JPH03111719A - Wet type method and apparatus for forming image - Google Patents

Abstract

PURPOSE:To employ only one developer and thereby to make it possible to make an apparatus small in size by coating an image forming member with a developing agent prepared by dispersing in a dispersion medium two color materials charged to have different polarities, and by forming each color image collectively thereafter by control means of electric fields of two polarities. CONSTITUTION:A developing agent 8 containing toner of two colors is applied in a prescribed thickness on the surface of an image bearing body 4, and positive ions are made to stick selectively on the surface of a developing agent layer in a first ion current control device 6. Next, negative ions are made to stick thereon selectively in a second ion current control device 7. When a transfer roller 2 is brought into pressure contact with the image bearing body 2, subsequently, only a toner image is transferred onto the transfer roller 2 and made to stick thereon by a mechanical adhesion. Since the image bearing body 4 and the roller 2 are in the pressure contact with each other on the occasion, a surplus of a developing liquid is pressed out and removed and a surplus of the developing agent is not transferred onto the roller 2. By applying a pressure between the roller 2 and a pressure roller 1 with recording paper 3 interposed, subsequently, the toner image in a wet state is transferred mechanically onto the recording paper 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming method and apparatus for forming two-color images.

[Conventional technology]

As a conventional multicolor image forming apparatus, a method is known in which a dry toner is used, a toner image is formed for each color on a photosensitive drum, and the toner image is repeatedly transferred onto recording paper. Another known method is to use dry toner to form positive and negative electrostatic latent images on a photoreceptor, develop them with two colored toners charged with different polarities, and transfer them all at once to recording paper. 1-15869).

[Problem to be solved by the invention]

In the former case, in the conventional apparatus described above, it is necessary to provide a developing device for each color and arrange it around the photoreceptor. Further, since each color is transferred to the recording paper, the toner images of each color are likely to be misaligned on the recording paper, which poses a difficulty in the construction of the apparatus. These problems have resulted in the device being complicated and large in size. In the latter case, it is also necessary to provide a developing device for each color, and furthermore, it is necessary to use a photoreceptor of a special construction, resulting in a complicated and expensive apparatus.

An object of the present invention is to solve these problems and realize a compact two-color image forming apparatus with a simple configuration.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a method for applying a liquid developer in which a first color and a second color colorant charged with different polarities are dispersed in a dispersion medium to an image forming member, and then applying a liquid developer to the image forming member. This constitutes a wet image forming method in which a two-color image is formed on an image forming member by selectively controlling an electric field, and the apparatus used to carry out this method includes a first color and a second color charged to different polarities. a coating means for applying a liquid developer dispersed in a coloring material dispersion medium to the image forming member; and a liquid developer provided close to the surface of the image forming member and applied to the image forming member by the coating means. A wet image forming apparatus was constructed which includes electric field control means for selectively controlling the electric field near the agent.

〔Example〕

Next, the method and apparatus of the present invention will be explained based on examples. FIG. 1 is a diagram showing the configuration of a printer showing an embodiment of the present invention. Reference numeral 4 denotes an image forming member, which is constituted by a hollow drum-shaped image carrier made of metal. A developer 8 in which a positively charged first color pigment and a negatively charged second color pigment are dispersed in a dispersion medium is stored around the image carrier 4, and the developer 8 is applied to the image carrier 4. liquid coating device 5;
First and second ion flow control devices 6 as electric field control devices
．． 7, a transfer roller 2 and a pressure roller 1 are arranged.

The developer 8 includes a positively charged resin (hereinafter referred to as first color toner) containing a first color pigment in an insulating carrier liquid solvent, and a negatively charged resin containing a second color pigment. It is composed of a resin (hereinafter referred to as second color toner) dispersed therein. The application roller 9 applies the liquid developer 8 to the surface of the image carrier 4, and the regulating plate 10 controls the application thickness. The configurations of the first and second ion flow control devices 6.7 are shown in FIG. An opening 22 is provided in the center of an insulating substrate 21 with a thickness of 0.1 mm, a common electrode 24 is formed on one side, and a 1/300 inch electrode is formed on the other side.
Control electrodes 23 are formed at a pitch of h. An ion generator using a corotron is installed on top of this. In other words, a tungsten wire 25 having a diameter of 0.05 mm is shielded with a stainless steel housing 26 at a distance of about 5 mm. As shown in FIG. A potential difference is provided, and by connecting the switch 30 to the terminal 31, the ion flow of positive ions generated in the ion generator is blocked, and by connecting it to the terminal 32, the positive ion flow is directed to the developer on the image carrier 34. selectively deposited over layer 36; In this embodiment, the power supply 33 is 3KV, and the power supply 34 is 900V.
(2) The power source 3.5 is set to 900 V, and a predetermined ion flow control is performed so that positive ions generated around the wire 25 pass through the opening 22 and reach the developer surface. The second ion flow control device 7 has the same configuration as the first ion flow control device 6, and controls the negative ion flow generated by connecting a power source with a different polarity.

The transfer roller 2 is composed of a metal roller having an elastic layer 11 on its surface, and is pressed between the pressing roller 1 and the image carrier 4 facing each other.

Next, the image forming operation will be explained. A developer 8 containing two color toners is applied to the surface of the image carrier 4 to a constant thickness,
In the first ion flow control device 6, positive ions are selectively attached to the surface of the developer layer.

Next, in the second ion flow control device 7, negative ions are selectively attached. FIG. 4 shows positively charged toner particles 42 of the first color, negatively charged toner particles 43 of the second color, positive charges 44 and negative charges 45 on the surface of the developer in the developer layer 41 of the image carrier 4.
2 schematically shows how a toner image adheres on an image carrier. Note that the charged toner in a non-attached state dispersed in the developer and the counter charges are not shown for the sake of simplicity. As shown in this figure, since the developer dispersion medium is insulating, the ions remain on the developer surface and form an electric field between it and the image carrier surface.

The positively charged toner 42 receives electrostatic force from the electric field generated by the positive charges on the developer surface and moves by electrophoresis toward the surface of the image carrier, forming a toner image on the surface of the image carrier. The toner 43 having a negative charge similarly moves toward the surface of the image carrier by the electric field generated by the negative charge on the surface of the developer and forms a toner image.

Next, when the transfer roller 2 is brought into pressure contact with the image carrier 4, the toner (
Only the image is transferred and adhered onto the transfer roller 2 by mechanical adhesive force. At this time, since the image carrier 4 and the transfer roller 2 are in pressure contact, the excess developer is pushed out and removed, and the excess developer is not transferred to the transfer roller 2. Next, by applying pressure between the transfer roller 2 and the pressure roller 1 with the recording paper 3 interposed, the wet toner image is mechanically transferred onto the recording paper 3. After this, a fixing step for drying the toner image on the paper may be provided, but in this embodiment, natural drying is performed.

In the above configuration, the image carrier 4 and the transfer roller 2 can be transferred without any deterioration by making their outer peripheral surfaces smooth. Furthermore, since the outer peripheral surface of the transfer roller 2 has elasticity, even when the surface of the recording paper has low smoothness, the toner image can be transferred onto the recording paper 3 by pressure without causing image deterioration. Ions remaining on the surface of the liquid developer are removed by the ion flow control device 6.
Since the electrostatic field continues to be applied to the toner even after passing step 7, it is sufficient to complete the image formation on the image carrier before the transfer step, and there is no restriction on the time required for the electrophoretic movement of the toner.

As an electric field control device, a stylus-shaped electrode having the structure of this embodiment is arranged close to and opposite the surface of the image carrier, and the electric field in the vicinity is selectively controlled to cause toner to adhere. You can also do it.

The transfer from the image carrier 4 to the recording paper 3 may be performed by directly bringing the recording paper 3 and the image carrier 4 into contact without using the transfer roller 2.

As described above, according to this embodiment, toners having positive and negative charges are mixed in advance and used as a single developer 8 on the image carrier 8.
The structure is such that only the desired toner is applied to the surface of the toner and the nearby electric field is controlled to adhere only the desired toner, so only one developing device is required and image formation can be performed continuously by using two electric field control devices. Further, a two-color image can be formed by one rotation of the image carrier 4. Therefore, the image carrier 4 may have a small diameter, and the apparatus can be made simple and compact. Furthermore, since the formed two-color toner image is transferred to the recording paper 3 all at once, it can be transferred without any color shift. Furthermore, since a wet developer is used, images with vivid colors and high resolution can be obtained.

〔Effect of the invention〕

As explained above, the present invention applies a liquid developer in which two color materials charged with different polarities are dispersed in a dispersion medium to an image forming member, and then forms images of each color at once using a bipolar electric field control means. Therefore, only one developing device is required, and the apparatus can be miniaturized.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a printer showing an embodiment of the present invention. FIG. 2 is a diagram showing the configuration of an electric field control device used in a printer showing an embodiment of the present invention. FIG. 3 is a diagram showing the electrical relationship of an electric field control device used in a printer showing an embodiment of the present invention. FIG. 4 is a diagram showing a toner image forming process. 4.31 Transfer roller Image carrier Developer coating device Ion flow control device Developer and above

Claims (2)

[Claims] (1) After applying a liquid developer in which first color and second color coloring materials charged with different polarities are dispersed in a dispersion medium to an image forming member, an electric field is selectively controlled on this image forming member. A wet image forming method characterized by forming a two-color coloring material image on an image forming member. (2) a coating means for coating the image forming member with a liquid developer in which first color and second color coloring materials charged with different polarities are dispersed in a dispersion medium; and a coating means provided close to the surface of the image forming member. is,
A wet type image forming apparatus comprising: an electric field control means for controlling an electric field near the liquid developer applied to the image forming member by the application means.