JP3175481B2 - Electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member having a photosensitive layer on a conductive support. More specifically, the present invention relates to an electrophotographic photoreceptor having high sensitivity and excellent repetition stability.

[0002]

2. Description of the Related Art In recent years, electrophotographic photosensitive members used in copying machines, printers, and the like have been replaced with inorganic photosensitive materials.
Organic photosensitive materials are often used because of their advantages such as low cost and excellent productivity.
Organic electrophotographic photoreceptors include a photoconductive resin type represented by polyvinyl carbazole (PVK), PVK-TN
Charge transfer complex type represented by F (2,4,7-trinitrofluorenone), pigment dispersion type represented by phthalocyanine-binder, function-separated type photoreceptor using a combination of a charge generation material and a charge transport material, etc. Is known,
In particular, since a function-separated type photoreceptor has light sensitivity comparable to that of an inorganic photoreceptor, it has been put to practical use (for example, a combination with a phthalocyanine pigment is disclosed in
No. 4942, No. 60-59355, No. 61-2034
Nos. 61, 62-47054 and 62-67094). However, in the case of an organic electrophotographic photoreceptor, even if any of the above-mentioned types of photoreceptors are used, changes over time in the photoreceptor characteristics due to repeated use are inevitable. In particular, the rise in the residual potential determines the life of the photoconductor,
Function-separated type photoconductors are no exception, and improvements over time are strongly desired.

[0003]

By the way, in order to obtain high sensitivity and excellent repetition stability in an electrophotographic photoreceptor, it is necessary to 1) efficiently absorb light absorbed by a charge generating material. Charge generation; 2) the generated charge is smoothly injected from the charge generation material into the charge transport material; and 3) the charge injected into the charge transport material can move at high speed in the charge transport layer. It is required that the conditions be met. In other words, even if there are a charge generating material that efficiently generates charges satisfying the conditions 1) and 3) and a charge transporting material that can move charges at high speed, the charge generation satisfies the condition 2). Unless the material and the charge transporting material are combined, it is impossible to obtain electrophotographic characteristics having high sensitivity and excellent repetition stability. Further, in order to commercialize an electrophotographic photoreceptor is for satisfying the above conditions, sensitivity, acceptance potential, the potential holding property, potential stability, residual potential, electrophotographic such partial light characteristics Materials that satisfy all aspects, such as properties, mechanical durability such as abrasion resistance, and chemical stability against heat, light, and discharge products, must be selected. However, it is very difficult to select a material combination that satisfies all of these points, and the above-mentioned conditions are sufficiently satisfied for a conventionally proposed combination of a charge generation material and a charge transport material. At present, nothing to do is obtained. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrophotographic photoconductor having high sensitivity and excellent repetition stability.

[0004]

Means for Solving the Problems The present inventors have studied the relationship between high sensitivity and residual potential in a laminated photoreceptor while using the same materials as in the prior art. It has been found that, when the ionization potential and the work function have a certain relationship, an electrophotographic photoreceptor having high sensitivity and a suppressed increase in the residual potential even by repeated use can be obtained. .

Namely, the electrophotographic photoreceptor of the present invention includes at least a charge generation layer and a hole transport-type laminated electrophotographic photoreceptor having a charge transport layer on a conductive support, a positive
The hole transporting material is a triaryl represented by the following general formula (II)
An amine compound, and the ionization potential Ip (CGM) and work function W (CGM) of the charge generating material
Potential Ip (HTM) of GaN and Hole Transport Material
And the work function W (HTM) satisfies Expression (1). [Ip (HTM) -W (HTM)]-[Ip (CGM) -W (CGM)] ≦ 0.65 eV (1)

Embedded image (In the formula, Ar ₁ and Ar ₂ each represent an alkyl group, an alkoxy group, a substituted amino group, or an aryl group or an aralkyl group which may have a halogen atom as a substituent.)

[0006] The measurement method of the ionization potential of the charge generating material and a hole transportation <br/> feed material in the present invention, the atmosphere ultraviolet photoelectron spectrometer (manufactured by Riken Keiki Co., AC-
A method using 1), a method using vacuum ultraviolet spectroscopy (USP), and the like are employed. Further, as a method of measuring the work function of the charge generating material and a hole transportation <br/> feed material, the contact potential for materials having a known work function based on the above vacuum ultraviolet spectroscopy (USP) (This device can determine the work function in addition to the ionization potential of the substance.)
Or a method of measuring by the Kelvin method using a change in vibration capacity.

Hereinafter, the structure of the electrophotographic photosensitive member of the present invention will be described with reference to the drawings. 1 to 4 are schematic views showing a cross section of the electrophotographic photoreceptor of the present invention. In FIG. 1, a charge generation layer 1 is provided on a conductive support 3, and a charge transport layer 2 is provided thereon. In FIG. 2, an undercoat layer 4 is further provided on the conductive support 3, and in FIG. 3, a protective layer 5 is provided on the surface. Further, in FIG. 4, both the undercoat layer 4 and the protective layer 5 are provided.

Examples of the conductive support include metals such as aluminum, nickel, chromium, and stainless steel; and aluminum, titanium, nickel, chromium, stainless steel, gold, vanadium, tin oxide, indium oxide, and ITO.
And the like, and a plastic film provided with a thin film. These conductive supports are used in an appropriate shape such as a drum shape, a sheet shape, and a plate shape, but are not limited thereto. Further, if necessary, the surface of the conductive support can be subjected to various treatments within a range that does not affect the image quality. For example, oxidation treatment, chemical treatment, coloring treatment, or the like, or irregular reflection treatment such as graining can be performed on the surface.

Further, an undercoat layer may be provided between the conductive support and the charge generation layer. The undercoat layer is an adhesive layer that prevents charge injection from the conductive support into the photosensitive layer when the photosensitive layer having a laminated structure is charged, and that integrally holds the photosensitive layer on the conductive support. Acting as
Alternatively, in some cases, a light reflection preventing function of the conductive support is performed. As the binder resin used for the undercoat layer, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, polyamide resin, vinyl chloride resin, vinyl acetate resin, phenol resin, polycarbonate resin,
Polyurethane resin, polyimide resin, vinylidene chloride resin, polyvinyl acetal resin, vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol resin, water-soluble polyester resin, nitrocellulose, casein, gelatin,
Known materials such as polyglutamic acid, starch, starch thiacetate, amino starch, polyacrylic acid, polyacrylamide, zirconium chelate compound, titanyl chelate compound, titanyl alkoxide compound, organic titanium compound, and silane coupling agent can be used. The thickness of the undercoat layer is suitably in the range of 0.01 to 10 μm, and preferably in the range of 0.05 to 2 μm. As an application method used when providing the undercoat layer, a commonly used method such as a blade coating method, a Meyer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, a curtain coating method, or the like is used. it can.

The charge generation layer is formed by dispersing a charge generation material in a binder resin.
Organic pigments and dyes such as phthalocyanine, squarium, anthantrone, perylene, azo, anthraquinone, pyrene, and pyrylium salts are used. Examples of the phthalocyanine pigment include metal-free phthalocyanine, oxytitanium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, and hydroxygallium phthalocyanine. As the chlorogallium phthalocyanine crystal, Cu
In the X-ray diffraction spectrum using Kα as the source, the Bragg angles (2θ ± 0.2 °) of 7.4, 16.6, 25.
5, a chlorogallium phthalocyanine crystal (I-1) having a strong diffraction peak at 28.3 °, a Bragg angle (2θ)
(± 0.2 °) 6.8, 17.3, 23.6, 26.9
Chlorogallium phthalocyanine crystal (I-2) having a strong diffraction peak at 0 °, and a Bragg angle (2θ ± 0.
8.7-9.2, 17.6, 24.0, 27.
A chlorogallium phthalocyanine crystal (I-3) having a strong diffraction peak at 4, 28.8 ° is preferred. As the dichlorotin phthalocyanine crystal, in the X-ray diffraction spectrum using CuKα as a source, the Bragg angle (2θ ±
0.2 °) of 8.3, 12.2, 13.7, 15.9,
Dichlorotin phthalocyanine crystal (I-4) having strong diffraction peaks at 18.9 and 28.2 °, 8.5, 11.2, 14.5 and 2 with Bragg angles (2θ ± 0.2 °)
Dichlorotin phthalocyanine crystal (I-5) having a strong diffraction peak at 7.2 °, Bragg angle (2θ ± 0.2)
°) 8.7, 9.9, 10.9, 13.1, 15.
A dichlorotin phthalocyanine crystal (I-6) having strong diffraction peaks at 2, 16.3, 17.4, 21.9, and 25.5 °, and a Bragg angle (2θ ± 0.2 °) of 9.2; 12.2, 13.4, 14.6, 17.0, 2
Dichlorotin phthalocyanine crystal (I-7) having a strong diffraction peak at 5.3 ° is preferable.

The hydroxygallium phthalocyanine crystal has a Bragg angle (2θ ± 0.2 °) of 7.7, 1 in an X-ray diffraction spectrum using CuKα as a radiation source.
Hydroxygallium phthalocyanine crystal (I-8) having strong diffraction peaks at 6.5, 25.1 and 26.6 °,
7.9, 16.5 of Bragg angle (2θ ± 0.2 °),
Hydroxygallium phthalocyanine crystal (I-9) having strong diffraction peaks at 24.4 and 27.6 °, 7.0, 7.5, 10.5 with Bragg angles (2θ ± 0.2 °).
11.7, 12.7, 17.3, 18.1, 24.5,
Hydroxygallium phthalocyanine crystal (I-10) having strong diffraction peaks at 26.2 and 27.1 °, and 7.5, 9.9, and 12 at Bragg angles (2θ ± 0.2 °).
Hydroxygallium phthalocyanine crystal (I-11) having strong diffraction peaks at 5, 16.3, 18.6, 25.1, and 28.3 °, and a Bragg angle (2θ ± 0.2)
°) of hydroxygallium phthalocyanine crystal (I-12) having strong diffraction peaks at 6.8, 12.8, 15.8, and 26.0 °. As the metal-free phthalocyanine crystal, X-type metal-free phthalocyanine crystal (I-1)
3) is preferred. The oxytitanium phthalocyanine crystal has a Bragg angle (2θ ± 0.2 °) of 9.3, 1 in an X-ray diffraction spectrum using CuKα as a source.
0.6, 13.2, 15.1, 15.7, 16.1, 2
Oxytitanium phthalocyanine crystal (I-14) having strong diffraction peaks at 0.8, 23.3, and 26.3 °,
7.6, 10.2 of Bragg angle (2θ ± 0.2 °)
12.6, 13.2, 15.1, 16.3, 17.3,
18.3, 22.5, 24.2, 25.3, 28.6 °
Oxytitanium phthalocyanine crystal (I-15) having a strong diffraction peak at
9.7, 11.7, 15.0, 23.5, 2)
Oxytitanium phthalocyanine crystal (I-16) having a strong diffraction peak at 7.3 ° is preferred.

Table 1 shows the ionization potential and the work function of the phthalocyanine crystal.

[Table 1]

The binder resin can be selected from a wide range of insulating resins. Further, poly-N-vinyl carbazole, polyvinyl anthracene, polyvinyl pyrene,
It can also be selected from organic photoconductive polymers such as polysilane. Preferred binder resins include polyvinyl butyral resin, polyarylate resin (polycondensate of bisphenol A and phthalic acid, etc.), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, vinylidene chloride resin, polyamide Resins, acrylic resins, polyacrylamide resins, polyvinyl pyridine resins, cellulose resins, urethane resins, epoxy resins, caseins, polyvinyl alcohol resins, and insulating resins such as polyvinyl pyrrolidone resins, but are not limited thereto. Absent. These binder resins can be used alone or in combination of two or more. The compounding ratio (weight ratio) is preferably in the range of 10: 1 to 1:10. As a method for dispersing these, a usual method such as a ball mill dispersion method, an attritor dispersion method, and a sand mill dispersion method can be used. In addition, as a solvent used for these dispersions, methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, Ordinary organic solvents such as tetrahydrofuran, methylene chloride and chloroform can be used alone or as a mixture of two or more. The thickness of the charge generation layer is generally 0.1 to 5 μm.
Is appropriate, and preferably in the range of 0.2 to 2.0 μm. The coating method used when providing the charge generation layer is usually used such as a blade coating method, a Meyer bar coating method, a dip coating method, a spray coating method, a bead coating method, an air knife coating method, and a curtain coating method. The method can be adopted.

The charge transport layer is formed by including a hole transport material in a suitable binder resin. In the present invention, a hole transporting material is used as the charge transporting material. Specifically, a triarylamine compound represented by the general formula (II) is used. These hole transport materials may be used alone or in combination of two or more.

[0015]

Here, specific examples of the triarylamine-based compound are listed in Table 2 together with the values of the ionization potential and the work function.

[Table 2]

[0017]

[0018]

Further, as the binder resin used for the charge transport layer, polycarbonate resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer Copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-
Known resins such as alkyd resin and poly-N-vinylcarbazole can be used, but are not limited thereto. These binder resins may be used alone or in combination.
A mixture of more than one species can be used. The compounding ratio (weight ratio) of the hole transport material and the binder resin is preferably from 10: 1 to 1: 5. The thickness of the charge transport layer is generally 5 to 50 μm
Is appropriate, and preferably in the range of 10 to 30 μm. As a coating method, a blade coating method,
A commonly used method such as a Meyer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, and a curtain coating method can be employed. Further, as the solvent used when providing the charge transport layer, benzene, toluene, xylene, aromatic hydrocarbons such as chlorobenzene,
Commonly used organic solvents such as ketones such as acetone and 2-butane, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform and ethylene chloride, and cyclic or linear ethers such as tetrahydrofuran and ethyl ether are used alone or Two or more kinds can be used in combination.

In the electrophotographic photoreceptor of the present invention, the charge generation layer or the charge transport layer is provided with the purpose of preventing deterioration of the photoreceptor due to ozone or oxidizing gas generated in a copying machine, light or heat. Additives such as antioxidants and light stabilizers can be added. For example, as an antioxidant, hindered phenol, hindered amine, paraphenylenediamine, arylalkane, hydroquinone, spirochroman, spiroidanone and derivatives thereof,
Organic sulfur compounds, organic phosphorus compounds and the like can be mentioned. Examples of the light stabilizer include derivatives such as benzophenone, benzotriazole, dithiocarbamate, and tetramethylpiperidine.

Further, if necessary, a protective layer may be provided on the charge transport layer. This protective layer has the function of preventing the charge transport layer from being chemically altered when the photosensitive layer having a laminated structure is charged, and improving the mechanical strength of the photosensitive layer. The protective layer is formed by including a conductive material in a suitable binder resin. Examples of the conductive material include metallocene compounds such as N, N'-dimethylferrocene and N, N'-diphenyl-N, N'-bis (3-methylphenyl)-[1,1 '
-Biphenyl] -4,4'-diamine, etc., and materials such as antimony oxide, tin oxide, titanium oxide, indium oxide, and metal oxides such as tin oxide-antimony oxide. However, the present invention is not limited to this. As the binder resin used for the protective layer, polyamide resin, polyurethane resin, polyester resin, epoxy resin, polyketone resin, polycarbonate resin,
Known resins such as a polyvinyl ketone resin, a polystyrene resin, and a polyacrylamide resin are exemplified. Further, it is preferable that the protective layer is configured to have an electric resistance of 10 ⁹ to 10 ¹⁴ Ω · cm. Electric resistance is 10 ¹⁴ Ω · cm
Above this, the residual potential rises, resulting in a copy with a lot of fog, and below 10 ⁹ Ω · cm, blurring of the image and reduction of the resolving power occur. Also, the protective layer must be configured so as not to substantially hinder the transmission of light used for image exposure. The thickness of the protective layer is 0.5 to
The range of 20 μm is appropriate, preferably 1 to 10 μm
Range. Application methods include blade coating, Meyer bar coating, spray coating, dip coating, bead coating,
Conventional methods such as an air knife coating method and a curtain coating method can be used.

In the present invention, the charge generation material in the charge generation layer and the hole transport material in the charge transport layer are:
The charge generating material and the charge generating material are set so as to satisfy the relationship of the above formula (1 ).
It is necessary to select a hole transport material. The hole transportation <br/> feed material in the charge transport layer and charge generating material in the charge generating layer, if satisfies the relation of the formula (1), the optical carriers generated in the charge generation layer, the charge generation layer It is considered that the number of carriers injected smoothly into the charge transport layer from the substrate and accumulated at the interface between the charge generation layer and the charge transport layer is extremely small. When the relationship between the charge generation material and the hole transport material does not satisfy the above (1 ) , the residual potential increases,
In addition, by repeatedly performing copying for a long period of time, the charging potential decreases and the residual potential increases.

[0023]

Hereinafter, the present invention will be described with reference to Examples.
The examples are for describing the present invention in detail, and the present invention is not limited by the examples. In addition,
In Examples and Comparative Examples, all “parts” are “parts by weight”. . Examples 1 to 8 10 parts of a zirconium compound (trade name: Organix ZC540, manufactured by Matsumoto Pharmaceutical Co., Ltd.) and 1 part of a silane compound (trade name: A1110, manufactured by Nippon Unicar), 40 parts of i-propanol and butanol on an aluminum substrate A solution consisting of 20 parts was applied by a dip coating method,
Heat and dry at 50 ° C. for 10 minutes to form a film having a thickness of 0.5 μm
Was formed. Next, 1 part of the phthalocyanine crystal shown in Table 4 was mixed with 1 part of a polyvinyl butyral resin (trade name: ESLEC BM-S, manufactured by Sekisui Chemical Co., Ltd.) and 100 parts of n-butyl acetate, and the mixture was mixed with glass beads for 1 hour using a paint shaker. After the treatment and dispersion, the obtained coating solution is applied on the undercoat layer by a dip coating method.
Heat and dry at 00 ° C for 10 minutes, 0.15μm thick
Was formed. Next, 2 parts of the hole transport material shown in Table 4 and the following structural formula

Embedded image Mw = 39,000 (viscosity average molecular weight) 3 parts of poly (4,4'-cyclohexylidenediphenylene carbonate) expressed by monochlorobenzene 20
Part, and the obtained coating solution is applied by dip coating on the aluminum substrate on which the charge generation layer is formed,
The resultant was dried by heating at 120 ° C. for 1 hour to form a charge transport layer having a thickness of 20 μm. The electrophotographic characteristics of the electrophotographic photoreceptor thus obtained were measured using an electrostatic copying paper test apparatus (electrostatic analyzer EPA-8100,
Using normal temperature and humidity (20 ° C, 40% R)
In the environment of H), after charging by performing a corona discharge of -6 kV, using a light of a tungsten lamp, the light is converted into a monochromatic light of 800 nm using a monochromator, and 1 μm on the surface of the photoreceptor.
It was adjusted to W / cm ² and irradiated. And
The surface potential V _O (volt), the half-exposure amount E _1/2 (er
g / cm ² ) and then irradiated with 10 lux white light for 1 second to measure the residual potential V _R (volt). Further, V _O , E _1/2 , and V _R after the above-mentioned charging and exposure were repeated 1000 times were measured, and the variation was ΔV
_{O, ΔE 1/2,} expressed as [Delta] V _R, and the results are shown in Table 4.

Comparative Example 1 A photoconductor was prepared in the same manner as in Example 3, except that the compound represented by the following structural formula (V) was used instead of the hole transporting material. A measurement was made. The values of the ionization potential Ip (HTM) and the work function W (HTM) of the compound (V) are 5.53 eV and 4.
67 eV. Table 4 shows the results.

Embedded image

Comparative Example 2 A photoconductor was prepared in the same manner as in Example 3, except that the compound represented by the following structural formula (VI) was used instead of the hole transporting material. A measurement was made. The values of the ionization potential (HTM) and the work function W (HTM) of the compound (VI) were 5.42 eV and 4.62, respectively.
eV. Table 4 shows the results.

Embedded image

Comparative Example 3 In Example 3, a compound represented by the following structural formula (VII) was used in place of the hole transporting material.
A photoreceptor was prepared in the same manner as described above, and the same measurement was performed. The values of ionization potential (HTM) and work function W (HTM) of compound (VII) are 5.55 eV and 4.
72 eV. Table 4 shows the results.

Embedded image

[0027]

[0028]

[0029]

[Table 4]

[0030]

According to the electrophotographic photoreceptor of the present invention,
Since the charge generation material in the charge generation layer and the hole transport material in the charge transport layer used the specific combination described above, the electrophotographic photoreceptor of the present invention,
As is clear from the above comparison, it has high light sensitivity and excellent repetition stability.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an example of the electrophotographic photosensitive member of the present invention.

FIG. 2 is a schematic cross-sectional view of another example of the electrophotographic photosensitive member of the present invention.

FIG. 3 is a schematic sectional view of another example of the electrophotographic photosensitive member of the present invention.

FIG. 4 is a schematic cross-sectional view of another example of the electrophotographic photosensitive member of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Charge generation layer, 2 ... Charge transport layer, 3 ... Conductive support,
4: Undercoat layer, 5: Protective layer.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-95405 (JP, A) JP-A-6-75408 (JP, A) JP-A-4-155347 (JP, A) 11353 (JP, A) JP-A-1-29752 (JP, A) JP-A-3-148669 (JP, A) JP-A-6-59468 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) G03G 5/00-5/16

Claims (3)

(57) [Claims] 1. A laminated electrophotographic photosensitive member having at least a charge generation layer and a hole transport type charge transport layer on a conductive support, wherein the hole transport material is represented by the following general formula (II).
The charge generation material ionization potential Ip (CGM) and work function W (CGM) and the hole transport material ionization potential I
A photoconductor for electrophotography, wherein the relationship between p (HTM) and work function W (HTM) satisfies Expression (1). [Ip (HTM) -W (HTM)]-[Ip (CGM) -W (CGM)] ≦ 0.65 eV (1) (In the formula, Ar ₁ and Ar ₂ each represent an alkyl group, an alkoxy group, a substituted amino group, or an aryl group or an aralkyl group which may have a halogen atom as a substituent.) 2. The method according to claim 1, wherein the charge generation material is a phthalocyanine pigment.
2. The electrophotographic photoconductor according to claim 1, wherein: 3. The method according to claim 1, wherein the charge generation material is a metal-free phthalocyanine.
, Dichlorotin phthalocyanine, chlorogallium lid
Russianin and hydroxygallium phthalocyanine
A phthalocyanine pigment selected from the group consisting of
The electrophotographic photoconductor according to claim 1 or 2, wherein: