PHOTOLUMINESCENT FILM HAVING DIGITAL IMAGES AND METHODS OF PREPARING AND USING SAME

Abstract: A film having a photoluminescent surface and a digital image thereon is disclosed. The digital image can be electrostatic toner or ink jet ink. Methods of preparing and using the imaged film are also disclosed.

Description: Photoluminescent Film Having Digital Images and Methods of Preparing and Using Same Field of Invention This invention relates to images created on photoluminescent film. Background of Invention Photoluminescent films are known and are commercially used to - provide signage that warns, cautions, and provides other messages conveying safety information. Frequently, these films are combined with an adhesive to form a photoluminescent tape. Sometimes also characterized as "Glow-in-the-Dark", "luminous", or "luminescent", these films or tapes are based on materials that absorb photons and emit visible light. Photoluminescent films and tapes can be found in commercial catalogs such as the Seton Identification Products Catalog (Seton Products, Branford CT, page AE33, 1996); D&G Sign and Label Catalog WK (D&G Sign and Label, Northford, CT, page W37, (Summer 1996); and Bradv-Signmark Division Catalog s- 17 (W.H. Brady Co., Milwaukee, WI, p. 46, 1996). Typical messages include "Danger— High Voltage"; "Exit"; "Fire Alarm"; "Fire Extinguisher"; "Oxygen No Smoking"; and the like. Some of the messages include graphics and multiple colors such as the "Danger— High Voltage" sign with the "Danger" printed in photoluminescent white in a red oval within a black rectangle above "High Voltage" printed in black within a photoluminescent white rectangle. The messages are prepared using silk-screening or other analog printing techniques. The art of electronic graphic systems has become quite advanced and very popular for using digital, computer-generated techniques to produce multiple color, precise images on a variety of substrates, including durable substrates suitable for long-term interior or exterior use. Minnesota Mining and Manufacturing Company of St. Paul, MN (3M) has developed two different types of electronic graphic systems. The Scotchprint™ Electronic Graphics Systems from 3M uses an electrostatic deposition of a latent image on a transfer medium, toning of that image on the medium, and transfer of the toned image from the transfer medium to a durable substrate such as Scotchcal™ branded vinyl, adhesive-backed film. The imaged film can then be applied to a variety of surfaces to display the image, including truck trailer sidewalls and walls, fascia and floors of buildings. U.S. Pat. Nos. 5,045,391 (Brandt et al.): 5,262,259 (Chou et al.); 5,106,710 (Wang et al.); and 5,114,520 (Wang et al.) disclose the electrostatic transfer process and materials used therewith. Media used to receive the latent image and media used to receive the transferred image are specially prepared to receive the electrostatic digital images. The 3M Thermal Ink Jet Materials uses thermal inkjet deposition of pigmented, durable inks from commercially available thermal inkjet printers onto receptor media (either opaque or transparent) to generate a multiple color images. U.S. Pat. No. 5,342,688 (Kitchin et al.) and PCT Patent Publication WO 96/08377 media from 3M used in thermal inkjet image production. Media used for inkjet digital printing is specially prepared to receive the inkjet inks. Photoluminescent film is commercially available from 3M as 3M™ Scotchcal™ Luminous Film Series 5700 that provides a luminosity that lasts up to six hours after photon excitation in the film ends. Basic lettering messages, such as "Exit" have been tested by 3M on such luminous film where the non-luminous lettering has been printed using silk-screening techniques or the non-luminous lettering has been electrocut using a cutter commercially available from Gerber Scientific Products and adhesively applied to the luminous film. The Luminous Film Series 5700 has a surface of photoluminescent material to generate the luminosity and previously has not been considered as a medium to receive either electrostatic toned images or inkjet inks, both of which have been generated using digital techniques. Summary of Invention One aspect of the present invention is the generation of digital images on a photoluminescent surface. An imaged film, comprises (a) a photoluminescent surface on the film, and (b) a digital image contacting the photoluminescent surface. Another aspect of the present invention is a method of making a digital image on a photoluminescent surface. A method of making a digital image on a photoluminescent surface, comprises the steps of (a) obtaining a digital image and a film having a photoluminescent surface, and (b) printing the digital image on the surface. Yet another aspect of the present invention is a method of using a digital image on a photoluminescent surface. A method of using a digital image on a film having a photoluminescent surface, comprises the steps of (a) illuminating the digital image and surface; and (b) ending illumination of the digital image and surface to reveal a photoluminescent image. A feature of the present invention is the unexpected discovery of the receptivity of a photoluminescent surface on Luminous Film Series 5700 from 3M to electrostatic transfer processes disclosed in U.S. Pat. Nos. 5,045,391 (Brandt et al.): 5,262,259 (Chou et al.); 5,106,710 (Wang et al.); 5,114,520 (Wang et al.); and 5,071,728 (Watts et al). Another feature of the present invention is the ability to generate luminosity in the image in differing and controlled degrees based on any method of digital printing that relies on the color of the substrate to create the final image. In other words, any image that relies on the "white" substrate to generate a lighter hue of color also results in a glow in the dark on that portion of the image based on the amount of "white" substrate showing through the image. Another feature of the present invention is the ability to generate a different photoluminescent image from the illuminated image, such that a "new" message or picture "emerges" from the digitally printed image seen in natural or artificial light. Another feature of the present invention is the ability to generate an emphasized photoluminescent image from the illuminated image, such that a message or picture "becomes more prominent" in an image after lighting of the image is diminished or "remains" in an darkened image after lighting of the image is removed. An advantage of the present invention is the unexpected use of commercially available digital printing methods and commercially available films to generate new and exciting ways of displaying different images depending on the level of lumens reaching the surface of the image. Another advantage of the present invention is the versatility of the digital imaging techniques combined with rapidly emerging computer imaging techniques wherein any image of any combination of colors from any source can be captured, manipulated, and printed using known digital imaging techniques and commercially available materials to produce unexpected beautiful, eerie, informative, or entertaining images that glow in the dark. Other features and advantages become apparent in the discussion of embodiments of the invention and the following drawings. Brief Description of Drawings Fig. 1. is a top plan view of film of the present invention bearing one image in an illuminated environment and an emphasized photoluminescent image in a darkened environment. Fig. 2 is an illustrative cross-sectional view of how a photoluminescent surface of a film or tape contributes to the resulting photoluminescence of an image digitally printed on that film or tape. Fig. 3 is an illustrative cross-sectional view of an alternative embodiment of the invention where digital imaging is provided on a middle layer contacting a photoluminescent surface of a film or tape. Embodiments of Invention Photoluminescent Films or Tapes Any film or tape having a photoluminescent major surface that is capable of receiving an image from a digital printing process is suitable for use in the present invention. Nonlimiting examples of such films or tapes include 3M™ Scotchcal™ Luminous Film Series 5700 from 3M of St. Paul, MN, USA. Series 5700 film is an adhesively-backed film having excellent chemical and stain resistance and bears a light yellowish green, environmentally benign, photoluminous major surface. Digital Imaging: Electrostatic Hardware and Software Electrostatic transfer for digital imaging employs a computer to generate an electronic digital image, an electrostatic printer to convert the electronic digital image to a multicolor toned image on a transfer medium, and a laminator to transfer the toned image to a durable substrate. Nonlimiting examples of electrostatic printing systems include the Scotchprint™ Electronic Graphics System from 3M. This system employs the use of personal computers and electronically stored and manipulated images. Nonlimiting examples of electrostatic printers are single-pass printers (Models 9510 and 9512 from Nippon Steel Corporation of Tokyo, Japan and the Scotchprint™ 2000 Electrostatic Printer from 3M) and multiple-pass printers (Model 8900 Series printers from Xerox Corporation of Rochester NY, USA and Model 5400 Series from Raster Graphics of San Jose, CA, USA) Nonlimiting examples of electrostatic toners include Model 8700 Series toners from 3M. Nonlimiting examples of transfer media include Model 8600 media (e.g., 8601, 8603, and 8605) from 3M. Nonlimiting examples of laminators for transfer of the digital electrostatic image include Orca III laminator from GBC Protec, DeForest, WI. With transfer of the digital electrostatic image from the transfer medium to a photoluminescent film or tape, optionally but preferably, a protective layer is applied to the resulting imaged photoluminescent film or tape. Nonlimiting examples of protective layers include liquid-applied "clears" or overlaminate films. Nonlimiting examples of protective clears include the Model 8900 Series Scotchcal™ Protective Overlaminate materials from 3M. Nonlimiting examples of protective overlaminates include those materials disclosed in U.S. Pat. No. 5,681,660 (Bull et al.) and copending, coassigned, PCT Pat. Appln. Serial No. US96/07079 (Bull et al.) designating the USA and those materials marketed by 3M as Scotchprint™ 8626 and 3645 Overlaminate Films. Fig. 1 is a top view of an image generated by a Scotchprint™ Electronic Graphics System having 400 dots per inch (dpi) or 100 pixels per inch. Images can be prepared on equipment able to accept from about 25 pixels per inch to about 600 pixels per inch. Fig. 1 displays an image graphic 10 having at least one portion 12 where toner obscures the photoluminescent substrate, at least one portion 14, a highlight point, where almost no toner covers the photoluminescent substrate and yields almost total photoluminescence; and at least one remaining portion 16 where partial coverage of toner over the photoluminescent substrate yields a diminished but visible photoluminescence. Fig. 2 is an illustration of a cross-sectional view of an image graphic 20 comprising a film 22 having a photoluminescent surface 24 and an electrostatic image portion 26 obscuring the surface 24 and an electrostatic image portion 28 partially covering surface 24. Optional overlaminate 29 adheres to and protects imaged portions 26 and 28 and exposed portions of surface 24. Fig. 3 is an illustration of a cross-sectional view of an image graphic 30 comprising a film 32 having a photoluminescent surface 34 and an imaging layer 35 which has an electrostatic image portion 36 obscuring the surface 34 and an electrostatic image portion 38 partially covering surface 34. An overlaminate 39 adheres to and protects layer 35 and the imaged portions 36 and 38. Digital Imaging: Ink Jet Hardware and Software Thermal inkjet hardware is commercially available from a number of multinational companies, including without limitation, Hewlett-Packard Corporation of Palo Alto, CA, USA; Encad Corporation of San Diego, CA, USA; Xerox Corporation of Rochester, NY, USA; LaserMaster Corporation of Eden Prairie, MN, USA; and Mimaki Engineering Co., Ltd. of Tokyo, Japan. The number and variety of printers changes rapidly as printer makers are constantly improving their products for consumers. Printers are made both in desk-top size and wide format size depending on the size of the finished graphic desired. Nonlimiting examples of popular commercial scale thermal inkjet printers are Encad's NovaJet Pro printers and H-P's 650C and 750C printers. Nonlimiting examples of popular desk-top thermal inkjet printers include H-P's DeskJet printers. 3M markets Graphic Maker Ink Jet software useful in converting digital images from the Internet, ClipArt, or Digital Camera sources into signals to thermal ink jet printers to print such images. Inkjet inks are also commercially available from a number of multinational companies, particularly 3M which markets its Series 8551; 8552; 8553; and 8554 pigmented inkjet inks. The use of four principal colors: cyan, magenta, yellow, and black permit the formation of as many as 256 colors or more in the digital image. Usefulness of the Invention Digital imaging of photoluminescent films using the present invention offers a myriad of opportunities to entertain, educate, decorate, adorn, warn, or inform those who encounter the imaged films in a darkened environment. Nonlimiting examples of uses of imaged films of the present invention include complex graphic images of warning signage in factories, novelty displays in amusement parks, and artistic or architectural embellishments on walls, ceilings, or floors. Illumination can be provided by natural sunlight, artificial incandescent light, artificial mercury light, artificial fluorescent light, or "black lights". Those skilled in the art of government regulated warning signage can provide specific images of particular machinery with different warnings depending on the illumination or darkened area in which the machinery is placed. Those skilled in the art of military identification can provide detailed escape instructions for military service personnel working below deck of a warship. Those skilled in the art of digital mapping can provide glow-in-the- dark travel routes for persons driving or piloting in a darkened environment. Those skilled in the art of interior decoration can provide children's entertainment images for floors, ceilings, and walls where one image is seen in an illuminated environment and a different photoluminescent image seen in a darkened environment. If sufficient photoluminescent images remain in a darkened environment, the image can provide a soothing image to view as children are falling asleep. Those skilled in the art of novelty entertainment can emphasize photoluminescent images for a teenage audience by alternating light strobes for an illuminated sinister image and an even more grotesque photoluminescent image in the totally dark environment. Those skilled in the art of advertising products can employ image graphics of the present invention to emphasize specific features of the product by darkening the illuminated image periodically or episodically. The image graphic can become a passive alternative to neon light illumination of a sign. Further embodiments will be found in the following examples. Examples An image from a popular movie and an image of a popular consumer product were generated in a Scotchprint Electronic Graphics System and printed on No. 8601 Electrostatic Paper using a Nippon Steel Corporation 9512 Electrostatic Paper. The toned images were transferred from the 8601 Electrostatic Paper to Series 5700 Scotchcal™ Luminous Film using an Orca III Laminator at a rate ranging from about 1.5 feet per minute (0.45 meters/min.) to 2.8 ft/min. (0.85m/min.) at a hot roll heated to 290°F (143 °C). A 3M No. 8626 overlaminate was applied to both imaged films. The images were unexpectedly and remarkably precise approaching photographic quality and true in color to the original image, except for a slightly yellowish green tint in the normally white areas of the images After illumination under fluorescent light, a view of the imaged films in the dark produced a glow of photoluminescent images with portions in one of the images of a helmet in dimmed photoluminescence and "light reflection points" of bright photoluminescence. A small area of that image has been used in this application as Fig. 1. The other imaged film had a photoluminescent image that emphasized the highlights of a bottle shape. The invention is not limited to the above embodiments. The claims follow.

Claims: What is claimed is: 1. An imaged film, comprising: (a) a photoluminescent surface on the film, and (b) a digital image contacting the photoluminescent surface. 2. The imaged film of Claim 1, wherein the image is an image of electrostatic toner. 3. The imaged film of Claim 1 , wherein the image is an image of an inkjet ink. 4. The imaged film of Claim 1, wherein at least one portion of the photoluminescent surface is uncovered by the digital image. 5. The imaged film of Claim 1, further comprising a protective layer covering the digital image and the surface. 6. The imaged film of Claim 1, further comprising an imaging layer contacting the photoluminescent surface and wherein the digital image resides on the imaging layer. 7. A method of making a digital image on a photoluminescent surface, comprising the steps of: (a) obtaining a digital image and a film having a photoluminescent surface, and (b) printing the digital image on the surface. 8. The method of Claim 7, wherein the printing step comprises electrostatic printing. 9. The method of Claim 7, wherein the printing step comprises ink jet printing. 10. The method of Claim 7, further comprising a step (c) of protecting the image and the surface with a protective layer. 11. A method of using a digital image on a film having a photoluminescent surface, comprising the steps of: (a) illuminating the digital image and surface; and (b) ending illumination of the digital image and surface to reveal a photoluminescent image. 12. The method of Claim 11, wherein the photoluminescent image emphasizes the digital image when illuminated. 13. The method of Claim 12, wherein the photoluminescent image is replaces the digital image. 14. The method of Claim 13, wherein photoluminescent image remains for about 6 hours after illumination ends.

Inventors: MURPHY DAVID J, REIMER DAVID J, MURPHY, DAVID, J., REIMER, DAVID, J.
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1998
Main classification: B41M3
IPC codes: B41J2, B41M3, B44F1, G09F13