A METHOD OF MANUFACTURING A COMBINED PHOTOLUMINESCENT AND RETROFLECTIVE SHEET MATERIAL

Abstract

A method of manufacturing a combined photoluminescent and retroreflective sheet material is disclosed. The method comprises the coating of at least part of one side of a sheet of a substrate (3) such as a fabric substrate, with a mixture of an adhesive and a photoluminescent pigment. The mixture preferably comprises between 20% and 70% inclusive of a photoluminescent pigment having a size between 20 microns and 60 microns inclusive. The adhesive is preferably a transparent adhesive. The coated sheet of substrate (7) is then cured prior to the securement of one or more pieces of a retroreflective sheet (9) o one or more predetermined areas of said one side of the sheet of the substrate to form the sheet material such that at least 5% of visible area of said one side of the sheet material is photoluminescent.

Claims

1. A method of manufacturing a combined photoluminescent and retroreflective sheet material comprising the steps of coating at least part of one side of a sheet of a substrate with a mixture of an adhesive and a photoluminescent pigment; curing the coating; and securing one or more pieces of a retroreflective sheet to one or more predetermined areas of said one side of the sheet of the substrate to form the sheet material such that at least 5% of visible area of said one side of the sheet material is photoluminescent.

2. A method as claimed in claim 1, wherein the mixture comprises between 20% and 70% inclusive of a photoluminescent pigment comprised of particles having a size of up to 150 m.

3. A method as claimed in claim 2, wherein, the mixture comprises 50% of the photoluminescent pigment.

4. A method as claimed in claim 1, wherein the pigment is comprised of particles having a size between 20 m and 60 m inclusive.

5. A method as claimed in claim 1, wherein the photoluminescent pigment is phosphorescent.

6. A method as claimed in claim 5, wherein the photoluminescent pigment comprises strontium aluminate.

7. A method as claimed in claim 1, wherein the adhesive is a transparent adhesive.

8. A method as claimed in claim, wherein after curing the adhesive is cross-linked.

9. A method as claimed in claim 1, wherein the substrate is coated with a coating weight of between 200 g/m2 and 750 g/m2.

10. A method as claimed in claim 9, wherein the coating weight is 350 g/m2 using a mixture that comprises at least 50% photoluminescent pigment comprised of particles having a size between 20 m and 40 m inclusive.

11. A method as claimed in claim 1, wherein the substrate is a fabric substrate.

12. A method as claimed in claim 11, wherein the substrate is a woven cotton fabric or a woven polyester cotton fabric.

13. A method as claimed in claim 1, wherein the substrate is a white fabric.

14. A method as claimed in claim, comprising the additional initial step of coating or impregnating the fabric substrate with titanium dioxide.

15. A method as claimed in claim 1, wherein the substrate is comprised of a blackout fabric or a blackout fabric backing on a side opposite that which is coated with the photoluminescent coating.

16. A method as claimed in claim 1, comprising the additional step of coating the other side of the sheet of the substrate with a pressure-sensitive adhesive.

17. A method as claimed in claim 1, wherein the fabric substrate is coated with the mixture of adhesive and photoluminescent pigment in the form of stripes.

18. A method as claimed in claim 17, wherein the stripes are between 5 mm and 75 mm inclusive wide and between 5 mm and 75 mm inclusive apart.

19. A method as claimed in claim 17, wherein the retroreflective sheet is applied and secured to the substrate in strips in the gaps between the photoluminescent stripes.

20. A method as claimed in claim 1, comprising the additional step of cutting the coated substrate up to produce at least one strip to which the retroreflective material is applied and secured to produce sheet material in the form of a tape.

21. A method as claimed in claim 20, wherein the retroreflective sheet is applied to the coated substrate in strips that are at least 20 mm wide.

22. A method as claimed in claim 1, wherein the retroreflective sheet is in the form of a transfer film that is applied directly to the coated substrate and adhered thereto.

23. A method as claimed in claim 22, wherein the transfer film is secured to the coated substrate by a heat-sensitive adhesive that has an activation temperature that is lower than that of the adhesive forming part of said mixture.

24. A method as claimed in claim 22, wherein the transfer film comprises discontinuous retroreflective segments that are removable disposed on a carrier film.

25. A method as claimed in claim 24, wherein the transfer film is heat press laminated to the coated substrate and the carrier film is thereafter removed to leave the discontinuous retroreflective segments secured to the substrate.

26. A method as claimed in claim 1, wherein the material is manufactured in the form of a tape and the photoluminescent visible area comprises a border along one longitudinal edge of the tape.

27. A method as claimed in claim 1, wherein the material is manufactured in the form of a tape and the photoluminescent visible area comprises two borders along opposite edges of the tape.

28. A method as claimed in claim 27, wherein the borders are at least 5 mm wide and at least 20 mm apart.

29. A combined photoluminescent and retroreflective sheet material comprising a substrate coated on at least one side with a mixture of a transparent adhesive and a photoluminescent pigment and over which has been secured a retroreflective sheet in one or more predetermined areas of said one side such that at least 5% of the visible area of said one side is photoluminescent.

30. A method of manufacturing a combined photoluminescent and retroreflective sheet material substantially as described herein with reference to the accompanying drawings.

31. (canceled)

Description

[0026] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0027] FIG. 1 is a schematic perspective view of apparatus for use in a first part of a manufacturing process to produce a combined photoluminescent and retroreflective sheet material in accordance with the present invention;

[0028] FIG. 2 is a schematic perspective view of apparatus for use in a second part of the manufacturing process, the dimensions of layers of the sheet material shown being exaggerated for clarity;

[0029] FIG. 3 is a diagram of one side of a substrate forming part of the sheet material showing a pattern used for a photoluminescent coating;

[0030] FIG. 4 is a diagram of one side of an embodiment of a combined photoluminescent and retroreflective sheet material in the form of a tape;

[0031] FIG. 4a is a diagram similar to FIG. 4, but of another embodiment of tape;

[0032] FIG. 5 is a diagram similar to FIG. 4 but of another embodiment of tape;

[0033] FIGS. 6a, 6b and 6c are diagrams similar to FIG. 5 showing three alternative arrangements; and

[0034] FIGS. 7a and 7b are front and rear views of a high visibility vest including areas of tape as shown in FIG. 4 thereto.

[0035] With reference to FIG. 1, a first part of a method for manufacturing a combined photoluminescent and retroreflective sheet material is shown that uses an air knife coating apparatus 1. Here, a roll of blackout fabric 2 is used to supply a sheet of a substrate 3 that is passed under an air knife 4 to be coated with a mixture of a transparent adhesive and a photoluminescent pigment. The air knife 4 is of conventional form wherein the coating is applied to the substrate 3 and spread to a predetermined thickness by the knife 4 which is set so that its edge is this predetermined distance above the substrate 3. This produces an even coating across the substrate 3. After passing under the air knife 4 the coated substrate 5 is fed into a curing oven 6. Dependent on the type of adhesive that forms part of the coating, the curing oven 6 either heats the coated substrate 5 to cure the coating or irradiates it with UV radiation. The coated substrate 7 emerging from the oven 6 is then fed onto a roll 8 to complete the first part of the manufacturing process wherein the photoluminescence is applied to the substrate. As described below, in some embodiments, the photoluminescent coating may be applied in stripes along the length of the substrate 3. This may be accomplished using a slot die coating process.

[0036] The next step in the manufacturing process is to apply a retroreflective material to the coated substrate. One method of accomplishing this is shown in FIG. 2. Here, a retroreflective sheet in the form of a tape 9 of transfer film to which a strip of retroreflective material 10, which may comprise a series of retroreflective segments (see segments 17 in FIGS. 5, 6a, 6b and 6c), has been applied is fed from a roll 11 and applied to the coated side of the substrate 7 which is taken from a roll such as the roll 8, as described above. The tape 9 has an adhesive 12 pre-applied to its back surface, which is that facing the substrate 7, and has a carrier film 13 covering the retroreflective material 10. The adhesive 12 is pressure and/or heat sensitive. The substrate ii and overlying tape 9 are then led between nip rollers 14, which may be heated. The nip rollers 14 activate the adhesive and cause the retroreflective material 10 of the tape 9 to be adhered to the substrate 11.

[0037] Finally, the overlying carrier film 13 is removed to leave a photoluminescent and reflective sheet material in accordance with the invention. If the photoluminescent coating has been applied to the substrate in stripes, then several tapes 9 of transfer film may be applied to the coated substrate 7 simultaneously across its width, typically in uncoated areas. In this case, after application of the retroreflective material, the finished material has to be cut into separate tapes. Alternatively, the coated substrate 7 may be cut into strips prior to application of the tape 9 of transfer film thereto so that each strip of substrate 7 is then individually overlaid by a tape 9.

[0038] As described above, in the first process, the substrate 3 may be coated over the whole of one side with the photoluminescent mixture. Alternatively, if it is desired to produce finished material in tape form then the mixture may be applied to the substrate 3 in stripes as shown in FIG. 3. Here longitudinal stripes 15 of the mixture are applied across the width of the substrate 3. The stripes themselves can be of any desired width but to produce tapes suitable for use on high visibility clothing each stripe preferably has a width W.sub.1 of at least 20 mm with the stripes 15 at each longitudinal edge of the substrate have a width W.sub.2 half that of W.sub.1 , namely 10 mm in the present example. The distance W.sub.3 between adjacent stripes 15A, 15B is preferably at least 20 mm wide but is most likely to be 25 mm (1 inch), 35 mm or 50.08 mm (2 inches) wide to meet most international standards for tapes used on high visibility clothing as the width W.sub.3 is identical to the width of the retroreflective material that is to be applied to cover it. The width W.sub.3 should be selected to satisfy the required standard for use of the finished material but it will be appreciated that the relative dimensions of the retroreflective material and substrate and in particular the widths W.sub.1, W.sub.2 and W.sub.3 may be varied as required. Once coated, the substrate may be cut into separate strips down the middle of the stripes 15 to produce tapes as shown in FIG. 4, for example that have a 10 mm wide stripe 15 of photoluminescent coating down each side and a 50.08 mm strip down the centre that is then covered by retroreflective material 16 as described above.

[0039] In an alternative arrangement as shown in FIG. 5, the substrate is coated over the whole of one side with the photoluminescent mixture and is still cut into strips that are, for example, 60.08 mm wide similar to those shown in FIG. 4. Here, a 50.08 mm strip of retroreflective material is secured down the centre of each strip to leave 5 mm wide borders of photoluminescent coating 16 down each side of the tape, as in FIG. 4. Alternatively, and as shown in FIG. 4a, a 50.08 mm strip of retroreflective material is secured along one longitudinal edge of each strip to leave a 10 mm border of photoluminescent coating 16 down one side of the tape only. As shown in FIG. 5, the retroreflective material in the central area between the borders is not continuous but comprises discontinuous retroreflective segments 17 that are disposed in angled stripes across the width of the central area. As the underlying substrate 18 is fully photoluminescent, the central area has discontinuous retroreflective areas, provided by the segments 17, located between photoluminescent areas 18. Although the retroreflective segments 17 are in the form of stripes in FIG. 5, it will be appreciated that they could be made in any suitable shape or size and angled in any direction, for example as shown in FIGS. 6a, 6b and 6c wherein the retroreflective segments are labelled 19 and the underlying photoluminescent substrate is labelled 20. The retroreflective segments 17 may take the form of chevrons.

[0040] Finally, if it is desired to produce a transfer tape, the side of the substrate opposite that covered by the retroreflective material may also be coated with a heat-sensitive adhesive with the appropriate properties as previously mentioned.

[0041] In use, a combined photoluminescent and retroreflective sheet material in accordance with the invention may be used in variety of situations, in particular in signage and in high visibility clothing. A vest suitable for use as a high visibility garment is shown in FIGS. 7a and 7b. photoluminescent and retroreflective sheet material in the form of tapes 21, as described above with reference to FIG. 4, have been applied to its front and back in appropriate areas in accordance with international or local standards. The tape 21 is preferably sewn to the garment through the photoluminescent strips 15 at the edges of the tape 21 leaving the retroreflective central stripes 16 undamaged by stitching. This minimizes interference with the retroreflective areas. It will be appreciated that tapes 21 with other patterns of photoluminescence and retroreflectivity could be used, as appropriate. In other applications, for example signage, the combined photoluminescent and retroreflective sheet material may be adhered, stapled or otherwise applied to appropriate surfaces and backing sheets.