JP2022019238A - Color shift device - Google Patents

Abstract

To provide a color shift device that exhibits special optical effect of change in color between front view and reverse view and that enables the change in color between the front view and reverse view to be viewed instantaneously even under slightly different conditions of a viewing angle etc.SOLUTION: There is provided a color shift device consisting of at least a relief structure formation layer and a reflection layer formed on a surface of a corrugated structure of the relief structure formation layer. The color shift device has an uneven structure which extends in a first direction parallel with a display surface of the color shift device, and is arrayed in a second direction perpendicular to the first direction, and the uneven structure consists of a diffraction grating which has a corrugated reflection surface consisting of an A inclined surface as one of opposed inclined surfaces and the other B inclined surface, wherein A inclined surfaces and B inclined surfaces are arrayed alternately in the second direction, and while the array of the A inclined surfaces has periodicity, the array of the B inclined surfaces has aperiodicity.SELECTED DRAWING: Figure 1

Description

The present invention relates to a color shift device which is a kind of optical variable device.

In recent years, optical variable devices (OVD: optical variable device), which not only enhance the design of articles and give excellent decorative effects but also have an effect of preventing counterfeiting, have been used for many articles and the like. OVD is a general term for devices that exhibit a special optical effect in which the color changes or the image changes depending on the viewing angle.

For the OVD, a relief type diffraction grating having a fine uneven pattern, a diffraction structure such as a striped pattern having a different refractive index, and a multilayer film in which thin films having different optical characteristics are laminated are used, and the diffraction and interference of light due to this are used. Causes a unique image or color change (color shift) depending on the viewing angle.

Relief type diffraction gratings include those having a rectangular cross section perpendicular to the length direction of the groove (see Patent Document 1), those having a sinusoidal shape, and those having a serrated shape.

A general diffraction grating having a rectangular cross section is illuminated with white light from the normal direction, and this diffraction grating is rotated 180 ° around the normal and observed at the same angle from an oblique direction. Then, of course, the image is inverted before and after the rotation, but the image of the same color is displayed.

Also, when a general diffraction grating having a sinusoidal cross section is observed under the above conditions, the image is inverted before and after rotation, similar to the diffraction grating having a rectangular cross section. However, it displays an image of the same color.

On the other hand, in the diffraction grating 10 having a wavy cross section shown in FIG. 1, the diffraction grating 10 is illuminated with white light from the normal direction, and the diffraction grating is rotated by 180 ° around the normal direction, and this is rotated in the diagonal direction. When observing at the same angle θ, there is a technique in which the image is inverted and the color changes (color shift) before and after rotation as described above.

As mentioned above, common diffraction gratings with a rectangular or sinusoidal cross section are illuminated with white light from the normal direction, these gratings are inverted and observed at the same angle from an oblique direction. (That is, forward and reverse viewing are performed at the same angle θ), the image is inverted before and after rotation, but the angle (diffraction angle) θ with respect to the normal direction of the diffracted light is the same in the forward and reverse directions. Therefore, an image of the same color is displayed.

On the other hand, as shown in FIG. 3A, in the diffraction grating 10 having the above-mentioned wavy cross section, one of the inclined surfaces facing each other in the wavy structure is an A inclined surface, the other is a B inclined surface, and the A inclined surface. If there is a difference between the period T1 of the above and the period T2 of the B inclined surface (T1 <T2 in this example), the diffraction angle (diffraction angle of the A inclined surface) depends on the shorter period T1 in the case of forward viewing. ) Becomes larger. Therefore, when forward viewing and reverse viewing are performed from the same angle θ, the image is inverted and the color changes (color shift) (see FIG. 3 (b)). For example, if the forward view is green, the reverse view changes to red.

It can be said that the color shift device 20 according to the conventional technique as described above exhibits a special optical effect in which the color changes between forward viewing and reverse viewing when the image is inverted. However, although the difference can be seen under certain observation conditions, the color shift device 20 can be seen in the forward direction and the reverse direction when the viewing angle is slightly deviated from the position of the eyes in the forward view and the reverse direction view. , Each of them can feel various colors, and it is difficult to instantly discriminate the change in color between forward-looking and reverse-looking. In some cases, it may not be possible to clearly see the color change in forward and reverse vision.

Japanese Unexamined Patent Publication No. 2016-173596

The present invention addresses the above problems, and in a color shift device exhibiting a special optical effect in which colors change between forward and reverse viewing, even if observation conditions such as viewing angles change slightly, the present invention is instantly positive. It is an object of the present invention to provide a color shift device capable of visually recognizing a change in color between directional and reverse vision.

The invention according to claim 1 is a color shift device comprising at least a relief structure forming layer and a reflective layer formed on the surface of the wavy structure of the relief structure forming layer.
The color shift device has a concavo-convex structure extending in a first direction parallel to the display surface of the color shift device and arranged in a second direction perpendicular to the first direction.
The uneven structure has a wavy reflective surface composed of one A inclined surface and the other B inclined surface facing each other.
The A inclined surface and the B inclined surface are arranged alternately in the second direction.
It is a color shift device characterized in that the arrangement of the A inclined surface has periodicity and the arrangement of the B inclined surface is composed of a diffraction grating having aperiodicity.

The color shift according to claim 1, wherein the cross section of the A inclined surface and the B inclined surface perpendicular to the first direction is curved. It is a device.

According to the present invention, in a color shift device exhibiting a special optical effect in which colors change between forward and reverse vision, even if observation conditions such as a viewing angle change slightly, forward and reverse vision can be instantaneously performed. It is possible to provide a color shift device that can visually recognize a color change.

It is a schematic cross-sectional view explaining the shape of the reflection surface included in the laminated structure of the color shift device by the prior art. It is a schematic cross-sectional view explaining the shape of the reflection surface included in the laminated structure of the color shift device by this invention. (A) A schematic cross-sectional view showing a mode in which the wavy structural surface of a color shift device according to the prior art is illuminated with white light from its normal direction and visually recognized from forward and reverse directions, and (b) at the same angle θ. It is a visual image of the normal view and the reverse view performed. (A) A schematic cross-sectional view showing an aspect in which the wavy structural surface of the color shift device according to the present invention is illuminated with white light from its normal direction and visually recognized from forward and reverse directions, and (b) at the same angle θ. It is a visual image of the forward view and the reverse view performed. It is a figure which shows an example of the visual image of the forward view and the reverse direction view of the color shift device by this invention and the prior art, when the observation condition changes.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the color shift device of the present invention and the prior art, elements having the same or similar functions are designated by the same reference numerals, and duplicate description will be omitted.

<Laminate structure>
FIG. 2 is a schematic cross-sectional view illustrating an example of the laminated structure of the color shift device 20 according to the present invention and the shape of the reflective surface included in the laminated structure.

In FIG. 2, the first direction (X direction) is a direction parallel to the display surface 2 of the color shift device 20. Here, the "display surface" is a surface perpendicular to the thickness direction (Z direction) of the color shift device 20, and is a front surface facing the observer. The second direction (Y direction) is a direction parallel to the display surface 2 of the color shift device 20 and perpendicular to the first direction (X direction). The Z direction is a direction perpendicular to the X direction and the Y direction.

The color shift device 20 is in the form of a film or a sheet. The color shift device 20 has a relief structure forming layer 11 and a reflecting layer 12 on a wavy surface formed on the surface of the relief structure forming layer 11. As the reflective layer 12, for example, a metal layer made of aluminum or the like can be used. Although not shown, a protective layer, an intermediate layer, an adhesive layer, or the like may be further provided on the reflective layer 12.

In the color shift device 20 shown in FIG. 2, the reflective layer 12 side may be the display surface 2 and the relief structure forming layer 11 may be the back surface. Or vice versa.

The relief structure forming layer 11 has visible light transmission. According to one example, the relief structure forming layer 11 is a colorless and transparent film or sheet. The relief structure forming layer 11 may be provided on a base material (not shown), but the base material does not necessarily have to be provided, and the relief structure forming layer 11 may be composed of only the relief structure forming layer 11 and the reflective layer 12. ..

<Reflective surface shape>
As shown in FIG. 2, the interface between the relief structure forming layer 11 and the reflective layer 12 and the surface of the reflective layer 12 are wavy reflecting surfaces 12a, and the wavy reflecting surface 12a is one of the facing surfaces of the wavy structure. It includes an inclined surface (A inclined surface) and another inclined surface (B inclined surface). Each of the plurality of A inclined surfaces and B inclined surfaces has a shape extending in the first direction (X direction) parallel to the display surface 2.

The A inclined surface is perpendicular to the display surface 2 and is inclined at a positive angle (clockwise angle) with respect to the reference surface parallel to the X direction. Further, the B inclined surface is inclined at a negative angle (counterclockwise angle) with respect to the reference surface. The A inclined surface and the B inclined surface are parallel to the display surface 2 and are arranged alternately in the Y direction perpendicular to the X direction.

As shown in FIG. 2, the A inclined planes are regularly arranged in the period T1. The arrangement of the A inclined planes constitutes a first diffraction grating having a first lattice constant corresponding to the period. The period T1 is set to the wavelength level of visible light so that the wavelength of the diffracted light emitted by the array of period T1 does not deviate from the visible light region. As an example, the period here refers to the middle distance from the top to the bottom of a wave to the middle from the top to the bottom of the next wave (= the distance at the middle position of the height of the wave).

On the other hand, as shown in FIG. 2, the B inclined surfaces are arranged at irregular intervals and have no periodicity. It should be noted that the case where the B inclined surfaces are regularly arranged in the period T2 and the period T1 and the period T2 are different corresponds to the color shift device of the prior art.

The cross section perpendicular to the first direction (X direction) of each of the A inclined surface and the B inclined surface is curved. When not curved, if the cross-sectional shape is rectangular (a cross section in which the upper and lower bases are horizontal and have corners without side inclination), the periodic components of the A inclined surface and the B inclined surface are on the A inclined surface side and B. Since it acts on both the inclined surface side and there is no difference between when viewed from the A inclined surface side and when viewed from the B inclined surface side, it is important to provide an inclination on the side surface and to blur the corners.

When the side surface is inclined and the corners are rounded, the wavy structure approaches the configuration of only the A inclined surface and the B inclined surface, and since the inclined directions of the A inclined surface and the B inclined surface are opposite to each other, the reflection action is combined. The A period component can be moved to the A inclined surface side and the B period component can be moved to the B inclined surface side, and the difference between the A inclined surface side and the B inclined surface side can be clarified. Will be. The optimization of the cross-sectional shape may be performed in any process such as drawing data, materials, and development process.

FIG. 4A shows the wavy structural surface of the color shift device 20 of the present invention illuminated with white light from its normal direction, and the first observation position OP1 (forward direction) and the second observation position OP2 (reverse direction). ) Is a schematic cross-sectional view showing an aspect of visual recognition, and FIG. 4 (b) is a visual image of forward viewing and reverse viewing performed at the same angle θ. The first observation position OP1 and the second observation position OP2 are symmetrical with respect to a plane passing through the center of the color shift device 20 and perpendicular to the Y direction. In the present application, the case of viewing from the first observation position OP1 is referred to as forward viewing, and the case of viewing from the second observation position OP2 is referred to as reverse viewing. As a matter of course, when viewed in the reverse direction, the top, bottom, left, and right of the design are both reversed when viewed in the forward direction.

As mentioned above, a general diffraction grating having a rectangular or sinusoidal cross section is illuminated with white light from the normal direction, these gratings are inverted, and at the same angle from the diagonal direction. When observing (that is, forward and reverse viewing are performed at the same angle θ), the image is inverted before and after rotation, but the angle (diffraction angle) θ with respect to the normal direction of the diffracted light in the forward and reverse directions is Since they are the same, images of the same color are displayed.

On the other hand, as shown in FIG. 3A, in the conventional color shift device 10, one of the inclined surfaces facing each other in the wavy structure is an A inclined surface, and the other is a B inclined surface. Moreover, the period T1 of the A inclined surface and the period T2 of the B inclined surface are different (T1 <T2 in this example). In the case of forward viewing, the diffraction angle (diffraction angle on the A-plane side) becomes larger by the amount depending on the shorter period T1. Therefore, when forward viewing and reverse viewing are performed from the same angle θ, the image is inverted and the color changes (color shift) (see FIG. 3 (b)). For example, if the forward view is green, the reverse view changes to red.

On the other hand, in the color shift device 20 of the present invention, as shown in FIG. 4A, the A inclined surfaces are regularly arranged in the period T1, and the B inclined surfaces are irregularly spaced. It is arranged and has no periodicity. Here, when the period T1 is set to the wavelength level of visible light, the arrangement of the A inclined planes constitutes the first diffraction grating having the first lattice constant corresponding to the period, so that the white light is used from the normal direction. When illuminated, chromatic light that differs depending on the angle can be visually confirmed by diffraction and interference of light due to the wavy structural surface that is regularly and finely carved.

On the other hand, since the B inclined surfaces are arranged at irregular intervals and have no periodicity, the arrangement of the B inclined surfaces is achromatic because the light is scattered on the wavy structure surface when illuminated with white light from the normal direction. Light is observed. Therefore, as shown in the visual views of the forward view and the reverse view in FIG. 4B, the color shift device 20 of the present invention is chromatic in the forward view, achromatic color in the reverse view, or forward view. This means that you can see achromatic light and chromatic light in the opposite direction.

By the way, the conventional color shift device 10 exhibits a special optical effect in which the color changes between forward viewing and reverse viewing when the image is inverted, but the position of the eyes is slightly displaced due to the deviation of the observation conditions, for example. As mentioned above, when the viewing angle changes slightly, various colors can be seen in the forward and reverse directions. FIG. 5 shows an example of a visual image of a color shift device according to the present invention and the prior art, in which the color shift device is viewed in the forward direction and the reverse direction.

As can be seen from FIG. 5, in the color shift device 10 of the prior art, since the chromatic colors change between the chromatic colors in the forward view and the reverse view, the position of the eyes may shift slightly and the angle after inversion may change. If it is not the same as before inversion, the color that should be visible will shift, and the same color may be seen depending on the angle, making it impossible to exhibit a special optical effect.

However, in the color shift device 20 of the present invention, a chromatic color is visually recognized in a forward view and an achromatic color (and vice versa) are visually recognized in a reverse direction view. Does not bother me, and I can see the difference in color regardless of the angle of inversion. The structure of the color shift device 20 can be incorporated into the display device by itself, thereby forming various images.

<How to make a display device>
The wavy structural surface 12a includes a wavy facing A inclined surface and the other B inclined surface. The period of the A inclined surface is arranged at equal intervals to give periodicity, and the interval of the B inclined surface is made random and non-periodic. Such a wavy structure is created by photolithography technology.

Next, an example of a manufacturing method for manufacturing a display device made of a color shift device will be described. First, as a template for forming a wavy structure, a metal stamper is manufactured as follows using photolithography.

First, a photosensitive resist material is applied to a smooth substrate (a glass substrate is generally used) to form a resist material layer having a uniform film thickness. As the photosensitive resist material, a known positive type material or negative type material can be used. The charged particle beam then draws a desired pattern on the resist material layer based on the wavy structure data for the display device. Then, the resist material layer is developed to obtain a structure having a desired wavy structure.

Next, using this structure as an original plate, a metal stamper is produced from this original plate by a method such as electroforming. In addition, electroforming is a kind of surface treatment technique in which an object to be electroformed is immersed in a predetermined aqueous solution and energized to form a metal film on the object by the reducing power of electrons. By using such a method, the fine wavy structure provided on the surface of the original plate can be accurately reproduced. The surface of the object to be electroformed needs to be energized, but in general, the photosensitive resist does not conduct electricity, so before electroforming, the surface of the structure is subjected to sputtering, vacuum deposition, etc. A metal thin film is provided in advance by a vapor deposition method or the like.

The stamper is then used to replicate the wavy structure on the surface of the relief cambium. First, a thermoplastic resin, a thermosetting resin, a radiation curable resin, or the like is applied onto a light-transmitting substrate made of, for example, polycarbonate or polyester. Next, a metal stamper is brought into close contact with the coating film, heat pressure is applied in this state, irradiation with light or an electron beam is performed, and then the metal stamper is peeled off from the resin layer to provide a wavy structure. Obtain a relief structure forming layer.

In the above, photolithography was used as the method for producing the original plate, but as another method, a method of processing the surface of metal or the like by cutting or etching can be adopted. By using such a method, it is possible to directly process the surface of the metal plate, and in this case, the metal stamper can be directly produced without producing the metal stamper by a method such as electroforming. ..

Next, a metal such as aluminum or a dielectric is deposited on the relief structure forming layer in a single layer or in multiple layers by, for example, a gas phase deposition method such as a vacuum vapor deposition method or a sputtering method to form a reflective layer. When only a part of the relief structure forming layer is covered with the reflective layer, for example, a method such as forming the reflective layer as a continuous film by a gas phase deposition method and then removing a part of the reflective layer with a chemical or the like. Can be obtained by. A display device can be manufactured by such a method.

The display device obtained as described above may be appropriately provided with various known functional layers such as an intermediate layer, a print layer, a protective layer, an adhesive layer or an adhesive layer, and the display device may be used alone. It may be used, or it may be attached to some kind of article and used. As a method of attaching the display device to the article, a label may be attached via an adhesive or the like, or a display device may be manufactured as a structure of a transfer foil and attached to the article. Is also good.

In the color shift device of the present invention, chromatic colors are visually recognized in forward viewing and achromatic colors (and vice versa) are visually recognized in reverse viewing. You can see the difference in color regardless of.

2 ... Display surface 10 ... Conventional color shift device 11 ... Relief structure forming layer 12 ... Reflective layer 12a ... Wavy structure Surface 20 ・ ・ ・ ・ ・ ・ ・ ・ Color shift device OP1 ・ ・ ・ ・ ・ 1st observation position OP2 ・ ・ ・ ・ ・ 2nd observation position of the present invention

Claims (2)

A color shift device comprising at least a relief structure forming layer and a reflective layer formed on the surface of the wavy structure of the relief structure forming layer.
The color shift device has a concavo-convex structure extending in a first direction parallel to the display surface of the color shift device and arranged in a second direction perpendicular to the first direction.
The uneven structure has a wavy reflective surface composed of one A inclined surface and the other B inclined surface facing each other.
The A inclined surface and the B inclined surface are arranged alternately in the second direction.
A color shift device characterized in that the arrangement of the A inclined surfaces has periodicity and the arrangement of the B inclined surfaces is composed of a diffraction grating having aperiodicity. The color shift device according to claim 1, wherein the cross sections of the A inclined surface and the B inclined surface perpendicular to the first direction are both curved.

Images