JPH01315751A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance durability by incorporating a specified biphenyl compound in a photosensitive layer. CONSTITUTION:The photosensitive layer formed on a conductive substrate contains one of the biphenyl compounds represented by formula I, thus permitting potential stability at the time of repeated uses to be enhanced and a remarkable effect on resistance to memory phenomenon remaining after pause to be exhibited, and superior durability to be obtained. In formula I, R<1> is optionally substituted small alkyl, such as methyl, ethyl, propyl, and butyl; R<2> is optionally substituted aralkyl, such as benzyl, phenetyl, naphthylmethyl, and anthrylmethyl; each of R<3> and R<4> is optionally substituted aryl, such as phenyl, naphthyl, and anthryl, optionally same as or different from each other; and each of Ar and Ar' is optionally substituted arylene, such as a divalent benzene, naphthalene, and anthracene ring group, optionally same or different.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor having a low molecular weight organic photoconductor that provides improved electrophotographic properties to the electrophotographic photoreceptor. It is something.

[Prior art]

In recent years, many electrophotographic photoreceptors using organic compounds as photoconductive materials have been developed. Most of the photoconductors that have been put to practical use have a structure in which the photoconductor is functionally separated into a charge generating material and a charge transporting material.

However, one major drawback of these photoreceptors has been that they generally have lower durability than inorganic photoreceptors. Sensitivity as durability.

Residual potential, charging capacity 1 The durability of electrophotographic physical properties such as image blurring, and mechanical durability such as abrasion and scratches on the surface of the photoreceptor due to rubbing, but regarding the durability of electrophotographic physical properties, corona Ozone generated by electrical discharge.

It is known that the main cause is deterioration of the charge transport material contained in the surface layer of the photoreceptor due to NOx etc. or light irradiation.

As an organic charge transport material, U.S. Patent No. 4,150゜9
hydrazone compounds described in US Pat. No. 87, triazole pyrazoline compounds described in US Pat.
Stilbene compounds described in Publication No. 043, etc.
JP-A-61-295558 and JP-A-62-201
A large number of benzidine compounds, such as those described in Japanese Patent No. 447, have been proposed, and although the above-mentioned durability is being improved considerably, the current situation is that it is still not sufficient.

Furthermore, in recent years, a photoconductor pause memory phenomenon has been pointed out as a new problem as the durability of photoconductors has been improved and image quality has been improved. The dormant memory phenomenon is basically a deterioration phenomenon caused by corona products, but after copying is completed, the rotation of the photoreceptor stops, and the charging ability of the part that stops near the corona charger decreases. In the case of normal development, the image density decreases in that area, and in the case of reverse development, the image density increases.

This phenomenon tends to occur after a photoreceptor is used for a long period of time, and has become a serious problem as the lifespan of photoreceptors has increased in recent years.

[Problems to be Solved by the Invention] The purpose of the present invention is to solve not only the durability of electrophotographic properties such as the aforementioned sensitivity, residual potential, and chargeability, but also to solve the problem of dormant memory, which has become a big problem in recent years. The object of the present invention is to provide a novel photoreceptor that does not cause this phenomenon.

[Means for solving problems]

That is, the present invention relates to an electrophotographic photoreceptor having a structure in which a photosensitive layer is laminated on a conductive support, wherein the photosensitive layer contains a biphenyl compound represented by the following general formula. be.

In the formula, R1 represents an alkyl group such as methyl, ethyl, propyl, butyl, which may have a substituent, and R2 represents benzyl, phenethyl, naphthylmethyl, which may have a substituent,
Indicates an aralkyl group such as anthrylmethyl. R3 and R
4 represents an aromatic ring group such as phenyl, naphthyl, anthryl, etc. which may have a substituent, and Ar and Ar' represent a divalent aromatic group such as a benzene ring, naphthalene ring, anthryl ring, etc. which may have a substituent. Indicates a ring group. R', R', Ar and Ar' may be the same or different.

R', R", R", R', Ar and Ar'
Examples of substituents that may have include alkyl groups such as methyl, ethyl, and propyl; alkoxy groups such as methoxy, ethoxy, and propoxy; alkylthio groups such as methylthio, ethylthio, and butylthio; halogen atoms such as fluorine, chlorine, and bromine; Examples include nitro group.

The main cause of the dormant memory phenomenon is HNO generated by the reaction between NOx generated by corona charging and moisture in the atmosphere.
It is thought that this is because 3 has an adverse effect on the photosensitive layer and reduces the charging ability. We focused on the influence of HNO3 on biphenyl compounds, and in particular, we controlled the basicity of the biphenyl compound itself by using specific groups for R1 and R2 of the biphenyl compound having the structure shown in general formula (1). It has been found that the dormant memory phenomenon caused by the influence of HNOa can be prevented, and sensitivity reduction and potential fluctuation can be prevented.

That is, when R1 and R2 in general formula (I) are both aralkyl groups or both aryl groups, the basicity of the biphenyl compound itself is weak, so HN Oa
If the photosensitive layer is, for example, a charge generation layer and a charge transport layer, HNO3 passes through the charge transport layer and reaches the interface of the charge generation layer, reducing the charging ability and causing a dormant memory phenomenon. Put it away. In addition, when R1 and R2 are both alkyl groups, the biphenyl compound itself has strong basicity, so it forms salts with HNO3, and the biphenyl compound itself deteriorates, resulting in decreased sensitivity and wide potential fluctuations during durability ( Become.

On the other hand, when R1 is an alkyl group and R2 is an aralkyl group as in the present invention, the basicity is moderately controlled and becomes intermediate between the previous two cases, and although some HNO3 is adsorbed, salt formation is still possible. However, with time, HNO
Since desorption of 3 also occurs, HNO3 does not reach the charge generation layer interface, and the biphenyl compound itself is not degraded by HNO3. Therefore, it is possible to prevent the pause memory phenomenon, and to prevent a decrease in sensitivity and potential fluctuations during durability.

Representative examples of the compounds represented by the general formula [I] are listed below.

Compound example> CI]3 2H5 SCH3 Among these compounds, R1 is selected from the group consisting of methyl group, ethyl group and propyl group, from the viewpoint of extremely excellent prevention of dormant memory and prevention of sensitivity decrease and potential fluctuation. R1 is preferably a group selected from a benzyl group, a phenethyl group and a cafthylmethyl group, and in particular R1 is a methyl group or an ethyl group,
R2 is preferably a benzyl group.

Further, R3 and R4 are preferably phenyl groups, and Ar and Ar' are preferably divalent benzene ring groups.

In particular, among these, R', R", R", R',
A group in which Ar and Ar' are all unsubstituted is preferred.

, Next, a synthesis example of the above compound will be shown.

(Synthesis method of Compound Example No. (1)) 5.70 g of 4-(N-methylamino)-4'-diphenylaminobiphenyl obtained by monomethylating 4-amino-4'-diphenylaminobiphenyl by a known method.
(16,3 mmoj!) in anhydrous tetrahydrofuran 4
Dissolve in 0 mf and add 0.72 g (18,0 mmoj) of oily sodium hydride (content 60%) while stirring under water cooling.
! ) was added slowly. After addition, return to room temperature 15
After stirring for a minute, benzyl bromide 3.08 g (18,0 mmo
A) was slowly added dropwise, and after the completion of the addition, the mixture was stirred at room temperature for 30 minutes, and then heated and stirred for an additional 2 hours. After the reaction is complete, pour the reaction solution into water at 200mA! After extraction with ethyl acetate and drying over anhydrous magnesium sulfate, the solvent was evaporated to dryness under reduced pressure, and the precipitated crystals were purified by recrystallization to obtain 6.91 g of Exemplified Compound (1). Elemental analysis was as follows as C32H2B N2.

C (%) H (%) N (%) Calculated value 87
．． 23 6.41 6.36 Actual value 87.20
6.45 6.35 Infrared absorption spectrum (KB
(Tablet method) is shown in FIG.

Note that compounds other than those on the synthesis side are generally synthesized using the same method.

In a preferred embodiment of the present invention, a compound represented by the above general formula [l] is used as a charge transport substance contained in the charge transport layer of an electrophotographic photoreceptor in which the photosensitive layer is functionally separated into a charge generation layer and a charge transport layer. be able to.

The charge transport layer according to the present invention is preferably formed by applying a solution prepared by dissolving the compound represented by the above general formula and a binder in an appropriate solvent and drying the solution. Examples of the binder used here include polyarylate resin, polysulfone resin, polyamide resin, acrylic resin, acrylonitrile resin, methacrylic resin, and vinyl chloride resin.

Vinyl acetate resin, phenolic resin, epoxy resin.

polyester resin, alkyd resin, polycarbonate,
Polyurethane or copolymer resins, e.g. styrene-
Mention may be made of butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, and the like. In addition to such insulating polymers, organic photoconductive polymers such as polyvinylcarbazole, polyvinylanthracene, and polyvinylpyrene can also be used.

The blending ratio of the binder and the charge transport material of the present invention is preferably 10 to 500 parts by weight of the charge transport material per 100 parts by weight of the binder.

The charge transport layer is electrically connected to the charge generation layer below and has the function of receiving charge carriers injected from the charge generation layer in the presence of an electric field and transporting these charge carriers to the surface. ing. In this case, this charge transport layer may be laminated on (or under) the charge generation layer. However, the charge transport layer may be laminated on the charge generation layer. It is desirable to be present.

Since this charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. Generally, it is 5 to 40 μm, but the preferred range is 10 μm.
~30 μm.

The organic solvent used when forming such an electric field transport layer is
The binder varies depending on the type of binder used, and it is preferable to select one that does not dissolve the charge generation layer or underlying subbing layer. Specific organic solvents include alcohols such as methanol, ethanol, and impropatol, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide. sulfoxides such as tetrahydrofuran, dioxane, ethers such as ethylene glycol methyl ether, esters such as methyl acetate and ethyl acetate, aliphatic halogenated compounds such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, and trichloroethylene. Hydrocarbons or aromatics such as benzene, toluene, xylene, monochlorobenzene, dichlorobenzene, etc. can be used.

Coating can be performed using a known coating method such as a dip coating method, a spray coating method, or a blade coating method. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying is generally preferably carried out at a temperature of 30° C. to 200° C. for a period of time ranging from 5 minutes to 2 hours, either stationary or under ventilation.

The charge transport layer of the present invention may contain various additives. For example, diphenyl.

Plasticizers such as m-terphenyl and dibutyl phthalate,
Surface lubricants such as silicone oil, graft type silicone polymers, various fluorocarbons, potential stabilizers such as dicyanovinyl compounds and carbazole derivatives, β-carotene, Ni complexes, 1,4-diazabicyclo(2,2,2
) Antioxidants such as octane can be mentioned.

The charge generation layer used in the present invention is an inorganic charge generation substance such as selenium, selenium-tellurium, or amorphous silicon, biryllium dye, thiapyrylium dye, azulenium dye, or thiacyanine dye.

Cationic dyes such as quinocyanine dyes and azulenium dyes, polycyclic quinone pigments such as squbarium salt dyes, phthalocyanine pigments, anthorone pigments, dibenzpyrenequinone pigments, and pyranthrone pigments, indigo pigments, and quinacridone pigments. Materials selected from organic charge generating substances such as , azo pigments, etc. can be used alone or in combination for the vapor deposited layer or coating layer.

Among the charge-generating substances used in the present invention, there are a wide variety of azo pigments in particular, but typical structural examples of particularly effective azo pigments are shown below.

The general formula of azo pigments is that the central skeleton is A as shown below.
.

A(-N=N-Cp)n If a portion of the coupler is expressed as Cp (here, n=2 or 3), the following are specific examples of A.

8-11 Further, specific examples of Cp include Cp-2 Cp-a Cp-5 O Cp-6 and the like. The central skeleton A and the coupler Cp form a pigment serving as a charge-generating substance by appropriate combination.

The charge-generating layer can be formed by dispersing the above-mentioned charge-generating substance in a suitable binder and coating it on a support, or can be obtained by forming a vapor-deposited film using a vacuum evaporation device. You can also do it.

The binder can be selected from a wide variety of insulating resins and organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylpyrene. Preferably polyvinyl butyral.

Polyarylates (condensation polymers of bisphenol A and phthalic acid, etc.), polycarbonates, polyesters.

Examples include insulating resins such as polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, cellulose resin, urethane resin, epoxy resin, and polyvinyl alcohol. The resin contained in the charge generation layer is
A content of 80% by weight or less, preferably 40% by weight or less is suitable. Organic solvents used during coating include alcohols and ketones.

amides, sulfoxides, ethers, esters,
Aliphatic halogenated hydrocarbons or aromatics can be used.

The charge generation layer contains as much of the organic photoconductor as possible to obtain sufficient absorbance and a thin film layer, e.g. 5 μm, to inject carriers into the charge transport layer within the lifetime of the generated charge carriers. Below, preferably 0.01-1
It is preferable to form a thin film layer having a thickness of μm.

A photosensitive layer having such a laminated structure of a charge generation layer and a charge transport layer is provided on a conductive support.

As the conductive support, materials that have conductivity themselves, such as aluminum, aluminum alloy, stainless steel, etc., can be used, and in addition, aluminum, aluminum alloy, and indium oxide can be used.

Plastics having a layer formed with tin oxide or the like by vacuum evaporation, supports in which conductive particles are coated on plastic or the above-mentioned conductive support together with a suitable binder, plastics or paper impregnated with conductive particles. A support, a plastic having a conductive polymer, etc. can be used.

A subbing layer having barrier and adhesive functions can also be provided between the conductive support and the photosensitive layer. The subbing layer is casein, polyvinyl alcohol, nitrocellulose, and ethylene-acrylic acid copolymer.

It can be formed from polyamide, aluminum oxide, etc.

The thickness of the subbing layer is 0.1 to 5 μm, preferably 0.5 to 5 μm.
3 μm is appropriate.

The photosensitive layer may be a single layer type photosensitive layer containing the above-mentioned charge generating substance and the charge transporting substance represented by the general formula [1] in the same layer. In this case, the thickness of the photosensitive layer is 10 to 5
0 μm1, particularly preferably 15 to 30 μm.

The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines, but also for laser printers, CRT printers,
It can also be widely used in electrophotographic application fields such as electrophotographic plate making systems.

According to the present invention, it is possible to provide a highly sensitive electrophotographic photoreceptor, and it not only has the advantage of having small fluctuations in bright area potential and dark area potential when repeatedly charged and exposed, but also has the advantage of having the above-mentioned It has the advantage of not causing the dormant memory phenomenon.

The present invention will be described below with reference to Examples, but the present invention is not limited thereto.

〔Example〕

Example 1 An aluminum cylinder with a diameter of 80 mm and a length of 360 mm was used as a conductive support, and a polyamide resin (
Product name Amiran CM-8000. A 5% methanol solution (manufactured by Toshi Co., Ltd.) was applied by dipping to form a 0.5 μm thick subbing layer. Next, as a charge generating substance, 10 parts (by weight, the same applies hereinafter) of a disazo pigment having the following structural formula, 6 parts of polyvinyl butyral resin (trade name: S-LEC BL-3, manufactured by Sekisui Chemical Co., Ltd.), and 50 parts of cyclohexanone were added using glass beads. Dispersed using a sand mill device. 100 parts of methyl ethyl ketone was added to this dispersion and applied onto the undercoat layer to form a charge generation layer having a thickness of 0.2 μm.

Next, 10 parts of the exemplified compound (1) as a charge transport material was added to polycarbonate resin (trade name Panlite L-125).
A solution prepared by dissolving 10 parts (manufactured by Teijin Kasei) in 50 parts of dichloromethane and 10 parts of monochlorobenzene was coated on the charge generation layer to form a charge transport layer with a thickness of 19 μm, thereby producing a photoreceptor drum.

Examples 2 to 6 Exemplary compound (1) used in Example 1 as a charge transport substance
Instead of, exemplified compounds (5), (13), (1
9).

A photosensitive drum was manufactured in the same manner as in Example 1 except that (20) and (25) were used.

Comparative Examples 1 to 4 Photoreceptor drums were manufactured in the same manner as in Example 1, except that the following structural formulas (26) to (29) were used as charge transport materials.

Blade intrusion fi1. omm.

It was installed in a Canon copier NP-3525 modified to have a cleaning roller relative speed of 106%, and its characteristics were evaluated as follows. First, latent image conditions were set so that the dark potential (VD) and bright potential (VL) of the photoreceptor were -650V and -150V, respectively. The image exposure amount at that time was determined and used as the initial sensitivity.

Next, the potential was measured after 5,000 sheets were continuously copied. and the rate of change in vL was determined. For example, the rate of change in vI) of 2% means that we want to change 2% of 650V, that is, 13V.

Thereafter, the photoreceptor was left in a copying machine, and the surface potential was measured after 10 hours.

During this time, the part of the photoconductor located directly under the corona charger was marked and the difference (△V) from other parts was marked.
o) was calculated. Further, 5000 sheets were continuously copied (a total of 6 copies of xo and oo) and the same settings as above were made. The portion of the photoreceptor located directly below the corona charger is made to be the same as in the case of the initial 5,000 sheets. The results are shown in Table 1.

As is clear from Table 1, when the compound of the present invention is used in the charge transport layer, sensitivity and durable potential fluctuation (V in Table 1, v
It can be seen that not only is the change rate of L (change rate of L) excellent, but also the potential fluctuation (ΔV[)) under the charger, which has become a problem in recent years, is extremely small.

Example 7 3 parts of 4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium perchlorate and poly(4,4
'-isopropylidene diphenylene carbonate) 3
After fully dissolving 1 part in 200 mj7 of dichloromethane,
Toluene 1,000m7! was added to precipitate the eutectic complex. After filtering off this precipitate, dichloromethane was added to redissolve it, and then 100 mj of n-hexane was added to this solution. was added to obtain a precipitate of a eutectic complex. 5 g of this eutectic complex was added to 95 ml of a methanol solution containing 2 g of polyvinyl butyral.
rrl and dispersed in a ball mill for 6 hours. This dispersion was applied onto an amino board having a casein layer so that the film thickness after drying was 0.
．． A charge generation layer was formed by coating with a Mayer bar to a thickness of 4 μm.

Next, 10% of the above-mentioned exemplary compound (11) was added as a charge transport material.
10 parts of poly(4,4-isopropylidene diphenylene carbonate) and 50 parts of dichloromethane.

A charge transport layer coating solution was prepared by dissolving in 10 parts of monochlorobenzene. This was coated on the charge generation layer using a Mayer bar so that the film thickness after drying was 19 μm to produce a photoreceptor. Example 1 The photoreceptor manufactured in this way was attached to the photosensitive drum cylinder used in Example 1.
The electrophotographic properties were evaluated using the same method as described above.

Comparative Example 5 For comparison, a photoreceptor was produced in the same manner using the following structural formula (30) in place of the exemplified compound (11) and evaluated in the same manner.

The results are shown in Table 2.

Example 8 Soluble nylon (6-66-610-12
A 5% methanol solution of (quaternary nylon copolymer) was applied to form an undercoat layer having a dry film thickness of 0.7 μm.

Next, 5 g of a disazo pigment represented by the following structural formula as a charge generating substance was dispersed in 95 ml of tetrahydrofuran using a sand mill for 200 hours. Next, the exemplified compound (14
) 5g and 10g of bisphenol Z type polycarbonate resin (viscosity average molecular weight 30,000) and 30m of monochlorobenzene I! This solution was added to the previously formed dispersion and further dispersed for 2 hours using a sand mill.

This dispersion was applied to the previously formed subbing layer so that the film thickness after drying was 2.
It was coated with a Mayer bar to a thickness of 0 μm, dried, and a single-layer type photosensitive layer was formed. The thus produced photoreceptor was attached to the photosensitive drum cylinder used in Example 1, and the electrophotographic properties were evaluated in the same manner as in Example 1.

Comparative Example 5 A photoreceptor was produced in the same manner as in Example 8, except that the following structural formula (31) was used in place of the exemplary compound (14) used in Example 8, and evaluated in the same manner.

The results are shown in Table 3.

〔Effect of the invention〕

As described above, the electrophotographic photoreceptor containing the compound according to the present invention has good potential stability during durability, and is particularly effective against the dormant memory phenomenon that has become a problem in recent years. It is possible to provide a photographic photoreceptor.

[Brief explanation of the drawing]

FIG. 1 shows an infrared absorption spectrum diagram of an exemplary compound in the present invention.

Claims (1)

[Claims] (1) An electrophotographic photoreceptor having a structure in which a photosensitive layer is laminated on a conductive support, wherein the photosensitive layer contains a biphenyl compound represented by the following general formula. General formula▲There are mathematical formulas, chemical formulas, tables, etc.▼[I] [In the formula, R^1 represents an alkyl group, and R^2 represents an aralkyl group. R^3 and R^4 represent an aromatic ring group, and A
r and Ar' represent a divalent aromatic ring group. ]