JP2001166116A - Prism sheet, surface light source and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the use efficiency of light in a liquid crystal display device. SOLUTION: The liquid crystal display device 10 comprises a surface light source device 20 including a prism sheet 22, and a liquid crystal panel 30 disposed in the exit face side of the surface light source device 20. The surface light source device 20 comprises a light source 24, a light guide body 26 to guide the incident light from the light source 24 to exit through the upper face as directional light having the maximum intensity in a first specified direction D1, and a prism sheet 22 in which the directional light in the first specified direction D1 is made to exit to the liquid crystal panel 30 while the directional light is converted into a specified second direction D2 so that the maximum luminance is obtained in the observation side of the liquid crystal panel 30 and while the polarizing direction S of the polarized light is controlled, and a light diffusion reflection sheet 29 disposed in the opposite side of the light guide body 26 to the prism sheet 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display device having good light use efficiency, a prism sheet used for the liquid crystal display device, and a surface light source device.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable spread of liquid crystal display devices using a surface light source device as a display, and currently widespread liquid crystal display devices use polarized light (by transmitting light through a polarizing plate). ) Is modulated by a liquid crystal layer.

FIG. 13 shows a conventional typical surface light source device 70,
And a configuration of a liquid crystal display device 72 including the same. In the surface light source device 70, light emitted from the light source 52 enters the light guide 54 and travels while repeating total reflection. A part of the light traveling inside the light guide 54 is changed its traveling direction by the light scatterer 56 and is emitted outside the light guide. 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 light emitted upward in the figure is diffused by the diffusion sheet 60, The light is condensed by the prism sheet 62, enters the liquid crystal cell 64 sandwiched between the front and back by the polarizing plates 66 and 68, and is used as a back light source.

FIGS. 14 and 15 also show conventional surface light source devices 70A and 70B and a liquid crystal display device 72 including the same.
A, 72B. In the surface light source device 70A shown in FIG. 14, the order of the diffusion sheet 60 and the prism sheet 62 is reversed with respect to the surface light source device 70 shown in FIG. It was the configuration that was. The surface light source device 70 in FIG.
In B, the prism sheet 6 is placed on the prism sheet 62.
In this configuration, another prism sheet 62A having a triangular prism orthogonal to the direction of the second triangular prism is stacked.

As described above, the polarizing plate 6 used
No. 6,68 absorbs about half of the incident light, so that the light use efficiency was low. Therefore, in order to achieve satisfactory brightness, more light must be incident on the polarizing plate, but not only does the power consumption of the light source increase, but also the heat from the light source adversely affects the liquid crystal. There have been various problems such as the display becoming difficult to see.

From such a viewpoint, various proposals as described below have been made up to the present. One of them is to use a polarized light separator that separates unpolarized light from a light source into two linearly polarized light beams that are orthogonal to each other, and directly uses one of the separated polarized light beams while reusing the other. There are things to use. That is, of the polarized light components separated by the polarized light separator, one of the polarized light components 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 or the like and reused. This is a technique for improving the light use efficiency.

For example, first, Japanese Patent Application Laid-Open No. 4-184429
The technology disclosed in the above publication separates unpolarized light from the light source device into two polarized lights having an orthogonal relationship with each other with a polarization separator, and emits one polarized light directly to a liquid crystal cell, and the other. After returning the polarized light to the light source side and converging, the reflected light is reflected and reused again as the light source light.

Secondly, there is a backlight disclosed in Japanese Patent Application Laid-Open No. 6-265892. The backlight is provided on the light exit surface side of the planar light guide so that the emitted light is directed to the surface of the planar light guide. A light control sheet that is substantially perpendicular to the light control sheet is provided, and a polarization separation unit is further disposed thereon.

[0009] Third, Japanese Patent Laid-Open Publication No. Hei 7-26111
Japanese Patent Laid-Open Publication No. 22-222, discloses a backlight in which a polarization beam splitter is arranged on the exit surface side of a parallel light beam generating element formed of a light scattering light guide including a volume region having a wedge-shaped cross section.

[0010]

However, each of the above-mentioned prior arts has the following problems.

The first technique is directed to a projection type liquid crystal display device, and the configuration of the illumination device requires a spatial space. Not applicable.

The second technique is suitable for thinning. However, when the polarized light separating body is formed by forming a polarized light separating layer on an inclined surface of a columnar prism array having a triangular cross section, Although excellent light use efficiency is obtained, the structure of the polarization separator is complicated, and it is particularly difficult to form a polarization separation layer on the slope of a columnar prism array with a triangular cross section, which is excellent in mass productivity. It was hard to say.

According to the third technique, when a parallel light beam forming element composed of a specific light scattering light guide including a volume region having a wedge-shaped cross section is used as the light guide, excellent light use efficiency is obtained. However, it is difficult to make the light-scattering light guide a specific light-scattering ability, and it is hard to say that it can be generally used.

The present invention has been made in view of the above problems,
Provided are a prism sheet, a surface light source device, and a liquid crystal display device that can control light directivity and polarization direction to improve light use efficiency, have a relatively simple structure, can be thin, and have excellent mass productivity. The purpose is to do.

[0015]

According to the present invention, a polarizing plate is disposed on a light incident side of a polarizing plate so as to be substantially parallel thereto.
A prism layer is provided on at least one surface of a birefringent light-transmitting substrate laminated on at least one sheet, and the polarization direction of polarized light that has passed through the light-transmitting substrate is the polarization direction of the polarizing plate. A prism sheet characterized in that the polarization axis direction of the light-transmitting substrate is arranged at a predetermined angle with respect to the ridge direction of the prism constituting the prism layer so as to be substantially in the same direction as the axis. Is the solution.

That is, the prism sheet controls the emission direction of the incident polarized light by the prism layer, and changes the polarization direction of the incident polarized light by the transparent base material having birefringence. On the surface side, the direction is set to be substantially the same as the polarization axis of the polarizing plate arranged substantially in parallel with the exit surface.

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 use efficiency can be improved.

According to a second aspect of the present invention, in the first aspect, the prism layer side is a plane of incidence of the polarized light, and the polarization direction of the polarized light that has passed through the translucent substrate is the polarization direction of the polarizing plate. A prism sheet characterized by being substantially in the same direction as an axis.

According to a third aspect of the present invention, there is provided a light source, a light guide that emits light from the light source from a side surface and emits polarized light having directivity having a maximum intensity in a first predetermined direction, and the light guide. The polarized light in the first predetermined direction, which is disposed on the emission surface side of the light body,
3. The prism sheet according to claim 1, wherein the prism sheet emits light in a second predetermined direction within a certain angle around a normal line direction of the light guide exit surface. 4. Surface light source device.

The light emitted from the light guide in the first predetermined direction is polarized directional light having a high s component ratio, and is used as incident light on the prism sheet according to claim 1 or 2. Thus, a surface light source device with high light use efficiency in the liquid crystal display device is obtained.

According to a fourth aspect of the present invention, in the third aspect, the light guide has a plate shape, and has light scattering means for emitting the internal light from the emission surface. A light scattering layer optically in contact with the light exit surface or the light exit surface, a rough surface formed on the light exit surface or the surface opposite to the light exit surface, or inside the light guide. A surface light source device characterized by being one of the light scattering agents contained in the surface light source.

According to a fifth aspect of the present invention, in the third or fourth aspect, the prism sheet has the prism layer formed on the light guide side, and the prism layer includes a plurality of unit prisms, and has an uneven surface. And a surface light source device.

According to a sixth aspect of the present invention, there is provided the prism sheet and the surface light source device according to any one of the first to fifth aspects, wherein the translucent substrate is a polyethylene terephthalate film.

According to a seventh aspect of the present invention, there is provided the surface light source device according to any one of the third to sixth aspects, wherein a diffusion sheet is disposed on the exit surface side of the prism sheet.

According to an eighth aspect of the present invention, the surface light source device according to any one of the third to seventh aspects, the polarizing plate, the liquid crystal cell, and the second polarizing plate are arranged in this order. A polarization direction of polarized light emitted from the surface light source device and a polarization axis of the polarizing plate are substantially the same direction.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a liquid crystal display device including a prism sheet and a surface light source device according to an embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, according to an embodiment of the present invention, a liquid crystal display device 10 includes a surface light source device 20 including a prism sheet 22 and a light emitting surface side of the surface light source device 20. And a liquid crystal panel 30 arranged.

The surface light source device 20 transmits at least a light source 24 and light incident from the light source 24 to a left side end surface 26A in FIG.
Light guide 26 which emits as the directional light having the maximum intensity
And directs the directional light in the first predetermined direction D1 in the second predetermined direction D2 such that the luminance is maximized on the viewing side of the liquid crystal panel 30, and controls the polarization direction S of the polarized light. The prism sheet 22 that emits light to the liquid crystal panel 30
And a light diffusion / reflection sheet 29 disposed on the opposite side of the light guide 26 from the prism sheet 22. As the light source 24, a cold cathode tube or the like is used.

The light guide 26 converts directional light, which is polarized light having a maximum intensity in the first predetermined direction D1 and having a high ratio of the s component, from the exit surface, from the light incident from one side end surface 26A. It has the characteristic of emitting light.

The principle that the light guide guides the light is that the incident angle θ1 reaches θc of the following equation 1 at the boundary surface between the optically dense (refractive index n1) and sparse (refractive index n2) medium. Then, the fact that total reflection occurs is used, and θc is called a critical angle.

Sin θc = n2 / n1 (Equation 1)

Therefore, the light emitted 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 a region where the incident angle is slightly smaller than the critical angle as shown in FIG.
Thus, in the s component light having an amplitude perpendicular to the p component light,
Due to the incident angle θ1, the reflectance of the p component becomes smaller than the reflectance of the s component, so that polarized light having a high ratio of the s component can be obtained. For example, assuming that n1 is 1.5 and n2 is 1.0, when θ1 is 33 ° 41′24 ″, the reflectance of the p component is 0, so that only the s component can be polarized light.

As described above, 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 only the s component, and Since θ1 is a specific small area,
The exit angle is also limited to a specific small area. That is,
The polarized light having the maximum intensity in the first predetermined direction D1 and having a high ratio of the s component can be emitted from the emission surface 26B.

The material of the light guide is not particularly limited as long as it has a property of transmitting light efficiently, and examples thereof include acrylic resin such as PMMA, polycarbonate resin, and glass.

As shown in FIG. 1, the first predetermined direction D1 is generally defined with respect to a normal direction of the light exit surface 26B when the light exit surface 26B of the light guide 26 is considered as a reference. This is the direction opposite to the light source 24 arranged near the one side end surface 26A.

As means for emitting, for example, diffused light (this diffused light is not completely diffused light having no directivity) from the light guide 26 as directional light having the maximum luminance in the first predetermined direction D1, The shape of the light guide 26 is plate-like (for example, a plate-like shape, or the one end face 26A on which the light source 24 is disposed).
, Etc.), and the light guide 26 is provided with light scattering means.

When the thickness of the light guide is reduced as the distance from the light source increases, in the case of a so-called two-lamp surface light source in which the light source is provided near both end surfaces, as shown in FIG. The part has the thinnest shape, and the first in two directions
The predetermined directions D1 and D1A exist.

As the light scattering means, for example, as shown in FIG. 1, a light scattering layer in which a light scattering agent such as silica is dispersed in a resin is provided on the surface of the light guide 26 opposite to the emission surface 26B. 2
There is a structure in which 8A (usually a dot shape or the like) is provided by printing or the like and brought into optical contact.

In addition, as shown in FIG. 2, a light scattering layer 28B in which a light scattering agent such as silica is dispersed in a resin is provided on the emission surface 26B of the light guide 26 by printing or the like. 3, a structure in which the light exit surface of the light guide 26 is a rough surface 28C as shown in FIG. 3, and as shown in FIG.
A structure in which the surface (back surface) opposite to the light exit surface 26B is a rough surface 28D. As shown in FIG.
The material that makes up most of the light guide 26 (for example, PMMA:
A substance having a refractive index different from that of the refractive index (1.49) and being translucent (for example, silicone resin: refractive index of 1.4)
3) The light scattering agent 28E having a particle size of 5 μm or less is contained in the light guide plate at 1% by weight or less to make the light guide material itself light scattering. You may adopt it.

When the light scattering agent 28E is used, if the particle diameter is larger than 5 μm, the directivity of the light emitted from the light guide 26 approaches the completely diffused light. The brightness uniformity of the light emitting surface 26B is undesirably deteriorated.

The prism sheet 22 is a means for changing the course of the light beam. In this case, as shown in FIG. 7, the light beam in the first predetermined direction D1 incident from the light guide 26 is totally reflected inside the prism. In the second predetermined direction D2.

More specifically, as shown in an enlarged manner in FIG. 10A, the prism sheet 22 has a prism structure in which a triangular prism having a triangular cross section is a unit prism 22A and a large number of unit prisms are arranged. And the unevenness due to the prism structure makes the cross-sectional shape on the light guide 26 side substantially V
It is shaped like a letter.

The slope of the triangular prism is a scalene triangle in which the slope 23A on the light source side is steeper than the slope 23B on the side opposite to the light source. This is the light guide exit surface 26
This is because the directional light that is inclined and emitted from B is inclined with respect to the prism light entrance surface, for example, in a substantially normal direction.

As shown in FIG. 10B, a prism sheet 32 having a prism 32B formed on a base sheet 32A may be provided.

The prism 3 of the prism sheet 32
On the non-prism surface on the opposite side to 2B, there is a diffusivity for expanding the viewing angle and interference prevention due to close contact with other members, or
The mat surface 32C may be formed as necessary to hide defects such as scratches in appearance. As means for forming the mat surface 32C, coating with a matting agent, embossing, or the like can be used.

As the material for forming the prism sheet,
It functions as long as it is a material having a property of transmitting light efficiently, and examples thereof include polyester resins such as polycarbonate (PC) and polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), and glass. Above all, a base sheet 32A such as PET or PC can be formed with a high degree of accuracy in forming a fine prism shape.
A prism 32B formed by using an ultraviolet curable resin on the above is preferable, and it is also preferable in terms of being most excellent in mass productivity.

In this case, it is preferable that the refractive index of the prism formed of the ultraviolet curable resin is large, and specifically, 1.4.
Above, more preferably 1.5 or more. In order to form a prism shape on the base film with an ultraviolet curable resin, a technique disclosed in Japanese Patent Application Laid-Open No. 5-169015 may be used.

That is, an ultraviolet curable resin liquid is applied to a rotating roll intaglio having a concave portion having an inversely convex and concave shape with respect to the prism shape, and then a base sheet is supplied thereto to form a roll intaglio from above the resin liquid on the plate surface. The prism sheet can be continuously manufactured by pressing, pressing, pressing and irradiating ultraviolet rays to cure the resin liquid, and then peeling off the solidified ultraviolet curable resin from the roll intaglio rotating with the base sheet.

As will be described later, if necessary, a stretched film may be used as the base sheet 32A.
The material of the stretched film is not particularly limited as long as it has translucency. Polyester resins such as polyethylene terephthalate (PET), acrylic resins such as polycarbonate (PC) and polymethyl methacrylate (PMMA), and TAC
(Cellulose triacetate) and the like, especially mechanical, chemical,
From the optical performance, biaxially stretched PET is particularly desirable.

Next, a method of controlling the polarization direction in the prism sheet 22 and its effect will be described. FIG. 8 shows that the light of the first predetermined direction D1 emitted from the light guide is directed in the second predetermined direction (in this case, the normal direction of the liquid crystal panel) D2 by the prism of the prism sheet 22. It is shown.

At this time, for example, when the refractive index n1 of the prism portion is 1.50, since the refractive index n2 of air is 1.0, θc is 41 ° 48'37 ″, and the incident angle θ2 ≧ 2.
If θc, incident light is totally reflected.

As shown in FIGS. 9 (B) and 9 (C), in the total reflection area (θ2 ≧ θc), a p-component light having an amplitude within the incident plane and an s having an amplitude perpendicular to the p-component light are provided. The component light exits with a different phase depending on the incident angle θ2. Although the reason is not clear, this affects the polarization direction of the polarized light to be emitted.

By aligning the polarization direction of the 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 is effectively used. It is possible to improve the light use efficiency by controlling the incident angle θ2.

However, since it is difficult to control both the reflection angle and the polarization direction of the polarized light at the incident angle θ2 in practice, it is difficult to control both the reflection angle and the polarization direction of the polarized light. The stretched stretched film is applied to the prism sheet 3
The base sheet 32A or a stretched film is laminated on the exit surface side of the prism sheets 22 and 32 and used as a means for controlling the polarization direction of polarized light.

The material of the stretched film is not particularly limited as long as it has translucency, and polyethylene terephthalate (PE)
T) and other polyester resins, polycarbonate (P
C), acrylic resin such as polymethyl methacrylate (PMMA), TAC (cellulose triacetate), etc., and biaxially stretched PET is particularly desirable from the viewpoint of mechanical, chemical and optical performance.

As shown in FIG. 11, a general biaxially stretched PE
T is stretched in the machine flow direction and the width direction at the time of roll production, and its molecules are also oriented obliquely left and right with respect to the center of the machine. With such orientation, the refractive index in the width direction and the refractive index in the flow direction are different, and the polarization direction of polarized light can be adjusted by passing through such a film.

FIG. 12 shows the relationship between the polarization direction D3 of the polarized light emitted from the prism sheet 22 and the polarization axis D4 of the first polarizing plate 30B used in the liquid crystal cell 30A. As described above, in the stretched film used as the base sheet 32A of the prism sheet 32, molecules are oriented in either the left or right oblique direction with respect to the length direction of the raw material roll, and the polarization axis D5 of the base sheet 32A is It forms a predetermined angle α with the ridge direction of the prism. The polarization direction D3 of the polarized light passing through the base sheet 32A and the first polarizing plate 3 on the surface light source side
When the polarization axis D4 of 0B is in the same direction, the light use efficiency is improved. Reference numeral 30C denotes a second polarizing plate.

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, having a high s component ratio and having the maximum intensity in the first predetermined direction D1. Is directed in a second predetermined direction (usually the normal direction of the liquid crystal display device) D2 using the above-described prism sheet 22, and the polarization direction of the polarized light is set so that the transmittance in the liquid crystal panel is maximized. By controlling D3, the light use efficiency in the liquid crystal display device can be improved.

Moreover, since the prism sheets 22 and 32 are flat, a thin surface light source can be obtained as compared with the case where the multilayer film is provided on the inclined surface, and it is preferable because the liquid crystal display device is not bulky.

The surface light source device of the present invention may further include, if necessary, conventionally known surface light source devices 70, 70A, 70B.
Similarly to (see FIGS. 13 to 15), a lens sheet or the like may be used in addition to the diffusion sheet 40 shown by the two-dot chain line in FIG. 1, and the above-described embodiment is described without departing from the gist of the present invention. However, the present invention is not limited to this example.

[0061]

EXAMPLES Examples and comparative examples of the present invention will be described below.

As shown in FIG. 1, a light source 24, a light guide 26 which emits a diffused light beam having a maximum intensity in an oblique direction, and prints a dot-shaped light scattering layer 28A on the back surface, and a unit prism 22A A prism sheet 22 having a triangular prism (an inequilateral triangle whose cross section has a steeper slope on the light source side than the opposite light source side), and a prism surface facing the light guide 26 side;
A light diffusion reflection sheet 29 made of a white polyethylene terephthalate sheet is disposed near the back surface of the light guide, and the base sheet 32A of the prism sheet 32 is arranged as shown in FIG.
Using a biaxially stretched PET raw material having different molecular orientations in the width direction of the roll raw material, the polarization direction D3 of polarized light generated by the stretching direction is changed by the polarization axis of the first polarizing plate 32B on the surface light source side. A prism sheet having a direction substantially the same as that of D4 was prepared and arranged on a surface light source.

Further, the polarizing plate was arranged on the surface light source according to the direction of the polarization axis used in the liquid crystal panel, and the luminance of the light beam emitted from the polarizing plate was measured. In the opposite direction, the maximum luminance (luminance in the direction giving the maximum value) is 1020 cd / m2.
2,910 cd / m2, and a difference of about 10% was recognized.

[0064]

According to the present invention, with a relatively simple configuration,
Light use efficiency of the liquid crystal display device can be improved. In addition, since the surface light source device and the prism sheet are flat and can be reduced in thickness, the thickness of the liquid crystal display device can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a second example of the embodiment of the light guide.

FIG. 3 is a sectional view showing a third example of another embodiment of the light guide.

FIG. 4 is a sectional view showing a fourth example of another embodiment of the light guide.

FIG. 5 is a sectional view showing a fifth example of another embodiment of the light guide.

FIG. 6 is a sectional view showing a sixth example of another embodiment of the light guide.

FIG. 7 is a sectional view showing an example of an embodiment of a prism sheet.

FIG. 8 is a schematic diagram showing the prism principle of a prism sheet.

FIG. 9A is a graph showing the reflectance of s component and p component light with respect to the incident angle.

FIG. 9B is a graph showing a phase change of s component and p component light with respect to an incident angle.

FIG. 9C is a graph showing a change in a phase difference between s component light and p component light with respect to an incident angle.

FIG. 10A is an enlarged perspective view showing an example of an embodiment of a prism sheet.

FIG. 10B is an enlarged perspective view showing an example of another embodiment of the prism sheet.

FIG. 11 is a schematic view showing a stretching direction and a molecular orientation direction when producing biaxially stretched PET.

FIG. 12 is a schematic diagram showing a relationship between a polarization axis of a base material of a prism sheet, a polarization axis of a first polarizing plate on a liquid crystal cell side, and a polarization direction of polarized light.

FIG. 13 is a cross-sectional view illustrating an example of a conventional surface light source and a liquid crystal display device.

FIG. 14 is a sectional view showing another example of a conventional surface light source and a liquid crystal display device.

FIG. 15 is a sectional view showing another example of a conventional surface light source and a liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display device 22, 32 ... Prism sheet 24 ... Light source 26 ... Light guide 26B ... Outgoing surface of light guide 28A ... Light scattering layer 28B ... Light scattering layer 28C, 28D ... Rough surface 28E ... Light scattering agent 29 ... Light diffusion 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

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G02F 1/13357 G02F 1/1335 530 (72) Inventor Fumihiro Arakawa 1-1-1, Ichigaya-Kagacho, Shinjuku-ku, Tokyo No. 1 Inside Dai Nippon Printing Co., Ltd. (72) Nobuo Naito, Inventor 1-1-1, Ichigaya Kagacho, Shinjuku-ku, Tokyo Inside Dai Nippon Printing Co., Ltd. (72) Eisaburo Higuchi 2-9-1 Hiratsuka, Shinagawa-ku, Tokyo No. 29 Nitto Juju Kogyo Co., Ltd. (72) Inventor Kazuaki Yokoyama 2-30-1, Namiki, Kawaguchi-shi, Saitama F-term in Enplas Co., Ltd. 2H042 AA02 AA03 AA04 AA16 AA26 BA02 BA03 BA20 CA06 CA12 CA17 2H049 BA02 BB03 BB62 BB63 2H091 FA08X FA08Z FA23Z FA32Z FA41Z FA42Z FD08 LA11 LA16

Claims (8)

[Claims] 1. A prism layer is disposed on at least one surface of a birefringent light-transmitting substrate which is disposed substantially parallel to a light incident side of a polarizing plate and which is laminated and has one or more sheets. The prism constituting the prism layer is formed by changing the direction of the polarization axis of the light-transmitting substrate so that the polarization direction of the polarized light that has passed through the light-transmitting substrate is substantially the same as the polarization axis of the polarizing plate. A prism sheet arranged at a predetermined angle with respect to the ridge line direction of the prism sheet. 2. The polarizing plate according to claim 1, wherein the prism layer side is a plane of incidence of polarized light, and a direction of polarization of the polarized light passing through the light-transmitting substrate is substantially the same as a polarization axis of the polarizing plate. A prism sheet characterized in that: 3. A light source, a light guide that emits light from the light source from a side surface and emits polarized light having directivity having a maximum intensity in a first predetermined direction, and an emission surface of the light guide. 3. The light source is disposed on the side, and emits the polarized light in the first predetermined direction in a second predetermined direction within a certain angle around a normal direction of the light guide exit surface. And a prism sheet according to (1). 4. The light guide according to claim 3, wherein the light guide has a plate shape, and has light scattering means for emitting the light inside from the emission surface. A light scattering layer optically contacted with a surface on the side opposite to the exit surface, a rough surface formed on the surface on the side opposite to the exit surface or the exit surface,
Alternatively, the light source is a light scattering agent contained in the light guide. 5. The prism sheet according to claim 3, wherein the prism sheet has the prism layer formed on the light guide side, and the prism layer is composed of a plurality of unit prisms, and has an uneven surface. Characteristic surface light source device. 6. A prism sheet and a surface light source device according to claim 1, wherein said translucent substrate is a polyethylene terephthalate film. 7. The surface light source device according to claim 3, wherein a diffusion sheet is disposed on an exit surface side of the prism sheet. 8. The surface light source device according to claim 3, wherein the polarizing plate, a liquid crystal cell, a second polarizing plate,
Are arranged in this order, and the polarization direction of the polarized light emitted from the surface light source device is substantially the same as the polarization axis of the polarizing plate.