JP2010044270A - Light diffusion plate, optical sheet, back light unit and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light diffusion plate which can reduce a lamp image and further can improve front luminance, and to provide an optical sheet, a back light unit and a display device using the same. <P>SOLUTION: The light diffusion plate 10 obtained by dispersedly mixing light scattering particles into a resin 12 includes at least two layers of the first resin layer 20 comprising first light scattering particles 13 with the average particle diameter of 0.2 to 0.6 μm and a refractive index of 2.4 to 2.72, the second resin layer 21 comprising the second spherical light scattering particles 14 with the average particle diameter of 1 to 12 μm and the third spherical light scattering particles 15 with the average particle diameter of 30 to 60 μm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light diffusing plate mounted on a liquid crystal backlight device or a lighting device having a light source such as a fluorescent tube, LED, EL, and the like, and an optical sheet, a backlight unit, and a display device using the light diffusing plate.

In recent years, display devices using TFT-type liquid crystal panels and STN-type liquid crystal panels have been commercialized mainly in color notebook PCs (personal computers) in the OA field, for example.
Such a display device employs a so-called backlight system in which a light source is arranged on the back side of the liquid crystal panel and the liquid crystal panel is illuminated with light from the light source.
The backlight units used in this type of backlight system can be broadly divided into multiple light sources such as cold cathode fluorescent lamps (CCFL) within a flat light guide plate made of acrylic resin with excellent light transmission. There are a “light guide plate light guide method” (so-called edge light method) and a “direct type method” that does not use a light guide plate.

As a display device on which a light guide plate light guide type backlight unit is mounted, for example, the display device shown in FIG. 8 is generally known.
This display device includes a liquid crystal panel 172 sandwiched between polarizing plates 171 and 173, and a light guide plate 179 made of a transparent base material such as a substantially rectangular plate-like PMMA (polymethyl methacrylate) or acrylic is installed on the back side thereof. A diffusion film (diffusion layer) 178 is provided between the upper surface (light emitting side) of the light guide plate 179 and the polarizing plate 173 on the rear side.

  On the back side of the light guide plate 179, a scattering reflection pattern portion (not shown) for scattering and reflecting the light introduced into the light guide plate 179 so as to be uniform in the direction of the liquid crystal panel 172 is printed. A reflective film (reflective layer) 177 is provided on the further back side of the scattering reflection pattern portion.

  Further, a light source lamp 176 is attached to one side end of the light guide plate 179, and covers the back side of the light source lamp 176 in order to make the light of the light source lamp 176 enter the light guide plate 179 efficiently. A high-reflectance lamp reflector 181 is provided. The scattering reflection pattern portion is formed by printing a mixture of white titanium dioxide (TiO2) powder in a transparent adhesive or the like in a predetermined pattern, for example, a dot pattern, and drying and forming the light guide plate 179. A directivity is imparted to the light incident on the inside of the light to guide it to the light exit surface side, thereby increasing the brightness.

  Recently, in order to improve the light utilization efficiency and increase the luminance, as shown in FIG. 9, a prism film (prism layer) having a condensing function between the diffusion film 178 and the liquid crystal panel 172 is used. 174, 175 have been proposed. The prism films 174 and 175 are for emitting the light emitted from the light exit surface of the light guide plate 179 and diffused by the diffusion film 178 to the effective display area of the liquid crystal panel 172 with high efficiency.

  On the other hand, the direct type backlight unit is used in a display device such as a large liquid crystal TV in which it is difficult to use a light guide plate. As an example of using this backlight unit, for example, a display as shown in FIG. Devices are generally known.

  In this display device, a liquid crystal panel 172 sandwiched between polarizing plates 171 and 173 is provided, and a light source 151 made of a fluorescent tube or the like is provided on the back side thereof. And the light radiate | emitted from the light source 151 is diffused by the diffusion film 182, and is condensed on the effective display area of the liquid crystal panel 172 with high efficiency. In order to efficiently use the light from the light source 151 as illumination light, a reflector 152 is disposed on the back surface of the light source 51.

  In a display device equipped with such a direct type backlight unit, light scattering particles are blended to prevent the occurrence of uneven brightness by preventing the light source image (lamp image) from being seen on the display screen. The formed resin plate is provided as a light diffusion plate for diffusing light emitted from the light source.

This light diffusing plate is required to have a high transmission and high diffusion function of preventing the lamp image from being visually recognized by diffusing the light while transmitting the light. Trial and error is performed by changing the type, particle size, and blending amount.
In this regard, in the case of a light diffusing plate using spherical particles as light scattering particles to be blended with the resin, it has been confirmed that the light diffusing characteristics expand the viewing angle. Therefore, since the lamp image is visually recognized in a state where only the bright part is spread, stripe-like luminance unevenness occurs between the wide bright part and the narrow dark part. Therefore, in order to suppress this luminance unevenness, it is necessary to reduce the light transmittance so that the difference between light and dark becomes difficult to be visually recognized. As a result, there is a problem that the front luminance becomes insufficient.

  Further, in the liquid crystal display device shown in FIG. 10, since the control of the viewing angle is left only to the diffusibility of the diffusion film 182, the control is difficult, and the central portion in the front direction of the liquid crystal display screen is bright, The characteristic that becomes darker toward the periphery cannot be avoided. For this reason, when the liquid crystal display screen is viewed from the side, the luminance is greatly reduced, and the light utilization efficiency is reduced.

Therefore, as one method for solving such a problem, as shown in FIG. 11, a brightness enhancement film (BEF) 185, which is a registered trademark of 3M USA, is placed above the illumination light source 190 for the backlight. There has been proposed a method of improving the front luminance by arranging a light diffusion film (not shown) on the light emitting surface side above the BEF 185 (see, for example, Patent Documents 1 to 5).
As shown in FIGS. 11 and 12, the BEF 185 is a film in which unit prisms 187 having a triangular cross section are arranged at a constant pitch in one direction on the upper surface of the transparent substrate 186.
The unit prism 187 has a size (pitch) larger than the wavelength of light. BEF collects light from “off-axis” and redirects this light “on-axis” to the viewer, or “recycle”. To do.

When using the display device (when observing), the BEF increases the on-axis brightness by reducing the off-axis brightness. Here, “on-axis” is a direction that coincides with the visual direction of the viewer, and is generally on the normal direction side with respect to the display screen.
When this BEF is used alone, the repetitive array structure of unit prisms is arranged in only one direction, so that only the direction change or recycling in the parallel direction is possible. Therefore, in order to control the luminance of the display light in the horizontal and vertical directions, generally, two sheets are combined and used so that the parallel directions of the unit prism groups are substantially orthogonal to each other.
Japanese Patent No. 3374316 Japanese Patent No. 3684587 Japanese Patent Publication No. 1-378001 JP-A-6-102506 Japanese National Patent Publication No. 10-506500

  By the way, when the BEF is used together with the light diffusing plate as described above, it is possible to increase the intensity of light in the viewer's visual direction and improve the front luminance, but the light component due to the refraction action is in the viewer's visual direction. There is a problem that the side lobe light is unnecessarily emitted in the lateral direction without traveling.

  For this reason, as shown in the luminance distribution diagram of FIG. 13, the luminance distribution emitted from the BEF has the highest front luminance at an angle of 0 ° with respect to the visual direction of the viewer, and is around ± 90 ° from the front. There was a problem that a small light intensity peak was generated and the light could not be collected efficiently.

  In addition, when only the luminance in the front direction is excessively improved, the peak width of the curve of the luminance distribution becomes extremely narrow, and the viewing area is extremely limited. Therefore, in order to increase the peak width appropriately, it is necessary to newly provide a light diffusion film which is a separate member from BEF (prism sheet), which increases the number of parts. Therefore, not only does it lead to an increase in material cost, but the operation for assembling the display becomes complicated, which is not preferable.

  The present invention has been made in view of such problems, and provides a light diffusing plate capable of reducing a lamp image and improving front luminance, an optical sheet using the same, a backlight unit, and a display device. The purpose is to do.

In order to solve the above problems, the present invention proposes the following means.
That is, the light diffusing plate according to the present invention is a light diffusing plate in which light scattering particles are dispersed and mixed in a resin, and has an average particle size of 0.2 to 0.6 μm and a refractive index of 2.4 to 2.72. A first resin layer containing the first light scattering particles, a second light scattering particle having an average particle diameter of 1 to 12 μm, and a third light scattering having an average particle diameter of 30 to 60 μm. It consists of at least two layers with the 2nd resin layer containing particle | grains, It is characterized by the above-mentioned.

  In the light diffusing plate having such characteristics, the first resin layer in which the first light scattering particles are dispersed and mixed in the resin has light transmittance and light reflectivity, while the second light scattering particles and the third light are included in the resin. The second resin layer in which the scattering particles are dispersed and mixed has light transmittance and light diffusibility. Therefore, by laminating the first resin layer and the second resin layer having such characteristics, it is possible to achieve effective use of light by light reflectivity while obtaining a good balance between light transmittance and light diffusibility, The front luminance can be improved while reducing the lamp image.

  The light diffusing plate according to the present invention is a light diffusing plate in which light scattering particles are dispersed and mixed in a resin. The light diffusing plate has an average particle size of 0.2 to 0.6 μm and a refractive index of 2.4 to 2.72. A first resin layer containing the first light scattering particles, a second resin layer containing second light scattering particles having a true spherical shape with an average particle diameter of 1 to 12 μm, and a true resin with an average particle diameter of 30 to 60 μm. It may consist of at least three layers with a third resin layer containing third light scattering particles having a spherical shape.

  In the light diffusing plate having such characteristics, the first resin layer in which the first light scattering particles are dispersed and mixed in the resin has light transmittance and light reflectivity, and the second light scattering particles are dispersed and mixed in the resin. The second resin layer has high light diffusibility, and the third resin layer in which the third light scattering particles are dispersed and mixed in the resin has light diffusibility and light transmittance. Therefore, by stacking the first resin layer, the second resin layer, and the third resin layer having such characteristics, it is possible to effectively use light by light reflectivity while obtaining a good balance between light transmittance and light diffusibility. It is possible to improve the front luminance while reducing the lamp image.

  In the light diffusing plate comprising at least two layers according to the present invention, the total mixing amount of the second light scattering particles and the third light scattering particles in the second resin layer is 0.3 to 35% by weight. Preferably there is.

  In the light diffusing plate comprising at least two layers or three layers according to the present invention, the amount of the first light scattering particles mixed in the first resin layer is preferably 1 to 10% by weight.

  Furthermore, in the light diffusing plate comprising at least two layers or three layers according to the present invention, a difference in refractive index between the second light scattering particles and the resin is 0.10 to 0.18, and the third light The refractive index difference between the scattering particles and the resin is preferably 0.05 to 0.10.

  An optical sheet according to the present invention is an optical sheet that emits incident light from the light source to the other surface side when the light source is disposed on one surface side, and includes any one of the light diffusing plate and the light diffusing plate. And a lens sheet that is disposed on the other surface side opposite to the light source and converts the optical characteristics of the light of the light source that has passed through the light diffusion plate and emits the light.

  According to the optical sheet having such a feature, a lens sheet having a condensing function in the front direction is laminated on the light diffusing plate. Therefore, in addition to the function of the light diffusing plate, the collecting by the lens sheet is performed. Optical function can be obtained. Therefore, it is possible to obtain a high front luminance while reducing the lamp image.

  The optical sheet according to the present invention is an optical sheet that emits incident light from the light source to the other surface side when the light source is disposed on the one surface side, the light diffusion plate according to any one of the above, and the light diffusion A light diffusing film that is disposed on the other surface side opposite to the light source of the plate and converts the optical characteristics of the light of the light source that has passed through the light diffusing plate and emits the light may be provided.

  Also in the optical sheet having such a feature, in addition to the function of the light diffusing plate, it is possible to obtain a light collecting function by the light diffusing film. Therefore, it is possible to obtain a high front luminance while reducing the lamp image.

  A backlight unit according to the present invention includes the optical sheet and a light source disposed on one surface side of the optical sheet.

  According to the backlight unit having such a feature, since the light diffusing plate and the optical sheet are used, the optical characteristics relating to the light diffusing property and the light transmitting property are optimized and the light is effectively used. Thus, it is possible to emit light with a reduced lamp image and improved brightness in the front direction.

  The display device according to the present invention includes the backlight unit, and an image display unit that is disposed on an emission surface side of the backlight unit and displays an image using light from the backlight unit as display light. Features.

  According to the display device having such a feature, since the backlight unit is mounted, it is possible to provide an image with good display quality in which the lamp image is reduced and the front luminance is improved. .

  According to the light diffusing plate, the optical sheet, the backlight unit, and the display device according to the present invention, it is possible to reduce the lamp image and improve the front luminance.

Hereinafter, a light diffusion plate, an optical sheet, a backlight unit, and a display device according to a first embodiment of the present invention will be described in detail with reference to the accompanying drawings. Here, the light diffusing plate according to the embodiment of the present invention will be described together with an optical sheet, a backlight unit, and a display device using the same.
FIG. 1 is a schematic cross-sectional view showing a schematic configuration of the display device according to the first embodiment.

As shown in FIG. 1, the display device 70 according to the first embodiment is configured by overlapping a liquid crystal panel (image display unit) 100 on the light emission side of the backlight unit 35 that emits light upward. The liquid crystal display device displays an image by emitting display light whose display is controlled by an image signal from the liquid crystal panel 100 upward.
Hereinafter, based on such an arrangement, the upper direction in FIG. 1 may be simply referred to as a display screen side, and the lower direction may be simply referred to as a back side.

  The display device 70 is a liquid crystal display device including the liquid crystal panel 100, but any type of display device that displays an image with light, such as a projection screen device, a plasma display, or an EL display, may be used.

The liquid crystal panel 100 includes, for example, a liquid crystal layer (display element or panel) 9 that controls a light transmission state according to an image signal for each of a plurality of pixel regions formed in a rectangular lattice shape. Glass substrates 81 and 82 are laminated on the emission surface 9b.
A polarizing plate 62 that controls the polarization direction of incident light is disposed on the light incident side of the liquid crystal panel 100, and a polarizing plate that controls the polarization direction of emitted light is disposed on the light output side of the liquid crystal panel 100. 61 is provided.

The backlight unit 35 is a light emitting device having a light emitting surface having substantially the same area as the display screen of the liquid crystal panel 100. The backlight unit 35 emits a direct light source 11 and light from the light source 11 in the light emission direction and emission. An optical sheet 25 that emits light while controlling at least one of a range and a luminance distribution.
The optical sheet 25 includes a lens sheet 17a and a light diffusion plate 10 stacked on the light incident surface side of the lens sheet 17a.

As the light source 11, for example, it is possible to use a direct type system configured by arranging lamps made of cylinder-shaped linear light sources extending in the depth direction of the drawing at a constant pitch. The light source 11 is not limited to this, and may be a so-called edge light system.
As the linear light source, a cathode ray tube (CCFL), an LED, an EL, a semiconductor laser, or the like can be used. Furthermore, light from an array of red, green, and blue LEDs is mixed with a light guide plate or a diffusing plate and emitted as white light, or a yellow fluorescent light emitter is applied to a blue LED and emitted as pseudo white light. It is also possible to use a light source such as a light source in which a light emitting material of each color is applied to a single color LED.

Such light emitted from the light source 11 for the backlight has a characteristic that the portion near the lamp is bright and the space between the lamps is dark. Therefore, there arises a problem that the shape (lamp image) of each lamp is visually recognized by an observer in the front direction (observer side) f.
However, since the backlight unit 35 has an optical sheet 25 as will be described later and is configured to diffuse light from the light source 11, either the direct type or the edge light method is used as the backlight unit 35. In such a case, the visibility problem due to the lamp image can be suppressed.

The lens sheet 17a includes a translucent base material 18 that is formed in a film shape and has light transmissivity, and a plurality of unit lenses 16 that are integrally provided on an emission surface 18b of the translucent base material. .
Each unit lens 16 extends in the depth direction of the paper surface, and has a flat surface facing the emission surface 18a of the translucent substrate 18 and a convex curved surface formed so as to protrude from the emission surface 18a. A plurality of cylindrical shapes are arranged along the emission surface 18a. As described above, the unit lens 16 has a cylindrical shape, so that a high light collecting effect can be exhibited. However, the shape is not limited to the shape, and any other shape may be used as long as the light direction is controlled and condensed. It may be a shape.

  The unit lens 16 may be molded on the translucent substrate 18 using UV or radiation curable resin. For example, PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), COP (Cycloolefin polymer), an acrylonitrile styrene copolymer, or the like may be integrally formed with the translucent substrate 18 by a known extrusion molding method, injection molding method, or hot press molding method.

  The light diffusing plate 10 plays a role of diffusing light emitted from the light source 11 toward the display screen, and is configured to reduce a lamp image by suppressing luminance unevenness due to the light source 11. .

As shown in FIG. 1, the light diffusing plate 10 includes a first resin layer 20 in which a resin 12 in which the first light scattering particles 13 are dispersed and mixed is formed in a substantially plate shape, the second light scattering particles 14 and the first light scattering particles 14. It is configured by laminating the second resin 21 in which the three light scattering particles 15 are dispersed and mixed.
In the present embodiment, the first resin layer 20 is disposed on the back side, and the second resin layer 21 is disposed on the display screen side.
When the first resin layer 20 and the second resin layer 21 are formed in this way, the first resin layer 20 and then the second resin layer 21 are arranged in this order on the light source 11 side. Even when the two resin layers 21 and then the first resin layer 20 are arranged in this order, the same performance is exhibited.

  The resin 12 used for the light diffusing plate 10 may be a transparent resin, a colored resin, or an opaque resin. For example, a polycarbonate resin, an acrylic resin, a fluorine acrylic resin, a silicone acrylic resin, or an epoxy acrylate resin. Polystyrene resin, acrylonitrile styrene resin, cycloolefin polymer, methyl styrene resin, fluorene resin, PET, polypropylene and the like can be used.

  Here, the first resin layer 20 has high light transmittance and light reflectivity, and the property is given by the first light scattering particles 13 dispersed and mixed in the resin 12.

The first light scattering particles 13 have an average particle size set in a range of 0.2 to 0.6 μm. Within the above-mentioned range, there is no light loss because there is no light absorption in the visible light wavelength region, and yellowing can be suppressed in color, which is preferable.
The refractive index of the first light scattering particle 13 is set in the range of 2.4 to 2.72. If it is the said range, since the refractive index difference with resin 12 is large, light-scattering property can be expressed highly and high reflectivity can be obtained. When the average particle diameter of the first light scattering particles 13 is less than 0.2 μm or more than 0.6 μm, the reflection performance is deteriorated, so that the high light reflectivity of the first resin layer 20 cannot be exhibited. Absent.

  Furthermore, the mixing amount of the first light scattering particles 13 in the first resin layer 20 is set within a range of 1 to 10% by weight, thereby imparting appropriate light transmittance and light reflectivity.

  On the other hand, the second resin layer 21 has high light transmittance and light diffusibility, and this property is provided by the second light scattering particles 14 and the third light scattering particles 15 dispersed and mixed in the resin 12.

  As the second light scattering particles 14, spherical particles are used, and the average particle diameter is set in a range of 1 to 12 μm, and particularly preferably in a range of 2 to 6 μm. Further, the refractive index difference between the second light scattering particles 14 and the resin 12 is set in a range of 0.1 to 0.18. Thereby, sufficient light diffusibility can be obtained and the viewing angle distribution can be adjusted.

  As the third light scattering particles 15, spherical particles are used, and the average particle diameter is set in a range of 30 to 60 μm, and particularly preferably set in a range of 31 to 55 μm. Further, the refractive index difference between the second light scattering particles 14 and the resin 12 is set in a range of 0.05 to 0.10. Thereby, both the light diffusibility and the light transmissive property can be obtained, and the viewing angle distribution can be adjusted. In addition, when the average particle diameter of the light-scattering particle | grains 15 is less than 30 micrometers or exceeds 60 micrometers, the high light transmittance of the 2nd resin layer 21 cannot be exhibited, and it is unpreferable.

  Furthermore, the total mixing amount of the second light scattering particles 14 and the third light scattering particles 15 in the second resin layer 21 is set within a range of 0.3 to 35% by weight. And light diffusibility are imparted.

  As materials for the first light scattering particle 13, the second light scattering particle 14, and the third light scattering particle 15, particles made of inorganic fine particles or organic fine particles are used. Examples of this include acrylic particles, styrene particles, styrene acrylic particles and crosslinked products thereof, melamine-formalin condensate particles, polyurethane particles, polyester particles, silicone particles, fluorine particles, copolymers thereof, Clay compound particles such as smectite, kaolinite, talc, inorganic oxide particles such as silica, titanium oxide, alumina, silica alumina, zirconia, zinc oxide, barium oxide, strontium oxide, calcium carbonate, barium carbonate, barium chloride, barium sulfate And inorganic fine particles such as barium nitrate, barium hydroxide, aluminum hydroxide, strontium carbonate, strontium chloride, strontium sulfate, strontium nitrate, strontium hydroxide, and glass particles.

The light diffusing plate 10 may have a plate shape, a plate shape, or a sheet shape, and the thickness thereof is preferably set within a range of 0.5 to 5 mm.
When the thickness of the light diffusing plate 10 is less than 0.5 mm, there is a problem that bending occurs because it is thin and has no stiffness. On the other hand, when the thickness of the light diffusing plate 10 exceeds 5 mm, there is a problem that the transmittance of light from the light source 11 is lowered.

Such a light diffusing plate 10 can be manufactured by integrally forming the first resin layer 20 and the second resin layer 21 by an extrusion method, a coextrusion method, or the like.
The extrusion method is a method in which a thermoplastic resin is heated and melted with an extruder, extruded from a T-die, and formed into a plate shape or a sheet shape. The coextrusion method is used when forming a laminated plate or a laminated sheet. Using a plurality of extruders, a multilayer extrusion is performed from a laminated die such as a feed block die or a manifold die. It is the method of shape | molding.

The surface of the light diffusing plate 10 is preferably matted. In this case, since the light from the light source 11 is scattered on the surface, it is possible to obtain effects such as reducing the lamp image and making it difficult to confirm the pins. Further, when the light emitting surface 10b of the light diffusing plate 10 is matted, a gap can be obtained between them without contacting the member (lens sheet 17a in the present embodiment) superimposed on the display screen. Therefore, it is possible to prevent optical influences such as Newton rings due to the close contact between the light diffusion plate 10 and the lens sheet 17a.
Instead of mat processing, processing for providing discontinuous minute protrusions may be performed.

Moreover, the light diffusing plate 10 may be one in which an ultraviolet absorber is added to at least one layer of the first resin layer 20 disposed on the light source 11 side.
Thereby, deterioration of the light diffusing plate 10 itself due to ultraviolet rays irradiated from the light source 11 can be suppressed, and the life can be extended. Furthermore, it is possible to suppress deterioration of the lens sheet 17a and the diffusing films 61 and 62 arranged facing the light emitting surface 10b of the light diffusing plate 10 due to ultraviolet rays.
Examples of the ultraviolet absorber include benzotriazole compounds such as 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, benzophenone compounds such as 2-hydroxy-4-methoxybenzophenone, 4-t- Salicylic acid ester compounds such as butylphenyl salicylate; Oxalic acid anilide compounds such as 2-ethoxy-2'-ethyl oxalic acid bisanilide; Cyanoacrylates such as ethyl-2-cyano-3,3-diphenylacrylate A system or the like can be used.

  The optical sheet 25 formed by laminating the light diffusion plate 10 and the lens sheet 17a may be bonded by a fixing element such as an adhesive or a spacer. As an example of this fixing element, an adhesive sheet obtained by, for example, applying an acrylic adhesive to a film can be mentioned.

Further, a gap (air layer) 200 is formed between the lens sheet 17 a and the light diffusion plate 10. In this case, in addition to the light condensing effect in the unit lens 16, the diffusion effect by the gap 200 can be obtained, so that the light passing through the optical sheet 25 is emitted with an optical gain of 1 or more.
Here, the optical gain is one of the indexes indicating the diffusibility of the diffusing member, and is expressed as a ratio with respect to the luminance of the diffuser that completely diffuses as 1. When the diffusivity of the diffusing member is biased depending on the direction to be measured, the optical gain for each direction is obtained, and the diffusion characteristics of the diffusing member can be shown by counting them. Note that complete diffusion refers to an ideal diffusing member that has zero light absorption by the diffusing member and has a certain intensity in any direction. That is, an optical gain of 1 or more indicates that there is an effect of collecting light in the measurement direction, and that the larger the value, the stronger the light collection effect.

Next, the operation of the display device 70 having the above configuration will be described.
The light emitted from the light source 11 is incident on the incident surface 10a of the light diffusing plate 10 and is scattered by the light diffusing plate 10 and proceeds as diffused light. The light having a divergence angle reaches the emission surface 10b of the light diffusion plate 10.

  The light that has reached the exit surface 10b of the light diffusing plate 10 is refracted according to Snell's law according to the refractive index of the gap 200 between the light diffusing plate 10 and the lens sheet 17a, and enters the lens sheet 17a. To do. The light incident on the lens sheet 17a is refracted by the incident surface 18a, then refracted by each unit lens 16 and emitted to the display screen side. Then, after being appropriately polarized by passing through the polarizing film 62, light is transmitted as display light from a predetermined pixel region via the polarizing plate 82, the liquid crystal layer 9, and the polarizing plate 81 of the liquid crystal panel 100, and By passing through the polarizing film 61, an image having a viewing angle is displayed.

Here, the first resin layer 20 formed by dispersing and mixing the first light scattering particles 13 in the resin 12 has high light transmittance and light reflectivity as described above.
The light transmission will be described in detail. The luminance distribution of the light passing through the first resin layer 20 protrudes and is high only in the front direction f as shown in FIG. 2, and falls sharply when it deviates from the front direction f. View angle characteristics such as maintaining the spread over a wide angle. Therefore, the brightness in the front direction f can be obtained even when passing through the first resin layer, and further, a certain level of brightness is expressed over a wide range near the vertical direction with respect to the incident light. Therefore, there is an effect of making the dark place between the lamps of the light source 11 uniform brightness, and a lamp image reduction effect can be obtained.
Further, the light reflectivity will be described in detail. The light reflected by the first resin layer 20 is returned to the light source 11 side as reflected light, and further reflected by a reflector provided on the light source 11 side. It enters the light diffusing plate 10 again. By repeating this process, the light can be reused, and at the same time, an oblique lamp image reduction effect can be obtained.

  On the other hand, the second resin layer 21 formed by dispersing and mixing the second light scattering particles 14 and the third light scattering particles 15 in the resin 12 has high light transmittance and light diffusibility as described above. .

  The characteristics of the second light scattering particles 14 will be described in detail. For example, when only the second light scattering particles 14 are dispersed and mixed in the resin 12 to form a light diffusing member, the light diffusing member has high light diffusibility and passes therethrough. As shown in FIG. 3, the luminance distribution of light shows a viewing angle characteristic such that the spread of the viewing angle from the front direction f is maintained, the forward diffusibility is high, and the light falls sharply at a wide angle. Therefore, the bright place of the lamp on the light source 11 can be greatly widened to obtain high light diffusibility, so that the effect of reducing the lamp image can be obtained.

  Further, the characteristics of the third light scattering particle 15 will be described in detail. For example, when a light diffusing member is formed by dispersing and mixing only the third light scattering particle 15 in the resin 12, the light transmission property and the light diffusing property are combined. As shown in FIG. 4, the luminance distribution of the light passing therethrough has a viewing angle characteristic that gently falls toward a wide angle while maintaining a wide viewing angle from the front direction f. . Therefore, it is possible to maintain the central brightness while exhibiting an action similar to the light collecting effect while maintaining the transparency and diffusing the light.

  That is, the second resin layer 21 in which the second light scattering particles 14 and the third light scattering particles 15 having such characteristics are dispersed and mixed can exhibit both high light transmittance and light diffusibility. it can.

Therefore, the light diffusing plate 10 is configured by laminating the first transparent resin layer 20 having light transmittance and light reflectivity and the second transparent resin layer 21 having light transmittance and light diffusibility. Therefore, it is possible to effectively use light by light reflectivity while obtaining a good balance between light transmittance and light diffusivity, and it is possible to improve the front luminance while reducing the lamp image.
Furthermore, since a high diffusion function can be obtained only with the light diffusion plate 10 as described above, it is not necessary to provide a separate diffusion film or the like. Therefore, it is possible to reduce the number of parts and reduce the manufacturing cost.

  In addition, since the optical sheet 25 of the present embodiment is configured by laminating the lens sheet 17a having a light condensing function in the front direction (observer side) f on the light diffusion plate 10, the light diffusion plate 10 described above. In addition to the above function, the light collecting function by the lens sheet 17a can be obtained. Therefore, according to the optical sheet 25, it is possible to obtain a very high front luminance while reducing the lamp image.

The optical sheet 25 can increase the strength of the optical sheet 10 itself even when the light diffusing plate 10 is formed thin, and the display device 70 has excellent image display quality. Therefore, it is preferable to use for a large display.
Further, the optical sheet 25 is used as a sheet for controlling the viewing angle of the display or a sheet for improving the contrast, in addition to the use for improving the luminance of the light from the light source 11 for the backlight. It is also possible to do.
Furthermore, for example, it can also be used for a sheet for improving the luminance of light projected on the projection screen or a sheet for performing light control for solar cells.
Moreover, since the optical sheet 25 can uniformly diffuse and collect light from the illumination source, it can be used for illumination covers, signboards, building materials, and the like.

Furthermore, according to the backlight unit 35 of the present embodiment, since the light diffusing plate 10 and the optical sheet 25 are used, the optical characteristics relating to the light diffusibility and the light transmittance are optimized, and the front surface Light having improved luminance in the direction (observer side) f can be incident on the liquid crystal panel 100. Therefore, the display device 70 equipped with the backlight unit 35 can display an image with high brightness and reduced lamp image.
Further, since the lamp image reduction effect and the brightness are high, the distance to the light source 11 can be reduced, and the number of lamps of the light source 11 can be reduced, so that the backlight unit 35 and the display device 70 can be saved. It becomes.
Since the optical sheet 25 is used, a thin backlight unit 35 can be obtained, and a large display device 70 can be easily configured.

Next, the display apparatus 80 of the 2nd Embodiment of this invention is demonstrated. FIG. 5 is a schematic cross-sectional view showing a schematic configuration of a display device according to the second embodiment.
In the display device 80 of the second embodiment, the display device 70 of the first embodiment includes the light diffusion plate 10 having a two-layer structure of the first resin layer 20 and the second resin layer 21. The third embodiment is different from the first embodiment in that a light diffusing plate 40 having a three-layer structure including one resin layer 20, a second resin layer 22, and a third resin layer 23 is provided.
Therefore, in FIG. 5, the same components as those in FIG.

As shown in FIG. 5, the light diffusion plate 40 includes a first resin layer 20 in which the resin 12 in which the first light scattering particles 13 are dispersed and mixed is formed in a substantially plate shape, and the second light scattering particles 14 are dispersed. The second resin layer 22 in which the mixed resin 12 is formed in a substantially plate shape and the third resin layer 23 in which the third light scattering particles 15 are dispersed and mixed are laminated.
In the present embodiment, the first resin layer 20, the second resin layer 21, and the third resin layer 23 are laminated in this order from the back side. Arranged on the display screen side.

  When the first resin layer 20, the second resin layer 21, and the third resin layer 22 are formed in this way, the first resin layer 20, then the second resin layer 21, and then the light source 11 side. Even when arranged in the order of the third resin layer, also when arranged in the order of the second resin layer 21, then the third resin layer 22, and then the first resin layer 20, the third resin layer 22, Next, when the first resin layer 20 and then the second resin layer 21 are arranged in this order, the first resin layer 20, then the third resin layer 22, and then the second resin layer 21. Even when the second resin layer 21, the third resin layer 22, and then the first resin layer 20 are arranged in this order, the second resin layer 21 and then the first resin layer 20 are arranged. When the third resin layer 22 is arranged in that order, the same performance is exhibited.

In this light diffusion plate 40, the configuration of the first resin layer 20 is the same as that of the light diffusion plate 10 of the first embodiment. That is, the first resin layer 20 has high light transmittance and light reflectivity by the first light scattering particles 13 being dispersed and mixed.
On the other hand, the second resin layer 22 has a high light diffusibility by dispersing and mixing the second light scattering particles 14, and the third resin layer 23 has the third light scattering particles 15 dispersed and mixed. Thus, both light diffusibility and light transmissive properties are imparted.
The particle diameter and refractive index of the first light scattering particle 13, the second light scattering particle 14, and the third light scattering particle 15 are as described in the first embodiment.

Here, the luminance distribution of the light passing through the first resin layer 20 shows the viewing angle characteristics as shown in FIG. 2 as in the first embodiment. The brightness in the direction f can be obtained, and a uniform brightness can be obtained over a wide range. Therefore, a lamp image reduction effect can be obtained.
Further, the light reflected by the first resin layer 20 is returned to the light source 11 side as reflected light, and further reflected by the reflector provided on the light source 11 side, so that it is incident on the light diffusion plate 10 again as recursive light. The By repeating this process, the light can be reused, and at the same time, an oblique lamp image reduction effect can be obtained.

  As shown in FIG. 3, the luminance distribution of the light passing through the second resin layer 22 has a high forward diffusivity while maintaining a wide viewing angle from the front direction f, and falls sharply at a wide angle. Viewing angle characteristics are shown. Therefore, the bright place of the lamp on the light source 11 can be greatly widened to obtain high light diffusibility, so that the effect of reducing the lamp image can be obtained.

  Furthermore, as shown in FIG. 4, the luminance distribution of light passing through the third resin layer 23 maintains a wide viewing angle from the front direction f, and has a viewing angle characteristic that gradually falls toward a wide angle. Indicates. Therefore, it is possible to maintain the central brightness while exhibiting an action similar to the light collecting effect while maintaining the transparency and diffusing the light.

Therefore, the light diffusing plate 40 includes a first transparent resin layer 20 having a light transmitting property and a light reflecting property, a second resin layer 22 having a high light diffusing property, and a third having a light transmitting property and a light diffusing property. Since the transparent resin layer 23 is laminated, the optical characteristics relating to light diffusibility and light transmission are optimized while making effective use of light by light reflectivity, similar to the light diffusion plate 10 of the first embodiment. Accordingly, it is possible to improve the front luminance while reducing the lamp image.
Furthermore, since a high diffusion function can be obtained only with the light diffusion plate 40 as described above, it is not necessary to provide a separate diffusion film or the like. Therefore, it is possible to reduce the number of parts and reduce the manufacturing cost.

Next, a display device 90 according to a third embodiment of the present invention will be described. FIG. 6 is a schematic cross-sectional view showing a schematic configuration of a display device according to the third embodiment.
In the display device 90 according to the second embodiment, the display device 70 according to the first embodiment includes the lens sheet 17a. However, as shown in FIG. 6, a light diffusion film 17b is used instead of the lens sheet 17a. It differs from 1st Embodiment by the point provided.
Therefore, in FIG. 6, the same components as those in FIG.

  In the third embodiment, the optical sheet 25 is configured by laminating the light diffusing film 17b on the light emitting surface 10a side of the light diffusing plate 10, and further using this optical sheet 25, the backlight unit 35 is configured. And the display apparatus 90 is comprised.

The light diffusing film 17b has an effect of uniformly diffusing the light emitted from the light diffusing plate 10 and an effect of condensing the emitted light, and is formed in a film shape and has a light transmitting property. A light transmissive substrate 191 and a light diffusing portion 192 formed on the light emitting surface of the light transmissive substrate 191 are provided, and the light diffusing portion 192 includes a plurality of convex portions. The shape of the convex portion is not particularly limited as long as it has a shape that exhibits light diffusibility and a light collecting effect.
The light diffusion film 17b may be configured to totally reflect a part of incident light, or may be a laminate of a plurality of sheets.

  Further, a gap (air layer) 200 is formed between the light diffusion film 17 b and the light diffusion plate 10. In this case, in addition to the light condensing effect in the unit lens 16, the diffusion effect by the gap 200 can be obtained, so that the light passing through the optical sheet 25 is emitted with an optical gain of 1 or more.

  Further, the optical sheet 25 in which the light diffusing plates 10 and 17b are laminated may be joined by a fixing element such as an adhesive or a spacer in the same manner as the optical sheet 25 of the first embodiment. In this case, the gap 200 can be easily provided.

In the display device 80 shown in FIG. 6 configured as described above, the light emitted from the light source 11 and transmitted through the light diffusing plate 10 is incident from the light incident surface 19a of the light diffusing film 17b. Is emitted from the light exit surface 19b of the light diffusion film 17b with an optical gain of 1 or more. At this time, since the light condensing effect is expressed by the light diffusion film 17b, high front luminance can be obtained.
The optical sheet 25 in the third embodiment is formed by laminating a light diffusion film 17b having a light condensing effect on the light diffusion plate 10 in the front direction (observer side) of the light diffusion plate 10 to form the optical sheet 25. Accordingly, it is possible to reduce the lamp image by diffusing light due to the contribution of the light diffusion plate 10 described above, and it is possible to improve the front luminance by condensing the light and increasing the light use efficiency.

As a modification of the third embodiment, for example, a display device 91 as shown in FIG. 7 may be used.
The display device 91 of this modification includes the light diffusion plate 40 having the three-layer structure described in the second embodiment, instead of the light diffusion plate 10 having the two-layer structure. Also by this, since the condensing effect by the light-diffusion film 17b is expressed, high front luminance can be obtained.

  As described above, the light diffusion plates 10 and 40, the optical sheet 25, the backlight unit 35, and the display devices 70, 80, 90, and 91 according to the embodiment of the present invention have been described, but the present invention is not limited thereto, Modifications can be made as appropriate without departing from the technical idea of the invention.

For example, in the light diffusing plate 10 having the two-layer structure, the first resin layer 20 is disposed on the back surface side and the second resin layer 21 is disposed on the display screen side. The second resin layer 21 may be one in which the first resin layer 20 is disposed on the display screen side.
In the light diffusion plate 40 having a three-layer structure, the order in which the first resin layer 20, the second resin layer 22, and the third resin layer 23 are laminated can be appropriately changed.

  Furthermore, in order to further improve the brightness enhancement or lamp image reduction effect, a lens shape or a convex portion may be formed on one side or both sides of the light diffusing plate 10. In this case, the difference between the maximum and minimum roughness of the surface is preferably up to about 200 μm.

An optical sheet using the light diffusing plate shown in this embodiment was produced, and its physical properties were evaluated. Hereinafter, specific configurations, test methods, and test results of the produced light diffusion plate and optical sheet will be described.
As described in the first embodiment, the optical sheet was prepared by laminating a light diffusion plate and a lens sheet.

(Lens sheet)
A lens sheet constituting an optical sheet was produced using thermoplastic polycarbonate resin beads as a material. Specifically, after melting the thermoplastic polycarbonate resin beads, the sheet is extruded by an extruder, and a convex cylindrical unit lens is molded by a mold roll before the sheet is cooled and cured. . The unit lens pitch was 60 μm.

(Light diffusion plate with two layers)
Next, a light diffusion plate having a two-layer structure composed of a first resin layer and a second resin layer was prepared, and this was laminated with the above lens sheet to prepare an optical sheet, and physical properties were evaluated.

(Light diffusing plate of Examples 1-8)
A first resin layer obtained by adding one kind of light scattering particles (corresponding to the first light scattering particles in the embodiment) to polystyrene resin (PS) having a refractive index of 1.59 and two kinds of light scattering particles (second embodiment). A two-layer light diffusion plate made of a second resin layer added with light scattering particles and third light scattering particles) was prepared as Examples 1-8. Table 1 shows the thickness of each resin layer, the average particle diameter of the light scattering particles, the refractive index, and the mixing amount (% by weight).
Specifically, a light diffusing plate was produced by extruding a laminated sheet composed of the first resin layer and the second resin layer while adjusting the extrusion amount with a laminated extruder. At this time, the die temperature of the extruder was set to 200 ° C., and the roll temperature (temperature of the second roll) was set to 100 ° C.

(Light diffusion plate of Comparative Examples 1 to 14)
A first resin layer obtained by adding one kind of light scattering particles (corresponding to the first light scattering particles in the embodiment) to polystyrene resin (PS) having a refractive index of 1.59 and two kinds of light scattering particles (second embodiment). Two layers of light diffusing plates made of the second resin layer to which light scattering particles and third light scattering particles were added) were produced as Comparative Examples 1-14.

(Evaluation)
Then, the light diffusion plates of Examples 1 to 8 and Comparative Examples 1 to 14 and the lens sheet were overlapped to form an optical sheet, and the lamp image effect and brightness were evaluated. The results are shown in Table 2. In addition, the brightness set 7000 cd / m < ² > or more as the pass.

From Table 1 and Table 2, the first resin layer containing 1 to 10% by weight of first light scattering particles having an average particle diameter of 0.2 to 0.6 μm and a refractive index of 2.4 to 2.72; A second resin containing a total of 0.3 to 35% by weight of a second light scattering particle having an average particle diameter of 1 to 12 μm and a third light scattering particle having an average particle diameter of 30 to 60 μm The refractive index difference between the second light scattering particles and the resin is 0.10 to 0.18, and the refractive index difference between the third light scattering particles and the resin is 0.05 to 0.10. In Examples 1 to 8, the lamp image was not visually recognized, the image display was good, and the brightness was 7000 cd / m ² or more, which was a favorable result.

On the other hand, in Comparative Examples 1 to 14 that do not satisfy any of the above conditions, at least one of the lamp image and the brightness was not preferable. In Table 1, items that do not satisfy the above conditions are clearly shown by applying colors.
Therefore, it was found that a light diffusing plate and an optical sheet capable of reducing the lamp image and improving the front luminance can be produced by satisfying the above conditions.

(Three-layer light diffuser)
Next, a light diffusing plate having a three-layer structure including a first resin layer, a second resin layer, and a third resin layer was produced, and physical properties were evaluated.

(Light diffusion plate of Examples 9 to 16)
First resin layer with one kind of light scattering particles added to polystyrene resin (PS) with a refractive index of 1.59, second resin layer with one kind or two kinds of light scattering particles, one kind or two kinds of resin Examples 9 to 16 were prepared as light diffusion plates having a three-layer structure composed of a third resin layer to which light scattering particles were added.
Table 1 shows the thickness of each resin layer, the average particle diameter of the light scattering particles, the refractive index, and the mixing amount (% by weight). The light diffusion plate is configured to sandwich the second resin layer between the first resin layer and the third resin layer.
As a specific production method, a light diffusing plate was produced by extruding a laminated sheet composed of the first resin layer and the second resin layer while adjusting the extrusion amount with a laminated extruder. At this time, the die temperature of the extruder was set to 200 ° C., and the roll temperature (temperature of the second roll) was set to 100 ° C.

(Light diffusion plate of Comparative Examples 15 to 21)
Comparative Example 15 to a light diffusion plate having a three-layer structure composed of a first resin layer, a second resin layer, and a third resin layer obtained by adding one kind of light scattering particles to polystyrene resin (PS) having a refractive index of 1.59. 21 was produced.
The specific manufacturing method is the same as in Examples 1 to 7.

(Evaluation)
Then, the light diffusion plates of Examples 9 to 16 and Comparative Examples 15 to 21 and the lens sheet were overlapped to form an optical sheet, and the lamp image effect and the brightness were evaluated. The results are shown in Table 4. In addition, the brightness set 7000 cd / m < ² > or more as the pass.

From Tables 3 and 4, as in Example 9, the first resin layer containing 1% by weight of light scattering particles having an average particle size of 0.2 μm and a refractive index of 2.72, and an average particle size of 1 μm If the light diffusing plate is provided with a light scattering particle having a spherical shape and a second resin layer containing a light scattering particle having an average particle size of 35 μm, the lamp image is not visually recognized and the image display is not In addition to being good, the brightness was 7000 cd / m ² or more, which was a favorable result. As long as the configurations of the first resin layer and the second resin layer are those shown in Example 9, it is presumed that the same result is obtained regardless of the configuration of the third resin layer.

Further, as in Examples 10, 12, 14, and 15, the first resin layer containing light scattering particles having an average particle diameter of 0.2 to 0.6 μm and a refractive index of 2.4 to 2.72. And a second resin layer containing light-scattering particles having an average particle diameter of 1 to 12 μm and a third resin layer containing light-scattering particles having an average particle diameter of 30 to 60 μm In the light diffusion plate having three layers, it was found that the lamp image was not visually recognized and the image display was good.
Further, as in Examples 11 and 13, the first resin layer containing light scattering particles having an average particle size of 0.2 to 0.6 μm and a refractive index of 2.4 to 2.72, and the average particle From three layers of a second resin layer containing first light scattering particles having a true spherical shape with a diameter of 30 to 60 μm and a third resin layer containing light scattering particles having a true spherical shape with an average particle diameter of 1 to 12 μm Even with the light diffusion plate, it was found that the lamp image was not visually recognized and the image display was good. That is, it was found that good results were obtained even if the configurations of the second resin layer and the third resin layer were interchanged.

On the other hand, in Comparative Examples 15 to 21 that did not satisfy any of the above conditions, at least one of the lamp image and the brightness was not preferable. In Table 3, items that do not satisfy the above conditions are clearly shown by applying colors.
Therefore, it was found that a light diffusing plate and an optical sheet capable of reducing the lamp image and improving the front luminance can be produced by satisfying the above conditions.

It is typical sectional drawing which shows schematic structure of the display apparatus which concerns on 1st Embodiment. It is a luminance distribution map of the light which passes the light diffusing plate in which the 1st light-scattering particle was disperse-mixed. It is a luminance distribution map of the light which passes the light diffusing plate with which 2nd light-scattering particle was disperse-mixed. It is a luminance distribution figure of the light which passes the light diffusing plate with which the 3rd light-scattering particle was mixed. It is typical sectional drawing which shows schematic structure of the display apparatus which concerns on 2nd Embodiment. It is typical sectional drawing which shows schematic structure of the display apparatus which concerns on 3rd Embodiment. It is typical sectional drawing which shows schematic structure of the display apparatus which concerns on the modification of 3rd Embodiment. It is a longitudinal cross-sectional view of the display apparatus in which the light guide plate light guide type backlight unit is mounted. It is a longitudinal cross-sectional view of the display apparatus which provided the prism film between the diffusion film and the liquid crystal panel. It is a longitudinal cross-sectional view of the display apparatus provided with the direct type backlight unit. It is a perspective view of the light control sheet provided with the brightness emphasis film. It is a longitudinal cross-sectional view of the principal part of the display apparatus by which the light control sheet provided with the brightness | luminance emphasis film is arrange | positioned. It is a figure which shows the light intensity distribution of the light control sheet provided with the brightness | luminance emphasis film.

Explanation of symbols

10 light diffusion plate 11 light source 12 resin 13 first light scattering particle 14 second light scattering particle 15 third light scattering particle 17a lens sheet 17b light diffusion film 20 first resin layer 21 second resin layer 22 second resin layer 23 first 3 resin layer 25 optical sheet 35 backlight unit 40 light diffusion plate 70 display device 80 display device 90 display device 91 display device 100 liquid crystal panel (image display unit)

Claims (9)

In a light diffusing plate in which light scattering particles are dispersed and mixed in a resin,
A first resin layer containing first light scattering particles having an average particle size of 0.2 to 0.6 μm and a refractive index of 2.4 to 2.72;
It consists of at least two layers of a second light scattering particle having a true spherical shape with an average particle diameter of 1 to 12 μm and a second resin layer containing a third light scattering particle having a true spherical shape with an average particle diameter of 30 to 60 μm. A light diffusing plate characterized by In a light diffusing plate in which light scattering particles are dispersed and mixed in a resin,
A first resin layer containing first light scattering particles having an average particle size of 0.2 to 0.6 μm and a refractive index of 2.4 to 2.72;
A second resin layer containing second light scattering particles having a true spherical shape with an average particle diameter of 1 to 12 μm;
A light diffusing plate comprising at least three layers including a third resin layer containing third light scattering particles having a true spherical shape with an average particle diameter of 30 to 60 μm.   2. The light diffusing plate according to claim 1, wherein a total mixing amount of the second light scattering particles and the third light scattering particles in the second resin layer is 0.3 to 35 wt%.   4. The light diffusion plate according to claim 1, wherein an amount of the first light scattering particles mixed in the first resin layer is 1 to 10 wt%. The refractive index difference between the second light scattering particles and the resin is 0.10 to 0.18,
5. The light diffusion plate according to claim 1, wherein a difference in refractive index between the third light scattering particles and the resin is 0.05 to 0.10. 6. An optical sheet that emits incident light from the light source to the other surface side when the light source is disposed on the one surface side,
A light diffusing plate according to any one of claims 1 to 5;
An optical sheet comprising: a lens sheet that is disposed on the other surface side opposite to the light source of the light diffusing plate, converts the optical characteristics of the light of the light source that has passed through the light diffusing plate, and emits the light. . An optical sheet that emits incident light from the light source to the other surface side when the light source is disposed on the one surface side,
A light diffusing plate according to any one of claims 1 to 5;
An optical device comprising: a light diffusing film that is disposed on the other surface side opposite to the light source of the light diffusing plate, converts the optical characteristics of the light of the light source that has passed through the light diffusing plate, and emits the light. Sheet. The optical sheet according to claim 6 or 7,
And a light source disposed on one side of the optical sheet. The backlight unit according to claim 8,
A display device, comprising: an image display unit that is disposed on an emission surface side of the backlight unit and displays an image using light from the backlight unit as display light.

Images