JP6070023B2 - Optical element - Google Patents

Description

  The present invention relates to an optical element.

  At present, various optical elements suitable for security applications (for example, diffraction gratings and polarization separation elements) have been devised.

  In general, a diffraction grating and a polarization separation element are created by periodically changing optical characteristics such as reflection, transmission, and absorption.

  For example, a diffraction grating made of silver salt is created by forming a striped absorption layer by exposing two light beams of interference light on a silver salt film.

  The wire grid polarization separation element is formed by forming a fine metal stripe.

JP 2008-275740 A

  However, the optical element produced by the above-described production method has a disadvantage that the productivity is low and the produced optical element itself is expensive.

  Accordingly, an object of the present invention is to provide an optical element (diffraction grating or polarization separation element) excellent in productivity.

A first aspect of the present invention relates to an optical element. The optical element of the present invention has a relief structure and a plurality of fine relief regions having a low visible light reflectance,
A plurality of specular areas that reflect light, and
Each fine relief region and each mirror surface region are provided periodically adjacent to each other ,
Each fine relief region and each mirror surface region each include a resin layer and a metal layer, and the resin layer is entirely covered by the metal layer,
The pair of adjacent fine relief regions and specular regions adjacent to each other has a pitch within a range of 0.5 μm to 10 μm for functioning as a diffraction grating, or 0.1 μm to 1.0 μm for functioning as a polarization separation element. Having a pitch in the range of .

In the above optical element, the material of the metal layer is preferably at least one metal material selected from the group consisting of Al, Sn, Cr, Ni, Cu, Au, Ag, and alloys thereof. Further, the metal layer on the fine relief region preferably has a visible light reflectance of 60% or more.

2nd aspect of this invention is a manufacturing method of the said optical element. This manufacturing method is
(A) a step of producing a relief structure forming layer including a substrate and a resin layer formed thereon, wherein the resin layer has a main surface including a plurality of fine relief regions and mirror regions adjacent to each other; ,
(B) forming a metal layer on the whole of the plurality of fine relief regions and the specular region;
including.

In the optical element manufacturing method, the material of the metal layer is preferably at least one metal material selected from the group consisting of Al, Sn, Cr, Ni, Cu, Au, Ag, and alloys thereof. . The metal layer formed on the fine relief region preferably has a visible light reflectance of 60% or more.

  The present invention makes it possible to provide an optical element excellent in productivity.

It is a top view which shows roughly the optical element which concerns on 1 aspect of this invention. It is sectional drawing along the IV-IV line shown in FIG. FIG. 3 is an enlarged cross-sectional view showing a part of the optical element shown in FIG. 2. It is sectional drawing which shows the manufacturing method of an optical element roughly. It is sectional drawing which shows the manufacturing method of an optical element roughly.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same referential mark is attached | subjected to the component which exhibits the same or similar function, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a plan view schematically showing an optical element according to an aspect of the present invention. 2 is a cross-sectional view taken along line IV-IV shown in FIG. Further, FIG. 3 is an enlarged sectional view showing a part of the optical element shown in FIG.

  In the optical element 10 shown in FIGS. 1 and 2, a plurality of fine relief regions R1 and mirror regions R2 are periodically provided adjacent to each other. In this embodiment, as shown in FIGS. 1 and 2, the width of a pair of fine relief regions R1 and mirror region R2 adjacent to each other is referred to as “pitch” P.

  Each of these fine relief regions R1 and each mirror surface region R2 includes a relief structure forming layer 100 and a reflective layer 200, as shown in FIG. A concave structure and / or a convex structure is periodically provided on one main surface of the relief structure forming layer 100 (that is, the concave structure and / or the convex structure is provided only at a position corresponding to each fine relief region R1. Provided). The reflective layer 200 covers the entire main surface of the relief structure forming layer 100.

  Below, the manufacturing method of the optical element 10 is demonstrated, referring FIG.4 and FIG.5 first.

  4 and 5 are cross-sectional views schematically showing a method for manufacturing an optical element.

  In this method, first, as shown in FIG. 4, a relief structure forming layer 100 having a main surface including a plurality of adjacent fine relief regions R1 and mirror region R2 is prepared. However, the pitch P is in the range of 0.5 μm to 10 μm, or in the range of 0.1 μm to 1.0 μm. That is, all the pitches P need to be in the range of 0.5 μm to 10 μm, or all the pitches P need to be in the range of 0.1 μm to 1.0 μm.

  Each fine relief region R1 is provided with a concave structure and / or a convex structure. Each mirror surface region R2 is a flat surface. The concave structure and the convex structure are each composed of a plurality of concave parts and convex parts. These concave portions or convex portions are arranged in a stripe shape, for example.

  Although not shown, a diffractive structure surface and a scattering structure surface can also be provided.

  The shape of the cross section perpendicular to the length direction of the plurality of concave portions or convex portions is, for example, a tapered shape such as a V shape and a U shape, or a rectangular shape. In FIG. 4, the case where said cross-sectional shape is V shape is drawn as an example.

  The relief structure forming layer 100 is formed by, for example, a method in which a thermoplastic resin is applied on a base material, and an original plate provided with the above convex portions and a flat surface is pressed against the original plate while applying heat. In this case, for example, an acrylic resin, an epoxy resin, a cellulose resin, a vinyl resin, a mixture thereof, or a copolymer thereof is used as the thermoplastic resin.

  Alternatively, the relief structure forming layer 100 applies a heat while applying a thermosetting resin on a base material, pressing the original plate provided with the above-described convex portions and a flat surface, and then removes the original plate. It may be formed by a method. In this case, as the thermosetting resin, for example, a urethane resin, a melamine resin, an epoxy resin, a phenol resin, a mixture thereof, or a copolymer thereof is used. In addition, this urethane resin is obtained, for example, by adding polyisocyanate as a crosslinking agent to acrylic polyol and polyester polyol having a reactive hydroxyl group and crosslinking them.

  Alternatively, the relief structure forming layer 100 is formed by applying a radiation curable resin on a base material, irradiating the material with ultraviolet rays or the like while pressing the original plate on the substrate, curing the material, and then removing the original plate. May be. Alternatively, the relief structure forming layer 100 may be formed by pouring the composition between a substrate and an original, irradiating with radiation to cure the material, and then removing the original.

  The radiation curable resin typically contains a polymerizable compound and an initiator.

  As the polymerizable compound, for example, a compound capable of photo radical polymerization is used. As a compound capable of radical photopolymerization, for example, a monomer, oligomer or polymer having an ethylenically unsaturated bond or an ethylenically unsaturated group is used. Alternatively, as a compound capable of photo radical polymerization, 1,6-hexanediol, neopentyl glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol pentaacrylate and dipentaerythritol hexaacrylate Monomers such as epoxy acrylate, urethane acrylate and polyester acrylate, or polymers such as urethane-modified acrylic resin and epoxy-modified acrylic resin may be used.

  When a compound capable of photoradical polymerization is used as the polymerizable compound, a photoradical polymerization initiator is used as the initiator. Examples of the photo radical polymerization initiator include benzoin compounds such as benzoin, benzoin methyl ether and benzoin ethyl ether, anthraquinone compounds such as anthraquinone and methylanthraquinone, acetophenone, diethoxyacetophenone, benzophenone, hydroxyacetophenone, 1-hydroxy Phenyl ketone compounds such as cyclohexyl phenyl ketone, α-aminoacetophenone and 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, benzyl dimethyl ketal, thioxanthone, acylphosphine oxide, or Michler's ketone Is used.

  Alternatively, a compound capable of photocationic polymerization may be used as the polymerization compound. As the compound capable of photocationic polymerization, for example, a monomer, oligomer or polymer having an epoxy group, an oxetane skeleton-containing compound, or vinyl ethers are used.

  When a compound capable of photocationic polymerization is used as the polymerizable compound, a photocationic polymerization initiator is used as the initiator. As this photocationic polymerization initiator, for example, an aromatic diazonium salt, an aromatic iodonium salt, an aromatic sulfonium salt, an aromatic phosphonium salt, or a mixed ligand metal salt is used.

  Alternatively, a mixture of a compound capable of photoradical polymerization and a compound capable of photocationic polymerization may be used as the polymerizable compound. In this case, as the initiator, for example, a mixture of a radical photopolymerization initiator and a cationic photopolymerization initiator is used. Alternatively, in this case, a polymerization initiator that can function as an initiator for both photoradical polymerization and photocationic polymerization may be used. As such an initiator, for example, an aromatic iodonium salt or an aromatic sulfonium salt is used.

  The ratio of the initiator to the radiation curable resin is, for example, in the range of 0.1 to 15% by mass.

  Radiation curable resins are sensitizing dyes, dyes, pigments, polymerization inhibitors, leveling agents, antifoaming agents, anti-sagging agents, adhesion improvers, coating surface modifiers, plasticizers, nitrogen-containing compounds, and epoxy resins. An agent, a release agent, or a combination thereof may be further included. The radiation curable resin may further contain a non-reactive resin in order to improve its moldability. As this non-reactive resin, for example, the above-mentioned thermoplastic resin and / or thermosetting resin can be used.

  The above-described original plate used for forming the relief structure forming layer 100 is manufactured using, for example, an electron beam drawing apparatus or a nanoimprint apparatus. If it carries out like this, the several recessed part or convex part mentioned above can be formed with high precision. Usually, a reverse plate is manufactured by transferring the concavo-convex structure of the original plate, and a duplicate plate is manufactured by transferring the concavo-convex structure of the reverse plate. Then, if necessary, a reversal plate is manufactured using the copy plate as an original plate, and the concavo-convex structure of the reverse plate is transferred to further manufacture a copy plate. In actual production, a copy obtained in this way is usually used.

  The relief structure forming layer 100 typically includes a base material and a resin layer formed thereon. As this base material, a film base material is typically used. As the film substrate, for example, a plastic film such as a polyethylene terephthalate (PET) film, a polyethylene naphthalate (PEN) film, or a polypropylene (PP) film is used. Alternatively, paper, synthetic paper, plastic multilayer paper, or resin-impregnated paper may be used as the substrate. The base material may be omitted.

  The resin layer is formed by, for example, the method described above. The thickness of the resin layer is, for example, in the range of 0.1 μm to 10 μm. If this thickness is excessively large, resin protrusion and / or wrinkle formation is likely to occur due to pressure during processing. If this thickness is excessively small, it may be difficult to form a desired concave structure and / or convex structure. Moreover, the thickness of the resin layer is made equal to or greater than the depth or height of the concave portion or convex portion to be provided on the main surface. This thickness is, for example, in the range of 1 to 10 times the depth or height of the concave portion or convex portion, and typically in the range of 3 to 5 times thereof.

  The relief structure forming layer 100 is formed by, for example, the “pressing method” disclosed in Japanese Patent No. 4194073, the “casting method” disclosed in Japanese Utility Model Registration No. 2524092, or Japanese Patent Application Laid-Open No. 2007-2007. The “photopolymer method” disclosed in JP-A-118563 may be used.

  Next, as shown in FIG. 5, a material different from the material of the relief structure forming layer 100 is vapor-phased with respect to the entire fine relief region R1 and mirror surface region R2 (that is, the entire main surface of the relief structure forming layer 100). By depositing, the reflective layer 200 is formed.

  As a material for forming the reflective layer 200, a material that does not transmit visible light and has a high reflectance of visible light, for example, a material having a refractive index difference of 0.2 or more from the material of the relief structure forming layer 100 is used. use. If this difference is small, reflection at the interface between the relief structure forming layer 100 and the reflective layer 200 may be difficult to occur. A metal material can also be used.

  As the material, typically, at least one metal material selected from the group consisting of Al, Sn, Cr, Ni, Cu, Au, Ag, and alloys thereof is used.

In addition, it is preferable that the film thickness of a reflection layer is set so that the following (1) and (2) Formula may be satisfy | filled. Here, t represents the film thickness of the reflective layer 200, k represents the extinction coefficient, α represents the absorption coefficient, and λ _min represents the shortest wavelength in the visible light region.

t> 1 / α (1)
α = 4πk / λ _min (2)
In general, metals and their compounds each exhibit intrinsic light absorption, but in any case, if the conditions shown in the above formulas (1) and (2) are satisfied, a high reflectance can be obtained over almost the entire visible light range. . For example, in the case of Al, if the shortest wavelength λ _min in the visible light region is 380 nm, the extinction coefficient k is about 4.6, and the film thickness may be 6 nm to 7 nm or more.

  However, it should be noted that the apparent film thickness of the reflective layer 200 varies depending on the viewing angle. For example, when the reflective layer 200 is formed in the fine relief region R1, the film thickness of the reflective layer 200 when observed from the normal direction with respect to the optical element 10 is different from the film thickness when observed from an oblique direction. For this reason, it is preferable to set the film thickness in the direction perpendicular to the tangent of the outline forming the reflective layer 200 in each fine relief region R1 so as to satisfy the above expressions (1) and (2).

  The reflective layer 200 formed in the fine relief region R1 is preferably a reflective layer having a visible light reflectance of 60% or more. When the visible light reflectance is 60% or more, transmission of incident light is prevented, and when the optical element 10 is observed from the normal direction, it appears blacker than usual.

  The vapor deposition of the material is performed using, for example, a vacuum deposition method, a sputtering method, or a chemical vapor deposition method (CVD method).

  The optical element 10 shown in FIG. 3 is obtained as described above. The optical element 10 obtained by the method described above has the following characteristics.

  When the optical element 10 is produced with the pitch P in the range of 0.5 μm to 10 μm, the optical element 10 functions as a reflective diffraction grating. Since the fine relief region R1 that absorbs light and the mirror surface region R2 that reflects light are alternately provided, and the fine relief region R1 serves as a slit in a normal diffraction grating, the optical element 10 has a diffraction grating. Function as.

  In addition, when the optical element 10 is formed with the pitch P in the range of 0.1 μm to 1.0 μm, the optical element 10 functions as a reflective polarization separation element. Since the diffraction grating made of metal, that is, the diffraction grating formed in the fine relief region R1 is arranged at an interval smaller than the wavelength of light, the optical element 10 functions as a polarization separation element.

  In the present embodiment described above, it has been described that the reflective layer 200 is formed in the flat portion of the relief structure forming layer 100 in each mirror surface region R2. However, for example, a crystalgram is formed in each mirror surface region R2. It is good.

  In this embodiment, all the pitches P may have the same length, or the pattern may be formed by partially changing the length. Similarly, the stripe direction may be uniform, or the pattern may be formed by partially changing the direction.

  Further, when the optical element 10 is formed with the pitch P in the range of 0.5 μm to 10 μm, the fine relief regions R1 and the specular regions R2 are not alternately provided in the optical element 10, but a cross pattern or checkered pattern is used. Even if it is provided like a pattern, the optical element 10 functions as a reflective diffraction grating.

  Further, even if a part of the reflective layer 200 deposited on the relief structure forming layer 100 is removed by etching, it functions as a diffraction grating or a polarization separation element according to the length of the pitch P.

  Furthermore, the optical element 10 described above can be applied to a transfer foil, a sticker, a thread, and the like.

  According to the aspect described above, it is possible to efficiently manufacture a reflective diffraction grating and a polarization separation element, that is, it is possible to provide an optical element with excellent productivity.

  Further, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, you may delete some components from all the components shown by the said aspect. Furthermore, you may combine the component covering a different aspect suitably.

  First, a shape corresponding to the fine relief region R1 is drawn on the electron beam resist using an electron beam drawing device. This resist was developed to form a desired concave portion or convex portion. Thereafter, a conductive layer was formed by vapor deposition, conduction was made to the surface of each concave or convex portion by nickel sputtering, and a die was prepared by nickel electroforming. In this way, a plate was produced.

  Next, a release layer made of a radiation curable resin was applied on the relief structure forming layer 100 made of polyethylene terephthalate resin. The thickness of this release layer was 2 μm. In this way, an original fabric was created.

  Subsequently, the mold is pressed against the surface of the layer made of the original fabric resin, the radiation curable resin is cured by irradiating the radiation from the relief structure forming layer 100 side, and the mold is peeled to duplicate. went. In this way, a relief structure forming layer 100 having a plurality of concave portions or convex portions on one main surface was obtained.

  Thereafter, aluminum was deposited on the relief structure forming layer 100. Thus, the reflective layer 200 was obtained and the optical element 10 was obtained. The thickness of the reflective layer 200 was 50 μm.

  DESCRIPTION OF SYMBOLS 10 ... Optical element, 100 ... Relief structure formation layer, 200 ... Reflective layer, R1 ... Fine relief area | region, R2 ... Mirror surface area | region.

Claims (6)

A plurality of fine relief regions having a relief structure and low visible light reflectance;
A plurality of specular areas that reflect light, and
Each fine relief region and each mirror surface region are provided periodically adjacent to each other ,
Each fine relief region and each mirror surface region each include a resin layer and a metal layer, and the resin layer is entirely covered by the metal layer,
The pair of adjacent fine relief regions and specular regions adjacent to each other has a pitch within a range of 0.5 μm to 10 μm for functioning as a diffraction grating, or 0.1 μm to 1.0 μm for functioning as a polarization separation element. An optical element having a pitch within the range of . The optical material according to claim 1, wherein the material of the metal layer is at least one metal material selected from the group consisting of Al, Sn, Cr, Ni, Cu, Au, Ag, and alloys thereof. element. The optical element according to claim 1, wherein the metal layer on the fine relief region has a visible light reflectance of 60% or more. It is a manufacturing method of the optical element according to claim 1,
(A) a step of producing a relief structure forming layer including a substrate and a resin layer formed thereon, wherein the resin layer has a main surface including a plurality of fine relief regions and mirror regions adjacent to each other; ,
(B) forming a metal layer on the whole of the plurality of fine relief regions and the specular region;
The manufacturing method of the optical element characterized by the above-mentioned. The optical material according to claim 4, wherein the material of the metal layer is at least one metal material selected from the group consisting of Al, Sn, Cr, Ni, Cu, Au, Ag, and alloys thereof. Device manufacturing method. The optical layer according to claim 4 or 5, wherein in step (b), the metal layer formed on the plurality of fine relief regions is formed so that a visible light reflectance is 60% or more. Device manufacturing method.

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