JPH044590B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a reversal image forming method using electrophotography that does not require a charging device.

BACKGROUND ART Conventionally, in apparatuses or printers for copying images, documents, etc., the Carlson electrophotographic method, in which a photoreceptor is repeatedly used, has been used as an image recording method that can use plain paper. In this method, the surface of a photosensitive layer made of a photoconductor is charged, imagewise exposed, the electrostatic latent image formed thereby is developed with toner, and then transferred and fixed onto transfer paper. be. After the toner is transferred, the photoreceptor is cleaned and used repeatedly. In this method, the final recording paper obtained is plain paper, and the art material does not change over time, maintaining high quality images semi-permanently.

However, this method generally requires that the photoreceptor be uniformly charged in advance. Therefore, a charging device such as a corona charging device is required, making the entire device complicated. Furthermore, when using a corona charging device as a charging device, there is the problem of environmental deterioration due to the generation of ozone, and the deterioration of the photoreceptor due to the ozone and the occurrence of charging unevenness due to toner adhesion to the corona charging device. However, there is also the problem that reliability deteriorates after long-term use.

In order to improve the problems of the Carlson method, a method called charging development has been proposed as a method that does not use a corona charger. In this method, a photoreceptor with sustained photoconductivity is irradiated with light to form an electrical latent image with different conductivity in image areas and non-image areas, and then a voltage is applied to conductive toner or semiconductive toner. By bringing the toner into contact with the electrical latent image while being applied, toner adheres to high resistance areas, that is, non-exposed areas on the photoreceptor, thereby forming a toner image. According to this method, the problems of the Carlson method described above are solved because a corona charger is not used, but only positive-positive images are obtained, and a positive image is obtained for a negative original, and a negative image is obtained for a positive original. It is not possible to obtain an image or perform reversal image formation.

OBJECTS OF THE INVENTION Accordingly, it is an object of the present invention to provide a reversal image forming method using electrophotography, which does not require a charging device and can perform exposure on the same side as development.

Structure of the Invention That is, according to the present invention, image exposure is performed on a photoreceptor in which a persistent photoconductive layer and a transparent insulating layer are laminated on a conductive support, and a magnet is provided inside and a voltage is applied. Inversion characterized in that non-insulating magnetic toner held on a developing means is brought into contact with the imagewise exposed surface of the transparent insulating layer of the photoreceptor to form a toner image on the transparent insulating layer. An image forming method is provided.

EXAMPLES The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view showing the basic structure of a photoreceptor used in the image forming method according to the present invention. The photoreceptor 1 is comprised of a conductive support 2 on which a permanent photoconductive layer 3 and a transparent insulating layer 4 are coated and laminated. As the conductive support 2, a support such as a metal plate, paper, or plastic on which a metal is vapor-deposited, or a resin in which quaternary ammonium salt, carbon, metal powder, or the like is dispersed and coated can be used. Materials for the persistent photoconductive layer include photosensitive fine particles such as zinc oxide, titanium dioxide, and cadmium sulfide dispersed in a binder, and organic semiconductors such as polyvinylcarbazole and protonic acids such as dinitrobenzoic acid or , organic halogen compounds, and dyes added thereto can be used.

As the material for the transparent insulating layer, vinyl resin, urethane resin, epoxy resin, polyester resin, polycarbonate resin, cellulose acetate resin, etc. can be used.

Next, an image forming method according to the present invention will be explained.
FIGS. 2 and 3 are schematic cross-sectional views showing the exposure step and development step of the image forming method according to the present invention, respectively. As shown in FIG. 2, light from a lamp 6 is irradiated from the transparent insulating layer side of the photoreceptor 1 through the transparent original 5. As shown in FIG. Due to this exposure, the resistance of the exposed part 7 of the continuous photoconductive layer 3 decreases, and this state continues even after the exposure irradiation, while the resistance of the non-exposed part 8 remains unchanged.
A latent image of different conductivity is formed in the persistent photoconductive layer 3.

The developing roller 9 is rubbed against the surface of the insulating layer 4 of the photoreceptor 1 on which a latent image due to the difference in conductivity of the persistent photoconductive layer 3 has been formed as described above. This developing roller 9 has a magnet (not shown) inside and has at least a conductive surface, and conductive or semiconductive magnetic toner, that is, non-insulating magnetic toner 10 is applied to the surface by magnetic force. It absorbs and holds. The conductive surface of the developing roller 9 is electrically connected to one terminal of a power source 11, and the other terminal of the power source 11 is electrically connected to the conductive support 2 of the photoreceptor 1. In the above state, the developing roller 9
When the surface of the photoconductor 1 on the insulating layer side is rubbed, toner adheres to the surface of the photoconductor on the exposure section 7,
Toner does not adhere to the surface portion of the photoreceptor on the non-exposed area 8 .

To explain this toner image forming process in detail, the resistance of the exposed area 7 of the persistent photoconductive layer 3 continues to decrease, and in the developing process, the developing roller and the non-insulating toner are mixed with the conductive support 2. When an electric field is applied through the insulating layer 4, the electric field acts to sandwich only the insulating layer 4, and a large electrostatic force acts on the non-insulating toner on the exposed area 7, strongly weakening the charge held in the toner. Attract each other electrostatically. This force transfers the toner to the developing roller 9.
If the force is stronger than the magnetic attraction force held by the photoreceptor, the non-insulating magnetic toner 10 will adhere to the photoreceptor. In the unexposed parts of the persistent photoconductive layer 3, there is no such change, so that the insulating layer 4 and the persistent photoconductive layer 3
Since an electric field acts through the toner, the electrostatic force acting on the toner is weak, and the toner remains held on the developing roller.

The voltage applied to non-insulating magnetic toner varies from -2000 to + depending on the characteristics of the toner used, photoreceptor, etc.
Selected between 2000V. Further, the resistance of the non-insulating toner is preferably 10 ¹² Ω·cm or less, but even higher resistance can be used if charge can be injected into the toner.

The toner image formed as described above is transferred and fixed onto a transfer paper by a conventional transfer method, or directly fixed onto a photoreceptor without any transfer.

Next, specific examples of the present invention will be explained.

Example 1 A permanent photoconductive layer having a dry film thickness of about 10 microns was formed by coating an aluminum support with a ball milled solution of a material having the following composition in toluene.

ZnO: 90 parts by weight Acrylic resin (A-405: manufactured by Nippon Reichhold): 10 parts by weight Rose Bengal: 0.05 wt% (based on ZnO) Copper stearate: 0.05 wt% (based on ZnO) Furthermore, on top of this, An ethanol solution of polyvinyl alcohol was applied and dried to form an insulating layer with a thickness of about 1 μm, thereby forming a photoreceptor. After image exposure is performed from the insulating layer side of the photoconductor through a negative original, a conductive developing roller that has a magnet inside and holds conductive magnetic toner on its surface is connected to the aluminum support of the photoconductor. While a voltage of 100 V was applied between them, the developing roller was rubbed against the photoreceptor so as to bring the conductive magnetic toner into contact with the photoreceptor. As a result, a positive image was formed on the upper surface of the insulating layer of the photoreceptor with respect to the negative original.

Example 2 A solution of the following materials dispersed and dissolved in a Pall mill with tetrahydrofuran and dichloroethane was coated on an aluminum support and dried.
A sustained photoconductive layer with a thickness of 10μ was formed.

Polyvinylcarbazole: 10 parts by weight 3.5-dinitrobenzoic acid: 2 parts by weight Chlorescein: 1 part by weight Further, an ethanol solution of polyvinyl alcohol was applied thereon and dried to form an insulating layer of about 1 μm to form a photoreceptor. After image exposure is performed from the insulating layer side of the photoconductor through a negative original, a conductive developing roller having a magnet inside and holding conductive magnetic toner on the surface is connected to the aluminum support of the photoconductor. A developing roller was rubbed against the photoreceptor so as to bring the conductive magnetic toner into contact with the photoreceptor while a voltage of 70 V was applied therebetween. As a result, a positive image was obtained for the negative original.

Effects of the Invention As is clear from the above, according to the method of the present invention, since toner adheres to the exposed area, a reversed image can be formed in an electrophotographic method that does not use a charging device. Further, in order to obtain a reverse image, it is not necessary to perform exposure from the support layer, so a complicated exposure system is not required.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing the basic structure of a photoreceptor used in the present invention. Figures 2 and 3 are
FIG. 3 is a schematic side view showing each step of the image forming method of the present invention. DESCRIPTION OF SYMBOLS 1... Photoreceptor, 2... Conductive support, 3... Photoconductive layer, 4... Transparent insulating layer, 5... Original, 6
...Lamp, 7...Exposed part, 8...Non-exposed part, 9
...developing roller, 10...non-insulating magnetic toner,
11...Power supply.

Claims (1)

[Claims] 1 A photoreceptor in which a persistent photoconductive layer and a transparent insulating layer are laminated on a conductive support is subjected to image exposure from the transparent insulating layer side, a magnet is provided inside, and a steady-state DC voltage is applied. A non-insulating magnetic toner held on a developing means is brought into contact with the imagewise exposed surface of the transparent insulating layer of the photoreceptor to form a toner image on the exposed portion of the transparent insulating layer. A reversal image forming method characterized by: