JPH0230505B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of forming an electrostatic image using light-transmitting particles, which is applied to copying machines and printers.

Structures of Conventional Examples and Their Problems A typical conventional image forming method using light-transmitting particles is the method disclosed in Japanese Patent Publication No. 110574/1983. In this method, light-transmitting particles are used as image-forming particles, are electrostatically deposited on a charged photoreceptor, and imagewise exposed from the particle surface. No light passed through it. Alternatively, the photoreceptor under the particle that is not exposed to light retains the same charge as before exposure, and a strong electrostatic attraction is exerted between the particle and the photoreceptor. The photoreceptor beneath the particle through which the light passes loses its charge, and the electrostatic attraction between the particle and the photoreceptor weakens. After exposure, this difference in electrostatic attraction is used to remove the particles whose electrostatic attraction has weakened from the photoreceptor, thereby obtaining an image of the particles on the photoreceptor. When attempting to reproduce a white background area using this method, the exposure potential of the photoreceptor had to be lowered to OV, requiring an excessive amount of exposure. Furthermore, when a photoreceptor with a large residual potential is used, there are disadvantages in that background fog tends to remain in white background areas and color purity deteriorates.

OBJECT OF THE INVENTION It is an object of the present invention to solve such drawbacks of the prior art,
To provide an image forming method capable of obtaining a copy without background fog even with a small amount of exposure.

Structure of the Invention In the present invention, an electrophotographic photoreceptor containing a photoconductive substance is charged, light-transmitting particles are electrostatically deposited thereon, and then imagewise exposed from the particle surface of the photoreceptor. The image forming method is characterized by comprising the step of: after making the potential of the particle surface substantially the same as the exposure potential of the electrophotographic photoreceptor, the particles through which light has passed are removed from the electrophotographic photoreceptor. .

DESCRIPTION OF EMBODIMENTS Next, an image forming method using the present invention will be described in detail with reference to the drawings.

First, a photoreceptor 1 used in ordinary electrophotography is charged with a corona charger 4 to which a high voltage is applied by a high voltage power supply 3.
(Figure 1). As the photoreceptor 1, one in which amorphous selenium, CdS, zinc oxide, or the like is deposited or coated on a conductive substrate 2 is used. For example, when zinc oxide is used for the photoreceptor 1,
The high voltage power source is set to negative polarity to negatively charge the surface of the photoreceptor. Thereafter, as shown in FIG. 1, conductive light-transmitting particles 5 are sprinkled onto the charged photoreceptor 1. As shown in FIG. An enlarged view of this state is shown in FIG. Since the particles 5 are conductive, they receive electrostatic induction from the charged photoreceptor 1, become positively charged, and are strongly electrostatically attached to the photoreceptor 1. At this time, it is preferable that the light-transmissive particle layer adheres to one layer. For this purpose, after dispersing the particles 5, if the back surface of the photoreceptor 1 is lightly vibrated, the particle layer will easily become one layer. .

The light-transmitting particles used here include transparent particles such as polymethyl methacrylate or glass beads whose surfaces are colored with a coloring agent, and resins with good transparency such as acrylic resin, styrene resin, and styne-butadiene copolymer. Some have colorants dispersed in them. Furthermore, the light-transmitting particles useful in the present invention include triazene dyes, triphenylmethane-based leuco dyes, which develop color by reacting with electron-accepting substances such as bisphenol A and activated clay, instead of the above-mentioned colorants. There are those in which color formers such as phenazine dyes and stilbene dyes are dispersed, or those in which they are used in combination with the above-mentioned colorants.

The shape of such light-transmitting particles is preferably spherical in order to prevent scattering of incident light, and the particle size is preferably from several microns to 80 microns from the viewpoint of resolution. Further, the light-transmitting particles used in the present invention are preferably electrically conductive particles. This is because the use of conductive particles facilitates the adhesion of a single layer of particles to a charged photoreceptor, and facilitates charge injection into the particles due to corona charging of the particle surface after exposure. The conductive light-transmitting particles can be easily obtained, for example, by applying cuprous iodide, which is a transparent conductive material, to the surface of the light-transmitting particles.

Next, as shown in FIG. 3, the surface of the photoreceptor particles is exposed through the transparent original 6. As shown in FIG. The state of electrostatic adhesion of the particles 5 at this time is shown in FIG. Particles 5a are particles that are not exposed to light or do not allow light to pass therethrough, and their electrostatic attraction with photoreceptor 1 remains strong. Particles 5b are particles through which light passes, and the charges in photoreceptor 1 and particles 5b have disappeared, and the electrostatic attraction between them has disappeared.

However, the potential of the photoreceptor under the particle through which light passes,
In other words, an excessive amount of exposure is required in order to bring the exposure potential to OV, and if a photoreceptor with a large residual potential is used, the residual potential will not disappear even if the exposure amount is increased, causing static between the particles and the photoreceptor. Electric attraction remains. In this way, even if you try to remove only the particles through which light passes while the charge remains on the exposed part of the photoreceptor, it cannot be completely removed, resulting in background fog or an image with poor color purity. It was hot.

A feature of the present invention is that the particles 5a through which light passes can be removed from the surface of the photoreceptor 1 by making the potential of the particle surface after exposure as shown in FIGS. 3 and 4 approximately the same potential as the exposure potential of the photoreceptor. The objective is to easily obtain images with good color purity and no background fog.

The method of the present invention will be explained using FIG. Third
The exposed particle surface shown in the figure is charged using a corona charger 4 as shown in FIG. At this time, the polarity of the voltage applied to the corona charger 4 must be the same as the polarity of the voltage used to charge the photoreceptor 1 in FIG. For example, if zinc oxide is used for the photoreceptor 1, the power source 3 must be negative.
The potential of the particles at this time is made approximately equal to the exposure potential of the photoreceptor measured in advance. The potential on the particle surface can be more easily controlled by using a scorotron charger provided with a grid electrode 4', as shown in FIG. When a scorotron charger is used, if the voltage applied to the grid 4' is set to the exposure potential of the photoreceptor 1, the potential of the particle surface becomes equal to the exposure potential of the photoreceptor. The state of electrostatic adhesion between the particles 5 and the photoreceptor 1 at this time is shown in FIG. Although the particles 5a that do not transmit light or are not exposed to light have a smaller amount of charge than the state shown in FIG. 4, sufficient electrostatic attraction remains between them and the photoreceptor 1. . On the other hand, since the light-transmitting particles 5b have the same potential as the exposure potential of the photoreceptor 1, there is no electrostatic attraction between the photoreceptor 1 and the particles. In this state,
When the photoreceptor 1 is vibrated from the back using the vibrator 7 as shown in FIG. 7, only particles 5b without electrostatic attraction are removed from the photoreceptor 1. Methods for removing particles through light include a method of vibrating the photoreceptor, a method of blowing the particles away with an air stream, a method of using electrostatic attraction, etc., but the method of vibrating the photoreceptor is the easiest.

An example of obtaining a positive full-color image from a negative original using this method will be described below.

Example First, red, green, and blue-purple solutions were prepared according to the following formulations.

(1) Red solution SBR resin binder: Naugatex 2752 (manufactured by Sumitomo Naugataku Co., Ltd., the same hereinafter) ...100 parts by weight Silica: Snowtex N (manufactured by Nissan Chemical Co., Ltd., the same hereinafter) ...80 parts by weight CI Pigment Red 5 …2.6 parts by weight CI Pigment Orange 21115 …5.3 parts by weight Anionic activator …1.0 parts by weight Water …130 parts by weight Sublimable color fumer: 3,7-bis-diethylamino-10-trichloroacetyl-phenoxazine …8 parts by weight (2) Green solution SBR resin binder...100 parts by weight Silica...80 parts by weight CI Pigment Green 36...5.4 parts by weight CI Batsuto Yellow 20...0.8 parts by weight β-type copper phthalocyanine...2.2 parts by weight Anionic activator...0.3 parts by weight Nonionic Activator...0.46 parts by weight Water...160 parts by weight Sublimation color forumer: 4-(5-chloro-1,
3,3-trimethyl-indolino)methyl-
7-(N-methylN-phenyl)amino-
5'-Chloro-1',3',3'-trimethyl-spiro[2H-1-benzopyran-(2H)-indole]...3 parts by weight (3) Blue-violet solution SBR resin binder...100 parts by weight Silica... 80 parts by weight CI Pigment Blue 15...3 parts by weight Dioxazine violet...0.5 parts by weight Methyl violet lake...0.5 parts by weight Anionic activator...0.3 parts by weight Sublimable color former: N-(1,2-dimethyl-3- yl) Methylidene-2,4-dimethoxyaniline...5 parts by weight Water...160 parts by weight Each of the above three types of solutions was dispersed separately in a ball mill for 3 hours to form an ink, which was then spray dried to form an ink of 5 to 50 microns. Red, green, and blue-violet spherical particles were obtained. Next, for 100 parts by weight of the particles,
200 parts by weight of a copper iodide solution having the following formulation was separately flow-coated and then classified to obtain particles of 15 to 20 μm. The specific resistance of the particles was approximately 10 ³ Ω·cm.

Copper iodide solution prescription Copper iodide 2 parts by weight Acetonitrile 100 parts Next, the zinc oxide photoreceptor 1 with an exposure potential of -30V was charged with -400V by the corona charger 4 which applied -6kV in the dark.
When a mixture 5 of equal amounts of the three types of light-transmitting particles described above was sprayed on the photoreceptor, the light-transmitting particles 5
received electrostatic dielectricity, became positively charged, and electrostatically adhered to the photoreceptor 1. Next, the color negative original 6 was imagewise exposed from the particle-attached surface on the photoreceptor (FIG. 3). Thereafter, using a scorotron charger 4 equipped with a grid electrode 4', a voltage of -30 V was applied to the grid electrode and a voltage of -6 kV was applied to the corona wire to bring the particle surface to -30 V.
Next, the vibrator 7
When the photoreceptor 1 was vibrated, only the particles 5b through which light passed fell, and only the particles through which light did not pass remained on the photoreceptor 1 (FIG. 7). After this photoreceptor is completely exposed to white light to remove static electricity, the clay surface 9 of the clay paper 10 is brought close to the particle image, and the back surface of the clay paper is charged with a corona charger 4 applying a voltage of +6 kV, and the particle image is transferred to the clay paper. (Fig. 8). The clay paper on which the particles were transferred was heated to about 200°C to sublimate the colorless sublimable dye and develop color in the clay layer (Figure 9), and the particles were removed from the clay paper using the cleaning brush 13 (Figure 10). A full-color copy with good color purity and no background fog was obtained.

Effects of the Invention As described above, when the present invention is used, an image with less background fog can be obtained in an image forming method using light-transmitting particles even when the exposure potential of the photoreceptor is relatively high.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a method of attaching light-transmitting particles to a charged photoconductor, FIG. 2 is a diagram explaining how the light-transmitting particles in FIG. 1 are attached to a photoconductor, and FIG.
The figure shows image exposure on the photoconductor surface using a transparent original, and FIG. 4 is a diagram illustrating the state of adhesion of the light-transmissive particles in FIG. , FIG. 5 is a diagram showing the method of charging the particle surface after exposure using a scorotron charger, FIG. 6 is a diagram explaining the state of electrostatic adhesion of the particles to the photoreceptor in FIG. 5, and FIG. Figure 8 is a diagram illustrating a developing method by vibrating the back surface of a photoreceptor, Figure 8 is a diagram showing a method for transferring a particle image remaining on a photoreceptor onto clay paper, and Figure 9 is a diagram showing a method of transferring a particle image remaining on a photoreceptor onto clay paper. By heating the colorless sublimable dye contained,
FIG. 10 is a diagram showing a method of developing color on clay paper, and FIG. 10 is a diagram showing a method of removing light-transmitting particles on clay paper with a cleaning brush. 1... Zinc oxide photosensitive plate, 2... Conductive substrate, 3... High voltage power supply, 4... Corona charger, 4'... Grid electrode,
5... Light-transmitting particles, 5a... Particles that did not pass light or were not exposed to light, 5b... Particles that allowed light to pass through, 6... Transparent original, 7... Vibrator, 8... High-voltage power supply, 9... Clay Layer, 10... Clay paper, 11... Heating roller, 12... Pressure roller, 13... Cleaning brush.

Claims (1)

[Scope of Claims] 1. After charging an electrophotographic photoreceptor containing a photoconductive substance and electrostatically adhering light-transmitting particles thereon, imagewise exposure is performed from the particle surface of the photoreceptor, and then the particle surface An image forming method comprising the step of: adjusting the potential of the electrophotographic photoreceptor to approximately the same potential as the exposure potential of the electrophotographic photoreceptor, and then removing particles through which light has passed from the electrophotographic photoreceptor. 2. The image forming method according to claim 1, wherein the method of bringing the potential of the particle surface to approximately the same potential as the exposure potential of the electrophotographic photoreceptor is a method using a scorotron charger having a grid electrode.