JP6136636B2 - PRESSURE ROLLER, FIXING DEVICE AND IMAGE FORMING DEVICE EQUIPPED WITH THE SAME - Google Patents

Description

  The present invention relates to a pressure member having a fluororesin layer suitable for use in a copying machine, a printer, and the like, a fixing device using the pressure member, and an image forming apparatus.

  An electrophotographic color image forming apparatus such as a copying machine or a printer has an image forming unit that forms a color image composed of toners of four colors (cyan, magenta, yellow, and black) on a recording medium, and a formed color image. Is fixed on the recording medium. The fixing device includes a fixing member that heats and fixes a color image on the recording medium, and a pressure member that forms a fixing nip with the fixing member. When the recording medium passes through the fixing nip, unfixed toner is used. The formed color image is heated and pressed to be fixed on the recording medium.

  The fixing member and the pressure member have a width corresponding to the largest recording medium that can be output. Of course, an image may be output on a recording medium smaller than that. At that time, in the area where the recording medium passes through the nip (hereinafter referred to as a paper passing area), the thermal energy is taken away by the recording medium in order to fix the toner image, but the temperature drops, but the maximum width of the recording medium is exceeded. In this area (hereinafter referred to as a non-sheet passing area), the heat energy is not lost and the temperature is maintained, and a temperature difference occurs between the sheet passing area and the non-sheet passing area. In particular, the temperature difference becomes more prominent as the number of images to be output continuously increases, and the non-sheet passing area is raised to a temperature at which normal fixing processing cannot be performed unless output is temporarily stopped. If the image is abnormal or worse, the member may be damaged.

  Therefore, as a measure for solving the above problems, a low heat dissipation portion formed so as to form a concavo-convex surface and a high heat dissipation portion formed so as to form a smooth surface have an axial direction. Although a heat-dissipating roller (for example, Patent Document 1) is proposed, which is characterized by being arranged in parallel with each other, an increase in the number of parts increases the cost, which is not a preferable measure.

The pressure roller has a cored bar and an elastic layer containing carbon fiber, and pores are dispersed in the elastic layer (Patent Document 2, for example, Patent Document) 2) has been proposed, but the deterioration of image quality such as uneven gloss is recognized due to the hardness of the member being too large.
Further, the pressure roller has a cored bar and an elastic layer containing a needle-shaped filler, and pores are dispersed in the elastic layer (for example, Patent Document 2) However, since the hardness of the member is too large, deterioration of image quality such as uneven gloss is recognized.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a pressure roller that is excellent in heat transfer and can suppress image quality abnormalities such as uneven gloss and offset of an image. And

The said subject is solved by following (1)-(4) of this invention.
That is, the present invention provides (1) “a first elastic layer made of a heat-resistant rubber containing pores, a second elastic layer made of a heat-resistant rubber containing pores and a fibrous filler, and fluorine A release layer made of a resin is sequentially provided, and the volume content of the pores exceeds 10% in both the first and second elastic layers, and the second elastic layer is more than the first elastic layer. Also relates to a pressure roller characterized by a high thermal diffusivity.
Also, (2) “the pressure roller according to (1) above, wherein the thermal diffusivity in the in-plane axial direction and the circumferential direction of the second elastic layer is larger than the thermal diffusivity in the thickness direction”. Include.
The present invention also includes (3) “a fixing device including the pressure roller according to (1) or (2)”.
Further, the present invention includes (4) “an electrophotographic image forming apparatus having at least the fixing device according to (3)”.

The pressure roller according to the present invention (1) includes a first elastic layer made of a heat resistant rubber containing holes and a second elastic layer made of a heat resistant rubber containing holes and fibrous filler on a cored bar. In addition, a release layer made of a fluorine-based resin is sequentially provided, and the volume content of the voids exceeds 10% in both the first and second elastic layers, so that the entire roller surface has sufficient elasticity. In addition to contributing to the achievement of the necessary nip, it is possible to keep the hardness of the member low, and it is possible to suppress deterioration in image quality such as uneven gloss due to insufficient followability to the paper surface. Further, even if a temperature difference occurs between the paper passing area and the non-paper passing area of the fixing member due to the passage of the recording medium, the second elastic layer has a larger thermal diffusivity than the first elastic layer. While suppressing the temperature outflow to the gold, the surface temperature of the fixing member is averaged through the pressure roller, whereby abnormal overheating can be suppressed and image quality deterioration due to hot offset of toner can be suppressed.
In the pressure roller according to the present invention (2), in the first elastic layer, since the thermal diffusivity in the in-plane axial direction and the circumferential direction is larger than the thermal diffusivity in the thickness direction, the member surface is more efficiently The temperature can be averaged. Therefore, image quality abnormality (hot offset) due to abnormal temperature rise of the member can be suppressed even if many continuous outputs are performed.
In addition, since the fixing device according to the present invention (3) includes a pressure roller capable of efficiently soaking the fixing member, a fixing device capable of outputting a high-quality image can be provided. .
Furthermore, since the image forming apparatus according to the present invention (4) includes a fixing device that is excellent in productivity and can output a high-quality image, it is possible to provide an image forming apparatus that can output a high-quality image. it can.

(A) It is sectional drawing of the pressure roller in this invention. (B) It is an expanded sectional view of the pressure roller in this invention. 1 is a schematic configuration diagram for explaining a belt-type fixing device according to the present invention. 1 is a schematic configuration diagram showing an example of an image forming apparatus incorporating a fixing device according to the present invention.

Hereinafter, the present invention will be described in detail.
The pressure roller is provided in a fixing device of the image forming apparatus and plays a role of fixing the toner image on the transfer body in the image forming process. The form of the pressure roller for carrying out the present invention will be described with reference to the drawings.
As an example of the present invention, a cross-sectional view of a pressure roller 1 used for fixing toner is shown in FIG. The pressure roller 1 is formed by sequentially laminating an elastic layer 3 made of heat-resistant rubber and a release layer 4 made of a fluorine-based resin on a rigid metal core 2 such as a metal, The first elastic layer 3a is made of a heat-resistant rubber containing holes, and the second elastic layer 3b is made of a heat-resistant rubber containing holes 5 and fibrous fillers 6. These enlarged sectional views are shown in FIG.
The first elastic layer in the present invention is preferably 50 to 100 microns, and preferably has a thickness equal to or greater than that of the second elastic layer. If it is too thin, the effects of heat insulation and elasticity may not be obtained. If it is too thick, the cost may increase.
The second elastic layer is preferably 50 to 100 microns. If it is too thin, it is difficult to obtain a soaking effect. On the other hand, if it is too thick, it may be disadvantageous for image quality due to increased hardness.

Here, the heat resistant rubber will be described.
The heat resistant rubber in the present invention refers to a rubber that is not modified by heating up to about 200 ° C. Examples thereof include silicone rubber, fluorocarbon siloxane rubber, fluorosilicone rubber, fluoro rubber, and a mixture thereof.
The silicone rubber is not particularly limited as long as it has a siloxane structure, but includes a rubber having a structural unit represented by the following general formula (1).

(In the formula, R1 and R2 are unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bond, but they may be the same or different from each other, particularly carbon. Those having formulas 1 to 8 are preferred, and specific examples include an alkyl group, a cycloalkyl group, and an aryl group, with a methyl group, an ethyl group, and a phenyl group being particularly preferred.

  The fluorocarbon siloxane rubber is not particularly limited as long as it has a fluorocarbon siloxane structure. For example, the rubber | gum which has a structural unit represented by following General formula (2) is mentioned.

Wherein R1 is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, a cycloalkyl group or an aryl group, a and e are each independently 0 or 1, and b and d are And each independently represents an integer of 1 to 4, and c is an integer of 0 to 8.)

  The fluorosilicone rubber is not particularly limited as long as it has a fluoroorganosiloxane structure. For example, the rubber | gum which has a structural unit represented by following General formula (3) is mentioned.

（式中、ｎは、０〜２０の整数である。）

(In the formula, n is an integer of 0 to 20.)

  The fluororubber is not particularly limited as long as it is an elastic polymer polymerized using vinylidene fluoride or tetrafluoroethylene as a monomer component. For example, the rubber | gum which has the structural unit represented by the following general formula (4), general formula (5), or / and general formula (6) is mentioned.

（式中、ｍ、ｎは、いずれも整数である。）

(In the formula, m and n are both integers.)

DY35-2083 (Toray Dow Corning) etc. are mentioned as a commercial item of a silicone rubber compound.
Examples of commercially available fluorocarbon siloxane rubber compounds include SIFEL (registered trademark) series (Shin-Etsu Chemical Co., Ltd.).
Examples of commercially available fluorosilicone rubber compounds include FSL7641 (Momentive Performance Materials).
Commercially available fluororubber compounds include vinylidene fluoride (FKM) such as Viton (registered trademark) series (DuPont), tetrafluoroethylene propylene (FEPM) such as Afras (registered trademark) series (Asahi Glass), Kalrez (Registered trademark) (DuPont) series etc. Tetrafluoroethylene perfluoromethyl vinyl ether type (FFKM) is mentioned.

The heat-resistant rubber constituting the elastic layer 3 may be added with a filler, a reinforcing agent, a conductivity control agent, an anti-aging agent, a colorant, a plasticizer, a wax, an oil, a diluent, etc., as necessary. An agent may be added within a range not impeding the effects of the present invention.
Further, the heat-resistant rubber constituting the first elastic layer and the second elastic layer may be the same or different, but is preferably the same in consideration of adhesion between layers.

Here, the fluororesin will be described.
The fluororesin in the present invention is selected from, for example, tetrafluoroethylene-polyethylenefluorovinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polytetrafluoroethylene (PTFE), and the like. A fluorine resin, a mixture thereof, or a polymer in which these polymers are dispersed in a heat resistant resin or rubber can be applied.

Here, the holes will be described.
The pore in the present invention refers to a portion where gas exists in the elastic layer, and is a microcapsule structure microparticle in which a low-boiling substance is contained as a core by a thermoplastic shell or a bubble formed by a foaming agent In the case where (foamed particles) are expanded, the case where particles having a predetermined size such as a balloon made of resin or glass are mixed is included.
Examples of foaming agents include inorganic foaming agents such as sodium bicarbonate and ammonium bicarbonate, p, p′-oxybis (benzenesulfonylhydrazide), dinitrosopentamethylenetetramine, azodicarbonamide, azobisisobutyronitrile, etc. Organic foaming agents. Water can also be used as a foaming agent. Examples of the expanded particles include ADVANCEL EM series (Sekisui Chemical Co., Ltd.) and Matsumoto Microsphere (registered trademark) F series (Matsumoto Yushi Seiyaku Co., Ltd.) in which liquid low-boiling hydrocarbons are sealed with an acrylonitrile resin shell. Can be mentioned.
Examples of balloons include, for example, 3M (TM) Glass Bubbles (Sumitomo 3M) made of soda-lime borosilicate glass, Shirasu Balloon made of natural volcanic glassy deposits, and Matsumoto Microsphere made of acrylonitrile resin. (Registered trademark) F-DE series, MFL series (Matsumoto Yushi Seiyaku Co., Ltd.), and the like.
It is essential that the void volume content exceeds 10 vol%. This is because if the number of pores is smaller than this, the rubber hardness becomes too high during blending to obtain the necessary heat transfer. Further, if the voids exceed 50 vol%, the durability of the member becomes poor, such being undesirable.
The size of the hole may be a size that does not easily affect the surface shape of the pressure roller, that is, about 100 μm or less, but is preferably smaller than the length of the fibrous filler described later. The reason will be described later.
The amount of microballoon added is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, based on 100 parts by weight of silicone rubber. If the amount added is too small, the effects of heat insulation and elasticity may not be obtained. If the amount added is too large, the strength and surface smoothness of the molded member may be reduced.

Here, the fibrous filler will be described.
The fibrous filler in the present invention refers to a filler having an aspect ratio (length / diameter) of 5 or more and 100 or less. When the aspect ratio is less than 5, thermal conductivity anisotropy is hardly exhibited, and when it exceeds 100, dispersion is poor when mixed with rubber, or the surface of the elastic layer becomes rough.
In addition, as an average length of a fibrous filler, 30 um or more and 1 mm or less are preferable. If the length is less than 30 μm, thermal conductivity anisotropy is hardly exhibited, and if it exceeds 1 mm, poor dispersion occurs when mixed into rubber, and the surface of the elastic layer becomes undesirably rough. Moreover, as a magnitude relationship with the said void | hole, it is preferable that the length of a fibrous filler is larger than the diameter of a void | hole. This is because when the diameter of the pores is larger than the length of the fibrous filler, the fibrous filler becomes difficult to be oriented and desired heat transfer is difficult to obtain.
Examples of the fibrous filler include organic synthetic fibers such as polyamide, polyester, polyethylene, polypropylene, polyacryl, vinylon, aramid, rayon, glass, metal, metal oxide, carbon fiber, ceramic, Examples include inorganic fibers such as rock wool, and natural fibers such as cotton, hemp, pulp, silk, wool, collagen, chitin, chitosan, etc., but carbon fibers are advantageous in terms of heat transfer. Are preferably used.

Here, the carbon fiber will be further described.
The carbon fiber suitably used in the present invention is obtained by carbonizing a precursor (a material obtained by fiberizing a carbon fiber raw material), and various elastic moduli, strengths, and thermal conductivities are obtained depending on the conditions of the production method. . As an example, examples of pitch-based carbon fibers include GRANOC (registered trademark) milled XN-100-05M (50 μm), XN-100-15M (150 μm) (Nippon Graphite Fiber Co., Ltd.), and the like. Examples of the PAN-based carbon fiber include TORAYCA (registered trademark) milled fiber MLD-30, MLD-300, MLD-1000 (Toray Industries, Inc.), pyrofil chopped fiber (Mitsubishi Rayon), and the like. Pitch-based carbon fibers have a thermal conductivity of about 500 W / mK, but PAN-based carbon fibers have a maximum thermal conductivity of about 50 W / mK. Therefore, the heat transfer required for the configuration of the present invention can be satisfactorily ensured by using pitch-based carbon fibers having a thermal conductivity higher by one digit or more than PAN-based carbon fibers.
The amount of the fibrous filler added is preferably 1 to 60 parts by weight, more preferably 5 to 50 parts by weight with respect to 100 parts by weight of the silicone rubber. If the amount added is too small, there is often no improvement in thermal conductivity. If the amount is too large, the strength, flexibility and surface smoothness of the member may be reduced.

FIG. 2 shows an example of a fixing device 10 incorporating a pressure roller according to the present invention as an example of the fixing device of the present invention.
The fixing device 10 is provided with a fixing roller 11 having an elastic layer made of heat-resistant rubber on the surface of a cored bar, and a heating roller 13 having a halogen heater 12 built in the cored bar, and between these two rollers. Then, the fixing belt 14 is stretched. A pressure roller 15 according to the present invention is pressed against the fixing roller 11 via a fixing belt 14 to form a nip portion N where the recording medium P passes and the toner image T is fixed.
The fixing belt 14 is stretched without slack by urging the heating roller 13 away from the fixing roller 11 or by separately providing a tension roller (not shown). The surface temperatures of the heating roller 13 and the pressure roller 15 are detected by the thermistors 16a and 16b, and are controlled so as to reach a predetermined set temperature. Further, the surface temperature of the heating roller 13 may be detected by the thermistor 16 c on the fixing belt 14 stretched between the fixing roller 11 and the heating roller 13.

FIG. 3 shows an example of the image forming apparatus of the present invention.
The image forming apparatus 20 irradiates the electrostatic latent image by irradiating the belt fixing device 10, the photosensitive drum 21, the charging roller 22 that contacts and charges the photosensitive drum 21, and the laser beam L to the charged photosensitive drum 21. An exposure device (not shown) for forming, a developing roller 23 for developing the electrostatic latent image formed on the photosensitive drum 21 with toner to form a toner image, and a toner image formed on the photosensitive drum 21 as a recording medium A transfer roller 24 for transferring to P and a cleaning device 25 for cleaning the photosensitive drum 21 to which the toner image has been transferred are provided. Further, the image forming apparatus 20 includes a power source 26 that applies a DC voltage to the charging roller 22 and a surface potential meter 27 that measures the surface potential of the photosensitive drum 21.
Next, a method for forming an image using the image forming apparatus 20 will be described. First, a photosensitive layer (not shown) formed on the photosensitive drum 21 is uniformly charged using the charging roller 22 while rotating the photosensitive drum 21. Next, an electrostatic latent image is formed by irradiating the charged photosensitive layer with laser light L using an exposure apparatus (not shown). Further, using the developing roller 23, toner is attached to the electrostatic latent image formed on the photosensitive layer and developed to form a toner image T. Next, the toner image T formed on the photosensitive layer is transferred to the recording medium P using the transfer roller 24. Then, the toner image T transferred to the recording medium P is fixed using the belt fixing device 10.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited by these Examples.

[Example 1]
The pressure roller was produced through the following steps in sequence.
Step A: Silicone rubber primer DY39-051 (Toray Dow Corning) has a thickness of 0.5 μm on the surface of a stainless steel core having an outer diameter of 30 mm, a width of 320 mm, and a thickness of 0.5 mm. After coating in this manner, it was air-dried at room temperature for 30 minutes and heated at 150 ° C. for 30 minutes to form a first primer layer.
Step B: Matsumoto Microsphere (registered trademark) F65-DE (Matsumoto Yushi Seiyaku Co., Ltd., average particle size: 40-60 um) with respect to 100 parts by weight of addition-curable silicone rubber DY35-2083 (Toray Dow Corning) A rubber composition was prepared by adding 1.5 parts by weight. In addition, the void | hole volume content rate of this composition is 34 vol%.
Step C: Matsumoto Microsphere (registered trademark) F65-DE (Matsumoto Yushi Seiyaku Co., Ltd., average particle size: 40-60 um) with respect to 100 parts by weight of addition-curable silicone rubber DY35-2083 (Toray Dow Corning) A rubber composition was prepared by adding 1.5 parts by weight and 40 parts by weight of pitch-based carbon fiber XN-100-10M (Nippon Graphite Fiber Co., Ltd., aspect ratio: 10). In addition, the void | hole volume content rate of this composition is 30 vol%.
Step D: On the primer layer formed in Step A, the silicone rubber composition prepared in Step B was applied by dipping to form a 500 μm coating layer. Thereafter, the first elastic layer was formed through heating at 120 ° C. for 5 minutes.
Step E: On the first elastic layer formed in Step D, the silicone rubber composition prepared in Step C was applied by dipping to form a 500 μm coating layer. Thereafter, the second elastic layer was formed through heating at 120 ° C. for 10 minutes.
Step F: On the elastic layer formed in Step E, a PFA primer (Mitsui / Dupont Fluorochemical) was spray-coated, and this was naturally dried to form a second primer layer having a thickness of 2 μm. On the surface, PFA topcoat EM-500CL (Mitsui / DuPont Fluorochemical Co., Ltd.) is spray-coated to a film thickness of 20 μm to form a fluororesin coating layer, which is then placed in a firing furnace at 340 ° C. After being baked for 30 minutes, it was taken out from the furnace and allowed to cool to obtain a pressure roller.
In addition, when the 1st elastic layer and the 2nd elastic layer (each 300um thickness) were each shape | molded on the PTFE board in another process, it peeled off from the board, and the thermal diffusivity was measured with thermowave analyzer TA3 (Bethel company). The thermal diffusivity in the thickness direction was found to be greater in the second elastic layer than in the first elastic layer. Also in the following examples and comparative examples, the thermal diffusivity of the elastic layer was measured by the same method.

[Example 2]
Step B: A rubber composition was prepared in the same manner as in Example 1, except that F65-DE in Step B of Example 1 was changed to 2.0 parts by weight. In addition, the void | hole volume content rate of this composition is 48 vol%.
Step C: A rubber composition was prepared in the same manner as in Example 1, except that F65-DE in Step C of Example 1 was changed to 2.0 parts by weight. In addition, the void | hole volume content rate of this composition is 46 vol%.

[Example 3]
Step B: A rubber composition was prepared in the same manner as in Example 1, except that F65-DE in Step B of Example 1 was changed to 0.5 parts by weight. In addition, the void | hole volume content rate of this composition is 13 vol%.
Step C: A rubber composition was prepared in the same manner as in Example 1, except that F65-DE in Step C of Example 1 was changed to 0.5 parts by weight. In addition, the void | hole volume content rate of this composition is 15 vol%.
A pressure roller was obtained in the same process as in Example 1 except for the above process.

[Comparative Example 1]
Step B: A rubber composition was prepared in the same manner as in Example 1, except that F65-DE in Step B of Example 1 was changed to 0.3 parts by weight. In addition, the void | hole volume content rate of this composition is 8 vol%.
Step C: A rubber composition was prepared in the same manner as in Example 1, except that F65-DE in Step C of Example 1 was changed to 0.3 parts by weight. In addition, the void | hole volume content rate of this composition is 9 vol%.
A pressure roller was obtained in the same process as in Example 2 except for the above processes.

[Comparative Example 2]
A pressure roller was obtained in the same process as in Example 1 except that the B process and the D process were omitted and a 1000 μm coating layer was formed in the E process.

[Comparative Example 3]
A pressure roller was obtained in the same process as in Example 1 except that the C process and the E process were omitted and a 1000 μm coating layer was formed in the D process.

[Comparative Example 4]
Step B: Example B, except that 60 parts by weight of pitch-based carbon fiber XN-100-10M (Nippon Graphite Fiber Co., Ltd., aspect ratio: 10) was added and no hollow filler was added in Step B of Example 1. A pressure roller was obtained in the same process as in No. 1.

  The following evaluation was performed about the pressure roller produced in the said Examples 1-3 and Comparative Examples 1-4.

<Output of image for evaluation>
The fixing belts obtained in Examples 1 to 3 and Comparative Examples 1 to 3 are mounted on RICOH imagio MP C2500 (Ricoh), and after outputting a certain number of solid images in A4 portrait, solid images are printed on A3 paper. Output. Detailed evaluation conditions are as follows.
Copy original: solid image (black, 600 dpi, image area ratio 100%)
Copy mode: Black and white, single-sided recording medium: ASKUL Multi-paper Super White (ASKUL)
Toner: imagio spot toner C3000 (black, Ricoh)

<Evaluation of device rise time>
The pressure roller of the fixing unit used for outputting the evaluation image was replaced with the pressure roller according to the present invention, and the rise time of the image forming apparatus was measured. The rise time of the apparatus was measured by turning on the image forming apparatus that had been turned off for 1 hour or longer until the image forming apparatus can output the image. As a judgment standard, 25 seconds or less is OK. The heating source of the fixing unit is a 1,000 W halogen heater provided inside the heating roller.

<Evaluation of fixed image quality>
In the solid image of A3 size output under the above conditions, the image quality evaluation of the portion corresponding to the edge of the A4 paper was performed. The evaluation results were determined according to the following criteria.
Evaluation item: Gloss unevenness and occurrence of offset Evaluation criteria for evaluation rank ○: Gloss unevenness and offset are not recognized.
X: Clear gloss unevenness or offset is recognized.
The evaluation results are shown in Table 1 below.

<Comprehensive evaluation>
In the above two types of evaluation, the result of which both results are OK is marked as ◯. If any one of them is NG, it is marked as “X”.

In all the examples, the start-up time of the apparatus was shortened. In addition, since the temperature rise in the non-sheet passing area after continuous sheet feeding was suppressed, an image quality equivalent to or higher than that of the comparative example was obtained.
In Example 1, it was considered that the fibrous filler was oriented in the plane, particularly in the axial direction, by molding by dipping coating, and the soaking effect by the pressure roller was well expressed. In addition, the combination of the first elastic layer with high heat insulation and the second elastic layer with high thermal diffusivity could suppress the outflow of heat to the pressure roller at the time of starting up the device, thereby realizing high-speed start-up. Conceivable.
Regarding Example 2, the same effect as in Example 1 was obtained, and it was found that the desired effect could be obtained even when the vacancy content was increased.
Also in Example 3, the same effect as in Example 1 was obtained, and it was found that the desired effect was obtained even if the pore content was reduced.
About the comparative example 1, the void | hole content rate is further reduced rather than Example 3. FIG. This is thought to be because gloss unevenness occurred because the hardness of the member increased and heat transfer at the nip portion was insufficient.
About the comparative example 2, the elastic layer of the same thickness is comprised only by the mixing | blending of the 2nd elastic layer. In such a configuration, the image quality is hardly affected, but it is considered that the rise time of the apparatus is increased because the heat from the fixing belt is easily transmitted to the core of the pressure roller.
Comparative Example 3 is composed only of a sponge-like elastic layer including pores. In this configuration, temperature equalization by the pressure roller did not occur, and an offset due to abnormal overheating of the fixing belt was observed in the fixed image.
About the comparative example 4, the 2nd elastic layer of the structure by this invention is provided in the outer side of the solid 1st elastic layer containing a fibrous filler. In such a configuration, the image quality is hardly affected, but it is considered that the rise time of the apparatus is increased because the heat from the fixing belt is easily transmitted to the core of the pressure roller.

  As described above, it has been found that if the pressure roller of the present invention is used, it is possible to provide a pressure roller that is excellent in heat transfer and can suppress image quality anomalies such as uneven glossiness and offset of an image.

DESCRIPTION OF SYMBOLS 1 Pressure roller 2 Metal core 3 Elastic layer 3a 1st elastic layer 3b 2nd elastic layer 4 Release layer 5 Hole 6 Fibrous filler 10 Fixing device 11 Fixing roller 12 Halogen heater 13 Heating roller 14 Fixing belt 15 Addition Pressure roller 16a, b, c Thermistor 20 Image forming device 21 Photosensitive drum 22 Charging roller 23 Developing roller 24 Transfer roller 25 Cleaning device 26 Power supply 27 Surface potential meter L Laser light P Recording medium T Toner image

JP 2008-89897 A JP 2012-37874 A

Claims (4)

A pressure roller used in a fixing unit of an image forming apparatus, comprising: a first elastic layer made of a heat-resistant rubber that does not include a fibrous filler but includes a hole; and a hole and a fibrous filler on a cored bar A second elastic layer made of heat-resistant rubber and a release layer made of fluororesin are sequentially provided, and the volume content of the pores exceeds 10% in both the first and second elastic layers. The pressure roller is characterized in that the second elastic layer has a larger thermal diffusivity than the first elastic layer.   The pressure roller according to claim 1, wherein a thermal diffusivity in an in-plane axial direction and a circumferential direction of the second elastic layer is larger than a thermal diffusivity in a thickness direction.   A fixing device comprising the pressure roller according to claim 1.   An electrophotographic image forming apparatus comprising at least the fixing device according to claim 3.

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