JP2003227938A - Polarization conversion element and reflection liquid crystal projector using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarization conversion element for a reflection liquid crystal projector of which the display quality is stable for a long time, and to obtain the reflection liquid crystal projector of stable display quality using the polarization conversion element. <P>SOLUTION: A polarization conversion element 40 is provided where a phase difference plate 42 made of a resin having ≥140°C glass transition point and 50×10<SP>-13</SP>cm<SP>2</SP>/dyn photo-elastic coefficient is laminated on a glass base material 41 and the surface contact angle on an exposed surface 46 of the phase difference plate 42 is ≥80°. It is preferable that an antireflection layer 49 is provided on the exposed surface 46 of the phase difference plate 42. A linearly polarizing plate 43 may be laminated besides the glass base material 41 and the phase difference plate 42. The polarization conversion element 40 is arranged on the side opposite to the reflection face of a reflection liquid crystal cell to constitute the reflection liquid crystal projector. <P>COPYRIGHT: (C)2003,JPO

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 used in a liquid crystal projector, and further,
It is also related to a reflective liquid crystal projector using the same.

[0002]

2. Description of the Related Art Liquid crystal projectors are widely used as devices capable of enlarging and projecting images such as personal computers, televisions, and videos on a screen. In the past, a projector using a transmissive liquid crystal cell was mainstream, but in recent years, a reflective liquid crystal projector using a reflective liquid crystal cell has been developed for the purpose of miniaturization and high definition.

The concept of the reflection type liquid crystal projector will be described with reference to FIG. 1. Such a liquid crystal projector usually comprises a light source system 10, an image forming system 20 and a magnifying projection system 30. The light source system 10 includes a white light source 11, a UV / IR cut filter 12, and a condenser lens 13. The white light L from the white light source 11 is passed through the UV / IR cut filter 12 to cut ultraviolet rays and infrared rays. Then, the light is condensed by the condenser lens 13 and sent to the image forming system 20. In the light source system 10, it is general that the light is converted into P-polarized light or S-polarized light by a polarization beam splitter 14 (sometimes abbreviated as PBS). White light source 1
A high-intensity lamp such as a metal halide lamp or a high-pressure mercury lamp is usually used for 1.

The image forming system 20 splits the white light L into red light R, green light G and blue light B by a dichroic mirror or a dichroic prism, and forms an image of each color in a liquid crystal cell corresponding to each color. The image is formed, then color-synthesized, and then sent to the magnifying projection system 30. FIG. 1 shows an example using the dichroic mirrors 21 and 22. That is, the first dichroic mirror 21
Is for transmitting only red light R and blue light B,
The red light R and the blue light B transmitted therethrough are sent to the second dichroic mirror 22. The green light G reflected by the first dichroic mirror 21 is reflected by the total reflection mirror 2
3 and is reflected here, and then sent to the polarizing beam splitter 24G for green. On the other hand, the second dichroic mirror 22 transmits only the blue light B, and the red light R out of the red light R and the blue light B which have reached the first dichroic mirror 21 through the first dichroic mirror 21 is the first light. The light is reflected by the second dichroic mirror 22 and sent to the red polarization beam splitter 24R, and the blue light B passes through the second dichroic mirror 22 and is sent to the blue polarization beam splitter 24B.

The polarized light thus split and reaching the respective polarization beam splitters 24R, 24G, and 24B is P-polarized light or S-polarized light, so that the respective polarized beam splitters 24R, 24G, and 24B enter the P-polarized light. Alternatively, if the S-polarized light is reflected to the liquid crystal cells 26R, 26G, and 26B side, each splitter surface reflects it to the rear surface side, and the polarization conversion elements 40R and 40R corresponding to the respective colors.
After passing through G and 40B, the reflection type liquid crystal cells 26R, 26G and 2
6B, where an image of each color is formed. Then, the polarized light reflected by the reflecting surface provided on the back side of the reflective liquid crystal cells 26R, 26G, and 26B is again reflected by the liquid crystal cell 26.
R, 26G, 26B, polarization conversion elements 40R, 40G, 4
0B and polarization beam splitters 24R, 24G, 24B
And is sent to the color combining prism 28, where the colors are combined and sent to the magnifying projection system 30. If the polarization beam splitter 14 is not provided in the light source system 10, the necessary P-polarized light or S-polarized light is reflected by the polarization beam splitters 24R, 24G, 24B corresponding to the respective colors provided in the image forming system 20. Liquid crystal cells 26R, 26G, 2
6B, and the rest is consumed by transmission or reflection on the light source side.

The image forming system 20 may include an element for rotating linearly polarized light of a specific wavelength. An example of such an element is "Color Select" manufactured by Color Link Co., Ltd. Further, the polarization conversion elements 40R, 40G, 40B
Is used to rotate the plane of polarization of linearly polarized light or to convert linearly polarized light into substantially circularly polarized light. In FIG. 1, the polarization beam splitters 24R, 24G and 24B and the liquid crystal cell 2 are shown.
Polarization conversion elements 40R, 4 between 6R, 26G, 26B
Although the example in which 0G and 40B are arranged is shown, in some cases, the polarization beam splitters 24R and
The front side of 24G, 24B, that is, between the dichroic mirror 22 and the polarization beam splitter 24R, between the dichroic mirror 22 and the polarization beam splitter 24B,
A polarization conversion element may be disposed between the total reflection mirror 23 and the polarization beam splitter 24G. Further, here, the format in which the green light is first split and then the red light and the blue light are split is shown, but the order of the splitting can be arbitrarily changed by selecting the dichroic mirror.

The magnifying projection system 30 has a projection lens 31, where an image corresponding to each light is magnified and a magnified image is projected on the screen 32.

Various proposals have been made for such a reflection type liquid crystal projector, or a polarization beam splitter and a polarization conversion element used therefor (see, for example, Patent Documents 1 to 4).

[0009]

[Patent Document 1] Japanese Patent Laid-Open No. 2000-206463

[Patent Document 2] Japanese Patent Laid-Open No. 2001-209024

[Patent Document 3] Japanese Patent Laid-Open No. 2001-215491

[Patent Document 4] Japanese Patent Laid-Open No. 11-231132

[0010]

Since the polarization conversion element used in the reflection type liquid crystal projector generates heat by strong light, its surface is cooled by an air-cooling fan. However, if the air volume is increased to improve the cooling efficiency, Dust adheres to the surface of the polarization conversion element by blowing air for a long time, and if the efficiency of blowing air is reduced, heat is accumulated in the polarization conversion element and the characteristics change.
There is a problem that the display quality such as color balance, contrast, brightness, and uniformity of an image displayed during long-term use deteriorates.

Therefore, the present inventor has conducted research to develop a polarization conversion element that can realize a reflection type liquid crystal projector with stable display quality for a long time. As a result, in the polarization conversion element in which the retardation plate is attached to the glass substrate, the performance change due to heat can be suppressed by configuring the retardation plate with a specific material. By making the surface a specific property, even if the cooling efficiency by the air cooling fan is improved, there is no adhesion of dust, etc.
The color balance, contrast, and brightness of the projected image,
The present inventors have found that a reflective liquid crystal projector can be provided with less deterioration in display quality such as uniformity, and have reached the present invention.

[0012]

That is, the present invention provides a glass substrate with a glass transition temperature of 140 ° C. or higher and 50 × 1.
It is intended to provide a polarization conversion element in which retardation plates made of a resin having a photoelastic coefficient of 0 ^-13 cm ² / dyne or less are laminated, and a surface contact angle on the exposed surface of the retardation plate is 80 degrees or more. . In this polarization conversion element, a linear polarizing plate may be laminated in addition to the glass base material and the retardation plate.

This polarization conversion element is used by being incorporated in a reflection type liquid crystal projector. Therefore, the present invention also provides a reflective liquid crystal projector in which the above-mentioned polarization conversion element is arranged on the side opposite to the reflective surface of the reflective liquid crystal cell. More specifically, this reflective liquid crystal projector is a white light source and white light from the white light source is red light.
An optical component having a dichroic coating layer for splitting into three primary colors of green light and blue light, a polarization beam splitter for reflecting only P-polarized light or S-polarized light of each color to the liquid crystal cell side, and a reflective liquid crystal It has a cell and the above-mentioned polarization conversion element.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The glass substrate applied to the polarization conversion element of the present invention is not particularly limited as long as it is transparent.
For example, it may be a white plate glass, a blue plate glass, a sapphire glass plate, a quartz glass plate, or the like. Of these, a sapphire glass plate and a quartz glass plate are preferable because they have a large thermal conductivity coefficient and excellent heat dissipation efficiency. The sapphire glass plate is a single crystal body of alumina (Al ₂ O ₃ ), and for example, a plate-shaped plate formed by the EFG method (Edge-defined Film-fed Growth method) is used. The quartz glass plate is a single crystal of SiO ₂ , and may be natural quartz or artificial quartz. When a sapphire glass plate or a quartz glass plate is used, it is necessary to make the crystal axis of the sapphire glass plate and the stretching axis of the retardation plate substantially coincide with each other or to shift them by about 90 degrees. Also,
When a polarizing plate is laminated on a sapphire glass plate or a quartz glass plate, the crystal axis of the glass and the absorption axis of the polarizing plate need to be substantially coincident with each other, or they should be shifted by approximately 90 degrees.

In the case of a glass plate, its thickness is usually 0.1-
It is about 3 mm, preferably about 0.3 to 2 mm.
The shape and external dimensions of the glass plate are appropriately selected according to the shape and external dimensions of the target reflective liquid crystal projector, particularly the liquid crystal cell used therein. There are rectangles or squares of -100 mm, circles or ellipses of 5-100 mm in diameter, and the like.

The glass substrate preferably has an antireflection layer on the surface opposite to the side where the retardation film is laminated, that is, on the exposed surface. Further, the glass base material may have a characteristic that a dichroic coating layer is formed on one surface or both surfaces of the glass base material to transmit only light in a specific wavelength range and not transmit light in other wavelength ranges. When the dichroic coat layer is provided on one surface, the retardation plate may be laminated on the dichroic coat layer, or the retardation plate may be laminated on the surface opposite to the dichroic coat layer. Further, the glass substrate may be a polarization beam splitter in which two or more glass parts are bonded together. The glass surface of the polarization beam splitter may have the above dichroic coat layer. Further, a plano-convex lens or a plano-concave lens can be used.

A retardation plate is laminated on the glass substrate,
This retarder has a glass transition temperature of 140 ° C. or higher and 5
It is made of a resin having a photoelastic coefficient of 0 × 10 ⁻¹³ cm ² / dyne or less. When a retardation plate made of a resin having a glass transition temperature lower than 140 ° C. or a photoelastic coefficient larger than 50 × 10 ⁻¹³ cm ² / dyne is used, when a liquid crystal projector incorporating it is used for a long time, The display quality is likely to deteriorate. Photoelasticity is a phenomenon that isotropic, that is, when an external force is applied to a substance having a birefringence of 0 to cause internal stress, it exhibits optical anisotropy and exhibits birefringence. Say. When the stress acting on a substance (force acting on a unit area) is σ and the birefringence is Δn, the stress σ and the birefringence Δn are theoretically proportional to each other and may be expressed as Δn = Cσ. Yes, this 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.

In the present invention, the retardation plate has a glass transition temperature of 140 ° C. or higher and a photoelastic coefficient of 50 × 10 ^-13 cm ² /
The resin below dyne is used. This glass transition temperature is 15
The temperature is preferably 0 ° C or higher, and more preferably 160 ° C or higher. The photoelastic coefficient is 10 × 10.
^-13 cm ² / dyne or less, preferably 6 × 1
More preferably, it is not more than 0 ^-13 cm ² / dyne. There is no particular limitation on the upper limit of the glass transition temperature of the resin forming the retardation plate, and for example, a resin having a glass transition temperature of about 300 ° C. may be used. Also, there is no particular limitation on the lower limit of the photoelastic coefficient. For example, the photoelastic coefficient is 0.1 × 10 ⁻¹³ cm ² / d.
It may be a resin of about yne.

Examples of the resin having a glass transition temperature of 140 ° C. or higher and a photoelastic coefficient of 50 × 10 ^-13 cm ² / dyne or less include, for example, a cyclic polyolefin resin using a norbornene monomer and a polycarbonate resin. resin,
Examples thereof include polysulfone-based resin, polyether sulfone-based resin, polyester-based resin, polyimide-based resin, polyamide-based resin, and polyarylate-based resin. Commercially available norbornene-based resin films include "Arton" (trade name) manufactured by JSR Co., Ltd. and "Zeonex" (trade name) manufactured by Nippon Zeon Co., Ltd. In addition, commercially available polycarbonate resin films include Teijin Ltd.
There is "Pure Ace WR" (trade name) manufactured by the company.

To produce a retardation plate from these resins, for example, a film made of these resins may be stretched, and a retardation plate having a desired retardation can be obtained depending on the degree of stretching. . Alternatively, a commercially available retardation plate can be used. The thickness of the retarder is usually about 10 to 500 μm, preferably 50.
It is not less than μm and not more than 150 μm.

When the retardation plate is a quarter-wave plate, its retardation value is about 145 to 175 nm when the light passing through it is red light, and 125 to 175 nm when it is green light. It is about 145 nm, and in the case of blue light, it is about 108 to 125 nm. Phase difference plate is 1/2
In the case of a wave plate, the retardation value thereof is about 290 to 350 nm when the light passing therethrough is red light, about 250 to 290 nm when the light is green light, and blue light. In this case, it is about 216 to 250 nm.

The retardation plate is laminated on one surface side of the glass base material, for example, via an adhesive layer. As the adhesive in this case, a transparent and optically isotropic adhesive is usually used. Specifically, an acrylic pressure-sensitive adhesive,
A pressure sensitive adhesive such as a urethane pressure sensitive adhesive or a silicone pressure sensitive adhesive is preferable. The thickness of the adhesive layer is usually 1
It is about 0 to 60 μm, preferably 10 to 30 μm.
The pressure sensitive adhesive is also called an adhesive.

This adhesive is preferably a pressure-sensitive adhesive having a relaxation elastic modulus reduction rate at 25 ° C. in the range of -0.14 to -0.09. Adhesives generally exhibit viscoelasticity, and if the strain γ ₀ is momentarily applied to the viscoelastic body and then kept constant, the stress σ (t) decreases with time and approaches a constant value. Is called stress relaxation. At this time, the stress σ (t) to be relaxed can be expressed as σ (t) = G (t) · γ _0, and G
(t) is a time-dependent elastic modulus, which is called relaxation elastic modulus. In other words, the relaxation elastic modulus is the ratio of the stress σ (t) that decreases with time and the constant strain γ ₀ applied from the outside. And, the decrease rate of the relaxation elastic modulus at 25 ° C. is the temperature 2
The relaxation elastic modulus G (t) measured at 5 ° C. is plotted on the vertical axis and the time t
(Unit: second) means the temporal gradient when plotted in logarithmic scale on the horizontal axis, and the following equation log ₁₀ [G (t)] = a · log ₁₀ [t] + b (where a and b are constants) Is the value a in. The relaxation rate a of relaxation elastic modulus is relative to log ₁₀ [t]
It can be obtained from the value of log ₁₀ [G (t)] by the method of least squares.

In the polarization conversion element of the present invention, two or more retardation plates may be laminated. In this case, the retardation values of the plurality of retardation plates may be the same or different. When laminating two or more retardation plates, the laminating angles may be such that the slow axis directions are substantially the same, or the directions may be shifted. If the two quarter-wave plates are bonded so that their slow axes are substantially the same, the same function as that of the half-wave plate is exhibited. Also, if a retardation plate having a retardation value in the range of 275 nm ± 10 nm and a retardation plate having a retardation value in the range of 140 nm ± 5 nm are laminated so that the slow axis is shifted by 60 degrees, a wide wavelength range can be obtained. The function of the quarter wave plate is exhibited.

The polarization conversion element of the present invention may be a laminate of a linear polarizing plate in addition to the glass substrate and the retardation plate. As the linearly polarizing plate, one having a protective film laminated on one side or both sides of a polarizer film is usually used. As the polarizer film, for example, a polyvinyl alcohol-based resin film in which a dichroic dye or iodine is adsorbed and oriented is used. It is preferable in terms. As the protective film for the linear polarizing plate, for example, a film made of a cellulose resin such as diacetyl cellulose or triacetyl cellulose is used.

The linear polarizing plate is laminated between the retardation plate and the glass substrate, or on the surface of the glass substrate opposite to the surface on which the retardation plate is bonded, for example, with an adhesive layer interposed therebetween. It As the adhesive constituting the adhesive layer, the same pressure-sensitive adhesive as described above is preferably used, and in this case as well, at 25 ° C.
The pressure sensitive adhesive having a relaxation elastic modulus reduction rate of -0.14 to -0.09 is preferable. The thickness of the adhesive layer is usually about 10 to 60 μm, preferably 10 to 30 μm.

The arrangement of the retardation plate and the linearly polarizing plate is appropriately selected, and examples thereof include the following forms. Align the slow axis of the retardation plate with the absorption axis of the linear polarizing plate, shift the slow axis of the retardation plate and the absorption axis of the linear polarizing plate by 45 degrees, absorb the slow axis of the retardation plate and the linear polarizing plate 67.5 axis
Stagger.

The retardation plate having the retardation value in the range of 275 nm ± 10 nm and the retardation plate having the retardation value in the range of 140 nm ± 5 nm, which are exemplified above, are laminated with the slow axis shifted by 60 degrees. For the laminated retardation plate, the absorption axis of the linear polarizing plate and the retardation value of 275 nm
It is preferable to dispose the retardation plate in the range of ± 10 nm so that the slow axis is displaced by 15 degrees. Regarding the stacking order, for example, the following configurations are preferable.

Retardation value 140 nm ± 5 nm retardation plate / retardation value 275 nm ± 10 nm retardation plate / linear polarizing plate / glass substrate, retardation value 140 nm ± 5 nm retardation plate / retardation value 275 nm ± 10 nm Retardation plate / glass substrate / linear polarizing plate, retardation value 140 nm ± 5 nm retardation plate / glass substrate / retardation value 275 nm ± 10 nm retardation plate / linear polarizing plate.

In the polarization conversion element of the present invention, one surface of the retardation plate is exposed to the air layer, and the reflectance on this exposed surface is 2% or less, further 1% or less. It is preferable since stray light caused by reflected light can be suppressed. To reduce the reflectance in this way, for example, an antireflection layer may be formed on the exposed surface of the retardation film.
The antireflection layer can be provided on the surface of the retardation plate by a usual method. The reflectance on the exposed surface of the retardation plate may be 2% or less over the entire visible light range, but it is effective if it is 2% or less with respect to the wavelength range of light passing therethrough.

Examples of the antireflection layer include those usually used, for example, a single layer or a multi-layer 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.

The antireflection layer is formed by physical vapor deposition (PVD: Physical Vapor Deposition) such as a vacuum vapor deposition method, a sputtering method and an ion plating method.
) Method, coating method and the like.

A hardened film layer may be provided between the antireflection layer and the retardation plate. Examples of the cured film layer include a layer formed by curing a layer made of a curable resin such as an acrylic resin, a silicone resin, a melamine resin, a urethane resin, and an epoxy resin. Such a layer is usually called a hard coat layer. As the acrylic resin constituting the cured film layer, epoxy acrylate resin, polyester acrylate resin, acrylic ester resin, methacrylic ester resin,
Acrylic urethane resins and the like are exemplified. The layer made of a curable resin can be provided, for example, by applying a curable resin to the surface of the retardation film. The curable resin may contain additives such as a leveling agent and a polymerization initiator. The thickness of the cured coating layer is 1-10 μm
It is preferably about 3 to 5 μm, more preferably about 2 to 5 μm.

The method of applying the curable resin is not particularly limited,
For example, it can be applied by a roll coating method, a gravure coating method, a spray coating method, or the like. The curable resin layer thus obtained is cured by a method such as ultraviolet irradiation, electron beam irradiation, or heat curing to form a cured film layer. The thickness of the cured film layer is usually 1
0 μm or less, preferably 1 μm or more, and 6 μm
Is. If the thickness of the cured film layer exceeds 10 μm, the cured film tends to crack. On the other hand, its thickness is 1
If it is smaller than μm, interference with visible light is likely to occur.

An example of a suitable layer structure of the polarization conversion element according to the present invention will be described with reference to FIG. In FIG. 2A, the retardation plate 42 is laminated on one surface of the glass substrate 41 via an adhesive layer (not shown) to form the polarization conversion element 40. An antireflection layer 48 is formed on the exposed surface 45 of the glass substrate 41. An antireflection layer 49 is also formed on the exposed surface 46 of the retardation plate 42. On the other hand, in FIG. 2B, the linear polarizing plate 43 and the retardation plate 42 are laminated in this order on one surface of the glass substrate 41 with an adhesive layer (not shown), respectively, and the polarized light The conversion element 40 is configured. Also in this example, the antireflection layer 48 is formed on the exposed surface 45 of the glass substrate 41, and the antireflection layer 4 is also formed on the exposed surface 46 of the retardation plate 42.
9 is formed.

The polarization conversion element according to the present invention comprises the retardation plate 4
The second outer surface, for example, the surface having the antireflection layer 49 has a contact angle of 80 degrees or more. This surface contact angle is more preferably 100 degrees or more. The contact angle here is a value when water is used as the liquid. When the contact angle is less than 80 degrees, fine particles such as dust and dirt are likely to be attached, and therefore a liquid crystal projector using a polarization conversion element having such a surface has a reduced contrast when used for a long period of time. It tends to be easy.
The upper limit of the contact angle is 180 degrees.

Although a retardation plate having an antireflection layer is commercially available, a usual antireflection layer does not have the contact angle defined here. Therefore, a layer made of a fluorine compound can be provided on the upper surface of the antireflection layer 49 so that the contact angle is 80 degrees or more. The fluorine compound used for this purpose is
The contact angle is not particularly limited as long as the contact angle can be 80 degrees or more, and examples thereof include those usually used for preventing surface contamination, such as fluorine-containing silane compounds. Such a fluorine compound is usually used to prevent dirt such as fingerprints from adhering to the surface. Specific examples of preferred fluorine-containing silane compounds include those represented by the following general formula (I).

[0038]

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).

[0041]

The reflection type liquid crystal projector using the polarization conversion element of the present invention causes little deterioration in the display quality of the projected image. Specifically, the polarization conversion element is used by being arranged on the front side of the liquid crystal cell forming the reflection type liquid crystal projector, that is, on the side opposite to the reflection surface of the reflection type liquid crystal cell. More specifically, in the reflection type liquid crystal projector as shown in FIG. 1, the liquid crystal cell 2 corresponding to each of the three primary colors is used.
It can be used as at least one of the polarization conversion elements 40R, 40G, and 40B arranged in front of the 6R, 26G, and 26B. In some cases, the front side of the polarization beam splitters 24R, 24G, 24B, that is, between the dichroic mirror 22 and the polarization beam splitter 24R,
Dichroic mirror 22 and polarization beam splitter 24
Between B and the total reflection mirror 23 and the polarization beam splitter 2
A polarization conversion element may be arranged between 4G. In any case, a white light source 11 and an optical component having a dichroic coat layer for splitting the white light L from the light source 11 into lights of three primary colors of red light R, green light G and blue light B (usually a dichroic mirror and Called) 21,22
And P-polarized light or S-polarized light of each color
Polarizing beam splitters 24R, 24G and 24B for reflecting to the 6R, 26G and 26B sides, and a liquid crystal cell 26.
R, 26G, 26B and the liquid crystal cells 26R, 26G,
26B, and the polarization conversion element of the present invention arranged on the front side (not necessarily immediately before) of at least one of 26B.

Of the three primary colors of light that are dispersed in the reflective liquid crystal projector, blue light has a high optical energy, so that the present invention is applied to the polarization conversion element 40B of the liquid crystal cell 26B corresponding to the blue light B. A polarization conversion element is preferably used, but it is of course possible to apply the polarization conversion element of the present invention to the polarization conversion element 40R corresponding to the red light R and the polarization conversion element 40G corresponding to the green light G. . It is also effective to apply the polarization conversion element of the present invention to all of the polarization conversion elements 40R, 40G, 40B.

In such a reflection type liquid crystal projector, when the polarization conversion element of the present invention is arranged at the position shown in FIG. 1, that is, between the polarization beam splitters 24R, 24G and 24B and the liquid crystal cells 26R, 26G and 26B, The retardation plate 42 side of the polarization conversion element 40 shown in FIG. 2 can be arranged toward either the liquid crystal cell 26R, 26G or 26B side or the polarization beam splitter 24R, 24G or 24B side in FIG. In many cases, the phase difference plate 42 side of the conversion element 40 is arranged toward the liquid crystal cell 26R, 26G or 26B side.

[0045]

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 A cyclic polyolefin resin film "ARTON" (manufactured by JSR Co., Ltd., glass transition temperature of about 170 ° C., photoelastic coefficient of 4 × 10 ^-13 cm ² / dyne) was stretched to give a retardation value. The retardation plates were 112 nm, 138 nm and 153 nm. An acrylic-based curable resin was applied to one surface of each retardation plate, dried, and then ultraviolet-cured to form an acrylic-based resin cured layer having a thickness of about 3 μm. An antireflection layer was formed on the surface of the cured acrylic resin layer by vapor deposition. Further, the surface of the antireflection layer was coated with a fluorine-containing silane compound having a molecular weight of about 4,500 corresponding to the formula below.

[0047]

The contact angle of the obtained coated surface of the fluorine-containing silane compound was 110 degrees. And, the retardation plate obtained above on the non-reflection-treated surface of the glass whose one surface has been subjected to antireflection treatment, on the surface not coated with the fluorine-containing silane compound, through an acrylic pressure-sensitive adhesive. And bonded to form a polarization conversion element. This polarization conversion element has the layer structure shown in FIG.

Among these polarization conversion elements, the one using a retardation plate having a retardation value of 112 nm is effective for the blue channel of a projection type liquid crystal display device (reflection type liquid crystal projector), and the retardation value is also used. Is 138 nm
The one using the retardation plate of No. 3 is also effective for the green channel, and the one using the retardation plate having a retardation value of 153 nm is also effective for the red channel. When these polarization conversion elements are set and used in each channel of the reflection type liquid crystal projector, the deterioration of display quality becomes small.

Example 2 The same cyclic polyolefin resin film "Arton" as used in Example 1 was stretched to give a retardation value of 11
Phase retarders of 2 nm, 138 nm and 153 nm were produced. An antireflection layer was formed on these one surfaces by vapor deposition. Further, on the surface of the antireflection layer, the same fluorine-containing silane compound having a molecular weight of about 4,500 as that used in Example 1 was applied. The contact angle of the obtained coated surface of the fluorine-containing silane compound was 11
It was 0 degrees. And, the retardation plate obtained above on the non-reflection-treated surface of the glass whose one surface has been subjected to antireflection treatment, on the surface not coated with the fluorine-containing silane compound, through an acrylic pressure-sensitive adhesive. And bonded to form a polarization conversion element. This polarization conversion element also has the layer structure shown in FIG.

Among these polarization conversion elements, one using a retardation plate having a retardation value of 112 nm is effective for the blue channel of a projection type liquid crystal display device (reflection type liquid crystal projector), and the retardation value is also used. Is 138 nm
The one using the retardation plate of No. 3 is also effective for the green channel, and the one using the retardation plate having a retardation value of 153 nm is also effective for the red channel. When these polarization conversion elements are set and used in each channel of the reflection type liquid crystal projector, the deterioration of display quality becomes small.

[0052]

INDUSTRIAL APPLICABILITY The polarization conversion element of the present invention is effectively used for a reflection type liquid crystal projector, and the reflection type liquid crystal projector in which this polarization conversion element is arranged in front of a liquid crystal cell has a color balance and a contrast of a projected image. In addition, the display quality such as the brightness and the uniformity is less deteriorated.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration example of a reflective liquid crystal projector.

FIG. 2 is a schematic sectional view showing an 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, 14 ... Polarizing beam splitter for light source, 20 ... Image forming system, 21, 22 ... Dichroic mirror, 23 ... total reflection mirror, 24R, 24G, 24B ... Polarizing beam splitter, 26R, 26G, 26B ... Reflective liquid crystal cell, 28: Color synthesis prism, 30 ... Enlarged projection system, 31 ... Projection lens, 32 ... screen, L: White light (light source), R ... red light, G: green light, B ... blue light 40, 40R, 40G, 40B ... Polarization conversion element, 41 ... Glass substrate, 42 ... Retardation plate, 43 ... Linear polarizing plate, 45 ... exposed surface of glass substrate, 46 ... exposed surface of retardation plate, 48, 49 ... Antireflection layer.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) G03B 21/00 G02B 1/10 AF term (reference) 2H049 BA02 BA06 BA25 BA27 BB03 BB43 BB44 BB45 BB48 BB51 BB65 BC03 BC14 BC22 2H088 EA12 EA16 HA17 HA18 HA21 2H091 FA08 FA11 FA14 FA37 FD06 GA01 2K009 AA04 AA05 AA06 AA07 AA15 BB02 BB11 BB24 CC03 CC06 CC24 CC33 CC34 CC35 CC42 DD02 DD03 DD04 DD05 2K103 A1905AA14 AA10 AB14 A14

Claims (6)

[Claims] 1. A retardation plate made of a resin having a glass transition temperature of 140 ° C. or higher and a photoelastic coefficient of 50 × 10 ⁻¹³ cm ² / dyne or lower is laminated on a glass substrate, and the retardation plate is exposed. A polarization conversion element having a surface contact angle of 80 degrees or more. 2. The polarization conversion element according to claim 1, wherein the retardation plate has an antireflection layer on its exposed surface. 3. The polarization conversion element according to claim 1, wherein two or more retardation plates are laminated. 4. The polarization conversion element according to claim 1, wherein the retardation plate is a quarter wavelength plate. 5. The polarization conversion element according to claim 1, wherein a linear polarizing plate is laminated between the glass substrate and the retardation plate. 6. A reflection type liquid crystal projector, wherein the polarization conversion element according to any one of claims 1 to 5 is arranged on a side opposite to a reflection surface of a reflection type liquid crystal cell.