JPS6127574A - Fixing roll - Google Patents

Abstract

PURPOSE:To improve remarkably the durability of a fixing roll by covering the fixing roll with a compound whose main components are a methyl vinyl silicone raw rubber whose bridge density is >=2X10<-4>mol/cc, and silica. CONSTITUTION:A rubber compound whose main components are a methyl vinyl silicone raw rubber and silica is bridged, and the surface is formed by a covering layer in which a bridge density of a polymer only is >=2X10<-4> at the time of bridge, and fixing roll is obtained thereby. In a heat roll fixing device using this fixing roll, an image supporting member 12 such as paper, etc. on which an image is formed by a toner 10 passes through between a fixing roll 14 and a pressure roll 16, the toner 10 is heated by the fixing roll 14 and fixed to the image supporting part 12, and an image 11 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a fixing roll mainly made of silicone rubber used in electrostatographic processes and the like.

Prior Art ElectrophotographyIn any electrostatographic process, generally,
A toner image is formed on an image supporting member such as paper during transfer or development, and the toner image is heated or pressurized to obtain an image. Many types of fixing means such as heating and pressurization have been developed in the past, but the common feature is that silicone rubber rolls are used.

However, the durability of conventional fuser rolls is limited to about 60,000 to 80,000 sheets when used in, for example, an electrophotographic copying machine, and the development of a fuser roll with even greater durability is required. It's crowded.

Purpose The present invention provides a fixing roll with significantly improved durability.

The fixing roll of the present invention has its shin surface crosslinked with a rubber compound mainly composed of methylvinyl silicone raw rubber and silica, and the crosslinking density of the polymer alone at the time of crosslinking is 2X.
I P'mol! It is characterized by being formed with a coating layer having a rating of e/c, c or higher.

This coating layer may be formed, for example, directly on the core metal or on the thermally conductive elastic body j@ which is laminated and adhered to the core metal, and in short, it is sufficient to form a surface layer.

On a side note, the present inventor has developed a fixing roll that can achieve the same purpose as described above, with a total crosslinking density of 6 x 1 containing methylvinyl silicone raw rubber and silica.
The present invention has proposed a fixing roll in which a coating layer having a coating thickness of about 0'''4 mm/cc is formed.The present invention further improves the fixing roll.

The present invention will be explained in more detail below.

Methylvinyl silicone raw rubber has the polysiloxane structure shown by m,
By changing the ratio of n, that is, by changing the proportion of vinyl groups, the crosslinking density can be adjusted. Also, crosslinks are formed between the silica and the siloxane polymer. That is, in silicone rubber, both the /IJ mom-crosslinks formed by vinyl groups and the crosslinks formed between silica-polymer by silica exist.

The crosslink density of the polymer alone can be measured by a toluene swelling method in an ammonia atmosphere, and the total crosslink density including both crosslink densities can be measured by a toluene swelling method. These measurement methods are described later.

By the way, the fixing roll of the present invention achieves great durability by making the crosslinking density of the polymer alone be 2×10 mo/@/cc or more, and in particular, it uses polyester as a release agent. This effect is remarkable in a fixing roll that is used by supplying siloxane oil to the roll surface.

Silicone rubber is continuously supplied to the roll surface as a release agent in order to prevent the occurrence of toner offset, but the inventor of the present invention has found that the swelling property of the rubber with respect to this oil is a major cause of deterioration of the rubber roll. I have found that it is the cause. When rubber swells with oil, the mechanical strength of the rubber decreases, making it vulnerable to external forces, and at the same time, the impregnated oil itself generates internal stress in the rubber, accelerating its deterioration. Furthermore, the oil acts as a carrier that selects into the rubber deterioration-promoting substances contained in image supporting members such as toner or paper. Conventional rubber rolls tend to have a large degree of swelling initially, and the degree of swelling increases at a large rate as they are used, resulting in a significant loss of durability.

As mentioned above, in the present invention, the crosslinking density of the polymer alone by vinyl groups is set to 2×10″″4 mol/cc or more,
Preferably, high durability can be obtained by setting the mole ratio to 2 to 5×10. If it is more than 5×10″″4 mol/cc, flexibility will be reduced and rubber elasticity will be lost, leading to cracks during polishing of the fixing roll and deterioration in the image quality of the post-fixed image.

The silica may be either wet silica (precipitated silica) or dry silica (fumed silica), but wet silica is preferable in terms of releasability from toner. The amount of silica blended in the rubber container land can be adjusted as appropriate in order to obtain a desired total crosslinking density, and is preferably 20 to 50% by weight. If the content is less than 20% by weight, flexibility tends to be impaired and abrasion resistance decreases, while if it exceeds 50% by weight, the releasability against toner decreases, and when mounted in a copying machine etc. Inorganic fillers other than silica, crosslinking agents, heat stabilizers, processing aids, and the like may be added to the rubber compound of the present invention, which may cause toner offset.

Inorganic fillers include diatomaceous earth, quartz powder, iron oxide, zinc oxide, titanium oxide, calcium oxide, magnesium oxide, talc, aluminum silicate, aluminum oxide powder, carbon black, potassium titanate, asbestos, glass, etc. Examples include fibers such as carzene, powders such as Teflon, and boron nitride, among which diatomaceous earth is preferred8. As a cross-linking agent, II-oxide etc. are used, and a preferred cross-linking agent is 2,5-dimethyl- 2,5
-di(tert-butylperoxy)hexane, dicumyl oxide, and the like.

The fixing roll of the present invention can be effectively used without deterioration even in a fixing device that is used in a state where polysiloxane oil is supplied. It has also been found that increasing the group content improves mold release properties.

This eliminates the so-called hot offset and the wrapping of paper around the fixing roller.
6X
The durability is more improved than that of a fixing roll provided with a coating layer having a concentration of about 10-4 mol/CC.

This is thought to be due to the fact that by increasing the crosslinking density of the polymer alone, the mechanical strength is increased, and in addition, decomposition of the polymer by deterioration accelerating substances is prevented.

Note that the fixing roll of the present invention is not limited to a fixing method in which an offset prevention liquid such as silicone oil is supplied during fixing, but is also fully applicable to a fixing method that does not require the supply of such a liquid. Furthermore, although the fixing roll of the present invention is effective for use in a pressure heating method, it can also be used in a pressure fixing method.

FIG. 1 of the accompanying drawings shows an example of the configuration of a heat roll fixing device using the fixing roll of the present invention. An image supporting member 12 such as paper on which an image is formed with toner 10 is attached to a fixing roll (
passing between the fixing roll) 14 and the pressure roll 16,
Toner 10 is heated by fixing roll 14 and fixed on image supporting member 12 to form image 11 . A release agent (liquid for preventing offset) is selected from a release agent tank 22 to the fixing roll 14 by a release agent coated felt 24, and the amount of application is adjusted by a blade 26. 28.29 is the separation claw,
30 represents a cleaning material, and 32 represents a heater.

Next, examples will be shown.

Example 1 During crosslinking, the crosslinking density of f IJ Mama-Germany was 1.5.
X10-4, 3X10-4, 4.5X10→mol/
30.50.80 parts by weight of wet silica was added to 100 parts by weight of methylvinyl silicone raw rubber (CC) to produce a total of 9 types of silicone rubber comparan) 'Oi7'
c.

100 parts of this silicone rubber comparan) is added with a crosslinking agent [RO-4,
- dimethyl-2,5-di(tajarizotylperoxy)hexane] and red iron were added in an amount of 1 part by weight, and the silicone rubber layer was formed on the aluminum core bar by pressing using a mold) under the following conditions. A fixing roll was prepared by forming a fixing roll. This was installed in the fixing device of a copying machine shown in FIG. 1, and the number of copies it could endure was measured.

Press pressure: 200 Kg/d Press temperature: 170℃ Press time: 10 minutes Secondary vulcanization temperature: 200℃ Secondary vulcanization time: 4 hours Table 1 shows the total crosslink density during each crosslinking process.

Table 1 and Figure 2 show the number of durable sheets for each compound. Even if the total crosslinking density is the same, the number of durable sheets will vary greatly due to the difference in the crosslinking density of the polymer alone.Polymer crosslinking density 2
It can be seen that high durability of about 300,000 sheets or more can be obtained at 10-' mole/cc.

Rubber Ohem, Technol, 48
．． 795 (1975) and J. Appl. Poly.
m, Sci, 7.861. (1963).

In other words, 5w is made from a rubber sheet vulcanized to a thickness of 2vm.
A sample of n×20 m is cut and immersed in a test containing 50 g of toluene. This is placed in a desiccator containing 100-ml concentrated ammonia water in the bottom to create an ammonia atmosphere. Replace the ammonia water every 24 hours. Then, the weight of the sample containing toluene is measured at appropriate intervals. The difference between two measurements taken 24 hours apart is
When the sample weight is less than one factor of the sample weight, the sample weight is expressed as W(
I'm going to meet you.

Next, the sample was air-dried, then dried at 120°C for 3 hours to remove toluene, and the weight Wo(f) was measured.Then, it was placed on a platinum shade and heated to 900°C at a heating rate of 10°C/min or less in a nitrogen stream. After heating to 900° C. for 10 minutes, cooling and measuring the weight Wf (f) of the remaining sample valve.

Using the above measured values, the number of crosslinks contained per lcc of vulcanized rubber (No/Vo (mo)e/cc) is calculated from the following formula and used as the crosslink density.

Here, the total crosslink density was measured by the toluene swelling method.The measurement was carried out in exactly the same manner as described above, except that the density was left in the air instead of being placed in a desiccator with an ammonia atmosphere.

Durability evaluation method: Outer diameter 40I! Continuous copying was carried out using the apparatus shown in FIG. 1 using a fixing roll having a surface of a hollow aluminum core metal I11 coated with silicone rubber to a thickness of 0.5 va. Here, polydimethylsiloxane was used as a release agent, the fixing roll linear speed was 15cm, 4cm, and the fixing roll surface temperature was 180±3°C, and an 8-inch black twill pattern image was printed on B4 size paper. Formed by vertical feed (15 sheets/min),
The durability limit was defined as the point in time when at least one of unfixed areas caused by the fixing roll, offset, and non-uniform gloss of flat areas occurred on the copy image.

Example 2 During crosslinking, the crosslink density of the polymer alone was 1.2
10-4, 2.15 x 10-', 3.2
30 parts by weight of wet silica (D-17, manufactured by Degussa Corporation) was added to 100 parts by weight of methylvinyl silicone raw rubber of X 10-4 mo/l//CC to obtain a silicone rubber powder. A rubber sheet was prepared from this in the same manner as in Example 1.

The releasability of these products was evaluated by the adhesive strength test described below.

The results were as shown in Figure 3. Note that adhesive strength is a guideline for the frequency of toner hot offset, paper wrapping around the fixing roll, etc., and the lower the value, the less likely it is.
01F/2.25cJ or less is considered to pose no problem in actual use.

It can be seen from FIG. 3 that the higher the crosslinking density of Shibolimer alone, the lower the adhesive strength and the better the mold releasability.

Method for Measuring Adhesive Strength A 15 m + 2-hole rubber sheet was pasted on a sheathed heater.Meanwhile, paper was fixed on another sheathed heater, and a toner made of a melt-kneaded pulverized product with the following composition was applied onto the paper. on the layer in an amount of 5×1 o-s f /al,
After setting the rubber sheet surface temperature and toner temperature to 120°C using a sheath heater, place the rubber sheet on the toner surface at approximately 3 Kf! / Press the rubber sheet with a pressure of 15 cm x 15 cm for 2 minutes, then pull the rubber sheet apart at a speed of 40 cm/min.
At this time, the maximum value of the force applied between the rubber sheet and the toner was defined as the adhesive force with the toner (f/2.25d).

The toner composition was as follows: 100 parts by weight of unsaturated polyester resin and 45 parts by weight of carbon black.

Effects The fixing roll of the present invention uses a specific silicone rubber as a coating layer. This makes it resistant to abrasion and scratches and has excellent durability, and improved releasability prevents toner hot offset and wrapping around the fixing roll.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an example of a hot roll fixing device using the fixing roll of the present invention, and FIG. 2 is a diagram showing the total crosslink density and number of durable copies when the crosslink density of the polymer alone in the present invention is varied. Figure 3 is a graph examining the relationship between the crosslinking density and adhesive force of the polymer in the present invention. 12... Image support member 14... Fixing roll 16
... Pressure roll 26 ... Blade 32 ...
Heater fan 1 figure total a size (mole/ccJ 3 flash

Claims (1)

[Scope of Claims] 1. A coating layer in which a rubber compound containing methylvinyl silicone raw rubber and silica as main components is crosslinked, and the crosslinking density of the polymer alone at the time of crosslinking is 2 × 10^-^4 mol/cc or more. A fixing roll characterized by having a surface formed thereon.