JP2018132717A - Rubber roller for heat fixation - Google Patents

Abstract

The present invention provides a rubber roller for heat fixing that can improve image quality and achieve a long life. In the rubber roller for heat fixing of the present invention, the roller surface comes into contact with a transfer material onto which a toner image is transferred. The arithmetic average waviness Wa (μm) of the roller surface satisfies the relationship shown in the following formula (1). At the same time, the maximum height waviness Wz (μm) of the roller surface satisfies the relationship shown in the following equation (2). 0.5 ≦ Wa ≦ 1.5 Equation (1) 4.0 ≦ Wz ≦ 7.0 Equation (2) [Selection] FIG.

Description

  The present invention relates to a heat fixing rubber roller.

  In electrophotographic image forming apparatuses (copiers, laser beam printers, etc.), a heat fixing method is generally employed as a fixing method for fixing toner transferred onto a transfer material (plain paper, plastic film, etc.). Yes. In the thermal fixing method, the toner image is fixed to the transfer material by applying pressure to the toner image melted by heat. In the heat fixing method, a heat fixing rubber roller is used. When the toner image is heat fixed, the roller surface (outer peripheral surface) of the heat fixing rubber roller is transferred to the transfer material onto which the toner image is transferred. Contact with.

  For example, a sponge layer and a release layer are sequentially provided on the outer peripheral surface of a cylindrical core shaft. In the heat fixing rubber roller, the core shaft is made of a metal material such as iron or aluminum. In order to ensure sufficient heat resistance, the sponge layer is formed of, for example, a porous body of silicone rubber. The release layer is made of, for example, a fluororesin so as to have a release property for the toner.

  The rubber roller for heat fixing is used to prevent the outer diameter of the fixed image from increasing due to a rise in temperature in order to prevent deterioration in the image quality of the fixed image and change in the transfer speed of the transfer material (plain paper, plastic film, etc.). There is a demand for little change and little change in surface hardness. For this reason, in the heat fixing rubber roller, bubbles (holes) are continuously formed in the sponge layer in order to improve air permeability.

  The sponge layer is formed by a forming method such as “(a) a method using a heating type foaming agent”, “(b) a method using a hollow filler”, or “(c) an elution method”.

  In “(a) a method using a heating type foaming agent”, when the rubber is crosslinked, the foaming agent is decomposed to generate gas (bubbles), thereby forming a sponge layer. In this case, the odor of gas generated when the foaming agent is decomposed may be a problem. In addition, when an addition reaction type silicone rubber is cured using a platinum catalyst as a curing catalyst, curing may be insufficient due to the foaming agent.

  In “(b) Method of using hollow filler”, a sponge layer is formed by mixing a hollow filler with rubber. In this case, since the difference between the density of the rubber and the density of the hollow filler is large, the bubbles may be non-uniform in the sponge layer. Moreover, since a hollow filler is used, a manufacturing cost may become high.

  On the other hand, in the “(c) elution method”, after the rubber mixed with the water-soluble powder is cross-linked, the water-soluble powder is eluted into water to form a sponge layer. In this method, unlike the “(a) method using a heating type foaming agent”, since the heating type foaming agent is not used, the problem of odor does not occur. Unlike the “(b) method using a hollow filler”, an inexpensive water-soluble powder is used without using a hollow filler, so that the manufacturing cost can be reduced.

  In “(c) elution method”, various techniques have been proposed in order to improve the performance of the sponge layer. For example, after forming a silicone rubber layer containing triethylene glycol together with water-soluble powder (sugar powder), the water-soluble powder and triethylene glycol are eluted from the silicone rubber layer into water. As a result, in the sponge layer, bubbles are uniformly formed and the open cell rate is increased (for example, see Patent Document 1).

  In addition, various technologies have been proposed for the heat fixing rubber roller for the purpose of improving the image quality (see, for example, Patent Documents 2 and 3).

Japanese Patent Laid-Open No. 2006-8990 JP 2012-53354 A JP 2001-1000051 A

  However, in the above-described rubber roller for heat fixing, it may not be easy to obtain sufficient image quality. Specifically, image defects such as gloss unevenness, fixing unevenness, and dirt may occur on the surface on which the toner image is fixed. The image defect is caused by uneven pressure applied to the nip portion due to a difference in hardness partially on the roller surface due to the undulation of the heat fixing rubber roller. That is, since the degree of melting of the melting component (wax or the like) contained in the toner varies depending on the pressure, when the pressure is not uniform, the gloss and the fixing are not uniform in the fixed toner image.

  In addition, the heat-fixing rubber roller may be partially consumed by applying pressure and heat locally to a portion with a large swell, and the life may be shortened.

  Therefore, the problem to be solved by the present invention is to provide a rubber roller for heat fixing that can improve the image quality and can realize a long life.

In the heat fixing rubber roller of the present invention, the roller surface comes into contact with the transfer material onto which the toner image is transferred. The arithmetic average waviness Wa (μm) of the roller surface satisfies the relationship shown in the following formula (1). At the same time, the maximum height waviness Wz (μm) of the roller surface satisfies the relationship shown in the following equation (2).
0.5 ≦ Wa ≦ 1.5 Formula (1)
4.0 ≦ Wz ≦ 7.0 Formula (2)

  According to the present invention, it is possible to provide a heat-fixing rubber roller that can improve image quality and achieve a long life.

FIG. 1 is a side view schematically showing a heat fixing rubber roller according to an embodiment. FIG. 2 is a cross-sectional view schematically showing the heat fixing rubber roller according to the embodiment. FIG. 3 is a diagram schematically showing the maximum length L (μm) of the voids included in the sponge layer 30.

  Hereinafter, embodiments of the invention will be described with reference to the drawings. The invention is not limited to the contents of the drawings. Further, the drawings show an outline, and the dimensional ratio of each part does not necessarily match the actual one. In addition, about the same component, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted suitably.

[A] Configuration FIGS. 1 and 2 are views schematically showing a heat fixing rubber roller according to an embodiment. FIG. 1 shows a side surface of the heat fixing rubber roller 1, and the vertical direction is an axial direction z along the rotation axis AX of the heat fixing rubber roller 1. FIG. 2 shows a cross section of the X1-X1 portion in the heat fixing rubber roller 1 shown in FIG. 1, and the direction perpendicular to the paper surface is the axial direction z.

  As shown in FIGS. 1 and 2, the heat-fixing rubber roller 1 has a cylindrical shape and includes a core shaft 10, a sponge layer 30, and a release layer 40. Each part constituting the heat fixing rubber roller 1 will be described in order.

[A-1] Core shaft 10
The core shaft 10 is a cylindrical base material and is formed of a metal material. Here, the core shaft 10 is formed using, for example, iron or aluminum.

[A-2] Sponge layer 30
The sponge layer 30 is provided on the outer peripheral surface of the core shaft 10. In the present embodiment, the sponge layer 30 is a porous layer formed using silicone rubber, and includes a large number of bubbles. The thickness of the sponge layer 30 is, for example, in the range of not less than 1.0 mm and not more than 20 mm.

[A-3] Release layer 40
The release layer 40 is provided so as to cover the outer peripheral surface of the core shaft 10 via the sponge layer 30. The release layer 40 is made of, for example, a release resin such as a fluororesin in order to obtain release properties for the toner. Specifically, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), ethylene / tetrafluoroethylene copolymer Fluorine resins such as (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), and polyvinylidene fluoride (PVdF) are suitably used as the release resin. The release layer 40 may be formed using a release resin such as a polyimide resin or a polyamideimide resin in addition to the fluororesin. The thickness of the release layer 40 is, for example, 10 μm or more and 100 μm or less. The release layer 40 may not be provided on the heat fixing rubber roller 1 if unnecessary.

[A-4] Others (characteristics)
[A-4-1] Arithmetic mean waviness Wa (μm) of roller surface, maximum height waviness Wz (μm)
The heat fixing rubber roller 1 constitutes a heat fixing portion (not shown) in an electrophotographic image forming apparatus (not shown). The heat fixing unit includes, for example, a pressure roller (not shown) together with the heat fixing rubber roller 1, and the transfer material onto which the toner image is transferred by the transfer unit (not shown) is a heat fixing rubber roller and a pressure roller. The toner image is thermally fixed by being conveyed to the nip portion between the two. When heat-fixing the toner image, the heat-fixing rubber roller 1 comes into contact with the transfer material onto which the toner image is transferred. Here, the outer peripheral surface of the release layer 40 functions as a roller surface of the heat fixing rubber roller 1 and comes into contact with the transfer material onto which the toner image has been transferred.

  In the present embodiment, in the heat fixing rubber roller 1, the arithmetic average waviness Wa (μm) of the roller surface satisfies the relationship represented by the following formula (1). At the same time, in the heat fixing rubber roller 1, the maximum height waviness Wz (μm) of the roller surface satisfies the relationship shown in the following formula (2).

  0.5 ≦ Wa ≦ 1.5 Formula (1)

  4.0 ≦ Wz ≦ 7.0 Formula (2)

  In the above, the arithmetic average waviness Wa (μm) and the maximum height waviness Wz (μm) are values measured under the following measurement conditions under a measurement method based on “JIS B0601: 2001” (ISO 4287: 1997). . In other words, the arithmetic average waviness Wa (μm) is obtained by blocking the long wavelength component at the following cutoff wavelength λf and blocking the short wavelength component at the following cutoff wavelength λc. That's it. The maximum height waviness Wz (μm) is the maximum height of the “waviness curve” obtained in the same manner as described above. The maximum height waviness Wz (μm) corresponds to the sum of the maximum peak height Wz and the maximum valley depth Wv of the “swell curve” at the reference length.

[Measurement condition]
・ Standard length: 25mm
・ Number of sections: 1
Cut-off wavelength λf: 25mm
Cut-off wavelength λc: 0.08mm
・ Filter: Gaussian ・ Measurement speed: 2.0mm / sec

  Based on the above equations (1) and (2), the difference value [Wz−Wa] (μm) obtained by subtracting the arithmetic average waviness Wa (μm) from the maximum height waviness Wz (μm) is expressed by the following equation ( The relationship shown in X) is satisfied.

  2.5 ≦ Wz−Wa ≦ 6.5 Formula (X)

  The image quality of the fixed image can be improved by satisfying the relationship shown in the equation (1) and the relationship shown in the equation (2) (that is, satisfying the equation (X)). Specifically, when the heat fixing rubber roller 1 of the present embodiment is used, it is possible to suppress the occurrence of image defects such as uneven gloss and uneven fixing. In addition, the heat fixing rubber roller 1 according to the present embodiment can prevent a part of the roller from being consumed and prevent the peeling between the sponge layer 30 and the release layer 40.

  When the arithmetic average waviness Wa (μm) of the roller surface is smaller than the range shown in the equation (1), even if the maximum height waviness Wz satisfies the range shown in the equation (2), the roller surface A portion with large undulation exists locally. That is, a portion having a large value of [Wz−Wa] locally exists on the roller surface. For this reason, the roller surface has a local hardness difference. As a result, the pressure on the roller surface is likely to be non-uniform, and image defects may occur.

  On the other hand, when the arithmetic average waviness Wa (μm) of the roller surface is larger than the range shown in the formula (1), even if the maximum height waviness Wz satisfies the range shown in the formula (2). Since the individual undulations are in a large state, the number of places where the roller surface has a hardness difference increases. As a result, similarly, the pressure on the roller surface is likely to be non-uniform, which may cause image defects.

  Even when the arithmetic average waviness Wa (μm) of the roller surface satisfies the range shown in the formula (1), the maximum height waviness Wz (μm) of the roller surface is smaller than the range shown in the formula (2). The roller surface is in a state where there are many undulations. For this reason, the dispersion | variation in the hardness difference of a roller surface increases. As a result, the pressure on the roller surface is likely to be non-uniform, and image defects may occur.

  On the other hand, even when the arithmetic average waviness Wa (μm) of the roller surface satisfies the range shown in the equation (1), the maximum height waviness Wz (μm) of the roller surface is in the range shown in the equation (2). Is larger, the swell height is extremely large. That is, a portion having a large value of [Wz−Wa] locally exists on the roller surface. For this reason, the roller surface has a local hardness difference. As a result, the pressure on the roller surface is likely to be non-uniform, and image defects may occur.

  Further, when the heat fixing rubber roller 1 does not satisfy the relationship shown in the formula (1) and the relationship shown in the formula (2), the toner is fixed due to pressure variation when fixing the toner on a transfer material such as plain paper. The toner tends to remain on the roller surface without being removed. As a result, when the toner image is next fixed, the remaining toner may become dirty and fixed.

[A-4-2] Maximum length L of the air gap in the sponge layer 30 (μm)
In the heat fixing rubber roller 1, the sponge layer 30 is a porous layer having a large number of voids, and the maximum length L (μm) of the voids preferably satisfies the relationship represented by the following formula (3). .

  50 ≦ L ≦ 450 Formula (3)

  The “maximum length L (μm)” of the void was measured using a cross-sectional photograph of the sponge layer 30 taken with a scanning electron microscope (SEM). FIG. 3 is a diagram schematically showing the maximum length L (μm) of the voids included in the sponge layer 30. As shown in FIG. 3, the maximum distance between a pair of points facing each other on a straight line was measured as “maximum length L (μm)” in the outline of the void taken by the cross-sectional photograph.

  Since the heat-fixing rubber roller 1 can form a uniform sponge layer having a high continuous bubble rate when the sponge layer 30 satisfies the relationship represented by the formula (3), it is possible to obtain good image quality.

  In the sponge layer 30, when the maximum length L (μm) of the gap is smaller than the range shown in the formula (3), there is a possibility that the continuous bubble rate of the sponge layer 30 is lowered and good image quality cannot be obtained. is there. On the other hand, in the sponge layer 30, when the maximum length L (μm) of the gap is larger than the range shown in the formula (3), undulation occurs on the surface of the sponge layer 30, and a good image is obtained. There is a risk that quality may not be obtained.

[B] Manufacturing Method Each process executed when manufacturing the above-described heat fixing rubber roller 1 will be sequentially described.

[B-1] Sponge Layer Formation Step When manufacturing the above heat fixing rubber roller 1, first, the sponge layer 30 is formed on the outer peripheral surface of the core shaft 10. Here, the sponge layer 30 is formed by an elution method.

  When forming the sponge layer 30 in this embodiment, a curable silicone rubber composition containing a water-soluble powder and triethylene glycol is prepared as a raw material for the sponge layer 30. The core shaft 10 is coaxially installed inside a cylindrical mold (not shown). Then, the prepared silicone rubber composition is injected into a space located between the outer peripheral surface of the core shaft 10 and the inner peripheral surface of the cylindrical mold. Thereafter, the silicone rubber layer is formed by performing primary vulcanization (curing treatment) on the silicone rubber composition.

  And after taking out core axis 10 in which a silicone rubber layer was formed from a metallic mold, it is immersed in water. Thus, the water-soluble powder and triethylene glycol are eluted from the silicone rubber layer into water, so that the silicone rubber layer becomes porous. Thereafter, secondary vulcanization is performed on the porous silicone rubber layer. In this way, a silicone rubber layer that is a porous layer is formed on the outer peripheral surface of the core shaft 10 as the sponge layer 30. Note that at least a part of the triethylene glycol remaining in the sponge layer 30 is discharged to the outside along with the secondary vulcanization.

  The formation of the sponge layer 30 will be described more specifically.

  In this embodiment, the silicone rubber composition that is a raw material of the sponge layer 30 includes, for example, liquid silicone rubber as a base polymer, and is prepared by mixing water-soluble powder and triethylene glycol.

  Of the silicone rubber composition that is the raw material of the sponge layer 30, the liquid silicone rubber can be used in both addition reaction type and condensation curing type. In particular, it is preferable to use an addition reaction type liquid silicone rubber that is cured at a temperature of about 80 ° C. to 150 ° C. The addition-reactive silicone rubber is a polysiloxane having an addition-reactive group, and is a material that is cured by being crosslinked with a crosslinking agent.

  In the silicone rubber composition, the water-soluble powder is, for example, a sugar powder and is soluble in water as a solvent. As the sugar powder, powders such as glucose, lactose, sucrose, trehalose, and fructose can be used. The sugar powder may be one kind or plural kinds of powders of the above materials. Here, for example, commercially available sugar containing sucrose as a main component can be used. In particular, granulated sugar and powdered sugar can be suitably used as a water-soluble sugar powder because of its high water solubility.

  The particle size of the sugar powder is preferably 1 μm or more and 1000 μm or less. When the particle size is less than the above lower limit, a long time is required for elution of the sugar powder, and the possibility that the sugar powder remains in the sponge layer 30 increases. Further, when the particle diameter exceeds the above upper limit, the strength of the sponge layer 30 may decrease, and the durability of the heat fixing rubber roller 1 may decrease. From the above viewpoint, the particle size of the sugar powder is more preferably 10 μm or more and 400 μm or less, and still more preferably 10 μm or more and 100 μm or less. As the sugar powder, for example, a powder classified into the above particle size range using a sieve can be used.

  The content of the sugar powder is preferably 50 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the liquid silicone rubber. When the content is less than the lower limit, it becomes difficult to form the sponge layer 30 so as to include continuous bubbles. On the other hand, when the content exceeds the above upper limit value, the strength of the sponge layer 30 is lowered, and the durability of the heat fixing rubber roller 1 may be lowered. From the above viewpoint, the content of the sugar powder is more preferably 100 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the liquid silicone rubber.

  In the silicone rubber composition, triethylene glycol is a component added to increase the open cell rate of the sponge layer 30. Triethylene glycol has low compatibility with silicone rubber and high compatibility with sugar powder. For this reason, since the layer of triethylene glycol is formed around sugar powder, it can suppress that the skin layer of silicone rubber is formed between some sugar powder. Accordingly, sugar powder is easily eluted from the silicone rubber layer, and triethylene glycol is easily eluted from the silicone rubber layer. As a result, the sponge layer 30 having a high open cell rate can be formed.

  The content of triethylene glycol is preferably 1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the liquid silicone rubber. When the content is less than the lower limit, it becomes difficult to form the sponge layer 30 having a sufficiently high open cell rate. On the other hand, when the content exceeds the upper limit, a large amount of triethylene glycol may remain in the sponge layer 30 and bleed from the sponge layer 30 in some cases. From the above viewpoint, the content of triethylene glycol is more preferably 5 parts by mass or more and 50 parts by mass or less, and further preferably 20 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the liquid silicone rubber.

  Similar to triethylene glycol, other polyhydric alcohols such as ethylene glycol can be suitably used because of their low compatibility with silicone rubber and high compatibility with sugar powder. Here, a monomer or oligomer having a plurality of alcoholic hydroxyl groups can be used as the polyhydric alcohol. For example, as the monomer having a plurality of alcoholic hydroxyl groups, glycerin, propylene glycol, pentaerythritol, glycerin-α-monochlorohydrin and the like can be used in addition to ethylene glycol. In addition to triethylene glycol, diethylene glycol, dipropylene glycol, polyglycerin, or the like can be used as the oligomer having a plurality of alcoholic hydroxyl groups. However, when triethylene glycol is used, the sponge layer 30 having a high open cell ratio can be formed, in particular, as compared with the case where other polyhydric alcohols are used. However, other polyhydric alcohols such as ethylene glycol may be appropriately contained in the silicone rubber composition.

  The temperature at which the primary vulcanization is performed is appropriately set depending on the type of silicone rubber used in the silicone rubber composition. For example, when the silicone rubber is a low temperature curing type (LTV silicone rubber), the primary vulcanization temperature is preferably in the range of 80 ° C. or higher and 150 ° C. or lower, and more preferably in the range of 100 ° C. or higher and 130 ° C. or lower.

  Similarly to the temperature of the primary vulcanization, the temperature at which the secondary vulcanization is performed is appropriately set depending on the type of silicone rubber used in the silicone rubber composition. For example, when the silicone rubber is a low temperature curing type (LTV silicone rubber), the secondary vulcanization temperature is preferably in the range of 180 ° C. or higher and 230 ° C. or lower, and more preferably in the range of 200 ° C. or higher and 220 ° C. or lower.

  The temperature of water used for immersion is preferably 60 ° C. or higher and 90 ° C. or lower, for example, in order to efficiently dissolve sugar powder and triethylene glycol from the silicone rubber layer. Further, the immersion time is usually 1 hour or more and 8 hours or less, and is arbitrarily set according to the thickness of the silicone rubber layer and the temperature of water used for immersion. In addition, by providing a mechanism for continuously or intermittently supplying water to the immersion tank and a mechanism for discharging the water, an elution process for eluting the sugar powder and triethylene glycol can be performed efficiently.

  In the above description, regarding the formation of the sponge layer 30, the case where the core shaft 10 taken out from the mold is immersed in water is shown, but the present invention is not limited thereto. The core shaft 10 mounted on the mold may be immersed in water without removing the core shaft 10 from the mold.

  Moreover, although the case where liquid silicone rubber was used as the base polymer of the sponge layer 30 was described above, solid silicone rubber may be used. Further, the sponge layer 30 may be formed without using a mold.

  In this case, for example, a silicone rubber sheet is prepared from a silicone rubber composition obtained by mixing sugar powder and triethylene glycol with solid silicone rubber. Then, the silicone rubber sheet is wound around the outer peripheral surface of the core shaft 10 and then vulcanized. Then, the sponge layer 30 can be formed by performing the elution process similar to the above.

  In addition, a silicone rubber cylindrical body may be produced by extrusion molding from a silicone rubber composition obtained by mixing sugar powder and triethylene glycol with solid silicone rubber. In this case, the silicone rubber cylindrical body is attached to the outer peripheral surface of the core shaft 10 and then vulcanized. Thereafter, the sponge layer 30 is formed by executing the above elution process.

[B-2] Release Layer Formation Step Next, the release layer 40 is formed on the outer peripheral surface of the core shaft 10 where the sponge layer 30 is provided.

  In the present embodiment, the release layer 40 is formed by attaching a tube formed of a release resin such as a fluororesin to the outer peripheral surface of the core shaft 10 via the sponge layer 30. In this case, the inner diameter of the tube formed of the releasable resin is 90% or more of the outer diameter of the core shaft 10 on which the sponge layer 30 is formed in order to bring them into close contact with each other. Is preferred.

  In addition, you may adhere | attach a tube on the outer peripheral surface of the sponge layer 30 using an adhesive agent. Moreover, you may perform the roughening process by the process which apply | coats a primer, chemical etching, etc. about the internal peripheral surface of a tube. In addition, in addition to the case of using a tube formed of a releasable resin, the release layer 40 may be formed by applying a releasable resin.

  In the present embodiment, by adjusting the ratio of the material constituting the sponge layer 30, it is possible to manufacture the heat fixing rubber roller 1 that satisfies the relationship expressed by the equations (1) to (3).

[C] Modifications While the embodiment of the invention has been described above, the invention is not limited to the above description, and various omissions, replacements, and modifications are naturally made without departing from the scope of the invention. Can do.

  For example, in the above embodiment, the case where the sponge layer 30 is formed by the elution method is described, but the present invention is not limited to this. For example, the sponge layer 30 may be formed using a mixed liquid in which a hollow filler is dispersed in silicone rubber. However, in this case, aggregation of the hollow filler is likely to occur in the above-described mixed solution, and therefore it is not easy to satisfy the relationship represented by the equations (1) and (2) for the roller surface. On the other hand, when the sponge layer 30 is formed by the above elution method, the water-soluble powder has high compatibility between the water-soluble powder such as sugar powder and the tripolyhydric alcohol such as triethylene glycol. Is surrounded by polyhydric alcohol, so water-soluble powder is less likely to agglomerate. Therefore, in order to efficiently manufacture the heat fixing rubber roller 1 of this embodiment, it is preferable to form the sponge layer 30 by the above-described elution method.

  Hereinafter, Examples and Comparative Examples of the heat fixing rubber roller 1 will be described with reference to Tables 1 and 2. Tables 1 and 2 show an overview of the examples and comparative examples. In Table 1, in each example, the maximum height waviness Wz (μm) of the roller surface is the same, and the arithmetic average waviness Wa (μm) of the roller surface is different from each other. On the other hand, in Table 2, in each example, the arithmetic average waviness Wa (μm) of the roller surface is the same, and the maximum height waviness Wz (μm) of the roller surface is different from each other. In addition, in order to make an understanding easy, in description of an Example and a comparative example, the code | symbol is attached | subjected to each part similarly to said embodiment (refer FIG. 1, FIG. 2).

[Example 1]
In Example 1, the heat fixing rubber roller 1 was manufactured so that the maximum height waviness Wz (μm) of the roller surface and the arithmetic average waviness Wa (μm) of the roller surface were the values shown in Table 1.

  Specifically, when producing the heat fixing rubber roller 1 of this example, first, a cylindrical core shaft 10 (outer diameter: 18 mm, material: aluminum) was prepared.

  Next, a sponge layer 30 was formed on the outer peripheral surface of the core shaft 10. Here, as shown in Table 1, first, the following components were mixed at the following mass ratios for 30 minutes using a stirrer, and then the mixture was subjected to vacuum defoaming treatment to obtain a curable silicone rubber composition. An article was prepared as a raw material for the sponge layer 30.

LTV silicone rubber (manufacturer: Shin-Etsu Chemical, model: G91S): 100 parts by mass Granulated sugar powder (manufacturer: Nissin sugar, particle size: 10 to 400 μm (classified with a sieve)): 130 parts by mass Triethylene glycol: 40 parts by mass

  After the core shaft 10 is coaxially installed inside a cylindrical mold (not shown), the space between the outer peripheral surface of the core shaft 10 and the inner peripheral surface of the cylindrical mold is The prepared silicone rubber composition was injected. Thereafter, primary vulcanization (curing) was performed on the silicone rubber composition. The primary vulcanization was performed under the conditions that the temperature was 120 ° C. and the heating time was 30 minutes. Thereby, the silicone rubber composition was cured to form a silicone rubber layer.

  And after taking out the core axis 10 in which the silicone rubber layer was formed from the metal mold | die, it was immersed in water. Here, the core shaft 10 was immersed in water having a temperature condition of 80 ° C. for 2 hours. As a result, granulated sugar powder and triethylene glycol were eluted from the silicone rubber layer into water to make the silicone rubber layer porous.

  Thereafter, the porous silicone rubber layer was subjected to secondary vulcanization. The secondary vulcanization was performed under the conditions that the temperature was 220 ° C. and the heating time was 4 hours. Thereby, the sponge layer 30 having a thickness of 3.0 mm was formed. In this example, the open cell rate of the sponge layer 30 was 95%.

  The open cell ratio X (%) was calculated based on the following formula (A). In the formula (A), “OG” is the specific gravity of the silicone rubber composition that is the raw material of the sponge layer 30. “FG” is the specific gravity of the sponge layer 30. “DW” is the weight of the sponge layer 30. “WW” is the weight after the sponge layer 30 has absorbed water. The measurement of “WW” was performed according to the following procedure. First, in the vacuum vessel, the inside of the vacuum vessel was depressurized (10 mmHg or less) in a state where the sponge layer 30 was immersed in the vessel containing water. Then, the inside of the vacuum vessel was returned to normal pressure and left for 5 minutes, so that the sponge layer 30 absorbed water. Thereafter, the weight of the sponge layer 30 after water absorption was measured as “WW”.

  X (%) = [(WW−DW) /1.00] / [(1− (FG / OG)) × (DW / FG)] × 100] Expression (A)

  As described above, after the sponge layer 30 was formed, the release layer 40 was formed on the outer peripheral surface of the core shaft 10 where the sponge layer 30 was formed. Here, an adhesive (manufacturer: Shin-Etsu Chemical Co., Ltd., trade name: KE-1880 (RTV silicone rubber)) was applied to the outer peripheral surface of the sponge layer 30. Thereafter, as the release layer 40, a PFA tube (manufacturer: Mitsui DuPont Fluorochemical Co., Ltd., trade name: 451HPJ) was installed. And it heated on the conditions whose temperature is 120 degreeC and heating time is 1 hour.

  In this manner, the heat fixing rubber roller 1 of this example was manufactured so that the maximum height waviness Wz (μm) and the arithmetic average waviness Wa (μm) were the values shown in Table 1.

[Other examples]
In other examples, as shown in Table 1 and Table 2, the material ratio (parts by mass) of the sponge layer was changed from that in Example 1 to produce a heat fixing rubber roller 1. Thus, as shown in Table 1 and Table 2, the heat fixing rubber roller 1 of each example having different maximum height waviness Wz (μm) of the roller surface and arithmetic average waviness Wa (μm) of the roller surface was produced. .

<Evaluation>
As shown in Table 1 and Table 2, various evaluations were performed for each example. Here, as an evaluation of image quality, an evaluation was made regarding fixing unevenness. When the image quality was evaluated, the heat fixing rubber roller prepared in each example was incorporated into the fixing device of the image forming apparatus as a fixing roller. Then, after the image was output using the image forming apparatus, the image quality was visually evaluated. Here, fixing unevenness was evaluated as an image quality evaluation.

[Fixing unevenness]
The fixing unevenness was evaluated according to the following criteria.
Specifically, when the pattern shape of the fixed toner image is not the designed pattern shape (for example, when a part of the fill pattern (solid pattern) is missing or dark or shaded), uneven fixing occurs. It was determined that there was.
・ ○… No fixing unevenness ・ ×… There is uneven fixing

[Summary of evaluation]
As shown in Table 1 and Table 2, each Example (Examples 1-4, Examples 11-14) satisfy | fills the relationship shown to Formula (1), and the relationship shown to Formula (2). For this reason, in each of the examples, uneven fixing does not occur in the image.

  On the other hand, in Comparative Example 1, the maximum height waviness Wz (μm) of the roller surface is within the range shown in Equation (2), but the arithmetic average waviness Wa (μm) of the roller surface is in Equation (1). It is smaller than the range shown. For this reason, uneven fixing occurs in the image.

  In Comparative Example 2, the maximum height waviness Wz (μm) of the roller surface is within the range shown in the equation (2), but the arithmetic average waviness Wa (μm) of the roller surface is larger than the range shown in the equation (1). . For this reason, fixing unevenness occurs in the image.

  In Comparative Example 11, the arithmetic average waviness Wa (μm) of the roller surface is within the range shown in the formula (1), but the maximum height waviness Wz (μm) of the roller surface is smaller than the range shown in the formula (2). . For this reason, uneven fixing occurs in the image.

  In Comparative Example 12, the arithmetic average waviness Wa (μm) of the roller surface is within the range shown in the equation (1), but the maximum height waviness Wz (μm) of the roller surface is larger than the range shown in the equation (2). . For this reason, fixing unevenness occurs in the image.

  From this result, the heat-fixing rubber roller 1 satisfies the relationship shown in the formula (1) and the relationship shown in the formula (2), thereby preventing the occurrence of fixing unevenness in the image and improving the image quality. be able to.

DESCRIPTION OF SYMBOLS 1 ... Thermal fixing rubber roller 10 ... Core shaft, 30 ... Sponge layer, 40 ... Release layer, AX ... Rotating shaft

Claims (3)

A heat fixing rubber roller in which a roller surface is in contact with a transfer material onto which a toner image has been transferred,
The arithmetic average waviness Wa (μm) of the roller surface satisfies the relationship shown in the following formula (1), and
The maximum height waviness Wz (μm) of the roller surface satisfies the relationship represented by the following formula (2).
Rubber roller for heat fixing.
0.5 ≦ Wa ≦ 1.5 Formula (1)
4.0 ≦ Wz ≦ 7.0 Formula (2) A core shaft, a sponge layer provided on the outer peripheral surface of the core shaft, and a release layer provided on the outer peripheral surface of the core shaft via the sponge layer,
The outer peripheral surface of the release layer is the roller surface and satisfies the relationship shown in the formula (1) and the relationship shown in the formula (2).
The rubber roller for heat fixing according to claim 1. In the sponge layer, the maximum length L (μm) of the gap satisfies the relationship represented by the following formula (3).
The heat fixing rubber roller according to claim 2.
50 ≦ L ≦ 450 Formula (3)

Images