AU3211084A - Method for making permanent colored images apparatus therefor - Google Patents

Description

METHOD FOR MAKING PERMANENT COLORED IMAGES AND APPARATUSTHEREFOR

TECHNICAL FIELD

This invention relates to image reproduction for the graphic arts. More particularly/ the invention contemplates the manufacturing of permanent, photographic resolution, single or multiple colored signs, display boards, posters, exhibits, vehicle identification numbers and logos, door panel decorations and billboards.

BACKGROUND ART

In the field of image reproduction and more particularly the technology of creating usable photographic quality colored images on a broad range of receiving substrates, conventional imaging means have changed little over time. Silkscreening, the most popular tool for such work, has experienced virtually no changes in its basic method. To perform a silkscreen reproduction operation of a complex image, a photographic quality negative of the image must be procured. A positive print of the negative must be made and the fabric necessary for silkscreening must be stretched tauntly over a wooden frame commonly known as a screenchase. Once these items are ready, the silkscreening process is initiated.

In the event a multicolored product is desired, a negative and positive image must be made for each color. Where different sections of the same item are necessarily different colors, the entire preparation process must be repeated for each specific color and its corresponding image. The preparation cost of silkscreening is high in both time and money.

In addition to the basic material costs, silkscreening generally requires skilled and experienced artisans to achieve results of satisfactory quality. Silkscreening is not only notoriously labor intensive but also demands that the operator have artistic skill.

OMPI As noted, silkscreening requires separate operations for each desired color on the imaged target. For instance, a threecolored vehicle logo necessitates three complete and separate operations. The multiplicity of operation not only extends the time required to complete a process but also often results in blurred lines because the screenchases for each color are not perfectly aligned. Repeated applications of colors inherently decrease the probability of a perfect or near perfect image replication. More technologically advanced imaging processes have been made available. Several of these processes incorporate photo, thermal or chemical exposure techniques for image reproduction. Generally, the processes involve the use of specially prepared inks and coatings. Moreover, the processes are complex and do not contemplate preparation of finished imaged targets. For instance, the Coloron process sold by- Image Distributors, Inc., of Harrisburg, Pennsylvania, requires specially manufactured coating materials and, like silkscreening the process must he repeated for each color desired. The Matro Color method manufactured by Matro Color of Chicago, Illinois, contemplates the production of nondurable single colored printing proofs or nonporous surfaces by a photoresist process with specialized coating materials. In practice, these and other imaging processes have been found to be inconvenient. Furthermore, the processes have contributed little in a manner to reduce the requirements for skilled labor.

SUMMARY OF THE INVENTION It is an object of the instant invention to provide an imaging method yielding finished, photographic- quality single or multicolored images.

It is another object of this invention to provide an imaging system minimizing preparation materials, time and costs, by eliminating the requirement for both a positive and negative image, a frame and half of a screenchase.

It is yet another object of this invention to

" l E eliminate the requirement for skilled and experienced operators in order to achieve photographic quality results.

It is still another object of this invention to provide a method requiring a minimum of repeated applications for a multicolored product.

Still yet another object of this invention is to provide a method which produces a product exceeding the reproduction quality of conventional imaging methods such as silkscreening. Another object is to make available a product of equal or greater versatility and quality and overcome the shortcomings of silkscreening and other imaging techniques. A further object of this invention is to provide a work station for convenient and efficient implementation of the method.

Yet still another object of this invention is to provide a work station incorporating an image projection means and a satisfactory working surface.

These and other objects are fulfilled by the present invention which provides a method for permanent color imaging including the steps of (a) locally applying a colorant or colorants to specifically desired zones of a selected target surface, (b) locally applying a photoresist material to said zones, (c) exposing said surface with light projected through a desired image, and (d) removing from said surface undesired colorant with a developer solution. The present invention further satisfies the objects by providing a method using enamel or lacquer colorant, an ultraviolet sensitive photoresist coating material, a low level ultraviolet emission source to activate the photoresist material, a petroleum based developer solution for resoluabilizing the colorant unprotected by activated photoresist and an emulsion suspension for washing from the target surface any undesired colorant and developer.

To satisfy the remaining objects of this invention, a work station for using the method is provided which includes (a) a housing; (b) a sink within said housing; (c) a work surface pivotally mounted to said housing and contained with said sink; (d) means for

OMPI dispersing water onto said work surface; (e) means for blowing air whereby the blown air moves across and dries said work surface and objects thereon; (f) air exhausting means for disposing of said blown air; and (g) a light source for projecting onto the work surface.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of the colorant application step.

Figure 2 is a perspective view of the work station.

Figure 3 is a side view of the work station

Figure 4 is a top view of the light projection box.

Figure 5 is a side view of the pivotal connection.

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, a smooth surfaced substrate may be imaged with photographic resolution in single or multiple colors. The substrate is the operational surface material comprising the target of the imaging process, preferably a smooth sheetlike flat material for best results. However, the invention may also be practiced on curved or irregularly shaped targets.

The target in the following embodiment is preferably composed of a transparent or transulcent material. These materials include polystyrene, polyacrylics, polycarbonates, polyesters, polyvinylhalides, foam boards like Art Core produced by Amoco, treated wood pulp paper, and glass. Opaque materials like wood and metals may still be used but require additional care.

The benefit of transparency or translucency is understood in the direct contact method as described below. When a right reading image is properly positioned and projected through the target, the operator can evaluate precisely where the subsequent colorant and coating steps must be performed on the target's operational surface. However, the benefits of transparency or translucency are eliminated when using a later described image production device. The second preparatory step is the selection of a negative of the image to be reproduced. The negative can be made or obtained by available photographic technology. The negative may be of a size corresponding 1:1 with the ultimate product. Generally, in the field of graphic arts, a black and white, unshaded negative known as a lithographic negative or "litho neg" is employed. For the purposes of the present description, a negative corresponding in a 1:1 size ratio to the desired product will be discussed. This method is defined as the direct contact method.

To initiate the process, the negative 1 is placed in a right reading position on the transparent surface of a light projection table 2. The light is activated and in the case of a transparent or translucent target substrate 3, the image negative will be projected through the substrate and will appear on the operational surface of the target 4. The visible image will correspond exactly with the finished product. In Figure 1 a colorant 5 or multiple colorants are locally applied to operational target surface 3. Therefore, the colorant(s) 5 is placed on those areas where it is needed. However, there is no need to apply the colorant in an exacting manner. As it will become obvious from the description, all unexposed colorant will be later washed away because it forms no part of the final image. Where different areas of the target are to be imaged in different colors, the specific colorants may be applied in the same step. Accordingly, application of colorant or colorants in this manner eliminates waste of material and enhances the efficiency of the system. The colorant is applied by any appropriate available means like brushing, rolling or spraying. In Figure 1, colorant 5 is shown being applied to target 2 by roller 6. It has been found that in the case of rolling colorants onto the target surface, enamels are best applied with a urethane foam sponge roller and lacquers with a cotton roller. The colorant is then allowed to dry for approximately ten minutes in air or in approximately one minute by forced heated air. The colorants are solutions comprised of a colloidal suspension including solvents., pigments, drying agents and bulking agents. Primarily, the colorants may be classified as enamels or lacquers. Enamels are generally composed of alkyl resins, pigments, petroleum distillates, silica and dryers. In contrast, lacquers include cellulose nitrate, pigments, acetone toluene and xylene. For the purpose of this invention, commercially available industrial grade, flat or glossy, enamels and lacquers used in the graphic arts like those manufactured by DuPont, McCormick and P.P.G., prove satisfactory.

The colorant must meet two requirements. It must be compatible with the target substrate and be resoluable in the developer solution discussed below. Regarding substrate compatibility, both types of colorants may be used on most substrates. However, some specific solutions are necessary. Where the substrate is a wood pulp paper product, the substrate must be treated in order to prevent damage from later water washings. To protect such. products, a lacquer coating should be applied to both sides of the paper and dried. In such a case the use of a lacquer colorant would resoluablize the coating. In order to prevent such resoluablizing, the colorant should be selected from the enamel category. Foam boards like "Art Core" produced by Amoco also require the use of enamels. Polystyrene substrates also dissolve with application of lacquers so enamel colorants must be used.

Optionally, a little talc may be sprinkled and lightly rubbed on the dried colorant to abrade the surface and insure proper adhesion of the next applied photoresist layer. Any commercially available talc may be used.

The next step of the method is the application of the photoresist material. This layer may be applied by any conventional means producing a smooth, even coating. A cloth pad is quite satisfactory for this purpose. It should be noted that the photoresist layer may be applied even when the talc powder has not been completely removed from the target surface. After coating the photoresist material onto the colorant, it is allowed to dry either in air or by forced hot air.

^ E The photoresist material may be made by the user or may be purchased. If made by the user, approximately 28.3 gms of ammonium dichromate or a diazo salt like p- diazodiphenylamine sulfate should be mixed with 8 ounces (.24 1) of water. This solution is then added to 16 ounces (.47 1) of medium viscosity polyvinyl alcohol and 128 ounces (3.78 1) of water. After the combined solution is heated to 190°F (87°C), and then cooled, it is ready for use. Alternatively, diazoaminobenzene based sensitizers may be employed. RAYSOL Photoscreen Sensitizer No. Dye 488xx Extra Strength, manufactured by Advance Process Supply Co. is an excellent product for this purpose.

In the direct contact method, the litho neg is inverted into a wrong reading position. The surface facing the operator may be sprayed with a weak artist's adhesive like "SPRAYMOUNT"^' manufactured by 3M under the "Scotch" brand name. Catalogue No,. 6065, to facilitate alignment of the litho neg on the colorant. The negative is then placed on the colored target surface to which it adheres. The negative can be bordered by opaque strips of material

(photomasks) to avoid unwanted exposure of colorant along the edges of the litho neg. The target having the negative adhered thereto is inverted so that the coated surface faces the light source. The photoresist coated surface with attached negative is exposed to light of an appropriate frequency for between ten seconds to six minutes. It has been found that exposure to light for approximately two minutes provides very adequate results in most cases. However, to achieve best results, the time of light exposure is determined by several factors including the type of light source, the photoresist material, colorants and substrate. A person of ordinary skill in the art, by conducting and observing a few experiments, can easily determine the exposure time producing optimal results.

The selection of appropriate light source is based on the photoresist material used and the safety of the operator. In the case of the aforementioned photoresist materials, light in the ultra-violet frequency is required. Three commonly known sources emit ultra-violet radiation,

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/ OMPI ~ fluorescent, "blue" light, and "black" light. The preferred light source for the purposes of this invention is ordinary fluorescent light. Fluorescent light is the safest for the operator because it emits a relatively low level of potentially hazardous ultra-violet radiation.

"Blue" light, although much safer than "black" light, is too concentrated a source for continuous safe operation of the system. Frequently, fluorescent lighting is used in shops. The concentration of ultraviolet light is not sufficient to affect the final product made by this system. Therefore, the process may be employed under general shop conditions.

Once sufficient exposure time is attained, the light source is turned off, the target turned over, and the negative removed. The coated surface is rinsed with water, wiped off and dried. The target surface is developed by a solution applied by spraying, rolling or brushing. The ultimate requirement for the developer is that it resoluablizes the colorant not protected by activated photoresist material. Therefore, upon applying the developer and rubbing the surface with a urethane sponge, all colorant except that which has been imaged should loosen from the target surface.

The developer composition must be compatible with the type of colorant employed. For enamel colorants, volatile petroleum distillates like pure mineral spirits or naphtha having a small amount of acetone or low molecular weight alcohol, function best. Lacquer colorants are resoluablized with 15 parts thinner, 85 parts mineral spirit solution. The thinner is comprised of toluene, acetone and isopropyl alcohol. The user must be aware of the developer's potential capacity to affect the integrity of the target substrate, particularly in the case of lacquers. Therefore, a solution containing a high ratio of petroleum distillate to thinner reduces this necessity for caution.

An emulsifier solution should next be applied to and wiped over the developed target surface. To completely remove the resoluablized colorant from the target surface is important in order to produce a professional appearing

OMPI product. The emulsifier should contain a surfactant and an antiredisposition agent. Commercially available, liquid laundry detergents agitated into a suspension with mineral spirits are effectious for this step. In actual practice the developing and emulsifying steps may be combined. However, the combined solution must be soluable in water. Upon completing the application of each the developer and emulsifier or the combined solution, the imaged target surface is rinsed with water and dried. The resulting product may be used at this point.

One optional finishing step includes wiping a mild acid (HC1) or alkaline (bleach) solution to remove the photoresist from the colorant surface and then drying the target surface. The resulting product should possess photographic resolution of the image in one or multiple colors and is ready for use.

In the event the imaged product should have multiple overlapping colored surfaces, the process must first be performed with the underlying image for whatever background color or colors are desired and then the operation must again be performed using the litho neg for the overlapping image with whatever colors are desired. In reference to silkscreening, such an imaged product made in accordance with the present invention would take approximately two to four hours to complete when silkscreening would require up to three days.

The basic steps involved with the litho neg direct contact method are summarized as follows: A selected translucent or transparent target substrate is coated with an appropriate colorant(s) on surface areas generally defined by the projection of the right reading litho neg therethrough. Once dry, talc powder is dispersed and brushed off the colorant. A photoresist material is then coated over the colorant. The litho neg is then reversed and adhered to the coated target surface. The target surface is exposed to light, the litho neg is removed and the imaged target surface developed with developer and emulsifier solution. The resulting photographic quality image may be washed with photoresist material remover, dried and is ready for use.

The direct contact method described may be substituted with a lensed projection method. This method employs the same basic steps as those described above except that the image is projected from above the work surface. Therefore, the litho neg inversion step is eliminated. Projecting the image permits the operator to vary the image size by adjustment of the projector height and further, for colorant application, defines the boundaries of the image on opaque substrates which is not possible when using the direct contact method. As a consequence, the value of transparent or translucent substrates is eliminated.

The use of a specially constructed table or work station facilitates use of the method by permitting all steps to be carried out in one place. One embodiment of the work station is constructed for direct contact litho neg imaging as described above. Another embodiment utilizes a camera projection means to produce an image on the operational surface of the target. As noted, use of image projection allows an operator to vary the size of the image on the target.

The work station shown in Figure 2 incorporates the elements of both embodiments and includes epoxy coated, solventproof, housing 10 containing wraparound sink 12 which includes a drain for disposal of waste liquids resulting from use of the process. Pivotally disposed within sink 12 is exposure unit 14. The operator can pivot unit 14 to promote faster waste elimination and more easily work on the now angled target. Exposure unit 14 is positioned in sink 12 in such a manner to permit a peripheral gap between the unit and housing 10. Exposure unit 14 houses a bank of fluorescent lights 16. The number and length of the lights can be determined by the requirements of the particular system user. Twelve lights have proven quite satisfactory in use. To seal and protect the lights and to provide a large smooth working area, clear plate glass 18 comprises the upper surface of exposure unit 14. Ideally, glass sheet 18 should be removably fastened to unit 14 to facilitate maintenance on

OMPI light bank 16. Moreover, to prevent water or other solutions from entering the interior of unit 14, gasketing should be employed along the contact edges of glass 18 with unit 14. The distance between light bank 16 and glass 18 should be between three to twelve inches.

As stated, exposure unit 14 should be pivotally mounted in sink 12 to enhance efficient system operation. As further illustrated in Figure 5, the pivotal connection includes two saddles 19, one affixed to the interior center of housing 10 and the other to the center of unit 14 and a connecting central pin 20. Accordingly, it is possible to pivotally adjust the angle of unit 14 in respect to housing 10. The central pin 20 is hollow in order to house the electrical power source for light bank 16. Moving adjustment lever 22, which passes through gasketed slot 24 in housing 10 to engage unit 14, pivots or tilts unit 14. Lever 22 rotates about a pin (not shown) centrally disposed within slot 24. Ratcheting 26 is pro¬ vided along the interior edge of slot 24 to lock lever 22 into a fixed position. The ratcheting 26 prevents exposure unit 14 from freely pivoting within sink 12.

One side of housing 10 contains electric forced hot air unit 28. Air unit 28 includes air intake manifold 30 and an air output slot 32. Air is drawn through intake 30 by at least one electric fan, heated by electric coils and blown out through slot 32 in a manner to evenly distri¬ bute heated air across the surface of glass 18.

To insure an even flow of air and to reduce operator exposure to undesirable fumes, a fume takeoff slot (not shown) is provided on the opposite side of hou¬ sing 10 from hot air unit 28. An exhaust fan is placed in housing 10 to actively extract undesirable fumes from the exposure unit area and force the exhaust through exhaust port 32 incorporated into the side of housing 10. To further provide an efficient, clean work support for use with the imaging system, a raised splash guard 34 may be placed along the sides and back of housing 10. Splash ^• guard 34 contains water sprayed with nozzle 36 during the rinsing or washing steps of the imaging method. Centralized control switches 38 may be incorpor-

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OMPI ated into housing 10 for easy operation. Switches 38 should control power to light bank 16, the heating elements contained in hot air unit 28, the fan for unit 28 and the fan for fume exhaust 32. A timer switch for light bank 16 will further enhance control during the exposure step.

Water control valve 40 can also be placed within frame 10 to assure ease of proper maintenance of nozzle 36 and its flexible feed pipe.

The aforementioned alternative embodiment for projection of images shown in Figure 3 is by employing image projector 50.

Image projector 50 is mounted to support member 52 which is securely attached to housing 10.

Projector 50 is affixed to support 52 by clamp 54. Clamp 54 can be any appropriate device so long as it securely holds projector 50 in position above the work suface. Clamp 54 is firmly attached to the top of light box 56. Figure 4 illustrates light box 56 which contains an ultra¬ violet light source. It has been found that six Norelco, PL9, cool fluorescent lights 58 when secured within the box emit sufficient ultraviolet radiation to actuate the photoresist material but are cool enough so as not to affect the integrity of the negative.

Negative carrier chamber 60 containing negative carrier 62 is affixed to the open bottom of light box 56. Negative carrier 62, constructed primarily of two glass sheets with metal hinges and edge protectors, slides in and out of chamber 60. After the litho neg is placed between the glass sheets, much in the fashion of microfische read- ers, carrier 62 is inserted into chamber 60.

Bellows 64 is secured to the bottom of chamber 60 at one end and affixed to lens carrier 66 at the other end. Bellows 64 permits focusing of the image projected onto the target. Lens 68 is carried by member 66. Lens 68, for the purposes of this invention, is appropriately two inches in diameter. In order to focus the image on the target as projected from the litho neg through lens 68, adjustment knob 70 is provided on the side of box 56. Knob 70 is connected to a precise adjustment device like a toothed shaft affixed at one end to box 56 and at the opposite end to lens carrier 66 better known as a rack and pinion. When knob 70 is turned, a rotatably engaged gear directly connected thereto causes the shaft to move. As a result, lens 68 is moved up or down relative to negative carrier 62.

Another rack and pinion may be used in conjunction with support 52 to insure precise height adjustment of the entire projection unit 50. The rotating gear in this case can be connected to crank 72 which extends below the front of frame 10 to support 52 attached to the rear of frame 10 for efficient adjustment.

Projection of images eliminates the benefit from use of translucent or transparent materials in the case of the direct contact method. Metals and opaque surfaces may be imaged with the same efficiency. Projection unit 50 actually enhances the speed of operation by eliminating the need to invert the litho neg into a wrong reading position as required by the direct contact method.

For definiton purposes, in the context of this invention, colorant means a substance imparting any color, shaded or black and white surface to the desired image. Locally is used herein to indicate application of materials to at least the area on which the colored image is to be produced without covering the entire target surface. This invention, by opening the doors to a new technology, is not intended to be limited to the specific embodiments disclosed. The invention contemplates the use of alternative photoresist materials which are sensitive to radiation of frequencies other than that in the ultra- violet range. For instance, infra-red sensitive thermal resis material will require the use of infra-red radiation sources.

Furthermore, the means for exposing an image onto a target may be automated or computerized to more reduce the necessity for human labor. Variations of the preferred embodiments of the invention and their alternatives and modifications will become apparent to those skilled in the art based on the foregoing description. Accordingly, the invention is intended to embrace all such modifications and alternatives within the scope of the claims. .PA

Claims (30)

I claim:

1. A method for making permanent colored images on an article comprising steps of: (a) locally applying a colorant or colorants to specifically desired zones of a selected target surface; (b) locally applying a photoresist material to said zones; (c) passing light through the desired image to cause a portion of said photoresist material, conforming to said image, to hold the colorant in place; and (d) removing from said surface undesired colorant with a developer solution.

2. A method according to claim 1 further including colorant of an enamel or lacquer type.

3. A method according to claim 2 further including applying the colorant by spraying, brushing or rolling.

4. A method according to claim 3 further including a photoresist material composed of poly vinyl alcohol, water and either ammonium dichromate or diazo salts.

5. A method according to claim 4 further including applying said photoresist material with a cloth pad comprised of natural or synthetic fibers.

6. A method according to claim 4 further including drying said colorant and said photoresist material by a forced hot air dryer.

7. A method according to claim 3 further including exposing said target with light projected through negative of the desired image.

8. A method according to claim 7 further including said negative being in an abutting relation with said target.

9. A method according to claim 7 further including projecting light through the negative onto the target surface.

10. A method according to claim 3 including sprinkling a powder onto and slightly abrading the surface of the colorant.

11. A method according to claim 6 including exposing the photoresist material on the target for ten seconds to six minutes.

12. A method according to claim 11 further including exposing the target for two minutes.

13. A method according to claim 11 further including the step of applying a developer solution to the exposed target surface.

14. A method according to claim 13 further including application of a developer solution and rubbing developer on the target surface.

15. A method according to claim 14 further including a developer solution for enamel colorants composed of pure mineral spirits and a low molecular weight ketone or alcohol.

16. A method according to claim 14 further including a developer solution for lacquer colorants composed of volatile petroleum distillates and lacquer thinner.

17. A method according to claim 16 further including a solution of 85 parts petroleum distillate and 15 parts thinner composed of tolune, acetone and isopropyl alcohol.

18. A method according to claim 13 further including the step of applying an emulsifier suspension to the developing solution on the target surface.

19. A method according to claim 18 further including an emulsifier suspension composed of a surfactant and redisposition agent in mineral spirits.

20. A method according to claim 19 further including the step of rinsing with water said developer solution and emulsifier suspension from the target surface.

21. A method for making permanent colored images on an article, comprising the steps of: (a) projecting an image onto the surface of a smooth target to be imaged; (b) applying multiple enamel or lacquer colorants to zones to be imaged on the target surface; (c) drying said colorants; (d) sprinkling and wiping the colorant coated areas with a powder to abrade the colorant; (e) applying an ultra violet sensitive photoresist material over the colorants; (f) exposing the image on the photoresist material to ultra violet light; (g) applying and rubbing a petroleum-based developer solution on the exposed target surface; (h) applying an emulsion suspension to the developer solution; (i) removing the developer solution and the emulsion suspension from the target surface; and (j) removing the photoresist material from said surface.

22. A work station for making a permanent colored image on an article, comprising: (a) a housing; (b) a sink within said housing; (c) a work surface contained within said sink, said work surface being pivotally mounted to enable it to be adjusted; (d) means for dispersing water onto said work surface; (e) an air blower for directing air over said work surface and thereafter exhausting the air; and (f) means for projecting an image onto said work surface.

23. A work station according to claim 22 further including a solvent resistant epoxy resin coated housing and a sheet plate glass work surface.

24. A work station according to claim 22 further including a light source contained within the work surface under the surface to project light therethrough.

OMPI J-o

25. A work station according to claim 23 further including a lensed light projection means positioned above the work surface to project light thereon.

26. A work station according to claim 25 further including means for supporting a lithographic negative, said means being slidably positioned between said light source and said lens means whereby an image on the negative will be projected onto said work surface.

27. A work station according to claim 22 further including a light source contained within said work surface support under said work surface and a lensed light projection means positioned above said work surface to project light thereon.

28. A work station according to claim 22 further including heater coils with said forced air blower.

29. A work station according to claim 28 further including an electric fan- for blowing air across said work surface.

30. A work station according to claim 29 further including an electric fan for exhausting the blown air from said work surface.