JPH0220093B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes a mixture of phthalocyanine, zinc oxide and zinc sulfide as a photoconductor element to improve sensitivity,
This invention relates to an electrophotographic photoreceptor that has excellent durability and is safe and hygienic.

Generally, in electrophotography, like the xerography method, a photoreceptor in which a photoconductor element such as selenium or cadmium sulfide is formed into a thin film on a metal drum is charged in a dark place, and a light image is irradiated (exposed). After forming an electrostatic latent image, a visible image is created using toner (development), and this is transferred and fixed onto paper, etc., or a photoconductive layer (photosensitive layer) is conductive as in the electrofax method. There is a method in which a permanent visible image is obtained on a photoconductive layer by forming the photoconductive layer on paper, charging it, exposing it to light, developing it, and fixing it on the photoreceptor.

Photoconductor elements currently widely used for electrophotographic photoreceptors include inorganic compounds such as amorphous selenium, cadmium sulfide, and zinc oxide.
Amorphous selenium has good properties as a photoconductor element, but it is difficult to manufacture because it must be manufactured by vapor deposition, the vapor-deposited film is not flexible, requires careful handling, and is expensive. There is a drawback. Cadmium sulfide and zinc oxide are used in the form of a photoconductive layer dispersed in a binder resin, but practical sensitivity cannot be obtained unless the resin/photoconductor element weight ratio is 0.2 to 0.3 or less. However, the photosensitive layer has disadvantages in mechanical properties such as flexibility, smoothness, hardness, tensile strength, and abrasion resistance. Therefore, it cannot withstand repeated use as it is. Additionally, hygienic issues with cadmium sulfide also need to be considered.

On the other hand, phthalocyanine is known as an organic compound, which can be dispersed in a binder resin and coated on a conductive substrate, and has excellent flexibility and processability, but when used alone, it has low sensitivity. This is not sufficient for practical use, and sensitization can be achieved by using chemical sensitization and optical sensitization in combination. As a chemical sensitizer,
2,4,7-trinitro-9-fluorenone (TNF), 2,4,5,7-tetranitro-9-
Polycyclic or heterocyclic nitro compounds such as fluorenone (TENF), quinones such as anthraquinone, aromatic amines such as tetramethyl-P-phenylenediamine, and nitrile compounds such as tetracyanoethylene are known. Furthermore, xanthene dyes and quinoline dyes are known as optical sensitizers. However, if these substances are added until a sensitivity sufficient for practical use is achieved, these substances themselves have problems in charging resistance, light resistance, etc., and fatigue phenomena due to continuous charging and exposure to light become a significant problem in practical use. In addition, TNF, as a chemical sensitizer,
TEZF has a particularly excellent sensitizing effect, and is actually often used for organic photoconductors. However, these substances are very expensive, and if a large amount of these substances is added to obtain the sensitivity required for practical use, the photoreceptor becomes very expensive. Furthermore, TNF, TENF, etc. have hygiene problems for the human body, and their use is questionable.

The present invention solves the above-mentioned drawbacks, and particularly relates to an electrophotographic photoreceptor that has significantly improved charging characteristics, has excellent sensitivity and durability after repeated use, and is inexpensive.
As described below, by using a specific phthalocyanine derivative, it is possible to obtain an electrophotographic photoreceptor that does not require chemical sensitizers that pose problems such as hygiene.

That is, the present invention provides an electrophotographic photoreceptor characterized in that a photoconductor element is a mixture of phthalocyanine (A), zinc oxide (B), and zinc sulfide (C).

In the present invention, a mixture of phthalocyanine (A), zinc oxide (B) and zinc sulfide (C) is used as a photoconductor element, and the photoconductor element is dispersed in a binder resin and coated on a conductive support. By using zinc oxide and zinc sulfide, the electrophotographic properties such as the stability of repeated charging are improved, and when cadmium sulfide, etc. is used as a photoconductor element with an appropriate combination. It is possible to obtain the same level of photosensitivity, etc., and even greater durability. A mixture of only phthalocyanine (A) and zinc oxide (B) does not have sufficient charge retention and dark decay characteristics for positive charges, and a mixture of only phthalocyanine (A) and zinc sulfide (C) does not have sufficient charge retention and dark decay properties for positive charges. Although it has good charge retention and dark decay characteristics with respect to charging, it has the disadvantage of large residual charge. On the other hand, the mixture of phthalocyanine (A), zinc oxide (B), and zinc sulfide (C) showed almost no decrease in photosensitivity, and the charge retention and dark decay characteristics for positive charges were significantly improved. In this photoreceptor, since the phthalocyanine pigment is in charge of photosensitivity, the electrophotographic properties with respect to positive charging are better.

In the present invention, in order to make an electrophotographic photoreceptor using the above mixture, the mixture is uniformly dispersed together with a binder resin, a solvent, etc. using a kneading and dispersing machine such as a ball mill or an attractor, and then coated on a conductive support. do,
A method known per se is used to form a photosensitive layer.

The phthalocyanine used in the present invention includes metal-free phthalocyanine and various metal phthalocyanines, and those in various crystal forms are used. Examples of metal phthalocyanines include copper phthalocyanine, tin phthalocyanine, aluminum phthalocyanine, nickel phthalocyanine, cobalt phthalocyanine, zinc phthalocyanine, and vanadyl phthalocyanine. It is preferable to select.

In addition, when a phthalocyanine derivative having an electron-withdrawing group such as a nitro group is acid-pasted, TNF
Practically sufficient sensitivity can be obtained without using sensitizers such as sensitizers. Examples of phthalocyanine having an electron-withdrawing group include a halogen atom, a nitro group, a cyano group, a sulfone group, a carboxyl group,
It is substituted with an electron-withdrawing group such as a sulfamide group or a carboamide group. This phthalocyanine derivative can be obtained by using phthalonitrile, phthalic acid, phthalic anhydride, or phthalimide substituted with the above-mentioned substituent as the raw material for phthalocyanine during phthalocyanine synthesis, or by using It can be obtained by using both. The method for producing the phthalocyanine derivative is not particularly limited. Further, the number of substituents in one molecule of the phthalocyanine derivative is 1 to 16.

The above-mentioned phthalocyanine having an electron-withdrawing group is subjected to acid pasting treatment with other phthalocyanine having no electron-withdrawing group, if necessary, to obtain a phthalocyanine derivative. Here, acid pasting treatment refers to phthalocyanine or other phthalocyanine having the above-mentioned electron-withdrawing group to This is a treatment method in which a salt is formed with an inorganic acid such as an acid, and the phthalocyanine derivative is poured into water as known in the organic pigment industry, and the precipitated phthalocyanine derivative is filtered, washed with water, and dried. can get. This phthalocyanine derivative can be used in combination with other phthalocyanines, and desired sensitivity can be obtained by selecting the composition.

In the present invention, any zinc oxide commonly used in powder form for electrophotography can be used, and as the zinc sulfide, commercially available ones, such as general reagents, can be used.

Phthalocyanine (A), zinc oxide (B) and zinc sulfide
The mixing ratio of (C) is phthalocyanine (A)/zinc oxide (B) +
It is good when the zinc sulfide (C) is 20 to 60% by weight and the zinc sulfide (C)/zinc oxide (B) is 10 to 50% by weight. That is, if the phthalocyanine (A) content is less than 20% by weight, it is difficult to obtain sufficient photosensitivity, while if it exceeds 60% by weight, the charge retention property decreases. In addition, if the ratio of zinc sulfide (C) to zinc oxide (B) is less than 10% by weight, charge retention and dark decay characteristics are insufficient;
If it exceeds , the residual potential will increase and it is inappropriate.

Examples of binder resins include melamine resins, butyral resins, epoxy resins, silicone resins, polyurethane resins, acrylic resins, xylene resins, vinyl chloride-vinyl acetate copolymer resins, polycarbonate resins, and cellulose derivatives with a volume resistivity of 10. ^7Ωcm
A known material having the above insulation properties is used.
In addition, solvents include aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, alcohols such as methanol, ethanol, and isopropanol, esters such as ethyl acetate, and methyl cellosolve, and carbon tetrachloride. , halogenated hydrocarbons such as chloroform and dichloromethane, ethers such as tetrahydrofuran and dioxane, and dimethylformamide and dimethyl sulfoxide.

The binder resin should be phthalocyanine/binder resin = 20 to 50% by weight in terms of film properties and charge retention properties.
It was good in this case.

Examples of the conductive support include an aluminum plate, conductively treated paper, and conductively treated plastic film. To form a photosensitive layer on a conductive support, phthalocyanine (A) and zinc oxide are used as described above.
(B), and zinc sulfide (C) are dispersed in a binder resin,
If necessary, a solvent may be added to adjust the viscosity, and a known method may be employed in which the coating is applied using an air knife coater, a blade coater, a rod coater, a reverse roll coater, a spray coater, a hot coater, a squeeze coater, or a printing method, followed by drying.

The electrophotographic photoreceptor of the present invention may include not only an electrophotographic photoreceptor with only a photosensitive layer on a conductive support, but also an electrophotographic photoreceptor with a barrier layer, an insulating layer, and a photosensitive layer of another photoconductor element laminated thereon. It is also possible to use a sensitizer in combination.

The present invention will be explained below by giving examples. In the examples, "parts" indicate parts by weight.

Example 1 ε-type copper phthalocyanine (Lionol blue)
ESPS, manufactured by Toyo Ink Manufacturing Co., Ltd., product name) 10 parts acrylic polyol (Takeraktsu UA-702,
Takeda Pharmaceutical Co., Ltd., trade name) 25 parts Epoxy resin (Epicote #1007, Ciel Chemical Co., Ltd., trade name) 2 parts Methyl ethyl ketone 26 parts Cellosolve acetate 26 parts The above composition was milled in a magnetic ball mill for 48 hours, and then zinc oxide was added. (Sakai Chemical Industry SAZEX #2000,
(trade name) and 5 parts of zinc sulfide are added and kneaded for further 24 hours to obtain a photoconductive composition.

Next, this photoconductive composition was applied onto aluminum in a laminate film of 5μ thick aluminum foil and 75μ thick polyester film to a dry film thickness.
It was roll coated to a thickness of 10 μm and placed in an oven uniformly heated to 110° C. for 1 hour to prepare an electrophotographic photoreceptor. A corona discharge is applied to the sample thus obtained at +6.0 KV, a corona gap of 10 mm, and a charging speed of 10 m/min, and 10 seconds after the discharge stops, it is exposed to light with a 2854〓 tungsten light source at an illuminance of 10 Lux. The amount of light irradiation required for the potential immediately before exposure to decrease by 50% at this time was defined as the sensitivity. The sample measured in this way had a maximum surface potential of 890V,
Dark decay rate 2%, sensitivity 2.5Lux・sec., residual potential 15V
Both chargeability and sensitivity showed values sufficient for practical use. Using this photoreceptor, an image was created by the following development and transfer method.

Positive charge is given to the photoreceptor by corona discharge at 100W.
A positive film original image is projected at 10 Lux for 1 second using a tungsten light source for enlargement to form an electrostatic latent image on the photoreceptor, and then a visible image is obtained using negatively charged powder toner. A piece of high-quality paper was placed on top of it, and a visible image was transferred from the back of the paper using a positively charged corona discharge with an applied potential of +5KV, and fixed using an infrared lamp. The image obtained by this operation was extremely faithful to the original, and a clear, high-contrast image with no background smudges was obtained. Furthermore, regarding charge retention, there is no change in electrophotographic properties even after repeated copying.
The 20,000 copies were comparable to the initial images.

Comparative Example 1 When the electrophotographic properties were investigated when an electrophotographic photoreceptor was prepared as a photoconductive composition using titanium oxide instead of the zinc sulfide shown in Example 1, the maximum surface potential was 340 V, and the dark Attenuation rate 40.2%, sensitivity
The value was 21.3 Lux·sec. and the residual potential was 25 V, which was an impractical value.

Comparative Example 2 ε-type copper phthalocyanine (same as Example 1) 10 parts Acrylic polyol (same as Example 1) 36 parts Epoxy resin (same as Example 1) 6 parts Methyl ethyl ketone 20 parts Cellosolve acetate 20 parts The above composition After milling in a magnetic ball mill for 48 hours, only zinc oxide (same as in Example 1) was added,
When examining the electrophotographic characteristics when an electrophotographic photoreceptor was prepared in the same manner as in Example 1, the maximum surface potential was 580V,
Dark decay rate 11%, sensitivity 2.5Lux・sec., residual potential 20V
Although an improvement in sensitivity was observed, there was a problem with repeated charge retention, and there was a decrease in image density after 1000 sheets.

Comparative Example 3 When examining the electrophotographic properties of an electrophotographic photoreceptor prepared in the same manner as in Example 1 using the photoconductive composition shown in Example 1 except for zinc oxide and zinc sulfide, it was found that the maximum surface Potential 480V, dark decay rate 58%,
The sensitivity was 2.0 Lux·sec., the residual potential was 20 V, and the dark decay rate increased significantly, making these values impractical.

Comparative Example 4 Electrophotographic properties were determined when an electrophotographic photoreceptor was prepared in the same manner as in Example 1 using a composition in which 35 parts of zinc sulfide was used instead of zinc oxide in the photoconductive composition shown in Example 1. When investigated, the maximum surface potential was 920 V, the dark decay rate was 12%, the sensitivity was 28.3 Lux·sec., and the residual potential was 18 V, which were values that significantly lowered the sensitivity and were of little practical use.

Example 2 40 parts of copper phthalocyanine and 0.5 parts of tetranitrocopper phthalocyanine are added to 500 parts of 98% concentrated sulfuric acid with thorough stirring and dissolved. The dissolved solution is poured into 5000 parts of water to precipitate a composition of copper phthalocyanine and tetranitrocopper phthalocyanine, which is then filtered, washed with water, and dried at 120°C under reduced pressure.

50 parts of the composition thus obtained and 100 parts of ε-type copper phthalocyanine (Lionol Blue ER, manufactured by Toyo Ink Mfg. Co., Ltd., trade name) are dispersed in 5000 parts of methanol to form a uniform mixed dispersion. Thereafter, it is filtered and dried at 120° C. under reduced pressure to obtain a mixture [], and a photoconductive composition is prepared based on the following formulation.

Mixture [] 10 parts acrylic polyol (same as Example 1) 25 parts epoxy resin (same as Example 1) 2 parts methyl ethyl ketone 26 parts cellosolve acetate 26 parts The above composition was ground in a magnetic ball mill for 48 hours, then oxidized. Added 27 parts of zinc (same as in Example 1) and 8 parts of zinc sulfide (same as in Example 1), and further added 18 parts of zinc (same as in Example 1).
The mixture is kneaded for a time to obtain a photoconductive composition. Thereafter, as a result of measuring the electrophotographic characteristics when an electrophotographic photoreceptor was prepared in the same manner as in Example 1, the maximum surface potential was
920V, dark decay rate 1.5%, sensitivity 1.8Lux.sec.Residual potential
8V, with good sensitivity and repeated chargeability.
It was extremely practical.

Example 3 40 parts of copper phthalocyanine and 0.5 part of tetracyanocobalt phthalocyanine were dispersed in 200 parts of glacial acetic acid,
10 parts of 98% sulfuric acid was added dropwise with stirring, and after stirring for 10 hours, the solid matter was filtered out, and the phthalocyanine composition was precipitated through ammonia gas, washed with water, and heated at 120°C under reduced pressure. Dry with.

A photoconductive composition is prepared from the mixture thus obtained according to the following formulation.

Mixture [] 10 parts β-type copper phthalocyanine 5 parts branched polyester polyol (Desmofene #800, manufactured by Nippon Polyurethane Industries, trade name)
52 parts Cellosolve acetate 120 parts Polyisocyanate compound (Desmodyur N
−75, manufactured by Nippon Polyurethane Industries, product name)
8.4 parts With the above composition, the upper 4 points of the above 5 points were kneaded in a magnetic ball mill at room temperature for 30 hours, and 38 parts of zinc oxide (same as in Example 1) and 38 parts of zinc sulfide (same as in Example 1) were milled. Same.) 12 parts are milled for 18 hours, and then a polyisocyanate compound is added to form a photoconductive composition.

The resulting photoconductive composition was coated with 99.99% pure aluminum powder on a 75μ polyester film.
Roll coated to a film thickness of 15μ on a substrate vacuum-deposited to a thickness of approximately 1μ under a vacuum degree of 10torr. After the film was formed, it was placed in an oven uniformly heated to 120°C for 30
This was left for a minute to obtain an electrophotographic photoreceptor.

The photoreceptor thus obtained was measured in the same manner as in Example 1, and the maximum surface potential was 1200V.
A photoreceptor with a dark decay rate of 1.2%, a sensitivity of 2.1 Lux·sec, excellent charge retention and repeated chargeability, and a high coating strength was obtained. Example 1 using this photoreceptor
When an image was created in the same manner as above, a clear image that was faithful to the original pattern was obtained.

Claims (1)

[Claims] 1. An electrophotographic photoreceptor characterized in that a photoconductor element is a mixture of phthalocyanine (A), zinc oxide (B) and zinc sulfide (C).