JP2556572B2 - Electrophotographic photoreceptor - Google Patents

Description

The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor having a low molecular weight organic photoconductor that provides improved electrophotographic properties. .

[Prior art]

Conventionally, inorganic photoconductive materials such as selenium, zinc oxide, and cadmium sulfide have been widely used for electrophotographic photoreceptors, but in recent years, research using organic photoconductive materials has been actively conducted. The basic characteristics required for an electrophotographic photoreceptor are 1) being charged to an appropriate potential by corona discharge in a dark place, 2) having a good charge retention rate in a dark place, and 3) irradiating with light. To rapidly discharge the electric charge, and 4) the residual potential after irradiation with light is small.

An electrophotographic photoreceptor using a conventional inorganic photoconductive material is
Although it has basic characteristics to some extent, it has manufacturing problems such as difficulty in film formation, poor flexibility, and high manufacturing cost.

On the other hand, organic photoconductive materials have advantages such as light weight, excellent film formability and flexibility, and low manufacturing cost. In recent years, electrophotographic photosensitive materials using organic photoconductive materials have been used. Many bodies have been proposed and put into practical use.

A typical organic photoconductive material is poly-N.
-Various organic photoconductive polymers such as vinylcarbazole have been proposed. These polymers are superior to inorganic photoconductive materials in light weight and film forming property, However, it was difficult to put into practical use because it was inferior in terms of durability, stability due to environmental changes, and mechanical strength. Further, hydrazone compounds disclosed in US Pat. No. 4,150,987, triarylpyrazoline compounds described in US Pat. No. 3,837,851, and JP-A-51-94828.
JP-A-51-94829 and the like propose low molecular weight organic photoconductors such as 9-styrylanthracene compounds. Such low molecular weight organic photoconductor, by properly selecting the binder to be used, it has become possible to solve the drawback of film-forming property which has been a problem in the field of organic photoconductive polymers, It is not enough in terms of sensitivity.

Under these circumstances, a laminated structure type photosensitive layer in which the photosensitive layer is functionally separated into a charge generation layer and a charge transport layer has been proposed in recent years. The electrophotographic photosensitive member using this laminated structure as a photosensitive layer has been improved in terms of sensitivity to visible light, charge retention, surface strength and the like.

Among these, many organic compounds have been mentioned as the charge transport material. For example, JP-A-52-72231
Japanese Patent Laid-Open No. 842,431 and Japanese Patent Laid-Open No. 55-52063, and Japanese Patent Laid-Open No. 52063.
7-195254 and JP-A-54-58445, triphenylamine compounds, JP-A-54-151955 and JP-A-
The stilbene compound and the like disclosed in JP-A 58-198043 are known.

Further, the carbazole compounds described in JP-A-54-59142, JP-A-62-283341 and JP-A-63-58451 are reported as charge transporting substances.

However, the sensitivity and characteristics are not necessarily sufficient in the conventional electrophotographic photoreceptor using a low-molecular weight organic compound as the charge transport material, and the potential in the bright area and the dark area in the repeated charging and exposure are not sufficient. The potential changes greatly and there are still points to be improved.

[Problems to be solved by the invention]

An object of the present invention is to provide an electrophotographic photosensitive member which eliminates various drawbacks of the conventional photosensitive member.

Another object of the present invention is to provide an electrophotographic photosensitive member which is easy to manufacture, relatively inexpensive, and excellent in durability.

[Means for solving problems]

The present invention is an electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a compound represented by the following general formula [I].

In the formula, R ₁ , R ₂ , R ₃ and R ₄ represent an alkyl group, an aralkyl group, an aryl group or a heterocyclic group. Examples of the alkyl group include methyl, ethyl, propyl, butyl, etc., examples of the aralkyl group include benzyl, phenethyl, etc., examples of the aryl group include phenyl, diphenyl, naphthyl, etc., and examples of the heterocyclic group include , Pyridyl, quinolyl, carbazolyl, thienyl, furyl and the like. R ₅ represents a hydrogen atom, an alkyl group, an aralkyl group, an aryl group or a heterocyclic group. Specific examples of these groups are the same as above.

The groups represented by R _{1 to} R ₅ may each have a substituent,
These substituents include hydroxyl groups, fluorine, halogen atoms such as chlorine, bromine and iodine, methyl, ethyl,
Alkyl groups such as propyl and butyl, alkoxy groups such as methoxy, ethoxy, propoxy and butoxy, aryl groups such as phenyl, diphenyl and naphthyl, aryloxy groups such as phenyloxy, amino groups, dimethylamino, diethylamino, diphenylamino, ditolylamino, dianim Examples thereof include substituted amino groups such as silamino, nitro groups, cyano groups or acyl groups such as acetyl and benzoyl.

Furthermore, in the present invention, at least one of R _{1 to} R ₅ is an aryl group.

Among these, any one of R _{1 to} R ₄ , and further R ₁
When R ₃ , especially R ₁ , R ₂ , R ₃ and R ₄ are all aryl groups, the electrophotographic properties are further improved.

Hereinafter, typical examples of the compound represented by the general formula [I] will be given.

Next, a synthesis example of the compound will be shown.

(Synthesis method of compound example No. 3) 3.6-diamino-N-ethylcarbazole 3 g (13.3 mmo
l), iodobenzene 30 g (147 mmol), anhydrous potassium carbonate 12.5 g (90.6 mmol), and copper powder 5 g with heating under reflux with stirring 1 g.
I went for 0 hours. After cooling, suction filtration was performed, and iodobenzene was removed from the filtrate under reduced pressure. Methanol was added to the residue to precipitate crystals, and the crude crystals were separated and purified with a silica gel column to obtain 4.2 g of the target compound (3) (yield 59.7).
%). The melting point was 219.4-220.5 ° C. Elemental analysis is C ₃₈ H
₃₁ N ₃ was as follows.

Calculated value Measured value% C86.17 86.15 H5.90 5.91 N7.93 7.94 Infrared absorption spectrum (KBr tablet method) is shown in FIG.

As described above, this compound can be obtained in a single reaction and can be manufactured at low cost.

It should be noted that compounds other than the synthesis examples are also synthesized by the same method.

In a preferred embodiment of the present invention, the compound represented by the above general formula can be used as a charge-transporting substance of an electrophotographic photoreceptor in which a photosensitive layer is functionally separated into a charge-generating layer and a charge-transporting layer.

The charge transport layer is preferably formed by applying a solution prepared by dissolving the compound represented by the above general formula and a binder in a suitable solvent and drying. Examples of the binder used here include polyarylate resin, polysulfone resin, polyamide resin, acrylic resin, acrylonitrile resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, phenol resin, epoxy resin, polyester resin, alkyd resin, and polycarbonate. , Polyurethane or copolymer resins such as styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer and the like. In addition to such insulating polymers, organic photoconductive polymers such as polyvinylcarbazole, polyvinylanthracene and polyvinylpyrene can be used.

The compounding ratio of this binder and the charge transport substance is 10
It is preferable that the charge transport material is 10 to 500 parts by weight per 0 parts by weight.

The charge transport layer is electrically connected to the charge generation layer described below, and has a function of receiving the charge carriers injected from the charge generation layer in the presence of an electric field and capable of transporting these charge carriers to the surface. are doing. At this time, the charge transport layer may be laminated on the charge generation layer,
Further, it may be laminated thereunder. However, the charge transport layer is preferably laminated on the charge generation layer. Since the charge transport layer has a limit for transporting charge carriers, it cannot be made thicker than necessary. Generally, it is 5 μm to 40 μm, but a preferable range is 10 μm to 30 μm.

The organic solvent used when forming such a charge transport layer varies depending on the kind of the binder used, or is preferably selected from those which do not dissolve the charge generation layer or the undercoat layer described below. Specific organic solvents include methanol,
Alcohols such as ethanol and isopropanol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, amides such as N, N-dimethylformamide and N, N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, tetrahydrofuran, dioxane, ethylene glycol monomethyl Ethers such as ethers, 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, monochlorobenzene, Aromatic compounds such as dichlorobenzene can be used.

The coating can be performed by using a coating method such as a dip coating method, a spray coating method, a spinner coating method, a Meyer bar coating method, a blade coating method and the like. Drying is preferably performed by touch drying at room temperature and then heating and drying. Heat drying
Generally, it is preferable to carry out at a temperature of 30 ° C. to 200 ° C. for a time in the range of 5 minutes to 2 hours while still or under blowing air.

The charge transport layer can also be used by incorporating various additives. For example, diphenyl, m-terphenyl,
Plasticizers such as dibutyl phthalate, silicone oil, graft type silicone polymers, surface lubricants such as various fluorocarbons, potential stabilizers such as dicyanovinyl compounds and carbazole derivatives, β-carotene, Ni complex, 1,4
And antioxidants such as diazabicyclo [2,2,2] octane.

The charge generating layer used in the present invention is an inorganic charge generating substance such as selenium, selenium-tellurium, or amorphous silicon, pyrylium dye, thiapyrylium dye, azurenium dye, thiacyanine dye, quinocyanine dye, azurenium dye, etc. Charge generation of polycyclic quinone pigments such as cationic dyes, squabarium salt dyes, phthalocyanine pigments, anthanthrone pigments, dibenzpyrenequinone pigments, pyrantrone pigments, indigo pigments, quinacridone pigments, azo pigments, etc. A material selected from substances can be used.

Among the above-mentioned charge generating substances used in the present invention, the azo pigments are particularly wide-ranging, but typical structural examples of the azo pigments having particularly high effects are shown below.

As a general formula of an azo pigment, the central skeleton is represented by A, and AN = N-Cp) _{n The} coupler portion is represented by Cp (where n = 2, or
3) First, the following are specific examples of A.

Also, as a concrete example of Cp, Etc. The central skeleton A and the coupler Cp are appropriately combined to form a pigment which is a charge generating substance.

The charge generation layer can be formed by dispersing the above-described charge generation substance in an appropriate binder and applying the same to a support, or by forming a deposition film with a vacuum deposition device. Can be. The binder can be selected from a wide range of insulating resins, and can be selected from organic photoconductive polymers such as poly-N-vinyl carbazole, polyvinyl anthracene and polyvinyl pyrene. Preferably, polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinyl pyridine, cellulosic resin, urethane Insulating resins such as resins, epoxy resins, casein, polyvinyl alcohol, and polyvinylpyrrolidone can be mentioned.

The amount of the resin contained in the charge generation layer is suitably 80% by weight or less, preferably 40% by weight or less. The organic solvent used in the coating, methanol, ethanol, alcohols such as isopropanol, acetone, methyl ethyl ketone, ketones such as cyclohexanone, N, N-dimethylformamide, amides such as N, N-dimethylacetamide, dimethyl Sulfoxides such as sulfoxide,
Tetrahydrofuran, ditoxane, ethers such as 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, Aromatic compounds such as toluene, xylene, monochlorobenzene, and dichlorobenzene can be used.

The charge generation layer contains as much of the organic photoconductor as possible to obtain sufficient absorbance, and a thin film layer, e.g., to inject the carrier into the charge transport layer within the life of the generated charge carrier. 5μm or less, preferably 0.01μm
It is preferable to use a thin film layer having a film thickness of ˜1 μm. This means that most of the amount of incident light is absorbed by the charge generation layer to generate a large number of charge carriers, and the generated charge carriers are not deactivated by recombination or capture (trap) to the charge transport layer. It is due to the need to inject.

The photosensitive layer having such a laminated structure of the charge generation layer and the charge transport layer is provided on a conductive support. As the conductive support, one having conductivity itself, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, or the like can be used. In addition, aluminum, aluminum alloy, indium oxide, tin oxide, indium oxide can be used. -Plastics having a layer formed by coating a tin oxide alloy or the like by a vacuum deposition method, conductive particles (for example, aluminum powder, titanium oxide, tin oxide, zinc oxide, carbon black, silver particles, etc.) together with a suitable binder. Alternatively, a support coated on the metal support, a plastic with conductive particles or a paper impregnated with paper, a plastic with a conductive polymer, or the like can be used.

An undercoat layer having a barrier function and an adhesive function can be provided between the conductive support and the photosensitive layer. The subbing layer is made of 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. it can.

The thickness of the undercoat layer is 0.1 μm to 5 μm, preferably 0.5 μm
m to 3 μm is suitable.

In another embodiment of the present invention, the above-mentioned disazo pigment or U.S. Pat.Nos. 3,554,745, 3,567,438, 3,
Sensitize photoconductive pigments and dyes such as pyrylium dyes, thiapyrylium dyes, serenapyrylium dyes, benzopyrylium dyes, benzothiapyrylium dyes, naphthopyrylium dyes, and naphthothiapyrylium dyes disclosed in Japanese Patent No. 586,500. It can also be used as an agent.

In another specific example, a eutectic complex of a pyrylium dye disclosed in US Pat. No. 3,684,502 or the like and an electric insulating polymer having an alkylidene diarylene moiety can be used as a sensitizer. This eutectic complex is, for example, 4-
[4-bis- (2-chloroethyl) aminophenyl]-
2,6-diphenylthiapyrylium perchlorate and poly (4,4'-isopropylidene diphenylene carbonate) are combined with halogenated hydrocarbon solvents (e.g. dichloromethane, chloroform, carbon tetrachloride, 1,1-dichloroethane, 1 , 2-dichloroethane, 1,1,2-trichloroethane,
After dissolving in chlorobenzene, bromobenzene, 1,2-dichlorobenzene), a non-polar solvent (e.g., hexane, octane, decane, 2,2,4-trimethylbenzene, ligroin) is added to the particulate co-solvent. And a styrene-butadiene copolymer, a silicone resin,
Containing vinyl resin, vinylidene chloride-acrylonitrile copolymer, styrene-acrylonitrile copolymer, vinyl acetate-vinyl chloride copolymer, polyvinyl butyral, polymethyl methacrylate, poly-N-butyl methacrylate, polyesters, cellulose esters, etc. as a binder. Can be.

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, and electrophotographic plate making systems.

According to the present invention, it is possible to provide a high-sensitivity electrophotographic photosensitive member, and there is an advantage that variations in the light portion potential and the dark portion potential upon repeated charging and exposure are small.

 Hereinafter, a description will be given according to an embodiment of the present invention.

Example 1 The following structural formula 5 g of the disazo pigment represented by 2 was dissolved in 100 ml of cyclohexanone for 2 g of butyral resin (degree of butyralization: 63 mol%) and dispersed in a sand mill for 24 hours to prepare a coating solution.

This coating solution was applied onto an aluminum sheet with a Meyer bar so that the dry film thickness would be 0.2 μm to form a charge generation layer.

Next, 10 g of the above exemplified compound No. (2) as a charge transport material
And 10 g of a polycarbonate resin (weight average molecular weight 20000) are dissolved in 70 g of monochlorobenzene, and this solution is applied on the above charge generation layer with a Meyer bar to form a charge transport layer having a dry film thickness of 20 μm. It was made.

The electrophotographic photosensitive member thus produced was corona-charged at -5 KV by a static method using an electrostatic copying paper tester Model-SP-428 manufactured by Kawaguchi Electric Co., Ltd., and held for 1 second in a dark place. It was exposed at an illuminance of 20 lux and the charging characteristics were examined.

As the charging characteristics, the exposure amount (E) required to attenuate the surface potential (V ₀ ) and the potential (V ₁ ) when dark attenuated for 1 second (1/2) is used.
_^1/2) was measured.

Furthermore, in order to measure the fluctuation of the light potential and the dark potential when repeatedly used, the photoconductor prepared in this example was PP
C Copy machine (NP-3525: made by Canon) was attached to the cylinder for the photosensitive drum and the same machine was used to make 5000 copies.
Changes in the light potential (V _L ) and the dark potential (V _D ) after 5,000 copies were measured. The initial V _D and V _L are -700 V and -200, respectively.
It was set to be V. The results are shown below.

Examples 2 to 10 and Comparative Examples 1 to 2 In each of these Examples, as the charge transport substance used in Example 1, the exemplified compound Nos. (3) and (5) were used instead of the exemplified compound No. (2). , (12), (15), (19), (3
0), (34), (37), (40) and the following structural formula An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the above pigment was used.

The electrophotographic characteristics of each photoconductor were measured by the same method as in Example 1.

For comparison, a compound having the following structural formula was used as a charge-transporting substance, an electrophotographic photosensitive member was produced by the same method, and electrophotographic characteristics were measured. The respective results are shown below.

Comparative compound As is clear from the above Examples and Comparative Examples, high sensitivity and high durability can be realized by introducing an aryl group into R _{1 to} R ₄ of the general formula [I].

Example 11 A solution prepared by dissolving 5 g of methoxymethylated nylon resin (number average molecular weight 32000) and 10 g of alcohol-soluble copolymerized nylon resin (number average molecular weight 29000) in methanol 95 g was applied on an aluminum substrate with a Meyer bar, and dried. Film thickness is 1 μm
An undercoat layer was provided.

Next, the following structural formula Were dispersed in a ball mill disperser for 48 hours using 10 g of the charge generating substance represented by the following formula, 5 g of butyral resin (butyralization degree: 63 mol%), and 200 g of dioxane. This dispersion is applied onto the undercoat layer prepared above by a blade coating method,
A charge generation layer having a film thickness after drying of 0.15 μm was produced.

Next, 10 g of the exemplified compound No. (3) and 10 g of a polymethylmethacrylate resin (weight average molecular weight of 50,000) were dissolved in 70 g of monochlorobenzene, and applied on the previously formed charge generation layer by a blade coating method, and after drying. A charge transport layer having a thickness of 19 μm was prepared.

A corona discharge of -5 KV was applied to the thus prepared photoconductor. The surface potential at this time was measured (initial potential V ₀ ). Furthermore, the surface potential of this photoreceptor was measured after leaving it in the dark for 1 second. The sensitivity was evaluated by measuring the exposure dose (E1 / 2, μJ / cm ² ) required to attenuate the potential V ₁ after dark decay to 1/2. At this time, a gallium / aluminum / arsenic ternary semiconductor laser (output: 5 mW; oscillation wavelength: 780 nm) was used as a light source. The results were as follows.

_{V 0: -720V V 1: -713V} E 1/2: 0.33μJ / cm 2 and then the laser beam printer is an electrophotographic type printer reversal development system having a semiconductor laser of the same (LBP-CX: manufactured by Canon Inc.) The above photoconductor was replaced with and set, and an actual image forming test was used. The conditions are as follows. Surface potential after primary charging: -700 V, surface potential after image exposure: -150 V (exposure amount 2.0 μJ / cm ² ), transfer potential: +
700V, developer polarity; negative polarity, process speed; 50mm / se
c, development condition (development bias): -450V, image exposure scan method; image scan, exposure before primary charging; 50lux.se
The entire red exposure and image formation of c were performed by line scanning with a laser beam according to the character signal and the image signal, and good prints were obtained for both the character and the image. Furthermore,
When continuous printing of 3000 sheets was performed, stable and good prints were obtained from the initial stage to 3000 sheets.

Example 12 Titanyloxyphthalocyanine 10 g dioxane 485 g
Was added to a solution in which 5 g of phenoxy resin was dissolved and dispersed by a ball mill for 2 hours. This dispersion is applied on an aluminum sheet with a Meyer bar and dried at 80 ° C for 2 hours to give a film thickness of 0.5 μm.
The charge generation layer of was prepared. Next, the exemplified compound No. (2
8) 10 g of bisphenol Z type polycarbonate resin (weight average molecular weight 50,000) dissolved in 70 g of monochlorobenzene was applied on the charge generation layer previously formed with a Meyer bar and dried at 110 ° C for 1 hour. A charge transport layer having a film thickness of 19 μm was prepared. The photoconductor thus produced was measured in the same manner as in Example 11. The results are shown below.

_{V 0: -715V V 1: -709V} E 1/2: 0.48μJ / cm 2 Example 13 4- (4-dimethylamino-phenylalanine) -2,6-diphenyl Eni Lucia pyrylium perchlorate 3g and the charge transporting material As an example, 5 g of the exemplified compound No. (31) was mixed with 100 g of a toluene (50 parts by weight) -dioxane (50 parts by weight) solution of a polyester resin (weight average molecular weight 49,000), and the mixture was dispersed by a ball mill for 6 hours. This dispersion was applied on an aluminum sheet with a Meyer bar and dried at 100 ° C for 2 hours to give a film thickness of 15 μm.
To prepare a photosensitive layer. The photoconductor thus prepared was measured in the same manner as in Example 1. The results are shown below.

Example 14 Aqueous ammonia solution of casein (casein
11.2 g, 1 g of 28% aqueous ammonia, and 222 ml of water) were applied with a Meyer bar to form an undercoat layer having a dry film thickness of 1 μm. The charge transport layer and the charge generation layer of Example 5 were sequentially laminated thereon,
A photoconductor was prepared in exactly the same manner as in Example 1 except that the layer structure was changed, and the charging characteristics were measured in the same manner as in Example 1. However, the charging polarity was used. The results are shown below.

_{V 0: 698V V 1: 683V} E 1/2: 5% methanol solution of a soluble nylon (6-66-610-12 four yuan nylon copolymer) is coated 2.3lux · sec Example 15 aluminum plate, An undercoat layer having a dry film thickness of 0.5 μm was prepared.

Next, the following structural formula 5 g of the pigment shown by was dispersed in 95 ml of tetrahydrofuran by a sand mill for 20 hours. Next, a solution prepared by dissolving 5 g of the exemplified compound No. (25) as a charge transport material and 10 g of bisphenol Z-type polycarbonate resin (weight average molecular weight of 50,000) in 30 ml of monochlorobenzene was added to the dispersion liquid prepared above, and further added with a sand mill. Dispersed for 2 hours. The dispersion was applied onto the previously formed undercoat layer with a Meyer bar so that the film thickness after drying was 20 μm, and dried. The electrophotographic characteristics of the thus prepared photoconductor were measured by the same method as in Example 1. The results are shown below.

_{V 0: -716V V 1: -705V} E 1/2: 2.8lux · sec As described [Effect of the Invention, an electrophotographic photoreceptor containing a carbazole compound according to the invention are highly sensitive, also repeatedly It is possible to provide an electrophotographic photosensitive member excellent in durability, in which fluctuations in the light portion potential and the dark portion potential are small during continuous image formation by charging and exposure.

[Brief description of drawings]

FIG. 1 shows the infrared absorption spectrum of the compound of the present invention measured by the KBr tablet method.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norihiro Kikuchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-1-234855 (JP, A) JP-A-2 -72369 (JP, A) JP 62-283341 (JP, A) JP 54-59142 (JP, A) JP 63-58451 (JP, A)

Claims (1)

(57) [Claims] 1. An electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a carbazole compound represented by the following general formula [I]. General formula [I] (In the formula, R ₁ , R ₂ , R ₃ and R ₄ represent an alkyl group, an aralkyl group, an aryl group or a heterocyclic group, and R ₅ represents a hydrogen atom, an alkyl group, an aralkyl group, an aryl group or a heterocyclic group. However, at least one or more of R _{1 to} R ₅ is an aryl group.)