JP2019067732A - Planar light source device and display device - Google Patents

Abstract

To provide a planar light source device and a display device capable of having a peak of brightness in a direction excluding a normal direction with a simple constitution, and improving symmetry of an azimuth direction and an elevation angle direction in the distribution of brightness in the peak direction as a center.SOLUTION: A planar light source device 20 has a light guide plate 30 having a light emission face 31, a back face 32, and side faces positioned between the light emission face and the back face and applying the arbitrary side face of the side faces as an incident face 33, a light source 24 disposed in opposition to the light incident face, and an optical sheet 60 disposed in opposition to the light emission face 31. The optical sheet has a sheet-shaped main body portion 65, and a plurality of structure rows 70 disposed on a face at a light guide plate side, of the main body portion. When a direction vertical to the light incident face 33 is a first direction d1, and an arrangement direction of the structure rows 70 is a third direction d3, the first direction d1 and the third direction d3 are not parallel to each other, and prescribed conditions are satisfied in measuring the brightness of the light emitted from a center of the face (light emission face) 61 at a side opposite to the light guide plate of the optical sheet.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a surface light source device and a display device.

  BACKGROUND ART A surface light source device having a light emitting surface that emits light in the form of a plane is widely used, for example, as a backlight for illuminating a liquid crystal display panel from the back side (for example, Patent Document 1). Surface light source devices for liquid crystal display devices are roughly classified into a direct type in which a light source is disposed immediately below an optical member and an edge light type in which a light source is disposed on the side of an optical member. The edge light type surface light source device is superior to the direct type surface light source device in that thinning, cost reduction and power consumption can be achieved.

The edge light type surface light source device of Patent Document 1 includes a light guide plate, a light deflection element disposed facing the light exit surface of the light guide plate, and a light source disposed facing the one side surface of the light guide plate. have. The light guide plate distributes the light from the light source so that the amount of light along the light guide direction becomes uniform. The specific shape of the light deflection element is described in FIG. 6, and the incident-side surface of the light deflection element facing the light guide plate has a plurality of tilts arranged in a direction parallel to the light guide direction of the light guide plate. The surface on the output side that is opposite to the light guide plate side of the light deflection element has a plurality of lens surfaces arranged in the direction parallel to the light guide direction of the light guide plate. In this light deflection element, the light emission direction is controlled by the combination of the refraction of the surface on the incident side and the refraction of the surface on the emission side.
Further, Patent Document 2 discloses a method of shifting a light emission peak with a lens or the like in an azimuth angle direction or an elevation angle direction of a screen, such as multiview or 3D display.

Japanese Examined Patent Publication 7-66122 JP, 2005-78078, A

At present, liquid crystal display devices provided with edge light type surface light source devices have come to be applied to various devices. The liquid crystal display device ideally has a peak of luminance in the normal direction of the display surface in many of its applications.
However, in some applications, it may be preferable for the display surface to have a peak of luminance in a direction inclined from the normal direction. For example, a liquid crystal display device applied to a center console of a car is observed by a driver of the car from obliquely above. Therefore, in such a liquid crystal display device, it is preferable that the peak of luminance appears obliquely upward.

In the liquid crystal display device of Patent Document 1, it is described that the peak of luminance is aligned with the center of the viewing angle characteristics of the liquid crystal display element by the configuration of the surface on the light incident side and the surface on the light output side of the light deflection element.
However, in Patent Document 1, only the matching of the peaks of luminance is examined, and the luminance distribution centering on the peaks is not examined at all. In addition, although light is emitted in various directions, Patent Document 1 does not study the luminance distribution in multiple directions at all.
In the first place, as in FIG. 6 of Patent Document 1, when the peak direction of the luminance is adjusted by the combination of the refraction on the incident side surface of the light deflection element and the refraction on the emission side surface of the light deflection element Since it is necessary to align the positions on the front and back, fine patterns can not be designed, and multi-faceted design of the luminance distribution becomes difficult, and the configuration becomes complicated and the yield decreases.
In Patent Document 2, although it is possible to provide a luminance peak in a desired direction, the spread in the azimuth and elevation directions was not controlled.

  The present invention has been made in consideration of the above-described points, and it is possible to generate a peak of luminance in a direction other than the normal direction by a simple configuration, and an azimuth angle of the luminance distribution centering on the direction showing the peak. An object of the present invention is to provide a surface light source device and a display device in which the symmetry in the direction and the elevation direction is improved.

In order to solve the above problems, the present invention provides the following surface light source device and display device.
(1) A light guide plate having a light exit surface, a back surface opposite to the light exit surface, and a side surface located between the light exit surface and the back surface, and any of the side surfaces is a light entrance surface, A surface light source device comprising: a light source disposed facing the light entrance surface; and an optical sheet disposed facing the light exit surface of the light guide plate, wherein the optical sheet has a sheet shape And a plurality of structural rows provided on the surface of the main portion on the light guide plate side, a direction perpendicular to the light incident surface of the light guide in a first direction d ₁ , an array of the structural rows upon the direction third direction d _3, the first direction d ₁ and a third direction d ₃ is non-parallel, the brightness of the light emitted from the center of the surface opposite to the optical sheet of the light guide plate A surface light source device satisfying the following condition 1-1 and condition 2-1 when measuring.
<Condition 1-1>
The maximum luminance when measuring the luminance distribution of light emitted from the center of the surface opposite to the light guide plate of the optical sheet in a matrix at an elevation angle of 0.5 ° and at an azimuth angle of 0.5 ° is P _max I assume. Here, when the surface light source device is viewed from the normal direction, the direction of the perpendicular drawn from the center to the light incident surface side is the “azimuth angle 0 °”, and the surface of the optical sheet opposite to the light guide plate The direction from normal direction to the normal direction is "elevation 0 °".
When the elevation angle indicating P _max is EA _max and the azimuth angle indicating P _max is DA _max , the EA _max indicates a value other than 0 °.
<Condition 2-1>
Based on the brightness of each angle measured in condition 1-1, a brightness distribution map A for each azimuth angle at the elevation angle EA _max is created. In the luminance distribution map A, it is assumed that all luminances are normalized with the luminance of P _max as 1.0.
The integrated value of luminance in the range of azimuth angle “(DA _max −45 °) to (DA _max + 45 °)” of the luminance distribution map A is DA _{−45 / + 45} , and the azimuth angle “(DA _max of the luminance distribution map A An integral value of luminance in a range of −20 °) to DA _max to (DA _max + 20 °) is set to DA _{−20 / + 20} .
Based on the brightness of each angle measured in condition 1-1, a brightness distribution chart B for each elevation angle at the azimuth angle DA _max is created. In the luminance distribution diagram B, it is assumed that all luminances are normalized with the luminance of P _max as 1.0.
The integrated value of the brightness in the range of elevation angles “(EA _max −45 °) to (EA _max + 45 °)” of the brightness distribution chart B is EA _{−45 / + 45} , and the azimuth angle “(EA _max − Let the integral value of the luminance in the range of 20 °) to (EA _max + 20 °) be EA _{-20 / + 20} .
In the above, 0.77 ≦ (DA− _{20 / + 20} / DA− _{45 / + 45} ) / (EA− _{20 / + 20} / EA− _{45 / + 45} ) ≦ 1.30 is satisfied.
(2) The surface light source device according to (1), further satisfying the condition of 27 ° ≦ EA _max ≦ 60 ° in the condition 1-1.
(3) The surface light source device according to (1) or (2), further satisfying the following condition 1-2.
<Condition 1-2>
DA _max has a value other than 0 ° or 180 °.
(4) The surface light source device according to (3), which satisfies the condition of 240 ° ≦ DA _max ≦ 310 ° under the condition 1-2.
(5) The surface light source device according to any one of the above (1) to (4), which satisfies the following condition 2-3.
<Condition 2-3>
Based on the brightness of each angle measured in condition 1-1, a brightness distribution map A for each azimuth angle at the elevation angle EA _max is created. In the luminance distribution map A, it is assumed that all luminances are normalized with the luminance of P _max as 1.0.
The azimuth angle DA _max is a reference azimuth angle, and at an azimuth angle on the negative direction side from the reference azimuth angle of the brightness distribution map A, an azimuth angle angle indicating a brightness that is first 1/3 or less of P _max is -β DA _max , An azimuth angle indicating a luminance that is firstly 1⁄3 or less of P _max at an azimuth angle on the positive direction side from the reference azimuth angle is + β DA _max .
The interval between the reference azimuth angle and the angle -βDA _max is β _D1 , and the interval between the reference elevation angle and the + β DA _max is β _D2 .
In the above, the condition of 20 ° ≦ (β _D1 + β _D2 ) / 2 ≦ 60 ° is satisfied.
(6) The surface light source device according to any one of the above (1) to (5), which satisfies the following condition 2-4.
<Condition 2-4>
Based on the brightness of each angle measured in condition 1-1, a brightness distribution chart B for each elevation angle at the azimuth angle DA _max is created. In the luminance distribution diagram B, it is assumed that all luminances are normalized with the luminance of P _max as 1.0.
An elevation angle EA _max is taken as a reference elevation angle, and an elevation angle inclined toward the normal direction is referred to as an “elevation angle on the minus direction side”, and an elevation angle inclined toward the side away from the normal direction is referred to as an elevation angle on the plus direction.
First P _max at first elevation angle of elevation showing luminance as a third or less of P _max -βEA _max, the reference elevation angle of plus direction side from the reference elevation angle in the elevation of the minus side of the luminance distribution diagram B 1/3 the angle of elevation showing the following become luminance + βEA _max to.
The interval between the reference elevation angle and the angle -βEA _max is β _E1 , and the interval between the reference elevation angle and the + β EA _max is β _E2 .
In the above, the condition of 20 ° ≦ (β _E1 + β _E2 ) / 2 ≦ 30 ° is satisfied.
(7) the first direction _{d 1} and the third angle theta _D1d3 formed between the direction _{d 3} is found above satisfy _{15 ° ≦ θ d1d3 ≦ 50 °} (1) a surface light source device according to any one of - (6) .
(8) Furthermore, the surface light source device in any one of said (1)-(7) which satisfy | fills the following conditions 1-3.
<Condition 1-3>
A first direction d ₁ and the third direction d ₃ is the comparison surface light source device a surface light source device is a parallel in the surface light source device. When the luminance of light emitted in the normal direction from the center of the surface opposite to the light guide plate of the optical sheet of the comparative surface light source device is measured, and the luminance is Ref, 1.0 ≦ P _max / Ref Meet.
(9) In the above condition 2-1, the above-mentioned DA _{-20 / + 20} / DA _{-45 / + 45} is 0.55 or more and the above-mentioned EA _{-20 / + 20} / EA _{-45 / + 45} is 0.70 or more 1) The surface light source device (10) according to any one of (8) to (10), the surface light source device according to any one of the above (1) to (9), and a display panel disposed facing the surface light source device A display device comprising:

  The surface light source device and the display device of the present invention can generate luminance peaks in directions other than the normal direction with a simple configuration, and are symmetrical in the azimuth angle direction and the elevation angle direction of the luminance distribution centering on the direction showing the peaks. It is possible to improve the quality.

It is a sectional view showing one embodiment of a surface light source device and a display of the present invention. It is sectional drawing of the surface light source device of FIG. 1, Comprising: It is a figure for demonstrating an effect | action of a surface light source device. It is a top view from the light emission surface side of the surface light source device of FIG. It is a perspective view from the light emission surface side of the light-guide plate integrated in the surface light source device of FIG. It is a perspective view from the back side of the light-guide plate integrated in the surface light source device of FIG. It is sectional drawing of the light-guide plate along the VI-VI line of FIG. 4, Comprising: It is a figure for demonstrating the effect | action of a light-guide plate. It is a perspective view from the surface of the light-incidence side of the optical sheet integrated in the surface light source device of FIG. It is the elements on larger scale of the cross section of the optical sheet along the VIII-VIII line of FIG. It is the figure which expanded the cross section similar to FIG. 2 to a part of optical sheet, Comprising: It is a figure for demonstrating the effect | action of an optical sheet. It is a figure for demonstrating the effect | action of the optical sheet at the time of changing the optical sheet of FIG. 9 into another optical sheet. In the normal direction and the first direction d ₁ of both the plane parallel is a graph showing the angular distribution of luminance on the light exit surface of the light guide plate. In the normal direction and the second direction d a plane parallel to both ₂ is a graph showing the angular distribution of luminance on the light exit surface of the light guide plate. It is a graph which shows angular distribution of the brightness | luminance on the light emission surface of an optical sheet in, when the bias angle of an optical sheet is 0 degree. It is a graph which shows angular distribution of the brightness | luminance on the light emission surface of an optical sheet in, when the bias angle of an optical sheet is 10 degrees. It is a graph which shows angular distribution of the brightness | luminance on the light emission surface of an optical sheet in, when the bias angle of an optical sheet is 20 degrees. It is a graph which shows angular distribution of the brightness | luminance on the light emission surface of an optical sheet in, when the bias angle of an optical sheet is 30 degrees. It is a graph which shows angular distribution of the brightness | luminance on the light emission surface of an optical sheet in, when the bias angle of an optical sheet is 40 degrees. In the case where a bias angle of the optical sheet as 0 °, is a graph showing the luminance distribution of each azimuth in elevation EA _max. In the case where a bias angle of the optical sheet and 10 °, is a graph showing the luminance distribution of each azimuth in elevation EA _max. In the case where a bias angle of the optical sheet and 20 °, is a graph showing the luminance distribution of each azimuth in elevation EA _max. In the case where a bias angle of the optical sheet and 30 °, is a graph showing the luminance distribution of each azimuth in elevation EA _max. In the case where a bias angle of the optical sheet and 40 °, is a graph showing the luminance distribution of each azimuth in elevation EA _max. In the case where a bias angle of the optical sheet as 0 °, is a graph showing a luminance distribution of each elevation in azimuth DA _max. In the case where a bias angle of the optical sheet and 10 °, is a graph showing a luminance distribution of each elevation in azimuth DA _max. In the case where a bias angle of the optical sheet and 20 °, is a graph showing a luminance distribution of each elevation in azimuth DA _max. In the case where a bias angle of the optical sheet and 30 °, is a graph showing a luminance distribution of each elevation in azimuth DA _max. In the case where a bias angle of the optical sheet and 40 °, is a graph showing a luminance distribution of each elevation in azimuth DA _max.

Hereinafter, embodiments of the surface light source device and the display device of the present invention will be described mainly with reference to the drawings.
In the drawings attached to the present specification, there are cases in which the dimensional ratio and the like of the real thing are changed from the viewpoint of ease of illustration.

Further, in the present specification, the “light output side” refers to the light source, light guide plate, and components of the surface light source device such as an optical sheet, etc. The downstream side in the traveling direction is meant, and the “light entrance side” means the upstream side in the traveling direction.
Moreover, in the present specification, terms such as “sheet”, “film”, “plate” and the like are not distinguished from one another. For example, a sheet is a concept including a member that can also be called a film or a plate.

Further, in the present specification, the “sheet surface (plate surface, film surface)” corresponds to the planar direction of the target sheet-like member when the target sheet-like member is viewed generally and globally. Point to the face. In the present embodiment, the plate surface of the light guide plate, the sheet surface of the optical sheet, the sheet surface of the reflective sheet, the panel surface of the display panel, the display surface of the display device, and the light emission surface of the surface light source device are substantially parallel to one another. It has become.
Further, in the present specification, “normal direction” means the normal direction to the light emitting surface of the surface light source device, and in the present embodiment, the normal direction to the light emitting surface of the surface light source device, It also corresponds to the normal direction to the plate surface of the light plate, the normal direction to the sheet surface of the optical sheet, the normal direction to the display surface of the display device, and the like.

  Furthermore, in the present specification, "pentagon" and "square" are not only pentagons and squares in a strict sense, but also substantially pentagons and substantially in consideration of the limit of precision in manufacturing technology and errors in molding, etc. Contains a square. Similarly, other terms used herein (eg, parallel, orthogonal, symmetric, etc.) to identify other shapes or geometric conditions may also be expected to have equivalent optical functions without being bound by a strict meaning. It shall be interpreted including an error of degree.

[Surface light source device]
The surface light source device of the present embodiment is
A light guide plate having a light exit surface, a back surface opposite to the light exit surface, and a side surface located between the light exit surface and the back surface, and any of the side surfaces is a light entrance surface;
A light source disposed facing the light entrance surface;
A surface light source device comprising: an optical sheet disposed to face the light exit surface of the light guide plate;
The optical sheet has a sheet-like main body portion and a plurality of structural rows provided on the surface of the main body portion on the light guide plate side,
When the direction perpendicular to the light incident surface of the light guide plate is a first direction d ₁ and the arrangement direction of the structural rows is a third direction d ₃ , the first direction d ₁ and the third direction d ₃ are not parallel And
When the luminance of light emitted from the center of the surface opposite to the light guide plate of the optical sheet is measured, the following condition 1-1 and condition 2-1 are satisfied.
The arrangement direction of the plurality of structural rows is usually perpendicular to the extending direction of the structural rows in the sheet plane. In addition, although the extension direction of a structure row | line is normally linear form, it is the same whether it is curvilinear form, it is meandering, and they are mixed.

<Condition 1-1>
The maximum luminance when measuring the luminance distribution of light emitted from the center of the surface opposite to the light guide plate of the optical sheet in a matrix at an elevation angle of 0.5 ° and at an azimuth angle of 0.5 ° is P _max I assume. Here, when the surface light source device is viewed from the normal direction, the direction of the perpendicular drawn from the center to the light incident surface side is the “azimuth angle 0 °”, and the surface of the optical sheet opposite to the light guide plate The direction from normal direction to the normal direction is "elevation 0 °".
When the elevation angle indicating P _max is EA _max and the azimuth angle indicating P _max is DA _max , the EA _max indicates a value other than 0 °.

<Condition 2-1>
Based on the brightness of each angle measured in condition 1-1, a brightness distribution map A for each azimuth angle at the elevation angle EA _max is created. In the luminance distribution map A, it is assumed that all luminances are normalized with the luminance of P _max as 1.0.
The integrated value of luminance in the range of azimuth angle “(DA _max −45 °) to (DA _max + 45 °)” of the luminance distribution map A is DA _{−45 / + 45} , and the azimuth angle “(DA _max of the luminance distribution map A An integral value of luminance in a range of −20 °) to DA _max to (DA _max + 20 °) is set to DA _{−20 / + 20} .
Based on the brightness of each angle measured in condition 1-1, a brightness distribution chart B for each elevation angle at the azimuth angle DA _max is created. In the luminance distribution diagram B, it is assumed that all luminances are normalized with the luminance of P _max as 1.0.
The integrated value of the brightness in the range of elevation angles “(EA _max −45 °) to (EA _max + 45 °)” of the brightness distribution chart B is EA _{−45 / + 45} , and the azimuth angle “(EA _max − the integrated value of luminance in the range of _{20 °) ~EA max ~ (EA} max + 20 °) "and _{EA -20 / + 20.}
In the above, 0.77 ≦ (DA− _{20 / + 20} / DA− _{45 / + 45} ) / (EA− _{20 / + 20} / EA− _{45 / + 45} ) ≦ 1.30 is satisfied.
When (DA _{-20 / + 20} / DA _{-45 / + 45} ) / (EA _{-20 / + 20} / EA _{-45 / + 45} ) is less than 0.77 or more than 1.30, the peak direction is centered The luminance distribution is less likely to be symmetrical in the azimuth and elevation directions.
It is preferable to satisfy 0.80 ≦ (DA− _{20 / + 20} / DA− _{45 / + 45} ) / (EA− _{20 / + 20} / EA− _{45 / + 45} ) ≦ 1.25, and 0.83 ≦ (DA− _{20 / + 20} / DA- _{45 / + 45} ) / (EA- _{20 / + 20} / EA- _{45 / + 45} ) ≦ 1.20 is more preferable, and 0.91 ≦ (DA- _{20 / + 20} / DA- _{45 / + 45} ) / (EA) _It is further preferred that _{-20 / + 20} / EA- _{45 / + 45} ) .ltoreq.1.10.

Satisfying the condition 1-1 means that the peak of luminance occurs in directions other than the normal direction.
Satisfying the condition 2-1 means that the luminance distribution centered on the direction showing the peak has good symmetry in the azimuth direction and the elevation direction.

It is preferable that the surface light source device of the present embodiment further satisfy the following condition 1-2.
<Condition 1-2>
DA _max has a value other than 0 ° or 180 °.

Satisfying the conditions 1-2, which means that the peak of luminance is generated in a direction other than the first direction d _1.
However, in the present specification, “a value other than 0 ° or 180 ° in DA _max ” is strictly dependent on not only 0 ° or 180 °, but also the type of light source, stability, measurement error, etc. However, in view of the azimuth measurement points (every 0.5 °) and the measurement conditions of luminance described later, DA _max is 0 ° ≦ DA _max <2.0 °, 358.0 ° <DA _max ≦ 360. ° _{(DA max} is 360 ° and 0 ° is assumed to be the same.), or 178.0 ° _<meant to indicate a value other than DA max <182.0 °.

It is preferable that the surface light source device of the present embodiment further satisfy the following condition 1-3.
<Condition 1-3>
The first direction d ₁ of the surface light source device and the third direction d ₃ is the comparison surface light source device a surface light source device are parallel. When the luminance of light emitted in the normal direction from the center of the surface opposite to the light guide plate of the optical sheet of the comparative surface light source device is measured, and the luminance is Re, 1.0 ≦ P _max / Re Meet.

  Satisfying the condition 1-3 while satisfying the condition 1-1 means that the peak of the luminance occurs in directions other than the normal direction while maintaining a constant luminance peak.

In the condition _{1-1, EA max} is preferably _{27 ° ≦ EA max ≦ 60 °} , more preferably _{29 ° ≦ EA max ≦ 50 °} , further preferably _{31 ° ≦ EA max ≦ 45 °} .

In the condition 1-2, DA _max is more preferably 240 ° ≦ DA _max ≦ 310 °, and still more preferably 250 ° ≦ DA _max ≦ 290 °.

It is preferable that the surface light source device of the present embodiment further satisfy the following condition 2-3.
<Condition 2-3>
Based on the brightness of each angle measured in condition 1-1, a brightness distribution map A for each azimuth angle at the elevation angle EA _max is created. In the luminance distribution map A, it is assumed that all luminances are normalized with the luminance of P _max as 1.0.
The azimuth angle DA _max is a reference azimuth angle, and at an azimuth angle on the negative direction side from the reference azimuth angle of the brightness distribution map A, an azimuth angle angle indicating a brightness that is first 1/3 or less of P _max is -β DA _max , An azimuth angle indicating a luminance that is firstly 1⁄3 or less of P _max at an azimuth angle on the positive direction side from the reference azimuth angle is + β DA _max .
The interval between the reference azimuth angle and the angle -βDA _max is β _D1 , and the interval between the reference elevation angle and the + β DA _max is β _D2 .
In the above, it is preferable to satisfy the condition of 20 ° ≦ (β _D1 + β _D2 ) / 2 ≦ 60 °, more preferably 20 ° ≦ (β _D1 + β _D2 ) / 2 ≦ 50 °, and 20 ° ≦ ((β _D1) More preferably, + β _D2 ) / 2 ≦ 40 °.
When (β _D1 + β _D2 ) / 2 is in the above range, the condition 1-2, the condition 1-3, and the condition 2-1 are easily satisfied.

Furthermore, it is preferable that the surface light source device of the present embodiment satisfy the following condition 2-4.
<Condition 2-4>
Based on the brightness of each angle measured in condition 1-1, a brightness distribution chart B for each elevation angle at the azimuth angle DA _max is created. In the luminance distribution diagram B, it is assumed that all luminances are normalized with the luminance of P _max as 1.0.
An elevation angle EA _max is taken as a reference elevation angle, and an elevation angle inclined toward the normal direction is referred to as an “elevation angle on the minus direction side”, and an elevation angle inclined toward the side away from the normal direction is referred to as an elevation angle on the plus direction.
First P _max at first elevation angle of elevation showing luminance as a third or less of P _max -βEA _max, the reference elevation angle of plus direction side from the reference elevation angle in the elevation of the minus side of the luminance distribution diagram B 1/3 the angle of elevation showing the following become luminance + βEA _max to.
The interval between the reference elevation angle and the angle -βEA _max is β _E1 , and the interval between the reference elevation angle and the + β EA _max is β _E2 .
In the above, it is preferable to satisfy the condition of 20 ° ≦ (β _E1 + β _E2 ) / 2 ≦ 30 °, more preferably 20 ° ≦ (β _E1 + β _E2 ) / 2 ≦ 27 °, and 20 ° ≦ ((β _E1) More preferably, + β _E2 ) / 2 ≦ 24 °.
When (β _E1 + β _E2 ) / 2 is in the above range, the condition 1-3 and the condition 2-1 are easily satisfied.

FIG. 1 is a cross-sectional view of a display device 10 including the surface light source device 20 of the present embodiment.
The surface light source device 20 of FIG. 1 is configured as an edge light type surface light source device, and faces the light guide plate 30, the light source 24 disposed on the light entrance surface 33 of the light guide plate, and the light exit surface 31 of the light guide plate. The optical sheet 60 is disposed, and the reflection sheet 28 disposed to face the surface of the light guide plate opposite to the light exit surface. Further, the surface light source device 20 of FIG. 1 has a light emitting surface 21 for emitting light in a planar shape, and the light emitting surface 61 of the optical sheet (surface on the opposite side to the light guide plate of the optical sheet) 61 It is formed.
Such a surface light source device 20 is installed on the back of the display panel 15 such as the liquid crystal display panel 15A, as shown in FIG. 1, and has a role of illuminating the display panel 15 from the back.

<Light source>
Examples of the light source 24 include a linear light source such as a cold cathode tube, and a point light source such as an LED. The light source 24 of FIG. 3 is a point light source. Further, in FIG. 3, the light source 24 is formed by a large number of point light sources 25 disposed along the longitudinal direction of the light incident surface of the light guide plate.
In the light guide plate shown in FIG. 4 and FIG. 5, the arrangement positions of a large number of point light sources forming the light source 24 are indicated by marks of “+”.

<Reflection sheet>
The reflective sheet 28 is disposed to face the back surface 32 of the light guide plate. Such a reflection sheet 28 is a member for reflecting the light leaked from the back surface 32 of the light guide plate 30 and causing the light to enter the light guide plate 30 again.
As the reflection sheet 28, a sheet provided with a reflection layer containing high reflectance particles, a sheet provided with a layer having a large number of air holes, a sheet provided with a metal thin film layer, etc. may be mentioned.
The reflection on the reflection sheet 28 may be regular reflection or diffuse reflection. The diffuse reflection may be isotropic diffuse reflection or anisotropic diffuse reflection.
From the viewpoint of maintaining directivity, that is, making it easier to efficiently cause the reflected light of the light leaked from the back surface 32 to enter the light guide plate 30 again, the sheet provided with the metal thin film layer in which regular reflection is easily obtained preferable.

<Light guide plate>
In the present embodiment, the light guide plate 30 is formed between a pair of main surfaces consisting of the light emitting surface 31 which is the surface on the display panel 15 side and the back surface 32 opposite to the light emitting surface, and the pair of main surfaces. And four sides.
Further, in the present embodiment, one of the four side surfaces constitutes the light entrance surface 33. Direction perpendicular to the light incident surface 33 is the first direction _{d 1.} As shown in FIG. 2, light incident from the light incident surface 33 into the light guide plate 30 travels in the light guide plate 30 along the first direction d ₁ (light guide direction) and becomes less than the critical angle. Light is emitted from the light exit surface 31.

  As the light guide plate 30, one in which a dot-like reflection pattern is printed on the back surface 32, one in which a concavo-convex pattern is formed on the back surface 32, and the like can be mentioned. From the viewpoint of easily satisfying the conditions 1-1, 2-1 and the like by combination with an optical sheet to be described later, it is preferable that the concavo-convex pattern is formed on the back surface 32.

Hereinafter, an embodiment of the light guide plate 30 will be described in detail, mainly with reference to FIGS.
The light guide plate 30 of FIGS. 2 to 6 includes a base 40 formed in a plate shape and a plurality of optical elements formed on one side surface (a surface on the observer side, a surface on the light emission side) 41 of the base 40. And 50. The base 40 is configured as a flat member having a pair of parallel main surfaces. And the back surface 32 of a light-guide plate is formed of the surface (surface on the side facing the reflective sheet 28) of the other side of the base 40. As shown in FIG.

The uneven | corrugated pattern formed in the back surface 32 of a light-guide plate is demonstrated using FIG.2 and FIG.5.
The uneven pattern of FIGS. 2 and 5 has an inclined surface 37, a step surface 38 extending in the normal direction nd of the light guide plate, and a connecting surface 39 connecting the inclined surface and the step surface.
In the light guide plate 30, light is guided from the light incident surface side to the opposite side to the light incident surface by the total reflection action on the pair of main surfaces 31, 32 of the light guide plate. On the other hand, the inclined surface 37 is inclined with respect to the plate surface of the light guide plate so as to approach the light exit surface 31 as it goes from the light incident surface 33 side to the opposite surface 34 side. Therefore, the incident angle at which the light reflected by the inclined surface 37 enters the pair of main surfaces 31 and 32 gradually decreases, and the light is emitted from the light guide plate when the incident angle becomes smaller than the total reflection critical angle Become. That is, the inclined surface 37 functions as an element for extracting light from the light guide plate.

By adjusting the distribution of the inclined surface 37 along the first direction d ₁ is a light guide direction in the back surface 32, the distribution can be adjusted along the first direction d ₁ of the amount of light emitted from the light guide plate 30 .
In the example shown in FIGS. 2 to 6, the inclined surface of the back surface 32 as moving away from the light incident surface 33 along the light guide direction (as approaching the opposite surface 34 opposite to the light incident surface) The ratio of 37 is high. According to this configuration, emission of light from the light guide plate 30 in a region away from the light incident surface 33 along the light guide direction is promoted, and reduction in the amount of emitted light can be suppressed as the distance from the light incident surface 33 increases. .

In one example shown, the arrangement pitch Ps of the inclined surface 37 in the first direction d ₁ (FIG. 3) is constant. Further, the angles of the inclined surfaces 37 are the same among the plurality of connection surfaces 39. On the other hand, the length of one inclined surface 37 in the first direction d ₁ is different among the plurality of connection surfaces 39. More specifically, the length in the first direction d ₁ of the inclined surface 37, as position of the connecting surface 39 toward the other side from the one side (the side having a light source) in the first direction d _1, gradually lengthened It will be.
Note that "gradually longer", not always necessary to continue to change as long, the length in the first direction d ₁ of the two inclined surfaces 37 adjacent in the first direction d ₁ are identical to each other It is also good. That is, in “more and more gradually”, the lengths of the plurality of inclined surfaces 37 in the first direction d ₁ are not constant, and the length of one inclined surface in the first direction d ₁ is greater than that of the inclined surfaces. means that does not become shorter than the length in the first direction d ₁ of the other inclined surface located on the light source side.

The arrangement pitch Ps of the inclined surfaces 37 is preferably 20 μm to 500 μm, and more preferably 50 μm to 300 μm.
The angle between the inclined surface 37 and the sheet surface (horizontal surface) is 0.5 to 5.0 °, and preferably 1.0 to 3.0 °.
The ratio of the length of the first direction _{d 1} of the inclined surface 37 with respect to the array pitch Ps is preferably 10-50% by near the light source side (light incident surface 33 side), and more preferably 20 to 50%. 50 to 90% is preferable on the side far from the light source (the opposite surface 34 side), and 50 to 80% is more preferable.

Next, an embodiment of a plurality of optical elements 50 provided on the surface 41 on one side of the base 40 will be described.
As shown in FIG. 4, the plurality of optical elements 50, on one side face 41 of the base portion 40, they are arranged side by side without gaps in the second direction d ₂ perpendicular to the first direction d _1. Therefore, in FIG. 4, the light exit surface 31 of the light guide plate is formed by the inclined surfaces 35 and 36 of the optical element 50. The optical element 50, extends in a straight line along the first direction d ₁ perpendicular to the orientation direction d _2. Furthermore, the optical element 50 is formed in a columnar shape, and has the same cross-sectional shape along its longitudinal direction.
Also, the plurality of optical elements 50 in FIG. 4 are configured identical to one another.

6 shows a cross section parallel to both the arrangement direction of the optical elements 50 (second direction d ₂ ) and the normal direction nd to the plate surface of the light guide plate 30 (a light guide plate along the VI-VI line in FIG. Hereinafter, the cross-sectional shape of the optical element 50 in “a main cut surface of the light guide plate” may be shown.
In FIG. 6, the cross-sectional shape of each optical element 50 in the main cross section of the light guide plate is a shape that tapers toward the light output side. That is, in the main cut surface of the light guide plate, the width of the optical element 50 parallel to the plate surface of the light guide plate decreases with distance from the base 40 along the normal direction nd of the light guide plate.

Further, in FIG. 6, the outer contour 51 of the main cutting plane of each optical element 50 has a light emitting surface angle θ _{a which} is an angle formed by the outer contour with respect to the surface 41 on one side of the base 40. It is changed so as to increase from (the outer contour of the position farthest from the base 40) to the proximal end 52b (the outer contour of the position closest to the base 40). This light exit surface angle theta _a can be set as the disclosure of, for example, Japanese 2013-51149 JP.

A light exit surface angle theta _a, in the main cutting face of the light guide plate, the light exit-side surface (outer contour) 51 of the optical element 50 is an angle formed with respect to one side surface 41 of the base 40.
As shown in FIG. 6, when the outer contour (surface on the light output side) of the main cross section of each optical element 50 is formed in a broken line, the surface of one straight line constituting each broken line and one side of the base 40 (strictly, the smaller the angle of the ones of the two angles formed (angle of minor angle)) the angle formed between the 41 becomes the light exit surface an angle theta _a.
In the case with a curved outer profile in the main cut surface of the optical element, the angle formed between the tangent and the base 40 of the curved surface becomes a light exit surface angle theta _a.

The optical element shown in FIG. 6 is a pentagon having one side located on the surface 41 on one side of the base 40 and two sides located between the distal end 52a and each proximal end 52b in the main cutting plane of the light guide plate. It has a shape or a shape obtained by chamfering one or more corners of the pentagonal shape.
Further, in the optical element of FIG. 6, the cross-sectional shape of the main cutting plane of the optical element 50 has symmetry about the normal direction nd. That is, as shown in FIG. 6, the outer contour 51 of each optical element 50 is constituted by a pair of bending surfaces 35 and 36 configured symmetrically about the normal direction. The pair of bending surfaces 35, 36 are connected to each other to form a tip 52a. Each of the folds has a first surface 35a, 36a forming the tip 52a, and a second surface 35b, 36b connecting the first surface and the base 40. The pair of first inclined surfaces 35a, 36a has a symmetrical configuration about the normal direction nd, and the pair of second inclined surfaces 35b, 36b also has a symmetrical configuration about the normal direction nd ing.

The ratio (H _a / W) of the height (protruding height along the normal direction from the base 40) H _a of each optical element to the width W _{a in} the arrangement direction of each optical element in the main cutting plane of the light guide plate _a ) is preferably 0.30 or more and 0.45 or less.
According to the optical element 50, the refraction and reflection at the surface 51 on the light output side make it possible to obtain an excellent condensing action also on the light component along the arrangement direction (second direction d ₂ ) of each optical element 50. It can be exhibited and the occurrence of side lobes (leakage light) can be suppressed. Further, the conditions 1-3 can be easily satisfied by the light collecting action.

The width W _a is preferably 10 μm to 500 μm. The thickness of the base 40 is preferably 0.2 mm to 6.0 mm.
The plurality of optical elements 50 may have a concave shape, and may have a curved surface or a flat surface (horizontal surface).

In the present embodiment, it is preferable that the luminance of light emitted from the center of the light exit surface 31 of the light guide plate 30 satisfy the following condition 3-1. Satisfying the conditions 3-1, the angle indicating the maximum luminance of the light exiting from the light guide plate, the more deviated from the normal direction in the first direction d _1. By satisfying the condition 3-1, the conditions 1-1 and 1-2 can be easily satisfied.
The condition 3-1 can be satisfied, for example, by the light guide plate having the above-described shape.

<Condition 3-1>
The luminance of light emitted from the center of the light exit surface of the light guide plate, a maximum luminance when measured every elevation 0.5 ° in a direction along the first direction d ₁ and P _d1max. Here, the direction of light emitted in the normal direction from the light exit surface of the light guide plate is referred to as “elevation angle 0 °”, and the elevation angle inclined to the light entrance surface side of the light guide plate from the normal direction is referred to as “elevation angle on the minus direction side” .
Maximum brightness _P the angle indicating the _{d1max EA d1max,} the angle of elevation showing the luminance is 1/2 or less of the first _{P d1max} from _{EA d1max} in the elevation of the minus direction upon a -αEA _d1max, 60 ° ≦ EA _{The conditions of d1max} ≦ 80 ° and 5 ° ≦ EA _d1max − (− αEA _d1max ) ≦ 25 ° are satisfied.

It is more preferable to satisfy the condition of 70 ° ≦ EA _d1max ≦ 80 ° and 5 ° ≦ EA _{d1 max} − (− αEA _d1max ) ≦ 15 ° under the condition _3-1 .

In the present embodiment, it is preferable that the luminance of light emitted from the center of the light exit surface 31 of the light guide plate 30 satisfy the following condition 3-2. Satisfying the conditions 3-2, the angle indicating the maximum luminance of the light exiting from the light guide plate, which means that no deviated from the normal direction in the second direction d _2. By satisfying the condition 3-2, the conditions 1-3 and 2-1 can be easily satisfied.
Condition 3-2 can be satisfied by, for example, the light guide plate having the above-described shape.

<Condition 3-2>
The luminance of light emitted from the center of the light exit surface of the light guide plate, a maximum luminance when measured every elevation 0.5 ° in a direction along the second direction d ₂ and P _D2max. Here, the direction of light exiting in the normal direction from the light exit surface of the light guide plate is “elevation angle 0 °”, and the elevation angle inclined to the left in the normal direction when viewed from the light entrance surface side of the light guide plate is “minus direction An elevation angle which is inclined to the right in the normal direction when viewed from the light incident surface side of the light guide plate is referred to as an elevation angle on the plus direction side.

The absolute value of the angle indicating the maximum brightness P _d2max is | EA _d2max |, and the absolute angle of the elevation angle indicating the brightness which is less than half of P _d2max at an elevation angle on the negative direction side from | EA _d2max | Assuming that the absolute value of the elevation angle representing the luminance at which the elevation angle on the positive direction side is first half or less of P _d2max from αEA _d2max |, | EA _d2max | is | + αEA _d2max |, 0 ° ≦ | EA _{The conditions of d2max} | ≦ 3 ° and 12 ° ≦ (| −αEA _d2max | + | + αEA _d2max |) / 2 ≦ 27 ° are satisfied.
In condition 3-2, it is more preferable to satisfy the condition of 0 ° ≦ | EA _d2max | ≦ 5 ° and 10 ° ≦ (| −αEA _d2max | + | + αEA _d2max |) / 2 ≦ 30 °.

The light guide plate 30 having the above configuration can be manufactured by forming the back surface pattern or the optical element 50 on the light transmitting substrate, or by extrusion molding or the like.
Although various materials can be used as a material of the base 40 of a light-guide plate, and the optical element 50, the material which is excellent in a mechanical characteristic, an optical characteristic, stability, and workability is preferable. Examples of such materials include transparent resins such as thermoplastic resins such as acrylic resins, polystyrene resins, polycarbonate resins, polyester resins and polyacrylonitrile, and ionizing radiation curable resins such as epoxy acrylate resins and urethane acrylate resins.
A light diffusion component can also be added to the light guide plate as needed. Examples of the light diffusion component include inorganic particles and organic particles having an average particle diameter of about 0.5 to 100 μm.

  In the case of forming an optical element or a concavo-convex pattern on a light transmitting substrate, a sheet-like layer (hereinafter referred to as "land portion") between the substrate and the optical element or between the substrate and the concavo-convex pattern The “land portion” may be formed of the same material as the optical element or the concavo-convex pattern and formed simultaneously with the formation of the optical element or the concavo-convex pattern. In this case, the base 40 is composed of the light transmitting base and the lands. On the other hand, in the optical sheet manufactured by extrusion molding, the base 40, the plurality of optical elements 50 on the surface on one side of the base, and the concavo-convex pattern on the surface on the other side of the base are integrally formed.

<Optical sheet>
The optical sheet 60 is disposed to face the light exit surface 31 of the light guide plate, as shown in FIG.
As shown in FIG. 7, such an optical sheet 60 has a sheet-like main body portion 65 and a plurality of structural rows 70 provided on the surface (light incident side surface) 67 of the main light body side. It consists of basic composition. The main body portion 65 is configured as a flat plate-like member having a pair of parallel main surfaces. The light exit surface 61 of the optical sheet 60 is formed by the surface 66 on the light exit side of the main body located on the side not facing the light guide plate 30.
Further, as shown in FIG. 3, when the optical sheet 60 has a first direction d ₁ as a direction perpendicular to the light incident surface of the light guide plate and a third direction d ₃ as the arrangement direction of the structural rows of the optical sheet, a first direction d ₁ and the third direction d ₃ is arranged so as to be non-parallel.

First, the plurality of structural rows 70 provided on the surface on the light entrance side of the main body portion 65 will be described.
As shown in FIG. 2 and FIG. 7, the respective structural rows 70 are arranged side by side on the surface (surface on the light incident side) 67 of the main body portion 65 on the light guide plate side. Each structural row 70 is formed in a columnar shape, and extends in a direction intersecting the arrangement direction of the structural rows.

In the present embodiment, each structural row 70 extends in a straight line. Further, each structural row 70 is formed in a columnar shape, and has the same cross-sectional shape along the longitudinal direction. Furthermore, the plurality of structural rows 70 are arranged without gaps on the surface 67 on the light entrance side of the main body along the direction orthogonal to the longitudinal direction. As described above, the light incident surface of the optical sheet is formed by the surface of the structural row 70 arranged on the main body 65 without a gap.
Further, as shown in FIG. 7, a plurality of structural columns 70 are arranged in the third direction d _3. Each structure column 70 extends in the fourth direction _{d 4} perpendicular to the third direction _{d 3.}
As described above, the condition 2-1 can be easily satisfied by making the structure of the surface on the light guide plate side of the optical sheet into a linearly extending structure row. In the case of a non-structured row (for example, a pyramid type) in which the structures arranged on the light guide plate side of the optical sheet do not extend linearly, the condition 2-2 is difficult to satisfy.

As shown in FIG. 7, a plurality of structural columns 70 of the present embodiment, the first structured surface 71 of the arrangement direction of the structure column 70, i.e. along a third direction d _3, are arranged opposite to each other And a second structured surface 72.
The first structured surface 71 of each structural column is located on one side in the third direction d _3, second structured surface 72 is positioned on the other side in the third direction d _3. Further, in FIG. 1, FIG. 2, in the cross section of the surface light source device along the main cut surface of the light guide plate shown in FIGS. 9 and 10, one side in the third direction d _3, the first direction d ₁ becomes one side, the other side in the third direction d ₃ is a other side in the first direction d _1.

Accordingly, in the surface light source device 20, a first structured surface 71 of each structural column is positioned on the side of the light source 24 in the third direction d _3, facing one side in the first direction d _1. The second structured surface 72 of each structural column is located on the side away from the light source 24 in a third direction d _3, facing the other side in the first direction d _1. As described later, the first structured surface 71 functions as an incident surface when light emitted from the light guide plate 30 enters the optical sheet 60. On the other hand, the second structured surface 72 has a function of reflecting the light incident on the optical sheet 60 and correcting the light path of the light.

As shown in FIG. 8, the first structured surface 71 and the second structured surface 72 respectively extend from the main body 65 and are connected to each other. At a position where the first structured surface 71 and the second structured surface 72 connect to the main body portion 65, a base end 75b of the structural row is formed. Further, at a position where the first structured surface 71 and the second structured surface 72 connect to each other, a tip (apex portion) 75 a of each structural row is formed.
Note that FIG. 8 is a cross section parallel to both the normal direction nd to the sheet surface of the main body and the third direction d ₃ that is the arrangement direction of the structural rows (hereinafter simply referred to as “main cutting surface of optical sheet” Shows the cross-sectional shape of the structural row 70 in some cases.

  Although the cross-sectional shape of the structural row 70 described above is a quadrangle, the cross-sectional shape of the structural row 70 is not limited to a quadrilateral, and may be a polygon such as a triangle or a pentagon. Furthermore, the cross-sectional shape of the structural row 70 may have a curved shape at least in part. For example, at least a part of one or both of the first structured surface 71 and the second structured surface 72 may be a curved surface.

In the present embodiment, as shown in FIG. 3, in the optical sheet 60, the direction perpendicular to the light incident surface of the light guide plate is the first direction d ₁ , and the arrangement direction of the structural rows of the optical sheets is the third direction d ₃ . when the a first direction d ₁ and the third direction d ₃ is arranged so as to be non-parallel.
In the display device, by the first direction d ₁ and the third direction d ₃ is arranged an optical sheet such that the non-parallel, easily the elevation angle EA _max indicating the maximum luminance P _max a value other than 0 ° The above condition 1-1 can be easily satisfied. Further, by disposing the optical sheet as described above, the azimuth angle DA _max indicating the maximum brightness P _max can be easily set to a value other than 0 ° or 180 °, and the above condition 1-2 can be easily satisfied. Further, by the first direction d ₁ and the third direction d ₃ is arranged an optical sheet such that the non-parallel, the luminance distribution of each azimuth in elevation EA _max is, the negative direction relative to the DA _max, plus The luminance distribution of each elevation angle at the azimuth angle DA _max is likely to be symmetrical in the direction, and is likely to be symmetrical in the negative direction and the positive direction with reference to EA _max , making it easier to satisfy the condition 2-1.
Narrow angle of the angle between the first direction d ₁ and the third direction d ₃ (hereinafter, sometimes referred to as "bias angle of the optical sheet".), I.e. the bias angle theta _D1d3 optical sheet, 15 ° ≦ (Θ _{d1 d3} ) ≦ 50 ° is preferable, 18 ° ≦ (θ _{d1 d3} ) ≦ 45 ° is more preferable, and 20 ° ≦ (θ _{d1 d3} ) ≦ 40 ° is more preferable. When the bias angle of the optical sheet is in the above range, the condition 1-1 and the condition 1-3 are easily satisfied.
Furthermore, in order to facilitate satisfying the above conditions 1-1 and conditions 2-1, the first direction d ₁ and the third direction d ₃ not only in non-parallel, is exiting from the light exit surface of the light guide plate It is preferable to make the shape of the structural row of the optical sheet be in the range described later, while the luminance distribution satisfies the condition 3-2.

Hereinafter, the cross-sectional shape of each structural row 70 in the main cutting plane of the optical sheet will be described in more detail.
FIG. 8 shows a cross section of the optical sheet (a cross section corresponding to the main cut surface of the optical sheet) taken along line VIII-VIII in FIG. 7. On the other hand, in FIGS. 9 and 10, a cross section obtained by cutting the light guide plate and the optical sheet in a direction parallel to both the first direction (light guide direction) d ₁ and the normal direction nd of the plate surface of the light guide plate. The shape is shown.
As shown in FIG. 8, in the present embodiment, the cross-sectional shape of each structural row 70 in the main cross section of the optical sheet has a shape that tapers toward the light incident side (the light guide plate side). There is. That is, in the main cut surface of the optical sheet, the width of the structural row 70 becomes narrower as it is separated from the main body portion 65 along the normal direction nd of the main body portion 65.

The second structured surface 72 forming a part of the outer contour of the structural row 70 of the optical sheet makes an angle with respect to a surface parallel to the sheet surface of the optical sheet (for example, a surface parallel to the broken line in FIG. 8) Assuming that “inclination angle θ _t ”, the inclination angle θ _t is not constant in the second structured surface 72 in the illustrated example. In FIG. 8, in the second structured surface 72, the inclination angle θ _t is from the tip 75 a of the structural row farthest from the main body 65 to the proximal end 75 b of the structural row closest to the main body 65. It has changed to become larger.

In FIGS. 9 and 10, L91 and L101, which are light traveling in a direction in which the inclination angle with respect to the normal direction nd is relatively small, are incident on a region near the base end 75b of the second structured surface 72. It will be easier. In addition, L92 and L102, which are light traveling in a direction in which the inclination angle with respect to the normal direction nd is relatively large, easily enter the region near the tip 75a of the second structured surface 72. Then, by changing the inclination angle θ _t in the second structured surface 72, the second structured surface 72 of the light entering the light incident surface of the optical sheet (the light emitted from the light exit surface of the light guide plate) As a result, it is possible to adjust the degree of collection of light having passed through the light exit surface of the optical sheet.

Furthermore, although n to be described later in FIG. 8 shows only the case of two, in the main cross-section of the optical sheet, toward the side of the base end portion 75b inclined angle theta _t is from the side of the distal end portion 75a of the structure column It is also possible to include n (n is a natural number of 2 or more) element faces 73 arranged to be gradually larger, that is, a plurality of element faces 73.
In FIG. 8, the outline of the second structured surface 72 of the structural row 70 has a shape in which the straight portions are joined or the straight portions are joined and the joint is chamfered. In other words, the outer contour of the second structured surface 72 of the structural row 70 is formed in a broken line shape or a shape obtained by chamfering the corner of the broken line. In the illustrated example, the second structured surface 72 has a first element surface 73a forming the tip 75a and a second element surface 73b adjacent to the first element surface 73a from the main body 65 side. ing. Then, as shown in FIG. 8, the inclination angle theta ₂ of the second element surface 73b is larger than the inclination angle theta ₁ of the first element surface 73a.
However, the present invention is not limited to this example, and the second structured surface 72 may have three or more element surfaces, may be a curved surface, or may be a single element surface. .

As described above, the inclination angles θ _t , θ ₁ and θ ₂ are the angles that the second structured surface of the structural row forms with the surface parallel to the sheet surface of the optical sheet in the main cut surface of the optical sheet 60 It is. More specifically, an angle formed between each element surface 73 forming a broken line in the main cut surface of the optical sheet 60 and a plane parallel to the sheet surface of the optical sheet (strictly speaking, two formed The smaller one of the two angles (the angle of the minor angle) is the inclination angles θ _t , θ ₁ and θ ₂ .
When the first structured surface and the second structured surface have a curved surface, the inclination angles θ _t , θ ₁ , and θ ₂ are determined by the angle formed by the tangent of the curved surface with respect to the surface parallel to the sheet surface of the optical sheet. It may be calculated.

In the main cutting plane of the optical sheet, the width of the structural row along the arrangement direction of the structural rows 70 is “W _b ”, and the height of the structural row along the normal direction nd of the main body 65 is “H _b ” In this case, the aspect ratio (W _b / H _b ) of the second structured surface and the inclination angle θ _t of each element surface forming the second structured surface 72 indicate the light collecting property of the optical sheet 60 and the direction of light collecting. , Affect the direction showing the maximum brightness.

In FIG. 9, the light L91 and light L92 emitted from the light exit surface 31 of the light guide plate are not reflected with the normal nd passing through the tip portion 75a after being reflected by the element surface 73, thereby achieving a position showing maximum brightness. It is caused in a direction inclined to the first direction d _1.
In order to obtain the light emission as shown in FIG. 9, the aspect ratio (W _b / H _b ) of the structural row, the inclination angle θ ₁ of the first element surface 73 a and the inclination angle θ ₂ of the second element surface 73 _b It is preferable to
The aspect ratio (W _b / H _b ) of the structural row is preferably 1.15 or more and 1.50 or less. The first inclination angle theta ₁ element surface 73a is 38 ° or more 53 ° or less, the inclination angle theta ₂ of the second element surface 73b is preferably set to 43 ° or more 57 ° or less.
When the second structured surface 72 has three element surfaces, the aspect ratio (W _b / H _b ) of the structure row is 1.15 or more, where the third element surface is 73 c and the inclination angle is θ _3. preferably to 1.50 or less, the inclination angle theta ₁ of the first element surface 73a is 38 ° or more 53 ° or less, the inclination angle theta ₂ of the second element surface 73b is 42 ° or more 56 ° or less, the third element surface the inclination angle theta ₃ of 73c is preferably set to 53 ° or more 64 ° or less.
By setting W _b / H _b , θ ₁ , θ ₂ or W _b / H _b , θ ₁ , θ ₂ and θ ₃ in the above ranges, the above conditions 1-1, 1-2, _1-3 , ₂ are satisfied. It can be made easy to satisfy -1.

In FIG. 10, the light L 101 and L 102 emitted from the light exit surface 31 of the light guide plate is reflected by the element surface 73 and then intersects with the normal nd passing through the tip 75 a to show the position having the maximum luminance. and causing the direction inclined with respect to one direction d _1.
In order to obtain the light emission as shown in FIG. 10, the aspect ratio (W _b / H _b ) of the structural row, the inclination angle θ ₁ of the first element surface 73 a and the inclination angle θ ₂ of the second element surface 73 _b are in the following ranges. It is preferable to
The aspect ratio (W _b / H _b ) of the structural row is preferably 1.15 or more and 1.50 or less. The inclination angle theta ₁ is 53 ° or more 68 ° of the first element surface 73a below, the inclination angle theta ₂ of the second element surface 73b is preferably set to 72 ° or less 59 ° or more.
When the second structured surface 72 has three element surfaces, the aspect ratio (W _b / H _b ) of the structure row is 1.15 or more, where the third element surface is 73 c and the inclination angle is θ _3. preferably to 1.50 or less, the inclination angle theta ₁ of the first element surface 73a is 52 ° or more 68 ° or less, the inclination angle theta ₂ of the second element surface 73b is 56 ° or more 68 ° or less, the third element surface the inclination angle theta ₃ of 73c is preferably set to 63 ° or more 76 ° or less.
In the embodiment of FIGS. 9 and 10, the angle formed between the first structured surface and the surface parallel to the sheet surface of the optical sheet (strictly speaking, of the two angles formed) The smaller angle (the angle of the minor angle) is not particularly limited, but is usually 50 to 80 °.

Other dimensions of the optical sheet 60 may be set as follows, as an example.
For example, the arrangement pitch of the structural rows (corresponding to the width W _{b of the} structural rows in the illustrated example) can be 10 μm to 200 μm. However, in recent years, high definition of the arrangement of each structural row 70 is rapidly progressing, and it is preferable to set the arrangement pitch of the structural rows 70 to 10 μm or more and 35 μm or less.
The width W _b2 of the second structured surface of the structural row 70 can be 5 μm or more and 100 μm or less, and preferably 5 μm or more and 20 μm or less in consideration of the recent tendency.
Further, the height H _b of the structural row from the main body 65 along the normal direction nd of the sheet surface of the optical sheet can be 5.5 μm or more and 180 μm or less, and in consideration of the recent tendency, 5.5 μm The thickness is preferably 30 μm or less.

The optical sheet 60 configured as described above can be manufactured by forming the structural row 70 on a light transmitting substrate, or by extrusion molding or the like.
Although various materials can be used as a material of the main-body part 65 of an optical sheet, and the structure row | line | column 70, The material which is excellent in a mechanical characteristic, an optical characteristic, stability, and workability is preferable. Examples of such materials include transparent resins such as thermoplastic resins such as acrylic resins, polystyrene resins, polycarbonate resins, polyester resins and polyacrylonitrile, and ionizing radiation curable resins such as epoxy acrylate resins and urethane acrylate resins.

  When forming a structural row on a light transmitting substrate, a sheet-like land may be formed between the substrate and the structural row. In this case, the main body portion 65 is configured of the light transmitting base and the land portion. On the other hand, in the optical sheet manufactured by extrusion molding, the main outer portion 65 and a plurality of structural rows 70 on the surface on the light incident side of the main body portion are integrally formed.

<Operation of surface light source device>
Next, the operation of the surface light source device 20 will be described.

As shown in FIGS. 1 and 2, the light emitted by the light emitter 25 forming the light source 24 is incident on the light guide plate 30 through the light incident surface 33. Then, as shown in FIG. 2, the light L21 and L22 incident on the light guide plate 30 repeats total reflection on the light exit surface 31 and the back surface 32 of the light guide plate 30, and the surface 34 opposite to the light incident surface 33 of the light guide plate 30. And the direction (first direction d ₁ , light guiding direction) connecting

The back surface 32 of the light guide plate 30 has an inclined surface 37 inclined so as to approach the light exit surface 31 as it goes from the light entrance surface 33 to the opposite surface 34. The respective inclined surfaces 37 are connected via the step surface 38 and the connection surface 39. The step surface 38 extends in the normal direction nd of the light guide plate 30.
Therefore, most of the light traveling in the light guide plate 30 from the side of the light incident surface 33 to the side of the opposite surface 34 does not enter the step surface 38 in the back surface 32, and is incident on the inclined surface 37 or the connection surface 39. It will be incident and reflected. Then, when the light is reflected by the inclined surface 37 of the back surface 32, the incident angles of the light to the light exit surface 31 and the back surface 32 become smaller. Therefore, the incident angles of the light traveling in the light guide plate 30 to the light exit surface 31 and the back surface 32 gradually decrease due to the reflection on the inclined surface 37 of the back surface 32 and become less than the total reflection critical angle. It comes out from the surface 31 or the back surface 32.
The lights L21 and L22 emitted from the light exit surface 31 travel toward the optical sheet 60 disposed on the light exit side of the light guide plate 30. On the other hand, the light emitted from the back surface 32 is reflected by the reflection sheet 28 disposed on the back surface of the light guide plate 30, and enters the light guide plate again to travel in the light guide plate.

In the illustrated example, as the surface 34 opposite to the light incident surface 33 is approached, the proportion of the inclined surface 37 in the back surface 32 is high. Specifically, the inclined surface 37 has been arranged at a predetermined pitch Ps in the first direction d _1, the length along the first direction d ₁ of the inclined surface 37 is one in the first direction d ₁ It is getting longer gradually from one side to the other. For this reason, even in the area away from the light incident surface 33, it is possible to secure a sufficient amount of light emitted from the light emitting surface 31 of the light guide plate 30, and to achieve uniformity of the emitted light amount along the light guiding direction.

The light exit surface 31 of the light guide plate 30 illustrated is constituted by a plurality of optical elements 50, and the cross-sectional shape of each optical element 50 in the main cutting plane is a pentagon or a pentagon symmetrical symmetrical about the normal direction. It has a shape in which one or more corners are chamfered. More specifically, as described above, the light exit surface 31 of the light guide plate 30 is configured as a broken surface inclined with respect to the plane parallel to the plate surface of the light guide plate (see FIG. 6).
The broken surface is formed of inclined surfaces 35a, 36a, 35b, 36b which are inclined in opposite directions with respect to the normal direction nd to the surface 41 on the light output side of the base 40.
The light which is totally reflected by the inclined surfaces 35 and 36 and travels in the light guide plate 30 and the light which passes through the inclined surfaces and is emitted from the light guide plate is exerted by the inclined surfaces as described below. It will be.

First, the action of light that is totally reflected by the inclined surfaces 35 and 36 and travels in the light guide plate 30 is described.
FIG. 6 shows the optical paths of the lights L61 and L62 traveling in the light guide plate 30 while repeating total reflection on the light exit surface 31 and the back surface 32.
As described above, the inclined surfaces 35 and 36 forming the light output surface 31 of the light guide plate 30 are two types of surfaces inclined in opposite directions with respect to the normal direction nd to the surface 41 on the light output side of the base 40. Contains. Also, two inclined surfaces 35 and 36 inclined in opposite side each other, are arranged alternately along the second direction d _2.
And as shown in FIG. 6, the light L61, L62 which injects into the light emission surface 31 is normal direction to the surface 41 of the light emission side of the base 40 among the two types of inclined surfaces 35 and 36 in many cases. The light is incident on an inclined surface that is inclined to the side opposite to the traveling direction of the light with reference to nd.

As a result, as shown in FIG. 6, the light L61, L62 traveling in the light guide plate 30 are often totally reflected by the inclined surfaces 35 and 36, as component along the second direction d ₂ is reduced Become. Furthermore, in the main cutting plane, the traveling direction of the totally reflected light also becomes opposite to the normal direction nd.
As described above, the inclined surfaces 35 and 36 forming the light exit surface 31 of the light guide plate 30 restrict the light emitted radially at a certain light emitting point to continue to spread in the second direction d ₂ as it is. In other words, the light from the light emitter 25 is incident largely inclined emitted toward the light guide plate 30 with respect to the first direction d ₁ of the light source 24 also while being restricted from moving in the second direction d _2, primarily the first It will proceed in the direction d ₁ .

Next, the action of the light passing through the light exit surface 31 and emitted from the light guide plate 30 will be described.
As shown in FIG. 6, when the light L 61 and L 62 emitted from the light guide plate 30 through the light output surface 31 is emitted from the light guide plate 30, the light L 61 and L 62 is refracted at the light output surface of the optical element 50.
Compared with the traveling direction of light in the light guide plate 30, the traveling direction (emission direction) of the light L61 and L62 traveling in a direction inclined from the normal direction nd in the main cutting plane by this refraction is in the normal direction nd It bends to approach. Such action, the optical element 50, the component of light along the second direction d ₂ perpendicular to the light guiding direction, the traveling direction of the transmitted light can be narrowed down in the normal direction nd side.
That is, the optical element 50, the component of light along the second direction d ₂ perpendicular to the light guiding direction, so exert a light condensing effect. In this manner, the emission angle of light emitted from the light guide plate 30 is narrowed within a narrow angle range centered on the normal direction in a plane parallel to the arrangement direction of the optical elements 50 of the light guide plate 30.

As described above, the emission angle of light emitted from the light guide plate 30 is narrowed within a narrow angle range centered on the normal direction nd in the arrangement direction of the optical elements of the light guide plate 30. On the other hand, the emission angle of the light emitted from the light guide plate 30 is, as shown in FIG. In the light direction d ₁ , the emission angle θ _k is relatively large and inclined from the normal direction nd. That is, the emission angle θ _k of the component in the first direction of the light emitted from the light guide plate 30 is a relatively large angle.
Especially, in this embodiment, the back surface 32 of the light guide plate 30 includes a plurality of inclined surfaces 37 arranged in the first direction d _1, the inclined surfaces 37, from one side in the first direction d ₁ The light guide plate 30 is inclined with respect to the normal direction nd of the light guide plate 30 and the first direction d1 so as to approach the light exit surface 31 toward the other side.
As a result, as shown in FIG. 2, in the first direction (light guiding direction) d ₁ , the luminance distribution emitted from the light guide plate 30 tends to be biased to a narrow angle range relatively largely inclined from the normal direction nd. It occurs.
The light emitted from the light exit surface 31 of the light guide plate 30 satisfies the conditions 3-1 and 3-2 described above by the above-described operation.

FIGS. 11 and 12 show an example in which the angular distribution of the luminance emitted from the light exit surface 31 of the light guide plate 30 having the configuration shown in FIGS. 4 to 6 is actually measured.
Indicated luminance distribution in FIG. 11 is an example of a first direction d ₁ and the normal direction nd actually measured results the luminance distribution of each direction within a plane parallel to both directions. In the graph shown in FIG. 11, the normal direction is 0 °, and the angle inclined from the normal direction to the side opposite to the light incident surface of the light guide plate is the positive direction angle. Here, Iamax1 is the luminance peak, θaImax1 is the angle at which the luminance peak is obtained, (1/2) Iamax1 means (1/2) of the luminance peak, and θaIα1 is (1/2) the luminance peak. It means the change of the angle from θaImax1 to become).
Figure 12 shows the luminance distribution is an example of a second direction d ₂ and the normal direction nd actually measured results the luminance distribution of each direction within a plane parallel to both directions. In the graph shown in FIG. 12, the angle inclined to the left in the normal direction when viewed from the light incident surface side of the light guide plate is the angle in the negative direction (y), and the normal direction viewed from the light incident surface side of the light guide plate The angle inclined to the right of is the angle (x) in the plus direction (x). Here, Iamax2 is a luminance peak, θaImax2 is an angle at which the luminance peak is obtained, (1/2) Iamax2 is (1/2) of the luminance peak, and θaIα2x and θaIα2y are (1/1). 2) is a variation of the angle from θaImax2 to θ2Imax2, and θaIα2 represents an average value of them (θaIα2 = (θaIα2x + θaIα2y) × (1/2)).

The luminance emitted from the light exit surface 31 of the light guide plate 30 and the luminance distribution of light emitted from the light exit surface of the optical sheet can be measured by scanning a light receiver disposed on the light exit surface side every 0.5 °. In the case of luminance (light intensity) measurement, the aperture angle of the light receiver detected by the diaphragm of the light receiver is 0.5 °. Therefore, for example, in the measurement of 0 °, the range of ± 0.25 ° is measured, in the measurement of 0.5 °, the range of 0.25 to 0.75 °, and in the measurement of −1 °, −0 The range of 25 to -0.75 ° will be measured.
The apparatus for measuring the luminance is not particularly limited, and can be measured, for example, using a general-purpose luminance meter or the like. In the present invention, a viewing angle measurement device (EZCONTRAST 160R, manufactured by ELDIM) capable of measuring the brightness of elevation angle and azimuth angle was used.

The light emitted from the light guide plate 30 then enters the optical sheet 60. As described above, the optical sheet 60 has the structural row 70 in which the tip end portion 75 a protrudes toward the light guide plate 30 side.
As shown in FIG. 3, the structure column 70 extends in a direction (fourth direction d ₄₎ intersecting with being arranged in the third direction d _3, light guiding direction (the first direction d _1).

As a result, the light L21 toward the optical sheet 60 through the light guide plate 30, L22 is one of the first structured surface 71 and a second structured surface 72 connected to each other, the light source 24 side in the first direction _{d 1} The light is incident on the structural array 70 via the first structured surface 71 located at
Then, as shown in FIG. 2, the light L21, L22 is then totally reflected by the second structured surface 72 located on the opposite side (right side in the plane of FIG. 2) and the light source in the first direction d ₁ The direction of travel is changed.

Then, due to total reflection on the second structured surface 72 of the structural row 70, in a direction inclined from the normal direction nd in a cross section parallel to both the first direction d ₁ (light guiding direction) and the normal direction nd. The traveling lights L91, L92, L101, and L102 are bent so that the angle between the traveling direction and the normal direction nd is small (see FIGS. 9 and 10).
However, in the present embodiment, by adjusting the inclination angle θ _{t and the} like of the second structured surface 72, the structural array 70 can control the light component along the light guiding direction (the first direction d ₁ ) The traveling direction of the transmitted light can be narrowed in the direction inclined from the front direction nd. That is, the optical sheet 60, the component of light along the first direction d _1, it will exert a focusing effect in a direction inclined from the normal direction nd.

In the present embodiment, the first structured surface 71 faces the one side (light source side) in the third direction d ₃ and forms an incident surface of light emitted from the light exit surface 31 of the light guide plate 30. And the second structured surface 72 which is directed to the other side of the third direction d ₃ (opposite to the light source) and totally reflects the light which has passed through the first structured surface 71 and entered the structural row have. The light collecting function by the structural array 70 is due to the total reflection function at the second structured surface 72.
Therefore, the optical sheet 60 can largely change the traveling direction of light, and can adjust the focusing direction with a high degree of freedom. In the example shown in FIG. 9, the peak of the luminance with respect to the first direction d ₁ is set so that the traveling directions of the lights L 91 and L 92 advancing from the light exit surface 31 of the light guide plate 30 do not return to the normal direction nd. It is produced in the inclined direction. On the other hand, in the example shown in FIG. 10, the traveling direction of the lights L101 and L102 advancing from the light exit surface 31 of the light guide plate 30 is changed over the normal direction nd to change the peak of luminance in the first direction d. It is generated in the direction inclined with respect to ₁ .
That is, according to the surface light source device 20 having the optical sheet 60 of the present embodiment, the peak of the luminance on the light emitting surface 21 can be generated in directions other than the normal direction with a simple configuration.

13 to 17 show the luminance of light emitted from the center of the light exit surface of the optical sheet (the surface on the opposite side to the light guide plate of the optical sheet) 61 at an elevation angle of 0.5 ° and an azimuth angle of 0.5 °. It is an example of the result measured in the shape of a matrix for every.
The surface light source device 20 used for the luminance distribution measurement of FIGS. 13 to 17 includes the light guide plate 30 having the light emission characteristics of FIGS. 11 and 12 and the optical sheet A having the following dimensions.
<Dimension of optical sheet A (reference numeral refers to FIG. 8)>
· Width W _b of the structure row 70 along the third direction d ₃ : 18 μm
· Height H _b along the normal direction nd of the structural row 70: 14 μm
· Width W _{b of} second structured surface 72 along third direction d ₃ 2: 7.5 μm
· Inclination angle θ ₁ of the first element surface 73 a of the second structured surface 72: 63.0 °
· Inclination angle θ ₂ of the second element surface 73 b of the second structured surface 72: 63.5 °
・ Inclination angle of the first structured surface: 53.13 °

Moreover, in the surface light source device 20 used for the luminance distribution measurement of FIGS. _13-17 , bias angle (theta) _{d1 d3} of the said optical sheet is _changed into 0 degree, 10 degrees, 20 degrees, 30 degrees, and 40 degrees. In this measurement, the direction shown in FIG. 3 a third direction d ₃ to the first direction d ₁ (based on the arbitrary structure column 70, the direction of the structured surface of the arbitrary structure column 70 approaches the light source side) And change the bias angle of the optical sheet as described above.

Direction connecting the 0 and 180 in the circular graph shown in FIGS. 13 to 17 show a first direction _{d 1.} Meanwhile, the direction connecting the 90 and 270 in the circular graph shown in FIGS. 13 to 17 show a second direction _{d 2.}
Further, the center of the circular graph indicates the luminance measured in the normal direction (elevation angle of 0 °), and indicates the luminance measured at a large elevation angle as the distance from the center of the circular graph increases. The minimum value of the elevation angle is 0 ° in the normal direction (the center of the circular graph is the normal direction), and the maximum value of the elevation angle is 90 ° in the horizontal direction.
Further, in the direction connecting 90 and 270 in the circular graph, the side of 270 has a normal direction nd in a cross section parallel to both the second direction d ₂ and the normal direction nd to the sheet surface of the optical sheet. The left side as the reference is shown, and the side 90 shows the right side with respect to the normal direction nd in the cross section.
Further, in the direction connecting 0 and 180 in the circular graph, the side of 0 has a normal direction nd in a cross section parallel to both the first direction d ₁ and the normal direction nd to the sheet surface of the optical sheet. The light source side as a reference is shown, and the side of 180 shows the side opposite to the light source based on the normal direction nd in the cross section.

The luminance distributions of FIGS. 13 to 17 divide the relative ratio of the luminance of each angle to the maximum luminance shown in FIG. 13 into five parts (Z1: 90% or more, Z2: 80% or more and less than 90%, Z3: 70). % To less than 80%, Z4: 50% to less than 70%, Z5: less than 50%, and the like.
From 13 to 17, the simple configuration of tilting the third direction d ₃ to the first direction d _1, the direction in which the maximum brightness of on the light emitting surface 21 appears (the direction in which the region Z1 appears) not only offset from the normal direction to the first direction d _1, it can be confirmed that can be shifted in the second direction d _2.
That the direction of maximum brightness appears shifted in the first direction d ₁ and the second direction d ₂ is meant to satisfy the above conditions 1-1. Further, the direction in which the maximum brightness appears be shifted in the second direction d _2, it means that fulfill the above conditions 1-2.

In the example shown in FIG. 13 (the bias angle of the optical sheet is 0 °), the elevation angle indicating the maximum brightness is 22.0 °, and the azimuth angle indicating the maximum brightness is 359.0 °.
That is, in the example shown in FIG. 13, although the condition 1-1 is satisfied, the condition 1-2 is not satisfied.
On the other hand, in the example shown in FIG. 14 (the bias angle of the optical sheet is 10 °), the elevation angle indicating the maximum brightness is 25.5 °, and the azimuth angle indicating the maximum brightness is 320.0 °. In the example shown in FIG. 15 (the bias angle of the optical sheet is 20 °), the elevation angle indicating the maximum brightness is 33.0 °, and the azimuth angle indicating the maximum brightness is 285.0 °. In the example shown in FIG. 16 (the bias angle of the optical sheet is 30 °), the elevation angle indicating the maximum brightness is 35.0 °, and the azimuth angle indicating the maximum brightness is 270.0 °. In the example shown in FIG. 17 (the bias angle of the optical sheet is 40 °), the elevation angle indicating the maximum brightness is 41.5 °, and the azimuth angle indicating the maximum brightness is 253.3 °.
That is, in the example shown in FIGS. 14 to 17, the condition 1-1 and the condition 1-2 are satisfied.
As described above, according to the surface light source device of the present embodiment, a simple structure that tilts the third direction d ₃ to the first direction d _1, causing a peak of the brightness in addition to the normal direction Can.

When the maximum luminance of the example shown in FIGS. 14, 15, 16 and 17 is P _max where Re is the maximum luminance of the example shown in FIG. _max / Re shows the following values.
Figure 14: 1.01, Figure 15: 1.02, Figure 16: 1.01, Figure 17: 0.96.
That is, in the example shown in FIGS. 14 to 16, 1.0 ≦ P _max / Ref, and the condition 1-3 is satisfied. This indicates that the surface light source device of the present embodiment can generate a peak of luminance in directions other than the normal direction while maintaining a constant peak of luminance.

Moreover, FIGS. 18-22 is luminance distribution diagram A regarding the said conditions 2-1 created based on the brightness | luminance measured in creating FIGS. 13-17.
The horizontal axis of the luminance distribution chart A, as shown in the azimuth in elevation EA _max, the reference azimuth azimuth DA _max giving the luminance of P _max (0 ° denoted; in brackets the actual indicates the value) and The relative angles on the minus direction side and the plus direction side from the reference azimuth angle are described.
After calculating the _{DA -20 / + 20 / DA -45} / + 45 conditions 2-1 from 18 to 22, FIG. _{18 DA -20 / + 20 / DA} -45 / + 45 of the (bias angle 0 °) is 0.49 In FIG. 19 (bias angle 10 °), DA _{-20 / + 20} / DA _{-45 / + 45} is 0.51, and in FIG. 20 (bias angle 20 °), DA _{-20 / + 20} / DA _{-45 / + 45} is 0.59. 21 (bias angle 30 °), DA _{−20 / + 20} / DA _{−45 / + 45} is 0.62, FIG. 22 (bias angle 40 °) is DA _{−20 / + 20} / DA _{−45 / + 45} 0.66. It is.
That is, in the example shown by FIGS. 20-22, it is satisfy _| filling 0.55 <= DA- _{20 / + 20} / DA- _{45 / + 45} .

When 0.55 ≦ DA _{−20 / + 20} / DA _{−45 / + 45} is satisfied, it indicates that the luminance distribution in the azimuthal direction centered on the direction showing the peak is sharp in a specific range and the degree of light collection is high. ing.

Further, FIG. 23 to FIG. 27 are luminance distribution diagrams B for the above-mentioned condition 2-1, which are created based on the luminances measured when creating FIGS. 13 to 17.
The horizontal axis of the luminance distribution diagram B indicates the elevation angle at the azimuth angle DA _max, but the elevation angle EA _max giving the luminance of P _max is taken as a reference elevation angle (denoted as 0 °; in parentheses indicates actual value) The relative angles on the minus direction side and the plus direction side from the elevation angle are indicated.
After calculating the _{EA -20 / + 20 / EA -45} / + 45 conditions 2-1 from 23 to _{27, EA -20 / + 20 /} EA -45 / + 45 in FIG. 23 (bias angle 0 °) is 0.76 In FIG. 24 (bias angle 10 °), EA _{−20 / + 20} / EA _{−45 / + 45} is 0.76, and in FIG. 25 (bias angle 20 °), EA _{−20 / + 20} / EA _{−45 / + 45} is 0.76. In FIG. 26 (bias angle 30 °), EA _{−20 / + 20} / EA _{−45 / + 45} is 0.76, and in FIG. 27 (bias angle 40 °), EA _{−20 / + 20} / EA _{−45 / + 45} is 0.69. It is.
That is, in the example shown by FIGS. 23-26, it is satisfy | filling EA- _{20 / + 20} / EA- _{45 / + 45} > = 0.70.
In FIGS. 23 to 27, the positive direction of the elevation angle is, for example, the maximum luminance when the position of the elevation angle giving the maximum luminance and the center position are connected by a straight line in the circular graphs of FIGS. The direction from the position of the elevation angle to be given toward the outer peripheral direction of the circular graph indicates the negative direction of the elevation angle toward the central direction.

Meeting EA _{−20 / + 20} / EA _{−45 / + 45} 0.70.70 indicates that the luminance distribution in the elevation direction around the peak direction is sharp in a specific range and the degree of light collection is high. There is.

From the above, when (DA _{-20 / + 20} / DA _{-45 / + 45} ) / (EA _{-20 / + 20} / EA _{-45 / + 45} ) is calculated from FIGS. 18 to 22 and 23 to 27, the bias angle is 0 °. (DA- _{20 / + 20} / DA- _{45 / + 45} ) / (EA- _{20 / + 20} / EA- _{45 / + 45} ) at 1.54 and a bias angle of 10 ° (DA- _{20 / + 20} / DA- _{45 / + 45)} ) / (EA- _{20 / + 20} / EA- _{45 / + 45} ) is 1.47, bias angle 20 (DA- _{20 / + 20} / DA- _{45 / + 45} ) / (EA- _{20 / + 20} / EA- _{45 / + 45)} ) At a bias angle of 30 ° (DA _{-20 / + 20} / DA _{-45 / + 45} ) / (EA _{-20 / + 20} / EA _{-45 / + 45} ) at a bias angle of 40 ° (DA _{- 20 / + 20} / DA- _{45 / + 45} ) / (EA- _{20 / + 20} / EA- _{45 / + 45} ) is 1.05.
That is, in the example shown in FIGS. 20-22 and 25-27, 0.77 ≦ (DA− _{20 / + 20} / DA− _{45 / + 45} ) / (EA− _{20 / + 20} / EA− _{45 / + 45)} It becomes ≦ 1.30, and the condition 2-1 is satisfied.

Satisfying the condition 2-1 indicates that the symmetry of the luminance distribution between the azimuth angle direction and the elevation angle direction with respect to the direction indicating the luminance peak is high.
When the condition 2-1 and 0.55 ≦ DA _{−20 / + 20} / DA _{−45 / + 45} and EA _{−20 / + 20} / EA _{−45 / + 45} ≦ 0.70 are simultaneously satisfied, the peak direction is taken as the center It shows that the degree of focusing in the azimuth and elevation directions is high and the symmetry is high.

When (β _D1 + β _D2 ) / 2 of the above condition 2-3 is calculated from FIG. 18 to FIG. 22, (β _D1 + β _D2 ) / 2 of FIG. (Β _D1 + β _D2 ) / 2 at a bias angle of 10 ° is 63.0 °, and (β _D1 + β _D2 ) / 2 at FIG. ) of _{(β D1 + β D2) /} 2 is _{37.3 °, (β D1 + β} D2) / 2 in FIG. 22 (bias angle 40 °) is 33.0 °.
That is, in the example shown in FIGS. 20 to 22, 20 ° ≦ (β _D1 + β _D2 ) / 2 ≦ 60 °, which satisfies the condition 2-3.

In order to satisfy the condition 2-3, the luminance distribution of an azimuth angle centered on the direction showing the luminance peak is the above specific range ((β _D1 + β _D2 ) / 2: an angle showing 1/3 of the luminance peak ) Indicates that it can be controlled over

After calculating the above conditions 2-4 _{(β E1 + β E2) /} 2 from 23 to 27, FIG. 23 (bias angle _{0 °) (β E1 + β} E2) / 2 is 18.8 °, FIG. 24 ( bias angle 10 °) of _{(β E1 + β E2) /} 2 is 18.3 °, 25 (bias angle 20 °) of _{(β E1 + β E2) /} 2 is 20.8 °, 26 (bias angle 30 ° ) of _{(β E1 + β E2) /} 2 is 20.8 °, FIG. 27 (bias angle _{40 °) (β E1 + β} E2) / 2 is 21.0 °.
That is, in the example shown in FIGS. 25 to 27, 20 ° ≦ (β _E1 + β _E2 ) / 2 ≦ 30 °, which satisfies the condition 2-4.

In order to satisfy the condition 2-4, the luminance distribution of the elevation angle centered on the direction showing the luminance peak is in the above specific range ((β _E1 + β _E2 ) / 2: angle showing 1/3 of luminance peak) It shows that it can control over.

  Examples of applications in which display in a specific direction is important include a display device for a center console of a car, a display device for a rearview mirror of a car, a display device for a side mirror of a car, and the like.

  The surface light source device of this embodiment can add various changes to the embodiment described above, as described below.

For example, with regard to the optical sheet 60, the plurality of structural rows 70 may have different configurations.
Also, although an example having two element surfaces 73 has been shown as the second structured surface 72 of the optical sheet 60, the present invention is not limited to this, and the second structured surface 72 has three or more element surfaces 73. May be Furthermore, the cross-sectional shape of the main cutting plane of the structural row 70 is not limited to the quadrilateral shape, and may be a pentagonal shape, a hexagonal shape, or may include a curved surface in at least a part of the cross-sectional shape.

In addition, a light diffusion layer may be provided on the light exit surface 61 opposite to the surface formed by the structural rows 70 of the optical sheet 60. The light diffusion layer includes, for example, a configuration including a transparent resin and light diffusion particles. Such a light diffusion layer causes internal diffusion due to the difference in refractive index of the transparent resin and the light diffusion particles and / or external diffusion due to the surface unevenness, and makes the defects generated in the optical sheet 60 and the light guide plate 30 less noticeable. It is possible to smooth the luminance distribution emitted from the light emitting surface of the surface light source device.
Examples of the transparent resin include acrylic resins, polyester resins, urethane resins and epoxy resins. In addition, as a curing form, a thermosetting type or ionizing radiation curing type (a resin of these curing forms is also called a thermosetting resin or an ionizing radiation curing type resin), or a solvent drying curing type made of a thermoplastic resin, A curing form such as a heating melting cooling solidification type can be mentioned. Among these, ionizing radiation curable acrylic resins having excellent processability and high transmittance are preferably used.

  In addition, regarding the light guide plate 30, the plurality of optical elements 50 may be configured to have different optical elements. Furthermore, the cross-sectional shape in the main cutting plane of the optical element 50 is not limited to the pentagonal shape, and may be triangular or semicircular.

  A light emitting surface angle θa, which is an angle formed by the outer contour 51 of the main cutting surface of the optical element 50 and the surface 41 on one side of the base 40, is from the tip 52a on the outer contour 51, contrary to FIG. It may change to become smaller toward the proximal end 52b. Moreover, although the optical element 50 is formed as a convex part which protruded from the base 40 in FIG. 6, it may be formed as a concave part which dented.

  Further, in the surface light source device 20, a reflective polarizer, light is formed between the light emitting surface (the light emitting surface 21 in FIG. 1) of the optical sheet 60 and the lower polarizer 14 of the display panel 15 (liquid crystal display panel 15A). It may have a diffusion sheet or the like.

  Also, the light source 24 may be installed not only on one side of the light guide plate 30 but also on the side opposite to the one side. In this case, the azimuth angle of 0 ° may be set with reference to one of the light sources. Specifically, when the surface light source device is viewed from the normal direction, the direction from the center of the light emitting surface of the surface light source device to the opposite side to the reference light source may be set as “azimuth angle 0 °”.

[Display device]
A display device of the present invention comprises a surface light source device of the present invention described later and a display panel disposed facing the surface light source device.

FIG. 1 is a cross-sectional view showing an embodiment of a display device of the present invention.
In FIG. 1, the display device 10 includes a display panel 15 and a surface light source device 20 which is disposed on the back side of the display panel and illuminates the display panel in a planar manner from the back side. The display device 10 has a display surface 11 for displaying an image.

In FIG. 1, the display panel 15 is a liquid crystal display panel 15A. The liquid crystal display panel 15A functions as a shutter for controlling transmission or blocking of light from the surface light source device 20 for each pixel, and is configured to display an image on the display surface 11.
The liquid crystal display panel 15A of FIG. 1 is disposed between the upper polarizer 13 disposed on the light output side, the lower polarizer 14 disposed on the light incident side, and the polarizer 14 as the upper polarizer 13. The liquid crystal cell 12 is provided. The polarizers 13 and 14 separate the incident light into two linearly polarized components (P wave and S wave), and vibrate the linearly polarized component (for example, P wave) in one direction (direction parallel to the transmission axis). It has a function of absorbing linearly polarized light components (for example, S waves) which are transmitted and oscillated in the other direction (parallel to the absorption axis) orthogonal to the one direction.
The upper polarizer 13 and the lower polarizer 14 are preferably covered on both sides with a transparent plate such as a plastic film.

An electric field can be applied to the liquid crystal layer 12 for each area forming one pixel. Then, the alignment direction of the liquid crystal molecules in the liquid crystal layer 12 changes depending on the presence or absence of the application of the electric field. As an example, the polarization component in the specific direction transmitted through the lower polarizer 14 disposed on the light incident side rotates its polarization direction by 90 ° when passing through the liquid crystal layer 12 to which the electric field is not applied, When passing through the liquid crystal layer 12 to which an electric field is applied, the polarization direction is maintained. In this case, whether the polarized light component vibrating in the specific direction transmitted through the lower polarizer 14 is further transmitted through the upper polarizer 13 disposed on the light exit side of the lower polarizer 14 depending on the presence or absence of an electric field application to the liquid crystal layer 12 Alternatively, it can be controlled to be absorbed by the upper polarizer 13 and blocked.
Thus, in the liquid crystal display panel 15A, transmission or blocking of light from the surface light source device 20 can be controlled for each pixel.

DESCRIPTION OF SYMBOLS 10 display 11 display surface 12 liquid crystal layer 13 upper polarizer 14 lower polarizer 15 display panel 15 A liquid crystal display panel 20 surface light source device 21 light emitting surface 24 light source 25 light emitting body 28 reflective sheet 30 light guide plate 31 light emitting surface 32 back surface 33 light incident Surface 34 Opposite surface 35 Inclination surface 35a First surface 35b Second surface 36 Inclination surface 36a First surface 36b Second surface 37 Inclination surface 38 Stepped surface 39 Connection surface 40 Base surface 41 One side surface 42 Other side surface 50 Optical element 51 outer contour 52a tip portion 52b base end portion 60 optical sheet 61 light emitting surface 65 main body portion 66 light emitting side surface 67 light incident side surface 70 structured row 71 first structured surface 72 second structured surface 73 element surface 73 a second surface 1 element surface 73 b second element surface 75 a distal end 75 b proximal end

Claims (10)

A light guide plate having a light exit surface, a back surface opposite to the light exit surface, and a side surface located between the light exit surface and the back surface, and any of the side surfaces is a light entrance surface;
A light source disposed facing the light entrance surface;
A surface light source device comprising: an optical sheet disposed to face the light exit surface of the light guide plate;
The optical sheet has a sheet-like main body portion and a plurality of structural rows provided on the surface of the main body portion on the light guide plate side,
When the direction perpendicular to the light incident surface of the light guide plate is a first direction d ₁ and the arrangement direction of the structural rows is a third direction d ₃ , the first direction d ₁ and the third direction d ₃ are not parallel And
The surface light source device which satisfy | fills the following conditions 1-1 and conditions 2-1, when the brightness | luminance of the light radiate | emitted from the center of the surface on the opposite side to the light-guide plate of the said optical sheet is measured.
<Condition 1-1>
The maximum luminance when measuring the luminance distribution of light emitted from the center of the surface opposite to the light guide plate of the optical sheet in a matrix at an elevation angle of 0.5 ° and at an azimuth angle of 0.5 ° is P _max I assume. Here, when the surface light source device is viewed from the normal direction, the direction of the perpendicular drawn from the center to the light incident surface side is the “azimuth angle 0 °”, and the surface of the optical sheet opposite to the light guide plate The direction from normal direction to the normal direction is "elevation 0 °".
When the elevation angle indicating P _max is EA _max and the azimuth angle indicating P _max is DA _max , the EA _max indicates a value other than 0 °.
<Condition 2-1>
Based on the brightness of each angle measured in condition 1-1, a brightness distribution map A for each azimuth angle at the elevation angle EA _max is created. In the luminance distribution map A, it is assumed that all luminances are normalized with the luminance of P _max as 1.0.
The integrated value of luminance in the range of azimuth angle “(DA _max −45 °) to (DA _max + 45 °)” of the luminance distribution map A is DA _{−45 / + 45} , and the azimuth angle “(DA _max of the luminance distribution map A An integral value of luminance in a range of −20 °) to DA _max to (DA _max + 20 °) is set to DA _{−20 / + 20} .
Based on the brightness of each angle measured in condition 1-1, a brightness distribution chart B for each elevation angle at the azimuth angle DA _max is created. In the luminance distribution diagram B, it is assumed that all luminances are normalized with the luminance of P _max as 1.0.
The integrated value of the brightness in the range of elevation angles “(EA _max −45 °) to (EA _max + 45 °)” of the brightness distribution chart B is EA _{−45 / + 45} , and the azimuth angle “(EA _max − Let the integral value of the luminance in the range of 20 °) to (EA _max + 20 °) be EA _{-20 / + 20} .
In the above, 0.77 ≦ (DA− _{20 / + 20} / DA− _{45 / + 45} ) / (EA− _{20 / + 20} / EA− _{45 / + 45} ) ≦ 1.30 is satisfied. The surface light source device according to claim 1, further satisfying a condition of 27 ° ≦ EA _max ≦ 60 ° under the condition 1-1. Furthermore, the surface light source device of Claim 1 or 2 which satisfy | fills the following conditions 1-2.
<Condition 1-2>
DA _max has a value other than 0 ° or 180 °. The surface light source device according to claim 3, wherein the condition 1-2 satisfies the condition of 240 ° ≦ DA _max ≦ 310 °. The surface light source device according to any one of claims 1 to 4, wherein the following condition 2-3 is satisfied.
<Condition 2-3>
Based on the brightness of each angle measured in condition 1-1, a brightness distribution map A for each azimuth angle at the elevation angle EA _max is created. In the luminance distribution map A, it is assumed that all luminances are normalized with the luminance of P _max as 1.0.
The azimuth angle DA _max is a reference azimuth angle, and at an azimuth angle on the negative direction side from the reference azimuth angle of the brightness distribution map A, an azimuth angle angle indicating a brightness that is first 1/3 or less of P _max is -β DA _max , An azimuth angle indicating a luminance that is firstly 1⁄3 or less of P _max at an azimuth angle on the positive direction side from the reference azimuth angle is + β DA _max .
The interval between the reference azimuth angle and the angle -βDA _max is β _D1 , and the interval between the reference elevation angle and the + β DA _max is β _D2 .
In the above, the condition of 20 ° ≦ (β _D1 + β _D2 ) / 2 ≦ 60 ° is satisfied. The surface light source device according to any one of claims 1 to 5, wherein the following condition 2-4 is satisfied.
<Condition 2-4>
Based on the brightness of each angle measured in condition 1-1, a brightness distribution chart B for each elevation angle at the azimuth angle DA _max is created. In the luminance distribution diagram B, it is assumed that all luminances are normalized with the luminance of P _max as 1.0.
An elevation angle EA _max is taken as a reference elevation angle, and an elevation angle inclined toward the normal direction is referred to as an “elevation angle on the minus direction side”, and an elevation angle inclined toward the side away from the normal direction is referred to as an elevation angle on the plus direction.
First P _max at first elevation angle of elevation showing luminance as a third or less of P _max -βEA _max, the reference elevation angle of plus direction side from the reference elevation angle in the elevation of the minus side of the luminance distribution diagram B 1/3 the angle of elevation showing the following become luminance + βEA _max to.
The interval between the reference elevation angle and the angle -βEA _max is β _E1 , and the interval between the reference elevation angle and the + β EA _max is β _E2 .
In the above, the condition of 20 ° ≦ (β _E1 + β _E2 ) / 2 ≦ 30 ° is satisfied. The first direction _{d 1} and the third angle theta _D1d3 formed between the direction _{d 3} is the surface light source device according to any one of claims 1 to 6 satisfying _{15 ° ≦ θ d1d3 ≦ 50 °} . The surface light source device according to any one of claims 1 to 7, further satisfying the following conditions 1-3.
<Condition 1-3>
A first direction d ₁ and the third direction d ₃ is the comparison surface light source device a surface light source device is a parallel in the surface light source device. When the luminance of light emitted in the normal direction from the center of the surface opposite to the light guide plate of the optical sheet of the comparative surface light source device is measured, and the luminance is Ref, 1.0 ≦ P _max / Ref Meet. In Condition 2-1, the DA _{-20 / + 20} / DA _{-45 / + 45} is 0.55 or more, and the EA _{-20 / + 20} / EA _{-45 / + 45} is 0.70 or more. Surface light source device according to any one of   A display device comprising: the surface light source device according to any one of claims 1 to 9; and a display panel disposed to face the surface light source device.