JPH1020528A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an electrophotographic photoreceptor high in sensitivity, good in color-sensitivity and excellent especially in sensitivity than a compd. in which the same kind coupler residual groups are connected by providing a photosensitive layer containing a specified bisazo based compd. on a conductive supporting body. SOLUTION: In the electrophotographic photoreceptor having the photosensitive layer on the conductive supporting body, the bisazo based compd. expressed by formula I is incorporated in the photosensitive layer. In the formula I, Z is expressed by formula II, Y is hydrogen atom, halogen atom, alkyl or alkoxy group. Each R1 and R2 is hydrogen atom, 1-6C fluorine substd. alkyl group substd. with at least more than one fluorine atoms or 1-6C fluorine substd. alkoxy group substd. with at least more than one fluorine atom and may be the same or different with each other. Concretely, trifluoromethyl, perfluoroethyl, tetrafluoroethyl group, etc., are preferable. But the case in which R1 and R2 are hydrogen atoms simultaneously is excluded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic photosensitive member. More specifically, the present invention relates to a highly sensitive electrophotographic photoreceptor containing a novel bisazo compound.

[0002]

2. Description of the Related Art As an electrophotographic photoreceptor, a photoreceptor using an inorganic photoconductive substance such as selenium, cadmium sulfide, or zinc oxide has been used. Organic photoconductive compound (hereinafter referred to as OPC) having many advantages such as easy handling, good image quality, and easy to obtain photoconductors of various shapes such as drums, sheets and belts. The so-called OPC photoreceptor using OPC photoreceptors has been adopted for plain paper copiers and printers, and its ratio is increasing year by year.

[0003]

The OPC photoreceptor has many advantages over the conventional inorganic photoreceptor, but is inferior in sensitivity, durability and the like. Used in the machine field. For this reason, development of OPC excellent in both sensitivity and durability is desired.

[0004]

The present inventors have conducted intensive studies on a novel OPC in order to obtain an electrophotographic photosensitive member having high sensitivity and high durability. As a result, a specific coupler asymmetric bisazo compound is suitable. The inventors have found that the present invention has been achieved. That is, the gist of the present invention is that the following general formula [I]

[0005]

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[In the above formula,

[0007]

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Wherein (Y is a hydrogen atom, a halogen atom,
It represents an alkyl group or an alkoxy group. R ¹ and R ² may be the same or different and each is a hydrogen atom, a fluorine-substituted alkyl group having 1 to 6 carbon atoms substituted with at least one fluorine atom, or at least one fluorine atom. And represents a substituted C1-C6 fluorine-substituted alkoxy group. However, this excludes the case where R ¹ and R ² are simultaneously hydrogen atoms. An electrophotographic photoreceptor comprising a photosensitive layer containing a bisazo compound represented by the following formula:

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The bisazo compound contained in the electrophotographic photoreceptor of the present invention has a structure represented by the general formula [I]. In the general formula [I], R ¹ and R ² may be the same or different, and may be a hydrogen atom, a fluorine-substituted alkyl group having 1 to 6 carbon atoms substituted by at least one fluorine atom, or at least one or more A fluorine-substituted alkoxy group having 1 to 6 carbon atoms, which is substituted by a fluorine atom (except when R ¹ and R ² are simultaneously a hydrogen atom); specifically, a trifluoromethyl group, a perfluoroethyl group, Fluoroethyl group, 1H, 1H-trifluoroethyl group,
Perfluoropropyl group, 1H, 1H-pentafluoropropyl group, 1H, 1H, 3H-tetrafluoropropyl group, 2H-hexafluoropropyl group, perfluorobutyl group, 1H, 1H-heptafluorobutyl group,
H, 1H, 4H-hexafluorobutyl group, perfluoropentyl group, 1H, 1H, 5H-octafluoropentyl group, perfluorohexyl group, trifluoromethoxy group, perfluoroethoxy group, tetrafluoroethoxy group, 2,2 , 2-trifluoroethoxy group, perfluoropropoxy group, 1H, 1H-pentafluoropropoxy group, 1H, 1H, 3H-tetrafluoropropoxy group, 2H-hexafluoropropoxy group, perfluorobutoxy group, 1H, 1H-hepta Fluorobutoxy group,
1H, 1H, 4H-hexafluorobutoxy group, perfluoropentoxy group, 1H, 1H, 5H-octafluoropentyloxy group, perfluorohexyloxy group, etc., among which straight-chain fluorine-substituted alkyl groups, Preferred are a fluoromethyl group, a trifluoromethoxy group, a tetrafluoroethoxy group, a 1H, 1H, 3H-tetrafluoropropoxy group, a 1H, 1H, 5H-octafluoropentyloxy group and the like.

In the general formula [I], Y is a hydrogen atom,
Represents a halogen atom, an alkyl group or an alkoxy group,
Specifically, for example, a halogen atom such as a fluorine atom, a chlorine atom and an iodine atom; a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group and an n-hexyl group Alkyl group; alkoxy group such as methoxy group, ethoxy group, propoxy group and butoxy group. Among them, a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, a methoxy group and the like are preferable. The bisazo compound of the present invention can be produced by various methods, and the first method is represented by the following general formula [III]:

[0011]

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One of the diamines represented by the formula (1) may be protected with a protecting group or converted into a nitro group to make the diazotization reaction impossible, and only the other amine is subjected to a diazotization reaction followed by a coupling reaction. To synthesize the monoazo compound, and then remove the protecting group of the remaining amine or reduce the nitro group to form the amine, and then perform the diazotization reaction, and then use a different coupler as described above. This is a method for producing a bisazo compound represented by the general formula [I] by performing a ring reaction. Second
The method of the following general formula [IV]

[0013]

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[In the above formula, X represents an anionic functional group. Represented by the following general formulas [V] and [VI]

[0015]

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[In the above general formulas [V] and [VI], R ¹ , R
² and Y have the same meanings as in the general formula [I]. And producing a bisazo compound represented by the above general formula [I].

As the bisazo compound of the present invention, a bisazo compound produced by any method can be used.
The method has the disadvantage that the number of reaction steps is large and the production cost of the azo compound is high. In the second method, the manufacturing method is the same as before, and instead of using a single coupler,
The only difference is that two types of couplers are used.
It has the advantage of being easy to manufacture as compared to the first method. However, in the second method, since the couplers are mixed and reacted, the azo compound to be synthesized is not limited to the bisazo compound represented by the general formula [I] having a different coupler, but also the bisazo compound having the same coupler (the following general formula [VII] ] And [VII
I]) may be generated.

[0018]

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[In the above general formulas [VII] and [VIII],
R ¹ , R ² and Z have the same meanings as in the general formula [I]. There is no problem when the mixing ratio of the compound of the above general formula [VII] or [VIII] is small, but when the mixing ratio is large, the performance of the bisazo compound [VII] of the present invention is lower than that of the bisazo compound [I] of the present invention.
And [VIII], it is necessary to select reaction conditions that increase the amount of the bisazo compound [I] as much as possible.

The present inventor has studied on this point, and the reactivity of the coupling reaction differs depending on the structure of the coupler molecule. By appropriately selecting the reaction conditions such as the mixing ratio of the coupler, It has been found that the azo compound of the present invention represented by the general formula [I] can be synthesized with high purity. In other words, the bisazo compound of the present invention
The compound can be easily synthesized by the method described above. When the synthesis reaction is specifically described, the following general formula (IV)

[0021]

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[Wherein X represents an anionic functional group. ]
The tetrazonium salt represented by the following general formula [V] and [V
I]

[0023]

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The mixture of the following general formula [I] is subjected to a coupling reaction by a known method.

[0025]

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[In the above general formulas [V], [VI] and [I],
R ¹ , R ² , Y and Z have the same meanings as in the general formula [I]. Is produced.
Reaction solvents include water and / or dimethylformamide, dimethylacetamide, dimethylsulfoxide, N
Organic solvents such as methylpyrrolidone, methanol, ethanol, isopropanol and the like, and in the presence of a base such as sodium acetate at a temperature of 30 ° C. or less for 30 minutes to 1 hour;
The reaction may be performed for about 0 hours.

The two types of couplers may be mixed in equimolar amounts or a low-reactivity coupler may be used in excess due to a difference in reactivity. One mole of the tetrazonium salt may be used in an amount of 1 to 1.5 moles. It is preferred to react at a ratio. Each coupler can be synthesized by a known method. The coupler represented by the general formula [VI] is, for example, a hydroxynaphthalic anhydride [IX] according to the following reaction formula (a).
And a diamine [X] are heated in an organic solvent such as acetic acid and dehydrated and condensed. (Japanese Patent Publication No. 61-302
No.65)

[0028]

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The coupler [VI] obtained by the above synthesis method is a mixture of isomers. In the present invention, any of the isomers can be used. Usually, the isomer formed by the reaction is not separated and the cup is used as a mixture. Used for ring reaction. Representative electrophotographic photoreceptors of the present invention include bisazo compounds as shown in Table 1 below.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

The electrophotographic photoreceptor of the present invention has a photosensitive layer containing one or more bisazo compounds represented by the above general formula [I]. The photosensitive layer is well known in various forms, but in the photosensitive member of the present invention, any of these types may be used. Particularly preferred is a layered photoreceptor in which the bisazo compound of the present invention is dispersed in a binder as a charge generating material, and this is used as a charge generating layer, including a well-known charge carrier transport medium, and a charge transport layer laminated thereon. A single-layer type photoreceptor in which a well-known charge carrier transporting medium is added to a dispersion layer of a bisazo compound is exemplified.

The bisazo compound represented by the general formula [I] of the present invention has a high charge carrier generation efficiency and a high carrier injection efficiency into the charge carrier transporting medium, and is a laminated type or single layer type function-separated type photoreceptor. Has extremely excellent performance as a charge generation material.

The charge carrier transporting medium used in combination with the bisazo compound of the present invention is generally classified into two types, an electron transporting medium and a hole transporting medium. Both can be used for the photoreceptor of the present invention. Also, a mixture thereof can be used. Nitro groups, cyano groups,
An electron-withdrawing compound having an electron-withdrawing group such as an ester group, for example, 2,4,7-trinitrofluorenone,
Examples include nitrated fluorenone such as 4,5,7-tetranitrofluorenone or tetracyanodimethane. Examples of the hole transport medium include electron-donating organic photoconductive compounds, for example, heterocyclic compounds such as carbazole, indole, imidazole, oxazole, thiazole, oxadiazole, pyrazole, pyrazoline, and thiadiazole; Reel alkane derivatives (for example, JP-A-60-87334);
Triarylamine derivatives such as triphenylamine (for example, JP-A-56-4148, 58-203446); phenylenediamine derivatives (for example, JP-A-54-148546)
No. 110836); N-phenylcarbazole derivatives (Japanese Patent Publication No. 63-18738); stilbene derivatives (for example, JP-A-58-65440, 58-19804).
3,58-198425); hydrazone compounds (for example, JP-A-57-1350, 57-6794).
0,58-108359,54-150128,58-
159,536), and particularly, substituted amino groups such as dialkylamino group and diphenylamino group;
Alternatively, an electron donating group such as an alkoxy group or an alkyl group, or a compound having a large electron donating property substituted by an aromatic ring group substituted by these electron donating groups may be used.
Further, a polymer having a group consisting of these compounds in a main chain or a side chain, such as polyvinylcarbazole, may also be used. And as a preferred compound to be combined with the azo compound of the present invention, the following general formula (II)

[0036]

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[In the above formula, R ³ represents a styryl group which may have a substituent. ]. The electrophotographic photosensitive member of the present invention can be manufactured according to a conventional method. That is, the electrophotographic photoreceptor of the present invention is a laminated type having a charge generation layer and a charge transport layer containing the bisazo compound of the present invention on a conductive support, or a single layer having a photosensitive layer in which a bisazo compound is dispersed. In addition to these, an intermediate layer such as an adhesive layer and a blocking layer, and a layer for improving performance such as electrical characteristics and mechanical characteristics such as a protective layer may be provided.

As the conductive support, any of those used for known electrophotographic photosensitive members can be used. Specifically, for example, a metal drum of aluminum, copper nickel, etc.,
Seat belts or laminates of these metal foils,
An evaporation material is mentioned. Further, plastic films, plastic drums, paper, and the like, which are subjected to conductive treatment by applying a conductive substance such as metal powder, carbon black, copper iodide, and polymer electrolyte together with a suitable binder, may be used. In addition, a conductive plastic sheet or drum containing a conductive substance such as metal powder, carbon black, or carbon fiber, or a plastic film having a conductive metal oxide layer such as tin oxide or indium oxide on its surface. And the like.

In the above-mentioned laminated photoreceptor, a charge generation layer is usually formed on a conductive support, and a charge transport layer is formed thereon, but the structure may be reversed. The charge generation layer is formed by applying and drying a coating solution containing the bisazo compound of the present invention and a binder polymer. The bisazo compound may be dissolved, but is usually applied as a coating solution in a dispersed state. Butylamine as a solvent for preparing a coating solution,
Basic solvents such as ethylenediamine; ethers such as tetrahydrofuran and 1,4-dioxane; ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene and xylene; N, N-dimethylformamide, acetonitrile and N-methylpyrrolidone And aprotic polar solvents such as dimethyl sulfoxide; alcohols such as methanol, ethanol, and isopropanol;
Esters such as ethyl acetate, methyl formate and methyl cellosolve acetate; and chlorinated hydrocarbons such as dichloroethane and chloroform.

When dispersing the bisazo compound, 1 μm
m or less, preferably 0.5 μm or less. As the binder, styrene, vinyl acetate, acrylic acid ester, methacrylic acid ester, vinyl alcohol, polymers and copolymers of vinyl compounds such as ethyl vinyl ether, phenoxy resin, polysulfone, polyvinyl acetal, polycarbonate, polyester, polyamide, polyurethane, Examples include cellulose ester, cellulose ether, epoxy resin, silicon resin and the like.

The ratio of the bisazo compound to the binder polymer of the present invention is not particularly limited, but generally, 5 to 500 parts by weight, preferably 20 to 300 parts by weight, of the binder polymer is used per 100 parts by weight of the bisazo compound. I do. In addition to the above, a dispersion stabilizer, a coating property improving agent, and a dye, an electron-withdrawing compound, and other additives for improving performance may be added to the coating solution. The thickness of the charge generation layer is adjusted to 0.05 to 5 μm, preferably 0.1 to 2 μm.

One or more of the above charge carrier transporting media are dissolved in the above coating solution for the charge generation layer, and the conductive support is adjusted so that the film thickness after drying is 5 to 50 μm, preferably 10 to 30 μm. When applied on top, a single-layer type photoreceptor is obtained. The ratio of the bisazo compound to the binder polymer and the charge carrier transport medium is usually 10
10 to 1000 parts by weight, preferably 30 to 500 parts by weight, and 5 to 1000 parts by weight, preferably 20 to 500 parts by weight of the charge carrier transporting medium, are based on parts by weight.
Parts by weight.

In the laminate type photoreceptor, a charge transport layer is formed by applying a coating solution containing a charge carrier transport medium on the charge generating layer and drying the coating solution. When the charge carrier transporting medium is a polymer compound having a film forming property, a binder polymer may not be particularly used, but may be mixed for improving flexibility and the like. In the case of a low molecular compound, a binder polymer is used for forming a film. The above-mentioned binder polymer is used, and its amount is usually 30 to 300 parts by weight, preferably 40 to 20 parts by weight, per 100 parts by weight of the charge carrier transporting medium.
The range is 0 parts by weight. The thickness of the charge transport layer is 5 to 70 μm
m, preferably in the range of 10 to 50 μm.

In addition to the above, various additives can be used in the charge transport layer in order to improve the performance and the mechanical strength and durability of the coating film. Examples of such additives include electron-withdrawing compounds and dyes, stabilizers such as ultraviolet absorbers and antioxidants, coatability improvers, plasticizers, and crosslinking agents.

[0045]

Next, the present invention will be described more specifically with reference examples and examples, but the present invention is not limited to the following examples unless it exceeds the gist. In the Reference Examples and Examples, “parts” means “parts by weight”.

Reference Example 8.0 g of m-aminophenol was suspended in 65 mL of DMF, 5.8 g of sodium hydroxide was added, and the mixture was stirred at room temperature for 30 minutes. 25.0 g of 1H, 1H, 5H-octafluoropentyl iodide was added dropwise thereto in 1 hour, and the mixture was added at 40 ° C.
For 8 hours. The reaction solution was poured into 300 mL of ice water and extracted with toluene. The organic layer was dried over magnesium sulfate, concentrated under reduced pressure, and dried under reduced pressure to obtain 13.7 g of m-1.
H, 1H, 5H-octafluoroheptyloxyaniline was obtained.

8.0 g of 2-hydroxy-3-naphthoic acid
Was dissolved in toluene (48 mL), and DMF (0.2 mL) was added.
The temperature was raised to 0 ° C. To this, 5.3 g of thionyl chloride was added dropwise, and the mixture was stirred at 70 ° C. for 2 hours and allowed to cool to room temperature. In a separate reaction vessel, the entire amount of the aniline derivative was dissolved in 16 mL of N, N-dimethylacetamide, and 5.7 g of sodium carbonate was dissolved.
Was added. The whole amount of 2-hydroxy-3-naphthoic acid chloride was added dropwise thereto and reacted at room temperature for 2 hours. The solid was separated by filtration, the filtrate was concentrated under reduced pressure, poured into 450 mL of water, and neutralized with a 2N aqueous sodium hydroxide solution. The solvent was removed by decantation, recrystallization from ethanol-water, purification on a silica gel column, and recrystallization from ethanol-water to give 2-hydroxy-3- (3-1H, 1
3.0 g of (H, 5H-octafluoropentyloxyphenyl) carbamoylnaphthalene was obtained.

Production Example 1 2-hydroxy or 5-hydroxy-7H-benzimidazo [2,1-a] benzo [de] isoquinoline-7
-One 0.84 g and 2-hydroxy-3- (3-1H,
1H, 5H-octafluoropentyloxyphenyl)
0.72 g of carbamoylnaphthalene is dissolved in 156 mL of dimethyl sulfoxide, and the solution is kept at a temperature of 18 to 23 ° C., and 2,5-bis (p-aminophenyl)-
A solution of 0.66 g of tetrazonium borohydrofluoride obtained by diazotizing 1,3,4-oxadiazole in 9 mL of dimethyl sulfoxide was added, and then 0.87 g of sodium acetate was added to 3 mL of water with stirring. Was added dropwise, and the mixture was stirred as it was for 3 hours. The deposited precipitate was separated by filtration, washed successively with 10% acetic acid, water, and THF, and then dried to obtain a bisazo compound (No. 1-15) as a target substance
0.42 g was obtained.

Production Examples 2 to 20 Bisazo compounds shown in Table 1 were obtained in the same manner as in Production Example 1, except that two types of couplers and tetrazo components were used.

Examples 1 to 20 Bisazo compounds No. 1 having a structure corresponding to the general formula [I] and exemplified in Table 1. 0.4 parts of each of 1-1 to 1-20 was dispersed together with 30 parts of 4-methoxy-4-methyl-2-pentanone by a sand grinder,
Polyvinyl butyral (made by Sekisui Chemical Co., Ltd.)
0.4 parts of Esrec BH-3) was added and dissolved.
The obtained azo compound dispersion was applied on a 75 μm-thick polyester film deposited on an aluminum vapor-deposited layer with a wire bar so as to have a dry film thickness of 0.4 g / m ^2, and then dried. On the charge generation layer thus obtained,
4'-bis {N- [4- (α-styryl) phenyl]-
A solution prepared by dissolving 90 parts of N-phenylamino diphenoxymethane and 100 parts of a polycarbonate resin (manufactured by Mitsubishi Chemical Corporation, Novarex 7025) in 670 parts of dioxane is applied so that the dry film thickness becomes 28 μm, and the electric charge is applied. A transport layer was formed. Thus, an electrophotographic photosensitive member having a two-layer photosensitive layer was obtained.

Table 3 shows the values of the half-life exposure amount (E _1/2 ) as the sensitivity of these photosensitive members. The numbers of the bisazo compounds in Table 3 are the numbers in Table 1 above. The half-exposure amount was measured for the photoreceptor using an electrostatic copying paper test apparatus (Model SP-428 manufactured by Kawaguchi Electric Works). First, in the dark
Charged by corona discharge at 6.5 kV, then illuminance 5
The substrate was exposed to lux white light, and the amount of exposure required to reduce the surface potential to half of the initial surface potential was determined.

Comparative Example In the following general formula [I], Y is a hydrogen atom and a methyl group, and R ¹ and R ² are a hydrogen atom, an alkyl group,
Bisazo compounds having an alkoxy group No. 21 to 27 were produced in the same manner as in Production Example 1, and photoconductors were produced in the same manner as in Examples 1 to 20. These photosensitive members No. 21-27
Are shown in Table 3 as comparative examples.

[0053]

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[0054]

[Table 4]

[0055]

[Table 5]

As is evident from the results in Table 3, a fluorine-substituted alkyl group or a fluorine-substituted alkoxy group is located at the m-position of the phenyl group of the 2-hydroxy-3-carbamoylphenylnaphthalene derivative as one of the couplers. Shows the same or higher sensitivity as compared to the unsubstituted phenyl group, and is clearly more sensitive than the alkyl- or alkoxy-substituted compound having the corresponding carbon number. It can be seen that the effect appears in the sensitivity.

[0057]

The electrophotographic photoreceptor containing the bisazo compound of the present invention has high sensitivity and good color sensitivity, and is particularly superior in sensitivity to a compound having the same type of coupler residue bonded thereto. Not only electrophotographic plain paper copiers, but also laser printers that require particularly stable performance and reliability,
The photosensitive member is suitable for a photosensitive member for a printer such as a liquid crystal, a shutter printer, and an LED printer.

Claims (2)

[Claims] 1. An electrophotographic photosensitive member having a photosensitive layer on a conductive substrate, wherein the photosensitive layer contains a bisazo compound represented by the following general formula [I]. Embedded image [In the above formula, And (Y represents a hydrogen atom, a halogen atom, an alkyl group,
Alternatively, it represents an alkoxy group. R ¹ and R ² may be the same or different and each is a hydrogen atom, a fluorine-substituted alkyl group having 1 to 6 carbon atoms substituted with at least one fluorine atom, or at least one fluorine atom. And represents a substituted C1-C6 fluorine-substituted alkoxy group. However, this excludes the case where R ¹ and R ² are simultaneously hydrogen atoms. ] 2. An electrophotographic photoreceptor comprising a charge transport layer containing a compound represented by the following general formula [II] and a charge generation layer containing a bisazo compound represented by the following general formula [I]. Embedded image [In the above formula, R ³ represents a styryl group which may have a substituent. ]