Optical structure, transfer foil, and article

Abstract

This optical structure is provided with a multilayer relief having an uneven shape on a first surface, and a reflection layer formed above the first surface and reflecting visible light. The multilayer relief has a first resin layer having a non-radiation curable resin as a main component, and constituting the first surface, and a second resin layer having a radiation curable resin as a main component and adjacent to the first resin layer. The thickness of the first resin layer is smaller than the unevenness of the uneven shape.

Description

[Technical field]

[0001] Embodiments of the present invention relate to an optical structure having an optical relief and a method for producing the same. Additionally, reference is made to transfer foils and articles comprising the optical structure. This application claims priority to Japanese Patent Application No. 2019-073860, filed on April 9, 2019, the contents of which are incorporated by reference. [Background technology]

[0002] An optical relief is composed of a periodic or random uneven structure of micrometer to nanometer size. Optical reliefs are used as various optical structures such as relief holograms, diffraction gratings, sub-wavelength gratings, microlenses, polarizing elements, Fresnel lens plates and lenticular plates used in screens, optical disks, backlight-related parts and diffusion plates for liquid crystal devices, and anti-reflection films. Optical reliefs are also used as elements for authenticating objects. Identification objects and valuable objects equipped with optical reliefs can be significantly more resistant to counterfeiting and tampering, thus increasing the value of the objects themselves.

[0003] Known representative methods for continuously mass-producing optical reliefs include the "pressing method" (see Patent Document 1), the "casting method" (see Patent Document 2), and the "photopolymer method" (see Patent Document 3).

[0004] The photopolymer method is also called the 2P method or the photosensitive resin method. In the photopolymer method, a radiation-curable resin that is cured by exposure to a broad range of radiation, such as ultraviolet (UV) or electron beam (EB), is poured between an optical relief duplication mold and a flat substrate such as a plastic film, and cured by exposure to radiation to obtain a cured film. By peeling this cured film together with the substrate from the duplication mold, high-definition optical reliefs can be continuously replicated in large quantities. Compared to the pressing method and casting method that use thermoplastic resins, the photopolymer method has high molding precision for the concave-convex shape that constitutes the optical relief, and is excellent in heat resistance and chemical resistance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent No. 4194073 [Patent Document 2] Japanese Utility Model Registration No. 2524092 [Patent Document 3] Japanese Patent No. 4088884 Summary of the Invention [Problem to be solved by the invention]

[0006] Optical reliefs made of radiation-curable resins produced by the photopolymer method have the advantages of excellent molding precision and heat resistance, but they have the disadvantage of poor adhesion with the reflective layer that comes into contact with them. One of the reasons for this is thought to be the volumetric shrinkage of the radiation-curable resin when it hardens. Because radiation-curable resins shrink more in volume when hardened than non-radiation-curable resins, strain stress remains at the interface with the reflective layer, and it is thought that poor adhesion caused by the strain stress is likely to occur.

[0007] In view of the above circumstances, an object of the present invention is to provide an optical structure having excellent molding precision and heat resistance, and excellent adhesion between an optical relief and a reflective layer, and a method for manufacturing the same. [Means for solving the problem]

[0008] A first aspect of the present invention is an optical structure including a multilayer relief having a concave-convex shape on a first surface, and a reflective layer that reflects visible light and is formed on the first surface. The multi-layer relief is made of a non-radiation-curable urethane resin as a main component and does not contain a silicate compound, and is made of a first resin layer constituting a first surface, and a second resin layer constituting a second surface, the first resin layer being made of a radiation-curable resin as a main component. on the surface opposite to the first surface and an adjacent second resin layer. The melting point of the radiation curable resin is higher than the melting point of the urethane resin, or the radiation curable resin does not have a distinct melting point. The thickness of the first resin layer is smaller than the unevenness of the uneven shape. fence, At the boundary between the first resin layer and the second resin layer, the radiation curable resin and the urethane resin are mixed. .

[0009] A second aspect of the present invention is a transfer foil comprising the optical structure of the present invention. A third aspect of the present invention is an article comprising the optical structure of the present invention. Effect of the Invention

[0011] The optical structure of the present invention is excellent in molding precision and heat resistance, and has good adhesion between the optical relief and the reflective layer. [Brief description of the drawings]

[0012] [Figure 1] 1A and 1B are diagrams conceptually illustrating a structure of an optical structure according to a first embodiment of the present invention. [Diagram 2] 3A to 3C are diagrams illustrating a process for manufacturing the optical structure. [Diagram 3] 3A to 3C are diagrams illustrating a process for manufacturing the optical structure. [Figure 4] 3A to 3C are diagrams illustrating a process for manufacturing the optical structure. [Diagram 5] FIG. 4 is a diagram conceptually illustrating the structure of a transfer foil according to a second embodiment of the present invention. [Figure 6] FIG. 2 is a diagram conceptually illustrating an example of an article equipped with the optical structure. [Figure 7] 7 is a diagram conceptually explaining a cross-sectional structure taken along line II in FIG. 6. [Figure 8] 1 is a cross-sectional image of an example optical structure taken with a scanning electron microscope. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A first embodiment of the present invention will be described below with reference to Figs. 1 to 4. The embodiments of the present invention are a group of embodiments based on a single unique invention from the background. Also, each aspect of the present invention is an aspect of a group of embodiments based on a single invention. Each configuration of the present invention may have each aspect of the present invention. Each feature of the present invention can be combined to form each configuration. Therefore, each feature of the present invention, each configuration of the present invention, each aspect of the present invention, and each embodiment of the present invention can be combined, and the combination has a synergistic function and can produce a synergistic effect. 1 is a diagram conceptually illustrating the structure of an optical structure 1 of this embodiment. The optical structure 1 includes a reflective layer 10, a first resin layer 20 located on the reflective layer 10, a second resin layer 30 located on the first resin layer 20, and a carrier 40 located on the second resin layer 30. The first resin layer 20 and the second resin layer 30 form a multilayer relief 2 having an uneven shape on a first surface 2a.

[0014] The reflective layer 10 is a translucent or opaque layer that reflects visible light, and allows the optical effect of the multilayer relief 2 to be easily visible. The material of the reflective layer 10 can be a metal. The metal can be a pure metal or an alloy. A reflective layer made of a metal material can be an opaque layer. The material of the reflective layer 10 can be a metal compound. A reflective layer made of a metal compound material can be a translucent layer. The material of the reflective layer 10 can be aluminum, an aluminum alloy, zinc sulfide, or titanium dioxide. Aluminum or an aluminum alloy is an inexpensive metal that is easy to handle. Zinc sulfide is a metal compound that has a high refractive index in visible light and is easy to process. Titanium dioxide is a translucent metal compound that has a high refractive index.

[0015] The first resin layer 20 is formed mainly from a non-radiation curable resin. The first resin layer 20 constitutes the first surface 2a of the multilayer relief. The adhesion of the first resin layer 20 to the reflective layer 10 is higher than that of the second resin layer 30. The material of the first resin layer 20 is preferably one that can form a thin film of uniform thickness and has flexibility that allows it to follow the uneven shape of the optical relief in the multilayer relief. Examples of the material of the first resin layer 20 include acrylic resin, cellulose resin, urethane resin, epoxy resin, polyester resin, etc. These resins may have a fluorine molecular structure or a silicone molecular structure. The first resin layer 20 may contain additives other than the non-radiation curable resin, such as inorganic powder, release agent, leveling agent, polymer powder, wax, etc. The ratio of the non-radiation curable resin in the first resin layer 20 can be 90% or more by weight. An example of the inorganic powder is silica powder. An example of the polymer powder is fluorine body and silicone powder. An example of the wax is polypropylene wax and polyethylene wax. An example of the release agent is silicone, fluoropolymer, and aliphatic polymer. An example of the leveling agent is silicone, fluoropolymer, and aliphatic polymer. These additives can have the functions of both release agent and leveling agent. Or, wax can be used as the release agent or the leveling agent. Examples of aliphatic polymers are ether esters, sulfates, phosphates, amines, carboxylates. The weight percentage of the additive can be greater than or equal to 0.3% and less than or equal to 3%. The thickness of the first resin layer 20 depends on the form of the optical relief, but can be about 0.05 μm to 1 μm. The first resin layer 20 can be formed by coating. The first resin layer 20 may be formed by printing. As the coating, gravure coating and die coating can be applied. As the printing, gravure printing and silk screen printing can be applied. The first resin layer 20 may cover the entire second resin layer 30.

[0016] The second resin layer 30 is formed from a radiation curable resin as a main component. The second resin layer 30 is adjacent to the surface of the first resin layer 20 opposite to the first surface 2a. The radiation curable resin is a resin in which a relatively low molecular weight polymerizable compound is polymerized and cured (reacted) by irradiation with radiation. The radiation used to cure the second resin layer 30 may be ultraviolet light (UV), visible light, gamma rays, X-rays, electron beams (EB), or the like, with ultraviolet light being preferred. When ultraviolet light is used as the radiation, polymerization may be controlled by adding a photopolymerization initiator, a polymerization inhibitor, and / or a photopolymerization accelerator. The polymerizable compound that is the material of the second resin layer 30 can be an epoxy acrylate, a urethane acrylate, or the like having an unsaturated bond.

[0017] The second resin layer 30 may contain other resins as long as the main component is a radiation curable resin. The thickness of the second resin layer 30 depends on the form of the optical relief, but can be about 1 μm to 10 μm. The second resin layer 30 can be formed by coating. The second resin layer 30 may be formed by printing or the like. As the coating, gravure coating and die coating can be applied. As the printing, gravure printing and silk screen printing can be applied. The elastic modulus of the first resin layer 20 may be lower than that of the second resin layer 30. The elastic modulus of the precursor layer 30p (described later), which is the second resin layer 30 before curing, may be lower than that of the second resin layer 30. This makes it easier to improve moldability. The elastic modulus may be Young's modulus. The elastic modulus may be a value when the temperature of the resin is 200°C. The elastic modulus may be a condition for preventing deformation when the optical structure is thermocompression laminated onto a card.

[0018] The carrier 40 is transparent at least in the wavelength band of visible light and in the wavelength band of radiation that cures the radiation curable resin that is the main component of the second resin layer 30. The carrier 40 can be a plastic film. The material of the plastic film can be polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polypropylene (PP), or the like.

[0019] The multilayer relief 2 composed of the first resin layer 20 and the second resin layer 30 has a fine uneven shape on the surface on the side of the reflective layer 10, and this uneven shape functions as an optical relief. The optical effects of the optical relief include an optical diffraction effect, a selective reflection effect or an anti-reflection effect, an isotropic or anisotropic scattering effect, a light collecting effect, a polarizing reflection effect, etc., and exert effects such as prevention of counterfeiting and tampering and improvement of aesthetics when observed visually or mechanically. The optical relief can be formed by combining one or more unit reliefs having an optical effect. The repetition period of the unit reliefs can be 0.01 μm to 10 μm. The optical relief can also be formed by randomly arranging the unit reliefs.

[0020] A distance D1 in the thickness direction of the optical structure 1 between the most convex portion 2b and the most concave portion 2c on the first surface 2a of the multilayer relief 2 (hereinafter referred to as "concave-convex difference") may be larger than the thickness T1 of the first resin layer 20. The concave-convex difference can be 0.03 μm or more and 5 μm or less. The optical relief may have unit reliefs with different unevenness differences. In an optical relief having unit reliefs with different unevenness differences, the peelability from the embossing cylinder during molding differs from site to site due to the unevenness difference, but the first resin layer 20 can reduce the difference. The reflective layer 10 can be formed to a uniform thickness in accordance with the uneven shape of the multilayer relief 2.

[0021] An example of a manufacturing procedure for the optical structure 1 of this embodiment configured as described above will be described below. This procedure includes a manufacturing method for the optical structure according to this embodiment.

[0022] First, as shown in FIG. 2, a precursor layer 30p which becomes the second resin layer 30 and the first resin layer 20 are formed in this order on a carrier 40 (Step A). The low molecular weight polymerizable compound constituting the precursor layer 30p is generally easily dissolved in an organic solvent. Therefore, when the first resin layer 20 is formed on the precursor layer 30p, the precursor layer 30p may be partially re-dissolved. The re-dissolution itself has merits as described below and is not particularly problematic. However, if the re-dissolution causes cloudiness or the like, it may adversely affect the curing of the precursor layer 30p and the optical effect of the optical structure 1. Clouding and the like can be prevented by considering the compatibility between the material of the precursor layer 30p and the material of the first resin layer 20. By selecting the materials of the precursor layer 30p and the first resin layer 20 so that either a carboxyl group, an amino group, or a hydroxyl group is contained in both of them, the compatibility between the two is good, and clouding and the like can be suitably prevented. In addition, the material of the first resin layer 20 can be a urethane resin, and the material of the precursor layer 30p can be a urethane (meth)acrylate.

[0023] 3, an embossed cylinder 100 having a surface shape corresponding to the shape of the optical relief is pressed against the first resin layer 20 to transfer the surface shape of the embossed cylinder 100 to the first resin layer 20 (step B). The unevenness difference D2 of the surface shape of the embossed cylinder 100 corresponds to the unevenness shape of the multilayer relief 2 to be formed. The unevenness difference D2 may be larger than the thickness T1 of the first resin layer 20. In other words, the unevenness difference may not be completely absorbed by the first resin layer 20, and the surface of the second resin layer 30 on the first resin layer 20 side may also be deformed to correspond to the surface shape of the embossed cylinder 100. The thickness of the first resin layer 20 can be uniform. On the other hand, the thickness of the second resin layer 30 varies depending on the shape of the surface. The standard deviation of the thickness of the first resin layer 20 can be within 30% of the average thickness. The difference in thickness of the second resin layer 30 can be 80% or more and less than 100% of the unevenness difference D2. The thickness of each resin layer can be determined by extracting 10 measurement points from the cross section and averaging the values ​​at the measurement points.

[0024] By pressing the moderately heated embossing cylinder 100 against the first resin layer 20 and the precursor layer 30p, the surface shape can be transferred while softening the first resin layer 20 and the precursor layer 30p, so that the optical relief can be formed with high accuracy. The processing conditions for step B are, for example, 50 to 200° C. and 1 to 50 kgf / cm 2 It can be done as follows.

[0025] With the embossed cylinder 100 pressed against the first resin layer 20, the precursor layer 30p is irradiated with the corresponding radiation Ra from the carrier 40 side (step C). The radiation penetrates the carrier 40 and reaches the precursor layer 30p. The precursor layer 30p is cured by exposure to radiation to become the second resin layer 30. Step B and step C may be performed in that order or simultaneously. When step C is performed after step B, the embossing cylinder 100 may be separated from the first resin layer 20. However, if the embossing cylinder 100 and the first resin layer 20 are in contact with each other at a constant pressure, the optical relief is easily formed with high accuracy.

[0026] Next, a reflective layer is formed on the first resin layer 20 by vacuum deposition, sputtering, or the like (Step D). As a pretreatment for forming the reflective layer, the first resin layer 20 may be surface-treated. Examples of the surface treatment include corona treatment and plasma treatment. Through the above steps, the optical structure 1 of this embodiment is completed.

[0027] In the optical structure 1 of this embodiment, the multilayer relief 2 has a first resin layer 20 mainly made of a non-radiation curable resin and a second resin layer 30 mainly made of a radiation curable resin, First resin layer 20 is in contact with the reflective layer 10. By bringing the first resin layer 20, which has higher adhesion to the reflective layer 10 than the second resin layer 30, into contact with the reflective layer 10, it is possible to improve adhesion between the multilayer relief and the reflective layer, as compared to a configuration using a general photopolymer method in which the multilayer relief is formed only from a radiation-cured resin layer.

[0028] In addition, since the second resin layer 30 and the reflective layer 10 are not in direct contact with each other, even if volume shrinkage occurs when the precursor layer 30p is cured, the non-radiation curable first resin layer 20 is present between the second resin layer 30 and the reflective layer 10, so that the influence does not directly act on the interface between the first resin layer 20 and the reflective layer 10. As a result, distortion is unlikely to occur at the interface between the multilayer relief and the reflective layer, and bonding failure due to distortion is easily prevented. Furthermore, although metal compounds have low elasticity and are prone to bonding failure due to distortion of the metal compounds, even a reflective layer made of a metal compound material can prevent bonding failure due to distortion.

[0029] Furthermore, if the thickness of the first resin layer 20 is smaller than the unevenness of the multilayer relief 2, the second resin layer 30 will necessarily deform in accordance with the uneven shape of the embossed cylinder 100 in step B, and will be cured in the deformed state in step C. As a result, the first resin layer 20 is supported by the second resin layer 30, which has a shape corresponding to the uneven shape of the multilayer relief 2, and the first resin layer strongly affects the molding accuracy of the multilayer relief. This makes it possible to achieve high molding accuracy in the multilayer relief 2, even though the outermost surface of the multilayer relief 2 is the first resin layer 20, which is mainly composed of a non-radiation curable resin, which has inferior molding accuracy compared to radiation curable resin. This effect becomes even more remarkable when the second resin layer 30 is made thicker than the first resin layer 20.

[0030] In addition, if the melting point of the second resin layer 30 is higher than that of the first resin layer 20, even when the manufactured optical structure 1 is subjected to a temperature equal to or higher than the melting point of the main component of the first resin layer 20, the concave-convex shape of the multilayer relief 2 is likely to be maintained by the second resin layer 30. In other words, the heat resistance of the multilayer relief 2 of the optical structure 1 can be improved. The material of the second resin layer 30 does not need to have a clear melting point. In this case, the concave-convex shape of the multilayer relief 2 is easily maintained by the second resin layer 30.

[0031] Furthermore, in step C, since the precursor layer 30p is covered with the first resin layer 20 and is not exposed to the atmosphere, polymerization inhibition due to oxygen in the atmosphere is unlikely to occur during the curing reaction of the precursor layer.

[0032] In the optical structure 1 of this embodiment, when the precursor layer 30p is remelted in step A, the resin materials of the precursor layer 30p and the first resin layer 20 are mixed at the boundary between them, and a clear interface between the precursor layer 30p and the first resin layer 20 may not exist. When the precursor layer 30p is cured in step C in this state, the first resin layer 20 and the second resin layer 30 are integrated, resulting in a structure in which delamination is unlikely to occur. That is, a thin mixed layer or mixed region is formed between the first resin layer 20 and the second resin layer 30. As a result, in addition to the adhesion between the multilayer relief and the reflective layer, the adhesion between the layers in the multilayer relief can be increased, and unnecessary reflected light generated at the interface between the first resin layer and the second resin layer is also reduced. If a mixed layer or mixed region exists between the first resin layer 20 and the second resin layer 30, the region where the resin of the first resin layer and the resin of the second resin layer are mixed is identified by dyeing or the like, and the middle part in the thickness direction is defined as the boundary between the first resin layer 20 and the second resin layer 30.

[0033] A second embodiment of the present invention will be described with reference to Figures 5 to 7. In the following description, configurations common to those already described will be given the same reference numerals and duplicated description will be omitted.

[0034] 5 is a diagram conceptually showing the structure of a transfer foil 51 according to this embodiment. The transfer foil 51 includes an optical structure 1, and further includes a release layer 52 and an adhesive layer 53.

[0035] The release layer 52 is a layer provided between the carrier 40 and the second resin layer 30. The release layer 52 reduces the interlayer adhesive force at the interface between the carrier 40 and the second resin layer 30, making it easier to peel the carrier 40 from the optical structure 1.

[0036] The release layer 52 can be a mixture of a resin and a lubricant. The resin can be a thermoplastic resin. The thermoplastic resin can be an acrylic resin, a polyester resin, a cellulose resin, etc. The lubricant can be a polyethylene powder, a silicone, and a wax such as carnauba wax. The thickness of the release layer 52 can be set to be not less than 0.01 μm and not more than 2 μm.

[0037] The adhesive layer 53 is a layer provided on the reflective layer 10. The adhesive layer 53 enables the optical structure 1 to be attached to another medium. The adhesive layer 53 may be configured to always exhibit adhesiveness and to be covered with a separator or the like. Alternatively, the adhesive layer 53 may be configured not to exhibit adhesiveness at room temperature and to exhibit adhesiveness in response to an external factor such as heat, light, or pressure. The material of the adhesive layer 53 can be a thermoplastic resin. The thermoplastic resin can be a modified acrylic resin, a polyester resin, an epoxy resin, a urethane resin, or the like. The adhesive layer 53 may partially contain an elastomer material. The elastomer material can be a block copolymer or a mixture of a styrene-based, vinyl chloride-based, olefin-based, or urethane-based material.

[0038] The transfer foil 51 of this embodiment having the above-mentioned configuration can function as an element for verifying the authenticity of an object by bonding the adhesive layer 53 to the object and peeling off the carrier 40.

[0039] An application example of the transfer foil 51 is shown in FIGS. 6 shows a card 60 as an example of an article including the optical structure 1. FIG 7 is a cross-sectional view taken along line II in FIG 6.

[0040] The card 60 can be used as an identification document. The authenticity of the card can be verified by the optical structure 1 of the card 60. In addition to the optical structure 1, the card 60 is provided with a laser marking 61 and a print 62 that can be visually confirmed.

[0041] As shown in Fig. 6, the card 60 includes a first sheet 71, a second sheet 72, and two laminate materials 73 sandwiching the first sheet 71 and the second sheet 72. The first sheet 71 has a print 62 formed thereon. The second sheet 72 has a laser marking 61 formed thereon, and the optical structure 1 is bonded to the first sheet 71 through an adhesive layer 53. The first sheet 71 and the second sheet 72 are sandwiched between the laminate materials 73 from both sides in the thickness direction in a stacked state, and a heat and pressure lamination process is performed, whereby the card 60 in which the first sheet 71, the second sheet 72, and the laminate materials 73 are integrated can be manufactured. In the card 60, the optical structure is embedded inside. The optical structure 1 can be attached to the second sheet 72 by bonding the adhesive layer 53 of the transfer foil 51 to the second sheet 72 and peeling off the carrier 40 . In the optical structure 1, the second resin layer 30 after hardening is less susceptible to thermal deformation. On the other hand, the first resin layer 20 has low elasticity and is hard, so that the second resin layer 30, which retains the uneven shape, is less susceptible to the effects of the heat and pressure lamination treatment, and even if it tries to deform, it is suppressed by the first resin layer 20. As a result, a card 60 can be formed in which the surface shape of the multilayer relief is suitably retained.

[0042] The first sheet 71, the second sheet 72, and the laminate material 73 may be made of a transparent plastic film. The lower surface of the first sheet 71 and the laminate material 73 on the lower side may be made concealable by full-surface printing or the like. The plastic film may be made of PET, PEN, PP, polyvinyl chloride (PVC), glycol-modified PET (PET-G), polycarbonate (PC), etc. Among these, plastic films made of PVC, PET-G, or PC are usually used as laminating materials for various cards and passports. These plastic films are preferred because they can be easily processed to be integrated by heat or pressure.

[0043] The thickness of the first sheet 71, the second sheet 72, and the laminate material 73 is preferably 50 μm or more and 500 μm or less, and more preferably 75 μm or more and 400 μm or less. A thickness of 50 μm or more provides sufficient physical strength and makes the material easy to handle. A thickness of 500 μm or less makes it difficult for thickness variations and warping to affect the manufacture of the product.

[0044] The print 62 is provided in any color over the entire surface or in a pattern such as letters or pictures in order to provide the information to be communicated. The print 62 can be formed using ink. The ink can be offset ink, letterpress ink, gravure ink, etc. depending on the printing method. Alternatively, the ink can be resin ink, oil-based ink, water-based ink, etc. depending on the composition. Furthermore, the ink can be oxidative polymerization type ink, penetration drying type ink, evaporation drying type ink, ultraviolet curing type ink, etc. depending on the drying method. As the ink, a functional ink that changes color depending on the illumination angle or observation angle of light can be used. The functional ink can be optical variable ink, color shift ink, pearl ink, etc.

[0045] Print 62 can also be formed by electrophotography using toner. Toner is prepared by attaching color particles such as graphite and pigment to electrically charged plastic particles, and the toner is transferred to the printing medium using static electricity generated by the charge, and then heated and fixed to form print 62.

[0046] The article to which the optical structure 1 is attached is not limited to an identification document such as the card 60. The optical structure 1 can also be attached to a valuable article with high brand value itself or a tag or the like attached to a valuable article, and the optical structure 1 can function as an element for verifying the authenticity of the valuable article.

[0047] The experimental evidence of the optical structure of the present invention is illustrated by the following Experiments and Comparative Experiments. In the following description, unless otherwise specified, "parts" means parts by weight.

[0048] (Fabrication of Optical Structure According to Experimental Example 1) A 25 μm thick PET film (Lumirror 25T60 manufactured by Toray Industries, Inc.) was used as the carrier. The precursor layer ink was coated on the carrier to a thickness of 2 μm by gravure printing, and the organic solvent was removed by volatilization to form a precursor layer. Furthermore, the first resin layer ink was coated on the precursor layer to a thickness of 0.1 μm by gravure printing, and the organic solvent was removed by volatilization to form a first resin layer. A cylindrical metal embossing cylinder having a concave-convex pattern with a concave-convex difference of 0.3 μm and a period of 2 μm was applied to the first resin layer at a pressure of 2 kgf / cm. 2 The uneven shape was transferred to the first resin layer and the precursor layer by pressing the first resin layer and the precursor layer at a temperature of 160° C. and a speed of 10 m / min. mercury lamp 300mJ / cm for the precursor layer using 2 The precursor layer was cured by exposure to ultraviolet light for 100 s to form a second resin layer. Finally, a reflective layer 10 made of zinc sulfide (ZnS) and having a thickness of 60 nm was formed on the first resin layer by vacuum deposition to prepare an optical structure.

[0049] The compositions of the precursor layer ink and the first resin layer ink used in Experimental Example 1 are shown below. (Precursor layer ink) Urethane (meth)acrylate 100 parts (Multifunctional, molecular weight 20,000, nv=30%) Methyl ethyl ketone 60 parts Ethyl acetate 40 parts Photoinitiator (Ciba Specialty Irgacure 184) 3 parts (First resin layer ink) Urethane resin (softening point 140℃) 5 parts Methyl ethyl ketone 35 parts Ethyl acetate 60 parts

[0050] (Fabrication of optical structure according to Experimental Example 2) Experimental Example 2 is an example of a configuration in which the first resin layer contains an additive. A 25 μm thick PET film (Lumirror 25T60) was used as the carrier. The precursor layer ink was coated on the carrier to a thickness of 2 μm by gravure printing, and the organic solvent was removed by volatilization to form a precursor layer. Furthermore, the first resin layer ink was coated on the precursor layer to a thickness of 0.1 μm by gravure printing, and the organic solvent was removed by volatilization to form a first resin layer. A cylindrical metal embossing cylinder having a concave-convex pattern with a concave-convex difference of 0.3 μm and a period of 2 μm was applied to the first resin layer at a pressure of 2 kgf / cm. 2 The uneven shape was transferred to the first resin layer and the precursor layer by pressing the first resin layer and the precursor layer at a temperature of 160° C. and a speed of 10 m / min. mercury lamp 300mJ / cm for the precursor layer using 2 The precursor layer was cured by exposure to ultraviolet light for 100 s to form a second resin layer. Next, a corona treatment was performed on the first resin layer as a pretreatment for forming a reflective layer under the conditions of a speed of 5 m / min, an output of 0.2 kW, and a discharge distance of 2 mm. Finally, a reflective layer 10 made of ZnS and having a thickness of 60 nm was formed on the first resin layer by vacuum deposition to prepare an optical structure.

[0051] The compositions of the precursor layer ink and the first resin layer ink used in Experimental Example 2 are shown below. (Precursor layer ink) Urethane (meth)acrylate 100 parts (Multifunctional, molecular weight 20,000, nv=30%) Methyl ethyl ketone 60 parts Ethyl acetate 40 parts Photoinitiator (Irgacure 184) 3 parts (First resin layer ink) Urethane resin (softening point 140℃) 5 parts Phosphate ester salt 0.05 parts Methyl ethyl ketone 35 parts Ethyl acetate 60 parts

[0052] (Comparative experiment 1) An optical structure of Comparative Experiment 1 was produced in the same manner as in Experimental Example 1, except that the first resin layer was not provided and a reflective layer was formed on the second resin layer.

[0053] (Comparative experiment 2) Except for the fact that the thickness of the first resin layer was set to 1 μm, an optical structure of Comparative Experiment 2 was produced in the same manner as in Experimental Example 1. The thickness of the first resin layer in Comparative Experiment 2 was three times or more the unevenness difference of the uneven shape of the multilayer relief.

[0054] (Comparative experiment 3) Except for the fact that the second resin layer was not provided and the thickness of the first resin layer was set to 2.1 μm, an optical structure of Comparative Experiment 3 was produced in the same manner as in Experimental Example 1. Since the second resin layer was not provided, ultraviolet exposure was not performed.

[0055] The optical structures of the respective examples were evaluated for the following items. (Molding precision) The molding precision was evaluated based on the degree of agreement between the concave-convex shape of the embossed cylinder and the concave-convex shape of the multilayer relief. The concave-convex shape of the embossed cylinder and the concave-convex shape of the multilayer relief can be measured by observing them with various microscopes. First, the unevenness difference and the unevenness interval were measured for the uneven shape of the embossed cylinder in a predetermined range and the uneven shape of the multilayer relief in the corresponding range. Next, for each of the unevenness difference and the unevenness interval, the measured value of the multilayer relief was divided by the measured value of the embossed cylinder to calculate the degree of agreement (%), and the results were evaluated according to the following criteria. ○(good): Match rate of 90% or more ×(bad): Match rate less than 90% (Adhesion between multi-layer relief and reflective layer) Tape was applied to the reflective layer of each example, and the presence or absence of peeling was judged in accordance with JISH8504 "Test method for adhesion of plating." ○ (good): No reflective layer was found on the peeled tape ×(bad): Reflective layer remains on the peeled tape (Heat resistance) The optical structures of each example were subjected to a flat press at 200°C and a pressure of 200 N / cm 2After that, the optical effect of the multilayer relief was visually evaluated according to the following two-level scale to see if it was maintained. 〇(good): No change in optical effect ×(bad): Optical effect is lost The results are shown in Table 1.

[0056] [Table 1]

[0057] The optical structures of each example had good molding accuracy of the uneven shape of the multilayer relief and good adhesion between the multilayer relief and the reflective layer. The optical effect of the multilayer relief was maintained even under high temperature and high pressure conditions, and sufficient heat resistance was demonstrated. Experimental Example 2 was particularly excellent in anti-fouling properties during embossed cylinder processing, and the amount of the first resin layer material adhering to the cylinder surface after processing was significantly small.

[0058] In Comparative Experiment 1, the adhesion between the multilayer relief and the reflective layer was low, which was believed to be due to the absence of the first resin layer. In Comparative Experiment 2, the molding precision and heat resistance were insufficient. This was thought to be because the first resin layer was too thick, which prevented the second resin layer from functioning sufficiently. In Comparative Experiment 3, the molding precision and heat resistance were insufficient. This was thought to be due to the absence of the second resin layer.

[0059] A cross-sectional image of Experimental Example 1 obtained by a scanning electron microscope (SEM) is shown in Fig. 8. It can be seen that the unevenness difference D1 of the surface shape of the multilayer relief 2 is larger than the thickness T1 of the first resin layer 20, and as a result, the second resin layer 30 is cured in a state in which unevenness occurs on the surface (indicated by the dashed line S) on the first resin layer 20 side.

[0060] Although each embodiment and experimental example of the present invention have been described in detail above with reference to the drawings, the specific configurations are not limited to these embodiments, and configuration changes and combinations that do not deviate from the gist of the present invention are also included. The terms "part," "element," "pixel," "cell," "segment," "unit," "display," and "article" used in this disclosure are physical entities. A physical entity can refer to a material form or a spatial form surrounded by a material. A physical entity can be a structure. A structure can have a specific function. A combination of structures having specific functions can produce a synergistic effect by combining the functions of each structure. Terms used in this disclosure, and particularly in the appended claims (e.g., the body of the appended claims), are generally intended as "open" terms (e.g., the term "having" should be interpreted as "having at least," the term "including" should be interpreted as "including but not limited to," etc. Various embodiments of the present invention are described herein with reference to the associated drawings. Alternative embodiments may be devised without departing from the scope of the present invention. Although various connections and relationships (e.g., above, below, adjacent, etc.) are shown between elements in the following description and drawings, these connections and / or relationships may be direct or indirect unless otherwise specified, and the present invention is not intended to be limited in this respect. Thus, coupling of entities refers to either direct coupling or indirect coupling. The relationship between entities may be direct or indirect. As an example of an indirect relationship, reference herein to forming layer "A" on layer "B" includes the situation where one or more intermediate layers (e.g., layer "C") are between layer "A" and layer "B", as long as the relevant properties and functions of layer "A" and layer "B" are not substantially altered by the intermediate layer. The following definitions and abbreviations are used in interpreting the claims and specifications. As used herein, the terms "comprises," "comprising," "including," "including," "having," "having," "containing," or other variations thereof, mean, for example, that a composition, mixture, process, method, article, or apparatus that includes a list of elements is not necessarily limited to only those elements and may include other elements not expressly listed or inherent to such composition, mixture, process, method. Additionally, the term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or design described herein as "exemplary" should not necessarily be construed as preferred or advantageous over other embodiments or designs. The terms "at least one" and "one or more" are understood to include any integer greater than or equal to one, i.e., 1, 2, 3, 4, etc. The term "multiple" is understood to include any integer The term "connected" can include indirect and direct "connections." References herein to "one embodiment," "embodiment," "exemplary embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but all embodiments may or may not include a particular function, structure, or characteristic, and further, such phrases do not necessarily refer to the same embodiment. Moreover, when a particular feature, structure, or characteristic is described in connection with an embodiment, whether such feature, structure, or characteristic has an impact in connection with other embodiments may not be explicitly described, if it is within the knowledge of one of ordinary skill in the art. For purposes of description, the terms "top", "bottom", "right", "left", "vertical", "horizontal", "upper", "lower" and their derivatives shall refer to the structure described and the manner shown in the drawing figures. The terms "on", "above", "on top", "disposed on" or "disposed on" mean that a first element, such as a first structure, is present on a second element, such as a second structure. Intervening elements, such as interface structures, may be present between the first and second elements. The terms "about", "substantially", "approximately", and variations thereof are intended to include the degree of error associated with the measurement of a particular quantity based on equipment available at the time of filing. For example, "about" may include a range of ±8% or 5%, or 2% of a given value. As used herein, the term "about" modifying the amount of an ingredient, component, or reactant of the invention used refers to the variation of the numerical value that may occur through, for example, typical measuring and liquid processing procedures used to produce the concentrate. Additionally, variations may result from inadvertent errors in measuring procedures, differences in the manufacture, source, or purity of ingredients used to make the composition or carry out the method, and the like. In one aspect, the term "about" means within 10% of the stated numerical value. In another aspect, the term "about" means within 5% of the stated numerical value. In yet another aspect, the term "about" means within 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% of the stated numerical value. It will also be understood that when an element, such as a layer, region, etc., is referred to as being "on" or "on" another element, it may be directly on the other element, or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" or "directly on" another element, there are no intervening elements present. The description of the various embodiments of the present invention has been presented for illustrative purposes, but is not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terms used herein have been selected to best explain the principles of the embodiments, practical applications or technical improvements to the technology found in the marketplace, or to enable those skilled in the art to understand the embodiments described herein. In addition, when interpreting terms, configurations, features, aspects, and embodiments, drawings should be referred to as necessary. Matters that can be directly and unambiguously derived from the drawings should be the basis for amendment in the same manner as the text. Furthermore, where a particular number of introduced claim recitations is intended, such intent shall be expressly recited in the claim, and in the absence of such recitation, such intent does not exist. For example, to aid in understanding, the following appended claims include the use of the introductory phrases "at least one" and "one or more" to introduce the enumeration of claims. However, the use of such phrases should not be construed as meaning that the introduction of a claim recitation with the indefinite article "a" or "an" limits a particular claim that includes such a claim to an embodiment that includes only one such recitation. The opening phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and / or "an") should be construed to mean at least "at least one" (e.g., "one" or "one or more"). The same applies to the use of express articles used to introduce claim recitations. [Explanation of symbols]

[0061] 1 Optical structure 2 Multi-layered relief 2a Front page 10 reflective layer 20 First resin layer 30 Second resin layer 30p precursor layer 40 Career 51 Transfer foil 60 Cards (items, identification documents) 100 embossed cylinder D1 (multi-layer relief) concave-convex difference D2 (Embossed cylinder surface shape) unevenness T1 (first resin layer) thickness

Claims

1. A multilayer relief having a concave-convex shape on a first surface; a reflective layer formed on the first surface and configured to reflect visible light; Equipped with The multi-layer relief comprises: a first resin layer that is mainly composed of a non-radiation curable urethane resin and does not contain a silicate compound and that constitutes the first surface; a second resin layer that is mainly composed of a radiation curable resin and is adjacent to a surface of the first resin layer opposite to the first surface, The melting point of the radiation curable resin is higher than the melting point of the urethane resin, or the radiation curable resin does not have a distinct melting point; The thickness of the first resin layer is smaller than the unevenness difference of the uneven shape, the radiation curable resin and the urethane resin are mixed at the boundary between the first resin layer and the second resin layer; optical structure.

2. The thickness of the second resin layer is greater than the thickness of the first resin layer. The optical structure of claim 1 .

3. at least one of a carboxyl group, an amino group, and a hydroxyl group is contained in both the radiation curable resin and the urethane resin; The optical structure of claim 1 .

4. A transfer foil having an optical structure described in any one of claims 1 to 3.

5. An article comprising an optical structure described in any one of claims 1 to 3.

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