Card – picture – or sign exhibiting – Illuminated sign – Edge illuminated
Reexamination Certificate
2001-05-15
2003-07-01
Morano, S. Joseph (Department: 3617)
Card, picture, or sign exhibiting
Illuminated sign
Edge illuminated
C040S542000, C040S581000
Reexamination Certificate
active
06584714
ABSTRACT:
The invention relates to an optical display for the rendition of pictorial representations, colour patterns or items of information. The pictorial representations, colour patterns or items of information are rendered by optically exciting fluorescent substances in a transparent or semitransparent shaped plastic article which is provided with means for controlled light output.
Shaped articles made of transparent or semitransparent plastics, which are dyed using fluorescent substances, are known (EP 0 025 136 and EP 0 032 670). They are, for example, used for objects of furniture or decoration. The light is applied flat to such known shaped articles using an external source. The fluorescent light becomes visible at the edges of the shaped articles. The light source used in this case is ambient light from lamps or sunlight. These known shaped articles have no internal structuring or surface structuring and are not used for the rendition of pictorial representations, colour patterns or items of information.
Recently, fluorescent substances have been used to coat blue light-emitting diodes in order, by means of luminescent conversion, to produce white light or light of any other desired colour. Such light-emitting diodes are referred to as LUCOLEDs (Luminescent Conversion LEDs) “Die wei&bgr;e LED ist da” [white LEDs have arrived] Fraunhofer Institut für Angewandte Festkörperphysik in elektronik industrie 6, 1997, “NICHIA CHEMICAL Develops Efficient White LED Lamp”, N. S. Shinbun in Supplement to TECHNICAL NEWSLETTER, 10, Ref. No. 21, 1996). Here again, there is no structuring of the coating containing the fluorescent substances.
The object of the present invention is to use the fluorescent emission from shaped articles made of transparent or semitransparent plastics, which contain fluorescent substances, in combination with the waveguide properties of the shaped articles, in particular for the pictorial representation and rendition of colour patterns or items of information.
The invention relates to an optical display containing one or more shaped articles and a light source. The term shaped articles includes articles configured in any way, for example sheets, plates, ropes, threads, fibres, tubes, spheres, cuboids, cylinders, hollow bodies or rings. The shaped articles consist of one or more transparent or semitransparent plastics. Each plastic contains one or more fluorescent substances. One or more light sources are arranged in such a way that their light is applied to the surface of the shaped article at particular regions of it and propagates through the shaped article. The shaped article contains means for controlled light output, so that the light is output from the shaped article in a controlled way at quite particular regions on the surface of the shaped article.
The light input into the shaped article, usually visible light or UV light, is absorbed through excitation of the fluorescent substances in the shaped article. The fluorescent light emitted by the fluorescent substances has a longer wavelength than the light originally input. The shaped article acts as an optical waveguide for the fluorescent light. Total reflection of a major part of the light takes place at the walls of the shaped article.
Examples of possible means for the scattering of light include structuring in the interior of the shaped article (internal structure), structuring of its surface or a light-scattering layer on particular regions of the surface of the shaped article.
The internal structuring of the shaped article, the structuring of the surface or the coating of the surface with a light-scattering layer, causes scattering of the fluorescent light in the shaped article, so that it no longer strikes the inner walls of the shaped article at the correct angle for total reflection. This causes the scattered light to be output. The regions on the surface of the shaped article where the fluorescent light is radiated are defined by the structuring, that is to say controlled output is involved. Through appropriate structuring, it is possible for the fluorescent light to be radiated, for example, in the form of pictorial figures, characters or patterns.
The shaped article consists of a transparent or semitransparent plastic, such as thermoplastic, elastomer or thermoset, in which the fluorescent substances are incorporated. Examples of particularly suitable transparent plastics include polycarbonates, polyesters, polyacrylates, polystyrenes, polyvinyl polymers, copolymers of styrene and acrylates, polyacrylonitrile, polysulphones, polyether sulphones, cyclic polyolefins and copolymers and cellulose acetates. Further examples of suitable plastics can be found in H. Domininghaus, “Die Kunststoffe und ihre Eigenschaften” [plastics and their properties] 4th edition 1992 VDI Verlag, Dusseldorf and “Encyclopaedia of Polymer Science and Engineering”, 2nd edition J. Wiley & Sons, New York or J. Brandrup, E. H. Immergut, “Polymer Handbook”, 3
rd
edition, J. Wiley & Sons, New York.
According to the invention, suitable fluorescent substances include all low molecular weight, oligomeric and polymeric substances which exhibit photofluorescence. Examples of low molecular weight substances include organic fluorescent and laser dyes such as coumarins, perylenes, phthalocyanines, stilbenes and distilbenes, distyrenes, methines, azomethines, phenanthrenes, rubrene, quinacridones or optical brighteners based on heterocyclic compounds. Photofluorescent metal and transition metal complexes such as aluminium oxinate, europium complexes, boron chelates or gallium chelates may furthermore be used. For example, poly(para-phenylene vinylene) (PPV) and PPP derivatives such as methoxy-ethylhexyl-oxy PPV (MEH-PPV) are suitable as polymeric fluorescent materials. Polymers with fluorescent segments in the main or side chain may also be used. Various fluorescent substances with different absorption and emission spectra may also be contained in a shaped article.
The internal structuring may consist of light-scattering particles such as glass spheres, glass fibres, metal oxides, SiO
2
or minerals, which are incorporated in the shaped article. The particles act as scattering centres for the incident fluorescent light and deviate it in such a way that it strikes the surface of the shaped article at a steep angle and does not undergo total reflection but is instead output. The same effect can be obtained from gas inclusions in the shaped article, which form, inside the shaped article, interfaces at which the incident light is scattered. The particles may themselves also contain fluorescent substances.
Structuring of the surface of the shaped article may consist of light-scattering particles which are incorporated in the surface of the shaped article. The particles act as scattering centres on the surface and output the incident light.
The surface may also be structured using grooves and/or holes. With this type of surface structuring, the scattering centres are created on the surface of the shaped article. The edges of grooves formed in the shaped article may be chamfered.
Printing pastes—for example screen printable formulations or blends or dyes—which are applied using known methods, may be used as a light-scattering layer on particular regions of the surface of the shaped article. At points on the surface which are coated in this way, the incident light is not reflected corresponding to the angle of incidence, but is scattered back into the shaped article. It then strikes the opposite surface of the shaped article at angles which do not allow total reflection, and is output there.
At regions on the surface where no light is output, the shaped article may be coated with a reflecting material, for example a metal layer of aluminium, gold or silver or with another layer having a refractive index which permits total reflection. A coating which is nontransparent over its entire surface is also possible. These reflecting layers improve the waveguide properties, at the points which are not structured or scatter light, and
Heuer Helmut-Werner
Wehrmann Rolf
Bayer Aktiengesellschaft
Bellinger Jason R.
Gil Joseph C.
Morano S. Joseph
Preis Aron
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