GB2457433A

GB2457433A - Flexible electroluminescent light source

Info

Publication number: GB2457433A
Application number: GB0801792A
Authority: GB
Inventors: Richard Aldrich
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-01-31
Filing date: 2008-01-31
Publication date: 2009-08-19
Also published as: GB0801792D0

Abstract

A bendable illumination device for covering or tiling surfaces such as walls, stairs and floors comprises an electroluminescent (EL) lamp attached to a flexible polymer substrate layer 307 and a transparent polymer coating 306.A preferred material for the flexible substrate 307 is a polyester. The transparent polymer coating 306 is preferably abrasion resistant and may also have non-slip properties when used as flooring. A preferred material for the transparent coating is a polyurethane. One or more device may be electrically connected in series or parallel to form surface lighting array (figs 6, 7).

Description

JMPROVEMENTS IN AND RELATING TO FLOORING

Field of the Invention

The present invention relates to a flexible illumination device for covering or s tiling surfaces such as walls, steps, stairs or floors, which is arranged, in use, to provide an illuminated surface.

Background to the Invention

Electroluminescence and more specifically electroluminescent lamps (EL) and devices are very well known in commercially available products since the 1980's. An overview can be found, for example, in US 5976613, US 5491377, US 20003/0003837 or US 5045755, which are hereby incorporated by reference.

Figure 1 shows a schematic drawing of a prior art EL device including a front electrode 101, a phosphor layer 102, a dielectric layer 103, a rear electrode 104 and a coating layer 105. The thickness of a commercial available EL device is usually between 2 and 6 mm.

The advantages of EL devices are that: * ** * * S * S* * they are thin * they are flexible * * they are lightweight S..

* no heat is produced * they are not affected by vibration * they are not prone to sudden failure * there is very low power consumption * they are very long lasting light sources * they are dimmable * they do not emit UV light * they illuminate evenly An EL device can be used indoors or outdoors. Due to the bending properties, EL devices can be arranged in numerous forms and shapes.

Accordingly EL devices are bendable, flexible and rollable.

An EL device can also have any suitable colour (such as red, yellow, orange, green, pink, blue, but also white). The colours can also be combined to give multi-coloured arrangements.

Despite all of its advantages, a major problem or disadvantage of EL devices is that they are not abrasion resistant. This means that when, for example, they are used as floor lighting they can be damaged quite easily, especially in areas with a lot of foot traffic. The abrasion damages the barrier lamination of the EL device and deteriorates the lighting properties of the EL device. Usually this problem is solved by covering the EL device with a rigid self-supporting layer of abrasion resistant material such as glass or polycarbonate, and a gap is left between the EL device and the protective surface. Such embodiments are usually used in places like disco's or dance halls. s. * * S...

This solution of the problem is very time consuming and therefore very *..: expensive, because the device must be placed in a hole and covered by the protective layer. Furthermore, once the device is installed a rearrangement cannot easily be done. Figure 2 shows the use of a prior art EL device as floor lighting. The floor lighting includes a protective layer 201, which is usually made out of glass or polycarbonate, which is arranged to be co -planar with the floor surface 202. It can be seen that for the installation of an EL device a cavity has to be made in which the EL device can be installed. The cavity is then covered by the protective layer 201. There is usually a gap 203 between the protective layer and the EL to avoid damaging the EL.

An aim of the present invention is to overcome at least one problem associated with the prior art whether referred to herein or otherwise.

Another aim of the present invention is to avoid a complicated and expensive installation of an EL device when used on a surface especially surfaces like walls, steps, stairs or floors.

Summary of the Invention

According to a first aspect of the present invention there is provided a flexible illumination device comprising (i) at least one electroluminescent lamp, and (ii) a backbone polymer layer, wherein the electroluminescent lamp is fixed on said backbone polymer layer, charactensed in that the device is coated with a transparent polymeric coating layer.

By the term flexible or bendable it means that the device can be flexed or bent easily by hand and that it usually does not keep its flexed or bended form without fixing. It means that the device can be fitted to any possible form. * ** * . * * *.

Preferably the device is resilient. *Sw.

By the term transparent it means that the device should emit more or less *** . * the same amount of light as emitted by the electroluminescent lamp.

* 25 Depending on the use of the device it is also possible to use coatings which are opaque and/or coloured as well.

Surprisingly it has been found that when an electroluminescent device is coated with a transparent (or mostly transparent) polymeric material (such as polyurethane), then very thin (as less as 3mm) devices can be obtained, which are very flexible, but which have excellent abrasion resistance. Such devices can be used for example as tiles for walls as well as floors, It can also be used to mark the edges of steps. In general it can be used for marking a specific spot on a surface, or for any other suitable purpose (for warning or directing, etc).

Brief Description of the Drawings

For a better understanding of the invention and to show how the same may be carried out into effect, there will now be descnbed by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which: Figure 1 is a schematic cross section of an electroluminescent lamp (EL) of

the prior art;

Figure 2 is a schematic cross section of the use of the prior art EL as a floor lighting device; Figure 3 is a schematic cross section of a preferred embodiment of the present invention; Figure 4a is a schematic horizontal section of a preferred embodiment of the present invention in the form of a strip; *... * * * �.s

Figure 4b is a schematic cross section of a preferred embodiment of the *:*. present invention in the form of a strip; S..

Figure 5a is a schematic drawing of a preferred embodiment of the present invention in the form of a tile; Figure 5b is a schematic cross section of a preferred embodiment of the present invention in the form of a tile; Figure 6a is a schematic drawing of a preferred embodiment of the present invention in the form of a tile with electric conductors suitable for a serial arrangement; Figure 6b is a schematic drawing of a preferred embodiment of the present invention of figure 6a when used in a serial arrangement; Figure 7 is a schematic cross section of a preferred embodiment of the present invention in the form of tiles used in a parallel arrangement; and Figure 8 is a schematic drawing of a preferred embodiment of the present invention in the form of a strip to mark the edges of a stair.

Detailed Description

There will now be described by way of example a specific mode contemplated by the inventors. In the following description numerous specific details are set forth in order to provide a thorough understanding. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to

unnecessarily obscure the description. * .

Figure 3 to figure 8, illustrate in a very schematical way, embodiments of the present invention as well their use.

In figure 3 the schematic cross-section of a device of the present invention can be seen. The electroluminescent lamp (EL) device comprises a front electrode 302, a phosphor layer 303, a dielectric layer 304, a rear electrode 305, a coating layer 301 and a transparent polymeric coating layer 306 and a backbone polymer layer 307. The rear electrode 305 is a split electrode through which an alternating current is supplied. The thickness of a commercial available EL is between 2 and 5 mm.

The EL material comprises the front electrode 302, the coating layer 301, the phosphor layer 303, the dielectric layer 304 and the rear electrode 305. Any kind of known suitable EL material can be used for the device of the present invention.

A suitable EL material usually comprises: (a) a front electrode; (b) a phosphor layer; (c) a dielectric layer; (d) a rear electrode; (e) a coating covering all elements (a) to (d) Such an EL can for example be found in US 5491377.

The front electrode (a) is usually a transparent electrode. A suitable electrode comprises indium oxide compounds (50 -85 wt -%, based on the total weight of the front electrode), 2 -(2-ethoxyethoxy) -ethyl acetate (5-25 wt -%, based on the total weight of the front electrode), 2 -butoxyethyl acetate (5 -25 wt -%, based on the total weight of the front electrode) and polyvinylidene S. fluoride (2 -30 wt -%, based on the total weight of the front electrode). A typical size of a front electrode is 20-25 microns (when dry). S.

S

* 25 The phosphor layer (b) can be any conventional phosphor such as copper activated zinc sulfide in a binder such as mixture of fluoropolymer resin 2 -(2 -ethoxyethoxy) -ethyl acetate, 2 -butoxyethyl acetate and polyvinylidene fluoride).

Suitable phosphors are commercially available for example from Osram under the tradename Sylvania.

The phosphor layer usually has a thickness of 45-50 microns dry.

The dielectric layer (c) can comprise any suitable conventional white dielectric powder in the binder described above and screen-printed to a thickness of 10 -15 microns dry. In the preferred embodiment, the powder may be a mixture of titanium dioxide (20 -60 wt -%, based on the total weight of the dielectric layer) silicon dioxide (3 -10 wt -%), and aluminum silicate (3 -10 wt - %, based on the total weight of the dielectric layer) and the binder in the same proportions described for the phosphor layer.

The rear electrode (d) is usually screen printed to a thickness of 2 -25 microns dry, and may include any suitable conventional conductive ink of silver, carbon, or ceramic, or blends of carbon silver or nickel silver in a binder as disclosed above. Typically the rear electrode comprise metallic silver (50 -85 wt is -%, based on the total weight of the rear electrode) in the binder, which is a mixture of 2 -(2 -ethoxyethoxy) -ethyl acetate (5 -25 wt -%, based on the total weight of the rear electrode), 2 -butoxyethyl acetate (5 -25 wt -% based on the weight of the rear electrode) and polyvinylidence fluoride (2 -30 wt -%, based on the total weight of the rear electrode).

The coating covering all elements (a) to (d) may comprise any suitable S...

S....' conventional material such as Teflon� PFA powder in the binder screen as described above printed to a thickness of 15 -20 microns. Typically a suitable coating covering comprises 15 -25 wt -%, based on the total weight of the coating, of Teflon� powder in a binder which comprises 2 -(2 -ethoxyethoxy) - ethyl acetate (10 -45 wt -%, based on the total weight of the binder), 2 -butoxyethyl acetate (10-45 wt -%, based on the total weight of the binder), and polyvinylidence fluoride (20-80 wt -%, based on the total weight of the binder).

Also suitable as a coating are polychlorotrifluoroethylene (PCTFE) films, which are commercially available under the Trade name Aclar from Honeywell.

Such an EL has an usual current consumption of 0.30 to 90 milliamps per inch2.

The device may have power consumption of 0.2 to I watt per linear foot based on brightness settings.

An average lifetime of EL material is around 10,000 hours.

The EL is placed on a (thin) bendable backbone polymer layer. The layer needs not to be transparent because it is the rear of the device. To fix the device to a surface it is possible to make the backbone polymer layer with an adhesive or to fix it to a surface by an external fixing mean (such as glue, mechanical means, etc).

Any kind of polymeric material, which is bendable, can be used. A preferred material is polyester.

The inventive device is top coated with a transparent polymer layer 306.

This top coating layer must be flexible bendable and transparent. This top coating can be made from homo -as well as from copolymers or from mixtures thereof. A very suitable group of polymers is the group of polyurethanes. * * se

The device can be produced layer by layer using commonly known :: processes. It is also possible to use commercially available so-called light tapes S. (available under the trade names such as TapeLight, Lighttape, NeonTape, LightStrip, FlatLight, etc), which are then coated with a transparent polymeric material.

The inventive device can have any suitable form or shape. One preferred form is the form of a strip with illuminated widths of upto 6.5 inches (or even more). It is also possible to combine such strips as shown in figure 4a. 401 is the backbone polymer layer and 402 is the EL, which emits the light. On top of both layers, there is the coating layer made from a transparent polymeric material.

In such an embodiment the EL can cover a large amount of the surface of the backbone polymer layer. That means that the EL does nearly have the same dimension of the thin flexible polymeric material on which it is fixed. Usually there is always a border at both sides present. As already said above it is also possible to attach more than one EL on such a strip.

In figure 4b which is a cross section of the same embodiment of figure 4a, 401 and 402 are the same as in figure 4a and 403 is the coating layer made from a transparent polymeric material.

Also preferred is that the device is in a form of a tile which can have any form. Usually a tile is a rectangle (or square). The EL is attached to a thin flexible polymeric material, which is larger than the EL.

In figure 5a there is a schematic drawing of two devices in the form of a rectangular tile, 501 is the polymeric backbone layer and 502 is the EL. The device is also covered by the top coat layer made from the bendable and transparent polymeric layer. * .* * * * * ** *.**

This can be seen in figure 5b, wherein 503 is a transparent polymeric layer. As already said above it is also possible to attach more than one EL on * such a tile. 501 and 502 are the same as in figure 5a.

The inventive device always comprises at least one EL. Therefore the device must have a power supply. The citations above disclose details of the power supply offer a prior art EL. Such a power supply can also be used for the device of the present invention, It can be for example done in the way that two electrodes of the EL are provided with an external silver or copper lead or by using a ribbon connector to connect the EL to a suitable source of power. The power supply usually is in the range of 12V to 220V. In the case of high voltages, there may be a need of a transformer.

In case the device is in the form of a strip, the device can be connected to s the power supply at one spot. Usually the connection to the power supply is done at one of the ends of the strip, but it is also possible to do it at the back of the device, that means where the device is fixed to the surface. The same applies in case the device is in a form of tile and only a single tile is used.

When more than one of the devices are used it is possible to connect each single device with a power supply or to connect each of the device in the form of a daisy chain (serial) or to have a surface bet ow the device which can connect each of the devices in parallel manner.

This is shown in figure 6a wherein a single tile is shown, 601 are the electric conductors, 602 are the contact spots for the electric conductors of another device, 603 is the EL, 604 is the polymeric backbone. It is clear that the device is also covered by the polymeric bendable top coat.

Figure 6b shows the 3 tiles connected in a daisy chain, wherein the free electric conductors 605 are designed for the external power source. 602 -604 S...

are the same as in figure 6a. * . * * S

Figure 7 shows parallel arrangement of tiles wherein 701 is the polymeric backbone, 702 is the EL, 703 is the top coating, 704 is the surface (such as wall, floor), 705 are the electrical conductors, and 706 is the electrical connection to the power supply.

The device can be attached to the desired surface by any well-known means. Usually the device is glued to the surface. This is done by either using a sticky backbone polymer layer, by using a glue or by using a double-sided sticky tape. The person skilled in art will know what kind of glue is needed.

It is clear that the fixing mean must be chosen dependant of the material of the surface.

The device as according to present invention can be used for lighting the surface, it means that the device is fixed to the surface, which needs to be lighted. The device can be used for showing the way to an (emergency) exit, warning of hazards, or ornamental reasons, etc. The surface can be made from any material which can be natural or artificial. Examples of surfaces are stone, concrete, carpet, wood, plastic, metal etc. This is a big advantage of the present invention that it can be used for any kind of surface. A preferred use of the present invention, especially for the device in form of a strip, is that the device can be easily be bended or fixed over the edge of a step.

This can be seen in figure 8, wherein two steps are shown and the device is in the form of a strip and it is bended over the edge of the step. 801 is the inventive device folded around the edge of a step of a stair (802).

The devices according to the present invention can also be used for skirting board, door matting, feature stripping, boarder walk logos and pictures, carpet tilling, door plates/threshold stnps. It is also possible to use devices S...

according to the present invention for projecting pictures on a surface (like a screensaver or TV). S..

Depending on the use of the device as well as of the size and positioning of the device it can be useful to use a top coating which has non-slip properties or to add an additional layer comprising such a material. Such a coating can be added to the device which means that the device would have an additional layer.

In this case this specific layer should be bendable and transparent as well.

Another option would be that such a non-slip layer is put onto the device after it is fixed to the surface. In such a case the layer should also be transparent. Non-slip properties are especially important when the device covers a large area of the floor.

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Claims

Claims: 1. A flexible illumination device comprising: s (I) at least one electroluminescent lamp, (ii) a backbone polymer layer, wherein the electroluminescent lamp is fixed on the backbone polymer layer, charactensed in that the device is coated with at least one transparent polymeric coating layer.
2. A flexible illumination device according to claim I wherein the electroluminescent lamp comprises: (a) a front electrode; (b) a phosphor layer; (c) a dielectric layer; and S''. (d) arearelectrode. C. * * . S * .*
3. A flexible illumination device according to any of the preceding claims wherein the backbone polymer layer can be made from any homo -or copolymeras well as mixture thereof which are bendable.
4. A flexible illumination device according to claim 3 wherein the homo -or copolymer can be chosen from the group consisting of polyester.
5. A flexible illumination device according to any of the preceding claims which is from 3 to 6 mm thick.
6. A flexible illumination device according to any of the preceding claims wherein the polymeric coating layer can be chosen from the group consisting of polyurethane.
7. A flexible illumination device according to any of the preceding claims wherein the device is a strip.
8. A flexible illumination device according to any one of claims I to 6 wherein the device is a tile.
9. A method of illuminating a surface comprising securing a flexible illumination device to a surface wherein the flexible illumination device is in accordance with any one of claims 1 to 8.
10. A method of illuminating a surface according to claim 9, wherein the surface is a wall, a stair and/or a floor. * *. * . * * .* **** * * Se.. ** S * S * **S S..I * S... * S