JP2589182B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor, and more particularly, to an electrophotographic photoreceptor in which a photosensitive layer contains a polymethine compound having a specific structure.

[Prior Art] Conventionally, inorganic photoconductive materials such as selenium, cadmium sulfide, and zinc oxide have been widely used as electrophotographic photoreceptors.

On the other hand, as an electrophotographic photoreceptor using an organic photoconductive substance, a photoconductive polymer represented by poly-N-vinylcarbazole or 2,5-bis (p-diethylaminophenyl) -1,3,4- There are known those using a low-molecular organic photoconductive substance such as oxadiazole, and those combining such an organic photoconductive substance with various dyes and pigments.

An electrophotographic photoreceptor using an organic photoconductive substance has advantages in that it has good film-forming properties, can be produced by coating, and can provide an extremely high productivity and inexpensive photoreceptor. Further, there is an advantage that color sensitivity can be freely controlled by selecting a sensitizer such as a dye or a pigment to be used, and wide studies have been made so far. Particularly recently, with the development of a function-separated type photoreceptor in which a charge generation layer containing an organic photoconductive dye or pigment and a charge transport layer containing the above-mentioned photoconductive polymer or low molecular organic conductive material are laminated. Significant improvements have been made in sensitivity and durability, which have been disadvantages of conventional organic electrophotographic photosensitive members.

The polymethine dye has a methine chain connected by a conjugated double bond in the molecule and has absorption from visible to near infrared due to π-π ^* transition.

For this reason, development from the standpoint of a functional dye has been actively promoted, and many compounds have been proposed so far.

For example, squarium pigments such as JP-A-62-450 and cyanine dyes such as JP-A-57-188043 and JP-A-59-49546 are known.

However, conventional polymethine pigments generally have low light fastness and cannot always be said to be sufficient in terms of potential stability when used repeatedly. It's just

[Problems to be Solved by the Invention] An object of the present invention is to provide a novel photoconductive material, and to provide an electrophotographic photoreceptor having stable potential characteristics when repeatedly used for practical use.

[Means for Solving the Problems and Action] The present invention is characterized in that in an electrophotographic photosensitive member having a photosensitive layer on a conductive support, the photosensitive layer contains a polymethine compound represented by the following general formula (I). It is composed of an electrophotographic photoreceptor.

General formula In the formula, R represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent which may be bonded via a bonding group, and X is 2,3-pyridinediyl, 3,4 -Pyridinediyl or 2,3-pyrazinediyl, Y and Z are the same or different and represent an oxygen atom, a sulfur atom or a dicyanomethylene group, m is an integer of 1, 2 or 3,
n is an integer of 0, 1 or 2.

More specifically, examples of the bonding group include groups such as a carbonyl group, an imino group, and a nitroso group.Examples of the aromatic hydrocarbon group include groups such as phenyl, naphthyl anthryl and pyrenyl, and examples of the aromatic heterocyclic group include pyridyl. , Pyrazil,
Groups such as quinolyl, thienyl, thiazolyl, carbazolyl, benzimidazolyl, and furyl; examples of the substituent include a fluorine atom, a chlorine atom, a halogen atom such as a bromine atom, an alkyl group such as methyl, ethyl, and propyl;
Examples thereof include an alkylamino group such as dimethylamino and diethylamino, a nitro group, and a cyano group.

Hereinafter, typical examples of the polymethine compound used in the present invention are listed, but the material used in the present invention is not limited to these.

Compound example (1) Compound example (2) Compound example (3) Compound example (4) Compound example (5) Compound example (6) Compound example (7) Compound example (8) Compound example (9) Compound example (10) Synthesis Example (Synthesis of Compound Example (1)) 1.00 g of the following compound (II) is dissolved in 50 ml of ethanol by heating, and 0.66 g of the following compound (III) is added thereto, followed by stirring at 75 ° C. for 3 hours. Was. After completion of the reaction, the reaction mixture was cooled to 0 ° C., separated by filtration, washed repeatedly with cold methanol, and dried to obtain a target compound. 0.92g yield Elemental analysis value Actual measurement value (%) Calculated value (%) C 83.70 83.55 H 3.61 3.65 N 3.95 3.90 The electrophotographic photoreceptor of the present invention comprises a conductive support containing the polymethine compound represented by the general formula (I). With layers.

The form of the photosensitive layer may be any known form, but a photosensitive layer containing a polymethine compound represented by the general formula (I) is used as a charge generation layer, and a charge transport layer containing a charge transport substance is added thereto. A laminated function-separated type photosensitive layer is particularly preferred.

The charge generation layer can be formed by applying a coating solution obtained by dispersing a polymethine compound represented by the general formula (I) together with a binder resin in an appropriate solvent onto a conductive support by a known method. The film thickness is, for example, 5 μm
Hereinafter, it is desirable to form a thin film layer of preferably 0.1 to 1 μm.

The binder resin used at this time is selected from a wide range of insulating resins or organic photoconductive polymers. And the like, and the amount used is 80 in terms of the content in the charge generation layer.
% By weight, preferably 40% by weight or less.

The solvent used is preferably selected from those which dissolve the resin and do not dissolve the charge transport layer and the undercoat layer described below.

Specifically, tetrahydrofuran, ethers such as 1,4-dioxane, cyclohexanone, ketones such as methyl ethyl ketone, amides such as N, N-dimethylformamide, methyl acetate, esters such as ethyl acetate, toluene, xylene, Examples include aromatic compounds such as chlorobenzene, alcohols such as methanol, ethanol, and 2-propanol; and aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, and trichloroethylene.

The charge transport layer is stacked on or below the charge generation layer, and has a function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting the charge carriers to the surface.

The charge transporting layer is formed by dissolving a charge transporting material in a solvent together with a suitable binder resin if necessary, and applying the solution. The thickness of the charge transporting layer is generally 5 to 40 μm.
-30 μm is preferred.

The charge transporting substance includes an electron transporting substance and a hole transporting substance. Examples of the electron transporting substance include 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, chloranil, and tetralane. Examples thereof include electron-withdrawing substances such as cyanoquinodimethane, and those obtained by polymerizing these electron-withdrawing substances.

Examples of the hole transporting substance include polycyclic aromatic compounds such as pyrene and anthracene, carbazole-based, indole-based, imidazole-based, oxazole-based, thiazole-based, oxadiazole-based, pyrazole-based, pyrazoline-based, thiadiazole-based, and triazole-based compounds. Heterocyclic compounds such as
hydrazone compounds such as p-diethylaminobenzaldehyde-N, N-diphenylhydrazane, N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, α-phenyl-4′-N, N-diphenylaminostilbene, A styryl compound such as 5- [4- (di-p-tolylamino) benzylidene] -5H-dibenzo [a, d] cycloheptene, a benzidine compound, a triarylmethane compound, triphenylamine, or a mixture of these compounds Polymers having a group in the main chain or side chain (for example, poly-N-vinyl caribasol, polyvinyl anthracene, etc.) are exemplified.

In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide can be used.

These charge transport materials can be used alone or in combination of two or more.

When the charge transport material does not have a film-forming property, an appropriate binder resin can be used, and specifically, an acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, polyacrylamide, polyamide, Examples thereof include insulating resins such as chlorinated rubber and organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene.

As the conductive support, for example, a metal or alloy such as aluminum, an aluminum alloy, and stainless steel can be used.

A support or conductive material obtained by coating such a metal or alloy with plastic or conductive particles (eg, carbon black, silver particles, etc.) coated on a plastic or metal support with a suitable binder resin by vacuum evaporation. For example, a support obtained by impregnating a conductive particle with plastic or paper can be used.

An undercoat layer having a barrier function and an adhesive function may be provided between the conductive support and the photosensitive layer.

The undercoat layer can be formed of casein, polyvinyl alcohol, nitrocellulose, polyamide (nylon 6, nylon 66, nylon 610, copolymer nylon, alkoxymethylated nylon, etc.), polyurethane, aluminum oxide, or the like.

The thickness of the undercoat layer is 5 μm or less, preferably 0.1 to 3 μm.
m is appropriate.

As another specific example of the present invention, an electrophotographic photoreceptor in which the polymethine compound represented by the general formula (I) and the charge transporting substance are contained in the same layer can be mentioned. In this case, a charge transfer chain composed of poly-N-vinylcarbazole and trinitrofluorenone can be used as the charge transport material.

The electrophotographic photoreceptor of this embodiment can be formed by applying and drying a liquid in which polymethine represented by the general formula (I) and a charge transporting substance are dispersed in a resin solution. The crystal form of the polymethine compound represented by the general formula (I) used in any of the electrophotographic photoreceptors may be amorphous or crystalline;
If necessary, two or more polymethine compounds represented by the general formula (I) may be used in combination, or may be used in combination with a known charge generating substance.

The electrophotographic photoreceptor of the present invention can be widely used not only for electrophotographic copying machines but also for electrophotographic applications such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.

[Examples] Examples 1 to 10 5 g of methoxymethylated nylon (number average molecular weight 32,000) and 10 g of alcohol-soluble copolymerized nylon (number average molecular weight 29,000) on an aluminum support 95 g of methanol
The solution dissolved in is coated with a Myer bar, and the film thickness after drying is
An undercoat layer of 1.0 μm was provided.

Next, 5 g of the pigment of the above compound example (1) was added to 95 g of cyclohexanone and 2 g of butyral resin (butyralization degree: 62 mol%).
Was added to the solution, and dispersed by a sand mill for 20 hours. The thickness of this dispersion after drying on the undercoat layer formed earlier is
The resultant was coated with a Meyer bar and dried to a thickness of 0.2 μm to form a charge generation layer.

Then, 5 g of a hydrazone compound having the following structure 5 g of polymethyl methacrylate (number average molecular weight 100,000) was dissolved in 40 g of chlorobenzene, and this was coated on a charge generation layer with a Meyer bar and dried to form a 20 μm charge transport layer. It was created.

Electrophotographic photoreceptors corresponding to Examples 2 to 10 were prepared in exactly the same manner except that the pigment of Compound Example (1) was used in place of the pigment of Compound Example (1).

The electrophotographic photoreceptor thus prepared was negatively charged by corona discharge at −5 KV using an electrostatic copying paper tester (Model SP-428, manufactured by Kawaguchi Electric Co., Ltd.) and left in a dark place for 1 second. Thereafter, exposure was performed with an illuminance of 10 lux using a halogen lamp, and charging characteristics were evaluated.

As the charging characteristics, the surface potential (V _O ) and the exposure amount (E1 / 2) required for the surface potential after being left in a dark place to attenuate to half were measured. The results are shown.

Comparative Examples 1 and 2 An electrophotographic photosensitive member was prepared in exactly the same manner as in Example 1 except that the compound having the following structure was used instead of the compound of Compound Example (1), and the charging characteristics were evaluated in the same manner.

(Comparative Example 1) V _O : -670V E1 / 2: 8.74lux · sec (Comparative Example 2) V _O : -710V E1 / 2: 10.09lux · sec From these results, it can be seen that all of the electrophotographic photoreceptors of the present invention have sufficient charging ability and excellent sensitivity.

Examples 11 to 14 Using the electrophotographic photoreceptor prepared in Example 1, fluctuations in the light portion potential and the dark portion potential during repeated use were measured.

As a method, the above-mentioned photoreceptor was attached to a cylinder of an electrophotographic copying machine equipped with a corona charger of -6.5 KV, an exposure optical system, a developing device, a transfer charger, a charge removing exposure optical system and a cleaner.

The initial dark potential (V _D ) and bright potential (V _L ) were set to around -700 V and -200 V, respectively, and the amount of change in the dark potential (△ V _D ) and the bright potential when used 5,000 times repeatedly Was measured (ΔV _L ).

The electrophotographic photoreceptors prepared in Examples 3, 5 and 8 were similarly evaluated.

Example 11 corresponds to the photoreceptor of Example 1 and Example 1 corresponds to the photoreceptors of Examples 3, 5, and 8.
2, 13, and 14.

Note that a negative sign in the fluctuation amount of the potential indicates a decrease in the absolute value of the potential, and a positive sign indicates an increase in the absolute value of the potential.

Comparative Examples 3 and 4 The potential fluctuations during repeated use of the electrophotographic photosensitive members prepared in Comparative Examples 1 and 2 were measured in the same manner as in Example 11, respectively. The results are shown.

From the above results, it can be seen that the electrophotographic photoreceptor of the present invention has a small potential fluctuation upon repeated use.

Example 15 An undercoat layer of polyvinyl alcohol having a thickness of 0.5 μm was formed on an aluminum surface of an aluminum-deposited polyethylene terephthalate film.

On this, the dispersion liquid of the pigment of the compound example (1) used in Example 1 was applied with a Meyer bar so that the film pressure after drying was 0.2 μm, and dried to form a charge generation layer.

Then 5 g of styryl compound represented by the following structural formula A solution prepared by dissolving 5 g of polycarbonate (weight-average molecular weight: 55,000) in 40 g of tetrahydrofuran was applied on the charge generation layer so that the film thickness after drying was 20 μm, and dried to form a charge transport layer.

The charging characteristics and durability characteristics of the electrophotographic photoreceptors thus prepared were measured by the same methods as in Examples 1 and 11. The results are shown.

V _O : −730 V E1 / 2: 2.87 lux · sec ΔV _D : 0 V ΔV _L : +5 V Example 16 The charge generation layer and the charge mailing layer of the photoreceptor prepared in Example 15 were applied and laminated in reverse order. An electrophotographic photosensitive member was prepared, and the charging characteristics were evaluated in the same manner as in Example 1. However, the charging polarity was positive.

 The results are shown.

V _O : + 760V E1 / 2: 3.50lux · sec [Effect of the Invention] The electrophotographic photoreceptor of the present invention has high sensitivity and repeated use by using the polymethine compound represented by the general formula (I) in the charge generation layer. This has a remarkable effect that the potential stability at the time is excellent.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Gen Miyazaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-57-204550 (JP, A) JP-A-63 -173061 (JP, A) JP-A-61-63846 (JP, A) JP-A-57-201236 (JP, A)

Claims (2)

(57) [Claims] 1. An electrophotographic photosensitive member having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a polymethine compound represented by the following general formula (I). General formula In the formula, R represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent which may be bonded via a bonding group, and X is 2,3-pyridinediyl, 3,4 -Represents a pyridinediyl or 2,3-pyrazindiyl group, Y and Z
Are the same or different and each represent an oxygen atom, a sulfur atom or a dicyanomethylene group; m is an integer of 1, 2 or 3;
Is an integer of 0, 1 or 2. 2. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer comprises at least two layers of a charge generation layer containing a polymethine compound represented by the general formula (I) and a charge transport layer.