JPH04353857A - Photosensitive material for electrophotography - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive material having high sensitivity and high durability by incorporating a specified styryl compd. into the photosensitive layer. CONSTITUTION:The photosensitive layer formed on a conductive supporting body contains a styryl compd. of formula I. In formula I, A and B are same or different aryl groups which may have substituents, heterocyclic groups which may have substituents, alkyl groups of 1-4 carbon number, or hydrogen atom. (However, it is not allowed that both of A and B are hydrogen.) R is an aryl group or aralkyl group which may have a substituent, an alkyl group of 1-4 carbon number, or an alkenyl group of 2-4 carbon number. R' is an alkyl group or alkoxy group of 1-2 carbon number. Thereby, the obtd. photosensitive material has excellent stability against temp. and humidity, high electrifying property and causes almost no reduction of photosensitivity when repeatedly used.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor in which a specific styryl compound is contained in a photosensitive layer formed on a conductive support. be.

0002

[Prior Art and Problems to be Solved by the Invention] Conventionally, in electrophotographic technology, inorganic materials such as selenium, cadmium sulfide, amorphous silicon, and zinc oxide have been widely used in the photosensitive layer of electrophotographic photoreceptors. However, in recent years, much research has been conducted on the use of organic photoconductive materials as electrophotographic photoreceptors.

[0003] Here, the basic properties required for an electrophotographic photoreceptor are (1) high chargeability due to corona discharge in a dark place; (2) The resulting corona charge has little attenuation in the dark. (3) Charges are quickly dissipated by light irradiation. (4) There is little residual charge after irradiation with light. (5) There is little increase in residual potential or decrease in initial potential due to repeated use. (6) There is little change in electrophotographic characteristics due to temperature and humidity.

Conventional inorganic electrophotographic photoreceptors such as selenium and cadmium sulfide meet the requirements for photoreceptors in terms of basic properties, but there are manufacturing problems such as high toxicity and film formation. It has disadvantages such as difficulty in plasticity, poor plasticity, and high manufacturing cost. Furthermore, in the future, it is desired to use photoreceptors made of organic materials instead of inorganic materials, since the production of these inorganic materials is limited due to resource depletion, and also from the viewpoint of pollution due to toxicity.

In view of these points, research on electrophotographic photoreceptors made of organic materials has been actively conducted in recent years.
As a result, electrophotographic photoreceptors using various organic materials have been proposed, and some have been put into practical use. Generally speaking, organic materials have better transparency than inorganic materials.
It has advantages such as being lightweight, easy to form a film, having both positive and negative chargeability, and easy to manufacture photoreceptors.

Typical organic electrophotographic photoreceptors that have been proposed so far include polyvinyl carbazole and its dielectric materials, but these do not necessarily have sufficient film properties, plasticity, solubility, adhesive properties, etc. In addition, polyvinylcarbazole is sensitized with a pyrillium salt dye (Japanese Patent Publication No. 48-25658), and polyvinylcarbazole and 2,4,7-trinitrofluorenone are sensitized (US Pat. No. 3,484). , No. 237), but there is still not enough material that satisfies the basic properties required as a photoreceptor, as well as mechanical strength and high durability. Not obtained.

[0007]

[Means for Solving the Problems] An object of the present invention is to provide an electrophotographic photoreceptor having high sensitivity and high durability. In particular, it is an object of the present invention to provide a photoreceptor that has excellent stability against temperature and humidity, has high charging characteristics, and exhibits almost no decrease in photosensitivity even after repeated use.

The present inventors have conducted research on photoconductive materials having high sensitivity and high durability for the above-mentioned purposes, and have found that a styryl compound represented by the following general formula (I) is effective. reached.

[0009]

[C6]

[In the formula, A and B are the same or different and are an aryl group which may have a substituent, a heterocyclic group which may have a substituent, an alkyl group having 1 to 4 carbon atoms, or Hydrogen atom (except when A and B are both hydrogen atoms), R
is an aryl group which may have a substituent, an aralkyl group which may have a substituent, an alkyl group having 1 to 4 carbon atoms, or an alkenyl group having 2 to 4 carbon atoms, and R' is an aryl group which may have a substituent.
2 alkyl or alkoxy groups, respectively. ] An electrophotographic photoreceptor comprising a styryl compound.

The styryl compound of general formula (I) according to the present invention is usually synthesized by the following synthesis process.

3,5-electron donating group (i.e., carbon number 1 to
A suitable halogen compound (for example, an iodobenzene derivative,
N,N-disubstituted, 3,5-dielectron donating group-substituted aniline (formula (VI)) by reacting with benzyl chloride (bromide) derivative, alkyl chloride (bromide)), etc.
get.

[0013]

[C7]

(R and R' have the same meaning as defined in general formula (I)) The aniline derivative represented by formula (A) obtained in this way is treated at the 4-position with phosphorus oxychloride and dimethylformamide or phenylmethylamide. was subjected to a formylation substitution reaction to obtain a 3,5-dielectron donating group-substituted N,N-
A disubstituted aminobenzaldehyde (formula (VII)) is obtained.

[0015]

[Chemical formula 8]

(Each symbol in the formula has the same meaning as above) The styryl compound of the present invention ( I) can be obtained.

[0017]

[Chemical formula 9]

(A and B have the same meaning as defined in general formula (I)) In general formula (I), in the definition of A, B and R, the aryl group of "aryl group which may have a substituent" means an aryl group having 6 to 12 carbon atoms, such as phenyl and naphthyl. Examples of substituents for the aryl group include alkyl groups having 1 to 2 carbon atoms such as methyl, ethyl, methoxy, and ethoxy, or alkoxy groups, and halogen atoms such as chloro and bromine. The number of substituents is preferably 1 or 2.

[0019] In the definition of A and B, the heterocyclic group of "optionally substituted heterocyclic group" refers to a 5- or 6-membered heterocyclic group containing a nitrogen atom and/or a sulfur atom, such as Examples include pyridyl, pyrrolyl, and thiazolyl. These heterocyclic groups may be fused with one or two benzene rings. Examples of substituents for these heterocyclic groups include alkyl groups having 1 to 2 carbon atoms such as methyl and ethyl.

In the definition of A, B, and R, examples of the "alkyl group having 1 to 4 carbon atoms" include methyl, ethyl, propyl, isopropyl, and butyl. In the definition of R, "alkenyl group having 1 to 4 carbon atoms" includes allyl and propenyl.

In the definition of R, the aralkyl in the "aralkyl group which may have a substituent" is phenyl C1-2
Mention may be made of alkyl groups such as benzyl. Examples of the substituent include the same substituents as those on the aryl group.

Specific examples of R include methyl, ethyl, propyl, i-propyl, n-butyl; p-tolyl, m-
Tolyl, p-chlorophenyl, 3,5-xylyl, p-
Methoxyphenyl, p-ethoxyphenyl, phenyl,
1-naphthyl, 2-naphthyl, p-methoxybenzyl,
Examples include p-methylbenzyl, benzyl, and allyl. Among these, p-tolyl, m-tolyl, 3,5-xylyl, p-methoxyphenyl, phenyl, p-methylbenzyl and benzyl are preferred.

As R', substituted electron-donating groups such as methyl group, ethyl group, methoxy group, and ethoxy group were more effective than unsubstituted substances and electron-withdrawing substituted substances such as chloro. Specific examples of A and B include phenyl, 1-naphthyl,
Examples include p-tolyl, methyl, ethyl, benzyl, p-methylbenzyl, and 1-pyridyl. Particularly effective were compounds in which either A or B was a phenyl group or a phenyl group substituted with an electron-donating group.

Next, specific examples of the styryl compound of the present invention represented by the general formula (I) include those having the following structure.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

[Table 5]

[0030]

[Table 6]

[0031]

[Table 7]

[0032]

[Table 8]

Among these exemplified compounds, those which are particularly excellent in electrophotographic properties, cost, and synthesis are those in which R is a benzyl group,
Examples include styryl compounds in which R' is a phenyl group, p-tolyl group, or p-methoxyphenyl group, R' is a methyl group or methoxy group, and A and B are a methyl group, phenyl group, or p-tolyl group.

The electrophotographic photoreceptor according to the present invention is obtained by containing one or more of the above-mentioned compounds, and as a result has extremely high performance. Additionally, other styryl compounds such as β-phenyl-[4-(dibenzylamino)]stilbene, β-phenyl-[4-(
N-ethyl-N-phenylamino)]stilbene, β-
Phenyl-[4-[(di(p-methylphenylamino)
[Stilbene, 1,1-bis(4-diethylaminophenyl)-4,4-diphenylbutadiene), triphenylamine compounds (e.g. 4-methoxy-4'-(4-
It can also contain methoxystyryltriphenylamine, 4-methoxy-4'-styryltriphenylamine), and the like.

Various methods can be considered for using these styryl compounds as electrophotographic photoreceptors. For example, a photoreceptor or a photoconductor may be formed by dissolving or dispersing a styryl compound and a sensitizing dye in a binder resin, with the addition of a chemical sensitizer or an electron-withdrawing compound if necessary, on a conductive support. , a carrier provided mainly with a sensitizing dye or a pigment such as an azo pigment or a phthalocyanine pigment on a conductive support in the form of a laminated structure that can serve as a carrier generation layer with high charge carrier generation efficiency and a carrier transport layer. There is a laminated photoreceptor in which the styryl compound of the present invention is dissolved or dispersed in a binder with the addition of an antioxidant compound or an electron-withdrawing compound if necessary, and is provided as a carrier transport layer on a generation layer. It is possible to apply in either case.

In preparing photoreceptors using the compounds of the present invention, they are applied onto a support such as a metal drum, metal plate, conductively treated paper, or plastic film with the aid of a polymeric film-forming binder. Borrow it and make it into a film. in this case,
In order to further increase the sensitivity, it is desirable to add a sensitizer and a substance that imparts plasticity to the polymerizable film-forming binder as described below to form a uniform photoreceptor film.

Various types of polymerizable film-forming binders can be used depending on the field of use.

That is, in the field of photoreceptors for copying machines or printers, polystyrene resin, polyvinyl acetal resin, polysulfone resin, polycarbonate resin, polyphenylene oxide resin, polyester resin,
Alkyd resins, polyarylate resins, etc. are preferred. These may be used alone or in combination of two or more. Among them, resins such as polystyrene, polycarbonate, polyarylate, and polyphenylene oxide have a volume resistivity of 10 13 Ω or more and are also excellent in film properties, potential characteristics, and the like.

[0039] The amount of these binders added to the styryl compound of the present invention is 0.2 to 20 times, preferably 0.5 to 5 times, by weight, and is 0.5 or less. , there is a drawback that the styryl compound precipitates from the surface of the photoreceptor, and when the amount is 5 times or more, the sensitivity is significantly lowered. Especially alkaline binders are required for use in printing plates. An alkaline binder is an acidic group that is soluble in water or an alcoholic alkaline solvent (including mixed systems), such as an acid anhydride group, a carboxyl group, a phenolic hydroxyl group,
It is a polymeric substance having a sulfonic acid group, a sulfonamide group, or a sulfonimide group. It is preferable that these alkaline binders usually have a high acid value of 100 or more.

[0040] A binder resin having a high acid value is easily soluble or easily swollen in an alkaline solvent. These binder resins include, for example, styrene: maleic anhydride copolymer, vinyl acetate: maleic anhydride copolymer, vinyl acetate: crotonic acid copolymer, methacrylic acid: methacrylic acid ester copolymer, phenolic resin, methacrylate Acid: styrene: methacrylic acid ester copolymer, etc. The ratio of these resins to the photoconductive organic substance may be approximately the same as in the case of a photoreceptor for a copying machine.

Next, the sensitizing dyes added to the photosensitive layer include triphenylmethane dyes such as methyl violet, crystal violet, night blue, and Victoria blue, erythrosine, rhodamine B, rhodamine 3R, and acridine orange. , acridine dyes such as frapeosin, thiazine dyes such as methylene blue and methylene green, oxazine dyes such as capri blue and meldora blue, other cyanine dyes, styryl dyes, pyrylium salt dyes, thiopyrylium salt dyes, etc. There is. In addition, in the photosensitive layer,
Photoconductive pigments that generate charge carriers with extremely high efficiency through light absorption include phthalocyanine pigments such as various metal phthalocyanines, metal-free phthalocyanines, halogenated metal-free phthalocyanines, perylene imides,
Examples include perylene pigments such as perylene acid anhydride, azo pigments such as bisazo pigments and trisazo pigments, and quinacridone pigments and anthraquinone pigments.

In particular, pigments that generate charge carriers include metal-free phthalocyanine pigments, titanyl phthalocyanine pigments,
Those using bisazo pigments containing fluorene and florenone rings, bisazo pigments consisting of aromatic amines, and trisazo pigments provide high sensitivity and provide excellent electrophotographic photoreceptors.

The dyes mentioned above may also be used as charge carrier generating substances. These dyes may be used alone, but in many cases, charge carriers can be generated with even higher efficiency by coexisting with a pigment. In addition to the above-mentioned spectral sensitizers, it is sometimes necessary to add various chemical substances to prevent increases in residual potential, decreases in charging potential, decreases in sensitivity, etc. due to repeated use. .

These substances to be added include 1-chloroanthraquinone, benzoquinone, 2,3-dichloronaphthoquinone, naphthoquinone, 4,4'-dinitrobenzophenone, 4,4'-dichlorobenzophenone, 4-nitrobenzophenone, 4-nitroben Zalmalondinitrile, α-cyano-β-(p-cyanophenyl)ethyl acrylate, 9-anthracenylmethylmalondinitrile,
1-cyano-1-(p-nitrophenyl)-2-(p-
Examples include electron-withdrawing compounds such as (chlorophenyl)ethylene and 2,7-dinitrofluorenone.

In addition, antioxidants, anti-curling agents, leveling agents, and the like may be added to the photoreceptor as necessary.

The styryl compound of the present invention is dissolved or dispersed in an appropriate solvent together with the various additives mentioned above depending on the form of the photoreceptor, and the coating solution is coated on the conductive support mentioned above. , and dry to produce a photoreceptor. As a coating solvent, aromatic hydrocarbons such as benzene, toluene, xylene, and monochlorobenzene, solvents such as methylene chloride, dichloroethane, dioxane, dimethoxymethyl ether, and dimethylformamide may be used alone or in combination of two or more, or as necessary. Alcohols, acetonitrile,
A solvent such as methyl ethyl ketone can be further added and used.

[0047]

EXAMPLES Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited by these in any way.

Synthesis Example 1 (Exemplary Compound No. 47) N,N-
4-N,N-dibenzylamino-3,5-dimethylbenzaldehyde (melting point 135~
136.5°C). Exemplary compound No. 47 (melting point 154.5-155.5°C) can be easily obtained. Note that ethanol was used as the recrystallization solvent.

Synthesis Example 2 (Exemplified Compound No. 8) N,N-di(p-tolyl)-3,5-xylidine was converted to 4-N,N-di(p-tolyl)amino-3 with dimethylformamide and phosphorus oxychloride. , 5-dimethylbenzaldehyde (melting point 126.0-128.0°C) is obtained. The benzaldehyde compound thus obtained, potassium t-butoxide, and Witteich reagent (structural formula (C)-A=hydrogen, B=1
-naphthyl group) in tetrahydrofuran at 0°C to produce exemplified compound No. 8 (melting point 162.5-16
3.5°C) was obtained. Note that recrystallization was performed using ethanol.

Examples 1 to 5 An aluminum vapor-deposited polyester film (thickness: 80μ) was used as a support, and the following structural formula was placed on it.

[0051]

[Chemical formula 10]

A bisazo pigment represented by the following formula was added to a 1% THF solution containing polyvinyl butyral resin (S-LEC B manufactured by Nissin Chemical Industries, Ltd.) in an amount equal to the weight of the resin, and then added to a paint conditioner (manufactured by Red Level Co., Ltd.). Dispersion was carried out for about 2 hours together with glass beads having a diameter of 1.5 mm, and the mixture was coated and dried using a doctor blade method. The film thickness after drying was 0.2μ.

Exemplary compounds of the present invention (No. 4, No. 8, No. 14, No.
46, No. 70) was coated with a 15% solution of 1.2 g of polyarylate resin (Unitika U-100) dissolved in methylene chloride using a squeezing doctor to form a resin-styryl compound solid solution phase (with a dry film thickness of 25 μm). A charge transfer layer) was created.

The laminated electrophotographic photoreceptor thus produced was tested using an electrostatic recording paper tester (SP-428 manufactured by Kawaguchi Denki).
Electrophotographic retention was evaluated. The measurement conditions are (applied potential -6
KV, static No. 3), and the exposure amount E100 (lux seconds) and initial potential V0 (-volt) required to attenuate from -700V to -100V by white light irradiation (irradiation light = 5lux) were measured, and the values were determined. are shown in Table 1.

Furthermore, using the same device, charging and neutralization (static discharge light:
The initial potential V0 (-volt) and E100 (lux seconds) were measured after performing the same operation 10,000 times, with one cycle of irradiation with white light at 40 lux for 1 second.
and E100 changes were investigated. Further, as a comparative example, an electrophotographic photoreceptor was prepared in exactly the same manner except that a styryl compound having the structure shown below was used instead of the styryl compound of the present invention to form a charge transfer layer. In addition, the electrophotographic characteristics of this photoreceptor were measured in the same manner, and the values are shown in Table 1 as Comparative Example 1.

[0056]

[Chemical formula 11]

[0057]

[Table 9]

Table 2 shows that the styryl compound of the present invention has good sensitivity repeatability characteristics, whereas the exemplified styryl compound of Comparative Example 1 has poor sensitivity and a decrease in sensitivity due to repetition and an increase in initial potential V0 due to poor sensitivity. ing.

Example 6 An x-type metal-free phthalocyanine (Fastgen Blue 8, manufactured by Dainippon Ink Co., Ltd.) was deposited on a polyester film deposited with aluminum.
120) Add 0.4 g of PVC and 0.3 g of vinyl acetate copolymer resin (Slex M, manufactured by Sekisui Chemical Co., Ltd.) to 30 ml of ethyl acetate solution, disperse in paint conditioner for about 20 minutes, and apply the doctor blade method. A charge generation layer was formed so that the film thickness after drying was 0.4 μm.

Exemplary compound No. 62 is applied on this charge generation layer.
A photoreceptor having a two-layer structure was prepared by laminating polyarylate layers containing 50% by weight of a styryl compound. The energy required to reduce the 780 nm spectral sensitivity of this photoreceptor by half (E50) and the initial potential (-V0) were found to be extremely high: V0 = 970 (-volt), E50 = 3.0 (erg/cm2). It was a highly sensitive and highly chargeable photoreceptor. In addition, Sharp laser printer (W
D-580P) was modified and this photoconductor was attached to the drum section to perform continuous blank copying (Non Copy Aging).
) was repeated 10,000 times, and the degree of initial potential drop and sensitivity drop was examined. The results are V0 = 960 (-volts), E1/2 =
3.0 (erg/cm2), which showed almost no change in value compared to the first test.

Comparative Example 2 A laminated photoreceptor was prepared in exactly the same manner except that the styryl compound shown in the following structural formula and shown in Japanese Patent Publication No. 63-19867 was used in place of Exemplified Compound No. 62.
The spectral sensitivity in nm, the initial potential, and the degree of decrease in each of the initial potential and spectral sensitivity were investigated by conducting a 10,000-time non-copy test (Non Copy Aging).

As a result, the initial potential (-V) is 940(-
volt) to 920 (-volt), spectral sensitivity (E50)
is 3.4 (erg/cm2) to 4.2 (erg/c
m2).

[0063]

[Chemical formula 12]

Although there was no significant difference in the initial potential and the degree of its decrease, the spectral sensitivity (E50) was
Initial sensitivity tended to be relatively poor. Furthermore, the sensitivity reduction rate after 10,000 repetitions was 3.
%, whereas that of the comparative styryl compound was as high as 24%, and it was found that the sensitivity reduction rate was quite remarkable.

Examples 7 to 10 Alumite processing of the aluminum substrate surface (7 μm of alumite layer)
1 g each of the styryl compound of the present invention was placed on a support of the present invention, and 1.1 g of a polyarylate resin represented by the following structural formula and N,
N-3.5-xylyl-3.4-xylyl-3.4,9
, 10-perylenetetracarboxylimide 0.15g
A solution of 0.05 g of ultraviolet absorber dissolved in methylene chloride (the imide compound was partially dispersed) was applied using an applicator to obtain a single-layer photoreceptor with a dry film thickness of 20 μm.

[0066]

[Chemical formula 13]

The electrophotographic properties of the photoreceptor were thus measured using an electrostatic recording paper tester. The measurement conditions are (applied voltage +
5.5KV, static No. 3). The exposure amount E100 (lux seconds) required to reduce the voltage from +700V to +100V by white light irradiation was measured, and the values are shown in Table 3. Table 3 also shows the degree of decrease in sensitivity (E100) after conducting a blank copy test 10,000 times.

[0068]

[Table 10]

It has been found that the photoreceptor using the styryl compound of the present invention has excellent sensitivity and durability even when positively charged.

Claims (6)

[Claims] Claim 1: A photosensitive layer formed on a conductive support has the general formula (I) [In the formula, A and B are the same or different aryl which may have a substituent] group, a heterocyclic group which may have a substituent, an alkyl group having 1 to 4 carbon atoms, or a hydrogen atom (excluding cases where A and B are both hydrogen atoms), R has a substituent; an aryl group which may have a substituent, an aralkyl group which may have a substituent, an alkyl group having 1 to 4 carbon atoms or an alkenyl group having 2 to 4 carbon atoms, R' is an alkyl or alkoxy group having 1 to 2 carbon atoms; each meaning. ] An electrophotographic photoreceptor comprising a styryl compound. 2. The styryl compound of the general formula (I) has the formula (II) [Chemical formula 2] (wherein R'' is an alkyl or alkoxy group having 1 to 2 carbon atoms or a hydrogen atom, and a is a hydrogen atom having 1 to 4 carbon atoms. The electrophotographic photoreceptor according to claim 1, wherein the electrophotographic photoreceptor is a compound of an alkyl or alkoxy group or a hydrogen atom, and B and R' have the same meanings as above. 3. The styryl compound of general formula (I) has the formula (III): The electrophotographic photoreceptor according to claim 1, which is a compound. 4. A claim in which the styryl compound of general formula (I) is a compound of formula (IV): (wherein a' has the same meaning as a, and other symbols have the same meanings as above) 1. The electrophotographic photoreceptor according to 1. 5. The electrophotographic photoreceptor according to claim 1, wherein the styryl compound of general formula (I) is a compound of formula (V): (wherein each symbol has the same meaning as above). 6. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer contains a carrier transfer substance and a carrier generation substance, and the carrier transfer substance is a styryl compound of general formula (I).