JPS5933107B2 - Manufacturing method of rotating body for powder image fixing - Google Patents

Description

Detailed Description of the Invention The present invention uses a powder image (so-called toner image) formed by electrophotography or electrostatic recording to be fused or fixed onto a support such as paper. The present invention relates to a method of manufacturing a rotating body.

More specifically, the present invention relates to a method for producing a rotating body for fixing powder images, which comprises curing and molding a curable liquid raw material of silicone rubber in a cylindrical mold. Conventionally, in the field of image forming technology such as electrophotography or electrostatic recording, powder images made of so-called toner mainly composed of thermoplastic resin used to develop electrical latent images have been used. As a method of fixing it on the image receiving surface, for example, radiant heating using infrared rays, hot plate heating,
Many methods are known, such as a heat fixing method such as heating with a ribbon heater, a fixing method using solvent vapor, or a pressure fixing method.

By the way, in this technical field, there has recently been a demand for particularly high-speed image formation, and in order to satisfactorily satisfy this demand, the powder image carrier is placed in direct contact between a pair of rotating bodies, such as rollers. A fixing method in which heat and pressure are applied to the toner while passing the toner through the toner is increasingly being put into practice. FIG. 1 shows a typical example of such a heat roller type fixing device in sectional view.

That is, the roller 1 on the side that comes into contact with the powder image T on the copying material (for example, paper) C is made of a rigid body such as a conductive metal tube, and a heat source 3 is provided inside the roller 1. The roller 2, which is paired with the roller 1, is made of an elastic material such as rubber.

Furthermore, a prevention liquid 4 is applied to the surface of the roller 1 to prevent toner offset. Generally, the roller 1 is called a fixing roller or a heating roller, and a sleeve 5 made of aluminum or copper alloy is used.

The other roller 2 is called a pressure roller, and has a core metal 6 as its central axis and a layer T of an elastic material such as silicone rubber on its circumferential surface. FIG. 2 shows another example of the heat roller type fixing device. In the second illustrated example, a coating 8 of a material having releasability, such as silicone rubber or polytetrafluoroethylene, is added to the outermost side of the roller 1, so that the copying material C can be wrapped around or The purpose is to prevent 6 offset 7.

In FIGS. 1 and 2, rollers 1 and 2 are pressed together with appropriate pressure and rotated in the direction of the arrow. A copying material C made of paper carrying a heat-fusible toner powder image T is conveyed in the direction of the arrow and heated and pressed between rollers 1 and 2. The roller 1 is heated by an internal heat source 3, and provides sufficient heat to the copying material C to melt the powder image T at its contact surface with the roller 2. Note that the surface temperature of the roller 1 is always controlled within a constant temperature range by a temperature detection element 9 such as a thermistor. Incidentally, 10 is an entrance guide for carrying the copy material C between the rollers 1 and 2, 11 and 12 are separating claws for reliably separating the copy material after fixing, and 13 and 14 are for separating the copy material after fixing. This is a guide plate for conveying copy materials.

In this type of fixing method, a combination of a heating roller (of course, it can be replaced with an endless belt-like rotating body, but to simplify the explanation, it will simply be referred to as a roller hereafter) and a pressure roller are functionally divided. used.

Generally, a heated roller is placed in direct contact with the powder image. Such heating rollers can be broadly classified into either a rigid body such as metal, or an elastic body such as rubber. In addition, since the roller comes into contact with the softened powder image, in order to prevent offset, at least the outer surface of the roller is coated with a liquid with low cohesive energy such as silicone oil, or coated with silicone elastomer, polytetrafluoroethylene, etc. It is coated with a material with low surface energy such as. On the other hand, the pressure roller is also made of a rigid body or an elastic body, and when the heating roller is a rigid body, it is generally an elastic roller, and conversely, when the heating roller is an elastic body, it is a rigid roller.
However, this is not absolute, and if an appropriate nip 7 can be formed when the two are pressed together, it is also possible to combine elastic rollers as appropriate. There are two types: one has a heating element built into it, and the other type heats it from the outside. Among the rollers used in the hot roller type fixing method described above, the roller made of a rigid body such as metal as shown in the first diagram can meet the required performance by ordinary mechanical processing such as grinding. It is relatively easy to complete. However, when manufacturing the elastic rollers shown in Figure 1 or 2, or the rollers coated with silicone rubber, it is extremely difficult to meet the required performance through mechanical processing. It is. For example, in order to prevent toner offset from occurring as a fixing roller, the circumferential surface of the roller needs to be finished with a surface roughness of approximately 1μ or less, but it is extremely difficult to achieve the above surface accuracy by grinding, etc. It's a difficult place. In particular, when the material is made of highly plastic rubber with a hardness of 50 HS or less, it is almost impossible. Therefore, when manufacturing rollers made of silicone rubber, rather than using mechanical force methods such as grinding,
The so-called molding method is advantageous and has become widely used because its manufacturing method is simple and easy to mass-produce, and rollers of the same specification can be stably supplied at a high yield. It's here. Here, one example of a conventional molding method will be explained with reference to FIG.
FIG. 3 schematically shows a cross section of the split mold. The roller core shaft 15 is clamped and fixed between an upper mold 16 and a lower mold 17.
Of course, the core shaft 15 may have a built-in heat source in advance. ) From either the opening 18a or 18b of the upper mold 16,
Curing rubber or resin, liquid raw material is injected. Thereafter, for example, if RTV type silicone rubber is used, it is solidified at room temperature. When polytetrafluoroethylene is used, it is heated and melted into a liquid, which is then cooled and solidified after casting. Incidentally, 19 is a mold space corresponding to the thick part of the roll to be molded, and the dotted line L indicates the seam of the split molds. As described above, when liquid rubber or resin is cast and solidified and then removed from the mold, a resultant product as shown in FIG. 4 is obtained. In the figure, 20 is a thick portion of solidified rubber or resin.
21a, 21b, and 21c are so-called burrs that are generated due to the shape of the joints of the split molds.

Since the occurrence of such burrs is almost unavoidable in the manufacturing method using the mold shown in Figure 3, the mold space is set in advance to be slightly larger than the specified roller diameter and length, and the resulting product is It is finished by performing secondary processing such as grinding to the specified dimensions (shown as dotted line S). Another conventional method is explained with reference to FIG.

This method has been evaluated as a method for eliminating burrs caused by the use of split molds.

In the figure, reference numeral 22 has a seamless cylindrical shape, and one side end 22a has an opening 23 into which the roller core shaft 15 can be inserted and fixed, and the other side end 22b has an injection port 24. Liquid rubber or resin is injected into the mold space 25 through the injection port 24 and solidified or hardened here. Thereafter, the mold is demolded to obtain a resultant product as shown in FIG. Incidentally, 26 is a thick portion of rubber or resin, and at least one side edge 27 has a wave surface. Therefore,
Grinding is completed to the dotted line Q position. 15 is a roller core shaft.

According to the conventional method described above, rollers are extremely frequently found to have various defects as described below.

In other words, since the conventional method is simply a casting method, Fig. 7A, b
As schematically shown in the cross-section of the rotating body shown in , many pinholes or voids remain in the thick part after molding. For example, in the figure, 28 is a pinhole generated on the surface of the roller thick part 29, 30 is a bubble generated and remaining in the thick part 29, and 31 is a bubble generated near the interface between the roller core shaft 32 and the thick part 29. The bubbles 33 are bubbles generated and remaining on the surface of the thick portion 29, and are larger in diameter and depth than the pinholes 28.
In addition, a large number of bubbles such as 34 may be generated continuously and remain. 30a, 31a, 34a are bubbles 30, 31, respectively.
, 34 shows the recessed portions on the roller surface caused by this.

The defects shown in FIGS. 7A and 7B described above frequently occur in common with the conventional manufacturing method described based on FIGS. 3 and 5 described above. The following FIG. 8 mainly explains the defects that frequently occur in the conventional manufacturing method explained based on FIG. 5 above. On the circumferential surface of the roller thick portion 35, belt-shaped recesses such as 36 and 37 are seen in the longitudinal direction of the roller.

Numeral 38 is a crack-shaped recess formed on the end face of the thick portion 35, and a recess like 38a is left on the peripheral surface of the roller.

Incidentally, 39 is the roller core shaft. As detailed above, in conventional molding methods, air bubbles are unavoidably mixed into the liquid raw material in the process of casting and curing the curable liquid raw material. It often leaves countless pinholes or holes in objects. However, such pinholes or voids become a fatal defect for the fixing rotating body. For example, if there are defects such as pinholes or voids on the surface or inside the roller, a part of the fixed image that should appear will not appear, which is the so-called "whiteout phenomenon," or a fixing failure due to uneven pressure contact (fixing Moreover, since the toner is not sufficiently fused onto the copy material, problems such as image transfer occur. Furthermore, if there are pinholes or recesses on the roller surface, toner will become clogged there, promoting the adhesion and remaining of molten toner, causing the so-called "offset phenomenon 1", and causing separation between the copying material and the roller circumferential surface. The shape deteriorates, causing problems such as the copy material being wrapped around the copy material.As mentioned above, if there are pinholes or holes in the fixing rotor, it will cause various serious problems. The main object of the present invention is to provide a method for manufacturing a rotary body having a good fixing function with a high yield by eliminating the inconveniences seen in conventional manufacturing methods.

The present invention, which achieves the above object, includes a rotating body made of silicone rubber for fixing a powder image made of toner on a support thereof, having an inner diameter almost equal to the outer diameter of the rotating body, and a side mold. A curable liquid raw material of silicone rubber is press-fitted into a cylindrical mold that is substantially sealed by the mold and has an inner circumferential surface with a surface roughness of 1 μ or less by applying a pressure of 10 Kf/d or more in a direction against gravity, and the inside of the mold is A rotation for fixing powder images, which is characterized by curing a curable liquid raw material without heating, thereby obtaining a surface roughness of 1 μm or less on the outer peripheral surface and virtually no pinholes or voids. It is a method of manufacturing the body. The present invention will be specifically explained with reference to the following drawings. FIG. 9 is a sectional view showing an outline of the apparatus used in the present invention.

In FIG. 9, 40 is a seamless cylindrical shape made of a rigid body such as metal, and the inner surface 40a thereof is machined to have a perfect cylindrical shape. Inner peripheral surface 4 of cylindrical shape 40
Since the shape of 0a almost defines the outer peripheral surface shape of the roller to be molded, in order to maintain the roundness and parallelism of the outer periphery of the molding roller, the cylindrical mold 40 is It should have an inner diameter that is almost the same as the diameter and uniform throughout its length. Further, in order to prevent foreign matter such as toner from clogging the surface of the forming roller, the inner circumferential surface 40a is preferably finished in advance to a smooth surface (mirror surface) with a surface roughness of 1 μm or less. By doing so, the surface roughness of the circumferential surface of the roller can be suppressed to less than lμ.
This is also more advantageous when demolding the forming roller. 4
1 is a lower mold, which together with an upper mold 42 forms a cylindrical mold 40.
It has a function of supporting and fixing the roller core shaft 43 and the roller core shaft 43 in a predetermined positional relationship.

41a is a roller core bearing part provided on the lower mold 41, 42a is a roller core bearing part provided on the upper mold 42, 41b is a joint with the cylindrical mold 40 provided on the lower mold 41, and 42b is provided on the upper mold 42. Department.

Furthermore, both the lower mold 41 and the upper mold 42 are guides for regulating the cylindrical mold 40 and the roller core shaft 43 to coaxial positions, that is, to positions where the respective shaft centers (indicated by dashed lines) coincide with each other. The parts 41c and 42c are integrally included in each structural part. The joint portions 41b and 42b can be joined to each other with screws or the like. The lower mold 41 also includes a conduit 44 and an opening 45 for guiding the curable liquid raw material into the mold.
46 is a support stand for supporting and fixing the lower mold 41;
At position 7, the two are joined using screws or the like.

After connecting the above-described mold devices, a roller made of silicone rubber is molded in the following manner.

48 is a container for silicone curable liquid raw material 49, and its upper lid 50 has a through hole 51, which is connected to the support base 4.
It is connected to the conduit 44 of the lower mold 41 through the through hole 52 of No.6.

53 is a bottom plate for pushing up the liquid raw material 49 at pressure P1, and is equipped with a movable sealing mechanism 54 such as an O ring. In the conventional method, the liquid raw material 49 is injected from the top of the mold at normal pressure. Therefore, at that time, air bubbles are trapped in the liquid raw material, and as a result, defects such as pores and pinholes are left in the cured product.

In addition, the liquid raw material itself, for example, RTV type silicone rubber, is usually applied by mixing two parts, a main ingredient and a catalyst, but at the same time, a large number of air bubbles are mixed in during mixing, and at the same time, after adding the catalyst,
The curing reaction proceeds rapidly, the viscosity increases, and it becomes almost impossible to defoam even if the pressure is reduced.For this reason, the above-mentioned defects are often left on the forming roller. In contrast, in the present invention, a curable liquid raw material with a viscosity of approximately 50 poise or more is not simply cast under normal pressure, but is applied with a pressure of approximately 10 KP/d or more (the pressure applied in P1 above). It was discovered that by press-fitting (pressing), no pinholes or holes are left in the forming roller. Furthermore, the present invention will be understood more specifically by the following examples explained with reference to FIGS. 9 and 10.

Example 1 Container 4 with bottom plate 53 with movable ceiling 54
With the upper lid 50 removed, the space 55 of No. 8 is filled with a mixture of 100 parts by weight of liquid silicone rubber, [trade name KE-12RTV silicone rubber: manufactured by Shin-Etsu Chemical] and 0.5 parts by weight of catalyst.

Next, the container 48 is sealed with the upper lid 50, and the liquid raw material 49 is sealed.
The support base 46 and the lower mold 41 are connected to the upper lid 50. Furthermore, after installing the core shaft 43 and the seamless cylindrical mold 40 at a predetermined position of the lower mold 41, they are fixed by being held down by the upper mold 42 under pressure P2. At this stage, the seamless cylindrical mold 40 and the core shaft 43 are coaxially fixed with high precision.
Each position will not shift. Note that the pressure P2 must be higher than the internal pressure when the mold space 56 is filled with the liquid raw material 49.

In this example, a seamless metal cylindrical mold with an inner diameter of 30.35 φ and a length of 321 mm and a mirror-finished inner peripheral surface was used.
In this state, the bottom plate 53 was gradually pushed up at a pressure of about 30 KP/Clll, and the liquid raw material 49 was press-filled into the mold space 56 through the opening 45 along the route of the through holes 51, 52 and the conduit 44. At this time, the joints 41b and 42b are designed to allow a low viscosity substance such as air to pass therethrough, but not to allow a high viscosity liquid such as a silicone rubber liquid raw material to pass therethrough.

In this state, when the bottom plate 53 is pushed up further, the internal pressure of the mold space 56 and the push-up pressure P1 are balanced, and the check valve 5
7 is activated, and the internal pressure of the mold space 56 is maintained while being pressurized until the submerged raw material is hardened or solidified. In this example, an appropriate push-up pressure P1 should be selected depending on the viscosity of the liquid raw material used, and the viscosity of the liquid silicone rubber used in the present invention is approximately 50 poise or more. , 30K2/(not limited to the pressure of 7i1 shown earlier, but about 10K
The push-up pressure can be selected within the range of P/Cll or more. In addition, due to the action of the check valve 57, the liquid material in the mold space 56 is maintained in a pressurized state until it hardens, thereby eliminating pinholes or voids caused by residual air bubbles. Defects can be completely eliminated. This is the above-mentioned press-fit pressure,
If the internal pressure is maintained until curing, the relationship between the viscosity of the gas and liquid will change even if the defoaming of the liquid raw material is incomplete or if air is trapped inside the mold. Since the gas is a liquid, only the gas becomes extremely mobile, and by the time the liquid raw material hardens, it is properly discharged through the joint parts 41b and 42b, and air bubbles are formed in the thick part of the roller. This is thought to be to avoid leaving any traces behind. Next, in this example, while maintaining the pressurized state as described above, the sample was left for two days under conditions of 25° C1 and 65% relative humidity.

Thereafter, as shown in Figure 10, a required pressure P3 was applied to the core shaft 43 to remove the mold, yielding a silicone rubber roller having an outer diameter of 30.0 mm and a roll thickness of 320 mm.
No discernible pinholes or voids were observed in the thick rubber portion of the roller, and it could be used satisfactorily as a roller for a fixing device in a copying machine. Incidentally, in the fixing operation as shown in FIGS. 1 and 2, it withstood continuous use for fixing about 20,000 sheets without causing fixing failure, toner offset, or copy paper wrapping. Although the above-mentioned core axis is not specified, it may be a cylindrical rigid body or, of course, may be a tubular body with a heat source provided therein. According to the manufacturing method of the present invention, a part of the burr 59 remains on the end surface of the roller thick part 58 on the lower mold 41 side, but this does not affect the roller performance and the opening of the lower mold 41 Since the diameter of 45 is specified to be smaller than the roller wall thickness diameter, after curing, the cylindrical mold 40 and the lower mold 41
When disconnecting the roller from the roller, there is no need for thread cutting, especially secondary processing of the roller end face. Furthermore, in the manufacturing method of the present invention, the hardened roller is placed in a cylindrical mold 4 as shown in FIG.
The mold is removed from the cylindrical mold 40, but in order to facilitate this operation, it is desirable to perform a mold release treatment on the inner surface 40a of the cylindrical mold 40 in advance. Example 2 The same manufacturing equipment and liquid raw materials as Example 1 were used,
Silicone rubber rollers were molded in exactly the same manner except for the press-fitting conditions.

100 rollers were each molded under the same conditions, and the incidence of defective products was determined. In this example, if there are pinholes or holes in the mouth roller, it is considered a defective product.The results are summarized in the table below. By the way, according to the findings of the present inventors, it has been found that not only the number of pinholes or holes formed in the roller but also their size are factors that have a significant influence on the fixing operation. .

In other words, the depth of concave parts such as pinholes on the roller surface must be approximately 0.1 degrees or less, and the depth of defects such as holes in the thick part of the roller must be at least 0.1 mm in diameter in the longitudinal direction. ．．
5! It is necessary to keep it below WL.

In any case, it is desirable that there be no pinholes, holes, etc., and even if some do occur, it is necessary to satisfy the above size conditions. As described above in detail, according to the present invention, a rotating body that fully satisfies the required performance as a fixing rotating body can be manufactured with a high yield without particularly requiring secondary processing.

In addition, the manufactured rotating body does not cause uneven contact or clogging of toner, etc. during pressure welding, and exhibits very effective fixing performance over a long period of time. Although only the method for manufacturing a roller-like rotating body has been described above, the present invention can of course also be applied to a method for manufacturing an endless belt. In addition, the cylindrical type to be used is not limited to the above-mentioned ones, but for example, if the liquid raw material of the rotating body to be obtained contracts when it hardens or solidifies, the required specified roller diameter and length may be used. Use a mold with an inner diameter and length that take into account the shrinkage rate. Conversely, when using a liquid raw material that expands, it is common to use a mold sized to take into account the expansion rate.

[Brief explanation of the drawing]

1 and 2 are schematic cross-sectional views for explaining a known example of a heat roller type fixing device, and FIGS. 3 and 5 are schematic sectional views of a manufacturing apparatus shown for explaining a conventional rotary body manufacturing method. 4 is a schematic diagram showing the rotating body obtained in the third illustrated example, FIG. 6 is a schematic diagram showing the rotating body obtained in the fifth illustrated example, and FIGS. 7A, b, and 8 The figure is a schematic diagram illustrating defects in a rotating body obtained by the conventional method, and FIGS. 9 and 10 are explanatory diagrams relating to the manufacturing method of the present invention.

Claims (1)

[Claims] 1. A rotating body made of silicone rubber for fixing a powder image made of toner to its support, which has an inner diameter approximately equal to the outer diameter of the rotating body, is substantially sealed by a side mold, and has a surface roughness of 1 μ or less. A curable liquid raw material of silicone rubber is placed in a cylindrical mold having an inner peripheral surface of 10 kg from the direction against gravity.
By applying a pressure of /cm^2 or more and hardening the curable liquid raw material in the mold without heating, the surface roughness of the outer peripheral surface is 1μ or less and there are virtually no pinholes or A method for producing a rotating body for fixing powder images, characterized in that the rotating body is obtained in a state free of pores.