JP7159631B2 - Information recording medium - Google Patents

Description

The present invention relates to an information recording medium provided with an optical modulation element that reproduces an optical image by modulating the phase of incident light.

Various types of light modulation elements have been proposed as light modulation elements such as holograms capable of reproducing an original image.

For example, Patent Literature 1 and Patent Literature 2 disclose a phase modulation type light modulation element having an uneven pattern, which reproduces an optical image by diffracting light over the entire visible light wavelength band.

Both of the optical modulation elements of Patent Documents 1 and 2 diffract light almost evenly over the entire visible light wavelength band. A light image is reproduced, and a rainbow-colored light image is reproduced as a whole.

JP-A-10-153943 JP-A-2004-126535

By the way, it is desired to improve the design of the information recording medium provided with the light modulation element as described above, or to facilitate the authentication of the information recording medium. In particular, an information recording medium that reproduces an optical image with good visibility even with light from a general light source so that the observer can enjoy the design including the optical image, or can easily judge the authenticity. Realization is desired.

However, as in the light modulation elements of Patent Documents 1 and 2, when white light, which is the light of a general light source, is incident and a light image is reproduced in rainbow colors, various lines (for example, contour lines) become thicker. Therefore, the visibility of the reproduced image is poor.

The present invention has been made in view of the above-mentioned circumstances, and a light image with good visibility is reproduced even by white light, which is the light of a general light source, so that the observer can enjoy the design including the light image. It is an object of the present invention to provide an information recording medium that can be authenticated or easily authenticated.

The information recording medium according to this embodiment is
an optical modulation element including an element element that reproduces an optical image by modulating the phase of incident light;
a printing layer that provides display associated with the optical image,
The element element has an uneven surface,
The maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the 1st-order diffracted light and the wavelength distribution of the -1st-order diffracted light of the element element is the diffraction efficiency including the maximum diffraction efficiency. The present invention relates to an information recording medium that forms a maximum value with a full width at half maximum of 200 nm or less in wavelength distribution.

In the information recording medium according to this embodiment,
When observed from a certain observation direction, the relationship between the optical image and the display is shown,
When viewed from some other viewing direction, the light image may not be associated with the display.

In this case, when viewed from a certain viewing direction, the light image and the display have the same color,
When viewed from some other viewing direction, the light image and the display may have non-same colors.

Alternatively, the optical image is observed when observed from a certain observation direction,
The light image may not be observed when observed from some other observation direction.

Moreover, the information recording medium according to the present embodiment may further include viewing direction display means for displaying the viewing direction.

In this case, the viewing direction display means may display a viewing direction in which a relationship between the optical image and the display can be observed.

Alternatively, the viewing direction display means may display a viewing direction in which the relationship between the optical image and the display cannot be observed.

Also, the information recording medium according to the present embodiment may be an ID card, a passport (passport), a credit card, or the like on which personal information is recorded. In this case, the ID card may be, for example, a national ID card, driver's license, membership card, employee card, or student card. Information other than personal information may be recorded on the information recording medium according to the present embodiment. For example, banknotes, cash vouchers, gift certificates, other tickets, other media recording various types of information such as official documents and confidential information, and other media with monetary value may be used.

According to the present invention, even when white light, which is general ambient light, is incident, a light image with good visibility is reproduced, and the observer can enjoy the design including the light image, or Therefore, it is possible to provide an information recording medium that can be easily authenticated.

FIG. 1 is a diagram for explaining an embodiment according to the present invention, and is a plan view showing an example of an information recording medium. FIG. 2 is a plan view showing the information recording medium shown in FIG. 1 on which incident light is incident and the light modulation element reproduces an optical image. FIG. 3 is a cross-sectional view taken along line II of FIG. FIG. 4 is a conceptual diagram of a transmissive hologram structure. FIG. 5 is a conceptual diagram of a reflective hologram structure. FIG. 6 is a conceptual diagram showing the planar structure of the hologram structure. FIG. 7 is a cross-sectional view of an element element showing an outline of an example of a stepped structure of an uneven surface. FIG. 8 is a cross-sectional view of an element element schematically showing another example of the stepped structure of the uneven surface. FIG. 9 is a graph showing an example of the relationship between the wavelength distribution of first-order diffracted light and the diffraction efficiency of each element element. FIG. 10 is a schematic diagram for explaining a light image reproduced by a general hologram structure. FIG. 11 is a schematic diagram for explaining a light image reproduced by the hologram structure of this embodiment. FIG. 12 is a schematic diagram for explaining a light image reproduced by the hologram structure of this embodiment. FIG. 13 is a schematic diagram for explaining a light image reproduced by the hologram structure of this embodiment. FIG. 14 is a graph showing an example of diffraction characteristics of each element element. FIG. 15 is a diagram showing an example of a light image reproduced by a hologram structure provided with element elements having diffraction characteristics shown in FIG. FIG. 16 is a graph showing another example of diffraction characteristics of each element. FIG. 17 is a plan view showing an information recording medium according to a modification, in which incident light is incident at an incident angle of 0° and an optical modulation element reproduces an optical image. FIG. 18 is a plan view showing the information recording medium shown in FIG. 17 on which incident light is incident at an incident angle of 30° and the light modulation element reproduces an optical image. FIG. 19 is a graph showing an example of the diffraction characteristics of each element element, showing the case where the incident angle of incident light to each element element is 0°. FIG. 20 is a graph showing diffraction characteristics of each element element shown in FIG. 19, and shows a case where the incident angle of incident light to each element element is 30°. FIG. 21 is a graph showing diffraction characteristics of each element element shown in FIG. 19, and shows a case where the incident angle of incident light to each element element is 50°. FIG. 22 shows an example of a light image reproduced by a hologram structure provided with element elements having diffraction characteristics shown in FIG. FIG. 23 shows an example of a light image reproduced by a hologram structure provided with element elements having diffraction characteristics shown in FIG. FIG. 24 shows an example of a light image reproduced by a hologram structure provided with element elements having diffraction characteristics shown in FIG. FIG. 25 is a diagram corresponding to FIG. 6 and a conceptual diagram showing a planar structure of a modified example of the hologram structure. 26 is a schematic diagram for explaining a light image reproduced by the hologram structure of FIG. 25. FIG.

An information recording medium according to an embodiment of the present invention will be described below. In the drawings attached to this specification, for the convenience of illustration and ease of understanding, the scale and the ratio of vertical and horizontal dimensions are changed and exaggerated from those of the real thing.

In addition, terms such as "parallel", "perpendicular", "identical", length and angle values, etc. that specify shapes and geometric conditions and their degrees used in this specification are strictly It is interpreted to include the extent to which similar functions can be expected without being bound by any particular meaning.

FIG. 1 shows an information recording medium 1 of this embodiment. 2 shows a state in which white light is incident on the light modulation element of the information recording medium 1 shown in FIG. 1 and an optical image 100 is reproduced by the light modulation element. 3 shows a cross section of the information recording medium 1 shown in FIG. 1 along line II. As can be understood from FIG. 2, in the information processing medium 1 of the present embodiment, even when white light, which is light from a general light source, is incident, the light modulation element reproduces a light image 100 with good visibility. In addition, the optical image 100 and the display provided by printing on the information processing medium 1 are devised to indicate the mutual relationship. An observer can enjoy the design of such an information recording medium 1 using a general light source. Alternatively, it is possible to easily determine the authenticity of the information recording medium 1 by determining the relationship between the optical image and the display without using a special light source.

The light modulation element of this embodiment is configured as a hologram holder having a phase modulation type hologram structure that modulates the phase of incident light to reproduce an optical image. The hologram carrier contains elemental elements which are constituted in particular by Fourier transform holograms. A Fourier transform hologram is a hologram produced by recording wavefront information of a Fourier transform image of an original image, and functions as a so-called Fourier transform lens. In particular, the phase modulation type Fourier transform hologram is a hologram with an uneven surface that is produced by recording the phase information of the Fourier transform image into multiple values and recording it as depth on the medium. is used to reproduce a light image of the original image from the incident light. This Fourier transform hologram, for example, is advantageous in that it can reproduce a desired optical image (that is, the original image) with high precision and that it can be produced relatively easily. Such a phase modulation type optical modulation element is also called a kinoform. However, the element elements of the light modulation element to which the present invention can be applied are not limited to Fourier transform holograms, and the present invention can be applied to light modulation elements having other structures such as holograms that reproduce optical images by other methods. can be applied.

In the following description, white light containing various wavelengths is taken as an example of light (incident light) to be incident on the hologram structure, but the incident light does not necessarily have to be white light. That is, the wavelength included in the incident light is not particularly limited as long as it includes light of a wavelength corresponding to the color of the optical image reproduced by the hologram structure. Further, in the following description, unless otherwise specified, it is assumed that the incident angle of the incident 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, the specific values of the refractive index shown in this specification are based on light with a wavelength of 589.3 nm unless otherwise specified. In the following description, unless otherwise specified, the refractive index and the characteristic values of the uneven surface shown for the hologram structure 12 are based on the case where the hologram structure 12 is used in an air environment with a refractive index of 1.0. It is a value derived on assumption.

In this 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 two or more optical images having the same size. Two or more light images that are different from each other and have the same shape (that is, light images that have similar shapes to each other) are also included. That is, two or more light images having the same shape may or may not have the same size as long as they have the same shape. two or more optical images possessed”. Therefore, two or more optical images having different reproduced sizes due to different constituent wavelengths of the optical images correspond to "two or more optical images having the same shape" if they have the same overall shape. do.

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

Hereinafter, the information recording medium of the present embodiment will be described in more detail with reference to FIGS. 1 to 16. FIG.

As shown in FIG. 3, the information recording medium 1 includes a hologram holder 10 that reproduces an optical image by modulating the phase of incident light, and a print layer 30 that is laminated on one side of the hologram holder 10 . Prepare. The hologram holder 10 includes a hologram layer 11 and a transparent substrate 14 laminated on one side of the hologram layer 11 (thus, between the hologram layer 11 and the printed layer 30). A hologram structure 12 is provided on a part of the hologram holder 10 . In this hologram structure 12, the other surface of the hologram layer 11 forms an uneven surface 12a. The uneven surface 12a of the hologram structure 12 has an uneven pattern corresponding to the Fourier transform image of the original image, and has an uneven depth corresponding to each pixel of the Fourier transform image. For example, a resin (e.g., UV curable resin or thermoplastic resin) that forms the hologram layer 11 is formed on the substrate 14 (e.g., PET: polyethylene terephthalate) by coating, and the hologram layer 11 is subjected to UV curing treatment. The hologram holder 10 shown in FIG. 3 can be manufactured by performing the concave-convex shaping process in which the concave-convex surface of the original is pressed together with the heat-pressing process. Note that the hologram holder 10 may not include the substrate 14 if the uneven surface 12 a can be formed on the hologram layer 11 without being supported by the substrate 14 .

When a light beam is incident on the hologram structure 12 from a point light source or the like, a light image (that is, an original image) corresponding to the uneven pattern of the uneven surface 12a 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. , design applications, security applications, or other applications, and can be widely used with good convenience. The optical image that can be reproduced by such an optical modulation element is not particularly limited, and for example, characters, symbols, line drawings, pictures, patterns, combinations thereof, etc. can be used as the original image and the optical image that can be reproduced.

The hologram holder 10 shown in FIG. 3 having the hologram structure 12 as described above can suitably constitute an information recording medium such as a passport as an example. For example, the hologram structure 12 can be authenticated by designing the hologram structure 12 so that the optical image reproduced by the hologram structure 12 represents information based on at least one of characters, symbols, and patterns. It can be suitably used for security applications such as.

The hologram structure 12 includes a transmission hologram structure in which an observer 50 and a light source 51a are arranged on different sides of the hologram structure 12 as shown in FIG. 4, and an observer 50 as shown in FIG. and a reflection hologram structure in which the light source 51b is arranged on the same side with respect to the hologram structure 12 . The hologram structure 12 shown in FIG. 3 is intended to be used as the transmission hologram structure shown in FIG.

In the case of a reflective hologram structure, an additional layer such as a reflective layer (for example, Al, ZnS, or TiO ₂ ) is generally provided on the uneven surface 12a of the hologram structure 12 to reflect incident light. It is formed. However, the reflection-type hologram structure is not limited to this, and the uneven surface 12a of the hologram layer 11 is exposed to the air without providing an additional reflective layer, and the space between the hologram layer 11 such as a UV curable resin and the air is possible. Incident light may be reflected by utilizing the difference in refractive index between the two.

There is a difference between the transmission hologram structure and the reflection hologram structure as described above. They are common in that a desired optical image is reproduced by a diffraction phenomenon caused by . Here, with regard to the specific unevenness depth of the uneven surface 12a, there is an optimum value for each of the transmission hologram structure and the reflection hologram structure. Although a transmission hologram structure will be described below as an example, the contents are basically applicable to a reflection hologram structure unless otherwise specified. In addition, the contents described below for the reflection hologram structure can also be applied to the transmission hologram structure unless otherwise specified.

FIG. 6 is a conceptual diagram showing the planar structure of the hologram structure 12. As shown in FIG. The hologram structure 12 of this embodiment includes a plurality of element elements (also called “hologram cells”) 21 that are regularly arranged two-dimensionally. Each element element 21 has the uneven surface 12a described above, and has a planar size of several nm to several mm square (for example, 2 mm square), and modulates the phase of incident light to reproduce an optical image.

The uneven surface 12a has a multi-stage shape (that is, two or more steps), and the number of stages of the uneven surface 12a is not particularly limited. When an optical image is reproduced with a plurality of colors, the uneven surface 12a preferably has three or more steps, and in particular, the uneven surface 12a having four or more steps can reproduce an original image having a complicated composition with high definition. It is possible to play. 7 and 8 are cross-sectional views of an element element 21 showing an outline of the stepped structure of the uneven surface 12a. FIG. 7 shows an 8-step type uneven surface 12a, and FIG. 8 shows a 4-step type uneven surface 12a. show. 7 and 8 show the element element 21 having the uneven surface 12a formed by periodically repeating the same stepped shape. ) has a stepped shape according to The pixel size of the concave-convex pattern of the concave-convex surface 12a (the dimension of each surface corresponding to each pixel of the Fourier transform image (see the symbol "T" shown in FIGS. 7 and 8)) is It is preferably in the range of 0.1 μm to 80.0 μm, and usually preferably 1 μm or more.

FIG. 9 is a graph showing an example of the relationship between the wavelength distribution of first-order diffracted light and the diffraction efficiency of each element element 21. In FIG. In FIG. 9, the horizontal axis indicates wavelength, and the vertical axis indicates diffraction efficiency. The diffraction efficiency is expressed 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 denoted by P, and the incident radiant flux is denoted by P0. , the diffraction efficiency η is a dimensionless number expressed by "η=P/P0". Each element element 21 exhibits a unique diffraction efficiency depending on the wavelength, and in the example shown in FIG. 9, light having a wavelength near 580 nm (see symbol “H1” in FIG. 9) has a maximum value Dmax with respect to first-order diffracted light. show. FIG. 9 shows an example of the wavelength distribution of 1st-order diffracted light, and the wavelength distribution of -1st-order diffracted light also exhibits a characteristic diffraction efficiency depending on the wavelength and a maximum value of the diffraction efficiency at a specific wavelength.

In the present embodiment, the maximum diffraction efficiency Dmax in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the 1st-order diffracted light and the wavelength distribution of the -1st-order diffracted light of each element element 21 is In the wavelength distribution of the diffraction efficiency including the diffraction efficiency Dmax, a maximum value having a full width at half maximum FWHM of 200 nm or less is formed. The full width at half maximum FWHM referred to here indicates a wavelength band (wavelength width) at a position having a value (Dmax/2) half the maximum diffraction efficiency Dmax in the diffraction efficiency wavelength distribution (see FIG. 9).

Since each element element 21 has such a diffraction characteristic, the light of the wavelength corresponding to the maximum diffraction efficiency Dmax and the wavelengths in the vicinity thereof are diffracted more efficiently than the light of other wavelength bands, contributing to the reconstruction of the image. . Therefore, even when white light including light of various wavelengths is incident on each element element 21, each element element 21 is exposed to light having a wavelength corresponding to the maximum diffraction efficiency Dmax and wavelengths in the vicinity thereof. reproduces the light image in the colors of Therefore, by adjusting the diffraction characteristics of each element element 21 (especially the wavelength distribution of the 1st-order diffracted light and the wavelength distribution of the −1st-order diffracted light) and making the wavelength corresponding to the maximum diffraction efficiency Dmax correspond to the color of the reproduced image, white Even if light is incident on each element element 21, it is possible to reproduce a light image in a specific color.

The uneven surface 12a of each element element 21 has three or more different heights, and the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the 1st-order diffracted light and the wavelength distribution of the diffraction efficiency of the −1st-order diffracted light. It is preferred that there be no other maxima at which the diffraction efficiency is more than half the maximum diffraction efficiency. That is, the second largest diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the 1st-order diffracted light and the -1st-order diffracted light of each element element 21 (marked " in FIG. 9) H2”) is preferably less than half the maximum diffraction efficiency Dmax. In this case, it is possible to effectively prevent color blurring and thickening of lines in the reproduced image, and to reproduce the optical image with high definition.

FIG. 10 is a schematic diagram for explaining an optical image 100 reproduced by a general hologram structure 12. As shown in FIG. 11 to 13 are schematic diagrams for explaining the optical image 100 reproduced by the hologram structure 12 of this embodiment. 10 to 13, the light source used in the transmissive hologram structure 12 is denoted by reference numeral 51a, and the light source used in the reflection hologram structure 12 is denoted by reference numeral 51b. . Also, in the following description, these light sources 51a and 51b are collectively represented using the symbol "51".

Generally, in the diffraction phenomenon, the larger the wavelength of incident light, the larger the diffraction angles of diffracted lights other than the 0th order diffracted light. Therefore, when white light from the light source 51 is incident on a general hologram structure 12 having the same degree of diffraction efficiency over the entire visible light wavelength band, the hologram structure 12 has rainbow colors as shown in FIG. Reproduce the optical image 100 . On the other hand, when white light from the light source 51 is incident on the hologram structure 12 of the present embodiment, which has the maximum diffraction efficiency in the wavelength band of 380 nm or more and 780 nm or less, the hologram structure 12 is as shown in FIGS. Reproduces a monochromatic light image 100 as shown. That is, the hologram structure 12 (especially the uneven surface 12a) of the present embodiment has a diffraction structure optimized for light of a specific wavelength and a wavelength band near it, and and the light of the wavelength band in the vicinity thereof are selectively used to reproduce a light image 100 of a specific color. For example, the hologram structure 12 in FIG. 11 exhibits the maximum diffraction efficiency in the blue wavelength band and reproduces the blue optical image 100 . The hologram structure 12 of FIG. 12 exhibits maximum diffraction efficiency in the green wavelength band and reproduces a green optical image 100 . The hologram structure 12 of FIG. 13 exhibits the maximum diffraction efficiency in the red wavelength band and reproduces the red optical image 100 . The optical images 100 shown in FIGS. 11 to 13 have different sizes, which is caused by the difference in wavelength of the light (that is, 1st-order diffracted light and/or -1st-order diffracted light) forming the optical image 100. This is based on the difference in diffraction angles.

Thus, the hologram structure 12 of this embodiment can reproduce the monochromatic optical image 100 even when white light is incident. The optical image 100 reproduced in this way is a clear image with little blur due to chromatic dispersion. In addition, since the optical 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 to clearly convey to the observer 50 the concept that the light image 100 represents. Furthermore, since the hologram structure 12 is configured to reproduce a specific monochromatic optical image 100, for example, in authenticity determination, not only the "pattern" of the reproduced optical image 100 but also the light The "color" of the image 100 can be used, allowing reliable authentication. In addition, since the hologram structure 12 of the present embodiment does not require an additional layer that selectively transmits or reflects light in a specific wavelength band, the manufacturing cost can be reduced, and the observer 50 can see the surroundings through the hologram structure 12. There is no sense of incongruity in the observed image.

As an example, in FIG. 14, the refractive index of the hologram layer 11 is 1.5, the number of steps on the uneven surface 12a is set to 8, and the depth of each step (see symbol “d” in FIG. 7) is 200 nm. and the diffraction characteristics of the reflective hologram structure 12 (that is, the reflective element element 21) with a maximum depth (see symbol "D" in FIG. 7) of 1400 nm. In FIG. 14, 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 indicated by "W1". The wavelength distribution of the -1st order diffracted light is indicated by "W-1".

In the example shown in FIG. 14, in each element element 21, the wavelength indicating the maximum value of the 0th-order diffracted light is set to 600 nm, and the wavelength indicating the maximum value of the 1st-order diffracted light is set to 533 nm in the wavelength band from 380 nm to 780 nm. The wavelength indicating the maximum value of the -1st order diffracted light is set to 685 nm.

As shown in FIG. 15, each element element 21 having such a diffraction characteristic has an optical image 100a by 0th-order diffracted light (hereinafter also referred to as "0th-order diffracted light image 100a") and an optical image 100b by 1st-order diffracted light ( An optical image 100 including an optical image 100c by -1st-order diffracted light (hereinafter also referred to as a "1st-order diffracted light image 100c") is reproduced. More specifically, the optical image 100 reproduced by each element element 21 having the diffraction characteristics shown in FIG. It includes an order diffracted light image 100b and a red −1st order diffracted light image 100c. The 1st-order diffracted light image 100b and the −1st-order diffracted light image 100c have the same shape (“F” shape in the illustrated example). Note that the 0th-order diffracted light image 100a has a color that depends on the non-diffractive wavelength and the diffraction efficiency.

As another example, in FIG. 16, the refractive index of the hologram layer 11 is 1.5, the number of steps in the uneven surface 12a is set to 8, and the depth per step (see symbol "d" in FIG. 7) ) is 234 nm and the maximum depth (see symbol “D” in FIG. 7) is 1638 nm. In FIG. 16, 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 indicated by "W1". The wavelength distribution of the -1st order diffracted light is indicated by "W-1".

In the example shown in FIG. 16, in each element element 21, the wavelength indicating the maximum value of the 0th-order diffracted light is set to 702 nm, and the wavelength indicating the maximum value of the 1st-order diffracted light is set to 642 nm. The wavelength showing the maximum value is set to a wavelength greater than 780 nm (specifically, 802 nm).

Each element element 21 having such diffraction characteristics also reproduces a light image 100 including a 0th-order diffracted light image 100a, a 1st-order diffracted light image 100b, and a −1st-order diffracted light image 100c as shown in FIG. . However, while the optical image 100b by the 1st-order diffracted light is reproduced as a visible red optical image, the optical image 100c by the −1st-order diffracted light is not reproduced as a visible optical image. In reality, the optical image 100c mainly composed of light outside the visible light wavelength band includes some light inside the visible light wavelength band, and thus may be visible depending on the observer 50. Even in such a case, it is recognized as a very unclear light image.

As shown in FIG. 2, the hologram structure 12 shown in FIG. 3, when white light is incident as incident light, has a 0th-order diffracted light image 100a and 100-order diffracted light image 100a arranged point-symmetrically around the 0th-order diffracted light image 100a. A diffracted light image 100b of order and a diffracted light image of −1st order 100c are reproduced. The 1st-order diffracted light image 100b and the −1st-order diffracted light image 100c are semicircular light images that open toward the outer region of the hologram structure 12 when viewed in the direction from the printing layer 30 toward the hologram structure 12. . The 0th order diffracted light image 100a is reproduced as a yellow to orange light image, the 1st order diffracted light image 100b is reproduced as a green light image, and the −1st order diffracted light image 100c is reproduced as a red light image. be done.

Next, the print layer 30 will be described. The print layer 30 is provided on one surface of the substrate 14 in the information recording medium 1 shown in FIG. The print layer 30 has openings 30a and covers the substrate 14 in areas other than the openings 30a. As shown in FIG. 1, the opening 30a overlaps at least a part of the hologram structure 12 when viewing the information recording medium 1 from the print layer 30 toward the hologram structure 12 . Then, as shown in FIG. 2, an optical image 100 reproduced by the hologram structure 12 is observed in the opening 30a. As shown in FIG. 3, a hole (space) may be provided in the opening 30a, and only the opening 30a may be transparent (i.e. transparent substrate). Also, the print layer 30 may be provided on one surface of the hologram layer 11 .

The print layer 30 provides a display associated with the optical image 100 reproduced by the hologram structure 12 (in particular, the optical images 100b and 100c). The display associated with the optical image 100 includes, for example, display having a shape relationship with the optical image 100 . The representation having shape relatedness here includes, for example, a pair of light images having visually the same shape or nearly the same shape (e.g., a pair of light images whose shapes are identical, similar or symmetrical to each other). , the sizes of these light images may be the same or different. Further, the display having shape relevance includes, for example, display that forms a pattern, characters, character strings, etc. with a specific intention by being combined with the light image 100 .

In addition, the display associated with the light image 100 includes the moon and stars, parent and child, male and female, a pattern and characters indicating the content of the pattern (for example, a pattern representing a gesture meaning OK and the character OK). A representation conceptually associated with the light image 100 is also included.

Further, the display associated with the optical image 100 includes a display associated with the optical image 100 in terms of color, such as display of the same color. In this specification, the term "same color" means that the color difference ΔE between the optical image and the display is 25 or less, more preferably 13 or less. In addition, the value of ΔE in this specification is obtained by measuring the lightness index L and the chromaticity values a and b using a colorimeter CR310 (measuring area diameter 8 mm) manufactured by Minolta Co., Ltd., and using the color difference formula:
ΔE=((ΔL) ² +(Δa) ² +(Δb) ² ) ^1/2
It is a value calculated by

In the illustrated example, the display of the print layer 30 includes a first display portion 31 and a second display portion 32 corresponding to the 1st order diffracted light image 100b and the -1st order diffracted light image 100c, respectively. These display portions 31 and 32 are semicircular 1st-order diffracted light images 100b and -1st-order diffracted light images 100c that open toward the outer region of the hologram structure 12 (therefore, the outer region of the aperture 30a). , two semicircles that open toward the inner region of the opening 30a are displayed. The first display unit 31 forms a circle together with the first-order diffracted light image 100b. Also, the second display unit 32 forms a circle together with the -1st order diffracted light image 100b.

As described above, the information recording medium 1 of the present embodiment can reproduce the monochromatic optical images 100b and 100c even when white light is incident, and the optical images 100b and 100c serve as the display of the printed layer 30. Relevant. That is, even if white light, which is light from a general light source, is incident, a light image with good visibility is reproduced by the hologram holder 10, and the observer 50 can see the light images 100b and 100c and the printed layer 30. You can enjoy the association with the display of Alternatively, the optical images 100b and 100c and the display of the printed layer 30 can be observed without using a special light source, and authenticity determination can be easily performed based on whether there is a relationship between them.

Furthermore, in the illustrated example, the first display unit 31 displays in the same color as the first-order diffracted light image 100b. Also, the second display unit 32 displays in the same color as the -1st order diffracted light image 100c. Therefore, the relationship between the optical images 100b and 100c and the display of the printed layer 30 can be easily grasped.

In the information recording medium 1 shown in FIGS. 1 to 3, the printed layer 30 includes a portion 33 other than the display portions 31 and 32, and the display portions 31 and 32 and the portion 33 cover the base material 14. there is However, the printed layer 30 does not have to include the portion 33 other than the display portions 31 and 32 . That is, only the display portions 31 and 32 may be formed as the print layer 30 . Moreover, the print layer 30 may not be opaque, and may be transparent or translucent as long as the display portions 31 and 32 are visible. Here, "transparent or translucent" in this specification means that the transmittance of light in the visible light range is not 0%. Furthermore, if the printed layer 30 is transparent or translucent and the optical images 100b and 100c are visible through the printed layer 30, the opening 30a may not be formed.

Furthermore, if an opaque base material is used instead of the transparent base material 14, the base material 14 may be provided with openings 14a as shown in FIG. In this case, the opening 14a is formed so that the opening 14a overlaps at least a part of the hologram structure 12 when the hologram holder 10 is viewed from the base 14 toward the hologram structure 12. . If the opening 14a is formed, the observer 50 can observe the optical images 100b and 100c through the opening 14a. A hole (space) may be provided in the opening 14a, or only the opening 14a is made of a transparent body (that is, a transparent base material) together with the hole (space) or instead of providing the hole (space). You may

[Method for producing hologram structure 12]
Next, an example of a method for manufacturing the hologram structure 12 (in particular, the uneven surface 12a) will be described. The method described below is merely an example, and other methods capable of appropriately manufacturing the hologram structure 12 including the desired uneven surface 12a can be adopted. Further, the manufacturing method described below can be applied to both the transmission type hologram structure 12 (see FIG. 4) and the reflection type hologram structure 12 (see FIG. 5).

First, a two-dimensional image of an original image is read by a computer (Step 1). Then, the computer obtains a two-dimensional complex amplitude image by setting each pixel value of the read two-dimensional image as an amplitude value and assigning a random value between 0 and 2π to each pixel as a phase value ( Step 2). The computer then obtains a two-dimensional Fourier transform image by performing a two-dimensional Fourier transform on this two-dimensional complex amplitude image (Step 3). Note that the computer may perform arbitrary optimization processing, such as an iterative Fourier transform method or a genetic algorithm, if necessary (Step 4). Then, the computer converts the phase value of each pixel of the two-dimensional Fourier transform image into multiple stages (for example, four stages of "0", "π/2", "π" and "3π/2", or "0", " π/4”, “π/2”, “3π/4”, “π”, “5π/4”, “3π/2” and “7π/4”) (Step 5).

Then, a hologram structure 12 (in particular, an uneven surface 12a) corresponding to the two-dimensional Fourier transform image is produced so that each pixel has a depth corresponding to the corresponding discretized phase value (Step 6). For example, when the pixel values of the two-dimensional Fourier transform image are discretized into four stages in Step 5 described above, an uneven surface 12a (see FIG. 8) having four stages of depth is formed on the hologram layer 11 in Step 6. be. The depth of the concave-convex surface 12a is determined by taking into consideration not only the diffraction efficiency characteristic to be achieved but also various other related parameters (for example, the refractive index of the material forming the hologram structure 12 (especially the hologram layer 11)). determined by For example, as a reflection type hologram structure 12 for reproducing a blue light image, a hologram structure 12 having four steps of the uneven surface 12a and an optical path length of 330 nm per step of the uneven surface 12a is manufactured. be able to. The reflection type hologram structure 12 and the transmission type hologram structure 12 each have a unique depth structure of the uneven surface 12a. A specific value of the depth of the uneven surface 12a of the body 12 differs between the reflective type and the transmissive type.

The apparatus for manufacturing the hologram structure 12 is not particularly limited, and may be, for example, an apparatus controlled by a computer that executes Steps 1 to 5 described above, or may be an apparatus provided separately from the computer. . Further, if necessary, a matrix (that is, a master original) corresponding to the structure of the hologram structure 12 (particularly, the concave-convex surface 12a) may be made using an exposure device, an electron beam lithography device, or the like based on photolithography technology. (Step 7). For example, a liquid ultraviolet curable resin is dropped onto the matrix, and the ultraviolet curable resin sandwiched between the substrate film (for example, PET film (polyethylene terephthalate film)) and the matrix is irradiated with ultraviolet rays. The hologram structure 12 having the desired uneven surface 12a can be produced by curing the UV-curable resin together with the base film from the mold. As other methods, 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 employed. By using the matrix in this way, it is possible to easily and mass-produce the hologram structure 12 having the desired uneven surface 12a.

In the case of the reflective hologram structure 12, a reflective layer (for example, a reflective layer made of Al or a reflective layer (high refractive index layer) made of ZnS or _TiO2 ) is further formed on the uneven surface 12a by a manufacturing apparatus. may be However, in the case of the hologram structure 12 that reflects incident light by utilizing the difference in refractive index between the hologram layer 11 and air, the uneven surface 12a of the hologram layer 11 can be obtained without additionally providing a reflective layer. can be left exposed to air. Furthermore, other functional layers such as an adhesive layer (for example, a heat seal layer, a primer layer for enhancing adhesion between adjacent layers, etc.) may be formed on the hologram layer 11 as necessary. Further, for example, when a reflective layer is formed on the uneven surface 12a of the hologram layer 11, an adhesive layer is formed on the surface of the reflective layer having an uneven shape (the surface opposite to the hologram layer 11). You may make it fill the recessed part of the surface of a reflection layer.

[Depth of uneven surface]
As an example, in the reflection hologram structure 12, the refractive index of the hologram layer 11 is 1.5, and the depth of each step of the uneven surface 12a (see symbol "d" in FIGS. 7 and 8) is 110 nm. In this case, the optical path length per step of the uneven surface 12a is 330 nm. In this case, since the uneven surface 12a has a four-step depth structure, the hologram structure 12 exhibits the above-described maximum diffraction efficiency in the blue wavelength band and reproduces a blue optical image.

As another example, in the reflection-type hologram structure 12, the hologram layer 11 has a refractive index of 1.5, the uneven surface 12a has an eight-step depth structure, and each step has a depth of 130 nm. In this case, the hologram structure 12 reproduces a blue light image. In the transmissive hologram structure 12, when the hologram layer 11 has a refractive index of 1.5, the uneven surface 12a has a four-step depth structure, and the depth of each step is 660 nm, the hologram structure Body 12 reproduces a blue light image. In the reflective hologram structure 12, when the hologram layer 11 has a refractive index of 1.5, the uneven surface 12a has a depth structure of 8 steps, and the depth of each step is 230 nm, the hologram structure Body 12 reproduces a red light image. Further, in the reflective hologram structure 12, when the hologram layer 11 has a refractive index of 1.5, the uneven surface 12a has a six-step depth structure, and the depth of each step is 220 nm, the hologram structure Body 12 reproduces a green light image.

The color (wavelength band) of the optical image reproduced by the transmission type hologram structure 12 described above assumes that it is used in an air environment with a refractive index of 1.0. When an observer observes the optical image 100 reproduced by the reflection hologram structure 12, the uneven surface 12a of the hologram layer 11 is arranged on the opposite side of the observer, and the observer can see the uneven surface through the hologram layer 11. The structure (that is, the uneven surface 12a) is to be observed. When the uneven surface 12a of the hologram layer 11 is arranged on the same side as the observer, the reflected image from the hologram structure 12 observed by the observer is formed by the light reflected on the surface without passing through the hologram layer 11. Configured. For example, when an uneven surface 12 a is formed on the surface of the card-shaped hologram holder 10 , the observer observes the light reflected by the uneven surface 12 a without passing through the hologram layer 11 . In such a case, the optical path length is based not on the refractive index of the hologram layer 11 but on the refractive index of the medium closer to the viewer than the hologram layer 11, for example, the refractive index of air is 1.0. You need to set the depth of hit. Therefore, an observer can observe a desired image by designing the structure of the uneven surface 12a while assuming that the refractive index of the hologram layer 11 (hologram structure 12) is 1.0, which is the refractive index of air. be. Specifically, when the refractive index of air is 1.0 and the depth of one step of the uneven surface 12a is 165 nm, the optical path length of one step of the uneven surface 12a is 330 nm. In this case, since the uneven surface 12a has a four-step depth structure, the hologram structure 12 exhibits the maximum diffraction efficiency in the blue wavelength band and reproduces a blue optical image.

[Relationship between depth of uneven surface and peak wavelength of diffracted light]
When the number of steps of the uneven surface 12a of the hologram structure 12 is represented by N, the optical path length modulated per step of the uneven surface 12a is represented by l, and the natural number is represented by m, the peak wavelength λ of the diffracted light is given below. is represented by the formula

λ=N·l/(mN±1)

As described above, the hologram structure 12 of the present embodiment can reproduce a monochromatic optical image even when white light is incident. This is realized, for example, when one of the 1st-order diffracted light and the -1st-order diffracted light of the hologram structure 12 has only one peak wavelength λ in the range of the visible light wavelength band for an arbitrary natural number m. It is possible. For example, when the optical path length l is 330 nm and the step number N of the uneven surface 12a is 4, λ=1320/(4m±1). Thus, λ=440 nm and 264 nm for m=1, λ=188 nm and 146 nm for m=2, and λ=120 nm and 101 nm for m=3. When m is 4 or more, the peak wavelength λ becomes even smaller. Of these, the peak wavelength λ included in the visible light wavelength band is only λ=440 nm when m=1. Therefore, when using the hologram structure 12 in which the number of steps of the uneven surface 12a is N=4 and the optical path length per step is l=330 nm, the observer 50 can visually recognize light with a wavelength of 440 nm and wavelengths in the vicinity thereof. Possible monochromatic light images can be reproduced.

[Modification]
Various modifications can be made to the embodiment described above. Modifications of the above-described embodiment will be described below with reference to the drawings. In the following description and the drawings used in the following description, the same reference numerals as those used for the corresponding portions in the above-described embodiment are used for the portions that can be configured in the same manner as in the above-described embodiment. Description is omitted.

17 and 18 show front views of an information recording medium 1a according to a modification. 17 and 18 respectively show how incident light enters the hologram structure 12 of the information recording medium 1a and an optical image 100 is reproduced. However, FIG. 17 shows the case where the incident light enters each element element 21 at an incident angle of 0°, and FIG. 18 shows the case where the incident light enters each element element 21 at an incident angle of 30°. showing.

Compared with the information recording medium shown in FIG. 1, the information recording medium 1a shown in FIGS. is not shown, and the relationship between the optical image 100 (especially the optical images 100b and 100c) and the display of the printed layer 30 is shown when observed from a different observation direction. . Further, the information recording medium 1a is different in that it has observation direction display means. Other configurations are substantially the same as those of the information recording medium 1 shown in FIG.

The relationship between the optical image 100 and the display of the printed layer 30 is shown when observed from a certain observation direction, such as the information recording medium 1a shown in FIGS. An information recording medium that does not show the relationship between the optical image 100 and the display of the printed layer 30 when observed allows the observer 50 to enjoy changes in the relationship between the optical image 100 and the display of the printed layer 30. . Therefore, the designability of the information recording medium is improved. In addition, based on the change in the relationship between the optical image 100 and the display of the printed layer 30 due to the difference in observation direction, it is possible to easily determine the authenticity.

An information recording medium 1a according to a modification will be described below with reference to FIGS. 17 to 24. FIG.

First, with reference to FIGS. 19 to 24, the relationship between the incident angle of incident light with respect to each element element 21 and its diffraction characteristics will be described.

19 to 21 are diagrams corresponding to FIG. 19, the refractive index of the hologram layer 11 is 1.5, the number of steps on the uneven surface 12a is 8, the depth of each step (see symbol “d” in FIG. 6) is 200 nm, and the maximum depth is 200 nm. 6 shows diffraction characteristics when incident light is made incident at an incident angle of 0° to the element element 21 having a thickness (see symbol "D" in FIG. 6) of 1400 nm. 20 and 21 show diffraction characteristics when incident light is incident on the element element 21 at angles of incidence of 30° and 50°, respectively. 19 to 21, 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 indicated by "W1". , and the wavelength distribution of the −1st order diffracted light is indicated by “W−1”.

22 to 24 show optical images 100 reproduced when incident light is made incident on the element element 21 described above at angles of incidence of 0°, 30° and 50°, respectively. That is, the optical images 100 shown in FIGS. 22 to 24 are optical images reproduced by the element elements 21 exhibiting the diffraction characteristics shown in FIGS. 19 to 21, respectively. 15, in the optical images 100 shown in FIGS. 22 to 24, the 1st-order diffracted light image 100b and the -1st-order diffracted light image 100c have the same shape (“F” shape in the illustrated example). have and are reproduced point-symmetrically.

In the element element 21, as shown in FIG. 19, in the wavelength band of 380 nm or more and 780 nm or less, when the incident angle of the incident light is 0°, the wavelength showing the maximum value of the 0th-order diffracted light is set to 600 nm, and the 1st-order The wavelength showing the maximum value of diffracted light is set to 533 nm, and the wavelength showing the maximum value of −1st order diffracted light is set to 685 nm. Further, in the element element 21, as shown in FIG. 20, when the incident angle of the incident light is 30°, the wavelength showing the maximum value of the 0th-order diffracted light is set to around 519 nm, indicating the maximum value of the 1st-order diffracted light. The wavelength is set to 457 nm, and the wavelength indicating the maximum value of the −1st order diffracted light is set to 601 nm. Further, in each element element 21, as shown in FIG. 21, when the incident angle of the incident light is 50°, the wavelength showing the maximum value of the 0th-order diffracted light and the wavelength showing the maximum value of the 1st-order diffracted light are visible light wavelengths. It is set outside the band (that is, a wavelength band smaller than 380 nm), and the wavelength showing the maximum value of the −1st order diffracted light is set to 449 nm.

As can be seen from FIGS. 19 to 21, when the incident angle of incident light is 30°, the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light are higher than when the incident angle of incident light is 0°. is shifted to the short wavelength side as a whole. Further, when the incident angle of the incident light is 50°, the main lights constituting each of the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light are shifted to the shorter wavelength side as a whole. Thus, as the incident angle of the incident light 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, the optical image 100 reproduced from the incident white light by the hologram structure 12 is as shown in FIGS. 22 to 24. FIG. That is, when the incident angle of the incident light is 0°, as shown in FIG. 22, a green 1st-order diffracted light image 100b and a red 1st-order diffracted light image 100b are arranged point-symmetrically around a yellow to orange 0th-order diffracted light image 100a. -1 order diffracted light image 100c is reproduced. Further, when the incident angle of the incident light is 30°, as shown in FIG. 23, a blue 1st order diffracted light image 100b and a yellow -1 order diffracted light image 100b are arranged point-symmetrically around a green 0th order diffracted light image 100a. A next-order diffracted light image 100c is reproduced. Further, when the incident angle of the incident light is 50°, as shown in FIG. 24, the −1st-order diffracted light image 100c of blue 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, reproduced as an invisible ultraviolet light image). In reality, these optical images mainly composed of light outside the visible light wavelength band contain some light inside the visible light wavelength band. Although it may be possible, even in such a case, it is recognized as a very blurred light image.

In this way, as the incident angle of the incident light to each element element 21 is increased from 0°, the reproduced optical image 100 (that is, each of the 0th-order diffracted light image 100a, the 1st-order diffracted light image 100b, and the −1st-order diffracted light image 100c). ) changes color.

Based on the characteristics of the element elements 21 as described above, in the illustrated example, the display of the first display portion 31 of the printed layer 30 is reproduced by incident light incident at an incident angle of 0° or an incident angle in the vicinity thereof. Although it is not the same color as the second-order diffracted light image 100b, it is the same color as the first-order diffracted light image 100b reproduced by the incident light incident at an incident angle of 30°. In addition, the display of the second display portion 32 of the printed layer 30 is not the same color as the −1st-order diffracted light image 100c reproduced by the incident light incident at an incident angle of 0° or at an incident angle in the vicinity thereof, but the incident angle is the same color as the −1st-order diffracted light image 100c generated by the incident light incident at 30°. Specifically, in the hologram structure 12 shown in FIGS. 17 and 18, the color of the 1st-order diffracted light image 100b and the -1st-order diffracted light image 100c reproduced by the incident light incident at an incident angle of 0° or its vicinity is are green and red, respectively. The first-order diffracted light image 100b and the −1st-order diffracted light image 100c reproduced by the incident light at an incident angle of 30° are blue and orange, respectively. Correspondingly, the display portions 31 and 32 of the print layer 30 are displayed in blue and orange, respectively.

Therefore, as shown in FIG. 17, when the information recording medium 1a is observed at an observation angle (observation direction) corresponding to incident light incident at an incident angle of 0° or at an incident angle in the vicinity thereof, the first display of the printed layer 30 The display of the portion 31 and the first-order diffracted light image 100b have non-identical colors. At this time, the display of the second display portion 32 of the print layer 30 and the −1st order diffracted light image 100c also have non-same colors.

On the other hand, as shown in FIG. 18, when the information recording medium 1a is observed at an observation angle (observation direction) corresponding to incident light incident at an incident angle of 30°, the display on the first display portion 31 of the print layer 30 and the first-order diffracted light image 100b have the same color. At this time, the display on the second display portion 32 of the printed layer 30 and the −1st order diffracted light image 100c also have the same color.

In such an information recording medium 1a, for example, by tilting the information recording medium 1a to change the observation direction, the observer 50 enjoys changing the relationship between the optical images 100b and 100c and the display of the printed layer 30. be able to. In addition, based on the change in the relationship between the optical images 100b and 100c and the display of the printed layer 30 due to the difference in observation direction, authenticity can be easily determined.

19 to 21, the element element 21 adjusts its diffraction characteristics to reproduce the optical images 100b and 100c as visible optical images or It is also possible to reproduce as an impossible optical image. That is, the element element 21 can make the optical images 100b and 100c appear (observed) or disappear (not observed) depending on the observation direction. Therefore, in the information recording medium 1a in this modified example, when observed from a certain viewing direction, the optical images 100b and 100c appear, showing the relationship between the optical images 100b and 100c and the display of the printed layer 30. , the optical images 100b and 100c may disappear when viewed from another viewing direction, and the relationship between the optical images 100b and 100c and the display of the printed layer 30 may not be shown. In this case, the optical images 100b and 100c and the display of the printed layer 30, which are related to each other, can be easily grasped.

Next, the viewing direction display means 15 will be described. In the illustrated example, the observation direction display means 15 displays the observation direction in which the relationship between the optical image 100 (especially the optical images 100b and 100c) and the display of the printed layer 30 can be observed. Such an observation direction display means 15 can guide the observer 50 to an observation direction in which the relationship between the optical image 100 and the display of the printed layer 30 can be observed. If the observer 50 wants to prevent the observer 50 from observing the relationship between the optical image 100 and the display of the printed layer 30, the viewing direction display means 15 may may be used to display an observation direction in which the image cannot be observed. In this case, the observation direction display means 15 can guide the observer 50 so that the observation direction is different from the observation direction in which the relationship between the optical image 100 and the display of the printed layer 30 can be observed. . Such observation direction display means 15 can be configured using a lenticular lens or the like. For example, the viewing direction display means 15 can be produced by providing a printed layer on the hologram holder 10 and further disposing a lenticular lens on the printed layer. In this case, an image designed to give different impressions (color, pattern, sharpness, etc.) depending on the viewing angle when viewed through a lenticular lens is printed on the printed layer. According to the observation direction display means 15, the observation direction can be indicated by the change in the impression obtained when the image observed through the lenticular lens is observed, depending on the observation angle. That is, for example, when the observation direction display means 15 is observed from the observation direction in which the relationship between the optical image 100 and the display of the printed layer 30 can be observed, a specific impression can be grasped from the image through the lenticular lens. Thus, the observation direction display means 15 can indicate the observation direction in which the above relationships can be observed. The observation direction display means 15 can also be produced by the following method. That is, a laser coloring layer is provided on the hologram holder 10, and a lenticular lens is arranged on the laser coloring layer. Then, a laser beam is incident on the laser coloring layer from a specific direction through a lenticular lens to mark the laser coloring layer by laser marking. The observation direction display means 15 manufactured in this way allows the marking provided on the laser coloring layer to be clearly observed when observed from the direction coinciding with the incident direction of the laser light. Therefore, for example, by matching the incident direction of the laser beam with the observation direction in which the relationship between the optical image 100 and the display of the printed layer 30 can be observed, the observation direction display means 15 can observe the relationship. When viewed from the possible viewing direction, the marks provided on the laser coloring layer are most clearly observed. That is, the observation direction display means 15 can indicate the observation direction in which the above-mentioned relationship can be observed, by the change in the definition of the mark of the laser coloring layer due to the change in the observation direction. Of course, the viewing direction display means 15 may indicate the viewing direction by characters or figures printed on the substrate 14 or the printed layer 30 .

According to the above embodiments and modifications, the information recording medium 1, 1a includes the optical modulation element 10 including the element element 21 that reproduces the optical image 100 by modulating the phase of the incident light, and the optical image 100 and a printed layer 30 that provides an indication associated with. The element element 21 has an uneven surface 12a, and the maximum diffraction in the wavelength band of 380 nm or more and 780 nm or less in the wavelength distribution of the diffraction efficiency of the 1st-order diffracted light and the wavelength distribution of the -1st-order diffracted light of the element element 1a. The efficiency forms a maximum with a full width at half maximum of less than or equal to 200 nm in the wavelength distribution of diffraction efficiency containing the maximum diffraction efficiency. According to the information recording medium 1, 1a, the optical image 100 with good visibility is reproduced even by white light, which is the light of the general light source 51, so that the observer 50 can see the optical image 100 and the printed layer 30. You can enjoy the association with the display. As a result, the designability of the information recording medium 1, 1a is improved. Moreover, the authenticity of the information recording medium 1, 1a can be easily determined based on the relationship between the optical image 100 and the display of the printed layer 30 without using a special light source.

Further, in the information recording medium 1a according to the modified example described above, when observed from a certain observation direction, the relationship between the optical image 100 and the display of the printed layer 30 is shown, and when observed from another certain observation direction , no relevance between the optical image 100 and the display of the printed layer 30 is shown. In such an information recording medium 1a, the observer 50 can enjoy changes in the relationship between the optical image 100 and the display of the printed layer 30 due to changes in the viewing direction. As a result, the designability of the information recording medium 1a is further improved. Further, based on the difference in the relationship between the optical image 100 and the display of the printed layer 30 due to the difference in observation direction, it is possible to easily determine the authenticity of the information recording medium 1a.

Further, in the information recording medium 1a according to the modified example described above, when observed from a certain viewing direction, the optical image 100 and the display have the same color, and when observed from a certain other viewing direction, the optical image 100 and the display on the printed layer 30 are not the same color. In such an information recording medium 1a, it is easy to grasp the relationship between the optical image 100 and the display of the print layer 30. FIG.

Further, in the information recording medium 1a according to the above modification, the optical image 100 is observed when observed from a certain observation direction, and the optical image 100 is not observed when observed from another observation direction. It may be. In this case, it is possible to easily grasp the optical image 100 and the display of the printed layer 30 that are related to each other.

Further, the information recording medium 1a according to the modified example described above further includes viewing direction display means 15 for displaying the viewing direction. The observation direction display means 15 displays the observation direction in which the relationship between the optical image 100 and the printed layer 30 can be observed. Such an observation direction display means 15 can guide the observer 50 so that the observation direction is a direction in which the relationship between the optical image 100 and the display of the printed layer 30 can be observed. Note that the observation direction display means 15 may display an observation direction in which the relationship between the optical image 100 and the display of the printed layer 30 cannot be observed. In this case, the observation direction display means 15 can guide the observer 50 so that the observation direction is a direction in which the relation between the optical image 100 and the display of the printed layer 30 cannot be observed.

[Use]
The above-described information recording media 1 and 1a are not particularly limited in usage and application, and can be used for entertainment purposes such as reproduction of character images and design purposes, for example. The information recording media 1 and 1a include, for example, passports, ID cards, banknotes, credit cards, cash vouchers, gift certificates, other tickets, public documents, other media recording various information such as personal information and confidential information, and other media of monetary value. The ID card referred to here includes, for example, a national ID card, a driver's license, a membership card, an employee card, and a student card. In the hologram holder 10, the base material (see reference numeral 14 in FIG. 3) that holds the hologram structure 12 can be made of, for example, paper, resin, metal, synthetic fiber, or a combination thereof.

Further, it is possible to apply the hologram structure 12 according to the present invention to the hologram holder 10 described above by any method. Alternatively, techniques such as embedding can be used to hold the hologram structure 12 according to the present invention on any object (that is, the hologram holder 10). Therefore, the hologram structure 12 may be formed using a part of the members constituting the hologram holder 10 , or the hologram structure 12 may be additionally provided to the hologram holder 10 .

[Constituent material of hologram layer]
The material forming the hologram layer 11 is not particularly limited, but the hologram layer 11 can be formed from various resins as described above. Specific examples of various resins are listed below.

Thermosetting resins forming the hologram layer 11 include, for example, unsaturated polyester resins, acrylic-modified urethane resins, epoxy-modified acrylic resins, epoxy-modified unsaturated polyester resins, alkyd resins, and phenol resins. Examples of thermoplastic resins constituting the hologram layer 11 include polycarbonate (PC), polyethylene terephthalate (PET), glycol-modified polyethylene terephthalate (PET-G), polyvinyl chloride (PVC), acrylic acid ester resin, and acrylamide. resins, nitrocellulose resins, polystyrene resins, and the like. These resins may be homopolymers or copolymers composed of two or more constituents. Moreover, these resins may be used alone, or two or more of them may be used in combination.

The above-mentioned thermosetting resins or thermoplastic resins include various isocyanate compounds, metallic soaps such as cobalt naphthenate and zinc naphthenate, organic peroxides such as benzoyl peroxide and methyl ethyl ketone peroxide, benzophenone, acetophenone, anthraquinone, naphthoquinone, A thermal or ultraviolet curing agent such as azobisisobutyronitrile, diphenyl sulfide, etc. may be included.

Examples of the ionizing radiation-curable resin constituting the hologram layer 11 include epoxy-modified acrylate resins, urethane-modified acrylate resins, acrylic-modified polyester resins, and the like. A urethane-modified acrylic resin represented by a chemical formula shown in a publication is preferred.

When curing the ionizing radiation-curable resin, 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. etc. In addition, as the bifunctional or higher monomers, when classified by the skeleton structure, polyol (meth)acrylate (e.g., epoxy-modified polyol (meth)acrylate, lactone-modified polyol (meth)acrylate, etc.), polyester (meth)acrylate, epoxy (meth)acrylate, ) acrylates, urethane (meth)acrylates, polybutadiene-based, isocyanuric acid-based, hydantoin-based, melamine-based, phosphoric acid-based, imide-based, and phosphazene-based poly(meth)acrylates having a skeleton. In addition, various monomers, oligomers and polymers that are UV and electron beam curable are available.

More specifically, examples of bifunctional monomers and oligomers include polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth) acrylates and the like. Examples of trifunctional monomers, oligomers, and polymers include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and aliphatic tri(meth)acrylate. Examples of tetrafunctional monomers and oligomers include pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and aliphatic tetra(meth)acrylate. Penta- or higher-functional monomers and oligomers include, for example, dipentaerythritol penta(meth)acrylate and dipentaerythritol hexa(meth)acrylate. Also included are (meth)acrylates having a polyester skeleton, a urethane skeleton, and a phosphazene skeleton. The number of functional groups is not particularly limited, but when the number of functional groups is less than 3, the heat resistance tends to decrease, and when the number of functional groups exceeds 20, the flexibility tends to decrease. Those within the range of 3 to 20 are preferred.

Although the content of the monofunctional or polyfunctional monomers and oligomers as described above can be adjusted as appropriate, it is usually preferably 50 parts by weight or less with respect to 100 parts by weight of the ionizing radiation curable resin, especially 0.5 parts by weight. parts to 20 parts by weight is preferred.

Further, the hologram layer 11 may optionally contain a photopolymerization initiator, a polymerization inhibitor, a deterioration inhibitor, a plasticizer, a lubricant, a coloring agent such as a dye or a pigment, a surfactant, an antifoaming agent, a leveling agent, and Additives such as thixotropic agents may be added as appropriate.

When the hologram layer 11 has self-supporting properties, the film thickness of the hologram layer 11 is preferably in the range of 0.05 mm to 5 mm, more preferably in the range of 0.1 mm to 3 mm. On the other hand, when the hologram layer 11 is formed on the substrate without self-supporting properties, the film thickness of the hologram layer 11 is preferably in the range of 0.1 μm to 50 μm, more preferably in the range of 2 μm to 20 μm. preferably. Also, the size of the hologram layer 11 (for example, the size in plan view) can be appropriately set according to the application of the hologram structure 12 .

[Other Modifications]
The hologram structure 12 used in each of the above-described embodiments and modifications is composed of a plurality of element elements 21 as shown in FIG. may be

Also, the planar view size and planar view shape of each element element 21 are not particularly limited, and each element element 21 can have any size and shape. For example, the planar shape of each element element 21 may be a quadrangle such as a square, rectangle, or trapezoid, another polygonal shape (for example, a triangle, a pentagon, a hexagon, etc.), a perfect circle, an ellipse, another circle, a star shape, or the like. It may have a heart shape or the like, and the hologram structure 12 may have two or more types of element elements 21 having a plan view shape.

Also, the hologram structure 12 may include at least two or more types of element elements 21 having diffraction characteristics different from each other. Such a hologram structure 12 will be described with reference to FIGS. 25 and 26. FIG.

FIG. 25 is a conceptual diagram showing a planar structure of a transmission hologram structure 12 according to a further modified example of the embodiment described above. FIG. 26 is a schematic diagram for explaining the optical image 100 reproduced by the transmission hologram structure 12 of FIG. The hologram structure 12 shown in FIG. 25 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 has an uneven surface 12a capable of reproducing a blue light image 100, and the plurality of second element elements 21b are capable of reproducing a red light image 100. The plurality of third element elements 21c has an uneven surface 12a that enables the green light image 100 to be reproduced. Note that this is based on the case where the incident angle of incident light is 0°. In this case, the hologram structure 12 can reproduce not only the red, blue, and green optical images 100 but also optical images 100 of other colors by overlapping two or more of these optical images 100. . For example, as shown in FIG. 26, by superimposing the optical image 100 of the red circle, the optical image 100 of the green circle, and the optical image 100 of the blue circle and reproducing them, the overlapping portion of the red circle and the green circle is the yellow optical image. 100, the portion where the green circle and the blue circle overlap becomes a light blue light image 100, the portion where the blue circle and the red circle overlap becomes a purple light image 100, and the portion where the red circle and the green circle and the blue circle overlap becomes A white optical image 100 is obtained.

By using such a hologram structure 12, the optical image 100 and the display of the printed layer 30 can be made to be the same color other than red, blue, and green.

The hologram structure 12 may also be provided with optional functional layers, for example, the hologram structure 12 may be covered with a transparent deposited layer. The hologram structure 12 can be concealed by preventing the hologram structure 12 from being glossy by providing a transparent deposition layer that does not have luster. From the viewpoint of hiding the hologram structure 12, the total light transmittance of such a transparent deposition layer is preferably 80% or more, and more preferably 90% or more. Also, in the reflective hologram structure 12, the hologram structure 12 can be covered with a reflective deposited layer. Examples of constituent materials of the reflective deposition layer include Mg, Al, Ti, Cr, Fe, Co, Ni, Cu, Zn, Ga, Ge, Se, Rb, Pd, Ag, Cd, In, Sn, Sb, Te, Metals such as Au, Pb, or Bi can be used. In addition, as a constituent material of the transparent deposited layer, for example, oxides of the above metals such as ZnS and TiO ₂ can be used. These materials may be used alone to form the vapor deposition layer, or two or more materials may be combined to form the vapor deposition layer.

The thickness of the deposited layer provided on the hologram layer 11 (especially on the uneven surface 12a) can be appropriately set from the viewpoint of desired reflectivity, color tone, design, application, etc., and is, for example, within the range of 50 Å to 1 μm. It is preferably within the range of 100 Å to 1000 Å. In particular, when the transparency of the deposited layer is given priority, the thickness of the deposited layer is preferably 200 Å or less, while when the concealability of the deposited layer is given priority, the thickness of the deposited layer is more than 200 Å. is preferred. As a method for forming the vapor deposition layer, a general method for forming a vapor deposition layer can be employed, and examples thereof include a vacuum vapor deposition method, a sputtering method and an ion plating method.

The invention is not limited to the embodiments and variants described above. For example, various modifications may be made to each element of the embodiments and modifications described above. Forms including components and/or methods other than the components and/or methods described above may also be included in embodiments of the present invention. Forms that do not include some of the components and/or methods described above may also be included in embodiments of the present invention. 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 may also be included in the present invention. can be included in an embodiment. Therefore, the components and/or methods included in each of the above-described embodiments and modifications, and other embodiments of the present invention may be combined with each other, and the forms according to such combinations may also be implemented in the present invention. can be included in the form. Further, the effects achieved by the present invention are not limited to those described above, and specific effects according to the specific configurations of the respective embodiments can also be exhibited. Thus, various additions, changes, and partial deletions can be made to each element described in the claims, specification, abstract, and drawings without departing from the technical idea and gist of the present invention. is.

1, 1a information recording medium 11 hologram layer 10 hologram holder 12 hologram structure 12a uneven surface 14 substrate 14a openings 21, 21a, 21b, 21c element element 30 printed layer 31 first display section 32 second display section 50 Observer 51 Light source 51a Light source 51b Light source 100 Light image 100a 0th order diffraction light image 100b 1st order diffraction light image 100c −1st order diffraction light image

Claims (8)

an optical modulation element including an element element that reproduces an optical image by modulating the phase of incident light;
a printed layer that provides a shape-related or conceptually-related display that is color-related to the light image;
The element element has an uneven surface,
Wavelength distribution of diffraction efficiency of 1st-order diffracted light and wavelength distribution of diffraction efficiency of -1st-order diffracted light for the element element when the incident angle of the incident light to the element element is any angle between 0° and 50°. wherein the maximum diffraction efficiency in a wavelength band of 380 nm or more and 780 nm or less in . When observed from a certain observation direction, the relationship between the optical image and the display is shown,
2. The information recording medium according to claim 1, wherein the relationship between said optical image and said display is not shown when viewed from another viewing direction. When observed from the certain observation direction, the light image and the display have the same color,
3. The information recording medium according to claim 2, wherein said optical image and said display have different colors when viewed from said different viewing direction. The optical image is observed when observed from the certain observation direction,
4. The information recording medium according to claim 2, wherein said optical image is not observed when viewed from said different viewing direction. 5. The information recording medium according to claim 2, further comprising viewing direction display means for displaying the viewing direction. 6. The information recording medium according to claim 5, wherein said observation direction display means displays an observation direction in which a relationship between said optical image and said display can be observed. 6. The information recording medium according to claim 5, wherein said observation direction display means displays an observation direction in which a relationship between said optical image and said display cannot be observed. 8. The information recording medium according to any one of claims 1 to 7, wherein personal information is recorded.

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