JP6303649B2 - Surface light source device, transmissive display device - Google Patents

Description

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

2. Description of the Related Art Conventionally, a transmissive display device that displays an image by illuminating a transmissive display unit such as an LCD (Liquid Crystal Display) panel from the back with a surface light source device (backlight) is known.
Surface light source devices are broadly classified into a direct type in which a light source is arranged directly under an optical member such as various optical sheets and an edge light type in which a light source is arranged on a side surface side of the optical member. This edge light type surface light source device has an advantage that the surface light source device can be made thinner than the direct type because the light source is arranged on the side surface side of the optical member such as a light guide plate, and is widely used. It has been.

Generally, in an edge light type surface light source device, a light source is disposed at a position facing a light incident surface that is a side surface of a light guide plate, and light emitted from the light source enters the light guide plate from the light incident surface, The light advances from the light incident surface to the surface facing the light incident surface while repeating reflection at the light exit surface and the back surface facing the light exit surface (the light traveling direction is referred to as the light guide direction).
In recent years, a light guide plate in which a prism shape having a slope that reflects light and changes an incident angle on a light exit surface and a plurality of V-shaped grooves are arranged on the back surface has been widely used.
In such an edge-light type surface light source device, a reflective member such as a reflective sheet is often disposed on the back side of the light guide plate in order to increase the light use efficiency. Optical adhesion occurs between the light plates, and the light that is incident and reflected on the part where the optical contact is made travels in a direction outside the original optical design and is emitted from the light guide plate, resulting in a partially brightened area and uneven brightness. There is a problem that the brightness of a region far from the light source is reduced.
In order to prevent this optical adhesion, a surface light source device using a reflecting member or the like in which an uneven shape is provided on the surface of the reflecting member on the light guide plate side has been proposed (for example, Patent Documents 1 and 2).

JP 2000-82313 A JP 2002-333510 A

  Here, in a light guide plate having a prism shape or the like on the back surface, a guide portion provided with a flat portion on a part of the prism shape or the like is provided for the purpose of preventing damage to the prism shape or extending the light guide distance. An optical plate has also been developed. In that case, the surface light source devices of Patent Documents 1 and 2 described above may not be able to sufficiently prevent optical adhesion between the reflecting member and the light guide plate.

  An object of the present invention is to provide a surface light source device and a transmissive display device that can significantly suppress optical contact with a light guide plate.

The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this.
The first invention has light incident surface on which light is incident (13a), the light exit surface that before crossing the light incident surface of light is emitted and (13c), a rear (13d) facing the light exit surface A light guide plate (13) that emits light incident from the light incident surface in the light guide direction and exits from the light exit surface, and is disposed on the back side of the light guide plate and exits from the back surface of the light guide plate A reflective member (14) that reflects light toward the light guide plate, the reflective member having a fine irregular shape on the surface of the light guide plate, and a total reflectance of 90% or more, and The diffuse reflectance is formed within a range of 0.5% to 8%, and the light guide plate has a plurality of back unit optical shapes (131) arranged in the light guide direction on the back surface, The side unit optical shape is convex on the back side, parallel to the arrangement direction, and in the thickness direction of the light guide plate. In the cross section, the cross-sectional shape is a substantially square shape, and at least a part of the incident light positioned on the other side opposite to the first inclined surface portion (132) located on the light incident surface side. a second slope portion (133) for total reflection, has a top wall (134) located between said first inclined surface portion and the second inclined surface portion, at least one of said top of said rear-side unit optical shape The surface portion includes a plurality of surfaces having different heights in the thickness direction, and a surface located closest to the reflecting member among the plurality of surfaces is a contact portion (134a) that contacts the reflecting member, A ratio (A1 / A2) of the total contact area (A1) of each contact portion and the area (A2) of the back surface of the light guide plate when the back surface of the optical plate is disposed on a flat plate (T) is S1. And satisfying 35% ≦ S1 ≦ 45%. The source is a device (10).
2nd invention is the surface light source device (10) of 1st invention, The said contact part (134a) is located in the said 2nd slope part (133) side most in the said top surface part (134). The surface light source device characterized by the above.
According to a third aspect of the present invention, in the surface light source device (10) of the first or second aspect, the plurality of surfaces provided with the top surface portion (134) decrease as the distance from the light incident surface increases. The surface light source device characterized by the above.
According to a fourth invention, in the surface light source device (10) from the first invention to the third invention, the rear unit optical shape (131) has a constant arrangement pitch (P1) in the arrangement direction. There is a surface light source device characterized by being.
According to a fifth invention, in the surface light source device (10) according to any one of the first invention to the fourth invention , the reflection member when the surface of the reflection member on the light guide plate side is disposed on a flat plate. 35% ≦ S1 + S2 where S2 is the ratio (B1 / B2) of the total contact area (B1) of each convex portion of the concavo-convex shape to the area (B2) of the surface of the reflecting member on the light guide plate side It is a surface light source device characterized by satisfying ≦ 50%.
A sixth invention is a surface light source device according to the fifth aspect of the invention , wherein 0% <S2 <5% is satisfied.
According to a seventh invention, in the surface light source device (10) according to any one of the first invention to the sixth invention, the light is observed when the light guide plate (13) is disposed on the flat plate (T). The ratio (a1 / A2) between the contact area (a1) of each contact portion (134a) within the effective range reaching the person side and the area (A2) of the back surface (13d) of the light guide plate is S3, A surface light source device characterized by satisfying S3min / S3max> 95% when the minimum value is S3min and the maximum value is S3max among S3 of each contact portion.
According to an eighth aspect of the present invention, in any one of the surface light source devices (10) from the first aspect to the seventh aspect, the back unit optical shape (131) is columnar and orthogonal to the light guide direction. The surface light source device is characterized by being arranged in the light guide direction with a direction as a longitudinal direction.
A ninth invention comprises any one of the surface light source devices (10) from the first invention to the eighth invention, and a transmissive display unit (11) illuminated from the back side by the surface light source device. It is a transmissive display device (1).

  According to the present invention, there is an effect that it is possible to provide a surface light source device and a transmissive display device that can significantly suppress optical contact with a light guide plate.

It is a figure explaining the transmissive display apparatus of embodiment. It is a figure explaining the shape of the light-guide plate of embodiment. It is a figure explaining the back side unit optical shape of an embodiment. It is a figure which shows the shape in each part of the arrangement direction of the back side unit optical shape of embodiment. It is a figure which shows the cross-sectional shape of the reflective sheet of embodiment. It is a figure explaining the prism sheet of an embodiment. It is a figure explaining each contact area of the light-guide plate and reflection sheet of embodiment. It is a figure explaining the evaluation method of the presence or absence of the optical contact between the light-guide plate of a measurement example, and a reflective sheet.

Embodiments of the present invention will be described below with reference to the drawings. In addition, each figure shown below including FIG. 1 is the figure shown typically, and the magnitude | size and shape of each part are exaggerated suitably for easy understanding.
In this specification, the terms “plate”, “sheet”, and the like are used, but these are generally used in the order of thickness, “plate”, “sheet”, “film”. Above all, it uses it. However, there is no technical meaning in such proper use, so these terms can be replaced as appropriate.
Numerical values such as dimensions and material names of the respective members described in the present specification are examples of the embodiment, and the present invention is not limited thereto, and may be appropriately selected and used.
In this specification, terms that specify shape and geometric conditions, for example, terms such as parallel and orthogonal, are strictly meanings, have similar optical functions, and can be regarded as parallel and orthogonal It also includes a state having an error of.
In this specification, the sheet surface (plate surface, film surface) is the planar direction of the sheet (plate, film) when viewed as the entire sheet (plate, film) in each sheet (plate, film). It is assumed that the surface to be

(Embodiment)
FIG. 1 is a diagram illustrating a transmissive display device 1 according to the present embodiment.
The transmissive display device 1 of the present embodiment includes an LCD panel 11 and a surface light source device 10. The transmissive display device 1 illuminates the LCD panel 11 with the surface light source device 10 from the back side, and displays video information formed on the LCD panel 11.
In addition, in the following drawings including FIG. 1 and the following description, in order to facilitate understanding, when the transmissive display device 1 is in use, the transmissive display device 1 is parallel to the screen of the transmissive display device 1 and orthogonal to each other. The directions are the X direction (X1-X2 direction) and the Y direction (Y1-Y2 direction), and the direction orthogonal to the screen of the transmissive display device 1 is the Z direction (Z1-Z2 direction). In the Z direction, the Z1 side is the back side, and the Z2 side is the observer side.
The screen of the transmissive display device 1 of the present embodiment corresponds to the surface 11a closest to the viewer (hereinafter referred to as a display surface) 11a of the LCD panel 11, and the “front direction” of the transmissive display device 1 is the display. The normal direction of the surface 11a is parallel to the Z direction, and coincides with the normal direction to the sheet surface of the prism sheet 15 to be described later, the normal direction to the plate surface of the light guide plate 13, and the like.

The LCD panel 11 is a transmissive display unit that is formed of a transmissive liquid crystal display element and forms video information on its display surface.
The LCD panel 11 has a substantially flat plate shape. The outer shape of the LCD panel 11 and the display surface 11a are rectangular when viewed from the Z direction, and have two opposite sides parallel to the X direction and two opposite sides parallel to the Y direction.

The surface light source device 10 is a device that illuminates the LCD panel 11 from the back side, and includes a light source unit 12, a light guide plate 13, a reflection sheet 14, a prism sheet 15, and a light diffusion sheet 16. The surface light source device 10 is a so-called edge light type surface light source device (backlight).
The light guide plate 13, the reflection sheet 14, the prism sheet 15, the light diffusion sheet 16, etc. that constitute the surface light source device 10 are rectangular when viewed from the front direction (Z direction) and are opposed to two sides parallel to the X direction. And two opposite sides parallel to the Y direction.

The light source unit 12 is a part that emits light that illuminates the LCD panel 11. The light source unit 12 is disposed along the Y direction at a position facing the light incident surface 13a that is one end surface (X1 side) of the light guide plate 13 in the X direction (X1 side).
The light source unit 12 is formed by arranging a plurality of point light sources 121 at predetermined intervals in the Y direction. The point light source 121 uses an LED (Light Emitting Diode) light source. The light source unit 12 may be, for example, a line light source such as a cold cathode tube, or may have a form in which a light source is disposed on an end surface of a light guide extending in the Y direction. Further, from the viewpoint of improving the utilization efficiency of light emitted from the light source unit 12, a reflection plate (not shown) may be provided so as to cover the outside of the light source unit 12.

The light guide plate 13 is a substantially flat member that guides light. In the present embodiment, the light incident surface 13a and the opposing surface 13b are located at both ends of the light guide plate 13 in the X direction (X1 side end, X2 side end) and from the normal direction (Z direction) of the plate surface. They are two sides extending in parallel to the Y direction as viewed. The plate surface of the light guide plate 13 is parallel to the XY plane, and the light output surface 13c is a surface parallel to the plate surface.
The light guide plate 13 allows light emitted from the light source unit 12 to be incident from the light incident surface 13a, and is totally reflected by the light output surface 13c and the back surface 13d, to the opposite surface 13b side (X2 side) facing the light incident surface 13a. The light is appropriately emitted from the light exit surface 13c to the prism sheet 15 side (Z2 side) while being guided mainly in the X direction.
Hereinafter, each part of the light guide plate 13 will be described.

FIG. 2 is a diagram illustrating the shape of the light guide plate 13 of the present embodiment. FIG. 2A is a diagram for explaining the light exit side unit optical shape 135, and FIG. 2B is a diagram for explaining the back side unit optical shape 131. In FIG. 2A, a part of the cross section parallel to the YZ plane of the light guide plate 13 is shown enlarged, and in FIG. 2B, a part of the cross section parallel to the XZ plane of the light guide plate 13 is enlarged. Show.
FIG. 3 is a diagram for explaining the back-side unit optical shape 131 of the present embodiment. In FIG. 3, a part of a cross section parallel to the XZ plane of the light guide plate 13 shown in FIG.
As shown in FIG. 2, the light guide plate 13 is formed by arranging a plurality of light output side unit optical shapes 135 on the light output surface 13c, and formed by arranging a plurality of back side unit optical shapes 131 on the back surface 13d. ing.

As shown in FIGS. 1 and 2A, the light exit side unit optical shape 135 has a triangular prism shape that is convex on the light output side (LCD panel 11 side, Z2 side), and the longitudinal direction (ridge line direction) is the X direction. And a plurality of them are arranged in the Y direction.
As shown in FIG. 2A, the light exit side unit optical shape 135 has a cross-sectional shape in a cross-section (YZ plane) that is parallel to the arrangement direction and orthogonal to the plate surface of the light guide plate 13, and the apex angle is γ. The isosceles triangle shape. Further, the arrangement pitch of the light output side unit optical shapes 135 is P2, and the arrangement pitch P2 is equal to the width W2 in the arrangement direction of the light output side unit optical shapes 135 (P2 = W2).

The arrangement pitch P2 is preferably about 10 to 100 μm.
If the arrangement pitch P2 is smaller than this range, it is difficult to manufacture the light output side unit optical shape 135, and the designed shape cannot be obtained. Further, if the arrangement pitch P2 is larger than this range, moire with the pixels of the LCD panel 11 is likely to occur, or the pitch of the light output side unit optical shape 135 is easily recognized in the usage state as the surface light source device 10 or the like. It becomes. Therefore, the arrangement pitch P2 is preferably in the above range.

  The light exit side unit optical shape 135 is not limited to the above example. For example, a polygonal column shape having a trapezoidal shape, a pentagonal shape, or the like in cross section, or a long axis on the plate surface (light output surface 13c) of the light guide plate 13. It may be a partial shape of orthogonal elliptic cylinders, a partial shape of a cylinder, or a shape formed by combining a plurality of types of curved surfaces and planes.

  The light output side unit optical shapes 135 are arranged in a direction (Y direction) orthogonal to the light guide direction (X direction) of the main light of the light guide plate 13, and the arrangement direction with respect to the light emitted from the light output surface 13c Has a light beam control action. Therefore, the light emission side unit optical shape 135 can improve the uniformity of the brightness in the Y direction of the light emitted from the light guide plate 13. In addition, when such a light beam control action is not required, the light output side unit optical shape 135 may not be formed on the light output surface 13c.

As shown in FIGS. 1, 2B, and 3, the back side unit optical shape 131 is a columnar shape that is convex on the back side (Z1 side), and the longitudinal direction (ridge line direction) is the Y direction. A plurality are arranged in the X direction, which is the light direction.
As shown in FIG. 2B, the back-side unit optical shape 131 has a substantially trapezoidal cross-sectional shape in a cross section (XZ plane) in a direction parallel to the arrangement direction and orthogonal to the plate surface of the light guide plate 13. is there. The back side unit optical shape 131 is located on the light incident surface side (X1 side) and the second inclined surface portion 132, and is located on the opposite surface side (X2 side), and totally reflects at least part of the incident light. It has a slope part 133 and a top face part 134 located between the first slope part 132 and the second slope part 133.
The arrangement pitch of the back side unit optical shapes 131 is P1, and the arrangement pitch P1 is equal to the width W1 in the arrangement direction of the back side unit optical shapes 131 (P1 = W1). In the present embodiment, the arrangement pitch P1 is constant in the arrangement direction.

The first inclined surface portion 132 forms an angle β with the plate surface of the light guide plate 13 (a surface parallel to the light exit surface 13c, a surface parallel to the XY plane). Further, the second slope portion 133 forms an angle α with the plate surface of the light guide plate 13. At this time, the angles α and β are α <β.
The first inclined surface portion 132 is located on the light incident surface 13a side (X1 side) in the rear side unit optical shape 131, and the end portion on the opposite surface 13b side (top surface portion side) is the rear surface than the light incident surface 13a side end portion. It is inclined so as to be on the 13d side (Z1 side), and light that guides light from the light incident surface 13a side to the opposing surface 13b side (from the X1 side to the X2 side) is not easily incident on the first inclined surface portion 132. .

The second inclined surface portion 133 is located on the facing surface 13b side (X2 side) in the back side unit optical shape 131, and the light incident surface 13a side (top surface side) end portion is the back surface 13d rather than the facing surface 13b side end portion. It inclines so that it may become the side (Z1 side). The second inclined surface portion 133 receives a part of the light guided through the light guide plate 13 and totally reflects at least a part of the incident light. Then, when the light is totally reflected by the second inclined surface portion 133, the traveling direction of the light is changed in a direction in which the incident angle of the light with respect to the light exit surface 13c (a surface parallel to the XY plane) decreases. Therefore, from the viewpoint of improving both the uniformity of brightness in the light guide direction and the light extraction efficiency, the angle α preferably satisfies 1 ° <α ≦ 5 °.
If α ≦ 1 °, when the light traveling in the light guide direction (X direction) is totally reflected by the second inclined surface portion 133, the light exit surface 13c (a surface parallel to the XY plane) before and after the total reflection. The amount of change in the angle formed becomes too small, so that the light cannot be extracted sufficiently, and the light extraction efficiency decreases.
Also, if α> 5 °, when the light traveling in the light guide direction (X direction) is totally reflected by the second inclined surface portion 133, the light exit surface 13c before and after total reflection (a surface parallel to the XY plane) ), The amount of change in the angle becomes too large, resulting in uneven brightness and a decrease in brightness in a region far from the light incident surface 13a. Further, since the variation in the light output direction from the light guide plate 13 is also increased, the deflection action at the prism sheet 15 described later becomes insufficient, the convergence is lowered, and the front luminance is lowered.
From the above, the angle α preferably satisfies 1 ° <α ≦ 5 °.

The top surface portion 134 has a plurality of surfaces with different heights h to the back surface side (Z1 side). Here, the height h to the back side (Z1 side) refers to a plane parallel to the plate surface of the light guide plate 13 (parallel to the light exit surface 13c), passing through the point v located at the valley bottom between the back side unit optical shapes 131. The dimension from the right surface) to the back side (Z1 side).
As an example, the top surface portion 134 shown in FIG. 3 has surfaces 134a, 134b, 134c, and 134d. The surfaces 134 a to 134 d are surfaces parallel to the light exit surface 13 c (the plate surface of the light guide plate 13), and the longitudinal direction (Y direction) of the back unit optical shape 131 is the longitudinal direction, and the back unit optical shape 131 of the back side unit optical shape 131. They are arranged along the arrangement direction (X direction). Further, the surfaces 134a to 134d have different heights h from the back side.

Of the surfaces 134a to 134d, the height h to the back side of the surface 134d located closest to the first slope portion 132 side (light incident surface side, X1 side) is the smallest, and the second slope portion 133 side (opposite surface side) , X2 side), the height h toward the back side gradually increases, and the height h toward the back side of the surface 134a located closest to the second slope portion 133 side is the largest. And the top surface part 134 has step shape along the sequence direction by having these surfaces 134a-134d. The difference in height h from the back surface to the back surface may be constant or different.
A slope 134e is formed between the surfaces 134a to 134d. The inclined surface 134e is an inclined surface that forms an angle β with the plate surface of the light guide plate 13 (a surface parallel to the XY plane) and is parallel to the first inclined surface portion 132.
In the present embodiment, the surfaces 134a to 134d are described with an example in which the widths in the arrangement direction are equal to each other, but the widths in the arrangement direction may be different from each other.

FIG. 4 is a diagram illustrating the shape of each part in the arrangement direction of the back side unit optical shape 131 of the present embodiment. 4A shows the back side unit optical shape 131 in the vicinity of the light incident surface 13a, FIG. 4B shows the back side unit optical shape 131 at the center in the arrangement direction, and FIG. The back side unit optical shape 131 of the surface 13b vicinity is shown.
In the arrangement direction of the back-side unit optical shapes 131, the width W1 of the back-side unit optical shapes 131 is assumed to be the dimension Wa of the top surface part 134, and the dimension Wb occupied by the first slope part 132 and the second slope part 133.
The rear unit optical shape 131 has a constant arrangement pitch P1, width W1, and angles α, β in the arrangement direction. However, the ratio Wb / W1 of the dimension Wb of the first inclined surface portion 132 and the second inclined surface portion 133 with respect to the width W1 of the back unit optical shape 131 increases as the distance from the light incident surface 13a increases in the arrangement direction. . In addition, the ratio Wa / W1 of the dimension Wa of the top surface portion 134 to the width W1 of the back unit optical shape 131 decreases as the distance from the light incident surface 13a increases in the arrangement direction.

That is, as shown in FIG. 4A, in the vicinity of the light incident surface 13a (on the light source side), the ratio Wa / W1 occupied by the dimension Wa of the top surface portion 134 with respect to the width W1 of the back unit optical shape 131 is large. The ratio Wb / W1 occupied by the dimension Wb of the first slope portion 132 and the second slope portion 133 is small with respect to the width W1 of the back unit optical shape 131.
As proceeding to the facing surface side (X2 side), as shown in FIG. 4B, the ratio Wa / W1 gradually decreases and the ratio Wb / W1 increases. As shown in FIG. 4C, the ratio Wb / W1 is large and the ratio Wa / W1 is small in the vicinity of the facing surface 13b.
As described above, by increasing the ratio of both slope portions (particularly, the second slope portion 133) toward the facing surface side, light can be emitted efficiently and the brightness in the light guide direction is uniform. Also improves.

  In this embodiment, the ratio Wb / W1 is about 20/100 on the most light incident surface side (X1 side) and about 80/100 on the most opposite surface side (X2 side). However, the present invention is not limited to this, and the ratio Wb / W1 can be appropriately set according to the desired optical performance and the like, and is about 10/100 on the most light incident surface side and about 90/100 on the most opposite surface side. If it is in such a range, you may set suitably.

In the light guide plate 13 of the present embodiment, a surface 134a having the highest height h toward the back surface 13d is a surface in contact with the reflection sheet 14 (hereinafter referred to as a contact surface 134a). The contact surface 134a is formed so that the width Wc in the arrangement direction is constant.
As described above, in the light guide plate 13, the arrangement pitch P1 (width W1), the width Wc of the contact surface 134a, and the angles α and β are constant, and as shown in FIG. ) In order to increase the ratio of the width Wb of both inclined surfaces (especially the second inclined surface portion 133) to the width W1 of the back unit optical shape 131, the number of surfaces forming the top surface portion 134 is decreased. doing.
Further, the width Wa of the top surface portion 134 is sufficiently small on the most facing surface side and in the vicinity thereof, and the influence of the optical contact between the reflection sheet 14 and the top surface portion 134 is small, so that it is located on the most facing surface side and in the vicinity thereof. In the back unit optical shape 131, the top surface part 134 may be formed of only one surface, that is, the contact surface 134a.

The arrangement pitch P1 is preferably about P1 = 50 to 300 μm.
If the arrangement pitch P1 is smaller than this range, it is difficult to manufacture the back unit optical shape 131, and the designed shape cannot be obtained. Further, when the arrangement pitch P1 is larger than this range, moire tends to occur, and the pitch of the back-side unit optical shape 131 can be easily recognized when used as the surface light source device 10 or the like.
Therefore, the arrangement pitch P1 is preferably in the above range.

The light guide plate 13 of the present embodiment is manufactured by cutting a concave mold that shapes the back unit optical shape 131 with a cutting tool or the like, and using the mold to perform an extrusion molding method or an injection molding. It is formed by. The thermoplastic resin to be used is not particularly limited as long as it has high light transmittance, and examples thereof include acrylic resins, COP (cycloolefin polymer) resins, and PC resins.
The light guide plate 13 is not limited to this, and the back side unit optical shape 131 and the light exit side unit optical shape 135 are integrally formed on both surfaces of a sheet-like member formed by extrusion molding or the like by an ultraviolet molding method. Also good.

Returning to FIG. 1, the reflection sheet 14 is a sheet-like member capable of reflecting light, and is disposed on the back side (Z1 side) of the light guide plate 13. The reflection sheet 14 has a function of reflecting light traveling from the light guide plate 13 toward the Z1 side and directing the light into the light guide plate 13.
The reflective sheet 14 has specular reflectivity (regular reflectivity) from the viewpoint of increasing the light utilization efficiency and the like. Specifically, the reflection sheet 14 is formed so that the total reflectance is 90% or more and the diffuse reflectance is in the range of 0.5% to 8%.

FIG. 5 is a diagram showing a cross-sectional shape of the reflection sheet 14 of the present embodiment. In FIG. 5, a part of a cross section parallel to the direction (Z direction) orthogonal to the sheet surface of the reflection sheet 14 and the light guide direction (X direction) is shown enlarged.
As shown in FIG. 5, the reflection sheet 14 includes a resin base layer 141, a reflection layer 142 formed on the surface of the base layer 141 on the light guide plate 13 side, and a reflection layer 142 on the light guide plate 13 side. And a mat layer 143 formed on the surface.
The base material layer 141 is a layer that serves as a base of the reflection sheet 14.
The base material layer 141 uses a sheet-like member made of PET (polyethylene terephthalate) resin. The base material layer 141 may be a sheet-like member made of PC resin, acrylic resin, PP (polypropylene) resin, TAC (triacetyl cellulose) resin, or the like. The base material layer 141 may be colored white or the like, or may be transparent, translucent, opaque, or the like.

The reflection layer 142 is a layer having a function of specularly reflecting light. The light reflected from the back surface 13d of the light guide plate 13 is regularly reflected and returned to the light guide plate 13 side, thereby reducing the front luminance of the light guide plate 13. Suppress. The reflective layer 142 includes a transparent base layer 142a and a vapor deposition layer 142b. The reflective layer 142 is bonded to the base material layer 141 with an adhesive (not shown) so that the vapor deposition layer 142b faces.
The transparent base material layer 142a is a sheet-like member made of a transparent or substantially transparent PET resin. The transparent base material layer 142a is not limited to PET resin, and a sheet-like member such as PC resin, acrylic resin, PP (polypropylene) resin, and TAC (triacetyl cellulose) resin can also be used.
The vapor deposition layer 142b is a layer having a light reflection function formed by vapor-depositing a metal material having a high reflectance such as silver or aluminum on one surface side of the transparent base material layer 142a.

Here, the reflective layer 142 preferably has a total reflectance of 90% or more and a diffuse reflectance Rd of 8% or less.
If the total reflectivity is less than 90%, the light reflection characteristics of the reflective layer 142 are deteriorated, which is not preferable. On the other hand, if the diffuse reflectance Rd is larger than 8%, it is not preferable because the regular reflection property of light in the reflective layer is lowered.

The mat layer 143 is a layer having a fine uneven shape formed on the surface of the reflective layer 142 on the transparent base material layer 142a side. The mat layer 143 is formed from an ultraviolet curable resin containing fine particles. Here, the mat layer 143 is formed not on the vapor deposition layer 142b but on the transparent base material layer 142a from the viewpoint of ensuring adhesion with the reflective layer 142.
As the ultraviolet curable resin of the mat layer 143, for example, urethane resin, epoxy resin, or the like is preferably used.
Further, the content of fine particles with respect to the ultraviolet curable resin is appropriately determined according to the uneven shape required for the mat layer 143. For example, urethane beads having high impact resilience can be used as the fine particles, and the hardness of the mat layer 143 can be adjusted by adjusting the content of the ultraviolet curable resin. By adjusting the hardness of the mat layer 143 so as to be equal to or approximate to the hardness of the light guide plate 13, it is possible to suppress damage to one of the reflective sheet 14 and the light guide plate 13 when they are laminated. Can do. Here, when the content of fine particles is increased, the hardness of the mat layer 143 increases, and when the content is decreased, the hardness of the mat layer 143 tends to decrease. For the fine particles of the mat layer 143, beads such as styrene, acrylic, glass, silica and the like can be used in addition to the urethane beads described above.
The fine particles contained in the ultraviolet curable resin desirably have a particle size in the range of 1 to 30 μm from the viewpoint of adjusting the uneven shape of the mat layer 143 and the hardness. In addition, the thickness of the mat layer 143 in this embodiment means the thickness of the layer in the position where the above-mentioned fine particle does not exist.
Note that the mat layer 143 may be formed of only an ultraviolet curable resin without containing fine particles. In this case, the unevenness of the mat layer 143 can be formed by embossing or the like, and the hardness of the mat layer 143 can be changed by changing the type of the UV curable resin, the UV irradiation amount, or the photopolymerization. It can be formed to a desired hardness by appropriately adjusting the distribution amount of the initiator.

FIG. 6 is a diagram illustrating the prism sheet 15 of the present embodiment. In FIG. 6, a part of a cross section parallel to the XZ plane of the prism sheet 15 is shown enlarged.
The prism sheet 15 is disposed closer to the LCD panel 11 (Z2 side) than the light guide plate 13 (see FIG. 1). The prism sheet 15 has a function of deflecting (condensing) the traveling direction of light emitted from the light exit surface 13c of the light guide plate 13 in the front direction (Z direction) or in a direction having a small angle with the Z direction. It is.
The prism sheet 15 includes a prism base layer 152 and a plurality of unit prisms 151 that are arranged in a plurality on the light guide plate 13 side (Z1 side) of the prism base layer 152.

The prism base material layer 152 is a portion that becomes a base (base material) of the prism sheet 15. For the prism base material layer 152, a resin-made sheet-like member having optical transparency is used.
The unit prism 151 has a triangular prism shape convex toward the light guide plate 13 side (Z1 side), and the longitudinal direction (ridge line direction) is set to the Y direction on the back side (Z1 side) surface of the prism base material layer 152. A plurality are arranged in the direction. That is, the arrangement direction of the unit prisms 151 is parallel to the arrangement direction of the rear unit optical shapes 131 of the light guide plate 13 when viewed from the normal direction (Z direction) of the display surface of the transmissive display device 1, and the light exit side The unit optical shape 135 is orthogonal to the arrangement direction.

The unit prism 151 of the present embodiment is an isosceles triangle whose cross-sectional shape in a cross section (XZ plane) parallel to the arrangement direction (X direction) and the direction orthogonal to the sheet plane (Z direction) is an apex angle ε. The example which is a shape is shown. However, the present invention is not limited to this, and the cross-sectional shape of the unit prism 151 may be an unequal triangular shape. Further, the unit prism 151 may have a bent surface shape in which at least one surface is composed of a plurality of surfaces, or may have a shape in which a curved surface and a flat surface are combined, or a cross-sectional shape that is asymmetric in the arrangement direction. It is good.
The unit prism 151 has an arrangement pitch P3 and a width in the arrangement direction W3, and the arrangement pitch and the lens width in the arrangement direction are equal in the arrangement direction (P3 = W3).
The prism sheet 15 is emitted from the light guide plate 13 and totally reflected by the other surface (for example, the surface 151b) the light L1 incident from one surface (for example, the surface 151a). Z direction) or deflected (condensed) in a direction where the angle formed with respect to the front direction becomes smaller.

The prism sheet 15 is a unit prism made of, for example, an ionizing radiation curable resin such as an ultraviolet curable resin on one side of a sheet-like prism base layer 152 made of PET (polyethylene terephthalate) resin or PC (polycarbonate) resin. 151 is formed.
For example, the prism sheet 15 may be a PC resin, an MBS (methyl methacrylate / butadiene / styrene copolymer) resin, an MS (methyl methacrylate / styrene copolymer) resin, a PET resin, or PS (polystyrene). You may form by extruding thermoplastic resins, such as resin.

Returning to FIG. 1, the light diffusion sheet 16 is a sheet-like member having an action of diffusing light. The light diffusion sheet 16 is provided on the prism panel 15 on the LCD panel 11 side (Z2 side).
By providing such a light diffusing sheet 16, it is possible to obtain an effect of appropriately widening the viewing angle or reducing moire or the like caused by pixels (not shown) of the LCD panel 11 and the unit prism 151.
The light diffusing sheet 16 is appropriately selected from various general-purpose light-diffusing sheet-like members in accordance with the optical performance desired for the surface light source device 10 and the display device 1, the optical characteristics of the light guide plate 13, and the like. May be used.

  As such a light diffusing sheet 16, a resin sheet-shaped member containing a diffusing material, or a member in which a binder containing a diffusing material is coated on at least one surface of a resin sheet-like member serving as a base material. Alternatively, a microlens sheet or the like in which a microlens array is formed on one surface of a resin sheet-like member serving as a substrate can be used.

  In addition, a fine uneven shape is formed on the light output side (Z2 side) surface of the prism base layer 152 of the prism sheet 15 in order to prevent optical adhesion with the light diffusion sheet 16 and to provide a light diffusion function. May be. As such a concavo-convex shape, a mat layer formed by coating a binder containing a bead-like filler is suitable, but not limited thereto.

In addition, not only the light diffusion sheet 16 but also a polarized light having a function of transmitting light in a specific polarization state to the LCD panel 11 side (Z2 side) from the prism sheet 15 and reflecting light in other polarization states. A selective reflection sheet may be arranged. When such a polarization selective reflection sheet is used, the transmission axis of the polarization selective reflection sheet is parallel to the transmission axis of a polarizing plate (not shown) located on the light incident side (Z1 side) of the LCD panel 11. Such arrangement is preferable from the viewpoint of improving luminance and improving light utilization efficiency. As such a polarization selective reflection sheet, for example, DBEF series (manufactured by Sumitomo 3M Limited) can be used.
In addition to the light diffusion sheet 16, various optical sheets such as a lenticular lens sheet may be disposed.
Further, a polarization selective reflection sheet as described above, various optical sheets, and the like may be further disposed on the LCD panel 11 side of the light diffusion sheet 16.

Next, the relationship between the contact area of the light guide plate 13 and the contact area of the reflection sheet 14 will be described.
FIG. 7 is a diagram illustrating the contact areas of the light guide plate and the reflection sheet of the present embodiment. Fig.7 (a) is a figure explaining the state which has arrange | positioned the light-guide plate on the flat plate, FIG.7 (b) is a figure explaining the state which has arrange | positioned the reflective sheet on the flat plate.
The contact surface 134a provided on the top surface part 134 of the back unit optical shape 131 provided on the light guide plate 13 suppresses optical adhesion between the light guide plate 13 and the reflection sheet 14, and the light guide plate. In order to prevent the reflection sheet 14 from being damaged by the 13 back side unit optical shapes 131, it is desirable to form so as to satisfy the following expression (1).

(Formula 1) 35% ≦ S1 ≦ 45%

Here, S1 represents the total contact area (A1) of each contact surface 134a when the light guide plate 13 is disposed on the flat plate T with the back surface 13d facing down, as shown in FIG. 13 is a ratio (A1 / A2) to the area (A2) of the back surface 13d of 13.
Further, the total contact area (A1) of the contact surface 134a refers to the total sum of the contact areas (a1) of the contact surfaces of the back-side unit optical shapes 131 arranged in the light guide direction. Moreover, the contact area (a1) of each contact surface 134a means an area which contacts when the back surface 13d of the light guide plate 13 is disposed on the flat plate T, and not only the area of the contact surface 134a but also on the flat plate T. When the light guide plate 13 is disposed, the light guide plate 13 includes an area where the member of the light guide plate 13 is compressed and deformed by its own weight. In this embodiment, the area when 0.2 μm of compression deformation is performed in the thickness direction from the contact surface 134a is included.
Moreover, the area (A2) of the back surface 13d of the light guide plate 13 refers to an area obtained from the outer shape when viewed from the back side in the thickness direction (Z direction) of the light guide plate 13.

  By satisfy | filling said Formula (1), generation | occurrence | production of the damage | wound to the reflection sheet 14, and the optical contact | adherence of the light-guide plate 13 and the reflection sheet 14 can be suppressed more effectively. If S1 <35%, the total contact area of the contact surface 134a with respect to the area of the back surface 13d of the light guide plate 13 is narrowed, so that the width Wc of each contact surface 134a tends to be narrowed, and the light guide plate 13 is reflected on the reflection sheet. When laminated on 14, the reflective sheet 14 may be damaged. Further, when S1> 45% or more, the total contact area of the contact surface 134a with respect to the area of the back surface 13d of the light guide plate 13 is increased, so that the contact area between the light guide plate 13 and the reflection sheet 14 is increased, and the optical contact is increased. May occur.

  Further, the contact surface 134 a provided on the top surface part 134 of the back-side unit optical shape 131 provided on the light guide plate 13 and the mat layer 143 of the reflective sheet 14 have optical adhesion between the light guide plate 13 and the reflective sheet 14. In order to suppress the occurrence and to prevent the reflection sheet 14 from being damaged by the back-side unit optical shape 131 of the light guide plate 13, it is more desirable to satisfy the following expression (2).

(Formula 2) 35% ≦ S1 + S2 ≦ 50%

Here, as shown in FIG. 7 (b), S2 is the uneven shape of the mat layer 143 when the surface of the reflective sheet 14 on the mat layer 143 side (light guide plate 13 side) is disposed on the flat plate T. The ratio (B1 / B2) of the total contact area (B1) of the part and the area (B2) of the surface on the light guide plate 13 side of the reflection sheet 14 is shown.
Further, the total contact area (B1) of the concavo-convex convex portions of the mat layer 143 refers to the sum of the contact areas (b1) of the fine concavo-convex convex portions provided on the mat layer 143. Moreover, the contact area (b1) of each convex-concave part of an uneven | corrugated shape means the area which contacts when the surface at the side of the light-guide plate 13 of the reflection sheet 14 is arrange | positioned on the flat plate T, and the uneven | corrugated shape of the mat | matte layer 143 This includes not only the area of the top of the convex part, but also the area where the convex part of the mat layer 143 is compressed and deformed by its own weight when placed on the flat plate T. In the present embodiment, the mat layer 143 includes an area when the mat layer 143 is compressed and deformed by 0.2 μm in the thickness direction from the top of the convex portion.
Further, the area (B2) of the surface of the reflection sheet 14 on the light guide plate 13 side refers to an area obtained from the outer shape when viewed from the light guide plate 13 side in the thickness direction (Z direction) of the reflection sheet 14.

  Further, it is more desirable that the above S2 satisfies the following formula (3).

(Formula 3) 0% <S2 <5%

  By satisfy | filling said Formula (3), generation | occurrence | production of the optical contact of the light-guide plate 13 and the reflective sheet 14 can also be suppressed more effectively. If S1 ≧ 5%, the total contact area of the concavo-convex convex portion with respect to the area of the mat layer 143 of the reflective sheet 14 is increased, so that the adhesion area of the reflective sheet 14 and the light guide plate 13 is increased. This is not preferable because optical adhesion may occur.

Further, as described above, since the width Wc of the contact surface 134a is constant in the light guide direction, the light guide plate 13 of the present embodiment is guided with the back surface 13d down as shown in FIG. When the optical plate 13 is disposed on the flat plate T, the contact area between each contact surface 134a and the flat plate T is constant or substantially constant.
Thus, when the light guide plate 13 and the reflection sheet 14 are laminated by the contact area between each contact surface 134a and the flat plate T being constant or substantially constant, each contact surface 134a and the reflection sheet 14 are The close contact range can be evenly dispersed in the light guide direction, and the occurrence of optical contact can be suppressed.
Here, in order to more effectively suppress the optical contact, the light guide plate 13 has a contact area (a1) of each contact surface 134a within an effective range in which the image light reaches the observer side when arranged on the flat plate T. ) And the area (A2) of the back surface 13d of the light guide plate 13 is S3, and among S3 of each contact surface 134a, the minimum value is S3min, and the maximum value is S3max, It is desirable to satisfy the following formula (4).
Here, the effective range in which the image light reaches the observer side refers to a region inside the outer shape when the light guide plate is viewed from the thickness direction (Z direction), and the outer shape of the region is the outer shape of the light guide plate. It is formed within a range of 90% or more of the dimension.

Formula (4) S3min / S3max> 95%

  By satisfying the above formula (4), the variation in the contact area of each contact surface 134a is reduced, so that the range in which each contact surface 134a and the reflection sheet 14 are in close contact can be evenly distributed in the light guide direction. In addition, optical adhesion between the light guide plate 13 and the reflection sheet 14 can be more effectively suppressed.

(Evaluation on optical adhesion and damage)
Next, a plurality of light guide plates with different S1 and reflection sheets with different S2 are prepared and combined (Measurement Example 1 to Measurement Example 5), the presence or absence of optical adhesion between the light guide plate and the reflection sheet, The presence or absence of damage was evaluated.
In addition, the test body of each measurement example is obtained by laminating a light guide plate on the mat layer of the reflection sheet so that the back side unit optical shapes face each other.

FIG. 8 is a diagram for explaining an evaluation method for the presence or absence of optical adhesion between the light guide plate and the reflection sheet in the measurement example. Fig.8 (a) shows the side view of the test body for evaluation, and FIG.8 (b) is a bb arrow line view of Fig.8 (a). In FIG. 8, in order to facilitate understanding, the shapes of the light guide plate 13 and the prism sheet 15 are simplified.
As shown in FIG. 8, the test specimen T for evaluating the optical adhesion is similar to the case where it is actually assembled as the transmissive display device 1, on the evaluation table D, the reflection sheet, the light guide plate, and the prism sheet 15 of the measurement example. The light diffusion sheet 16 is laminated in order, and the light source unit 12 is disposed on the light incident surface side of the light guide plate.
In the evaluation test, a weight Q is placed on the surface of the light diffusion sheet 16 of the test body T and the geometric center O of the test body T on the XY plane, and a load is applied to the test body.

In the state shown in FIG. 8, with the light source unit 12 turned off, the test specimen T is left for 2 hours in an environment at room temperature of 50 degrees and humidity of 25%, and then at room temperature and normal humidity (room temperature of 25 degrees and humidity of 50%). The light source unit 12 was turned on for 30 minutes. Thereafter, the weight Q is removed from the specimen T, and the observer observes the region where the weight Q is disposed through the light diffusion sheet 16 and the prism sheet 15 from the Z2 side at an angle of 0 ° with respect to the Z axis. When the reflective sheet and the light guide plate in the example are in optical close contact with each other, it is visually determined whether or not wet out (wet out), which is an irregular, bright spot-like optical unevenness, is observed.
In the evaluation of the presence or absence of the occurrence of wet-out, it was determined that optical adhesion did not occur for those in which occurrence was not observed, and was evaluated as “◯”. Also, the area where the wet-out is observed, its brightness, and clarity are not remarkable, and those that are judged to be usable as a product are also judged as having no optical contact, and “△” It was evaluated. On the other hand, areas where wet-out was observed, their brightness and clarity were remarkable, and those that could not be used as products were determined to have optical contact and were evaluated as “x”.

In addition, the evaluation of the scratches on the light guide plate and the reflection sheet is made by removing the laminated light guide plate from the reflection sheet and visually checking each contact surface, and confirming whether the scratches are confirmed on the light guide plate or the reflection sheet. Even if the damage was not noticeable to the extent that it could be used as a product, the evaluation was rated as “Good”.
Table 1 below summarizes the results of the optical adhesion evaluation and the scratch evaluation of each measurement example. In Table 1, when the evaluation of the optical adhesion described above is Δ or ○, and the evaluation of scratch is ○, the overall evaluation is ○, and when either is included, the overall evaluation is × It was.

In addition, S1 and S2 of each measurement example according to evaluation of optical adhesion are as follows.
The test body of Measurement Example 1 has S1 = 35% and S2 = 3%.
In the test sample of Measurement Example 2, S1 = 40% and S2 = 7%.
The test body of Measurement Example 3 has S1 = 40% and S2 = 3%.
In the test sample of Measurement Example 4, S1 = 50% and S2 = 3%.
The test body of Measurement Example 5 has S1 = 10% and S2 = 3%.

Moreover, the light guide plate of each measurement example has substantially the same form except that the value of S1 described above is different, and the dimensions of each part are as follows. Moreover, the light guide plate of each measurement example satisfies the above-described formula (4).
External dimensions: 300 mm × 175 mm, made of acrylic resin, total thickness of about 550 μm.
Back unit optical shape 131: arrangement pitch P1 = 100 μm, angle α = 2 °, angle β = 15 °.
Output side unit optical shape 135: arrangement pitch P2 = 50 μm, angle γ = 120 °.
S3min / S3max = 100%

The reflective sheet 14 has substantially the same configuration except that the value of S2 described above is different, and the dimensions and the like of each part are as follows.
Reflective layer 142: formed of a metal thin film on which silver is deposited. Note that the reflection layer of each measurement example has a total reflectance of 90% or more and a diffuse reflectance of 0.5% to 8%.
Mat layer 143: formed of a urethane-shaped ultraviolet curable resin containing urethane-based beads.
External dimensions: 300 mm × 175 mm, thickness 150 μm.
Prism sheet 15: 175 mm (X direction) × 300 mm (Y direction), thickness of about 180 μm, inverted prism sheet with apex angle ε = 66 ° formed from a PET film with an acrylic ultraviolet curable resin having a refractive index of 1.51 .
Light diffusion sheet 16: 175 mm (X direction) × 300 mm (Y direction), thickness of about 160 μm, manufactured by Sumitomo 3M Limited.
Weight Q: A prismatic member made of stainless steel. 15 mm (X direction) × 15 mm (Y direction), height 50 mm, mass 500 g.

As shown in Table 1 above, the test sample of Measurement Example 4 had a scratch evaluation of ◯, but the optical adhesion evaluation was x, and the overall evaluation was x. This is because the value of S2 satisfies the above formula (3), but the value of S1 exceeds the upper limit (45%) of the above formula (1) and does not satisfy the formula (1). Since the total contact area of 134a was too large, it is considered that the effect of suppressing optical adhesion was lowered. It was also confirmed that the test specimen of Measurement Example 4 did not satisfy the above formula (2).
In the test sample of Measurement Example 5, the evaluation of optical adhesion was “good”, but the evaluation of scratch was “poor”, and the overall evaluation was “poor”. This is considered to be caused by the fact that the width Wc of the contact surface of the rear unit optical shape of the light guide plate is narrowed because the value of S1 is below the lower limit value of the above formula (1). It was also confirmed that the test sample of Measurement Example 5 did not satisfy the above formula (2).

On the other hand, in the test body of Measurement Example 2, the evaluation of scratches was “good”, the evaluation of optical adhesion was “good”, and the overall evaluation was “good”. Although this test body does not satisfy the above formula (3), but satisfies the above formulas (1) and (2), it is considered that the evaluation of optical adhesion is Δ instead of x.
In the test samples of Measurement Examples 1 and 3, both the evaluation of scratches and the evaluation of optical adhesion were “good”, and the overall evaluation was also “good”. It was confirmed that the light guide plate and the reflection sheet of this test body satisfy not only the above formulas (1) and (2) but also the formula (3), so that the evaluation of optical adhesion becomes “good”.
From the above, by satisfying the above formulas (1) and (2), it is confirmed that the optical adhesion between the light guide plate and the reflection sheet can be significantly suppressed, and damage to the reflection sheet by the light guide plate can be suppressed. In addition, it was confirmed that the above-described effect can be achieved more effectively by further satisfying the above formula (3).

According to the present embodiment, the surface light source device 10 suppresses the occurrence of optical adhesion between the light guide plate and the reflection sheet, since the light guide plate 13 and the reflection sheet 14 satisfy the above formula (1). When the light guide plate is laminated on the reflection sheet, the reflection sheet can be prevented from being damaged.
In addition, since the surface light source device 10 satisfies the above formula (2), more specifically, the above-described effect of suppressing the occurrence of optical adhesion and the effect of suppressing damage can be achieved.
Furthermore, since each contact surface 134a of the back unit optical shape 131 satisfies the above formula (4), the surface light source device 10 disperses the range in which the reflection sheet 14 and the light guide plate 13 are in close contact with each other in the light guide direction. This can also suppress the occurrence of optical adhesion.
Moreover, since the reflective sheet 14 satisfy | fills said Formula (3), the surface light source device 10 can show | play the effect of suppressing generation | occurrence | production of optical contact more effectively.

(Deformation)
The present invention is not limited to the embodiment described above, and various modifications and changes are possible, and these are also within the scope of the present invention.
(1) In the embodiment, the top surface part 134 of the back side unit optical shape 131 has been illustrated as being configured from a plurality of surfaces (134a to 134d), but is not limited thereto. For example, as long as the above formula (1) or the like is satisfied, the top surface portion 134 may be configured by only one surface, that is, the contact surface 134a.
(2) In the embodiment, the example in which the reflective layer 142 is configured by a metal thin film having a high reflectance such as silver by vapor deposition has been described, but the embodiment is not limited thereto. For example, the reflective layer 142 may have a multilayered structure as long as the reflection characteristics of the reflection sheet 14 (total reflectance is 90% or more and diffuse reflectance is 0.5% or more and 8% or less) are satisfied. You may make it comprise a deflection | deviation film etc.

(3) The rear-side unit optical shapes 131 are arranged in the light guide direction, and if the cross-sectional shape in the direction orthogonal to the light guide direction and the plate surface of the light guide plate 13 is the above-described form, the light guide direction in the plate surface. It may be formed in a discontinuous island shape in a direction orthogonal to the direction (Y direction).
For example, the back side unit optical shape 131 is a substantially square trapezoidal shape that is convex on the back side, and may be arranged in a light guide direction and a direction (X direction and Y direction) perpendicular thereto.

(4) In the surface light source device 10, the facing surface 13b may be the second light incident surface 13b, and the light source unit 12 may be further disposed at a position facing this surface. In this case, for example, the rear unit optical shape 131 is the shape of the above-described embodiment from the light incident surface 13a to the center point of the light guide plate 13 in the arrangement direction, and from the center point to the opposing surface 13b. In the above embodiment, the X direction is reversed, and the ratio Wb / W1 gradually decreases from the center point to the second light incident surface 13b toward the X2 side (the ratio Wa / W1 gradually increases). It is preferable to do. At this time, the back surface of the light guide plate 13 has a symmetrical shape about a straight line passing through the center of the light guide direction and parallel to the Z direction in a cross section parallel to the XZ plane.

(5) In the present embodiment, the light emitting unit optical shape 135 has an example in which the arrangement pitch P2 is equal to the width W2 in the arrangement direction, but the present invention is not limited to this, and the arrangement pitch P2 is the width W2 in the arrangement direction. It is also possible to use a shape in which a flat portion, a concave portion, or the like is formed between the light exit side unit optical shapes 135.
The same applies to the back unit optical shape 131.

(6) The total thickness of the light guide plate 13 may be a shape in which the light incident surface side (X1 side) is thick and gradually becomes thinner toward the opposite surface side (X2 side).

(7) The surface light source device 10 may be arranged by combining a prism sheet 15 and the LCD panel 11 with an optical sheet having a diffusing action, other optical sheets formed with various lens shapes or prism shapes, and the like. Good. Further, the surface light source device 10 may use an optical sheet having a deflecting action other than the prism sheet 15.
Various optical sheets used in combination with the light guide plate 13 as the surface light source device 10 can be appropriately selected and used in accordance with the use environment and desired optical performance.

  In addition, although this embodiment and modification can also be used in combination as appropriate, detailed description is abbreviate | omitted. Further, the present invention is not limited by the above-described embodiments and the like.

DESCRIPTION OF SYMBOLS 1 Transmission type display apparatus 10 Surface light source device 11 LCD panel 12 Light source part 121 Point light source 13 Light guide plate 131 Back side unit optical shape 132 1st slope part 133 2nd slope part 134 Top surface part 134a-134c surface 134d Contact surface 135 Light emitting side Unit optical shape 14 Reflective sheet 141 Base material layer 142 Reflective layer 143 Matte layer 15 Prism sheet 16 Light diffusion sheet

Claims (9)

A light incident surface on which light is incident; a light exit surface that intersects the light incident surface and emits light; and a back surface that faces the light exit surface, and guides light incident from the light incident surface in a light guide direction. A light guide plate that emits from the light exit surface while illuminating;
A reflective member that is disposed on the back side of the light guide plate and reflects light emitted from the back side of the light guide plate to the light guide plate side;
The reflecting member has a fine uneven shape on the surface on the light guide plate side, has a total reflectance of 90% or more, and a diffuse reflectance of 0.5% to 8%. Has been
The light guide plate has a plurality of back side unit optical shapes arranged in the light guide direction on the back surface,
The back-side unit optical shape is convex on the back side, is parallel to the arrangement direction, and is parallel to the thickness direction of the light guide plate, and the cross-sectional shape is a substantially square shape. A first slope portion located between the first slope portion and the second slope portion, the second slope portion facing the opposite side and totally reflecting at least part of incident light; Having a top surface located at
The top surface portion of at least one of the back side unit optical shapes has a plurality of surfaces having different heights in the thickness direction, and a surface located closest to the reflecting member among the plurality of surfaces is the reflecting member. A contact part that contacts,
When the ratio between the total contact area of each contact portion and the area of the back surface of the light guide plate when the back surface of the light guide plate is disposed on a flat plate is S1,
Satisfy 35% ≦ S1 ≦ 45%,
A surface light source device. The surface light source device according to claim 1,
The contact portion is located closest to the second slope portion in the top surface portion;
A surface light source device. In the surface light source device according to claim 1 or 2,
The plurality of surfaces provided with the top surface portion decrease as the distance from the light incident surface decreases.
A surface light source device. In the surface light source device according to any one of claims 1 to 3,
The rear unit optical shape has a constant arrangement pitch in the arrangement direction,
A surface light source device. In the surface light source device according to any one of claims 1 to 4 ,
The ratio of the total contact area of each convex part of the concavo-convex shape of the reflective member to the area of the surface of the reflective member on the light guide plate side when the surface of the reflective member on the light guide plate side is disposed on a flat plate Is S2,
Satisfy 35% ≦ S1 + S2 ≦ 50%,
A surface light source device. The surface light source device according to claim 5 ,
Satisfy 0% <S2 <5%,
A surface light source device. The surface light source device according to any one of claims 1 to 6 ,
When the light guide plate is disposed on a flat plate, the ratio of the contact area of each contact portion within the effective range within which the light reaches the observer side and the area of the back surface of the light guide plate is S3, Of S3 of the contact portion, when the minimum value is S3min and the maximum value is S3max,
Satisfying S3min / S3max> 95%,
A surface light source device. In the surface light source device according to any one of claims 1 to 7 ,
The back side unit optical shape is a columnar shape, and a direction perpendicular to the light guide direction is a longitudinal direction and is arranged in the light guide direction,
A surface light source device. A surface light source device according to any one of claims 1 to 8 ,
A transmissive display unit illuminated from the back side by the surface light source device;
A transmissive display device.

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