JP2015197603A - Fixing member and fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing member improving fixing properties by improving followability to recesses of a paper surface by softening a hard fluororesin layer according to the surface shape thereof, while retaining releasability as an advantage of the surface layer composed of the fluororesin layer.SOLUTION: An elastic layer and a surface layer composed of fluororesin are sequentially laminated on the outer peripheral layer of a cylindrical base material, where the surface of the surface layer includes dimples. The dimple has a reduced value depth Rvk of 0.8 μm or more and 2.0 μm or less as a lubricity evaluation parameter of a plateau structure surface, and a relationship between the reduced valley depth Rvk and the projection crest height Rpk of the surface of the surface layer is 1.8≤Rvk/Rpk≤20.0.

Description

  The present invention relates to a fixing member and a fixing device used in a heat fixing device of an image forming apparatus using an electrophotographic system.

  As a fixing member used in a heat fixing device of an electrophotographic image forming apparatus such as a printer, a copier, or a facsimile, there are a belt-shaped member and a roller-shaped member. For the belt base material, a heat-resistant resin material such as polyimide or a metal material such as nickel electroforming or SUS is used. An elastic layer made of heat-resistant rubber such as silicone rubber is provided on the belt-shaped or roller-shaped base material. By providing an elastic layer, when a recording material such as paper to which toner is transferred passes through a nip portion formed by press-fitting two opposing fixing members, that is, a heating member and a pressure member, Due to the flexibility of the rubber constituting the elastic layer, the surface of the fixing member is deformed along the toner image on the recording material, and the contact area is widened to reduce the contact thermal resistance. Thus, the toner can be uniformly melted and fixed on the recording material, and a high-quality image with high gloss can be obtained without uneven fixing.

  In such a fixing member, a method of impregnating the surface of the elastic layer with silicone oil has been used in order to ensure releasability with respect to the toner. However, in this method, silicone oil must be replenished in order to maintain releasability, and a fixing member that does not use silicone oil is required due to problems such as a burden on user maintenance and an increase in system cost. It had been. Therefore, a fixing member that does not use silicone oil has been proposed in which a release layer is formed on the surface of the elastic layer (Patent Document 1). Materials constituting such a release layer include tetrafluoroethylene resin (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin (PFA), and tetrafluoroethylene / hexafluoropropylene. Fluorine resins such as copolymer resins (FEP) have been used.

  A fixing member having a release layer provided on the surface of the elastic layer described above, that is, as a release layer forming means in the fixing roller and the fixing belt, is mainly composed of the above-mentioned fluororesin on the surface of the elastic layer. A method of coating a dispersion (water-based dispersion paint) or powder paint and heating it to the melting point or higher, or a method of coating a separately prepared fluororesin tube on the surface of the elastic layer is used. Yes.

  However, the fluororesin essential for ensuring releasability has a problem that the heating efficiency of the fixing member is low because the thermal conductivity is low. In addition, a fixing member in which a fluororesin layer harder than the rubber constituting the elastic layer is formed on the surface of the elastic layer is necessary for reducing the contact thermal resistance with the recording material described above due to the influence of the fluororesin layer. Since flexibility, which is a characteristic, is impaired, there is a problem that defects such as uneven fixing occur.

  In the electrophotographic image forming apparatus, toner images are formed on various recording materials. Among them, the most frequently used paper as a recording material has irregularities due to paper fibers on the surface, and toner images are formed on the irregularities. Is formed. That is, with respect to the toner on the recording material having a large surface undulation, the portion that is “convex” due to the surface undulation adheres well to the surface of the fixing member and transfers heat and pressure well. On the other hand, since the adhesion to the surface of the fixing member covered with the hard fluororesin layer is deteriorated in the portion located in the “concave”, the degree of toner crushing in each portion is different. In some cases, local fixing deterioration and density unevenness were caused.

Japanese Patent Laid-Open No. 10-148988

  As a result of studies by the present inventors for such problems, the following findings were obtained. That is, it has been found that by forming dimples on the surface layer of the fixing member, the micro hardness of the surface of the fixing member is lowered, that is, the surface is softened. It was also found that the toner image fixed on the recording material by the electrophotographic image forming apparatus equipped with the fixing member can be reduced in density by a rubbing test when evaluating fixability.

  An object of the present invention is to form a dimple on the surface of a hard fluororesin layer to soften the surface layer while maintaining the releasability, which is an advantage of the surface layer made of fluororesin, so that the concave portion on the paper surface can be obtained. It is an object of the present invention to provide a fixing member having improved followability and improved fixing performance. Another object of the present invention is to provide a fixing device capable of stably forming a high-quality electrophotographic image without fixing unevenness.

  In order to achieve the above object, a first invention is an electrophotographic fixing member in which an elastic layer and a surface layer made of a fluororesin are sequentially laminated on an outer peripheral surface of a cylindrical base material, and the surface of the surface layer is The dimple has a projecting valley depth Rvk of 0.8 μm or more and 2.0 μm or less, which is a lubricity evaluation parameter of the plateau structure surface, and the projecting valley depth Rvk and the surface layer surface The relationship of the protruding peak height Rpk is 1.8 ≦ Rvk / Rpk ≦ 20.0.

  According to a second aspect of the present invention, in the fixing member according to the first aspect, the dimple has an average maximum length D of 15 μm at a depth of 1.0 μm from a position of zero height of the surface roughness data of the surface layer. The variation coefficient CV = σ / D defined as a ratio of the standard deviation σ of the maximum length distribution and the average maximum length D is less than 1.0.

  According to a third invention, in the fixing member according to the first or second invention, the thickness of the surface layer is 8 μm or more and 25 μm or less.

  According to a fourth invention, in the fixing member according to the third invention, the surface layer is formed by heat-curing a coating film formed by applying a fluororesin dispersion. And

  According to a fifth invention, in the fixing member according to the fourth invention, the dimple is formed by applying a dispersion containing a fluororesin and a fine powder wax that decomposes below the melting temperature of the fluororesin. The film is formed by decomposing the fine wax when the coating film is heated and cured.

  A sixth invention is a fixing device having any one of the fixing members according to the first to fifth inventions.

  According to the present invention, it is possible to provide a fixing member that can contribute to the stable formation of an electrophotographic image without fixing unevenness. Furthermore, according to the present invention, it is possible to obtain a fixing device that can contribute to stably forming a high-quality electrophotographic image without fixing unevenness.

1 is a schematic configuration diagram (cross-sectional view) of a fixing device according to the present invention. The upper left figure of this drawing is a partially enlarged view (cross-sectional view) of the fixing belt. It is a bearing curve obtained from the Example which concerns on this invention. It is the binarized image obtained from the Example which concerns on this invention. It is a figure which shows the relationship between Rvk and surface micro hardness in an Example and a comparative example.

  Hereinafter, the present invention will be described in more detail.

  In the fixing member according to the present invention, an elastic layer and a surface layer made of fluororesin are sequentially laminated on the outer peripheral surface of a cylindrical base material, and the surface layer has dimples. The dimples lubricate the surface of the plateau structure. The protruding valley depth Rvk, which is a property evaluation parameter, is 0.8 μm or more and 2.0 μm or less, and the relationship between the protruding valley depth Rvk and the protruding peak height Rpk of the surface layer is 1.8. ≦ Rvk / Rpk ≦ 20.0.

[Unevenness of surface layer]
Here, the numerical range of the projecting valley depth Rvk is defined by the balance between the flexibility and releasability of the fixing member. The lower limit value of Rvk, “0.8 μm”, is the minimum required for a fixing member having a surface layer made of a fluororesin on the surface of the elastic layer to lower the surface micro hardness and soften the surface layer. Value. When Rvk is less than 0.8 μm, the surface layer is insufficiently flexible, so that the effect of improving the fixability cannot be obtained. On the other hand, when Rvk exceeds “2.0 μm”, the surface layer retains the toner adhering to the valleys of the dimples, so that the release performance of the surface layer is impaired.

  The numerical range of “Rvk / Rpk”, which is the ratio of the protruding valley depth Rvk to the protruding peak height Rpk on the surface of the surface layer, is the limit of the improvement in the flexibility of the fixing member and the realizable unevenness. It is specified from the viewpoint. When the value of “Rvk / Rpk” is less than “1.8”, the above-described softening is hindered by the convex portions present at the same level as the dimples composed of the concave portions, and a sufficient fixing effect is improved. I can't get it. Also, reducing Rpk does not impede flexibility, but it can be realized even when the convex portion is reduced and Rpk is sufficiently reduced within a range not exceeding the upper limit value of Rvk of 2.0 μm. The upper limit value of “Rvk / Rpk” is defined as “20.0” as a value.

  The dimples preferably have an average maximum length D of 15 μm or more and 26 μm or less at a depth of 1.0 μm from a position of zero height in the surface roughness data of the surface layer. If it is 15 μm or more, the toner hardly adheres to the dimples and the release performance of the surface layer is not impaired. Further, if it is 26 μm or less, since the ratio of flat portions where no dimples are present is relatively large, there is no problem in terms of durability of the surface layer, that is, wear resistance strength.

  Further, the average maximum length D is preferably such that a variation coefficient CV = σ / D defined as a ratio of the standard deviation σ of the maximum length distribution and the average maximum length D is less than 1.0. Within this range, it is possible to determine the quality of releasability and durability from the average value without being greatly affected by the dispersion of the distribution with respect to the average value.

  Next, embodiments of the present invention will be described with reference to the drawings.

<Fixing device>
The fixing device according to the present invention will be described. A fixing device according to the present invention is a fixing device used in an electrophotographic image forming apparatus, in which the fixing member of the present invention as described above is arranged as a fixing belt or a fixing roller. The electrophotographic image forming apparatus includes a photosensitive member, a latent image forming unit, a unit for developing the formed latent image with toner, a unit for transferring the developed toner image to a recording material, and fixing the toner image on the recording material. An electrophotographic image forming apparatus having means and the like can be mentioned.

  FIG. 1 is a sectional view showing one embodiment of the fixing device according to the present invention. In the following description, regarding the fixing device and the members constituting the fixing device, the longitudinal direction is a direction orthogonal to the recording material conveyance direction on the surface of the recording material. The short side direction is a direction parallel to the conveyance direction of the recording material on the surface of the recording material. The length is a dimension in the longitudinal direction. The width is a dimension in the short direction. Regarding the recording material, the width direction is a direction orthogonal to the conveying direction of the recording material on the surface of the recording material. The width is a dimension in the width direction.

  Such a fixing device includes a ceramic heater 1 as a heating body, a heater holder 2 as a support member, an endless fixing belt 3 as a heating rotator, a pressure roller 4 as a pressure rotator (backup member), and the like. have.

  The heater holder 2 is formed in a substantially bowl shape with a rigid heat-resistant material. A ceramic heater (hereinafter referred to as “heater”) is supported by a groove provided in the lower surface of the center in the short direction of the heater holder.

  The fixing belt 3 is loosely fitted around the outer periphery of the heater holder that supports the heater. Further, grease is applied to the inner peripheral surface (inner surface) of the fixing belt in order to improve the slidability with the heater.

  The pressure roller 4 is disposed below the fixing belt and in parallel with the fixing belt. The fixing belt and the heater press the fixing belt to the heater side by a predetermined pressing mechanism. As a result, the outer peripheral surface (surface) of the pressure roller is brought into contact with the outer peripheral surface (surface) of the fixing belt in a pressurized state, and an elastic layer described later is elastically deformed to thereby form a surface between the surface of the fixing belt and the surface of the pressure roller. A fixing nip portion (nip portion) N having a predetermined width is formed therebetween.

<Fixing member>
A fixing belt will be described in more detail as a representative example of an electrophotographic fixing member. The fixing belt 3 is an endless belt member having a multilayer structure in which a base material 5, an elastic layer 6, and a surface layer 7 are provided from the inside, as shown in a partially enlarged view of the fixing belt in FIG.

〔Base material〕
The cylindrical substrate is, for example, a thin endless belt having flexibility. As the base material, a thin heat resistant resin such as polyimide, polyamideimide, polyetheretherketone (PEEK) or the like is used. In order to further increase the thermal conductivity, a thin metal such as SUS or Ni may be used. Moreover, since it is necessary for the base material to satisfy the quick start property by reducing the heat capacity and to satisfy a certain mechanical strength, the thickness is desirably 5 μm or more and 100 μm or less, preferably 20 μm or more and 85 μm or less. .

[Elastic layer]
An elastic layer 6 made of silicone rubber or the like is formed on the outer peripheral surface of the base material. By providing the elastic layer, it is possible to obtain a high-quality image with high gloss and no fixing unevenness. That is, the elastic layer is deformed with respect to the toner on the recording material P and the shape of the paper fiber of the recording material P at the fixing nip portion N, and wraps an unfixed toner image, thereby uniformly heating the toner image. Will be able to give. If the thickness of the elastic layer is too thin, the elasticity cannot be exhibited sufficiently, so that an image having high gloss and no fixing unevenness cannot be obtained, and if it is too thick, the heat capacity of the fixing belt is increased and the quick start property is lowered. Therefore, the thickness of the elastic layer is desirably 30 μm or more and 500 μm or less, preferably 100 μm or more and 300 μm or less.

  The raw material of the silicone rubber that constitutes the elastic layer according to the present invention is a polymer having fluidity at room temperature, which cures by heating, has a moderately low hardness after curing, It is a liquid silicone rubber having sufficient heat resistance and deformation recovery ability to be used. In particular, it is more preferable to use an addition reaction cross-linkable liquid silicone rubber because it has excellent processability, high dimensional accuracy stability, and excellent productivity such that no reaction by-product is generated during the curing reaction.

  The liquid silicone rubber is a composition containing, for example, an organopolysiloxane (A liquid) and an organohydrogenpolysiloxane (B liquid), and further containing a catalyst and other additives as appropriate. Organopolysiloxane is a base polymer of a silicone rubber raw material, and its molecular weight is a number average molecular weight of 5,000 to 100,000 in order to bring the mixing and stirring of various fillers and the fluidity of the resulting mixture into an appropriate range. The weight average molecular weight is preferably 10,000 or more and 500,000 or less.

When the elastic layer is composed of silicone rubber alone, the thermal conductivity is low. When the thermal conductivity is low, it becomes difficult to effectively transfer heat from the heater to the recording material, and there is a risk of causing image defects such as uneven fixing due to insufficient heating. In order to increase the thermal conductivity of the elastic layer, a high thermal conductive filler (hereinafter referred to as “filler”) can be mixed in the silicone rubber constituting the elastic layer. As the filler, SiC, ZnO, Al ₂ O ₃ , AlN, MgO, carbon or the like is used. These fillers may be used alone or in combination of two or more. It is also possible to impart conductivity to the elastic layer by mixing these fillers into the elastic layer.

[Surface layer]
On the outer peripheral surface of the elastic layer, for example, a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin (PFA), a tetrafluoroethylene resin (PTFE), a tetrafluoroethylene / hexafluoropropylene copolymer resin ( A surface layer 7 made of a fluororesin such as FEP) is provided.

  The surface layer is preferably formed by heating a coating film formed by applying a fluororesin dispersion. Also, the dimples present in the surface layer heat cure the coating film formed by applying a dispersion containing a fluororesin and a fine wax that decomposes below the melting temperature of the fluororesin. It is preferably formed by decomposing the fine powder wax.

  The thickness of the surface layer is 1 μm or more and 50 μm or less, preferably 8 μm or more and 25 μm or less, and the elastic layer may be covered with a tube, or the surface of the elastic layer may be coated with a paint.

  When a PFA tube is used as the surface layer, the thickness of the PFA tube is preferably 15 μm or more because it is difficult to form and coat a uniform tube if the film thickness is 10 μm or less. On the other hand, since the tube itself is hard when the film thickness exceeds 25 μm, even if dimples are formed on the tube, the surface of the fixing belt cannot be made flexible enough to improve the followability to the paper surface and improve the fixing performance. For this reason, the film thickness of the PFA tube as the surface layer is preferably 25 μm or less.

  When the surface layer is a fluororesin coating layer, the surface hardness is less likely to be harder than that of the tube. The film thickness of the fluororesin coating layer is preferably 8 μm or more and 30 μm or less in practice because a problem arises in durability when the coating is thin and a problem occurs in uniformity when the coating is thick.

  Hereinafter, details of the present invention will be described by way of examples. First, the evaluation method in an Example and a comparative example is demonstrated.

<1. Method for analyzing surface shape of fixing member>
[1-1. Rvk and Rvk / Rpk]
For measuring the surface shape of the fixing member, a non-contact surface shape system (trade name: VertScan 2.0 / R3300G Lite, manufactured by Ryoka System Co., Ltd.) using an optical interference method is used.

  The protruding valley depth Rvk and protruding peak height Rpk, which are the lubricity evaluation parameters, are calculated from the bearing curve obtained by bearing analysis of the surface image of the fixing member. Here, the bearing curve in the measurement system is synonymous with the “load curve” defined in JIS B 0601: 2001, and is calculated from all measurement points of the surface height data at each pixel in the visual field image. It is. FIG. 2 shows a bearing curve obtained from the embodiment according to the present invention. The details of the protruding valley depth Rvk and protruding peak height Rpk are defined in JIS B 0671: 2002. The values of Rvk and “Rvk / Rpk” are the average values of five measurement values obtained at arbitrary five locations for each fixing member.

[1-2. Maximum dimple length)
The maximum length of dimples formed on the surface layer is calculated by hole analysis using the measurement system. Below, the specific method of a hole analysis is demonstrated.

  First, the surface height data of each pixel in the field-of-view image is subjected to curved surface correction for every 100 pixels of the block size, and -1.0 μm from the position of zero height of the obtained roughness data is binarized threshold value Set to. At this time, considering the possibility that the base surface (surface with zero height) at the time of binarization will contain the data of the hole itself, the surface that does not include the hole is increased by performing the “rebinarization” process. Set to zero plane. An area where pixels below the binarization threshold plane (−1.0 μm) are adjacent is labeled, and the maximum length is calculated for each label area. Here, the maximum length refers to the longest diameter passing through the center of gravity in one label region. As a reference for determining as a “hole” area among the found label areas, an upper limit value of the maximum length is set to 100 μm and a lower limit value is set to 1 μm.

  FIG. 3 shows a binarized image obtained from the embodiment according to the present invention. The average maximum length D is an average value of the maximum length of each “hole” region in the binarized image. The average maximum length D described in the examples and comparative examples is an average value of average maximum lengths obtained at arbitrary five positions in each fixing member. Further, a ratio between the standard deviation σ calculated from the maximum length distribution in the binarized image and the average maximum length D is defined as a variation coefficient CV = σ / D. As a precondition for the average maximum length D to be meaningful as an average value, CV representing a variation in the maximum length in the binarized image is less than 1.0.

<2. Measurement of surface layer hardness of fixing member>
The hardness of the surface layer of the fixing member is measured in a peak hold mode in an environment of a temperature of 23 ° C. and a relative humidity of 55% using a JIS-A type micro hardness meter MD-1 type (manufactured by Kobunshi Keiki Co., Ltd.). To do. The micro hardness tester is suitable for measuring the hardness of thin materials having a thickness of 2 mm or less, such as rubber materials, thermoplastic elastomers, and soft plastics. For a total of three points at both ends and the center of the fixing member at a position of 15 mm or more and 25 mm or less, a total of four points are measured every 90 ° in each point circumferential direction. The average value of the measured values obtained in total 12 points is defined as micro hardness.

  The lower the hardness of the silicone rubber of the elastic layer, the lower the surface micro hardness of the fixing member, so that the fixing property is improved. On the other hand, use a material with excessively low hardness to easily cause thermal deterioration. I can't. Microhardness is also related to the thickness of the elastic layer, and as the elastic layer thickness is increased, the microhardness can be lowered.However, as described above, if the thickness is too large, the heat capacity of the fixing member increases, and the quick start property is improved. descend.

  In the present invention, since the purpose is to compare the hardness (flexibility) due to the shape of the surface layer and the fixability, the rubber hardness and thickness of the elastic layer that can affect the micro hardness are determined in each of the examples and comparative examples. Identical. That is, as the elastic layers of the examples and comparative examples, a silicone rubber layer having a JIS-A hardness of 10 ° mixed with 50 parts by volume of SiC, which is a high thermal conductive filler, is provided with a thickness of 200 μm.

<3. Evaluation of fixing property of fixing member>
Fixability is evaluated in a laboratory maintained in an environment with a temperature of 15 ° C. and a relative humidity of 20%. The fixing member is mounted on the fixing device shown in FIG. 1, and this fixing device is incorporated in a laser beam printer capable of high-speed fixing at 60 sheets / minute (process speed 350 mm / sec). The surface temperature of the fixing belt during paper passing is set to 200 ° C. As a recording material, a basis weight of 75 g / cm ² and letter-sized rough paper (Fox River Bond manufactured by Fox River Paper) are used.

Here, the fixability is expressed as a density reduction rate (unit:%). The density reduction rate means that the fixing device fixes the recording material P in which nine unfixed images of 5 mm square of black and halftone (gray) are arranged on the letter size paper from the state where the fixing device is cooled, When the output image of the recording material P is rubbed under a certain condition, the density decrease obtained by subtracting the density after rubbing from the density before rubbing is calculated by dividing the density by the density before rubbing. At this time, the density of the image is measured by a density measuring device (manufactured by Macbeth). Therefore, the smaller the density reduction rate by this rubbing test, the better the fixability. This density reduction rate is calculated for all nine black and halftone images on letter-size paper, 250 sheets are continuously printed, and displayed according to the following evaluation criteria.
X: One or more locations where the density reduction rate exceeds 20% for 250 sheets.
○: Not applicable to the above “x”.

<4. Evaluation of releasability (fouling adhesion) of fixing member surface>
Evaluation of releasability is performed by incorporating the fixing member into a fixing device and a laser beam printer similar to the evaluation of fixing property. As the recording material, a basis weight of 68 g / cm ² , A4 size CS-680 (manufactured by Canon Inc.) is used. The surface of the fixing member after continuously printing 10,000 sheets is visually and visually observed with a VertScan, and the degree of contamination of the fixing member is evaluated based on the degree of contamination. That is, when the surface of the fixing member is easily soiled, the toner adheres to the dimples formed on the surface layer, so that the hole is closed. By comparing the results of the hole analysis before and after passing 10,000 sheets, You can know how difficult the surface is to get dirty. The evaluation criteria are as follows.
○: More than half of the dimples remain compared to before passing.
X: Dimples are less than half due to adhesion of paper dust and toner as compared to before paper passing.

<Example 1>
A cylindrical base material made of stainless steel (SUS) having an outer diameter of 30 mm, a thickness of 35 μm, and a length of 240 mm was used. A primer (trade name: DY39-051, manufactured by Toray Dow Corning Co., Ltd.) was applied to the outer peripheral surface of the substrate, and heat-treated in a hot air circulation oven at 150 ° C. for 30 minutes. On the outer peripheral surface of the base material after the primer treatment, a two-component addition-type liquid silicone rubber mixture was applied and formed as an elastic layer with a thickness of 200 μm by a ring coating method, and was cured by heating at 180 ° C. Thereafter, secondary curing was carried out in a hot air circulation oven at 200 ° C. for 4 hours to form an elastic layer.

  Next, the surface of the elastic layer was subjected to ultraviolet irradiation treatment (UV treatment). This UV treatment is not essential, but this treatment can reduce the tackiness of the silicone rubber surface and change the water repellency to make it hydrophilic. After this UV treatment, a solution obtained by diluting 3-aminopropyltriethoxysilane (trade name: KBE-903, manufactured by Shin-Etsu Chemical Co., Ltd.) with ethanol as a silane coupling agent to a mass ratio of 5 times is an elastic layer. The surface was coated with spray and allowed to air dry at room temperature. The film thickness after drying was set to 1.0 μm. Next, a primer (trade name: PR-990CL, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was applied by spraying so that the film thickness after drying was 3 μm. Then, it was heated and dried at a temperature of 150 ° C. for 10 minutes in a hot air circulating oven to form a coating film.

  Next, with respect to 100 parts by mass of a fluororesin dispersion paint (EM-500, manufactured by Mitsui DuPont Fluoro Chemical Co., Ltd.) in which PFA having an average particle size of 0.1 μm is dispersed in water, a fine powder type polyethylene wax (trade name) : Ceridust 3620, manufactured by Clariant Japan Co., Ltd.) was mixed to prepare a coating material for forming a surface layer. It was applied by spraying on the surface of the primer coating so that the thickness of the surface layer was 15 μm. Then, it was made to dry for 10 minutes at room temperature, and the coating film of the coating material for surface layer formation was formed.

  Thereafter, the coating film of the primer and the coating material for forming the surface layer was heated at 380 ° C. for 3 minutes by a hot air circulation type high temp oven to melt the fluororesin particles in the coating film. At that time, the fine powder wax mixed in the paint was melted and decomposed while being separated from the fluororesin, and dimples were formed on the surface layer composed of the fluororesin. Subsequently, it was rapidly cooled with cold air to obtain a fixing belt. The Rvk of the surface layer of the fixing belt thus formed was 1.2 μm, and “Rvk / Rpk” was 1.8. The average maximum length D of dimples formed on the surface layer at a depth of 1.0 μm from the position of zero height in the surface roughness data was 26 μm. Each evaluation result is shown in Table 2.

<Examples 2 to 5>
Fixing belts 2 to 5 were obtained and evaluated in the same manner as in Example 1 except that the type and amount of fine powder type wax were changed to the conditions shown in Table 1. The evaluation results are shown in Table 2.

<Comparative Example 1>
A fixing belt C1 was obtained and evaluated in the same manner as in Example 1 except that the fine powder type wax was not used. The evaluation results are shown in Table 2. Since fine powder wax was not mixed in the paint, dimples were not formed on the surface layer, and the average maximum length D at a depth of 1.0 μm from the position of zero height in the surface roughness data was 0 μm.

<Comparative Example 2>
As an aqueous fluororesin-dispersed paint, a fluororesin-dispersed paint (trade name: EM-500, manufactured by Mitsui / Dupont Fluoro Chemical Co., Ltd.) in which PFA having an average particle diameter of 0.1 μm is dispersed in water; A dispersion in which a fluororesin dispersion paint (trade name: FEP120-JR, manufactured by Mitsui DuPont Fluoro Chemical Co.) in which 2 μm FEP was dispersed in water was mixed at 7/3 (mass ratio) was used. A coating material for forming a surface layer was prepared by mixing 14 parts by mass of fine powder type polyethylene wax (trade name: Ceridust 3610, manufactured by Clariant Japan) with respect to 100 parts by mass of this dispersion. Except for these, the fixing belt C2 was obtained and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

<Comparative Example 3>
As an aqueous fluororesin-dispersed paint, a fluororesin-dispersed paint (trade name: EM-500, manufactured by Mitsui / DuPont Fluoro Chemical Co.) in which PFA having an average particle diameter of 0.1 μm is dispersed in water, and an average particle diameter of 10 μm A dispersion in which a fluororesin dispersion paint (trade name: PFA350-J, manufactured by Mitsui DuPont Fluoro Chemical Co.) in which PFA is dispersed in water was mixed at 8/2 (mass ratio) was used. Also, no fine powder type wax was used. Except for these, the fixing belt C3 was obtained and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2. Since fine powder wax was not mixed in the paint, dimples were not formed on the surface layer, and the average maximum length D at a depth of 1.0 μm from the position of zero height in the surface roughness data was 0 μm.

<Comparative Examples 4 and 5>
Fixing belts C4 and C5 were obtained and evaluated in the same manner as in Example 1 except that the type and amount of fine powder type wax were changed to the conditions shown in Table 1. The evaluation results are shown in Table 2.

[Relationship between Rvk and surface micro hardness]
FIG. 4 shows the relationship between Rvk and surface micro hardness in the configurations of the above examples and comparative examples. The micro hardness is expressed as a relative hardness ΔMD when the micro hardness of Comparative Example 1 having the smallest value of Rvk is zero. From this result, it can be seen that as the value of Rvk increases, the microhardness of the surface of the fixing member decreases, that is, the surface layer becomes softer.

  From these results, it is possible to follow the recesses on the paper surface by forming dimples on the surface of the hard fluororesin layer and softening it while maintaining the releasability that is an advantage of the surface layer made of the fluororesin layer. It can be seen that there is provided a fixing member that improves the fixing performance and improves the fixing performance.

DESCRIPTION OF SYMBOLS 1 Ceramic heater 2 Heater holder 3 Fixing belt 4 Pressure roller 5 Base material 6 Elastic layer 7 Surface layer

Claims (6)

  An elastic layer and a surface layer made of a fluororesin are sequentially laminated on the outer peripheral surface of the cylindrical base material, and the surface layer has dimples. The dimples are protruding valleys that are parameters for evaluating the lubricity of the plateau structure surface. The depth Rvk is 0.8 μm or more and 2.0 μm or less, and the relationship between the protruding valley depth Rvk and the protruding peak height Rpk of the surface layer is 1.8 ≦ Rvk / Rpk ≦ 20 A fixing member for electrophotography, wherein the fixing member is.   The dimple has an average maximum length D of 15 μm or more and 26 μm or less at a depth of 1.0 μm from the position of zero height in the surface roughness data of the surface layer, and a standard deviation σ and an average of the maximum length distribution The electrophotographic fixing member according to claim 1, wherein a coefficient of variation CV = σ / D defined as a ratio to the maximum length D is less than 1.0.   The fixing member for electrophotography according to claim 1, wherein the thickness of the surface layer is 8 μm or more and 25 μm or less.   The fixing member for electrophotography according to claim 3, wherein the surface layer is formed by heat-curing a coating film formed by applying a fluororesin dispersion.   When the dimple is heat-cured on a coating film formed by applying a dispersion containing a fluororesin and a fine powder wax that decomposes below the melting temperature of the fluororesin, the fine powder wax The fixing member for electrophotography according to claim 4, wherein the fixing member is formed by decomposing.   A fixing device comprising the electrophotographic fixing member according to claim 1.

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