JPH0445162A - Azo-based compound and photoreceptor for electrophotography using the same compound - Google Patents

Abstract

NEW MATERIAL:Compounds of formula I (A is coupler residue). EXAMPLE:A compound of formula II. USE:A charge-producing material in a photoreceptor for electrophotography. PREPARATION:Sodium nitrite, etc., is added dropwise to an acidic aqueous solution of a diamine of formula III with stirring at -10 to 5 deg.C and hydrogen boronfluoride, etc., is added thereto. A tetrazonium salt of formula IV is obtained by crystallization and a coupling reaction is then carried out between the resultant tetrazolium salt and a coupler in an organic solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an azo compound suitable as a charge generating material in an electrophotographic photoreceptor and an electrophotographic photoreceptor using the same.

<Prior art> In recent years, organic photoreceptors have been used as electrophotographic photoreceptors in image forming devices such as copying machines because they have excellent processability, are advantageous in terms of manufacturing costs, and have a large degree of freedom in functional design. ing.

Further, when forming a copy image using an electrophotographic photoreceptor, the Carlson process is widely used. The Carlson process consists of a charging process in which a photoreceptor is uniformly charged by corona discharge, an exposure process in which an original image is exposed to the charged photoreceptor to form an electrostatic latent image corresponding to the original image, and an electrostatic latent image is formed in the electrostatic latent image. A development process in which a toner image is formed by developing with a developer containing toner, a transfer process in which the toner image is transferred to a base material such as paper, a fixing process in which the toner image transferred to the base material is fixed, and a transfer process. After the process, a cleaning process is included to remove toner remaining on the photoreceptor. To form high quality images in this Carlson process,
Electrophotographic photoreceptors are required to have excellent charging characteristics and photosensitive characteristics, and to have a low residual potential after exposure.

Inorganic photoconductors such as selenium and cadmium sulfide have been known as materials for electrophotographic photoreceptors, but these are toxic and expensive to produce, making them undesirable.

Therefore, so-called organic electrophotographic photoreceptors using various organic substances in place of these inorganic substances have been proposed. Such organic electrophotographic photoreceptors usually have a photosensitive layer made of a charge-generating material that generates charges upon exposure to light, and a charge-transporting material that has a function of transporting the generated charges.

In order to satisfy various conditions desired for such an organic electrophotographic photoreceptor, it is necessary to appropriately select these charge generation materials and charge transport materials.

Examples of charge-generating materials include organic photoconductive polymers such as polyvinyl carbazole, low-molecular organic photoconductors such as hydrazone compounds, phthalocyanine compounds, perylene compounds, quinacridone compounds, anthanthrone compounds, and azo compounds. Compounds have been proposed. For example, as azo compounds, those disclosed in JP-A-47-37543 are known.

<Problems to be Solved by the Invention> However, many of the conventional charge-generating materials described above have a narrow photosensitive wavelength range or have strong absorption in the near-infrared region.
It does not have photosensitive wavelength characteristics over the entire visible light region.

Therefore, electrophotographic photoreceptors using the above-mentioned conventional charge-generating materials have the problem that it is difficult to faithfully reproduce a color original depending on the absorption wavelength characteristics of the photoreceptor, and the overall sensitivity is insufficient.

In particular, conventionally known azo compounds as charge-generating materials have the disadvantage that the photosensitive characteristics of the photoreceptor change when used for a long period of time, resulting in insufficient durability and a decrease in sensitivity. There were very few that reached that point.

This invention solves the above problems, and provides a novel azo compound that has superior photosensitive properties, excellent repeatability, and stable sensitivity to light, and a novel azo compound using the same. The purpose is to provide an electrophotographic photoreceptor.

Means and Effects for Solving the Problems> The azo compound of the present invention has the general formula (■): [wherein A represents a coupler residue]. ] It is an azo compound represented by

An electrophotographic photoreceptor can be obtained by providing a photosensitive layer containing the azo compound of the present invention on a conductive substrate.

The electrophotographic photoreceptor of the present invention containing this azo compound has high sensitivity in the visible light region, particularly in the visible region from 450 to 600 nm, and can prevent surface potential from decreasing due to repeated use. Furthermore, it has stable high sensitivity and excellent photostability against long-term light exposure or light exposure at high temperatures.

The reason why the azo compound of the present invention has such high durability and stable sensitivity is considered to be as follows.

That is, the azo compound of the present invention has, for example, the following general formula (■
]: Compared to conventional disazo compounds shown by This is presumed to be because the interaction between them is strengthened.

In the azo compound of the present invention represented by the general formula (I), the coupler residue is represented by the following general formula (al~
The group represented by (g) is exemplified.

R'' In each of the above formulas, R1 is a hydroxyl group, a group NR7R8
(In the formula, R7 and R8 are the same or different and represent a hydrogen atom or an alkyl group.) or a group (NHSO2)
R9 (wherein R9 represents a hydrogen atom, an alkyl group, an alkenyl group, or an aryl group).

R2 represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, a carbamoyl group, an aryl group, or a sulfamoyl group, and the alkyl group or alkoxy group is a halogen atom, a phenyl group, a naphthyl group, a nitro group, It may have a substituent such as a cyano group.

Further, the carbamoyl group or sulfamoyl group may have a substituent such as a halogen atom, a phenyl group, a naphthyl group, an alkyl group, an alkenyl group, a carbonyl group, or a carboxyl group.

R3 represents an atomic group necessary to form an aromatic ring, aliphatic ring or heterocycle by condensing with the benzene ring having R1 and R2, and these rings may have the same substituents as above. good.

R4 represents a hydrogen atom, an amino group, an N-substituted amino group, an alkyl group, an alkenyl group, a hydroxyl group, a carbamoyl group, a carboxyl group, or an alkoxycarbonyl group. Further, the alkyl group, alkenyl group, and carbamoyl group may have the same substituents as above.

R5 represents a hydrogen atom, an alkyl group or an aryl group,
The alkyl group or aryl group may have the same substituents as above.

R6 represents a phenylene group or a naphthylene group.

These phenylene groups or naphthylene groups may also have the same substituents as above.

Examples of the alkyl group include methyl, ethyl, propyl, inpropyl, butyl, isobutyl, tert-
Examples include lower alkyl groups having 1 to 6 carbon atoms such as butyl, pentyl, and hexyl.

Examples of the alkenyl group include vinyl 5-allyl, 2-
Examples include lower alkenyl groups having 2 to 6 carbon atoms such as -butenyl, 3-butenyl, 1-methylallyl, 2-pentenyl, and 2-hexenyl.

Examples of the halogen atom include a chlorine atom, a bromine atom, an iodine atom, and a fluorine atom.

Examples of the alkoxy group include lower alkoxy groups in which the alkoxy moiety has 1 to 6 carbon atoms, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, pentyloxy, and hexyloxy.

Examples of the alkoxycarbonyl group include methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl,
isobutoxycarbonyl, pentyloxycarbonyl,
Examples include lower alkoxycarbonyl groups in which the alkoxy moiety has 1 to 6 carbon atoms, such as hexyloxycarbonyl.

Further, in R3, the atomic group necessary for condensing with the benzene ring having R' and R2 to form an aliphatic ring includes, for example, a methylene group, an ethylene group, a propylene group,
Examples include alkylene groups having 1 to 4 carbon atoms such as a butylene group.

In R3, the atomic group necessary to form a heterocycle by condensing with the benzene ring having R1 and R2 includes, for example, benzofuranyl, benzothiophenyl, indolyl, IH-indolyl, bezooxazolyl, benzothiazolyl, IH-imidazolyl, benzimidazolyl. , chromenyl, chromanyl, inchromanyl, quinolinyl, isoquinolinyl, cinnolinyl, phthalazinyl, quinazonilyl, quinoxalinyl, dibenzofuranyl, carbazolyl, xanthenyl, acridinyl, phenoxazinyl,
Examples include phthalazinyl, phenoxazinyl, and thianthrenyl.

The azo compound of the present invention represented by the above-Funzo (I) is:
It can be synthesized in various ways. For example, as shown in the reaction formula below, it can be easily produced by diazotizing a diamine to form a tetradiazonium salt, and then coupling this with a predetermined coupler in an organic solvent.

[In the formula, A is the same as above, X is C4BrN Os -B
Indicates an anion such as F2-. ] Diazotization is carried out by adding sodium nitrite or nitrous acid dropwise to an acidic aqueous solution of diamine (1) at a low temperature (usually -10 to 5°C) while stirring, and then adding borofluoride, hydrogen halide, sulfuric acid, etc. is added to obtain a crystallized tetrazonium salt (2).

In the coupling reaction, a predetermined amount of the coupler is added to the tetrazonium salt (2) in an organic solvent and allowed to react.

Examples of the organic solvent include dimethylformamide and dimethyl sulfoxide.

The azo compound of the present invention can be used alone as a charge generating material or in combination with other conventionally known charge generating materials.

Examples of other charge-generating materials include amorphous silicon, pyrylium salts, anthanthrone pigments, phthalocyanine pigments, indigo pigments, triphenylmethane pigments, threne pigments, toluidine pigments, pyrazoline pigments, and perylene pigments. , quinacridone pigments, etc.

These charge generating materials may be used alone or in combination of two or more so that they have absorption wavelengths in desired regions.

The azo compound of the present invention can be applied to both so-called single layer type and laminated type electrophotographic photoreceptors.

In order to obtain a single-layer electrophotographic photoreceptor, a photosensitive layer containing the azo compound of the present invention as a charge transporting material, a charge generating material, a binder resin, etc. is formed on a conductive substrate by means such as coating. Bye.

Further, in order to obtain a laminated electrophotographic photoreceptor, a charge generation layer containing a charge generation material containing the azo compound of the present invention is formed on a conductive substrate by means such as coating, and the charge generation layer is A charge transport layer containing a charge transport material and a binder resin may be formed on the generation layer. Also, contrary to the above,
A charge transport layer similar to that described above may be formed on a conductive base material, and then a charge generation layer containing a charge generation material may be formed by means such as coating. Furthermore, the charge generation layer may be formed by dispersing and coating a charge generation material and a charge transport material in a binder resin.

As the charge transport material, conventionally known materials can be used, such as oxadiazole compounds such as 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazole, 9- Styryl compounds such as (4-diethylaminostyryl)anthracene, carbazole compounds such as polyvinylcarbazole, 1-phenyl-3-(
Pyrazoline compounds such as p-dimethylaminophenyl) pyrazoline, hydrazone compounds, triphenylamine compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds compounds, nitrogen-containing cyclic compounds such as triazole compounds, and fused polycyclic compounds.

These charge transport materials may be used alone or in combination of two or more. Note that when using a charge transporting material having film-forming properties such as polyvinylcarbazole, a binder resin is not necessarily required.

Furthermore, various resins can be used as the binder resin used in the single-layer type or laminated type photoreceptor.
For example, styrene polymers, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-
Maleic acid copolymer, acrylic polymer, styrene-acrylic copolymer, polyethylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polyvinyl chloride, polypropylene, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane,
Thermoplastic resins such as polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin, silicone resin, epoxy resin, phenol resin, urea resin, melamine resin, and other crosslinkable thermosetting resins Examples include various polymers such as resins and photocurable resins such as epoxy acrylate and urethane acrylate.

These binder resins may be used alone or in combination of two or more.

Further, a solvent is used when forming a charge generation layer or a charge transport layer by a coating method or the like. Various organic solvents can be used as this solvent, including alcohols such as methanol, ethanol, isopropanol, butanol, aliphatic hydrocarbons such as n-hexane, octane, and cyclohexane, and benzene. , aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as dichloromethane, dichloroethane, carbon tetrachloride, and chlorobenzene, ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether;
Examples include ketones such as acetone, methyl ethyl ketone, and cyclohexanone, esters such as ethyl acetate and methyl acetate, and various solvents such as dimethyl formaldehyde, dimethyl formamide, and dimethyl sulfoxide.

These solvents can be used alone or in combination of two or more.

Further, in order to improve the sensitivity of the charge generation layer, a known sensitizer such as terphenyl, halonaphthoquinones, acenaphthylene, etc. may be used together with the charge generation material. Furthermore, the dispersibility of charge transport materials and charge generation materials,
Surfactants, leveling agents, etc. may be used to improve dyeability.

As the conductive base material, various materials having conductivity can be used. For example, aluminum, copper, tin, platinum, gold, silver, vanadium, molybdenum, chromium,
Examples include simple metals such as cadmium, titanium, nickel, palladium, indium, stainless steel, and brass, plastic materials on which the above metals are vapor-deposited or laminated, and glass coated with aluminum iodide, tin oxide, indium oxide, etc. Ru.

The above-mentioned conductive base material may be in the shape of a belt or a drum, and it is sufficient that either the base material itself has conductivity or the surface of the base material has conductivity. The base material preferably has sufficient mechanical strength during use.

Each of the single-layer type and laminated type organic photosensitive layers can contain additives such as a sensitizer, a fluorene compound, an antioxidant, a deterioration inhibitor such as an ultraviolet absorber, and a plasticizer.

The amount of the charge transport material added in the single-layer photosensitive layer is suitably 40 to 200 parts by weight, preferably 50 to 100 parts by weight, based on 100 parts by weight of the binder resin. Also,
The amount of the charge transport material added in the laminated charge transport layer is suitably 10 to 500 parts by weight, preferably 25 to 200 parts by weight, based on 100 parts by weight of the binder resin.

The amount of the charge generating material added in the single-layer type photosensitive layer is suitably 2 to 20 parts by weight, preferably 3 to 15 parts by weight, based on 100 parts by weight of the combined weight. Further, the amount of the charge generating material added in the laminated charge generating layer is suitably 5 to 500 parts by weight, preferably 10 to 250 parts by weight, based on 100 parts by weight of the binder resin.

The thickness of the photosensitive layer formed is 10 to 50 mm in the case of a single layer type.
It is preferably about μm, particularly about 15 to 25 μrn. On the other hand, in the case of a laminated type, the thickness of the charge generation layer is about 0.01 to 5 μm, preferably about 0.1 to 3 μm, and the thickness of the charge transport layer is about 2 to 100 μm.
It is preferably about 5 to 30 μm.

In addition, in a single-layer electrophotographic photoreceptor, between the base material and the photosensitive layer, and in a laminated electrophotographic photoreceptor, between the base material and the charge generation layer. A barrier layer may be formed between the base material and the charge transport layer, and between the charge generation layer and the charge transport layer, as long as it does not impede the characteristics of the photoreceptor. A layer may be formed.

When the charge generation layer and charge transport layer are formed by coating, the charge generation material and the binder resin are mixed using a known method such as a roll mill, ball mill, attritor, paint shaker, or ultrasonic disperser. The coating composition may be prepared by dispersing and mixing using the following methods, and then applied and dried by known means.

Note that, as described above, the charge generation layer may be formed by vapor depositing the charge generation material.

Hereinafter, the present invention will be explained in detail with reference to Examples.

<Example> (1) Synthesis example of charge generating material Example 1 7.09 g (0,023 mol) of diamine represented by formula 010: was added to 75 mL of 10% hydrochloric acid, and the mixture was stirred while cooling in an ice water bath. The liquid temperature was maintained at -1°C. Next, add 3.54 g of sodium nitrite (0
. Then 4 to this
20 mJ of 2% fluoroboric acid was added, and the resulting crystals were filtered, washed with ethanol, and dried to obtain 9.26 g (yield: 79.6%) of tetrazonium difluoroborate.

Next, this tetrazonium salt 1. Olg (0,002 mol) and 1.06 g (0,004 mol) of a coupler with the formula 1M:
was dissolved in 100 mJ of N,N-dimethylformamide, and a solution prepared by dissolving 0.35 g (0,0043 mol) of sodium acetate in 5 m of water was added dropwise over 5 minutes while maintaining the temperature at 17 to 21°C. After stirring for an additional 3 hours, the precipitate formed was filtered and washed with N.

Washed 5 times with 200 mJ of N-dimethylformamide.

Next, after washing with water twice, dry under reduced pressure and use the following general 2M
1.4 g (yield: 78%) of the purified compound represented by 2 was obtained.

The results of elemental analysis of the obtained azo compound are described below.

Calculated value (%) as C56H36N b 04 C78,49H4,23N9.81 Experimental value (%) C70,33H4,29N9.78 Example 2 The same procedure as in Example 1 was carried out except that p-cresol was used as the coupler. An azo compound was obtained.

Calculated value (%) as C36H26N < 0□ C79,10) 14.79 Nl'
0.25 Experimental value (%) C79, H3H4, 92N1
0.03 Example 3 An azo compound was obtained in the same manner as in Example 1 above, except that 4-hydroxyindoline was used as the coupler.

Calculated value (%) as C3aH28N 602 C75,98 [(4,70N13.9
9 Experimental value (%) C76,071 (4,53N14.
22 Example 4 An azo compound was obtained in the same manner as in Example 1 above, except that N-methylaniline was used as the coupler.

Calculated value (%) as C36H2ON 6 C79,39H5,18N15.43
Experimental value (%) C79,51,H5,04N15.6
2 Example 5 An azo compound was obtained in the same manner as in Example 1 above, except that 1-methyl-5-hydroxypyrazole was used as the coupler.

Calculated value (%) as C30H22N 802 CH,43H4,21N21.28 Experimental value (%) CEi8.2L H4,50N21.
14 Example 6 An azo compound was obtained in the same manner as in Example 1 above, except that a substance represented by the following formula was used as a coupler.

Calculated value (%) as CH3 CasH211N 6 C73,46 H3,GO N10.71 Experimental value (%) C73,17 )13.73 N10.86 Example 7 Other than using the substance represented by the following formula as the coupler , Calculated value (%) C79,62H3,46N9.61 Experimental value (%) C79,85H3,24N9.79 (2
) Preparation of electrophotographic photoreceptor Preparation of single-layer electrophotographic photoreceptor 8 parts by weight of the compounds of the present invention synthesized in Examples 1 to 7 above as a charge generation material, 33'-dimethyl-N, N, N as a charge transport material ',N'-tetrakis-4-methylphenyl(1,1'-biphenyl)-4,4'-diamine 100 parts by weight, poly-(4,4'
100 parts by weight of -cyclohexylidene diphenyl) carbonate (manufactured by Mitsubishi Gas Chemical Co., Ltd., Polycarbonate 2200) and a predetermined amount of tetrahydrofuran were mixed and dispersed using an ultrasonic disperser to prepare a coating liquid for a single-layer photosensitive layer. After applying this coating liquid onto the aluminum tube, 1 coat in a dark place.
The resulting product was dried by heating at 00° C. for 30 minutes to produce a drum-shaped electrophotographic photoreceptor having a single-layer photosensitive layer with a thickness of 24 μm.

Polyvinyl butyral (manufactured by Hakuhon Kagaku Co., Ltd.,
10'0 parts by weight of the trade name Kosuretsuku BLI) and the compound 1 of the present invention synthesized in Examples 1 to 7 above as a charge generating material.
00 parts by weight and a predetermined amount of tetrahydrofuran were placed in a ball mill and stirred and mixed for 24 hours to prepare a charge generation layer coating solution. A charge generation layer having a thickness of 0.5 μm was formed by drying with hot air for a minute and curing.

Next, 100 parts by weight of polycarbonate resin (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name: Niepiron) was added as a binder resin, and 3,3'-dimethyl-N, N, N', as a charge transport material.
N'-tetrakis-4-methylphenyl (1,1'-
A charge transport layer coating solution was prepared by stirring and mixing 100 parts by weight of (biphenyl)-4,4' diamine and a predetermined amount of toluene using a homomixer. This coating solution was applied to the surface of the charge generation layer by a dipping method, and dried with hot air at 90° C. for 30 minutes to form a charge transport layer with a thickness of about 20 μm.
A laminated electrophotographic photoreceptor was created.

Comparative Example Single-layer type and laminated type electrophotographic photoreceptors were prepared in the same manner as described above, except that chlorodiane blue represented by the following -Shipboard VO: was used as the charge-generating material.

(3) Evaluation of electrophotographic photoreceptor Measurement of surface potential VSP Each of the above-mentioned single-layer electrophotographic photoreceptors was loaded into an electrostatic copying tester (Dientic Sincere 30M, manufactured by Dientic Co., Ltd.), and its surface was The surface potential Vsp (V) of each photoreceptor was measured.

Measurement of half-decreased exposure amount E17□ and residual potential vrp Each electrophotographic photoreceptor in the above charged state was exposed to light at an intensity of 101 using a halogen lamp which is the exposure light source of the electrostatic copying tester.
ux, and find the time until the surface potential Vsp (V) reaches 172, and calculate the half-reduced exposure amount El/2 (1ux
-sec) was calculated, and the surface potential 0.15 seconds after the start of the exposure was defined as the residual potential Vrp (V).

Table 1 shows the measurement results of the electrophotographic properties of the electrophotographic photoreceptors obtained in Examples 1 to 7 and Comparative Example.

(Margins below) Table 1 As shown in Table 1, both the single-layer type and the laminated type photoreceptor using the azo compound of the present invention as a charge-generating material have a residual potential Vrp smaller than that of the comparative example. , it can be seen that it has excellent stability against light. Also, half-exposure ILE
I/2 was also low, and the sensitivity was stable. moreover,
It also had excellent repeatability.

<Effects of the Invention> As described above, the azo compound of the present invention has high sensitivity in the visible light region and excellent photostability.

By using this azo compound, it is possible to obtain an electrophotographic photoreceptor with high sensitivity, excellent photostability, and excellent repeatability.

Claims (1)

[Claims] 1. General formula (I): ▲There are numerical formulas, chemical formulas, tables, etc.▼(I) [In the formula, A represents a coupler residue. ] An azo compound represented by. 2. An electrophotographic photoreceptor, characterized in that a photosensitive layer containing the azo compound according to claim 1 is provided on a conductive substrate.