JP2013089479A - Light guide plate, backlight unit and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide plate excellent in luminance even if it has a multilayer shape.SOLUTION: The light guide plate has a main layer, an upper layer laminated on the upper part than the main layer, and a lower layer laminated on the lower part than the main layer. The main layer is a layer containing light diffusing particulates, the upper layer is a layer of which on the surface concavo-convex patterns are formed, and the lower layer is a layer of which on the surface concavo-convex patterns are formed. Since the light diffusion particulates are contained in the main layer inside the light guide plate, light which has advanced in the main layer is diffused in many directions by the light diffusion particulates. Accordingly, polarization of light in the advancing direction of the light by the interface between the layers can be suppressed, and a light guide plate of multilayer shape excellent in luminance can be provided.

Description

  The present invention relates to a light guide plate used for optical path control, a backlight unit using the light guide plate, and a display device incorporating the backlight unit.

  A backlight system has been proposed for display devices. The backlight system is a system in which a light source is arranged on the back side (the side opposite to the observer side) of a panel (liquid crystal panel or the like) whose design is to be changed, and the panel is illuminated with light from the back of the panel.

  In the backlight unit used in the backlight system, (1) a “direct type” in which a light source is disposed directly under the light guide plate, and (2) an “edge light system” in which a light source is disposed on a side end surface of the light guide plate. Proposed.

  Further, liquid crystal display devices are strongly required as market needs to be thin, high brightness, light weight, and low power consumption. For this reason, the backlight unit mounted on the liquid crystal display device is particularly required to be lightweight, high brightness, and low power consumption. In particular, in a color liquid crystal display device, the transmittance of the liquid crystal panel is much lower than that of a monochrome-compatible liquid crystal panel. Therefore, it is essential to improve the luminance of the backlight unit in order to obtain low power consumption of the device itself. It has become.

  In addition, with the diversification of video media, the demand for liquid crystal display devices capable of 3D display is increasing due to the need for higher image quality and the desire to experience the realism of video. In the case of performing 3D display with a liquid crystal display device, an “active shutter system” that requires special glasses has been proposed. In the active shutter method, right-eye and left-eye images are alternately displayed, and the shutter in dedicated glasses is opened and closed, so that the images are distributed and displayed three-dimensionally for the right-eye and left-eye. For this reason, it is known that in the active shutter system, the light emission time is reduced to half of the normal time, and there is a loss such as a polarizing plate and reflection of the dedicated glasses, and the luminance is lower than that in normal 2D display. For this reason, the liquid crystal display device for 3D is required to have higher luminance than a normal liquid crystal display device for 2D display.

  For example, for the purpose of increasing the brightness of a liquid crystal display device, a triangular prism sheet (see Patent Document 1) having an apex angle of 90 ° is incorporated as a brightness adjustment sheet in a backlight unit, thereby improving the brightness of the display screen. Has been proposed (see Patent Document 2).

JP 60-70601 A Japanese National Patent Publication No. 10-506500

  As described above, various optical sheets are combined in the backlight unit. For this reason, from the viewpoint of reducing the number of components and reducing the thickness, it is conceivable to use a multilayer light guide plate in which layers capable of optical operation are laminated on the light guide plate itself.

  However, in a multi-layered light guide plate, an interface is formed between the layers for each layer, and light is refracted at the interface, so that the light traveling direction is biased and the front luminance is lowered.

  Therefore, the present invention has been made to solve the above-described problem, and an object of the present invention is to provide a light guide plate having excellent luminance even in a multilayer shape.

  An embodiment of the present invention is a light guide plate that diffuses light in a plane direction, and includes a main layer, an upper layer stacked above the main layer, and a lower layer stacked below the main layer. The main layer is a layer containing light diffusing fine particles, the upper layer is a layer having a concavo-convex pattern formed on the surface, and the lower layer is a layer having a concavo-convex pattern formed on the surface. The light guide plate.

  Moreover, the heat fluidity of the resin used for the main layer may be higher than the heat fluidity of the resin used for the upper layer and the heat fluidity of the resin used for the lower layer.

  Further, when the mean free path L (mm) of light in the main layer and the refractive index difference D between the main layer and the light diffusing fine particles, L / D satisfies 1000 ≦ L / D ≦ 4000. It may be.

  One embodiment of the present invention is a backlight unit using the light guide plate described above.

  One embodiment of the present invention is a display device using the backlight unit described above.

  In the present invention, since the light diffusion fine particles are included in the main layer inside the light guide plate, the light entering the main layer is diffused in multiple directions by the light diffusion fine particles. Therefore, it is possible to suppress the deviation of the light traveling direction due to the interface between layers, and even a multilayered light guide plate can uniformly guide light in the surface direction.

It is the schematic which shows an example of the light-guide plate of this invention. It is the schematic which shows an example of the display apparatus of this invention. It is a figure which shows the result of the computer simulation about the light-guide plate of this invention. It is a figure which shows the result of the Example about the light-guide plate of this invention.

Hereinafter, the light guide plate of the present invention will be described.
The light guide plate of the present invention is a multilayer light guide plate having three or more layers including an upper layer / main layer / lower layer.
The light guide plate of the present invention comprises a main layer, an upper layer laminated above the main layer, and a lower layer laminated below the main layer, and the main layer is a layer containing light diffusing fine particles. The upper layer is a layer having a concavo-convex pattern formed on the surface, and the lower layer is a layer having a concavo-convex pattern formed on the surface. In the present invention, since the light diffusion fine particles are included in the main layer inside the light guide plate, the light entering the main layer is diffused in multiple directions by the light diffusion fine particles. Therefore, it is possible to suppress the deviation of the light traveling direction due to the interface between the layers, and it is possible to provide a multilayer light guide plate having excellent luminance.

  In the light guide plate of the present invention, the material used for the upper layer / main layer / lower layer may be any material that has optical transparency to the light emitted from the light source. The materials used for the upper layer / main layer / lower layer may be the same or different. For example, when the light source is visible light, polycarbonate resin, polystyrene resin, fluorine-based acrylic resin, epoxy acrylate resin, methylstyrene resin, fluorene resin, cycloolefin polymer, polyethylene terephthalate, polypropylene, acrylic-styrene copolymer, styrene-butadiene -You may use the material containing an acrylonitrile copolymer, an acrylic resin, PMMA (polymethylmethacrylate), etc. An acrylic resin, particularly PMMA (polymethyl methacrylate) is preferable as a main material used for the light guide plate of the present invention because it has a good light transmittance to visible light. Here, the main material means a material having a weight ratio of 90% or more in the weight of the entire light guide plate.

  An uneven pattern is formed on the upper layer and the lower layer of the present invention. The concavo-convex pattern may be formed in a rectangular shape that is appropriately optically designed according to the specifications of the desired light guide plate. For example, a convex cylindrical shape pattern, a lens shape pattern, a triangular prism shape pattern, a dot pattern, or the like may be used as the concavo-convex pattern.

  Moreover, it is preferable that the uneven | corrugated pattern formed in an upper layer is an uneven | corrugated pattern which can diffuse / condense light to a surface direction. Luminance when viewed from the observation surface can be improved by diffusing / condensing light in the surface direction. For example, as a concavo-convex pattern formed on the upper layer, a pattern in which triangular prism shapes are arranged in parallel may be used.

  Moreover, it is preferable that the thickness of the upper layer is about 5% to 20% of the total thickness with respect to the total thickness of the light guide plate of the present invention. When the thickness of the upper layer is 5% or less, the saddle shape of the uneven pattern is lowered. On the other hand, when the thickness of the upper layer is 20% or less, the thickness of the main layer is reduced and the mechanical strength is lowered.

  Moreover, it is preferable that the uneven | corrugated pattern formed in a lower layer is an uneven | corrugated pattern (light rising pattern) which radiate | emits the light incident from the side end surface of one side to the upper layer side. By forming the light rising pattern in the lower layer, it can be used as an edge light type light guide plate. Examples of the light rising pattern include a pattern that gradually increases the pattern density as the distance from the light source increases. For example, a gradation dot pattern or a gradation stripe pattern may be used as the uneven pattern formed in the lower layer.

  Moreover, it is preferable that the thickness of a lower layer is about 5% or more and 20% or less of the total thickness with respect to the total thickness of the light guide plate of the present invention. If the thickness of the lower layer is 5% or less, the shape of the concavo-convex pattern is lowered. On the other hand, if the thickness of the lower layer is 20% or less, the thickness of the main layer is reduced and the mechanical strength is lowered.

  Moreover, it is preferable that the thermal fluidity of the resin used for the main layer is higher than the thermal fluidity of the resin used for the upper layer and the thermal fluidity of the resin used for the lower layer. In general, MFR (melt flow rate, g / 10 minutes) is used as an index of resin fluidity. In the case of a resin having a small MFR, the molecular weight is large and the strength is high. On the other hand, (1) the flowability is low and the flow into the pattern formed on the mold is hindered. When trying to form a pattern, there is a risk that bubbles may be generated due to air entrainment. In addition, in the case of a resin having a large MFR, the fluidity is high and a precise uneven pattern can be formed, but the mechanical strength is difficult. For this reason, by making the MFR of the resin used for the main layer smaller than the MFR of the resin used for the upper layer and the lower layer, it is possible to transfer an excellent concavo-convex pattern and simultaneously maintain the mechanical strength of the light guide plate itself.

  Moreover, it is preferable that MFR of resin used for a main layer exists in the range of about 0.2 g / 10min or more and 5 g / 10min or less. When MFR is less than 0.2 g / 10 min, it is difficult to flow, and there is difficulty in moldability by an extrusion method or the like. Moreover, when MFR is larger than 5 g / 10min, it is unpreferable from a viewpoint of maintenance of the mechanical strength of light-guide plate itself.

  Moreover, it is preferable that MFR of resin used for an upper layer and a lower layer exists in the range of about 5 g / 10min or more and 30 or less. If the MFR is less than 5 g / 10 min, the rugged pattern cannot be satisfactorily formed due to difficulty in fluidity. On the other hand, if the MFR is less than 5 g / 10 min, air may be entrained in forming the concavo-convex pattern and bubbles may be generated in the resin. On the other hand, if the MFR is greater than 30 g / 10 min, the resin having an MFR greater than 30 g / 10 min is generally a resin having a low molecular weight, so that the upper layer and the lower layer become very brittle. For this reason, it is not preferable from the viewpoint of maintaining the mechanical strength of the light guide plate itself.

  The light diffusing fine particles are added in the main layer in order to diffuse the light guided to the light guide plate. Examples of the light diffusing fine particles include: (1) silica particles, calcium carbonate particles, barium sulfate particles, titanium oxide particles, aluminum hydroxide particles, inorganic particles such as talc, (2) (meth) acrylic polymer particles, styrene type Organic particles such as polymer particles and siloxane polymer particles may be used.

  Further, assuming that the mean free path L (mm) of light in the main layer and the refractive index difference D between the main layer and the light diffusing fine particles, L / D satisfies 1000 ≦ L / D ≦ 4000. In addition, it is preferable to control the particle size, addition amount, etc. of the light diffusing fine particles. Light incident on the main layer is scattered while colliding with the light diffusing fine particles in the main layer. For this reason, the mean free path L of light in the main layer is the average of the distance traveled by the light between the collision with the light diffusing fine particles. Therefore, the mean free path L is obtained by the following equation (1).

なお、数１において、ｎは、散乱源の密度（単位の次元は個／ｍｍ^３）、
σは散乱時の有効断面積（単位の次元はｍｍ^２）である。

In Equation 1, n is the density of the scattering source (the unit dimension is pieces / mm ³ ),
σ is an effective cross-sectional area at the time of scattering (the unit dimension is mm ² ).

  The light guide plate of the present invention is preferably manufactured by an extrusion method. In the extrusion method, materials used for the upper layer / main layer / lower layer can be laminated and extruded by the co-extrusion method. Further, by using a mold roll engraved with a concavo-convex pattern, the concavo-convex pattern can be imparted inline to the upper and lower layers of the outer surface. For this reason, the light-guide plate of this invention can be manufactured continuously.

FIG. 1 schematically shows an example of the light guide plate 50 of the present invention.
FIG. 1 shows a light guide plate 50 of the present invention in which an upper layer 55 / main layer 53 / lower layer 52 are laminated in this order. On the outer surface of the upper layer 55, an upper lens pattern arranged in parallel is formed as an upper layer uneven pattern 54. In addition, a dot pattern is formed on the outer surface of the lower layer 52 as the lower layer uneven pattern 181 so that the pattern becomes denser toward the center. In addition, light diffusion particles 51 are added inside the main layer 53. The light guide plate 50 can be used as an edge light type light guide plate by arranging a light source at a side end.

Hereinafter, the backlight unit of the present invention will be described.
The backlight unit of the present invention includes the light guide plate described above, and a surface light source that receives light from the light guide plate.

  As the light source, a known light source that emits light having a desired characteristic may be used depending on the application and specifications. For example, you may use light sources, such as a fluorescent tube, a cold cathode tube, a hot cathode tube, an external electrode tube, LED, organic EL, inorganic EL.

  The number of light sources arranged for one backlight unit may be appropriately determined according to specifications, and it is sufficient that at least one light source is provided. In particular, in the case of a point light source such as an LED light source, it is preferable to arrange a plurality of light sources. For example, LED groups arranged in a row or semiconductor laser groups arranged in a row may be used. Further, when a plurality of light sources are arranged, they may be arranged around the light guide plate. For example, in the case of a quadrilateral light guide plate, 1) a configuration in which light sources are arranged on one side, 2) a configuration in which light sources are arranged on two sides, 3) a configuration in which light sources are arranged on three sides, and 4) light sources on four sides. Any of the arrangement to arrange may be sufficient.

  Moreover, when arrange | positioning a light source, it is preferable that the depth dimension of a light source is comparable as the depth dimension of a light-guide plate. By making the depth dimension of the light source approximately the same as the depth dimension of the light guide plate, when the light source is arranged on the side end surface of the light guide plate as an edge light type light guide plate, the light guide plate does not lose light from the light source Can be guided in.

  Moreover, the above-described backlight unit may further include an optical sheet disposed on the emission surface of the light guide plate. A display device having desired display performance can be provided by appropriately combining with a known optical sheet. Moreover, you may combine multiple types of optical sheets so that desired brightness | luminance and a viewing angle may be acquired.

  For example, as the optical sheet, a sheet in which unit prisms having a triangular cross section are arranged at a constant pitch in one direction may be used. The unit prism has a size (pitch) larger than the wavelength of the incident light, and therefore collects light from “off-axis” and directs this light toward the viewer “on-axis”. (On-axis) "can be redirected or" recycled ".

  Further, for example, an optical sheet on which a lenticular lens in which convex cylindrical lenses are arranged in parallel, a micro lens arranged in a matrix shape, or the like may be used. At this time, as the lens shape, a well-known appropriate lens surface shape, for example, a spherical surface, an elliptical surface, or the like may be adopted according to the required light collecting performance. Further, in order to improve the light collection efficiency, an aspherical shape in which an ellipsoidal surface is used as a reference surface and correction is performed by a high-order term may be used.

  Further, in the above-described backlight unit, a reflector may be disposed at a lower portion on the lower layer side of the light guide plate. By disposing a reflector having light reflectivity, light that has passed to the lower layer side can be reflected to the upper layer side, and the light extraction efficiency can be improved. As a reflector, for example, (1) a resin sheet in which a void is formed by kneading and stretching a filler in PET, PP or the like to increase the reflectance, and (2) a mirror surface by aluminum deposition on the surface of a transparent or white resin sheet (3) A metal foil such as aluminum or a resin sheet carrying a metal foil, (4) a metal thin plate having sufficient reflectivity on the surface, or the like may be used.

The display device of the present invention will be described below.
The display device of the present invention includes the above-described backlight unit and an image display element arranged so that light emitted from the backlight unit is incident from the back side.

  The image display element can display a desired image as a display image by switching a plurality of pixels. As the image display element, for example, a liquid crystal display element, a liquid crystal display element provided with a color filter, an organic EL element, an inorganic EL element, a film, or the like may be used. Depending on the image display element to be used, a projection screen device, a plasma display, an EL display, a liquid crystal display device, and the like are obtained.

FIG. 2 shows an example of the display device 1 of the present invention.
FIG. 2 shows the display device 1 in which the liquid crystal display element 3 / backlight unit 2 are arranged in order as viewed from the observation surface direction S. FIG.
The liquid crystal display device 3 has a configuration in which a liquid crystal element 10 is sandwiched between polarizing plates 9.
The backlight unit 2 has a configuration in which an optical sheet is disposed in the lamp house 6.
In FIG. 2, three types of optical sheets are arranged, and when viewed from the observation surface direction S, a polarizing optical sheet 31 having a polarization function / light collecting in which prismatic patterns 43 are arranged in parallel so as to spread light uniformly. The optical sheet 33 / a diffusing optical sheet 35 / molded with a lens pattern 43a on the transparent substrate 41 so as to have a light collecting function is arranged in this order.
In the lamp house 6, the light source 176 is disposed on the light incident surfaces 56 that are the side ends of the both ends of the light guide plate 50 of the present invention, the reflector 60 is disposed on the lower layer 52 side of the light guide plate 50, and light is emitted from the light emitting surface 57. Is emitted.
In the light guide plate 50, an upper layer 55 / main layer 53 / lower layer 52 are laminated in this order, and an upper layer uneven pattern 54 is formed on the outer surface of the upper layer 55, and a lower layer uneven pattern 181 is formed on the outer surface of the lower layer 52.

  In FIG. 2, the light emitted from the light source 176 enters the light guide plate 50 directly or after being reflected by the reflector 60. The light incident on the light guide plate 50 passes through the inside of the light guide plate 50 and is emitted from the emission surface 57 directly after being reflected by the fine uneven pattern 181. The light emitted from the light guide plate 50 passes through the diffusing optical sheet 35, the condensing optical sheet 33, and the polarizing optical sheet 31, and in the liquid crystal display unit 3, each pixel region controlled by a driving unit (not shown) based on the image signal. Depending on the polarization state, light from a predetermined pixel region is transmitted as display light, and image display is performed when observed from the observation plane direction S.

<Simulation>
In the light guide plate of the present invention, the relationship between (L / D) and luminance when the mean free path L (mm) of light in the main layer and the refractive index difference D between the main layer and the light diffusing fine particles are as follows: A simulation using a computer was performed. The condition settings are shown below.

(Light guide plate set by simulation)
Upper layer: PMMA resin (refractive index: 1.4907, thickness: 0.15 mm, uneven pattern: lenticular lens pattern)
Main layer: PMMA resin (refractive index: 1.4912, thickness: 1.7 mm)
Lower layer: PMMA resin (refractive index: 1.4907, thickness: 0.15, uneven pattern: dot pattern) Total thickness: 2 mm

(Variables set by simulation)
For the diffusing fine particles in the main layer, the refractive index was set as a variable, and (L / D) was set. Cases 1 to 6 are shown below. In addition, the structure which does not contain diffusion fine particles as a reference was prepared as Reference Example 1. In Comparative Example 1, since the refractive index difference D = 0.000, the light in the main layer travels to infinity, so L / D is also infinite.

Case 1: (Refractive index difference D: 0.005, mean free path L: 1.5 mm, L / D: 300)
Case 2: (Refractive index difference D: 0.005, mean free path L: 3.2 mm, L / D: 650)
Case 3: (Refractive index difference D: 0.005, mean free path L: 6.0 mm, L / D: 1200)
Case 4: (Refractive index difference D: 0.110, mean free path L: 319.0 mm, L / D: 2900)
Case 5: (Refractive index difference D: 0.090, mean free path L: 315.0 mm, L / D: 3500)
Case 6: (Refractive index difference D: 0.005, mean free path L: 20.0 mm, L / D: 4000)
Comparative Example 1: (Refractive index difference D: 0.000, mean free path L: infinity, L / D: infinity)

(Luminance evaluation set by simulation)
The light guide plate set in the simulation was set to be incorporated in a backlight unit of LG 23 inch monitor E2360 (horizontal visual field direction 520 mm width), and the luminance of the observation surface and the horizontal visual field direction were evaluated. At this time, the integrated luminance of Comparative Example 1 was set to 1, and cases 1 to 6 were evaluated as an integrated luminance ratio.

(simulation result)
The simulation results are shown in Table 1 and FIG.

  Table 1 shows the relationship between the integrated luminance ratio and L / D. From Table 1, it was confirmed that the luminance was improved by 1% or more as compared with the structure containing no diffusing fine particles when the L / D was 4000 or less.

  FIG. 3 is a graph showing the results showing the L / D and the luminance distribution in the horizontal direction of the screen. At this time, the horizontal axis indicates the horizontal direction (mm) of the screen, and 0 is the light source position. As can be seen from FIG. 3, when L / D is less than 1000, more light is emitted toward the light source than the center position of the screen, and the luminance is attenuated at a position far from the light source. Therefore, it was confirmed that L / D is preferably 1000 or more.

  From the above results, it was suggested from the simulation results that the luminance is improved when L / D satisfies the relationship of 1000 ≦ L / D ≦ 4000.

<Example 1>
The light guide plate of the present invention was actually produced and evaluated for luminance.

<Production of light guide plate>
The material of the upper layer / main layer / lower layer was put into an extrusion die, and three layers were co-extruded to form an uneven pattern on the upper layer and the lower layer, and the light guide plate of the present invention was produced by an extrusion method. Hereinafter, the specification of the used material and a light-guide plate is shown.

(Material of light guide plate: Example 1)
Upper layer: PMMA resin (Product name: Acrypet (registered trademark) TF9 manufactured by Mitsubishi Rayon, MFR = 20, uneven pattern: lenticular lens pattern)
Main layer: PMMA resin (Product name: Acrypet VH000 manufactured by Mitsubishi Rayon, MFR = 2)
Lower layer: PMMA resin (Product name: Acrypet TF9 manufactured by Mitsubishi Rayon, MFR = 20, uneven pattern: dot pattern)
Total thickness: 2mm
Diffusion fine particles: Spherical fine particles (Product name: True Spherical Techpolymer (registered trademark) manufactured by Sekisui Plastics Co., Ltd., particle size 10 μm, refractive index 1.495)
Mean free path D of main layer D = 5.0
L / D = 1000

<Luminance evaluation>
The above-mentioned light guide plate was placed in the backlight so that the light source was located on the end surface on the light guide plate side, and the integrated luminance was measured from the observation surface side. At this time, evaluation was performed using a backlight unit system of an LED light source liquid crystal TV (LG 23inch monitor E2360). In addition, a spatial luminance meter (product name: ProMetric (PM-1200) manufactured by Cybernet) was used for measurement of integrated luminance.

<Example 2>
A light guide plate was produced in the same manner as in Example 1, and the integrated luminance was measured.
However, the addition amount of the diffusing fine particles in the main layer was adjusted so that the mean free process D = 19.0, and L / D = 3800.

<Example 3>
A light guide plate was produced in the same manner as in Example 1, and the integrated luminance was measured.
However, the diffusion fine particles to be used were spherical fine particles (product name: Sekisui Plastics Co., Ltd. true spherical techpolymer, particle size 10 μm, refractive index 1.530), and the addition amount was adjusted so that L / D = 1500.

<Example 4>
A light guide plate was produced in the same manner as in Example 1, and the integrated luminance was measured.
However, the diffusion fine particles to be used were spherical fine particles (product name: Sekisui Plastics Co., Ltd. true spherical techpolymer, particle size 8 μm, refractive index 1.590), and the addition amount was adjusted so that L / D = 3000.

<Comparative example 2>
A light guide plate was produced in the same manner as in Example 1, and the integrated luminance was measured.
However, the main layer does not contain diffusion fine particles.

<Integrated luminance evaluation result>
The evaluation of integrated luminance for Examples 1 to 4 and Comparative Example 2 are summarized in Table 2 and FIG.

  Table 2 shows the relationship between the integrated luminance ratio and L / D. From Table 2, as in the simulation, the light guide plate of the present invention containing the light diffusing fine particles was confirmed to improve the integrated luminance as compared with Comparative Example 2 not containing the light diffusing fine particles.

  FIG. 4 is a graph showing the results showing the L / D and the luminance distribution in the horizontal direction of the screen. At this time, the horizontal axis indicates the horizontal direction (mm) of the screen, and 0 is the light source position. As can be seen from FIG. 4, when L / D is less than 1000, more light is emitted toward the light source than the center position of the screen, and the luminance is attenuated at a position far from the light source. Therefore, it was confirmed that L / D is preferably 1000 or more.

  From the above, it was confirmed that the actually produced light guide plate of the present invention shows the same tendency as in the simulation. Therefore, it was confirmed that the luminance is improved when L / D satisfies the relationship of 1000 ≦ L / D ≦ 4000.

  The light guide plate of the present invention can be widely used for applications in which incident light from a light source is diffused in the surface direction. For example, it is expected to be used for applications such as image display devices typified by flat panel displays, 3D liquid crystal display devices, color notebook PCs (personal computers), lighting fixtures, and building materials.

Light guide plate ... 50
Upper layer ... 55
Main layer ... 53
Lower layer ... 52
Light diffusing particles ... 51
Upper layer uneven pattern ...... 54
Lower layer uneven pattern 181
Liquid crystal display element 3
Backlight unit ...... 2
Display device ... 1
Liquid crystal element ... 10
Polarizing plate ...... 9
Lamp house …… 6
Polarizing optical sheet ... 31
Prism pattern ...... 43
Condensing optical sheet ... 33
Transparent substrate ...... 41
Lens pattern ... 43a
Diffusion optical sheet ...... 35
Light incident surface ... 56
Light source 176
Reflector ... 60
Light exit surface ...... 57

Claims (5)

A light guide plate that diffuses light in a plane direction,
The main layer,
An upper layer laminated above the main layer;
A lower layer laminated below the main layer,
The main layer is a layer containing light diffusing fine particles,
The upper layer is a layer having a concavo-convex pattern formed on the surface,
The light guide plate according to claim 1, wherein the lower layer is a layer having a concavo-convex pattern formed on a surface thereof.   2. The light guide plate according to claim 1, wherein the thermal fluidity of the resin used for the main layer is higher than the thermal fluidity of the resin used for the upper layer and the thermal fluidity of the resin used for the lower layer. Mean free path L (mm) of light in the main layer,
When the refractive index difference D between the main layer and the light diffusing fine particles,
L / D satisfies 1000 <= L / D <= 4000, The light-guide plate in any one of Claim 1 or 2 characterized by the above-mentioned.   The backlight unit using the light-guide plate in any one of Claim 1 to 3.   A display device using the backlight unit according to claim 4.

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