Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
2002-10-24
2004-11-16
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C428S143000, C428S156000, C359S642000, C359S707000, C359S741000
Reexamination Certificate
active
06818276
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a light management film. In a preferred form, the invention relates to a light management film with a layer capable of receiving a colorant density of at least 0.5 useful for use in a backlit display application or an overhead projection system.
BACKGROUND OF THE INVENTION
Current printing operations rely on flat media in which to print on. Thermal media producers go to great lengths to ensure that the thermal print media is flat. Thermal media needs to be flat to ensure even color density printing because the print head and paper must hit at the same point. As disclosed in U.S. Pat. No. 5,244,861, the thermal print media must have an average surface roughness of less than 0.2 micrometers or else there will be dropout. Dropout occurs when there are valleys or peaks in the thermal print media and the print head (because the thermal media is then closer or farther from the print head) so that a density differential occurs. If there is a valley in the thermal paper, less colorant will be transferred and it will show up as a light colored spot on the image.
Current light management films work by incorporating light shaping elements and typically have a surface roughness over 3 micrometers. It has been difficult to print over these light-shaping films to add color of high density.
Thermal printing is a term broadly used to describe several different families of technology for making an image on a substrate. Those technologies include hot stamping, direct thermal printing, dye diffusion printing and thermal dye sublimation printing. In order to use thermal dye sublimation printing on a non-compatible surface, the most common methods of improving print quality is to increase the thermal energy of the print head and to increase the pressure applied to the print head by the backup roll. However, increasing thermal energy and pressure can lead to decreased printer head life, ribbon wrinkling, lower print quality and mechanical stresses in the printing system.
It would be desirable to have a light management film that has excellent light shaping characteristics and is able to reproduce highly saturated colors. It would also be desirable to be able to color to monochromatic displays, such as LCD's for cell phones and personal digital assistants (PDAs) to create interesting static displays with coloration or personalization.
Prior art diffuser films with uniform diffusion across the film must have the diffusion efficiency to diffuse the most intense, specular areas of the display across the entire diffuser leading to high levels of diffusion efficiency causing lower percentages total transmission across the entire film. It would be desirable to have the amount of diffusion, light shaping, and color vary across the diffusion film, whether a bulk or surface diffuser, to compensate for uneven brightness across a backlit display.
Current overhead projection media typically consists of a transparent film with printing of some color and density. The projection film is placed on a light source where light is transmitted through the projection film and collected by the collection lens. The collection lens then projects the light to a projection screen. The projected image is much larger than the original projection film, making this system suitable for multiple viewers, as in a conference room or a classroom.
Because the bright white background of the projected image is bright, the viewers cannot easily view light colors printed on the transparency. In addition to the light coming from the overhead projector and comprising the image information, ambient light will be incident on the projection screen and reflected by this screen towards the audience. To obtain an image on the projection screen that is sufficiently rich in contrast during a presentation, at which illustrations, graphs and the like are shown by means of an overhead projector, the audience space will have to be darkened considerably. An increase of the power of the lamp in the illumination system, so that the signal light will be considerably more intense than the ambient light, causes heat build up in the lamp with causes early failure of the bulb or installation of a noisy fan. It would be advantageous to have a transparency film that could be projected with bright and dark areas with colors.
The current barcode system has a number of drawbacks. The typical black and white barcodes take up valuable packaging space and are unattractive. Where a packaging label is small (on a pack of chewing gum for example) the barcode might take up half of the label. Because the barcode takes of space and is unattractive, it is typically only placed in one part of the package. The operator of the barcode scanning system, for example a cashier at a grocery store, has to know where the barcode is on each package to quickly scan the item. If it is a new package design or a new item, the cashier might have to turn the package over a few times to find the barcode. It would be desirable to have a barcode system that could be placed in multiple areas of the package, without taking up addition space of the label, so it is more easily scanned.
Light diffusing elements that scatter or diffuse light generally function in one of two ways: (a) as a surface light diffusing element utilizing surface roughness to refract or scatter light in a number of directions; or (b) as a bulk light diffusing element flat outer surfaces and embedded light-scattering elements. The surface light diffusing elements normally utilize the rough surface, typically with a lens, exposed to air, affording the largest possible difference in index of refraction between the material of the diffuser and the surrounding medium and, consequently, the largest angular spread for incident light. The bulk diffuser diffuses the light within the film. Examples are small particles, spheres, or air voids of a particular refractive index are embedded another material with a differing refractive index. Light shaping elements tend to direct or deflect light using geometries and an index of refraction change. A prism is one example of a light shaping clement. Light shaping elements tend to be surface light shaping elements, though there are a few bulk light shaping elements. The geometry, materials, and environment determine how much light is shaped or directed by a light shaping element.
U.S. Pat. No. 4,774,224 describes using a resin-coated paper with a surface roughness measurement of 0.19 micrometers or less. This type of paper is generally used for photographic bases, and consequently, it has the photographic look. This base has excellent curl properties both before and after printing, and due to its simple design is relatively inexpensive to manufacture. However, it is not very conformable and under printing conditions with low pressure between a print head and a printer drum, it does not yield high uniformity prints (most commercial printers are now being built with low printing pressures to make them more cost effective). Also higher energy levels are needed to achieve a given density. It has been shown that typical resin coated paper cannot achieve high density because polyolefin, the polymer typically used in resin-coated paper, is not as good a thermal dye sublimation receiver as other polymers.
In U.S. Pat. No. 6,381,068 (Harada et al.), the diffusing element may be a bulk diffuser including a transparent base material and at least one light-diffusing material, such as a pigment and/or beads, dispersed in the transparent base material. The pigments used may include a white pigment (for example, titanium oxide) and may also include one or more colored pigments. The pigments in this invention are only used with a uniform diffuser and not a variable diffuser. Furthermore, the colored pigments must be a single color tone and density across the display.
In U.S. Pat. No. 6,266,476 (Shie et al.), a monolithic element comprises a substrate body and a macro-optical characteristic produced by surface micro-structures. These micro-structures can be n
Arrington Eric E.
Bourdelais Robert P.
Kaminsky Cheryl J.
Eastman Kodak Company
Kluegel Arthur E.
Nordmeyer Patricia L.
Pyon Harold
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