JP2003140491A - Pressure roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure roller with which the film thickness of a release layer disposed on the outer periphery of a silicone rubber elastic layer can be reduced and bright fixed images can be obtained without the occurrence of abnormality on the surface and without degrading the releasability to toners even after continuous use for a long period of time from an initial period of use. SOLUTION: The pressure roller is provided with the silicone rubber elastic layer on the outer periphery of an arbor and the release layer as a surface layer, in which the adhesiveness of the release layer is produced by a fluororesin primer and the release layer consists of a fluororesin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used to heat and fix a toner image on a recording material in an image forming apparatus using an electrophotographic method such as a copying machine or a printer, and more particularly to a recording device. The present invention relates to a pressure roller that holds a recording material for conveying the material and receives heat from a heat source to apply pressure to the recording material and toner to solidify and fix an unfixed toner image.

[0002]

2. Description of the Related Art Image fixing devices for electrophotographic copying machines and laser beam printers use a fixing roller or a fixing film as a method for fixing an unfixed toner image on paper by heat and pressure. Has been adopted.

In the fixing roller system, a pressure rotator (pressure roller), which is arranged as a pair with a roller (fixing roller) having a heat source as a heating rotator, is pressed to form a nip. By passing the recording material (paper) carrying the unfixed toner image, the toner is melted and pressed to form a fixed image.

On the other hand, in the fixing film system, as a heating rotator, a pressure rotator (pressure roller) arranged in pair with a fixing unit in which a heat source is covered with a heat-resistant film (fixing film) forms a nip. As the recording material (paper) carrying the unfixed toner image passes through the nip portion, the toner is melted and pressed to form a fixed image.

Further, in the fixing device of the fixing film system, since a film material having a small heat capacity and a rapid temperature rise can be used as the film material, it takes a short time until the film is ready to be used after the power is turned on, and the power consumption in the standby mode is consumed. Can be suppressed. Since power saving is possible in this way, the fixing film system has been actively developed in recent years, and the present invention is mainly directed to the pressure roller used in the fixing film system.

The pressure roller used must have an elastic layer in order to obtain a proper nip by pressure contact, and 20
Heat resistance is required to withstand use at a toner fixing temperature of around 0 ° C. Further, in order to prevent toner from adhering to the roller surface, toner releasability is required.
For this reason, the roller structure has conventionally been such that a silicone rubber elastic layer is formed on the outer circumference of a metal cored bar, and a fluororubber dispersion paint and a fluororesin dispersion paint are coated on the outer circumference to impart toner releasability. Or, those coated with a fluororesin tube have been used.

As a method of forming the release layer by coating, there has been a method of sequentially coating the outer periphery of the silicone rubber elastic layer with a silicone resin-based primer and a fluorine latex composed of a mixture of fluorine rubber and fluorine resin. However, in this case, since the primer was diluted with the solvent, the primer components aggregated when volatilized, resulting in unevenness, and the fluorine latex coated thereon had cracks.

As a solution to such a problem, there is a method proposed in Japanese Patent Laid-Open No. 11-185934. According to this method, it is possible to coat the primer used thinly and uniformly by increasing the dilution ratio of the primer used in the solvent, and the unevenness due to the aggregation of the primer components is suppressed, and cracks are eliminated. Moreover, the above-mentioned problems could be solved by using a primer which becomes an elastic body after drying instead of the conventional primer.

However, when a high-performance fixing device having higher speed and higher durability is required, the release layer formed by the fluorine latex is not sufficient, and therefore, the fixing layer further formed on the fluorine latex. A method of coating fluororesins has been adopted.

As a pressure roller having such a structure, Japanese Patent Application Laid-Open Nos. 2000-227110 and 2000-305 have been used.
The one described in Japanese Patent No. 396 has been proposed. These are configured such that a fluoro-latex layer made of a mixture of fluoro-rubber and fluoro-resin for adhering the fluoro-resin layer on the outer periphery of the silicone rubber elastic layer is coated through a primer, and then the fluoro-resin is coated thereon. Has become.

Of the layers below the fluororesin layer, the primer layer is for adhering the silicone rubber elastic layer and the fluorolatex layer, and the fluorolatex layer is for adhering the fluororesin in place of the conventional release layer. There is for. However, since it is a three-layer coat, the total film thickness of these becomes thick and the process becomes complicated, which causes a cost increase. Further, since the microscopic hardness of the roller surface is increased, the releasability of the toner is lowered, and the surface of the roller is soiled, so that the recording material is also soiled.

The toner stain due to the reduction in the releasing property of the pressure roller is considered as follows.

It is desirable that all of the toner transferred to the recording material be fixed by the fixing device, but the unfixed toner (offset toner) electrostatically adheres to the fixing film and moves to the pressure roller side. To do. However, if the offset toner immediately melts and adheres to the recording material and is discharged, it is at a level that cannot be visually confirmed, but if it accumulates on the pressure roller, it becomes a large stain when it adheres to the recording material. Further, in the film fixing method, since the heat capacity of the film is small, it is possible to raise the temperature of the heater in the fixing unit in a short time, which is effective for power saving, while the pressure roller is heated except when the paper is being fed. Since the toner does not easily get warm, the offset toner attached to the pressure roller is less likely to melt, and is less likely to be attached to the recording material and discharged. Moreover, the tendency becomes more remarkable in the intermittent operation under the environment of low temperature and low humidity.

At this time, it is considered that the toner adhering to the pressure roller adheres to the recording material and is discharged.

When the toner attached to the pressure roller passes through the nip by rotation, a lateral force is applied to the nip of the pressure roller. At this time, due to the difference between the deformation amount of the toner due to the stress and the deformation amount of the surface of the pressure roller, the toner adhered to the pressure roller is peeled off from the pressure roller and adhered to the recording material and discharged.

At this time, the softer the surface of the pressure roller, the greater the amount of deformation, and the more easily the adhered toner is peeled off. Further, the softness of the surface of the pressure roller is governed by the thickness of the surface layer, and the smaller the thickness, the softer the surface. Therefore, it has become necessary to design such that the thickness of the surface layer is smaller than that of the above-mentioned conventional example while ensuring sufficient releasability, durability and heat resistance.

[0017]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a simple coating on the outer periphery of a silicone rubber elastic layer by coating a fluororesin-based primer with a thin film. A release layer made of fluororesin is formed by the process. This makes it possible to reduce the film thickness on the outer circumference of the silicone rubber elastic layer, and the release property for toner does not deteriorate even after continuous use for a long time from the initial use, and a clear fixed image can be obtained. Is to provide.

[0018]

The inventors of the present invention have completed the present invention as a result of intensive studies to solve the above problems.

A silicone rubber elastic layer on the outer periphery of the cored bar,
In a pressure roller provided with a release layer as a surface layer, the adhesiveness of the release layer is caused by a fluororesin-based primer, and the release layer is made of a fluororesin. The purpose is achieved.

In this case, the thickness of the primer is 3 to 5 μm.
The object of the present invention is more preferably achieved by a pressure roller having a release layer thickness of 4 to 11 μm.

In particular, in the embodiment of the present invention described in (2) above, the adhesiveness of the release layer having releasability with the toner is caused by the fluororesin-based primer, and the release layer is made of the fluororesin. As a result, the microscopic hardness of the roller surface does not increase more than necessary, and good toner releasability can be secured.

[0022]

DETAILED DESCRIPTION OF THE INVENTION A pressure roller according to an embodiment of the present invention will be described below.

A metal core made of aluminum is used as the shaft of the roller. Further, in order to obtain adhesiveness with silicone rubber, the surface of the cored bar is cleaned by degreasing or the like and then subjected to a primer treatment. Specifically, a two-component primer containing a silicone polymer and silane as a main component is applied thinly and uniformly and then dried by heating.

Silicone rubber is used as the elastic layer because of its excellent heat resistance, low hardness of rubber itself, and high elasticity and sufficient nip width. The hardness is not particularly limited, but is adjusted so that the mechanical strength is not lowered and the durability is not insufficient.

As the primer layer, the total thickness of the surface layer can be reduced, and the primer layer is sufficiently adhered to the fluororesin layer provided as a release layer on the surface layer, and is excellent in durability and heat resistance. A fluororesin-based primer is used. The type and grade of the fluororesin are not particularly limited.

As the release layer, it is preferable to select a fluororesin because it has excellent durability and heat resistance. It has a low coefficient of friction and good releasability from toner. In addition, a coating film obtained by spray coating an aqueous dispersion of a fluororesin is particularly preferable because the film thickness can be controlled and the surface smoothness is excellent.
This fluororesin is a material that also contributes to the releasability of the pressure roller from the toner. Specifically, it is tetrafluoroethylene-
Hexafluoropropylene resin (FEP), tetrafluoroethylene-
It is preferable to select at least one kind from perfluoroalkyl vinyl ether resin (PFA) and tetrafluoroethylene resin (PTFE).

Further, the release layer can obtain good release property and durability in the above thickness range, but if it deviates from this range, the effect due to the function of the pressure roller may not be expected. In this case, the thickness of the primer is preferably 3-5 μm. If the thickness of the primer is too thin, sufficient adhesiveness may not be obtained, while if it is too thick, the surface smoothness may deteriorate. The release layer preferably has a thickness of 4 to 11 μm. If the thickness of the release layer is too thin, the durability and abrasion resistance may be insufficient, and if it is too thick, the surface of the pressure roller may be hard and the toner adhering to the surface may be difficult to peel off.

[0028]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

(Examples 1 and 2) A pressure roller having the structure shown in FIG. 1 was produced.

A primer (Toray Dow Corning Co., Ltd .: DY3) is attached to the outer circumference of an aluminum cored bar 111 having an outer diameter of 14 mm.
9-110) and apply it thinly and uniformly.
It was dried for 0 minutes. After setting the core metal 111 subjected to the primer treatment in a pipe-shaped mold, silicone rubber (DY35-1198, manufactured by Toray Dow Corning Co., Ltd.) was injected and cured by heating to remove it from the pressure roller. An elastic layer 112 having a thickness of 3.6 mm was molded so that the diameter was 21.2 mm. On the outer periphery of this elastic layer 112, a fluororesin-based primer 113 for adhering silicone rubber and fluororesin
(Mitsui DuPont Fluorochemicals Co., Ltd .: PRM027
-12) was spray coated to the thickness shown in Table 1. Further, an FEP dispersion liquid (EN-201CL manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.) was spray-coated on the outer periphery with the thickness shown in Table 1, and then baked at 300 ° C. for 40 minutes to form a release layer 114.

(Comparative Examples 1 to 3) An elastic layer was formed in the same manner as in the examples. The constitution of the surface layer differs depending on each example. In Comparative Example 1, only the fluorine latex is used, in Comparative Example 2, the fluorine latex with an increased resin ratio is used, and in Comparative Example 3, the fluorine latex is applied over the fluorine latex. . These surface layers were obtained by spray coating with the thickness shown in Table 1.

Next, a fixing device equipped with the pressure roller of the present invention will be described.

FIG. 2 is a schematic view illustrating a schematic configuration of an embodiment of a film fixing type image fixing device equipped with a pressure roller of the present invention. The image fixing device 20 includes a pressure roller 23 and a heating mechanism. The pressure roller 23 is the pressure roller according to claims 1 and 2 of the invention. The heating mechanism mainly includes the fixing film 21 and the heater 22. The fixing film 21 is supported by a film guide (not shown) made of thermosetting plastic, and a heater 22 is attached to the lower surface of this film guide.

The image fixing device 20 is driven by the pressure roller 23, and the recording material T and the fixing film 21 are driven by the pressure roller 23. The recording material T is supplied with the unfixed toner TT ′ carried on the surface, and the heated toner is melted and pressed at the nip portion N between the heater 22 and the pressure roller 23 to form a fixed image TT. Is discharged.

Table 1 shows the results of performance evaluation in which the produced pressure roller was incorporated into a film type fixing device. In toner stain test, 2 sheets / 1 in low temperature and low humidity environment
When the dirt was not counted after passing 5000 sheets in the intermittent operation for 0 minutes, the mark was ◯, and when the stain was counted, it was x. In the durability test, ⊚ indicates that no abnormalities such as peeling or stains occurred after passing 150,000 sheets, and ∘ indicates 100,000 sheets.

The adhesion between the elastic layer and the release layer is represented by ◯ when cohesive failure occurs when a cut is made in the pressure roller and when the release layer is pulled almost vertically, and as x when peeled off due to interface failure. did.

The hardness of the surface is measured by a micro rubber hardness meter MD-1 type A manufactured by Kobunshi Keiki Co., Ltd. and expressed as the surface hardness. The surface roughness, which represents the smoothness of the surface, was measured by a surface roughness measuring instrument SE3500 manufactured by Kosaka Laboratory Ltd.

[0038]

[Table 1]

In Examples 1 and 2, there were no troubles related to the conveyance during the performance evaluation, and no toner stain was found on the surface of the pressure roller after completion. In addition, all the pressure rollers showed good durability.

In Comparative Examples 1 and 2, since the surface layer was thick and the surface hardness was high, the releasability was deteriorated, toner stains were observed, and sufficient durability was not obtained.

In Comparative Example 3, the toner was not stained, but the durability was insufficient.

[0042]

According to the present invention, the adhesiveness of the release layer having releasability with the toner is generated by the fluororesin-based primer, and the release layer is made of the fluororesin, so that the surface microscopic The hardness does not increase more than necessary, and thus good toner releasability can be secured.

Further, in the conventional pressure roller, since the fluororesin is adhered to the rubber elastic layer, a fluorine latex is provided between the primer layer and the fluororesin layer as an adhesive layer which is not necessary for the original function of the pressure roller. Had to provide layers. However, according to the present invention, it is possible to obtain a pressure roller having a desired function without a complicated process.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a pressure roller of the present invention.

FIG. 2 is a schematic view illustrating a schematic configuration of an embodiment of a film fixing type image fixing device equipped with a pressure roller of the present invention.

[Explanation of symbols]

11, 23 Pressure roller 111 core metal 112 elastic layer 113 Primer layer 114 Release layer 20 Image fixing device 21 Fixing film 22 heater

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H033 AA09 AA21 AA23 BB29 BB30                 3J103 AA02 AA14 AA32 AA51 BA41                       EA02 EA07 EA11 FA07 FA15                       GA02 GA57 GA58 HA03 HA12                       HA43 HA53

Claims (2)

[Claims] 1. A pressure roller having a silicone rubber elastic layer on the outer periphery of a core metal and a release layer as a surface layer, wherein the release layer has adhesiveness due to a fluororesin-based primer, and A pressure roller, wherein the layer is made of fluororesin. 2. The pressure roller according to claim 1, wherein the primer has a thickness of 3 to 5 μm and the release layer has a thickness of 4 to 11 μm.