JP2002258654A - Image fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device which has a sufficient offset prevention effect even when image liquid is very little and can realize low energy fixing with a small and a simple configuration while obtaining reliable fixation by increasing cohesive force between coloring particulates or between coloring particulates and a recording medium through the use of the electrical property of coloring particulates. SOLUTION: In a fixing device which fixes an image formed on a recording medium 21 by developers 9b, 10b, 11b and 12b (image liquid) containing thermoplastic coloring particulates by using a fixing roller 22 (heating member) in contact with the image surface, and a pressure roller 24 (recording medium supporting member) which presses the recording medium 21 to the fixing roller 22, and which forms a potential difference between the surface of the fixing roller 22 and the surface of the recording medium supporting member at fixing, the surface of the fixing roller 22 has an e-TFE porous layer 27, and the porous layer 27 is impregnated with a liquid of almost the same component with the image liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet image forming apparatus such as a copying machine, a facsimile, and a printer which forms an image by a wet method.

[0002]

2. Description of the Related Art For example, Japanese Patent Application Laid-Open No. 2000-003061 (Japanese Patent Application No.
18164). In this wet image forming apparatus, a part of the image liquid present in the image on the recording medium is adhered to the fixing heating member in the fixing step, thereby improving the releasability between the heating member and the colored fine particles. And a fixing device for preventing offset.

In a fixing device, by forming a potential difference between a heating member and a recording medium support or applying an electric current, colored fine particles on the recording medium are aggregated to improve the fixing property. It is also conceivable to use a potential difference method.

[0004]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Laid-Open No. 2000-
In a wet image forming apparatus as disclosed in Japanese Patent Application Publication No. 003061, when a sufficient amount of image liquid is present in an image on a recording medium, a sufficient offset prevention effect can be obtained by a fixing process.

On the other hand, in such a wet image forming apparatus, when a nonvolatile liquid is used as an image liquid, the nonvolatile liquid remains in the recording medium after the completion of the fixing step.

However, when the amount of the residual liquid is large,
In addition to impairing the texture of the recording medium (for example, thin paper is seen through), liquid transfer to other objects that come into contact with the imaged recording medium (for example, liquid adhering to a desk) occurs. There is a risk that it will.

Further, the remaining liquid tends to cause a decrease in fixability due to a decrease in adhesion between the colored fine particles or between the colored fine particles and the recording medium. In such a case, it is possible to secure a sufficient fixing property, for example, by employing the above-described fixing method of the potential difference method.

[0008] From such a background, efforts have been made to minimize the amount of liquid adhering to a recording medium. For example,
When forming an image of a liquid developer by an electrophotographic process, the amount of the solvent in the developer itself is reduced (higher concentration), and a liquid removing step is provided in addition to the developing step and the transfer step.

However, a reduction in the amount of image liquid contained in an image on a recording medium is a factor that makes it difficult to obtain the effect of preventing offset in the fixing step without repairing.

Therefore, in order to expect the effect of preventing the offset, it is preferable that the surface layer material of the heating member is made of a fluorine-based resin having excellent releasability.

However, the fact that the releasability of the heating member is excellent means that not only the adhesion of the colored fine particles to the heating member is reduced, but also that the image liquid is easily repelled by the heating member. That is, it is difficult to form a release layer of an image liquid for preventing offset on the surface of the heating member.

In the case where a mechanism for separately applying a release liquid such as silicone oil to the heating member is provided for the purpose of preventing offset, efforts are made to reduce the amount of image liquid in the upstream process. On the contrary, the liquid is supplied into the recording medium. further,
Providing a release liquid application mechanism to the heating member means that
In addition to increasing the size and complexity of the fixing device, the side effect of increasing energy consumption due to an increase in heat capacity is also significant.

In the present invention, the fixing property can be obtained by increasing the cohesive force between the colored fine particles or between the colored fine particles and the recording medium by utilizing the electrical characteristics of the colored fine particles. It is an object of the present invention to provide a fixing device which has a sufficient offset prevention effect even when the number is small, and can realize low-energy fixing with a small and simple configuration.

[0014]

In order to achieve the above object, an image fixing apparatus according to the first aspect of the present invention is an image fixing apparatus for transferring an image formed on a recording medium by an image liquid containing thermoplastic colored fine particles. Fixing is performed by a heating member that contacts the image surface and a recording medium supporting member that presses the recording medium against the heating member, and at the time of fixing, a potential difference is generated between the surface of the heating member and the surface of the recording medium supporting member. Is characterized in that the surface of the heating member is a porous layer, and the porous layer is impregnated with a liquid having substantially the same components as the image liquid.

Further, in order to achieve the above object, the present invention provides a second aspect.
The image fixing device according to the invention described in (1), an image formed on a recording medium by an image liquid containing thermoplastic colored fine particles,
The fixing is performed by a heating member that contacts the image surface and a recording medium supporting member that presses the recording medium against the heating member, and at the time of fixing, the fixing member is disposed between the surface of the heating member and the surface of the recording medium supporting member. The fixing device for forming a potential difference is characterized in that the surface of the heating member is a porous layer, and the porous layer is impregnated with a liquid having substantially the same components as the image liquid.

According to a third aspect of the present invention, there is provided an image fixing apparatus comprising:
The image fixing device according to claim 1 or 2, wherein the liquid supply to the porous layer is performed by an image liquid contained in an image formed on a recording medium.

An image fixing device according to a fourth aspect of the present invention comprises:
The image fixing device according to any one of claims 1 to 3, wherein the porous layer is a PTFE (polytetrafluoroethylene) porous film.

The image fixing device according to the present invention is characterized in that:
In the image fixing device according to the fourth aspect, the porous PTFE membrane is an expanded porous PTFE membrane (hereinafter, e-PTFE) formed through a stretching step.

An image fixing device according to the invention according to claim 6 is:
The image fixing device according to any one of claims 1 to 5, wherein the porosity of the porous layer is 25% or more and 90% or less.

An image fixing device according to the invention according to claim 7 is:
The image fixing device according to any one of claims 1 to 6, wherein the average pore diameter of the porous material is smaller than the average particle size of the colored fine particles.

An image fixing apparatus according to the invention of claim 8 is:
The image fixing device according to claim 7, wherein the maximum pore size of the porous material is smaller than the minimum particle size of the colored fine particles.

The image fixing device according to the ninth aspect of the present invention provides
9. The image fixing device according to claim 1, wherein a member capable of regulating an amount of liquid adhering to the surface of the porous layer is in contact with the surface of the heating member. And

According to a tenth aspect of the present invention, there is provided the image fixing device according to any one of the first to ninth aspects, wherein the porous layer has semiconductivity. And

[0024]

Embodiments of the present invention will be described below with reference to the drawings. [Structure] FIG. 1 shows a wet full-color image forming apparatus (wet image forming apparatus) according to the present invention. This wet type full-color image forming apparatus includes a photosensitive device group 1 in a tandem arrangement, a developing device group 2 for developing the photosensitive device group 1, an intermediate transfer device 3, and a fixing device 4. <Photosensitive Device Group 1> The photosensitive device group 1 includes a yellow photosensitive device 5, a magenta photosensitive device 6, a cyan photosensitive device 7, and a black photosensitive device 8.

The yellow photosensitive device 5 includes a drum-shaped yellow photosensitive member (yellow photosensitive drum) 5a, a charging roller 5b, a photosensitive member cleaning blade 5c, and a neutralization lamp 5.
d. The magenta photosensitive device 6 includes a cylindrical magenta photosensitive member (magenta photosensitive drum) 6a, a charging roller 6
b, photoconductor cleaning blade 6c, static elimination lamp 6d
Having. Further, the cyan photosensitive device 7 includes a cylindrical cyan photosensitive member (cyan photosensitive drum) 7a, a charging roller 7b, a photosensitive member cleaning blade 7c, and a discharging lamp 7d. The black photosensitive device 8 has a cylindrical black photosensitive member (black photosensitive drum) 8a, a charging roller 8b, a photosensitive member cleaning blade 8c, and a discharging lamp 8d.

Each of the photosensitive members 5a, 6a, 7a, 8a and the like is composed of a latent image carrier such as an amorphous silicon photosensitive material, and the charging rollers 5b, 6b, 7b and 8b are composed of an epichlorohydrin rubber roller and the like. The cleaning blades 5c, 6c, 7c, 8c are made of urethane rubber or the like.

The photosensitive members 5a, 6a, 7a, 8a
Are arrows 5e and 6e, respectively, by exposure means (not shown).
Exposure is performed as shown by e, 7e, and 8e, so that an electrostatic latent image of each color is formed. Laser light from a laser diode (LD) is used for writing on the photoconductors 5a to 8a by exposure means. At the time of this writing, the surface speed of the charging roller associated with the rotational drive of the photoconductors 5a to 8a is set to 150 mm / s, the charging potential on the photoconductors of the photoconductors 5a to 8a is set to +800 V, and The post-exposure image portion potentials of 8a to 8a are set to + 50V. <Developing Device Group 2> The developing device 2 includes a yellow developing device 9,
It has a magenta developing device 10, a cyan developing device 11, and a black developing device 12.

The yellow developing device 9 includes a developing solution tank 9a.
And a yellow developer 9b in a developer tank 9a, and a developer application roller 9 having a lower part immersed in the yellow developer 9b.
c, a developing roller 9d in contact with the developer application roller 9c and the yellow photoconductor 5a, a metering blade 9e facing the developer application roller 9c, and a cleaning blade 9f for the development roller 9d.

The magenta developing device 10 includes the developer tank 1
0a and the magenta developer 10b in the developer tank 10a.
A developer application roller 10c whose lower portion is immersed in the magenta developer 10b, a development roller 10d that contacts the developer application roller 10c and the magenta photoconductor 6a, and a metering blade 10e facing the developer application roller 10c.
It has a cleaning blade 10f for the developing roller 10d.

The cyan developing device 11 includes a developer tank 11
a, a cyan developer 11b in a developer tank 11a,
A developer application roller 11c having a lower part immersed in the cyan developer 11b, a development roller 11d contacting the developer application roller 11c and the cyan photoconductor 7a, a metering blade 11e facing the developer application roller 11c, and a development roller It has a cleaning blade 11f of 11d.

The black developing device 12 includes the developer tank 1
2a and the black developer 12b in the developer tank 12a
A developer application roller 12c having a lower part immersed in the black developer 12b, a development roller 12d contacting the developer application roller 12c and the black photoconductor 8a, and a metering blade 12e facing the developer application roller 12c.
It has a cleaning blade 12f for the developing roller 12d.

Yellow developer 9b, magenta developer 10
b, cyan developer 11b, black developer 12b, and other image liquids (development liquids) include carrier liquids, colored particles, and other charge control agents, dispersants, and the like. And
Examples of the carrier liquid and the colored particles include: “Carrier liquid: 100 cSt dimethylpolysiloxane Colored fine particles: modified epoxy resin (Tg = 50 ° C.) + Colored pigment of each color Others: charge control agent, dispersant Colored fine particle average particle size: 3 μm Colored fine particle charging polarity: positive ”or the like is used. The coloring materials for each color here include a yellow coloring pigment, a magenta coloring pigment, a cyan coloring pigment, a black coloring pigment, and the like.
A yellow color pigment is used for the yellow developer 9b, a magenta color pigment is used for the magenta developer 10b, a cyan color pigment is used for the cyan developer 11b, and a black developer 12b is used for the black developer 12b. Black color pigments are used.

The developer application rollers 9c, 10c, 1
Stainless steel gravure rollers and the like are used for 1c and 12c. Developing rollers 9d, 10d, 11d, 12d
The low hardness silicone rubber (hardness ~
Shore A 5 °) and a 50 μm-thick conductive PFA tube (volume resistivity〜105 Ωcm) are used. Metering blades 9e, 10e, 11e, 1
Stainless steel is used for 2e.

Developer rollers 9c, 10c, 11c, 12
The thickness of the developer layer applied to the surface of (c) is about 7 μm.
The surface movement speed of the developer rollers 9c, 10c, 11c, and 12c is the same as that of the developer rollers 9c, 10c, 11c, and 1.
At a contact portion (nip width: 1 mm) between the developing roller 2c and the developing rollers 9d, 10d, 11d, and 12d, the speed is set to 250 mm / s in a direction opposite to the moving direction of the developing roller surface.

Developing rollers 9c, 10c, 11c, 12c
The surface movement speed of the photoconductors 5a, 6a, 7a, 8a and the photoconductors (latent image carriers) 5a,
150mm / s in the same direction as the moving speed of the surface of 6a, 7a, 8a
Is set to Further, the developing rollers 9c, 10c, 1
The surface potential of 1c and 12c is set to 400V. The cleaning blades 9f, 10f, 11f are formed from 12f stainless steel. <Intermediate Transfer Apparatus 3> The intermediate transfer apparatus 3 includes a yellow primary transfer roller 1 disposed above a yellow photoconductor 5a.
3, a yellow primary transfer roller 14 disposed above the magenta photoconductor 6a, a cyan primary transfer roller 15 disposed above the cyan photoconductor 7a, and a black photoconductor 8
a, a black primary transfer roller 16 disposed above
An intermediate transfer belt driving roller 17 is provided. This roller 1
The rollers 3 and 17 are formed larger than the diameters of the rollers 14, 15 and 16.

The intermediate transfer device 3 includes an intermediate transfer belt 18 wrapped around a yellow primary transfer roller 13 and an intermediate transfer belt driving roller 17, and an intermediate transfer belt cleaning blade 19 for cleaning the surface of the intermediate transfer belt 18. Having. Then, the lower side of the intermediate transfer belt 18 is moved by the primary transfer rollers 13 to 16 to the photosensitive members 5a and 5b.
6a, 7a and 8a.

Further, the intermediate transfer device 3 has a secondary transfer roller 20 disposed adjacent to the intermediate transfer belt driving roller 17 via the intermediate transfer belt 18. Between the intermediate transfer belt 18 and the secondary transfer roller 20, a roller 1
The sheet-shaped recording medium 21 is supplied between the positions 7 and 20. Moreover, the intermediate transfer belt 18
And the secondary transfer roller 20 are the intermediate transfer belt driving roller 1
The recording medium 21 is supplied to the fixing device 4 by being driven to rotate in the opposite directions by the recording medium 21.

Incidentally, an epichlorohydrin rubber roller is used for the primary transfer rollers 13 to 16, and a voltage of 300 V (constant voltage control) is applied as a primary transfer roller bias potential. The intermediate transfer belt 18 has a thickness
A stainless steel base material having a thickness of 0.1 mm coated with a conductive urethane rubber having a thickness of 1.5 mm is used. The surface moving speed of the intermediate transfer belt 18 is set to 150 mm / s. In addition, the intermediate transfer belt cleaning blade 19
Is used, and an intermediate transfer belt driving roller 17 is an epichlorohydrin rubber roller.
As the secondary transfer roller 20, an epichlorohydrin rubber roller is used. The current flowing from the secondary transfer roller 20 to the intermediate transfer belt 18 is set to 100 μA. <Fixing Device 4> Further, as shown in FIG. 1, the fixing device 4 includes a fixing roller (heating member) 22, a liquid amount regulating member 23 for regulating the amount of liquid on the surface of the fixing roller 22, and an adjoining member. Pressurizing roller (recording medium support member) 24. This liquid amount regulating member 23 is formed of fluoro rubber.

The fixing roller 22 includes a hollow aluminum core 25.
And a halogen lamp (halogen heater) 26 disposed in the hollow aluminum core 25 and an e-PTFE porous layer 27 covering the outer peripheral surface of the hollow aluminum core 25.
The e-PTFE porous layer 27 is formed in a tubular shape by coating a layer of semiconductive e-PTFE (maximum pore diameter 0.2 μm) fiber with a thickness of 80 μm on the outer peripheral surface of the hollow aluminum core 25. It is. This e-PTFE porous layer 2
In No. 7, the volume resistivity is set to 1012 Ωcm. Also,
The surface temperature of the fixing roller 22 due to the heating of the halogen lamp (fixing roller heating means) 26 is set to 85 ° C.

The pressing roller 24 is made of a stainless steel rod 28
And a semiconductive foamed silicone base material covering the stainless steel core rod 28 and a radiated layer 29 of a 100 μm thick semiconductive PFA tube. Further, the nip width of the pressure holding portion (fixing portion) of the sheet-shaped recording medium 21 by the fixing roller 22 and the pressure roller 24 is set to 6 mm. Further, the core metal potential of the fixing roller 22 is grounded to be 0 V (GND), and the core rod potential of the pressure roller 24 is set to 800 V (when there is no recording medium). The current flowing from the fixing roller 22 to the pressure roller 24 is controlled to 500 μA (constant current control), and the surface moving speed of the fixing roller 22 is set to 150 mm / s. [Operation] Next, the operation of the wet full-color image forming apparatus having such a configuration will be described.

In such a configuration, each photoconductor 5a, 6
When rotating in the clockwise direction in FIG. 1, a, 7a, and 8a remove the developer remaining on the surface after the electrostatic latent image on the surface is removed by the discharging lamp 5d, and remove the cleaning blades 9f, 10f, 11f. After this,
Each of the photoconductors 5a, 6a, 7a, 8a is charged to 800V by charging rollers 5b, 6b, 7b, 8b rotating in a counterclockwise direction.

The photosensitive members 5a, 6a, 7a,
Reference numeral 8a denotes a position immediately after charging, which is indicated by arrows 5e, 6e, 7e, and 8e by an unillustrated exposure unit (image writing unit).
Exposure is performed in accordance with the image of each color as shown by (2), and an electrostatic latent image for each color is formed on the surface of each photoconductor 5a, 6a, 7a, 8a.

On the other hand, the developer application rollers 9c, 10c, 1
1c and 12c have developer tanks 9a, 10a and 1 at the bottom.
Developers 9b, 10b, 11b, 12b in 1a, 12a
In the state of being immersed in, it is rotated counterclockwise in FIG. By this rotation, the developer tanks 9a, 10a, 1
Developers 9b, 10b, 11b, 12b in 1a, 12a
Are attached to the surfaces of the developer application rollers 9c, 10c, 11c, and 12c, respectively, and then formed to a predetermined thickness by metering blades 9e, 10e, 11e, and 12, respectively. The developer application rollers 9c, 10c,
The developer of each color adhered to the surface of each of the developing rollers 9c, 10c, 11c, and 12c is formed on the surface of each of the developing rollers 9c, 10c, 11c, and 12c to form a layer having a thickness of about 7 μm. , 6a, 7a, and 8a are offset (attached) to portions of the electrostatic latent image formed on the surfaces of the electrostatic latent images. The remainder of the developer of each color adhered to the surfaces of the developer application rollers 9c, 10c, 11c, and 12c, respectively,
The developer is returned into the developer tanks 9a, 10a, 11a, and 12a, respectively.

On the other hand, when the intermediate transfer belt driving roller 17 rotates counterclockwise, the intermediate transfer belt 18 and the yellow primary transfer roller 13 are driven to rotate counterclockwise, and the primary transfer rollers 14 to 16 are moved intermediately. The transfer belt 18 and the photoconductors 5a, 6a, 7a, 8a are rotated counterclockwise by rotation. At this time, the contact portions between the intermediate transfer belt 18 and the photoconductors 5a, 6a, 7a, 8a are moved at the same speed in synchronization in the same direction.

With this rotation, the photosensitive members 5a, 6a, 7
The developers of the respective colors offset to the portions of the electrostatic latent images a and 8a are transferred to the surface of the intermediate transfer belt 18 by the pressing action of the primary transfer rollers 13 to 16,
The intermediate transfer belt 18 is pressed by the pressing force of the secondary transfer roller 20.
From the surface of the recording medium 21. <Operation of Fixing Device 4> The recording medium 21 onto which the image of each color developer is transferred is supplied between the fixing roller 22 and the pressing roller 28, and When passing through the gap, the image formed by the developer transferred to the recording medium 21 is fixed by the heat of the fixing roller 22 and the pressing force of the pressing roller 24.

By the way, the 80 μm thick e-PTFE porous layer 27 provided on the surface layer of the fixing roller 22 is formed as shown in FIG.
As shown in the figure, it is composed of many small nodules and extremely fine fibers connecting them. The size of the knots, the length and thickness of the fibers, or the average pore diameter determined by these, and the porosity can be controlled by manufacturing conditions such as drawing conditions. Here, as shown in FIG. 2, an e-PTFE porous layer (e-PTFE fiber layer) 27 having an average pore diameter of about 0.1 μm or less and a maximum pore diameter of about 0.2 μm was used.

FIG. 2 also shows the particle size distribution of the colored fine particles for forming an image (average particle size: about 3 μm, minimum particle size: about 1 μm). According to such a combination of the pore size distribution of the e-PTFE porous layer 27 and the colored fine particle distribution, the colored fine particles cannot enter the e-PTFE porous layer 27, so that the contamination of the fixing roller by the colored fine particles is limited. Does not occur without.

When another developer having an average particle size of about 0.2 μm was used, a slight amount of contamination on the fixing roller 22 was confirmed, but it was at a level that would not interfere with practical use.
When this developer having an average particle diameter of about 0.2 μm is used and the e-PTFE porous layer 27 having an average pore diameter of about 0.5 μm is used, the degree of contamination of the fixing roller 22 by the coloring fine particles is severe. It was determined that the pores might be filled with the colored fine particles due to long-term use.

Further, an appropriate amount of conductive material is mixed in the e-PTFE porous layer 22, and the volume resistivity is 1012 Ω · cm.
Has been adjusted.

A new fixing roller 22 that has never undergone a fixing step is previously impregnated with 100 cSt of dimethylpolysiloxane, which is a main component of the developer carrier liquid (FIG. 3A )reference). A recording medium and an image as shown in FIG. 3 are brought into contact with such a fixing roller 22 at the time of fixing (see FIG. 3B). At this time, a current flows through the image layer, and the current increases the cohesion between the colored fine particles and between the colored fine particles and the recording medium. At the same time, part of the carrier liquid extruded due to the aggregation of the particles forms a carrier liquid layer on the surface of the fixing roller. However, when the amount of the carrier liquid originally contained in the image is small, the carrier layer is hardly formed.

The colored fine particles are softened and melted in the process of contact of the fixing roller 22 with the image surface, and a bonding force is generated between the colored fine particles or between the colored fine particles and the recording medium (FIG. 3).
(C)). At this time, a part of the carrier liquid existing in the space between the colored fine particles moves to the inside of the recording medium 21 and a part moves to the surface of the fixing roller 22. Since there is a lot of space inside the recording medium 21, the carrier liquid permeates more and more inside the recording medium 22, but the carrier liquid moved to the fixing roller 22 has no place to go (already,
Since the porous layer is filled with liquid), the fixing roller 2
A carrier liquid layer is further formed between the surface of No. 2 and the colored resin image layer.

When the toner is released from the fixing nip, separation is performed in the portion having the lowest cohesive force, that is, in the carrier liquid layer (see FIG. 3D), and the fixing of the image is completed.
Since the carrier liquid that has moved from the inside of the image is excessively attached to the surface layer of the fixing roller 22, the excess amount is removed by the blade-shaped liquid amount regulating member 23 (see FIG. 3E).

At the time of removing the surplus liquid, replacement of the 100 cSt dimethylpolysiloxane originally impregnated inside the porous layer with the developer carrier liquid is carried out. Fixing characteristics are stable for a long time. Since the surface of the fixing roller 22 is always wet with the liquid, the effect of reducing the offset is maintained for a long time.

By the above-described process, a reliable fixing property and an effect of preventing offset can be obtained. Fixing roller 2
When the amount of current flowing from 2 to the pressure roller 24 was set to 0 μA, good fixing performance was obtained when the temperature of the fixing roller 22 was set to 95 ° C., but a current of 500 μA was applied as in this embodiment. In this case, good fixability was obtained at 85 ° C., which is lower by 10 ° C., and it was confirmed that the fixing step with lower power consumption was realized.

Further, in the above, the e-PTFE porous layer used was a semiconductive one. However, an e-PTFE porous layer having an electrical insulating property was used unless a conductive material was provided. good. An electric field of 800 V is formed between the core of the fixing roller and the core of the pressure roller as above, so that an electric field is applied to the developer layer in an area between the fixing roller and the recording medium. Can be formed. As in the above example, the current does not flow, so that a large aggregation effect of the colored fine particles cannot be obtained. However, since the force for attracting the colored fine particles toward the recording medium acts, it is effective in reducing the offset ratio. .

The present invention is not limited to the field of electrophotography, but also fixes a visualized image on a recording medium by using a coloring fine particle capable of temporarily or permanently retaining electric charge in a solvent and the solvent. For example, the present invention can be applied to an image forming process that does not use an electrophotographic process, such as a field where an image is directly formed on a recording medium typified by an ink jet system or a field of a printed matter using a plate.

[0057]

According to the first aspect of the present invention described above, since the surface of the heating member is always wet by the image liquid, it acts as a release agent between the colored particles and the heating member. . Therefore, even when the amount of image liquid contained in the image formed on the recording medium is very small,
Provides perfect offset prevention effect. In addition, since the liquid having substantially the same components as the image liquid is impregnated, even if the heating member comes into contact with the recording medium on which the image is formed and the liquid in the porous layer is transferred, the liquid always remains in the porous layer. Since the liquid components are the same, a stable offset prevention effect can be maintained semipermanently.

Also, the electric field formed by the potential difference between the surface of the heating member and the surface of the recording medium supporting member enhances the bonding force between the colored fine particles of the image and between the recording medium and the colored fine particles, thereby increasing the colored fine particles of the image. Is adhered to the recording medium, so that a reliable fixing property can be achieved. In addition, the fact that the image liquid floats on the colored fine particles and the image liquid layer is easily formed between the heating member and the colored fine particles contributes to the effect of preventing offset.

According to the second aspect of the present invention, in addition to the effect of the first aspect of the present invention, only a potential difference is formed by flowing a current between the surface of the heating member and the surface of the recording medium supporting member. As compared with the case where the coloring is performed, the coloring fine particles can be made to have a stronger cohesive force and can be more strongly adhered to the recording medium, so that more reliable fixing property can be achieved.

According to the third aspect of the present invention, the liquid supply to the porous layer on the surface of the heating member can be performed simultaneously with the fixing step by the image liquid in the image on the recording medium. There is no need to provide a coating device or the like on the outer periphery of the heating member. Therefore, not only the compact and simple configuration, but also the heat capacity of the entire fixing device can be reduced, so that the fixing process with low energy consumption can be performed.

According to the fourth aspect of the present invention, the use of the porous PTFE membrane not only impregnates the liquid into the surface layer of the heating member but also significantly reduces the adhesive force between the colored fine particles and the surface of the heating member. This is effective for the offset prevention effect.

According to the fifth aspect of the present invention, the average pore diameter, the porosity, and the layer thickness of the porous layer can be controlled relatively freely by manufacturing conditions such as stretching conditions. A porous layer can be formed. Since a porous layer can be formed in a tubular shape, a roller-shaped heating member can also be manufactured.

According to the sixth aspect of the present invention, the amount of liquid impregnated in the porous layer becomes an appropriate amount, so that the offset reducing effect is high. If the porosity is less than 25%, the amount of liquid that can be retained by the porous layer is too small to obtain a sufficient offset prevention effect. ) Is disadvantageous.

According to the seventh aspect of the present invention, it is possible to reduce the opportunity for colored fine particles to enter the porous portion, so that a sufficient offset preventing effect can be obtained.

According to the eighth aspect of the present invention, since the colored fine particles do not enter the porous portion at all, the effect of preventing offset in a very stable state for a long time can be obtained.

According to the ninth aspect of the present invention, the excess amount of the image liquid transferred to the surface of the heating member can be removed from the recording medium on which the image is formed, so that the total amount of the liquid held by the heating member can be reduced. Can be kept constant, and stable fixability can be maintained. In the event that colored fine particles adhere to the surface layer of the heating member, it also acts as a cleaning member for removing it.

According to the tenth aspect of the present invention, since the porous layer has semiconductivity, the porous layer is stably provided between the heating member and the recording medium support over the entire image area on the recording medium. It is possible to pass current.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an image forming apparatus including an image fixing device according to the present invention.

FIG. 2 is an explanatory diagram showing the relationship between the particle size distribution of colored fine particles used in the developer (image liquid) shown in FIG. 1 and the pore size distribution and size of e-TFE of a fixing roller.

FIG. 3 is an operation explanatory view of the fixing device according to the present invention.

[Explanation of symbols]

 9b, 10b, 11b, 12b ... developer (image liquid) 21 ... recording medium 22 ... fixing roller (heating member) 24 ... pressure roller (recording medium support member) 27 ... e -TFE porous layer

Claims (10)

[Claims] A heating member for contacting an image formed on the recording medium with an image liquid containing thermoplastic colored fine particles on the image surface; and a recording medium support member for pressing the recording medium against the heating member. A fixing device that forms a potential difference between the surface of the heating member and the surface of the recording medium supporting member at the time of fixing, the heating member surface being a porous layer, and An image fixing device characterized in that it is impregnated with a liquid having substantially the same components as the image liquid. 2. A heating member which contacts an image formed on a recording medium with an image liquid containing thermoplastic colored fine particles, and a recording medium supporting member which presses the recording medium against the heating member. A fixing device that forms a potential difference between the surface of the heating member and the surface of the recording medium supporting member at the time of fixing, the heating member surface being a porous layer, and An image fixing device characterized in that it is impregnated with a liquid having substantially the same components as the image liquid. 3. An image fixing apparatus according to claim 1, wherein the liquid is supplied to the porous layer by an image liquid contained in an image formed on a recording medium. Fixing device. 4. The image fixing device according to claim 1, wherein said porous layer is made of PTFE (polytetrafluoroethylene).
An image fixing device characterized by being a porous film. 5. An image fixing apparatus according to claim 4, wherein said porous PTFE membrane is formed through a stretching step by stretching.
An image fixing device characterized by being a TFE porous film (hereinafter, e-PTFE). 6. The image fixing device according to claim 1, wherein the porosity of the porous layer is 25% or more and 90% or less. 7. The image fixing device according to claim 1, wherein the average pore diameter of the porous material is smaller than the average particle size of the colored fine particles. 8. The image fixing device according to claim 7, wherein the maximum pore size of the porous material is smaller than the minimum particle size of the colored fine particles. 9. The image fixing device according to claim 1, wherein a member capable of regulating the amount of liquid adhering to the surface of the porous layer is in contact with the surface of the heating member. An image fixing device, characterized in that: 10. The image fixing device according to claim 1, wherein said porous layer has semi-conductivity.