GB2265630A

GB2265630A - Temperature indicating road markings

Info

Publication number: GB2265630A
Application number: GB9307075A
Authority: GB
Inventors: Stephen Long
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-04-04
Filing date: 1993-04-05
Publication date: 1993-10-06
Also published as: GB9307075D0

Abstract

A method and composition are provided for marking a road to indicate a change in the roads environment, such as a change in temperature. In this way a driver or other road user receives a warning of conditions conducive to the formation of ice. The composition preferably involves the use of encapsulated liquid crystals and may be in the form of a paint or a self adhesive film. The composition may change from transparent to blue or black to blue as the temperature passes below 0 DEG C. This colour change reverses as the temperature rises.

Description

TEMPERATURE INDICATING ROAD MARKINGS This invention relates to road markings and in particular, though not exclusively, the line road markings applied to define lanes on a road.

Many of the road traffic accidents which occur each year are a result of the presence of ice on the road. During a prolonged spell of sub-zero temperatures ice is expected by drivers and they may moderate their speed accordingly. However, there are many occasions where the temperature will be close to the freezing point of water and local variations in temperature or a change in temperature, as night approaches for instance, will make the difference between ice forming or not. It is in these circumstances that the majority of accidents occur when a driver suddenly encounters a patch of ice.

Some locations are prone to local variation of this sort and have a reputation for the formation of ice when none is present elsewhere, and can be so called "accident black spots".

Presently it is known to warn drivers of sections of road which are prone to icing by displaying conventional wording to this effect. Such signs are usually left in situ all year round and give no indication of conditions at any particular time.

Consequently driver complacency leads to them being widely ignored.

According to a first aspect of the invention I provide a composition for marking roads such that the composition undergoes a change in appearance, which is detectable by a vehicle driver, or other road user, in response to a change in its environment.

Preferably the change in appearance as a result of the change in environment is a change in the colour or the appearance of colour in the composition.

The change in appearance may be a change in the intensity of reflected light.

Preferably the change in appearance results from a change in the temperature of the composition's environment. Most preferably the change occurs substantially at a threshold value. Preferably the change reverses as the temperature crosses the threshold value in the other direction.

The threshold value is preferably determined by the composition of the marking and is most preferably set by the applier to his predetermined requirements.

Preferably the threshold value remains substantially constant throughout the life of the marking.

Preferably the threshold value is at or around the freezing point of water on the road. The threshold value may be in the range + 20C to - 50C, preferably in the range OOC to -50C, or OOC to -20C, or -20C to -50C, and most preferably substantially at - 20C Alternatively the threshold value may be substantially OOC.

Preferably the colour change as the temperature drops below the threshold value. The colour change may be from white to blue and as it rises above the threshold value again from blue to white.

Alternatively a change from black to blue and back again is possible.

Preferably the composition becomes translucent at, or below the threshold temperature.

Alternatively the composition may become more translucent at or below the threshold temperature than above the threshold temperature. The level of translucency may increase gradually as temperature decreases.

The reflectivity of the composition may vary in a manner similar to the . translucency of the matter as disclosed above.

Alternatively a more highly visible or detectable colour change may occur.

The temperature at which the composition reverts to its above the threshold temperature colour may be different from that at which it changes to the below the threshold temperature colour when temperatures drop.

The threshold value as the temperature drops may be between 0 and 50C lower or higher than the temperature threshold at which the composition changes as the temperature rises again.

In this way a delay occurs between the temperature at which the ice will start to melt and at which the road markings indicate that the road temperature is not conducive for ice forming. This means that a false indication will not occur where the road markings indicate a temperature above the melting point of ice but the ice has not yet had a chance to melt.

The change in the environment could alternatively or additionally be the road becoming wet.

According to a second aspect of the invention I provide a method for increasing the safety of a road by applying markings to the road which have a composition which indicates to a driver changes in the road environment.

Preferably the safety of the road is increased because the markings composition changes to indicate the possibility that ice may form.

Most preferably the change is a change in the colour of the road marking.

Preferably the change in the road marking occur as a result of a change in temperature.

Alternatively the change may occur because of the presence of water or moisture on the road.

Most preferably the change occurs as a result of both the presence of water and a temperature likely to cause ice to form.

According to a third aspect of the invention I provide a road marked with a composition in accordance with the first aspect of the invention.

According to a fourth aspect of the invention I provide a method of marking a road comprising applying a composition to a road which changes its appearance in response to a change in its environment.

A number of potential embodiments of the invention will now be described, by way of example only.

In a first embodiment a composition is applied, to a road surface, in the form of a line. The composition has the capacity to display a bright blue colour when the temperature falls to below OOC. Above OOC the composition is transparent and so shows only the colour of its background, which for a road surface will normally be black.

A material having this property is commercially available and is based on a heat fusible powder system.

The system comprises two layers, a black under layer and a temperature insensitive ink layer. The black layer provides a consistent flat backing layer for the temperature insensitive layer in use. The presence of this layer considerably improves the brightness of the ink layer's colour, when present, by absorbing the unreflected colour. The black layer is normally an ink.

The temperature insensitive layer is of the type known in the art as a single colour, monochromatic or clearing point mixture.

The mixture consists of liquid crystals which are encased in a gelatine shell. The desired characteristics of the liquid crystals being formulated prior to encapsulation. These microcapsules are mixed with an aqueous resin to form an ink or surface coating.

The system is formed by screening printing the temperature insensitive ink onto a suitable release paper. A suitable paper is available under the Trade mark AQUACOTE from Hobart McIntosh.

Once applied to the paper the ink is allowed to dry thoroughly, temperatures up to 900C are allowable.

The black ink layer can then be printed onto the completely dry temperature insensitive layer.

After allowing the black layer to dry, a further layer of release paper is applied to form a sandwich structure. By heating the composite to 1500C for 10-15 seconds, with a medium pressure applied a very thin film can be produced. The film can alternatively be used at its original thickness.

When applying the film to the road to be marked the release paper, in contact with the black layer, is removed and the exposed black layer is placed on the road surface. Application of a medium pressure and heating to 1500C will cause the composite to bind to the road surface.

In use the material will appear as a black area on the road surface. As the temperature falls below OOC the temperature insensitive ink will change from transparent to a bright blue colour, as the ink reflects lIght from that part of the spectrum.

The change is due to a rearrangement, on a molecular scale, of the microcapsules provided in the ink. Because it is a physical arrangement rather than a chemical reaction, the change is completely reversible and there is practically no limit to the number of times it can change. Other colours such as green, yellow or red are also possible.

In an alternative embodiment a thermochromic ink can be used. This may be selected from the type which passes from colourless to red and through the spectrum to blue and colourless again with increasing temperature.

In this type of ink the red change can be set at -10 C and the blue change of OOC. Hence the ink provides a way of monitoring the change of temperature, providing more information than a single change. The boundaries can be varied as desired from a red change at -300C up to 1000C as required. The blue change being up to 200C higher than the red change for the particular material.

The threshold value desired can be set as required by mixing the liquid crystals of the desired type.

Thermochromic materials of this type can be obtained from Merck Ltd. under the Trade Mark LICRITHERM. The composite produced has a fairly rugged resistance to abrasion and is water resistant.

Inks of the types mentioned above may be applied by means of techniques such as direct or transfer screen printing, flexo or gravure printing, ink-jet printing, spraying or dipping.

It is also possible to produce the gelatine encased liquid crystals in paint form for subsequent application to a road. The paint layer is best applied over a black layer, which has fully dried.

Suitable aqueous binder resins and additives are added to the paint to control its physical characteristics to with acceptable limits.

With inks or paints a temperature indicating layer of approximately 25m is desirable.

It is desirable to apply a further coating to the composite, either in situ or during its formation. The additional coating, preferably a varnish, protects the liquid crystals from ultraviolet light and so increases the working life of the road marking.

In certain circumstances it may be necessary to use an adhesive or other binder to improve the attachment of the composite to the road surface.

It is also possible to apply the black layer and liquid crystal containing layer to the road surface direct. The liquid crystals need not be in encapsulated form.

The application of suitable composites in a number of forms is envisaged. As previously described the material can be produced in a thin film. This can then be cut to the shape required. Production of the material in the form of a tape is also envisaged. The tape may be of the self-adhesive type. Application as a paint can be performed at the same time as the conventional road markings are being applied, thus saving time and money.

The composite can be applied in a wide variety of configurations. It could be applied as a continuous line, a broken line or as a series of dashes or dots alongside existing lines. Alternatively the material could be provided in the gaps between existing lines.

Of course the material need not be applied in every gap, merely at intervals or where the road is prone to icing. Alternatively the material could be applied as a ring around cats-eyes or other such road features.

Claims

1. A composition for marking roads such that the composition undergoes a change in appearance which is detectable by a vehicle driver or other road user, in response to a change in its environment.

2. A composition in accordance with claim 1 in which the change in appearance is a change in colour.

3. A composition in accordance with claim 1 in which the change in appearance is the appearance of colour in the composition.

4. A composition in accordance with any preceding claim in which the change in the environment is a change in temperature.

5. A composition in accordance with claim 4 in which the change occurs at a substantially constant threshold value.

6. A composition in accordance with any preceding claim in which the change in the appearance of the composition is reversible.

7. A composition in accordance with any one of claims 4 to 6 in which the change in the composition's appearance occurs substantially at the freezing point of water.

8. A composition in accordance with any one of claims 4 to 8 in which the colour change is from white to blue as the temperature drops below the threshold value and is from blue to white as the temperature rises above the threshold value.

9. A composition in accordance with any one of claims 4 to 8 in which the change is from black to blue as the temperature drops below the theshold value and is from blue to black as the temperature rises above the threshold value.

10. A composition in accordance with claims 4 to 8 in which the composition reverts to its above the threshold temperature colour at a temperature different from that at which it changes to the below the threshold temperature colour when the temperature drops.

11. A composition accordance to claim 10 in which the difference in threshold temperatures is between 10 and 5 centigrade.

12. A composition according to any preceding claim in which the composition contains liquid crystals.

13. A composition according to claim 12 in which the liquid crystals are contained in microcapsules.

14. A method for increasing the safety of a road by applying markings to the road which have a composition which indicates to a driver, or other road user, changes in the road environment.

15. A method according to claim 14 in which the safety of the road is increased because the markings change appearance to indicate the possibility that ice may form.

16. A method according to claim 14 or claim 15 in which the change is a change in the colour of the road marking.

17. A method according to any one of claims 14 to 16 in which the change is a change in temperature.

18. A road marked with a composition which undergoes a change in appearance which is detectable by a vehicle driver, or other road user in response to a change in its environment.

19. A method of marking a road comprising apply a composition to a road which changes its appearance in response to a change in its environment.

20. A composition substantially as described herein.