GB2405022A

GB2405022A - Electroluminescent traffic sign

Info

Publication number: GB2405022A
Application number: GB0318848A
Authority: GB
Inventors: Wai Hung Au; Po Wang Larry Leung
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-08-12
Filing date: 2003-08-12
Publication date: 2005-02-16
Also published as: GB0318848D0

Abstract

A traffic sign (10) has a multi-layered structure that comprises a front panel (100) and a rear panel (200) attached to the back of the front panel (100). The front panel (100) bears a sign content (100) having a visually distinctive regions (112 and 114), at least one of which (114) is light transmissive. The rear panel has an active light illuminating layer, and a reflective layer. In one embodiment the sign is used as a vehicle license/ registration plate, and in a further embodiment the sign is used as a road sign. The light illuminating layer is preferably electroluminescent, and the reflective layer is preferably a wide angle prismatic layer. The light illuminating layer may also comprise a honeycomb arrangement of apertures allowing incident light to pass through and strike the reflective layer.

Description

TRAFFIC SIGN

The present invention relates to a traffic sign that may be used for all traffic or traffic-related purposes.

BACKGROUND OF THE INVENTION

Existing traffic signs, including vehicle license plates and road signs, are often made reflective to incident light so that they can be read or seen, for example by the driver of an approaching vehicle, from a long distance. There are however limitations in sight, especially when the incident light is weak or directed to the signs at a relatively small angle.

The subject invention seeks to mitigate or at least alleviate such problems by providing an improved traffic sign.

SUMMARY OF THE INVENTION

According to the invention, there is provided a traffic sign having a multi-layered structure comprising a front panel bearing a sign content having visually distinctive regions, at least one of which is light transmissive, and a rear panel attached to the back of the front panel, the rear panel comprising an active light illuminating layer for illuminating through the sign content to enhance its visibility and a reflective layer to reflect incident light from the front.

Preferably, the illuminating layer comprises an electroluminescent layer.

It is preferred that the reflective layer comprises a wide angle prismatic reflective layer that incorporates numerous minute prismatic lenses.

As an alternative, the reflective layer may comprise a glass bead reflective layer that incorporates numerous minute glass bead lenses.

In a preferred embodiment, the rear panel includes an optically transmissive layer that is electrically conductive and acts as an electrode for the illuminating layer located behind it.

: ' :,'''' More preferably, the reflective layer and the optically transmissive layer are integrated.

In an alternative construction, the reflective layer is provided behind the illuminating layer, and the illuminating layer is apertured to permit transmission of incident light. s

More preferably, the illuminating layer includes a honeycomb arrangement of apertures.

It is preferred that the rear panel includes an opaque electrically conductive layer behind the illuminating layer, acting as an or another electrode therefor.

The illuminating layer may comprise a light diffuser and a plurality of electrical light sources attached thereto for illuminating the same.

As an example, the traffic sign may be used as a licence plate for a motor vehicle.

As another example, the traffic sign may be used as a road sign.

BRIEF DESCRIPTION OF DRAWINGS

The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which: Figure l is a front view of an embodiment of a traffic sign in accordance with the invention, said sign having front and rear panels; Figure 2 is a perspective view of a first construction of the rear panel of Figure l; Figure 3 is a perspective view of a second construction of the rear panel of Figure l; and Figure 4 is a perspective view of a third construction of the rear panel of Figure 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring to the drawings, there is shown a traffic sign embodying the invention, which sign lo has a multi- layered structure comprising a front panel 100 bearing a sign content ll0 and a rear panel 200 attached to the back of the front panel 100. The two panels 100 and 200 have the same oblong rectangular shape and size, and are mutual aligned.

The front panel 100 is a transparent or translucent flexible plastic (protective) sheet that is printed or adhered, preferably on its inner surface, with the word "RETROREFLECTIVE" 112 as the sign content 110. The word 112 itself is opaque and/or in a distinct colour such that it is clearly distinguishable from its background 114. This results in the sign content 110 having at least two visually contrasting regions 112 and 114, i.e. the

word 112 itself and the background 114.

The rear panel 200 has a number of layers which have the same shape and size and are mutually aligned and integrated into a flexible panel. One of the layers is an active light illuminating layer 210, which is preferably an electroluminescent layer 210, for illuminating through the sign content 110 and in particular its transparent background region 114, thereby improving or enhancing the visibility of the content 110. Another layer is a reflective layer 220 for reflecting incident light from the front.

Electronic luminescence is a kind of physical phenomenon using an AC voltage applied to two electrodes in order to produce an alternating electric field. The electrons activated by the electric field dash zinc sulphide, thereby causing the electronic energy level to bounce, vary, compound and then launch a high efficiency cold light.

In the construction of the rear panel 200 of Figure 2, the reflective layer 220 is the top layer. This layer 220 is an optically transmissive wide angle prismatic retro- reflective sheet that incorporates numerous minute prismatic lenses and is built on an ITO (indium tin oxide) substrate. The ITO substrate is transparent, and is electrically conductive acting as one electrode for the electro-luminescent layer 210 lying immediately behind the reflective layer 220.

Also included in the rear panel 200 are a bottom opaque conductive layer 230 that acts as the other electrode for the electroluminescent layer 210, and a dielectric layer 240 between the electroluminescent layer 210 and the conductive layer 230. The dielectric layer 240 acts an insulator electrically between the two electrodes 220 and 230, across which electrodes 220 and 230 an AC voltage source is applied by a controller 300 to generate an alternating electric field for energizing the electro luminescent layer 210.

In use and upon energization, the electroluminescent layer 210 illuminates the rear panel 200. The light shines through the front panel 100, thereby rendering the sign content 110 visible far more clearly and from a much longer distance than the conventional traffic signs that does not incorporates an active light source. The sign content 110 can easily be read by reason of its visually contrasting word 112 and background 114. The reflective layer 210 further improves the visibility by diffusing the electroluminescent light in different directions to thereby generate brighter spots amidst dimmer spots.

While the electroluminescent layer 210 is an inactive state, the traffic sign 10 works essentially like a conventional passive traffic sign, with the frontmost reflective layer 220 of the rear panel 200 reflecting incident light.

In Figure 3, an alternative rear panel 200 has generally the same construction as described above, with equivalent parts designated by the same reference numerals, except the reflective layer 220 albeit serving the name purpose.

This layer 220 is likewise light transmissive and built on an ITO substrate, but it is a glass bead retroreflective sheet i.e. incorporating numerous minute glass bead lenses 222 for reflecting light. This rear panel 200 operates in the same manner as the earlier one.

In Figure 4, there is shown another alternative rear panel 200A that has a different structure. Like the two earlier rear panels 200, this rear panel 200A includes an electroluminescent layer 210A, a dielectric layer 240A and a conductive layer 230A, which are stacked together in the same order and have the same basic nature and function as their earlier counterparts. However, these layers 210A, 240A and 230A are apertured in an identical honeycomb pattern with the apertures arranged in alignment, such that they are practically transparent or transmissive, though opaque by nature, to incident light.

The rear panel 200A includes a simple ITO layer 250A as the top layer and a retroreflective glass bead layer 220A as the bottom layer. The ITO layer 250A is transparent and acts as one electrode for the electroluminescent layer 210A, with the other electrode provided by the conductive layer 230A. The glass bead lenses of the reflective layer 220A serve to reflect incident light - 9 - that passes through the front panel 100 and the four rear panel layers 250A, 210A, 240A and 230A in front of it.

In all three rear panels 200/200A, the dielectric layers 240/240A are included as required for the electro luminescent layers 210/210A that are of a standard known type. In a new type, generally known as an active electroluminescent panel, a dielectric layer is no longer required or otherwise built-into the panel, in which case the dielectric element is visually undistinguishable.

Figure 5 shows a second traffic sign 20 embodying the invention, which has generally the same construction, albeit having an octagonal shape, and operates in the same manner as the first traffic sign 10. The only other difference lies in the sign content that consists of the word "STOP" and an octagonal border, both in white colour, on a red background, all these regions being light transmissive.

Figure 6 shows a further possible illuminating/reflective panel 200B for the front panel 100, which is implemented by a single, optically transmissive wide angle prismatic retroreflective panel 220B that incorporates six light emitting diodes 210B (or any other suitable electrical light sources). The panel 220B has an oblong rectangular transparent or translucent body, and the diodes 210B are i integrated or preferably located in its four corners and in mid-length of its longer sides. Light from the diodes 210B enters laterally into the panel body, which in turn acts as a light diffuser to provide uniform illumination.

The subject traffic sign can be used for all traffic or traffic-related purposes, for example as the licence plate 10 (Figure 1) on a motor vehicle or as a road sign (Figure 5). The use of electroluminescent sheet 210/210A, including its electrodes and dielectric film, is particularly preferred as it can provide a uniform illumination and be cut to any shape for immediate use, and is typically flexible.

The invention has been given by way of example only, and various modifications and/or variations to the described embodiment may be made by persons skilled in the art without departing from the scope of the invention as specified in the accompanying claims.

Claims

l. A traffic sign having a multi-layered structure comprising a front panel bearing a sign content having visually distinctive regions, at least one of which is light transmissive, and a rear panel attached to the back of the front panel, the rear panel comprising an active light illuminating layer for illuminating through the sign content to enhance its visibility and a reflective layer to reflect incident light from the front.
2. The traffic sign as claimed in claim l, wherein the illuminating layer comprises an electroluminescent layer.
3. The traffic sign as claimed in claim l or claim 2, wherein the reflective layer comprises a wide angle prismatic reflective layer that incorporates numerous minute prismatic lenses.
4. The traffic sign as claimed in claim l or claim 2, wherein the reflective layer comprises a glass bead reflective layer that incorporates numerous minute glass bead lenses.
5. The traffic sign as claimed in any one of claims 1 to 4, wherein the rear panel includes an optically transmissive layer that is electrically conductive and acts as an electrode for the illuminating layer located behind it.
6. The traffic sign as claimed in claim 5, wherein the reflective layer and the optically transmissive layer are integrated.
7. The traffic sign as claimed in claim 5, wherein the reflective layer is provided behind the illuminating layer, and the illuminating layer is apertured to permit transmission of incident light.
8. The traffic sign as claimed in claim 7, wherein the illuminating layer includes a honeycomb arrangement of apertures.
9. The traffic sign as claimed in any one of claims 1 to 8, wherein the rear panel includes an opaque electrically conductive layer behind the illuminating layer, acting as an or another electrode therefor.
10. The traffic sign as claimed in claim 1, wherein the illuminating layer comprises a light diffuser and a plurality of electrical light sources attached thereto for illuminating the same.
11. The traffic sign as claimed in any one of claims 1 to 10, being a licence plate for a motor vehicle.
12. The traffic sign as claimed in any one of claims 1 to 10, being a road sign.