JPH04285670A - Diphenoquinone-based compound and electrophotographic photosensitive sheet using the same compound - Google Patents

Abstract

PURPOSE:To obtain a new compound having low subliming properties, excellent safety, sensitivity, recurring characteristics and compatibility with binder resins and useful for electrophotographic photosensitive sheet, etc. CONSTITUTION:A compound expressed by formula I (R<1> to R<4> are fluorine- substituted alkyl), e.g. a compound expressed by formula II. Furthermore, the compound expressed by formula I is obtained by dissolving a compound expressed by formula III (R is R<1> to R<4>) in a solvent such as dichloromethane, etc., and oxidizing the compound expressed by formula III with an oxidizing agent such as potassium permanganate. The electrophotographic photosensitive sheet having a photosensitive layer containing the above-mentioned compound has excellent sensitivity and recurring characteristics.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel diphenoquinone compound and an electrophotographic photoreceptor using the same.

0002

BACKGROUND OF THE INVENTION In recent years, organic photoreceptors have been widely used as electrophotographic photoreceptors in image forming apparatuses such as copying machines, printers, facsimile machines, etc., as they are excellent in processability and economical efficiency and have a large degree of freedom in functional design. Further, when forming a copy image using an electrophotographic photoreceptor, the Carlson process is widely used. The Carlson process is
A charging process in which the photoconductor is uniformly charged by corona discharge, an exposure process in which the charged photoconductor is exposed to an original image to form an electrostatic latent image corresponding to the original image, and the electrostatic latent image is developed using toner. A developing process in which a toner image is formed by developing with a toner image, 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 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 high-quality images, an electrophotographic photoreceptor is required to have excellent charging characteristics and photosensitive characteristics, and to have a low residual potential after exposure.

Conventionally, inorganic photoconductors such as selenium and cadmium sulfide have been known as materials for electrophotographic photoreceptors.
These have the disadvantage of being toxic and having high production costs. Therefore, so-called organic electrophotographic photoreceptors using various organic substances in place of these inorganic substances have been proposed. Such an organic electrophotographic photoreceptor has a photosensitive layer composed 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 electrophotographic photoreceptor, it is necessary to appropriately select the charge generating material and the charge transporting material. Various substances have been studied as charge transport materials, and many substances such as polyvinyl carbazole, oxadiazole compounds, pyrazoline compounds, and hydrazone compounds have been proposed. Since these charge transport materials are hole transport materials, a negative charging process is inevitably required in functionally separated photoreceptors, which are currently the mainstream of organic electrophotographic photoreceptors. However, negative polarity corona discharge is inherently unstable and has problems such as deterioration of the photoreceptor due to ozone generation and pollution of the environment in which it is used. In order to solve these problems, it is sufficient to adopt an organic electrophotographic photoreceptor that operates with positive charging and uses an electron transport material as a charge transport material. Compounds with a diphenoquinone structure have been proposed. This is an electron acceptor with a delocalized π-electron system, and can transport electrons through an electron transfer reaction involving an anion radical state.

[0005]

[Problems to be Solved by the Invention] However, for example, the structure of the substituent represented by the following formula (A) has low compatibility with the binder resin constituting the photoreceptor, and therefore a large amount of the diphenoquinone compound cannot be contained in the photosensitive layer, so there is a drawback that sufficient sensitivity cannot be obtained.

[0006]

[Chemical formula 3]

[0007] Furthermore, since the diphenoquinone compound has sublimation property, there is also a risk that the sensitivity may decrease over time. That is, the properties of diphenoquinone compounds are greatly influenced by the type and type of substituents. The purpose of the present invention is to solve such technical problems and to provide a diphenoquinone compound that has high electron acceptability, excellent compatibility with a binder resin, and low sublimation property, and a diphenoquinone compound that has high sensitivity and excellent repeatability. An object of the present invention is to provide an electrophotographic photoreceptor.

[0008]

[Means and effects for solving the problems] The diphenoquinone compound of the present invention for achieving the above object has the general formula (1):

[0009]

[C4]

(wherein R1, R2, R3 and R
4 are the same or different and represent a fluorine-substituted alkyl group. ). Such diphenoquinone compounds of the present invention are effective as charge transport materials, particularly electron transport materials. Furthermore, since the diphenoquinone compound of the present invention has an alkyl group substituted with a fluorine atom, it has excellent compatibility with a binder resin, and its sublimability is reduced by the fluorine atom.

Therefore, the electrophotographic photoreceptor of the present invention is characterized in that a photosensitive layer containing a diphenoquinone compound represented by the above general formula (1) is provided on a conductive substrate. As a result, the electrophotographic photoreceptor of the present invention has excellent sensitivity and charging ability, and has high repeatability. Examples of the fluorine-substituted alkyl group include a methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group substituted with one or more fluorine atoms,
Examples include a pentyl group and a hexyl group, and preferably an alkyl group in which all hydrogen atoms are replaced with fluorine atoms, such as a trifluoromethyl group.

Specific examples of the diphenoquinone compound represented by the general formula (1) include the following.

[0013]

[C5]

The compound represented by the general formula (1) is:
For example, it can be produced using the following reaction formula. Reaction formula:

[0015]

[C6]

(In the formula, R is the above R1, R2, R3
, R4. ) That is, by dissolving the phenolic compound represented by formula (a) in a solvent and oxidizing it with an oxidizing agent, the product (
1') is obtained (Meneger et al., J
．． Org. Chem. , 50, 3927 (1
985)). As the above-mentioned solvent, for example, chloroform, dichloromethane, etc. can be used. Further, as the oxidizing agent, for example, potassium permanganate,
Potassium ferricyanide and the like can be used. The reaction is carried out by heating at a temperature of about 50 to 55°C. The amount of the oxidizing agent used is suitably 4 moles or more per 1 mole of the phenolic compound.

The photosensitive layer in the present invention has the general formula (1).
) Contains one or more compounds represented by: 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 laminated type electrophotographic photoreceptor, a charge generation layer containing a charge generation material is formed on a conductive base material, and a charge transport material having the above general formula is formed on this charge generation layer. A charge transport layer containing the represented compound may be formed. Furthermore, the stacking order may be reversed and the charge generation layer may be provided on the charge transport layer. As charge generating materials, conventionally used selenium, selenium-tellurium, selenium-arsenic, amorphous silicon, pyrylium salts, azo compounds, disazo compounds, phthalocyanine compounds, anthanthrone compounds, perylene compounds,
Examples include indigo compounds, triphenylmethane compounds, threne compounds, toluidine compounds, pyrazoline compounds, perylene compounds, quinacridone compounds, and pyrrolopyrrole compounds. These charge generating materials can be used alone or in combination of two or more.

Further, the compound represented by the above general formula, which is a charge transporting material, can be used in combination with other conventionally known charge transporting materials. Conventionally known charge transport materials include, for example, oxadiazole compounds such as 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazole, and 9-(4-diethylaminostyryl).
Styryl compounds such as anthracene, carbazole compounds such as polyvinylcarbazole, 1-phenyl-3-
Pyrazoline compounds such as (p-dimethylaminophenyl) pyrazole, triphenylamine compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, triazoles Examples include nitrogen-containing cyclic compounds such as system compounds, and fused polycyclic compounds. Note that a binder resin is not necessarily required when a charge transporting material having film-forming properties such as polyvinylcarbazole is used.

Various resins can be used as the binder resin, such as styrene polymers, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, and acrylic copolymers. Union,
Styrene-acrylic acid copolymer, polyethylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polyvinyl chloride, polypropylene, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, polycarbonate, polyarylate , thermoplastic resins such as polysulfone, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin, silicone resin, epoxy resin, and other crosslinkable thermosetting resins, as well as photosensitive resins such as epoxy acrylate and urethane-acrylate. Examples include curable resins. These binder resins can be used alone or in combination of two or more.

[0021] Examples of the solvent for dissolving the charge generating material, charge transporting material and binder resin to prepare a coating solution include methanol, ethanol, isopropanol,
Alcohols such as butanol, aliphatic hydrocarbons such as n-hexane, octane, and cyclohexane, aromatic hydrocarbons such as benzene, toluene, and xylene, halogenated hydrocarbons such as dichloromethane, dichloroethane, carbon tetrachloride, and chlorobenzene, and dimethyl ether. , ethers such as diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, esters such as ethyl acetate and methyl acetate, 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, a surfactant, a leveling agent, etc. may be used to improve the dispersibility, dyeability, etc. of the charge transport material and charge generation material.

[0023] Examples of the conductive substrate include aluminum, copper, tin, platinum, silver, vanadium, molybdenum,
Chromium, cadmium, titanium, nickel, palladium,
Single metals such as indium, stainless steel, and brass, and plastic materials on which the above metals are vapor-deposited or laminated;
Examples include glass coated with aluminum iodide, tin oxide, indium oxide, and the like.

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. Also,
The substrate preferably has sufficient mechanical strength during use. In the laminated electrophotographic photoreceptor, the charge generation material and the binder resin constituting the charge generation layer can be used in various ratios, but 100 parts of the binder resin (parts by weight,
It is preferable to use 5 to 500 parts, particularly 10 to 250 parts, of the charge generating material (the same applies hereinafter).

[0025] The charge generation layer may have an appropriate thickness, but it may have a thickness of 0.01 to 5 μm, particularly 0.1 to 3 μm.
It is preferable that the diameter is about m. The compound represented by the above general formula (1) (charge transport material) constituting the charge transport layer and the binder resin can be used in various ratios, but the charge generated in the charge generation layer by light irradiation can be 10 to 500 parts, especially 25 to 2 parts, of the compound represented by the above general formula is added to 100 parts of the binder resin so that it can be easily transported.
Preferably, it is used in a proportion of 0.00 parts.

The charge transport layer is preferably formed to have a thickness of about 2 to 100 μm, particularly about 5 to 30 μm. In a single-layer type electrophotographic photoreceptor, the amount of the charge generating material is 2 to 20 parts, especially 3 to 15 parts, and the amount of the compound represented by the above general formula (charge transporting material) is 40 to 40 parts per 100 parts of the binder resin. 2
00 parts, especially 50 to 150 parts is suitable. Further, the thickness of the single-layer type photosensitive layer is preferably about 10 to 50 μm, particularly about 15 to 30 μm.

When a photosensitive layer including a charge generation layer and a charge transport layer is formed by a coating method, the charge generation material or the charge transport material and the binder resin are mixed by a conventionally known method such as a roll mill, a ball mill, an attritor, or a binder resin. Prepare the coating solution using a paint shaker, ultrasonic disperser, etc.

[0028]

[Examples] The present invention will be explained in detail below with reference to Examples and Comparative Examples. Example 1 (Synthesis of compound represented by the above formula (2)) M
Eneger et al. , J. Org. Ch
em. , 50, 3927 (1985). That is, 5.52 g (24 mmol) of 2,6-bistrifluoromethylphenol was dissolved in 50 ml of chloroform, and 15 g (96 mmol) of potassium permanganate was further suspended therein as an oxidizing agent, followed by stirring at 55°C for 2 hours. did. Then, after filtering out insoluble matter from the reaction mixture, the solvent was distilled off to obtain a reddish brown solid. This was recrystallized from ethanol to give purple-brown needle crystals, which were thoroughly dried under reduced pressure at 60°C. Elemental analysis value: Calculated value as C16H4 O2 F12 (
%) C42.12 H0.91 Actual value (%
) C42.01 H1.01 Example 2 (Laminated photosensitive layer) 1 part of metal-free phthalocyanine as a charge generating material, polyvinyl butyral resin ("S-le" manufactured by Sekisui Chemical Co., Ltd.)
cBM-5)” 1 part, 120 parts of tetrahydrofuran,
The mixture was dispersed for 2 hours using a paint shaker using zirconia beads (2 mm diameter). The obtained dispersion was coated onto an aluminum sheet using a wire bar, and
It was dried at ℃ for 1 hour to obtain a charge generation layer of 0.5 μm.

On this charge generation layer, 75 parts of the diphenoquinone compound (charge transport material) represented by the above formula (2) obtained in Example 1 and poly(4,4'-cyclohexylidene diphenyl) carbonate resin were applied. (Mitsubishi Gas Chemical Co., Ltd. "Polycarbonate Z-200") A solution of 100 parts dissolved in a predetermined amount of toluene was applied with a wire bar,
It was dried at 100° C. for 1 hour to form a charge transport layer of 22 μm, thereby obtaining a positively charged electrophotographic photoreceptor. Comparative Example 1 (Laminated Photosensitive Layer) As a charge transport material, the following formula (A):

[0030]

[C7]

A positively charged electrophotographic photoreceptor was obtained in the same manner as in Example 1, except that the diphenoquinone compound represented by the formula was used at a ratio of 30 parts to 100 parts of the resin. The reason why the amount of diphenoquinone compound added was 30 parts was because
This is because this compound reached the limit of its solubility in the binder resin and could not be dissolved any further. Example 3 (single layer type photosensitive layer) (components)
(Part) Metal-free phthalocyanine
1
Binder resin
100 (
"Polycarbonate Z-200" mentioned above)
Diphenoquinone compound represented by the above formula (2) 60 N, N, N',
N'-tetrakis(3-methylphenyl)-1,3-diaminobenzene
40 Each of these components was added to a predetermined amount of tetrahydrofuran and dispersed for 2 hours using a paint shaker using zirconia beads (2 mm diameter). The resulting dispersion was coated onto an aluminum sheet using a wire bar, dried at 100°C for 1 hour, and coated with a 20μ
A photosensitive layer of m was formed to obtain an electrophotographic photoreceptor. Comparative Example 2 (Single-layer type photosensitive layer) Example except that the diphenoquinone compound represented by the above formula (A) was used instead of the diphenoquinone compound represented by the above formula (2) as the charge transport material. An electrophotographic photoreceptor was obtained in the same manner as in 2. However, the amount of diphenoquinone compound (A) used was 30 parts, the same as in Comparative Example 1 above.

(Evaluation test) The surface potential, half-decreased exposure (E1/2), and residual potential of the photoreceptor obtained in each example and comparative example were measured using an evaluation tester ("EPA8100" manufactured by Kawaguchi Electric Co., Ltd.).
”). The measurement conditions are as follows. Light intensity: 10 μW/cm 2 Exposure time: 2 seconds Surface potential: The inflow current value was adjusted to be around (±)700V.

Light source: 780 nm light Static neutralization: 200 lux Measurement of residual potential: The potential was measured 1 second after the start of exposure. The test results of Examples 2 and 3 and Comparative Examples 1 and 2 are shown in Table 1. Note that the photoreceptors having single-layer type photosensitive layers of Example 3 and Comparative Example 2 were tested for positive charging and negative charging, respectively. .

[0034]

[Table 1]

From the test results, it can be seen that the photoreceptors of the examples are superior in half-life exposure and residual potential, and have significantly improved sensitivity, compared to those of the comparative examples.

[0036]

Effects of the Invention As described above, the diphenoquinone compound of the present invention has excellent compatibility with the binder resin and has low sublimation property. Therefore, the electrophotographic photoreceptor of the present invention using this diphenoquinone compound It has the advantage of having excellent sensitivity and repeatability.

Claims (2)

[Claims] [Claim 1] A diphenoquinone compound represented by the general formula (1): [In the formula, R1, R2, R3 and R4 are the same or different and represent a fluorine-substituted alkyl group.] 2. An electrophotographic photoreceptor characterized in that a photosensitive layer containing a diphenoquinone compound represented by the following general formula (1) is provided on a conductive substrate. (In the formula, R1, R2, R3 and R4 are the same or different and represent a fluorine-substituted alkyl group.)