JPS63236048A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a laminate type electrophotographic sensitive body high in sensitivity to visible light and also to light of 780nm wavelength by using specified 2 kinds of pigments for an electric charge generating layer. CONSTITUTION:The charge generating layer forward on a conductive supporting body together with a charge transfer layer contains a combination of an N- methyldiphenylamine disazo pigment represented by formula I and an anthraquinone type disazo pigment represented by formula II in which A is a coupler residue having a phenolic hydroxyl group or a coupler residue of a 2-methylindolenine derivative, thus permitting the obtained electrophotographic sensitive body to be high in sensitivity to the visible light and also to light of 780nm and superior in repeated use characteristics by using such a combination of charge generating materials.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor, and more particularly to a laminated electrophotographic photoreceptor having a charge generation layer containing two types of disazo pigments having a specific structure at the same time. .

[Prior Art] Electrophotographic photoreceptors using inorganic photoconductors such as selenium, cadmium sulfide, and zinc oxide as photosensitive components are well known.

On the other hand, since the discovery that certain organic compounds exhibit photoconductivity, many organic photoconductors have been developed. For example, organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene, low-molecular organic photoconductors such as carbazole, anthracene, pyrazolines, oxadiazoles, hydrazones, and polyarynylalkane, and phthalocyanine pigments. , azo pigments, cyanine dyes, polycyclic quinone pigments, perylene pigments, indigo dyes,
Organic pigments and dyes such as squaric acid methine dyes are known. In particular, organic pigments and dyes with photoconductivity are
Many photoconductive organic pigments and dyes have been proposed because they are easier to synthesize than inorganic materials, and the variety of compounds that exhibit photoconductivity in the appropriate wavelength range has expanded.

For example, US Patent No. 4,123,270, US Pat. No. 4,247,614, US Pat.
3 specification, US Patent No. 4,251,614, US Patent No. 4,256,821, US Patent No. 42,606
No. 72, US Pat. No. 4,268,596, US Pat. No. 4,278,747, US Pat. No. 4,293
628, an electrophotographic photoreceptor is known that uses a disazo pigment exhibiting photoconductivity as a charge generation substance in a photosensitive layer that is functionally separated into a charge generation layer and a charge transport layer.

Electrophotographic photoreceptors using such organic photoconductors can be produced by coating by appropriately selecting a binder, making it possible to provide photoreceptors with extremely high productivity and low cost. It has the advantage that the sensitive wavelength range can be freely controlled by selection.

A multilayer photoconductor obtained by laminating a charge transport layer and a charge generation layer mainly composed of a charge generation substance has advantages over other single-layer photoconductors in terms of sensitivity and increased residual potential after durability tests. However, it was still not at a sufficient level.

In addition, when controlling the photosensitive wavelength range by selecting organic pigments and dyes, a photoreceptor with a wide photosensitive wavelength range from short wavelengths to long wavelengths (panchromatic) has been proposed.
The stability of the photoreceptor was still not at a sufficient level.

[Problems to be Solved by the Invention] An object of the present invention is to improve the above-mentioned drawbacks and to provide a laminated electrophotographic photoreceptor having high sensitivity and excellent repeatability. Another object of the present invention is to provide a laminated electrophotographic photoreceptor that has visible light sensitivity and is also sensitive to 780 nm light.

[Means and effects for solving the problems] The present invention achieves the above object by forming two layers, a charge generation layer containing a charge generation substance as a main component and a charge transport layer containing a charge transport substance as a main component, on a conductive support. This is achieved by using two types of specific pigments in the charge generation layer in a multilayer electrophotographic photoreceptor having the following characteristics.

That is, the present invention provides a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, in which the charge generation layer is an N-methyldiphenylamine type disazo pigment having the following structural formula (I). and an anthraquinone type disazo pigment represented by the following general formula (1).

Structural Formula (I) General Formula (1) In the formula, A represents a coupler residue having a phenolic OH group or a coupler residue of a 2-methylindolenine derivative.

In the laminated electrophotographic photoreceptor of the present invention, the charge generation layer contains as much charge generation material as possible in order to obtain sufficient absorbance, and in order to efficiently inject the generated charge carriers into the charge transport layer. , a thin film layer, e.g. 10ILm
Hereinafter, it is desirable to use a thin film layer with a thickness of preferably 0.01 to Ipm. This means that most of the incident light is absorbed by the charge generation layer and many charge carriers are generated, and This is due to the fact that generated charge carriers need to be injected into the charge transport layer without being deactivated by recombination or trapping.

The charge generating substance used in the present invention has the following structural formula (I)
and an anthraquinone type disazo pigment represented by the following general formula (1).

Structural Formula (I) In the formula, A represents a coupler residue having a phenolic OH group or a coupler residue of a 2-methylindolenine derivative.

More specifically, the coupler residue A in the above general formula (1) is selected from, for example, groups represented by any of the following general formulas (2) to (8).

:,,X,+hυ In the formula, R1 and R2 are a hydrogen atom, an alkyl group that may have a substituent, an aralkyl group, an aryl group, a heterocyclic group, an imino group, or a nitrogen atom to which R,, R2 is bonded. represents a cyclic amino group together with R3, or represents a residue condensed with a benzene ring to form a polycyclic aromatic ring or a heterocycle;
and R4 represents an alkyl group, aralkyl group, or aryl group which may have a substituent, Y represents a divalent group of aromatic hydrocarbon or a divalent group forming a heterocycle with a nitrogen atom, and R5 and R8 represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a cyano group or a nitro group.

In the above definitions, examples of alkyl groups, aralkyl groups, aryl groups, alkoxy groups and heterocyclic groups include alkyl groups such as methyl, ethyl and propyl; aralkyl groups such as benzyl and naphthylmethyl; and aryl groups such as phenyl. , diphenyl, naphthyl, anthryl, etc.; examples of alkoxy groups include methoxy, ethoxy, propoxy, etc.; examples of heterocyclic groups include dibenzofuran, benzimidacylon, benzthiazole, thiazole, pyridine, etc.

Substituents for the above alkyl groups, aralkyl groups, aryl groups, alkoxy groups, heterocyclic groups, and imino groups include, for example, halogen atoms, nitro groups, cyan groups, substituted amine groups (for example, dimethylamino, diphenylamino, dibenzylamino, etc.) , an alkyl group, an alkoxy group, and the like.

Examples of residues that form a polycyclic aromatic ring or heterocycle with the benzene ring of Can be mentioned.

Further, examples of the divalent group of Y include a phenylene group and a naphthylene group.

Representative examples of the anthraquinone type disazo pigment represented by the general formula (1) are illustrated below.

Since the exemplified pigment has the following basic type, the exemplified content should describe only the coupler residue portion having a phenolic OH group or the coupler residue portion of the 2-methylindolenine derivative shown by A in the different portion. shall be.

Hi I xHg The ratio of the charge generating substance can be arbitrarily selected.

The charge generation layer can be formed by coating the above-mentioned pigment and, if necessary, a charge transporting substance together with a suitable binder (or without a binder) on the substrate, or by forming a vapor deposited layer using a vacuum vapor deposition apparatus. can.

The binder that can be used to form the charge generating layer by coating can be selected from a wide variety of insulating resins, and can also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene. Preferably polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.),
Examples include insulating resins such as polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide, polyamide, polyvinylpyridine, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone.

The resin contained in the charge generation layer is suitably 80% by weight or less, preferably 40% by weight or less.

The solvent that dissolves these resins varies depending on the type of resin, and is preferably selected from those that do not dissolve the charge transport layer and undercoat layer described below.

Specific organic solvents include methanol, ethanol,
Alcohols such as isopropanol, ketones such as acetone, methyl ethyl ketone, cyclohexanone, N
, amides such as N-dimethylformamide and N,N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, and ethylene glycol monomethyl ether;
Esters such as methyl acetate and ethyl acetate, aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, and trichloroethylene, or benzene, toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene, etc. aromatic hydrocarbons and the like can be used.

Coating methods include dip coating, spray coating, spinner coating, bead coating,
This can be carried out using a coating method such as a layer coating method, a blade coating method, a roller coating method, or a curtain coating method.

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°C for 5 minutes or more
It can be carried out stationary or under blown air for a time in the range of 2 hours.

The charge transport layer is electrically connected to the charge generation layer described above, and has the function of receiving and taking charge carriers injected from the charge generation layer in the presence of an electric field, and transporting these charge carriers to the surface. have. At this time, this charge transport layer may be laminated on or under the charge generation layer.

The substance that transports charge carriers (charge transport material) in the charge transport layer is preferably substantially insensitive to the wavelength range of electromagnetic waves to which the charge generation layer is sensitive. The electromagnetic waves referred to here are broadly defined to include γ-rays, X-rays, far-infrared rays, and the like.

When it coincides with or overlaps that of the charge transport layer, the charge carriers generated in both trap each other,
As a result, this causes a decrease in sensitivity.

The charge transport material used in the present invention may be any general charge transport material used in laminated electrophotographic photoreceptors, such as pyrazoline compounds, hydrazone compounds, stilbene compounds, triphenylamine compounds,
Examples include benzidine compounds and oxazole compounds.

Further, in the present invention, the charge transport substance used in the charge transport layer can be added to the charge generation layer, and the sensitizing effect thereof becomes even more remarkable.

When adding a charge transport substance to the charge generation layer, the charge transport substance should be 10 times or less (weight ratio) of the charge generation substance, preferably 0.01 to 1 times, from the viewpoint of high sensitivity, low residual potential, and repetition stability. Appropriate.

To form a charge transport layer containing a charge transport substance, a film can be formed by selecting an appropriate binder.

Resins that can be used as binders include, for example, acrylic resins, polyarylates, polyesters, polycarbonates, polystyrene, acrylonitrile-styrene copolymers, acrylonitrile-butadiene copolymers, polyvinyl butyral, polyvinyl formal, polysulfones, polyacrylamides, polyamides, chlorinated rubbers, etc. (7) Organic photoconductive polymers such as polyvinylcarbazole, polyvinylanthracene, and polyvinylpyrene.

Since there is a limit to the charge transport layer's ability to transport charge carriers, it is impossible to make the film thicker than necessary. Generally, the thickness is 5 to 30 ILm, but the preferable range is 8 to 20 ILm.
ILm. When forming the charge transport layer by coating, an appropriate coating method as described above can be used.

A photosensitive layer having such a laminated structure of a charge generation layer and a charge transport layer is provided on a substrate having a conductive layer, that is, a conductive support. As the substrate having the conductive layer, a substrate which itself is conductive is used, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, and platinum.

In addition, plastics with a layer formed by vacuum deposition of aluminum, aluminum alloy, indium oxide, tin oxide, indium oxide-tin oxide alloy, etc., conductive particles (e.g. carbon black, silver particles, etc.)
A substrate obtained by coating a plastic with a suitable binder, a substrate obtained by impregnating plastic or paper with conductive particles, a plastic 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 subbing layer can be formed from 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 appropriate thickness of the undercoat layer is O11-5ILm, preferably 0.5-37Lm.

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 in the charge transport layer is made of an electron transporting material, the surface of the charge transport layer must be positively charged. When exposed to light after being charged, electrons 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 positive charge, causing a decrease in surface potential between the unexposed area and the exposed area. Electrostatic contrast occurs. A visible image is obtained by developing the electrostatic latent image thus formed with a negatively charged toner.

This can be directly fixed, or the toner image can be transferred to paper or plastic film and 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, and then visualized and fixed. The type of developer, the developing method, and the fixing method may be any known ones or methods, and are not limited to specific ones.

On the other hand, when the charge transport material is made of a hole transport material, the surface of the charge transport layer must be negatively charged, and when exposed to light after charging, holes generated in the charge generation layer are injected into the charge transport layer in the exposed area. , which then reaches the surface and neutralizes the negative charges, resulting in attenuation of the surface potential and an electrostatic contrast between the surface potential and the unexposed area. During development, it is necessary to use a positively charged toner, contrary to when an electron transporting substance is used.

The electrophotographic photoreceptor of the present invention is susceptible to deterioration due to ultraviolet rays, ozone, etc., dirt from oil, scratches from metal chips, etc., and scratches and scraping of the photoreceptor due to photoreceptor contact members such as developing members, transfer members, and cleaning members. A protective layer may be further provided on the charge generation layer or the charge transport layer for the purpose of preventing this.

In order to form an electrostatic latent image on this protective layer, it is desirable that the surface resistivity is 10 11 Ω or more.

The protective layer used in the present invention is made of polyvinyl butyral, polyester, polycarbonate, acrylic resin, methacrylic resin, nylon, polyimide, polyarylate, urethane resin, styrene-butadiene copolymer, styrene-
It can be formed by applying a solution prepared by dissolving a resin such as an acrylic acid copolymer or a styrene-acrylonitrile copolymer in a suitable organic solvent onto the photosensitive layer and drying it.

Additionally, additives such as ultraviolet absorbers can be added to the resin solution. The thickness of this protective layer is generally 0.05~
20 pm, preferably in the range of 0.2 to 5 pm.

[Example] Example 1 An ammonia aqueous solution of casein (11.2 g of casein, 1 g of 28% ammonia water, 222 mJl of water) was coated on an aluminum cylinder and dried to a coating amount of 1.0 g/m
A second subbing layer was formed.

Next, 0.5 parts by weight of a charge generating substance which is an N-methyldiphenylamine type disazo pigment of the above structural formula (I) and the following structural formula (TI) belonging to an anthraquinone type disazo pigment shown by the above general formula (1) are added. 0.5 parts by weight of a charge-generating substance which is a disazo pigment, 1 part by weight of polyvinyl butyral (trade name: Kosuretsu BM-2, manufactured by Tsukiku Kagaku ■), and 30 parts by weight of isopropyl alcohol.
parts by weight were dispersed for 4 hours using a ball mill disperser. This dispersion was dip coated onto the previously formed subbing layer and dried to form a charge generating layer. The film thickness was 0.31 Lm.

Next, 1 part by weight of a charge transport material which is a hydrazone compound having the following structural formula, 1 part by weight of polysulfone (product name P-1700, manufactured by UCC), and 6 parts by weight of monochlorobenzene were mixed and dissolved by stirring with a stirrer. . This liquid was dip coated onto the charge generation layer and dried to form a charge transport layer.

E (1/2, λ=780): 1.0ILJ/cm
The thickness of the second film was 12 ILm.

A corona discharge of 15 KV was applied to the electrophotographic photoreceptor thus produced.

The surface potential at this time [initial potential V (0) ] was measured.

Furthermore, the surface potential [V (5) ] was measured after this photoreceptor was left in a dark place for 5 seconds.

Sensitivity was evaluated by measuring the exposure amount [E (1/2) Jlux, sec] required to attenuate the potential v5 after dark decay to 172. Show the results.

V (0) Knee 600V V (5) Knee 585V E (1/2): 1.91ux, sec Also, using this photoreceptor with a 780nm semiconductor laser, ■ (5) is 1
The amount of energy required to attenuate to /2 [E (1/2
, λ=780) ILJ/cm2].

v (o) knee 5oov V (5) knee 585V EC1/2. Input = 780'l: Acidity 17 Comparative Example 1 Of the charge generating substances used in Example 1, structural formula (I)
A photoreceptor was prepared in exactly the same manner as in Example 1, except that 1 part by weight of only the substance was used, and the characteristics of this photoreceptor were measured. Show the results.

V (0) Knee 590V V (5) Knee 570V E (1/2): 6.31ux, 5ea E (1/2, λ=780): 1.1 pJ/Cm
2 Comparative Example 2 A photoreceptor was prepared in exactly the same manner as in Example 1, except that 1 part by weight of only the substance with the structural formula (■) was used among the charge generating substances used in Example 1. Body characteristics were measured.The results are shown below.

V (0) knee 605V V (5) knee 595V E (1/2): 2, flux, sec Example 2 The ratio of the charge generating substance used in Example 1 was expressed by the structural formula (I
), 0.25 parts by weight of a charge generating substance represented by the structural formula (
A photoreceptor was prepared in exactly the same manner as in Example 1, except that the charge generating substance shown in II) was used in an amount of 0.75 parts by weight.
The characteristics of this photoreceptor were measured. Show the results.

v (o) knee 5oov V (5) knee 590V E (1/2): 1.6jLux, 5eeE (1/2
, λ=780): 1.2 pJ/cm 2 Example 3 An ammonia aqueous solution of casein (described above) was coated on an aluminum cylinder and dried to a coating amount of 1,000 g.
A subbing layer of /cm2 was formed.

Next, 0.4 parts by weight of a charge generating substance of structural formula (I) and 0.4 parts by weight of a charge generating substance having the following structural formula (m), which belongs to the anthraquinone type disazo pigment represented by the general formula (1), were added.
4 parts by weight of polyvinyl butyral (example 1) and 30 parts by weight of isopropyl alcohol were dispersed for 4 hours using a ball mill disperser. This dispersion was applied by dip coating onto the previously formed subbing layer and dried to form a charge generating layer. The film thickness at this time was 0.3 m.

Next, a charge transport material having the following structural formula was mixed with 1 part by weight of a single polycarbonate resin (trade name: Niepilon S-2000, manufactured by Mitsubishi Gas Chemical Corporation) and 6 parts by weight of dichloromethane, and the mixture was stirred and dissolved using a stirrer. This liquid was applied onto the charge generation layer by dip coating and dried to form a charge transport layer. The film thickness at this time was 16 μm.

Next, a methanol solution of polyvinyl butyral (saponification degree 100%, butyralization degree 75 mol%, number average molecular weight 30,000) is coated on this charge transport layer by dip coating, and dried to form a protective layer. Formed. The film thickness at this time is 3
It was #Lm.

The characteristics of the electrophotographic photoreceptor thus prepared were measured in exactly the same manner as in the examples. Show the results.

V (0) Knee 610V V (5) Knee 595V E (1/2): 1.71ux, 5eeE (1/2
, λ=780): 1.2 pJ/cm 2 Example 4 An ammonia aqueous solution of casein (7 m output) was coated on an aluminum cylinder and dried to a coating amount of 1.0 g/m2.
A subbing layer was formed.

Next, 1.0 parts by weight of the charge generating material of structural formula (I) and 30 parts by weight of inpropyl alcohol based on 1 part by weight of polyvinyl butyral (example 1) were dispersed using a ball mill disperser for 4 hours. This dispersion was applied onto the previously formed subbing layer by dip coating and dried to form a first charge generation layer. The film thickness at this time is 0. It was IILm.

Next, 1.0 parts by weight of the charge generating substance having the structural formula (II) belonging to the anthraquinone type disazo pigment represented by the general formula (1), 1 part by weight of polyvinyl butyral and 30 parts by weight of isopropyl alcohol were mixed in a ball mill dispersion machine. The mixture was dispersed for 4 hours, and this dispersion was applied by dip coating onto the previously formed first charge generation layer and dried to form a second charge generation layer. The film thickness at this time is 0, I
Next, 1 part by weight of a charge transport substance which is a hydrazone compound having the following structural formula, 1 part by weight of polycarbonate resin (example 3) and 6 parts by weight of dichloromethane were mixed and dissolved by stirring with a stirrer. . This liquid was applied onto the charge generation layer by dip coating and dried to form a charge transport layer. The film thickness at this time was 16 gm.

The characteristics of the photoreceptor thus prepared were measured in exactly the same manner as in Example 1. Show the results.

V (0) Knee 600V V (5) Knee 585V E (1/2): 1.4JLux, se cE (1
/2, λ=780): 1.0 JLJ/cm 2 Examples 5 to 9 Instead of the charge generating substance belonging to the anthraquinone type disazo pigment represented by the general formula (1) used in Example 1, the above-mentioned exemplary pigment (4 ), (5), (6), (7), and (8) were used, but a photoreceptor was produced in the same manner as in Example 1.

The characteristics of each of these photoreceptors were measured in exactly the same manner as in Example 1.

Show the results.

5 595 585 2.0 1.26 590
580 2.1 1.07 590
575 2.0 1.08 59
5 585 2.2 1.19 6
00 590 2.4 1.3 Generally, when charge generating substances are used in combination, it is difficult to bring out the sensitivity of each charge generating substance. However, as is clear from the results of the above examples, the laminated electrophotographic photoreceptor of the present invention has the same sensitivity in visible light as compared to the photoreceptor of Comparative Example 1, but has extremely high sensitivity in light of 780 nm. It is observed that a photoreceptor is obtained.

Furthermore, it is observed that compared to the photoreceptor of Comparative Example 2, a photoreceptor with extremely high sensitivity in visible light, with no change in sensitivity when exposed to light of 80 nm, was obtained.

Further, the electrophotographic photoreceptors of Examples 1 to 9 were imaged 50,000 times using a copying machine (trade name NP-3525, manufactured by Canon ■). As a result, good quality images were obtained for all photoreceptors even after repeating the test 50,000 times. From this, it is recognized that the electrophotographic photoreceptor of the present invention has extremely excellent durability.

[Effects of the Invention] The electrophotographic photoreceptor of the present invention has extremely high sensitivity to visible light and 780 nm light compared to conventional electrophotographic photoreceptors by using a specific charge-generating substance in combination. This makes it possible to provide an electrophotographic photoreceptor with excellent repeatability.

Furthermore, by appropriately selecting the mixing ratio of charge-generating substances,
This has the remarkable effect of being able to freely modify the sensitivity.

Claims (2)

[Claims] (1) In a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, the charge generation layer contains an N-methyldiphenylamine type disazo pigment having the following structural formula (I) and the following: An electrophotographic photoreceptor characterized in that it also contains an anthraquinone-type disazo pigment represented by general formula (1). Structural formula (I) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ General formula (1) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ In the formula, A is a coupler residue having a phenolic OH group or 2-methylindolenine The coupler residues of the derivatives are shown. (2) The electrophotographic photoreceptor according to claim 1, wherein the coupler residue A in the general formula (1) is a coupler residue selected from the groups represented by the following general formulas (2) to (8). General formulas ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (2) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (3) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (4) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼(5) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (6) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (7) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (8) In the formula, R_1 and R_2 are A hydrogen atom, an alkyl group that may have a substituent, an aralkyl group, an aryl group, a heterocyclic group, an imino group, or a cyclic amino group together with the nitrogen atom to which R_1 and R_2 are bonded, and X is fused with a benzene ring. represents a residue forming a polycyclic aromatic ring or a heterocycle, R_3 and R_4 represent an alkyl group, an aralkyl group, or an aryl group that may have a substituent, and Y represents a divalent aromatic hydrocarbon. It represents a divalent group that forms a heterocycle with a group or a nitrogen atom, and R_5 and R_6 represent a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a cyano group, or a nitro group.