Infrared curing of fluoroelastomer coatings formed over silicone rubber in a fuser member

Abstract

A method of curing a fuser member suitable for use in an image forming system using a radiant energy source. The fuser member comprises a substrate, a silicone rubber coating and a cross-linkable fluoroelastomer outer coating. The radiant energy source emits infrared energy directed towards the fluoroelastomer outer coating of the fuser member. The flouroelastomer coating is cured using infrared energy directed at specific bonds within the fluoroelastomer layer, so as to form directly with the infrared heat a cross-linked fluoroelastomer coating.

Description

BACKGROUND

[0001] This invention relates to fuser members for an image forming system, and in particular relates to a method of curing fuser members used in the image forming system.

[0002] In a typical image forming process, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive imaging member, and the latent image is subsequently rendered visible by the application of thermoplastic resin particles, commonly known as toner. The visible toned image is then in a loose powdered form and can be easily disturbed or destroyed. The toned image is usually fixed or fused upon a support member, such as plain paper, transparency, specialty coated paper, and the like.

[0003] The use of thermal energy for fixing toned images onto a support member is well known. In order to fuse toner material onto a support surface permanently by heat, it is necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner material cools, solidification of the toner material causes the toner material to be firmly bonded to the support.

[0004] Typically, toner particles are fused to a print substrate by heating to a temperature of between about 90° C. to about 160° C. or higher, depending upon the softening range of the particular resin used in the toner. It is not desirable, however, to raise the temperature of the substrate substantially higher than about 200° C. because of the tendency of the substrate to discolor at such elevated temperatures, particularly when the substrate is paper.

[0005] Several approaches to thermal fusing of electroscopic toner images have been described in the prior art. These methods include providing the application of heat and pressure substantially concurrently by various means, including a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, and the like. Heat may be applied by heating one or both of the rolls, plate members or belt members. The fusing of the toner particles generally takes place when the proper combination of heat, pressure and contact time is provided. The balancing of these parameters to bring about the fusing of the toner particles is well known in the art, and they can be adjusted to suit particular machines, process conditions, and printing substrates.

[0006] During operation of a fusing system in which heat is applied to cause thermal fusing of the toner particles onto a support, both the toner image and the support are passed through a nip formed between the roll pair, or plate and/or belt members. The concurrent transfer of heat and the application of pressure in the nip effects the fusing of the toner image onto the support. It is important in the fusing process that no offset of the toner particles from the support to the fuser member takes place during normal operations. Toner particles offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thus, increasing the background or interfering with the material being copied. The so called “hot offset” occurs when the temperature of the toner is raised to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member.

[0007] The hot offset temperature or degradation of the hot offset temperature is a measure of the release property of the fuser roll, and accordingly it is desired to provide a fusing surface that has a low surface energy to provide the necessary release. To ensure and maintain good release properties of the fuser roll, it has become customary to apply release agents to the fuser members to ensure that the toner is completely released from the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, silicone oils to prevent toner offset.

[0008] Generally, fuser and fixing members are formed by providing a suitable substrate, and then applying one or more layers to the substrate. For example, cylindrical fuser and fixer rolls typically comprise an aluminum core, an intermediate silicone rubber layer and an outer fluoroelastomer layer. The coated roll is heated in a convection oven to cure the fluoroelastomer material. Such processing is disclosed in, for example, U.S. Pat. Nos. 5,729,813 and 6,037,092 the contents of which are herein incorporated by reference.

[0009] A problem with conventional processing, however, is that the convection oven curing of the fuser or similar members requires lengthy processing time. For example, U.S. Pat. No. 5,729,813 discloses that the coating is cured by a stepwise heating process totaling about 24 hours, such as 2 hours at 95° C., 2 hours at 150° C., 2 hours at 175° C., 2 hours at 200° C., and 16 hours at 230° C., followed by cooling and sanding. Such lengthy curing processes, in addition to being time-consuming, are energy intensive and often require batch, rather than continuous, process operation. Additionally, the thermal cure process is inefficient, as a substantial amount of the thermal energy is wastefully absorbed in the substrate.

[0010] Another disadvantage of conventional convection oven curing of the fuser or fixing members is that the convection curing process can be detrimental in cases where the cure temperature of the coating is higher than the recommended use or operating temperature of the substrate and/or subsequent coatings. In these cases, the high temperatures needed to cure the fluoroelastomer coating can degrade and depolymerize the underlying silicone rubber layer, reducing the durability and adhesion strength of the silicone rubber, and limiting the lifetime of the fuser member as a whole.

SUMMARY OF THE INVENTION

[0011] The present invention provides a method of curing a fuser member using a radiation source, such as an infrared source: The fuser member comprises a substrate, a silicone rubber coating and a cross-linkable fluoroelastomer outer coating. The flouroelastomer coating is cured using infrared energy directed at specific bonds within the fluoroelastomer and cross-linking agent layer, so as to form directly with the infrared heat a cross-linked fluoroelastomer coating.

[0012] According to one aspect, the present invention provides a method of curing a fuser member comprising the steps of providing a fuser member having a metal substrate, a silicone rubber base coating, and an outer cross-linkable fluoroelastomer polymer coating and subsequently exposing the polymer coating to infrared radiation for a selected curing time to stimulate specific bonds in the cross-linkable fluoroelastomer polymer coating to generate a cross-linked fluoroelastomer polymer.

[0013] According to another aspect, the present invention provides a fuser member comprising a substrate, a silicone rubber coating disposed about the substrate, and a cross-linked flouroelastomer coating disposed on the silicone rubber coating, wherein said fluoroelastomer coating has been cross-linked with infrared radiation.

[0014] According to yet another aspect, the infrared radiation used to cure and cross-link the fluoropolymer is substantially absorbed by the polymer coating so as not to affect the properties of the metal substrate and the silicone rubber base coating of the fuser member.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a sectional view of an image forming system that employs the fuser member according to the present invention.

[0016] FIG. 2 is a cross-sectional view of a fuser member according to the present invention.

[0017] FIG. 3 is a cross-sectional view of an exemplary radiant energy curing oven according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0018] According to embodiments of the present invention, a system and method of curing fuser members is provided. In embodiments, the fuser members are made according to any of the various known processes in the art, except that a radiant heat process is used to cure one or more of the applied layers or materials, in place of a convection curing process. The term “fuser member” as used herein refers to fusing members suitable for use in the fusion process for fixing of thermoplastic toner images to a suitable substrate in an image forming system and which can include fusing rolls, belts, films, sheets and the like; donor members, including donor rolls, belts, films, sheets and the like; and pressure members, including pressure rolls, belts, films, sheets and the like; and other members useful in the fusing system of an image forming system. The fuser member of the present invention may be employed in a wide variety of machines or image forming systems and is not specifically limited in its application to the particular embodiment depicted herein. An image forming system may be an ionographic, electrographic, electrophotographic, ink jet, or other similar system that is adapted to capture, store, form, produce and/or reproduce image data associated with a particular object, such as a document.

[0019] Referring to FIG. 1, in a typical image forming system, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive imaging member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles, which are commonly referred to as toner. Specifically, imaging member 10 is charged on its surface by a charger 12 to which a voltage has been supplied from power supply 11. The imaging member is then imagewise exposed to light from an optical system or an image input apparatus 13, such as a laser and light emitting diode, to form an electrostatic latent image thereon. Generally, the electrostatic latent image is developed by bringing a developer mixture from a developer station 14 into contact therewith. Development can be effected by use of a magnetic brush, powder cloud, or other known development process.

[0020] After the toner particles have been deposited on the imaging surface, they are transferred to a copy sheet 16 by a transfer system 15, which can effect transfer by pressure or electrostatic transfer techniques. Alternatively, the developed image can be transferred to an intermediate transfer member and subsequently transferred to a copy sheet.

[0021] After transfer of the developed image is completed, copy sheet 16 advances to a fusing system 19, depicted in FIG. 1 as fusing and pressure rolls, wherein the developed image is fused to copy sheet 16 by passing copy sheet 16 between the fusing roll 20 and pressure roll 21, thereby forming a permanent image. The pressure roll 21 cooperates with the fusing roll 20 to form a nip or contact arc through which the copy sheet 16 passes, such that the developed toned image contacts the surface of the fusing roll 20. Fusion of the image is effected thought a combination of heat from the fuser members and pressure. Sump 23 supplies polymeric release agent to donor roll 24, which transports the release agent to the surface of the fusing roll 20. Imaging member 10, subsequent to transfer, advances to cleaning station 17, where any toner left on imaging member 10 is cleaned therefrom by use of a blade 22 (as shown in FIG. 1), brush, or other cleaning apparatus.

[0022] FIG. 2 illustrates a cross-sectional view of a fuser member of the present invention, illustrates as fusing roll 20. In embodiments of the present invention, the fuser member 20 is comprised of a core with a coating, usually continuous, of a thermally conductive and resilient compressible material that preferably has high thermomechanical strength. Various designs for the fuser member are known in the art and are described in, for example, U.S. Pat. Nos. 4,373,239, 5,501,881, 5,512,409 and 5,729,813, the contents of which are herein incorporated by reference. The illustrated fuser member is formed of a hollow cylindrical metal core 25, an intermediate silicone rubber layer 26, and an outer layer of a selected cross-linkable fluoroelastomer 27. The intermediate silicone rubber layer 26 between the substrate 25 and the fluoroelastomer outer layer 27 provides compliance and flexibility to the fuser roll 20. The fuser member 20 may further include a primer layer (not shown) between the substrate 25 and the silicone rubber layer 26 and an adhesive layer (not shown) between the silicone rubber layer 26 and the outer fluoroelastomer layer 27. The primer layer and the adhesive layer are comprised of silane-based or hypoxy-based materials.

[0023] Generally, the core 25 of the fuser member 20 can be formed of any suitable supporting material, around or on which the subsequent layers are formed. Suitable core materials include, but are not limited to metals, such as aluminum, anodized aluminum, steel, nickel, copper, and the like.

[0024] The intermediate layer 26 of the fuser member 20 can be formed of any suitable or desired material having suitable thermal and mechanical properties, good dimensional stability, chemical stability, thermal stability, and flexibility and compliance to a print substrate, such as paper. For example, the intermediate layer 26 can comprise silicone rubber of a thickness sufficient to form a conformable layer. Suitable silicone rubbers include room temperature vulcanization (RTV) silicone rubbers, high temperature vulcanization (HTV) silicone rubbers, low temperature vulcanization (LTV) silicone rubbers, and liquid silicone rubbers (LSR). These rubbers are known and are readily available commercially such as BM-1000 LSR, SILASTIC® 735 black RTV and SILASTIC® 732 RTV, all available from Dow Corning, and 106 RTV Silicone Rubber and 90 RTV Silicone Rubber, both available from General Electric. The silicone rubber layer may be a thermally conductive silicone elastomer, and can optionally include filler materials, such as an alumina, boron nitride or iron oxide filler. Thermally conductive fillers aid in the transmission of heat from the core 25 to the outer layer 27.

[0025] The intermediate layer 26 typically has a thickness of from about 0.05 to about 20 millimeters, although the thickness can also be outside of this range. More specifically, on a fusing roll, the intermediate layer typically has a thickness of from about 1 to about 10 millimeters, preferably from about 3 to about 7 millimeters, although the thickness can be outside of this range. On a pressure member in a fusing system, the intermediate layer typically has a thickness of from about 0.05 to about 5 millimeters, preferably from about 0.1 to about 3 millimeters and more preferably from about 0.5 to about 1 millimeter, although the thickness can be outside of these ranges. In a preferred embodiment, the thickness of the intermediate layer of a fusing roll is higher than that of a pressure roll, so that the fusing roll is more deformable than the pressure roll. On a donor roll, the intermediate layer has a thickness of from about 10 to about 15 millimeters, and preferably from about 12 to about 13 millimeters.

[0026] An outer coating 27, which is preferably formed of a thermally conductive and resilient compressible material, is applied to the silicone rubber coating. The coating of the invention can provide sufficient toughness, durability and hardness, as well as chemical, physical and thermal stability. The outer coating 27 can comprise any suitable material including, but not limited to, a thermally conductive cross-linkable fluoropolymer, such as a fluoroelastomer. Other fluoroelastomers useful in the practice of the present invention include those described in detail in U.S. Pat. No. 4,257,699, the disclosure of which is incorporated herein by reference, as well as those described in U.S. Pat. Nos. 5,017,432 and 5,061,965, the disclosures of which are incorporated herein by reference. As described therein, these fluoroelastomers, particularly from the class of copolymers and terpolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoroethylene, are known commercially under various designations as Viton A, Viton E60C, Viton E430, Viton 910, Viton GH and Viton GF. The Viton designation is a Trademark of E. I. DuPont de Nemours, Inc. Other commercially available materials include Fluorel 2170, Fluorel 2174, Fluorel 2176, Fluorel 2177 and Fluorel LVS 76, Fluorel being a Trademark of 3M Company. Additional commercially available materials include Aflas a poly(propylene-tetrafluoroethylene), Fluorel II (LII900) a poly(propylene-tetrafluoroethylene-vinylidenefluoride) both also available from 3M Company as well as the Tecnoflons identified as FOR-60KIR, FOR-LHF, NM, FOR-THF, FOR-TFS, TH, TN505 available from Montedison Specialty Chemical Co. Other suitable elastomers include silicone elastomers, ethylene propylene hexadiene, polytetrafluoroethylene, perfluoroalkoxy resins and mixtures thereof.

[0027] In a particularly preferred embodiment, the fluoroelastomer is one having a relatively low quantity of vinylidenefluoride, such as in Viton GF, available from E. I DuPont de Nemours, Inc. The Viton GF has 35 weight percent vinylidenefluoride, 34 weight percent hexafluoropropylene and 29 weight percent tetrafluoroethylene with 2-weight percent cure site monomer. The outer layer 27 further includes a suitable curative agent, including bisphenol curatives, diamine curatives, and silane curatives.

[0028] The coatings 26, 27 can be applied to the core member 25 as a thin layer by any suitable method known in the art. Such methods include, but are not limited to, spraying, dipping, flow coating, casting or molding. Typically the surface layer of the fuser member is from about 10 to about 250 microns, and preferably from about 20 to about 80 microns, in thickness, as a balance between conformability and cost and to provide thickness manufacturing latitude.

[0029] Once the desired layers are applied to the core member 25, the fluoroelastomer materials are cured. Although various curing methods are known in the art, such as convection oven drying, the present invention uses a radiant energy source 40, such as an infrared heat source, to cross-link and cure the fluoroelastomer material 27, as illustrated in FIG. 3. The fuser member 20 is preferably moved, placed into or disposed relative to radiant energy source 40 and radiant energy, such as infrared energy, is applied at a sufficient level and for a sufficient time to effect the desired degree of curing.

[0030] The illustrated radiant energy source 40 includes a shell or casing 30 having attached thereto (or supported therein) a number of radiant energy emitting lamps 32. The lamps can be arranged in groups of any size in an axial direction of the oven, with groups being spaced around the periphery of the oven. As shown, the lamps 32 can be uniformly spaced around the inside of the oven 40. The fuser member 20 can be passed through the oven in any conventional means (not shown), such as by a conveyor or the like. In a preferred embodiment, the infrared oven includes thirty-six 16-inch quartz lamps, with eighteen lamps located above fuser member, and eighteen lamps located below the fuser member.

[0031] The radiant energy source 40, illustrated as a curing oven, can be provided either in a batch-curing mode or a continuous curing mode. In a continuous curing mode, for example, the oven can be provided in an elongated shape, with lamps 32 located along the length of the oven, so that curing can be effected as fuser members are passed continuously through the oven. Such a continuous curing oven is preferred in embodiments, because the shortness of curing time lends the radiant energy curing process to a continuous operation, which is more easily integrated into an overall production process. Furthermore, the continuous curing process, when used in-line with the member manufacturing process, helps to ensure that all manufactured members have similar properties, in that they are processed a comparable length of time after the coating is applied, rather than having some members wait a longer time before a batch curing operation can be performed.

[0032] Preferably, the intensity of the infrared radiation generated by the radiant energy source 40 is sufficient to raise the temperature of the desired material to be cured to the desired curing temperature. For example, in the case of fuser members, it is generally desired that the material be raised to a temperature of from about 200 to about 500° F., preferably from about 350 to about 475° F., and more preferably from about 400° F. to about 450° F. Of course, these temperatures depend on the material being cured, and can be varied as desired. A temperature significantly greater than 500° F. degrades both the silicone rubber and the fluoroelastomer materials used in the fuser members of the present invention. The temperature at which the fuser member is cured is preferably less than the continuous use temperatures of the substrate and the silicone rubber coating during fusing operations. Heat intensities of from about 50 dial units to about 500 dial units, preferably from about 300 to about 400. The heat intensity dial units of the infrared lamps corresponds to 2 times the voltage applied to the T3 Quartz Infrared Lamps. Adjusting the voltage applied to the infrared lamps affects the temperature of the tungsten filament within the quartz, thereby adjusting the amount of infrared energy emitted by the lamps. The radiant energy curing time is generally selected to be from about 2 to about 60 minutes, more preferably from about 10 to about 50 minutes, and more preferably from about 15 to about 30 minutes. Ideally, the emission range of the lamps during the cure process is in the short infrared range, between about 0.76 microns and about 1000 microns, although other ranges can also be used. The fluoroelastomeric material in the outer layer preferably absorbs infrared energy within the wavelength range that is emitted from the lamps.

[0033] The infrared radiation generated by the source and directed towards the fuser member cures the fluoroelastomer outer coating. The IR radiation directly stimulates specific chemical bonds of the fluoroelastomer layer, in order to cross-link these bonds. Cross-linking attaches the chains of a polymer to another adjacent polymer to form a single polymer network exhibiting increased strength and resistance to solvents. After the flouroelastomer has been cross-linked, the configuration and structure of the molecules are permanent, and the flouroelastomer cannot be reprocessed. In conventional thermal energy curing techniques, all molecules in the fuser member may be stimulated and affected without creating, promoting or enhancing cross-linking. The infrared energy generated by the radiant source is directed only to particular molecules in the fluoroelastomer layer, thereby forming a cross-linked flouroelastomer layer without influencing or changing other molecules in the materials, such as an intermediate silicone rubber layer, that comprise the fuser member.

[0034] The infrared curing process of the present invention enhances the quality of the fluoroelastomer. A fuser member cured with infrared energy possesses increased tensile strength, improved adhesion between layers, lower extractability, indicating improved cross-link density, and enhanced released properties. As a result, the quality of the printed image is significantly improved.

[0035] An additional benefit of the radiant energy curing over conventional oven curing is that the radiant energy curing is much more efficient in terms of process time and energy consumption. For example, time efficiency is realized in that radiant energy curing can be effected in about an order of magnitude less time than used for conventional convection oven curing. Whereas conventional convection oven curing can take from about 18 to about 24 hours, radiant energy curing according to the present invention can be conducted in from about 15 to about 30 minutes.

[0036] Efficiency in terms of energy usage is realized in a number of ways. The shorter curing time, discussed above, results in immediate energy savings. Additionally, energy savings are realized because the applied radiant energy, acting in a line-of-sight manner, acts first on the outer fluoroelastomer layer of the member, rather than on the entire member as a whole. The fluoroelastomer absorbs nearly all of the infrared energy, preventing the passage of energy to underlying layers. Absorption of the infrared lightwaves allows the fluoroelastomer material to be heated while transferring a minimum of infrared and thermal energy to the underlying materials. This is achieved by selecting a fluoroelastomer composition that absorbs substantially all incident energy in the wavelength spectrum. Thus, for example, the substrate layer, the silicone rubber layer, and any intervening layers, which generally need not be cured, are not heated to the necessary curing temperature of the outer layer.

[0037] For example, a typical convection oven, such as available from Grieve Oven Company, rated at 800 kW for an 18-hour curing operation, uses 14.4 kW-hr of energy. In contrast, a radiant energy oven utilizing 36 T3 lamps, each being 16 inches long and requiring 100W/in. of lamp, and operating for a 30-minute curing operation, uses 1.66 kW-hr of energy. Accordingly, a comparable curing operation in a convection oven can use about 9 times the energy of a radiant energy curing operation.

[0038] Although the design of the radiant energy curing oven is not particularly important, the particular design can affect overall process time. For example, if the radiant energy curing oven has only a single exposure lamp, then rotation of the lamp and/or the substrate may be required in order to effect desired curing of the entire substrate. Accordingly, in embodiments, it is preferred that the radiant energy curing oven be provided with a plurality of lamps, preferably located substantially uniformly around the substrate, such that the entire substrate can be cured at the same time. If necessary, one or more masks can be used to mask or block portions of the substrates from direct exposure to the lamps.

[0039] As described above, the radiant energy curing process of the present invention provides many significant advantages not realized in the art. For example, the present invention provides the above-described time and energy savings, which permit efficient operations, particularly in a continuous manufacturing process. In addition, however, there are still other significant advantages of the present invention.

[0040] One such advantage is that exhaust temperatures from the curing process are significantly lower than in the prior art. For example, in order to cure a part in a convection oven, it is generally necessary that the heated air be at a temperature equal to or higher than the desired cure temperature. As a result, the effluent air from the convection oven can be about 450° F. or more, resulting in a very high stack temperature. In contrast, the radiant energy curing of the present invention results in an air temperature of only about 165° F., resulting in a significantly lower stack temperature.

[0041] In addition to the time and energy savings discussed above with respect to the curing operation itself, additional time and energy savings are realized in process start-up. For example, because convection ovens generally require lengthy start-up times in order to reach the desired temperature, it has been common practice to leave convection ovens on, even when not in use. In contrast, the radiant energy ovens of the present invention have a much shorter warm-up time, which allows them to be shut down during periods of non-use. These benefits thus decrease the process start-up time when the ovens have been shut down, and decrease energy costs during periods of non-use.

[0042] Furthermore, space savings in production facilities can be drastically reduced. For example, immediate space savings can be realized in that the radiant energy curing ovens are generally smaller than comparable convection ovens and supporting equipment. Moreover, however, because of the shorter process times, discussed above, fewer radiant energy curing ovens are required to perform the same amount of work. For example, in one particular process, one radiant energy curing oven can be used in place of up to five conventional convection curing ovens.

[0043] Still further, the radiant energy curing of the present invention can also result in increased product quality. In convection curing ovens, heated air is generally passed over the part to heat the part to the curing temperature. However, the heated air can contain contaminants, which can be deposited on and incorporated into the part. This problem can be overcome in the present invention, because less air is blown across the part, thereby decreasing the contamination problem.

[0044] Even further, the radiant energy curing process of the present invention can be applied to a wider variety of materials as compared to the conventional convection curing process. According to the present invention, the radiant energy is applied to the outer layer in preference to the underlying layers of the part, since the radiant energy operates in a line-of-sight manner. This permits the outer layer of a part to be heated to a sufficient curing temperature, without also raising the underlying layers to the same temperatures, which could result in changed chemical and/or physical properties of the underlying layers. Substantially all of the infrared energy is absorbed in the outer fluoroelastomer layer. Efficient absorption of the infrared energy in the fluoroelastomer layer prevents degradation of the underlying silicone rubber layer, and wasteful absorption of energy by the substrate. Thus, for example, the substrate layer, the silicone rubber layer, and any intervening layers, which generally need not be cured, are not heated to the necessary curing temperature of the outer layer.

[0045] For example, a metal roll coated with silicone rubber and overcoated with Viton fluoroelastomer can generally not be adequately cured in a convection oven without degrading the silicone rubber physical properties. The Viton requires 12 hours at 450° F. to adequately cross-link. At a curing temperature of 450° F. for four hours, the strength of the silicone rubber is degraded, as evidenced by a loss of hardness (up to 10%), measured by a Shore A durometer reading. However, the same material set cured in an infrared oven to adequately cross-link the fluoroelastomer only results in a 2-3% loss of hardness.

[0046] As another example, it is sometimes desirable to produce parts having a plastic substrate and an elastomer coating. However, the elastomer generally cannot be cured in a convection oven because the curing will melt the plastic substrate. However, radiant energy curing can be effectively used, because any uncoated parts can be masked, and the radiant energy selectively applied to the elastomer coating.

[0047] The following examples illustrate specific embodiments of the present invention. One skilled in the art will recognize that the appropriate reagents, and component ratios/concentrations may be adjusted as necessary to achieve specific product characteristics. All parts and percentages are by weight unless otherwise indicated.

EXAMPLES

Example 1

[0048] A coated fuser roll is made by coating a layer of Viton® rubber with an A0700 curative (N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, available from United Chemical Technologies, Inc.) on a metallic substrate. The fuser roll substrate is a cylindrical aluminum fuser roll core about 3 inches in diameter and 16 inches long, which is degreased, grit blasted, degreased and covered with a silane adhesive as described in U.S. Pat. No. 5,332,641, the contents of which are herein incorporated by reference.

[0049] The elastomer coating material includes the A0700 curative at a level from about 2 to about 20 parts per hundred (pph). “Parts per hundred” refers to parts of curative agent per 100 parts of Viton® in a solution that is coated on the fuser member. The solution is sprayed upon the 3 inch cylindrical roll to a nominal thickness of about 250 microns. The coated fuser member is then cured in an infrared radiant energy oven for thirty minutes at a heat intensity of 200, in order to promote or enhance the cross-linking of the polymers in the coating.

[0050] The fuser roller is then tested for the cross-linked density of the elastomer layer, as well as for toughness, tensile strength and elongation. The results are set forth in Table 1 below.

Examples 2-8

[0051] Fuser rolls are prepared as in Example 1 above, except that the curative level, curing time, and/or heat intensity are altered, as set forth in Table 1 below. The fuser rolls are tested as in Example 1, and the results are presented in Table 1 below. The A0700 is the curative used in the Viton® coating. 1 TABLE I Cross-link A0700 density Tensile level Time Heat (moles of strength Elongation Example (pph) (min.) intensity chains/cc) Toughness (psi) (%) 1 5 30 200 4.29 · 10−5 4137 2085 578 2 5 15 200 4.45 · 10−5 4461 2431 531 3 2 30 200 4.50 · 10−6 1925 731 652 4 5 30 150 1.24 · 10−4 3025 1929 449 5 2 15 200 6.96 · 10−6 2941 1288 706 6 2 30 150 2.21 · 10−5 3416 1505 726 7 2 15 150 2.43 · 10−5 2313 1003 641 8 5 15 150 1.47 · 10−4 2355 1507 428

Examples 9-16

[0052] Eight (8) Viton® films are cured in an infrared radiant energy source and tested for physical properties. The films are coated on a fuser roll substrate to a thickness of about 20 microns. Two factors are varied for each film: the curative level (pph of VC50 curative in Vitrons®), and heat intensity. The time that takes the IR source to reach a temperature of about 550° F. is also recorded. Formulations of Viton® with three levels of VC50 curative are tested. The two levels of VC50, 3 pph and 5 pph, are selected based on results obtained from previous scouting experiments. The two levels of heat intensity, 350 and 500 are also selected based on previous scouting experiments. The experiment uses centerpoints, giving an extra level of VC50, 4 pph and an extra level of heat intensity, 425.

[0053] The fuser rolls are analyzed and tested. The results are set forth in Table 2 below. 2 TABLE 2 Response Response 2 Response Factor 1 Fac- 1 Surface 3 A: VC50 tor 2 Extract- Energy Time to RUN BLOCK pph B: HI ables % Dynes/cm temp. min. 1 Block 1 3 500 21.82 31.47 3.36 2 Block 1 5 500 2.04 35.99 4.38 3 Block 1 4 425 7.68 29.46 5 4 Block 1 3 350 9.4 31.83 8.43 5 Block 1 4 425 6.43 27.79 6.15 6 Block 1 5 350 0.74 31.25 10.12 7 Block 1 4 425 6.94 31.79 4.3 8 Block 1 4 425 9.55 32.24 4.3

[0054] As illustrated in Table 2, the lowest parts per hundred (pph) of VC50 (3) results in a higher percent of extractables (21.82) compared to the highest pph of VC50 (5). The lowest heat intensity (350) results in lower percent extractables compared to the highest heat intensity (500). The results of the percent extractables range between 0.74% to 21.82%. “Percent extractables” is a measure of the cross-linked density of the fluoroelastomer coating after curing. A higher cross-linked density corresponds to a lower percent extractables.

[0055] The lowest pph of VC50 result in lower surface energy compared to the highest pph of VC50, which result in higher surface energy. The lowest Heat Intensity results in lower surface energy compared to the highest Heat Intensity, which results in higher surface energy.

[0056] A convection-cured roll was analyzed for surface energy and the value obtained was 32.16 dynes/cm. The surface energy for the IR cured rolls ranges between 27.79 to 35.99 dynes/cm. The surface energy for the IR cured rolls differs from the surface energy of the convection-cured roll by between +/−4 dynes/cm.

[0057] The highest heat intensity resulted in less curing time than the lowest heat intensity, which resulted in longer curing times.

[0058] The optimum parameters for conducting an infrared cure for a fluoroelastomer coating are the highest curative level and the lowest heat intensity. In this example, the highest curative level is 5 pph of VC50, and the lowest heat intensity is 350. The heat intensity corresponds to twice the voltage applied to the infrared lamp. While a lower heat intensity results in a longer curing time, this combination provides a superior cure. A preferred cure process results in lower percent extractables in the cured fluoroelastomer layer, indicating a higher cross-linked density, and lower surface energy.

[0059] The present invention provides fuser members, and similar coated members, as well as processes for the production thereof. The present invention provides a wide range of benefits not previously available in the art, including cost savings, space savings, lessened environmental impact, improved physical and operational properties, continuous process operation, and the like. A significant advantage of the present invention is a curing process that has a higher throughput rate while still providing economic and material advantages in forming fusing members, fixing members, and the like. These and other advantages are provided by the present invention.

[0060] Although specific features of the invention are included in some embodiments and drawings and not others, it should be noted that certain features may be combined with other features in accordance with the invention. In addition, it should be noted that the invention is not intended to be limited to the specific materials and construction described herein. It should be understood that the foregoing description of the invention is intended to be merely illustrative thereof, that the illustrative embodiments are presented by way of example only, and that other modifications, embodiments, and equivalents may be apparent to those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. A method of curing a fuser member suitable for use in an image forming system, comprising the steps of:

providing a fuser member having a substrate, a silicone rubber base coating disposed about the substrate, and an outer cross-linkable fluoropolymer coating;

exposing the polymer coating to infrared radiation for a selected curing time to stimulate specific bonds in the cross-linkable fluoropolymer coating to generate a cross-linked fluoropolymer.

2. The method of claim 1, wherein the cross-linkable fluoropolymer coating absorbs substantially all of the infrared radiation.

3. The method of claim 2, wherein the infrared radiation is substantially completely absorbed by the fluoropolymer coating so as not to affect the properties of the metal substrate and the silicone rubber base coating of the fuser member.

4. The method of claim 1, wherein the temperature at which the fuser member is cured is less than continuous use temperatures of the substrate and the silicone rubber coating.

5. The method of claim 1, wherein the curing time is in the range between about 2 minutes and about 60 minutes.

6. The method of claim 1, wherein the properties of the cross-linked fluoropolymer are fixed after stimulation with the infrared radiation.

7. The method of claim 4, wherein the temperature at which the fuser member is cured is less than about 500° F.

8. The method of claim 1, wherein the cross-linked fluoropolymer forms a permanent polymer matrix.

9. The method of claim 5, wherein the curing time is in the range between about 15 minutes and about 30 minutes.

10. The method of claim 1, wherein the cross-linkable fluoropolymer comprises a curable material selected from a group consisting of fluoroelastomers, ethylene propylene hexadiene, polytetrafluoroethylene, perfluoroalkolxy resins, and mixtures thereof.

11. The method of claim 1, wherein the cross-linkable fluoropolymer comprises a fluoroelastomer selected from a group consisting of class of a) copolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoroethylene and b) terpolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoroethylene.

12. The method of claim 1, wherein the fluoropolymer is curable by a curing agent selected from the group consisting of bisphenol curatives and silane curatives.

13. A fuser member made by the process of claim 1.

14. A fuser member suitable for use in an image forming system, comprising:

a substrate,

a silicone rubber coating disposed about the substrate, and

a cross-linked flouroelastomer coating disposed on the silicone rubber coating,

wherein said fluoroelastomer coating has been cross-linked with infrared radiation.

15. The fuser member of claim 14, wherein the substrate comprises a hollow metal cylinder.

16. The fuser member of claim 14, wherein the fluoroelastomer is selected from a group consisting of class of a) copolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoroethylene and b) terpolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoroethylene.

17. The fuser member of claim 14, wherein the silicone rubber layer has a thickness of from about 0.05 to about 20 millimeters.

18. The fuser member of claim 14, wherein the fluoroelastomer layer has a thickness of from about 10 to about 250 microns.