JP2013164491A - Hologram image forming body and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which: when a material having a refractive index higher than that of a low refractive index material that forms a relief type diffraction grating is transferred to the relief type diffraction grating, diffraction efficiency changes depending on a difference of the refractive index; by taking advantage of the change in efficiency, unit elements made of a high refractive index material are arranged on relief structure of a low refractive index material on the basis of image information so as to form a hologram image having brightness gradation; in this case, in order to transfer a hologram transfer body to a transferred body to form an image, a printer using ink including pigment or dye cannot transfer the hologram transfer body, and therefore, a dedicated printer is required.SOLUTION: Several types of unit elements made of a material having a refractive index higher than that of a relief structure-type diffraction grating made of a low refractive index material are arranged on the relief structure-type diffraction grating so as to control diffraction efficiency, and thereby a hologram image having brightness gradation in diffraction light is formed.

Description

  According to the image on the diffraction grating surface of a hologram forming layer having a relief type diffraction grating structure of a low refractive index material, this patent has several refractive index unit elements having a refractive index higher than that of the hologram forming layer material. The present invention relates to a hologram forming body that forms a hologram image by arranging.

  Holograms are very often used in fields that require a high degree of security. For example, as an example used in a passport, individual character information such as name and nationality is converted into character information as a character image in addition to a face image. Then, an ink image is created, and the image receiving sheet is transferred to a passport to print individual information on the passport. When a thermal transfer image receiving sheet is used, a high quality image can be provided without being influenced by the paper quality of a passport as a transfer target.

  However, since security is weak only with an ink image, a technique of increasing security by using it for a thermal transfer sheet on which a hologram is formed is often used. An example of the structure of a thermal transfer image receiving sheet on which a hologram is formed is shown in FIG. As shown in the figure, the thermal transfer image-receiving sheet containing a hologram has a structure in which a peeling layer, a hologram layer, and an image-receiving layer are laminated on a substrate in this order. A hologram image is formed by partially forming a relief structure on the hologram layer. In order to obtain a higher-brightness hologram, a reflective layer may be formed at the interface between the hologram layer and the image receiving layer, thereby increasing the diffraction efficiency of the relief structure and providing a high-brightness hologram image.

  In the structure of the thermal transfer image receiving sheet having such a structure, it is very difficult to change the formed hologram image. Therefore, in order to further enhance the security, the hologram transfer body in which the diffraction grating is uniformly formed in addition to the ink image is used. There is also a method of forming a hologram image by arranging holograms in the form of element pieces. In this method, in addition to the ink image, the hologram image is also different for each transfer target, so that forgery is difficult and security is significantly improved (Patent Document 1).

JP 2005-234559 A

  By locally heating a hologram transfer body having a uniform diffraction grating forming surface as shown in FIG. 2, it is possible to transfer the hologram transfer element to the transfer object in an elemental manner. The hologram image can be formed by performing according to the above. As shown in FIG. 2, the hologram transfer body has a multilayer structure. Further, by optimizing the conditions of materials and transfer energy, it is possible to prevent the diffraction grating from being broken by heat during transfer.

Embossing is often used to form a diffraction grating. In this method, the diffraction grating mold is formed by applying heat to the sheet-shaped resin, pressing the diffraction grating mold against the resin, and removing the mold when the mold is formed. Therefore, since it is difficult to peel off the mold when embossed on a substrate of several microns as used in an ink sheet, a substrate having a thickness of 10 microns or more is required. On the other hand, when transferring the formed diffraction grating, the superheater that can be locally heated from the direction of the substrate in FIG. Melt and transfer to transfer target. For example, when transferring according to image information, an element transfer body transferred by local heating becomes one pixel constituting the image. When the base material of the transfer body is thick, heat is not easily transmitted to the transfer body, so that the energy required for transfer is larger than that of the ink sheet. In such a case, since a conventional printer designed for an ink sheet cannot supply sufficient energy to the hologram transfer body, the transfer of the hologram becomes very difficult. In addition, when very high energy is supplied to the transfer body, the amount of energy diffused to the transfer body also increases, and the temperature increases over a wide range. If this happens, the intended local transfer cannot be performed, and an image with high resolution cannot be realized.

  From the viewpoint of manufacturing an ink sheet and a hologram transfer body, it is very difficult to form both of these on a single sheet from a technical and cost standpoint. In order to form a hologram image, a dedicated printer or printer unit for transferring the hologram transfer member is required in addition to the hologram transfer member and the printer for printing the ink image.

  In view of the above problems, the present invention newly forms an image in which an ink image and a hologram image are formed without preparing a printer dedicated to a hologram transfer sheet and without preparing a hologram transfer member separately from the ink sheet. It is about the body.

  As means for solving the above problems, the invention according to claim 1 is characterized in that one or more kinds of refractive indexes higher than the refractive index of the hologram forming layer are formed in the diffraction grating forming portion of the hologram forming layer having the relief type diffraction grating structure. A hologram image forming body characterized in that unit gradations of materials are arranged according to image information, and brightness gradation is expressed by utilizing the diffraction efficiency of the diffraction grating depending on the refractive index difference between the hologram forming layer and the unit element. is there.

  The invention according to claim 2 is the hologram image forming body, wherein the hologram forming layer has a refractive index of 1.4 or less.

  The invention described in claim 3 is characterized in that, in the material used in the unit element, the refractive index of the material having the smallest refractive index is 0.1 or more of the refractive index of the hologram forming layer. 3. A hologram image forming body according to claim 1 and claim 2.

  The invention according to claim 4 is the hologram image forming body according to any one of claims 1, 2, and 3, wherein the hologram forming layer and the unit element both have an internal transmittance of 80% or more.

  Further, the invention according to claim 5 is provided with a base material, and a hologram forming layer composed of the material according to claim 2 and 4 in a state that can be brushed on one side of the base material. Is a hologram image forming method for producing a hologram image by transferring at least one unit element according to claim 3 to a relief structure formed on the opposite surface according to image information.

  The reflectivity at the interface of different refractive index materials depends on the difference in refractive index, and the reflectivity increases as the difference in refractive index increases. By utilizing this property, unit elements of several kinds of refractive index materials higher than the refractive index of this layer material are applied to a layer of a low refractive index material having a relief type diffraction grating structure (referred to as a hologram forming layer) according to image information prepared in advance. Deploy. By controlling the luminance by the difference in refractive index between the hologram forming layer and each unit element, a hologram image having luminance gradation is formed. Usually, a ribbon for forming an ink image is manufactured by applying a colored resin. The high refractive index material layer, which is an element of the present invention, can also be formed on the same substrate as the ink ribbon by applying a high refractive index resin.

  The most general method for forming such an image forming body is a method of transferring a unit element of a high refractive index material to a hologram forming body of a low refractive index material. Hereinafter, the present invention will be described taking transfer as an example of the image forming method.

  Since this method does not require a multilayer structure such as a hologram transfer body as a unit element, it is not necessary to increase the thickness of the transfer body itself as well as the base material, so it can be transferred to a transfer target with a printer for ink image printing. It is. Further, as described above, since it can be formed on the same ribbon as the ink, it is possible to form an ink image and a hologram image with one printer.

  Since the hologram diffraction efficiency can be increased as the refractive index difference between the hologram forming layer and the high refractive index transfer body is larger, the number of brightness gradations can be increased. As a practical method for forming a sheet, coating is generally used. Looking at the refractive index of high-refractive-index materials that can be coated, there are materials used in the core of plastic optical fibers (refractive index of about 1.9), and hologram forming layer materials are materials used in plastic optical fiber cladding. (The refractive index is about 1.3), and if these are used, the refractive index difference at the interface can be about 0.6.

  For example, taking this example, an attempt is made to realize a luminance gradation of 4 gradations. The reflectance at the interface of the materials having refractive indexes of n1 and n2 (n2> n1) can be expressed by (n2−n1) / (n2 + n1). When n2 = 1.9 and n1 = 1.3, the reflectance is 0.1875. If this is the maximum luminance, and the refractive indices of the other two-tone unit elements are 1.47 and 1.67, respectively, four gradations of luminance can be expressed.

  As the extinction coefficient increases in both the high refractive transfer body and the hologram forming layer, the light absorption increases, and the diffracted light intensity decreases. For example, taking ZnSe as an optical material as an example, ZnSe is not used as an optical material in the blue visible region. This is because, as shown in FIG. 3, when the extinction coefficient of ZnSe exceeds the green range, it rapidly increases and absorption increases, so that blue light is hardly transmitted. With reference to this optical characteristic, considering that the thickness of both the high refractive transfer member and the hologram forming layer is usually about 1 micron, the transmittance of both the high refractive transfer member and the hologram forming layer is desirably 80% or more.

  As described above, according to the present invention, an intended hologram image can be formed only with a conventional thermal transfer printer for ink, without requiring a dedicated printer for forming a hologram image.

Example of thermal transfer image-receiving layer Example of hologram transfer body Graph of extinction coefficient of ZnSe Example of hologram forming layer Configuration example of ink ribbon including high refractive index transfer body Example of transferring a high refractive index transfer material to the hologram forming layer Example of transferring the adhesive layer to the hologram forming layer onto which the high refractive index transfer body has been transferred Example of forming personal information on the adhesive layer Example of transfer to transfer target

Next, an embodiment of the present invention will be described. As described above, an example in which a high refractive index transfer body is transferred to a hologram forming body of a low refractive index material will be described, but the embodiment of the present invention is not limited to this. Several types of high-refractive-index transfer bodies with different refractive indexes processed into a ribbon shape as shown in FIG. 5 are transferred in units of elements to the relief type diffraction grating structure of the hologram forming layer as shown in FIG. 6 is formed.

  Hologram image formation is thus completed, but in reality, the following steps are required in consideration of using the present invention for security. This is because when a hologram image is usually used for security purposes, it is necessary to transfer the hologram image to a transfer target having security. Since the hologram forming layer on which the hologram image is formed cannot be transferred as it is, the adhesive transfer layer is transferred to the hologram forming body as shown in FIG. 7 to form the adhesive layer. Information with high security such as personal information is formed using ink on the adhesive layer. At this time, if the hologram image and the security information forming unit are overlapped as shown in FIG. 8, the hologram image is effective in preventing falsification of the security information.

  After protecting the security information with the hologram image in this way, both the hologram image and the security information are transferred to the transfer body as shown in FIG. 9, and the hologram forming layer is peeled off from the base material to complete a series of operations.

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Stripping layer 3 ... Hologram formation layer 4 ... Hologram layer 5 ... High refractive index transfer body 6 ... Adhesion layer 7 ... Personal information formation area 8 ..Transfer material 9 ... Ink ribbon 10 ... Ink sheet 1
11: Ink sheet 2
12: Ink sheet 3
13 ... High refractive index transfer sheet 1
14 ... High refractive index transfer sheet 2
15 ... High refractive index transfer sheet 3

Claims (5)

  A unit element of one or more kinds of refractive index materials higher than the refractive index of the hologram forming layer is arranged in the diffraction grating forming portion of the hologram forming layer having a relief type diffraction grating structure according to the image information, and the hologram forming layer and the unit element are refracted. A hologram image forming body, characterized in that brightness gradation is expressed by utilizing the fact that the diffraction efficiency of a diffraction grating varies depending on the rate difference.   A hologram image forming body, wherein the hologram forming layer has a refractive index of 1.4 or less.   3. The hologram image forming body according to claim 1, wherein the refractive index of the material having the smallest refractive index is 0.1 or more of the refractive index of the hologram forming layer among the materials used in the unit element. .   4. The hologram image forming body according to claim 1, 2, or 3, wherein both the hologram forming layer and the unit element have an internal transmittance of 80% or more.   A relief structure formed on a surface opposite to the base material, wherein the hologram forming layer made of the material according to claim 2 and 4 is formed on one side of the base material in a state that can be brushed. An image forming method for producing a hologram image by transferring at least one unit element according to claim 3 according to image information.