Luminescent articles and methods of manufacturing luminescent articles

Field of the invention

[001] This invention relates to luminescent articles such as safety equipment, clothing, footwear, headgear, helmets and accessories, and to methods of manufacturing such articles.

Background of the invention

[002] Luminescence is the phenomenon of material adsorbing energy, usually, but not exclusively, in the visible light range, and emitting the energy as light at the same or another wavelength. Photoluminescence is the phenomenon of a material absorbing light and emitting light at the same or a different wavelength. Phosphorescence is the phenomenon of material absorbing energy and emitting it over a time period. There are a number of applications in articles made of luminescent, photoluminescent and phosphorescent plastics. Some materials exhibit both photoluminescence and phosphorescence.

[003] Safety helmets can be made from fluorescent material which glows while subject to light illumination so they can be seen when illuminated by approaching vehicle lights at night. However, the persistence of this fluorescence is short.

[004] Photoluminescent materials such as ZnS: Cu have relatively short persistence and produce relatively low levels of visible light.

[005] The addition of photoluminescent material to plastics materials in particulate form can weaken the plastics material.

Summary of the invention

[006] It is desirable to produce products which mitigate one or more of the above problems or which provide improved photoluminescent performance.

[007] hi this specification and claims, the word "luminescent" will be used to refer to materials which are luminescent, photoluminescent, or phosphorescent. Luminescent materials include luminescent plastics. Generally, luminescent materials include particles of luminescent substance in a carrier matrix. In the embodiments described, the luminescent or phosphorescent effect can be supplemented by reflective material. The carrier can be a resin or a plastics material.

[008] Some alkaline earth aluminates with alkaline earth silicates exhibit strong photoluminescence with excellent persistence.

[009] In one embodiment, the invention provides a photoluminescent helmet including a base helmet and a photoluminescent coating including one or more layers incorporating a photoluminescent material.

[010] The helmet can be made of Acrylonitrile Butadiene Styrene (AB S) .

[011] The helmet can include a buffer layer between the base helmet and the photoluminescent layer.

[012] The coating can include three layers incorporating photoluminescent material.

[013] The helmet can include a clear protective coating over the photoluminescent coating.

[014] The photoluminescent material can have the general formula

M _a N _b O ₀ XEu ²⁺ , yRE ³⁺ , where M is an alkaline earth metal, N is Si or Al, RE is any rare earth element and Eu is Europium.

[015] The composition of the coating can include 7 parts by weight of photoluminescent powder, 9 parts by weight of hardener, 13 parts by weight clear paint, and 5 parts by weight thinner or solvent.

[016] Alternatively the composition of the coating can include 35 parts by weight of photoluminescent powder, 10 parts by weight of hardener, 40 parts by weight clear polyurethane based paint or resin, and 5 parts by weight thinner or solvent.

[017] The invention also provides a method of manufacturing a photoluminescent safety helmet including the steps of applying a coating including a photoluminescent material to the outer surface of a base helmet.

[018] The method can include the step of rotating the base helmet while applying the photoluminescent coating.

[019] The helmet can be inclined during rotation.

[020] The rim of the helmet can be inclined to the horizontal during rotation, and rotation is about an axis transverse to the base of the helmet.

[021 ] The method can include the step of rotating the helmet until the coating is sufficiently dry to prevent the coating from running.

[022] The method can include the step of drying the helmet after applying a layer of photoluminescent coating.

[023] The method can include the step applying two or more layers of photoluminescent coating, each subsequent layer being applied after the preceding layer has dried sufficiently.

[024] In one embodiment of the invention, the photoluminescent material used can have the formula MaNbOc xEu ²⁺ , y RE ³⁺ , where M is an alkaline earth metal, N is Si or Al, RE is any rare earth element. Depending on the selected parameters, the material is capable of producing photoluminescence in the following colours, white, purple, blue, gray, light yellow- green, yellow-green, blue-green, having significantly greater intensity and persistence than normal ZnS: Cu luminescent materials.

[025] The invention proposes articles which are coated with a thin layer or stratum including luminescent material, or in which photoluminescent particles are distributed in a clear matrix carrier.

[026] At least part of the luminescent material can be located within a recess.

[027] One embodiment of the invention provides a road marker having one or more luminescent portions adapted to direct light towards oncoming traffic.

[028] The road markers can include one or more protective recesses and the luminescent portion can be located at least partially within the or each recess.

[029] The road markers can be coated on all visible surfaces with a layer containing luminescent material.

[030] The road marker can have grooves approximately aligned with a predetermined direction

[031] The direction can be the direction of traffic flow.

[032] The road marker can have luminescent portion around its perimeter.

[033] The road marker can have a portion having a conic section.

[034] The road marker can be circular.

[035] The road marker can have a circumferential luminescent portion.

[036] The road marker can have one or more annular luminescent portions.

[037] The road marker can include reflective material.

[038] The reflective material can be combined with the luminescent material in a matrix.

[039] The road marker can include a self-cleaning arrangement

[040] The self-cleaning arrangement can include a reservoir with an outlet adapted to deliver fluid to at least part of the luminescent portion.

[041] The reservoir can be connected to the outlet by a duct.

[042] The reservoir can be pressurizable.

[043] The reservoir can be compressible.

[044] The reservoir can have a fluid inlet.

[045] The fluid inlet can have a one way valve.

[046] The luminescent portion can be resiliently or flexibly mounted so that it can be pressed into the reservoir.

[047] The invention also provides footwear including at least a portion of the surface of the footwear coated with a layer containing luminescent material.

[048] The footwear can have recesses in the sole, at least a portion of the recess being coated with luminescent material.

[049] The footwear can have a wear sole and a mid sole, and the mid sole can include luminescent material.

[050] The footwear can be an overshoe.

[051] The footwear can have a wear sole and an mid sole, at least the outer rim of the mid sole including luminescent material.

[052] The footwear can be made of polyurethane.

[053] The footwear can have an outer layer of thermoplastic polyurethane.

[054] The invention also provides a method of manufacturing articles having a luminescent material including providing a first moulded layer within a mould, the first layer including luminescent material, and forming a second layer within the first layer.

[055] The first layer can be formed using blow moulding.

[056] The second moulded portion can be blow moulded.

[057] The second moulded portion can be injection moulded.

[058] The luminescent material can be applied by spraying. [059] The first layer can be thermoplastic polyurethane. [060] The second layer can be polyurethane. [061] The material can include up to 20% luminescent material in a matrix material. [062] The material can include at least 2% luminescent material in a matrix material.

[063] The material can include from 8% to 10% luminescent material in a matrix material.

Brief description of the drawings

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

[065] Figure 1 is a section view of a road marker made according to an embodiment of the invention;

[066] Figure 2 is an end view of the road marker of Figure 1 ;

[067] Figure 3 is a partial view of the road marker of Figure 1;

[068] Figure 4 is a side view of the road marker of Figure 1 ;

[069] Figure 5 is a side view of a modified road marker shown in Figure 4;

[070] Figure 6 is a side view of a road marker according to an embodiment of the invention;

[071 ] Figure 7 is a plan view of the road marker of Figure 6;

[072] Figure 8 is a section view of the road marker of Figure 6;

[073] Figure 9 is a view of a road marker with a weatherproof cover;

[074] Figure 10 illustrates a typical illumination pattern of a road marker;

[075] Figure 11 shows an annular insert in relation to a road marker;

[076] Figure 12 shows a view of the annular insert;

[077] Figure 13 shows an other road marker according to an embodiment of the invention;

[078] Figure 14 shows a marker with a self-cleaning arrangement;

[079] Figure 15 shows a marker with an alternative self-cleaning arrangement;

[080] Figure 16 shows a marker with differently inclined reflective faces;

[081] Figure 17 shows an overshoe or gumboot according to an embodiment of the invention;

[082] Figure 18 shows an outline of a safety footwear sole with a serrated outline for receiving luminescent segments;

[083] Figure 19 illustrates a process for manufacturing a helmet in accordance with an embodiment of the invention.

[084] The numbering convention used in the drawings is that the first digit of three digit numbers and the first two digits of four digit numbers indicate the drawing number.

Detailed description of the embodiment or embodiments

[085] Figures 1 to 4 are views of a road marker according to an embodiment of the invention. The road marker has a base with a sloping base 102 with sloping edges 312, 412. Protective recesses are formed between raised protrusions or ribs 310. The ribs can also extend over the major part of the length of the road marker as shown at 304, but this is not essential for the functioning of the road marker. The recesses between the sloping ribs 310 contain a layer of luminescent material 308. The ribs 310 protect the luminescent layer 308 from wear when a vehicle tyre passes over the road marker.

[086] In the embodiment of Figure 4, the ribs do not extend to the bottom of the base, while in the embodiment of Figure 5, the ribs extend to bottom of the base. Thus the arrangement of Figure 4 can be used in applications where the lower part of the road marker may become obscured.

[087] Figures 6 to 8 show a round shaped road marker having a base 602, 702, 802, and a pair of recesses 680, 610, 708, 710, 808, 810.

[088] Referring to Figure 6, the road marker includes a top 606 and an intermediate rib 604 separating the recesses 608, 610. The recesses 608, 610 are at least partially covered by a luminescent layer. The top 606 and the rib 604 partially overhang the recesses so that, when the road marker is compressed by a vehicle tyre, at least some of the luminescent layer is not contacted by the tyre.

[089] Figure 7 shows the circular shape of the road marker of Figure 6, with base

702, rib 704, top 708, recess 708 and recess 710.

[090] The sectional view of Figure 8 shows the profile of the recesses 808 and 810.

[091] Preferably, the body of the road marker of Figure 6 is made of a one piece construction to which the luminescent material is applied at least in ^" the recesses. [092] Preferably the material is flexible or resilient.

[093] Figure 9 shows a protective housing 920 applied to the road marker of Figure

6. The housing is a transparent flexible jacket which is used to prevent foreign matter collecting in the recesses. The edge of the housing 920 can be sealed to the base 902 or completely enclose the road marker.

[094] Figure 10 illustrates the apparent illumination from the road marker of Figure 6 as seen by an approaching vehicle driver. The road marker provides a pair of parallel light strips 1022, 1024 which, to the view of the driver, are brighter in the centre than towards the edges.

[095] Figures 11 and 12 illustrate a luminescent annulus 1126, 1226 which can be fitted into the recess 1110. The annulus 1126 and or the top 1106 can be flexible to enable the annulus to be press-fit in the recess 1110. The face 1128 of the annulus 1126 can be luminescent or can include a luminescent layer. The annulus can be dimensioned so that the top 1106 extends beyond the face 1128 to protect it from traffic.

[096] A similar, larger diameter annulus can be provided for recess 1108.

[097] Figure 13 illustrates a road marker having a base 1302 a recess 1308, and a top

1306. This marker differs from that of the earlier figures in that the inner wall 1330 of the recess slopes downwardly. This assists in preventing a build up of foreign matter on the luminescent surface.

[098] Figure 14 illustrates a further embodiment of a road marker in which the base

1402 houses a reservoir 1440. Water can enter the reservoir through one or more holes 1442 in the upper rim of the housing. A one-way valve 1444 can close the aperture 1442 when the pressure in the reservoir exceeds the external pressure. The valve 1444 can be within a first duct 1446 which has an opening slightly above the lower wall of the reservoir 1440. A second duct connects the interior of the reservoir to an outlet 1450 which permits water within the reservoir to be applied to the luminescent surface of the recess 1408. The outlet can be in the form of a nozzle to increase the outlet velocity of the water. The reservoir 1440 can be made of a flexible of resilient material. Thus, when a vehicle tyre passes over the road marker, the reservoir will be compressed, the valve 1444 will close, and water will be forced up the duct 1448, from whence it will be sprayed on the luminescent surface of recess 1408.

[099] A plurality of inlets 1442, valves 1444 and outlets 1450 can be provided to provide all-around cleaning of the luminescent surface.

[0100] Alternatively, as shown in Figure 15, the road marker can have the recess resiliently mounted to the reservoir 1540 by a flexible mounting arrangement 1550, for example a U or V shaped resilient membrane so that, when a vehicle tyre passes over the road marker, the luminescent portion 1508 of the recess is forced into the reservoir. The membrane is shown in section. The spray holes other than the end holes are shown in dotted outline as they are behind the inner wall of the membrane. ^" When the top and luminescent portions are forced down, water in the reservoir is forced through the spray holes onto the luminescent portion 1508. The inlet holes 1542 also include associated one way valves (not shown).

[0101] The resilient mounting arrangement can be in the form of an annular spring with spray holes 1552 to direct a spray onto the surface 1508.

[0102] Alternatively, there can be apertures in the annular spring to permit water to wash over the face 1508, or discrete spring elements can be provided to provide the same effect. Where the water is not applied under pressure, the one-way valves are not required.

[0103] Figure 16 illustrates an arrangement in which the luminescent surfaces 1608,

1609 are inclined at different angles.

[0104] In one embodiment, the luminescent faces at different angles can have different colours. The overhang of the rib of top can be arranged to occlude the upper part of the luminescent surface when the viewer is outside a specific viewing cone, so that only the lower luminescent portion is visible. That is, if a viewer is at one height, then, when the viewer approaches within a specific distance, the top or rib will block the view of the upper part of the luminescent face, so that only the lower part is visible. Thus, if the two luminescent parts are of different colours, the distance at which the colour change appears to the viewer can be known approximately. This feature can be used as a distance indicator.

[0105] In a further embodiment, the marker can be moulded from a material having luminescent material dispersed throughout. Part of the marker can be washed by a washing mechanism as described above.

[0106] There is a trade off between the size of the particles and the resulting brightness of the photoluminescence, and between the size of the particles and the effect on the mechanical strength of the product. Thus, where strength of the photoluminescent product

is paramount, smaller particles are preferred, while, where the optical characteristics, brightness persistence are important, larger particles are preferable.

[0107] The proportion of photoluminescent particles used in a material is another factor which can effect both the optical and physical characteristics of the product.

[0108] In one embodiment, a coating mixture for a helmet included 7 parts by weight of photoluminescent powder, 9 parts by weight of hardener, 13 parts by weight clear paint, and 5 parts by weight thinner or solvent.

[0109] The proportions can be 6 to 8 parts by weight photoluminescent material, 8 to

10 parts by weight hardener, 12 to 14 parts by weight clear paint, 4 to 6 parts by weight thinner.

[0110] hi one embodiment, the luminescent pigment used can be of a size of 5 to 200 micron.

[0111] In a further embodiment, the luminescent pigment can within 80 to 95 micron mixed with resin at about 10% by premixing or master batch.

[0112] The invention is applicable to safety equipment such as headgear, such as helmets, and footwear, such as shoes and boots. In the case of boots with luminescent portions can be provided as shown in Figure 17. Overshoes or gum boots 1700 can be made of polyurethane with a coating, preferably a thin coating, of thermoplastic polyurethane containing the luminescent pigment on the foot 1702 and leg 1704 portions.

[0113] The footwear can have a sole having at least two layers, for example, a hard wearing outer sole 1706, 1708 and a mid sole 1710 as shown in Figure 17. The outer sole can be made of thermoplastic polyurethane, and upper sole can be polyurethane. The upper sole can include luminescent material. The mid sole can be at least partially visible above the outer sole.

[0114] The outer sole 1706, 1708 can have a tread pattern and the inner portions of the outer sole tread pattern can also be coated with a luminescent material.

[0115] Preferably the luminescent portions are at least in part in protective recesses.

Instead of the whole upper sole being made luminescent, an upper sole can be made which has at least part of its periphery luminescent. Figure 18 illustrates an upper sole 1802 with a peripheral recess formation providing a plurality of recesses 1804 at least part of which is coated with a luminescent material. The recesses can be filled with a transparent material to prevent the recesses from becoming entangled.

[0116] We have found that, in some cases, the use of the photoluminescent material in some plasties products can weaken the material. This can be problematic in some applications, such as safety helmets. Figure 19 illustrates a method of manufacturing a helmet in accordance with an embodiment of the invention. A pre-formed helmet 1902 (referred to herein as a "base helmet") having the required strength characteristics is mounted on a rotatable block 1906 and one or more spray nozzles can be used to apply one or more layers containing the photoluminescent material is applied to the outer surface of the helmet.

[0117] The mounting block can also carry a shield 1920 to prevent the underside of the helmet peak, if present, from being coated. By not coating the underside of the helmet peak, this will aid, when such a helmet is in use, by not having photoluminescent portion radiating light into the eyes of a user, which would otherwise have an undesirable impact on a user's night vision, and it may even be annoying or an inconvenience during daytime.

[0118] The helmet can be rotated relative to the paint spray nozzles 1910, 1914 to ensure an even coating. It is preferable that the base of the helmet is not horizontal during the spraying and drying processes. The helmet can be mounted at an angle θ to reduce the possibility of the coating running towards the lowest point, ha addition, the helmet can be rotated during drying.

[0119] Applying the photoluminescent material as a coating avoids weakening of the helmet due to the presence of the particles in the material matrix on the helmet.

[0120] The process can be carried out according to the following steps: the helmet is mounted on the mounting block 1906; the spindle 1908 commences rotation of the block 1906 and helmet 1902; a first photoluminescent coating is applied through spray nozzles 1910, 1912 while the helmet is being rotated; the coated helmet is then dried while still mounted on the rotating block. Subsequent treatment of the coating can include a buffing process. If a second or subsequent coating layer is to be applied, the dried coating can also be roughened to improve adhesion between layers. Such roughening can be performed by any known means such as fine or coarse sandpapering or abrasive, or 1000 grade abrasive paper etc.

[0121] In an automated process, the spraying can be carried out in a spray cabinet

1930 and drying of each coating layer can be carried out drying cabinet 1932 having drying lamps or radiators 1922, 1924.

[0122] The mounting blocks 1906, and their rotating spindles 1908 and drive mechanisms (not shown) can be mounted on a conveyor system illustrated schematically at

1926. The conveyor system can be a belt system, a trolley system, or other suitable conveyor system.

[0123] The process can be a batch system in which several helmets are coated while one or more previous batches are being dried.

[0124] In one embodiment, a buffering layer can be applied to the helmet surface to be coated before the photoluminescent coating is applied. This can assist in avoiding damage to the helmet material due to solvents in the photoluminescent coating.

[0125] Application of two or more layers in a clear carrier material can improve the brightness of the photo-luminance.

[0126] Because the photoluminescent material is applied as a coating and is not incorporated into the plastics material of the helmet, large particles can be used in this application.

[0127] TABLE 1 lists items in which the invention can be embodied. The items in column 1 can be made by coating the item with a coating including photoluminescent powder in a clear carrier. The items in column 2 can be made by applying an adhesive layer or otherwise affixing a layer having a substrate such as vinyl ,cotton or the like, coated with a photoluminescent powder in a suitable resin or plastics matrix. The items in column 3 can be moulded from a mixture of photoluminescent powder and a plastics material or resin.

[0128] Suitable plastics and resins include: ABS, polycarbonate (PC), ABS/PC,

HDPE, high density polyethylene, PVC/plasticizers, ABS/PS, talc/mineral, acrylates, rubbers, nylon, reinforced nylon, glass fibre, as well as other polymers and synthetics.

[0129] Safety products will usually be made from high impact plastics. UV stabilizers and fire retardants can also be added.

[0130] In another embodiment the photoluminescent coating mixture is preferably made from a base in either liquid, resin or paste form. Such a liquid, resin or paste is preferably clear, as this gives the best photoluminescent qualities. Photoluminescent material of some 25 to 35 microns size as described above is then added as follows:

[0131] The base coating, whether in liquid, resin or paste form, is preferably a 2 part or pack polyurethane coatings such as the one marketed under the DUPONT trade mark by E I Du Pont De Nemours and Company, under the trade name 555 Line 2K Pofyurethane™. The base coating is formed by mixing 555 Line 2K Polyurethane™ with "2K Industrial Hardener" in accordance with the manufacturer's specification, which requires mixing in the ratio of 4:1 with "2K 4:1 Industrial Hardener". Then the base coating is optionally finalised

by then reducing the mixture by 10% to 20% with 555 Series™ Thinners according to gloss requirements. While pigments or tints such as 555 2K TINTERS (Lead free range from DUPONT) can be used, these will have varying adverse affects on the photoluminescence quality of the finished product, and preferably no pigments or tints are added other than the photoluminescent material, in the manner described below.

[0132] To this base coating is added the photoluminescent material described above in the following proportions: 15 to 60 parts photoluminescent material to 45 to 60 parts of the 555 Line 2K base coating to produce what will be called hereinafter "the photoluminescent coating". The most preferred proportion to give what we consider to be preferred results is preferably 35 parts photoluminescent material to 55 parts of the 555 Line 2K base coating.

[0133] When applying the photoluminescent coating, preferably 1 to 5 coats are applied. This mixture flashes off, that is the solvents dry off, in approx 5 minutes at 20° C after application of the photoluminescent coating. Once sufficiently flashed off, if further coats of the photoluminescent coating are being applied, then preferably the previous coat is roughened, by any means such as sand papering-coarse or fine, and another coating applied.

[0134] Application of the photoluminescent coating can be by spraying, brushing or other possible means such as dipping, however care should be had to prevent streaks and drips from excess coating forming, as this will mar the final appearance of the product, which will not be helpful if the final appearance is important.

[0135] Ih testing, it has been found that this composition of the photoluminescent coating works best when 3 coats are applied to products such as helmets manufactured from white plastic material such as ABS.

[0136] Once the final coat of the photoluminescent coating has been applied, it is best to leave the final coat to dry/set for 10 to 15 minutes at 20° C, and then a final flashing off of solvent by a stove or baking process for some 40 to 60 minutes at 60° C, however it is expected that satisfactory results could be obtained at lower temperatures but it is expected that longer times will be required.

[0137] If desired, once the final coating of the photoluminescent coating has been made and flashed off, a first and or last coating of a clear 555 Line base coating can be applied to the helmet.

[0138] It is expected that after 3 coats of the photoluminescent coating and one coating of clear base coating, that approximately 30 to 40 grams of coatings would be applied per standard sized "one size fits all" safety helmet.

[0139] It may be necessary before applying the first coating of the photoluminescent coating to the article/helmet, it may be necessary to roughen the surface to provide better adhesion of the first coat of the photoluminescent coating.

[0140] The use of the revolving cradle system as described above helps to ensure an even coating of the photoluminescent coating is applied to the article/helmet.

[0141] The 555 Line 2K Polyurethane™ product is best used with cleaned unprimed

ABS, rigid PVC, polycarbonate and ABS/polycarbonate alloys, primed polypropylene, HDPE, LDPE, EPDM, Nylon, with suitable primers including 8844, 8855 8877 Techprime Series. Other suitable 2K primers include epoxies and urethane.

[0142] During development of the photoluminescent coating it was found that some settling would occur of the photoluminescent pigment or material. To decrease the rate at which this occurs, anti settling agents can be added to the mixture.

[0143] As described above a preferred base coating is a polyurethane 2 part/pack base coat such as that described above. However, other base coats such as other paint or lacquer, thermoplastic urethanes, or other coatings may be used.

[0144] The micron size of the photoluminescent material combined into the base coat influences the photoluminescence performance time. From our tests using a micron size of approx 25 to 35 will, if several photoluminescent coatings are applied to a white helmet, and a clear base coat is used, will photoluminesce in the finished product for approx 12 hours or more, once the finished product has been exposed to bright sunlight for approximately 30 min.

[0145] With respect to the manufacture of a material to act as cone sleeves for use with traffic cones and the like, and in particular reflective cone sleeves, one or more coating of the photoluminescent coating can be applied to a PVC sheet or woven material (or other suitable material), with a retro-reflective or reflective coating having a clear base, which may contain glass beads or prisms, then added over the photoluminescent coating. It will be readily understood that such a material once made can also be used for forming indicia or markers for attachment to clothing footwear and head gear for increased safety of the wearer.

[0146] Where ever it is used, the word "comprising" is to be understood in its "open" sense, that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense of "consisting only of. A corresponding meaning is to be attributed to the corresponding words "comprise", "comprised" and "comprises" where they appear.

[0147] It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text. All of these different combinations constitute various alternative aspects of the invention.

[0148] While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, and all modifications which would be obvious to those skilled in the art are therefore intended to be embraced therein.