JPH09197692A - Photoreceptor for electrophotography - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability and residual electric potential, and to provide the excellent performance on the electric characteristic and the image forming characteristic by including titanyl phthalocyanine or the like as a charge generating material, and including the specified diphenoquinone group compound as a charge transporting material. SOLUTION: A photosensitive layer having the single structure, which includes the charge generating material and the charge transporting material, is provided on a conductive support. As the charge generating material, one kind or more of material, which is selected among a group of titanyl phthalocyanine and the reaction products of the titanyl phthalocyanine and 2,3-butane diol, is included, and as the charge transporting material, the positive hole transporting arterial and the diphenoquinone group compound expressed with a formula is included. In the formula, R<1> -R<8> separately means hydrogen atom and halogen atom or the like. Removal efficiency of the trapped electron is optimized by combining the charge generating material and the charge transporting material, and the excellent electric characteristic is thereby realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoconductor for electrophotography, and more specifically, it has high sensitivity, a small residual potential, a good repetitive property, and an electrophotographic image having a single layer structure. For photoconductors.

[0002]

2. Description of the Related Art Generally, an electrophotographic photoreceptor is formed by forming a photosensitive layer made of a photoconductive material on a conductive support. And a charge-transporting layer, and a function-separated type laminated electrophotographic photoreceptor is often used.

Following the history of the development of the organic photoreceptor for electrophotography, the single compound which was first put into practical use as an organic compound by the poly-N-vinylcarbazole / trinitrofluorenone complex disclosed in US Pat. No. 3,484,237. Layer type electrophotographic photoreceptor, phthalocyanine resin dispersion type electrophotographic photoreceptor disclosed in U.S. Pat. No. 3,397,086, "Journal of Applied Physics"
(Journal of Applied Physics) Vol. 49, No. 11, No. 5
As can be seen in electrophotographic photoreceptors and the like in which a eutectic of a thiapyrylium salt and a polycarbonate resin is used in combination with a triphenylmethane-based charge-transporting material, which is disclosed in pp. Although development has been carried out exclusively for single-layer electrophotographic photoconductors, these single-layer type electrophotographic photoconductors have the advantages that the coating process is simple and that they can be used with positive charging, but on the other hand However, there are many restrictions on materials, and there are problems such as insufficient sensitivity and durability. Since then, a multi-layer type electrophotographic photoconductor comprising a charge generation layer and a charge transport layer, which can solve these problems, has become widespread due to its advantages, and thus it is hardly used at present.

However, the layer structure of a general laminate type electrophotographic photoreceptor is such that a charge transport layer composed of a relatively thick layer is laminated on a thin charge generation layer of usually 1 μm or less. The difficulty of forming a thin film of the generation layer is a factor that reduces the yield. As the charge transport material used for the charge transport layer, a hole transport material is generally used because of its abundance of compound groups, electrical stability, and safety as a material. Therefore, such a laminated type electrophotographic photoreceptor is inevitably capable of exhibiting sensitivity only by negative charging.

In recent years, harmful ozone generated from minus corona discharge in the electrophotographic process has become an environmental problem, and it has been desired to commercialize a positively charged electrophotographic photoreceptor which can be used in a plus corona which generates a small amount of ozone. I have. Further, since the positive charging type electrophotographic photoconductor has the same polarity as that of the conventionally used inorganic electrophotographic photoconductors such as a-Se and a-Si, there is an advantage that many peripheral members can be shared.

In response to the demand for realizing such a practical positive charging type electrophotographic photoconductor, for example, improvement of the conventional single-layer type electrophotographic photoconductor or development of a new electron transporting substance, In addition, although efforts have been made to review the layer structure itself and other efforts have been made, it has not been possible to sufficiently meet the requirements.

[0007] For example, in JP-A-59-49545, charge transport in which a hole transport material is resin-dispersed between a charge generation layer containing a charge generation material and a hole transport material and a conductive support is disclosed. Techniques for providing layers are disclosed. This electrophotographic photoreceptor is basically intended to be positively charged by reversing the stacking order of the conventional laminated type electrophotographic photoreceptor. In principle, this type of electrophotographic photoreceptor has a hole transport layer provided under a single-layer type electrophotographic photoreceptor of charge generating substance / hole transporting substance / resin dispersion system. The basic characteristics of the electrophotographic photosensitive member are very close to those of a single-layer type electrophotographic photosensitive member having only an upper layer. Further, the upper layer used in the electrophotographic photoreceptor proposed in this publication can increase the charge mobility by adding a hole transporting substance to the conventional charge generating layer, and can be made thicker than before. There is a limit to thickening the film, and in actual continuous use, characteristic changes due to abrasion of the upper layer are unavoidable, and since a high concentration of the charge-generating substance is exposed on the surface, even a small amount of positive corona discharge can occur. The deterioration caused by the adsorption of generated ozone and nitrogen oxides was large, and the durability was extremely poor.

In order to improve the drawbacks of the above-mentioned electrophotographic photoreceptor, the content of the charge generating substance in the charge generating layer provided in the single-layer photosensitive layer or the upper layer is extremely reduced to improve the hole transporting property. Electrophotographic photoreceptor dispersed in the binder resin,
For example, "Journal of Imaging Science" Vol. 28, No. 5
No., pp. 191-195 (1984). In this case, the content of the charge-generating substance was 5% by weight or less with respect to the photosensitive layer, which was extremely low, so that the influence of surface deterioration was small and the durability was equivalent to that of the conventional laminated electrophotographic photoreceptor. There was a merit that a positive / negative charging type electrophotographic photoreceptor can be realized.

However, in the electrophotographic photosensitive member according to this structure, the amount of the charge generating substance is greatly reduced in order to obtain the sensitivity and durability, so that the electron transport is not sufficiently performed and the residual potential is reduced. There was a defect in electrical characteristics that it was easy to increase.

[0010]

The problem to be solved by the present invention is to improve various points such as durability and residual potential, which have been problems in practical application of the conventionally proposed single-layer type electrophotographic photoreceptor. And to provide a single-layer type electrophotographic photoreceptor having favorable performance in terms of electrical and image characteristics.

[0011]

In order to solve the above problems, the present invention provides an electrophotographic photoreceptor having a single-layer photosensitive layer containing a charge generating substance and a charge transporting substance on a conductive support. In (1) charge generating substances, titanyl phthalocyanine and titanyl phthalocyanine and 2,3
-Containing at least one material selected from the group consisting of reaction products with butanediol, and (2) as a charge transport material, (a) a hole transport material and (b) a general formula (1)

Embedded image (Wherein R ^{1 to} R ⁸ each independently represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an alkoxyl group or an aryl group). An electrophotographic photoreceptor is provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An example of the structure of a photosensitive layer of an electrophotographic photoreceptor of the present invention is shown in FIG. The thickness of the photosensitive layer is
A range of 5 to 50 μm is preferred. When the photosensitive layer is formed by dip coating, the desired thickness can be easily obtained by adjusting various physical properties such as a coating speed, a viscosity of a paint, and a cutting power. In addition to the single-layer photosensitive layer, a functional layer such as an intermediate layer or a surface protective layer may be appropriately used.

Examples of the conductive support used in the electrophotographic photoreceptor of the present invention include metals or alloys such as aluminum, copper, zinc, stainless steel, chromium, nickel, molybdenum, vanadium, indium, gold and platinum. The used metal plate, metal drum, metal belt, or conductive polymer, conductive compound such as indium oxide, aluminum, palladium, gold or other metal or alloy coated, vapor deposited or laminated paper, plastic film, belt, etc. Can be mentioned.

As the charge generating substance used in the photosensitive layer, titanyl phthalocyanine or a reaction product of titanyl phthalocyanine and 2,3-butanediol is used.

Here, titanyl phthalocyanine and the reaction product of titanyl phthalocyanine and 2,3-butanediol are represented by the general formula (3), respectively.

[0016]

Embedded image

And the general formula (4)

[0018]

Embedded image

(In the formula, Pc represents a substituted or unsubstituted phthalocyanine residue).

Here, the phthalocyanine residue is represented by the formula

[0021]

[Chemical 6]

In the electrophotographic photoconductor of the present invention, the hydrogen atom of the benzene ring of the phthalocyanine residue is unsubstituted, a halogen atom, an alkyl group,
It may be substituted with an alkoxyl group, an aryl group, a nitro group, a cyano group, a hydroxyl group, an amino group or the like.

The 2,3-butanediol used in the reaction with titanyl phthalocyanine is particularly preferably an optically active substance in terms of characteristics.

As the charge-generating substance used in the photosensitive layer, when used, those listed here can be used alone, but two or more kinds of charge-generating substances are mixed with other charge-generating substances. It can also be used.

In the electrophotographic photoreceptor of the present invention, the ratio of the charge generating substance in the photosensitive layer is about 0.1 to the total weight of the photosensitive layer.
The range of 2-5% by weight is preferred. When the proportion of the charge generating substance is more than 5% by weight, the mobility of the charge in the photosensitive layer tends to decrease, resulting in a decrease in sensitivity and a large amount of the charge generating substance exposed on the surface of the photosensitive layer. Therefore, durability tends to deteriorate, which is not preferable. Further, if the proportion of the charge generating substance is less than 0.2% by weight, the absolute amount of the charge generating substance contributing to the charge generation tends to be insufficient, and the sensitivity tends to be deteriorated, which is not preferable.

The charge transport material in the electrophotographic photoreceptor of the present invention is composed of a hole transport material and an electron transport material in combination.

As the hole transporting substance which can be used in the photosensitive layer of the electrophotographic photoreceptor of the present invention, examples of low molecular weight compounds include pyrene type, carbazole type, hydrazone type, oxazole type, oxadiazole type and pyrazoline. System, arylamine-based, arylmethane-based, benzidine-based, thiazole-based, stilbene-based, butadiene-based compounds, and the like, and examples of the polymer compound include poly-N.
-Vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, pyrene-formaldehyde resin, ethylcarbazole-formaldehyde resin, ethylcarbazole-formaldehyde resin, triphenylmethane polymer, polysilane and the like. However, among these, the use of the arylamine compound represented by the general formula (2) is particularly preferable from the viewpoint of electrical characteristics.

The hole-transporting substance used in the electrophotographic photoreceptor of the present invention is not limited to those listed here, and may be used singly or in a mixture of two or more kinds. .

Further, in the electrophotographic photoreceptor of the present invention, in addition to these hole transporting substances, a diphenoquinone compound represented by the general formula (1) which is an electron transporting substance is added to the photosensitive layer. , Its electrical characteristics are remarkably improved, and the performance of the photoconductor is made practical.

The proportion of the diphenoquinone compound and the hole transporting substance in the photosensitive layer is determined by the balance of the mobility of holes and electrons, but in the constitution of the electrophotographic photoreceptor of the present invention, the diphenoquinone compound: Weight ratio of hole transport material is 1: 1
It is preferable to use within the range of 0 to 1: 1 in terms of overall characteristics. If the ratio of the diphenoquinone compound is less than 1:10, it is not preferable because electrons cannot be sufficiently transported, the residual potential becomes large, and the repeating characteristics tend to deteriorate. On the other hand, when the amount of the diphenoquinone compound is more than 1: 1 on the contrary, the hole transporting ability tends to decrease and the sensitivity tends to deteriorate, which is not preferable.

The proportion of the charge transporting substance in the photosensitive layer varies depending on the transporting ability of the charge transporting substance used, but in the case of a low molecular weight compound, it is 10 to 60% by weight based on the total weight of the photosensitive layer.
Is preferred. If the amount is less than 10% by weight, the charge transport ability becomes insufficient, the sensitivity becomes insufficient, and the residual potential tends to increase.
If the content is more than 10% by weight, the content of the resin in the photosensitive layer becomes small, and the mechanical strength of the photosensitive layer tends to decrease. However, as a hole transport material, poly-
When a polymer compound such as N-vinylcarbazole is used, the hole transporting substance itself has a function as a binder, and therefore the entire amount except the charge generating substance and the diphenoquinone compound can be used as the hole transporting substance.

As the binder used in the photosensitive layer, a high molecular polymer capable of forming an electrically insulating film is preferable. Examples of such a high-molecular polymer include polycarbonate, polyester, methacrylic resin, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, styrene-butadiene copolymer,
Vinylidene chloride-acrylonitrile polymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N -Vinyl carbazole,
Polyvinyl butyral, polyvinyl formal, polysulfone, casein, gelatin, polyvinyl alcohol, ethyl cellulose, phenolic resin, polyamide,
Examples include, but are not limited to, carboxy-methylcellulose, vinylidene chloride-based polymer latex, polyurethane, and the like. These binders may be used alone or in combination of two or more.

In addition to these binders, it is also possible to use additives such as dispersion stabilizers, plasticizers, surface modifiers, antioxidants and photodegradation inhibitors.

Examples of the plasticizer include biphenyl, biphenyl chloride, terphenyl, dibutyl phthalate, diethylene glycol phthalate, dioctyl phthalate, triphenyl phosphoric acid, methylnaphthalene, benzophenone, chlorinated paraffin, polypropylene, polystyrene and various fluorohydrocarbons. Can be mentioned.

Examples of the surface modifier include silicone oil and fluororesin.

Examples of the antioxidant include phenol-based, sulfur-based, phosphorus-based, and amine-based compounds.

Examples of the photodeterioration preventing agent include benzotriazole type compounds, benzophenone type compounds, hindered amine type compounds and the like.

When the intermediate layer or the photosensitive layer is formed by dip coating, a paint prepared by dissolving or dispersing in a solvent a mixture of the above-mentioned charge generating substance, charge transporting substance or the like with a binder or the like is used. The solvent that dissolves the binder varies depending on the kind of the binder, and it is preferable to select and use an optimum solvent. Examples of such organic solvents include alcohols such as methanol, ethanol and n-propanol; ketones such as acetone, methyl ethyl ketone and cyclohexanone; amides such as N, N-dimethylformamide and N, N-dimethylacetamide. Ethers such as tetrahydrofuran, dioxane and methyl cellosolve; Esters such as methyl acetate and ethyl acetate; Sulfoxides and sulfones such as dimethyl sulfoxide and sulfolane; Aliphatic halogenation such as methylene chloride, chloroform, carbon tetrachloride and trichloroethane hydrocarbon;
Benzene, toluene, xylene, monochlorobenzene,
And aromatics such as dichlorobenzene.

[0039]

The operation of the electrophotographic photoreceptor of the present invention will be described in detail below, and the reason why the electrophotographic photoreceptor of the present invention can exhibit excellent electrical characteristics will be clarified.

The proportion of the charge generating substance used in the electrophotographic photoreceptor of the present invention is 0.2 to the total weight of the photosensitive layer.
It is preferably in the range of 5% by weight. However, in the electrophotographic photosensitive member having such a low concentration of the charge generating substance, as described in the section of the prior art, the electron transport is not sufficiently performed, so that the residual amount is Problems such as a large potential and deterioration of repetitive characteristics occur. In this case, by containing an electron transporting substance in the photosensitive layer, the electron transporting ability can be improved and these problems can be improved, but the effect is significantly different depending on the combination of the charge generating substance and the electron transporting substance used. Indicates. Because electrons as charge carriers are hardly allowed to localize in the hole transport material or the binder resin, the generated electrons are necessarily concentrated near the surface of the charge generating material. This is because the energetic affinity between the charge-generating substance and the electron-transporting substance is considered to be a major controlling factor for trapping and efficient release from the trap.

In the electrophotographic photoreceptor of the present invention, in the electrophotographic photoreceptor having such a constitution, the charge generating substance, titanyl phthalocyanine, or the reaction product of titanyl phthalocyanine and 2,3-butanediol, and the electron It is a great feature that the best photoconductor characteristics were derived by the combination of the diphenoquinone-based compound which is a transport substance. It is considered that the combination of the charge-generating substance and the electron-transporting substance in the electrophotographic photosensitive member of the present invention optimizes the efficiency of releasing the trapped electrons and exhibits excellent electrical characteristics.

[0042]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the examples. In addition, "part" in the following synthetic examples, examples and comparative examples means "part by weight".

(Synthesis Example 1) 20 parts of β-type titanyl phthalocyanine and (2R, 3R) -2,3-butanediol 2.
2 parts and 240 parts of α-chloronaphthalene were reacted with stirring at 200 ° C. for 1.5 hours. After cooling the reaction mixture to room temperature, the reaction product was filtered off, washed with benzene, methanol, dimethylformamide and water in this order, and then dried under reduced pressure to obtain a phthalocyanine compound.

The phthalocyanine compound thus obtained had a mass spectrum of m / Z = 648 and m / Z = 648.
Since a peak was shown at Z = 576, the formula (6)

[0045]

Embedded image

It was found to be a mixed composition of the compound represented by and unreacted titanyl phthalocyanine.

The X-ray diffraction spectrum of Cu-Kα of this composition is shown in FIG. As shown in FIG. 2, the composition had strong peaks at 8.3 °, 24.7 ° and 25.1 ° at the Bragg angle 2θ.

Example 1 0.3 part of the phthalocyanine composition obtained in Synthesis Example 1, formula (7)

[0049]

Embedded image

9 parts of an arylamine compound represented by the formula:
Formula (8)

[0051]

Embedded image

3 parts of the diphenoquinone compound represented by and 14 parts of a polycarbonate resin ("Upilon Z-200" manufactured by Mitsubishi Gas Chemical Co., Inc.) were dissolved in 76 parts of chloroform and dispersed using a vibration mill to prepare a photosensitive layer. Created the paint.

Using this paint, it is applied on an aluminum plate having a thickness of 0.3 mm so that the film thickness after drying becomes 20 μm, and then dried to form a photosensitive layer. A photoreceptor was obtained.

Example 2 In Example 1, as the diphenoquinone compound, the compound represented by the formula (9)

[0055]

Embedded image

An electrophotographic photosensitive member was obtained in the same manner as in Example 1 except that the compound represented by

Example 3 In Example 1, as the diphenoquinone compound, the compound represented by the formula (10)

[0058]

Embedded image

An electrophotographic photosensitive member was obtained in the same manner as in Example 1 except that the compound represented by

Example 4 In Example 1, as the diphenoquinone compound, the compound represented by the formula (11)

[0061]

Embedded image

An electrophotographic photoreceptor was obtained in the same manner as in Example 1 except that the compound represented by the formula (1) was used.

Comparative Example 1 An electrophotographic photosensitive member was obtained in the same manner as in Example 1, except that the diphenoquinone compound was not used.

(Comparative Example 2) In Example 1, except that X-type metal-free phthalocyanine was used as the charge generating substance,
An electrophotographic photosensitive member was obtained in the same manner as in Example 1.

(Comparative Example 3) In Example 1, instead of the diphenoquinone compound as the electron transport material, the compound represented by the formula (1) was used.
2)

[0066]

Embedded image

An electrophotographic photosensitive member was obtained in the same manner as in Example 1 except that the fluorenone compound represented by

(Comparative Example 4) In Example 1, instead of the diphenoquinone compound as the electron transport material, the compound represented by the formula (1)
3)

[0069]

Embedded image An electrophotographic photoreceptor was obtained in the same manner as in Example 1 except that the thiopyran compound represented by

(Electrical Properties) Obtained in Examples and Comparative Examples
In order to evaluate the electrical characteristics of the electrophotographic photoconductor,
Electrophotographic copying paper testing device (made by Kawaguchi Electric Co., Ltd.)
"EPA-8100") to measure the electrostatic characteristics.
Was. The measurement method is to first apply voltage to the electrophotographic photoreceptor in a dark place.
Charged by corona discharge of pressure + 6kV.
Surface potential is initial potential V₀ Was used to evaluate the charging ability.
Next, the potential was measured after leaving it in the dark for 10 seconds, and V_Ten
And Where V_Ten/ V₀ Evaluation of potential holding capacity
did. Then, with monochromatic light of 780 nm,
Exposure intensity is 1μW / cm^Two Set so that the photosensitive layer
The surface is irradiated with light for 15 seconds and the decay curve of the surface potential is recorded.
Was. Here, measure the surface potential after 15 seconds, and
Rank V_R And Also, the surface potential is V due to light irradiation._TenOf 1
Exposure amount until it decreases to / 2, and half exposure amount E _1/2 
The sensitivity was evaluated as. Furthermore, after charging 3000 lux
1 step every 1 second to irradiate white light for 0.1 second
Immediately after repeating 00 times, repeat the same measurement.
The properties were evaluated. In addition, the same measurement was applied voltage-
It performed also on the conditions of negative charging of 6 kV. Table 1 shows these results.
And summarized in Table 2.

[0071]

[Table 1]

[0072]

[Table 2]

As is clear from the results shown in Tables 1 and 2, the electrophotographic photoconductors obtained in Examples 1 to 4 of the present invention were the electrophotographic photoconductors of Comparative Example 1 containing no diphenoquinone compound. Compared to the body, in either positive or negative polarity,
The characteristics were improved in the initial sensitivity, and in particular, the deterioration of the sensitivity and the increase of the residual potential after the repetition were remarkably improved. On the other hand, the electrophotographic photoreceptors using phthalocyanine generally used as the charge generation material obtained in Comparative Example 2 are significantly inferior in sensitivity to the electrophotographic photoreceptors obtained in the respective Examples. It was Further, the electrophotographic photoconductors using the general electron transporting materials other than the diphenoquinone compounds obtained in Comparative Examples 3 and 4 have a higher potential holding ability than the electrophotographic photoconductors obtained in the respective examples. , And the sensitivity and residual potential after repetition were very poor.

[0074]

INDUSTRIAL APPLICABILITY The electrophotographic photoconductor of the present invention is a positive and negative electrophotographic photoconductor which is positively and negatively chargeable, has excellent electrical characteristics, and has good repeating characteristics.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view illustrating an example of a layer configuration of an electrophotographic photoconductor of the present invention.

[Explanation of symbols]

 1 Conductive Support 2 Charge Generating Material 3 Hole Transport Material / Diphenoquinone Compound / Binder 4 Photosensitive Layer

2 is a mixture composition X of the reaction product of the titanyl phthalocyanine represented by the formula (1) and (2R, 3R) -2,3-butanediol obtained in Synthesis Example 1 and unreacted titanyl phthalocyanine. It is a line diffraction spectrum.

Claims (4)

[Claims] 1. In an electrophotographic photoreceptor having a photosensitive layer having a single layer structure containing a charge generating substance and a charge transporting substance on a conductive support, (1) as the charge generating substance, titanyl phthalocyanine and titanyl phthalocyanine are used. And 2,
It contains at least one material selected from the group consisting of reaction products with 3-butanediol, and (2) as a charge transport material, (a) a hole transport material and (b) a general formula (1): Chemical 1] (Wherein R ^{1 to} R ⁸ each independently represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an alkoxyl group or an aryl group). A photoreceptor for electrophotography, which is characterized by: 2. The electrophotographic photoreceptor according to claim 1, which contains an arylamine compound as a hole transporting substance. 3. The arylamine compound is represented by the general formula (2): A compound represented by the formula (wherein Ar ^{1 to} Ar ⁴ each independently represents an aryl group which may have a substituent). body. 4. The ratio of the charge generating substance contained in the photosensitive layer is in the range of 0.2 to 5% by weight based on the total weight of the photosensitive layer. Electrophotographic photoconductor.