JPH06308755A - Image forming method - Google Patents

Abstract

PURPOSE:To improve wear resistance and solvent resistance and to extend the life of a photosensitive body by constituting a photosensitive body of an org. photosensitive layer and an amorphous carbon film surface protective layer on the photosensitive layer as an electrostatic latent image carrier body. CONSTITUTION:A photosensitive body as an electrostatic latent image carrier body consists of an org. photosensitive layer and an amorphous carbon film surface protective layer. The protective layer is formed by plasma polymn. method to 0.3mum film thickness. The charge generating agent of the org. photosensitive layer is tau-type nonmetal phthalocyanine dispersed with vinyl chloride- vinyl acetate copolymer resin and tetrahydrofurane to prepare a coating liquid. This coating liquid is applied to form a charge producing layer. 1-phenyl-1,2,3,4- tetrahydroquinoline-6-carboxyaldehyde-1',1'-diphenylhydrazone as a charge transfer material and polyester resin are dissolved in methylene chloride, which is then applied on the charge producing layer and dried to form a charge transfer layer. By this method, the life of the photosensitive body is long as corresponding to >=100000 sheets of copies.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a liquid developer which has been recently reviewed in response to higher speed and full color in processes such as electrophotography, electrostatic recording and electrostatic printing. The toner image developed on the electrostatic latent image carrier is transferred to an intermediate transfer roller before being transferred to a transfer target such as paper,
The present invention relates to an image forming method corresponding to speeding up by half-solidifying the toner by heat on the intermediate transfer roller.

2. Description of the Related Art Conventionally, a liquid developer is used as a method for developing an electrostatic latent image formed on an electrostatic latent image carrier in a process such as an electrophotographic method, an electrostatic recording method and an electrostatic printing method. There is also a method of using a dry developer, which is used properly by making the best use of each characteristic. That is, the liquid developer is suitable for high-resolution applications by taking advantage of the fineness of the particle size of the dispersed toner, and the dry developer is selected because it is easy to handle. In any case, the image visualized by these developing methods is transferred to a transfer-receiving member such as paper and fixed thereafter, or fixed as it is on the electrostatic latent image carrier. Among high-speed technologies such as electrophotography, electrostatic recording, and electrostatic printing, USP49 is a technology that uses an intermediate transfer member.
It is proposed in 45387, USP 4984025 and the like. WO 90/05942 also proposes a technique in which the transferred toner image is partially solidified by heat on an intermediate transfer roller to improve transferability and fixing is omitted. Such a technique is effective for speeding up the process. Electrostatic latent image bearing members used in electrophotography, electrostatic recording, etc. are roughly classified into inorganic photoconductive substances and organic photoconductive substances. Conventionally, inorganic photoconductive substances such as zinc oxide, cadmium sulfide, and selenium have been put to practical use as electrostatic latent image bearing members. Organic photoconductive substances such as phthalocyanine compounds and azo compounds have also been developed as electrostatic latent image bearing members. However, when a selenium-based photoconductive material is used as the electrostatic latent image bearing member, the Vickers hardness sharply decreases at 40 ° C. or more and is easily scratched, and the organic photosensitive layer is used as the electrostatic latent image bearing member. When used, there were problems that the film hardness was low and the film was easily scratched, and that the solvent resistance to the insulating solvent that was the dispersion medium of the liquid developer was low.

SUMMARY OF THE INVENTION The present invention is directed to an image forming method using an intermediate transfer roller, which has a low film hardness when an organic photosensitive layer is used as an electrostatic latent image bearing member, because of its low film hardness. It is intended to provide a method for solving the problem that the wear resistance is impaired, or the photoreceptor life is shortened due to the low solvent resistance to a liquid developing solvent.

SUMMARY OF THE INVENTION According to the present invention, a liquid toner is visualized on a rotating electrostatic latent image carrier having an electrostatic latent image and then electrostatically transferred onto an intermediate transfer roller, Then, in the image forming method in which the toner image is half-solidified by heat and transferred to the transfer target, the electrostatic latent image bearing member has an organic photosensitive layer and a surface protective layer of an amorphous carbon film thereon. The image forming method is characterized by Examples of the charge generator used in the photosensitive layer as the electrostatic latent image carrier include, for example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, azo dyes such as monoazo dyes and disazo dyes, indigo pigments,
Quinacridone-based pigments, indanthrene-based pigments, xanthene-based dyes, benzimidazole-based pigments, perylene-based pigments, dyes and pigments such as squaric menane dyes, eutectic complexes formed from pyrylium salt dyes and polycarbonate resins, polyvinylcarbazole, etc. And a charge transfer complex composed of an electron-donating substance and an electron-accepting substance such as TNF. Examples of the charge transport agent used in the photosensitive layer include hydrazone compounds, styryl compounds, pyrazoline compounds, oxazole compounds, thiazole compounds and the like. The photosensitive layer according to the invention may contain a known sensitizer. Further, if necessary, a surfactant, a plasticizer, an antioxidant, an ultraviolet absorber, a dispersion aid, an anti-settling agent, etc. can be appropriately used. Furthermore, the photoreceptor of the present invention has a structure in which a charge generating agent and a charge transporting agent are provided in the same layer, which is usually called a single layer type photoreceptor, or a first layer mainly containing a charge generating agent, The second layer containing the charge transport agent is placed on the alumite tube 2
It is possible to adopt a structure which is usually referred to as a laminated type photoreceptor, which is formed by a laminated structure. In the case of a laminated type photoreceptor, which of the charge generation layer and the charge transport layer is to be the upper layer is determined by whether the chargeability is positive or negative. In general, when negatively charged, it is advantageous in terms of characteristics that the charge transport layer is an upper layer. The amorphous carbon film of the present invention may be produced by a plasma polymerization method, a sputtering method, a carbon vapor deposition method, an ion plating method or the like, and the plasma polymerization method is preferable. The thickness of the amorphous carbon film is 0.0
5 to 2 μm. The image forming method of the present invention will be described with reference to the drawings. The charge was charged by the charger 14 on the electrostatic latent image carrier 15 of the photoconductor having the organic photosensitive layer pretreated by the corona generator 13 for static elimination and the surface protective layer of the amorphous carbon film thereon. After that, a latent image is formed by the optical system 18 such as a laser writing device. Next, the liquid toner is brought into contact with the latent image on the electrostatic latent image carrier 15 to visualize it. As the liquid toner, toner particles containing a resin colored with a pigment or a dye as a main component are suspended in a solvent having an electric resistivity of 1010 Ωcm or more and a dielectric constant of 3 or less, and lecithin and stearic acid are further used as charge control agents. It is possible to use one to which metal soap such as barium is added. The liquid toner is transferred from a liquid developer tank (not shown) through a liquid toner supply pipe 16 to a developing roller 2 to form an electrostatic latent image bearing member 15.
Contact. The latent image on the electrostatic latent image carrier 15 is a liquid toner.
Is visualized by. The surplus liquid toner on the electrostatic latent image carrier 15 is scraped off by the reverse roller 3, and the electrostatic latent image carrier 15 is further removed by the squeeze roller 4 to which a reverse bias is applied.
Is fixed in. The liquid developer scraped off by the river roller 3 is collected in the tank through the discharge pipe 17. Then, the visualized image on the electrostatic latent image carrier 15 is brought into contact with the intermediate transfer roller 6 and electrostatically transferred. Intermediate transfer roll
The layer 6 can be made of a material such as metal or plastic as long as it is made of a substance having resistance to a highly insulating organic solvent which is one of the constituent components of the liquid toner. Preferably, a transfer blanket that functions to receive ink from the plate surface and further transfer it to paper in offset printing can be used. When it is necessary to further improve the release of the toner from the intermediate transfer roller 6, a releasability improving agent such as a silicone resin may be applied onto the nitrile rubber. The visible image on the electrostatic latent image carrier 15 that has been transferred is the cleaning sponge roll 11 and the cleaning image.
The cleaning liquid supplied from the cleaning liquid supply pipe 10 is cleaned by the cleaning blade 12. Next, the image transferred to the intermediate transfer roller 6 is heated by the heating device 5 and concentrated. This step is accomplished by volatilizing the highly insulating organic solvent, which is one of the constituents of the liquid toner. The heating device 5 may be provided outside the intermediate transfer roller 6 or may be provided inside the intermediate transfer roller 6. In the figure, the surface of the intermediate transfer roller 6 is preheated. In addition, the semi-solidified state may be a state in which the image can be transferred onto the transfer target without any trouble. Then, the concentrated image is transferred onto the transfer target 7 by the pressure between the intermediate transfer roll 6 and the impression cylinder 8. The transfer target 7 may be not only paper but also fiber, plate, synthetic resin film, metal or the like. Next, the present invention will be described with reference to examples, but the present invention is not limited to the following examples. Hereinafter, in the examples, "parts" in the examples means parts by weight.

EXAMPLE An organic photosensitive layer was used as an electrostatic latent image carrier on a liquid developing type copying machine using a heated intermediate transfer roller, and an amorphous film having a thickness of 0.3 .mu.m formed by a plasma polymerization method thereon. -The test was carried out by mounting a photoreceptor having a surface protective layer of a Bonn film. It should be noted that 3 parts of τ type metal-free phthalocyanine as a charge generating agent for the organic photosensitive layer, a vinyl chloride-vinyl acetate copolymer resin (trade name VMCH manufactured by Union Carbide).
A coating solution prepared by dispersing 3 parts with 94 parts of tetrahydrofuran in a ball mill for 2 hours was applied and dried at 100 ° C. for 2 hours to form a 0.25 μm charge generation layer. Next, as a charge transfer agent, 1-phenyl-1,2,3,4-tetrahydroquinoline-6-carboxaldehyde-1 ′,
A solution prepared by dissolving 10 parts of 1'-diphenylhydrazone and 10 parts of a polyester resin (manufactured by Toyobo Co., Ltd., BYRON 200) in 100 parts of methylene chloride was applied onto the charge generation layer and dried to form a 20 μm charge transport layer. Intermediate transfer roll
The toner on the rack was heated to 70 to 80 ° C. and solidified halfway, and then transferred to paper to obtain a final image. In order to measure the charge receptivity, charge retention property, photosensitivity (potential after exposure) and residual potential as the electrostatic properties of the electrostatic latent image carrier, an organic photosensitive layer and a surface protective layer of an amorphous carbon film thereon are measured. The surface potentials of the photoconductors with were measured simultaneously. A part of the result is shown in Table 1. As a result of conducting an image test up to 100,000 sheets, no particular problematic change was observed as compared with the initial stage, and the life of the photoconductor was 100,000 sheets or more. Also, in terms of appearance, there was no deterioration of the film due to the liquid developing solvent or abrasion or scratches of the film due to contact with the intermediate transfer roller.

COMPARATIVE EXAMPLE 1 For comparison, a photoreceptor having an organic photosensitive layer having the above-mentioned structure without a surface protective layer was used as an electrostatic latent image carrier.
Table 1 shows the results when the organic photoreceptor having the surface protective layer of the amorphous carbon film was replaced according to the above method. The decrease of the surface potential became more remarkable as the number of printed sheets was increased. It was found that the background image was fogged when the image state was 10,000 and the photoconductor was not suitable as the electrostatic latent image carrier of the process. Further, dissolution of the film components, especially the charge transfer agent, which was considered to be due to the liquid developing solvent, was observed.

Comparative Example 2 For comparison, a selenium photoreceptor was used as an electrostatic latent image carrier. This photoconductor is selenium doped with arsenic, and has a Vickers hardness of 130 kg / mm @ 2 at 25.degree.
Is. The results obtained when the selenium photoreceptor was replaced according to the above method are shown in Table 1. When an image test of 10,000 sheets was performed, noise was generated in the image from about 7,000 sheets. When the photoconductor was examined, it was detected by an X-ray microanalyzer that there were scratches corresponding to the image and that silica was present inside the scratches. It is presumed that the cause of this is that the temperature of the photoconductor rises due to the contact with the intermediate transfer roller, and as a result, the hardness of the photoconductor decreases and the photoconductor is scratched by paper dust. Was done.

[Table 1]

The liquid toner is visualized on the rotating electrostatic latent image carrier having the electrostatic latent image, electrostatically transferred onto the intermediate transfer roller, and then the toner image is thermally transferred. In the image forming method of semi-solidifying and transferring to a transfer target, an organic photosensitive layer is formed on the electrostatic latent image carrier and an amorphous cover is formed thereon.
When a photoconductor having a surface protection layer of a Bonn film is used, it has high hardness, excellent printing durability and durability without deteriorating the electrostatic properties of the photoconductor, and has excellent solvent resistance against liquid developing solvent properties. As a photoconductor, the life of the photoconductor can be remarkably extended.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an image forming method of the present invention. DESCRIPTION OF SYMBOLS 1-Liquid developer 6-Intermediate transfer roll 7-Transfer member 9-Cleaning unit 15-Electrostatic latent image carrier

Front page continuation (72) Inventor Toshio Seta 2-33 Kyobashi, Chuo-ku, Tokyo Toyo Inki Manufacturing Co., Ltd.

Claims (1)

[Claims] 1. A liquid toner is visualized on a rotating electrostatic latent image carrier having an electrostatic latent image, electrostatically transferred onto an intermediate transfer roller, and then the toner image is thermally transferred. In the image forming method of semi-solidifying and transferring to a transfer target, the electrostatic latent image bearing member comprises an organic photosensitive layer and an amorphous cover on the organic photosensitive layer.
An image forming method comprising a photoconductor having a surface protective layer of a Bonn film.