JP2004280010A - Display device having blazed diffraction grating pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device which has a plurality of minute diffraction grating cells arranged on the surface of a substrate, has a plurality of diffraction grating patterns constituted by the combinations of desired diffraction grating cells, has improved brightness of images to be observed, allows image changing to be distinctly performed, and further allows more blazed diffraction grating patterns capable of image changing to be set. <P>SOLUTION: A plurality of diffraction grating cells constituting one diffraction grating pattern have the diffraction grating directions set to one direction so that this direction is different from diffraction grating directions of a plurality of diffraction grating cells constituting other diffraction grating patterns. In at least one of the plurality of diffraction grating patterns, the diffraction gratings of the plurality of diffraction grating cells constituting this diffraction grating pattern are blazed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
INDUSTRIAL APPLICABILITY The present invention is suitable for use in image display and security (forgery prevention), in which a plurality of minute diffraction grating cells are arranged, and a plurality of diffraction gratings are formed by combining desired diffraction grating cells among them. The present invention relates to a display in which a pattern is formed, and a plurality of images are observed corresponding to the plurality of diffraction grating patterns.
[0002]
[Prior art]
Conventionally, as a method of expressing a moving image or an image that changes by changing the viewpoint on a flat substrate, an image using a lenticular lens, an image using holographic stereograms and holograms There is a changing technology. There is also an image changing technique using a diffraction grating pattern composed of a plurality of minute diffraction gratings. (For example, refer to Patent Document 1.)
[0003]
Diffraction grating patterns composed of diffraction gratings can express directional luster and colors that cannot be expressed by ordinary printing technology, and are widely used for display applications and security products aimed at preventing forgery. ing. In such a diffraction grating pattern and a display having the diffraction grating pattern, it is required to produce a more diversified and highly original one.
[0004]
By the way, among such conventional image changing technologies, those using a lenticular lens cannot observe a change in an image unless the observer moves even if the position of the light source is changed. Also, with the image changing technology using holographic stereograms and holograms, it has been difficult for a plurality of images to enter the eyes at the same time or to cause blurring, and to express a clear image.
[0005]
On the other hand, in the conventional image changing using a diffraction grating, an initial diffraction grating pattern is formed on a substrate by using a plurality of minute diffraction grating cells having a binary diffraction grating of an arbitrary spatial frequency, and then the diffraction grating is formed. The next diffraction grating pattern is the same by using a plurality of small diffraction grating cells having a binary diffraction grating with an arbitrary spatial frequency set to a diffraction grating direction different from the diffraction grating direction of the diffraction grating cell constituting the grating pattern. After that, the same operation as above is repeated by the number of desired diffraction grating patterns, so that the diffraction grating patterns are successively formed on the same substrate, and the light source, the observer, or the substrate. A method in which a plurality of images corresponding to a plurality of diffraction grating patterns can be expressed relatively clearly by changing the relative positions of the three elements. A.
[0006]
As a method of producing a diffraction grating pattern, for example, a fine dot (diffraction grating cell) having interference fringes (diffraction grating) obtained by two-beam interference of laser light is changed in pitch, direction, and light intensity. Then, a method of sequentially exposing the photosensitive film in a pattern is adopted (for example, see Patent Document 2).
[0007]
On the other hand, by using an electron beam from an electron beam exposure apparatus instead of a laser beam, while controlling the movement of an XY stage on which a planar substrate is mounted by a computer, a plurality of minute gratings composed of a diffraction grating are formed on the surface of the substrate. A method of producing a diffraction grating pattern by arranging dots (diffraction grating cells) in a pattern has also been proposed (for example, see Patent Document 3).
[0008]
The parameters of the diffraction grating pattern formed on the substrate surface in this manner include the spatial frequency or the grating interval (grating pitch) of the diffraction grating, the direction of the diffraction grating (the direction of the diffraction grating), and the diffraction grating pattern. There are three arrangements of minute diffraction grating cells. By changing the spatial frequency or the grating interval (grating pitch) of the diffraction grating, the visible color changes, and by changing the direction of the diffraction grating (grating direction), the direction in which light appears can change. The image (picture) to be displayed is determined depending on the arrangement of the diffraction grating cells constituting the diffraction grating pattern.
[0009]
The relationship between the wavelength and the incident angle of the incident light irradiating the diffraction grating, the grating interval of the diffraction grating, and the emission angle of the diffracted light emitted from the diffraction grating will be described as follows. That is, FIG. 6 shows a state of the diffracted light observed when the monochromatic incident light 1 having the wavelength λ is incident on the diffraction grating cell 5 at a specific angle. The diffraction phenomenon for an arbitrary order by the diffraction grating cell in an arbitrary plane perpendicular to the plane is expressed by the following equation.
d = mλ / (sin α−sin β)
[0010]
In FIG. 6 and the above equation, d is the grating interval (reciprocal of the spatial frequency) of the diffraction grating on the surface of interest, m is the diffraction order, and α is the 0th-order diffracted light 3 on the surface (transmission light of illumination light or specular reflection light). In FIG. 6, β is the emission angle (diffraction angle) of the first-order diffracted light 2 on the surface.
Therefore, based on such a relationship, the diffraction grating cell surface is set to the XY plane, and the direction of the diffracted light in the three-dimensional space is variously changed in a desired state with respect to the XZ plane and the YZ plane orthogonal thereto. It can be set.
[0011]
However, the diffraction grating pattern formed on the substrate surface in consideration of such a relationship, even in a situation in which a plurality of images corresponding to a plurality of diffraction grating patterns different in design can be changed and observed, has been previously described. Due to the noise of the diffraction grating corresponding to the observed image and the scattering due to unevenness on the substrate surface, the previously observed image overlaps with the newly seen image and appears blurry, and the image switching occurs. I could not do it clearly.
[0012]
In addition, there are various types of diffraction gratings. In the above-described image changing using the diffraction grating, when a binary type is adopted as the diffraction grating, a range in which a plurality of images can be expressed by the image changing technique is used. Is limited to a range in which the diffraction direction of the diffraction grating pattern corresponding to the image is from 0 degree to less than 180 degrees. For example, in the case of a diffraction grating pattern in which the grating directions of the diffraction grating differ every 45 degrees, only four types of images corresponding to the diffraction grating pattern can be expressed as shown in FIG. In short, the binary diffraction grating has the disadvantage that the diffraction grating directions are equal to 0 degree and 180 degrees, and the number of changing images that can be expressed in image changing is small.
[0013]
[Patent Document 1]
Patent No. 2630047 [Patent Document 2]
JP 60-156004 A [Patent Document 3]
JP-A-2-72320
[Problems to be solved by the invention]
The present invention has been made in view of the above situation, and a plurality of minute diffraction grating cells are arranged on a substrate surface, and a plurality of diffraction grating cells are combined by a desired combination of the diffraction grating cells. A display in which a plurality of patterns are configured and a plurality of images are observed corresponding to the plurality of diffraction grating patterns. It is an object of the present invention to provide a display having a blazed diffraction grating pattern, wherein the display can be performed sharply and the number of diffraction grating patterns involved in image changing can be set more.
[0015]
[Means for Solving the Problems]
The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 includes a plurality of minute diffraction grating cells arranged on the surface of a planar substrate, and In a display in which a plurality of diffraction grating patterns are formed by a combination of desired diffraction grating cells in the display, and each image is observed corresponding to each of the plurality of diffraction grating patterns, The plurality of diffraction grating cells constituting the diffraction grating pattern have the same direction of the diffraction grating, and are set so as to be different from the diffraction grating directions of the plurality of diffraction grating cells constituting the other diffraction grating patterns. And at least one of the plurality of diffraction grating patterns is such that the diffraction gratings of the plurality of minute diffraction grating cells constituting the pattern are blazed diffraction gratings. A display having a blazed diffraction grating pattern characterized.
[0016]
According to a second aspect of the present invention, in the display having the blazed diffraction grating pattern according to the first aspect, each of the diffraction gratings of the diffraction grating cells constituting the diffraction grating pattern is a blazed diffraction grating. Features.
[0017]
Further, according to a third aspect of the present invention, in the display having the blazed diffraction grating pattern according to the first or second aspect, the diffraction grating directions of the diffraction grating cells constituting the diffraction grating pattern are other diffraction grating patterns. Is different from the diffraction grating direction of the diffraction grating cell by 5 degrees or more.
[0018]
Still further, according to a fourth aspect of the present invention, in the display having the blazed diffraction grating pattern according to any one of the first to third aspects, the plurality of diffraction grating patterns are in the same region, and the area occupied by them is the same. It is characterized by being.
[0019]
According to a fifth aspect of the present invention, there is provided a display having a blazed diffraction grating pattern according to any one of the first to fourth aspects, wherein a diffraction grating cell forming a diffraction grating pattern forms another diffraction grating pattern. Are arranged so as to be adjacent to each other.
[0020]
Here, the blazed diffraction grating is a diffraction grating having a sawtooth-shaped cross-sectional shape, as shown in FIG. 9, and when the angle of reflection or refraction of incident light on the slope matches the diffraction angle, It is known that a very high diffraction efficiency can be obtained as compared with a binary diffraction grating described later. It is also known that high diffraction efficiency can be obtained even in a diffraction grating having a step-like cross-sectional shape as shown in FIG. In this specification, this stepped diffraction grating is also included in the blazed diffraction grating.
[0021]
Further, the binary diffraction grating is generally a diffraction grating having a rectangular wave-like cross-sectional shape as shown in FIG. In a hot embossed duplicate product or the like manufactured using a press plate having such a cross-sectional shape, a diffraction grating having a cross-sectional shape close to a sinusoidal shape, such as that found in a relief hologram, is generally formed. In this specification, such a sinusoidal diffraction grating is also included in the binary diffraction grating (see FIG. 7).
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, all the drawings are illustrated in an enlarged manner than the actual diffraction gratings and the size of the grating intervals for easy understanding.
[0023]
FIG. 1 schematically shows a display 18 of the present invention and two types of images 19 and 20 which can be expressed by two types of blazed diffraction grating patterns included in the display 18.
This display 18 has a plurality of two types of minute diffraction grating cells 18A and 18B arranged on the surface of a planar substrate (not shown), and a combination of the diffraction grating cells 18A and 18B. Different types of diffraction grating patterns are configured, and two types of images 19 and 20 are respectively observed corresponding to the two types of diffraction grating patterns. A plurality of diffraction grating cells 18A... Constituting one diffraction grating pattern have their diffraction grating directions set in the same direction (the direction of the diffraction grating is obliquely downward to the right) and constitute the other diffraction grating pattern. Are set to be different from the diffraction grating direction (the diffraction grating direction is the diagonally downward left direction) of the plurality of diffraction grating cells 18B, and two types of diffraction grating cells 18A constituting each diffraction grating pattern. The 18B diffraction grating is a blazed diffraction grating.
[0024]
The two types of minute diffraction grating cells 18A and 18B have the same outer shape, the directions of the respective diffraction gratings are different by 90 degrees (one is obliquely downward to the right and the other is obliquely downward to the left), and each diffraction grating is different. The lattice cells are arranged adjacent to each other and are arranged on the substrate surface to form a display 18.
[0025]
In the illustrated embodiment, as the diffraction grating cells 18A, 18B constituting the diffraction grating pattern, those having a rectangular outer shape are applied, and further, individual diffraction grating cells 18A, 18B,. The size is set to 300 μm or less to make it impossible to recognize the presence of. The expression regions of the two types of diffraction grating patterns 18A and 18B are set so as to be located in the same region. The outer shape of the diffraction grating cell in the display of the present invention is not limited to the rectangular shape described above, and various shapes such as a triangular shape, a circular shape, and a polygonal shape can be applied.
[0026]
By the way, when the expression regions of the two types of diffraction grating patterns composed of the two types of diffraction grating cells described above are not set to be the same, the region where only a single diffraction grating pattern is expressed Is present, and even when it is desired to show only one diffraction grating pattern, the other diffraction grating pattern can be found due to various optical noises and scattering. However, when the expression area of a plurality of diffraction grating patterns is the same, the diffraction efficiency of the diffraction grating is increased by making the diffraction gratings of the diffraction grating cells constituting the diffraction grating pattern blazed, thereby increasing the brightness of the diffracted light. This makes it possible to conceal noises and the like of other diffraction grating patterns, so that image changing can be performed clearly without the above-mentioned concerns.
Further, by disposing the diffraction grating cell forming one diffraction grating pattern adjacent to the diffraction grating cell forming the other diffraction grating pattern as in the present embodiment, noise and scattering of the other diffraction grating pattern can be further improved. Can be alleviated, and the observed image can be more clearly expressed.
[0027]
When the display 18 having such a configuration is irradiated with light from the light source 23 installed diagonally below and to the right, as shown in FIG. 2, the display 18 corresponds to a diffraction grating pattern composed of a diffraction grating cell 18A having a blazed diffraction grating. The image 21 is clearly recognized by the observer 24. This is because, as described above, the diffraction grating of the diffraction grating cell 18A constituting this diffraction grating pattern is of a blazed type, and the diffraction grating cell constituting one diffraction grating pattern is replaced with the other diffraction grating pattern. This is because they are arranged so as to be adjacent to the constituent diffraction grating cells.
If the diffraction grating of the diffraction grating cell is of a binary type as in the prior art, other images will be blurred (see image 22).
[0028]
On the other hand, as shown in FIG. 3, when the display 18 is irradiated with light from the light source 23 installed diagonally below and to the left, the display 18 is switched to a separate image 25 so that the observer 24 can clearly recognize the image. Become. In this case as well, if the diffraction grating of the diffraction grating cell forming the diffraction grating pattern is of a binary type, other images will be blurred (see image 26).
[0029]
As described above, in the conventional image changing technology using the binary diffraction grating, the image may be blurred due to the noise of the diffraction grating or the scattering due to the unevenness of the substrate surface, even if the image is hidden in design, By making the diffraction grating of the diffraction grating cell constituting the diffraction grating pattern a blazed type as in the present invention, the brightness of an image observed corresponding to the diffraction grating pattern is improved by a factor of 2 to 3 and other diffraction Noise and scattering of the lattice pattern can be reduced, and unnecessary images (images to be concealed) do not appear vague when changing images.
[0030]
This is because diffraction efficiency of diffracted light with respect to incident light from the positive direction and the negative direction is almost the same in a diffraction grating whose cross-sectional shape is symmetric such as a binary diffraction grating, so that the difference should be judged visually. In contrast, in a blazed diffraction grating whose cross-sectional shape is not symmetrical, the diffraction efficiency of diffracted light differs greatly for incident light from the positive direction and the negative direction, and the difference is determined by visual observation or mechanical reading. It is because it becomes possible to clearly distinguish.
[0031]
Hereinafter, this phenomenon will be described in detail with reference to FIGS.
FIG. 4 shows diffracted light when incident light 6 in the positive direction (incident light irradiated from above) and incident light 11 in the negative direction (incident light illuminated from below) enter the blazed diffraction grating 10. The difference between the appearance of the diffracted light 8 and that of the diffracted light 12 is shown in FIG. 5. In FIG. The difference in the appearance of the diffracted light 15 and the diffracted light 17 when the incident light (illuminated light) is incident is conceptually shown.
As is apparent from the figure, in the case of the blazed diffraction grating 10, when the incident light 6 is illuminated from the positive direction, the diffracted light 8 is remarkably brightly recognized by the observer 9, but when the incident light 11 is illuminated from the negative direction. The diffracted light 12 is perceived by the observer 9 as being very slight or too dark to be seen (see FIG. 4). On the other hand, in the case of the binary diffraction grating 13, the appearance does not change when the incident light 14 is irradiated from the positive direction or when the incident light 16 is irradiated from the negative direction (see FIG. 5).
Therefore, in image changing using a diffraction grating, by using a blazed diffraction grating, as described above, the diffraction efficiency of diffracted light is significantly different between incident light from the positive direction and the light from the negative direction. The distinction can be made clearly by visual inspection or machine reading, and the switching of the image can be properly recognized.
In this case, if all of the diffraction gratings of the diffraction grating cells constituting the diffraction grating pattern are of a blazed type, the image changing will be performed sharply. However, the present invention is not limited to this. By making the diffraction grating of the diffraction grating cells constituting at least one of the diffraction grating patterns into a blazed type, the image change can be more clearly recognized as compared with the related art.
[0032]
On the other hand, when the direction angle difference between the direction of the diffraction grating forming one diffraction grating pattern and the direction of the diffraction grating forming the other diffraction grating pattern is less than 5 degrees, the respective diffraction grating patterns overlap. It is preferable not to use it except for the purpose of depicting moving images. However, when the irradiation light is sunlight, a direction angle difference of about 5 degrees is sufficient, but when irradiating light from a point light source such as a halogen lamp, it is 10 degrees or more, such as a fluorescent lamp. When there are a plurality of light sources or point light sources having a wide light emitting portion, it is preferable that the direction angle difference between the diffraction gratings is 20 degrees or more.
[0033]
FIG. 12 shows an image observed when a diffraction grating pattern using a blazed diffraction grating is set with a direction angle difference of 45 degrees between the diffraction grating directions of the binary diffraction gratings of the diffraction grating cells constituting them. However, as is clear from the figure, up to eight types of 0 °, 45 °, 90 °, 135 °, 180 °, 225 °, 270 °, and 315 ° can be displayed and observed using a blazed diffraction grating. Become like As described above, a conventional display using a binary diffraction grating can represent only a range of 180 degrees, while a display using a blazed diffraction grating can represent a changing image over a range of 360 degrees.
That is, in the image changing using the blazed diffraction grating, the maximum number of images that can be changed by changing the viewpoint on one substrate surface can be twice as large as that using the binary diffraction grating. .
[0034]
Further, in the display having such a configuration, when the stationary observer observes the image while moving the light source, images 21 and 25 as shown in FIGS. 2 and 3 are seen one after another. In addition, if each diffraction grating pattern of the plurality of diffraction grating patterns sequentially represents a continuous operation, an animation effect can be obtained. Furthermore, various images can be displayed by sequentially displaying a plurality of messages at the same position or simultaneously displaying a plurality of diffraction grating patterns.
[0035]
In the illustrated embodiment, an example has been described in which a diffraction grating having the same cross-sectional shape is realized by changing only the direction of the diffraction grating, but the present invention is not limited to this. By combining various directions and directions, images can be displayed with more variety and improved security.
[0036]
By the way, in the display having such a blazed diffraction grating pattern, a stamper (copying plate) is obtained by plating or the like based on these surface shapes, and the thermoplastic resin is embossed with the stamper, or a UV curable resin is formed. By UV molding, large-scale replication is inexpensive.
[0037]
【The invention's effect】
As described above, in the display of the present invention, different images can be observed when the observer changes the viewpoint. Further, even in the case of a stationary observer, a different image corresponding to the position of the light source can be observed by changing the position of the light source. Further, even when a stationary observer observes the display with a stationary light source, different images can be observed by arbitrarily moving the display.
[0038]
Also, since the intensity of the diffracted light depends on the direction of the incident light, clear and accurate image changing can be performed.
Furthermore, the influence of the noise of the diffraction grating of the diffraction grating cell constituting the diffraction grating pattern corresponding to the image that was seen before the image changing and the scattering due to the unevenness of the substrate surface on the image that is seen after the image changing is also affected by the diffraction. The number of changing images that can be mitigated by improving the diffraction efficiency (brightness) of the grating pattern itself and that can be represented at the same position on one display is also represented on a display using a conventional binary diffraction grating pattern. This can be twice the number of possible changing images.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a schematic configuration of a display of the present invention and a schematic of a changing image observed on the display.
FIG. 2 shows a state in which light is applied to the display of the present invention from the lower right, an image observed at this time, and an image observed on a display using a sinusoidal binary diffraction grating. FIG.
FIG. 3 shows a state in which light is emitted from the lower left to the display of the present invention, an image observed at this time, and an image observed on a display using a sinusoidal binary diffraction grating. FIG.
FIG. 4 is an explanatory view showing a state of diffracted light observed when incident light is applied to a blazed diffraction grating from a positive direction and a negative direction.
FIG. 5 is an explanatory diagram showing a state of diffracted light observed when incident light is irradiated on a binary diffraction grating from a positive direction and a negative direction.
FIG. 6 is an explanatory diagram showing a state of diffracted light observed when monochromatic incident light is irradiated to a diffraction grating cell at a specific angle.
FIG. 7 is an explanatory diagram showing a cross-sectional shape of a sinusoidal binary diffraction grating.
FIG. 8 is an explanatory diagram illustrating a cross-sectional shape of a binary diffraction grating.
FIG. 9 is an explanatory diagram showing a cross-sectional shape of a blazed diffraction grating.
FIG. 10 is an explanatory diagram showing a cross-sectional shape of a blazed diffraction grating having a stepped shape.
FIG. 11 is an explanatory diagram showing various changing images observed on a display using a binary diffraction grating.
FIG. 12 is an explanatory diagram showing various changing images observed on a display using a blazed diffraction grating.
[Explanation of symbols]
1, 6, 11, 14, 16 ... incident light 2 ... first-order diffracted light 3 ... 0th-order diffracted light 4, 9, 24 ... observer 5 ... diffraction grating cell 7, 20, ... Light sources 8, 12, 15, 17 diffracted light 10 blazed diffraction grating 13 binary diffraction grating 18 displays 19, 21, 22, 25, 26 (observed Image)

Claims (5)

A plurality of minute diffraction grating cells are arranged on the surface of a planar substrate, and a plurality of diffraction grating patterns are formed by a combination of desired diffraction grating cells among them. In a display in which each image is observed corresponding to each of a plurality of diffraction grating cells constituting one diffraction grating pattern, the diffraction grating directions thereof are set in the same direction, and The diffraction grating directions of the plurality of diffraction grating cells constituting the other diffraction grating patterns are set so as to be different from each other, and at least one of the plurality of diffraction grating patterns has a plurality of minute diffraction grating cells constituting the same. A display having a blazed diffraction grating pattern, wherein the diffraction grating is a blazed diffraction grating. 2. A display having a blazed diffraction grating pattern according to claim 1, wherein each of the diffraction gratings of the diffraction grating cells constituting the diffraction grating pattern is a blazed diffraction grating. 3. A diffraction grating direction of a diffraction grating cell of a diffraction grating cell forming a diffraction grating pattern is different from a diffraction grating direction of another diffraction grating cell forming a diffraction grating pattern by 5 degrees or more. A display having the blazed diffraction grating pattern as described. 4. A display having a blazed diffraction grating pattern according to claim 1, wherein a plurality of diffraction grating patterns are located in the same region and occupy the same area. 4. The blazed device according to claim 1, wherein a diffraction grating cell forming a diffraction grating pattern is arranged adjacent to a diffraction grating cell forming another diffraction grating pattern. Having a diffraction grating pattern.

Images