms.

  The aryl group having 6 to 14 carbon atoms is unsubstituted. Examples of the aryl group having 6 to 14 carbon atoms include a phenyl group, a naphthyl group, an indacenyl group, a biphenylenyl group, an acenaphthylenyl group, an anthryl group and a phenanthryl group.

  The cycloalkyl group having 3 to 10 carbon atoms and the cycloalkyl group having 5 to 8 carbon atoms are each unsubstituted. Examples of the cycloalkyl group having 3 to 10 carbon atoms include cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group and cyclodecyl group. Examples of the cycloalkyl group having 5 to 8 carbon atoms are groups having 5 to 8 carbon atoms among the groups described as examples of the cycloalkyl group having 3 to 10 carbon atoms.

  The aralkyl group having 7 to 20 carbon atoms is unsubstituted. Examples of the aralkyl group having 7 to 20 carbon atoms include an alkyl group having 1 to 6 carbon atoms substituted with an aryl group having 6 to 14 carbon atoms.

  Examples of the heterocyclic group include a heterocyclic group having 5 to 14 members. The 5- to 14-membered heterocyclic group contains at least one hetero atom other than carbon atoms and is unsubstituted. The hetero atom is one or more selected from the group consisting of a nitrogen atom, a sulfur atom and an oxygen atom. The 5-membered to 14-membered heterocyclic group is, for example, a 5-membered or 6-membered monocyclic heterocycle containing 1 to 3 heteroatoms other than carbon atoms (hereinafter referred to as heterocycle (H). A heterocyclic group in which two heterocycles (H) are fused; a heterocycle in which the heterocycle (H) is condensed with a 5- or 6-membered monocyclic hydrocarbon ring Group; Heterocyclic group in which 3 heterocycles (H) are condensed; Heterocyclic group in which 2 heterocycles (H) are condensed with 1 5- or 6-membered monocyclic hydrocarbon ring; or Heterocycle Examples of the heterocyclic group include (H) one fused with two 5-membered or 6-membered monocyclic hydrocarbon rings. Specific examples of the heterocyclic group having 5 to 14 members include piperidinyl group, piperazinyl group, morpholinyl group, thiophenyl group, furanyl group, pyrrolyl group, imidazolyl group, pyrazolyl group, isothiazolyl group, isoxazolyl group, oxazolyl group, thiazolyl group. Group, flazanyl group, pyranyl group, pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, indolyl group, 1H-indazolyl group, isoindolyl group, chromenyl group, quinolinyl group, isoquinolinyl group, purinyl group, pteridinyl group, triazolyl group, tetrazolyl Group, 4H-quinolizinyl group, naphthyridinyl group, benzofuranyl group, 1,3-benzodioxolyl group, benzoxazolyl group, benzothiazolyl group, benzimidazolyl group, carbazolyl group, phenanthridinyl group, acridinyl group, phenazinyl group And a phenanthrolinyl group.

<Electrophotographic photoreceptor>
An electrophotographic photoreceptor (hereinafter, also referred to as “photoreceptor”) according to an embodiment of the present invention includes a conductive base and a photosensitive layer directly or indirectly provided on the conductive base. Prepare The photosensitive layer includes a charge generation layer and a charge transport layer which are sequentially provided from the side of the conductive substrate. The charge transport layer contains a binder resin, a hole transport agent, and titanyl phthalocyanine. The binder resin includes a first repeating unit represented by the following general formula (1) (hereinafter sometimes referred to as repeating unit (1)) and a second repeating unit represented by the following general formula (2) ( Hereinafter, a polyarylate resin (hereinafter sometimes referred to as a repeating unit (2)) and a terminal group represented by the following general formula (3) (hereinafter sometimes referred to as an end group (3)) ( Hereinafter, it may be described as a polyarylate resin (PA)). Titanyl phthalocyanine has a main peak at 27.2° of the Bragg angle (2θ±0.2°) in the CuKα characteristic X-ray diffraction spectrum. The content of titanyl phthalocyanine in the charge transport layer is 0.1 parts by mass or more and 0.8 parts by mass or less based on 100 parts by mass of the binder resin.

In formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or a methyl group. R ⁵ and R ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R ⁵ and R ⁶ may be bonded to each other to represent a divalent group represented by the following general formula (X). In the general formula (2), X ¹ represents a divalent group represented by the following chemical formula (2A), (2B), (2C) or (2D). In the general formula (3), R ^f represents a chain aliphatic group having 1 to 20 carbon atoms, which is substituted with one or more fluorine atoms.

  In general formula (X), t represents an integer of 1 or more and 3 or less. * Represents a bond.

  First, the structure of the photoconductor will be described with reference to FIGS. 1 and 2. 1 and 2 are cross-sectional views each showing an example of the photoconductor 1 according to the embodiment of the present invention.

  As shown in FIG. 1, the photoconductor 1 is, for example, a layered photoconductor including a conductive substrate 2 and a photosensitive layer 3 directly provided on the conductive substrate 2. The photosensitive layer 3 includes a charge generation layer 3a and a charge transport layer 3b which are sequentially provided from the side of the conductive substrate 2.

  As shown in FIG. 2, for example, the photoreceptor 1 includes a conductive substrate 2, an intermediate layer 4 (undercoat layer) directly provided on the conductive substrate 2, and an intermediate layer 4 directly on the intermediate layer 4. It may be a laminated-type photoreceptor including the provided photosensitive layer 3. That is, the photosensitive layer 3 may be indirectly provided on the conductive substrate 2. Each of the photoconductors 1 in FIGS. 1 and 2 may further include a protective layer (not shown) provided on the photosensitive layer 3.

  The thickness of the charge generation layer 3a is not particularly limited, but is preferably 0.01 μm or more and 5 μm or less, more preferably 0.1 μm or more and 3 μm or less. The thickness of the charge transport layer 3b is not particularly limited, but is preferably 2 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less.

  From the viewpoint of improving the abrasion resistance of the photoconductor 1 and suppressing the reflection of exposure light, the charge transport layer 3b is preferably disposed as the outermost surface layer of the photoconductor 1. That is, it is preferable that the photoconductor 1 does not include a protective layer. The photoreceptor 1 has been described above with reference to FIGS. 1 and 2.

  The photoconductor according to the exemplary embodiment of the present invention has excellent sensitivity and abrasion resistance, and can suppress reflection of exposure light. The reason is presumed as follows. In the multilayer type photoreceptor, it is desirable to reduce the amount of additives in the charge transport layer as much as possible from the viewpoint of high sensitivity. However, such a layered type photoconductor is likely to reflect the exposure light on its surface, which may cause an LSU light reflection stripe described later. In order to suppress the reflection of exposure light on the surface of the multi-layer photosensitive member, it is effective to add a pigment to the charge transport layer so that the charge transport layer absorbs the exposure light. However, when a pigment is added to the charge transport layer of the laminated photoreceptor, the exposure light reaching the charge generation layer is attenuated, and the sensitivity of the laminated photoreceptor tends to decrease. From the above, it is difficult to achieve both suppression of reflection of exposure light and improvement of sensitivity in the laminated-type photoreceptor.

  The photoconductor according to the embodiment of the present invention has a titanyl phthalocyanine (hereinafter referred to as Y-type titanyl phthalocyanine) having a main peak at 27.2° of Bragg angle (2θ±0.2°) in a CuKα characteristic X-ray diffraction spectrum. Sometimes) is contained in the charge transport layer in a fixed amount. The Y-type titanyl phthalocyanine absorbs exposure light and suppresses its reflection. Further, since Y-type titanyl phthalocyanine is a highly efficient charge generating agent, it generates charges in the charge transport layer. As described above, in the photoconductor according to the exemplary embodiment of the present invention, the reduction in the amount of charges generated in the charge generation layer is compensated by the generation of charges in the charge transport layer, so that excellent sensitivity is maintained. Further, the polyarylate resin (PA) has excellent strength because it has a repeating unit having a specific structure, and has a terminal group containing a chain aliphatic group substituted with a fluorine atom to reduce frictional resistance. Improves wear resistance of the transport layer. From the above, it is considered that the photoconductor according to the exemplary embodiment of the present invention has excellent sensitivity and abrasion resistance and can suppress reflection of exposure light.

  The LSU light reflection stripe will be described. The photoconductor forms an electrostatic latent image by being irradiated with exposure light from a laser scanning unit (LSU) in an image forming apparatus, for example. However, part of the exposure light emitted by the LSU may be reflected by the surface of the photoconductor and returned to the LSU. The light returning to the LSU may be further reflected on the surface of the LSU to expose a non-exposed portion (a region that would normally not be exposed) of the photoconductor. The streak generated in the image due to such a phenomenon is called an LSU light reflection streak. The photoconductor according to the exemplary embodiment of the present invention can suppress LSU light reflection stripes by suppressing the reflection of exposure light.

[Conductive substrate]
The conductive substrate is not particularly limited as long as it can be used as the conductive substrate of the photoconductor. At least the surface portion of the conductive substrate may be made of a material having conductivity. An example of the conductive substrate is a conductive substrate composed only of a material having conductivity. Another example of the conductive substrate is a conductive substrate obtained by coating a material having conductivity with a material having no conductivity. As the material having conductivity, for example, aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, and alloys containing these (eg, aluminum alloy, stainless steel, etc. Steel and brass). As the material having conductivity, aluminum or aluminum alloy is preferable from the viewpoint of facilitating transfer of charges from the photosensitive layer to the conductive substrate.

  The shape of the conductive substrate is appropriately selected according to the structure of the image forming apparatus. Examples of the shape of the conductive substrate include a sheet shape and a drum shape. Moreover, the thickness of the conductive substrate is appropriately selected according to the shape of the conductive substrate.

[Photosensitive layer]
The photosensitive layer is directly or indirectly provided on the conductive substrate. The photosensitive layer has a charge generation layer and a charge transport layer that are sequentially provided from the side of the conductive substrate.

[Charge generation layer]
The charge generation layer contains a charge generation agent. The charge generation layer may contain a binder resin for the charge generation layer (hereinafter sometimes referred to as a base resin). The charge generation layer may further contain an additive, if necessary.

(Charge generating agent)
Examples of the charge generating agent include phthalocyanine pigments, perylene pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, indigo pigments, azurenium pigments, cyanines. Pigment, inorganic photoconductive material (for example, selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide or amorphous silicon) powder, pyrylium pigment, anthanthrone pigment, triphenylmethane pigment, slene pigment, toluidine pigment, Examples include pyrazoline pigments and quinacridone pigments.

  Examples of the phthalocyanine pigment include metal-free phthalocyanine and metal phthalocyanine. Examples of the metal phthalocyanine include titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine. The metal-free phthalocyanine is represented by the following chemical formula (CGM-1). Titanyl phthalocyanine is represented by the following chemical formula (CGM-2).

  The phthalocyanine-based pigment may be crystalline or non-crystalline. Examples of the metal-free phthalocyanine crystals include X-type crystals of metal-free phthalocyanine (hereinafter, sometimes referred to as X-type metal-free phthalocyanine). Examples of the crystal of titanyl phthalocyanine include α-type, β-type, and Y-type crystals of titanyl phthalocyanine (hereinafter, may be referred to as α-type, β-type, and Y-type titanyl phthalocyanine, respectively).

  In the CuKα characteristic X-ray diffraction spectrum, the Y-type titanyl phthalocyanine crystal has a main peak at 27.2° of the Bragg angle (2θ±0.2°), for example. The α-type titanyl phthalocyanine crystal has a main peak at 28.6° of the Bragg angle (2θ±0.2°) in the CuKα characteristic X-ray diffraction spectrum.

  The main peak in the CuKα characteristic X-ray diffraction spectrum is a peak having the first or second highest intensity in the range where the Bragg angle (2θ±0.2°) is 3° or more and 40° or less.

  An example of the method for measuring the CuKα characteristic X-ray diffraction spectrum will be described. A sample (titanyl phthalocyanine) was filled in a sample holder of an X-ray diffractometer (for example, "RINT (registered trademark) 1100" manufactured by Rigaku Corporation), and an X-ray tube Cu, a tube voltage of 40 kV, a tube current of 30 mA, and CuKα. The X-ray diffraction spectrum is measured under the condition that the characteristic X-ray wavelength is 1.542Å. The measurement range (2θ) is, for example, 3° or more and 40° or less (start angle 3°, stop angle 40°), and the scanning speed is, for example, 10°/min.

  For a digital optical image forming apparatus (for example, a laser beam printer or a facsimile using a light source such as a semiconductor laser), it is preferable to use a photoconductor having sensitivity in a wavelength region of 700 nm or more. Since it has a high quantum yield in the wavelength region of 700 nm or more, the charge generating agent is preferably a phthalocyanine-based pigment, more preferably metal-free phthalocyanine or titanyl phthalocyanine, and further preferably X-type metal-free phthalocyanine or Y-type titanyl phthalocyanine. , Y-type titanyl phthalocyanine is particularly preferable.

  An anthanthrone-based pigment is preferable as a charge generating agent for a photoreceptor applied to an image forming apparatus using a short wavelength laser light source (for example, a laser light source having a wavelength of 350 nm to 550 nm).

  The content of the charge generating agent in the charge generating layer is preferably 5 parts by mass or more and 1,000 parts by mass or less, and 30 parts by mass or more with respect to 100 parts by mass of the base resin from the viewpoint of further improving the sensitivity of the photoreceptor. It is more preferably 500 parts by mass or less.

(Base resin)
Examples of the base resin include thermoplastic resins, thermosetting resins, and photocurable resins. Examples of the thermoplastic resin include polycarbonate resin, polyarylate resin, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic acid polymer, styrene-acrylic acid copolymer, Polyethylene resin, ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer resin, vinyl chloride-vinyl acetate copolymer, alkyd resin, polyamide resin, urethane resin, polysulfone resin, diallyl phthalate Resins, ketone resins, polyvinyl butyral resins, polyester resins, polyvinyl acetal resins and polyether resins can be mentioned. Examples of the thermosetting resin include silicone resin, epoxy resin, phenol resin, urea resin and melamine resin. Examples of the photocurable resin include acrylic acid adducts of epoxy compounds and acrylic acid adducts of urethane compounds. As the base resin, a polyvinyl acetal resin is preferable.

(Additive)
Examples of the additives include deterioration inhibitors (eg, antioxidants, radical scavengers, singlet quenchers or ultraviolet absorbers), softening agents, surface modifiers, extenders, thickeners, dispersion stabilizers. , Waxes, acceptor compounds (eg electron acceptor compounds), donors, surfactants, plasticizers, sensitizers and leveling agents. Examples of the antioxidant include hindered phenol compounds, hindered amine compounds, thioether compounds, and phosphite compounds. Examples of the leveling agent include dimethyl silicone oil. Examples of the sensitizer include metaterphenyl.

[Charge transport layer]
The charge transport layer contains a binder resin, a hole transport agent, and Y-type titanyl phthalocyanine. The binder resin includes polyarylate resin (PA).

  The absorbance of light having a wavelength of 780 nm in the charge transport layer is preferably 0.50 or more and 0.90 or less, more preferably 0.55 or more and 0.80 or less, and further preferably 0.60 or more and 0.70 or less. By setting the above-mentioned absorbance to 0.50 or more, the exposure light can be efficiently absorbed by the charge transport layer, and the reflection of the exposure light on the surface of the photoconductor can be efficiently suppressed. By setting the above-mentioned absorbance to 0.90 or less, excessive absorption of exposure light in the charge transport layer can be suppressed, and the sensitivity of the photoconductor can be further improved. In measuring the absorbance of the charge transport layer, first, a sample film having the same composition and the same thickness as the charge transport layer of the target photoreceptor is formed. Then, the absorbance measured using this sample film can be regarded as the absorbance of the charge transport layer.

(Polyarylate resin (PA))
The polyarylate resin (PA) has a main chain and an end group (3). Hereinafter, the main chain of the polyarylate resin (PA) and the terminal group (3) will be described.

  The main chain of the polyarylate resin (PA) contains at least one repeating unit (1) and at least one repeating unit (2).

  The main chain of the polyarylate resin (PA) has no halogen atom. Since the terminal group (3) of the polyarylate resin (PA) has a fluorine atom and the main chain does not have a halogen atom, the polyarylate resin has excellent compatibility with the hole transfer agent and can suppress crystallization of the photosensitive layer. it is conceivable that. Further, in the polyarylate resin (PA), since the terminal group (3) has a fluorine atom and the main chain does not have a halogen atom, the main chains are easily entangled with each other, resulting in mechanical strength of the photosensitive layer. Is expected to improve.

The repeating unit (1) will be described below. The alkyl group having 1 to 4 carbon atoms represented by R ⁵ and R ⁶ in the general formula (1) is preferably a methyl group or an ethyl group.

  As t in the general formula (X), 1 or 2 is preferable, and 2 is more preferable.

When R ⁵ and R ⁶ in the general formula (1) are bonded to each other to represent a divalent group represented by the general formula (X), R ¹ and R ³ each represent a methyl group, and R ² and Each R ⁴ preferably represents a hydrogen atom.

  As the repeating unit (1), repeating units represented by the following chemical formulas (1-1), (1-2), (1-3) or (1-4) (hereinafter, referred to as repeating units (1-1 ), (1-2), (1-3) or (1-4) may be described).

  The polyarylate resin (PA) may include only one type of repeating unit (1) or may include two or more types (for example, two types) of the repeating unit (1).

  When the polyarylate resin (PA) contains two types of repeating units (1), the ratio of the number of one repeating unit (1) to the total number of repeating units (1) (hereinafter may be referred to as ratio r) Is preferably 0.10 or more and 0.90 or less.

Next, the repeating unit (2) will be described. As the repeating unit (2), a repeating unit represented by the following general formula (2-1) or (2-2) (hereinafter, referred to as a repeating unit (2-1) or (2-2), respectively. Is preferred). In the following general formula (2-2), X ² represents a divalent group represented by the chemical formula (2A), (2B) or (2D).

  As the repeating unit (2-1), a repeating unit represented by the following chemical formula (2-1C) is preferable. The repeating unit (2-2) is preferably a repeating unit represented by the following chemical formula (2-2A), (2-2B) or (2-2D). Hereinafter, the repeating units represented by the following chemical formulas (2-1C), (2-2A), (2-2B) or (2-2D) are respectively represented by repeating units (2-1C) and (2-2A). , (2-2B) or (2-2D).

The polyarylate resin (PA) may include only one type of repeating unit (2) or may include two or more types (for example, two types) of the repeating unit (2). When the polyarylate resin (PA) contains only one type of repeating unit (2), X ¹ in the general formula (2) is a divalent group represented by the chemical formula (2A), (2B) or (2C). Is preferably represented.

  From the viewpoint of further improving the abrasion resistance of the photoreceptor, the polyarylate resin (PA) preferably has two or more kinds of repeating units (2), and the repeating unit (2-1) and the repeating unit (2-2). ) And are more preferable. From the same viewpoint, it is particularly preferable that the polyarylate resin (PA) has only one type of repeating unit (2-1) and one type of repeating unit (2-2) as the repeating unit (2). ..

  When the polyarylate resin (PA) has two or more kinds of repeating units (2), the combination thereof includes a combination of a repeating unit (2-1C) and a repeating unit (2-2A) and a repeating unit (2-1C). And a repeating unit (2-2B) or a repeating unit (2-1C) and a repeating unit (2-2D).

  From the viewpoint of further improving the abrasion resistance of the photoconductor, the ratio of the number of repeating units (2-1) to the total number of repeating units (2) (hereinafter sometimes referred to as ratio p) is 0.05. It is preferably not less than 1.00 and less than 1.00, more preferably 0.20 or more and 0.80 or less, still more preferably 0.40 or more and 0.60 or less.

The ratio p and the ratio r described above are not values obtained from one molecular chain, but are obtained from the entire polyarylate resin (PA) contained in the photosensitive layer (a plurality of molecular chains). It is the average of the values. The proportion of each repeating unit can be calculated from the ¹ H-NMR spectrum obtained by measuring the ¹ H-NMR spectrum of the polyarylate resin (PA) using a proton nuclear magnetic resonance spectrometer.

Next, the terminal group (3) will be described. The chain aliphatic group substituted with a fluorine atom for R ^f in the general formula (3) is, for example, a straight chain or branched chain group. The number of fluorine atoms substituting the chain aliphatic group is, for example, 1 or more and 13 or less. The terminal group (3) is acyclic. By making the terminal group (3) a chain-like aliphatic group instead of a cyclic group, the abrasion resistance of the photoreceptor can be improved. Here, the “chain aliphatic group” refers to a monovalent chain hydrocarbon group (particularly, an alkyl group) or a group in which —O— is inserted between the carbon-carbon bonds of the chain hydrocarbon group. ..

  As the terminal group (3), the terminal group represented by the following general formula (3-1) (hereinafter sometimes referred to as the terminal group (3-1)) is preferable. Since the polyarylate resin (PA) has the terminal group (3-1), the friction resistance on the surface of the photosensitive layer can be further reduced, and as a result, the abrasion resistance of the photoreceptor can be further improved.

In formula (3-1), Q ¹ represents a linear or branched perfluoroalkyl group having 1 to 6 carbon atoms. Q ² represents a linear or branched perfluoroalkylene group having 1 to 6 carbon atoms. n represents an integer of 0 or more and 2 or less. When n represents 2, two Q ^2's may be the same or different from each other.

The perfluoroalkyl group represented by Q ¹ in the general formula (3-1) is preferably a linear or branched perfluoroalkyl group having 3 to 6 carbon atoms, and a linear carbon atom. A perfluoroalkyl group having a number of 3 or more and 6 or less is more preferable, and a heptafluoro n-propyl group or a tridecafluoro n-hexyl group is further preferable.

The perfluoroalkylene group represented by Q ² in the general formula (3-1) is preferably a linear or branched perfluoroalkylene group having 2 or 3 carbon atoms, and 1-fluoro-1-tri A fluoromethyl-methylene group or a 1,1,2-trifluoro-2-trifluoromethyl-ethylene group is more preferable.

  It is preferable that n represents 0 or 2.

  From the viewpoint of further improving the abrasion resistance of the photoconductor, the end group (3) is represented by the following chemical formula (M1), (M2), (M3) or (M4) (hereinafter, end group (3)). (M1), (M2), (M3) or (M4) may be referred to).

  From the viewpoint of further improving the abrasion resistance of the photoreceptor, the terminal group (3) is more preferably the terminal group (M1), (M3) or (M4). Further, the terminal group (3) tends to have a reduced frictional resistance on the surface of the photosensitive layer as the carbon chain thereof is longer and the number of fluorine atoms is larger. For these reasons, the terminal group (3) is more preferably the terminal group (M1) or (M3), and particularly preferably the terminal group (M3).

  As the combination of the repeating unit (1), the repeating unit (2) and the terminal group (3) in the polyarylate resin (PA), the combinations (j-1) to (j-11) shown in Table 1 below are preferable.

  In addition, in Table 1 below, when two repeating units are described in the repeating unit (1) or the repeating unit (2), it indicates that both have both. Specifically, in Table 1 below, for example, "1-2/1-3" indicates that it has both the repeating units (1-2) and (1-3). Further, the "unit (1)" or "unit (2)" indicates the repeating unit (1) or (2), respectively. The above description also applies to Tables 2 to 5 below.

  As the polyarylate resin (PA), the polyarylate resins (R-1-M1) to (R-10-M1) and (R-1-M2) to (R-1-M4) shown in Table 2 below are preferable. ..

In the polyarylate resin (PA), the repeating unit derived from the aromatic diol and the repeating unit derived from the aromatic dicarboxylic acid are adjacently bonded to each other. Further, in the polyarylate resin (PA), the terminal group (3) is adjacent to and bonded to the repeating unit derived from the aromatic dicarboxylic acid. From these, in the polyarylate resin (PA), the number N _BP of repeating units derived from an aromatic diol and the number N _DC of repeating units derived from an aromatic dicarboxylic acid are calculated by the formula “N _DC =N _BP +1” Meet When the polyarylate resin (PA) is a copolymer, the polyarylate resin (PA) may be, for example, a random copolymer, an alternating copolymer, a periodic copolymer or a block copolymer.

  The repeating unit derived from an aromatic diol is, for example, the repeating unit (1). When the polyarylate resin (PA) contains two or more kinds of repeating units (1), the arrangement of one kind of repeating unit (1) and another kind of repeating unit (1) is not particularly limited. One type of repeating unit (1) and another type of repeating unit (1) can be arranged randomly, alternately, cyclically or block by block via the repeating unit (2). The repeating unit derived from the aromatic dicarboxylic acid is, for example, the repeating unit (2). When the polyarylate resin (PA) contains two or more kinds of repeating units (2), the arrangement of one kind of repeating unit (2) and another kind of repeating unit (2) is not particularly limited. One type of repeating unit (2) and the other type of repeating unit (2) can be arranged randomly, alternately, cyclically or block by block via the repeating unit (1).

  The polyarylate resin (PA) preferably has only repeating units (1) and (2) as repeating units. However, the polyarylate resin (PA) may further have a repeating unit derived from an aromatic diol other than the repeating unit (1), and further may have a repeating unit derived from an aromatic dicarboxylic acid other than the repeating unit (2). You may.

  The viscosity average molecular weight of the polyarylate resin (PA) is preferably 10,000 or more, more preferably 20,000 or more, further preferably 30,000 or more, particularly preferably 40,000 or more. By setting the viscosity average molecular weight of the polyarylate resin (PA) to 10,000 or more, the abrasion resistance of the binder resin can be further improved. On the other hand, the viscosity average molecular weight of the binder resin is preferably 80,000 or less, more preferably 70,000 or less. When the viscosity average molecular weight of the binder resin is 80,000 or less, the polyarylate resin (PA) is easily dissolved in the solvent for forming the charge transport layer, so that the charge transport layer is easily formed.

  The method for producing the polyarylate resin (PA) is not particularly limited, but for example, an aromatic diol and an aromatic dicarboxylic acid for forming the main chain, and an end terminating agent for forming the terminal group (3). The method of polycondensation is mentioned. As the method of polycondensation, a known synthesis method (more specifically, solution polymerization, melt polymerization, interfacial polymerization, or the like) can be adopted.

The aromatic diol for forming the main chain is represented by, for example, the following general formula (BP-1). The aromatic dicarboxylic acid for forming the main chain is represented by, for example, the following general formula (DC-2). The terminal terminator for forming the terminal group (3) is represented by, for example, the following general formula (T-3). R< ¹ >, R< ² >, R< ³ >, R< ⁴ >, R< ⁵ >, R< ⁶ >, X< ^{1 >} and R ^<f > in the following general formulas (BP-1), (DC-2) and (T-3) are each general It has the same meaning as R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , X ¹ and R ^{f in the} formulas (1), (2) and (3). Hereinafter, the compounds represented by the following general formulas (BP-1), (DC-2) and (T-3) are referred to as compounds (BP-1), (DC-2) and (T-3), respectively. May be described.

  As the compound (BP-1), compounds represented by chemical formulas (BP-1-1) to (BP-1-4) (hereinafter, referred to as compounds (BP-1-1) to (BP-1-4), respectively. ))) is preferable.

  As the compound (DC-2), compounds represented by the following chemical formulas (DC-2-1C), (DC-2-2A), (DC-2-2B) and (DC-2-2D) (hereinafter, Each of them may be described as a compound (DC-2-1C), (DC-2-2A), (DC-2-2B) and (DC-2-2D).

  As the compound (T-3), compounds represented by the following chemical formulas (T-M1) to (T-M4) (hereinafter, may be referred to as compounds (T-M1) to (T-M4), respectively). ) Is preferred.

  The aromatic diol (for example, the compound (BP-1)) for forming the main chain may be used by transforming it into an aromatic diacetate. The aromatic dicarboxylic acid (for example, the compound (DC-2)) for constituting the main chain may be derivatized and used. Examples of the aromatic dicarboxylic acid derivative include aromatic dicarboxylic acid dichloride, aromatic dicarboxylic acid dimethyl ester, aromatic dicarboxylic acid diethyl ester, and aromatic dicarboxylic acid anhydride. Aromatic dicarboxylic acid dichloride is a compound in which two "-C(=O)-OH" groups of an aromatic dicarboxylic acid are each substituted by "-C(=O)-Cl" groups.

  In the polycondensation of aromatic diol and aromatic dicarboxylic acid, one or both of a base and a catalyst may be added. The base and catalyst can be appropriately selected from known bases and catalysts. Examples of the base include sodium hydroxide. Examples of the catalyst include benzyltributylammonium chloride, ammonium chloride, ammonium bromide, quaternary ammonium salt, triethylamine and trimethylamine.

  The binder resin preferably contains only the polyarylate resin (PA), but may further contain a binder resin other than the polyarylate resin (PA) (hereinafter sometimes referred to as other binder resin). The content of the polyarylate resin (PA) in the binder resin is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass. Examples of the other binder resin include the same resins as the resins exemplified as the base resin.

  The content ratio of the polyarylate resin (PA) in the charge transport layer is preferably 50% by mass or more and 85% by mass or less, and more preferably 60% by mass or more and 70% by mass or less. By setting the content ratio of the polyarylate resin (PA) to 50% by mass or more and 85% by mass or less, the abrasion resistance of the photoconductor can be further improved.

(Hole transfer agent)
Examples of the hole transfer agent include triphenylamine derivatives, diamine derivatives (eg, N,N,N′,N′-tetraphenylbenzidine derivatives, N,N,N′,N′-tetraphenylphenylenediamine derivatives, N,N,N',N'-tetraphenylnaphthylenediamine derivative, N,N,N',N'-tetraphenylphenanthrylenediamine derivative or di(aminophenylethenyl)benzene derivative), oxadiazole type Compounds (e.g. 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazole), styryl compounds (e.g. 9-(4-diethylaminostyryl)anthracene), carbazole compounds (e.g. , Polyvinylcarbazole), organic polysilane compounds, pyrazoline compounds (for example, 1-phenyl-3-(p-dimethylaminophenyl)pyrazolin), hydrazone compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds. Examples thereof include compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds and triazole compounds.

  The hole transport material preferably contains a compound represented by the following general formula (10) (hereinafter sometimes referred to as a hole transport material (10)). When the charge transport layer contains the hole transport material (10), the abrasion resistance and sensitivity of the photoreceptor can be further improved.

In formula (10), R ¹⁰¹ , R ¹⁰³ , R ¹⁰⁴ , R ¹⁰⁵ , R ¹⁰⁶ , R ¹⁰⁷ and R ¹⁰⁸ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and the number of carbon atoms. It represents a phenyl group which may be substituted with an alkyl group having 1 or more and 8 or less, or an alkoxy group having 1 or more and 8 or less carbon atoms. Adjacent two of R ¹⁰³ , R ¹⁰⁴ , R ¹⁰⁵ , R ¹⁰⁶ and R ¹⁰⁷ may be bonded to each other to represent a cycloalkane having 5 to 7 carbon atoms. R ¹⁰² and R ¹⁰⁹ each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. b ₁ and b ₂ each independently represent an integer of 0 or more and 5 or less.

In general formula (10), the alkyl group represented by R ^{101 to} R ¹⁰⁹ is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and a methyl group or n. -Butyl group is more preferred.

In formula (10), the phenyl group represented by R ^{101 to} R ¹⁰⁹ may be substituted with an alkyl group having 1 to 8 carbon atoms. As the alkyl group substituting the phenyl group, an alkyl group having 1 to 6 carbon atoms is preferable, an alkyl group having 1 to 4 carbon atoms is more preferable, and a methyl group is further preferable.

In general formula (10), the alkoxy group represented by R ^{101 to} R ¹⁰⁹ is preferably an alkoxy group having 1 to 4 carbon atoms, and more preferably a methoxy group or an ethoxy group.

In formula (10), adjacent two of R ¹⁰³ , R ¹⁰⁴ , R ¹⁰⁵ , R ¹⁰⁶ and R ¹⁰⁷ may be bonded to each other to represent a cycloalkane having 5 to 7 carbon atoms. For example, R ¹⁰⁶ and R ¹⁰⁷ adjacent one of ^{R 103, R 104, R 105} , R 106 and R ¹⁰⁷ may be bonded to each other to form a 5 carbon atoms to 7 cycloalkane. When adjacent two of R ¹⁰³ , R ¹⁰⁴ , R ¹⁰⁵ , R ¹⁰⁶ and R ¹⁰⁷ are bonded to each other to form a cycloalkane having 5 or more and 7 or less carbon atoms, the cycloalkane is R ¹⁰³ , R ¹⁰⁴ , It is condensed with a phenyl group to which R ¹⁰⁵ , R ¹⁰⁶ and R ¹⁰⁷ are bonded to form a bicyclic condensed ring group. In this case, the condensation site between the cycloalkane and the phenyl group may contain a double bond. Cyclohexane is preferred as the cycloalkane represented by two adjacent R ¹⁰³ , R ¹⁰⁴ , R ¹⁰⁵ , R ¹⁰⁶ and R ¹⁰⁷ bonded to each other.

When b ₁ represents an integer of 2 or more and 5 or less, a plurality of R ¹⁰² may be the same or different from each other. When b ₂ represents an integer of 2 or more and 5 or less, a plurality of R ¹⁰⁹ may be the same or different. It is preferable that b ₁ and b ₂ each independently represent 0 or 1.

In general formula (10), R ¹⁰¹ and R ¹⁰⁸ preferably represent a hydrogen atom. R ¹⁰² and R ¹⁰⁹ preferably represent an alkyl group having 1 to 8 carbon atoms. Each of R ¹⁰³ , R ¹⁰⁴ , R ¹⁰⁶ and R ¹⁰⁷ preferably represents a hydrogen atom. R ¹⁰⁵ preferably represents an alkyl group having 1 to 8 carbon atoms, and more preferably an n-butyl group. It is preferable that b ₁ and b ₂ each independently represent 0.

  As the hole transfer agent (10), a compound represented by the following chemical formula (HTM-1) (hereinafter, sometimes referred to as hole transfer agent (HTM-1)) is preferable.

  The charge-transporting layer layer preferably contains only the hole-transporting agent (10) as a hole-transporting agent, but may further contain another hole-transporting agent. The content ratio of the hole transport material (10) to the total amount of the hole transport material is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass.

  The content of the hole transport material in the charge transport layer is preferably 10 parts by mass or more and 200 parts by mass or less, and more preferably 20 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the binder resin.

[Y-type titanyl phthalocyanine]
The charge transport layer contains titanyl phthalocyanine (Y-type titanyl phthalocyanine) having a main peak at 27.2° of Bragg angle (2θ±0.2°) in the CuKα characteristic X-ray diffraction spectrum. Y-type titanyl phthalocyanine is represented by a chemical formula (CGM-2). The Y-type titanyl phthalocyanine is considered to be effective in improving the sensitivity of the photoconductor and suppressing the reflection of the exposure light, because it is superior in the absorption efficiency of the exposure light and the generation efficiency of the charge as compared with other pigments.

  The content of Y-type titanyl phthalocyanine in the charge transport layer is 0.1 parts by mass or more and 0.8 parts by mass or less, and 0.2 parts by mass or more and 0.4 parts by mass or less with respect to 100 parts by mass of the binder resin. More preferable.

(Other pigments)
The charge transport layer may further contain other pigments in addition to the Y-type titanyl phthalocyanine. Examples of other pigments include phthalocyanine pigments other than Y-type titanyl phthalocyanine, perylene pigments, azo pigments, polycyclic quinone pigments, squarylium pigments, pyranthrone pigments, perinone pigments, isoindoline pigments, quinacdrine pigments. System pigments, pyrazolone pigments, and benzimidazolone pigments.

  Examples of the perylene pigment include compounds represented by the following general formula (P).

In formula (P), R ²¹ and R ²² each independently represent a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. Examples of the monovalent organic group represented by R ²¹ and R ²² include an alkyl group having 1 to 6 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aryl group having 6 to 14 carbon atoms, And a heterocyclic group having 3 to 14 carbon atoms. The alkyl group, aralkyl group, aryl group or heterocyclic group represented by R ²¹ and R ²² may be substituted with a substituent. Examples of the substituent include an alkyl group having 1 to 6 carbon atoms (preferably a methyl group), an alkoxy group having 1 to 6 carbon atoms, a phenyl group, a halogen atom (preferably a chlorine atom), hydroxy. Group, cyano group, or nitro group.

  As the perylene pigment, a compound represented by the following chemical formula (K3) (hereinafter sometimes referred to as compound (K3)) is preferable.

  An azo pigment is a compound containing an azo group (-N=N-) in its structure. Examples of azo pigments include monoazo pigments and polyazo pigments (more specifically, bisazo pigments, trisazo pigments, tetrakisazo pigments, etc.). Further, the azo pigment may be a tautomer of a compound having an azo group. The compound having an azo group may have a chlorine atom.

  Examples of azo pigments include Pigment Yellow (more specifically, 14, 17, 49, 65, 73, 83, 93, 94, 95, 128, 166, 77, etc.), Pigment Orange (more specifically, Is 1, 2, 13, 34, or 36), or Pigment Red (more specifically, 30, 32, 61, or 144, etc.).

  As the azo pigment, a compound represented by the following chemical formula (K2) or (K5) (hereinafter, each may be referred to as compound (K2) or (K5)) is preferable.

  As the other pigment, compound (K2) or (K3) is preferable. By using the Y-type titanyl phthalocyanine in combination with the compound (K2) or (K3), the sensitivity of the photoconductor can be further improved.

  The content of the other pigment in the charge transport layer is preferably 0.1 parts by mass or more and 0.5 parts by mass or less based on 100 parts by mass of the binder resin.

(Additive)
Examples of the additives that may be added to the charge transport layer include the same additives as those exemplified in the charge generation layer. The charge transport layer preferably contains an antioxidant or an acceptor compound as an additive, and more preferably contains a hindered phenol compound or an electron acceptor compound.

  The content of the antioxidant in the charge transport layer is preferably 0.1 parts by mass or more and 10 parts by mass or less, and more preferably 0.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the binder resin.

  Examples of the electron acceptor compound include quinone compounds, diimide compounds, hydrazone compounds, malononitrile compounds, thiopyran compounds, trinitrothioxanthone compounds, 3,4,5,7-tetranitro-9-fluorenone compounds, Examples thereof include dinitroanthracene compounds, dinitroacridine compounds, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, succinic anhydride, maleic anhydride, and dibromomaleic anhydride. Examples of the quinone compound include diphenoquinone compounds, azoquinone compounds, anthraquinone compounds, naphthoquinone compounds, nitroanthraquinone compounds and dinitroanthraquinone compounds.

  The electron acceptor compound is preferably a compound represented by the following general formula (E-1).

In formula (E-1), R ^E1 , R ^E2 , R ^E3 and R ^E4 each independently represent an alkyl group having 1 to 6 carbon atoms. It is preferable that R ^E1 , R ^E2 , R ^E3 and R ^E4 each independently represent an alkyl group having 3 to 5 carbon atoms.

  As the compound represented by the general formula (E-1), a compound represented by the following chemical formula (ET1) (hereinafter sometimes referred to as electron acceptor compound (ET1)) is preferable.

  The content of the electron acceptor compound in the charge transport layer is preferably 0.1 parts by mass or more and 10 parts by mass or less, and more preferably 0.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the binder resin.

(combination)
As the combination of the polyarylate resin (PA) and the pigment (Y-type titanyl phthalocyanine and other pigments) in the charge transport layer, the combinations (k-1) to (k-16) shown in Table 3 below are preferable. Further, as the combination of the polyarylate resin (PA), the pigment, the hole transfer agent and the additive in the charge transport layer, any one of the combinations (k-1) to (k-16) shown in Table 3 below is used. A combination of an arylate resin (PA) and a pigment, a hole transfer agent (HTM-1), a hindered phenol compound, and an electron acceptor compound (ET1) is preferable. In Table 3 below, “K1” represents Y-type titanyl phthalocyanine. The above description also applies to Tables 4 and 5 below.

[Middle layer]
The intermediate layer (undercoat layer) contains, for example, inorganic particles and a resin used for the intermediate layer (resin for intermediate layer). It is considered that the presence of the intermediate layer makes it possible to smooth the flow of a current generated when the photosensitive member is exposed and suppress an increase in resistance while maintaining an insulating state to the extent that leakage can be suppressed.

  Examples of the inorganic particles include particles of metal (for example, aluminum, iron or copper), particles of metal oxide (for example, titanium oxide, alumina, zirconium oxide, tin oxide or zinc oxide) and non-metal oxide (for example, silica). Particles.

  The intermediate layer resin is not particularly limited as long as it can be used as a resin forming the intermediate layer. The intermediate layer may contain an additive. The examples of the additives contained in the intermediate layer are the same as the examples of the additives contained in the photosensitive layer.

<Method for manufacturing photoconductor>
Examples of the method of manufacturing the photoconductor according to the present exemplary embodiment include a manufacturing method including a charge generation layer forming step and a charge transport layer forming step. In the charge generation layer forming step, first, a coating liquid for forming the charge generation layer (hereinafter, also referred to as a charge generation layer coating liquid) is prepared. Then, the charge generation layer coating liquid is applied onto the conductive substrate. Next, at least a part of the solvent contained in the applied charge generation layer coating liquid is removed to form a charge generation layer. The charge generation layer coating liquid contains, for example, a charge generation agent, a base resin, and a solvent. Such a charge generating layer coating liquid is prepared by dissolving or dispersing a charge generating agent and a base resin in a solvent. The charge generation layer coating liquid may further contain an additive, if necessary.

  In the charge transport layer forming step, first, a coating liquid for forming the charge transport layer (hereinafter sometimes referred to as a charge transport layer coating liquid) is prepared. Then, the charge transport layer coating liquid is applied onto the charge generation layer. Next, at least a part of the solvent contained in the applied coating liquid for the charge transport layer is removed to form the charge transport layer. The charge transport layer coating liquid contains a hole transport agent, a polyarylate resin (PA) as a binder resin, Y-type titanyl phthalocyanine, and a solvent. The charge transport layer coating solution can be prepared by dissolving or dispersing a hole transport agent, a polyarylate resin (PA), and Y-type titanyl phthalocyanine in a solvent. The charge transport layer coating liquid may further contain other pigments or additives, if necessary.

  The solvent contained in the charge generation layer coating liquid and the charge transport layer coating liquid (hereinafter, these may be referred to as coating liquid) is not particularly limited as long as it can dissolve or disperse other components. Examples of the solvent include alcohols (more specifically, methanol, ethanol, isopropanol, butanol, etc.), aliphatic hydrocarbons (more specifically, n-hexane, octane, cyclohexane, etc.), aromatic hydrocarbons ( More specifically, benzene, toluene or xylene, etc., halogenated hydrocarbons (more specifically, dichloromethane, dichloroethane, carbon tetrachloride or chlorobenzene, etc.), ethers (more specifically, dimethyl ether, diethyl ether, Tetrahydrofuran, ethylene glycol dimethyl ether or diethylene glycol dimethyl ether, etc.), ketone (more specifically, acetone, methyl ethyl ketone, cyclohexanone, etc.), ester (more specifically, ethyl acetate or methyl acetate, etc.), dimethylformaldehyde, dimethylformamide, and Dimethyl sulfoxide may be mentioned. As a solvent for the coating liquid, a non-halogen solvent (a solvent other than halogenated hydrocarbon) is preferable.

  It is preferable that the solvent contained in the charge transport layer coating liquid and the solvent contained in the charge generation layer coating liquid are different kinds of solvents. This can prevent the charge generation layer from being dissolved in the solvent of the charge transport layer coating solution when the charge transport layer coating solution is applied onto the charge generation layer.

  Each coating liquid is prepared by mixing the respective components and dispersing them in a solvent. For mixing or dispersing, for example, a bead mill, roll mill, ball mill, attritor, paint shaker or ultrasonic disperser can be used.

  In order to improve the dispersibility of each component or the surface smoothness of each layer formed, each coating liquid may further contain a surfactant or a leveling agent.

  The method of applying each coating solution is not particularly limited as long as it is a method capable of uniformly applying each coating solution. Specific coating methods include, for example, a dip coating method, a spray coating method, a spin coating method or a bar coating method.

  The method for removing at least a part of the solvent contained in each coating solution is not particularly limited as long as it is a method capable of evaporating the solvent in each coating solution. Specific methods for removing the solvent include, for example, heating, reduced pressure, or combined use of heating and reduced pressure. As a more specific method, a method of heat treatment (hot air drying) using a high temperature dryer or a reduced pressure dryer can be mentioned. The heat treatment conditions are, for example, a temperature of 40° C. or higher and 150° C. or lower, and a time of 3 minutes or longer and 120 minutes or shorter.

  The method for producing the photoreceptor may further include a step of forming an intermediate layer, if necessary. A known method can be appropriately selected for the step of forming the intermediate layer.

  Hereinafter, the present invention will be described more specifically with reference to Examples. However, the present invention is in no way limited to the scope of the examples.

(Pigment)
The following pigments (K1) to (K6) were prepared as Y-type titanyl phthalocyanine and other pigments.
K1: Titanyl phthalocyanine (Y-type titanyl phthalocyanine) represented by the chemical formula (CGM-2) of the embodiment and having a main peak at 27.2° of Bragg angle (2θ±0.2°) in a CuKα characteristic X-ray diffraction spectrum.
K2: a compound represented by the chemical formula (K2) of the embodiment K3: a compound represented by the chemical formula (K3) of the embodiment K4: an X-type crystal (X of the compound represented by the chemical formula (CGM-1) of the embodiment Type metal-free phthalocyanine)
K5: Compound represented by the chemical formula (K5) of the embodiment K6: Represented by the chemical formula (CGM-2) of the embodiment, at a Bragg angle 2θ±0.2° of 28.6° in a CuKα characteristic X-ray diffraction spectrum. Titanyl phthalocyanine having a main peak (α-type titanyl phthalocyanine)

(Hole transfer agent)
As the hole transfer material, the hole transfer material (HTM-1) described in the embodiment was prepared.

(Binder resin)
As the binder resin, each of polyarylate resins (R-1-M1) to (R-1-M4), (R-2-M1) to (R-10-M1) and (R-1-MA) was synthesized. did. Of the polyarylate resins, the polyarylate resins (R-1-M1) to (R-1-M4) and (R-2-M1) to (R-10-M1) are the polyarylate resins described in the embodiment. It was a resin (PA). The repeating unit (1), the repeating unit (2) and the terminal group contained in each polyarylate resin and the ratio p are shown in Tables 4 and 5 below. In Table 5 below, the terminal group “MA” represents a group represented by the following chemical formula (MA). In addition, in the present embodiment, the yield of each polyarylate resin was obtained by conversion into a molar ratio.

(Synthesis of polyarylate resin (R-1-M1))
In the synthesis of the polyarylate resin (R-1-M1), a 2-necked three-necked flask equipped with a thermometer and a three-way cock was used as a reaction vessel. In a reaction vessel, 20.01 g (82.56 mmol) of compound (BP-1-1), 0.281 g (0.826 mmol) of compound (TM1), 7.84 g (196 mmol) of sodium hydroxide, and 0.240 g (0.768 mmol) of benzyltributylammonium chloride was added. The air in the reaction vessel was replaced with argon gas. 600 mL of water was further added to the contents of the reaction vessel. The contents of the reaction vessel were stirred at 20°C for 1 hour. Then, the content of the reaction container was cooled until the temperature of the content of the reaction container reached 10° C., to obtain an alkaline aqueous solution A.

  On the other hand, 2,6-naphthalenedicarboxylic acid dichloride (dichloride of compound (DC-2-1C)) 9.84 g (38.9 mmol), and 4,4′-oxybisbenzoic acid dichloride (compound (DC-2-2A 11.47 g (38.9 mmol) of dichloride)) was dissolved in 300 g of chloroform. Thereby, chloroform solution B was obtained.

  While stirring the alkaline aqueous solution A in the reaction vessel at 10° C., the chloroform solution B was added to the alkaline aqueous solution A. This initiated the polymerization reaction. While adjusting the temperature (liquid temperature) of the contents of the reaction container to 13±3° C., the contents of the reaction container were stirred for 3 hours to allow the polymerization reaction to proceed. Then, the upper layer (aqueous layer) in the contents of the reaction vessel was decanted to obtain an organic layer. Next, 500 mL of ion-exchanged water was placed in a 2 L Erlenmeyer flask. The obtained organic layer was further added to this flask. Chloroform (300 g) and acetic acid (6 mL) were further added to the flask. The flask contents were then stirred at room temperature for 30 minutes. Then, the upper layer (water layer) in the flask contents was removed by decanting to obtain an organic layer. The obtained organic layer was washed with 500 mL of ion-exchanged water using a separating funnel. Washing with ion-exchanged water was repeated 8 times to obtain a washed organic layer.

  Next, the organic layer washed with water was filtered to obtain a filtrate. A beaker having a volume of 3 L was charged with 1.5 L of methanol. The obtained filtrate was slowly added dropwise to methanol in the beaker to obtain a precipitate. The precipitate was filtered off. The taken-out precipitate was vacuum dried at a temperature of 70° C. for 12 hours. As a result, a polyarylate resin (R-1-M1) was obtained (yield 28.6 g, yield 82.9%). The viscosity average molecular weight of the polyarylate resin (R-1-M1) was 50,500.

  Regarding polyarylate resins (R-1-M2) to (R-1-M4), (R-2-M1) to (R-10-M1) and (R-1-MA), the following points are changed. Other than the above, it was synthesized by the same method as the synthesis of the polyarylate resin (R-1-M1).

(Synthesis of polyarylate resin (R-2-M1))
In the synthesis of the polyarylate resin (R-2-M1), the dichloride of the compound (DC-2-2A) was changed to 38.9 mmol of the dichloride of the compound (DC-2-2B). The obtained polyarylate resin (R-2-M1) had a yield of 27.8 g, a yield of 82.1%, and a viscosity average molecular weight of 52,200.

(Synthesis of polyarylate resin (R-3-M1))
In the synthesis of the polyarylate resin (R-3-M1), the compound (BP-1-1) was changed to 82.56 mmol of the compound (BP-1-2). The obtained polyarylate resin (R-3-M1) had a yield of 31.0 g, a yield of 80.1%, and a viscosity average molecular weight of 48,100.

(Synthesis of polyarylate resin (R-4-M1))
In the synthesis of the polyarylate resin (R-4-M1), the compound (BP-1-1) was changed to 82.56 mmol of the compound (BP-1-2). In the synthesis of the polyarylate resin (R-4-M1), the amount of the dichloride of the compound (DC-2-1C) used was changed to 23.3 mmol, and the dichloride of the compound (DC-2-2A) was used. The amount was changed to 54.5 mmol. The obtained polyarylate resin (R-4-M1) had a yield of 31.3 g, a yield of 79.6%, and a viscosity average molecular weight of 47,600.

(Synthesis of polyarylate resin (R-5-M1))
In the synthesis of the polyarylate resin (R-5-M1), the compound (BP-1-1) was changed to 8.26 mmol of the compound (BP-1-2) and 74.30 mmol of the compound (BP-1-3). changed. In the synthesis of the polyarylate resin (R-5-M1), the amount of the dichloride of the compound (DC-2-1C) used was changed to 7.8 mmol, and the dichloride of the compound (DC-2-2A) was used. The amount was changed to 70.0 mmol. The obtained polyarylate resin (R-5-M1) had a yield of 31.2 g, a yield of 80.0%, and a viscosity average molecular weight of 49,500. Further, the obtained polyarylate resin (R-5-M1) has two kinds of repeating units (1-2) and (1-3) as the repeating unit (1), and its molar ratio (repeating unit: (1-2): The repeating unit (1-3)) was 1:9.

(Synthesis of polyarylate resin (R-6-M1))
In the synthesis of the polyarylate resin (R-6-M1), the compound (BP-1-1) was changed to 82.56 mmol of the compound (BP-1-2). Moreover, in the synthesis of the polyarylate resin (R-6-M1), the dichloride of the compound (DC-2-2A) was changed to 38.9 mmol of the dichloride of the compound (DC-2-2B). The obtained polyarylate resin (R-6-M1) had a yield of 30.5 g, a yield of 76.8%, and a viscosity average molecular weight of 48,900.

(Synthesis of polyarylate resin (R-7-M1))
In the synthesis of the polyarylate resin (R-7-M1), the compound (BP-1-1) was changed to 82.56 mmol of the compound (BP-1-2). Moreover, in the synthesis of the polyarylate resin (R-7-M1), the dichloride of the compound (DC-2-2A) was changed to 38.9 mmol of the dichloride of the compound (DC-2-2D). The obtained polyarylate resin (R-7-M1) had a yield of 28.9 g, a yield of 78.6%, and a viscosity average molecular weight of 47,600.

(Synthesis of polyarylate resin (R-8-M1))
In the synthesis of the polyarylate resin (R-8-M1), the compound (BP-1-1) was changed to 82.56 mmol of the compound (BP-1-4). The obtained polyarylate resin (R-8-M1) had a yield of 27.8 g, a yield of 80.6%, and a viscosity average molecular weight of 55,100.

(Synthesis of polyarylate resin (R-9-M1))
The dichloride of the compound (DC-2-1C) was not used in the synthesis of the polyarylate resin (R-9-M1). Moreover, in the synthesis of the polyarylate resin (R-9-M1), the amount of dichloride of the compound (DC-2-2A) used was changed to 77.8 mmol. The obtained polyarylate resin (R-9-M1) had a yield of 28.8 g, a yield of 79.7%, and a viscosity average molecular weight of 60,000.

(Synthesis of polyarylate resin (R-10-M1))
In the synthesis of the polyarylate resin (R-10-M1), the compound (BP-1-1) was changed to 82.56 mmol of the compound (BP-1-2). In the synthesis of the polyarylate resin (R-10-M1), the amount of the dichloride of the compound (DC-2-1C) used was changed to 54.5 mmol, and the dichloride of the compound (DC-2-2A) was used. The amount was changed to 23.3 mmol. The obtained polyarylate resin (R-10-M1) had a yield of 30.0 g, a yield of 78.9%, and a viscosity average molecular weight of 49,700.

(Synthesis of polyarylate resin (R-1-M2))
In the synthesis of the polyarylate resin (R-1-M2), the compound (T-M1) was changed to 0.826 mmol of the compound (T-M2). The obtained polyarylate resin (R-1-M2) had a yield of 27.5 g, a yield of 79.7%, and a viscosity average molecular weight of 53,500.

(Synthesis of polyarylate resin (R-1-M3))
In the synthesis of the polyarylate resin (R-1-M3), the compound (T-M1) was changed to 0.826 mmol of the compound (T-M3). The obtained polyarylate resin (R-1-M3) had a yield of 28.6 g, a yield of 82.9%, and a viscosity average molecular weight of 56,100.

(Synthesis of polyarylate resin (R-1-M4))
In the synthesis of the polyarylate resin (R-1-M4), the compound (T-M1) was changed to 0.826 mmol of the compound (T-M4). The obtained polyarylate resin (R-1-M4) had a yield of 28.4 g, a yield of 82.4%, and a viscosity average molecular weight of 54,200.

(Synthesis of polyarylate resin (R-1-MA))
In the synthesis of the polyarylate resin (R-1-MA), the compound (TM1) was changed to 0.826 mmol of the compound (p-tert-butylphenol) represented by the chemical formula (T-MA) below. The polyarylate resin (R-1-MA) had a yield of 29.0 g, a yield of 84.1%, and a viscosity average molecular weight of 58,100.

<Manufacture of photoconductor>
Photoconductors of Examples 1 to 20 and Comparative Examples 1 to 8 were manufactured by the following method.

(Example 1)
First, the intermediate layer was formed on the conductive substrate. Surface-treated titanium oxide (“Prototype SMT-A” manufactured by Teika Co., Ltd., average primary particle size 10 nm) was prepared. SMT-A was particles in which titanium oxide was surface-treated with alumina and silica, and the surface-treated titanium oxide was wet-dispersed and further surface-treated with methylhydrogenpolysiloxane. Next, SMT-A (2 parts by mass) and polyamide resin ("Amylan (registered trademark) CM8000" manufactured by Toray Industries, Inc., polyamide 6, polyamide 12, quaternary copolymerized polyamide resin of polyamide 66 and polyamide 610) (1 part by mass) Part) was added to a solvent containing methanol (10 parts by mass), butanol (1 part by mass) and toluene (1 part by mass). These materials and the solvent were mixed for 5 hours using a bead mill to disperse the material in the solvent. This prepared the coating liquid for intermediate|middle layers. The obtained coating liquid for intermediate layer was filtered using a filter having an opening of 5 μm. Then, the dip coating method was used to apply the intermediate layer coating solution to the surface of the conductive substrate. An aluminum drum-shaped support (diameter 30 mm, total length 246 mm) was used as the conductive substrate. Subsequently, the applied coating solution for intermediate layer was dried at 130° C. for 30 minutes to form an intermediate layer (film thickness 1.5 μm) on the conductive substrate. In this way, a laminated body including the conductive substrate and the intermediate layer (hereinafter, sometimes referred to as a first laminated body) was obtained.

  Next, a charge generation layer was formed on the intermediate layer of the first stacked body. Specifically, a pigment (K1) (Y-type titanyl phthalocyanine) (1.5 parts by mass) and a polyvinyl acetal resin as a base resin (“S-REC (registered trademark) BX-5” manufactured by Sekisui Chemical Co., Ltd.) (1 part by mass) Parts) and propylene glycol monomethyl ether (40 parts by mass) and tetrahydrofuran (40 parts by mass). These materials and a solvent were mixed for 12 hours using a bead mill, and the materials were dispersed in the solvent to prepare a coating solution for charge generation layer. The obtained charge generation layer coating liquid was filtered using a filter having an opening of 3 μm. Then, the obtained filtrate was applied on the intermediate layer of the first laminate by a dip coating method, and dried at 50° C. for 5 minutes. As a result, a charge generation layer (film thickness 0.3 μm) was formed on the intermediate layer. As a result, a laminated body (hereinafter, also referred to as a second laminated body) including a conductive substrate, an intermediate layer provided on the conductive substrate, and a charge generation layer provided on the intermediate layer is obtained. Obtained.

  Next, a charge transport layer was formed on the charge generation layer of the second laminated body. Specifically, 50 parts by mass of a hole transport material (HTM-1), 2 parts by mass of a hindered phenol compound (“IRGANOX (registered trademark) 1010” manufactured by BASF Corporation) as an antioxidant, and an electron acceptor compound. 2 parts by weight of 3,3′,5,5′-tetra-tert-butyl-4,4′-diphenoquinone, 100 parts by weight of polyarylate resin (R-1-M1) as a binder resin, and as a pigment 0.1 part by mass of the pigment (K1) was added to a solvent containing 550 parts by mass of tetrahydrofuran and 150 parts by mass of toluene. These materials and a solvent were mixed for 12 hours using a circulation type ultrasonic dispersion device, and the materials were dispersed in the solvent to prepare a coating solution for the charge transport layer. This charge transport layer coating liquid was applied onto the charge generation layer of the second laminate by a dip coating method. The second laminate coated with the charge transport layer coating solution was placed in an oven and dried at a temperature of 120° C. for 40 minutes using the oven. As a result, a charge transport layer (thickness 30 μm) was formed on the charge generation layer. As a result, the photoreceptor of Example 1 was obtained. The photoreceptor of Example 1 includes a conductive substrate, an intermediate layer provided on the conductive substrate, a charge generation layer provided on the intermediate layer, and a charge transport layer provided on the charge generation layer. I was prepared.

(Examples 2 to 20 and Comparative Examples 1 to 8)
Photoconductors of Examples 2 to 20 and Comparative Examples 1 to 8 were produced by the same method as the production of the photoconductor of Example 1 except that the following points were changed. In the production of the photoconductor of Example 1, the binder resin and pigment described above were used. On the other hand, in the production of the photoconductors of Examples 2 to 20 and Comparative Examples 1 to 8, as shown in Tables 4 and 5 below, the type of binder resin, the type of pigment, and the amount used were used.

<Measurement and evaluation>
With respect to the photoconductors of Examples 1 to 20 and Comparative Examples 1 to 8, measurement of absorbance for light having a wavelength of 780 nm of the charge transport layer and evaluation of sensitivity characteristics, abrasion resistance and LSU light reflection stripes were performed by the following method. went. The results are shown in Tables 4 and 5 below.

[Absorbance]
After coating the charge transport layer coating liquid used in the production of each photoconductor on an overhead projector sheet (OHP sheet), it is dried at a temperature of 120° C. for 40 minutes using an oven to form a sample film on the OHP sheet. Formed. The thickness of the sample film was adjusted to be the same as the thickness of the charge transport layer of the photoconductor (that is, 30 μm). The OHP sheet on which this sample film was formed was used as an evaluation sample.

  With respect to the evaluation sample and the OHP sheet on which the charge transport layer was not formed, the absorbance for light having a wavelength of 780 nm was measured using a spectrophotometer (“U-3000” manufactured by Hitachi, Ltd.). Then, the absorbance of the sample film was calculated by correcting the absorbance of the evaluation sample with the absorbance (baseline) of the OHP sheet. The absorbance of this sample film was used as the absorbance of the charge transport layer of each photoconductor.

[Abrasion resistance]
In the evaluation of wear resistance, a color printer (“C711dn” manufactured by Oki Data Co., Ltd.) was used as an evaluation machine. The toner cartridge of the evaluation machine was filled with cyan toner.

First, the thickness T ₁ of the charge transport layer of the photoconductor was measured. Next, the photoconductor was mounted on the evaluation machine. Next, under normal temperature and normal humidity environment (temperature 23° C. and relative humidity 50% RH: hereinafter sometimes referred to as NN environment), image I (printing rate 1 % Pattern image). Then, under a high temperature and high humidity environment (temperature of 32° C. and relative humidity of 85% RH: hereinafter sometimes referred to as HH environment), an image machine was used to print the image I on 10,000 sheets of paper. Then, under a low temperature and low humidity environment (temperature 10° C. and relative humidity 15% RH: hereinafter sometimes referred to as LL environment), an image machine was used to print the image I on 10,000 sheets of paper. After printing under the LL environment, the evaluation machine was left standing for 2 hours. Then, a solid image (image having an image density of 100%) was printed on one sheet under the LL environment. Then, the film thickness T ₂ of the charge transport layer of the photoconductor was measured. Then, the amount of wear (T ₁ -T ₂ , unit: μm), which is the amount of change in the thickness of the charge transport layer before and after printing, was determined. The obtained wear amounts are shown in Tables 4 and 5 below. The wear resistance of the photoconductor is more excellent as the wear amount is smaller, and the wear amount of 2.5 μm or less can be evaluated as good, and the wear amount of more than 2.5 μm can be evaluated as defective.

[Sensitivity characteristics]
Each photoreceptor was exposed under the following two conditions, and the post-exposure potential (sensitivity characteristics A and B) under each condition was measured.

(Sensitivity characteristic A)
The sensitivity characteristic A was measured for the photoconductor in an environment of a temperature of 23° C. and a relative humidity of 50% RH. Specifically, the surface of the photoconductor was charged to −550V using a drum sensitivity tester (manufactured by Gentec Co., Ltd.). Then, monochromatic light (wavelength: 780 nm, exposure amount: 1.0 μJ/cm ² ) was extracted from the light of the halogen lamp using a bandpass filter, and was irradiated on the surface of the photoreceptor. The surface potential (post-exposure potential, unit: -V) of the photoconductor was measured when 50 milliseconds had elapsed from the end of monochromatic light irradiation. Regarding the sensitivity characteristic A, when the absolute value is 90 V or more, it can be judged as pass, and when the absolute value is less than 90 V, it can be judged as fail.

(Sensitivity characteristic B)
The sensitivity characteristic B was measured by the same method as the measurement of the sensitivity characteristic A except that the following points were changed. In the measurement of the sensitivity characteristic B, the exposure amount was changed to 0.1 μJ/cm ² when the photosensitive member was irradiated with monochromatic light. In the evaluation of the sensitivity characteristic B, it can be judged that the case where the potential after exposure is 280 V or less in absolute value is a pass, and the case where the potential after exposure is more than 280 V is a failure.

  The sensitivity of the photoconductor can be evaluated as good when both the sensitivity characteristics A and B are acceptable. The exposure condition in the measurement of the sensitivity characteristic B corresponds to the exposure condition for expressing a halftone. Therefore, it is determined that the photoconductor having the sensitivity characteristic B that is acceptable is excellent in expressing halftone.

[LSU light reflection stripe]
In the evaluation of the LSU light reflection streak, a monochrome multifunction machine ("MultiXpress SL-K4350LX" manufactured by Samsung Electronics) was used as an evaluation machine. First, each photoconductor was mounted on the evaluation machine. Then, under a normal temperature and normal humidity environment (temperature of 23° C. and relative humidity of 50% RH), a halftone image (image with a printing rate of 30%) is printed on one sheet of paper using an evaluation machine, and this is used as an evaluation image And The evaluation image was visually observed, and the degree of white stripes (LSU light reflection stripes) was judged according to the following judgment criteria. The photoconductor can be evaluated as capable of suppressing the LSU light reflection streak when the white streak determination result is “A” or “B”, and can be suppressed when the white streak determination result is “C”. It can be evaluated as not.

(Criteria)
A: No white streak was observed in the evaluation image.
B: Slight white streaks were confirmed in the evaluation image, but there was no problem in actual use.
C: White streaks were clearly confirmed in the evaluation image.

  The photoconductors of Examples 1 to 20 each had a conductive base and a photosensitive layer indirectly provided on the conductive base. The photosensitive layer contained a charge generation layer and a charge transport layer which were sequentially provided from the side of the conductive substrate. The charge transport layer contained a binder resin, a hole transport agent, and Y-type titanyl phthalocyanine. The binder resin contained a polyarylate resin (PA) having a repeating unit (1), a repeating unit (2), and a terminal group (3). The content of Y-type titanyl phthalocyanine in the charge transport layer was 0.1 parts by mass or more and 0.8 parts by mass or less based on 100 parts by mass of the binder resin. As a result, as is clear from Table 4, the photoconductors of Examples 1 to 20 were excellent in sensitivity and abrasion resistance and were able to suppress LSU light reflection streaks.

  In particular, the photoconductor of Example 4 had excellent sensitivity characteristics despite the fact that the charge transport layer had an extremely high absorbance at a wavelength of 780 nm and exposure light was difficult to reach the charge generation layer. From this, it is considered that adding Y-type titanyl phthalocyanine to the charge transport layer is very effective in order to achieve both suppression of LSU light reflection stripes and sensitivity in the photoconductor.

  On the other hand, the photoconductors of Comparative Examples 1 to 8 did not satisfy the above configuration. Therefore, as is clear from Table 5, at least one of the sensitivity characteristics, the abrasion resistance, and the suppression of the LSU light reflection streak was defective in the photoconductors of Comparative Examples 1 to 8.

  Specifically, in the photoreceptor of Comparative Example 1 in which the pigment was not added to the charge transport layer, the sensitivity characteristics were poor, and the LSU light reflection stripes could not be suppressed. Further, in the photoconductors of Comparative Examples 2 and 3 in which pigments other than the blue pigment were added to the charge transport layer, LSU light reflection streaks could not be suppressed.

  Further, in the photoconductors of Comparative Examples 4 and 5 in which a blue pigment other than Y-type titanyl phthalocyanine was added to the charge transport layer, LSU light reflection streaks could be suppressed, but the sensitivity characteristics were poor.

  Further, even the photoconductor of Comparative Example 7 in which the α-type titanyl phthalocyanine, which is different from the Y-type titanyl phthalocyanine only in the crystal structure, is added to the charge transport layer, can achieve both excellent sensitivity characteristics and suppression of LSU light reflection stripes. There wasn't.

  Further, the photoreceptor of Comparative Example 6 using a polyarylate resin other than the polyarylate resin (PA) had poor wear resistance.

  Further, in the photoconductor of Comparative Example 8 in which Y-type titanyl phthalocyanine was excessively added to the charge transport layer, LSU light reflection streaks could be suppressed, but the sensitivity characteristics were poor.

  From the above, in order to improve the sensitivity and abrasion resistance of the photoconductor and suppress LSU light reflection streaks, it is necessary to use a polyarylate resin (PA) and a certain amount of Y-type titanyl phthalocyanine in the charge transport layer. Is determined to be important.

  The photoconductor according to the present invention can be used in an image forming apparatus.

1 Electrophotographic Photoreceptor 2 Conductive Substrate 3 Photosensitive Layer 3a Charge Generation Layer 3b Charge Transport Layer 4 Intermediate Layer

Claims (9)

An electrophotographic photoreceptor comprising a conductive substrate and a photosensitive layer directly or indirectly provided on the conductive substrate,
The photosensitive layer includes a charge generation layer and a charge transport layer that are sequentially provided from the side of the conductive substrate,
The charge transport layer contains a binder resin, a hole transport agent, and titanyl phthalocyanine,
The binder resin is
Polyarylate resin having a first repeating unit represented by the following general formula (1), a second repeating unit represented by the following general formula (2), and an end group represented by the following general formula (3). Including,
The titanyl phthalocyanine has a main peak at 27.2° of Bragg angle (2θ±0.2°) in a CuKα characteristic X-ray diffraction spectrum,
The content of the titanyl phthalocyanine in the charge transport layer is 0.1 parts by mass or more and 0.8 parts by mass or less based on 100 parts by mass of the binder resin.

(In the general formula (1),
R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or a methyl group,
R ⁵ and R ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ⁵ and R ⁶ are bonded to each other to form a divalent group represented by the following general formula (X). May represent a group,
In the general formula (2), X ¹ represents a divalent group represented by the following chemical formula (2A), (2B), (2C) or (2D),
In the general formula (3), R ^f represents a chain aliphatic group having 1 to 20 carbon atoms, which is substituted with one or more fluorine atoms. )

(In the general formula (X),
t represents an integer of 1 or more and 3 or less,
* Represents a bond. )

  The electrophotographic photoreceptor according to claim 1, wherein the charge transport layer has an absorbance of light having a wavelength of 780 nm of 0.50 or more and 0.90 or less. The electrophotographic photosensitive member according to claim 1, wherein the first repeating unit is represented by the following chemical formula (1-1), (1-2), (1-3) or (1-4).

The said 2nd repeating unit is represented by following chemical formula (2-1C), (2-2A), (2-2B), or (2-2D), The statement in any one of Claims 1-3. Electrophotographic photoreceptor.

The electrophotographic photoreceptor according to claim 1, wherein the terminal group is represented by the following chemical formula (M1), (M2), (M3) or (M4).

The electrophotographic photoreceptor according to any one of claims 1 to 5, wherein the hole transport material contains a compound represented by the following general formula (10).

(In the general formula (10),
R ¹⁰¹ , R ¹⁰³ , R ¹⁰⁴ , R ¹⁰⁵ , R ¹⁰⁶ , R ¹⁰⁷ and R ¹⁰⁸ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an alkyl group having 1 to 8 carbon atoms. Represents a phenyl group which may be substituted with or an alkoxy group having 1 to 8 carbon atoms, which is a carbon atom in which two adjacent R ¹⁰³ , R ¹⁰⁴ , R ¹⁰⁵ , R ¹⁰⁶ and R ¹⁰⁷ are bonded. It may represent a cycloalkane of the number 5 or more and 7 or less,
R ¹⁰² and R ¹⁰⁹ each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group or an alkoxy group having 1 to 8 carbon atoms,
b ₁ and b ₂ each independently represent an integer of 0 or more and 5 or less. ) The electrophotographic photosensitive member according to claim 6, wherein the hole transport material contains a compound represented by the following chemical formula (HTM-1).

The electrophotographic photoreceptor according to claim 1, wherein the charge transport layer contains an electron acceptor compound represented by the following general formula (E-1).

(In the general formula (E-1), R ^E1 , R ^E2 , R ^E3 and R ^E4 each independently represent an alkyl group having 1 to 6 carbon atoms.) The electrophotographic photoreceptor according to claim 8, wherein the electron acceptor compound includes a compound represented by the following chemical formula (ET1).

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