GB2249974A - Coloured material - Google Patents

Abstract

A material for a sign, advertisement or the like which is coloured with at least two different colours so that the overall effect is to produce a colour different to the individual colours. The individual different colours are applied discontinuously or apparently discontinuously and/or are included within the make-up of the material itself.

Description

COLOURS MATERIAL This invention relates to improved methods of manufacturing sign materials particularly retrorefleotive ones and especially in relation to achieving the minimum standards required for colour and brightness (luminance) by a variety of international and national technical standards for road and other signs.

The need to address this problem is increased by the work about to commence within the European Community at meetings of the C.E.N.226 and other technical committees.

The historic requirements for colour and luminance of road signs is contained in such standards as B8:873 Part 8:1985 - BS:873 Part 6:1983, ISO 3864 and other equivalent or similar Norm Francais, DIN Standards etc. Other documents are available from the United Nations and the C.I.E.

amongst others such as C.I.E. publication No.39-2 (TL-1.6) 1983, but examples of the definitions of colours are contained in ISO 3864.

Different kinds of retroreflective materials have long been manufact zoed The two main differences in the types of retroreflective materials are the base techniques of a) Type 1 based on glass microspheres which are in some way partially mirrored and b) Type 2, the employment of microprismatic or corner cube arrays. Both techniques have the resulting property of being able to reflect light substantially back along the path or parallel to the path by which it arrived.

There are a large number of sub techniques which employ the main techniques, but the initial result of employing them is to produce a retroreflective sheet which can be attached to a sign plate surface or attached to devices such as bollards, cones, barriers etc., or for the creation of retroreflective patches for attachment to items such as high visibility clothing, car number plates, cycle guards, safety and identification signs and commercial advertising displays.

The initial retroreflective films produced by these techniques have,to the inventors knowledge, resulted in a white (as defined in ISO 3864 Fig.2) or substantially white appearance surfaces Some techniques result in a dull white or grey but unless intentionally coloured, they remain white (as defined in Iso 3864 Pig.2) or as their luminance decreases move to black (as shown in rig.l of the standard).

To achieve colours other than white, it is customary to colour the cover of these films in some way. This has been done by overprinting by silk screen process or other printing or coating process with a translucent or transparent or opaque lacquer, or by including a colorant within the polymer used to produce the top layer, or other convenient layer of the retroreflective sheet to change its hue.

The glass microspheres where employed have themselves also been coloured in some of the techniques and the material used to produce the microprismatic sheetings have been coloured.

Whichever technique has been used to date, the inventors believe that all of the coloured sheetings or overprinted sheetings have a substantially or almost totally uniform presentation of colour where used (i.e., if red is desired, a single red colour is applied, where green, a single green etc).

The colours permitted are described within the standard previously mentioned and are defined (white and black are also colours) by four co-ordinates (as illustrated in ISO 3864 1984). It will be seen from this standard that the achievement of white, black, red, yellow, blue will require the careful control of pigment to ensure that the x, y, co-ordinates of a given material are contained within the relevant colour box.

The need to use a single colour has the effect of restricting the choice of available pigments, since the pigments may be compatible with a limited number of ink base lacquers or polymers and in some instances, the ink base lacquer or the pigments themselves may not be suitable for use with the materials making up the retroreflective film.

In addition to the obligation for precise colours to be used, limiting available choice, there is a requirement in these standards that the colours shall have a certain brightness or vividness which is termed the luminance factor.

For instance, the luminance factor for white retroreflective materials called for in ISO 3864 is greater than 0.27 or 0.35 depending on the class of material also in BS:873 Part 6:1983 it is 0.25. The fact that there may be differences in the requirements, underlines the importance of the luminance factor. The ~requirement for green is greater than 0.04 and 0.03 in ISO 3864 etc. etc.

The measurement of these colour co-ordinates and the luminance factors are described in CIE Publication 15 and are well known internationally.

The result of readings for colour as conducted under CIE Publication 15 0/45 geometry is a pair of co-ordinates x and y which are plotted to give the single colour "point" on the graph.

Some colours which may seem at first to be available to the retroreflective sign sheet maker are not suitable since the luminance factor of the pigment may be below the requirement, thus causing it to be eliminated from the possible list.

It was in attempting to overcome all of these problems that this invention was discovered.

According to the invention there is provided a material that is coloured at least in part, characterised in that the apparent colour is made up of two or more different colours, the effect of which is to produce a resultant colour measurably different to the individual colours, the colours being applied discontinuously or apparently discontinuously and/or included within the make-up of the material itself.

In a preferred embodiment of the invention the material is wholly or partially retroreflective. It is preferred that the individual colours should not be distinguishable at more than about 15 metres preferably more than 10 metres at which distance they blend to form a uniform colour. Preferably individual colours should not be distinguishable at a distance beyond about 1 metre, preferably less than 30 centimetres.

It is within the ambit of the invention to modify the luminance factor of a predominant colour by one or more further colours. Moreover it is possible to combine colours together in such a way as to comply with a standard, such as a colour and/or luminance standard when the individual colours do not comply with the standard.

There are various ways in which the colours may be applied to or incorporated in the material. For example a continuous or discontinuous colour may be partially obscured by one or more discontinuous colour layer.

If Desired one or more of the colours may be fluorescent. In addition one or more of the colours, for example by virtue of the chemical composition thereof, may transmit or emit more visible radiation than the visible radiation it receives due to wavelength modification. Further, one or more of the colours may be comprised of a specularly reflecting metal layer.

The invention also includes articles such as signs, advertisements and textile material which include materials as defined above.

When obtaining colour co-ordinate readings for different colours bordering on or within "white" "red" "yellow" and "blue" as defined in CIE and ISO 3864, and attempting to choose the ones with the highest luminance factors, it was perceived that colours which were outside the "white" "red" "yellow" and blue definition could have high luminance factors, but would regrettably, not comply with the colour requirements of the standard and would consequently be unsuitable.

It was then discovered that if two of these colours and initially, particularly yellows and blues, or alternatively red, yellow and white, were placed side by side and a reading of the area where they touched or intersected was taken, unexpected readings were obtained. Surprisingly, in both tests, the resultant readings were close to a plain white reading and markedly different to the impression on the eye of a casual observer.

This phenomenon was examined further to reveal the following.

If two or more of these colours which lie outside the relevant colour box or toward the edge of the colour box but inside it are combined, not as a single pigment (which may not be possible) but as separate or over lapping small dots on a surface or by other representations such as lines or geometric shapes, the resulting x, y co-ordinates of a 150mm square sample when measured in accordance with CIE 15 will be an approximate average relative to the proportion of the area covered and strength of the colours employed, and the luminance will be according to the luminance factors of each pigment, together with the background if this is exposed.

Further, if the same principle is employed but one or more of the colours chosen is fluorescent, the luminance factor may be enhanced. Fluorescent whites are rare, but several non-white colours of or more of which is fluorescent in a balanced relationship can combine to give an apparent fluorescent or high luminance white.

It has been found that the inclusion of a fluorescent dye or pigment in an overall pigment may reduce the effectiveness of the fluorescence by absorption or obscuration. The use of the fluorescent pigment discreetly in the way described in this invention, enables its full potential to be realised.

If colours chosen are at partially or totally opposed or compensating vectors (value, direction and distance) from the centre of the desired colour box, then the sum of the effect of the dots in their proportions and individual x, y co-ordinates will produce an average or combined single pair of x, y co-ordinates when a larger area is tested.

(i.e., an area larger than a single group of the two or more dots, such as an area 150mm x 150mm). It is not necessary to cover the whole area of the sheeting to achieve this effect and consequently, a variable but predetermined area of background may be shown, and it is then one of the contributory colours.

The actual shape of the colour patches is not limited to "dots", geometrical shapes or other designs, such as logos, lines etc., can be used and will be technically as effective, although in practise, some arrangements will be more effective to the human eye.

It is also not necessary to overprint the retroreflective sheeting on all occasions.

For instance, if two or three colours are chosen to modify the background colour in the way described, they would be applied by overprinting the retroreflective sheeting with a regular or apparently random but averagely regular pattern composed of the three or more colours. A substantially similar result of colour and luminance modification would be achieved by overprinting one less colour but allowing a coloured layer to show through from below the retroreflective layer by discontinuously constructing the retroreflective layer.

Similarly, the colour pattern may be applied inside the top cover sheet or outside. It may be desirable to apply the pattern to a substrate below the top cover layer but above the retroreflective layer. The number of colours used is not limited, since the object is a balance. The balance could demand two colours or ten colours to achieve it.

In most chases, it will be advantageous to use transparent or translucent inks or lacquers since the less transparent the lacquer or ink, the greater will be the reduction in retroreflective performance which is generally undesirable.

However, inks or lacquers or other pigmentation means that has a significant degree of opacity is not precluded, since it is possible that some colours may only be achieved by this means.

Further experimentation with the principles of this invention revealed some far more surprising results than initially thought possible.

In the following description reference is made to the accompanying drawing which is a part of the chromaticity diagram from British Standard 873 Part 6 1983.

As a specific example of the invention the following colours individually are quite striking to the human eye; White x,0.315 y,0.331 luminance > 0.63 Fluorescent yellow (as used in Staedtler Textmarker 365) x,03858 y,0.4788 Luminance greater than 0.96 Light blue x,0.2522 y,0.313 < Luminance > 0.68 Bright red x,0.4900 y,3102 Luminance > 0.25 But when combined in a dot pattern of approximately 0.75mm o dots and approximately%40% red, 30% yellow, 5% blue and 20% white by proportion, they combined to give a white colour (as determined by CIE/IS0/BS standards) with coordinates of x,0.3453 y,o.3S42 and a luminance value of > 0.75. (Note - the proportions given above could not be determined more precisely than 95%).

At close distances, the eye-can easily detect the distinct colours, but at a distance of a few feet, a 10mm circular display of these dots apparently disappears when displayed on a white background of a similar luminance value.

Against a white background of a different luminance value, no colour difference is observed and the circle appears to be a slightly lighter or darker white.

It is notable that when the same proportion of the same colours were overlaid, there was a marked reduction in luminance, due apparently to the obscuration of the yellow.

The discreet dots were markedly more effective than a mixed pigment, but the overlapping of dots is not eliminated as an option to use.

A further unsuspected benefit arising from this invention was discovered from the above example. If the approximate proportions of colour were to be made up of a company's name or logo or any other code, legend, symbol etc., then identification or discreet advertising can be achieved.

The message or identity will be observable at close distances, but will apparently disappear as the observer moves away.

Conversely, should the dots or other shapes be so small that they cannot be distinguished except by microscopic examination they will be equally effective.

Whilst the example given uses very- striking individual colours, it may be beneficial in practise to use more subtle colours which are less obvious to the sye at close quarters. The principle is, however, exactly the same.

Also, from the production complexity and cost standpoint, the fewer the number of colours employed, the better. A calculated example which is likely to be very-bneficial to enhancing poor luminance white or near white base materials as now outlined.

The present requirement for retroreflective-aterials in some European countries is 0.25 and in others it is higher luminance.

If a requirement to conform with 0.35 emerges in the future, a material with a low (less than) 0.35 background luminance factor will need to be improved.

In the past, this improvement has been achieved by adding white in some way (U.K. patent n*.,. 2171335 for example). The whites used fdr this purpose have significantly higher (typically 0.80) luminance factors and their effect has been proportionate to area and luminance factor.

It can be observed from the example described that the inclusion of a fluorescent very high luminance factor (0.96 in the example) colour will be more effective than the limited improvement offered by white. However, the use of only one colour may take the overall material colour outside the requirement of the standard to which they are intended to conform. If a second or more high luminance colour is added to compensate for the first, luminance will be improved even more whilst the resultant colour will comply with the standard.

Moreover, the historic practise of adding white to a low luminance retroreflective sheeting is only of major benefit to white materials. It may be a distinct disadvantage to add white to a red material for instance, although luminance may increase, it may cause the risk of the red no longer meeting the colour requirement.

This discovery allows for a proportion of high luminande- fluorescent yellow and/or orange for example to be added to a low luminance, but otherwise satisfactory, red with a low ly value'. The result would not only improve the overall luminance factor of the red but also may improve the conformity to standard of a red which is close to or outside the red limits. For example, a red of co-ordinates x,0.67 and y,0.30 is outside BS:873 sign red co-ordinates.

It may also have a marginal luminance factor. If â proportion of fluorescent yellow as previously described is added (possibly over a white backing) then the overall modified red will move into the colour limits required by standard and the luminance will also be improved.

Two other reds with co-ordinates of A) x,0.64 and y,0.34 B) x,0.61 y,0.30 if combined in the proper proportions as a dot pattern will have combined x.y co-ordinates lying on an approximate line between the two colour reference of the individual colours.

This new resultant colour would almost certainly satisfy the requirements of BS:873 for sign red, whereas neither of the two separate colours would. It may be that the two reds A and B have been chosen for high luminance factors and the two combined may have higher luminance than a single colour currently used to meet the standard.

NOTE: All the examples illustrate enhancing luminance. It is just as valid to reverse the procedure to result in low luminance but still control colour by choosing colours as required that have low luminance factors.

The purpose of this invention is to achieve the modification of a colour of a retroreflective sheeting whilst at the same time, modifying its luminance factor or controlling its luminance factor.

For the sake of clarity, the inventor has studied the following, but consider that they are not prior art relative to this invention, since they address substantially different problems and have very different end results.

1) Printing techniques employing coloured dots to produce a pictorial representation such as in newspapers and magazines.

2) The practise of creating a picture in a television tube by exiting phosphorescent or fluorescent dots which are in a closely packed matrix.

3) The inclusion of white in a road cone retroreflective surface to improve its luminance as described in British Patent No 2171335 In the case of 1) and 2) It is not the purpose of the printed dots to achieve a colour modification and luminance factor modification to achieve a constant colour. The intention is to represent the varying hues, intensities and colours in a photographed scene in a constantly and infinitely variable way without particular regard for translucency or luminous intensity in regard to retroreflective materials performance standards. In most cases, two areas of a magazine photograph each measuring 150mm x 150mm taken in close proximity to each other will not have the same colour x, y co-ordinates, since the picture content will have varied between them. In contrast, the results obtained from two pieces 150mm x 150mm of a retroreflective film material made using this invention, will have substantially the same x, y colour coordinates and luminous intensity.

In the case of item 3), the techniques described show no intention of altering colour to one of those defined in ISO 3864. The intention was declared to be to improve or alter the luminance factor of the material by adding white to an already white material, or a material that has the same x, y colour co-ordinates as white but a luminescence factor below that of white.

This invention has a substantially greater effect in that both colour and luminance factors are being altered or controlled at the same time by a second or more colours which may themselves have different luminance factors.

In another utilis:atl n of colour to modify the luminance factor of a retroreflective sign material known to the inventors, a retroreflective road cone sleeve has been produced which was intended to meet the requirements of BS:873 Part 8:1985 in terms of luminance for white materials. The background luminance factor of the unaltered material was normally approximately 0.17 to 0.21.

was applied A partially coloured overprinted pattern/ to the background material, the coloured portion of which had the co-ordinates of x.301 y.282 approximately with a luminance factor of approximately 0.61. The area covered was approximately 15 to 18%. This had the intended effect of raising the luminance of the retroreflective sleeve from 0.17 to 0.26 or even 0.27. However, the effect of the colour applied was to take the colour performance of the overall sleeve outside that permitted for white retroreflective materials as specified in BS:873 Part 8:1985.

This invention corrects for this fault by allowing a balance of individual colours resulting in an average colour as tested under CIE 15 requirements that conforms to a specific requirement. These specific requirements are those in respect of the use to which the retroreflective sheeting or material is being put and the technical standard to which it is intended to conform.

For example, in respect of U.K. road signage BS:873, other standards may apply for clothing, car number plates or marine use. Safety signage for industry will require other performances. The intention is the same for each of these areas if this invention is employed to meet these varied standards.

Claims (17)

1. A material that is coloured at least in part characterised in that the apparent colour is made up of two or more different colours, the effect of which is to produce a resultant colour measurably different to the individual colours, the different colours being applied discontinuously or apparently discontinuously or are included within the make-up of the material itself.

2. A material as claimed in Claim 1, wherein the apparent colour is made up of three or more colours.

3. A material as claimed in Claim 1 or Claim 2, wherein the material is wholly or partially retro-reflective.

4. A material as claimed in any preceding claim, wherein the different individual colours appear as a substantially uniform colour at a distance of greater than 15 metres from the material.

5. A material as claimed in any preceding claim, wherein the different colours can only be individually distinguished at a distance less than 1 metre and preferably less than 30 centimetres from the material.

6. A material as claimed in any preceding claim, wherein the different colours cannot be individually distinguished with the naked eye.

7. A material as claimed in any preceding claim, wherein one colour is more predominant than the other colour or colours and wherein the luminance of the predominant colour is modified by at least one other colour.

8. A material as claimed in any preceding claim, wherein at least one colour does not individually comply with a predetermined standard and wherein compliance with said standard is achieved by the combination of said one colour with at least one different colour.

9. A material as claimed in Claim 8, wherein the predetermined standard is a luminance factor.

10. A material as claimed in Claim 8, wherein the predetermined standard is a colour standard.

11. A material as claimed in any preceding claim, wherein one colour is applied continuously and is partially obscured by a second colour applied discontinuously whereby said one colour appears to be discontinuous.

12. A material as claimed in any preceding claim, wherein at least one colour is fluorescent.

13. A material as claimed in any preceding claim, wherein at least one of the colours can modify the wavelength of received radiation whereby it transmits or emits more visible radiation than the visible radiation it receives.

14. A material as claimed in any preceding claim, wherein at least one colour comprises a specularly reflecting metal layer.

15. An article such as a sign, advertisement or the like comprising material as claimed in any preceding claim.

16. Textile articles such as clothing or the like comprising material as claimed in any of Claims 1 to 14.

17. A material as claimed in Claim 1 substantially as described herein.