JP2019049621A - Light modulation element and information recording medium - Google Patents

Abstract

To efficiently form an image reproduction structure for reproducing an image within a limited area in a light modulation element, where the light modulation element is used as, for example, an information recording medium.SOLUTION: A light modulation element 20 includes a first image reproduction structure 30 for reproducing a first image I1 with 0-th order reflected light, and a second image reproduction structure 40 for reproducing a second image I2 with diffracted light. The first image reproduction structure 30 and the second image reproduction structure 40 are efficiently disposed within a planar region of the light modulation element 20 by being formed on top of each other in a common planar region.SELECTED DRAWING: Figure 10

Description

  The present disclosure relates to a light modulation element for reproducing an image, and an information recording medium including the light modulation element.

  Conventionally, light modulation elements capable of reproducing an image are widely used in various fields, for example, for the purpose of entertainment and security. For use for entertainment purposes, it is useful to reproduce an image that has a distinctive character. On the other hand, for use for security purposes as disclosed in Patent Document 1, for example, it is required to make it possible to reproduce an image that is easy to confirm authenticity and hard to forge. In other words, in the case where the light modulation element is used for security purposes, it is preferable that both the authenticity determination function and the forgery prevention function be excellent.

  In order to satisfy these requirements, a complex structure for reproducing an image is to be provided within the limited area of the light modulation element. However, the area of the light modulation element is limited. Therefore, how to efficiently form an image reproduction structure for reproducing an image in the light modulation element becomes a problem.

Unexamined-Japanese-Patent No. 08-184273

  The present disclosure has been made in consideration of the above points, and has an object to efficiently provide an image reproduction structure for reproducing an image within a limited area.

The light modulation device according to the present disclosure is
A first image reproduction structure for reproducing a first image by a zero-order reflected light;
And a second image reproducing structure for reproducing a second image by diffracted light.

  In the light modulation element according to the present disclosure, the first image reproduction structure and the second image reproduction structure may be provided in a common planar region.

In the light modulation device according to the present disclosure,
The first image reproduction structure has a concavo-convex shape including concave and convex portions alternately arranged in one direction,
The recess and the protrusion may extend linearly in a direction not parallel to the one direction.

In the light modulation device according to the present disclosure,
The first image reproduction structure is provided in a first array area and a second array area,
The first image reproduction structure has a concavo-convex shape including concave portions and convex portions alternately arranged in a certain direction in the first array region, and the concave portions and the concave portion in the first array region. The convex portion linearly extends in a direction not parallel to the one direction, and
The first image reproduction structure has a concavo-convex shape including concave and convex portions alternately arranged in the other direction not parallel to the one direction in the second array region, and the second array In the region, the recess and the protrusion may extend linearly in a direction not parallel to the other direction.

  In the light modulation element according to the present disclosure, the second image reproduction structure may be a hologram having a concavo-convex shape.

  In the light modulation element according to the present disclosure, the concavo-convex shape of the second image reproduction structure may be formed so as to overlap with the concavo-convex shape of the first image reproduction structure in common.

  In the light modulation element according to the present disclosure, the second image reconstruction structure may be a binary or higher value phase Fourier transform hologram.

In the light modulation device according to the present disclosure,
The second image reproduction structure includes one phase region and the other phase region divided by binarizing phase information of a Fourier transform image of the second image,
The arrangement of the concave portions and the convex portions of the first image reproduction structure is a position of the concave portions and the convex portions at a position which is a boundary between the one phase region and the other phase region of the second image reproduction structure. It may be shifted by a length which is less than the arrangement pitch.

The light modulation device according to the present disclosure is
A first element area and a second element area arranged in two dimensions;
The first image reproduction structure is provided in the first element region,
The second image reproduction structure may be provided in the second element region.

  In the light modulation element according to the present disclosure, the second reproduction structure may be a phase type hologram, and may be provided offset from the first reproduction structure in the thickness direction.

  In the light modulation element according to the present disclosure, the second reproduction structure may be a volume hologram, and may be provided offset from the first reproduction structure in the thickness direction.

  An information recording medium according to the present disclosure includes any of the light modulation elements according to the present disclosure described above.

  According to the present disclosure, an image reproduction structure for reproducing an image can be efficiently formed in a limited area.

FIG. 1 is a view for explaining an embodiment, and is a plan view showing an information recording medium including a light modulation element. FIG. 2 is a cross-sectional view taken along line II-II of FIG. FIG. 3 is a view for explaining a first image reproducing structure that can be included in the light modulation element shown in FIG. 1, and shows a reproduced image by the first image reproducing structure observed from a predetermined direction. There is. FIG. 4 is a diagram corresponding to FIG. 3 and shows a reconstructed image by the first image reconstruction structure observed from a direction different from that in FIG. 3. FIG. 5 is a view showing a first image reproduction structure in the cross section of the light modulation element corresponding to FIG. FIG. 6 is a view for explaining a second image reproducing structure that can be included in the light modulation element shown in FIG. 1, and shows an image reproduced by the second image reproducing structure formed of a reflection type hologram. ing. FIG. 7 is a view corresponding to FIG. 6 and shows an image reproduced by the second image reproducing structure formed of a reflection type hologram. FIG. 8 is a plan view showing the light modulation element, and is a view for explaining element regions of the light modulation element. FIG. 9 is a view showing a second image reproduction structure in the cross section of the light modulation element corresponding to FIG. FIG. 10 is a view showing a first specific example of the light modulation element in a cross section corresponding to FIG. FIG. 11 is a plan view showing the light modulation element shown in FIG. FIG. 12 is a cross-sectional view showing a first image reproduction structure incorporated in the light modulation element shown in FIG. FIG. 13 is a cross-sectional view showing a second image reproduction structure incorporated in the light modulation element shown in FIG. FIG. 14 is a view showing a second specific example of the light modulation element in a cross section corresponding to FIG. FIG. 15 is a plan view showing the light modulation element shown in FIG. FIG. 16 is a diagram for explaining the third specific example of the light modulation device, and is a plan view showing the light modulation device. FIG. 17 is a view corresponding to FIG. 2 and showing a modified example of the light modulation element. FIG. 18 is a view corresponding to FIG. 2 and showing another modification of the light modulation element. FIG. 19 is a view corresponding to FIG. 2 and showing still another modification of the light modulation element.

  Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the drawings attached to the present specification, for the sake of easy illustration and understanding, the scale, the dimensional ratio in the vertical and horizontal directions, etc. are appropriately changed from those of the actual one and exaggerated.

  FIGS. 1-19 is a figure for demonstrating one Embodiment by this indication, and its specific example. FIG. 1 is a plan view showing an information recording medium including a light modulation element. FIG. 2 is a cross-sectional view of the information recording medium of FIG. 1 at a position including the light modulation element.

  In the present embodiment, the light modulation element 20 has a first image reproduction structure 30 for reproducing the first image I1, and a second image reproduction structure 40 for reproducing the second image I2. The first image reproduction structure 30 can reproduce the first image I1 by the zero-order reflected light. The second image reproduction structure 40 can reproduce the second image I2 by diffracted light, mainly by first order diffracted light. The first image reconstruction structure 30 and the second image reconstruction structure 40 are typically structures in the nm order.

  The use form and application of the light modulation element 20 are not particularly limited, and for example, it is used for the purpose of entertainment and security. The light modulation element 20 can typically be applied to the information recording medium 10 in which some information is recorded. As a specific example of the information recording medium 10, exemplify a medium on which various information such as personal information and confidential information such as a bill, an ID card, a passport, a cash voucher, a ticket, and a public document are recorded Can.

  The light modulation element 20 applied to the information recording medium 10 displays a character image, characters, symbols, patterns, etc. related to the items recorded in the information recording medium 10 as a first image I1 or a second image I2. You may do so. In such an example, the light modulation element 20 can provide the information recording medium 10 with designability and entertainment. In addition, the light modulation element 20 applied to the information recording medium 10 displays characters, symbols, patterns, etc. representing the authenticity of the information recording medium 10 as the first image I1 or the second image I2, one specific example It is also possible to display "OK" or "genuine" as In this example, the light modulation element 20 can exhibit the function of directly displaying the authenticity of the information recording medium 10. In particular, in the present embodiment, the light modulation element 20 is recorded with the first image I1 and the second image I2 that can be observed according to different principles. The light modulation element 20 can make the authenticity determination easy and accurate by its authenticity display function, and can also exhibit an excellent forgery prevention function.

  The light modulation element 20 can be typically formed as a sheet-like member as in the illustrated example. In this case, the light modulation element 20 includes the planar direction and the normal direction. The plane direction is a direction along a plane that coincides with the light modulation element 20 when the light modulation element 20 is viewed as a whole and globally, and the normal direction is a direction orthogonal to the plane. It is Further, the two-dimensional direction in the following description corresponds to the plane direction of the light modulation element 20.

  Hereinafter, the information recording medium 10 and the light modulation element 20 according to the present embodiment will be described with reference to the illustrated specific example.

  1 and 2 show an ID certificate as a specific example of the information recording medium 10. Examples of the ID card to which the light modulation element 20 is applied include a national ID card, a driver's license, a membership card, an employee card, a student card and the like. In the example shown in FIGS. 1 and 2, the information recording medium 10 has a medium body 11 for holding information, and a light modulation element 20 supported by the medium body 11. The illustrated medium body 11 is provided with information about the ID in a visually recognizable manner by characters, photographs, and the like. Examples of the base member 12 to which information is given in the medium body 11 include paper, resin, metal and synthetic fiber. In the example shown in FIG. 2, the light modulation element 20 is bonded to the medium body 11 via the bonding layer 13. However, the present invention is not limited to this example, and the light modulation device 20 can be held on the base member 12 of the medium body 11 by various techniques, for example, using techniques such as transfer, paste, sandwich, or embedding. As another specific example, an opening or a recess may be formed in the base member 12 and the light modulation element 20 may be fixed in the opening or the recess.

  In the example shown in FIG. 2, the light modulation element 20 has the uneven surface 25 in accordance with the first image reproducing structure 30 and the second image reproducing structure 40 having the uneven shapes 35 and 45. In an example in which both the first image reproducing structure 30 and the second image reproducing structure 40 have the concavo-convex shapes 35, 45, the first image reproducing structure 30 and the second image reproducing structure 40 are collectively formed by resin molding. Can. More specifically, by molding and curing an ionizing radiation curable resin applied on a resin base 22a such as polyethylene terephthalate, as shown in FIG. 2, the base 22a and the base 22a are supported. The light modulation element 20 including the uneven layer 22b can be manufactured. The light modulation element 20 including the base 22a and the concavo-convex layer 22b can also be manufactured by subjecting a thermoplastic resin provided on the resin base 22a such as polyethylene terephthalate to hot pressing and cooling. By collectively forming the first image reproduction structure 30 and the second image reproduction structure 40 by resin molding, it is advantageous in terms of labor and cost in mass production of the light modulation element 20.

  Further, in the example shown in FIG. 2, as the first image reproduction structure 30 forms the images I1 and I2 by the reflected light, the light modulation element 20 includes the element body 22 including the base 22a and the concavo-convex layer 22b. In addition to the above, a reflective layer 23 covering the element body 22 is provided. The reflective layer 23 is provided along the uneven surface of the element body 22. The thickness of the reflective layer 23 is, for example, not less than 20 nm and not more than 200 nm, and is such that the uneven surface of the element main body 22 is not backfilled. As a result, the uneven surface 25 of the light modulation element 20 is formed by the reflective layer 23. The reflective layer 23 is formed as a layer made of a material having a high refractive index, for example, a deposited film of zinc sulfide ZnS or titanium oxide TiO2. However, the reflective layer 23 is not an essential layer, and the one obtained by omitting the reflective layer 3 from the example of FIG. 1 is also included in the light modulation element of the present embodiment.

  Next, the first image reproduction structure 30 will be described mainly with reference to FIGS. 3 to 5. FIG. 3 shows a first image I1 observed when the light modulation element 20 is observed from a predetermined direction. FIG. 4 is a view showing a first image I1 observed when the light modulation element 20 is observed from a direction not parallel to the predetermined direction. 5 is a cross-sectional view showing an example of the first image reproduction structure 30 in the same cross section as FIG.

  As described above, the first image reproduction structure 30 is a structure of nm order, and can reproduce the first image I1 by the zero-order reflected light. The first image reproduction structure 30 has a first image concavo-convex shape 35 including a first image convex portion 36 and a first image concave portion 37 alternately arranged in one direction dx. The first image convex portion 36 and the first image recess 37 linearly extend in a direction dy not parallel to the one direction dx. Such a first image reconstruction structure 30, also referred to as a color switch, can change the color of the observed image I1 depending on the viewing direction. That is, by changing the first image reproduction structure 30, the color of the first image I1 changes. The arrangement pitch P1 of the first image convex portion 36 and the first image concave portion 37 in the one direction dx can be, for example, 200 nm or more and 500 nm or less. The height difference between the first image convex portion 36 and the first image concave portion 37, in other words, the depth D1 of the first image concave and convex shape 35 can be, for example, 70 nm or more and 100 nm or less. Further, the width W1a of the first image convex portion 36 and the width W1b of the first image concave portion 37 coincide with each other or substantially coincide with each other in the certain direction dx.

  In such a first image reproduction structure 30, only light of a predetermined wavelength range within the visible light wavelength range is specularly reflected when observed from one direction. On the other hand, light in other wavelength ranges within the visible light wavelength range travels in a direction different from the regular reflection direction by the diffraction at the first image concavo-convex shape 35. As a result, it is possible to observe the first image I1 having the same pattern as the area in which the first image concavo-convex shape 35 is provided, in a color corresponding to the wavelength range of the specularly reflected light. Then, by changing the observation direction of the light modulation element 20, more specifically, when the light modulation element 20 is rotated about the normal direction of the light modulation element 20 and observed, the light is diffracted by the first image uneven shape 35. The wavelength range of the specularly reflected light changes. As a result, the first image I1 can be observed in different colors, or the regular reflection wavelength range is out of the visible light wavelength range, and the first image I1 can not be observed. According to such a first image reproducing structure 30, it is possible to perform display of the first image I1 rich in surprise by a simple procedure, and to improve the design of the light modulation element 20. Moreover, the authenticity determination function of the light modulation element 20 can also be improved.

  By the way, in the example shown in FIG. 3 and FIG. 4, the light modulation element 20 includes the first array region 30 a and the second array region 30 b. In the illustrated example, in particular, the light modulation element 20 is divided into a first array area 30a and a second array area 30b. That is, the illustrated light modulation element 20 is divided into a first array region 30a and a second array region 30b. Each position in the light modulation element 20 belongs to one of the first array region 30a and the second array region 30b.

  The first image reproduction structure 30 includes a first image first convex portion 36a and a first image first concave portion 37a alternately arranged in the first direction d1 in the first array region 30a. It has an uneven shape 35a. In the first array region 30a, the first image first convex portion 36a and the first image first concave portion 37a linearly extend in a direction not parallel to the first direction d1. In the illustrated example, the first image first convex portion 36a and the first image first concave portion 37a linearly extend in a second orientation d2 orthogonal to the first direction d1.

  In addition, the first image reproducing structure 30 includes a first image second convex portion 36b and a first image second concave portion 37b alternately arranged in another direction not parallel to the first direction d1 in the second array region 30b. And the first image second concavo-convex shape 35b. In the second array region 30b, the first image second convex portion 36b and the first image second concave portion 37b linearly extend in a direction non-parallel to the other direction. In particular, in the illustrated example, the first image second convex portion 36b and the first image second concave portion 37b are arranged in a second orientation d2 orthogonal to the first direction d1. Further, the first image second convex portion 36 b and the first image second concave portion 37 b linearly extend in the first direction d 1 orthogonal to the second orientation d 2.

  In the example shown in FIGS. 3 and 4, the first array area 30 a is an area of the same pattern as the letter D of the alphabet. The second array area 30b is a background area which is an area other than the area D formed by the first array area 30a. In the first image first concavo-convex shape 35a, the arrangement pitch of the first image first convex portion 36a and the first image first concave portion 37a is 370 nm, and the first image first convex portion 36a and the first image first concave portion 37a The height difference is 100 nm. Similarly, in the first image second concavo-convex shape 35b, the arrangement pitch of the first image second convex portion 36b and the first image second concave portion 37b is 370 nm, and the first image second convex portion 36b and the first image second The height difference of the recess 37 b is 100 nm. In such a first image reproduction structure 30, in the observation of FIG. 3, the letter D to be the first array area 30a is observed in green, and the background to be the second array area 30b is observed in red. On the other hand, in the observation of FIG. 4, the letter D to be the first array area 30a is observed in red, and the background to be the second array area 30b is observed in green.

  Next, the second image reproduction structure 40 will be described mainly with reference to FIGS. 6 to 9.

  As described above, the second image reproduction structure 40 can reproduce the second image I2 by the diffracted light. Such a second image reconstruction structure 40 can typically be a hologram. In the present embodiment, the hologram forming the second image reproduction structure 40 is not particularly limited. Therefore, the second image reconstruction structure 40 may be a phase hologram or an amplitude hologram. In addition, the second image reproduction structure 40 may be a reflection type hologram or a transmission type hologram. Furthermore, the second image reconstruction structure 40 may be a volume hologram or a computer generated hologram (CGH). As a specific example, the second image I2 can be reproduced in a three-dimensional space by using the computer-generated holograms disclosed in Japanese Patent Application Laid-Open Nos. 2000-214750 and 2008-191540 as the second image reproduction structure 40. The second image reproduction structure 40 can also be a diffraction grating having a pixel arrangement disclosed in, for example, JP-A-6-337622.

  In the examples shown in FIGS. 6 to 9, the second image reproduction structure 40 is a hologram having a concavo-convex shape (also referred to as “a second image concavo-convex shape”) 45. The second image reproduction structure 40 is a structure on the nm order. The second image reconstruction structure 40 that reproduces the second image I2 by the second image concavoconvex shape 45 is as described above in combination with the first image reconstruction structure 30 that reproduces the first image I1 by the first image concavoconvex shape 35 In addition, it is convenient in terms of labor and cost in mass production.

  Particularly in the examples shown in FIGS. 6 to 9, the second image reconstruction structure 40 is constituted by a phase modulation type hologram that modulates the phase of the incident light to reproduce the second image I2, and in particular, it is a Fourier transform. It is constituted by a hologram. The Fourier transform hologram is a hologram produced by recording wavefront information of a Fourier transform image of an original image to be reproduced, and functions as a so-called Fourier transform lens. In particular, a phase modulation type Fourier transform hologram is a hologram having a concavo-convex surface 44 manufactured by recording the phase information of the Fourier transform image as a multi-leveled depth on the medium, and diffraction based on the optical path length difference of the medium The phenomenon is used to reproduce the light image of the original image from the reproduction light. This Fourier transform hologram is advantageous in that, for example, a desired image, that is, an original image can be reproduced with high accuracy, and can be produced relatively easily.

  The second image reproduction structure 40 has an uneven surface 44 formed by the second image uneven shape 45. When light is incident on the concavo-convex surface 44 of the second image reproduction structure 40 from a point light source or a parallel light source, a second image I2 corresponding to the concavo-convex pattern of the second image concavo-convex shape 45 is reproduced. This type of image reproduction structure does not require a screen or the like for projecting a light image, and reproduces the light image particularly well when light from a specific light source such as a point light source or a parallel light source is incident. It can be conveniently and widely used for design applications, security applications, or other applications. The image that can be reproduced by such a second image reproduction structure 40 is not particularly limited. For example, characters, symbols, line drawings, patterns, patterns, and combinations thereof may be used as an original image and an image that can be reproduced. The point light source and the parallel light source only need to include light in the wavelength range used for the reproduction of the second image I2 by the second image reproduction structure 40, and it is not necessary to emit white light.

  In the light modulation element 20 shown in FIG. 6, the second image reproduction structure 40 is configured by a reflection type hologram. In the example shown in FIG. 6, the light source LS is located on the same side as the observer with respect to the light modulation element 20. On the other hand, in the light modulation element 20 shown in FIG. 7, the second image reproduction structure 40 is configured of a transmission type hologram. In the example shown in FIG. 7, the light source LS is located on the opposite side of the light modulation element 20 to the viewer. The reflection type hologram and the transmission type hologram are common in that a desired image is reproduced by the diffraction phenomenon caused by the optical path length difference in the plane generated by the second image asperity shape 45.

  The second image reproduction structure 40 is used in combination with the first image reproduction structure 30 that reproduces the first image I1 by the specular reflection light. Then, as in the example shown in FIG. 2, in the case where the light modulation element 20 has the reflection layer 23, the second image reproduction structure is that the reflection layer 23 can be used together with the first image reproduction structure 30. It is advantageous to construct 40 by a reflective hologram.

  Here, FIG. 8 is a conceptual view showing the light modulation element 20 in a plan view. The light modulation element 20 includes a plurality of element regions 21 arranged in the planar direction of the light modulation element 20. That is, the plurality of element areas 21 are two-dimensionally arranged. In the illustrated example, the light modulation element 20 is divided into a plurality of element regions 21 in plan view. That is, each position in the illustrated light modulation element 20 belongs to any one of the plurality of element regions 21. On the other hand, the second image concavoconvex shape 45 of the second image reproduction structure 40 has a concavo-convex pattern corresponding to the Fourier transform image of the original image. The second image reproduction structure 40 has a minute region corresponding to each pixel of the Fourier transform image, and the depth of the second image asperity shape 45 in each minute region corresponds to the phase information of the corresponding pixel of the Fourier transform image doing. Then, the second image reconstruction structure 40 formed in one element region 21 includes the region corresponding to all the pixels of the Fourier transform image. That is, one element region is plane-divided into the same number as the number of pixels of the Fourier transform image, and each plane-divided region in one element region corresponds to any one pixel of the Fourier transform image. There is. Therefore, the entire second image I2 can be reproduced by diffracted light from one element region 21. Then, by utilizing the diffracted light from the plurality of element regions 21, the second image I2 can be brightly and clearly reproduced. The element area 21 is an area called a hologram cell in the hologram. The planar size of each element 21 can be several μm to several mm square (for example, 2 mm square).

  The second image concavo-convex shape 45 of the second image reproduction structure 40 has a multistage shape, that is, two or more stages, and the number of stages is not particularly limited. When the light image is reproduced by plural colors, the second image concavo-convex shape 45 preferably has three or more steps, and in particular, the second image concavo-convex shape 45 having four or more steps has a complicated composition. It is possible to reproduce the second image I2 with high definition. FIG. 9 is a cross-sectional view of the second image reproduction structure 40 showing an outline of the stepped structure of the second image concavo-convex shape 45. As shown in FIG. The second image reconstruction structure 40 shown in FIG. 9 has a four-step type second image asperity shape 45. The pitch P2 of the concavo-convex pattern of the second image concavoconvex shape 45, that is, the pixel pitch P2 is preferably in the range of 0.1 μm to 80.0 μm from the viewpoint of reproducing the second image I2 accurately, usually 1 μm. It is preferable that it is more than. Further, the asperity depth of the second image asperity shape 45, that is, the maximum height difference D2 is preferably in the range of 0.01 μm to 10 μm, and usually more preferably 0.05 μm to 3 μm.

  By the way, in the present embodiment, the light modulation element 20 has the first image reproduction structure 30 and the second image reproduction structure 40 described above. In particular, in the present embodiment, a device for efficiently installing the first image reproducing structure 30 and the second image reproducing structure 40 in the limited plane area of the light modulation element 20 is configured.

  First, a first specific example will be described with reference to FIGS. 10 to 14. In the first specific example, the first image reconstruction structure 30 and the second image reconstruction structure 40 are provided in a common planar region. More specifically, the second image concavo-convex shape 45 of the second image reconstruction structure 40 is formed so as to overlap with the first image concavo-convex shape 35 of the first image reconstruction structure 30 in the same plane region. According to the first specific example, it is also possible to form the first image asperity shape 35 in the entire area of the light modulation element 20 and to form the second image asperity shape 45 in the whole area of the light modulation element 20.

  FIG. 10 shows a cross section along the normal direction of the light modulation element 20. FIG. 11 is a plan view of the light modulation element 20. FIG. The uneven surface 25 of the light modulation element 20 shown in FIG. 10 corresponds to the first image uneven shape 35 of the first image reproduction structure 30 shown in FIG. 12 and the second image reproduction structure 40 shown in FIG. The second image asperity shape 45 is added. The second image reconstruction structure 40 shown in FIG. 13 is composed of a binary phase Fourier transform hologram. That is, by binarizing the phase information of the Fourier transform image of the original image forming the second image I2, as shown in FIG. 11, the area in which the second image reproduction structure 40 of the light modulation element 20 is provided is The first phase region 40a and the second phase region 40b are divided. Then, the first phase area 40a corresponds to the second image convex portion 46 of the second image uneven shape 45 shown in FIG. 13, and the second phase area 40b corresponds to the second image uneven shape shown in FIG. It corresponds to the 45 second image recess 47.

  The uneven surface 25 of the light modulation element 20 shown in FIG. 10 has the first image convex portion 36 and the first image in the first image uneven shape 35 of the first image reproduction structure 30 at each position forming the uneven surface 25. The reference plane SS is determined depending on which of the concave portions 37 corresponds, and which of the second image convex portions 46 and the second image concave portions 47 of the second image concavo-convex shape 45 of the second image reconstruction structure 40 corresponds. The depth from is determined. Specifically, at the position assigned to the first image convex portion 36 of the first image convex-concave shape 35 and to the second image convex portion 46 of the second image convex-concave shape 45, the concavo-convex surface 25 is the same as the reference plane SS. It has a height. At the position assigned to the first image convex portion 36 of the first image concavo-convex shape 35 and to the second image concave portion 47 of the second image concavo-convex shape 45, the concavo-convex surface 25 is a second image relative to the reference plane SS. The depth Db is the same as the depth D2 of the recess 47. At a position assigned to the first image concave portion 37 of the first image concave and convex shape 35 and to the second image convex portion 46 of the second image concave and convex shape 45, the concave and convex surface 25 is a first image relative to the reference surface SS. The depth Dc is equal to the depth D1 of the recess 37. At a position assigned to the first image recess 37 of the first image recess and protrusion shape 35 and to the second image recess 47 of the second image recess and protrusion shape 45, the recess and protrusion surface 25 is the first image recess with respect to the reference surface SS. The depth D1 is obtained by adding the depth D1 of 37 and the depth D2 of the second image concave portion 47 together.

  The concavo-convex surface 25 of the light modulation element 20 shown in FIGS. 10 and 11 is formed by overlapping the first image concavo-convex shape 35 of the first image reconstruction structure 30 and the second image concavo-convex shape 45 of the second image reconstruction structure 40. It is done. That is, both the information related to the reproduction of the first image I1 and the information related to the reproduction of the second image I2 are recorded in a common area of the uneven surface 25. The light incident on such a concavo-convex surface 25 is subjected to the optical action by the first image concavo-convex shape 35 and the optical action by the second image concavo-convex shape 45. As a result, the first image reproduction structure 30 The image I1 is reproduced, and the second image I2 is reproduced by the second image reproducing structure 40.

  According to the light modulation element 20 according to the first specific example, by effectively utilizing the limited area, the formation area of the first image reproduction structure 30 and the formation area of the second image reproduction structure 40 are effectively expanded. be able to. As a result, the first image I1 and the second image I2 can be displayed large, brightly and clearly. That is, the visibility of the first image I1 and the second image I2 can be improved. Further, complex and highly designable images can be reproduced as the first image I1 and the second image I2. Furthermore, since the concavo-convex shape 45 of the second image reproduction structure 40 can be formed in the same area as the concavo-convex shape 35 of the first image reproduction structure 30 in the thickness direction, the thickness of the light modulation element 20 It is also possible to make In addition, the first image reproduction structure 30 and the second image reproduction structure 40 can be produced by the same process such as, for example, resin molding using a mold, and furthermore, they can be produced simultaneously. . Therefore, it is also possible to mass-produce the light modulation element 20 in which a large amount of information is recorded easily and inexpensively.

  The second image asperity shape 45 shown in FIG. 13 is a two-step asperity shape. However, in the first example, the second image asperity shape 45 may have three or more steps of asperities. For example, the second image reconstruction structure 40 can be a ternary or higher phase type Fourier transform image.

  Next, a second specific example will be described with reference to FIG. 14 and FIG. Also in the second specific example, the first image reconstruction structure 30 and the second image reconstruction structure 40 are provided in a common planar region.

  In the second specific example shown in FIGS. 14 and 15, as in the first specific example, the second image reconstruction structure 40 binarizes the phase information of the Fourier transform image of the original image of the second image I2. The first phase area 40a and the second phase area 40b are separated by the division. However, the first phase area 40a and the second phase area 40b are not recorded on the uneven surface 25 as areas having different heights as in the first specific example, but the first phase area 40a and the second phase area The position of the boundary b of 40 b is recorded on the uneven surface 25. Specifically, the arrangement pitch of the first image convex portion 36 and the first image concave portion 37 forming the first image concavo-convex shape 35 of the first image reproduction structure 30 is the boundary between the first phase area 40a and the second phase area 40b. The information of the boundary b is recorded in the light modulation element 20 by making it discontinuous in b.

  As shown in FIGS. 14 and 15, the arrangement of the first image convex portion 36 and the first image concave portion 37 of the first image reproduction structure 30 is the same as the first phase area 40a and the second phase area of the second image reproduction structure 40. At a position to be a boundary b with 40b, the position is shifted by a length which is less than the arrangement pitch P1 of the first image convex portion 36 and the first image concave portion 37 at other positions. That is, although the first image convex portion 36 and the first image concave portion 37 are arranged at a constant arrangement pitch P1 in the first arrangement region 30a or in the second arrangement region 30b, the first phase region 40a and The arrangement pitch is arranged to be discontinuous at the boundary b with the second phase region 40 b. In other words, the arrangement of the first image convex portion 36 and the first image concave portion 37 of the first image reconstruction structure 30 in the first phase region 40a is the same as the arrangement of the first image reconstruction structure 30 in the second phase region 40b. The arrangement of the image convex portion 36 and the first image concave portion 37 is deviated by a length less than the arrangement pitch P1.

  In the illustrated example, the direction in which the arrangement of the first image convex portion 36 and the first image concave portion 37 is shifted is from the viewpoint of improving the visibility of the second image I2 which is a reproduced image by the second image reproducing structure 40. The first image convex portion 36 and the first image concave portion 37 are parallel to the arrangement direction dx. However, the present invention is not limited to the illustrated example, but the direction of shifting the arrangement of the first image convex portion 36 and the first image concave portion 37 may be inclined or inclined with respect to the arrangement direction dx of the first image convex portion 36 and the first image concave portion 37 It may be orthogonal.

  As described above, the concavo-convex surface 25 of the light modulation element 20 is formed by providing the first image reproduction structure 30 and the second image reproduction structure 40 in a common flat region. That is, both the information related to the reproduction of the first image I1 and the information related to the reproduction of the second image I2 are recorded in a common area of the uneven surface 25. The light incident on the uneven surface 25 is subjected to the optical action of the first image uneven shape 35 and the optical action of the second image uneven shape 45. As a result, the first image reproducing structure 30 causes the first image I1 is reproduced, and the second image I2 is reproduced by the second image reproducing structure 40.

  According to the light modulation device 20 according to the second example, by effectively utilizing the limited area, the formation area of the first image reproduction structure 30 and the formation area of the second image reproduction structure 40 are effectively expanded. be able to. As a result, the first image I1 and the second image I2 can be displayed large, brightly and clearly. That is, the visibility of the first image I1 and the second image I2 can be improved. Further, complex and highly designable images can be reproduced as the first image I1 and the second image I2. Furthermore, since the second image reproduction structure 40 can be formed in the same area as the first image reproduction structure 30 in the thickness direction, the thickness of the light modulation element 20 can be reduced. . In addition, the first image reproduction structure 30 and the second image reproduction structure 40 can be produced by the same process such as, for example, resin molding using a mold, and furthermore, they can be produced simultaneously. . Therefore, it is also possible to mass-produce the light modulation element 20 in which a large amount of information is recorded easily and inexpensively.

  The amount of misalignment of the arrangement of the first image convex portion 36 and the first image concave portion 37 of the first image reproduction structure 30 at the position that becomes the boundary b between the first phase region 40a and the second phase region 40b is as described above. In addition, the length which is less than the arrangement pitch P1 of the first image convex portion 36 and the first image concave portion 37 can be obtained. However, from the viewpoint of clearly reproducing the second image I2, it is preferable to set this shift amount to a length of 40% or more and 60% or less of the arrangement pitch P1 of the first image convex portion 36 and the first image concave portion 37, More preferably, the length is half the arrangement pitch P1 of the first image convex portion 36 and the first image concave portion 37.

  Next, a third specific example will be described with reference to FIG.

  In the third specific example, the light modulation element 20 is divided into a plurality of areas in plan view. The area where the first image reproduction structure 30 is formed and the area where the second image reproduction structure 40 is formed are different. However, in the light modulation element 20, the region where the first image reproduction structure 30 is formed is dispersed. And one area in which the first image reproduction structure 30 is formed is small, and typically, it is small to the extent that it can not be decomposed by the human eye. Similarly, in the light modulation element 20, the region where the second image reproduction structure 40 is formed is also dispersed. And one area in which the second image reproduction structure 40 is formed is small, and typically, it is small to such an extent that it can not be decomposed by human eyes. As a result, the first image reproduction structure 30 is observed as if formed over the entire area of the light modulation element 20, and the second image reproduction structure 40 is observed as if formed over the entire area of the light modulation element 20. Ru.

  FIG. 16 is a conceptual view showing a planar structure of the light modulation element 20. As shown in FIG. In one specific example shown in FIG. 16, the light modulation device 20 includes a plurality of element regions 21 arranged in the planar direction of the light modulation device 20. The light modulation element 20 is divided into a plurality of element regions 21 by being plane-divided in the plane direction. In the illustrated example, the plurality of element regions 21 are arranged in a square.

  The plurality of element areas 21 include a plurality of first element areas 21 a and a plurality of second element areas 21 b. A first image reproduction structure 30 is formed in each first element region 21a, and a second image reproduction structure 40 is formed in each second element region 21b. That is, in each first element region 21 a, the first image convex portion 36 and the first image concave portion 37 which form the first image uneven shape 35 of the first image reproduction structure 30 are formed. In each second element region 21 b, a second image convex portion 46 and a second image concave portion 47 which form a second image uneven shape 45 of the second image reproduction structure 40 are formed. The plurality of first element regions 21a and the plurality of second element regions 21b are disposed in a distributed manner, and one or more second element regions 21b are adjacent to each first element region 21a, and similarly, One or more first element regions 21a are adjacent to the two-element region 21b. Specifically, the plurality of first element regions 21a may be arranged in a staggered arrangement, and similarly, the plurality of second element regions 21b may be arranged in a staggered arrangement. In another example, the plurality of first element regions 21a and the plurality of second element regions 21b may be arranged in a stripe arrangement, respectively. Further, the light modulation element 20 is divided into small areas in a honeycomb array or an array of triangles, and each small area is allocated to either the first element area 21a or the second element area 21b. It is also good. Furthermore, the first element region 21a and the second element region 21b may be arranged in various other arrangements.

  In this example, by making the sizes of the first element region 21a and the plurality of second element regions 21b sufficiently small, as in the case where the first image reproduction structure 30 is formed on the entire surface of the light modulation element 20. The first image I1 is observed, and the second image I2 is observed as in the case where the second image reproduction structure 40 is formed on the entire surface of the light modulation element 20. From such a viewpoint, the planar size of each element element 21 can be several μm to several mm square (for example, 2 mm square).

  Also in the light modulation element 20 according to the third specific example described above, the first image I1 and the second image I2 can be obtained by dispersing the first element region 21a and the second element region 21b sufficiently small. The first image reconstruction structure 30 and the second image reconstruction structure 40 can be efficiently formed within a limited area so as to be observed with excellent visibility.

  In the third specific example, various structures can be adopted for the second image reconstruction structure 40 formed in the second element region 21 b. For example, the second image reconstruction structure 40 may be a phase hologram or an amplitude hologram.

  In the embodiment described above, the light modulation device 20 performs the first image reproducing structure 30 for reproducing the first image I1 by the zero-order reflected light, and the second image reproducing for reproducing the second image I2 by the diffracted light. And a structure 40. According to such a light modulation element 20, it is possible to observe the first image I1 as a reproduced image by the first image reproducing structure 30 by using ambient light. Further, for example, by using light from the light source LS, it is possible to observe the second image I2 as a reproduced image by the second image reproducing structure 40. Then, in the light modulation element 20, two types of image reproducing structures 30, 40 capable of reproducing the images I1 and I2 that can be visually recognized visually according to different principles are efficiently installed within a limited area. There is. As a result, a large amount of information can be recorded within a limited area, and reproduction of an image excellent in design, ease of authenticity determination, and improvement in anti-counterfeit property can be realized.

  By configuring the first image reproduction structure 30 as a so-called color switch, the color of the first image I1 can be changed depending on the direction in which the light modulation element 20 is observed. Such a first image I1 makes it possible to recognize that the light modulation element 20 is provided with some image reproduction function. Therefore, it is also possible to make an authenticity determination without requiring specialized knowledge.

  In the specific example described above, the first image reconstruction structure 30 and the second image reconstruction structure 40 are formed in a common planar region. By effectively utilizing such a limited area, it is possible to effectively widen the formation area of the first image reproduction structure I1 and the formation area of the second image reproduction structure I2. Thereby, the visibility of the first image I1 and the second image I2 can be improved.

  In the embodiment described above, the first image reproduction structure 30 has the concavo-convex shape 35 including the concave portions 37 and the convex portions 36 alternately arranged in one direction dx. The concave portion 37 and the convex portion 36 of the first image reproduction structure 30 linearly extend in a direction dy not parallel to a certain direction dx. According to such a first image reproduction structure 30, it is possible to reproduce the first image I1 of the pattern corresponding to the outline of the area in which the concave portion 37 and the convex portion 36 are formed. Moreover, it is also possible to change the color of the first image I1 or eliminate the first image I1 according to the direction in which the light modulation element 20 is observed. The light modulation element 20 can be provided with a useful image reproduction function rich in surprise.

  In the above-described specific example, the first image reproduction structure 30 is provided in the first array region 30a and the second array region 30b. The first image reproduction structure 30 has a concavo-convex shape 35a including concave portions 37a and convex portions 36a alternately arranged in one direction d1 in the first arrangement region 30a, and in the first arrangement region 30a, The recess 37 a and the protrusion 36 a extend linearly in a direction not parallel to the one direction d 1. Furthermore, the first image reproduction structure 30 has a concavo-convex shape 35b including concave portions 37b and convex portions 36b alternately arranged in the other direction not parallel to the one direction d1 in the second array region 30b. In the second array region 30b, the concave portions 37b and the convex portions 36b linearly extend in a direction non-parallel to the other direction. According to such a first image reproduction structure 30, it is possible to reproduce the first image I1 of the pattern corresponding to the outline of the first array area 30a and the outline of the second array area 30b in two colors. Moreover, depending on the direction in which the light modulation element 20 is observed, it is also possible to change the color of the first image I1 or to eliminate part or all of the first image I1. That is, the light modulation element 20 can be provided with a useful image reproduction function rich in surprise.

  In the specific example described above, the second image reproduction structure 40 is a hologram having the concavo-convex shape 45. In such a light modulation element 20, the first image reproducing structure 30 having the concavo-convex shape 35 and the second image reproducing structure 40 having the concavo-convex shape 45 are similarly processed, for example, by resin molding using a mold. It can also be made at the same time. That is, it is possible to easily and inexpensively mass-produce the light modulation elements 20 in which a large amount of information is recorded.

  In the first specific example described above, the second image reproduction structure 40 is a hologram having the concavo-convex shape 45. The concavo-convex shape 45 of the second image reproduction structure 40 can be formed so as to overlap with the concavo-convex shape 35 of the first image reproduction structure 30 and a common flat region. According to such a light modulation element 20, the formation area of the first image reproduction structure 30 and the formation area of the second image reproduction structure 40 can be effectively expanded by effectively using the limited area. . Therefore, in addition to being mass-produced easily and inexpensively, the visibility of the first image I1 and the second image I2 can be improved. Further, since the concavo-convex shape 45 of the second image reproduction structure 40 can be formed in the same region as the concavo-convex shape 35 of the first image reproduction structure 30 in the thickness direction, the thickness of the light modulation element 20 It is also possible to make Also, in this example, the second image reconstruction structure 40 can be a binary or higher value phase Fourier transform hologram. By employing a binary or higher value phase type Fourier transform hologram, the second image I2 can be reproduced with high accuracy by the second image reproducing structure 40 which can be designed and manufactured relatively easily.

  In the second specific example described above, the second image reconstruction structure 40 includes one phase region 40a and the other phase region 40b divided by binarizing phase information of the Fourier transform image of the second image I2. And contains. The arrangement of the concave portions 37 and the convex portions 36 of the first image reproduction structure 30 is a concave portion 37 at another position at a position that becomes the boundary b between one phase region 40 a and the other phase region 40 b of the second image reproduction structure 40. And it has shifted only by the length used as arrangement pitch P1 of convex part 36 is less. More specifically, the arrangement of the concave portions 37 and the convex portions 36 of the first image reproduction structure 30 is continuous at a constant arrangement pitch P1 except at the position which becomes the boundary b between one phase region 40a and the other phase region 40b. Are arranged in order. On the other hand, the concave portions 37 and the convex portions 36 of the first image reproduction structure 30 have a length which is less than the predetermined arrangement pitch P1 at the position which becomes the boundary b between one phase region 40a and the other phase region 40b. Only the array has been offset. According to such a light modulation element 20, the second image reproduction structure 40 can be formed in an overlapping manner in the area where the first image reproduction structure 30 is provided. Therefore, by effectively utilizing the limited area, the formation region of the first image reproduction structure 30 and the formation region of the second image reproduction structure 40 can be effectively expanded. Thereby, the visibility of the first image I1 and the second image I2 can be improved. In addition, since the second image reproduction structure 40 can be formed in the same area as the concavo-convex shape 35 of the first image reproduction structure 30 also in the thickness direction, the thickness of the light modulation element 20 should be reduced. Is also possible. Furthermore, the first image reproduction structure 30 and the second image reproduction structure 40 can be manufactured by the same process such as, for example, resin molding using a mold, and can also be manufactured simultaneously. Therefore, it is also possible to mass-produce the light modulation element 20 in which a large amount of information is recorded easily and inexpensively.

  In the third example described above, the light modulation element 20 has a first element region 21a and a second element region 21b two-dimensionally arranged. The first image reproduction structure 30 is provided in the first element region 21a, and the second image reproduction structure 40 is provided in the second element region 21b. According to such a light modulation element 20, the first element region 21a and the second element region 21b are made sufficiently small and dispersed, and the first image I1 and the second image I2 are observed with excellent visibility. As a result, the first image reconstruction structure 30 and the second image reconstruction structure 40 can be efficiently formed within a limited area.

  Although one embodiment has been described above by using a plurality of specific examples, these specific examples are not intended to limit the one embodiment. The embodiment described above can be implemented in various other specific examples, and various omissions, replacements, and changes can be made without departing from the scope of the invention.

  Hereinafter, an example of a modification will be described with reference to the drawings. In the following description and the drawings used in the following description, with respect to parts that can be configured in the same manner as the specific example described above, the same reference numerals as those used for the corresponding parts in the specific example described above are used Omit.

  In the example described above, the first image concavoconvex shape 35 constituting the first image reproduction structure 30 and the second image concavoconvex shape 45 constituting the second image reproduction structure 40 are formed on one surface of the light modulation element 20. Although an example is shown, it is not limited to this example. As shown in FIG. 17, a pair of opposing surfaces of the light modulation element 20 includes a first image concavoconvex shape 35 constituting the first image reconstruction structure 30 and a second image concavoconvex shape 45 constituting the second image reconstruction structure 40. May be formed respectively. In this case, any one of the surface on which the first image concavoconvex shape 35 constituting the first image reconstruction structure 30 is formed and the surface on which the second image concavoconvex shape 45 constituting the second image reconstruction structure 40 is formed Can form the surface of the light modulation element 20 and the other can form the back surface of the light modulation element 20.

  Further, although the example in which the second image reproduction structure 40 is configured by the phase type Fourier transform hologram has been shown, as described above, the present invention is not limited to this example. The second image reproduction structure 40 may be a reflection type hologram or a transmission type hologram. In particular, also in the first to third specific examples described above, the second image reconstruction structure 40 made of a transmission type hologram can be used instead of the second image reconstruction structure 40 made of a reflection type hologram.

  Furthermore, as in the example shown in FIG. 18, the second image reconstruction structure 40 may be configured by an amplitude type hologram. In the example shown in FIG. 18, the light modulation element 20 has an element main body 22 having a concavo-convex surface 25 and a hologram layer 27 stacked on the element main body 22. The hologram layer 27 can be, for example, a printing layer formed by printing. The print layer 27 has a pattern corresponding to the Fourier transform layer of the original image of the second image I2, and can reproduce the second image I2 as an amplitude type hologram. Also in this example, the first image reconstruction structure 30 and the second image reconstruction structure 40 are provided in a common flat region, and the limited area of the light modulation element 20 is effectively used as in the above-described example. Thus, the formation area of the first image reproduction structure 30 and the formation area of the second image reproduction structure 40 can be effectively expanded. Thereby, the visibility of the first image I1 and the second image I2 can be improved.

  Furthermore, as in the example shown in FIG. 19, the second image reconstruction structure 40 may be configured by a volume hologram. The volume hologram is produced by recording interference fringes of the object light and the reference light from the original image of the second image I2. In the example shown in FIG. 19, the light modulation element 20 has an element main body 22 having a concavo-convex surface 25 and a hologram layer 28 stacked on the element main body 22. Also in this example, the first image reconstruction structure 30 and the second image reconstruction structure 40 are provided in a common flat region, and the limited area of the light modulation element 20 is effectively used as in the above-described example. Thus, the formation area of the first image reproduction structure 30 and the formation area of the second image reproduction structure 40 can be effectively expanded. Thereby, the visibility of the first image I1 and the second image I2 can be improved.

  As another modification, in the above-described example, the example in which the first image I1 and the second image I2 are different has been described, but the first image I1 and the second image I2 may be the same. For example, the first image reconstruction structure 30 and the second image reconstruction structure 40 may reproduce the same or similar images in an overlapping manner. In general, in the first image reproduction structure 30 functioning as a color switch, the viewing area of the reproduced image tends to be narrowed. By making the first image I1 and the second image I2 the same image, it is possible to widen the viewing area of the reproduced image and improve the visibility of the reproduction increase.

DESCRIPTION OF SYMBOLS 10 information recording medium 11 medium main body 12 base member 13 bonding layer 20 light modulation element 21 element area 21a first element area 21b second element area 22 element body 22a base 22b uneven layer 23 reflective layer 25 uneven surface 27 printed layer 28 hologram Layer 30 First image reproduction structure 30a First arrayed region 30b Second arrayed region 35 first image uneven shape 35a first image first uneven shape 35b first image second uneven shape 36 first image raised portion 36a first image first portion 1 convex portion 36 b first image second convex portion 37 first image concave portion 37 a first image first concave portion 37 b first image second concave portion 40 second image reproduction structure 40 a first phase region 40 b second phase region 44 uneven surface 45 Second image asperity shape 46 second image convex portion 47 second image concave portion b boundary b
I1 first image I2 second image SS reference plane LS light source

Claims (9)

A first image reproduction structure for reproducing a first image by a zero-order reflected light;
And a second image reproducing structure for reproducing a second image by diffracted light.   The light modulation element according to claim 1, wherein the first image reproduction structure and the second image reproduction structure are provided in a common flat area. The first image reproduction structure has a concavo-convex shape including concave and convex portions alternately arranged in one direction,
The light modulation element according to claim 1, wherein the concave portion and the convex portion extend linearly in a direction not parallel to the one direction. The first image reproduction structure is provided in a first array area and a second array area,
The first image reproduction structure has a concavo-convex shape including concave portions and convex portions alternately arranged in a certain direction in the first array region, and the concave portions and the concave portion in the first array region. The convex portion linearly extends in a direction not parallel to the one direction, and
The first image reproduction structure has a concavo-convex shape including concave and convex portions alternately arranged in the other direction not parallel to the one direction in the second array region, and the second array The light modulation element according to claim 1, wherein in the region, the concave portion and the convex portion linearly extend in a direction not parallel to the other direction.   The light modulation element according to any one of claims 2 to 4, wherein the second image reproduction structure is a hologram having a concavo-convex shape.   The light modulation element according to claim 5, wherein the concavo-convex shape of the second image reproduction structure is formed so as to overlap with the concavo-convex area of the first image reproduction structure in common with the planar area. The second image reproduction structure includes one phase region and the other phase region divided by binarizing phase information of a Fourier transform image of the second image,
The arrangement of the concave portions and the convex portions of the first image reproduction structure is a position of the concave portions and the convex portions at a position which is a boundary between the one phase region and the other phase region of the second image reproduction structure. The light modulation element according to claim 3 or 4, which is shifted by a length which is less than the arrangement pitch. A first element area and a second element area arranged in two dimensions;
The first image reproduction structure is provided in the first element region,
The light modulation element according to any one of claims 1, 3 and 4, wherein the second image reproduction structure is provided in the second element region.   The information recording medium provided with the light modulation element as described in any one of Claims 1-8.

Images