JP2600993B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member that performs processes such as charging, exposure, and development, and an electrophotographic photosensitive member suitable for a positive charging system.

2. Description of the Related Art Conventionally, electrophotographic photoreceptors include those using an inorganic photoconductive substance as a photosensitive material and those using an organic photoconductive substance. Examples of the former inorganic photoconductive substance include selenium, zinc oxide, titanium oxide, and cadmium sulfide, and examples of the latter organic photoconductive substance include phthalocyanine pigments and disazo pigments.

A photoreceptor using the former inorganic photoconductive substance is not sufficient in terms of thermal stability and durability, or is toxic to the inorganic photoconductive substance, causing problems in production and handling. There is a disadvantage that there is.

On the other hand, a photoreceptor using an organic photoconductive substance (hereinafter referred to as “OPC” as appropriate) has no pollution and has excellent productivity and economical efficiency. Therefore, it has been developed and put to practical use, and is now becoming a mainstay of electrophotographic photoconductors.

OPC is usually used in a double-layer structure consisting of a charge generation layer (CG layer) that absorbs light to generate carriers and a charge transfer layer (CT layer) that moves generated carriers. ing. In general, in a double-layer structure, the CG layer is formed with a thickness of several μm and the CT layer is formed with a thickness of several tens μm in order to increase the sensitivity. At this time, the CG layer is usually formed on the basic side and the CT layer is usually formed on the front side for reasons such as strength and printing durability. Since only a CT agent (charge transfer agent) that operates by the movement of holes has been put to practical use, the photoconductor is necessarily of a negative charge type.

Problems to be Solved by the Invention However, such negatively charged photoconductors include:
Oxygen in the air becomes ozone due to the negative charge used for charging (ozone is not only harmful to the human body, but also often reacts with the photoreceptor and degrades the photoreceptor). There is a problem that it is easy to receive.

In order to solve such a problem, development of OPC using a positive charging method is currently active. Conventionally, in order to realize the positive charging method, an inverted double layer structure OPC (OPC) in which the GC layer and the CT layer are reversely configured to the case of the negative charging, both the CG agent and the CT agent are used as the polymer compound for the binder. Single-layer OPC (OPC) dispersed together A single-layer OPC (OPC) in which copper phthalocyanine is dispersed in a polymer compound has been studied.

However, in OPC, there is a problem that the CG layer, which needs to be essentially thin, is placed on the surface of the photoreceptor, resulting in reduced printing durability and reduced life characteristics. Due to the complexity of the process and the problem of delamination, it has not been put to practical use.

In the case of a single layer structure such as OPC, if the dispersion of the CG agent and the CT agent is uniform, there is an advantage that even if the photoreceptor is worn, it does not immediately reduce the printing durability. This is presumably because, even if the photoreceptor is worn, its photosensitive characteristics hardly change. In addition, single-layer OPC is easier to manufacture than double-layer OPC. But these OPCs,
Is inferior to the OPC having a multilayer structure of positively or negatively charged in terms of sensitivity, charging characteristics (the charging potential gradually decreases with repeated use), and residual potential. This is probably because the ozone resistance is not sufficient.

In view of the above circumstances, an object of the present invention is to provide a high-quality electrophotographic photosensitive member having excellent ozone resistance.

Means for Solving the Problems The inventors studied OPCs having a single-layer structure having various configurations, and as a result, using an X-type phthalocyanine, combined with an appropriate polymer compound for a binder, a single-layer OPC was used. It has previously been found that the OPC having the structure is excellent in the positive charging system (see Japanese Patent Application No. 1-181044).

However, as a result of a detailed study of the OPC found by the inventors, it was found that the repetition stability (particularly the stability of the charging characteristics) was not sufficient. As a result of further study, the inventors have found that, again, ozone resistance is a problem. When subjected to 10,000 or more repetitive tests, it was found that chemical fatigue due to ozone appeared in charging voltage, darkening and the like.

Therefore, the inventors focused on a polymer compound for a binder, and as a result of deeply studying for improvement of ozone resistance,
We found that a single-layer OPC with excellent ozone resistance can be realized by using a polymer compound having a vinylphenol structure in combination with a metal-free phthalocyanine having a new crystal system as the polymer compound for the binder. Thus, the present invention was completed.

As the polymer compound having a vinyl phenol structure, a compound having many OH groups on an aromatic ring is preferable. Specifically, for example, as described in claim 2, a vinyl phenol polymer represented by the following structural formula is used. Is exemplified.

The vinylphenol polymer can be a copolymer with styrene, methyl methacrylate, hydroxyethylene methacrylate, or the like, and can be used in the form of such a copolymer.

Other polymer compounds for binders may be used in combination. Polymer compounds used in combination include polyester, polycarbonate, acrylic resin, acryl-styrene resin, urethane resin, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polyvinyl acetoacetal, polystyrene, polyacrylonitrile, and polymeta. Methyl acrylate, polyvinyl carbazole and their copolymers, poly (vinyl chloride / vinyl acetate /
Vinyl alcohol), poly (vinyl chloride / vinyl acetate /
Maleic acid), poly (ethylene / vinyl acetate), poly (vinyl chloride / vinylidene chloride), melamine resin, alkyd resin, cellulose polymer, various siloxane polymers, and the like.

The weight ratio of the phthalocyanine to the polymer compound for a binder is usually selected from about 1:10 to 1: 1.

In the present invention, the photosensitive agent is phthalocyanine. As the phthalocyanine, X-type phthalocyanine is preferably used, but copper phthalocyanine may also be used.
Even if the photosensitizer is various perylene compounds, thiapyrylium compounds, anthrone compounds, squarylium compounds, bisazo compounds, trisazo pigments, azurenium dyes, etc., the effect of improving ozone resistance is seen, but the most effective in the case of phthalocyanine Met.

And, as described in claim 3, it may further contain metal-free phthalocyanine which is molecularly dispersed.

The photoconductor for electrophotography according to the present invention uses a polymer compound having a vinylphenol structure as a polymer compound for a binder, so that ozone resistance is improved, chemical fatigue is suppressed, a charged voltage, dark decay, The sensitivity becomes stable. It is considered that the reason why the ozone resistance is improved is that when a polymer compound having a vinylphenol structure is used, a hard film is formed.

EXAMPLES Examples of the electrophotographic photoreceptor of the present invention will be described below. It goes without saying that the present invention is not limited to the following embodiments.

The phthalocyanine includes a metal phthalocyanine having a metal atom at the center and a metal-free phthalocyanine having no metal atom. The latter metal-free phthalocyanine (hereinafter, H ₂ −
Heretofore, two types, α-type and β-type, have been known as representatives.

In contrast, recently developed a X-type H ₂ -Pc Xerox (Xerox) company has excellent electrophotographic characteristics, their synthesis, the relationship between the crystal form and electrophotographic characteristics, research on structure analysis (See US Pat. No. 3,357,989). X type H
_2- Pc is prepared by converting β-type H ₂ -Pc synthesized by a conventional method into α-type by sulfuric acid treatment, and ball milling this for a long time. Its crystal structure is clearly different from the conventional α-type and β-type. X-ray diffraction pattern of X-type H ₂ -Pc (Cu
According to Kα ray), the diffraction line is 2θ = 7.
4,9.0,15.1,16.5,17.2,20.1,20.6,20.7,21.4,22.2,23.
Appears at 8,27.2,28.5,30.3 (unit ゜). The diffraction line having the highest intensity is a diffraction line near 7.5 ° (corresponding to the plane distance d = 11.8 °). If the intensity is 1, the diffraction line intensity near 9.1 ° (plane distance d = 9.8 °) Is 0.66.

The H ₂ -Pc having a crystal form other than these, tau-type H ₂ -
There is Pc. This is obtained by ball milling the α, β, X type crystals together with a grinding aid in an inert solvent at 5 to 10 ° C. for 20 hours. Its X-ray diffraction pattern is essentially similar to that of the X form. However, in this case, the ratio of the diffraction intensity around 7.5 ° to the diffraction line intensity around 9.1 ° is 1: 0.8
It has become.

X-type H ₂ -Pc and / or τ-type H ₂ -Pc are added to a solvent together with a polymer compound for a binder, and the mixture is stirred, mixed (kneaded) and dispersed. X-type H ₂ -Pc and τ-type
H ₂ -Pc some soon as they are atomized is solubilized (considered from the viscosity is increased are solubilized). The mixture (including a new H ₂ -Pc crystals different from the X-type or τ-type.) Different molecules like H ₂ -Pc and X-type H ₂ -Pc and τ-type H ₂ -Pc granular cause It is thought that it was. In particular, X-type H ₂
When using -Pc, X-ray diffraction pattern, the diffraction diagram of X-type H ₂ -Pc alone clearly different, also clearly different both diffraction diagram of α-type and β-type H ₂ -Pc That is, the X-ray diffractogram of the X-type H ₂ -Pc is 2θ =
The diffraction line of 21.4 ° or more tends to disappear, and the diffraction line near 16.5 ° tends to increase. The most notable change is H ₂
The most characteristic diffraction line of -Pc, ie 7.5 ° (d = 11.8
Of the two diffraction lines near (Å) and 9.1 ° (d = 9.8 °), only the diffraction line near 7.5 ° is selectively reduced. From this, it is inferred that at least a part of the X-type H ₂ -Pc has been changed to a new one.

The degree of stirring and mixing (usually one day or more of stirring is required), time, temperature and the like differ depending on the solvent used. An appropriate degree of processing can be seen from the above-mentioned X-ray diffraction pattern at a diffraction line intensity ratio (I _11.8 / I _9.8 ) around 7.5 ° and 9.1 °. It is preferred that this ratio be between 1 and 0.1.

Of course, in the present invention, a part of the distributed X-type H ₂ -Pc may be such that no change to the others.

As described above, after dissolving the X-type metal-free phthalocyanine and the polymer compound for the binder in a solvent and mixing them by a method using a ball mill, an attritor, a sand mill, a sand ground, etc., the surface of the substrate (drum, belt, etc.) To form a film. The coating is performed using, for example, a bar coater, a calendar coater, a spin coater, a blade coater, a dip coater, a gravure coater, or the like. Examples of the solvent include, but are not limited to, tetrahydrofuran and cyclohexanone.

During the mixing process, the phthalocyanine, as the process proceeds,
At the same time, a part is solubilized and formed into fine particles to be in an appropriately dispersed state. Further, the viscosity is increased, and the light absorption of the formed film is also improved. The reason why the light absorptivity of the film is improved is not clear, but it is speculated that an interaction between the solubilized X-type phthalocyanine and the polymer compound for a binder occurs during the mixing treatment.

X-type phthalocyanine is treated with a polymer compound for a binder and a solvent to change at least a part of the crystal form, but the single-layer OPC has the following characteristics.

The OP that also contains a CT agent because it does not contain a heat-sensitive CT agent
There is a remarkable feature that heat resistance is better than C.

Because of the single-layer structure, manufacture is easy and at the same time, reduction in printing durability due to abrasion of the photoreceptor is eliminated.

High sensitivity compared to conventional single-layer OPC. 0.5-2.
It reaches 0 Iux · sec.

It has excellent photosensitive characteristics such that it has good sensitivity in a wide wavelength range of 550 to 800 nm.

 It is suitable for a positive charging system.

Superior in stability and chargeability compared to conventional single-layer OPC.

The electrophotographic photoreceptor of the present invention is used, for example, in equipment such as a copying machine, a printer, and a facsimile, but may be used for other purposes.

The present invention particularly preferably has a single-layer structure, but is not limited to this. A charge transfer layer is laminated, a surface protective layer is laminated with an insulating resin, or a blocking layer is provided between the photosensitive layer and the substrate. The structure may be different.

 Next, a more detailed description will be given.

-Example 1- X-type metal-free phthalocyanine (Fastogen Blue 8120B manufactured by Dainippon Ink Co., Ltd.) and p-vinylphenol resin as a polymer compound for a binder (MARUKA LYCUR-M manufactured by Maruzen Petrochemical) Was dissolved in tetrahydrofuran at a weight ratio of 1: 4, and dispersed and mixed by a ball mill method.The resulting solution was applied to the surface of an aluminum drum plate by a dipping method, and heat-treated at 60 ° C. for 1 hour in the air. An OPC having a single layer (15 to 20 μm thickness) structure was obtained.

The photosensitive characteristics and the like of the obtained OPC were examined. The measurement was carried out using a EPA-8100 paper analyzer manufactured by Kawaguchi Electric Co., Ltd., by irradiating a positively charged OPC with white light from a tungsten lamp using a tungsten lamp, and measuring the light sensitivity (half exposure, E _1/2 ) and residual potential Vr. Was. After that, an ozone generator (CLEAN LOA manufactured by Simon Corporation)
D 300), the paper analyzer was set to an ozone atmosphere, and the same measurement as above was performed. The ozone concentration was set to 5 ppm or more. Table 1 shows the measurement results.

-Example 2-X-type metal-free phthalocyanine (Fastogen Blue 8120B manufactured by Dainippon Ink and Chemicals, Inc.) and two compounds as polymer compounds for binders,
p-Vinylphenol resin (Maruzen Petrochemical MARUKA LY
CUR-M) and FOC-10 (manufactured by Fuji Pharmaceutical Co., Ltd.) represented by the following formula were dissolved in tetrahydrofuran in a weight ratio of 1: 2: 2,
After being dispersed and mixed by a ball mill method, the resulting solution is applied to the surface of an aluminum drum plate by a dipping method,
Heat-treated at 60 ° C for 1 hour in air to form a single layer (15 to 20
μm) OPC having a structure was obtained.

The same measurement as in Example 1 was performed for the obtained OPC. Table 2 shows the measurement results.

Comparative Example 1 X-type metal-free phthalocyanine (Fastogen Blue 8120B manufactured by Dainippon Ink and Chemicals, Inc.) and FOC-10 used in Example 2 as a polymer compound for a binder
(Manufactured by Fuji Pharmaceutical Co., Ltd.) was dissolved in tetrahydrofuran at a weight ratio of 1: 4, and dispersed and mixed by a ball mill method. The resulting solution was applied to the surface of an aluminum drum plate by a dipping method, and then in air at 60 ° C. for 1 hour. To obtain an OPC having a single-layer (15-20 μm thickness) structure.

The same measurement as in Example 1 was performed for the obtained OPC. Table 3 shows the measurement results.

As can be seen from Tables 1 to 3, it can be clearly seen that the photoreceptors of the examples have significantly improved ozone resistance.

Effect of the Invention As described above, the electrophotographic photoreceptor according to the present invention is obtained by combining a polymer compound having a vinylphenol structure as a polymer compound for a binder with a metal-free phthalocyanine having a new crystal system. Since it is used, ozone resistance is improved, chemical fatigue is suppressed, and characteristics such as charged voltage, dark decay, and sensitivity are stable.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-256058 (JP, A) JP-A-1-216362 (JP, A) JP-A-5-1223035 (JP, A) JP-A 64-64 62648 (JP, A) JP-A-63-301049 (JP, A) JP-A-63-55553 (JP, A) JP-B-49-4338 (JP, B1)

Claims (4)

(57) [Claims] An X-type metal-free phthalocyanine is stirred with a solvent for dissolving the X-type metal-free phthalocyanine and a polymer compound for a binder to change at least a part of the crystal system of the X-type metal-free phthalocyanine. An electrophotographic photoconductor comprising: a metal-free phthalocyanine; and the polymer compound for a binder, wherein the polymer compound for a binder has a polymer compound having a vinylphenol structure. 2. The electrophotographic photoconductor according to claim 1, wherein the high molecular compound having a vinylphenol structure is a vinylphenol polymer. 3. The electrophotographic photoconductor according to claim 1, further comprising a metal-free phthalocyanine molecularly dispersed. 4. The electrophotographic photosensitive member according to claim 1, wherein the weight ratio of the metal-free phthalocyanine to the polymer compound for a binder is in the range of 1: 1 to 1:10.