JPH05281765A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body having stable initial potential, small dark decay, excellent sensitivity and durability and showing little deterioration caused by repetition of use. CONSTITUTION:This electrophotographic sensitive body has a conductive supporting body and a photosensitive layer as essential components and contains a charge trasnfer material of distyryl compd. expressed by formula in the photosensitive layer. In formula, R<1> is hydrogen or alkyl group or aryl group which may be substd., R<2> and R<3> are same or differnt hydrogen or alkyl groups or alkoxy groups which may be substd., Ar<1> ms an aryl group or heterocyclic group which may be substd., Ar<2> is an arylene group or heterocyclic group which may be substd., and Y is a methylene group, ethylene group, vinylene group, oxygen atom or sulfur atom.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly sensitive and highly durable electrophotographic photoreceptor using a distyryl compound as a charge transport material.

[0002]

2. Description of the Related Art In recent years,
The development of electrophotographic copying machines and printers has been remarkable, and various types of models, types and functions have been developed according to the application, and correspondingly a wide variety of photoconductors have been developed. It's starting. Conventionally, inorganic compounds have been mainly used as electrophotographic photoreceptors from the viewpoint of sensitivity and durability. For example, zinc oxide, cadmium sulfide, selenium, etc. can be mentioned. However, these often use harmful substances, and their disposal poses a problem and causes pollution. Further, when selenium having a good sensitivity is used, it is necessary to form a thin film on a conductive substrate by a vapor deposition method or the like, resulting in poor productivity and high cost.

In recent years, amorphous silicon has attracted attention as a non-polluting inorganic photoconductor, and research and development thereof have been advanced. However, although these are also excellent in sensitivity, the productivity is extremely poor because the plasma CVD method is mainly used when forming a thin film, and the photoreceptor cost and the running cost are large.

On the other hand, the organic photoreceptor can be incinerated,
It has the advantage of being pollution-free, and many of them can be formed into thin films by coating and are easy to mass-produce. Therefore, it has an advantage that the cost can be significantly reduced and that various shapes can be processed according to the application. However, with respect to the organic photoconductor, problems remain in its sensitivity and durability, and it is strongly desired to develop an organic photoconductor with high sensitivity and high durability. Various methods have been proposed as means for improving the sensitivity of the organic photoconductor, but at present, a function-separated photoconductor mainly having a two-layer structure in which the functions are separated into a charge generation layer and a charge transport layer has become mainstream. There is. For example, the charge generated in the charge generation layer by exposure is injected into the charge transport layer, transported through the charge transport layer to the surface, and the surface charge is neutralized to form an electrostatic latent image on the surface of the photoreceptor. To be done. Compared to the single-layer type, the function-separated type has a smaller possibility of trapping the generated charges, and each layer can efficiently transport the charges to the surface of the photoconductor without hindering the function of each layer (US Patent (2803541).

As the organic charge generating material used in the charge generating layer, a compound which absorbs the energy of irradiated light and efficiently generates charges is selected and used.
Azo pigments (JP-A-54-14967), metal-free phthalocyanine pigments (JP-A-60-19146), metal phthalocyanine pigments (JP-A-57-146255), and squarium salts (JP-A-63). -113462 gazette) etc. can be mentioned. As the charge transport material used in the charge transport layer, it is necessary to select a compound having a high charge injection efficiency from the charge generation layer and a high charge mobility in the charge transport layer. For that purpose, a compound having a small ionization potential and a compound which easily generates a cation radical are selected. For example, a triarylamine derivative (JP-A-58-123542) and a hydrazone derivative (JP-A-57-101844) are selected. , Oxadiazole derivatives (JP-B-34-5466), pyrazoline derivatives (JP-B-52-4188), stilbene derivatives (JP-A-58-198043), triphenylmethane derivatives (JP-B-45-555). Gazette), 1, 3-
Butadiene derivatives (JP-A-62-287257) and the like have been proposed.

However, the charge mobility of these charge transport materials is smaller than that of inorganic materials, and the sensitivity is still unsatisfactory. Against this background, many reports have been made on styryl compounds, stilbene compounds and the like among the above charge transport materials because of their ease of synthesis and high charge mobility. For example,
JP-A-63-30851 describes a styryl compound represented by the following general formula.

[0007]

[Chemical 2]

(Wherein R ¹ , R ² , Ar ¹ , Ar ² , A
r ³ represents the one described in the above publication. ) JP-A-63-
In Japanese Patent No. 139354, a stilbene compound represented by the following general formula is described.

[0009]

[Chemical 3]

(In the formula, R ¹ , R ² , X and n represent those described in the above publication.) JP-A-63-269156 describes a distyryl compound represented by the following general formula. There is.

[0011]

[Chemical 4]

(In the formula, R ¹ , Ar ¹ , Ar ² and Ar ³ represent those described in the above publication.) JP-A 1-2425
No. 5 discloses a styryl compound represented by the following general formula.

[0013]

[Chemical 5]

(Wherein R ¹ , R ² , R ³ , R ⁴ , A
r ¹ and X represent those described in the above publication. However, since these compounds are not always satisfactory in charge mobility, they have drawbacks that the sensitivity of the photoreceptor is low and the residual potential is large. As a matter of fact, a material that is practically satisfactory as a charge transport material for an electrophotographic photoreceptor has not been found yet. The object of the present invention is to solve the above problems by using a distyryl compound having a large charge mobility as a charge transport material, thereby providing high sensitivity,
An object is to provide a highly durable electrophotographic photoreceptor.

[0015]

The present inventors have completed the present invention as a result of intensive research to solve the above problems. That is, the gist of the present invention is to provide an electrophotographic photoreceptor having an electroconductive support and a photosensitive layer formed thereon as an essential component, and to use a distyryl compound represented by the general formula (I) as a charge transport material. The present invention relates to an electrophotographic photosensitive member characterized by being contained in a layer.

[0016]

[Chemical 6]

(In the formula, R ¹ represents a hydrogen atom, or an optionally substituted alkyl group or aryl group,
R ² and R ³ are the same or different and each represent a hydrogen atom or an optionally substituted alkyl group or alkoxy group. Ar ¹ represents an optionally substituted aryl group or heterocyclic group, and Ar ² represents an optionally substituted arylene group or heterocyclic group. Y represents a methylene group, an ethylene group, a vinylene group, an oxygen atom or a sulfur atom. )

In the general formula (I), the optionally substituted alkyl group represented by R ¹ includes those having 1 to 6 carbon atoms such as methyl group, ethyl group and n-butyl group. When it is substituted, the substituent is usually an alkoxy group, an aryl group or the like. Examples of the optionally substituted aryl group include a phenyl group and a naphthyl group, and when the aryl group is substituted, the substituent is usually an alkyl group, an alkoxy group, a dialkylamino group, a diarylamino group or the like. R ¹ may be any of these other than hydrogen atom and is not particularly limited, but a hydrogen atom or an optionally substituted aryl group is preferable from the viewpoint of easy production.

R in the general formula (I)², R³Represented by
An optionally substituted alkyl group is methyl.
Group, ethyl group, n-butyl group, etc., usually having 1 to 6 carbon atoms
And when substituted, the substituent is usually
Examples thereof include a lucoxy group and an aryl group. May be replaced
Examples of the alkoxy group include methoxy group and ethoxy group.
As a substituent when it is substituted, usually,
A phenyl group and the like. R ², R³Are the same or different
Other than hydrogen atom, any of these may be used and is not particularly limited.
Although it is not a thing, hydrogen atoms and substituted
Alkyl groups which may be present are preferred.

With respect to the general formula (I), examples of the optionally substituted aryl group represented by Ar ¹ include a phenyl group and a naphthyl group. When the aryl group is substituted, the substituent is usually an alkyl group. , An alkoxy group, a dialkylamino group, a diarylamino group and the like. Examples of the optionally substituted heterocyclic group include a pyridyl group and a carbazolyl group, and when the heterocyclic group is substituted, the substituent is usually an alkyl group, an alkoxy group, an aryl group or the like.
Ar ¹ may be any of these and is not particularly limited, but an aryl group which may be substituted is preferable from the viewpoint of easy production.

With respect to the general formula (I), the arylene group which may be substituted represented by Ar ² includes a phenylene group and a naphthylene group, and when it is substituted, the substituent is usually an alkyl group. , An alkoxy group and the like. Examples of the heterocyclic group which may be substituted include a thienyl group, a divalent carbazole ring group and the like, and in the case of being substituted, the substituent is usually an alkyl group, an alkoxy group,
An aryl group and the like. Ar ² may be any of these and is not particularly limited, but an arylene group which may be substituted may be preferable from the viewpoint of easy production.

The distyryl compounds represented by the general formula (I) are specifically exemplified below (compounds (1) to (65)), but the present invention is not limited thereto.

[0023]

[Chemical 7]

[0024]

[Chemical 8]

[0025]

[Chemical 9]

[0026]

[Chemical 10]

[0027]

[Chemical 11]

[0028]

[Chemical 12]

[0029]

[Chemical 13]

[0030]

[Chemical 14]

[0031]

[Chemical 15]

[0032]

[Chemical 16]

[0033]

[Chemical 17]

[0034]

[Chemical 18]

[0035]

[Chemical 19]

[0036]

[Chemical 20]

[0037]

[Chemical 21]

[0038]

[Chemical formula 22]

[0039]

[Chemical formula 23]

The distyryl compound represented by formula (I) used in the present invention can be easily synthesized by any known method. For example, general formula (II)

[0041]

[Chemical formula 24]

An ethylene compound represented by the formula (wherein R ¹ and Ar ¹ have the same meanings as in the general formula (I))
9-15251) and general formula (III)

[0043]

[Chemical 25]

(In the formula, R ² , R ³ , Ar ² and Y have the same meanings as in the general formula (I). X represents a halogen atom.)
By reacting it with a styryl compound represented by the formula (III) in the presence of a Group VIII transition metal compound, a triarylphosphine and a basic compound (JP-A-58-65275, J. Org. Chem., 37 , 2320 ( 197
2)), the distyryl compound in the present invention can be obtained. Examples of the Group VIII transition metal compound used at this time include cobalt metal, nickel metal, palladium metal, and rhodium metal. Examples of triarylphosphine used include triphenylphosphine, tri-o-tolylphosphine, tris (2-methyl-5-t-butylphenylphosphine), tris (2,
Examples thereof include 5-diisopropylphenyl) phosphine. Examples of the basic substance used include potassium hydroxide, sodium hydroxide, sodium hydrogen carbonate, potassium carbonate, amines and the like. The reaction can be carried out without solvent or in a solvent such as dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone, dioxane, toluene and xylene. The reaction temperature is room temperature to 200 ° C., and the reaction is usually 0.5 to 30.
Finish in time.

The thus-produced distyryl compound represented by the general formula (I) has a broader molecular conjugation, and has a larger charge mobility than the conventionally known distyryl compounds. It also has excellent thermal stability and durability. In addition, these compounds are soluble in many solvents, for example, aromatic solvents such as benzene, toluene, xylene, tetralin, chlorobenzene; dichloromethane, chloroform,
Halogen-based solvents such as trichlorethylene, tetrachloroethylene and carbon tetrachloride; ester-based solvents such as methyl acetate, ethyl acetate, propyl acetate, methyl formate and ethyl formate; ketone-based solvents such as acetone and methyl ethyl ketone;
Diethyl ether, dipropyl ether, dioxane,
Ether solvent such as tetrahydrofuran; methanol,
Alcohol solvents such as ethanol and isopropyl alcohol; dimethylformamide, dimethylacetamide,
It is soluble in dimethyl sulfoxide and the like.

From the above performances, in the electrophotographic photosensitive member of the present invention, by using the distyryl compound represented by the general formula (I) as the charge transport material, the electrophotographic photosensitive member has high sensitivity and high durability. Can be realized.

The electrophotographic photosensitive member of the present invention comprises a conductive support and a photosensitive layer formed thereon as an essential constituent element. In producing such a photosensitive member, for example, a conductive support is used. A charge generation layer and a charge transport layer are formed on the body as a thin film. As the base material of the conductive support, a metal such as aluminum or nickel, a metal vapor-deposited polymer film, a metal laminated polymer film, or the like can be used, and the conductive support is in a drum shape, a sheet shape, or a belt shape. To form.

The charge generating layer is composed of a charge generating material and, if necessary, a binder and an additive, and is formed by vapor deposition or plasma CVD.
It can be prepared by a method such as a coating method or a coating method. The charge generating material is not particularly limited, and any organic material or inorganic material can be suitably used as long as it absorbs light having a specific wavelength and is capable of efficiently generating charges.

Examples of the organic charge generating material include perylene pigments, polycyclic quinone pigments, metal-free phthalocyanine pigments, metal phthalocyanine pigments, bisazo pigments, trisazo pigments, thiapyrylium salts, squarium salts, and azurenium pigments. These can be dispersed mainly in a binder, and a charge generation layer can be formed by coating. As the inorganic charge generating material, selenium, selenium alloy,
Examples thereof include cadmium sulfide, zinc oxide, amorphous silicon, amorphous silicon carbide and the like. Among them, the X-type metal-free phthalocyanine pigment and the oxotitanyl phthalocyanine pigment are most excellent in the wavelength region of the semiconductor laser, and the dibromoanthanthrone pigment is most excellent in the visible light region. The thickness of the formed charge generation layer is preferably 0.1 to 2.0 μm, more preferably 0.1.
It is 1 to 1.0 μm.

Next, a charge transport layer containing the distyryl compound represented by the general formula (I) is formed in a thin film on the charge generation layer. As a thin film forming method, a coating method is mainly used. A distyryl compound represented by the general formula (I) is optionally dissolved in a solvent together with a binder, coated on the charge generation layer, and then dried. Good.

At this time, the distyryl compound represented by the general formula (I) can be used alone or in combination of two or more kinds. In addition, in the present invention, known charge transporting agents such as the above-mentioned triarylamine derivative, hydrazone derivative, oxadiazole derivative, pyrazoline derivative, stilbene derivative, triphenylmethane derivative, and 1,3-butadiene derivative may be used, if necessary. It is also possible to use the material together with the distyryl compound represented by the general formula (I). When used in combination with a known charge transporting material as described above, the amount of the distyryl compound represented by the general formula (I) is 50% by weight or more based on the total amount of the charge transporting material used in terms of sensitivity and durability of the photoreceptor. Is preferred. In addition, the total amount of the charge transport material including the distyryl compound represented by the general formula (I) is usually 0.2 to 10 with respect to the amount of the binder used below.
It is a weight ratio, and preferably 0.5 to 5 weight ratio. If the amount of the charge transport material is less than this range, the concentration of the charge transport material in the charge transport layer will be low and the sensitivity will be poor. On the other hand, if it is larger than this range, the strength of the charge transport layer becomes small, which is not practically preferable.

The solvent used is not particularly limited as long as it is a solvent in which the distyryl compound and the binder used as the case requires, and the charge generation layer does not dissolve. The binder used as necessary is not particularly limited as long as it is an insulating resin, and examples thereof include condensation polymers such as polycarbonate, polyarylate, polyester, polyamide; polyethylene, polystyrene, styrene-
Acrylic copolymer, polyacrylate, polymethacrylate, polyvinyl butyral, polyacrylonitrile,
Addition polymers such as polyacrylamide, acrylonitrile-butadiene copolymer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer; polysulfone, polyether sulfone, silicone resin, etc. are appropriately used. It can be mixed and used.

The means for coating the charge transport layer is not particularly limited, and for example, a dip coater, a bar coater, a calendar coater, a gravure coater, a spin coater, etc. can be appropriately used, and electrodeposition can be performed. It is also possible to paint. The thickness of the charge transport layer thus formed is preferably 10 to 50 μm, more preferably
It is 10 to 30 μm. When the film thickness is larger than 50 μm, it takes much time to transport the charges, and the probability of trapping the charges becomes large, which causes a decrease in sensitivity.
On the other hand, if it is less than 10 μm, the mechanical strength is lowered and the life of the photoreceptor is shortened, which is not preferable.

As described above, an electrophotographic photoreceptor containing the distyryl compound represented by the general formula (I) in the charge transport layer can be prepared, but in the present invention, it is further required between the conductive support and the charge generating layer. Depending on the situation, an undercoat layer, an adhesive layer, a barrier layer, etc. can be provided, and polyvinyl butyral, phenol resin, polyamide, etc. are used for these layers. Further, a surface protective layer may be provided on the surface of the photoconductor.

When the electrophotographic photosensitive member of the present invention thus obtained is used, the surface of the photosensitive member is first negatively charged by a corona charger or the like. After being charged and exposed, a charge is generated in the charge generation layer, a positive charge is injected into the charge transport layer, this is transported through the charge transport layer to the surface, and the negative charge on the surface is neutralized. To be done. On the other hand, negative charges remain in the unexposed areas. In the case of regular development, positively charged toner is used, and the toner is attached to the portion where the negative charge remains to be developed. In the case of reversal development, negatively charged toner is used, and the toner adheres to the portion where the charge is neutralized, and the toner is developed. The electrophotographic photosensitive member of the present invention can be used in any developing method and can provide high image quality.

Further, in the present invention, an electrophotographic photosensitive member can be prepared by first providing a charge transport layer on a conductive support and then providing a charge generating layer thereon. In this case,
First, the surface of the photoconductor is positively charged, and after exposure, the generated negative charge neutralizes the surface charge of the photoconductor, and the positive charge is transported to the conductive support through the charge transport layer. Further, in the present invention, it is also possible to use a single-layer type photoreceptor containing a charge generating material and a charge transporting material in the same layer. It may be dispersed and coated on the support in a film thickness of 10 to 30 μm.

[0057]

[Examples] The present invention will be specifically described below with reference to Synthesis Examples, Examples and Comparative Examples, but the present invention is not limited thereto.

Synthesis Example 1: Synthesis of compound (17) 3 equipped with a stirrer, a cooling pipe, a nitrogen introducing pipe, and a thermometer
00 ml-in a four-neck flask, 5- (2-bromobenzylidene) -5H-dibenzo [a, d] cycloheptene 7.18 g (0.02 mol), 4-diethylaminostyrene 3.50 g (0.02 mol), tri- O-tolylphosphine 0.12 g, palladium acetate 0.045
g, 3.71 g of tributylamine, and 40 g of N-methylpyrrolidone were added, and nitrogen gas was blown thereinto, while stirring 1
The mixture was heated to 40 ° C. and reacted for 15 hours. The reaction solution was cooled to room temperature and 50 ml of ethyl acetate was added. Then, 50 ml of water was added and mixed well, and the ethyl acetate layer was separated. This solution was washed with water three times and dried over anhydrous sodium sulfate, and then ethyl acetate was distilled off. The obtained yellow solid was recrystallized from hexane / ethyl acetate to give the above compound (17).
7.08 g (yield 78%) was obtained.

Synthesis Example 2: Synthesis of compound (54) 3 equipped with a stirrer, cooling pipe, nitrogen introducing pipe, thermometer
00 ml-in a four-necked flask, 7.18 g (0.02 mol) of 5- (4-bromobenzylidene) -5H-dibenzo [a, d] cycloheptene, 6.44 g of 1,1-bis (4-diethylaminophenyl) ethylene (0.02
mol), tri-o-tolylphosphine 0.12 g, palladium acetate 0.045 g, tributylamine 3.71.
g and 40 g of dimethylformamide were added, nitrogen gas was blown thereinto, and the mixture was heated to 130 ° C. with stirring and reacted for 14 hours. The reaction solution is cooled to room temperature and ethyl acetate 50m
1 was added. Then add 50 ml of water and mix well,
The ethyl acetate layer was separated. The ethyl acetate solution was washed 3 times with water and dried over anhydrous sodium sulfate, and then ethyl acetate was distilled off. The obtained yellow solid was recrystallized from hexane / ethyl acetate to give 9.69 g of the compound (54) (yield 81
%) Was obtained.

Example 1 5 g of oxotitanyl phthalocyanine as a charge generating material,
5 g of butyral resin (S-REC BM-2, manufactured by Sekisui Chemical Co., Ltd.) was dissolved in 90 ml of cyclohexanone and kneaded in a ball mill for 24 hours. The obtained dispersion liquid was applied onto an aluminum plate with a bar coater so that the dry film thickness was 0.2 μm, and dried to form a charge generation layer. next,
As a charge transport material, 5 g of the distyryl compound (compound (17)) obtained in Synthesis Example 1 and 5 g of a polycarbonate resin (Lexan 141-111, manufactured by Engineering Plastics Co., Ltd.) were dissolved in 90 ml of dioxane, which was previously formed. A charge coat layer was formed by coating the charge generation layer with a blade coater to a dry film thickness of 25 μm and drying.

The electrophotographic photosensitive member produced in this way was manufactured by Kawaguchi Electric Co., Ltd., an electrostatic copying paper test apparatus EPA.
When charged with a corona voltage of -6.0 kV using -8100, the initial surface potential V ₀ was -775 V. The surface potential V ₅ after standing for 5 seconds in the dark became −685V. Next, when monochromatic light of 790 nm was irradiated to determine the half-exposure amount E _1/2 , it was 0.31 μJ / cm ² , and the residual potential V _R was −5V. Next, perform the above operation 1
After repeating 10,000 times, V ₀ , V ₅ , E _1/2 , and V _R were measured and found to be −770 V, −680 V, and 0.31 respectively.
μJ / cm ² , -9V, while maintaining high sensitivity,
The performance of the photoreceptor was not deteriorated.

Examples 2 to 10 Table 1 obtained in the same manner as in Synthesis Example 1 as charge transport materials
An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the compound shown in 1 was used, and the performance was evaluated. The results are shown in Table 1.

[0063]

[Table 1]

As described above, it was found that the electrophotographic photosensitive member according to the present invention is very excellent in terms of sensitivity and durability both at the first time and after 10,000 times.

Comparative Example 1 An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that the compound (CT-1) was used as the charge transport material instead of the compound (17), and the performance was evaluated. ..

[0066]

[Chemical formula 26]

As a result, V ₀ , V ₅ , E _1/2 and V _R are -695 V, -555 V, 0.58 μJ / cm ² , respectively.
It was -47V. Next, after repeating 10,000 times, V ₀ , V
_5, E _1/2, was measured for V _R, respectively -650
V, −520V, 0.92 μJ / cm ² , and −72V, and the results were inferior in both chargeability and sensitivity.

Comparative Example 2 An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that the compound (CT-2) was used as the charge transport material instead of the compound (17), and the performance was evaluated. ..

[0069]

[Chemical 27]

As a result, V ₀ , V ₅ , E _1/2 and V _R are -730 V, -600 V, 0.51 μJ / cm ² , respectively.
It was -66V. Next, after repeating 10,000 times, V ₀ , V
₅ , E _1/2 , and V _R were measured and found to be −705, respectively.
V, −560 V, 0.86 μJ / cm ² , and −93 V, and the results were inferior in both chargeability and sensitivity.

[0071]

The electrophotographic photosensitive member of the present invention contains a distyryl compound having a large charge mobility in the photosensitive layer as a charge transport material, and therefore, unlike the conventional photosensitive member, the initial potential is stable and the dark decay is small. , With excellent sensitivity.
Further, it has little deterioration due to repeated use and has excellent durability, and can be sufficiently put into practical use as an electrophotographic photoreceptor.

Claims (1)

[Claims] 1. An electrophotographic photoreceptor comprising a conductive support and a photosensitive layer formed thereon as an essential component, wherein a distyryl compound represented by the general formula (I) is used as a charge transport material in the photosensitive layer. An electrophotographic photosensitive member comprising: [Chemical 1] (In the formula, R ¹ represents a hydrogen atom, or an optionally substituted alkyl group or aryl group, and R ² and R ³ are the same or different and are a hydrogen atom, or an optionally substituted alkyl group or Represents an alkoxy group, Ar ¹ represents an optionally substituted aryl group or heterocyclic group, and Ar 1
² represents an optionally substituted arylene group or heterocyclic group. Y represents a methylene group, an ethylene group, a vinylene group, an oxygen atom or a sulfur atom. )