JP2000321800A - Electrophotographic photoreceptor - Google Patents

Abstract

(57) [Problem] To provide a high-performance photoreceptor having a function equivalent to or higher than the conventional one without using a halogen-based solvent as a solvent for forming a charge transport layer. And SOLUTION: As a charge transport material, a photosensitive layer has a general formula (I): (Wherein R ₁ is a hydrogen atom, a methyl group or an ethyl group; n is an integer of 1 to 3; when n is 2, two R
_The above-mentioned problems are solved by using a bishydrazone compound represented by the formula (1), which may combine with each other to form an unsaturated carbocycle).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic photoreceptor containing a specific bishydrazone compound as a charge transport material. The present invention also relates to an electrophotographic photoreceptor containing a specific bishydrazone compound as a charge transport material and a specific matrix resin.

[0002]

2. Description of the Related Art In recent years, electrophotographic technology has been widely used not only in the field of copiers but also in the fields of various printers and facsimile machines because of its immediacy, high quality and high storability. The technical field is expanding greatly. At present, most of these copiers and printers use electrophotographic photoreceptors (hereinafter
OPC (Organic Phot)
o Conductor) is used. As a result of the performance improvement of the OPC, the general era of copying in recent years has entered. However, since OPCs have been developed with an emphasis on improving the functionality, there is a lack of consideration for the environment of chemical substances handled in the production of photoconductors.

[0003] Conventionally, improvement of the functionality of the photoreceptor has been the first point in the development of materials such as a charge generation material and a charge transport material for the photoreceptor. The main physical properties required for these materials include high sensitivity, high chargeability, low light and thermal deterioration, and high charge generation efficiency or charge transport efficiency. In addition, material development in this field is active, and intensive research has been promoted. On the other hand, matrix resins (also referred to as “binder resins”) that form the photosensitive layer of the photoreceptor are also being developed from the standpoint of emphasizing the improvement in the functionality of the photoreceptor, similar to charge generation materials and charge transport materials. Have been.

In the development of the above-mentioned materials, consideration has been given to the harmfulness of the material itself and the harmfulness at the time of forming the photoreceptor, but the consideration has not been given to the organic solvent used for forming the photoreceptor. That is, a halogen-containing organic solvent such as methylene chloride (dichloromethane), dichloroethane, and monochlorobenzene is used as an organic solvent for dispersing or dissolving a charge generating material or a charge transporting material and, if necessary, a matrix resin for forming a photosensitive layer. It is currently used as a major solvent.

The basic chemical structure of the bishydrazone compound used as the charge transport material of the photoreceptor of the present invention is disclosed in JP-A-58-131954. However, this prior art relates to a plate-making material for printing, and does not suggest a photoreceptor for a copying machine or a printer, which is the object of the present invention.

[0006]

SUMMARY OF THE INVENTION The present invention provides a high-performance photoreceptor having a function equivalent to or better than that of the prior art without using a halogen-based solvent as a solvent when forming a charge transport layer by coating. The challenge is to obtain.

[0007]

Means for Solving the Problems In view of this situation, the present inventors have conducted intensive studies and have found that by using a specific bishydrazone compound as a charge transport material, an environmentally friendly organic compound can be used instead of a halogenated solvent. The photosensitive layer can be formed using a solvent, and a highly sensitive and highly charged photoconductor can be obtained.By combining this bishydrazone compound with a specific matrix resin, the performance of the photoconductor can be improved. The inventors have found that a highly versatile photoreceptor can be obtained by a next-generation environment-friendly manufacturing method without lowering it, and the present invention has been accomplished.

Thus, according to the present invention, there is provided an electrophotographic photosensitive member having a photosensitive layer formed on a conductive support, wherein the photosensitive layer has the general formula (I):

[0009]

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[0010] (wherein, R ₁ represents a hydrogen atom, a methyl group or an ethyl group; n is an integer from 1 to 3; when n is 2, two R _1, taken together unsaturated carbocycle ), Which comprises a bishydrazone compound represented by the formula:

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The bishydrazone compound used as the charge transport material of the photoreceptor of the present invention has the general formula (I)
And known methods, for example, JP-A-58-13195.
It can be produced by the method described in Japanese Patent Publication No.

Table 1 shows specific examples of the bishydrazone compound of the general formula (I). Among these, the following compounds are particularly preferable. R ₁ : methyl group (substitution position: 4-position), n = 1, R ₁ : methyl group (substitution position: 3-, 4-position or 3,5)
Position), n: 2 R ₁ : ethyl group (substitution position: 3, 4 position, two R ₁ are bonded to each other to form an unsaturated carbon ring), n: 2

When a bishydrazone compound is used as a charge transporting material, it is preferable to purify it by recrystallization in advance, if necessary. "Recrystallization solvent" in the table indicates a preferred solvent used when recrystallizing each bishydrazone compound after treatment with activated carbon.

[0014]

[Table 1]

The photosensitive layer of the photoreceptor is usually prepared by dissolving a charge generating material or a charge transporting material and, if necessary, a matrix resin in an organic solvent, and applying this solution on a conductive support or another photosensitive layer. It is formed by this. The bishydrazone compound of the present invention has a characteristic that, despite its high melting point, it is easily dissolved in a non-halogen organic solvent. Accordingly, one of the features of the present invention is that a non-toxic organic solvent having low toxicity can be used for forming the photosensitive layer.

Examples of non-halogen organic solvents include ester solvents such as methyl acetate and ethyl acetate; ketone solvents such as methyl ethyl ketone, methyl butyl ketone and cyclopentanone; tetrahydrofuran, dioxane, 1,3-dioxane and Ether solvents such as 2-dimethoxyethane; and aromatic hydrocarbon solvents such as toluene and xylene. Among them, methyl ethyl ketone, ethyl acetate, tetrahydrofuran and the like are preferable.

These organic solvents can be used as a mixture of two or more kinds, and are appropriately selected depending on the concentration of the coating solution, drying conditions, and required film properties of the photosensitive layer. The mixed solvent is preferable because the solubility of the bishydrazone compound can be further improved, and in consideration of various conditions such as physical properties and cost, a mixed solvent of ethyl acetate and toluene and a mixed solvent of ethyl acetate and tetrahydrofuran are preferable. Particularly preferred is a combination of ethyl acetate and toluene.

Further, the bishydrazone compound of the present invention comprises
An electrophotographic photoreceptor having high sensitivity and high chargeability can be obtained without lowering the charge transport efficiency as well as having good solubility in an organic solvent.

Since the bishydrazone compound of the present invention itself has poor film-forming ability, it is usually preferable to form a photosensitive layer using a matrix resin. The matrix resin is not particularly limited as long as it is excellent in solubility in an organic solvent and film forming ability, but there are not many that can be applied to an electrophotographic photosensitive member.

That is, as the matrix resin, various types of ester resins (particularly, polycarbonate resins) have been mainly used. However,
Ester-based resins are soluble only in halogen-based solvents such as methylene chloride or high-boiling solvents such as dimethylsulfoxide, and have problems not only in terms of environment but also in terms of use.

As the matrix resin suitable for the bishydrazone compound of the present invention, diallyl phthalate resin, polyphenylene oxide resin, nonyl resin which is a blend of polyphenylene oxide resin and polystyrene resin, and the like are preferably used. The diallyl phthalate resin has the general formula (II):

[0022]

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(Wherein R ₂ is a hydrogen atom, a halogen atom,
A methyl group or an ethyl group). Substituent R
Examples of the halogen atom ₂ include fluorine, chlorine, bromine and iodine. This diallyl phthalate resin,
A commercially available DAP resin can be used. Diallyl phthalate resin has good solubility in organic solvents, not only is it easy to form a photosensitive layer by coating, but also
Since it does not adversely affect the charge transport material, a photoreceptor excellent in electrophotographic characteristics (sensitivity, repetition characteristics) and coating properties can be obtained.

The polyphenylene oxide resin has the general formula (III):

[0025]

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(Wherein R ₃ is a methyl group or an ethyl group). The polyphenylene oxide resin also has good solubility in organic solvents and does not adversely affect the charge transport material, so that a photoreceptor having excellent electrophotographic characteristics (sensitivity, repetition characteristics) and coating properties can be obtained.

When a nonyl resin, which is a blend of a polyphenylene oxide resin and a polystyrene resin, is used as the matrix resin of the photoreceptor of the present invention, the proportion of the polystyrene resin in the matrix resin should be 50% by weight or less. preferable. 50 polystyrene resin
If the content is more than 10% by weight, the repetition characteristics of the obtained photoreceptor deteriorate (the residual potential increases), which is not preferable.

As the matrix resin of the photoreceptor of the present invention, in addition to the above, various lower alkyl group methacrylate resins such as styrene-butadiene copolymer resin, methyl methacrylate resin and n-butyl methacrylate resin can be used. However, when these resins are used, the repetition characteristics of the obtained photoreceptor may be reduced, or the film strength may be reduced.Therefore, in the mixing ratio of these resins and the bishydrazone compound of the present invention, It is preferable to increase the resin component by about 10%.

A commercially available matrix resin for an electrophotographic photosensitive member can be used as it is.
When these resins are used, it is preferable to remove additives and the like in the resin by reprecipitation and purify the resin before use.

At present, function-separated type photoconductors are widely used as photoconductors for copiers and printers. The structure of this function-separated type photoreceptor is basically, on a conductive support, as a photosensitive layer, a charge generation layer mainly composed of a charge generation material,
It consists of a laminated layer formed on this charge generation layer and on which a charge transport (transfer) layer mainly composed of a charge transport material is formed. The bishydrazone compound of the present invention is suitably used as a charge transporting (transferring) material for the above-mentioned function-separated type photoreceptor. Further, the bishydrazone compound of the present invention is a single-layer photoreceptor comprising a single layer of a photosensitive layer containing a charge generating material and a charge transporting material, or an intermediate layer is provided between a conductive support and a photosensitive layer. It can also be applied to a photoreceptor.

The conductive support in the photoreceptor of the present invention is not particularly limited as long as it is usually used as this type of conductive support. As the material thereof, for example, a material having conductivity in the support itself, for example, a metal material such as aluminum, aluminum alloy, copper, zinc, stainless steel, nickel, and titanium can be used. In addition, aluminum, gold, Silver, copper, palladium,
Plastic (eg, polyethylene) on which zinc, nickel, titanium, indium oxide, tin oxide, etc. are deposited
Paper, plastic containing a conductive polymer, and the like. Examples of the shape thereof include a drum shape, a sheet shape, and a seamless belt shape.

As the charge generating material of the photoreceptor of the present invention,
Known compounds, that is, azo pigments such as bisazo pigments and trisazo pigments, and phthalocyanine pigments such as metal-free phthalocyanine pigments and titanium phthalocyanine pigments are used. Specific examples include bisazo pigments described in Examples 1 to 3 described below and titanium oxide phthalocyanine described in Examples 4 to 6. The charge generation material has a function of generating charges in a target wavelength region of the photoconductor, and is appropriately selected depending on the use of the photoconductor. Generally, azo pigments are preferred for copier applications, and phthalocyanine pigments are preferred for printer applications.

Next, a method for forming a photosensitive member will be described. (Formation of Charge Generation Layer) The charge generation layer can be formed by dispersing the above-described charge generation material and matrix resin in a solvent, and applying the resulting dispersion on a conductive support.

For example, a matrix resin and a solvent are added to the charge generation material, and the mixture is pulverized by a ball mill, a dyno mill, a laboratory mill, a sand grinder, a paint shaker (paint conditioner), an ultrasonic disperser, or the like.
The coating liquid obtained by dispersion is applied by a method such as an applicator, dip, bar coater, casting and spin coating in the case of a sheet, a spray method, a vertical ring method and a dip coating method in the case of a drum. Then, a charge generation layer is formed. In preparing the coating liquid, the dispersion particles may be adjusted using a filter as necessary.

As the matrix resin, polyvinyl butyral, polyester, polyvinyl acetate, polyacrylate, polymethacrylate, polycarbonate, polyvinyl acetoacetal, phenoxy resin, epoxy resin, urethane resin, cellulose ester, cellulose ether and vinyl chloride -Vinyl acetate copolymer and the like, and these may be used as a mixture. Among them, polyvinyl butyral and phenoxy resin are particularly preferred.

As the solvent, ketone solvents such as acetone, ethyl methyl ketone, methyl isobutyl ketone and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; ether solvents such as tetrahydrofuran and dioxane; alcohols such as methanol and ethanol Aromatic solvents such as benzene, toluene and xylene; aprotic polar solvents such as N, N-dimethylformamide and dimethylsulfoxide; and these may be used as a mixture.

The mixing ratio of the matrix resin and the charge generating material in the charge generating layer is appropriately selected according to the type of each compounding component and the performance required for the photoreceptor. The thickness of the charge generation layer is usually about 0.1 to 0.5 μm.

(Formation of Charge Transport Layer) Next, a charge transport layer is formed on the charge generation layer. The charge transport layer can be formed by a known method similarly to the charge generation layer. For example, as a charge transport material, the bishydrazone compound of the present invention is dissolved in the above-mentioned solvent, the same matrix resin as above is added, and the obtained solution is formed into a sheet or a sheet in the same manner as in the case of the charge generation layer. Coating on a drum to form a charge transport layer.

The mixing ratio of the matrix resin and the charge transporting material in the charge transporting layer is appropriately selected depending on the type of each component and the performance required for the electrophotographic photosensitive member. The thickness of the charge transport layer is usually about 15 to 40 μm.

Various additives such as a leveling agent, an antioxidant and a sensitizer may be added to the charge generation layer and / or the charge transport layer, if necessary. As antioxidants, vitamin E, hydroquinone, hindered amine,
Hindered phenols, paraphenylenediamines, arylalkanes and their derivatives, organic sulfur compounds and organic phosphorus compounds are included. On the charge transport layer, an overcoat layer mainly composed of, for example, a thermoplastic or thermosetting polymer, which is conventionally known, may be provided as the outermost surface layer.

[0041]

EXAMPLES The present invention will be described more specifically with reference to examples, but the present invention is not limited by these examples.

Example 1 A polyester film (80 μm thick) on which an aluminum evaporated film was formed was used as a conductive support. Phenoxy resin (manufactured by Union Carbide, PKHH) was dissolved in 50 ml of a 1% methyl ethyl ketone solution,
0.5 g of a bisazo pigment represented by the following structural formula was added, and the obtained solution was treated with a paint conditioner (manufactured by Red Devel Co., Ltd.) to obtain 100 g of glass beads having a diameter of 1.5 mm.
For about 30 minutes. The resulting dispersion is applied on the conductive support by an application method,
After drying, a charge generation layer having a thickness of 0.3 μm was formed.

[0043]

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Next, 1 g of a bishydrazone compound (No. 1) shown in Table 1 as a charge transport material, and a diallyl phthalate resin (manufactured by Daiso, prepolymer: MIL-M-14G, ethanol purification treatment) as a matrix resin 1 .2 g was dissolved in 10 ml of methyl ethyl ketone. The obtained solution was immediately applied on the above-mentioned charge generation layer by an application method and dried (condition: temperature 60 ° C., humidity 30%) to form a charge transport layer having a thickness of 22.0 μm. As the bishydrazone compound, a compound previously purified by treatment with activated carbon using ethanol as a solvent and recrystallization was used. As described above, a sheet-shaped function-separated electrophotographic photosensitive member composed of the charge generation layer and the charge transport layer was obtained.

The electrophotographic properties of the obtained photoreceptor were evaluated using an electrophotographic measuring device (SP-428, manufactured by Ryokudenki Co., Ltd.). The measurement conditions were as follows: applied voltage: -5 kV, light source: tungsten lamp. Table 2 shows the obtained results. In the table,
V ₀ indicates the initial potential, and V _R indicates the potential after irradiation at 50 lux for 0.2 seconds.

The adhesive properties of the obtained photoreceptor were determined by JI
Cross-cut method of S-5 standard K-5400 (JIS Handbook 1
995). Table 2 shows the obtained results.
Shown in In the table, the adhesive properties are shown on a scale of 1 to 10.

Examples 2 to 3 Bishydrazone compound Nos. In place of Bishydrazone compound No. 1 shown in Table 1, 3
And No. In the same manner as in Example 1 except that each of No. 6 was used, a sheet-shaped electrophotographic photosensitive member having a separated function was obtained. The bishydrazone compound used was one that had been previously treated with activated carbon and recrystallized using the recrystallization solvent shown in Table 1. The electrophotographic properties and adhesion properties of the obtained photoreceptor,
Evaluation was performed in the same manner as in Example 1. Table 2 shows the obtained results.

Reference Examples 1 to 3 Except that dichloromethane was used in place of methyl ethyl ketone as a solvent for dissolving the charge transporting material, a sheet-shaped electrophotographic photoreceptor was obtained in the same manner as in Examples 1 to 3, respectively. . The electrophotographic properties and adhesive properties of the obtained photoreceptor were evaluated in the same manner as in Example 1. Table 2 shows the obtained results.

[0049]

[Table 2]

From the results shown in Table 2, it was found that a photoreceptor having no inferior electrophotographic characteristics can be obtained by using methyl ethyl ketone which is a non-halogen solvent instead of dichloromethane as a solvent for dissolving the charge transporting material. did.

Examples 4 to 6 A polyester film (80 μm thick) on which an aluminum evaporated film was formed was used as a conductive support. 0.5 g of titanium oxide phthalocyanine as a charge generating material was added to a 40 ml solution of 2% polybutyral (Eslex M, manufactured by Nissin Chemical Co., Ltd.), and the obtained solution was treated with a paint conditioner (manufactured by Red Devel) to a diameter of 1. The dispersion treatment was performed for about 30 minutes together with 80 g of 5 mm glass beads. The obtained dispersion was applied onto the above-mentioned conductive support by a squeezing doctor and dried to form a charge generation layer having a thickness of 0.2 μm.

Next, 1 g of the bishydrazone compound (No. 4) shown in Table 1 as the charge transport material and the resin shown in Table 3 (shown as “binder resin” in the table) as the matrix resin were used in the same amount. Each was dissolved in a solvent shown in Table 3 (in the table, “ethyl acetate” means ethyl acetate) to prepare a solution having a solid concentration of 15%. The obtained solution was immediately laminated on the above-mentioned charge generating layer by an applicator and dried (condition: temperature: 100 ° C.).
A 5 μm charge transport layer was formed. As described above, a sheet-shaped function-separated electrophotographic photosensitive member composed of the charge generation layer and the charge transport layer was obtained. The electrophotographic properties and adhesive properties of the obtained photoreceptor were evaluated in the same manner as in Example 1. Table 3 shows the obtained results.

[0053]

[Table 3]

Examples 7 to 9 and Reference Example 4 As the matrix resin of the charge transport layer, a polycarbonate resin (Polyka Z, manufactured by Mitsubishi Gas Chemical Co., Ltd.) widely used for photoreceptors was used, and dichloroethane was used as a solvent. In the same manner as in Examples 4 to 6, respectively, sheet-shaped electrophotographic photosensitive members having separated functions were obtained (Reference Example 4).

The photosensitive members obtained in Examples 4 to 6 were used in Example 7
9 and the wear characteristics of the photoconductors of Reference Example 4 were evaluated by the wear test method of JIS K-7204 (JIS).
Evaluation was made based on the Handbook 1995). Specifically, using a tester described in the above JIS standard,
The number of rotations until the blue layer of the charge generation layer was included in the abrasion powder was measured by a rotating wheel under a constant load, and the state was visually observed.

In each of the photoconductors of Examples 7 to 9 and Reference Example 4, the number of rotations was in the range of 100 to 120 times / min, and no significant difference was observed between these photoconductors. From these results, even if the matrix resin shown in Table 3 was used as the matrix resin of the charge transport layer instead of the polycarbonate resin that is currently widely used,
It has been found that a photoreceptor that is not inferior in abrasion resistance, that is, printing durability, can be obtained as compared with photoreceptors for copiers and printers that are currently widely used.

[0057]

By using a specific bishydrazone compound as the charge transporting material, an electrophotographic photosensitive member having high sensitivity and high chargeability can be obtained. In addition, since the bishydrazone compound is thermally stable and has good solubility in an organic solvent, not only is its synthesis and purification easy, but also as a solvent used for forming a charge transport layer by coating. And a non-halogen organic solvent. Therefore, by combining with a specific matrix resin, it is possible to obtain a next-generation high-performance photoconductor that is environmentally friendly.

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Claims (8)

[Claims] 1. An electrophotographic photosensitive member having a photosensitive layer formed on a conductive support, wherein the photosensitive layer is represented by the general formula (I): (Wherein R ₁ is a hydrogen atom, a methyl group or an ethyl group; n is an integer of 1 to 3; when n is 2, two R
Wherein ₁ may be bonded to each other to form an unsaturated carbocycle). 2. The electrophotographic photoreceptor according to claim 1, wherein in the general formula (I), R ₁ is a methyl group, n is 1, and the substitution position of R ₁ is 4-position. 3. The electrophotograph according to claim 1, wherein, in the general formula (I), R ₁ is a methyl group, n is 2, and the substitution position of R ₁ is 3, 4 or 3,5. Photoconductor. 4. In the general formula (I), R ₁ is an ethyl group, n is 2, the substitution position of R ₁ is 3, 4 and 2,
One of the electrophotographic photosensitive member according to claim 1 wherein R ₁ combine to form an unsaturated carbocyclic ring formed by mutually. 5. A photosensitive layer having a laminated structure of a charge generating layer containing a charge generating material and a charge transporting layer containing a charge transporting material, wherein the charge transporting layer contains a bishydrazone compound as a charge transporting material. The electrophotographic photoreceptor according to any one of claims 1 to 4, wherein 6. The charge transporting layer wherein the matrix resin is represented by the general formula (II): (Wherein, R ₂ is a hydrogen atom, a halogen atom, a methyl group or an ethyl group) electrophotographic photosensitive member according to claim 5, characterized in that it contains diallyl phthalate resin represented by. 7. The charge transporting layer wherein the matrix resin is represented by the general formula (III): (Wherein, R ₃ is a methyl or ethyl group) electrophotographic photosensitive member according to claim 5, characterized in that it contains a polyphenylene oxide resin represented by. 8. The charge transport layer as a matrix resin,
The electrophotographic photosensitive member according to claim 7, further comprising a polystyrene resin.