JPH04199059A - 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 [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor used in copying machines, printers, and the like.

[Prior Art] Inorganic materials such as selenium, cadmium sulfide, and zinc oxide have been conventionally known as photoconductive materials for electrophotographic photoreceptors. However, these inorganic materials do not necessarily satisfy the characteristics such as photosensitivity, thermal stability, and durability required for electrophotographic photoreceptors, as well as the manufacturing conditions.

In contrast to electrophotographic photoreceptors using these inorganic photoconductive materials, photoreceptors using organic photoconductive materials are being actively researched due to their light weight, ease of film formation, manufacturing cost, and wide variation as organic compounds. Development is underway. Among photoreceptors using organic photoconductive materials, laminated photoreceptors with separated functions into a charge generation layer and a charge transport layer are highly sensitive and highly durable electrophotographic photoreceptors due to the flexibility of materials. It is promising and attracting attention.

However, the charge generation layer of a laminated photoreceptor has the role of absorbing light and generating charges, and the film thickness is determined from the viewpoint of preventing recombination and trapping of generated photocarriers.
0 to shorten the range of the carrier. It is generally as thin as C1 to 5 μm.

Therefore, during film formation, it is easily influenced by the surface condition of the support, and it is necessary to make the surface roughness of the support fairly uniform and small. For this reason, the material of the support and the manufacturing cost due to processes such as cutting and polishing become expensive, which is a major obstacle in reducing the cost of photoreceptors. Therefore, it is desired to put into practical use an electrophotographic photoreceptor that has a simplified processing and polishing process, uses a support made of low-cost materials, and has a photosensitive layer that is less affected by the surface condition of the support.

In order to solve these problems, it has been proposed to provide an intermediate layer between the support and the photosensitive layer, which is made of powder (pigment) and resin and has a thickness of several μm to several tens of μm.

In the case of such an intermediate layer, powder (P) and resin (R) are generally used.
The ratio by volume is preferably in the range of 171 to 3/1,
If P/R is less than 1/1, the intermediate layer will be easily influenced by the characteristics of the resin, and if it exceeds 3/1, there will be a lot of space in the intermediate layer, and bubbles will easily occur when forming two photosensitive layers. Become. However, in such an intermediate layer, if the film thickness is increased to make it less susceptible to the surface condition of the support, the M conductivity improves, but the photosensitivity decreases and the residual potential increases. There are drawbacks. Furthermore, if a material with relatively low resistance that does not increase the residual potential is used, although the film thickness can be increased, the charging property will be insufficient.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned state of the prior art, and its purpose is to be free from the influence of the support, and to improve residual potential, photosensitivity, and chargeability. The problem to be solved is to provide an electrophotographic photoreceptor with good properties such as properties.

[Means to solve the problem]

As a result of various studies to solve the problem described in item 1, the present inventors have discovered an electrophotographic photoreceptor in which an intermediate layer is provided between a support and a photosensitive layer, in which the intermediate layer is made of titanium oxide powder. It has been found that the above problems can be solved by dispersing conductive zinc oxide powder in a resin.

Furthermore, it has been found that when the crystal structure of titanium oxide is anatase type, the effect is more pronounced even under low temperature and low humidity conditions.

In the present invention, conductive zinc oxide is the most cost effective among the many transparent or white conductive powders,
Furthermore, since the shape of the powder particles is amorphous compared to other conductive powders, it is effective in preventing interference when the image forming light is a coherent laser beam.

The proportion of this conductive zinc oxide is 5 to 30% by weight of the entire powder.
If the amount is less than this, there will be no effect on residual potential or photosensitivity, and if it is more than this, the charging property will be insufficient.

Among commonly used powders, the pigment to be dispersed in the intermediate layer is white titanium oxide, which has almost no absorption in near-infrared light, and is most desirable when considering high sensitivity.

Furthermore, it is desirable that the titanium oxide has no hygroscopicity and is subject to little environmental fluctuation.

That is, the pigment contains impurities such as Na, Ol, and hygroscopic substances such as O, which absorb moisture at high humidity and cause deterioration of the photoreceptor characteristics.

Therefore, the purity of the pigment is preferably 99.0% or more.

Titanium oxide has rutile and anatase types with different crystal systems, or the anatase type has a lower specific resistance than the rutile type, which reduces the residual potential and speeds up the sensitivity even if the intermediate layer is thickened. That's great that it's possible. Particularly in low-temperature, low-humidity environments, even when rutile-type titanium oxide is used, the residual potential can be reduced to a certain extent by increasing the amount of zinc oxide added to the intermediate layer, but in terms of chargeability, anatase-type titanium oxide It is better to use

The thickness of the intermediate layer of the present invention can be about 2 to 30 μm, and if it is thicker than this range, residual potential, photosensitivity, etc. will be affected. As mentioned above, in the present invention, the ratio of gold powder (P) to resin (R) is preferably in the range of 171 to 3/1 in terms of volume, and if it is less than that, it will be difficult to increase the thickness of the intermediate layer Residual potential and photosensitivity deteriorate when the amount is exceeded, and when the amount exceeds this amount, there are many spaces in the intermediate layer, and bubbles are likely to be generated when the upper photosensitive layer is formed.

Various resins can be used for the intermediate layer used in the present invention, but considering that a photosensitive layer is coated on top of it with a solvent, resins with high solvent resistance to general organic solvents are recommended. is desirable.

Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacylate; alcohol-soluble resins such as copolymerized nylon, and methylated nylon; and three-dimensional network structures such as polyurethane, melamine resin, and epoxy resin. Examples include curable resins that form.

The photosensitive layer of the electrophotographic photoreceptor of the present invention is a charge generation layer.

A single layer type or a functionally separated type can be obtained by combining charge transport layers.

In the case of a single layer structure, a conductive support or an intermediate layer as described above is formed, and then a photosensitive layer in which a 11-generating substance and a charge transporting substance are dispersed in a resin is provided. In the case of a functionally separated type, a charge generating layer containing a charge generating substance and a resin is formed on a support similar to the single layer type, and a charge transporting layer containing a charge transporting substance and a resin is formed thereon.
In the case of positively charging type, the charge generation layer and the charge transport layer may be stacked in reverse order. Further, in the case of a functionally separated type, a charge transporting substance may be contained in the charge generation layer, and particularly in the case of a positively charging type in which a charge transport layer and a charge generation layer are sequentially laminated, sensitivity is improved.

When producing a photoreceptor having a layer structure as described in (2) below, there is a preferable range for the film thickness and the ratio of materials.

In the case of a negatively charged type (laminated support/charge generation layer/charge transport layer), the ratio of resin to the charge generation substance in the charge generation layer is preferably 0 to 400% by weight, and the film thickness is preferably 0.1 to 5 μm. In the charge transport layer, the ratio of the charge transport substance to the resin is 20 to 200% by weight, and the film thickness is 5 to 50 μm.
is preferred.

In the case of positively charged type (support / charge transport layer / 1 charge generation layer),
In the charge transport layer, the ratio of the charge transport material to the resin is preferably 20 to 200% by weight, and the film thickness is preferably 5 to 50 μm. In the charge generation layer, the charge generation substance is preferably 10 to 500% by weight based on the resin, and the film thickness is preferably 0.1 to 10 μm. Furthermore, it is preferable to include a charge transporting substance in the charge generation layer, which is effective in suppressing residual potential and improving sensitivity. In this case, the charge transport material is preferably contained in an amount of 20 to 200% by weight based on the resin.

In the case of a single layer type, the proportions of the charge transport substance and charge generation substance to the resin are 50 to 150% by weight and 10% by weight, respectively.
~50% by weight, and the film thickness is preferably 5 to 50 μm. As the charge generating material that can be used in the electrophotographic photoreceptor of the present invention, both inorganic and organic materials can be used as long as they absorb light and generate charge carriers.

Examples of the inorganic substance include amorphous selenium, trigonal selenium, selenium-arsenic alloy, selenium-tellurium alloy, cadmium sulfide, zinc oxide, and amorphous silicon.

Examples of organic substances include CI Pigment Blue 25 [Color Index 41 (C12+180)]
], Sissy Eye Pigmen L/Rado (C121200
), CI Acid Red 52 (CI 451
00), C.I. Basic Red 3 (C[452
10) In addition, phthalocyanine pigments having a porphyrin skeleton, azulenium salt pigments, squalic salt pigments, and azo pigments having a carbazole skeleton (Japanese Patent Laid-Open No. 53-9
5033), an azo pigment having a styrylstilbene skeleton (described in JP-A-53-133229),
Azo pigment with triphenylamine skeleton (JP-A-53
-132547), azo pigments with a dibenzothiophene skeleton (described in JP-A-54-21728), azo pigments with an oxadiazole skeleton (described in JP-A-54-21728),
4-12742), an azo pigment having a fluorenone skeleton (described in JP-A-54-22834), an azo pigment having a bisstilbene skeleton (described in JP-A-54-17)
733), azo pigments having a distyryloxadiazole skeleton (described in JP-A-54-2129)
, an azo pigment having a distyrylcarbazole skeleton (described in JP-A-54-17734), a trisazo pigment having a carbazole skeleton (described in JP-A-57-195767 and JP-A-57-195768), and C.I. Indigo pigments such as Bat Brown 5 (Ci 73410) and CI Bat Dye (J 73030), perylene pigments such as Argo Scarlet B (manufactured by Violet) and Indus Thread Scarlet R (manufactured by Bayer), anthraquinone or Examples include ring quinone pigments, quinone imine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, bishenzimidazole pigments, and the like.

Charge transport materials include hole transport materials and electron transport materials.

Hole transport substances include poly-N-vinylcarbazole and its derivatives, poly-γ-carbazolylethylglutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylpyrene, polyvinyltoenthrene, oxazole derivatives, oxadiazole. derivatives, imidazole derivatives, triphenylamine derivatives, 9-(p-diethylaminostyryl)anthracene, 1,1-bis-(4-dibenzylaminophenyl)propane, styrylanthracene, styrylpyrazoline,
Examples include electron-donating substances such as phenylhydrazones and α-phenylstilbene derivatives.

Examples of electron transport substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinone methane, 2,4.7-dolinitro-9-fluorenone, 2
,4,5.7-titranitro 9-fluorenone 12S
L517-Titranitroxanthone, 2,4.8-trinitrothioxantho, 2,6.8-trinitro-41
(-indeno(1,2-b)thiophen-4-one,
1.3.7-trinitrodipenzothiophene-5.5-
Examples include electron-accepting substances such as dioxide.

These charge transport materials may be used alone or in a mixture of two or more.

Binder resins used in the present invention include boristyrene, styrene-agrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-
Vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyltoluene, poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxy resin , thermoplastic or thermosetting resins such as melamine resin, urethane resin, phenol resin, and alkyd resin.

Further, in the present invention, a plasticizer or a leveling agent may be added to the charge transport layer. As the plasticizer, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the appropriate amount to be used is about 0 to 30% by weight based on the binder resin. As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil are used, and the appropriate amount thereof is about 0 to 1% by weight based on the binder resin.

In the present invention, it is also possible to further provide an insulating layer or a protective layer on the photosensitive layer.

The photosensitive layer and auxiliary layers such as the intermediate layer and the protective layer can be formed by dip coating, spray coating, bead coating, or the like.

The conductive supports used in the electrophotographic photoreceptor of the present invention include metal drums and sheets made of aluminum, brass, stainless nickel, etc., polyethylene terephthalate,
Examples include materials such as polypropylene, nylon, and paper on which metals such as aluminum and nickel are vapor-deposited, laminated, or coated with conductive paint, and plastic drums and sheets in which conductive pigments such as carbon are dispersed.

[Example] Next, the invention will be explained in more detail with reference to Examples.

Example 1 118 parts by weight of alkyd resin [Betsukosol TD-50-30 (manufactured by Dainippon Ink and Chemicals)] and 4 parts by weight of melamine resin [Bekkamin P-138 (manufactured by Dainippon Ink and Chemicals)] were added to 30 parts by weight of methyl ethyl ketone. Rutile titanium oxide (TM-1) with a purity of 99.7% is dissolved in this.
Fuji Titanium Industries) 150 parts by weight and conductive zinc oxide [N
o, l (manufactured by Honjo Chemical Co., Ltd.)] Add parts by weight of IQ,
The mixture was dispersed in a ball mill for 24 hours, and further diluted by adding 30 parts by weight of methyl ethyl ketone to prepare an intermediate layer solution. This is an aluminum plate (A1080) with a thickness of 0.2 mm.
(manufactured by Sumitomo Light Metal Co., Ltd.)] and dried at +50°C for 20 minutes to form an intermediate layer with a thickness of 10 μm. Next, parts by weight of polyester resin [Vylon 200 (manufactured by Toyobo)] were dissolved in 50 parts by weight of cyclohexanone, 2 parts by weight of the trisazo pigment of the above structural formula (1) was added, and the mixture was dispersed in a ball mill for 72 hours. . In addition, cyclopak shark 250
Parts by weight were added and dispersed for 12 hours, and the mixture was diluted with cyclohexanone while stirring to give a solid content of 1% by weight.

The charge generation layer coating solution thus obtained was spray-coated onto the intermediate layer and dried at 150°C for 20 minutes to a thickness of 0° and 1 μm.
A charge generation layer of m was formed.

Next, as a charge transport material, 8 parts by weight of a phenylstilbene compound of the following structural formula (II), 1 part by weight of polycarbonate resin (Panlite L-1250 (manufactured by Konjin Kasei Co., Ltd.)),
Silicone oil [KF-50 (manufactured by Shin-Etsu Chemical Co., Ltd.)
] 00.001 weight was dissolved in 90 parts by weight of methylene chloride. The charge transport layer coating solution thus obtained was dip coated onto the charge layer generation layer, dried for 20 minutes in loo'c,
A charge transport layer having a thickness of 25 μm was formed to produce an electrophotographic photoreceptor of Example 1.

Example 2 The intermediate layer thickness of Example 2 was 10 μm in the same manner as in Example 1, except that the rutile-type titanium oxide and conductive zinc oxide in the intermediate layer were changed to 55 parts by weight and 5 parts by weight, respectively.
An electrophotographic photoreceptor was prepared.

Comparative Example 1 Comparative Example 1 was prepared in the same manner as in Example 1 except that 60 parts by weight of rutile titanium oxide alone was added to the intermediate layer.
An electrophotographic photoreceptor having an intermediate layer thickness of 10 μm was prepared.

Comparative Example 2 Electrons with a thickness of 10 μm in the intermediate layer of Comparative Example 2 were prepared in the same manner as in Example 1, except that the amounts of titanium oxide and conductive zinc oxide in the intermediate layer were changed to 40 parts by weight and 20 parts by weight, respectively. A photographic photoreceptor was created.

Example 3 An electrophotographic photoreceptor of Example 3 was prepared in the same manner as in Example 1 except that the thickness of the intermediate layer was changed to 25 μm.

Example 4 In Example 1, rutile type titanium oxide [TM
-1 (manufactured by Fuji Titanium Industries)], anatase type titanium oxide with a purity of 99.9% [TP-2 (manufactured by Fuji Titanium Industries)]
An electrophotographic photoreceptor of Example 4 having an intermediate layer thickness of 15 μm was prepared in the same manner as Example 1 except that the following was changed.

Example 5 The intermediate layer thickness of Example 5 was 15 in the same manner as in Example 4, except that the anatase titanium oxide and conductive zinc oxide in the intermediate layer were changed to 55 parts by weight and 5 parts by weight, respectively.
A μm electrophotographic photoreceptor was prepared.

Comparative Example 4 An electrophotographic photoreceptor having an intermediate layer thickness of I5 μm was prepared in the same manner as in Example 4 except that 60 parts by weight of anatase titanium oxide alone was added to the intermediate layer.

Comparative Example 5 The intermediate layer thickness of Comparative Example 5 was changed to 1 in the same manner as in Example 4, except that the anatase titanium oxide and conductive zinc oxide in the intermediate layer were changed to 40 parts by weight and 20 parts by weight, respectively.
A 5 μm electrophotographic photoreceptor was prepared.

Example 6 An electrophotographic photoreceptor of Example 6 was prepared in the same manner as in Example 1 except that the intermediate layer thickness was changed to 15 μm.

Comparative Example 6 An electrophotographic photoreceptor of Comparative Example 6 was prepared in the same manner as in Example 6 except that conductive zinc oxide was not added.

Example 7 An electrophotographic photoreceptor of Example 7 was prepared in the same manner as in Example 4 except that the intermediate layer thickness was changed to 30 μm.

The electrostatic properties of the electrophotographic photoreceptor obtained as described above were measured by a dynamic method using a paper analyzer EPA-8100 (manufactured by Kawaguchi Denki Seisaku Shin). first,
After being charged for 20 seconds at an applied voltage of -6, dark decay was performed for 20 seconds, and then exposed to white light for 30 seconds at a surface illuminance of 6 (12 ux).

The charging characteristics are determined by calculating the charge retention rate Vo/~'m from the surface potential Vm (-V) after 20 seconds of charging and the surface potential Vo (-V) after 20 seconds of dark decay, and the sensitivity is determined by the surface potential after exposure to light. The exposure amount E,...o (Qux-sec) required for the potential to become one-tenth of the surface potential immediately before exposure, and the residual potential is the exposure 3
The surface potential V3° (-■) after 0 seconds was measured.

After that, tungsten light 51Q with a color temperature of 2856°,
Electrostatic properties after 5,000 repetitions of ux irradiation and charging at -6 to ~ - charge retention $"v'o/Vm', sensitivity E
/,,'(Q ux-sec), residual potential~”31
．．゛ was measured in the same way as before.

Table 1 shows the results of measuring the influence of the proportion of zinc oxide in the gold powder contained in the intermediate layer in the case of rutile-type titanium oxide at room temperature and room temperature.
Table 2 shows the results of measuring the effect of the ratio of zinc oxide in the gold powder contained in the intermediate layer at 0% RH) while comparing anatase-type titanium oxide and rutile-type titanium oxide.

Comparative Example 7 In Example 6, rutile type titanium oxide (TM-1 (manufactured by Fuji Titanium Industries) 1 with a purity of 99.7% for the intermediate layer was used with a purity of 99.7%).
An electrophotographic photoreceptor of Comparative Example 7 having an intermediate layer thickness of 15 μm was prepared in the same manner as in Example 6 except that 7% rutile titanium oxide (JR (manufactured by Teikoku Kako) 1 was used).

Comparative Example 8 In Example 4, anatase titanium oxide (TP-2 (manufactured by Fuji Titanium Co., Ltd.) with a purity of 99.9% for the intermediate layer was replaced with anatase titanium oxide (JA-1 (manufactured by Teikoku Kogyo Co., Ltd.) with a purity of 98%). ) An electrophotographic photoreceptor of Comparative Example 8 having an intermediate layer thickness of 15 μm was prepared in the same manner as in Example 4 except that the thickness was changed to 1.

The electrophotographic photoreceptors of Example 6 and Comparative Example 7 and Example 4 and Comparative Example 8 thus obtained were heated to 80% R at 30°C.
The effect of the purity of titanium oxide on the electrostatic properties under high temperature and high humidity was evaluated using a paper analyzer in the same manner as described above. Table 3 shows the influence of the purity of rutile titanium oxide, and Table 4 shows the effect of anatase titanium oxide.

[Effect 3 As explained above, the electrophotographic photoreceptor according to the present invention shows little deterioration in chargeability, residual potential, etc. due to repeated fatigue, has stable electrostatic properties even under high temperature and high humidity, and has stable electrostatic properties in the intermediate layer. Because thicker films are possible.

An electrophotographic photoreceptor that is not affected by the surface condition of the support can be expected.

Claims (2)

[Claims] (1) In an electrophotographic photoreceptor having an intermediate layer between a support and a photosensitive layer, the intermediate layer is made of titanium oxide powder and conductive zinc oxide powder dispersed in a resin. ,
An electrophotographic photoreceptor, wherein the titanium oxide powder has a purity of 99.0% or more, and the proportion of conductive zinc oxide is 5 to 30% by weight of the entire powder. (2) The electrophotographic photoreceptor according to claim (1), wherein the titanium oxide powder is anatase-type titanium oxide powder.