JPH0527636A - Image fixing device - Google Patents

Abstract

PURPOSE:To prevent the swelling of silicone rubber by the excess impregnation of a silicone oil into the rubber and to provide the pressure roller which is strong to an offset and has a longer service life by forming the rubber layer of the fixing roller into multiple layers and combining the specific silicone rubber and silicone oil. CONSTITUTION:This device has the fixing roller 1, the surface layer of which is made of the silicone rubber, a pressure roller 2 and a coating means 3 for coating the fixing roller 1 with the silicone oil. A toner image T is fixed onto a recording material P by the fixing roller 1 and the pressure roller 2. The surface layer of the fixing roller 1 is formed as the multilayered roller constituted by providing a silicone oil layer of a methyl phenyl system on a silicone oil layer of a methyl system. The silicone oil of the methyl phenyl system is used for the silicone oil. Namely, the wettability of the upper layer of the fixing roller 1 and the oil is good and the release property of the toner T on the recording material P at the time of fixing is good and, therefore, an offset preventive layer is formed. Since the offset preventive layer is formed as a thin layer on the roller surface, the bulging of the rubber does not arise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image fixing apparatus for fixing a toner image transferred onto a recording material in an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus, an unfixed toner image transferred onto a recording material is fixed by an image fixing apparatus installed in the apparatus.

Particularly, in the fixing step in the full-color image formation, various toners of yellow, magenta, cyan and black are laminated on the recording material. As described above, in the fixing device of the color image forming apparatus, in order to reproduce the color close to that of the original document, the toners of the plural layers as described above are heated and melted to mix the colors, so that the softening point is low (that is, the low melting point). In), it is necessary to use sharp melt toner.

In this case, the sharp melt toner is not only fixed in a state of extremely low viscosity, but also a plurality of colors are laminated and the toner layer becomes thick, so that the toner is easily offset to the fixing roller. Further, the meltability of each color toner is different due to the difference in the pigment contained in each color toner. Therefore, each fixing temperature range (temperature range where proper fixing can be performed)
Occurs, the common fixing temperature range becomes narrower than that in the case of a single color, and the offset easily occurs. Therefore, in a color image fixing device, it is difficult to use a fluororesin-based material such as Teflon (trade name) commonly used in a black and white image fixing device for a fixing roller, and a silicone rubber or a silicone resin is used. To be done. This is because a release agent such as silicone oil is indispensable for preventing the offset of the color toner described above, but the wettability between the silicone oil and the fluororesin used for the fixing roller is extremely poor. ..

In such an image fixing device, as shown in FIG. 6, a fixing roller 51 and a pressure roller 5 facing the fixing roller 51.
2, an oil application unit 53 that applies silicone oil that acts as a release agent to the fixing roller 51, and the fixing roller 51.
And roller cleaning means 54 for cleaning.

The fixing roller 51 is formed to have an outer diameter of 40 mm by coating an HTV (high temperature vulcanization type) silicone rubber layer 56 made of dimethyl silicone rubber on an aluminum cored bar 55 to a thickness of 3 mm.

The pressure roller 52 is a 1 mm thick HTV in which the surface is coated with a fluororesin layer on a cored bar 58 made of aluminum.
The silicone rubber layer 59 is formed, and the fixing roller 51 is formed.
Has an outer diameter similar to.

Halogen heaters 57 and 61, which are heating sources, are provided in the core metal 55 of the fixing roller 51 and the core metal 58 of the pressure roller 52, and the surface temperature of the pressure roller 52 is brought into contact with the halogen heaters 57 and 61. The temperature control device 62 controls the halogen heaters 57 and 61 to be turned on / off by the thermistor 62a, and the surface temperatures of the fixing roller 51 and the pressure roller 52 are constantly maintained at about 170 ° C.

The oil applying means 53 uses dimethyl silicone oil having a viscosity of 300 cs as the silicone oil 64 contained in the container 63, and the upper and lower supply rollers 65A, 6A.
5B is drawn up and applied to the silicone rubber layer 56 of the fixing roller 51. Silicone oil 64 to the rubber layer 56
The application amount is adjusted by the application amount adjusting blade 60 which is brought into contact with the upper supply roller 65A.

The roller cleaning means 54 removes the toner offset on the surface of the silicone rubber layer 56 of the fixing roller 51. In this case, a web 66 made of a fibrous member (for example, Nomex (trade name)) is attached to the fixing roller 5.
No. 1 (see Japanese Patent Laid-Open No. 50-57237), and one in which a cleaning roller or a cleaning blade is in contact with the surface of the fixing roller 51.

Paper P as a recording material carrying the unfixed toner image T is conveyed in the direction of arrow a by a conveying device (not shown), and the paper P is indicated by arrow b by a driving device (not shown). Fixing roller 51 and pressure roller 52 which rotate in the direction of
The rollers 51,
The toner and the toner image T are fixed on the paper P by melting the toner by heat and pressure between 52.

However, the following problems occur in the fixing in the image fixing device as described above. That is, dimethyl silicone oil 64 which is a general release agent applied on the silicone rubber layer 56 of the fixing roller 51.
Is transferred to the toner and the paper P at the time of fixing, but the silicone oil 64 remains in a small amount on the fixing roller and easily penetrates into the silicone rubber layer 56 over time.

The phenomenon of the silicone oil 64 penetrating into the silicone rubber layer 56 is further promoted when the fixing roller 51 is heated or when the silicone rubber layer is stressed by the pressure roller 52.

The silicone oil 64 thus infiltrated into the silicone rubber layer 56 promotes the thermal decomposition of the HTV silicone rubber constituting the rubber layer 56 by heat, pressure and the like. As a result, the silicone rubber layer 56 undergoes thermal decomposition to cause a decrease in hardness and swelling, and finally the chemical bond of the HTV silicone rubber is broken and the rubber is broken, so that the silicone rubber layer 56 is peeled off from the fixing roller 51.

This phenomenon is likely to occur particularly near the core metal 55 of the silicone rubber layer 56. It is considered that this is because the temperature near the core 55 of the silicone rubber layer 56 is the highest temperature and the rubber decomposes quickly. For example, a certain silicone rubber has a maximum temperature gradient of about 40 ° C./mm in the thickness direction from the core metal to the surface layer. In this case, in the case where the rubber layer is a roller having a thickness of 3 mm and the roller surface temperature is 170 ° C., the temperature in the vicinity of the core metal is 290 which is close to the limit heat resistance temperature of the silicone rubber.
Rises to ℃. (However, these are the outside temperature and the heater 57
The phenomenon is not limited to the above-mentioned HTV silicone rubber, but RTV (room temperature vulcanization type) such as dimethyl silicone rubber or methyl vinyl silicone rubber is used. The same applies to silicone rubber and LTV (low temperature vulcanization type) silicone rubber.

From the above, in order to prevent the HTV silicone rubber forming the rubber layer of the fixing roller from swelling with silicone oil, fluororubber, fluororesin or fluorosilicone rubber is provided in the middle of the silicone rubber layer of the fixing roller. It has been conventionally proposed to provide an oil barrier layer based on the above. (Japanese Patent Publication No. 54-413
No. 30, 41331) Further, it has been proposed that rubber which is difficult to swell is mixed in the lower layer of the rubber layer of the fixing roller. (Japanese Patent Publication Sho 5
4-41332, JP-B-57-46068, JP-B-60-21860) However, among the above proposals, those provided with an oil barrier layer have a two-layer structure of an offset prevention layer and an oil barrier layer or an elastic layer in the lower layer. In order to have a three-layer structure with layers,
The rubber layer structure of the fixing roller becomes complicated. Also,
The fluorine-based rubber material used for the oil barrier layer as described above is relatively expensive and it is difficult to bond the rubber layers to each other, which increases the cost of the fixing roller. Further, it is technically difficult to mix a system in which a rubber which is difficult to swell is mixed in the lower layer.

Further, as another method, Japanese Patent Publication No. 54-26
No. 373 discloses a silicone rubber and a silicone oil that minimize the swelling of the rubber layer by selecting the type of silicone rubber that constitutes the rubber layer of the fixing roller and the type of silicone oil that is applied. Combinations have been proposed.

In the above proposal, as the silicone oil,
Chlorine-based, fatty acid-modified, nitrile- or fluor-based ones are used, and as the silicone rubber, methyl-based, methylvinyl-based or methylphenyl-based ones are used.
Alternatively, as the silicone oil, use a methyl-based, methylphenyl-based, methylhydrogen-based, chlor-based, fatty acid-modified, nitrile- or fluor-based one, and use a nitrile- or fluor-based one as the silicone rubber (however, , If a nitrile type or fluor type is used as the silicone oil, the same type of silicone rubber is excluded).

The combination of the above silicone oil and silicone rubber prevents swelling of the silicone rubber forming the rubber layer of the fixing roller or the like with the silicone oil.

However, the present inventors have found that even the following combinations, which are not preferable in the above proposal, can prevent the swelling of rubber by oil.

This is the case where a methyl-based or methylvinyl-based one is used as the silicone rubber that constitutes the fixing roller, and a methylphenyl-based one is used as the silicone oil applied to the fixing roller.

[0022]

However, in the case of this combination, the wettability of the oil on the surface of the fixing roller is lower than that when the methyl-based silicone oil is used. Therefore, 1) image unevenness due to uneven application of oil ( The gloss of the image may differ depending on the amount of oil). 2) Toner external additives such as toner resin, silica and alumina, and various components of paper are firmly adhered to the roller surface even if the above-described roller cleaning means is provided, and these accumulate in a durable manner and are originally used as the roller. Since the wettability of silicone oil on the surface and the releasability from the toner cannot be obtained, offset occurs relatively early. There was a problem.

Therefore, an object of the present invention is to solve the above problems, prevent swelling of silicone rubber constituting a fixing roller due to excessive impregnation of silicone oil with a simple and inexpensive fixing roller, and prevent offset. An object is to provide an image fixing device that is strong and has a long life.

[0024]

According to the present invention, the above object is to provide a fixing roller having a surface made of silicone rubber, an oil applying unit for applying silicone oil to the fixing roller, and a pressure contact member for the fixing roller. The recording material on which the toner image is transferred is sandwiched between the fixing roller and the pressure roller, and the recording material is heated and pressed to fix the toner image on the recording material. In the image fixing device, the fixing roller is a multi-layer roller in which the surface layer is a methyl- or methylvinyl-based silicone rubber layer and a methylphenyl-based silcon rubber layer is provided, and the silicone oil is a methylphenyl-based silicone oil. It is achieved by doing.

[0025]

According to the present invention, the rubber layer of the fixing roller is a multi-layer in which a methylphenyl-based silicone rubber layer is provided on a methyl-based or methylvinyl-based silicone rubber layer, and a methylphenyl-based silicone is used as a release agent. As a result of using oil, it was found that the oil impregnation rate of the rubber layer was lowered and the swelling of rubber was prevented.

[0026]

An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic block diagram showing an embodiment of the image fixing device of the present invention.

As shown in FIG. 1, the image fixing device 26 includes a fixing roller 1, a pressure roller 2 facing the fixing roller 1,
The fixing roller 1 is provided with a release agent applying means 3 for applying a release agent silicone oil and a roller cleaning means 4 for polishing the fixing roller 1.

The fixing roller 1 is made of an aluminum core metal 5
A silicone rubber layer 6 having an outer diameter of 40 mm is coated on the upper surface, and the details thereof will be described later.

The pressure roller 2 is made of an aluminum core metal 8
1mm thick HTV with fluororesin layer coated on top
(High temperature vulcanization type) Like the fixing roller having the silicone rubber layer 9, the outer diameter is 40 mm.

In the core metal 5 of the fixing roller 1 and the core metal 8 of the pressure roller 2, halogen heaters 7 and 1 as heating sources are respectively provided.
1, the surface temperature of the pressure roller 2 is detected by the thermistor 12a that is in contact with the pressure roller 2, and the temperature control device 12 controls the heaters 7 and 11 to turn on and off. The temperature is kept constant at about 170 ° C.

The release agent applying means 3 is a methylphenyl silicone oil having a viscosity of 450 cs as the silicone oil contained in the container 13 (KF- manufactured by Shin-Etsu Chemical Co., Ltd.).
54) is drawn up by the upper and lower supply rollers 15A and 15B and applied onto the silicone rubber layer of the fixing roller 1. The application amount of the silicone oil 14 on the silicone rubber layer 6 is adjusted by the application amount adjusting blade 10 that is brought into contact with the upper supply roller 15A. Here, the proper application amount is 0.01 to 0.
2 g, preferably 0.03 to 0.1 g.

The roller cleaning means 4 cleans deposits (toner external additives such as toner resin, silica and alumina, and various components of paper) on the surface of the silicone rubber layer 6 of the fixing roller 1. Here, the cleaning member is a fibrous cleaning web that is a conventional cleaning member that is brought into contact with the fixing roller 1 by the pressing roller 42, and at least the cleaning surface side is nickel-plated web 41. This nickel-plated web 41 has a conventional heat-resistant non-woven fabric Nomex (trade name) and nickel as an abrasive by an electroless plating method, with a thickness of about several μm on the surface of the cleaning side of the web per square meter of the web. It is plated to have a weight of 3g. The nickel-plated web 41 configured as described above is fed by the feed roller 43 in the direction of arrow C in the figure and is also wound up by the winding roller 44.

As shown in FIG. 2, the fixing roller 1 used in the apparatus of the present embodiment as described above has a core metal 5 and a rubber layer 6 having an upper layer 61 of 0.2 mm thick methylphenyl silicone rubber. The lower layer 62 is a 3 mm-thick two-layer roller in which 2.8 mm-thick dimethyl silicone rubber (manufactured by Toray Industries, Inc.) is formed. The methylphenyl silicone rubber layer of the upper layer 61 has a good wettability with the methylphenyl silicone oil applied to the roller and has a good releasability from the toner T on the recording material at the time of fixing and thus serves as an offset prevention layer. Further, since this offset prevention layer is formed as a thin layer on the roller surface, swelling of rubber does not occur.

On the other hand, the dimethyl silicone rubber layer of the lower layer 62 does not cause the rubber to swell due to the methylphenyl silicone oil applied to the roller surface, as described above. Therefore, the elastic layer does not require an oil barrier layer. By optimizing the thickness, hardness, etc. of this elastic layer, it is possible to prevent wrinkling of the recording material during fixing and to adjust the contact area between the recording material and the roller.

In this embodiment, after the fixing roller 1 is molded, it is immersed in a 200 ° C. oil bath of dimethyl silicone oil (KF96-100cs, manufactured by Shin-Etsu Chemical Co., Ltd.) to preliminarily impregnate the rubber with oil. ..

Thus, pre-impregnation of silicone rubber with silicone oil is effective for initial offset. As the silicone oil to be impregnated, if the weight ratio to the rubber is within 20%, preferably 5 to 10%, dimethyl silicone oil, methylphenyl silicone oil, etc. are not particularly limited, but dimethyl silicone oil is more preferable. It was effective. Here, as the impregnation method, the silicone rubber may be impregnated by immersing the silicone rubber in the silicone oil, or the silicone oil may be internally added and impregnated during the compounding of the silicone rubber.

As the silicone rubber used for the fixing roller, one having a high crosslinking density is desirable in order to prevent excessive impregnation of silicone oil. Further, it is more desirable that the amount of the filler in the silicone rubber is large because the same effect as described above is enhanced. However, if the amount of the filler is excessive, the releasability of the fixing roller deteriorates. Therefore, an appropriate amount is determined in consideration of the releasability and the degree of swelling of rubber.

Next, an experiment conducted on the silicone rubber layer 6 of the fixing roller 1 and the silicone oil of the release agent applying means 3 will be described.

The experimental method was to cure several types of methyl-type and methylvinyl-type silicone rubbers by a conventionally known method or a method recommended by a rubber maker to prepare 1 g of rubber pieces, and to preheat the temperature to 170 to 180 ° C. It was immersed in heated dimethyl silicone oil and methylphenyl silicone oil. These were taken out at regular intervals and the weight change was measured to measure the change in the oil impregnation rate (corresponding to the swelling amount) of the rubber piece. Here, the impregnation rate (%) = weight after immersion / initial weight × 100-10
Set to 0.

As the rubber used, methyl-based and methylvinyl-based silicone rubbers manufactured by Toray Industries, Inc. were used.
As dimethyl silicone oil and methylphenyl silicone oil, K manufactured by Shin-Etsu Chemical Co., Ltd.
F96-300cs and KF54-450cs were used respectively.

As a representative example, when dimethyl silicone oil is used as shown in FIG.
The impregnation rate is above 100% and continues to increase even after 30 hours. In addition, swelling was also confirmed in some of the others (not shown) exceeding 70%. However, in the case of methylphenyl silicone oil, the impregnation rate was 20% or less after 20 hours in all the rubbers to be saturated and no swelling was observed.

As described above, since methylphenyl silicone oil has a low impregnation rate with respect to methyl-based or methylvinyl-based silicone rubber, it is clear that the rubber does not swell. The reason for this is considered to be that the ratio of methyl groups contained in oils and rubbers and affecting their respective affinities is low in the case of methylphenyl silicone oil.

This can also be explained by the fact that the impregnation rate into dimethyl silicone rubber decreases as the number of moles of phenyl groups in methylphenyl silicone rubber increases, as shown in a representative example in FIG.

The methylphenyl silicone oil used here is KF54-450cs (the number of moles of the phenyl group = 25%) KF514-300cs (the number of moles of the phenyl group = 15)
%) Manufactured by Shin-Etsu Chemical Co., Ltd.

From the above, it can be seen that in the case of methylphenyl silicone oil, the number of moles of phenyl groups is one condition for the oil impregnation rate of rubber. That is, when the number of moles of phenyl groups in the methylphenyl silicone oil is small, the oil is excessively impregnated into the rubber and the swelling prevention effect is weakened. Therefore, the number of moles of phenyl groups of methylphenyl silicone oil is preferably 5 mol% or more.

The viscosity of the methylphenyl silicone oil is 10 to 100, which is generally used in the image forming apparatus.
There was no problem if it was about 00 cs.

Next, the operation of the fixing device of this embodiment will be described with reference to FIG.

The recording material P carrying the unfixed toner image T is conveyed by a conveying device (not shown) in the direction of arrow a in the drawing, and is driven by a driving device (not shown) in the direction of arrow b in the drawing. An unfixed toner image is formed on the recording material P by heat and pressure that are passed between the rotating fixing roller 1 and the pressure roller 2 and are supplied from the halogen heater 7 via the fixing roller 1 and the pressure roller 2, respectively. T is fixed. Although the unfixed toner image T which is thermally fixed on the recording material P in the above-described heat fixing step is slightly offset on the surface of the fixing roller 1,
The offset toner (as described above, the toner resin, external additives such as silica and alumina, and various components of paper) is removed by the roller cleaning means 4 as follows.

That is, the nickel-plated web 41 is wound around the winding roller 44 at a predetermined speed while being pressed by the pressing roller 42. Then, the nickel-plated web 41 is brought into contact with the surface of the fixing roller 1 to clean the adhered matter on the surface of the fixing roller 1 as the fixing roller 1 rotates.

In this case, since the nickel-plated web 41 is fibrous, the state of contact with the surface of the fixing roller 1 is very good, and the rubber scraped from the surface of the fixing roller 1 and the adhered matter on the surface are well separated between the fibers of the web 41. Adsorbs and has high cleaning performance.

In the above-mentioned embodiment, the lower layer 62 may be made of methyl vinyl silicone rubber. Further, as shown in FIG. 5, the fixing roller 1 is mounted on the core metal 5 with the rubber layer 6
As the upper layer 61, a methyl phenyl silicone rubber having a thickness of 0.2 mm, the intermediate layer 63 having a dimethyl silicone rubber having a thickness of 2.0 mm, and the lower layer 62 having a dimethyl silicone rubber having a thickness of 0.8 mm (manufactured by Toray Industries, Inc.) are formed to have a thickness of 3 mm. It may be a three-layer roller. In this case, the intermediate layer 63 is used as an elastic layer, and dimethyl silicone rubber having a low rubber hardness is used.
It is more desirable to use dimethyl silicone rubber which is excellent in heat resistance.

Similarly, methyl vinyl silicone rubber may be used for the lower layer 62 and the intermediate layer 63, or dimethyl silicone rubber and methyl vinyl silicone rubber may be combined.

The fixing device according to the present invention is particularly effective for fixing a full-color image forming device in which toner is mixed in color during fixing, but is also effective for a monochrome image fixing device.

[0055]

As described above, according to the present invention, the methylphenyl type silicone oil is used as the silicone oil applied to the fixing roller, and the surface layer of the fixing roller is formed on the methyl type or methylvinyl type silicone rubber layer. Since it has a multi-layer structure with a methylphenyl silicone rubber layer, the swelling of the silicone rubber that composes the fixing roller due to excessive impregnation of silicone oil can be prevented with a simple and inexpensive fixing roller, and it is resistant to offset and has a long service life. Can be extended.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an image fixing device of the present invention.

FIG. 2 is a sectional view showing a schematic configuration of a fixing roller of the apparatus shown in FIG.

FIG. 3 is a graph showing an example of a time transition of an oil impregnation rate of a rubber piece, which was performed for silicone rubber and silicone oil used in the present invention.

FIG. 4 is a graph showing an example of the time transition of the oil impregnation rate when the number of moles of phenyl groups of methylphenyl silicone rubber is changed.

FIG. 5 is a schematic configuration diagram showing an embodiment in which the fixing roller of the present invention has three rubber layers.

FIG. 6 is a sectional view showing a schematic configuration of a conventional image fixing device.

[Explanation of symbols]

 1 Fixing Roller 2 Pressure Roller 3 Oil Applying Means 14 Silicone Oil 61 Methylphenyl Silicone Rubber 62 Dimethyl Silicone Rubber

Claims (1)

Claim: What is claimed is: 1. A fixing roller having a surface layer made of silicone rubber, an oil applying unit for applying silicone oil to the fixing roller, and a pressure roller arranged in pressure contact with the fixing roller. In the image fixing device for fixing the toner image on the recording material by sandwiching and heating and pressing the recording material on which the toner image is transferred by the fixing roller and the pressure roller. Image fixing characterized in that the roller is a multi-layer roller in which a methylphenyl or methylvinyl type silicone rubber layer is provided on a methylphenyl type silcon rubber layer, and the silicone oil is methylphenyl type silicone oil. apparatus.