Patent Application
20110203473
The present invention relates generally to forming graphic images, and more particularly to a method of forming a graphic image on a reflective metal sheet.
Graphic images and designs have been formed on metal surfaces for a variety of uses for many years. One common practice employed in the electronics industry is to create printed circuit boards using a technique known as “print and etch”. This method uses a polymeric photoresist that is laminated onto a copper clad dielectric medium. The photoresist is photopolymerized with an ultraviolet light in selected areas, and the unpolymerized resist is washed off with chemicals, exposing the copper in certain areas. The exposed copper is then etched with strong acids to dissolve and chemically remove the copper. The remaining polymerized resist is then removed with additional harsh and environmentally damaging chemicals, to yield the patterned circuit. Numerous variations of this technique are used today thoughout various industries to provide patterned metal surfaces for a wide variety of uses. The problem with all of these techniques is that they require expensive equipment, they use large quantities of toxic chemicals that are harmful to the environment, and thus are subject to strict government regulation.
Alternate techniques seek to provide visual designs on metal surfaces by mechanically carving into the metal surface, removing some measurable amount of material by cutting, burning, or otherwise vaporizing the metal using cutting tools or lasers. Still other techniques emboss or stamp the metal surface to create a design.
Each of these techniques removes metal or distends the metal in one way or another, creating a three dimensional surface with measurable texture. They are limited in that they can only be used on metal substrates of sufficient thickness to allow for metal removal. And they are costly and slow. There is a continuing need to improve the quality, reduce the cost, and to simplify the manufacture of graphic images on a two dimensional metal surface that does not harm the environment.
The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
Before describing in detail embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in combinations of method and apparatus components related to forming a graphic image on a reflective metal surface, which comprises a two-dimensional metal substrate, a substantially planar metal substrate, or other metal substrate. Accordingly, the apparatus components and methods have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.
A method for creating a graphic image on a reflective metal surface in accordance with various embodiments will now be described. A digital representation of the graphic image is created on a computer and stored in memory. The digital file is then sent to an inkjet printer, where ultraviolet light curable ink representative of the image, or optionally of a negative version of the image, is printed onto the reflective metal surface using the inkjet printer. The portions of the reflective metal surface that are not covered with the ink remain exposed. The reflective metal in the exposed areas is mechanically scuffed to render it less reflective and visually distinct from the covered portions. The ultraviolet light curable ink is then removed with a high pressure water spray to reveal the graphic image made by the contrast between the original reflective metal surface and the scuffed metal surface.
Referring now to
The terms “reflective”, “polished”, and “shiny”, as interchangeably used herein refer to a surface that is capable of specular reflection. Referring now to
Referring now to
After ink jetting the negative image onto the reflective substrate, areas of the reflective metal surface that represent the “white space” or negative portions of the visual design are covered with cured ink, and those areas that will correspond to positive portions remain exposed or not covered. The exposed portions of the reflective surface are then mechanically roughened 36 to render the specularly reflective surface diffusely reflective. Some exemplary means of mechanical roughening are scuffing, grazing, brushing, scratching, and scrubbing, among others. This operation can be performed by sanding, bead blasting, or abrading with a synthetic pad such as a nylon web impregnated with aluminum oxide abrasive. I find that the well known synthetic Scotch Brite pads sold by the 3M Company are useful to scuff exposed portions of the surface sufficient to alter the reflectance so as to cause a distinct difference between the original reflective polished surface and the scuffed surface. The pads are manually worked across the surface in a unidirectional motion, but can also be moved in two or more directions, or can be circular or random to create a variety of effects. Although the intent is to scuff the surface of the exposed polished metal, one does not need to be selective and only touch the metal. The UV cured ink, having been formulated to withstand harsh climates, is robust enough to withstand the scuffing and not detach from the metal surface or otherwise become degraded. Some roughening or scratching of the ink may occur, but this is inconsequential, and will not alter the appearance of the end product. Mechanical roughening can be performed manually or manually with assist by a portable power tool, or even completely automatic with a dedicated machine. The roughening is typically performed dry, although some type of lubricant may be used if desired. It is important to note that this operation is not intended to remove macro amounts of material from the surface, but merely to render it diffuse, i.e. microscopically rough. It is not necessary to etch or abrade into the surface.
After mechanically roughening the reflective surface, the UV-cured ink needs to be removed 37. Since the ink has been cured and strongly bonds to the metal surface, and since it has been formulated to withstand water and mechanical abuse for years, conventional wisdom dictates that it would require harsh chemicals to remove. Indeed, in the prior art, ink resists have been commonly removed using a plethora of exotic chemicals such as chlorinated solvents, oxygenated solvents, acids, bases, etc. I have found that a novel method to remove the ink jetted UV-cured ink is to impart a very high pressure spray of water 37 onto the ink. A high pressure in excess of approximately 1000 pounds per square inch (PSI), and more preferably in excess of 1500 PSI, imparted by a pressure washer, is sufficient to remove this tenacious ink. The nozzle of the pressure washer is typically aimed at the cured ink at a shallow angle to remove the ink.
It is not necessary to heat the water, and no chemicals are needed, with standard tap water from a metropolitan water supply at a neutral pH. As an example, the high pressure spray may be water having a neutral pH and less than 500 ppm total dissolved solids applied at a pressure greater than 1000 pounds per square inch. Once the ink has been pressure-washed off, and the metal article has been dried, the finished graphic design image is revealed 38. The difference in reflection between those portions 44 of the original specular reflective surface and the scuffed portions 42 that are now diffused, creates the visual design, apparent to the human eye, where the diffuse areas form a positive representation of the visual design.
In one alternate embodiment, instead of printing inkjet ink in a negative pattern, the ink is printed in a positive pattern, and the reflective areas form a positive representation of the visual design on a diffuse background. The choice of whether to print a positive pattern of ink or a negative pattern of ink is a design choice left to the practioner.
In another alternate embodiment of the invention, the process of ink jetting, scuffing, and removing the ink with high pressure water spray can optionally 39 be repeated one or more times. These second and subsequent repetitions may use a different version of the visual design that exposes only some of those portions that were previously exposed and abraded. The second mechanical roughening process creates areas that are even more diffuse than those created during the first process, giving those areas greater intensity. Optionally, subsequent processes can also abrade the surface in a direction that is different than the first abrasion direction, for example, orthogonal or random. The surface can be mechanically roughened using a different type of scuffing media. A variety of effects can be achieved by the practioner to create visual designs or graphic images on a reflective metal surface.
In yet other alternate embodiments of the invention shown in
In summary, a method for creating a graphic image on a reflective metal surface utilizes a digital representation of the graphic image that is printed by an inkjet printer onto a reflective metal surface. The exposed portions of the reflective metal surface that are not covered with the ink are mechanically scuffed to render them less reflective and visually distinct from the covered portions. The ink is durable enough to withstand the brief scuffing imparted by the Scotch Brite pads or other scuffing implements. The ultraviolet light curable ink is then removed with a high pressure water spray to reveal a graphic image formed by the contrast between the original reflective metal surface and the scuffed metal surface.
In the foregoing specification, specific embodiments of the present invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.
