JPH04300970A - Dianthraquinone-based compound and photosensitizer using the same - Google Patents

Abstract

PURPOSE:To provide a novel dianthraquinone-based compound having a high electron-accepting property and useful as an electric charge-transfer material in photosensitizers. CONSTITUTION:A dianthraquinone compound of formula I (R<1>, R<2> are H, hydroxyl, nitro, cyano. amino, halogen-substituted alkyl, alkoxy; R<3> IS H, halogen- substituted alkyl; R<4> is halogen-substituted alkyl; p.q,r,s are 0-4). For example, 1,4-naphtoquinone is reacted with a diene of formula II in an anhydrous alcohol solution containing potassium hydroxide to produce an anthraquinone compound of formula III, which is reduced with Na2S2O4 and NaOH to produce a compound of formula IV. On the other hand, 1,4-naphtoquinone is reacted with a compound of formula V to produce an anthraquinone compound of formula VI, which is reduced to produce a compound of formula VII. Subsequently, the compound of formula IV is thermally reacted with the compound of formula VII in the presence of SOCl2. in a solvent to provide the dianthraquinone-based compound.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dianthraquinone compound suitable as a charge transport material in a photoreceptor, and a photoreceptor using the same.

0002

[Prior Art and Problems to be Solved by the Invention] In recent years, organic photoreceptors have been widely used as photoreceptors in image forming devices such as copying machines, which have excellent processability and economic efficiency, and have a large degree of freedom in functional design. There is. Further, when forming a copy image using a 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 developing 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 paper, etc., a fixing process in which the transferred toner image is fixed, and after the transfer process, a toner image is formed on the photoreceptor. and a cleaning step to remove residual toner. In this Carlson process, in order to form a high-quality image, the photoreceptor is required to have excellent charging characteristics and photosensitivity characteristics, and to have a low residual potential after exposure.

Inorganic photoconductors such as selenium and cadmium sulfide have heretofore been known as photoreceptor materials, but these have the drawbacks of being toxic and having high production costs. Therefore, so-called organic photoreceptors using various organic substances in place of these inorganic substances have been proposed. Such an organic photoreceptor has 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.

[0004] In order to satisfy various conditions desired for such an organic photoreceptor, it is necessary to appropriately select the charge generating material and the charge transporting material. Various organic compounds have been proposed as charge transport materials. For example, JP-A-1-206349 describes a compound having a diphenoquinone structure as a charge transport material. This material has an electron-withdrawing group as a substituent and has electron-accepting properties, so it is used as an electron-transporting material.

However, the above-mentioned compound having a diphenoquinone structure has a low electron donating property, does not have sufficient charge transport ability, and when used as a photoreceptor, does not have sufficient sensitivity.
There is a problem of high residual potential. The object of the present invention is to provide a dianthraquinone compound suitable as a charge transport material;
It is an object of the present invention to provide a photoreceptor using the same which has high sensitivity and excellent repeatability.

[0006]

[Means and effects for solving the problems] The dianthraquinone compound of the present invention has the following general formula (1):

00
07]

[Chemical formula 3]

(In the formula, R1 and R2 are the same or different and represent a hydrogen atom, a hydroxyl group, a nitro group, a cyano group, an amino group, a halogen-substituted alkyl group, or an alkoxy group that may have a substituent. R3 is a hydrogen atom. or represents a halogen-substituted alkyl group. R4 represents a halogen-substituted alkyl group. p, q, r and s are the same or different and represent an integer of 0 to 4. However, R1, R2,
At least one of R3 and R4 is a halogen-substituted alkyl group, and p, q, r and s are not 0 at the same time. ).

Further, the photoreceptor of the present invention for achieving the above object is characterized in that it has a photosensitive layer containing a dianthraquinone compound represented by the above general formula (1) on a conductive substrate. It is said that Such a dianthraquinone compound of the present invention has R3 in the above general formula (1).
Since R4 contains a halogen atom with high electronegativity, electron injection from the charge-generating material is improved, and the charge transport ability is improved. Further, by introducing a halogen atom, the molecular weight of the dianthraquinone compound can be increased, so that sublimation can be suppressed to a low level, and compatibility with the binder resin can also be improved.

Furthermore, since the dianthraquinone compound represented by the above general formula (1) has excellent charge transport ability, by incorporating it into the photosensitive layer as a charge transport material,
A photoreceptor having excellent sensitivity and charging ability and high repeatability can be obtained. Examples of the alkyl group include lower alkyl groups having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, pentyl group, and hexyl group.

Examples of the alkoxy group include lower alkoxy groups having 1 to 6 carbon atoms such as methoxy group, ethoxy group, isopropoxy group, butoxy group, t-butoxy group, and hexyloxy group. In addition, the above substituents include:
For example, halogen atom, amino group, hydroxyl group, optionally esterified carboxyl group, cyano group, C1-C
Examples thereof include a C2-C6 alkyl group, a C1-C6 alkoxy group, and a C2-C6 alkenyl group that may have an aryl group.

[0012] Examples of the halogen atom include fluorine, chlorine, bromine, and iodine, with fluorine being particularly preferred in terms of improving chemical stability. Specific examples of dianthraquinone compounds represented by the above general formula include those shown in the following formulas (2) and (3).

[0013]

[C4]

The dianthraquinone compound of the present invention can be synthesized by various methods, for example, by the following reaction formula.

[0015]

[C5]

[0016]

[C6]

[0017]

[C7]

(In the formula, R1, R2, R3, R4
, q, r and s are the same as above) This reaction formula is:
A naphthoquinone compound (dienophile) represented by formula (a) is reacted with a diene compound represented by formula (b) in an anhydrous alcohol solution of potassium hydroxide using the Diels-Alder reaction, and the formula An anthraquinone compound represented by (c) is produced, and Na2 S2 O4 and N are added to this anthraquinone compound (c).
Reduction is performed using a reducing agent such as a combination with aOH to produce a compound represented by formula (I). Next, in the same manner as above, a diene compound represented by formula (e) is added to the naphthoquinone compound (dienophile) represented by formula (d), and an anthraquinone compound represented by formula (f) is obtained. This anthraquinone compound (f) is further reduced to produce a compound represented by formula (II).

Compounds represented by formula (I) and formula (II)
When the compound represented by the formula (1') is heated in a solvent in the presence of SOCl2 in the same manner as described above, the dianthraquinone compound of the present invention represented by the formula (1') is obtained. The above formula (I
) The compound represented by formula (II) and the compound represented by formula (II) are used in approximately equimolar amounts, and in an organic solvent, about 40
Obtained by reaction at ~60°C. As the organic solvent, for example, chloroform, carbon tetrachloride, benzene, etc. can be used.

The photosensitive layer in the present invention contains one or more dianthraquinone compounds represented by the above general formula (1) as a charge transport material. The photosensitive layer in the present invention includes a single-layer type in which a charge-generating material, a charge-transporting material, which is a compound represented by the general formula (1) and a binder resin, and a charge-generating layer and a charge-transporting layer are laminated. Although there is a laminated type, the photosensitive layer of the present invention can be applied to either type.

In order to obtain a single-layer type photoreceptor, a photosensitive layer containing a compound represented by the general formula (1) as a charge transporting material, a charge generating material, a binder resin, etc. is placed on a conductive substrate. It should be formed as follows. In addition, in order to obtain a laminated photoreceptor, a charge generation layer containing a charge generation material is formed on a conductive substrate by means such as vapor deposition or coating, and a charge transport material is applied on the charge generation layer. A charge transport layer containing a compound represented by the general formula (1) and a binder resin may be formed. Further, contrary to the above, a charge transport layer similar to the above may be formed on a conductive substrate, and then a charge generation layer containing a charge generation material may be formed by means such as vapor deposition or coating. Furthermore, the charge generation layer may be formed by coating a charge generation material and a charge transport material dispersed in a binder resin.

As charge generating materials, conventionally used selenium, selenium-tellurium, selenium-arsenic, amorphous silicon, pyrylium salts, azo compounds, disazo compounds, phthalocyanine compounds, anthanthrone compounds, and perylene compounds are used. compounds, indigo-based compounds, triphenylmethane-based compounds, threne-based compounds, toluidine-based compounds, pyrazoline-based compounds, perylene-based compounds, quinacridone-based compounds, pyrrolopyrrole-based compounds, and the like. These charge generating materials can be used alone or in combination of two or more so that they have absorption wavelengths in desired regions.

The dianthraquinone compound represented by the general formula (1), which is a charge transporting material, can be used alone or in combination with other conventionally known charge transporting materials. As the conventionally known charge transport material, various electron-withdrawing compounds and electron-donating compounds can be used. As the electron-withdrawing compound, for example, 2
, 6-dimethyl-2',6'-ditert-dibutyldiphenoquinone and other diphenoquinone compounds, malononitrile, thiopyran compounds, tetracyanoethylene, 2
, 4,8-trinitrothioxanthone, 3,4,5,7
Examples include -tetranitro-9-fluorenone, dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, dinitroanthraquinone, succinic anhydride, maleic anhydride, dibromomaleic anhydride, and the like.

[0024] Further, as the electron donating compound, 2,5
-Oxadiazole compounds such as di(4-methylaminophenyl), 1,3,4-oxadiazole, 9-(4
- styryl compounds such as (diethylaminostyryl) anthracene, carbazole compounds such as polyvinylcarbazole, pyrazoline compounds such as 1-phenyl-3-(p-dimethylaminophenyl)pyrazoline, hydrazone compounds, triphenylamine compounds, indole compounds Examples include nitrogen-containing cyclic compounds such as compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds, and fused polycyclic compounds.

These charge transport materials may be used alone or in combination of two or more. In addition, when using a charge transport material with film-forming properties such as polyvinylcarbazole,
A binder resin is not necessarily required. Various resins can be used as the binder resin in the photosensitive layer, charge generation layer and charge transport layer. For example, styrene polymers, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers,
Acrylic copolymer, styrene-acrylic acid 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 cross-linkable thermoplastic resins. Examples include curable resins and photocurable resins such as epoxy acrylate and urethane-acrylate. These binder resins can be used alone or in combination of two or more.

Further, when forming the charge generation layer and the charge transport layer by coating means, a solvent is used to prepare the coating solution. Various organic solvents can be used as this solvent, including alcohols such as methanol, ethanol, isopropanol, and butanol, aliphatic hydrocarbons such as n-hexane, octane, and cyclohexane, and aromatic solvents such as benzene, toluene, and xylene. group hydrocarbons, 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, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, and ethyl acetate. , esters such as methyl acetate, dimethyl formaldehyde, dimethyl formamide, dimethyl sulfoxide, and the like. 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, a surfactant, a leveling agent, etc. may be used to improve the dispersibility, dyeability, etc. of the charge transport material and charge generation material.

[0028] As the conductive substrate, various conductive materials can be used, such as aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, and indium. Examples include simple metals such as 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.

The conductive substrate may be in the form of a sheet or a drum, as long as the substrate itself is conductive or the surface of the substrate is conductive. Further, the conductive substrate preferably has sufficient mechanical strength during use. In the laminated photoconductor, the charge generation material and the binder resin that constitute the charge generation layer can be used in various ratios, but the charge generation material and the binder resin can be used in various proportions, but the charge 5 to 500 parts of generated material, especially 1
It is preferable to use it in a proportion of 0 to 250 parts. Further, the charge generation layer may have an appropriate thickness, but may have a thickness of 0.01
It is preferably formed to have a thickness of about 5 μm, particularly about 0.1 to 3 μm.

The above general formula (1) constituting the charge transport layer
Dianthraquinone compound (charge transport material) represented by
and the binder resin can be used in various ratios as long as they do not inhibit charge transport and do not crystallize. , 2 parts of the dianthraquinone compound represented by the above general formula (1) per 100 parts of the binder resin.
It is preferably used in a proportion of 5 to 200 parts, particularly 50 to 150 parts. Further, the charge transport layer is preferably formed to have a thickness of about 2 to 100 μm, particularly about 5 to 30 μm.

[0031] In a single-layer type photoreceptor, the binder resin 10
0 parts to 2 to 20 parts of the charge generating material, especially 3 to 15 parts.
part, the dianthraquinone compound (charge transport material) represented by the above general formula (1) is 40 to 200 parts, particularly 50 to 200 parts.
150 copies is appropriate. Further, the thickness of the single-layer type photosensitive layer is preferably about 10 to 50 μm, particularly about 15 to 30 μm.

In a single-layer electrophotographic photoreceptor, there is a gap between the conductive substrate and the photosensitive layer, and in a laminated photoconductor, there is a gap between the conductive substrate and the charge generation layer. Alternatively, a barrier layer may be formed between the conductive substrate and the charge transport layer and between the charge generation layer and the charge transport layer to the extent that it does not impede the characteristics of the photoreceptor. , a protective layer may be formed.

When the charge generation layer and the 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, a ball mill, an attritor, a paint shaker, or an ultrasonic wave. A coating liquid may be prepared by dispersing and mixing using a disperser or the like, and this may be 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.

Example 1 <Synthesis of dianthraquinone compound represented by the above formula (2)> 8 g of 1,4-naphthoquinone and the following formula (4)
In 100 ml of anhydrous alcohol solution of potassium hydroxide, 8.5 g of the diene represented by System compound (5)
was reduced with 43 g of Na2 S2 O and 4 g of NaOH to obtain a compound represented by the following formula (6).

[0035]

[Chemical formula 8]

8 g of 1,4-naphthoquinone and the following formula (7
) is reacted in the same manner as above to produce an anthraquinone compound represented by the following formula (8), and further this anthraquinone compound (8)
In the same manner as above, a compound represented by the following formula (9) was obtained.

[0037]

[Chemical formula 9]

Compound (6) thus obtained and compound (9) were combined in the same manner as above to obtain the formula (2).
A dianthraquinone compound represented by (hereinafter referred to as dianthraquinone compound 2) was obtained. The yield of this dianthraquinone compound 2 was 62%, and the melting point was 322.
It was yellow microcrystals at ~325°C. Further, when the compound 2 was subjected to elemental analysis, the following results were obtained.

Elemental analysis value: Calculated value as C38H30O2 F6 (
%) C72.13 H4.79 actual value (%) C72.
00 H4.71 Example 2 <Synthesis of dianthraquinone compound represented by the above formula (3)> Instead of the compound represented by the above formula (7), 15 g of a diene represented by the following formula (10) was added. A dianthraquinone compound represented by the formula (3) (hereinafter referred to as dianthraquinone compound 3) was obtained in the same manner as in Example 1, except that the compound was used.

[0040]

[Chemical formula 10]

The yield of this dianthraquinone compound 3 was 65%, and it was yellow microcrystals with a melting point of 340 to 344°C. In addition, elemental analysis of Compound 3 revealed that
The following results were obtained. Elemental analysis value: Calculated value (%) as C38H30O2 Cl6 C62.40 H4.14 actual value (%) C62
．． 21 H4.20 Examples 3 and 4 (Laminated photoreceptor) Metal-free phthalocyanine as charge generating material 2.
A dispersion consisting of 5 parts, 100 parts of polyvinyl butyral resin (S-LECBH-5H manufactured by Sekisui Chemical Co., Ltd.) and 150 parts of tetrahydrofuran was applied onto an alumite-treated aluminum cylinder, dried,
A charge generation layer having a thickness of 0.3 μm was obtained.

A solution of 100 parts of electron transport material and 100 parts of polycarbonate resin dissolved in 460 parts of toluene was applied onto this charge generation layer using a wire bar, and dried to form a charge transport layer with a thickness of 20 μm. A photoreceptor was obtained. The electron transport materials used in Examples 3 and 4 are shown in Table 1 by the numbers of the compounds shown in the above-mentioned specific examples. Comparative Example 1 (Laminated Photoreceptor) A photoreceptor was obtained in the same manner as in Examples 3 and 4 above, except that 100 parts of a compound represented by the following formula (11) was used as an electron transport material.

[0043]

[Chemical formula 11]

Examples 5 and 6 (single-layer photoreceptor) 2.0 parts of metal-free phthalocyanine, 10 parts of polycarbonate resin
0 parts, 500 parts of tetrahydrofuran, hole transport material 5
A dispersion consisting of 0 parts and 50 parts of electron transport material is applied onto an anodized aluminum cylinder,
It was dried to form a photosensitive layer having a thickness of 20 μm, and a photoreceptor was obtained. In Table 1, the charge transport materials used at this time are represented by the respective chemical structural formula numbers as in the above examples. In addition, as a hole transport material, the following formula (12
) was used.

[0045]

[Chemical formula 12]

Comparative Example 2 (Single-layer photoreceptor) A photoreceptor was obtained in the same manner as in Examples 4 and 5 above, except that 50 parts of the compound represented by formula (11) above was used as the electron transport material. Ta. Comparative Example 3 (Single-layer photoreceptor) Except that only 100 parts of the hole transport material was used without using the dianthraquinone compound as the electron transport material.
A photoreceptor was obtained in the same manner as in Examples 4 and 5 above.

(Evaluation test) The potential of the unexposed area, the potential of the exposed area, and the half-decreased exposure amount (E1/2) of the photoconductor obtained in each example and comparative example were measured using "Cynthia 30M" manufactured by Gentech.
Measured using a drum sensitivity tester. A xenon lamp was used as a light source, and 780 nm light was extracted with a monochromator and irradiated onto the photoreceptor.

Table 1 shows the test results of Examples 3 to 6 and Comparative Examples 1 to 3.

[0049]

[Table 1]

From these test results, it can be seen that the photoreceptors of Examples 3 to 6 have significantly improved sensitivity compared to the photoreceptors of Comparative Examples 1 to 3.

[0051]

As described above, the dianthraquinone compound of the present invention has high electron-accepting properties and can be suitably used as a charge transport material. Further, by using this dianthraquinone compound as a charge transport material, a highly sensitive photoreceptor can be obtained.

Claims (2)

[Claims] Claim 1: The following general formula (1): [Formula 1] (wherein R1 and R2 are the same or different and are a hydrogen atom, a hydroxyl group, a nitro group, a cyano group, an amino group, a halogen-substituted alkyl group, or a substituent) R3 represents a hydrogen atom or a halogen-substituted alkyl group. R4 represents a halogen-substituted alkyl group. p, q, r and s are the same or different and represent an integer of 0 to 4. .However, R1 , R2 , R3 and R4
At least one of them is a halogen-substituted alkyl group, and p, q, r and s are not 0 at the same time. ) is a dianthraquinone compound represented by 2. A photoreceptor characterized in that a photosensitive layer containing a dianthraquinone compound represented by the following general formula (1) is provided on a conductive substrate. [Formula 2] (wherein, R1 and R2 are the same or different and represent a hydrogen atom, a hydroxyl group, a nitro group, a cyano group, an amino group, a halogen-substituted alkyl group, or an alkoxy group that may have a substituent. R3 is hydrogen represents an atom or a halogen-substituted alkyl group. R4 represents a halogen-substituted alkyl group. p, q, r and s are the same or different and represent an integer of 0 to 4. However, R1, R2, R3 and R4
At least one of them is a halogen-substituted alkyl group, and p, q, r and s are not 0 at the same time. )