JP7654502B2 - Fixing member for electrophotography, fixing device and electrophotographic image forming apparatus - Google Patents

Description

This disclosure relates to a fixing member, a fixing device, and an electrophotographic image forming apparatus used in an electrophotographic image forming apparatus.

In general, in a heat fixing device used in an electrophotographic image forming apparatus such as a copying machine or a printer, a pair of heated rollers, a film and a roller, a belt and a roller, or a belt and a belt are pressed against each other. These rotating bodies are called fixing members. Then, a recording material holding an image formed by unfixed toner is introduced into the pressure contact area (fixing nip) formed between these rotating bodies. Then, the unfixed toner is heated together with the recording material, and the toner is softened and melted while being pressed against the recording material, so that the image is fixed to the recording material. The rotating body that the toner held on the recording material comes into direct contact with functions as a heating member, and may be in the form of, for example, a roller, a film, or a belt. The rotating body that forms the fixing nip together with the heating member functions as a pressure member, and may be in the form of, for example, a roller, a film, or a belt, just like the heating member. Among these fixing members, the fixing member (heating member) that comes into direct contact with the toner held on the recording material and heats the toner is required to be able to supply heat to the recording material and toner in the fixing nip to soften and melt the toner. For this reason, it has been proposed to include a thermally conductive filler such as magnesium oxide or metal silicon in the elastic layer of the fixing member in order to increase its thermal conductivity (Patent Documents 1 and 2).

Japanese Patent Application Publication No. 3-221982 JP 2007-171946 A

However, according to the study by the present inventors, a fixing member having an elastic layer containing a thermally conductive filler to improve thermal conductivity may have a tendency to break when used at high temperatures for a long period of time, and this tendency is particularly noticeable when the hardness of the elastic layer is reduced.
Therefore, in order to extend the service life of a fixing member having an elastic layer whose thermal conductivity is enhanced by the inclusion of a thermally conductive filler, the inventors have come to recognize that it is necessary to develop a new technology for preventing breakage of the elastic layer caused by the inclusion of the thermally conductive filler.
One aspect of the present disclosure is directed to providing an electrophotographic fixing member having excellent durability, in which the elastic layer does not break even after long-term use despite having an elastic layer containing a thermally conductive filler. Another aspect of the present disclosure is directed to providing a fixing device and an electrophotographic image forming apparatus capable of stably forming high-quality electrophotographic images.

According to one aspect of the present disclosure, there is provided an electrophotographic fixing member having, in this order, a substrate, an elastic layer on the substrate, and a surface layer, the elastic layer containing silicone rubber and a thermally conductive filler dispersed in the silicone rubber, the thermally conductive filler being metal oxide particles or metal particles having at least a portion of a surface constituted by a metal oxide, and the elastic layer further containing a charge control agent negatively charged with respect to the thermally conductive filler. According to another aspect of the present disclosure, there is provided a fixing device including the fixing member. According to another aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including the fixing member.

1A and 1B are explanatory diagrams of a presumed mechanism of the manifestation of the effect of the fixing member according to one embodiment of the present disclosure. 2A is an overhead view of a corona charger for forming an elastic layer of a fixing member according to one embodiment of the present disclosure, and FIG. 2B is a cross-sectional view of a corona charger for forming an elastic layer of a fixing member according to one embodiment of the present disclosure. 3A and 3B are schematic cross-sectional views of fuser members according to the present disclosure in belt and roller configurations, respectively. FIG. 2 is a schematic diagram illustrating an example of a step of laminating a fluororesin surface layer. 1 is a schematic cross-sectional view of an example of a fixing device in which a fixing member according to the present disclosure is disposed. FIG. 2 is a schematic perspective view of a jig for evaluating the pressure resistance durability of an elastic layer according to the present disclosure. FIG. 2 is an explanatory diagram of the arrangement of thermally conductive fillers formed in a mixture layer whose surface is charged.

The present inventors speculate as follows as to the reason why the elastic layer breaks when the fixing roll according to Patent Document 1 or the fixing belt according to Patent Document 2 is used at high temperatures for a long period of time.
1A, in the elastic layer 4, the thermally conductive filler 4b is dispersed in the silicone rubber 4a serving as a binder, and it is believed that there are aggregated portions 401 of the filler 4b. Then, in the process of repeatedly compressing the elastic layer 4, fracture occurs in the elastic layer 4 starting from the aggregated portions 401 of the filler 4b. Here, if the degree of cross-linking of the silicone rubber 4a is reduced to reduce the hardness of the elastic layer 4, the strength of the silicone rubber itself around the aggregated portions 401 is reduced, and it is believed that fracture of the elastic layer 4 is more likely to occur.
Based on these considerations, the inventors conducted further research and discovered that an elastic layer containing, in addition to silicone rubber and a thermally conductive filler, a charge control agent (hereinafter simply referred to as "charge control agent") that is negatively charged relative to the thermally conductive filler can have excellent durability.
The reason why such an elastic layer can have excellent durability is presumed to be as follows. That is, the elastic layer is formed by curing an addition-curing liquid silicone rubber mixture in which a thermally conductive filler is dispersed. In this addition-curing liquid silicone rubber mixture, the thermally conductive filler is positively charged by shear with the liquid silicone rubber, but the amount of charge of the thermally conductive filler is non-uniform. Therefore, it is considered that the thermally conductive filler that is almost not charged or the thermally conductive filler with a small amount of charge generates the aggregation part 401. On the other hand, the elastic layer according to one embodiment of the present disclosure is formed by curing an addition-curing liquid silicone rubber mixture in which a thermally conductive filler and a charge control agent are dispersed. In the preparation process of the addition-curing liquid silicone rubber mixture, as shown in FIG. 1B, the thermally conductive filler 4b and the charge control agent 4c are close to each other or contact each other, so that the thermally conductive filler 4b is positively charged. It is believed that the charge control agent 4c is used to actively charge the thermally conductive filler 4b positively, thereby making it difficult for differences in the amount of charge of the thermally conductive filler 4b to occur. As a result, in the addition-curing liquid silicone rubber mixture, the aggregation of the thermally conductive filler 4b is suppressed, and the formation of the aggregation portion 401 (see FIG. 1A) of the thermally conductive filler 4b is inhibited. As a result, it is believed that the breaking energy of the elastic layer 4 becomes large. The breaking energy is the area of the stress-strain curve obtained by subjecting the elastic layer to a tensile breaking test, and the larger the breaking energy, the more difficult it is for the elastic layer to break.

The present disclosure will now be described in detail with reference to the drawings.
(1) Fixing Member The configuration of the fixing member for electrophotography according to the present disclosure will be described with reference to the drawings.
3A and 3B are schematic cross-sectional views showing two aspects of the fixing member according to the present disclosure. FIG. 3A shows a fixing member having an endless belt shape (hereinafter, also referred to as a "fixing belt"), and FIG. 3B shows a fixing member having a roller shape (hereinafter, also referred to as a "fixing roller"). The fixing members according to FIG. 3A and FIG. 3B have, in this order, a base 3, an elastic layer 4 containing silicone rubber that covers the outer peripheral surface of the base 3, and a surface layer 6 that covers the outer peripheral surface of the elastic layer 4. Note that the adhesive layer 5 between the elastic layer 4 and the surface layer 6 is optional. For example, when the surface layer 6 is formed by melting fluororesin particles attached to the outer peripheral surface of the elastic layer 4, the adhesive layer 5 may not be included.

(2) Substrate When the fixing member is a fixing belt as shown in FIG. 3A, the substrate can be made of a metal such as an electroformed nickel sleeve or a stainless steel sleeve, or a heat-resistant resin such as polyimide. A layer for imparting a function of improving adhesion with the elastic layer can be provided on the outer surface (the surface on the elastic layer side) of the substrate. That is, the elastic layer only needs to be provided on the outer peripheral surface of the substrate, and other layers can be provided between the elastic layer and the substrate. In addition, a layer for imparting functions such as wear resistance and lubricity can be further provided on the inner surface (the surface opposite to the outer surface) of the substrate.
When the fixing member is a fixing roller as shown in Fig. 3B, the base only needs to have a strength that can withstand the heat and pressure applied by the fixing device, and can be, for example, a core made of a metal such as aluminum or iron or an alloy. In Fig. 3B, a solid core is used as the base, but a hollow core may also be used for the base, and a heat source such as a halogen lamp may be provided inside.

(3) Elastic layer The fixing member according to the present disclosure can be used as either a heating member or a pressure member in a fixing device. When used as a heating member, the elastic layer functions as a layer for making the outer surface of the heating member follow the unevenness of the paper during fixing. When used as a pressure member, the elastic layer functions as a layer for ensuring a sufficient width of the fixing nip formed between the heating member and the pressure member. In order to realize these functions in an environment where the non-paper passing area is as high as 240°C, the elastic layer contains silicone rubber with excellent heat resistance as a binder. That is, the elastic layer contains silicone rubber and a heat conductive filler dispersed in the silicone rubber.
The elastic layer can be formed by curing an addition-curing liquid silicone rubber mixture containing, for example, a thermally conductive filler and an addition-curing liquid silicone rubber. That is, the elastic layer can be a cured product of the addition-curing liquid silicone rubber mixture. The elastic layer can also contain a cured product of the addition-curing liquid silicone rubber, a thermally conductive filler present in the cured product, and a charge control agent that is negatively charged with respect to the thermally conductive filler.
The Asker C hardness (hereinafter, simply referred to as "hardness") of the elastic layer based on Japanese Industrial Standards (JIS) K7312: 1996 is preferably 50° or less. By having a hardness of 50° or less, the elastic layer does not break or plastically deform even when repeatedly compressed at high temperatures, and has excellent flexibility.
The hardness of the elastic layer can be adjusted, for example, by changing the type and amount of component (a), the type and amount of component (b), and the type and amount of component (c) in the addition-curing liquid silicone rubber described below.
The silicone rubber, the thermally conductive filler and the charge control agent, which are the components of the elastic layer, will be described in detail below.
(3-1) Silicone Rubber The addition-curing liquid silicone rubber contains at least the following components (a), (b) and (c), and also contains component (d) as necessary.
(a) an organopolysiloxane having an unsaturated aliphatic group in the molecule; (b) an organopolysiloxane having active hydrogen bonded to a silicon atom; (c) a hydrosilylation catalyst; and (d) a cure retarder.

Component (a): Organopolysiloxane having an unsaturated aliphatic group in the molecule Examples of organopolysiloxanes having an unsaturated aliphatic group in the molecule include organopolysiloxanes containing an unsaturated aliphatic group such as a vinyl group that is bonded to at least two silicon atoms in one molecule. Specific examples include organopolysiloxanes according to the following (i) and (ii).

(i) A linear organopolysiloxane having one or both of intermediate units selected from the group consisting of intermediate units represented by R ₁ R _{1 Si} O and intermediate units represented by R ₁ R _{2 Si} O, and a molecular end represented by R ₁ R ₁ R _{2 Si} O _1/2 (see structural formula 1 below).

(ii) A linear organopolysiloxane having one or both of intermediate units selected from the group consisting of intermediate units represented by R ₁ R _{1 Si} O and intermediate units represented by R ₁ R ₂ SiO, and a molecular end represented by R ₁ R ₁ R ₁ SiO _1/2 (see structural formula 2 below).

In Structural Formula 1 and Structural Formula 2, R ₁ 's each independently represent an unsubstituted hydrocarbon group not containing an unsaturated aliphatic group, R ₂ 's each independently represent an unsaturated aliphatic group, and m and n each independently represent an integer of 0 or more.

In addition, examples of the unsubstituted hydrocarbon group not containing an unsaturated aliphatic group represented by R ₁ in Structural Formula 1 and Structural Formula 2 include alkyl groups such as a methyl group, an ethyl group, and a propyl group, and aryl groups such as a phenyl group. Of these, it is preferable that R ₁ is a methyl group. In addition, examples of the unsaturated aliphatic group represented by R ₂ in Structural Formula 1 and 2 include alkenyl groups such as a vinyl group, an allyl group, and a 3-butenyl group. Of these, it is preferable that R ₂ is a vinyl group.

In structural formula 1, linear organopolysiloxanes with n=0 have unsaturated aliphatic groups only at both ends, while linear organopolysiloxanes with n=1 or more have unsaturated aliphatic groups at both ends and in the side chain. The linear organopolysiloxanes of structural formula 2 have unsaturated aliphatic groups only in the side chain. The (A) component may be used alone or in combination of two or more types.

Furthermore, when the component (A) is used in the elastic layer of the fixing member, from the viewpoint of moldability, the viscosity is preferably 100 mm ² /s or more and 50,000 mm ² /s or less.
(b) an organopolysiloxane having active hydrogen bonded to a silicon atom;
The crosslinking agent for component (a), which is an organopolysiloxane having active hydrogen atoms bonded to silicon atoms, is a crosslinking agent that forms a crosslinked structure through a hydrosilylation reaction with unsaturated aliphatic groups in component (a) due to the catalytic action of component (c), which will be described later.
As the component (b), any organopolysiloxane having a Si-H bond can be used, and examples thereof include the following organopolysiloxanes (iii) to (iv). Note that the component (b) may be used alone or in combination of two or more types.

(iii) From the viewpoint of forming a crosslinked structure by reaction with an organopolysiloxane having an unsaturated aliphatic group, an organopolysiloxane having an average of 3 or more hydrogen atoms bonded to silicon atoms per molecule.
(iv) Organopolysiloxanes in which the organic group bonded to the silicon atom is an unsubstituted hydrocarbon group that does not contain an unsaturated aliphatic group as described above. The unsubstituted hydrocarbon group is preferably a methyl group.
In the organopolysiloxane which is component (b), the siloxane skeleton (-Si-O-Si-) may be linear, branched or cyclic. The Si-H bond may be present in any siloxane unit in the molecule. Specifically, linear organopolysiloxanes shown in the following structural formulas 3 and 4 can be used as component (b).

In structural formula 3 and structural formula 4, _R1 each independently represents an unsubstituted hydrocarbon group not containing an unsaturated aliphatic group, p represents an integer of 0 or greater, and q represents an integer of 1 or greater. Examples of the unsubstituted hydrocarbon group not containing an unsaturated aliphatic group include the same groups as those represented by _R1 in structural formulas 1 and 2, and a methyl group is preferable.

The amount of component (b) is preferably 0.1 to 20 parts by mass, and more preferably 0.3 to 10 parts by mass, per 100 parts by mass of component (a).

(c) Hydrosilylation Catalyst As the hydrosilylation (addition curing) catalyst, for example, a platinum compound can be used. Specific examples include platinum carbonylcyclovinylmethylsiloxane complex and 1,3-divinyltetramethyldisiloxane platinum complex. The amount of component (c) blended is preferably 0.0001 to 0.1 parts by mass, and more preferably 0.001 to 0.05 parts by mass, per 100 parts by mass of component (a).

(d) Curing Retarder A curing retarder can be blended to adjust the curing reaction rate of hydrosilylation (addition curing). Specific examples of the curing retarder include 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane, 2-methyl-3-butyn-2-ol, and 1-ethynyl-1-cyclohexanol. The blending amount of component (d) is preferably 0.01 to 2 parts by mass, and more preferably 0.05 to 1 part by mass, per 100 parts by mass of component (a).

(3-2) Thermally Conductive Filler The thermally conductive filler may be at least one type selected from the group consisting of metal oxide particles and metal particles at least a portion of the surface of which is composed of a metal oxide.
Such thermally conductive fillers include, for example, magnesium oxide, silicon metal, alumina and zinc oxide.
The thermal conductivity of magnesium oxide is 45 to 60 W/m·K, that of metal silicon is 150 W/m·K, that of zinc oxide is 50 W/m·K, and that of alumina is 40 W/m·K.
Since the thermal conductivity of silicone rubber that does not contain a filler is about 0.2 W/m·K, by incorporating these thermally conductive fillers in the silicone rubber, the thermal conductivity of the elastic layer can be increased.
The content of the thermally conductive filler in the elastic layer is preferably 10% or more and 55% or less in terms of volume percentage of the total filler content. If the total filler content is 10% or more in volume percentage, the thermal conductivity of the elastic layer made of silicone rubber can be sufficiently increased, and if it is 55% or less, the elastic layer made of silicone rubber can fully exhibit its elastic function as rubber.

(3-3) Charge Control Agent The metal oxide particles as the thermally conductive filler described above and metal particles at least part of whose surface is composed of a metal oxide can have a positive charge. The order of ease of being positively charged is considered to be magnesium oxide, metal silicon at least part of whose surface is oxidized, zinc oxide, and alumina.
Examples of negatively chargeable charge control agents capable of imparting a positive charge to these thermally conductive fillers include salicylic acid metal complexes and azo metal complexes.
Among them, azo metal complexes are more preferable from the viewpoint of heat resistance. Examples of azo metal complexes include iron-based and chromium-based complexes. As for heat resistance, since the temperature of the fixing member at the non-paper passing portion may reach about 240°C, heat resistance that is stable at a temperature range higher than that is desirable, and it is particularly desirable that the thermal decomposition starting temperature of the charge control agent is 300°C or higher. Specific examples of charge control agents having such heat resistance include compounds represented by the following structural formulas (i) and (ii).

The compound according to structural formula (i) is commercially available, for example, under the trade name "S-215S" (manufactured by Orient Chemical Industries, Ltd.), and the compound according to structural formula (ii) is commercially available, for example, under the trade name "S-34" (manufactured by Orient Chemical Industries, Ltd.) Other candidates for negatively charged charge control agents include those that are mainly used in toners.
The amount of the charge control agent is preferably 1 part by weight or more and 5 parts by weight or less per 100 parts by weight of the silicone rubber. When the amount is 1 part by weight or more, the effect of increasing the breaking energy is obtained. When the amount is 5 parts by weight or less, sufficient hardness is obtained in the non-paper passing portion of the silicone rubber elastic layer.
The dispersion state of the charge control agent is not particularly limited, but it is more preferable that the charge control agent be dispersed in the silicone rubber in the form of particles having a diameter of 1 μm or less, since this may facilitate the effect of increasing the breaking energy.

(3-4) Manufacturing method of the elastic layer As a non-limiting manufacturing method of the elastic layer according to one embodiment of the present disclosure, for example, it can be formed through a process of curing a layer of an addition curing type liquid silicone rubber mixture (hereinafter also referred to as a "mixture layer"). Here, it is preferable to charge the outer surface of the mixture layer prior to curing the mixture layer. This allows the thermally conductive filler in the mixture layer to be aligned in the thickness direction, and the thermal conductivity of the elastic layer in the thickness direction can be further increased.
As an embodiment for arranging the thermally conductive filler in the mixture layer in the thickness direction, a method using a corona charger will be described. Corona charging methods include a scorotron method having a grid electrode between the corona wire and the charged body, and a corotron method not having a grid electrode. From the viewpoint of controllability of the surface potential of the charged body, the scorotron method is preferred.

As shown in Figures 2A and 2B, the corona charger 2 includes blocks 201 and 202, shields 203 and 204, and a grid 206. A discharge wire 205 is stretched between the blocks 201 and 202. A high voltage is applied to the discharge wire 205 by a high voltage power supply (not shown), and the ion flow obtained by discharge to the shields 203 and 204 is controlled by applying a high voltage to the grid 206, thereby charging the surface of the mixture layer 401. At this time, since the base 3 or the core 1 holding the base 3 is grounded (not shown), it is possible to generate a desired electric field in the mixture layer 401 by controlling the surface potential of the surface of the mixture layer 401.

2A, the corona chargers 2 are disposed closely facing each other along the width direction of the mixture layer 401. Then, a voltage is applied to the grid 206 of the corona charger 2, and in a discharged state, the core 1 is rotated in the direction of the arrow A2 to rotate the base 3 having the mixture layer 401 on its outer circumferential surface at 100 rpm for 20 seconds, for example, to charge the outer surface of the mixture layer 401. The distance between the outer surface of the mixture layer 401 and the grid 206 can be 1 mm to 10 mm.
In this way, the surface of the mixture layer 401 is charged, and an electric field is generated in the mixture layer 401. As a result, as shown in FIG. 7, among the thermally conductive fillers in the mixture layer 401, for example, small particle size fillers 701 having a circle equivalent diameter of less than 5 μm can be aligned in the thickness direction of the mixture layer 401. On the other hand, among the thermally conductive fillers, for example, large particle size fillers 703 having a circle equivalent diameter of 5 μm or more hardly change position in the mixture layer 401, and are polarized to generate a local electric field between the large particle size fillers. This electric field can align the small particle size fillers located between the large particle size fillers. In FIG. 7, the arrow 705 indicates the thickness direction of the mixture layer. Here, the reason why the small particle size fillers can be highly aligned while suppressing the alignment of the large particle size fillers by charging the surface of the mixture layer 401 is considered to be as follows. That is, even if the surface of the mixture layer 401 is charged, it is considered difficult to apply a force to the large particle size filler 703 that is sufficient to move the position of the large particle size filler 703 in the mixture layer by dielectrophoresis. However, dielectric polarization occurs in the large particle size filler 703, and a local electric field is formed between the large particle size fillers 703. As a result, the local electric field acts on the small particle size filler 701 present between the large particle size fillers 703, and it is considered that the small particle size filler 701 is highly aligned between the large particle size fillers 703. As a result, it is considered that a heat conduction path is formed in the thickness direction of the mixture layer, in which the large particle size fillers 703 are connected by the small particle size fillers.

From the viewpoint of generating effective electrostatic interactions in the thermally conductive filler, the voltage applied to the grid 206 is preferably in the range of 0.3 kV to 3 kV, and particularly 0.6 kV to 2 kV, in absolute value. Note that in Figures 2A and 2B, an example is shown in which the surface of the mixture layer 401 is positively charged, but if the sign of the applied voltage is made the same as the sign of the voltage applied to the wire, the electric field direction will be reversed whether the voltage is negative or positive, but the effect obtained will be the same.

The ease of arranging the small particle size filler in the mixture layer 401 is considered to depend, for example, on the dielectric constant of the binder raw material and the thermally conductive filler. For example, when there is a large difference between the dielectric constant of the binder raw material and the dielectric constant of the thermally conductive filler, the small particle size filler can be arranged with a relatively small applied voltage. Therefore, it is preferable to appropriately adjust the voltage applied to the grid depending on the combination of the material used for the binder raw material and the type of thermally conductive filler.

The range of potential control in the longitudinal direction of the surface of the mixture layer 401 is preferably equal to or larger than the paper passage area of the fixing member. For example, the configuration shown in FIG. 2A can be used, and while a voltage is being applied to the grid 206, the entire mixture layer 401 can be charged by rotating the substrate having the mixture layer 401 around its central axis as the axis of rotation. The rotation speed of the fixing belt is preferably 10 rpm to 500 rpm, and the treatment time is preferably 5 seconds or more from the viewpoint of stably forming an arrangement of small particle size fillers. From the above, the formation of an arrangement of small particle size fillers can be controlled by controlling the surface potential and the time for applying the electric field.

The discharge wire 205 may be made of stainless steel, nickel, molybdenum, tungsten, or other suitable materials, but it is preferable to use tungsten, which is one of the most stable metals. The shape of the discharge wire 205 stretched inside the shields 203 and 204 is not particularly limited, and may be, for example, a sawtooth shape or a circular cross-sectional shape when the discharge wire is cut vertically (circular cross-sectional shape). The diameter of the discharge wire 205 (at the cut surface when cut vertically to the wire) is preferably 40 μm or more and 100 μm or less. If the diameter of the discharge wire 205 is 40 μm or more, it is easy to prevent the discharge wire from being cut or broken due to the collision of ions caused by the discharge. Also, if the diameter of the discharge wire 205 is 100 μm or less, it is easy to apply an appropriate voltage to the discharge wire 205 when obtaining a stable corona discharge, and it is easy to prevent the generation of ozone.

2B , the flat grid 206 can be disposed between the discharge wire 205 and the mixture layer 401 disposed on the substrate 3. Here, from the viewpoint of making the charged potential on the surface of the mixture layer 401 uniform, the distance between the surface of the mixture layer 401 and the grid 206 is preferably in the range of 1 mm to 10 mm.
Incidentally, when the mixture layer 401 does not contain a charge control agent, the above-mentioned charging process may result in the formation of convex bumps on the outer surface of the mixture layer 401. It is believed that this is because unevenness in the surface potential occurs when the outer surface of the mixture layer 401 is charged, and the convex bumps are formed in parts with locally low surface potential. It is believed that the cause of the unevenness in the surface potential is shear unevenness in the preparation process of the addition-curing liquid silicone rubber mixture and variation in the surface composition of the thermally conductive filler. It is speculated that shear unevenness and variation in the surface composition of the thermally conductive filler cause parts with locally high charge in the thermally conductive filler, causing the surface potential of those parts to be low.
However, when an addition-curing liquid silicone rubber mixture according to the present disclosure that contains a charge control agent is used, the occurrence of convex bumps on the outer surface can be prevented. This is believed to be because the charge control agent makes the charge amount of the thermally conductive filler uniform, making it difficult for locally high charge amounts to occur.

(4) Surface Layer of Fixing Member The surface layer may be, for example, a fluororesin layer, more specifically, a layer made of any of the following resins: Examples of fluororesins include tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer (PFA), polytetrafluoroethylene (PTFE), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP).
Furthermore, the surface layer may contain a filler for the purpose of improving thermal properties and abrasion resistance, within a range that does not impair moldability and toner releasability.
The thickness of the surface layer (e.g., fluororesin layer) is preferably 10 μm or more and 100 μm or less. If the thickness of the surface layer is 10 μm or more, sufficient durability can be obtained. If the thickness is 100 μm or less, the excellent flexibility of the silicone rubber-containing elastic layer can be utilized.

The method for forming the surface layer is not particularly limited, and for example, the following method 1) or 2) can be used.
1) Method of forming a surface layer by covering with a fluororesin tube Fig. 4 is a schematic diagram for explaining the method 1) above. An adhesive is applied to the surface of an elastic layer 4 made of silicone rubber to form an adhesive layer 5. The adhesive will be described later. A fluororesin molded into a tube shape is covered and laminated on the outer surface of this adhesive layer 5 as a surface layer 6. The inner surface of the fluororesin tube can be activated and its adhesiveness improved by previously treating it with sodium, excimer laser, ammonia, or the like.

As the adhesive, it is preferable to use an addition-curing silicone rubber containing a self-adhesive component. Specifically, this silicone rubber can contain an organopolysiloxane having multiple unsaturated aliphatic groups in the molecular chain, such as vinyl groups, a hydrogenorganopolysiloxane, and a platinum compound as a crosslinking reaction catalyst. This silicone rubber cures by an addition reaction. Any known adhesive made of this type of addition-curing silicone rubber can be used.

This is not necessary when the base 3 is a core metal capable of retaining its shape, but when using a thin-walled base such as a resin belt or metal sleeve used in a belt-shaped fixing member, it is preferable to hold the base 3 by fitting it to the core to prevent deformation during processing. The method of covering the fluororesin tube is not particularly limited, but a method of covering it with an adhesive as a lubricant, a method of expanding the fluororesin tube from the outside, and the like can be used. After covering, the excess adhesive remaining between the elastic layer 4 made of silicone rubber and the fluororesin tube 6 can be removed by squeezing it out using a means not shown. The thickness of the adhesive layer 5 after being squeezed out is preferably 20 μm or less. If the thickness of the adhesive layer is 20 μm or less, it is easy to suppress the hardness increase of the fixing member, and when used as a fixing member, it has excellent conformity to the unevenness of the paper. Next, the adhesive layer is hardened by heating for a predetermined time with a heating means such as an electric furnace, and both ends are processed to the desired length as necessary to obtain the fixing member according to the present disclosure.

2) Formation of the surface layer by fluororesin coating Fluororesin coating processing for forming the surface layer can be performed by electrostatic coating of fluororesin fine particles or spray coating of fluororesin paint. When using electrostatic coating, first, electrostatic coating of fluororesin fine particles is performed on the inner surface of the mold, and the mold is heated to the melting point of the fluororesin or higher to form a thin film of fluororesin on the inner surface of the mold. After that, the inner surface is subjected to an adhesive treatment, and then the substrate is inserted. Between the substrate and the fluororesin, the addition-curing liquid silicone rubber mixture according to the present disclosure, which contains at least a thermally conductive filler, a negatively charged charge control agent, and, for example, an addition-curing liquid silicone rubber component, is injected. After that, the rubber mixture is cured and then demolded to obtain the fixing member according to the present disclosure.

(5) Manufacturing Method of Fixing Member The manufacturing method of the fixing member according to the present disclosure includes, for example, the following step of forming an elastic layer containing silicone rubber.
A step of preparing a liquid silicone mixture containing a liquid silicone polymer, a thermally conductive filler dispersed in the liquid silicone polymer, and a charge control agent having a negative charge with respect to the thermally conductive filler;
forming a layer of said liquid silicone mixture on a surface of a substrate having an endless shape;
a step of disposing a corona charger across the width of the substrate and facing the surface of the layer of the liquid silicone mixture; a step of charging the surface of the layer of the liquid silicone mixture using the corona charger;
curing the layer of the liquid silicone mixture to obtain the elastic layer. The method for producing a fixing member according to the present disclosure may also include the following steps.
A step of laminating an adhesive layer and a surface layer (e.g., a fluororesin surface layer) on an elastic layer containing silicone rubber.
In addition, in the manufacturing method of the fixing member according to the present disclosure, the order of each process can be appropriately set, and these processes can be performed simultaneously (in parallel). When forming the surface layer, the above-mentioned method for forming the adhesive layer and the surface layer can be used.

(6) Fixing device in which the fixing member of the present disclosure is arranged The fixing device according to the present disclosure will be described. The fixing device according to the present disclosure is a fixing device used in an electrophotographic image forming apparatus, in which the fixing member according to the present disclosure is arranged as a fixing belt, a fixing roller, or a fixing film. Examples of the electrophotographic image forming apparatus include electrophotographic image forming apparatuses having a photoconductor, a latent image forming means, a means for developing the formed latent image with toner, a means for transferring the developed toner image to a recording material, and a means for fixing the toner image on the recording material.

FIG. 5 is a schematic diagram showing the configuration of one embodiment of a fixing device according to the present disclosure.
FIG. 5 is a schematic diagram showing an example of a fixing belt-pressure roller type thermal fixing device using a ceramic heater as a heating body. In FIG. 5, 501 is a fixing belt according to one embodiment of the present disclosure. The fixing belt 501 is loosely fitted around a belt guide 503. A pressure roller 509 is disposed below the fixing belt 501 so as to face the fixing belt 501. The pressure roller 509 has a core metal 509a and an elastic layer 509b containing silicone rubber provided on the outer circumferential surface of the core metal 509a. The pressure roller 509 is rotatably held by bearings between the front side chassis side plate and the rear side chassis side plate (not shown). The pressure roller 509 may be provided with a surface layer (not shown) containing a fluororesin such as PFA (tetrafluoroethylene/perfluoroalkyl ether copolymer) in order to improve the toner releasability of the surface.
Pressure springs (not shown) are disposed between both ends of the pressure rigid stay 507 and spring bearing members (not shown) on the chassis side of the fixing device, respectively, to apply a downward force to the pressure rigid stay 507. As a result, a fixing nip N is formed between the lower surface of the ceramic heater 505 disposed on the lower surface of the belt guide 503 and the upper surface of the pressure roller 509, with the fixing belt 501 sandwiched therebetween.
The pressure roller 509 is driven to rotate in the direction indicated by an arrow 511 by a driving means (not shown). A rotational force acts on the fixing belt 501 due to friction between the outer surfaces of the pressure roller 509 and the fixing belt 501 caused by the rotational drive of the pressure roller 509. The fixing belt 501 rotates around the belt guide 503 in the direction indicated by an arrow 513 at a speed corresponding to the rotational speed of the pressure roller 509, while the inner surface of the fixing belt 501 slides in close contact with the lower surface of the ceramic heater 505 at the fixing nip portion N.
Based on a print start signal, the pressure roller 509 starts to rotate, and the ceramic heater 505 starts to heat. After that, the recording medium S carrying the unfixed toner image t as the heated material is introduced between the fixing belt 501 and the pressure roller 509 in the fixing nip portion N with the toner image carrying surface side facing the fixing belt 501. Then, the recording medium S is in close contact with the lower surface of the ceramic heater 505 via the fixing belt 501 in the fixing nip portion N, and moves through the fixing nip portion N together with the fixing belt 501. In the process, the heat of the fixing belt 501 is applied to the recording medium S, and the toner image t is fixed on the surface of the recording medium S. The recording medium S that has passed through the fixing nip portion N is separated from the outer surface of the fixing belt 501 and is transported.
The ceramic heater 505 as a heating element has, for example, a heater substrate 505a made of aluminum nitride, a heat generation layer 505b provided on the surface of the heater substrate 505a along its length, and a protective layer 505c formed of a material with excellent heat resistance such as glass or fluororesin provided thereon. The heat generation layer 505b is made of an electric resistance material such as Ag/Pd (silver/palladium) and is provided by screen printing or the like to a thickness of 10 μm and a width of 1 to 5 mm.
When electricity is applied to both ends of the heat generating layer 505b of the ceramic heater 505, the heat generating layer 505b generates heat, and the temperature of the ceramic heater 505 rises. The ceramic heater 505 is fixed by fitting the protective layer 505c upward into a groove formed along the longitudinal direction of the belt guide 503 at approximately the center of the lower surface of the belt guide 503. In the fixing nip N that contacts the fixing belt 501, the surface of the sliding member 505d of the ceramic heater 505 and the inner peripheral surface of the fixing belt 501 contact and slide against each other. A temperature detection element 515 for controlling the temperature of the ceramic heater 505 is provided on the protective layer 505c.
As described above, in the thermal fixing device using the fixing belt 501 according to the present disclosure as a heating belt, the heat supplied to the fixing belt by the heating means (heater) arranged in contact with the inner circumferential surface of the fixing belt 501 easily flows in the thickness direction of the elastic layer, so that the energy input to the fixing belt can be efficiently utilized for thermal fixing of unfixed toner.
Although a fixing device having a fixing belt and a pressure roller has been given as an example here, the fixing device according to the present disclosure need only have the fixing member according to the present disclosure as a fixing belt, fixing roller or fixing film, and is not limited to that shown in FIG.

According to one aspect of the present disclosure, it is possible to obtain an electrophotographic fixing member having excellent durability, in which the elastic layer does not break or undergo plastic deformation even with long-term use, despite being provided with an elastic layer containing a thermally conductive filler. According to another aspect of the present disclosure, it is possible to obtain a fixing device and an electrophotographic image forming apparatus capable of stably forming high-quality electrophotographic images.

The present disclosure will now be described in more detail with reference to examples.
First, a method for determining whether a charge control agent is negatively or positively charged with respect to a thermally conductive filler will be described. A solution in which a charge control agent is dissolved is spin-coated to form a film made of the charge control agent. A thermally conductive filler is placed on the film, and the charge control agent and the thermally conductive filler are rubbed together by moving the film or the like. The surface potential of the film at that time is measured, and it is possible to determine whether the film is negatively or positively charged from the result of whether it is negatively or positively charged.

Next, a method for measuring the thermal decomposition onset temperature of the charge control agent will be described. Using a thermogravimetric analyzer (TGA/SDTA851e, manufactured by METTLER TOLEDO), the temperature was raised from 40°C to 400°C at 3°C/min. The onset temperature of the sample weight curve during the temperature rise (the intersection of the tangent at the inflection point of the curve and the extension of the baseline) was taken as the thermal decomposition onset temperature.

Next, a method for evaluating the dispersion state of the charge control agent will be described. First, the cross section of the elastic layer is polished using an ion beam. For example, a cross-section polisher can be used for polishing the cross section with an ion beam. Polishing the cross section with an ion beam can prevent the filler from falling off the sample and the abrasive from being mixed in, and can also form a cross section with few polishing marks. The cross section of the elastic layer formed in this way was evaluated using time-of-flight secondary ion mass spectrometry (TOF-SIMS) by sputter cleaning the sample surface and then measuring the distribution of ions thought to be derived from the charge control agent.

Example 1
(1) Preparation of an addition-curing liquid silicone rubber mixture;
First, 100 parts by mass of a silicone polymer (viscosity 5000 ^mm2 /s, hereinafter referred to as "Vi") was prepared as component a, which had vinyl groups, which are unsaturated aliphatic groups, only at both ends of the molecular chain and had methyl groups as unsubstituted hydrocarbon groups containing no other unsaturated aliphatic groups.
Next, 271.4 parts by mass of magnesium oxide powder (product name: SL-WR, manufactured by Konoshima Chemical Co., Ltd.) was weighed out and added to Vi.
Next, 3 parts by mass of sodium=bis{1-[(5-chloro-2-hydroxy-phenyl)azo]-phenylcarbamoyl)-2-naphtholato}iron(III) (product name: S-215S, manufactured by Orient Chemical Industry Co., Ltd., thermal decomposition starting temperature 312° C.), which is a negatively charged charge control agent for the magnesium oxide powder, was weighed out and added to Vi.
Next, 0.1 parts by mass of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (product name: SIT7900.0, manufactured by Gelest Co., Ltd.), which is a cure retarder as component (d), was added to the mixture of Vi and magnesium oxide powder.
Next, 0.03 parts by mass of a hydrosilylation catalyst (platinum catalyst, product name: SIP6829.2, manufactured by Gelest Co., Ltd.) as component c was added to the mixture of Vi, magnesium oxide powder, and cure retarder.
Furthermore, 1.2 parts by mass of a silicone polymer (viscosity 30 ^mm2 /s, hereafter referred to as "SiH") with a linear siloxane skeleton and having active hydrogen groups bonded to silicon only on the side chains was weighed out as component b. This was added to a mixture of Vi, magnesium oxide powder, negative charge control agent, cure retarder, and platinum catalyst, and thoroughly mixed to obtain an addition-curing liquid silicone rubber mixture containing 43 volume % magnesium oxide powder.

(2) Formation of an elastic layer;
Next, a fixing belt was produced as follows using the obtained magnesium oxide powder and an addition-curing liquid silicone rubber mixture containing a negatively charged charge control agent.
An endless sleeve made of electroformed nickel having an inner diameter of 30 mm, a width of 400 mm, and a thickness of 40 μm was prepared as a substrate. During the series of manufacturing steps, the endless sleeve (endless sleeve) was handled with a core inserted therein.
First, a primer (product name: DY39-051 A/B, manufactured by Dow Corning Toray Co., Ltd.) was applied almost uniformly to the outer peripheral surface of the substrate, and after the solvent was dried, the substrate was baked in an electric furnace at a temperature of 160° C. for 30 minutes.
The silicone rubber mixture was applied to this primer-treated substrate by ring coating to a thickness of 300 μm to form a mixture layer.
Next, a corona charger 2 was arranged so that its longitudinal direction was approximately parallel to the axial direction (longitudinal direction) of the substrate 3 on which the mixture layer was formed (see FIG. 2). Then, while the substrate on which the mixture layer was formed was being rotated at 141 rpm, the surface of the mixture layer was charged using the corona charger.
The charging conditions were as follows:
・Current supplied to the corona charger wire: AC 0.7Hz ±150μA (square wave)
Grid electrode potential: AC 0.7Hz ±900V (square wave)
Charging time: 160 seconds Distance between grid electrode and substrate 1 with silicone rubber mixture applied before curing: 3 mm

Next, the substrate having the charged surface mixture layer was placed in an electric furnace and heated at 160° C. for 1 minute to cure the mixture layer, and then heated at 200° C. for 30 minutes to cure the mixture layer. Thus, an elastic layer was formed. In the obtained elastic layer, the charge control agent was dispersed in the form of particles with a diameter of 1 μm.
(3) Evaluation of elastic layer characteristics

(3-1) Measurement of hardness and breaking energy of elastic layer The hardness of the elastic layer was measured in peak hold mode using a micro rubber hardness tester (MD-1 Type C, manufactured by Kobunshi Keiki Co., Ltd.). The measurement was performed by contacting the indenter of the micro rubber hardness tester with the surface of the elastic layer opposite to the substrate side at a total of 40 points, including 8 points in the circumferential direction of the elastic layer and 5 points in the direction perpendicular to the circumferential direction, and the average value of the measured values was used as the value of this evaluation. The hardness measurement was performed in an environment with a temperature of 23°C and a relative humidity of 40%.
The breaking energy of the elastic layer was measured by cutting out a measurement sample from the elastic layer using a punching die specified in Japanese Industrial Standards (JIS) K 6251-8, and measuring the rubber thickness near the center, which was the measurement point. Next, the measurement sample was tested at room temperature (25°C) using a tensile tester (product name: Strograph EII-L1, manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a tensile speed of 200 mm/min. The breaking energy was measured by creating a graph from the measurement results with the sample strain on the horizontal axis and the tensile stress on the vertical axis, and integrating the measurement data in the range from 0% strain to the strain at which the rubber broke. As a result, the hardness of the elastic layer was 74° and the breaking energy was 23 kJ/ ^m2 .

(3-2) Heat Capacity per Unit Volume of Elastic Layer The heat capacity per unit volume, CV, was calculated from the following formula.
CV = CP × ρ
In the formula, Cp represents the specific heat at constant pressure (J/(kg·K)) and ρ represents the density (kg/m ³ ).
The values of the specific heat at constant pressure and the density in the above formula were determined by the following method.
・Specific heat at constant pressure CP
The constant pressure specific heat of the elastic layer was measured using a differential scanning calorimeter (product name: DSC823e, manufactured by Mettler Toledo K.K.).
Specifically, aluminum pans were used as the sample pan and the reference pan. First, as a blank measurement, both pans were empty and kept at a constant temperature of 15°C for 10 minutes, then the temperature was raised to 215°C at a heating rate of 10°C/min, and the temperature was kept at a constant temperature of 215°C for another 10 minutes. Next, 10 mg of synthetic sapphire with a known constant pressure specific heat was used as a reference material, and the same program was used for measurement. Next, 10 mg of a measurement sample, the same amount as the reference sapphire, was cut out from the elastic layer portion, set in the sample pan, and measurement was performed using the same program. These measurement results were analyzed using specific heat analysis software attached to the differential scanning calorimeter, and the constant pressure specific heat CP at 25°C was calculated from the average value of five measurement results. As a result, the constant pressure specific heat of the silicone rubber-containing elastic layer was 1.12 J/(g·K).
- Density ρ
The density of the elastic layer was measured using a dry automatic density meter (product name: Accupyc 1330-01, manufactured by Shimadzu Corporation).
Specifically, a 10 cm ³ sample cell was used, and a sample was cut out from the elastic layer so as to fill approximately 80% of the cell volume. The mass of this sample was measured and then the sample was placed in the sample cell.
The sample cell was set in the measuring section of the device, and after gas replacement, helium was used as the gas for measurement, and volume measurements were performed 10 times. The density of the sample was calculated from the mass of the sample and the measured volume for each measurement, and the average value was calculated. As a result, the density of the silicone rubber-containing elastic layer was 2.05 g/cm ^3. The heat capacity per unit volume CV was calculated from the constant pressure specific heat CP and density ρ of the silicone rubber-containing elastic layer thus obtained, and was 2.30 MJ/m ³ ·K.

(3-3) Thermal Conductivity in the Thickness Direction of Elastic Layer The thermal conductivity λ of the elastic layer in the thickness direction was calculated from the following formula.
λ = α × Cp × ρ
In the formula, λ is the thermal conductivity of the elastic layer in the thickness direction (W/(m·K)), α is the thermal diffusivity in the thickness direction (m2/s), Cp is the specific heat at constant pressure (J/(kg·K)), and ρ is the density (kg/ ^m3 ). Here, the specific heat at constant pressure Cp and density ρ of the elastic layer were converted into units from the values obtained by the above-mentioned method. The thermal diffusivity in the thickness direction was obtained by the following method.
- Thermal diffusivity α
The thermal diffusivity in the thickness direction of the elastic layer was measured at room temperature (25°C) using a periodic heating method thermal property measuring device (product name: FTC-1, manufactured by ULVAC-RIKO Co., Ltd.). The elastic layer was cut into sample pieces with an area of 8 x 12 mm with a cutter to prepare a total of five samples, and the thickness of each sample was measured. Next, each sample was measured five times in total, and the average value (m ² /s) was calculated. The thermal conductivity λ of the silicone rubber-containing elastic layer was calculated from the unit-converted constant pressure specific heat Cp (J/(kg·K)) and density ρ (kg/m ³ ) of the elastic layer, and the measured thermal diffusivity α (m ² /s), and was found to be 1.3 W/(m·K).
(4) Preparation of Fixing Belt A substrate having an elastic layer was prepared in the same manner as in (1) to (3) above.
Next, while rotating the base so that the surface of the elastic layer was rotating at a speed of 20 mm/sec in the circumferential direction, the surface of the elastic layer was irradiated with ultraviolet light using an ultraviolet lamp installed at a distance of 10 mm from the surface of the elastic layer. A low-pressure mercury ultraviolet lamp (product name: GLQ500US/11, manufactured by Toshiba Lighting & Technology Corporation (formerly: Harrison Toshiba Lighting Corporation)) was used as the ultraviolet lamp, and irradiation was performed in the air at room temperature (temperature of 25° C.) for 6 minutes.

Next, an addition-curing silicone rubber adhesive (product name: SE1819CV A/B, manufactured by Dow Corning Toray Co., Ltd.) was applied to the ultraviolet-irradiated surface of the elastic layer to a thickness of 20 μm. A fluororesin tube (product name: KURANFL ON-LT, manufactured by Kurabo Industries, Ltd.) with an inner diameter of 29 mm and a thickness of 30 μm was then laminated onto the adhesive to produce an endless belt. This endless belt was then heated at a temperature of 200°C for 1 hour in an electric furnace to cure the adhesive and fix the surface layer made of the fluororesin tube onto the elastic layer. Next, both ends of the endless belt with the fluororesin tube fixed onto the elastic layer were cut to obtain a fixing belt with a width of 341 mm.

(5) Evaluation of Fixing Belt (5-1) Evaluation of Pressure Resistance Durability of Elastic Layer The fixing belt produced in (4) above was cut open in a direction perpendicular to its circumferential direction to form a single sheet, and four samples measuring 50 mm in length x 50 mm in width were cut out from the sheet.
The pressure resistance durability of this sample was evaluated using a jig shown in FIG. 6. Specifically, the sample 601 was placed on a stainless steel plate 605 placed on a heater 603 so that the surface layer side of the sample 601 was in contact with the stainless steel plate 605. The temperature of the surface 601-1 of the elastic layer of the sample 601 was adjusted to 240° C. using a thermistor 607 placed on the surface 601-1. The pressing roller 609 (width 10 mm, diameter 15 mm) was pressed on the surface 601-1 with a load of 10 N, while rotating in the direction of the arrow 611 and reciprocating on the surface 601-1 in the direction of the arrow 613. In this way, the time until the elastic layer of the sample 601 was broken by visual observation (hereinafter, also referred to as the “breakage time”) was measured. The average value of the breakage times of the four samples was calculated, and was used as the evaluation result of the pressure resistance durability of the elastic layer of the fixing belt according to this embodiment.

(5-2) Actual Machine Evaluation (i) The fixing belt prepared in the same manner as in (4) above was attached to the fixing device of a full-color electrophotographic image forming apparatus (product name: imageRUNNERADVANCE C5051; manufactured by Canon Inc.). Using this multifunction machine, cyan solid images were continuously formed on 300,000 sheets of A4-sized plain paper. The 10th image (hereinafter, "initial image") and the 300,000th image (hereinafter, "durability image") were visually observed, and the presence or absence of gloss unevenness was evaluated according to the following criteria.
Rank A: No uneven gloss caused by poor fixing is observed.
Rank B: Slight unevenness in gloss due to poor fixing is observed.
Rank C: Gloss unevenness due to poor fixing is clearly observed.
(ii) The fixing belt used in the above (i) for forming 300,000 images was removed from the fixing device. The hardness was measured by contacting the surface of the surface layer of the removed fixing belt with the indenter of a micro rubber hardness tester (MD-1 Type C, manufactured by Kobunshi Keiki Co., Ltd.). The hardness was measured in an environment of a temperature of 23° C. and a relative humidity of 40%. The difference in hardness between the surface of the surface layer of the fixing belt before being used for forming 300,000 images, which was measured in advance by the same method as above, was determined.

[Examples 2 to 3]
A liquid addition-curing silicone rubber mixture was prepared in the same manner as in Example 1, except that the amount of the charge control agent was 1 part by mass or 5 parts by mass. An elastic layer was formed on a substrate in the same manner as in Example 1, except that this addition-curing liquid silicone rubber mixture was used. The properties of the obtained elastic layer were evaluated in the same manner as in Example 1. A fixing belt was also produced and evaluated in the same manner as in Example 1, except that the addition-curing liquid silicone rubber mixture prepared above was used. The results of the property evaluation of the elastic layer and the evaluation results as a fixing belt are shown in Table 1.
Example 4
An addition-curing liquid silicone rubber mixture was prepared in the same manner as in Example 1, except that aluminum 3,5-di-tert-butylsalicylate (product name: E-101, manufactured by Orient Chemical Industry Co., Ltd., thermal decomposition onset temperature 203° C.) was used as the charge control agent. An elastic layer was formed on a substrate in the same manner as in Example 1, except that this addition-curing liquid silicone rubber mixture was used. The properties of the obtained elastic layer were evaluated in the same manner as in Example 1. A fixing belt was also produced and evaluated in the same manner as in Example 1, except that the addition-curing liquid silicone rubber mixture prepared above was used. The results of the property evaluation of the elastic layer and the evaluation results as a fixing belt are shown in Table 1.

Example 5
An addition-curing liquid silicone rubber mixture was obtained in the same manner as in Example 1, except that a silicone polymer (viscosity 20,000 ^mm2 /s, hereafter referred to as "Vi-2") having vinyl groups, which are unsaturated aliphatic groups, at both molecular chain terminals and in side chains, and having methyl groups as unsubstituted hydrocarbon groups containing no other unsaturated aliphatic groups, was used as component a, and 162.2 parts by mass of metal silicon powder (product name: #600WB, manufactured by Kinsei Matec Co., Ltd.) was used as the thermally conductive filler. The volume proportion of the metal silicon powder in the resulting addition-curing liquid silicone rubber mixture was 40% by volume.
Except for using this addition-curing liquid silicone rubber mixture, an elastic layer was formed on a substrate in the same manner as in Example 1. The properties of the resulting elastic layer were evaluated in the same manner as in Example 1. In addition, a fixing belt was produced and evaluated in the same manner as in Example 1, except for using the addition-curing liquid silicone rubber mixture prepared above. The results of the property evaluation of the elastic layer and the evaluation results as a fixing belt are shown in Table 1.

Example 6
An addition-curing liquid silicone rubber mixture was obtained in the same manner as in Example 5, except that bis[1-(5-chloro-2-hydroxyphenylazo)-2-naphtholato]chromium(III)iron (trade name: S-34, manufactured by Orient Chemical Industry Co., Ltd., thermal decomposition onset temperature 325°C) was used as the charge control agent. An elastic layer was formed on a substrate in the same manner as in Example 1, except that this addition-curing liquid silicone rubber mixture was used. The properties of the obtained elastic layer were evaluated in the same manner as in Example 1. A fixing belt was also produced and evaluated in the same manner as in Example 1, except that the addition-curing liquid silicone rubber mixture prepared above was used. The results of the property evaluation of the elastic layer and the evaluation results as a fixing belt are shown in Table 1.

Example 7
An addition curing type liquid silicone rubber mixture containing 35% by volume of zinc oxide powder was obtained in the same manner as in Example 1, except that 317 parts by mass of zinc oxide powder was used as the thermally conductive filler. An elastic layer was formed on a substrate in the same manner as in Example 1, except that this addition curing type liquid silicone rubber mixture was used and the surface of the addition curing type liquid silicone rubber mixture layer was not subjected to an electrostatic charging treatment. The obtained elastic layer was subjected to a characteristic evaluation in the same manner as in Example 1. In addition, a fixing belt was produced and evaluated in the same manner as in Example 1, except that the addition curing type liquid silicone rubber mixture prepared above was used and the surface of the addition curing type liquid silicone rubber mixture layer was not subjected to an electrostatic charging treatment. The results of the characteristic evaluation of the elastic layer and the evaluation results as a fixing belt are shown in Table 1.

Example 8
An addition-curing liquid silicone rubber mixture containing 46% by volume of alumina powder was obtained in the same manner as in Example 5, except that 350 parts by mass of alumina powder was used as the thermally conductive filler. An elastic layer was formed on a substrate in the same manner as in Example 7, except that this addition-curing liquid silicone rubber mixture was used. The properties of the obtained elastic layer were evaluated in the same manner as in Example 1. A fixing belt was also produced and evaluated in the same manner as in Example 7, except that the addition-curing liquid silicone rubber mixture prepared above was used. The results of the property evaluation of the elastic layer and the evaluation results as a fixing belt are shown in Table 1.

Example 9
Except for not carrying out the electrostatic charging treatment on the surface of the addition-curing liquid silicone rubber mixture layer, an elastic layer was formed on a substrate in the same manner as in Example 1. The properties of the resulting elastic layer were evaluated in the same manner as in Example 1.
A fixing belt was produced and evaluated in the same manner as in Example 1, except that the surface of the addition-curing liquid silicone rubber mixture layer was not subjected to an electrostatic charging treatment. The results of the evaluation of the properties of the elastic layer and the evaluation results as a fixing belt are shown in Table 1.

Example 10
Except for not carrying out the electrostatic charging treatment on the surface of the addition-curing liquid silicone rubber mixture layer, an elastic layer was formed on a substrate in the same manner as in Example 5. The properties of the resulting elastic layer were evaluated in the same manner as in Example 1.
A fixing belt was also produced and evaluated in the same manner as in Example 5, except that the surface of the addition-curing liquid silicone rubber mixture layer was not subjected to the charging treatment.
Table 1 shows the results of the evaluation of the properties of the elastic layer and the evaluation results as a fixing belt.

Comparative Example 1
An addition-curing liquid silicone rubber mixture containing 43 volume % magnesium oxide powder was obtained in the same manner as in Example 1, except that no charge control agent was used. An elastic layer was formed on a substrate in the same manner as in Example 1, except that this addition-curing liquid silicone rubber mixture was used. The properties of the obtained elastic layer were evaluated in the same manner as in Example 1. A fixing belt was also produced and evaluated in the same manner as in Example 1, except that the addition-curing liquid silicone rubber mixture prepared above was used. The results of the property evaluation of the elastic layer and the evaluation results as a fixing belt are shown in Table 1.

Comparative Example 2
An addition-curing liquid silicone rubber mixture containing 40 volume percent metal silicon powder was obtained in the same manner as in Example 5, except that no charge control agent was used. An elastic layer was formed on a substrate in the same manner as in Example 5, except that this addition-curing liquid silicone rubber mixture was used. The properties of the obtained elastic layer were evaluated in the same manner as in Example 1. A fixing belt was also produced and evaluated in the same manner as in Example 5, except that the addition-curing liquid silicone rubber mixture prepared above was used. The results of the property evaluation of the elastic layer and the evaluation results as a fixing belt are shown in Table 1.

Comparative Example 3
An addition-curing liquid silicone rubber mixture containing 35 volume % zinc oxide powder was obtained in the same manner as in Example 7, except that no charge control agent was used. An elastic layer was formed on a substrate in the same manner as in Example 7, except that this addition-curing liquid silicone rubber mixture was used. The properties of the obtained elastic layer were evaluated in the same manner as in Example 7. A fixing belt was also produced and evaluated in the same manner as in Example 7, except that the addition-curing liquid silicone rubber mixture prepared above was used. The results of the property evaluation of the elastic layer and the evaluation results as a fixing belt are shown in Table 1.

Comparative Example 4
An addition-curing liquid silicone rubber mixture containing 46 volume % alumina powder was obtained in the same manner as in Example 8, except that no charge control agent was used. An elastic layer was formed on a substrate in the same manner as in Example 8, except that this addition-curing liquid silicone rubber mixture was used. The properties of the obtained elastic layer were evaluated in the same manner as in Example 8. A fixing belt was also produced and evaluated in the same manner as in Example 8, except that the addition-curing liquid silicone rubber mixture prepared above was used. The results of the property evaluation of the elastic layer and the evaluation results as a fixing belt are shown in Table 1.

[Evaluation results]
The evaluation results of the Examples and Comparative Examples shown in Table 1 above will be described.
The elastic layers according to Examples 1 to 10, which contain a negatively charged charge control agent, have a larger breaking energy and improved pressure resistance durability compared to the elastic layers according to the comparative examples. Furthermore, even after forming images on 300,000 sheets, the elastic layers of the fixing belts according to Examples 1 to 10 did not show any breakage in the non-paper passing portion of the fixing belt, which is particularly prone to breakage due to contact with the edge of the paper.

3: Substrate 4: Elastic layer 4a: Silicone rubber 4b: Thermally conductive filler 4c: Negatively charged charge control agent 6: Surface layer

Claims (9)

An electrophotographic fixing member having, in this order, a substrate, an elastic layer on the substrate, and a surface layer,
the elastic layer includes a silicone rubber and a thermally conductive filler dispersed in the silicone rubber;
The thermally conductive filler is a metal oxide particle or a metal particle at least a part of whose surface is composed of a metal oxide,
The electrophotographic fixing member is characterized in that the elastic layer further contains a charge control agent which is negatively chargeable with respect to the thermally conductive filler. The electrophotographic fixing member according to claim 1, wherein the thermally conductive filler is at least one selected from the group consisting of magnesium oxide, metal silicon, alumina, and zinc oxide. The electrophotographic fixing member according to claim 1 or 2, wherein the thermal decomposition starting temperature of the charge control agent is 300°C or higher. The electrophotographic fixing member according to any one of claims 1 to 3, wherein the charge control agent is an azo metal complex. The electrophotographic fixing member according to claim 4, wherein the azo metal complex is a compound represented by the following structural formula (i) or (ii):

The electrophotographic fixing member according to any one of claims 1 to 5, wherein the amount of the charge control agent is 1 part by mass or more and 5 parts by mass or less per 100 parts by mass of the silicone rubber. The electrophotographic fixing member according to any one of claims 1 to 6, wherein the charge control agent is dispersed in silicone rubber in the form of particles having a diameter of 1 μm or less. A fixing device comprising a heating member and a pressure member disposed opposite to the heating member, wherein at least one of the heating member and the pressure member is an electrophotographic fixing member having a substrate, an elastic layer on the substrate, and a surface layer in this order,
the elastic layer includes a silicone rubber and a thermally conductive filler dispersed in the silicone rubber;
The thermally conductive filler is a metal oxide particle or a metal particle at least a part of whose surface is composed of a metal oxide,
The elastic layer further comprises a charge control agent that is negatively charged with respect to the thermally conductive filler.
A fixing device comprising: An electrophotographic image forming apparatus including a fixing device,
The fixing device includes a heating member and a pressure member disposed opposite the heating member,
At least one of the heating member and the pressure member is an electrophotographic fixing member having a substrate, an elastic layer on the substrate, and a surface layer in this order,
the elastic layer includes a silicone rubber and a thermally conductive filler dispersed in the silicone rubber;
The thermally conductive filler is a metal oxide particle or a metal particle at least a part of whose surface is composed of a metal oxide,
The elastic layer further comprises a charge control agent having a negative charging property with respect to the thermally conductive filler.

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