JPH0243567A - Fixing system in wet image formation - Google Patents

Abstract

PURPOSE:To obtain lustrous, excellent color reproducibility and to improve coloring by performing the heating processing of a wet toner image with a liquid carrier left in the wet toner image, as it is. CONSTITUTION:The wet toner image on a recording sheet is heated with the liquid carrier left in the wet toner image, as it is. The wet toner image is heated so that it repeats fine vibration as the one generated when toner is boiled while volatilizing liquid carrier gas. When liquid carrier gas is volatilized, toner particles are agitated as if they were boiled. The toner particles become almost uniformly compatible and are rearranged by the agitating action, whereby a toner image surface is changed into a smooth, transparent one. Thus, lustrous, excellent color reproducibility can be obtained and coloring can be improved.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a fixing method in wet image formation, and more specifically, the present invention relates to a fixing method in wet image formation. The present invention relates to a fixing method in wet image formation in which a wet 1-toner image is heated and fixed.

[Prior Art] In various image forming apparatuses such as electrostatic copying machines, facsimile machines, and printers that employ a wet development method, an electrostatic latent image formed on the surface of a photoreceptor in accordance with image information is transferred to a liquid carrier. A wet toner image is obtained by developing with a liquid developer in which toner particles are dispersed, and the wet toner image is transferred to recording paper by electrophoresis, and then the wet toner image on the recording paper is heated. I'm trying to fix it. The toner particles used in the wet development method have an extremely small particle size compared to the toner particles used in the dry development method (approximately 1 μm or less in the wet method compared to approximately 1 μm in the dry method), so they have excellent resolution and toner transparency, and can produce high-quality color images. It has the advantage of being able to obtain images.

For example, in the wet electrophotographic method described in JP-A No. 61-205954, a band is formed on the surface of a photoreceptor.
After repeating each cycle of exposure, wet development, and drying for each 3 to 4 color developer to form a dried full-color toner image, a resin liquid is applied to the dried full-color toner image or recording paper. Then, a recording paper is brought into pressure contact with the dried full-color toner image, so that the full-color toner image is transferred to the recording paper side with adhesive force.As a result, the full-color toner image is encapsulated in the resin liquid. It is becoming established.

Although it is possible to obtain good color reproducibility and fixability with such wet image formation, it is complicated and costly because it requires appropriate handling using a resin liquid in addition to a developer. ing.

As a wet image type that does not use resin liquid, 1, for example, US Patent 4
, 547,061. In this method, each cycle of charging, exposure, wet development, toner image transfer to pre-wet paper, and drying is repeated for each three to four color developer. This method is a so-called color proofing method, and the toner image is dried each time one color is transferred.

The transfer principle of wet toner images is exactly the same as development,
Toner particles are electrophoresed through a liquid carrier to which a constant transfer electric field is applied. Therefore, at the time of transfer, unless a suitable amount of liquid carrier is filled between the surface of the photoreceptor and the surface of the recording paper, uniform transfer of the toner image is impossible. If there is too much, image blurring or blurring will occur. In a color image forming process in which such a transfer process is repeated multiple times, the first
The liquid carrier absorption characteristics of the recording paper change depending on the transfer state of the color and the transfer state of the second and subsequent colors that are superimposed thereon. A method for obtaining the same transfer characteristics as the first color for the second and subsequent colors is to dry the wet toner image after each color transfer, as in the wet electrophotographic method described in the above-mentioned U.S. Pat. No. 4,547.061. How to maintain the initial state of recording paper and how to remove excess developer remaining on the photoreceptor.
There is a method of controlling the color so that it changes between the color and the second and subsequent colors.

[Problems to be Solved by the Invention] However, the conventional wet image forming method that has been improved in this way is intended to obtain a uniform transferred image, and it is difficult to improve the color reproducibility and color development in fixing the transferred image. It's not something you do. That is, these conventional methods have a problem in that the compatibility of each color toner is poor and color reproducibility is poor.

Therefore, the present invention provides a fixing method for wet image formation, which makes it possible to obtain glossy and good color reproducibility through a fixing action consisting of simple steps, and to obtain high-quality images with improved color development. The purpose is to do.

[Means for Solving the Problems] In order to achieve the above object, the present invention develops an electrostatic latent image formed on the surface of a photoreceptor using a liquid developer made of toner particles dispersed in a liquid carrier. obtain a toner image,
In a fixing method in wet image formation in which the wet toner image is transferred to a recording paper by electrophoresis and then fixed by heating the wet toner image on the recording paper, the step of heating the wet toner image has a configuration in which it is carried out with the liquid carrier remaining in the liquid toner image.

[Function] In the means having such a configuration, the wet toner image on the recording paper is heated while the liquid carrier remains in the wet toner image. By heating the wet toner image, the liquid carrier gas is volatilized while the wet toner image repeats micro-vibrations similar to boiling, and when the liquid carrier gas is volatilized, the toner particles are disturbed in a boiling-like manner. Due to this disturbing action, the toner particles are almost uniformly dissolved and rearranged, so that the toner image surface becomes smooth and transparent.

[Implementation example] Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 2 shows an example of a fixing device for implementing the present invention. As shown in this figure, the recording paper 2 onto which the toner image 1 has been transferred is guided by a pair of entrance guide rollers 3, 3 and fed into a nip portion between a fixing hot plate 4 and a fixing guide roller 5.

Concave and convex portions 3a and 5a are formed extending in the axial direction on the surfaces of one of the entrance guide rollers 3 and the fixing guide roller 5 that come into contact with the toner image forming surface side of the recording paper 2. The area of contact with the imaging surface is reduced. The above fixing heat plate 4
A plurality of heaters 4a are provided inside the fixing heat plate 4, and the surface portion of the fixing heat plate 4 has a certain curved surface configuration for good contact with the recording paper 2.

Furthermore, the recording paper 2 sent out from the nip between the fixing heat plate 4 and the fixing guide roller 5 is guided by a pair of paper discharge guide rollers 6.6 and discharged. An uneven portion 6a is formed extending in the axial direction on one surface of the paper discharge guide roller 6 that comes into contact with the toner image forming surface of the recording paper 2, thereby reducing the contact area with the toner image forming surface. is now being reduced.

An embodiment of the present invention will be described based on FIG.

In the embodiment shown in FIG. 1, magenta toner and cyan toner are transferred onto the recording wcZ in a superimposed manner to form a wet toner image. That is, in the state immediately after transfer shown in FIG. 1(a),
Magenta toner (marked by O), which is the first color toner, is transferred onto the recording paper 2, and cyan toner (marked by *) is also transferred onto this magenta toner. Since the transfer operation of each of these toner particles is performed based on electrophoresis, the liquid carrier is also attached to the side of the recording paper 2 together with the toner particles, and the liquid carrier covers the toner particles to transfer the wet toner. The image is constructed.

In the conventional method, drying is performed immediately after transfer to volatilize the liquid carrier gas from the wet toner image.

However, when such drying is performed, the liquid carrier gas is simply evaporated, and the arrangement of the toner particles and the unevenness of the surface remain unchanged. Even if the toner image in such a dried state is sent to a fixing step and heated, the image density and gloss remain almost unchanged except for slight deformation due to melting of the toner particles.

-6 In the present invention, the wet toner image with the liquid carrier remaining without drying as described above is sent to the fixing step and heated. That is, as shown in FIG. 1(b), the wet toner image with the liquid carrier remaining is heated in the fixing step.

In this heat fixing step, the liquid carrier gas is volatilized from the wet toner image while repeating micro-vibrations similar to boiling, and when the liquid carrier gas is volatilized, the toner particles are agitated in a boiling-like manner. Due to this disturbance, the toner particles of each color, which were superimposed in two layers, are more or less uniformly dissolved and rearranged, as shown in Figure 1 (C), and the toner image surface changes to be smooth and transparent. That will happen. As a result, the color development is improved, the surface gloss becomes better, the color tone becomes more vivid, and
Furthermore, image density is also improved.

The present invention is even more effective when using a liquid developer in which toner particles contain wax-like substances or polyolefin resins having a softening point below the boiling point of the liquid carrier. When using such a liquid developer,
During heating, the wax-like substances or polyolefin resins are melted and liquefied and are completely compatible with the liquid carrier, increasing the amount of liquid carrier in the liquid toner image, resulting in a layer with low viscosity. Disturbance and rearrangement of the toner particles (in this case rather the colorant particles) will be promoted in the solidified form.

Suitable examples include paraffin wax with a softening point of 60 to 80°C and low molecular polyethylene with a softening point of 80 to 116°C.

The following table shows the comparison results between the present invention and the conventional example. Both of them are color copies of Kodak Power Patch, and the developing method used in the present invention is to reduce the amount of excess developer on the surface of the photoreceptor for the second and subsequent colors than for the first color. In addition, as a conventional fixing method, a method is adopted in which a toner image obtained by drying a transferred image for each color is heated and fixed.

In the present invention, the amount of liquid carrier deposited on the recording paper is 90 μ/A4, and the density is measured using a Macbeth RD-915 reflection densitometer. has been done. The glossiness was measured using a gloss meter of Nippon Heavy Industries G-2P-D3 model, and is expressed as a light reflectance (%) at an incident angle of 60°.

As is clear from the table, the image density and glossiness of the present invention are significantly improved compared to the conventional example.

[Effects of the Invention] As described above, the present invention has the advantage that the heating process of a wet toner image is carried out by the wet toner image so that the toner particles in the wet toner image on the recording paper are disturbed and arranged uniformly during the fixing process. Since the process is performed with the liquid carrier remaining in the toner image, it is possible to obtain glossy and good color reproducibility with a simple fixing process without performing processes such as overcoating with resin liquid. It is possible to obtain high-quality images with improved performance.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (c) are schematic diagrams showing the state immediately after transfer, the state of carrier gas volatilization, and the state after carrier gas volatilization in a fixing method according to an embodiment of the present invention, respectively; FIG. 2 is an explanatory side view showing an example of a fixing device for implementing the present invention. 1... Toner image, 4a... Heater 2... Recording paper, 4... Fixing hot plate,

Claims (1)

[Claims] The electrostatic latent image formed on the surface of the photoreceptor is developed with a liquid developer made of toner particles dispersed in a liquid carrier to obtain a wet toner image, and the wet toner image is transferred to recording paper by electrophoresis. In a fixing method for wet image formation, in which the wet toner image on the recording paper is fixed by heating the wet toner image, the heating step of the wet toner image does not cause the liquid carrier to remain in the wet toner image. 1. A fixing method in wet image formation, characterized in that the fixing method is performed as it is.