Patent Document

BACKGROUND 
       [0001]    a. Field of the Invention 
         [0002]    The present invention relates to the fields of illuminated signs and displays, and to decorative and specialist lighting fixtures. 
         [0003]    b. Related Art 
         [0004]    Illuminated displays or signs are commonly used to illuminate advertisements or images. Similar light-emitting devices are also used as decorative lights, for example recessed ceiling lights, or in the form of a light-box for viewing transparencies. 
         [0005]    One type of illuminated display is known as an edge lit display. These displays have a light source directed to the edge of a light transmissive panel, and conventionally a cover is required to enclose both the panel and the light source. The need for this cover makes the displays both impractical and aesthetically unpleasant in some desired uses. 
       SUMMARY OF THE INVENTION 
       [0006]    Aspects of the invention are specified in the independent claims. Preferred features are specified in the dependent claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The invention will now be further described, by way of example only, and with reference to the accompanying drawings, in which: 
           [0008]      FIG. 1  is a perspective view of a light transmissive device according to a preferred embodiment of the invention; 
           [0009]      FIG. 2  is a perspective view of a light-emitting device showing light transmitting sheets and edge covering according to one embodiment of the invention; 
           [0010]      FIG. 3  is a partial cross-sectional view of one embodiment of a light-emitting device showing location of a light source; 
           [0011]      FIG. 4  is a partial cross-sectional view of one embodiment of a light-emitting device, showing the arrangement of a light transmissive device, two light transmitting sheets and an edge covering. This edge covering can be applied with inks or similar; 
           [0012]      FIGS. 5 and 6  are partial cross-sectional views of a light-emitting device showing alternative light sources; 
           [0013]      FIG. 7  is a partial cross-sectional view of a light-emitting device showing an alternative cavity to contain a light source; 
           [0014]      FIG. 8  is a partial cross-sectional view of a light transmissive device showing the incorporation of a reflection strip in a further embodiment of the invention; 
           [0015]      FIGS. 9 and 10  are partial cross-sectional views of light-emitting devices showing alternative edge coverings according to further embodiments of the invention; 
           [0016]      FIG. 11  is a perspective view of a light-emitting device showing the position of magnetic attachment means according to one embodiment of the device; 
           [0017]      FIG. 12  is a partial cross-sectional view of a light-emitting device showing magnetic and metal plates for attaching light transmitting sheets to both faces of a light transmissive panel in one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]      FIG. 1  shows a light transmissive device  1  including a substantially rectangular light transmissive panel  2 . In a preferred embodiment the panel  2  has a slim profile, so that the thickness of the panel  2  is much less than the width or length. The panel  2  comprises cavities  4  to house an appropriate light source  6 . The cavities  4  may extend fully ( FIG. 7 ) or only partially through the thickness of the panel  2 . The cavities  4  may be formed by moulding, drilling, cutting, etching, routing or by any other appropriate means. 
         [0019]    The panel is made from an appropriate material such that light emitted from a light source in the cavity  4  propagating along the panel will be substantially internally reflected. One or both faces, or major surfaces, of the light transmissive panel  2  are patterned  8  or treated to produce regions of the surface that allow light to be emitted from the surface of the panel, as shown in  FIG. 3 . The patterning  8  on the faces of the panel  2  may be in the form of v-cut grooves, laser-etched areas, a printed pattern or similar. In a preferred embodiment the patterning  8  is in the form of dots or lines. The arrangement of the patterned  8  or treated regions on the face of the panel  2  is such that the light emitted from the panel is essentially even over the face of the panel. The result is that the entire panel acts as a substantially even light source. 
         [0020]    A light source  6  housed within a cavity  4  may be any suitable light source, and may be light emitting diodes (LEDs) or linear fluorescent lamps. Furthermore, the light source may be designed to emit light only towards the centre of the light transmissive panel  2 , as shown in  FIG. 5 . In one embodiment, the light source may comprise one lamp  6   a  emitting light towards the centre of the panel  2 , and a second lamp  6   b  emitting light towards the edge of the panel  2 , as shown in  FIG. 6 . The lamps  6   a  and  6   b  may be chosen to be different colours or different types. Additionally, the light source  6  may be programmed by a controller (not shown) to switch on and off to produce a desired lighting effect. 
         [0021]    The edges  13  of the panel  2  are such that light is emitted from the edges when a light source  6  contained within a cavity  4  is switched on. The panel  2  may have rounded or bevelled edges around all or part of the perimeter. Additionally, an edge covering  14  may be provided around at least part of the perimeter of the light transmissive panel  2 . This edge covering  14  may be opaque or translucent. Where the covering  14  is able to transmit light, it may be coloured or patterned to add to the aesthetic quality of the light emitting device  1 . The edge covering could be chosen to contain fluorescent pigments. The chosen edge covering  14  may be made from vinyl, polyethylene, rubber or other suitable material. 
         [0022]    To create a more diffuse light emission from the panel  2 , further translucent layers  10  may be provided adjacent to one or both of the faces of the panel  2  to cover the surface treatment or patterning  8 , as shown in  FIG. 4 . The translucent layers  10  may be attached to the faces of the light transmissive panel  2  or may form part of light transmitting sheets  12  placed over one or both faces of the panel  2 . 
         [0023]    The light transmitting sheets  12  comprise transparent or translucent material which permits the light from the panel  2  to pass through. The light transmitting sheets  12  may be coloured and may incorporate a graphic representation. The graphic representation may be in the form of an image or design or text and may be formed by regions of different coloured material or opaque material, printed areas on the surface of the sheets  12 , or similar. 
         [0024]    The light transmitting sheets  12  are attached to one or both faces of the light transmissive panel  2 , as shown in  FIG. 4 . In embodiments in which only one light transmitting sheet is used, the other face of the panel  2  may be covered by an opaque board (not shown) to block any light emitted from that face of the panel. 
         [0025]    In certain embodiments of the invention, additional blocking layers  16  may be provided between the light transmissive panel  2  and the light transmitting sheets  12 , immediately adjacent to the light source  6 , as shown in  FIG. 4 . These layers act to limit or block the amount of light emitted by the light source  6  that passes directly through the light transmitting sheets  12  which would otherwise create an area of increased brightness in the device. This blocking region may be provided on the surface of the panel  2  or may be provided by a printed area on a face of a light transmitting sheet  12 , or similar. 
         [0026]    In the embodiments shown in the figures, the light transmissive panel  2  and the light transmitting sheets  12  are substantially planar. However, it would also be possible for the light transmitting sheets  12  to be curved and attached to a planar light transmissive panel  2 , or for both the panel  2  and the sheets  12  to be curved in a complementary manner such that faces of the panel  2  and sheets  12  come into contact over the majority of the area of the faces. The panel  2  and sheets  12  may be curved using any conventional forming means, such as thermoforming. 
         [0027]    In embodiments of the invention including light transmitting sheets  12 , the edge covering  14  may be arranged to cover ( 14   a ) or enclose ( 14   b ) the perimeter of both the light transmissive panel  2  and light transmitting sheets  12 . 
         [0028]    In one embodiment of the invention, the light transmitting sheets  12  are attached to the light transmissive device  1  by magnetic plates  18 . As shown in  FIGS. 11 and 12 , magnetic plates  18  are located at various points on the faces of the panel  2 , and suitable metal plates  20  are provided in corresponding positions on one face of the light transmitting sheets  12 , so that the magnetic plates  18  and metal plates  20  come into contact when the light transmitting sheets  12  are placed in the correct position in relation to the light transmissive panel  2 . Other means of attachment may also be used such as screws, clips, adhesives or similar. 
         [0029]    Therefore, embodiments of this invention provide a backlit lighting device and a compact and slim display. The incorporation of a light source in a cavity within the panel of the light-emitting device is an improvement over previous edge-lit displays as a separate light enclosure is not required. Furthermore, the light-emitting device allows light to be emitted both from the centre of the display and from the edges. The edges may have illuminated light in any colour; the colour given by either of the colour filter applied to a cavity close to the edge, the edge covering or the colour of the light source embedded in the cavity of the central panel.

Technology Category: 4