JP2582607B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor using two kinds of charge generating substances.

BACKGROUND OF THE INVENTION Electrophotographic photoreceptors are widely used in electrophotographic copying machines, printers, and the like, but the characteristics required of the electrophotographic photoreceptor differ depending on the application. For example, in an electrophotographic copying machine, particularly an office copying machine, emphasis is placed on the reproducibility of a copy image of a red image (for example, a character with a red mark, an underline, etc.) as well as the reproducibility of a copy image of a black or blue original. You. In order to achieve such reproduced image reproducibility, it is desired that the electrophotographic photosensitive member has a sufficient spectral sensitivity in the range of 450 nm to 600 nm (at most 620 nm). When the spectral sensitivity of the electrophotographic photoreceptor extends to around 660 nm or 700 nm, the reproducibility of the above-described red image is inferior, which is not preferable for an office copying machine. For this reason, an electrophotographic photoreceptor using a normal azo pigment, particularly a disazo pigment or a trisazo pigment, as a charge generating substance (for example, see JP-A-47-375)
No. 4, No. 53-133445, No. 58-70232, No. 58-140745), the spectral sensitivity extends to around 700 nm.
Light with a wavelength of 630nm or more is cut with a filter to reduce red sensitivity. However, when such a filter is used, not only the red sensitivity but also the short-wavelength sensitivity is reduced, and there is a disadvantage that the sensitivity is reduced as a whole. Furthermore, when such an azo pigment is used as a charge generating substance, it is necessary to form the film of the charge generating layer as a thin film having a thickness of about 0.1 to 0.3 μm because of its low charge transporting ability.
When such a thin film is applied by a dip coating method, which is a general manufacturing method, coating defects such as unevenness in a step, liquid dripping, and aggregation are likely to occur, leading to a decrease in yield and an increase in cost.

Polycyclic quinone pigments are known as pigments having good copy image reproducibility (see JP-A-57-67933). The polycyclic quinone pigment has a high sensitivity in the range of 450 nm to 570 nm, and therefore has excellent red image copy reproducibility, and has a higher sensitivity and sensitivity than azo compounds and phthalocyanine compounds.
It has a feature that the repetition characteristics with respect to the charging potential, the residual potential, and the like are extremely stable. However, when this polycyclic quinone pigment is used, the sensitivity is greatly reduced in the region of 570 nm or more, and there is almost no sensitivity in the region around 580 to 620 nm, so high-speed copying requiring high sensitivity is required. Insufficient sensitivity for use in copiers and small copiers.

Japanese Patent Application Laid-Open No. 61-292158 discloses a technique in which two types of charge generating materials having different photo memories are used in combination. This technique has high sensitivity, but has a disadvantage of a charge generating material having a large photo memory. No attempt has been made to improve the reproducibility of copying a red image as described above.

As described above, the technology capable of achieving the above-described copy image reproducibility and high sensitivity has not been sufficiently studied in the past.

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional problems. First, an electrophotographic photosensitive member having spectral sensitivity characteristics suitable for an electrophotographic copying machine, a printer, and the like and having high sensitivity is provided. It is another object of the present invention to provide a high-sensitivity electrophotographic photoreceptor excellent in reproducibility of red image copying, and thirdly to provide an electrophotographic photoreceptor excellent in repetition characteristics.

[Constitution of the Invention] The object of the present invention is to provide an electrophotographic photoreceptor having at least a charge generation layer and a charge transport layer on a conductive support, wherein the charge generation layer has a polycyclic quinone compound and the following general formula [I The electrophotographic photoreceptor is characterized by containing the compound represented by the formula:

General formula [I] Where A is Or Represents

Here, Ar ₁ represents an aromatic ring group or a heterocyclic group. Ar ₂
And Ar ₃ each represent an aromatic ring group. R ₁ and R ₃ each represent a hydrogen atom, an alkyl group or an aryl group.
R ₂ represents an alkyl group, a carboxyl group or an ester group thereof. Z represents an atom group necessary for forming an aromatic ring or a heterocyclic ring.

The aromatic ring group represented by Ar ₁ , Ar ₂ and Ar ₃ is, for example, a phenyl group, a naphthyl group or the like, and the heterocyclic group represented by Ar ₁ is, for example, a dibenzofuran ring, a carbazole ring, an indole ring or the like. The alkyl group represented by R ₁ , R ₂ or R ₃ is, for example, a lower alkyl group such as a methyl group or an ethyl group, and the aryl group represented by R ₁ or R ₃ is, for example, a phenyl group. Specific examples of the aromatic ring or heterocyclic ring formed by Z are the same as the specific examples of Ar _{1 to} Ar ₃ described above.

Each group represented by Ar _{1 to} Ar ₃ , R _{1 to} R ₃ and Z may have a substituent, for example, a halogen atom, an alkyl group, an alkoxy group, a nitro group, a substituted amino group, Examples include an acylamino group, a cyano group, a carboxyl group, a sulfonic acid group, and a sulfamoyl group.

Representative specific examples of the compound represented by the general formula [I] (hereinafter, referred to as the azo compound of the present invention) are shown below, but are not limited thereto.

The azo compound as described above can be easily synthesized, for example, by the method described in JP-A-53-22834.

The polycyclic quinone-based compound used in the present invention includes an anthrone-based pigment represented by the following general formula [A], a dibenzpyrene quinone-based pigment represented by the following general formula [B], and a compound represented by the following general formula [C]. At least one selected from pyranthrone-based pigments can be used, but the general formula [A] is particularly preferable.

In the formula, X represents a halogen atom, a nitro group, a cyano group, an acyl group or a carboxyl group, n represents an integer of 0 to 4, and m represents an integer of 0 to 6.

Specific compounds of the anthantrone-based pigment represented by the general formula [A] are as follows.

Specific compound examples of the dibenzpyrenequinone pigment represented by the general formula [B] are as follows.

Specific examples of the pyranthrone-based pigment represented by the general formula [C] are as follows.

The polycyclic quinone-based compound as described above can be synthesized by a known method, but can also be obtained as a commercial product.

Although various configurations are known for the configuration of the electrophotographic photosensitive member, the electrophotographic photosensitive member of the present invention can take any of these forms.

Normally, the configuration is as shown in FIGS. 1 and 2, a charge generation layer 2 containing the above-mentioned polycyclic quinone-based compound and the azo compound of the present invention on a conductive support 1,
A photosensitive layer 4 composed of a laminate of a charge transport layer 3 containing a charge transport substance as a main component, which will be described later, is provided. In FIGS. 1 and 2, the order of lamination of the charge generation layer 2 and the charge transport layer 3 is shown. Are different. As shown in FIG. 3 and FIG.
May be provided on a conductive support via an intermediate layer 5 such as an adhesive layer or a barrier layer. Thus, when the photosensitive layer 4 has a two-layer structure, a photosensitive member having the best electrophotographic characteristics can be obtained. In the present invention, FIGS.
As shown in the figure, a photosensitive layer 4 formed by dispersing the polycyclic quinone-based compound and the azo compound of the present invention in a layer 6 containing a charge transport material can be directly provided on the conductive support 1, or the intermediate layer 5 can be provided. It may be provided via. In the present invention,
A protective layer may be provided as the outermost layer.

The charge generation layer 2 constituting the two-layered photosensitive layer 4 is formed directly on the conductive support 1 or the charge transport layer 3 or, if necessary, on an intermediate layer 5 such as an adhesive layer or a barrier layer. For example, it can be formed by the following method.

M-1) A method in which a solution in which the polycyclic quinone compound and the azo compound of the present invention are dissolved together or separately in an appropriate solvent, or a solution in which a binder resin is added and mixed and dissolved as required, is applied.

M-2) The polycyclic quinone compound and the azo compound of the present invention are formed together or separately into fine particles (preferably 5 μm or less, more preferably 1 μm or less) in a dispersion medium by a ball mill, a homomixer, or the like. A method in which a binder resin is added and a dispersion liquid mixed and dispersed is applied.

Solvents or dispersion media used for forming the charge generation layer include n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, acetone, methyl ethyl ketone, cyclohexanone, benzene, and toluene. , Xylene, chloroform, 1,
2-dichloroethane, 1,2-dichloropropane, 1,1,2
-Trichloroethane, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethane, dichloromethane, tetrahydrofuran, dioxane, methanol, ethanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cellosolve and the like.

The charge transport layer can be formed in the same manner as the charge generation layer.

As the binder resin used for forming the charge generation layer or the charge transport layer, any binder resin can be used, but it is preferable to use a hydrophobic, high dielectric constant, and electrically insulating film-forming polymer. preferable. Examples of such a high-molecular polymer include the following, but are not limited thereto.

P-1) Polycarbonate P-2) Polyester P-3) Methacrylic acid P-4) Acrylic resin P-5) Polyvinyl chloride P-6) Polyvinylidene chloride P-7) Polystyrene P-8) Polyvinyl acetate P-9 ) Styrene-butadiene copolymer P-10) Vinylidene chloride-acrylonitrile copolymer P-11) Vinyl chloride-vinyl acetate copolymer P-12) Vinyl chloride-vinyl acetate-maleic anhydride copolymer P-13) Silicon resin P-14) Silicon-alkyd resin P-15) Phenol formaldehyde resin P-16) Styrene-alkyd resin P-17) Poly-N-vinylcarbazole P-18) Polyvinyl butyral P-19) Polyvinyl formal The binder resin can be used alone or as a mixture of two or more. Wear.

In the charge generation layer formed as described above, the weight ratio of the charge generation material composed of the polycyclic quinone compound and the azo compound of the present invention to the binder is preferably 100: 0 to 1
000. If the content of the charge generating substance is less than this, photosensitivity is low and the residual potential is increased, and if it is more than this, dark decay and accepting potential are reduced.

Further, the combined ratio of the polycyclic quinone compound and the azo compound of the present invention is preferably 100: 1 to 100: 30 by weight ratio, and when the ratio of the azo compound is larger than this, copy reproducibility of a red image is improved. descend.

The average particle size of the particles of the polycyclic quinone compound used in the present invention is preferably larger than the average particle size of the particles of the azo compound of the present invention.

The thickness of the formed charge generation layer is preferably 0.01 to 10
μm.

Further, in the charge transport layer formed as described above, the charge transport material is a binder resin 100 in the charge transport layer.
20 to 200 parts by weight per part by weight is preferred, and particularly preferably 3 to 200 parts by weight.
0 to 150 parts by weight.

The thickness of the formed charge transport layer is preferably 5
To 50 μm, particularly preferably 5 to 30 μm.

The charge transporting material used in the present invention is not particularly limited, but includes, for example, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, and bisimidazolidines. Derivatives, styryl compounds, hydrazone compounds, pyrazoline derivatives, amine derivatives, oxazolone derivatives,
Benzothiazole derivatives, benzimidazole derivatives,
Quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, poly-N-vinylcarbazole, poly-1-vinylpyrene, poly-9-vinylanthracene, and the like.

As the charge transporting material used in the present invention, in addition to having an excellent ability to transport holes generated during light irradiation to the support side, those suitable for combination with the polycyclic quinone compound and the azo compound of the present invention are preferable. Preferred as such a charge transport material are those represented by the following general formula (A):
(B) and (C).

General formula (A) However, Ar ₁ , Ar ₂ , Ar ₄ each represents a substituted or unsubstituted aryl group, Ar ₃ represents a substituted or unsubstituted arylene group, R ₁ is a hydrogen atom, a substituted or unsubstituted alkyl group, or Represents a substituted or unsubstituted aryl group.

Specific examples of such compounds are described in JP-A-58-65440, No. 3
On pages 4 to 4 and pages 3 to 6 of JP-A-58-198043.

General formula (B) Here, R ₁ represents a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, and R ₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Are described in JP-A-58-134642 and JP-A-58-166354.

General formula (C) Here, R ₁ is a substituted or unsubstituted aryl group, R ₂ is a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted amino group,
A hydroxy group, R ₃ is a substituted or unsubstituted aryl group,
Represents a substituted or unsubstituted heterocyclic group. Methods for synthesizing these compounds and examples thereof are described in detail in JP-B-57-148750, which can be incorporated in the present invention.

Other preferred charge transporting substances of the present invention include hydrazone compounds described in JP-A-57-67940, JP-A-59-15252, and JP-A-57-101844.

As the conductive support used in the electrophotographic photoreceptor of the present invention, a metal plate including an alloy, a metal drum or a conductive polymer, a conductive compound such as indium oxide or an alloy including aluminum, palladium, gold, etc. Conductive paper by applying, depositing or laminating a thin metal layer,
Plastic films and the like. As the intermediate layer such as the adhesive layer or the barrier layer, an organic polymer substance such as polyvinyl alcohol, ethyl cellulose, carboxymethyl cellulose, aluminum oxide, or the like is used in addition to the polymer used as the binder resin.

Organic amines can be added to the photosensitive layer of the invention for the purpose of improving the charge generation function of the charge generation substance, and it is particularly preferable to add a secondary amine.

Such secondary amines include, for example, dimethylamine,
Diethylamine, di-n-propylamine, di-isopropylamine, di-n-butylamine, di-isobutylamine, di-n-amylamine, di-isoamylamine, di-
n-hexylamine, di-isohexylamine, di-n-pentylamine, di-isopentylamine, di-n-octylamine, di-isooctylamine, di-nnonylamine, di-isononylamine, di-ndecylamine, Jee
Examples thereof include isodecylamine, di-n-monodecylamine, di-isomonodecylamine, di-n-dodecylamine, and di-isododecylamine.

Further, the amount of the organic amine to be added is 1 time or less, preferably 0.2 to 0.005 times the mole of the charge generating substance.

Further, an antioxidant can be added to the photosensitive layer of the present invention for the purpose of preventing ozone deterioration.

Representative specific examples of such antioxidants are shown below, but are not limited thereto.

Group (I): hindered phenols dibutylhydroxytoluene, 2,2'-methylenebis (6-t-butyl-4-methylphenol), 4,4'-
Butylidenebis (6-t-butyl-3-methylphenol), 4,4'-thiobis (6-t-butyl-3-methylphenol), 2,2'-butylidenebis (6-t-butyl-4-methylphenol) ), Α-tocopherol, β
-Tocopherol, 2,2,4-trimethyl-6-hydroxy-7-tert-butylchroman, pentaerythyltetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2, 2'-thiodiethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 1,6-hexanediolbis [3- (3,5-di-t-butyl-4 -Hydroxyphenyl) propionate], butylhydroxyanisole,
Dibutylhydroxyanisole, 1- [2-｛(3,5-
Di-tert-butyl-4-hydroxyphenyl) propionyloxydiethyl] -4- [3- (3,5-di-tert-
Butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidyl.

Group (II): paraphenylenediamines N-phenyl-N'-isopropyl-p-phenylenediamine, N, N'-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl-p -Phenylenediamine, N, N'-diisopropyl-p-phenylenediamine, N, N'-dimethyl-N, N'-di-tert-butyl-p-phenylenediamine and the like.

Group (III): hydroquinones 2,5-di-t-octylhydroquinone, 2,6-didodecylhydroquinone, 2-dodecylhydroquinone,
-Dedosyl-5-chlorohydroquinone, 2-t-octyl-5-methylhydroquinone, 2- (2-octadecenyl) -5-methylhydroquinone and the like.

Group (IV): organic sulfur compounds such as dilauryl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, ditetradecyl-3,3'-thiodipropionate and the like.

Group (V): Organophosphorus compounds Triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine and the like.

These compounds are known as antioxidants for rubbers, plastics, oils and the like, and commercially available products can be easily obtained.

These antioxidants may be added to any of the charge generation layer, the charge transport layer, and the protective layer, but are preferably added to the charge transport layer. In this case, the amount of the antioxidant added is 0.1 to 100 parts by weight, preferably 1 to 50 parts by weight, particularly preferably 1 to 25 parts by weight based on 100 parts by weight of the charge transporting substance.

In the present invention, one or two or more electron accepting substances can be contained in the charge generation layer for the purpose of improving sensitivity, reducing residual potential or reducing fatigue during repeated use.

Electron accepting substances that can be used here include
For example, succinic anhydride, maleic anhydride, dibromo maleic anhydride, phthalic anhydride, tetrachloro phthalic anhydride, tetrabromo phthalic anhydride, 3-nitro phthalic anhydride, 4-nitro phthalic anhydride, pyromellitic anhydride, merit anhydride Acid, tetracyanoethylene, tetracyanoquinodimethane, o-dinitrobenzene, m-dinitrobenzene, 1,3,5-trinitrobenzene, paranitrobenzonitrile, picryl chloride, quinone chlorimide,
Chloranil, bulmanil, dichlorodicyanoparabenzoquinone, anthraquinone, dinitroanthraquinone, 2,
7-dinitrofluorenone, 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, 9-fluorenylidene [dicyanomethylenemalonodinitrile],
Polynitro-9-fluorenylidene- [dicyanomethylenemalonodinitrile], picric acid, o-nitrobenzoic acid, p-nitrobenzoic acid, 3,5-dinitrobenzoic acid, pentafluorobenzoic acid, 5-nitrosalicylic acid, 3,5 −
Examples thereof include dinitrosalicylic acid, phthalic acid, melitic acid, and other compounds having a high electron affinity.

The amount of the electron-accepting substance to be added depends on the weight ratio of the charge generating substance:
Electron accepting substance = 100: 0.01 to 200, preferably 100: 0.1 to
It is 100.

The electron accepting substance may be added to the charge transport layer. The amount of the electron-accepting substance to be added to such a layer is 100: 0.01 to 100, preferably 100:
0.1 to 50.

In addition, the photoreceptor of the present invention may further contain, if necessary, an ultraviolet absorber or the like for the purpose of protecting the photosensitive layer, or may contain a dye for correcting color sensitivity.

The electrophotographic photoreceptor of the present invention is configured as described above, and has high sensitivity, as is clear from the examples described later,
Further, it has a spectral sensitivity characteristic suitable for an electrophotographic copying machine, a printer, and the like, is particularly excellent in the reproducibility of copying a red image, and has stable characteristics even when repeatedly used.

Further, the electrophotographic photoreceptor of the present invention has good characteristics as a photoreceptor even when a relatively thick charge generating layer is formed, and therefore has few coating defects at the time of production as described above and is advantageous in production. is there.

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples.
This does not limit the embodiments of the present invention.

Example 1 After dissolving 5 g of a polycarbonate resin (Panlite L-1250, manufactured by Teijin Chemicals Ltd.) in 200 ml of 1,2-dichloroethane, 10 g of an exemplary polycyclic quinone compound [A3] was mixed as a charge generating substance CGM2. Then, the mixture was dispersed with a sand grinder for 10 hours. This is designated as solution A.

Next, after dissolving 1 g of the above polycarbonate resin in 120 ml of 1,2-dichloroethane, an azo compound No. 9 as an example of the charge generating substance CGM1 and 2 g were mixed, and 10 g was mixed with a sand grinder.
Time dispersed. This is designated as solution B.

200 ml of the solution A and 20 ml of the solution B were stirred and mixed to form a coating solution for forming a charge generation layer. The coating solution was applied on a polyester base on which Al was deposited by a wire bar, and dried to a film thickness of about 0.3.
A μm charge generation layer was formed.

Next, using a coating solution for forming a charge transport layer having the following composition, a charge transport layer having a thickness of about 20 μm after drying was laminated on the charge generation layer by a blade using a blade to obtain a photoreceptor.

1,2-Dichloroethane 100 ml Polycarbonate resin (as above) 15 g The obtained photoreceptor is designated as Sample No. 1.

Next, the sample No. 1 was changed except that the charge generating substance used or its combination ratio was changed as shown in Table 1.
Samples Nos. 2 to 8 were prepared in the same manner as in the above.

Characteristics evaluation tests of the photoconductor samples Nos. 1 to 8 thus obtained were performed as follows.

[Sensitivity test] Using an electrostatic charging tester EPA-8100 (manufactured by Kawaguchi Electric Co., Ltd.), the exposure amount E1 / 2 (lux · sec) required for the photoconductor surface potential to be reduced by half from the initial potential is measured. did.

[Repeatability test] Using the electrostatic charging tester EPA-8100, measure the change in charge potential ΔV ^{0 → 100} (V) at the first and 100th repetitions when charging → exposure → discharge is repeated 100 times. did.

[Red reproducibility test] Electrophotographic copier "U-Bix 1550" (manufactured by Konica Corporation)
Using a copier equipped with a surface potentiometer and using a Kodak color control patch as a document, the black paper potential in it is adjusted to -600 V, and the white paper potential is adjusted to -100 V. Surface potential Vred
(V) was measured.

The lower the value of Vred, the lower the reproducibility of the red image.

 Table 1 summarizes the obtained results.

From the results shown in Table 1, it is clear that the photoreceptor of the present invention shows superior performance in all respects in sensitivity, red image copy reproducibility, and repetition characteristics as compared with the comparative photoreceptor.

Example-2 The combination of the charge generating substances used was changed as shown in Table 2, and the polycarbonate resin used for the coating solution for forming the charge transport layer was changed to Iupilon Z-200 (manufactured by Mitsubishi Gas Chemical Co., Ltd.). A sample was prepared in the same manner as in Example 1 except that the sample was replaced.
Nos. 9 to 14 were prepared, and these samples were subjected to the same property evaluation test as in Example 1. The obtained results are shown in Table 2.

From the results in Table 2, the photoreceptor of the present invention shows that in all respects of sensitivity, red image copy reproducibility and repetition characteristics,
It turns out that it shows excellent performance.

Example 3 The charge generation materials used were changed as shown in Table 3, and the polycarbonate resin used for the coating solution for forming the charge transport layer was changed to Iupilon Z-200 (described above). To Sample Nos. 15 to 18 in the same manner as in Example 1 except that
Were prepared, and the same property evaluation test as in Example 1 was performed on these samples, and the obtained results are shown in Table-3.

From the results shown in Table 3, it can be seen that the photoreceptor of the present invention shows excellent performance in all respects of sensitivity, red image copy reproducibility and repetition characteristics.

Example 4 Charge-transporting substances were changed as shown in Table 4, and the polycarbonate resin used for the coating solution for forming the charge-transporting layer was changed to Iupilon Z-200 (described above). To Sample Nos. 19 to 22 in the same manner as in Example 1 except that
, And the same characteristic evaluation test as in Example 1 was performed on these samples. The obtained results are shown in Table-4.

From the results shown in Table 4, it can be seen that the photoreceptor of the present invention shows excellent performance in all respects of sensitivity, red image copy reproducibility and repetition characteristics.

[Brief description of the drawings]

1 to 6 are cross-sectional views each showing an example of the configuration of the photoreceptor of the present invention. DESCRIPTION OF SYMBOLS 1 ... Conductive support 2 ... Charge generation layer 3 ... Charge transport layer 4 ... Photosensitive layer 5 ... Intermediate layer 6 ... Layer containing a charge transport material

Claims (1)

(57) [Claims] 1. An electrophotographic photosensitive member having at least a charge generation layer and a charge transport layer on a conductive support, wherein the charge generation layer contains a polycyclic quinone compound and a compound represented by the following general formula [I]. An electrophotographic photoreceptor characterized in that: General formula [I] [Where A is Or Represents Here, Ar ₁ represents an aromatic ring group or a heterocyclic group. Ar ₂ and Ar ₃ each represent an aromatic ring group. R ₁ and R ₃ each represent a hydrogen atom, an alkyl group or an aryl group. R ₂
Represents an alkyl group, a carboxyl group or an ester group thereof. Z represents an atom group necessary for forming an aromatic ring or a heterocyclic ring. ]