JPH0625431A - Silicone rubber roller for electrophotography and its production - Google Patents

Abstract

PURPOSE:To readily and efficiently obtain a silicone rubber roller which does not foul a photoreceptor both immediately after the initiation of use and over a long period thereafter by molding a specific silicone rubber compound into a roller form, crosslinking the rubber, and heating the resulting roller in a vacuum. CONSTITUTION:A molding material containing a rubber compound which comprises a raw silicone rubber as the base polymer and in which the concentration of the sum of siloxanes with low degrees of polymerization and a silicone oil with no functional groups is 5,000ppm or lower is molded into a roller form and crosslinked. The molding is heated in a vacuum to obtain the silicone rubber roller. The heat treatment is conducted in, e.g. a vacuum oven preferably under conditions of a maximum degree of vacuum of 5mmHg or lower, a temp. of 150-250 deg.C, and a treating time of about 3-25hr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicone rubber roller used in an electrophotographic apparatus such as an electrostatic copying machine or a laser beam printer.

[0002]

2. Description of the Related Art In electrophotography, a photoconductor having an insulating photoconductor formed on a conductive substrate is used, and an image is formed by the following steps. First, the surface of the photoconductor is uniformly charged in a dark place (charging step). Next, the image is exposed on the surface of the uniformly charged photoreceptor. As a result, electron-hole pairs are generated in the exposed area to neutralize the surface electrostatic charge in that area, and an imagewise distribution of electrostatic charge corresponding to the exposed image, a so-called electrostatic latent image, is formed on the surface of the photoconductor. (Exposure step).

Next, when a colored powder (toner) is brought into contact with the surface of the photoconductor on which the electrostatic latent image is formed, the toner electrostatically adheres to the surface of the photoconductor in accordance with the electrostatic charge of the electrostatic latent image. Thus, the electrostatic latent image is visualized as a toner image (developing step). Next,
When an electric field is applied to the toner image while a transfer target such as paper is in contact therewith, the toner image is transferred to the surface of the transfer target (transfer process).

After that, the residual charge on the surface of the photoconductor is removed (static elimination step) and the toner remaining on the surface is removed (cleaning step), and one cycle of image formation by electrophotography is completed. Further, the toner image transferred to the surface of the transferred material is heat-treated by a heat roller or the like to be fixed on the surface of the transferred material (fixing step).

Conventionally, corona discharge by a discharge wire stretched near the surface of the photosensitive member has been used for the charging step, the transfer step and the charge removing step in the image formation by the electrophotographic method. However, the corona discharge by the discharge wire has a problem that air is contaminated due to the generation of a large amount of ozone and the photoreceptor is deteriorated. Therefore, in recent years, a contact charging method using a rubber roller brought into contact with a photoconductor is being put into practical use as a charging method that does not easily cause the above problems.

[0006]

The rubber roller used in the contact charging method is required to have excellent environmental resistance stability, ozone resistance, heat resistance stability, and the like. The use of physically stable silicone rubber is being considered. However, the roller made of silicone rubber can obtain a very good image quality immediately after the start of use, but when used for a long time, a trace of the roller appears in the projected image, so-called touch memory is generated, and the image quality is gradually improved. There is a problem that makes it worse.

This problem is caused by a relatively low degree of polymerization of cyclic siloxane represented by the formula: (CH ₃ ) ₂ SiO _n (where n is about 3 to 30) or dimethyl silicone from the surface of the silicone rubber roller. It is believed that this is caused by non-functional silicone oil such as oil, methylphenyl silicone oil, and methyl hydrogen silicone oil leaching (bleeding) and transferring to the photoreceptor.

That is, the low-polymerization degree siloxane and the non-functional silicone oil transferred to the photoconductor deteriorate the insulating photoconductor constituting the photoconductor to deteriorate its function. Further, since these substances have high water repellency and insulation properties, the presence of these substances hinders the function of the photoconductor. Then, when the silicone rubber roller is in contact with a part of the photoconductor for a relatively long time (for example, when the apparatus is stopped), these substances locally contaminate the photoconductor, which is a trace of the roller (touch memory). Appears in the image as. Further, as the silicone rubber roller is used for a long period of time, the entire photoconductor is contaminated with these substances and the accumulated concentration thereof gradually increases, so that the image quality gradually deteriorates.

Bleeds of low-polymerization degree siloxane and non-functional silicone oil have been conventionally known, and commercially available silicone rubber compounds (silicone raw rubber as a base polymer to which a reinforcing filler and the like are added)
Some of these grades are provided with a grade in which these substances are forcibly sucked and removed to some extent. For ordinary applications such as touch panels, this level solves the problem of bleeding, but in the case of rollers for electrophotography, the removal of commercially available products is not sufficient, and a small amount of residual low-polymerization siloxane or The non-functional silicone oil causes contamination of the photoreceptor as described above.

It is known that siloxane having a low degree of polymerization can be removed to some extent by heating during crosslinking. For example, in the case of a millable type silicone rubber material, about 180 to 22
By the secondary cross-linking by heating at a temperature of 0 ° C. for about 2 to 5 hours,
It can scatter and remove siloxane having a low degree of polymerization to some extent. However, the effect is not yet sufficient, and under the heating conditions such as the degree of secondary cross-linking, particularly those having a relatively high degree of polymerization among siloxanes having a low degree of polymerization and nonfunctional silicone oils can hardly be removed. That is, contamination of the photoconductor cannot be completely prevented only by heat treatment under normal pressure.

Low-polymerization degree siloxanes and non-functional silicone oils can be removed by a solvent extraction treatment, but the effect is insignificant, and if this treatment alone is used to obtain a sufficient removal effect, it will take an extremely long time. Therefore, it is not suitable for practical use in terms of productivity. The present invention has been made in view of the above circumstances, which could not be removed by the conventional treatment method, and almost completely removed even a trace amount of low-polymerization degree siloxane and nonfunctional silicone oil, It is an object of the present invention to provide a silicone rubber roller for electrophotography and a method for producing the same, which does not cause contamination of the photoreceptor for a long period of time after the start of use, not to mention immediately after the start of use.

[0012]

In order to solve the above problems, the present inventors have investigated various treatment methods, and as a result, when the silicone rubber is heat treated under vacuum, the cause is not clear, It was found that, unlike heat treatment under pressure, even low-polymerization degree siloxanes and non-functional silicone oils with a considerably high degree of polymerization can be effectively removed by suction. Therefore, as a result of further study, we used a grade of silicone rubber-based compound in which low degree of polymerization siloxane and non-functional silicone oil were removed to some extent,
When it is vacuum heat treated after molding, low-polymerization degree siloxane and non-functional silicone oil are almost completely removed,
The present invention has been completed by finding that a silicone rubber roller for electrophotography can be obtained which is not likely to contaminate the photoconductor for a long period of time, not to mention immediately after the start of use.

That is, the silicone rubber roller for electrophotography of the present invention contains a rubber compound containing silicone raw rubber as a base polymer, and the total concentration of the low-polymerization degree siloxane and the non-functional silicone oil in the rubber compound is 5000 ppm or less. It is characterized in that the material is formed by cross-linking and molding into a roller shape, and after molding, vacuum heat treatment is performed.

In the silicone rubber roller for electrophotography according to the present invention, the low-polymerization degree siloxane and the non-functional silicone oil are almost completely removed as described above, and the photoreceptor is contaminated for a long period immediately after the start of use. Therefore, it is possible to put the contact charging type image forming apparatus into practical use, which does not cause air pollution or deterioration of the photoconductor due to a large amount of ozone generation.

The method for producing a silicone rubber roller for electrophotography of the present invention includes a rubber compound containing silicone raw rubber as a base polymer, and the total concentration of the low-polymerization degree siloxane and the nonfunctional silicone oil in the rubber compound is 5000 ppm. It is characterized in that the following molding material is subjected to vacuum heating treatment after being cross-linked and molded into a roller.

According to the production method of the present invention, the silicone rubber roller for electrophotography of the present invention can be produced simply and efficiently. The property of the molding material used in the present invention may be either liquid or millable type, but in particular, a kneadable millable type molding material capable of producing a roller in the same process as a conventional rubber material is preferably used. The millable molding material is based on a gel-like silicone raw rubber (linear organopolysiloxane polymer) having a degree of polymerization of about 5,000 to 10,000, and is mixed with an anhydrous silica-based reinforcing filler such as Aerosil and a dispersion accelerator. Commercially available silicone rubber compound, cross-linking agent, catalyst,
It is prepared by blending various additives such as a non-reinforcing (extending) filler and a resistance control agent, and melt-kneading with a roll mill or the like. Further, the silicone rubber roller for electrophotography of the present invention is preferably in the form of a flexible sponge in order to increase the contact area with the photoconductor and stabilize the charging characteristics. Therefore, the molding material should be primary crosslinked or secondary crosslinked. A foaming agent that foams when heated may be added. The amount of these additives to be added may be similar to the conventional amount.

As the silicone raw rubber as the base polymer, various known series such as dimethyl silicone type, methyl vinyl silicone type, methyl phenyl vinyl silicone type and fluorosilicone type can be used. The total concentration of the low-polymerization degree siloxane and the non-functional silicone oil contained in the silicone rubber compound is limited to 5000 ppm or less as described above. If the total concentration of both exceeds 5000 ppm, both substances cannot be completely removed only by vacuum heat treatment after molding, and the problem of contamination of the photoconductor does not occur immediately after the start of use of the roller, but inside the roller The remaining low-polymerization degree siloxane or non-functional silicone oil gradually bleeds on the surface to contaminate the photoconductor, and the removal effect is lost.

In order to adjust the total concentration of both components contained in the silicone rubber-based compound to 5000 ppm or less, a method of vacuum treating the silicone raw rubber to forcibly remove both components can be mentioned. However, as mentioned above, some of the commercially available silicone rubber compounds have already been adjusted so that the total concentration of both components is within the above range, so using it as it is is in terms of productivity and cost. desirable. Examples of commercially available silicone rubber-based compounds in which the total concentration of the low-polymerization degree siloxane and the non-functional silicone oil has been adjusted within the above range include, for example, Shin-Etsu Chemical Co., Ltd.'s product number X-30-1807U (conductive silicone compound) and X. -30-1807M (insulating silicone compound) and the like.

As the crosslinking agent, for example, an organic peroxide type crosslinking agent can be used. Examples of such organic peroxide-based cross-linking agents include benzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, p-monochlorobenzoyl peroxide,
2,5-dimethyl-2,5-bis- (tert-butylperoxy) hexane, tert-butylcumyl peroxide and the like can be mentioned. Further, a fatty acid azo compound, sulfur or the like can be used as a crosslinking agent.

As the extender filler, a reinforcing filler, an inorganic filler such as calcium carbonate, hard clay, barium sulfate, talc, mica, asbestos, graphite, recycled rubber, powder rubber, asphalt, styrene resin, glue, etc. The organic filler can be mentioned. In order to manufacture a silicone rubber roller for electrophotography from a molding material containing each of the above components, the manufacturing method of the present invention is employed in which the molding material is crosslinked and molded into a roller shape, and then vacuum heat treatment is performed.

In order to crosslink and mold the molding material into a roller shape, a molding method similar to the conventional one is adopted. For example, in the case of a millable type molding material, primary cross-linking is performed at the same time as molding by a molding method such as compression molding, injection molding, transfer molding, or a roller shape is formed by a method such as calendar roll molding or extrusion molding. After performing primary cross-linking by a conventionally known cross-linking method such as (normal pressure hot air vulcanization) method, secondary cross-linking may be performed using a hot air dryer or the like. Further, the vacuum heat treatment described below can be used instead of the secondary crosslinking.

An apparatus such as a vacuum oven is used to vacuum heat the formed roller. The conditions of the vacuum heat treatment are not particularly limited, but the ultimate vacuum of 5
mmHg or less, heating temperature 150 to 250 ° C., processing time 3
It is preferably about 25 hours. The ultimate vacuum is significantly higher than 5 mmHg, the heating temperature is lower than 150 ° C,
Alternatively, if the treatment time is significantly shorter than 3 hours, the low-polymerization degree siloxane and the nonfunctional silicone oil may not be sufficiently removed. The heating temperature is 2
If the temperature is much higher than 50 ° C. or if the treatment time is longer than 25 hours, not only energy is wasted but also the roller may be deteriorated or deteriorated.

The heating temperature is optimally measured directly, but if it cannot be measured directly, it can be substituted by, for example, the temperature of the furnace wall of the furnace used for the treatment. By this vacuum heat treatment, the low-polymerization degree siloxane and the non-functional silicone oil are almost completely removed, and the silicone rubber roller for electrophotography of the present invention which does not contaminate the photoreceptor is completed.

In the present invention, the molded roller may be subjected to solvent extraction treatment either before or after the above vacuum heating treatment. When solvent extraction treatment is performed, it is possible to reliably remove relatively large molecular weight non-functional silicone and low polymerization degree siloxane, which may not be completely removed by vacuum heat treatment alone. It can be further reduced.

As the solvent, various solvents capable of dissolving low-polymerization degree siloxane and non-functional silicone can be used,
Particularly preferred are acetone, hexane, ethyl acetate, toluene and the like. The electrophotographic silicone rubber roller of the present invention produced by the above-described production method of the present invention has a low photopolymerization siloxane and a non-functional silicone oil which are almost completely removed by vacuum heat treatment and hardly remain. Even if it is placed in contact with the surface, there is no risk of contaminating the photoconductor for a long period of time, not to mention immediately after the start of use. Therefore, the silicone rubber roller for electrophotography according to the present invention is formed on the surface of the photoconductor and the charging roller for uniformly charging the surface of the photoconductor in an image forming apparatus such as an electrostatic copying machine or a laser beam printer. As a roller for contact charging such as a transfer roller for transferring a toner image to a transfer target such as paper and a charge eliminating roller for removing residual charges on the surface of the photoconductor, which is arranged in contact with the surface of the photoconductor It can be used preferably.

When the silicone rubber roller for electrophotography of the present invention is used as the roller for contact charging, the resistance value thereof is preferably 10 ³ to 10 ¹⁰ Ω. When the resistance value is less than 10 ³ Ω, when used as a charging roller, for example, what is once charged may be absorbed by the roller, and it may not be possible to charge the photoconductor to a predetermined charge. The resistance value is 10 ¹⁰ Ω
If it exceeds, the applied voltage for charging the photoconductor to a predetermined electric charge becomes high, and a higher voltage power source is required, which may lead to an increase in size of the apparatus.

In order to keep the resistance value of the electrophotographic silicone rubber roller within the above range, a conductive silicone rubber compound and an insulative silicone rubber compound are used together, and the compounding ratio thereof is appropriately adjusted. It suffices to adjust the added amount of the resistance adjusting agent as an additive. The silicone rubber roller for electrophotography of the present invention is preferably in the form of a flexible sponge in order to increase the contact area with the photoconductor and stabilize the charging characteristics, as described above.

Although the silicone rubber roller for electrophotography of the present invention does not directly contact the surface of the photoconductor other than the contact charging roller, the components in the roller are transferred to the photoconductor using paper as a medium. It can also be applied to a paper feed roller, a conveyance roller, etc. that may cause contamination of the photoconductor. As described above, according to the present invention, a low-polymerization degree siloxane or a non-functionalized siloxane or a non-functionalized silicone rubber-based compound is used, which is obtained by removing a low-polymerization degree siloxane or a non-functionalized silicone oil to some extent Since the silicone oil is almost completely removed, it is possible to manufacture a silicone rubber roller for electrophotography which is not likely to contaminate the photoreceptor not only immediately after the start of use but also for a long period thereafter. Therefore, according to the present invention, it is possible to put a contact charging type image forming apparatus into practical use, which does not cause air pollution or deterioration of a photoreceptor due to generation of a large amount of ozone.

[0029]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples. Example 1 A conductive silicone rubber-based compound (product number X- manufactured by Shin-Etsu Chemical Co., Ltd., in which the total concentration of low-polymerization degree siloxane and nonfunctional silicone oil was adjusted to 5000 ppm or less.
30-1807 U) 60 parts by weight, and an insulating silicone rubber compound (Shin-Etsu Chemical Co., Ltd. product number X-3) in which the total concentration of both components is adjusted to 5000 ppm or less.
0-1807M) 40 parts by weight was mixed with the following additives and melt-kneaded by a roll mill to prepare a millable molding material.

Additives Amount to be added Foaming agent: Shin-Etsu Chemical Co., Ltd. product number X-30-1847U 5 phr Crosslinking agent: Shin-Etsu Chemical Co., product number X-30-1848U 2.5 phr Shin-Etsu Chemical product No. X-30-1849U 2.0 phr Catalyst: product number PL-2 0.03 phr manufactured by Shin-Etsu Chemical Co., Ltd. Catalyst control agent: product number X-30-253 0.03 phr manufactured by Shin-Etsu Chemical Co., Ltd. Then, the above molding material was extruded into a roller shape. , H
A roller was formed by primary crosslinking under the conditions of 200 ° C. and 30 minutes by the AV method.

Then, using a vacuum oven (vacuum constant temperature dryer, DP61 type manufactured by Yamato Scientific Co., Ltd.),
A vacuum heat treatment was performed together with secondary crosslinking for 6 hours under the conditions of ultimate vacuum of 2 mmHg and furnace wall temperature of 240 ° C. to produce a silicone rubber roller for electrophotography. Examples 2 to 6 A roller obtained by primary crosslinking and molding from the same molding material as in Example 1 under the same molding conditions as in Example 1 was subjected to HAV using an atmospheric pressure constant temperature dryer (DNF64 type manufactured by Yamato Scientific Co., Ltd.). After secondary cross-linking by the method at 200 ° C. for 4 hours, the same vacuum oven as described above was subjected to vacuum heat treatment under the conditions shown in Table 1 to produce a silicone rubber roller for electrophotography.

[0032]

[Table 1]

Comparative Example 1 60 parts by weight of a conductive silicone rubber compound (product number X-30-289U manufactured by Shin-Etsu Chemical Co., Ltd.) in which the total concentration of the low-polymerization degree siloxane and the nonfunctional silicone oil is not adjusted to 5000 ppm or less. Similarly, 40 parts by weight of an insulating silicone rubber compound (product number KE-1551U manufactured by Shin-Etsu Chemical Co., Ltd.) in which the total concentration of both components is not adjusted to 5000 ppm or less is mixed with the following additives, and a roll mill is used. The mixture was melt-kneaded to prepare a millable molding material.

Additives Addition amount Blowing agent: Shin-Etsu Chemical Co., Ltd. product number KEP-13 5 phr Crosslinking agent: Shin-Etsu Chemical Co., Ltd. product number C-3M 2.5 phr Shin-Etsu Chemical Co., Ltd. product number HC-101 2.0 phr Catalyst: Product number PL-2 0.03 phr manufactured by Shin-Etsu Chemical Co., Ltd. Catalyst control agent: Product number X-30-253 0.03 phr manufactured by Shin-Etsu Chemical Co., Ltd. Then, using the above-mentioned molding material, primary crosslinking is carried out under the same molding conditions as in Example 1. The molded roller and the molded roller are not subjected to the vacuum heat treatment, and the atmospheric pressure and constant temperature dryer (Yamato Scientific Co., Ltd. DNF64
Type) under normal pressure by the HAV method at 200 ° C. for 4 hours to carry out secondary cross-linking to produce a silicone rubber roller for electrophotography.

Comparative Example 2 Using the same molding material as in Comparative Example 1, a roller obtained by primary cross-linking and molding under the same molding conditions as in Example 1 was vacuum-treated with secondary cross-linking under the same vacuum heat treatment conditions as in Example 1. Heat treatment was performed to produce a silicone rubber roller for electrophotography. Comparative Example 3 A roller obtained by using the same molding material as in Example 1 and subjected to primary cross-linking and molding under the same molding conditions as in Comparative Example 1 above was subjected to the same conditions as in Comparative Example 1 under normal pressure without vacuum heat treatment. Secondary cross-linking was performed to produce a silicone rubber roller for electrophotography.

Comparative Example 4 A silicone rubber roller for electrophotography was manufactured in the same manner as in Comparative Example 3 except that the condition of secondary crosslinking under atmospheric pressure was 250 ° C. for 4 hours. Comparative Example 5 A roller obtained by primary crosslinking and molding from the same molding material as in Example 1 under the same molding conditions as in Example 1 was subjected to 10% by using trichloroethane heated to 80 ° C. without vacuum heat treatment.
After washing for a minute, a silicone rubber roller for electrophotography was manufactured.

Comparative Examples 6 to 10 Rollers primary-crosslinked and molded from the same molding material as in Example 1 under the same molding conditions as in Example 1 were immersed in the solvent shown in Table 2 without being subjected to vacuum heat treatment. Extraction treatment was carried out at room temperature for 76 hours to produce a silicone rubber roller for electrophotography.

[0038]

[Table 2]

The electrophotographic silicone rubber roller of each of the above Examples and Comparative Examples was pressure-bonded to the photoconductor of a laser beam printer (Laser Shot Printer A404 manufactured by Canon Inc.), and the environmental temperature was 23.5 ° C. and the environmental humidity was 55%. RH
After being left for 72 hours under the conditions of No. 5, five black solid test charts were continuously drawn. Next, in this test chart, a test area of 5 mm square was set on a portion of the surface of the photoconductor corresponding to the portion where the roller was pressure-bonded, and the luminance of the portion was set to the image processing device [pierce ( PIAS
Personal Image Analysis System LA-5
55], and a brightness of 0 (black) to 255 (white)
It was classified into 56 stages. Then, the photoconductor contamination was evaluated based on the following evaluation criteria. ◯: Brightness average value 0 to 62 (without touch memory) Δ: Brightness average value 63 to 68 (slightly with touch memory) ×: Brightness average value 69 to 255 (obviously with touch memory) The results are shown in Table 3.

[0040]

[Table 3]

As shown in Table 3, Comparative Examples 1, 3 and 4 which were not subjected to the vacuum heat treatment and only were subjected to secondary crosslinking at atmospheric pressure, Comparative Examples 5 which were not subjected to the vacuum heat treatment and were just washed with a solvent, and Comparative Examples 6, 8 which were subjected to solvent extraction treatment without vacuum heat treatment
Rolls 9 and 10 all resulted in contamination of the photoreceptor, regardless of the total concentration of low degree of polymerization siloxane and nonfunctional silicone oil in the raw silicone rubber. In Comparative Example 7 in which hexane was used as the solvent among the Comparative Examples in which only the solvent extraction treatment was performed without performing the vacuum heat treatment, the photoreceptor was not contaminated so much, but it took 76 hours for the treatment to be practical. It was confirmed that it was not.

On the other hand, a molding material containing a silicone rubber compound in which the total concentration of the low-polymerization degree siloxane and the nonfunctional silicone oil was adjusted to 5000 ppm or less was used, and the roller after molding was subjected to vacuum heat treatment. All of the rollers of Examples 1 to 6 did not cause contamination of the photoconductor regardless of the conditions of the vacuum heat treatment and the presence or absence of secondary crosslinking at normal pressure.

Further, Example 3 (vacuum heat treatment), Comparative Example 1
With respect to the rollers of (normal pressure heating treatment) and Comparative Example 4 (solvent extraction treatment), the concentration of low-polymerization degree siloxane having a degree of polymerization of 4 to 25 was measured by a gas chromatography method. As shown in FIG. It was confirmed that the roller of Example 3 had a significantly lower concentration of low-polymerization degree siloxane than the rollers of Nos. 1 and 4.

From the above results, it was found that it is most effective to subject the formed roller to vacuum heating treatment in order to prevent the contamination of the photoreceptor. The roller of Comparative Example 2 in which a molding material containing a silicone rubber-based compound in which the total concentration of the low-polymerization degree siloxane and the non-functional silicone oil was not adjusted to 5000 ppm or less was used, and the roller after molding was subjected to vacuum heat treatment was As in Examples 1 to 6, the photoconductor did not stain. Then, the roller of Comparative Example 2 was left for 18 days together with the rollers of Examples 2, 3 and 4 and the same test was conducted again. As shown in Table 4, the rollers of Examples 2, 3 and 4 were obtained. Did not stain the photoconductor, but the roller of Comparative Example 2 did stain the photoconductor.

[0045]

[Table 4]

On the roller surface of Comparative Example 2 described above, the concentration of the low-polymerization degree siloxane having a polymerization degree of 4 to 25 was measured by the gas chromatography method immediately after the production and 26 days later, and as shown in FIG. It was confirmed that the concentration of the low-polymerization degree siloxane increased with the passage of time. From the above results, the total concentration of both substances is 5000
When a molding material containing a silicone rubber compound that is not adjusted to ppm or less is used, both substances cannot be completely removed only by vacuum heat treatment, and the low polymerization degree siloxane and non-functional silicone remaining inside the roller It was found that the oil gradually bleeded to the surface and the removal effect was lost.

The total concentration of both substances is 5000 p
It was confirmed that the photoreceptor can be prevented from being contaminated for a long period of time only by using a molding material containing a silicone rubber compound adjusted to pm or less and subjecting it to a vacuum heat treatment. Examples 7 and 8 and Comparative Examples 11 to 15 Rollers that were primary crosslinked and molded from the same molding material as in Example 1 under the same molding conditions as in Example 1 were dried under atmospheric pressure and constant temperature dryer (Yamato Scientific Co. DNF64 type). 2) by the HAV method at 200 ° C. for 4 hours, and then subjected to vacuum heat treatment under the conditions shown in Table 5 using the same vacuum oven as described above to obtain a silicone rubber roller for electrophotography. Manufactured.

[0048]

[Table 5]

With respect to the electrophotographic silicone rubber rollers of the above Examples and Comparative Examples, the presence or absence of the touch memory of the formed image was observed in the same manner as described above, and the contamination of the photoconductor was evaluated based on the above evaluation criteria. In Comparative Example 13, the roller was deformed during the vacuum heat treatment, and the contamination of the photoconductor could not be evaluated. The results are shown in Table 6.

[0050]

[Table 6]

Comparing the results of Example 7 and Comparative Example 11 in Table 6 above, and Example 3 in Table 3 above, Examples 3 and 7 in which the ultimate vacuum during vacuum heat treatment was 5 mmHg or less.
In each case, the contamination of the photoconductor is less than that of Comparative Example 11 in which the ultimate vacuum degree is 10 mmHg. From this, it was found that the ultimate vacuum degree during the vacuum heat treatment is preferably 5 mmHg or less. When the results of Example 3 and Example 7 are compared, the ultimate vacuum degree is 2 mm from Example 7 in which the ultimate vacuum degree is 5 mmHg.
It was also found that in Example 3 in which Hg was used, the photoreceptor was less contaminated, and thus, the ultimate vacuum degree was preferably as low as possible even within the above range.

Comparing the results of Example 8 with Comparative Examples 12 and 13 and Examples 3 and 5 in Table 3 above, Examples 3 and 5 in which the temperature during the vacuum heat treatment was 150 ° C. or higher.
In all of Examples 8 and 9, the photoreceptor was less contaminated as compared with Comparative Example 12 in which the temperature was 100 ° C., and thus it was found that the temperature during the vacuum heat treatment is preferably 150 ° C. or higher. Further, in Comparative Example 13 in which the temperature during the vacuum heat treatment was 300 ° C., the roller was deformed, which indicates that the temperature during the vacuum heat treatment is preferably 250 ° C. or lower. Comparing the results of Examples 3, 5 and 8, the higher the processing temperature is, the less the contamination of the photoconductor is. Therefore, the processing temperature is
It was also found that the higher the ratio is within the above range, the more preferable.

Further comparing the results of Comparative Examples 14 and 15 with the results of Examples 3, 4 and 5 in Table 3 above, Examples 3, 4, and 5 in which the vacuum heat treatment time is within the range of 3 to 25 hours. Compared with Comparative Example 14 in which the treatment time was 1 hour and Comparative Example 15 in which the treatment time was 30 hours, the contamination of the photoconductor was less, and thus the vacuum heat treatment time was in the range of 3 to 25 hours. It turned out that the inside is preferable.

Example 9 The electrophotographic silicone rubber roller produced in Example 2 was immersed in hexane and subjected to extraction treatment at room temperature for 3 hours. With respect to the electrophotographic silicone rubber roller after the treatment, the presence or absence of the touch memory of the formed image was observed in the same manner as described above, and the contamination property of the photoconductor was evaluated based on the evaluation criteria. The results are shown in Table 7 together with the results of Example 2.

[0055]

[Table 7]

From the results shown in Table 7 above, it was found that the contamination of the photoreceptor can be further reduced by using the vacuum heating treatment and the solvent extraction treatment together.

[0057]

As described above, according to the present invention, a grade of silicone rubber-based compound in which low-polymerization degree siloxane and nonfunctional silicone oil are removed to some extent is used,
After molding, it is vacuum heat treated to almost completely remove low-polymerization siloxane and non-functional silicone oil, so it may stain the photoreceptor not only immediately after the start of use but also for a long time thereafter. It is possible to manufacture a silicone rubber roller for electrophotography which does not have any material. Therefore, according to the present invention, it is possible to put a contact charging type image forming apparatus into practical use, which does not cause air pollution or deterioration of a photoreceptor due to generation of a large amount of ozone.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the concentration of low-polymerization degree siloxane having a degree of polymerization of 4 to 25 and the method for treating a roller.

FIG. 2 is a graph showing changes over time in the concentration of low-polymerization siloxane in the roller of Comparative Example 2.

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Claims (9)

[Claims] 1. A molding compound comprising a rubber compound containing silicone raw rubber as a base polymer, wherein the total concentration of low-polymerization degree siloxane and non-functional silicone oil in the rubber compound is 5000 ppm or less is cross-linked and molded into a roller shape. The silicone rubber roller for electrophotography is characterized in that it is vacuum heat treated after molding. 2. The silicone rubber roller for electrophotography according to claim 1, which has been subjected to solvent extraction treatment after molding, either before or after vacuum heat treatment. 3. The silicone rubber roller for electrophotography according to claim 1, which is in the form of a flexible sponge. 4. A molding material containing a rubber compound containing silicone raw rubber as a base polymer, wherein the total concentration of the low-polymerization degree siloxane and the non-functional silicone oil in the rubber compound is 5000 ppm or less is cross-linked and molded into a roller shape. Then, a method for producing a silicone rubber roller for electrophotography, which is characterized by subjecting to vacuum heat treatment. 5. The method for producing a silicone rubber roller for electrophotography according to claim 4, wherein the ultimate vacuum during vacuum heat treatment is 5 mmHg or less. 6. The heating temperature during vacuum heat treatment is 150 to 25.
The method for producing a silicone rubber roller for electrophotography according to claim 4, wherein the temperature is 0 ° C. 7. The silicone rubber roller for electrophotography according to claim 4, wherein the vacuum heat treatment time is 3 to 25 hours. 8. The method for producing a silicone rubber roller for electrophotography according to claim 4, wherein after the molding, a solvent extraction treatment is carried out either before or after the vacuum heat treatment. 9. The method for producing a silicone rubber roller for electrophotography according to claim 4, wherein the roller is foam-molded into a flexible sponge by blending a molding material with a foaming agent which is foamed by heat during crosslinking and molding.