JP2014062992A - Optical medium and optical article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide effect identical to that in conventional de-metalization process through transmissivity improvement by means of a change in light reflection layer resulting from the shape, pitch, depth, or the like of a rugged structure in an optical medium according to the invention, by solving a problem in that, a conventional de-metalization process requires complex steps such as mask formation and etching, the line width of the reflection layer de-metalized relies on the position accuracy of mask print, making de-metalization process difficult at a nano-level of line width, and etching requires large-scale equipment, requiring time for setting etching conditions and so on.SOLUTION: An optical medium has a simple configuration in which a light reflection layer is disposed on a transparency formation layer formed from a rugged area where a rugged structure is formed and a non-rugged area where no rugged structure is formed. Transmissivity varies with a change in the film thickness of the light reflection layer, resulting from the shape, depth, pitch, or the like of the rugged structure. Its transmissivity is higher than that in the area where no rugged structure is formed.

Description

  The present invention relates to an optical medium, and more particularly to an optical medium for preventing counterfeiting and copying of securities such as gift certificates and official documents such as passports, and an optical article to which the optical medium is attached. About.

  Securities such as gift certificates and official documents such as passports and driver's licenses are provided with optical media with a fine structure such as holograms to prevent counterfeiting and copying of such securities and official documents. ing. As these optical media, a structure in which a light reflecting layer such as aluminum is arranged in a fine structure is generally known, and a visual effect that shines in seven colors is obtained, which is well recognized by the general public. It is the place where it is.

  However, in recent years, forgery that counterfeits fake is genuine, or falsification by improper use by counterfeiters, such as counterfeiting by falsification by obtaining the real thing and falsifying it, is given examples of counterfeit holograms that imitate the appearance Has come to be seen.

  Therefore, as one means for obtaining a higher anti-counterfeit effect, demetallized processing is known in which the light reflecting layer is removed by etching or the like. As a conventional demetallized process, in a light reflection layer made of aluminum or the like, a mask treatment is performed only on a portion where the light reflection layer is to be left using a material having alkali resistance, and then immersed in an alkaline solution. A method of removing a light reflection layer in a portion that has not been processed is known.

  If the mask is formed on an arbitrary pattern using the above method, the light reflecting layer can be formed in an arbitrary shape, and forgery prevention when used for securities such as improved design of optical media and securities. The resistance improvement can be realized.

  In recent years, a processing technique has been realized in which the light reflection layer is removed with a line width of the order of nanometers to form an arbitrary pattern. In the optical media used for securities, the above demetallized processing is realized. Is becoming an indispensable technology. By applying the demetalized process, the conventional hologram can be made into a pattern with higher definition and higher accuracy, and the effect of preventing forgery can be further improved.

  Patent Document 1 proposes a printed matter in which two anti-counterfeit elements demetallized with a set of fine points are produced, and an arbitrary image can be expressed when the two anti-counterfeit elements are overlapped.

  Further, Patent Document 2 proposes a security device that realizes an action combining a diffraction effect from a concavo-convex structure and a color shift effect by combining a demetallized layer and an optically variable ink.

  Furthermore, in Patent Document 3, an uneven structure having different aspect ratios is formed, and a metal layer formed on the uneven structure is etched to make use of the difference in etching rate depending on the shape of the uneven structure, so that an arbitrary There has been proposed a manufacturing process of a multilayer body in which demetallized processing is performed along a concavo-convex structure formed in a shape.

JP 2010-1111072 A JP 2007-304601 A Special table 2008-530600 gazette

  In any of the above-mentioned Patent Documents 1 to 3, an arbitrary pattern is formed by demetallizing the metal layer to generate a new visual effect or optical effect. 1 is a method of performing demetallized processing as a collection of fine points, such as using a method of engraving a pattern on a metal-deposited foil on the entire surface, or using a method such as chemical etching or laser etching of a metal film. It is stated that it is possible. Similarly, Patent Document 2 describes that chemical etching, oil ablation, or the like is used as a demetallized processing method.

  In these methods, a mask is applied to the metal layer, and the portion of the metal layer without the mask is removed, so that the pattern of the metal layer is formed only in the portion having the mask. As a result, a pattern such as a picture can be expressed by the presence or absence of the metal layer. Therefore, by applying a chemical etching etc. after applying a mask to an arbitrary pattern to be expressed, it is possible to remove the metal layer other than the mask portion and enable fine pattern expression by the metal layer. The accuracy such as width depends on the mask manufacturing method. For this reason, the finer pattern expression by the metal layer becomes possible as the mask manufacturing method becomes higher in definition and accuracy.

  However, the mask is usually produced by a technique such as screen printing, and patterning with a line width of several hundreds of μm to several tens of μm is the limit. Furthermore, there is a problem that a mask is produced at a location deviated from the target position due to the limit of the screen printing position accuracy. In this case, there is a problem that a desired metal layer pattern shape cannot be obtained.

  Further, in Patent Document 3, a concavo-convex structure with different aspect ratios is provided as a mask, which improves the problem of positional accuracy during mask fabrication. In addition, it is possible to fabricate a mask with a positional accuracy on the order of nanometers by forming an uneven structure with high accuracy.

  However, in Patent Document 3, etching is performed as a process for removing the metal layer, which requires a large-scale facility and manufacturing time for etching, which contributes to high costs during device production. Yes. In addition, various problems and annoyances still remain in subsequent processes such as disposal of the etching solution used for etching.

  The problem concerning this etching is similar to the problem in the demetallized processing proposed in Patent Document 1 and Patent Document 2.

  The present invention has been made in view of the above-described conventional problems, and in the present invention, on a transparent molding layer composed of a concavo-convex region where a concavo-convex structure is formed and a non-concave region where a concavo-convex structure is not formed, Simple structure with a light reflecting layer, the transmittance changes due to the change in the thickness of the light reflecting layer due to the shape, depth, pitch, etc. of the concavo-convex structure. An object of the present invention is to provide an optical medium characterized by being higher than a region where no is formed.

  Further, in the optical medium according to the present invention, the transmittance can be improved by the change of the light reflecting layer due to the shape, pitch, depth, etc. of the concavo-convex structure, so that the same effect as the demetallized processing described so far is provided. It becomes possible.

  The optical medium according to claim 1 is provided with a concavo-convex structure in which a concavo-convex region having a concavo-convex structure formed on at least one surface of a transparent substrate and a non-convex region other than the concavo-convex structure are disposed. When the dimension from the apex of the convex part to the bottom side of the concave part is the depth H of the concavo-convex structure, the depth of the concavo-convex structure is 100 nm or more and less than 500 nm, and light is projected on the transparent substrate. The optical medium is characterized in that a reflection layer is provided, the transmittance of the uneven region varies depending on the uneven structure, and the transmittance in the uneven region is higher than that of the non-recessed region.

  The optical medium according to claim 2 is the optical medium according to claim 1, wherein the concavo-convex structure has at least one concave portion, convex portion, and inclined surface, and the cross-sectional shape of the concavo-convex structure has a sinusoidal shape. And a pitch of the diffraction grating is 300 nm or more and 800 nm or less.

  The optical medium according to claim 3 is the optical medium according to claim 1, wherein the concavo-convex structure is at least one or more, a concave portion, a convex portion, a surface or a slope with a steep rise from the concave portion to the convex portion, A blazed grating in which the rising from a concave part to a convex part has a slope having a gentle slope compared to the steeply inclined surface or the slope, and the cross-sectional shape of the concavo-convex structure is a sawtooth shape, and the pitch of the blazed grating Is 300 nm or more and 800 nm or less.

  The optical medium according to claim 4 is the optical medium according to claim 1, wherein the concave-convex structure is a light scatterer that scatters incident light using a concave portion or a convex portion as a light scattering element, A plurality of the light scattering elements having different lengths of each side of the rectangle are arranged in each of x and y directions perpendicular to each other on the plane of the medium, and the light scattering elements are formed inside the light scattering body. Each light scattering property is arbitrarily changed by changing the density.

  The optical medium according to claim 5 is the optical medium according to claim 2, wherein the light reflecting layer is an aluminum thin film, and the film thickness of the light reflecting layer is the non-concave region, and the concave portion of the diffraction grating. The film thickness in the non-concave region is 40 nm or more and 60 nm or less, and the film thickness in the recess is 1 nm or more and 30 nm or less, The film thickness is 20 nm or more and 40 nm or less, and the film thickness on the inclined surface is 1 nm or more and 20 nm or less.

  The optical medium according to claim 6 is the optical medium according to claim 3, wherein the light reflecting layer is an aluminum thin film, and the film thickness of the light reflecting layer is the non-concave region, and the concave portion of the blazed grating. The convex portion, the slope having a steep slope, and the slope having a gentle slope, the film thickness in the non-concave region is 40 nm or more and 60 nm or less, and the film thickness in the concave portion is 1 nm or more and 30 nm or less, the film thickness at the convex portion is 20 nm or more and 40 nm or less, and the film thickness at the slope having the steep slope is 1 nm or more and 5 nm or less, and the gentle inclination The film thickness on the inclined surface having a thickness of 20 nm or more and 40 nm or less.

  The optical medium according to claim 7 is the optical medium according to claim 4, wherein the light reflecting layer is an aluminum thin film, and the film thickness of the light reflecting layer is the non-concave region, and the light scattering element is the optical medium. The thickness of the non-concave region is 40 nm or more and 60 nm or less, the thickness of the recess is 1 nm or more and 30 nm or less, and the thickness of the projection is It is 20 nm or more and 40 nm or less.

  The optical medium according to claim 8 is the optical medium according to any one of claims 1 to 7, wherein the light reflecting layer is formed by a vapor deposition method of either a vacuum evaporation method or a sputtering method. It is characterized by being an aluminum thin film.

  An optical article according to a ninth aspect is the optical medium according to any one of the first to eighth aspects, wherein an adhesive layer is disposed on the light reflecting layer, and the optical member is made of a transparent substrate or an opaque group. It is an optical article that is affixed to a material.

  In the present invention, at least one surface of a transparent substrate is provided with a transparent molded layer composed of a concavo-convex region in which a concavo-convex structure is formed and a non-concave region in which the concavo-convex structure is not formed. A light reflecting layer is arranged on the top. Since the concavo-convex structure is formed in the concavo-convex region, the surface area of the transparent molding layer is larger than that of the non-concave region where the concavo-convex structure is not formed.

  Therefore, when the light reflection layer is a thin film using a metal material, even if a thin film is formed in an arbitrary thickness in the non-recessed region, the unevenness whose surface area is locally increased by arranging the uneven structure In the region, the thickness of the metal layer as the light reflecting layer is thinner than the thickness in the non-concave region where the uneven structure is not formed.

  By selectively changing the shape, pitch, and depth of the concavo-convex structure formed in the transparent molding layer, the surface area of the transparent molding layer having the concavo-convex region can be increased. By changing the surface area, the film thickness of the light reflecting layer disposed on the uneven region can be changed.

  If the thickness of the light reflecting layer is thin, the transmittance at that portion becomes high, and it becomes possible to cause a difference in transmittance from the non-concave region where the thickness of the light reflecting layer is thicker than the uneven region.

When an aluminum thin film is used as the light reflecting layer, the thinner the thin film is, the higher the transmittance is (the relationship between the film thickness and the transmittance will be shown later). As a result, it is possible to produce the same effect.

  Due to the shape, pitch, and depth of the concavo-convex structure, the film thickness of the light reflecting layer changes depending on the concavo-convex convex part, concave part, and slope, for example, concavo-convex structure with asymmetric cross-sectional shape such as a blazed grating In this case, it is possible to increase the thickness of the light reflecting layer only on one side of the slope. As a result, when the optical medium is observed from the side where the thickness of the light reflecting layer is thick, the reflected light can be observed. When the optical medium is observed from the side where the thickness is thin, since the light is transmitted, what is in the back can be observed. That is, it becomes possible to produce an optical medium having an effect of observing different images depending on the viewing direction.

  If the method of the present invention is used, it is a maskless process that does not require mask fabrication, which is necessary for conventional demetallized processing, and therefore the problem of positional accuracy during mask fabrication can be solved. In addition, since an etching process is not required, such equipment is not required, and it is possible to obtain a region having a high transmittance similar to that obtained by removing the metal layer by demetalized processing without performing a complicated process. .

  By using the method of the present invention, it becomes possible to easily form a light-reflective layer pattern with higher definition and higher accuracy than the conventional demetallization process without a mask manufacturing process and without an etching process.

The top view which showed an example of the form of the optical medium in this invention. FIG. 2 is a perspective view of the optical medium shown in FIG. The figure which showed an example of the cross section in the XX 'line | wire in FIG. The figure which showed an example of the cross section of the diffraction grating used as uneven structure in this invention. The figure which showed an example of the cross section of the blazed grating used as an uneven structure in this invention. The perspective view which showed an example of the form of the optical medium in this invention. Sectional drawing which showed an example of the light-scattering structure used as an uneven structure in this invention in the cross section in the XX 'line | wire in FIG. The figure which showed the change of the transmittance | permeability by the film thickness of a light reflection layer. The top view which showed an example of the form of the optical article in this invention. The figure which showed an example of the cross section in the YY 'line | wire in FIG.

  The preferred embodiments of the present invention will be described below. The embodiments described below are preferred specific examples of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. As long as there is no description, it is not restricted to these forms.

  FIG. 1 is a plan view showing an example of the optical medium of the present invention. FIG. 2 is a perspective view of the optical medium shown in FIG.

  The surface of the optical medium 10 here includes a concavo-convex region 5 where the concavo-convex structure 4 is formed and a non-concave region 6 where the concavo-convex structure 4 is not formed. In FIGS. 1 and 2, the shape of “TIT” is displayed as an example by the uneven region 5 provided with the uneven structure 4. A region other than the uneven region 5 is occupied by a non-recessed region 6 where the uneven structure 4 is not formed.

  FIG. 3 is a cross-sectional view of the optical medium 10 taken along line X-X ′ shown in FIG. 1. In the optical medium 10, the transparent molding layer 2 is disposed on one surface of the transparent substrate 1. As a material of the transparent substrate 1, a film or sheet made of a resin having optical transparency such as polyethylene terephthalate (PET), polycarbonate (PC), and triacetyl cellulose (TAC) is preferable. Further, as the material of the transparent substrate 1, an inorganic material such as glass may be used. The transparent substrate 1 may be subjected to treatments such as antireflection treatment, low antireflection treatment, hard coat treatment, antistatic treatment and antifouling treatment.

  As a material of the transparent molding layer 2, for example, a resin having optical transparency can be used. In addition, a resin having visible light permeability such as acrylic, polycarbonate, epoxy, polyethylene, and polypropylene can be used. Among these, for example, when a thermoplastic resin or a photocurable resin is used, the transparent molding layer 2 having the concavo-convex structure 4 on at least one surface is obtained by transfer using an original plate on which the concavo-convex structure 4 described later is formed. It can be easily manufactured.

  The transparent molding layer 2 is composed of a concavo-convex region 5 in which the concavo-convex structure 4 is formed and a non-concave region 6 in which the concavo-convex structure 4 is not formed, and the light reflecting layer 3 is disposed on the transparent molding layer 2. ing.

  As the concavo-convex structure 4, as shown in FIG. 4, a diffraction grating having a sine wave cross-sectional shape that vertically cuts the concavo-convex structure 4, a blazed grating having a saw-tooth cross-section as shown in FIG. As shown, a light scattering structure having a concave or convex portion as a light scattering element can be used. Here, the surface area of the concavo-convex region is increased depending on the shape of the concavo-convex structure 4, the pitch, the depth, and the like, and the film thickness of the light reflecting layer 3 can be changed. The effect of changing these parameters will be described later.

  Moreover, the light reflection layer 3 plays the role which raises the reflectance of the interface of the transparent shaping | molding layer 2 in which the uneven structure 4 was provided. As a material of the light reflection layer 3, for example, a metal material having a high reflectance such as aluminum, silver, and an alloy thereof can be used. As a method for producing the light reflecting layer 4 using a metal material, for example, it can be formed by a vapor deposition method such as a vacuum evaporation method or a sputtering method. In the present invention, the light reflecting layer 2 is preferably an aluminum thin film. An aluminum thin film has an advantage that it can be obtained at a lower cost than gold or silver. Furthermore, it is known that aluminum can be easily formed with high accuracy by either a vacuum deposition method or a sputtering method, and an advantage of handling at the time of manufacturing an optical medium can be mentioned as an advantage.

  Here, a more detailed description will be given regarding the concavo-convex structure 4. FIG. 4 shows an example of a cross-sectional view of a diffraction grating having at least one concave portion, convex portion, and slope, which is one of the concavo-convex structures according to the present invention, and the concavo-convex structure 4 has a sinusoidal cross section. .

  As shown in FIG. 4, the depth H of the concavo-convex structure 4 is defined from the top of the convex portion of the concavo-convex structure 4 to the bottom side of the concave portion. Further, the interval from the convex portion to the convex portion or from the concave portion to the concave portion is defined as the pitch P of the concave-convex structure 4.

  In the present invention, since the concavo-convex region 5 is formed with the concavo-convex structure 4, the concavo-convex region 5 has a larger surface area than the non-concave region 6 where the concavo-convex structure 4 is not formed. Further, a distribution occurs in the film thickness of the light reflecting layer 3. Specifically, since the uneven area 5 has a large surface area, the film thickness AL of the light reflecting layer 3 is thinner than the light reflecting layer 3 disposed on the non-concave area 6.

  Here, the case where the material of the light reflection layer 3 is an aluminum thin film is considered. FIG. 8 is a graph showing the film thickness dependence of transmittance at wavelengths of 442 nm, 532 nm, and 633 nm when an aluminum thin film is disposed on a material having a refractive index of 1.5.

  From the data shown in FIG. 8, the transmission is about 85% when the film thickness is about 2 nm, about 70% when about 5 nm, about 60% when about 7 nm, and about 40% when about 10 nm. Thus, it can be seen that as the film thickness increases, the transmittance decreases (in contrast, the reflectance increases). Further, the transmittance rapidly decreases in a relatively thin film thickness range, but thereafter the transmittance gradually decreases.

  For example, the film thickness of the aluminum thin film constituting the light reflecting layer 3 disposed on the uneven area 5 is 2 nm, and the film thickness of the aluminum thin film constituting the light reflecting layer 3 disposed on the non-uneven area 6 is 40 nm. In this case, the transmittance in the uneven region 5 is about 85% (reflectance is about 15%), and the transmittance in the non-concave region 6 is about 10% (the reflectance is 90%). For this reason, a big difference can be produced in the transmittance | permeability of the uneven | corrugated area | region 5 and the non-uneven | corrugated area | region 6. FIG. If a light source such as a fluorescent lamp is seen through, the light and the external shape of the fluorescent lamp can be clearly confirmed in the uneven area 5 with a transmittance of about 85%, but the non-light with a transmittance of about 10%. In the concavo-convex region 6, almost no light from the fluorescent lamp can be confirmed, and it is difficult to confirm the external shape of the fluorescent lamp.

  When the diffraction grating as shown in FIG. 4 is used as the concavo-convex structure 4, the surface area of the concavo-convex region 5 increases as the pitch P is finer and the depth H is deeper. Accordingly, the film thickness AL of 3 is reduced accordingly, and a difference in film thickness from the non-concave area 6 occurs, so that it is possible to cause a large difference in transmittance between the uneven area 5 and the non-concave area 6. Therefore, in the present invention, it is preferable that the pitch P is 300 nm or more and 800 nm or less, and the depth H is 100 nm or more and less than 500 nm.

  Further, by making the concavo-convex structure 4 have a fine pitch P and a depth H of nano order, the surface area is increased, and the film thickness AL of the light reflecting layer 3 disposed on the concavo-convex region 5 is reduced. The transmittance of region 5 increases.

  On the other hand, the surface area of the optical medium 10 in plan view is such that the uneven structure 4 is not formed in the non-recessed region 6, so that the surface area (real area) of the non-recessed region 6 is greater than the surface area (actual area) of the uneven region 5. Therefore, the film thickness AL of the light reflection layer 3 disposed on the non-concave area 6 is thicker than the film thickness AL of the light reflection layer 3 disposed on the uneven area 5. As a result, when an aluminum thin film is used as the light reflecting layer 3, the difference in film thickness AL between the uneven region 5 and the non-recessed region 6 appears as a difference in transmittance.

  The transmittance becomes higher as the film thickness AL of the aluminum thin film is thinner (see the graph of FIG. 8). The uneven region 5 having a thinner film thickness and a higher transmittance has a high transmittance obtained by removing the metal layer by demetallization. It produces the same effect as the area. Furthermore, by setting the pitch to 300 nm or more and 800 nm or less, it is possible to observe diffracted light when the concave and convex region 5 is observed from a steep angle direction, and an effect such as demetallized by transmission observation, It becomes possible to produce the effect of diffracted light shining iridescent in a complex manner.

  The light reflecting layer in the present invention is preferably an aluminum thin film formed by either vacuum evaporation or sputtering. Although it is known that the vacuum deposition method or the sputtering method can be easily formed with high accuracy, the thickness is controlled by managing the thickness of the film formed on a flat surface by either method. For example, in the vacuum vapor deposition method, a film is formed on a crystal resonator, and the film thickness is managed from fluctuations in the resonance frequency of the crystal resonator. That is, the film thickness formed on the flat surface is controlled, but the film thickness formed on the concavo-convex structure such as a diffraction grating is not normally controlled.

  Therefore, when the film is formed with an arbitrary film thickness on the non-concave area 6 (flat surface) in the present invention, the film thickness of the light reflecting layer disposed on the uneven area 5 on which the uneven structure 4 is formed is Due to the increase in surface area due to the concavo-convex structure, it becomes thinner than the film thickness of the non-concave area 6 (flat surface).

  Actually, when a film is formed on a diffraction grating or the like, the film thickness is different at the convex, concave, and inclined surfaces, which are parts of the concavo-convex structure. . In addition, as in the case of the present invention, if both the pitch P and the depth H of the concavo-convex structure are in the nano-order range, the film thickness of the concave portion tends to be thinner than the convex portion of the concavo-convex structure. This is due to the fact that the deposition material is difficult to enter the concave portion because it has a nano-order fine structure.

  Consider a case where a diffraction grating having a pitch P defined in the present invention of 300 nm to 800 nm and a depth H of 100 nm to less than 500 nm is used as the concavo-convex structure 4. When an aluminum thin film having a thickness of 40 nm or more and 60 nm or less is formed on the non-concave region 6, the aluminum thin film formed on the concavo-convex structure 4 made of a diffraction grating has a concave portion of 1 nm or more and 30 nm or less. 20 nm or more and 40 nm or less at the part, and 1 nm or more and 20 nm or less at the slope.

  Moreover, the transmittance | permeability when a different film thickness is each formed into the recessed part of a concavo-convex structure, a convex part, and a slope can be considered as an average value of each film thickness. Further, the transmittance changes as shown in FIG. 8 occur depending on the film thickness values formed on the concave portions, the convex portions, and the slopes. From the results shown in FIG. 8, the thinner the film thickness, the higher the transmittance, and the same transmittance as that obtained by removing and patterning the light reflecting layer such as metal as in the case of demetalized processing can be obtained.

  Next, the case where a blazed grating is used for the concavo-convex structure 4 in the present invention will be described. FIG. 5 shows that at least one or more concave portions, convex portions, a surface or a slope having a steep inclination from the concave portion to the convex portion, and a rising portion from the concave portion to the convex portion have a gentler slope than the steep slope. An example of a cross-sectional view of a blazed grating having an inclined surface and a cross-section of the concavo-convex structure having a sawtooth shape is shown. In FIG. 5, the depth H of the concavo-convex structure 4 is defined from the top of the convex portion of the concavo-convex structure 4 to the bottom side of the concave portion. Further, the interval from the convex portion to the convex portion or from the concave portion to the concave portion is defined as the pitch P of the concave-convex structure 4. Similar to the case where a diffraction grating is used for the concavo-convex structure 4, the concavo-convex region 5 where the blazed grating is formed in the concavo-convex structure 4 has a larger surface area than the non-concave region 6 where the concavo-convex structure is not formed. When the light reflecting layer 3 is provided on the region 6 with an arbitrary thickness, the film thickness AL of the light reflecting layer 3 disposed on the uneven region 5 adjacent to the non-recessed region 6 is higher than the non-recessed region 6. It becomes thinner than the film thickness of the light reflecting layer 3 disposed on the surface.

  When a metal layer such as an aluminum thin film is used for the light reflecting layer 3, there is a relationship (the relationship shown in FIG. 8) that the transmittance increases as the film thickness decreases. It is possible to obtain the same high transmittance as when removing.

  Even when a blazed grating is used for the concavo-convex structure 4, the surface area increases as the pitch P is finer and the depth H is deeper, as in the case of using a diffraction grating, and therefore the light reflecting layer 3 disposed thereon is increased. The film thickness AL is reduced. In the present invention, it is preferable that the pitch P is 300 nm or more and 800 nm or less, and the depth H is 100 nm or more and less than 500 nm.

  Further, the non-concave area 6 where the uneven structure 4 is not formed has a smaller surface area than the uneven area 5 where the uneven structure 4 is formed. Therefore, the film thickness AL of the light reflection layer 3 disposed on the non-concave area 6 is thicker than the film thickness AL of the light reflection layer 3 disposed on the uneven area 5.

  On the other hand, the concavo-convex region 5 adjacent to the non-concave region 6 is arranged on the concavo-convex region 5 because the surface area is increased by setting the concavo-convex structure 4 to a nano-order fine pitch P and depth H. The film thickness AL of the light reflecting layer 3 is reduced, and the transmittance of the uneven region 5 is increased. As a result, when an aluminum thin film is used as the light reflecting layer 3, the difference in film thickness AL between the uneven region 5 and the non-recessed region 6 appears as a difference in transmittance.

  As the thin film thickness AL of the aluminum thin film becomes thinner, the transmittance becomes higher (see the graph in FIG. 8). Therefore, the light reflective layer such as metal is removed and patterned in the portion where the film thickness is thin and the transmittance is high as in the case of demetalized processing. The same high transmittance can be obtained.

  Unlike the diffraction grating, the blazed grating has a function of strongly diffracting light in one direction. For this reason, only when observed from a certain direction, a rainbow-colored diffracted light can be emitted as reflected light, and a combined effect can also be exhibited, in which transmission observation of a high transmittance portion is possible.

  Even when a blazed grating is used for the concavo-convex structure 4, the light reflecting layer 3 is preferably an aluminum thin film formed by either a vacuum evaporation method or a sputtering method. Further, the film thickness and transmittance of the aluminum thin film have a relationship as shown in FIG. When a film is formed on a blazed grating, the film thickness differs depending on the film forming mechanism between the convex part, concave part, slope having a steep slope and slope having a gentle slope.

  If both the pitch P and the depth H of the concavo-convex structure are in the nano-order range as in the present invention, the thickness of the concave portion tends to be thinner than the convex portion of the structure. This is due to the fact that it is difficult for the vapor deposition material to enter the recess because it has a nano-order fine structure. In addition, the slope having a steep inclination tends to reduce the thickness of the light reflecting layer.

  Also, if anisotropic vapor deposition (sputtering) or oblique vapor deposition (sputtering) is performed, it is possible to produce a special optical medium in which an aluminum thin film is formed only on one side of the blazed grating. .

  Consider a case where a blazed grating having a pitch P defined in the present invention of 300 nm to 800 nm and a depth H of 100 nm to less than 500 nm is used as the concavo-convex structure 4. When an aluminum thin film having a thickness of 40 nm or more and 60 nm or less is formed on the non-concave region 6, the film thickness AL of the aluminum thin film formed on the concavo-convex structure 4 made of a blazed lattice is 1 nm or more and 30 nm respectively in the recess. Hereinafter, the film thickness on a slope having a steep slope is 1 nm or more and 5 nm or less, and the film thickness on a slope having a gentle slope opposite to the slope having a steep slope is 40 nm or more and 60 nm or less.

  As described above, even if the film thickness is extremely thick only on one side of the blazed grating, the transmittance is the thickness of each film thickness of the concave portion of the concavo-convex structure, the slope having a steep slope, and the slope having a gentle slope. It can be considered as an average value. In that case, the transmittance varies depending on the value of the film thickness. Specifically, the transmittance varies as shown in FIG. From the results of FIG. 8, the thinner the film thickness is, the higher the transmittance is. Therefore, a high transmittance equivalent to that obtained by removing the light reflecting layer such as metal and patterning as in the case of demetalized processing can be obtained.

  Next, a case where a light scattering structure is used for the uneven structure 4 will be described. FIG. 6 shows an example of a perspective view of the optical medium 10 when a light scattering structure is used for the uneven structure 4.

  The concavo-convex structure 4 shown in FIG. 6 is a light scatterer that scatters incident light using concave portions or convex portions as light scattering elements, and is rectangular in each of the orthogonal x and y directions on the plane of the optical medium 10. By arranging a plurality of the light scattering elements having different lengths on each side and changing the density at which the light scattering elements are formed inside the light scatterer, each light scattering property is arbitrarily changed. I am doing so. FIG. 7 shows a cross section taken along line XX ′ of FIG. In the present invention, the light reflecting layer 3 is formed as the concavo-convex structure 4 having a rectangular cross section as shown in FIG.

  The spread of light scattered by the light scattering element composed of the concave portion or the convex portion in the light reflecting layer 3 can be regarded as being equal to the distribution of diffracted light obtained by handling the diffraction phenomenon with the light scattering element as an opening. Therefore, if the size of the light scattering element is large, the scattered light is not spread, and if the size is small, the scattered light is greatly spread. In addition, the result of integrating the light intensity distribution for light scattering elements of different sizes by randomly arranging light scattering elements of different sizes (different lengths of each side of the rectangle) at different densities. The actual light intensity distribution is obtained. Therefore, scattered light having a continuous distribution over a wide range can be obtained, and display with little change in brightness depending on the observation position is possible.

  If a light scattering element of a single size is used, the light intensity distribution has a vibration component, and the light intensity change with respect to the emission direction differs for each light wavelength. For this reason, a sudden change in brightness or darkness depending on the observation position or a rainbow-colored light scatterer occurs.

  The intensity of the scattered light by the light scatterer can be changed by the density of the light scattering elements in the light scatterer or the depth of the light scatterer. Particularly in the present invention, the density of the light scattering elements is preferably about 50%. When the density is about 50%, the maximum scattered light intensity can be obtained, and the scattered light intensity decreases as the density leaves this value. Therefore, since the gradation expression of the uneven area 5 can be performed depending on the density, it is possible to produce a light and dark expression in white.

  FIG. 7 shows a cross-sectional view taken along the line XX ′ of FIG. 6. In this case, the light reflecting layer 3 disposed on the concavo-convex structure 4 having a rectangular cross section as shown in FIG. A thin film is preferred. The thin film is preferably formed by either a vacuum evaporation method or a sputtering method.

  When the uneven structure 4 having a rectangular cross-sectional structure as shown in FIG. 7 uses a light scattering structure having a depth H of 100 nm or more and less than 500 nm as defined in the present invention, the structure depth H is nano. Because of the fine structure of the order, the film thickness of the concave portion tends to be thinner than the convex portion of the concavo-convex structure due to the difficulty of the deposition material entering the concave portion of the concavo-convex structure.

  Consider a case where a light scattering structure having a depth H of 100 nm or more and less than 500 nm defined in the present invention is used as the concavo-convex structure 4. When an aluminum thin film having a thickness of 40 nm to 60 nm is formed on the non-recessed region 6, the aluminum thin film formed on the uneven structure 4 made of a light scattering structure has a concave portion of 1 nm to 30 nm and a convex portion. It becomes 40 nm or more and 60 nm or less.

  The transmittance when different film thicknesses are formed on the concave and convex portions of the concavo-convex structure can be considered as an average value of the respective film thicknesses. The reflectance changes as shown in FIG. 8 occur depending on the film thickness values formed on the concave and convex portions. Therefore, the transmittance also changes. From the results shown in FIG. 8, the thinner the film thickness, the higher the transmittance. Therefore, the same high transmittance as that obtained by removing the light reflecting layer such as metal and patterning as in the case of demetallized processing can be obtained.

  Also, if a light scattering structure is used for the concavo-convex structure, even when the optical medium is tilted, the concavo-convex area does not shine in seven colors due to the influence of diffracted light, and is visually recognized as a transparent area with high transmittance in a wide observation range. It becomes possible.

  The optical medium of the present invention can also be used as an optical article by disposing an adhesive layer on a light reflecting layer and attaching it to a transparent substrate or an opaque substrate. As the adhesive layer, a thermosetting or ultraviolet curable transparent adhesive can be used. Moreover, as a transparent base material, the film or sheet | seat which consists of resin which has optical transparency, such as a polyethylene terephthalate (PET), a polycarbonate (PC), and a triacetyl cellulose (TAC), etc. are suitable. Moreover, you may use inorganic materials, such as glass.

  The opaque base material may be attached to paper such as gift certificates or banknotes, and if the opaque base material is printed, the uneven area of the optical medium of the present invention, that is, demetallized processing, etc. It is also possible to express a pattern such as a picture in combination with a portion where a light reflection layer such as a metal is removed and a transmittance similar to that obtained by patterning is obtained.

  FIG. 9 shows an example of a plan view of an optical article using the optical medium of the present invention. FIG. 10 shows an example of a cross-sectional view taken along line YY ′ of the optical article shown in FIG.

  The optical article expresses a character “TOP”, a number “1000”, and a star-shaped symbol by arranging the uneven region and the non-recessed region. The character “TOP”, the number “1000”, and the star symbol are formed by the uneven region, and the other ranges are formed by the non-recessed region.

  The optical medium is integrated with an opaque substrate printed with color ink by an adhesive layer. Moreover, the optical medium has arrange | positioned the transparent shaping | molding layer on the transparent base material.

  Polyethylene terephthalate (PET) was used for the transparent substrate. In general, PET has high transparency and is used in many applications as an inexpensive material.

  An ultraviolet curable resin was used for the transparent molding layer. The UV curable resin is poured into a pattern such as a mold, closely adhered to a transparent base material that has been subjected to easy adhesion treatment, etc., cured by irradiating with UV light, and then peeled off from the mold. Can be easily replicated.

  In this example, a diffraction grating was formed as a concavo-convex structure on the transparent molding layer to produce a concavo-convex region. For the formation of the diffraction grating, a method was used in which the diffraction grating produced in the mold as described above was duplicated with an ultraviolet curable resin. The pitch of the diffraction grating was 300 nm, and the depth H of the structure was about 400 nm. Furthermore, a light reflection layer is disposed on the transparent molding layer.

  In this example, an aluminum thin film was used as the light reflecting layer by vacuum deposition. In the formation of the aluminum thin film, the film was formed under the condition that the film thickness of the aluminum thin film on the non-concave region was about 50 nm.

  In this example, the film thickness of the formed light reflecting layer was about 50 nm in the non-concave region, about 20 nm in the convex portion of the concave-convex structure, about 10 nm in the concave portion, and about 5 nm in the inclined surface.

Since the aluminum thin film in the non-recessed region has a thickness of about 50 nm, it can be seen from the graph shown in FIG. 8 that the transmittance is about 10%.

  On the other hand, the aluminum thin film in the concavo-convex region is different for each of the concave, convex, and inclined surfaces of the concavo-convex structure, but the transmittance can be considered as an average value for each film thickness, and therefore it is about 50% I understand. As a result, since the transmittance is high in the uneven region, it is possible to observe the pattern of the color ink printed on the opaque base material through the uneven region. On the other hand, since the transmittance is low in the non-recessed region, it is difficult to observe the opaque base material through the non-recessed region.

  The pattern disposed on the opaque base material is not limited to color ink, and may be formed using fluorescent ink, magnetic ink, hologram, or the like. For example, in the case where a pattern is formed with fluorescent ink, it is possible to produce an effect that fluorescent coloring is confirmed through the uneven region only when the optical article of the present invention is irradiated with black light.

  The optical medium in the present invention may be combined with a transparent substrate. In such a case, a method of use is also conceivable in which a pattern of contrast with a non-recessed area is confirmed by observing the uneven area through transmission.

  As described above, various effects can be expected by combining the optical medium of the present invention with another base material.

DESCRIPTION OF SYMBOLS 1 ... Transparent base material 2 ... Transparent shaping | molding layer 3 ... Light reflection layer 4 ... Uneven structure 6 ... Uneven area 7 ... Non-relief area 7 ... Adhesive layer 8 ... Opaque substrate 10 ... Optical medium H ... Depth P ... Pitch AL ... Thickness

Claims (9)

On at least one surface of the transparent substrate, a concavo-convex region in which a concavo-convex structure is formed, and a transparent molding layer composed of a non-concave region other than the concavo-convex structure,
When the dimension from the top of the convex portion of the concave-convex structure to the bottom side of the concave portion is the depth H of the concave-convex structure, the depth of the concave-convex structure is 100 nm or more and less than 500 nm, and the top of the transparent substrate With a light reflection layer,
The optical medium, wherein the uneven region has a different transmittance depending on the uneven structure, and the transmittance in the uneven region is higher than that of the non-recessed region.   The concavo-convex structure is a diffraction grating having at least one concave portion, a convex portion, and a slope, and the cross-sectional shape of the concavo-convex structure is a sine wave shape, and the pitch of the diffraction grating is 300 nm or more and 800 nm or less. The optical medium according to claim 1, wherein:   Compared with a surface or slope having a steep slope where the rise from the concave portion to the convex portion is at least one, and the rise from the concave portion to the convex portion is more than the steep surface or slope. 2. The blazed grating having a slope with a gentle inclination and a cross-sectional shape of the concavo-convex structure having a sawtooth shape, wherein a pitch of the blazed grating is 300 nm or more and 800 nm or less. Optical medium.   The concavo-convex structure is a light scatterer that scatters incident light using a concave portion or a convex portion as a light scattering element, and has a rectangular shape in each of x and y directions orthogonal to each other on a plane of the optical medium. A plurality of the light scattering elements having different lengths are arranged, and the light scattering property is arbitrarily changed by changing the density at which the light scattering elements are formed inside the light scattering body. The optical medium according to claim 1. The light reflecting layer is an aluminum thin film;
The film thickness of the light reflecting layer is different in each of the non-concave region, the concave portion of the diffraction grating, the convex portion, and the slope.
The film thickness in the non-convex region is 40 nm or more and 60 nm or less,
The film thickness in the recess is 1 nm or more and 30 nm or less,
The film thickness at the convex portion is 20 nm or more and 40 nm or less,
The film thickness on the slope is 1 nm or more and 20 nm or less,
The optical medium according to claim 2. The light reflecting layer is an aluminum thin film;
The thickness of the light reflecting layer is different in the non-concave region, the concave portion of the blazed grating, the convex portion, the steep slope, the slope having a gentle slope,
The film thickness in the non-convex region is 40 nm or more and 60 nm or less,
The film thickness in the recess is 1 nm or more and 30 nm or less,
The film thickness at the convex portion is 20 nm or more and 40 nm or less,
The film thickness on the slope having the steep slope is not less than 1 nm and not more than 5 nm;
The optical medium according to claim 3, wherein the film thickness on the slope having the gentle inclination is 20 nm or more and 40 nm or less. The light reflecting layer is an aluminum thin film;
The thickness of the light reflecting layer is different in the non-concave region, the concave portion of the light scattering element, and the convex portion,
The film thickness in the non-convex region is 40 nm or more and 60 nm or less,
The film thickness in the recess is 1 nm or more and 30 nm or less,
The optical medium according to claim 4, wherein the film thickness at the convex portion is 20 nm or more and 40 nm or less.   The optical medium according to claim 1, wherein the light reflecting layer is an aluminum thin film formed by a vapor deposition method of either a vacuum evaporation method or a sputtering method. .   The optical article according to any one of claims 1 to 8, wherein an adhesive layer is disposed on the light reflecting layer, and the optical medium is attached to a transparent substrate or an opaque substrate. .

Images