Abstract:
A sign plate for an edge-illuminated sign including a transparent sheet with a front face, a rear face and a transparent edge that connects the front face to the rear face, wherein the transparent edge is positioned to receive light from a light source for transmission along the transparent sheet. The sign plate further includes a front image layer disposed on a front face of the transparent sheet, wherein the front image layer has a reflective surface. A rear image layer is disposed on a rear face of the transparent sheet substantially in registry with the front image layer, wherein the front image layer and the rear image layer are positioned so that the light within the transparent sheet is reflected from the reflective surface onto the rear image layer thereby to enhance illumination of the rear image layer. The sign plate has a structure such that a portion of the light within the transparent sheet forms an image of a halo or aura of light surrounding the rear image layer.

Description:
This application is a continuation of application Ser. No. 08/706,626, filed Sep. 6, 1996, (now U.S. Pat. No. 5,829,177); which application is incorporated by reference herein. 
    
    
     The present invention relates to an illuminated sign and to a sign plate for an illuminated sign. 
     DESCRIPTION OF THE RELATED ART 
     Edge-illuminated signs are known in which a transparent plastics sheet is illuminated by a light source disposed along one edge thereof so that light passes through the sheet material in a direction along the plane of the sheet. An image to be displayed is formed on one of the faces of the sheet whereby the light contrast between the image and the remainder of the sheet increases the visual impact of the image to a person viewing the sign. A typical known edge-illuminated sign as illustrated in FIG.  1 . 
     Referring to FIG. 1, a transparent plastics sheet  2 , typically of acrylic plastic material, which is rectangular in shape has one edge  4  thereof received in a lamp housing  6  in which an elongate bulb  7 , typically a fluorescent bulb, and electrical fittings  9  therefor are received, the bulb extending substantially along the length of the edge  4 . In use, an end cap  8  is fitted over each end  10  of the lamp housing  6 . In FIG. 1, which is a partially exploded view, one end cap  8  is shown in its removed configuration and the bulb and electrical fittings  9  are partially removed so that the edge  4  of the sheet  2  is readily visible. The sheet  2  is provided either on its frontmost face  12  of its rearmost face  14 , the direction being with respect to the intended position of a view of the sign, with an image  16 . The image  16  may be formed by engraving the surface of the sheet  2  or by printing a partially transmissive printed ink layer on the surface of the sheet, for example by screen printing. When the bulb  7  is illuminated, light emitted from the bulb  7  passes along the sheet  2  from the edge  4  and is internally reflected at the sheet/air interfaces. When the image  16  is engraved, light passing along the sheet  2  is reflected and refracted at the engraved edges thereby illuminating the edge of the image  16 . When the image  16  is printed, the internally reflected light is incident on the rear surface of the image  16  and is partially transmitted to the front surface of the image  16  thereby to provide an illuminated image. 
     When the image is engraved this increases the cost and complexity of manufacture of the illuminated sign. When the image is printed, the degree of contrast of the image is not particularly high and so the sign is not particularly effective in ambient conditions of high light intensity. Furthermore, for both prior arrangements the nature of the images which can be conveyed by the signs is relatively limited. 
     U.S. Pat. No. 5,009,019 and WO-A-93/07605 are both in the name of the present inventor and relate to sign plates for illuminated signs. Both of these prior specifications disclose a sign plate for an illuminated sign which is intended to be illuminated by a light source disposed behind a rearmost face of the sign plate. 
     An aim of the present invention is to provide an improved edge-illuminated sign. It is a further aim of the present invention to provide an edge-illuminated sign which can be manufactured cost-effectively and can provide enhanced illumination of the image as compared to known edge-illuminated signs. It is a further aim of the present invention to provide an edge-illuminated sign which enables a wide variety of images to be displayed. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention provides an illuminated sign comprising a light source, a transparent sheet having one edge thereof which one edge is assembled adjacent the light source of receiving light therefrom which, in use, is transmitted along the transparent sheet, a front image layer which is disposed on a front face of the transparent sheet and has a rearwardly-directed reflective surface and a rear image layer which is disposed on a rear face of the transparent sheet substantially in registry with the front image layer whereby, in use, light is reflected from the reflective surface onto the rear image layer thereby to enhance the illumination of the rear image layer. 
     The present invention further provides a sign plate for an edge-illuminated sign, the sign plate comprising a transparent sheet having one transparent edge thereof for receiving from a light source light for transmission along the transparent sheet, a front image layer which is disposed on a front face of the transparent sheet and has a rearwardly-directed reflective surface and a rear image layer which is disposed on a rear face of the transparent sheet substantially in registry with the front image layer whereby, in use, light is reflected from the reflective surface onto the rear image layer thereby to enhance the illumination of the rear image layer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which: 
     FIG. 1 is a partially exploded perspective view of a known edge-illuminated sign; 
     FIG. 2 is a perspective view of an edge-illuminated sign in accordance with a first embodiment of the present invention; 
     FIG. 3 is a cross-section on line A—A of the edge-illuminated sign illustrated in FIG. 2; 
     FIGS. 4 &amp; 5 are schematic view similar to that of FIG. 3 illustrating the mechanism of the transmission of light along and out of the transparent plastic sheet of the sign illustrated in FIG. 2; and 
     FIG. 6 is a cross-section through an edge-illuminated sign in accordance with a second embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 2 and 3, there is shown an edge-illuminated sign, designated generally as  20 , in accordance with a first embodiment of the present invention. The sign  20  comprises a lamp housing  22  in the form of a cylindrical tube. At opposed ends of the lamp housing  22  are provided electrical fittings  24  for a fluorescent bulb  26  which extends along the length of the lamp housing  22 . The lamp housing  22  is provided in its lower surface with an axially directed elongate slot  28  which receives the uppermost edge  30  of a transparent plastic sheet  32  which is supported by and depends downwardly from the lamp housing  22 . In the illustrated embodiment, the transparent plastics sheet  32  is rectangular in shape, having two upright side edges  34 , 36  and a lowermost edge  38 . 
     As is shown clearly in FIG. 3, the lowermost edge  38  is inclined to the plane of the sheet  32  with the internal face of the edge  38  facing towards the front face  40  and away from the rear face  42  of sheet  32 . The inclined edge  38  is preferably at an angle of less than about 45° to a line perpendicular to the sheet  32  so that light is reflected back from the edge  38  into the sheet  32  at a relatively low angle so as to subsequently be internally reflected back up through the sheet  32  with minimal loss of light intensity. In an alternative arrangement, the inclined edge  38  faces towards the rear face  42  rather than the front face  40 . The front face  40  of the sheet  32  is coated with a front image layer  44  which is patterned in the shape of an image to be displayed by the sign  20  (in the illustrated embodiment, the letter A which is shown merely by way of example). The rear face  42  of the sheet  32  is coated with a correspondingly shaped rear image layer  46  which is disposed in registry with the front image layer  44 . In the illustrated embodiment, the width of the rear image layer  46  (in the plane of the layer  46 ) is dimensionally larger than that of the front image layer  44  whereby the rear image layer  46  defines, in regions such as regions  48 , 50 , 52 , 54  illustrated in FIG. 3, a peripheral margin  56  surrounding and highlighting the image conveyed by the front image layer  44 . The front image layer  44  has a rearwardly directed surface  58  which is reflective. Preferably, the front image layer  44  comprises a self-adhesive plastic (e.g. vinyl) film which has an underlying self-adhesive reflective surface  58 . The plastic film may be fluorescent and translucent. The front image layer  44  or its reflective surface may be provided by a metallic and/or brightly colored (e.g. white) paint layer or by a metallised or brightly colored coating on or in the plastic film. The paint layer  44  may be fluorescent and at least partially translucent. The front surface  60  of such a front image layer  44  may have been provided with any suitable color, pattern or image, either by such a colour, pattern or image being present in the film or having been applied thereto. The front image layer  44  may alternatively comprise a printed film of any desired color or colors. The rear image layer  46  comprises a layer of fluorescent material of any desired color or combination of colors which preferably has been printed, for example by screen printing, onto the rear face  42  of the sheet  32 . Preferably, the rear image layer  46  is partially transmissive for visible light. In an alternative embodiment, the rear image layer may comprise a self-adhesive plastic (e.g. vinyl) film which is preferably fluorescent and translucent. The front and rear image layers may incorporate phosphorescent materials. 
     A backing sheet  62  is mounted behind and parallel with the sheet  32 . The backing sheet  62  has a front face  64  which is preferably spaced slightly from the rear face  42  of the sheet  32 . The backing sheet  62  preferably comprises a substantially opaque plastic sheet having a desired color and/or a fluorescent coating. The backing sheet  62  may have any desired image or pattern or the front face  64  or the rear face  66  thereof when the backing sheet  62  is translucent. Alternatively, the backing sheet  62  may comprise a transparent plastic sheet having a substantially opaque coating on the front face  64 . The lamp housing  22  is configured to provide a mount  68  for the upper edge  70  of the backing sheet  62 . A bottom mount  72  is provided along the respective adjacent bottom edges  38 , 74  of the transparent sheet  32  and the backing sheet  74 . Preferably the inner surface  76  of the bottom mount  72  which abuts the inclined bottom edge  38  of the transparent sheet  32  is reflective. As shown schematically in FIG. 3, clamping devices  78 , 80  may be provided for holding together the assembly of the transparent sheet  32  and the backing sheet  62 . 
     The operation of the edge-illuminated sign  20  will now be described with reference to FIGS. 4 and 5. 
     In use, the fluorescent bulb  26  is illuminated and as shown in FIG. 4, light beams, such as light beam  82 , which are not parallel to the plane of the transparent sheet  32  are transmitted through the plane of the sheet  32  by internal reflection at alternatively the inner and outer faces  40 , 42  of the transparent sheet  32 . It will be seen that since in the illustrated embodiment the only layers which are formed on the front and rear faces  40 , 42  of the transparent sheet  32  are the front and rear image layers  44 , 46 , there is an enhanced degree of internal reflection of light being transmitted along the sheet  32 , the light being internally reflected at the sheet/air interfaces. If additional layers were present intimately covering the sheet faces, then the degree of internal reflection would be reduced because light would be absorbed into these additional layers, thereby reducing correspondingly the level of illumination of the desired image. For this reason, the backing sheet  62  may be adjacent to, but not ahdered or otherwise intimately connected, bonded or adhered to the transparent sheet because this would reduce the total amount of light internally reflected in the transparent sheet. 
     As shown in FIG. 5, any light beam  84  which is parallel to the plane of the transparent sheet  32  is transmitted down the entire length of the sheet  32  and subsequently reflected by internal reflection at the inclined face  38 , or reflected by reflection at the reflecting face  76  of the lower mount  72 , and the reflected beam  86  is transmitted back up the transparent sheet  32  and subsequently internally reflected at the inner and outer faces  40 , 42  of the transparent sheet  32 . In this way, light from the bulb  26  is transmitted throughout the whole body of the transparent sheet  32 . 
     Light beams which are not parallel to the plane of the transmitting sheet  32  are reflected to a significant extent at the reflective surface  58  of the front image layer  44 . This reflected light (e.g. at arrow  88 ) is reflected to a significant extent back onto the fluorescent rear image layer  46 . This provides an enhanced illumination of the fluorescent rear image layer  46  so that the edges of the rear image layer  46  which are not directly covered by (i.e. are at least partially exposed by) the front image layer  44  appear very bright to a viewer of the sign (e.g. at arrow  90 ). This brightness is enhanced by the fluorescent effect of the rear image layer  46  which strongly emits fluorescent radiation as a result of being illuminated by light from the bulb  26 . The overall illumination effect to a viewer of the sign  20  is a strongly illuminated fluorescent annular border or highlight surrounding the image defined by the front image layer  44 . This provides an illuminated outline at least partially around indicia defined by the front image layer. 
     The front image layer  44  may be subsequentially opaque or partially transmitting. If the front image layer  44  is partially transmitting, then as shown in FIG. 4 some light (e.g. at arrow  92 ) is reflected from the rear face  42  of the sheet  32  forwardly through the front image layer  44  whereby the image defined by the front image layer  44  is partially illuminated. 
     The fluorescent layer  46  is partially transmitting and accordingly light (e.g. at arrow  94 ) passes rearwardly through the fluorescent layer  46  and onto the backing sheet  62 . Such light is reflected from the backing sheet  62  at its front face  64  (e.g. at arrow  94 ) and such reflected light is transmitted forwardly through the transparent sheet  32 . Such reflected light from the backing sheet  62  provides an image of a halor or aura of light surrounding the image defined by light reflected from the fluorescent rear image layer  46 . The halo of light is illustrated in FIG.  1 . The color of the halo of light is preferably the same as that of the fluorescent rear image layer  46 . The color may be varied by applying an additional colored layer to the back of the rear image layer or to the front of the backing sheet. The lateral width of the halo may be varied by altering the spacing between the transparent sheet  32  and the backing sheet  62 . 
     A further embodiment of an illuminated sign  90  in accordance with the present invention is illustrated in FIG. 6 which is similar to the embodiment illustrated in FIGS. 2 to  5  except that the opaque backing sheet  62  is replaced by a transparent backing sheet  96  having a reflecting coating  98  on its rear face  100 . The reflecting coating  94  comprises a self-adhesive plastic film  102  having a reflection front surface  104 . Alternatively, the reflecting coating  94  is a printed layer. In a similar manner to that illustrated in and described with reference to FIGS. 4 and 5, a halo effect is provided around the fluorescent rear image layer  46  by light being reflected off the reflecting surface of the film  98  (e.g. at arrow  106 ). Since the reflecting film  102  is on the face  100  of the backing sheet  96  which is remote from the transparent sheet  32 , there is no requirement for the backing sheet  96  to be spaced in order to provide a visible halo effect. 
     It will be apparent to those skilled in the art that various modifications can be made to the illustrated embodiments within the scope of the invention. In the illustrated embodiments, the front image layer lies wholly within the lateral periphery of the rear image layer so that a peripheral highlight is defined by a border portion of the rear image layer which surrounds the front image layer. In alternative embodiments, although the rear image layer would generally be in registry with the front image layer, the rear image layer may be laterally offset relative to the front image layer or may have smaller dimensions than the front image layer on one side thereof so as to provide a highlight which is offset and does not extend all the way around the periphery of the front image layer. Thus the highlight may appear as a highlighted shadow on one side of the image defined by the front image layer. In a further embodiment, the front and rear image layers may be aligned and have the same size and shape. With this embodiment a highlight or outline can be seen by a viewer looking at the sign at an angle. 
     In the embodiments of the invention, the front and rear image layers are separated by a distance corresponding to the thickness of the transparent sheet. When the front and rear image layers are illuminated in the manner described hereinabove, the viewer is able to detect a spacial difference between the front and rear image layers. This creates a three dimensional effect whereby the front and rear image layers appear to be connected by an inclined edge, giving the overall indicia a massive and solid appearance. The thickness of the three dimensional image corresponds to the thickness of the transparent sheet. The shape and angle of inclination of the inclined edge can be varied by altering the relative sizes and disposition of the front and rear image layers. For example, if the rear image layer is slightly larger in lateral dimension than the front iamge layer all around its periphery, then a relatively steep inclined edge will be apparent to a viewer of the sign when the sign is illuminated. 
     The images to be conveyed may comprise alphanumeric characters or other pictorial images. The front image layer may itself be printed or otherwise provided with images on its front surface. 
     Although the transparent sheet is illustrated as depending downwardly from the lamp housing  22 , in alternative configurations the lamp housing may be provided beneath the transparent sheet and may constitute a support stand for the entire sign. In addition, although the illustrated embodiments utilise a fluorescent bulb as the light source for the illuminated sign, any other suitable light source may be employed, for example an incandescent bulb, a neon bulb, etc. 
     In alternative embodiments, a light reflective self-adhesive plastic layer, for example white or silver in colour, is adhered over the edge of the sheet which is remote from the light source in order to reflect light back through the sheet. The mount along that edge may be square rather than inclined, particularly for small dimension signs. 
     In accordance with the invention, the provision of a fluorescent layer at least partially surrounding the front image layer on the transparent sheet, together with the provision of a reflecting surface on the rear of that front image layer, provides real technical advantage as opposed to edge-illuminated signs in the prior art by forming an illuminated image having a relatively high intensity. This means that the edge-illuminated sign is clearly visible to a viewer even in relatively high intensity ambient light and when the sign is intended to be seen from a substantial distance away. The sign of the present invention also has great flexibility in use by enabling a wide variety of visual effects to be reproduced. For example different colours can be displayed with or without fluorescent layers. An aura of one or more colors may wholly or partially surround the indicia. The color, size, shape and orientation of a highlight around the indicia may be selected as desired. Printed or patterned images defining or surrounding the indicia may be provided. The sign can be manufactured very cost effectively by using known printing techniques and known techniques for applying patterned self-adhesive plastic films to rigid plastic sheets in the required positions. 
     The provision of a light reflection device at the edge of the sheet which is away from the light source ensures that the amount of light internally reflected in the sheet to cause illumination of the indicia is substantially maximised. This not only increases the visibility of the sign but also provides even and uniform illumination of the indicia on both sides thereof, i.e. on the sides which are near to and remote from the light source.