JP2001305762A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor having improved photomemory characteristics and very high performance in practical use while maintaining such basic characteristics of an electrophotographic photoreceptor as high sensitivity, low residual potential, high mobility and high durability. SOLUTION: In the electrophotographic photoreceptor with a photosensitive layer on an electrically conductive substrate, the photosensitive layer contains an electric charge generating material, an electric charge transferring material having >70 (Å) calculated value (αcal of polarizability α by structure optimizing calculation using semiempirical molecular orbital calculation using PM3 parameter and <1.8 (D) calculated value Pcal of dipole moment P by the structure optimizing calculation and a compound having 50% transmittance at a longer wavelength than the electric charge transferring material.

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. More specifically, the present invention relates to a high-sensitivity and high-performance electrophotographic photosensitive member having a photosensitive layer containing an organic photoconductive substance.

[0002]

2. Description of the Related Art Conventionally, inorganic photoconductive substances such as selenium, cadmium sulfide, and zinc oxide have been widely used for a photosensitive layer of an electrophotographic photosensitive member. However, selenium and cadmium sulfide need to be recovered as poisons, selenium crystallizes due to heat and therefore has poor heat resistance, cadmium sulfide and zinc oxide have poor moisture resistance, and zinc oxide has no printing durability. It has drawbacks and efforts to develop new photoreceptors are ongoing. Recently, studies have been made on the use of organic photoconductive materials for the photosensitive layer of an electrophotographic photoreceptor, and some of them have been put to practical use. Organic photoconductive materials have advantages over inorganic ones, such as being lighter, easier to form films, easier to manufacture photoconductors, and capable of manufacturing transparent photoconductors depending on the type. Have.

Electrophotographic photoreceptors using these organic photoconductive compounds are often used as function-separated type photoreceptors in which a charge transport layer and a charge generation layer are laminated. This is because it is easy to design an electrophotographic photosensitive member that satisfies both electrical and mechanical characteristics. Here, the electrical and mechanical properties to be satisfied by the electrophotographic photoreceptor include not only having an initially excellent performance but also having a sufficient durability when used repeatedly. .

[0004] In an electrophotographic process of a so-called reversal development system in which toner is adhered to an exposed portion of an electrophotographic photoreceptor, initially excellent performance means optimum sensitivity and electrical characteristics matching the electrophotographic process to be used. Sufficient durability when used repeatedly means that it is added directly to the surface of the electrophotographic photosensitive member during repeated use, by corona or direct charging, image exposure, toner development, transfer process, surface cleaning, etc. It has durability against deterioration due to electrical and mechanical external forces.

When the electrophotographic photosensitive member is repeatedly used, the electrical deterioration that occurs occurs,
The so-called photo memory, which appears as a decrease in the dark potential (Vo) and an increase in the exposure potential (VL) when used repeatedly, and carriers accumulate in the light-irradiated part, causing a potential difference with the part not irradiated with light. Also appears as a phenomenon.

[0006]

As one means for satisfying the above-mentioned various properties, it is desired to develop a charge transporting material having excellent electric and mechanical properties. As such a charge transport material, for example, JP-A-10-3120
No. 71 discloses that a charge transport material satisfying specific parameters provides an electrophotographic photosensitive member having high sensitivity, low residual potential, high mobility, and high durability.

[0007] However, depending on the configuration of the electrophotographic process used, even the charge transport materials having the specific parameters disclosed above still have insufficient photo memory characteristics. Further, the problem of the photo memory occurs not only when the electrophotographic photosensitive member is repeatedly used in the electrophotographic process as described above, but also when the electrophotographic photosensitive member is irradiated at the time of manufacturing a copying machine or a printer. Or in the market
In some cases, light is emitted when the electrophotographic photosensitive member is taken out during maintenance of the printer, which is a technical problem that cannot be neglected due to the characteristics of the electrophotographic photosensitive member.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies in view of the above-mentioned circumstances, and as a result, provided these electrophotographic photosensitive members having high sensitivity, low residual potential, high mobility and high durability. By using a charge transport material having specific parameters to be used, and by including a specific compound in the photosensitive layer, various types of high sensitivity, low residual potential, high mobility, high durability, etc. expressed by the charge transport material can be obtained. It has been found that the photo memory characteristics can be further improved without impairing the advantages of the present invention, and the present invention has been completed.

That is, a first gist of the present invention is that, in an electrophotographic photosensitive member having a photosensitive layer on a conductive carrier, the photosensitive layer is formed by a semi-empirical molecular orbital calculation using a charge generating substance and PM3 parameters. The calculated value of the polarizability α _cal by the structural optimization calculation (hereinafter referred to as “semi-empirical molecular orbital calculation”) using

[0010]

## _EQU3 ## The calculated value P _cal of the dipole moment P which satisfies α _cal > 70 (Å) and is obtained by semi-empirical molecular orbital calculation is expressed by the following equation.

[0011]

## EQU4 ## Charge transport material satisfying P _cal <1.8 (D), and transmittance 5 of the charge transport material
An electrophotographic photoreceptor characterized in that it contains a compound having a wavelength at which the transmittance becomes 50% on the longer wavelength side than the wavelength at which it becomes 0%.

A second aspect of the present invention resides in an electrophotographic method characterized in that an electrostatic latent image is formed on the electrophotographic photosensitive member with light of 500 nm or more.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The electrophotographic photoreceptor of the present invention has a photosensitive layer containing a charge generating substance and a specific charge transporting substance described below on a conductive support, and further has an absorption edge in the photosensitive layer that is higher than the charge transporting substance. By including a substance on the long wavelength side,
An electrophotographic photosensitive member having high sensitivity, low residual potential, high mobility, high durability, and excellent photo memory characteristics can be obtained. <Conductive Support> As the conductive support, any of those used in known electrophotographic photosensitive members can be used. Specifically, for example, a drum made of a metal material such as aluminum, aluminum alloy, stainless steel, copper, nickel,
Examples thereof include a sheet or a laminate of these metal foils, a vapor-deposited material, or an insulating support such as a polyester film or paper provided with a conductive layer such as aluminum, copper, palladium, tin oxide, or indium oxide on the surface. Further, a plastic film, a plastic drum, paper, a paper tube, and the like, which are subjected to a conductive treatment by applying a conductive substance such as metal powder, carbon black, copper iodide, and a polymer electrolyte together with an appropriate binder, may be mentioned. Further, a plastic sheet or drum containing a conductive substance such as a metal powder, carbon black, or carbon fiber to become conductive may be used. Further, plastic films and belts which have been subjected to conductive treatment with a conductive metal oxide such as tin oxide or indium oxide may be used. Among them, an endless pipe made of metal such as aluminum is a preferable support. <Barrier Layer> In the present invention, a known barrier layer which is generally used may be provided between the conductive support and the photosensitive layer.

Examples of the barrier layer include an anodized aluminum film, an inorganic layer such as aluminum oxide and aluminum hydroxide, polyvinyl alcohol, casein, polyvinylpyrrolidone, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, polyamide and the like. An organic layer using the above resin is used. When using an organic layer as a barrier layer alone or titania,
A metal oxide such as alumina, silica and zirconium oxide or a fine metal powder such as copper, silver and aluminum may be dispersed and used. In the case of an organic layer, the above-mentioned resin is dissolved or dispersed alone or together with the above-mentioned metal oxide / metal fine powder in a solvent, and a wire bar, a doctor blade, a film applicator, a dip,
It can be formed by coating by a coating method such as spraying and drying. The thickness of these barrier layers can be set as appropriate, but is preferably in the range of 0.05 to 20 μm, preferably 0.1 to 10 μm. <Photosensitive layer> On the above-mentioned barrier layer, a photosensitive layer containing a charge generating substance and a charge transporting substance is formed. (1) Charge Transport Material The photosensitive layer according to the invention may be a single-layer type in which the charge transport material and the charge generation material are contained in the same layer. It may be of a laminated type separated into a charge generation layer to be contained, but in any case, it is necessary to use a specific charge transporting substance described in detail below.

The charge transport material used in the present invention has a calculated value α _cal of the polarizability α by semi-empirical molecular orbital calculation.
Next formula

[0016]

The calculated value Pcal of the dipole moment P that satisfies α _cal > 70 (Å) and is obtained by semi-empirical molecular orbital calculation is expressed by the following equation.

[0017]

It is necessary to satisfy P _cal <1.8 (D). The calculated values in the present invention are calculated using the PM3 parameter set as a semi-empirical parameter and using the semi-empirical molecular orbital calculation program MOPAC version MOPAC93 (for PM3 and MOPAC, see JJ. P St
ewart, Journal of Compute
r-Aided Molecular Design,
4, 1 (1990) and references therein).

The calculated value α _polar of the polarizability is preferably

[0019]

Α _cal > 80 (Å), and more preferably,

[0020]

(Equation 8) α_cal> 85 (Å), and most preferably

[0021]

(9) α _cal > 90 (Å) The calculated value P _cal of the total pole moment is preferably

[0022]

P _cal <1.7 (D), and more preferably,

[0023]

P _cal <1.65 (D) (For a consideration that a charge transporting material having a specific polarizability and total pole moment exhibits high-performance electrophotographic characteristics, see JP-A-10-312071. ).

Examples of the charge transporting material corresponding to the above include arylamine compounds represented by the following general formula (2).

[0025]

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(In the general formula (1), R ₁ , R ₂ , R ₃ , R ₄ ,
R ₅ and R ₆ are a halogen atom, an alkyl group which may have a substituent, an alkoxy group which may have a substituent, an aryl group which may have a substituent, or a substituted amino group, respectively. And these may be the same or different from each other. k, l, m, n, o and p are each 0 to 4
It represents an integer, R ₁ there are a plurality in the case of 2 or more integer
To R ₆ may be the same or different. Further, in the general formula (2), X ₁ is represented by the following general formula (3), X ₂
Represents the following general formula (4). )

[0027]

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[0028]

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(In the general formulas (3) and (4), i represents an integer of 1 or 2, h represents an integer of 0 to 2, and R ₇ , R ₈ ,
R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ , and R ₁₆
May have a hydrogen atom, an alkyl group which may have a substituent, an alkoxy group which may have a substituent, an aryl group which may have a substituent, or a substituent, respectively. Represents a heterocyclic group, which may be the same or different from each other. Further, the pair consisting of R ₁₀ and R ₁₁ or the pair consisting of R ₁₅ and R ₁₆ may be fused to form a carbocyclic group or a heterocyclic group. However pair consisting R ₁₀ and R _11, or pairs of pair of R ₁₅ and R _16, when either is a hydrogen atom or an alkyl group and the other is an aryl group or a heterocyclic group. When i = 2, each R ₇ and R ₈ may be the same or different, and when h = 2, each R ₁₅ and R ₁₆ may be the same or different. X ₁ and X ₂ may be the same or different. Examples of specific compounds of the charge transport material include, for example, Compounds such as 1-3 are mentioned. The structure is
Starting from various possible initial structures, the most stable structure was determined. If a single structure was not obtained, the average of these was determined.

[0030]

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[0031]

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[0032]

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The above compound No. Table 1 shows the calculated value α _cal of the polarizability α of 1 to 3, and the calculated value P _cal of the dipole moment P.

[0034]

[Table 1]

(2) A compound having a wavelength at which the transmittance becomes 50% on a longer wavelength side than the wavelength at which the transmittance of the charge transport material becomes 50% In the present invention, the transmittance of the charge transport material is 50% in the photosensitive layer. %, A compound having a wavelength at which the transmittance becomes 50% on the longer wavelength side than the wavelength at which the transmittance becomes% is also added. Here, the “wavelength at which the transmittance becomes 50%” means that a 5% by weight solution using toluene as a solvent is prepared for each of the charge transporting substance and the compound, and the transmittance of the solution is measured with a spectrophotometer. It means a wavelength at which the transmittance becomes 50% in the case of performing the above.

The amount of the compound is usually 1 to 80 parts by weight, preferably 2 to 50 parts by weight, more preferably 3 to 30 parts by weight, based on 100 parts by weight of the charge transport substance. This substance is added to improve the photo memory, but may function not only as an additive but also as a charge transporting substance. A typical example of such a compound is a hydrazone compound, for example, a compound represented by the following general formula (1).

[0037]

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(In the general formula (1), R ₁ and R ₂ represent an alkyl group, an aralkyl group or an aryl group which may have a substituent, n represents 1 or 2, and A represents a substituent. Represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may be present.) Specific examples of the compound represented by the general formula (1) include:
The following hydrazone compounds (NO. 4) are mentioned.

[0039]

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Specifically, the charge transport material (No.
1) and the above hydrazone compound (No. 4)
FIG. 1 shows the transmittance of a solution dissolved in a toluene solvent to a concentration of 5% by weight. Here, the transmittance was measured using a spectrophotometer U-3210 manufactured by Hitachi, Ltd. From Figure 1, the charge transport material (No. 1)
The wavelength of the 50% transmittance of the hydrazone compound (No. 4) was around 520 nm, while the wavelength of the 50% transmittance of the hydrazone compound (No. 4) was around 520 nm.
It can be seen that the wavelength of 50% transmittance in 4) is on the longer wavelength side. (3) Laminated Photosensitive Layer Charge Generating Layer In the case of the laminated type, a charge generating layer may be laminated on the charge generating layer, or a charge generating layer may be laminated on the charge transporting layer.

First, the charge generation layer will be described. A charge generation layer is preferably formed on the undercoat layer. The charge generation layer can also be formed by depositing a charge generation material, but the charge generation material and, if necessary, other organic photoconductive compounds, dyes, electron-withdrawing compounds, etc. are dissolved in a solvent together with a binder resin. Alternatively, it can be formed by applying a known coating method such as a wire bar, a doctor blade, a film applicator, immersion, spraying or the like, dispersing and applying the obtained coating liquid, and drying.

As the charge generating substance, selenium, selenium-
Inorganic photoconductive particles such as tellurium alloy, selenium-arsenic alloy, cadmium sulfide, amorphous silicon, metal-free phthalocyanine, metal-containing phthalocyanine, perinone pigment,
Organic photoconductive particles such as thioindigo, cycridone, perylene pigment, anthraquinone pigment, azo pigment, bisazo pigment, trisazo pigment, tetrakis azo pigment, and cyanine pigment. Further, various organic pigments and dyes such as polycyclic quinone, pyrylium salt, thiopyrylium salt, indigo, anthantrone and pyranthrone can be used. Among them, metals such as metal-free phthalocyanine, copper, indium chloride, gallium chloride, tin, oxytitanium, zinc, and vanadium, or oxides thereof, phthalocyanines with coordinated chlorides, azos such as monoazo, bisazo, trisazo, and polyazos Pigments and perylene pigments are preferred,
Further, oxytitanium phthalocyanine is preferred.

As the binder resin, polyester,
It may be used in a dispersion layer in the form of being bound with various binder resins such as polyvinyl acetate, polycarbonate, polyvinyl acetoacetal, polyvinyl propional, polyvinyl butyral, phenoxy, epoxy, urethane, cellulose ester, and cellulose ether. Further, as the binder resin, styrene, vinyl acetate,
Examples thereof include polymers and copolymers of vinyl compounds such as vinyl chloride, acrylic acid esters, methacrylic acid esters, vinyl alcohol, and ethyl vinyl ether, polyamides, and silicon resins.

In this case, the charge generating substance is used in an amount of usually 20 to 2,000 parts by weight, preferably 30 to 500 parts by weight, more preferably 33 to 500 parts by weight, based on 100 parts by weight of the binder resin. The thickness of the charge generation layer is usually 0.05 to 5 μm, preferably 0.1 to 2 μm.
m, more preferably 0.15 to 0.8 μm. Further, the charge generation layer may contain various additives such as a leveling agent, an antioxidant, and a sensitizer for improving coating properties. Charge Transport Layer In the case of a stacked type, a charge transport layer mainly composed of the above-described charge transport material and binder resin used in the present invention is formed on the charge generation layer.

Examples of the binder resin include vinyl polymers such as polyester, polymethyl methacrylate, polystyrene and polyvinyl chloride, and copolymers thereof, polycarbonate, polyester, polyester carbonate, polysulfone, polyimide, phenoxy, epoxy and silicone resins. A polymer or a copolymer thereof may be used, and a partially cross-linked cured product thereof may also be used. Further, two or more kinds of the binder resins may be blended and used. The ratio between the binder resin and the charge transport material is
It is used in an amount of 30 to 90 parts by weight, preferably 40 to 70 parts by weight, based on 100 parts by weight of the binder resin.
The charge transport layer may contain various additives such as an antioxidant and a sensitizer as needed. The thickness of the charge transport layer is 10 to 60 μm, preferably 10 to 45 μm, and more preferably 25 to 40 μm.

As a method for forming the charge transport layer, a coating solution obtained by dissolving or dispersing a substance contained in the layer in a solvent is coated with a known coating method such as a wire bar, a doctor blade, a film applicator, immersion, and a spray. It can be formed by coating by a method and drying. (4) Single-layer type photosensitive layer Next, the case where the photosensitive layer is a single-layer type will be described. When a single-layer photosensitive layer is provided by a casting method, a function-separation type layer composed of a charge generating substance and a charge transporting substance is often used. That is, the above-mentioned materials can be used as the charge generating substance and the charge transporting substance. Particularly, in the present invention, the above-mentioned material is used as the charge transporting substance. The single-layer photosensitive layer can be formed by dissolving or dispersing the charge generating substance, the charge transport material, and the binder resin in a suitable solvent, and applying and drying this. If necessary, a plasticizer, a leveling agent, an antioxidant, an electron transporting agent and the like can be added. As the binder resin, in addition to using the binder resin described above for the laminated charge transport layer as it is, a mixture of the binder resin described above for the laminated charge generation layer may be used.

In the case of a single-layer type photosensitive layer, the charge generating substance, the charge transporting substance and the binder resin are made of tetrahydrofuran, cyclohexanone, dioxane, dichloroethane,
Using a solvent such as butanone, ball mill, attritor,
It can be formed by dispersing with a sand mill or the like, diluting the dispersion liquid appropriately, and applying. The coating can be performed using a known coating method such as a wire bar, a doctor blade, a film applicator, and dipping or spraying. A photoreceptor in which a charge transporting substance is added to an amorphous complex formed from a beryllium-based dye or bisphenol A-based polycarbonate can also be formed from a suitable solvent by a similar coating method. The thickness of the single-layer photoreceptor is suitably about 5 to 100 μm. <Electrophotographic Photoreceptor> The electrophotographic photoreceptor of the present invention is provided with at least a photosensitive layer on a conductive support as described above, and if necessary, between the conductive conductive support and the photosensitive layer. Although a barrier layer is provided, it goes without saying that an intermediate layer, a transparent insulating layer, a surface protective layer, and the like may be further provided as necessary.

For example, when a surface protective layer is provided on the present photoreceptor, the thickness of the protective layer can be 0.01 to 20 μm.
Preferably it is 0.1 to 10 μm. The above-mentioned binder can be used for the protective layer, and the protective layer may contain the above-mentioned charge generating agent, charge transporting agent, additive, conductive material such as metal and metal oxide, and lubricant. Further, an overcoat layer mainly composed of a conventionally known thermoplastic or thermosetting polymer may be provided as the outermost surface layer.

The electrophotographic photoreceptor thus obtained is a photoreceptor that maintains excellent printing durability for a long period of time, and is suitable for electrophotographic fields such as copying machines, printers, fax machines and plate making machines. <Electrophotographic Apparatus and Electrophotographic Method> An electrophotographic apparatus such as a copying machine or a printer using the electrophotographic photoreceptor of the present invention includes at least each process of charging, exposure, development, and transfer. Any of the methods described above may be used.

As a charging method (charging device), for example, any of corotron or scorotron charging using corona discharge, contact charging using a conductive roller, a brush, a film, or the like may be used. Among them, in the charging method using corona discharge, scorotron charging is often used in order to keep the dark area potential constant. In the present invention, exposure is usually performed using a wavelength of 500 nm or more, and specifically, laser light such as He-Ne, or a halogen lamp or a fluorescent lamp is used. preferable.

As a developing method, a general method of developing by contacting or non-contacting a magnetic or non-magnetic one-component developer, a two-component developer or the like is used. As a transfer method, any of a method using corona discharge, a method using a transfer roller or a transfer belt, and the like may be used. The transfer may be performed directly on paper, an OHP film, or the like, or may be once transferred onto an intermediate transfer body (belt or drum shape) and then transferred onto paper or an OHP film.

Usually, after the transfer, a fixing process of fixing the developer to paper or the like is used, and as a fixing means, generally used heat fixing, pressure fixing and the like can be used. In addition to these processes, a process such as cleaning and static elimination that is usually used may be provided.

[0053]

EXAMPLES Specific examples of the present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the present invention.
In the examples, “parts by weight” indicates “% by weight”. Example 1 The experiment was conducted using an electrophotographic photosensitive member having an undercoat layer between a conductive support and a photosensitive layer. As the undercoat layer, a layer containing titanium oxide whose surface is coated with a silicon compound and a polyamide resin was used. The specific forming method is as follows. That is, the titanium oxide treated with methylhydrogenpolysiloxane surface oxidized titanium oxide used in the experiment was first manufactured by Ishihara Sangyo Co., Ltd. under the product name TTO-55N (crystal rutile primary particle size: 0.03-0.05 um) as titanium oxide. It was prepared by uniformly applying 3% by weight of methyl hydrogen polysiloxane to the surface. The thus obtained methyl hydrogen polysiloxane treated titania was dispersed in a ball mill for 16 hours together with a mixed alcohol (methanol / 1-propanol = 7/3). Next, the obtained titanium oxide dispersion was mixed with a mixed alcohol (methanol / 1-propanol = 70) of a random copolymer polyamide having the following structure produced by the production method described in Examples of JP-A-4-31870. / 30) was added to the solution. Finally titanium oxide /
A dispersion having a solid content of 16% by weight was prepared at a nylon ratio of 3/1 (weight ratio).

[0054]

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An undercoat layer was provided on an aluminum-deposited surface of this dispersion liquid on a polyester film so that the film thickness after drying with a bar coater was 1.3 μm.
In the powder X-ray diffraction spectrum, the black angle (2θ ±
0.2 °) shows the maximum diffraction peak at 27.3 °, and 7.4
10 parts by weight of a crystalline oxytitanium phthalocyanine having diffraction peaks at °, 9.7 ° and 24.2 °
In addition to 4 parts by weight of 4-methoxy-4-methylpentanone-2, pulverization and dispersion treatment was carried out with a sand blind mill to prepare a pigment dispersion preliminary liquid. This was mixed with a 10% methanol solution of 5 parts by weight of polyvinyl butyral (trade name “Denka butyral” # 6000C, manufactured by Denki Kagaku Kogyo KK) to prepare a dispersion.

Then, a charge generation layer was provided on the undercoat layer of the dispersion by a bar coater so that the film thickness after drying was 0.4 μm. On this charge generation layer, 40 parts by weight of the charge transporting substance (No. 1) and 3 parts by weight of the hydrazone compound (No. 4) manufactured by the method disclosed in JP-A-9-244278. Parts, further 0.3 parts by weight of the following cyan compound

[0057]

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And dibutylhydroxytoluene (BH
T) 8 parts by weight, 100 parts by weight of the following polycarbonate resin (monomer molar ratio 1: 1) having two repeating structural units, produced by the production method described in Examples of JP-A-3-221962.

[0059]

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A solution prepared by dissolving 1000 parts by weight of a mixed solution of tetrahydrofuran and toluene was applied by a film applicator, and a charge transport layer was provided so that the film thickness after drying was 30 μm. The photoconductor formed in this manner is referred to as photoconductor A. Comparative Example 1 A photoconductor was prepared by the same way as that of Example 1 except that the charge transport layer was provided using the charge transport layer coating solution except for 3 parts by weight of the hydrazone compound (No. 4).
The photoconductor formed in this manner is referred to as photoconductor B.

Example 2 The charge transporting substance (No. 1) was prepared according to the method described in
A photoreceptor was prepared in the same manner as in Example 1, except that the charge transporting substance (No. 2) was manufactured by the method disclosed in Japanese Patent Application Laid-Open Publication No. H11-209,078. The photoconductor formed in this manner is referred to as photoconductor C. Comparative Example 2 In Example 2, the hydrazone compound (No. 4)
A photoconductor was prepared in the same manner as in Example 2, except that the charge transport layer was provided using the charge transport layer coating solution except for 3 parts by weight. The photoconductor formed in this manner is referred to as photoconductor D.

Comparative Example 3 In Example 1, the hydrazone compound (No. 4)
Was prepared in the same manner as in Example 1, except that a charge transport layer was provided using a charge transport layer coating solution prepared by adding 3 parts by weight of the following hydrazone compound. The photoconductor formed in this manner is referred to as photoconductor E.

[0063]

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FIG. 2 shows the result of measuring the transmittance of a solution in which 5% by weight of the above hydrazone compound was dissolved in a toluene solvent.
Shown in From FIG. 2, the 50% transmittance of the hydrazone compound is around 450 nm, and the charge transporting substance (No.
It can be seen that it is on the shorter wavelength side than that of 1). <Evaluation of Electrophotographic Photoreceptor> The electrophotographic photoreceptor having the photosensitive layer obtained as described above was mounted on a photoreceptor characteristic measuring device, and subjected to a temperature of 25 ° C./relative humidity of 50% (NN environment) and a temperature of 5 ° C. The electrical characteristics in each environment of ° C / relative humidity 10% (LL environment) were measured. The measurement items were as follows: after the surface potential was charged to -700 V, the half-exposure amount (E _1/2 ) when irradiating with 780 nm light, and further, the potential was held at −700 V and left for 5 seconds. Rate (DDR5), L at 660 nm
Vr (residual potential) after irradiation with ED light. The results are shown in Table-2.

[0065]

[Table 2]

From these results, it was found that the hydrazone compound (N
o. It can be seen that the addition of 4) hardly impairs the initial electrical characteristics which are the basic characteristics of the photoreceptor. further,
The durability of each of the photoconductors A and B was evaluated by repeating the electrophotographic process of charging, exposing, and removing static electricity 40,000 times. Table 3 shows dark area potential (Vo) and exposure potential (VL) before and after repeated use. VL
Was determined by measuring the surface potential of the photoconductor when the photoconductor was exposed to light having a wavelength of 780 nm and an intensity of 2.9 uJ / cm ² .

[0067]

[Table 3]

From the results shown in Table 3, the decrease in Vo and the increase in VL, which are indicators for the durability of the electrophotographic photosensitive member, are almost the same regardless of the presence or absence of the hydrazone compound (No. 4). You can see that. That is, it can be seen that the durability as an electrophotographic photosensitive member is not impaired by the addition of the hydrazone compound. Next, the photo memory properties of the photoconductor A, the photoconductor B, the photoconductor C, the photoconductor D, and the photoconductor E were measured. The photo memory property was evaluated by measuring the dark area potential (Vo) before and after irradiating a 3000 lux fluorescent lamp for 5 minutes, and measuring Vo after 190 times of charging and exposure after irradiation. In addition, Model EPA-8 manufactured by Kawaguchi Electric Works, Ltd. was used as an evaluation machine for measuring the photo memory property.
100 was used. Table 4 shows the results. In the table, numbers shown in parentheses are differences from Vo before irradiation.

[0069]

[Table 4]

It can be said that an electrophotographic photosensitive member having a small variation in the potential of the photosensitive member even with irradiation with a fluorescent lamp is more excellent in photo-memory properties. By adding the four compounds to the charge transport layer, 300
It can be seen that the amount of decrease in Vo after irradiation with 0 lux light for 5 minutes is greatly reduced, and as a result, the recovery of Vo when charge-exposure is repeated is quickened. In other words, the results show that the addition of the hydrazone compound (No. 4) significantly improves the photomemory property.

On the other hand, in the photoconductor E containing a hydrazone compound having a structure different from that of the hydrazone compound (No. 4), almost no improvement in the photomemory property is observed. This is presumably because, as shown in FIG. 2, the wavelength of the 50% transmittance is on the shorter wavelength side than the charge transport material (No. 1). That is, the cause of photo memory generation is
It is considered that carriers generated more than necessary due to repeated exposure of the electrophotographic photosensitive member during the electrophotographic process or exposure of the electrophotographic photosensitive member to external light stay in the photosensitive layer. In the present invention, by including in the photosensitive layer a compound having absorption on a longer wavelength side than the charge transporting substance, this substance causes carriers to be generated more than necessary, so-called “extra”. It is thought that the photo-memory property is improved by absorbing the "light irradiated to the photoconductor". Therefore, the hydrazone compound added in the photoconductor E is
It is considered that the photo-memory property was not improved because the material had absorption on the shorter wavelength side than the charge transport material (does not absorb extra light irradiated on the photoreceptor).

However, any compound may be added as long as it has absorption on the longer wavelength side than the charge transporting substance. That is, even if the compound is added,
This is because it is necessary to maintain the initial electrical characteristics and the durability, which are the basic characteristics of the electrophotographic photoreceptor, enough to withstand actual use. According to the present invention, it is possible to obtain an electrophotographic photoreceptor that further improves the photo memory property without impairing the basic characteristics of the electrophotographic photoreceptor.

[0073]

According to the present invention, while maintaining the basic characteristics of an electrophotographic photosensitive member such as high sensitivity, low residual potential, high mobility, and high durability while maintaining high performance, the photo memory characteristics are further improved. An extremely high performance electrophotographic photosensitive member can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing the transmittance of a solution in which a charge transporting substance (No. 1) and a hydrazone compound (No. 4) are each dissolved in a toluene solvent so as to be 5% by weight.

FIG. 2 is a graph showing transmittance of a solution in which a charge transporting substance (No. 1) and a hydrazone compound of Comparative Example 3 are each dissolved in a toluene solvent so as to be 5% by weight.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/04 G03G 15/04 (72) Inventor Ringo 1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa-ken Mitsubishi Chemical Inside Yokohama Research Laboratory Co., Ltd.

Claims (8)

[Claims] 1. An electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the photosensitive layer is a structure optimization calculation using semi-empirical molecular orbital calculation using a charge generating substance and PM3 parameters The calculated value α _cal of the polarizability α by “semi-empirical molecular orbital calculation” satisfies the following equation: α _cal > 70 (Å), and the dipole moment P by semi-empirical molecular orbital calculation calculated P _cal is a charge transport material which satisfies the following equation 2] P _cal <1.8 (D), and the transmittance of the charge transporting substance 5
An electrophotographic photoreceptor comprising a compound having a wavelength at which the transmittance becomes 50% on the longer wavelength side than the wavelength at which 0% is obtained. 2. The electrophotographic photoreceptor according to claim 1, wherein the compound having a transmittance of 50% on a longer wavelength side than the wavelength at which the transmittance of the charge transporting substance is 50% has a charge transporting property. 3. The hydrazone compound according to claim 1, wherein the compound having a wavelength at which the transmittance becomes 50% on a longer wavelength side than the wavelength at which the transmittance of the charge transport material becomes 50% is a hydrazone compound. Electrophotographic photoreceptor. 4. The electrophotographic photoreceptor according to claim 3, wherein the hydrazone compound is represented by the following general formula (1). Embedded image (In the general formula (1), R ₁ and R ₂ represent an alkyl group, an aralkyl group or an aryl group which may have a substituent, n represents 1 or 2, and A has a substituent. Represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may 5. The electrophotographic photosensitive member according to claim 1, wherein the charge transporting substance is an arylamine-based compound represented by the following general formula (2). Embedded image (In the general formula (2), R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R
₈ represents a halogen atom, an alkyl group which may have a substituent, an alkoxy group which may have a substituent, an aryl group which may have a substituent, or a substituted amino group, May be the same or different from each other.
k, l, m, n, o, and p each represent an integer of 0 to 4, and when R is an integer of 2 or more, each of a plurality of R _{3 to} R ₈ may be the same or different. In the general formula (2), X ₁ represents the following general formula (3), and X ₂ represents the following general formula (4). ) Embedded image (In the general formulas (3) and (4), i represents an integer of 1 or 2, h represents an integer of 0 to 2, and R ₉ , R ₁₀ , R ₁₁ ,
R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ , R ₁₆ , R ₁₇ and R ₁₈ are each a hydrogen atom, an alkyl group which may have a substituent, an alkoxy group which may have a substituent, Represents an aryl group which may have a group or a heterocyclic group which may have a substituent, and these may be the same or different. Further, the pair consisting of R ₁₂ and R ₁₃ or the pair consisting of R ₁₇ and R ₁₈ may be fused to form a carbocyclic group or a heterocyclic group.
However, when one of the pair consisting of R ₁₂ and R ₁₃ or the pair consisting of R ₁₇ and R ₁₈ is a hydrogen atom or an alkyl group, the other is an aryl group or a heterocyclic group. i =
In the case of 2, each of R ₉ and R ₁₀ may be the same or different, and in the case of h = 2, each of R ₁₇ and R ₁₈ may be the same or different. X ₁ and X ₂ may be the same or different. ) 6. The electrophotographic photoreceptor according to claim 1, wherein the charge generating substance is oxytitanium phthalocyanine. 7. An electrophotographic method comprising forming an electrostatic latent image on the electrophotographic photosensitive member according to claim 1 by using light of 500 nm or more. 8. The electrophotographic method according to claim 7, wherein the light for forming an electrostatic latent image on the electrophotographic photosensitive member is a laser beam.