CN102426401A - Polarization conversion element and reflective liquid crystal projector using it - Google Patents

Abstract

The invention provides a polarized light conversion element of a reflection type liquid crystal projector capable of realizing stable display quality for a long time, and further provides a reflection type liquid crystal projector using the polarized light conversion element. The present invention provides a glass substrate (41) laminated with a glass transition temperature of 140 ℃ or higher and a glass transition temperature of 50X 10^-13cm²A retardation sheet (42) made of resin having a photoelastic coefficient of no more than dyne, and a polarization conversion element (40) having a surface contact angle of 80 degrees or more on an exposed surface (46) of the retardation sheet (42). An antireflection layer (49) is preferably provided on the exposed surface (46) of the retardation plate (42). In addition to the glass substrate (41) and the retardation plate (42), a line polarizing plate (43) may be laminated. The polarization conversion element (40) is disposed on the side opposite to the reflection surface of the reflection type liquid crystal cell, and is used as a reflection type liquid crystal projector.

Description

Polarization conversion element and reflective liquid crystal projector using it

This application is a divisional application of:

Title of Invention: Polarized Light Conversion Element and Reflective Liquid Crystal Projector Using It

Application date: July 31, 2003

Application number: 03152230.0

technical field

The present invention relates to a polarized light conversion element used in a liquid crystal projector, and further relates to a reflective liquid crystal projector using the same.

Background technique

Liquid crystal projectors are widely used as devices such as personal computers and televisions that can enlarge images such as video and project them on a screen. Further, projectors using transmissive liquid crystal cells have been the mainstream in the past, but in recent years, reflective liquid crystal projectors using reflective liquid crystal cells have been developed for the purpose of miniaturization and high definition.

As the concept of a reflective liquid crystal projector is described with reference to FIG. 1 , such a liquid crystal projector is generally composed of a light source system 10 , an image forming system 20 and a magnifying projection system 30 . The light source system 10 has a white light source 11, a UV·IR color filter 12 and a condensing lens 13, and the white light L from the white light source 11 passes through the UV·IR color filter 12 to filter out ultraviolet rays and infrared rays, and then condenses the light with the condensing lens 13, and makes It is sent to the image forming system 20. Furthermore, in the light source system 10, generally, the polarization beam splitter 14 (also often abbreviated as PBS) is used to convert the light into P-polarized light or S-polarized light. As the white light source 11, a high-intensity lamp such as a metal halide lamp or a high-pressure mercury lamp is generally used.

In the image forming system 20, a dichroic mirror and a dichroic prism are used to split white light L into red light R, green light G, and blue light B, and liquid crystal cells corresponding to the respective colors are used to form images of respective colors, and then, After color synthesis, it is transmitted to the enlarged projection system 30 . In FIG. 1 , an example using dichroic mirrors 21 and 22 is shown. That is, the first dichroic mirror 21 transmits only the red light R and the blue light B, and the red light R and the blue light B transmitted therethrough are transmitted to the second dichroic mirror 22 . The green light G reflected by the first dichroic mirror 21 is transmitted to the total reflection mirror 23 , reflected there, and then transmitted to the polarization beam splitter 24G for green light. On the other hand, the second dichroic mirror 22 only transmits the blue light B, and among the red light R and the blue light B reaching here through the first dichroic mirror 21, the red light R is reflected by the second dichroic mirror 22 , is transmitted to the polarizing beam splitter 24R for red light, and the blue light B passes through the second dichroic mirror 22 and is transmitted to the polarizing beam splitter 24B for blue light.

In this way, since the polarized light that is split and reaches the respective polarization beam splitters 24R, 24G, and 24B becomes P-polarized light or S-polarized light, if the respective polarization beam splitters 24R, 24G, and 24B are set in advance, the incident P-polarized light or S-polarized light is reflected to the side of the liquid crystal cell 26R, 26G, 26B, then is reflected to the back side by the surface of each polarization beam splitter, and passes through the polarization conversion elements 40R, 40G, 40B corresponding to each color, It reaches the reflective liquid crystal cells 26R, 26G, and 26B, where images of each color are formed. And, the polarized light reflected by the reflective surface provided on the back side of the reflective liquid crystal cell 26R, 26G, 26B passes through the liquid crystal cell 26R, 26G, 26B, the polarization conversion element 40R, 40G, 40B, and the polarization beam splitter again. 24R, 24G, 24B are sent to the color synthesis prism 28 where color synthesis is performed and sent to the magnification projection system 30 . Furthermore, when the polarization beam splitter 14 is not provided in the light source system 10, in the polarization beam splitters 24R, 24G, and 24B corresponding to the respective colors provided in the image forming system 20, the desired P-polarized light or S-polarized light The light is reflected and sent to the liquid crystal cell 26R, 26G, 26B side, and the rest is consumed by transmission or reflection to the light source side.

Also in the image forming system 20, an element that rotates linearly polarized light of a specific wavelength is often used. As such a device, there is "Colour Select" manufactured by Color Link Co., Ltd., and the like. In addition, the polarization conversion elements 40R, 40G, and 40B are used to substantially convert linearly polarized light into circularly polarized light while rotating the plane of polarization of linearly polarized light. 1 shows an example of disposing polarization conversion elements 40R, 40G, 40B between polarization beam splitters 24R, 24G, 24B and liquid crystal cells 26R, 26G, 26B, but depending on the situation, it is often not at this position On the front side of the polarizing beam splitters 24R, 24G, and 24B, that is, between the dichroic mirror 22 and the polarizing beam splitter 24B, and between the total reflection mirror 23 and the polarizing beam splitter 24G, polarization conversion elements are arranged. . In addition, here, a form in which green light is first split and then red light and blue light are split is shown, but the order of splitting can be changed arbitrarily by selection of dichroic mirrors.

The magnification projection system 30 has a projection lens 31 where images corresponding to respective lights are magnified and the magnified images are projected onto a screen 32 .

Regarding such a reflective liquid crystal projector or a polarization beam splitter and a polarization conversion element used therein, various proposals have been made (for example, JP-A-2000-206463, JP-A-2001-209024, JP-A 2001-215491 and JP-A-11-231132).

The polarized light conversion element used in reflective liquid crystal projectors generates heat under the irradiation of strong light, so the surface is cooled by an air-cooled fan. However, in order to improve the cooling efficiency, if the air volume is increased, the polarized light will be damaged by long-term air supply. Dust adheres to the surface of the conversion element, and if the air blowing efficiency is lowered, heat will be stored in the polarization conversion element and the characteristics will change, so there will be problems in the color balance, contrast, brightness, uniformity, etc. of the displayed image during long-term use. Displays grade-reduced issues.

Contents of the invention

Therefore, the inventors of the present invention have conducted studies to develop a polarization conversion element for a reflective liquid crystal projector that can realize a stable display quality over a long period of time. As a result, it was found that, for a polarization conversion element in which a retarder is bonded to a glass base material, by constituting the retarder with a specific material, it is possible to suppress a change in performance due to heat, and further, by forming the surface of the retarder with a specific Performance, even if the air-cooling fan is used to improve the cooling efficiency, dust will not adhere, and the color balance, contrast, brightness, and uniformity of the projected image can be obtained. A reflective liquid crystal projector with little reduction in display quality, thereby achieving the present invention the goal of.

That is, the present invention provides a glass base material laminated with a retarder 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, and where the retarder is exposed A polarized light conversion element having a surface contact angle of 80 degrees or more on one surface. 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 incorporated into a reflective liquid crystal projector and used. 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, the reflective liquid crystal projector has: a white light source; an optical component having a dichroic coating for splitting white light from the white light source into three primary colors of red light, green light, and blue light; A polarizing beam splitter for reflecting only P-polarized light or S-polarized light of each color to the liquid crystal cell side; a reflective liquid crystal cell; and the above-mentioned polarization conversion element.

Description of drawings

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

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

Detailed ways

The glass base material used in the polarization conversion element of the present invention is not particularly limited as long as it is transparent, and examples thereof include white plate glass, blue plate glass, sapphire glass plate, and quartz glass plate. In particular, the sapphire glass plate and the quartz glass plate are ideal because of their high thermal conductivity and excellent heat dissipation efficiency. The sapphire glass plate is a single crystal of alumina (Al ₂ O ₃ ), and can be used after being formed into a plate shape by, for example, EFG (Edge-Defined Film Feed Growth). The quartz glass plate is a single crystal of SiO ₂ , and both natural quartz and artificial quartz are available. In addition, when using a sapphire glass plate or a quartz glass plate, it is necessary to make the crystal axis substantially coincide with the extension axis of the retarder, or deviate by approximately 90 degrees. In addition, when laminating a polarizing plate on a sapphire glass plate and a quartz glass plate, it is necessary to make the crystal axis of the glass substantially coincide with the absorption axis of the polarizing plate, or deviate by approximately 90 degrees.

In the case of a glass plate, its thickness is usually about 0.1 to 3 mm, preferably about 0.3 to 2 mm. In addition, the shape and external dimensions of the glass plate are appropriately selected according to the target reflective liquid crystal projector, especially the shape and external dimensions of the liquid crystal cell used therein. Rectangular or square with a length of 10-100 mm, round or oval with a diameter of 5-100 mm, etc.

The glass base material preferably has an antireflection layer on the surface opposite to the side on which the retarder is laminated, that is, the exposed surface. In addition, a dichroic coating is formed on one or both sides of the glass base material, which may have the property of only transmitting light in a specific wavelength range and not transmitting light in other wavelength ranges. When there is a dichroic coating on one side, a retarder may be laminated on the dichroic coating, or a retarder may be laminated on the side opposite to the dichroic coating. In addition, the glass base material may be a polarizing beam splitter in which two or more glass members are bonded together. The above-mentioned dichroic coatings may also be present on the glass side of the polarizing beam splitter. A plano-convex lens, a plano-concave lens, or the like may also be used.

A retarder 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 base material. If a retarder made of a resin with a glass transition temperature lower than 140°C or a photoelastic coefficient greater than 50×10 ^-13 cm ² /dyne is used, the liquid crystal projector incorporating the retarder is easily damaged when used for a long time. Incurs a reduction in display quality. In addition, photoelasticity refers to a phenomenon in which an isotropic, ie, birefringence-zero substance exhibits optical anisotropy and birefringence when an external force is applied to a substance having a birefringence of 0 and internal stress is generated. When it is assumed that the stress (force acting on a unit area) acting on the material is σ and the birefringence is Δn, the stress σ and birefringence Δn are theoretically proportional, which can be expressed as Δn=Cσ, where C is the light modulus of elasticity. In other words, if the stress σ acting on the material is taken as the horizontal axis, and the birefringence Δn when the stress acts is taken as the vertical axis, then in theory the relationship between the two is a straight line, and the slope of the straight line is the photoelastic coefficient.

In the present invention, 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 can be used as the retarder. The glass transition temperature is preferably 150°C or higher, more preferably 160°C or higher. In addition, the photoelastic coefficient is preferably not more than 10×10 ^-13 cm ² /dyne, more preferably not more than 6×10 ^-13 cm ² /dyne. The upper limit of the glass transition temperature of the resin constituting the retarder is not particularly limited, and may be, for example, a resin having a glass transition temperature of about 300°C. In addition, the lower limit of the photoelastic coefficient is not particularly limited, for example, it may be a resin with a photoelastic coefficient of about 0.1×10 ⁻¹³ cm ² /dyne.

Examples of resins exhibiting properties such as a glass transition temperature of 140°C or higher and a photoelastic coefficient of 50×10 ^-13 cm ² /dyne or lower include cyclic polyolefins using norbornene-based monomers, for example. Resin, polycarbonate resin, polysulfone resin, polyethersulfone resin, polyester resin, polyimide resin, polyamide resin, polyarylate resin, etc. Commercially available norbornene-based resin films include "Art-n" (trade name) manufactured by Geyesuar Co., Ltd., "Zeonex" (trade name) manufactured by Nippon Zeon Co., Ltd., and the like. In addition, there are "Puyuae-su WR" (trade name) manufactured by Teijin Co., Ltd. among the commercially available polycarbonate-based resin films.

When producing a retarder from these resins, for example, a film made of these resins can be stretched, and a retarder having a desired retardation can be produced according to the degree of stretching. Alternatively, a commercially available retarder can also be used. The thickness of the retarder is usually about 10 to 500 μm, preferably not less than 50 μm and not more than 150 μm.

When the retarder is a 1/4 wavelength plate, the retardation value is about 145-175nm when the light passing through the retarder is red light, about 125-145nm when it is green light, and about 125-145nm when it is blue light. It is about 108-125nm. When the retarder is a 1/2 wavelength plate, the retardation value is about 290-350nm when the light passing through the retarder is red light, about 250-290nm when it is green light, and about 250-290nm when it is blue light. It is about 216-250nm.

Such a retarder is laminated on one side of a glass base material via, for example, an adhesive layer. As the binder at this time, a transparent optically isotropic substance is usually used. Specifically, pressure-sensitive adhesives such as acrylic pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, and silicone-based pressure-sensitive adhesives are preferable. The thickness of the adhesive layer is usually about 10 to 60 μm, preferably 10 to 30 μm. In addition, the pressure-sensitive adhesive is also referred to as an adhesive.

The adhesive is preferably a pressure-sensitive adhesive whose relaxation elastic modulus decrease rate is in the range of -0.14 to -0.09 at 25°C. Adhesives generally exhibit viscoelasticity. If the viscoelastic body is given a strain γ ₀ instantaneously and kept constant, the stress σ(t) decreases with time, and finally tends to a constant value, which is called stress However, at this time, the relaxed stress σ(t) can be expressed as σ(t)=G(t)·γ ₀ , G(t) is the elastic modulus related to time, called the relaxed elastic modulus. In other words, the relaxed modulus of elasticity is the ratio of the stress σ(t) decreasing with time to the constant strain _γ0 applied from the outside. In addition, the decrease rate of the relaxation modulus at 25°C means that when the relaxation modulus G(t) measured at a temperature of 25°C is plotted on the vertical axis and the time t (unit: second) is on the horizontal axis, a log-logarithmic graph is drawn. The temporary slope of , is the value a in the following formula,

log ₁₀ [G(t)] = a·log ₁₀ [t] + b

(where a and b are constants). The reduction rate a of the relaxation elastic modulus can be obtained from the value of log ₁₀ [G(t)] to log ₁₀ [t] by the least square method.

In the polarization conversion element of the present invention, it is preferable to laminate two or more retardation films. At this time, the retardation values of the plurality of retarders may be the same or different. In addition, the lamination angle when two or more retardation plates are stacked may be such that the respective retardation axis directions are substantially aligned, or these directions may be deviated. When two 1/4 wavelength plates are bonded together so that their respective retardation axes are substantially aligned, it is found that the same function as that of the 1/2 wavelength plate is obtained. In addition, when a retarder with a retardation value in the range of 275nm±10nm and a retarder with a retardation value in the range of 140nm±5nm are stacked, and the phase retardation axis is shifted by 60 degrees, it is found that a 1/4 The function of the wavelength plate.

The polarization conversion element of the present invention may be a polarization conversion element in which a linear polarizing plate is laminated in addition to the glass base material and the retardation plate. As a linear polarizing plate, a polarizing plate in which a protective film is laminated on one or both sides of a polarizer film is generally used. As the polarizer film, for example, a polarizer film in which a dichroic dye or iodine is adsorbed into a polyvinyl alcohol resin film to align it can be used, and especially a polarizer film in which a dichroic dye is adsorbed and aligned is heat-resistant. It is ideal in terms of sex and so on. As a protective film of a linear polarizing plate, for example, a film made of a cellulose-based resin such as diacetyl cellulose or triacetyl cellulose can be used.

The linear polarizing plate is laminated, for example, between the retarder and the glass base material via an adhesive layer, or is laminated on the surface of the glass base material opposite to the surface on which the retarder is bonded. As the adhesive constituting the adhesive layer, it is preferable to use the same pressure-sensitive adhesive as described above, and at this time, it is preferable that the decrease rate of the elastic modulus of relaxation at 25°C be -0.14 to -0.09 pressure-sensitive adhesive. 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 linear polarizing plate should be appropriately selected, and examples include the following forms.

① Make the phase lag axis of the retarder coincide with the absorption axis of the linear polarizer,

② Make the phase lag axis of the retarder and the absorption axis of the linear polarizer stagger by 45 degrees,

③ Make the retardation axis of the retarder and the absorption axis of the linear polarizer stagger by 67.5 degrees.

In addition, it is preferable to laminate a retarder having a retardation value in the range of 275nm ± 10nm and a retardation film having a retardation value in the range of 140nm ± 5nm and shift their retardation axes by 60 degrees. The absorption axis of the linear polarizing plate and the retardation axis of the retardation plate having a retardation value in the range of 275 nm±10 nm were arranged so as to be shifted by 15 degrees. For this lamination order, the following structure can be mentioned as an ideal structure, for example.

①Retardation film with a retardation value of 140nm±5nm/retardation film with a retardation value of 275nm±10nm/linear polarizer/glass base material,

②Retardation film with a retardation value of 140nm±5nm/retardation film with a retardation value of 275nm±10nm/glass base material/linear polarizer,

③Retardation film with retardation value of 140nm±5nm/glass matrix material/retardation film/linear polarizer with retardation value of 275nm±10nm.

In the polarization conversion element of the present invention, one surface of the retarder is exposed in the air layer, and the reflectance of the exposed surface is 2% or less, and can also be 1% or less, because the occurrence of stray light caused by reflected light can be suppressed. , this value is ideal. In this way, in order to reduce the reflectance, for example, an antireflection layer may be formed on the exposed surface of the retarder. The antireflection layer can be provided on the surface of the retarder by a usual method. In addition, the reflectance of the exposed surface of the retarder may be 2% or less in the entire range of visible light, but it is effective if it is 2% or less for the wavelength range of light passing there.

As the antireflection layer, generally used substances include, for example, single-layer or multilayer substances selected from metals, metal oxides, and metal fluorides. Examples of metals include silver and the like; examples of metal oxides include silicon oxide, aluminum oxide, titanium oxide, tantalum oxide, yttrium oxide, and zirconium oxide; and examples of metal fluorides include magnesium fluoride. wait. The antireflection layer may be a single layer, or may be a multilayer composed of 2, 3, 4 or more layers. The thickness of the antireflection layer or the thickness of each layer when it is multilayered can be appropriately selected according to the number of layers, the refractive index of the substance used in each layer, and the like.

Such an antireflection layer can be deposited by a usual method such as vacuum evaporation, sputtering, physical vapor deposition (PVD) such as ion plating, or coating.

Furthermore, there may be a cured film layer between the antireflection layer and the retarder. As a cured film layer, the layer which hardened the layer which consists of curable resins, such as an acrylic resin, a silicone resin, a melamine resin, a urethane resin, and an epoxy resin, is mentioned, for example. Such layers are often referred to as hardcoats. Examples of the acrylic resin constituting the cured film layer include epoxy acrylate resins, polyester acrylate resins, acrylate resins, methacrylate resins, and acrylic urethane resins. The layer made of curable resin can be provided, for example, by applying a curable resin on 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 preferably about 1 to 10 μm, more preferably about 2 to 5 μm.

The coating method of the curable resin is not particularly limited, and it can be applied by methods such as roll coating, gravure coating, and spray coating, for example. The curable resin obtained in this way can be cured by methods such as ultraviolet irradiation, electron beam irradiation, and thermal curing to form a cured film layer. The thickness of the cured film layer is usually less than 10 μm, preferably more than 1 μm, and can also be 6 μm. When the thickness of the cured film layer exceeds 10 μm, the cured film layer tends to easily cause cracks. On the other hand, when the thickness is less than 1 μm, interference with visible light tends to occur.

A suitable layer structure of the polarization conversion element of the present invention will now be described with reference to FIG. 2 . In (a) of FIG. 2 , a retarder 42 is laminated on one surface of a glass base material 41 via an adhesive layer (not shown) to form a polarization conversion element 40 . Furthermore, an antireflection layer 48 is formed on the exposed surface 45 of the glass base material 41 . In addition, an antireflection layer 49 is also formed on the exposed surface 46 of the retarder 42 . On the other hand, in (b) of FIG. 2 , on one surface of the glass base material 41, a linear polarizing plate 43 and a retardation plate 42 are sequentially stacked via respective adhesive layers (not shown) to form a polarization conversion Element 40. Also in this example, an antireflection layer 48 is formed on the exposed surface 45 of the glass substrate 41 , and an antireflection layer 49 is also formed on the exposed surface 46 of the retarder 42 .

For the polarization conversion element of the present invention, the contact angle on the outer surface of the retarder 42, for example, the surface with the antireflection layer 49, is 80 degrees or more. This surface contact angle is more preferably 100 degrees or more. The contact angle mentioned here is a value when water is used as a liquid. If the contact angle is less than 80 degrees, particles such as dust and stains tend to adhere, and a liquid crystal projector using a polarizer conversion element having such a surface tends to decrease contrast when used for a long time. In addition, the upper limit of the contact angle is 180 degrees.

For example, when the retarder 42 has the antireflection layer 49, the exposed surface of the antireflection layer 49 (the surface opposite to the retarder 42) may have a contact angle of 80 degrees or more.

Retarders with antireflection layers are also commercially available, but typical antireflection layers do not have the contact angles specified here. Therefore, a layer made of fluoride is deposited on the upper surface of the antireflection layer 49, and the contact angle can be set to 80 degrees or more. The fluoride used for this purpose is not particularly limited as long as it can make the contact angle at least 80 degrees. For preventing surface contamination, commonly used ones include, for example, fluorine-containing silane compounds. This fluoride is commonly used to prevent stains such as fingerprints from adhering to the surface. Specific examples of desirable fluorine-containing silane compounds include compounds represented by the following general formula (I).

In the formula, ^R represents a linear or branched perfluoroalkyl group with 1 to 16 carbons, X represents an iodine atom or a hydrogen atom, Y represents a hydrogen atom or a lower alkyl group, and Z represents a fluorine atom or a trifluoroform ^R1 represents a hydrolyzable group, ^R2 represents a hydrogen atom or an inactive monovalent organic group, a, b, c and d each independently represent an integer from 0 to 200, e represents 0 or 1, and m represents An integer of 0 to 1, n represents an integer of 0 to 2, and p represents an integer of 1 or more.

More specifically, examples thereof include fluorine-containing silane compounds represented by the following formula (II) and having a molecular weight of about 4,500 (for these fluorine-containing silane compounds, see JP-A-1-294709, for example).

In the reflective liquid crystal projector using the polarization conversion element of the present invention, deterioration in display quality of projected images is reduced. Specifically, the polarization conversion element is arranged and used on the front side of the liquid crystal cell constituting the reflective liquid crystal projector, that is, on the side opposite to the reflective surface of the reflective liquid crystal cell. More specifically, in the reflective liquid crystal projector shown in FIG. 1, at least one of the polarization conversion elements 40R, 40G, and 40B arranged on the front surfaces of the liquid crystal cells 26R, 26G, and 26B corresponding to the three primary colors use. The polarized light conversion elements are also often arranged on the front side of the polarized beam splitters 24R, 24G, and 24B, that is, between the dichroic mirror 22 and the polarized beam splitter 24R, and between the dichroic mirror 22 and the polarized beam splitter 24B. Between, and between the total reflection mirror 23 and the polarizing beam splitter 24G. In any case, there are: a white light source 11; an optical component with a dichroic coating for splitting the white light L from the light source 11 into the three primary colors of red light R, green light G and blue light B (usually Referred to as dichroic mirrors) 21, 22; polarized beam splitters 24R, 24G, 24B that only reflect P-polarized light or S-polarized light of respective colors to the liquid crystal cell 26R, 26G, 26B side; liquid crystal cell 26R, 26G , 26B; the polarization conversion element of the present invention arranged on the front side (not directly in front) of at least one of the liquid crystal cells 26R, 26G, and 26B.

For reflective liquid crystal projectors, among the three primary colors of light after being split, the light energy of blue light is particularly high, so for the polarization conversion element 40B of the liquid crystal cell 26B corresponding to this blue light B, it is suitable to use It goes without saying that the polarization conversion element of the present invention can also be used for the polarization conversion element 40R corresponding to red light R and the polarization conversion element 40G corresponding to green light G. The polarization conversion element of the present invention can be effectively used for all of the polarization conversion elements 40R, 40G, and 40B.

For such a reflective liquid crystal projector, the polarized light conversion element of the present invention is arranged at the position shown in FIG. 2, the side of the retardation plate 42 of the polarization conversion element 40 shown in FIG. However, the retarder 42 side of the polarization conversion element 40 is often arranged facing the liquid crystal cell 26R, 26G, or 26B side.

[Example]

Hereinafter, specific examples will be given to further describe the present invention in detail, but the present invention is not limited by these examples.

example 1

The cyclic polyolefin-based resin film "A-TON" [manufactured by Jiei Esual Co., Ltd., with a glass transition temperature of about 170°C and a photoelastic coefficient of 4×10 ^-13 cm ² /dyne] was stretched to produce Retarders with retardation values of 112nm, 138nm and 153nm. An acrylic cured resin was coated and dried on one side of each retarder, and then cured with ultraviolet rays to form a cured acrylic resin layer with a thickness of about 3 μm. On the surface of the cured acrylic resin layer, an antireflection layer was formed by vapor deposition. Furthermore, a fluorine-containing silane compound having a molecular weight of about 4,500 corresponding to the following formula was coated on the surface of the antireflection layer.

The contact angle of the obtained fluorine-containing silane compound-coated surface was 110 degrees. Then, the above-obtained retardation plate was bonded to the non-antireflection-treated side of a single-side antireflection-treated glass using the side not coated with the fluorine-containing silane compound via an acrylic adhesive. On, the polarized light conversion element is made. This polarization conversion element has a layer structure shown in FIG. 2( a ).

Among these polarization conversion elements, the polarization conversion element using a retardation film with a retardation value of 112nm is effective for the blue channel of a projection type liquid crystal display device (reflection type liquid crystal projector). The polarization conversion element using a 138nm retarder is also effective for the green channel, and the polarization conversion element using a retardation film with a retardation value of 153nm is also effective for the red channel. Furthermore, if these polarization conversion elements are installed and used in each channel of a reflective liquid crystal projector, the degradation of display quality can be minimized.

Example 2

The same cyclic polyolefin-based resin film "A-ton" as used in Example 1 was stretched to prepare retarders having retardation values of 112 nm, 138 nm, and 153 nm. On one side of them, an antireflection layer was formed by vapor deposition. Further, the same fluorine-containing silane compound having a molecular weight of about 4,500 as used in Example 1 was coated on the surface of the antireflection layer. The contact angle of the obtained fluorine-containing silane compound-coated surface was 110 degrees. Then, the above-obtained retardation plate was bonded to the non-antireflection-treated side of a single-side antireflection-treated glass using the side not coated with the fluorine-containing silane compound via an acrylic adhesive. On, the polarized light conversion element is made. This polarization conversion element also has the layer structure shown in FIG. 2( a ).

Among these polarization conversion elements, the polarization conversion element using a retardation film with a retardation value of 112nm is effective for the blue channel of a projection type liquid crystal display device (reflection type liquid crystal projector). The polarization conversion element using a 138nm retarder is also effective for the green channel, and the polarization conversion element using a retardation film with a retardation value of 153nm is also effective for the red channel. Furthermore, if these polarization conversion elements are installed and used in each channel of a reflective liquid crystal projector, the degradation of display quality can be minimized.

[Effect of the invention]

The polarized light conversion element of the present invention is effectively used in a reflective liquid crystal projector, and the reflective liquid crystal projector in which the polarized light conversion element is arranged on the front of the liquid crystal cell can improve the color balance, contrast, and brightness of the projected image. , uniformity, and other display quality decreases.

Claims (3)

1. A polarized light conversion element for a reflective liquid crystal projector, characterized in that, have: glass matrix material; A 1/4 wavelength retarder is directly laminated on one surface of the above-mentioned glass base material through an adhesive layer; The first anti-reflection layer is formed on the exposed surface of the 1/4 wavelength retarder; and The second anti-reflection layer is formed on the exposed surface of the above-mentioned glass base material, Wherein, the above-mentioned 1/4 wavelength retarder is 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, The surface contact angle of the above-mentioned first antireflection layer is 80 degrees or more. 2. The polarization conversion element according to claim 1, characterized in that, Two or more retarders are laminated. 3. A reflective liquid crystal projector, characterized in that, The polarization conversion element according to claim 1 or 2 is arranged on the side opposite to the reflective surface of the reflective liquid crystal cell.

Images