JPH03226760A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body superior in reproduction performance of an original red color and in characteristics at the times of preexposure and repeated uses and high in sensitivity and small in residual potential by forming a photosensitive layer containing a specified azo pigment on a conductive substrate. CONSTITUTION:The photosensitive layer formed on the conductive substrate contains the azo pigment represented by formula I in which each of R<1> - R<3> is H, halogen, alkyl, or the like; Cp is a group represented by formula II, III, or the like; each of R<4> and R<5> is alkyl, phenyl, or the like, thus permitting the obtained electrophotographic sensitive body to be superior in reproduction performance of an original red color and in characteristics at the times of preexposure and repeated uses and high in sensitivity and small in residual potential.

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.

(B) Prior Art and its Problems Conventionally, electrophotographic photoreceptors having photosensitive layers containing inorganic photoconductors such as selenium, zinc oxide, and cadmium sulfide as main components have been 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 limitations in manufacturing and handling due to their toxicity. .

On the other hand, an electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductive compound as a main component must be relatively easy to manufacture. 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, poly-N rubinylcarbazole is well known, and it has a 2.4
．． 7-) Electrophotographic photoreceptors having a photosensitive layer mainly composed of a charge transfer complex formed with a Lewis acid such as Lielow 9-fluorenone are not necessarily satisfactory in terms of sensitivity and durability.

On the other hand, in laminated or dispersed function-separated photoreceptors, in which the carrier generation function and the carrier movement function are assigned to separate substances, each material has a wide selection range, and the charging characteristics, sensitivity, and durability are improved. 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, the carrier generation layer made of amorphous selenium has the disadvantage of poor durability.

In addition, various proposals have been made to use organic dyes and pigments as carrier-generating substances. 52-424
Publication No. 1, Japanese Unexamined Patent Publication No. 1983-46558, Special Publication No. 1983
-11945 publication etc. are already publicly known.

However, these azo pigments are not necessarily satisfactory in characteristics such as sensitivity, residual potential, and stability upon repeated use.

By the way, in addition to the above-mentioned characteristics, photoreceptors used in general copying machines that use a halogen lamp or the like as a light source have a maximum spectral sensitivity in the range of about 500 nm to about 600 nm for the red reproducibility of originals. It is desirable that long wavelengths be cut off as sharply as possible.

However, among azo pigments having such spectral sensitivity characteristics, electrophotographic photoreceptors having a photosensitive layer containing azo pigments have high sensitivity, low residual potential, and excellent pre-exposure characteristics and repeatability characteristics. The reality is that it is hardly known.

(C) Purpose of the Invention The purpose of the present invention is to provide excellent red reproducibility of originals, high sensitivity,
An object of the present invention is to provide an electrophotographic photoreceptor having a low residual potential and excellent pre-exposure characteristics and repeated use characteristics.

(D) Structure of the Invention The above object of the present invention is to apply the following general formula C on a conductive support.
This was achieved by an electrophotographic photoreceptor characterized by having a photosensitive layer containing an azo pigment represented by I).

General formula (1) [In the formula, R1, R2 and R3 represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group or a substituted product thereof, and Cp is H 4 6 1 10 Q X is a hydroxy group represents an atomic group necessary to form an aromatic ring or a heterocycle (these rings may be substituted or unsubstituted) by condensing with the benzene ring in the above formula to which Y is bonded, or - R4 and R5 represent an alkyl group, a phenyl group, or a substituted product thereof, and R6 is a hydrogen atom, an alkyl group, a carbamoyl group, a carboxyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, or Represents a substituted or unsubstituted amino group, R7, R@ and R'6 represent an alkyl group, an aromatic ring group, a heterocyclic group or a substituted product thereof, and R9 to R+5 represent a hydrogen atom, an alkyl group, an aromatic group. Represents a cyclic group, a heterocyclic group, or a substituted product thereof.

However, R'' and R'', R'' and R'3, and RI4 and R'' are not hydrogen atoms at the same time.

W represents a divalent aromatic hydrocarbon group or a substituted or unsubstituted heterocyclic divalent group containing a nitrogen atom in the ring. ] That is, in the present invention, by using the azo pigment represented by the general formula (1) as a photoconductive substance constituting the photosensitive layer of an electrophotographic photoreceptor, the azo pigment of the present invention can also be used as an excellent carrier. By utilizing only the generation ability and using it as a carrier generation material in a so-called function-separated electrophotographic photoreceptor in which carrier generation and transfer are performed using separate substances, the film has excellent physical properties, such as charge retention, sensitivity, and An electrophotographic photosensitive material that has excellent electrophotographic properties such as residual potential, has little fatigue deterioration even after repeated use, and exhibits stable properties without changing the above-mentioned properties even when exposed to heat or light. You can create a body.

Specific examples of the azo pigment useful in the present invention represented by the above general formula include those having the following structural formula.

(Left below) (1) (A) (R' = R" = R" = H, 4-phenyl body] (I) (B) (R' = R' = H, R" = 4-CHI,
4- (4-tri(1) [1) (F) (R' = 2' -CI, R" = 2
-OCL, R" = Cl-13,5-(4-1yl)
] The azo pigment represented by the general formula (I) is obtained by converting the divalent amino form represented by the following general formula 1 112 (in the formula, R1 to R2 and R3 are the same as those of the formula (I)) by a conventional method. azotization, and then coupling the corresponding coupler in the presence of an alkali, or the diazonium salt of the divalent amino compound described above in the form of a borofluoride salt or zinc chloride double salt, -
Once isolated, a suitable solvent (e.g. N,N-dimethylformamide, dimethyl sulfoxide, ethanol,
It can be easily synthesized by carrying out a coupling reaction with a coupler in dioxane) in the presence of an organic or inorganic alkali.

Next, a method for synthesizing a representative example of the azo pigment used in the present invention will be shown.

Synthesis Example (?1 Compound 4) 10.9 g of 4-phenylimidazole, 8.1 ml of 4-fluoronitrobenzene and anhydrous sodium carbonate 8.
Dissolve 3g in 11.0ml of DMF and add 1 while stirring.
React at 30° for 200 hours. Pour the reaction solution into ice water,
The precipitated crystals are collected by filtration, washed with water, further washed with methanol, and recrystallized with acetone to obtain 18.5 g of crystals (a).

Melting point 206.5-207.5°, yield 92%.

13 g of crystals of (a) and 40 g of 37% formalin aqueous solution
After reacting for 26 hours at 165°C in a sealed M1 tube, the reaction solution was extracted with ethyl acetate, washed with water, dried, and the solvent was distilled off. The resulting residue was purified by column chromatography (
3.9 g of crystals of b) are obtained.

Melting point 206.5-208.5°, yield 27%.

3.84 g of crystals of composition (b) and potassium dichromate 1.
Dissolve 28g in 50ml of acetic acid and react at 80° for 2.5 hours. The reaction solution is poured into ice water, extracted with ethyl acetate, washed with water, dried, and the solvent is distilled off. The resulting residue is purified by column chromatography to obtain 2.11 g of crystals of (C).

Melting point 157-162°, yield 55%.

Synthesis of Sol (C) Crystal 2.11. g, 2.25 g of 4-nitrobenzyldiethylphosphonate, and 1.04 g of potassium-t-butoxide are reacted in 20 ml DMF for 5.5 hours. The reaction solution is poured into ice water, extracted with ethyl acetate, washed with water, dried, and then the solvent is distilled off. The resulting residue is purified by column chromatography to obtain 0.6 g of crystals of (d).

Melting point 179-182° Yield 20%.

Synthesis of Sol 0.53 g of the crystals from (d) were reduced using 2 g of iron powder and 0.6 ml of acetic acid in a mixed solvent of dioxane and water (e).
Obtain 0.4 g of crystals.

Melting point 69-72° Yield 88%.

(f) Synthesis of Exemplified Compound 4 Dissolve 352 ml of crystals of (e) in 50 ml of DMF;
Add 3 ml of 2N hydrochloric acid and dropwise add a solution of 145 mg of sodium nitrite in 1 ml of water at -10° C. while stirring, and react for 30 minutes to obtain a tetrazonium salt.

The tetrazonium salt solution thus obtained was mixed with 427 μl of 2-hydroxy-3-naphthoic acid p-chloroanilide and 1.6 ml of triethanolamine in DMF 20
ml of the solution was added dropwise to the cooled and stirred medium, and after stirring for about 2 hours, the formed crystals were collected by filtration, and DM
1? , water, and acetone to obtain 525 cm of crystals of the desired exemplified compound 4.

Melting point 330° or higher, yield 76%.

Other azo pigments of the present invention can also be obtained according to the above synthesis examples.

The electrophotographic photoreceptor of the present invention contains the bisazo pigment in the photosensitive layer, and the bisazo pigment can be used in various embodiments. For example, use a bisazo pigment as a binder (
It can be used as a photoconductive layer by dispersing it in a binder) and coating this dispersion on a conductive support. Alternatively, a photosensitive layer can be formed by dispersing a bisazo pigment as a charge generating agent in a charge transporting material and coating this dispersed mixture on a conductive support.

In yet another embodiment, it can be used as a laminated photoreceptor in which a charge generation layer containing a bisazo pigment as a charge generation agent is provided on a conductive support, and a charge transport layer is provided thereon. In this case, the charge generation layer may be formed by depositing an azo pigment on the conductive support, or by dispersing the azo pigment in a binder resin and coating the dispersion. .

Examples of the binder resin used for dispersing the charge generating agent in the above embodiment include polyester resin, acrylic resin, styrene resin, silicone resin, alkyd resin, vinyl chloride-vinyl acetate copolymer resin, and styrene-butadiene copolymer. Coalescence, polyvinyl acetal resin, diallyl phthalate resin, polysulfone resin, polycarbonate resin, acetic acid-bicrotonic acid copolymer resin, polyarylate resin, butyral resin, styrene-maleic anhydride copolymer resin, rosin-phenol modified resin, casein etc.,
These can be used alone or in combination as a copolymer. The amount of these binders to be used is 0.1 to 5 times the weight of the bisazo pigment, preferably 0.2 to 3 times.

Further, as the charge transport material forming the charge transport layer, a known conductive compound can be used.

For example, as the hole transport substance, polyvinylcarbazole, phenanthrene, N-ethylcarbazole, 2.5
-diphenyl-1,3,4-oxadiazole, 2,5
-bis(4-diethylaminophenyl)-1,3,4-
Oxadiazole, 4,4'-bis(diethylamino)
-2,2'dimethyltriphenylmethane, 2,4.5-
) lis(p-diethylaminophenyl)oxazole,
2.5-bis(p-diethylaminophenyl) = 1,
3. 4-) Lyazole, 1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)-2-pyrazoline, p-diethylaminobenzaldehyde-diphenylhydrazone, N-ethyl-carbazole-3-carboxa Examples of the electron transport substance include aldehyde-diphenylhydrazine, and examples of the electron transport substance include 2-nitro-9-fluorenone, 2,7-sinitro-9-fluorenone, 2,4.7-)linitro-9-fluorenone, and 2-nitrobenzothiophenone. , dinitroanthracene, dinitroacridine, dinitroanthraquinone, and the like.

These charge transport substances can be used by being dispersed or dissolved in a binder resin, and the resins mentioned above can be used as the binder resin. The amount of the binder used is 0.1 to 10 times the weight of the charge transport material, preferably 0.2 to 5 times the amount by weight.

Examples of the conductive support used for producing the photoreceptor of the present invention include a metal plate, conductive paper, conductive plastic film, metallized film, metal cylinder, and plastic cylinder treated with metallization or metal foil. and so on. Examples of solvents used for coating these supports by dispersing or dissolving azo pigments and charge transport substances together with binders include toluene, xylene, monochlorobenzene, chloroform, dichloroethane, trichloroethylene, methylene chloride, Dioxane, tetrahydrofuran, ethyl acetate, butyl acetate, methyl cellosolve,
Methyl cellosolve acetate, cyclohexanone, methyl ethyl ketone, dimethyl formamide, dimethyl sulfoxide, ethyl alcohol, propyl alcohol,
Butyl alcohol etc.

(E) Example Next, examples of the present invention will be shown.

Example 1 Exemplary Pigment 4 according to the present invention and the following pigments R-1, R-2, R-3 and R-4 as -1 -2 -3 -4 were each mixed with 1 part by weight of a polyarylate resin. (Unitika U-1
00) was mixed with 100 parts by weight of dichloroethane and dispersed together with glass beads for 2 hours using a paint conditioner device. The pigment dispersion thus obtained was coated with a wire bar on an aluminum support for PS plates (anodized, manufactured by Agfa), and the film thickness was approximately 0.
A charge generating layer of 2-0.3 microns was provided.

Next, a coating solution prepared by dissolving 1 part by weight of p-dibenzylaminobenzaldehyde-diphenylhydrazone and 1 part by weight of polyarylate resin as a charge transport material in 10 parts by weight of dichloroethane is applied onto the charge generation layer using a wire bar. In this way, a laminated photoreceptor having a charge transport layer with a thickness of 15 microns was produced.

Regarding this photoreceptor, an electrostatic recording tester (Kawaguchi Electric type 5p-
428), the following characteristic tests were conducted.

That is, a voltage of -6 KV is applied to the charger to charge the photosensitive layer by corona discharge for 5 seconds, and the potential at that time vo (V
), find the potential Vd (V) after standing for 10 seconds, DD=
Vd/Vox 100 (%) was measured. In addition, the exposure amount E 1/2 (LUX
・Seconds) was calculated. Next, this photoreceptor was heated to 5000 LU.
After exposing it to the light of a fluorescent lamp with an illuminance of
(V), El/2 (LUX ・sec) DD (%)
I asked for The results are shown in Table 1.

The upper row of Table 1 shows the initial characteristics, and the lower row shows the characteristics after light irradiation.

(The following is a blank space.) From the results in Table 1, it can be seen that the photoreceptor using Azo Pigment 4 of the present invention has very good charging potential (■0), sensitivity, and pre-exposure characteristics.

Next, the surface potential after exposing these photoreceptors at an exposure amount of 5QLUX seconds, that is, the residual potential E5° (V)
I asked for Similar measurements were repeated 500 times.

Incidentally, a tungsten lamp was used as a light source to eliminate residual potential, and further exposure was performed at 300 LUX for 0.3 seconds to completely reduce the residual potential to O. The results are shown in Table 2.

(The following is a blank space) From the results in Table 2, it can be seen that the photoreceptor using Azo Pigment 4 of the present invention has excellent repeated use characteristics.

Example 2 Exemplary pigments 11.14 and 17 of the present invention as described above,
For comparison, 2 parts by weight of each of the following pigments R-5, R-6 and R-7 (hereinafter blank) -7 and 1 part by weight of polycarbonate resin (Teijin Kasei Panlite-1250) were added to 50 parts by weight of dichloroethane. and dispersed with paint conditioner for 2 hours. This dispersion was applied onto the surface of an aluminum cylinder having an outer diameter of 60 m+n by a cylindrical pull-up coating method. Film thickness is approximately 0
．． It was 5 microns.

On this charge generation layer, 1 part by weight of 1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, 2 parts by weight of polyester resin (Vylon-200) and 25 parts by weight of dichloroethane were added. A charge transport layer having a thickness of 15 microns was formed by applying the dissolved solution to produce a cylindrical photoreceptor. The charged potential Vo (V) and general sensitivity El/2 (L[IX -5ec) of this photoconductor were determined in the same manner as in Example 1, and then monochromatic light with a wavelength of 600 nm was obtained by spectroscopy of a halogen lamp with a spectrometer. (Surface illuminance at photoreceptor 1 μW
/ctl), the time (seconds) required for the surface potential to decrease to 1/2 of the initial potential was measured, and the half-reduction exposure amount (El/2 <600>) was determined as the spectral sensitivity at 600 nm. The results are shown in Table 3.

From the above results, it was confirmed that all of the photoreceptors of the present invention have higher general sensitivity (and lower red sensitivity, that is, excellent red reproducibility) than the comparative photoreceptors.

(The following is a blank space) Example 3 Exemplary pigment 5.29.53.77.1 according to the present invention described above
01 and 125 For comparison, 1 part by weight of each of the following pigments R-8, polyarylate resin (Unitika U-1)
00) was mixed with 100 parts by weight of dichloroethane and dispersed in the same manner as in Example (1) above to obtain a coating dispersion. Coating was performed in the same manner using an aluminum support for PS plates (anodized, manufactured by Agfa) as a support, and the film thickness was 0. After providing a charge generation layer of 2 to 0.3 microns, a coating solution prepared by dissolving 1 part by weight of p-benzylaminobenzaldehyde-diphenylhydrazone and 1 part by weight of polyarylate resin as a charge transport material in 10 parts by weight of dichloroethane was charged. A laminated photoreceptor having a charge transport layer having a thickness of 15 microns was prepared by coating the same on the generation layer. The white light sensitivity and spectral sensitivity at 600 nm of this photoreceptor were measured in the same manner as in Example 2. The results are shown in Table 4.

(The following is a blank space) From the above results, it is concluded that the photoreceptors of the present invention have higher general sensitivity and lower red sensitivity, that is, superior red reproducibility, than the characteristics of comparative photoreceptors. confirmed.

(F) Effects of the Invention As is clear from the above, the method of the present invention provides an electrophotographic photoreceptor that has excellent red reproducibility of originals, high sensitivity, low residual potential, and excellent pre-exposure characteristics and repeated use characteristics. can be obtained.

Claims (1)

[Scope of Claims] An electrophotographic photoreceptor comprising a photosensitive layer containing an azo pigment represented by the following general formula [I] on a conductive support. General formula [I] ▲ Numerical formulas, chemical formulas, tables, etc. Also, Cp has ▲mathematical formulas, chemical formulas, tables, etc.▼, ▲mathematical formulas, chemical formulas,
There are tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼
, ▲There are mathematical formulas, chemical formulas, tables, etc.▼,▲Mathematical formulas, chemical formulas,
There are tables, etc. ▼ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. represents an atomic group necessary to form an aromatic ring or a heterocycle (these rings may be substituted or unsubstituted), and Y is a ▲ mathematical formula, chemical formula, table, etc. , tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, R^4 and R^5 represent an alkyl group, phenyl group, or a substituent thereof, and R^6 is a hydrogen atom or an alkyl group. ,
Represents a carbamoyl group, carboxyl group, alkoxycarbonyl group, aryloxycarbonyl group, or substituted or unsubstituted amino group, R^7, R^8 and R^1
^6 represents an alkyl group, an aromatic ring group, a heterocyclic group, or a substituent thereof, and R^9 to R^1^5 represent a hydrogen atom, an alkyl group, an aromatic ring group, a heterocyclic group, or a substituent thereof represent the body. However, R^1^0 and R^1^1, R^1^2 and R^1^
3. R^1^4 and R^1^5 are never hydrogen atoms at the same time. W represents a divalent aromatic hydrocarbon group or a substituted or unsubstituted heterocyclic divalent group containing a nitrogen atom in the ring. ]