Patent Application
20070237900
The present invention relates to a method of controlling surface characteristics on an image forming device component. The image forming device may be, for example, an electrophotographic printer, an inkjet printer, a fax device, a copier, an all-in-one device or a multipurpose device.
Many components used in image forming apparatus may benefit from a textured coating surface. These benefits may include modification of electrical, physical and chemical properties such as resistivity, roughness, or surface energy. The components upon which the coatings may be applied may include photo-conductive devices and non-photoconductive devices such as developer rollers, doctor blades, etc.
In an exemplary embodiment, the present invention relates to a process for coating a component for use in an image forming apparatus which may then induce a surface finish. The process may include application of a coating to a component, the component having a first surface area A1 and altering the surface area of the component to provide a second surface area A2 where A2≠A1. The coating may have a modulus E1 and the component may have a modulus E2, where E1>E2.
In another exemplary embodiment the present invention relates to a process for modifying the surface of a component for use in an image forming apparatus, the component having a surface and a corresponding surface area. The process may then include modifying the surface of the component to develop a surface modulus E1, where the component has a modulus E2, wherein E1>E2. This may then be followed by altering (e.g. reducing) the surface area of the component which may then increase surface roughness such as a mean peak-to-valley height, Rz.
The detailed description below may be better understood with reference to the accompanying figures which are provided for illustrative purposes and are not to be considered as limiting any aspect of the invention.
The present invention relates to a method of controlling surface characteristics of an image forming device component. The surface characteristics may be altered by coating or by modifying the mechanical properties of the surface, when under tension, by methods such as exposure to energy sources such UV radiation, plasma, heat, chemical modifiers, etc. Accordingly, the coating or step of surface modification may be carried out when the surface of the component is in a stressed configuration. Such stressed state may include an increase in surface area or volume, followed by a release of stress wherein the component may return completely, or even partially, to its original dimensions.
The image forming device component may then be advantageously employed in an electrophotographic printer, an inkjet printer, a fax device, a copier, an all-in-one device or a multipurpose device. The component may also be utilized in a printer cartridge, such as a toner cartridge. The component surface characteristics which may be controlled may include surface texture. Such texture may be specifically monitored by parameter values such as average overall roughness (Ra) and mean peak-to-valley height (Rz).
The component may be formed from a variety of polymeric materials including both thermoplastic and thermoset (crosslinked) materials. The component may be specifically formed from elastomeric material (materials which may recover substantially from an applied stress) such as diene rubber materials, synthetic rubber (SBR), natural rubber (polyisoprenes) and specialty types elastomers. For example, the rubbers may include silicone rubber and/or epichlorohydrin rubber, etc. The materials may be relatively compliant exhibiting a Shore A durometer of less than or equal to about 50, including all increments and values therein, such as 40, 30, etc. The materials therefore may be cellular or foam-based type resins. In all cases, the polymeric materials may also include additives to adjust other bulk properties, such as electrical conductivity. Accordingly, the component may amount to, e.g., a developer roller suitable for use in an electrophotographic printer that relies upon the use of a conductive elastomeric core and a resistive type coating.
To develop a stress in the component, the physical dimensions of the component may be altered. For example, the volume “V” of the component may be altered prior to or during a selected surface modification procedure. The volume may therefore be increased or decreased through the application of solvents, exposure to mechanical stress, including stretching or even vacuum application, or due to thermal expansion by the application of heat. For example, the component may be volumetrically increased or decreased by about 1-500%, including all ranges and values therein, including 100%, 200%, etc. Expansion or contraction may be isotropic or anisotropic.
A stress may also be introduced into the component wherein the surface area “A” of the component is altered. Such surface area alteration may similarly take place prior to or during a given surface modification procedure. This option may therefore apply even if the component volume itself is not substantially altered. Illustrative of such a situation may be where a substrate is stretched or compressed and the volume change is relatively minor (e.g., less than or equal to about 5.0%). The component surface area may therefore be selectively increased or decreased by about 1-500%, including all ranges and values therein, including 100%, 200%, etc. The surface area alteration may be isotropic or anisotropic.
Once altered and stressed, the component may return to about its initial volume or surface area or within about 0.01% to about 10.00% of an initial volume or surface area, including all increments and ranges therein. For example, where the component has been exposed to a solvent, which causes a volume or surface area change, the solvent may be allowed to evaporate. Alternatively, where the component has been exposed to a mechanical or thermal stress, the component may be allowed to relax or substantially return to an unstressed state or initial temperature.
The coatings herein may also be understood as coatings that include a chemical compound which may increase in viscosity and/or molecular weight though a polymerization and/or crosslinking type reaction. The chemical may therefore include monomers and/or oligomers which may react (cure) and undergo polymerization to form a solid. Such monomers or oligomers may also have one or a plurality of functional groups to allow for higher polymerization rates, high relative amounts of branching, and/or higher relative degrees of crosslinking. Initiation and/or curing may be triggered by variable or mixed energy sources such as heat curing, UV radiation, catalysts. Initiation or curing may also be developed by addition of one or more co-reactants, etc. Accordingly, the coatings as applied may have an initial viscosity of about 0.5 to 100,000 centipoise, including all values and increments therebetween, and undergo reaction and solidification upon the component surface.
The coating may include up to 100% (wt.) reactive chemical (e.g. monomer) and may also include solvents, such as an organic solvent or even water. The coating may also include up to 100% (wt.) formed polymer resin, or polymer resin within a solvent, such that upon solvent evaporation, the resin remains as the coating material. For example, the coating may include a polyurethane type polymer dissolved in a solvent, such as an organic solvent. In either case it may be appreciated that the solvents utilized in the coating may be such that they also serve to alter the volume or surface area of the component to which they may be applied. Accordingly, the solvents used herein may be selected such that they serve to partially dissolve and reversibly swell or reversibly increase the volume of, e.g., an underlying polymeric or crosslinked material. In that regard, one may select a solvent that provides a solubility parameter (δ1) measured in (cal/cm3)0.5 that is within about +/−5.0 units of the solubility parameter (δ2) of the component to be coated, including all values and/or increments therein, such as within +/− 1-2 units, +/−0.25-1 units, etc.
The coatings may also contain fillers which may affect initial component (e.g. monomer) viscosity as well as viscosity build-up prior to gel or solidification. In addition the fillers may also influence ultimate texture at the surface of the cured resin. Fillers may include particulate, metallic, ceramic, ionic or even polymeric type materials. Fillers may also influence the final bulk properties of the coating, such as electrical conductivity, as noted above.
As illustrated in
Returning then to a description of the coating process illustrated in
It should also be appreciated that the coating herein may be physically applied to component 14 by, for example, spray coating, dip coating, gravure coating, etc. The coating may also be applied to the substrate between about 1 to 150 microns in thickness, including all increments and values therein, such as 10 microns, 20 microns, etc. The coating may be reacted prior to, during or after application of the coating to the surface of the component 14. In addition, a delay may be present between the application of the coating to the component and reacting the coating. For example, a delay in the range of about 1 minute to about 6 hours, including all increments and ranges therein, may occur between the application and initiation of curing of the coating. Furthermore, the coating may be reacted prior to, during or after alteration of the volume or surface area of the substrate. It should also be appreciated that only the exposed surface or a portion of the surface of the coating may be reacted. For example, the surface may be reacted (cured) to between about 1-50% of the coating depth, including all values and increments therein, such as 10%, 20%, etc.
Attention is now directed to
Texture may be understood herein as the provision of relatively short range or long range features formed in the surface of the coating. For example, texture may include projections from or depressions into the coating surface. The texture may be regular or irregular across a selected component surface area. It should therefore be appreciated that the degree of texture provided may depend upon the change in the volume or surface area of the substrate, the delay between application of the coating and reaction of the coating, the depth in which the coating is cured, etc. As noted above, texture may be monitored by consideration of parameters such as average roughness (Ra) and mean peak-to-valley height (Rz) and the present invention therefore may provide a method to control such variables over a relatively wide range. Ra may be calculated by an algorithm that measures the average length between the peaks and valleys and the deviation from the mean line on the entire surface within the sampling length. Ra averages all peaks and valleys of the roughness profile and then neutralizes the few outlying points so that the extreme points have less significant impact on the final results. Rz may be calculated by measuring the vertical distance from the highest peak to the lowest valley within five sampling lengths, then averaging these distances. Rz averages only the five highest peaks and the five deepest valleys. Typical scans are conducted over 4.8 mm utilizing a cutoff wavelength of 0.8 mm for a Gaussian filter as given by ISO Standard 11562:1996.
It can be appreciated that although the textured surface is illustrated as being generally uniform about the surface of the roller, the textured surface may also be non-uniform in its surface roughness. Again, surface features may be characterized by the parameters of Ra and Rz noted above. Along such lines, mean peak-to-valley height as developed herein may be greater than about 0.01 microns, and on the order of about 0.01-500 microns, including all values and increments therein. For example, the value of Rz may be greater than about 1.0 micron. In addition, it should now be appreciated that in lieu of a coating step, the roller surface may be exposed to an energy source such that the resin surface is crosslinked, thereby increasing the values of modulus at or within a given surface layer, and upon release of the radial stress, a texture may similarly be developed which may similarly have the aforementioned values of Rz.
The foregoing description is provided to illustrate and explain the present invention. However, the description hereinabove should not be considered to limit the scope of the invention set forth in the claims appended here to.
