JPH06100875B2 - Toner image fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention introduces an unfixed toner image support material between a pair of parallel rollers composed of a fixing roller and a pressure roller, which are pressed and brought into contact with each other to rotate, thereby forming a toner image. The present invention relates to a toner image fixing device of a type in which heat fixing, pressure fixing, or heat pressure fixing is performed on an image supporting material surface.

As the roller type toner image fixing device as described above, a heating and pressurizing fixing type has been widely used in the related art, and therefore, description will be given below by taking that type as an example. FIG. 1 is a cross-sectional side view showing a very schematic structure of the example. 1 in the figure
Reference numerals 2 and 2 denote a fixing roller and a pressure roller, which are in proper pressure contact with each other and are vertically supported in parallel by bearings, and are rotationally driven in the direction of the arrow.

The fixing roller 1 has a hollow metal roller 11 made of aluminum or the like as a core metal, and its outer peripheral surface is relatively thinly coated with a heat-resistant and wear-resistant toner releasable material layer 12 (for example, about 0.5 mm thick).
The outer diameter is, for example, about 60 mm, and a heater 13 such as a halogen heater is inserted and built in the hollow cored bar. The fixing roller 1 is entirely heated by the heater 13, and the temperature of the outer peripheral surface of the roller is always kept constant by an unillustrated automatic temperature control circuit (14 indicates a fixing roller surface temperature sensor such as a thermistor, which is one of its constituent members). Almost constant temperature (for example 180 ~ 200
℃) will be maintained.

The pressure roller 2 uses a metal roller 21 made of iron, aluminum or the like as a core metal, and the outer peripheral surface of the pressure roller 2 is covered with a heat-resistant and wear-resistant toner releasable material layer 22 to be thicker than that of the fixing roller 1. It has an overall outer diameter (for example, 5 mm thickness) of, for example, about 60 mm (substantially the same as the fixing roller 1). Pressure roller 2 of this example
Shows that the cored bar 21 is hollow and a sheathed heater 23 is inserted thereinto so that the roller 2 is also appropriately heated. However, there is a case where the roller 2 is not heated.

Reference numeral 3 is a mutual contact nip portion between the fixing roller 1 and the pressure roller 2, and W is a width of the nip portion.

Reference numeral 4 is a fixing roller surface cleaning device, and this embodiment is a web type device. That is, reference numeral 41 is a cleaning web wound by a roll which is loaded and held by a payout shaft 42. The free end of the web is locked to a take-up shaft 43 and a web portion between the shafts 42 and 43 is pressed against a roller (for example, silicone). (Rubber sponge) 44 is pressed against the outer surface of the fixing roller 1, and the roll-winding web on the payout shaft side is slowly wound onto the take-up shaft side at low speed (for example, 1 m / 10,000 sheets (A4 size) paper feed). )
By doing so, the outer surface of the fixing roller is cleaned.

Reference numeral 5 is an unfixed toner image supporting material. Specifically, electrophotography, electrostatic recording, and other conventionally known appropriate image forming principles
A transfer paper, an electro-fax paper, an electrostatic recording paper, etc., on the surface of which an unfixed toner image T has been formed in an image forming section (A) (not shown) of the system, and the fixing roller 1 and the pressure applied in a rotationally driven state. The toner image bearing surface side is fixed between the rollers 2 by the fixing roller 1.
Be introduced on the side. Reference numeral 6 denotes an unfixed toner image support material introduction guide member between the rollers 1 and 2. Thus, the unfixed toner image T is heated on the surface of the image supporting member 5 as a permanently fixed image by the heat of the fixing roller 1 and the mutual pressing force of the rollers 1 and 2 while passing through the nip portion 3 between the rollers 1 and 2. It is fixed under pressure.

In the fixing roller 1, the thickness of the coating layer 12 is set thin so that the heater heat can be quickly supplied to the outer surface of the layer, that is, the outer peripheral surface of the fixing roller.

The fixing roller 1 has a coating layer 12, that is, heat resistance and wear resistance.
PTFE (tetrafluoroethylene resin) as toner releasable material layer
-A so-called Teflon-coated roller that uses a fluorine-based resin such as PFA (tetrafluoroethylene-fluoroalkoxyethylene copolymer resin) and an elastic material such as silicone rubber, fluorine rubber, EPDM, hydrin rubber, or fluorosilicone rubber. There is an elastic covering roller. The cover layer 22 of the pressure roller 2 is formed by using the latter elastic material.

When a Teflon-coated roller is used as the fixing roller 1 (denoted by A) and when an elastic-coated roller is used (denoted by B), a, toner releasability; offset of toner with respect to outer peripheral surface of the fixing roller Preventive property, b, long-term sustainability of toner releasability, c, fixing property; fixing force of fixing roller image to the image support material surface, d, image property; toner image is extremely crushed or pops up In comparison, the following characteristics are obtained: (1) fixing without substantially fixing the image quality in the unfixed state, (e) curl; fixing without substantially curling the image support material. The long-term sustainability of A is better than that of B, and the fixability, imageability, and curl of B are better than A.

Therefore, as the fixing roller 1, there is a tendency to use the elastic body-covered roller more than the Teflon-covered roller from the viewpoint of emphasizing image quality (particularly, high-speed machine, system machine, automatic double-sided machine, etc.), and in this case, the outer circumference of the roller. Toner releasability of the roller and its continuity are provided by providing means for applying a large amount of toner offset preventing liquid such as dimethyl silicone oil having a relatively low viscosity to the surface or applying a small amount of high viscosity toner offset preventing liquid. To improve as much as possible.

However, when the toner offset preventing liquid having a relatively low viscosity is applied in a large amount, the following new problems occur.

B. Permeation of the applied toner offset prevention liquid into the image supporting member 5 and deterioration of image quality due to the permeation.

(B) Uneven swelling of the elastic coating layer 12 of the fixing roller 1 and by extension, the elastic coating layer 22 of the pressure roller 2 due to the permeation of the toner offset preventing liquid over time, and the wrinkles of the image support 5 due to the uneven swelling. Occurrence and uneven fixing.

C, mechanical strength deterioration of the roller coating layer due to excessive swelling,
Damage to the coating layer due to the decrease and peeling of the adhesion between the coating layer and the core metal.

Although the above problems can be avoided if the composition is such that a small amount of high viscosity toner offset prevention liquid is applied,
The toner releasability decreased with time, and the effect of prolonging the roller life was low.

The present invention is also a fixing device which uses an elastic body-covered roller as a fixing roller and utilizes a toner offset prevention liquid to improve the toner releasability of the roller and to achieve long-term sustainability thereof. In a constitution in which the above-mentioned conventional toner offset prevention liquid is applied to the outer peripheral surface of the fixing roller by preliminarily containing the prevention liquid in the elastic body coating layer of the fixing roller and holding the contained liquid for a long period of time. It is an object of the present invention to provide a roller bearing that does not have such a problem and that can significantly extend the roller life.

That is, the present invention has a fixing roller having an elastic layer in contact with a toner image, and a pressure roller having an elastic layer in pressure contact with the fixing roller to form a nip, and a recording carrying an unfixed toner image. In a toner image fixing device that holds and conveys a material at the nip for fixing, the elastic layer of the fixing roller is impregnated with a toner offset preventing liquid in advance, and the surface of the elastic layer of the pressure roller is a fluororubber water-based paint. A gist of a toner image fixing device is characterized by being applied and baked.

The elastic coating layer 12 of the fixing roller 1 can be made to contain the toner offset preventing liquid in its flesh quality by, for example, swelling after vulcanization of the rubber material as the elastic coating layer to form a vulcanized rubber flesh. For example, a toner offset prevention liquid may be permeated and contained, or a toner offset prevention liquid may be added and mixed when kneading a raw rubber material.

Specifically, one example of obtaining the silicone rubber-coated fixing roller 1 containing the silicone oil as the toner offset preventing liquid by the swelling method will be described. To the silicone raw rubber, a crosslinking agent, and if necessary, a filler (silica or the like), other Mold a raw rubber mixture containing additives into a sheet,
It is wrapped around the outside of the roller core metal via a primer and adhered. It is placed in a press mold and heated / pressurized for vulcanization. Silicone rubber is generally of the thermal vulcanization type (HTV) or addition reaction type (LTV). In the case of the thermal vulcanization type, the organic peroxide, which is a crosslinking agent, is decomposed and vulcanized at the stage of primary vulcanization. A decomposition residue is produced at the same time as sulfurization. Therefore, a secondary vulcanization treatment is performed to remove this. Even in the case of the addition reaction type, the characteristics are more stable when the high temperature heat treatment is performed. Next, the vulcanized roller of the coating layer is immersed in silicone oil to impregnate the coating layer with the silicone oil. If the thickness of the coating layer at this oil immersion step is considerably thicker than the required thickness, the oil may be soaked after grinding to a substantially required thickness. After the completion of the oil immersion, the outer periphery of the coating layer is ground to finish the roller having a predetermined outer diameter.

The oil immersion conditions are not particularly limited. For example, in the case of the fixing roller 1 having the coating layer 12 having a thickness of 0.5 mm, the oil content is generally 180 ° C. and the immersion time is 8 to 24 hours. (Swelling degree) can be permeated and contained in the meat quality of the coating layer. Further, if the oil dipping treatment is performed under heat and pressure, the dipping time can be shortened.

The impregnating silicone oil is selected and used in the range of, for example, about 20 to 1000 cs in order to allow the oil to permeate and be contained in the meat quality of the coating. Those of 20 cs or less are not suitable because they have good permeability into the coated meat but have poor heat resistance and volatilize and disappear due to heat from the fixing roller. Those with a high viscosity of 1000 cs or more are not effective because they have poor penetrability into the coating meat and require a long time for oil immersion treatment, and even when impregnated, they bleed to the coating surface. For the fixing roller, the amount of silicone oil to be impregnated into the coated meat should be 10% or more when the equilibrium swelling (saturated impregnation) of the oil with respect to the coated meat is 100%. The extension effect is low.

The swelling liquid (%) of the coated meat oil (toner offset prevention liquid) is defined as the saturated content rate (equilibrium swelling amount) of the oil per unit weight of the coating material, and the actual oil content per unit weight of the coating material. It is calculated by the following formula, where b is (measured by extraction method or the like).

In this specification, the viscosity number (cs, centistokes) of silicone oil is 25 ° C. Further, the oil is not an oil prepared by blending silicone oils having various viscosities to have a predetermined viscosity number, but one having a single viscosity peak from the beginning is synthetically produced.

By preliminarily containing the toner offset preventing liquid (hereinafter referred to as oil) in the elastic coating layer 12 of the fixing roller 1, the oil contained in the coating 12 is introduced between the fixing roller 1 and the pressure roller 2. A very small amount of the toner is transferred to the surface of the unfixed toner image supporting material 5 (hereinafter referred to as copy paper), which causes good toner releasability of the fixing roller 1. As long as the amount of oil contained in the fixing roller 1 is substantially limited to the small amount of transfer to the copy paper each time, the fixing roller is good even if no external oil is applied to the fixing roller. The toner releasability is maintained for a fairly long time, and the roller life is long.

However, as a factor for decreasing the oil content of the fixing roller 1 with time, in addition to the amount of transfer to the copy paper, the scattering due to the heating of the fixing roller 1 (mainly low molecular weight of oil) and the pressure roller 2 side Transition is mentioned. In the former case, the amount of decrease due to heat dispersion is very small when the fixing roller temperature is set to 200 ° C or lower. The decrease due to the transfer to the pressure roller 2 side of the latter is as follows: i, the trailing edge of the preceding copy paper 5 ₁ (Fig. 2) is the fixing roller 1
And the pressure roller 2 and the rollers 1 and ₂ in the period until the leading edge of the succeeding copy paper 52 reaches the nip.
2 direct contact period, ii, when the introduced copy paper is smaller than the maximum size that can be passed, the non-paper feed area other than the paper feed area P (FIG. 2) through which the copy paper passes Part Q, ie both rollers 1
2, direct contact rotation area, iii, both rollers for warming up period of the device, etc.
During the direct contact rotation period, the oil contained in the fixing-roller-side coating layer 12 permeates into the pressure-roller-side coating layer 22 having a large oil-containing capacity over time.

The degree of time-dependent migration of oil from the fixing roller 1 side to the pressure roller 2 side varies depending on the material of the coating layers 12 and 22, the type and amount of filler, the viscosity and content of oil, etc. However, from this fixing roller 1 side to the pressure roller 2
The amount of oil transferred to the side over time is larger than the amount of oil transferred from the fixing roller 1 side to the copy paper introduced each time, and this is actually the case of the fixing roller 1 in which the elastic body coating layer 12 contains oil in advance. Good toner releasability is deteriorated at an early stage.

In the present invention, the toner offset migration preventing layer 24 formed on the surface layer of the elastic body releasability 22 of the pressure roller 2 is formed from the elastic body coating layer 12 of the fixing roller 1 to the elastic body coating layer of the pressure roller 2.
It serves to prevent the toner offset prevention liquid from migrating to 22 and retain the toner offset prevention liquid in the elastic body coating layer 12 of the fixing roller 1 for a long period of time. This layer 24 can be formed by applying and drying (or baking) a coating composition of an oil resistant substance on the outer peripheral surface of the elastic body coating layer 22 of the pressure roller 2, or laminating a film of an oil resistant substance. . The layer 24 is an elastic coating layer 22 of the pressure roller 2.
It is desirable to form it as a thin layer having a thickness of, for example, 70 μm or less so as not to substantially impair the elasticity that it should have.

Thus, according to the present invention, since the toner offset preventing liquid is previously contained in the elastic body coating layer 12 of the fixing roller 1 to improve the toner releasability, the elastic body of the fixing roller 1 is formed as described above. The above-mentioned problems (1) to (3) occur in a structure in which a large amount of a relatively low-viscosity toner offset preventing liquid is applied and supplied to the outer peripheral surface of the coating layer 12 to improve the toner releasability of the fixing roller. Absent. Further, the elastic coating layer of the fixing roller 1
The toner offset prevention liquid previously contained in 12 is prevented from moving to the elastic body coating layer 22 on the pressure roller 2 side, which is the main cause of the decrease over time, by the presence of the layer 24, and the elastic body fixing roller of the fixing roller 1 is prevented. It will be held within 12 for a long time. As a result, as shown in Examples below, the fixing roller 1 maintains good toner releasability for a long period of time without separately applying a toner offset preventing liquid coating treatment to the outer peripheral surface of the fixing roller.
The roller life is greatly extended. The fixing roller 1
A means for applying a small amount of the toner offset prevention liquid to the outer peripheral surface of may be used together.

Example A fixing device having the following specifications according to the present invention was constructed.

(1) Fixing roller 1 (HTV silicone rubber coated roller containing dimethyl silicone oil) Was sufficiently kneaded to obtain an unvulcanized rubber sheet, which was left at room temperature for 3 days.

A hollow body made of aluminum (A5056) with an outer diameter of 58.4 mm and a wall thickness of 7 mm and a blasted outer surface is used as the core metal 11,
An adhesive was applied to the outer surface, left at 25 ° C for 5 hours, and then baked at 120 ° C for 20 minutes. The outer peripheral surface of the core metal was covered with the unvulcanized rubber sheet, and primary vulcanization was performed using a press vulcanizer at a pressure of 150 kg / cm ² , a temperature of 170 ° C. for 30 minutes. After secondary vulcanization at 200 ° C. for 4 hours, the rubber coating layer was ground to give a rubber coated roller having an outer diameter of 59.3 mm (rubber coating layer thickness 0.45 mm).

The rubber-coated roller was set to dimethyl silicone oil at 180 ° C (toner offset prevention liquid, viscosity at 25 ° C is 100c
s) for 8 hours to swell the rubber coating layer with oil (62% swelling), and then finish polishing the swelling rubber coating layer to obtain an HV containing dimethyl silicone oil with an outer diameter of 59.4 mm.
A fixing roller coated with T silicone rubber was used.

(2) Pressure roller 2 (HTV silicone rubber coated roller) Was sufficiently kneaded to obtain an unvulcanized rubber sheet, which was allowed to stand at room temperature for 2 days.

As the core metal 21, a stainless steel (SUS430) rod having an outer diameter of 50 and having an outer surface blasted was used, and an adhesive layer was formed on the outer surface in the same manner as the fixing roller.

The outer peripheral surface of the cored bar was covered with the above-mentioned unvulcanized rubber sheet, and then baking and primary vulcanization were performed in the same manner as the fixing roller. Then, the rubber coating layer was polished to obtain a rubber coating roller having an outer diameter of 60 mm (rubber coating layer thickness 5 mm). The rubber hardness of this rubber coating layer was 40 degrees (JIS A).

Next, the outer surface of the rubber-coated roller is coated with a fluororubber water-based paint (trade name: Daiel GLS213, Daikin Industries, Ltd.) to a thickness of 20 μm and baked at 300 ° C. for 20 minutes to prevent toner offset prevention liquid (dimethyl silicone oil) transfer layer 24. Was formed. Since the outermost layer is as thin as 20 μm, the pressure roller 2 is rich in elasticity and a sufficient nip width can be obtained.

(3) Fixing roller temperature (surface control temperature): 185 ° C (4) Nip width W: 8.5mm (5) Process speed (paper passing speed): 445mm / sec (60 sheets / minute (A4)) A 100,000-sheet continuous fixing test was conducted on the fixing device. As a result, a good fixing process was continued without any problem even if a separate toner offset preventing liquid coating means was not provided on the outer peripheral surface of the fixing roller 1.

In addition, when a means for applying and supplying a high-viscosity offset preventing liquid little by little to the fixing roller 1 is also used, no problem occurs even if 200,000 sheets are passed, and further copy processing can be performed. Met.

When the pressure roller 2 without the toner offset prevention liquid migration prevention layer 43 is used, the toner offset sticking to the outer peripheral surface of the fixing roller becomes remarkable around the time of passing about 30,000 sheets, and a paper jam trouble occurs. began. This is the period or area where the fixing roller 1 and the pressure roller 2 are in direct contact with each other as described in the above paragraphs i and ii, and the toner offset prevention liquid in the rubber coating layer 12 of the fixing roller 1 is on the pressure roller 2 side. This is because the toner is removably transferred to the rubber coating layer 22 successively, and as a result, the toner releasability of the fixing roller 1 deteriorates within a relatively short time.

The toner offset prevention liquid is not contained in advance in the elastic roller coating layer of the fixing roller, and a large amount of toner offset prevention liquid having a relatively low viscosity is applied and supplied to the outer peripheral surface of the coating layer as described above. Not only does the anti-offset liquid easily contaminate the copy paper and deteriorate the copy quality, but the elastic body swells with the anti-offset liquid and its temporal strength decreases, and the elastic layer is damaged after 100,000 sheets or less. An accident occurred in which the core metal and the elastic layer were separated. Also, before that, wrinkles occurred in a high temperature environment.

The roller life of the conventional method that applies and supplies the high-viscosity toner offset prevention liquid little by little was less than 100,000 sheets.

[Brief description of drawings]

FIG. 1 is a very schematic configuration diagram of a roller type toner image fixing device, FIG. 2 is a perspective view of a fixing / pressure roller pair, and FIG. 3 is a partially enlarged view of an elastic body coating layer of the pressure roller. 1 is a fixing roller, 2 is a pressure roller, 11 and 21 are cored bars, 12 and
22 is an elastic coating layer, and 24 is a toner offset prevention liquid migration prevention layer.

Claims (1)

[Claims] 1. A recording bearing an unfixed toner image, comprising: a fixing roller having an elastic layer in contact with a toner image; and a pressure roller having an elastic layer in pressure contact with the fixing roller to form a nip. In a toner image fixing device for sandwiching and conveying a material at the nip for fixing, the elastic layer of the fixing roller is preliminarily impregnated with a toner offset preventing liquid, and the surface of the elastic layer of the pressure roller is a fluororubber aqueous paint. A toner image fixing device characterized by being coated and baked.