JP3635116B2 - Diffraction grating recording medium - Google Patents

Description

[0001]
[Industrial application fields]
  The present inventionRegarding diffraction grating recording mediaEspecially suitable for use in security diffraction grating seals to prove authenticityThe present invention relates to a diffraction grating recording medium.
[0002]
[Prior art]
Hologram stickers are used as means for preventing counterfeiting of credit cards, bankbooks, cash vouchers, and the like. In addition, hologram stickers are also used for products such as videotapes and luxury watches to prevent pirated copies from circulating. In addition, hologram stickers are also used for decoration and sales promotion purposes. ing. Such a hologram seal often uses a two-dimensional pattern as a motif instead of a three-dimensional stereoscopic image.
[0003]
As a method for creating a hologram seal, an optical hologram photographing method in which interference fringes are formed using laser light is generally used. That is, prepare a manuscript with a two-dimensional pattern motif, irradiate this manuscript with one of the two branched laser beams, and cause the reflected beam to interfere with the other branched laser beam. Interference fringes are recorded on the photosensitive material. Once the hologram master is prepared in this way, the hologram seal can be mass-produced by a pressing method using this master.
[0004]
  However, recently, since image processing technology by a computer and drawing technology by an electron beam have advanced, a method of creating a pseudo hologram master by scanning an electron beam based on image data prepared by a computer has been put into practical use. Yes. That is, a fine diffraction grating is recorded on the medium, and a two-dimensional pattern motif is expressed by the diffraction grating. For example,JP-A-6-337622Proposed a new method of forming a diffraction grating recording medium by expressing a two-dimensional pattern with a plurality of pixels and assigning a pixel pattern formed by arranging a number of diffraction gratings to each pixel. . Also,JP-A-7-146537Discloses an efficient production method for mass-producing such a diffraction grating recording medium,JP-A-7-146635Has disclosed improvements to express a pattern with gradation,JP-A-8-075912Discloses an improved point for expressing a picture having a color.
[0005]
[Problems to be solved by the invention]
In the diffraction grating recording medium described above, when a plurality of different motifs are expressed on the same plane, a plurality of pixel patterns having different grid line arrangement angles are used for each motif. For example, a pixel pattern having a grid line arrangement angle of 45 ° is assigned to the pixels constituting the motif A, and a pixel pattern having a grid line arrangement angle of 90 ° is assigned to the pixels constituting the motif B. It is possible to create a diffraction grating recording medium in which only the motif A is observed when observed from the above, and only the motif B is observed when observed from another angle.
[0006]
However, when the motif A and the motif B overlap on a plane, some device is required. Therefore, conventionally, a method of dividing one pixel into a plurality of sub-pixels and assigning a pixel pattern to each sub-pixel is employed. For example, one pixel is divided into four sub-pixels each consisting of 2 rows and 2 columns, the pixel pattern for motif A is assigned to the upper left and lower right sub pixels, and the motif B is assigned to the lower left and upper right sub pixels. If the pixel pattern is assigned, the motif A and the motif B may overlap in pixel units, but do not overlap in sub-pixel units, and each sub-pixel has a grid line arrangement angle. Only one of the 45 ° pixel pattern and the pixel pattern with the grid line arrangement angle of 90 ° is assigned, and no trouble occurs.
[0007]
However, in the diffraction grating recording medium that employs a method in which one pixel is divided into a plurality of sub-pixels and a pixel pattern is assigned and a plurality of motifs are recorded in duplicate, the luminance and image quality are reduced during observation. There is. For example, when divided into four sub-pixels as described above, diffracted light is not obtained from the entire pixel during observation, and only diffracted light from the upper left and lower right sub-pixels is obtained when observing motif A. First, when the motif B is observed, only diffracted light from the lower left and upper right subpixels can be obtained. For this reason, compared to the case where each motif is recorded individually, the luminance is halved, and only a dark image as a whole can be obtained. In addition, since the sub-pixel is used instead of the pixel, the image quality is also lowered.
[0008]
  Therefore, the present invention does not reduce luminance and image quality even when a plurality of motifs are superimposed.Diffraction grating recording mediumThe purpose is to provide.
[0009]
[Means for Solving the Problems]
[0015]
  (1) First aspect of the present inventionIs a diffraction grating recording medium in which a plurality of motifs are represented by a diffraction grating.
  Pixels in which a large number of grid lines are arranged in a predetermined pixel closed region are defined by changing the grid line arrangement angle, and these pixel patterns are pixels whose grid line arrangement angles approximate each other. Divide the pattern into multiple groups and associate one group for each of the multiple motifs to be expressed.
  For two pixel patterns belonging to different groups, a multiple pixel pattern obtained by arranging the grid lines arranged in each group in the same pixel closed region is defined,
  A pixel pattern belonging to a group associated with the motif is assigned to a pixel constituting only a single motif, and two pixels associated with each motif are assigned to pixels constituting two motifs. A multiple pixel pattern defined for the pixel pattern to which it belongs is assigned.
[0016]
  (2) Second aspect of the present inventionIs a diffraction grating recording medium in which a plurality of motifs are represented by a diffraction grating.
  Pixels in which a large number of grid lines are arranged in a predetermined pixel closed region are defined by changing the grid line arrangement angle, and these pixel patterns are pixels whose grid line arrangement angles approximate each other. Divide the pattern into multiple groups and associate one group for each of the multiple motifs to be expressed.
  For two pixel patterns belonging to different groups, a multiple pixel pattern obtained by arranging the grid lines arranged in each group in the same pixel closed region is defined,
  For pixels that make up only a single motif, assign a pixel pattern belonging to the group associated with that motif to each sub-pixel obtained by dividing this,
  For pixels that make up multiple motifs, each subpixel obtained by dividing this motif is assigned a pixel pattern belonging to each of the groups associated with each motif or its multiple pixel pattern, and related to each group. The grid lines arranged at the grid line arrangement angle are configured to appear in at least one sub-pixel.
[0017]
  (3) According to a third aspect of the present invention, in the diffraction grating recording medium according to the first or second aspect described above,
  A lattice line is used between the line width dL and the space width dS so as to obtain a relationship of dS ≧ 2 · dL.
  (Four) According to a fourth aspect of the present invention, in the diffraction grating recording medium according to the third aspect described above,
The grid line is configured such that the line portion forms a convex portion and the space portion forms a concave portion.
[0018]
  (Five) According to a fifth aspect of the present invention, in the diffraction grating recording medium according to the fourth aspect described above,
For a predetermined visible wavelength λ, a lattice line having a space width dS that satisfies the expression dS> λ is used.
  (6) According to a sixth aspect of the present invention, in the diffraction grating recording medium according to the fifth aspect described above,
A predetermined observation angle θ is defined with respect to a normal line standing on the surface of the recording medium, and lattice lines having a line width dL and a space width dS that satisfy the expression (dS + dL) · sin θ = λ are used. It is a thing.
[0019]
[Operation]
The basic concept of the present invention is to multiplex-record a plurality of motifs using a multiple diffraction grating in which two types of grating lines having different directions are recorded in the same closed region. A diffraction grating is formed by forming a large number of grooves having a three-dimensional uneven structure on the surface of a medium. The grooves, that is, the grating lines are all formed in parallel and in a single direction. It was an existing concept. The inventor of the present application has found that even when two types of grid lines having different directions are recorded in an overlapping manner, a diffraction phenomenon can be caused for each grid line.
[0020]
However, in order to cause a practical diffraction phenomenon with such a multiple diffraction grating, specific conditions must be set. According to experiments conducted by the inventors of the present application, a medium that functions as a multiple diffraction grating can be obtained by using a grating line that provides a relationship of dS ≧ 2 · dL between the line width dL and the space width dS. It was confirmed that In addition, if the line portion of the grating line is formed as a convex portion and the space portion is formed as a concave portion on the medium, a brighter multiple diffraction grating can be obtained practically. In the case of a multiple diffraction grating having a human observer, a space width dS that satisfies the expression dS> λ is required for a predetermined visible wavelength λ. This indicates a condition that the space width dS constituting the concave portion is larger than the visible wavelength λ, and is a necessary condition for introducing the light having the visible wavelength λ into the concave portion. In addition, when the diffraction grating recording medium is used as a forgery prevention seal, a specific observation angle is generally determined. For example, when used as an anti-counterfeit seal for a credit card, it is common to define an angle inclined about 30 ° to the normal line standing on the surface of the credit card as a temporary observation angle. is there. The inventor of the present application defines a predetermined observation angle θ according to the application, and has a line width dL and a space width dS satisfying the expression (dS + dL) · sin θ = λ for a predetermined visible wavelength λ. It was confirmed that a diffraction grating recording medium optimum for the intended use can be formed by using a grating line. The equation (dS + dL) · sin θ = λ is an equation obtained by setting the diffraction order n = 1 in the Bragg equation when the pitch of the diffraction grating is (dS + dL). This is a necessary condition for obtaining at the observation angle.
[0021]
If such a multiple diffraction grating is used, it is not necessary to use a sub-pixel as in the prior art even when a plurality of overlapping motifs are expressed on the same plane. For example, when the motif A is expressed by a pixel pattern having a grid line arrangement angle of 45 ° and the motif B is expressed by a pixel pattern having a grid line arrangement angle of 90 °, the pixels constituting only the motif A have 45 ° A pixel pattern is allocated, and a 90 ° pixel pattern may be allocated to the pixels constituting only the motif B. The pixels constituting both the motifs A and B are assigned a multiple pixel pattern in which the lattice lines arranged in the 45 ° direction and the lattice lines arranged in the 90 ° direction are overlapped and recorded. That's fine. Since it is not necessary to divide one pixel into sub-pixels, there is no problem that the luminance and image quality are lowered as in the prior art.
[0022]
The multiple pixel pattern can be easily generated by calculation using a computer. In addition, when drawing a multiple pixel pattern with an electron beam, efficient work can be performed by drawing a quadrangular region surrounded on four sides by grid lines.
[0023]
【Example】
Hereinafter, the present invention will be described based on some embodiments illustrated in the drawings.
[0024]
  §1. Conventional diffraction grating recording medium
  First of all,JP-A-6-337622The configuration of the conventional diffraction grating recording medium disclosed in the above will be briefly described. First, a conventional method for expressing a motif (showing the English letter “A”) as shown in FIG. 1A on a diffraction grating recording medium will be described. First, as pixel data corresponding to the motif shown in FIG. 1A, motif pixel information as shown in FIG. 1B is prepared. In the example shown here, pixels are arranged in 7 rows and 7 columns, and each pixel has a pixel value of “0” or “1”, which is information indicating a so-called binary image. Such information is general image data called so-called “raster image data”, and can be created by a normal drawing device. Alternatively, such motif pixel information may be prepared by capturing a design image drawn on a paper surface with a scanner device.
[0025]
Subsequently, as shown in FIG. 2, a pixel pattern is defined in which lines L having a line width dL and spaces S having a space width dS are alternately arranged in the closed region V. The line L is a portion that becomes a lattice line on the medium, and a large number of lattice lines having a width dL are formed at a distance dS from each other. The pitch p of such a diffraction grating is p = dL + dS, and the lines L (grating lines) are all arranged with the same angle θ. Here, the closed region V is a region constituting one pixel, and actually becomes a very small element. In other words, the size corresponds to each pixel in the 7 × 7 array shown in FIGS. 1 (a) and 1 (b). In this example, as the closed region V, a rectangle having a size of 50 μm × 45 μm in length × width is used, but a square having a size of 50 μm × 50 μm may be used, for example. In addition, the width dL of the line L and the width dS of the space S arranged in the closed region V also have minute dimensions according to the wavelength of light. In this example, the line width dL = 0.6 μm. The space width dS = 0.6 μm and the pitch p = 1.2 μm.
[0026]
In short, the lines L need to be arranged with a line width dL and a pitch p that function as a diffraction grating. The arrangement angle θ of the line L is an angle set with respect to a predetermined reference axis. In the present specification, an XY coordinate system having the X axis and the Y axis in the direction shown in the figure is defined, and the arrangement angle θ of the line L is expressed with the X axis as a reference axis. Of course, such a pixel pattern is prepared as image data in the computer. Next, based on each pixel value in the motif pixel information as shown in FIG. 1B, the pixel pattern as shown in FIG. 2 is associated with a predetermined pixel, and the corresponding pixel pattern is arranged at each pixel position. Perform the process. Specifically, in the motif pixel information shown in FIG. 1B, the pixel pattern shown in FIG. 2 is associated with each pixel having a pixel value “1”. A pixel pattern is not associated with a pixel having a pixel value “0”. A pixel pattern is assigned to each pixel position thus associated. In other words, if the arrangement shown in FIG. 1 (b) is compared to a wall, a tile as shown in FIG. 2 is applied to each area labeled “1” in the wall. . As a result, an image pattern as shown in FIG. 3 is obtained. This image pattern is a pattern finally recorded on the diffraction grating recording medium. Although the motif shown in FIG. 1A is expressed as it is, each pixel is formed of a diffraction grating, and a visual effect as a diffraction grating can be obtained.
[0027]
The basic example of assigning the diffraction grating pattern in units of pixels has been described above. Next, a conventional method for expressing a plurality of motifs will be described. Since the diffracted light obtained from the diffraction grating has directionality, it may or may not be observed depending on the observation direction. Therefore, for example, as shown in FIG. 4, if pixel patterns P1 (lattice line arrangement angle 45 °) and P2 (lattice line arrangement angle 90 °) having different grid line arrangement angles are allocated on the same medium, Only the pixel pattern P1 is observed from a certain observation angle, and only the pixel pattern P2 is observed from another observation angle. Therefore, if motif A is represented by pixel pattern P1 and motif B is represented by pixel pattern P2, two different motifs can be represented on the same plane, and only motif A is observed from a certain observation angle. Thus, it becomes possible to form a recording medium in which only the motif B is observed from another observation angle. This is a basic method for expressing a plurality of different motifs on the same medium.
[0028]
However, when two motifs in which pixels overlap each other are expressed on the same medium, some device is required. For example, the above basic method is applied as it is to two motifs A and B as shown in FIGS. Here, it is assumed that the pattern A shown in FIG. 4 corresponds to the motif A, and the pattern P2 shown in FIG. 4 corresponds to the motif B. Then, correspondence information R1 as shown in FIG. 6 (a) is created for motif A, and correspondence information R2 as shown in FIG. 6 (b) is created for motif B. However, if an attempt is made to actually assign a pixel pattern based on the two correspondence information R1 and R2, pixel pattern collision occurs with respect to the pixels surrounded by a solid line in FIG. For example, looking at the pixel in the second row and the fourth column, the correspondence information R1 indicates that the pixel pattern P1 is assigned, whereas the correspondence information R2 indicates that the pixel pattern P2 is assigned. Has been. For this reason, it is impossible to determine which pixel pattern should actually be allocated.
[0029]
Therefore, conventionally, this problem is solved by introducing the concept of sub-pixels. For example, when a predetermined motif is represented by the pixel arrangement of 7 rows and 7 columns shown in FIGS. 5A and 5B, each pixel is divided into 2 rows and 2 columns of sub-pixels, and the upper left and lower right. If the motif A is expressed by the sub-pixels and the motif B is expressed by the lower-left and upper-right sub-pixels, both motifs will not overlap in the sub-pixel unit even if both motifs overlap in the pixel unit. FIGS. 7A and 7B show pixel pattern arrangements for such sub-pixels. Here, each rectangle surrounded by a solid line is a pixel, and a small rectangle obtained by dividing this pixel into four as shown by a broken line is a sub-pixel. In FIG. 7A, in order to express the motif A, the pixel whose pixel value is “1” in the motif A (the pixel shown in black in FIG. 5A) is the upper left in the pixel. FIG. 7B shows a state in which the pixel pattern P1 having a grid line arrangement angle of 45 ° is assigned to the lower right sub-pixel. FIG. 7B shows the pixel value “1” in the motif B in order to express the motif B. A pixel (a pixel shown in black in FIG. 5B) shows a state in which a pixel pattern P2 having a grid line arrangement angle of 90 ° is assigned to the lower left and upper right subpixels in the pixel. The sub-pixel to which the pixel pattern is assigned in FIG. 7 (a) and the sub-pixel to which the pixel pattern is assigned in FIG. 7 (b) never come to the same position. A diffraction grating recording medium as shown in FIG. 8 can be obtained.
[0030]
In the diffraction grating recording medium shown in FIG. 8, the motif A and the motif B are expressed in an overlapping manner. Moreover, since the subpixels representing motif A and the subpixels representing motif B have different grid line formation angles, motif A can be recognized when observed from a certain direction (as shown in FIG. 7 (a)). The motif B can be recognized when observed from another direction (a pattern as shown in FIG. 7B can be recognized). By using such a method, it is possible to express a plurality of motifs with overlapping pixels on the same plane.
[0031]
However, as described above, such a method using sub-pixels has a problem that luminance and image quality are lowered. For example, if the motif A expressed by a normal pixel as shown in FIG. 3 is compared with the motif A expressed by a sub-pixel as shown in FIG. 7A, diffracted light is obtained in the latter. The area obtained is half that of the former, and it can be seen that the overall luminance is reduced to half. Further, when comparing the sizes of the individual pixels, the size of the latter pixel is 1/4 with respect to the former pixel, and the diffraction grating aperture surface is small and the luminance is further lowered. As a method for recording a plurality of motifs in an overlapping manner without reducing the size of each pixel, the description of FIG. 28 of Japanese Patent Application No. 5-148681 also discloses a method of thinning out pixels. If the pixels are thinned out, deterioration of the image quality is inevitable. The present invention provides a novel technique for solving such a conventional problem. Hereinafter, the method of the present invention will be described in detail.
[0032]
§2. Diffraction grating recording medium according to the present invention
Here, the method according to the present invention will be described by taking as an example the case of recording two motifs A and B as shown in FIGS. 5 (a) and 5 (b). In the method according to the present invention, three types of pixel patterns are prepared as shown in FIG. The pixel patterns P1 and P2 are exactly the same as the pixel patterns used in the conventional method described in section 1 above. The pixel pattern P1 (lattice line arrangement angle 45 °) is a pattern for expressing the motif A, and the pixel pattern P2 (lattice line arrangement angle 90 °) is a pattern for expressing the motif B. In the present invention, a multiple pixel pattern P12 is further prepared. The multiple pixel pattern P12 is a pattern in which the pixel patterns P1 and P2 are overlapped. A grid line having an arrangement angle of 45 ° existing in the pixel pattern P1 and a grid line having an arrangement angle of 90 ° existing in the pixel pattern P2. And a pattern in which both are arranged. In this way, a diffraction grating having two types of grating lines having different directions is referred to as a multiple diffraction grating.
[0033]
Under a normal illumination environment, the diffraction grating recording medium on which the pixel pattern P1 is formed looks bright when observed from the observation direction D1 shown in the lower part of FIG. 9, and the diffraction grating recording medium on which the pixel pattern P2 is formed is It looks bright when observed from the observation direction D2 shown in the lower part of FIG. However, the multiple pixel pattern P12 has both of these properties, and looks bright even when observed from either of the observation directions D1 and D2. Therefore, the pixel pattern P1 is assigned to the pixels constituting only the motif A, the pixel pattern P2 is assigned to the pixels constituting only the motif B, and the multiple pixel pattern P12 is assigned to the pixels constituting both the motif A and the motif B. If both are assigned, both patterns can be expressed without using sub-pixels.
[0034]
Specifically, in order to express both motifs A and B as shown in FIGS. 5 (a) and 5 (b), correspondence information as shown in FIG. 10 is prepared and based on the correspondence information. The three types of pixel patterns P1, P2, and P12 shown in FIG. FIG. 11 shows a diffraction grating recording medium obtained by performing such assignment. In this diffraction grating recording medium, a grid line with an angle of 45 ° is always arranged at the pixel position shown in black in the motif A shown in FIG. 5A, and if observed from the observation direction D1 shown in FIG. Motif A will be observed. On the other hand, at the pixel position shown in black in the motif B shown in FIG. 5 (b), a grid line with an angle of 90 ° is always arranged, and if observed from the observation direction D2 shown in FIG. Will be.
[0035]
According to the method using such a multiple diffraction grating as a pixel, the problem of deterioration in luminance and image quality as in the conventional method using a sub-pixel is solved. For example, when the motif A expressed by a normal pixel as shown in FIG. 3 is compared with the motif A expressed by a pixel including a multiple pixel pattern as shown in FIG. 11, the diffracted light is detected at a predetermined observation angle. The obtained area is the same for both, and the shape of the pixel is a complete rectangle. Therefore, theoretically, the brightness and the image quality are the same, and problems such as a method using subpixels do not occur. In practice, however, the luminance of the latter is slightly lower than that of the former. This is because, when the multiple pixel pattern P12 shown in FIG. 9 is formed on an actual recording medium, it is necessary to form a physical concavo-convex structure. Therefore, an ideal multiple diffraction grating that serves as both the pixel patterns P1 and P2 is used. This is because it is physically difficult to form. The physical structure of the multiple diffraction grating will be described in detail later. In an actual multiple diffraction grating, the luminance obtained when the multiple pixel pattern P12 is observed from the observation direction D1 is the same as the observation direction of the pixel pattern P1. The luminance is slightly lower than the luminance obtained when observed from D1, and the luminance obtained when observing the multiple pixel pattern P12 from the observation direction D2 is obtained when the pixel pattern P2 is observed from the same observation direction D2. It is slightly lower than the brightness. However, compared with the conventional method using sub-pixels, the method using the multiple pattern according to the present invention can provide sufficient luminance.
[0036]
§3. Conditions for multiple diffraction gratings
The basic concept of the present invention is to multiplex-record a plurality of motifs using a multiple diffraction grating in which two types of grating lines having different directions are recorded in the same closed region. However, in order to cause a practical diffraction phenomenon with such a multiple diffraction grating, specific conditions must be set. The inventor of the present application performs multiplex recording of a diffraction grating having a grating line arrangement angle of 0 ° as shown in FIG. 12 (a) and a diffraction grating having a grating line arrangement angle of 90 ° as shown in FIG. 12 (b). As a result of trial manufacture of a grating as shown in FIG. 13, diffracted light could not be observed at all from any observation direction. The diffraction grating shown in FIG. 12 (a) and the diffraction grating shown in FIG. 12 (b) are both standard diffraction gratings that have been generally used. That is, all the diffraction gratings are diffraction gratings having a condition that the width dL of the line L is equal to the width dS of the space S and dL: dS = 1: 1.
[0037]
As described above, no diffraction phenomenon was observed in the grating obtained by superimposing two kinds of diffraction gratings having a very standard condition of “dL: dS = 1: 1”. It was found that the diffraction phenomenon occurs by changing the ratio of “dL: dS” from 1: 1. For example, a diffraction phenomenon occurs in a grating obtained by superposing two types of diffraction gratings having a condition of “dL: dS = 1: 2”. That is, a diffraction grating having a grating line arrangement angle of 0 ° as shown in FIG. 14A and a diffraction grating having a grating line arrangement angle of 90 ° as shown in FIG. When a prototype as shown in FIG. 14 was made, a longitudinal direction (a direction in which the diffracted light with respect to the diffraction grating shown in FIG. 14A can be observed) and a lateral direction (a diffracted light with respect to the diffraction grating shown in FIG. 14B) were obtained. The diffracted light could be observed when observed from any direction. However, the brightness of the diffracted light observed for this multiple diffraction grating is slightly darker than the diffracted light observed for the original diffraction grating (the diffraction grating shown in FIGS. 14A and 14B).
[0038]
In order to find the critical condition regarding the ratio “dL: dS” for forming the multiple diffraction grating, an experiment was conducted by changing this ratio variously. As a result, the condition “dL: dS = 1: 2” was found. It was confirmed that it was a critical condition for obtaining diffracted light within the range recognized by a person. That is, between the line width dL and the space width dS,
dS ≧ 2 · dL (Basic conditions)
Multiple diffraction gratings can be obtained by superimposing two types of diffraction gratings having grating lines that can obtain the following relationship. Of course, since this is a light diffraction phenomenon, it is needless to say that the pitch p (p = dL + dS) of the lattice lines needs to have a length close to the wavelength of the light. A theoretical analysis of why the condition “dL: dS = 1: 2” becomes a critical condition for forming a multiple diffraction grating has not been made at this stage, but this ratio is 1: 2 or more. The inventors of the present application believe that a multiple diffraction grating can be formed as long as the pitch p is a pitch that causes diffraction. As an extreme example, even if “dL: dS = 1: infinity”, it can be expected that a multiple diffraction grating can be formed as long as the pitch p is a pitch causing diffraction. However, in order to realize the ratio of “1: infinity”, it is necessary to set the line width dL = 0, and in reality, it is impossible to form such a multiple diffraction grating. However, it is sufficient for the line L formed on the actual medium to function as a light shield, and even if the line width dL approaches zero as long as the line L has a function of shielding light, It is possible to form a multiple diffraction grating according to the invention.
[0039]
Further, the two types of diffraction gratings (the diffraction gratings shown in FIGS. 14A and 14B) that are the basis of the multiple diffraction gratings shown in FIG. 15 have the same line width dL and the same space width dS. Although the diffraction gratings are equal, it is not always necessary to use two types of diffraction gratings in which they are equal. If the relationship of dS ≧ 2 · dL (basic conditions) is obtained in each diffraction grating, multiple diffraction gratings can be obtained even if two kinds of diffraction gratings having different line width dL and space width dS are overlapped. It is possible to get
[0040]
Incidentally, although the multiple diffraction grating shown in FIG. 15 is shown as a black and white pattern, the multiple diffraction grating actually formed on the medium is a structure having a fine concavo-convex structure. For example, in the black-and-white pattern shown in FIG. 15, the black portion (that is, the portion of the line L) is a convex portion, and the white portion (the portion of the square space SS surrounded by the lines L) is the concave portion. A side sectional view of the diffraction grating recording medium 80 is shown in FIG. Here, a portion of the space SS forms a recess 85, and light enters the recess 85 to cause a diffraction phenomenon, and a portion of the line L functions as a shielding wall 86 for the incident light ( As described above, the thickness may theoretically be zero if it has a function as the shielding wall 86). However, in contrast to the concavo-convex structure shown in FIG. 16, even if a diffraction grating recording medium having a black portion as a concave portion and a white portion as a convex portion in the black and white pattern shown in FIG. Function as. However, practically, as shown in FIG.
The black part (line part) is a convex part,
The white part (space part) is a recess (practical condition 1).
Is preferred. This is because the width dS of the white portion is more than twice as long as the width dL of the black portion due to the basic condition of dS ≧ 2 · dL. This is because light can be taken into the depression 85 and more diffracted light can be obtained.
[0041]
Further, in the structure shown in FIG. 16, in order to cause a diffraction phenomenon with respect to light having a predetermined wavelength λ, the width of the recess 85, that is, the space width dS needs to be larger than the wavelength λ. This is because light having a wavelength larger than the space width dS cannot enter the recess 85 and is not diffracted. However, the diffracted light in the ultraviolet region or infrared region is useless as a diffraction grating recording medium for human observation. Therefore, as a condition as a practical diffraction grating recording medium,
For visible wavelength λ dS> λ (Practical condition 2)
This condition is necessary.
[0042]
By the way, when the diffraction grating recording medium is used as an anti-counterfeit seal, a specific observation angle is generally determined. Usually, as shown in FIG. 16, it is common to observe from within a range of ± 45 ° with respect to a normal line standing on the surface of the medium 80. For example, when used as an anti-counterfeit seal for a credit card, it is common to define an angle inclined about 30 ° to the normal line standing on the surface of the credit card as a temporary observation angle. is there. This observation angle is the most natural observation angle when a credit card is held.
[0043]
In this way, if a specific observation angle can be determined, more preferable conditions can be set as a diffraction grating recording medium. For example, light is incident on the upper surface of the multiple diffraction grating recording medium 80 from vertically above, and the condition for diffracting the light in the direction of a predetermined observation angle θ is the Bragg equation.
p · sin θ = nλ
Given by. Here, p is the pitch of the diffraction grating, and in the present invention, p = (dS + dL). Further, as described above, θ is an observation angle (angle formed with a normal line standing on the surface of the medium), λ is a wavelength of light to be observed, and n is an order of diffracted light to be obtained (n = 1, 2, 3, ...). In practice, it is preferable to use the brightest first-order diffracted light, and n = 1. Therefore, from the above black equation, as a conditional expression of a practical multiple diffraction grating recording medium,
(DS + dL) · sin θ = λ (Practical condition 3)
The following formula is obtained.
[0044]
After all, the basic conditions for obtaining the multiple diffraction grating recording medium and the practical conditions necessary for putting this into practical use are summarized as follows.
<Basic conditions> dS ≧ 2 · dL
<Practical condition 1> The line part is a convex part and the space part is a concave part.
<Practical condition 2> For visible wavelength λ dS> λ
<Practical condition 3> (dS + dL) · sin θ = λ
Specific examples of the present invention include:
dL = 0.4 μm, dS = 0.8 μm (pitch p = 1.2 μm)
θ = 30 ° (sin θ = 1/2)
λ = 0.6μm (visible wavelength)
Is set. In this setting, dS = 2 · dL and the basic condition is satisfied, and dS> λ and the practical condition 2 is also satisfied. Furthermore, (dS + dL) · sin θ = (0.4 μm + 0.8 μm) · 1/2 = 0.6 μm = λ, which satisfies Practical Condition 3. Therefore, according to the above setting, a practical multiple diffraction grating recording medium satisfying all the above conditions can be produced.
[0045]
§4. Drawing method of multiple diffraction grating pattern
Next, a method for forming a multiple diffraction grating pattern according to the present invention on a medium will be described. As shown in FIG. 16, the multiple diffraction grating recording medium 80 according to the present invention is a medium having a concavo-convex structure on the surface. When producing such a medium, it is common to first produce an original plate having an inverted concavo-convex structure and mass-produce the medium by press working using this original plate. In order to prepare an original plate, a resist layer is formed on the original plate constituent layer, this resist layer is patterned into a pattern as shown in FIG. 15, and then an exposed portion of the original plate constituent layer is etched. However, since the diffraction grating pattern is generally a fine pattern of submicron order in both the line width dL and the space width dS, it is difficult to expose the resist layer using a photomask. Therefore, a method of directly exposing the resist layer using an electron beam is usually employed.
[0046]
When the multiple diffraction grating original plate according to the present invention is prepared, the resist layer is exposed using an electron beam as in the case of forming a conventional general diffraction grating original plate. Conventionally, an electron beam is scanned based on image data as shown in FIG. 14 (a) or (b) to form a monochrome pattern as shown on the resist layer. That is, a black region corresponding to the line L is irradiated with a beam to form an exposure portion. Therefore, in the present invention, an electron beam may be scanned based on image data as shown in FIG. 15 to form a black and white pattern on the resist layer.
[0047]
However, an electron beam drawing apparatus currently on the market generally employs a method of designating a drawing target as a set of rectangular graphic data. In other words, a general electron beam drawing apparatus has only a function of scanning an electron beam in an area within a quadrilateral connecting the four vertices based on four given vertex coordinate values. It is easy to draw a normal diffraction grating pattern as shown in FIG. 14 (a) or (b) using such an electron beam drawing apparatus. That is, each line L is a very long rectangle with a width dL, and can be drawn by giving the four vertex coordinate values to the electron beam drawing apparatus. However, in order to draw the multiple diffraction grating pattern according to the present invention as shown in FIG. In order to perform drawing with a general electron beam drawing apparatus, it is necessary to divide the multiple diffraction grating pattern into several squares.
[0048]
One possible method is to divide the pattern shown in FIG. 15 into the pattern shown in FIG. 14 (a) and the pattern shown in FIG. 14 (b). That is, if the pattern shown in FIG. 14A is drawn and then the pattern shown in FIG. 14B is overlaid, the pattern shown in FIG. 15 is obtained. However, this method is not preferable because double drawing is performed in the intersection region CC of the two lines L as shown by hatching in FIG. That is, the resist layer corresponding to the intersecting region CC is irradiated with the electron beam twice, so that the exposure amount is doubled compared with the normal line L portion. For this reason, when the resist layer is developed, a difference occurs between the portion of the normal line L and the portion of the intersection region CC. In order to prevent such a difference from occurring, as shown in FIG. 17B, one line L is divided at the intersection, and a plurality of rectangles that do not overlap each other are defined, and exposure is performed for each rectangle. Can also be taken. However, in such a method, since the distance between adjacent squares becomes very small, troubles are likely to occur when performing a process of exposure / development on the resist layer.
[0049]
Therefore, in this embodiment, electron beam writing is performed by the following method. That is, the black and white of the multiple diffraction grating pattern shown in FIG. 15 is inverted to form a negative pattern as shown in FIG. In this negative pattern, the portion of the line L is white and the portion of the square space SS is black. Then, the area of the square space SS shown in black is drawn by the electron beam. All of the space SS portions are quadrangular, and the electron beam lithography apparatus can be easily rendered simply by giving four vertex coordinate values of the square.
[0050]
Note that such black-and-white reversal processing is only required to replace “1” and “0” when the pattern is expressed as binary raster image data. However, in order to reduce the amount of data, the pattern is preferably expressed as vector data. In this case, the following processing may be performed. First, the patterns shown in FIGS. 14A and 14B are prepared as two-dimensional graphic data (vector data) in which the outline of the space area between grid lines (the white area in the figure) is expressed by a rectangle. Then, a logical operation is performed between these two two-dimensional graphic data to obtain two-dimensional graphic data in which the intersecting area of each square is represented by a new square (white area in FIG. 15 or black area in FIG. 18). Good.
[0051]
When the negative pattern shown in FIG. 18 is used instead of the pattern shown in FIG. 17, it is necessary to use as the resist layer a negative resist in which a portion exposed by an electron beam remains by development. Hereinafter, a process for producing an original plate using such a negative resist will be described step by step with reference to side sectional views of FIGS.
[0052]
First, as shown in FIG. 19, an original constituting layer 2 is formed on a substrate 1, and a negative resist layer 3 is formed thereon. In this embodiment, a glass substrate is used as the substrate 1 and a metal layer (for example, copper) is used as the original plate constituent layer 2. Subsequently, the electron beam is scanned based on the negative pattern as shown in FIG. 18 to expose only the area of the square space SS shown in black in the drawing. As a result, as shown in FIG. 20, an exposed portion 3 a and a non-exposed portion 3 b are formed on the resist layer 3. The exposed portion 3a is a portion corresponding to the black region in FIG. 18, and the non-exposed portion 3b is a portion corresponding to the white region in FIG. Subsequently, when the resist is developed, since it is a negative resist, the non-exposed portion 3b is eluted and removed, and only the exposed portion 3a remains as shown in FIG. Therefore, the original exposed layer 3 is etched using the remaining exposed portion 3a as a mask. Then, as shown in FIG. 22, the exposed portion of the original constituting layer 2 is removed by etching, and the remaining layer 2a and the exposed portion 3a remain only in a region corresponding to the square space SS. When mass producing a diffraction grating recording medium by a press method, the structure shown in FIG. 22 can be used as the original 60 as it is. Of course, after that, the resist (exposed portion 3a) may be peeled off and the structure shown in FIG. Such an original plate 60 is an original plate in which a rectangular space SS is convex. Therefore, if a pressing process is performed using this original plate, a multiple diffraction grating recording medium as shown in FIG. 16 can be produced.
[0053]
By the way, as already described in §2, in the present invention, a motif is expressed by assigning various pixel patterns as shown in FIG. 9 to predetermined pixel positions. In FIG. 9, for convenience of explanation, each pixel pattern P1, P2, P12 is shown by drawing a line L at a predetermined angle within a predetermined pixel region. Also becomes a rectangle. FIG. 24 is a diagram highlighting the point that the three types of pixel patterns P1, P2, and P12 shown in FIG. In this example, the ratio dL: dS = 1: 2 between the line width dL and the space width dS is set in order to satisfy the basic condition described above. As specific dimension values, in this embodiment, dL = 0.4 μm, dS = 0.8 μm, and the size of one pixel is about 45 μm × 50 μm or 50 μm × 50 μm. More lines L and spaces S are formed.
[0054]
As described above, a quadrangular four-vertex coordinate value is generally used as a drawing instruction given to the electron beam drawing apparatus. In addition, in a generally used electron beam drawing apparatus, when an XY two-dimensional coordinate system is defined as shown in the figure, a parallelogram such that two sides are parallel to the X axis or two sides are Y axes. If a parallelogram that is parallel to the line is drawn, a very efficient drawing work can be performed and the drawing time is shortened. Therefore, in this embodiment, the portions constituting the spaces S and SS are expressed by any of the parallelograms described above, and the coordinate values of the four vertices are given to the electron beam drawing apparatus so that efficient drawing can be performed. Is possible.
[0055]
For example, in the pixel pattern P1, the four vertex coordinate values of the parallelogram ABCD in the figure are given to the electron beam drawing apparatus, and the region of the space S shown by hatching in the figure is drawn. Strictly speaking, a region T shown by hatching with dots in the figure is also a region to be originally drawn, but a parallelogram ABCD having two sides parallel to the X axis is given to the electron beam drawing apparatus. In order to be a region, the region T is excluded from the drawing region. In this way, a part of the area near the contour is excluded from the drawing target, and the drawing area of the pixel pattern P1 is defined only by the parallelogram whose two sides are parallel to the X axis. Drawing is possible.
[0056]
In the pixel pattern P2, the four-vertex coordinate values of the parallelogram ABCD (actually rectangular) in the figure are given to the electron beam drawing apparatus, and the area of the space S shown by hatching in the figure is drawn. . As described above, when the grid line arrangement angle is 90 ° or 0 °, all the areas of the space S are rectangular, and it is not necessary to provide an area to be excluded from the drawing target.
[0057]
On the other hand, in the multiple pattern P12, the four vertex coordinate values of the parallelogram ABCD in the figure are given to the electron beam drawing apparatus, and the area of the rectangular space SS shown by hatching in the figure is drawn. In this case, the rectangular space SS shown by hatching in the figure is a parallelogram whose two sides are parallel to the Y axis, so that efficient drawing is also possible. Note that the irregularly shaped space TT in the vicinity of the contour (shown by hatching with dots in the figure) is also an area to be originally drawn, but is excluded from the drawing target because it causes a reduction in drawing efficiency. .
[0058]
In FIG. 24, the regions of the spaces T and TT are drawn with emphasis. Actually, these regions are only a part of the region near the contour. There is no problem in practical use.
[0059]
§5. Diffraction grating recording medium producing apparatus according to the present invention
Subsequently, an example of an apparatus for efficiently producing the above-described diffraction grating recording medium will be described. FIG. 25 is a block diagram showing an embodiment of a diffraction grating recording medium producing apparatus according to the present invention. Here, the motif image data input device 10 is a device for inputting image data about a motif as shown in FIG. For example, if motif image data is input based on a motif pattern drawn on paper, a scanner device may be used as the motif image data input device 10. Alternatively, if motif image data is input based on a picture drawn by graphic software using a computer, for example, a floppy disk drive device may be used as the motif image data input device 10.
[0060]
The workstation 20 is equipped with a program for performing a process of assigning a predetermined pixel pattern to each pixel of the input motif or a process of creating a multiple pixel pattern by superimposing two pixel patterns. A computer is connected to input devices such as a keyboard and a mouse and output devices such as a display and a printer. The storage device 30 is an external storage device such as a floppy disk drive device or a hard disk drive device connected to the workstation 20. The storage device 30 stores imposition instruction data, assignment instruction data, pixel pattern data, and multiple pixel pattern data. The contents of each data will be described later.
[0061]
On the other hand, the format conversion device 40 converts the imposition instruction data, the allocation instruction data, the pixel pattern data, and the multiple pixel pattern data given from the workstation 20 into drawing data that conforms to the format required by the electron beam drawing device 50. It is a device with functions. The format-converted data is given to the electron beam drawing apparatus 50 as drawing data. As described in §4, this drawing data is a set of coordinate values of four vertices of a quadrangle that constitutes a drawing area. In this way, drawing on the resist layer is performed by the electron beam drawing apparatus 50, and the diffraction grating recording master 60 is created. The press device 70 is a device that presses the diffraction grating pattern on the film using the diffraction grating recording original plate 70, and the diffraction grating recording medium 80 is mass-produced by this pressing.
[0062]
In this apparatus, various image data forming a diffraction grating pattern are handled as data having a hierarchical structure. First, the motif input from the motif image data input device 10 is divided into a plurality of areas in the workstation 20 as necessary. For example, as shown in FIG. 26, it is assumed that a region in which a motif is drawn is divided into four regions A1 to A4. At this time, imposition instruction data indicating where each area should be impositioned is created. In this example, the position of the lower left corner of each area is used as imposition instruction data. That is, the regions A1 to A4 are impositioned so that the lower left corners are at the positions of the points Q1 to Q4, respectively. In this embodiment, in addition to the areas A1 to A4 in which the original motif is displayed, an accessory area A0 in which position information U (so-called register marks) necessary for a process such as alignment is displayed is defined. In addition to this, a serial number or the like can be described in the accessory area A0. In short, process management information necessary for a subsequent process can be recorded.
[0063]
After performing the area division in this manner, a process for creating allocation instruction data is performed for each area. For example, when two motifs A and B as shown in FIG. 5 are allocated in the area A1, correspondence information as shown in FIG. 10 is prepared as allocation instruction data. In the storage device 30, pixel patterns P1 and P2 and a multiple pixel pattern P12 as shown in FIG. 9 are prepared. Here, it is convenient to prepare the pixel patterns P1 and P2 in the storage device 30 in advance, but the multiple pixel pattern P12 can be generated by calculation as necessary.
[0064]
Here, consider the relationship between the allocation instruction data and the pixel pattern data. The pixel pattern data is data indicating a pattern constituting one pixel as shown in FIG. 9, and the assignment instruction data is assigned to each pixel position as in the correspondence information shown in FIG. This is data for instructing. Therefore, if the pixel pattern data is considered as data in the lower hierarchy of the allocation instruction data, the drawing data finally formed on the diffraction grating recording medium is the pixel pattern data in the lower hierarchy and the allocation instruction data in the upper hierarchy. It will be expressed by. Further, considering that the area division as shown in FIG. 26 is performed, the drawing data finally formed on the diffraction grating recording medium is the upper-layer imposition instruction data, the middle layer as shown in FIG. It can be seen that it is expressed by each allocation instruction data in the lower hierarchy and each pixel pattern data in the lower hierarchy.
[0065]
In this way, if the expression having a hierarchical structure is performed, the amount of data can be considerably reduced as compared with the case where the actual lattice line pattern data is developed in the entire region. For example, since a large number of grid lines are formed in one pixel, the amount of data for this pixel is considerable. However, if a representation having a hierarchical structure is performed, pixel pattern data is used as lower-layer data. It is sufficient to prepare as many pixel patterns as possible.
[0066]
In this way, the workstation 20 generates three types of layer data, that is, the upper layer imposition instruction data, the middle layer allocation instruction data, and the lower layer pixel pattern data, which are independently stored in the storage device 30. The Moreover, each of these hierarchical data is also given to the format conversion device 40 separately with a hierarchical structure, and the drawing data output from the format conversion device 40 is also data with the hierarchical structure. . The electron beam drawing apparatus 50 that is currently popular can usually perform drawing processing based on drawing data having such a hierarchical structure. Therefore, the image data can be handled as data having a hierarchical structure until the data is delivered to the electron beam drawing apparatus 50, and efficient data processing becomes possible.
[0067]
§6. Embodiment using a plurality of pixel patterns for one motif
The embodiments described so far are examples in which one pixel pattern is used for one motif. That is, the pixel pattern P1 shown in FIG. 9 is used for the motif A shown in FIG. 5 (a), and the pixel pattern P2 shown in FIG. 9 is used for the motif B shown in FIG. 5 (b). The pixel pattern P12 shown in FIG. 9 was used only for these pixels. However, it is also possible to use a plurality of pixel patterns for one motif. For example, in the example shown in FIG. 28, three types of pixel patterns P1, P2, and P3 are used for the motif A, and three types of pixel patterns P4, P5, and P6 are used for the motif B. All of the six types of pixel patterns P1 to P6 shown in FIG. 28 are slightly different in the grid line arrangement angle. However, these six types of pixel patterns can be classified into two groups in which the arrangement angles of the lattice lines approximate each other. That is, the first group is pixel patterns P1 to P3 in which the grid line arrangement angle is set to around 45 °, and these are used for the motif A. On the other hand, the second group is pixel patterns P4 to P6 in which the grid line arrangement angle is set to around 90 °, and these are used for the motif B.
[0068]
  Pixel patterns with extremely different grid line arrangement angles such as 45 ° and 90 ° are not simultaneously observed when observed from a predetermined direction. However, pixel patterns (for example, pixel patterns P1 to P3 shown in FIG. 28) that are close to each other and have an angle difference of about ± 5 ° can be observed simultaneously when observed from a predetermined direction. . However, the brightness is slightly different from each other.JP-A-7-146635Discloses a technique for expressing a motif having a gradation using such a property. For example, in the above example, only the binary value “0” or “1” is defined as the pixel value of the pixels constituting the motif A, but an 8-bit pixel value represented by 0 to 255 is defined. The pixel pattern P1 is assigned to pixels having pixel values 0 to 100, the pixel pattern P2 is assigned to pixels having pixel values 101 to 200, and the pixel pattern P3 is assigned to pixels having pixel values 201 to 255. This makes it possible to express a motif with gradation. Similarly, for the motif B, any one of the three types of pixel patterns P4 to P6 may be assigned according to the pixel value.
[0069]
As described above, if the present invention is applied to a method in which any one of the pixel patterns P1 to P3 is assigned to the motif A and any one of the pixel patterns P4 to P6 is assigned to the motif B, For the pixels constituting both, a multiple pixel pattern obtained by superimposing the respective pixel patterns may be assigned. For example, the pixel pattern P1 is used as the pixel for the motif A, and the pixel pattern P5 is used as the pixel for the motif B, and the multiple pixel pattern obtained by superimposing the pixel patterns P1 and P5 at the pixel positions that need to be assigned to each other. Can be assigned.
[0070]
In the case of the example shown in FIG. 28, the multiple pixel pattern obtained by combining the pixel patterns P1 to P3 for the motif A and the pixel patterns P4 to P6 for the motif B is P14 (meaning the combination of P1 and P4) ), P15, P16, P24, P25, P26, P34, P35, and P36. Therefore, if these nine types of multiple pixel patterns are prepared, the present invention can be applied. However, since these nine types of multiple pixel patterns can be generated at any time based on the image data of the original pixel patterns P1 to P6, it is not necessary to prepare all the multiple pixel patterns in advance. What is necessary is just to generate | occur | produce by a calculation each time as needed.
[0071]
§7. Example of recording three or more motifs
The embodiment described so far is an example in which two motifs, motif A and motif B, are recorded in an overlapping manner. Here, an embodiment will be described in which three or more motifs are recorded in an overlapping manner. Now, as shown in FIG. 29, pixel pattern P1 (grid line arrangement angle 0 °) is used for motif A, pixel pattern P2 (grid line arrangement angle 45 °) is used for motif B, and pixel C is used for motif C. Consider a case where three types of motifs A, B, and C are recorded on a diffraction grating recording medium using a pattern P3 (grating line arrangement angle of 90 °). Pixel patterns with extremely different grid line arrangement angles such as 0 °, 45 °, and 90 ° are not simultaneously observed when observed from a predetermined direction. B and C will be observed separately.
[0072]
The basic principle of the present invention is that multiple diffraction gratings are assigned to pixels constituting a plurality of motifs. Therefore, when recording such three motifs, double diffraction gratings P12, P23, P13 and triple diffraction grating P123 are prepared as shown in the lower part of FIG. , B are assigned to the double diffraction grating P12, and the pixels constituting both the motifs B and C are assigned to the double diffraction grating P23 to constitute both the motifs A and C. Is assigned the double diffraction grating P13, and further, the triple diffraction grating P123 may be assigned to the pixels constituting all of the three motifs A, B, and C.
[0073]
Let's look at this for a specific motif. Now, consider that three types of motifs A, B, and C as shown in FIGS. 30 (a), 30 (b), and 30 (c) are recorded on one diffraction grating recording medium. In this case, correspondence information as shown in FIG. 30 (d) is obtained. In each pixel of the correspondence information, a motif name that the pixel configures is indicated by an alphabet. Here, the pixel patterns P1, P2, and P3 shown in FIG. 29 may be assigned to the pixels having the single alphabets “A”, “B”, and “C”, respectively. Further, the double pixel patterns P12, P23, and P13 shown in FIG. 29 may be assigned to the pixels having two alphabets “AB”, “BC”, and “CA”, respectively. Furthermore, a triple pixel pattern P123 shown in FIG. 29 may be assigned to a pixel (enclosed by a solid line in the drawing) on which three alphabets “ABC” are written.
[0074]
In this way, if multiple diffraction gratings such as double, triple, quadruple,... Are used, it is theoretically possible to record any number of multiple motifs. However, the technique of recording three or more motifs by such a method is not practically applicable. This is because double diffraction gratings such as multiple pixel patterns P12, P23, and P13 can be realized by satisfying the conditions described in §3. It is very difficult to realize the above diffraction grating. Actually, the triple diffraction grating P123 was experimentally produced, but practically sufficient diffracted light could not be obtained from any observation direction. Of course, if specific conditions are set, the possibility that a practical triple diffraction grating P123 can be created cannot be denied, but at present, no such conditions have been found.
[0075]
Accordingly, the inventor of the present application has come up with a novel method for recording three or more motifs by using a double diffraction grating and a sub-pixel together. First, each pixel constituting the motif shown in FIG. 30 is divided into four, and subpixels arranged in two rows and two columns are defined. Then, based on the alphabet written in each pixel of the correspondence information shown in FIG. 30 (d), as shown in FIG. 31, pixel patterns P1, P2, P3 or multiple patterns P12, P23 in each sub-pixel. , P13. For example, for a pixel with a single alphabet “A”, the pixel pattern P1 may be assigned to each of the sub-pixels divided into four. Similarly, for a pixel with a single alphabet "B", a pixel pattern P2 is assigned to each of the sub-pixels divided into four, and a pixel with a single alphabet "C" is assigned. The pixel pattern P3 may be assigned to each of the sub-pixels obtained by dividing this into four.
[0076]
Also, for the pixels with two alphabets “AB”, the pixel pattern P1 is assigned to, for example, the upper left and lower right subpixels of the subpixels divided into four, and the lower left and upper right subpixels are assigned. The pixel pattern P2 is assigned. Alternatively, the multiple pixel pattern P12 is assigned to each of the four divided pixels. In order to improve luminance, the latter assignment is preferably performed. The assignment for the pixels marked with two alphabets “BC” and the pixels marked with “CA” is exactly the same.
[0077]
Further, for the pixels marked with three alphabets “ABC”, among the subpixels divided into four, for example, the multiple pixel pattern P13 is assigned to the upper left and lower right subpixels, and the lower left and upper right subpixels are assigned. The multiple pixel pattern P12 is assigned to. Alternatively, the multiple pixel patterns P12 and P13 may be assigned in combination, or the multiple pixel patterns P13 and P23 may be assigned in combination. Of course, any multiple pixel pattern may be assigned to any position of the sub-pixel. If such an assignment is made, a pixel with three alphabets “ABC” is not necessarily the entire region of the pixel, but a grid line with an arrangement angle of 0 ° and a lattice with an arrangement angle of 45 °. There are three grid lines, that is, a grid line and a grid line with an arrangement angle of 90 °, and it can also serve as three pixel patterns P1, P2, and P3.
[0078]
The same technique can be used when recording four motifs in an overlapping manner. In other words, among the four motifs A, B, C, and D, the pixels in which two or three motifs overlap may be assigned as shown in FIG. 31, and the pixels in which all four motifs overlap. 32, for example, as shown in FIG. 32, a multiple pattern P12 (a pattern obtained by superimposing a pixel pattern for motif A and a pixel pattern for motif B) on each sub-pixel divided into four, and a multiple pattern P34 (a pattern obtained by superimposing the pixel pattern for the motif C and the pixel pattern for the motif D) may be assigned.
[0079]
In short, each pixel is divided into a plurality of subpixels, and lattice lines arranged at a lattice line arrangement angle of a pixel pattern associated with a motif formed by the pixels appear in at least one subpixel. If a pixel pattern or a multiple pixel pattern is assigned to a sub-pixel, it is possible to record three or more motifs in an overlapping manner. Of course, as described in §6, this method can also be applied to an embodiment using a plurality of pixel patterns for one motif.
[0080]
Although the present invention has been described based on some embodiments shown in the drawings, the present invention is not limited to these embodiments and can be implemented in various other modes.
[0081]
【The invention's effect】
  As described above, according to the present inventionDiffraction grating recording mediumAccording to the above, since a plurality of motifs are expressed by multiple diffraction gratings, it is possible to realize a diffraction grating recording medium in which luminance and image quality do not deteriorate even if a plurality of motifs are expressed in an overlapping manner.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a pattern and pixel information used as a motif of a diffraction grating recording medium according to the present invention.
FIG. 2 is a diagram showing an example of a pixel pattern used in a diffraction grating recording medium according to the present invention.
3 is a diagram showing a diffraction grating recording medium created using the motif shown in FIG. 1 and the pixel pattern shown in FIG.
4 is a diagram illustrating an example of a pixel pattern used for each of the two motifs illustrated in FIG. 5. FIG.
FIG. 5 is a diagram showing an example of two motifs recorded in duplicate on the diffraction grating recording medium according to the present invention.
6 is a diagram showing correspondence information defining the correspondence between the two motifs shown in FIG. 5 and the two pixel patterns shown in FIG.
7 is a diagram illustrating a state in which the two motifs illustrated in FIG. 5 are expressed by sub-pixels, respectively.
FIG. 8 is a diagram showing a diffraction grating recording medium created by arranging two motifs shown in FIG. 7 in an overlapping manner.
9 is a diagram showing an example of pixel patterns P1 and P2 respectively used for the two motifs shown in FIG. 5 and a multiple pixel pattern P12 obtained by superimposing them. FIG.
10 is a diagram showing correspondence information defining the correspondence between the two motifs shown in FIG. 5 and the three patterns shown in FIG. 9;
11 is a diagram showing a diffraction grating recording medium created by assigning each pattern based on the correspondence information shown in FIG.
FIG. 12 is a diagram showing two types of diffraction grating patterns in which the ratio of the line width dL to the space width dS is 1: 1.
13 is a diagram showing a multiple diffraction grating pattern obtained by superimposing two types of diffraction grating patterns shown in FIG.
FIG. 14 is a diagram showing two types of diffraction grating patterns in which the ratio between the line width dL and the space width dS is 1: 2.
15 is a diagram showing a multiple diffraction grating pattern obtained by superimposing two types of diffraction grating patterns shown in FIG.
16 is a side sectional view showing the structure of the diffraction grating recording medium having the multiple diffraction grating pattern shown in FIG.
17 is a diagram showing an example of a method for drawing the multiple diffraction grating pattern shown in FIG.
18 is a diagram showing a negative pattern of the multiple diffraction grating pattern shown in FIG.
FIG. 19 is a side sectional view showing an initial stage of a manufacturing process of an original plate used for mass production of a diffraction grating recording medium according to the present invention.
20 is a side sectional view showing a state in which drawing is performed on the resist layer 3 in the state shown in FIG.
FIG. 21 is a side sectional view showing a state in which a resist layer is developed in the state shown in FIG.
22 is a side cross-sectional view showing a state in which the original constituting layer 2 has been etched in the state shown in FIG. 21. FIG.
23 is a side cross-sectional view showing a state in which the remaining resist is peeled and removed from the state shown in FIG. 22 to complete the production of the original plate.
FIG. 24 is a plan view showing a technique for drawing the diffraction grating pattern and the multiple diffraction grating pattern according to the present invention with an electron beam.
FIG. 25 is a block diagram showing an example of an apparatus configuration for creating a diffraction grating recording medium according to the present invention.
FIG. 26 is a diagram for explaining imposition instruction data used in the apparatus shown in FIG. 25;
27 is a diagram showing a hierarchical structure of data handled by the apparatus shown in FIG. 25. FIG.
FIG. 28 is a diagram illustrating an example in which a plurality of pixel patterns are used for one motif.
FIG. 29 is a diagram illustrating a pixel pattern and a multiple pixel pattern used when three motifs are recorded in an overlapping manner.
30 is a diagram showing three motifs expressed using the pixel pattern and the multiple pixel pattern shown in FIG. 29 and the correspondence between the pixels.
FIG. 31 is a diagram illustrating an example in which three motifs are recorded in an overlapping manner using subpixels.
FIG. 32 is a diagram illustrating an example in which four motifs are superimposed and recorded using sub-pixels.
[Explanation of symbols]
1 ... Board
2… Original composition layer
3 ... resist layer
3a: Exposure part
3b ... non-exposed part
10. Motif image data input device
20 ... Workstation
30 ... Storage device
40. Data format conversion device
50. Electron beam drawing apparatus
60 ... Diffraction grating recording master
70 ... Pressing device
80. Multiple diffraction grating recording medium
85 ... depression
86 ... Shielding wall
A, B, C ... Motif
CC ... Intersection area
D1, D2 ... Observation direction
L ... Lattice line
P1 to P6: Pixel pattern
P12, P13, P23, P123 ... Multiple pixel pattern
R1, R2 ... correspondence information
S ... Lattice line space
SS ... Rectangular space
T ... Space excluded from drawing
TT: Space excluded from drawing objects
U ... Dragonfly mark (location information)
V: Closed region where grid lines are placed
X, Y ... coordinate axes
dL: Line width of the lattice line
dS: Grid line space width
p ... Pitch of lattice line
θ: Arrangement angle of grid lines

Claims (6)

In a diffraction grating recording medium expressing a plurality of motifs by a diffraction grating,
Pixels in which a large number of grid lines are arranged in a predetermined pixel closed region are defined by changing the grid line arrangement angle, and these pixel patterns are approximated by the grid line arrangement angles. Divide the pattern into multiple groups and associate one group for each of the multiple motifs to be expressed.
For two pixel patterns belonging to different groups, a multiple pixel pattern obtained by arranging the grid lines arranged in each group in the same pixel closed region is defined,
A pixel pattern belonging to a group associated with the motif is assigned to a pixel constituting only a single motif, and two pixels associated with each motif are assigned to pixels constituting two motifs. A diffraction grating recording medium characterized by assigning a multiple pixel pattern defined for a pixel pattern to which it belongs. In a diffraction grating recording medium expressing a plurality of motifs by a diffraction grating,
Pixels in which a large number of grid lines are arranged in a predetermined pixel closed region are defined by changing the grid line arrangement angle, and these pixel patterns are approximated by the grid line arrangement angles. Divide the pattern into multiple groups and associate one group for each of the multiple motifs to be expressed.
For two pixel patterns belonging to different groups, a multiple pixel pattern obtained by arranging the grid lines arranged in each group in the same pixel closed region is defined,
For pixels that make up only a single motif, assign a pixel pattern belonging to the group associated with that motif to each sub-pixel obtained by dividing this,
For pixels that make up multiple motifs, each subpixel obtained by dividing this motif is assigned a pixel pattern belonging to each of the groups associated with each motif or its multiple pixel pattern, and related to each group. A diffraction grating recording medium, wherein the grating lines arranged at the grating line arrangement angle appear in at least one subpixel. The diffraction grating recording medium according to claim 1 or 2 ,
A diffraction grating recording medium, wherein a grating line is used between the line width dL and the space width dS so that a relationship of dS ≧ 2 · dL is obtained. The diffraction grating recording medium according to claim 3 ,
A diffraction grating recording medium, characterized in that a line portion of a grating line is a convex portion and a space portion is a concave portion. The diffraction grating recording medium according to claim 4 , wherein
A diffraction grating recording medium using a grating line having a space width dS satisfying an expression of dS> λ for a predetermined visible wavelength λ. The diffraction grating recording medium according to claim 5 , wherein
A predetermined observation angle θ is defined with respect to a normal line standing on the surface of the recording medium, and lattice lines having a line width dL and a space width dS satisfying the expression (dS + dL) · sin θ = λ are used. A diffraction grating recording medium characterized by the above.

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