WO2019182050A1

WO2019182050A1 - Optical element, transfer foil, authentication object, and method for verifying authentication object

Info

Publication number: WO2019182050A1
Application number: PCT/JP2019/011841
Authority: WO
Inventors: 華子山本; 啓太郎杉原; 智子田代; 彰人籠谷
Original assignee: 凸版印刷株式会社
Priority date: 2018-03-20
Filing date: 2019-03-20
Publication date: 2019-09-26
Also published as: JP2023160830A

Abstract

In the present invention, a subwavelength grating displays a colored image exhibiting a color corresponding to a grating period of the subwavelength grating in a direction of reflection, which includes a direction of regular reflection. A relief surface displays a reflected image from monochromatic reflected light in a direction of reflection, which includes a direction different from the direction of regular reflection. An optical element has a first state where the colored image and the reflected image are not displayed, a second state where primarily the colored image is displayed, and a third state where primarily the reflected image is displayed. An angle formed by a plane in which the optical element spreads and a plane that includes an observer's gaze is an observation angle. The optical element is observed in the first state, the second state, or the third state, depending on the observation angle.

Description

Optical element, transfer foil, authentication body, and verification method of authentication body

Each embodiment of the present invention relates to an optical element, a transfer foil, an authentication body, and an authentication body verification method. This application claims priority based on Japanese Patent Application No. 2018-053545 filed in Japan on March 20, 2018 and Japanese Patent Application No. 2019-014299 filed in Japan on January 30, 2019, and the contents thereof. Is hereby incorporated by reference.

Optical elements that use holograms, diffraction gratings, multilayer interference films, etc., for the purpose of preventing counterfeiting of securities such as gift certificates, banknotes, and credit cards, and for the purpose of product brand protection Is attached. Since manufacturing of such an optical element is not easy, the optical element has an effect of preventing forgery of an article to which the optical element is attached.

As optical elements described above, optical elements that can be verified only by visual inspection without using a special verification instrument when verifying the authenticity of the optical element are widely used. Among them, those in which the color in which the optical element is visually recognized or the image displayed by the optical element change according to the angle at which the optical element is observed are widely used. Among these, examples of the optical element whose color changes according to the angle at which the optical element is observed include the above-described diffraction grating and multilayer interference film.

The diffraction grating and the multilayer interference film have a feature that when the angle at which these optical elements are observed is changed, the color of the optical elements visually recognized by the observer changes continuously. As described above, since a plurality of colors are observed by the observer, it is difficult to clearly specify the color to be visually recognized when verifying that the optical element is an authentic optical element in authenticity verification. In addition, when verifying the authenticity of the optical element, it is difficult for the observer to find an appropriate angle range among the angles at which the optical element is observed.

In order to solve such a problem, a sub-wavelength grating is used as an optical element that develops a predetermined color. The period of the fine structure in the sub-wavelength grating is less than the wavelength of visible light. The sub-wavelength grating has a characteristic of emitting only light of a specific wavelength in the regular reflection direction among the light incident on the sub-wavelength grating. Therefore, according to the sub-wavelength grating, the observer cannot visually recognize light having a predetermined color in the optical element when observing the optical element from a direction other than the regular reflection direction. Therefore, according to the sub-wavelength grating, unlike the diffraction grating and the multilayer interference film, the angle at which the optical element should be observed and the color visually recognized at the angle can be defined. Therefore, a method for authenticating the optical element can be clearly described. Examples of the anti-counterfeit optical element using such a sub-wavelength grating include the optical element described in Patent Document 1.

Special table 2013-527938 gazette

By the way, in the optical element described in Patent Document 1, after viewing the optical element at the first angle at which the first color is visually recognized, the optical element is rotated with the normal to the plane in which the optical element spreads as the rotation axis. . Then, the authenticity of the optical element is verified by visually recognizing the optical element at the second angle at which the second color is visually recognized.

Here, the hand movement performed by the observer to rotate the optical element is not a natural movement compared to the movement of tilting the optical element. Therefore, the workability of the verification work by the observer tends to be low, and the verification efficiency tends to be low. Further, as described above, the sub-wavelength grating emits light having a predetermined color only in the regular reflection direction. Therefore, at the moment when the observer picks up the optical element or when the observer places the optical element on a flat surface and then observes the optical element, the observer can visually recognize the color that the optical element exhibits. Unlikely. That is, it is unlikely that the observer will observe the optical element in the regular reflection direction at that moment. Therefore, the observer rotates the optical element after finding an angle at which the color exhibited by the optical element can be visually recognized, and further, the angle at which another color exhibited by the optical element can be visually recognized even after rotating the optical element. I need to find it. As a result, since it takes time for the observer to verify the authenticity of the optical element, an optical element that can verify the authenticity more easily is demanded.

An object of the present invention is to provide an optical element, a transfer foil, an authentication body, and a verification method for the authentication body that can easily perform authentic verification.

An optical element for solving the above problems includes a first layer, a second layer in contact with the first layer, and a third layer in contact with the second layer, and each layer has light transmittance. The first layer is a resin layer having a first refractive index, has a first surface in contact with the second layer, includes a subwavelength grating in at least a part of the first surface, and The layer is a dielectric layer having a second refractive index higher than the first refractive index, and has a second surface in contact with the first surface of the first layer, and the first surface is The third layer is a resin layer having a third refractive index lower than the second refractive index. Any one of the first layer, the second layer, and the third layer is a relief layer, and the relief layer includes a relief surface including a plurality of reflection surfaces, and a pitch between the reflection surfaces adjacent to each other. Is larger than the pitch of the sub-wavelength grating. When observing from the light source side that the optical element is irradiated with light from a light source located on the opposite side of the third layer with respect to the second layer, the sub-wavelength grating is specularly reflected. A colored image having a color corresponding to a grating period of the sub-wavelength grating is displayed in a reflection direction including a direction, and the relief surface is a reflection image by monochrome reflected light in a reflection direction including a direction different from the regular reflection direction. That is, a monochrome image is displayed, and the optical element has a first state in which the colored image and the reflected image are not displayed, a second state in which the colored image is mainly displayed, and a third state in which the reflected image is mainly displayed. And an angle formed by a plane in which the optical element spreads and a plane including the observer's line of sight is an observation angle, and the optical element has the first state, the second state, depending on the observation angle, and, Serial observed by any of the third state.

An optical element for solving the above problems includes a first layer, a second layer in contact with the first layer, and a third layer in contact with the second layer, and each layer has light transmittance. The first layer is a resin layer having a first refractive index, has a first surface in contact with the second layer, includes a subwavelength grating in at least a part of the first surface, and The layer is a dielectric layer having a second refractive index higher than the first refractive index, and has a second surface in contact with the first surface of the first layer, and the second surface is The third layer is a resin layer having a third refractive index lower than the second refractive index. The optical element further includes a relief layer including a relief surface different from the first surface and the second surface, the relief surface includes a plurality of reflection surfaces, and a pitch between the reflection surfaces adjacent to each other is A state in which light is applied to the optical element from a light source that is larger than the pitch of the sub-wavelength grating and located on the side opposite to the third layer with respect to the second layer is observed from the light source side. The sub-wavelength grating displays a colored image exhibiting a color corresponding to the grating period of the sub-wavelength grating in the regular reflection direction, and the relief surface is reflected by monochrome reflected light in a direction different from the regular reflection direction. Displaying a reflected image, and the optical element has a first state in which the colored image and the reflected image are not displayed, a second state in which the colored image is mainly displayed, and a third state in which the reflected image is mainly displayed. Above The angle formed by the plane in which the scientific element spreads and the plane including the observer's line of sight is the observation angle, and the optical element is in the first state, the second state, and the plane according to the observation angle. Observed in any of three states.

A transfer foil for solving the above problems includes an adhesive body including the optical element and an adhesive layer for bonding the optical element to a transfer target.
The authentication body for solving the said subject is provided with the said optical element.

According to each of the above configurations, the optical element displays a reflected image formed by monochrome reflected light, that is, a monochrome image, and a colored image formed by light having a specific wavelength, that is, a chromatic image. To do. Here, the discrimination between the monochrome image and the chromatic image is performed by discriminating between the first monochrome image and the second monochrome image, or distinguishing the first chromatic color image and the second chromatic color image. Compared to the case where the difference between the two images is different, there is less individual difference between the two images. Therefore, in the optical element, compared with the case where the authenticity of the optical element is verified based on two chromatic color images or two monochrome images, individual differences are less likely to occur in the authenticity verification. Standards for verifying are easily written. Thereby, according to the optical element, authenticity verification can be performed more easily.

1 is a cross-sectional view schematically illustrating the structure of an optical element according to a first embodiment of the present invention. 1 is a plan view schematically illustrating the structure of an optical element according to a first embodiment of the present invention together with an enlarged view. FIG. 3 is a cross-sectional view schematically illustrating a structure in a cross section taken along line II in FIG. 2. The operation of the first embodiment of the present invention is schematically illustrated. The operation of the first embodiment of the present invention is schematically illustrated. The top view by which the structure of the other example of 1st Embodiment of this invention was illustrated schematically with the enlarged view. The azimuth angle in the pixel area is schematically illustrated. The top view by which the structure in another example of 1st Embodiment of this invention was illustrated schematically with the enlarged view. Sectional drawing in which the structure in the cross section along the II-II line in FIG. 8 and the structure in the cross section along the III-III line were illustrated schematically. The relationship between the azimuth angle and the wavelength of light emitted from the subwavelength grating is schematically illustrated. The relationship between the azimuth angle and the wavelength of light emitted from the subwavelength grating is schematically illustrated. Sectional drawing with which the structure in the optical element of 2nd Embodiment of this invention was illustrated schematically with the enlarged view. Sectional drawing with which the structure in the other example in the optical element of 2nd Embodiment of this invention was illustrated schematically. Sectional drawing with which the structure in another example of the optical element of 2nd Embodiment of this invention was illustrated schematically. Sectional drawing with which the structure in the optical element of 3rd Embodiment of this invention was illustrated schematically. Sectional drawing with which the structure of the 1st example in the optical element of 4th Embodiment of this invention was illustrated schematically. Sectional drawing with which the structure of the 2nd example in the optical element of 4th Embodiment of this invention was illustrated schematically. Sectional drawing with which the structure in the 1st example of the optical element of 5th Embodiment of this invention was illustrated schematically. The operation of the first example of the optical element according to the fifth embodiment of the present invention is schematically illustrated. The top view in which the 1st state in the 1st example of the optical element of a 5th embodiment of the present invention was illustrated schematically. The top view in which the 2nd state in the 1st example of the optical element of a 5th embodiment of the present invention was illustrated schematically. The top view in which the 3rd state in the 1st example of the optical element of a 5th embodiment of the present invention was illustrated schematically. The top view in which the 4th state in the 1st example of the optical element of a 5th embodiment of the present invention was illustrated schematically. Sectional drawing with which the structure in the 2nd example of the optical element of 5th Embodiment of this invention was illustrated schematically. Sectional drawing which shows the structure of a deformation | transformation in the optical element of 5th Embodiment of this invention. The top view which shows the quantization phase difference structure in the planar view which opposes a relief surface in the deformation | transformation in the optical element of 5th Embodiment of this invention. The graph which shows the peak in the spatial frequency component of the quantization phase difference structure which FIG. 25 shows. FIG. 26 is a cross-sectional view schematically showing a quantization phase difference structure shown in FIG. The top view which shows the 1st example of the 1st image and 2nd image which the optical element of 5th Embodiment of this invention displays. The top view which shows the 2nd example of the 1st image and 2nd image which the optical element of 5th Embodiment of this invention displays. The top view which shows the 3rd example of the 1st image and 2nd image which the optical element of 5th Embodiment of this invention displays. Sectional drawing with which the structure in the 1st example of the optical element of 6th Embodiment of this invention was illustrated schematically. Sectional drawing with which the structure in the 2nd example of the optical element of 6th Embodiment of this invention was illustrated schematically. Sectional drawing with which the structure in the 3rd example of the optical element of 6th Embodiment of this invention was illustrated schematically. Sectional drawing with which the structure in the 4th example of the optical element of 6th Embodiment of this invention was illustrated schematically. Sectional drawing with which the structure of the transfer foil of 7th Embodiment of this invention was illustrated schematically. The top view by which the structure in the authentication body of 8th Embodiment of this invention was illustrated schematically. FIG. 38 is a cross-sectional view schematically illustrating a structure in a cross section taken along line IV-IV in FIG. 37. Sectional drawing with which the structure in the authentication body of 9th Embodiment of this invention was illustrated schematically. The operation in the first example of the authentication body of the ninth embodiment of the present invention is schematically illustrated. The operation in the first example of the authentication body of the ninth embodiment of the present invention is schematically illustrated. The operation in the first example of the authentication body of the ninth embodiment of the present invention is schematically illustrated. The operation in the first example of the authentication body of the ninth embodiment of the present invention is schematically illustrated. The operation in the second example of the authentication body of the ninth embodiment of the present invention is schematically illustrated. The operation in the second example of the authentication body of the ninth embodiment of the present invention is schematically illustrated. The operation in the second example of the authentication body of the ninth embodiment of the present invention is schematically illustrated. The image which imaged the 1st image which the ID card of Experiment 1 displays. The image which imaged the 2nd image which the ID card of Experiment 1 displays.

[First Embodiment]
A first embodiment of the optical element of the present invention will be described with reference to FIGS. Note that, in each drawing, the same reference numerals are assigned to the constituent elements that exhibit the same or similar functions, and redundant descriptions are omitted. Also, the embodiments of the present invention of the present disclosure are a group of embodiments based on a unique single invention from the background. In addition, each aspect of the present disclosure is an aspect of a group of embodiments based on a single invention. Each configuration of the present disclosure may have each aspect of the present disclosure. Each feature of the present disclosure is combinable and can be configured. Accordingly, each feature of the present disclosure, each configuration of the present disclosure, each aspect of the present disclosure, and each embodiment of the present disclosure can be combined, and the combination has a synergistic function, Can be effective.

As shown in FIG. 1, the optical element 10 includes a first layer 11, a second layer 12 in contact with the first layer 11, and a third layer 13 in contact with the second layer 12. Each layer has optical transparency. The optical element 10 can be all or part of a security seal. In other words, the security seal can include the optical element 10. The optical element 10 can be a visible motif. Security seals can be in the form of patches, stripes, overlays and stickers. In the optical element 10, the state in which light is irradiated from the light source located on the opposite side to the third layer 13 with respect to the second layer 12 is from the side opposite to the third layer 13 with respect to the second layer 12. Observed. In the optical element 10, the surface of the first layer 11 opposite to the surface in contact with the second layer 12 is an observation surface 10S that is observed by an observer.

The first layer 11 is a resin layer having a first refractive index. The first layer 11 includes a sub-wavelength grating 11G on at least a part of the surface 11S in contact with the second layer 12. The second layer 12 is a dielectric layer having a second refractive index higher than the first refractive index. The second layer 12 has an uneven shape that follows the sub-wavelength grating 11G. The third layer 13 is a resin layer having a third refractive index lower than the second refractive index. The sub-wavelength grating 11G is formed by a plurality of grating patterns GP arranged along one direction. The lattice pattern GP can be one in which a plurality of convex surfaces and concave surfaces are alternately arranged along one direction. The lattice pattern GP extends over the surface 11S. Each convex surface and each concave surface can be long and thin with a major axis in a direction orthogonal to the direction in which they are arranged. In the sub-wavelength grating 11G, the period of the grating pattern GP can be less than the visible wavelength. As an illustration, the period of the grating pattern GP can be less than 680 nm. Further, the period of the lattice pattern GP may be equal to or shorter than the shortest wavelength of visible light. That is, the period of the lattice pattern GP may be 400 nm or less. The sub-wavelength grating 11G can diffract the incident light. The sub-wavelength grating 11G can guide the diffracted light having a wavelength corresponding to the grating period into the second layer 12. The light guided into the second layer 12 is guided light. The guided light is diffracted in the regular reflection direction of the incident light. That is, the sub-wavelength grating 11G selectively emits incident light in the regular reflection direction.

The refractive index of the first layer 11 may be the same as or different from the refractive index of the third layer 13. The difference between the refractive index of the first layer 11 and the refractive index of the third layer 13 is preferably 0.2 or less, and more preferably 0.1 or less. The difference between the refractive index of the first layer 11 and the refractive index of the second layer 12 and the difference between the refractive index of the third layer 13 and the refractive index of the second layer 12 can be 0.3 or more, respectively. Can be 0.5 or more.

In the surface 11S of the first layer 11, the region where the sub-wavelength grating 11G is located is an uneven surface. In the present embodiment, the entire surface 11S is an uneven surface, but only a part of the surface 11S may be an uneven surface.

FIG. 2 shows the structure of the optical element 10 in plan view facing the observation surface 10S. In the following, for convenience of illustration and explanation, the surface 11S of the first layer 11, that is, the interface with the second layer 12 in the first layer 11 is used using a structure in plan view facing the observation surface 10S. The surface to be formed will be described. In FIG. 2, for the convenience of illustration, the extending direction of the grating pattern GP included in the sub-wavelength grating 11 G is indicated by a straight line.

As shown in FIG. 2, the surface 11S, which is an example of the uneven surface, includes a first region 11S1 and a second region 11S2 that surrounds the first region 11S1 in a plan view facing the surface 11S. In the present embodiment, the surface 11S includes the first region 11S1 and the second region 11S2, but the surface 11S may include regions other than the first region 11S1 and the second region 11S2.

The sub-wavelength grating belonging to the first region 11S1 is the first sub-wavelength grating 11G1. The sub-wavelength grating belonging to the second region 11S2 is the second sub-wavelength grating 11G2. The azimuth angle of the first sub-wavelength grating 11G1 and the azimuth angle of the second sub-wavelength grating 11G2 can be equal to each other. The grating period of the first sub-wavelength grating 11G1 and the grating period of the second sub-wavelength grating 11G2 may be different from each other. The grating period in the sub-wavelength grating 11G is the period of the grating pattern GP described above. The azimuth angle in the sub-wavelength grating 11G is an angle formed by the reference line set in the plane in which the first layer 11 extends and the grating pattern GP.

In the first region 11S1 and the second region 11S2, a plurality of pixel regions Px are partitioned. The area of each pixel region Px is preferably 0.1 mm ² or less. On the entire surface 11S of the first layer 11, the plurality of pixel regions Px are arranged without gaps. In the present embodiment, each pixel region Px has a square shape in a plan view facing the surface 11S, but the pixel region Px may have a regular triangular shape, a regular hexagonal shape, or the like. Each pixel region Px may have a polygonal shape and include sides having different lengths. In each pixel region Px, the length of one side is preferably 0.3 mm or less. In addition, it is more preferable that the length of one side is 0.08 mm or less. In this case, since the length of one side of the pixel region Px is smaller than the resolution of the human eye, each pixel region Px is not visually recognized by the observer. Thereby, the optical element 10 can display a high-resolution image.

FIG. 3 shows a cross-sectional structure of the sub-wavelength grating 11G along the line II in FIG. In FIG. 3, for the convenience of illustration, the cross-sectional structure of the first sub-wavelength grating 11G1 and the cross-sectional structure of the second sub-wavelength grating 11G2 are shown side by side in the vertical direction of the drawing. The cross-sectional structure of each sub-wavelength grating schematically shows the cross-sectional structure of the sub-wavelength grating located in one pixel region Px. In FIG. 3, for convenience of illustration, each sub-wavelength grating is shown as a surface constituting a convex portion protruding in a direction away from the flat surface.

As shown in FIG. 3, the grating period of the first sub-wavelength grating 11G1 and the grating period of the second sub-wavelength grating 11G2 are different from each other. The grating period in the first subwavelength grating 11G1 is the first period d1, and the grating period in the second subwavelength grating 11G2 is the second period d2. In the present embodiment, the first period d1 is smaller than the second period d2, but the first period d1 may be larger than the second period d2. In this embodiment, each sub-wavelength grating is a grating pattern GP that has a wave shape that repeats in one direction, and each wave constitutes a sub-wavelength grating. The distance between two grating patterns GP adjacent to each other is the grating period of each sub-wavelength grating.

In the cross section along the direction in which the grating patterns GP are arranged, the plurality of grating patterns GP included in the first sub-wavelength grating 11G1 have the same shape. In the cross section along the direction in which the grating patterns GP are arranged, the plurality of grating patterns GP included in the second sub-wavelength grating 11G2 have the same shape.

In the sub-wavelength grating, the wavelength of light emitted from the sub-wavelength grating changes according to the grating period of the sub-wavelength grating. That is, according to the grating period of the sub-wavelength grating, the hue exhibited by the optical element 10 including the sub-wavelength grating, in other words, the color visually recognized by the observer as the hue of the optical element 10 changes.

As shown in FIG. 4, in the optical element 10, the light source LS and the observer OB are positioned on the plane perpendicular to the observation surface 10 S of the optical element 10 so that they are targets with respect to the normal line of the observation surface 10 S. When doing so, the observer OB can visually recognize the zero-order diffracted light emitted by the optical element 10. In other words, the optical element 10 can emit light having a wavelength corresponding to the grating period of the sub-wavelength grating 11G in the direction of regular reflection with respect to incident light incident from the light source LS.

As described above, in this embodiment, the grating period of the sub-wavelength grating is set to be shorter than the shortest wavelength of visible light, that is, 400 nm or less. However, the grating period for emitting only light having a specific wavelength by the zero-order diffracted light in a specific direction depends on the refractive index of the sub-wavelength grating and the incident angle of the incident light incident on the sub-wavelength grating. change. Hereinafter, a condition for the sub-wavelength grating to emit only the zero-order diffracted light, in other words, a condition for the sub-wavelength grating not to emit the first-order diffracted light will be described.

It is known that the following expression (1) holds in a reflective diffraction grating.
sin θ1 + sin θ2 = mλ / nd (1)
In Equation (1), θ1 is an incident angle of incident light with respect to the diffraction grating, θ2 is a diffraction angle of diffracted light emitted from the diffraction grating, and m is a diffraction order of the diffracted light. λ is the wavelength, n is the refractive index of the diffraction grating, and d is the grating period of the diffraction grating.

Here, consider the first-order diffracted light when it is assumed that the refractive index n is 1 and light perpendicular to the plane on which the diffraction grating is arranged is incident. At this time, the incident angle θ1 is 0 °, and the diffraction order m is 1. Therefore, substituting these numerical values into equation (1) leads to the following equation (2).

sin θ2 = λ / d Equation (2)
Since sin θ2 is not less than −1 and not more than 1, Equation (2) does not hold when the right side (λ / d) in Equation (2) is larger than 1. In other words, when the right side (λ / d) is larger than 1, the first-order diffracted light is not emitted from the diffraction grating. Therefore, under the above assumption, when the grating period of the diffraction grating is smaller than the wavelength, the diffraction grating emits only zero-order diffracted light.

On the other hand, when the refractive index is not 1 and the incident angle θ1 is not 0 °, the diffraction grating may emit diffracted light of a non-zero order. For example, consider first-order diffracted light when it is assumed that the incident angle θ1 is 30 ° and the wavelength λ is 600 nm. At this time, the incident angle θ1 is 30 °, the wavelength λ is 600 nm, and the diffraction order m is 1. Therefore, substituting these numerical values into equation (1) leads to the following equation (3).

1/2 + sin θ2 = 600 / nd Formula (3)
Since sin θ2 is −1 or more and 1 or less, the left side (1/2 + sin θ2) of Equation (3) is −0.5 or more and 1.5 or less, and the product of the refractive index n and the grating period d is 0 or more and 400 or less. When satisfying the above, the diffraction grating emits the first-order diffracted light by the combination of the refractive index n and the grating period d. For example, the combination (n, d) of the refractive index n and the grating period d when the first-order diffracted light is emitted is as follows.

(N, d) = (1,400), (1.5,200), (2,100)
Thus, depending on the refractive index n of the diffraction grating, even when the grating period d of the diffraction grating is less than or equal to the wavelength λ, the first-order diffracted light or higher-order diffracted light may be emitted. In other words, by adjusting the grating period d of the diffraction grating and the refractive index n of the diffraction grating, the diffraction grating emits zero-order diffracted light while diffracting so as not to emit higher-order diffracted light than zero-order diffracted light. It is possible to form a lattice.

On the other hand, by designing the diffraction angle θ2 of the first-order diffracted light to be significantly larger than the diffraction angle θ2 of the zero-order diffracted light, the zero-order diffracted light can be generated in a state where the relative position of the diffraction grating with respect to the observer is fixed. It is also possible to configure the diffraction grating so that the first-order diffracted light is not visually recognized by the observer while visually recognized by the observer. Thereby, the freedom degree in selection of the material which forms a diffraction grating, and the freedom degree in the grating period of a diffraction grating can be raised.

As shown in FIG. 5, in a state where the light source LS and the viewpoint of the observer OB are fixed, the optical element 10 is tilted so that the above-described plane and the optical element 10 intersect at an angle other than vertical. In this case, since the optical element 10 does not emit zero-order diffracted light in the direction of the line of sight of the observer OB, the observer cannot visually recognize the zero-order diffracted light emitted by the optical element 10. In other words, the observer cannot visually recognize the color that the optical element 10 exhibits.

In the optical element 10, in both the first sub-wavelength grating 11G1 and the second sub-wavelength grating 11G2, the onset and disappearance of the color due to each sub-wavelength grating occurs in synchronization. For this reason, in the entire optical element 10, the color state and the monochrome state are switched. Therefore, in authenticity verification of the optical element 10, the optical element 10 has a first region 11S1 that exhibits a color derived from the first sub-wavelength grating 11G1 and a second region 11S2 that exhibits a color derived from the second sub-wavelength grating 11G2. Can be grasped at a time. As a result, the authenticity of the optical element 10 can be verified more easily by rotating the optical element 10 than when determining whether or not the optical element 10 has a state of two colors.

FIG. 6 is another example of the optical element 10 of the present embodiment. FIG. 6 shows the structure of the optical element 10 in plan view facing the observation surface 10S, as in FIG.
As shown in FIG. 6, the plurality of pixel regions Px may include a pixel region Px including a first sub-wavelength grating 11G1 located in a part of each pixel region Px in a plan view facing the surface 11S. In the example described above with reference to FIG. 3, the first sub-wavelength grating 11G1 is located in the entire pixel region Px. Not limited to this, in each pixel region Px, the first sub-wavelength grating 11G1 may be located only in a part of the pixel region Px. In each pixel region Px, the ratio of the area of the first sub-wavelength grating 11G1 to the area of the pixel region Px is the area ratio. The plurality of pixel regions Px may include pixel regions Px having different area ratios.

The higher the area ratio in each pixel region Px, the higher the luminance of each pixel region Px. For this reason, the plurality of pixel regions Px include pixel regions Px having different area ratios, whereby in the colors exhibited by the first region 11S1, it is possible to form shades of brightness in the same hue. The shading can be a continuous change. The shade may be gradation. Thereby, it is also possible to display a pseudo stereoscopic image in the first region 11S1. In this case, the area ratio can be determined according to the level of brightness in the stereoscopic image to be displayed by the first region 11S1, that is, the gradation value.

In the present embodiment, the optical element 10 includes a portion where the area ratio in the pixel region Px decreases along the direction from the center of the first region 11S1 toward the outer edge of the first region 11S1, and the optical region 10 of the first region 11S1. The area ratio at the outer edge is the smallest.

The optical element 10 of the present embodiment may have a configuration described below with reference to FIGS. Hereinafter, the azimuth angle in the sub-wavelength grating described above will be described in more detail before another example of the optical element 10 is described.

As shown in FIG. 7, an arbitrary direction along the observation surface 10S of the optical element 10 is the X direction, and a direction orthogonal to the X direction is the Y direction. In the present embodiment, the X direction is a reference direction in the azimuth angle, and the angle formed by the X direction and the direction in which the lattice pattern extends is the azimuth angle θ. Therefore, the azimuth angle θ in the first pixel region Px1 is 0 °, and the azimuth angle θ in the second pixel region Px2 is 45 °. The azimuth angle θ in the third pixel region Px3 is 90 °, and the azimuth angle θ in the fourth pixel region Px4 is 135 °.

FIG. 8 shows the structure of the optical element 10 in plan view facing the observation surface 10S, as in FIG.
As shown in FIG. 8, the first region 11S1 includes a first element S1A and a second element S1B adjacent to the first element S1A. Each element S1A, S1B has a shape that follows the contour of the first region 11S1 in a plan view facing the surface 11S of the first layer 11. In the present embodiment, the first region 11S1 is formed of a first element S1A and a second element S1B, and the first element S1A is located outside the second element S1B. The outline of the first element S1A and the outline of the second element S1B are similar in shape to the outline of the first region 11S1.

Among the first sub-wavelength gratings 11G1, the sub-wavelength grating belonging to the first element S1A is the first grating G1A. Of the first sub-wavelength grating 11G1, the sub-wavelength grating belonging to the second element S1B is the second grating G1B. The grating period of the first grating G1A and the grating period of the second grating G1B are equal to each other. On the other hand, the azimuth angle θ of the first grating G1A and the azimuth angle θ of the second grating G1B are different from each other, and the difference between the azimuth angle θ of the first grating G1A and the azimuth angle θ of the second grating G1B is 90 ° or less. In the present embodiment, the azimuth angle θ in the first grating G1A is 0 °, and the azimuth angle θ in the second grating G1B is 45 °. Therefore, the difference between the azimuth angle θ of the first grating G1A and the azimuth angle θ of the second grating G1B is 45 °.

FIG. 9 shows a cross-sectional structure of the first lattice G1A along the line II-II in FIG. 8 and a cross-sectional structure of the second lattice G1B along the line III-III. In FIG. 9, for the convenience of illustration, the cross-sectional structure of the first lattice G1A and the cross-sectional structure of the second lattice G1B are shown side by side in the vertical direction of the drawing. Note that the cross-sectional structure of each grating schematically shows the cross-sectional structure of a sub-wavelength grating located in one pixel region Px. Further, in FIG. 9, as in FIG. 3, for convenience of illustration, each sub-wavelength grating is shown as a surface constituting a convex portion protruding in a direction away from the flat surface.

As shown in FIG. 9, the grating period of the first grating G1A and the grating period of the second grating G1B are equal to each other. That is, the grating period of the first grating G1A is the first period d1, and the grating period of the second grating G1B is also the first period d1. As described above, the distance between two lattice patterns GP adjacent to each other is the lattice period of each lattice.

In the sub-wavelength grating, between the two sub-wavelength gratings having the same grating period and azimuth angle θ, the colors exhibited by the two sub-wavelength gratings are the same. On the other hand, in the sub-wavelength grating, while the grating periods of the sub-wavelength gratings are equal to each other, two sub-wavelength gratings having different azimuth angles θ have different colors. That is, the color exhibited by the first lattice G1A and the color exhibited by the second lattice G1B are different from each other under certain observation conditions. With reference to FIGS. 10 and 11, the reason why the color exhibited by the first lattice G1A and the color exhibited by the second lattice G1B are different from each other will be described.

FIG. 10 shows a perspective structure of the sub-wavelength grating 11G having an azimuth angle θ of 0 °. On the other hand, FIG. 11 shows a perspective structure of the subwavelength grating 11G having an azimuth angle θ of 90 °. Of the polarization components included in the light incident on the sub-wavelength grating 11G, the polarization whose electric field oscillates perpendicularly to the incident surface of the sub-wavelength grating 11G is s-polarized light. On the other hand, the polarized light whose electric field is oscillating in parallel with the incident surface of the sub-wavelength grating 11G is p-polarized light. The incident surface is a plane that is perpendicular to the plane in which the sub-wavelength grating spreads and includes incident light and reflected light. Further, each of the s-polarized light and the p-polarized light does not depend on the azimuth angle θ of the sub-wavelength grating 11G. In other words, both incident light incident on the sub-wavelength grating 11G shown in FIG. 10 and incident light incident on the sub-wavelength grating 11G shown in FIG. 11 include s-polarized light and p-polarized light.

Here, in a structure having a groove like a diffraction grating, the relationship between the wavelength of light and the diffraction efficiency at that wavelength varies depending on the relationship between the direction in which the groove extends, that is, the azimuth angle θ, and the vibration direction of the electric field. Among the light incident on the diffraction grating, a component in which the vibration direction of the electric field is parallel to the azimuth angle θ of the diffraction grating is a TE wave. On the other hand, among the light incident on the diffraction grating, a component in which the vibration direction of the electric field is orthogonal to the azimuth angle θ of the diffraction grating is a TM wave. As described above with reference to FIG. 10, in the diffraction grating having an azimuth angle θ of 0 °, the p-polarized light whose component is a component in which the vibration direction of the electric field is parallel to the azimuth angle θ of the diffraction grating is equal to the TE wave. . On the other hand, as described above with reference to FIG. 11, in the diffraction grating having the azimuth angle θ of 90 °, the p-polarized light that is a component in which the vibration direction of the electric field is orthogonal to the azimuth angle θ of the diffraction grating is , Equal to TM wave.

It is known that when light is incident on the interface between the diffraction grating and the medium surrounding the diffraction grating, the reflectivity changes depending on the polarization direction of the incident light with respect to the incident surface. Furthermore, in the diffraction grating, it is known that the diffraction efficiency at each wavelength included in the incident light is different between the TE wave and the TM wave. For this reason, it can be said that the light having what wavelength distribution is emitted from the diffraction grating as zero-order diffracted light depends on whether each of the s-polarized light and the p-polarized light corresponds to the TE wave or the TM wave. Therefore, the color exhibited by the sub-wavelength grating 11G shown in FIG. 10 is different from the color exhibited by the sub-wavelength grating 11G shown in FIG. The color presented by the sub-wavelength grating 11G shown in FIG. 10 is the first color, and the color presented by the sub-wavelength grating 11G shown in FIG. 11 can be the second color. The second color is a color different from the first color.

The optical element 10 described above with reference to FIG. 8 can include the sub-wavelength grating 11G shown in FIG. 10 as the first grating G1A, and the sub-wavelength grating 11G shown in FIG. 11 as the second grating G1B. It is possible to provide. In this case, the state in which the first element S1A including the first grating G1A exhibits the first color and the second element S1B including the second grating G1B exhibits the second color is the optical element 10, the observer, and , The initial position in the relative position of the light source. When the optical element 10 is rotated 90 ° from the initial position with the ray of the optical element 10 as the rotation axis, the s-polarized light corresponds to the TE wave and the p-polarized light corresponds to the TM wave in the first grating G1A. On the other hand, in the second grating G1B, the s-polarized light corresponds to the TM wave, and the p-polarized light corresponds to the TE wave. Accordingly, the first element S1A exhibits the second color, and the second element S1B exhibits the first color. Therefore, the observer recognizes that the color of the first element S1A and the color of the second element S1B are reversed by the rotation of the optical element 10.

As described above, according to the sub-wavelength grating 11G, the light incident on the sub-wavelength grating 11G from the direction in which the grating line of the sub-wavelength grating 11G extends and the light incident from the direction orthogonal to the direction in which the grating line extends Since the refractive index of the optical element 10 changes as viewed from the above, light of different wavelengths is emitted.

As described above, the azimuth angle θ of the first grating G1A and the azimuth angle θ of the second grating G1B are preferably 90 ° or less for the following reason. The angle formed by the observation surface 10S of the optical element 10 and the plane including the observer's line of sight is the observation angle. The observation angle at which the color exhibited by the sub-wavelength grating is visually recognized is affected only by the relationship between the relative positions of the light source, the observer, and the optical element 10. Therefore, even if the azimuth angle θ of the first grating G1A and the azimuth angle θ of the second grating G1B are different from each other, the observation angle at which the color exhibited by the first grating G1A is visually recognized, and the color exhibited by the second grating G1B The viewing angles at which are visually recognized are equal to each other. In other words, the observation angle at which the color exhibited by each grating G1A, G1B appears and the observation angle at which the color exhibited by each grating G1A, G1B disappears are equal to each other between the two gratings.

When the difference between the azimuth angle θ of the first grating G1A and the azimuth angle θ of the second grating G1B is 90 °, the wavelength of the zero-order diffracted light emitted from the first grating G1A and the second grating G1B are emitted. The wavelengths of the zero-order diffracted light are different from each other. Thereby, the first color exhibited by the first lattice G1A and the second color exhibited by the second lattice G1B are different from each other. When the difference between the azimuth angle θ of the first grating G1A and the azimuth angle θ of the second grating G1B is set to an angle that is greater than 0 ° and less than 90 °, the first grating G1A and the second grating G1A At least one of the two lattices G1B exhibits an intermediate color between the first color and the second color. The color exhibited by the first grating G1A and the color exhibited by the second grating G1B vary depending on the difference in azimuth angle θ. Therefore, depending on the difference between the azimuth angle θ of the first grating G1A and the azimuth angle θ of the second grating G1B, in the pixel area Px arranged along one direction, the color exhibited by each pixel area Px is gradually changed, The color exhibited by each pixel region Px can be changed abruptly between adjacent pixel regions Px.

In the sub-wavelength grating 11G, when the difference between the azimuth angle θ in the first grating G1A and the azimuth angle θ in the second grating G1B is set to 90 °, the wavelength of light emitted by the first grating G1A The difference from the wavelength of the light emitted from the second grating G1B is the largest. On the other hand, even if the difference between the azimuth angle θ in the first grating G1A and the azimuth angle θ in the second grating G1B is larger than 90 °, the wavelength of the light emitted by the first grating G1A and the second The difference from the wavelength of light emitted by the grating G1B does not increase.

In addition, the smaller the difference between the azimuth angle θ in the first grating G1A and the azimuth angle θ in the second grating G1B, the difference between the shape accuracy in the first grating G1A and the shape accuracy in the second grating G1B. Hard to occur. Therefore, the maximum difference between the azimuth angle θ in the first grating G1A and the azimuth angle θ in the second grating G1B is preferably 90 °.

As described above, according to the first embodiment of the optical element, the effects listed below can be obtained.
(1) In authenticity verification of the optical element 10, the optical element 10 has a first region 11S1 exhibiting a color derived from the first sub-wavelength grating 11G1 and a second region 11S2 exhibiting a color derived from the second sub-wavelength grating 11G2. Can be grasped at a time. As a result, the authenticity of the optical element 10 can be verified more easily by rotating the optical element 10 than when determining whether or not the optical element 10 has a state of two colors.

(2) The higher the area ratio in each pixel region Px, the higher the luminance of each pixel region Px. For this reason, the plurality of pixel regions Px include pixel regions Px having different area ratios, whereby in the colors exhibited by the first region 11S1, it is possible to form shades of brightness in the same hue.

(3) Since the azimuth angle θ of the first grating G1A and the azimuth angle θ of the second grating G1B are different from each other, the color exhibited by the first grating G1A and the color exhibited by the second grating G1B are different from each other.

[Modification of First Embodiment]
The first embodiment of the present invention described above can be implemented with appropriate modifications as follows.
[Lattice period]
The azimuth angle θ of the first grating G1A and the azimuth angle θ of the second grating G1B may be equal to each other, and the grating period of the first grating G1A may be different from the grating period of the second grating G1B. In this case, the following effects can be obtained.

(4) When the grating period of the first grating G1A and the grating period of the second grating G1B are different from each other, the color exhibited by the first grating G1A and the color exhibited by the second grating G1B are different from each other.

Note that the colors that the first grating G1A can exhibit by changing the grating period compared to the case where the azimuth angle θ is different between the first grating G1A and the second grating G1B, and The types of colors that can be presented by the two-grating G1B can be increased. Thereby, the freedom degree of the color which the optical element 10 exhibits increases.

The azimuth angle θ of the first grating G1A and the azimuth angle θ of the second grating G1B may be different from each other, and the grating period of the first grating G1A and the grating period of the second grating G1B may be different from each other.

[Second Embodiment]
A second embodiment of the optical element will be described with reference to FIGS. The optical element according to the second embodiment of the present invention differs from the optical element according to the first embodiment in the shape of the grating pattern included in the sub-wavelength grating. Therefore, in the following, such differences will be described in detail. On the other hand, in the optical element of the second embodiment, the components corresponding to the optical element of the first embodiment are denoted by the same reference numerals as those in the first embodiment. Detailed description is omitted. In FIGS. 12 to 14 referred to below, the sub-wavelength grating is shown as a structure in which convex portions protruding in a direction away from the flat surface are arranged for convenience of illustration. In the optical element of the second embodiment, the color of the sub-wavelength grating observed by the observer may be based on higher-order diffracted light than zero-order diffracted light. Therefore, in the following, the angle at which the sub-wavelength grating has the highest color development efficiency is the mth order, and the diffracted light at the mth order is the mth order diffracted light.

As described above, the sub-wavelength grating 11G includes a plurality of grating patterns. The direction in which the plurality of lattice patterns are repeated is the first direction D1, and the direction orthogonal to the first direction D1 is the second direction D2. In each lattice pattern, the shape in a cross section perpendicular to the plane in which the first layer 11 extends along the first direction D1 is a cross-sectional shape. Each lattice pattern has a shape in which the cross-sectional shape continues along the second direction D2. The plurality of lattice patterns include lattice patterns having different cross-sectional shapes. Hereinafter, the optical element of this embodiment will be described in more detail.

As shown in FIG. 12, the optical element 20 includes a first layer 11, a second layer 12, and a third layer 13, similar to the optical element 10 of the first embodiment. The optical element 20 includes three portions in the first direction D1. That is, the optical element 20 includes a first portion 20A, a second portion 20B, and a third portion 20C. The first portion 20A, the second portion 20B, and the third portion 20C are arranged in the order described in the direction in which the lattice pattern is repeated.

In the sub-wavelength grating 11G, the plurality of grating patterns belonging to each part have the same cross-sectional shape. On the other hand, the cross-sectional shapes of the lattice patterns belonging to each part are different from each other. In the subwavelength grating 11G, the portion belonging to the first portion 20A is the first grating 20AG, the portion belonging to the second portion 20B is the second grating 20BG, and the portion belonging to the third portion 20C is the third grating 20CG. .

The first lattice 20AG includes a plurality of first lattice patterns AGP. The plurality of first lattice patterns AGP are repeated along the first direction D1. The cross-sectional shape of the first lattice 20AG is wavy. The grating period of the first grating 20AG is the first period d1. The first lattice pattern AGP has a shape in which one peak is sandwiched between two valleys in the cross section along the first direction D1. The first lattice pattern AGP has a slope connecting one valley and the mountain and a slope connecting the mountain and the other valley. Each slope has an inclination with respect to the plane in which the first layer 11 extends.

In the cross section along the first direction D1, an angle formed by a tangent to one slope and a straight line connecting a plurality of valleys is a first tangent angle θ1. A straight line connecting the plurality of valleys is a straight line substantially parallel to the surface of the first layer 11. In addition, the first tangent angle θ1 is equal to the angle formed by the plane on which the first layer 11 extends and the slope.

The second grid 20BG includes a plurality of second grid patterns BGP. The plurality of second lattice patterns BGP are repeated along the first direction D1. The cross-sectional shape of the second grating 20BG is wavy. The grating period of the second grating 20BG is the second period d2. The second period d2 is equal to the first period d1. Similarly to the first lattice pattern AGP, the second lattice pattern BGP has a shape in which one peak is sandwiched between two valleys in the cross section along the first direction D1. The second lattice pattern BGP has a slope connecting one valley and the mountain and a slope connecting the mountain and the other valley. Each slope has an inclination with respect to the plane in which the first layer 11 extends.

In the cross section along the first direction D1, the angle formed by the tangent to one slope and the straight line connecting the plurality of valleys is the second tangent angle θ2. The second tangent angle θ2 is an angle different from the first tangent angle θ1. The second tangent angle θ2 is equal to the angle formed by the plane on which the first layer 11 extends and the slope. In the present embodiment, the second tangent angle θ2 is smaller than the first tangent angle θ1. On the other hand, as described above, the second period d2 of the second grating 20BG is equal to the first grating period d1 of the first grating 20AG. Therefore, in the cross section along the first direction D1, the cross sectional shape of the second lattice pattern BGP and the cross sectional shape of the first lattice pattern AGP are different from each other.

The third grid 20CG includes a plurality of third grid patterns CGP. The plurality of third lattice patterns CGP are repeated along the first direction D1. The cross-sectional shape of the third lattice 20CG is wavy. The grating period of the third grating 20CG is the third period d3. The third period d3 is equal to the first period d1 and the second period d2. Similar to the first lattice pattern AGP, the third lattice pattern CGP has a shape in which one peak is sandwiched between two valleys in the cross section along the first direction D1. The third lattice pattern CGP has a slope connecting one valley and the mountain and a slope connecting the mountain and the other valley. Each slope has an inclination with respect to the plane in which the first layer 11 extends.

In the cross section along the first direction D1, the angle formed by the tangent to one slope and the straight line connecting the plurality of valleys is the third tangent angle θ3. The third tangent angle θ3 is an angle different from the first tangent angle θ1 and also an angle different from the second tangent angle θ2. Note that the third tangent angle θ3 is equal to the angle formed by the plane on which the first layer 11 extends and the inclined surface. In the present embodiment, the third tangent angle θ3 is smaller than the first tangent angle θ1 and smaller than the second tangent angle θ2. On the other hand, as described above, the third period d3 of the third grating 20CG is equal to the first period d1 and the second period d2. Therefore, in the cross section along the first direction D1, the cross sectional shape of the third lattice pattern CGP is different from both the cross sectional shape of the first lattice pattern AGP and the cross sectional shape of the second lattice pattern BGP.

That is, in the present embodiment, the above-described cross-sectional shape in each lattice pattern includes a slope having an inclination with respect to the plane in which the first layer 11 extends. The plurality of lattice patterns include lattice patterns having different slope angles with respect to the first layer 11.

According to the sub-wavelength grating 11G, the angle at which the light incident on the optical element 20 is diffracted can be changed by changing the tangent angles θ1, θ2, and θ3 on each slope. That is, by changing the tangent angles θ1, θ2, and θ3 between the first grating 20AG, the second grating 20BG, and the third grating 20CG, m-order diffracted light is emitted from the gratings 20AG, 20BG, and 20CG. The angles can be different from each other. Thereby, compared with the case where the tangent angle is equal in the whole sub-wavelength grating 11G, the range of the angle at which m-order diffracted light is emitted can be expanded. In other words, it is possible to widen the range of observation angles at which the observer can observe the mth order diffracted light. In addition, in each grating | lattice 20AG, 20BG, and 20CG, since cross-sectional shapes differ, a grating | lattice period is equal, Therefore The color which each grating | lattice 20AG, 20BG, and 20CG exhibits is substantially the same. Therefore, a set of m-th order diffracted lights emitted from the gratings 20AG, 20BG, and 20CG does not generate monochrome light.

In the first direction D1, the width of each of the gratings 20AG, 20BG, and 20CG is preferably 300 μm or less, and more preferably 85 μm or less. Since the widths of the respective gratings 20AG, 20BG, and 20CG are 300 μm or less, the respective gratings 20AG, 20BG, and 20CG cannot be separated with human eye resolution. Therefore, the observer cannot recognize that the gratings 20AG, 20BG, and 20CG are diffracting light at different angles.

Note that the width of each of the gratings 20AG, 20BG, and 20CG is more preferably 85 μm or less for the following reason. In general, it is known that a distance at which a person whose visual acuity is 1.0 can be separated in 1 minute from a position 5 m away from an observation target is 1.454 mm. These matters are explained using the Landolt ring. One minute is 1 / 60th of 1 °. When it is assumed that the observer observes the optical element 20 from a position 30 cm away from the optical element 20, the interval that can be separated by the observer's eyes, that is, the resolution R, is derived from the following equation (4). Can do.

R = 1454 × (30/500) (μm) Formula (4)
In the right side of Equation (4), the unit of the first term is μm and the unit of the second term is cm. From equation (4), the resolution R is 87.24 μm. Therefore, if the width of each of the gratings 20AG, 20BG, and 20CG is 85 μm or less, it is possible to increase the certainty that the gratings 20AG, 20BG, and 20CG cannot be decomposed with human eye resolution.

It is preferable that the cross-sectional shapes of the respective grating patterns AGP, BGP, and CGP have wave shapes having different tangent angles from the viewpoint that the direction in which the m-th order diffracted light is emitted can be controlled by the tangential angles. . On the other hand, when the cross-sectional shape of the grating pattern is a rectangular shape formed from a surface parallel to the surface of the optical element 20 and a surface orthogonal to the surface, m-order diffracted light, that is, zero next time The folded light is emitted in the direction of regular reflection with respect to the incident light. For example, when the incident angle of the incident light with respect to the surface of the optical element 20 is 45 °, the emission angle of the regular reflection light is also 45 °. Therefore, the observer cannot observe the light emitted from the optical element 20 unless the observer observes the optical element 20 from the direction where the observation angle is 45 °.

When the optical element 20 is observed at the emission angle of the regular reflection light, the regular reflection light of the light emitted from the light source toward the optical element 20 is also observed by the observer. Therefore, it may be difficult for an observer to visually recognize the light emitted by the sub-wavelength grating. Further, depending on the relative position of the light source with respect to the optical element 20, it may be difficult to observe the optical element 20 from the regular reflection angle. In this respect, since the direction in which the m-th order diffracted light is emitted can be controlled by the tangential angle, the degree of freedom in the angle at which the optical element 20 emits the m-th order diffracted light is increased. Therefore, it becomes possible to solve the above-described problem.

The sub-wavelength grating 11G including the three grating patterns may have the following structure.
As shown in FIG. 13, the sub-wavelength grating 11G includes a first grating pattern AGP, a second grating pattern BGP, and a third grating pattern CGP. In the sub-wavelength grating 11G, the first grating pattern AGP, the second grating pattern BGP, and the third grating pattern CGP constitute one pattern group GPG. In one pattern group GPG, the first lattice pattern AGP, the second lattice pattern BGP, and the third lattice pattern CGP are arranged in the order described in the first direction D1. In the sub-wavelength grating 11G, a plurality of pattern groups GPG are repeated along the first direction D1.

In the first direction D1, the grating period of the first grating pattern AGP is the first period d1, the grating period of the second grating pattern BGP is the second period d2, and the grating period of the third grating pattern CGP is the third period. d3. The first period d1, the second period d2, and the third period d3 are equal to each other.

In the first direction D1, the period D of the pattern group GPG is preferably 20 μm or more. As the period D of the pattern group GPG is larger, higher-order diffracted light is included in the same observation angle. In other words, the larger the period D of the pattern group GPG, the narrower the range of observation angles including the same order of diffracted light. Thus, by reducing the difference between the observation angle of the mth-order diffracted light and the observation angle of other diffracted light, the observer can visually recognize a plurality of diffracted lights simultaneously with the mth-order diffracted light. Thereby, the range of the observation angle in which the observer can visually recognize the light emitted from the optical element 20 is expanded.

For example, in the case of a diffraction grating having a rectangular cross-sectional shape as described above, the angle formed by the incident light and the ray of the diffraction grating is the angle α, and the angle formed by the diffraction light and the ray of the diffraction grating is the angle. When β is set, the following equation (5) is established. Note that the angle α is an incident angle, and the angle β is a diffraction angle.

d (sin α + sin β) = mλ (5)
In equation (5), d is the period of the diffraction grating, m is the diffraction order, and λ is the wavelength of light. The unit of period and wavelength is nm. In the sub-wavelength grating 11G shown in FIG. 13, the period d corresponds to the period D of the pattern group GPG described above. In equation (5), when the angle α is set to 45 ° and the wavelength λ is set to 500 nm, the diffraction order m and the angle β are determined as follows when the period d is set to 5000 nm.
(M, β) = (1, −37.4), (2, −30.5), (3−24.0)...

When the period d is changed to 10000 nm, the diffraction order m and the angle β are determined as follows.
(M, β) = (1, -41.1), (2, -37.4), (3, -33.9) ...

When the period d is changed to 20000 nm, the diffraction order m and the angle β are determined as follows.
(M, β) = (1, -43.0), (2, -41.1), (3, -39.2) ...

Thus, as the period d increases, the difference in the angle β decreases between diffracted lights having different diffraction orders.

Here, it is assumed that the pupil diameter in the human eye is 5 mm and the distance that the observer observes the optical element 20 is 30 cm. In this case, of the light emitted from a certain point in the optical element 20, light included within an observation angle of about 1 ° enters the eyes of the observer. That is, the observer visually recognizes the result of integrating the light within the observation angle of about 1 °. That is, when diffracted light having a wavelength within the range of the observation angle of about 1 ° is included, the diffraction efficiency is increased within the range of the observation angle. In addition, when the observer observes the optical element 20 while tilting it so that the observation angle changes, the color exhibited by the optical element 20 is held at a specific color while the observer changes the observation angle by 2 ° or more. Thus, the observer can easily recognize the color exhibited by the optical element 20. Therefore, the optical element 20 is preferably configured to emit at least two diffracted lights having different orders within a range of 2 ° in the observation angle. In this respect, the period D in the optical element 20 is preferably 20 μm or more.

The sub-wavelength grating 11G including the three grating patterns may have the following structure.
As shown in FIG. 14, the sub-wavelength grating 11G includes a first grating pattern AGP, a second grating pattern BGP, and a third grating pattern CGP. In the sub-wavelength grating 11G, the first grating pattern AGP, the second grating pattern BGP, and the third grating pattern CGP constitute one pattern group GPG. In one pattern group GPG, the first lattice pattern AGP, the second lattice pattern BGP, and the third lattice pattern CGP are arranged in the order described in the first direction D1. In the sub-wavelength grating 11G, a plurality of pattern groups GPG are repeated along the first direction D1.

The grating period of the first grating pattern AGP is the first period d1, the grating period of the second grating pattern BGP is the second period d2, and the grating period of the third grating pattern CGP is the third period d3. The first period d1, the second period d2, and the third period d3 are different from each other. It is preferable that the difference in the grating period is 20 nm or less between the grating patterns adjacent to each other in the first direction D1. For example, the first period d1 can be set to 300 nm, the second period d2 can be set to 310 nm, and the third period d3 can be set to 290 nm.

Since the grating periods are different between the grating patterns, the diffraction angles are different between the grating patterns. The smaller the difference in grating period between grating patterns, the smaller the difference in diffraction angle. As described above, when the difference in the grating period between the grating patterns adjacent to each other in the first direction D1 is 20 nm or less, the diffraction angles of the m-th order diffracted lights emitted from the grating patterns are substantially equal to each other. Thereby, the observer cannot separate the m-th order diffracted light emitted from each grating pattern. Therefore, the observation angle at which the observer can observe the light emitted from the optical element 20 can be widened.

As described above, according to the second embodiment of the optical element, the following effects can be obtained.
(5) In a plurality of grating patterns, as compared with the case where the cross-sectional shapes along the first direction D1 are the same, the observation angle at which the observer can visually recognize the light emitted from the sub-wavelength grating 11G is widened. be able to.

(6) In the plurality of grating patterns, the sub-wavelength grating 11G corresponds to the difference in the inclination angle between the grating patterns as compared with the case where the inclination angles of the slopes included in the cross-sectional shape along the first direction D1 are the same. The observation angle at which the observer can visually recognize the light emitted from the projector can be expanded.

[Modification of Second Embodiment]
The second embodiment described above can be implemented with appropriate modifications as follows.
[Cross-sectional shape]
The sub-wavelength grating 11G may include four or more types of grating patterns having different cross-sectional shapes as described above. Further, the plurality of types of grating patterns may be randomly positioned in the sub-wavelength grating 11G. Further, the plurality of types of lattice patterns may be regularly arranged.

· The cross-sectional shape of the sub-wavelength grating 11G is not limited to the wave shape described above. Even when the sub-wavelength grating 11G has a shape other than the wave shape, the sub-wavelength grating 11G includes the grating patterns having different cross-sectional shapes, thereby obtaining the effect according to the above (5). I can.

[Third Embodiment]
A third embodiment of the optical element will be described with reference to FIG. The optical element according to the third embodiment of the present invention is different from the optical element 10 according to the first embodiment in that the first layer includes a filler. Therefore, in the following, such differences will be described in detail. On the other hand, in the optical element of the third embodiment, the components corresponding to the optical element of the first embodiment are denoted by the same reference numerals as in the first embodiment. Detailed description thereof will be omitted.

As shown in FIG. 15, the first layer 11 included in the optical element 30 includes a filler 31 dispersed in the resin forming the first layer 11. The average particle diameter of the filler 31 is 400 nm or less. At least a part of the light incident on the first layer 11 is scattered by the filler dispersed in the first layer 11. Therefore, the light incident on the sub-wavelength grating 11G includes light having different incident angles. Thereby, each grating pattern GP included in the sub-wavelength grating 11G reflects light in the regular reflection direction according to the incident angle of the light incident on the grating pattern GP. The light reflected by the lattice pattern GP is emitted to the outside of the optical element 30 without being scattered by the filler 31 or after being scattered by the filler 31. Therefore, compared with the case where the 1st layer 11 does not contain a filler, the range of the emission angle of the light inject | emitted from the optical element 30 spreads. As a result, the range of observation angles at which the observer can observe the colors exhibited by the optical element 30 is expanded.

As described above, the average particle diameter of the filler 31 is preferably 400 nm or less. Thereby, since Mie scattering is suppressed, the transparency of the first layer 11 is improved to some extent. The shape of the filler 31 is not limited to a spherical shape. Therefore, in this embodiment, the average value in a plurality of diameters that can be defined in each filler 31 is the average particle diameter of each filler 31. Here, the following is known about the relationship between the size of the scatterer such as the filler 31 and the scattering phenomenon. When the average particle size of the scatterer is included in the range of 400 nm or more and 700 nm or less, Mie scattering is generated by the scatterer. In Mie scattering, the light included in the visible range is scattered to the same extent regardless of the wavelength of the light, so that the light scattered by the Mie scattering is visually recognized as white light. In Mie scattering, the light scattering angle is affected by the particle size of the scatterer. In Mie scattering, the larger the particle size of the scatterer, the stronger the scattering toward the front in the light traveling direction.

On the other hand, when the scatterer is smaller than 1/10 with respect to the wavelength of light, Rayleigh scattering occurs. In Rayleigh scattering, the direction in which light is scattered does not depend on the particle size of the scatterer. In Rayleigh scattering, light is scattered with a distribution that draws a figure of 8 in the traveling direction of light regardless of the particle size of the scatterer. In Rayleigh scattering, the shorter the light wavelength, the stronger the light scattering.

When transparency is required for the first layer 11 in which the filler 31 as a scatterer is dispersed as in the present embodiment, the average particle size of the filler 31 is at least equal to or less than the wavelength of light, and It is necessary for the filler 31 to cause Rayleigh scattering. Therefore, the average particle diameter of the filler 31 is preferably 400 nm or less. When the average particle diameter of the filler 31 is D and the wavelength of light is λ, the scattering cross section α can be calculated by the following equation (6).

α = πD / λ Formula (6)
By using Expression (6), it is possible to easily determine whether the scattering phenomenon caused by the filler 31 is Rayleigh scattering or Mie scattering. When the scattering cross section α is 0.4 or less, Rayleigh scattering mainly occurs. On the other hand, when the scattering cross section α is greater than 0.4 and less than 3, the M It is known that scattering occurs. Therefore, when the light incident on the filler 31 is light in the visible range and the wavelength of the light is 400 nm, if the average particle size of the filler 31 is 50 nm or less, the filler 31 mainly causes Rayleigh scattering. Can be generated. Thereby, the light incident on the first layer 11 can be scattered by the filler 31 in a state where the transparency in the first layer 11 is high.

As described above, according to the optical element of the third embodiment, the following effects can be obtained.
(7) Compared to the case where the first layer 11 does not include a filler, the range of the emission angle of light emitted from the optical element 30 is widened. Therefore, the range of observation angles at which the observer can observe the colors exhibited by the optical element 30 is expanded.

[Fourth Embodiment]
A fourth embodiment of the optical element will be described with reference to FIGS. 16 and 17. The optical element according to the fourth embodiment of the present invention differs from the optical element 10 according to the first embodiment in the state of the surface of the third layer 13 opposite to the surface in contact with the second layer 12. Therefore, in the following, such differences will be described in detail, and in the optical element of the third embodiment, the same reference numerals are given to the components corresponding to those of the optical element 10 of the first embodiment, and detailed description thereof will be omitted. . Hereinafter, the first example and the second example in the fourth embodiment will be described in order.

[First example]
As shown in FIG. 16, in the optical element 40, the third layer 13 is an adhesive layer having thermoplasticity. The third layer 13 includes a filler 41 dispersed in a portion closer to the surface opposite to the surface in contact with the second layer 12 than the center in the thickness direction of the third layer 13. In the third layer 13, the surface in contact with the second layer 12 is the front surface 13F, and the surface opposite to the front surface 13F is the back surface 13R. In the third layer 13, as described above, the filler 41 is preferably located closer to the back surface 13R than the center in the thickness direction of the third layer 13, and is preferably located in the vicinity of the back surface 13R.

As described above, the third layer 13 is an adhesive layer having thermoplasticity. As a material for forming the third layer 13, an adhesive having thermoplasticity can be used. Since the third layer 13 is an adhesive layer having thermoplasticity, heat and pressure are applied to the optical element 40 in a state where the third layer 13 is in contact with the transfer target, thereby transferring the optical element 40 to the transfer target. be able to. At this time, the heat and pressure applied to the third layer 13 cause unevenness due to the filler 41 on the back surface 13 R of the third layer 13, thereby causing unevenness on the surface 13 F of the third layer 13. As a result, in the first layer 11 and the second layer 12, unevenness also occurs in a portion overlapping with the unevenness formed in the third layer 13 when viewed from the thickness direction of the optical element 40. Thereby, the unevenness | corrugation resulting from the filler 41 is added with respect to the subwavelength grating 11G in the interface of the 1st layer 11 and the 2nd layer 12. FIG. Examples of the transfer object can be bills, passports, cards, and the like.

The unevenness at the interface between the first layer 11 and the second layer 12 is adjusted by the size of the filler 41, the thickness of each

layer

11, 12, 13 and the conditions of heat and pressure when transferring the optical element 40. can do.

Since the unevenness due to the filler 41 is added to the sub-wavelength grating 11G, the plurality of grating patterns GP forming the sub-wavelength grating 11G have different grating patterns GP with different incident angles of light with respect to the grating pattern GP. included. Each grating pattern GP reflects m-th order diffracted light at an exit angle corresponding to the incident angle of light in the grating pattern GP. The range of the emission angle at which each grating pattern emits m-th order diffracted light varies depending on the curvature of the unevenness imparted to each grating pattern GP. In other words, the observation angle at which the observer can observe the color exhibited by the sub-wavelength grating 11G varies depending on the curvature of the unevenness imparted to each grating pattern GP.

As described above, the color exhibited by the optical element 40 is preferably maintained in a range of 2 ° or more in the observation angle. On the other hand, if the observation angle range in which the color exhibited by the optical element 40 can be observed is too wide, the intensity of light emitted from the optical element 40 at each observation angle is lowered. Therefore, the range of the observation angle in which the color exhibited by the optical element 40 can be observed is preferably 2 ° or more and 10 ° or less, and more preferably 2 ° or more and 5 ° or less. It is preferable that the range of the observation angle includes the emission angle of the m-th order diffracted light emitted by all the grating patterns GP.

Therefore, it is preferable that the curvature of the unevenness caused by the filler 41 is not excessively large. The following two methods can be used as a method for suppressing the uneven curvature due to the filler 41 from becoming excessively large. In the first method, the heat and pressure conditions in the transfer are adjusted so that the filler 41 is uniformly dispersed in the third layer 13 and the curvature of the irregularities does not become excessively large. In the second method, a filler having a flat shape is used as the filler 41 instead of a spherical filler, and the diameter of the filler 41 decreases in the thickness direction of the third layer 13. Filler 41 is dispersed in layer 13.

[Second example]
As shown in FIG. 17, the optical element 40 further includes a fourth layer 42 in contact with the third layer 13. The fourth layer 42 includes a surface 42 F that contacts the third layer 13. The surface 42F includes irregularities.

The unevenness on the surface 42F of the fourth layer 42 can be formed by various methods. When transferring the third layer 13 to the fourth layer 42 as the transfer target, unevenness may be formed on the surface 42F of the fourth layer 42 so as to follow the third layer 13 deformed by heat and pressure. it can. In this case, an adhesive layer having thermoplasticity can be used for the third layer 13. The fourth layer 42 can be made of paper or a resin film. Alternatively, irregularities can be formed on the surface 42F of the fourth layer 42 by dispersing fine particles and fibers in the fourth layer 42. Further, the surface 42F of the fourth layer 42 can be made uneven by defoaming or unevenness generated when the fourth layer 42 is formed. Also in the second example, as in the first example, the unevenness caused by the surface 42F of the fourth layer 42 can be added to the sub-wavelength grating 11G. Therefore, the same effect as the optical element 40 of the first example can be obtained by the optical element 40 of the second example.

When the fourth layer 42 is a transfer target and the fourth layer 42 includes fine particles, the average particle diameter of the fine particles is approximately the same as the thickness of the third layer 13 that is an adhesive layer. Is preferred. Further, in the transfer to the fourth layer 42, by adjusting the conditions of heat and pressure, it is possible to suppress the unevenness imparted to the sub-wavelength grating 11G from becoming excessively large.

Also, the paper-made fourth layer 42 can be used as the fourth layer 42 in which the fibers are dispersed. In this case, the fibers forming the fourth layer 42 are arranged in parallel to the surface 42F of the fourth layer 42. The pulp fiber has a diameter of 20 μm or more and 50 μm or less and a length of about 1 mm or more and 5 mm or less. Therefore, the unevenness imparted to the sub-wavelength grating 11G may become excessively large. On the other hand, the cellulose nanofiber has a diameter of 4 nm or more and 100 nm or less and a length of about 5 μm or more. Therefore, it is possible to suppress the unevenness imparted to the sub-wavelength grating 11G from becoming excessively large. Cellulose nanofibers are fibers obtained by decomposing pulp fibers.

As described above, according to the optical element of the fourth embodiment, the following effects can be obtained.
(8) Since the unevenness caused by the filler 41 is imparted to the sub-wavelength grating 11G, the plurality of grating patterns GP can include grating patterns GP having different incident angles of light with respect to the grating pattern GP. Thereby, since the emission angle in the grating pattern GP is also different, the observation angle at which the light emitted from the sub-wavelength grating 11G is observed can be widened.

(9) Since the unevenness due to the surface 42F of the fourth layer 42 is imparted to the sub-wavelength grating 11G, the plurality of grating patterns GP include grating patterns GP having different incident angles of light with respect to the grating pattern GP. it can. Thereby, since the emission angle in the grating pattern GP is also different, the observation angle at which the light emitted from the sub-wavelength grating 11G is observed can be widened.

[Fifth Embodiment]
A fifth embodiment of the optical element will be described with reference to FIGS. The optical element of the fifth embodiment of the present invention is different from the optical element of the first embodiment in that it includes a relief layer having a relief surface. Therefore, in the following, such differences will be described in detail. On the other hand, in the optical element of the fifth embodiment, the components corresponding to those of the optical element 10 of the first embodiment are denoted by the same reference numerals as those of the optical element 10 of the first embodiment. Therefore, the detailed description is omitted. Hereinafter, two examples of the optical element of the fifth embodiment will be described in order.

[First example]
[Configuration of optical element]
With reference to FIG. 18, the structure in the optical element of a 1st example is demonstrated.

As shown in FIG. 18, the optical element 50 includes the first layer 11, the second layer 12 in contact with the first layer 11, and the second layer 12 in contact with the second layer 12, as in the optical element 10 in the first embodiment described above. And three layers 13. The first layer 11 is a resin layer including the sub-wavelength grating 11G on at least a part of the back surface 11R in contact with the second layer 12. The back surface 11R is an example of the first surface. In FIG. 18, for convenience of illustration, a cross-sectional shape in which the sub-wavelength grating 11G is located on the entire back surface 11R is shown. Is formed.

In the second layer 12, the surface 12F in contact with the back surface 11R of the first layer 11 has an uneven shape following the sub-wavelength grating 11G. The surface 12F is an example of the second surface. The second layer 12 is a dielectric layer having a second refractive index higher than the first refractive index. The third layer 13 is a resin layer having a third refractive index lower than the second refractive index.

The optical element 50 includes a relief layer including a relief surface 13Re different from the back surface 11R and the front surface 12F. The relief surface 13Re includes a plurality of reflecting surfaces, and the pitch between the reflecting surfaces adjacent to each other is larger than the pitch of the sub-wavelength grating 11G. In the present embodiment, the relief layer is the third layer 13 described above. More specifically, the back surface 13R which is the surface opposite to the surface in contact with the second layer 12 in the third layer 13 is the relief surface 13Re.

In FIG. 18, for convenience of illustration, the relief surface 13Re is located on the entire surface 13F, but in the optical element 50 of the present embodiment, the relief surface 13Re is located on a part of the surface 13F. Further, the relief surface 13Re may be formed at a position overlapping the sub-wavelength grating 11G in the surface 13F when viewed from the thickness direction of the optical element 50.

The sub-wavelength grating 11G displays a colored image exhibiting a color corresponding to the grating period of the sub-wavelength grating 11G in the reflection direction including the regular reflection direction. The relief surface 13Re displays a reflected image by monochrome reflected light in a reflection direction including a direction different from the regular reflection direction. Examples of monochrome reflected light colors are white, silvery white, silvery, semi-white, pearl white, silky white, milky white, gray, sepia. The optical element 50 includes a first state in which the colored image and the reflected image are not displayed, a second state in which the colored image is mainly displayed, a third state in which the reflected image is mainly displayed, and a fourth state in which the colored image and the reflected image are mainly displayed. Have a state. The angle formed by the plane on which the optical element 50 spreads and the plane including the observer's line of sight is the observation angle. The optical element 50 has one of the states depending on the observation angle. That is, the optical element 50 is observed in any one of the first state, the second state, and the third state according to the observation angle. The sub-wavelength grating 11G displays a colored image exhibiting a color corresponding to the grating period of the sub-wavelength grating in a predetermined range including the regular reflection direction at the observation angle. The relief surface 13Re displays a reflected image of monochrome reflected light in a predetermined range including a direction different from the regular reflection direction at the observation angle.

The optical element 50 further includes a fourth layer 51. The fourth layer 51 may be a reflective layer or a refractive layer. When the fourth layer 51 is a refractive layer, the refractive index of the fourth layer 51 is different from the refractive index of the third layer 13. Since the refractive index of the fourth layer 51 is different from the refractive index of the third layer 13, the fourth layer 51 can increase the reflectance at the relief surface 13Re. In two layers adjacent to each other, the reflectivity at the interface is determined by the difference in refractive index between the two layers. Therefore, when the refractive index of the fourth layer 51 is different from the refractive index of the third layer 13, the same effect as when the fourth layer 51 is a reflective layer can be obtained.

As described above, the optical element 50 is observed from the side opposite to the third layer 13 with respect to the second layer 12. Therefore, the fourth layer 51 may have light transmittance or may not have light transmittance. The fourth layer 51 may be composed of a single layer or a plurality of layers. When the fourth layer 51 is a refractive layer and includes a plurality of layers, the fourth layer 51 includes a layer having a relatively low refractive index and a layer having a relatively high refractive index. be able to.

The relief surface 13Re includes a plurality of reflecting surfaces as described above. The relief surface 13Re displays a reflected image formed by monochrome light by at least one of diffraction, scattering, and reflection. As described above, the relief surface 13Re includes a plurality of reflection surfaces, and the plurality of reflection surfaces may be arranged in a predetermined rule or irregularly in the relief surface 13Re. In the relief surface 13Re, the emission direction of light emitted from the relief surface 13Re can be controlled by the direction and angle of each reflection surface.

The direction of the reflecting surface can be the direction of the normal vector of the reflecting surface projected on the plane in which the first layer 11 spreads. The angle of the reflection surface can be an angle formed by the normal vector of the plane in which the first layer 11 extends and the normal vector of the reflection surface. The direction of the reflecting surface can be the same as or perpendicular to the orientation of the sub-wavelength grating 11G. Further, when there are a plurality of orientations of the sub-wavelength grating 11G, the average of the orientations can be set as the orientation of the sub-wavelength grating 11G. The average can be a weighted average weighted by the area of each region where a plurality of sub-wavelength gratings are formed. Accordingly, when the observer OB tilts the card 100 forward with respect to the reference plane Ph0, the card 100 displays the first image P1 and the second image P2 according to the position of the card 100. In other words, when the observer OB brings the surface 100F of the card 100 close to the observer OB in a state where the position of the portion held by the observer OB in the card 100 is substantially fixed in the observation space, the card 100 Depending on the position, the card 100 displays the first image P1 and the second image P2 (see FIG. 40).

The sub-wavelength grating 11G emits light in the range of the emission direction including the above-described regular reflection direction. Of the light emitted from the sub-wavelength grating 11G, the intensity of the light emitted in the regular reflection direction is the highest. On the other hand, the relief surface 13Re emits light in an emission direction range including a direction different from the regular reflection direction. Of the light emitted from the relief surface 13Re, the intensity of the light emitted in a direction different from the regular reflection direction is the highest. In other words, on the relief surface 13Re, the direction and angle of the reflection surface are set so that the intensity of the light emitted in the direction different from the regular reflection direction is the largest among the light emitted from the relief surface 13Re. Yes.

In the relief surface 13Re, the period of the reflection surface may be greater than 400 nm and 1000 nm or less, or may be greater than 1000 nm. In order to prevent the relief surface 13Re from emitting diffracted light, it is preferable that the period of the reflection surface is larger than 1000 nm. In the relief surface 13Re, the shape in a cross section orthogonal to the direction in which the reflecting surface extends may be a sawtooth shape.

The colored image displayed by the sub-wavelength grating 11G is an image formed by light having a specific wavelength included in the wavelength of visible light. Illustrative examples of chromatic images include chromatic images such as red, green, and blue images. When the sub-wavelength grating 11G displays a red image, the light emitted from the sub-wavelength grating 11G includes, for example, light having a wavelength of 620 nm or more and 750 nm or less. When the sub-wavelength grating 11G displays a green image, the light emitted from the sub-wavelength grating 11G includes light having a wavelength of 495 nm or more and 570 nm or less as an example. When the sub-wavelength grating 11G displays a blue image, the light emitted from the sub-wavelength grating 11G includes light having a wavelength of 450 nm or more and 495 nm or less as an example. Note that the sub-wavelength grating 11G displaying a colored image is synonymous with the sub-wavelength grating 11G exhibiting a chromatic color.

The reflection image displayed on the relief surface 13Re is an image formed by monochrome light generated by reflection, scattering, and diffraction on the relief surface 13Re. In other words, the reflected image displayed by the relief surface 13Re is a monochrome image and an image having no hue. The relief surface 13Re may be configured such that the intensity of the monochrome light emitted from each position is different from each other. Thereby, the relief surface 13Re can display an image by a difference in light intensity, in other words, by a difference in brightness. In addition, that the relief surface 13Re displays a monochrome reflected image is synonymous with the relief surface 13Re exhibiting monochrome.

[Operation of optical element]
The operation of the optical element 50 will be described with reference to FIGS.
As shown in FIG. 19, the angle at which the incident light IL emitted from the light source LS enters the optical element 50 is the incident angle α, and the angle at which the emitted light EL emitted from the optical element 50 is emitted is the emission angle β. . An angle formed by a plane including the viewing direction of the observer OB and a plane on which the optical element 50 spreads is an observation angle θOB. The above-described regular reflection direction is the direction in which the emitted light EL is emitted at an emission angle β having the same magnitude as the incident angle α. In the optical element 50, the sub-wavelength grating 11G displays a colored image in the reflection direction including the regular reflection direction, while the relief surface 13Re displays the reflected image by the monochrome light in the reflection direction including a direction different from the regular reflection direction. indicate. The optical element 50 has one of the following four states according to the observation angle θOB.

In the present embodiment, an example will be described in which the colored image displayed by the sub-wavelength grating 11G has a moon shape, and the reflected image displayed by the relief surface 13Re has a star shape. However, the shape of the colored image displayed by the sub-wavelength grating 11G and the shape of the reflected image displayed by the relief surface 13Re can be any shape. The image displayed by the sub-wavelength grating 11G is the first image, and the image displayed by the relief surface 13Re is the second image.

FIG. 20 shows a first state of the optical element 50.
As shown in FIG. 20, in the first state of the optical element 50, both the first image P1 and the second image P2 disappear in the optical element 50. In the first state, the first image P1 and the second image P2 are not identified by the observer OB because of the luminance in the light for forming the first image P1 and the luminance in the light for forming the second image P2. To a low degree. In other words, at the observation angle θOB where the observer OB observes the optical element 50, the brightness of the light reflected by the sub-wavelength grating 11G and the light reflected by the relief surface 13Re are both media on which the optical element 50 is affixed. Therefore, the first image P1 and the second image P2 are not identified by the observer OB.

FIG. 21 shows a second state of the optical element 50.
As shown in FIG. 21, in the second state of the optical element 50, the first image P1 appears and the second image P2 disappears in the optical element 50. The appearance of the first image P1 means that the optical element 50 displays the first image P1 in a state where the luminance of light in the first image P1 is higher than the luminance of light in the second image P2. Therefore, the second state includes a state in which the first image P1 is identified while the second image P2 is not identified. In the second state, the first image P1 and the second image P2 appear in the optical element 50, and the luminance of light in the first image P1 is higher than the luminance of light in the second image P2. included.

In other words, at the observation angle θOB where the observer OB observes the optical element 50, the observer can easily perceive the light reflected by the sub-wavelength grating 11G, while the observer does not easily perceive the light reflected by the relief surface 13Re. .

FIG. 22 shows a third state of the optical element 50.
As shown in FIG. 22, in the third state of the optical element 50, the second image P 2 appears in the optical element 50. The appearance of the second image P2 means that the luminance of light in the second image P2 is higher than the luminance of light in the first image P1, and the optical element 50 displays at least the second image P2. Therefore, the third state includes a state in which the second image P2 is identified while the first image P1 is not identified. In the third state, the optical element 50 displays the second image P2 and the first image P1, and the light intensity in the second image P2 is higher than the light intensity in the first image P1. included.

In other words, at the observation angle θOB at which the observer OB observes the optical element 50, the brightness of the light reflected by the relief surface 13Re is such that the observer can identify the image, and the brightness of the light reflected by the sub-wavelength grating 11G is Not enough for an observer to identify.

FIG. 23 shows a fourth state of the optical element 50.
As shown in FIG. 23, in the fourth state of the optical element 50, both the first image P1 and the second image P2 appear in the optical element 50. When both the first image P1 and the second image P2 appear, the optical element 50 identifies both the first image P1 and the second image P2 to the observer. In this state, the luminance of light in the first image P1 may be substantially equal to the luminance of light in the second image P2. In other words, at the observation angle θOB where the observer OB observes the optical element 50, the intensity of the light reflected by the sub-wavelength grating 11G and the light reflected by the relief surface 13Re is such that the observer OB can distinguish. In addition, the optical element 50 should just have a 3rd state from a 1st state. In the optical element 50, the fourth state is not essential.

As described above, the optical element 50 displays a reflected image formed by monochrome reflected light, that is, a monochrome image, and a colored image formed by light having a certain wavelength range, that is, a chromatic image. Here, the discrimination between the monochrome image and the chromatic color image is performed by discriminating between the first monochrome image and the second monochrome image, or discriminating between the first chromatic color image and the second chromatic color image. Compared with the case where it does, an individual difference does not arise easily in discrimination | determination of two images. Therefore, in the optical element 50, compared with the case where the authenticity of the optical element 50 is verified based on two chromatic images or two monochrome images, individual differences are less likely to occur. Standards for verifying authenticity can be easily described.

The optical element 50 does not display both the second state in which the first image P1 is mainly displayed, the third state in which the second image P2 is mainly displayed, and the first image P1 and the second image P2. Including the first state. Here, since the second state or the third state and the first state are in contrast with each other, individual differences are unlikely to occur in the discrimination between the second state or the third state and the first state. Therefore, individual differences are less likely to occur in authenticity verification, and the criteria for verifying authenticity can be easily described.

[Second example]
A second example of the optical element 50 will be described with reference to FIG.
As shown in FIG. 24, the optical element 50 in the second example includes the first layer 11, the second layer 12, and the third layer 13, as in the optical element 50 in the first example. On the other hand, in the optical element 50 of the second example, the second layer 12 is a relief layer. In the second layer 12, the relief surface 12Re may be on the surface opposite to the surface 12F of the second layer 12, that is, on the back surface 12R. In FIG. 24, the relief surface 12Re is positioned on the entire back surface 12R, but the relief surface 12Re may be positioned on the entire back surface 12R or only a part of the back surface 12R.

In the optical element 50 of the second example, a colored image by the light reflected by the sub-wavelength grating 11G can be displayed by the difference between the refractive index of the first layer 11 and the refractive index of the second layer 12. Further, in the optical element 50 of the second example, a reflection image by the light reflected by the relief surface 12Re can be displayed by the difference between the refractive index of the second layer 12 and the refractive index of the third layer 13.

In the optical element 50 of the second example, the surface of the third layer 13 opposite to the surface in contact with the second layer 12 may be a flat surface, or uneven in the relief surface 12Re of the second layer 12. You may have the shape to follow.

As described above, according to the fifth embodiment of the optical element, the following effects can be obtained.
(10) Since the optical element 50 displays a colored image and a reflected image by monochrome light, individual differences are unlikely to occur between the two images. Therefore, in the optical element 50, individual differences are less likely to occur in authenticity verification, and the criteria for verifying authenticity can be easily described.

(11) Since the second layer 12 includes the sub-wavelength grating 11G and the relief surface 12Re, the reflectance at the sub-wavelength grating 11G is determined by the difference between the refractive index of the first layer 11 and the refractive index of the second layer 12. The reflectance at the relief surface 12Re can be increased by the difference between the refractive index of the second layer 12 and the refractive index of the third layer 13.

[Modification of Fifth Embodiment]
The fifth embodiment described above can be implemented with appropriate modifications as follows.
[Subwavelength grating]
In the optical element 10 of the first embodiment, the sub-wavelength grating 11G includes the first region 11S1 and the second region 11S2, but the sub-wavelength grating 11G included in the optical element 50 is configured by only one region. Also good.

[Relief layer]
In the optical element 50, the first layer 11 may be a relief layer. That is, in the first layer 11, the surface opposite to the surface including the sub-wavelength grating 11G may include a relief surface. Even in such a case, the effect according to the above (10) can be obtained.

In the optical element 50 of the second example, the surface that is in contact with the relief surface 12Re in the third layer 13 has a shape that follows the relief surface 12Re. Therefore, the surface of the third layer 13 can also function as a relief surface.

[Relief surface]
As shown in FIG. 25, in the optical element 50, the back surface 11R of the first layer 11 may include a sub-wavelength grating 11G and a relief surface 11Re. In this case, since the sub-wavelength grating 11G and the relief surface 11Re can be formed simultaneously using one original plate, the accuracy of the position of the relief surface 11Re with respect to the position of the sub-wavelength grating 11G can be improved. .

As shown in FIG. 25, the sub-wavelength grating 11G and the relief surface 11Re are located on the same plane, and the region where the first image P1 is displayed when viewed from the direction facing the back surface 11R of the first layer 11 And a part of the area where the second image P2 is displayed can be overlapped. Further, the area where the first image P1 is displayed and the area where the second image P2 is displayed may overlap. Furthermore, a part or all of the outline of the area where the first image P1 is displayed may overlap with a part or all of the outline of the area where the second image P2 is displayed. Since the outlines of the first image P1 and the second image P2 overlap, it is easy to compare the two patterns. In this case, in a region where a part of each region overlaps, the sub-pixel region that is the pixel region Px where the sub-wavelength grating 11G is located and the relief pixel region where the relief surface 11Re is located are arranged as follows. Can do. As an example, the arrangement of the sub-pixel area and the relief pixel area may be a checkered pattern, a stripe pattern, a honeycomb pattern, a concentric pattern, or the like.

When a part of the area where the first image P1 is displayed and a part of the area where the second image P2 is displayed are overlapped when viewed from the direction facing the back surface 11R of the first layer 11, the following is performed. It is also possible to arrange the sub-pixel area and the relief pixel area as described above. That is, in the region for displaying the first image P1, from the region where a part of the region where the first image P1 is displayed and a part of the region where the second image P2 is displayed overlap, The proportion of the sub-pixel region can be increased along the direction toward the outer edge. In addition, in the region for displaying the second image P2, from the region where a part of the region where the first image P1 is displayed and a part of the region where the second image P2 is displayed overlap, The proportion of the relief pixel region can be increased along the direction toward the outer edge. Thereby, in the area where a part of the area where the first image P1 is displayed and a part of the area where the second image P2 is displayed, the ratio of each of the sub pixel area and the relief pixel area is another area. A decrease in luminance due to being smaller than the first is recognized as a design in each of the first image P1 and the second image P2.

The layer provided with the relief surface may have a quantization phase difference structure described below, and display a reflective layer formed by monochrome light with the structure. With reference to FIGS. 26 to 28, the structure of the layer having the relief surface will be described.

FIG. 26 shows a structure in plan view facing the relief surface. As shown in FIG. 26, in the quantization phase difference structure 52, a plurality of quantization convex portions 52a having a constant size and a plurality of quantization concave portions 52b having a constant size are aligned. In FIG. 26, the bright part is the quantization convex part 52a, and the dark part is the quantization concave part 52b. The quantization convex part 52a and the quantization concave part 52b are arrange | positioned by the fixed space | interval. The quantization convex part 52a is adjacent to the quantization concave part 52b or the quantization convex part 52a at a constant interval. In addition, the quantized concave portions 52b are adjacent to the quantized convex portions 52a or the quantized concave portions 52b at regular intervals. As an actual example, the quantized convex portions 52a and the quantized concave portions 52b of the quantized phase difference structure 52 are alternately arranged one by one, or a plurality of quantized convex portions 52a and a plurality of quantized concave portions 52b are alternately arranged. Or

In the quantized phase difference structure 52, the spatial frequency component with a coarse period and the spatial frequency component with a fine period are superimposed on the relief surface by the arrangement of the quantized convex part 52a and the quantized concave part 52b. The relief surface can be a cell containing the quantized phase difference structure 52. In the quantized phase difference structure 52 on the relief surface, a rib-shaped convex portion in which the quantized convex portions 52a are aligned in one direction and a quantized concave portion that is a concave portion having a constant size as an element structure are parallel to the rib-shaped convex portion. The groove-like recesses aligned in a row may be arranged adjacent to each other and alternately.

The size of the quantized convex portion 52a can be set to 1/20 or more of the center wavelength at the visible wavelength and to half or less of the center wavelength. The size of the quantization recess 52b can be set to 1/20 or more of the center wavelength at the visible wavelength and to half or less of the center wavelength. Specifically, the size of the quantization convex part 52a can be 25 nm or more and 250 nm or less. The size of the quantization recess 52b can be 25 nm or more and 250 nm or less. The quantization convex part 52a can be made into a square in the plan view facing the relief surface.

The quantization recess 52b can be a square in a plan view facing the relief surface. In a plan view facing the relief surface, the corners of the quantized convex portions 52a can be rounded. In a plan view facing the relief surface, the corners of the quantization recess 52b can be rounded.

The quantization convex portion 52a and the quantization concave portion 52b may be aligned with the virtual grid. Moreover, the height of the quantization convex part 52a can be made the same height as the reference height or an integral multiple of the reference height. The depth of the quantization recess 52b can be the same as the reference depth or an integral multiple of the reference depth. The reference height and the reference depth may be the same value. When the reference height and the reference depth are the same value, the integer multiple value can be 1 to 4 times. The integer multiple may be 1 to 8 times. The reference height and the reference depth can be 10 nm or more and 500 nm or less.

FIG. 27 shows the peak of the spatial frequency component calculated along one direction D shown in FIG. A spatial frequency component is calculated along a predetermined direction D in the relief plane. When the hologram reproduction image reproduced by the relief surface is a reproduction point group of five points, discrete five-point peaks are recognized in the spatial frequency components F1 to F5 corresponding to the reproduction points. In FIG. 27, the horizontal axis represents the spatial frequency (1 / mm), and the vertical axis represents the intensity of the spatial frequency component.

When the discrete spatial frequency components are sparse, the reconstructed image is a rainbow image, and when it is dense, it is a monochrome image. It is also possible to adjust the density of the spatial frequency component distribution so that the reproduced image at a certain observation angle is an iridescent image, and the reproduced image at other observation angles is monochrome.

FIG. 28 is a cross-sectional view schematically showing the quantized phase difference structure 52. In FIG. 28, the relief surface formed by the quantized phase difference structure 52 is shown as the upper surface.
The layer including the quantized retardation structure 52 has a substantially flat shape. The quantized phase difference structure 52 is located on one surface of the surfaces facing each other in the layer. In the quantization phase difference structure 52, the length L from the top surface 52c of the quantization convex portion 52a to the bottom surface 52d of the quantization concave portion 52b is constant regardless of the position on the relief surface. The top surface 52c of the quantization convex portion 52a and the bottom surface 52d of the quantization concave portion 52b may be substantially parallel to the surface of the carrier when the optical element 50 is formed. In the layer including the quantized phase difference structure 52, the color of the reflected light of the quantized phase difference structure 52 changes according to the length L. In addition, the uneven direction of the quantized phase difference structure 52, that is, the vertical direction in FIG. 28, is a rib-shaped recess and a groove-shaped recess formed by the top surface 52c of the quantized convex portion 52a and the bottom surface 52d of the quantized concave portion 52b. It is perpendicular to the extending direction. With such a structure, it is possible to control the emission distribution of reflected light and the color of reflected light without breaking the emission distribution of reflected light and without damaging the color of the light. In the quantization phase difference structure 52, each of the top surface 52c of the quantization convex portion 52a and the bottom surface 52d of the quantization concave portion 52b functions as a reflection surface.

The quantized convex part 52a and the quantized concave part 52b have a width that is an integral multiple of the unit length and a vertical width that is an integral multiple of the unit length in a plan view facing the relief surface. The unit length may be not less than 1/20 of the center wavelength at the visible wavelength and not more than half of the center wavelength. The unit length may be 25 nm or more and 250 nm or less.

Note that the quantized phase difference structure 52 may be located on both of a pair of surfaces facing each other in the layer including the quantized phase difference structure 52. The relief surface includes a phase angle recording area. The quantized phase difference structure 52 described above is formed in the phase angle recording area. The extending direction of the groove-shaped concave portion or rib-shaped convex portion and the orientation of the sub-wavelength grating 11G are equal or orthogonal. In other words, the arrangement direction of the groove-shaped concave portions and rib-shaped convex portions and the azimuth angle of the sub-wavelength grating 11G can be orthogonal or equal. Further, when there are a plurality of orientations of the sub-wavelength grating 11G, the average of the orientations can be set as the orientation of the sub-wavelength grating 11G. The average can be a weighted average weighted by the area of each region where a plurality of sub-wavelength gratings are formed. Accordingly, when the observer OB tilts the card 100 forward with respect to the reference plane Ph0, the card 100 displays the first image P1 and the second image P2 according to the position of the card 100. In other words, when the observer OB brings the surface 100F of the card 100 close to the observer OB in a state where the position of the portion held by the observer OB in the card 100 is substantially fixed in the observation space, the card 100 Depending on the position, the card 100 displays the first image P1 and the second image P2 (see FIG. 40).

The optical element 50 may include a reflective layer on the quantization phase difference structure 52. The reflective layer may be translucent or concealed. The reflective layer may be formed from a metal material. Examples of metal materials are Al, Ag, Sn, Cr, Ni, Cu, Au, and alloys thereof. The reflective layer formed from a metal material can be a concealable reflective layer.

Alternatively, the reflective layer may be a dielectric layer having a refractive index different from that of the relief structure forming layer. Alternatively, the reflective layer may be a laminate of dielectric layers having different refractive indexes between adjacent layers, that is, a dielectric multilayer film. Of the dielectric layers included in the dielectric multilayer film, the refractive index of the layer in contact with the relief surface is preferably different from the refractive index of the layer including the relief surface.

The material for forming the dielectric layer can be a metal compound or silicon oxide. The metal compound can be a metal oxide, a metal sulfide, and a metal fluoride. Examples of the material for forming the dielectric layer are TiO ₂ , ZnO, Si ₂ O ₃ , SiO, Fe ₂ O ₃ , ZnS, CaF, and MgF. The reflective layer of the dielectric layer can be translucent.

The reflective layer can be formed by a vapor deposition method. As the vapor deposition method, a vacuum deposition method, a sputtering method, or the like can be applied. The thickness of the reflective layer can be 10 nm or more and 1000 nm or less.

The reflective layer may be formed using ink. The ink for forming the reflective layer may be offset ink, letterpress ink, gravure ink, or the like depending on the printing method. Moreover, the ink which forms a reflection layer may be resin ink, oil-based ink, water-based ink, etc. according to the difference in composition. Further, the ink for forming the reflective layer may be an oxidation polymerization type ink, a permeation drying type ink, an evaporation drying type ink, and an ultraviolet curable ink depending on the difference in the drying method.

The ink for forming the reflective layer may be a functional ink whose color changes according to the illumination angle or the observation angle. The functionality may be optically variable ink (Optical Variable Ink), color shift ink, and pearl ink.

[First image and second image]
The observation angle range in which the second image displayed on the relief surface is observed may be larger than the observation angle range in which the first image displayed on the sub-wavelength grating 11G is observed. That is, the optical element 50 is observed in a state where the first image is displayed at the observation angle in the first range, and is observed in a state where the second image is displayed in the observation angle in the second range. The range may be larger than the first range. In this case, when the optical element 50 is tilted, the size of the observation angle range in which the first image is observed is equal to the size of the angle range in which the second image is observed. The uniformity in changing the image displayed by the optical element 50 is disturbed. This makes it easier for the image displayed by the optical element 50 to catch the eyes of the observer. That is, the attractiveness by the image displayed by the optical element 50 is enhanced.

The first image displayed by the subwavelength grating 11G and the second image displayed by the relief surface may have a correlation with each other. As a result, compared with the case where the first image and the second image have no correlation with each other, the observer who observed the optical element 50 notices the correlation between the first image and the second image, thereby observing. It is possible to draw the attention of the person. Hereinafter, examples of the first image and the second image in a case where the first image and the second image have a correlation will be described in more detail with reference to FIGS. 29 to 31. 29 to 31 show a state where both the first image and the second image are displayed for convenience of explanation.

As shown in FIG. 29, in the first example of the first image P1 and the second image P2, the second image P2 is positioned outside the first image P1 and has a shape that follows the contour of the first image P1. Have. According to the first example, since the outline of the first image P1 is bordered by the second image P2 having a contrasting color with the first image P1, the outline of the first image P1 can be made to stand out. It is. Thereby, the attractiveness of the 1st image P1 and the 2nd image P2 can be improved.

When the relief surface forming the second image P2 includes a plurality of pixel regions Px and each pixel region Px includes a plurality of reflecting surfaces extending along one direction, the relief surface is as follows. It may be the structure. That is, in a plurality of pixel regions Px, the azimuth angle of the reflecting surface may change along the direction from the contour of the first image P1 toward the contour of the second image P2. Thereby, it is possible to produce the brightness gradation in the 2nd image P2 according to the azimuth angle of a reflective surface. Thereby, the smooth texture and attractiveness by the 1st image P1 and the 2nd image P2 can be improved.

As shown in FIG. 30, in the second example of the first image P1 and the second image P2, one of the first image P1 and the second image P2 has a shape representing a predetermined symbol or a predetermined object. The other of the first image P1 and the second image P2 is a character representing the shape. In the actual example shown in FIG. 30, the first image P1 has the shape of the symbol Euro (EURO), and the second image P2 is a character representing the shape. In addition, while the second image P2 has a shape representing a predetermined symbol or a predetermined object, the first image P1 may be a character representing the shape.

Thereby, the first image P1 and the second image P2 showing the same meaning may or may not be displayed depending on the observation angle. Therefore, it is possible to increase the degree of recognition of the contents meant by the first image P1 and the second image P2, and the attractiveness of the first image P1 and the second image P2.

As shown in FIG. 31, in the third example of the first image P1 and the second image P2, the first image P1 has a shape representing a set of objects together with the second image P2. In the example shown in FIG. 31, each of the first image P1 and the second image P2 has a shape forming a pair of legs. The first image P1 has a left foot shape, and the second image P2 has a right foot shape. Thereby, it is possible to improve the attractiveness of the first image P1 and the second image P2. Note that the first image P1 and the second image P2 only need to have a shape that represents a set of objects with each other. For example, the first image P1 and the second image P2 may have a shape that forms a set of hands.

Note that the first image P1 and the second image P2 may have shapes representing different objects, and may form one image that is complemented by each of the first image P1 and the second image P2. That is, the first image P1 and the second image P2 may form one trick picture. Also by this, the attractiveness of the first image P1 and the second image P2 can be enhanced.

[Sixth Embodiment]
With reference to FIGS. 32 to 35, a sixth embodiment of the optical element will be described. The optical element according to the sixth embodiment of the present invention is different from the optical element 50 according to the fifth embodiment in that the layers other than the first layer 11, the second layer 12, and the third layer 13 are relief layers. Different. Therefore, in the following, such differences will be described in detail. On the other hand, in the optical element of the sixth embodiment, components corresponding to the optical element 50 of the fifth embodiment are denoted by the same reference numerals as those in the fifth embodiment. Detailed description thereof is omitted. Hereinafter, four examples will be described in order as the optical element of the sixth embodiment.

[First example]
The optical element of the first example will be described with reference to FIG.
As shown in FIG. 32, the optical element 60 includes a first layer 11, a second layer 12, and a third layer 13. The optical element 60 further includes a relief layer 61 including a relief surface 61Re. The relief surface 61Re is a surface different from the back surface 11R and the front surface 12F described above. The relief surface 61Re includes a plurality of reflecting surfaces, and the pitch between the reflecting surfaces adjacent to each other is larger than the pitch of the sub-wavelength grating 11G. The relief surface 61Re is included in the back surface 61R of the relief layer 61.

The optical element 60 further includes a reflective layer 62 and an adhesive layer 63. The reflective layer 62 is in contact with the relief surface 61Re and has a shape that follows the unevenness of the relief surface 61Re. The adhesive layer 63 is in contact with the reflective layer 62 on the side opposite to the relief layer 61 with respect to the reflective layer 62. In the optical element 60, the third layer 13 functions as an adhesive layer. Thereby, the multilayer body formed of the first layer 11 and the second layer 12 is attached to the relief layer 61 by the third layer 13. Therefore, in the optical element 60, the sub-wavelength grating 11G and the relief surface 61Re overlap each other when viewed from the thickness direction of the optical element 60.

The adhesive layer 63 may be located on the entire surface of the reflective layer 62 opposite to the surface in contact with the relief layer 61 or may be located on a part thereof.
According to the optical element 60 of the first example, the first multilayer body composed of the first layer 11, the second layer 12, and the third layer 13, the relief layer 61, the reflective layer 62, and the adhesive layer 63. The second multilayer body composed of the above can be manufactured individually. Further, according to the optical element 60 of the first example, the optical element 60 can be attached to the adherend using the adhesive layer 63.

[Second example]
The optical element of the second example will be described with reference to FIG.
As shown in FIG. 33, the optical element 60 includes a relief layer 61, a reflective layer, in addition to the first layer 11, the second layer 12, and the third layer 13, in the same manner as the optical element 60 in the first example described above. 62 and an adhesive layer 63. The optical element 60 of the second example further includes a base material 64 between the third layer 13 and the relief layer 61. In the pair of surfaces facing each other in the base material 64, the third layer 13 is positioned on one surface and the relief layer 61 is positioned on the other surface. The base material 64 has optical transparency. The base material 64 can function as a support layer for the first layer 11 and the relief layer 61 formed with respect to the base material 64 when the optical element 60 is manufactured. The optical element 60 of the second example is observed from the base material 64 side with respect to the relief layer 61.

[Third example]
The optical element of the third example will be described with reference to FIG.
As shown in FIG. 34, in the optical element 60, in the same manner as the optical element 60 in the first example described above, in addition to the first layer 11, the second layer 12, and the third layer 13, a relief layer 61, a reflective layer 62 and an adhesive layer 63. The optical element 60 of the third example further includes a first base material 65 and a second base material 66. The first base material 65 is located between the third layer 13 and the relief layer 61. The third layer 13 functions as an adhesive layer, whereby the multilayer body composed of the first layer 11 and the second layer 12 is bonded to the first base material 65 by the third layer 13. The adhesive layer 63 is adhered to the second base material 66. The first base 65 has light transmittance. On the other hand, the 2nd base material 66 may have a light transmittance, and does not need to have a light transmittance.

The first multilayer body composed of the first layer 11, the second layer 12, and the third layer 13 is located in a part of the first base material 65 in a plan view facing the sub-wavelength grating 11G. . The second multilayer body including the relief layer 61, the reflective layer 62, and the adhesive layer 63 is located at a part of the second base material 66 in a plan view facing the relief surface 61Re. The first layer 11 overlaps the relief layer 61 when viewed from the thickness direction of the optical element 60.

[Fourth example]
With reference to FIG. 35, the optical element of the fourth example will be described.
As FIG. 35 shows, in addition to the first layer 11, the second layer 12, and the third layer 13, the optical element 60 includes a relief layer 61, a reflective layer 62, An adhesive layer 63 is provided. The optical element 60 further includes a first base material 65 and a second base material 66. The third layer 13 functions as an adhesive layer, and the third layer 13 is bonded to the relief layer 61. The adhesive layer 63 is adhered to the second base material 66.

The first multilayer body described above is located in a part of the first base material 65 in a plan view corresponding to the sub-wavelength grating 11G. The second multilayer body is located at a part of the second base material 66 in a plan view facing the relief surface 61Re. The first layer 11 overlaps the relief layer 61 when viewed from the thickness direction of the optical element 60.

The optical element 60 is observed from the reflective layer 62 side with respect to the adhesive layer 63. Therefore, the 1st base material 65 has light transmittance. On the other hand, the 2nd base material 66 may have a light transmittance, and does not need to have a light transmittance.

In the first to third examples of the optical element 60, paper, plastic film, or the like can be used for each substrate. Each substrate may be printed. Alternatively, each base material is a multilayer body, and printing may be performed on at least some of the plurality of layers constituting the base material.

As described above, according to the optical element of the sixth embodiment, in addition to the above (10), the following effects can be obtained.
(12) Since the layers other than the first layer 11, the second layer 12, and the third layer 13 are relief layers having a relief surface, the degree of freedom in designing the relief layer is increased.

[Modification of Sixth Embodiment]
The sixth embodiment described above can be implemented with appropriate modifications as follows.
[Base material]
In the optical element 60 of the first example to the third example, each base material may be smaller than at least one of the first multilayer body and the second multilayer body in a plan view facing the sub-wavelength grating 11G.

The first multilayer body including the first layer 11 and the second multilayer body including the relief layer 61 may be included between the two base materials. In other words, each of the first multilayer body and the second multilayer body may be laminated while being sandwiched between two substrates.

-Each substrate may be a laser coloring layer that develops color when irradiated with a laser beam. And the base material 64 in a 1st example may also contain the information memorize | stored in the base material 64 by irradiation of the laser beam.

Further, in the optical element 60 of the second example, at least one of the first base material 65 and the second base material 66 can include information stored by laser beam irradiation. When the first base material 65 includes information, the second image displayed by the relief surface 61Re and the information included in the first base material 65 are overlapped with each other when viewed from the thickness direction of the optical element 60. Only part of the two images is visible. Thereby, in the optical element 60, the tolerance with respect to forgery increases. On the other hand, when the second substrate 66 includes information, the entire first image displayed by the sub-wavelength grating 11G and the second surface displayed by the relief surface are viewed from the thickness direction of the optical element 60. The entire image is visible.

In the optical element 60 of the third example, when the first base material 65 includes information, the first image displayed by the sub-wavelength grating 11G and the relief surface 61Re are viewed from the thickness direction of the optical element 60. By overlapping the second image to be displayed and the information included in the first base material 65, only a part of the first image and a part of the second image are visually recognized. Thereby, in the optical element 60, the tolerance with respect to forgery increases. On the other hand, when the second substrate 66 includes information, the entire first image displayed by the sub-wavelength grating 11G and the second surface displayed by the relief surface are viewed from the thickness direction of the optical element 60. The entire image is visible.

[Seventh Embodiment]
A transfer foil provided with an optical element will be described with reference to FIG. In the seventh embodiment of the present invention, a case where the optical element included in the transfer foil is a first example of the optical element 50 of the fifth embodiment will be described as one form of the transfer foil.

As shown in FIG. 36, the transfer foil 70 includes an adhesive body including the optical element 50 and an adhesive layer 71 for bonding the optical element 50 to the transfer target body. The transfer foil 70 further includes a support layer 72 and a release layer 73. In the transfer foil 70, the support layer 72, the release layer 73, the optical element 50, and the adhesive layer 71 are stacked in the order described. The optical element 50 after being transferred to the transfer medium is observed from the side opposite to the optical element 50 with respect to the release layer 73. Therefore, the release layer 73 is light transmissive. On the other hand, since the peeling layer 73 is peeled from the support layer 72 when the optical element 50 is transferred, the support layer 72 may or may not have light transmittance. .

The transfer foil 70 includes a sub-wavelength grating 11G and a relief surface 13Re. Therefore, the optical element 50 that displays the first image P1 and the second image P2 can be transferred to the transfer target body only by transferring a part of the transfer foil 70. For the transfer of the optical element 50, a hot stamp method can be used.

[Modification of the seventh embodiment]
[Transfer foil]
It is possible to prepare a first transfer foil including the sub-wavelength grating 11G and a second transfer foil including the relief surface 13Re, and form an optical element using the two transfer foils. In this case, when viewed from the thickness direction of the optical element, the first sub-wavelength grating 11G included in the first transfer foil and the relief surface 13Re included in the second transfer foil overlap with each other on the first transfer object. A part of the transfer foil and a part of the second transfer foil may be transferred. In this case, when forming the optical element, it is necessary to align the position where a part of the first transfer foil is transferred and the position where a part of the second transfer foil is transferred. Therefore, the resistance against counterfeiting is enhanced in the optical element.

[Optical element]
The transfer foil is replaced with the optical element 50 described above, the optical element 10 of the first embodiment, the optical element 20 of the second embodiment, the optical element 30 of the third embodiment, and the optical element of the fourth embodiment. 40 may be included. Further, the transfer foil may include the optical element 50 of the second example in the fifth embodiment, and the optical element 60 of the first example and the second example in the sixth embodiment, instead of the optical element 50 described above.

[Eighth Embodiment]
With reference to FIGS. 37 and 38, an authenticator according to an eighth embodiment of the present invention will be described. Below, the card | curd which is an example of an authentication body is demonstrated. Examples of the card according to the embodiment of the present invention are an ID card, a license, a license card, a member card, and a credit card. The card includes the third example of the optical element 60 of the sixth embodiment as a part of the card.

[Card configuration]
As shown in FIG. 37, the card 80 has a plate shape that spreads two-dimensionally in a plan view facing the surface 80F of the card 80. The card 80 displays the first image 81, the second image 82, and the third image 83 via the surface 80F. Further, the card 80 displays the first image P1 and the second image P2 via the surface 80F.

In the present embodiment, the first image 81 includes a face image 81a and a background image 81b. The face image 81a is an image showing the face of the owner of the card 80. The background image 81b includes a face image 81a inside, and forms the background of the face image 81a. The second image 82 includes information regarding the owner of the card 80. The second image 82 includes information expressed by letters and numbers. The third image 83 includes information regarding the card 80. The information included in the third image 83 is the name of the card 80. The face image 81a and the second image 82 are identification information for identifying the card owner. The card 80 only needs to be able to display the first image P1 and the second image P2 via the surface 80F. The above-described image is an example of an image that can be displayed by the card 80.

FIG. 38 shows a cross-sectional structure of the card 80 taken along line IV-IV in FIG.
As shown in FIG. 38, a card 80 that is an example of an authentication body includes an optical element 60. The optical element 60 may cover the identification information. In the optical element 60 included in the card 80, the first multilayer body including the first layer 11, the second layer 12, and the third layer 13 further includes a release layer 68. The release layer 68 covers the first layer 11. The second multilayer body including the relief layer 61, the reflective layer 62, and the adhesive layer 63 further includes a release layer 69. The release layer 69 covers the relief layer 61. In the optical element 60, the second multilayer body is covered with the first base material 65.

The whole or a part of the second base material 66 may have a characteristic of color development by laser beam irradiation before laser beam irradiation. Coloring by laser beam irradiation can be carbonized. That is, the whole or a part of the second base material 66 may have a characteristic of being carbonized by the laser beam irradiation before the laser beam irradiation. The second base material 66 included in the card 80 includes a first color development part 66a and a second color development part 66b, which are parts colored by irradiation with a laser beam. The first color developing unit 66a is a part that displays the face image 81a, and the second color developing unit 66b is a part that displays the second image 82.

The card 80 includes a white layer 91, a lower protective layer 92, and an upper protective layer 93. The white layer 91 is a white layer and is in contact with the second base material 66. In the white layer 91, printing 94 is applied to a part of the surface in contact with the second base material 66. When viewed from the thickness direction of the card 80, the print 94 is located in an area overlapping with the first color development portion 66a. The print 94 displays a background image 81b.

The lower protective layer 92 is located on the surface of the white layer 91 opposite to the surface in contact with the second base material 66. The upper protective layer 93 covers the first base material 65 and encloses the first multilayer body with the first base material 65. The upper protective layer 93 is light transmissive. On the other hand, the lower protective layer 92 may have light transmittance or may not have light transmittance.

[Modification of Eighth Embodiment]
[Authentication body]
The authentication body is not limited to a card, and may be embodied as another authentication body used for authenticating an owner such as a passport.

[Optical element]
The authentication body is replaced with the optical element 60 described above, the optical element 10 of the first embodiment, the optical element 20 of the second embodiment, the optical element 30 of the third embodiment, the optical element 40 of the fourth embodiment, And the optical element 50 of 5th Embodiment may be included. Further, the authentication body may include the optical element 60 in the first example, the second example, and the fourth example of the sixth embodiment instead of the optical element 60 described above.

[Ninth Embodiment]
With reference to FIGS. 39 to 46, an authentication body according to a ninth embodiment of the present invention will be described. Hereinafter, another example of the card will be described as an example of the authentication body.

[Card configuration]
The configuration of the card will be described with reference to FIG. As an example of the card, a card including the optical element 10 of the first embodiment will be described. However, the card is not limited to the optical element 10 of the first embodiment, and the optical element in each of the second to sixth embodiments. May be provided.

The card 100 further includes a display layer 101 in addition to the first layer 11, the second layer 12, and the third layer 13. The display layer 101 can display predetermined information. The display layer 101 can display predetermined information using characters, numbers, figures, QR codes (registered trademark), and the like. In the card 100, the surface of the first layer 11 opposite to the surface in contact with the second layer 12 is the surface 100F.

The display layer 101 can display predetermined information by printing performed on the display surface 101F in contact with the third layer 13. The display surface 101F can be printed by letterpress printing, gravure printing, offset printing, or screen printing. A functional ink can be used as the printing ink. The functional ink is ink that changes color according to the type or state of the light source that irradiates the card 100, and ink that changes color or gloss according to the observation angle of the observer. The ink whose color changes depending on the type or state of the light source can be phosphorescent ink, fluorescent ink, and photochromic ink. The ink whose color and gloss change according to the observation angle can be pearl ink, magnetic ink, and color shift ink.

Storing ink absorbs and stores light energy emitted from sunlight, fluorescent lamps, etc., and has a function of gradually emitting light in the dark. Phorochromic ink is ink that develops color in response to ultraviolet light. The photochromic ink has a function of exhibiting different colors such as red, blue, purple, and yellow according to the irradiation amount of ultraviolet rays to the photochromic ink. Pearl ink is ink to which a pearl pigment is added. The gloss of the pearl ink changes depending on the observation angle. The pearl ink contains a pearl pigment formed from a polarized pearl as a pearl pigment, so that the color tone changes depending on the observation angle. According to the functional ink, it can be easily confirmed whether or not the color of the printing formed on the display surface 101F changes. Therefore, the authenticity of the card 100 can be reliably verified based on the printing color.

In addition, as a method for printing on the display surface 101F, an ink jet method, a thermal printer method, a laser method, or the like may be used. According to these methods, the information to be formed on the display surface 101F can be set for each card 100. Therefore, a pattern or the like common to a plurality of cards 100 is printed at a relatively high speed by the above-described printing, and identification information for identifying each card 100 is an ink jet method, a thermal printer method, a laser method, or the like. It is preferable to print using.

As described above, the optical element included in the card 100 is not limited to the optical element 10 of the first embodiment, and may be the optical element in each of the fifth embodiment and the sixth embodiment. That is, the card 100 may be capable of displaying the first image P1 displayed by the sub-wavelength grating 11G, the second image P2 displayed by the relief surface, and the third image displayed by the display layer 101. . In such a card 100, when the luminance of the first image P1 and the luminance of the second image P2 are sufficiently high, the observation angle at which the first image P1 is displayed and the observation at which the second image P2 is displayed. At each angle, the third image is hardly visible. On the other hand, the third image is visually recognized at an observation angle at which both the first image P1 and the second image P2 are not displayed. Therefore, the observer can visually recognize the third image.

The observation angle at which each of the first image P1 and the second image P2 is visually recognized is arbitrary depending on the observation angle at which each of the first image P1 and the second image P2 appears, that is, the shape of the sub-wavelength grating 11G and the relief surface. Can be set.

In the card 100, the multilayer body composed of the first layer 11, the second layer 12, and the third layer 13 preferably has a transmittance of 70% or more in the direction in which the three layers are stacked. Thereby, the image displayed on the card 100 is easily visually recognized. In this case, in particular, when an optical element that is a multilayer body composed of the first layer 11, the second layer 12, and the third layer 13 covers the identification information, the ease of identification is improved. For example, Article 195 in the safety standard for road transport vehicles requires that the transmittance of each of the front glass and side glass of an automobile is 70% or more. Even in view of these standards, it can be said that it is preferable that the transmittance of a transmission body through which light for displaying information is transmitted is 70% or more in order for a person to view information clearly and reliably.

The transmittance of the transparent multilayer body can be measured using a spectrophotometer. In an environment where the card 100 is observed, it is assumed that the light source is sunlight or a fluorescent lamp. Therefore, it is preferable to measure the transmittance at a wavelength of 500 nm as the transmittance of the multilayer body used in the card 100. The transmittance of the multilayer body is preferably measured by a method in accordance with JIS K7375: 2008 “How to obtain total light transmittance and total light reflectance of plastic”.

[Card effects]
The operation of the card 100 will be described with reference to FIGS. Below, the effect | action in the 1st example of the card | curd 100 and the effect | action in the 2nd example of the card | curd 100 are demonstrated in order. In addition, the 1st example of the card | curd 100 is a structure provided with the optical element containing the subwavelength grating 11G and a relief surface, and the authenticity of the card | curd 100 is verified by an observer's visual observation. On the other hand, the second example of the card 100 is configured to include an optical element that includes the sub-wavelength grating 11G but does not include a relief surface, and the verifier verifies the authenticity of the card 100.

[First example]
The operation of the card 100 in the first example will be described with reference to FIGS.
FIG. 40 schematically shows a method in which the observer OB verifies the authenticity of the card 100 by visual observation.

40, the observer OB visually recognizes the card 100 while holding the card 100 in his / her hand. The reference plane Ph0 is a plane on which the card 100 is arranged when the observer OB starts observing the card 100. The reference plane Ph0 is a base plane used when verifying the authenticity of the card 100. The observer OB tilts the card 100 arranged on the reference plane Ph0 along each of the first plane Ph1, the second plane Ph2, and the third plane Ph3. The observer OB observes the card 100 when the card 100 is positioned on each of the planes Ph1, Ph2, and Ph3. The angle formed by the reference plane Ph0 and the first plane Ph1 is the first angle θ1, the angle formed by the reference plane Ph0 and the second plane Ph2 is the second angle θ2, and the reference plane Ph0 and the third plane Ph3. Is the third angle θ3. The first angle θ1 is larger than the second angle θ2 and the third angle θ3, and the second angle θ2 is larger than the third angle θ3.

The light source LS is located on the side opposite to the observer OB with respect to the card 100. In other words, the light source LS is located in front of the observer OB. The light source LS, the card 100, and the observer OB are arranged at relative positions such that the light of the light source LS incident on the card 100 is reflected toward the observer OB on the card 100. When observing the card 100, it is preferable that light from a point light source is incident on the card 100 from one direction. However, in actuality, when the card 100 is observed, light from a fluorescent lamp or external light enters the card 100 from various directions. Even in this case, if the light incident on the card 100 includes light reflected toward the observer OB in the card 100, the luminance of the light emitted from the card 100 is reduced, but the observation is performed. The person OB can visually recognize the information displayed on the card 100.

41 to 43 show images displayed on the card 100, respectively. FIG. 41 is an image that the card 100 shows when the card 100 is arranged on the first plane Ph1, and FIG. 42 is an image that the card 100 shows when the card 100 is arranged on the second plane Ph2. FIG. 43 is an image that the card 100 shows when the card 100 is arranged on the third plane Ph3. The card 100 is configured to be able to display the first image P1, the second image P2, and the third image P3.

41, when the observer OB places the card 100 on the first plane Ph1, the card 100 displays only the third image P3. The third image P3 may include identification information for identifying the card 100. The identification information that can identify the owner included in the third image P3 includes the face image, name, and ID number of the owner. When the observer OB places the card 100 on the first plane Ph1, the card 100 displays the entire third image P3 to the outside through the surface 100F.

42, when the observer OB places the card 100 on the second plane Ph2, the card 100 displays the second image P2. In a plan view facing the surface 100F of the card 100, the second image P2 overlaps a part of the third image P3. Therefore, in the present embodiment, a part of the third image P3 is concealed by the second image P2. The luminance of the second image P2 may be a luminance that does not completely hide part of the third image P3.

43, when the observer OB places the card 100 on the third plane Ph3, the card 100 displays the first image P1. On the other hand, the card 100 does not display the second image P2. In a plan view facing the surface 100F of the card 100, the first image P1 overlaps a part of the third image P3. Therefore, in the present embodiment, a part of the third image P3 is hidden by the first image P1. Note that the luminance of the first image P1 may be a luminance that does not completely hide a part of the third image P3.

Thus, when the observer OB tilts the card 100 forward with respect to the reference plane Ph0, the card 100 displays the first image P1 and the second image P2 according to the position of the card 100. In other words, when the observer OB brings the surface 100F of the card 100 close to the observer OB in a state where the position of the portion held by the observer OB in the card 100 is substantially fixed in the observation space, the card 100 Depending on the position, the card 100 displays the first image P1 and the second image P2.

Even when the observer OB tilts the card 100 left and right with the second plane Ph2 as the base surface, the observer OB visually recognizes the first image P1 and the second image P2 displayed on the card 100. Is possible. In other words, even when the observer OB tilts the card 100 without substantially changing the distance between the surface 100F of the card 100 and the observer OB in the observation space, the observer OB does not change the first image P1. It is possible to visually recognize the second image P2. However, the observer OB can easily view the second image P2, while the observer OB can observe the first image P1 only under limited observation conditions for the following reason.

As described above, the first image P1 is viewed by the observer OB only when the light source LS and the observer OB are positioned at a target angle with respect to the plane including the ray with respect to the surface of the card 100. Therefore, when the card 100 is tilted left and right with respect to the second plane Ph2, the angle formed by the second plane Ph2 and the reference plane Ph0 needs to be the third angle θ3. Here, the second plane Ph2 is a plane on which the card 100 is arranged when the observer OB unconsciously picks up the card 100. Therefore, the probability that the angle formed by the second plane Ph2 and the reference plane Ph0 matches the third angle θ3 is low. In contrast, when the observer OB tilts the card 100 back and forth with respect to the reference plane Ph0, the probability that the observer OB places the card 100 on the third plane Ph3 is high.

Therefore, when observing the card 100 as the authentication body, the observer OB tilts the card 100 back and forth while the light source LS is positioned obliquely upward with respect to the plane including the line of sight of the observer OB. Can be determined. This increases the probability that the observer OB observes both the first image P1 and the second image P2. Therefore, the authentic verification of the card 100 by the observer OB is easily performed accurately.

[Second example]
The operation of the card 100 in the second example will be described with reference to FIGS.
FIG. 44 schematically shows a method of verifying the authenticity of the card 100 by the verifier V.

As shown in FIG. 44, the card 100 is designed such that the light from the light source LS is incident on the surface 100F of the card 100 at the incident angle α and the reflected light reflected at the emission angle β is input to the verifier V. An environment for verifying the authenticity of 100 is set. The verifier V can be a camera capable of reading an image, a sensor capable of reading a luminance distribution, and the like. The verifier V may be any device that can process the first image P1 as an image or optical information such as luminance.

FIG. 45 shows an image displayed by the genuine card 100. On the other hand, FIG. 46 shows an image displayed by the fake card 200. 45 and 46 show images displayed on the

cards

100 and 200 under certain observation conditions.

As shown in FIG. 45, the genuine card 100 shows a QR code (registered trademark) P3a as a part of the third image P3.
On the other hand, as shown in FIG. 46, the fake card 200 displays the QR code P3a as a part of the third image P3 and at the same time displays the first image P1 through the surface 200F. Here, the verifier V verifies that the card 100 is authentic when the QR code P3a displayed on the card 100 is read under the above-described observation conditions. In this case, since the card 100 displays the QR code P3a as a part of the third image P3 and the QR code P3a does not overlap with other images, the verifier V determines that the card 100 is a genuine card. It can be verified that it is 100. In contrast, the card 200 displays the QR code P3a as a part of the third image P3, but displays the first image P1 so as to overlap the QR code P3a when viewed from the thickness direction of the card 100. In other words, the information read by the verifier V includes information other than the QR code. Therefore, the verifier V can verify that the card 200 is a fake.

In the present embodiment, the QR code P3a is shown as the code displayed on the

cards

100 and 200, but the code displayed on the

cards

100 and 200 may be another code that can be read by the verifier V. Other codes can be bar codes. For verification by the verifier V, the first image P1 or the second image P2 may be used instead of the third image P3.

Further, in the above-described example, the position of the verifier V is fixed at one place. The light emitted from the card 100 may be read even at an angle γ that is different from the angle γ. In this case, the authenticity of the card 100 can be verified in two stages by using two pieces of information obtained at different angles. Thereby, the accuracy of authenticity verification can be further increased.

[Optical element forming material]
Hereinafter, materials that can be used for forming the optical element will be described. Below, the material for forming each of the 1st layer 11, the 2nd layer 12, and the 3rd layer 13 in an optical element is demonstrated.

[First and third layers]
Each material of the first layer 11 and the third layer 13 can essentially contain the following various resins. Examples of materials forming each layer are poly (meth) acrylic resin, polyurethane resin, fluorine resin, silicone resin, polyimide resin, epoxy resin, polyethylene resin, polypropylene resin, methacrylic resin, poly Methylpentene resin, cyclic polyolefin resin, polystyrene resin, polyvinyl chloride resin, polycarbonate resin, polyester resin, polyamide resin, polyamideimide resin, polyarylphthalate resin, polysulfone resin, polyphenylene sulfide Resins, polyethersulfone resins, polyethylene naphthalate resins, polyetherimide resins, acetal resins, and cellulose resins can be used. As the material for forming the first layer and the third layer, only one of these resins may be used, or two or more of them may be mixed or combined. The materials for forming the first layer 11 and the third layer 13 are a curing agent, a plasticizer, a dispersant, various leveling agents, an ultraviolet absorber, an antioxidant, a viscosity modifier, a lubricant, and a light stabilizer. It may contain at least one such as an agent.

The method of forming each of the first layer 11 and the third layer 13 can be a heat embossing method, a casting method, and a photopolymer method. In the photopolymer method, a radiation curable resin is poured between a flat substrate such as a plastic film and a metal stamper. Then, after the radiation curable resin is cured by irradiation with radiation, the cured resin film is peeled off from the metal stamper together with the base material. In the photopolymer method, compared with the press method and the cast method using a thermoplastic resin, the transfer accuracy of the fine concavo-convex structure is high, and the heat resistance and chemical resistance are also excellent.

[Second layer]
As the material of the second layer 12, as described above, a light-transmitting dielectric can be used. As the dielectric, a metal, a metal compound, a silicon compound, or a mixture thereof can be used. Examples of dielectrics can be ZnS, ZnO, ZnSe, SiN _x , SiO _x , Ti _x O _x , Ta ₂ O ₅ , Cr ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ , and ITO.

The method of forming the second layer 12 can be a physical vapor deposition method, a chemical vapor deposition method, or the like. The physical vapor deposition method can be a vacuum deposition method, a sputtering method, an ion plating method, and an ion cluster beam method. The chemical vapor deposition method can be a plasma chemical vapor deposition method, a thermal chemical vapor deposition method, or a photochemical vapor deposition method. The vacuum deposition method is easy to improve productivity. The ion plating method makes it easy to obtain a reflective layer with good film quality. Note that film formation conditions in the physical vapor deposition method and the chemical vapor deposition method may be appropriately selected according to the material for forming the reflective layer.

The second layer 12 can also be formed by various printing methods, casting methods, die coating methods, and the like. In this case, the second layer 12 can be formed of a resin in which at least one of the dielectrics described above is dispersed.

[Test example]
[Test Example 1]
Hereinafter, Test Example 1 will be described. Test Example 1 is a test example corresponding to the authentication body of the eighth embodiment described above. In Test Example 1, a first transfer foil including the first layer 11 and a second transfer foil including the relief layer 61 were prepared. A part of the first transfer foil was transferred to the first base material 65, and a part of the second transfer foil was transferred to the second base material 66. As the second base material 66, a base material that develops color when irradiated with a laser beam was used. By laminating the first base material 65 and the second base material 66, an ID card was obtained as an authentication body of Test Example 1.

More specifically, when manufacturing the first transfer foil, first, a PET film (Lumirror (registered trademark), Toray Industries, Inc.) having a thickness of 38 μm was prepared as a support layer. The release layer 68 was obtained by applying the release layer ink to one surface of the support layer and drying the release layer ink. The thickness of the release layer 68 was 1 μm. Next, the first layer ink was applied onto the release layer 68 by a gravure printing method, and then the first layer ink was dried. The thickness of the first layer ink after drying was 2 μm. And the subwavelength grating 11G was shape | molded by pressing the original for forming the subwavelength grating 11G to the ink for 1st layers after drying. At the time of molding, the press pressure was set to ² kgf / cm ² , the press temperature was set to 80 ° C., and the press speed was set to 10 m / min.

Simultaneously with the molding, the first layer ink was irradiated with ultraviolet rays from the side opposite to the release layer 68 with respect to the support layer. A high pressure mercury lamp was used for ultraviolet irradiation, and the output of the high pressure mercury lamp was set to 300 mJ / cm ² . Thereby, the 1st layer 11 was obtained by hardening the ink for 1st layers. Then, a TiO ₂ film having a thickness of 50 nm was formed on the first layer 11 by vacuum deposition. Thereby, the second layer 12 was obtained. Next, the adhesive layer ink was applied, and the adhesive layer ink was dried to obtain a third layer 13 having a thickness of 2.5 μm to 4 μm and functioning as an adhesive layer. The drying temperature was set to 120 ° C., and the time was set to 45 seconds. When forming the second transfer foil, the same method as the first transfer foil was used, except that the original used for forming the relief surface 61Re was different from the original used for forming the sub-wavelength grating 11G.

The ink having the following composition was used as the above-described release layer ink, first layer ink, relief layer ink, third layer ink, and adhesive layer ink.

[Ink for release layer]
Acrylic resin 70.0 parts by mass Methyl ethyl ketone 30.0 parts by mass

[Ink for first layer / ink for relief layer]
UV curable acrylic acrylate resin 70.0 parts by weight Methyl ethyl ketone 30.0 parts by weight

[3rd layer ink / adhesive layer ink]
Urethane resin 50.0 parts by mass Silica filler 10.0 parts by mass Methyl ethyl ketone 40.0 parts by mass

A transparent polycarbonate substrate (LEXAN SD8B14, manufactured by SABIC) (LEXAN is a registered trademark) having a thickness of 100 μm was prepared as the first substrate 65. As the second base material 66, a polycarbonate base material (LEXAN SD8B94, manufactured by SABIC) which has a thickness of 100 μm and develops color when irradiated with a laser beam was prepared. After the first transfer foil was transferred to the first substrate 65, the support layer was removed. Further, after the second transfer foil was transferred to the second substrate 66, the support layer was removed. At the time of transfer, an electric hot stamping machine is used, the temperature of the surface in contact with the transfer foil is set to 120 ° C., the pressure is set to 1.05 t / cm ² , and the pressurizing time is set to 1 second. did.

Next, a white resin film (LEXAN SD8B24, manufactured by SAVIC) having a thickness of 400 μm was prepared as the white layer 91. As the lower protective layer 92 and the upper protective layer 93, a transparent resin film (LEXAN SD8B14) having a thickness of 100 μm was prepared. And these layers were laminated in the state which accumulated the lower protective layer 92, the white layer 91, the 2nd base material 66, the 1st base material 65, and the upper protective layer 93 in order of description. At the time of lamination, the temperature was set to 200 ° C., the pressure was set to 80 N / cm ² , and the heating and pressurizing time was set to 25 minutes. Then, a part of the laminated multilayer body was cut out in a card shape.

Using a laser printer, the multilayer body was irradiated with a laser beam having a wavelength of 1064 nm. As a result, the first coloring portion 66a and the second coloring portion 66b were formed on the second base material 66. As a result, the ID card of Test Example 1 was obtained.

47 is an image of a first image that is a colored image displayed on the ID card, and FIG. 48 is an image of a second image that is a monochrome image displayed on the ID card. As FIG. 47 and FIG. 48 show, it was recognized that the ID card can display both the first image and the second image.

[Test Example 2]
Hereinafter, Test Example 2 will be described. The transfer foil of Test Example 2 is a test example corresponding to the transfer foil of the seventh embodiment described above. In Test Example 2, first, the same support layer 72 as in Test Example 1 was prepared. A release layer 73 was formed on one surface of the support layer by the same method as in Test Example 1. Then, the first layer 11 was formed on the release layer 73 and the second layer 12 was formed on the first layer 11 by the same method as in Test Example 1.

Next, the third layer ink was applied and the third layer ink was dried in the same manner as when the first layer 11 was formed using the first layer ink. And the relief surface 13Re was shape | molded by pressing the original plate for forming the relief surface 13Re to the ink for 3rd layers after drying. Various conditions at the time of molding were set to the same conditions as when the sub-wavelength grating 11G was molded.

Subsequently, the fourth layer 51 was formed on the relief surface 13Re in the same manner as when the second layer 12 was formed. In addition, the adhesive layer 71 was formed on the fourth layer 51 in the same manner as when the third layer 13 was formed in Test Example 1. Thereby, the transfer foil of Test Example 2 was obtained. In Test Example 2, an ink having the same composition as that of the first layer ink in Test Example 1 was used as the third layer ink for forming the third layer 13.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and the design and scope of the present invention are within the scope of the present invention. It is possible to include all embodiments that provide an effect equivalent to the above. Further, the scope of the present disclosure is not limited to the features of the invention defined by the claims, but also includes all the disclosed individual features, any combination of the features. .

The terms “part”, “element”, “pixel”, “segment”, “unit”, “printed body”, and “article” used in the present disclosure are physical entities. A physical entity can refer to a physical form or a spatial form surrounded by a substance. A physical entity can be a structure. The structure may have a specific function. A combination of structures having specific functions can exhibit a synergistic effect by a combination of functions of the structures.

Terms used in this disclosure and specifically the appended claims (eg, the body of the appended claims) are generally intended as “open” terms (eg, “have”). The term should be construed as “at least”, the term “including” should be construed as “including but not limited to” and the like.

Also, when interpreting terms, configurations, features, aspects, and embodiments, drawings should be referenced as necessary. Matters that can be derived directly and unambiguously from the drawings should be the basis for amendment, equivalent to the text.

Furthermore, if a specific number of introduced claims are intended to be stated, such intention is explicitly stated in the claims, and if there is no such description, such intention does not exist. For example, to assist in understanding, the following appended claims can use the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases constrains the introduction of claim descriptions by the indefinite article “a” or “an” to limit specific claims that contain such claims to embodiments that contain only one such description. Should not be construed to mean to do. The opening phrase of “one or more” or “at least one” and an indefinite article such as “a” or “an” (eg, “a” and / or “an”) are interpreted to mean at least “at least”. It should be. “One” or “one or more”). The same is true for the use of clear articles used to introduce claim statements.

Claims

An optical element comprising a first layer, a second layer in contact with the first layer, and a third layer in contact with the second layer, each layer having light transparency,
The first layer is a resin layer having a first refractive index, has a first surface in contact with the second layer, and includes a sub-wavelength grating in at least a part of the first surface;
The second layer is a dielectric layer having a second refractive index higher than the first refractive index, and has a second surface in contact with the first surface of the first layer, and the second layer The surface is an uneven shape following the sub-wavelength grating,
The third layer is a resin layer having a third refractive index lower than the second refractive index,
Any one of the first layer, the second layer, and the third layer is a relief layer, and the relief layer includes a relief surface including a plurality of reflection surfaces, and a pitch between the reflection surfaces adjacent to each other. Is larger than the pitch of the sub-wavelength grating,
When observing a state in which light is applied to the optical element from a light source located on the side opposite to the third layer with respect to the second layer,
The sub-wavelength grating displays a colored image exhibiting a color corresponding to a grating period of the sub-wavelength grating in a reflection direction including a regular reflection direction;
The relief surface displays a reflected image by monochrome reflected light in a reflection direction including a direction different from the regular reflection direction,
The optical element has a first state in which the colored image and the reflected image are not displayed, a second state in which the colored image is mainly displayed, and a third state in which the reflected image is mainly displayed.
The angle formed by the plane in which the optical element spreads and the plane including the observer's line of sight is the observation angle,
The optical element is observed in any one of the first state, the second state, and the third state according to the observation angle.
An optical element comprising a first layer, a second layer in contact with the first layer, and a third layer in contact with the second layer, each layer having light transparency,
The first layer is a resin layer having a first refractive index, has a first surface in contact with the second layer, and includes a sub-wavelength grating in at least a part of the first surface;
The second layer is a dielectric layer having a second refractive index higher than the first refractive index, and has a second surface in contact with the first surface of the first layer, and the second layer The surface is an uneven shape following the sub-wavelength grating,
The third layer is a resin layer having a third refractive index lower than the second refractive index,
The optical element further includes a relief layer including a relief surface different from the first surface and the second surface, the relief surface includes a plurality of reflection surfaces, and a pitch between the reflection surfaces adjacent to each other is Larger than the pitch of the sub-wavelength grating,
When observing a state in which light is applied to the optical element from a light source located on the side opposite to the third layer with respect to the second layer,
The sub-wavelength grating displays a colored image exhibiting a color according to the grating period of the sub-wavelength grating in the regular reflection direction,
The relief surface displays a reflected image by monochrome reflected light in a direction different from the regular reflection direction,
The optical element has a first state in which the colored image and the reflected image are not displayed, a second state in which the colored image is mainly displayed, and a third state in which the reflected image is mainly displayed.
The angle formed by the plane in which the optical element spreads and the plane including the observer's line of sight is the observation angle,
The optical element is observed in any one of the first state, the second state, and the third state according to the observation angle.
The optical element is observed in a state where the colored image is displayed at an observation angle in a first range, and is observed in a state where the reflected image is displayed at an observation angle in a second range;
The optical element according to claim 1, wherein the second range is larger than the first range.
The optical element according to any one of claims 1 to 3, wherein the colored image and the reflected image have a correlation with each other.
The optical element according to claim 4, wherein the reflected image has a shape that is located outside the colored image and that follows a contour of the colored image.
One of the colored image and the reflected image has a shape representing a predetermined symbol or a predetermined object,
The optical element according to claim 4, wherein the other of the colored image and the reflected image is a character representing the shape.
The optical element according to claim 4, wherein the colored image has a shape representing a set of objects together with the reflected image.
The second layer is the relief layer;
The optical element according to claim 1, wherein the relief surface is a surface opposite to the second surface in the second layer.
An optical element according to any one of claims 1 to 8,
A transfer foil comprising an adhesive including an adhesive layer for adhering the optical element to a transfer target.
An authentication body comprising the optical element according to any one of claims 1 to 8, wherein the optical element covers identification information.
The authentication body according to claim 10, further comprising a display layer that displays predetermined information.
The authentication body according to claim 11 is observed by tilting the authentication body back and forth by the observer in a state where the light source is positioned obliquely upward with respect to a plane including the line of sight of the observer. Authenticator verification method that verifies authenticity.