JPH03168788A - Image fixing device - Google Patents

Abstract

PURPOSE:To prevent the silicone rubber of a fixing roller from swelling and to enable excellent fixation by coating the fixing roller with methyl phenyl silicone oil, and forming the fixing roll by using specific methyl or methyl vinyl silicone rubber. CONSTITUTION:The fixing roller 1 is formed by coating a mandrel 5 made of aluminum with a silicone rubber layer 6 and dimethyl silicon rubber which is <=0% in saturation swell quantity is used for the rubber layer 6. A releasing agent coating means 3 scoops up the methyl phenyl silicone oil put in a container 13 by supply rolls 15A and 15B and the silicone rubber layer 6 of the fixing roller 1 is coated. The coating amount of the silicone oil to the rubber layer 6 is adjusted by a coating amount adjusting blade 10 which is made to abut on the supply roller 15A. Consequently, the silicone rubber constituting the fixing roller 1 is prevented from swelling and the excellent fixation becomes possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image fixing device for fixing a toner image transferred onto a transfer material in an image forming apparatus.

The unfixed toner image transferred onto the transfer material in the image forming apparatus is fixed by a fixing device installed within the apparatus.

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

The fixing roller 1 is made by coating an aluminum core 5 with an ITV (high temperature vulcanization type) silicone rubber layer 6 to a thickness of 3 mm.
It is formed to have an outer diameter of 40 mmφ.

The pressure roller 2 has a 1mm thick HT on an aluminum core 8.
It is coated with a V silicone rubber layer, and a fluororesin layer 9 is formed on the surface thereof, and the outer diameter is similarly 40 mmφ.

Halogen heaters 7 and 11 as heat sources are provided in the core metal 5 of the fixing roller l and the core metal 8 of the pressure roller 2, respectively, and the temperature of the pressure roller 2 is controlled by a thermistor 1 in contact with the halogen heaters 7 and 11, respectively.
2a, the temperature control device 12 turns on and off the halogen heaters 7 and 11 to maintain the temperatures of the fixing roller 1 and the pressure roller 2 constant at about 170°C.

The release agent application means 3 pumps up dimethyl silicone oil with a viscosity of 300 CS as the silicone oil 14 stored in a container 13 using upper and lower supply rollers 15A and 15B, and applies it to the silicone rubber layer 6 of the fixing roller 1. It has become.

The amount of silicone oil applied to the rubber layer 6 is adjusted by an application amount adjusting blade 10 brought into contact with the upper supply roller 15A.

The cleaning means 4 removes toner offset from the silicone rubber layer 6 of the fixing roller 1.

The transfer paper P carrying the unfixed toner image T is transported in the direction of arrow a by a transport device (not shown), and the transfer paper P
By passing the toner while sandwiching it between a fixing roller 1 and a pressure roller 2, which are rotated in the direction of arrow b by a drive device (not shown), the toner is melted by the heat and pressure between the rollers 1 and 2, and a toner image T is formed. is fixed on the transfer paper P.

However, it has been found that the following problems occur when fixing with such a fixing device.

That is, the dimethyl silicone oil 14 as a release agent applied on the silicone rubber layer 6 of the fixing roller 1 is transferred to the toner and the transfer paper P during fixing, and the toner image T is fixed on the transfer paper P. However, this silicone oil 14
remains on the fixing roller 1 in a considerable amount and penetrates into the silicone rubber layer 6 over time.

This phenomenon of silicone oil 14 entering into silicone rubber layer 6 occurs when fixing roller 1 is heated.
This is further promoted when rotated and when the silicone rubber layer 6 receives stress from the pressure roller 2 due to rotation.

Silicone oil 14 that has entered the silicone rubber layer 6
promotes thermal decomposition of the HTV silicone rubber constituting the rubber layer 6 by heat and pressure. If this state continues for a long time, thermal decomposition of the silicone rubber layer 6 progresses and the hardness decreases, and the rubber layer 6 further swells with the silicone oil 14, and eventually the chemical bonds of the HTV silicone rubber are broken and the rubber becomes A state of tearing occurs. As a result, a phenomenon occurs in which the silicone rubber layer 6 peels off from the fixing roller 1.

Such a phenomenon is particularly likely to occur near the aluminum core 5 of the HTV silicone rubber layer 6. This is thought to be because the portion of the silicone rubber layer 6 that is close to the core metal 5 is particularly high in temperature, and the decomposition of the rubber progresses significantly. For example, the thermal conductivity of HTV silicone rubber is 1. OX 1 0-
Even if the temperature is as high as ``caI2/cm・sec-deg'', the temperature near the core metal 5 changes depending on conditions such as the outside temperature, the amount of heat from the heater 7, and the rotation of the roller 1, but When the temperature is 170°C, it may be close to 200°C.

This is not limited to HTV silicone rubber, but also RTV (room temperature vulcanizable) silicone rubber such as dimethyl silicone rubber and methyl vinyl silicone rubber, LT
A similar phenomenon occurs with V (low temperature vulcanization type) silicone rubber.

The above phenomenon depends on the usage time of the image fixing device that involves heating. Heating time of roller 1, pressure conditions,
Although it changes to some extent depending on the rotation conditions, the difference is not that big.

For the above reasons, in order to prevent the HTV silicone rubber that makes up the rubber layer of the fixing roller from swelling due to silicone oil, an oil barrier made of fluororubber, fluororesin, or fluorosilicone rubber is installed between the silicone rubber of the fixing roller. It has been previously proposed to provide a layer (Japanese Patent Publication No. 54-41330, Japanese Patent Publication No. 54-41331). , It has also been proposed that the lower layer of the rubber layer of the fixing roller be made of a mixture of rubber that does not swell easily.
No. 41332, Special Publication No. 57-46068, Special Publication No. 2
No. 1860).

However, in the above proposal, in order to provide an anti-offset layer on the surface layer of the fixing roller, the structure of the rubber layer of the fixing roller is changed to two.
The fixing roller is complicated with ~4 layers, which increases the cost of the fixing roller, and because it is difficult to adhere each rubber layer, there is a drawback that peeling occurs between the rubber layers during use of the fixing roller. Furthermore, even if a rubber that does not easily swell is used as the lower layer of the rubber layer of the fixing roller, the above-mentioned phenomenon of rubber peeling cannot be completely prevented, and silicone oil gradually enters the rubber, resulting in This will lead to the rubber breaking down in the not too distant future.

As another method, Japanese Patent Publication No. 54-26373 discloses a method for forming a rubber layer by selecting the type of silicone rubber constituting the rubber layer of the fixing roller, etc. and the type of silicone oil to be applied. It has been proposed to combine rubber and silicone oil so that the rubber does not swell or swells only slightly.

In the above proposal, chlorine-based, fatty acid-modified, nitrile-based, or fluor-based silicone oil is used,
As the silicone rubber, methyl, methylvinyl or phenyl is used. Alternatively, methyl, phenyl, methylhydrogen, methylphenyl, dimethylphenyl, chloro, fatty acid modified, nitrile or fluoro-based silicone oil may be used, and nitrile or fluoro-based silicone rubber may be used. (However, if nitrile-based or fluoro-based silicone oil is used, the silicone rubber must not be of the same type as the oil). The above combination of silicone oil and silicone rubber is said to prevent the rubber constituting the rubber layer of the fixing roller from swelling due to the silicone oil.

The following table 1 is a selection of some combinations from the above proposal. According to this, if methyl, methylvinyl, or phenyl silicone rubber is used, and if methyl or phenyl silicone oil is used, the rubber will swell, so these combinations are preferable. It is said that there is no.

Table 1 However, the present inventors have found that even among the combinations shown in Table 1 above, there are some that can prevent rubber from swelling with oil.

If a methyl-based or methyl-vinyl-based silicone rubber is used to make up the fixing roller, and a methylphenyl-based silicone oil is used as the silicone oil supplied to the fixing roller, some combinations of Some rubbers have a saturated swelling amount of 0% or less, which means that silicone oil hardly penetrates into the silicone rubber and the rubber can be prevented from swelling due to oil.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image fixing device that prevents the silicone rubber constituting the fixing roller from swelling due to silicone oil and allows good fixing.

The above objects are achieved by the image fixing device according to the present invention. In summary, the present invention applies silicone oil to a fixing roller made of silicone rubber, while sandwiching a transfer material on which a toner image has been transferred between the fixing roller and a pressure roller, and heats and pressurizes the transfer material. Edict Toner/! 8
In an image fixing device that fixes to fJ-front i, +cτHL, applying methylphenyl-based silicone oil as the silicone oil to the fixing roller,
The image fixing device is characterized in that the fixing roller is formed using a methyl-based or methyl-vinyl-based silicone rubber having a saturated swelling amount of the methylphenyl-based silicone oil of 0% or less as the silicone rubber.

exemption Examples of the present invention will be described in detail below.

As mentioned above, the inventors of the present invention have found that when methyl-based or methyl-vinyl-based silicone rubber is used for the fixing roller and methylphenyl-based silicone oil is used as the silicone oil supplied to the fixing roller, It has been found that some combinations have a saturated swelling amount of silicone rubber relative to silicone oil of 0% or less, and that this prevents the silicone oil from penetrating into the silicone rubber and prevents the rubber from swelling due to the oil.

The present invention has been achieved based on the above findings.

The present invention will be described below based on experiments conducted by the inventors.

The present inventors conducted an experiment to determine the amount of saturated swelling of the silicone rubber constituting the fixing roller in methylphenyl silicone oil at 200°C.

Experiment Methyl-based and methyl-vinyl-based silicone rubbers were cured using conventionally known methods or methods recommended by rubber manufacturers, and rubber pieces of 2 mm in height, 20 mm in width, and 10 mm in length were created, and these rubber pieces were used as they were. , methylphenyl silicone oil was immersed in an oil bath heated to 200°C.

The methyl silicone rubber or methyl vinyl silicone rubber used was KE1300%K manufactured by Shin-Etsu Chemical Co., Ltd.
E1603 and KE1406. The methylphenyl silicone oil used was K manufactured by Shin-Etsu Chemical Co., Ltd.
It is F54 450cs.

The saturated swelling amount (%) of silicone rubber with respect to silicone oil is calculated as follows: (B-A)/ It was calculated using the formula AX 1 00 .

As a result, the saturated swelling amount of silicone rubber with respect to silicone oil was as follows.

KE1300: +20% KE1603: +15% KE1406: -3% According to the above results, as shown in the above-mentioned Japanese Patent Publication No. 54-26373, methyl-based or methyl-vinyl-based silicone rubber and methylphenyl-based silicone oil In some combinations, the rubber swells with oil, but the above results show that there are also combinations in which the rubber does not swell with oil (in this experiment, the weight actually decreases). It turns out. It is difficult to say with certainty that the combination of methyl-based or methyl-vinyl-based silicone rubber and methylphenyl-based silicone oil causes the rubber to swell with the oil.

In the above results, silicone rubber KE1406 is -3%
The reason why the weight decreases from the initial state is that the oil contained in the silicone rubber or the low molecular weight content in the rubber oozes out of the rubber and loses weight, and the rubber loses weight due to heating in a 200℃ oil bath. This is the result of one or both of these phenomena.

As mentioned above, among methyl-based and methylvinyl-based silicone rubbers, there are rubbers that swell with methylphenyl silicone oil and rubbers that do not. It was found that this was largely due to the crosslink density. That is, by increasing the crosslinking density of silicone rubber, swelling due to methylphenyl silicone oil can be suppressed, and the amount of saturated swelling can be controlled from 20% or more to 0% or less, as shown in experiments. There was found.

Another cause is the amount of filler in the silicone rubber, which also has a large effect.

The larger the amount of filler, the less silicone oil will enter the silicone rubber, and as a result, the amount of saturated swelling of the rubber with respect to oil can be suppressed.

In addition to the above causes, the curing temperature and curing time applied to the rubber when molding it into a silicone rubber fixing roller also have an effect, and the curing conditions when molding the rubber also control the amount of rubber saturated swelling with oil. be done.

As described above, by adjusting the crosslinking density of methyl silicone rubber or methyl vinyl silicone rubber, the amount of filler in the silicone rubber, etc., the amount of swelling of silicone rubber with respect to methylphenyl silicone oil can be controlled. Swelling can be prevented. However, as a condition for methylphenyl silicone oil,
One factor is the number of moles of phenyl groups. That is,
When the number of moles of phenyl groups in the methylphenyl silicone oil is less than 5 moβ%, the effect of preventing rubber from swelling against the methylphenyl silicone oil decreases. This is because when the number of moles of phenyl groups in methylphenyl silicone oil is less than 5mol12%, the physical properties of methylphenyl silicone oil become almost the same as dimethyl silicone oil, so methylphenyl silicone oil easily penetrates into the rubber. This is because it is difficult to swell and the effect is weakened.

Therefore, it is desirable that the number of moles of phenyl groups in the methylphenyl silicone oil is 5 mo12% or more.

Further, there is no problem as long as the viscosity of the methylphenyl silicone oil is about 10 to 10,000 cs, which is generally used in image forming apparatuses.

Next, an image forming apparatus equipped with the image fixing device of the present invention will be described. FIG. 1 is a block diagram showing an embodiment of an electrophotographic image forming apparatus which is equipped with an image fixing device of the present invention and is capable of forming a single color image.

As shown in FIG. 1, this image forming apparatus includes an apparatus main body 10
A transfer material conveying system (2) is provided extending from one side of 0 (right side in FIG. 1) to approximately the center of the apparatus main body 100, and the apparatus main body 100
A latent image forming section (2) is provided approximately in the center of the transfer drum 18 which is rotatable in the direction of the arrow and constitutes the transfer material transport system I, and a latent image forming section (2) is provided on the other side of the apparatus main body 100. It basically consists of a developing means, ie, a rotary developing device m, arranged close to the section H.

The transfer material conveyance system I includes transfer material supply trays 101 and 102 that can be attached and detached from an opening formed on one side of the apparatus main body 100 (on the right side in FIG. 1), and these trays 101 and 1.
Paper feeding rollers 103 and 104 arranged almost directly above 02
, a paper feed guide 24a having paper feed rollers 106, 107 at both ends disposed close to these rollers 103, 104, a paper feed guide 24b following this, and r! of the transfer drum l8. A transfer material contacting roller l7, a gripper 16, a transfer material separation charger 22, and a separation claw 20 are provided in order from the lower end to the upper end in the @I rotation direction around the
and a transfer charger l9 disposed inside the transfer drum 18.
and a transfer material separation charger 23, a conveyance belt means 25 provided above the paper feed guide 24a and close to the separating claw 20, and an extension of the terminal end of the means 25 in the conveyance direction outside the apparatus main body 100. A device main body 1 provided extending to
00, and an image fixing device 26 according to the present invention, which is disposed between the conveyor belt means 25 and the discharge tray 27.

The latent image forming section (2) includes an image carrier rotatable in the direction of the arrow, which is disposed substantially on the upper end of the transfer drum 18 and in contact with the transfer drum 18;
That is, the photoreceptor drum 32, the charger 3o for static elimination provided around the drum 32 in the rotational direction from its upper end to the side ends, the cleaning means 31, the primary charger 33, and the static charger 3o on the outer peripheral surface of the photoreceptor drum 32. It is equipped with an image exposure means such as a laser beam for forming an electrostatic latent image, and an image exposure reflection means such as a polygon mirror.

The rotary developing device ■ consists of a rotating body 3 consisting of a freely rotatable housing.
4, a yellow developer 34Y, a magenta developer 34M, and a cyan developer, which are mounted on the rotating body 34 and are configured to visualize, or develop, an electrostatic latent image at a position facing the outer peripheral surface of the photoreceptor drum 32. It has a developing device 34C and a black developing device 34BK.

The overall sequence of the image forming apparatus with the above configuration will be briefly explained using the case of full color mode as an example.
It is as follows.

That is, when the photosensitive drum 32 rotates in the direction of the arrow shown in FIG. The image is exposed to the light E, and an electrostatic latent image of a yellow image is formed on the photoreceptor drum 32. This electrostatic latent image of the yellow image is developed by the yellow developing device 34Y, which is previously set at the developing position by the rotation of the rotating body 34 of the developing device (2).

On the other hand, a transfer material (not shown) transported via the paper feed guide 24a, paper feed roller 106, and paper feed guide 24b
is held by the gripper 16 at a predetermined timing,
It is electrostatically wound around the transfer drum 18 by the abutting roller 17 and the electrode facing the abutting roller 17 . The transfer drum 18 rotates in the direction of the arrow shown in FIG. 1 in synchronization with the photoreceptor drum 32, and the visible image developed by the yellow developer 34Y is transferred between the outer peripheral surface of the photoreceptor drum 32 and the transfer drum. Transfer is performed by the transfer charger 19 at the portion where the outer circumferential surface of the transfer charger 18 is in contact. The transfer drum 18 continues to rotate and transfers the next color (magenta in FIG. 1).
Prepare for transcription.

On the other hand, the photosensitive drum 32 is neutralized by the neutralizing charger 30, cleaned by the cleaning means 31, and then charged again by the temporary charger 33, and subjected to image exposure as described above with the next magenta image signal. The developing device (3) rotates while an electrostatic latent image based on the magenta image signal is formed on the photoreceptor drum 32 by the image exposure, and fixes the magenta developing device 34M at the developing position;
Perform predetermined magenta development. Subsequently, the above-mentioned process is carried out for cyan color and black color respectively, and when the transfer of four colors is completed, the visible image of four colors formed on the transfer material is charged by each charger 22 and 23. When the transfer material is released from the gripper 16, the transfer material is separated from the transfer drum 18 by the separating claws 24 and sent to the image fixing device 26 by the conveyor belt means 25, where the colors are mixed by heat and pressure. Then, the full-color printing sequence is completed and the desired full-color print image has been formed.

Next, the developer used in this image forming apparatus will be explained.

The developer color toner used in color image forming devices must have good melting properties and color mixing properties when heated, and use sharp-melt toners with a low softening point and low melt viscosity. It is preferable to do so. That is, by using such a sharp melt toner, it is possible to widen the color reproduction range of a copy and obtain a color copy that is faithful to the original image.

Such a sharp melt toner is produced by melt-kneading, for example, a polyester resin, a styrene-acrylic resin, a colorant (dye, sublimation dye), a charge control agent, etc., followed by pulverization and classification. Various external additives can be added to the toner as needed.

Considering the fixing properties and sharp melt properties of the color toner, it is particularly preferable to use a sharp melt polyester resin as the binder resin.

A sharp-melt polyester resin is a high molecular compound having an ester bond in the main chain of a molecule synthesized from a diol compound and a dicarboxylic acid.

The sharp-melt color toner used in this image forming apparatus has a sharp-melt polyester resin with a softening point of 60 to 150°C, preferably 80 to 120°C.

The softening properties of this sharp-melt toner are shown in FIG.

Figure 2 shows a flow tester CFT-500 type (manufactured by Shimadzu Corporation) with a nozzle diameter of 0.5 mm and thickness of 1.0 mm, a load of 50 kg applied, and a preheating time of 300 at an initial temperature of 80°C. A Blunger drop-temperature curve (hereinafter referred to as a softening S-curve) of the toner is obtained when the temperature is raised at a constant rate of 5° C./min after 2 seconds. The sample color toner used was 1 to 3 g of purified fine powder, and the plunger had a cross-sectional area of 1.0 cm.

The softening S-shaped curve of color toner is as shown in FIG. That is, as the humidity increases at a constant rate, the toner is gradually heated and begins to flow out (Blunger descent A).
-B). As the temperature rises further, the molten toner flows out (B→C-D), and the plunger stops descending (D→E). The height of the S-curve indicates the total amount of toner flowing out, and H/2 C of
The temperature To corresponding to the point indicates the softening point of the toner.

The sharp-melt resin that provides such color toners has a melting temperature of 10'cp at a temperature of T+
When the temperature at which 5X10' cp is exhibited is T2, 'r,=90 to 150°C, 1ΔTl=lT, -T. l
= Refers to a resin that satisfies the condition of 5 to 30°C.

Sharp-melt resins having temperature-melt viscosity characteristics as described above are characterized by an extremely sharp decrease in viscosity when heated. This decrease in viscosity causes proper mixing of the top toner layer and the bottom toner layer of the color toner layer, and also rapidly increases the transparency of the toner layer itself, resulting in good discoloration mixing. be. Sharp melt color toners using such resins have a high affinity and are easily offset by the fixing roller.

Next, the image fixing device of the present invention will be explained.

FIG. 3 is a schematic configuration diagram showing an embodiment of the image fixing device of the present invention.

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

The fixing roller 1 has an aluminum core 5 coated with a silicone rubber layer 6, which will be described later, and has an outer diameter of 40 mm.

The pressure roller 2 has a 1mm thick HT on an aluminum core 8.
It is coated with a V (high temperature vulcanization type) silicone rubber layer, and a fluororesin layer 10 is formed on the surface thereof, and similarly has an outer diameter of 40 mmφ.

Halogen heaters 7 and 11 as heat sources are provided in the core metal 5 of the fixing roller l and the core metal 8 of the pressure roller 2, respectively, and the temperature of the pressure roller 2 is controlled by a thermistor 1 in contact with the halogen heaters 7 and 11, respectively.
2a, temperature-based off control is performed to maintain the temperatures of the fixing roller 1 and the pressure roller 2 constant at about 170°C.

The release agent application means 3 uses methylphenyl silicone oil (KF54 450c manufactured by Shin-Etsu Chemical Co., Ltd.) with a viscosity of 450CS as the silicone oil 14 housed in a container 13.
s) is drawn up by upper and lower supply rollers 15A and 15B and applied to the silicone rubber layer 6 of the fixing roller 1. The amount of silicone oil applied to the rubber layer 6 is adjusted by an application amount adjusting blade 10 brought into contact with the upper supply roller 15A.

The cleaning means 4 removes toner offset from the silicone rubber layer 6 of the fixing roller 1.

The transfer paper P carrying the unfixed toner image T is transported in the direction of arrow a by a transport device (not shown), and the transfer paper P
The toner image T is fixed on the transfer paper P by melting the toner with heat and pressure between the fixing roller 1 and the pressure rollers 1 and 2, which are rotated in the direction of arrow b by a drive device (not shown).

According to this embodiment, the fixing roller 1 uses dimethyl silicone rubber (KE1406 manufactured by Shin-Etsu Chemical Co., Ltd.) with a saturated swelling amount of -3% for the rubber layer 6 so as not to swell with methylphenyl silicone oil. It has become.

Normally, when fixing a color toner image, it is necessary to apply a large amount of silicone oil as a release agent to the rubber layer 6 of the fixing roller 1, but in this embodiment, the oil application amount is measured using the oil application amount measurement method described later. Accordingly, 0.08 g of methylphenyl silicone oil was applied per sheet of A4 transfer paper.

When the toner image was fixed by the image fixing device 26 under the above conditions, no swelling of the silicone rubber layer 6 due to silicone oil or destruction of the rubber of the rubber layer 6 occurred even if the fixing roller 1 was heated and used for one year. Good results were obtained.

As described above, in the present invention, methyl-based or methyl-vinyl-based silicone rubber is used as the silicone rubber constituting the rubber layer 6 so that the saturated swelling amount of silicone oil in the silicone rubber layer 6 of the fixing roller 1 is 0% or less. ,
By selecting and combining methylphenyl-based silicone oil as the release agent silicone oil applied to the rubber layer 6, the release effect of the methylphenyl-based silicone oil as the release agent and the release of the rubber that oozes out from the rubber are improved. The mold release effect from the inner surface of the rubber due to the low molecular weight content can be obtained, and the fixing roller 1 can have a long life and high mold releasability.

Furthermore, since the silicone oil does not enter the rubber, deformation due to swelling of the fixing roller 1 and thermal decomposition and destruction of the rubber due to heating from the inside can be prevented.

Conventionally, silicone rubber (KE1300 manufactured by Shin-Etsu Chemical Co., Ltd.) is used, which has a saturated swelling amount of 20% with respect to dimethyl silicone rubber or methylphenyl silicone oil, so if the fixing roller is heated, the rubber oil will disappear in two months. Swelling occurs, resulting in a decrease in hardness, and the rubber is destroyed by heat, resulting in it peeling off from the core metal.

Rubber with the same saturated swelling amount of 15% (Shin-Etsu Chemical Co., Ltd.)
When using KE1603), similar rubber damage occurred after heating the fixing roller for 6 months.

As is clear from the above, the present invention is suitable for an image fixing device in which a fixing roller is coated with silicone oil in order to obtain releasability, particularly in a fixing device in a color image forming apparatus in which a large amount of silicone oil is coated.

In this example, the amount of silicone oil applied to the fixing roller l is calculated as 0.08 g per sheet of A4 transfer paper.
The case is shown as A4, but the coating amount is 0.00 1 g
/A4 or larger is valid.

The amount of silicone oil applied is determined as follows.

In other words, the weight of 50 sheets of A4 size blank paper is A1 (g), and the fixing roller and pressure roller are connected without transferring an image onto the blank paper or applying silicone oil to the rubber layer of the fixing roller. The weight of 50 sheets of blank paper after passing through the gap is B
(g), and similarly, the weight of another 50 sheets of A4 size blank paper is A2 (g), and no image is transferred onto this white paper, but silicone oil is not applied to the rubber layer of the fixing roller. , if the weight of 50 blank sheets of paper after passing between the fixing roller and the pressure roller is C (g), then the amount of silicone oil applied per one A4 size blank sheet of paper is X (g).
) is calculated as follows.

X= (C+A.-B-A.)/50 In the present invention, the silicone rubber constituting the rubber layer 6 of the fixing roller 1 can be either methyl-based or methyl-vinyl-based, but is especially effective for release. Methyl type R with high
TV (room temperature vulcanizable) silicone rubber is preferred. Even with other types of silicone rubber other than RTV, peelability from the toner image can be obtained by applying methylphenyl silicone oil, but P, which suppresses the offset phenomenon in which toner is transferred to the fixing roller during fixing, This is because methyl-based RTV silicone rubber is preferred because it can extend the service life of the fixing roller until it is removed and reloaded.

Similarly, when considering swelling resistance to methylphenyl silicone oil, condensation type methyl RTV silicone rubber is preferable to addition type methyl RTV silicone rubber because it has higher swelling resistance. Although this is not certain, the addition type crosslinked structure is ~S i-CH2 -CHz -S i~, while the condensed type crosslinked structure is different, as ~Si-0-St~ It is thought that this difference in crosslinked structure causes a difference in interaction with methylphenyl silicone oil, and that the condensed type has higher swelling resistance against silicone oil.

As described above, in the image fixing device of the present invention, the fixing roller is coated with methylphenyl-based silicone oil as the silicone oil, and the fixing roller is coated with the methylphenyl-based silicone oil as the silicone rubber. Since the fixing roller is formed using methyl-based or methyl-vinyl-based silicone rubber whose saturated swelling amount with respect to silicone oil is 0% or less, the silicone rubber of the fixing roller is prevented from swelling due to silicone oil, and thermal decomposition of the rubber is prevented. It is possible to prevent the toner from peeling off from the core bar and to perform good fixing.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram showing an embodiment of an image forming apparatus equipped with an image fixing device of the present invention. FIG. 2 is a graph showing the softening characteristics of the sharp-melt toner used in the image forming apparatus shown in FIG. FIG. 3 is a schematic configuration diagram showing an embodiment of the image fixing device of the present invention. 1: Fixing roller 2 2 Pressure roller 3: Release agent application means 6: Silicone rubber layer 9: Fluororesin layer 18: Transfer drum 26: Image fixing device 32: Photosensitive drum Softening point in Figure 2

Claims (1)

[Claims] 1) While applying silicone oil to a fixing roller made of silicone rubber, the fixing roller and pressure roller sandwich the transfer material on which the toner image has been transferred, and heat and pressurize the transfer material to transfer the toner image. In an image fixing device for fixing onto a material, a methylphenyl-based silicone oil is applied as the silicone oil to the fixing roller, and methyl having a saturated swelling amount of 0% or less with respect to the methylphenyl-based silicone oil is used as the silicone rubber. An image fixing device characterized in that the fixing roller is formed using silicone rubber of silicone rubber or methylvinyl silicone rubber.