JPS6255777B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor, and more particularly, to an electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductive substance made of a hydrazone compound. Conventionally, inorganic photoconductive materials such as selenium, cadmium sulfide, and zinc oxide have been used in the photosensitive layer of electrophotographic photoreceptors. Photoreceptors using such inorganic photoconductors have several advantages and at the same time have various disadvantages.To give a specific example of a disadvantage, in the case of selenium, productivity is reduced due to vacuum evaporation. The manufacturing cost is high due to the low price, difficult manufacturing conditions, and loss of raw materials, and the selenium vapor-deposited film itself is extremely susceptible to heat and mechanical shock, and is extremely susceptible to crystallization depending on environmental conditions. In the case of cadmium sulfide, it is sensitive to humidity and poses a pollution problem except for photoreceptors coated with an insulating layer. In the case of zinc oxide, it is sensitized with a dye with low fastness, such as rose bengal, so there are problems such as deterioration due to electrical conduction due to corona charging and photofading. In addition, the surface smoothness of the photosensitive layer due to the resin dispersion system of zinc oxide particles,
There are also drawbacks to hardness, wear resistance, etc. On the other hand, organic photoconductive materials have advantages over inorganic materials, such as having a highly flexible photosensitive layer, being easy to manufacture, and being able to obtain photoreceptors with stable electrophotographic properties at a lower cost. , many proposals have been made in recent years. Types of photoreceptors using organic photoconductive substances include (i) those in which a charge transfer complex is formed by a combination of an electron donating compound and an electron accepting compound (e.g.
(USP 3484237) (ii) Organic photoconductors sensitized by adding dyes (e.g. Japanese Patent Publication No. 48-25658) (iii) Pigments dispersed in hole- or electron-active matrices (e.g. Japanese Patent Publication No. 1982-25658) (47-30328, Japanese Patent Publication No. 47-18545) (iv) Functionally separated charge generation layer and charge transport layer (e.g., Japanese Patent Application Laid-open No. 49-105537) (v) Dyes and Those whose main component is a eutectic complex consisting of a resin (e.g., JP-A-47-10785); (vi) Those in which an organic pigment or an inorganic charge-generating material is added to a charge transfer complex; (e.g., Japanese Patent Application Publication 1973-
Publication No. 91648) (vii) Others. Although some of these photoreceptors are practical, the current situation is that further improvements in sensitivity, durability, environmental stability, etc. are desired. Organic photoconductive substances used in such photoreceptors include polymeric substances such as poly-N-vinylcarbazole and low-molecular substances such as pyrazoline derivatives described in JP-A-49-105537. be. Polymer type coatings generally have brittle coatings and have problems with film formability and flexibility, and adding plasticizers to solve this problem leads to problems such as decreased sensitivity. On the other hand, low-molecular type materials can overcome the above-mentioned drawbacks of high-molecular type materials because an appropriate binder can be selected. Therefore, the present inventors conducted intensive research on organic low-molecular photoconductive materials in order to eliminate the above-mentioned drawbacks, and as a result,
The present invention was achieved by discovering that a specific hydrazone compound has extremely excellent properties. The hydrazone compound used in the present invention is represented by the following general formula. In the formula, R ₁ and R ₂ represent an alkyl group, an aralkyl group, or an aryl group that may have a substituent, except when both R ₁ and R ₂ are an alkyl group. More specifically, R ₁ and R ₂ are alkyl groups such as methyl group, ethyl group, propyl group, butyl group,
A group selected from aralkyl groups such as benzyl group, phenethyl group, and naphthylmethyl group, and aryl groups such as phenyl group, naphthyl group, anthryl group, and pyrenyl group, and these alkyl groups, aralkyl groups, and aryl groups have substituents. Examples of substituents include alkyl groups such as methyl group and ethyl group, alkoxy groups such as methoxy group and ethoxy group, dialkylamino group such as dimethylamino group, diethylamino group, dipropylamino group, and dibutylamino group. Examples include halogen atoms such as groups, chlorine atoms, bromine atoms, and iotho atoms. The hydrazone compound represented by the general formula (1) has the general formula

It can be produced by a conventional method from hydrazine or its mineral acid salt represented by the formula: (wherein R ₁ and R ₂ have the same meanings as above) and glyoxal. That is,
Add a small amount of acid (glacial acetic acid or inorganic acid) as a condensing agent if necessary, and mix alcohol, DMF, DMSO
It can be obtained by condensing the above hydrazine and aldehyde in a solvent such as. As the electrophotographic photoreceptor containing the hydrazone represented by the general formula (1), any of the photoreceptor types (i) to (vii) using the above-mentioned organic photoconductive substances can be applied. When a hydrazone compound represented by general formula (1) is used as a charge transport material for the charge transport layer of a (iv) type photoreceptor, that is, a photoreceptor that is functionally separated into two layers: a charge generation layer and a charge transport layer. In particular, the sensitivity of the photoreceptor becomes high and the residual potential is low. Further, in this case, the decrease in surface potential and sensitivity during repeated use is small, and the increase in residual potential is negligible, resulting in a photoreceptor with extremely excellent durability. Therefore, the (iv) type photoreceptor will be explained in detail. The layer structure requires a conductive layer, a charge generation layer, and a charge transport layer, and the charge generation layer may be either above or below the charge transport layer, but in an electrophotographic photoreceptor of the type that is used repeatedly. It is preferable to laminate a conductive layer, a charge generation layer, and a charge transport layer in this order mainly from the viewpoint of physical strength and in some cases from the viewpoint of chargeability. An adhesive layer may be provided as necessary for the purpose of improving the adhesiveness between the conductive layer and the charge generation layer. As the conductive layer, a metal plate or foil made of aluminum or the like, a plastic film coated with a metal such as aluminum or aluminum foil glued to paper, or paper treated with conductivity is used. Effective materials for the adhesive layer include resins such as casein, polyvinyl alcohol, water-soluble polyethylene, and nitrocellulose. The thickness of the adhesive layer is
A suitable value is 0.1 to 5μ, preferably 0.5 to 3μ. For the charge generation layer, selenium, selenium-tellurium, selenium, which absorbs light and generates charge carriers with extremely high efficiency.
Inorganic substances such as selenium-arsenic, cadmium sulfide, amorphous silicon, and pyrylium dyes,
Thiopyrylium dyes, triarylmethane dyes, thiazine dyes, cyanine dyes, cyanine pigments, phthalocyanine pigments, perylene pigments, indigo pigments, thioindigo pigments, azo pigments,
A separate vapor deposited layer selected from various charge generating materials made of organic substances such as polycyclic quinone pigments, a layer consisting of a charge generating material and a binder resin, or a layer consisting of a dye or pigment without resin can be used. and is not limited to combinations with specific materials. The thickness of the charge generation layer is 5μ or less, preferably 0.01~
1μ is desirable. When the charge generation layer is formed by applying a resin dispersion or solution of the charge generation material, the proportion of the binder in the charge generation layer must be adjusted, since a large amount of binder used will affect the sensitivity.
80% or less, preferably 40% or less. Binders used include polyvinyl butyral, polyvinyl acetate, polyester, polycarbonate, phenoxy resin, acrylic resin, polyacrylamide, polyamide, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol, etc. Various resins are used. A charge transport layer is provided on the charge generation layer thus formed. The thickness of the charge transport layer is 5 to 30 microns, preferably 8 to 20 microns. Since the hydrazone compound used in the present invention does not have a film-forming ability by itself, a solution dissolved in a suitable organic solvent together with various binder resins is coated and dried by a conventional method to form a charge transport layer. As the binder, acrylic resin, polystyrene resin, polyester resin, phenoxy resin, polycarbonate resin, silicone resin, epoxy resin, polyurethane resin, etc. can be used. Matapoly-N
- Hole transporting polymers such as vinyl carbazole can also be used as binders. 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, it is necessary to charge the surface of the charge transport layer negatively, and when exposed to light after charging, the surface of the charge transport layer must be negatively charged. In the exposed area, holes generated in the charge generation layer are injected into the charge transport layer, and then reach the surface to neutralize the negative charges, causing attenuation of the surface potential and creating an electrostatic contrast with the unexposed area. A visible image can be obtained by developing the electrostatic latent image thus formed with a positively charged toner. This can be directly fixed, or the toner image can be transferred to paper or plastic film and then developed and fixed. Alternatively, a method may be used in which the electrostatic latent image on the photoreceptor is transferred onto an insulating layer of transfer paper, then developed and fixed. The type of developer, the developing method, and the fixing method may be any known one or any known method and are not limited to a specific one. Photoreceptors other than the type (iv) are described in detail in the respective literatures, so they will be briefly explained. In the (i) type photoreceptor, a charge transfer complex is formed when the hydrazone compound used in the present invention is combined with an electron-withdrawing substance. It can be obtained by applying and drying a conductive layer provided with an adhesive layer by a conventional method. Examples of electron-withdrawing substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2.4.
7-trinitro-9-fluorenone, 2.4.
5,7-tetranitrofluorenone, 2,4,7
-trinitro-9-dicyanomethylenefluorenone, 2,4,5,7-tetranitroxanthone,
These include low-molecular substances such as 2,4,8-trinitrothioxanthone, and polymers of electron-withdrawing monomers as described in USP 4122113. As a binder (iv)
Any of the various binders mentioned with respect to the type of photoreceptor can be used. The (ii) type photoreceptor is prepared by dissolving the hydrazone compound used in the present invention and the binder for the charge transport layer described in relation to the (iv) type photoreceptor in a suitable solvent, and further dissolving the same as described in relation to the (iv) type photoreceptor. It can be obtained by adding various dyes such as, applying this liquid to a conductive layer or a conductive layer provided with an adhesive layer by a conventional method and drying. The (iii) type photoreceptor can be obtained by using the hydrazone compound used in the present invention as a hole matrix and adding the various pigments mentioned regarding the (iv) type photoreceptor. (v) type photoreceptor is 2,6-diphenyl-4-
(N.N-dimethylaminophenyl)thiapyrylium perchlorate and other pyrylium dyes, resins that form eutectic complexes with such dyes, such as polycarbonate resins, and the hydrazone compound used in the present invention. can. The charge transfer complex in the (vi) type photoreceptor is similar to the (i) type charge transfer complex, and the charge generating material to be added can be any of the various materials mentioned for the (iv) type photoreceptor. The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines, but also for laser printers,
It can also be widely used in electrophotographic applications such as CRT printers and electrophotographic plate making systems. Next, examples of the present invention will be shown. Example 1 An ammonia aqueous solution of casein (11.2 g of casein, 1 g of 28% ammonia water, 222 g of water) was placed on an aluminum plate.
ml) with a Mayer bar and dry, coating amount 1.0
An adhesive layer of g/m ² was formed. Next, 5 g of a disazo pigment having the following structural formula, Butyral resin (degree of butyralization 63 mol%) 2g
was dispersed in a ball mill with a solution of 95 ml of ethanol, and then coated on the adhesive layer with a Mayer bar to form a charge generating layer having a coating weight of 0.2 g/m ² after drying. Next, a charge was generated by dissolving 5 g of glyoxal-bis(N・N-diphenylhydrazone) and 5 g of poly-4,4'-dioxydiphenyl-2,2'-propane carbonate (molecular weight 30,000) in 70 ml of dichloromethane. After coating on the layer and drying, the coating amount is 10g/
A charge transport layer of m ² was formed. The electrophotographic photoreceptor prepared in this way was heated at 20℃65
% (relative humidity), corona charged with KV statically using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd., held in a dark place for 10 seconds, and then exposed to an illuminance of 5 lux. The charging characteristics were investigated. The charging characteristics of this photoreceptor are shown by setting the initial potential as Vo (-V), the potential holding rate for 10 seconds in the dark as Vk (%), and the half-decay exposure amount as E1/2 (lux.sec.). Vo600V, Vk98%, E1/29.3lux.sec. Example 2 The following was added to a solution in which 5g of glyoxal-bis(N/N-diphenylhydrazone) and 5g of poly-N-vinylcarbazole (molecular weight 300,000) were dissolved in 70ml of dichloromethane. Structural formula pigment 1.0g was added, dispersed in a ball mill, and applied with a Mayer bar onto the casein layer of the aluminum plate with the casein layer used in Example 1, with a coating amount of 10 g/m ² after drying.
And so. Charge measurement of the photoreceptor thus prepared was carried out in the same manner as in Example 1, and the results are shown below. However, the charging polarity was determined. VO540V, Vk90%, E1/216lux.sec Examples 3 to 5 Selenium-tellurium (10% tellurium) was vapor-deposited to a thickness of 0.8μ on a 100μ thick aluminum plate to form a charge generation layer. Next, polyester resin (Vyron
200 (Toyobo Co., Ltd.) and 5 g of the hydrazone compound shown in the following table dissolved in 70 ml of dichloromethane was coated on the charge generation layer and dried to form a charge transport layer with a coating weight of 10 g/m ² . 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 the following table.

[Table] Example 6 After setting an aluminum substrate with a thickness of 0.2 mm in a vacuum device and thoroughly evacuation, hydrogen gas and silane gas (15% by volume relative to hydrogen gas) were introduced, and then 13.5 MHz
A charge generation layer of amorphous silicon with a thickness of 0.3μ was formed on the substrate by glow discharge by applying a high-frequency electric field of . After returning the inside of the vacuum apparatus to atmospheric pressure, the sample was taken out, and a charge transport layer was formed on the charge generation layer in exactly the same manner as in Example 1. The photoreceptor obtained in this way was installed in a charging/exposure experimental device,
Corona charging was performed at 5KV and a light image was immediately irradiated. The light image was illuminated through a transmission test chart using a tungsten lamp light source. Thereafter, a good toner image was obtained on the photoreceptor surface by immediately cascading a charged developer (including toner and carrier) onto the photoreceptor surface. Example 7 The same charge transport layer and charge generation layer as in Example 6 were sequentially laminated on an aluminum plate having a thickness of 0.2 mm. A good toner image was obtained by performing the same operations as in Example 6 using the photoreceptor thus obtained. However, the corona charge was set to 5KV, and a chargeable developer was used.

Claims (1)

[Claims] 1. General formula (In the formula, R ₁ and R ₂ represent an alkyl group, an aralkyl group, or an aryl group that may have a substituent. However, this excludes the case where both R ₁ and R ₂ are an alkyl group.) An electrophotographic photoreceptor comprising a photosensitive layer containing a hydrazone compound. 2. The electrophotographic photoreceptor according to claim 1, comprising at least three layers: a conductive layer, a charge generation layer, and a charge generation layer containing a charge transport material represented by general formula (1).