Image fixing rotatable member and image fixing apparatus using same

Abstract: An image fixing rotatable member including a base member; a silicone rubber layer (4, 14) on the base member; a primer layer on the silicone rubber layer (5, 15); and a fluorine resin layer (6, 16) on the primer layer; wherein the primer layer (5, 15) is binder material containing the fluorine resin and aminosilane compound.

Description: The present invention relates to an image fixing rotatable member and to an image fixing apparatus using the member. The member may be used with electrophotographic apparatus such as copying apparatus, a laser beam printer and an electrostatic recording apparatus such as a multi-stylus printer. The image fixing rotatable member can be used to fix an unfixed toner image on a recording material. Image fixing apparatus is widely used in which heat and/or pressure is applied to an unfixed toner image by a roller or by a pair or rollers. In such apparatus it is necessary to prevent toner off-set, and therefore the surface of the roller is required to have sufficient release properties. This requirement is particularly significant where the fixing apparatus brings about heat fusion of the toner. A widely used type of fixing roller in which these requirements are intended to be made is shown in Figure 3A. The roller generally indicated by the reference numeral 33 comprises a metallic core 31 which is coated with a fluorine resin 32 such as PTFE and PFA. These resins have good release properties, and this roller can be used as heating roller for applying heat to a toner during image fixation. The fixing roller 33 exhibits good release and durability properties, but since the resin layer 32 is hard, the recording material conveying property and the image fixation property are not sufficient. Figure 3B shows fixing roller 44 having a metallic core 31 and an elastic layer 42 e.g. of silicone rubber and fluorine resin. This roller exhibits good image fixing properties and good conveyance of the recording material during the initial stage of use, but the durability of the surface of the roller is poor and it is subject to deterioration with long term use resulting in poor release properties. The toner off-set preventing properties and the conveying properties also deteriorate with the result that the recording can be wrinkled and curled. Furthermore, the roller can easily be damaged when it is subject to an overload. It is therefore difficult to provide a toner fixing roller in which both the image fixing properties and the release properties are maintained over a long period. In order to solve this problem, US patent application Nos 857023 and 094418, both of which have been assigned to the assignee of this application, have proposed a roller as shown in Figure 3C in which a metallic core 51 is coated with an elastic layer 52 made of silicone rubber, fluorine rubber or the like which is in turn coated with a resin layer 53 made of PTFE, PFA resin or the like. However, in the roller as shown in Figure 3C the affinity between the elastic layer 52 and the resin layer 53 is insufficient, so that the bond between them can break down with the possible result that the resin layer 53 partly peels off the elastic layer 32. For a further example of the prior art see JP-A-61-38957. In one aspect the invention provides an image fixing rotatable member, comprising: a base member; a silicone rubber layer on said base member; a primer layer on said silicone rubber layer; and a fluorine resin layer on said primer layer; characterised in that said primer layer is of binder resin comprising an aminosilane compound and a larger amount of fluorine resin. In a further aspect the invention provides a fixing apparatus, comprising a pair of rotatable members forming a nip through which an image bearing member carrying an unfixed toner image is passed to fix the unfixed toner image, at least one of the rotatable members being an image fixing rotatable member as aforesaid. The invention also provides a method for making an image fixing rotatable member, the method comprising the steps of: adhering a silicone rubber layer) to a base member; coating said silicone rubber layer with a primer layer; and coating the primer layer with fluorine resin; characterised in that a primer layer is of binder resin comprising an aminosilane compound and a larger amount of fluorine resin, and the member is heated to sinter said fluorine and if necessary to cure the binder. The image fixing rotatable member as aforesaid can exhibit high resistance to peeling between the fluorine resin layer and the silicone rubber layer. The invention will now be further described with reference to the accompanying drawings: BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a sectional view of an image fixing apparatus according to an embodiment of the present invention. Figure 2 is an enlarged view of a part of a heating roller of the apparatus shown in Figure 1. Figures 3A, 3B and 3C are sectional views of conventional heating rollers. DESCRIPTION OF THE PREFERRED EMBODIMENTS The inventors have made various investigations and experiments for improving an image fixing roller having a resin layer on an elastic layer, which involves both of various advantages and some problems, and found that high durability to wear, good releasing properties, image fixing properties and recording material conveying properties can be provided for a long period of time by providing a primer layer made of binder material containing aminosilane compound between the silicone rubber elastic layer and the fluorine resin coating layer. In conjunction with the accompanying drawings, an image fixing roller and an image fixing apparatus using the same will be described in detail. Referring now to Figure 1, there is shown an image fixing apparatus in cross-section, using the image fixing roller according to the present invention. Figure 2 is an enlarged sectional view of a major part of the fixing roller. The image fixing apparatus comprises a heating roller 1 having a heating source H therein and contactable with a toner image T which is unfixed and carried on a recording sheet 1 of paper and a back-up or pressing roller 10 for pressing the recording sheet P carrying the toner image to the heating roller 1. Each of the heating roller 1 and the pressing roller 10 comprises a core metal 2 or 12 made of metal, a first primer layer 3 or 13 of silane material, an elastic layer 4 or 14 of silicone rubber, a second primer layer 5 or 15 of binder material containing fluorine resin and aminosilane compound, and a fluorine resin layer 6 or 16 having good releasing properties for preventing toner off-set, in the order named from the inside thereof. The fixing apparatus further comprises temperature control means G for detecting a temperature of the surface of the fixing roller 1 and to control the amount of heat generation by the heater H to provide an optimum surface temperature for fusing the toner, for example, a predetermined temperature between 160 - 200 °C. The fixing apparatus further comprises toner off-set preventing liquid applying means C for applying toner off-set preventing liquid such as silicone or the like on the surface of the heating roller 1 and other means. The core metal 2 is preferably made of a high thermal conductivity material such as aluminum. The first primer layer of silane material is made of, for example, DY 39-012, available from Toray Silicone Kabushiki Kaisha, Japan. The silicone rubber is not limited but is preferably vulcanized silicone rubber mainly made of high polymer polyorganosiloxane and added with a great amount of extender filler material such as quartz powder, and having a rubber hardness of 40 - 95 degrees (JIS A), particularly 60 - 80 degrees. On the elastic layer 4, a second primer layer 5 made of binder material containing fluorine resin material and aminosilane compound is formed. The fluorine resin is contained in order to strengthen the contact with the upper layer, that is, the fluorine resin coating layer, and it may be of monopolymer or copolymer of tetrafluoroethylene. The main content of the binder material is a heat resistive resin material having good affinity with the fluorine resin, for example, aromatic polyamideimide resin, polyimide resin, polyarylenesulfide resin such as polyphenylene sulfide resin, and silicon compound such as alkali or amine silicate, alkyl silicate, lithium polysilicate or silca colloid. By containing the aminosilane compound, the affinity of the silicone rubber is assured. Typical examples thereof are, α-aminopropyltriethoxysilane, N-β-aminoethyl-α-aminopropyltrimethoxysilane, N-(trimethoxysilylpropyl)ethylenediamine, N-β-aminoethyl-α-aminopropylmethyldimethoxysilane, α-ureidepropyltriethoxysilane, β-aminoethyl-β-aminoethyl-α-aminopropyltrimethoxysilane. The content of the aminosilane compound is preferably 1 - 30 parts, further preferably 1 - 20 parts, by weight on the basis of 100 parts by weight of the binder material. It is prepared as aqueous dispersion, which is the second primer. On the second primer layer 5, a resin layer having a good resistance to wear, more particularly, a fluorine resin layer 6 having also good releasing properties, is formed. The material of the resin layer 6 is preferably PFA resin (copolymer of tetrafluoroethylene resin and perfluoroalkoxyethylene resin) or PTFE resin (tetrafluoroethylene resin). The pressing roller 10 will be described. The pressing roller 10 has a similar structure, and the core metal 12 is made of stainless or another steel, and on the core metal 12 a (first) primer layer 13 of silane material is formed. On the first primer layer 13 an elastic layer 14 of silicone rubber having good thermal conductivity is formed. The silicone rubber of the elastic layer may be made of the same material as the heating roller 1, but the rubber hardness is preferably lower than that of the heating roller in order to assure a sufficient width of a nip formed with the heating roller, more particularly 20 - 60 degrees (JIS A), further preferably 30 - 50 degrees. On the elastic layer 14, a second primer layer 15 made of a binder material containing fluorine resin and aminosilane compound is formed. On the second primary layer 15, a resin layer, more particularly a fluorine resin layer 16 of PFA resin or PTFE resin or the like is formed. The heating roller 1 is preferably reversely crowned, that is, the diameter thereof at the longitudinal center is slightly smaller than that of the longitudinal ends thereof. As described, the fixing roller of the present invention is provided between the silicone rubber elastic layer 4 or 14 and the fluorine resin coating layer 6 or 16 with a primer layer made of a binder material containing fluorine resin and the aminosilane compound exhibiting good contactness or affinity with those layers, and therefore, the bonding and contactness properties with the elastic layer 4 or 14 and with the resin layer 6 or 16 are excellent, so that the surface layer is prevented from partly peeling for a long period of time, without deterioration of the elasticity of the elastic layer. Thus, the problem of the surface layer being partly removed is solved, and therefore, the advantages of the roller having the resin layer on the elastic layer are used to the maximum extent. The method of manufacturing the heating roller 1 and the pressing roller 10 according to the embodiment will be described. For the manufacturing of the heating roller 1, a core metal 2 is made of aluminum so as to be reversely crowned and to have a thickness of 6.5 mm and the outer diameter of 58.3 mm at the longitudinal center thereof (amount of reverse crown is 150 microns). The surface thereof is sand-blasted to be degreased and is dried. Then, silane primer DY 39-012 available from Toray Silicone Kabushiki Kaisha, Japan is applied thereon in a thickness of 7 microns, and it is heated at 120 °C for 20 minutes. Thereafter, a heat-vulcanized silicone rubber sheet having a good thermal conductivity is wrapped, and is press-vulcanized at 160 °C for 30 minutes. The rubber was machined to have a thickness of 0.5 mm. Thus, the silicone rubber roller is produced. The wrapped silicone rubber sheet is produced by kneading the following and is formed into a sheet having a thickness of approximately 2 mm: Rubber stock SE1186: (Toray Silicone Kabushiki Kaisha) 100 Iron Oxide Red CP21: (Toray Silicone Kabushiki Kaisha) 2 Cross Rinker RC4: (Toray Silicone Kabushiki Kaisha) [2,5-dimethyl-2,5-(tert-butylperoxy)-hexane 50 % paste] 0.8 Quartz powder crystelite VX-S: (Tsuchiya Kaorin Kabushiki Kaisha) 80 A mixture of a first component which is TPS (Liton U-I) available from Phylips, U.S.A. particulated to the average particle size of 10 microns and a second component which contains liquid solution of N-methylpyrrolidone (polyamideimide (PAI) resin), available from ROAN PULAN under the trade name of Rodephtal R200) having a concentration of 30 % and aqueous dispersion of polyamideimide (resin content of approximately 30 % and surface active agent content of 10 %/PAI) produced by pulverizing and mixing for 48 hours by ball mill ion exchange water and acrylic sodium sulfate are prepared. The first component and the second component are mixed so that PPS/PAI is 10/1, and it was pulverized and mixed for 20 hours in a ball mill, and the product is mixed with 60 % PTFE suspension (polyflon dispersion D-I available from Daikin Kabushiki Kaisha, Japan) and α-aminopropyltriethoxysilane so that the weight ratio PAI + PPS/PTFE/α-aminopropyltriethoxysilane is 100/100/20, by which a aqueous dispersion is prepared as for the primer. The primer is applied on the silicone rubber layer and is dried at the temperature of 100 °C and then, the roller is kept under a low temperature condition of 10 °C. After sufficient period of time, PTFE solution is applied by a roll coater under a temperature of 10 °C in a thickness of 20 microns, and is dried for three minutes under 250 °C. The fluorine resin liquid is coated under a low temperature condition because the fluorine resin is prevented from cracking during the drying process. The roller thus produced is maintained in an oven and is heated at 450 °C for 2 minutes to sinter the PTFE resin, and then it is quickly cooled. By the quick cooling after the sintering, a sintered fluorine resin layer having a degree of crystallinity of not more than 95 %, a tensile strength of not less than 50 kg/cm² and a contact angle relative to water of not less than 100 degrees is formed on the silicone rubber roller with a high bonding strength and with sufficient thickness. By producing the surface layer by sintering resin liquid, it is bonded with resin powder in the primer layer, and therefore, a strong bonding can be produced. The resin material mixed into the primer layer is preferably the same as the surface layer. An image fixing durability test was performed using the heating and pressing rollers produced in the manner described above. The surface temperature of the heating roller 1 was controlled at 180 °C, and the sheet feeding speed was 440 mm/sec, and the process speed was 70 sheets (A4)/minute. The image fixing properties were good when the temperature is 15 °C, and the amount of toner off-set was as small as one fifth the conventional off-set amount. Even when the temperature was 32.5 °C and the humidity was 85 %, the transfer sheet was not wrinkled, and the curling was very small so that the sheets were properly stacked on a sorter or the like. The image was not collapsed, and the quality of the image was good. Those good conditions were maintained even after 300,000 sheets were processed by the pressing and heating rollers, and there was not observed any problem even after 500,000 sheets were processed. The image fixing roller described in the foregoing is preferably used for each of the heating and pressing rollers, but the advantages can be provided if it is used for one of the rollers. However, it is preferable that the present invention is used at least for the lower contactable with the unfixed image. While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the scope of the following claims.

Claims: An image fixing rotatable member, comprising: a base member (2,12); a silicone rubber layer (4,14) on said base member; a primer layer (5,15) on said silicone rubber layer; and a fluorine resin layer (6,16) on said primer layer; characterised in that said primer layer (5,15) is of binder resin comprising an aminosilane compound and a larger amount by weight of fluorine resin. A member according to claim 1, wherein the binder layer comprises the aminosilane compound, the fluorine resin, and as main component a heat resistive resin material that has affinity with the fluorine resin and silicon compound. A member according to claim 2, wherein the heat resistive resin is an aromatic polyamideimide resin, a polyimide resin or a polyarylenesulphide resin. A member according to claim 2 or 3, wherein the silicon compound is an alkali or amine silicate, alkyl silicate, lithium polysilicate or silica colloid. A member according to any one of claims 1 to 4, wherein the aminosilane compound is selected from α-aminopropyltriethoxysilane, N-β-aminoethyl-α-aminopropyltrimethoxysilane, N-(trimethoxysilylpropyl)ethylenediamine, N-β-aminoethyl-α-aminopropylmethyldimethoxysilane, α-ureidepropyltriethoxysilane, β-aminoethyl-β-aminoethyl-α-aminopropyltrimethoxysilane. A member according to any preceding claim wherein the fluorine resin layer is a PFA or PTFE resin. A member according to any preceding claim, wherein the binder material contains 1 to 30 parts by weight of the aminosilane compound on the basis of 100 parts by weight of the binder material. A member according to any preceding claim, wherein the binder material contains 1 to 20 parts by weight of the aminosilane compound on the basis of 100 parts by weight of the binder material. A member acording to any preceding claim, wherein said fluorine resing layer (6,16) is produced by applying and sintering a fluorine resin material. A member according to any preceding claim, further comprising an additional primer layer (3,13) between said base member (2,12) and said silicone rubber layer (4,14), wherein the additional primer layer is of silane material. A fixing apparatus, comprising: a pair of rotatable members (1,10) forming a nip through which an image bearing member (P) carrying an unfixed toner image (T) is passed to fix the unfixed toner image; at least one of said rotatable members being an image fixing rotatable member as claimed in any preceding claim. An apparatus according to claim 11, wherein said at least one of the rotatable members (1,10) is a rotatable member (1) contactable to the unfixed toner image (T) and is heated by a heating source (H). An apparatus according to claim 11 or claim 12, wherein said at least one of the rotatable members (1,10) is a rotatable member (10) not contactable to the unfixed toner image (T). A method for making an image fixing rotatable member, the method comprising the steps of: adhering a silicone rubber layer(4,14) to a base member (2,12); coating said silicone rubber layer with a primer layer (5,15); and coating the primer layer with fluorine resin (6,16); characterised in that a primer layer (5,15) is of binder resin comprising an aminosilane compound and a larger amount by weight of fluorine resin, and the member is heated to sinter said fluorine and if necessary to cure the binder.

Inventors: KISHINO KAZUO, MIYABAYASHI TOSHIYUKI, SAKURAI MASAAKI, KISHINO, KAZUO, MIYABAYASHI, TOSHIYUKI, SAKURAI, MASAAKI
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1988
Main classification: G03G15
IPC codes: B32B15, G03G15