JP6909437B2 - Light modulation element - Google Patents

Description

The present invention relates to a light modulation element that reproduces an optical image by modulating the phase of incident light.

For example, as described in Patent Document 1 and Patent Document 2, a light modulation element such as a hologram, which diffracts incident light and can reproduce an original image by the diffracted light, is known. ..

Japanese Unexamined Patent Publication No. 10-228870 Japanese Unexamined Patent Publication No. 2017-37772

By the way, there are the following two methods for observing the light image reproduced by the light modulation element. One is reflection observation in which the light source is arranged on the same side as the observer with respect to the light modulation element, and the observer observes the light reflected by the light modulation element. The other is transmission observation in which the light source is arranged on the side opposite to the observer with respect to the light modulation element, and the observer observes the light transmitted through the light modulation element.

Normally, in a light modulation element, the same light image is reproduced and observed in both reflection observation and transmission observation. In this case, the reproduced image may be observed unexpectedly. For example, when the light modulation element is used by superimposing it on the reflective hologram structure, the optical image generated by the reflective hologram structure and the reproduced image generated by the light modulation element are observed overlapping. As described above, when the light modulation element and the reflective hologram structure are superposed, it is difficult to observe only the optical image generated by the reflective hologram structure. As another problem, for example, when a reproduced image generated by a light modulation element is used as hidden information for security purposes (so-called covert information), the optical image is easily observed by both reflection observation and transmission observation. There is a problem that hidden information can be found in.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a light modulation element capable of observing a reproduced image by reflection observation but not observing a reproduced image by transmission observation. Another object of the present invention is to provide a light modulation element capable of observing a reproduced image by transmission observation but not observing a reproduced image by reflection observation. Alternatively, it is an object of the present invention to provide a light modulation element capable of observing different reproduced images in reflection observation and transmission observation.

The light modulation element according to the first embodiment is
It is equipped with an element element that reproduces an optical image by modulating the phase of incident light.
The element element has an uneven surface and has an uneven surface.
The maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection of the element element is 20% or more. The maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission of the element element is 10% or less.

Alternatively, the light modulation element according to the second embodiment is
It is equipped with an element element that reproduces an optical image by modulating the phase of incident light.
The element element has a concavo-convex surface containing five or more different heights.
The maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission of the element element is 20% or more. The maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection of the element element is 10% or less.

In the light modulation device according to the first and second embodiments, the element element may be configured as a Fourier transform hologram.

Alternatively, the light modulation element according to the third embodiment is
It is provided with a first element element and a second element element that reproduce an optical image by modulating the phase of incident light.
The first element element has an uneven surface, and the second element element has an uneven surface including five or more different heights.
When the maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection of the first element element is 20% or more. The maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission for the first element element is 10%. Is below
When the maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission of the second element element is 20% or more. The maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection of the second element element is 10%. It is as follows.

In the light modulation element according to the third embodiment, the first element element and the second element element may be configured as a Fourier transform hologram.

Further, in the optical modulation element according to the third embodiment, an optical image of a primary diffracted light due to reflection or a -1st diffracted light due to reflection on the first element element and a primary diffracted light or a primary diffracted light due to transmission on the second element element. It may be different from the optical image of the -1st order diffracted light due to transmission.

Further, in the light modulation element according to the third embodiment, the first element element and the second element element may be arranged side by side on the same plane.

Alternatively, in the light modulation element according to the third embodiment, the first element element and the second element element may be arranged side by side in the thickness direction of the light modulation element.

According to the present disclosure, it is possible to provide a light modulation element capable of observing a reproduced image by reflection observation but not observing a reproduced image by transmission observation. Alternatively, according to the present disclosure, it is possible to provide a light modulation element capable of observing a reproduced image by transmission observation but not observing a reproduced image by reflection observation. Alternatively, according to the present disclosure, it is possible to provide a light modulation element capable of observing different reproduced images in reflection observation and transmission observation.

FIG. 1 is a schematic plan view showing a typical example of a light modulation element holder. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. FIG. 3 is a conceptual diagram showing a planar structure of the light modulation element. FIG. 4 is a cross-sectional view of an element element showing an outline of an example of a stepped structure of an uneven surface. FIG. 5 is a cross-sectional view of an element element showing an outline of another example of a stepped structure of an uneven surface. FIG. 6A is a diagram for explaining a case where the light modulation element according to the first embodiment is reflected and observed. FIG. 6B is a diagram for explaining a case where the light modulation element according to the first embodiment is transmitted and observed. FIG. 7A is a graph showing an example of the relationship between the wavelength distribution of the first-order diffracted light and the first-order diffracted light due to reflection and the diffraction efficiency of each element element. FIG. 7B is a graph showing an example of the relationship between the wavelength distribution of the first-order diffracted light and the first-order diffracted light due to transmission for each element element and the diffraction efficiency. FIG. 8A is a diagram for explaining a case where the light modulation element according to the second embodiment is reflected and observed. FIG. 8B is a diagram for explaining a case where the light modulation element according to the second embodiment is transmitted and observed. FIG. 9A is a graph showing an example of the relationship between the wavelength distribution of the first-order diffracted light and the first-order diffracted light due to reflection and the diffraction efficiency of each element element. FIG. 9B is a graph showing an example of the relationship between the wavelength distribution of the first-order diffracted light and the first-order diffracted light due to transmission for each element element and the diffraction efficiency. FIG. 10A is a diagram for explaining a case where the light modulation element according to the third embodiment is reflected and observed. FIG. 10B is a diagram for explaining a case where the light modulation element according to the third embodiment is transmitted and observed. FIG. 11 is a conceptual diagram showing an example of the planar structure of the light modulation element according to the third embodiment. FIG. 12A is a diagram for explaining a case where the light modulation element according to the comparative example is reflected and observed. FIG. 12B is a diagram for explaining a case where the light modulation element according to the comparative example is transmitted and observed. FIG. 13A is a graph showing an example of the relationship between the wavelength distribution of the first-order diffracted light and the first-order diffracted light due to reflection and the diffraction efficiency of each element element according to the comparative example. FIG. 13B is a graph showing an example of the relationship between the wavelength distribution of the first-order diffracted light and the first-order diffracted light due to transmission and the diffraction efficiency of each element element according to the comparative example.

Hereinafter, the light modulation element according to the embodiment of the present disclosure will be described with reference to the drawings. In the drawings attached to the present specification, the scale, aspect ratio, etc. are appropriately changed from those of the actual product and exaggerated for the convenience of illustration and comprehension.

In addition, the terms such as "parallel", "orthogonal", and "same", and the values of length and angle, etc., which specify the shape and geometric conditions and their degrees as used in the present specification, are strictly referred to. It is interpreted to include the range in which similar functions can be expected, without being bound by any meaning.

The light modulation element of each of the following embodiments includes an element element that reproduces an optical image by modulating the phase of incident light. Element The element has an uneven surface. In the illustrated example, the element element is a diffraction grating. Specifically, the element element is composed of a hologram structure, and particularly is composed of a Fourier transform hologram. The Fourier transform hologram is a hologram produced by recording the wavefront information of the Fourier transform image of the original image, and functions as a so-called Fourier transform lens. In particular, the phase-modulated Fourier transform hologram is a hologram having an uneven surface produced by multi-valued the phase information of the Fourier transform image and recording it on a medium as a depth, and is a diffraction phenomenon based on the optical path length difference of the medium. Is used to reproduce the optical image of the original image from the reproduced light. This Fourier transform hologram is advantageous in that, for example, a desired optical image (that is, an original image) can be reproduced with high accuracy, but it can be produced relatively easily. However, the element elements of the light modulation element to which the present invention can be applied are not limited to the Fourier transform hologram, and the present invention is also applied to a hologram that reproduces an optical image by another method or a light modulation element having another structure. Can be applied.

In the following description, white light containing various wavelengths is given as an example of incident light to the element element, but the incident light does not necessarily have to be white light. Further, unless otherwise specified, the specific value of the refractive index shown in the present specification is based on light having a wavelength of 589.3 nm. Further, in the following description, the refractive index and the characteristic value of the uneven surface shown with respect to the element element are derived assuming that the element element is used in an air environment having a refractive index of 1.0 unless otherwise specified. Value.

Further, as a method of observing the diffracted light diffracted by the element element, for example, as shown in FIG. 12A, the observer and the light source are arranged on the same side with respect to the element element, and the diffracted light due to the reflection of the element element is observed. There are two types of reflection observation: as shown in FIG. 12B, the observer and the light source are arranged on different sides of each other via the element element, and the diffracted light due to the transmission of the element element is observed. In the following description, unless otherwise specified, the angle of incidence of the incident light on the element element is 0 ° (that is, the angle along the normal direction of the incident surface of the element element) in both the reflection observation and the transmission observation. Is assumed.

Further, in the present specification, the concept of "two or more optical images having the same shape" includes not only two or more optical images having the same size and the same shape (overall shape), but also light. Two or more optical images in which the reproduced sizes are slightly different from each other due to the different constituent wavelengths of the images are also included.

[First Embodiment]
FIG. 1 is a schematic plan view showing a typical example of the light modulation element holder 10. FIG. 2 is a cross-sectional view taken along the line II-II of FIG.

The light modulation element holder 10 shown in FIGS. 1 and 2 is formed on the hologram layer 1, the transparent reflective layer 2 laminated on one surface of the hologram layer 1, and the other surface of the hologram layer 1. It includes a laminated transparent base material 4. A light modulation element 11 configured as a hologram structure is provided in a part of the light modulation element holder 10. In the light modulation element 11, one surface of the hologram layer 1 forms an uneven surface 1a, and the reflection layer 2 covering the uneven surface 1a also has an uneven shape. The uneven surface 1a of the light modulation element 11 has an uneven pattern corresponding to the Fourier transformed image of the original image, and has a corresponding uneven depth for each pixel of the Fourier transformed image. For example, a resin (for example, a UV curable resin or a thermoplastic resin) constituting the hologram layer 1 is formed on a transparent base material 4 (for example, PET: polyethylene terephthalate) by coating or the like, and the hologram layer 1 is UV-cured. Along with the treatment and thermal pressure treatment, the uneven surface shaping process of pressing the uneven surface of the original plate is performed, and then the reflective layer 2 (for example, ZnS, TiO ₂ or the like) is formed on the uneven surface 1a of the hologram layer 1. The optical modulation element holder 10 shown in FIGS. 1 and 2 can be manufactured. Although not shown, other members such as an adhesive, an adhesive, and / or a heat seal layer may be further formed on the reflective layer 2.

When light is incident on such a light modulation element 11 from a point light source or a parallel light source, an optical image (that is, an original image) corresponding to the uneven pattern of the uneven surface 1a is reproduced. This type of light modulation element does not require a screen or the like for projecting an optical image, and reproduces an optical image particularly well when light from a specific light source such as a point light source or a parallel light source is incident. , Convenient and widely available for design, security, or other uses. The optical image reproducible by such a light modulation element is not particularly limited, and for example, characters, symbols, line drawings, patterns, patterns, combinations thereof, and the like can be used as an original image and a reproducible optical image.

FIG. 3 is a conceptual diagram showing a planar structure of the light modulation element 11. The light modulation element 11 of the present embodiment includes a plurality of element elements (also referred to as “hologram cells”) 21 arranged two-dimensionally and regularly. Each element element 21 has the above-mentioned uneven surface 1a and has a plane size of several nm to several mm square (for example, 2 mm square), and modulates the phase of incident light to reproduce an optical image.

The uneven surface 1a has a multi-step shape (that is, a step shape of two or more steps), and the number of steps of the uneven surface 1a is not particularly limited. When reproducing an optical image with a plurality of colors, the uneven surface 1a preferably has three or more steps, and in particular, the uneven surface 1a having four or more steps makes an original image having a complicated composition high-definition. It is possible to reproduce. 4 and 5 are cross-sectional views of the element element 21 showing an outline of the step structure of the uneven surface 1a, FIG. 4 shows an 8-step type uneven surface 1a, and FIG. 5 shows a 4-step type uneven surface 1a. show. Note that FIGS. 4 and 5 show element elements 21 having uneven surfaces 1a having the same step shape, but the actual uneven surface 1a is a step corresponding to the reproduced light image (that is, the original image). Has a shape. The pitch of the uneven pattern on the uneven surface 1a (that is, the pixel pitch (see the sign “P” shown in FIGS. 4 and 5)) is in the range of 0.1 μm to 80.0 μm from the viewpoint of accurately reproducing the optical image. It is preferably present, and usually 1 μm or more is preferable.

By the way, in general, in a light modulation element that reproduces an optical image by modulating the phase of incident light, the optical image is reproduced in both reflection observation and transmission observation. The reproduced light image corresponds to the uneven pattern of the light modulation element, and as shown in FIGS. 12A and 12B, the same light image is observed in both reflection observation and transmission observation. However, as shown in FIGS. 6A and 6B, the light modulation element according to the first embodiment is devised so that the light image is observed in the reflection observation but not in the transmission observation. ing.

Hereinafter, the structure of the element element 21 will be described in more detail.

6A and 6B are diagrams for explaining a case where the light modulation element of the first embodiment is observed by reflection and a case where the light modulation element is observed through transmission, respectively. In FIGS. 6A and 6B, the sign "51" indicates a light source. Further, in FIG. 6A, the reference numeral “100a” indicates an optical image to be reproduced by the light modulation element. 7A and 7B are graphs showing the diffraction efficiency characteristics of each element element constituting the light modulation element shown in FIGS. 6A and 6B.

First, among the lights diffracted by the element element 21, the first-order diffracted light and the first-order diffracted light mainly contribute to the reproduction of the intended light image 100a. The second-order or higher-order diffracted light in the element element 21 does not contribute to the clear reproduction of the optical image 100a. Further, a part of the incident light incident on the element element 21 passes through the element element 21 without being diffracted by the element element 21 and becomes the 0th order light, but the 0th order light only generates an optical image of a point. Therefore, it does not contribute to the reproduction of the optical image 100a.

The element element 21 of the first embodiment is designed such that a light image is observed in reflection observation, but no light image is observed in transmission observation. Since each element element 21 has such a diffraction characteristic, the light modulation element 11 composed of the element element 21 observes a light image 100a in reflection observation, but does not observe a light image 100a in transmission observation. , Can be provided. As shown in FIG. 6A, each element element 21 reproduces an optical image 100a of a star figure in the entire plurality of element elements 21 shown in FIG. 3 by diffracted light due to reflection of each element element 21. There is.

Specifically, each element element 21 has the following diffraction efficiency characteristics. That is, each element element 21 has a maximum wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection for each element element 21. It is designed so that the diffraction efficiency is 20% or more. Further, each element element 21 has a maximum wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission for each element element 21. It is designed so that the diffraction efficiency is 10% or less.

The element element 21 having such a diffraction efficiency characteristic is realized, for example, by designing the optical path length difference of the reflected light in each element element 21 to be 45 nm per step.

With reference to FIGS. 7A and 7B, the primary diffracted light by reflection and transmission and -1 next time for the element element 21 designed so that the optical path length difference of the reflected light in the element element 21 is 45 nm per step. The relationship between the wavelength distribution of the folding light and the diffraction efficiency will be described.

FIG. 7A is a graph showing the relationship between the wavelength distribution of the first-order diffracted light and the first-order diffracted light due to the reflection of the element element 21 and the diffraction efficiency. Further, FIG. 7B is a graph showing the relationship between the wavelength distribution of the first-order diffracted light and the first-order diffracted light due to transmission of the element element 21 and the diffraction efficiency. In FIGS. 7A and 7B, the horizontal axis indicates the wavelength [unit: nm], and the vertical axis indicates the diffraction efficiency [unit:%]. Diffraction efficiency is expressed by the amount obtained by dividing the radiant flux of light diffracted in a certain direction [unit: μW or μJ / cm ² ] by the radiant flux of light incident on the element element 21, and the diffraction radiant flux in a certain direction is expressed. When represented by P and the incident radiant flux is represented by P0, the diffraction efficiency η is a dimensionless number represented by “η = P / P0”.

In the example shown in FIGS. 7A and 7B, the element element 21 is made of a material having a refractive index n of 1.5, and the concave-convex surface 1a has eight steps, and the concave-convex surface 1a has one step. The step d is 15 nm. The optical path length difference of the reflected light in the element element 21 configured in this way is 45 nm per step.

As can be understood from FIG. 7A, the maximum in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection for the element element 21. Diffraction efficiency is 20% or more. On the other hand, as can be understood from FIG. 7B, in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission for the element element 21. The maximum diffraction efficiency of is 10% or less.

Specifically, as can be understood from FIG. 7A, the primary diffracted light reflected by the element element 21 is diffracted with sufficient diffraction efficiency to reproduce the optical image 100a in the wavelength band of 380 nm or more and 780 nm or less. Will be done. On the other hand, as can be understood from FIG. 7B, the first-order diffracted light and the first-order diffracted light transmitted through the element element 21 are both sufficient to reproduce the optical image 100a in the wavelength band of 380 nm or more and 780 nm or less. It is not diffracted with diffraction efficiency. This means that when the light modulation element 11 is reflected and observed, the light image 100a can be observed, but when the light modulation element 11 is transmitted and observed, the light image 100a cannot be observed. ..

The element element 21 that satisfies the above-mentioned diffraction efficiency characteristics is not limited to the element element 21 designed so that the optical path length difference of the reflected light in the element element 21 is 45 nm per step. For example, the above condition can be satisfied by the element element 21 designed so that the optical path length difference of the reflected light in the element element 21 is 15 nm per step. Therefore, for example, even when the element element 21 is made of a material having a refractive index n of 1.5, the number of steps of the uneven surface 1a is eight, and the step d per step is 5 nm, the element is an element. The element 21 can have the above-mentioned diffraction efficiency characteristics.

Further, it is preferable that the element element 21 is designed to have a concavo-convex surface 1a including five or more different heights. Here, according to the knowledge obtained by the present inventors, when the uneven surface 1a includes different heights of 5 steps or more, it is easy to obtain the element element 21 satisfying the above-mentioned diffraction efficiency characteristics.

Next, an example of a method for manufacturing the light modulation element 11 (particularly the uneven surface 1a) will be described. The method described below is only an example, and it is possible to adopt another method capable of appropriately manufacturing the light modulation element 11 including the desired uneven surface 1a.

First, a two-dimensional image of the original image is read by a computer (Step 1). Then, the computer obtains a two-dimensional complex amplitude image by using each pixel value of the read two-dimensional image as an amplitude value and assigning a random value between 0 and 2π as a phase value for each pixel (). Step2). Then, the computer obtains a two-dimensional Fourier transform image by performing a two-dimensional Fourier transform of the two-dimensional complex amplitude image (Step 3). If necessary, the computer may perform arbitrary optimization processing such as an iterative Fourier transform method or a genetic algorithm (Step 4). Then, the computer sets the phase value of each pixel of the two-dimensional Fourier transform image in four stages (for example, "0", "π / 2", "π" and "3π / 2", or "0", " It is discreteized into 8 stages of "π / 4", "π / 2", "3π / 4", "π", "5π / 4", "3π / 2" and "7π / 4" (Step 5).

Then, the light modulation element 11 (particularly the uneven surface 1a) corresponding to the two-dimensional Fourier transformed image is manufactured so that each pixel has a depth corresponding to the discretized corresponding phase value (Step 6). For example, when the pixel values of the two-dimensional Fourier transformed image are discretized in four steps in Step 5, a concave-convex surface 1a (see FIG. 5) having a depth of four steps is formed in the hologram layer 1 in Step 6. NS. The depth of the uneven surface 1a is determined by considering not only the diffraction efficiency characteristics to be realized but also various other related parameters (for example, the refractive index of the material constituting the light modulation element 11 (particularly the hologram layer 1)). Is determined by. The light image is observed only in the light modulation element 11 (particularly the uneven surface 1a) in which the light image is observed only in the reflection observation shown in FIGS. 6A and 6B, and in the transmission observation shown in FIGS. 8A and 8B described later. The light modulation element 111 (particularly the uneven surface 101a) can be manufactured by the same method, but each has a unique depth structure of the uneven surfaces 1a and 101a, and for example, the same diffraction characteristics can be realized. Even in the case of It is different from the light modulation element 111.

The manufacturing apparatus of the light modulation element 11 is not particularly limited, and may be, for example, an apparatus controlled by a computer that executes Steps 1 to 5 described above, or an apparatus provided separately from the computer. .. Further, if necessary, a master mold (that is, a master master plate) corresponding to the structure of the above-mentioned light modulation element 11 (particularly the uneven surface 1a) may be made by an exposure apparatus based on a photolithography technique, an electron beam drawing apparatus, or the like. (Step 7). For example, a liquid ultraviolet curable resin is dropped on a mother mold, and the ultraviolet curable resin sandwiched between a base film (for example, PET film (polyethylene terephthalate film)) and the mother mold is irradiated with ultraviolet rays. The photomodulating element 11 having a desired uneven surface 1a can be produced by peeling the ultraviolet curable resin together with the base film from the base film. As another method, for example, a method using a thermoplastic ultraviolet curable resin, a method using a thermoplastic resin, a method using a thermosetting resin, and a method using an ionizing radiation curable resin may be adopted. By using the master mold in this way, it is possible to easily and in large quantities to duplicate the light modulation element 11 having the desired uneven surface 1a.

_{A transparent reflective layer 2 (for example, a reflective layer composed of ZnS and TiO 2} ) is further formed by the manufacturing apparatus on the uneven surface 1a of the light modulation element 11 obtained as described above. However, in the case of the light modulation element 11 that reflects the reproduced light by utilizing the difference in the refractive index between the hologram layer 1 and the air, the uneven surface of the hologram layer 1 is not provided additionally. You may leave 1a exposed to the air. Further, if necessary, another functional layer such as an adhesive layer (for example, a heat seal layer or a primer layer for enhancing the adhesion between adjacent layers) may be formed on the hologram layer 1. Further, for example, when the reflective layer 2 is formed on the uneven surface 1a of the hologram layer 1, an adhesive layer is formed on the surface of the reflective layer 2 having an uneven shape (the surface opposite to the hologram layer 1), and the adhesive layer is formed. The layer may fill the recesses on the surface of the reflective layer 2.

According to the first embodiment as described above, the light modulation element 11 includes an element element 21 that reproduces an optical image 100a by modulating the phase of incident light. The element element 21 has an uneven surface 1a. The maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the -1st diffracted light due to reflection of the element element 21 is 20% or more. be. Further, the maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the -1st order diffracted light due to transmission of the element element 21 is 10% or less. be.

According to such a light modulation element 11, the first-order diffracted light and / or the first-order diffracted light reflected by the constituent element elements 21 reproduces the optical image 100a in the wavelength band of 380 nm or more and 780 nm or less. It is diffracted with sufficient diffraction efficiency. Therefore, when the light modulation element 11 is reflected and observed, the light image 100a can be observed. On the other hand, neither the first-order diffracted light or the -1st-order diffracted light transmitted through the element element 21 is diffracted with sufficient diffraction efficiency to reproduce the optical image 100a in the wavelength band of 380 nm or more and 780 nm or less. Therefore, when the light modulation element 11 is observed through transmission, the light image 100a cannot be observed.

Further, in the light modulation element 11 of the present embodiment, each element element 21 is configured as a Fourier transform hologram. Thereby, the element element 21 capable of accurately reproducing the desired optical image (that is, the original image) can be produced relatively easily.

[Second Embodiment]
Next, the second embodiment will be described with reference to FIGS. 8A to 9B. As shown in FIGS. 8A and 8B, the light modulation element 111 according to the second embodiment is devised so that the light image 100b is observed in the transmission observation, but the light image 100b is not observed in the reflection observation. It has been done.

In the following description and the drawings used in the following description, the same reference numerals as those used for the corresponding parts in the above-mentioned first embodiment are used for the parts that can be configured in the same manner as in the above-mentioned first embodiment. It will be used, and duplicate description will be omitted.

8A and 8B are diagrams for explaining a case where the light modulation element of the second embodiment is observed by reflection and a case where the light modulation element is observed through transmission, respectively. In FIG. 8B, reference numeral "100b" indicates an optical image to be reproduced by the light modulation element. 9A and 9B are graphs showing the diffraction efficiency characteristics of each element element constituting the light modulation element shown in FIGS. 8A and 8B.

Similar to the cases shown in FIGS. 6A to 7B, among the lights diffracted by the element element 121, the first-order diffracted light and the -1st-order diffracted light mainly contribute to the reproduction of the intended light image 100b. The second-order or higher-order diffracted light in the element element 121 does not contribute to the clear reproduction of the optical image 100b. Further, a part of the incident light incident on the element element 121 passes through the element element 121 without being diffracted by the element element 121 and becomes the 0th order light, but the 0th order light only generates an optical image of a point. Therefore, it does not contribute to the reproduction of the optical image 100b.

Hereinafter, the structure of the element element 121 will be described in more detail.

Each element element 121 of the second embodiment is designed such that a light image is not observed in reflection observation, but a clear light image is observed in transmission observation. Since each element element 121 has such a diffraction efficiency characteristic, the light modulation element 111 composed of the element element 121 observes an optical image 100b in transmission observation, but observes an optical image 100b in reflection observation. It can have the characteristic that it is not done. As shown in FIG. 8B, each element element 121 reproduces an optical image 100b of a figure of the character "OK" in the entire plurality of element elements 121 shown in FIG. 3 by diffracted light transmitted from each element element 121. It has become like.

Specifically, the element element 121 has the following diffraction efficiency characteristics. That is, the element element 121 has a maximum diffraction efficiency in a wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission of the element element 121. Is designed to be 20% or more. Further, the element element 121 has a maximum diffraction efficiency in a wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection of the element element 121. Is designed to be 10% or less. Further, the element element 121 is designed to have an uneven surface 101a including five or more different heights. Here, according to the knowledge obtained by the present inventors, when the uneven surface 101a includes different heights of 5 steps or more, it is easy to obtain the element element 121 satisfying the above-mentioned diffraction efficiency characteristics.

The element element 121 having such a diffraction efficiency characteristic is realized, for example, by designing the optical path length difference of the transmitted light in the element element 121 to be 35 nm per step.

With reference to FIGS. 9A and 9B, the primary diffracted light by reflection and transmission and -1 next time for the element element 121 designed so that the optical path length difference of the transmitted light in the element element 121 is 35 nm per step. The relationship between the wavelength distribution of the folding light and the diffraction efficiency will be described.

FIG. 9A is a graph showing the relationship between the wavelength distribution of the first-order diffracted light and the first-order diffracted light due to reflection and the diffraction efficiency of each element element 121. Further, FIG. 9B is a graph showing the relationship between the wavelength distribution of the first-order diffracted light and the first-order diffracted light due to transmission and the diffraction efficiency of each element element 121. In FIGS. 9A and 9B, the horizontal axis indicates the wavelength [unit: nm], and the vertical axis indicates the diffraction efficiency [unit:%].

In the example shown in FIGS. 9A and 9B, the element element 121 is made of a material having a refractive index n of 1.5, and the concave-convex surface 101a has eight steps, and the concave-convex surface 101a has one step. The step d is 70 nm. The optical path length difference of the transmitted light in the element element 121 configured in this way is 35 nm per step when used in an air environment having a refractive index of 1.0.

As can be understood from FIG. 9B, the maximum in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission for the element element 121. Diffraction efficiency is 20% or more. On the other hand, as can be understood from FIG. 9A, in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection of the element element 121. The maximum diffraction efficiency of is 10% or less.

Specifically, as can be understood from FIG. 9B, the primary diffracted light transmitted through the element element 121 is diffracted with sufficient diffraction efficiency to reproduce the optical image 100b in the wavelength band of 380 nm or more and 780 nm or less. Will be done. On the other hand, as can be understood from FIG. 9A, both the first-order diffracted light and the first-order diffracted light reflected by the element element 121 are sufficient to reproduce the optical image 100b in the wavelength band of 380 nm or more and 780 nm or less. It is not diffracted with good diffraction efficiency. This means that the light image 100b can be observed when the light modulation element 111 is transmitted and observed, but the light image 100b cannot be observed when the light modulation element 11 is reflected and observed. ..

The element element 121 that satisfies the above-mentioned diffraction efficiency characteristics is not limited to the element element 121 designed so that the optical path length difference of the transmitted light in the element element 121 is 35 nm per step. For example, the above condition can be satisfied by the element element 121 designed so that the optical path length difference of the reflected light in the element element 121 is 70 nm per step. Therefore, for example, when the element element 121 is used in an air environment having a refractive index of 1.0, the element element 121 is made of a material having a refractive index n of 1.5, and the number of stages of the uneven surface 101a is eight. Even when the step d per step is 140 nm, the element element 121 can have the above-mentioned diffraction efficiency characteristics.

As a matter of course, when the light modulation element 111 is used in an environment other than the air environment, or when the concave portion of the uneven surface 101a of the light modulation element 111 is filled with an adhesive layer or the like, the light modulation element 111 is in the environment. Considering the refractive index of the medium and the refractive index of the material constituting the adhesive layer, etc., the refractive index of the material constituting the light modulation element 111 (element element 121), the number of steps of the uneven surface 101a, and 1 of the uneven surface 101a The step d per step should be determined.

As described above, the light modulation element 111 of the present embodiment includes the element element 121 that reproduces the light image 100b by modulating the phase of the incident light. The element element 121 has an uneven surface 101a including five or more different heights. The maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the -1st order diffracted light due to transmission of the element element 121 is 20% or more. be. Further, the maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the -1st order diffracted light due to reflection of the element element 121 is 10% or less. be.

According to such a light modulation element 111, the first-order diffracted light and / or the first-order diffracted light transmitted through the constituent element elements 121 can reproduce the optical image 100b in the wavelength band of 380 nm or more and 780 nm or less. It is diffracted with sufficient diffraction efficiency. Therefore, when the light modulation element 111 is transmitted and observed, the light image 100b can be observed. On the other hand, neither the primary diffracted light due to the reflection of the element element 121 nor the -1st diffracted light is diffracted with sufficient diffraction efficiency to reproduce the optical image 100b in the wavelength band of 380 nm or more and 780 nm or less. Therefore, when the light modulation element 11 is reflected and observed, the light image 100b cannot be observed.

[Third Embodiment]
Next, a third embodiment will be described with reference to FIGS. 10A to 11. In the light modulation element according to the third embodiment, as shown in FIGS. 10A and 10B, an optical image is observed in both reflection observation and transmission observation, but the light image observed in reflection observation and transmission observation are observed. Ingenuity has been made to make it different from the optical image.

The following description and the drawings used in the following description correspond to the above-mentioned first embodiment or second embodiment with respect to a portion that can be configured in the same manner as the above-mentioned first embodiment or second embodiment. The same code as that used for the part will be used, and duplicate description will be omitted.

10A and 10B are diagrams for explaining a case where the light modulation element of the third embodiment is observed by reflection and a case where the light modulation element is observed through transmission, respectively. Further, FIG. 11 is a diagram showing the configuration of the light modulation element shown in FIGS. 10A and 10B.

Hereinafter, the structure of the light modulation element according to the third embodiment will be described in more detail.

As described above, in the light modulation element 211 of the third embodiment, an optical image is observed in both reflection observation and transmission observation, but the light image 100a observed in reflection observation and the light image 100b observed in transmission observation are observed. Is designed to be different (see FIGS. 10A and 10B).

As shown in FIG. 11, the light modulation element 211 includes a first element element 21 and a second element element 121 that reproduce an optical image by modulating the phase of incident light. The first element element 21 is configured in the same manner as the element elements shown in FIGS. 6A to 7B, and the second element element 121 is configured in the same manner as the element elements shown in FIGS. 8A to 9B. In the example shown in FIG. 11, a plurality of first element elements 21 and a plurality of second element elements 121 are arranged side by side in a checkered pattern on the same plane.

More specifically, each first element element 21 has an uneven surface 1a. Each first element element 21 has a wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection for each first element element 21. The maximum diffraction efficiency of is 20% or more, and is 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission for each first element element 21. It is designed so that the maximum diffraction efficiency in the wavelength band is 10% or less. Then, each first element element 21 reproduces the optical image 100a of the star figure in the entire plurality of first element elements 21 shown in FIG. 11 by the diffracted light due to the reflection of each first element element 21. ing.

Further, each second element element 121 has an uneven surface 101a including five or more different heights. Each second element element 121 has a wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission for each second element element 121. The maximum diffraction efficiency of is 20% or more, and is 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection for each second element element 121. It is designed so that the maximum diffraction efficiency in the wavelength band is 10% or less. Then, each of the second element elements 121 reproduces the optical image 100b of the figure of the character "OK" in the entire plurality of the second element elements 121 shown in FIG. 11 by the diffracted light transmitted by each of the second element elements 121. It is designed to do.

By providing the light modulation element 211 with the first element element 21 and the second element element 121 as described above, it is possible to realize the light modulation element 211 in which different optical images 100a and 100b are observed in the reflection observation and the transmission observation. Can be done.

In the light modulation element 211 shown in FIG. 11 above, the first element element 21 and the second element element 121 are arranged side by side in a checkered pattern on the same plane, but the first element element 21 and the second element element The arrangement mode of 121 is not particularly limited. For example, the light modulation element 11 may include a first element element 21 and a second element element 121 arranged in a striped pattern on the same plane. Further, the first element element 21 and the second element element 121 may be arranged side by side in the thickness direction of the light modulation element 211.

As described above, the light modulation element 211 of the third embodiment includes the first element element 21 and the second element element 121 that reproduce the optical images 100a and 100b by modulating the phase of the incident light. The first element element 21 has an uneven surface 1a, and the second element element 121 has an uneven surface 101a including five or more different heights. When the maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection of the first element element 21 is 20% or more. The maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission for the first element element 21 is 10%. It is as follows. Further, the maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission of the second element element 121 is 20%. As described above, the maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection of the second element element 121 is as described above. It is 10% or less.

According to such a light modulation element 211, the first-order diffracted light and / or the first-order diffracted light reflected by the first element element 21 reproduces the optical image 100a in the wavelength band of 380 nm or more and 780 nm or less. It is diffracted with sufficient diffraction efficiency. On the other hand, neither the primary diffracted light due to the reflection of the second element element 121 nor the -1st diffracted light is diffracted with sufficient diffraction efficiency to reproduce the optical image 100b in the wavelength band of 380 nm or more and 780 nm or less. Therefore, when the light modulation element 211 is reflected and observed, only the light image 100a can be observed.

Further, the first-order diffracted light and / or the first-order diffracted light transmitted through the second element element 121 is diffracted with sufficient diffraction efficiency to reproduce the optical image 100b in the wavelength band of 380 nm or more and 780 nm or less. On the other hand, neither the first-order diffracted light or the -1st-order diffracted light transmitted through the first element element 21 is diffracted with sufficient diffraction efficiency to reproduce the optical image 100a in the wavelength band of 380 nm or more and 780 nm or less. Therefore, when the light modulation element 211 is observed through transmission, only the optical image 100b can be observed.

[Use]
The usage patterns and uses of the above-mentioned light modulation elements 11, 111, 211 and the light modulation element holder 10 are not particularly limited, and can be used for entertainment and design purposes such as reproducing a character image. Further, in security applications, for example, the light modulation elements 11, 111, 211 can be applied to the following objects. When the light modulation element holder 10 is used as an information recording medium, various information such as passports, ID certificates, banknotes, credit cards, cash vouchers, gift certificates, other tickets, official documents, personal information and confidential information can be stored. The light modulation element according to the present invention can be applied to other recorded media, other media having monetary value, and the like, and counterfeiting of these can be prevented. The ID card referred to here includes, for example, a national ID card, a license, a membership card, an employee ID card, a student ID card, and the like. In the light modulation element holder 10, the base material (see the symbol “4” in FIG. 2) that holds the light modulation elements 11, 111, 211 can be configured by, for example, paper, resin, metal, synthetic fiber, or a combination thereof. Is.

Further, the light modulation element according to the present invention can be applied to the above-mentioned light modulation element holder 10 by any method. The light modulation element according to the present invention can be held by an arbitrary object (that is, the light modulation element holder 10) by using a technique such as sticking, sandwiching, or embedding. Therefore, the light modulation elements 11, 111, 211 may be formed by using a part of the members constituting the light modulation element holder 10, or the light modulation elements 11, 111 may be formed with respect to the light modulation element holder 10. , 211 may be additionally provided.

Further, the above-mentioned light modulation elements 11, 111, 211 may be used alone for various purposes, or may be used together with other functional layers such as a printing layer and used for various purposes.

[Constituent material of hologram layer]
The material constituting the hologram layer 1 is not particularly limited, but as described above, the hologram layer 1 can be composed of various resins. Specific examples of various resins are listed below.

Examples of the thermosetting resin constituting the hologram layer 1 include polycarbonate (PC), polyethylene terephthalate (PET), glycol-modified polyethylene terephthalate (PET-G), polyvinyl chloride (PVC), unsaturated polyester resin, and acrylic-modified. Examples thereof include urethane resin, epoxy-modified acrylic resin, epoxy-modified unsaturated polyester resin, alkyd resin, and phenol resin. Examples of the thermoplastic resin constituting the hologram layer 1 include acrylic acid ester resin, acrylamide resin, nitrocellulose resin, and polystyrene resin. These resins may be homopolymers or copolymers composed of two or more kinds of constituent components. Further, these resins may be used alone or in combination of two or more.

The thermosetting resin or thermoplastic resin described above includes various isocyanate compounds, metal soaps such as cobalt naphthenate and zinc naphthenate, organic peroxides such as benzoyl peroxide and methyl ethyl ketone peroxide, benzophenone, acetophenone, anthraquinone and naphthoquinone. It may contain a thermosetting agent such as azobisisobutyronitrile or diphenylsulfide.

Examples of the ionizing radiation curable resin constituting the hologram layer 1 include epoxy-modified acrylate resin, urethane-modified acrylate resin, and acrylic-modified polyester resin. Among them, urethane-modified acrylate resin is preferable, and Japanese Patent Application Laid-Open No. 2007-017643 is particularly preferable. A urethane-modified acrylic resin represented by the chemical formula shown in the publication is preferable.

When the ionizing radiation curable resin is cured, a monofunctional or polyfunctional monomer, oligomer or the like can be used in combination for the purpose of adjusting the crosslinked structure and viscosity. Examples of the monofunctional monomer include mono (meth) acrylates such as tetrahydrofurfuryl (meth) acrylate, hydroxyethyl (meth) acrylate, vinylpyrrolidone, (meth) acryloyloxyethyl succinate, and (meth) acryloyloxyethyl phthalate. And so on. The bifunctional or higher functional monomers are classified by skeletal structure and are classified into polyol (meth) acrylate (for example, epoxy-modified polyol (meth) acrylate, lactone-modified polyol (meth) acrylate, etc.), polyester (meth) acrylate, and epoxy (meth). ) Acrylate, urethane (meth) acrylate, other polybutadiene-based, isocyanuric acid-based, hydantin-based, melamine-based, phosphoric acid-based, imide-based, phosphazene-based poly (meth) acrylate and the like. In addition, various monomers, oligomers and polymers that are UV and electron beam curable are available.

More specifically, examples of the bifunctional monomer and oligomer include polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and 1,6-hexanediol di (meth). Examples include acrylate. Examples of the trifunctional monomer, oligomer, and polymer include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, and aliphatic tri (meth) acrylate. Examples of the tetrafunctional monomer and oligomer include pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, and aliphatic tetra (meth) acrylate. Examples of the pentafunctional or higher functional monomers and oligomers include dipentaerythritol penta (meth) acrylate and dipentaerythritol hexa (meth) acrylate. Moreover, (meth) acrylate having a polyester skeleton, urethane skeleton, phosphazene skeleton and the like can be mentioned. The number of functional groups is not particularly limited, but if the number of functional groups is smaller than 3, the heat resistance tends to decrease, and if it exceeds 20, the flexibility tends to decrease, so that the number of functional groups is particularly high. Those in the range of 3 to 20 are preferable.

The content of the monofunctional or polyfunctional monomer or oligomer as described above can be adjusted as appropriate, but it is usually preferably 50 parts by weight or less with respect to 100 parts by weight of the ionizing radiation curable resin, and 0.5 weight by weight in particular. It is preferably in the range of parts to 20 parts by weight.

Further, the hologram layer 1 is provided with a photopolymerization initiator, a polymerization inhibitor, a deterioration inhibitor, a plasticizer, a lubricant, a colorant such as a dye or a pigment, a surfactant, a defoaming agent, a leveling agent, and a leveling agent, if necessary. Additives such as a thixotropic property-imparting agent may be added as appropriate.

When the hologram layer 1 has self-supporting property, the film thickness of the hologram layer 1 is preferably in the range of 0.05 mm to 5 mm, and more preferably in the range of 0.1 mm to 3 mm. On the other hand, when the hologram layer 1 is formed on a transparent substrate without having self-supporting property, the film thickness of the hologram layer 1 is preferably in the range of 0.1 μm to 50 μm, particularly in the range of 2 μm to 20 μm. Is preferable. Further, the size of the hologram layer 1 (for example, the size in a plan view) can be appropriately set according to the use of the light modulation elements 11, 111, 211.

[Other variants]
The light modulation elements 11 and 111 used in each of the above-described embodiments are composed of a plurality of element elements 21 and 121 as shown in FIG. 3, but the light modulation elements 11 and 111 are formed by a single element element 21 and 121. 111 may be configured. Further, the light modulation element 211 used in the third embodiment is composed of a plurality of first element elements 21 and a plurality of second element elements 121 as shown in FIG. 11, but is a single first element. The light modulation element 211 may be composed of the element 21 and a single second element element 121.

Further, the plan view size and the plan view shape of the element elements 21 and 121 are not particularly limited, and the element elements 21 and 121 may have any size and shape. For example, the plan view shape of each element element 21, 121 can be changed to a quadrangle such as a square, a rectangle, or a trapezoid, another polygonal shape (for example, a triangle, a pentagon, a hexagon, etc.), a perfect circle, an ellipse, another circular shape, or a star shape. Alternatively, it may have a heart shape or the like, and the optical modulation elements 11, 111, 211 may have two or more types of element elements 21, 121 having a plan view shape.

Further, an arbitrary functional layer may be added to the light modulation elements 11, 111, 211, and the light modulation elements 11, 111, 211 may be covered with, for example, a transparent thin-film deposition layer. In particular, by providing a transparent vapor deposition layer having no gloss, it is possible to prevent the light modulation elements 11, 111, 211 from having gloss and conceal the light modulation elements 11, 111, 211. From the viewpoint of concealing the light modulation elements 11, 111, 211, the total light transmittance of such a transparent vapor-deposited layer is preferably 80% or more, and more preferably 90% or more. Further, by covering the light modulation elements 11, 111, 211 with a reflective thin-film layer, a transparent reflective layer can be formed. Examples of the constituent material of the reflective thin-film deposition layer include ZnS and TiO ₂ . These materials may be used alone to form a thin-film deposition layer, or two or more materials may be combined to form a thin-film deposition layer.

The thickness of the thin-film deposition layer provided on the hologram layer 1 (particularly on the uneven surfaces 1a and 101a) can be appropriately set from the viewpoint of desired reflectivity, color tone, design, application, etc., and is, for example, in the range of 50 Å to 1 μm. It is preferably in the range of 100 Å to 1000 Å. In particular, when the transparency of the thin-film deposition layer is prioritized, the thickness of the vapor-deposited layer is preferably 200 Å or less, while when the concealment of the thin-film deposition layer is prioritized, the thickness of the thin-film deposition layer exceeds 200 Å. Is preferable. Further, as a method for forming the thin-film deposition layer, a general method for forming the thin-film deposition layer can be adopted, and examples thereof include a vacuum deposition method, a sputtering method, and an ion plating method.

[Comparison example]
Next, a comparative example of the above-described embodiment will be described with reference to FIGS. 12A to 13B.

12A and 12B are diagrams showing the light modulation elements of this comparative example. 13A and 13B are graphs showing the diffraction efficiency characteristics of the element elements constituting the light modulation element of this comparative example.

The light modulation element 311 shown in FIGS. 12A and 12B is a conventional light modulation element, and the same light image 100c can be observed in both reflection observation and transmission observation. In the examples shown in FIGS. 13A and 13B, the element element 321 constituting the light modulation element 311 is made of a material having a refractive index n of 1.5, and the uneven surface 301a has four steps, and the uneven surface 301a has four steps. The step d per step of the surface 301a is 150 nm. The optical path length difference of the reflected light of the element element 321 configured in this way is 450 nm per step. Further, the optical path length difference of the transmitted light of the element element 321 configured in this way is 75 nm per step when used in an air environment having a refractive index of 1.0.

As can be understood from FIG. 13A, the maximum in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection for the element element 321. Diffraction efficiency is 20% or more. Further, as can be understood from FIG. 13B, in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission for the element element 321. The maximum diffraction efficiency of is 20% or more.

Specifically, as can be understood from FIG. 13A, both the first-order diffracted light and the first-order diffracted light reflected by the element element 321 reproduce the optical image 100c in the wavelength band of 380 nm or more and 780 nm or less. It is diffracted with sufficient diffraction efficiency. On the other hand, as can be understood from FIG. 13B, the primary diffracted light transmitted through the element element 121 is diffracted with sufficient diffraction efficiency to reproduce the optical image 100c in the wavelength band of 380 nm or more and 780 nm or less. This means that the light image 100c can be observed regardless of whether the light modulation element 311 is reflected or transmitted.

Then, as shown in FIGS. 12A and 12B, the light image observed when the light modulation element 311 is reflected and observed and the light image observed when the light modulation element 311 is transmitted and observed are the same light image. It is 100c.

The present invention is not limited to the above-described embodiments. For example, various modifications may be added to each element of the above-described embodiment and modification. In addition, embodiments that include components and / or methods other than the components and / or methods described above may also be included in the embodiments of the present invention. In addition, an embodiment of the present invention may include a form in which some of the above-mentioned components and / or methods are not included. In addition, a form including some components and / or methods included in one embodiment of the present invention and some components and / or methods included in other embodiments of the present invention is also included in the present invention. It may be included in the embodiment. Therefore, the components and / or methods included in each of the above-described embodiments and modifications and the embodiments of the present invention other than the above may be combined, and the embodiments related to such combinations are also the embodiments of the present invention. Can be included in the form. Further, the effect produced by the present invention is not limited to the above-mentioned effect, and a peculiar effect according to the specific configuration of each embodiment can be exhibited. In this way, various additions, changes and partial deletions can be made to each element described in the claims, the specification, the abstract and the drawings without departing from the technical idea and purpose of the present invention. Is.

1 Hologram layer 1a, 101a, 301a Concavo-convex surface 2 Reflective layer 4 Transparent base material 10 Light modulation element holder 11, 111, 211, 311 Light modulation element 21, 121, 321 Element element 51 Light source 100a, 100b, 100c Light image

Claims (8)

It is equipped with an element element that reproduces an optical image by modulating the phase of incident light.
The element element has an uneven surface and has an uneven surface.
The maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection of the element element is 20% or more. Ri 1 maximum diffraction efficiency der 10% or less in a wavelength band of 380nm or more 780nm or less in wavelength distribution of the diffraction efficiency of the -1st-order diffracted light by wavelength distribution and transmission of the diffraction efficiency of the diffracted light by transmission of the said element element ,
The element element is a light modulation element configured as a Fourier transform hologram. It is equipped with an element element that reproduces an optical image by modulating the phase of incident light.
The element element has a concavo-convex surface containing five or more different heights.
The maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission of the element element is 20% or more. The maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection of the element element is 10% or less. Optical modulation element. The light modulation element according to claim 2 , wherein the element element is configured as a Fourier transform hologram. It is provided with a first element element and a second element element that reproduce an optical image by modulating the phase of incident light.
The first element element has an uneven surface, and the second element element has an uneven surface including five or more different heights.
When the maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection of the first element element is 20% or more. The maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission for the first element element is 10%. Is below
When the maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the primary diffracted light due to transmission and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to transmission of the second element element is 20% or more. The maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection and the wavelength distribution of the diffraction efficiency of the first-order diffracted light due to reflection of the second element element is 10%. The following is an optical modulation element. The light modulation element according to claim 4, wherein the first element element and the second element element are configured as a Fourier transform hologram. The optical image of the primary diffracted light due to reflection or the -1st diffracted light due to reflection of the first element element is different from the optical image of the primary diffracted light due to transmission or the -1st diffracted light due to transmission of the second element element. , The optical modulation element according to claim 4 or 5. The light modulation element according to any one of claims 4 to 6, wherein the first element element and the second element element are arranged side by side on the same plane. The light modulation element according to any one of claims 4 to 6, wherein the first element element and the second element element are arranged side by side in the thickness direction of the light modulation element.

Images