JPS6255778B2 - - 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 substances such as selenium, cadmium sulfide, and zinc oxide have been widely 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 low quality, difficult manufacturing conditions, and loss of raw materials.Also, 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, since it is sensitized with a dye with low fastness, such as rose bengal, there are problems such as deterioration due to electrical conduction due to corona charging and photofading. Furthermore, since the photosensitive layer is a resin dispersion system of zinc oxide particles, it has problems in surface smoothness, hardness, abrasion resistance, etc. On the other hand, organic photoconductive materials have advantages over inorganic ones, 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 materials 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 photoconductive materials; Sensitized by adding dye to the body (e.g., Special Publication No. 48-25658)
(3) Pigment dispersed in a hole- or electron-active matrix (e.g., JP-A-47-30328, JP-A-47-18545), (iv) Charge generation layer and charge transport A layer with functions separated into layers (e.g., JP-A-49-
105537), (v) those whose main component is a eutectic complex consisting of a dye and a resin (e.g., JP-A-10785-10785), (vi) those containing an organic pigment or inorganic in the charge transfer complex. Added charge-generating material (e.g., JP-A-49-
Publication No. 91648) (vii) Others, etc. 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, flexibility, etc. If plasticizers are added to solve this problem, problems such as decreased sensitivity arise. On the other hand, low-molecular type materials can be used by selecting an appropriate binder and can overcome the above-mentioned drawbacks of high-molecular type materials. As a result of intensive research into organic low-molecular photoconductive materials that eliminate the above-mentioned drawbacks, the present inventors discovered that a specific hydrazone compound has extremely excellent properties and arrived at the present invention. 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. However, this excludes the case where both R ₁ and R ₂ are alkyl groups. More specifically, R ₁ and R are alkyl groups such as methyl group, ethyl group, propyl group, butyl group, aralkyl group such as benzyl group, phenethyl group, naphthylmethyl group, phenyl group, naphthyl group, anthryl group, pyrenyl group. These alkyl groups, aralkyl groups, and aryl groups may have a substituent. Substituents include alkyl groups such as methyl and ethyl groups, and methoxy groups. , an alkoxy group such as an ethoxy group, a dialkylamino group such as a dimethylamino group, a diethylamino group, a dipropylamino group, a dibutylamino group, and a halogen atom such as a chlorine atom, a bromine atom, an iotho atom, and the like. 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: (in which R ₁ and R ₂ have the same meanings as above) and P-pyrrolidinobenzaldehyde. That is, it can be obtained by condensing the hydrazine and aldehyde in a solvent such as alcohol, DMF, or DMSO, with the addition of a small amount of acid (glacial acetic acid or inorganic acid) as a condensing agent, if necessary. As the electrophotographic photoreceptor containing the hydrazone compound represented by the general formula (1), any of the photoreceptor types (i) to (vii) using the above-mentioned organic photoconductive substances can be applied. However, the hydrazone compound used in the present invention functions only as a hole activation matrix in the (iii) type photoreceptor. In the present invention, as a charge transport material for use in the charge transport layer of the (iv) type photoreceptor, that is, a photoreceptor that is functionally separated into two layers: a charge generation layer and a charge transport layer, the general formula
When using the hydrazone compound shown in (1),
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 an extremely durable photoreceptor. 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 electrophotographic photoreceptors of the type that are used repeatedly, it is mainly From the viewpoint of physical strength and, in some cases, chargeability, it is preferable to laminate a conductive layer, a charge generation layer, and a charge transport layer in this order. 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 0.1 to 5μ, preferably 0.5
~3μ is appropriate. For the charge generation layer, inorganic materials such as selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, and amorphous silicon, which absorb light and generate charge carriers with extremely high efficiency, as well as pyrylium dyes, thiopyrylium dyes, and thoria, can be used. Reelmethane dyes, thiazine dyes, cyanine dyes, pigments, phthalocyanine pigments, perylene pigments, indigo pigments, thioindigo pigments,
Separately deposited layers selected from various charge generating materials consisting of organic substances such as quinacridone pigments, azo pigments, polycyclic quinone pigments, layers consisting of charge generating materials and binder resins, or resin-free dyes and pigments. It is not limited to the combination with a specific charge generating material. The thickness of the charge generation layer is preferably 5μ or less.
A value of 0.01 to 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 is preferably 80% or less, since a large amount of binder used will affect the sensitivity. Desirably 40% or less.
Various binders used include polyvinyl butyral, polyvinyl acetate, polyester, polycarbonate, phenoxy resin, acrylic resin, polyacrylamide, polyamide, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, and polyvinyl alcohol. 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 applied 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. Matatapoly
Hole transporting polymers such as N-vinylcarbazole can also be used as binders. The hydrazone compound used in the present invention has hole-transporting 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, and exposure after charging is required. Then, in the exposed area, holes generated in the charge generation layer are injected into the charge transport layer, and then reach the surface, neutralize the negative charge, and attenuate the surface potential, 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 type (iv) are detailed in the cited literature, but will be briefly explained. In the type (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, so a solution prepared by dissolving this charge transfer complex and a binder resin in an appropriate solvent is used as a conductive layer or adhesive. It can be obtained by coating and drying a conductive 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,
There are polymers of low molecular weight substances such as 2,4,8-trinitrothioxanthone and electron-withdrawing monomers as described in USP 4122113. As the binder, the various binders mentioned in connection with the type (iv) 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 for the (iv) type photoreceptor in a suitable solvent, and then dissolving the same as described for the (iv) type photoreceptor. It can be obtained by adding various kinds of dyes, applying this liquid to a conductive layer or a conductive layer provided with an adhesive layer, and drying it by a conventional method. 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-
It can be produced from a pyrylium dye such as (N/N-dimethylaminophenyl)thiapyrylium perchlorate, a resin that forms a eutectic complex with such a dye, such as a polycarbonate resin, and the hydrazone compound used in the present invention. . The charge transfer complex in the (vi) type photoreceptor is similar to the charge transfer complex of the (i) type, and the charge generating material to be added can be any of the materials mentioned for the (iv) type photoreceptor. be. The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines, but also for laser printers, CRTs, etc.
It can also be widely used in electrophotographic applications such as 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, 5g 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 dissolved in 95 ml of ethanol, and then coated on the adhesive layer with a Mayer bar to form a charge generation layer with a coating weight of 0.2 g/m ² after drying. Next, 5 g of P-pyrrolidinobenzaldehyde-N/N-diphenylhydrazone, poly-
A solution prepared by dissolving 5 g of 4,4'-dioxydiphenyl-2,2'-propane carbonate (molecular weight 30,000) in 70 ml of tetrahydrofuran was applied onto the charge generation layer and dried, resulting in charge transport with a coating weight of 10 g/ ^m2. formed a layer. The electrophotographic photoreceptor prepared in this way was heated at 20℃65
% (relative humidity), corona charged at 5KV 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 5lux. The charging characteristics were investigated. The initial potential is Vo (-V), and the potential retention rate for 10 seconds in the dark is
The charging characteristics of this photoreceptor are shown with Vk (%) and the half-attenuation exposure amount as E1/2 (lux.sec.). Vo560V, Vk91%, E1/2 7.5lux.sec. Examples 2 to 4 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
A solution obtained by dissolving 5 g of 200 Toyobo Co., Ltd. and the hydrazone compound shown in the following table in 70 ml of tetrahydrofuran was applied onto the charge generation layer and dried to form a charge transport layer with a coating weight of 11 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 5 5 g of P-pyrrolidinobenzaldehyde-N/N-diphenylhydrazone and 5 g of polyvinylcarbazole (molecular weight 300,000) were added to 70 ml of tetrahydrofuran.
Add 1.0g of the pigment with the following structural formula to the solution dissolved in After dispersion using a ball mill, the dispersion was applied using a Mayer bar onto the casein layer of the aluminum plate provided with the casein layer used in Example 1, and the coating amount after drying was 10 g/m ² . Example 1: Charge measurement of the photoreceptor prepared in this way
The results are shown below. However, the charging polarity was determined. Vo520V, Vk86%, E1/2
14lux.sec. Example 6 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 0.3 μm was formed on the substrate by glow discharge by applying a high frequency electric field of 13.5 MHz. After returning the inside of the vacuum apparatus to atmospheric pressure, take out the sample and add 5 g of polyester resin (Vylon 200) and 5 g of a hydrazone compound having the following structural formula on the charge generation layer in dichloromethane.
Apply the solution dissolved in 150ml

[Formula] It was dried to form a charge transport layer with a coating weight of 10 g/m ² . 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. Immediately thereafter, a positively charged developer (including toner and carrier) was cascaded onto the surface of the photoreceptor to obtain a good toner image on the surface of the photoreceptor. 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 negatively charged 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 transport layer containing a charge transport material represented by general formula (1). 3. The electrophotographic photoreceptor according to claim 2, wherein the compound represented by general formula (1) is a compound represented by the following structural formula.