JP4501369B2 - Optical sheet having light scattering elements - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical sheet having a light scattering element that controls transmission and reflection of light, and more particularly to an optical sheet that can freely change the light emission direction and the amount of light.
[0002]
[Prior art]
A pattern displayed on the basis of light scattering (hereinafter referred to as “light scattering pattern”) is usually formed by processing the surface of a base material of a display body or an optical sheet into a concavo-convex shape. As the processing method, (1) a method by etching, (2) a method of roughening the surface with chemicals or the like, or (3) an electron beam (hereinafter referred to as “EB”) drawing device continuously over the entire surface. There are methods for forming irregularities.
[0003]
FIGS. 17 and 18 are cross-sectional views showing an example of the light scattering element 20 continuously processed into a concavo-convex shape on the surface of the base material of the display body or the optical sheet by a normal surface relief shape, and FIG. 17 (b) shows a convex light scattering element 20 and a concave light scattering element 21 processed by a method of roughening with etching or chemicals, and FIGS. 18 (a) and 18 (b) show an EB drawing apparatus. The convex-shaped light scattering element 20 and the convex-shaped light scattering element 21 processed by the above are respectively shown.
[0004]
In the above-described method using etching or chemicals, as shown in FIG. 17, the uneven shapes of the light scattering elements 20 and 21 after processing are in a considerably rough state. Therefore, it is not easy to control the degree of scattering, that is, the direction of scattered light, the amount of light, and the like by adjusting the unevenness ratio of the light scattering elements 20 and 21 formed in each minute region of the substrate surface.
[0005]
On the other hand, if the EB drawing apparatus is used, as shown in FIG. 18, the uneven shape of the light scattering elements 20 and 21 can be processed fairly precisely as compared with the state of FIG. Therefore, it is possible to arbitrarily control the ratio of each concavo-convex shape formed in each minute region, the shape of the concave portion or the convex portion, and pattern the surface of the substrate, and the degree of scattering, that is, the direction and amount of scattered light Etc. can be controlled to some extent.
[0006]
However, by any of the above processing methods, the shape of the upper side portion (in the case of a convex portion) of the light scattering element 20 or the bottom side portion (in the case of a concave portion) of the light scattering element 21 is substantially parallel to the substrate surface, or Often has a rough shape with no regularity. When light enters the light scattering element 20 perpendicularly and is reflected by the light scattering element 20, isotropic scattering with the regular reflection direction as the center is performed as shown in FIG. . When this light is scattered through the light scattering element 20, as shown in FIG. 20, the isotropic scattering pattern shown in FIG. 19 and the isotropic scattering pattern that is symmetric about the optical sheet. It becomes.
[0007]
As described above, in the display body and the optical sheet composed of the light scattering elements 20 and 21 continuously processed into the uneven shape on the surface of the base material, the distribution of scattered light is limited, and the degree of freedom in optical function and design is also limited. End up.
[0008]
Therefore, for example, Patent Document 1 below discloses an invention relating to an optical sheet in which a number of minute light scattering elements each having an uneven shape are arranged on the surface.
[0009]
In this type of optical sheet, the area, number, or arrangement density of each light scattering element can be adjusted,
(1) Display of characters and patterns by light scattering patterns (2) Sophisticated and diverse expressions (3) Further improvement in design freedom can be realized.
[0010]
[Patent Document 1]
JP 2002-333854 A
[Problems to be solved by the invention]
However, even in the optical sheet having such a conventional light scattering element, as shown in FIG. 21, the shape of the upper side portion (in the case of the convex portion) of each light scattering element 20 is substantially parallel to the surface of the substrate. There is a limit to displaying complex characters and designs with a wide variety of light scattering patterns. There is also a limit to the degree of freedom in design.
[0012]
In addition, it is not possible to sufficiently satisfy the demand for giving anisotropy to light scattering by individually controlling each light scattering element in an optical sheet having a plurality of light scattering elements.
[0013]
The present invention has been made in view of such circumstances, and a plurality of minute light scattering elements are formed by unevenness having an inclined light scattering surface, and the direction and amount of light scattering of each light scattering element are determined. An optical sheet having a light scattering element that can be controlled by adjusting the shape and inclination angle of each light scattering surface, and that can easily control the direction and amount of light scattering for each light scattering element. The purpose is to provide.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention takes the following measures.
[0015]
That is, the optical sheet according to the first aspect of the present invention includes a plurality of cells arranged in a matrix on the substrate surface, and each cell includes a protrusion having a light scattering surface having an inclination angle with respect to the substrate surface. A first cell in which a plurality of light scattering elements are arranged, and a second cell in which a plurality of light scattering elements consisting of depressions provided with a light scattering surface having an inclination angle with respect to the substrate surface are arranged And a third cell in which at least one light scattering element composed of a protrusion and at least one light scattering element composed of a depression belong to each other. Further, in at least one cell belonging to the first cell, at least one light scattering element has the same inclination angle and light scattering surface length as those of other light scattering elements disposed in the same cell. The at least one light scattering element is arranged in the same cell in the at least one cell belonging to the second cell , or the protrusion, or the protrusion having a different inclination angle or light scattering surface length . It consists of a depression having the same inclination angle and light scattering surface length as that of other light scattering elements , or a depression having a different inclination angle or light scattering surface length .
[0016]
Therefore, in the optical sheet of the invention of claim 1, as described above, each light scattering element is formed by unevenness having an inclined light scattering surface, and the shape and inclination angle of each light scattering surface are adjusted. Then, it becomes possible to emit scattered light having directivity and freely control the direction and amount of light scattering for each light scattering surface.
[0019]
According to a second aspect of the present invention, in the optical sheet of the first aspect of the invention, the normal direction with respect to the light scattering surface of the light scattering element composed of the protrusions arranged in the same cell is substantially the same, and the depression arranged in the same cell. The normal direction with respect to the light-scattering surface of the light-scattering element consisting of a portion is made substantially the same.
[0020]
Therefore, in the optical sheet of the invention of claim 2 , by taking the above-described means, the emission direction of the scattered light can be controlled for each cell.
[0021]
According to a third aspect of the invention, in the optical sheet of the first aspect of the invention, the absolute values of the inclination angles of the light scattering surfaces of the light scattering elements arranged in the same cell with respect to the substrate surface are substantially the same.
[0022]
Therefore, in the optical sheet of the invention of claim 3 , by taking the above-described means, the emission direction of the scattered light can be controlled in units smaller than the cell.
[0025]
The invention according to claim 4 is the optical sheet according to any one of claims 1 to 3 , wherein the length per side of each cell is not less than the length at which the light scattering element can be arranged and not more than 300 μm. Yes.
[0026]
Therefore, in the optical sheet of the invention of claim 4 , by taking the above-mentioned means, each cell constituting the light scattering element can be made so small that it cannot be identified with the naked eye. As described above, when the optical sheet is observed, it is possible to perform light scattering control at a resolution that does not cause a sense of incongruity with the naked eye without recognizing the roughness of the resolution due to the cell shape.
[0027]
According to a fifth aspect of the present invention, in the optical sheet according to any one of the first to fourth aspects, the deepest dimension from the substrate surface of the light scattering element comprising the recessed portion is provided on the substrate surface by the recessed portion. It is made to become below the length dimension along the direction which projects the inclination direction of the light-scattering surface in an opening part.
[0028]
Therefore, in the optical sheet of the invention of claim 5 , by taking the above-described means, the effects obtained by the optical sheet of the invention of claims 1 to 4 can be obtained while efficiently using incident light. Can do.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0030]
(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS.
[0031]
FIG. 1 is a perspective view showing an example of an optical sheet according to the first embodiment.
[0032]
2 is a cross-sectional view taken along line AA in FIG.
[0033]
FIG. 3 is a sectional view taken along line BB in FIG.
[0034]
That is, the optical sheet 10 according to the present embodiment has a plurality of cells 12 (# 1 to # 12) arranged in a matrix on the surface of the substrate 11, as shown in FIG. FIG. 1 illustrates an optical sheet 10 including 12 cells 12 (# 1 to # 12) as an example, and the number of cells arranged in the optical sheet 10 according to the present embodiment is 12. It is not limited to individual.
[0035]
Each cell 12 belongs to one of the following three patterns.
[0036]
That is, in the first pattern, as shown in FIG. 2, a single or a plurality of light scattering elements 14 each including a protrusion having a light scattering surface f ₁ having an inclination angle φ ₁ with respect to the surface of the substrate 11 are arranged. is doing. When a plurality of light scattering elements 14 are arranged, even if all of the plurality of light scattering elements 14 have the same inclination angle φ and light scattering surface f length, the inclination angle φ or the light scattering surface f length Any one of them may be different. The plurality of light scattering elements 14 in the cell 12 may be arranged at regular intervals, irregularly arranged, or only partially arranged regularly.
[0037]
In the second pattern, as shown in FIG. 3, a single or a plurality of light scattering elements 16 each including a hollow portion provided with a light scattering surface f ₂ having an inclination angle φ ₂ with respect to the surface of the substrate 11 are arranged. is doing. When a plurality of light scattering elements 16 are arranged, even if all of the plurality of light scattering elements 16 have the same inclination angle φ and light scattering surface f length, the inclination angle φ or the light scattering surface f length Any one of them may be different. The plurality of light scattering elements 16 in the cell 12 may be arranged at regular intervals, irregularly arranged, or only partially arranged regularly.
[0038]
Further, the third pattern is a combination of the first pattern and the second pattern, and includes a light scattering element 14 as shown in FIG. 2 and a light scattering element 16 as shown in FIG. At least one each is arranged. Even if all the light scattering elements arranged in the third pattern cell have the same inclination angle φ and light scattering surface f length, either the inclination angle φ or the light scattering surface f length is used. May be different. The plurality of light scattering elements in the cell 12 may be arranged at regular intervals, irregularly arranged, or only partially arranged regularly.
[0039]
Then, the shape of the light scattering surface f of each of the light scattering elements 14 and 16 is processed with high accuracy and is inclined to realize scattered light having anisotropy with respect to incident light.
[0040]
For example, as shown in FIG. 4, incident light from the normal direction to the surface of the substrate 11 is scattered and transmitted by the light scattering elements 14 and 16 processed so as to decrease toward the right side in the figure. In this case, the light quantity distribution is such that it is large on the left side in the figure and small on the right side in the figure, thereby realizing anisotropy of transmitted light.
[0041]
On the other hand, when such incident light from the normal direction with respect to the surface of the substrate 11 is scattered and reflected by the light scattering elements 14 and 16, it is increased on the right side in the figure and decreased on the left side in the figure. The light intensity distribution becomes uniform and the anisotropy of reflected light is realized. As described above, when the incident light is reflected by the optical sheet 10, a reflective material made of metal such as silver or aluminum may be disposed on the surface of the substrate 11 by vapor deposition or the like, as shown in FIG.
[0042]
Note that the cross section of the light scattering surface f of each of the light scattering elements 14 and 16 does not have to be a strict linear cross section, and is slightly curved as shown in FIG. Even if it is a cross section with fluctuation as shown in (b), if the tendency of the whole cross section is almost inclined, the controllability of light is slightly lowered, but the effect of the present invention is realized. Can do.
[0043]
Further, each cell 12 has a length per side that is not less than the size at which the light scattering elements 14 and 16 can be disposed and not more than 300 μm. That is, each cell 12 is smaller than the resolution by the human naked eye, and has a size that an observer can hardly identify. Thus, even when observed by an observer, the roughness of the resolution due to the shape of the cell 12 is not recognized, so that a sense of incongruity is not generated with the naked eye.
[0044]
As described above, the optical sheet according to the present embodiment can strictly control light scattering by processing the light action surfaces f of the light scattering elements 14 and 16 each having a minute uneven shape. . Since this light action surface f has a simple configuration having only an inclination with respect to the surface of the substrate 11, it can be easily processed and directivity can be easily realized.
[0045]
In addition, it is not necessary to use multiple layers for light scattering, and light scattering can be strictly controlled by only one layer, so that the thickness of the optical sheet is not increased and the manufacturing process is simplified. Can do.
[0046]
In addition, since it has a surface relief structure, it can be realized by duplication by plastic molding or by duplication with thermoplastic resin, UV curable resin, etc., and it has excellent high weather resistance compared to scattering films using photosensitive materials Can be expected.
[0047]
The optical sheet according to the present embodiment having such a function effect prevents counterfeiting by performing authenticity determination by changing the appearance depending on the display part of a mobile terminal such as a mobile phone or a handheld PC or ambient light. It can be applied to a display or the like.
[0048]
(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIGS.
[0049]
The optical sheet according to the present embodiment is the same as the optical sheet according to the first embodiment except that the shapes and dimensions of the light scattering elements 14 and 16 and the inclination angle φ of the light scattering surface f are limited. Therefore, the same parts as those in FIG. 1 are denoted by the same reference numerals and the description thereof is omitted, and only different parts are described.
[0050]
FIG. 7 is a perspective view showing an example of an optical sheet according to the second embodiment.
[0051]
That is, in the optical sheet according to the present embodiment, the shape and size of the light scattering elements 14 and 16 disposed in the same cell 12 and the inclination angle φ absolute value of the light scattering surface f with respect to the surface of the substrate 11 are the same. Yes. Accordingly, as long as the light scattering elements 14 and 16 have the same shape, dimensions, and inclination angle φ absolute value, they may be arranged in the same cell 12 as shown in FIG. Even if the 14 light scattering surfaces f face the same direction, or as shown in FIG. 9, the directions of the light scattering surfaces f of the light scattering elements 14 arranged in the same cell 12 are arranged randomly. Anyway.
[0052]
In particular, as shown in FIGS. 10 and 11, the light scattering elements 14, 16 having the same shape, dimensions, and the same inclination angle φ absolute value and direction of the light scattering surface f for each same cell 12. By arranging, a unique light scattering characteristic can be obtained for each cell.
[0053]
Then, by changing the direction of the light scattering surface f of the light scattering elements 14 and 16 for each cell 12, the emission direction of the scattered light can be controlled for each cell 12, as shown by the arrows in FIG. That is, in each cell 12, if the light scattering elements 14 and 16 are directed in the same direction, bright scattered light is perceived only in a certain direction, and generation of scattered light in other directions can be suppressed. If scattered light is obtained in different directions for each cell 12 as shown in FIG. 12, the scattered light distribution as shown in FIG. 13 or FIG. 14 can be realized in an arbitrary direction.
[0054]
The direction of the light action surface f of the light scattering elements 14 and 16 can be freely set at 360 °, and the location of the observation region can be made not restricted accordingly.
[0055]
(Third embodiment)
A third embodiment of the present invention will be described with reference to FIGS.
[0056]
The optical sheet according to the present embodiment is the optical sheet according to the first embodiment, in which the shape of each light scattering element 16 is particularly limited. Therefore, the same parts as those in FIG. 1 are denoted by the same reference numerals and the description thereof is omitted, and only different parts are described.
[0057]
FIG. 15 is a cross-sectional view showing an example of a cell forming an optical sheet according to the third embodiment.
[0058]
That is, in the optical sheet according to the present embodiment, as shown in FIG. 15, the depth h from the surface of the substrate 11 of the light scattering element 16 formed of the depression is provided on the surface of the substrate 11 by the depression. It is made to become below length p along the direction which projects the inclination direction of the light-scattering surface f in an opening part.
[0059]
When the depth h of the light scattering element 16 exceeds the length p of the opening (h> p), as the depth h increases with respect to the constant length p of the opening as shown in FIG. h ₁ <h ₂ <h ₃ ), the area of the light non-acting surface g which is an inclined surface that does not contribute to the directional scattering of light increases, and processing becomes difficult. Moreover, since the structure of an optical sheet becomes thick, it is not preferable.
[0060]
On the other hand, the convex light scattering element 14 can realize light scattering regardless of its height h. Therefore, when creating a light scattering element having a steep light acting surface f, the concave light scattering element 16 is used. It is preferable to use a light scattering element 14 having a convex shape.
[0061]
As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, this invention is not limited to this structure. Within the scope of the invented technical idea of the scope of claims, a person skilled in the art can conceive of various changes and modifications. The technical scope of the present invention is also applicable to these changes and modifications. It is understood that it belongs to.
[0062]
【The invention's effect】
As described above, according to the present invention, a plurality of minute light scattering elements are formed by projections and depressions having an inclined light scattering surface, and the light scattering direction and the amount of light of each light scattering element are changed to each light scattering surface. This can be controlled by adjusting the shape and the inclination angle.
[0063]
By the above, the optical sheet which has a light-scattering element which can control easily the light scattering direction and light quantity for each light-scattering element is realizable.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of an optical sheet according to a first embodiment. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. FIG. 3 is taken along line BB in FIG. Cross-sectional view [FIG. 4] Schematic diagram for explaining the light-scattering effect by the light-scattering element having an inclined light-acting surface [FIG. 5] Cross-sectional view showing an example of an optical sheet having a reflector disposed on the surface [FIG. FIG. 7 is a schematic view showing an example of the cross-sectional shape of the light scattering surface of the light scattering element. FIG. 7 is a perspective view showing an example of the optical sheet according to the second embodiment. FIG. 9 is a perspective view showing another example of a cell in which light scattering elements are arranged. FIG. 10 is a perspective view showing an example of an optical sheet in which the light scattering effect is changed for each cell. ] Cross-sectional view showing a part of an optical sheet in which the light scattering effect is changed for each cell. [FIG. 12] FIG. 13 is a conceptual diagram showing an example of the direction of light emission. FIG. 13 is a conceptual diagram showing an example of the correlation between the direction of the light scattering surface and the distribution characteristics of the scattered light. FIG. 15 is a conceptual diagram showing an example of a correlation with a cell. FIG. 15 is a cross-sectional view showing an example of a cell forming an optical sheet according to the third embodiment. FIG. 16 is an optical sheet according to the third embodiment. FIG. 17 is a cross-sectional view showing an example of a light-scattering element that has been concavo-convex processed on the substrate surface by a conventional technique (when processed by a method of roughening with etching or chemicals)
FIG. 18 is a cross-sectional view showing an example of a light scattering element that has been processed to be uneven on the substrate surface by a conventional technique (when processed by an EB drawing apparatus).
FIG. 19 is a conceptual diagram for explaining the reflection intensity distribution when light is incident on the light scattering element and is regularly reflected. FIG. 20 is the transmission intensity distribution when light is incident on the light scattering element and is transmitted. FIG. 21 is a perspective view showing an optical sheet having a light scattering element according to the prior art.
f ... light acting surface, g ... light non-acting surface, 10 ... optical sheet, 11 ... substrate, 12 ... cell, 14, 16, 20, 21 ... light scattering element

Claims (5)

A plurality of cells arranged in a matrix on the substrate surface,
Each cell is
A first cell in which a plurality of light scattering elements comprising protrusions provided with a light scattering surface having an inclination angle with respect to the substrate surface;
A second cell in which a plurality of light scattering elements each including a hollow portion provided with a light scattering surface having an inclination angle with respect to the substrate surface;
It belongs to any one of the light scattering element composed of the protrusion and the third cell in which at least one light scattering element composed of the depression is arranged,
In at least one cell belonging to the first cell, at least one light scattering element is a protrusion having the same inclination angle and light scattering surface length as that of other light scattering elements disposed in the same cell. Or a protrusion having a different inclination angle or light scattering surface length ,
In at least one cell belonging to the second cell, the at least one light scattering element is a depression whose inclination angle and light scattering surface length are the same as those of other light scattering elements arranged in the same cell. Or an optical sheet comprising depressions having different inclination angles or light scattering surface lengths . The optical sheet according to claim 1,
The normal direction with respect to the light scattering surface of the light scattering element composed of the protrusions arranged in the same cell is substantially the same, and the normal direction with respect to the light scattering surface of the light scattering element composed of the depressions arranged in the same cell An optical sheet that is almost identical. The optical sheet according to claim 1,
An optical sheet in which absolute values of inclination angles of light scattering surfaces of light scattering elements arranged in the same cell with respect to the substrate surface are substantially the same.   The optical sheet according to any one of claims 1 to 3, wherein a length per side of each cell is not less than a length at which the light scattering element can be arranged and not more than 300 µm.   The deepest dimension from the substrate surface of the light scattering element composed of the depression is not more than the length dimension along the direction formed by projecting the inclination direction of the light scattering surface in the opening provided on the substrate surface by the depression. The optical sheet according to any one of claims 1 to 4, wherein the optical sheet is formed as follows.

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