JPS62296149A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve the sensitivity, electric charge characteristic and durability of a photosensitive body by incorporating a specific azo pigment as a carrier generating material into a photosensitive layer. CONSTITUTION:The azo pigment expressed by formula I or the compd. expressed by formula II is incorporated into the photosensitive layer on a conductive substrate. In formula, A denotes H, lower alkyl, phenyl, B denotes H, alkyl, phenyl, allyl, propargyl, etc. R denotes H, halogen, CP denotes a coupler residue. The azo pigment expressed by formula is stable with heat and light and has excellent carrier generating capacity. The photosensitive body having the high sensitivity, small residual potential and excellent durability is, therefore, obtd. if such pigment is used as the carrier generating material.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application Field The present invention relates to an electrophotographic photoreceptor, and more particularly to a novel electrophotographic photoreceptor having a photosensitive layer containing an azo pigment.

More specifically, the present invention relates to a highly durable electrophotographic photoreceptor that has high sensitivity and is suitable for repeated use.

CB) Prior art and its problems ゛Conventionally, electrophotographic photoreceptors used include selenium, zinc oxide,
Those having a photosensitive layer mainly composed of an inorganic photoconductor such as cadmium sulfide were widely known.

However, these are not necessarily satisfactory in terms of sensitivity, thermal stability, moisture resistance, durability, etc. In particular, selenium and cadmium sulfide have restrictions in manufacturing and handling due to their toxicity. there were.

On the other hand, an electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductive compound as a main component must have a relatively simple structure. In addition, they generally have many advantages over selenium photoreceptors, such as superior thermal stability, and have attracted much attention in recent years.

As such an organic photoconductive compound, BoIJ-N
-Vinylcarbazole has been widely used, and 2.
4.7-) Electrophotographic photoreceptors having a photosensitive layer containing as a main component a charge transfer complex formed with a Lewis acid such as dinitro-9-fluorenone are not necessarily satisfactory in terms of sensitivity and durability.

On the other hand, laminated or dispersed functionally separated photoreceptors, in which the carrier generation function and the carrier transport function are assigned to separate substances, have a wide selection range of materials, and have excellent charging characteristics, sensitivity, and durability. It has the advantage that an electrophotographic photoreceptor having arbitrary electrophotographic properties can be produced relatively easily.

Conventionally, various carrier-generating substances or carrier-transferring substances have been proposed.

For example, an electrophotographic photoreceptor has been put into practical use that has a photosensitive layer that combines a carrier generation layer made of amorphous selenium and a carrier transfer layer mainly composed of poly-N-vinylcarbazole.

However, a carrier generation layer made of amorphous selenium has a drawback of poor durability.

In addition, various proposals have been made to use organic dyes and pigments as carrier-generating substances.
Japanese Patent Publication No. 48-30513, Japanese Patent Publication No. 52-4241
Publication No. 1983-46558, Japanese Patent Publication No. 1987-46558
11945 and the like are already known.

However, these azo pigments are not necessarily satisfactory in terms of characteristics such as sensitivity, residual potential, or stability when used repeatedly, and the selection range of carrier transfer substances is also limited, making them difficult to use in electrophotographic processes. The reality is that nothing that fully satisfies the wide range of demands has yet to be obtained.

(C) Object of the Invention An object of the present invention is to provide an electrophotographic photoreceptor containing an azo pigment that is stable to heat and light and has excellent carrier generation ability.

Another object of the present invention is to provide high sensitivity, low residual potential,
Another object of the present invention is to provide an electrophotographic photoreceptor with excellent durability, whose characteristics do not change even after repeated use.

Still another object of the present invention is to provide an electrophotographic photoreceptor containing an azo pigment that can effectively function as a carrier generating substance even in combination with a wide variety of carrier transfer substances.

(D) Structure of the Invention As a result of intensive research to achieve the above object, the present inventors discovered that an azo pigment represented by the following general formula (I) can act as an active ingredient of a photoreceptor, and the present invention This is the completed version.

(In the formula, B is hydrogen, a lower alkyl group, a phenyl group which may contain a substituent), B may contain hydrogen, an alkyl group, a phenyl group which may contain a substituent, an allyl group, a propargyl group, a substituted Mf benzyl group, phenethyl group,
R represents hydrogen or halogen, and is a Cp ketupler residue. ) Cp represents a residue of a coupler that reacts with a diazo group, and a coupler residue having a structure represented by the following general formula (n) is particularly effective.

ゝY' (In the formula, Yi is condensed with a benzene ring to form a polycyclic aromatic ring such as a naphthalene or anthracene ring, or a heterocyclic ring such as a carbazole ring, benzocarbazole ring, or dibendifuran ring by bonding with a benzene ring) R1 represents an alkyl group that may be directly substituted (e.g., methyl group, ethyl group, n-propyl group, 1so-propyl group,
n-butyl group, 5ec-butyl group, amyl group, 1-ofdel group, benzyl group, p-chlorobenzyl us 31
4-dichlorobenzyl Lp-methylbenzyl group, 2-phenylethyl group, α-naphthylmethyl group, β-naphthylmethyl group], aryl group (e.g. phenyl group, tolyl group, xylyl group, biphenyl group, chlorophenyl group, dichlorophenyl group) group, bromphenyl group, methoxyphenyl group, ethoxyphenyl L7') xyphenyl group, phenoxyphenyl group, nitrophenyl group, cyanophenyl group, hydroxyphenyl group, carboxyphenyl M, N,
N-dimethylaminophenyl group, a, α, α-trifluoromethylphenyl group, methylthiophenyl group, α-naphthyl group, β-naphthyl group, etc.) R2 represents R1 and a heterocyclic group (e.g., thiazolyl group, 5-nitrodeazolyl group) group, carbazolyl group, indolyl group, pyrrolyl group, acridyl group, benzo(b)thiophenyl,
benzimidazolyl group, oxasilyl group, chlorooxasilyl group, triazolyl group, piperidyl group, pyridyl group, quinolyl group).

R3 represents 0.5l-NH, and R4 and R5 represent hydrogen, an alkyl group that may be directly substituted, a nitro group, a methoxy group, an ethoxy group, an acetyl group, a cyano group, or a halogen.

Z is a chain hydrocarbon necessary to form a 5-membered ring or a 6-membered ring. That is, in the present invention, by using the azo pigment represented by the general formula (11) as a photoconductive substance constituting the photosensitive layer of an electrophotographic photoreceptor, the advantages of the azo pigment of the present invention can be realized. By utilizing only the carrier generation ability of the carrier and using it as a carrier generation material for a so-called function-separated electrophotographic photoreceptor in which carrier generation and transfer are performed using separate substances, the film has excellent physical properties and charge retention. Power,
It has excellent electrophotographic properties such as sensitivity and residual potential, and even when used repeatedly, there is little fatigue deterioration, and the above-mentioned properties do not change due to heat or light, and it exhibits stable properties. It is possible to create an electrophotographic photoreceptor.

Specific examples of the azo U pigment for use in the present invention represented by the above general formula include those having the following structural formula, but this does not limit the ab pigment of the present invention. do not have.

Exemplary Azo Pigments By using the azo pigments of the present invention as described above, an electrophotographic photoreceptor with extremely high sensitivity can be obtained. Further, among these exemplified azo pigments, there are some that are suitable for photoreceptors having high sensitivity in the range of 750 nm to 800 nm. Specifically, it is exemplified azo pigment 33.39.70. Also 2.3.6.9.12.13.18.25.28.
29.34.35.36.38.40.42.45.4
6.50.51.55.57.59.64.65 is 65
It has high spectral sensitivity from 0 nm to 700 nm.

The azo pigment of the present invention is synthesized by the following synthesis method.

Synthesis method 1 (Reaction formula 1) (Reaction formula 2) (In synthesis method 1, AlBIR has the same meaning as above,
indicates halogen. ) Synthesis method 2 ゛ (Reaction formula 4) (Reaction formula 5) (Reaction formula 6) (In synthesis method 2, A%B and R are as defined above and Pl.

) Reaction formulas 1 and 4 can be easily carried out by heating and refluxing them in a suitable solvent (for example, alcohol) and adding a small amount of hydrochloric acid, if necessary.

Reaction formula 2 is achieved by adding a little more BX, dissolving it in dimethyl sulfoxide, and reacting it in a suitable alkali catalyst.]
Can be synthesized. As the alkali catalyst, caustic soda, caustic potash, sodium acetate, etc. can be used.

Reaction formulas 3 and 6 may be reduced by hydrochloric acid-tin chloride, hydrochloric acid-tin, Fe powder-hydrochloric acid, and fused reduction methods.

Reaction formula 5 can be synthesized by dissolving in sulfuric acid or acetic acid and then reacting with fuming nitric acid.

The diamino and triamino compounds thus obtained are cydiazotized to give diazonium salts by a conventional method, and the diazonium salts and the corresponding couplers are mixed in a suitable organic solvent such as N,N-dimethylformamide with sodium acetate or It can be easily produced by performing a coupling reaction using a basic substance such as triethanolamine.

The electrophotographic photoreceptor of the present invention has a photosensitive layer containing one or more types of azo pigment represented by the general formula (I). Various forms of photosensitive layers are well known, and the photosensitive layer of the electrophotographic photoreceptor of the present invention may be in any of them.

Usually, the photosensitive layer is of the type exemplified below.

■ A photosensitive layer made of an azo pigment ■ A photosensitive layer containing an azo pigment dispersed in a binder ■ A photosensitive layer containing an azo pigment dispersed in a well-known charge transfer substance The azo pigment represented by the above general formula generates charge carriers with extremely high efficiency when it absorbs light. Although the generated carrier can be transferred using an azo pigment as a medium, it is preferable to transfer the generated carrier using a well-known charge transfer material as a medium. From this point of view, photosensitive layers having the forms (1) and (2) are particularly preferred.

Charge transfer substances are generally classified into two categories: electron transfer substances and hole transfer substances, but both can be used in the photosensitive layer of the photoreceptor of the present invention, and a mixture of substances having the same type of function can be used. Mixtures of substances with different functions can also be used. Examples of substances having electron transfer include electron-withdrawing compounds having electron-withdrawing groups such as nitro groups, cyan groups, and ester groups; examples of these include 2.
Nitrated fluorenone such as 4.7-dolinitrofluorenone, 2,4,5.7-tetranitrofluorenone, or tetracyanoquinodimethane, tetracyanoethylene, 2,4,5.7-tetranitroxanthone, 2.4
．． 8-) Compounds such as linitrothioxanthone and polymerized products of these electron-absorbing compounds can be mentioned.

In addition, examples of electron-donating organic photoconductive compounds that can be used as hole nine-movement media include the following.

hydrazones 　2Hs (15) , C2H5 Pyrazolines (6) C2H5 diaryl alkanes n-c, H7 2H5 Alkylene diamines Dibenzylanilines Triphenylamines Diphenylbenzylamines Doaryl alkanes OCR.

Examples include oxadiazoles, anthracenes, oxazoles, and oxathiazoles. Other polymeric compounds include poly-N-vinylcarbazole, halokenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene,
polyvinyl acridine, polyglycidyl carbazole,
Polyvinylacenaphthylene, ethylcarbazole-formaldehyde resin, etc. can also be used.

The carrier transfer substances are not limited to those described here, and when used, one type or a mixture of two or more types of carrier transfer substances can be used.

The electrophotographic photoreceptor of the present invention can be manufactured according to a conventional method.

For example, in an electrophotographic photoreceptor having a photosensitive layer of the type (2) above, a coating solution obtained by dissolving or dispersing the azo pigment represented by the general formula (1) in an appropriate medium is coated on a conductive support. Coating and drying, usually several 0.1 μm to several 10 μm
It can be manufactured by forming a photosensitive layer with a thickness of m.

Examples of media for preparing the coating solution include basic solvents that dissolve azo pigments such as n-butylamine and ethylenediamine; ethers such as tetrahydrofuran and 1,4-dioxane; and ketones such as methyl ethyl ketone and cyclohexanone; toluene and xylene. Aromatic hydrocarbons such as: N
, N-dimethylformamide, acetonitrile, N-methylpyrrolidone, dimethyl sulfoxide and other aprotic polar solvents: methanol, ethanol, ingropanol and other alcohols @: ethyl acetate, methyl acetate, methyl cellosolve acetate and other esters dichloroethane, Examples include media for dispersing azo pigments such as chlorinated hydrocarbons such as chloroform.

When using a medium for dispersing the azo pigment, the particle size of the azo pigment is 5 μm or less, preferably 3 μm or less, and optimally 1 μm or less.
It is necessary to make the particles smaller than μm.

Furthermore, as the conductive support on which the photosensitive layer is formed, any of those employed in well-known electrophotographic photoreceptors can be used.

Specifically, for example, a metal drum made of aluminum, copper, etc.
Examples include sheets, laminates and vapor deposits of these metal foils.

Further examples include plastic films, plastic drums, paper, etc. which are coated with a conductive substance such as metal powder, carbon black, copper iodide, or polymer electrolyte together with a suitable binder to conductivity treatment.

Other examples include plastic sheets and drums that contain conductive substances such as metal powder, carbon black, and carbon fibers and are made conductive.

If a binder is dissolved in the coating liquid used to form the photosensitive layer of the type (2) above, it is possible to produce an electrophotographic photoreceptor having the photosensitive layer of the type (2).

In this case, the medium of the coating liquid is preferably one that dissolves the binder.

The binder includes polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylic esters, and methacrylic esters, phenoxy resins, polysulfones, arylate resins, polycarbonates, polyesters,
Various polymers such as cellulose ester, cellulose ether, urethane resin, epoxy resin, and acrylic polyol resin can be used.

The amount of binder used is usually 0°1 to 5% relative to the azo pigment.
The range is magnified.

In addition, in forming this type of photosensitive layer,
It is preferable that the azo pigment be present in the binder in the form of fine particles, for example, with a particle size of 3 μm or less, particularly 1 μm or less.

Similarly, by dissolving a charge transfer medium in the coating liquid used to form the photosensitive layer of the type (2) above, an electrophotographic photoreceptor having the photosensitive layer of the type (2) above can be manufactured.

As the charge transfer medium, any of those exemplified above can be used.

Apart from charge transport media which can themselves be used as binders, such as polyvinylcarbazole and polyglycidylcarbazole, it is preferred to use other binders.

As the binder, any of those exemplified above can be used.

In this case, the amount of binder used is usually 0 for the azo pigment.
．． The amount of the charge transfer medium used is usually 0.2 to 3.0 times the binder by weight.
Preferably it is in the range of 0.3 to 1.2 times by weight. In the case of a charge transport medium which itself can be used as a binder, it is usually used in an amount of 1 to 10 times the weight of the azo pigment.

In this type of photosensitive layer, it is preferable that the azo pigment is present in the charge transport medium and the binder in the form of fine particles, similarly to the photosensitive layer of type (2) above.

If a coating solution obtained by dissolving a charge transfer medium in a suitable medium is applied onto the photosensitive layer of the types ① to ① above and dried to form a charge transfer layer, the electron Photographic photoreceptors can be manufactured.

In this case, the photosensitive layers of types (1) to (4) above serve as charge generation layers. The charge transfer layer does not necessarily need to be provided above the charge generation layer, but may be provided between the charge generation layer and the conductive support.

However, the former is preferable in terms of durability.

The formation of the charge transfer rigJ layer is carried out in the same manner as the formation of the photosensitive layer (2) above. That is, the coating liquid for forming the photosensitive layer described in (1) above, except that the azo pigment is removed, may be used as the coating liquid.

Typically the charge transport layer is 5-50 μm thick.

Of course, the photosensitive layer of the electrophotographic photoreceptor of the present invention may contain a known sensitizer.

Suitable sensitizers include Lewis acids and dyes that form charge transfer complexes with organic photoconductive materials.

Examples of Lewis acids include quinones such as chloranil, 2,3-dichloro-1,4-naphthoquinone, 2-methylanthraquinone, 1-nitroanthraquinone, 1-chloro-5-nitroanthraquinone, 2-chloroanthraquinone, and phenanthrenequinone. aldehydes such as 4-nitrobenzaldehyde, 9-benzoylanthracene, indanedione, 3,5-dinitrobenzophenone,
Ketones such as 3t3'L5.5'-tetranitrobenzophenone, acid anhydrides such as phthalic anhydride and 4-chloronaphthalic anhydride, tetracyanoethylene, tele7tarmalondinitrile, 4-nitrobenzalmalonenitrile, etc. cyano compound: 3-benzalphta IJ)", 3-(α
-cyano-p-nitrobenzal)phthalide, 3-(α-
Examples include electron-withdrawing compounds such as cyano-p-chlorobenzal) phthalides.

Examples of dyes include triphenylmethane dyes such as methyl violet, brilliant green, and crystal violet, thiazine dyes such as methylene blue, quinone dyes such as quinizarin, cyanine dyes, pyrylium salts, thiapyrylium salts, and benzopyrylium salts.

In addition to these, it may contain inorganic photoconductive fine particles such as selenium and selenium-arsenic alloys, and organic photoconductive pigments such as copper-7 talocyanine pigments and perylene pigments.

Furthermore, the photosensitive layer of the electrophotographic photoreceptor of the present invention may contain a well-known plasticizer in order to improve film formability, flexibility, and mechanical strength. As a plasticizer, phthalate ester,
sic acid ester, epoxy compound, chlorinated paraffin,
Salt-accumulated fatty acid esters, aromatic compounds such as methylnaphthalene, etc. are added.

Moreover, it goes without saying that it may have an adhesive layer, an intermediate layer, and a transparent insulating layer, if necessary.

The photoreceptor using the azo pigment of the present invention has high sensitivity and good color sensitivity, and when used repeatedly, there is little variation in sensitivity and chargeability, little optical fatigue, and extremely high durability. It is.

Further, the photoreceptor of the present invention can be widely used in electrophotographic applications such as photoreceptors for printers using lasers, cathode ray tubes (CRTs), and light emitting diodes (LEDs) as light sources in addition to electrophotographic copying machines.

(B) Examples Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Example 1 Polyester film laminated with aluminum foil (Alpet 85 manufactured by Daido Kako, aluminum film thickness 10 μm)
) on a conductive support consisting of vinyl chloride: vinyl acetate: maleic anhydride copolymer (Eslec MF-
10) Form an intermediate layer with a thickness of 0.05μ, and add the exemplary azo pigment A17 22 and polyarylate resin (Unitika fiU 100) Is' to 1,2-dichloroethane 100- in a paint conditioner. The azo pigment dispersion obtained by dispersing for about 1 hour was added to the intermediate J
A carrier-generated N is formed by coating and drying the film on J to a dry film thickness of 0.3μ, and further a carrier-transfer substance N, N-dibenzylaminopenzaldehyde-1,1-
A solution prepared by dissolving 5t of diphenylhydrazone together with polyarylate resin 71 in 50-1,2-dichloroethane is coated and dried to a film thickness of 18 μm to form a carrier transfer layer, and the electrophotographic photosensitive material of the present invention is The body was created. After storing this photoreceptor at room temperature 30°C in a dark place for -week,
This electrophotographic photoreceptor was tested using an electrostatic paper tester 1'-8P-428.
J (newly manufactured by Kawaguchi Electric), and the following characteristic tests were conducted.

That is, a voltage of '/ is applied to the charger-6 to charge the photosensitive layer by corona discharge for 5 seconds, and the potential at that time Vo(-V
), then 1 g light amount E'(l
ux・sec) was calculated.

Further, the surface potential after exposure at an exposure time of 50 lux·sec, that is, the residual potential Eso (-V) was determined. Similar measurements were repeated 500 times to save labor. In addition, a 300 l tungsten lamp was used as a light source to eliminate residual potential.
Further exposure was performed for 0.3 seconds at ux to completely reduce the residual potential to 0.

The results are shown in Table 1.

Table 1 Examples 2 to 6 Examples of azo pigments A2 and A as carrier generating substances, respectively.
Example 1 except that 8, Melon 28, &36, and A50 were used.
A total of five types of electrophotographic photoreceptors of the present invention were prepared in the same manner as above, and the characteristics of each of them were tested in the same manner.

The results are shown in Table 2.

(Left below) Example 7 On the outer surface of a drum made of aluminum with a diameter of 60 days, an intermediate layer of butyral resin (manufactured by Wako Pure Chemical Industries, Ltd. with a degree of polymerization of about 700) with a thickness of 0.2 μm was formed, and an illustrative example was prepared. Azo pigment%4
A dispersion obtained by adding 21 of 8 to 100 g of tetrahydrofuran in which 2 ff of polyarylate resin was dissolved and dispersing it for about 3 hours using a paint conditioner was applied to the intermediate layer so that the film thickness after drying was 0.5 μm. A carrier generation layer was formed by coating and drying to form a carrier generating layer. A carrier transfer substance represented by the structural formula N,N-diethylaminobenzaldehyde-1-(4'-methoxybenzyl)-
1-phenylhydrazone 10f'i polycarbonate resin (Kijin Panlite L-1250) 12? with 1,
A solution dissolved in 100 g of 2-dichloroethane was applied and dried to a film thickness of 20 μm after drying to form a carrier transfer layer, thereby producing a drum-type electrophotographic photoreceptor according to the present invention.

When this electrophotographic photoconductor was installed in our modified IJ-type electrophotographic copying machine (commercially available) and a copied image was formed, it was found that the contrast was high and the image was clear and faithful to the original. was gotten.

Further, although the copying was repeated 1000 times, a visible image equivalent to that of the first copy was obtained until the end.

Example 8 The reflection spectrum of the drum-type electrophotographic photoreceptor obtained in Example 7 was measured using a spectrophotometer equipped with an integrating sphere (Shimadzu UV-365).
), and it was found that the maximum absorption wavelength of this photoreceptor in the visible region was around 570 nm.

Further, the spectral sensitivity of this photoreceptor between 500 nm and 700 nm was measured using a monochromator, and the results are shown in FIG.

Example 9 Styrene: n-butyl methacrylate: methacrylic acid copolymer (styrene: n-
Butyl methacrylate = 1:2 weight ratio, acid value 250) and the exemplified azo pigment Nogake 33 and N.

N-diethylaminobenzaldehyde-1-phenyl-
1-ethylhydrazone 1.5: 0.25: 1
A solution prepared by dissolving (resin component, hydrazone compound) and dispersing (azo pigment) in dioxane was applied and dried, and a single-layer photoconductor with a film thickness of 7 μm was tested using the electrostatic paper test device described above. An electrophotographic property test was carried out.

Applied voltage +6KV Vo = 480 Volt E' 2.0 lu
It was x e see.

In addition, this photoreceptor is visualized with a developer (toner), and then an alkaline treatment aqueous solution (for example, 3-hydroethanolamine, 10% ammonium carbonate, 15% average molecular weight 190
-210 polyethylene glycol, 5-thibenzyl alcohol), the non-toner-adhered areas are easily eluted,
Next, by washing with water containing sodium silicate, a printing original plate could be easily prepared.

When offset printing was performed using this original plate, it was found that it could withstand printing of about 100,000 sheets.

In addition, in order to obtain a toner visible image (light source: halogen lamp)
The optimum exposure amount was 60 lux * sec, and when creating the printing plate, direct plate making was performed without using any printing material.

[Brief explanation of drawings]

FIG. 1 is a spectral sensitivity curve of the photoreceptor of the present invention in Example 8.

Claims (3)

[Claims] (1) An electrophotographic photoreceptor comprising a photosensitive layer containing an azo pigment represented by the following general formula (I) on a conductive support. ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・( I
) (wherein A is hydrogen, a lower alkyl group, a phenyl group that may contain a substituent, and B is hydrogen, an alkyl group, a phenyl group that may contain a substituent, an allyl group, a propargyl group,
They are a benzyl group or a phenethyl group that may contain a substituent, R represents hydrogen or halogen, and Cp is a coupler residue. ) (2) The electrophotography according to claim 1, wherein the photosensitive layer contains a carrier transfer substance and a carrier generating substance, and the carrier generating substance is an azo pigment represented by the general formula (I). Photoreceptor. (3) The electrophotographic photoreceptor according to claim 1, wherein the azo pigment represented by the general formula (I) is a compound represented by the following structural formula. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, Cp is a coupler residue.)