GB2445561A

GB2445561A - Marker for safety, decorative or lighting purposes

Info

Publication number: GB2445561A
Application number: GB0700550A
Authority: GB
Inventors: Philip Lancaster; Michael Upton
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-01-11
Filing date: 2007-01-11
Publication date: 2008-07-16
Also published as: GB0700550D0

Abstract

The marker comprises a reflecting layer 10, a phosphorescent layer 12 provided on the reflecting layer and which is formed from at least one phosphorescent layer, and an at least partially transparent retro-reflective layer 14 which is provided on the phosphorescent layer and arranged so that the phosphorescent layer is positioned between the reflecting layer and the retro-reflective layer. An at least partially transparent cover layer 22 is preferably provided on the retro-reflective layer and the retro-reflective layer may comprise glass elements 18 or plastic corner cube reflector prisms which may be arranged in an array which covers a portion of the retro-reflective layer. The phosphorescent layer is preferably formed from an at least partially transparent layer, e.g. of glass or plastic, within which particles of phosphor are embedded and the layer may comprise portions which have differing phosphorescent properties. The marker preferably includes a fixing portion to locate the marker which may comprise a bezel. Also claimed is a method of manufacturing a marker.

Description

1 2445561

PHOSPHORESCENT MARKER DEVICE

Field of the Invention

The present invention relates to a marker device, and more particularly to a phosphorescent marker device for safety, decorative or lighting purposes.

Background

Various kinds of devices for safety, decorative or lighting purposes are known.

Such devices typically rely on electricity to generate and emit light or are designed to be at least partially retro-refiective so that they reflect a significant amount of incident light back towards its source.

A disadvantage associated with electrically powered devices is that their use is limited to locations where a continual source of electricity is available. Attempts to overcome this problem have been made by using a stored-energy cell (commonly known as a battery) to provide the electrical power for the device. Such batteries can be integrated with the device and be of sufficiently small size and weight that the device remains portable. However, the major drawback of using batteries is that they can only store a finite amount of energy and therefore have a limited lifespan before they need to be replaced or recharged. The requirement to replace depleted batteries on a regular basis is expensive and time-consuming. There is also likely to exist a period of time between a battery being depleted and replaced, thereby resulting in a period of time that an associated device cannot operate.

Retro-reflective devices have been developed in an attempt to overcome the above detailed problems, by removing the requirement to generate light. Retro-reflective devices are, instead, designed to reflect incident light back towards the source of the incident light. Such devices, of course, still require illumination from a source and are therefore only noticeable to people when such a source of illumination is present.

There is therefore a need to devise a marker device that can function at a location where no electricity is available or when conventional lighting sources stop working. There is also a need for such a device to be noticeable even when there is no incident illumination or a when a source of iLlumination is not present.

It is known to provide a marking device having a luminescent property whereby the device comprises a polymer that absorbs light during the day or during a period of illumination and then radiates light during the night or a period of no illumination. Such a device is disclosed in United Kingdom Patent Application Number GB 2,312,458 Al.

Summary of the Invention

According to an aspect of the invention, there is provided a marker for safety, decorative or lighting purposes, the marker comprising; a reflecting layer adapted to reflect a least a portion of incident light; a phosphorescent layer provided on the reflecting layer and being formed from at least one phosphorescent material; and an at least partially transparent retro-reflective layer provided on the phosphorescent layer and arranged such that the phosphorescent layer is positioned between the reflecting layer and the retro-reflective layer, the retro-reflective layer comprising retro-reflective means.

The marker may further comprise a cover layer provided on the retro-reflective layer and arranged such that the retro-reflective layer is positioned between the cover layer and the phosphorescent layer. Such a cover may be formed from a plastic material or toughened glass and can help to protect the underlying layers from damage by external forces.

To produce predetermined images or text, the retro-reflective means may be arranged in an array covering a portion of the retro-reflective layer. Further, such image or text can be made from differing colours and/or brightness of emitted light by forming the phosphorescent layer such that it comprises portions having different phosphorescent properties.

According to another aspect of the invention, there is provided a method of manufacturing a marker for safety, decorative or lighting purposes, comprising; forming a reflecting layer adapted to reflect a least a portion of incident light; forming a phosphorescent layer at least one phosphorescent material and providing the phosphorescent layer on the reflecting layer; and forming an at least partially transparent retro-reflective layer on the phosphorescent layer such that the phosphorescent layer is positioned between the reflecting layer and the retro-reflective layer, wherein the retro-reflective layer comprises retro-reflective means.

Thus, there is provided a marker device that may function at a location where no electricity is available which can also be noticeable even when there is no incident illumination or a when a source of illumination is not present.

Brief Description of the Drawings

For a better understanding of the invention, embodiments will now be described, purely by way of example, with reference to the accompanying drawings, in which: Figure 1 is plan view of a marker according to an embodiment of the invention; Figure 2 is a cross- sectional view along the line X-X of Figure 1; Figure 3 shows a modification to the marker of Figure 1; Figure 4 is shows a marker according to an alternative embodiment of the invention; Figure 5a is a plan view of a marker according to another embodiment of the invention; Figure 5b is a cross-sectional view along the line Y-Y of Figure 5a; and Figure 6 shows a cross-sectional view of a marker according to an alternative embodiment of the invention.

Detailed Description

While the present invention is susceptible of embodiment in various forms, there is described and shown in the drawings presently preferred embodiments. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout. Further, the drawings are not to scale.

Referring to Figures 1 and 2, a marker according to a first aspect of the invention comprises a reflecting layer 10 for reflecting a least a portion of incident light. Above the reflective layer 10 is formed a partially transparent phosphorescent layer 12.

In the embodiment illustrated, the reflecting layer 10 is approximately 1mm thick and formed of silver coloured, highly reflective material such as polished aluminium foil. It will, however, be understood that the reflective layer 10 may be of any suitable thickness and/or reflectively so as to reflect a finite amount of incident light. For example, the reflecting layer 10 may be a reflective coating, such as a white titanium oxide paint, that is provided on a major surface of the phosphorescent layer 12.

The phosphorescent layer 12 is approximately 3-4mm thick and made from a mix of phosphorescent materials embedded or suspended in a transparent plastic. The phosphorescent layer 12 may, of course, be of any suitable thickness and formed from one or more phosphorescent materials.

Phosphorescence is a type of photoluminescence that is related to fluorescence.

Unlike fluorescence, however, a phosphorescent material does not immediately discharge the radiation it has absorbed. In other words, phosphorescence is a process in which energy stored in a substance is released slowly and continuously in as light.

Phosphorescent materials are therefore "glow in the dark" materials which are charged up by exposure to light and slowly release stored energy by emitting radiation in the form of light. Because the rate of energy release from a phosphorescent material is characteristically slow, the material can glow for long periods of time (for example, up to several hours). The slower time scales of the re-emission of the radiation are associated with quantum mechanically forbidden energy state transitions, which result in light emission having a very low probability of occurrence and almost being forbidden by quantum mechanics.

In the embodiment shown in Figures 1 and 2, the phosphorescent layer 12 comprises an epoxy plastic with grains of phosphor embedded therein. More specifically, the phosphorescent layer 12 of Figures 1 and 2 is formed from grains of a rare earth phosphor mixed with an epoxy plastic such that the phosphorescent layer 12 is at least partially transparent.

A phosphor is a substance that exhibits the phenomenon of phosphorescence and known phosphors are transition metal compounds or rare earth compounds of various types. investigations have shown that preferable phosphors include Nichia type NP-2810 violate, NP-2820 cyan, NP-2830 green, NP-2840 amber, arid NP-2850 orange. More colours may be made by combining phosphors of different colours, for example blue may be made from mixing violate and cyan. Although stated has being preferable, it is envisaged that NP-2840 amber and NP-2850 orange may be less preferable since they have short glow times when compared to the other phosphors.

Further, it has been found that the choice of epoxy is also important since temperature variations may cause the marker to delaminate or crack. Investigations have shown that Huntsman type Aruldite 2020 glass epoxy is preferable, although it is envisaged that other forms of epoxy will also be preferable.

The distribution of grains of phosphor within the epoxy can affect the mechanical strength of the phosphorescent layer 12, in addition to the amount of light it emits. Uneven distribution of phosphor grains can be attributed to low viscosity of the liquid epoxy allowing the grains of phosphor to sink under the influence of gravity, thereby forming a dense layer of phosphor. For this reason it is preferable to add 40%- 90%, and more preferably 50-80%, by volume of colloidal silica so as to achieve a more even distribution phosphor in the phosphorescent layer 12.

The amount of phosphor provided in the phosphorescent layer 12 is preferably in the range of approximately 10-40% by volume, more preferably in the range of 15- 25% by volume, arid even more preferably approximately 20% by volume, since higher amounts have not been found to provide an equivalent increase in light emission.

It is also preferable to manufacture the phosphorescent layer 12 under vacuum conditions, because small bubbles trapped in the plastic can reduce the amount light that is emitted from the phosphorescent layer 12.

Light emitted from the phosphor of the phosphorescent layer 12 and incident on the reflective layer 10, is reflected back towards the phosphorescent layer 12 and s transmitted through the phosphorescent layer 12 to be emitted from the surface of the phosphorescent layer 12 that is opposite to the reflective layer 10. Thus, when arranged so that the reflective layer 10 is provided at the lower surface of the phosphorescent layer 12, the light emitted by the phosphorescent layer 12 is manipulated so that a larger proportion of light is emitted from the upper surface of the phosphorescent layer 12 in a generally upward direction.

In addition to arranging a reflective layer 12 on the lower surface of the phosphorescent layer 12, a reflective layer may also be provided on the sides of the phosphorescent layer 12 to reflect and manipulate light from the phosphorescent layer 12 so that substantially all of the emitted light is directed outwardly of the phosphorescent layer's upper surface. Such an arrangement may help to maximise the amount of useful emitted light, wherein useful light is that which is transmitted in a desired direction (i.e. towards a person).

Provided above the phosphorescent layer 12 is a transparent retro-reflective layer 14. Thus, the phosphorescent layer 12 is sandwiched between the reflecting layer and the retro-reflective layer 14.

The retro-reflective layer 14 is approximately 2mm thick and is formed from a plastic material. Of course, the retro-reflective layer may be less than 2mm thick in alternative arrangements (for example, 1mm thick), or greater than 2mm thick in other embodiments). Provided within the retro-reflective layer 14 are first 16a to third 16c groups of retro-reflective structures, preferably in a certain pattern. The first 1 6a and third I 6c groups of retro-reflective glass structures are each formed from an array arrangement of glass sphere or beads 18. The second group I 6b of retro-reflective structures is formed from an array arrangement of glass rods 20 disposed parallel to each other. Alternative embodiments may use other types of suitable retro-reflective structures such as plastic corner cube reflector prisms. It should also be understood that that it is not essential to form the groups of retro-reflective structures using two layers structures. The groups of retro-reflective structures may be formed form one or more layers of retro-reflective structures.

The purpose of the retro-reflective layer 14 is to reflect incident light (such as light emitted from a torch, a cycle lamp or a car head light) back towards the source of the incident light. Such devices, of course, still require illumination from a source and are therefore only noticeable to people when a source of illumination is present.

Although illustrated as being formed in individually separated groups, the retro- reflective glass structures may instead be formed to cover the entire area of the retro-reflective layer 14. It should also be understood that it is not essential to the invention that the retro-reflective structures be formed from glass, although it may be preferable Further, the retro-reflective structures may be formed by imprinting a pattern in the material of the retTro-reflective layer 14.

Disposed on top of the retro-reflective layer 14 is an at least partially transparent cover layer 22 so that the retro-reflective layer 14 is sandwiched between the cover layer 22 and the phosphorescent layer 12. The cover layer 22 is approximately 1-4mm thick and formed from toughened glass or plastic so as to protect its underlying layers.

The transparent cover layer 22 is not essential to the invention and its pnmary purpose is to provide abrasion resistance and protection for underlying layers. It may be made of a suitable plastic or glass, depending on the required strength, quality and finish. Glass may be preferable due to its appearance, longevity and low moisture absorption qualities. However, glass is generally more expensive than plastic and so there may be numerous applications where use of a plastic to form the transparent cover layer 22 is preferable.

It is also envisaged that it may be preferable to make use of polycarbonate to replace the use of epoxy and glass in future application of the marker.

Referring to Figure 3, a marker according to an alternative embodiment of the invention further comprises a bezel 24 having a recess 26 formed in its upper surface for receiving and securing the reflecting layer 10 of the marker of Figures 1 and 2. The bezel 24 is adapted to be adhered or fixed to a surface of a predetermined location.

Although preferably formed using a suitable plastic, the bezel 24 may be made from metal, glass reinforced plastic or glass reinforce high density rubber. The preferable choice of material will be understood to be dependent on the specific application of the marker and manufacturing considerations such as cost. For example, a metal bezel may be more appropriate for outdoor environments such as parks or gardens where the aesthetic quality of the bezel is important.

Although the bezel 24 may be adapted to be releasably coupled to a predetermined surface, it is likely that particular applications for a marker according to the invention will require the marker to be fixed securely at a location. For such applications, an alternative embodiment of the marker (such at that shown in Figure 4) is expected to be preferable.

Referring to Figure 4, the marker of Figures 1 and 2 (indicated generally by the arrow labelled "40") is secured in a recess 42 of a base unit 44 such that the reflecting layer 10, the phosphorescent layer 12, the retro-reflective layer 14 and the cover layer 22 are arranged within the recess and the cover layer 22 is substantially flush with the upper surface of the base unit 44. The base unit 44 is also provided with anchoring means 46, such as a threaded screw, extending from the recess 42 through the bottom portion of the base unit 44 and protruding outwardly from bottom of the base unit 44.

Thus, the base unit 44 may be secured at a predetermined location using the anchoring means 46.

In the specific example shown in Figure 4, the base unit 44 is secured in a recess 48 formed in an upper surface of a fixed body 50, wherein the anchoring means 46 is screwed into a threaded reception hole 52 formed at the bottom of the recess 48 provided in the fixed body. In this way, the marker is securely fixed at a location within the fixed body 50 such that both the upper surface of the base unit 44 and the cover layer 22 are substantially flush with the upper surface of the fixed body 50. In addition to screwing the anchoring means 46 into the threaded reception hole 52, the base unit 44 may also be bonded to the recess 48.

Figures 5a and 5b show yet another marker according to the invention, wherein the phosphorescent layer 12 is formed such that it comprises portions 55a and 55b having different phosphorescent properties. More specifically, the phosphorescent layer 12 is formed with different coloured phosphors positioned in different portions 55a and 55b of the phosphorescent layer 12 so that a predetermined pattern is formed. In this way, specific designs such as images or text can be produced by different coloured light emitted from the different phosphors.

A mould in the shape of a predetermined pattern may be used to provide the phosphor of a first colour, and then a second moulding process can be used to cover the remaining area with a different colour phosphor. Of course, this may be extended to the provision of more than two colours.

To provide a sharper contrast between the areas of differing phosphor, it may be preferable to provide a light proof layer between the areas so as to separate the two mouldings.

It will be appreciated by those skilled in the art that changes may be made to the embodiments described without departing from the principles of the invention. For example, it should be understood that it is not essential to the invention to form the retro-reflective layer 14 by providing retro-reflective structures in a plastic. An alternative method of forming the retro-reflective layer 14 may be to provide a pattern of adhesive on the lower surface of the cover layer 22 or on the upper surface of the phosphorescent layer 12 and then dust fme retro-reflective glass beads (i.e having a diameter in range of l0jtm -2mm, and more preferably in the range of l0..trn-1OOjirn) over the adhesive.

Investigations using this method have indicated that it is preferable that the adhesive has a low refractive index (i.e. in the range of 1.1 to 1.6) and the glass beads have higher refractive index (i.e. in the range of 1.7 to 2.5). In particular, it is envisaged that the specific embodiments of the invention may use silicone type ACC Q-Sil 215 adhesive with type NEG K60 beads. There are, however, numerous other adhesives, encapsulating plastics and beads that may be suitable.

Alternative embodiments of the invention may, instead, be formed by moulding corner cube reflectors on the back of the cover layer 22.

Figure 6 shows a marker according to an alternative embodiment of the invention. It is similar to the marker of Figures 1 and 2, but is instead formed with a retro-reflective layer 14 having a single layer of retro reflective glass beads 16 backed with an air space 62.

A thin layer of Aruldite 2020 adhesive 64 is formed on the lower side of the cover layer 22 and the retro reflective beads 16 are applied to the adhesive layer 64. In this way, the retro reflective beads 16 are adhered to the lower side of the cover layer 22. An air space 62 is ensured by placing a thin (approximately 0.1mm thick) semi-ridged transparent plastic sheet 66 below the retro reflective beads 16 so that they are sandwiched between the adhesive layer 64 and the plastic sheet 66. The air space 62 is sealed by surrounding the thin plastic sheet 66 with a line of adhesive 68 (typically screen printed). Many adhesives could be used for this although Aruldite 2020 thickened with colloidal silica is preferable.

The remaining arrangement of the marker is similar to that of Figures 1 and 2, with a phosphorescent layer 12 being provided on a reflecting layer 10, and the retro-reflective layer 14 being provided on the phosphorescent layer 12 such that the phosphorescent layer 12 is positioned between the reflecting layer 10 and the retro-reflective layer 14.

Although the layers of the marker have been illustrated as being flat, they may, of course, be non-flat. For example, any or all of the reflective layer, phosphorescent layer, the reiro-reflective layer, and the cover layer may be curved such that they form a dome or cylindrical shape.

Claims

1. A marker for safety, decorative or lighting purposes, the marker comprising; a reflecting layer adapted to reflect a least a portion of incident light; a phosphorescent layer provided on the reflecting layer and being formed from at least one phosphorescent material, and an at least partially transparent retro-reflective layer provided on the phosphorescent layer and arranged such that the phosphorescent layer is positioned between the reflecting layer and the retro-reflective layer, the retro-reflective layer comprising retro-reflective means.

2. A marker according to claim 1, further comprising an at least partially transparent cover layer provided on the retro-reflective layer and arranged such that the retro-reflective layer is positioned between the cover layer and the phosphorescent layer.

3. A marker according to claim I or 2, wherein the retro-reflective means are glass elements or plastic corner cube reflector prisms.

4. A marker according to any preceding claim, wherein the retro-reflective means are arranged in an array covering a portion of the retro-reflective layer.

5. A marker according to any preceding claim, wherein the phosphorescent layer is formed from an at least partially transparent material, such as plastic or glass, with particles of phosphor embedded therein.

6. A marker according to any preceding claim, wherein the phosphorescent layer is formed such that it comprises portions having different phosphorescent properties.

7. A marker according to any preceding claim, further comprising fixing means for fixing the maker at a predetermined location.

8. A marker according to claim 7, wherein the fixing means comprises a bezel adapted to receive at least the reflecting layer of the marker and to be adhered to a surface of the predetermined location.

9. A method of manufacturing a marker for safety, decorative or lighting purposes, comprising; forming a reflecting layer adapted to reflect a least a portion of incident light; forming a phosphorescent layer at least one phosphorescent material and providing the phosphorescent layer on the reflecting layer; and forming an at least partially transparent retro-reflective layer on the phosphorescent layer such that the phosphorescent layer is positioned between the reflecting layer and the retro-reflective layer, wherein the retro-reflective layer comprises retro-reflective means.

10. A method according to claim 9, further comprising forming an at least partially transparent cover layer on the retro-reflective layer such that the retro-reflective layer is positioned between the cover layer and the phosphorescent layer.

II. A method according to claim 9 or 10, wherein the retro-reflective means are glass elements.

12. A method according to any of claims 9 to 11, further comprising arranging the retro-reflective means in an array covering a portion of the retro-reflective layer.

13. A method according to any of claims 9 to 12, wherein the phosphorescent layer is formed from a plastic with particles of phosphor embedded therein.

14. A method according to any of claims 9 to 13, further comprising forming the phosphorescent layer such that it comprises portions having different phosphorescent properties.