JP6909439B2 - Light modulation elements and information recording media - Google Patents

Description

The present invention relates to a light modulation element that modulates the phase of incident reproduced light to reproduce an optical image, and an information recording medium including such a light modulation element.

Various types of light modulation elements have been proposed as light modulation elements such as holograms that can reproduce the original image.

For example, Patent Document 1 and Patent Document 2 disclose a phase modulation type light modulation element having a concavo-convex pattern, which diffracts light over the entire visible light wavelength band and reproduces an optical image. Further, Patent Document 3 describes a region in which a first light diffraction structure in which recorded information can be read mechanically is formed and a region in which a second light diffraction structure in which recorded information can be visually read is formed. Disclose a light modulation element (information recording medium) provided so as not to superimpose.

Japanese Unexamined Patent Publication No. 2004-126535 Japanese Unexamined Patent Publication No. 10-153943 Japanese Unexamined Patent Publication No. 07-320014

Since the optical modulation elements of Patent Document 1 and Patent Document 2 diffract light almost evenly over the entire visible light wavelength band, when white light, which is general ambient light, is incident, the white light is dispersed. The light image is reproduced at a different position for each wavelength, and the rainbow-colored light image is reproduced as a whole. When the light image is reproduced in rainbow colors in this way, various lines (for example, contour lines) are thickened, so that the visibility of the reproduced image is poor and a desired light image cannot be reproduced with high definition. Further, if the color of the reproduced image is limited to the rainbow color, the optical image cannot be reproduced with a specific color (for example, a single color such as red or blue), and the specific color may give a specific impression to the observer. Can not.

As a method of reproducing an optical image in a specific color, a filter layer such as a color filter that allows only light in a specific wavelength band to enter the optical modulation element or selectively transmits only light in a specific wavelength band is used as the optical modulation element. It is possible to add it. However, when only light in a specific wavelength band is incident on the light modulation element, the light sources that can be used are limited, so that the use of the light modulation element is very limited. Further, when the filter layer is provided, the manufacturing cost increases, and the color of the scene observed through the light modulation element is limited to the color of the specific wavelength band, which causes a sense of discomfort to the observer.

Further, Patent Document 3 is provided with first and second optical diffraction structures that diffract two types of wavelengths, whereas the first optical diffraction structure reproduces mechanically readable recorded information. , The second light diffraction structure reproduces visually readable recorded information. Therefore, similarly to the other documents described above, the light modulation element of Patent Document 3 cannot visually reproduce an optical image having a desired specific color when white light is incident, and the observation image can be visually recognized. The sex is not always good.

As described above, the conventional light modulation element has not always been able to properly reproduce an optical image having a desired visibility. In particular, there is a demand and need for an optical modulation element that can reproduce a generally used white light as a reproduction light and can reproduce a desired light image with good visibility without devising the original image. Very expensive. Such a reproduced image with excellent visibility is not only suitable for design applications, but also suitable for security applications such as authenticity determination.

In particular, the light modulation element used for authenticity determination is required to enable an observer to easily and accurately determine authenticity by observing a reproduced image. As such an authenticity determination method, there is a method of determining authenticity depending on whether or not the reproduced image shows a predetermined change that can be easily visually recognized by changing the incident angle of the reproduced light with respect to the light modulation element. .. There are various aspects of such a change in the reproduced image, and in particular, at least a part of the reproduced image is visible and difficult to be visually recognized (or completely visible) depending on the change in the incident angle of the reproduced light. It is considered that the mode of transitioning between the state and the state in which the light cannot be formed is very effective.

However, conventional light modulation elements such as holograms have not been able to realize such a change in the reproduced image. Further, it has not been considered to provide highly reliable security performance by using an optical modulation element that realizes such a change in the reproduced image for security purposes such as authenticity determination.

The present invention has been made in view of the above circumstances, and by changing the incident angle of the reproduced light, at least a part of the reproduced light image can be visually recognized and difficult to be visually recognized (or invisible). It is an object of the present invention to provide a light modulation element capable of transitioning to and from a possible state, and an information recording medium including such a light modulation element.

One aspect of the present invention includes an element element that reproduces an optical image by modulating the phase of the incident reproduced light, and the element element has an uneven surface, and the diffraction efficiency of the primary diffracted light with respect to the element element is high. At least one of the wavelength distribution and the diffraction efficiency of the -1st order diffracted light has a maximum value of the diffraction efficiency in at least one of the wavelength band of 380 nm or more and 600 nm or less and the wavelength band of 780 nm or more and 1200 nm or less. Regarding optical modulation elements.

The full width at half maximum with respect to the maximum value of the diffraction efficiency included in at least one of the wavelength distribution of the diffraction efficiency of the first-order diffracted light and the wavelength distribution of the diffraction efficiency of the first-order diffracted light may be 200 nm or less.

One of the wavelength distribution of the diffraction efficiency of the primary diffracted light and the wavelength distribution of the diffraction efficiency of the -1st diffracted light for the element element is at least one of the wavelength band of 380 nm or more and 600 nm or less and the wavelength band of 780 nm or more and 1200 nm or less. In addition, it may have a maximum value of diffraction efficiency, and the other may have a maximum value of diffraction efficiency in a wavelength band larger than 600 nm and smaller than 780 nm.

Another aspect of the present invention includes an element element that reproduces an optical image by modulating the phase of the incident reproduced light, and the element element has an uneven surface, and the angle of incidence of the reproduced light on the element element is determined. The present invention relates to an optical modulation element capable of making the wavelength band of light for reproducing an optical image smaller than 380 nm or smaller than 780 nm by changing the light.

Another aspect of the present invention includes an element element that reproduces an optical image by modulating the phase of the incident reproduced light, and the element element has an uneven surface, and the angle of incidence of the reproduced light on the element element is determined. The present invention relates to a light modulation element capable of making an optical image invisible by changing the light image.

Element The element is a Fourier transform hologram.

Another aspect of the present invention relates to an information recording medium including any of the above light modulation elements.

The light image may represent information based on at least one of letters, symbols and patterns.

The information recording medium may further include a base material having an opening of a predetermined size, and at least a part of the light modulation element may be arranged at a position corresponding to the opening.

According to the present invention, by changing the incident angle of the reproduced light, at least a part of the reproduced light image can be seen between a state in which it is visually recognized and a state in which it is difficult to see (or a state in which it is completely invisible). It is possible to provide a light modulation element that can be changed and an information recording medium including such a light modulation element.

FIG. 1 is a schematic plan view showing a typical example of a hologram holder. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. FIG. 3 is a conceptual diagram of a reflective hologram structure. FIG. 4 is a conceptual diagram of a transmissive hologram structure. FIG. 5 is a conceptual diagram showing the planar structure of the hologram structure. FIG. 6 is a cross-sectional view of an element element showing an outline of an example of a stepped structure of an uneven surface. FIG. 7 is a cross-sectional view of an element element showing an outline of another example of a stepped structure of an uneven surface. FIG. 8 is a graph showing an example of the relationship between the wavelength distribution of the primary diffracted light of each element element and the diffraction efficiency. FIG. 9 is a schematic diagram for explaining an optical image reproduced by the hologram structure. FIG. 10 is a schematic diagram for explaining an optical image reproduced by the hologram structure. FIG. 11 is a schematic diagram for explaining an optical image reproduced by the hologram structure. FIG. 12 is a schematic diagram for explaining an optical image reproduced by the hologram structure. FIG. 13 is a graph showing the diffraction characteristics of each element element according to the first embodiment, and shows a case where the incident angle of the regenerated light with respect to each element element is 0 °. FIG. 14 is a graph showing the diffraction characteristics of each element element according to the first embodiment, and shows a case where the incident angle of the regenerated light with respect to each element element is 30 °. FIG. 15 is a graph showing the diffraction characteristics of each element element according to the first embodiment, and shows a case where the incident angle of the regenerated light with respect to each element element is 50 °. FIG. 16 shows an example of an optical image reproduced by the hologram structure including each element element according to the first embodiment, and shows an optical image when the incident angle of the reproduced light with respect to each element element is 0 °. FIG. 17 shows an example of an optical image reproduced by the hologram structure including each element element according to the first embodiment, and shows an optical image when the incident angle of the reproduced light with respect to each element element is 30 °. FIG. 18 shows an example of an optical image reproduced by the hologram structure including each element element according to the first embodiment, and shows an optical image when the incident angle of the reproduced light with respect to each element element is 50 °. FIG. 19 is a graph showing the diffraction characteristics of each element element according to the second embodiment, and shows a case where the incident angle of the regenerated light with respect to each element element is 0 °. FIG. 20 is a graph showing the diffraction characteristics of each element element according to the second embodiment, and shows a case where the incident angle of the regenerated light with respect to each element element is 30 °. FIG. 21 shows an example of an optical image reproduced by the hologram structure including each element element according to the second embodiment, and FIG. 21 shows an optical image when the incident angle of the reproduced light with respect to each element element is 0 °. Is shown. FIG. 22 shows an example of an optical image reproduced by the hologram structure including each element element according to the second embodiment, and FIG. 22 shows an optical image when the incident angle of the reproduced light with respect to each element element is 30 °. Is shown. FIG. 23 is a graph showing the diffraction characteristics of each element element according to the third embodiment, and shows a case where the incident angle of the regenerated light with respect to each element element is 0 °. FIG. 24 is a graph showing the diffraction characteristics of each element element according to the third embodiment, and shows a case where the incident angle of the regenerated light with respect to each element element is 30 °. FIG. 25 shows an example of an optical image reproduced by the hologram structure including each element element according to the third embodiment, and shows an optical image when the incident angle of the reproduced light with respect to each element element is 0 °. FIG. 26 shows an example of an optical image reproduced by the hologram structure including each element element according to the third embodiment, and shows an optical image when the incident angle of the reproduced light with respect to each element element is 30 °. FIG. 27 is a conceptual diagram showing an example of the planar structure of the transmissive hologram structure according to the second embodiment. FIG. 28 is a schematic diagram for explaining an optical image reproduced by the transmissive hologram structure of FIG. 27. FIG. 29 is a conceptual diagram showing another example of the planar structure of the transmissive hologram structure according to the second embodiment. FIG. 30 is a schematic diagram for explaining an optical image reproduced by the transmissive hologram structure of FIG. 29. FIG. 31 is a schematic diagram for explaining an optical image reproduced by another example of the transmissive hologram structure according to the second embodiment.

Hereinafter, the light modulation element according to the embodiment of the present invention will be described.

The light modulation element of each of the following embodiments is composed of a phase modulation type hologram structure that modulates the phase of the incident reproduced light and reproduces an optical image, and in particular, an element element composed of a Fourier transform hologram. including. 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. Such a phase modulation type light modulation element is also called quinoform. 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 the reproduced light incident on the hologram structure, but the reproduced light does not necessarily have to be white light. That is, the wavelength included in the reproduced light is not particularly limited as long as the light having a wavelength corresponding to the color of the light image reproduced by the hologram structure is included. Further, in the following description, unless otherwise specified, it is assumed that the incident angle of the reproduced light with respect to the hologram structure is 0 ° (that is, the angle along the normal direction of the incident surface of the hologram structure). 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 hologram structure 11 are the cases where the hologram structure 11 is used in an air environment having a refractive index of 1.0 unless otherwise specified. It is a value derived by assuming it.

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 the size. Two or more optical images that are different from each other and have the same shape are also included. That is, two or more optical images having the same shape may or may not have the same size as long as they have the same shape, and two or more optical images having a similar relationship with each other have the same shape. It corresponds to "two or more light images having". Therefore, two or more optical images having different sizes to be reproduced due to different constituent wavelengths of the optical images correspond to "two or more optical images having the same shape with each other" if the overall shape is the same. do.

Further, in the present specification, the concept of two optical images having a "point symmetry" relationship includes not only two optical images having the same size and the same shape (overall shape), but also mutual sizes. Also included are two light images that are different and have the same shape. That is, as long as the two optical images having the same shape have the same shape and the reproduction position and the reproduction direction have point symmetry, it does not matter whether the sizes are the same or not. Therefore, for example, two optical images having a similar relationship with each other and having a point symmetry in the reproduction position and the reproduction direction correspond to "two optical images having a point symmetric relationship with each other". .. Therefore, if two or more optical images having different reproduction sizes due to different constituent wavelengths of the optical images have the same shape, and the reproduction position and the orientation of the optical image have point symmetry. , "Two or more optical images having a point-symmetrical relationship with each other".

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

The hologram holder 10 shown in FIGS. 1 and 2 includes a hologram layer 1, a reflection layer 2 laminated on one surface of the hologram layer 1, and a base material 4 laminated on the other surface of the hologram layer 1. And. A reflective hologram structure 11 is provided in a part of the hologram holder 10. In the hologram structure 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 hologram structure 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, UV curable resin or thermoplastic resin) constituting the hologram layer 1 is formed on a base material 4 (for example, PET: polyethylene terephthalate) by coating or the like, and the hologram layer 1 is subjected to UV curing treatment. Along with the heat and 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, Al, ZnS, TiO _2, etc.) is formed on the uneven surface 1a of the hologram layer 1. Therefore, the hologram 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 hologram structure 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.

As an example, the hologram holder 10 shown in FIGS. 1 and 2 including the hologram structure 11 that functions as a light modulation element as described above and the base material 4 that supports the hologram structure 11 records information such as a passport. The medium can be suitably configured. For example, the hologram structure 11 is determined to be authentic by designing the hologram structure 11 so that the light image reproduced by the hologram structure 11 represents information based on at least one of characters, symbols, and patterns. It can be suitably used for security applications such as. Although the transparent base material 4 is used in the hologram holder 10 shown in FIGS. 1 and 2, an opaque base material may be used instead. In that case, for example, an opening 4a (see FIG. 2) having a predetermined size is formed on the base material, and at least a part of the hologram structure 11 provided as the light modulation element is arranged at a position corresponding to the opening 4a. Therefore, the hologram holder 10 can preferably form an information recording medium such as a passport. The opening 4a may be provided with a hole (space), or instead of providing the hole (space) or the hole (space), only the opening 4a is composed of a transparent body (that is, a transparent base material). You may. Even when the transparent base material 4 is used, for example, by providing a printed body that regulates the transmission of light in a portion of the base material 4 other than the opening 4a, the opening portion of the base material 4 is basically used. The hologram holder 10 may be configured so that light is transmitted only through 4a. Further, an opening may be formed in an information recording medium such as a passport, and the hologram holder 10 may be arranged in the opening. In this case, a hole (space) and / or a transparent body may be provided in the opening portion of the information recording medium, and a printing body that regulates the transmission of light is provided in a portion of the information recording medium other than the opening portion. The information recording medium may be configured so that light transmits only through the openings of the information recording medium.

The hologram structure 11 includes a reflective hologram structure in which the observer 50 and the light source 51a are arranged on the same side with respect to the hologram structure 11 as shown in FIG. 3, and the observer 50 and the light source as shown in FIG. 51b can be classified into a transmission type hologram structure in which 51b is arranged on different sides from each other via the hologram structure 11. As the reflective hologram structure, in addition to the structure provided with an additional layer for reflecting the reproduced light such as the reflection layer 2 shown in FIG. 2, the hologram layer 1 is provided without an additional reflection layer. There is a structure in which the uneven surface 1a is exposed to air and the regenerated light is reflected by utilizing the difference in the refractive index between the hologram layer 1 such as a UV curable resin and the air. On the other hand, the transmissive hologram structure is not provided with such a reflective layer. However, the reflective hologram structure and the transmissive hologram structure are common in that the concave-convex surface 1a is formed on the hologram layer 1 and a desired light image is reproduced by a diffraction phenomenon caused by the difference in optical path length of the uneven surface 1a. do. Regarding the specific unevenness depth of the uneven surface 1a, there are optimum values for each of the transmissive hologram structure and the reflective hologram structure. In the following, the contents described only for either the reflective hologram structure or the transmissive hologram structure are basically described for both the reflective hologram structure and the transmissive hologram structure unless otherwise specified. On the other hand, it can be applied.

FIG. 5 is a conceptual diagram showing the planar structure of the hologram structure 11. The hologram structure 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 the incident reproduced 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. 6 and 7 are cross-sectional views of the element element 21 showing an outline of the step structure of the uneven surface 1a, FIG. 6 shows an 8-step type uneven surface 1a, and FIG. 7 shows a 4-step type uneven surface 1a. show. Note that FIGS. 6 and 7 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. 6 and 7)) 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.

FIG. 8 is a graph showing an example of the relationship between the wavelength distribution of the primary diffracted light of each element element 21 and the diffraction efficiency. In FIG. 8, the horizontal axis represents the wavelength and the vertical axis represents the diffraction efficiency. Diffraction efficiency is represented by the amount obtained by dividing the radiant flux of light diffracted in a certain direction by the radiant flux of light incident on each element element 21, the diffracted radiant flux in a certain direction is represented by P, and the incident radiant flux is P0. When represented by, the diffraction efficiency η is a non-dimensional number represented by “η = P / P0”. Each element element 21 exhibits a unique diffraction efficiency depending on the wavelength, and in the example shown in FIG. 8, light having a wavelength near 580 nm (see the sign “H1” in FIG. 8) has a maximum value Dmax with respect to the first-order diffracted light. show. Although FIG. 8 shows an example of the wavelength distribution of the primary diffracted light, the wavelength distribution of the -1st diffracted light also shows a peculiar diffraction efficiency according to the wavelength and also shows a maximum value of the diffraction efficiency at a specific wavelength.

9 to 12 are schematic views for explaining the light image 100 reproduced by the hologram structure 11. In each of FIGS. 9 to 12, the light source used in the reflective hologram structure 11 is indicated by the code “51a”, and the light source used in the transmissive hologram structure 11 is indicated by the code “51b”. .. Further, in the following description, these light sources 51a and 51b are collectively represented by using the sign "51".

Generally, in the diffraction phenomenon, the larger the wavelength of the incident light, the larger the diffraction angle of the diffracted light other than the 0th-order diffracted light. Therefore, when white light is incident on a general hologram structure 11 having the same degree of diffraction efficiency over the entire visible light wavelength band from the light source 51, the hologram structure 11 has an iridescent color as shown in FIG. The optical image 100 is reproduced. On the other hand, in the wavelength band of 380 nm or more and smaller than 780 nm included in the wavelength band of visible light, either one of the first-order diffracted light and the first-order diffracted light has the maximum value of diffraction efficiency (for example, the number of stages of the uneven structure of the hologram structure 11). Has only one maximum value showing a diffraction efficiency of 0.15 or more when there are two stages, and a maximum value showing a diffraction efficiency of 0.3 or more when the number of stages of the concave-convex structure is three or more. When white light is incident on the hologram structure 11 from the light source 51, the hologram structure 11 reproduces a monochromatic light image 100 as shown in FIGS. 10 to 12.

That is, the hologram structure 11 (particularly the uneven surface 1a) of FIGS. 10 to 12 has a diffraction structure optimized for light having a specific wavelength and a wavelength band in the vicinity thereof, and is specified among light having various wavelengths. The light image 100 of a specific color is reproduced by selectively using the light of the wavelength band of the above and the wavelength band in the vicinity thereof. For example, in the hologram structure 11 of FIG. 10, the diffraction efficiency of the primary diffracted light or the -1st diffracted light shows a maximum value in the blue wavelength band, and the blue light image 100 is reproduced. In the hologram structure 11 of FIG. 11, the diffraction efficiency of the primary diffracted light or the -1st diffracted light shows a maximum value in the green wavelength band, and the green light image 100 is reproduced. The hologram structure 11 of FIG. 12 shows a maximum value in the diffraction efficiency of the primary diffracted light or the -1st diffracted light in the red wavelength band, and reproduces the red light image 100. The light images 100 of FIGS. 10 to 12 are different in size from each other, which is caused by the difference in wavelength of the light (that is, the first-order diffracted light and / or the first-order diffracted light) constituting the light image 100. It is based on the difference in refraction angle.

As described above, the hologram structure 11 having a maximum diffraction efficiency (particularly a single maximum value) in a wavelength band of 380 nm or more and smaller than 780 nm reproduces a monochromatic light image 100 even when white light is incident. be able to. The light image 100 reproduced in this way is a clear image with almost no blurring due to color dispersion. Further, since the light image 100 can be reproduced in a specific color, it is possible to give the observer 50 a specific impression based on the color. It is also possible to reproduce the light image 100 in color and clearly convey the concept of the light image 100 to the observer 50. Further, since the hologram structure 11 is configured to reproduce a specific monochromatic light image 100, for example, in the authenticity determination, not only the "picture" of the reproduced light image 100 but also the light concerned is used as the basis of the determination. The "color" of the image 100 can be used, enabling highly reliable authenticity determination. Further, the hologram structure 11 of the present embodiment described below does not need to add a layer that selectively transmits or reflects light in a specific wavelength band, so that the manufacturing cost can be reduced and the observer 50 can use the hologram structure. Even when observing the surroundings through the body 11, there is no sense of discomfort in the observed image.

Based on the above characteristics, in the hologram structure 11 of the present embodiment, at least one of the wavelength distribution of the diffraction efficiency of the primary diffracted light and the wavelength distribution of the diffraction efficiency of the -1st diffracted light for each element element 21 is 380 nm. It has a maximum value of diffraction efficiency in at least one of the wavelength band of 600 nm or more and the wavelength band of 780 nm or more and 1200 nm or less. That is, the wavelength band and 780 nm in which both the primary diffracted light and the -1st diffracted light of each element element 21 of the present embodiment, or only one of the primary diffracted light and the -1st diffracted light is 380 nm or more and 600 nm or less. In at least one of the wavelength bands of 1200 nm or less, the maximum value of the diffraction efficiency (for example, when the number of stages of the concave-convex structure of the hologram structure 11 is two, the maximum value of the diffraction efficiency is 0.15 or more, and the uneven structure When the number of stages is 3 or more, the diffraction efficiency can have a maximum value of 0.3 or more). Specifically, as described later, each element is adjusted by adjusting the number and depth of the uneven surface 1a, the refractive index of the material constituting the hologram structure 11 (particularly the hologram layer 1), and other related parameters. It is possible to give the element 21 a desired diffraction characteristic. According to the hologram structure 11 having such a wavelength distribution of diffraction efficiency, the color of the light image reproduced by the primary diffracted light and the -1st diffracted light by changing the incident angle of the reproduced light with respect to each element element 21. Can be changed, at least a part of the light image can be visually extinguished, or at least a part of the light image can be visually made to appear.

As the incident angle of the regenerated light with respect to each element element 21 is increased from 0 °, the wavelength showing the maximum value of the diffraction efficiency of each diffracted light shifts to the short wavelength side. Therefore, at least one of the first-order diffracted light and the first-order diffracted light has a maximum value of diffraction efficiency in the wavelength band of 380 nm or more and 600 nm or less (for example, when the number of steps of the concave-convex structure of the hologram structure 11 is two steps, the diffraction efficiency In the hologram structure 11 having a maximum value of 0.15 or more, and a maximum value of diffraction efficiency of 0.3 or more when the number of stages of the concave-convex structure is 3 or more), the reproduced light for each element element 21 By increasing the incident angle, it is possible to make the wavelength showing the maximum value of the diffraction efficiency of at least one of the first-order diffracted light and the first-order diffracted light smaller (that is, shorter) than 380 nm. In this case, the maximum value of the diffraction efficiency shown in the visible light wavelength band (that is, the wavelength band of 380 nm or more and 600 nm or less) before increasing the incident angle of the reproduced light increased the incident angle of the reproduced light. Later, it is shown outside the visible light wavelength band (that is, the ultraviolet wavelength band). Therefore, as the incident angle of the reproduced light increases, the optical image composed of the light having the wavelength showing the maximum value and the light in the wavelength band in the vicinity thereof is invisible (or difficult to recognize) from the visually visible state. State) changes.

On the other hand, at least one of the first-order diffracted light and the first-order diffracted light has a maximum value of diffraction efficiency in the wavelength band of 780 nm or more and 1200 nm or less (for example, when the number of steps of the concave-convex structure of the hologram structure 11 is two steps, the diffraction efficiency In the hologram structure 11 having a maximum value of 0.15 or more, and a maximum value of diffraction efficiency of 0.3 or more when the number of stages of the concave-convex structure is 3 or more), the reproduced light for each element element 21 By increasing the incident angle, it is possible to make the wavelength showing the maximum value of the diffraction efficiency of at least one of the first-order diffracted light and the first-order diffracted light smaller than 780 nm. In this case, the maximum value of the diffraction efficiency shown outside the visible light wavelength band (that is, the infrared wavelength band) before increasing the incident angle of the reproduced light becomes visible light after increasing the incident angle of the reproduced light. It is shown within the wavelength band (ie, a wavelength band smaller than 780 nm). Therefore, as the incident angle of the reproduced light increases, the optical image composed of the light having the wavelength showing the maximum value and the light in the wavelength band in the vicinity thereof becomes visually invisible (or difficult to recognize). It changes to a visible state.

As described above, the hologram structure 11 of the present embodiment makes the wavelength band of the light for reproducing the optical image smaller than 380 nm or smaller than 780 nm by changing the incident angle of the reproduced light on each element element 21. It is configured to be able to. In general, light in a wavelength band smaller than 380 nm corresponds to ultraviolet rays, and light in a wavelength band of 780 nm or more corresponds to infrared rays, and neither ultraviolet rays nor infrared rays are usually visible or difficult to see. Therefore, before changing the incident angle of the reproduced light on each element element 21, the wavelength band of the main light constituting the optical image is 380 nm or more and smaller than 780 nm (particularly 380 nm or more and 600 nm or less). The diffraction characteristics of each element element 21 may be set so that the wavelength band of the main light constituting the optical image becomes smaller than 380 nm after the incident angle of the reproduced light on each element element 21 is changed. .. In this case, the reproduced light image can be changed from a visually recognizable state to a visually difficult state (or a completely invisible state) according to a change in the incident angle of the reproduced light. As described above, according to the hologram structure 11 of the present embodiment, the optical image can be made invisible by changing the incident angle of the reproduced light on each element element 21. On the other hand, before changing the incident angle of the reproduced light on each element element 21, the wavelength band of the main light constituting the optical image is set to 780 nm or more (particularly 780 nm or more and 1200 nm or less), and the element element 21 is charged. After changing the incident angle of the reproduced light, the diffraction characteristics of each element element 21 may be set so that the wavelength band of the main light constituting the optical image is 380 nm or more and smaller than 780 nm. In this case, the reproduced light image can be changed from a state in which it is difficult to see (or a state in which it is completely invisible) to a state in which it can be visually recognized according to a change in the incident angle of the reproduced light.

Such changes in the appearance and disappearance of the visual image can be recognized very easily and reliably by the observer. Therefore, the hologram structure 11 of the present embodiment is very useful not only for design applications but also for security applications such as authenticity determination. For example, when the hologram structure 11 is used for design purposes and the optical image of a symbol such as a specific character is reproduced by the hologram structure 11, the symbol is before and after the incident angle of the reproduced light on each element element 21 is changed. By making a part of the optical image of No. 1 disappear or appear, it is possible to reproduce a pattern accompanied by movement (that is, a visual change) as an optical image. Further, when the hologram structure 11 is used for authenticity determination and the optical image of a predetermined authenticity determination symbol is reproduced by the hologram structure 11, the incident angle of the reproduced light on each element element 21 is changed to change the incident angle of the symbol. By making a part of the optical image disappear or appear, it is possible to easily and surely perform the authenticity determination based on the disappearance or appearance of such a symbol.

For example, one of the wavelength distribution of the diffraction efficiency of the primary diffracted light and the wavelength distribution of the diffraction efficiency of the -1st diffracted light for each element element 21 is a wavelength band of 380 nm or more and 600 nm or less and a wavelength of 780 nm or more and 1200 nm or less. At least one of the bands may have a maximum value of diffraction efficiency, and the other may have a maximum value of diffraction efficiency in a wavelength band larger than 600 nm and smaller than 780 nm.

That is, one of the wavelength distribution of the diffraction efficiency of the primary diffracted light and the wavelength distribution of the diffraction efficiency of the -1st diffracted light for each element element 21 is the maximum value of the diffraction efficiency in the wavelength band of 380 nm or more and 600 nm or less (for example). When the number of steps of the concave-convex structure of the hologram structure 11 is two, the diffraction efficiency is a maximum value of 0.15 or more, and when the number of steps of the concave-convex structure is three or more, the diffraction efficiency is a maximum of 0.3 or more. The maximum value of the diffraction efficiency in the wavelength band having the value) and the other being larger than 600 nm and smaller than 780 nm (for example, when the number of steps of the concave-convex structure of the hologram structure 11 is two, the diffraction efficiency is 0.15. It may have the above maximum value, or the maximum value of diffraction efficiency of 0.3 or more when the number of stages of the uneven structure is 3 or more. In this case, before changing the incident angle of the reproduced light with respect to each element element 21, both the optical image of the primary diffracted light and the optical image of the -1st diffracted light can be reproduced in a visually recognizable state. After changing the incident angle of the regenerated light with respect to the element element 21, one of the light image of the primary diffracted light and the light image of the -1st diffracted light is visually extinguished, and the other is maintained in a visually recognizable state. be able to.

Further, the maximum value of the diffraction efficiency (for example, hologram structure) in the wavelength band in which one of the wavelength distribution of the diffraction efficiency of the primary diffracted light and the wavelength distribution of the diffraction efficiency of the -1st diffracted light for each element element 21 is 780 nm or more and 1200 nm or less. When the number of steps of the concave-convex structure of the body 11 is two, the diffraction efficiency is a maximum value of 0.15 or more, and when the number of steps of the concave-convex structure is three or more, the diffraction efficiency is a maximum value of 0.3 or more). And the other is larger than 600 nm and smaller than 780 nm, the maximum value of diffraction efficiency (for example, when the number of steps of the concave-convex structure of the hologram structure 11 is two, the diffraction efficiency is 0.15 or more. It may have a maximum value, or a maximum value of diffraction efficiency of 0.3 or more when the number of stages of the uneven structure is 3 or more. In this case, before changing the incident angle of the reproduced light with respect to each element element 21, only one of the optical image of the primary diffracted light and the optical image of the -1st diffracted light can be reproduced in a visually recognizable state. After changing the incident angle of the regenerated light with respect to each element element 21, the other of the first-order diffracted light image and the -1st-order diffracted light image is visually made to appear, and the light images of both diffracted lights are visually recognized. It can be played in the possible state.

In each element element 21 of the hologram structure 11 of the present embodiment described above, the maximum value of the diffraction efficiency included in at least one of the wavelength distribution of the diffraction efficiency of the primary diffracted light and the wavelength distribution of the diffraction efficiency of the -1st diffracted light. The full width at half maximum FWHM with respect to is preferably 200 nm or less. In this case, the first-order diffracted light and / or the first-order diffracted light can be formed by the light having a limited wavelength band, the color mixing in the reproduced light image is prevented, and the incident angle of the reproduced light with respect to each element element 21 is changed. It is possible to visually clearly recognize the disappearance or appearance of the light image accompanying the phenomenon. The full width at half maximum FWHM referred to here indicates a wavelength band (wavelength width) at a position having a half value (Dmax / 2) of the maximum value Dmax in the wavelength distribution of diffraction efficiency (see FIG. 8).

In the hologram structure 11 of the present embodiment, the specific incident angle of the reproduced light with respect to each element element 21 is not particularly limited, but the incident angle is generally set in the range of 0 ° or more and 80 ° or less, for example. For example, it is possible to improve the convenience of use by setting the incident angle in the range of 0 ° or more and 70 ° or less, 60 ° or less, 50 ° or less, or 40 ° or less. In normal use, the angle of incidence of the reproduced light on the hologram structure 11 is 0 ° or an angle near 0 ° (for example, an angle in the range of 0 ° to 45 °, an angle in the range of 0 ° to 30 °, or 0. Angles in the range of ° to 20 °) are often assumed. Therefore, these assumed angles may be set to "the angle before the change in the incident angle of the reproduced light with respect to each element element 21 required for the disappearance or appearance of at least a part of the optical image". The "angle before the change in the incident angle of the reproduced light with respect to each element element 21 required for the disappearance or appearance of at least a part of the optical image" as used herein means the reproduction before and after the change (disappearance or appearance) of the optical image. Of the incident angles of light (ie, the first incident angle and the second incident angle), the incident angle is smaller (that is, the incident angle closer to 0 °). Further, the "change angle of the incident angle of the reproduced light with respect to each element element 21 (= | incident angle after change-incident angle before change |)" required for the disappearance or appearance of at least a part of the optical image as described above is There is no particular limitation. However, the "change angle of the incident angle of the reproduced light with respect to each element element 21" required for the disappearance or appearance of at least a part of the optical image is usually preferably an angle in the range of 10 ° to 50 °, and 20 ° to 40 °. An angle in the range of 30 ° is more preferable, and an angle in the vicinity of 30 ° (for example, 25 ° to 35 °) is further preferable. It should be noted that these angles can be set by appropriately adjusting the diffraction characteristics of the hologram structure 11.

Therefore, as an example, the incident angle of the reproduced light with respect to each element element 21 is 0 ° or an angle near 0 ° (for example, an angle in the range of 0 ° to 45 °, an angle in the range of 0 ° to 30 °, or 0 ° to 0 ° to In the case of an angle in the range of 20 °), at least one of the wavelength distribution of the diffraction efficiency of the primary diffracted light and the wavelength distribution of the diffraction efficiency of the -1st diffracted light for each element element 21 is 380 nm or more and 600 nm or less. Maximum value of diffraction efficiency in at least one of the wavelength band and the wavelength band of 780 nm or more and 1200 nm or less (for example, when the number of steps of the concave-convex structure of the hologram structure 11 is two, the maximum value of diffraction efficiency is 0.15 or more. Further, the hologram structure 11 of the present embodiment may be configured so as to have a diffraction efficiency of 0.3 or more when the number of stages of the uneven structure is 3 or more. In this case, the change angle of the incident angle of the reproduced light with respect to each element element 21 required for the disappearance or appearance of at least a part of the optical image is, for example, 40 ° or less, 30 ° or less, 20 ° or less, 10 ° or less, or 5 It may be set to an angle of ° or less.

The disappearance or appearance of at least a part of the optical image as described above may be caused by an increase in the incident angle of the regenerated light with respect to each element element 21, or the incident angle of the regenerated light with respect to each element element 21. It may be generated according to the reduction of. As described above, by increasing the incident angle of the reproduced light with respect to each element element 21, the wavelength showing the maximum value of the diffraction efficiency of each diffracted light can be shifted to the short wavelength side. This also means that the wavelength showing the maximum value of the diffraction efficiency of the diffracted light can be shifted to the long wavelength side by reducing the incident angle of the regenerated light with respect to each element element 21.

Therefore, for example, before at least one of the wavelength distribution of the diffraction efficiency of the primary diffracted light and the wavelength distribution of the diffraction efficiency of the -1st diffracted light for each element element 21 changes the incident angle of the regenerated light with respect to each element element 21. In the wavelength band smaller than 380 nm, the maximum value of the diffraction efficiency (for example, when the number of steps of the concave-convex structure of the hologram structure 11 is two, the maximum value of the diffraction efficiency is 0.15 or more, and the number of steps of the concave-convex structure is three. In the case of steps or more, the diffraction efficiency is a maximum value of 0.3 or more), and the diffraction efficiency is in the wavelength band of 380 nm or more and 600 nm or less after changing the incident angle of the reproduced light with respect to each element element 21. It may have a maximum value. In this case, at least a part of the light image that could not be visually recognized before the change in the incident angle of the reproduced light with respect to each element element 21 is visually made to appear after the change in the incident angle of the reproduced light with respect to each element element 21. Can be done. Further, at least one of the wavelength distribution of the diffraction efficiency of the primary diffracted light and the wavelength distribution of the diffraction efficiency of the -1st diffracted light for each element element 21 is 780 nm before changing the incident angle of the reproduced light with respect to each element element 21. Maximum value of diffraction efficiency in a wavelength band smaller than (for example, when the number of steps of the concave-convex structure of the hologram structure 11 is two, the maximum value of diffraction efficiency is 0.15 or more, and the number of steps of the concave-convex structure is three or more. In the case of, the diffraction efficiency has a maximum value of 0.3 or more), and the maximum value of the diffraction efficiency is in the wavelength band of 780 nm or more and 1200 nm or less after changing the incident angle of the reproduced light with respect to each element element 21. May have. In this case, at least a part of the light image visually recognized before the change in the incident angle of the reproduced light with respect to each element element 21 may be visually disappeared after the change in the incident angle of the reproduced light with respect to each element element 21. can.

Hereinafter, a representative example (implementation mode) of the hologram structure 11 having various characteristic diffraction characteristics will be illustrated.

[First implementation mode]
13 to 15 are graphs showing the diffraction characteristics of each element element 21 according to the first embodiment mode, and FIG. 13 shows a case where the incident angle of the regenerated light with respect to each element element 21 is 0 °, and FIG. Shows the case where the incident angle of the regenerated light with respect to each element element 21 is 30 °, and FIG. 15 shows the case where the incident angle of the regenerated light with respect to each element element 21 is 50 °. In FIGS. 13 to 15, the horizontal axis indicates the wavelength (nm), the vertical axis indicates the diffraction efficiency, the wavelength distribution of the 0th-order diffracted light is indicated by “W0”, and the wavelength distribution of the 1st-order diffracted light is “W1”. Shown, the wavelength distribution of the -1st order diffracted light is indicated by "W-1".

16 to 18 show an example of an optical image 100 reproduced by the hologram structure 11 including each element element 21 according to the first embodiment, and FIG. 16 shows an incident angle of the reproduced light with respect to each element element 21. The light image 100 at 0 ° is shown, FIG. 17 shows the light image 100 when the incident angle of the regenerated light with respect to each element element 21 is 30 °, and FIG. 18 shows the incident angle of the regenerated light with respect to each element element 21. The optical image 100 at 50 ° is shown. That is, the light image 100 shown in FIG. 16 is an optical image reproduced by the element element 21 exhibiting the diffraction characteristics of FIG. 13, and the light image 100 shown in FIG. 17 is reproduced by the element element 21 exhibiting the diffraction characteristics of FIG. It is an optical image, and the optical image 100 shown in FIG. 18 is an optical image reproduced by the element element 21 having the diffraction characteristic of FIG. In the light images 100 shown in FIGS. 16 to 18, the first-order diffracted light image 100b and the first-order diffracted light image 100c have the same shape (“F” shape in the illustrated example) and are reproduced point-symmetrically.

In each element element 21 according to this mode, as shown in FIG. 13, in a wavelength band of 380 nm or more and smaller than 780 nm, when the incident angle of the reproduced light is 0 °, the wavelength indicating the maximum value of the 0th-order diffracted light is 600 nm. The wavelength indicating the maximum value of the primary diffracted light is set to 533 nm, and the wavelength indicating the maximum value of the -1st diffracted light is set to 685 nm. Further, in each element element 21 according to this mode, as shown in FIG. 14, when the incident angle of the regenerated light is 30 °, the wavelength indicating the maximum value of the 0th-order diffracted light is set to around 519 nm, and the first-order diffracted light has a wavelength of around 519 nm. The wavelength showing the maximum value is set to 457 nm, and the wavelength showing the maximum value of the -1st order diffracted light is set to 601 nm. Further, in each element element 21 according to this mode, as shown in FIG. 15, when the incident angle of the reproduced light is 50 °, the wavelength indicating the maximum value of the 0th-order diffracted light and the wavelength indicating the maximum value of the 1st-order diffracted light are It is set outside the visible light wavelength band (that is, a wavelength band smaller than 380 nm), and the wavelength indicating the maximum value of the first-order diffracted light is set to 449 nm.

As described above, when the incident angles of the reproduced light are 0 ° and 30 °, all of the 0th-order diffracted light, the 1st-order diffracted light and the -1st-order diffracted light are mainly composed of the light included in the visible light wavelength band. ing. However, when the incident angle of the regenerated light is 30 °, the main light constituting each of the 0th-order diffracted light, the 1st-order diffracted light and the -1st-order diffracted light is as a whole as compared with the case where the incident angle of the regenerated light is 0 °. It is shifting to the short wavelength side. When the incident angle of the reproduced light is 50 °, the main light constituting each of the 0th-order diffracted light, the 1st-order diffracted light and the -1st-order diffracted light is shifted to the shorter wavelength side as a whole, and the -1st-order diffracted light is generated. The main light constituting the light remains in the visible light wavelength band, but the main light constituting the 0th-order diffracted light and the 1st-order diffracted light deviates from the visible light wavelength band and shifts to the wavelength band of ultraviolet rays which cannot be visually recognized.

Therefore, the optical image 100 reproduced from the reproduced light of the white light by the hologram structure 11 according to the present embodiment is as shown in FIGS. 16 to 18. That is, when the incident angle of the reproduced light is 0 °, as shown in FIG. 16, the green first-order diffracted light image 100b and the red first-order diffracted light image 100b arranged point-symmetrically around the yellow-orange 0th-order diffracted light image 100a. The -1st order diffracted light image 100c of the above is reproduced. When the incident angle of the reproduced light is 30 °, as shown in FIG. 17, the blue first-order diffracted light image 100b and the yellow -1 are arranged point-symmetrically with respect to the green-based 0th-order diffracted light image 100a. The next diffracted light image 100c is reproduced. When the incident angle of the reproduced light is 50 °, as shown in FIG. 18, the blue -1st-order diffracted light image 100c is visibly reproduced, but the 0th-order diffracted light image 100a and the 1st-order diffracted light image 100b are reproduced. It is not reproduced as a visible light image (that is, it is reproduced as an invisible ultraviolet light image). In reality, these optical images mainly composed of light outside the visible light wavelength band include some light within the visible light wavelength band, so that some observers can visually recognize these light images 100a and 100b. In some cases, it can be done, but even in such a case, it is recognized as a very unclear light image.

In this way, as the incident angle of the reproduced light incident on each element element 21 is increased from 0 °, the reproduced light image 100 (that is, the 0th-order diffracted light image 100a, the 1st-order diffracted light image 100b, and the -1st-order diffracted light image 100c). The wavelength of the light constituting each of these) shifts to the short wavelength side. Then, when the incident angle of the reproduced light becomes larger than a certain angle (a certain angle between 30 ° and 50 ° in this embodiment), at least a part of the light image 100 becomes invisible.

For such diffraction characteristics, for example, the refractive index of the hologram layer 1 is 1.5, the number of steps on the uneven surface 1a is set to 8, and the depth per step (see the sign “d” in FIG. 6) is set. It can be realized by a reflective hologram structure 11 (that is, a reflective element element 21) having a maximum depth of 200 nm and a maximum depth (see the sign “D” in FIG. 6) of 1400 nm.

As another form, for example, the hologram layer 1 has a refractive index of 1.5, the number of steps on the uneven surface 1a is eight, the depth per step is 225 nm, and the maximum depth is 1575 nm. The above-mentioned diffraction characteristics can also be realized by the type hologram structure 11 (that is, the reflective element element 21). According to this embodiment, when the incident angle of the reproduced light is 0 °, the wavelength indicating the maximum value of the 0th-order diffracted light is set to 675 nm, the wavelength indicating the maximum value of the 1st-order diffracted light is set to 600 nm, and -1. The wavelength indicating the maximum value of the second-order diffracted light is set to 771 nm, and the 0th-order diffracted light image 100a, the first-order diffracted light image 100b and the first-order diffracted light image 100c are reproduced as visible light images. On the other hand, when the incident angle of the reproduced light is 50 °, the wavelength indicating the maximum value of the 0th-order diffracted light is set to 432 nm, the wavelength indicating the maximum value of the 1st-order diffracted light is set to 376 nm, and the maximum value of the -1st-order diffracted light is set. The wavelength indicating the value is set to 508 nm, and the 0th-order diffracted light image 100a and the -1st-order diffracted light image 100c are reproduced as visible light images, but the 1st-order diffracted light image 100b is basically an invisible light image. Will be played.

[Second implementation mode]
19 to 20 are graphs showing the diffraction characteristics of each element element 21 according to the second embodiment, and FIG. 19 shows a case where the incident angle of the regenerated light with respect to each element element 21 is 0 °, and FIG. Indicates a case where the incident angle of the regenerated light with respect to each element element 21 is 30 °. In FIGS. 19 to 20, the horizontal axis indicates the wavelength (nm), the vertical axis indicates the diffraction efficiency, the wavelength distribution of the 0th-order diffracted light is indicated by “W0”, and the wavelength distribution of the 1st-order diffracted light is “W1”. Shown, the wavelength distribution of the -1st order diffracted light is indicated by "W-1".

21 to 22 show an example of an optical image 100 reproduced by the hologram structure 11 including each element element 21 according to the second embodiment, and FIG. 21 shows an incident angle of the reproduced light with respect to each element element 21. The light image 100 when the temperature is 0 ° is shown, and FIG. 22 shows the light image 100 when the incident angle of the regenerated light with respect to each element element 21 is 30 °. That is, the light image 100 shown in FIG. 21 is an optical image reproduced by the element element 21 exhibiting the diffraction characteristics of FIG. 19, and the light image 100 shown in FIG. 22 is reproduced by the element element 21 exhibiting the diffraction characteristics of FIG. It is an optical image. In the light image 100 shown in FIGS. 21 to 22, the first-order diffracted light image 100b and the first-order diffracted light image 100c have the same shape (“F” shape in the illustrated example) and are reproduced point-symmetrically.

In each element element 21 according to this mode, as shown in FIG. 19, when the incident angle of the reproduced light is 0 °, the wavelength indicating the maximum value of the -1st order diffracted light is set to 439 nm within the visible light wavelength band. However, the wavelength showing the maximum value of the 0th-order diffracted light and the 1st-order diffracted light (particularly, the maximum value having a diffraction efficiency of 0.3 or more) is set to a wavelength smaller than 380 nm. Further, in each element element 21 according to this mode, as shown in FIG. 20, when the incident angle of the reproduced light is 30 °, both the 0th-order diffracted light, the 1st-order diffracted light and the -1st-order diffracted light have maximum values (particularly diffraction). The wavelength showing (maximum value of efficiency of 0.3 or more) is set to a wavelength smaller than 380 nm.

As described above, when the incident angle of the reproduced light is 0 °, the 0th-order diffracted light and the 1st-order diffracted light are mainly composed of light outside the visible light wavelength band, and the -1st-order diffracted light is mainly within the visible light wavelength band. It is composed of the light of. On the other hand, when the incident angle of the regenerated light is 30 °, the main light constituting each of the 0th-order diffracted light, the 1st-order diffracted light and the -1st-order diffracted light is overall as compared with the case where the incident angle of the regenerated light is 0 °. The 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light are mainly composed of light outside the visible light wavelength band.

Therefore, the optical image 100 reproduced from the reproduced light of the white light by the hologram structure 11 according to the present embodiment is as shown in FIGS. 21 to 22. That is, when the incident angle of the reproduced light is 0 °, as shown in FIG. 21, the blue -1st-order diffracted light image 100c is visibly reproduced, but the 0th-order diffracted light image 100a and the first-order diffracted light image 100b are reproduced. It is not reproduced as a visible light image (that is, it is reproduced as an invisible ultraviolet light image). When the incident angle of the reproduced light is 30 °, as shown in FIG. 22, the 0th-order diffracted light image 100a, the 1st-order diffracted light image 100b and the 1st-order diffracted light image 100c are both reproduced as visible light images. Not (that is, reproduced as an invisible light image of ultraviolet light), and the light image 100 is not visible as a whole. In reality, since these light images mainly composed of light outside the visible light wavelength band include some light within the visible light wavelength band, some observers may be able to visually recognize these light images. However, even in such a case, it is recognized as a very unclear light image.

As described above, also in this embodiment, as the incident angle of the reproduced light incident on each element element 21 is increased from 0 °, the reproduced light image 100 (that is, the 0th-order diffracted light image 100a, the first-order diffracted light image 100b and − The wavelength of the light constituting each of the first-order diffracted light images 100c) is shifted to the short wavelength side. Then, when the incident angle of the reproduced light becomes larger than a certain angle (a certain angle between 0 ° and 30 ° in this embodiment), the entire light image 100 becomes invisible (see FIG. 22). Therefore, by changing the inclination of the incident light incident on the hologram structure 11, the visible reproduction of at least a part of the optical image 100 (the -1st order diffracted light image 100c in this embodiment) is substantially turned ON / OFF. be able to.

As for such diffraction characteristics, for example, the refractive index of the hologram layer 1 is 1.5, the number of steps on the uneven surface 1a is set to 8, the depth per step is set to 128 nm, and the maximum depth is set to 896 nm. It can be realized by the reflective hologram structure 11 (that is, the reflective element element 21).

[Third implementation mode]
23 to 24 are graphs showing the diffraction characteristics of each element element 21 according to the third embodiment mode, and FIG. 23 shows a case where the incident angle of the regenerated light with respect to each element element 21 is 0 °. Indicates a case where the incident angle of the regenerated light with respect to each element element 21 is 30 °. In FIGS. 23 to 24, the horizontal axis indicates the wavelength (nm), the vertical axis indicates the diffraction efficiency, the wavelength distribution of the 0th-order diffracted light is indicated by “W0”, and the wavelength distribution of the 1st-order diffracted light is “W1”. Shown, the wavelength distribution of the -1st order diffracted light is indicated by "W-1".

25 to 26 show an example of an optical image 100 reproduced by the hologram structure 11 including each element element 21 according to the third embodiment, and FIG. 25 shows an incident angle of the reproduced light with respect to each element element 21. The light image 100 when the temperature is 0 ° is shown, and FIG. 26 shows the light image 100 when the incident angle of the regenerated light with respect to each element element 21 is 30 °. That is, the light image 100 shown in FIG. 25 is an optical image reproduced by the element element 21 exhibiting the diffraction characteristics of FIG. 23, and the light image 100 shown in FIG. 26 is reproduced by the element element 21 exhibiting the diffraction characteristics of FIG. 24. It is an optical image. In the light images 100 shown in FIGS. 25 to 26, the first-order diffracted light image 100b and the first-order diffracted light image 100c have the same shape (“F” shape in the illustrated example) and are reproduced point-symmetrically.

In each element element 21 according to this mode, as shown in FIG. 23, when the incident angle of the reproduced light is 0 °, the wavelength indicating the maximum value of the primary diffracted light is set to 642 nm, and the maximum value of the 0th diffracted light is set. The wavelength indicating the above is set to 702 nm, but the wavelength indicating the maximum value of the -1st order diffracted light (particularly the maximum value having a diffraction efficiency of 0.3 or more) is set to a wavelength larger than 780 nm (specifically, 802 nm). ing. Further, in each element element 21 according to this mode, as shown in FIG. 24, when the incident angle of the reproduced light is 30 °, the wavelength indicating the maximum value of the 0th-order diffracted light is set to 606 nm, and the maximum value of the 1st-order diffracted light is set. The wavelength indicating the value is set to 533 nm, and the wavelength indicating the maximum value of the -1st order diffracted light is set to 705 nm.

When the incident angle of the reproduced light is 0 °, the 0th-order diffracted light and the 1st-order diffracted light are mainly composed of light within the visible light wavelength band, and the -1st-order diffracted light is mainly outside the visible light wavelength band. It is composed of light. On the other hand, when the incident angle of the regenerated light is 30 °, the main light constituting each of the 0th-order diffracted light, the 1st-order diffracted light and the -1st-order diffracted light is overall as compared with the case where the incident angle of the regenerated light is 0 °. The 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light are mainly composed of light in the visible light wavelength band.

Therefore, the optical image 100 reproduced from the reproduced light of the white light by the hologram structure 11 according to the present embodiment is as shown in FIGS. 25 to 26. That is, when the incident angle of the reproduced light is 0 °, as shown in FIG. 25, the 0th-order diffracted light image 100a and the 1st-order diffracted light image 100b are reproduced as visible red light images, but the -1st-order diffracted light. The image 100c is not reproduced as a visible light image (ie, reproduced as an invisible infrared light image). Actually, since this light image mainly composed of light outside the visible light wavelength band contains some light within the visible light wavelength band, the light image may be visible depending on the observer. Even in such a case, it is recognized as a very unclear light image. On the other hand, when the incident angle of the reproduced light is 30 °, as shown in FIG. 26, the 0th-order diffracted light image 100a, the 1st-order diffracted light image 100b and the -1st-order diffracted light image 100c are both visible light images. It is reproduced, and a green first-order diffracted light image 100b and a red -1st-order diffracted light image 100c having the same shape at point-symmetrical positions centered on the red 0th-order diffracted light image 100a are reproduced.

As described above, also in this embodiment, as the incident angle of the reproduced light incident on each element element 21 is increased from 0 °, the reproduced light image 100 (that is, the 0th-order diffracted light image 100a, the first-order diffracted light image 100b and − The wavelength of the light constituting each of the first-order diffracted light images 100c) is shifted to the short wavelength side. Then, when the incident angle of the reproduced light becomes larger than a certain angle (a certain angle between 0 ° and 30 ° in this embodiment), the entire light image 100 can be visually recognized (see FIG. 26). Therefore, by changing the inclination of the incident light incident on the hologram structure 11, the visible reproduction of at least a part of the optical image 100 (particularly the -1st-order diffracted light image 100c) can be substantially turned ON / OFF. ..

As for such diffraction characteristics, for example, the refractive index of the hologram layer 1 is 1.5, the number of steps on the uneven surface 1a is set to 8, the depth per step is set to 234 nm, and the maximum depth is set to 1638 nm. It can be realized by the reflective hologram structure 11 (that is, the reflective element element 21).

[Manufacturing method of hologram structure 11]
Next, an example of a method for manufacturing the hologram structure 11 (particularly the uneven surface 1a) will be described. The method described below is only an example, and another method capable of appropriately producing the hologram structure 11 including the desired uneven surface 1a can be adopted. Further, the manufacturing method described below can be applied to both the reflective hologram structure 11 (see FIG. 3) and the transmissive hologram structure 11 (see FIG. 4).

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 hologram structure 11 (particularly the uneven surface 1a) corresponding to the two-dimensional Fourier transformed image is produced 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. 7) 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 hologram structure 11 (particularly the hologram layer 1)). Is determined by. For example, as a reflective hologram structure 11 for reproducing a blue light image, a hologram structure 11 in which the number of steps of the uneven surface 1a is four and the uneven surface 1a has an optical path length of 330 nm per step is produced. be able to. The reflective hologram structure 11 and the transmissive hologram structure 11 each have a unique concave-convex surface 1a depth structure, and even when trying to realize the same diffraction characteristics, for example, the hologram structure The specific value of the depth of the uneven surface 1a of the body 11 differs between the reflective type and the transmissive type.

The manufacturing apparatus of the hologram structure 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 hologram structure 11 (particularly the uneven surface 1a) described above 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 hologram structure 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 hologram structure 11 having the desired uneven surface 1a.

In the case of the reflective hologram structure 11, a reflective layer 2 (for example, a reflective layer composed of Al or a reflective layer composed of ZnS or TiO ₂ (high refractive index layer)) is further formed on the uneven surface 1a by the manufacturing apparatus. It may be formed. However, in the case of the hologram structure 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.

[Relationship between the depth of the uneven surface and the peak wavelength of the diffracted light]
When the number of steps of the concave-convex surface 1a of the hologram structure 11 is represented by N, the optical path length modulated per step of the concave-convex surface 1a is represented by l, and the natural number is represented by m, the peak wavelength λ of the diffracted light is as follows. It is expressed by the formula of.

λ = N · l / (mN ± 1)

For example, when either the first-order diffracted light or the first-order diffracted light of the hologram structure 11 has only one peak wavelength λ in the visible light wavelength band for an arbitrary natural number m, white light is incident. Even in this case, it is possible to realize the hologram structure 11 capable of reproducing an optical image in a single color. For example, when the optical path length l is 330 nm and the number of steps N of the uneven surface 1a is 4, λ = 1320 / (4 m ± 1) holds. Therefore, for m = 1, λ = 440 nm and 264 nm, for m = 2, λ = 188 nm and 146 nm, and for m = 3, λ = 120 nm and 101 nm. When m is 4 or more, the peak wavelength λ becomes a smaller value. Of these, the peak wavelength λ included in the visible light wavelength band is only λ = 440 nm when m = 1. Therefore, when the hologram structure 11 in which the number of stages N = 4 of the uneven surface 1a and the optical path length per stage is l = 330 nm is used, the observer 50 can visually recognize the light having a wavelength of 440 nm and a wavelength in the vicinity thereof. It is possible to reproduce a possible monochromatic optical image.

The color (wavelength band) of the light image reproduced by the hologram structure 11 described above is assumed to be used in an air environment having a refractive index of 1.0. Further, when the observer observes the light image 100 reproduced by the above-mentioned reflective hologram structure 11, the uneven surface 1a of the hologram layer 1 is arranged on the opposite side to the observer, and the observer passes the uneven surface 1 through the hologram layer 1. The structure (that is, the uneven surface 1a) will be observed. When the uneven surface 1a of the hologram layer 1 is arranged on the same side as the observer, the reflected image from the hologram structure 11 observed by the observer is due to the light reflected on the surface without passing through the hologram layer 1. It is composed. For example, when the uneven surface 1a is formed on the surface of the card-shaped hologram holder 10, the observer observes the light reflected by the uneven surface 1a without passing through the hologram layer 1. In such a case, the optical path length based on the refractive index of the medium on the observer side of the hologram layer 1, for example, the refractive index of air 1.0, rather than the refractive index of the hologram layer 1, is one step of the uneven surface 1a. It is necessary to set the hit depth. Therefore, the observer can observe the desired image by designing the structure of the uneven surface 1a while assuming that the refractive index of the hologram layer 1 (hologram structure 11) is 1.0 of the refractive index of air. be. Specifically, when the refractive index of air is 1.0 and the depth of the uneven surface 1a per step is 165 nm, the optical path length of the uneven surface 1a per step is 330 nm. In this case, since the uneven surface 1a has a four-step depth structure, the hologram structure 11 exhibits the maximum diffraction efficiency in the blue wavelength band and reproduces a blue light image.

[Second Embodiment]
The hologram structure 11 includes at least two or more types of element elements 21, and at least one or more of these at least two or more types of element elements 21 is the same as the element element 21 according to the first embodiment described above. It may be configured.

FIG. 27 is a conceptual diagram showing an example of the planar structure of the transmissive hologram structure 11 according to the second embodiment. FIG. 28 is a schematic diagram for explaining the light image 100 reproduced by the transmissive hologram structure 11 of FIG. 27. The hologram structure 11 shown in FIGS. 27 and 28 includes a plurality of first element elements 21a and a plurality of second element elements 21b arranged in a checkered pattern. For example, the plurality of first element elements 21a have an uneven surface 1a that enables reproduction of the light image 100 of the blue letter "O", and the plurality of second element elements 21b have a red "K". It has an uneven surface 1a that makes it possible to reproduce the light image 100 of the characters "." It should be noted that this is based on the case where the incident angle of the reproduced light is 0 °. In this case, when white light is incident on the hologram structure 11 at an incident angle of 0 °, the hologram structure 11 reproduces a blue “O” and a red “K” as shown in FIG. 28. As described above, the hologram structure 11 of the present modification can visually reproduce the two types of monochromatic light images 100.

In the hologram structure 11 shown in FIGS. 27 and 28, at least one of the first element element 21a and the second element element 21b is the element element of the hologram structure 11 described in the first embodiment described above. It may be configured in the same manner as 21. That is, at least one of the first element element 21a and the second element element 21b has a wavelength distribution of the diffraction efficiency of the first-order diffracted light and a wavelength distribution of the diffraction efficiency of the first-order diffracted light of 380 nm. The maximum value of the diffraction efficiency in at least one of the wavelength band of 600 nm or more and the wavelength band of 780 nm or more and 1200 nm or less (for example, when the number of steps of the concave-convex structure of the hologram structure 11 is two, the diffraction efficiency is 0.15. It may have the above maximum value, or the maximum value of diffraction efficiency of 0.3 or more when the number of stages of the uneven structure is 3 or more. In this case, at least a part of the reproduced light image 100 can be erased or appear as the angle of incidence of the reproduced light on the hologram structure 11 increases.

For example, only one of the first element element 21a and the second element element 21b may be configured in the same manner as the element element 21 of the hologram structure 11 described in the first embodiment described above. In this case, at least a part of the "O" light image 100 and the "K" light image 100 is visually disappeared or appears by changing the incident angle of the reproduced light with respect to the hologram structure 11. Can be done. Further, when both the first element element 21a and the second element element 21b are configured in the same manner as the element element 21 of the hologram structure 11 described in the first embodiment described above, the reproduced light with respect to the hologram structure 11 By changing the incident angle of the light image 100, at least a part of both the “O” and “K” light images 100 can be visually disappeared or appear.

At least one of the first element element 21a and the second element element 21b has the wavelength distribution of the diffraction efficiency of the first-order diffracted light and the -1st-order diffracted light, similarly to the element element 21 of the first embodiment described above. Only one of the wavelength distributions of diffraction efficiency has a maximum value of diffraction efficiency (for example, the number of steps of the concave-convex structure of the hologram structure 11 is two steps) in at least one of the wavelength band of 380 nm or more and 600 nm or less and the wavelength band of 780 nm or more and 1200 nm or less. In some cases, the diffraction efficiency may have a maximum value of 0.15 or more, and when the number of steps of the uneven structure is 3 or more, the diffraction efficiency may have a maximum value of 0.3 or more). Both the diffraction efficiency wavelength distribution of the folding light and the diffraction efficiency wavelength distribution of the -1st order diffracted light are the maximum values of the diffraction efficiency (for example, hologram) in at least one of the wavelength band of 380 nm or more and 600 nm or less and the wavelength band of 780 nm or more and 1200 nm or less. When the number of steps of the uneven structure of the structure 11 is 2, the maximum value of the diffraction efficiency is 0.15 or more, and when the number of steps of the uneven structure is 3 or more, the maximum value of the diffraction efficiency is 0.3 or more. ) May have.

In the example shown in FIG. 28, the first element element 21a and the second element element 21b reproduce the independent optical image 100, but the optical image reproduced by the first element element 21a and the second element The light image reproduced by the element 21b may overlap at least in part. In this case, the light image of the overlapping portion has a color in which the color of the light image reproduced by the first element element 21a and the color of the light image reproduced by the second element element 21b are mixed.

FIG. 29 is a conceptual diagram showing another example of the planar structure of the transmissive hologram structure 11 according to the second embodiment. FIG. 30 is a schematic diagram for explaining an optical image 100 reproduced by the transmissive hologram structure 11 of FIG. 29. The hologram structure 11 shown in FIGS. 29 and 30 includes a plurality of first element elements 21a, a plurality of second element elements 21b, and a plurality of third element elements 21c arranged in a checkered pattern. For example, the plurality of first element elements 21a have an uneven surface 1a capable of reproducing the blue light image 100, and the plurality of second element elements 21b reproduce the red light image 100. It has an uneven surface 1a that enables it, and the plurality of third element elements 21c have an uneven surface 1a that enables the reproduction of the green light image 100. It should be noted that this is based on the case where the incident angle of the reproduced light is 0 °. In this case, the hologram structure 11 can reproduce not only the red, blue, and green light images 100, but also the light images 100 of other colors by superimposing two or more of these light images 100. .. For example, as shown in FIG. 30, by superimposing and reproducing the light image 100 of the red circle, the light image 100 of the green circle, and the light image 100 of the blue circle, the portion where the red circle and the green circle overlap is a yellow light image. It becomes 100, the part where the green circle and the blue circle overlap becomes the light blue light image 100, the part where the blue circle and the red circle overlap becomes the purple light image 100, and the part where the red circle, the green circle and the blue circle overlap becomes 100. It becomes a white light image 100.

FIG. 31 is a schematic diagram for explaining an optical image 100 reproduced by another example of the transmissive hologram structure 11 according to the second embodiment. Each element element 21 can reproduce an optical image with a color having an arbitrary gradation, and the first element element 21a for reproducing a red optical image and the second element for reproducing a blue optical image. Each of the element 21b and the third element element 21c that reproduces a green light image can include a plurality of types of element elements having different gradations. Further, even when each element element 21 is designed based on an original image having an arbitrary gradation, it is possible to reproduce an optical image with a color having an arbitrary gradation. In these cases, the hologram structure 11 can also reproduce the full-color optical image 100 as shown in FIG. 31 when white light is incident.

In the hologram structure 11 shown in FIGS. 29 to 31, at least one of the first element element 21a, the second element element 21b, and the third element element 21c is described in the above-described first embodiment. It may be configured in the same manner as the element element 21 of the hologram structure 11 formed above. That is, at least one of the first element element 21a, the second element element 21b, and the third element element 21c has a wavelength distribution of the diffraction efficiency of the first-order diffracted light and a wavelength distribution of the diffraction efficiency of the -1st-order diffracted light. When at least one of them has a maximum value of diffraction efficiency (for example, the number of stages of the concave-convex structure of the hologram structure 11 is two) in at least one of the wavelength band of 380 nm or more and 600 nm or less and the wavelength band of 780 nm or more and 1200 nm or less. May have a maximum value of diffraction efficiency of 0.15 or more, and a maximum value of diffraction efficiency of 0.3 or more when the number of stages of the concave-convex structure is 3 or more. In this case, at least a part of the reproduced light image 100 can be erased or appear as the angle of incidence of the reproduced light on the hologram structure 11 increases.

In the hologram structure 11 shown in FIGS. 27 and 29 described above, the types of element elements 21 arranged adjacent to each other in both the vertical direction and the horizontal direction are different from each other, but the arrangement mode of the plurality of types of element elements 21 is different. There is no particular limitation. For example, the hologram structure 11 may include a plurality of types of element elements 21 arranged in a stripe shape, and the types of element elements 21 arranged adjacent to each other in one of the vertical direction and the horizontal direction may be included. Although different, the types of element elements 21 arranged adjacent to each other may be the same for the other. Further, a plurality of types of element elements 21 may be arranged depending on the arrangement mode in which the above-mentioned checkered pattern arrangement and the striped arrangement are combined.

[Use]
The usage mode and use of the hologram structure 11 (light modulation element) and the hologram holder 10 described above 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 hologram structure 11 (light modulation element) can be applied to the following objects. When the hologram holder 10 is used as an information recording medium, various information such as passports, ID cards, banknotes, credit cards, cash vouchers, gift certificates, other tickets, official documents, personal information and confidential information are recorded. The optical modulation element and the information recording medium according to the present invention can be applied to other media, other media having monetary value, and the like, and their counterfeiting 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 hologram holder 10, the base material that holds the hologram structure 11 (see the symbol “4” in FIG. 2) can be composed of, for example, paper, resin, metal, synthetic fiber, or a combination thereof. When an opening (see the symbol “4a” in FIG. 2) is formed in the base material, the entire area of the opening may be covered with the hologram structure 11, or only a part of the opening may be covered with the hologram structure. Body 11 may be placed. The hologram structure 11 may be configured as a transparent member in appearance. For example, a point light source is arranged on the back surface side of the hologram holder 10 that holds the transmissive hologram structure 11, and the observer observes the point light source through the hologram structure 11 from the front surface side of the hologram holder 10. The observer can visually recognize the security information recorded in the hologram structure 11. This security information can be used, for example, for determining the authenticity of the hologram holder 10.

Further, the light modulation element according to the present invention can be applied to the above-mentioned hologram holder 10 by any method. For example, unevenness formation, transfer, sticking, and sandwiching on the surface of the hologram holder 10 can be applied. Alternatively, the light modulation element according to the present invention can be held by an arbitrary object (that is, the hologram holder 10) by using a technique such as embedding. Therefore, the hologram structure 11 may be formed by using a part of the members constituting the hologram holder 10, or the hologram structure 11 may be additionally provided to the hologram holder 10.

Further, the above-mentioned hologram structure 11 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 unsaturated polyester resin, acrylic-modified 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 polycarbonate (PC), polyethylene terephthalate (PET), glycol-modified polyethylene terephthalate (PET-G), polyvinyl chloride (PVC), acrylic acid ester resin, and acrylamide. Examples thereof include resins, nitrocellulose resins, and polystyrene resins. 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 the base material 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. It is preferable to do so. 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 hologram structure 11.

[Other variants]
The hologram structure 11 used in each of the above-described embodiments and modifications is composed of a plurality of element elements 21 as shown in FIG. 5, but the hologram structure 11 is composed of a single element element 21. You may be.

Further, the plan view size and the plan view shape of each element element 21 are not particularly limited, and each element element 21 may have an arbitrary size and shape. For example, the plan view shape of each element element 21 can be a quadrangle such as a square, a rectangle, a trapezoid, another polygonal shape (for example, a triangle, a pentagon, a hexagon, etc.), a perfect circle, an ellipse, another circular shape, a star shape, or a star shape. It may have a heart shape or the like, and the hologram structure 11 may have two or more types of element elements 21 having a plan view shape.

Further, an arbitrary functional layer may be added to the hologram structure 11, and the hologram structure 11 may be covered with, for example, a transparent thin-film deposition layer. In particular, by providing a transparent vapor-deposited layer having no gloss, it is possible to prevent the hologram structure 11 from having gloss and conceal the hologram structure 11. From the viewpoint of hiding the hologram structure 11, the total light transmittance of such a transparent vapor-deposited layer is preferably 80% or more, and more preferably 90% or more. Further, in the reflective hologram structure 11, the hologram structure 11 can be covered with a reflective vapor-deposited layer (see the reflective layer 2 in FIG. 2). As constituent materials of the reflective vapor deposition layer, for example, Mg, Al, Ti, Cr, Fe, Co, Ni, Cu, Zn, Ga, Ge, Se, Rb, Pd, Ag, Cd, In, Sn, Sb, Te, Examples include metals such as Au, Pb, and Bi. Further, examples of the constituent material of the transparent thin-film deposition layer include oxides and sulfides of the above metals such as _{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 surface 1a) can be appropriately set from the viewpoint of desired reflectivity, color tone, design, application, etc., and may be in the range of, for example, 50 Å to 1 μm. It is preferable, and above all, 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.

The present invention is not limited to the above-described embodiments and modifications. 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 Concavo-convex surface 2 Reflective layer 4 Base material 4a Opening 10 Hologram holder 11 Hologram structure 21 Element element 50 Observer 51 Light source 51a Light source 51b Light source 100 Light image 100a 0th-order diffracted light image 100b Primary diffracted light image 100c- Primary diffracted light image

Claims (6)

It is equipped with an element element that reproduces an optical image by modulating the phase of the incident reproduced light.
The element element has an uneven surface and has an uneven surface.
At least one of the wavelength distribution of the diffraction efficiency of the primary diffracted light and the wavelength distribution of the diffraction efficiency of the -1st diffracted light for the element element is a wavelength band of 380 nm or more and 600 nm or less and a wavelength band of 780 nm or more and 1200 nm or less. at least one, have a maximum value of the diffraction efficiency,
A light modulation element having a full width at half maximum with respect to the maximum value of the diffraction efficiency included in at least one of the wavelength distribution of the diffraction efficiency of the first-order diffracted light and the wavelength distribution of the diffraction efficiency of the first-order diffracted light. One of the wavelength distribution of the diffraction efficiency of the primary diffracted light and the wavelength distribution of the diffraction efficiency of the -1st diffracted light for the element element is at least one of the wavelength band of 380 nm or more and 600 nm or less and the wavelength band of 780 nm or more and 1200 nm or less. The optical modulation element according to claim 1, wherein one has a maximum value of the diffraction efficiency, and the other has a maximum value of the diffraction efficiency in a wavelength band larger than 600 nm and smaller than 780 nm. The light modulation element according to claim 1 or 2 , wherein the element element is a Fourier transform hologram. An information recording medium including the light modulation element according to any one of claims 1 to 3. The information recording medium according to claim 4 , wherein the optical image represents information based on at least one of characters, symbols, and patterns. Further provided with a substrate having a predetermined size opening,
The information recording medium according to claim 4 or 5 , wherein at least a part of the light modulation element is arranged at a position corresponding to the opening.

Images