JPH05297612A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To suppress reduction of surface potential for repeated exposure while maintaining excellent sensitivity by incorporating a polycyano compd. having double bonds in conjugate with cyano groups in the molecule into a photosensitive layer containing a specified charge generating pigment and a charge transfer material. CONSTITUTION:A photosensitive layer containing a disazo pigment (charge generating material) expressed by formula and a charge transfer material is formed on a conductive supporting body. This sensitive layer contains a polycyano compd. having double bonds in conjugate with cyano groups in the molecule. In formula, Cp is a coupler residue, (n) is 0 or 1, A is a hydrogen atom, substd. or unsubstd. alkyl group, aryl group, or univalent heterocyclic ring group. The polycyano compd. has lots of cyano groups excellent in electron accepting property on both ends of the molecular chains, and further has such a structure having double bonds conjugate with cyano groups all over the molecular chains, so that electrons can be easily moved and accepted in the structure of this compd. Thus, excellent result can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic organic photoconductor used for electrophotographic copying, printers, fax machines and the like, and more particularly to an electrophotographic photoconductor having resistance to deterioration of various characteristics due to light. Regarding the body

[0002]

2. Description of the Related Art Organic photoconductors (OPC), amorphous silicones (α-S) are used as photoconductors for electrophotography.
i), some selenium (Se) photoconductors, etc. are used, but from a comprehensive viewpoint of sensitivity, cost, etc., use of OPC is becoming widespread. Examples of the OPC include a so-called function-separated type organic photoreceptor, that is, a laminated type photoreceptor in which a charge generation layer (CGL) and a charge transport layer (CTL) are laminated on a conductive substrate, and charge in a medium of a charge transport material. There is a single-layer dispersion type organic photoconductor in which a generating substance is dispersed, but the latter is superior in terms of easiness of production and stability of performance.

Various inorganic or organic charge-generating pigments are known as charge-generating substances. Examples of organic charge-generating substances include pyrylium salts, azo pigments, disazo pigments, ansanthrone pigments, phthalocyanine pigments and indico pigments. Pigments, threnic pigments, toluidine pigments, pyrazolone pigments, perylene pigments, quinacridone pigments and the like are known.

In JP-A-1-202757, Cp is a coupler residue, n is a number of 0 or 1, A is a hydrogen atom, or a substituted or unsubstituted group. Which is an alkyl group, an aryl group or a monovalent heterocyclic group,
Describes a photoconductor provided with a photosensitive layer having an azo pigment represented by the following formula, and it is shown that this azo pigment is stable to heat and light and has an excellent carrier generating ability.

[0005]

In general, organic photoreceptors are easy to manufacture and have easy control of electrophotographic characteristics, but on the other hand, they lack in stability to light and have a relatively short period of time during repeated use. There is a problem that it deteriorates in the inside. Even though the disazo pigment in the above-mentioned prior art is excellent in the ability to generate a carrier, it also has the drawbacks generally recognized in organic photoconductors, and there is a problem that the surface potential drops considerably when exposure is repeated. .. The reduction of the surface potential naturally leads to the reduction of the image density and the contrast of the image and the reduction of the life of the photoconductor. Therefore, the improvement of this property is a key point in the development of the organic photoconductor. But it's not an exaggeration.

Therefore, an object of the present invention is to improve the stability against light and to significantly suppress the tendency of the surface potential to decrease during repeated exposure, and particularly to use an organic photoconductor for electrophotography, particularly a charge generating substance-charge transporting substance. An object is to provide a layer-dispersed organic photoreceptor.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention have proposed an electronic device in which a photosensitive layer containing a disazo pigment (charge generating agent) represented by the chemical formula 1 and a charge transporting agent is provided on a conductive substrate. In the photographic photosensitive member, when the photosensitive layer contains a polycyano compound having a double bond in a molecule in a conjugated relationship with a cyano group, the above-mentioned drawbacks of the conventional organic photosensitive member are effectively eliminated, and repeated exposure is repeated. It was found that the tendency of the surface potential to decrease with time is effectively suppressed.

In the present invention, the above-mentioned polycyano compound acts to effectively suppress a decrease in surface potential during repeated exposure, even if it is added in a small amount to the photosensitive layer.
Generally, this polycyano compound is the above-mentioned disazo pigment 1
It is preferably used in an amount of 0.1 to 1.25 parts by weight, particularly 0.25 to 1 part by weight, per part by weight.

[0009]

In the present invention, among the various disazo pigments, the disazo pigment of the above "Chemical formula 1" is selected and used in combination with the charge transfer agent because it has excellent sensitivity (charge generating ability). And the residual potential is also at a considerably low level. It is a feature of the present invention that the photosensitive layer containing the above charge generating pigment and the charge transfer agent contains a polycyano compound containing a double bond in a molecule in a conjugated relationship with a cyano group. It is possible to remarkably suppress a decrease in surface potential during repeated exposure without deteriorating the excellent sensitivity and the like of the disazo pigment.

As shown in "Table 1" described later, the photosensitive layer containing the disazo pigment (charge generating agent) of "Chemical formula 1" and the charge transporting agent has a half-exposure amount (E1 / 2) of 1.23 Lux.
It has a high sensitivity of sec and a relatively low residual potential of 68 V, but after repeating 1000 times of exposure, the surface potential is -315 V lower than the surface potential at the time of the first exposure. The drawback of doing is recognized.

On the other hand, when the above-mentioned specific polycyano compound is blended in the above-mentioned photosensitive layer, as shown in Table 1, while maintaining excellent sensitivity and low residual potential of the above-mentioned photosensitive layer, 1
The surface potential decrease amount (ΔSP) after 000 exposures is -1
It is possible to suppress the voltage to 70 V or less.

Generally, the tendency of the surface potential of the photosensitive layer to decrease due to repeated exposure is that, for example, in the positively charged type photosensitive layer, the opposite charge electrons remain in the photosensitive layer, especially trapped in the pigment, and repeated exposure. It is considered that the material constituting the photosensitive layer is deteriorated by the activation by the above or the attack of the active gas by the corona discharge. On the other hand, the specific polycyano compound used in the present invention is
As an acceptor (electron acceptor), it eliminates trap electrons in the above-mentioned photosensitive layer and also acts effectively as a quencher for the activated light-irradiated photosensitive layer, thereby lowering the surface potential during repeated exposure. Seems to suppress.

The polyacino compound used in the present invention is structurally characterized in that it has a large number of cyano groups having excellent electron accepting properties at both ends of the molecular chain and also has a double bond in a conjugated relationship with the entire molecular chain. It is believed that the above-mentioned excellent results are obtained because the structure has the above-mentioned property, and that the transfer of electrons in the structure is easy and the transfer of electrons is easy. Also, the fact that the reduction potential is within a certain range seems to be useful for facilitating the transfer of electrons.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Polycyano Compound The polycyano compound used in the present invention is a compound having a large number of cyano groups (-C≡N) at the terminal of the molecule and having a double bond in the molecule in a conjugated relationship with the cyano group. Is. Suitable examples thereof include, but are not limited to, the following. In the formula "Chemical formula 2", m is an integer of 0 to 2, and Y is a group represented by the formula "Chemical formula 3" in which ring A may be unsubstituted or substituted. A tetracyano compound having:

In the above formula, when ring A is substituted, the substituent is an alkyl group having 6 or less carbon atoms, for example, a methyl group, an ethyl group, a propyl group, a t-butyl group; an alkoxy group having 4 or less carbon atoms. , For example, methoxy group, ethoxy group, t
-Butoxy group; it may be an aryl group having 6 to 10 carbon atoms, for example, a phenyl group, a tolyl group, an ethylphenyl group and the like.

Suitable polycyano compounds have the formula

[Chemical 4] Of tetracyanoethylene, formula

[0017]

[Chemical 5] 7,7,8,8-tetracyanoquino-dimethane of the formula

[0018]

[Chemical 6] And tetracyanodiphenoquino-dimethane.

Photosensitive Layer and Photoreceptor The disazo charge generating pigment used in the photosensitive layer of the present invention is described in the above-mentioned JP-A-1-202757. In the above-mentioned “Chemical formula 1”, the alkyl group of the group A may be an alkyl group having a carbon number of 4 or less such as a methyl group, an ethyl group, an n-propyl group and a butyl group,
Examples of the aryl group of the group A include aryl groups having 6 to 10 carbon atoms such as phenyl group, tolyl group, ethylphenyl group, methoxyphenyl group and naphthyl group, and the monovalent heterocyclic group includes furyl. Group, pyridyl group, etc.
And 6-membered heterocyclic groups can be mentioned.

Further, the coupling residue Cp in the above "Chemical formula 1" is represented by the formula:

[Chemical 7] In the formula, X is a hydrogen atom, a halogen atom, an alkyl group having a carbon number of 4 or less, an alkoxy group having a carbon number of 4 or less, or a phenyl group, and p is 1 or 2.

[0021]

[Chemical 8] In the formula, X and p have the meanings described in "Chemical Formula 7";

[0022]

[Chemical 9] In the formula, X and p have the meanings described in "Chemical Formula 7";

[0023]

[Chemical 10] In the formula, X and p have the meanings described in "Chemical formula 7".

As the charge transfer agent, a hole transfer agent such as an oxadiazole compound, a styryl compound, a carbazole compound, an organic polysilane compound, a pyrazoline compound, a hydrazone compound, a triphenylamine compound,
Nitrogen-containing cyclic compounds such as indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, triazole compounds, and condensed polycyclic compounds can be used. Among these, those having an ionization potential of 5.3 to 5.6 eV are used. In addition, the electric field strength is 3 × 10 ⁻⁵ V / cm and 10 ⁻⁶ Vcm.
Those having the above mobility are particularly preferable.

Suitable hole transport agents include, but are not limited to, 1,1-bis (p-diethylaminophenyl)-
4,4-diphenyl-1,3-butadiene, N, N'-
Bis (o, p-dimethylphenyl) -N, N'-diphenylbenzidine, 3,3'-dimethyl-N, N, N ',
N'-tetrakis-4-methylphenyl (1,1'-biphenyl) -4,4'-diamine, N-ethyl-3-carbazolylaldehyde-N, N'-diphenylhydrazone, 4- [N, N -Bis (p-toluyl) amino] -β
-Phenylstilbene and the like.

Various resins can be used as the resin medium in which the above-mentioned respective agents are dispersed. For example, a styrene-based polymer, an acrylic-based polymer, a styrene-acrylic-based polymer, an ethylene-vinyl acetate copolymer. ,polypropylene,
Olefin-based polymers such as ionomers, polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, polyesters,
Alkyd resin, polyamide, polyurethane, epoxy resin, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, silicone resin, ketone resin, polyvinyl butyral resin, polyether resin,
Examples include various polymers such as a phenol resin and a photocurable resin such as epoxy acrylate. These binder resins may be used alone or in combination of two or more.
Suitable resins include styrene polymers, acrylic polymers,
Examples thereof include styrene-acrylic polymer, polyester, alkyd resin, polycarbonate, polyarylate and the like.

In the photosensitive layer used in the present invention, the charge generating agent (CGM) is preferably contained in the photosensitive layer in an amount of 0.1 to 5% by weight, particularly 1 to 3% by weight, based on the solid content,
On the other hand, the charge transfer agent (CTM) is preferably present in an amount of 5 to 55% by weight, particularly 30 to 50% by weight, based on the solid content, and the weight ratio of the two is CGM: CTM = 1: 10 to 1:30. It is preferably in the range of: 13 to 1:25.

The composition for forming a photoreceptor of the present invention contains various compounding agents known per se, such as an antioxidant, a radical scavenger, within a range that does not adversely affect electrophotographic characteristics.
Singlet quencher, UV absorber, softener, surface modifier, defoamer, extender, thickener, dispersion stabilizer, wax,
An acceptor, a donor, etc. can be blended. According to the present invention, when the sterically hindered phenolic antioxidant is added in an amount of 0.1 to 50% by weight based on the total solid content, the durability of the photosensitive layer is remarkably improved without adversely affecting the electrophotographic characteristics. It turns out that it can be improved.

As the solvent used for forming the coating liquid, various organic solvents can be used, and alcohols such as methanol, ethanol, isopropanol, butanol,
Aliphatic hydrocarbons such as n-hexane, octane and cyclohexane, aromatic hydrocarbons such as benzene, toluene and xylene, halogenated hydrocarbons such as dichloromethane, dichloroethane, carbon tetrachloride and chlorobenzene, dimethyl ether, diethyl ether, tetrahydrofuran, Ethylene glycol dimethyl ether, ethers such as diethylene glycol dimethyl ether, acetone, methyl ethyl ketone, ketones such as cyclohexanone, ethyl acetate, esters such as methyl acetate, dimethylformamide, dimethylsulfoxide, etc., various solvents are exemplified, and one or more kinds Used as a mixture. Generally, the solid content concentration of the coating liquid is preferably 5 to 50%.

As the conductive substrate, various conductive materials can be used. For example, aluminum, copper, tin, platinum, gold, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, indium, stainless steel. ,
Simple metals such as brass, plastic materials in which the above metals are vapor-deposited or laminated, aluminum iodide, tin oxide,
Examples thereof include glass coated with indium oxide or the like.
The photoconductor of the present invention is a single-layer dispersion type photoconductor, and since there is no occurrence of interference patterns, a normal aluminum tube,
In particular, it is one of the advantages that an alumite-treated raw tube having a film thickness of 1 to 50 μm can be used.

In order to form the coating liquid, the charge generating material and the binder resin are prepared by a conventionally known method such as roll mill, ball mill, attritor, paint shaker or ultrasonic disperser. It may be applied and dried by a conventionally known applying means. The thickness of the photosensitive layer is not particularly limited, but is preferably in the range of generally 5 to 100 μm, particularly 10 to 50 μm.

[0032]

EXAMPLES The present invention will be described in more detail based on the following examples. Examples 1 to 4 4 parts by weight of the charge generating material and 3, as the charge transporting material
3'-dimethyl-N, N, N ', N'-tetrakis-4
-Methylphenyl (1,1'-biphenyl) -4,4 '
80 parts by weight of diamine, a specific amount of polycyano compound, and 100 parts by weight of bisphenol A-type polycarbonate resin are dispersed together with a predetermined amount of tetrahydrofuran for 2 minutes using an ultrasonic disperser to prepare a single-layer type photosensitive layer. A coating solution of was prepared. Then, this coating solution is applied to the surface of an aluminum sheet that has been subjected to an alumite treatment as a conductive substrate by a bar coating method using a wire bar and dried at 110 ° C. for 30 minutes to obtain a single layer type having a film thickness of 30 μm. A photosensitive layer was formed to obtain a positive charging type single layer type electrophotographic photosensitive member.

Comparative Examples 1 to 10 A positively chargeable single-layer electrophotographic photosensitive material was prepared in the same manner as in each of the above Examples except that a specific amount of benzoquinone derivative was used instead of the specific amount of polycyano compound. Got the body In addition,
The charge generating material used in Table 1 is represented by the following formula (A1)
The compound number is shown. Further, the polycyano compound is represented by using the compound numbers of the following formulas (B1) to (B2), and the benzoquinone derivative is represented by the following (C1) to (C4).
The compound number is used, and the addition amount is specifically shown by a numerical value.

Charge Generating Material (CGM)

[Chemical 11]

Polycyano compound (PC)

[0036]

[Chemical 12] Benzoquinone derivative (BQ)

(C1): 2,3-dichloro-5,6-dicyano- P- benzoquinone reduction potential -2.08 V (C2): 2,6- ditert -butyl-1,4-benzoquinone reduction potential-1 .26V (C3): bromanil reduction potential -0.3V (C4): chloranil reduction potential -0.3V above embodiments perform the following test the electrophotographic photosensitive member of Comparative example, and their characteristics were evaluated.

Electrical characteristics Electrostatic copying tester (EPA-810 manufactured by Kawaguchi Electric Co., Ltd.
0) to adjust the flow-in current value to +700 on the surface of the sheet-shaped electrophotographic photosensitive member prepared in Examples and Comparative Examples.
The initial surface potential (V) when charged near V was measured. Next, after 1 second of dark decay, a white halogen lamp as an exposure light source was used to reduce the light intensity of 10 LUX to a half exposure amount E1 /.
2 (lux.sec), and 0.5 after the start of exposure
The surface potential at the time when a second has passed is the residual potential Vr. It was measured as p (V).

Repeatability Characteristics The sheet-shaped electrophotographic photoreceptors obtained in the above Examples and Comparative Examples were adhered to a 78φ aluminum tube using a vinyl tape, and then an electrostatic copying machine (Mita Kogyo Co., Ltd.) was used. Manufactured by DC-1657) and the copying process was repeated 1000 times. Then, using a surface electrometer installed in the electrostatic copying machine, the surface potential when charged was measured, and 10
The value obtained by subtracting the initial surface potential from the surface potential after the 00th copying step is repeated as the characteristic ΔVs. It was calculated as p (V). The above results are shown in Table 1.

[0040]

[Table 1]

As is clear from Table 1, the electrophotographic photoreceptors of Examples 1 to 4 favorably maintain the residual potential and the sensitivity characteristics, which are important as electrophotographic characteristics, and greatly improve the repeating characteristics. You can see that However,
In the process of increasing the addition amount of the polycyano compound, the repeating characteristics are improved, but the sensitivity tends to be deteriorated.

Further, the electrophotographic photosensitive member of Comparative Example 1 to which the polycyano compound was not added had poor repetitive characteristics, and a BQ derivative having a reduction potential outside the range of -0.5 V to -1.2 V was used. The electrophotographic photoconductors of Comparative Examples 2 to 10 have slightly improved repetitive characteristics as compared with the electrophotographic photoconductor of Comparative Example 1, but they did not show results that could be practically used.

[0043]

EFFECTS OF THE INVENTION According to the present invention, a polycyano compound having a conjugated relationship with a cyano group in its molecule is contained in a photosensitive layer containing a disazo type charge generating pigment of "Chemical Formula 1" and a charge transporting agent. While maintaining excellent sensitivity and low residual potential, it has become possible to effectively suppress the decreasing tendency of residual potential during repeated exposure. This photoconductor is of a single-layer dispersion type and has the additional advantage that it can be used for image formation by positive charging with less generation of ozone and generation of interference.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Keisuke Sumita, 1-2-2 Tamatsukuri, Chuo-ku, Osaka City, Mita Industrial Co., Ltd. Within Kogyo Co., Ltd.

Claims (7)

[Claims] 1. The following formula on a conductive substrate: In the formula, Cp is a coupler residue, n is a number of 0 or 1, and A is a hydrogen atom or a substituted or unsubstituted alkyl group, aryl group or monovalent heterocyclic group. An electrophotographic photoreceptor comprising a photosensitive layer containing a charge generating pigment and a charge transporting agent, wherein the photosensitive layer contains a polycyano compound containing a double bond having a conjugated relationship with a cyano group in the molecule. An electrophotographic photosensitive member characterized by being formed. 2. A polycyano compound has the formula: Where m is an integer from 0 to 2 and Y is of the formula: The electrophotographic photosensitive member according to claim 1, wherein A in the formula is a tetracyano compound represented by the following formula, which may be unsubstituted or substituted. 3. The electrophotographic photosensitive member according to claim 1, wherein the polycyano compound is tetracyanoethylene. 4. The electrophotographic photosensitive member according to claim 1, wherein the polycyano compound is 7,7,8,8-tetracyanoquinodimethane. 5. The electrophotographic photosensitive member according to claim 1, wherein the polycyano compound is tetracyanodiphenoquinodimethane. 6. The electrophotographic photosensitive member according to claim 1, wherein the polycyano compound is contained in an amount of 0.1 to 1.25 parts by weight per 1 part by weight of the charge generating pigment. 7. The electrophotographic photosensitive member according to claim 1, wherein the charge transfer agent is a triphenylamine electron transfer agent.