JP2000221324A - Polarizing device and liquid crystal display device having that polarizing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal display device of high display quality in which light from a light source can be effectively utilized. SOLUTION: The liquid crystal display device is formed by disposing a back light 6, a reflection polarizing device 5, and a liquid crystal panel 2 equipped with polarizing plates 1a, 1b, in this order. The reflection polarizing device 5 consists of an isotropic layer 3 and an anisotropic layer 4 laminated with each other, and a geometric structure face 11 composed of plural prism faces 10 is formed on the interface between the isotropic layer 3 and the anisotropic layer 4. When unpolarized light 7 from a back light 6 enters the surface of the reflection polarizing device 5 facing the anisotropic layer 4, the P-polarized light 8 in the light 7 is condensed along the normal line direction of the liquid crystal panel 2 by the geometric structure face 10 and reaches the liquid crystal panel 2 to increase the luminance of the liquid crystal panel 2 in the front face direction. The S-polarized light 9 is reflected by the geometric structure face 10 foward the back light 6 and then reused. Therefore, the reflection polarizing device 5 has little loss of light, which increases the utilization efficiency of light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a polarizing element used for a liquid crystal display and a liquid crystal display having the polarizing element.

[0002]

2. Description of the Related Art FIG. 5 is a sectional view showing the structure of a conventional liquid crystal display device. In the conventional liquid crystal display device, in order to increase the luminance in the normal direction of the display surface of the liquid crystal panel, FIG.
The prism sheet 105 is disposed on the front surface of the backlight 107 as shown in FIG. Prism sheet 105
Of the liquid crystal panel 1 on the side opposite to the backlight 107 side.
02 is arranged. A polarizing plate 101b is attached to a surface of the liquid crystal panel 102 on the side of the prism sheet 105, and a polarizing plate 101a is attached to a surface of the liquid crystal panel 102 opposite to the side of the prism sheet 105.

[0003] Since the prism sheet 105 is provided in the liquid crystal display device, the prism sheet 1 is provided.
Backlight 1 using the refraction effect of prism surface 05
07 is improved. However,
When light transmitted through the prism sheet 105 passes through the polarizing plate 101b, light in the absorption axis direction of the polarizing plate 101b is absorbed by the polarizing plate 101b, so that the amount of light from the backlight 107 is reduced to half or less. When the brightness of the backlight 107 is increased to increase the brightness of the liquid crystal panel 102,
The power consumption and the amount of heat generated from the backlight 107 increase,
The reliability and display quality deteriorate.

Heretofore, several liquid crystal display devices have been proposed in which light in the direction of the absorption axis of a polarizing plate is used as light for irradiating a liquid crystal panel.

For example, a conventional liquid crystal display device is disclosed in JP-A-9-326205 and JP-A-9-2741.
No. 09 publication. FIG.
It is sectional drawing which shows the structure of the backlight used for the liquid crystal display device of -326205. FIG.
FIG. 2 is a cross-sectional view illustrating a configuration of a sheet-like polarizing element used in the liquid crystal display device of Japanese Patent Application No. -274109.

As shown in FIG. 6, a backlight used in a liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 9-326205 has a light source 201, a light source 201 attached to a side surface, and a reflection dot 221 formed on a lower surface. A reflective light guide plate 202, a diffuse reflection film 231 disposed on the lower surface of the reflective light guide plate 202, and a polarization beam splitter (dielectric multilayer film) 230 disposed on the upper surface of the reflective light guide plate 202. ing. Light source 201 to reflective light guide plate 202
Incident on the diffuse reflection film 231 and the reflection dot 2
After being guided to the upper surface of the reflective light guide plate 202 by 21,
The light enters the polarization beam splitter 230. Light having a specific polarization plane among the light incident on the polarization beam splitter 230 is returned to the reflection type light guide plate 202 by the polarization beam splitter 230 and reused as light for illuminating the liquid crystal display element.

In a liquid crystal display device using a backlight shown in FIG. 6, the luminance of a liquid crystal display panel is improved by reusing light of a specific polarization plane. However, in order to improve the display quality by obtaining a greater effect than the improvement in brightness by reusing light, a prism lens or the like that condenses light in a direction perpendicular to the display surface of the liquid crystal display panel is used for liquid crystal display. Further equipment must be provided.

On the other hand, as shown in FIG. 7, a sheet-like polarizing element used in the liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 9-274109 includes a polarization splitting prism 320, a right-angled triangular prism 330, and a polarization plane modulator. 340 and light scattering unit 3
50. Polarization splitting prism 320
Is to split the non-polarized light 310 into polarized light. The slope of the triangular prism 330 overlaps the slope of the polarization splitting prism 320. The polarization plane modulation unit 340 modulates the phase of the reflected polarized light that has been polarized and separated by the polarization splitting prism 320. The light scattering section 350 scatters light converted from non-polarized light 310 into polarized light in a random direction. This sheet-shaped polarizing element has a function of scattering light, and has a shape formed by continuously processing units constituting the polarizing element.

The polarization splitting section in the sheet-like polarizing element comprises a polarization splitting prism 320 having a high refractive index and a right-angled triangular prism 330 having a low refractive index. Polarization splitting prism 320, an inclined surface 321 that the angle of incidence of the unpolarized light 310 is inclined to be substantially Brewster angle theta _B, and a emitting surface 322 for emitting a polarized light in one direction. The right-angled triangular prism 330 outputs the unpolarized light 31
It has an incident surface 332 having a right angle of incidence of 0 and an inclined surface 331 having the same inclination as the inclined surface 321.

[0010] The polarization splitting section includes inclined surfaces 321 and 331.
At the interface with, functions as a division unit that divides the non-polarized light 310 into transmitted light and reflected light whose polarization planes are orthogonal to each other. Here, the interface between the inclined surfaces 321 and 331 functions as a dividing unit that divides P-polarized light and S-polarized light whose vibration planes are orthogonal to each other. Specifically, the interface between the inclined surfaces 321 and 331 transmits the P-polarized light 311 having a vibration plane perpendicular to the interface and reflects the S-polarized light 312 having a vibration plane parallel to the interface. Has characteristics.

The reflected light split by the polarization splitting unit is modulated by the polarization plane modulation unit 340. On the other hand, the inclined surface 3 located on the back surface of the inclined surface 321 of the polarization splitting prism 320
The angle of the light incident on the prism 23 depends on the external medium on the opposite side of the polarization splitting prism 320 (the right-angled triangular prism 33 having a low refractive index).
0) or more than the critical angle. Therefore, the inclined surface 32
Reference numeral 3321 functions as a total reflection surface that totally reflects the reflected light.

The polarization plane modulation section 340 is a half-wavelength provided between the surfaces 334 and 324 of the low refractive index right-angled triangular prism 330 and the polarization splitting prism 320 that are parallel to the non-polarized light 310. It is a board. This polarization plane modulator 3
The reference numeral 40 functions as a phase modulator that changes the polarization plane of the reflected light reflected by the inclined surface 321 and matches the polarization plane with the polarization plane of the transmitted light. Here, the polarization plane modulation unit 340
Is a reflection S having a vibration surface parallel to the inclined surface 321.
P-polarized light 313 by modulating the phase of the polarized light by 波長 wavelength
Has the property of converting to Therefore, the polarization plane modulation unit 3
The 40 functions as a modulator that converts the phase of the incident linearly polarized light by half wavelength and modulates the output linearly polarized light orthogonal to the polarization plane of the incident light.

The light scattering section 350 includes the polarization splitting prism 32.
The light-scattering sheet is provided in parallel with the zero polarization output surface 322 and has a non-uniform refractive index structure composed of at least two or more kinds of substances having different refractive indexes. The light scattering section 350 has a function of scattering the polarized light emitted from the polarized light emitting surface 322 as polarized light having no directivity. Here, the P-polarized light that has entered the incident surface 351 of the light scattering unit 350 is scattered by a refractive index interface made of a material having a different refractive index due to the non-uniform refractive index structure of the light scattering unit 350. Therefore, the light scattering section 350 has a function of scattering the P-polarized light incident on the incident surface 351 as P-polarized light having no directivity.

In such a polarizing element, since the inclined surfaces of the respective prisms are inclined such that the incident angle of the non-polarized light 310 as the incident light source is substantially in the vicinity of the Brewster angle θ _{B, the} light is made incident. The random polarized light is separated into a P-polarized light 311 and an S-polarized light 312 on the inclined surface 321. Next, only the S-polarized light 312 of the reflected light is converted into the P-polarized light 313 by a half-wave plate as a polarization plane modulator 340 parallel to the incident light.
Is converted to The transmitted P-polarized light 311 and the converted P-polarized light 313 respectively enter the light scattering unit 350,
The P-polarized light is scattered by the light scattering section 350. As a result, the unpolarized light 310, which is randomly polarized light, is aligned with linearly polarized light having no directivity and polarized in one direction, and is used in the liquid crystal display device without light loss.

[0015]

However, in the sheet-like polarizing element shown in FIG. 7, when the non-polarized light 310 is obliquely incident on the incident surface 332, the non-polarized light 310 does not enter the inclined surface 321 of the prism. May enter the half-wave plate 340. At this time, the function of the sheet-shaped polarizing element was achieved in that the light that did not enter the inclined surface 321 of the prism and was incident on the half-wave plate was emitted from the sheet-shaped polarizing element while being made linearly polarized light. Not done. For this reason, there is a problem that the function of the polarizing element is deteriorated and light absorbed in the absorption axis direction of the polarizing element is increased. Further, by using a light diffusion sheet as the light scattering section 350, the amount of light incident on the light diffusion sheet is reduced by the light diffusion sheet when passing through the light diffusion sheet.

An object of the present invention is to provide a polarizing element capable of effectively utilizing light from a backlight in a liquid crystal display device and obtaining high display quality, and a liquid crystal display device using the polarizing element. Is to do.

[0017]

In order to achieve the above object, the present invention provides a polarizing element which transmits one linearly polarized light oscillating in a predetermined oscillating direction in light emitted from a light source, and the like. When the light from the light source is incident on a surface of the anisotropic body opposite to the isotropic body, the light vibrates in a predetermined vibration direction of the light. One linearly polarized light is transmitted through the interface between the isotropic body and the anisotropic body so as to be collected in a direction substantially parallel to the laminating direction of the isotropic body and the anisotropic body, and Of the other, so that the other linearly polarized light that vibrates in a direction orthogonal to the predetermined vibration direction is reflected at the interface between the isotropic body and the anisotropic body,
A geometric structure surface is formed at an interface between the isotropic body and the anisotropic body.

In the above invention, the polarizing element is formed by laminating the isotropic body and the anisotropic body, and the above-mentioned geometric structure surface is formed at the interface between the isotropic body and the anisotropic body. When light from a light source is incident on the surface of the anisotropic body on the side opposite to the isotropic body, one of the linearly polarized light vibrating in a predetermined predetermined vibration direction of the light becomes an isotropic body. Then, the light passes through the geometric structure surface so as to converge light in a direction parallel to the stacking direction of the anisotropic body. At the same time, of the light incident on the anisotropic body, the other linearly polarized light that oscillates in a direction orthogonal to the predetermined vibration direction is reflected by a geometric structure surface between the isotropic body and the anisotropic body. You. At this time, since the polarizing element is composed of an isotropic body and an anisotropic body, one linearly polarized light is transmitted and collected while the light from the light source is hardly attenuated, and the other linearly polarized light is reflected. Can be done. For example, when a liquid crystal display device is configured using this polarizing element, in the optical path between the light source and the liquid crystal panel, the anisotropic surface of the polarizing element is the light source side, and the isotropic surface is the liquid crystal panel side. The polarizing element is arranged so that In this case, when one linearly polarized light of the light from the light source passes through the polarizing element, it is collected by the geometric structure surface of the polarizing element, and the collected linearly polarized light reaches the liquid crystal panel. As described above, the front surface brightness of the liquid crystal panel is increased by the effect of condensing light on the geometric structure surface, and the display quality of the liquid crystal display device is improved. The other linearly polarized light of the light from the light source is reflected by the geometric structure of the polarizing element. Here, for example, the other linearly polarized light included in the light from the light source also illuminates the liquid crystal panel by converting the other reflected linearly polarized light into the one linearly polarized light and re-entering the polarized light again. It can be used as light. As described above, by using the polarizing element, two linearly polarized lights of the light from the light source, which vibrate in directions perpendicular to each other, can be used as light for illuminating the liquid crystal panel. Since there is almost no attenuation of light, the light use efficiency of the liquid crystal display device can be improved.

In the above-mentioned polarizing element, a plurality of the above-mentioned isotropic bodies and the above-mentioned anisotropic bodies may be alternately laminated so that a plurality of the above-mentioned geometrically structured surfaces are formed. Specifically, the shape of the geometric structure surface is such that the prism surface for condensing the one linearly polarized light in a direction substantially parallel to the laminating direction is continuously formed in a direction perpendicular to the laminating direction. It is configured by arranging a plurality.

Further, the present invention utilizes a light source, a polarizing element that transmits one of linearly polarized light vibrating in a predetermined vibration direction out of light emitted from the light source, and a linearly polarized light transmitted through the polarizing element. A liquid crystal display device having a liquid crystal panel that displays an image on the display device, wherein the polarizing element is formed by laminating an isotropic body and an anisotropic body, and light from the light source is applied to the anisotropic body of the polarizing element. When the light enters the polarizing element from the body-side surface, one of the lights that vibrates in a predetermined vibration direction is condensed in a direction substantially parallel to the lamination direction of the isotropic body and the anisotropic body. And at the same time, the other linearly polarized light of the light that vibrates in the direction orthogonal to the predetermined vibration direction is transmitted through the interface between the isotropic body and the anisotropic body. The isotropic body and the anisotropic body are reflected at the interface with the Geometry surface interface is formed between the.

In the above invention, the polarizing element formed by laminating the above-described isotropic body and the anisotropic body is provided in the liquid crystal display device, so that the light from the light source is provided on the anisotropic side of the polarizing element. When the light is incident on a surface, one of the lights, which vibrates in a predetermined vibration direction, transmits through the polarizing element. At this time,
One of the linearly polarized lights is condensed by the geometric structure of the polarizing element and reaches the liquid crystal panel. As described above, the front surface brightness of the liquid crystal panel is increased by the effect of condensing light on the geometric structure surface, and the display quality of the liquid crystal display device is improved. Also, the other linearly polarized light of the light from the light source is reflected by the geometric structure surface of the polarizing element. Here, for example, the other linearly polarized light included in the light from the light source also converts the other reflected linearly polarized light into the one linearly polarized light and makes it incident on the polarizing element again. It can be used as illuminating light. In a polarizing element formed by laminating an isotropic body and an anisotropic body so that such a geometric structure surface is formed, light is hardly attenuated, so that light use efficiency is high and display quality is high. A liquid crystal display device is obtained.

[0022] The polarizing element is formed by alternately laminating a plurality of the isotropic bodies and the anisotropic bodies so that a plurality of the geometrically structured surfaces are formed on the polarizing element. Is also good. Further, specifically, the shape of the geometric structure surface is such that the prism surface for condensing the one linearly polarized light in a direction substantially parallel to the laminating direction is continuous in a direction perpendicular to the laminating direction. It is configured by arranging a plurality of lines.

[0023]

Next, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 is a sectional view showing the structure of a liquid crystal display device according to a first embodiment of the present invention.

As shown in FIG. 1, in the liquid crystal display device of this embodiment, a polarizing plate 1a is attached to one surface of a liquid crystal panel 2, and a polarizing plate 1b is attached to the other surface of the liquid crystal panel 2. On the polarizing plate 1b side of the liquid crystal panel 2, a reflective polarizing element 5 is arranged. Liquid crystal panel 2 of reflective polarizing element 5
On the side opposite to the side, a backlight 6 as a light source is arranged. The reflective polarizing element 5 includes an isotropic layer 3 made of a film-like isotropic member and an anisotropic layer 4 made of a film-like anisotropic member. The surfaces of the cubic layer 4 are bonded together. Anisotropic layer 4
Are disposed on the backlight 6 side, and the isotropic layer 3 is disposed on the liquid crystal panel 2 side.

At the interface between the isotropic layer 3 and the anisotropic layer 4, a geometric structure surface 11 composed of a plurality of prism surfaces 10 is formed as described later. This reflective polarizing element 5
Is for transmitting linearly polarized light oscillating in a predetermined vibration direction and extracting the linearly polarized light from the light emitted from the backlight 6. The front and back surfaces of the reflective polarizing element 5 are flat.

The backlight 6 includes a cold cathode fluorescent lamp, a light guide plate on which light from the cold cathode fluorescent lamp is incident,
The light source is a surface light source including a reflector that reflects light incident on the light guide plate toward the reflective polarizing element 5 and a diffusion sheet that converts light emitted from the light guide plate into uniform planar light. On the light guide plate of the backlight 6, a uniform surface light source is obtained.
A dot pattern that scatters light is printed. The liquid crystal panel 2 displays an image using P-polarized light, which is linearly polarized light that vibrates in a predetermined vibration direction, of the light from the backlight 6.

FIG. 2 is a perspective view of the reflective polarizing element 5. As shown in FIGS. 1 and 2, on the surface of the anisotropic layer 4 on the side of the isotropic layer 3, a triangular prism-shaped prism portion having a cross-sectional shape of an isosceles triangle is parallel to the anisotropic layer 4. The two side surfaces having the same surface area in each prism portion are prism surfaces 10 on the surface of the anisotropic layer 4 on the side of the isotropic layer 3. A plurality of prism portions are also formed on the surface of the isotropic layer 3 on the side of the anisotropic layer 4, and each prism portion has a shape between two adjacent prism portions in the anisotropic layer 4. It has a shape corresponding to the recess. The isotropic layer 3 and the anisotropic layer 4 are bonded together such that the inclined surfaces of the prism portions of the isotropic layer 3 and the anisotropic layer 4 face each other. Accordingly, a plurality of prism surfaces of the isotropic layer 3 and the anisotropic layer 4 are continuously arranged in a direction perpendicular to the laminating direction of the isotropic layer 3 and the anisotropic layer 4. The surface constitutes a geometrically structured surface 11.

The direction parallel to the ridge line of each prism portion of the isotropic layer 3 and the anisotropic layer 4 is defined as the X direction, and is perpendicular to the X direction and parallel to the front and back surfaces of the reflective polarizing element 5. Let the direction be the Y direction. Further, a direction perpendicular to the front and back surfaces of the reflective polarizing element 5 is defined as a Z direction. Here, _assuming that the refractive index of the anisotropic layer 4 in the X direction is N _x1 , the refractive index in the Y direction is N _y1 , and the refractive index in the Z direction is N _z1 ,
_x1> N _y1 = N _z1 made has a relationship, X in the isotropic material layer 3
Assuming that the refractive index in the direction is N _x2 , the refractive index in the Y direction is N _y2 , and the refractive index in the Z direction is N _z2 , the relationship is N _x2 = N _y2 = N _z2 . The relationship between the refractive indices of the isotropic layer 3 and the anisotropic layer 4 is as follows: N _x1 > N _x2 (= N _y2 = N _z2 )> N _y1 (= N _z1 )
It has become. The ridge direction of each prism portion in the reflective polarizing element 5 matches the transmission axis of the polarizing plate 1b.

Next, the operation of the reflective polarizing element 5 with respect to light from the backlight 6 will be described with reference to FIG.
FIG. 3 is a diagram for explaining the effect of the reflective polarizing element 5 on light from the backlight 6.

As shown in FIG.
The emitted unpolarized light 7 is reflected on the anisotropic layer 4 side of the reflective polarizing element 5.
When the light enters the reflective polarizing element 5 from the surface, the unpolarized light 7
After passing through the cubic layer 4, it reaches the geometric surface 11.
Here, of the unpolarized light 7, parallel to the Y and Z directions
P-polarized light 8 oscillating in a simple plane has a refractive index N_y1And N_y2To the difference
More refracted, each prism of the geometric surface 11
Light in the direction perpendicular to the reflective polarizing element 5
Is done. Refractive index N_y1And N_y2N which is the ratio of_y1/ N _y2Is the value of
The smaller the value, the greater the effect of condensing the P-polarized light 8
However, in this case, the P-polarized light 8 is reflected on the prism surface,
Light that does not proceed in the direction toward the panel 2 increases. Reverse
And N_y1/ N_y2Is closer to 1, the geometrically structured surface 1
1. The reflection of P-polarized light on each prism surface is small.
However, in this case, the light collecting effect is reduced. P bias
Improvement of the effect of condensing light 8 and reduction of light attenuation due to reflection
N with good balance with suppression_y1/ N_y2Is 0.7
5 to 0.95.

Of the light emitted from the backlight 6 in various directions, the traveling direction of the light having the largest light amount is generally the normal direction of the backlight 6. In order to minimize the light attenuation due to the reflection of the P-polarized light on the geometrically structured surface 11 of the reflective polarizing element 5, the apex angle θ of each prism portion of the anisotropic layer 4 shown in FIG. Preferably satisfies the following expression.

Θ = (90−arctan (N _y2 / N _y1 )) × 2

The pitch of each prism portion of the isotropic layer 3 and the anisotropic layer 4 may be 30 to 300 μm. In order to prevent moire with the pixel arrangement of the liquid crystal panel 2, the pitch of the prism portion is required. Is desirably 50 μm or less.

On the other hand, of the unpolarized light 7 arriving at the geometric structure surface 11, the S-polarized light 9 oscillating in a plane parallel to the X direction and the Z direction is represented by the difference between the refractive indexes N _x1 and N _x2 . As shown in FIG. N _x1 / N _x2
May be 1.03 or more, and the larger the value, the higher the reflection efficiency of the S-polarized light 9 on the geometric structure surface 11. The reflected S-polarized light 9 is reflected by the reflector of the backlight 6, is scattered by the dot pattern printed on the light guide plate of the backlight 6, and is reused as light for illuminating the liquid crystal panel 2. .

In such a liquid crystal display device, since the S-polarized light component conventionally absorbed by the absorption axis of the polarizing plate 1b is reflected by the backlight 6 by the reflective polarizing element 5 and reused, the light use efficiency is increased. Is improved. Further, since the P-polarized light 8 is condensed in the normal direction of the liquid crystal panel 2 by the geometric structure surface 11 of the reflective polarizing element 5, the front luminance of the liquid crystal panel 2 can be further increased.

As the material of the anisotropic layer 4, either polymethyl methacrylate or polycarbonate having excellent transparency, or polystyrene or olefin resin having excellent moldability and mechanical strength and low water absorption is used. be able to. As a method of forming the anisotropic layer 4, for example, there is a method of elongating the formed body at a temperature equal to or lower than the melting point of the constituent material of the anisotropic layer 4 in an extrusion molding process. By stretching the molded body and orienting the polymer in the tensile direction in this way, the anisotropic layer 4 capable of generating birefringence is produced. In addition, when one of the two rollers for extending the molded body when producing the anisotropic layer 4 is provided with irregularities corresponding to the shape of the prism portion of the anisotropic layer 4, the anisotropic layer 4 is formed. Can be formed by molding.

As another material of the anisotropic layer 4, a liquid crystal compound can be used. As a method of forming the anisotropic layer 4 using a liquid crystal compound, first, an alignment agent is applied to a transparent substrate, for example, a triacetyl cellulose film and baked. Examples of the aligning agent include, for example, JALS- manufactured by JSR Corporation.
428 can be used. The alignment film formed on the transparent substrate is rubbed in the Y direction, and a mixture of a nematic liquid crystal and an ultraviolet curable resin is applied to the surface of the alignment film. In such an alignment film, the liquid crystal molecules are aligned in a direction perpendicular to the rubbing direction, and the pretilt angle becomes 0 degree, so that the above-described refractive index distribution of the anisotropic layer 4 can be maintained. . From the top of the alignment film, the ridge direction of the prism part is X
The mold aligned in the direction is pressed against the alignment film, and in this state, the mixture on the alignment film is cured by irradiating ultraviolet rays from the transparent substrate side. As nematic liquid crystals, cyano-based,
Any liquid crystal such as fluorine-based and chlorine-based can be used. Also, a polymer liquid crystal can be used instead of the nematic liquid crystal. As the ultraviolet curable resin, a monofunctional acrylate compound, a monofunctional methacrylate compound, a polyfunctional acrylate compound or a polyfunctional methacrylate compound can be used, and it is possible to use only one of these, or to use two or more copolymers. Can also be used. Since the ultraviolet curable resin is hard to cure alone, it is preferable to add a photopolymerization initiator to the ultraviolet curable resin. As the photopolymerization initiator, thioxanthone-based, diazonium-based, sulfonium-based, iodonium-based, and selenium-based salts can be used.

In order to produce the isotropic layer 3 so as not to cause the phenomenon of birefringence when light is incident on the isotropic layer 3, an ultraviolet curable resin is used as the material of the isotropic layer 3. preferable. In the present embodiment, as the material of the isotropic layer 3, the above-mentioned compound used as the material of the anisotropic layer 4, excluding the liquid crystal, is used. In the method of forming the rectangular parallelepiped layer 4, the step of the alignment agent is omitted.

When the anisotropic layer 4 and the isotropic layer 3 are attached to each other, an ultraviolet-curable transparent adhesive is used. For example, as the UV-curable transparent adhesive, a low-viscosity liquid crystal composition using a fluorinated epoxy or acrylate resin as a base resin can be used. When this adhesive is used, the refractive index of the adhesive can be controlled by adjusting the content of fluorine in the adhesive. By adjusting the fluorine content in the adhesive, the reflective polarizing element 5 used in the present embodiment is adjusted.
In this example, the refractive index of the adhesive is the same as that of the isotropic layer 3. As a method of attaching the isotropic layer 3 and the anisotropic layer 4, first, the transparent adhesive is applied to the surface of the isotropic layer 3 on the prism portion side. Next, the anisotropic layer 4 is placed on the transparent adhesive on the isotropic layer 3, and the anisotropic layer 4 and the isotropic layer 4 are pressed while the isotropic layer 3 and the anisotropic layer 4 are pressed. The transparent adhesive is irradiated with ultraviolet light from the third side.

The thickness of the isotropic layer 3 and the anisotropic layer 4 is preferably 50 to 200 μm which is easy to handle.

The shape of the geometric structure surface 11 formed at the interface between the isotropic layer 3 and the anisotropic layer 4 is shown in FIGS. 1 and 2 in addition to the shape of the continuous triangular prism surface. A trapezoid in which the apex of each triangular prism portion is cut on a plane parallel to the isotropic layer and the anisotropic layer may have a continuous shape. In this case, the boundary between the surfaces is doubled, and the apparent pitch of the prism is also doubled.
Moiré with the pixel array is less likely to occur. Or,
By making the tip of each prism part of the isotropic layer 3 and the anisotropic layer 4 a curved surface, the isotropic layer 3 and the anisotropic layer 4 are formed.
Is less likely to be scratched, and the workability in manufacturing the reflective polarizing element 5 is improved.

As described above, in the liquid crystal display device of the present embodiment, the reflected polarized light obtained by laminating the isotropic layer 3 and the anisotropic layer 4 so as to form the geometric structure surface 11 is formed. Element 5
Was provided. Thereby, when the unpolarized light 7 from the backlight 6 is incident on the surface of the reflective polarizing element 5 on the anisotropic layer 4 side, the P-polarized light 8 of the unpolarized light 7 transmits through the reflective polarizing element 5. At this time, the P-polarized light 8 is condensed by the geometric structure surface 11 in the laminating direction of the isotropic layer 3 and the anisotropic layer 4 and reaches the liquid crystal panel 2. Thus, the geometric surface 11
Due to the effect of condensing the P-polarized light 8, the front luminance of the liquid crystal panel 2 is increased, and the display quality of the liquid crystal display device is improved. The S-polarized light 9 of the light from the backlight 6 is reflected by the geometric structure surface 11. Here, for example, by converting the reflected S-polarized light 9 into P-polarized light and re-entering the polarizing element, the backlight 6
S-polarized light 9 included in the light from the liquid crystal panel 2 can also be used as light for illuminating the liquid crystal panel 2. Since the reflective polarizing element 5 formed by laminating the isotropic layer 3 and the anisotropic layer 4 so as to form such a geometric structure surface 11 hardly attenuates light, the light use efficiency is high. In addition, a liquid crystal display device with high display quality can be obtained.

(Second Embodiment) FIG. 4 is a sectional view showing the structure of a reflective polarizing element used in a liquid crystal display device according to a second embodiment of the present invention. The liquid crystal display of the present embodiment uses the reflection polarizing element shown in FIG. 4 instead of the reflection polarizing element 5 in the liquid crystal display of the first embodiment. The following description focuses on the differences from the first embodiment.

As shown in FIG. 4, the reflective polarizing element 15 used in the liquid crystal display device of the present embodiment has a structure in which isotropic layers and anisotropic layers are alternately laminated as shown in FIG. And the anisotropic layer 14a, the isotropic layer 13a, and the anisotropic layer 14
b, isotropic layer 13b, anisotropic layer 14c, isotropic layer 13c
Are stacked in this order. A geometric structure surface 21a is formed between the anisotropic layer 14a and the isotropic layer 13a, and a geometric structure surface 21b is formed between the anisotropic layer 14b and the isotropic layer 13b. A geometric structure surface 21c is formed between the anisotropic layer 14c and the isotropic layer 13c. Each of the anisotropic layers 14a, 14b, and 14c is composed of a film-like anisotropic member, and is an isotropic layer 13c.
Is composed of a film-like isotropic member.

The geometric structure surface 21a is composed of a plurality of prism surfaces 20a that are continuously arranged in a direction perpendicular to the direction in which the isotropic body and the anisotropic body are stacked. Geometric surface 2
1b is composed of a plurality of prism surfaces 20b continuously arranged in a direction perpendicular to the stacking direction of the isotropic body and the anisotropic body,
The geometric structure surface 21c includes a plurality of prism surfaces 20 that are continuously arranged in a direction perpendicular to the stacking direction of the isotropic body and the anisotropic body.
c. Prism surfaces 20a, 20b, 2
0c has the same shape as the prism surface 10 in the first embodiment, and the geometric structure surface 2
Each of the shapes 1a, 21b, and 21c has the same shape as the geometric structure surface 11 in the first embodiment.

In the reflective polarizing element 15, when light from the backlight enters the reflective polarizing element 15 from the surface of the reflective polarizing element 15 on the side of the anisotropic layer 14 a, the geometrically structured surface 2
Each of 1a, 21b, and 21c reflects S-polarized light. Therefore, by using the reflective polarizing element 15 in a liquid crystal display device, the number of times of reflection of S-polarized light is increased as compared with the liquid crystal display device of the first embodiment, so that the light use efficiency is improved.

The formation of the anisotropic layers 14a, 14b and 14c is performed by extrusion and a stretching process in the same manner as the anisotropic layer 4 used in the first embodiment. Anisotropic layer 14b,
Since both surfaces of the anisotropic material 14c have a prism shape, both of the rollers for extending the anisotropic material have irregularities in a shape corresponding to the prism portions of the anisotropic layers 14b and 14c, so that the anisotropic layers 14b and 14c are formed. It becomes possible to mold. As a material of the isotropic layers 13a and 13b, an ultraviolet-curing transparent adhesive used for bonding the isotropic layer 3 and the anisotropic layer 4 in the first embodiment is used.

[0049]

As described above, according to the present invention, one of linearly polarized light of light incident on the surface on the anisotropic body side of a polarizing element formed by laminating an isotropic body and an anisotropic body is converted into an isotropic body. When light is condensed by the geometric structure surface formed at the interface of the anisotropic body and transmitted through the polarizing element, and at the same time the other linearly polarized light is reflected by the geometric structure surface, attenuation of light in the polarizing element is reduced. Since there is almost no use of this polarizing element in a liquid crystal display device, there is an effect that a liquid crystal display device with high light use efficiency and high display quality can be obtained.

Further, according to the present invention, a liquid crystal display device is constituted by the above-mentioned polarizing element and a liquid crystal panel for displaying an image by using one of the linearly polarized light transmitted through the polarizing element after being emitted from the light source. As a result, an image is displayed on the liquid crystal panel by linearly polarized light condensed in the normal direction of the liquid crystal panel in the geometric structure of the polarizing element, so that the brightness in the front direction of the liquid crystal panel is improved, and There is an effect that display quality is improved. In addition, the polarizing element has little loss of light and can be reused by converting the other linearly polarized light reflected on the geometric structure surface to the one linearly polarized light. Has the effect that it is possible to increase

[Brief description of the drawings]

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

FIG. 2 is a perspective view of the reflective polarizing element shown in FIG.

FIG. 3 is a diagram for explaining an operation of a reflective polarizing element with respect to light from the backlight shown in FIG.

FIG. 4 is a cross-sectional view illustrating a configuration of a reflective polarizing element used in a liquid crystal display device according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a configuration of a conventional liquid crystal display device.

FIG. 6 is a cross-sectional view illustrating a configuration of a backlight used in a conventional liquid crystal display device.

FIG. 7 is a cross-sectional view illustrating a configuration of a sheet-like polarizing element used in a conventional liquid crystal display device.

[Explanation of symbols]

 1a, 1b Polarizing plate 2 Liquid crystal panel 3, 13a-13b Isotropic layer 4, 14a-14b Anisotropic layer 5, 15 Reflective polarizing element 6 Backlight 7 Unpolarized light 8 P polarized light 9 S polarized light 10, 20a-20c Prism surface 11, 21a-21c Geometric structure surface

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H049 BA02 BA05 BA06 BB03 BB63 BC22 2H091 FA08X FA08Z FA14Z FA21Z FA23Z FA41Z FA42Z FD04 FD06 LA03 LA16 5C094 AA10 AA22 BA43 EA05 EB02 ED01 ED11 ED14 FA01 FA02

Claims (6)

[Claims] 1. A polarizing element that transmits one linearly polarized light that vibrates in a predetermined vibration direction out of light emitted from a light source, and is configured by laminating an isotropic body and an anisotropic body, and When light of the anisotropic body is incident on a surface on the side opposite to the isotropic body side, one of linearly polarized lights vibrating in a predetermined vibration direction of the light is the isotropic body and the anisotropic body. While transmitting through the interface between the isotropic body and the anisotropic body so as to be condensed in a direction substantially parallel to the laminating direction of the other, and vibrating in the direction perpendicular to the predetermined vibration direction, of the light. A polarizing element having a geometrically structured surface formed at the interface between the isotropic body and the anisotropic body so that the linearly polarized light is reflected at the interface between the isotropic body and the anisotropic body. 2. The polarizing element according to claim 1, wherein a plurality of said isotropic bodies and said anisotropic bodies are alternately laminated so that a plurality of said geometrically structured surfaces are formed. 3. The shape of the geometric structure surface is such that the prism surface for condensing the one linearly polarized light in a direction substantially parallel to the laminating direction is continuously formed in a direction perpendicular to the laminating direction. 3. The polarizing element according to 1 or 2, wherein a plurality of the polarizing elements are arranged. 4. A light source, a polarizing element that transmits one linearly polarized light that vibrates in a predetermined vibration direction out of light emitted from the light source, and displays an image using the linearly polarized light that has passed through the polarizing element. In the liquid crystal display device having a liquid crystal panel, the polarizing element is configured by laminating an isotropic body and an anisotropic body, and light from the light source is emitted from a surface of the polarizing element on the anisotropic body side. When entering the polarizing element, one linearly polarized light of the light vibrating in a predetermined vibration direction is condensed in a direction substantially parallel to the laminating direction of the isotropic body and the anisotropic body. At the same time as passing through the interface between the isotropic body and the anisotropic body, of the light, the other linearly polarized light that vibrates in a direction orthogonal to the predetermined vibration direction is the same as that of the isotropic body and the anisotropic body. Some reflections occur at the interface between the isotropic body and the anisotropic body so as to reflect at the interface. LCD anatomy surface is formed. 5. The polarizing element is formed by alternately laminating a plurality of the isotropic bodies and the anisotropic bodies so that a plurality of the geometrically structured surfaces are formed on the polarizing element. 5. The liquid crystal display device according to 4. 6. The shape of the geometric structure surface is such that the prism surface for condensing the one linearly polarized light in a direction substantially parallel to the laminating direction is continuously formed in a direction perpendicular to the laminating direction. 6. A device according to claim 4, wherein a plurality of the devices are arranged.
The liquid crystal display device according to the above.