JP2003240957A - Polarization conversion element and projection type liquid crystal display - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a polarization conversion element which provides a projection type liquid crystal display device with little deterioration of display quality, and further using the same,
A projection type liquid crystal display device having stable display quality is provided. SOLUTION: At least one side of a polarizing film 55 made of a polyvinyl alcohol-based resin film has a temperature of 130 ° C.
Polarized light obtained by laminating a polarizing plate 52 to which a protective film 54 or 55 made of a resin having the above glass transition temperature and a photoelastic coefficient of 50 × 10 ⁻¹³ cm ² / dyne or less is laminated on a transparent glass substrate 51. A conversion element 50 is provided. A retardation plate 57 may be laminated between the transparent glass substrate 51 and the polarizing plate 52. A projection type liquid crystal display device in which the polarization conversion element 50 is arranged in the optical path is also provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization conversion element preferably used in a projection type liquid crystal display device. The present invention also relates to a projection type liquid crystal display device using this polarization conversion element.

[0002]

2. Description of the Related Art A projection type liquid crystal display device is also called a liquid crystal projector and is widely used as a device capable of enlarging and projecting a screen of a personal computer, a television or the like. In such a projection type liquid crystal display device, many optical elements such as a polarization conversion element in which a linear polarizing plate and a retardation plate are laminated on a transparent substrate are used.

The projection type liquid crystal display device is of a single plate type in which the spectral light from the color filter is directly expanded, and of the type in which a transmission type liquid crystal cell corresponding to each light is transmitted after being split into three primary colors. There is a type in which the light is split into three primary colors and then reflected by a reflective liquid crystal cell corresponding to each light. Here, the outline of the configuration of a projection type liquid crystal display device using a transmission type liquid crystal cell corresponding to the three primary colors, which is currently the mainstream, will be described with reference to FIG.

Such a projection type liquid crystal display device usually has a light source system 10, a reflection / spectroscopic system 20, and a magnifying projection system 40. The light source system 10 has a white light source 11, a UV / IR cut filter 12, and a condenser lens 13. In this example, the white light L from the white light source 11 is condensed lens 1
The light is condensed at 3, and further cuts ultraviolet rays and infrared rays by the UV / IR cut filter 12 and is sent to the reflection / spectroscopic system 20. As the white light source 11, a high brightness lamp such as a metal halide lamp or a high pressure mercury lamp is usually used. Although illustration is omitted, a polarization beam splitter (PBS) is arranged in the light source system 10 to convert natural light into almost polarized light and send it to the reflection / spectroscopic system 20.

The reflection / spectroscopic system 20 includes four types of dichroic mirrors 21, 22, 23 and 24, two total reflection mirrors 25 and 26, red light R, green light G and blue light B, respectively.
Corresponding liquid crystal cells 27R, 27G and 27B, incident side polarization conversion elements 28R, 28G and 28B, emission side polarization conversion elements 29R, 29G and 29B, and a condenser lens 3.
It has 0R, 30G and 30B.

Then, the first dichroic mirror 21
Receives the white light L from the light source system 10 and transmits only the red light R and the green light G. The red light R and the green light G transmitted through the light are transmitted through the second dichroic mirror 2
Sent to 2. The blue light B reflected by the first dichroic mirror 21 is sent to the first total reflection mirror 25, is reflected there, and then is condensed by a condenser lens 30B for blue, an incident side polarization conversion element 28B, and a liquid crystal cell 27B. Then, it is sent to the third dichroic mirror 23 through the output side polarization conversion element 29B.

The second dichroic mirror 22 transmits only the red light R, and out of the red light R and the green light G transmitted through the first dichroic mirror 21, the second dichroic mirror 22 is transmitted. The red light R passes through the red condenser lens 30R, the incident side polarization conversion element 28R, the liquid crystal cell 27R, and the emission side polarization conversion element 29R, and is sent to the second total reflection mirror 26. The green light G reflected by the second dichroic mirror 22 passes through a green condenser lens 30G, an incident side polarization conversion element 28G, a liquid crystal cell 27G and an emission side polarization conversion element 29G.
It is sent to the third dichroic mirror 23.

The third dichroic mirror 23 transmits only the blue light B, and the first total reflection mirror 2
The blue light B reflected from 5 is transmitted through the third dichroic mirror 23 as it is, and the green light G reflected from the second dichroic mirror 22 is reflected by the third dichroic mirror 23, and is reflected by the fourth dichroic mirror 23, respectively. To the dichroic mirror 24. The fourth dichroic mirror 24 transmits only the green light G and the blue light B, the green light G and the blue light B from the third dichroic mirror 23 are transmitted therethrough as they are, and the second total reflection. The red light R from the mirror 26 is reflected here and is sent to the magnifying projection system 40, respectively.

[0009] Here, first, the blue light is split into
Next, the form of splitting red light and green light was shown, but the order of splitting can be arbitrarily changed by combining dichroic mirrors.

The magnifying projection system 40 has a projection lens 41, where an image corresponding to each light is magnified and a magnified image is projected on the screen 42. The incident side polarization conversion elements 28R, 28G, 28B and the emission side polarization conversion elements 29R, 29G, 29B of the liquid crystal cells 27R, 27G, 27B corresponding to the respective colors are the liquid crystal cells 2
7R, 27G, 27B may be used by being stuck together, but it is usually arranged at a distance from the liquid crystal cells 27R, 27G, 27B, and this distance serves as a ventilation passage for cooling. Further, the incident side polarization conversion elements 28R, 28G, 28B
May be attached to the condenser lenses 30R, 30G, and 30B, or may be arranged with a space therebetween. Polarization conversion elements 28R, 28G, 28B, 29R,
When the 29G and 29B are arranged apart from the liquid crystal cells 27R, 27G and 27B and the condenser lenses 30R, 30G and 30B, a linear polarizing plate is used by being attached to a reinforcing material such as glass.

In such a projection type liquid crystal display device, each of the liquid crystal cells 27R, 27G and 27B has two
One polarization conversion element, that is, the incident side polarization conversion element 28
R, 28G, 28B and exit side polarization conversion elements 29R, 2
It is arranged between 9G and 29B. As described above, the polarization conversion elements 28 and 29 are formed by laminating a linear polarizing plate on a reinforcing material such as glass.

Here, the linear polarizing plate transmits only polarized light in a specific vibration direction and blocks polarized light in a direction orthogonal thereto, and is a polarized light in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin film. Films fall under this category, but polyvinyl alcohol-based resin films are inferior in mechanical properties and durability.Therefore, a film made of a cellulose-based resin such as triacetyl cellulose is attached on both sides for protection. It is used. Also,
A retardation plate is laminated on a linear polarizing plate, which is used as a polarization conversion element 2
In some cases, a protective film made of a cellulosic resin is laminated on both surfaces of the polarizing film to form a linear polarizing plate, and a retardation plate is laminated on the linear polarizing plate. Then, the polarization conversion elements 28, 2
In No. 9, the amount of light necessary for enlarging and projecting the image on the screen is transmitted, so that the heat generation is large.

[0013]

In a projection type liquid crystal display device, in order to enlarge and project an image formed by a liquid crystal cell having a small area, a high brightness light source such as the metal halide lamp or the high pressure mercury lamp described above is used. Is used. Therefore, the amount of light incident on the polarization plate of the polarization conversion element is very strong, and a large amount of light is absorbed by the linear polarization plate and converted into heat, so that the polarization conversion element in use has a high temperature. At a high temperature, color unevenness is likely to occur in the projected image due to the heat shrinkage of the polarizing plate.

In order to prevent the temperature of the polarization conversion element from rising,
Usually, it is often cooled by an air cooling fan or the like.
However, due to the vibration noise of the air cooling fan, it may not be possible to perform sufficient air cooling. Further, recent projection type liquid crystal display devices are required to be smaller and brighter,
The amount of light incident on the polarization conversion element per unit area is increasing. Along with this, the temperature rise of the polarization conversion element is also increased, and the deterioration of the display quality such as the occurrence of color unevenness in the projected image becomes remarkable.

Therefore, the present inventor has conducted diligent research to develop a polarization conversion element capable of providing a projection type liquid crystal display device with little deterioration in display quality. As a result, a specific protective film is attached to at least one surface of a polarizing film. By doing so, they have found that a projection type liquid crystal display device with less deterioration in display quality can be provided, and completed the present invention.

[0016]

That is, the present invention provides a protective film made of a resin having a glass transition temperature of 130 ° C. or higher and a photoelastic coefficient of 50 × 10 ⁻¹³ cm ² / dyne or lower on at least one surface of a polarizing film. The polarizing plate to which is bonded is provided on the transparent glass substrate to provide a polarization conversion element. The present invention also provides a projection type liquid crystal display device in which this polarization conversion element is arranged in the optical path.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a polarizing plate is obtained by laminating a specific protective film on at least one surface of a polarizing film, and laminating this on a transparent glass substrate to obtain a polarization conversion suitable for a projection type liquid crystal display device. As an element. The protective film used here is made of a resin having a glass transition temperature of 130 ° C. or higher and a photoelastic coefficient of 50 × 10 ⁻¹³ cm ² / dyne or less. Further, the polarizing film is made of a polyvinyl alcohol-based resin film, and specifically, a polyvinyl alcohol-based resin film in which a dichroic dye, that is, a dichroic dye or iodine is adsorbed and oriented is exemplified. . The protective film and the polarizing film are laminated via an adhesive. In the present specification, a polyvinyl alcohol-based resin film in which a dichroic dye is adsorbed and oriented is referred to as a “polarizing film”, and a film in which a protective film is attached to one or both surfaces thereof is referred to as “polarized light”. They are called "plates" or "linear polarizers" to distinguish them.

A specific example of the polarization conversion element according to the present invention is shown in FIG.
5 shows a schematic sectional view. Hereinafter, the description will proceed with reference to these figures.

In the example of FIG. 2, a polarizing plate 52 is laminated on a transparent glass substrate 51 via a pressure sensitive adhesive 58 to form a polarization conversion element 50. The polarizing plate 52 includes a polarizing film 53 and a first protective film 54 attached to both surfaces thereof.
And a second protective film 55. In the present invention, at least one of the first protective film 54 and the second protective film 55 has a glass transition temperature of 130 ° C. or higher and a photoelastic coefficient of 50 × 10 ⁻¹³ cm ² /
Resin film below dyne. Of course, both the first protective film 54 and the second protective film 55 may be resin films having a high glass transition temperature and a small photoelastic coefficient. At least the side in contact with air, that is, the first protective film 54 is preferably a resin film having a high glass transition temperature and a small photoelastic coefficient. When the protective film 55 on the opposite side is made of another resin film, it may have a glass transition temperature lower than 130 ° C. and / or a photoelastic coefficient higher than 50 × 10 ⁻¹³ cm ² / dyne. Cellulose resins such as triacetyl cellulose and diacetyl cellulose, which are widely used as protective films for ordinary polarizing plates, can be used.

In the arrangement shown in FIG. 2, the second protective film 55 located on the transparent glass substrate 51 side may be omitted, and an example of this case is shown in FIG. In this example, a protective film 54 is attached to one surface of a polarizing film 53 to form a polarizing plate 52, and a transparent glass substrate 51 is laminated on a surface where the protective film 54 is not attached via a pressure sensitive adhesive 58. Then, the polarization conversion element 50 is configured.
In this case, the protective film 54 is made of the resin film having a high glass transition temperature and a small photoelastic coefficient.

The polarizing plate 52 is laminated on the transparent glass substrate 51 via a pressure sensitive adhesive to form a polarization conversion element, but it is also possible to laminate a retardation plate. An example of this case is shown in FIGS.

FIG. 4 shows the phase difference plate 5 in the layer structure shown in FIG.
7 is added, and the second pressure-sensitive adhesive 59 is added accordingly. That is, on the transparent glass substrate 51,
A retardation plate 57 is laminated via a pressure-sensitive adhesive 58, and on the surface of the retardation plate 57 opposite to the transparent glass substrate 51, the first protective film 5 is formed on both sides of the polarizing film 53.
Polarizing plate 52 to which 4 and the second protective film 55 are attached
One surface is laminated with a pressure sensitive adhesive 59 interposed therebetween to form the polarization conversion element 50. Also in this case, as in the case of FIG. 2, at least one of the first protective film 54 and the second protective film 55 has a glass transition temperature of 130 ° C. or higher and a photoelastic coefficient of 50 × 10 5.
^-13 cm ² / dyne or less resin film. Of course, both the first protective film 54 and the second protective film 55 may be resin films having a high glass transition temperature and a small photoelastic coefficient. At least the side in contact with air, that is, the first protective film 54 is preferably a resin film having a high glass transition temperature and a small photoelastic coefficient.

FIG. 5 shows the phase difference plate 5 in the layer structure shown in FIG.
7 is added, and the second pressure-sensitive adhesive 59 is added accordingly. That is, in this example, the protective film 54 is attached to one surface of the polarizing film 53 to form the polarizing plate 52, and the phase difference plate 57 is attached to the surface where the protective film 54 is not attached via the pressure sensitive adhesive 59. The polarization conversion element 50 is configured by laminating and further laminating the transparent glass substrate 51 on the surface of the retardation plate 57 opposite to the surface on which the polarizing plate 52 is bonded via the pressure sensitive adhesive 58. ing. In this case, the protective film 54 is made of the resin film having a high glass transition temperature and a small photoelastic coefficient.

In the example shown in FIGS. 2 to 5, the transparent glass substrate 51 may be, for example, an optically isotropic glass flat plate, or a dichroic coating layer may be provided on one or both surfaces of the glass flat plate. A trimming filter or the like which has the above-mentioned and transmits only the light in the specific wavelength range but does not transmit the light in the other wavelength range may be used. The material of the transparent glass substrate 51 may be, for example, soda glass, silicate glass, borosilicate glass, crown glass, titanium silicate glass, quartz glass, or sapphire glass or quartz glass having high thermal conductivity. The transparent glass substrate 51 usually has a thickness of about 0.3 to 2 mm. In addition, the transparent glass substrate 51
Area is appropriately selected according to the size of the intended projection type liquid crystal display device.

In the present invention, a specific protective film is attached to at least one surface of the polarizing film 53. The polarizing film 53 itself may be one that has been used in a conventional projection type liquid crystal display device, and as described above, a dichroic dye, that is, a dichroic dye or iodine, is added to a polyvinyl alcohol resin film. Although it is adsorption-aligned, a so-called dye-based polarizing film in which a dichroic dye is adsorption-aligned is particularly preferably used in a projection type liquid crystal display device because it has excellent durability. Polarizing film 53
Usually has a thickness of about 6 to 50 μm.

The protective film 5 is provided on one side of the polarizing film 53.
In the case of laminating No. 4, the protective film 54, and in the case of laminating the protective films 54, 55 on both surfaces of the polarizing film 53, at least one of them, preferably the first protective film on the side that comes into contact with air. 54 has a glass transition temperature of 130 ° C. or higher and a photoelastic coefficient of 50 × 10 ⁻¹³ cm ² /
Resin film below dyne. The glass transition temperature of the resin constituting the protective film 54 is preferably 140 ° C. or higher, and the photoelastic coefficient is preferably 10 × 10.
^-13 cm ² / dyne or less. As described above, by using the protective film made of a resin having a high glass transition temperature and a small photoelastic coefficient, it is possible to prevent the retardation unevenness of the protective film caused by the thermal deformation or strain of the polarizing film. When the glass transition temperature of the resin forming the protective film 54 is lower than 130 ° C., the thermal deformation of the protective film becomes remarkable. Also, its photoelastic coefficient is 50 × 10 ^-13 c
When it is larger than m ² / dyne, a new phase difference is generated due to the distortion caused by heat, and the polarization is disturbed, so that color unevenness is likely to occur in the image. There is no particular limitation on the upper limit of the glass transition temperature of the protective film 54, and for example, a resin having a glass transition temperature of about 300 ° C. may be used. The lower limit of the photoelastic coefficient is not particularly limited, and for example, a resin having a photoelastic coefficient of about 0.1 × 10 ⁻¹³ cm ² / dyne may be used.

Photoelasticity means isotropic property, that is, when an external force is applied to a substance having a birefringence of 0 to cause stress inside, it exhibits optical anisotropy and exhibits birefringence. A phenomenon. If the stress acting on the substance (force acting on a unit area) is σ and the birefringence is Δn, the stress σ
And birefringence Δn are theoretically proportional to each other, and can be expressed as Δn = Cσ, where C is the photoelastic coefficient. In other words, when the stress σ acting on a substance is plotted on the horizontal axis and the birefringence Δn when the stress acts is plotted on the vertical axis, theoretically the relationship between the two becomes a straight line, and the gradient of this straight line is the photoelasticity. It is a coefficient.

Specific examples of the resin having a high glass transition temperature and a small photoelastic coefficient specified in the present invention include a modified polycarbonate resin film and a cyclic polyolefin resin film containing a cyclic olefin such as norbornene as a monomer. To be Examples of the modified polycarbonate resin film include “Pure Ace WR” (trade name; glass transition temperature of about 223 ° C., manufactured by Teijin Ltd.,
The photoelastic coefficient is about 45 × 10 ⁻¹³ cm ² / dyne). The cyclic polyolefin resin film is, for example, "Arton" (trade name; manufactured by JSR Co., Ltd.).
Glass transition temperature about 170 ℃, photoelastic coefficient about 4 × 10 ^-13 c
m ² / dyne), Sekisui Chemical Co., Ltd. "ESCINA" (trade name; glass transition temperature about 140 ° C, photoelastic coefficient about 6 × 1)
0 ^-13 cm ² / dyne) Ya "SCA40" (trade name; glass transition temperature of about 140 ° C., the photoelastic coefficient of about ^{6 × 10 -13 cm 2 / dyne} ) and the like.

The thickness of the protective films 54, 55 is usually 2
0 to 200 μm, preferably 30 μm or more,
Further, it is preferably 120 μm or less. When the resin film having a high glass transition temperature and a low photoelastic coefficient defined in the present invention is used as the protective film, its thickness is more preferably 60 μm or less. Protective film 54,5
The in-plane retardation of 5 is preferably small, for example, 50 nm or less, further preferably 30 nm or less.

When a protective film having a high glass transition temperature and a low photoelastic coefficient defined in the present invention is attached to the polarizing film 53, for example, a polyvinyl alcohol adhesive layer, a urethane adhesive layer, an epoxy adhesive layer is used. It is attached via an adhesive layer or the like. On the other hand, a protective film having the above-mentioned high glass transition temperature and a small photoelastic coefficient is attached to one side of the polarizing film 53, and 130 ° C. is attached to the other side.
Lower glass transition temperature and / or 50 × 10 ^-13 cm ² /
When laminating a protective film having a photoelastic coefficient larger than that of dyne, for example, a cellulose-based resin film as the protective film, the latter protective film and the polarizing plate 55 are laminated, for example, via a polyvinyl alcohol-based adhesive layer. Is done.

As shown in FIGS. 4 and 5, the polarizing plate 52
In addition to this, when laminating the phase difference plate 57,
No. 7 may be the same as that used in a normal projection type liquid crystal display device, and generally, one made of a polymer film is used. As the polymer constituting the retardation plate, for example, polycarbonate resin, cellulose resin such as triacetyl cellulose or diacetyl cellulose, polysulfone resin, polyether sulfone resin, polyester resin such as polyethylene terephthalate,
Examples include polyimide resins, polyamide resins, polyarylate resins, cyclic polyolefin resins using cyclic olefins such as norbornene as monomers, polyvinyl alcohol resins, and the like. A film made of these resins can be made into a retardation film, for example, by stretching it in a uniaxial direction.

The polymer film forming the retardation plate 57 may be a single film or a laminate of two or more films. As an example of the retardation plate in which two or more polymer films are laminated, polymer films having the same retardation are laminated so that their slow axes intersect each other at a certain angle, so that they are substantially equal over a wide wavelength range. A so-called broadband retardation film that can provide retardation can be used. The thickness of the retardation plate 57 is usually about 20 to 1,000 μm, preferably 2
It is about 0 to 150 μm.

It is advantageous that the retardation plate 57 usually exhibits a retardation of ½ wavelength with respect to the light on the optical path in which the polarization conversion element 50 having the laminated layers is arranged.
Specifically, the retardation plate of the polarization conversion element used for the red optical path has a retardation of 290 to 320 nm,
Especially, it is 300 to 310 nm, which is 1 for red light.
What functions as a / 2 wavelength plate is preferable. The retardation plate of the polarization conversion element used for the green optical path has a retardation of 260 to 290 nm, especially 270 to 280 nm.
Those having a wavelength of nm and functioning as a half-wave plate for green light are preferable. Further, the retardation of the polarization conversion element used for the blue optical path has a retardation of 210
˜240 nm, especially 220 to 230 nm, and those which function as a ½ wavelength plate for blue light are preferable. Also, as a phase compensator, "Wide View" film (trade name) manufactured by Fuji Photo Film Co., Ltd. and Nippon Petrochemical
A film in which a liquid crystalline substance is applied and oriented on a base resin film, such as "Nisseki LC Film" (trade name) manufactured by KK may be further laminated.

The polarizing plate 52 and the retardation plate 57 are laminated via a pressure sensitive adhesive 59. The pressure-sensitive adhesive is a viscoelastic body that can be adhered to the surface of another substance only by pressing it and can be peeled off from the adherend to be removed, and is also called an adhesive. Pressure-sensitive adhesives include acrylate-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, and rubber-based pressure-sensitive adhesives. Among these, select a transparent and optically isotropic adhesive. You can use it. Of these, acrylate-based pressure-sensitive adhesives are preferably used.

For the polarizing plate 52 and the retardation plate 57, the angle formed by the optical axes of the polarized light to be emitted and the polarized light to be emitted may be appropriately selected. Examples include a mode in which the slow axis of the retardation plate 57 intersects at an angle of about 45 degrees, and a mode in which the absorption axis of the polarizing plate 52 and the slow axis of the retardation plate 57 intersect at an angle of about 67.5 degrees. Further, the polarizing plate 52 and the retardation plate 57 usually have substantially the same area, and it is preferable that the respective areas are substantially the same as or slightly smaller than the area of the transparent glass substrate 51.

The polarization conversion element 50 of the present invention preferably has an antireflection layer on the outermost surface thereof. For example, as shown in FIGS. 2 to 5, when the protective film 54 is laminated on the polarizing film 53, an antireflection layer can be provided on the outermost surface 60 of the protective film 54. When the retardation plate 57 is the outermost layer, an antireflection layer can be provided on the outermost surface of the retardation plate. Furthermore, a transparent film having an antireflection layer may be laminated, and the outermost layer may be used as the antireflection layer. Here, the antireflection layer is a layer that reduces the reflected light at the interface with the air layer, and prevents the generation of stray light due to the reflected light. The reflectance of the surface having the antireflection layer is preferably 2% or less, and more preferably 1% or less.

Examples of the antireflection layer include those usually used, for example, a single layer or multiple layers selected from metals, metal oxides and metal fluorides. Examples of the metal include silver and the like, and examples of the metal oxide include
For example, silicon oxide, aluminum oxide, titanium oxide,
Examples thereof include tantalum oxide, yttrium oxide, zirconium oxide, and the like, and examples of the metal fluoride include magnesium fluoride and the like. This antireflection layer may be a single layer or a multilayer consisting of two layers, three layers, four layers or more layers. The thickness of the antireflection layer and the thickness of each layer when it is a multilayer are appropriately selected depending on the number of layers, the refractive index of the substance used for each layer, and the like. A protective film is laminated on one side of the polarizing film, and a linear polarizing plate having an antireflection layer on the surface of the protective film is used, and on the polarizing film surface on the side opposite to the protective film, a transparent glass via a pressure sensitive adhesive. It is also possible to stack substrates or retardation plates.

In the polarization conversion element of the present invention, the contact angle on the outermost surface 60 on the side opposite to the transparent glass substrate 51, or the antireflection surface when an antireflection layer is present, is preferably 80 degrees or more. Further, those having a contact angle of 100 degrees or more are more preferable. The contact angle here is a value when water is used as the liquid. If the contact angle of the surface of the polarization conversion element that comes into contact with air is less than 80 degrees, fine particles such as dust are likely to adhere to the projection conversion liquid crystal display device using the polarization conversion element having such a surface. When used over a period of time, the contrast tends to decrease. The upper limit of the contact angle is 180 degrees.

When a protective film is laminated on one surface of a polarizing film and an antireflection layer is formed on the surface of the protective film, and the surface having the antireflection layer satisfies the contact angle defined here, the antireflection film is formed. The linear polarizing plate having a layer can be used as it is for the polarization conversion element of the present invention. However, since many ordinary antireflection layers do not have the contact angle defined here, in this case, a layer made of a fluorine compound may be provided on the upper surface of the antireflection layer.

The fluorine compound used for this purpose is not particularly limited as long as the contact angle can be 80 degrees or more,
Examples thereof include those usually used for preventing surface contamination, such as fluorine-containing silane compounds.
Such a fluorine compound is usually used in order to prevent dirt such as fingerprints from adhering to the surface. Specific examples of such a fluorine-containing silane compound include those represented by the following general formula (I).

[0041]

In the formula, R ⁰ is a linear or branched perfluoroalkyl group having 1 to 16 carbon atoms, X is an iodine atom or a hydrogen atom, Y is a hydrogen atom or a lower alkyl group, and Z is a fluorine atom. Or a trifluoromethyl group, R ¹ is a hydrolyzable group, R ² is a hydrogen atom or an inert monovalent organic group, and a, b, c and d each independently represent an integer of 0 to 200. , E is 0 or 1, m is an integer of 0 to 2, and n is 0.
˜2, and p represents an integer of 1 or more.

More specifically, for example, a fluorine-containing silane compound represented by the following formula (II) and having a molecular weight of about 4,500 can be mentioned (for these fluorine-containing silane compounds, see, for example, JP-A-1- (See Japanese Patent No. 294709).

[0044]

In the polarization conversion element 50 of the present invention, it is preferable to provide an antireflection layer also on the outermost surface 61 of the transparent glass substrate 51 on which no film is laminated. Further, on this surface, for example, a layer of the above-mentioned fluorine-containing silane compound may be provided to make the contact angle 80 degrees or more.

The polarization conversion element of the present invention can be suitably used in a projection type liquid crystal display device (liquid crystal projector). For example, in a projection type liquid crystal display device, in the optical path of white light from a white light source, or red light after white light is dispersed,
It can be used by inserting it in the optical path of each primary color light of green light and blue light.

Specifically, in the case of the projection type liquid crystal display device as shown in FIG. 1, the liquid crystal cell 27 corresponding to each of the three primary colors is used.
R, 27G, 27B incident side polarization conversion elements 28R, 28
G, 28B, and output side polarization conversion elements 29R, 29G,
It can be used as at least one of 29B. In the polarization conversion element, as shown in FIGS. 2 to 5, when the protective film 54 of the polarizing plate 52 forms the outermost surface, the polarizing plate 52 side normally faces the surface of the liquid crystal cells 27R, 27G, 27B. Is arranged as. In this case, the projection type liquid crystal display device includes a white light source 11 and white light L emitted from the light source 11.
Optical components (generally called dichroic mirrors) 21 and 2 having a dichroic coat layer for separating the red light R, the green light G, and the blue light B into three primary color lights.
2, 23, 24 and liquid crystal cells 27R, 27G, 27B
And the polarization conversion element of the present invention arranged in the optical path.

[0048]

The present invention will be described in more detail with reference to specific examples, but the present invention is not limited to these examples.

Example 1 Sekisui Chemical Co., Ltd. was used on both sides of a dye-based polarizing film in which dichroic dyes C.I. Direct Orange 39 and C.I. Direct Red 81 were adsorbed on a uniaxially stretched polyvinyl alcohol film. "SCA40" (trade name; glass transition temperature of about 140 ° C, photoelastic coefficient of about 6 × 10 ^-13 cm ² / dyne), which is a cyclic polyolefin resin film having a thickness of 40 μm, obtained from K.K. It pasted through and the polarizing plate was produced. An antireflection layer was formed on one surface of this polarizing plate by vapor deposition. A fluorine-containing silane compound having a molecular weight of about 4,500 corresponding to the formula below was coated on the antireflection layer.

[0050]

The contact angle of the obtained coated surface of the fluorine-containing silane compound was 110 degrees.

A retardation value of 2 is applied to the surface of the glass plate which has been subjected to antireflection treatment on one surface, to which the antireflection treatment has not been applied.
A 25 nm retardation plate [“Sumikalite SEF460225B” manufactured by Sumitomo Chemical Co., Ltd.], the above-mentioned polarizing plate with an antireflection layer, and the antireflection layer of the above polarizing plate is exposed on the surface, respectively. A pressure-sensitive adhesive was used for bonding to obtain a polarization conversion element. At this time, the absorption axis of the polarizing plate and the slow axis of the retardation plate were arranged so as to intersect at an angle of 45 degrees.

This polarization conversion element has the layer structure shown in FIG. 4, and the first protective film 54 and the second protective film 55 both have a glass transition temperature of 130.degree.
An antireflection layer and a fluorinated silane compound layer are formed in this order on the outermost surface of the first protective film 54, which is the outermost surface and is made of a resin having a photoelastic coefficient of 0 × 10 ⁻¹³ cm ² / dyne or less. On the other hand, an antireflection layer is also provided on the outermost surface 61 on the transparent glass substrate 51 side. If this polarization conversion element is set in the blue channel of a projection type liquid crystal display device and used, blue in-plane color unevenness becomes small.

[0054]

According to the present invention, at least one surface of the polarizing film has a glass transition temperature of 130 ° C. or higher and 50 ×.
A protective film made of a resin having a photoelastic coefficient of 10 ^-13 cm ² / dyne or less is laminated and laminated on a transparent glass substrate to form a polarization conversion element. Projection using this polarization conversion element The liquid crystal display device can maintain good display quality of the projected image even when used for a long period of time.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a projection type liquid crystal display device.

FIG. 2 is a schematic cross-sectional view showing an example of the layer structure of the polarization conversion element according to the present invention.

FIG. 3 is a schematic sectional view showing another example of the layer structure of the polarization conversion element according to the present invention.

FIG. 4 is a schematic sectional view showing another example of the layer structure of the polarization conversion element according to the present invention.

FIG. 5 is a schematic sectional view showing still another example of the layer structure of the polarization conversion element according to the present invention.

[Explanation of symbols]

10 ... Light source system, 11 ... White light source, 12 …… UV / IR cut filter, 13 ... Condensing lens, 20 ... Reflection / spectroscopic system, 21, 22, 23, 24 ... Dichroic mirror, 25, 26 ... total reflection mirror, 27R, 27G, 27B ... Transmissive liquid crystal cell, 28R, 28G, 28B ... Incident side polarization conversion element, 29R, 29G, 29B ... Emission side polarization conversion element, 30R, 30G, 30B ... Condensing lens, 40 ... Enlarged projection system, 41 ... Projection lens, 42 ... screen, L: White light (light source), R ... red light, G: green light, B ... blue light 50 ... Polarization conversion element, 51: transparent glass substrate, 52 ... Polarizing plate, 53 ... Polarizing film, 54 ... the first protective film, 55 …… Second protective film, 57 ... Retardation plate, 58, 59 ... Pressure sensitive adhesive, 60, 61 ... Outermost surface of the polarization conversion element.

Continued front page    F-term (reference) 2H049 BA02 BA06 BA26 BB03 BB22                       BB27 BB43 BB44 BB45 BB49                       BB51 BB65 BC14 BC22                 2H088 EA14 HA13 HA18 HA21 HA24                       MA02 MA20                 2H091 FA05X FA05Z FA08X FA08Z                       FA14Z FA26Z FA41Z FD06                       LA04 LA17 MA07                 2K009 AA04 BB02 BB11 BB24 CC06                       DD02 DD03                 2K103 AA01 AA05 AA12 AB06 BC16                       BC51

Claims (7)

[Claims] 1. A protective film made of a resin having a glass transition temperature of 130 ° C. or higher and a photoelastic coefficient of 50 × 10 ⁻¹³ cm ² / dyne or less is attached to at least one surface of a polarizing film made of a polyvinyl alcohol-based resin film. A polarization conversion element, wherein the combined polarizing plate is laminated on a transparent glass substrate. 2. The polarization conversion element according to claim 1, wherein the polarizing film is a polyvinyl alcohol resin film in which a dichroic dye is adsorbed and oriented. 3. The polarization conversion element according to claim 1, wherein the transparent glass substrate / polarizing film / protective film are laminated in this order. 4. A transparent glass substrate side surface of a polarizing film,
The polarization conversion element according to claim 3, wherein a second protective film, which is the same as or different from the protective film, is laminated, and a polarizing plate is constituted by the protective film, the polarizing film and the second protective film. 5. The polarization conversion element according to claim 3, wherein a retardation plate is laminated between the transparent glass substrate and the polarizing plate. 6. The polarization conversion element according to claim 3, further comprising an antireflection layer on the outermost surface of the protective film arranged outside. 7. A projection type liquid crystal display device, wherein the polarization conversion element according to claim 1 is arranged in an optical path.