JP2012225986A - Fixing belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing belt which has excellent fixability to be sufficiently applicable to even a color machine.SOLUTION: The fixing belt includes a tubular base member, an elastic layer provided on the outer periphery of the base member, and a surface layer provided on the outer periphery of the elastic layer. The elastic layer is formed by mixing a filler in rubber, and a thermal effusivity expressed by formula ((heat conductivity)×(density)×(specific heat capacity))on the basis of the heat conductivity, the density, and the specific heat capacity of the elastic layer is 1.2 or more.

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a facsimile machine, or a laser beam printer, and more particularly, an image forming apparatus using a plurality of types of color toners, and heats and fixes a toner image transferred onto a transfer object. The present invention relates to a fixing belt used for the purpose.

  In image forming apparatuses such as electrophotographic copying machines, facsimile machines, and laser beam printers, at the final stage of printing and copying, a fixing belt (fixing sleeve), a fixing roller, and a pressure roller provided with a heating source are provided. In general, a thermal fixing method is used in which a material to which a toner image is transferred is passed while being pressed against each other, and unfixed toner is heated and melted. As the fixing belt used here, a resin layer or the like for providing elasticity is provided on a cylindrical base material made of polyimide resin or the like, and further on the surface of the base material (surface in contact with the transfer object). In order to impart releasability, a material provided with a fluororesin coating layer is widely used.

  In order to improve the fixability, it is necessary that the transfer object is sufficiently heated by a heating source provided inside the belt. Therefore, excellent heat conductivity is required for the fixing belt. Further, in fixing in an image forming apparatus (color machine) using a plurality of types of color toners, it is necessary to mix a plurality of types of color toners in a molten state at the time of fixing. Accordingly, the fixing belt for this application (compatible with color machines) is also required to have an appropriate elasticity that can sufficiently wrap and melt and mix color toner.

  As described above, the fixing belt is required to have excellent thermal conductivity and appropriate elasticity. Therefore, in Patent Document 1, a heat-resistant elastomer layer (elastic layer) is formed on the outer periphery of a tubular substrate. ) And a fluororesin layer thereon, the thickness of the tubular substrate, the fluororesin layer and the heat-resistant elastomer layer is defined, and the thickness, hardness and heat of the heat-resistant elastomer are defined. There has been proposed a fixing belt (Claim 2) in which the relationship of conductivity is defined to be within a predetermined range.

  Patent Document 2 discloses a fixing belt having a laminated structure in which a heat-resistant elastomer layer is formed on the outer periphery of a metal tube or a heat-resistant plastic tube, and a layer of silicone rubber or fluororesin is formed on the outer periphery. A fixing belt is disclosed in which the amount of strain with respect to the load, the thickness of each layer, and the hardness and thermal conductivity of the heat-resistant elastomer layer are within a predetermined range (claim 1). And in order to make the heat conductivity of a heat-resistant elastomer layer into a predetermined range, the method of mix | blending high heat conductive fillers, such as a silica, an alumina, a boron nitride, is proposed (paragraph 0012).

  Further, in Patent Document 3, a fixing belt having a tubular base material, an elastic layer provided on the outer periphery of the base material, and a surface layer provided on the outer periphery of the elastic layer, the elastic layer is made of rubber. 10% + 3Y <750, 3X + 30Y> 170, where X is the volume% of the filler and Y is the volume% of the carbon nanotubes in the elastic layer. A fixing belt characterized by satisfying Y> 0.1 is disclosed. Further, it is stated that this configuration can achieve both high thermal conductivity and appropriate elasticity and does not lower the mechanical strength.

Japanese Patent No. 3735991 Japanese Patent No. 3712086 JP 2010-92008 JP

  As described above, conventionally, excellent fixing properties have been achieved by the high thermal conductivity of the fixing belt. However, as a result of studies by the present inventors, it has been found that sufficient fixability may not be obtained only by high thermal conductivity. The present invention provides a fixing belt capable of providing excellent fixability that can withstand high-speed printing, based on a range of an index that can be used as an alternative to thermal conductivity and that can reliably provide excellent fixability. The task is to do.

As a result of intensive studies, the present inventor has determined, based on the thermal conductivity, density, and specific heat capacity of the elastic layer of the fixing belt, the thermal permeability represented by the formula: (thermal conductivity × density × specific heat capacity) ^0.5 It was found that a fixing belt exhibiting excellent fixing properties can be obtained when the value is high. Further, it has been found that if an elastic layer is formed using a heat-resistant elastomer such as silicone rubber or fluororubber and the heat permeation rate is 1.2 or more, a fixing belt having high fixability capable of withstanding high-speed printing can be obtained. The present invention having the following configuration was completed.

The invention according to claim 1 is a fixing belt having a tube-shaped base material, an elastic layer provided on the outer periphery of the base material, and a surface layer provided on the outer periphery of the elastic layer, wherein the elastic layer comprises: Heat represented by formula: (thermal conductivity × density × specific heat capacity) ^0.5 , which is formed by blending a heat-resistant elastomer with a filler and based on the thermal conductivity, density and specific heat capacity of the elastic layer A fixing belt having a penetration rate of 1.2 or more.

By setting the heat permeability of the elastic layer to 1.2 or more, it is possible to obtain a fixing belt that can provide excellent fixing properties that can withstand high-speed printing. The thermal conductivity is calculated with the unit of W / m · K, the density of unit kg / m ³ , and the specific heat capacity of unit J / Kg · K.

  The invention according to claim 2 is the fixing belt according to claim 1, wherein the heat permeability is 2.0 or more. By setting the heat permeability of the elastic layer to 2.0 or more, it is possible to obtain a fixing belt that can provide further excellent fixing properties.

  The invention according to claim 3 is the fixing belt according to claim 1 or 2, wherein the filler is a filler having a specific gravity of 3.0 or more. As a method for increasing the thermal permeability of the elastic layer, a method of blending a filler having a high specific gravity and high thermal conductivity into a matrix material constituting the elastic layer, and a high specific heat capacity such as a microballoon The method of mix | blending this filler in a matrix material etc. can be mentioned. In particular, it is preferable to add a high specific gravity filler having a specific gravity of 3.0 or more because the heat penetration rate is easily increased. More preferably, a filler having a specific gravity of 5.0 or more is blended, and a filler having a specific gravity of 7.0 or more is more preferably blended.

  According to a fourth aspect of the present invention, in the fixing belt according to the third aspect, the filler is a powder of zinc oxide, iron, copper, or iron-silicon alloy. As the high specific gravity filler, zinc oxide, iron, copper or iron silicon alloy powder is preferably used. In addition, alumina, metal silicon, silicon carbide, etc. can be used as the filler.

  As the matrix material constituting the elastic layer, a heat-resistant elastomer that is used as a matrix material for a resin layer that imparts elasticity in a conventional fixing belt can be used. As the heat resistant elastomer, those which are not easily deteriorated by heating during the production and use of the fixing belt and have high elasticity are preferable. It is not necessarily limited to vulcanized rubber. As the heat-resistant elastomer, silicone rubber or fluororubber is preferably used since it has excellent heat resistance. The invention according to claim 5 corresponds to this preferable aspect, and the matrix material constituting the elastic layer is silicone rubber or fluororubber. The fixing belt as described in 1. above.

  As the material for the surface layer, a fluororesin having excellent toner releasability and excellent durability and color toner fixability is preferably used.

  Examples of the tube-shaped (tubular) base material include a tube-shaped base material and a cylindrical base material made of a flexible material. Accordingly, the fixing belt of the present invention includes a tube-shaped base material made of a flexible material, an elastic layer provided on the outer periphery thereof, a fixing sleeve having a structure in which a surface layer is formed on the outer periphery of the elastic layer, and a cylindrical shape. And a fixing roller having a structure in which a surface layer is formed on the outer peripheral side of the elastic layer.

  Specifically, a metal tube or a heat-resistant plastic tube can be used as the material of the tube-shaped base material, but the tube-shaped base material made of a flexible material can be a tube made of polyimide or polyamideimide. The film (tube) is preferably used because it has excellent heat resistance and mechanical strength. In order to improve the thermal conductivity of the equipment, an inorganic filler or the like may be added as long as the mechanical strength allows. A metal tube etc. can also be used as a cylindrical base material.

  In the fixing belt of the present invention, if the adhesion between the layers is insufficient, the layers may be peeled off during use of the printer (copier). Therefore, usually, a primer layer is provided between the base material and the elastic layer and between the elastic layer and the surface layer in order to improve the adhesion between the layers.

  The primer layer provided between the base material and the elastic layer is referred to as a lower primer layer, and the primer layer provided between the elastic layer and the surface layer is referred to as an upper primer layer. The material of the primer layer is not particularly limited, but from the viewpoint of adhesion, a rubber primer is preferable for the lower primer layer, and a fluorine primer is preferable for the upper primer layer.

  Although what is marketed can be used as resin for rubber-type primers, Preferably, the kind is selected according to a base material. For example, if the base material is a metal, X-33-173 (manufactured by Shin-Etsu Silicone Co., Ltd.) can be cited as a preferable rubber-based primer resin. If the base material is a resin such as polyimide, X-33 -174 (manufactured by Shin-Etsu Silicone).

  In addition, by selecting a silicone rubber as the rubber constituting the elastic layer and adding a proper amount of an adhesive component such as a silane coupling agent in the silicone rubber, or adding a silicone rubber to the lower primer layer, the substrate / Adhesion between the lower primer layer / elastic layer is improved.

  The method for producing the fixing belt of the present invention is not particularly limited. For example, a resin in which a vulcanizing agent and a filler for increasing the heat permeability are mixed with a heat-resistant elastomer such as silicone rubber or fluororubber on the outer periphery of a tubular base material or a cylindrical base material which is the innermost layer The composition is applied with a dispenser and then vulcanized to form an elastic layer, and then a dispersion of fluororesin is applied onto the elastic layer, heat treated and sintered to form a surface layer. it can. Preferably, in order to improve the adhesion between the layers, before applying the heat resistant elastomer, a lower primer layer is formed on the outer periphery of the base material, and before applying the fluororesin dispersion, the elastic layer An upper primer layer is formed on the outer periphery of the substrate.

  A heat-shrinkable tube made of a heat-resistant elastomer composition containing a vulcanizing agent and a filler for increasing the heat permeability is prepared, and this is used as a base material (or a base material on which a lower primer layer is formed). The elastic layer may be formed by covering the outer periphery of the substrate and causing heat shrinkage.

  The fixing belt of the present invention is used in a fixing unit of various image forming apparatuses. In the fixing unit, a heating source is provided in the fixing belt, and the fixing belt is opposed to and pressed against a pressure roller made of a rubber roller or the like. Fix the toner by melting it by heating.

  The fixing belt of the present invention has an excellent fixing property corresponding to the recent increase in printing speed.

FIG. 3 is a cross-sectional view orthogonal to a rotation axis of an example of a fixing belt of the present invention.

  Next, although the form for implementing this invention is demonstrated, the range of this invention is not limited only to this form, What was changed in the range which does not impair the meaning of this invention is also included in this invention. It is.

  FIG. 1 is a diagram schematically showing an example of a fixing belt (roller) according to the present invention, and is a cross-sectional view orthogonal to the rotation axis of the fixing belt. In FIG. 1, 1 is a base material, 3 is an elastic layer, and 5 is a surface layer. Furthermore, a primer layer 2 (lower primer) and a primer layer 4 (upper primer) are provided between the base material 1 and the elastic layer 3 and between the elastic layer 3 and the surface layer 5 for improving adhesion. .

  The base material 1 in the example of FIG. 1 is an endless belt made of a polyimide resin. In addition, as the substrate 1, a resin or metal cylinder or columnar solid (roller) can be used. As the resin material for the endless belt, polyamideimide resin or the like can be used instead of polyimide resin, but polyimide resin is preferable in terms of heat resistance, elastic modulus, strength, and the like.

  The substrate 1 is formed by applying an organic solvent solution (polyimide varnish) of a polyimide precursor (polyamic acid) in which an appropriate amount of a filler for improving thermal conductivity is blended to the outer peripheral surface of a metal cylindrical core body by a dispenser method. , Heated to about 350 ° C. to 450 ° C., and the precursor is dehydrated and ring-closed to form a polyimide. Examples of the polyimide varnish include Ube Industries U Varnish S, and examples of the organic solvent include N-methyl-2-pyrrolidone and dimethylacetamide, but are not limited thereto.

  The thickness of the endless belt made of such a polyimide resin is preferably about 30 to 80 μm from the viewpoint of durability and elasticity.

  As the matrix material constituting the elastic layer 3, as described above, silicone rubber and fluorine rubber excellent in heat resistance are preferable. A two-layer structure in which the silicone rubber layer is disposed on the substrate 1 side and the fluororubber layer is disposed on the surface layer side may be employed. This two-layered elastic layer has a fluororubber layer on the surface layer 5 side, so that it has excellent adhesion to the surface layer 5 using a fluororesin as a matrix material. Further, since fluororubber has good heat resistance, The silicone rubber layer is prevented from being damaged by the heat, and the silicone rubber layer is preferable because of its elasticity.

  In order to provide excellent heat conduction and appropriate elasticity, the thickness of the elastic layer 3 is preferably 0.1 to 0.5 mm, and more preferably 0.2 mm or more.

  Examples of the fluororesin used as the material for the surface layer 5 provided on the outer peripheral side of the elastic layer 3 include tetrafluoroethylene resin (PTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), and tetrafluoroethylene. -A propylene hexafluoride copolymer etc. are mentioned. In particular, it is preferable to use PTFE or PFA from the viewpoint of heat resistance.

  The thickness of the surface layer 5 made of a fluororesin is preferably 10 to 50 μm, more preferably 10 to 35 μm, and still more preferably 10 to 25 μm. If the thickness of the fluororesin layer is too thin, the durability is inferior, and as the number of copies increases, there is a risk of early wear and loss of mold releasability. When the thickness of the fluororesin layer is too thick, the surface of the fixing belt becomes hard and the fixing property of the color toner is lowered.

Examples 1-21 and Comparative Examples 1-3
A fixing belt shown in FIG. 1 (that is, a fixing sleeve having a base material 1, a primer layer 2, an elastic layer 3, a primer layer 4, and a surface layer 5) was prepared by the following procedure.

[Preparation of Substrate 1]
Dispensing the organic solvent solution of polyimide precursor (polyimide varnish, Ube Industries, trade name: U varnish S) with a suitable amount of filler for improving thermal conductivity on the outer peripheral surface of a metal cylindrical core The precursor was dehydrated and ring-closed to form a polyimide by heating at 350 ° C. to 450 ° C., and then removed from the cylindrical core to obtain a tubular substrate 1. The substrate 1 has a thickness of 50 μm, an inner diameter of 26 mm, and a length of 24 cm.

[Formation of primer layer 2]
X-33-174A / B (rubber-based primer) manufactured by Shin-Etsu Silicone Co., Ltd. was applied on the outer periphery of the substrate obtained above, and air-dried for 30 minutes or more to form primer layer 2 (lower primer layer).

[Production of Elastic Layer 3]
Fillers A and B shown in Tables 1 to 5 were added to the well-known two-liquid silicone rubber with the compositions shown in Tables 1 to 5, and mixed by a rotation and revolution type stirrer. The obtained mixture was applied to the outer peripheral surface of the primer layer 2 obtained above with a dispenser and then molded by thermal vulcanization to obtain an elastic layer 3 having a thickness of 275 μm. In addition, the filler used as the filler A and the filler B is shown below.

(filler)
1. Alumina: Alumina CB-A10 (trade name) manufactured by Showa Denko KK, shape: sphere, average particle size: 10 mm (shown as “alumina” in the table below)
2. Metallic silicon powder: M-Si # 600 (trade name) manufactured by Kinsei Matech Co., Ltd., crushed shape, average particle size: about 6.0 μm (in the following table, indicated as “metal Si”)
3. SiC: SiC having an average particle diameter of 1 μm
4). Zinc oxide: Hakusuitec Co., Ltd., large particle zinc oxide, average particle size: 16.8 μm
5. Copper powder: manufactured by Fukuda Metal Foil Co., Ltd., Cu-HWQ, average particle size: 5 μm
6). Iron powder: manufactured by Höganäs, S110i, average particle size: 40 μm
7). Iron silicon alloy powder: Epson Atmix Co., Ltd., Fe-6.5% Si powder, average particle size: 10 μm

  The thermal conductivity, density, and specific heat capacity of the obtained elastic layer 3 were measured by the following methods. The results are shown in Tables 1-5.

(Measurement method of thermal conductivity)
The thermal conductivity is obtained by multiplying the thermal diffusivity obtained by measuring with the periodic heating method measuring device FTC-1 manufactured by ULVAC-RIKO, the specific heat measured by JIS K 7123 and the density measured by the JIS K 7112A method. Value.
(Measurement method of specific heat capacity)
It was measured according to JIS K 7123.

[Formation of primer layer 4]
DuPont PL-992CL (fluorine-based primer) is applied on the outer periphery of the elastic layer 3 obtained above, dried at 220 ° C. for 2 hours, and a primer layer 4 (upper primer layer) having a thickness of 5 μm. Formed.

[Preparation of surface layer 5]
On the primer layer 4 obtained above, a fluororesin coating (PFA: EM-565CL manufactured by DuPont) is applied and treated at about 340 ° C. to form a surface layer 5 (fluororesin layer). A fixing belt represented by the formula: The thickness of the fluororesin layer was 15 μm.

  With respect to the fixing belt manufactured as described above, fixing property and durability (mechanical strength) were measured by the following method. The results are shown in Tables 1-5.

(Evaluation of fixability)
Using the produced fixing belt, a color image was actually printed and evaluated. The surface temperature during printing was 150 ° C., and the pressing force was 6 kg. In addition, the condition of paper passing at the time of printing was determined by visually checking whether or not there was uneven color and unevenness after printing A4 printing paper continuously at 25 sheets / min. The results are shown in Tables 1 to 5 based on the following criteria.
A: There is no color unevenness and roughness.
○: There is no uneven color, but there is roughness.
X: Both color unevenness and roughness are present.

(Durability evaluation)
A color image was actually printed using the fixing belt produced above. The surface temperature during printing was 150 ° C., and the pressing force was 6 kg. In addition, the condition of paper passing at the time of printing is that A4 printing paper is continuously printed at 25 sheets / minute, and the presence / absence of peeling between the base material 1 / primer layer 2 / elastic layer 3 of the fixing belt is visually confirmed. Evaluation was made based on the following evaluation criteria.

[Evaluation criteria]
○: Peeling hardly occurs.
(Triangle | delta): Although peeling may occur, it is a level which does not interfere with practical use.
X: Numerous peeling occurs and is not at a practical level.

The following are shown from Tables 1-5.
In Comparative Examples 1, 2, and 3 having a heat penetration rate of less than 1.2, the fixability is poor and it is difficult to use as a fixing belt for a color machine.
On the other hand, Examples 1 to 21 having a heat permeability of 1.2 or more have good fixability, can be used as a fixing belt for a color machine, and can be used at a durability level. .
-Among them, Examples 10, 12, 14, 16, 20, and 21 having a heat permeability of 2.0 or more show particularly good fixability.

1 Base material 2 Lower primer layer 3 Elastic layer 4 Upper primer layer 5 Surface layer

Claims (5)

A fixing belt having a tubular base material, an elastic layer provided on the outer periphery of the base material, and a surface layer provided on the outer periphery of the elastic layer, wherein the elastic layer comprises a heat-resistant elastomer and a filler. The thermal permeability represented by the formula: (thermal conductivity × density × specific heat capacity) ^0.5 based on the thermal conductivity, density and specific heat capacity of the elastic layer is 1.2 or more. A fixing belt characterized by being.   The fixing belt according to claim 1, wherein the heat permeability is 2.0 or more.   The fixing belt according to claim 1, wherein the filler is a filler having a specific gravity of 3.0 or more.   The fixing belt according to claim 3, wherein the filler is a powder of zinc oxide, iron, copper, or an iron-silicon alloy.   The fixing belt according to claim 1, wherein the matrix material constituting the elastic layer is silicone rubber or fluorine rubber.

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