JP2007171280A - Seamless cylindrical member and fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a seamless cylindrical member which conducts heat to a recording medium by conducting heat to a release layer through an elastic layer, the seamless cylindrical member capable of securing sufficient heat conductivity along the length of the cylinder while securing high heat conductivity along the thickness of the elastic layer, i.e. high heat conductivity to the recording medium. <P>SOLUTION: The seamless cylindrical member is characterized in that the elastic layer is made of heat-resistant rubber containing a 5 to 40% by volume of needlelike heat conductive filler of 0.5 to 5 mm in length and has a heat conductivity along the thickness of 0.5 W/m.K. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a seamless cylindrical member, in particular, a fixing member used for toner fixing in an electrophotographic process, and a fixing device.

  In a member that fixes an electrophotographic toner on a recording medium by heating and pressing, when a structure in which at least a base layer, an elastic layer, and a release layer are sequentially laminated, in the elastic layer, a function imparting technique relating to thermal characteristics is It is an important development item.

  When paying attention to thermal characteristics, among several techniques, a technique that uses carbon fiber as one of the constituent elements in the elastic layer has recently been known.

  Patent Document 1 discloses a configuration in which the elastic layer of the fixing belt contains hollow carbon fibers formed by a vapor phase growth method. The purpose of Patent Document 1 is mainly to prevent oxidative degradation of surrounding silicone rubber by trapping oxygen in a hollow portion.

  Patent Document 2 discloses a configuration in which the elastomer layer of the heating fuser member contains a fluorocarbon powder having a major axis and a minor axis. The purpose of Patent Document 2 is mainly to provide anisotropic thermal conductivity in the thickness direction of the layer.

Furthermore, in patent document 3, the structure in which the elastic layer of a pressurization member contains carbon fiber is disclosed. About this patent document 3, it is mainly limited to the pressurization member which does not have a heating source inside, and thermal conductivity (axial direction) / thermal conductivity (direction perpendicular to an axis) is about 500-1000. The purpose is to extremely increase the thermal conductivity in the axial direction.
JP 2002-268423 A JP 2000-39789 JP 2002-351243 A

  In the prior art, there is no focus on simultaneously increasing both the thermal conductivity in the thickness direction of the elastic layer and the thermal conductivity in the axial direction (longitudinal direction of the cylinder). The invention was aimed at a combination and was not fully satisfactory.

  Therefore, in the present invention, in a configuration having a heat source inside, that is, a seamless cylindrical member that transfers heat to the release layer through the elastic layer and transfers heat to the recording medium, the thermal conductivity in the thickness direction of the elastic layer, that is, An object of the present invention is to obtain a seamless cylindrical member capable of sufficiently ensuring the thermal conductivity in the longitudinal direction of the cylinder while ensuring a large thermal conductivity to the recording medium.

  Thermal conductivity to the recording medium is necessary for efficient toner fixing in terms of thermal energy, and can contribute to energy saving and higher fixing speed. In addition, the thermal conductivity in the longitudinal direction of the cylinder affects the temperature uniformity of the member, and in particular, improves the temperature non-uniformity as typified by the temperature rise in the non-sheet passing area after passing small-size paper. As a result, it is possible to contribute to high durability such as high image quality such as uniformity of a fixed image and suppression of thermal deterioration of a member due to a partial overheating state.

  In order to solve the problem of the present application, as a result of intensive studies by the authors, the elastic layer is a heat-resistant rubber containing 5 to 40 vol% of a needle-like thermally conductive filler having a length of 0.5 to 5 mm, By using a seamless cylindrical member characterized in that the thermal conductivity in the thickness direction of this elastic layer is 0.5 W / mK or more, the thermal conductivity in the longitudinal direction of the cylinder is secured while ensuring a large thermal conductivity to the recording medium. It was found that the purpose of sufficiently securing the sex could be achieved.

  Furthermore, the elastic layer is applied to a seamless cylindrical member having a thickness of 50 to 500 μm, pitch-based carbon fiber is used as a needle-like thermally conductive filler, silicone rubber, or fluorine as heat-resistant rubber It has been found that the effect can be more suitably exhibited by using rubber.

  In addition, by using this seamless cylindrical member incorporated in a heat fixing device, heat fixing that can suitably carry out the purpose of sufficiently ensuring the heat conductivity in the longitudinal direction of the cylinder while ensuring large heat conductivity to the recording medium. Equipment can be provided.

  By means of the means of the present application, in particular, by adding a needle-shaped thermally conductive filler having a length of 0.5 to 5 mm to the heat-resistant rubber, the relatively long thermally conductive filler increases the heat conduction in the longitudinal direction of the cylinder. In addition, the thermal conductivity in the thickness direction can be increased moderately, and the object of the present invention can be achieved. Moreover, the heat conductivity of a suitable range and manufacture ease are securable by setting it as 5-40 vol% as a compounding quantity of a filler.

  Furthermore, when the thickness of the elastic layer is 50 to 500 μm, the direction in which the elastic layer can exist in the layer is regulated, and the acicular heat conductive filler is easily oriented in the longitudinal direction of the cylinder in the layer. You will be able to achieve your goals more effectively. In addition, the use of pitch-based carbon fibers for the heat conductive filler can achieve the object more suitably because the thermal conductivity of the filler itself is very high compared to the case of using other types of carbon fibers. become. The use of silicone rubber or fluoro rubber as the heat resistant rubber can achieve the object more suitably due to the superiority of the heat resistance and flexibility.

  As a result, by incorporating these seamless cylindrical members into a heat fixing device, the purpose of sufficiently ensuring the thermal conductivity in the longitudinal direction of the cylinder can be suitably implemented while ensuring a large thermal conductivity to the recording medium. A heat fixing device can be provided.

  As described above, it has been found that the object of the present invention can achieve the purpose of sufficiently ensuring the thermal conductivity in the longitudinal direction of the cylinder while ensuring a large thermal conductivity to the recording medium.

  In carrying out the present invention, the best mode is shown below.

-Description of seamless cylindrical member-
FIG. 1 shows a configuration diagram of a typical seamless cylindrical member embodying the present invention. 11 is a base material, 12 is an elastic layer, 13 is a surface layer.

  The present invention can be carried out when the substrate 11 is a roller or belt made of metal or heat-resistant resin. Specifically, a roller metal core made of aluminum or iron having a thickness of about several millimeters, a belt base made of nickel, stainless steel (SUS), or polyimide having a thickness of about several tens of micrometers can be exemplified.

  The surface layer 13 is required to have heat resistance and difficulty in toner adhesion. Although the material is not particularly limited with respect to the main effect of the present invention, in view of the characteristics of various fixing members, the fluororesin is a material that can more effectively implement the present invention, and at this time, its thickness By making the thickness 5 to 50 μm, the effect of the present invention is more effectively brought out.

  The kind of fluororesin can be a known kind of material, and is not particularly limited. Commonly known single or complex species such as polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP) It is preferable to use a material.

  The elastic layer 13 is a main component of the present invention, and is configured by including a needle-like thermally conductive filler in heat resistant rubber.

  FIG. 2 schematically shows the shape of the needle-like thermally conductive filler. In this way, the needle shape refers to a shape having a length in only one direction compared to the other directions, and the shape can be represented mainly by a short axis diameter 21 and a long axis length 22. Although the short axis diameter is not particularly limited, a material having a diameter of about 5 to 15 μm can be used relatively easily. The major axis length is preferably 0.5 to 5 mm. If the length is longer than 5 mm, the difficulty of manufacturing the member becomes high. If the length is shorter than 0.5 mm, the effects of the present invention cannot be fully exhibited. More preferably, the long axis length is 1 to 2 mm.

  As the needle-like thermally conductive filler, pitch-based carbon fibers are particularly preferably used. An example of the pitch-based carbon fiber is trade name “Granock” (manufactured by Nippon Graphite Fiber Co., Ltd.). Such pitch-based carbon fibers can be obtained by cutting to a desired length.

  As the heat resistant rubber, silicone rubber or fluorine rubber can be preferably used. Both heat-resistant rubbers have sufficient heat resistance and durability when used in a heat fixing device, and have favorable elasticity (softness), and are suitable as the main matrix material of the elastic layer. is there. Both heat-resistant rubbers may contain various compounding agents to such an extent that the effect of the present invention is not greatly changed. A typical example of the silicone rubber is an addition reaction type dimethyl silicone rubber obtained by crosslinking a dimethylpolysiloxane with an addition reaction between a vinyl group and a silicon-bonded hydrogen group. In addition, as fluororubber, a binary copolymer of vinylidene fluoride and hexafluoropropylene, or a terpolymer of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene is used as a base polymer, and a radical based on peroxide. A typical example is a binary or ternary radical-reactive fluororubber obtained by rubber cross-linking by reaction.

  Regarding the silicone rubber used in this example, the following addition reaction type silicone rubber stock solutions A and B were obtained. The liquid A contains a trace amount of a platinum compound as a catalyst, and is composed of a composition mainly composed of a polysiloxane compound having a vinyl group, which is one of addition reaction sites, in a siloxane bond side chain. Liquid B is composed of a composition composed mainly of a polysiloxane compound having silicon-bonded hydrogen, which is another addition reaction site. The liquids A and B contain a trace amount of iron oxide so as not to affect the thermal conductivity in the present invention. The viscosity of this silicone rubber stock solution was 13 Pa.s for Liquid A and 14 Pa.s for Liquid B. (Both measured in a room temperature environment at 25 ° C with a BH type rotational viscosity system) The hardness of a sample obtained by mixing the silicone rubber stock solutions A and B in a weight ratio of 1: 1 and heat-curing was measured. 7 This hardness was read within 1 second after adhesion using an Asker C type hardness tester (manufactured by Kobunshi Keiki Co., Ltd.) in a room temperature environment of 25 ° C.

  The amount of the acicular heat conductive filler to be blended with the heat resistant rubber is preferably 5 to 40 vol%. If the length is more than 40 vol%, the difficulty in producing the member becomes high, and if it is less than 5 vol%, the effect of the present invention cannot be fully exhibited. More preferably, a content of 10 to 30 vol% is desirable.

  The effect of the present invention can be expected more preferably when the thickness of the elastic layer is 50 to 500 μm. When it is thicker than 500 μm, the direction in which the dimension can exist in the layer becomes relatively free, and the effect of the present invention is diminished. When the thickness is less than 50 μm, the softness as the original elastic layer cannot be sufficiently exerted and the image quality is affected. A range of 100 to 500 μm is more preferable.

  The seamless cylindrical member can be manufactured as follows. First, a base material is prepared, and the surface is treated with a silicone-based primer (trade name: DY39-051, manufactured by Toray Dow Corning Silicone Co., Ltd.), and an uncrosslinked heat-resistant rubber material is coated on the surface to a predetermined thickness. . The heat-resistant rubber raw material may be diluted with a soluble solvent as necessary. Various known methods can be used as the coating method. In this embodiment, the heat-resistant rubber material is extruded from a ring-shaped slit concentrically provided on the outer side of the base material, and is formed in the longitudinal direction of the base material of the base material. The elastic layer was formed by a method of coating to a uniform thickness by moving the slit. This elastic layer can be obtained as a rubber-crosslinked elastic layer by heat treatment for 30 minutes to 4 hours at a curing temperature specified by the material, for example, a temperature of 100 to 200 ° C. for silicone rubber. . After curing, the surface of the elastic layer is treated with a silicone primer, and a heat shrinkable fluororesin tube (for example, available from Gunze Co., Ltd.) whose inner diameter is slightly larger and whose inner surface is defluorinated is coated and heated. Thus, the seamless cylindrical member according to the present invention can be manufactured.

-Description of heat fixing device-
An example of the heat fixing device of the present invention will be described. Heat Fixing Device Example FIG. 3 is a schematic cross-sectional view of an example of a belt (film) heating type fixing device according to the present invention. The fixing device of this example is a pressure roller driving type fixing device using a cylindrical seamless belt.

  Reference numeral 31 denotes a heating body (heater), 32 denotes a heater holder (heating body holding member) that fixes and supports the heating body, 33 denotes a cylindrical seamless belt, and the assembly of the heating body 31 and the heater holder 32 described above. On the other hand, it is loosely fitted as a heating assembly. Reference numeral 34 denotes an elastic pressure roller as a pressure member.

  The elastic pressure roller 34 has bearings rotatably supported at both end shafts. The heating assembly is arranged in parallel on the pressure roller 34 with the heating body 31 facing downward. A pressure stay (not shown) is pressed from above with a predetermined pressing force against the elasticity of the pressure roller 34, and the belt 33 is sandwiched between the heating body 31 and the elastic pressure roller 34 to have a predetermined width. A nip portion (heating nip portion, fixing nip portion) N is formed.

  The pressure roller 34 is rotationally driven by the driving means M in the counterclockwise direction indicated by the arrow b. As the pressure roller 34 rotates, the inner surface of the belt 33 slides on the surface of the heating body 31 and rotates around the heater holder 32 in the clockwise direction indicated by the arrow a. The heater holder 32 also functions as a guide member for the rotating belt 33.

  The heating body 31 is a ceramic heater in the apparatus of this example, and the temperature is quickly raised by energization and is adjusted to a predetermined fixing temperature.

  Then, the pressure roller 34 is driven to rotate, and the belt 33 is driven to rotate. As a result, the heater 31 is energized to rise to a predetermined fixing temperature, and the temperature is adjusted to a predetermined fixing temperature. A recording material P on which an unfixed toner image t is formed as a heated material conveyed from the image forming mechanism is introduced, and is nipped and conveyed between the nip N, that is, the belt 33 and the pressure roller 34. c is a material to be heated (recording material) conveyance direction.

  In the process in which the recording material P is nipped and conveyed through the nip portion N, the unfixed toner image t on the recording material P is heated and fixed on the recording material P surface by the heat from the heating body 31 via the belt 33. The recording material P that has exited the nip N is separated from the surface of the belt 33 and discharged and conveyed.

  The heating body 31 can use various known heating means, and more specifically, a heating body using a resistance heating element as a heat source, a heating body using a halogen lamp as a heat source, or electromagnetic induction heating as a heat source. The heating body etc. which were made can be utilized.

  For the purpose of solving the problems in a heating element (ceramic heater) formed of ceramic having a resistance heating element therein, as the heating element, for example, a ceramic substrate having heat resistance, insulation and good thermal conductivity In addition, a resistance heating element pattern made of silver-palladium is formed in the longitudinal direction of the ceramic substrate by a known method such as screen printing, with the direction orthogonal to the conveying direction of the heated material as the longitudinal direction. It is possible to use those formed by coating with a glass of as a protective layer.

  In this example apparatus, the heating element 31 is a ceramic heater, and a silver-palladium resistance heating element line pattern is formed in the longitudinal direction on the alumina sintered body substrate surface having a longitudinal length of 220 mm, a width of 9 mm, and a thickness of 1 mm. A glass-coated surface was used.

  Temperature detection means (not shown) is provided on the surface of the belt 33 at the nip downstream position and on the back of the heating body, which is the surface opposite to the roller, and a voltage control device (not shown) is provided based on the temperature detection signal. The temperature control can be performed by controlling the voltage applied to the resistance heating element of the heating element.

  In this example apparatus, the material of the heater holder 32 is a liquid crystal polymer, the cross-sectional shape is a semicircular arc shape, and a groove for fitting the heating body 31 along the length is formed on the lower surface of the heater holder 32. Then, the heating body 31 was fitted into the groove and adhered and fixedly supported.

  In this apparatus, the heater holder 32 is pressed from above with a load of about 10 kg against the elasticity of the pressure roller 34 by means of a pressure stay (not shown), and the heating body 31 and the elastic pressure roller 34 are pressed. A nip portion N having a predetermined width is formed by sandwiching the belt 33 therebetween.

-Explanation of thermal conductivity meter-
Thermal conductivity and hardness were measured as characteristics of the elastic layer. For the measurement of these characteristics, the elastic layer of the seamless cylindrical member was molded without primer treatment, and only the elastic layer was peeled off and taken out, and a measurement sample was obtained by overlapping a 30 mm × 12 mm thickness. The thermal conductivity is measured in a room temperature environment of 25 ° C with a hot disk method thermophysical property measuring device (model: TPA-501, manufactured by Kyoto Electronics Industry Co., Ltd.), and anisotropic thermal conductivity analysis is performed to measure the heat in the thickness direction. Conductivity was calculated.

  The following members were manufactured as the seamless cylindrical member of Example 1. A pitch-based carbon fiber (manufactured by Nippon Graphite Carbon Co., Ltd.) with a minor axis diameter of 10μm and a major axis length of L = 1mm is blended at a rate of 10vol% into the prepared silicone rubber stock solution so that the elastic layer has a thickness of 500μm. A seamless cylindrical member was obtained by forming on a SUS cylindrical substrate having a thickness of 50 μm and covering the surface with a fluororesin tube.

  A seamless cylindrical member was obtained in the same manner as in Example 1 except that pitch-based carbon fiber (manufactured by Nippon Graphite Carbon Co., Ltd.) having a major axis length L = 2 mm was used as the seamless cylindrical member of Example 2.

  As the seamless cylindrical member of Example 3, pitch-based carbon fiber (manufactured by Nippon Graphite Carbon Co., Ltd.) was used in the same manner as in Example 1 except that 30 vol% was added to the prepared silicone rubber stock solution. Obtained.

  As a seamless cylindrical member of Example 4, pitch-type carbon fiber (manufactured by Nippon Graphite Carbon Co., Ltd.) was used in the same manner as in Example 2 except that 30 vol% was added to the prepared silicone rubber stock solution. Obtained.

  As a seamless cylindrical member of Example 5, a seamless cylindrical member was obtained in the same manner as in Example 1 except that the elastic layer was formed on a SUS cylindrical base material having a thickness of 50 μm so as to have a thickness of 100 μm.

(Comparative Example 1)
As a seamless cylindrical member of Comparative Example 1, a seamless cylindrical member was obtained in the same manner as in Example 1 except that no pitch-based carbon fiber was blended.

(Comparative Example 2)
A seamless cylindrical member was obtained in the same manner as in Example 1 except that pitch-based carbon fiber (manufactured by Nippon Graphite Carbon Co., Ltd.) having a major axis length L = 10 mm was used as the seamless cylindrical member of Comparative Example 2. However, it became difficult to form due to the length of the pitch-based carbon fiber, and a seamless cylindrical member could not be obtained.

(Comparative Example 3)
As a seamless cylindrical member of Comparative Example 3, pitch-based carbon fiber (manufactured by Nippon Graphite Carbon Co., Ltd.) was used in the same manner as in Example 1 except that 50 vol% was added to the prepared silicone rubber stock solution. Although it tried to obtain, it became difficult to form due to the large amount of pitch-based carbon fiber, and a seamless cylindrical member could not be obtained.

-Explanation of evaluation experiment-
In order to confirm the effect of the present invention, the following evaluation experiment was conducted. The seamless cylindrical member of Comparative Example 1 was mounted using the heat fixing apparatus of FIG. 3, the temperature was set so that the belt surface was 170 ° C., and the linear velocity was rotated to 60 mm / s.

  First, a first evaluation sample was obtained by passing A4 paper with unfixed toner on the entire surface in the vertical direction. For A4 paper with unfixed toner on the entire surface, prepare a commercially available electrophotographic color printer (trade name: LBP-2710, Canon Inc.) so that the paper can be taken out before the fixing device. It was obtained by printing a two-color solid image with a magenta density of 100% and a cyan density of 100%. The gloss of the first evaluation sample using the member of Comparative Example 1 was measured using a gloss meter (trade name: PG-1, angle 60 °, manufactured by Nippon Denshoku Co., Ltd.).

  Next, for the members of Examples 1 to 5, the set value of the belt surface temperature was changed so as to be the gloss value of the first evaluation sample using the member of Comparative Example 1. These set values of the belt surface temperature were evaluated as a difference from Comparative Example 1, that is, a set temperature difference. This set temperature difference serves as an index for measuring the thermal conductivity to the recording medium, and it can be evaluated that a member that can lower the set temperature has better thermal conductivity.

  Next, in each of the members of Examples 1 to 5 and Comparative Example 1, the paper (105 mm × 297 mm) obtained by cutting the A4 size paper in half vertically at the surface temperature set in the above evaluation, 100 sheets were passed at the position, and immediately thereafter, A4 paper on which the unfixed toner was placed on the entire surface was passed in the vertical direction to obtain a second evaluation sample.

  This second evaluation sample measures the gloss at a paper position corresponding to the belt longitudinal center position and a paper position corresponding to a position 30 mm from the belt longitudinal end, and a paper position corresponding to a position 30 mm from the belt longitudinal end. The difference in gloss was evaluated as ΔG = (Ge−Gc), and the difference in gloss as an index of image uniformity was evaluated.

All the papers used for these evaluations were named “Color Laser Copier Paper” (basis weight 82 g / m ² , manufactured by Canon Sales Co., Ltd.).

  FIG. 4 shows the evaluation results. As described above, in the example in which the present invention is implemented, the set temperature of the member surface necessary for melting the toner to the same degree can be set lower by 10 ° C. or more than the comparative example, and the thermal conductivity in the thickness direction can be set. It was confirmed that the thermal conductivity to the recording medium was largely secured.

  At the same time, it was confirmed that the difference in gloss was kept small, good image quality uniformity was obtained, and sufficient thermal conductivity in the longitudinal direction of the cylinder could be secured.

Seamless cylindrical member cross section and overview Needle-like thermally conductive filler Heat fixing device Examples and Comparative Examples

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Base material 12 Elastic layer 13 Surface layer 14 Seam race cylindrical member 21 Short axis diameter 22 Long axis length 31 Heater 32 Heater holder 33 Belt (seamless cylindrical member)
34 Pressure roller 34a Metal core 34b Elastic layer 34c Surface layer M Motor P Recording paper t Toner N Nip part a, b, c Movement direction

Claims (5)

A member that fixes electrophotographic toner onto a recording medium by heating and pressing,
At least a base layer, an elastic layer, and a release layer are sequentially stacked,
In a seamless cylindrical member that conducts heat to the release layer through the elastic layer,
This elastic layer is a heat-resistant rubber containing 5 or more and 40 vol% or less of a needle-like thermally conductive filler having a length of 0.5 or more and 5 mm or less, and the thermal conductivity in the thickness direction of this elastic layer is 0.5 W. A seamless cylindrical member characterized by being over / mK. The seamless cylindrical member according to claim 1,
A seamless cylindrical member, wherein the elastic layer has a thickness of 50 to 500 µm.   The seamless cylindrical member according to claim 1, wherein the needle-like thermally conductive filler is a pitch-based carbon fiber.   The seamless cylindrical member according to claim 1, wherein the heat-resistant rubber is silicone rubber or fluorine rubber. An apparatus for fixing electrophotographic toner onto a recording medium by heating and pressurization,
Comprising at least one seamless cylindrical member according to claims 1 to 4,
A heating and fixing apparatus having a heating means inside a seamless cylindrical member.

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