Abstract:
The present invention relates to a light emitting device ( 1 ) comprising a light emitter ( 10 ) and a support ( 13 ) to which a plurality of protruding fibers ( 11 ) are attached. The light emitter ( 10 ) and the protruding fibers ( 11 ) are arranged to interact with light emitted from the light emitter ( 10 ) so that the light may be diffused. The plurality of protruding fibers comprises fibers ( 11 ) which are inclined or perpendicular in relation to the support ( 13 ).

Description:
FIELD OF THE INVENTION 
     The invention relates to the field of light emitting devices, and more specifically to an improvement of the material characteristics of the diffusing element or elements. 
     BACKGROUND OF THE INVENTION 
     Light emitting diode (LED) lighting devices with a low resolution, that is with the LED&#39;s spaced apart so the individual LED spots can easily be distinguished, may be used in many different applications such as pictures, text and graphics in connection with, for example, textiles such as garments. However the fact that the individual LED&#39;s are visible can disturb the viewing of the pictures, text or graphics. The solution to this problem is to add a diffusive layer on top of the LED thus spreading the light to a larger area. This diffusive layer can be made of different materials such as woven or non-woven materials, flexible foams, or some combination thereof. 
     An example of this can be seen in US2008/0205035A1. Here LED&#39;s are placed under a diffusive layer comprising a layer of non-woven fabric having a lower density at a side facing the lighting unit and a higher density at a side opposite to the lighting unit. The lower density layer provides spacing in order for light cone from the light units to spread, before encountering the denser portion of the diffusive element. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a light emitting device that is more flexible and thinner than the solutions presently known. 
     The object is fulfilled by providing a light emitting device comprising a light emitter, a support and a plurality of protruding fibers attached to the support, the plurality of protruding fibers being arranged to interact with light emitted from the light emitter, wherein each fiber of the plurality of protruding fibers protrudes at an angle with the support, the angle being in a range of 10 degrees to 170. The fibers provide a thinner and more flexible solution. More light emitters may also be present. The light emitter may be a light emitting diode. The interaction between the light and the protruding fibers may comprise reflection of the light or the light may pass through the fibers. The fibers may be a part of the support, if e.g. the support is woven in such a way that the fibers are protruding from the surface. The protruding fibers create a three dimensional scattering structure, where the light may be scattered and/or shadowed in the air gap and by the fibers. The angle where the fibers are attached between the fiber and the support is at an angle greater than 0 degrees and less than 180 degrees, preferably the angle is in an interval between 5 degrees and 175 degrees, most preferably in an interval between 10 degrees and 170 degrees. All of the fibers do not have to have the same angle to the support, and they are not parallel to the support. The fibers may be placed in such a way that they surround the one or more light emitters. This structure allows for overall thinner diffusion structures to be fabricated in order to achieve the same results as equivalent thicker structures. With the thinner optical structure, the overall system can be engineered to also be more flexible. 
     According to an embodiment of the invention each fiber of the plurality of protruding fibers protrudes substantially perpendicular to the support. This means that the protruding fibers do not interact with light emitted from at least one direction, which may be light emitted from the top of the light emitter and this creates a different light effect. According to an embodiment of the invention the plurality of protruding fibers are substantially transparent, which may mean that 90% or more of the emitted light is conveyed through the fiber. This makes it possible for the light to propagate through the fibers, diffusing the light more because the light is not only scattered upwards/downwards, but also propagates in-plane as well. 
     According to an embodiment of the invention the light emitting device may further comprise a substrate. The substrate may be contributing to diffusing or reflecting the light depending on the type of material used and where it is located. The substrate may be located below the support, if e.g. the support is made of a transparent material. An example of this can be seen in  FIG. 6  where a substrate (not shown) may be placed below a layer of e.g. silicone. The layer construction would then be a substrate where upon one or more light emitters are attached. A layer of a transparent material is then e.g. poured over the substrate and the light emitters. In this layer fibers that may scatter the light is attached. Here a substrate of a reflective material such as a material comprising TiO 2  or a metallic or mirror like surface may provide reflection, contributing to the scattering of the light so the light is not absorbed. The substrate may be located opposite the support. An example of this can be seen in  FIGS. 5 and 8 . Here the fibers are located between the substrate and the support, the fibers pointing in the general direction of the substrate. Here materials with a diffusing characteristic for the support may be more useful. This could be a textile or non woven material or foam that is placed opposite the support and the light emitter and may provide the light emitting device with a smoother surface or may contribute to creating light effects, such as regulate the amount of light that escapes through the surface of the substrate or create coloring effects, if e.g. the substrate is colored. 
     According to an embodiment of the invention the support is placed in connection with the light emitter. The support may be located below the light emitter, where the support may be a fabric. The support may also be placed on top of the light emitter and between the light emitters if more are present, where the support advantageously is transparent and it may also be flexible. Silicone or a similar material may be used for this purpose, providing a support for the fibers to attach to. 
     According to an embodiment of the invention, the substrate is substantially parallel to the support, the plurality of protruding fibers being provided to a surface of the support facing the substrate, and the light emitter being provided on a surface of the substrate facing the support. In other words, the light emitter is located across from the support and the fibers attached thereto. With the wording substantially parallel is meant that angle between the substrate and the support is a maximum of 10 degrees. 
     According to an embodiment of the invention the plurality of protruding fibers is light reflecting. This contributes to the diffusing of the light, and for the light to propagate in-plane. The light may encounter several fibers before it leaves the structure. 
     According to an embodiment of the invention the plurality of protruding fibers are selected from a group consisting of Velcro, polymeric fibers, glass fiber, optical fibers, carbon fibers, metal fibers, ribbons, composite and any combination thereof. 
     With a variety of materials it may be possible to create a variety of effects, and different materials may be more appropriate to certain applications. The fibers cross section may be circular, but fibers may have other shapes such as thin narrow ribbons, like a fiber that has been squeezed flat a bit, or triangular, square, star shaped or any other shape. Basically anything with translational symmetry, to maximize in-plane scattering and minimize out-of-plane scattering may be applied. 
     According to an embodiment of the invention the plurality of protruding fibers are randomly distributed. This provides a more natural, random, non-engineered non-patterned look. 
     According to an embodiment of the invention the plurality of protruding fibers are arranged in a pattern. By arranging the protruding fibers or lateral structures in a pattern, it is possible to create specifically desired light effects. 
     According to an embodiment of the invention the support or the substrate is substantially reflective. This means that light is not absorbed and thus less light is lost. Normally this would be placed at that same side and/or in connection with the light emitter. The substrate may be conductive as well. 
     According to an embodiment of the invention the support or said substrate is substantially diffusive. In this way the light may be diffused and scattered out and different light effects may be obtained depending on the degree of diffusion. By substantially diffusive is meant that the light is isotropic and/or is not strongly directional. 
     According to an embodiment of the invention the support is selected from a group consisting of a mesh, woven fibers, non woven fibers, silicone, polymer, ceramic material, composite, glass, glue and any combination thereof. 
     This means that depending on what the light emitting device is to be used for, the appropriate material(s) may be selected. 
     According to an embodiment of the invention the light emitting device is attached to a textile. Because the structure is so flexible and thin and because of its textile like feel to it, the device can be used in garments or other application in e.g. interior decoration for cushions or the like. 
     Even though the word light emitter is used through out the text, it is to be construed as at least one light emitter or light emitting diode. The same applies to the support, which is defined as the material the fibers are attached to. Here several supports may also be present, even though only one may be mentioned. In this way fibers may be coming from several sides and cross each other, thus contributing to creating light effects. 
     All the features of the support may also apply to the substrate such as the location of the substrate in relation to the light emitter or fibers or the materials from which it is made. 
     The fibers can be manufactured in a common textile way such as weaving, shaving, flogging (surface roughening of a fabric), etc. An example of a product made in this way is Velcro. 
     It is noted that the invention relates to all possible combinations of features recited in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing currently preferred embodiments of the invention. Like numbers refer to like features throughout the drawings. 
         FIG. 1  shows a schematic three dimensional view of an embodiment of the present invention. 
         FIG. 2  shows a cross sectional top view of another embodiment of the present invention. 
         FIG. 3  shows a cross sectional top view of the embodiment as depicted in  FIG. 2 , but with regions of light rays. 
         FIG. 4  shows a horizontal cross-sectional side view showing different light rays propagating from a light emitter. 
         FIG. 5  shows a schematic drawing of an embodiment of how the fibers behave when pressed downwards, the fibers being attached substantially perpendicular to the support. 
         FIG. 6  shows a schematic drawing of an embodiment of an optical dome with fibers that are protruding from it. 
         FIG. 7  shows a schematic drawing of an embodiment of a woven scattering structure. 
         FIG. 8  shows a schematic drawing of an embodiment of how the fibers behave when pressed downwards, the fibers being attached at an angle between 10 to 170 degrees to the support. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  shows a schematic three dimensional view of an embodiment of the light emitting device  1 . A lighting source or light emitter  10  is mounted to a substrate  12  and is surrounded by a plurality of fibers  11 . Finally a support  13  is placed above the fibers  11 . The fibers may be pre-attached to the support  13 , and the support  13  may function as a diffusing layer as well. In this figure, the fibers  11  are shown in a periodic distribution with respect to each other, however, they can also be distributed in a random pattern with respect to each other as can be seen in  FIG. 2 . The substrate  12  should preferably be made from a material that is as reflective as possible in order to prevent light that is scattered backwards to be lost through absorption of the material. It should be noted that even though the substrate  12  and the support  13  are placed at the bottom and at the top respectively, it may also be that the fibers are attached to the substrate, and thus the substrate serves the purpose of being a support as well. The fibers  11  may be attached by means of glue, silicone or other transparent, semitransparent or materials containing reflective elements, if attached to the substrate  12 , in order to maintain the reflective qualities of the substrate  12 . If attached to the support  13 , the fibers might be a part of the support, if this is e.g. a fabric, for example produced by flogging. The fibers  11  can either have a periodic distribution or may be completely random with respect to each other&#39;s location. The fibers  11  can be made of many different types of materials, though transparent or reflective materials are the preferred optical materials. Light rays can either be reflected from the fibers and/or pass through them (if they are made of transparent or semitransparent materials). Moreover, these fibers  11  may cast a shadow or the light may pass around or through them, thus creating light effects. 
       FIG. 2  shows a cross sectional top view of another embodiment of the present invention. Here the fibers  11  are distributed randomly with respect to each other. The light emitter,  10 , is located in the middle of these lateral structures for illustrative purposes. 
       FIG. 3  shows the same construction found in  FIG. 2  except with regions defined on and around the fibers  11 . These regions correspond to the effects of light that is emitted from the light emitter  10 . Some of the light rays emitted from the light emitter  10  can pass undisturbed  31  while others may either scatter or partially scatter  32  off of the fibers  11 . Finally, light cast a complete or partial shadow  33  behind the fibers  11 . 
       FIG. 4  shows a horizontal cross-sectional side view of  FIG. 1  showing different light rays propagating from a light emitter. Because of the fibers  11 , an air gap  40  is formed between the substrate  12  and the support  13 . This air gap  40  helps further diffuse the light due to light&#39;s propagation through it. Once the light reaches the support  13 , it can then further diffuse based on the optical characteristics of the support  13 . Light rays  41 , can pass undisturbed through the air gaps, or light rays  42  pass through some of the fibers  11  and then reflect to the support  13 , or light rays  43  immediately be reflected at the first fiber  11  encountered. Once a light ray  44  has been reflected, the light ray  44  can either reflect off of an adjacent fiber  11  or the light ray  45  can continue past adjacent fibers  11 . The light rays may continue to propagate in-plane and they are not scattered upward/downward as in conventional diffusers like foams. This promotes the lateral spreading of the light. Diffusers that are directionally anisotropic and redistribute light predominantly in-plane may be used. 
       FIG. 5  shows a schematic drawing of an embodiment of how the fibers behave when pressed downwards. If the optical layers  11 ,  13 ,  40  are pushed further down and the fibers  11  are compressed and the light becomes more diffuse.  FIG. 5  shows that the compression causes the density of scattering points or fibers  11  to increase while still maintaining an air gap  40  in the system. This scattering density becomes larger because the fibers  11  bend when they are pushed downwards on top of the light emitter(s)  10 . The bend causes the density of lateral scattering points in a plane to increase because the bent fibers  11  will work as two (or more) fibers. The fibers may split but the fibers  11  may also just bend and create a higher density. The substrate  12  or the support  13  may also be a textile or a photonic textile. 
       FIG. 6  shows a schematic drawing of an embodiment of an optical dome, here being the support  13 , with fibers  11  that are protruding from it. 
     Fibers  11  can be molded into the top or bottom of a support  13  that is molded over a light emitter  10 . For instance, if a silicone dome is molded over a light emitter  10  on a textile substrate  12  (not shown), fibers  11  may be molded on top of this structure. The dome may be transparent and may contain light scattering particles. The dome may also be encapsulating the light emitter, so that there is no air gap between the light emitter  10  and the support  13 . 
       FIG. 7  shows a schematic drawing of an embodiment of a woven scattering structure  14 . The structure may be construed as a support  13  and the fibers  11  combined in one structure. Weaving technology can be used in order to alter the height and spacing of the fibers  11  in a weave, thereby helping making the fibers  11  have regular shapes and distributions. This method can be relatively cheap, reproducible and tailor made to LED displays. In a similar way, a woven surface can be roughened, or shaved, in order to produce protruding fibers to create patterned diffusion structures. 
       FIG. 8  shows a schematic drawing of an embodiment of how the fibers  11  behave when pressed downwards, the fibers being attached at an angle between 10 to 170 degrees to the support  13 . The angle  51  between the fibers  11  and the support  13  may be different for the individual fibers  11 . The fibers  11  may also be attached to the substrate  12 . 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.