CN1388387A - Polarized light conversion element and projection liquid crystal display using the same polarized light conversion element - Google Patents

Abstract

A polarization conversion element is provided to realize a projection type liquid crystal display device with high contrast, no black display unevenness, and high display quality, and a projection type liquid crystal display device suitable for the polarization conversion element. This polarization conversion element is constructed by laminating two optical compensation plates formed by coating a liquid crystal compound on a substrate film with one side of a linear polarizing plate. At this time, the two optical compensation plates are arranged such that their alignment axes are perpendicular to each other. The polarized light conversion element is more advantageously laminated on a transparent glass plate. The surface of the optical compensation plate in contact with the air is preferably provided with an anti-reflection layer. A retardation plate may be laminated on the surface opposite to the linear polarizing plate and the optical compensation plate. These polarization conversion elements are arranged on one side of the liquid crystal cell to form a projection type liquid crystal display device.

Description

Polarization conversion element and projection type liquid crystal display device using the polarization conversion element

technical field

The invention relates to a polarization conversion element suitable for a projection type liquid crystal display device, and a projection type liquid crystal display device using the polarization conversion element.

Background technique

A projection type liquid crystal display device, also called a liquid crystal projector (projector), is a device that can magnify the screen of a personal computer, television, etc. and write it on the screen, and has been widely used at present.

An example of the structure of a projection-type liquid crystal display device is schematically described with reference to FIG. 6 . A projection-type liquid crystal display device generally has a light source system, a reflective spectroscopic system, and an enlarged projection system. The light source system has a white light source 11 , a collecting lens 13 and a UVIR filter (cut filter) 14 . The white light from the white light source 11 is collected by the lens 13, and then the ultraviolet and infrared rays are removed by the UVIR filter 14, and then sent to the dichroic mirror (dichroic mirror) 1. The white light source 11 usually adopts a metal halide lamp or a high pressure mercury lamp or the like.

Reflective light splitting system has: 4 kinds of beam splitters 1, 2, 3, 4, 2 total reflection mirrors 5, 6, liquid crystal units (cells) 7R, 7G, 7B corresponding to red light R, green light G, and blue light B respectively , Incident-side polarization conversion elements 8R, 8G, 8B, exit-side polarization conversion elements 9R, 9G, 9B, and collecting lenses 10R, 10G, and 10B. A known polarization conversion element employs a linear polarizing plate, an optical compensation plate laminated on the linear polarizing plate, and a phase difference plate laminated on these plates.

Then, the first beam splitter 1 only transmits the green light G and the blue light B, and the transmitted green light G and blue light B are transmitted to the second beam splitter 2 . The red light R reflected by the first dichroic mirror 1 is transmitted to the first total reflection mirror 5, and after being reflected there, it passes through the red light collecting lens 10R, the incident side polarization conversion element 8R, the liquid crystal unit 7R and the exit side polarization conversion Element 9R transmits to the third beam splitter 3 . On the one hand, the second dichroic mirror 2 only passes through the blue light B, among the green light G and the blue light R which pass through the first dichroic mirror 1, the blue light B which passes through the second dichroic mirror 2 passes through the blue light collecting lens 10B, The incident-side polarization conversion element 8B, the liquid crystal cell 7B, and the exit-side polarization conversion element 9B are transmitted to the second total reflection mirror 6 . Moreover, the green light G reflected by the second beam splitter 2 is sent to the third beam splitter 3 through the green light collecting lens 10G, the incident side polarization conversion element 8G, the liquid crystal unit 7G and the exit side polarization conversion element 9G. The third dichroic mirror 3 only transmits the red light R, and passes through the red light collecting lens 10R from the first total reflection mirror 5, the incident side polarization conversion element 8R, the liquid crystal unit 7R and the exit side polarization conversion element 9R The red light R passes through the third dichroic mirror 3 intact, and then passes through the green light collecting lens 10G from the second dichroic mirror 2, the incident side polarization conversion element 8G, the liquid crystal unit 7G and the exit side polarized light The green light G from the conversion element 9G is reflected by the third beam splitter 3 and transmitted to the fourth beam splitter 4 . The fourth dichroic mirror 4 only transmits the red light R and the green light G, the red light R and the green light G from the third dichroic mirror 3 pass through the fourth dichroic mirror 4 intact, and pass through the second dichroic mirror 3 The blue light B from the reflector 6 is reflected here and transmitted to the projection lens 16 respectively.

The magnified projection system has a projection lens 16 for magnifying the images corresponding to the respective lights and projecting the magnified images to the screen 17 . Also, although the incident-side polarization conversion elements 8R, 8G, 8B and the exit-side polarization conversion elements 9R, 9G, 9B corresponding to the liquid crystal units 7R, 7G, 7B of each color are also bonded to the liquid crystal units 7R, 7G, 7B, however , generally arranged at intervals with liquid crystal units 7R, 7G, and 7B, and this interval is used as a ventilation path for cooling. Furthermore, the incidence-side polarization conversion elements 8R, 8G, and 8B are also separated from the collecting lenses 10R, 10G, and 10B. In this way, when the polarization conversion elements 8R, 8G, 8B, 9R, 9G, 9B are arranged away from the liquid crystal cells 7R, 7G, 7B and the collecting lens, the linear polarizing plate is made of a reinforcing material bonded to glass or the like.

In such a projection-type liquid crystal display device, each liquid crystal unit 7R, 7G, 7B is respectively disposed between two polarization conversion elements, that is, incident-side polarization conversion elements 8R, 8G, 8B and exit-side polarization conversion elements 9R, 9G, 9B. between. These polarization conversion elements 8, 9 generate a large amount of heat because they need to pass through the necessary amount of light to magnify the image and project it on the screen. In addition, when the red light R, the green light G and/or the blue light B are polarized, when they enter the liquid crystal cells 7R, 7G, and 7B, the plane of polarization will be rotated multiple times. Moreover, the polarized light emitted from the liquid crystal cells 7R, 7G, and 7B is also rotated to the polarized plane.

In order to rotate the polarization plane, a phase difference plate can be used, and the phase difference plate is generally arranged on the light source 11 side of the incident side polarization conversion elements 8R, 8G, 8B, or the projection lens 16 side of the exit side polarization conversion elements 9R, 9G, 9B . Retardation plates have advantages such as easy availability and low cost, and are generally made of resin. As the retardation plate, one bonded to a linear polarizing plate is used among the incident-side polarization conversion elements 8R, 8G, and 8B or the exit-side polarization conversion elements 9R, 9G, and 9B. (eg, Japanese Patent Application Nos. 2000-137202 and 2000-352615A)

Such a projection-type liquid crystal display device does not match well with the birefringence of the liquid crystal unit and the width of the light from the light source. There is a problem with poor display quality.

Contents of the invention

Here, the inventors of the present invention developed and researched the polarization conversion element to realize a projection-type liquid crystal display device with higher contrast and better display quality. As a result, it was found that the contrast of the image projected on the screen can be improved by laminating two optical compensation plates composed of a base film (film) coated with a liquid crystal compound on one side of the linear polarizing plate. , and a polarization conversion element for a projection-type liquid crystal display device with no black display unevenness and excellent display quality can be obtained.

The present invention provides a polarization conversion element. Two optical compensation plates formed by coating a liquid crystal compound on a substrate film are stacked on one side of a linear polarizer, and a projection-type liquid crystal display using the polarization conversion element is provided. device.

In this polarization conversion element, two optical compensation plates coated with a liquid crystal compound on the base film are used, and the second optical compensation plate and the first optical compensation plate are adjacent to each other, that is, the linear polarizer/the first optical compensation plate. Sequential arrangement of compensation plate/second optical compensation plate. On the other hand, the alignment axis of the second optical compensation plate is substantially perpendicular to the alignment axis of the first optical compensation plate. Such polarized light conversion elements are generally laminated on a transparent glass plate. In this case, it is more advantageous to configure a transparent polarizer on the surface of the linear polarizer opposite to the surface of the laminated optical compensation plate. glass plate. Preferably, an antireflection layer is provided on the surface in contact with the air. A phase difference plate may be laminated on the surface of the linear polarizing plate opposite to the surface on which the optical compensation plate is laminated.

Such polarization conversion elements are used and assembled on one side of the liquid crystal cell of a projection liquid crystal display device. This projection type liquid crystal display device, more specifically, has an optical system composed of a white light source, a beam splitter that splits the white light into three primary colors of red light, green light, and blue light from the white light source, a total reflection mirror, and a light-collecting lens. parts, liquid crystal unit, and the above-mentioned polarization conversion element.

Description of drawings

Fig. 1 is a cross-sectional schematic diagram of an example of the polarization conversion element of the present invention;

Fig. 2 is a schematic cross-sectional view of another example of the polarization conversion element of the present invention;

Fig. 3 is an exemplary configuration diagram of the axial angle relationship between two linear polarizers and optical compensation plates in the polarization conversion element of the present invention;

Fig. 4 is another exemplary configuration diagram of the axial angle relationship between the linear polarizing plate and the optical compensation plate in the polarization conversion element of the present invention;

Fig. 5 is another exemplary configuration diagram of the axial angle relationship between the two linear polarizing plates and the optical compensation plate in the polarization conversion element of the present invention; and

FIG. 6 is a schematic diagram showing a configuration example of a projection type liquid crystal display device.

Explanation of reference signs:

1, 2, 3, 4: dichroic mirrors

5, 6: total reflection mirror

7R, 7G, 7B: Liquid crystal unit

8R, 8G, 8B: incident side polarization conversion elements

9R, 9G, 9B: Exit side polarization conversion elements

10R, 10G, 10B: Concentrating lens

L: white light (light source light)

R: red light

G: green light

B: Blu-ray

11: white light source

13: Collecting lens

14: UVIR filter

16: Projection lens

17: screen

20: Polarization conversion element

21: linear polarizer

22: Optical compensation plate

23: Optical compensation plate

24: glass plate

25: phase difference plate

26: Transparent film with anti-reflection layer

27: anti-reflection layer

28: anti-reflection layer

Detailed ways

The linear polarizing plate used in the present invention may also have the property of absorbing linearly polarized light having a parallel vibration plane in the direction of the absorption axis, substantially preventing it from passing through, and having the property of transmitting linearly polarized light having a plane of vibration perpendicular to the direction of the absorption axis. properties of linearly polarized light. Generally, a linear polarizing plate is made by laminating a protective film on one or both sides of a polarizer film. The polarizer film is, for example, preferably formed by absorbing and aligning a dichroic dye on a polyvinylalcohol resin film. The thickness of the polarizer film is generally 1-50 microns. For the protective film, for example, a film made of a cellulose-based resin such as diacetyl cellulose or triacetyl cellulose, a film of a norborane-based resin such as Representative amorphous olefin (olefin) resin films include olefin films, acrylic resin films, polyester resin films, and the like. The thickness of the protective film is generally 10 to 200 microns. The polarizing film and the protective film are, for example, laminated via a polyvinyl alcohol-based adhesive layer. Such a linear polarizer can also be applied to known projection-type liquid crystal display devices.

In the present invention, a linear polarizing plate is used in combination with an optical compensation plate obtained by applying a liquid crystalline compound to the film surface of a substrate to achieve alignment. The base film of the optical compensation plate is, for example, a polycarbonate-based resin such as denatured polycarbonate having an olefin skeleton, a cellulose-based resin such as diacetyl cellulose or triacetyl cellulose, orthobornane Cyclic polyolefin resins, polysulfone resins, polyethersulfone resins, polyester resins, polyimides, polyamides, which are polymers of monomers Amine (polyamide), polyacrylate (polyarylate) resin, etc. The thickness of the base film is generally 10 to 1,000 micrometers. The liquid crystal compound coated thereon is, for example, a discotic liquid crystal compound, a polymer liquid crystal compound, and the like. Orientation of the liquid crystal compounds can also be carried out by a common method. For example, the method of aligning the substrate surface in advance, coating the liquid crystal compound on it, drying it, and then heat-treating the liquid crystal compound can be used. A commercially available optical compensation plate coated with an alignment liquid crystal compound is, for example, "WIDE VIEW A" sold by Fuji Photo Film Co., Ltd. or "Nisseok LC Film" sold by Nippon Mitsubishi Co., Ltd.

In the two optical compensation plates laminated on one side of the linear polarizing plate, it is preferable that the absorption axis of the former and the alignment axis of the latter be arranged to be substantially perpendicular or parallel. In addition, in the two optical compensation plates, it is preferable that the respective alignment axes are arranged so as to be perpendicular to each other. When two optical compensation plates are attached to the linear polarizer, the absorption axis of the linear polarizer and the alignment axis of the first optical compensation plate are perpendicular to each other, and the absorption axis of the linear polarizer is perpendicular to the alignment axis of the second optical compensation plate. , preferably arranged parallel to the absorption axis of the linear polarizer.

The polarization conversion element composed of a linear polarizer and an optical compensation plate is generally bonded to a transparent glass plate for use. In this case, both are laminated through an adhesive layer. As the adhesive constituting the adhesive layer, for example, pressure-sensitive adhesives such as acrylic pressure-sensitive adhesives and urethane pressure-sensitive adhesives are used. The pressure-sensitive adhesive is generally a transparent optically isotropic adhesive layer. The thickness of the adhesive layer is generally 10-60 microns. The pressure-sensitive adhesive can also be called adhesive.

As the transparent glass plate, a silicon-based glass plate generally called blue plate glass or white plate glass is used. Also, it is preferable to use sapphire glass with high thermal conductivity. Furthermore, crystal glass and quartz glass can also be used. The sapphire glass is a single crystal of aluminum (Al ₂ O ₃ ), and is formed in a plate shape by, for example, the EFG method (Edge-defined Film-fed Growth). It is preferable to have an antireflection layer on one side of the transparent glass plate, that is, the exposed surface. Also, a dichroic layer is formed to only transmit light of a specific wavelength, however, a tunable filter (trimming filter) that does not transmit light of other wavelength ranges may also be used. The thickness of the transparent glass plate is generally 0.1 to 2 mm, preferably more than 0.3 mm and less than 0.8 mm. The area of the transparent glass plate is appropriately selected according to the size of the intended projection-type liquid crystal display device. Representative examples are rectangles or squares with a side of 10 to 100 mm, circles or ellipses with a diameter of 5 to 100 mm, and the like.

A linear polarizing plate and an optical compensation plate are stacked on a transparent glass plate. The linear polarizing plate and the optical compensation plate are sandwiched by a transparent glass plate, and the two sides are separately bonded. However, the linear polarizing plate can also be laminated on one side of the transparent glass plate, and then laminated Combined optical compensation plate. The area of the linear polarizer and optical compensation is generally the same as that of the transparent glass plate, or slightly smaller. Those with a slightly smaller area are easy to stick to the glass surface, 0.5-5mm from the edge of the transparent glass plate to the inner side, and the smaller ones are better.

In the polarization conversion element of the present invention, the optical compensation plate preferably has an anti-reflection layer on its outer surface, that is, on a contact surface with air. The anti-reflection layer reduces the reflected light on the interface with the air layer to prevent stray light caused by reflected light. Here, it is preferable to provide an antireflection layer having a reflectance of 2% or less, particularly 1% or less, on this surface. As the antireflection layer, for example, a single layer or a multilayer selected from compounds of metals, metal oxides, and metal fluorides is generally used. The metal is, for example, silver, the metal oxide is, for example, silicon oxide, aluminum oxide, titanium oxide, tantalum oxide, yttrium oxide, zirconium oxide, etc., and the metal fluoride is, for example, magnesium fluoride. The antireflection layer may be a single layer or multiple layers, for example, 2 layers, 3 layers, or 4 or more layers. The thickness of the antireflection layer, or the thickness of each layer in the case of multiple layers, is appropriately selected in accordance with the number of layers, the curvature of the material used for each layer, and the like.

It is also possible to directly provide such an antireflection layer on the optical compensation plate, but in this case, the characteristics of the optical compensation plate will change. The antireflection film in which the antireflection layer is formed on the transparent base film is preferably laminated on the optical compensation plate. The film forming the antireflection layer is, for example, a polycarbonate-based resin such as polycarbonate or denatured polycarbonate having a fluorene skeleton, or a fiber such as diacetyl cellulose or triacetyl cellulose Plain resin, cyclic polyolefin resin, polysulfone resin, polyethersulfone resin, polyester resin, polyimide, polyamide, polyacrylate resin resin etc. In particular, cyclic polyolefin-based resins have a small photoelastic coefficient and are suitable as film base materials. Cyclic olefin-based resin film, for example, "ARTON" manufactured by JAYIDARE Co., Ltd. (glass transition temperature about 170 degrees Celsius, photoelastic coefficient about 4×10 ^-13 cm2/dyne), Sekisui Chemical Industry ( Co., Ltd.) "IDSHEENA" (glass transition temperature about 140 degrees Celsius, photoelastic coefficient about 6 × 10 ^-13 cm2/dyne) and other commercially available products. The thickness of the substrate on which the antireflection layer is provided is generally 10 to 1,000 micrometers.

In addition, in the composition of the linear polarizing plate/glass plate/two optical compensation plates, it is preferable that the above-mentioned antireflection layer is also provided on the outer surface of the linear polarizing plate. Since a linear polarizing plate having an antireflection layer is also commercially available, it can be used as it is for the linear polarizing plate in the above composition.

The contact angle of the surface of the antireflection layer is 80 degrees or more, preferably 100 degrees or more. Here, the contact angle is a value when water is used as a liquid. When the contact angle of the surface in contact with the air is less than 80 degrees, fine particles are likely to adhere, and a projection-type liquid crystal display device having a polarizing conversion element with such a surface tends to decrease the contrast after long-term use. . The upper limit of the contact angle is 180 degrees.

When the surface of the antireflection layer satisfies the contact angle specified here, the antireflection film having the antireflection layer or the linear polarizer can be applied to the polarization conversion element of the present invention as it is. Generally, when there are many antireflection layers, the contact angle specified here is not available. In this case, a layer made of fluoride is provided on the antireflection layer to achieve the contact angle. A layer composed of a fluorine compound can be provided by a coating liquid containing the compound. The fluoride used for this purpose is not particularly limited to a surface contact angle of 80 degrees or more, and is usually used to prevent surface contamination, for example, a fluorine-containing silane (siliane) compound can be used. Compounds like this prevent dirt such as fingerprints from sticking to the surface.

In the polarization conversion element in which a linear polarizing plate and an optical compensation plate are laminated, a retardation plate may be bonded to one side of the linear polarizing plate. The retardation plate used here may be made of resin, as is the case for general liquid crystal display devices, and for example, a retardation film in which a substrate film is extended in one axis direction may be used. Resins, for example, polyvinyl alcohol-based resins, polycarbonate-based resins containing denatured polycarbonate having a fluorene skeleton, cellulose-based resins such as diacetyl cellulose or triacetyl cellulose, orthobornane-based Cyclic polyolefin-based resins, polysulfone-based resins, polyethersulfone-based resins, polyester-based resins, polyimides, polyamides, polyacrylate-based resins, etc., which are polymers of monomers. The thickness of the retardation plate is generally 10 to 1,000 micrometers.

Retardation plate, it is preferable to use 1/2 wavelength plate, for example, for red light 1/2 wavelength plate is 290～320nm, preferably has the retardation (retardation) person of 300～310nm, for green light 1/2 The 2-wavelength plate is 260-290nm, preferably has a retardation of 270-280nm, and the blue 1/2-wavelength plate is 210-240nm, preferably has a retardation of 220-230nm. Commercially available retardation plates can be used. For example, for blue light, "SMICALITE SEF460225" (made of polycarbonate resin, with a glass transition temperature of about 150 degrees Celsius) sold by Sumitomo Chemical Co., Ltd. can be used. , the retardation is about 225nm), etc. For green light, "SMICALITESEF460275" (made of polycarbonate resin, with a glass transition temperature of about 150 degrees Celsius and a retardation About 275nm), etc., for red light, "SMICALITE SEF460305" (made of polycarbonate resin, glass transition temperature about 150 degrees Celsius, delay about 305nm) etc. The retardation film may be used as it is with a stretched film, and one or both sides thereof may be laminated with a protective film made of cellulose diacetate or cellulose-based resin such as cellulose diacetate.

The shape of the phase difference plate is generally the same as that of the linear polarizer, and the shape of the transparent glass plate is roughly the same, or it can be slightly smaller. On the other hand, when the phase difference plate has a surface in contact with the air, an anti-reflection layer is provided on the outside of the phase difference plate. Preferably, the contact angle of this surface is 80 degrees or more. The contact angle referred to here is also a value when water is used as a liquid. The antireflection layer provided on the outside of the phase difference is the same as the antireflection layer provided on the outside of the linear polarizing plate or the optical compensation plate as described above. Furthermore, when the surface having the antireflection layer satisfies the contact angle specified here, the polarized light conversion element of the present invention can also be applied to the retardation film having the antireflection layer as it is. However, in the case of many antireflection layers, there is no contact angle specified here. In this case, a layer made of fluoride may be provided on the antireflection layer. Specific examples and mounting methods of the layer made of fluoride are the same as those described above.

1 to 2 are examples of the polarization conversion element of the present invention. As shown in Fig. 1, the linear polarizing plate 21 and the optical compensation plates 22, 23 are stacked, and the glass plate 24 is laminated on the side of the linear polarizing plate 21, and the transparent film 26 provided with the anti-reflection layer 27 is placed on the optical compensation plate 23 side. The antireflection layer 27 is bonded on the outside to form the polarization conversion element 20 . An antireflection layer 28 is provided on the outer surface of the glass plate 24 on the opposite side to the surface to which the linear polarizer 21 is bonded. The optical compensation plates 22 and 23 are arranged such that their alignment axes are perpendicular to each other. Also, preferably, the surface on which the liquid crystalline compound is applied and the opposite surface are arranged so as to overlap. When the glass plate has anisotropy, the crystal axis and the polarization axis of transmitted polarized light must be parallel or perpendicular, and the C-axis of sapphire and the polarized axis of transmitted polarized light should be arranged in a parallel or perpendicular manner. In FIG. 2 , a layered structure is added to FIG. 1 , and a retardation plate 25 is arranged between a linear polarizer 21 and a glass plate 24 to form a polarization conversion element 20 .

Of course, the layer structure of the polarization conversion element of the present invention is not limited to the illustration in the figure. For example, as previously explained, a linear polarizer can be laminated to one side of a glass plate, and two optical compensation plates Fold to the other face. In this case, the phase difference plate may be disposed on the opposite side of the glass plate bonding surface of the linear polarizing plate. Preferably, an anti-reflection layer is provided on the surface of the linear polarizer or phase difference plate that is in contact with air, more preferably, an anti-reflection layer is provided on the surface that is in contact with the optical compensation plate.

Fig. 3 is the axis-angle relationship of the linear polarizer and the optical compensation plate constituting the polarization conversion element of the present invention. On the surface of one side of the linear polarizing plate 21, two optical compensation plates are superimposed, that is, the relation of the time axis angle when laminating the first optical compensation plate 22 and the second optical compensation plate 23, in this case, the absorption of the linear polarizing plate 21 The axis (arrow) and the alignment axis (arrow) of the first optical compensation plate 22 are arranged in a manner that is approximately perpendicular to the alignment axis (arrow) of the second optical compensation plate 23, and the alignment axis (arrow) of the second optical compensation plate 23 is perpendicular to the alignment axis of the first optical compensation plate. Therefore, It is arranged parallel to the absorption axis of the linear polarizer 21 . In addition, the two optical compensation plates are arranged such that the surface on which the liquid crystalline compound is applied faces the opposite surface. FIG. 4 and FIG. 5 show the relationship between the axis angles of the linear polarizer and the optical compensation plate constituting the polarization conversion element of the present invention. It shows, on the surface of one side of the linear polarizing plate 21, the relationship between the time axis angles of laminating two optical compensating plates, that is, laminating the first optical compensating plate 22 and the second optical compensating plate 23, in this case, the straight line The absorption axis of the polarizing plate 21 and the alignment axis of the first optical compensation plate 22 are configured in a substantially parallel manner, and the alignment axis of the second optical compensation plate 23 is perpendicular to the alignment axis of the first optical compensation plate. The absorption axes of the linear polarizers 21 are arranged so as to be perpendicular to each other. The two optical compensation plates are arranged in such a direction that the surface on which the liquid crystalline compound is applied and the opposite surface face each other, as in the case of FIG. 3 .

Preferably, the polarization conversion element of the present invention can be applied to a projection type liquid crystal display device. For example, in a projection-type liquid crystal display device, it can be inserted and used in the optical path of white light from a white light source, or in the optical path of each primary color light of red, green, or blue light after splitting the white light.

Specifically, in the projection-type liquid crystal display device shown in FIG. 6 , the incident-side polarization conversion elements 8R, 8G, and 8B of the liquid crystal units 7R, 7G, and 7B corresponding to the three primary colors, or the output-side polarization conversion elements 9R can be used. , 9G, 9B in one. In this polarization conversion element, the optical compensation plate is generally arranged on the side closer to the liquid crystal cells 7R, 7G, and 7B than the glass plate.

Although, there is also a projection type liquid crystal display device that directly amplifies the spectroscopic light coming from a color filter in the form of a single plate. In this case, the polarization conversion element of the present invention is arranged in the optical path of white light.

Example

Hereinafter, although the present invention will be described in detail using specific examples, the present invention is not limited to these examples.

Comparing the illuminance L1 of bright display and the illuminance L2 of dark display, it is calculated by the following formula.

Contrast C=L1/L2 Formula (1)

Example 1

On one side of a 0.9-inch diagonal sapphire glass plate sold by KYOCERA Co., Ltd., a polyvinyl alcohol/dichroic dye sold by Sumitomo Chemical Industry is a linear polarizer "SMICARANE SWW832A" through an adhesive. And two optical compensation plates "WIDE VIEW WVA02B" sold by Fuji Photo Co., Ltd. The linear polarizing plate and the two optical compensation plates are the same arrangement as shown in Fig. 3 . Two optical compensation plates are bonded face to face with the liquid crystal compound-coated side and the opposite side, respectively. On the contact surface between the optical compensation plate and the air, a transparent film with an anti-reflection layer thickness of 80 microns is made on the outside of the anti-reflection layer on one side, and bonded through an adhesive to produce a polarization conversion element.

In the projection type liquid crystal display device (liquid crystal projector), on the light source side of the liquid crystal cell of the green channel (channel), the polarization conversion element is set so that the optical compensation plate is closer to the liquid crystal cell side than the sapphire glass plate, Only green light was projected onto the screen and a contrast of 550 was measured. comparative example

Except that the optical compensation plate is not used, the rest is the same as that of Embodiment 1, and a polarization conversion element is fabricated. The contrast was more similarly measured and it was 300.

Example 2

On one side of a 0.9-inch diagonal sapphire glass plate sold by KYOCERA Co., Ltd., the polyvinyl alcohol-based phase difference plate "SMICALITE SEF460275" sold by Sumitomo Chemical Co., Ltd. and The polyvinyl alcohol/dichroic dye also sold by Sumitomo Chemical is a linear polarizing plate "SMICARANE SWW832A". On the surface of this linear polarizing plate, an optical compensation plate "Wide View WVA02B" sold by Fuji Photo Co., Ltd. was similarly arranged as shown in FIG. 3 . The two optical compensation plates are bonded face-to-face with the liquid crystal compound-coated surface and the opposite surface through the adhesive agent. On the contact surface of the optical compensation plate and the air, on one side as in Example 1, a transparent film having a thickness of 80 μm of an anti-reflection layer was attached through an adhesive to produce a polarization conversion element.

Example 3

Except that the retardation plate was changed to a polycarbonate-based retardation plate “SMICALITE SEF460305” sold by Sumitomo Chemical Co., Ltd., the rest was the same as in Example 2 to produce a polarization conversion element.

Example 4

In addition to changing the retardation plate to the polycarbonate-based retardation plate “SMICALITE SEF460225” sold by Sumitomo Chemical Co., Ltd., and changing the polarizer to polyvinyl alcohol/di Except that the chromatic dye is a linear polarizing plate, the rest are the same as in Example 2 to manufacture a polarization conversion element.

Example 5

On the exit side of the liquid crystal unit of the projection type liquid crystal display device (liquid crystal projector), the polarization conversion elements made in embodiment 2, embodiment 3, and embodiment 4 are set to be respectively in the green channel, red channel, blue channel On the projection lens side of the channel, the optical compensation plate is closer to the liquid crystal unit side than the sapphire glass plate. The contrast on the screen can be greatly improved, and the unevenness of the black display will be reduced, which improves the display quality. Comparative example 2

Except stacking 1 optical compensation plate, all the other are the same as embodiment 2, 3, 4, to make the polarization conversion element, and same as embodiment 5, when setting the projection type liquid crystal display device (liquid crystal projector), The on-screen contrast does not go up, nor does the display quality.

Example 7

Except that on the contact surface between the optical compensation plate and the air, there is no laminated transparent film with an anti-reflection layer on one side, all the other are the same as in Examples 2, 3, and 4 to make a polarization conversion element, and are the same as in Example 5, When it is set as a projection type liquid crystal display device (liquid crystal projector), the contrast on the screen will be slightly improved, and the unevenness of the black display screen will be reduced, but the display quality is not so high.

Because the polarization conversion element of the present invention is to configure a linear polarizing plate, and configure two optical compensation plates on one side of it, it can be effectively applied to a projection type liquid crystal display device, and this polarization conversion element is configured on the incident/ Or the projection-type liquid crystal display device on the output side, the contrast of the projected image is high, and the unevenness of the black display screen is reduced, so the display quality can be improved.

Claims (10)

1. polarization conversion element is characterized in that:

One straight line Polarizer; And

Two optical compensation plates, the face on superimposed one side in this linear polarization plate, wherein these two optical compensation plates are that coating fluid crystallinity compound constitutes on a substrate film.

2. polarization conversion element as claimed in claim 1 is characterized in that: wherein the orientation axle of these two optical compensation plates is configured to orthogonal out of the ordinary.

3. polarization conversion element as claimed in claim 1 is characterized in that: more be superimposed with a transparency glass plate.

4. polarization conversion element as claimed in claim 3 is characterized in that: this transparency glass plate is folded into and the face of this face opposition side of superimposed this optical compensation plate of this linear polarization plate.

5. polarization conversion element as claimed in claim 3 is characterized in that: this transparency glass plate is folded between this linear polarization plate and this optical compensation plate.

6. as each described polarization conversion element in the claim 3,4 or 5, it is characterized in that: this transparency glass plate is the sapphire glass plate.

7. polarization conversion element as claimed in claim 1 is characterized in that: on the face that this optical compensation plate and air join, have antireflection layer.

8. polarization conversion element as claimed in claim 1 is characterized in that: have this transparent base of an antireflection layer, the superimposed face that joins at this optical compensation plate and air.

9. polarization conversion element as claimed in claim 1 is characterized in that: with the face of this face opposition side of superimposed this optical compensation of this linear polarization plate on, be superimposed with polarizer.

10. projection-type liquid crystal display device is characterized in that:

Be configured on the liquid crystal cells face on one side as each described polarization conversion element in the claim 1 to 9.

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