JP2012063541A - Light control plate unit, surface light source device, and transparent type image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device capable of sufficiently and evenly dispersing light from point-like light sources.SOLUTION: A surface light source device comprises a plurality of point-like light sources having predetermined light distribution properties, and first to fourth light control plates 30to 30. The light control plates comprise respective ridge portions 33to 33, each of which extends in one direction on an upper surface of the light control plate. Lower surfaces 31and 31of the second and fourth light control plates are positioned so as to face upper surfaces 32and 32of the first and third light control plates, respectively. Extension directions of the ridge portions 33and 33are approximately orthogonal to extension directions of the ridge portions 33and 33. When the extension direction of each of the ridge portions are defined as v-axis and an axis line orthogonal thereto is defined as u-axis, a contour shape v(u) of each of the ridge portions satisfies 0.95v(u)≤v(u)≤1.05v(u), provided -0.475w≤u≤0.475w. v(u) satisfies a formula (1) shown below. (Where wrepresents a length of the ridge portion in the u-axis direction. hand keach represent a constant number.)

Description

  The present invention relates to a light control plate unit, a surface light source device, and a transmissive image display device.

  As a direct type image display device 40 which is an example of a transmission type image display device, for example, as shown in FIG. Examples of the transmissive image display unit 10 include a liquid crystal display panel in which linearly polarizing plates 12 and 13 are disposed on both surfaces of a liquid crystal cell 11. As the light source 43, a plurality of linear light sources such as a straight tube type cold cathode ray tube are arranged in parallel with each other.

  It is desirable that the direct image display device 40 can uniformly illuminate the transmissive image display unit 10 by uniformly dispersing light from the light source 43, and for this reason, between the light source 43 and the transmissive image display unit 10. A light control plate 42 such as a single light diffusing plate having a function of changing the direction of light incident from the light source 43 side and emitting it from the opposite transmissive image display unit 10 side is used. (For example, see Patent Document 1: Japanese Patent Laid-Open No. 7-198913). Since the light output from the light source 43 is emitted as planar light by the light control plate 42, the light source 43 and the light control plate 42 constitute a surface light source device 41.

JP-A-7-198913

  In recent years, it has been studied to use a light emitting diode as a light source from the viewpoint of energy saving instead of a straight tube type cold cathode ray tube. The light emitting diode is usually a point light source, and is used by arranging it in a discrete manner.

  However, when the light control plate of the conventional surface light source device is used in a direct type image display device in combination with a point light source such as a light emitting diode, the light from the point light source may be sufficiently uniform. However, the image displayed by the transmissive image display unit has a problem that the brightness differs between the vicinity of the point light source and the position away from the point light source.

  Therefore, an object of the present invention is to provide a surface light source device, a light control plate unit, and a transmissive image display device that can sufficiently uniformly disperse light from a point light source.

ただし、式（１）において、

（式（２）中、ｈ_ａは０．３２ｗ_ａ以上０．９７ｗ_ａ以下を満たす定数であり、ｋ_ａは−１．００以上０．７５以下を満たす定数である） The surface light source device according to the present invention includes a plurality of point light sources and a light control plate unit provided on the plurality of point light sources. The point light source included in the surface light source device according to the present invention has a light distribution characteristic having a maximum emission light intensity I _max in a range of light emission angles of 70 ° to 80 °, and (A) the emission angle is 0. The emitted light intensity I _{0 in} the case of ° is
0.12 × I _max ≦ I ₀ ≦ 0.20 × I _max
(B) The emission angle at which the emission light intensity is (I ₀ + I _max ) / 2 is 60 ° or more and 70 ° or less, and (C) the emission light intensity is (I ₀ + I _max ) / 4. The light distribution characteristic is such that the emission angle becomes 47.5 ° or more and 57.5 ° or less. The light control plate unit included in the surface light source device according to the present invention can emit light incident from the first surface from the second surface located on the side opposite to the first surface, and in one direction. A plurality of convex portions extending in parallel and arranged in a direction substantially orthogonal to the one direction are provided with first to fourth light control plates formed on the second surface; Plate, second light control plate, third light control plate, and fourth light control plate, the second light control plate is located above the first light control plate, and the fourth light control plate is It is provided in the thickness direction so as to be located above the third light control plate, and the first surface of the second light control plate is located on the second surface side of the first light control plate. The extending direction of the convex portion included in the second light control plate is substantially parallel to the extending direction of the convex portion included in the first light control plate, and the first light control plate includes the first light control plate. The surface of the third light control plate The extending direction of the convex portion included in the fourth light control plate is substantially parallel to the extending direction of the convex portion included in the third light control plate. The extending directions of the convex portions of the light control plate and the extending directions of the convex portions of the third and fourth light control plates are substantially orthogonal to each other. An axis passing through both ends in a cross section perpendicular to the extending direction of each of the convex portions of the light control plate is a u axis, and an axis passing through the center between both ends on the u axis is a v axis, When the length in the u-axis direction is w _a for each of the convex portions of the first to fourth light control plates, each of the convex portions of the first to fourth light control plates in the cross section. Is expressed by v (u) satisfying the expression (1) when −0.475 w _a ≦ u ≦ 0.475 w _a .

However, in Formula (1),

(In the formula (2), _{h a} is a constant satisfying the following 0.32 W _a more 0.97w _{a, k a} is a constant satisfying 0.75 -1.00 or higher)

  In this configuration, light that has passed through the first light control plate is incident on the second light control plate, and light that has passed through the third light control plate passes through the fourth light control plate. . Since the cross-sectional shape of each convex portion of the first and second light control plates is represented by v (u) satisfying the expression (1), the first and second light control plates are provided with the above-described light distribution. When the extending directions of the convex portions of the first and second light control plates are arranged substantially in parallel on a point light source having characteristics, the light from the point light source is linear light with uniform luminance. Can be converted to Similarly, the cross-sectional shape of each convex portion of the third and fourth light control plates is represented by v (u) satisfying the expression (1), so that the third and fourth light control plates are If the extending directions of the convex portions of the third and fourth light control plates are arranged substantially in parallel on the point light source having the above-described light distribution characteristics, the brightness of the light from the point light source is uniform. Can be converted into linear light. In the surface light source device according to the present invention, the extending direction of the convex portions of the first and second light control plates and the extending direction of the convex portions of the third and fourth light control plates are substantially the same. A set of first and second light control plates and a set of third and fourth light control plates are arranged so as to be orthogonal to each other. Therefore, the light of the point light source incident from the first surface side of the first light control plate is a set of the first and second light control plates, and a set of the third and fourth light control plates. Thus, the light is converted into linear light with uniform luminance in directions substantially orthogonal to each other. As a result, the surface light source device emits the light from the point light source as planar light that is uniformly dispersed and has high luminance uniformity on the surface perpendicular to the plate thickness direction. Is possible.

  In the surface light source device according to the present invention, the first surface of each of the first to fourth light control plates may be substantially flat.

ただし、式（３）において、

（式（４）において、ｈ_ａは、０．３２ｗ_ａ以上０．９７ｗ_ａ以下を満たす定数であり、ｋ_ａは−１．００以上０．７５以下を満たす定数である。） A transmissive image display device according to the present invention includes a plurality of point light sources, a light control plate unit provided on the plurality of point light sources, and provided on the light control plate unit, and is emitted from the light control plate unit. A transmissive image display unit that displays an image by being irradiated with the emitted light. The point light source included in the transmissive image display device according to the present invention has a light distribution characteristic in which the light emission angle has a maximum emission light intensity I _max in a range of 70 ° to 80 °, and (a) the emission angle. The emitted light intensity I ₀ when is 0 ° is
0.12 × I _max ≦ I ₀ ≦ 0.20 × I _max
(B) The emission angle at which the emission light intensity is (I ₀ + I _max ) / 2 is 60 ° or more and 70 ° or less, and (c) the emission light intensity is (I ₀ + I _max ) / 4. The light distribution characteristic is such that the emission angle becomes 47.5 ° or more and 57.5 ° or less. The light control plate unit included in the transmissive image display device according to the present invention can emit light incident from the first surface from the second surface located on the side opposite to the first surface, and A plurality of convex portions extending in a direction and arranged in parallel in a direction substantially orthogonal to the one direction are provided with first to fourth light control plates formed on the second surface; In the light control plate, the second light control plate, the third light control plate, and the fourth light control plate, the second light control plate is located above the first light control plate and the fourth light control plate is used. The plate is provided in the thickness direction so that the plate is positioned above the third light control plate, and the first surface of the second light control plate is the second surface side of the first light control plate. The extending direction of the convex portion of the second light control plate is substantially parallel to the extending direction of the convex portion of the first light control plate. 1 side is the third light system The extension direction of the convex portion of the fourth light control plate located on the second surface side of the plate is substantially parallel to the extension direction of the convex portion of the third light control plate, The extending directions of the convex portions of the first and second light control plates are substantially orthogonal to the extending directions of the convex portions of the third and fourth light control plates, and In the cross section perpendicular to the extending direction of each of the convex portions of the first to fourth light control plates, an axis passing through both ends is defined as the u axis, and an axis perpendicular to the u axis passing through the center between both ends on the u axis is defined as When the v-axis and the length in the u-axis direction with respect to each of the convex portions of the first to fourth light control plates are w _a , the first to fourth light control plates have protrusions in the cross section. Each contour shape of the shape portion is represented by v (u) satisfying the expression (3) when −0.475 w _a ≦ u ≦ 0.475 w _a .

However, in Formula (3),

(In the formula (4), _{h a} is a constant satisfying the following 0.32 W _a more 0.97w _{a, k a} is a constant satisfying 0.75 -1.00 or more.)

  In this configuration, light that has passed through the first light control plate is incident on the second light control plate, and light that has passed through the third light control plate passes through the fourth light control plate. . Since the cross-sectional shape of each convex portion of the first and second light control plates is represented by v (u) satisfying the expression (3), the first and second light control plates are provided with the light distribution described above. When the extending directions of the convex portions of the first and second light control plates are arranged substantially in parallel on a point light source having characteristics, the light from the point light source is linear light with uniform luminance. Can be converted to Similarly, since the cross-sectional shape of each convex portion of the third and fourth light control plates is represented by v (u) that satisfies Equation (3), the third and fourth light control plates are If the extending directions of the convex portions of the third and fourth light control plates are arranged substantially in parallel on the point light source having the above-described light distribution characteristics, the brightness of the light from the point light source is uniform. Can be converted into linear light. In the transmissive image display device according to the present invention, the extending direction of the convex portions of the first and second light control plates, and the extending direction of the convex portions of the third and fourth light control plates, Are arranged such that the first and second light control plate sets and the third and fourth light control plate sets are arranged so as to be substantially orthogonal to each other. Therefore, the light of the point light source incident from the first surface side of the first light control plate is a set of the first and second light control plates, and a set of the third and fourth light control plates. Thus, the light is converted into linear light with uniform luminance in directions substantially orthogonal to each other. As a result, the transmissive image display device uniformly emits the light from the point light source as planar light that is planar light and has high luminance uniformity on the surface orthogonal to the thickness direction. It is possible to illuminate the transmissive image display unit with the uniformly dispersed planar light.

ただし、式（５）において、

（式（６）において、ｈ_ａは、０．３２ｗ_ａ以上０．９７ｗ_ａ以下を満たす定数であり、ｋ_ａは−１．００以上０．７５以下を満たす定数である。ただし、第１〜第４の光制御板のうちの少なくも一つが有する凸状部において、ｈ_ａについて、上記０．３２ｗ_ａ以上０．９７ｗ_ａ以下の範囲から０．３２ｗ_ａ以上０．８０ｗ_ａ以下の範囲が除かれるか、またはｋ_ａについて、上記−１．００以上０．７５以下の範囲から−１．００以上０．２３以下の範囲が除かれる）。 The light control plate unit according to the present invention can emit light incident from the first surface from the second surface located on the opposite side of the first surface, and extends in one direction. A plurality of convex portions arranged in parallel in a direction substantially orthogonal to the one direction includes first to fourth light control plates formed on a second surface, the first light control plate, the second light control plate, The light control plate, the third light control plate, and the fourth light control plate are such that the second light control plate is located above the first light control plate and the fourth light control plate is the third light control. It is provided in the plate thickness direction so as to be located on the upper side of the plate, the first surface of the second light control plate is located on the second surface side of the first light control plate, and the second surface The extending direction of the convex portion of the light control plate is substantially parallel to the extending direction of the convex portion of the first light control plate, and the first surface of the fourth light control plate is the third surface. Located on the second surface side of the light control plate, The extending direction of the convex portion of the light control plate 4 and the extending direction of the convex portion of the third light control plate are substantially parallel, and the convex shape of the first and second light control plates. The extending directions of the first and fourth light control plates are substantially orthogonal to the extending directions of the convex portions of the third and fourth light control plates. Each of the first to fourth light control plates has a u-axis that is an axis passing through both ends in a cross section orthogonal to the extending direction of each of the convex portions of the first to fourth light control plates, and passes through the center between both ends on the u-axis. Is the v-axis, and the length in the u-axis direction is w _a for each of the convex portions of the first to fourth light control plates, the first to fourth lights in the cross section. each of the contour shape of the convex portion control plate has is represented by v (u) satisfying the equation (5) in -0.475w _a ≦ u ≦ 0.475w _a.

However, in Formula (5),

(In the formula (6), _{h a} is a constant satisfying the following 0.32 W _a more 0.97w _{a, k a} is a constant satisfying 0.75 -1.00 or more. However, first to in the convex portion at least is one having one of the fourth light control plate, the _{h a,} the 0.32 W _a more 0.97w _{a 0.32w a} more from the range of 0.80 W _a following range either eliminated, or for _{k a,} the range of -1.00 or 0.23 or less from the -1.00 to 0.75 range is removed).

  In this configuration, light that has passed through the first light control plate is incident on the second light control plate, and light that has passed through the third light control plate passes through the fourth light control plate. . Since the cross-sectional shape of each convex portion of the first and second light control plates is represented by v (u) satisfying the equation (5), the first and second light control plates are on the point light source. In addition, when the extending directions of the convex portions of the first and second light control plates are arranged substantially in parallel, the light from the point light source can be converted into linear light with uniform luminance. Similarly, the cross-sectional shape of each convex portion of the third and fourth light control plates is represented by v (u) that satisfies the equation (5), so the third and fourth light control plates are When the extending directions of the convex portions of the third and fourth light control plates are arranged substantially in parallel on the point light source, the light from the point light source is converted into linear light with uniform luminance. it can. In the light control plate unit according to the present invention, the extending direction of the convex portions of the first and second light control plates and the extending direction of the convex portions of the third and fourth light control plates are as follows. A set of first and second light control plates and a set of third and fourth light control plates are arranged so as to be substantially orthogonal. Therefore, the light of the point light source incident from the first surface side of the first light control plate is a set of the first and second light control plates, and a set of the third and fourth light control plates. Thus, the light is converted into linear light with uniform luminance in directions substantially orthogonal to each other. As a result, the light control plate unit disperses the light from the point light source uniformly and emits it as planar light that is planar light and has high luminance uniformity on the surface orthogonal to the plate thickness direction. It is possible.

  According to the present invention, it is possible to provide a surface light source device, a light control plate unit, and a transmissive image display device that can sufficiently uniformly disperse light from a point light source.

It is sectional drawing which shows typically the structure of one Embodiment of the transmissive image display apparatus which concerns on this invention. It is drawing which shows an example of arrangement | positioning of a point light source. It is drawing which shows the other example of arrangement | positioning of a point light source. It is drawing which shows an example of the light distribution of the point light source used for the transmissive image display apparatus shown in FIG. It is a perspective view which shows one Embodiment of the light control board unit shown in FIG. It is drawing which shows the example of the cross-sectional shape of the convex part which the 1st-4th light control board of the light control board unit shown in FIG. 5 has. It is drawing which shows the conditions which the cross-sectional shape of a convex-shaped part satisfy | fills. It is a perspective view which shows other embodiment of a light-control board unit. It is a perspective view which shows other embodiment of a light-control board unit. It is sectional drawing which shows typically the structure of the conventional transmissive image display apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or an equivalent element, and the overlapping description is abbreviate | omitted. The dimensional ratios in the drawings do not necessarily match those described.

(First embodiment)
FIG. 1 is a cross-sectional view schematically showing a configuration of an embodiment of a transmissive image display device according to the present invention. FIG. 1 shows the transmissive image display device 1 in an exploded manner.

  The transmissive image display device 1 includes a transmissive image display unit 10 and a surface light source device 20 disposed on the back side of the transmissive image display unit 10 in FIG. In the following description, as shown in FIG. 1, the arrangement direction of the surface light source device 20 and the transmissive image display unit 10 is referred to as a z direction (plate thickness direction), which is two directions orthogonal to the z direction and orthogonal to each other. Two directions are referred to as an x direction and a y direction.

  Examples of the transmissive image display unit 10 include a liquid crystal display panel in which linearly polarizing plates 12 and 13 are disposed on both surfaces of a liquid crystal cell 11. In this case, the transmissive image display device 1 is a liquid crystal display device (or a liquid crystal television). As the liquid crystal cell 11 and the polarizing plates 12 and 13, those used in the transmissive image display device 1 such as a conventional liquid crystal display device can be used. Examples of the liquid crystal cell 11 include known liquid crystal cells such as TFT type and STN type.

  The surface light source device 20 is a so-called direct type surface light source device. The surface light source device 20 includes a light diffusing plate unit (light control plate unit) 21A and a plurality of point light sources 22 arranged on the back side in FIG.

The light diffusion plate unit 21A includes a first light diffusion plate (first light control plate) 30 ₁ , a second light diffusion plate (second light control plate) 30 ₂ , and a third light diffusion plate (third). comprising a light control plate) 30 ₃ and the fourth light diffusing plate (fourth light control plate) 30 _4. The first to fourth light diffusing plates 30 ₁ to 30 ₄ are the first light diffusing plate 30 ₁ , the second light diffusing plate 30 ₂ , the third light diffusing plate 30 ₃ , and the fourth light diffusing plate 30. _{4 in} the thickness direction (z direction).

The planar view shapes (shapes viewed from the z direction) of the _first to _fourth light diffusion plates 30 ₁ to 30 4 constituting the light diffusion plate unit 21A are substantially the same, and are generally rectangular. The planar view shape of the _first to _fourth light diffusion plates 30 ₁ to 30 ₄ , in other words, the size of the planar view shape of the light diffusion plate unit 21 A is suitable for the screen size of the target transmissive image display device 1. Usually, it is 250 mm × 440 mm or more, preferably 1020 mm × 1800 mm or less. The planar view shapes of the _first to _fourth light diffusing plates 30 ₁ to 30 ₄ are not limited to rectangles, but may be squares, but will be described below as rectangles unless otherwise specified.

FIG. 2 is a drawing showing an example of the arrangement relationship of a plurality of point light sources. As shown in FIG. 2, the plurality of point light sources 22 can be arranged at equal intervals L _{x in the} x direction and at equal intervals L _y in the y direction. In FIG. 2, as an example, the interval Lx in the x direction is larger than the interval Ly in the y direction, but the interval Ly may be larger than the interval Lx, or the interval Lx and the interval Ly may be the same. The space | interval Lx and the space | interval Ly can be made into the distance between the light emission parts of the point light source 22, and are 10 mm-150 mm normally.

  The plurality of point light sources 22 may be arranged in a staggered pattern shown in FIG. Since FIG. 3 can be regarded as a modification of the case of FIG. 2, the distance between the point light sources 22 in the x direction and the y direction can be the same as in the case of FIG. This will be specifically described.

  The rectangular lattice shown in FIG. 2 can be regarded as a plurality of point light source arrays composed of a plurality of point light sources 22 arranged in the x direction arranged in parallel in the y direction. In this case, the staggered arrangement in FIG. 3 is such that adjacent point light source arrays out of a plurality of point light source arrays arranged in the y direction are arranged with a half cycle shift in the x direction. Therefore, also in the arrangement shown in FIG. 3, the interval Ly in the y direction can be the same as the case shown in FIG. 2, that is, the interval between the point light source arrays arranged in parallel in the y direction. In FIG. 3, as an example, the adjacent point light source arrays out of the point light source arrays arranged in parallel in the y direction are shifted by a half cycle in the x direction. However, in the above description, the x direction and the y direction are opposite. There may be.

  FIG. 4 is a diagram illustrating an example of a light distribution of a point light source included in the surface light source device. The horizontal axis of FIG. 4 indicates the outgoing angle θ (°), and the vertical axis indicates the normalized outgoing light intensity normalized by the maximum outgoing light intensity. In the present embodiment, θ = 0 corresponds to the z direction in FIG.

The point light source 22 is a so-called side emitting light source, and an example of the point light source 22 is a light emitting diode. The point light source 22 has a light distribution characteristic (directional characteristic) that satisfies the following conditions.
The outgoing angle θ ₁ (hereinafter referred to as peak angle θ ₁ ) of the maximum outgoing light intensity I _max where the outgoing light intensity is maximum is in the range of 70 ° to 80 °.
The intensity of emitted light increases substantially monotonically from the front direction (emitted angle θ is 0 °) to the peak angle θ ₁ .
・ When the emitted light intensity in the front direction is I ₀ , I ₀ is
0.12 × I _max ≦ I ₀ ≦ 0.20 × I _max
Meet.
The outgoing angle θ _{2 at} which the outgoing light intensity is (I _max + I ₀ ) / 2 is in the range of 60 ° to 70 °.
The outgoing angle θ _{3 at} which the outgoing light intensity is (I _max + I ₀ ) / 4 is in the range of 47.5 ° to 57.5 °.

In the light distribution characteristic illustrated in FIG. 4, since the vertical axis is the normalized output light intensity, I _max = 1.00000, and the corresponding output angle θ ₁ is 76.8 °. I ₀ is 0.140. In this case, (I _max + I ₀ ) /2=0.570, and the corresponding emission angle θ ₂ is 66.5 °. Further, (I _max + I ₀ ) /4=0.285, and the corresponding emission angle θ ₃ is 52.5 °. Therefore, the light distribution characteristics of the point light source 22 shown in FIG. 4 satisfy the above-described conditions.

FIG. 5 is a perspective view for illustrating a configuration of a light diffusion plate unit (light control plate unit). Referring to FIG. 5, the light diffusing plate ₃₀ 1 of the first to fourth constituting the light diffusing plate unit _21A, 30 _2, 30 3, 30 ₄ will be described. In Figure 5, for purposes of explanation, although spaced apart first to fourth light diffusing plate ₃₀ 1 to 30 _4, as described later, the second to the first upper light diffusion plate 30 ₁ a fourth of the light diffusion plate ₃₀ 2-30 ₄ may be provided to two adjacent contacts.

[First light diffuser]
The first light diffusion plate 30 ₁ is substantially the (first surface of the first light control plate) 31 ₁ flat lower surface, the convex portion is convex second light diffusion plate 30 ₂ side (the first of the convex portion of the light control plate) 33 ₁ is a plate-like body having a second surface) 32 of _the plurality forming top surfaces (first light control plate. However, it may be in the form of a sheet or film depending on the thickness. Convex portion 33 ₁ extends substantially parallel to the Y1 direction in the y-direction (first direction of the first light control plate), first in the X1 direction (the first light control plate which is substantially perpendicular to the Y1 direction 2 direction). The X1 direction and the Y1 direction are preferably parallel to the x direction and the y direction, respectively, but may be shifted by about ± 10 ° due to, for example, a manufacturing error. The cross-sectional shape of the plurality of convex portions 33 ₁ is substantially the same between the convex portions 33 ₁ . Further, in the extending direction of the convex portion 33 _1, the cross-sectional shape is substantially uniform. The ends 33a ₁ of the two adjacent convex portions 33 ₁ and 33 ₁ are at the same position in the X1 direction. First thickness _{d 1} of the light diffusing plate 30 ₁ is a z-direction distance between the top portion 33b ₁ of the lower surface 31 ₁ and the convex portion 33 _1, usually a 0.1 mm to 5 mm.

[Second light diffuser]
The second light diffusion plate 30 ₂ is substantially flat lower surface (second optical control plate first surface of) 31 _2, the convex portion is convex outward (convex portion of the second light control plate ) 33 ₂ is a second surface) 32 ₂ and the plate-like member having a plurality formed top (second light control plate. However, it may be in the form of a sheet or film depending on the thickness. Convex portion 33 ₂ extend in substantially parallel Y2 direction in the y direction (first direction of the second light control plate), first in the X2 direction (second light control plate which is substantially perpendicular to the Y2 direction 2 direction). It is preferred X2 direction and the Y2 direction is parallel to the x and y directions, respectively, but as in the case of the first light diffuser 30 _1, for example due to a manufacturing error or the like may be offset about ± 10 °. Cross-sectional shape of the plurality of convex portions 33 ₂ is substantially same in the convex portion 33 _2. Further, in the extending direction of the convex portion 33 _2, the cross-sectional shape is substantially uniform. End _33a 2 of two adjacent convex portions ₃₃ 2, 33 _2, 33a ₂ are in the same position in the X2 direction. Second thickness _{d 2} of the light diffusion plate 30 ₂ is a z-direction distance between the top portion 33b ₂ of the lower surface 31 ₂ and the convex portion 33 _2, usually a 0.1 mm to 5 mm.

[Third light diffusion plate]
Third light diffusing plate 30 _3, and (first surface of the third light control plate) 31 ₃ substantially flat lower surface, the convex portion is convex outward (convex portion of the third light control plate ) 33 ₃ is a plate-like body having and a second surface) 32 ₃ multiple formed top (third light control plate. However, it may be in the form of a sheet or film depending on the thickness. Convex portion 33 _3, extends substantially parallel to the direction X3 in the x-direction (first direction of the third light control plate), first of Y3 direction (third light control plate substantially perpendicular to the direction X3 2 direction). It is preferred X3 direction and Y3 direction is parallel to the x and y directions, respectively, but as in the case of the first light diffuser 30 _1, for example due to a manufacturing error or the like may be offset about ± 10 °. Cross-sectional shape of the plurality of convex portions 33 ₃ are substantially same in the convex portion 33 _3. Further, in the extending direction of the convex portion 33 _3, the cross-sectional shape is substantially uniform. The ends 33a ₃ and 33a ₃ of the two adjacent convex portions 33 ₃ and 33 ₃ are at the same position in the Y3 direction. The thickness d ₃ of the third light diffusing plate 30 ₃ is a distance in the z direction between the lower surface 31 ₃ and the top 33b ₃ of the convex portion 33 ₃ , and is usually 0.1 mm to 5 mm.

[Fourth diffuser]
Fourth light diffuser 30 ₄ has a substantially flat lower surface (fourth light control plate first surface of) 31 _4, the convex portion is convex outwardly (protruding portion of the fourth light control plate ) 33 ₄ is a plate-like body having and a second surface) 32 ₄ multi formed top (fourth light control plate. However, it may be in the form of a sheet or film depending on the thickness. Convex portion 33 _4, extends substantially parallel to the direction X4 in the x-direction (first direction of the fourth light control plate), first in the Y4 direction (fourth light control plate substantially perpendicular to the direction X4 2 direction). It is preferable X4 direction and Y4 direction is parallel to the x and y directions, respectively, but as in the case of the first light diffuser 30 _1, for example due to a manufacturing error or the like may be offset about ± 10 °. Cross-sectional shape of the plurality of convex portions 33 ₄ is substantially the same in the convex portion 33 _4. Further, in the extending direction of the convex portion 33 _4, the cross-sectional shape is substantially uniform. The ends 33a ₄ and 33a ₄ of the two adjacent convex portions 33 ₄ and 33 ₄ are at the same position in the Y4 direction. The thickness _{d 4} of the fourth light diffusing plate 30 ₄ is a z-direction distance between the top portion 33b ₄ of the lower surface 31 ₄ and the convex portion 33 _4, usually is 0.1 mm to 5 mm.

[Convex]
The first to fourth light diffusing plate _{30 1,} 30 _2, 30 3, 30 ₄ convex portion ₃₃ 1 each having _a, 33 _2, 33 3, 33 for ₄ shape described.

The convex portions 33 ₁ and 33 ₂ are provided with first and second light diffusion plates 30 ₁ and 30 ₂ in this order on the point light source 22 having the light distribution characteristics described with reference to FIG. When the portions 33 ₁ and 33 ₂ are arranged with their extending directions substantially parallel to each other, they have a cross-sectional shape that can convert light from the point light source 22 into linear light with substantially uniform luminance. Similarly, the convex portions 33 ₃ and 33 ₄ are provided with the third and fourth light diffusing plates 30 ₃ and 30 ₄ in this order on the point light source 22 having the light distribution characteristics described with reference to FIG. In addition, when the convex portions 33 ₃ and 33 ₄ are arranged with their extending directions in parallel, the cross-sectional shape that can convert the light from the point light source 22 into linear light with substantially uniform luminance is provided. Have. The cross-sectional shape of the convex portion ₃₃ to 333 ₄ will be described with reference to FIG.

Here, the convex portions 33 _{1 to} 33 ₄ will be referred to as convex portions 33 _i (i is any number from 1 to 4) unless otherwise specified. In FIG. 6, the uv coordinate system is set with the u-axis as the direction orthogonal to the extending direction of the convex portion 33 _i . U-axis direction corresponding to the convex portion 33 _1, the convex portion 33 _2, the convex portion 33 ₃ and the convex portion 33 _4, X1 directions, respectively, X2 direction, it corresponds to Y3 direction and Y4 directions. Further, the convex portion 33 _1, the convex portion 33 _2, v axis direction corresponding to the convex portion 33 ₃ and the convex portion 33 ₄ are both corresponding to the z-direction.

ただし、式（７）において、

式（８）において、ｗ_ａはｕ軸方向の凸状部３３_ｉの長さである。ｈ_ａは、凸状部３３_ｉの両端３３ａ_ｉ,３３ａ_ｉ間における最大高さに対応し、ｈ_ａは０．３２ｗ_ａ以上０．９７ｗ_ａ以下を満たす定数である。すなわち、ｈ_ａは、ｈ_ａ／ｗ_ａが０．３２以上０．９７以下を満たす定数である。ｋ_ａは−１．００以上０．７５以下を満たす定数である。凸状部３３_ｉの幅ｗ_aは、凸状部３３_ｉの形成が容易であることから、通常４０μｍ以上、好ましくは２５０μｍ以上であり、凸状部３３_ｉに起因する模様が肉眼で視認されにくいことから、通常８００μｍ以下、好ましくは４５０μｍ以下である。幅ｗ_aとして具体的には、ｗ_a＝４１０μｍ、ｗ_a＝４００μｍおよびｗ_a＝３２５μｍが例示できるが、ｗ_aの値はこれに限定されるものではない。 In the uv coordinate system, the cross-sectional shape of the convex portion 33 _i has both ends 33 a _i and 33 a _i on the u-axis. The contour line of the convex portion 33 _i is represented by v (u) that satisfies the following formula (7).

However, in Formula (7),

In Expression (8), w _a is the length of the convex portion 33 _{i in} the u-axis direction. h _a is across 33a _i of the convex portion 33 _i, corresponding to the maximum height between 33a _{i, h a} is a constant satisfying the following 0.32 W _a more 0.97w _a. That is, h _a is a constant that satisfies h _a / w _a of 0.32 or more and 0.97 or less. k _a is _a constant that satisfies −1.00 or more and 0.75 or less. Width w _a of the convex portion 33 _i, since formation of the convex portion 33 _i is easy, usually 40μm or more, preferably 250μm or more, the pattern caused by the convex portion 33 _i is visible to the naked eye Since it is difficult, it is usually 800 μm or less, preferably 450 μm or less. Specific examples of the width w _a include w _a = 410 μm, w _a = 400 μm, and w _a = 325 μm, but the value of w _a is not limited to this.

FIG. 6 exemplifies a shape in which v ₀ (u) is expanded and contracted by a predetermined multiple in the v direction within a range satisfying Expression (7) as an example of a cross-sectional shape of the convex portion 33 _i . In this case, the convex portion 33 _i has a contour line symmetrical with respect to the v-axis. The cross-sectional shape shown in FIG. 6 corresponds to v ₀ (u) when h _a / w _a = 0.45 and k _a = −0.20. However, the sectional shape of the convex portion 33 _i, as shown in FIG. 7, when determining the _v 0 (u) for a width _{w a,} contours represented by 0.95v ₀ (u) And a contour line passing through a region between the contour lines represented by 1.05v ₀ (u). Also in v ₀ (u) shown in FIG. 7, h _a / w _a = 0.45 and k _a = −0.20.

Furthermore, in the above description, it is assumed that the cross-sectional shape of the convex portion 33 _i is represented by v (u) that satisfies Expression (7). However, considering the effect on the manufacturing error and the intensity distribution at near both ends of the convex portion 33 _i, the cross-sectional shape of the convex portion 33 _i has the formula in -0.475w _a ≦ u ≦ 0.475w _a It may be expressed by v (u) that satisfies (7).

Further, the range of h _{a /} w a and k _a may if they meet the above-mentioned range, but the distance between two adjacent point light sources 22 is L, the light diffusion plate from the light emitting portion of the point light sources 22 When the distance to the surface of the unit 21A on the point light source 22 side (the lower surface 31 _{1 of the first} light diffusing plate 30 ₁ in FIG. 1 or 5) is D, h _a / preferable for L / D range of w _a and _{k a} is, as shown in Table 1. L in Table 1 are those for the convex portion ₃₃ 1, 33 ₂ of the contour shape corresponds to Lx, corresponding to Ly for convex portion ₃₃ 3, 33 ₄ of the contour shape And

The first to fourth light diffusing plate ₃₀ 1 to 30 ₄ of the convex portion ₃₃ to 333 _{4 w a,} h _{a, k} a is may be the same between the respective convex portions ₃₃ to 333 _4, different It may be. That is, the cross-sectional shape of the convex portion ₃₃ to 333 ₄ each of the first to fourth light diffusing plate ₃₀ 1 to 30 ₄ has may be the same cross-sectional shapes, each of the convex portions to the extent that 33 _to 333 ₄ of the cross-sectional shape of the contour satisfies the above formula (7) may be a different cross-sectional shapes. However, it is preferable that the cross-sectional shape of the convex portion 33 ₁ and the convex portion 33 ₂ is the same, it is preferred cross-sectional shape of the convex portion 33 ₃ and the convex portion 33 ₄ are the same.

[Layer configuration of first to fourth light diffusion plates]
The first to fourth light diffusion plates 30 ₁ to 30 ₄ may be single-layer plates made of a single transparent material, or have a multilayer structure in which layers made of different transparent materials are laminated. A multilayer board may be sufficient. When the _first to _fourth light diffusion plates 30 ₁ to 304 are multilayer plates, one or both sides of the _first to _fourth light diffusion plates 30 ₁ to 304 are usually 10 μm to 200 μm, preferably 20 μm to It is preferable to use a structure in which a skin layer having a thickness of 100 μm is formed, and a transparent resin material constituting the skin layer to which an ultraviolet absorber is added is used. By adopting such a configuration, it is possible to prevent the _first to _fourth light diffusion plates 30 ₁ to 304 from being deteriorated by the point light source 22 or ultraviolet rays that may be included in light from the outside. If the proportion of the light source 22 of ultraviolet rays using a relatively large, because it can prevent deterioration due to ultraviolet rays, it is preferable that the skin layer on the lower surface 31 _{1-31 4} is formed, this time the upper surface 32 ₁ to 32 that the ₄ not formed skin layer, more preferably in terms of cost. When the transparent resin material constituting the skin layer is added with an ultraviolet absorber, the content is usually 0.5% by mass to 5% by mass, preferably 1% by mass to 2% based on the transparent resin material. 0.5% by mass.

The first to fourth light diffusion plates 30 ₁ to 30 ₄ may be coated with an antistatic agent on one side or both sides. By applying an antistatic agent, dust adhesion due to static electricity can be prevented, and a decrease in light transmittance due to dust adhesion can be prevented.

[Constituent materials]
The first to fourth light diffusion plates 30 ₁ to 30 ₄ are made of a transparent material. The refractive index of the transparent material is usually 1.46 to 1.62. Examples of the transparent material include a transparent resin material and a transparent glass material. Examples of the transparent resin material include an acrylic ultraviolet curable resin (refractive index: 1.46 to 1.58) and a polycarbonate resin (refractive index: 1.59). MS resin (methyl methacrylate-styrene copolymer resin) (refractive index: 1.56-1.59), polystyrene resin (refractive index: 1.59), AS resin (acrylonitrile-styrene copolymer resin) ( Refractive index: 1.56-1.59) and the like are exemplified, and polystyrene resin is preferable in terms of cost and low moisture absorption.

  When a transparent resin material is used as the transparent material, additives such as an ultraviolet absorber, an antistatic agent, an antioxidant, a processing stabilizer, a flame retardant, and a lubricant can be added to the transparent resin material. These additives can be used alone or in combination of two or more.

  Examples of UV absorbers include benzotriazole UV absorbers, benzophenone UV absorbers, cyanoacrylate UV absorbers, malonic ester UV absorbers, oxalic anilide UV absorbers, and triazine UV absorbers. Preferred are benzotriazole ultraviolet absorbers and triazine ultraviolet absorbers.

  The transparent resin material is usually used without adding a light diffusing agent as an additive, but may be added with a light diffusing agent as long as it is a slight amount that does not impair the object of the present invention.

As the light diffusing agent, a powder having a refractive index different from that of the above-described transparent material mainly constituting the _first to _fourth light diffusing plates 30 ₁ to 30 4 is usually used and dispersed in the transparent material. Used. As the light diffusing agent, for example, organic particles such as styrene resin particles and methacrylic resin particles, inorganic particles such as potassium carbonate particles, silica particles, and silicone resin particles are used, and the particle diameter is usually 0.8 μm to 50 μm. .

  Further, the surface on the point light source 22 side can be a surface having light diffusibility in order to reduce moire. For example, the surface on the point light source 22 side may be constituted by a skin layer containing fine particles called a matting agent, or the surface on the point light source 22 side may be embossed or blasted, A matting layer may be formed by applying a coating solution containing a matting agent and a binder.

[Methods for producing first to fourth light diffusing plates]
The first to fourth light diffusion plates 30 ₁ to 30 ₄ can be manufactured, for example, by a method of cutting out from a transparent material. Moreover, when using a transparent resin material as a transparent material, it can manufacture by normal methods, such as an injection molding method, an extrusion molding method, a photopolymer method, a press molding method, for example.

[Disposition relationship of the first to fourth light diffusion plates]
The first to fourth light diffusion plates 30 ₁ to 30 ₄ are provided in the z direction so as to satisfy the following conditions.
(i) a second light diffusion plate 30 ₂ is the first light diffusing plate 30 ₁ located above and the fourth light diffusing plate 30 ₄ is positioned on the upper side of the third light diffusing plate 30 ₃ .
(ii) the lower surface ₃₁₂ of the second light diffusion plate 30 ₂ is located at the first upper surface 32 ₁ side of the light diffusion plate 30 _1.
(iii) Fourth underside 31 ₄ of the light diffusion plate 30 ₄ is positioned on the top surface 32 ₃ of the third light diffusing plate 30 _3.
(iv) a first light diffusing plate 30 ₁ of the convex portion 33 ₁ in the extending direction (Y1 direction), the second light diffusion plate 30 ₂ of the convex portion 33 ₂ in the extending direction (Y2 direction) and Are substantially parallel.
(v) and the third light diffusing plate 30 ₃ of the convex portion 33 ₃ of the extending direction (X3 direction), the fourth light diffusing plate 30 ₄ of the convex portion 33 ₄ of the extending direction (X4 direction) Are substantially parallel.
(vi) the first light diffusing plate 30 ₁ and the second light diffusion plate 30 ₂ and the first light diffusing plate set, the third light diffusing plate 30, _third and fourth light diffusing plate 30 ₄ second In the case of two light diffusion plate sets, the first light diffusion plate set and the second light diffusion plate set are convex with respect to the extending direction of the convex portion 33 ₁ (or the convex portion 33 ₂ ). It arrange | positions so that the extension direction of the part 33 ₃ (or convex part 33 ₄ ) may be substantially orthogonal. The angle formed by the extending direction of the convex portion 33 ₁ (or the convex portion 33 ₂ ) and the extending direction of the convex portion 33 ₃ (or the convex portion 33 ₄ ) is exemplified by 80 ° to 100 °. Preferably, it is 90 degrees.

In the present embodiment, the first to fourth light diffusion plates 30 ₁ to 30 ₄ satisfy the above six arrangement conditions (i) to (vi), and the first light diffusion plate 30 ₁ and the second light are satisfied. diffuser 30 ₂ is provided in the z direction in the order of the third light diffusing plate 30, _third and fourth light diffusing plate 30 _4.

The distance _{d 12} between the first and second light diffusing plate ₃₀ 1, 30 _2, first light diffusing plate 30 ₁ of the convex portion 33 ₁ apex 33b ₁ and the second light diffusion plate 30 ₂ a z-direction distance between the lower surface 31 _2, 5 mm or less can be exemplified. Similarly, the second and third light diffusion plate ₃₀ 2, 30 a distance _{d 23} between the _3, the second top portion 33b ₂ of the light diffusion plate 30 ₂ of the convex portion 33 ₂ and the third light diffusing plate The distance in the z direction between the lower surface 31 _{3 of} 30 ₃ and 5 mm or less can be exemplified. The distance _{d 34} between the third and fourth light diffusing plate ₃₀ 3, 30 _4, third convex portion 33 ₃ of the top portion 33b ₃ of the light diffusion plate 30 ₃ and the fourth light diffusing plate 30 a z-direction distance between the _fourth lower surface 31 _4, 5 mm or less can be exemplified.

From the viewpoint of the light diffusing plate unit 21A and compact _{ones, d 12, d 23} and _{d 34} are 0 mm, a second light diffusing plate to the first upper convex portion 33 ₁ of the light diffusing plate 30 ₁ 30 _2, 3 of the light diffusion plate 30, _third and fourth light diffusing plate 30 _4, the upper bottom surface _{31 2,} 31 3, 31 _4, and the lower convex portion _{33 1,} 33 2, 33 ₃ of the top _{33b 1,} 33b 2, it may be disposed in contact with 33b _3. Thus, the first to fourth light diffusing plate ₃₀ 1 to 30 second to the first upper light diffusion plate 30 ₁ located most point light source 22 side of the _four fourth light diffusion plate 30 ₂ 30 _4, in the case of providing such a plate of two adjacent light diffusion plate ₃₀ 1 to 30 upper and lower side in ₄ are in contact with each other, the thickness of the second to fourth light diffusion plate ₃₀ 2 to 30 ₄ the d ₂ to d ₄ are preferred to those first thinner than the thickness _{d 1} of the light diffusing plate 30 _1. For example, when the second to fourth light diffusing plate ₃₀ 2-30 ₄ shall thinner such filmy, supporting the first light diffusing plate 30 ₁ of the second to fourth light diffusing plate ₃₀ 2-30 ₄ This is because it can be used as a stand.

[Arrangement of light diffuser unit]
Light diffusing plate unit 21A which has first to fourth light diffusing plate ₃₀ 1 to 30 ₄ of the above configuration, the distance D from the point light sources 22 to the lower surface 31 of the _first light diffuser 30 _1, usually It arrange | positions with respect to the point light source 22 so that it may become 3 mm-50 mm. In the transmissive image display device 1 or the surface light source device 20, Lx, Ly, and D are values in which Lx / D and Ly / D are each 2 or more, and further 2.5 or more. Is preferable in that it can be made thinner.

Further, the light diffusion plate unit 21A, in the transmissive image display device 1, to the extending direction of the convex portion 33 ₁ may be arranged such that the longitudinal direction of the screen, arranged so as to be laterally May be.

  Next, the function and effect of the light diffusing plate unit 21A will be described by taking as an example the case where the surface light source device 20 including the light diffusing plate unit 21A is applied to the transmissive image display device 1, as shown in FIG. To do. Here, it is assumed that the X1, X2, X3, and X4 directions are parallel to the x direction, and the Y1, Y2, Y3, and Y4 directions are parallel to the y direction.

The convex portions 33 ₁ and 33 ₂ of the first and second light diffusing plate units 30 ₁ and 30 ₂ have a cross-sectional shape that satisfies Expression (7). Therefore, when the first and second light diffusing plate units 30 ₁ and 30 ₂ are arranged on the point light source 22 so that the extending directions of the convex portions 33 ₁ and 33 ₂ are substantially parallel to each other, The second light diffusing plates 30 ₁ and 30 ₂ can convert the light output from the point light source 22 into linear light with uniform luminance and emit the light. Further, since the third and fourth light diffusing plate unit 30 _3, 30 ₄ of the convex portion 33 _3, 33 ₄ also has a sectional shape satisfying the equation (7), first and second light diffusing as in the case of the plate unit 30 _1, 30 _2, are converted into the third and fourth light diffusing plate unit 30 _3, 30 ₄ is also the light from the point light sources 22 are luminance uniform linear light emitting it can.

In the light diffusing plate unit 21A, as described above, the first and second light diffusing plate units 30 ₁ and 30 _{2 that} can convert the light from the point light source 22 into linear light having substantially uniform luminance. Of the first and second light diffusing plate units 30 ₃ and 30 ₄ , the extending direction of the convex portion 33 ₁ (or the convex portion 33 ₂ ) and the convex portion 33 _{3 in the} z direction. It arrange | positions so that the extension direction of (or convex part 33 ₄ ) may cross substantially orthogonally. Therefore, the light from the point light sources 22, the first and second light diffusing plate unit 30 _1, 30 ₂ of the set and the third and fourth light diffusing plate unit ₃₀ 3, 30 ₄ pairs, luminance It is converted into linear light in a uniform and substantially orthogonal direction. As a result, the light diffusing plate unit 21A uniformly disperses the light from the plurality of point light sources 22 and is planar light, which is planar light having higher luminance uniformity in the plane orthogonal to the z direction. Can be emitted.

In addition, when the first light diffusing plate 30 ₁ second to 4 provided on the light diffusing plate _{30 2,} 30 3, 30 ₄ and film-like, in the configuration of the present embodiment, the third and fourth The light diffusion plates 30 ₃ and 30 ₄ can be the same film. As a result, the configuration of the light diffusing plate unit 21A shown in FIG. 5 is a configuration that contributes to a reduction in manufacturing cost.

  Since the surface light source device 20 includes the light diffusing plate unit 21A, the surface light that uniformly distributes the light from the plurality of point light sources 22 and has higher luminance uniformity in the surface orthogonal to the z direction. Can be emitted. Further, since the transmissive image display device 1 includes the light diffusing plate unit 21A, the luminance uniformity in the plane orthogonal to the z direction is higher because the light from the plurality of point light sources 22 is uniformly dispersed. It is possible to irradiate the transmissive image display unit 10 with planar light. As a result, a higher quality image can be displayed.

In the present embodiment, the _first to _fourth light diffusion plates 30 ₁ to 30 ₄ are sequentially provided in the z direction, but the first to fourth light diffusion plates 30 ₁ to 30 ₄ are arranged according to the arrangement conditions. It only needs to be provided in the z direction so as to satisfy (i) to (vi). Other embodiments of the light diffusing plate unit according to the modified example of the arrangement of the _first to _fourth light diffusing plates 30 ₁ to 304 will be described as second and third embodiments.

(Second Embodiment)
FIG. 8 is a perspective view showing a second embodiment of the light diffusing plate unit (light control plate unit). The light diffusing plate unit 21 </ _b > B includes first to fourth light diffusing plates 30 ₁ , 30 ₂ , 30 ₃ , and 30 ₄ as in the case of the first embodiment. First to configuration of the fourth light diffusing plate ₃₀ 1 to 30 ₄ are the same as the first to fourth light diffusing plate ₃₀ 1 to 30 ₄ configuration of the first embodiment, the light diffusing plate unit 21B Is different from the light diffusing plate unit 21 </ b> A in the order of arrangement of the _first to _fourth light diffusing plates 30 ₁ to 304. This difference will be mainly described.

In the light diffusing plate unit 21B, the first light diffusing plate 30 _1, the third light diffusing plate 30 _3, provided in the z direction in the order of the second light diffusion plate 30 ₂ and the fourth light diffusing plate 30 ₄ Yes. The first light diffusion plate 30 ₁ of the convex portion 33 ₁ in the extending direction and the second light diffusion plate 30 ₂ extending direction of the convex portion 33 ₂ is substantially parallel. Also, the third extending direction of the light diffusing plate 30 ₃ of the convex portion 33 ₃ of the extending direction and the fourth light diffusing plate 30 ₄ of the convex portion 33 ₄ are substantially parallel. Further, as in the case of the first embodiment, the first and second light diffusion plates 30 ₁ and 30 ₂ are set as a first light diffusion plate set, and the third and fourth light diffusion plates 30 _{3 are used.} , 30 ₄ is the second light diffusing plate set, the first light diffusing plate set and the second light diffusing plate set are the convex portion 33 ₁ (or the convex portion 33 ₂ ). It arrange | positions so that the extension direction and the extension direction of convex-shaped part 33 ₃ (or convex-shaped part 33 ₄ ) may cross substantially orthogonally. The angle between the extending direction of the convex portion 33 ₁ (or the convex portion 33 ₂ ) and the extending direction of the convex portion 33 ₃ (or the convex portion 33 ₄ ) is exemplified by 80 ° to 100 °, Preferably, it is 90 degrees.

In this configuration, the first to fourth light diffusion plates 30 ₁ to 30 ₄ satisfy the arrangement conditions (i) to (vi) described in the first embodiment.

The distance _{d 13} between the first and third light diffuser ₃₀ 1, 30 _3, the first top 33b ₁ of the light diffusing plate 30 ₁ of the convex portion 33 ₁ and the third light diffusing plate 30 ₃ a z-direction distance between the lower surface 31 _3, 5 mm or less can be exemplified. Similarly, the distance _{d 32} between the third and second light diffusing plate ₃₀ 3, 30 _2, and the third convex portion 33 ₃ of the top portion 33b ₃ of the light diffusing plate 30 ₃ second light diffusing plate a z-direction distance between the 30 ₂ of the lower surface 31 _2, 5 mm or less can be exemplified. The distance _{d 24} between the second and fourth light diffusion plate ₃₀ 2, 30 _4, the second light diffusion plate 30 ₂ of the convex portion 33 ₂ of the top portion 33b ₂ and the fourth light diffusing plate 30 a z-direction distance between the _fourth lower surface 31 _4, 5 mm or less can be exemplified.

From the viewpoint of the light diffusing plate unit 21B and compact _{ones, d 13, d 32} and _{d 24} are 0 mm, the third light diffusing plate to the first upper convex portion 33 ₁ of the light diffusing plate 30 ₁ 30 _3, a second light diffusion plate 30 ₂ and the fourth light diffusing plate 30 ₄ upper lower surface _{31 3,} 31 2, 31 _4, and the lower convex portion _{33 1,} 33 3, 33 ₂ of the top portion 33b ₁ , 33b ₃ , and 33b ₂ may be arranged so as to be in contact with each other as in the case of the first embodiment. The first light diffusion plate 30 ₁ second to fourth light diffusing plate ₃₀ 2-30 ₄ positioned to the first to the most point light sources 22 side of the fourth light diffusing plate ₃₀ 1 to 30 ₄ It is preferable to make it thicker. In this case, for example, the _second to _fourth light diffusion plates 30 ₂ to 304 can be formed into a film shape as in the case of the first embodiment.

The light diffusing plate unit 21B shown in FIG. 8 can be applied to the surface light source device 20 and the transmissive image display device 1 instead of the light diffusing plate unit 21A in FIG. In this case, the transmission type image display device 1, the light diffusing plate unit 21B is to the extending direction of the convex portion 33 ₁ may be arranged such that the longitudinal direction of the screen, arranged to be laterally May be.

In the optical diffusing plate unit 21B, and the second light diffusion plate 30 ₂ is provided satisfy the placement condition (ii) and (iv) a first upper optical diffuser 30 _1, the third light diffusing fourth light diffusing plate 30 ₄ are provided meets the arrangement conditions (iii) and (v) to the upper plate 30 _3. In this arrangement, the first and second light diffusing plates 30 ₁ and 30 ₂ can convert the light from the point light source 22 into linear light with substantially uniform luminance, and the third and fourth light diffusing plates. 30 ₃ and 30 ₄ can also convert light from the point light source 22 into linear light having substantially uniform luminance.

In the light diffusing plate unit 21B, the first and second light diffusing plates 30 ₁ and 30 ₂ and the third and fourth light diffusing plates 30 ₃ and 30 ₄ are arranged according to the arrangement condition (vi ) Is arranged. That is, the set of the first and second light diffusing plates 30 ₁ and 30 _{2 and} the set of the third and fourth light diffusing plates 30 ₃ and 30 ₄ are the convex portion 33 ₁ (or the convex portion 33). The extending direction of ₂ ) and the extending direction of the convex part 33 ₃ (or the convex part 33 ₄ ) are arranged so as to be substantially orthogonal to each other.

  Therefore, when the light diffusing plate unit 21B is used instead of the light diffusing plate unit 21A of FIG. 1, the light from the plurality of point light sources 22 is the light diffusing plate unit as in the first embodiment. By passing through 21B, it is possible to generate planar light that is uniformly dispersed and, as a result, has a higher luminance uniformity in a plane orthogonal to the z direction.

  Therefore, the surface light source device 20 and the transmissive image display device 1 including the light diffusing plate unit 21B and the plurality of point light sources 22 also have the same operational effects as in the case of the first embodiment.

Further, the light diffusion plate unit 21B, the first to fourth light diffusing plate ₃₀ 1 to 30 _4, the convex portion ₃₃ 1 in the _z-direction, 33 _2, 33 3, 33 ₄ in the extending direction is substantially alternately It arrange | positions so that it may orthogonally cross. Therefore, Moire fringes is unlikely to occur to a fourth planar light emitted from the light diffusion plate 30 _4. Therefore, even in the surface light source device 10 including the light diffusing plate unit 21 </ b> B and the plurality of point light sources 22, planar light with suppressed moire fringes can be emitted. Further, the transmissive image marking apparatus 1 including the light diffusing plate unit 21 </ b> B and the plurality of point light sources 22 can display a higher quality image.

(Third embodiment)
FIG. 9 is a perspective view showing a third embodiment of the light diffusion plate unit (light control plate unit). The light diffusing plate unit 21 </ b> C includes first to fourth light diffusing plates 30 ₁ , 30 ₂ , 30 ₃ , and 30 ₄ as in the case of the first embodiment. First to configuration of the fourth light diffusing plate ₃₀ 1 to 30 ₄ are the same as the first to fourth light diffusing plate ₃₀ 1 to 30 ₄ configuration of the first embodiment, the light diffusing plate unit 21C Is different from the light diffusing plate unit 21 </ b> A in the order of arrangement of the _first to _fourth light diffusing plates 30 ₁ to 304. This difference will be mainly described.

In the light diffusing plate unit 21C, the first light diffusing plate 30 _1, the third light diffusing plate 30 _3, the fourth order of the light diffusion plate 30 ₄ and the second light diffusion plate 30 _2, a first embodiment It is provided in the z direction so as to satisfy the arrangement relationships (ii) to (vi) described in the above. The first light diffusion plate 30 _1, the third light diffusing plate 30 _3, the fourth light diffusing plate 30 ₄ and the second order of the light diffusion plate 30 _2, so provided in z-direction, the In the embodiment, the arrangement relationship (i) described in the first embodiment is also satisfied.

The distance _{d 13} between the first and third light diffuser ₃₀ 1, 30 _3, the first top 33b ₁ of the light diffusing plate 30 ₁ of the convex portion 33 ₁ and the third light diffusing plate 30 ₃ a z-direction distance between the lower surface 31 _3, 5 mm or less can be exemplified. Similarly, the distance _{d 34} between the third and fourth light diffusing plate ₃₀ 3, 30 _4, and the third convex portion 33 ₃ of the top portion 33b ₃ of the light diffusing plate 30 ₃ fourth light diffusing plate a z-direction distance between the 30 ₄ of the lower surface 31 _4, 5 mm or less can be exemplified. The distance _{d 42} between the fourth and second light diffusing plate ₃₀ 4, 30 _2, the fourth convex portion 33 ₄ top 33b ₄ of the light diffusion plate 30 ₄ and the second light diffusion plate 30 _This is a distance in the z direction between the lower surface 312 of ₂ and 5 mm or less.

From the viewpoint of the light diffusing plate unit 21C and compact _{ones, d 13, d 34} and _{d 42} are 0 mm, the third light diffusing plate to the first upper convex portion 33 ₁ of the light diffusing plate 30 ₁ 30 _3, a fourth light diffusing plate 30 ₄ and the second light diffusion plate 30 _2, the upper bottom surface _{31 3,} 31 4, 31 _2, the lower convex portion _{33 1,} 33 3, 33 ₄ of the top It is the same as in the case of the first embodiment that it may be arranged so as to be in contact with 33b ₁ , 33b ₃ , 33b ₄ . First through thicker than the fourth light diffusing plate ₃₀ 1 to 30 first light diffusing plate 30 ₁ second to fourth light diffusing plate ₃₀ 2-30 ₄ located closest to the point light source 22 side of the _four In this case, for example, the _second to _fourth light diffusion plates 30 ₂ to 304 can be formed into a film shape as in the case of the first embodiment.

The light diffusing plate unit 21C shown in FIG. 9 can be applied to the surface light source device 20 and the transmissive image display device 1 instead of the light diffusing plate unit 21A in FIG. In this case, the transmission type image display device 1, the light diffusing plate unit 21C is to the extending direction of the convex portion 33 ₁ may be arranged such that the longitudinal direction of the screen, arranged to be laterally May be.

In the optical diffusing plate unit 21C, the second light diffusing plate 30 ₂ to the first upper light diffusion plate 30 ₁ is provided satisfy the placement condition (ii) and (iv), the third light fourth light diffusing plate 30 ₄ are provided meets the arrangement conditions (iii) and (v) the upper side of the diffusion plate 30 _3. In this arrangement, the first and second light diffusing plates 30 ₁ , 30 ₂ can convert the light from the point light source 22 into a linear light source having substantially uniform luminance by passing through them. The fourth light diffusing plates 30 ₃ and 30 ₄ can also be converted into a linear light source having substantially uniform luminance when light from the point light source 22 passes through them.

In the light diffusing plate unit 21C, the first and second light diffusing plates 30 ₁ and 30 ₂ and the third and fourth light diffusing plates 30 ₃ and 30 ₄ are arranged according to the arrangement condition (vi ) Is arranged. That is, the extending direction of the convex portion 33 ₁ (or the convex portion 33 ₂ ) and the extending direction of the convex portion 33 ₃ (or the convex portion 33 ₄ ) are arranged so as to be substantially orthogonal.

  Therefore, when the light diffusing plate unit 21C is used instead of the light diffusing plate unit 21A of FIG. 1, the light from the plurality of point light sources 22 is the light diffusing plate unit as in the case of the first embodiment. By passing through 21C, it is possible to generate planar light that is uniformly dispersed and, as a result, has a higher luminance uniformity in a plane orthogonal to the z direction.

  Accordingly, the surface light source device 20 and the transmissive image display device 1 including the light diffusing plate unit 21C and the plurality of point light sources 22 also have the same operational effects as in the case of the first embodiment.

Further, even in the light diffusion plate unit 21C, as in the case of the light diffusion plate unit 21A, since the third and fourth light diffusing plate 30 _3, 30 ₄ may be of the same construction as a film-like, production Cost can be reduced. Therefore, when the light diffusing plate unit 21C is applied to the surface light source device 10 and the transmissive image display device 1 instead of the light diffusing plate unit 21A, the manufacturing cost of the surface light source device 10 and the transmissive image display device 1 is reduced. be able to.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. In the above embodiment, the arrangement examples of the plurality of point light sources 22 are shown in FIGS. 2 and 3. For example, a square lattice, that is, between the point light sources 22 adjacent to each other in the x direction and the y direction as described above. The interval may be the same. Moreover, although the end 33a ₁ in the cross-sectional shape of the adjacent convex portion 33 ₁ has been described as overlapping in the arrangement direction of the convex portion 33a ₁ , it is slightly flat between the ends 33a _{1 of the} adjacent convex portions 33 _1. A part (for example, a part caused by a manufacturing error) may be generated. This also applies to each of the arrangement of the convex portion ₃₃ 2-33 _4. Moreover, the light diffusing plate units 21A to 21C may further include an optical film such as a diffusion film, a microlens film, or a reflective polarizing film on the transmissive liquid crystal display unit 10 side (for example, the liquid crystal panel side). . In addition, the transmissive image display device 1 further includes an optical film such as the above-described diffusion film, microlens film, or reflective polarizing film between the light diffusion plate units 21 </ b> A to 21 </ b> C and the transmissive liquid crystal display unit 10. It can also be configured.

  Furthermore, the surface light source device 20 and the transmissive image display device 1 may include a reflection unit such as a reflection plate that reflects the light output from the point light source 22 toward the light diffusion plate units 21A to 21C. In the schematic diagram shown in FIG. 1, the reflection means may be provided on the side opposite to the light diffusing plate units (light control plate units) 21 </ b> A to 21 </ b> C with respect to the point light source 22, for example, holding the point light source 22. The light source placement surface of the holding member for doing so can be a reflective surface.

In the description of the convex portion ₃₃ to 333 ₄ of the cross-sectional shape having the first to fourth light diffusing plate ₃₀ 1 to 30 ₄ respectively, _{h a} in the formula (8), _{h a} is 0.32 W _a or 0 is a constant that satisfies the following .97w _{a, k a} was a constant satisfying 0.75 -1.00 or more. However, the convex portions ₃₀ 1 to 30 ₄ in which at least one of the first to fourth light diffusing plate ₃₀ 1 to 30 ₄ has, _{h a} is, 0.32 W _a or from the scope of the _{h a} 0.80 W _a constant satisfies a range excluding the range of, or, k _a can also be a constant satisfying a range excluding -1.00 or more and 0.23 or less from the scope of the k _a.

Further, the first to fourth light control plate, was described as the first to fourth light diffusing plate 30 ₁ to 30 ₄ as an example, the first to fourth light control plate, the light of various directions convex portion 33 1 for dispersing the light by deflecting the _convex portion 33 _2, the convex portion 33 ₃ and the convex portion 33 ₄ is also said that the deflection structure plate formed respectively on the emission surface side. The first to fourth light control plates are arranged so that the light output from the plurality of point light sources is more uniformly dispersed to generate linear light, and the convex portion 33 ₂ , convex Jo portion 33 ₃ and the convex portion 33 ₄ may if the shaped plate-like optical component, respectively. In this case, the light control plate unit can be configured such that the four optical components are arranged in the relationship described using the light diffusion plate units 21A, 21B, and 21C. In addition, although demonstrated as plate shape, the thing of a film form and a sheet form is also included according to thickness.

  Further, in the light control plate unit having four light control plates as shown in FIGS. 5, 8, and 9, the light control plate located closest to the point light source has a thickness of 1.0 mm or more. It can be made into a sheet form. In this case, an extrusion molding method can be used for manufacturing the light control plate. As the material of the light control plate, polystyrene or polycarbonate having a refractive index of about 1.56 to 1.62 can be used. Moreover, light control boards other than the light control board located in the most point light source side can be made into a film-like thing less than 1.0 mm in thickness. In this case, a photopolymer method can be used for shaping the convex portion. As the material of the light control plate, an acrylic ultraviolet curable resin having a refractive index of 1.46 to 1.58 can be used. From the viewpoint of cost and prevention of yellowing deterioration of the film, the refractive index is about 1.51. It is preferable to use a low refractive index resin.

  In the light control plate unit having four light control plates as shown in FIGS. 5, 8, and 9, the light control plate located closest to the point light source is a sheet having a thickness of 1 mm or more and 5 mm or less. The light control plate other than the light control plate located closest to the point light source is preferably a film having a thickness of less than 1 mm.

1 ... transmission type image display apparatus, 10 ... transmission type image display unit, 20 ... surface light source device, 21A to 21C ... light diffuser plate unit (light control plate unit), 22 ... point light source, ₃₀ 1 to 30 4 _... first 1st to 4th light diffusing plate (1st to 4th light control plate), 31 _{1 to} 31 ₄ ... lower surface of the 1st to 4th light diffusing plate (first of the 1st to 4th light control plates) ), 32 _{1 to} 32 ₄ ... Upper surface of the first to fourth light diffusion plates (second surface of the first to fourth light control plates), 33 _i ... Convex portion (first to fourth) , 33 _{1 to} 33 ₄ ... Convex portions of the first to fourth light diffusion plates (convex portions of the first to fourth light control plates), 33 a _{1 to} 33 a _4. ... end of convex portion of first to fourth light diffusion plates (end of convex portion of first to fourth light control plates), Y1 ... extension direction of convex portion of first light control plate , X1 ... direction substantially orthogonal to Y1 direction, Y2 ... second Extending direction of the convex portion of the light control plate, X2 direction substantially orthogonal to the Y2 direction, X3 ... extending direction of the convex portion of the third light control plate, Y3 ... direction substantially orthogonal to the X3 direction, X4: Extension direction of the convex portion of the fourth light control plate, Y4: Direction substantially orthogonal to the X4 direction.

Claims (4)

A plurality of point light sources;
A light control plate unit provided on the plurality of point light sources;
With
The point light source is
A light distribution characteristic having a maximum emission light intensity I _max in a range of a light emission angle of 70 ° or more and 80 ° or less,
The outgoing light intensity I ₀ when the outgoing angle is 0 ° is
0.12 × I _max ≦ I ₀ ≦ 0.20 × I _max
Satisfy
The emission angle at which the emission light intensity is (I ₀ + I _max ) / 2 is 60 ° or more and 70 ° or less, and
The emission angle at which the emission light intensity is (I ₀ + I _max ) / 4 is 47.5 ° or more and 57.5 ° or less.
Having the light distribution characteristics;
The light control plate unit is
Light incident from the first surface can be emitted from the second surface located on the opposite side of the first surface, and extends in one direction and is substantially perpendicular to the one direction. A plurality of convex portions arranged in parallel are provided with first to fourth light control plates formed on the second surface,
The first light control plate, the second light control plate, the third light control plate, and the fourth light control plate have a second light control plate on the upper side of the first light control plate. And is provided in the plate thickness direction so that the fourth light control plate is located above the third light control plate,
The first surface of the second light control plate is located on the second surface side of the first light control plate;
The extending direction of the convex portion of the second light control plate and the extending direction of the convex portion of the first light control plate are substantially parallel.
The first surface of the fourth light control plate is located on the second surface side of the third light control plate;
The extending direction of the convex portion included in the fourth light control plate and the extending direction of the convex portion included in the third light control plate are substantially parallel.
The extending direction of each of the convex portions of the first and second light control plates and the extending direction of each of the convex portions of the third and fourth light control plates are substantially orthogonal. And
In the cross section perpendicular to the extending direction of each of the convex portions of the first to fourth light control plates, an axis passing through both ends is defined as a u-axis, and the u passes through the center between the both ends on the u-axis. When the axis perpendicular to the axis is the v-axis and the length in the u-axis direction is w _a for each of the convex portions of the first to fourth light control plates, the first to first in the cross section each of the contour shape of the convex portion having a fourth light control plate is expressed by v (u) satisfying the formula (1) in -0.475w _a ≦ u ≦ 0.475w _a,
Surface light source device.

However, in the formula (1),

(In the formula (2), _{h a} is a constant satisfying the following 0.32 W _a more 0.97w _{a, k a} is a constant satisfying 0.75 -1.00 or more.)   The surface light source device according to claim 1, wherein the first surface of each of the first to fourth light control plates is substantially flat. A plurality of point light sources;
A light control plate unit provided on the plurality of point light sources;
A transmission-type image display unit that is provided on the light control plate unit and that is irradiated with light emitted from the light control plate unit to display an image;
With
The point light source is
A light distribution characteristic having a maximum emission light intensity I _max in a range of a light emission angle of 70 ° or more and 80 ° or less,
The outgoing light intensity I ₀ when the outgoing angle is 0 ° is
0.12 × I _max ≦ I ₀ ≦ 0.20 × I _max
Satisfy
The emission angle at which the emission light intensity is (I ₀ + I _max ) / 2 is 60 ° or more and 70 ° or less, and
The emission angle at which the emission light intensity is (I ₀ + I _max ) / 4 is 47.5 ° or more and 57.5 ° or less.
Having the light distribution characteristics;
The light control plate unit is
Light incident from the first surface can be emitted from the second surface located on the opposite side of the first surface, and extends in one direction and is substantially perpendicular to the one direction. A plurality of convex portions arranged in parallel are provided with first to fourth light control plates formed on the second surface,
The first light control plate, the second light control plate, the third light control plate, and the fourth light control plate have a second light control plate on the upper side of the first light control plate. And is provided in the plate thickness direction so that the fourth light control plate is located above the third light control plate,
The first surface of the second light control plate is located on the second surface side of the first light control plate;
The extending direction of the convex portion of the second light control plate and the extending direction of the convex portion of the first light control plate are substantially parallel.
The first surface of the fourth light control plate is located on the second surface side of the third light control plate;
The extending direction of the convex portion included in the fourth light control plate and the extending direction of the convex portion included in the third light control plate are substantially parallel.
The extending direction of each of the convex portions of the first and second light control plates and the extending direction of each of the convex portions of the third and fourth light control plates are substantially orthogonal. And
In the cross section perpendicular to the extending direction of each of the convex portions of the first to fourth light control plates, an axis passing through both ends is defined as a u-axis, and the u passes through the center between the both ends on the u-axis. When the axis perpendicular to the axis is the v-axis and the length in the u-axis direction is w _a for each of the convex portions of the first to fourth light control plates, the first to first in the cross section each of the contour shape of the convex portion having a fourth light control plate is expressed by v (u) satisfying the following formula (3) in -0.475w _a ≦ u ≦ 0.475w _a,
Transmission type image display device.

However, in the formula (3),

(In the formula (4), _{h a} is a constant satisfying the following 0.32 W _a more 0.97w _{a, k a} is a constant satisfying 0.75 -1.00 or more.) Light incident from the first surface can be emitted from the second surface located on the opposite side of the first surface, and extends in one direction and is substantially perpendicular to the one direction. A plurality of convex portions arranged in parallel are provided with first to fourth light control plates formed on the second surface,
The first light control plate, the second light control plate, the third light control plate, and the fourth light control plate have a second light control plate on the upper side of the first light control plate. And is provided in the plate thickness direction so that the fourth light control plate is located above the third light control plate,
The first surface of the second light control plate is located on the second surface side of the first light control plate;
The extending direction of the convex part included in the second light control plate and the extending direction of the convex part included in the first light control plate are substantially parallel to each other. The first surface is located on the second surface side of the third light control plate,
The extending direction of the convex portion included in the fourth light control plate and the extending direction of the convex portion included in the third light control plate are substantially parallel.
The extending direction of each of the convex portions of the first and second light control plates and the extending direction of each of the convex portions of the third and fourth light control plates are substantially orthogonal. And
Each of the convex portions of the first to fourth light control plates has an axis passing through both ends in a cross section orthogonal to the extending direction of each of the convex portions of the first to fourth light control plates. Is the u-axis, and the axis that passes through the center between the both ends on the u-axis and is orthogonal to the u-axis is the v-axis, and the u-axis with respect to each of the convex portions of the first to fourth light control plates When the length in the axial direction is w _a , the contour shape of each of the convex portions of the first to fourth light control plates in the cross section is −0.475 w _a ≦ u ≦ 0.475 w _a It is represented by v (u) that satisfies the following formula (5).
Light control board unit.

However, in the formula (5),

In (Equation (6), _{h a} is a constant satisfying the following 0.32 W _a more 0.97w _{a, k a} is a constant satisfying 0.75 -1.00 or more. However, the first range in the least protruding portion having the one of the through fourth light control plate, the _{h a,} the from 0.32 W _a more 0.97W _a following range of not less than 0.32 W _a or 0.80 W _a for the either removed, or _{k a,} the -1.00 0.75 0.23 the range -1.00 or more of the following ranges are excluded)

Images