JPH05273821A - Electrostatic image forming device - Google Patents

Abstract

PURPOSE:To provide excellent hard copy of color image which allows the use of image receiving sheets of various types by the simple constitution by superimposing an image support, comprised of an extremely-thin peeling layer, and the image receiving sheet, pressurizing them under heat, and transferring a toner image together with the entire peeling layer. CONSTITUTION:A transfer sheet 1 is drawn out and fitted on a winding drum 5 and surface potential is made uniform by a pre-electrification electrode 9. Then, an electrostatic latent image is formed by an ion flow control head 2. The formed electrostatic latent image is developed by a developing unit 4 and a sensible image is formed. Subsequently the transfer sheet 1 which has finished development is peeled out of the winding drum 5 are passed through a thermal transfer unit 6 with the image receiving sheet 7 superimposed thereon. The peeling layer on the transfer sheet 1 and the image receiving sheet 7, pressurized under heat by the thermal transfer unit 6, are fused and joined together. When the transfer sheet 1 is peeled from the image receiving sheet 7 by a peeling device 28, the toner image is transferred to the image receiving sheet 7. Since the peeling layer is 1-3mum in thickness, physical incompatibility on the image receiving sheet 7 is hardly given.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of color printer technology by electrostatic recording, and more particularly to an electrostatic image forming apparatus for forming a color image using a paper which has been subjected to a liquid developing method and special processing. is there.

[0002]

2. Description of the Related Art In a conventional color process using electrophotography, an electrostatic latent image is formed around a photoconductor by a laser exposure system and is developed by a dry developing method using powder,
A general method is to electrostatically transfer this toner image onto paper to obtain a color image. Conventionally, in this method, a dither method or the like in which pseudo binary dots are reproduced in order to obtain gradation that is important for color image reproduction has been used. This method has the drawbacks that the resolution is sacrificed when trying to improve the gradation, and that smooth tones cannot be reproduced.
Further, in order to develop the electrostatic latent image, the diameter is 7 to 10 μm.
However, the resolution was poor and the dot size could not be faithfully reproduced, and there were problems in gradation and resolution.

On the other hand, there is an electrostatic latent image forming method in which the ion flow rate is controlled for each dot corresponding to an image to reproduce gradation. Examples of this include USP 3,715,762, USP 3,742,
There are methods and devices described in 516 USP 4,463,363. A liquid developing method is a method for faithfully developing an electrostatic latent image. As compared with the dry development method, this gives a high image quality because the toner has a small diameter. The combination of the two forms a color image which is extremely superior to the conventional electrophotographic method.

However, this method has a problem that good transfer to plain paper is basically difficult due to the electric and powder characteristics of the toner. Therefore, conventionally, there have been many cases in which a so-called direct recording system is used in which an electrostatic recording paper in which a conductive base paper is coated with an insulating layer is used, and an image is formed on the electrostatic recording paper to output the image.

As another method, there is a method described in USP 4,686,163 in which a toner image is transferred onto plain paper using a transfer material obtained by coating a special transfer material on a photoconductor. In this method, since exposure is performed to obtain an electrostatic latent image in the same manner as in the conventional electrophotographic method, it is necessary to have a function as a photoconductor, so that it is necessary to adopt a very complicated configuration.

[0006]

In the conventional electrophotographic method, it was difficult to achieve both high resolution and high gradation. Further, in the image forming method in which the ion control and the liquid developing method are combined, good transfer is difficult. The method of using so-called electrostatic recording paper, which has an insulating layer formed on a conductive base paper, provides high-speed, high-quality images with a simple mechanical structure, but the selection range of paper texture is extremely narrow, and it is limited to specific purposes. It had been.

An object of the present invention is to provide an electrostatic image forming apparatus having a small size and a simple structure capable of selecting not only plain paper but also various kinds of image receiving paper according to the purpose of use.

[0008]

In order to achieve the above object, in an electrostatic image forming apparatus of the present invention, an electric charge is selectively applied to an image support having an electrically conductive substrate and an insulating film formed thereon. An electrostatic latent image forming means for applying the electrostatic latent image to form an electrostatic latent image, a liquid developing device for developing the electrostatic latent image with liquid toner to visualize it, and heating and applying the toner image formed on the image support. In an electrostatic image forming apparatus provided with a fixing unit for pressing, an insulating release layer formed on a conductive substrate and a glass transition temperature formed on the release layer are higher than a heating temperature of the fixing unit. And a second image support having an insulating resin layer containing a pigment of a desired color formed on a conductive substrate. When the image support supplying means for supplying the latent image forming means and the first image support are selected, Image receiving paper supplying means for supplying the fixing means with the paper superposed on the first image support is provided, and the dielectric constant and electric resistance of the composite layer of the release layer and the release layer of the first image support are set to the second value. The dielectric constant and the electric resistance of the resin layer of the image support of No. 1 were set to be approximately the same.

[0009]

In the present invention, the first image support is selected when the transfer image is to be obtained. Then, a latent image is formed on the first image support by the electrostatic latent image forming means, and a toner image is formed by the liquid developing device. After that, the first image support and the image receiving paper are superposed and passed through a fixing device. When the first image support is heated and pressed at a temperature not lower than the glass transition temperature of the release layer by the fixing means, the image is transferred. The peeling layer on the surface of the support is melted and adhered to the image receiving paper together with the toner layer and transferred to complete printing. Further, in the case of the second image support composed of the resin layer and the pigment, the image receiving paper is not supplied and only the second image support is supplied to the fixing means after the development is completed, heated and pressed to be fixed and outputted. ..

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic diagram of an electrostatic image forming apparatus according to the present invention. This figure shows an example in which an image support having a release layer and a release layer formed on a conductive base paper (hereinafter referred to as a transfer sheet) is used. 1 is a transfer sheet roll around which a transfer sheet as an image support is wound, 2 is an ion flow control head for forming an electrostatic latent image on the transfer sheet, 3 is a blower for sending air to the head, and 4 is a blower.
Is a developing device group for developing an electrostatic latent image, 4a is a developing roller, 4b is a scraper roll, 5 is a winding drum for winding and rotating an image support, 6 is an image receiving paper and 7 an image support A thermal transfer device for stacking and heating and pressing, and a cutter 8 for cutting the transfer sheet into an appropriate size. In some cases, the transfer sheet may be pre-charged by the pre-charging device 9 before the latent image formation.

FIG. 2 shows the configuration when the electrostatic recording paper 27 is used.

FIG. 3 shows an example of a transfer sheet which is an image support. Reference numeral 13 is a conductive base paper, 12 is a release layer formed thereon, and 11 is a release layer formed on the release layer. The release layer 12 and the conductive base paper 13 are coated or coated so as to have a sufficient adhesive force. FIG. 4 shows the construction of an electrostatic recording paper which is another image support. Reference numeral 29 indicates a conductive base paper, and reference numerals 30 and 31 indicate a resin layer and a pigment. The material of the release layer 11 is polyester,
Resins such as phenyl resin, acrylic resin, vinyl polymer, cellulose and polyvinyl acetate are fried.
The glass transition temperature of the peeling layer 11 is set lower than the temperature at which the image support is heated by the heating of the thermal transfer device 6, and when heated by the thermal transfer device 6, the resin is in a molten state. The release layer 12 is obtained by coating the surface of the conductive base paper 13 with a substance having a large surface tension such as silicon or fluororesin.

FIG. 5 is a detailed view of the ion flow control head. 14 is a counter electrode, 15 is a control electrode, 16 is an aperture slit through which controlled ions emerge, 17 is a discharge electrode for generating ions, 18 is a control driver for controlling the voltage applied to the control electrode, 19 is a power supply for control, 2
Reference numeral 0 represents a high-voltage power supply for discharge, and reference numeral 21 represents an air flow inlet.

FIG. 6 shows a transfer mechanism by the thermal transfer device 6. 22 is a heat roll for heating, 23 is a backup roll for pressurization, 24 is a release layer of the transfer sheet,
25 is a transfer sheet after the release layer is transferred to the image receiving paper, 26
Indicates the transferred toner layers, respectively. 27 is an image support (referred to as electrostatic recording paper) in which a resin layer and a pigment layer are formed on a conductive base paper, and 28 is a transfer sheet which is heated and pressed to be integrated when a transfer sheet is selected. A peeling member that has the function of peeling off the image receiving paper and discharging only the image receiving paper outside the machine. In the case of electrostatic recording paper, the tip is lowered as shown in Fig. 2,
It also has a function to make it easier to pass.

Next, the operation will be described. When the transfer sheet is selected, first, the transfer sheet 1 is pulled out and cut into a certain size by the cutter 8, and the winding drum 5
Fixed to. This transfer sheet is made to have a uniform surface potential state by removing charges by AC discharge or charging by DC or DC + AC discharge so as to have a constant surface potential by the front electrode 9.

Next, an electrostatic latent image is formed by the ion flow control head. In the operation of this head, first, as shown in FIG. 5, a high voltage is applied to the discharge electrode 17 to cause corona discharge and generate a large amount of ions. A high-speed air flow is introduced into this space and is ejected together with some of the ions generated as a jet flow through the opening slit. Therefore, an ion flow having a constant velocity is generated in the opening, and the direction of the ion flow is changed by the electric field created by the control electrode 15 and the counter electrode 14 in the opening, and the amount of ions heading to the image support surface is controlled. There are various types of ion flow control heads, and some of them are already commercialized. In the present invention, the purpose is to obtain an electrostatic latent image on the transfer sheet, and the structure of the ion flow control head does not matter.

The electrostatic latent image thus formed is developed by the developing device 4 and visualized. The developing device is composed of a developing roller 4a and a scraper roller 4b, each of which rotates in the direction of the arrow. The electrostatic latent image is developed by a developing solution composed of an organic solvent and toner carried to the developing area by the developing roller. At this time, not only the toner but also a large amount of the organic solvent adheres to the transfer sheet and vapor of the organic solvent. Therefore, it is necessary to remove it as much as possible and return it to the developing device side. Therefore, the scraper roll 4b is used. This roller is rotating at high speed near the transfer sheet. By repeating this process for the number of colors on the transfer sheet on the winding drum, a color toner image is formed.

Next, the developed transfer sheet is peeled off from the winding drum, and is superposed on the image receiving paper 7, and is passed through the thermal transfer device. This thermal transfer device is almost the same as a fixing device that is usually used in a copying machine or the like. The image receiving paper 7 can be so-called plain paper, Japanese paper, cloth, etc., as long as it can be conveyed to the thermal transfer device 6, transfer is possible. The release layer 11 of the transfer sheet heated and pressed by the thermal transfer device 6 and the image receiving paper 7 are melted and adhered to each other. Here, when the transfer sheet and the image receiving paper are peeled off by the peeling device 28, the release layer 12 and the peeling layer 11 of the transfer sheet are easily separated, and the toner image is transferred to the image receiving paper. At this time, the peeling layer 1
Since No. 1 has a thickness of 1 to 3 μm, almost no feeling of discomfort on the image receiving paper is felt. In this way, the series of processes is completed.

The peeling layer 11 on the surface of the image support undergoes glass transition by superposing the image support and the image receiving paper and heating and pressurizing the resin support by the fixing device 6 to a temperature higher than the glass transition temperature of the resin thin film layer. Since the release layer 12 has a larger surface tension than the image receiving paper, the release layer 11 is made of a resin thin film in a molten state.
Is attached to the image receiving paper 7 having a smaller surface tension together with the toner layer and transferred to complete a color print. In this transfer process, not only heating but also pressure is applied, so the resin layer that has been heated to a temperature above the glass transition temperature and is in a molten state enters the gaps between the fibers of the paper and the irregularities on the surface, making it difficult for the image receiving paper and the resin layer to separate .. Therefore, when the image receiving paper and the image support are peeled off after cooling, the peeling layer 11 is completely separated from the release layer 12 and is transferred to the image receiving paper 7 for good transfer.

Next, when the electrostatic recording paper is selected, the electrostatic recording paper 27 is pulled out, cut into an appropriate size by the cutter 8, and then wound around the winding drum 5 and held. The subsequent image formation is the same as described above. The electrostatic recording paper 27 on which the toner image is formed is peeled off from the winding drum 5 and guided to the thermal transfer device 6, where the toner image is thermally fixed on the electrostatic recording paper.

When the transfer sheet and the electrostatic recording paper are switched and used as in the present invention, it is necessary to control the control electrodes in accordance with the electric characteristics of the paper in forming the latent image.
This may not be difficult in itself, but often requires complicated parameter control. In the present invention, the control of latent image formation is simplified by making the electric resistance and the dielectric constant of the composite layer of the release layer and the release layer of the transfer sheet substantially the same as those of the resin layer of the electrostatic recording paper and the composite layer of the pigment. did.

Table 1 shows an example of the results of examination of the layer structure of the transfer sheet.

[0023]

[Table 1]

As described above, in the apparatus of the embodiment of the present invention, the ion flow control device, the image support comprising the release layer formed on the conductive base paper and the extremely thin release layer, and the image support on the image support. It consists of a developing device that develops the formed electrostatic latent image by liquid development and a thermal transfer device, and the toner image is transferred together with the peeling layer by pressing and heating the image support and the image receiving paper, In addition to simplifying the developing mechanism and the transferring mechanism as compared with the photographic color printer, it was possible to construct a color printer that can obtain a hard copy of a color image having excellent resolution and gradation. Also, since an extremely thin release layer is used, the quality of the image-receiving paper after transfer is not impaired, and many types of image-receiving paper can be used. Further, when electrostatic recording paper is used, the selectivity of the texture of the paper is narrow, but at low cost, high-speed and high-quality continuous copying was obtained. Since the present invention can be easily selected according to the purpose of use, it is possible to provide an excellent image forming method having a wide range of applications and a high convenience with a simple mechanical structure which conventional color printers do not have. ..

In the present invention, many methods have been proposed for the structure of the ion flow control head 2, and any of them can be used. Further, the winding drum 5 does not have to be an essential problem because it is a drum, and may be a combination of rollers as long as the image position can be obtained with good reproducibility.

[0026]

As described above, according to the present invention, it is possible to provide an electrostatic image forming apparatus having a simple structure and capable of selecting not only plain paper but also various kinds of image receiving paper according to the purpose of use.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a configuration of an electrostatic image forming apparatus according to the present invention.

FIG. 2 is a configuration diagram when electrostatic recording paper is selected.

FIG. 3 is a diagram showing a configuration of an image support used in the present invention.

FIG. 4 is a diagram showing a configuration of an image support used in the present invention.

FIG. 5 is a diagram showing an ion flow control head used in an example of the present invention.

FIG. 6 is a diagram showing a transfer mechanism.

[Explanation of symbols]

 1 Transfer Sheet 2 Ion Flow Control Head 4 Developing Device 5 Winding Drum 6 Thermal Transfer Device 7 Image Receiving Paper 11 Release Layer (Resin Thin Film Layer) 12 Release Layer 13 Conductive Base Paper

Claims (3)

[Claims] 1. An electrostatic latent image forming means for selectively applying an electric charge to form an electrostatic latent image on an image support having an electrically conductive substrate and an insulating film formed thereon, and the electrostatic latent image. An electrostatic image forming apparatus comprising: a liquid developing device for developing a toner image with a liquid toner to visualize the toner image; and a fixing means for heating and pressurizing a toner image formed on the image support. A first image support having an insulating release layer formed on the release layer, and a release layer formed on the release layer and made of a resin having a glass transition temperature lower than the heating temperature of the fixing unit. A second image support having an insulative resin layer containing a pigment of a desired color formed on a conductive substrate; an image support supply means for selectively supplying the electrostatic latent image forming means; When the first image support is selected, the image receiving paper is overlaid on the first image support and the fixing device is And an image receiving paper supply means for supplying the image receiving paper to the first image support, wherein the dielectric constant and the electric resistance of the composite layer of the release layer and the release layer of the first image support are adjusted to the second value. An electrostatic image forming apparatus characterized in that a dielectric constant and an electric resistance of a resin layer of an image support are substantially equal to each other. 2. The ion generating device according to claim 1, wherein the electrostatic latent image forming means has a narrow slit portion formed on the front surface by a control electrode array and a counter electrode, and a corona discharge behind the narrow slit portion. And the electric field or fluid guides the ions to the slits to apply a voltage to the control electrode array to form an electric field in the slits, thereby controlling the outflow of the ions to the image support and statically controlling. An electrostatic image forming apparatus, which is an ion flow type electrostatic head for forming a latent image. 3. The first release wherein the release layer has a thickness of 10 to 100 μm, and the release layer has a thickness of 10 μm or less.
The electrostatic image forming apparatus according to claim 1, wherein the image support is used.