JPS60135975A - Toner image fixing device - Google Patents

Abstract

PURPOSE:To extend a roller life by incorporating a silicone oil in the rubber coat of a fixing roller and another silicone oil smaller in mol.wt. than that of said oil in the rubber coat of a pressing roller. CONSTITUTION:The silicone oil contained in the rubber coat 12 of a fixing roller 1 is higher in viscosity, that is, mol.wt. than that of a silicone oil contained in the rubber coat 22 of a pressing roller 2. Both silicone oils to be incorporated in both rubber coats 12, 22 are, preferably, be selected from ones having viscosity of 20-1,000cs, and the ones different in viscosity from each other are selected from this range of viscosity and used for both rubber coats 12, 22. The rubber coat 12 of the fixing roller 1 is impregnated with the silicone oil in such an amt. to cause swelling of >=10%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a permanent image of an unfixed toner image formed on the surface of an image support material such as a transfer material, electrofax paper, or electrostatic recording paper by electrophotography, electrostatic recording, or other appropriate image forming method. A device for fixing a fixed image on the surface of an image support material, more specifically, introducing and passing an unfixed toner image support material between a parallel pair of rollers consisting of a fixing roller and a pressure roller that are rotationally driven while in pressure contact with each other. The present invention relates to a roller-type toner image fixing device that fixes a toner image on the surface of an image support material using heat, heat and pressure, or pressure.

Since the roller fixing method is mainly a heat fixing method, an example of this method will be explained below. FIG. 1 is a cross-sectional side view showing a schematic configuration of a heat roller type toner image fixing device. In the figure, numerals 1 and 2 are a heat roller (hereinafter referred to as a fixing roller) and a pressure roller, which are supported by bearings vertically in parallel with each other in moderate pressure contact with each other, and are driven to rotate in the direction of the arrow.

The fixing roller l is a hollow roller 11 made of metal such as aluminum.
is used as a core metal, and its outer periphery is coated with a heat-resistant and abrasion-resistant #-type material layer 12 that does not easily cause toner off-sera I.
A heater 13 such as a halogen heater is inserted into the core metal, and the core metal is heated by the heat generated by the heater. Then, by an automatic temperature control means (not shown), the power supply to the heater 13 is controlled on/off or the amount of power is increased/decreased, so that the temperature of the outer peripheral surface of the fixing roller is always maintained at a predetermined approximately constant temperature (for example, 180 to 200'C). managed.

The pressure roller 2 is a roller made of metal such as iron or aluminum and has a core metal 21 whose outer periphery is coated with a relatively thick layer of rubber or the like with a layer 22 of a soft material.

3 is a device for applying silicone oil as a 2F type auxiliary agent to the outer circumferential surface of the fixing roller l; in this example, a long web member 31 impregnated in advance with fairly high viscosity silicone oil is wound into a roll. Bring out what you did +l+32
The free end of the rolled web member is locked to the winding shaft 33, and the part of the web member between the feeding shaft and the winding shaft is pressed against the surface of the fixing roller by the roller 34. At the same time, the rolled web member on the unwinding shaft side is wound little by little toward the winding shaft side (for example, 710,000 sheets per 1 m).
This is a configuration in which the outer circumferential surface of the fixing roller 1 is coated with the impregnation release agent of the web member by passing A4 paper. This web member also serves as a cleaning member for the outer surface of the fixing roller.

Therefore, when the fixing roller 1 and the pressure roller 2 are in a rotationally driven state, an unfixed toner image T is formed in the nip portion 4 between the two rollers.
When the image supporting material 5 carrying the toner image 11 is introduced with the fine side facing the fixing roller L and allowed to pass, the toner image T is exposed to the heat of the fixing roller 1 and the mutual pressure between the fixing roller 1 and the pressure roller 2. The image is sequentially heat-pressure-fixed as a permanently fixed image on the five surfaces of the image support material by pressure.

In addition, 6 is a separating claw member disposed to reliably separate the image support material 5 from the surface of the fixing roller 1, 7 is a sensor for detecting the outer circumferential temperature of the fixing roller 1 in order to adjust the temperature of the fixing roller 1, and W is a fixing roller. The width of the lobes at the mutual contact portion of the roller 1 and the pressure roller 2 is indicated by the lobes width.

In the fixing roller 1, the layer thickness of the releasable material 12 that covers the outer periphery of the core metal 11 is generally quite thin so that the heater heat can be quickly conducted and replenished to the outer surface of the material layer, that is, the outer peripheral surface of the fixing roller. (for example, about 0.5 mm).

The layer material 1 is generally a fluorine-based resin such as PTFE (tetrafluoroethylene resin) φPFA (tetrafluoroethylene-fluoroalkoxyethylene resin), or heat-resistant and wear-resistant rubber such as silicone rubber. is used.

A fixing roller coated with a fluorine-based resin has higher strength than one coated with silicone rubber, and has good releasability when coated with silicone oil.

However, because the coating layer lacks elasticity, the fixing performance of the toner image T on the 5 surfaces of the image support material is poor compared to a fixing roller coated with silicone rubber, and when fixing the toner image on the toner image support material, the image is It has the disadvantage that the crushing effect is large and reduces the image quality. Further, when there is an object such as a cleaning plate in contact with the fixing roller, if hard dirt sticks to the roller and enters the roller and the object in contact, there is no place for the force to escape, and scratches are likely to occur.

The above-mentioned difference in fixing properties is caused by the difference in fixing properties of silicone rubber, and in the case of an i-forming material coating, the outer surface of the elastic material covering corresponds to the unevenness of the surface of the support material 5 itself and the unevenness of the toner image T placed on the support material 2. It is considered that the fixing performance is good because the toner image T is deformed and uniformly contacts the uneven toner image T at each part. However, in the case of a rigid coating such as a fluororesin, due to the unevenness of the support material and toner image, the convex parts make strong contact with the roller, and the four parts only make unstable contact with the roller, resulting in poor fixation in the concave parts. is considered to be very sweet.

Therefore, from the viewpoint of emphasizing image quality, there is a tendency to use a silicone rubber-coated fixing roller rather than a fluororesin-coated fixing roller, and various improvement studies are being actively conducted on the silicone rubber-coated fixing roller. It is being said.

One of them is to add a toner release aid to the coating rubber layer 12 of the silicone rubber coated fixing roller 1 in order to improve the release property and maintain the release property over the long term (prolong the roller life). There is also a pressure roller 2 in which the covering rubber layer 22 is impregnated with silicone oil.

Silicone oil-containing rubber can be obtained, for example, by providing a swelling step after rubber vulcanization to allow silicone oil to penetrate into the flesh of the vulcanized rubber, or by adding and blending silicone oil during kneading of raw rubber. I can do it. 1. An example of obtaining a rubber-coated roller containing silicone oil using the swelling method is to produce a sheet of raw rubber dilate prepared by blending silicone raw rubber with a crosslinking agent, filler (such as silica), and other additives as necessary. Form into a shape,
It is wrapped around the outer circumference of the roller core metal via a primer and adhered. It is placed in a press mold and subjected to vulcanization treatment by heating and self-pressing. Silicone combs are generally of the heat vulcanization type (HTV) or the heat vulcanization type (LTV); in the case of the heat vulcanization type, the organic peroxide, which is a crosslinking agent, decomposes during the primary vulcanization stage. Generates decomposition residue at the same time as vulcanization. Therefore, a secondary vulcanization process is performed to remove this. Even in the case of addition reaction type, the properties are more stable if heat treated at high temperature. Next, the roller with the vulcanized coating layer is immersed in silicone oil to impregnate the silicone oil into the coating layer. If the thickness of the coating layer at this oil immersion step is considerably thicker than the required thickness, the coating layer may be ground to approximately the required thickness before being impregnated with oil. After completing the oil immersion, the outer periphery of the coating layer is ground to create a roller with a predetermined outer diameter. Although there are no particular limitations on the oil immersion conditions, for example, in the case of a fixing roller 1 whose coating layer 12 has a thickness of 0.5 mm, the oil temperature is generally about 180° C. and the immersion time is 8 to 24 hours. In the case of a pressure roller 2 in which the coating layer 22 is thicker than the fixing roller (for example, 5 mm), the immersion time is extended to, for example, about two days.

The silicone oil for impregnating the coating layer 12-22 of the Rollad 2 is selected from those having a range of, for example, about 20 to 1000 cs so that the oil can penetrate into the flesh of the coating. A resin having a molecular weight of 20 cs or less has good permeability into the coating, but is not suitable because it has poor heat resistance and is volatilized by the heat of the fixing roller. High viscosity products of 100 cs or more have poor permeability into the coated flesh and require a long time for oil immersion treatment, and even if impregnated, they bleed onto the coated surface and are therefore not effective. Also, regarding the amount of silicone oil to be impregnated into the coating flesh, for the fixing roller, if the equilibrium swelling (saturated impregnation) of the oil to the coating flesh is 100%, the amount should be 10% or more, and if it is less than that, the life of the roller will be shortened. The extension effect will be low.

In addition, the viscosity number (cs,
centistokes) at 25°C. Furthermore, the oil is not an oil prepared by blending silicone oils of various viscosities and adjusted to the desired viscosity number, but is synthetically produced so that the viscosity number has a single peak from the beginning.

As described above, as the rubber-coated fixing roller 1, a rubber coated layer 12 impregnated with silicone oil is used, and as for the pressure roller 2, the coated rubber layer 12 is also coated with silicone oil.
By using a coating layer pre-impregnated with silicone oil, the mold releasability is better than when the coating layer does not contain silicone oil, and the long-term maintenance of the MJi'j property is improved, that is, the roller Life is extended.

However, the effect of prolonging roller life was still insufficient and unsatisfactory. That is, as a conventional example, a fixing device having the following specifications was tested.

Fixing roller 1: φHmm, 0.51 thick silicone comb coating, immersed in 100 cs dimethyl silicone oil (product number KF96. Shin-Etsu Chemical) at 180°C for 8 hours, heated operating temperature (surface temperature) 180°C0 Pressure roller 2: φ
60mm, 5IlIm thick silicone rubber coated, ]0O
180 to C8 dimethyl silicone oil (same, same)
Soaking treatment at °C for 48 hours.

Oil application device 3: Web method as shown in the first diagram, product name: Nomex paper web (non-woven RFF), 10,000 C
Impregnated with S dimethyl silicone oil (product number !96) 1, same), web feeding speed 1m/10,000 sheets (A4 size).

Paper passing speed = 50 sheets/min Nip between fixing roller 1 and pressure roller 2 iJW: 9 to 10
The following tests (1) and (2) were conducted with the specimen facing mm.

(1) Forced jam test The unfixed toner image supporting material 5 is introduced one after another between the fixing roller 1 and the pressure roller 2, and at every 11ij points of the predetermined number of sheets passed, the gap between the rollers 1 and 2 is Image support material 5 in transit
is held between the rollers 2, and the rotational drive of the rollers 2 is stopped for one minute. Due to this 1-minute stoppage W of rotation of the roller 2, the toner image portion of the image support material 5 sandwiched between the roller 2 is transferred to the nip 1 of the fixing roller.
1” Forcibly offset to the W area surface. After one minute has elapsed, the roller rod 2 is returned to the rotating state. Then, when the toner forcibly offset onto the surface of the fixing roller passes through the oil application device δ3 which also serves as a cleaner, it is observed whether the toner is wiped off from the surface of the fixing roller. If the offset toner has been wiped off, the operation of continuing paper feeding until the next forced offset treatment number of sheets is repeated, and finally the number of sheets is counted at the time when the offset toner is no longer wiped off by device 3. .

Although this forced jam test itself is not directly related to normal line copying, the toner adheres to the roller and causes offset, so the toner offset on one side of the fixing roller during the forced jam test is not wiped away by the device 3. The smaller the number of sheets that pass through which the phenomenon of more firmly adhering to the fixing roller begins to occur, the shorter the roller life will be, and conversely, the more sheets the roller will have, the longer the roller life will be.

(2) Paper feeding life test The unfixed toner image supporting material 5 is introduced one after another between the fixing roller 1 and the pressure roller 2, and as the releasability gradually decreases due to the use of the fixing roller 1, the toner is transferred to one surface of the fixing roller. The quality of the fixed image deteriorates due to an increase in the amount of offset, or the toner image support material wraps around the fixing roller (i.e.,
Observe the presence of jam). Then, the number of sheets to be passed until the deterioration in quality reaches a practically acceptable limit or jams occur frequently is determined.

The test results of (1) and (2) above are shown in Table 1 for the conventional side fence. In other words, the forced jam test is from 230QO to 2800
The paper passing life test is about 100,000 to 150,000 sheets, and this level is still insufficient and cannot be considered to be a satisfactory performance.

The present invention is a roller-type toner image fixing device that uses a rubber-covered YΩ fixing roller that also contains silicone oil in advance and a rubber-covered pressure roller that also contains silicone oil, but this is further improved. The purpose of this product is to provide a product that can extend the roller life by 1 J compared to conventional products, and the silicone oil contained in the rubber coating of the fixing roller located on the toner image side is It is characterized by having a higher molecular weight than the silicone oil contained in the rubber coating.

That is, the present inventors conducted the following experiments during the research and development process of the present invention.

Experiment 1: Contained oil transfer experiment Two oil-containing silicone rubber test pieces A-B with the same or different silicone oil content (swelling degree) and viscosity (molecular weight) of the silicone oil (dimethyl silicone oil) contained The behavior of the oil contained in the re-tested specimen was investigated when it was left in a contact pressurized state. Table 2 1
Columns 6 to 6 are representative examples.

The relationship between the viscosity number η and the molecular weight M of silicone oil is expressed by the Warrik equation below, or A, J, Barrl).
The formula holds true: if the viscosity number is small, the molecular weight is also small, and conversely, if the viscosity number is large, it is large. Table 3 is a comparison table of viscosity and molecular weight of dimethyl silicone oil. In the following, explanations will be unified using viscosity for convenience.

Warrik's formula% formula% (However, molecular weight M is 40,000 or less, ηC is 40°
Viscosity (poise) at C) A, J, Barry's formula% formula% (However, molecule xM is 2.5oo or more, η"4'C is 25
Viscosity (centistokes) at °C) This experiment yielded the following results.

(a) For samples swollen with oil of the same viscosity (same molecular weight), if the degree of swelling is the same, no oil transfer will occur, but if the degrees of swelling are different, the oil will transfer from the higher to the lower. do.

(b) Among samples swollen with different viscosities (different molecular weights), in equilibrium swelling, the one with a lower viscosity will shift to a higher viscosity very slightly, and if the swelling degree of the higher viscosity is smaller, the lower viscosity will shift. If the swelling is below the equilibrium swelling and the degree of swelling is approximately the same, or if the degree of swelling of the higher viscosity is greater, almost no oil transfers between the two samples.

Experiment 2: Investigation of migration of oil contained in conventional equipment As shown in the second diagram, an undetermined size smaller than the maximum paper size that can be passed through a fixing device with the same specifications as used in the forced jam test and paper feeding life test described above The toner image supporting material 5 is introduced one after another by right or left one-sided reference conveyance, and 30,000 sheets are passed. In this case, the fixing roller 1 and pressure roller 2 before starting paper feeding
Silicone oil III in each rubber coating layer 12 and 22 of
The moisture content (initial W moisture content) was measured (extraction method). The results are shown in Table 1.

Further, the area of the circumferential surface of the fixing roller 1 that is in contact with the surface of the image supporting material 5 through which the sheet has passed is the paper passing section P, where the image supporting material 5 does not pass through and always rotates in direct contact with the surface of the pressure roller 2. The roller circumferential area outside the paper passing section is defined as a non-paper passing section Q.

After 30,000 sheets had been passed, the degree of swelling of the silicone oil in the rubber coating layer of both the paper passing section P and the non-paper passing section Q of the fixing roller 1 was measured. The results are shown in Table 1.

That is, the oil swelling degree of the rubber coating layer 12 of the fixing roller L is initially 62% in both the paper passing part P and non-paper passing part Q, but after 30,000 sheets have been passed, the oil swelling degree in the paper passing part P is 29%. The swelling was reduced to 38% in the non-sheet passing area Q. The decrease in the oil W measure in the non-sheet passing area Q is based on the findings from Experiment 1 above.
The surface of the rubber coating layer 12 of the fixing roller 1 is directly exposed to the surface of the rubber coating layer 12 of the fixing roller 1 while the paper passes through, and the oil contained in the rubber coating layer 12 of the fixing roller 1 with a high degree of oil swelling is replaced by the pressure roller 2 with a small degree of oil swelling. This is because it has migrated to the rubber coating layer 22 side.

Also, one of the reasons for the decrease in the paper passing section P is that very small amounts are sealed on the five sides of each image support material through which the paper passes and are carried away, but this is not a very large amount; The main reason is that each time the fixing roller l and the pressure roller 2 come into direct pressure contact at the sheet passing interval of each image support material 5, the rubber of the fixing roller l is This is because the contained oil moves from the coating layer 12 side to the rubber coating layer 22 side of the pressure roller 2.

In the case of a practical machine, there is almost no case where 30,000 sheets are continuously fed as in Experiment 2 above, and the machine is not used for a period of equipment downtime, a pre-rotation period before and after copying, a post-rotation period, and an idling period of 7t roller L and pressure roller. There are many total periods in which 2 and 2 are in direct suppressive contact over the entire length. Therefore, in a practical machine, the degree of decrease in oil swelling in the comb coating layer 12 of the fixing roller 1 is thought to be even greater than in the case of Experiment 2.

In the conventional device, the relationship between the initial oil swelling degree of the rubber coating layer 12 of the fixing roller 1 and that of the rubber coating layer 22 of the pressure roller 2 is such that the former is large and the latter is small because of the rubber coating of the fixing roller l. The layer 12 has a small warpage thickness and can be made to have a high degree of oil swelling with a relatively short oil immersion treatment, whereas the rubber coating layer 22 of the pressure roller 2 has a large thickness. Therefore, in order to achieve a high degree of oil swelling, it is necessary to perform oil immersion treatment over many days, and the pressure roller 2 is in contact with the back surface of the unfixed toner image support material 5, so that it is not fixed. From the point of view that it is not necessary to have toner releasability that can be affected by roller 1,
This is because the oil immersion treatment takes about two days at most due to manufacturing and cost considerations.

And the above actual price is ¥! 1il-2, the reason why the roller life extension effect of conventional fixing devices using silicone oil-containing processing rollers is still insufficient and unsatisfactory is that the silicone oil in the rubber coating layer 12 of the fixing roller 1 deteriorates over time. It has been found that the reason is that the degree of oil swelling in the rubber coating layer 12 of the fixing roller 1 decreases, that is, the mold releasability decreases relatively early as the oil transfers to the comb coating layer 22 side of the pressure roller 2. It was done.

Therefore, the present invention is based on the findings in (b) of Experiment 1 in order to significantly extend the roller life by suppressing the migration of silicone oil contained in it over time from the fixing roller 1 side to the pressure roller 2 side as much as possible. The silicone oil contained in the rubber coating layer 12 of the fixing roller 1 is based on the pressure roller 2.
The viscosity, that is, the molecular weight, of the silicone oil contained in the rubber coating layer 22 is greater than that of the silicone oil.

By doing this, the oil W measurement for the rubber coating layer 22 of the pressure roller 2 may be low, so there are no manufacturing or cost problems, and the oil content from the fixing roller l side to the pressure roller 2 side can be reduced. The migration of silicone oil is effectively slowed down as much as possible, and the life of the roller can be greatly extended.

In addition, the resulting fixed image is a soft image with good fixing properties, and sufficient fixing can be achieved even if the fixing temperature is set 5 to 10°C lower than that of a fixing roller coated with a fluorine-based resin. This makes it possible to obtain an energy-saving type device.

In the present invention, the silicone oil to be contained in each of the rubber coating layers 12 and 22 of the fixing roller 1 and the pressure roller 2 should be selected from those having a viscosity of about 20 to 1000 cs for the same reason as stated in the conventional device. Within this range, silicone oils containing different viscosity (molecular weight) in both the rubber coating layers 12 and 22 are selected and used.

Further, the oil impregnation of the rubber coating layer 12 of the fixing roller 1 is made such that it swells by 10% or more.

EXAMPLE A fixing device according to the present invention was constructed by replacing the fixing roller 1 with the one shown below in the fixing device having the specifications mentioned above as the conventional example.

φ[10mm, 9.5mm thick silicone rubber coating, 3
00cs dimethyl silicone oil at 180℃ x 1
Immersed for 5 hours, initial oil swelling degree 93%, heating temperature (surface temperature) 180°C.

For this fixing device, the forced jam tests (1) and (2) above, the paper feeding life test, and the oil migration investigation in Experiment 2 were conducted. The results are shown in the implementation side fence in Table 1.

In other words, in comparison with the conventional example, the results of the forced jam test and paper feeding life test are much better, and the results of the oil migration investigation show that even after 30,000 sheets have been passed, the oil swelling degree of the fixing roller rubber coating layer 12 remains normal. In both the paper section P and the paper non-passing section Q, the initial oil swelling degree is substantially maintained (to be precise, a very small amount of oil transfers from the fixing roller to the copy paper each time, and this causes the separation. ), fixing roller 1
This indicates that the migration of the contained oil from the side to the pressure roller 2 side was effectively suppressed, and the fixing device was an excellent fixing device with a sufficiently long roller life.

Table 3 *Dimethyl silicone oil (manufactured by Shin-Etsu Chemical) The coating rubber used for the fixing roller and pressure roller in Table 1, and the rubber used in test pieces A and B in Table 2 are all 10.
For 0cs oil, the amount of oil contained per 1QQg (saturated content) at 100% swelling (equilibrium dilation pupil saturated swelling) is 30g, and for 300cs oil it is 15g.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional side view showing a schematic configuration of a heat roller type toner image fixing device, and FIG. 2 is a perspective view of a pair of fixing/pressure rollers. 1 is a fixing roller, 2 is a pressure roller, 3 is a # type auxiliary agent coating device, 5 is an unfixed toner image support material, and T is an unfixed toner image. Continued from page 1 0 Inventor Susumu Hirai Kawasaki City J In-house @ Inventor Iwa 1) Toshimitsu Yosaki City J In-house @ Inventor Jun Fukahori - Yosaki City J In-house

Claims (3)

[Claims] (1) An unfixed toner image support material is introduced between a pair of rollers, a silicone oil-containing rubber-coated fixing roller and a silicone oil-containing rubber-coated pressure roller, which are in contact with the toner image surface and are brought into pressure contact and rotationally driven. In a toner image fixing device that fixes a toner image by passing it through, the molecular weight of the silicone oil contained in the rubber coating of the fixing roller is larger than the molecular weight of the silicone oil contained in the rubber coating of the pressure roller. A toner image fixing device characterized by: (2) The toner image fixing device according to claim (1), wherein the rubber coating of the constant Mo roller and the pressure roller is silicone rubber. (3) The toner image fixing device according to claim (1), wherein the silicone oil contained in the fixing roller rubber coating and the pressure roller rubber coating has a viscosity within a range of 20 to 1000 cs.