JP4673463B2 - Liquid crystal display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a good light utilization efficiency liquid crystal display equipment.
[0002]
[Prior art]
In recent years, there has been a remarkable spread of liquid crystal display devices using surface light source devices as displays, and currently popular liquid crystal display devices obtain polarized light (obtained by transmitting light through a polarizing plate). This is a method of modulating with a liquid crystal layer.
[0003]
Typical conventional surface light source device 70 in FIG. 1 2, and shows the configuration of a liquid crystal display device 72 including the same. In the surface light source device 70, the light emitted from the light source 52 enters the light guide 54 and travels while repeating total reflection. A part of the light traveling in the light guide 54 is changed in the traveling direction by the light scatterer 56 and is emitted to the outside of the light guide. The light emitted downward from the light guide 54 in the figure is reflected by the reflection sheet 58 and returned to the inside of the light guide 54 again, while the light emitted upward in the figure is diffused by the diffusion sheet 60, The light is condensed by the prism sheet 62, is incident on the liquid crystal cell 64 sandwiched between the polarizing plates 66 and 68, and used as a back light source.
[0004]
Also it indicates 1 3 and 1 4 is also of conventional surface light source device 70A, 70B, and a liquid crystal display device 72A including the same, and 72B. In in the surface light source device 70A in FIG. 1 3, relative to the surface light source device 70 of FIG. 1 2, a diffusion sheet 60 and the prism sequence of sheet 62 is reversed, and the prism surface light guide side 54 of the prism sheet 62 It is the structure which faced. Further, in the in the surface light source device 70B in FIG. 1 4, on the prism sheet 62, a structure of repeating different prism sheet 62A having a triangular prism perpendicular to the triangular prism the orientation of the prism sheet 62.
[0005]
As described above, since the used polarizing plates 66 and 68 absorb about half of the incident light, the light use efficiency is low. Therefore, in order to obtain satisfactory brightness, more light must be incident on the polarizing plate, but not only the power consumption of the light source increases, but also the heat from the light source adversely affects the liquid crystal. There were various problems such as making the display difficult to see.
[0006]
From this point of view, various proposals have been made to date. As one example, a polarization separator that separates non-polarized light from a light source into two linearly polarized lights that are orthogonal to each other is used, and one of the separated polarized lights is directly used, and the other polarized light is also regenerated. There is something to use. That is, out of the polarized light components separated by the polarized light separator, one polarized light component is incident on the liquid crystal cell, the other polarized light component is returned to the light source side, and the light is guided to the polarized light separator again by reflection and reused. This is a technique for improving the light utilization efficiency.
[0007]
For example, firstly, the technique disclosed in Japanese Patent Laid-Open No. 4-184429 separates non-polarized light from the light source device into two polarized lights that are orthogonal to each other by a polarization separator, and one polarized light is separated. The light is emitted directly toward the liquid crystal cell, and the other polarized light is returned to the light source side to be converged, and then reflected and reused as light source light again.
[0008]
Second, there is a backlight disclosed in Japanese Patent Laid-Open No. 6-265892. This is because the light emitted from the light guide surface side of the planar light guide is almost equal to the surface of the planar light guide. A light control sheet is provided so as to be vertical, and a polarization separating means is further disposed thereon.
[0009]
Furthermore, as the third, there is a backlight disclosed in Japanese Patent Application Laid-Open No. 7-261122, which is located on the exit surface side of a parallel light flux conversion element composed of a light scattering light guide including a volume region having a wedge-shaped cross section. A polarization separator is disposed.
[0010]
[Problems to be solved by the invention]
However, the conventional techniques have the following problems.
[0011]
The first technique is directed to a projection-type liquid crystal display device, and the configuration of the illumination device requires a spatial space and cannot be applied to a flat-type liquid crystal display device that is required to be thin.
[0012]
The second technique is suitable for thinning, but the polarization separator has excellent light when the polarization separation layer is formed on the slope of a columnar prism array having a triangular cross section. Although utilization efficiency has been obtained, the structure of the polarization separator is complicated, and it is difficult to form a polarization separation layer on the sloped part of the columnar prism array with a triangular cross section, and it is said to be excellent in mass productivity. It was difficult.
[0013]
The third technique has excellent light utilization efficiency when a parallel luminous element made of a specific light-scattering light guide including a volume region having a wedge-shaped cross section is used as the light guide. It is difficult to make the light scattering light guide have a specific light scattering ability, and it is difficult to say that it can be used generally.
[0014]
In view of the above problems, the present invention can improve the light utilization efficiency by controlling the light directivity and the polarization direction, and can be made thin with a relatively simple configuration and can be mass-produced. An object is to provide an excellent prism sheet, a surface light source device, and a liquid crystal display device.
[0015]
[Means for Solving the Problems]
According to a first aspect of the present invention, a light source, a light guide that makes light from the light source incident from a side surface, and emits polarized light having directivity having maximum intensity in a first predetermined direction, the light guide A prism that is arranged on the exit surface side of the body and directs the polarized light in the first predetermined direction in the second predetermined direction within a certain angle centered on the normal direction of the light guide output surface A liquid crystal display device comprising: a surface light source device including a sheet; and a first polarizing plate, a liquid crystal cell, and a second polarizing plate, which are sequentially disposed on the light guide, The prism sheet is arranged on the light incident side of the first polarizing plate, and is made of a biaxially stretched film in which molecules are oriented. The prism sheet has an in-plane refractive index anisotropy and passes therethrough. and the base sheet to control the polarization direction of the light, a prism layer provided on the light guide side of the base sheet Has, and a prism constituting the prism layer, the ridge line direction is made are arranged such that the side face the same direction as the incident light of the light guide, it passes through the base sheet polarized along with the polarization direction, and the first polarization axis substantially the same direction as the polarizing plate, it is arranged to have a ridge line direction and a predetermined angle of the prism, said base sheet, said first polarization A biaxially stretched film raw material is prepared so that the polarization axis direction of the plate, the polarization direction of the polarized light that has passed through the base sheet , and the ridge line direction of the prisms constituting the prism layer are arranged as described above. The above-described problems are solved by a liquid crystal display device characterized by the above.
[0016]
That is, the prism sheet controls the emission direction of the incident polarized light by the prism layer, and the polarization direction of the incident polarized light to the emission surface side by the translucent substrate having birefringence. The polarization axis of the polarizing plate disposed substantially parallel to the emission surface is set to be substantially in the same direction.
[0017]
Therefore, by using the prism sheet on the incident side of the liquid crystal cell, the amount of light absorbed by the polarizing plate can be reduced and the light utilization efficiency can be improved. Further, the light emitted from the light guide in the first predetermined direction is polarized directional light having a high p component ratio, and can be used as incident light of the prism sheet to increase the light use efficiency. can do.
[0021]
According to a second aspect of the present invention, in the first aspect , the light guide has a plate shape, and has light scattering means for emitting internal light from the emission surface. A light scattering layer in optical contact with a surface opposite to the surface or the exit surface, a rough surface formed on the exit surface or a surface opposite to the exit surface, or contained in the light guide. A liquid crystal display device characterized in that it is one of the light scattering materials.
[0022]
According to a third aspect of the present invention, in the first or second aspect , the prism sheet is formed by forming the prism layer on the light guide side, and the prism layer includes a plurality of unit prisms and has an uneven surface. This is a liquid crystal display device.
[0023]
A fourth aspect of the present invention is the liquid crystal display device according to any one of the first to third aspects, wherein the base sheet is a polyethylene terephthalate film.
[0024]
A fifth aspect of the present invention is the liquid crystal display device according to any one of the first to fourth aspects, wherein a diffusion sheet is disposed on the exit surface side of the prism sheet.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a liquid crystal display device including a prism sheet and a surface light source device according to an example of an embodiment of the present invention will be described in detail with reference to the drawings.
[0027]
As shown in FIG. 1, a liquid crystal display device 10 according to an example of an embodiment of the present invention is arranged on a surface light source device 20 including a prism sheet 22 and a light emission surface side of the surface light source device 20. And a liquid crystal panel 30.
[0028]
The surface light source device 20 includes at least a light source 24 and light from the light source 24 that is incident on the left side end surface 26A in FIG. 1 from a top surface with directional light having a maximum intensity in a first predetermined direction D1. And the directional light in the first predetermined direction D1 is directed in the second predetermined direction D2 having the maximum luminance on the viewing side of the liquid crystal panel 30, and polarized light. The prism sheet 22 that emits light to the liquid crystal panel 30 by controlling the polarization direction S of the light, and the light diffusion reflection sheet 29 disposed on the opposite side of the light guide 26 from the prism sheet 22. Yes. A cold cathode tube or the like is used for the light source 24.
[0029]
The light guide 26 emits directional light, which is polarized light having a maximum intensity in the first predetermined direction D1 and a high ratio of the p component, from the light exit surface from the light incident from the one side end face 26A. It is what has.
[0030]
The principle that the light guide guides light is that light is totally reflected when the incident angle θ1 reaches θc in the following equation 1 at the boundary surface of the optically dense (refractive index n1) and sparse (refractive index n2) medium. Is used, and θc is called a critical angle.
[0031]
sin θc = n2 / n1 (Formula 1)
[0032]
Therefore, the emitted light from the light guide is obtained by making the incident angle θ1 smaller than the critical angle θc by some method. At this time, in the region of incidence angle is slightly smaller than the critical angle as shown in FIG. 8 (A), in light of the s component having a vertical amplitude and the p-component light by the incident angle θ1 is, p components by the incident angle θ1 Therefore, the light reflected inward by the light guide exit surface can be converted into polarized light having a high ratio of the s component. For example, when n1 is 1.5 and n2 is 1.0, when θ1 is 33 ° 41′24 ″, the reflectance of the p component is 0. Therefore , this is not reflected and is emitted from the light guide exit surface. The reflected light can be polarized light having only the s component, and as a result, polarized light having a large p component is emitted from the exit surface of the light guide.
[0033]
In this way, by making the incident angle θ1 slightly smaller than the critical angle θc, the light emitted from the light guide 26 of the present invention is emitted as polarized light having a large p component, and the incident angle θ1 is specified. Therefore, the emission angle is also limited to a specific small area. That is, polarized light having the maximum intensity in the first predetermined direction D1 and a high ratio of the p component can be emitted from the emission surface 26B.
[0034]
The material of the light guide is not particularly limited as long as it has a property of transmitting light efficiently, and is, for example, an acrylic resin such as PMMA, a polycarbonate resin, or glass.
[0035]
As shown in FIG. 1, the first predetermined direction D1 is generally the one side end surface with respect to the normal direction of the emission surface 26B, considering the emission surface 26B of the light guide 26 as a reference. The direction is opposite to the light source 24 arranged in the vicinity of 26A.
[0036]
As a directional light having the maximum luminance in the first predetermined direction D1, for example, diffused light (this diffused light is not completely diffused light having no directivity) is emitted from the light guide 26 as a light guide. 26 is formed into a plate shape (for example, a plate shape, or a wedge shape whose thickness decreases as the distance from the one end surface 26A on which the light source 24 is disposed), and the light guide 26 is provided with light scattering means.
[0038]
As the light scattering means, for example, as shown in FIG. 1, a light scattering layer 28 </ b> A in which a light scattering agent such as silica is dispersed in a resin on the surface opposite to the exit surface 26 </ b> B of the light guide 26 (usually Has a structure in which dots are formed by printing or the like and optically contacted.
[0039]
In addition, as shown in FIG. 2, a light scattering layer 28 </ b> B in which a light scattering agent such as silica is dispersed in a resin is provided on the emission surface 26 </ b> B of the light guide 26 by printing or the like, and optically contacted. Structure, as shown in FIG. 3, a structure in which the exit surface of the light guide 26 is a rough surface 28C, and as shown in FIG. 4, a surface (back surface) opposite to the exit surface 26B is a rough surface 28D. As shown in FIG. 5, the inside of the light guide 26 has a refractive index different from that of the substance (for example, PMMA: refractive index 1.49) constituting most of the light guide 26, and A light scattering agent 28E made of a translucent substance (for example, silicone resin: refractive index 1.43) is contained in a particle diameter of 5 μm or less and 1% by weight or less of the entire light guide plate to guide the light. Any means of making the body material itself light-scattering may be adopted.
[0040]
In the case of using the light scattering agent 28E, if the particle diameter is larger than 5 μm, the directivity of the emitted light from the light guide 26 approaches that of completely diffused light, and even if the content exceeds 1% by weight, it is emitted from the light guide. The luminance uniformity of the surface 26B deteriorates, which is not preferable.
[0041]
The prism sheet 22 is a means for changing the path of the light beam. In this case, as shown in FIG. 6 , the light beam in the first predetermined direction D1 incident from the light guide 26 is secondly reflected by total reflection inside the prism. The predetermined direction D2 is changed to be emitted.
[0042]
To be more specific, as shown enlarged in FIG. 9 (A), the prism sheet 22 in cross section a triangular prism triangular prism triangular units prisms 22A, has a number sequence prismatic structure the unit prisms, The unevenness due to the prism structure makes the cross-sectional shape on the light guide 26 side substantially V-shaped.
[0043]
The slope of the triangular prism in cross section is an inequilateral triangle in which the light source side slope 23A is steeper than the anti-light source side slope 23B. This is because the directional light that is emitted from the light guide exit surface 26B is inclined with respect to the prism incident surface, for example, in a substantially normal direction.
[0044]
Incidentally, the prism sheet 32 may be provided forming a prism 32B on the base sheet 32A as shown in FIG. 9 (B).
[0045]
In addition, the non-prism surface on the opposite side of the prism 32B of the prism sheet 32 is for diffusibility for expanding the viewing angle, preventing interference due to close contact with other members, or concealing appearance defects such as scratches. The mat surface 32C may be formed as necessary. As means for forming the mat surface 32C, matting agent coating, embossing, or the like can be used.
[0046]
The prism sheet forming material functions as long as it has a property of efficiently transmitting light. For example, a polyester resin such as polycarbonate (PC) or polyethylene terephthalate (PET), or an acrylic such as polymethyl methacrylate (PMMA). There are resin, glass and the like. Among them, the one in which the prism 32B is formed on the base sheet 32A such as PET or PC by using an ultraviolet curable resin is preferable in that a fine prism shape can be accurately formed, and the most excellent in mass productivity. Is also preferable.
[0047]
In this case, the refractive index of the prism formed of the ultraviolet curable resin is preferably large, specifically 1.4 or more, more preferably 1.5 or more. In order to form a prism shape with an ultraviolet curable resin on the base film, a technique disclosed in JP-A-5-169015 may be used.
[0048]
That is, coating and filling the rotating roll intaglio plate having a concave and convex concave shape with respect to the prism shape with an ultraviolet curable resin liquid, then supplying the base sheet to this and pressing the roll intaglio plate over the resin liquid on the plate surface, In the pressed state, after curing the resin liquid by irradiating ultraviolet rays, the prism sheet can be continuously produced by peeling the solidified ultraviolet curable resin from the roll intaglio rotating with the base sheet.
[0049]
Further, as described later, a stretched film may be used as the base sheet 32A as necessary. The material of the stretched film is not particularly limited as long as it has translucency. Polyester resin such as polyethylene terephthalate (PET), acrylic resin such as polycarbonate (PC) and polymethyl methacrylate (PMMA), TAC (cellulose triacetate) Biaxially stretched PET is particularly desirable from the viewpoint of mechanical, chemical and optical performance.
[0050]
Next, a method of controlling the polarization direction in the prism sheet 22 and its effect will be described. FIG. 7 shows that the light in the first predetermined direction D1 emitted from the light guide is directed by the prism of the prism sheet 22 in the second predetermined direction (in this case, the normal direction of the liquid crystal panel) D2. It is shown.
[0051]
At this time, for example, when the refractive index n1 of the prism portion is 1.50, the refractive index n2 of air is 1.0, so θc is 41 ° 48′37 ″, and if the incident angle θ2 ≧ θc, Incident light is totally reflected.
[0052]
As shown in FIGS. 8B and 8C, in the total reflection region (θ2 ≧ θc), p-component light having an amplitude within the incident surface and s-component light having an amplitude perpendicular to the p-component light. In this case, the phase changes depending on the incident angle θ2, and the light is emitted. The reason for this is not clear, but this affects the polarization direction of the emitted polarized light.
[0053]
By aligning the polarization direction of polarized light incident on the liquid crystal panel with the polarization axis of the liquid crystal panel, the light absorbed by the polarizing plate can be reduced, so that the light incident on the liquid crystal panel can be used effectively. Thus, by controlling the incident angle θ2, it is possible to improve the light utilization efficiency.
[0054]
However, it is difficult to control both the reflection angle and the polarization direction of the polarized light at the incident angle θ2, and it is difficult in practice. Therefore, the film is stretched in a predetermined direction having anisotropy of refractive index in the plane. The stretched film is used as the base sheet 32A of the prism sheet 32, or the stretched film is laminated on the exit surface side of the prism sheets 22 and 32, and used as means for controlling the polarization direction of the polarized light.
[0055]
The material of the stretched film is not particularly limited as long as it has translucency. Polyester resin such as polyethylene terephthalate (PET), acrylic resin such as polycarbonate (PC) and polymethyl methacrylate (PMMA), TAC (cellulose triacetate) Biaxially stretched PET is particularly desirable from the viewpoint of mechanical, chemical and optical performance.
[0056]
General biaxially oriented PET, as shown in FIG. 1 0, during roll manufacturing are stretched in the machine flow direction and the width direction, the orientation in the lateral slanting directions a central alignment direction machines of the molecule as a boundary is doing. By being oriented in this way, the refractive index in the width direction and the flow direction are different, and the polarization direction of polarized light can be adjusted by passing through such a film.
[0057]
Figure 1 1 shows the relationship between the polarization axis D4 of the first polarizer 30B used in the polarization direction D3 and the liquid crystal cell 30A of the polarized light emitted from the prism sheet 22. As described above, in the stretched film used for the base sheet 32A of the prism sheet 32, the molecules are oriented in any one of the left and right oblique directions with respect to the length direction of the raw roll, and the polarization axis D5 of the base sheet 32A is It forms a predetermined angle α with the ridge line direction of the prism. The light utilization efficiency is improved because the polarization direction D3 of the polarized light passing through the base sheet 32A and the polarization axis D4 of the first polarizing plate 30B on the surface light source side are the same direction. Reference numeral 30C denotes a second polarizing plate.
[0058]
As described above, in the surface light source of the present invention, the emission direction of directional light, such as diffused light, emitted from the light guide and having a high p- component ratio and maximum intensity in the first predetermined direction D1 is described above. Using the prism sheet 22, the polarization direction D3 of the polarized light is controlled so as to be directed in the second predetermined direction (usually the normal direction of the liquid crystal display device) D2 and to have the maximum transmittance in the liquid crystal panel. As a result, the light utilization efficiency in the liquid crystal display device can be improved.
[0059]
Moreover, since the prism sheets 22 and 32 are planar, they can be formed as a thin surface light source as compared with the case where the multilayer film is provided on the inclined surface, and are preferable because they are not bulky even in the case of a liquid crystal display device.
[0060]
The surface light source device of the present invention, if necessary, as with conventional surface light source device 70 and 70A, 70B (see FIG. 1. 2 to FIG. 1 4), shown by the two-dot chain line in FIG. 1 diffusion In addition to the sheet 40, a lens sheet or the like may be used in combination, and the present invention is not limited to the example of the above embodiment without departing from the spirit of the present invention.
[0061]
【Example】
Examples of the present invention and comparative examples will be described below.
[0062]
As shown in FIG. 1, a light source 24, a light guide 26 that emits a diffused light beam having a maximum intensity in an oblique direction, and a dot-like light scattering layer 28A printed on the back surface, and a unit prism 22A is a triangular prism. (The cross section is an unequal triangle with the light source side steeper than the non-light source side), and a prism sheet 22 having a prism surface facing the light guide 26 side and a light diffusing and reflecting sheet 29 made of a white polyethylene terephthalate sheet are guided. placed near the optical body back side, as shown in FIG. 1 1, the orientation direction of molecules in the width direction of the roll to the base sheet 32A of the prism sheet 32 using a different biaxially oriented PET raw, the stretching Prepare a prism sheet so that the polarization direction D3 of the polarized light generated by the direction is substantially the same as the polarization axis D4 of the first polarizing plate 32B on the surface light source side, and arrange it on the surface light source. It was.
[0063]
Furthermore, when the polarizing plate was placed on the surface light source according to the polarization axis direction used in the liquid crystal panel and the luminance of the light emitted from the polarizing plate was measured, the polarization direction was opposite to that of the same direction. In the direction, the maximum luminance (the luminance in the direction giving the maximum value) was 1020 cd / m 2 and 910 cd / m 2, respectively, and a difference of about 10% was recognized.
[0064]
【The invention's effect】
According to the present invention, the light use efficiency in the liquid crystal display device can be improved with a relatively simple configuration. In addition, since the surface light source device and the prism sheet are planar and can be reduced in thickness, the liquid crystal display device can be reduced in thickness.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a liquid crystal display device according to an example of an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a second example of an embodiment of a light guide. FIG. 4 is a cross-sectional view showing a fourth example of another embodiment of the light guide. FIG. 5 is a cross-sectional view showing a fifth example of another embodiment of the light guide. 6] s component for the cross-sectional view showing an example of an embodiment of a prism sheet [schematic diagram FIG 7 shows the prism principle of a prism sheet [Fig. 8 (a)] incident angle, the graph showing the reflectance of light of the p component [Figure 8 (B)] s component with respect to the incident angle, s component for the graph Figure 8 (C)] incidence angle representing the phase change of the light p components, the graph [graph showing changes in phase difference of the light p components 9 (A)] Enlarged perspective view showing an example of an embodiment of a prism sheet. FIG. 9 (B)] Example of another embodiment of a prism sheet [FIG. 1 0 ] Schematic diagram of the direction of stretching and the direction of molecular orientation when producing biaxially stretched PET [FIG. 1 1 ] The polarization axis of the prism sheet substrate, the first on the liquid crystal cell side the polarization axis of the polarizing plate, and a cross-sectional view showing an example of a polarized light of a schematic view showing the relationship between the polarization direction [1 2] conventional surface light source and liquid crystal display device [1 3] conventional surface light source and liquid crystal cross-sectional view showing another example of a cross-sectional view FIG. 1 4] conventional surface light source and liquid crystal display device showing another example of a display device dESCRIPTION oF REFERENCE nUMERALS
DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display device 22, 32 ... Prism sheet 24 ... Light source 26 ... Light guide 26B ... Outgoing surface 28A ... Light scattering layer 28B ... Light scattering layer 28C, 28D ... Rough surface 28E ... Light scattering agent 29 ... Light diffuse reflection sheet 30 ... Liquid crystal panel 30A ... Liquid crystal cell 30B ... First polarizing plate 30C ... Second polarizing plate 32A ... Base sheet 32B ... Prism 40 ... Diffusion sheet D1 ... First predetermined direction D2 ... Second predetermined Direction D3: Polarization direction of polarized light D4: Polarization axis of first polarizing plate D5: Polarization axis of base sheet

Claims (5)

A light source, a light guide that enters light from the light source from a side surface and emits polarized light having directivity having a maximum intensity in a first predetermined direction, disposed on an output surface side of the light guide, A surface light source device comprising a prism sheet that emits polarized light in one predetermined direction in a second predetermined direction within a certain angle centered on a normal direction of the light guide output surface; A liquid crystal display device having a first polarizing plate, a liquid crystal cell, and a second polarizing plate, which are sequentially disposed on the light guide, wherein the prism sheet is formed of the first polarizing plate. A base sheet which is arranged on the light incident side substantially in parallel with the biaxially stretched film in which molecules are oriented, has an in-plane refractive index anisotropy, and controls the polarization direction of polarized light passing therethrough ; and a prism layer provided on the light guide side of the base sheet, and the prism Prisms constituting, the ridge line direction is made are arranged such that the side face the same direction as the incident light of the light guide, the polarization direction of the polarized light that has passed through the base sheet, the first It is arranged so as to have a predetermined angle with the direction of the ridge line of the prism, and substantially in the same direction as the polarization axis of the polarizing plate,
The base sheet is arranged so that the polarization axis direction of the first polarizing plate, the polarization direction of the polarized light that has passed through the base sheet , and the ridge line direction of the prisms constituting the prism layer are arranged as described above. A liquid crystal display device prepared from an axially stretched film original fabric. 2. The light guide according to claim 1 , wherein the light guide has a plate shape and has light scattering means for emitting internal light from the emission surface, and the light scattering means is opposite to the emission surface or the emission surface. Any of a light scattering layer optically in contact with the surface on the side, a rough surface formed on the exit surface or a surface opposite to the exit surface, or a light scattering material contained inside the light guide A liquid crystal display device characterized by the above. According to claim 1 or 2, wherein the prism sheet is made by forming the prism layer to the light guide side, the said prism layer is composed of a plurality of unit prisms, liquid crystal display, characterized by forming the uneven surface apparatus. In any one of claims 1 to 3, a liquid crystal display device wherein the base sheet, characterized in that it is a polyethylene terephthalate film. In any one of claims 1 to 4, a liquid crystal display device which is characterized in that the diffusion sheet is disposed on the exit surface side of the prism sheet.

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