JPH03260657A - Composition for charge generation layer of electrophotographic photoreceptor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and particularly to a composition for a charge generation layer of a functionally separated electrophotographic photoreceptor suitable for a laser beam printer.

[Prior Art] Many electrophotographic photoreceptors using organic and inorganic materials have been proposed. Among them, as a highly sensitive photoreceptor, a functionally separated photoreceptor in which a charge generation layer and a charge transport layer are separated has been put into practical use as a photoreceptor for copying machines and laser beam printers.

As the charge generating material in the charge generating layer, for example, phthalocyanine pigments (JP-A No. 59-15253), bisazo pigments (JP-A-56-116040), etc. are well known.

On the other hand, as charge transport materials for the charge transport layer, poly-N-vinylcarbazole compounds (Japanese Patent Application Laid-Open No. 52-77730), pyrazoline derivatives (Japanese Patent Application Laid-open No. 49-105537) are used.
, oxazole compounds.

Methods using thiazole compounds (Japanese Patent Laid-open No. 55-35319), hydrazone compounds (Japanese Patent Laid-Open No. 54-59143), and styryl compounds (Japanese Patent Laid-Open No. 62-30255) have been proposed.

The charge generating material and the charge transporting material do not have film-forming properties by themselves, but are dispersed or dissolved in a solvent together with the binding resin,
The film is formed by coating it on a conductive support and drying it.

The charge generation layer is a layer for efficiently injecting charges generated by light irradiation into the charge transport layer, and therefore, it is formed so that the charge generation substance is uniformly dispersed within the thinnest layer possible. need to be done. In particular, when the charge generating material is a dispersed type such as a phthalocyanine pigment, if it is not uniformly dispersed, the uniformity of the image will be poor.

In recent years, uniform dispersibility has become an important issue in electrophotographic process technology where there is a growing demand for higher definition. The dispersibility of the charge generating material also depends on the binding resin and solvent, so selection of these is also important.

Furthermore, if the water absorption rate of the binder resin is high, fogging will occur on images when used under high humidity, so a resin with a low water absorption rate is required. In addition, in an electrophotographic photoreceptor in which a charge transport layer is formed on the charge generation layer after the charge generation layer is formed, in addition to selecting a binding resin that has excellent adhesion between both layers, it is also important to It is also important that the lower charge generation layer is not easily dissolved by the solvent used to form the transport layer.

Furthermore, in the charge generation layer composition, during coating,
It goes without saying that the charge-generating material can be applied uniformly, but it is also important that the charge-generating material does not settle and separate during use or storage, that is, the composition has excellent storage safety. It is of industrial importance that

As mentioned above, there are strict requirements for compositions for charge generation layers, and at present no composition that fully satisfies these requirements has been obtained.

Conventionally, as binding resins used in the charge generation layer, polyester resins, phenol resins, butyral resins, melamine resins, formal resins, epoxy resins, silicone resins, urethane resins, cellulose resins, etc. have been used. However, these resins do not necessarily satisfy all of the above characteristics.

Note that among these binder resins, saturated linear polyester resins are promising in consideration of film formability, adhesion, and moisture resistance. However, when this resin is used alone, there is a problem that the saturated linear polyester resin is eluted by the coating liquid when forming the charge transport layer. As a method to improve this, a curing agent that reacts with the linear polyester resin is blended (Japanese Patent Application Laid-Open No. 62-242953).
and thermosetting resin (JP-A-63-8
No. 5562) has been proposed.

[Problems to be Solved by the Invention] In the above-mentioned prior art, it has not been found that the storage stability of the charge generation layer composition and the solvent resistance of the coating film formed from the composition are compatible. . Additionally, the dispersibility of the phthalocyanine pigment and the film-forming properties of the charge generation layer depend on the type of resin used.

Although it depends on the type of solvent and their blending ratio, sufficient consideration has not been given to this point as well.

SUMMARY OF THE INVENTION An object of the present invention is to provide a composition for a charge generation layer that is compatible with the storage stability of the composition, the film formability of the coating film, and the solvent resistance.

[Means for Solving the Problems] The gist of the present invention for achieving the above object is to provide a functionally separated electronic device having a charge generation layer provided on a conductive support and a charge transport layer provided on the layer. A coating liquid composition for forming a charge generation layer of a photographic photoreceptor, characterized by containing a mixed solvent containing at least one of a phthalocyanine pigment, a saturated linear polyester resin, a benzoguanami resin, and a chlorinated solvent. A composition for a charge generation layer of an electrophotographic photoreceptor is provided.

In the present invention, the blending ratio of the linear polyester resin and the benzoguanamine resin is 5 to 100 parts by weight, preferably 10 to 30 parts by weight, per 100 parts by weight of the former.

As a solvent, if the boiling point is too low, the concentration of the composition will change easily, and if the boiling point is too high, there is a risk that the coating thickness will be uneven when dip coating is performed. This is a practical problem because variations in characteristics occur depending on the position of the photoreceptor. The boiling point of the solvent is within 35°C to 135°C, preferably within 40°C to 120°C.

Further, the solvent must be able to completely dissolve the binding resin. Such solvents include chlorinated solvents such as methylene chloride, chloroform, carbon tetrachloride, 1,1-
Dichloroethane, 1,2-dichloroethane, 1,1.1
-trichloroethane, 1°1.2-)-dichloroethane. 1.2-dichloroethylene, trichlorethylene, 1
, 2-dichloropropane and the like.

If these solvents are used alone, the storage stability of the composition is good, but the film forming properties are poor, so it is necessary to use two or more of them as a mixed solvent.

Examples of organic solvents that dissolve the saturated linear polyester resin and benzoguanamine resin include tetrahydrofuran, toluene, and methyl ethyl ketone. However, these organic solvents alone have poor film-forming properties, and by mixing them with the chlorinated solvent, the stability and film-forming properties of the composition can be improved.

The blending ratio of the mixed solvent cannot be determined because the boiling point of each solvent is different, but the proportion of the chlorinated solvent is at least 5 to 95% by weight, preferably 10 to 95% by weight.
The content is selected to be in the range of 90% by weight.

Further, as the conductive support for the electrophotographic photoreceptor, for example, metal supports such as aluminum, aluminum alloy, copper, zinc, stainless steel, nickel, titanium, etc., or aluminum, aluminum alloy, tin oxide, indium oxide, indium oxide-tin oxide, etc. A plastic support or the like on which a conductive film is formed by vacuum deposition of an alloy or the like can be used.

[Function] In order to prevent the dispersed charge generating material, such as the phthalocyanine pigment, from causing precipitation and separation in the composition, the binding resin during storage should not undergo much curing or increase in molecular weight.
It is important not to cause splitting of chicks.

In the present invention, the saturated linear polyester resin and benzoguanamine resin have good compatibility, and the molecular weight of the benzoguanamine resin itself is increased, and the polymerization reaction between the saturated linear polyester resin and the benzoguanamine resin is
At room temperature, the composition is stable because it is very gradual. In addition, it is thought that the coated film, which has been layered for a long time, exhibits solvent resistance because the reaction has progressed appropriately.

In addition, the improved film-forming properties of the coating are thought to be partly due to the use of the resin composition described above, but the use of a mixed solvent containing a chlorinated solvent (as a solvent) also improved wettability. This is thought to be the main cause.

[Example] The present invention will be specifically explained with reference to Examples.

[Examples 1 to 10] Table 1 shows the compositions of the charge generation layer compositions of Examples 1 to 10.

The method for preparing the above composition will be described below.

Each mixed solvent shown in Table 1 was used so that the concentration of the binding resin, which is a mixture of saturated linear polyester resin and benzoguanamine resin in a weight ratio of 80:20, was 0.6% by weight. It was dissolved in [() shows the inner mold amount ratio]. After complete dissolution, metal-free phthalocyanine (τ
-H2Pc) and binding resin ratio is 80:20 by weight
-H and PC were blended (solid content concentration: 3% by weight) according to the ratio of -H and PC, and stirred for 5 hours using a shaking type stirrer to prepare a composition for a charge generation layer.

[Comparative Examples 1 to 7] Table 1 shows the compositions of the charge generation layer compositions of Comparative Examples 1 to 7.

The method for preparing the composition is the same as in Example 1.

However, in Comparative Example 4, a saturated linear polyester resin was used alone as the binding resin, and its concentration was also blended to be 0.6% by weight.

An aluminum plate was immersed in the composition shown in Table 1, pulled up at a constant speed, and dried at 40° C. for 1 hour to form a film to form a charge generation layer.

The storage stability of each composition was determined by placing one composition in a 100 mQ glass screw tube and allowing it to stand for one week, and checking the state of dispersion of τH2Pc, presence of sedimentation, etc.

The state of the coating film was compared between a case where the film was formed immediately after the composition was created and a case where the film was formed after the composition was left standing for one week.

The solvent resistance of the coating film was determined by immersing the coating film (after drying at 140°C for 1 hour) in methylene chloride and tetrahydrofuran, respectively.
The elution state of τ-)-I 2P c was prepared.

Table 2 summarizes these results.

When the surface of the coating film formed using each composition was observed by SEM, it was found that the film using the composition of this example was more glossy than that of the composition of the comparative example, and the dispersion of τ-H2P c was lower. was also uniform.

As is clear from Table 3, it can be seen that the compositions of Examples have excellent storage stability. It can also be seen that the film-forming properties are excellent, and the solvent resistance of the coating film is also excellent.

No. 2 table A high-performance photoreceptor can be provided.

Furthermore, since a charge generation layer with excellent solvent resistance can be formed, there is no elution by the charge transport layer composition applied thereon, and a photoreceptor with long life and high sensitivity can be provided.

○: Good △: Good S Good X: Poor [Effect of the invention]

Claims (1)

[Scope of Claims] 1. Coating liquid for forming a charge generation layer of a functionally separated electrophotographic photoreceptor having a charge generation layer provided on a conductive support and a charge transport layer provided on the layer. A composition for a charge generation layer of an electrophotographic photoreceptor, characterized in that the composition contains a mixed solvent comprising a phthalocyanine pigment, a saturated linear polyester resin, a benzoguanami resin, and at least one chlorinated solvent. Composition. 2. The solvent constituting the mixed solvent consists of a solvent that can dissolve the resin even when used alone, and has a boiling point of 35°C to 35°C.
2. The composition for a charge generation layer of an electrophotographic photoreceptor according to claim 1, wherein the temperature is 135°C.