JP2010085941A - Light diffusing plate, optical sheet, back light unit, and display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light diffusing plate that reduces a lamp image and has improved brightness for its front, and to provide an optical sheet, a back light unit, and a display that use the light diffusing plate. <P>SOLUTION: The light diffusing plate 1 includes at least three layers: a first resin layer 11 with a refractive index n1, a second resin layer 12 with a refractive index n2, and a third resin layer 13 with a refractive index n3. The first rein layer 11 faces the light source 41. The second resin layer 12 is laminated over the surface of the first resin layer 11, of which surface is opposite the light source 41. The third resin layer 13 is laid over the surface of the second resin layer 12, of which surface is opposite the first resin layer 11. A lens array having a plurality of unit lenses arranged parallel to one another is disposed on the surface of the first resin layer 11, of which surface is opposite the surface over which the second rein layer 12 is laminated. The refractive indexes n1, n2, and n3 satisfy a relation expressed by n1>n2>n3. <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. 7 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 brightness, as shown in FIG. 8, 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 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 178, 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 uniformly dispersed at a certain concentration by using spherical particles as light scattering particles to be blended with the resin, it has been confirmed that the light diffusing characteristic widens the viewing angle. Yes. 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.

  Furthermore, in the liquid crystal display device shown in FIG. 9, since the control of the viewing angle is left only to the diffusibility of the diffusion film 178, 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. 10, 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. 10 and 11, the BEF 185 is a film in which unit prisms 187 having a triangular cross section are arranged at a certain 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. 12, 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 that diffuses and emits light from a light source, and includes a first resin layer having a refractive index of n1 and a second resin layer having a refractive index of n2. It consists of at least three layers with a third resin layer having a refractive index of n3, the first resin layer faces the light source, and the second resin layer is laminated on the surface of the first resin layer opposite to the light source The third resin layer is laminated on the surface of the second resin layer opposite to the first resin layer, and the surface of the first resin layer opposite to the surface on which the second resin layer is laminated In addition, a lens array in which a plurality of unit lenses are arranged in parallel is provided, and the refractive index n1, the refractive index n2, and the refractive index n3 satisfy a relationship of n1>n2> n3.

In the light diffusing plate having such a feature, when the light goes from the light source side at the interface between the first resin layer and the second resin layer, when n1> n2, that is, when the refractive index is low, diffusion is performed. Performance will be improved.
Therefore, with such a configuration, it is possible to improve the diffusion performance and reduce the lamp image.

  In the light diffusing plate according to the present invention, at least one kind of light scattering particles is dispersed and mixed in at least one resin layer of the first, second, and third resin layers, and the light scattering particles have an average particle diameter. The refractive index difference between the light scattering particles and the first, second, and third resin layers is 0.02 to 0.5.

  According to the light diffusing plate having such characteristics, it has a very high light diffusibility while maintaining a certain degree of light transmittance. Therefore, it is possible to improve the diffusion performance and reduce the lamp image.

  Furthermore, the light diffusion plate according to the present invention has a ten-point average roughness Rz of 200 μm or less and an arithmetic average roughness Ra on the surface of the third resin layer opposite to the surface on which the second resin layer is laminated. Is provided with a concavo-convex structure of 3.0 μm or more and 1000 μm or less.

  According to the light diffusing plate having such a feature, since the emission surface of various angles is formed as compared with the case where the surface is substantially flat, the light can be emitted to a wider range, so that the diffusion performance As a result, the lamp image can be reduced.

  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 third resin layer side 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.

  On the other hand, 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 of any one of the above, and the light diffusion And a light diffusing film that is disposed on the third resin layer side 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. .

  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.

  The backlight unit according to the present invention includes the optical sheet and a light source disposed on the first resin layer side of the optical sheet.

  According to the backlight unit having such a feature, since the light diffusion plate and the optical sheet described above are used, the optical characteristics relating to diffusibility and transparency are optimized, the lamp image is reduced, and the front direction It is possible to emit light with improved brightness.

  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.

The best mode for carrying out the present invention will be described below.
First, an embodiment of the present invention is shown in FIG. 1, and a backlight unit 44 supplies a plurality of cylindrical light sources 41 housed in a lamp house 43 and light H from each light source 41 to a liquid crystal panel 32. An optical sheet 39 is provided. The liquid crystal panel 32 is configured by sandwiching liquid crystal 35 between polarizing plates 31 and 33, and 45 in the drawing is a light reflecting plate disposed on the back side of the plurality of light sources 41.
The display device L according to the embodiment of the present invention is a device that includes the light source 41, the optical sheet 39, and the liquid crystal panel 32 thereon. In this case, the display device L is a liquid crystal display device. However, the display device L is not limited to this, and is a display device that uses the light to display an image such as a projection screen device, plasma display, EL display, etc. There is no limitation on the type.

  The direct type backlight uses the light diffusing plate 1 that scatters and collects light, and is used on the light source 41 side to increase the light use efficiency. A film is placed.

  In this embodiment, the light source 41 is a linear light source such as a fluorescent lamp, and a cold cathode tube is usually used for a liquid crystal display.

  The light diffusing plate 1 is composed of a resin and a light diffusing material (particles) dispersed in the resin.

  The resin used for the light diffusion plate 1 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, an epoxy acrylate resin Polystyrene resin, acrylonitrile styrene resin, cycloolefin polymer, methyl styrene resin, fluorene resin, PET, polypropylene and the like can be used.

  In addition, as the light diffusing material dispersed in the transparent resin, 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.

Here, the light diffusing plate 1 may have a plate shape, a plate shape, or a sheet shape, and the thickness thereof is preferably set in a range of 0.5 to 5 mm, and the thickness direction One of the surfaces is a light incident surface 100 and the other surface is a light emitting surface 101.
When the thickness of the light diffusing plate 1 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 diffusion plate 1 exceeds 5 mm, there is a problem that the transmittance of light from the light source 41 is lowered.

Such a light diffusion plate 1 can be manufactured by integrally molding a transparent resin 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 light diffusing plate 1 is preferably provided with a concavo-convex structure on the light emitting surface 101 side so that the ten-point average roughness Rz is 200 μm or less and the arithmetic average roughness Ra is 3.0 μm or more and 1000 μm or less. In this case, since the light from the light source 41 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 101 of the light diffusing plate 1 is provided with a concavo-convex structure, an air gap can be obtained between the members (the lens sheet 4 in the present embodiment) superimposed on the display screen without being in surface contact. Therefore, it is possible to prevent optical influences such as Newton rings due to the close contact between the light diffusion plate 1 and the lens sheet 4.

FIG. 2 shows an embodiment of the light diffusing plate 1 according to the present invention, in which transparent resins having different refractive indexes are laminated above and below a diffusion layer in which a diffusing material 8 is dispersed in a transparent resin. It is a thing. The light diffusing plate 1 has a multilayer structure in which a plurality of diffusion layers are laminated, and is manufactured by a lamination extruder.
In addition, the surface state of the light incident surface 100 of the light diffusing plate 1 of the present invention is a lens array in which a plurality of unit lenses are arranged in parallel, and has the effect of improving the diffusion performance and reducing the lamp image. .
In other words, the light diffusing plate 1 includes at least three layers including a first resin layer 11 having a refractive index n1, a second resin layer 12 having a refractive index n2, and a third resin layer 13 having a refractive index n3. Become. The first resin layer 11 faces the light source 41, the second resin layer 12 is laminated on the surface of the first resin layer 11 opposite to the light source 41, and the third resin layer 13 is opposite to the first resin layer 11. Two resin layers 12 are laminated on the surface.
A lens array in which a plurality of unit lenses are arranged in parallel is provided on the surface of the first resin layer 11 opposite to the surface on which the second resin layer 12 is laminated.
The refractive index n1, the refractive index n2, and the refractive index n3 satisfy the relationship n1>n2> n3.
Further, at least one kind of light scattering particles is dispersed and mixed in at least one resin layer of the first, second, and third resin layers 11, 12, and 13, and the light scattering particles have an average particle diameter of 0.5 to 10 μm. Yes, the refractive index difference between the light scattering particles and the first, second and third resin layers is 0.02 to 0.5.
Further, on the surface of the third resin layer 13 opposite to the surface on which the second resin layer 12 is laminated, the ten-point average roughness Rz is 200 μm or less, and the arithmetic average roughness Ra is 3.0 μm or more and 1000 μm or less. Provide structure.

Moreover, the light diffusing plate 1 may be one in which an ultraviolet absorber is added to at least one of the resin layers disposed on the light source 41 side.
Thereby, deterioration of the light diffusing plate 1 itself by the ultraviolet rays irradiated from the light source 41 can be suppressed, and the life can be extended. Furthermore, it is possible to suppress deterioration of the lens sheet 4 and the diffusion film disposed facing the light emitting surface 101 of the light diffusing plate 1 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, and cyanoacrylates such as ethyl-2-cyano-3,3-diphenylacrylate A system or the like can be used.

A lens sheet is laminated on the observation surface side of the light diffusing plate 1 to optimize optical characteristics such as brightness and light distribution characteristics. The stacking method may be simply superimposing, or may be bonded via a fixing element.
In the present embodiment, an adhesive or pressure-sensitive adhesive is provided between the light exit surface 101 side of the light diffusing plate 1 and the incident surface 102 of the lens sheet 4 and holds the gap 200 between the light diffusing plate 1 and the lens sheet 4. It has a fixing element 3 that is fixed by, for example.
In other words, the lens sheet 4 that is disposed on the third resin layer 13 side of the light diffusing plate 1 and converts the optical characteristics of the light of the light source 41 that has passed through the light diffusing plate 1 is emitted.
In addition, when the film which laminated | stacked the diffused layer is laminated | stacked on the light-projection surface 101, since the same effect as mixing a several light-diffusion material in one transparent resin is obtained, and since several layers are used, By adding or removing a certain layer, fine adjustment of haze can be easily performed, which is advantageous in obtaining the light diffusing plate 1 having desired optical characteristics.
Further, a light diffusion film may be used in place of the lens sheet 4. In other words, a light diffusing film that is disposed on the third resin layer 13 side of the light diffusing plate 1 and converts the optical characteristics of the light of the light source 41 that has passed through the light diffusing plate 1 to be emitted may be provided.

The lens sheet 4 will be described.
The lens sheet 4 is formed by arranging a large number of convex cylindrical unit lenses in parallel on the emission surface 103, and is configured by dispersing particles in the lens sheet 4 made of a transparent resin.

  The above-described lens sheet 4 is incident from the incident surface 102 on which the light transmitted from the light source 41 through the light diffusing plate 1 and the air gap (air layer) 200 is incident as shown in FIG. Is emitted at 1 or more.

Here, the optical gain is one of indexes indicating the diffusibility of the optical diffusing member, and is expressed as a ratio to the luminance of the light, assuming that the luminance of the diffuser that completely diffuses is 1. When the diffusivity of the diffusing member to be measured is biased depending on the direction, the diffusion characteristic of the diffusing member can be shown by obtaining the optical gain for each direction.
Also, complete diffusion refers to an ideal diffuser that has zero absorption and a constant 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.

FIG. 3 is an explanatory diagram of a lens by optical simulation (RayTracing simulation).
FIG. 3A shows light rays emitted in the front direction (0 degree) from one unit lens of a normal unit lens sheet. From this, it can be seen that light rays are emitted from the entire surface of the lens.
FIG. 3B shows light that is emitted in the vicinity of the vertical diagonal direction (60 degrees to 90 degrees) instead of the front direction of the unit lens of the same unit lens sheet as that in FIG. From this, it can be seen that the light in the oblique direction in FIG.
That is, a portion called a side lobe that causes light loss in the entire luminance distribution emitted from the lens sheet 4 is light emitted from the vicinity of the apex of each unit lens of the lens sheet 4.

Here, in the backlight unit, the thickness is further reduced, and the distance between the light source 51 and the optical sheet 39 is shortened accordingly. However, if the light diffusing plate 1 of the present invention is used, the direct type or the figure is reduced. In the backlight unit using the side edge type light guide plate 47 shown in FIG. 4 or the backlight unit using the EL light source 49 shown in FIG. 5, there is no influence of visibility such as a dark spot generated between the light source lamps. Can be used fully.
Furthermore, the size of the optical sheet 39 is also increasing along with the increase in the size of the display device. However, the light diffusion plate 1 of the present invention is thin and strong, and the display quality is also excellent. Therefore, it can be sufficiently used for such a large display device.

  The light diffusing plate 1 of the present invention can be used for improving the brightness of a backlight, in addition to a viewing angle control film for a display such as an LCD, EL or PDP, a contrast improving film, a light control film for a solar cell, a projection screen, etc. Can be used.

  The light diffusing plate 1 of the present invention is applicable not only to a cold cathode fluorescent lamp as a light source but also to a display device using an LED, an EL (FIG. 5), a semiconductor laser or the like that has recently attracted attention as a light source for display. Can be used.

  Here, when an LED is used as the light source 51 of the display device, as shown in FIG. 6A, an array of red, green, and blue LEDs is used, and an array of red, green, and blue LEDs using a light guide plate or the like. Light that is mixed and emitted uniformly as white light, or light from an array of red, green, and blue LEDs using a diffuser or the like as shown in FIG. It can also be used for those that can emit light.

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.
In addition, as an optical sheet, what laminated | stacked the lens sheet | seat on the light diffusing plate was produced.

(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.

(Three-layer light diffuser)
First, the light diffusing plate 1 having a three-layer structure including the first resin layer 11, the second resin layer 12, and the third resin layer 13 was produced, and physical properties were evaluated.

(Examples 1-4, Comparative Examples 1-4)
A polycarbonate resin (PC) having a refractive index of 1.59 is used as the first resin layer 11, a methyl methacrylate-styrene copolymer resin (MS) having a refractive index of 1.54 is used as the second resin layer 12, and an acrylic resin having a refractive index of 1.49. Resin (PMMA) is used as the third resin layer 13 and 10 parts by weight of silicon beads having an average particle size of 0.5 to 10 μm are added to the second resin layer 12 as a diffusing material. A concavo-convex structure having a roughness Rz of 200 μm or less and an arithmetic average roughness Ra of 3.0 μm or more and 1000 μm or less was formed, and a laminated sheet was formed in which a lenticular shape was formed on the light incident surface 100 side.
Table 1 shows the refractive index of each resin layer, the average particle diameter of the light scattering particles, and the difference in refractive index between the resin and the light scattering particles.
As a specific production method, a light diffusing plate was produced by extruding the laminated sheet composed of the first to third resin layers 11, 12, and 13 while adjusting the extrusion amount using a laminated extruder.
At this time, the die temperature of the extruder was set to 250 ° C., and the roll temperature (temperature of the second roll) was set to 90 ° C.

  The light diffusing plate thus manufactured was installed on a display, and the above lens sheets were laminated under the conditions to confirm the lamp image effect. Table 1 shows the results.

  Table 1 shows the lamp image reduction effect results of Examples 1 to 4. In all cases, the lamp image was better than the comparative example.

  From the above, in the light diffusion plate having a three-layer structure, the refractive indexes n1 to n3 in the first to third resin layers 11, 12, and 13 are n1> n2> n3, and the second resin layer 12 has a difference in refractive index from the resin. It was found that the lamp image can be reduced when light scattering particles having an average particle diameter of 0.01 to 0.5 and an average particle diameter of 0.5 to 10 μm are included.

It is explanatory drawing which shows the illustrative display apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the light-scattering member perspective view which concerns on embodiment of this invention. (A) It is explanatory drawing which shows the optical simulation result of the cylindrical lens by a prior art. (B) It is explanatory drawing which shows the optical simulation result of the cylindrical lens by a prior art. It is explanatory drawing which shows the illustrative display apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the illustrative display apparatus which concerns on embodiment of this invention. (A) It is explanatory drawing which shows the exemplary display apparatus which concerns on embodiment of this invention, (b) It is explanatory drawing which shows the exemplary display apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. It is explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. It is explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. It is explanatory drawing which shows the perspective view of BEF by a prior art. It is explanatory drawing which shows the structural example of the optical sheet for liquid crystal displays by a prior art. It is explanatory drawing which shows the light intensity distribution radiate | emitted from the optical sheet using BEF.

Explanation of symbols

  H, K: Light, T: Lens support part thickness, L: Viewing surface (display display surface), 1 ... Light diffusion plate, 3 ... Fixed element, 4 ... Lens sheet, 8 ... Diffuser, 31, 33 ... Polarized light Plate, 32 ... Liquid crystal panel, 35 ... Liquid crystal layer, 39 ... Optical sheet, 41, 51 ... Light source, 43 ... Lamp house, 45 ... Light reflector, 47 ... Light guide plate, 49 ... EL light source, 51, 53 ... LED light source DESCRIPTION OF SYMBOLS 100 ... Light entrance surface of light diffusing plate, 101 ... Light exit surface of light diffusing plate, 102 ... Light entrance surface of lens sheet, 103 ... Light exit surface of lens sheet, 200 ... Air gap, 300 ... Diffusion sheet, 302 ... Near the apex of the unit lens.

Claims (7)

A light diffusing plate that diffuses and emits light from a light source,
It consists of at least three layers: a first resin layer having a refractive index n1, a second resin layer having a refractive index n2, and a third resin layer having a refractive index n3.
The first resin layer faces the light source, the second resin layer is laminated on the surface of the first resin layer opposite to the light source, and the third resin layer is opposite to the first resin layer. Laminated on the surface of the second resin layer,
A lens array comprising a plurality of unit lenses arranged in parallel on a surface of the first resin layer opposite to a surface on which the second resin layer is laminated;
The refractive index n1, the refractive index n2, and the refractive index n3 satisfy a relationship of n1>n2> n3.
A light diffusion plate characterized by that. At least one kind of light scattering particles is dispersed and mixed in at least one resin layer of the first, second, and third resin layers,
The light scattering particles have an average particle size of 0.5 to 10 μm,
2. The light diffusing plate according to claim 1, wherein a difference in refractive index between the light scattering particles and the first, second, and third resin layers is 0.02 to 0.5.   A concavo-convex structure having a ten-point average roughness Rz of 200 μm or less and an arithmetic average roughness Ra of 3.0 μm or more and 1000 μm or less on the surface of the third resin layer opposite to the surface on which the second resin layer is laminated. The light diffusing plate according to claim 1, wherein the light diffusing plate is provided. 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 diffusing plate according to any one of claims 1 to 3,
An optical sheet comprising: a lens sheet that is disposed on the third resin layer side of the light diffusing plate and that converts and outputs an optical characteristic of light of the light source that has passed through the light diffusing plate. 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 diffusing plate according to any one of claims 1 to 3,
An optical sheet, comprising: a light diffusing film that is disposed on the third resin layer side of the light diffusing 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. The optical sheet according to claim 4 or 5,
A backlight unit comprising a light source disposed on the first resin layer side of the optical sheet. The backlight unit according to claim 6;
A display device, comprising: an image display unit disposed on an emission surface side of the backlight unit and performing image display using light from the backlight unit as display light.

Images