WO2012036161A1

WO2012036161A1 - Light control plate unit, planar light source device, and transmissive image display device

Info

Publication number: WO2012036161A1
Application number: PCT/JP2011/070876
Authority: WO
Inventors: 寛史太田; 川口　裕次郎; 武志川上
Original assignee: 住友化学株式会社
Priority date: 2010-09-15
Filing date: 2011-09-13
Publication date: 2012-03-22
Also published as: JP2012063539A; TW201222082A

Abstract

Provided is a planar light source device that uniformly distributes light from a point light source. The planar light source device (10) comprises a plurality of point light sources (22) with prescribed light distribution characteristics and first to third light control plates (301 - 303) disposed in the plate thickness direction. Each light control plate has a plurality of protruding sections (331 - 333) extending in one direction. The parallel protruding sections (332, 333) and the extension direction of the protruding section (331) are substantially orthogonal to each other and the profile shape (v(u)) in a uv coordinate system, when an axis line that passes through both ends of the orthogonal cross section in the extension directions of each protruding section is the u axis, fulfills 0.95vo(u)≦v(u)≦1.05vo(u). vo(u) fulfills formula (1). (wa is the width of each protruding section. ha is 0.40wa-1.60wa for the protruding section (331) and 0.32wa-0.97wa for the protruding sections (332, 333). ka is -1-0.25 for the protruding section (331) and -1-0.75 for the protruding sections (332, 333).)

Description

Light control plate unit, surface light source device, and transmissive image display device

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. 12, a device in which a light source 43 is arranged on the back side of the transmission type image display unit 10 is widely used. 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: JP-A-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 capable of sufficiently uniformly dispersing light from a point light source.

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. Further, 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 The first to third light control plates each having a plurality of convex portions extending in the direction and arranged in parallel in a direction substantially orthogonal to the one direction are provided on the second surface. (D) The thickness of the first light control plate, the second light control plate, and the third light control plate is such that the third light control plate is positioned above the second light control plate. (E) the first surface of the third light control plate is located on the second surface side of the second light control plate, and (F) the second light control plate. The extending direction of the convex portion of the first light control plate is substantially parallel to the extending direction of the convex portion of the third light control plate, and (G) the extending direction of the convex portion of the first light control plate. And the extending direction of the convex portion of the second or third light control plate are substantially orthogonal to each other. In addition, an axis passing through both ends in a cross section perpendicular to the extending direction of each of the convex portions of the first to third light control plates is defined as a u axis, and the center between the both ends on the u axis is defined as the u axis. When the orthogonal 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 third light control plates, the first to third lights in the cross section are as follows. The contour shape of each convex portion of the control plate is represented by v (u) satisfying the following formula (1) when −0.475 w _a ≦ u ≦ 0.475 w _a .

However, in Formula (1),

(In Formula (2), h _a is _a constant that satisfies 0.40 w _a or more and 1.60 w _a or less with respect to the convex portion of the first light control plate, and k _a is −1.00 or more and is a constant satisfying 0.25 or less. Further, in the equation (2), for each of the convex portions of the second and third light control plate, _{h a} is, 0.32 W _a more 0.97W _a And k _a is _a constant satisfying −1.00 and 0.75.

In this configuration, light that has passed through the second light control plate enters the third light control plate and is emitted. Since the convex portion of the first light control plate has the cross-sectional shape described above, the first light control plate converts light from the point light source having the above-described light distribution characteristics into linear light with uniform luminance. Can be converted to Similarly, since the convex portions of the second and third light control plates have the above-described cross-sectional shape, the second and third light control plates are arranged on the point light source. When the extending directions of the convex portions of the light control plate are arranged substantially in parallel, the light from the point light source can be converted into linear light with uniform luminance. In the surface light source device according to the present invention, the extending direction of the convex portion of the first light control plate and the extending direction of the convex portion of the second or third light control plate are substantially orthogonal to each other. In addition, a first light control plate and a set of second and third light control plates are arranged. For this reason, the light of the point light source incident on the light control plate unit has a uniform luminance in a direction substantially orthogonal to each other by the first light control plate and the set of the second and third light control plates. Converted to linear light. 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 third light control plates can be substantially flat.

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. In addition, 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 opposite side of the first surface, and The first to third light control plates each having a plurality of convex portions extending in one direction and arranged in parallel in a direction substantially orthogonal to the one direction are provided on the second surface. (D) The thickness of the first light control plate, the second light control plate, and the third light control plate is such that the third light control plate is positioned above the second light control plate. (E) the first surface of the third light control plate is located on the second surface side of the second light control plate, and (f) the second light control plate. The extending direction of the convex portion of the first light control plate is substantially parallel to the extending direction of the convex portion of the third light control plate, and (g) the extending direction of the convex portion of the first light control plate. And the extending direction of the convex portion of the second or third light control plate are substantially orthogonal to each other. In addition, an axis passing through both ends in a cross section perpendicular to the extending direction of each of the convex portions of the first to third light control plates is defined as a u axis, and the center between the both ends on the u axis is defined as the u axis. When the orthogonal 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 third light control plates, the first to third lights in the cross section are as follows. The contour shape of each convex portion of the control plate is represented by v (u) that satisfies the following expression (3) when −0.475 w _a ≦ u ≦ 0.475 w _a .

However, in Formula (3),

(In Expression (4), h _a is _a constant that satisfies 0.40 w _a or more and 1.60 w _a or less with respect to the convex portion of the first light control plate, and k _a is −1.00 or more and is a constant satisfying 0.25 or less. Further, in the equation (4), for each of the convex portions of the second and third light control plate, _{h a} is, 0.32 W _a more 0.97W _a (K _a is _a constant satisfying −1.00 and 0.75)

In this transmissive image display device, light that has passed through the second light control plate enters and exits the third light control plate. Since the convex portion of the first light control plate has the cross-sectional shape described above, the first light control plate converts light from the point light source having the above-described light distribution characteristics into linear light with uniform luminance. Can be converted to Similarly, since the convex portions of the second and third light control plates have the above-described cross-sectional shape, the second and third light control plates are arranged on the point light source. When the extending directions of the convex portions of the light control plate are arranged substantially in parallel, the light from the point light source can be converted into linear light with uniform luminance. In the light control plate unit according to the present invention, the extending direction of the convex portion of the first light control plate is substantially orthogonal to the extending direction of the convex portion of the second or third light control plate. As described above, a first light control plate and a set of second and third light control plates are arranged. For this reason, the light of the point light source incident on the light control plate unit has a uniform luminance in a direction substantially orthogonal to each other by the first light control plate and the set of the second and third light control plates. Converted to linear light. 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.

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. The first light control plate, the second light control plate, and the second light control plate have a plurality of convex portions arranged in parallel in a direction substantially orthogonal to one direction. The light control plate and the third light control plate are provided in the plate thickness direction so that the third light control plate is located above the second light control plate. 1 surface is located on the second surface side of the second light control plate, the extending direction of the convex portion of the second light control plate and the extension of the convex portion of the third light control plate. The extending direction of the convex portion included in the first light control plate is substantially orthogonal to the extending direction of the convex portion included in the second or third light control plate. , Have first to third light control plate In the cross section orthogonal to the extending direction of each of the convex portions, an axis passing through both ends is defined as a u axis, and an axis passing through the center between the both ends on the u axis and orthogonal to the u axis is defined as a v axis. When the length in the u-axis direction is w _a for each of the convex portions of the light control plate, the contour shape of each of the convex portions of the first to third light control plates in the cross section is − It is represented by v (u) that satisfies the following formula (5) in 0.475 w _a ≦ u ≦ 0.475 w _a .

However, in the formula (5),

(In Expression (6), h _a is _a constant that satisfies 0.40 w _a or more and 1.60 w _a or less with respect to the convex portion of the first light control plate, and k _a is −1.00 or more and is a constant satisfying 0.25 or less. Further, in the equation (6), for each of the convex portions of the second and third light control plate, _{h a} is, 0.32 W _a more 0.97W _a is a constant that satisfies the following, _{k a} is a constant satisfying -1.00 or more and 0.75 or less. However, in the convex portion of the first light control plate, for _{k a} -1.00 or 0. 25 of the following -1.00 or -0.15 or less in the range of range is removed, or, in at least one of the convex portions of the second and third light control plate, 0.32 W for _{h a} the range 0.32 W _a or 0.80 W _a is removed from 0.97W _a following range of _a Luke, or a range of -1.00 or 0.23 or less from the scope of -1.00 to 0.75 for _{k a} is removed.)

In this configuration, light incident from the first surface of the first light control plate is emitted from the second surface. Then, the light emitted from the second surface of the first light control plate enters the first surface of the second light control plate and is emitted from the second surface of the second light control plate. Each of the first and second light control plates of the light control plate unit has a plurality of convex portions formed on the second surface. Since the convex portion of each of the first and second light control plates has a cross-sectional shape represented by v (u) that satisfies the above formula (5), the first and second light control plates are The light from the point light source having the light distribution characteristics described above can be converted into light that is linear light and has substantially uniform brightness in the extending direction. And in the light control board unit which concerns on this invention, it arrange | positions so that the extension direction of the convex part which each of the 1st and 2nd light control board has may be substantially orthogonal. Therefore, the light control plate unit can emit light from the point light source as planar light by sufficiently uniformly dispersing it.

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 light control board of the light control board unit shown in FIG. 5 has. It is drawing for demonstrating the conditions which the cross-sectional shape of the convex part which the 1st light control board of the light control board unit shown in FIG. 5 has satisfies. FIG. 6 is a view for explaining a cross-sectional shape of a convex portion included in the second and third light control plates of the light control plate unit shown in FIG. 5. It is drawing for demonstrating the conditions which the cross-sectional shape of the convex part which the 2nd and 3rd light control board of the light control board unit shown in FIG. 5 has satisfies. 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 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.

Light diffusing plate unit 21A includes a first light diffusing plate 30 _1, a second light diffusion plate 30 ₂ and the third light diffusing plate 30 ₃ arranged in this order in the thickness direction (z-direction).

The first to third light diffusing plates 30 ₁ to 30 ₃ constituting the light diffusing plate unit 21A have substantially the same shape in plan view (the shape seen from the z direction), and are usually rectangular. The planar view shape of the first to third light diffusion plates 30 ₁ to 30 ₃ , in other words, the size of the planar view shape of the light diffusion plate unit 21 A matches the target screen size of the transmissive image display device 1. Usually, it is 250 mm × 440 mm or more, preferably 1020 mm × 1800 mm or less. The shape of the first to third light diffusion plates 30 ₁ to 30 ₃ in plan view is not limited to a rectangle but may be a square, but in the following, it will be described as a rectangle 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 interval Lx and the interval Ly can be the distance between the light emitting portions of the point light source 22, and are usually 10 mm to 150 mm.

Further, 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 showing 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). With reference to FIG. 5, the first to third light diffusion plates 30 ₁ , 30 ₂ , 30 ₃ constituting the light diffusion plate unit 21A will be described. In Figure 5, for purposes of explanation, although spaced apart first to third light diffusing plate 30 _1-30 _3, as described later, the second to the first upper light diffusion plate 30 ₁ The third light diffusing plates 30 ₂ and 30 ₃ may be provided so that two adjacent plates contact each other.

[First light diffuser]
The first light diffusion plate 30 _1, ₁ a substantially planar lower surface (first surface of the first light control plate) 31, the outer convex portion is convex (second light diffusion plate 30 ₂ side) it is a (first convex portion of the light control plate) 33 ₁ is formed with a plurality of upper surface (second surface of the first light control plate) 32 ₁ and the plate-like body having a. The first light diffusion plate 30 ₁ is, for example, a light diffusion plate for dispersing the light by the difference of the emission position of the light from the convex portion 33 _1. The first light diffusion plate 30 _1, since the deflecting direction of light emission by emitting position of light from the convex portion 33 _1, deflecting plate both the shape to adjust the deflection of the light is applied I can say that. Here, although referred to as “plate”, 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 and 33a ₁ of the two adjacent convex portions 33 ₁ and 33 ₁ are at the same position in the X1 direction. First thickness d1 of the light diffusion 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, typically a 0.1 mm ~ 5 mm.

[Second light diffuser]
The second light diffusion plate 30 ₂ is substantially the (first surface of the second light control plate) 31 ₂ flat lower surface, an outer convex portion is (third light diffuser 30 ₃ side) in a convex is a (second convex portion of the light control plate) 33 ₂ is formed with a plurality of upper surface (second second surface of the light control plate) 32 ₂ and the plate-like body having a. The second light diffusion plate 30 _2, for example, a light diffusion plate for dispersing the light by the difference of the emission position of the light from the convex portion 33 _1. The second light diffusion plate 30 _2, since the deflecting direction of light emission by emitting position of light from the convex portion 33 _2, deflecting plate both the shape to adjust the deflection of the light is applied I can say that. Here, although referred to as “plate”, it may be in the form of a sheet or film depending on the thickness. Convex portion 33 ₂ extend in substantially parallel direction X2 in the x-direction (first direction of the second light control plate), first in the Y2 direction (the second light control plate substantially orthogonal to the X2 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 are in the same position in the Y2 direction. The second thickness d2 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, typically a 0.1 mm ~ 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 is convex outwardly (second light diffusion plate 30 ₂ and the opposite side) convex Jo unit is a (third convex portion of the light control plate) 33 ₂ is formed with a plurality of upper surface (3 of the second surface of the light control plate) 32 ₃ and the plate-like body having a. Third light diffusing plate 30 _3, a first light diffusing plate 30 ₁ in the same manner as in the light diffusing plate, it can be said that the deflection structure plate. Here, although referred to as “plate”, 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. Third thickness d3 of the light diffusion plate 30 ₃ are the z-direction distance between the lower surface ₃₁₃ and the convex portion 33 ₃ of the top 33b _3, usually a 0.1 mm ~ 5 mm.

[Convex part of first light diffusion plate]
The shape of the convex portion 33 ₁ in which the first light diffusing plate 30 ₁ has will be described. Convex portion 33 _1, when placing the first light diffusing plate 30 ₁ on the point light source 22 having a light distribution characteristic which has been described with use of FIG. 4, the light from the point light source 22, luminance Has a cross-sectional shape that can be converted into substantially uniform linear light. The cross-sectional shape of the convex portion 33 ₁ will be described with reference to FIG.

6 is set to _u I _{v I} coordinate system and the direction orthogonal to the extending direction of the convex portion 33 ₁ as _{u I} axis (u-axis). _{U I} axis direction with respect to the convex portion 33 ₁ corresponds to the X1 direction, _{v I} axis (v-axis) direction corresponds to the z-direction.

In the u _I v _I coordinate system, the cross-sectional shape of the convex portion 33 ₁ has both ends 33a ₁ and 33a ₁ on the u _I axis. Convex portion 33 ₁ of the contour line is represented by _v I _{(u I)} that satisfies the following expression (7).

However, in Formula (7),

In the formula _{(8), w Ia} is the length of the convex portion 33 ₁ of _{u I} axis. h _Ia corresponds to the maximum height between two ends 33a _1, 33a ₁ of the convex portion 33 _{_1, h Ia} is a constant satisfying the following 0.40 W _Ia or 1.60 W _Ia. That is, h _Ia is a constant that satisfies h _Ia / w _Ia from 0.40 to 1.60. k _Ia is a constant satisfying −1.00 or more and 0.25 or less. Width _{w Ia} of the convex portion 33 _1, since formation of the convex portion 33 ₁ is easy, usually 40μm or more, preferably 250μm or more, the pattern caused by the convex portion 33 ₁ 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 _1a include w _Ia = 410 μm, w _Ia = 400 μm, and w _Ia = 325 μm, but the value of w _Ia is not limited thereto.

Figure 6 illustrates a predetermined factor only stretch shape equation v _{I0 (u} _I) within a range satisfying (7) in the v _I direction as an example of the cross-sectional shape of the convex portion 33 _1. In this case, the convex portion 33 ₁ has a symmetrical contour relative to _{v I} axis. The cross-sectional shape shown in FIG. 6 corresponds to v _I0 (u _I ) when h _Ia / w _Ia = 0.55 and k _Ia = −0.25. However, the sectional shape of the convex portion 33 _1, as shown in FIG. 7, when determining the _v I0 _{(u I)} for a width _{w Ia,} represented by _0.95v I0 _{(u I)} Any contour line may be used as long as it passes through a region between the contour line and the contour line represented by 1.05v _I0 (u _I ). Also in v _I0 (u _I ) shown in FIG. 7, h _Ia / w _Ia = 0.55 and k _Ia = −0.25.

Further, in the above description, the cross-sectional shape of the convex portion 33 ₁ is to be represented by _v I _{(u I)} satisfying the equation (7). However, considering the effect on the manufacturing error and the intensity distribution at near both ends of the convex portion 33 _1, the cross-sectional shape of the convex portion 33 _1, in -0.475w _{_Ia} ≦ _{u I} ≦ 0.475w _Ia need only be represented by the formula (7) satisfies the _v I _{(u I).}

The range of h _Ia / w _Ia and k _Ia only needs to satisfy the above-described range. The distance between two adjacent point light sources 22 is L, and the light diffusing plate from the light emitting part of the point light source 22 is used. 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 control plate 30 ₁ in FIG. 1 or 5) is D, h _Ia / preferable for L / D The ranges of w _Ia and k _Ia are as shown in Table 1 below. L described in Table 1 is Lx for contour shape of the convex portion 33 _1.

[Convex portions of second and third light diffusion plates]
The shape of the convex portions 33 ₂ and 33 _{3 included in} each of the second and third light diffusion plates 30 ₂ and 30 ₃ will be described.

The convex portions 33 ₂ and 33 ₃ are provided with the second and third light control plates 30 ₂ and 30 ₃ in this order on the point light source 22 having the light distribution characteristics described with reference to FIG. When the shape portions 33 ₂ and 33 ₃ are arranged with their extending directions substantially parallel, they have a cross-sectional shape that can convert light from the point light source 22 into linear light having substantially uniform luminance. The cross-sectional shapes of the convex portions 33 ₂ and 33 ₃ will be described with reference to FIG.

Here, the convex portions 33 ₂ and 33 ₃ will be referred to as convex portions 33 _i (i is 2 or 3) unless otherwise specified. In FIG. 8, the u _II v _II coordinate system is set with the direction orthogonal to the extending direction of the convex portion 33 _i as the u _II axis (u axis). _{U II-axis} direction corresponding to the convex portion 33 ₂ and the convex portion 33 _3, respectively corresponding to the Y2 direction and the Y3 direction. Further, _{v II} axis corresponding to the convex portion 33 ₂ and the convex portion 33 ₃ (v-axis) direction both correspond to the z-direction.

In the u _II v _II 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 _II axis. The contour line of the convex portion 33 _i is represented by v _II (u _II ) that satisfies the following formula (9).

However, in Formula (9),

In Formula (10), w _IIa is the length of the convex portion 33 _{i in} the u _II axis direction. h _IIa corresponds to the maximum height between the two ends 33a _i, 33a _i of the convex portion 33 _{_i, h IIa} is a constant satisfying the following _{0.32 W IIa} or _{0.97w IIa.} That is, h _IIa is a constant that satisfies h _IIa / w _IIa from 0.32 to 0.97. k _IIa is a constant satisfying −1.00 or more and 0.75 or less. Width _{w IIa} 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 _IIa include w _IIa = 410 μm, w _IIa = 400 μm, and w _IIa = 325 μm, but the value of w _IIa is not limited thereto.

FIG. 8 illustrates a shape in which v _II0 (u _II ) is _{expanded and} contracted by a predetermined multiple in the v _II direction within the range satisfying Expression (9) as an example of the cross-sectional shape of the convex portion 33 _i . In this case, the convex portion 33 _i _has a symmetrical contour relative _{v II} axis. The cross-sectional shape shown in FIG. 8 corresponds to v _II0 (u _II ) when h _IIa / w _IIa = 0.45 and k _IIa = −0.20. However, the cross-sectional shape of the convex portion 33 _i is represented by 0.95v _II0 (u _II ) when v _II0 (u _II ) is determined for a certain width w _IIa as shown in FIG. _Any contour line may be used as long as it passes through a region between the contour line and the contour line represented by 1.05v _II0 (u _II ). Also in v _II0 (u _II ) shown in FIG. 9, h _IIa / w _IIa = 0.45 and k _IIa = −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 _II (u _II ) that satisfies the formula (9). 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, in -0.475w _{_IIa} ≦ _{u II} ≦ 0.475w _IIa need only be represented by the formula (9) satisfies the _v II _{(u II).}

The range of h _IIa / w _IIa and k _IIa only needs to satisfy the above-described range. The distance between two adjacent point light sources 22 is L, and the light diffusing plate from the light emitting portion of the point light source 22 is used. 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 diffusion plate 30 ₁ in FIG. 1 or FIG. 5) is D, h _IIa / preferable for L / D The ranges of w _IIa and k _IIa are shown in Table 2. L shown in Table 2 is Ly for the contour shape of the convex portions 33 ₂ and 33 ₃ .

Convex portion

₃₃ 2 of the second and third light diffusion plate 30 ₂ and 30 _3, 33 ₃ _w _{_IIa,} h _IIa, _k IIa is preferably the same between the respective convex portions ₃₃ 2, 33 ₃ But it can be different. That is, it is preferable that the cross-sectional shapes of the convex portions 33 ₂ and 33 _{3 included in} each of the second and third light diffusion plates 30 ₂ and 30 ₃ are the same cross-sectional shape. Different cross-sectional shapes may be used as long as the contour lines of the cross-sectional shapes of 33 ₂ and 33 ₃ satisfy the above formula (9).

[Layer structure of the first to third light diffusion plates]
The first to third light diffusion plates 30 ₁ to 30 ₃ may be single-layer plates made of a single transparent material, or may have a multilayer structure in which layers made of different transparent materials are laminated. A multilayer board may be sufficient. When the first to third light diffusion plates 30 ₁ to 30 ₃ are multilayer plates, one or both sides of the first to third light diffusion plates 30 ₁ to 30 ₃ 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 third light diffusion plates 30 ₁ to 30 ₃ from being deteriorated by the point light source 22 and ultraviolet rays that may be included in light from the outside. When a light source 22 having a relatively large proportion of ultraviolet rays is used, it is preferable to form a skin layer on the lower surfaces 31 ₁ to 31 ₃ , since deterioration due to ultraviolet rays can be prevented. At this time, the upper surface 32 ₁ that the ~ 32 ₃ not formed skin layer is further preferred in terms of cost. When a transparent resin material to which an ultraviolet absorber is added is used as the transparent resin material constituting the skin layer, the content thereof 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.

Also, 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 configured as described above with 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. Alternatively, the mat layer may be formed by applying a coating solution containing a matting agent and a binder.

The first to third light diffusion plates 30 ₁ to 30 ₃ 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 third light diffusion plates 30 ₁ to 30 ₃ are made of a transparent material. The refractive index of the transparent material is usually 1.46 to 1.62. Examples of transparent materials include transparent resin materials and transparent glass materials. Examples of transparent resin materials include polycarbonate resin (refractive index: 1.59), MS resin (methyl methacrylate-styrene copolymer resin) (refractive index: 1.56 to 1.59), polystyrene resin (refractive index: 1.59), AS resin (acrylonitrile-styrene copolymer resin) (refractive index: 1.56 to 1.59), acrylic ultraviolet curable resin ( A refractive index of 1.46 to 1.58) is exemplified, and a 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 meter 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 third light diffusing plates 30 ₁ to 30 ₃ 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. .

[Methods for producing first to third light diffusing plates]
The first to third light diffusion plates 30 ₁ to 30 ₃ can be manufactured by, for example, 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 third light diffusion plates]
The first to third light diffusion plates 30 ₁ to 30 ₃ are provided so as to satisfy the following conditions in the z direction and to allow light to enter from the lower surface 31 ₁ , 31 ₂ , 31 ₃ side.
(i) third of the light diffusion plate 30 ₃ is located above the second light diffusion plate 30 _2.
(ii) a third lower surface ₃₁₃ of the light diffusion plate 30 ₃ is located in the second upper surface 32 ₂ side of the light control pair 30 _2.
(iii) convex portions ₃₃ 2, 33 ₃ in the extending direction are substantially parallel.
(iv) the extending direction of the convex portion 33 _1, and the extending direction of the convex portion 33 ₂ or convex portion 33 ₃ are substantially orthogonal. Incidentally, the angle of the convex portion 33 ₁ of the extending direction and the convex portion 33 ₂ (or convex portion 33 _3), 80 ° ~ 100 ° are exemplified, and preferably, 90 °.

In the present embodiment, the first to third light diffusion plates 30 ₁ to 30 ₃ satisfy the arrangement conditions (i) to (iv), and the first light diffusion plate 30 ₁ and the second light diffusion plate It is provided in the z direction in the order of 30 ₂ and the third light diffusing plate 30 _3.

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.

From the viewpoint of the light diffusing plate unit 21A and compact _{ones, d 12} and _{d 23} are 0 mm, the second light diffusion plate 30 ₂ and the first upper convex portion 33 ₁ of the light diffusing plate 30 ₁ third light diffusing plate 30 _3, the upper of the lower surface ₃₁ 2, 31 ₃ may be arranged in contact with the top _33b 1, 33b ₂ of the lower convex portion ₃₃ 1, 33 _2. Thus, the first light diffusion plate 30 2 of the second and third on the light diffusing plate 30 _{_1,} 30 ₃ positioned closest to the point light source 22 side in the light diffuser plate unit 21A, two adjacent light When the upper and lower plates of the diffusion plates 30 ₁ to 30 ₃ are provided so as to contact each other, the thicknesses d2 and d3 of the second and third light diffusion plates 30 ₂ and 30 ₃ are set to the first light. it is preferable to use a thinner than the thickness d1 of the diffusion plate 30 _1. For example, the second and third light diffusion plate ₃₀ 2, if the 30 ₃ was assumed thinner such film-like, the first light diffusing plate 30 ₁ and the second and third light diffusion plate ₃₀ 2, 30 ₃ It is because it can be used as a support base for.

[Arrangement of light diffuser unit]
Light diffusing plate unit 21A having a first through third light diffusing plate ₃₀ 1-30 ₃ having the above-described structure, a distance D from the point light source 22 to the lower surface 31 of the _first light diffuser 30 _1, usually It is arranged on the point light source 22 so as to be 3 mm to 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, and X3 directions are parallel to the x direction, and the Y1, Y2, and Y3 directions are parallel to the y direction.

The first convex portion 33 ₁ of the light diffusing plate 30 _1, because it has a cross sectional shape represented by _v I _{(u I)} satisfying the equation (7), the first light diffusing plate on the point light source 22 when placing the 30 _1, the first light diffusing plate 30 _1, the light output from the point light sources 22, brightness can be emitted into a uniform linear light. In addition, since the convex portions 33 ₂ and 33 _{3 of} the second and third light diffusion plates 30 ₂ and 30 ₃ have a cross-sectional shape represented by v _II (u _II ) that satisfies Expression (9), When the second and third light diffusing plates 30 ₂ and 30 ₃ are arranged on the light source 22 so that the extending directions of the convex portions 33 ₂ and 33 ₃ are substantially parallel to each other, The light diffusing plates 30 ₂ and 30 ₃ can emit the light output from the point light source 22 by converting it into linear light with uniform luminance.

Then, the light diffuser plate unit 21A, as described above, the light diffusion plate 30 ₁ first convertible to a substantially uniform linear light luminance light from the point light source 22, the second and third In the z direction, the extending direction of the convex portion 33 _{1 and} the extending direction of the convex portion 33 ₂ (or the convex portion 33 ₃ ) are substantially orthogonal to each other in the set of the light diffusion plates 30 ₂ and 30 _3. Are arranged as follows. Therefore, the light from the point light sources 22, a first light diffuser 30 _1, the second and third set of the light diffusion plate 30 _2, 30 _3, respectively line substantially perpendicular direction with uniform brightness Is converted into light. 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.

Further, when the second and third light diffusion plate 30 _2, 30 ₃ provided in the first upper light diffusion plate 30 ₁ into a film-like, in the configuration of the present embodiment, the second and third light diffusing plate 30 ₂ and 30 ₃ 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 disperses the light from the plurality of point light sources 22 and has higher luminance uniformity on 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 third light diffusion plates 30 ₁ to 30 ₃ are provided in order in the z direction. However, the first to third light diffusion plates 30 ₁ to 30 ₃ are arranged according to the arrangement conditions. It may be provided in the z direction so as to satisfy (i) to (iv). Other embodiments of the light diffusing plate unit according to the modified example of the arrangement of the first to third light diffusing plates 30 ₁ to 30 ₃ will be described as second and third embodiments.

(Second Embodiment)
FIG. 10 is a perspective view showing a second embodiment of the light diffusing plate unit (light control plate unit) according to the present invention. The light diffusing plate unit 21B includes first to third light diffusing plates 30 ₁ , 30 ₂ , 30 ₃ as in the case of the first embodiment. The light diffusion plate unit 21B is different from the light diffusion plate unit 21A in the order of arrangement of the first to third light diffusion plates 30 ₁ to 30 ₃ . This difference will be mainly described.

In the light diffusing plate unit 21B, are provided in the z direction in the order of the second light diffusion plate 30 _2, the first light diffusing plate 30 ₁ and the third light diffusing plate 30 _3. Configuration of the first to third light diffusing plate ₃₀ 1-30 ₃ are the same as the first to third light diffusing plate ₃₀ 1-30 ₃ configuration in the first embodiment. In the first embodiment, the first light diffusing plate 30 ₁ is to be located most point light source 22 side in the light diffuser plate unit A, the first lower surface 31 ₁ and the point of the light diffusion plate 30 ₁ The distance from the light source 22 was defined as D. In contrast, in the first to third order of arrangement of the light diffusing plate 30 _1-30 ₃ of the present embodiment, the second light diffusion plate 30 ₂ is located at the most point light source 22 side. Therefore, the distance D in the description of the first embodiment, in this embodiment, the distance between the second light diffusion plate 30 ₂ of the lower surface 31 ₂ and the point light sources 22.

In the optical diffusing plate unit 21B, it is substantially parallel to the extending direction of the convex portion 33 ₂ of the extending direction and the convex portion 33 _3. Moreover, it is substantially perpendicular to the extending direction of the convex portion 33 ₁ of the extending direction and the convex portion 33 2 _(or convex portion 33 _3). Angle between the convex portion 33 ₁ of the extending direction and the convex portion 33 ₂ (or convex portion 33 _3), 80 ° ~ 100 ° are exemplified, and preferably, 90 °.

In this configuration, the first to third light diffusion plates 30 ₁ to 30 ₃ satisfy the arrangement conditions (i) to (iv) described in the first embodiment.

The second and the first distance _{d 21} between the light diffusion plate ₃₀ 2, 30 _1, second and top 33b ₂ of the light diffusion plate 30 and _second convex portions 33 ₂ first light diffusing plate 30 ₁ a z-direction distance between the lower surface 31 _1, 5 mm or less can be exemplified. Similarly, 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 The distance in the z direction between the lower surface 31 _{3 of} 30 ₃ and 5 mm or less can be exemplified.

From the viewpoint of the light diffusing plate unit 21B and compact _{ones, d 21} and _{d 13} are 0 mm, the first light diffusing plate 30 ₁ and the second light diffusion plate 30 ₂ on the convex portion 33 ₂ a third light diffusing plate 30 _3, the upper bottom surface ₃₁ 1, 31 ₃ that may be disposed in contact with the top _33b 2, 33b ₁ of the lower convex portion ₃₃ 2, 33 ₁ first This is the same as the case of the embodiment. The second light diffusion plate 30 ₂ of the first and third light diffuser ₃₀ 1, 30 ₃ positioned closest to the point light source 22 side of the first to third light diffusing plate ₃₀ 1-30 ₃ It is preferable to make it thicker. In this case, for example, the first and third light diffusing plates 30 ₁ and 30 ₃ can be formed into a film as in the case of the first embodiment.

The light diffusing plate unit 21B shown in FIG. 10 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.

Also in the light diffusion plate unit 21B, the second and third light diffusion plates 30 ₂ and 30 ₃ are provided so as to satisfy the arrangement conditions (i) to (iii). In this arrangement, the second and third light diffusing plates 30 ₂ and 30 ₃ can convert light from the point light source 22 into linear light having substantially uniform luminance. In this embodiment, the first light diffusing plate 30 _{1 that} can convert the light from the point light source 22 into light having uniform luminance between the second and third light diffusing plates 30 ₂ and 30 _3. Is provided to satisfy the arrangement condition (iv).

Therefore, when the light diffusing plate unit 21B is used in place 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.

In the light diffusing plate unit 21B, the first to third light diffusing plates 30 ₁ to 30 ₃ are arranged so that the extending directions of the convex portions 33 ₁ , 33 ₂ , and 33 ₃ are alternately substantially orthogonal in the z direction. Is arranged. Therefore, Moire fringes is unlikely to occur in the third planar light emitted from the light diffusion plate 30 _3. 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. 11 is a perspective view showing a third embodiment of a light diffusion plate unit (light control plate unit) according to the present invention. The light diffusing plate unit 21C has first to third light diffusing plates 30 ₁ , 30 ₂ , 30 ₃ as in the case of the first embodiment. The light diffusing plate unit 21C is different from the light diffusing plate unit 21A in the order of arrangement of the first to third light diffusing plates 30 ₁ to 30 ₃ . This difference will be mainly described.

In the light diffusing plate unit 21C, the second light diffusing plate 30 ₂ , the third light diffusing plate 30 _3, and the first light diffusing plate 30 ₁ are arranged in the order described in the first embodiment. It satisfies (iv) and is provided in the z direction. Also in this embodiment, as in the second embodiment, the distance D in the first embodiment, the lower surface ₃₁₂ of the second light diffusion plate 30 _2, between the point light sources 22 Distance.

The third and the first distance _{d 31} between the light diffusion plate ₃₀ 3, 30 _1, and the third top 33b ₃ of the convex portion 33 ₃ of the light diffusion plate 30 ₃ of the first light diffusing plate 30 ₁ a z-direction distance between the lower surface 31 _1, 5 mm or less can be exemplified. Since the distance d ₂₃ between the second and third light diffusion plates 30 ₂ and 30 ₃ is the same as that in the first embodiment, the description thereof is omitted.

From the viewpoint of the light diffusing plate unit 21C and compact _{ones, d 23} and _{d 13} are 0 mm, the third light diffusing plate 30 ₃ and the second light diffusion plate 30 ₂ on the convex portion 33 ₂ the first light diffusion plate 30 _1, the upper bottom surface ₃₁ 3, 31 ₁ may be disposed in contact with the top _33b 2, 33b ₃ of the lower convex portion ₃₃ 2, 33 _3, the This is the same as in the first embodiment. The second light diffusion plate 30 ₂ located closest to the point light source 22 among the first to third light diffusion plates 30 ₁ to 30 ₃ is replaced with the third and first light diffusion plates 30 ₃ and 30 _1. it is preferred to thicker, in which case, for example, the third and the first light diffusing plate 30 _3, also a 30 ₁ may be a film-like is the same as in the first embodiment.

The light diffusing plate unit 21C shown in FIG. 11 can be applied to the surface light source device 20 and the transmissive image display device 1 in place 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.

Also in the light diffusion plate unit 21C, the second and third light diffusion plates 30 ₂ and 30 ₃ are provided so as to satisfy the arrangement conditions (i) to (iii). In this arrangement, the second and third light diffusing plates 30 ₂ and 30 ₃ can convert light from the point light source 22 into linear light having substantially uniform luminance. Then, the light diffuser plate unit 21C, the first light diffusing plate 30 ₁ is on the third light diffusing plate 30 _3, are arranged satisfies the arrangement conditions (iv). That is, the extending direction of the convex portion 33 ₁ of the extending direction and the convex portion 33 2 _(or convex portion 33 ₃₎ 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.

Therefore, 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 exhibit the same operational effects as in the case of the first embodiment.

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. The same applies to the arrangement of the convex portions 33a ₂ to 33a ₃ . The light diffusing plate units 21A to 21C may further include an optical film such as a diffusing film or a microlens film on the transmissive liquid crystal display unit 10 side (for example, the liquid crystal panel side). The transmissive image display device 1 may further include an optical film such as the above-described diffusion film or microlens film between the light diffusing plate units 21A to 21C and the transmissive liquid crystal display unit 10. it can.

Furthermore, the surface light source device 20 and the transmissive image display device 1 may include a reflection means 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 reflecting means may be provided on the side opposite to the light diffusing plate units 21A to 21C with respect to the point light source 22, for example, a holding member for holding the point light source 22 The light source mounting surface can be a reflecting surface.

In the description of the first convex portion 33 ₁ of the cross-sectional shape which the light diffusion plate 30 ₁ has, _{k Ia} in the formula (8) was a constant satisfying 0.25 -1.00 or more. In the description of the cross-sectional shapes of the convex portions 33 ₂ and 33 _{3 included in} each of the second and third light diffusion plates 30 ₂ and 30 ₃ , h _IIa in the expression (10) is 0.32w _IIa or more and 0. 97w _IIa or less, and k _IIa is a constant satisfying −1.00 or more and 0.75 or less. However, the convex portion 33 ₁ having a first light diffusion plate 30 _{_1,} or _{k Ia} _are constants satisfying the ranges excluding -1.00 or -0.15 range from the range of _{k Ia} Alternatively, in at least one convex portion 33 ₂ , 33 ₃ of the second and third light diffusing plates 30 ₂ , 30 ₃ , h _IIa is 0.32 w _IIa or more from the above range of h _IIa . It is a constant that satisfies the range excluding the range of 80 w _IIa or less, or k _IIa can be a constant that satisfies the range excluding −1.00 and 0.23 from the above range of k _IIa. .

Further, the first to third light diffusing plate ₃₀ 1-30 ₃ includes a first light diffusion plate 30 _first, second and third light diffusion plate ₃₀ 2, 30 _3, respectively in combination form a plurality of points to the light output from the light source more uniformly dispersed to produce a linear light, the convex portion 33 _1, the convex portion 33 ₂ and the convex portion 33 ₃ are shaped respectively to the exit side of the light Any plate-like optical component may be used. In this case, the light diffusing plate unit may be one in which the three optical components are arranged in the relationship described using the light diffusing

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, as exemplified in the first embodiment, when the second and third light control plates 30 ₂ , 30 ₃ are formed in a film shape, a photo is formed in the shape of the convex portions 33 ₂ , 33 ₃ . Polymer methods can be used. In this case, an acrylic ultraviolet curable resin having a refractive index of 1.46 to 1.58 is often used as the material of the second and third light control plates 30 ₂ and 30 ₃ , and this leads to cost and yellowing of the film. From the viewpoint of preventing deterioration, it is preferable to use a low refractive index resin having a refractive index of about 1.51. Further, as exemplified in the second and third embodiments, when the light control plate other than the light control plate located closest to the point light source is in the form of a film, in the first embodiment. Similar to the second and third light control plates 30 ₂ and 30 ₃ , a photopolymer method can be used for shaping the convex portion. In this case as well, an acrylic ultraviolet curable resin having a refractive index of 1.56 to 1.62 and a refractive index of 1.46 to 1.58 can be used as the material for the light control plate. From the viewpoint of cost and prevention of yellowing deterioration of the film, a low refractive index resin having a refractive index of about 1.51 is preferably used.

Also, the light control plate located closest to the point light source is preferably in the form of a sheet of 1 mm to 5 mm, and the light control plates other than the light control plate located closest to the point light source are preferably in the form of a film of 1 mm or less.

In the surface light source device, the light control plate unit, and the transmissive image display device of the present invention, the light from the point light source can be dispersed sufficiently uniformly.

1 ... transmission type image display apparatus, 10 ... transmission type image display unit, 20 ... surface light source device, 21A-21C ... light diffusion plate unit, 22 ... point light source, ₃₀ 1 to 30 3 _... first to third light Diffusion plate 33a ₁ ... end of convex portion (end of convex portion of first light control plate), 31 ₁ to 31 ₃ ... bottom surface of first to third light diffusion plates (first to third First surface of light control plate), 32 ₁ to 32 ₃ ... Upper surface of first to third light diffusion plates (second surface of first to third light control plates), 33 ₁ to 33 ₃ . Convex portions of the first to third light diffusing plates, 33 _i ... convex portions (convex portions of the second and third light control plates), 33a ₁ to 33a ₃ ... ends of the convex portions (first To the end of the convex part of the third light control plate), 33a _i ... the end of the convex part (end of the convex part of the second and third light control plates), Y1 ... of the first light diffusion plate The extending direction of the convex portion, approximately orthogonal to the X1 ... Y1 direction Direction, X2 ... extension direction of the convex portion of the second light diffusion plate, Y2 ... direction substantially orthogonal to the X2 direction, X3 ... extension direction of the convex portion of the third light diffusion plate, Y3 ... X3 direction The direction that is approximately orthogonal to

Claims

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 have first to third light control plates formed on the second surface;
The first light control plate, the second light control plate, and the third light control plate are arranged in the thickness direction so that the third light control plate is positioned above the second light control plate. It is provided in
The first surface of the third light control plate is located on the second surface side of the second light control plate;
The extending direction of the convex portion that the second light control plate has and the extending direction of the convex portion that the third light control plate has are substantially parallel,
The extending direction of the convex part that the first light control plate has and the extending direction of the convex part that the second or third light control plate has are substantially orthogonal,
In the cross section perpendicular to the extending direction of each of the convex portions of the first to third light control plates, an axis passing through both ends is a u-axis, and the u-axis 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 third light control plates, the first cross section in the cross section A surface light source in which the contour shape of each of the convex portions of the third light control plate is represented by v (u) satisfying the following expression (1) when −0.475 w a ≦ u ≦ 0.475 w a apparatus.

However, in the formula (1),

(In Formula (2), h a is a constant that satisfies 0.40 w a or more and 1.60 w a or less with respect to the convex portion of the first light control plate, and k a is −1.00 or more and is a constant satisfying 0.25 or less. Further, in the equation (2), for each of the convex portions of the second and third light control plate, h a is, 0.32 W a more 0.97W a (K a is a constant satisfying −1.00 and 0.75)
The surface light source device according to claim 1, wherein the first surface of each of the first to third 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 have first to third light control plates formed on the second surface;
The first light control plate, the second light control plate, and the third light control plate are arranged in the thickness direction so that the third light control plate is positioned above the second light control plate. It is provided in
The first surface of the third light control plate is located on the second surface side of the second light control plate;
The extending direction of the convex portion that the second light control plate has and the extending direction of the convex portion that the third light control plate has are substantially parallel,
The extending direction of the convex part that the first light control plate has and the extending direction of the convex part that the second or third light control plate has are substantially orthogonal,
In the cross section perpendicular to the extending direction of each of the convex portions of the first to third light control plates, an axis passing through both ends is a u-axis, and the u-axis 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 third light control plates, the first cross section in the cross section A transmission type in which the contour shape of each of the convex portions of the third light control plate is represented by v (u) satisfying the following expression (3) when −0.475 w a ≦ u ≦ 0.475 w a Image display device.

However, in the formula (3),

(In Expression (4), h a is a constant that satisfies 0.40 w a or more and 1.60 w a or less with respect to the convex portion of the first light control plate, and k a is −1.00 or more and is a constant satisfying 0.25 or less. Further, in the equation (4), for each of the convex portions of the second and third light control plate, h a is, 0.32 W a more 0.97W a (K a is a constant satisfying −1.00 and 0.75)
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 have first to third light control plates formed on the second surface;
The first light control plate, the second light control plate, and the third light control plate are arranged in the thickness direction so that the third light control plate is positioned above the second light control plate. It is provided in
The first surface of the third light control plate is located on the second surface side of the second light control plate;
The extending direction of the convex portion that the second light control plate has and the extending direction of the convex portion that the third light control plate has are substantially parallel,
The extending direction of the convex part that the first light control plate has and the extending direction of the convex part that the second or third light control plate has are substantially orthogonal,
In the cross section perpendicular to the extending direction of each of the convex portions of the first to third light control plates, an axis passing through both ends is a u-axis, and the u-axis 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 third light control plates, the first cross section in the cross section A light control in which the contour shape of each of the convex portions of the third light control plate is represented by v (u) satisfying the following expression (5) when −0.475 w a ≦ u ≦ 0.475 w a Board unit.

However, in the formula (5),

(In Expression (6), h a is a constant that satisfies 0.40 w a or more and 1.60 w a or less with respect to the convex portion of the first light control plate, and k a is −1.00 or more and is a constant satisfying 0.25 or less. Further, in the equation (6), for each of the convex portions of the second and third light control plate, h a is, 0.32 W a more 0.97W a K a is a constant satisfying −1.00 or more and 0.75 or less, provided that, in the convex portion of the first light control plate, k a is −1.00 or more. 0.25 or below the range of -1.00 or -0.15 or less in the range of is removed, or, in at least one of the convex portions of the second and third light control plate, wherein the h a from 0.32w a more than 0.97w a following range of not less than 0.32w a more than 0.80w a Or scope is removed, or, k a range of -1.00 or 0.23 or less from the scope of the -1.00 to 0.75 for is removed.)