JPH03107181A - Fixing system in wet copying machine - Google Patents

Abstract

PURPOSE:To prevent image flowing and to maintain a prescribed image density and solid uniformity by employing an OHP sheet as transfer paper and specifying the amount of solvent attaching to the OHP sheet and the specific heat of the OHP sheet used. CONSTITUTION:An electrostatic latent image on a photosensitive drum is developed with thermal crosslinked toner on a transfer paper fed from a paper feeder not shown here, and the toner image on the photosensitive drum is transferred onto the transfer paper in a transfer part. The transfer paper is fed from the right of a shown fixing device, and fixed with press-contact between a fixing roller 2 possessing a heat source 1 and a pressure roller 3. The OHP sheet is used for the transfer sheet, and the amount of the solvent attaching to the OHP sheet is a minimum of 250mg/AA, and the specific heat of the OHP sheet used is lower than 0.25cal/g.C deg..

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fixing method that improves fixing performance by specifying the physical properties and shape of an OHP sheet used in a wet copying machine. .

[Conventional technology]

Conventionally, wet-type copying machines have been provided with a fixing device having the configuration shown in FIG. That is, the transfer paper P on which the toner image has been transferred from the photoreceptor drum is connected to the conveyance roller 12 and the heat source 1 inside.
The toner image on the transfer paper P is fixed by passing between the heat plate 14 on which the transfer paper P is placed.

With this type of fixing device, as the speed of copying machines increases and double-sided copying is implemented, especially during double-sided copying, the image surface is
This is causing problems such as images being moved due to sliding contact.

In order to solve this problem, the fixing device was improved as shown in FIG. In this fixing device, even during double-sided copying, when the transfer paper P passes between the heat roller 16 having heat a15 and the press roller 17, the image surface of the double-sided copy faces downward and comes into contact with the heat roller 16. Also, due to the rotation of the heat roller 16, double-sided copying can be performed without rubbing the image surface.

In this fixing device, when double-sided copying is performed in large quantities, since a metal roller is used as the heat roller 16, toner adheres to the heat roller 16, and this adhered toner is transferred between the heat roller 16 and the cleaning pad 18. Over time, the toner becomes a reservoir 19, and if it is left for a long time,
The heat roller 16 and cleaning pad 1 become stuck together.
8 is locked, resulting in problems such as damage to the drive gear.

Therefore, the present inventors developed a fixing device for a wet copying machine.
We are currently studying and developing a configuration as shown in Figure 1.

According to this device, the above-mentioned problems are solved by constructing both the fixing roller 2 and the pressure roller 3 using silicone rubber rollers that have a releasing property from toner components.

[Problem to be solved by the invention]

As a suitable means for fixing a large amount of double-sided copies as described above, in a fixing device in which the fixing roller and the pressure roller are made of silicone rubber rollers, OH is used as the transfer paper.
P (abbreviation for Over Head Projector)
When a sheet is used, a problem unique to wet-type copying machines is that the developer (solvent) does not penetrate into the OHP sheet, resulting in a problem of image smearing.

In order to solve this problem, reducing the amount of solvent attached to the OHP sheet eliminates the image flow and reduces the amount of solvent attached to the OHP sheet.
Although P fixability is improved, it has been confirmed that it is difficult to maintain image density and solid uniformity with the current process.

Based on this premise, the present invention uses an OHP sheet as the transfer paper in the fixing device of a wet-type copying machine, and eliminates the unique image flow of a wet-type copying machine without reducing the amount of solvent attached to the OHP sheet. It is an object of the present invention to provide a fixing method that can prevent the occurrence of such problems and maintain a predetermined image density and solid uniformity. This was confirmed through experiments and without changing the fixing device or process.
The purpose is to solve the above-mentioned problems by specifying the material and shape of the OHP sheet.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention performs development using a thermally crosslinkable toner, transfers the obtained toner image, and heats the transferred transfer paper by placing it on the toner image transfer surface side. 1 by the fixing roller and the pressure roller located on the opposite side.
- In a wet type copying machine that fixes a toner image, an OHP sheet is used as the transfer paper, and the amount of solvent attached on the OHP sheet is at least 250 mg/AA, and the OH
It is characterized in that the specific heat value of the P sheet is lower than 0.25 cal/g・℃, and instead of the specific heat value of the OHP sheet used, its thickness is characterized in that it is 100 μm or less.

[For production]

With the configuration of the present invention, a predetermined amount of solvent on an OHP sheet can be sufficiently volatilized in an existing fixing device without applying an excessive amount of heat, and the OHP fixing performance can be improved while avoiding the phenomenon peculiar to wet-type copying machines. It produces an effect that does not cause a certain flow of images.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

A fixing device of a wet type copying machine to which the present invention is applied will be explained with reference to FIG.

Transfer paper is fed from a paper feeder (not shown), which develops an electrostatic latent image on a photoreceptor drum using a thermally crosslinkable toner, and transfers the developed toner image on the photoreceptor drum to a transfer section. The image is transferred from the right side of the fixing device shown in FIG.

The transfer paper is fixed under pressure at a predetermined nip width between a fixing roller 2 having a heat source 1 inside and a pressure roller 3. Fixing roller 2. The pressure roller 3 is made of silicone rubber, and the fixing roller 2 is in contact with a silicone application pad 4 impregnated with silicone oil as a release agent, and excess silicone oil is collected in an oil sump 5. ing. The fixing roller 2 is formed by coating the surface of a hard roller with fluororesin, and the pressure roller 3
Forms a silicone rubber layer on the outer layer.

6 is a thermistor, and 7 is a temperature fuse provided close to the fixing roller 2. The thermistor 6 and the temperature fuse '1 control the heat source 1 so that the fixing roller 2 has a predetermined temperature.

In order to prevent the transfer paper that has passed between the fixing roller 2 and the pressure roller 3 from wrapping around the fixing roller 2, the fixing roller 2
A separation claw 8 is disposed in contact with the separation claw 8, and the transfer paper guided by the separation claw 8 is discharged to the outside of the machine by a paper discharge roller 9. A pressure cam 10 comes into contact with the pressure roller 3, and in order to urge the pressure roller 3 toward the fixing roller 2, the pressure spring 11 rotates the pressure cam 10 clockwise about the shaft 10a. are doing.

In a fixing device with such a configuration, when an OHP sheet is used as the transfer paper, the developer (solvent) does not permeate into the OHP sheet, which is a phenomenon peculiar to the wet development process. The amount of developer is large, and in order to volatilize this large amount of developer between the fixing nip of the two rollers, it is necessary to supply an excessive amount of heat. O
It is very difficult to supply the amount of heat necessary to volatilize the developer (solvent) on the HP sheet.

In the present invention, in a fixing device having such a configuration, by using an OHP sheet as a transfer paper, it is extremely difficult to supply the amount of heat necessary to volatilize the developer (solvent) on the OHP sheet. Therefore, the amount of developer (solvent) on the OHP sheet should be reduced, and the amount of solvent and OHP fixing properties (here, OHP fixing properties refers to the image area immediately after fixing and ejection, by rubbing the image area with your finger and fixing the image). (The degree of peeling of the parts is judged and ranked to decide whether it is good or bad.)

As a result, the amount of solvent deposited on OHP Sea F was 250mg/
If it is less than AA, preferably less than 200 mg/AA,
Problems with wet development such as image bleeding and OHP fixability are
It was confirmed that it was in good condition.

In the current fixing device and process shown in Fig. 1, in order to maintain image density and solid uniformity, if the amount of solvent attached is less than 250 mg/AA, a problem will occur, and the amount of attached solvent must be reduced. It cannot be lower than 25off1g/AA.

In order to eliminate image smearing, which is a problem with wet development, without deteriorating image density and solid uniformity, and to improve OHP fixing performance, OHP used for wet type copying machines is required.
We focused on identifying the material and shape of the sheet.

The polyester film used as an OHP sheet has a specific heat value of 0.32 cal/g・℃,
It was confirmed that the magnitude of the specific heat value has a large effect on OHP fixing properties.

In other words, when the specific heat of the OHP sheet is large, the amount of heat during fixing is absorbed by the OHP sheet, and there is insufficient heat to volatilize the amount of solvent on the OHP sheet. The fixing properties are poor.

In the present invention, the OHP sheet has a specific heat value of 0.25 c.
By using a polytetrafluoroethylene film with a low al/g·°C, OHP fixing properties can be significantly improved.

In this case, OHP fixability can be improved by keeping the thickness of the HP sheet constant and using a film with a small specific heat value.

01-I P sheet has a specific heat value of 0.3 cal/g
・Polyvinyl chloride (specific heat 0.2
4 cal/g・"C), which has a melting point of 212
℃, it has the disadvantage of being vulnerable to troubles such as when the temperature of the fixing roller rises abnormally or when the OHP sheet gets wrapped around the fixing roller.In contrast, the polytetrafluoroethylene film has a melting point of 327℃. This is extremely high, and even if the above-mentioned troubles occur, it has enough margin to withstand high temperatures.

Polyethylene film (specific heat: 0.3 cal/g・"c) currently used for wet-type copying machines and polytetrafluoroethylene film (specific heat: 0.25 cal/g・"c)
When using l/g·“C) under the same conditions, the latter film was able to obtain better OHP fixing properties.

Furthermore, in the present invention, good OHP fixing properties can be obtained by reducing the thickness of the OHP sheet in order to compensate for the lack of heat required to volatilize the molten metal on the OHP sheet.

In other words, assuming that when an OHP sheet is passed between the fixing roller and the pressure roller of the fixing device, a constant amount of heat is applied to the surface of the OHP sheet per unit area, the OHP sheets made of the same material Therefore, a thinner OHP sheet requires less heat per unit area, and therefore more heat can be supplied for solvent volatilization and toner melting, and good OHP fixing properties can be obtained. I can do it.

Polyester and polyethylene films currently used as OHP sheets (specific heat 0.3 cal/g ・'
The thickness t of C) is 110 um t 100 g m
, 50μm, and these three types of films have 2
Apply a solvent adhesion amount of 501 ng/AA, pass between the fixing roller and pressure roller of the fixing device shown in Figure 1, rub the image area with your finger immediately after ejection, and rank and judge the degree of peeling of the image area. did. Note that rank 5 indicates excellent fixing properties, and rank 1 indicates poor fixing properties.

The experimental results are shown in the table.

As described above, if the thickness of the OHP sheet is 100 μm or less, good OHP fixing properties can be obtained.

〔effect〕

According to the structure of the present invention, when an OHP sheet is used as a transfer paper, it is possible to improve the 0) IP fixability without applying an excessive amount of heat to the solvent on the OHP sheet.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a fixing device of a wet-type copying machine to which the configuration of the present invention can be applied, and FIGS. 2 and 3 are schematic cross-sectional views of a fixing device of a conventional wet-type copying machine, respectively. 1...Heat source, 2...Fixing roller, 3...Pressure roller, 4...Silicone application barad.

Claims (2)

[Claims] (1) Development is performed using a thermally crosslinkable toner, the resulting toner image is transferred, and the transferred transfer paper is placed between a heating fixing roller placed on the toner image transfer surface side and a heating roller placed on the opposite side. In a wet type copying machine that fixes a toner image using a pressure roller, an OHP sheet is used as the transfer paper, the amount of solvent attached on the OHP sheet is at least 250 mg/AA, and the value of the specific heat of the OHP sheet used is 0.25ca
A fixing method in a wet type copying machine characterized by having a value lower than l/g·°C. (2) Development is performed using a thermally crosslinkable toner, the resulting toner image is transferred, and the transferred transfer paper is placed between a heating fixing roller placed on the toner image transfer surface side and a heating roller placed on the opposite side. In a wet copying machine that fixes a toner image using a pressure roller, an OHP sheet is used as the transfer paper, the amount of solvent adhering on the OHP sheet is at least 250 mg/AA, and the thickness of the OHP sheet used is 100 μm or less. A fixing method in a wet copying machine, characterized by: