JPS6330869A - Two-color image forming method - Google Patents

Abstract

PURPOSE:To obtain a good two-color image whose picture quality is not deteriorated because of color mixture, by pressing an image carrier against an intermediate transfer body, and bringing a toner layer which contacts directly the intermediate transfer body, among toner layers of a second image into contact with the intermediate transfer body and transiting said layer. CONSTITUTION:A photosensitive body 1 is electrostatically charged uniformly to negative by a charger 2, and thereafter, a light beam from an original 3 having a red image part 3R and a black image part 3B is radiated on the photosensitive body 1 through a red filter 4R, a charge except the part corresponding to the black image part 3B is annihilated, and an electrostatic latent image corresponding to the black image 3B is formed on the photosensitive body 1. This electrostatic latent image is developed by black toner 5B, and a black toner image is obtained. Subsequently, this black toner image which has been reproduced by the black toner 5B is transferred onto an intermediate transfer body 6. In this case, by utilizing a contact transition phenomenon between silicone rubber, etc. and the toner, the toner of a first layer which is in direct contact with the intermediate transfer body 6 is transferred, but the toners of a second layer and a third layer which are in direct contact with each toner and not transferred to the intermediate transfer body 6.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an electrophotographic copying machine that eliminates the need for complicated color separation processes or special photosensitive materials (and eliminates color mixing by simple means). The present invention relates to a method of forming a two-color image.

[Conventional technology]

In a typical electrophotographic copying machine, a single color, generally black, is reproduced regardless of the color of the original.

However, many documents are made up of two colors, such as red and black, and in the case of copying, they are usually reproduced as a single color, making them difficult to distinguish. Further, in order to faithfully reproduce the colors of the original, it is possible to use a color electrophotographic copying machine, but there is a problem that the structure is complicated and the cost is very low.

In order to solve this inconvenience, Japanese Patent Application Laid-Open Nos. 49-117041, 51-120730, and 53-1447 reproduce specific multiple colors with a simple structure.
No. 37, JP-A-54-11732, JP-A-54-56
Many proposals have been made in various publications such as No. 445 and Japanese Patent Application Laid-open No. 73378/1983. However, the various methods that have been proposed so far have had problems in that the equipment is complicated and the selection of developer is also complicated.

An example of these conventional methods is described in Japanese Unexamined Patent Application Publication No. 49-11
The method described in Japanese Patent No. 7041 will be cited and explained.

In the method described in this publication, an image is finally formed by laminating red toner and black toner in order from the upper surface of the photoreceptor, and by controlling the transfer conditions, it is possible to prevent color mixture from being transferred. Moreover, it is possible to obtain a high-7 degree image.

First, the formation of two types of toner layers on the photosensitive material described in Japanese Patent Application Laid-Open No. 49-117041 will be described.

In the exposure process, no matter what wavelength of colored light or filters are used, the black color of the original absorbs all the light, so no light reaches the photosensitive material, and the charge on the photosensitive material is lost. will remain.

In other words, it is not possible to form a latent image from which the black image has been removed. On the other hand, by using a red filter, the red color of the document can be regarded as white to the extent that it is almost indistinguishable from the white background, and can be easily removed.

Therefore, by first exposing the entire image to red light, developing it with red toner, then exposing it to light from which the red has been removed, and developing it with black toner, the black toner is layered on top of the red toner only in the black areas; If only the black toner is transferred in the laminated portion without the red toner in the lower layer being transferred, a two-color retest can be obtained.

[Problem that the invention seeks to solve]

However, in the above-mentioned Japanese Patent Application Laid-Open No. 49-117041, in order to prevent development with a single layer of toner and obtain an image density above a certain level, a portion with a low surface potential is used in the transfer process. According to the content, 5 to 7 kV is an appropriate transfer voltage for corotron transfer.

The transfer voltage ν between 5 and 7 is particularly limited, except when the potential of the photosensitive material is extremely low or when the distance between the photosensitive material and the corotron wire of the transfer device is extremely different from normal conditions. In the range without conditions, the conditions are the same as those normally used in electrophotography, and there is no basis for avoiding color mixing.

Furthermore, even if this were possible, as shown in FIG. 5, when the transfer area is viewed microscopically, the toners 5R and 5B on the photoreceptor 1 have severe unevenness, and the paper 8 has such unevenness. Unable to follow the intense image surface, paper 8 and toner S
A space is formed between R and 5B, and in the case of electrostatic transfer, toner scatters into the space as shown by the arrow due to the orientation of the electric field, causing image blurring (plurer).

Furthermore, in the second developing step, a black toner image is developed on top of the previously formed red toner image, so there is a risk that color mixing may occur in the developing step and the purity of the black color may decrease.

Furthermore, although the conditions are not described in detail in JP-A-49-117041, conductive roller transfer and adhesive transfer are also described.

However, in the case of adhesive transfer, special paper is required, and when an intermediate is used, there is a problem in how to overcome the adhesive force from the intermediate to the paper and transfer. Furthermore, in the case of conductive roll transfer, since it is a press electric field transfer with transfer paper sandwiched between the transfer sheets, there is a drawback that hollowing out of the image causes a phenomenon.

The present invention eliminates the complexity of equipment and materials, which are the biggest drawbacks of the various methods proposed in the past, and in particular solves the problem of toner separation in the transfer process. The purpose of the present invention is to provide a two-color image forming method.

[Means for solving problems]

In order to achieve the object, the two-color image forming method of the present invention forms a first image on an intermediate transfer member using a toner layer of a first color, and forms a second image on an image carrier using a toner layer of a second color. By pressing the image carrier against the intermediate transfer body, the toner layer of the second image that is in direct contact with the intermediate transfer body is contact-transferred onto the intermediate transfer body. It is characterized by causing

[Effect]

The present invention will be described in detail with reference to FIG. 1, which explains the steps of this embodiment in order.

Step (a): The photoreceptor 1 is uniformly negatively charged by the charger 2.

Step (b): Light from the original 3 having the red image area 3R and the black image area 3B is irradiated onto the photoreceptor 1 via the red filter 4R to eliminate charges in areas other than those corresponding to the black image area 3B. . Therefore, by this exposure, an electrostatic latent image corresponding to the black image portion 3B is formed on the photoreceptor 1.

Step (C): This electrostatic latent image is developed with black toner 5B to obtain a black toner image. The image thus created is a reproduction of the black image area 3B obtained by removing the red image area 3R from the original 3 using the black toner 5B.

Step (d): Next, this black toner image reproduced with the black toner 5B is transferred onto the intermediate transfer body 6.

The intermediate transfer body 6 used here is made of, for example, silicone rubber, which has a function that allows one layer of toner to be peeled off and transferred from the surface of an image carrier such as a photoreceptor by the action of pressure, heat, or both. Use a rubber-like substance with

That is, the present invention utilizes the contact transfer phenomenon between silicone rubber or the like and toner, and the toner in the first layer that is in direct contact with the intermediate transfer member 6 is transferred, but the toner in the second and third layers that are not in direct contact is transferred. The toners in the layers come into contact with each other and are not transferred to the intermediate transfer body 6.

Step (e): Next, after cleaning the photoreceptor 1, it is uniformly charged again.

Step (f): Expose with light from the original 3 in the same manner as in step (b). At this time, if particularly necessary, exposure may be performed through the green filter 4G. In this way, the red image area 3R
and forms an electrostatic latent image corresponding to the black image portion 3B.

Step (g): This electrostatic layer image is developed with red toner 5R to obtain a red toner image. In this step, both the red image portion 3R and the black image portion 3B of the original 3 are reproduced as a red toner image.

Step (h): Apply pressure to the red toner image on the photoreceptor.

The toner is transferred onto the black toner image obtained in step (d) carried on the intermediate transfer member 6 by the action of heat or both. At this time, similarly to the case in step (d), the contact transfer effect between the intermediate transfer body 6 and the red toner 5R does not work on the part where the black toner 5B is present, so that the red toner in the red image area 3R Only the toner 5R will be transferred to the intermediate transfer member 6.

Step (i): Next, this black toner 5B and red toner 5
A transfer material 8 such as copy paper is passed between the intermediate transfer body 6 to which R is attached and the pressure roll 7, and the black toner 5B and red toner 5R are transferred and fixed onto the transfer material 8 by the heater lamp 9.

A two-color copy image can be obtained on the transfer material 8 through the above-mentioned steps.

In the embodiments of the present invention, the main purpose is to improve image quality,
Furthermore, in order to facilitate transfer control, it is basic practice to perform single-layer development as much as possible. At this time, although it depends on the toner particle size, it has been confirmed that a density of 1.0 or more can be sufficiently obtained even in the sheep layer, and this can be reproduced from the low density part of the original to the original density part. , and the restriction by concentration is removed.

Furthermore, the present invention employs transfer that utilizes a contact transfer phenomenon that occurs between a transfer target and toner. That is, the present inventors have discovered that by applying an appropriate pressure to the intermediate transfer member 6 such as silicone rubber on the toner layer, only the uppermost layer and only one layer of the toner layer is transferred onto the silicone rubber. , which takes advantage of this phenomenon.

The reason why this phenomenon occurs is not clear, but experimental results show that it is basically unrelated to the type of toner, but conductive toner is somewhat preferable.

Unlike transfer using static electricity, adhesive, etc., this type of transfer does not require a transfer material with special surface treatment or the application of myoelectric potential, and stable images can be obtained under easily controllable working conditions. .

By utilizing this contact transfer phenomenon, it is possible to transfer only the top layer of any laminated toner layer, which not only prevents color mixing when transferring to a car, but also prevents latent image formation and development. This has the effect of simplifying the pre-process. That is, it is possible to provide a system that does not require a foveal latent image potential as in the method described in JP-A-49-117041 and is stable against potential fluctuations.

Further, since it does not rely on electrostatic transfer, it is possible to use a stable conductive toner for development. Furthermore, those having a low latent image potential are also acceptable. Furthermore, since the paper is not sandwiched between the photosensitive material and the photosensitive material, control in the transfer section is further simplified.

Furthermore, according to the above image forming method, since the developing process is completely independent for each color, color mixing does not occur during development. Therefore, a high quality two-color image can be obtained.

Note that, although any image forming method can be used in this method, here, for convenience, an ordinary electrophotographic process has been explained as an example. The gist of the present invention is that it is possible to produce an effect similar to that of color separation when transferring the image formed by the toe formation. Further, although it is assumed that the original is an image consisting of two colors, red and black, and is reproduced in the same colors, it is of course not limited to this.

FIG. 2 shows an example of a system for implementing the invention.

In the figure, 1 indicates a drum-shaped photoreceptor, and the photoreceptor 1
around the charger 2. Exposure section 21. black developing section 22B,
A red developing section 22R, a cleaning section 23, etc. are provided. Note that the exposure section 21 includes a red filter for separating black color. Furthermore, it would be better if there was a green filter for separating red and black from other colors, and the black developing section 22B and the red developing section 22R could be operated independently. .

An intermediate transfer body 6 such as a roll is pressed against the photoreceptor 1, and a pressure roll 7 is further pressed against the intermediate transfer body 6. Note that the intermediate transfer body 6 and the pressure roll 7 may have an internal heater lamp 9.

Next, the operation will be explained using an example of a two-color document of red and black.

First, after the photoreceptor l is charged with the charger 2, the exposure section 21
The original is exposed to light that has passed through a red filter, and then developed in a black developing section 22B. The developed black toner image is pressed against the intermediate transfer body 6, and the toner in contact with the intermediate transfer body 6 is transferred to the intermediate transfer body 6.

Next, in the cleaning section 23, the black toner remaining on the photoreceptor 1 is removed.

Next, after the photoconductor 1 is charged again, the exposure section 2
1, the original is exposed to light that has passed through a green filter, and then developed in a red developing section 22R.

The developed red toner image is pressed against the intermediate transfer body 6, so that only the toner that has come into direct contact with the intermediate transfer body 6 is transferred to the intermediate transfer body 6. Therefore, a two-color image is formed on the intermediate transfer member 6 (see FIG. 1(h)), and then a transfer material 8 such as copy paper is passed between the pressure roll 7 and the intermediate transfer member 6. In this example, the toner is transferred and fixed simultaneously by heating. At this time, since the two-color images are aligned on the intermediate transfer body 6, there is no need for registration adjustment, which is required when adjusting and transferring onto a stretchable material such as copy paper, and the position control accuracy is improved. (Become.

Note that the structure of the photoconductor 1 or the intermediate transfer body 6 is not limited to that shown in FIG. 2, and as shown in FIG. The body 6a may be rotated by rolls 6b and 6c, and the photoreceptor may be a belt-shaped photoreceptor 1a as shown in FIG.
It is also possible to have a configuration in which the rotation is performed by the rotation speed, and furthermore, a configuration in which these are combined is also possible.

〔Example〕

Next, examples of the two-color image forming method according to the present invention will be described.

A negatively charged organic photoreceptor was used as the photoreceptor.

For the first development, conductive-component magnetic brush development was used, using black toner having a resistance of 10" Ω under the conditions of a development gap of 0.51 and a layer thickness formation gap of 0.3. It was developed with

For the second development, non-magnetic component flying development was employed, and development was carried out using red toner under the condition that the development gap was 0.3 va.

In addition, as an intermediate transfer roll, the hardness is 50° and the thickness is 2m.
m silicone rubber (RTV) was used.

Next, each process will be explained.

Step (a): The photoreceptor is negatively charged to -800V.

Step (b): Exposure through a red filter (Ufuten Filter Tone 25 manufactured by Kodak) Step Cc): First development with black toner. As a result, toner adheres only to the black image area of the document.

Step (d): First contact transfer onto an intermediate transfer roll.

That is, only the toner that has come into contact with the intermediate transfer roll is transferred. Therefore, the transferred image has approximately one layer. However, in this example, since conductive toner is used, the developed image is also approximately one layer.

Step (e): After cleaning the photoreceptor, it is negatively charged again to -800V.

Step (f) Exposure to light through a Nigeleen filter (Usoten filter series 58 manufactured by Kodak).

Step (g): Second development with red toner. As a result, red toner adheres to areas of the document corresponding to both red and black.

Step (h): A second contact transfer of red toner is performed on the black image on the intermediate transfer roll by adjusting the registration storage and superimposing it.

At this time, even if red toner overlaps, it will not adhere to areas where black toner has already adhered, so red toner corresponding to the original,
A two-tone black image is formed.

Step (i): A two-color image is transferred and fixed simultaneously onto copy paper under heat and pressure.

Through the above steps, it was possible to obtain a copy of a two-color image in which the two colors were reliably separated.

〔Effect of the invention〕

As described above, in the present invention, in the transfer process, the proximity force of silicone rubber or the like with respect to the toner, that is, the force exerted only on the toner in contact with the toner is utilized.

Therefore, only the toner of a predetermined color of the two-color toner layered can be transferred, and no mixing occurs in the transfer process. Therefore, with a simple configuration, a very good two-color image without deterioration of image quality due to color mixture can be obtained.

Furthermore, according to the above-mentioned image forming method, since the developing steps are completely independent for each color, color mixing does not occur during development, and therefore a two-color image with -layer quality can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a process diagram of a two-color image forming method according to the present invention, FIG. 2 is an embodiment of an image forming apparatus used in the two-color image forming method of the present invention, and FIGS. 3 and 4 are diagrams according to the present invention. FIG. 5 is a schematic cross-sectional view showing other different embodiments, and FIG. 5 is an enlarged cross-sectional view of the transfer section. 1, la: photoreceptor 1b, lc, ld, 6b, 6c
: Roll 2: Charger 3: Original

Claims (1)

[Claims] 1. A first image is formed on the intermediate transfer member using a toner layer of a first color, and a second image is formed on an image carrier using a toner layer of a second color, and then the image carrier is transferred to the intermediate transfer member. A two-color image forming method, characterized in that a toner layer of the second image that is in direct contact with the intermediate transfer body is contact-transferred onto the intermediate transfer body by pressing the toner layer against the intermediate transfer body.