JPH1039666A - Roller for fixing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an image of high quality, and to improve the durability and the workability, without lowering the mold release characteristic, by specifying the construction of a silicone rubber elastic layer. SOLUTION: In a fixing roller 23 having a silicone rubber elastic layer 22 on an outer periphery of a metal core 21, the silicone rubber elastic layer 22 is an additional reaction hardenable silicone rubber elastic layer in which 150-350 weight part of alumina of 5-25μm of average particle size, is added as a thermal conductivity application agent. The content of the alumina of not more than 3μm of particle size, is preferably not more than 30volume%, to the total content of alumina in the distribution of the particle size of the alumina, because the aggregation is occured rapidly in the case when the content of alumina of not more than 3μm, is more than 30volume%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
The present invention relates to a fixing device roller for thermally fixing an unfixed image on a recording material such as paper in an electronic printer or the like.

[0002]

2. Description of the Related Art Conventionally, as a method of fixing a toner image on a support such as paper in an electrophotographic copying machine or an electronic printer, pressure is applied between a pair of rollers in which at least one roller is heated. A heat-fixing roller system, in which fixing is performed by passing an unfixed toner image between the rollers, is most widely used.

[0003] For example, as shown in FIG.
Is a hollow pipe-shaped core metal 3 having a heater 2 inside.
And a pressure roller 5 provided with an elastic layer 7 such as silicone rubber or fluoro rubber on the outer periphery of a cored bar 6 is used as the pressure roller 5. The release layer of the fixing roller 1 is required to have heat resistance and high releasability from a toner image for a long period of time.
A fixing roller coated with a thickness of 1000 μm is most commonly used.

However, since a fixing roller using a fluororesin has no elasticity in the fluororesin, when an unfixed toner image is fixed on paper or the like, the image is crushed too much and the contact area with the toner image is small. Therefore, there is a problem that the fixability is inferior and a high image quality cannot be obtained.

As a method of solving this problem, it has been attempted to use a fixing roller in which a release layer of the fixing roller is formed of an elastic material such as silicone rubber or fluorine rubber. It has been known that a higher image quality can be obtained than a fixing roller using the same.

However, the heat resistance of silicone rubber and fluororubber is inferior to that of fluororesin, and there is a problem in that the rubber or fluororubber cannot be used in a short time due to deterioration of the elastic body as the release layer. In particular, if the thickness of the elastic layer is made sufficiently thick to obtain high image quality, the temperature difference between the fixing roller surface and the vicinity of the fixing roller core becomes large. The temperature near the core becomes high. Therefore, there is a problem that the deterioration of the elastic body near the core metal and the deterioration of the adhesive for bonding the core metal and the elastic body occur in a very short time, making it unusable for practical use. Therefore,
Attempts have also been made to increase the thermal conductivity by adding a thermal conductivity-imparting agent to the elastic raw material in order to suppress the temperature rise near the core metal.

[0007]

However, for example, when a thermal conductivity-imparting agent is added to a fluororubber raw material, there is a problem that the raw material is hardened by a small amount of addition, and cannot be processed. Also, peroxide vulcanized silicone rubber (HTV) having relatively high heat resistance among silicone rubbers
Also, as in the case of the fluororubber raw material, there is a problem that the addition of a small amount of the thermal conductivity-imparting agent deteriorates the processability and makes it impossible to process the fixing roller. Therefore, it was not possible to add to the raw material such an amount that the effect of suppressing the temperature rise near the cored bar was exhibited.

Further, the addition of the thermal conductivity-imparting agent hinders the high releasability characteristic inherently possessed by fluororesins and silicone rubbers. Even if a relatively small amount is added, the release layer on the surface of the fixing roller can be prevented. There was a problem that it became unusable.

The present invention has been made in view of such circumstances, and provides high image quality, sufficient durability without deteriorating the releasability from a toner image, and excellent workability. An object of the present invention is to provide a fixing device roller.

[0010]

The elastic layer of the fixing device roller used in the present invention includes, for example, (1) 100 parts by weight of a vinyl group-containing organopolysiloxane (2) 0.1 to 50 parts of an organohydrogenpolysiloxane. Parts by weight (3) 150 to 350 parts by weight of alumina having an average particle diameter of 5 to 25 μm (4) An addition reaction curing type (LT) obtained by curing a raw material composition comprising a platinum catalyst in a minute amount.
V) Silicone rubber elastic body.

The reason why the silicone rubber is limited to the addition-curable silicone rubber in the present invention is as follows. In other words, in the case of a raw material having a high viscosity such as a peroxide-cured silicone rubber, the raw material is so hard that it cannot be processed as a fixing roller even with the addition of a small amount of a thermal conductivity-imparting agent. is there. However, the condensation reaction-curable (RTV) silicone rubber, which is a liquid silicone rubber, has a very low curing rate, and must be left at room temperature for about one week to be completely cured in order to completely cure. There is an inferior problem. On the other hand, the addition reaction-curable silicone rubber can be made into a low-viscosity liquid and has a high curing speed of 100 ° C. to 150 ° C.
It is cured in a few minutes to tens of minutes by heating at ℃,
This is because the fixing roller is inexpensive because it has excellent workability and productivity.

The vinyl group-containing organopolysiloxane (1) has a side chain generally used in organopolysiloxanes such as a methyl group, an ethyl group, a propyl group, a phenyl group, and a trifluoropropyl group. And a vinyl group is present for the addition reaction.

The organohydrogenpolysiloxane (2) is called a crosslinking agent and has a methyl group, an ethyl group, a propyl group, a phenyl group, a trifluoropropyl group and the like as in (1). It has a hydrogen group that reacts with the vinyl group of (1).

The alumina of the above (3) is for making the silicone rubber elastic body of the present invention have high thermal conductivity to suppress the temperature rise near the core metal and to allow the toner image to adhere to the surface of the fixing roller for a long time. .

The platinum catalyst (4) is a catalyst for curing the raw material composition, and various platinum compounds can be used. In the present invention, the reason why alumina having an average particle size of 5 to 25 μm is used as the thermal conductivity imparting agent is as follows. In other words, if the average particle size is less than 5 μm, the alumina is likely to be aggregated. Even if the raw material composition is forcibly and uniformly dispersed once using various dispersants or the like, it is left for a long time. Otherwise, there is a problem that the alumina aggregates and the required thermal conductivity cannot be maintained. Agglomeration of alumina having an average particle size of less than 5 μm is very strong. For example, when alumina having a large particle size is mixed and sedimented and separated, it can be redispersed even with stirring with relatively low shearing force. It is not something that can be redistributed more easily than. On the other hand, if the average particle size of alumina exceeds 25 μm, the surface of the elastic body of the fixing roller becomes extremely rough, resulting in image unevenness when used as a fixing roller. Therefore, the average particle size of alumina needs to be 5 to 25 μm.

In the present invention, the particle size of the alumina is:
When the particle size of 3 μm or less in the particle size distribution exceeds 30 vol% in the total alumina, agglomeration occurs very quickly.
Therefore, particles having a particle size of 3 μm or less are
It is preferably 0 vol% or less.

In the present invention, it has also been found that the adhesion (toner offset) of the toner image on the surface of the fixing roller can be suppressed for a long time by the particle size and the amount of alumina. For example, a test was conducted in which alumina having a small particle size was forcibly mixed and a fixing roller was immediately manufactured, but toner offset occurred in a relatively short time.

The reason for this is that the addition of a large amount of the thermal conductivity-imparting agent deteriorates the releasability of the silicone rubber from the original toner, but also deteriorates the physical properties of the silicone rubber itself. It is considered that the surface is gradually abraded by paper or the like at the time of fixing, and a new surface always appears, thereby preventing rapid toner offset. This effect is due to the average particle size of 5 to 25 μm.
Most preferably, 150 to 350 parts by weight of alumina is added.

If the amount of alumina is less than 150 parts by weight, the thermal conductivity of the silicone rubber elastic layer is not sufficiently increased, so that the temperature rise near the core of the fixing roller cannot be suppressed. Accordingly, the deterioration of the silicone rubber and the adhesive near the metal core occurs in a short time, and the life of the fixing roll is significantly impaired.

If the amount of the alumina exceeds 350 parts by weight, the thermal conductivity increases, and the temperature rise near the core of the fixing roller is sufficiently satisfied, but the physical properties are too low, so that the fixing roller has a too low physical property. When used as an elastic body, the amount of wear increases, causing a problem that it cannot be used in a short time, resulting in poor durability.

Examples of high thermal conductive silicone rubber compositions include those disclosed in JP-A-58-219259 and JP-A-63-2514.
High thermal conductive silicone rubber compositions generally called potting agents such as No. 66 are known.
No. 259 also states that the use of a heat fixing roll of a copy machine can lower the temperature near the core metal. However, as described above, the addition of the thermal conductivity-imparting agent impairs the releasability of the silicone rubber from the original toner, and the addition of a large amount causes a toner offset in a very short time. In contrast, the average particle size of the present invention is 5 to 5.
It has been found that toner offset can be suppressed for a long period of time by using an addition-reaction-curable silicone rubber obtained by adding 150 to 350 parts by weight of 25 μm alumina as an elastic layer of a fixing roller. Not a thing.

In the present invention, the addition reaction silicone rubber composition (1), (2),
Other than (3) and (4), they do not disturb the compounding agents generally compounded in the silicone rubber composition, such as reinforcing silica, extender, heat-resistant agent, colorant, processing aid, and control agent. .

As a method for manufacturing the fixing roller of the present invention, a rotation molding method, an injection molding method, a press molding method, etc., which are general methods for manufacturing a fixing device roller, can be used. However, since a large amount of the thermal conductivity imparting agent is added to form a high-viscosity liquid silicone rubber, the liquid silicone rubber is applied to the outer periphery of the core while rotating, and the roll is heated to form a silicone rubber elastic body. The rotational molding method for forming a fixing device roller provided on the outer periphery is most preferable.

In the description of the present invention, the fixing roller having a heater inside the core has been described. However, the same effect can be obtained by a pressure roller having a heater inside the core used in a high-speed copying machine or a color copying machine. Of course you can get it.

In the present invention, if the thickness of the silicone rubber elastic layer is too thin, the effect of the softness of the elastic layer is not sufficiently exhibited, and high image quality cannot be obtained. When the layer is thickened, the temperature rise near the core of the fixing roller cannot be reached, so the thickness of the silicone rubber elastic layer is 300 μm (0.3 mm) or more and 4 m or more.
m or less is preferable.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) An embodiment of the present invention will be described with reference to FIG. First, the compounding agents shown in Table 1 below were mixed by a mixer to obtain an addition reaction-curable silicone rubber composition.

[0027]

[Table 1]

Next, an aluminum hollow core having an outer diameter of φ36 mm
21 was prepared, the surface was blasted, degreasing was performed, and an adhesive (not shown) was applied. Then, the addition reaction-curable silicone rubber composition was molded. This at 120 ° C for 2
Cured by heating for 2 hours to form a silicone rubber elastic layer 2
After vulcanizing at 00 ° C for 4 hours and cooling, the outer diameter is φ4
This was polished to 0 mm to obtain a fixing roller 23 having an elastic layer 22 having a thickness of 2 mm. Reference numeral 24 in the figure indicates a heater.

When the hardness of the silicone rubber elastic layer was examined, it was found to be 72 ° by a JIS A hardness tester and the thermal conductivity was 1.
The temperature was 30 × 10 ⁻³ cal / cm · sec · ° C. The composition was allowed to stand at room temperature.
Aggregation did not occur even after a lapse of months, and was stable.
Further, the particle size distribution of alumina having an average particle size of 5 μm used was examined.
1%.

When this fixing roller was used as a fixing roller of a commercially available copying machine having a copy speed of 60 sheets / min.
Even after copying 100,000 sheets, the elastic layer 22 deteriorates and the fixing roller 23
No toner offset occurred on the surface, and there was no problem.

(Examples 2, 3, 4, and 5) In Example 1, only the average particle size and the amount of alumina were changed as shown in Table 2 below to prepare a fixing roller, and the number of copies was examined. No problem with 200,000 copies. In addition,
Table 2 also shows the hardness and thermal conductivity of the elastic layer.

[0032]

[Table 2]

(Comparative Examples 1 and 2) As shown in Table 3, a fixing roller manufactured in the same manner as in Example 1 except that the average particle size of alumina was 1 μm and the blending amount was 250 parts by weight was used. And Further, Comparative Example 2 was a fixing roller having an average particle size of alumina of 3 μm and a compounding amount of 250 parts by weight.

When a copy test similar to that of Example 1 was performed using this fixing roller, toner offset occurred on the roller surface in a short time, and the copy paper was wound around the fixing roller, and the test was stopped.

Further, when the raw material composition was left at room temperature and the coagulation of alumina was examined. In both Comparative Examples 1 and 2, the coagulation of alumina occurred after about one week, and the sample was unusable. .

(Comparative Examples 3 and 4) Average particle size of alumina 17
Comparative Example 3 was a fixing roller manufactured by the same method as in Example 1 except that 400 parts by weight of a μm roller were blended. Further, Comparative Example 4 was a fixing roller in which the average particle size of alumina was 30 μm and 250 parts by weight were mixed.

When a copy test was carried out on each fixing roller by the method of Example 1, the fixing roller of Comparative Example 3 was unevenly worn due to large wear of the elastic layer. The copy test stopped at 80,000 sheets. Further, the fixing roller of Comparative Example 4
The surface roughness was so large that image unevenness appeared from the start of the copy test, and the copy test could not be performed.

[0038]

[Table 3]

Comparative Example 5 Average Particle Size of Alumina 17 μm
Comparative Example 5 was a fixing roll manufactured in the same manner as in Example 1 except that 120 parts by weight of the fixing roll was mixed. When a copy test was performed on this fixing roll by the method of Example 1, when 65,000 copies were made, peeling of the silicone rubber elastic body occurred at the bonded portion between the core metal and the silicone rubber elastic layer. Canceled.

[0040]

As described above in detail, according to the present invention, high image quality can be obtained, sufficient durability can be obtained without deteriorating releasability from a toner image, and excellent workability can be obtained. A roller for a fixing device can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a conventional fixing roller.

FIG. 2 is a sectional view of a fixing roller according to one embodiment of the present invention.

[Explanation of symbols]

 21: hollow core metal, 22: elastic layer, 23: fixing roller, 24: heater.

Claims (3)

[Claims] 1. A fixing roller having a silicone rubber elastic layer provided on the outer periphery of a metal core, wherein the silicone rubber elastic layer has 150 to 350 parts by weight of alumina having an average particle size of 5 to 25 μm as a thermal conductivity-imparting agent. A roller for a fixing device, which is an addition reaction-curable silicone rubber elastic layer. 2. The method according to claim 1, wherein said alumina has a particle size distribution of 3%.
2. The fixing device roller according to claim 1, wherein the particles having a particle size of not more than 30 [mu] m are not more than 30 vol% in the total alumina. 3. The method according to claim 1, wherein the thickness of the silicone rubber elastic layer is 0.3 mm to 4 mm.
4. The fixing device roller according to claim 1.