Silicone rubber composition

Abstract

To provide a liquid silicone rubber composition which allows for producing a cured product which offers high heat conductivity, low heat capacity and superior smoothness.SOLUTION: A liquid silicone rubber composition contains metal silicon particles, where the content of the metal silicon particles is in a range of 35 to 45 vol.%, inclusive, a volume-average particle diameter of the metal silicon particles is in a range of 1 to 20 μm, inclusive, and a ratio A / B of a viscosity A at a shear rate of 0.02 / sec and a viscosity B at a shear rate of 1 / sec is 2.0 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a liquid silicone rubber composition for a fixing member used in a thermal fixing device of an electrophotographic image forming apparatus. [Background technology]

[0002] In a thermal fixing device of an electrophotographic image forming apparatus, a pressure contact section is composed of a heating member and a pressure member disposed opposite the heating member. When a recording material carrying an unfixed toner image is introduced into this pressure contact section, the unfixed toner is heated and pressurized, the toner is melted, and the image is fixed to the recording material. The heating member is a member that comes into contact with the unfixed toner image on the recording material, and the pressure member is a member disposed opposite the heating member. Electrophotographic members such as the heating member and pressure member may have a rotatable shape such as a roller or an endless belt. The electrophotographic member may have an elastic layer containing, for example, rubber such as cross-linked silicone rubber and thermally conductive particles on a substrate formed of metal or heat-resistant resin.

[0003] In recent years, with the trend toward higher printing speeds and shorter start-up times, elastic layers are required to have high thermal conductivity and low heat capacity. Patent Document 1 discloses a silicone rubber composition containing metal silicon powder, a fixing roll, and a fixing belt as elastic layers with high thermal conductivity and low heat capacity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-171946 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a large amount of metal silicon particles is added to a silicone rubber composition in order to obtain an elastic layer with even higher thermal conductivity, the viscosity of the silicone rubber composition increases, and the surface smoothness of a molded article formed using the silicone rubber composition may decrease. In particular, when a method for producing the molded article includes a step of leveling the surface of a coating film of the silicone rubber composition, the surface smoothness of the molded article is particularly likely to decrease. One aspect of the present disclosure is to provide a liquid silicone rubber composition that can be used to produce components with high thermal conductivity, low heat capacity, and excellent surface smoothness, and a method for producing the same. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, there is provided a liquid silicone rubber composition containing metal silicon particles, wherein the content of the metal silicon particles is 35% by volume or more and 45% by volume or less, The volume average particle size of the metal silicon particles is 1 μm or more and 20 μm or less, The ratio (A / B) of the viscosity A of the composition at a shear rate of 0.02 / sec to the viscosity B at a shear rate of 1 / sec is 2.0 or less. The liquid silicone rubber composition is provided as follows:

[0007] According to another aspect of the present disclosure, there is provided a liquid silicone rubber composition containing metal silicon particles, wherein the mass loss rate of the metal silicon particles is 0.3% or more as measured by the following method. A 0.5g sample was taken from the liquid silicone rubber composition, mixed with 9ml of toluene at 25°C, and centrifuged at 10,000 rpm for 5 minutes. The resulting precipitate was then filtered and washed under reduced pressure three times with 10ml of toluene at 25°C. The metal silicon particles extracted from the sample were subjected to thermogravimetric analysis to measure the mass loss (%) at temperatures between 300 and 500°C.

[0008] Furthermore, according to yet another aspect of the present disclosure, there is provided a method for producing the above-mentioned liquid silicone rubber composition, which comprises the steps of mixing a silicone component containing an organopolysiloxane with metal silicon powder, and allowing the resulting mixture to stand for 30 days or more. Furthermore, according to yet another aspect of the present disclosure, there is provided a method for producing the above-mentioned liquid silicone rubber composition, comprising the steps of mixing a silicone component containing an organopolysiloxane and a metal silicon powder using a planetary mixer at an orbital speed of 5 to 15 rpm for a mixing time of 100 to 300 minutes, and allowing the resulting mixture to stand for four days or more. [Effects of the Invention]

[0009] According to one aspect of the present disclosure, there is provided a silicone rubber composition that can form a member that has high thermal conductivity, low heat capacity, and excellent smoothness. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a graph showing the relationship between shear rate and viscosity of liquid silicone rubber compositions, where (a) is a graph for a composition highly filled with metal silicon particles, (b) is a graph for a composition with reduced viscosity of the silicone polymer, and (c) is a graph for a composition according to one embodiment of the present disclosure. [Figure 2] 1A and 1B are schematic cross-sectional views of fixing members according to two embodiments of the present disclosure, in which (a) is a schematic cross-sectional view of a belt-shaped fixing member, and (b) is a schematic cross-sectional view of a roller-shaped fixing member. [Figure 3] FIG. 10 is a schematic diagram illustrating an example of a step of laminating a surface layer. [Figure 4] FIG. 1 is a cross-sectional view of an example of a heat fixing device using a heating belt and a pressure belt. [Figure 5] FIG. 1 is a cross-sectional view of an example of a heat fixing device using a heating belt and a pressure roller. DETAILED DESCRIPTION OF THE INVENTION

[0011] In this specification, the expressions "XX or more and YY or less" and "XX to YY" indicating a numerical range mean a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified. Furthermore, when a numerical range is described in stages, any combination of the upper and lower limits of each numerical range is disclosed. The electrophotographic member according to the present disclosure includes a heating member and a pressure member.

[0012] When a liquid silicone rubber composition contains a large amount of metal silicon particles, the viscosity of the liquid silicone rubber composition becomes shear rate dependent (see graph (a) in Figure 1). In particular, liquid silicone rubber compositions containing a large amount of metal silicon particles have a high viscosity A in the low shear rate range of 0.1 / sec or less, which is said to contribute to the leveling properties of the coating surface. As a result, the smoothness of the coating film decreases. On the other hand, if the viscosity of the liquid silicone rubber composition is reduced overall by lowering the viscosity of the liquid silicone polymer (see graph (b) in Figure 1), the viscosity B in the high shear rate range of 1 / sec or more, which is related to the coatability of the liquid silicone rubber composition, also decreases. As a result, sagging occurs when applying a coating of the liquid silicone rubber composition, making it difficult to form a coating with a smooth surface. According to the investigations of the present inventors, it has been found that the above-mentioned object can be achieved by reducing only the viscosity A in the low shear rate range without reducing the viscosity B in the high shear rate range (see the graph in Figure 1(c)).

[0013] A liquid silicone rubber composition according to one embodiment of the present disclosure includes metal silicon particles, The content of the metal silicon particles is 35% by volume or more and 45% by volume or less, The volume average particle size of the metal silicon particles is 1 μm or more and 20 μm or less, The ratio A / B of the viscosity A of the composition at a shear rate of 0.02 / sec to the viscosity B at a shear rate of 1 / sec is 2.0 or less.

[0014] The liquid silicone rubber composition according to one embodiment of the present disclosure will be described in detail below based on specific configurations.

[0015] The liquid silicone rubber composition typically contains the following components (a) to (d): Component (a): organopolysiloxane having an unsaturated aliphatic group; Component (b): an organopolysiloxane having silicon-bonded active hydrogen; Component (c): catalyst; Component (d): Metal silicon particles. Each component will be explained below. Components (a) to (d) are sometimes referred to as liquid silicone components.

[0016] Component (a) The organopolysiloxane having an unsaturated aliphatic group is an organopolysiloxane having an unsaturated aliphatic group such as a vinyl group, and examples thereof include those shown in the following structural formulas (1) and (2).

[0017] [ka]

[0018] In structural formula (1), m 1 indicates an integer of 0 or greater, and n 1 represents an integer of 3 or more. In addition, in the structural formula (1), R 1 each independently represents a monovalent unsubstituted or substituted hydrocarbon group that does not contain an unsaturated aliphatic group, provided that R 1 At least one of R represents a methyl group. 2 each independently represents an unsaturated aliphatic group.

[0019] [ka]

[0020] In structural formula (2), n 2 denotes a positive integer, and R 3each independently represents a monovalent unsubstituted or substituted hydrocarbon group that does not contain an unsaturated aliphatic group, provided that R 3 At least one of R represents a methyl group. 4 each independently represents an unsaturated aliphatic group.

[0021] In structural formula (1) and structural formula (2), R 1 and R 3 Examples of the monovalent unsubstituted hydrocarbon group containing no unsaturated aliphatic group and the substituted hydrocarbon group that can be represented by the formula (I) include the following groups. Unsubstituted hydrocarbon groups Alkyl groups (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl). Aryl groups (for example, phenyl groups). Substituted hydrocarbon groups Substituted alkyl groups (for example, chloromethyl, 3-chloropropyl, 3,3,3-trifluoropropyl, 3-cyanopropyl, 3-methoxypropyl).

[0022] The organopolysiloxanes represented by structural formula (1) and structural formula (2) usually have at least one methyl group directly bonded to the silicon atom forming the chain structure. However, for ease of synthesis and handling, R 1 and R 3 Preferably, 50% or more of each group is a methyl group, and all of the R 1 and R 3 is more preferably a methyl group.

[0023] In addition, in the structural formula (1) and the structural formula (2), R 2 and R 4 Examples of unsaturated aliphatic groups that can be represented by include the following groups. That is, examples of unsaturated aliphatic groups include vinyl groups, allyl groups, 3-butenyl groups, 4-pentenyl groups, and 5-hexenyl groups. Among these groups, R 2 and R 4is preferably a vinyl group.

[0024] From the viewpoint of moldability, the viscosity of component (a) is 1000mm 2 / s or more 50000mm 2 / s or less is preferable. 2 / s or more, it is easy to adjust the hardness required for the elastic layer, and 2 / s or less, the viscosity of the composition is such that it is easy to apply. The viscosity (kinematic viscosity) can be measured using a capillary viscometer, a rotational viscometer, or the like in accordance with JIS Z 8803:2011.

[0025] The blending amount of component (a) is preferably 55% by volume or more from the viewpoint of durability and 65% by volume or less from the viewpoint of heat conductivity, based on the liquid silicone rubber composition according to the present disclosure. That is, 55% by volume or more and 65% by volume or less are preferred.

[0026] Ingredient (b) The organopolysiloxane, which has active hydrogen bonded to silicon (Si-H bond), functions as a crosslinker that reacts with the unsaturated aliphatic groups of component (a) under the action of a catalyst to form a cured silicone rubber. Any organopolysiloxane having a Si-H bond can be used as component (b). In particular, from the viewpoint of reactivity with the unsaturated aliphatic group of component (a), those having an average of three or more hydrogen atoms bonded to silicon atoms (Si-H bonds) per molecule are preferably used.

[0027] Specific examples of component (b) include the linear organopolysiloxane shown in the following structural formula (3) and the cyclic organopolysiloxane shown in the following structural formula (4).

[0028] [ka]

[0029] In structural formula (3), m2 indicates an integer of 0 or greater, and n 3 represents an integer of 3 or more, and R 5 each independently represents a monovalent unsubstituted or substituted hydrocarbon group that does not contain an unsaturated aliphatic group.

[0030] [ka]

[0031] In structural formula (4), m 3 indicates an integer of 0 or greater, and n 4 represents an integer of 3 or more, and R 6 each independently represents a monovalent unsubstituted or substituted hydrocarbon group that does not contain an unsaturated aliphatic group.

[0032] R in structural formula (3) and structural formula (4) 5 and R 6 Examples of the monovalent unsubstituted or substituted hydrocarbon group not containing an unsaturated aliphatic group that can be represented by R 1 Among these, R 5 and R 6 Preferably, 50% or more of each group is a methyl group, and all of the R 5 and R 6 is more preferably a methyl group.

[0033] Ingredient (c) Examples of catalysts used in forming silicone rubber include hydrosilylation catalysts for accelerating the curing reaction. Known substances such as platinum compounds and rhodium compounds can be used as the hydrosilylation catalyst. The amount of catalyst used can be appropriately determined and is not particularly limited.

[0034] Ingredient (d) Metallic silicon particles have a heat capacity per unit volume of approximately 1.7 MJ / m 3·K, which is the heat capacity per unit volume of alumina, which is often used to improve the thermal properties of components formed using silicone rubber compositions, is approximately 3.0 MJ / m 3 ·K. The thermal conductivity of metallic silicon is high, at around 150 W / m·K.

[0035] The metal silicon particles have a volume average particle size ranging from 1 μm to 20 μm. By setting the volume average particle size of the metal silicon particles within this range, it is possible to incorporate more metal silicon particles into the liquid silicone rubber composition and to suppress the influence of the metal silicon particles on the surface smoothness of the film formed from the liquid silicone rubber composition. The volume average particle size of the metal silicon particles can be determined, for example, using a laser diffraction / scattering particle size distribution analyzer.

[0036] The metal silicon particles may be surface-treated to improve the thermal stability, compoundability, and durability of the silicone rubber composition. Specifically, they may be treated with a silane coupling agent, hexamethyldisilazane, or a silicone oligomer, or may be subjected to thermal oxidation or oxidation by washing with water to form a surface oxide film.

[0037] The content of the metal silicon particles is 35% by volume or more and 45% by volume or less of the volume of the liquid silicone rubber composition according to the present disclosure. If it is 35% by volume or more, the component obtained by curing the liquid silicone rubber composition is expected to have high thermal conductivity, and if it is 45% by volume or less, the component will have sufficient hardness and strength. The content of the metal silicon particles can be adjusted by the charge ratio (volume basis) when preparing the liquid silicone rubber composition, and is adjusted by the volume ratio of the silicone component excluding volatile components such as solvents to the metal silicon powder. The following method can be used to confirm the content of metal silicon particles in a part (cured product) made using the liquid silicone rubber composition according to the present disclosure.

[0038] The content of cured silicone rubber and metal silicon particles in a component can be confirmed using a thermogravimetric analyzer (TGA) (e.g., TGA / DSC 3+, manufactured by Mettler Toledo). The component is cut with a razor or similar tool, and a 20 mg sample, for example, is placed in an alumina pan used in the thermogravimetric analyzer. The alumina pan containing the sample is placed in the analyzer and heated in a nitrogen atmosphere from room temperature to 800°C at a rate of 20°C per minute, and then maintained at 800°C for one hour. By comparing the weights before and after the measurement, the weight-based content of the cured silicone rubber component and metal silicon particles contained in the component can be determined. Furthermore, the volume-based content of metal silicon particles in the component can be calculated by dividing the mass-based content of metal silicon particles by the specific gravity of the metal silicon, and by dividing the mass-based content of the cured silicone rubber by the specific gravity of the silicone rubber.

[0039] The content of metal silicon particles can also be confirmed by subjecting a cross section of the elastic layer to energy dispersive X-ray analysis (EDS) (for example, trade name: X-MAXN80, manufactured by OXFORD) and converting the obtained area ratio to a volume ratio.

[0040] The liquid silicone rubber composition according to the present disclosure has a ratio A / B of 2.0 or less, where A is the viscosity at a shear rate of 0.02 / sec and B is the viscosity at a shear rate of 1 / sec. When the ratio A / B is 2.0 or less, the liquid silicone rubber composition has excellent smoothness and coatability. The ratio A / B is preferably 1.8 or less, and more preferably 1.6 or less. Viscosity A is preferably in the range of 50 Pa·sec or more and 1000 Pa·sec or less, and viscosity B is preferably in the range of 50 Pa·sec or more and 600 Pa·sec or less. The viscosities A and B of the liquid silicone rubber composition according to the present disclosure can be measured using a rotational viscometer or a rheometer. In the examples described later in this disclosure, a rheometer (trade name: DHR-2; manufactured by TA Instruments) was used. The shear rate was measured at 10 decimal points between 0.01 / sec and 10 / sec, with a gap distance of 1 mm, a measurement temperature of 25°C, a pressure of 0.1 / sec for 10 seconds, and a waiting time of 5 seconds. The shear rate was measured at 10 points per decade, with an equilibration time of 3 seconds and a data acquisition time of 3 seconds. From the obtained relationship between shear rate and viscosity, the viscosity A at 0.02 / sec and the viscosity B at 1 / sec were read, and the ratio (A / B) was calculated.

[0041] In addition to the above components, the liquid silicone rubber composition according to the present disclosure may optionally contain reinforcing fillers such as fumed silica, precipitated silica, fused silica, spherical silica prepared by the sol-gel method, and crystalline silica. Furthermore, the liquid silicone rubber composition according to the present disclosure may also contain heat resistance improvers such as iron oxide and cerium oxide, and reaction inhibitors such as nitrogen compounds and acetylene compounds. These optional components may be added as desired within a range that does not impair the effects of the present invention.

[0042] As shown in Figure 1, the liquid silicone rubber composition according to the present disclosure has a high content of metal silicon particles, i.e., is highly loaded with metal silicon particles, yet has low shear rate dependency. That is, even if the viscosity B in the high shear rate range is relatively high, the viscosity A in the low shear rate range can be kept low. Therefore, the liquid silicone rubber composition suppresses the occurrence of sagging when forming a coating film. In addition, the resulting coating film has excellent surface leveling properties. As a result, the liquid silicone rubber composition according to the present disclosure can provide molded products with excellent surface smoothness. The reason why the liquid silicone rubber composition according to the present disclosure exhibits the above-mentioned properties is believed to be that so-called "bound rubber" is formed on the metal silicon particles contained in the liquid silicone rubber composition. "Bound rubber" is known in the tire industry and is observed in rubber compositions containing carbon black. Specifically, when carbon black is extracted from an unvulcanized rubber composition containing carbon black using a solvent that dissolves the unvulcanized rubber, the rubber that binds to the carbon black and is not dissolved by the solvent is called "bound rubber" (see Japanese Patent Publication No. 27313 / 1996). The present inventors used thermogravimetric analysis of metal silicon particles extracted from a liquid silicone rubber composition to measure the amount of silicone rubber remaining bonded to the metal silicon particles as the amount of bound rubber. As a result, they found that liquid silicone rubber compositions with low shear rate dependency have a high amount of bound rubber. It is generally said that the viscosity of a particle dispersion in the low shear rate range depends on the interfacial state between the particles and the matrix. In other words, a large amount of silicone rubber is bonded to the metal silicon particles in the liquid silicone rubber composition according to the present disclosure as bound rubber. As a result, it is believed that the viscosity in the low shear rate range is reduced due to improved sliding between the metal silicon particles and the silicone rubber as the matrix in which the metal silicon particles are dispersed.

[0043] From the above, the liquid silicone rubber composition according to the present disclosure can also be described as a silicone rubber composition in which a large amount of silicone rubber as bound rubber is bonded to metal silicon particles. In the present disclosure, this bound rubber amount is defined as the mass loss rate within a specific temperature range in thermogravimetric analysis of metal silicon particles extracted from a liquid silicone rubber composition by a specific method. That is, a liquid silicone rubber composition according to another embodiment of the present disclosure is a liquid silicone rubber composition containing metal silicon powder, and has a mass loss rate of 0.3% or more. It is believed that in the liquid silicone rubber composition according to the present disclosure, a certain amount or more of the silicone rubber as a bound rubber is bonded to the metal silicon particles because the mass loss rate of the metal silicon particles is 0.3% or more. As a result, the liquid silicone rubber composition according to the present disclosure can provide molded products with excellent surface smoothness. A method for measuring the amount of bound rubber bonded to metal silicon particles will now be described in detail.

[0044] The amount of bound rubber of metal silicon particles in the liquid silicone rubber composition was measured using a thermogravimetric analyzer (TGA). A 0.5g sample was taken from the liquid silicone rubber composition and mixed with 9ml of toluene at 25°C. The mixture was then centrifuged for 5 minutes at 25°C and 10,000 rpm using a centrifuge (Kubota Shoji Co., Ltd., High-Speed, Large-Capacity Refrigerated Centrifuge 7780) to precipitate the metal silicon particles. The resulting precipitate was filtered and washed under reduced pressure three times with 10ml of toluene at 25°C using a 40mm diameter Kiriyama funnel and Kiriyama funnel filter paper No. 5C (retained particles 1µm). The metal silicon particles were then separated and isolated. Because uncured silicone rubber components are soluble in toluene, silicone rubber that is not firmly adsorbed to the metal silicon particles is removed. The resulting metal silicon particles are dried at 120°C for 1 hour, weighed out, and subjected to TGA analysis. Specifically, the temperature is raised from 50°C to 500°C at a rate of 5°C / min under 80 ml / min of dry air, and the mass change is measured. From the obtained mass change data, the mass change at temperatures between 300 and 500°C is calculated, and the mass loss rate (%) is calculated. Because mass change data below 300°C is affected by residual moisture and toluene, the mass change between 300 and 500°C is used to represent the amount of bound rubber firmly adsorbed to the metal silicon particles. Between 300 and 500°C, the metal silicon particles alone show almost no mass change, or they are slightly oxidized and increase in mass. In contrast, metal silicon particles to which silicone rubber is firmly adsorbed show a mass loss due to the silicone rubber decomposing at temperatures above 300° C. The TGA measurement can be performed using a device such as a differential scanning calorimeter / thermogravimeter (trade name: TGA / DSC 3+, manufactured by Mettler Toledo).

[0045] Methods for increasing the amount of bound rubber of metal silicon particles include the following: In this disclosure, the state before being blended into the liquid silicone rubber composition may be referred to as "metal silicon powder." (i) A method in which a liquid silicone component containing organopolysiloxane is mixed with metallic silicon powder and then allowed to stand for a long period of time. (ii) A method in which the liquid silicone component containing organopolysiloxane and the metallic silicon powder are mixed under low shear conditions for a long time. Details are provided below.

[0046] (i) A method in which a liquid silicone component containing organopolysiloxane is mixed with metallic silicon powder and then allowed to stand for a long period of time. When a liquid silicone rubber composition, which is a mixture of a silicone component containing organopolysiloxane and metal silicon powder, is left standing, the amount of bound rubber increases over time. By leaving the composition standing for 30 days or more, the bound rubber is fully formed, reducing shear rate dependency and improving smoothness. Equipment such as a planetary mixer, a planetary mixer, or a kneader is used for mixing. The temperature during mixing can be room temperature or a high temperature of 100 to 200°C. The temperature during standing may be either room temperature or elevated. When mixing is carried out at elevated temperature, component (a) and component (d) may be mixed in advance, and the other components may be mixed after preparing the base compound.

[0047] Bound rubber formed from rubber used in the tire industry is usually formed within a few hours to a few days. In contrast, as described above, it takes a long time for bound rubber to form with the composition according to the present disclosure. The reason for this is that carbon black, a filler compounded with rubber used in the tire industry, has a small particle size of several tens of nanometers, easily forms a secondary structure, and has a very large surface area. Therefore, bound rubber is formed on carbon black within a relatively short period of time. However, the metal silicon powder according to the present disclosure has a larger particle size and a smaller surface area than carbon black. Therefore, it is thought that it takes a longer time to form a sufficient amount of bound rubber on the metal silicon powder.

[0048] (ii) A method in which the silicone component containing organopolysiloxane and the metal silicon powder are mixed under low shear conditions for a long time. Planetary mixers are often used to mix silicone components, including organopolysiloxane, with metal silicon powder. The planetary mixer referred to here is a device with one or more stirring blades that rotate and revolve around their axes, applying shear forces through planetary motion to mix the materials.

[0049] When mixing a liquid silicone rubber composition using a planetary mixer, the revolution speed is typically set to 40 to 200 rpm, the rotation speed approximately twice that speed, and the mixing time is typically approximately 5 to 40 minutes. However, according to the inventors' research, it is preferable to use a very low revolution speed of 5 to 15 rpm, preferably 8 to 12 rpm, and most preferably 10 rpm. Furthermore, the mixing time is preferably 100 to 300 minutes. After preparing a homogeneous liquid silicone rubber composition in this manner, it is allowed to stand for at least 4 days, preferably 4 to 6 days. Through this process, a sufficient amount of bound rubber is formed on the metal silicon powder. While the reason for this is unclear, it is thought that sufficient bound rubber is formed by the silicone polymer penetrating into minute gaps and defects on the metal silicon particle surface due to capillary action or other factors. It is believed that increasing the shear rate does not promote wetting of the silicone polymer onto the metal silicon particle surface, reducing capillary action and affecting the amount of bound rubber. As described above, the method for obtaining a liquid silicone rubber composition that satisfies the mass loss rate requirement according to the present disclosure is as follows: A method for producing a liquid silicone rubber composition, comprising the steps of mixing a silicone component containing an organopolysiloxane with a metal silicon powder and allowing the resulting mixture to stand for 30 days or more; and Silicone components including organopolysiloxane and metal silicon powder are mixed using a planetary mixer. mixing the mixture at a revolution speed of 5 to 15 rpm for a mixing time of 100 to 300 minutes, and allowing the mixture to stand for 4 days or more; and a method for producing a liquid silicone rubber composition.

[0050] The fixing member and thermal fixing device made using the liquid silicone rubber composition of the present disclosure will be described in detail below based on specific configurations.

[0051] -Outline of the fixing member configuration The fixing member according to one embodiment of the present disclosure will be described in detail with reference to the drawings. The fixing member according to the present disclosure can be, for example, a rotatable member such as a roller or an endless belt (hereinafter also referred to as a "fixing roller" and a "fixing belt", respectively). Fig. 2(a) is a circumferential cross-sectional view of a fixing belt, and Fig. 2(b) is a circumferential cross-sectional view of a fixing roller. As shown in Fig. 2(a) and Fig. 2(b), the fixing member has a base 3, an elastic layer 4 on the outer surface of the base 3, and a surface layer (release layer) 6 on the outer surface of the elastic layer 4. An adhesive layer 5 may also be provided between the elastic layer 4 and the surface layer 6, and in this case, the surface layer 6 is fixed to the outer peripheral surface of the elastic layer 4 by the adhesive layer 5.

[0052] -Method of manufacturing the fixing member The fixing member according to the present disclosure can be manufactured, for example, by a manufacturing method including the following steps.

[0053] -Preparing the substrate The material of the substrate is not particularly limited, and any material known in the field of fixing members can be used as appropriate. Examples of materials constituting the substrate include metals such as aluminum, iron, nickel, and copper, alloys such as stainless steel, and resins such as polyimide. Here, when the thermal fixing device is a thermal fixing device that heats the base by induction heating as a heating means for the fixing member, the base preferably contains at least one metal selected from the group consisting of nickel, copper, iron, and aluminum. Among them, alloys mainly composed of nickel or iron are particularly preferred from the viewpoint of heat generation efficiency. Here, the term "main component" refers to the component that is contained in the largest amount among the components that make up the target object (here, the base).

[0054] The shape of the substrate can be appropriately selected depending on the shape of the fixing member, and can be various shapes such as an endless belt, a hollow cylinder, a solid cylinder, or a film.

[0055] In the case of a fixing belt, the thickness of the substrate is preferably, for example, 15 to 80 μm. By setting the thickness of the substrate within the above range, it is possible to achieve both high levels of strength and flexibility. In addition, on the surface of the substrate opposite to the side facing the elastic layer, for example, a layer for preventing wear of the inner surface of the fixing belt when the inner surface of the fixing belt comes into contact with other members, or a layer for improving sliding properties with other members may be provided.

[0056] The surface of the substrate facing the elastic layer may be subjected to a surface treatment to impart a function such as adhesion to the elastic layer. Examples of surface treatments include physical treatments such as blasting, lapping, and polishing, and chemical treatments such as oxidation, coupling agent treatment, and primer treatment. Physical and chemical treatments may also be used in combination.

[0057] In particular, when using an elastic layer containing cross-linked silicone rubber, it is preferable to treat the outer surface of the substrate with a primer to improve adhesion between the substrate and the elastic layer. For example, a primer in the form of a paint in which additives are appropriately blended and dispersed in an organic solvent can be used. Such primers are commercially available. Examples of the additives include silane coupling agents, silicone polymers, hydrogenated methylsiloxanes, alkoxysilanes, reaction-promoting catalysts for hydrolysis, condensation, and addition reactions, and colorants such as iron oxide. The primer is applied to the outer surface of the substrate, followed by drying and baking processes to complete the primer treatment.

[0058] The primer can be appropriately selected depending on, for example, the material of the substrate, the type of elastic layer, and the reaction form during crosslinking. For example, when the material constituting the elastic layer contains a large amount of unsaturated aliphatic groups, a material containing a hydrosilyl group is preferably used as the primer because adhesion is imparted by reaction with the unsaturated aliphatic groups. Conversely, when the material constituting the elastic layer contains a large amount of hydrosilyl groups, a material containing an unsaturated aliphatic group is preferably used as the primer. In addition, the primer can be appropriately selected depending on the type of substrate and elastic layer to be adhered, such as a material containing an alkoxy group.

[0059] Elastic layer formation process The elastic layer forming step may include the following steps. (i) A step of preparing a liquid silicone rubber composition according to the present disclosure. (ii) A step of forming a layer containing the composition on a substrate (a step of forming a composition layer): The composition is applied to a substrate by a method such as blade coating, nozzle coating, or ring coating to form a layer of the composition. (iii) A step of curing the composition layer to form an elastic layer (curing step).

[0060] A process for forming an adhesive layer and a surface layer on an elastic layer FIG. 3 is a schematic diagram illustrating an example of a process for laminating a surface layer 6 in the direction of the arrow onto an elastic layer 4 containing crosslinked silicone rubber via an adhesive layer 5 formed using an addition-curing silicone rubber adhesive. First, an adhesive is applied to the surface of the elastic layer 4 formed on the outer periphery of the substrate 3. Any known adhesive can be used. However, from the perspective of ease of handling, it is preferable to use an addition-curing silicone rubber containing a self-adhesive component. This adhesive can contain, for example, a self-adhesive component, an organopolysiloxane having multiple unsaturated aliphatic groups, typically vinyl groups, in its molecular chain, a hydrogenorganopolysiloxane, and a platinum compound as a crosslinking catalyst. The adhesive applied to the surface of the elastic layer is cured by an addition reaction to form an adhesive layer 5 that bonds the surface layer 6 to the elastic layer 4.

[0061] Examples of the self-adhesive component include the following: A silane having at least one, preferably two or more functional groups selected from the group consisting of an alkenyl group such as a vinyl group, a (meth)acryloxy group, a hydrosilyl group (SiH group), an epoxy group, an alkoxysilyl group, a carbonyl group, and a phenyl group. · Organosilicon compounds such as cyclic or linear siloxanes having 2 to 30 silicon atoms, preferably 4 to 20 silicon atoms. A non-silicon-based (i.e., silicon-free) organic compound that may contain oxygen atoms in the molecule. However, the compound contains one to four, preferably one to two, aromatic rings such as phenylene structures in one molecule. The phenylene structure is monovalent to tetravalent, preferably divalent to tetravalent. Furthermore, the phenylene structure contains at least one, preferably two to four, functional groups (e.g., alkenyl groups, (meth)acryloxy groups) capable of participating in a hydrosilylation addition reaction in one molecule.

[0062] The above-mentioned self-adhesive components may be used alone or in combination of two or more. Furthermore, from the viewpoint of viscosity adjustment and ensuring heat resistance, a filler component may be added to the adhesive within the scope of the present invention. Examples of such filler components include the following: Silica, alumina, iron oxide, cerium oxide, cerium hydroxide, carbon black, etc.

[0063] The amount of each component contained in the adhesive is not particularly limited and can be set appropriately. Such addition-curing silicone rubber adhesives are commercially available and easily available. The thickness of the adhesive layer is preferably 20 μm or less. By making the thickness of the adhesive layer 20 μm or less, when the fixing belt is used as a heating belt in a thermal fixing device, the thermal resistance can be easily set low, and heat from the inner surface can be easily transferred to the recording medium.

[0064] Next, a resin tube for forming the surface layer 6 is coated and laminated on the outer surface of the formed adhesive layer 5. Note that the adhesiveness can be improved by previously treating the inner surface of the resin tube with sodium, excimer laser, ammonia, or the like.

[0065] The surface layer 6 preferably contains a fluororesin to function as a release layer that prevents toner from adhering to the outer surface of the fixing member. For this reason, the surface layer 6 is preferably formed using, for example, a fluororesin tube formed by molding the fluororesin exemplified below into a tube shape. Tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), etc. Among the resin materials exemplified above, PFA is particularly suitable from the viewpoint of moldability and toner releasability.

[0066] The thickness of the surface layer is preferably 10 μm to 50 μm, which makes it easier to maintain an appropriate surface hardness of the fixing member.

[0067] The method for covering the resin tube is not particularly limited, but methods such as covering with an addition-curing silicone rubber adhesive as a lubricant or expanding the resin tube from the outside to cover it can be used. Any excess addition-curing silicone rubber adhesive remaining between the elastic layer 4 and the surface layer 6 made of the resin tube can be removed by squeezing it out using a means not shown. From the viewpoint of heat conductivity, the thickness of the adhesive layer 5 after squeezing it out is preferably 20 μm or less.

[0068] Next, the addition-curing silicone rubber adhesive is cured and bonded by heating for a predetermined time in a heating means such as an electric furnace, thereby forming an adhesive layer 5 and a surface layer 6 on the elastic layer 4. The heating time, heating temperature, and other conditions can be set appropriately depending on the adhesive used, etc. The fixing member can be obtained by cutting both ends in the width direction of the obtained member to the desired length.

[0069] Thermal fixing device The thermal fixing device is configured so that a pair of heated rotating bodies, such as a pair of heated rollers, a pair of heated belts, or a pair of heated belts, are pressed against each other. The type of thermal fixing device is appropriately selected taking into consideration the processing speed, size, and other conditions of the entire electrophotographic image forming apparatus in which the thermal fixing device is installed.

[0070] In a thermal fixing device, a fixing nip is formed by pressing a heated fixing member and a pressure member together, and a recording medium, which serves as a heated object and has an image formed with unfixed toner, is sandwiched and conveyed through this fixing nip. The image formed with unfixed toner is called a toner image. This heats and pressurizes the toner image. As a result, the toner image is melted and mixed, and then cooled to fix the image on the recording medium. Hereinafter, the configuration of a specific example of a thermal fixing device will be described with reference to the drawings, but the scope and applications of the present disclosure are not limited to this.

[0071] Heating belt-pressure belt type heat fixing device FIG. 4 is a cross-sectional schematic diagram of an example of a so-called twin-belt type thermal fixing device in which a pair of rotating bodies, namely a heating belt 11 and a pressure belt 12, are pressed together, and which includes a heating belt as a heating member. Here, the width direction of the thermal fixing device or the components constituting the device is the direction perpendicular to the plane of FIG. 4. With respect to the thermal fixing device, the front is the surface on which the recording medium S is introduced. The left and right are left and right when viewed from the front of the device. The belt width is the belt dimension in the left-right direction when viewed from the front of the device. The width of the recording medium S is the dimension of the recording medium in a direction perpendicular to the transport direction. Furthermore, upstream and downstream refer to upstream and downstream with respect to the recording medium transport direction (direction of the arrow).

[0072] This thermal fixing device is equipped with a heating belt 11 as fixing members and a pressure belt 12. The heating belt 11 and the pressure belt 12 are each a heating belt including a flexible base made of a metal whose main component is nickel, as shown in Fig. 2(a), stretched over two rollers.

[0073] The heating belt 11 employs a heating source (induction heating member 13, excitation coil) capable of heating by energy-efficient electromagnetic induction heating as its heating means. The induction heating member 13 is composed of an induction coil 13a, an excitation core 13b, and a coil holder 13c that holds them. The induction coil 13a uses a litz wire wound flat in an oval shape and is placed inside a horizontal E-shaped excitation core 13b that protrudes from the center and both sides of the induction coil 13a. The excitation core 13b is made of a material with high magnetic permeability and low residual magnetic velocity density, such as ferrite or permalloy, which reduces loss in the induction coil 13a and excitation core 13b and enables the heating belt 11 to be heated efficiently.

[0074] When a high-frequency current is applied from the excitation circuit 14 to the induction coil 13a of the induction heating member 13, the base of the heating belt 11 is induced to generate heat, and the heating belt 11 is heated from the base side. The surface temperature of the heating belt 11 is detected by a temperature detection element 15 such as a thermistor. A signal related to the temperature of the heating belt 11 detected by this temperature detection element 15 is sent to a control circuit unit 16. The control circuit unit 16 controls the power supplied from the excitation circuit 14 to the induction coil 13a so that the temperature information received from the temperature detection element 15 is maintained at a predetermined fixing temperature, thereby adjusting the temperature of the heating belt 11 to the predetermined fixing temperature.

[0075] The heating belt 11 is stretched by a roller 17 and a heating side roller 18, which serve as belt rotating members. The roller 17 and the heating side roller 18 are supported by bearings that allow them to rotate freely between left and right side plates (not shown) of the device.

[0076] Roller 17 is, for example, a hollow iron roller having an outer diameter of 20 mm, an inner diameter of 18 mm, and a thickness of 1 mm, and functions as a tension roller that applies tension to heating belt 11. Heating side roller 18 is, for example, a highly slidable elastic roller having an iron alloy core having an outer diameter of 20 mm, an inner diameter of 18 mm, and a silicone rubber layer as an elastic layer provided on the core.

[0077] This heating side roller 18, as a drive roller, receives a driving force from a drive source (motor) M via a drive gear train (not shown), and is driven to rotate in the clockwise direction of the arrow at a predetermined speed. By providing this heating side roller 18 with an elastic layer as described above, the driving force input to the heating side roller 18 can be effectively transmitted to the heating belt 11, and a fixing nip can be formed to ensure separation of the recording medium from the heating belt 11. Providing the heating side roller 18 with an elastic layer also reduces heat conduction to the heating side roller, which is also effective in shortening the warm-up time.

[0078] When the heating side roller 18 is driven to rotate, the heating belt 11 rotates together with the roller 17 due to friction between the surface of the elastic layer of the heating side roller 18 and the inner surface of the heating belt 11. The arrangement and size of the roller 17 and the heating side roller 18 are selected according to the size of the heating belt 11. For example, the dimensions of the roller 17 and the heating side roller 18 are selected so that the heating belt 11 having an inner diameter of 55 mm when not mounted can be stretched over them.

[0079] The pressure belt 12 is tensioned by a tension roller 19 and a pressure side roller 20, which serve as belt rotation members. The inner diameter of the pressure belt when not attached is, for example, 55 mm. The tension roller 19 and the pressure side roller 20 are supported by bearings that allow them to rotate freely between left and right side plates (not shown) of the device.

[0080] The tension roller 19 is, for example, an iron alloy core having an outer diameter of 20 mm and an inner diameter of 16 mm, with a silicone sponge layer provided on it to reduce thermal conductivity and reduce heat conduction from the pressure belt 12. The pressure side roller 20 is, for example, a low-sliding, rigid roller made of an iron alloy having an outer diameter of 20 mm, an inner diameter of 16 mm, and a thickness of 2 mm. The dimensions of the tension roller 19 and the pressure side roller 20 are also selected to match the dimensions of the pressure belt 12.

[0081] Here, in order to form a nip portion N between the heating belt 11 and the pressure belt 12, the pressure side roller 20 is pressed toward the heating side roller 18 in the direction of arrow F with a predetermined pressure force by a pressure mechanism not shown at both left and right ends of the rotating shaft.

[0082] Furthermore, a pressure pad is employed to obtain a wide nip portion N without increasing the size of the device. Specifically, a fixing pad 21 serves as a first pressure pad that presses the heating belt 11 toward the pressure belt 12, and a pressure pad 22 serves as a second pressure pad that presses the pressure belt 12 toward the heating belt 11. The fixing pad 21 and the pressure pad 22 are supported and disposed between left and right side plates (not shown) of the device. The pressure pad 22 is pressed toward the fixing pad 21 with a predetermined pressure in the direction of arrow G by a pressure mechanism (not shown). The fixing pad 21, which is the first pressure pad, has a pad base and a sliding sheet (low-friction sheet) 23 that contacts the belt. The pressure pad 22, which is the second pressure pad, also has a pad base and a sliding sheet 24 that contacts the belt. This is because there is a problem of significant wear at the portion of the pad that rubs against the inner circumferential surface of the belt. By interposing the sliding sheets 23 and 24 between the belt and the pad substrate, the pad is prevented from being worn and the sliding resistance is reduced, so that good belt running performance and durability can be ensured.

[0083] The heating belt 11 is provided with a non-contact charge removal brush (not shown), and the pressure belt 12 is provided with a contact charge removal brush (not shown).

[0084] The control circuit unit 16 drives the motor M at least when image formation is being performed. This causes the heating side roller 18 to rotate, and the heating belt 11 to rotate in the same direction. The pressure belt 12 rotates following the rotation of the heating belt 11. Here, by configuring the most downstream portion of the fixing nip so that the heating belt 11 and the pressure belt 12 are sandwiched between the roller pair 18 and 20 and transported, it is possible to prevent the belts from slipping. The most downstream portion of the fixing nip is the portion where the pressure distribution (in the recording medium transport direction) in the fixing nip is greatest.

[0085] When the heating belt 11 is heated to a predetermined fixing temperature and maintained at that temperature (called temperature control), a recording medium S bearing an unfixed toner image t is transported (in the direction of the arrows) into the nip N between the heating belt 11 and the pressure belt 12. The recording medium S is introduced with the side bearing the unfixed toner image t facing the heating belt 11. As the unfixed toner image t of the recording medium S is nipped and transported while in close contact with the outer circumferential surface of the heating belt 11, heat is applied from the heating belt 11, and the unfixed toner image t is fixed to the surface of the recording medium S under pressure. At this time, heat from the heated substrate of the heating belt 11 is efficiently transported toward the recording medium S through an elastic layer with enhanced thermal conductivity in the thickness direction. The recording medium S is then separated from the heating belt by a separating member 25 and transported (in the direction of the arrows).

[0086] Heating belt-pressure roller type thermal fixing device FIG. 5 is a schematic diagram showing an example of a heat fixing device using a heating belt and pressure roller system with a ceramic heater as the heating element. In FIG. 5, 11 denotes a cylindrical or endless belt-shaped heating belt, and the fixing member described above can be used. A heat-resistant and heat-insulating belt guide 30 holds the heating belt 11. A ceramic heater 31 for heating the heating belt 11 is fitted into a groove formed along the length of the guide at a position where it comes into contact with the heating belt 11 (approximately the center of the underside of the belt guide 30) and fixedly supported thereon. The heating belt 11 is loosely fitted around the belt guide 30. A rigid pressure stay 32 is inserted inside the belt guide 30.

[0087] Meanwhile, a pressure roller 33 is disposed opposite the heating belt 11. In this disclosure, the pressure roller 33 is an elastic pressure roller, that is, a core 33a with an elastic layer 33b of silicone rubber provided on it to reduce hardness. Both ends of the core 33a are rotatably supported by bearings between the front and rear chassis side plates (not shown) of the device. The elastic pressure roller is covered with a PFA (tetrafluoroethylene / perfluoroalkyl ether copolymer) tube to improve surface properties.

[0088] Pressure springs (not shown) are respectively compressed between both ends of the pressure rigid stay 32 and spring bearing members (not shown) on the device chassis side, thereby applying a downward force to the pressure rigid stay 32. As a result, the lower surface of the ceramic heater 31 disposed on the lower surface of the heat-resistant resin belt guide 30 and the upper surface of the pressure roller 33 come into pressure contact with each other with the heating belt 11 sandwiched therebetween, forming a fixing nip N.

[0089] The pressure roller 33 is driven to rotate counterclockwise as indicated by the arrow by a driving means (not shown). This rotational drive of the pressure roller 33 generates friction between the pressure roller 33 and the outer surface of the heating belt 11, which causes a rotational force to act on the heating belt 11. The inner surface of the heating belt 11 comes into close contact with the lower surface of the ceramic heater 31 at the fixing nip N. The heating belt 11, which is in close contact with the lower surface of the ceramic heater 31, rotates clockwise as indicated by the arrow around the outside of the belt guide 30 at a peripheral speed that roughly corresponds to the rotational peripheral speed of the pressure roller 33, while sliding in close contact (pressure roller drive method).

[0090] The pressure roller 33 starts rotating based on a print start signal, and the ceramic heater 31 starts heating up. The rotational peripheral speed of the heating belt 11 due to the rotation of the pressure roller 33 becomes steady, and the temperature of the temperature detection element 34 on the upper surface of the ceramic heater rises to a predetermined temperature, for example, 180°C. At that moment, a recording medium S bearing an unfixed toner image t as a heated material is introduced in the direction of the arrow between the heating belt 11 and the pressure roller 33 in the fixing nip N, with the toner image bearing surface facing the heating belt 11. The recording medium S then comes into close contact with the lower surface of the ceramic heater 31 via the heating belt 11 in the fixing nip N and moves through the fixing nip N together with the heating belt 11. During this movement and passage, heat from the heating belt 11 is applied to the recording medium S, and the toner image t is heat-fixed to the surface of the recording medium S. After passing through the fixing nip N, the recording medium S is separated from the outer surface of the heating belt 11 and transported.

[0091] The ceramic heater 31 serving as the heating element is a horizontally elongated linear heating element with a low heat capacity, whose longitudinal direction is perpendicular to the direction of movement of the heating belt 11 and the recording medium S. The ceramic heater 31 preferably has a basic configuration consisting of a heater substrate 31a, a heat-generating layer 31b provided on the surface of the heater substrate 31a along its longitudinal direction, a protective layer 31c provided thereon, and a sliding member 31d. The heater substrate 31a can be made of aluminum nitride or the like. The heat-generating layer 31b can be formed by applying an electrically resistive material such as Ag / Pd (silver / palladium) to a thickness of approximately 10 μm and a width of 1 to 5 mm by screen printing or the like. The protective layer 31c can be made of glass, fluororesin, or the like. However, the ceramic heater used in the thermal fixing device is not limited to these materials.

[0092] When current is applied between both ends of the heat-generating layer 31b of the ceramic heater 31, the heat-generating layer 31b generates heat, causing the heater 31 to rapidly rise in temperature. The ceramic heater 31 is fixedly supported by being fitted, with the protective layer 31c side facing upward, into a groove formed along the longitudinal direction of the guide at approximately the center of the underside of the belt guide 30. In the fixing nip N that comes into contact with the heating belt 11, the surface of the sliding member 31d of the ceramic heater 31 and the inner surface of the heating belt 11 come into sliding contact with each other.

[0093] As described above, the heat belt 11 has high thermal conductivity in the thickness direction of the elastic layer containing silicone rubber and low hardness. With this configuration, the heat belt 11 can efficiently heat an unfixed toner image and, because of its low hardness, can fix a high-quality image onto the recording medium S at the fixing nip.

[0094] As described above, by using the liquid silicone rubber composition of the present disclosure, it is possible to provide a thermal fixing device equipped with a fixing member that has excellent fixing performance and image quality. [Example]

[0095] The present disclosure will be described in more detail below using examples.

[0096] [Example 1] (1) Preparation of liquid silicone rubber composition First, as component (a), 100 parts by mass of a silicone polymer (hereinafter referred to as "Vi") having vinyl groups, which are unsaturated aliphatic groups, only at both ends of the molecular chain and methyl groups as unsubstituted hydrocarbon groups containing no other unsaturated aliphatic groups, was prepared. Vi was a product name: DMS-V35, manufactured by Gelest, with a viscosity of 5000 mm. 2 The silicone polymer used was a silicone polymer represented by the structural formula (2) above, where R 3 are all methyl groups, and R 4 are polymers in which all of the groups are vinyl groups.

[0097] Next, surface-oxidized metal silicon powder (product name: M-Si#350WB, manufactured by Kinsei Matec Co., Ltd., average particle size 12 μm) was blended with Vi as component (d) at a volume ratio of 40% relative to the silicone component. The mixture was placed in a planetary mixer (manufactured by Thinky Corporation, model ARV-310) and stirred at 2000 rpm for 4 minutes to obtain mixture 1. Mixture 1 was then stored at room temperature for 46 days.

[0098] Next, 0.22 parts by mass of a 90 wt % IPA solution of 1-ethynyl-1-cyclohexanol (manufactured by Tokyo Chemical Industry Co., Ltd.) as a cure retarder, 0.1 parts by mass of a hydrosilylation catalyst (platinum catalyst: a mixture of 1,3-divinyltetramethyldisiloxane platinum complex, 1,3-divinyltetramethyldisiloxane, and 2-propanol) as component (c), and further, as component (b), a silicone polymer (trade name: HMS-301, manufactured by Gelest, viscosity 30 mm) having a linear siloxane skeleton and silicon-bonded active hydrogen groups only on the side chains were added. 2 1.5 parts by mass of (1 / s) was weighed out and added to Mixture 1, which was then placed in a planetary mixer (Thinky Corporation, Model ARV-310) and mixed under reduced pressure at 600 rpm for 4 minutes to obtain a liquid silicone rubber composition.

[0099] (2) Preparation of sample sheets The liquid silicone rubber composition was coated onto a 50 μm thick stainless steel (SUS304) film at a speed of 10 mm / sec using a film applicator (manufactured by Allgood Co., Ltd.) to a film thickness of 250 μm. The film was then heated at 160°C for 1 minute to primarily cure the liquid silicone rubber composition, and then heated at 200°C for 30 minutes to secondary cure the silicone rubber composition layer, producing a sample sheet.

[0100] [Comparative Example 1] A liquid silicone rubber composition and a sample sheet were prepared in the same manner as in Example 1, except that the static storage period was set to 3 hours.

[0101] [Example 2] A liquid silicone rubber composition and a sample sheet were prepared in the same manner as in Example 1, except that the amount of metallic silicon powder mixed was 37% by volume and the static storage period was 40 days.

[0102] Comparative Example 2 A liquid silicone rubber composition and a sample sheet were prepared in the same manner as in Example 2, except that the static storage period was set to 10 days.

[0103] [Example 3] The silicone polymer used as Vi was a product name: DMS-V41, manufactured by Gelest, with a viscosity of 10,000 mm 2 / s. The amount of metallic silicon powder was changed to 43 volume %, and the static storage period was set to 180 days. Other than these, a liquid silicone rubber composition and a sample sheet were prepared in the same manner as in Example 1.

[0104] Comparative Example 3 A liquid silicone rubber composition and a sample sheet were prepared in the same manner as in Example 3, except that the static storage period was changed to 6 days.

[0105] [Example 4] A liquid silicone rubber composition and a sample sheet were prepared in the same manner as in Example 1, except that metal silicon powder (product name: M-Si FineWB, manufactured by Kinsei Matec Co., Ltd., average particle size 3 μm) was used and the static storage period was set to 30 days.

[0106] Comparative Example 4 A liquid silicone rubber composition and a sample sheet were prepared in the same manner as in Example 4, except that the static storage period was set to 3 hours.

[0107] [Example 5] First, as Vi, product name: DMS-V42, manufactured by Gelest, viscosity 20000mm 2 100 parts by mass of silicone polymer / s was prepared. 3 are all methyl groups, and R 4 are polymers in which all of the groups are vinyl groups.

[0108] Next, surface-oxidized metal silicon powder (product name: M-Si#350WB, manufactured by Kinseimatec Co., Ltd., average particle size 12 μm) was blended with Vi as component (d) at a volume ratio of 40% relative to the silicone component. The mixture was placed in a planetary mixer (manufactured by Primix Corporation, Hibismix 2P-01 model) and stirred at 10 rpm for 160 minutes to obtain Mixture 2. Mixture 2 was then stored at room temperature for 5 days. The subsequent procedures were the same as in Example 1 to prepare a liquid silicone rubber composition and a sample sheet.

[0109] Comparative Example 5 A liquid silicone rubber composition and a sample sheet were prepared in the same manner as in Example 5, except that the mixture of component (a) and component (d) was placed in a planetary centrifugal mixer (Thinky Corporation, model ARV-310) in the same manner as in Example 1 and stirred and mixed at 2000 rpm for 4 minutes.

[0110] (evaluation) For the liquid silicone rubber compositions of Examples 1 to 5 and Comparative Examples 1 to 5, the viscosity was measured, and TGA measurement and calculation of the mass reduction rate were performed by the following methods. Specifically, it is as follows. <Viscosity measurement> The shear viscosity of the liquid silicone rubber composition was measured using a rotational shear rheometer (trade name: DHR-2; manufactured by TA Instruments). The measurement conditions were as follows: using parallel plates with a diameter of 20 mm, a gap distance of 1 mm, a temperature of 25°C, a pre-shear of 0.1 / sec for 10 seconds, a waiting time of 5 seconds, and measuring 10 points per decade between a shear rate of 0.01 / sec and 10 / sec. At each point, the measurement was performed with an equilibrium time of 3 seconds and a data acquisition time of 3 seconds. From the relationship between the obtained shear rate and viscosity, the viscosity A at a shear rate of 0.02 / sec and the viscosity B at a shear rate of 1 / sec were read, and their ratio (A / B) was calculated. <TGA measurement and calculation of the mass reduction rate> A 0.5 g sample was taken from the liquid silicone rubber composition, mixed with 9 ml of toluene at 25°C, and then centrifuged using a centrifuge (manufactured by Kubota Corporation: high-speed large-capacity cooling centrifuge 7780) at 25°C and 10,000 rpm for 5 minutes to precipitate metallic silicon particles. The obtained precipitate was subjected to vacuum filtration washing 3 times with 10 ml of toluene at 25°C using a 40 mm diameter Kiriyama funnel and Kiriyama funnel filter paper No. 5C (retained particles 1 μm) to extract the metallic silicon particles contained in the sample. The obtained metallic silicon particles were dried at 120°C for 1 hour, weighed 50 mg, and subjected to TGA measurement. As the TGA apparatus, "TGA / DSC 3+" (trade name) manufactured by Mettler Toledo was used, and the temperature was raised from 50°C to 500°C at 5°C / min under a dry air flow of 80 ml / min, and the mass change at that time was measured. From the obtained mass change data, the mass change from 300 to 500°C was calculated and used as the mass reduction rate (%). <Surface roughness> Also, the arithmetic mean surface roughness Ra was measured for the sample sheets of Examples 1 to 5 and Comparative Examples 1 to 5. For the measurement, a surface roughness measuring instrument (Surfcoder SE3500, manufactured by Kosaka Laboratory Ltd.) was used, and the evaluation length was 4 mm, the cut-off was 0.8 mm, and the speed was 0.2 mm / sec.

[0111] [Table 1]

[0112] Comparing the results in Table 1 between the Examples and Comparative Examples, it can be seen that in all formulations, when the ratio A / B (viscosity A at a shear rate of 0.02 / sec to viscosity B at 1 / sec) is 2.0 or less, the surface roughness value is small and smoothness is improved. Also, when the ratio A / B is 2.0 or less, the TGA reduction rate is 0.3% or more, and the amount of bound rubber is large. [Industrial Applicability]

[0113] The liquid silicone rubber composition of the present disclosure can be used to produce silicone rubber parts that have high thermal conductivity, low heat capacity, and excellent smoothness.

[0114] 1 Fuser belt 2 Fuser roller 3 Base 4 Elastic Layer 5 Adhesive layer 6 Surface layer

Claims

1. A liquid silicone rubber composition containing metal silicon particles, The content of the metal silicon particles is 35% by volume or more and 45% by volume or less, The volume average particle diameter of the metal silicon particles is 1 μm or more and 20 μm or less, A liquid silicone rubber composition characterized in that the ratio A / B of the viscosity of the composition at a shear rate of 0.02 / sec to the viscosity B at a shear rate of 1 / sec is 2.0 or less.

2. A liquid silicone rubber composition containing metal silicon particles, characterized in that the mass loss rate of the metal silicon particles measured by the following method is 0.3% or more: A 0.5 g sample was taken from the liquid silicone rubber composition, mixed with 9 ml of toluene at 25°C, and centrifuged at 10,000 rpm for 5 minutes. The resulting precipitate was then filtered and washed under reduced pressure three times with 10 ml of toluene at 25°C, and the mass loss rate at temperatures between 300 and 500°C was measured by thermogravimetric analysis of the metallic silicon particles extracted from the sample.

3. The liquid silicone rubber composition according to claim 1 or 2, comprising the following components (a) to (c) as silicone components: Component (a): an organopolysiloxane having an unsaturated aliphatic group; Component (b): an organopolysiloxane having silicon-bonded active hydrogen; Component (c): catalyst.

4. A method for producing the liquid silicone rubber composition according to any one of claims 1 to 3, comprising the steps of: A method for producing a liquid silicone rubber composition, comprising the steps of mixing a silicone component containing an organopolysiloxane with metallic silicon powder, and allowing the resulting mixture to stand for 30 days or more.

5. A method for producing the liquid silicone rubber composition according to any one of claims 1 to 3, comprising the steps of: Silicone components including organopolysiloxane and metal silicon powder are mixed using a planetary mixer. A method for producing a liquid silicone rubber composition, comprising the steps of mixing at a revolution speed of 5 to 15 rpm for a mixing time of 100 to 300 minutes, and then allowing the resulting mixture to stand for four days or more.

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