JPH053586B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing an azo pigment, and more particularly, to a method for producing a fine particulate azo pigment suitable for electrophotographic photoreceptors. BACKGROUND ART Conventionally, as electrophotographic photoreceptors made of inorganic photoconductive materials, those using selenium, cadmium sulfide, zinc oxide, etc. have been widely used. On the other hand, electrophotographic photoreceptors made of organic photoconductive substances include photoconductive polymers typified by poly-N-vinylcarbazole and 2,5-bis(P-diethylaminophenyl)-1,3,4-oxa Those using low-molecular organic photoconductive substances such as diazole, and furthermore, those in which such organic photoconductive substances are combined with various dyes and pigments are known. Electrophotographic photoreceptors using organic photoconductive substances have good film-forming properties, can be produced by coating, have extremely high productivity, and have the advantage of being able to provide inexpensive photoreceptors. Further, it has the advantage that color sensitivity can be freely controlled by selecting the sensitizer such as dye or pigment to be used, and a wide range of studies have been carried out to date. In particular, recently, with the development of a functionally separated photoreceptor in which an organic photoconductive pigment is used as a charge generation layer and a so-called charge transport layer made of the aforementioned photoconductive polymer or a low-molecular organic photoconductive substance is laminated, Significant improvements have been made in the sensitivity and durability, which were considered to be drawbacks of conventional organic electrophotographic photoreceptors, and they are now being put into practical use. Furthermore, various compounds and pigments that are suitable for functionally separated photoreceptors have also been discovered. In particular, azo pigments have excellent properties as charge-generating substances and are easy to manufacture, so their development is active and a large number of compounds have been proposed. On the other hand, since such a functionally separated photoreceptor is composed of at least two layers, a charge generation layer and a charge transport layer, charge carriers generated by light absorption in the charge generation layer are injected into the charge transport layer, and are distributed on the surface of the photoreceptor. This causes the charge to disappear and creates an electrostatic contrast. The sensitivity of this type of photoreceptor is affected by the particle size of the charge-generating substance contained in the charge-generating layer, and electrophotographic photoreceptors containing a large amount of coarse particles have a reduced hiding power. Not only does this cause a decrease in the number of carriers generated, but also a decrease in carrier mobility due to an increase in porosity due to coarse particles, and the large unevenness of the surface of the charge generation layer reduces the efficiency of carrier injection into the charge transport layer. It has many drawbacks in terms of sensitivity, and also has the drawback of worsening potential stability during long-term use. Generally, it is about 1μ or less, preferably 0.5μ or less, and more preferably the following: As can be seen from the examples, it is desirable to use a charge generating material with a particle size of 0.2μ or less. For this reason, in the conventional manufacturing method, after refining the pigment or dye obtained through a synthetic reaction, the powder is heated and dried for several hours together with a binder using a sand mill, ball mill, or attritor. A method is adopted in which the particles are micronized to about 1 μm or less, preferably in the form of fine particles. However, in conventional methods, pigment particles become hard secondary aggregates during drying, making it difficult to disperse them to the desired particle size.In order to prevent secondary agglomeration, pigment particles are easily dispersed by drying under reduced pressure, freeze drying, etc. Even if the pigment is made into a dry pigment or dispersed without drying into a paste pigment with a solvent, if the primary particles formed by the reaction of the pigment are large, it is difficult to disperse them to a smaller particle size. I had a problem. Problems to be Solved by the Invention An object of the present invention is to provide a method for producing a fine particulate azo pigment suitable for electrophotographic photoreceptors. Means and Effects for Solving the Problems In order to achieve the above object, the present inventors investigated a method for producing fine particulate azo pigments, and found that by using an excessive amount of coupler during the coupling reaction, the primary particle size could be significantly reduced. Small pigment particles are produced,
It has been discovered that an electrophotographic photoreceptor using this fine particle pigment exhibits extremely improved sensitivity and durable potential stability, and the present invention has been achieved. The amount of coupler used in the coupling reaction is stoichiometrically 1 mole per 1 mole of amino groups in the amine of the substrate, but generally the coupler is used in a slight excess of 1 mole of amino groups. The amount used is about 1.05 to 1.1 times the mole. The present inventors synthesized an azo pigment by increasing the amount of excess coupler, and found that the particle size of the resulting pigment after dispersion became smaller as the amount of coupler increased. This is achieved by using a large amount of couplers.
This effect is thought to be due to the large number of crystal nuclei in the primary particles of the pigment and the fact that the excess coupler hinders the subsequent ripening of the crystals. That is, the present invention provides an electrophotographic photosensitive method characterized in that, in the synthesis reaction of an azo pigment, a coupling reaction is carried out using 1.5 to 3.0 times the mole of the coupler per mole of the amino group of the amine that is the substrate. This is a method for producing an azo pigment for body use.
The production method of the present invention is applicable to all azo pigments such as monoazo pigments, disazo pigments, trisazo pigments, and other polyazo pigments, but disazo pigments and trisazo pigments are preferred from the viewpoint of electrophotographic properties. The present invention will be explained in more detail below using disazo pigments and trisazo pigments as examples. Diamines and triamines used in the present invention include Aromatic or heterocyclic amines such as the following are used.
R ₁ to _{R 31} in formulas (1) to (11) are hydrogen, halogen atoms such as chlorine, bromine, and iodine, alkyl groups such as methyl, ethyl, and propyl, alkoxy groups such as methoxy, ethoxy, and propoxy, and phenoxy groups. , nitro group, etc. X represents -O-, -S-, -N--R ₃₂
R ₃₂ represents an alkyl group. As the coupler, a coupler having an aromatic hydroxyl group is used. Particularly preferable couplers from the viewpoint of electrophotographic properties, particularly couplers having a phenolic hydroxyl group, include couplers represented by the following general formulas (12) to (14). . General formula (12) In the formula, Y is a residue that is condensed with a benzene ring to form a naphthalene ring, an anthracene ring, a carbazole ring, a benzcarbazole ring, or a dibenzofuran ring, and Z is -CONR ₃₃ R ₃₄ (However, R ₃₃ is a hydrogen atom, a substituted or R 34 represents a group selected from the group consisting of unsubstituted alkyl groups and phenyl groups; R ₃₄ represents a group selected from the group consisting of substituted or unsubstituted alkyl groups, phenyl groups and naphthyl groups; Substituents for the R ₃₃ and R ₃₄ groups include alkyl groups such as methyl, ethyl, propyl, butyl, halogen atoms, alkoxy groups such as methoxy, ethoxy, propoxy, butoxy, acyl groups such as acetyl and benzoyl, methylthio, Arylthio groups such as ethylthio, aryl groups such as phenyl,
Examples include aralkyl groups such as benzyl and phenethyl, nitro groups, cyano groups, and dialkylamino groups such as dimethylamino and diethylamino. General formula (13)

【formula】 General formula (14)

[Formula] In the formula, R ₃₅ represents a group selected from the group consisting of substituted or unsubstituted alkyl groups and phenyl groups. Specifically, _R35 is methyl, ethyl, propyl,
Alkyl groups such as butyl, hydroxyalkyl groups such as hydroxymethyl and hydroxyethyl, alkoxyalkyl groups such as methoxymethyl and ethoxyethyl, cyanoalkyl groups, aminoalkyl groups, N
-alkylaminoalkyl group, N,N-dialkylamino group, halogenated alkyl group, benzyl,
Aralkyl groups such as phenethyl, phenyl groups and substituted phenyl groups (substituents include general formula (14))
Examples include R ₃₃ and R ₃₄ ). The amine and coupler used in the present invention are not particularly limited to the exemplified substances. The pigment is obtained by tetrazotizing or hexazotizing diamines or triamines such as those exemplified above by a conventional method (diamines such as general formulas (3) and (3) are also expressed as tetrazotizing), and then coupling a coupler in the presence of an alkali. Alternatively, the tetrazonium salt or hexazonium salt of the diamine or triamine described above is once isolated in the form of a borofluoride salt or zinc chloride double salt, and then in a suitable solvent such as N,N-dimethylformamide or dimethyl sulfoxide. can be easily produced by coupling with a coupler in the presence of an alkali. The amount of coupler used in this case is 1.5 to 1 mole of amino group of diamine or triamine.
It is 3.0 times the mole, more preferably 2.0 to 3.0 times the mole. If it is less than 1.5 times the molar amount, it will not be very effective for atomization, and if it exceeds 3.0 times the molar amount, it will be difficult to remove the remaining coupler, and if this remains, problems such as decreased sensitivity and V _L up will occur. Then, after washing with water, dimethylformamide (DMF), dimethylacetamide (DMAC), methanol, ethanol, isopropyl alcohol (IPA), methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), benzene, xylene,
Clean and purify with solvents such as toluene and tetrahydrofuran (THF). Purified pigments are generally dried by heating, but if drying causes the formation of hard secondary agglomerated particles, it is preferable to dry them under reduced pressure or freeze drying, or to dry them without drying, as described below. It is preferable to make it into a paste form with a solvent such as a dispersion solvent.
Examples of pigment dispersion solvents include alcoholic solvents such as methanol, ethanol, and IPA, acetone,
MEK, MIBK, ketone solvents such as cyclohexanone, aromatic solvents such as benzene, toluene, xylene, chlorobenzene, tetrahydrofuran,
cyclic ether solvents such as 1,4-dioxane,
Various solvents such as DMF and DMAC can be used. The pigment is dispersed together with these solvents and binder resin using a sand mill, colloid mill, atrider, ball mill, etc. to form a fine particle pigment dispersion. As the binder resin, polyvinyl butyral, formal resin, polyamide resin, polyurethane resin, cellulose resin, polyester resin, polysulfone resin, styrene resin, polycarbonate resin, acrylic resin, etc. are used. Since the azo pigment synthesized by the method of the present invention has small primary particles at the time of production, it is easily dispersed to an extremely small particle size, and as is clear from the examples below, it has excellent sensitivity and potential characteristics during long-term use. You can see a big improvement. Next, a method for producing a functionally separated electrophotographic photoreceptor using the fine particulate azo pigment prepared as described above as a charge generating substance will be described. The charge generation layer can be formed by coating the above-mentioned dispersion directly on the conductive support or on the adhesive layer. It can also be formed by coating on the charge transport layer described below. The thickness of the charge generation layer is desirably a thin layer having a thickness of 5 microns or less, preferably 0.01 to 1 micron. Most of the incident light is absorbed by the charge generation layer to generate many charge carriers, and the generated charge carriers must be injected into the charge transport layer without being deactivated by recombination or trapping. , it is preferable to set it as the above-mentioned film thickness. Coating can be performed using coating methods such as dip coating, spray coating, spinner coating, bead coating, Meyer bar coating, blade coating, roller coating, and curtain coating. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying at a temperature of 30℃ to 200℃ for 5 minutes to 2
It can be carried out stationary or under blown air for a period of time within a range of hours. The charge transport layer is electrically connected to the charge generation layer described above, and has the function of receiving charge carriers injected from the charge generation layer in the presence of an electric field and transporting these electric carriers to the surface. ing. At this time, this charge transport layer may be laminated on or under the charge generation layer. However, it is desirable that the charge transport layer is laminated on the charge generation layer. Since the photoconductor generally has the function of transporting charge carriers, the charge transport layer can be formed by the photoconductor. The substance that transports charge carriers in the charge transport layer (hereinafter simply referred to as charge transport substance) is preferably substantially insensitive to the wavelength range of electromagnetic waves to which the charge generation layer is sensitive. The term "electromagnetic waves" used herein includes a broad definition of "light rays" that includes γ-rays, X-rays, ultraviolet rays, visible light, near-infrared rays, infrared rays, far-infrared rays, and the like. When the photosensitive wavelength range of the charge transport layer coincides with or overlaps that of the charge generation layer, charge carriers generated in both trap each other, resulting in a decrease in sensitivity. Charge transport substances include electron transport substances and hole transport substances, and electron transport substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, and 2,4,7-trinitro-9-fluorenone. , 2, 4, 5, 7-
Tetranitro-9-fluorenone, 2,4,7-
trinitro-9-dicyanomethylenefluorenone, 2,4,5,7-tetranitroxanthone,
Examples include electron-withdrawing substances such as 2,4,8-trinitrothioxanthone, and polymerized versions of these electron-withdrawing substances. Examples of hole-transporting substances include pyrene, N-ethylcarbazole, N-isopropylenecarbazole, and N-methyl-N-phenylhydrazino-3-
Methylidene-9-ethylcarbazole, N,N-
Diphenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3-methylidene-10-ethylphenothiazine, N,N-diphenylhydrazino-3-methylidene-10- Ethylphenoxazine, P-diethylaminobenzaldehyde-N,N-diphenylhydrazone, P-diethylaminobenzaldehyde-N-α-naphthyl-N-phenylhydrazone,
P-pyrrolidibenzaldehyde-N,N-diphenylhydrazone, 1,3,3-trimethylindolenine-ω-aldehyde-N,N-diphenylhydrazone, P-diethylbenzaldehyde-3-
Hydrazones such as methylbenzthiazolinone-2-hydrazone, 2,5-bis(P-diethylaminophenyl)-1,3,4-oxadiazole,
1-phenyl-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[quinolyl(2)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl) ) Pyrazoline, 1-[pyridyl(2)]-3-(P-
diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[6-methoxy-pyridyl(2)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1- [Pyridyl(3)]-3-(P-dielaminostyryl)-5-(P-diethylaminophenyl)pyralizone, 1-[Lepidyl(2)]-3-(P-
diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]-
3-(P-diethylaminostyryl)-4-methyl-5-(P-diethylaminophenyl)hilazoline, 1-[pyridyl(2)]-3-(α-methyl-P
-diethylaminostyryl)-5-(P-diethylaminophenyl)hilazoline, 1-phenyl-3
-(P-diethylaminostyryl)-4-methyl-
5-(P-diethylaminophenyl) hyazoline,
1-phenyl-3-(α-benzyl-P-diethylaminostyryl)-5-(P-diethylaminophenyl) hilazolines such as spirohylazoline, 2-(P-diethylaminostyryl)
-6-diethylaminobenzoxazole, 2-
Oxazole compounds such as (P-diethylaminophenyl)-4-(P-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole, 2
Thiazole compounds such as -(P-diethylaminostyryl)-6-diethylaminobenzothiazole, triarylmethane compounds such as bis(4-diethylamino-2-methylphenyl)-phenylmethane, 1,1-bis(4-N,N -diethylamino-2-methylphenyl)heptane, 1,
Polyarylalkanes such as 1,2,2-tetrakis(4-N,N-dimethylamino-2-methylphenyl)ethane, triphenylamine, poly-
N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine,
Examples include poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, and ethylcarbazole formaldehyde resin. In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide can also be used. Moreover, these charge transport substances may be one or two types.
More than one species can be used in combination. When the charge transport material does not have film-forming properties,
A film can be formed by selecting an appropriate binder. Resins that can be used as binders are:
For example, insulating resins such as acrylic resin polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, chlorinated rubber, or poly-N-vinyl Mention may be made of organic photoconductive polymers such as carbazole, polyvinylanthracene, polyvinylpyrene. Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. Generally, it is 5-30μ, but the preferred range is 8-20μ. When forming the charge transport layer by coating, an appropriate coating method as described above can be used. A photosensitive layer having a laminated structure of such a charge generation layer and a charge transport layer is provided on a substrate having a conductive layer. As the substrate having a conductive layer, materials that are themselves conductive can be used, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, and platinum. , other plastics having a layer formed by vacuum evaporation of aluminum, aluminum alloy, indium oxide, tin oxide, indium oxide-tin oxide alloy, etc. (e.g., polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyethylene fluoride, etc.), conductive particles (e.g. carbon black,
A base material in which plastic is coated with silver particles (silver particles, etc.) together with a suitable binder, a base material in which plastic or paper is impregnated with conductive particles, a plastic material containing a conductive polymer, etc. can be used. A subbing layer having barrier and adhesive functions can also be provided between the conductive layer and the photosensitive layer. The undercoat layer is made of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon
610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. The thickness of the undercoat layer is 0.1 to 5μ, preferably 0.3 to 3μ.
is appropriate. When using a photoreceptor in which a conductive layer, a charge generation layer, and a charge transport layer are laminated in this order, and the charge transport material is an electron transport material, the surface of the charge transport layer must be positively charged, and exposure after charging is required. Then, in the exposed area, electrons generated in the charge generation layer are injected into the charge transport layer, and then reach the surface and neutralize the positive charge, causing a decrease in surface potential and creating an electrostatic contrast with the unexposed area. . A visible image can be obtained by developing the electrostatic latent image thus formed with a negatively charged toner. It can be directly fixed, or the toner image can be transferred to paper, plastic film, etc., then developed and fixed. Alternatively, a method may be used in which the electrostatic latent image on the photoreceptor is transferred onto an insulating layer of transfer paper, then developed and fixed. The type of developer, the developing method, and the fixing method may be any known ones or known methods, and are not limited to specific ones. On the other hand, when the charge transport material consists of a hole transport material, the surface of the charge transport layer must be negatively charged.
After charging, when exposed to light, holes generated in the charge generation layer in the exposed area are injected into the charge transport layer, and then reach the surface and neutralize the negative charge, causing a decrease in surface potential and static electricity between the exposed area and the unexposed area. It can be used not only for electronic contrast, but also for a wide range of electrophotographic applications such as laser printers and CRT printers. Further, the photoconductive composition of the present invention can be used not only for the above-mentioned electrophotographic photoreceptor but also for solar cells and optical sensors. Hereinafter, the present invention will be explained according to examples. Example 1 In a 500ml beaker, 80ml of water and 16.6ml of concentrated hydrochloric acid (0.19
mole)

Add 6.53g (0.029mol) of diamine represented by the formula,
The mixture was stirred while being cooled in an ice-water bath to bring the liquid temperature to 3°C.
Next, a solution of 4.2 g (0.061 mol) of sodium nitrite dissolved in 7 ml of water was added dropwise over 10 minutes while controlling the temperature within the range of 3 to 10°C.
Stir for 1 minute. Carbon was added to the reaction solution to obtain a tetrazotized solution. Next, put 1.5 liters of water into 3 beakers and dissolve 42 g (1.06 mol) of caustic soda, then naphthol AS.
(3-hydroxy-2-naphthoic acid anilide)
38.6g (0.145mol) was added. The amount of this coupler corresponds to 2.5 times the molar amount of the amino group of the diamine. Cool this coupler solution to 6℃ and reduce the liquid temperature to 6-10℃.
Add the above-mentioned tetrazotization solution while controlling the temperature at
The mixture was added dropwise over 30 minutes with stirring, and then stirred at room temperature for 2 hours and further left overnight. After passing through the reaction solution, 1
The mixture was washed four times with water to obtain 20.3 g of a crude pigment. next,
Washing was repeated five times with 400 ml each of N,N-dimethylformamide. Thereafter, washing was repeated three times with each portion of MEK and drying was performed under reduced pressure at 40°C. Yield 17.1g
The yield was 79.3%. The resulting pigment has the following preparation. Elemental analysis analysis value (%) Calculated value (%) C 75.77 75.89 H 4.33 4.21 N 11.18 11.30 Next, 5 g of the above pigment was added to 93 g of cyclohexanone and 2 g of butyral resin (butyralization degree 63 mol%).
Add to the dissolved liquid and disperse with a sand mill for 10 hours,
A dispersion liquid (No. 1-1) having an average particle size of 0.08 μm was prepared (Figure 1). Next, place a solution of casein in ammonia (11.2 g of casein, 1 g of 28% ammonia water, 1 g of water) on an aluminum plate.
222ml) with a Mayer bar until the film thickness after drying is 1.0μ.
On top of the dried subbing layer, apply the previously obtained pigment dispersion using a Mayer bar so that the film thickness after drying is 0.2μ, and dry to form a charge generation layer. did. Next, 5 g of P-diethylaminobenzaldehyde-N,N-diphenylhydrazone and 5 g of polymethyl methacrylate resin (number average molecular weight 100,000) were added.
g was dissolved in 70 ml of benzene, and applied onto the charge generation layer using a Mayer bar so that the film thickness after drying was 1.2μ, and dried to form a charge transport layer. Electrophotographic photoreceptor (No. 1-
1) by static method using electrostatic copying paper manufactured by Kawaguchi Electric Co., Ltd. and test equipment “Modelsp-428”.
After corona charging with 5KV and holding for 1 second in the dark,
It was exposed to light at an illuminance of 51ux and its charging characteristics were investigated. As for the charging characteristics, the surface potential (V _D ) and the exposure amount (E1/2) required to attenuate the potential to 1/2 when dark decaying for 1 second were measured. Furthermore, in order to measure the fluctuations in bright area potential and dark area potential during repeated use, the photoreceptor fabricated in this example was equipped with a -5.6KV corona charger, an exposure optical system, a developer, a transfer charger, and a static eliminator. It was attached to the cylinder of an electrophotographic copying machine equipped with exposure optics and a cleaner. This copying machine is configured to produce an image on transfer paper as a cylinder is driven. Using this copying machine, the initial bright area potential (V _L ) and dark area potential (V _D ) were set to −600 V and −600 V, respectively.
The bright area potential (V _L ) and dark area potential (V _D ) were measured after being set at around 100 V and used 5000 times. The above results are shown in Table 1.

[Table] Comparative Example 1 The same pigment as in Example 1 was synthesized, purified and dried in the same manner as in Example 1, except that the usual amount of coupler (1.05 times the mole of the amino group of the amine) was used. As in Example 1, 5 g of this pigment was added to a solution prepared by dissolving 2 g of butyral resin (butyralization degree 63 mol%) in 93 g of cyclohexanone, and dispersed in a sand mill for 10 hours.
A 0.30μ dispersion (No. 1-2) was obtained (Figure 1). Next, a photoreceptor (No. 1-2) was prepared in exactly the same manner as in Example 1 except that a charge generation layer was formed using this dispersion. The charging characteristics and durability characteristics of this photoreceptor were measured in the same manner as in Example 1. The results are shown in Table 2.

[Table] From Example 1 and Comparative Example 1, the pigment obtained by the synthesis method of the present invention was dispersed to an extremely fine particle size, which resulted in excellent improvements in sensitivity and potential fluctuation during durability. I know that it will happen. Example 2 1500ml of water and 11.56ml of concentrated hydrochloric acid in a 5ml beaker
(1.31mol)

50.0 g (0.198 mol) of diamine represented by the formula was added and stirred while cooling in an ice water bath to bring the liquid temperature to 1°C. Next, a solution of 28.7 g (0.416 mol) of sodium nitrite dissolved in 60 ml of water was added dropwise over 40 minutes while controlling the temperature within the range of 1 to 7°C, and after completion of the addition, the mixture was stirred for an additional 30 minutes at the same temperature. After the reaction, carbon was added and filtered to obtain a tetrazotized solution, which was divided into 5 equal parts. On the other hand, in order to investigate the effect of the amount of coupler used,
A coupler solution was prepared by dissolving 2-hydroxynaphthoic acid methylamide, a coupler, in the following amount in a solution containing 11.6 g (0.29 mol) of caustic soda.

[Table] After cooling the coupler solution of ~ to 5℃, while controlling the liquid temperature at 5 to 10℃, the obtained tetrazo solution was added dropwise with stirring over a period of 25 to 30 minutes.
Thereafter, the mixture was stirred at room temperature for 2 hours and further left overnight. After filtering the reaction solution and washing 4 times with 1 part water each, 400 ml each
Washed five times with ml of N,N-dimethylformamide. Thereafter, the mixture was replaced twice with 400 ml of tetrahydrofuran to form a paste pigment with tetrahydrofuran. The resulting azo pigment has the following structure. The paste solids content and yield of each sample are shown.

[Table] Next, each of the above-mentioned pastes was dispersed in a sand mill for 5 hours with a tetrahydrofuran solution of butyral resin (butyralization degree: 63 mol%). The solid content ratio of the pigment and butyral resin is 5
g, butyral resin was adjusted to 2 g, and the dispersion concentration was adjusted to 7%. The dispersion progress of each pigment is shown in FIG. As is clear from FIG. 2, the larger the amount of coupler used, the finer the pigment becomes.
This is thought to be because, as mentioned above, the more couplers there are, the more crystal nuclei are formed, and the excess coupler hinders the growth of primary crystals, resulting in pigments with small primary crystal particles. Next, a photoreceptor was prepared in exactly the same manner as in Example 1, except that a charge generation layer was formed using each of the above dispersions, and its charging characteristics and durability characteristics were measured in the same manner as in Example 1. These results are shown in Table 3.

[Table] From Table 3, photoreceptors 2-2 to 2-5 using pigments atomized using the synthesis method of the present invention
It can be seen that all of the photoreceptors have better characteristics than photoreceptor 2-1 using pigments obtained by conventional methods. Example 3 Azo pigment 1 synthesized in Example 1 was dispersed in the same manner as in Example 1, and the dispersion times were 1, 2, 4, 6, and 1, respectively.
8 and 10 hours, and the average particle size of the dispersed particles was
Dispersions (Nos. 3-1 to 3-6) in which dispersions of 0.53μ, 0.35μ, 0.20μ, 0.14μ, 0.08μ, and 0.08μ were prepared. A photoreceptor (photoreceptor No. 3-
1 to 3-6) were prepared, and their charging characteristics and durability characteristics were measured in the same manner as in Example 1. These results are shown in Table 4.

[Table] From Table 4, pigment particles with an average particle size of 0.20μ or less show excellent characteristics in terms of sensitivity and potential fluctuation during durability, and azo pigments synthesized using the method of the present invention. In this case, as can be seen from Examples 1 and 2, it is possible to easily disperse the particles to 0.2 μ or less, and even 0.1 μ or less, and it can be seen that this is an extremely effective means. Example 4 On the charge generation layer prepared in Example 1, 2,
4,5,7-tetranitro-9-fluorenone 5
g and poly-4,4'-dioxanephenyl-2,2
- A coating solution prepared by dissolving 5 g of propane carbonate (molecular weight 300,000) in 70 ml of tetrahydrofuran was applied so that the coating amount after drying was 10 g/m ² and dried. The charging characteristics and durability characteristics of the electrophotographic photoreceptor thus prepared were measured in the same manner as in Example 1.
At this time, the charging polarity was set. The results are shown in Table 5.

[Table] Examples 5 to 8, Comparative Examples 5 to 8 Samples were prepared by synthesizing azo pigments with structures shown in Table 6 using the conventional method and the synthesis method of the present invention, and each pigment was extracted from MEK paste. It was dried under reduced pressure at 40°C. These pigments were dispersed in the same manner as in Example 1. Table 6 shows the structure of each azo pigment, the amount of coupler used, and the average particle size after dispersion.

【table】

[Table] Next, photoreceptors were prepared in the same manner as in Example 1, except that a charge generation layer was formed using each dispersion liquid No. 5-1 to No. 8-2, and the charging characteristics and durability characteristics were compared. .
The results are shown in Table 7.

Table 6 shows that for any azo pigment, the photoreceptor using the dispersion atomized using the method of the present invention has superior properties.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the dispersion time and average particle size of azo pigments in Example 1 and Comparative Example 1, and
The figure is a graph showing the dispersion time and average particle size of the azo pigment in Example 2. For the measurement, a centrifugal particle distribution analyzer CAPA-500 manufactured by Horiba, Ltd. was used.

Claims (1)

[Claims] 1. During the azo pigment synthesis reaction, 1.5 to 3.0 of the coupler is added per mole of the amino group of the amine substrate.
A method for producing an azo pigment for an electrophotographic photoreceptor, the method comprising carrying out a coupling reaction using twice the molar amount. 2. The method for producing an azo pigment for an electrophotographic photoreceptor according to claim 1, wherein the azo pigment has an average particle size of 0.2 μ or less.