JPH0256668B2 - - Google Patents

Abstract

Method for forming a protective transparent coating on a toner image formed electrophotographically by depositing a transparant protective toner electrophotographically and in registration on said toner image, using the same original.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method of applying a protective transparent coating to a toner image formed on a substrate, the image being formed by charging a photoconductive substrate, causing an image-wise discharge by exposure to light, and then It is obtained by developing the image using a colored toner and then transferring it to another substrate.

Electrophotography, the process of forming images using one or more colored toners that are adhered to a substrate, such as a sheet of paper, forms part of the technology in this field. It is. Although this electrophotographic technique has many advantages when compared to known printing techniques that utilize black or colored inks, it also has disadvantages, in which different types of toners are less well received than conventional inks. Although it does not adhere well to colored surfaces, this technique is nevertheless used for certain reasons. A known method is to cover the entire substrate, after forming an image with the aforementioned toner, with a thin layer consisting of a suitable protective substance, for example polymerized in a volatile solvent. Possible or soluble.

However, in this conventional method, the entire surface of the substrate, even the areas without toner, is coated with a protective coating, so that the resulting substrate has a different surface structure than that normally obtained by printing. It has the disadvantage that it contains, and its surface looks unnatural to the viewer. This is a decisive drawback, especially when test printing is performed by electrophotography.

It is therefore an object of this invention to provide a solution to the above mentioned problem. According to the invention, an identical image is formed on a photoconductive substrate from the same original image with another protective transparent toner, the transparent coating is transferred in registration with the colored image on the recipient substrate, and then It is here to stay.

Thus, in the method according to the invention, the protective toner covers only those areas where the colored toner image is present, so that the surface without the image retains its original surface structure. The final selected image, protected by a layer of protective toner, has the advantage of looking even more natural as a result.

The invention is particularly useful when proof printing is made from colored prints using known electrophotographic techniques, using multiple color separations from the original. Here, the operation of applying the protective toner can be performed accurately as many times as the color separation is performed, in each case using another color separation, but the formation of the protective toner image is also performed during the image formation. One can begin by exposing the photoconductive coating through all the color separations used and registered therein.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1a is a diagram illustrating the state in which toners of different colors are deposited on the substrate 1 depending on the image.
The first color toner is illustrated in the finely hatched area 2, and the second color toner is illustrated in the coarsely hatched area 3.

Image portions 2 and 3 are monochromatic image portions of different colors that are separately formed by a well-known electrophotographic method using color separation films 4 and 5 of different colors obtained from the original image. It is.

The color separation films 4 and 5 are obtained by photographing a color original using, for example, two types of filters of different colors, and are obtained as two different types of films.

The color separation film 4 consists only of information for forming the toner image 2, while the color separation film 5 consists only of information for forming the toner image 3.

To form this toner image 4, first the photoconductive surface is electrostatically charged, then the color separation film 4 is superimposed on the charged surface and exposed in this state.

This color separation film 4 consists of a transparent portion indicated by a hatch in the figure and an opaque portion indicated by a solid line.

All charges are removed in areas where the photoconductive layer is exposed to light that has passed through the transparent area, whereas in opaque areas the light is blocked and the charges in those areas are not removed but retained.

After exposure, the photoconductive layer is developed by depositing a toner of a first color, and the developed toner image is further transferred to the transfer substrate 1 to form a toner image corresponding to the second portion. Ru.

A similar procedure is repeated using another color separation film 5 and a toner image 3 is formed using a different color toner and aligned on the same transfer substrate 1.

Of course, there are locations where two different colored toner images overlap, and there are locations where no toner is present at all.

According to this invention, in the image obtained by this method, only the portion where the colored toner is present is
Be coated with a clear, untinted protective toner. For this purpose, two different methods can be used:

FIG. 1b shows the state in which a toner image is formed. On the photoconductive layer 6, a toner image is formed from the desired protective toner 7 using a first color separation film 4, and this toner coating is then applied onto the transfer substrate 1 to be protected. is transferred onto the image in precise alignment. Figure 1c is
The results are shown when only this protective toner layer 7 was formed.

No protective toner is applied to the points where only toner 3 of the second color is present. These areas are then coated with a protective toner.

Thus, according to FIG. 1d, an image is once again formed on the photoconductive layer 6 from the protective toner 8, in this case a second color separation film 5 is used. The first image is superimposed on the toner image 3 in FIG.
As shown in Figure e, said second protective toner layer 8
is transcribed. Thus, all colored toner areas are covered with a protective toner layer. Thereupon, the protective toner layers 7 and 8 are fused and fixed by heating the surface of the substrate.

As in FIGS. 1f and 1g, the protective toner layers 7, 8 can also be formed simultaneously in a single step. In this case, first, two color separation films 4 and 5 are aligned and used simultaneously to temporarily form a protective toner layer 9 on the photoconductive layer 10. Next, this protective toner layer 9
is transferred onto the toner images 2, 3 already deposited on the substrate 1 in precise alignment with the images 2, 3, and fixed by heating. Figure 1g
shows the final result.

[Brief explanation of drawings]

FIG. 1a is a schematic diagram showing a state in which the substrate 1 is imagewise covered with toners of imagewise different colors;
FIG. 1b shows that a toner image is formed from a protective toner 7 on a photoconductive coating 6 using a first color separation 4, the toner image being precisely registered on the image to be protected. FIG. 1c is a schematic diagram illustrating the result of the condition of FIG. 1b; FIG. Figure 1e is a diagram showing the good condition of Figure 1d, Figure 1f is developed with a protective toner. Image 2 where the toner image is protected,
Figure 1g is a diagram showing the final result. 1... Substrate, 2, 3... Toner part (toner image), 4, 5... Transparent color separation film, 6
...Photoconductive coating, 7,8...Protective toner, 9
...Toner image, 10...Photoconductive coating.

Claims (1)

[Scope of Claims] 1. A photoconductive substrate is electrically charged and discharged in accordance with a latent image formed by exposure to light, and then a colored toner is used to develop the latent image, and the resulting toner image is covered. A method of forming a protective transparent coating on a colored toner image obtained by transfer to a transfer substrate, the protective transparent coating being based on the same original image formed on the photoconductive substrate. , a toner image formed on a substrate, characterized in that the protective transparent coating is formed by a protective transparent toner, and is fixed after being obtained by vertically aligning the protective transparent coating with the image on the transfer substrate. A method of forming a protective transparent film on. 2. A plurality of color separation films are used to form the colored toner images, and a plurality of toner images of different colors are sequentially formed with accurate alignment by these color separation films. after,
A colored toner image is obtained by being transferred onto a transfer substrate, and the cycle of depositing the protective transparent film on the toner image is repeated the same number of times as the color separation film is used. A method of forming a protective transparent coating on a toner image formed on a substrate according to claim 1. 3. A plurality of color separation films are used to form the colored toner images, and a plurality of types of toner images of different colors are sequentially formed with accurate alignment by these color separation films. after,
A colored toner image is obtained by being transferred onto the transfer substrate, and further, all the color separation films used in each of the above steps are aligned with each other,
A protective transparent coating is applied to a toner image formed on a substrate according to claim 1, wherein formation of said second protective toner coating is initiated by a single exposure of a photoconductive coating layer. Method of forming a film. 4. A method of forming a protective transparent coating on a toner image formed on a substrate according to any one of claims 1 to 3, wherein the protective toner coating is colorless.