JP2008020514A - Polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive and practical polarizing plate excellent in mechanical strength, and moreover excellent in durability. <P>SOLUTION: The polarizing plate is constituted by stacking a transparent substrate 1, a polarizing film 2, a base plate film 3 and a transparent substrate 4 in this order, wherein a coefficient that represents the heat conductivity to the in-plain direction in the transparent substrate 1 exceeds a coefficient that represents the heat conductivity to the in-plain direction in the transparent substrate 4. The coefficient that represents the heat conductivity to the in-plain direction in a transparent substrate means a value obtained by multiplying the coefficient of heat conductivity of the substrate by a thickness of the substrate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polarizing plate suitable for a projection type liquid crystal display device such as a front projector or a rear projector.

In order to cope with an increase in screen size, a projection type liquid crystal display device is rapidly spreading for business use and home use instead of a conventional cathode ray tube type display device.
In the projection type, after separating the light from the light source into the three primary colors of RGB, each light passes through a liquid crystal element, a polarizing plate, etc. in each optical path, and is finally enlarged by a projection lens on the screen. This is a method of forming an image and displaying an image. In the projection-type liquid crystal display device, a front projector that is projected on the screen from the observer is mainly used for business use, and a rear projector that is projected from the back side of the screen to the observer is mainly used for home use. It is used for.
In recent years, projection-type liquid crystal display devices have increased in screen brightness, and accordingly, high-pressure mercury lamps that emit powerful light have come to be used as light sources. For this reason, the polarizing plate disposed in the optical path is required to have durability against strong light and heat, and the durability of the projection type liquid crystal display device including the liquid crystal element is not limited to the durability of the liquid crystal element. Durability has become an important factor that determines the life of a projection type liquid crystal display device.
As a polarizing plate excellent in durability, a configuration in which a transparent glass molded product is directly attached to at least one surface of a polarizing film based on polyvinyl alcohol (PVA) with an adhesive is used as a polarizing plate for a projector. Is disclosed. Patent Document 2 discloses that it is effective to use YAG (yttrium aluminum garnate) ceramics having high thermal conductivity as a transparent base material for a polarizing plate for a projector. A film (PVA) that has been attached to YAG ceramics without providing a substrate film is disclosed.

JP-A-10-39138 ([0005] [Example 1]) Japanese Patent Laid-Open No. 2002-55231 ([0027] [Example 1])

Since the polarizing film of patent documents 1 and 2 is pasted on a transparent base material without giving a substrate film, a polarizing film is very weak in mechanical strength and becomes a polarizing film at the time of handling. Because of cracks, practical application was difficult.
An object of the present invention is to provide a practical polarizing plate that is inexpensive, excellent in mechanical strength, and excellent in durability.

As a result of intensive studies in view of the above problems, it is a polarizing plate in which a substrate film that gives mechanical strength to at least one of polarizing films is bonded, and a transparent substrate is bonded to both surfaces, and one of the transparent substrates It has been found that such a problem can be solved when only a base material having a high coefficient representing the ease of conducting heat in the in-plane direction is used.
That is, this invention is a polarizing plate formed by laminating a transparent substrate (1), a polarizing film (2), a substrate film (3), and a transparent substrate (4) in order, The polarizing plate is characterized in that the coefficient representing the ease of heat conduction in the in-plane direction in 1) exceeds the coefficient representing the ease of heat conduction in the in-plane direction of the transparent base material (4). (However, the coefficient representing the ease of conducting heat in the in-plane direction of the transparent substrate represents a value obtained by multiplying the thermal conductivity of the substrate by the thickness of the substrate).

  The polarizing plate of the present invention is inexpensive because it uses only one transparent substrate having a high coefficient representing the ease of heat conduction in the in-plane direction, and is excellent in the mechanical strength of the polarizing plate. The specific configuration of the polarizing plate of the present invention efficiently releases the heat generated in the polarizing film to the surroundings, and as a result, the temperature of the polarizing film can be lowered. Thus, the polarizing plate of the present invention is a polarizing plate that can be put to practical use because of its long life and excellent durability.

First, the mechanism of heat generation and heat dissipation in the polarizing plate of the present invention will be described in detail with reference to FIG. First, in the light (7) incident on the polarizing plate (6), the electric field component in the absorption axis direction is absorbed by the polarizing film (2), and the energy is released to the surroundings as heat. For this reason, the part (8) irradiated with light becomes high temperature, and the heat generated at this time is the substrate film (3), the substrate film (5) to be installed as necessary, the transparent substrate (1), and the transparent substrate. Heat is radiated to the outside of the polarizing plate (6) through (4).
Specifically, as the main heat flow, the heat generated in the heat generating portion (8) is first (14), (9) through the substrate film (3) and the substrate film (5) installed as necessary. When diffusing in the thickness direction (the laminating direction of each film, that is, the direction parallel to the transmitted light) and reaching the transparent base material (1) and the transparent base material (4) as shown in FIG. As shown in (15), most of the light is diffused by conduction in the in-plane direction (the surface direction of each film, that is, the direction perpendicular to the transmitted light), and heat is dissipated from the side of the transparent substrate as shown in (13) and (17) Is done. The remaining heat conducted in the thickness direction of the transparent substrate is released from the surface of the transparent substrate as shown in (13) and (16), respectively.
Thus, in order to promote the heat radiation from the heat generating part (8), the inventors have a high coefficient representing the ease of heat conduction in the thickness direction of the substrate films (3) and (5). It has been found that it is effective to use a transparent substrate having a high coefficient representing the ease of heat conduction in the in-plane direction of the transparent substrates (1) and (4).

In other words, when the substrate film (5) in the polarizing plate is required, the coefficient representing the ease of heat conduction in the in-plane direction in the transparent substrate (1) is in the in-plane direction in the transparent substrate (4). The coefficient indicating the heat conductivity in the thickness direction of the substrate film (5) is superior to the coefficient indicating the heat conductivity of the substrate film (3) and the coefficient indicating the heat conductivity in the thickness direction of the substrate film (3). It has been found that a polarizing plate superior to a coefficient representing ease of conduction is excellent in heat radiation from the heat generating portion (8) in the polarizing plate.
Here, the coefficient representing the ease of heat conduction in the in-plane direction in the transparent substrate represents a value obtained by multiplying the thermal conductivity of the transparent substrate by the thickness of the substrate, and the thickness in the substrate film. The coefficient representing the ease of heat conduction in the vertical direction represents a value obtained by dividing the thermal conductivity of the film by the thickness of the substrate film.
A transparent substrate having good thermal conductivity in the in-plane direction, that is, a transparent base material having a high coefficient representing the ease of conducting heat in the in-plane direction is generally expensive and constitutes a polarizing plate. It is practically impossible to apply to both sides. And when applying the transparent base material with a high coefficient representing the ease of heat conduction in the in-plane direction to only one surface of the polarizing plate of the present invention, the heat radiation is increased by adopting a specific configuration. Thus, the lifetime of the polarizing plate can be extended.

The material of the transparent base materials (1) and (4) constituting the polarizing plate of the present invention is an inorganic transparent material, specifically, silicate glass, borosilicate glass, titanium silicate glass, fused quartz. (Quartz glass), quartz, sapphire, YAG crystal, fluorite and the like can be exemplified.
A transparent substrate having a high coefficient representing the ease of conducting heat in the in-plane direction is generally expensive, and it is practically impossible to apply it to both sides when forming a polarizing plate. The polarizing plate of the present invention has a structure having a transparent substrate having a high coefficient representing the ease of heat conduction in the in-plane direction only on one surface, and this structure can increase the heat dissipation effect of the polarizing film. It can be done.
In order to impart durability to the polarizing plate, the coefficient representing the ease of heat conduction in the in-plane direction of the transparent substrate (1) is the heat conduction in the in-plane direction of the transparent substrate (4). A configuration that exceeds the coefficient representing ease is required. The material of the transparent substrate (1) is preferably a material such as fused quartz, quartz, or sapphire, and in particular, sapphire having a high coefficient representing the ease of heat conduction in the in-plane direction is preferable. Although it does not specifically limit as a material of a transparent base material (4), Materials, such as silicate glass, borosilicate glass, and fused quartz, can be illustrated.
Silicate glass is commercially available under the name of white plate glass or blue plate glass for optical materials.
The coefficient representing the ease of heat conduction in the in-plane direction of the transparent base material represents the value obtained by multiplying the thermal conductivity of the transparent base material by the thickness of the base material. For example, a transparent base material having a high thermal conductivity has a high coefficient. Table 1 shows the thermal conductivity of the transparent substrate.

  Here, the coefficient representing the ease of heat conduction in the in-plane direction of the transparent substrate (1) is 2 to 2 than the coefficient representing the ease of heat conduction in the in-plane direction of the transparent substrate (4). It is preferable to exceed 500 times, preferably 5 to 300 times. When it is 500 times or less, the thickness of the transparent substrate (1) is decreased, and it is preferable because the transparent substrate tends to be easily obtained. Above all, it is preferable that the ratio is 5 to 300 times because both the price for realization and the heat dissipation effect from the polarizing film can be achieved.

  The thickness of the transparent base materials (1) and (4) is preferably 0.05 mm to 5 mm, more preferably 0.8 mm, from the viewpoint of yield in the case of industrialization and size matching with the projector optical system to be applied. It is 08-3 mm. A thickness of 0.05 mm or more is preferable because breakage of the glass is suppressed during processing and there is a tendency to stably produce the polarizing plate. When the thickness is 5 mm or less, the obtained polarizing plate tends to be reduced in size and weight. This is preferable.

  It is desirable that each of the transparent substrates (1) and (4) is subjected to an antireflection treatment according to the wavelength of light used on the surface in contact with air. Examples of the antireflection treatment include those using a dielectric multilayer film by sputtering or vacuum deposition, and providing a low refractive index layer by coating.

The polarizing film (2) used in the present invention is a dichroic dye or a polarizing film substrate such as polyvinyl alcohol resin, polyvinyl acetate resin, ethylene / vinyl acetate (EVA) resin, polyamide resin or polyester resin. Iodine is oriented by adsorption.
Here, the polyvinyl alcohol-based resin includes polyvinyl alcohol which is a partially saponified product of polyvinyl acetate; vinyl acetate such as saponified EVA resin and other copolymerizable monomers (for example, ethylene or propylene Such as olefins, saponified products of unsaturated carboxylic acids such as crotonic acid, acrylic acid, methacrylic acid, and maleic acid, unsaturated sulfonic acids, vinyl ethers, etc .; polyvinyl alcohol modified with aldehyde Formal, polyvinyl acetal and the like are included. As the polarizing film substrate, a film of a polyvinyl alcohol-based resin, particularly a film of polyvinyl alcohol itself, is preferably used from the viewpoints of dye adsorption and orientation.

A material that is adsorbed and oriented on the polarizing film substrate is preferably a dichroic dye from the viewpoint of durability.
By using dyes having different wavelength dependencies, it is possible to produce respective polarizing films for the blue channel, the green channel, and the red channel of the projection type liquid crystal display device.
Examples of the dichroic dye include compounds described in “Development of dichroic dyes for liquid crystal display devices” (Sone et al., Sumitomo Chemical, 2002-II, pp. 23-30).

（式中、Ｍｅは銅原子、ニッケル原子、亜鉛原子および鉄原子から選ばれる金属原子を示す。Ａ^１は置換されていてもよいフェニル基または置換されていてもよいナフチル基を示す。Ｂ^１は置換されていてもよいナフチル基を示し、Ｍｅに結合している酸素原子と−Ｎ＝Ｎ−で示されるアゾ基とは互いに隣接位置にある。Ｒ^１およびＲ^２はそれぞれ独立に炭素数１〜４のアルキル基、炭素数１〜４のアルコキシル基、カルボキシル基、スルホキシ基、スルホンアミド基、スルホンアルキルアミド基、アミノ基、アシルアミノ基、ハロゲン原子またはニトロ基を示す。）
で示される二色性染料、 Specifically, in the form of the free acid, the formula (I)

(In the formula, Me represents a metal atom selected from a copper atom, a nickel atom, a zinc atom and an iron atom. A ¹ represents an optionally substituted phenyl group or an optionally substituted naphthyl group. B ¹ Represents an optionally substituted naphthyl group, and the oxygen atom bonded to Me and the azo group represented by —N═N— are adjacent to each other, and R ¹ and R ² each independently represents the number of carbon atoms. (A 1-4 alkyl group, a C1-C4 alkoxyl group, a carboxyl group, a sulfoxy group, a sulfonamide group, a sulfonalkylamide group, an amino group, an acylamino group, a halogen atom, or a nitro group.)
A dichroic dye represented by

（式中、Ａ^３およびＢ^３はそれぞれ独立に置換されていてもよいフェニル基または置換されていてもよいナフチル基を示し、Ｒ^３およびＲ^４はそれぞれ独立に水素原子、炭素数１〜４のアルキル基、炭素数１〜４のアルコキシル基、カルボキシル基、スルホキシ基、スルホンアミド基、スルホンアルキルアミド基、アミノ基、ハロゲン原子またはニトロ基を示し、ｍは０または１を示す。）
で示される二色性染料、 Formula (II) in the form of the free acid

(In the formula, A ³ and B ³ each independently represent a phenyl group which may be substituted or a naphthyl group which may be substituted; R ³ and R ⁴ each independently represent a hydrogen atom, a carbon number of 1 to 4; An alkyl group, an alkoxyl group having 1 to 4 carbon atoms, a carboxyl group, a sulfoxy group, a sulfonamide group, a sulfonealkylamide group, an amino group, a halogen atom or a nitro group, and m represents 0 or 1.)
A dichroic dye represented by

または化学式（III−２）

で示される２価の残基を示す。Ｑ^２およびＱ^３はそれぞれ独立に置換されていてもよいフェニレン基をしめす。〕
で示される二色性染料、 Formula (III) in the form of the free acid
^{Q 1 -N = N-Q 2} -X-Q 3 -N = N-Q 4 (III)
[Wherein, Q ¹ and Q ⁴ each independently represent an optionally substituted phenyl group or an optionally substituted naphthyl group, and X represents a chemical formula (III-1)

Or chemical formula (III-2)

The bivalent residue shown by is shown. Q ² and Q ³ each independently represent an optionally substituted phenylene group. ]
A dichroic dye represented by

〔式中、Ｍｅは銅原子、ニッケル原子、亜鉛原子および鉄原子から選ばれる金属原子を示し、Ｑ^５およびＱ^６はそれぞれ独立に置換基を有していてもよいナフチを示し、Ｍｅと結合している酸素原子と−Ｎ＝Ｎ−で示されるアゾ基とは互いに隣接位置にある。Ｙは化学式（IV−１）

または

で示される２価の残基を示す。Ｒ^５およびＲ^６はそれぞれ独立に水素原子、炭素数１〜４のアルキル基、炭素数１〜４のアルコキシル基またはスルホキシ基を示す。〕
で示される二色性染料、並びに Formula (IV)

[In the formula, Me represents a metal atom selected from a copper atom, a nickel atom, a zinc atom and an iron atom, Q ⁵ and Q ⁶ each independently represents naphthi which may have a substituent, and is bonded to Me. And the azo group represented by -N = N- are adjacent to each other. Y is the chemical formula (IV-1)

Or

The bivalent residue shown by is shown. R ⁵ and R ⁶ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms, or a sulfoxy group. ]
A dichroic dye represented by

SH-I Direct Yellow-12, SH-I Direct Red 31, SH-I Direct Red 28, SH-I Direct Yellow-44, SH-I Direct Yellow -28, See Eye Direct Orange 107, See Eye Direct Red 79, See Eye Direct Red 2, See Eye Direct Red 81, See Eye Direct Red Color Index Generic Name (Color Index Generic) shown in the group consisting of Orange 26, Sea Eye Direct Orange 39, Sea Eye Direct Red 247 and Sea Eye Direct Yellow 142 A dichroic dye represented by (Name) is exemplified.

The dichroic dye may be used in the form of a free acid, or may be used in the form of an amine salt such as an ammonium salt, an ethanolamine salt, or an alkylamine salt. Usually, a lithium salt, a sodium salt, Used in the form of alkali metal salts such as potassium salts.
Such dichroic dyes may be used alone or in combination of two or more.

The following method can be illustrated as a manufacturing method of a polarizing film. First, a dye bath is prepared by dissolving a polarizing film dye in water so as to have a concentration of about 0.0001 to 10% by weight. If necessary, a dyeing assistant may be used. For example, a method using 0.1 to 10% by weight of sodium sulfate in a dyeing bath is suitable.
Dyeing is performed by immersing the polarizing film substrate in the dye bath thus prepared. The dyeing temperature is preferably 40 to 80 ° C. The dye is oriented by stretching a polarizing film substrate before dyeing or a dyed polarizing film substrate. Examples of the stretching method include a stretching method by a wet method or a dry method.
For the purpose of improving the light transmittance, polarization degree, and light resistance of the polarizing film, post-treatment such as boric acid treatment may be performed. The boric acid treatment varies depending on the type of polarizing film substrate used and the type of dye used, but usually with an aqueous boric acid solution prepared at a concentration in the range of 1 to 15% by weight, preferably 5 to 10% by weight, The polarizing film substrate is immersed in a temperature range of 30 to 80 ° C., preferably 50 to 80 ° C. Furthermore, if necessary, the fixing treatment may be performed with an aqueous solution containing a cationic polymer compound.

As the substrate film (3), an acetylcellulose film (TAC film) such as a triacetylcellulose film, a polyester resin film, an olefin resin film (for example, commercially available from ZEON as a registered trademark ZEONOR, and from JSR as a registered trademark ARTON). A polycarbonate resin film, a polyether ether ketone resin film, a polysulfone resin film, and the like.
By laminating the substrate film on the polarizing film, the strength of the polarizing film is improved and the durability is improved, and the handling property when processing with a single wafer is improved.
As thickness of a substrate film (3), it is 5-120 micrometers normally, Preferably, it is 10-90 micrometers. When the thickness is 120 μm or less, the coefficient representing the ease of heat conduction in the thickness direction is improved, and heat dissipation generated in the polarizing film (2) tends to be promoted, which is preferable. Moreover, it is preferable in it being 5 micrometers or more from the tendency for the intensity | strength of a polarizing film to improve.

In order to improve the strength of the polarizing film (2), a substrate film (5) may further be included between the transparent substrate (1) and the polarizing film (2). In order to promote heat dissipation to the transparent base material (1) on the incident light side, a coefficient representing the ease of heat conduction in the thickness direction in the substrate film (5) is in the thickness direction in the substrate film (3). It is preferable that the coefficient is larger than the coefficient representing the ease of heat conduction. Since the substrate film is a polymer material as is clear from the above examples, the thermal conductivity of the applied film is not so different as 0.1 to 0.3 W / (m · K). Therefore, the coefficient representing the ease of conducting heat in the thickness direction depends on the thickness of the substrate film to be used. Specifically, the thickness of the substrate film (5) is smaller than the thickness of the substrate film (3). Preferably, the thickness of the substrate film (5) is 80% or less, preferably 60% or less of the thickness of the substrate film (3).
The thickness of the substrate film (5) is preferably 80 μm or less, more preferably 50 μm or less. When the thickness is 80 μm or less, the coefficient representing the ease of heat conduction in the thickness direction is improved, and heat dissipation of heat generated in the polarizing film (2) tends to be promoted, which is preferable. If it is 50 μm or less, the coefficient representing the ease of heat conduction in the thickness direction is further improved, and the effect of the present invention becomes more remarkable.

When the structure of the polarizing plate is listed in the order of lamination, for example, [transparent substrate (1) / substrate film (5) / polarizing film (2) / substrate film (3) / transparent substrate (4)] (FIG. 1), [Transparent substrate (1) / polarizing film (2) / substrate film (3) / transparent substrate (4)] (FIG. 2) and the like.
In order to increase the heat radiation from the heat generating part (8) in the polarizing plate, it is preferable that the substrate film (5) is not required unlike the polarizing plate having the configuration shown in FIG.

  In the polarizing plate of the present invention, the incident direction of transmitted light is from the transparent substrate (1) side (incident light (7) in FIG. 1, transparent base having a high coefficient representing the ease of conducting heat in the in-plane direction) Although the light is incident from the material) or from the transparent base material (4) side (not shown) is not limited, the former is preferable because it can further promote the long life. In the heat generating part (8), the incident surface side has a larger amount of heat generation than the exit surface side, and the transparent substrate (1) having a high coefficient representing the ease of heat conduction in the in-plane direction is used as the incident surface of the heat generating part. This is because heat dissipation can be further promoted by making the distance closer to.

  In the case of the structure shown in FIG. 1 as a polarizing plate, the manufacturing method is, for example, bonding the substrate film (5) and the substrate film (3) to both surfaces of the polarizing film (2) by using an adhesive, and then polarizing the polarizing plate. After obtaining, the method of bonding a transparent base material (1) and a transparent base material (4) on both surfaces of a polarizing plate using an adhesive, an ultraviolet curable adhesive, etc. are mentioned. Furthermore, in the case of the structure shown in FIG. 2, the manufacturing method is, for example, bonding the substrate film (3) to one side of the polarizing film (2) with an adhesive to obtain a polarizing plate, and then applying both sides of the polarizing plate. The method of bonding a transparent base material (1) and a transparent base material (4) through an adhesive, an ultraviolet curable adhesive, etc. are mentioned. The ultraviolet curable adhesive is suitably used because it does not require a drying step and has a high bonding speed.

The polarizing plate of the present invention is used in, for example, a projection type liquid crystal display device (projector). The details will be described using the optical system of the rear projector shown in FIG. 3 as an example. The polarizing plates of the present invention are illustrated as 142 and 143 in FIG.
The light bundle using the high-pressure mercury lamp 111 as a light source is first made uniform and polarized in the cross-section of the anti-beam bundle by the first lens array 112, the second lens array 113, the polarization conversion element 114, and the superimposing lens 115. Is called.
Specifically, the light bundle emitted from the light source 111 is divided into a number of minute light bundles by the first lens array 112 in which minute lenses 112a are arranged in a matrix. The second lens array 113 and the superimposing lens 115 are provided such that each of the divided light bundles irradiates the entire three LCD panels 140R, 140G, and 140B that are the illumination target. The entire surface of the LCD panel incident side has substantially uniform illuminance.

The polarization conversion element 114 is usually configured by a polarization beam splitter array, and is disposed between the second lens array 13 and the superimposing lens 15. As a result, random polarized light from the light source is converted into polarized light having a specific polarization direction in advance, thereby reducing the light loss at the incident-side polarizing plate described later, thereby improving the screen brightness.
The light with uniform brightness and polarized light is sequentially separated into red channel, green channel, and blue channel by the dichroic mirrors 122, 123, 132 for separating the three primary colors of RGB through the reflection mirror 122, respectively. The light enters the LCD panels 140R, 140G, and 140B.

Regarding the LCD panels 140R, 140G, and 140B, the polarizing plate (incident side) 142 and the polarizing plate (exit side) 143 of the present invention are arranged on the incident side and the outgoing side, respectively.
A description will be given of two polarizing plates arranged on the incident side and the emission side with a liquid crystal panel sandwiched between the RGB optical paths. The polarizing plate (incident side) 142 and the polarizing plate (exit side) 143 arranged in each optical path are arranged in a configuration in which the absorption axis is orthogonal, and each LCD panel 140R, 140G, 140B arranged in each optical path. It fulfills the function of converting the polarization state controlled for each pixel by the image signal into light quantity.
The polarizing plate of the present invention has a configuration common to all the optical paths of the blue channel, the green channel, and the red channel, and is effective as a polarizing plate having excellent durability in any optical path. It is particularly effective.
An optical image created by transmitting incident light with different transmittance for each pixel according to the image data of the LCD panels 140R, 140G, and 140B is synthesized by the cross dichroic prism 150, and is projected by the projection lens 170 to the screen 180. Is enlarged and projected.

Examples are shown below, but the present invention is not limited to the examples.
(Example 1)
A polyvinyl alcohol film (VF-PX manufactured by Kuraray Co., Ltd., hereinafter referred to as “PVA”) is uniaxially stretched, dyed with a red dye, and dried. The polarization degree at a thickness of 28 μm and 440 nm is 99.9%, and the transmittance is 44. A polarizing film for a projector blue channel of 0% was obtained. An acetylcellulose film (KC4UY manufactured by Konica Corporation, hereinafter referred to as 4UYTAC) having a thickness of 40 μm was bonded to one surface of the polarizing film (PVA) with an epoxy adhesive to produce a polarizing film. A 0.7 mm sapphire glass (manufactured by Kyocera Corporation) is pasted on the PVA surface of the obtained polarizing film through an adhesive so that the 4 UTAC surface has a 0.1 mm blue plate glass as shown in FIG. The polarizing plate was obtained. The surfaces of both the sapphire glass and the blue plate glass that were in contact with air were subjected to antireflection treatment consisting of five dielectric layers by vacuum deposition.
It was 11 days when the polarizing plate (142) thus obtained was put into the blue channel optical path of the light resistance evaluation apparatus shown in FIG. 5 and the time until light leakage occurred was examined. The light resistance evaluation apparatus used at this time used a 100 W high-pressure mercury lamp manufactured by Philips as a light source, and the amount of light applied to the polarizing plate was 2.5 W per cm ² .
Here, the light leakage is a phenomenon in which the transmittance in the absorption axis direction of the polarizing plate increases after being put into the light resistance evaluation device, and the normal polarizing plate and the polarizing plate after being put into the light resistance evaluation device are crossed Nicols. In the case of the arrangement, the one that originally has a low transmittance is a phenomenon in which the transmittance increases due to a deterioration phenomenon and light leaks and transmits.

(Example 2)
A polarizing film for a projector blue channel is obtained from uniaxial stretching of PVA in the same manner as in Example 1, and an acetylcellulose-based film (Konica Corporation) having a thickness of 80 μm with an epoxy adhesive on one side of this polarizing film (PVA). KC8UY (hereinafter referred to as “8UYTAC”) and 4UYTAC were bonded to the other surface to prepare a polarizing film. On the 4UYTAC side of the obtained polarizing plate, 0.7 mm of sapphire glass (manufactured by Kyocera Corporation) is bonded to the 8UYTAC side via an adhesive to obtain a polarizing plate having a configuration shown in FIG. It was. The surfaces of both the sapphire glass and the blue plate glass in contact with air were subjected to antireflection treatment consisting of five dielectric layers by vacuum deposition.
When the thus obtained polarizing plate was put into the blue channel optical path of the light resistance evaluation apparatus in the same manner as in Example 1, light leakage due to deterioration of the polarizing plate occurred 8 days after the putting.

(Examples 3-5, Comparative Examples 1-2)
Polarizing plates were prepared according to Examples 1 and 2, and light resistance evaluation was performed. The results are summarized in Table 2 together with Examples 1 and 2.

  Since the polarizing plate of the present invention is inexpensive, excellent in mechanical strength, and excellent in durability against light and heat of transmitted light, it has a long life even when used as a polarizing plate in a projection type liquid crystal display device such as a front projector and a rear projector. It is excellent in practicality.

Configuration diagram of polarizing plates of Example 2, Example 3, Example 4, Example 5 and Comparative Example 2, and explanatory diagram of the heat dissipation mechanism of the polarizing plate of the present invention Configuration diagram of polarizing plate of Example 1 One aspect of projection type liquid crystal display device Configuration diagram of polarizing plate of Comparative Example 1 Light resistance evaluation apparatus used in the examples

Claims (8)

  A transparent substrate (1), a polarizing film (2), a substrate film (3), and a transparent substrate (4) are laminated in order, and are in-plane directions in the transparent substrate (1) A polarizing plate characterized in that the coefficient representing the ease of heat conduction to the substrate exceeds the coefficient representing the ease of heat conduction in the in-plane direction of the transparent substrate (4). However, the coefficient representing the ease of heat conduction in the in-plane direction of the transparent substrate represents a value obtained by multiplying the thermal conductivity of the substrate by the thickness of the substrate.   A substrate film (5) is further included between the transparent substrate (1) and the polarizing film (2), and the coefficient representing the ease of heat conduction in the thickness direction in the substrate film (5) is the substrate film (3). The polarizing plate according to claim 1, which exceeds a coefficient representing easiness of heat conduction in the thickness direction in). However, the coefficient representing the ease of heat conduction in the thickness direction of the substrate film represents a value obtained by dividing the thermal conductivity of the film by the thickness of the film.   The coefficient representing the ease of heat conduction in the in-plane direction of the transparent substrate (1) is 2 to 500 times the coefficient representing the ease of heat conduction in the in-plane direction of the transparent substrate (4). The polarizing plate according to claim 1, wherein the polarizing plate is large.   The polarization conversion element according to any one of claims 1 to 3, wherein the transparent substrate (1) is fused quartz, quartz or sapphire, and the transparent substrate (4) is silicate glass or borosilicate glass.   The polarizing plate according to claim 1, wherein the substrate film has a thickness of 10 to 45 μm.   The polarizing plate according to claim 1, wherein the substrate films (3) and (4) are a film mainly composed of triacetyl cellulose or an olefin resin film.   The polarizing plate is a polarizing plate formed by sequentially laminating a transparent substrate (1), a polarizing film (2), a substrate film (3), and a transparent substrate (4) in the light incident direction. The polarizing plate according to any one of claims 1 to 6. A projection type liquid crystal display device comprising the polarizing plate according to claim 1.

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