WO 2009/067752 PCT/AU2008/001760 ILLUMINATED LICENSE PLATE DISPLAY ASSEMBLY 5 BACKGROUND The present invention relates to license plates on vehicles and more particularly relates to improvements in displays of license status plates such as but not limited to Learner and 10 Provisional license plates. More particularly the invention relates to an assembly which provides illumination of such Learner and Provisional license plates. The invention further relates to license plates which include at least one indicia symbol and which is illuminated for night identification and improved day identification. The invention further provides an illuminated display assembly which uses back lighting to display a 15 license status symbol viewable by day and night. PRIOR ART Learner and Provisional license plates are mandatory during the stages of license 20 acquisition. A licensee and learner must display a plate on the front and rear of a vehicle indicating license status of the driver for policing purposes. Since learners and provisional license holders are restricted to maximum speeds, to enable policing while in transit, police determine compliance with reference to plates which display a P or an L. These plates are provided to drivers depending upon the stage of licensing they have 25 reached. P and L plates are usually manufactured cheaply on either a cardboard or plastics backing. They are cheap and non reflective as a result of which they arc difficult to see at night, This is a potential hazard for other drivers who might encounter an inexperienced driver without knowing and who -they might otherwise avoid for safety reasons. Also at night police find it difficult to identify L and P plate drivers unless 30 they are in close proximity to the P or L plate driver. Statistically, P and L plate drivers pose the highest safety risk to themselves and to other drivers as they are usually within the 17 - 25 year age group. It is therefore a safety hazard that L and P plate drivers cannot be identified at night and on occasions with difficulty during the day, Techniques are known for producing multi-colored lighting effects with LED's. Some such WO 2009/067752 PCT/AU2008/001760 techniques are shown in, for example, U.S. Pat. No. 6,016,038, U.S. patent application Ser. No. 09/215,624, and U.S. Pat. No. 6,150,774 the teachings of which are incorporated herein by reference. While these references teach systems for producing lighting effects, they do not address lighting of license plates. Lighting elements are sometimes used to 5 Illuminate consumer products, wearable accessory, novelty items, or the like. Existing illuminated systems, generally exhibit fixed illumination with one or more light sources. An existing wearable accessory, for example, might utilize a single white-light bulb as an illumination source, with the white-light shining through a transparent colored material. Such accessories exhibit an illumination of a single type (a function of the color of the 10 transparent material) or at best, by varying the intensity of the bulb output, a single colored illumination with some range of controllable brightness. Other existing systems, to provide a wider range of colored illumination, may utilize a combination of differently colored bulbs. Such accessories, are limited to a small number of different colored states For example, three distinct illumination colors: red bulb; blue bulb; and purple (both red 15 and blue bulbs) may be blended to produce a wide range of differing tones of color. As another example, ornamental devices are often lit to provide enhanced decorative effects. U.S. Pat. Nos. 6,086,222 and 5,975,717, for example, disclose lighted ornamental icicles with cascading lighted effects, Other examples of crude dynamic lighting may be 20 found in consumer products ranging from consumer electronics to home illumination (such as night lights) to toys to clothing, and so on. High-brightness LEDs, combined with a processor for control, can produce a variety of effects for display and illumination purposes. Systems are known, for example United 25 States Patent 7,064,498 which use high-brightness. processor-controlled LEDs in combination with diffuse materials to produce color-changing effects, The systems may be usefully employed to bring autonomous color-changing ability and effects to a variety of consumer products and other items. The system may also include sensors so that the illumination of the LEDs might change in response to environmental conditions or a user 30 input. 2 WO 2009/067752 PCT/AU2008/001760 United States Patent 7,046,160 discloses an LED warning light and communication system, comprising a controller for generating a first observable light signal and a second non-observable light signal within said first light signal. The second light signal is formed of packets of individual pulsed light which may be processed for comparison to data 5 stored in memory integral to a controller for communication of information to an individual through the use of pulsed light signals. In another example of prior art technology, United States Patent 7,195,381 discloses a vehicle lighting system for a vehicle interior and includes an accessory module assembly 10 that is adapted for attachment to an interior portion of a vehicle and configured to illuminate, for example, an area inside the vehicle. The module assembly includes a single high-intensity power light emitting diode that has a luminous efficiency of at least about I lumen per watt when the light emitting diode is operated and is preferably operated at a forward current of at least 100 milliamps. The system also includes a 15 voltage conversion element for converting the battery/ignition voltage of the vehicle to the forward operating voltage of the light emitting diode. United States Patent 5,005,306 discloses an illuminated vehicle display apparatus which has a flexible electroluminescent panel having a front planar surface which directly 20 generates illumination when excited by an alternating current. A thin flat flexible opaque shield has cutout areas to form designs and is attached over the electroluminescent panel planar surface so that portions of the panel are visible through the opaque shield so that indicia and graphic designs are defined by the visible electroluminescent light. A thin flexible magnetic sheet of material is attached over the rear surface of the 25 electroluminescent panel for removably attaching the vehicle sign to the side of a vehicle. United States Patent 4,255,887 discloses an Illuminated display device and motor license plate using sane The disclosed illuminant display device is to be used on a motor vehicle 30 for publicity or other purposes. In the device an opaque plate member contains perforations in the shape of a character or figure to be displayed, and tinted translucent 3 WO 2009/067752 PCT/AU2008/001760 pieces are set in the perforations transmit light which is projected from a light source provided behind the perforated plate. The display device can serve us an illuminant license plate which is arranged to illuminate the identifying characters continuously for a predetermined time period after the headlight or parking light of the motor vehicle has 5 been turned off and thereby foil a driver who tries to conceal the identity of the vehicle by turning off the lights for hit-and-run or other unlawful purposes. United States Patent 7,046,160 discloses a light emitting diode warning light and communication system comprising a controller for generating a first observable light 10 signal and a second non-observable light signal within said first light signal. The second light signal is formed of packets of individual pulsed light which may be processed for comparison to data stored in memory integral to a controller for communication of information to an individual through the use of pulsed light signals. 15 United States Patent 6,587,573 discloses a system for controlling exterior vehicle lights A system and method of automatically controlling exterior vehicle lights includes an image sensor and a controller to generate control signals. The control signals are derived based on information obtained from the image sensor as well as other detected parameters pertaining to the detected light source(s), the vehicle having the inventive control system, 20 and the ambient environment. The control circuit may simply turn certain exterior lights on or off, or change the brightness, aim, focus, etc. to produce various beam patterns that maximize the illuminated area in front of the vehicle without causing excessive glare in the eyes of other drivers. 25 There is a long felt want to provide an improved license display which can be easily identified day and night. The display of License status for P and L plate licensees is mandatory and allows police and other drivers to.know the status and limitations on a P or L plate driver. Failure to display the correct indicia can result in fines and loss of license points, The current P and L plate displays can fall off , degrade in sunlight and are 30 difficult to read at night and only when close to the vehicle. Currently the plastics or cardboard displays which are readily available and have been in use for years, have a 4 WO 2009/067752 PCT/AU2008/001760 contrasting colour to differentiate between the background and letter display. The plates must be displayed at the front and rear of a vehicle and must be visible from 20 metres within an arc of about 45 degrees. The minimum size of the display for compliance is 14.6cm x 14.6cm. 5 INVENTION The present invention seeks to ameliorate the disadvantages of the prior art plates by providing an illuminated license plate for illuminated display of an indicia which indicates license status of a driver during both day and night. The invention further provides license plates which include at least one indicia, symbol or the like and which is 10 illuminated for night identification and improved day identification. In one broad form the present invention comprises: a license display assembly for use on a motor vehicle to display driver license status, the display sign comprising a body, a connecting bracket to enable connection to a part of a 15 vehicle, lighting means integral with the assembly which allows illumination of a license plate releasably held by the assembly. According to one embodiment, the lighting means is in or on the assembly body. According to one embodiment the assembly comprises a first face having an array of 20 lights arranged so that at least two contrasting colours of the lights display a symbol viewable during day and night. Preferably the symbol displayed on the display sign is a letter indicating the type or grade of license possessed by the driver. Preferably the symbol is a P indicating provisional 25 license or an L indicating a learners permit. Preferably, the symbol displayed on the display sign is a letter indicating the type or grade of license possessed by the driver. Preferably the symbol is a P indicating provisional license or an L indicating a learner's permit. 30 5 WO 2009/067752 PCT/AU2008/001760 In one broad form the present invention comprises; an assembly for display of an illuminated license sign for use on a motor vehicle, the assembly comprising a body having a back and a front element and a peripheral wall defining an internal space; 5 a light source capable of illuminating the internal space; retaining means associated with the assembly to receive and retain a sign which is illuminated by the light source; the housing being manufactured from a translucent material which allows light from said light source to illuminate the sign so that when the sign is placed in said retaining means 10 the light source illuminates the sign to allow night visibility. According to a preferred embodiment the light source is located on the housing. The backing element is a backing plate and the front element is a planar closure, the front closure detachable from the bacdng plate. The retaining means comprises a mounting 15 member which receives and retains the sign. The sign is slidably retained in the mounting member. Preferably the light source is located in the internal space. A support bracket is attached to the housing which allows mounting of the housing on the body of a vehicle, Preferably the housing is waterproof. The display sign includes means to indicate the type or grade of license possessed by a driver. The signs include L and P 20 plates and are interchangeable. The front and rear backing plates of the housing are sealed using a rubber sealing 0 ring which locates in grooves in the housing. The Lights are preferably LED's and arc powered by a vehicle's own source of power which may be the battery or generator . According to an alternative embodiment the lights are solar powered. The mounting member provides a narrow recess which 25 releasably receives an edge of the sign. Preferably, the light source shines from behind the sign to illuminate the sign, In another broad form the present invention comprises: an illuminated license display sign for use on a motor vehicle, the display sign 30 comprising a first face having an array of lights arranged on the first face to be viewable from an exterior of the vehicle, the array of lights comprising a first set of lights of one 6 WO 2009/067752 PCT/AU2008/001760 colour and a second set of lights of a second colour wherein, when the lights of the second colour are viewed against the background of the first colour the lights of the second colour display a symbol which indicates the license status of the driver of the vehicle. 5 According to a preferred embodiment, the first colour is a white light and the second colour is darker such as red , black, green or blue. Alternatively the first colour is yellow in the case for instance where the display is an L plate with black letter l., and yellow background. Preferably, the array of lights is established with a plurality of light emitting diodes. 10 In another broad form the invention comprises: an illuminated license display assembly for attachment to a vehicle, the assembly comprising: a housing having a back and a front engagable with the back and co operating to form a housing having peripheral wall defining an internal space; 15 at least one lights inside the housing capable of illuminating the internal space; retaining means associated with the housing to receive and releasably retain a license plate which is back illuminated by the light means when the at least one light is on; the front of the housing being manufactured from a material which allows light transmission from said light source to illuminate the sign so that when the sign is placed 20 in said retaining means the light source illuminates the sign to allow night and improved day visibility of the sign. In another broad form the present invention comprises: 25 an illuminated license display sign for use on a motor vehicle, the display sign comprising a first face having an array of light emitting diodes viewable from an exterior of the vehicle, the array of diodes comprising a first set of LED's of one colour and a second set of LED's of a second colour, so that when the lights of the second colour are viewed against the background of the first colour the lights of the second colour display a 30 symbol which indicates the license status of the driver of the vehicle. 7 WO 2009/067752 PCT/AU2008/001760 Preferably, the illuminated license display is powered by the vehicle's existing electrical system and may be turned on and off as required. The contrasting colours are such that during daylight the license symbol such as a P or L can be viewed during the day with or without activation of the lights and can be activated at night by an isolation switch. 5 The present invention provides an alternative to the known prior art and the shortcomings identified. The foregoing and other objects and advantages will appear from the description to follow. In the description reference is made to the accompanying representations, which forms a part hereof, and in which is shown by way of illustration 10 specific embodiments in which the invention may be practiced. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. In the accompanying illustrations, like reference characters designate the same or similar parts 15 throughout the several views The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims. 20 BRIEF DESCRIPTION OF REPRSENTATIONS The examples referred to herein are illustrative and are not to be regarded as limiting the scope of the invention. While various embodiments of the invention have been described herein, it will be appreciated that these are capable of modification, and therefore the 25 disclosures herein are not to be construed as limiting of the precise details set forth, but to avail such changes and alterations as fall within the purview of the description . The invention will now be described according to a preferred but non limiting embodiment and with reference to the accompanying drawings wherein 30 Figure 1 shows an elevation view of the illuminated display assembly according to a preferred embodiment; 8 WO 2009/067752 PCT/AU2008/001760 Figure 2 shows an elevation view of an LED display assembly with a P symbol Figure 3 shows an elevation view of an LED display assembly with an L symbol Figure 4 shows a typical bracket assembly which receives and retains the display of figure 2 5 Figure 5 shows a rear view of a motor vehicle with illuminated display Figure 6 shows a front view of a motor vehicle with illuminated display Figure 7 shows a schematic arrangement of circuitry for powering LED's of a first colour Figure 8 shows a schematic arrangement of circuitry for powering LED's of a 10 second colour; and Figure 9 shows a schematic arrangement of circuitry for powering LED's of both colours. Figure 10 shows an exploded view of a display sign assembly according to. an alternative embodiment. 15 Figure t I shows an assembled rear view of the assembly of figure 10. Figure 12 shows an enlarged view of a mounting bracket connection which engages the display sign housing. Figure 13 shows an exploded plan view ofthe bracket assembly Figure 14 shows a side elevation view of the short leg portion of the bracket 20 assembly. Figure 15 shows a side elevation view of the long leg portion of the bracket assembly. Figure 16 shows a side elevation view of the mounting plate for the housing. Figure 17 shows a back view of the housing. 25 Figure 18 shows a top view of the housing. Figure 19 shows a side view of the housing. Figure 20 shows a front elevation of a license P plate exploded from a mounting recess. Figure 21, shows a front elevation of a license P plate with alternative status 30 exploded from its mounting recess. 9 WO 2009/067752 PCT/AU2008/001760 Figure 22 shows a front elevation of a license L plate exploded from its mounting recess. Figure 23 shows a front elevation view of a disabled driver plate exploded from its mounting recess. 5 DETAILED DESCRIPTION Referring to figure 1 there is shown a perspective view of a display sign assembly I including a primary display face 2. Display face 2 includes an array of lights 3 which are 10 preferably Light emitting diodes of at least two contrasting colours. Display face 2 is preferably a rigid or semi rigid material which receives and retains thereon the array 4 of lights of a light colour forming a background and a contrasting array 5 of.lights of a second and preferably darker colour. According to one embodiment, the light of the darker colour is red to display a P symbol indicating the provisional status of a driver. 15 According to another embodiment, the light of the darker colour is green to display a P symbol indicating the provisional status of a driver. According to one embodiment, the light of the darker colour is black to display an L symbol indicating the learner status of a driver. Assembly I is retained by bracket assembly 6 which is mountable on a vehicle and may be a known bracket assembly such that the display assembly may be retrofitted 20 to existing brackets. Display assembly 1 is energized by a power source which delivers power to each of the lights of an LED array 3. The plurality of LEDs is configured to produce light that includes at least two different spectra and to create a display that is a combination of the two different spectra. Assembly I may be adapted with a processor which changes the 25 colour configurations for different times of the day ( in a case for instance when the sun is shining directly on the display and would otherwise reflect the sun a colour change may be required). Although the invention is described with reference to the display of P and L plates it will be appreciated that the display assembly will be capable of displaying other letters and symbols as required. This may be effected by selecting certain LED's in 70 WO 2009/067752 PCT/AU2008/001760 the array so they display the shape of the symbol which may be a letter number or other symbol and allowing the remainder of the LED's of a contrasting colour or which are not switched on to form a contrasting background colour. A control signal activated by the driver may be employed to generate and control power delivered to one or more of the 5 plurality of LEDs, The control signal may be changed to produce from the device at least one of many potential display effects by use of the LED's. According to one embodiment a driver may activate the switch from the drivers position when illumination of the assembly is required. The driver may have a key pad which can operate the various modes of the display. In an alternative embodiment, the display may be activated by a 10 light sensor such that as daylight fades below a predetermined threshold, the illumination will automatically activate. The display may be located in a housing which protects the electric contacts but allows visual access to the symbol display. Figure 2 shows an elevation view of an LED display assembly 10 with a P symbol I I which is created by contrasting LED's 12 and 13. For example background lights 12 may 15 be light coloured and the symbol lights maybe a dark colour such as but not limited to red, blue, green or black. Figure 3 shows an elevation view of an LED display assembly 15 with an L symbol 16. Figure 4 shows a typical bracket assembly 20 including a recess 21 which receives and retains therein the display assembly 10 of figure 2. Bracket assembly 20 includes 20 connecting arms 22 and 23 which are used to fit bracket 20 to a vehicle., This allows the illuminated display 10 to be inserted and removed as required. The bracket assembly me be fitted externally or internally as required. Figure 5 shows a rear view of a motor vehicle 30 with illuminated P display 31 showing how it would appear to other drivers. Figure 6 shows a front view of the motor vehicle 25 30 with front illuminated display 32. Figure 7 shows a schematic arrangement of circuitry for powering LED's of a first colour. In the arrangement shown, the first colour is preferably red and the image of the letter P is to power the array of red LED's; Display 40 shows letter P 41 fonned from an 11 WO 2009/067752 PCT/AU2008/001760 array of LED's 42 which are powered from a power source 43. The second colour is preferably other than red to provide a contrasting background 47 to the first colour on display 40. Power source 43 is associated with isolation switch 44 with a power circuit formed by an active line 45 and negative 46 to form a circuit with the array of LED's 5 forming letter P 41. Figure 8 shows a schematic arrangement of circuitry for powering LED's of a second colour, forming display 40. In the arrangement shown, the second colour is preferably other than red to provide a contrasting background 47 to the image of the letter P 41. to 10 power the array of LED's on display 40. Background 47 of display 40 formed from an array of LED's are powered from a power source 48. Power source 48 is associated with isolation switch 49 with a power circuit formed by an active line 50 and negative 51. Figure 9 shows with corresponding numbering, a schematic arrangement of circuitry of figures 7 and 8 powering LED's of both colours, 15 Figure 10 shows an exploded view of a display sign assembly 60 for display of an illuminated license sign ( see figure 20) for use on a motor vehicle according to an alternative embodiment. Assembly 60 comprises a housing 61 having a back element 62, a front element 63 and a peripheral wall 64 defining an intemal space 65. Front element 20 63 includes a peripheral slotted recess saddle 66 which receives and retains therein a license plate such as a P or L plate. The sign is slidably retained in the mounting bracket. Back element 62 includes a groove 67 which receives a seal such as an 0 ring or other rubber gasket. Internal space 65 receives and houses a light source such as at least 25 one LED 68 which is capable of illuminating the internal space 65 to an intensity which allows back illumination of a sign inserted in saddle 66. Housing 61 is manufactured from a translucent material which allows light from said light source 68 to illuminate the sign so that when the sign 69 is placed in the recess 66 the light source 68 illuminates the sign to allow night visibility and improved day visibility. The back element 62 is a 30 backing plate and the front element 63 is a planar closure which co operates with back element 62 to provide sealed waterproof internal space 65. Front element 63 is 12 WO 2009/067752 PCT/AU2008/001760 detachable from the back plate 62 to allow access to electrics supplying and terminating at LED 68. Assembly 60 further comprises a support bracket assembly 70 attached to- the housing 61 which allows mounting of housing 61 on the body of a vehicle (not shown). Extending from backing plate 62 is a joining tab 71 which engages angled bracket 72. 5 Bracket 72 includes long leg 73 and short 74. Leg 74 includes a corrugated surface 75 which receives an opposing corrugated surface 76 on tab 71. Tab 71 combines with leg 77 to form a second mounting bracket 78 which engages back element 62 and may be secured via openings 79 and 80. Likewise, leg 73 includes openings 81 and 82 which enable assembly 60 to be fastened to a vehicle. Leg 74 of bracket 70 includes a slot 10 opening 83 which receives a fastener not shown and enables incremental adjustments in the distance between back 62 and leg 73 as required. Figure 11 shows an assembled rear view of the assembly 60 of figure 10 with corresponding numbering. Figure 12 shows an enlarged abbreviated view of leg 74 with ribbing 75 and slotted opening 83. Leg 73 is fastened to a vehicle ( not shown) via fasteners 84 and 85 which 15 penetrate openings 81 and 82 respectively. Leg 77 is fastened to housing 61 via fasteners 86 and 87 which penetrate openings 80 and 79 respectively. Short leg 74 engages leg 71 by means of fastener 88 which penetrates slotted opening 83 ( see figure 14), Figure 13 shows an exploded plan view of the bracket assembly 70- Figure 14 shows a 20 side elevation view of the short leg portion of the bracket assembly 70. Figure 15 shows a side elevation view of the long leg portion 73 of the bracket assembly 70. Figure 16 shows a side elevation view of the leg 77 for the housing 61. Figure 17 shows a back view of the housing 61 mounted to leg 77. leg 77 is shown fitted to housing 61 _via fasteners 79 and 80. In the case of fitting the assembly to a motor cycle, leg 77 will 25 traverse recess 89 and openings 90 and 91 will be used for fixation. Figure 18 shows a top view of the housing 61 with corresponding numbering. Figure 19 shows a side view of the housing 61. Figure 20 shows a front elevation of a license P plate 100 exploded from a mounting recess 66 as shown in figure 10. Plate 100 is inserted approximately one third the distance into recess 66. It can be seen that P plate 100 is 30 placed in front of lights 101, 102, 103, 104, 105 and 106. Those lights will be preferably mounted inside housing 61 and since front plate 63 will be manufactured from an opaque 13 WO 2009/067752 PCT/AU2008/001760 translucent or clear material the light emitted by the aforesaid lights will back illuminate P plate 100. w is Shown. Figure 21 shows with corresponding numbering a front elevation of a license P plate 107 with alternative status shown by different hatching form that of plate 100 exploded from its mounting recess 66 demonstrating that the license 5 plates are interchangeable. Figure 22 shows with corresponding numbering a font elevation of a license L plate 108 exploded from its mounting recess 66. Figure 23 shows a front elevation view of a disabled driver plate 109 exploded from its mounting recess 66. Although the invention has been described with reference to examples including P plates 10 and L plates, it will be appreciated that the invention is not limited specifically to illumination of such plates. Other display indicia can be adapted to the assembly described herein. Under New South Wales state rules a P plate is a plate that features an upper case red letter 'P' or an uppercase green letter 'P' on a white background. These plates are required by drives who have reached a provisional license stage. The colour 15 combinations may vary from state to state or country to country. Plates are normally required to be fitted to the front and rear of a vehicle and must be clearly visible from 20 m at any point within a 45 degree arc. The minimum size and colour of a P plate is 14.6 cm x 14.6 cm. The P plate may be larger than the minimum size requirement Of 14.6 cm x 14.6 cm but not so large that it will obscure view when driving. The display of P and L 20 plates alerts other drivers to the license status of a driver of a car bearing such plates. Illumination of such plates assists identification of such drivers and also assists enforcement officers identify which drivers are placed on license restrictions and what those restrictions are. The invention provides an efficient means of illumination of vehicle display signs such as but not limited to license plates and enables the light source 25 to be protected in a water proof housing. Lighting may be driver operated from inside the vehicle or it may be linked to the vehicle's own light circuitry It will be recognized by persons skilled in the art that numerous variations and modifications may be made to the invention as broadly described herein without departing from the overall spirit and scope of the invention. 30