JP2012220939A - Light control plate unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light control plate unit capable of uniformizing light emitted from a point light source and improving luminance of the light.SOLUTION: A light control plate unit 21 includes first and second light control plates 30and 30having a first surface on which a plurality of convex parts 33(i=1 to 2) extending in the same direction are arranged in a direction substantially orthogonal to the extending direction. The extending directions of the convex parts 33of each light control plate are substantially orthogonal, and with respect to an orthogonal cross section which is substantially orthogonal to the extending direction of the convex parts of each light control plate, cross-sectional shapes of the convex portions 33respectively and independently satisfy: 0.95z(x)≤z(x)≤1.05z(x) in -0.475w≤x≤0.475wwhen a width of the convex portion is represented by win an xz coordinate system in which an axial line passing through both ends of the convex portions is set as an x-axis. z(x) satisfies the expression below. [Expression 1] (In expression (1), Cfor k=1 to 8 is a prescribed constant).

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 transmissive image display device, for example, as shown in FIG. 17, a device in which a light source 43 is disposed on the back side of a transmissive image display unit 50 is widely used. Examples of the transmissive image display unit 50 include a liquid crystal display panel in which linearly polarizing plates 52 and 53 are disposed on both surfaces of a liquid crystal cell 51. 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 50 by uniformly dispersing light from the light source 43, and for this reason, between the light source 43 and the transmissive image display unit 50. 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 50 side is used. (For example, see Patent Document 1: Japanese Patent Laid-Open No. 7-198913). In addition, 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.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a light control plate unit, a surface light source device, and a transmissive image display device that can make light from a point light source uniform and improve luminance.

ただし、式（１）において、ｚ_０（ｘ）は式（２）で示される。

式(２)中、Ｃ_２＝０．７６２４６９８２４２５７５５３、Ｃ_４＝０．２９８０７５６６２２６２９２７、Ｃ_６＝−０．５５９６２９３３８１５３６６１、Ｃ_８＝０．８９６４６８２８０２５３２６５、Ｃ_１０＝−０．６５７１６４１６６２１３７１５、Ｃ_１２＝−０．６１５７２６４１８４９５９８５、Ｃ_１４＝１．２４５１５１３５３９３８５６０及びＣ_１６＝−０．５２０５５９０８３７６９４８２であるか、
Ｃ_２＝０．８２８０３４７９０３３８６４７、Ｃ_４＝０．３２２１６４１０８６２５２７５、Ｃ_６＝−０．６８３４０９３８８４０８３５３、Ｃ_８＝１．２２１６４５２３２７４８１４０、Ｃ_１０＝−１．２０４３８１２５９３３７２１０、Ｃ_１２＝−０．１４０９１３８７１７８７７２４、Ｃ_１４＝１．０３３１１０８５８２１９４２０、Ｃ_１６＝−０．４７５３８８３４５５４０７０８であるか、または、
Ｃ_２＝０．９０８７４３０５３４１３４７３、Ｃ_４＝０．４１２１３６０７４２４５７２９、Ｃ_６＝−１．０５２２４４４４１１０９３３０、Ｃ_８＝１．９３９７４６２１４２８４０２０、Ｃ_１０＝−２．０１３３００１１５２３１６２０、Ｃ_１２＝０．０７４６７８４８９２６１３５７、Ｃ_１４＝１．３７６９３２２９３６２３５７０、Ｃ_１６＝−０．６８００８１０６８８１５９４６である。 In the light control plate unit according to the present invention, a plurality of convex portions extending in one direction are formed on one surface, and the plurality of convex portions are arranged in parallel in a direction substantially orthogonal to the extending direction of the convex portions. The arranged first and second light control plates and a plurality of prism portions extending in one direction are formed on one side, and the plurality of prism portions are substantially perpendicular to the extending direction of the prism portions. First and second prism plates arranged in parallel, and at least one of the first and second light control plates contains a light diffusing agent, and the first and second light controls. The plate and the first and second prism plates are overlapped in the plate thickness direction with the first or second light control plate as the lowest step, and the extending direction of the convex portion of the first light control plate And the convex direction of the second light control plate are substantially perpendicular to the extending direction of the convex portion, and the prism of the first prism plate The extending direction of the portion and the extending direction of the prism portion included in the second prism plate are substantially orthogonal, and are orthogonally orthogonal to the extending direction of the convex portion included in each of the first and second light control plates. In the cross-section, the axis passing through both ends of the convex portion is the x-axis, the axis passing through the center of both ends on the x-axis and perpendicular to the x-axis is the z-axis, and the length of the convex portion in the x-axis direction is w _{As a} , the cross-sectional shape of the convex portion of the first light control plate and the cross-sectional shape of the convex portion of the second light control plate are each independently −0.475 × w _a ≦ x ≦ in 0.475 × _{w a} is represented by z (x) satisfying the equation (1).

However, in the formula _{(1), z} 0 (x) is represented by the formula (2).

In the formula (2), C ₂ = 0.762469824257553, C ₄ = 0.298075662622927, C ₆ = −0.5596293831533661, C ₈ = 0.89646682802533265, C ₁₀ = −0.65716441266137715, C ₁₂ = −0.61577261844995985 , C ₁₄ = 1.245151353938560 and C ₁₆ = −0.52055908376482,
C ₂ = 0.8280347903338647, C ₄ = 0.3221164108625275, C ₆ = −0.6834093884088353, C ₈ = 1.221645232748140, C ₁₀ = −1.20438125937210, C ₁₂ = −0.14099137787724, C ₁₄ = 1. 031108858219420, C ₁₆ = −0.47538835345540708, or
C ₂ = 0.9087430553413473, C ₄ = 0.412136074245729, C ₆ = -1.0522244441109330, C ₈ = 1.939462214284020, C ₁₀ = -2.013300115231320, C ₁₂ = 0.074667849261357, C ₁₄ = 1.376993293235370 , C ₁₆ = −0.68008101068815946.

  In this configuration, the extending direction of the convex portion included in each of the first and second light control plates is substantially orthogonal, and the extending direction of the prism portion included in each of the first and second prism plates is approximately orthogonal. It is provided to do. And each convex-shaped part has the outline shape represented by said z (x) on the single side | surface of a 1st and 2nd light control board. Further, at least one of the first and second light control plates contains a diffusing agent. Therefore, it is possible to make the light from the point light source uniform and improve the luminance.

  In the light control plate unit according to the present invention, at least one of the first and second light control plates can be a rough surface opposite to the surface on which the convex portion is formed. Thereby, the uniformity of the light from the point light source and the improvement of the luminance can be further achieved.

  In the light control plate unit according to the present invention, one of the first and second prism plates is disposed between the first and second light control plates, and the light control plate unit is disposed between the first and second light control plates. The extending direction of the prism portion included in the prism plate and the extending direction of the convex portion included in the lowermost light control plate can be substantially parallel to each other.

  The surface light source device according to the present invention includes the light control plate unit according to the present invention and a plurality of point light sources that supply light to the light control plate unit. In this surface light source device, the plurality of point light sources are separated from each other and disposed on the back side of the light control plate unit.

  Since the surface light source device according to the present invention includes the light control plate unit according to the present invention, the light from the point light source can be made more uniform and the luminance can be improved.

The point light source may be a point light source having the following first light distribution characteristic or second light distribution characteristic.
First light distribution characteristic: a light distribution characteristic having a maximum emission light intensity I _max in a range of light emission angle of 70 ° or more and 80 ° or less, and an emission light intensity I ₀ when the emission angle is 0 °. ,
0.12 × I _max ≦ I ₀ ≦ 0.20 × I _max
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. A light distribution characteristic of 5 ° or more and 57.5 ° or less.
Second light distribution characteristic: a light distribution characteristic having a maximum emission light intensity I _max in a range of the light emission angle of 65 ° to 75 °, and the emission light intensity I ₀ when the emission angle is 0 °. ,
0.22 × I _max ≦ I ₀ ≦ 0.30 × I _max
The emission angle at which the emission light intensity is (I ₀ + I _max ) / 2 is 45 ° or more and 55 ° or less, and the emission angle at which the emission light intensity is (I ₀ + I _max ) / 4 is 20 Light distribution characteristic that is not less than 30 ° and not more than 30 °.

  A transmissive image display device according to the present invention includes the surface light source device according to the present invention and a transmissive image display unit irradiated with light output from the surface light source device.

  Since the transmissive image display device according to the present invention has the surface light source device according to the present invention, the light from the point light source can be made more uniform and the luminance can be improved. Since the transmissive image display unit is illuminated with the uniformed light and the light with improved brightness, a higher quality image can be displayed.

  According to the light control plate unit, the surface light source device, and the transmissive image display device of the present invention, the light from the point light source can be made uniform and the luminance can be improved.

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 drawing which shows the other 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 and 2nd light control board of the light control board unit shown in FIG. 6 has. (A) It is a graph which shows an example of the coefficient which prescribes | regulates z (x) which shows the cross-sectional shape of the convex part of the 1st and 2nd light control board shown in FIG. (B) It is a table | surface which shows the other example of the coefficient which prescribes | regulates z (x) which shows the cross-sectional shape of the convex part of the 1st and 2nd light control board shown in FIG. (C) It is a table | surface which shows the further another example of the coefficient which prescribes | regulates z (x) which shows the cross-sectional shape of the convex part of the 1st and 2nd light control board shown in FIG. It is drawing which shows the conditions which the cross-sectional shape of the convex part which the 1st and 2nd light control board has satisfies. It is drawing which shows the other example of the cross-sectional shape of the convex part which the 1st and 2nd light control board of the light control board unit shown in FIG. 6 has. It is drawing which shows the further example of the cross-sectional shape of the convex part which the 1st and 2nd light control board of the light control board unit shown in FIG. 6 has. It is drawing for demonstrating the cross-sectional shape of the convex part which the 3rd and 4th light control board of the light control board unit shown in FIG. 6 has. 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 a schematic block diagram of the manufacturing apparatus which manufactures a resin sheet. It is the table | surface which showed the manufacturing conditions of the light control boards AF prepared in this experiment example, and the characteristic of the surface in each layer. 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. The same reference numerals are assigned to the same elements, and duplicate descriptions are omitted. The dimensional ratios in the drawings do not necessarily match those described. Further, in the description, words indicating directions such as “up” and “down” are convenient words based on the state shown in the drawings.

  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), and two directions orthogonal to the Z direction and orthogonal to each other. These are referred to as the X direction and the 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 liquid crystal cells and STN liquid crystal cells.

  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 control plate unit 21 and a plurality of point light sources 22 arranged on the back side (lower side in FIG. 1) in FIG. The light control plate unit 21 is a composite light control plate including a plurality of light control plates. As described above, the light control plate unit 21 includes a plurality of light control plates, which are schematically illustrated in FIG.

  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 Lx in the X direction and at equal intervals Ly in the Y direction. In FIG. 2, as an example, the interval Lx in the X direction is greater than the interval Ly in the Y direction, but the interval Ly may be greater 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 including 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.

  The point light source 22 is a so-called side emitting light source. An example of the point light source 22 is a light emitting diode. The point light source 22 may have the first light distribution characteristic illustrated in FIG. 4 or the second light distribution characteristic illustrated in FIG. 4 and 5 are diagrams showing examples of the light distribution of the point light sources included in the surface light source device. 4 and FIG. 5, the horizontal axis indicates the outgoing angle θ (°) (see FIG. 1), 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 first light distribution characteristic illustrated in FIG. 4 satisfies the following condition.
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.

Further, the second light distribution characteristic illustrated in FIG. 5 satisfies the following condition.
Peak angle theta ₁ is in the range of 65 ° or more 75 ° or less.
The intensity of emitted light increases substantially monotonically from the front direction (emitted angle θ is 0 °) to the peak angle θ ₁ .
- emission intensity I ₀ of the front direction,
0.22 × I _max ≦ I ₀ ≦ 0.30 × 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 45 ° to 55 °.
The outgoing angle θ _{3 at} which the outgoing light intensity is (I _max + I ₀ ) / 4 is in the range of 20 ° to 30 °.

In the light distribution characteristic illustrated in FIG. 5, since the vertical axis represents the normalized output light intensity, I _max = 1.00000, and the corresponding output angle θ ₁ is about 70 °. I ₀ is 0.265. In this case, (I _max + I ₀ ) /2=0.634, and the corresponding emission angle θ ₂ is about 49 °. Further, (I _max + I ₀ ) /4=0.317, and the corresponding emission angle θ ₃ is about 25 °. Therefore, the light distribution characteristics of the point light source 22 shown in FIG. 5 satisfy the above-described conditions.

Next, the light control plate unit 21 will be described. The light control plate unit 21 includes four first light control plates 30 ₁ , second light control plates 30 ₂ , third light control plates (first prism plates) 30 _3, and fourth light control plates. (second prism plate) and a 30 _4.

The planar view shapes (shapes viewed from the Z direction) of the _first to _fourth light control plates 30 ₁ to 30 ₄ are substantially the same, and are generally rectangular. The plan view shapes of the _first to _fourth light control plates 30 ₁ to 30 ₄ , in other words, the size of the plan view shape of the light control plate unit 21 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 shape of the _first to _fourth light control plates 30 ₁ to 30 ₄ 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.

The light control plate unit 21 having the _first to _fourth light control plates 30 ₁ to 30 ₄ has three embodiments in the arrangement order of the _first to _fourth light control plates 30 ₁ to 304. Hereinafter, first to third embodiments of the light control plate unit 21 will be described. The light control plate units 21 in the first to third embodiments are referred to as a light control plate unit 21A, a light control plate unit 21B, and a light control plate unit 21C, respectively.

(Light control plate unit 21A)
FIG. 6 is a perspective view for illustrating a configuration of an embodiment of the light control plate unit. Referring to FIG 6 showing a light control plate unit 21A, the light control plate ₃₀ 1 of the first to fourth common to the light control plate unit _{21A~21C, 30 2, 30 3,} 30 4 will be described. In Figure 6, for the sake of explanation, although spaced apart first through fourth light control plate ₃₀ 1 to 30 _4, as described later, the second to the first light control plate 30 ₁ on it may be provided as the fourth light control plate ₃₀ 2-30 ₄ are adjacent to each other.

[First light control board]
The first light control plate 30 ₁ has a lower surface 31 _1, the second convex portion is convex to the light control plate 30 ₂ side (the convex portion of the first light control plate) 33 ₁ is formed with a plurality a plate-like body having an upper surface 32 _1.

The first light control 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. Further, the first light control 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 (extending direction), are arranged in parallel in the X1 direction substantially perpendicular to the Y1 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 control plate 30 ₁ is the distance in the Z direction 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 control board]
The second light control plate 30 ₂ has a lower surface _312, (the convex portion of the second light control plate) convex portion is convex to the third light control plate 30 ₃ side 33 ₂ is formed with a plurality a plate-like body having an upper surface 32 _2. The second light control plate 30 ₂ is the first light control 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 ₂ extend in substantially parallel direction X2 in the X direction (extending direction), they are arranged in parallel in the Y2 direction substantially orthogonal to the X2 direction. It is preferred X2 direction and the Y2 direction is parallel to the X and Y directions, but as in the case of the first light control plate 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 Y2 direction. Second thickness _{d 2} of the light control plate 30 ₂ is the distance in the Z direction with the top 33b ₂ of the lower surface 31 ₂ and the convex portion 33 _2, usually a 0.1 mm to 5 mm.

[Third light control board]
Third light control plate (first prism plate) 30 _3, substantially flat bottom surface _313, convex portions is convex fourth light control plate 30 ₄ side (prism section) 33 ₃ Multiple forms a plate-like body having a top surface 32 _3, which is. Convex portion 33 ₃ in cross section a triangular prism portion, the third light control plate 30 ₃ is a so-called prism plate. Here, although referred to as “plate”, it may be in the form of a sheet or film depending on the thickness. The lower surface 31 _3, which substantially are flat, there may be slight irregularities without departing from the scope of the present invention. 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.

Convex portion 33 _3, extends substantially parallel Y3 direction in the Y direction (extending direction), are arranged in parallel in the X3 direction substantially perpendicular to the Y3 direction. It is preferred X3 direction and Y3 direction is parallel to the X and Y directions, but as in the case of the first light control plate 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 X3 direction. The thickness d ₃ of the third light control plate 30 ₃ is the 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 light control board]
Fourth optical control plate (second prism plate) 30 ₄ has a substantially flat lower surface 31 _4, and a top surface 32 ₄ convex portions (prism portions) 33 ₄ is formed with a plurality of convex outwardly It is a plate-like body. Convex portion 33 ₄ is a cross-section triangular prism portion. Fourth light control plate _{30. 4} is a third so-called prism plate in the same manner as the light control plate 30 _3. Here, it is referred to as “plate”, but it may be in the form of a sheet or a film depending on the thickness. The lower surface 31 ₄ is substantially are flat, like the third light control plate 30 _3, there may be slight irregularities without departing from the scope of the present invention. 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.

Convex portion 33 _4, extends substantially parallel to the direction X4 in the X direction (extending direction), are arranged in parallel in the Y4 direction substantially orthogonal to the direction X4. It is preferable X4 direction and Y4 direction is parallel to the X and Y directions, but as in the case of the first light control plate 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 control plate 30 ₄ is the distance in the Z direction with the top 33b ₄ of the lower surface 31 ₄ and the convex portion 33 _4, usually is 0.1 mm to 5 mm.

[Convex portions of first and second light control plates]
The shape of the convex portions 33 ₁ and 33 ₂ of the first and second light control plates 30 ₁ and 30 ₂ will be described. Here, the convex portions 33 ₁ and 33 ₂ will be described as convex portions 33 _i (i is 1 or 2) unless otherwise specified. In FIG. 7, the xz coordinate system is set with the direction orthogonal to the extending direction of the convex portion 33 _i as the x axis. X-axis direction corresponding to the convex portion 33 ₁ and the convex portion 33 ₂ is a X1 direction and the Y2 direction. Further, z-axis direction corresponding to the convex portion 33 ₁ and the convex portion 33 ₂ are both a Z-direction.

ただし、式（３）において、ｚ_０（ｘ）は、

を満たす。 In the xz plane of the xz coordinate system, both ends _33a i of the convex portion 33 _i, 33a _i is located on the x-axis, the contour shape (sectional shape) in a cross section of the convex portion 33 _i of the formula (3) Z (x) that satisfies

However, in Formula (3), z ₀ (x) is

Meet.

In formula (4), w _a is the length of the convex portion 33 _{i in} the x-axis direction. Moreover, the combinations of C ₂ , C ₄ , C ₆ , C ₈ , C ₁₀ , C ₁₂ , C _14, and C ₁₆ with respect to each of k = 1 to 8 in the equation (4) are shown in FIGS. It can be any of the charts shown in (b) and FIG. 8 (c), respectively.

FIG. 7 shows z (x) corresponding to the combination of C ₂ , C ₄ , C ₆ , C ₈ , C ₁₀ , C ₁₂ , C ₁₄ and C ₁₆ shown in FIG. The cross-sectional shape of the convex portion 33 _i illustrated in FIG. 7 exemplifies a shape in which z ₀ (x) is expanded and contracted by a predetermined multiple (for example, one time) in the Z direction within a range that satisfies Expression (3). In this case, the convex portion 33 _i has a symmetric cross-sectional shape with respect to the z axis.

The cross-sectional shape of the convex portion 33 _i is not limited to a shape in which z ₀ (x) is expanded and contracted by a predetermined multiple (for example, 1 time) in the Z direction, as long as the formula (3) is satisfied. In Expression (3), z (x) is an outline represented by 0.95 × z ₀ (x) when z ₀ (x) is determined for a certain width w _a as shown in FIG. Any cross-sectional shape represented by a contour line passing through a region between the line and a contour line represented by 1.05 × z ₀ (x) may be used. In other words, in Expression (3), z (x _n ) for an arbitrary position x _n corresponds to the height of the convex portion 33 _{i at} the position x _a . Therefore, it is only necessary that z (x _n ) for an arbitrary position x _n satisfies 0.95z ₀ (x _n ) or more and 1.05z ₀ (x _n ).

As described above, the combinations of C ₂ , C ₄ , C ₆ , C ₈ , C ₁₀ , C ₁₂ , C ₁₄ and C ₁₆ for each of k = 1 to 8 in the formula (4) are shown in FIG. It is not limited to what was shown, It can be set as what was shown in FIG.8 (b) and FIG.8 (c).

FIG. 10 is a diagram illustrating an example of z (x) for the combination of C _{2 to} C ₁₆ illustrated in FIG. In FIG. 10, in order to show the condition that z (x) satisfies, the contour line represented by 0.95 × z ₀ (x) and 1.05 × z ₀ (x) A contour line to be formed is also indicated by a one-dot chain line. The contour line based on the combination of C _{2 to} C ₁₆ shown in FIG. 8B is also represented by the contour line represented by 0.95 × z ₀ (x) and 1.05 × z ₀ (x). Any cross-sectional shape represented by a contour line passing through an area between the contour lines may be used.

FIG. 11 is a diagram illustrating an example of z (x) for the combination of C _{2 to} C ₁₆ illustrated in FIG. In FIG. 11, in order to show the condition that z (x) satisfies, the contour line represented by 0.95 × z ₀ (x) and 1.05 × z ₀ (x) are represented as in FIG. 9. A contour line to be formed is also indicated by a one-dot chain line. The contour line based on the combination of C _{2 to} C ₁₆ shown in FIG. 8C is also represented by a contour line represented by 0.95 × z ₀ (x) and 1.05 × z ₀ (x). Any cross-sectional shape represented by a contour line passing through an area between the contour lines may be used.

The width _{w a} of the convex portion 33 _i, visible since formation of the convex portion 33 _i is easy, usually 40μm or more, preferably 80μm or more, the pattern caused by the convex portion 33 _i is macroscopically Since it is hard to be done, it is usually 800 μm or less, preferably 450 μm or less. Specifically the width _{w a, 410μm, 400μm, 325μm} , 280μm and 100μm can be exemplified. However, the value of w _a is not limited to this.

In the above description, it is assumed that the cross-sectional shape of the convex portion 33 _i is represented by z (x) that satisfies Expression (3). However, the sectional shape of the convex portion 33 _i need only be represented by z (x) satisfying the equation (3) _{-0.475 × w a ≦ x ≦ 0.475} × w a. This is because the molding error tends to be relatively large in the vicinity of the bottom of the convex portion 33 _i (in the vicinity of the end), whereas the influence of the shape in the vicinity of the bottom on the light diffusibility is small.

The sectional shape of the convex portion 33 ₁ and the convex portion 33 ₂ may be the same, independently, it may be a shape represented by z (x) satisfying the equation (3).

[Convex portions of third and fourth light control plates]
Third and fourth light control plate ₃₀ 3, 30 ₄ convex portion 33 ₃ which has, 33 for ₄ cross-sectional shape will be described. Here, the convex portions 33 ₃ and 33 ₄ will be referred to as convex portions 33 _j (j is 3 or 4) unless otherwise specified. Figure 12 is a view for explaining the shape of the convex portion 33 _j, which illustrates a side when viewed from the extending direction of the convex portion 33 _j. Since the convex portion 33 _j has a substantially uniform shape in the extending direction, as shown in FIG. 12, the side shape viewed from the extending direction is a cross-section substantially orthogonal to the extending direction of the convex portion 33 _j. Corresponds to the shape.

The side surface shape (or cross-sectional shape) of the convex portion 33 _j is a substantially right triangle whose apex angle α is a substantially right angle, and is a substantially right isosceles triangle whose two sides constituting the apex angle are substantially equal in length. It is preferable. The apex angle α is preferably 90 °, but may be in the range of 80 ° to 100 °. The pitch P between two adjacent convex portions 33 _j and 33 _j can be 10 μm to 1000 μm, preferably 20 μm to 500 μm, and more preferably 40 μm to 250 μm. What is necessary is just to set the width _| variety of the convex part _{33j so that} the pitch P of the convex part _33j may become the predetermined value of the said range.

[Layer structure of first to fourth light control plates]
The first to fourth light control 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 control plates 30 ₁ to 304 are multilayer plates, one or both sides of the _first to _fourth light control 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 control plates 30 ₁ to 304 from being deteriorated by the point light source 22 or the ultraviolet rays that may be included in the 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 control 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 control 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 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), acrylic ultraviolet curable resin ( Refractive index: 1.46 to 1.58) is 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 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.

[Diffusion agent contained in first and second light control plates]
At least one of the first and second light control plates 30 ₁ and 30 ₂ contains a light diffusing agent. As the light diffusing agent, a powder having a refractive index different from that of the above-described transparent material mainly constituting the first and second light control plates 30 ₁ and 30 ₂ is used. In the present embodiment, the first and second light control plate 30 _1, 30 of the _two, the first light control plate 30 _1, a light diffusing agent is contained. The first light control plate 30 ₁ is composed of light diffusing agent in a transparent material is dispersed. 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. .

The addition amount of the light diffusing agent in the first and second light control plates 30 ₁ and 30 ₂ is usually in the range of 0.01 to 20 parts by mass, preferably 100 parts by mass of the composition of the transparent material. The range is 0.01 to 10 parts by mass with respect to 100 parts by mass of the transparent material composition. Moreover, when the ratio of the addition of the light diffusing agent in the first and second light control plates 30 ₁ and 30 _{2 is} represented by the total light transmittance Tt based on JIS K7361-1 (1997), it is usually 40% to It is in the range of 90%, preferably in the range of 50% to 90%.

[Surface roughness of the lower surfaces of the first and second light control plates]
Lower surface ₃₁ 1, 31 ₂ of the first and second light control plate ₃₀ 1, 30 _2, can be substantially flat, the first and second light control plate ₃₀ 1, 30 ₂ of at least one of lower surface ₃₁ 1, 31 _2, surface roughening may be a rough surface which has been subjected. In this case, the lower surface ₃₁ 1, 31 ₂ may be a surface having been subjected to embossing. Examples of the lower surface ₃₁ 1, 31 ₂ of the surface roughness, ISO4287: when expressed in maximum height Rz defined by 1997, it is 5μm or more. The surface roughness ISO4287: when expressed in a defined as the arithmetic average roughness Ra at 1997, the lower surface ₃₁ 1, 31 _2, Ra can be 2μm or more faces. Further, when the lower surface ₃₁ 1, 31 ₂ of the surface roughness was expressed in both of the maximum height Rz and the arithmetic average roughness Ra, lower surface ₃₁ 1, 31 _2, the maximum height Rz is 5μm or more and The arithmetic average roughness Ra can be a surface having a thickness of 2 μm or more.

In the case of the lower surface ₃₁ 1, 31 ₂ a rough surface, the lower surface ₃₁ of the first and second light control plate ₃₀ 1, 30 _2, 31 _2, the maximum height Rz is less than 25μm or 5μm crude The surface is preferably a surface, and more preferably a rough surface having the maximum height Rz of 25 μm or more and less than 200 μm. An example of the rough surface having the maximum height Rz of 5 μm or more and less than 25 μm is a rough surface having Rz of 10 μm or more and less than 20 μm.

The lower surface ₃₁ 1, 31 ₂ is preferably the arithmetic mean roughness Ra is a rough surface of less than 10μm more than 2 [mu] m, more preferably, the arithmetic mean roughness Ra is a rough surface of less than 100μm or 10μm .

Moreover, the example of the rough surface processing for obtaining the said rough surface is not limited to embossing. For example, the rough surface can be formed by blasting or the like. Further, for example, rough surfaces by constructing the lower surface 31 _1, 31 ₂ of the skin first and second light control plate in layers 30 _1, 30 ₂ containing fine particles called matting agent can be formed. Or the said rough surface may be formed by comprising a mat layer by apply | coating the coating liquid containing a matting agent and a binder.

[Method for Manufacturing First to Fourth Light Control Plates]
The first light control plate 30 ₁ may be, for example, a light diffusing agent in a transparent material is produced by a method cut out a plate material constituted are dispersed. In the case of using a transparent resin material as the transparent material, using a mixed material obtained by mixing a transparent resin material and a light diffusing agent, a first light control plate 30 _1, an injection molding method, extrusion molding method, a photopolymer It can be manufactured by a method, a press molding method or the like.

The _second to _fourth light control plates 30 ₂ to 304 can be manufactured, for example, by a method of scraping a plate material made of 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 first to fourth light control plates]
The first to fourth light control plates 30 ₁ to 30 ₄ are provided in the Z direction so as to satisfy the following conditions.
(i) Among the _first to _fourth light control plates 30 ₁ to 30 ₄ , the first or second light control plates 30 ₁ and 30 ₂ are positioned at the lowermost level, and the prism plates are positioned at the uppermost level. The third or fourth light control plates 30 ₃ and 30 ₄ are positioned.
(ii) The first to fourth light control plates 30 ₁ to 30 ₄ are provided so as to overlap each other in the plate thickness direction (Z direction). Of the two adjacent light control plates, the lower light control plate It arrange | positions so that an upper surface (surface in which the convex-shaped part is formed) and the lower surface of an upper light control board may oppose.
(iii) a first light control plate 30 ₁ of the convex portion 33 ₁ in the extending direction (Y1 direction), the second light control plate 30 _{and second} convex portion 33 ₂ in the extending direction (X2 direction) Are substantially orthogonal.
(iv) and the third light control plate 30 ₃ of the convex portion 33 ₃ of the extending direction (Y3 direction), the fourth light control plate 30 ₄ of the convex portion 33 ₄ of the extending direction (X4 direction) Are substantially orthogonal.
(v) one of the first and second and the extending direction of the light control plate 30 _1, 30 while the convex portion ₃₃ 1 of _2, 33 _2, third and fourth light control plate ₃₀ 3, 30 ₄ It is substantially parallel to the convex portion 33 _3, 33 ₄ in the extending direction.

  The “substantially orthogonal” means that the angle between the two directions satisfies the range of 80 ° to 100 °, and preferably the angle between the two directions substantially orthogonal is 90 °. Further, regarding “parallel”, it is preferable that the two directions coincide with each other, but the two directions may be shifted by about ± 10 °.

In the light control plate unit 21A shown in FIG. 6, the bottom has a first light control plate 30 ₁ is positioned, the fourth light control plate 30 ₄ as prism plate at the top is positioned. The first to fourth light control plates 30 ₁ to 30 ₄ are sequentially provided in the thickness direction (Z direction), and the lower light control plate 30 of the two adjacent light control plates 30 ₁ to 30 _4. the upper surface ₃₁ 1-31 _{3 1} - 30 _3, and the lower surface ₃₂ 2-32 ₄ of the upper light control plate ₃₀ 2-30 ₄ is arranged to face. The extending direction of the convex portion 33 _1, and substantially perpendicular to the extending direction of the convex portion 33 _2. Further, the extending direction of the convex portion 33 _3, are substantially perpendicular to the extending direction of the convex portion 33 _4. Furthermore, the extending direction of the convex portion 33 ₁ (or the convex portion 33 ₂ ) of the first light control plate 30 ₁ (or the second light control plate 30 ₂ ) and the third light control plate 30 ₃ ( Alternatively, the fourth light control plate 30 ₄ ) is substantially parallel to the extending direction of the convex portion 33 ₃ (or the convex portion 33 ₄ ). Therefore, the arrangement of the _first to _fourth light control plates 30 ₁ to 30 ₄ satisfies the arrangement conditions (i) to (v).

In the light control plate unit 21A, the distance _{d 12} between the first and second light control plate ₃₀ 1, 30 _2, the distance in the Z direction between the convex portion 33 ₁ of the top 33b ₁ and the lower surface 31 ₂ It is. Similarly, the second and third light control plate ₃₀ 2, 30 a distance _{d 23} between the ₃ is the distance in the Z direction between the convex portion 33 ₂ of the top portion 33b ₂ and the lower surface 31 _3. The distance _{d 34} between the third and fourth light control plate ₃₀ 3, 30 ₄ is the distance in the Z direction between the convex portion 33 ₃ top 33b ₃ and the lower surface 31 _4. d ₁₂ , d ₂₃ and d ₃₄ are, for example, 5 mm or less.

(Light control plate unit 21B)
FIG. 13 is a perspective view showing a schematic configuration of another embodiment of the light control plate unit. The first to fourth light control plate 30 ₁ having the light control plate unit 21B, 30 _2, 30 _3, 30 ₄ of the configuration, the first to fourth light control plate ₃₀ 1 to 30 of the first embodiment ₄ of the configuration to be the same. The light control plate unit 21B is different from the light control plate unit 21A in the arrangement order of the _first to _fourth light control plates 30 ₁ to 30 ₄ . This difference will be mainly described.

In the light control plate unit 21B, among the first to fourth light control plate ₃₀ 1 to 30 _4, at the bottom, the first light control plate 30 ₁ is located, at the top, first as a prism plate 4 of the light control plate 30 ₄ is located. Further, the first to fourth light control plates 30 ₁ to 30 ₄ are arranged from the light source 22 side to the first light control plate 30 ₁ , the third light control plate 30 ₃ , the second light control plate 302 and the _second light control plate 30 ₂ . It provided in a thickness direction (Z-direction) in the order of the light control plate 30 ₄ 4. In the optical control plate unit 21B, substantially perpendicular to the first light control plate 30 ₁ of the convex portion 33 ₁ in the extending direction and the second extending direction of the light control plate 30 _{and second} convex portions 33 ₂ ing. Moreover, it is substantially perpendicular to the third extending direction of the light control plate 30 ₃ of the convex portion 33 ₃ of the extending direction of the fourth light control plate 30 ₄ of the convex portion 33 _4. Furthermore, the extending direction of the convex portion 33 ₁ (or the convex portion 33 ₂ ) of the first light control plate 30 ₁ (or the second light control plate 30 ₂ ) and the third light control plate 30 ₃ ( Alternatively, the fourth light control plate 30 ₄ ) is substantially parallel to the extending direction of the convex portion 33 ₃ (or the convex portion 33 ₄ ). Therefore, the arrangement of the _first to _fourth light control plates 30 ₁ to 30 _{4 included in} the light control plate unit 21B satisfies the arrangement conditions (i) to (v).

In the light control plate unit 21B, the first and third light control plate ₃₀ 1, 30 a distance _{d 13} between the _3, first apex 33b ₁ of the convex portion 33 ₁ of the light control plate 30 ₁ and the third This is the distance in the Z direction between the lower surface 31 ₃ of the light control plate 30 ₃ . Similarly, the distance _{d 32} between the third and second light control plate ₃₀ 3, 30 _2, and the third top 33b ₃ of the convex portion 33 ₃ of the light control plate 30 ₃ second light control plate a distance in the Z direction between the 30 ₂ of the lower surface 31 _2. The distance _{d 24} between the second and fourth light control plate ₃₀ 2, 30 _4, the second light control plate 30 _{and second} convex portion 33 ₂ of the top portion 33b ₂ and the fourth light control plate 30 ₄ is the distance in the Z direction between the lower surface 314 of the _four members. d ₁₃ , d ₃₂ and d ₂₄ are, for example, 5 mm or less.

(Light control plate unit 21C)
FIG. 14 is a perspective view showing a schematic configuration of still another embodiment of the light control plate unit. The first to fourth light control plate 30 ₁ having the light control plate unit 21C, 30 _2, 30 _3, 30 ₄ of the configuration, the first to fourth light control plate ₃₀ 1 to 30 of the first embodiment ₄ of the configuration to be the same. The light control plate unit 21C is different from the light control plate unit 21A in the arrangement order of the _first to _fourth light control plates 30 ₁ to 30 ₄ . This difference will be mainly described.

In the light control plate unit 21C, among the first to fourth light control plate ₃₀ 1 to 30 _4, at the bottom, the first light control plate 30 ₁ is located, at the top, the third as a prism plate of the light control plate 30 ₃ is located. Also, the first to fourth light control plates 30 ₁ to 30 ₄ are arranged from the light source 22 side to the first light control plate 30 ₁ , the second light control plate 30 ₂ , the fourth light control plate 304, and the first light control plate 30 ₄ . in the order of the light control plate 30 ₃ 3 are provided in the thickness direction (Z-direction). In the optical control plate unit 21C, substantially perpendicular to the first light control plate 30 ₁ of the convex portion 33 ₁ in the extending direction and the second extending direction of the light control plate 30 _{and second} convex portions 33 ₂ ing. Moreover, it is substantially perpendicular to the third extending direction of the light control plate 30 ₃ of the convex portion 33 ₃ of the extending direction of the fourth light control plate 30 ₄ of the convex portion 33 _4. Furthermore, the extending direction of the convex portion 33 ₁ (or the convex portion 33 ₂ ) of the first light control plate 30 ₁ (or the second light control plate 30 ₂ ) and the third light control plate 30 ₃ ( Alternatively, the fourth light control plate 30 ₄ ) is substantially parallel to the extending direction of the convex portion 33 ₃ (or the convex portion 33 ₄ ). Therefore, the arrangement of the _first to _fourth light control plates 30 ₁ to 30 _{4 included in} the light control plate unit 21C satisfies the arrangement conditions (i) to (v). The arrangement of the light control plate unit 21C is obtained by rotating the third and fourth light control plates 30 ₃ and 30 ₄ by 90 ° in a plane orthogonal to the thickness direction in the arrangement of the first embodiment. Corresponding to

Further, the light control plate unit 21C, the distance _{d 24} between the second and fourth light control plate ₃₀ 2, 30 _4, the second light control plate 30 _{and second} convex portion 33 ₂ and the top 33b ₂ is the distance in the Z direction between the fourth light control plate 30 and _second lower surface 31 _4, 5 mm or less can be exemplified. The distance _{d 43} between the fourth and third light control plate ₃₀ 4, 30 _3, a fourth apex 33b ₄ of the convex portion 33 ₄ of the light control plate 30 ₄ of the third light control plate 30 ₃ is the distance in the Z direction between the lower surface 31 _3, 5 mm or less can be exemplified. The distance _{d 12} between the first and second light control plate ₃₀ 1, 30 ₂ are the same as in the first embodiment, the description thereof is omitted.

As an example of a plurality of embodiments of the light control plate unit 21, three light control plate units 21 </ b> A to 21 </ b> C are illustrated, but from the viewpoint of making the light control plate unit 21 compact, between two adjacent light control plates. The distance can be 0 mm. That is, the _first to _fourth light control plates 30 ₁ to 304 may be provided so that the lower surface of the upper light control plate is in contact with the top of the convex portion of the lower light control plate. In this case, it is preferable that the thickness of the light control plate on the upper side of the lowermost light control plate is smaller than the thickness of the lowermost light control plate (for example, a film-like one). This is because the lowermost light control plate can be used as a support for the upper light control plate.

This point will be specifically described using the light control plate unit 21A shown in FIG. D ₁₂ , d ₂₃ and d ₃₄ shown in FIG. 6 can be set to 0 mm. In this case, the first upper projecting portion 33 ₁ of the light control plate 30 _1, the second to fourth light control plate ₃₀ 2-30 _4, the lower convex portion _{33 1,} 33 2, 33 ₃ The top surfaces 33b ₁ , 33b ₂ , 33b ₃ are arranged so that the lower surfaces 31 ₂ , 31 ₃ , _{3 4} of the upper stage are in contact with the tops 33b ₁ , 33b ₂ , 33b ₃ . Thus, the first light control plate 30 ₁ on which is located most point light source 22 side of the light control plate unit 21A, the second to fourth light control plate ₃₀ 2-30 _4, two adjacent when the upper and lower plate is provided in contact with each other in One of the light control plate ₃₀ 1 to 30 _4, the second to fourth thickness _d 2 to d ₄ of the light control plate ₃₀ 2-30 ₄ first it is preferable that the thing thinner than the thickness d ₁ of the light control plate 30 _1. For example, when the second to fourth light control plate ₃₀ 2-30 ₄ shall thinner such filmy, supporting the first light control plate 30 ₁ of the second to fourth light control plate ₃₀ 2-30 ₄ This is because it can be used as a stand.

[Arrangement of light control board unit]
Light control plate unit 21 may be either of the light control plate unit 21A to 21C, in the embodiments illustrated here, the first light control plate 30 ₁ is located at the bottom. In this case, the light control plate unit 21, as the distance D from the point light sources 22 to the lower surface 31 ₁ of the first light control plate 30 ₁ is a bottom of the light control plate, a normal 3 mm to 50 mm, It is arranged on the point light source 22. 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 control plate unit 21, in the transmissive image display device 1, the extending direction of the convex portion 33 ₁ in which the first light control plate 30 ₁ has may be arranged such that the longitudinal direction of the screen However, they may be arranged in the horizontal direction.

  Next, the function and effect of the light control plate unit 21 will be described by taking as an example the case where the surface light source device 20 including the light control plate unit 21 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 first convex portion 33 of the light control plate 30 _{1 1} has a sectional shape represented by z (x) satisfying the equation (3), the third light control plate 30 ₃ of the convex portion 33 ₃ Is a prism portion whose cross-sectional shape is a substantially right triangle. In this configuration, the first and third light control plates 30 ₁ and 30 ₃ are provided on the point light source 22 that satisfies any of the first and second light distribution characteristics described with reference to FIGS. If the extending direction of the convex portion 33 _1, 33 ₃ are arranged substantially in parallel, the first and third light control plate 30 _1, 30 _3, the light output from the point light sources 22, It can be converted into linear light with uniform luminance and emitted. Similarly, the second convex portion 33 ₂ of the light control plate 30 ₂ has a cross sectional shape represented by z (x) satisfying the equation (3), the fourth light control plate 30 ₄ convex part 33 ₄ is a prism portion is substantially right-angled triangle cross-sectional shape. Therefore, as in the case of the first and third light control plates 30 ₁ and 30 ₃ , the second and fourth light control plates 30 ₂ and 30 ₄ also emit light from the point light source 22 with a uniform luminance. It can be converted into a light beam and emitted.

In the light control plate unit 21, as described above, the first and third light control plates 30 ₁ and 30 _{3 that} can convert the light from the point light source 22 into linear light having substantially uniform luminance. a pair and the second and fourth light control plate 30 _2, 30 ₄ set of, in the Z direction, the convex portion 33 ₁ (or the convex portion 33 ₃₎ the extending direction of the convex portion 33 ₂ (or The extending direction of the convex portion 33 ₄ ) is arranged so as to be substantially orthogonal. Therefore, the light from the point light sources 22, the first and third light control plate 30 _1, 30 ₃ of the set and the second and fourth light control plate ₃₀ 2, 30 ₄ set, uniform luminance Each is converted into linear light in a substantially orthogonal direction. Further, the light control plate unit 21, the first light control plate 30 ₁ is made of a transparent material containing a light diffusing agent. Therefore, it is possible to make the light from the point light source 22 uniform and improve the luminance.

  Since the surface light source device 20 includes the light control plate unit 21, 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 and light with higher luminance can be emitted. Further, since the transmissive image display apparatus 1 includes the light control plate unit 21, the light from the plurality of point light sources 22 is uniformly dispersed, and the luminance uniformity on the surface orthogonal to the Z direction is higher. It is possible to irradiate the transmissive image display unit 10 with planar light and light with higher luminance. As a result, a higher quality image can be displayed.

When the light control plate unit 21 </ b> A is adopted as the light control plate unit 21, the first to fourth light control plates 30 ₁ to 30 ₄ are convex portions 33 ₁ , 33 ₂ , 33 ₃ , in the Z direction. 33 ₄ in the extending direction are arranged so as to be substantially perpendicular to alternately. Therefore, Moire fringes is unlikely to occur to a fourth planar light emitted from the light control plate 30 _4. Therefore, even in the surface light source device 20 including the light control plate unit 21 </ b> A and the plurality of point light sources 22, planar light with suppressed moire fringes can be emitted. Further, the transmissive image display device 1 including the light control plate unit 21A and the plurality of point light sources 22 can display a higher quality image.

  Next, the light control plate unit 21 will be described based on experimental results with respect to the specific effects of the above-described effects. Hereinafter, the measurement results of the luminance and the luminance uniformity in Experimental Examples 1 to 4 will be described with reference mainly to FIGS. 15 and 16. FIG. 15 is a schematic configuration diagram of a manufacturing apparatus for manufacturing a resin sheet. FIG. 16 is a table showing the manufacturing conditions of the light control plates A to F prepared in this experimental example and the surface characteristics of each layer.

In this experimental example, the following were first prepared.
<Raw control plate materials>
The following materials (1) to (3) were prepared as materials for the light control plate.
(1) Transparent resin α
Styrene resin ("HRM40" manufactured by Toyo Styrene Co., Ltd., refractive index 1.59)
(2) Light diffusing agent β
Acrylic crosslinked particles (refractive index 1.49 weight average particle diameter 0.8 μm)
(3) Light diffusing agent master batch After 99.6 parts by mass of the transparent resin α and 0.4 parts by mass of the light diffusing agent β are dry blended, the blended product is put into a hopper of an extruder having a screw diameter of 30 mm. And melt mixed in the cylinder. And it prepared by extruding in the shape of a strand (string) in the state which melt-mixed the blend, and pelletizing.

<Prism sheet>
As a prism sheet (first and second prism plates), a light control plate P (Dai Nippon Printing "PM6") was prepared.

<Configuration of resin sheet manufacturing apparatus>
In this experimental example, a resin sheet manufacturing apparatus 60 as shown in FIG. 15 was used. At that time, four types of polishing rolls 68A, 68B, 68C and 68D (1) to (4) mounted as the lower roll 67 were prepared.

(1) Polishing roll 68A
The polishing roll 68A is a metal roll (diameter: 450 mm) provided with an intaglio transfer mold on the peripheral surface. On the peripheral surface of the polishing roll 68A, a plurality of concave portions that circulate around the polishing roll 68A in the circumferential direction are formed in a streak shape in parallel with each other. The shape of the cross section orthogonal to the circumferential direction of the concave portion is a semicircular arc shape. The pitch _{P A} of the concave portion adjacent a 280 .mu.m, the depth _{D A} of the concave portion is 123Myuemu.
(2) Polishing roll 68B
The polishing roll 68B is a metal roll (diameter: 450 mm) having a mat transfer mold on the peripheral surface. In other words, the peripheral surface of the polishing roll 68B is a mat surface on which many fine irregularities are formed. When the surface roughness of fine irregularities is expressed by the arithmetic average roughness Ra and the maximum height Rz defined by ISO 4287: 1997, Ra is 23.7 μm and Rz is 119.6 μm.
(3) Polishing roll 68C
The polishing roll 68C is a metal roll (diameter: 450 mm) having a mat transfer mold on the peripheral surface. That is, the peripheral surface of the polishing roll 68C is a mat surface on which many fine irregularities are formed. When the surface roughness of the fine irregularities is expressed by an arithmetic average roughness Ra and a maximum height Rz defined by ISO4287: 1997, Ra is 6.9 μm and Rz is 46.6 μm.
(4) Polishing roll 68D
The polishing roll 68D is a metal roll (diameter: 450 mm) whose peripheral surface is mirror-finished.

<Manufacture of light control plate A>
As shown in FIG. 15, a polishing roll 68 </ b> D as an upper roll 65, a polishing roll 68 </ b> B as an intermediate roll 66, and a polishing roll 68 </ b> A as a lower roll 67 in the resin sheet manufacturing apparatus 60. Next, 100 parts by mass of the styrene resin as the transparent resin α was melt-kneaded by the main extruder 61 having a temperature in the cylinder of 190 to 250 ° C., and then supplied to the two-layer distribution type feed block 63. Next, 100 parts by mass of the styrene resin as the transparent resin α was melt-kneaded by the auxiliary extruder 62 having a temperature in the cylinder of 190 to 250 ° C., and then supplied to the two-layer distribution type feed block 63.

  Next, the resin supplied from the main extruder 61 to the two-layer distribution type feed block 63 becomes a base layer, and the resin supplied from the auxiliary extruder 62 to the two-layer distribution type feed block 63 becomes a sublayer. The resin in the two-layer distribution type feed block 63 was co-extruded with a multi-manifold die (width: 1500 mm) at an extrusion resin temperature of 250 ° C. Then, as shown in FIG. 16, the co-extruded resin sheet 2 was pressed and cooled by a polishing roll 68D as an upper roll 65, a polishing roll 68B as an intermediate roll 66, and a polishing roll 68A as a lower roll 67. . In this way, a two-layer laminated resin sheet 2 composed of a width of 1300 mm and a total thickness of 1.5 mm (base material layer 1.45 mm, sublayer 0.05 mm) was produced. Thereafter, the resin sheet 2 was further cooled and cut to an appropriate size to produce a light control plate A (first light control plate).

  In the resin sheet manufacturing process, the resin coextruded from the die 64 is sandwiched between the polishing roll 68 </ b> A as the lower roll 67 and the polishing roll 68 </ b> B as the intermediate roll 66 and pressed, and then the base material of the resin sheet 2. The layer-side surface 2a is formed by transferring concave portions formed on the peripheral surface of the polishing roll 68A to form fine convex portions, and the sub-layer side surface 2b of the resin sheet 2 is formed on the peripheral surface of the polishing roll 68B. The fine irregularities thus transferred are transferred to form a fine irregular surface. Under the present circumstances, the light control board A which adjusted the transfer rate to 99% was produced by changing the surface temperature of polishing roll 68D as an upper roll.

<Manufacture of light control plate B>
In the manufacture of the light control plate B (first light control plate), as shown in the chart of FIG. 16, 86 parts by mass of the styrene resin as the transparent resin α and 14 parts by mass of the masterbatch have a temperature in the cylinder. After melt-kneading with a main extruder 61 at 190 to 250 ° C., the mixture was supplied to the two-layer distribution type feed block 63. Next, 100 parts by mass of the styrene resin as the transparent resin α was melt-kneaded by the auxiliary extruder 62 having a temperature in the cylinder of 190 to 250 ° C., and then supplied to the two-layer distribution type feed block 63. The following manufacturing process of the light control plate B is the same as the manufacturing process of the light control plate A.
<Manufacture of light control plate C>
As shown in the chart of FIG. 16, the light control plate C (first light control plate) is the light control plate except that 86 parts by mass of styrene resin as the transparent resin α and 28 parts by mass of the master batch are used. It was produced by the same method as B.
<Manufacture of light control plate D>
As shown in the chart of FIG. 16, the light control plate D (first light control plate) is the light control plate except that 86 parts by mass of styrene resin as the transparent resin α and 42 parts by mass of the master batch are used. It was produced by the same method as B.

<Manufacture of light control plate E>
As shown in the chart of FIG. 16, the light control plate E (second light control plate) is composed of a width of 1300 mm and a total thickness of 1.2 mm (base material layer 1.15 mm, sublayer 0.05 mm). It manufactured by the method similar to the said light-control board A except the point which manufactured the 2 layer laminated resin sheet 2. FIG.
<Manufacture of light control plate F>
The light control plate F (second light control plate) is a polishing roll 68D as the upper roll 65, a polishing roll 68C as the intermediate roll 66, and a polishing as the lower roll 67 in the resin sheet manufacturing apparatus 60, as shown in the chart of FIG. It was manufactured by the same method as that of the light control plate A except that the roll 68A was mounted.

<Evaluation of light control plates A to F>
About the produced said light-control board AF, the measurement and calculation of the following (1)-(3) were implemented.
(1) Total light transmittance Tt
The total light transmittance Tt of the light control plates A to F was measured according to JIS K7361-1 (1997). Specifically, the total light transmittance Tt was measured using a haze meter HM-150 type (manufactured by Murakami Color Research Laboratory Co., Ltd.). The measurement results are shown in the chart of FIG.
(2) Transfer rate of base material layer The cross-sectional shape of the convex part formed on the base material layer side surface of the light control plates A to F is observed with an ultra-deep shape measuring microscope ("VK-8500" manufactured by KEYENCE). Then, the height _HA of the semicircular arc shaped convex portion was measured. Then, by obtaining the ratio of the height H _A of the convex portion to the depth D _A of the concave portion formed on the circumferential surface of the polishing roll 68A, the transfer rate of the convex portion of the semicircular (= H _A / D _A × 100 (%)) was calculated. The calculation results are shown in the chart of FIG.

(3) Sublayer surface roughness (i) Arithmetic average roughness Ra
The arithmetic average roughness Ra of the sub-layer side surfaces of the light control plates A to F was measured according to ISO 4287: 1997. Specifically, the arithmetic average roughness Ra of the sub-layer side surfaces of the light control plates A to F was measured using a surface roughness meter (“SJ-201P” manufactured by Mitutoyo). The measurement conditions of the surface roughness meter were set to cut-off value: 0.8 × 1, measurement range: auto. The calculation results are shown in the chart of FIG.

(Ii) Maximum height Rz
The maximum height Rz of the sub-layer side surfaces of the light control plates A to F was measured according to ISO 4287: 1997. Specifically, the maximum height Rz of the sub-layer side surfaces of the light control plates A to F was measured using a surface roughness meter (“SJ-201P” manufactured by Mitutoyo). The measurement conditions of the surface roughness meter were set to cut-off value: 0.8 × 1, measurement range: auto. The calculation results are shown in the chart of FIG.

<Manufacture of light control plate G>
The light control plate G was manufactured by press molding. Specifically, two SUS plates were sandwiched between two aramid mats, and an intaglio transfer mold and a sheet of material of 100 parts by mass of styrene resin were placed between them on a press machine. In this intaglio transfer mold, a plurality of concave portions having a semicircular cross section are formed in parallel to each other in a streak shape. The pitch _{P A} of the concave portion adjacent a 330 [mu] m, the depth _{D A} of the concave portion is 145 .mu.m. Next, after the styrene resin was melted at 140 ° C. and pressurized from above and below, the temperature of the press machine was cooled. The light control plate G was formed into a 0.3 mm thick plate by inserting a 0.3 mm metal frame between the thick intaglio transfer mold and the SUS plate. The surface opposite to the transfer surface of the intaglio transfer mold of the light control plate G was not roughened.

<Evaluation of light control plate G>
The transfer rate of the produced light control plate G was measured and evaluated in the same manner as described above. The measurement results are shown in Table 1 below. Further, the same measurement as described above was performed on the surface roughness of the surface of the light control plate G that was not subjected to the rough surface processing on the side opposite to the intaglio transfer surface. The arithmetic average roughness Ra of the light control plate G was 0.1 μm or less, and the maximum height Rz was 0.5 μm or less.

[Experimental Example 1]
<Evaluation of brightness uniformity and brightness>
As a backlight device used in Experimental Example 1, a lamp box in which three LED light sources having a light distribution characteristic as shown in FIG. 4 are arranged in a short side direction at a light source interval of 55 mm and in a long side direction at a light source interval of 50 mm. Prepared. Next, the front side of the lamp box is directed upward and the rear side is arranged on the floor, and the open surface of the lamp box is closed with the light control plate unit U configured under the following conditions (i) to (v). It is. At this time, the backlight device was configured such that the distance (light source distance) between the lamp box and the light control plate was 12.5 mm, and the light control plate A side as the first light control plate was opposed to the lamp box.

(I) The light control plate A as a first light control plate, the light control plate G as a second light control plate, the light control plate P as a third light control plate, and a fourth light The light control plate P as a control plate was overlapped in this order from the bottom in the vertical direction.
(Ii) The light control plate A and the light control plate G were overlapped so that the surface on which the convex portion was formed was the upper surface.
(Iii) The overlapping was performed so that the extending direction of the convex portion of the light control plate A and the extending direction of the convex portion of the light control plate G were orthogonal to each other.
(Iv) The two light control plates P were overlapped so that the surface on which the prism portion was formed was the upper surface.
(V) The prism portions of the two light control plates P were overlapped so that the extending directions thereof were orthogonal to each other.

  Thereafter, the LED light source is turned on, and the in-plane luminance at the front surface of the light emitted from the backlight device is measured by using a luminance meter (“Eye Scale-3WS” manufactured by Eye System Co., Ltd.) (1) Measured according to (3). The luminance meter is a device that measures, evaluates and analyzes the luminance in a range where an image is captured by a CCD camera.

(1) The distance from the upper surface of the light control plate P as the fourth light control plate to the CCD camera in the luminance meter is 0.7 m so that the entire front surface of the light control plate unit U is reflected.
(2) A range of 165 mm × 250 mm centered on the central portion of the front surface of the light control plate unit U was designated as the measurement range.
(3) With respect to the measurement range, 51 measurement spots are set at 5 mm intervals in the long side direction, 33 spots are set at 5 mm intervals in the short side direction, and a total of 1683 (51 × 33) measurement spots are set. It was measured.

Next, the luminance and luminance uniformity calculated based on the luminance measured at each measurement spot were evaluated. The evaluation method of the luminance and luminance uniformity is as follows.
<Luminance>
It is the average value of the brightness | luminance of 1683 measurement spots demonstrated above. The brightness in Experimental Example 1 is as shown in Table 2 below.
<Luminance uniformity>
In the 1683 measurement spots described above, 31 points were extracted from the measurement center in the long side direction and 11 points in the short side direction. Among them, the standard deviation of the luminance profile in the long side direction and the short side direction was calculated, and the one with the largest standard deviation was selected. The ratio between the maximum value and the minimum value (maximum value / minimum value) in the luminance profile was calculated as the luminance uniformity. The luminance uniformity was measured in each of two directions, the V direction (the short side direction of the light control plate unit U) and the H direction (the long side direction of the light control plate unit U). The luminance uniformity in Experimental Example 1 is as shown in Table 2 below.

[Experiment 1a]
In the light control plate unit U, the luminance and the luminance uniformity were evaluated by the same method as in Experimental Example 1 except that the first light control plate was changed to the light control plate B. The evaluation results of luminance and luminance uniformity in Experimental Example 1a are shown in Table 2 below.
[Experiment 1b]
In the light control plate unit U, the luminance and the luminance uniformity were evaluated by the same method as in Experimental Example 1 except that the first light control plate was the light control plate C. The evaluation results of luminance and luminance uniformity in Experimental Example 1b are shown in Table 2 below.
[Experimental Example 1c]
In the light control plate unit U, the luminance and the luminance uniformity were evaluated by the same method as in Experimental Example 1 except that the first light control plate was the light control plate D. The evaluation results of the luminance and luminance uniformity in Experimental Example 1c are shown in Table 2 below.

<Evaluation results based on Experimental Example 1 and Experimental Examples 1a to 1c>
Table 3 shown below summarizes the evaluation results in Experimental Example 1 and Experimental Examples 1a to 1c. The upper numerical value in the column indicating each evaluation indicates the luminance, and the numerical value in parentheses indicates the ratio of the luminance in each experimental example 1a to 1c when the luminance in experimental example 1 is 100. . The lower numerical values indicate the above-described luminance uniformity and correspond to the numerical values in Table 2 above.

  It was confirmed that the luminance in Experimental Examples 1a to 1c was a better numerical value than the measurement result of the luminance in Experimental Example 1. Thus, forming the light control plates B to D as the first light control plate with a transparent material containing a light diffusing agent has the effect of achieving uniform luminance and improving luminance. Was confirmed.

[Experimental example 2]
In the light control plate unit U, the luminance and the luminance uniformity were evaluated by the same method as in Experimental Example 1 except that the second light control plate was the light control plate F. The evaluation results of luminance and luminance uniformity in Experimental Example 2 are shown in Table 4 below.
[Experiment 2a]
In the light control plate unit U, the luminance and the luminance uniformity were evaluated by the same method as in Experimental Example 1a except that the second light control plate was the light control plate F. The evaluation results of luminance and luminance uniformity in Experimental Example 2a are shown in Table 4 below.
[Experiment 2b]
In the light control plate unit U, the luminance and the luminance uniformity were evaluated by the same method as in Experimental Example 1b except that the second light control plate was the light control plate F. The evaluation results of luminance and luminance uniformity in Experimental Example 2b are shown in Table 4 below.
[Experiment 2c]
In the light control plate unit U, the luminance and the luminance uniformity were evaluated by the same method as in Experimental Example 1c except that the second light control plate was changed to the light control plate F. The evaluation results of luminance and luminance uniformity in Experimental Example 2c are shown in Table 4 below.

<Evaluation results based on Experimental Example 2 and Experimental Examples 2a to 2c>
Table 5 shown below summarizes the evaluation results in Experimental Example 2 and Experimental Examples 2a to 2c. The upper numerical value in the column indicating each evaluation indicates the luminance, and the numerical value in parentheses indicates the ratio of the luminance in each experimental example 2a to 2c when the luminance in experimental example 2 is 100. . The lower numerical values indicate the above-described luminance uniformity and correspond to the numerical values in Table 4 above.

  It has been confirmed that the luminance in Experimental Examples 2a to 2c is a better numerical value than the luminance measurement result of Experimental Example 2. Thereby, similarly to the evaluation results based on Experimental Example 1 and Experimental Examples 1a to 1c, forming the light control plates B to D as the first light control plate with a transparent material containing a light diffusing agent, It was confirmed that there was an effect of improving the luminance.

[Experimental Example 3]
In the light control plate unit U, the luminance and the luminance uniformity were evaluated by the same method as in Experimental Example 1 except that the second light control plate was the light control plate E. The evaluation results of luminance and luminance uniformity in Experimental Example 3 are shown in Table 6 below.
[Experiment 3a]
In the light control plate unit U, the luminance and the luminance uniformity were evaluated by the same method as in Experimental Example 1a except that the second light control plate was the light control plate E. The evaluation results of luminance and luminance uniformity in Experimental Example 3a are shown in Table 6 below.
[Experiment 3b]
In the light control plate unit U, the brightness and the brightness uniformity were evaluated by the same method as in Experimental Example 1b except that the second light control plate was the light control plate E. The evaluation results of luminance and luminance uniformity in Experimental Example 3b are shown in Table 6 below.
[Experiment 3c]
In the light control plate unit U, the luminance and the luminance uniformity were evaluated by the same method as in Experimental Example 1c except that the second light control plate was changed to the light control plate E. The evaluation results of luminance and luminance uniformity in Experimental Example 3c are shown in Table 6 below.

<Evaluation results based on Experimental Example 3 and Experimental Examples 3a to 3c>
Table 7 shown below summarizes the evaluation results in Experimental Example 3 and Experimental Examples 3a to 3c. The upper numerical value in the column indicating each evaluation indicates the luminance, and the numerical value in parentheses indicates the ratio of the luminance in each of Experimental Examples 3a to 3c when the luminance in Experimental Example 3 is 100. . The lower numerical values indicate the above-described luminance uniformity and correspond to the numerical values in Table 6 above.

  It has been confirmed that the luminance in Experimental Examples 3a to 3c is a better numerical value than the measurement result of the luminance in Experimental Example 3. Thereby, similarly to the evaluation results based on Experimental Example 1 and Experimental Examples 1a to 1c, forming the light control plates B to D as the first light control plate with a transparent material containing a light diffusing agent, It was confirmed that there was an effect of improving the luminance.

  Further, for example, the following could be confirmed from the measurement results of the luminance and luminance uniformity in Experimental Examples 1a, 2a, and 3a. That is, from the measurement result that the luminance and the luminance uniformity in Experimental Examples 2a and 3a are better than the luminance and the luminance uniformity in Experimental Example 1a, the lower surface of the light control plate arranged as the second light control plate is It was confirmed that the luminance and the luminance uniformity can be further improved by making the surface rough. Further, from the measurement result that the luminance and luminance uniformity in Experimental Example 3a are better than the luminance and luminance uniformity in Experimental Example 2a, the surface roughness of the lower surface of the light control plate arranged as the second light control plate is determined. It was confirmed that the luminance and the luminance uniformity can be improved as the thickness (expressed by the arithmetic average roughness Ra and the maximum height Rz) is increased.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment.
For example, the light control plate unit 21 of the above embodiment, although the first light control plate 30 ₁ has been described by way of example made of a transparent material containing a light diffusing agent is not limited thereto, the first and second light control plate 30 _1, 30 both ₂ or the second light control plate 30 ₂ may be made of a transparent material containing a light diffusing agent.

Further, the light control plate unit 21 of the above embodiment, the lower surface 31 _1, 31 ₂ of the above-described first and second light control plate 30 1 of the _embodiment, 30 ₂ has been described by way of example a rough surface The surface is not limited to this, and may be a substantially flat surface.

Further, for example, first and second light control plate ₃₀ 1, 30 ₂ of the lower surface ₃₁ 1, ₃₁ 2 of the above embodiments, ISO4287: 1997 in maximum height Rz as defined is 5μm or more, the arithmetic average roughness The example in which the rough surface processing is performed so that Ra becomes a rough surface of 2 μm or more has been described, but at least one of the maximum height Rz and the arithmetic average roughness Ra is configured to satisfy the above condition. Also good.

Further, for example, the light control plate unit 21 of the above embodiment has been described by way of example a bottom ₃₁ 1, 31 ₂ are rough surfaces of the first and second both of the light control plate ₃₀ 1, 30 ₂ , it is not limited thereto, at least one of the light control plate ₃₀ 1, 30 ₂ of the lower surface ₃₁ 1, 31 ₂ may be a rough surface.

Further, for example, the arrangement examples of the plurality of point light sources 22 are shown in FIGS. 2 and 3, but for example, a square lattice, that is, the interval between the point light sources 22 adjacent in the X direction and the Y direction as described above. 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 _i. 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.

  The light control plate unit 21 may further include an optical film such as a diffusion film, a microlens film, or a reflective polarizing film on the transmissive image display unit 10 side (for example, the liquid crystal panel side). 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 control plate unit 21 and the transmissive image display unit 10. You can also

  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 control plate unit 21 side. In the schematic diagram shown in FIG. 1, the reflecting means may be provided on the side opposite to the light control plate unit 21 with respect to the point light source 22. The placement surface can be a reflective surface.

The first and second light control plate 30 _1, 30 ₂ is described as a light control plate, if each convex portion 33 ₁ and the convex portion 33 ₂ optical component the shaped plate-like Good.

  Of the plurality of light control plates included in the light control plate unit 21 illustrated in FIGS. 6, 13, and 14, the light control plate located closest to the point light source 22 has a thickness of 1.0 mm or more. It can be a sheet. 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, polycarbonate, MS resin, or AS resin 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 22 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.

  The light control plate located closest to the point light source 22 is preferably a sheet having a thickness of 1 mm to 5 mm, and the light control plates other than the light control plate located closest to the point light source have a thickness of A film of less than 1 mm is desirable.

DESCRIPTION OF SYMBOLS 1 ... Transmission type image display apparatus, 10 ... Transmission type image display part, 11 ... Liquid crystal cell, 12, 13 ... Polarizing plate, 20 ... Surface light source device, 21,21A, 21B, 21C ... Light control board unit, 22 ... Point Light source, 30 ₁ , 30 ₂ ... First and second light control plates, 31 ₁ , 31 ₂ ... Bottom surface of first and second light control plates, 32 ₁ , 32 ₂ . Upper surface of control plate, 33 ₁ , 33 ₂ ... Convex portion of first and second light control plates, 33a ₁ , 33a ₂ ... End of convex portion (convex portion of first and second light control plates , 30 ₃ , 30 ₄ ... third and fourth light control plates (first and second prism plates), 31 ₃ , 31 ₄ ... lower surface of the third and fourth light control plates, 32 ₃ , 32 ₄ ... upper surfaces of the third and fourth light control plates (one side of the first and second prism plates), 33 ₃ , 33 ₄ ... convex portions of the third and fourth light control plates (first , Prism unit 2), 60 ... resin sheet manufacturing apparatus, 61 ... main extruder, 62 ... auxiliary extruder, 63 ... two-layer distribution type feed block, 64 ... die, 65 ... upper roll, 66 ... intermediate roll , 67 ... lower roll, 68A, 68B, 68C, 68D ... polishing roll, Y1 ... extension direction of the convex portion of the first light control plate, X1 ... direction substantially orthogonal to the Y1 direction, X2 ... second light Extension direction of the convex portion of the control plate, Y2... Direction substantially orthogonal to the X2 direction, Y3... Extension direction of the convex portion (prism portion) of the third light control plate (first prism plate), X3 ... a direction substantially orthogonal to the Y3 direction, X4 ... an extending direction of the convex portion (prism portion) of the fourth light control plate (second prism plate), Y4 ... a direction substantially orthogonal to the X4 direction.

Claims (6)

A plurality of convex portions extending in one direction are formed on one side, and the plurality of convex portions are arranged in parallel in a direction substantially orthogonal to the extending direction of the convex portions. A light control board of
A plurality of prism portions extending in one direction are formed on one side, and the plurality of prism portions are arranged in parallel in a direction substantially orthogonal to the extending direction of the prism portions. When,
With
At least one of the first and second light control plates contains a light diffusing agent,
The first and second light control plates and the first and second prism plates are overlapped in the thickness direction with the first or second light control plate as the lowest stage,
The extending direction of the convex portion of the first light control plate and the extending direction of the convex portion of the second light control plate are substantially orthogonal,
The extending direction of the prism portion of the first prism plate and the extending direction of the prism portion of the second prism plate are substantially orthogonal to each other,
In an orthogonal cross section substantially orthogonal to the extending direction of the convex portion included in each of the first and second light control plates, an axis passing through both ends of the convex portion is defined as an x axis, and the axis on the x axis an axis perpendicular to the x-axis as the center of both ends is z-axis, when the length of the x-axis direction of the convex portion was set to w _a, a cross section of the convex portion of the first light control plate has shape and the cross-sectional shape of the convex portion in which the second light control plate has _{independently, -0.475 × w a ≦ x ≦} 0.475 × w satisfies the equation (1) in _a z (x )
Light control board unit.

However, in the formula _{(1), z} 0 (x) is represented by the formula (2).

(In formula (2),
C ₂ = 0.762469824257553, C ₄ = 0.2980756626262927, C ₆ = -0.5596293831533661, C ₈ = 0.89644682802533265, C ₁₀ = -0.657164416166137715, C ₁₂ = -0.6157641844995985, C ₁₄ = 1. 245151353938560 and C ₁₆ = −0.52055908769482, or
C ₂ = 0.8280347903338647, C ₄ = 0.3221164108625275, C ₆ = −0.6834093884088353, C ₈ = 1.221645232748140, C ₁₀ = −1.20438125937210, C ₁₂ = −0.14099137787724, C ₁₄ = 1. 031108858219420, C ₁₆ = −0.47538835345540708, or
C ₂ = 0.9087430553413473, C ₄ = 0.412136074245729, C ₆ = -1.0522244441109330, C ₈ = 1.939462214284020, C ₁₀ = -2.013300115231320, C ₁₂ = 0.074667849261357, C ₁₄ = 1.376993293235370 , C ₁₆ = −0.68008101068815946. ) The surface of at least one of the first and second light control plates opposite to the surface on which the convex portion is formed is a rough surface.
The light control board unit according to claim 1. One of the first and second prism plates is disposed between the first and second light control plates;
The extending direction of the prism portion included in the first and second prism plates disposed between the first and second light control plates, and the extending direction of the convex portion included in the lowermost light control plate. Is substantially parallel,
The light control board unit according to claim 1 or 2. The light control plate unit according to any one of claims 1 to 3,
A plurality of point light sources for supplying light to the light control plate unit;
With
The plurality of point light sources are spaced apart from each other and disposed on the back side of the light control plate unit.
Surface light source device. The surface light source device according to claim 4, wherein the point light source has the following first light distribution characteristic or second light distribution characteristic.
First light distribution characteristic:
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
The emission angle at which the emission light intensity is (I ₀ + I _max ) / 2 is 60 ° or more and 70 ° or less, and
A light distribution characteristic in which 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.
Second light distribution characteristic:
A light distribution characteristic having a maximum emission light intensity I _max in a range of the light emission angle of 65 ° to 75 °,
The outgoing light intensity I ₀ when the outgoing angle is 0 ° is
0.22 × I _max ≦ I ₀ ≦ 0.30 × I _max
The emission angle at which the emission light intensity is (I ₀ + I _max ) / 2 is 45 ° to 55 °, and
A light distribution characteristic in which the emission angle at which the emission light intensity is (I ₀ + I _max ) / 4 is 20 ° or more and 30 ° or less. A surface light source device according to claim 4 or 5,
A transmissive image display unit irradiated with light output from the surface light source device;
A transmissive image display device.

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