JPH042184B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor containing a novel organic photoconductive substance comprising an azine compound. Electrophotography has already been covered by Carlson's U.S. Patent No.
As revealed in No. 2297691, its electrical resistance changes depending on the amount of radiation received during image exposure.
A photoconductive material consisting of a support coated with an insulating substance is used in the dark. The photoconductive material is generally first given a uniform surface charge in the dark after dark adaptation for a suitable period of time. The material is then imagewise exposed to a pattern of radiation that has the effect of reducing the surface charge depending on the relative energy contained in different parts of the radiation pattern. The surface charge or electrostatic latent image thus left on the surface of the photoconductive material layer (photosensitive layer) then becomes a visible image when that surface is contacted with a suitable electrometric indicator, ie, toner.
Toner, whether contained in an insulating liquid or in a dry carrier, can be deposited on the surface of the photosensitive layer depending on the charge pattern. The deposited display material can be fixed by known means such as heat, pressure, and solvent vapor. The electrostatic latent image can also be transferred to a second support (eg, paper, film, etc.). It is likewise possible to transfer the electrostatic latent image to a second support and develop it there. Electrophotography is one of the image forming methods in which images are formed in this manner. The basic characteristics required of the photoreceptor in such electrophotography are (1) ability to be charged to an appropriate potential in the dark, (2) low dissipation of charge in the dark, (3) For example, the charge can be quickly dissipated by light irradiation. It is true that conventionally used inorganic photoconductive materials such as selenium, cadmium sulfide, and zinc oxide have many advantages, but also have various disadvantages. For example, selenium, which is currently widely used, fully satisfies the conditions (1) to (3) above, but the manufacturing conditions are difficult, the manufacturing cost is high, it is not flexible, and it cannot be processed into a belt shape. It also has disadvantages, such as being difficult to handle and being sensitive to heat and mechanical shock, requiring careful handling. Cadmium sulfide and acertic oxide are used as photoreceptors by being dispersed in resin as a binder, but they have mechanical drawbacks such as smoothness, hardness, tensile strength, and abrasion resistance, so they cannot be used as is. and cannot be used. In recent years, in order to eliminate the drawbacks of these inorganic photoconductive materials, electrophotographic photoreceptors using various organic photoconductive materials have been proposed, and some of them are in practical use. For example, photoreceptors made of poly-N-vinylcarbazole and 2,4,7-trinitrofluoren-9-one (US Pat. No. 3,484,237), poly-N-
- Vinylcarbazole sensitized with pyrylium salt dyes (Japanese Patent Publication No. 48-25658), photoreceptors whose main component is a eutectic complex consisting of a dye and a resin (Japanese Patent Application Laid-open No. 10735-1987), etc. It is. Although electrophotographic photoreceptors using these organic photoconductors have improved mechanical properties and flexibility to some extent than those using the inorganic photoconductors, they generally have low photosensitivity and are not suitable for repeated use. First, it did not fully satisfy the requirements for an electrophotographic photoreceptor. Furthermore, a highly sensitive electrophotographic photoreceptor has been proposed that combines a substance that generates electric charges when exposed to light (called a charge-generating substance) and a substance that can transport the generated charges (called a charge-transporting substance). has been done. For example, US Pat. No. 3,791,826 discloses a photoreceptor in which a charge transport layer is provided on a charge generating layer.
No. 3,573,906 discloses a photoreceptor in which a charge generation layer is provided on a charge transport layer.
No. 3,764,315 describes a photoreceptor having a photosensitive layer in which a charge generating material is dispersed in a charge transporting material. Examples of charge transporting agents used in this charge generation layer include those disclosed in JP-A-54-59143 (U.S. Pat. No. 4,150,987).
hydrazone compounds described in U.S. Patent No.
Pyrazoline compounds described in 3180729, U.S. Pat.
Although triarylamine described in No. 3567450 can be mentioned, it has not been possible to obtain an electrophotographic photoreceptor having sufficient performance in terms of sensitivity. Regarding azine compounds, Japanese Patent Publication No. 42-5587
In JP-A No. 58-1989, it was also published as a photoconductive compound.
No. 132240 describes it as a charge transporting compound. Also, in Japanese Patent Application Laid-Open No. 57-90634,
Symmetrical ketazine compounds synthesized from 4'-di(N-disubstituted amino)benzophenones have been shown to have photoconductivity and charge transport properties. However, even when the azine compounds described in these patents are used as organic photoconductors or charge transport materials, it has not been possible to obtain electrophotographic photoreceptors with sufficient sensitivity. Furthermore, among the azine compounds described in these patents, the use of ketazine compounds in particular has the disadvantage that crystals of the ketazine compounds precipitate on the surface of the photoreceptor produced. An object of the present invention is to provide a new electrophotographic photoreceptor that solves the above-mentioned problems. Another object of the invention is to provide new organic photoconductive materials. Another object of the present invention is to provide a compound suitable as a charge transport material for use in a photosensitive layer having a laminated structure of a charge generation layer and a charge transport layer. As a result of extensive research, the present inventors found that among azine compounds, substituted ketones other than 4,4'-di(N-disubstituted amino)benzophenone and It has been discovered that an asymmetric azine compound synthesized from two different substituted aldehydes has particularly excellent performance both as a photoconductive compound and as a charge transport compound. This object of the present invention is achieved by an electrophotographic photoreceptor having a layer containing an azine compound represented by the following general formula (1). In the formula, R ₁ , R ₂ , R ₃ , and R ₄ may be the same or different, and each represents a linear or branched chain having 1 to 1 carbon atoms such as methyl, ethyl, propyl, butyl, etc.
12 alkyl groups, aralkyl groups such as benzyl and phenethyl, aryl groups such as phenyl and naphthyl, or residues that form a cyclic amino group together with nitrogen atoms such as pyrrolidino, piperidino and morpholino. In addition, these alkyl groups, aralkyl groups, and aryl groups may have a substituent, and examples of the substituent include alkyl groups such as methyl and ethyl;
In addition to alkoxy having 1 to 8 carbon atoms such as methoxy and ethoxy, halogen atoms such as chlorine and bromine, hydroxyl groups, cyano groups, etc. can be mentioned. R ⁵ is hydrogen, substituted or unsubstituted, having 1 to 12 carbon atoms,
Alkyl group, aralkyl group, unsubstituted or carbon number 1
-8 represents an aryl group containing an alkyl group, an alkoxy group, a halogen atom, a hydroxyl group, or a cyano group as a substituent. R ₆ has 1 to 8 carbon atoms,

[Formula] or

N-disubstituted amino group represented by the formula; alkoxy groups having 1 to 8 carbon atoms such as methoxy and ethoxy; aralkyloxy groups such as benzyloxy;
Aryloxy groups such as phenoxy and chlorine,
represents a halogen atom such as bromine, or R ₆ is R ₇
Alternatively, R ₈ and the benzene ring to which they are bonded may be combined to form a heterocycle such as a diurolidino ring, a carbazole ring, a phenothiazine ring, or a phenoxazine ring. R ₇ and R ₈ may be the same or different; hydrogen, an alkyl group having 1 to 8 carbon atoms such as methyl and ethyl, an alkoxy group having 1 to 8 carbon atoms such as methoxy and ethoxy, chlorine, It may represent a halogen atom such as bromine, or it may form a heterocycle together with R ₆ . Among the azine compounds used in the present invention, particularly preferred are those represented by the following general formula (2). R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₁₀ in the formula are general formula (1)
This shows the same as R ₁ , R ₂ , R ₃ , and R ₄ explained in . Specific examples of the compound represented by the general formula (1) used in the present invention are listed below. These compounds can be synthesized by a known method using compounds represented by the following general formulas (3) and (4) and hydrazine. Next, the azine compounds used in the present invention will be explained using synthesis examples. Synthesis of Exemplary Compound (1) 7.0 g of 4,4'-bis(dimethylamino)benzophenone hydrazone and 4.8 g of 4-diethylaminobenzaldehyde were heated under reflux in ethanol for 2 hours. After cooling the reaction solution, the resulting solid was filtered and dried.
Next, recrystallize from ethanol with a melting point of 167-167.5.
8.8 g of crystals were obtained. Yield 78% Elemental analysis value C ₂₈ H ₃₃ N ₅ Calculated value C: 76.15% H: 7.98% N:
15.85% Actual value C: 76.01% H: 8.20% N:
15.76% Synthesis of Exemplified Compound (3) 7.0 g of 4,4'-bis(dimethylamino)benzophenone hydrazone and 4-(N-phenyl-N
-Methylamino)benzaldehyde (5.3 g) was heated under reflux in ethanol for 2 hours. After the reaction was completed, the reaction solution was cooled, and the resulting solid was filtered and dried. Next, recrystallization was performed using a mixed solvent of benzene and n-hexane to obtain 9.2 g of crystals with a melting point of 133.5 to 134°C. Yield 78% Elemental analysis value C ₃₁ H ₃₃ N Calculated value as ₅ C: 78.27% H: 6.99% N:
14.72% Actual value C: 78.19% H: 7.22% N:
14.57% Other azine compounds used in the present invention can be synthesized in the same manner. When the azine compound represented by the general formula (1) is used in an electrophotographic photoreceptor, the azine compound (1) functions both as an organic photoconductive compound and as a charge transporting compound. It can be used as a photoreceptor. Type A: An electrophotographic photoreceptor having a substantially uniform and transparent photosensitive layer in combination with a sensitizer. Type B: Electrophotographic photoreceptor combined with a charge generating compound. Sensitizers used in the photosensitive layer of A-type electrophotographic photoreceptors include 2,4,7-trinitrofluoren-9-one, chloranil, tetracyanoethylene, and electron-withdrawing compounds described in U.S. Pat. No. 3,232,755. , pyrylium dyes described in U.S. Pat. No. 3,250,615, U.S. Pat. No. 4,315,983, U.S. Pat.
There are sensitizing dyes such as thiopyrylium dyes described in No. 4343948 and JP-A-57-46980, azacyanine dyes, triarylmethane dyes, thiazine dyes, and cyanine dyes described in JP-A-56-81852. The B-type electrophotographic photoreceptor is called a functionally separated photoreceptor, and is a single-layer type consisting of one photoreceptor layer in which a charge-generating compound is dispersed in the azine compound of the present invention, which is used as a charge-transporting compound. There is a photoreceptor, or a laminated photoreceptor consisting of two photosensitive layers: a charge generation layer containing a charge generation compound and a charge transport layer containing the azine compound of the present invention used as a charge transport compound. Preferably, a laminated type photoreceptor is useful in terms of sensitivity and charge retention of the electrophotographic photoreceptor. Type B charge generating compounds include inorganic ones such as cadmium sulfide, cadmium selenide, zinc oxide, zinc sulfide, titanium dioxide (especially lutherite type), and trigonal selenium, and organic ones such as: Azo pigments such as Sudan Red, Chlordiane Blue, and Jenas Green B;
Disazo pigments described in JP-A-54-2738, JP-A-57-152091, JP-A-58-123541, etc.;
Trisazo pigments described in JP-A-57-41642, JP-A-57-116345, etc., quinone pigments such as algol yellow, pyrenequinone, indanthrene brilliant violet RRP, perylene pigments, indigo such as indigo, thioindigo, etc. Pigments India First Orange Toner etc. Phthalocyanine pigments such as bisbenzimidazole pigments and copper phthalocyanine, quinacridone pigments, anthraquinone pigments, naphthoquinone pigments, squalium pigments, U.S. Pat. There are cyanine pigments and the like described in Publication No. 49-1231 and the like. The above-mentioned A and B types of electrophotographic photoreceptors containing the azine compound according to the present invention are used by a method in which the azine compound itself does not have a film-forming ability, so it is dissolved in a solution together with a binder, coated, and dried. As the binder, it is preferable to use a film-forming polymer that is hydrophobic, has a high dielectric constant, and is electrically insulating. Examples of such high molecular weight polymers include, but are not limited to, the following. Polycarbonate, polyester, methacrylic resin, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride -Vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-
N-Vinylcarbazole These binders can be used alone or as a mixture of two or more. The amount of binder is 0.2 parts by weight of the compound of the present invention in both type A and B photoreceptors.
It is used in a range of 20 parts by weight. If the amount of the binder is less than 0.2 parts by weight, the properties of the photosensitive layer as a film will be weakened, and if it exceeds 20 parts by weight, the sensitivity of the photosensitive layer will deteriorate. Preferably it is in the range of 0.5 to 10 parts by weight. In the A type photoreceptor, the amount of sensitizing dye is 0.0001 to 0.5 parts by weight per 1 part by weight of the compound of the present invention.
Parts by weight, preferably 0.001 parts by weight to 0.1 parts by weight. In addition, the amount of the electron-withdrawing compound is the compound 1 of the present invention.
It is used in an amount of 0.01 to 10 parts by weight, preferably 0.1 to 2 parts by weight. The amount of the charge generating compound used in the single-layer type photoreceptor among B type photoreceptors is in the range of 0.01 to 2 parts by weight, preferably 0.05 to 1 part by weight, per 1 part by weight of the compound of the present invention. is within the range of In the B type laminated photoreceptor, the charge generation layer is formed with 5 parts by weight or less of a binder per 1 part by weight of the charge generation compound. The thickness of the photosensitive layer is preferably in the range of 1 to 30 microns for both type A and B photoreceptors. In a type B laminated photoreceptor in which the photosensitive layer is composed of two layers, a charge generation layer and a charge transport layer, the charge generation layer has a thickness in the range of 0.01 to 5 microns, and the charge transport layer has a thickness in the range of 11 to 30 microns. used. As the coating method used to form the photosensitive layer of the present invention, a conventional method such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, a curtain coating method, etc. can be used. I can do it. The solvent used in forming the photosensitive layer of the present invention includes many useful organic solvents. Typical examples include benzene, naphthalene,
Aromatic hydrocarbons such as toluene, xylene, mesitylene, and chlorobenzene, ketones such as acetone and 2-butanone, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, and ethylene chloride, and cyclic hydrocarbons such as tetrahydrofuran and ethyl ether. or linear AELs, or a mixed solvent thereof. Furthermore, when coating a charge generating compound, an amine solvent such as ethylenediamine, diethylenetriamine, or tridimethylaminomethylphenol, or an amide solvent such as N,N-dimethylformamide may be added to the coating solvent to facilitate dispersion. can. The photosensitive layer of the present invention can contain various additives in order to increase the plasticity of the photosensitive layer and improve the film strength. Such additives include diphenyl, diphenyl chloride, o-terphenyl, P-terphenyl, dibutyl phthalate, dimethyl glycol phthalate, dioctyl phthalate, triphenyl phosphoric acid, methylnaphthalene, benzophenone, chlorinated paraffin, dilaurylthiopropionate, 3, 5-dinitrosalicylic acid, various fluorocarbons, silicone oil, silicone rubber or dibutylhydroxytoluene, 2,2'-
Phenolic compounds such as methylene-bis-(6-t-butyl-4-methylphenol), α-tocopherol, 2-t-octyl-5-chlorohydroquinone, 2,5-di-t-octylhydroquinone, etc. can be mentioned. The conductive support constituting the photoreceptor of the present invention may be a paper or plastic support made conductive by applying a conductive compound such as indium oxide or cuprous iodide or a thin metal layer to the surface, or a plastic support as required. Depending on the requirements, any material such as a metal plate made of forged or vacuum-deposited palladium, aluminum, or the like, or an aluminum plate may be used. In addition to the above-mentioned polymer binder, materials constituting intermediate layers such as adhesive layers and barrier layers that are provided as necessary include casein, gelatin, starch, polyvinyl alcohol, polyvinyl acetate, ethyl cellulose, carboxymethyl cellulose, Other patent applications include 194199, 1983, and
An organic polymer compound consisting of a ternary system or a metal oxide such as aluminum oxide described in the specification of No. 225302 is used. The electrophotographic photoreceptor of the present invention can be used not only in electrophotographic copying machines but also in a wide range of electrophotographic applications such as solar cells, microfilms, laser printers, CRT printers, and electrophotographic plate making systems. . Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In the following examples, all parts indicate parts by weight. Example 1 5 parts of a bisazo pigment with the following structure and 5 parts of a polyester resin (trade name: Vylon 200, manufactured by Toyo Rayon Co., Ltd.) were dissolved in 50 parts of tetrahydrofuran on a conductive support made of a 75μ polyethylene terephthalate film with aluminum vapor-deposited. The mixture was dispersed with a paint shaker for 1 hour and then coated with a wire bar to form a charge generation layer with a thickness of 0.7 μm. Next, a coating solution prepared by dissolving 7 parts of azine compound (1) and 7 parts of polycarbonate (trade name: Lexan 121, manufactured by Engineering Plastics Co., Ltd.) in a mixed solvent of 40 parts of methylene chloride and 80 parts of ethylene chloride was applied using a wire bar. A laminated photoreceptor having a thickness of 13 μm was prepared by coating the above-mentioned charge generation layer with two layers: a charge generation layer and a charge transport layer. No crystal precipitation due to the azine compound was observed on the surface of the photoreceptor. This photoreceptor was tested using an electrostatic copying paper tester (Kawaguchi Electric Co., Ltd.).
After setting the initial potential (Vo) of the photoreceptor surface to -650V by corona discharge of -5kV (manufactured by SP-428, manufactured by Kogyo Co., Ltd., SP-428 type), the photoreceptor surface was irradiated with light using tungsten light, and the potential of the photoreceptor surface was set to 50V.
Exposure required to attenuate by %, halved amount of light (E ₅₀ )
was measured. E ₅₀ was 2.5 lux・sec. Also, when measured after performing the charging and exposure process 1000 times, Vo was -645v and _E50 was 1 at 2.4lux・sec.
There were no major changes compared to the previous time. Examples 2 to 4 Laminated photoreceptors were prepared in the same manner as in Example 1, except that azine compounds (3), (6), and (10) were used instead of azine compound (1), and the half-decreased exposure amount was (E ₅₀ ) was measured. The results are shown in Table 1.

[Table] Comparative Examples 1 to 3 Comparative compounds (A-1), (A-2), (A-3) other than the azine compound according to the present invention in place of the azine compound (1) used in Example 1 In addition to using
A photoreceptor was produced in the same manner as in Example 1. The charging characteristics of this photoreceptor were measured in the same manner as in Example (1). The surface condition of the photoreceptor was also observed. The results are shown in Table 2.

[Table] As is clear from Example 1 and Comparative Examples 1 and 2, 4,4'-di(N-disubstituted amino) according to the present invention
Asymmetric azine-based compounds synthesized from benzophenone have better sensitivity and better charging characteristics after recycling than azine-based compounds synthesized from carbonyl compounds other than 4,4'-(N-disubstituted amino)benzophenone. ing. This indicates that the compound according to the present invention is different from the comparative compound (A-
Since it has one more N-disubstituted amino group than 1) and (A-2), the highest occupied level of the compound becomes higher, resulting in a higher hole injection efficiency from the charge generation layer to the charge transport layer. I think it's because he's getting better. Furthermore, as is clear from Example 1 and Comparative Example 3, the symmetric azine compound synthesized from 4,4'-di(N-disubstituted amino)benzophenone has a higher sensitivity than the asymmetric azine compound according to the present invention. In addition to its low solubility, it has the disadvantage that crystals tend to precipitate on the surface of the photoreceptor. Example 5 1 part by weight of azine compound (1) according to the present invention, 4-
0.01 part of [4-(N-2-chloroethyl, N-2-cyanoethyl)styryl]-2,6-di-t-butylthiopyrylium fluoroborate and 1.5 parts of polycarbonate (Lexan 121) were dissolved in methylene chloride.
A coating solution was prepared by dissolving in a mixed solvent of 40 parts of ethylene chloride and 80 parts of ethylene chloride. This coating solution was coated with a wire bar onto a transparent conductive film on which soot-doped indium oxide was deposited on the surface of a polyethylene terephthalate film, and dried to obtain a photoreceptor having a photosensitive layer with a film thickness of 5 μm. This photoreceptor was manufactured using the same equipment as in Example 1.
When charged to 250v and measured _E50 , it was 10lux・sec. Examples 6 to 8 Photoreceptors were prepared in the same manner as in Example 5, except that azine compound (1) was replaced with (2), (4), and (8), respectively, and the sensitivity was measured. The results are shown in Table 3.

[Table] Comparative Examples 4 to 6 Instead of the azine compound (4) used in Example 7, an azine compound (A-
4) A photoreceptor was produced in the same manner as in Example except that (A-5) and (A-6) were used. The charging characteristics of this photoreceptor were measured in the same manner as in Example 7. The results are shown in Table 4, and the sensitivity was lower than that of Example 7 in all cases.

[Table] Crystals were deposited on the photoreceptor surface of the photoreceptor prepared in Comparative Example 6 after being left at room temperature for one week. Example 9 1 part of bisazo pigment with the following structure, azine compound
(3) 5 parts, and polycarbonate (Lexan 121)
5 parts of methylene chloride were added to 95 parts of methylene chloride, and the mixture was shaken for 1 hour in a paint shaker to prepare a coating solution. This coating solution was applied with a wire bar to a conductive support made of a polyethylene terephthalate film on which aluminum was vapor-deposited, and dried to obtain a single-layer photoreceptor having a photosensitive layer with a thickness of 10 μm. Using the same apparatus as in Example 1, this electrophotographic photoreceptor was charged to +450V by +5kV corona discharge and exposed to tungsten light. The half-reduction exposure (E ₅₀ ) was measured and found to be 9 lux·sec. Even if the two steps of charging and exposure are repeated 1000 times,
E ₅₀ remained almost unchanged. Example 10 1 part of the bisazo pigment used in Example 9, 2 parts of the azine compound, and 6 parts of m-cresol formaldehyde resin were added to 30 parts of ethylene glycol monomethyl ether, and this was ground in a ball mill.
The coating solution was mixed and applied to a grained, anodized and sealed aluminum plate approximately 0.25 mm thick using a wire round rod.
It was dried at 50°C for 10 minutes and for 1 day to prepare a sample with a thickness of about 6 μm. Next, corona discharge was applied to this sample in a dark place so that the surface potential became 500 V, and after exposing the negative image to tungsten light (100 lux seconds), Mitsubishi Diafax Master LOM-ED toner (Mitsubishi Paper When reversal development was performed using a printing press (manufactured by Co., Ltd.), a very clear positive image could be obtained on the original printing plate.
This printing original plate was immersed for 1 minute in a 10-fold diluted etching solution DP-1 (manufactured by Fuji Photo Film Co., Ltd.; sodium silicate aqueous solution), and the photosensitive layer was removed from the areas to which toner was not attached (non-image areas). was dissolved and removed. As a result, the pigment in the non-image area was easily removed together with the binder, and a printing plate with a clear image could be formed.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer containing a compound represented by the following general formula (1). However, in the formula, R ₁ , R ₂ , R ₃ , R ₄ are substituted or unsubstituted alkyl groups, aralkyl groups, having 1 to 12 carbon atoms,
Represents a residue that forms a cyclic amino group with an aryl group or a nitrogen atom, R ₅ is hydrogen, substituted or unsubstituted, having 1 to 12 carbon atoms,
Alkyl group, aralkyl group, unsubstituted or carbon number 1
-8 represents an aryl group containing an alkyl group, an alkoxy group, a halogen atom, a hydroxyl group, or a cyano group as a substituent. Further, R ₆ represents an N-disubstituted amino group, an alkoxy group, an aralkyloxy group, an aryloxy group, or a halogen atom having 1 to 8 carbon atoms and represented by [Formula] or [Formula], or R ₆ represents R ₇ or
Represents the atoms necessary to form a heterocycle together with R ₈ and the benzene ring to which they are bonded. R ₇ and R ₈ may be the same or different,
It represents hydrogen, an alkyl group, an alkoxy group, a halogen atom having 1 to 8 carbon atoms, or an atom necessary to form a heterocycle with R ₆ .