Use of patterned reflective transfer foils recording materials

Abstract: A known hologram material (Fig. 1a) has a reflecting layer (2) having a fine dimple pattern (embossed by a stamper) on its surface and is adhered (5) to a substrate (6); portions of the reflective layer are selectively heated by heating means (8) so as to become non-reflective and form a recording of information (Fig. 1b). A hologram transfer foil (Fig. 2) consists of a base film (24) bearing a release layer (23), a hologram layer (21) of thermoplastic transparent resin, and a reflective metal film (22), and optionally a protective resin layer (28) thereon (Fig. 3). The hologram is selectively transferred by the application patternwise of an adhesive material (29, Fig.4) on substrate (2b) and placing of its reflective layer (22) thereon and peeling off the base film (24). Heat-activated, solvent-activated or pressure-sensitive adhesives are usable. Ink patterns can be used to add the transfer. The release layer has a peel strength of 1 to 5g/inch.

Description: BACKGROUND OF THE INVENTION The present invention relates to an information recording method wherein information recorded on a transfer foil is transferred to a substrate by a thermal recording head, for example, and information that is different from the information originally recorded on the transfer foil is recorded and displayed on the portion of the substrate where the original information has been transferred. Holograms, in which information is recorded generally in the form of interference patterns of light, are used in various fields as high-density information recording media for recording and displaying two- and three-dimensional images and other information. Among them, relief holograms are formed in such a manner that a holographic interference fringe pattern is recorded in the form of a dimple pattern on a photoresist, for example, and the dimple pattern is transferred by plating, for example, to form a stamper, which is then stamped on a transparent thermoplast resin material with or without a reflecting layer of a metal or the like formed on the surface thereof, thereby making a large number of duplicates. Relief holograms wherein a reflecting layer, e.g., a metal layer or a high refractive index layer, is provided on the relief surface and an image is reconstructed by light reflected and diffracted by the reflecting layer include two different types, in one of which the incident light is reflected substantially completely by the reflecting layer, while in the other part of the incident light is reflected to reconstruct a hologram image on a background of transmitted light. In this application, these two types are included in the reflection relief holograms. In addition, another type of relief hologram in which the dimple pattern comprises phase diffraction grating patterns properly arranged is also considered to be included in the reflection relief holograms. A typical reflection relief hologram has a sectional structure shown in Fig. 2 and it comprises a hologram layer 1 of a thermoplastic resin material or the like and a reflecting layer 2 formed on a dimple interference fringe surface (i.e., relief surface) defined by the surface of the hologram layer 1. The reflecting layer 2 comprises either a deposited metal film, e.g., aluminum or tin, or a high refractive index transparent film, e.g., zinc sulfide. With a deposited metal film, a reflection relief hologram that reflects the incident light substantially completely by the metal is formed. With a high refractive index transparent film, the resulting reflection relief hologram is of the type in which part of the incident light is reflected to reconstruct a hologram image on a background of transmitted light because of Fresnel reflection based on the refractive index difference between the hologram layer 1 and the reflecting layer 2. Such a reflection relief hologram may be produced by either of the following two methods: one in which holographic information is recorded in the form of a dimple pattern on a photoresist, for example, and the dimple pattern is transferred by plating, for example, to form a stamper, which is then stamped on a transparent thermoplastic resin material that constitutes a hologram layer 1 to duplicate the dimple pattern, and a reflecting layer 2 is formed on the duplicated dimple pattern by deposition or the like; and the other in which a reflecting layer 2 is previously formed on a transparent resin layer that forms a hologram layer 1, and a stamper formed with the above-described dimple pattern is hot-stamped on the reflecting layer 2 to duplicate the dimple pattern (for example, see Japanese Patent Application Laid-Open (KOKAI) No. 58-65466 (1983)). Incidentally, such a reflection relief hologram can be arranged in the form of a transfer foil (for example, see Japanese Patent Application Laid-Open (KOKAI) No. 01-283583 (1989)). Fig. 3 shows a section of the transfer foil. In order to enable the reflection relief hologram shown in Fig. 2 to be transferable, a base film 4 of PET (polyethylene terephthalate) or the like is provided on the side of the hologram layer 1 opposite to the side thereof where the reflecting layer 2 is provided, through a release layer 3 of wax or the like, and a heat-sensitive adhesive layer 5 of a vinyl chloride resin or the like is provided on the reflecting layer 2. The hologram layer 1 and the reflecting layer 2 in a desired profile region of a transfer foil having the above-described arrangement may be transferred to a substrate of vinyl chloride, for example, by using, for example, a thermal recording head or a hot stamper, as follows: The transfer foil is set in between a substrate 6 to which the hologram is to be transferred and a thermal recording head or not stamper 7 such that the heat-sensitive adhesive layer 5 faces the substrate 6, while the base film 4 faces the thermal recording head or hot stamper 7, and in this state the thermal recording head 7 is driven or the hot stamper 7 is pressed under heating. Thus, the reflection relief hologram has heretofore been transferred to the substrate 6, e.g., a card, as shown in Fig. 4, to display visible information, e.g. a mark, an image, etc., on a card or the like. However, it has been impossible to record and display in the transfer region image information, character information, etc., other than the information originally recorded on the transfer foil. EP-A-0 328 086 discloses a resin layer having a fine dimple pattern, e.g., a relief hologram on the surface thereof; a reflecting layer formed on the dimpled surface of said resin layer; and a releasable base film stacked on the side of said resin layer which is opposite to the side thereof where said reflecting layer is provided. EP-A-0 420 261, which is prior art under Article 54(3) EPC, discloses an information recording method similar to the present invention, but does not specify the use of a thermal head as a heating means. In view of the above-described circumstances, it is an object of the present invention to provide a method of adding to a hologram, transferred from a reflection relief hologram of the type described above, information, for example, an image or a character, other than the information originally recorded on the reflection relief hologram. To attain the object, the invention provides an information recording method comprising a step of preparing a transfer foil having a reflection relief hologram comprising at least a resin layer having a fine dimple pattern of a relief hologram or a relief diffraction grating formed on the surface thereof, and a reflecting layer formed on the dimpled surface of the resin layer, at least a part of the reflection relief hologram being formed as a transferable region; a step of transferring a predetermined portion of the transferable region to the surface of an object to which information is to be transferred; and a step of heating at least a part of the transferred portion with a thermal head, thereby destroying the reflecting layer, wherein said part of the transferred portion represents information, such as an image or character other than the information originally recorded on the reflection relief hologram, to the transferred hologram. The invention also provides an information recording method comprising a step of preparing a transfer foil having a reflection relief hologram comprising at least a resin layer having a fine dimple pattern of a relief hologram, a relief diffraction grating formed on the surface thereof, and a reflecting layer formed on the dimpled surface of the resin layer, at least a part of the reflection relief hologram being formed as a transferable region, a step of transferring a predetermined portion of the transferable region to the surface of an object to which information is to be transferred; and a step of heating at least a part of the transferred portion with a thermal head, thereby smoothing a dimple pattern formed by the surface of the resin layer and the reflecting layer, wherein said part of the transferred portion represents information, such as an image or character other than the information originally recorded on the reflection relief hologram, to the transferred hologram. According to the invention, it is possible to add information, e.g., an image or a character, other than information originally recorded on a reflection relief hologram by preparing a transfer foil having a reflection relief hologram comprising a resin layer and a reflecting layer, at least a part of the reflection relief hologram being formed as a transferable region, transferring a predetermined portion of the transferable region to the surface of an object to which information is to be transferred, and heating at least a part of the transferred portion with a heating means, thereby destroying the reflecting layer, or smoothing a dimple pattern formed by the surface of the resin layer and the reflecting layer. Thus, it is possible to diversify the recording and display forms of hologram transfer foils. Still other objects and advantages of the invention will in part by obvious and will in part be apparent from the specification. The invention accordingly comprises the features of construction, combinations of elements, and arrangements of parts which will be exemplified in the construction hereinafter set forth. In the accompanying drawings: Fig. 1 illustrates the information recording method according to the invention; Fig.2 shows a sectional structure of a typical reflection relief hologram; Fig.3 shows a sectional structure of the reflection relief hologram shown in Fig.2, which is arranged in the form of a transfer foil; and Fig.4 illustrates the way in which the transfer foil shown in Fig.3 is transferred by using a thermal recording head. Embodiments of the invention of this application will be described below with reference to the accompanying drawings. First, the information recording method of the invention will be explained with reference to Fig.1. Fig.1(a) shows a reflection relief hologram 10 transferred to the surface of a substrate 6. A hologram with a desired profile, which comprises a hologram layer 1 and a reflecting layer 2, is bonded to the surface of the substrate 6 by a heat-sensitive adhesive layer 5, as described above, and has image information 11 recorded thereon, as shown in the plan view of Fig.1(b). With a thermal recording head 7 pressed against such a transferred hologram region again, desired ones of the heating elements 8 are driven. In consequence, respective portions of the hologram layer 1 and the reflecting layer 2 which correspond to the driven heating elements 8 are heated rapidly. By the heating, the metal or other material constituting the thin reflecting layer 2 is melted and then cracks finely because of surface tension, thus losing its reflecting properties. As a result, this portion of the substrate 6 can be seen through the reflecting layer 2. Accordingly, if the substrate 1 is colored in advance, for example, and the heating elements 8 are selectively driven sequentially on the basis of information desired to record, information 12, for example, a character or an image, can be recorded and displayed in addition to the information 11 originally recorded on the hologram. It should be noted that the reflecting layer 2 is selectively evaporated and information is thus recorded when the heat temperature applied by the heating means is high, or depending upon the material or thickness of the reflecting layer 2. Even if the reflecting layer 2 is not destroyed, the dimpled surfaces of the hologram layer 1 and the reflecting layer 2 return to the flat surfaces because of melt softening and the hologram in a selected region is erased, so that the selected region becomes different in contrast, color, etc. from the other region, thus enabling information to be recorded and displayed in the same way. The following is a description of a material for each of the layers of the reflection relief hologram arranged in the form of a transfer foil and an embossing method employed. As a material for the base film 4, biaxially oriented polyethylene terephthalate film is most preferable from the viewpoint of dimensional stability, heat resistance, toughness, etc. Other materials usable for the base film 4 are synthetic films such as polyvinyl chloride film, polypropylene film, polyethylene film, polycarbonate film, regenerated cellulose, Vinylon (trademark) film, acetate film, nylon film, polyvinyl alcohol film, polyamide film on a polyamide-imide film, and paper such as condenser paper. The thickness of the base film 4 is preferably of the order of 6 µm to 12 µm. The release layer 3 is provided for the purpose of improving release characteristics and foil breaking characteristics. For the release layer 3, various known materials can be used in accordance with the kind of the base film 4, for example, polymethacrylate resin, polyvinyl chloride resin, cellulose resin, silicone resin, wax containing hydrocarbon as a principal component, polystyrene resin, chlorinated rubber, casein, various kinds of surface-active agent or metallic oxides, etc. These materials can be used alone or in the form of a mixture of two or more so that the peel strength of the release layer 3 is 1 g/inch to 5 g/inch (peeling at 90 degrees)) in combination with the base film 4. With these materials, the release layer 3 may be formed as a thin film on the base film 4 by a known method, for example, by coating the material in the form of ink. The thickness of the release layer 3 is preferably in the range of from 0.1 µm to 1.0 µm when the peel strength and foil breaking characteristics are taken into consideration. For the hologram layer 1, various kinds of resin material can be selected with the foil breaking characteristics and transfer heat resistance taken into consideration. Specific examples of materials usable for the hologram layer 1 are unsaturated polyester resin, acryl urethane resin, epoxy modified acrylic resin, epoxy modified unsaturated polyester resin, acrylic ester resin, acrylamide resin, nitrocellulose resin, polystyrene resin, alkyd resin, or phenolic resin, etc. These materials may be used alone or in the form of a mixture of two or more. It is also possible to add to these materials a proper amount of a heat- or ultraviolet- curing agent selected from among isocyanate resins, metallic soaps such as cobalt naphthenate and lead naphthenate, peroxides such as benzoyl peroxide and methyl ethyl ketone peroxide, benzophenone, acetophenone, anthraquinone, naphthoquinone, azobisisobutyronitrile and diphenyl sulfide. These materials are blended together so that the glass transition temperature is higher than the heat temperature applied during the heat transfer process. Specifically, it is preferable that the glass transition temperature should be 100°C to 200°C. The hologram resin layer 1 can be formed by coating the material in the form of ink according to a known method. When it is considered that the foil breaking characteristics (film breaking strength) should be set in the range of from 0.5 g/inch to 1.0 g/inch, the thickness of the hologram resin layer 1 is preferably in the range of from 0.5 µm to 2.0 µm. A reflective thin film layer for forming the reflecting layer 2 is provided on the surface of the hologram resin layer 1 by deposition, sputtering, ion plating, electrolytic plating, electroless plating, etc. using a metal, a metallic compound, glass, etc. In the case of a reflection hologram, a metal thin film that reflects light is employed as the reflective thin film layer 2, whereas in the case of a transparent hologram, a holographic effect thin film is employed which exhibits holographic effect in combination with the resin layer 1 and which does not conceal the underlying layer. Thus, the reflective thin film may be properly selected according to the purpose. Specific examples of metal thin films usable for a reflection hologram are metals such as Cr, Ti, Fe, Co, Ni, Cu, Ag, Au, Ge, Al, Mg, Sb, Pb, Pd, Cd, Bi, Sn, Se, In, Ga, Rb, and oxides and nitrides of these metals. These materials may be used alone or a combination of two or more. Among the above-mentioned metals, Al, Cr, Ni, Ag and Au are particularly preferable. The film thickness is preferably 10 Å to 10,000 Å, more preferably 200 Å to 2,000 Å. The holographic effect thin film that is employed for a transparent hologram may be made of any material as long as it transmits light so that the holographic effect can be exhibited. Examples of such material include a transparent material which is different in refractive index from the resin layer 1, and a reflective metal thin film layer having a thickness of not larger than 200 Å. In the case of the former, the refractive index may be either larger or smaller than that of the resin layer 1, but the refractive index difference is preferably 0.1 or more, more preferably 0.5 or more. According to an experiment carried out by the present inventors, a refractive index difference of 1.0 or more is the most suitable. By providing a transparent thin film layer 2 that is different in refractive index from the resin layer 1, the required holographic effect can be exhibited and, at the same time, the underlying layer can be seen through the layer 2. In the case of the latter, although it is a reflective metal film layer, since the thickness is not larger than 200 Å, the light wave transmission factor is large, so that the required holographic effect can be exhibited and, at the same time, the underlying layer can be seen through the layer 2. By setting the film thickness at 200 Å or less, the incongruity in the appearance that has heretofore been given by silver gray of high brightness is eliminated. Examples of materials usable for the thin film layer 2 include those described below (1) to (6). (1) Transparent continuous thin films having a larger refractive index than that of the resin layer 1: This type of thin film include those which are transparent in the visible region and those which are transparent in either the infrared or ultraviolet region. The former materials are shown in Table 1 below, and the latter materials in Table 2 below. In the Tables n denotes refractive index (the same is the case with the materials (2) to (5)). Materials which are transparent in either the infrared or ultraviolet region Materials n CdSe 3.5 CdTe 2.6 Ge 4.0 to 4.4 HfO 2 2.2 PbTe 5.6 Si 3.4 Te 4.9 TlCl 2.6 ZnTe 2.8 (2) Transparent ferroelectric materials having a larger refractive index than that of the resin layer 1 are shown in Table 3 below. (3) Transparent continuous thin films having a smaller refractive index than that of the resin layer 1 are shown in Table 4 below. Materials n LiF 1.4 MgF 2 1.4 3NaF·AlF 3 1.4 AlF 3 1.4 NaF 1.3 GaF 2 1.3 (4) Reflective metal thin films having a thickness of not larger than 200 Å. Reflective metal thin films have a complex index of refraction, which is expressed by n=n-iK, where n is refractive index, and K is absorption coefficient. Materials of reflective metal thin film layers usable in the first invention are shown in Table 5 below, together with n and K. Materials n K Be 2.7 0.9 Mg 0.6 6.1 Ca 0.3 8.1 Cr 3.3 1.3 Mn 2.5 1.3 Cu 0.7 2.4 Ag 0.1 3.3 Al 0.8 5.3 Sb 3.0 1.6 Pd 1.9 1.3 Ni 1.8 1.8 Sr 0.6 3.2 Ba 0.9 1.7 La 1.8 1.9 Ce 1.7 1.4 Au 0.3 2.4 It is also possible to use other materials such as Sn, In, Te, Fe, Co, Zn, Ge, Pb, Cd, Bi, Se, Ga or Rb. In addition, oxides and nitrides of the above-mentioned metals can be used alone or a combination of two or more. (5) Resins which are different in refractive index from the resin layer 1: The refractive index of these resins may be either larger or smaller than that of the resin layer 1. Examples of such resins are shown in Table 6 below. Resins n Polytetrafluoroethylene 1.35 Polychlorotrifluoroethylene 1.43 Vinyl acetate resin 1.46 Polyethylene 1.52 Polypropylene 1.49 Methyl methacrylate 1.49 Nylon 1.53 Polystyrene 1.60 Polyvinylidene chloride 1.62 Vinyl butyral resin 1.48 Vinyl formal resin 1.50 Polyvinyl chloride 1.53 Polyester resin 1.55 Phenol-formalin resin 1.60 It is possible to use ordinary synthetic resins in addition to the above, and it is particularly preferable to use a resin which is largely different in refractive index from the resin layer 1. (6) Laminates obtained by suitably combining the materials (1) to (5): The materials (1) to (5) may be combined with each other as desired, and the positional relationship between the layers of a laminate may be selected as desired. Of the thin film layers (1) to (6), the thin film layer (4) has a thickness of not larger than 200 Å, whereas the thickness of the thin film layers (1) to (3), (5) and (6) may be determined as desired as long as the material forming the thin film is transparent in the relevant spectral region; in general, the thickness is preferably 10 Å to 10,000 Å, more preferably 100 Å to 5,000 Å. When the thin film layer 2 is made of any of the materials (1) to (4), the holographic effect layer 2 can be formed on the resin layer 1 by using a conventional thin film forming means, e.g., vacuum deposition, sputtering, reactive sputtering, ion plating, electrolytic plating, etc., whereas, when the thin film layer 2 is made of the material (5), a conventional coating method can be employed. When the thin film layer 2 is made of the material (6), the above-mentioned means and methods may be properly combined together. In the invention, the thickness of the holographic effect layer 2 is preferably 100 Å to 600 Å, in general. If the thickness is less than 100 Å, the reflecting effect becomes inadequate, whereas, if the thickness exceeds 600 Å, the embossing characteristics lower considerably. A stamper for embossing such a transfer foil can be produced by a known method. However, the stamper needs high pressure resistance and satisfactorily high hardness and tensile strength because a fine dimple pattern on the surface thereof must be pressed into the mating substrate completely. For this reason, it is most suitable to obtain a stamper by electrolytic Ni plating method. The emboss substrate (comprising the base film 4, the release layer 3, the hologram layer 1 and the reflecting layer 2) and the stamper, which are obtained as described above, are put one on top of the other in such a manner that the reflecting layer 2 of the substrate film and the dimpled surface of the stamper are brought into contact with each other, and are then heat-pressed, thereby transferring the dimple pattern to both the reflecting layer 2 and the resin layer 1. Thereafter, a heat-sensitive adhesive layer 5 of a vinyl chloride resin or the like is provided on the reflecting layer 2 to complete a transfer foil. Example 1: A release layer of wax with a peel strength of 5 g/inch was provided to a thickness of 0.5 µm on the surface of a base film of PET having a thickness of 12 µm, and a hologram layer of acryl urethane resin with a thickness of 1.0 µm was coated on the release layer. Further, aluminum was evaporated to a thickness of 300 Å on the hologram layer to obtain a laminate for duplicate. A relief hologram stamper formed by nickel plating was pressed under heating against the reflecting layer side of the laminate to make a duplicate of the relief hologram. Thereafter, a heat-sensitive adhesive layer of a vinyl chloride-acetate resin was coated to a thickness of 3 µm on the duplicate side of the laminate and then dried to thereby produce a reflection relief hologram transfer foil. Then, the hologram transfer foil obtained in this way was laid on a PET film (188 µm) coated at the surface thereof with a vinyl chloride-acetate resin, and heat transfer was effected at 0.6 mJ/dot by using a thin-film thermal head (8 dots/mm). The transfer printed section thus obtained was superior in the foil breaking characteristics, adhesion, etc., and all the dots were resolved. The transfer printed section with the above-described contents was heated again at 1.0 mJ/dot with the thermal head. In consequence, the release layer, the resin layer and the reflecting layer in the reheated portion were melted and destroyed, and the reflecting layer disappeared in the reheated pattern. When the reheating was carried out with a printing energy of 0.2 mJ/dot, the reflecting layer was not melted, but the hologram pattern alone disappeared. As has been described above, according to the information recording method of the invention, it is possible to add information, e.g., an image or a character, other than information originally recorded on a reflection relief hologram by preparing a transfer foil having a reflection relief hologram comprising a resin layer and a reflecting layer, at least a part of the reflection relief hologram being formed as a transferable region, transferring a predetermined portion of the transferable region to the surface of an object to which information is to be transferred, and heating at least a part of the transferred portion with a heating means, thereby destroying the reflecting layer, or smoothing a dimple pattern formed by the surface of the resin layer and the reflecting layer. Thus, it is possible to diversify the recording and display forms of hologram transfer foils.

Claims: An information recording method comprising a step of preparing a transfer foil having a reflection relief hologram (10) comprising at least a resin layer having a fine dimple pattern (1) of a relief hologram or a relief diffraction grating, formed on the surface thereof, and a reflecting layer (2) formed on the dimpled surface of said resin layer, at least a part of said reflection relief hologram being formed as a transferable region; a step of transferring a predetermined portion of said transferable region to the surface of an object to which information is to be transferred; and a step of heating at least a part of the transferred portion with a thermal head (7), thereby destroying said reflecting layer wherein said part of the transferred portion represents information (12), such as an image or character other than the information (11) originally recorded on the reflection relief hologram, added to the transferred hologram. An information recording method comprising a step of preparing a transfer foil having a reflection relief hologram (10) comprising at least a resin layer having a fine dimple pattern (1) of a relief hologram or a relief diffraction grating, formed on the surface thereof, and a reflecting layer (2) formed on the dimpled surface of said resin layer, at least a part of said reflection relief hologram being formed as a transferable region; a step of transferring a predetermined portion of said transferable region to the surface of an object to which information is to be transferred; and a step of heating at least a part of the transferred portion with a heat thermal head (7), thereby smoothing a dimple pattern formed by the surface of said resin layer and said reflecting layer wherein said part of the transferred portion represents information (12), such as an image or character other than the information (11) originally recorded on the reflection relief hologram, added to the transferred hologram.

Inventors: TAHARA SHIGEHIKO, TAHARA, SHIGEHIKO, Tahara, Shigehiko, c/o Dai Nippon Printing Co.
Applicants: DAINIPPON PRINTING CO LTD, DAI NIPPON PRINTING CO., LTD.
Application year: 1992
Main classification: G03H1
IPC codes: G03H1