JPH0324660B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to electrophotographic photoreceptors, and more particularly to electrophotographic photoreceptors having improved sensitivity and durability characteristics. Inorganic photoconductive materials such as selenium, cadmium sulfide, and zinc oxide are known as photoconductive materials used in electrophotographic photoreceptors. These photoconductive materials have a number of advantages, such as being able to be charged to an appropriate potential in the dark, having little charge dissipation in the dark, or quickly dissipating the charge when irradiated with light. However, it also has various drawbacks. For example, selenium-based photoreceptors easily crystallize due to factors such as temperature, humidity, dust, and pressure. Especially when the ambient temperature exceeds 40°C, crystallization becomes significant, resulting in decreased charging performance and white spots on images. There is a drawback when this occurs. Furthermore, selenium-based photoreceptors and cadmium sulfide-based photoreceptors have the disadvantage that stable sensitivity and durability cannot be obtained when used over time under high humidity. In addition, zinc oxide photoreceptors require the sensitizing effect of sensitizing dyes such as rose bengal, but such sensitizing dyes cause charge deterioration due to corona charging and photobleaching due to exposure light, so it may take a long time. It has the disadvantage that it cannot provide a stable image over a long period of time. On the other hand, various organic photoconductive polymers including polyvinylcarbazole have been proposed, but these polymers have poor film formability, light weight, high productivity, etc. compared to the inorganic photoconductive materials mentioned above. Despite its excellent properties, it has been difficult to put it into practical use to date because it has not yet achieved sufficient film formation properties, and because of its sensitivity, durability, and stability against environmental changes, inorganic This was because it was inferior to photoconductive materials. Moreover, an appropriate sensitizer that can provide sufficiently high sensitivity has not yet been found. For this reason, in recent years, many efforts have been made to develop low molecular weight organic photoconductive substances in place of polymer-based organic photoconductive substances. The advantage of low molecular weight organic photoconductive substances is that the range of compounds that can be selected has expanded, and by selecting those with good sensitivity and charge retention, it is possible to It has become possible to improve the drawbacks of photoreceptors using polymers. Hitherto, hydrazone compounds disclosed in, for example, British Patent No. 930988, US Patent No. 4150987, and US Patent No. 4278747 have been proposed. Low molecular weight organic photoconductive substances such as hydrazone compounds have poor film-forming properties on their own, so insulating polymers such as polyester, polystyrene, polycarbonate, polyarylate, polymethacrylic acid esters, and phenoxy resin are used. It is necessary to use it as a binder. When selecting an insulating polymer to be used as a binder, consider that the photoreceptor is subjected to various processes in the copier (charging, exposure, development, transfer, cleaning, etc.).
It goes without saying that it has physical durability that can withstand repeated cycles, but it also has good compatibility with low-molecular-weight organic photoconductive substances. may cause crystallization. Furthermore, when a hydrazone compound is used as a charge transport material in a laminated photosensitive layer comprising a charge transport layer and a charge generation layer, it is required that the binder of the hydrazone compound does not form undesirable charge traps. When an unfavorable charge trap is formed in the combination of a hydrazone compound and an insulating polymer, the charge gradually accumulates in the charge transport layer during repeated exposure and charging, resulting in an increase in the residual potential. It turns out. Moreover, since the charges accumulated in this manner are released by external factors such as heat and electric fields, they also become a cause of increased instability of the charged potential. There is no lawful selection method for a suitable combination of a charge transport material and a binder, and the suitable combination must be determined through numerous experiments. An object of the present invention is to provide an electrophotographic photoreceptor that does not have the above-mentioned drawbacks. Another object of the present invention is to provide an electrophotographic photoreceptor that has high sensitivity and improved repeated durability characteristics. This object of the present invention is achieved by an electrophotographic photoreceptor characterized by having a photosensitive layer containing a hydrazone compound and an acrylonitrile-styrene copolymer resin. One specific example of the present invention is an electrophotographic photoreceptor having at least two layers consisting of a charge generation layer and a charge transport layer containing a hydrazone compound. The charge transport layer is in electrical contact with the charge generation layer such that the hydrazone compound can receive and transport charge carriers injected from the charge generation layer in the presence of an electric field. In this case, the hydrazone compound is preferably selected from those that are completely insensitive or have almost no sensitivity to wavelengths in the spectral region to which the charge generation layer is sensitive. The thickness of the charge transport layer is 2 to 100 microns, preferably 5 to 20 microns. The interaction between the hydrazone compound used in the present invention and the acrylonitrile-styrene copolymer resin (hereinafter simply referred to as "AS resin") does not simply depend on the solvent effect of the AS resin on the hydrazone solid mass; This is thought to be due to the formation of some kind of intermolecular compound, perhaps a charge transfer complex, between the hydrazone compound and the hydrazone compound. It is presumed that this intermolecular compound injects and transports the charges generated in the charge generation layer without accumulating them, thereby effectively acting to attenuate the surface potential. For this reason, it is thought that even when an electrophotographic photoreceptor using a combination of a hydrazone compound and an AS resin used in the present invention is used repeatedly, fluctuations in charging potential will not occur. The hydrazone compound used in the present invention is particularly preferably one represented by the following general formula (1). General formula (1) In the formula, R ₁ is an aryl group such as a phenyl group, a naphthyl group, an anthralyl group, or a carbazole ring, a pyridine ring, a furan ring, an oofene ring, a phenothiazine ring, a phenoxazine ring, a benzimidazole ring, a benzothiazole ring, a benzoxazole ring, etc. It shows a monovalent heterocyclic group derived from a heterocycle. The aryl group and heterocyclic group may have a suitable substituent atom or group. Specific atoms or groups include chlorine atom,
Halogen atoms such as bromine atoms, alkyl groups such as methyl, ethyl, propyl, butyl, amyl groups, 2-methoxyethyl, 3-methoxypropyl, 2-ethoxyethyl, 3-ethoxyethyl groups, Substituted alkyl groups such as 3-hydroxypropyl group, alkoxy groups such as methoxy group, ethoxy group, propoxy group, butoxy group, N,N-
dimethylamino group, N,N-diethylamino group,
N,N-dipropylamino group, N,N-dibutylamino group, N,N-diphenylamino group, N,N
Examples include di-substituted amino groups such as -ditolyl amino group and N,N-dibenzylamino group, and cyclic amino groups such as pyrrolidino group, piperidino group, and morpholino group. R ₂ is a hydrogen atom, an alkyl group such as a methyl group, ethyl group, propyl group, butyl group, or amino group,
Substituted alkyl groups such as 2-hydroxyethyl group, 2-methoxyethyl group, 2-ethoxyethyl group, 3-hydroxypropyl group, 3-ethoxypropyl group, 3-methoxypropyl group, phenyl group,
Aryl groups such as naphthyl groups, 4-N,N-dimethylaminophenyl groups, 4-N,N-diethylaminophenyl groups, 4-N,N-dipropylaminophenyl groups, 4-N,N-dimethylaminophenyl groups, Substituted aryl groups such as benzylaminophenyl group, 4-methoxyphenyl group, 4-ethoxyphenyl group, 4-butoxyphenyl group, 4-ethoxy-2-methylphenyl group, tolyl group, xylyl group, benzyl group, phenethyl group and substituted aralkyl groups such as 4-methoxybenzyl group, 4-ethoxybenzyl group, and 4-ethoxy-2-methylbenzyl group. R ₃ and R ₄ are alkyl groups such as methyl group, ethyl group, propyl group, butyl group, 2-methoxyethyl group, 2-ethoxyethyl group, 2-hydroxyethyl group, 3-methoxypropyl group, 3-ethoxy Substituted alkyl groups such as propyl group, 3-hydroxypropyl group, aryl group such as phenyl group, α-naphthyl group, β-naphthyl group, substituted aryl group such as tolyl group, xylyl group, methoxyphenyl group, ethoxyphenyl group group, benzyl group,
It represents an aralkyl group such as a phenethyl group, or a substituted aralkyl group such as a methylbenzyl group, a methoxybenzyl group, or an ethoxybenzyl group. n is 0 or 1. Specific examples of hydrazone compounds that can be used in the present invention are shown below. The charge transport layer of the present invention can contain various additives. Such additives include diphenyl, diphenyl chloride, O-terphenyl,
Examples include P-terphenyl, dibutyl phthalate, dimethyl glycol phthalate, dioctyl phthalate, triphenyl phosphoric acid, methylnaphthalene, benzophenone, chlorinated paraffin, dilaurylthiopropionate, 3,5-dinitrosalicylic acid, and the like. Organic solvents that dissolve hydrazone compounds and AS resins include ketones such as acetone, methiethyl ketone, and cyclohexyne, esters such as methyl acetate and ethyl acetate, and aromatic solvents such as benzene, xylene, triene, monochlorobenzene, and dichlorobenzene. family or chloroform, methylene chloride,
These include methylene dichloride, carbon tetrachloride, and trichlorethylene chlorinated aliphatic hydrocarbons. these
A solution containing AS resin has good solution stability and does not gel, so it can be stored for a long period of time. The weight ratio of the organic solvent to the AS resin may be about 1:1. The AS resin used in the present invention preferably contains 60 to 90 mol% styrene. The charge transport layer can contain a suitable insulating polymer in addition to the AS resin. For example, polyarylate consisting of bisphenol A and phthalic acid, polyethylene terephthalate, polymethyl methacrylate, etc. can be contained in an appropriate ratio. It can also contain photoconductive polymers such as poly-N-vinylcarbazole. A solution containing the hydrazone compound, AS resin, and organic solvent described above can be applied to the charge generation layer or substrate described below and dried to form a charge transport layer. When applying this solution, coating methods such as dip coating, spray coating, spinner coating, bead coating, blade coating, and curtain coating can be used, and drying is not necessary.
It can be carried out under blow drying or stationary drying at a temperature in the range of 10°C to 200°C, preferably 20°C to 150°C, for a time of 5 minutes to 5 hours, preferably 10 minutes to 2 hours. By combining a hydrazone compound and an AS resin, it is possible not only to impart physical strength such as dimensional stability, strength, rigidity, impact strength, and weather resistance, but also to improve the properties of this electrophotographic photoreceptor, such as sensitivity and surface It also provides an important factor in determining potential characteristics and stable durability characteristics. These points will be clarified in the Examples below. The charge generation layer includes azo pigments such as Sudan Red, Diane Blue, and Jenas Green B; quino pigments such as Algol Yellow, Pyrene Quinone, and Indanthrene Brilliant Violet RRP;
Indigo pigments such as quinocyanine pigments, perylene pigments, indigo and thioindigo, bisbenzimidazole pigments such as India First Orange toner, phthalocyanine pigments such as copper phthalocyanine, quinacridone pigments, pyrylium dyes or eutectics consisting of thiapyrylium dyes and polyarylates, etc. A charge-generating substance is dispersed in a binder resin such as polyester, polystyrene, polyvinyl chloride, polyvinyl acetate, acrylic, polyvinylpyrrolidone, polyvinyl butyral, methylcellulose, hydroxypropylmethylcellulose, etc., and the mixture is coated on a charge transport layer or a substrate to form the charge-generating material. has been known for some time. Alternatively, it is also effective to use a selenium deposited layer, a selenium-tellurium deposited layer, or an amorphous silicon layer (which can be formed by glow discharge or arc discharge) as the charge generation layer. When preparing the charge-generating layer, the charge-generating substance described above can be dispersed in the binder using a dispersing machine such as a pole mill, vibration mill, attritor, sand mill, or roll mill. Examples of the resin used as a binder include polyvinyl butyral, polyethylene terephthalate, polymethyl methacrylate,
Examples include polycarbonate, polystyrene, polyvinylidene chloride, polyamide, chlorinated rubber, polyvinyltoluene, polyvinyl chloride, ethylcellulose, polyvinylpyridine, styrene-maleic anhydride copolymer, and the like. The proportion of such a binder in the charge generation layer is preferably 80% by weight or less, preferably 50% by weight or less of the total weight of the charge generation layer. etc. can be mentioned. The organic solvent used at this time is preferably selected from those that do not dissolve the charge generation layer described above and the subbing layer described below. The thickness of the charge generation layer is such that it contains as much charge generation substance such as dye or pigment as possible in order to obtain sufficient absorbance, and is a thin film layer in order to shorten the range of the generated charge carriers. For example, it is necessary to form a thin film layer with a thickness of 1 micron or less, preferably 0.1 to 1 micron or less. This means that most of the incident light is absorbed by the charge generation layer, generating many charge carriers, and that the generated charge carriers must be injected into the charge transport layer without being deactivated by recombination or capture. This is due to the fact that The incident light is selected from the wavelength range to which the charge generation layer is sensitive, and typically the charge generation layer is sensitive to X-rays, ultraviolet light, visible light, near-infrared radiation, and infrared radiation. The charge transport layer is preferably laminated on the charge generation layer, but may have the opposite laminated structure. The base material is metal such as aluminum, brass, stainless steel, or polyethylene terephthalate, polybutylene terephthalate, polyethylene, polypropylene, nylon, polystyrene,
It is used by molding polymeric materials such as phenolic resin, hard paper, etc. into a cylindrical shape, or making it into a film or foil. In the case of an insulator, it is necessary to conduct conductive treatment, which can be done by impregnating it with a conductive substance, laminating metal foil, or vapor depositing metal. A subbing layer (adhesive layer) having a barrier function and a subbing function can be provided on these substrates. The undercoat layer is formed to improve adhesion of the charge transport layer, improve coating properties, protect the substrate, cover defects on the substrate, improve charge injection from the substrate, protect the photosensitive layer from electrical breakdown, etc. Ru. Known materials for the undercoat layer include polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethylcellulose, methylcellulose, ethylene-acrylic acid copolymer, casein, polyamide, copolymerized nylon, glue, gelatin, etc. .
These are each dissolved in a suitable solvent and applied onto the substrate. The film thickness is about 0.2 to 2μ. The hydrazone compound used in the present invention has hole transport properties, and when using a photoreceptor in which a conductive layer, a charge generation layer, and a charge transport layer are laminated in this order, the surface of the charge transport layer must be negatively charged. When exposed to light, holes generated in the charge generation layer are injected into the charge transport layer in the exposed area, and then reach the surface and neutralize the negative charge, causing a decrease in surface potential and creating an electrostatic contrast between it and the unexposed area. arise. Various conventionally used developing methods can be used for visualization. In another specific example of the electrophotographic photoreceptor of the present invention, a layer containing a hydrazone compound and an AS resin can be used as a photosensitive layer. This photosensitive layer contains a suitable sensitizer, such as U.S. Pat. No. 3,554,745;
Beryllium dyes disclosed in US Pat. No. 3,567,438, cyanine dyes as disclosed in US Pat. No. 3,560,207, and eutectics of biryllium dyes and polyarylates as disclosed in JP-A-47-10785 can be used. Hereinafter, the present invention will be explained according to examples. Example 1 10 parts (parts by weight, the same applies hereinafter) of New Zealand-produced lacquer casein were weighed out, dispersed in 90 parts of water, and then dissolved in 1 part of aqueous ammonia.
Separately, 3 parts of hydroxypropyl methylcellulose resin (trade name: Metrose 60SH50, manufactured by Shin-Etsu Chemical) was dissolved in 20 parts of water, and the two were then mixed to prepare a coating solution for the undercoat layer. This liquid was applied to an 80φ x 300mm Al cylinder by dipping and dried at 80°C for 10 minutes to form a 10μ thick undercoat layer. Next, add 10 parts of bisazo pigment with the following structural formula. Polyvinyl butyral resin (product name: ESLETSUKU)
8 parts of BXL (manufactured by Sekisui Chemical Co., Ltd.) and 60 parts of cyclohexanone were dispersed for 20 hours in a sand mill apparatus using 1φ glass beads. 100 parts of methyl ethyl ketone was added to this dispersion, which was applied onto the undercoat layer by dip coating, and dried at 100° C. for 5 minutes to form a charge generation layer with a thickness of 0.15 μm. Next, 10 parts of the hydrazone compound of Compound No. 5 and AS resin (trade name: Sunrex) were added.
C: manufactured by Mitsubishi Monsanto Chemical Co., Ltd.) was dissolved in 70 parts of monochlorobenzene. This was applied onto the charge generation layer and dried with hot air at 100° C. for 1 hour to form a charge transport layer with a thickness of 12 μm. Adhesion was examined from above the charge transport layer using the crosshatch method and was 100/100, with no peeling. An electrophotographic photoreceptor that has not been subjected to a peel test was subjected to -5.6KV corona charging, image exposure, dry toner development, toner transfer to plain paper, urethane rubber blade (hardness 70°,
The electrophotographic properties were evaluated by attaching it to an electrophotographic copying machine that has a cleaning process using a pressure of 5 gw/cm and an angle of 20° relative to the photoreceptor. The electrophotographic properties were evaluated by measuring the initial potential (Vo) and sensitivity, and the charging potential and sensitivity after repeated use 3000 times. Sensitivity is determined by measuring the exposure amount (E _1/10 lux seconds) required to attenuate the potential to 1/10 when dark decaying for 5 seconds after corona charging at -5.6 KV. evaluated. These results are shown in Table 1.

[Table] Comparative Examples 1-2 Instead of the hydrazone compound used in Example 1,
Example 1 except that 1-phenyl-3-(4-N,N-diethylaminostyryl)-5-(4-N,N-diethylaminophenyl)pyrazoline was used.
A comparative photoreceptor was prepared in exactly the same manner as described above. In addition, as another comparative sample, a photoreceptor was prepared using 2,2-bis(4-N,N-dimethylaminophenyl)propane. The electrophotographic properties of these photoreceptors were measured in the same manner as in Example 1. These results are shown in Table 2.

[Table] Comparative Examples 3 to 8 Charge transport layers using the combinations of charge transport materials and binders shown in Table 3 below were laminated on the charge generation layer prepared in Example 1 in the same manner. The characteristics of these comparative photoreceptors were measured in the same manner as in Example 1. These results are shown in Table 4.

[Table] Propane

[Table] Propane

[Table] In the comparative example using polycarbonate resin, the coating solution completely gelled on the second day. In addition, in the comparative example using polystyrene, cracks occurred when the temperature was 90% RH, and crack patterns caused by the cracks appeared in the image, but in the photoreceptor of the present invention shown in Example 1, these cracks appeared. No defects were observed. Example 2 A biaxially stretched polyethylene terephthalate film with a thickness of 100 μm that was subjected to aluminum vapor deposition was used as a base, and polyamide resin (trade name: Amilan) was applied to this.
A methanol-N-toluene solution (CM8000 manufactured by Toray Industries, Ltd.) was applied using a roll coater to form a 0.5 μm thick subbing layer. Next, 200 parts of methyl ethyl ketone was mixed into the charge generation layer dispersion prepared in Example 1 to prepare a coating solution.
A charge generation layer of 0.15 μm was formed on the subbing layer using a roll coater. Next, 10 parts of the hydrazone compound of Compound No. 9, AS resin (trade name: Lightac)
Prepare a coating solution by mixing 10 parts of A100PC (manufactured by Mitsui Toatsu Chemical), 50 parts of toluene, and 50 parts of methyl ethyl ketone, and apply this onto the previously formed charge generation layer so that the film thickness after drying is 12μ. coated with. The thus prepared sheet was wound around a cylinder of 136φ x 300 mm, electrical conductivity was established on the aluminum vapor-deposited surface of the sheet, and a photoreceptor was prepared, which was measured in the same manner as in Example 1. These results are shown in Table 5.

[Table] Examples 3 to 7 Selenium-tellurium (tellurium 10 wt%) was vapor-deposited to a thickness of 0.8 μm on an aluminum plate having a thickness of 100 μm to form a charge generation layer. Next, 5 g of AS resin (product name: Lighttack A100PC, manufactured by Mitsui Toatsu Chemical Co., Ltd.) and 5 g of the hydrazone compound shown in the following table were added to 70 g of monochlorobenzene.
ml of the solution was applied onto the charge generation layer and dried to form a charge transport layer with a thickness of 11 μm. The charging characteristics of the electrophotographic photoreceptor thus prepared were examined in the same manner as in Example 1, and the results are shown in Table 6.

[Table] Example 8 An aluminum substrate with a thickness of 0.2 mm was set in a vacuum device, and after sufficient evacuation, hydrogen gas and silane gas (15% by volume relative to hydrogen gas) were introduced, and then
A charge generation layer of amorphous silicon with a thickness of 0.3μ was formed on the substrate by applying a high frequency electric field of 13.5MHz and glow discharge. After returning the inside of the vacuum apparatus to atmospheric pressure, the sample was taken out on the charge generation layer. A solution prepared by dissolving 5 g of AS resin (trade name: Lighttack A100PC, manufactured by Mitsui Toatsu Chemical Co., Ltd.) and 5 g of the hydrazone compound of Compound No. 21 in 150 ml of monochlorobenzene was applied and dried to give a coating amount of 10 g/m ² . A charge transport layer was formed. The photoreceptor thus obtained was placed in a charging/exposure experimental device, charged with corona at 5KV, and immediately irradiated with a light image. The light image was illuminated through a transmission test chart using a tungsten lamp light source. Immediately thereafter, a positively charged developer (including toner and carrier) was cascaded onto the photoreceptor surface to obtain a good toner image on the photoreceptor surface.

Claims (1)

[Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer containing a hydrazone compound and an acrylonitrile-styrene copolymer resin.