WO2021079923A1

WO2021079923A1 - Diffusion plate, display device, projection device, and illumination device

Info

Publication number: WO2021079923A1
Application number: PCT/JP2020/039657
Authority: WO
Inventors: 有馬　光雄; 正之石渡; 駿介金杉
Original assignee: デクセリアルズ株式会社
Priority date: 2019-10-25
Filing date: 2020-10-22
Publication date: 2021-04-29

Abstract

[Problem] To suppress unevenness in luminance distribution in two directions of microlenses arranged in a rectangular grid array and to improve homogeneity in light distribution. [Solution] Provided is a microlens array-type diffusion plate which is provided with a substrate and a microlens array comprising a plurality of microlenses that are arrayed in conformity to a rectangular grid on an X-Y plane of at least one surface of the substrate, wherein: X-direction grid intervals Wx of the microlenses arrayed in the X-direction of the rectangular grid are mutually different from each other; Y-direction grid intervals Wy of the microlenses arrayed in the Y-direction of the rectangular grid are mutually different from each other; and the respective microlenses have surface shapes that are different from each other.

Description

Diffusing plate, display device, projection device and lighting device

The present invention relates to a diffuser, a display device, a projection device and a lighting device.

In order to change the diffusion characteristics of light, a diffuser plate that diffuses incident light in a desired direction is used. The diffuser plate is widely used in various devices such as a display device such as a display, a projection device such as a projector, and various lighting devices. There is a type of diffusing plate that diffuses incident light at a desired diffusion angle by utilizing the refraction of light due to the surface shape of the diffusing plate. As a diffuser of this type, a microlens array type diffuser in which a plurality of microlenses having a size of about several tens of μm are arranged is known.

In such a microlens array type diffuser plate, there is a problem that as a result of interference of the wave planes of light from each microlens, diffracted waves due to the periodic structure of the microlens array are generated, and the intensity distribution of diffused light is uneven. Therefore, a technique has been proposed for reducing unevenness in the intensity distribution of diffused light due to interference or diffraction by varying the arrangement of microlenses, the shape of the lens surface, and the shape of the aperture.

For example, in Patent Document 1, in a diffusion plate in which a plurality of microlenses are regularly arranged in a rectangular lattice pattern on a main surface, a plurality of microlenses having different cross-sectional shapes and having no axis of symmetry. Is described to be used. Further, Patent Document 2 describes that the lens apex positions of a plurality of microlenses arranged in a rectangular grid pattern are arranged so as to be offset from the grid points of the reference grid.

International Publication No. 2016/051785 International Publication No. 2015/182919

However, as described in Patent Document 1, in an array structure in which a plurality of microlenses having no target axis and having different cross-sectional shapes are regularly arranged in a rectangular lattice pattern, between microlenses adjacent to each other. The unevenness of the intensity distribution of the diffused light is reduced only by the phase change of the light. Therefore, the effect of uniformly distributing the diffused light in the two directions orthogonal to each other of the rectangular lattice is limited. Further, as described in Patent Document 2, in an array structure regularly arranged in a rectangular lattice shape, a arrangement having high homogeneity in two directions of the rectangular lattice can be obtained only by shifting the apex positions of each microlens. Optical control could not be realized.

Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to suppress unevenness of luminance distribution in two directions of microlenses arranged in a rectangular lattice pattern and to distribute light. The purpose is to improve the homogeneity of the lens.

In order to solve the above problems, according to a certain viewpoint of the present invention,
It is a microlens array type diffuser
With the base material
A microlens array composed of a plurality of microlenses arranged on an XY plane on at least one surface of the base material with reference to a rectangular grid, and a microlens array.
With
The lattice spacing Wx in the X direction of the microlenses arranged in the X direction of the rectangular lattice is different from each other.
The lattice spacing Wy in the Y direction of the microlenses arranged in the Y direction of the rectangular lattice is different from each other.
Diffusing plates are provided in which the surface shapes of the plurality of microlenses are different from each other.

The grid spacing Wx in the X direction randomly fluctuates at a volatility δWx within ± 10% to ± 50% with reference to the reference grid spacing Wx_k.
The grid spacing Wy in the Y direction may be randomly changed at a volatility δWy within ± 10% to ± 50% with reference to the reference grid spacing Wy_k.

The radius of curvature Rx of the microlenses arranged in the X direction in the X direction varies from each other.
The radius of curvature Ry of the microlenses arranged in the Y direction in the Y direction may be made to fluctuate with each other.

The radius of curvature Rx in the X direction randomly fluctuates at a volatility δRx within ± 10% to ± 50% with reference to the reference radius of curvature Rx_k.
The radius of curvature Ry in the Y direction may be randomly changed at a volatility δRy within ± 10% to ± 50% with reference to the reference radius of curvature Ry_k.

The grid spacing Wx in the X direction randomly fluctuates at a volatility δWx within ± 10% to ± 50% with reference to the reference grid spacing Wx_k.
The grid spacing Wy in the Y direction randomly fluctuates at a volatility δWy within ± 10% to ± 50% with reference to the reference grid spacing Wy_k.
The reference grid spacing Wx_k, Wy_k and the reference curvature radii Rx_k, Ry_k satisfy the following relational expressions (A) and (B).
The diffusion angle (full width at half maximum) by the diffusion plate may be 20 ° or less.
Rx_k / Wx_k ≧ 1.85 ・・・ (A)
Ry_k / Wy_k ≧ 1.85 ・・・ (B)

The plane positions of the vertices of the microlenses arranged in the X direction and the Y direction may be eccentric from the center point of the rectangular lattice.

The distances in the X and Y directions from the center point of the rectangular lattice to the plane position of the apex of the eccentric microlens are defined as the eccentric amount Ecx and the eccentric amount Ecy, respectively, and the lattice intervals Wx and Wy of the rectangular lattice. When the ratios of the eccentricity Ecx and Ecy to the eccentricity are the eccentricity δEcx and the eccentricity δEcy, respectively.
The plane position of the apex of the microlens may be randomly eccentric with eccentricity ratios δEcx and δEcy within ± 10% to ± 50%.

The height positions of the vertices of the plurality of microlenses arranged in the X direction and the Y direction may be different from each other.

The microlenses arranged in the X direction and the Y direction may be arranged continuously without any gaps between them.

The boundary lines of the microlenses adjacent to each other may include straight lines and curved lines.

The microlens array is composed of a plurality of unit cells, which is a basic arrangement pattern of the microlens.
The microlens array may be configured by arranging the plurality of unit cells without gaps while maintaining the continuity of the microlenses at the boundary portion between the plurality of unit cells.

The surface shape of the microlens may be a spherical shape or an aspherical shape having anisotropy in the X direction or the Y direction.

In order to solve the above problems, according to another aspect of the present invention, a display device including the above diffusion plate is provided.

In order to solve the above problems, according to another aspect of the present invention, a projection device including the above diffusion plate is provided.

In order to solve the above problems, according to another aspect of the present invention, a lighting device including the above diffusion plate is provided.

As described above, according to the present invention, it is possible to suppress unevenness of the luminance distribution and improve the homogeneity of the light distribution in the two directions of the microlenses arranged in a rectangular grid pattern.

It is explanatory drawing which shows typically the diffusion plate which concerns on one Embodiment of this invention. It is an enlarged plan view and the enlarged sectional view schematically showing the structure of the diffusion plate which concerns on this embodiment. It is an enlarged cross-sectional view which shows typically the vicinity of the boundary of the microlens which concerns on this embodiment. It is a top view which shows typically the plane shape (outer shape) of the microlens which concerns on this embodiment. It is a top view which shows typically the arrangement of the irregular rectangular grid-like microlenses which concerns on this embodiment. It is explanatory drawing which shows the example which changed the surface shape of a microlens from the state of FIG. It is explanatory drawing which shows the example which eccentric position of the apex of a microlens is eccentric from the state of FIG. It is explanatory drawing which shows the planar shape of the anamorphic shape microlens which concerns on this embodiment. It is a perspective view which shows the three-dimensional shape of the anamorphic shape microlens which concerns on the same embodiment. It is a perspective view which shows the curved surface of the anamorphic shape which concerns on this embodiment. It is explanatory drawing which shows the planar shape of the torus-shaped microlens which concerns on this embodiment. It is a perspective view which shows the three-dimensional shape of the torus-shaped microlens which concerns on this embodiment. It is a perspective view which shows the curved surface of the torus shape which concerns on this embodiment. It is a flowchart which shows the design method of the microlens which concerns on this embodiment. It is explanatory drawing which shows the rectangular grid generated in the grid generation step which concerns on the same embodiment. It is explanatory drawing which shows the rectangular grid generated in the grid eccentricity step which concerns on the same embodiment. It is explanatory drawing which shows the plurality of microlenses generated in the lens generation step which concerns on this embodiment. It is an image showing a lens pattern designed by the design method which concerns on the same embodiment. It is a flowchart which shows the manufacturing method of the diffusion plate which concerns on this embodiment. It is explanatory drawing about the diffusion plate which concerns on Comparative Example 1. FIG. It is explanatory drawing about the diffusion plate which concerns on Comparative Example 2. It is explanatory drawing about the diffusion plate which concerns on Comparative Example 3. It is explanatory drawing about the diffusion plate which concerns on Example 1. FIG. It is explanatory drawing about the diffusion plate which concerns on Example 2. FIG. It is explanatory drawing about the diffusion plate which concerns on Example 3. FIG. It is explanatory drawing about the diffusion plate which concerns on Example 4. FIG. It is explanatory drawing about the diffusion plate which concerns on Example 5. FIG. It is explanatory drawing about the diffusion plate which concerns on Example 6. It is explanatory drawing about the diffusion plate which concerns on Example 7. FIG. It is explanatory drawing about the diffusion plate which concerns on Example 7. FIG. It is explanatory drawing about the diffusion plate which concerns on Comparative Example 4. FIG. It is explanatory drawing about the diffusion plate which concerns on Example 8. FIG. It is explanatory drawing about the diffusion plate which concerns on Example 9. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

<1. Overview of diffuser>
First, an outline of the diffusion plate according to the embodiment of the present invention will be described.

The diffusing plate according to the present embodiment described in detail below is a microlens array type diffusing plate having a homogeneous light diffusing function. Such a diffuser has a microlens array formed on an XY plane on at least one surface (main surface) of the substrate. The microlens array is composed of a plurality of microlenses arranged and expanded in a rectangular grid pattern. The microlens has a convex structure (convex lens) or a concave structure (concave lens) having a light diffusing function, and has a lens diameter of about several tens of μm.

Then, in the diffuser plate according to the present embodiment, a plurality of microlenses are arranged in a rectangular grid shape (matrix shape) with reference to a rectangular grid having irregularities. In a rectangular grid having this irregularity, a plurality of grid spacing Wx in the X direction (row direction) randomly fluctuates and differ from each other, and a plurality of grid spacing Wy in the Y direction (column direction) also randomly fluctuates. It fluctuates and is different from each other. Furthermore, the radii of curvature Rx and Ry of the plurality of microlenses arranged in the X and Y directions fluctuate randomly (irregularly) so as to be different from each other. In addition, the plane position of the apex of each microlens randomly fluctuates (eccentricity) so as to deviate from the center point of the rectangular lattice. Further, the height positions of the vertices of the plurality of microlenses in the Z direction (positions in the thickness direction of the diffuser plate) also fluctuate randomly and are different from each other. By randomly changing the grid spacing Wx, Wy, the radius of curvature Rx, Ry, the plane position and the height position of the lens vertices, etc., the surface shape of the plurality of microlenses developed in a rectangular grid shape can be changed. It fluctuates randomly and has different shapes.

As described above, according to the diffuser plate according to the present embodiment, the three-dimensional surface structure of the microlens array with high randomness is realized by randomly changing each variable element of the plurality of microlenses. Thereby, it is possible to control the phase superposition state of the light emitted from each microlens. As a result, while having a highly transmissive luminance characteristic and satisfying the homogeneity of light distribution in two directions (X and Y directions) orthogonal to each other, sufficient anisotropy of light distribution and diffused light It is possible to provide a surface structure of a diffuser plate capable of controlling the cutoff property of the intensity distribution.

Further, according to the present embodiment, a plurality of microlenses are arranged on the XY plane with reference to an irregular rectangular grid having different grid spacings Wx and Wy. As a result, a plurality of microlens arrays can be continuously arranged on the surface of the diffuser without any gaps while ensuring the randomness of the surface shape of each microlens. Therefore, since the flat portion can be eliminated as much as possible at the boundary portion of the adjacent microlenses, the unevenness of the intensity distribution of the diffused light can be further reduced, and the homogeneity of the light distribution in the two directions (X and Y directions) can be further improved. Can be improved.

Hereinafter, the diffusion plate according to the present embodiment having the above characteristics will be described in detail.

<2. Overall configuration of diffuser>
First, with reference to FIG. 1, the overall configuration of the diffuser plate according to the embodiment of the present invention and the layout pattern of the microlens will be described. FIG. 1 is an explanatory diagram schematically showing the diffusion plate 1 according to the present embodiment.

The diffuser plate 1 according to the present embodiment is a microlens array type diffuser plate in which a microlens array composed of a plurality of microlenses (single lenses) is arranged on a substrate. As shown in FIG. 1, the microlens array of the diffuser plate 1 is composed of a plurality of unit cells 3. The unit cell 3 is a basic arrangement pattern of the microlens. A plurality of microlenses are arranged on the surface of each unit cell 3 in a predetermined layout pattern (arrangement pattern).

Here, FIG. 1 shows an example in which the shape of the unit cell 3 constituting the diffusion plate 1 is rectangular, particularly square. However, the shape of the unit cell 3 is not limited to the example shown in FIG. 1, and the shape of the unit cell 3 is not limited to the example shown in FIG. Any shape may be used as long as it can be filled.

In the example of FIG. 1, a plurality of square unit cells 3 are repeatedly arranged vertically and horizontally on the surface of the diffusion plate 1. The number of unit cells 3 constituting the diffusion plate 1 according to the present embodiment is not particularly limited, and the diffusion plate 1 may be composed of one unit cell 3 or from a plurality of unit cells 3. It may be configured. In the diffusion plate 1 according to the present embodiment, the unit cells 3 having different surface structures may be repeatedly arranged, or the unit cells 3 having the same surface structure may be repeatedly arranged.

Further, between the unit cells 3, as schematically shown in the enlarged view on the right side in FIG. 1, the layout pattern (arrangement pattern) of the plurality of microlenses provided in the unit cell 3 is the unit cell 3. It is continuous in the array direction (in other words, the array array direction). The microlens array is configured by arranging the unit cells 3 without gaps while maintaining the continuity of the microlenses at the boundary portion between the plurality of unit cells 3. Here, the continuity of the microlens means the microlens located on the outer edge of one unit cell 3 and the microlens located on the outer edge of the other unit cell 3 among the two adjacent unit cells 3. However, it means that the lenses are continuously connected without any deviation of the plane shape or steps in the height direction.

As described above, in the diffuser plate 1 according to the present embodiment, the unit cells 3 (basic structure) of the microlens array are arranged without gaps while maintaining the continuity of the boundaries, thereby forming the microlens array. .. As a result, it is possible to prevent the occurrence of unintended defects such as light diffraction, reflection, and scattering at the boundary portion between the unit cells 3, and obtain the desired light distribution characteristics by the diffuser plate 1.

<3. Diffusion plate configuration>
Next, the configuration of the diffusion plate 1 according to the present embodiment will be described in more detail with reference to FIGS. 2 to 4. FIG. 2 is an enlarged plan view and an enlarged cross-sectional view schematically showing the configuration of the diffusion plate 1 according to the present embodiment. FIG. 3 is an enlarged cross-sectional view schematically showing the vicinity of the boundary of the microlens 21 according to the present embodiment. FIG. 4 is a plan view schematically showing the planar shape (outer shape) of the microlens 21 when the microlens 21 is viewed in a plan view from a direction perpendicular to the surface of the base material 10.

As shown in FIG. 2, the diffuser plate 1 according to the present embodiment includes a base material 10 and a microlens array 20 formed on the surface of the base material 10.

First, the base material 10 will be described. The base material 10 is a substrate for supporting the microlens array 20. The base material 10 may be in the form of a film or in the form of a plate. The base material 10 shown in FIG. 2 has, for example, a rectangular flat plate shape, but is not limited to such an example. The shape and thickness of the base material 10 may be any shape and thickness depending on the shape of the device on which the diffusion plate 1 is mounted.

The base material 10 is a transparent base material capable of transmitting light. The base material 10 is formed of a material that can be regarded as transparent in the wavelength band of light incident on the diffuser plate 1. For example, the base material 10 may be made of a material having a light transmittance of 70% or more in a wavelength band corresponding to visible light.

The base material 10 is, for example, polymethylmethacrylate (PMMA), polyethylene terephthalate (PET), polycarbonate (PC), cyclic olefin copolymer (Cyclo Olefin Polymer: COC), cyclic olefin. It may be formed of a known resin such as Olefin Polymer (COP) and Triacetyl cellulose (TAC). Alternatively, the base material 10 may be formed of known optical glass such as quartz glass, borosilicate glass, and white plate glass.

Next, the microlens array 20 will be described. The microlens array 20 is provided on at least one surface (main surface) of the base material 10. The microlens array 20 is an aggregate of a plurality of microlenses 21 (single lenses) arranged on the surface of the base material 10. In this embodiment, as shown in FIG. 2, the microlens array 20 is formed on one surface of the base material 10. However, the present invention is not limited to this, and the microlens array 20 may be formed on both main surfaces (front surface and back surface) of the base material 10.

The microlens 21 is, for example, a fine optical lens on the order of several tens of μm. The microlens 21 constitutes a single lens of the microlens array 20. The microlens 21 may have a concave structure (concave lens) formed so as to be depressed in the thickness direction of the diffuser plate 1, or a convex structure (convex lens) formed so as to project in the thickness direction of the diffuser plate 1. It may be. In the present embodiment, an example in which the microlens 21 has a concave structure (concave lens) as shown in FIG. 2 will be described, but the present invention is not limited to such an example. The microlens 21 may have a convex structure (convex lens) depending on the desired optical characteristics of the diffuser plate 1.

The surface shape of each microlens 21 is not particularly limited as long as it is a curved surface shape including a curved surface component. The surface shape of the microlens 21 may be, for example, a spherical shape containing only a spherical component, an aspherical shape containing only a spherical component and an aspherical component, or a spherical shape containing only an aspherical component. It may have an aspherical shape.

As shown in FIG. 2, it is preferable that the plurality of microlenses 21 are densely arranged so as to be adjacent to each other without a gap. In other words, it is preferable that the plurality of microlenses 21 are continuously arranged so that there is no gap (flat portion) at the boundary portion between the microlenses 21 adjacent to each other. By arranging the microlens 21 on the base material 10 without gaps (in other words, arranging the microlens 21 so that the filling rate is 100%), the incident light is not scattered on the surface of the diffuser plate 1. It is possible to suppress a component that is transmitted as it is (hereinafter, also referred to as a "0th-order transmitted light component"). As a result, the diffusion performance can be further improved by the microlens array 20 in which the plurality of microlenses 21 are arranged so as to be adjacent to each other without a gap.

In order to suppress the 0th-order transmitted light component, the filling rate of the microlens 21 on the base material 10 is preferably 90% or more, and more preferably 100%. Here, the filling rate is the ratio of the area of the portion occupied by the plurality of microlenses 21 on the surface of the base material 10. When the filling rate is 100%, the surface of the microlens array 20 is formed of curved surface components and contains almost no flat surface components.

However, in the actual manufacturing of the microlens array 20, in order to continuously connect the curved surfaces of a plurality of microlenses 21, the vicinity of the inflection point at the boundary between adjacent microlenses 21 may become substantially flat. obtain. In such a case, the width of the region near the inflection point (the width of the boundary line between the microlenses 21) that becomes substantially flat at the boundary between the microlenses 21 is preferably 1 μm or less. As a result, the 0th-order transmitted light component can be sufficiently suppressed.

Further, in the microlens array 20 according to the present embodiment, the plurality of microlenses 21 are not randomly (irregularly) arranged, but as shown in FIG. 2, the grid spacing is in the X direction and the Y direction. It is arranged in a somewhat regular manner (hereinafter referred to as "quasi-regular") with reference to an irregular rectangular lattice (see FIG. 5) in which Wx and Wy are fluctuated. Here, "random" means that there is no substantial regularity in the arrangement of microlenses in any region of the microlens array. However, even if there is some regularity in the arrangement of the microlenses in the minute region, the one in which the arrangement of the microlenses does not have regularity in the entire arbitrary region is included in "irregularity".

In the present embodiment, the plurality of microlenses 21 are arranged semi-regularly with reference to a rectangular grid having irregularities. On top of that, the surface shape and the planar shape of the microlens 21 are randomly changed. As shown in FIGS. 2 and 4, the planar shape (outer shape) of the microlens 21 has a shape close to a substantially rectangular shape as a whole, but has a perfect rectangular shape (square shape or rectangular shape) corresponding to a rectangular grid. )is not it. Specifically, the planar shape of the microlens 21 has a shape close to a substantially polygon having four or more vertices, such as a substantially quadrangle, a substantially pentagon, and a substantially hexagon. The surface shape (three-dimensional curved surface shape) and the planar shape (shape projected onto the XY plane of the base material 10) of the plurality of microlenses 21 are different from each other. In this way, the reason why each microlens 21 has a shape that is irregularly collapsed from a rectangular shape is that the radius of curvature Rx, Ry, the aperture diameter Dx, Dy, and the plane position of the lens apex of each microlens 21. This is because the height position and the like fluctuate randomly within a range of a predetermined fluctuation rate. The details of the semi-regular arrangement method of the microlens 21 based on the rectangular grid according to the present embodiment will be described later (see FIGS. 5 to 7).

As described above, in the present embodiment, the radii of curvature Rx and Ry and the aperture diameters Dx and Dy of each microlens 21 vary randomly and have variations. The aperture diameters Dx and Dy of the microlens 21 correspond to the lens diameter of a single lens. The phase distribution of the optical aperture of each microlens 21 differs depending on the orientation. A plurality of microlenses 21 are continuously arranged on the surface of the base material 10 so as to overlap each other, and the radii of curvature Rx and Ry and the aperture diameters Dx and Dy (lens diameter) of the respective microlenses 21 vary. As a result, the shapes (surface shape and planar shape) of the plurality of microlenses 21 are not the same as each other. Therefore, the plurality of microlenses 21 come to have various shapes as shown in FIG. 2, and many of them do not have symmetry.

As a result, as shown in FIG. 3, while the curvature radius of the microlens 21A is R _A, the curvature radius of the microlens 21B adjacent to the microlenses 21A is a state that it is R _{B (≠} R _A) resulting Will be. The radius of curvature R _A of the microlenses 21 which are adjacent to each _other, if the R _B are different from each other, the boundary between the microlenses 21 which are adjacent to each other is not composed of only straight lines, configured to include a curve in at least a part Will be.

Specifically, as shown in FIG. 4, when the microlens 21 is viewed in a plan view from the Z direction perpendicular to the surface of the base material 10, the outline of the planar shape of the microlens 21 (the microlens 21 and the microlens 21). The boundary line between the plurality of adjacent microlenses 21) includes a plurality of curves having different curvatures from each other and a straight line. When the boundary line of the microlens 21 includes a plurality of curves having different curvatures from each other, the regularity of the boundary between the microlenses 21 is further broken, so that the diffraction component of the diffused light can be further reduced.

<4. How to place the microlens>
Next, the method of arranging the microlens 21 according to the present embodiment will be described in detail with reference to FIGS. 5 to 7. FIG. 5 is a plan view schematically showing the arrangement of the irregular rectangular lattice-shaped microlenses 21 according to the present embodiment. FIG. 6 is an explanatory view showing an example in which the surface shape of the microlens 21 is changed from the state of FIG. FIG. 7 is an explanatory view showing an example in which the plane position of the apex 22 of the microlens 21 is eccentric from the state of FIG.

The microlens array 20 in which a plurality of microlenses 21 having the above-mentioned characteristics are arranged can be realized by the arrangement method according to the present embodiment described below.

First, as shown in FIG. 5, a reference state (hereinafter, also referred to as "initial arrangement state") in which a plurality of microlenses 21 having a reference shape are arranged semi-regularly in a rectangular grid pattern is set for the time being. Next, from such an initial arrangement state, as shown in FIGS. 6 and 7, the shape of the microlens 21 (that is, the radius of curvature Rx, Ry, the aperture diameter Dx, Dy, etc.) and the position of the apex 22 of the microlens 21 are determined. It is changed to a randomly changed state (hereinafter, also referred to as "variable array state"). Hereinafter, such a method of arranging the microlens 21 will be referred to as a "reference arrangement method".

In this reference arrangement method, randomness is given to the shape and arrangement of the microlenses 21 after passing through a semi-regular arrangement of the microlenses 21 (see FIG. 5) (see FIGS. 6 and 7). Therefore, if the microlens array 20 (see FIGS. 2 and 7) in the final variable array state is viewed macroscopically to some extent, the semi-regular initial array state (see FIG. 5) can be estimated to some extent. The arrangement of the microlens 21 is as follows. The reference placement method will be described in detail below.

(1) Initial arrangement state of the microlens 21 based on an irregular rectangular lattice (FIG. 5)
In the reference arrangement method according to the present embodiment, first, the initial arrangement state that serves as the reference for the arrangement of the microlens 21 is set. Specifically, as shown in FIG. 5, in the initial arrangement state, a plurality of microlenses 21 are somewhat regular (quasi-regular) on the XY plane of the reference plane with reference to a rectangular grid having irregularities. ).

The rectangular grid according to the present embodiment may be a rectangular grid or a square grid. As shown in FIG. 5, the rectangular grid includes a plurality of grid lines 32 extending in the first direction (X direction) and a plurality of grid lines 31 extending in the second direction (Y direction). The first direction (X direction) and the second direction (Y direction) are orthogonal to each other. In such a rectangular grid, the grid spacing Wx in the X direction is the spacing between a plurality of grid lines 31 extending in the second direction (Y direction). The grid spacing Wy in the Y direction is the spacing between the plurality of grid lines 32 extending in the first direction (X direction).

Here, with the irregular rectangular grid, as shown in FIG. 5, the grid spacing Wx in the X direction fluctuates randomly and differs from each other, and the grid spacing Wy in the Y direction fluctuates randomly. It is a rectangular grid that is different from each other. In the example of the rectangular grid of FIG. 5, the three grid spacings Wx ₁ , Wx ₂ , and Wx ₃ in the X direction are different from each other, and the three grid spacings Wy ₁ , Wy ₂ , and Wy _{3 in} the Y direction are also different from each other. The grid spacing Wx and the grid spacing Wy may fluctuate independently and randomly without any correlation with each other. As a result, for example, the grid spacings Wx ₁ , Wx ₂ , Wx ₃ , Wy ₁ , Wy ₂ , and Wy _{3 in} the X and Y directions may be different from each other.

For example, the method of randomly changing the grid spacing Wx and the grid spacing Wy is as follows. First, constant reference values Wx_k and Wy_k (hereinafter referred to as reference grid spacing Wx_k and Wy_k) that serve as a reference for fluctuations in the grid spacing Wx and Wy in the X and Y directions are set. Next, the reference grid spacing Wx_k and Wy_k are randomly changed within a predetermined volatility δWx and δWy [±%] to set the grid spacing Wx and Wy (Wx = Wx_k × (100 ± δWx [%]). ), Wy = Wy_k × (100 ± δWy [%])). This is repeated for the number of grids of the rectangular grid, and a plurality of grid spacings Wx ₁ , Wx ₂ , Wx ₃ , ..., Wy ₁ , Wy ₂ , Wy ₃ , ... Are set in the X and Y directions, respectively. To do.

Here, the volatility δWx and δWy are preferably in the range of ± 10% to ± 50%. When the volatility δWx and δWy are set to less than ± 10%, the fluctuations of the lattice spacing Wx and Wy become insufficient, and it becomes difficult to impart sufficient aperiodicity to the microlens array 20. The homogeneity of diffused light may decrease. On the other hand, if the volatility δWx and δWy are set to more than ± 50%, the fluctuation of the lattice spacing W becomes excessively large, and it may be difficult to continuously arrange a plurality of microlenses 21 on the XY plane without gaps. There is.

For example, when the volatility δWx and δWy are set to “± 10%”, the grid spacing Wx and Wy are within the range of “± 10%” or less based on the reference grid spacing Wx_k and Wy_k (that is, Wx_k and Wy_k). 90% or more and 110% or less), and the values are set to randomly deviate from the reference grid spacings Wx_k and Wy_k.

As described above, in the present embodiment, the plurality of lattice spacings Wx ₁ , Wx ₂ , Wx ₃ , ..., Wy ₁ , Wy ₂ , Wy ₃ , ... In the X and Y directions are different from each other. Randomly set the value. Then, using the grid spacing Wx ₁ , Wx ₂ , Wx ₃ , ..., Wy ₁ , Wy ₂ , Wy ₃ , ..., Irregular rectangular grids with different grid spacing Wx, Wy (Fig.) 5) is set.

Next, a plurality of microlenses 21 are arranged on the XY plane as shown in FIG. 5 with the irregular rectangular lattice as a reference. This state is the initial arrangement state that serves as a reference for the arrangement of the microlens 21. In the initial arrangement state, the planar shape of each microlens 21 is a rectangular shape corresponding to a rectangular grid, and the outline of the planar shape of the microlens 21 coincides with the

grid lines

31 and 32 in the X and Y directions. .. Further, the position of the apex 22 of each microlens 21 coincides with the center point 23 of each rectangular grid surrounded by the

grid lines

31 and 32. Further, in this initial arrangement state, the aperture diameters Dx and Dy of each microlens 21 in the X direction and the Y direction correspond to the lattice spacings Wx and Wy in the X direction and the Y direction, respectively. Here, since the lattice spacings Wx and Wy fluctuate to different values, the aperture diameters Dx and Dy also fluctuate to different values.

Further, the surface shape of each microlens 21 in the initial arrangement state is a shape obtained by cutting out a predetermined reference shape (for example, a reference shape having an aspherical shape) set in advance by a rectangular lattice corresponding to each microlens 21. ing. Here, since the lattice spacings Wx and Wy corresponding to each microlens 21 are different from each other, the aperture diameters Dx and Dy and the surface shape of the plurality of microlenses 21 are different from each other. That is, by arranging the plurality of microlenses 21 with reference to the irregular rectangular lattice, in the initial arrangement state, the plurality of microlenses so that the aperture diameters Dx, Dy and the surface shape of the microlenses 21 are different from each other. 21 can be arranged.

(2) First variable arrangement state of the microlens 21 in which the radius of curvature Rx and Ry are varied (FIG. 6).
After setting the initial arrangement state as described above, as shown in FIG. 6, the first variation in which the surface shape of the microlens 21 is varied by randomly varying the radii of curvature Rx and Ry of the microlens 21. Set the array state. FIG. 6 shows an example in which the radius of curvature Rx and Ry of the aspherical shape are changed when the surface shape of the microlens 21 is an aspherical shape having anisotropy in the X direction.

The radius of curvature R includes the radius of curvature Rx of the cross-sectional shape of the microlens 21 cut in the cross section in the X direction and the radius of curvature Ry of the cross-sectional shape of the microlens 21 cut in the cross section in the Y direction. When the surface shape of the microlens 21 is spherical, Rx and Ry have the same value. On the other hand, when the surface shape of the microlens 21 is an aspherical shape having anisotropy, Rx and Ry can have different values.

The method of randomly changing the radii of curvature Rx and Ry of the microlens 21 in the initial arrangement state is as follows, for example. First, constant reference values Rx_k and Ry_k (hereinafter referred to as reference curvature radii Rx_k and Ry_k) that serve as a reference for fluctuations in the radius of curvature Rx and Ry in the X and Y directions are set. Next, the reference curvature radii Rx_k and Ry_k are randomly changed within a range of predetermined volatility δRx and δRy [%] to set the curvature radii Rx and Ry (Rx = Rx_k × (100 ± δRx [%])). , Ry = Ry_k × (100 ± δRy [%])). This is repeated for the number of each microlens 21, and for each microlens 21, the radii of curvature Rx ₁₁ , Ry ₁₁ , Rx ₂₁ , Ry ₂₁ , ..., Rx _nm , and Ry _nm in the X and Y directions are set, respectively. Set. In addition, n is the number of microlenses 21 arranged in the X direction, and m is the number of microlenses 21 arranged in the Y direction.

Here, the volatility δRx and δRy are preferably in the range of ± 10% to ± 50%. When the volatility δRx and δRy are set to less than ± 10%, the fluctuations of the radius of curvature Rx and Ry become insufficient, and it becomes difficult to impart sufficient aperiodicity to the microlens array 20. The homogeneity of diffused light may decrease. On the other hand, when the volatility δRx and δRy are set to more than ± 50%, the fluctuations of the radius of curvature Rx and Ry become excessively large, and it becomes difficult to continuously arrange a plurality of microlenses 21 on the XY plane without gaps. There is a risk of becoming.

As described above, the radii of curvature Rx and Ry of each microlens 21 in the initial arrangement state are randomly changed (first variation arrangement state). As a result, as shown in FIG. 6, the radius of curvature Rx of the microlenses 21 arranged in the X direction in the X direction has different values from each other. Similarly, the radius of curvature Ry of the microlenses 21 arranged in the Y direction in the Y direction have different values. Specifically, the radius of curvature Rx randomly fluctuates with a volatility δRx within ± 10% to ± 50% with reference to the reference radius of curvature Rx_k. Further, the radius of curvature Ry randomly fluctuates at a volatility δRy within ± 10% to ± 50% with reference to the reference radius of curvature Ry_k.

In the first variable arrangement state, as shown in FIG. 6, the planar shape of each microlens 21 is deviated from the rectangular lattice, and the outline of the planar shape of the microlens 21 is a lattice in the X direction and the Y direction. It may not match the

lines

31 and 32. However, the positions of the vertices 22 of each microlens 21 coincide with the center point 23 of each rectangular grid. Further, in the first variable arrangement state, the aperture diameters Dx and Dy of each microlens 21 in the X direction and the Y direction deviate from the lattice spacing Wx and Wy in the X direction and the Y direction.

In this way, in the first variable arrangement state in which the radii of curvature Rx and Ry of the microlens 21 are randomly changed, the aperture diameters Dx and Dy and the surface shape of the microlens 21 are further different from each other than in the initial arrangement state. As described above, a plurality of microlenses 21 can be arranged.

(3) The second variable arrangement state of the microlens 21 in which the lens apex position is changed (FIG. 7).
After setting the first variation array state as described above, as shown in FIG. 7, the plane position of the apex 22 of the microlens 21 is randomly eccentric from the center point 23 of the rectangular lattice. Set the array state. Here, the eccentricity means that the plane position of the apex 22 of the microlens 21 is changed so as to deviate from the center point 23 of the rectangular lattice on the XY plane. The center point 23 of the rectangular grid is an intersection of two diagonal lines of the rectangular grid (see FIG. 4).

For example, the method of randomly eccentricizing the plane position of the apex 22 of the microlens 21 in the first variable arrangement state is as follows.

First, the eccentricity Ec of the plane position of the apex 22 of the microlens 21 (hereinafter, may be referred to as the lens apex position 22) is set. The eccentricity Ec is the amount of deviation (distance) of the lens apex position 22 from the center point 23 of the rectangular lattice. The eccentricity Ec is represented by the eccentricity Ecx in the X direction and the eccentricity Ecy in the Y direction. The eccentricity Ecx is the amount of deviation of the lens apex position 22 from the center point 23 of the rectangular lattice in the X direction, and the eccentricity Ecy is the amount of deviation of the lens apex position 22 from the center point 23 of the rectangular lattice in the Y direction. is there.

Next, the eccentricities δEcx and δEcy in the X and Y directions are set. The eccentricity δEcx in the X direction is the ratio (percentage) of the eccentricity Ecx to the lattice spacing Wx of the rectangular lattice. The eccentricity δEcy in the Y direction is the ratio (percentage) of the eccentricity Ecy to the lattice spacing Wy of the rectangular lattice. The eccentricity δEcx and δEcy are expressed by the following equations.
δEcx [%] = Ecx / Wx × 100
δEcy [%] = Ecy / Wy × 100

Next, the lens apex position is eccentric based on the eccentricity δEcx and δEcy set above. Specifically, the lens apex position 22 of each microlens 21 is randomly eccentric with eccentricity ratios δEcx and δEcy within ± 10% to ± 50%.

Here, the eccentricity δEcx and δEcy are preferably in the range of ± 10% to ± 50%. When the eccentricity ratios δEcx and δEcy are set to less than ± 10%, the eccentricity amounts Ecx and Ecy at the lens apex position 22 become insufficient, and it becomes difficult to impart sufficient aperiodicity to the microlens array 20. There is a risk that the homogeneity of the diffused light in the X and Y directions due to the array 20 will decrease. On the other hand, when the eccentricities δEcx and δEcy are set to more than ± 50%, the eccentricities Ecx and Ecy at the lens vertices become excessively large, and it is difficult to continuously arrange a plurality of microlenses 21 on the XY plane without gaps. There is a risk of becoming.

As described above, the plane position of the apex 22 of each microlens 21 in the first variable arrangement state is randomly changed from the center point 23 of the rectangular lattice (second variable arrangement state). As a result, as shown in FIG. 7, the plane positions of the vertices 22 of each microlens 21 are shifted in random directions on the XY plane by random eccentricities Ecx and Ecy.

As a result, as shown in FIGS. 4 and 7, in the second variable arrangement state, the planar shape of each microlens 21 corresponds to a rectangular lattice more than in the first variable arrangement state (see FIG. 6). The shape deviates from the rectangular shape. Further, in the second variable arrangement state, the aperture diameters Dx and Dy of each microlens 21 in the X and Y directions are further deviated from the lattice spacings Wx and Wy in the X and Y directions.

In this way, in the second variable arrangement state in which the plane positions of the vertices 22 of the microlens 21 are randomly eccentric, the surface shape, opening diameters Dx, and Dy of the microlens 21 are further higher than those in the first variable arrangement state. A plurality of microlenses 21 can be arranged so as to be different from each other.

Further, in the second variable arrangement state, the height positions of the vertices 22 of the plurality of microlenses 21 (positions in the thickness direction of the diffusion plate 1) are mutually variable. Specifically, as shown in FIG. 2, the height positions of the apex 22 (the deepest point of the concave lens) of the plurality of microlenses 21 arranged in the X direction are different from each other, and the plurality of microlenses arranged in the Y direction are arranged. The height positions of the apex 22 (the deepest point of the concave lens) of the microlens 21 are also different from each other. As a result, the randomness of the shapes and arrangements of the plurality of microlenses 21 can be further enhanced, and sufficient aperiodicity can be imparted to the microlens array 20.

As described above, according to the method of arranging the microlenses 21 according to the present embodiment, first, a plurality of microlenses 21 are quasi-regularly based on an irregular rectangular grid having different grid spacings Wx and Wy. (Initial arrangement state: Fig. 5). As a result, the microlenses 21 are arranged semi-regularly in the XY plane so that the outer line of the planar shape of each microlens 21 is along the

grid lines

31 and 32 of the irregular rectangular lattice.

After that, the radius of curvature Rx, Ry, the surface shape, and the lens apex position 22 of the plurality of arranged microlenses 21 are randomly changed (first and second variable arrangement states: FIGS. 6 and 7). As a result, the surface shape (three-dimensional shape), aperture shape (planar shape), aperture diameters Dx, Dy, arrangement, and the like of the semi-regularly arranged microlenses 21 can be randomly dispersed. Therefore, it is possible to realize a three-dimensional surface structure of the microlens array 20 with high randomness while realizing a semi-regular arrangement of the microlens 21.

Therefore, according to the microlens array 20 according to the present embodiment, it is possible to suitably control the phase superposition state of the light emitted from each microlens 21. Therefore, interference of diffused light from each microlens 21 and diffraction due to the periodic structure of the microlens arrangement can be suitably suppressed. Therefore, the unevenness of the intensity distribution of the diffused light can be reduced, and the homogeneity of the light distribution in the X and Y directions orthogonal to each other can be improved. Further, it is possible to control the anisotropy of the light distribution in the X and Y directions and the cutoff property of the intensity distribution of the diffused light.

Note that the cutoff property means that the diffused light from the microlens array 20 has a so-called top hat type diffusion characteristic. The top hat type diffusion characteristic is the homogeneity of the energy distribution within the angular component in a certain region with respect to collimated light in the visible light region and telecentric light having a collimating main ray and a constant aperture. Is very high, and refers to an optical function in which the energy can be rapidly reduced when a certain region of this angular component is exceeded. By realizing such a top hat type diffusion characteristic, the luminance distribution of the diffused light of the light incident on the microlens array 20 becomes substantially uniform within a predetermined diffusion angle range, and the diffused light is within a predetermined diffusion angle range. A state in which the brightness value of is within the range of, for example, ± 20% with respect to the average value of the peak level is realized.

According to the microlens array 20 according to the present embodiment, a plurality of microlenses 21 are arranged in a rectangular grid by the above arrangement method, and the radius of curvature Rx, Ry, lens apex position 22 and the like of each microlens 21 are appropriately set. It is controlled or an aspherical shape is introduced into the surface shape of the microlens 21. As a result, the desired diffusion characteristics of the microlens array 20 can be realized, so that the top hat type diffusion characteristics can be more reliably realized.

Further, according to the present embodiment, a plurality of microlenses 21 are arranged semi-regularly on the XY plane with reference to an irregular rectangular lattice having different lattice intervals Wx and Wy (initial arrangement state). ), The radius of curvature Rx, Ry, and the lens apex position 22 are changed (first and second variable arrangement states). As a result, a plurality of microlenses 21 can be continuously arranged on the surface of the diffuser plate 1 without gaps while ensuring the randomness of the surface shape of each microlens 21. Therefore, since the flat portion can be prevented from existing at the boundary portion of the adjacent microlens 21 as much as possible, the component (0th-order transmitted light component) of the incident light that is transmitted as it is without being scattered on the surface of the diffuser plate is suppressed. It becomes possible. As a result, the homogeneity of the light distribution in the X and Y directions orthogonal to each other and the diffusion performance can be further improved.

<5. Example of aspherical shape of microlens>
Next, an example in which the surface shape of the microlens 21 according to the present embodiment is an aspherical shape having anisotropy will be described.

In the present embodiment, a plurality of microlenses 21 having anisotropy in a common direction may be arranged in a rectangular grid pattern over the entire microlens array 20. The anisotropy microlens 21 is, for example, a microlens having a planar shape in which the length in one direction (longitudinal direction) is longer than the length in the other direction (short direction) orthogonal to the one direction. A plurality of anisotropic microlenses 21 are arranged on the XY plane of the base material 10 so that the longitudinal directions of the microlenses 21 face the same direction.

This makes it possible to control the anisotropic shape of the diffused light on the projection surface. For example, in the diffuser plate 1, the diffusion width of light in the longitudinal direction of the microlens 21 is reduced, and the diffusion width of light in the lateral direction is increased. Thereby, the anisotropic shape of the light diffused by the diffuser plate 1 can be controlled according to the shape of the projection surface.

In the following, the case where the surface shape (three-dimensional three-dimensional shape) of each microlens 21 is an anisotropic aspherical shape will be described in more detail with reference to FIGS. 8 to 11. The microlens 21 has an aspherical shape having anisotropy extending in a predetermined direction. As the aspherical shape, for example, a first aspherical shape example (anamorphic shape) and a second aspherical shape example (torus shape) described below can be used.

(1) First aspherical shape example (anamorphic shape)
First, an example of the aspherical shape (anamorphic shape) of the microlens 21 will be described with reference to FIGS. 8 to 11. FIG. 8 is an explanatory view showing a planar shape of the anamorphic-shaped microlens 21. FIG. 9 is a perspective view showing the three-dimensional shape of the anamorphic-shaped microlens 21. FIG. 10 is a perspective view showing a curved surface having an anamorphic shape.

The microlens 21 shown in FIGS. 8 and 9 is a so-called anamorphic lens, and its surface shape is an aspherical shape including a curved surface of the anamorphic shape. As shown in FIG. 8, the planar shape of the microlens 21 is an anisotropy elliptical shape. The major axis of the elliptical shape in the Y-axis direction is Dy, and the minor axis in the X-axis direction is Dx. These Dx and Dy correspond to the aperture diameters of the microlens 21 in the X direction and the Y direction. As shown in FIG. 9, the three-dimensional shape of the microlens 21 is an aspherical curved surface having predetermined radius of curvature Rx and Ry in each of the major axis direction and the minor axis direction of the elliptical shape. The microlens 21 has an aspherical shape having anisotropy in the Y-axis direction.

Here, a method of setting the surface shape of the anamorphic microlens 21 will be described with reference to FIG. 10 and the following mathematical formula (1). FIG. 10 is a perspective view showing an anamorphic curved surface (aspherical surface) represented by the following mathematical formula (1). The following formula (1) is an example of a formula representing a curved surface (aspherical surface) having an anamorphic shape.

In addition, in Equation 1, each parameter is as follows.
Cx = 1 / Rx
Cy = 1 / Ry
Rx: Radius of curvature in the X direction Ry: Radius of curvature in the Y direction Kx: Conic coefficient in the X direction Ky: Conic coefficient in the Y direction A _x4 , A _x6 : 4th and 6th aspherical coefficients in the X direction A _y4 , A _y6 : 4th and 6th aspherical coefficients in the Y direction

As shown in FIG. 10, from the anamorphic curved surface defined by the above mathematical formula (1), the minor axis of the elliptical shape on the XY plane in the X direction is Dx, and the major axis in the Y direction is Dy. , Cut out a curved surface. A part of the curved surface shape cut out is set to the curved surface shape (anamorphic shape) of the microlens 21. Here, the elliptical major axis Dy, the minor axis Dx, the radius of curvature Ry in the Y direction (major axis direction), and the radius of curvature Rx in the X direction (minor axis direction) are set to a predetermined fluctuation rate δ for each microlens 21. Randomly fluctuate within the range of to make it vary. Thereby, the surface shapes of a plurality of microlenses 21 having different anamorphic shapes can be set.

(2) Second aspherical shape example (torus shape)
Next, another example (torus shape) of the aspherical shape of the microlens 21 will be described with reference to FIGS. 11 to 13. FIG. 11 is an explanatory view showing a planar shape of the torus-shaped microlens 21. FIG. 12 is a perspective view showing the three-dimensional shape of the torus-shaped microlens 21. FIG. 13 is a perspective view showing a torus-shaped curved surface.

As shown in FIGS. 11 to 13, the surface shape of the microlens 21 according to the second aspherical shape example is an aspherical shape including a part of the curved surface of the torus shape. A torus is a surface of revolution obtained by rotating a circle. Specifically, as shown in FIG. 13, the small circle (radius: r) is centered on the rotation axis (X-axis) arranged outside the small circle (radius: r) along the circumference of the large circle (radius: R). By rotating the circle, a so-called donut-shaped torus is obtained. The curved surface shape of the surface (torus surface) of this annular body is a torus shape. By cutting out the outer portion of the torus shape, the three-dimensional shape of the torus-shaped microlens 21 as shown in FIG. 12 can be obtained.

As shown in FIG. 11, the planar shape of the torus-shaped microlens 21 is an elliptical shape having anisotropy. The major axis of the elliptical shape in the Y-axis direction is R, and the minor axis in the X-axis direction is r. These r and R correspond to the aperture diameters Dx and Dy of the microlens 21 in the X and Y directions. As shown in FIG. 12, the three-dimensional shape of the microlens 21 is an aspherical curved surface having predetermined radius of curvature R and r in each of the major axis direction and the minor axis direction of the elliptical shape. The microlens 21 has an aspherical shape having anisotropy in the Y-axis direction.

Here, a method of setting the surface shape of the torus-shaped microlens 21 will be described with reference to FIG. 13 and the following mathematical formula (2). FIG. 13 is a perspective view showing an aspherical curved surface represented by the following mathematical formula (2). In Equation 2, R is the radius of the great circle and r is the radius of the small circle.

As shown in FIG. 13, from the torus-shaped curved surface defined by the above mathematical formula (2), the curved surface is such that the minor axis of the elliptical shape on the XY plane in the X direction is r and the major axis in the Y direction is R. Cut out. A part of the curved surface shape cut out is set to the curved surface shape (torus shape) of the microlens 21. Here, the elliptical major axis Dy, the minor axis Dx, the radius of curvature R in the Y direction (major axis direction) (corresponding to the radius of curvature Ry of the lens), and the radius of curvature r in the X direction (minor axis direction) (of the lens). The radius of curvature Rx) is randomly varied within a predetermined fluctuation rate δ for each microlens 21 to be dispersed. Thereby, the surface shapes of a plurality of microlenses 21 having different torus shapes can be set.

As the surface shape (aspherical shape having anisotropy) of the microlens 21 according to the present embodiment, in addition to the examples of the first and second aspherical shapes, for example, an aspherical surface cut out from an elliptical sphere. Shapes can be used.

<6. How to design a microlens>
Next, a method of designing a microlens according to the present embodiment will be described with reference to FIGS. 14 to 18. FIG. 14 is a flowchart showing a method of designing a microlens according to the present embodiment.

(S10) Setting of grid parameters As shown in FIG. 14, first, various parameters (grid parameters) relating to a rectangular grid (grid) as a reference for arranging a plurality of microlenses 21 on an XY plane are set (S10). .. The grid parameters include, for example, the following parameters.
Wx_k [μm]: Reference value of grid spacing Wx in the X direction (grid size in the X direction)
Wy_k [μm]: Reference value of grid spacing Wy in the Y direction (grid size in the Y direction)
δWx [±%]: Fluctuation rate of grid spacing Wx in the X direction (allowable fluctuation range of Wx in the X direction)
δWy [±%]: Fluctuation rate of grid spacing Wy in the Y direction (allowable fluctuation range of Wy in the Y direction)
δEcx [±%]: Eccentricity of the lens apex position in the X direction (eccentric range in the X direction)
δEcy [±%]: Eccentricity of the lens apex position in the Y direction (eccentric range in the Y direction)

Specifically, the setting value of the grid parameter can be set to the following numerical values, for example.
Wx_k: 120 μm
Wy_k: 90 μm
δWx: ± 20%
δWy: ± 10%
δEcx: ± 10%
δEcy: ± 10%

(S12) Generation of grid Next, a plurality of rectangular grids arranged in the X and Y directions are generated based on the grid parameters set in S10 (S12). FIG. 15 is an explanatory diagram showing a rectangular grid generated in this step S12. As shown in FIG. 15, an irregular rectangular grid in which the grid spacing Wx and Wy in the X and Y directions fluctuate randomly is set. The grid spacing Wx in the X direction is the spacing between grid lines 31 adjacent to the X direction. The grid spacing Wy in the Y direction is the spacing between grid lines 32 adjacent to the Y direction.

The grid spacing Wx in the X direction is set to a value obtained by randomly varying the reference grid spacing Wx_k [μm] at the volatility δWx [±%]. Similarly, the grid spacing Wy in the Y direction is set to a value obtained by randomly varying the reference grid spacing Wy_k [μm] at a volatility δWy [±%]. For example, when the set value of the grid parameter is the numerical value of the above specific example (Wx_k = 120 μm, δWx = ± 20%), the grid spacing Wx is 96 μm to 144 μm (80% of 120 μm) centered on 120 μm (Wx_k). It is set to a random value within the range of 120%). The grid spacing Wy is also set in the same manner. As a result, as shown in FIG. 15, the lattice spacings Wx and Wy of the plurality of rectangular lattices arranged in the X and Y directions are set to different values.

(S14) Eccentric processing of the center of the grid After that, an eccentric processing of randomly changing the position of the center point (hereinafter, referred to as “grid center”) of each rectangular grid is executed (S14). FIG. 16 is an explanatory diagram showing a rectangular grid whose grid center is eccentric in this step S14.

As shown in FIG. 16, the grid center before the eccentric processing is arranged at the coordinate position of the intersection of the two diagonal lines of each rectangular grid (the center point 23 of the rectangular grid described above). By the eccentric processing, the center of the grid moves to the X and Y coordinate positions corresponding to the eccentricities Ecx and Ecy randomly calculated using the eccentricity δEcx and the eccentricity δEcy. For example, when the set value of the grid parameter is the numerical value of the above specific example (δEcx = ± 10%, δEcy = ± 10%), the eccentricity Ecx and Ecy are 90% to 110% of the lattice spacing Wx and Wy. Set to a value within the range. Then, the center of the grid is moved in the X and Y directions by a distance corresponding to the eccentricities Ecx and Ecy. The position of the center of the grid after movement corresponds to the plane position (lens apex position 22) of the apex 22 of the microlens 21 described above. By repeating this eccentric processing for each rectangular lattice, the grid center of each rectangular lattice is eccentric to random positions within the range of the eccentricity δEcx and the eccentricity δEcy in each rectangular lattice.

(S16 to S24) Generation of Microlenses Next, the microlenses 21 corresponding to each rectangular grid are arranged based on the rectangular grid generated in S12 and the grid center eccentric in S14. Specifically, first, the basic shape of the surface shape (lens surface) of the microlens 21 is selected (S16). Next, parameters (lens parameters) related to the selected basic shape are set (S18, S20). After that, the shape of the microlens 21 in each rectangular lattice is determined based on the set lens parameters, and the Z coordinate position representing the shape of the microlens 21 is calculated to generate the microlens 21 (S22, S24). ..

Specifically, in the present embodiment, for example, an anamorphic shape or a torus shape is selected as the basic shape of the microlens 21 (hereinafter referred to as a lens shape) (S16). However, the present invention is not limited to this, and other types of aspherical shapes or spherical shapes may be selected as the lens shape.

When the anamorphic shape is selected in S16, various lens parameters related to the anamorphic shape are set (S18). The anamorphic shape lens parameters include, for example, the following parameters.
Rx_k [μm]: Reference value of radius of curvature Rx in the X direction Ry_k [μm]: Reference value of radius of curvature Ry in the Y direction δRx [±%]: Fluctuation rate of radius of curvature Rx in the X direction (allowable for Rx in the X direction) Fluctuation range)
δRy [±%]: Volatility of radius of curvature Ry in the Y direction (allowable fluctuation range of Ry in the Y direction)

Specifically, the set value of the lens parameter of the anamorphic shape can be set to the following numerical values, for example.
Rx_k: 240 μm
Ry_k: 200 μm
δRx: ± 10%
δRy: ± 10%

Next, the surface shape of the anamorphic microlens 21 is generated based on the lens parameters set in S18 (S22). Specifically, the surface shape of each microlens 21 is determined based on the lens parameters, and each microlens 21 is arranged on each rectangular lattice. That is, the Z coordinate value of each point on the anamorphic lens surface is calculated.

FIG. 17 is an explanatory diagram showing a plurality of microlenses 21 generated in this step S22. As shown in FIG. 17, each microlens 21 is arranged on each rectangular grid so that the lens apex position 22 coincides with the grid center position eccentric in S14. Further, the radius of curvature Rx and Ry of each microlens 21 in the X and Y directions fluctuate randomly. Therefore, a plurality of microlenses 21 having different surface shapes (anamorphic shapes) are arranged so as to overlap each other on the XY plane.

The radius of curvature Rx in the X direction is set to a value obtained by randomly varying the reference radius of curvature Rx_k [μm] at the volatility δRx [±%]. Similarly, the radius of curvature Ry in the Y direction is set to a value obtained by randomly varying the reference radius of curvature Ry_k [μm] with a volatility δRy [±%]. For example, when the set value of the lens parameter is the numerical value of the above specific example (Rx_k = 240 μm, δRx = ± 10%), the radius of curvature Rx is 216 μm to 264 μm (90% of 240 μm) centered on 240 μm (Rx_k). It is set to a random value within the range of 110%). The radius of curvature Ry is also set in the same manner. As a result, as shown in FIG. 17, the surface shapes (anamorphic shapes) of the plurality of microlenses 21 arranged in the X and Y directions are different from each other.

On the other hand, when the torus shape is selected in S16, various lens parameters related to the torus shape are set (S20). The torus-shaped lens parameters include, for example, the following parameters. The small circle radius r and the great circle radius R are radii of curvature that define the torus shape shown in FIGS. 11 to 13.
r_k [μm]: Reference value of small circle radius (radius of curvature Rx in X direction) R_k [μm]: Reference value of great circle radius (radius of curvature Ry in Y direction) δRx [±%]: Small circle radius (X direction) Rate of fluctuation of radius of curvature Rx) (allowable fluctuation range of r in the X direction)
δRy [±%]: Volatility of great circle radius (radius of curvature Ry in Y direction) (allowable fluctuation range of R in Y direction)

Specifically, the set value of the lens parameter of the torus shape can be set to the following numerical values, for example.
Rx_k: 240 μm
Ry_k: 200 μm
δRx: ± 10%
δRy: ± 10%

Next, the surface shape of the torus-shaped microlens 21 is generated based on the lens parameters set in S20 (S24). Specifically, the surface shape of each microlens 21 is determined based on the lens parameters, and each microlens 21 is arranged on each rectangular lattice. That is, the Z coordinate value of each point on the torus-shaped lens surface is calculated. Since the torus-shaped lens generation process in step S24 is the same as the anamorphic-shaped lens generation process in S22, detailed description thereof will be omitted.

(S26) Output of lens pattern After that, a lens pattern representing the shape and arrangement of the microlens 21 generated in S20 or S24 is output (S26). For example, a file of XYZ coordinate values representing the lens pattern and an image file expressing the Z coordinate values of the lens pattern in shade gradation are output.

FIG. 18 is an image showing a lens pattern designed by the design method according to the present embodiment. As shown in FIG. 18, a plurality of microlenses 21 are arranged in an irregular rectangular lattice pattern on the XY plane. The lens apex position 22 of each microlens 21 is randomly eccentric, and the radii of curvature Rx and Ry of each microlens 21 also randomly fluctuate.

Therefore, it can be seen that the plurality of microlenses 21 have different aspherical shapes (for example, anamorphic shape or torus shape). Further, the plurality of microlenses 21 have different planar shapes from each other. The planar shape of each microlens 21 generally has a substantially rectangular shape along the rectangular lattice, but has a shape that varies from one to another. Of the boundary lines between the microlenses 21, the four side portions are generally composed of straight lines, but the four corner portions are composed of curved lines.

Further, the plurality of microlenses 21 are arranged so as to overlap each other without a gap, and there is no flat portion at the boundary portion between the microlenses 21 adjacent to each other.

As described above, according to the method for designing the microlens 21 according to the present embodiment, a plurality of microlenses 21 are arranged semi-regularly with reference to the above-mentioned irregular rectangular lattice, and each of the microlenses 21 is arranged. The variable elements (lattice spacing Wx, Wy, radius of curvature Rx, Ry, lens apex position 22, etc.) are randomly changed. As a result, it is possible to impart different diffusion characteristics to each of the microlenses 21 while continuously arranging the plurality of microlens arrays 20 on the XY plane without any gaps. The microlens array 20 having such a configuration has a variety of highly homogeneous light distribution controllability, with small macro light amount fluctuations depending on the lens surface structure and light amount changes due to diffracted light.

<7. Manufacturing method of micro lens>
Next, a method for manufacturing the diffuser plate 1 according to the present embodiment will be described with reference to FIG. FIG. 19 is a flowchart showing a manufacturing method of the diffusion plate 1 according to the present embodiment.

As shown in FIG. 19, in the method for manufacturing the diffusion plate 1 according to the present embodiment, first, the base material (the base material of the master master or the base material 10 of the diffusion plate 1) is washed (step S101). The base material may be, for example, a roll-shaped base material such as a glass roll, or a flat plate-shaped base material such as a glass wafer or a silicon wafer.

Next, a resist is formed on the surface of the base material after cleaning (step S103). For example, a resist layer can be formed by a resist using a metal oxide. Specifically, a resist layer can be formed on a roll-shaped substrate by spray-coating or dipping the resist. On the other hand, a resist layer can be formed on a flat substrate by applying various coating treatments to the resist. As the resist, a positive type photoreactive resist may be used, or a negative type photoreactive resist may be used. Further, a coupling agent may be used in order to improve the adhesion between the base material and the resist.

Further, the resist layer is exposed using a pattern corresponding to the shape of the microlens array 20 (step S105). Such an exposure process is a known exposure method such as exposure using a gray scale mask, multiple exposure by superimposing a plurality of gray scale masks, or laser exposure using a picosecond pulse laser, a femtosecond pulse laser, or the like. May be applied as appropriate.

After that, the exposed resist layer is developed (S107). By such a developing process, a pattern is formed on the resist layer. The developing process can be executed by using an appropriate developer depending on the material of the resist layer. For example, when the resist layer is formed of a resist using a metal oxide, the resist layer can be alkaline-developed by using an inorganic or organic alkaline solution.

Next, by sputtering or etching using the developed resist layer (S109), a master master with the shape of the microlens array 20 formed on the surface is completed (S111). Specifically, a glass master can be manufactured by glass-etching a glass base material using a resist layer on which a pattern is formed as a mask. Alternatively, a metal master can be manufactured by performing Ni sputtering or nickel plating (NED treatment) on the resist layer on which the pattern is formed to form a nickel layer on which the pattern is transferred, and then peeling off the base material. .. For example, a metal master master is manufactured by forming a nickel layer to which a resist pattern is transferred by Ni sputtering having a film thickness of about 50 nm or nickel plating having a film thickness of 100 μm to 200 μm (for example, a Ni bath with sulfamic acid). can do.

Further, by transferring (imprinting) a pattern on a resin film or the like using the master master (for example, glass master master, metal master master) completed in S111, an inverted shape of the microlens array 20 is formed on the surface. The soft mold is created (S113).

Then, using a soft mold, the pattern of the microlens array 20 is transferred to a glass substrate, a film substrate, or the like (S115), and a protective film, an antireflection film, or the like is further formed as necessary. (S117), the diffuser plate 1 according to the present embodiment is manufactured.

In the above description, an example in which a soft mold is manufactured (S113) using the master master (S111) and then the diffusion plate 1 is manufactured (S115) by transfer using the soft mold has been described. However, the present invention is not limited to this, and a master master (for example, an inorganic glass master) in which the inverted shape of the microlens array 20 is formed may be manufactured, and the diffusion plate 1 may be manufactured by imprinting using the master master. .. For example, an acrylic photo-curing resin is applied to a base material made of PET (PolyEthylene Terephthalate) or PC (PolyCarbonate), the pattern of the master master is transferred to the applied acrylic photo-curing resin, and the acrylic photo-curing resin is UV. By curing, the diffuser plate 1 can be manufactured.

On the other hand, when the diffusion plate 1 is manufactured by directly processing the glass base material itself, the base material 10 is dried using a known compound such as _{CF 4 following the development treatment in step S107.} The diffusion plate 1 according to the present embodiment is manufactured by performing an etching process (S119) and then forming a protective film, an antireflection film, or the like as needed (S121).

The manufacturing method shown in FIG. 19 is merely an example, and the manufacturing method of the diffusion plate is not limited to the above example.

<8. Application example of diffuser plate 1>
Next, an application example of the diffusion plate 1 according to the present embodiment will be described.

The diffuser plate 1 as described above can be appropriately mounted on a device that needs to diffuse light in order to realize its function. Examples of such a device include display devices such as various displays (for example, LEDs and organic EL displays), projection devices such as projectors, and various lighting devices.

For example, the diffuser plate 1 can be applied to a backlight of a liquid crystal display device, a diffuser plate integrated lens, and the like, and can also be applied to an application of optical shaping. The diffuser plate 1 can also be applied to a transmission screen, a Fresnel lens, a reflection screen, and the like of a projection device. Further, the diffuser plate 1 can be applied to various lighting devices used for spot lighting, base lighting and the like, various special lightings, various screens such as an intermediate screen and a final screen, and the like. Further, the diffuser plate 1 can also be applied to applications such as diffusion control of light source light in an optical device, such as light distribution control of an LED light source device, light distribution control of a laser light source device, and incident light distribution to various light valve systems. It can also be applied to control and the like.

The device to which the diffusion plate 1 is applied is not limited to the above application example, and can be applied to any known device as long as it is a device that utilizes light diffusion.

Next, the diffusion plate according to the embodiment of the present invention will be described. The following examples are merely examples for showing the effect and feasibility of the diffusion plate according to the present invention, and the present invention is not limited to the following examples.

While changing the surface structure of the microlens array, the diffuser plates according to Examples and Comparative Examples were manufactured by the manufacturing method described below.

Specifically, first, after cleaning the glass base material, a photoreactive resist was applied to one surface (main surface) of the glass base material with a resist thickness of 2 μm to 15 μm. As the photoreactive resist, for example, a positive photoreactive resist such as PMER-LA900 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) or AZ4620 (registered trademark) (manufactured by AZ Electronic Materials Co., Ltd.) was used.

Next, a pattern was drawn on the resist on the glass substrate with a laser drawing apparatus using a laser having a wavelength of 405 nm, and the resist layer was exposed. The resist layer may be exposed by performing mask exposure on the resist on the glass substrate with a stepper exposure apparatus using g-rays.

Subsequently, a pattern was formed on the resist by developing the resist layer. As the developing solution, for example, a tetramethylammonium hydroxide (TMAH) solution such as NMD-W (manufactured by Tokyo Ohka Kogyo Co., Ltd.) or PMER P7G (manufactured by Tokyo Ohka Kogyo Co., Ltd.) was used.

Next, a diffuser plate was manufactured by etching the glass substrate with the resist on which the pattern was formed. Specifically, a diffusion plate was manufactured by forming a resist pattern on a glass substrate by glass etching using Ar gas or CF _{4 gas.}

Table 1 shows the design conditions of the surface structure of the microlens array and the evaluation result of the homogeneity of the light distribution by the diffuser plate with respect to the diffuser plates according to the examples and comparative examples manufactured as described above.

In each of the examples and comparative examples shown in Table 1, the microlens array was designed by the design method shown in FIGS. 14 to 18 described above. At this time, various parameters such as grid parameters (Wx_k, Wy_k, δWx, δWy, δEcx, δEcy) and lens parameters (Rx_k, Ry_k, δRx, δRy) shown in Table 1 are appropriately changed to surface different microlenses. A shape pattern was generated. Then, a lens pattern representing the shape and arrangement of the microlenses according to each Example and Comparative Example was output. Using this lens pattern, the diffuser plates according to each Example and Comparative Example were manufactured by the above manufacturing method.

As shown in Table 1, in Examples 1 to 9, when designing the surface structure of the microlens array, the lattice spacing Wx and Wy of each microlens were randomly changed. On the other hand, in Comparative Examples 1 to 4, the grid spacing Wx and Wy were not changed, and the grid spacing of all the microlenses was set to a constant reference grid spacing Wx_k and Wy_k.

As shown in Table 1, the radius of curvature Rx and the radius of curvature Ry were set to fixed values or randomly fluctuating values for each Example and Comparative Example. When the volatility δRx, δRy = ± 0%, the radius of curvature Rx, Ry of each microlens is fixed without fluctuating, and when the volatility δRx, δRy = ± 10%, ± 15%, the volatility δRx, δRy = ± 10%, ± 15%. It means that the radius of curvature Rx and Ry were randomly changed within the range of the volatility δRx and δRy. Regarding the eccentricity of the lens apex position on the XY plane, when the eccentricity δEcx, δEcy = ± 0%, the lens apex position is not eccentric and the eccentricity δEcx, δEcy = ± 10%, ± 15%. In this case, it means that the lens apex positions are randomly eccentric within the range of the eccentricity ratios δEcx and δEcy.

The surface shape of the microlens was a spherical shape in Examples 1 to 4, 8 and 9 and Comparative Examples 1 to 3, and an aspherical shape (for example, an anamorphic shape) in Examples 5 to 7. The planar shape of the microlens array was square in Examples 1 to 7 and Comparative Examples 1 to 3, and rectangular (long in the X direction) in Examples 8 and 9 and Comparative Example 4.

The surface shape of the microlens array of the diffuser according to Examples 1 to 9 and Comparative Examples 1 to 4 manufactured as described above was observed with a laser microscope. Further, the light distribution pattern of each diffuser is simulated by Virtual-Lab (manufactured by LightTrans), and the light distribution characteristics of each diffuser are measured by the light distribution characteristic measuring instrument Mini-Diff (manufactured by Light Tech). Was measured. Further, in order to measure the light distribution characteristics of the diffuser plate, the intensity distribution of the diffused light was measured from the captured image of the laser light intensity (farfield pattern measurement described later).

Simulation results and actual measurement results such as the surface shape pattern of the microlens array of the diffuser plate according to Examples 1 to 9 and Comparative Examples 1 to 4, the light distribution characteristics of the diffused light, the brightness distribution, etc. are shown in FIGS. 20 to 33, respectively. Shown.

In FIGS. 20 to 33 (Examples 1 to 9 and Comparative Examples 1 to 4), (a) is an image (BMP) showing a pattern of the surface shape of the microlens array or a confocal laser scanning microscope image (magnification 50 times). Is. (B) is an image showing the simulation result of light distribution by electromagnetic field analysis. (C) is a graph (horizontal axis: coordinate position, vertical axis: brightness) showing a simulation result of the brightness distribution of diffused light. (D) shows the diffusion angle (full width at half maximum (FWHM). Screen Z = 100 mm) in the luminance distribution of the above (c).

Further, in FIG. 30 (Example 7), (e) is a graph showing the actual measurement result of measuring the far field pattern (FFP) of the diffused light of the laser light source using the actually manufactured diffuser plate (horizontal). Axis: Diffuse angle, Vertical axis: Brightness). (F) indicates the diffusion angle (full width at half maximum (FWHM)) in the X and Y directions in the FFP of the (e). (G) is an FFP image showing the actual measurement result of (e).

Further, in FIGS. 32 and 33 (Examples 8 and 9), (e) is a graph showing the simulation results of the light distribution characteristics of the diffused light in the X and Y directions (horizontal axis: diffusion angle, vertical axis: vertical axis: Luminance) and (f) indicate the diffusion angles (half-value full width (FWHM)) in the X and Y directions in the luminance distribution of (c) above.

The light distribution characteristics (light distribution homogeneity, etc.) of the diffuser plates according to Examples 1 to 9 and Comparative Examples 1 to 3 as described above are evaluated in three stages (evaluation A, B, C) according to the following evaluation criteria. Evaluated in. The evaluation results are shown in Table 1.
Evaluation A: The homogeneity of the diffused light in the X and Y directions was sufficiently high, and uneven brightness distribution along the rectangular grid was not observed. The brightness distribution of the diffused light is substantially uniform in a predetermined diffusion angle range, and the brightness value of the diffused light is within ± 20% of the average value of the peak levels within the predetermined diffusion angle range. It was.
Evaluation B: The homogeneity of the diffused light in the X and Y directions was high, and there was some unevenness in the luminance distribution along the rectangular grid, but no large unevenness was observed. The brightness distribution of the diffused light is substantially uniform in a predetermined diffusion angle range, and the brightness value of the diffused light is within ± 40% of the average value of the peak levels within the predetermined diffusion angle range. It was.
Evaluation C: The homogeneity of the diffused light in the X and Y directions was insufficient, and a large unevenness of the luminance distribution was observed along the rectangular grid. The brightness distribution of the diffused light varied within a predetermined diffusion angle range, and the brightness value of the diffused light did not fall within the range of ± 40% centered on the average value of the peak level within the predetermined diffusion angle range.

The evaluation results of Examples 1 to 9 and Comparative Examples 1 to 4 will be described below in comparison.

(1) Comparison between Examples 1 to 9 and Comparative Examples 1 to 4 (effect of irregularity of lattice spacing)
In Comparative Examples 1 to 4, as shown in FIGS. 20 to 22 and 31, the brightness increases and decreases periodically in the brightness distribution of the diffused light, and the brightness distribution of the diffused light has unevenness in a rectangular grid pattern. , The homogeneity of the diffused light distribution was insufficient. The reason for this is considered to be as follows.

In Comparative Examples 1 to 4, the rectangular grid that serves as a reference for the arrangement of the microlenses is a regular rectangular grid, and the grid spacing in the X and Y directions is fixed to constant values Wx_k and Wy_k (δWx, δWy =). ± 0%). For this reason, it is considered that the periodic structure of the regular rectangular grid-like microlens array causes diffraction of the diffused light from each microlens, resulting in uneven brightness distribution and reduced light distribution homogeneity. Be done.

In this regard, the homogeneity of the luminance distribution can be improved to some extent by eccentricizing the lens apex position as in Comparative Example 2 or randomly varying the curvature radii Rx and Ry as in Comparative Example 3. it can. However, when the lattice spacings Wx and Wy are constant as in Comparative Examples 1 to 4, the brightness unevenness due to diffraction due to the periodicity of the lattice spacing is homogeneous due to fluctuations in the lens apex position and the radius of curvature Rx and Ry. It is considered that the homogeneity of the light distribution was hindered because the effect of improving the light distribution was exceeded.

On the other hand, in Examples 1 to 9, although the brightness fluctuates in the brightness distribution of the diffused light, no periodic increase or decrease or periodic peak is observed, and the unevenness of the brightness distribution of the diffused light is sufficiently suppressed. The homogeneity of the diffused light distribution was good. The reason for this is considered to be as follows.

In Examples 1 to 9, the microlenses are arranged on the XY plane with reference to the rectangular grid. Here, the rectangular lattices of Examples 1 to 9 are not regular rectangular lattices as in the comparative example, but quasi-regular rectangular lattices having irregularity of lattice intervals Wx and Wy. That is, as shown in FIG. 15, the lattice spacings Wx and Wy of the rectangular lattices of Examples 1 to 9 randomly fluctuate so as to have different values from each other, and the volatility δWx and δWy are ± 10. % Or more. By arranging a plurality of microlenses with reference to a rectangular lattice having such irregularity, the aperture diameters Dx, Dy and the planar shape of the microlenses are randomly scattered, and the position of the boundary line between adjacent microlenses is also located. It can be shifted randomly.

As a result, as shown in FIGS. 2, 4, 18, 18 and the like, the outer line of the planar shape of the microlens (the boundary line between the microlenses) is a combination of a curve having an arbitrary radius of curvature and a straight line. It will be composed. As a result, the regularity of arrangement at the boundary between the microlenses is further broken, and the diffraction component can be further reduced. Therefore, it is possible to suppress the diffusion of diffused light between the plurality of microlenses and improve the homogeneity of the diffused light distribution of the entire microlens array.

From the above results, it can be seen that by using the diffuser plate of the present invention, unevenness of the luminance distribution can be suppressed in two directions (X and Y directions) orthogonal to each other, and the homogeneity of the light distribution can be sufficiently improved.

(2) Comparison between Example 1 and Examples 2 to 9 (effect of fluctuation of radius of curvature and eccentricity of lens apex)
As shown in Table 1, in Example 1, only the lattice spacing Wx and Wy are changed. On the other hand, in Examples 2 to 9, in addition to the lattice spacing Wx and Wy, the radius of curvature Rx and Ry are changed and the lens apex position is eccentric.

As a result, Examples 2 to 9 (Evaluation A) were able to suppress unevenness of the luminance distribution more effectively than Example 1 (Evaluation B), and were able to improve the homogeneity of the light distribution of diffused light. From this, it can be seen that from the viewpoint of improving the homogeneity of the light distribution, it is effective to change the radius of curvature Rx and Ry and to eccentric the lens apex position in addition to the lattice spacing Wx and Wy.

Further, in Examples 2, 3 and 5, the radius of curvature Rx and Ry are changed or the lens apex position is eccentric. On the other hand, in Examples 4, 6 to 9, the radius of curvature Rx and Ry are varied, and the lens apex position is also eccentric. As a result, as shown in (b) electromagnetic field analysis image and (c) luminance distribution graph of FIGS. 24 to 29, 32, and 33, in Examples 4, 6 to 9, unevenness of the luminance distribution is further suppressed. It was possible to further improve the homogeneity of the diffused light distribution. Therefore, from the viewpoint of improving the homogeneity of the light distribution, it is more effective to perform both the fluctuation of the radius of curvature Rx and Ry and the eccentricity of the lens apex position in addition to the lattice spacing Wx and Wy. Understand.

(3) Comparison between Examples 1 to 4 and Examples 5 to 7 (effect of aspherical lens shape)
As shown in Table 1, a spherical lens was used in Examples 1 to 4 as the basic shape of the microlens. On the other hand, in Examples 5 to 7, aspherical lenses (for example, anamorphic-shaped lenses shown in FIGS. 8 to 10) were used. For non-spherical lenses of Examples 5-7, by correcting the aspherical coefficients A ₄ of 4 order term of the right side of equation (1) which defines the curved surface of the anamorphic shape described above, defining the lens shape.

As a result, as shown in (b) electromagnetic field analysis images and (c) luminance distribution graphs of FIGS. 23 to 29, the aspherical lenses of Examples 5 to 7 are more than the spherical lenses of Examples 1 to 4. , The unevenness of the brightness distribution could be suppressed, and a finer light distribution homogeneity could be realized. From this, it can be seen that it is more effective to use an aspherical lens than a spherical lens from the viewpoint of improving the homogeneity of the light distribution. Further, if an aspherical lens having anisotropy is used, the anisotropy of the diffused light projected from the diffuser plate can be controlled. Therefore, it is possible to control the light distribution angle to have anisotropy between the X direction and the Y direction while achieving high homogeneity of the diffused light.

(4) Diffusion characteristics of Example 7 (excellent light distribution homogeneity and cutoff property)
As shown in Table 1, in Example 7, the reference curvature vertices Rx_k and Ry_k are set to relatively large values (150 μm), and the curvature vertices Rx and Ry are varied within ± 10% of Rx_k and Ry_k. Moreover, the lens apex position is eccentric within the range of eccentricity δEcx and δEcy = ± 10%.

Further, the surface shape of the microlens of Example 7 satisfies the following relational expressions (A) and (B) in terms of the ratio of the reference radius of curvature Rx_k, Ry_k [μm] and the reference lattice spacing Wx_k, Wy_k [μm]. It has an aspherical shape. In Example 7, (Rx_k / Wx_k) = (Ry_k / Wy_k) = (150/80) = 1.875.
Rx_k / Wx_k ≧ 1.85 ・・・ (A)
Ry_k / Wy_k ≧ 1.85 ・・・ (B)

The surface shape of the microlens according to the seventh embodiment is an aspherical shape having the above-mentioned anisotropy, and the lattice spacing Wx, Wy, radius of curvature Rx, and Ry are changed under the conditions shown in Table 1, and the lens. The apex positions are eccentric, and the reference radius of curvature Rx_k, Ry_k [μm] and the reference lattice spacing Wx_k, Wy_k [μm] are adjusted so as to satisfy the above relational expressions (A) and (B). Further, the diffusion angle (full width at half maximum (FWHM)) of the diffused light emitted from the diffuser plate is within the range of 20 ° or less. This makes it possible to more reliably realize the so-called top hat type diffusion characteristics.

As shown in the graph of the FFP measurement result of FIG. 30 (e), the diffusion characteristic of Example 7 realizes the top hat type diffusion characteristic. That is, the brightness distribution of the diffused light of the light incident on the microlens array becomes substantially uniform within a predetermined diffusion angle range (a range of 20 ° or less in the full width at half maximum. In the example of FIG. 10, −5 to + 5 °). Within the diffusion angle range, a state in which the brightness value of the diffused light is within ± 20% of the average value of the peak level is realized.

From the above results, by using the same diffusion plate as in Example 7, light is distributed in two directions (X and Y directions) orthogonal to each other within a range where the diffusion angle (half-value full width) is 20 ° or less. It can be seen that the anisotropy of the light distribution in the X and Y directions and the cutoff property of the intensity distribution of the diffused light can be appropriately controlled while sufficiently improving the homogeneity of the light.

(7) Comparison between Examples 8 and 9 and Comparative Example 4 (effect of rectangular aspherical lens shape)
As the diffuser plates according to Examples 8 and 9 and Comparative Example 4, a rectangular microlens array extending in the X direction was used. The reference grid spacing Wx_k = 50 μm and Wy_k = 40 μm, and the reference grid spacing Wx_k in the longitudinal direction (X direction) of the microlens array was set to be larger than the reference grid spacing Wy_k in the lateral direction (Y direction) (Wx_k>. Wy_k).

In the rectangular microlens array, in Comparative Example 4, the lattice spacing Wx and Wy were not changed. On the other hand, in Examples 8 and 9, the lattice spacing Wx and Wy are randomly changed within the range of ± 10% or ± 15%, and the radius of curvature Rx and Ry are randomly changed within the range of ± 10% or ± 15%. It was changed to. Further, in Examples 8 and 9, the lens apex position was also randomly eccentric within the range of ± 10% or ± 15%.

As a result, in Comparative Example 4, as shown in FIG. 31, the luminance distribution of the diffused light increases and decreases periodically, and the rectangular grid-like unevenness is remarkably generated, and the homogeneity of the diffused light distribution is insufficient. there were. On the other hand, in Examples 8 and 9, no periodic increase or decrease or peak was observed in the brightness distribution of the diffused light, the unevenness of the brightness distribution of the diffused light was sufficiently suppressed, and the homogeneity of the light distribution of the diffused light was good. Met.

From the above results, even when a rectangular microlens array is used as in Examples 8 and 9, the homogeneity of light distribution can be sufficiently improved in two directions (X and Y directions) orthogonal to each other. Understand.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical idea described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

1 Diffusing plate 3 Unit cell 10 Base material 20 Microlens array 21 Microlens 22 Microlens apex 23 Center point of rectangular lattice Wx, Wy lattice spacing Rx, Ry radius of curvature Ecx, Ecy Eccentricity Wx_k, Wy_k Reference lattice spacing Rx_k, Ry_k Reference radius of curvature δWx, δWy Fluctuation rate δRx, δRy Fluctuation rate δEcx, δEcy Eccentricity R Great circle radius r Small circle radius

Claims

It is a microlens array type diffuser
With the base material
A microlens array composed of a plurality of microlenses arranged on an XY plane on at least one surface of the base material with reference to a rectangular grid, and a microlens array.
With
The lattice spacing Wx in the X direction of the microlenses arranged in the X direction of the rectangular lattice is different from each other.
The lattice spacing Wy in the Y direction of the microlenses arranged in the Y direction of the rectangular lattice is different from each other.
Diffusing plates in which the surface shapes of the plurality of microlenses are different from each other.
The grid spacing Wx in the X direction randomly fluctuates at a volatility δWx within ± 10% to ± 50% with reference to the reference grid spacing Wx_k.
The diffusion plate according to claim 1, wherein the grid spacing Wy in the Y direction randomly fluctuates with a volatility δWy within ± 10% to ± 50% with reference to the reference grid spacing Wy_k.
The radius of curvature Rx of the microlenses arranged in the X direction in the X direction varies from each other.
The diffuser according to claim 1 or 2, wherein the radius of curvature Ry in the Y direction of the microlenses arranged in the Y direction varies from each other.
The radius of curvature Rx in the X direction randomly fluctuates at a volatility δRx within ± 10% to ± 50% with reference to the reference radius of curvature Rx_k.
The diffusion plate according to claim 3, wherein the radius of curvature Ry in the Y direction randomly fluctuates with a volatility δRy within ± 10% to ± 50% with reference to the reference radius of curvature Ry_k.
The grid spacing Wx in the X direction randomly fluctuates at a volatility δWx within ± 10% to ± 50% with reference to the reference grid spacing Wx_k.
The grid spacing Wy in the Y direction randomly fluctuates at a volatility δWy within ± 10% to ± 50% with reference to the reference grid spacing Wy_k.
The reference grid spacing Wx_k, Wy_k and the reference curvature radii Rx_k, Ry_k satisfy the following relational expressions (A) and (B).
The diffusion plate according to claim 4, wherein the diffusion angle (full width at half maximum) by the diffusion plate is 20 ° or less.
Rx_k / Wx_k ≧ 1.85 ・・・ (A)
Ry_k / Wy_k ≧ 1.85 ・・・ (B)
The diffuser according to any one of claims 1 to 5, wherein the planar positions of the vertices of the microlenses arranged in the X direction and the Y direction are eccentric from the center point of the rectangular lattice.
The distances in the X and Y directions from the center point of the rectangular lattice to the plane position of the apex of the eccentric microlens are defined as the eccentric amount Ecx and the eccentric amount Ecy, respectively, and the lattice intervals Wx and Wy of the rectangular lattice. When the ratios of the eccentricity Ecx and Ecy to the eccentricity are the eccentricity δEcx and the eccentricity δEcy, respectively.
The diffuser according to claim 6, wherein the plane positions of the vertices of the microlens are randomly eccentric with eccentricity ratios δEcx and δEcy within ± 10% to ± 50%.
The diffuser according to any one of claims 1 to 7, wherein the height positions of the vertices of the plurality of microlenses arranged in the X direction and the Y direction are different from each other.
The diffuser according to any one of claims 1 to 8, wherein the microlenses arranged in the X direction and the Y direction are continuously arranged without a gap between them.
The diffuser according to any one of claims 1 to 9, wherein the boundary lines of the microlenses adjacent to each other include a straight line and a curved line.
The microlens array is composed of a plurality of unit cells, which is a basic arrangement pattern of the microlens.
Any of claims 1 to 10, wherein the microlens array is formed by arranging the plurality of unit cells without gaps while maintaining the continuity of the microlens at the boundary portion between the plurality of unit cells. The diffuser according to one item.
The diffusion plate according to any one of claims 1 to 11, wherein the surface shape of the microlens is a spherical shape or an aspherical shape having anisotropy in the X direction or the Y direction.
A display device including the diffuser according to any one of claims 1 to 12.
A projection device including the diffuser according to any one of claims 1 to 12.
A lighting device including the diffuser according to any one of claims 1 to 12.