WO1993004854A1

WO1993004854A1 - Flexible material having light diffracting characteristics and method of production

Info

Publication number: WO1993004854A1
Application number: PCT/US1992/007502
Authority: WO
Inventors: Roger E. Verden; Thomas F. Kostka
Original assignee: Prismagic, Inc.
Priority date: 1991-09-06
Filing date: 1992-09-03
Publication date: 1993-03-18
Also published as: EP0556378A1; KR930702148A; JPH06502028A; US5407729A

Abstract

A laminate of reflective (16) and light transmitting (18) material having a predetermined interface contour is releasably adhered to a carrier sheet (26) by a release agent (28) with the light transmitting material facing the carrier. An adhesive (20) is then applied to the reflective agent (16) in a predetermined, discontinuous pattern. Then a substrate (12) is pressed against the adhesive (20) to adhere the laminate (14) and carrier sheet (26) to the substrate (12). Thereafter, the carrier sheet (26) is peeled away from the substrate (12) taking therewith the laminate (14) except in those sections of the laminate (14) having adhesive (20) thereat which continue to adhere to the substrate (12) due to the greater bonding strength of the adhesive (20) in relation to the release agent (28). Thus, a composite material (10), having a substrate (12) with small pieces of light diffracting laminate (14) thereon, corresponding to the predetermined pattern of the adhesive (20), is formed which composite (10) does not significantly limit the flexibility of the substrate (12).

Description

FLEXEBLE MATERIAL HAVING LIGHT D_ΨRACTING CHARACTERISΗCS AND METHOD OF PRODUCTION

Field of the Invention

The present invention relates to the 5 manufacture of materials having light diffracting characteristics, and more particularly, relates to materials having light diffracting characteristics which are flexible, and their method of manufacture.

Background of the Invention

10 Holograms and other light diffraction sheets have been known in the art for some time. They are currently employed in a wide variety of applications including display advertising, greeting cards, die-cut letters and anticounterfeiting. In such applications,

15 holograms are mounted as unitary sheets to materials such as cardboard, plastic and metals.

Attempts have been made to incorporate this visually stimulating technology into flexible materials such as textiles and the like. However, current

20 techniques for applying holograms to flexible materials have been found to suffer from significantly limited flexibility in the end product.

For example, current methods for attaching holograms to textiles are illustrated in U.S. Patent Nos.

25 4,838,965 and 4,956,040 wherein the hologram sheets are adhered to the fabric as a continuous sheet, with adhesive extending across the entire hologram-fabric interface. The flexibility of the fabric at the location of the hologram is thereby significantly reduced and the

30 image is subject to cracking upon fairly minimal flexing of the fabric. Thus, there is a need for an improved method of affixing light diffracting sheets such as holograms to flexible materials which does not significantly limit the flexibility of the end product. 5 Additionally, the adherence of holograms to fabrics in a unitary, continuous sheet precludes "breathing" through the material thereat, which causes undesirable entrapment of heat beneath the surface of the shirt in the area of the affixed hologram. There is a need for a method of affixing holograms to fabrics which does not significantly limit "breathing" therethrough.

Furthermore, it is the striking visual image of holograms which makes the use of such materials on textiles so desirable. Therefore, it is important that the upper surface of the hologram or diffraction grating be as freely exposed as possible, with minimal materials covering any portion thereof. Current methods for attaching such images to textiles, as illustrated in the aforementioned U.S. Patent Nbs. 4,838,965 and 4,956,040, provide for at least the entire perimeter of the upper surface of the hologram to be covered with material of significant thickness, or the entire upper surface to be covered with a material of significant thickness in the process of adhering the hologram to the textile. Accordingly, there is a need for a method of attaching holograms which leaves the upper surface of the hologram as clear as possible, to take advantage of the full visual effect associated therewith.

Moreover, there is a need for such a product design which lends itself to economical manufacture. Summary of the Invention

In accordance with the present invention, a hologram or other light diffracting sheet is applied to a substrate in a discontinuous pattern with small sections of a hologram adhered to the substrate closely adjacent one another to give the appearance from a normal viewing distance of a continuous holographic image, similar to the dot pattern used in half-tone offset printing.

The hologram includes an upper, light transmitting layer and a lower, reflective layer and is laminated to a carrier sheet with the carrier sheet adjacent the upper, light transmitting layer. Adhesive is then applied to the lower, reflective layer in a predetermined discontinuous pattern. Thereafter, a substrate, such as cloth or other flexible material, is pressed against the applied adhesive pattern and the adhesive sufficiently cured to securely bond the hologram to the substrate at each of the locations having adhesive thereat. Both the bond between the upper and lower hologram layers and the adhesive bond at the interface of the substrate and the lower, reflective layer is stronger than the bond of the release agent which is between the upper, light transmitting layer and the carrier. Following curing of the adhesive, the carrier sheet is peeled away from the substrate, taking with it the light transmitting and reflective layers of the hologram or diffraction grating, except those portions having adhesive thereon which remain adhered to the substrate in a pattern corresponding to the pattern of the applied adhesive. The curing of the adhesive may or may not include the application of heat, depending upon the particulars of a given application, the important requirement of the present invention being that the adhesive bond be made stronger than the bond of the release agent prior to separating the application sheet from the substrate. The spacings between adjacent sections of hologram or diffraction grating laminate allows the formed composite material to bend and flex freely, without significant impediment to bending which would otherwise be realized due to the increased thickness at the hologram or diffraction grating upon application of the image as a continuous sheet. Also, the spacing between adjacent "dots" allows airflow or breathing through the material thereat to minimize undesirable heat build-up. Additionally, since the adhesive which adheres the hologram or diffraction grating to the substrate is only applied to the reflective underside thereof, the hologram or diffraction grating is not covered by any additional, undesirable layers of material so that a full, undiminished visual effect of the image is realized. That is, rather than envelope the reflective agent within a plastic coating, as is the current practice with holograms to protect the reflective surface from scratching and the like, this additional layer of plastic coating is eliminated in accordance with the preferred embodiment of the present invention to provide a thinner composite layer than what would be realized upon merely adhering a conventional, fully completed and enveloped hologram to the substrate. Thus, less weight, greater flexibility and a reduction in the usage of materials, and hence reduced production costs are realized with the present invention.

All these advantages over current hologram and diffraction grating adhering methods are attained in a method which lends itself to economical, large scale commercial production.

Brief Description of the Drawings FIG. l is a plan view of a section of composite material embodying various features of the present invention; FIG. 2 is a plan view of a section of composite material embodying various features of the present invention;

FIG. 3 is an enlarged fragmentary, perspective view of the composite fabric of FIG. 1, illustrating the circular dot pattern of laminate pieces the embodiment of FIG. 1;

FIG. 4 is a perspective view of an apparatus for forming the composite material of FIG. 1;

FIG. 5 is an enlarged fragmentary, perspective view of the adhesive-applying roller of the apparatus of FIG. 4; FIG. 6 is a perspective view of an apparatus for forming the composite material of FIG. 2;

FIG. 7 is an enlarged fragmentary, cross- sectional view showing the material at an intermediate stage of production, taken along the line 7-7 of FIG. 4; FIG. 8 is an enlarged fragmentary, cross- sectional view of the carrier; and

FIG. 9 is an enlarged fragmentary, cross- sectional view showing the carrier sheet being pulled from the substrate, taken along the line 8-8 of FIG. 4. Detailed Description of the Preferred Embodiments The preferred embodiment of the composite material of the present invention is illustrated in FIGS, l and 3 and indicated generally by the reference numeral 10. With reference to FIGS. 3 and 8, it will be seen that the composite material 10 has a substrate 12 which may be a textile, leather, plastic or any other suitable material. With particular reference now to FIG. 9, the cross-sectional view of the laminate pieces 14 bonded to the substrate 12 is shown at the upper right hand corner of the drawing. It can be seen that bonded to the substrate 12 are a plurality of pieces of laminate, indicated generally at 14, which are small holograms or diffraction gratings. The laminate pieces 14 of the preferred embodiment each comprise a thin layer of reflective agent 16 integral with a thin layer of light transmitting coating 18 on one side of the reflective agent 16, which coating is preferably a lacquer. The light transmitting coating 18 is clear in the preferred embodiment of the invention but may, alternatively, be dyed or tinted to a desired color, or translucent.

With continued reference to the upper right hand corner of FIG. 9, it is seen that each of the laminate pieces 14 is bonded to the substrate 12 by a thin layer of adhesive 20 at the interface of the reflective agent 16 and the substrate 12. Thus, the reflective agent 16 is bonded to the substrate 12 on the bottom side 16a of the reflective agent 16 with the light transmitting coating 18 on the opposite, top side 16b of the layer of reflective agent 16. Accordingly, an observer viewing the material 10 from the upper side 22 of the composite material 10 will see light which passes through the thin layer of light transmitting coating 18, reflecting off the top side 16b of the reflective agent 16, and then back through the thin layer of light transmitting coating 18.

By defining the interface of the reflective agent 16 and the light transmitting coating 18 to a predetermined contour, a predetermined light diffraction pattern can be obtained. The pattern can have holographic or other light diffracting characteristics. This is preferably achieved by embossing a layer of light transmitting coating 18 to a desired contour and then coating the indentations formed by the embossing with reflective agent 16. This is the preferred method of manufacture of the laminate 14 due to the relatively low cost of production, and this preferred method of manufacture is described further, below. Other methods of defining the interface can also be employed without departing from the inventive concept of the present invention.

In this regard, it is necessary that the layer of light transmitting coating 18 be made sufficiently thick to accept an image formed therein capable of providing the desired light diffracting characteristics. Whereas in the prior art metalized patterns were bonded to substrates, with the metal having a thin coating of light transmitting material such as plastic or lacquer to protect the metal, the present invention provides for a thicker layer of light transmitting coating 18 to receive and retain a light diffracting impression therein. With current technology, it is necessary to form the light transmitting coating 2 microns thick since the impressions therein must be made between approximately 0.5 to 1.5 microns deep. With the metalized patterns of the prior art, the layer of light transmitting coating was for protective purposes only, and therefore kept to a minimal thickness, generally at most 0.5 microns thick, and there was no motivation to form the light transmitting coating any thicker than this.

In the preferred embodiment of the composite material 10, the pieces of laminate 14 are small, are generally uniform in size and shape, and are positioned close to one another, but with a spacing between each of the pieces of laminate 14. This allows the composite material 10 to flex freely at each of the spacings between the pieces of laminate 14. This is in contrast with continuous holograms and diffraction gratings applied to a flexible material which become stiff due to the increased thickness and limited flexibility associated therewith. The present invention allows these same holograms and diffraction gratings, which are stiff when applied as a continuous sheet, to be applied to a flexible material without significant loss of flexibility. The composite material 10 remains generally as flexible as the substrate 12 to which the laminate pieces 14 are bonded.

By providing a large number of small laminate pieces 14 having holographic or diffraction grating characteristics in a dense arrangement on a substrate 12, two advantages are realized. First, when the composite material 10 is viewed from a normal viewing distance, the overall image appears to be continuous, and without close examination it cannot be discerned that the material in fact includes a large number of spaced laminate pieces. This illusion of a continuous image is further enhanced by the startling optical effects which the pieces of hologram and diffraction grating materials produce. The multicolored, varying patterns produced by the laminate pieces 14 detract from the spacings between the pieces.

The second advantage of using a large number of closely positioned, small laminate pieces 14 is that this provides the greatest overall flexibility to the composite material 10. A large number of closely positioned, small laminate pieces 14 results in a large number of small spacings between the laminate pieces 14 which allows the composite material 10 to flex freely at each and all of such spacings.

Larger laminate pieces 14 reduce the number of spacings between the laminate pieces 14. Since the composite material 10 flexes significantly more freely at the spacings than at the pieces of laminate 14, larger laminate pieces reduce the number of locations at which the composite material 10 can flex most easily. Thus, with large laminate pieces 14, the composite material 10 does not flex virtually everywhere in the same manner as the substrate 12, but instead flexes only at certain relatively distant locations on the composite material

10. Contrarily, the provision of a large number of small laminate pieces provides a large number of spacings between the laminate pieces 14 which spacings are close to one another, so that the composite material 10 can flex almost anywhere just as easily as the substrate 12 to which the laminate pieces 14 are bonded.

Distant spacing of the laminate pieces 14 provides greater flexibility of the composite material 10 than does a dense arrangement; however, the benefit of such greater flexibility realized by distant spacings must be weighed against the loss of the appearance of continuity of the laminate which is realized by a viewer with relatively distantly spaced laminate pieces 14. Thus, to attain the optical effect of a continuous overall image, the laminate pieces 14 must be positioned relatively close to one another. However, it is appreciated that in certain applications it may be desirable to form an arrangement of laminate pieces 14 on the substrate 12 in which spacings between applied sections of laminate 14 are discernable, and such visible spacings may form a part of the overall artwork of the composite material 10.

Since hologram and diffraction grating materials only provide their stunning optical effects on one side thereof, specifically when viewed from the side of the light transmitting coating, it is necessary that each of the laminate pieces 14 be bonded to the substrate 12 with the reflective agent 16 adjacent the substrate 12. The preferred method and apparatus for carrying this out is illustrated in FIGS. 4-9 and will now be described in detail.

With reference now to the cross-sectional view of FIG. 8, a laminated application sheet 24 is formed having a sheet of carrier sheet 26, with a laminate 14 comprising a thin layer of reflective agent 16 and thin layer of light transmitting coating 18 adhered to the carrier sheet 26 by the thin layer of release agent 28. The application sheet 24 is preferably formed in a manner which allows the contour of the interface between the reflective agent 16 and the light transmitting coating 18 to be accurately defined, and which allows the reflective agent 16 and light transmitting coating 18 to be easily separated from the carrier sheet 26 when acted upon by sufficient separating force. Also, the carrier sheet 26 should be thin enough to readily allow heat transfer therethrough for those applications in which heat curing of the adhesive 20 is required, although in many applications heat curing may or may not be desired or required.

A sheet of carrier sheet 26 has a thin layer of release agent 28 applied across the upper surface 30 thereof. A layer of light transmitting coating 18, of the type known in the art which can accept an embossing therein and retain the shape of the embossing, is applied onto the release agent 28 and thereafter embossed to a predetermined contour. After the light transmitting coating 18 has set sufficiently, a reflective agent 16 is applied onto the light transmitting coating 18. The reflective agent may be silver, aluminum, or other suitable material and coats the grooves of the light transmitting coating 18 which were formed by the embossing. Due to the high cost of the reflective agent 16, it is not applied so thick as to fill the grooves, but merely lines the grooves. Hence, an application sheet 24 is formed which allows the carrier sheet 26 to be disengaged from the laminate 14 of reflective agent 16 and light transmitting coating 18 when separated by sufficient force.

While it is possible to first cut sheets of laminate 14 into small laminate pieces 14 and individually bond each of the separate pieces to the substrate 12, this is extremely time consuming and results in a relatively inaccurate arrangement of the laminate pieces 14 on the substrate 12. The preferred method of adhering pieces of the laminate 14 to the substrate 12, is to apply adhesive 20 to the bottom side 16a of the reflective agent 16 of a preformed application sheet 20 in a pattern corresponding to the shape and location desired for the ultimate arrangement of the laminate pieces 14 on the composite material 10. Alternatively, the desired pattern of adhesive can be applied to the substrate 12, or both the application sheet 24 and the substrate 12, as explained in detail further below.

By way of example, in the illustrated embodiment, a pattern of closely arranged circular dots of adhesive 20 are applied to the bottom side 16a of the reflective agent 16 of the application sheet 24 to produce a substantially identical pattern of closely spaced circular laminate pieces 14 on the substrate. Accordingly, a virtually limitless variety of different sizes and shapes of laminate pieces can be adhered to the substrate 12 as desired. The process and apparatus for carrying this out are described below.

After the adhesive 20 has been applied in the desired pattern to either the bottom side 16a of the reflective agent 16 of the application sheet 24 and/or to the substrate 12, the substrate 12 and application sheet 24 are then pressed together. This bonds the application sheet 24 to the substrate 12 at the locations of the adhesive 20, with adhesive being at discreet locations along the interface of the application sheet 24 and the substrate 12. The remainder of the interface between the application sheet 24 and the substrate 12 does not have adhesive 20 thereat and therefore is not bonded to the substrate 12. This is illustrated in the cross-sectional views of FIGS. 7 and 9. By employing an adhesive 20 at the interface of the application sheet 24 and substrate 12 which has a bonding strength greater than that of the release agent 28 which is at the interface of the laminate 14 and the carrier sheet 26, the layers of laminate 14 of reflective agent 16 and light transmitting coating material 18 at which the adhesive is located will continue to adhere to the substrate 12 upon pulling the carrier sheet 26 away from the substrate 12. The remainder of the layers of reflective agent 16 and light transmitting coating material 18, at which there is not any adhesive bonding to the substrate 12, remain adhered to the carrier sheet 26 when the carrier sheet 26 is pulled away from the substrate 12. Hence, pieces of laminate 14, having reflective agent 16 and light transmitting coating 18 layers, remain bonded to the substrate 12 in the identical pattern in which the adhesive 20 was applied. This is illustrated in FIG. 9 which shows in its upper, left hand corner an application sheet 24 adhered to a substrate 12 by circular dots of adhesive 20. When the application sheet 24 is then pulled away from the substrate 12, the reflective agent 16 and light transmitting coating 18 layers of the application sheet 24 at which adhesive was applied remain adhered to the substrate, while the remainder of the laminate 14 of the application sheet 24 not having adhesive thereat remains adhered to the carrier sheet 26. Thus, essentially, small sections of the reflective agent and light transmitting coating laminate 14 are ripped off the application sheet 24 due to the fact that the laminate 14 adheres to the surface to which it is more strongly bonded.

Since, as discussed above, the adhesive 20 is chosen to have a greater bonding strength than the release agent 28, those sections of the laminate 14 having adhesive bonding them to the substrate 12 will separate from the carrier sheet 26 and remain bonded to the substrate 12. In this regard it is important that the laminate 14 be formed sufficiently thin to allow small sections thereof internal of the perimeter to be ripped from the remainder of the laminate 14 under the influence of a pulling or shearing force less than or equal to the bonding force of the adhesive 20. Hence, provided that the laminate is formed thin enough, relatively little separating force pulling the carrier sheet 26 and substrate 12 apart is needed. The relatively minimal force required with the process and apparatus of the present invention, which force is exerted in bringing the substrate 12 and application sheet 24 together about the adhesive 20 and the small separating force required to pull the carrier sheet 26 and substrate 12 apart, is in contrast with the very large pressures employed in other processes. For instance, in hot foil stamping operations, a thin layer of foil is pressed upon with a metal hot stamp die to adhere the foil to a substrate. Forces in the range of 450 tons per square inch are required when utilizing this process, in contrast with the significantly lower pressures employed with the present method and apparatus. Also, with the hot foil stamping, a heat seal bonding agent is applied over the entire surface of the foil with only those portions acted upon by heat and high pressure being transferred to the substrate. Thus, with such prior art processes, the shape of the die applying the heat and pressure determines the configuration of the applied pattern. Contrarily, in accordance with the present invention, adhesive is applied to only selective portions of the application sheet with the configuration of the applied pattern being determined by the configuration in which the adhesive is applied. This allows patterns to be transferred in any desired pattern, without the requirement of producing a die specific to that pattern.

The application of the adhesive 20 is preferably carried out by employing the apparatus 40 illustrated in FIGS. 4 and 5. The apparatus 40 lends itself to simple and inexpensive construction as well as inexpensive operation. As discussed above, the adhesive 20 can be applied to either or both the substrate 12 and the bottom side 16a of the reflective agent 16. Thus, while in the preferred embodiment the adhesive is applied to the reflective agent 16 of the application sheet 24, and the apparatus for carrying out the preferred method of production is accordingly illustrated as applying adhesive 20 to the application sheet 24, it is appreciated that the adhesive 20 may be applied to either or both the application sheet 24 and the substrate 12. The illustrated apparatus 40 lends itself to adhesive application on either the application sheet 24 or the substrate 12, though only application of adhesive 20 to the application sheet 24 is shown. This is discussed further, below.

Adhesive is preferably applied by an adhesive applying roller 42, which may be formed of rubber or other suitable materials, and which has a plurality of protrusions 44 corresponding in size and shape to the desired size and shape of the laminate pieces 14 on the composite material 10. For instance, in producing dots or circular laminate pieces 14, the protrusions 44 would be made cylindrical or frustoconical to provide a circular tip 46. An enlarged view of the adhesive applying roller 42 is illustrated in FIG. 5. Also, the adhesive applying roller 42 may employ indentations therein rather protrusions to facilitate application of the adhesive, as will be discussed below.

With reference now to FIG. 4, a series of delivery rollers 48 are employed to deliver a generally continuous and consistent supply of adhesive 20 to the adhesive applying roller 42, similar to the delivery system employed in delivering ink to the printing roller in offset printing operations. Thus, the tips 46 of the protrusions 44 of the adhesive applying roller 42 abut the adjacent roller 52, which thereby leaves a thin layer of adhesive 20 on the tips 46 of the protrusions 44.

Since only a very thin layer of adhesive 20 is required to be applied, a doctor blade 50 is preferably employed to scrape off excess adhesive 20 from the adhesive applying roller 42 prior to contact of the roller 42 against either the application sheet 24 or the substrate 12.

As mentioned above, rather than employing protrusions 44, the adhesive applying roller 24 may, alternatively, include a plurality of indentations or recesses which receive adhesive therein and distribute the adhesive to the substrate 12 or reflective coating layer 16 of the application sheet 24 when pressed thereagainst.

Other adhesive application methods can just as easily be employed without departing from the inventive concepts of the present invention. The adhesive 20 should be applied thick enough to fill in the recesses formed in the light transmitting coating, which recesses have been only partially filled in by the reflective agent. The application sheet 24 is brought into contact with the adhesive applying roller 42. With continued reference to FIG. 4, the application sheet 24 is positioned so that the top side 52 of the application sheet 24, at which the reflective agent 16 is located, is adjacent the adhesive applying roller 42, whereby the adhesive is applied to the bottom side 16a of the reflective agent 16. That is, the application sheet 24 is fed between the adhesive applying roller 42 and a backing roller 53 so that the top side 52 of the application sheet 24 which is reflective agent 16, is pressed against the adhesive applying roller 42. The adhesive 20 on the tips 46 of the protrusions 44 is thus transferred to the application sheet 24 in a predetermined pattern corresponding to the pattern of the tips 46 of the protrusions 44 of the adhesive applying roller 42.

The adhesive 20 having been applied to the application sheet 24 in the desired pattern, the substrate 12 is then brought into contact with, and pressed against, the applied adhesive 20. Both the substrate 12 and the application sheet 24 having a pattern of adhesive thereon, are fed between pressing rolls 54, with the adhesive side of the application sheet 24 being adjacent the substrate 12. Accordingly, the pressing rolls 54 press the substrate 12 and adhesive 20 together to adhere the application sheet 24 to the substrate 12 at each of the locations at which adhesive was applied. This results in an intermediate stage composite material 56 as illustrated in enlarged cross section in FIG. 7. The application sheet 24 is thus bonded to the substrate 12 at each of the locations having adhesive 20, with the remainder of the application sheet 24 not directly bonded to the substrate 12.

The intermediate stage composite material 56 is then advanced to a separating roller 58 at which the substrate 12 and the carrier sheet 26 of the application sheet 24 are pulled in separate directions. An enlarged view of the separating roller and the separation of the materials is illustrated in FIG. 9.

Due to the fact that the adhesive 20 is chosen to have a greater bonding strength than that of the release agent 28, upon separation, the laminate 14 layer, comprising the light transmitting coating 18 and reflective agent 16 layers of the application sheet 24, remains adhered to the substrate 12 rather than remaining adhered to the carrier sheet 26. This is so only at the locations having adhesive 20 thereat. The remainder of the application sheet 24, not having adhesive thereon to bond to the substrate 12, remains adhered to the carrier sheet 26 due to the bonding force of the release agent 28. Hence, at each of the locations of the application sheet 24 at which adhesive 20 was applied, the light transmitting coating 18 and reflective agent 16 layers will remain adhered to the substrate 12 in a pattern corresponding to the pattern in which the adhesive 20 was applied to the application sheet 24 by the adhesive applying roller 42. Essentially, small portions of the laminate 14 are ripped from the interior of the application sheet 24 upon separation of the application sheet 24 from the substrate 12, as illustrate in FIG. 9. Thereafter, the composite material 10 is rolled onto a first take up roll 60, and the remainder of the application sheet 24 is taken up on a second take up roll 62.

While this application method, and the apparatus 40 for carrying it out, result in laminate pieces 14 having a jagged perimeter due to the ripping of the laminate pieces 14 from the interior of the application sheet 24, the jaggedness is minimal in relation to the remainder of the laminate pieces 14, and the jaggedness can only be seen upon very close inspection of the laminate pieces 14. Thus, while upon close inspection of the composite material 10, such as the enlarged view of FIG. 3, the jaggedness at the perimeter of the laminate pieces 14 can be seen, when viewed from a normal viewing distance the jaggedness is not discernable and the pattern appears more like that shown in FIG. 1.

As discussed above, this apparatus and method allows holograms and diffraction gratings to be formed on the substrate 12 with virtually limitless shapes and arrangements. By forming the tips 46 of the protrusions 44 of the adhesive applying roller 42 to the desired shape and spacing, the desired holographic or diffraction grating pattern can be applied to the substrate 12.

An overall holographic image can be formed on the substrate 12 by forming a hologram having a reflective surface 16 and a light transmitting coating 18 on a carrier. A dense pattern of adhesive, resulting in a dense pattern of pieces of the hologram on the substrate 12, will result in the appearance of an overall hologram on the substrate 12 even though much of the hologram remains adhered to the carrier. Hence, pictures or selective or random images can be formed on the substrate 12.

After the application sheet 24 has been run through the apparatus 40, with pieces of laminate 14 removed therefrom to form the composite material 10 of FIG. 1, the application sheet will then still have laminate 14 thereon in a pattern corresponding to the negative of the pattern of the laminate applied to the substrate in the first run. For instance, if a plurality of circular dots of laminate 14 are removed from the application sheet 24 and adhered to the substrate 12, the application sheet 24 will then have laminate 14 remaining thereon everywhere except for small circular holes removed therefrom. To minimize waste and provide full utilization of materials, the roll of used application sheet 64 is then run through the apparatus 40 in the manner illustrated in FIG. 6 to apply the pattern of remaining laminate 14 to a substrate 12. Hence, adhesive 20 is applied to the entire top side 52 of the application sheet 24, over both the remaining reflective agent 16 and the carrier sheet 26 at the locations at which the laminate has been removed. The substrate 12 is then pressed against the adhesive 20 to cause all the remaining laminate 14 of the application sheet 24 to adhere to the substrate 12. This forms a composite material having an image which is the negative of the image applied in the previous run. For instance, with the image of FIG. 1 applied during a first run, the second run will form the image of FIG. 2, which is the negative of FIG. 1.

Since in the first run a discontinuous pattern of dots or other shaped laminate pieces 14 are generally adhered to the substrate, to attain the greater flexibility realized with discontinuous patterns of laminate 14, the laminate 14 remaining on the application sheet 24 is an integral sheet. This integral sheet of laminate 14, when transferred to the substrate 12, does not provide the same degree of flexibility to the composite material as discontinuous patterns, and this second run method is thus generally employed only with substrates which do not require great flexibility. Of course, rather than remove the entire remainder of the laminate 14 from the application sheet 24 in the second run, alternatively only a portion of the remainder of the laminate 14 can be removed in the second run to form a desired pattern. This may be desirable in applications wherein flexibility is desired of the composite material of the second run. While the preceding discussions have focused on the preferred embodiment of the invention wherein adhesive is applied in a predetermined discontinuous pattern to form a corresponding predetermined laminate pattern on the substrate, it should be appreciated that the inventive concept is broader than this and readily lends itself to a very wide range of applications.

The application sheet 24 allows the light diffracting laminate 14 of light transmitting coating 18 and reflective coating 16 layers to be applied to substrates 12 in a variety of ways. The only requirement being that any bond formed between the laminate 14 and the substrate 12 be stronger than the bond formed between the laminate 14 and the carrier sheet 26.

By way of example, an adhesive 20 may be applied over the entire surface of the reflective coating layer 16 of the application sheet 24 which adhesive 20 has a lesser bonding strength than that of the release agent 28 until heat is applied to the adhesive 20. Such an adhesive 20 would then attain a greater bonding strength than the release agent 28. Accordingly, a user can place an application sheet 24, having this type of heat activated adhesive 20 applied over the reflective coating 16, onto a substrate 12 with the adhesive adjacent the substrate 12, and the application sheet 24 will initially not adhere to the substrate 12.

Thereafter, by applying heat to selective portions of the adhesive 20, those portions of the laminate 14 thereat will be bonded to the substrate 12 with a greater bonding strength than that of the release agent 28. Hence, upon subsequent separation of the application sheet 24 from the substrate 12, those portions of the laminate 14 at which the adhesive 20 was heat activated will remain bonded to the substrate 12 in the pattern of the heat application.

For instance, a heated stick-like element can be rubbed across the carrier sheet 26 to draw or write an image, whereby the adhesive 20 is heat activated in the pattern of the drawn or written image, and the light diffracting laminate 14 thereby bonded to the substrate 12 in that pattern. Upon separation of the application sheet 24 from the substrate 12, the light diffracting laminate 14 remains adhered to the substrate 12 in the pattern drawn or written, with the remainder of the laminate 14 not heated remains with the application sheet 24 upon separation. Additionally, by choosing an adhesive 20 which requires low heat for activation, the light difracting laminate 14 can be bonded to the substrate 12 by simply rubbing the carrier sheet 26 over the portions of the application sheet 24 at which it is desired to bond the light diffracting laminate 14 to the substrate 12, the rubbing creating friction sufficient to heat activate the adhesive 20 at the desired portions. While the invention has been described with reference to preferred embodiments, it will be understood to those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

Whs-b Is Claimed Is:

1. A method of treating flexible sheet material to provide a composite material having light diffracting characteristics which nevertheless retains substantial flexibility, comprising the steps of: providing a substrate comprising flexible sheet material; forming an application sheet, comprising the steps of: providing a carrier; coating the carrier sheet with a release agent having a predetermined bonding strength; applying a thin layer of light transmitting coating having the capacity to retain a predetermined surface contour onto the release agent; forming a predetermined light diffracting contour in the light transmitting coating; and applying a reflective coating onto the contour formed in the coating; applying an adhesive, having a bonding strength greater than that of the release agent, in a predetermined, discontinuous pattern to the reflective coating of the application sheet or to the substrate; adhering the application sheet to the substrate; curing the adhesive; and separating the application sheet from the substrate except in the areas where they are adhered, whereat the light transmitting coating and reflective coating layers of the application sheet remain bonded to the substrate.

2. The method of Claim 1 wherein the light transmitting coating is embossed to form the predetermined contour.

3. A composite material formed by the process of Claim 1.

4. A method of forming a flexible material having light diffracting characteristics, the method comprising: providing a substrate; forming a hologram laminate having a reflective coating side and a viewing side; releasably adhering the hologram laminate to a carrier sheet with a release agent having a predetermined bonding strength, with the viewing side of the hologram laminate being between the reflective coating side of the laminate and the carrier; applying an adhesive, having a bonding strength greater than that of the release agent, to the reflective coating side of the application sheet in a predetermined, discontinuous pattern; adhering the application sheet to the substrate; and separating the application sheet from the substrate except in the areas where they are adhered, whereat the hologram laminate of the application sheet remains bonded to the substrate.

5. A material formed by the process of Claim

11.

6. A method of forming a composite material having light diffracting characteristics, comprising the steps of: providing a substrate; providing an application sheet which comprises: forming a laminate of light transmitting coating and reflective coating which define a predetermined contour at the interface thereof to provide predetermined light diffracting characteristics, the laminate having a plurality of apertures therein; and adhering the laminate to a carrier sheet by a release agent of predetermined bonding strength, with the light transmitting coating layer of the laminate adjacent the carrier, the application sheet thus having a reflective coating layer and carrier sheet layer on opposite sides thereof; applying adhesive, having a bonding strength greater than that of the release agent, over the entire surface of the reflective coating layer of the application sheet; adhering the application sheet to the substrate; and separating the application sheet from the substrate with the laminate layers thereof remaining bonded to the substrate.

7. A method of transferring a light diffracting image to a substrate, comprising the steps of: providing an application sheet which comprises: providing a layer of light transmitting coating of sufficient thickness to receive and retain an impression therein defining light diffracting characteristics; forming a predetermined contour in said light transmitting coating to provide the desired light diffracting characteristics thereto; applying a thin layer of reflective coating to the contoured surface of the light transmitting coating; and adhering the laminate of light transmitting coating and reflective coating to a carrier sheet_^ by a release agent of predetermined bonding strength, with the light transmitting coating layer of the laminate adjacent the carrier, the application sheet thus having a reflective coating layer and carrier sheet layer on opposite sides thereof; adhering selective portions of the reflective coating side of the application sheet to the substrate, with a bond of greater strength than that of the release agent; and separating the application sheet from the substrate except in the selective areas where they are adhered, whereat the light diffracting laminate of the application sheet remains bonded to the substrate.

8. An apparatus for treating flexible sheet material to provide a composite material having light diffracting characteristics which nonetheless retains substantial flexibility, comprising: means for forming an application sheet, comprising: means for coating a carrier sheet with a release agent having a predetermined bonding strength; means for applying a thin layer of light transmitting coating having the capacity to retain a predetermined surface contour onto the release agent; means for forming a predetermined surface contour in the coating to define a predetermined light diffraction; means for applying a thin layer of reflective agent onto the formed surface contour of the coating; means for applying an adhesive, having a bonding strength greater than that of the release agent, in a predetermined, discontinuous pattern to the substrate or the reflective agent surface of the application sheet; means for adhering the application sheet to the substrate; and means for separating the application sheet from the substrate except in the areas where they are adhered, whereat the light transmitting coating and reflective coating layers of the application sheet remain bonded to the substrate.

9. A flexible material having light diffracting characteristics, comprising: a substrate; a plurality of discrete pieces of holographic laminate, each of said laminate sections comprising: a thin layer of transparent material having a predetermined contour formed therein which defines the desired holographic image; and a thin layer of reflective material coating the contour formed in the layer of transparent material; and said pieces of holographic laminate being bonded to said substrate in a predetermined pattern with the reflective coating layer adjacent the substrate.

10. An application sheet for transferring a light diffracting laminate to a substrate, .the application sheet comprising: a light diffracting laminate, comprising: a layer of light transmitting coating having a predetermined contour formed therein, the light transmitting coating being of sufficient thickness and the contour formed sufficiently deep therein to provide light diffracting characteristics; and a layer of reflective material coating the contour formed in the light transmitting coating; and a carrier sheet adhered to the reflective material side of the light diffracting laminate with a low bonding strength.