JP5365184B2 - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device enabling observation of a bright image even in a state with a polarizing glasses put on. <P>SOLUTION: The liquid crystal display device has: a liquid crystal cell; a polarizer arranged on the display side of the liquid crystal cell; and an optical conversion layer which is arranged closer to the display side than the polarizer, and has a function for converting linear polarization having passed through the polarizer into elliptic polarization. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a liquid crystal display device capable of observing a display without being darkened even when polarized glasses are attached.

  In the current liquid crystal display device, the polarization state of the display light emitted from the display screen is linearly polarized light. For example, when the liquid crystal display device is viewed from the front, in the case of the TN mode, the polarization transmission axis is mostly set in the diagonal direction of the screen. On the other hand, in the VA mode and the IPS mode, there are many vertical directions, but the one used for outdoor indoor advertising is changed only in the circuit, installed vertically and vertically, and the polarization transmission axis is set in the horizontal direction. Is seen. The reason why the polarization transmission axis of linearly polarized light emitted from the liquid crystal display device is in this direction is that light that can be transmitted through the polarizing plate arranged on the display side of the liquid crystal display device is transmitted through the polarizing plate. This is because the linearly polarized light coincides with the direction of the axis. That is, in the TN mode, the polarization transmission axis of the polarizing plate disposed on the display side of the liquid crystal display device is set in the oblique direction, and in the advertising VA mode and IPS mode, it is set in the substantially horizontal direction.

  On the other hand, automotive display devices, navigation devices, aircraft cockpit display devices, mobile radios, mobile phones, fish detectors, wristwatches, indoor and outdoor display devices, etc., where TN mode is often used When the current liquid crystal display device as described above is used as a display unit used below, when such a liquid crystal display device is viewed through polarized glasses that are frequently used in such an environment, the liquid crystal display device The polarized light transmission characteristics of the polarizing glasses have an adverse effect on each other, the display is dark and difficult to see, and the visibility is extremely deteriorated.

  The reason is that the polarization transmission axis of the polarized glasses is set in the vertical direction, and the polarization transmission axis of the linearly polarized light from the display screen and the polarization transmission axis of the polarized glasses do not match, so the light transmittance of the polarized glasses is remarkably high. It is because it falls.

  Here, the reason why the direction of the polarization transmission axis of the polarizing lens of the polarizing glasses is substantially vertical is that the reflected light from the refractive index interface of the water surface has more S-polarized components than the P-polarized light. This is because it is set to prevent glare due to reflection at the refractive index interface.

  In view of the above problems, Patent Document 1 discloses a technique in which a λ / 4 phase difference plate is arranged on the display side constituting the liquid crystal display device to change the straight line into circularly polarized light. According to such a method, the linearly polarized light irradiated on the display side is eliminated, so that an image can be observed even when the polarizing glasses are worn. However, on the other hand, since the linearly polarized light is converted into circularly polarized light, the light provided for display is dispersed in all directions, and the image that can be observed with the polarizing glasses worn becomes dark. There was a problem.

  Further, Patent Document 2 discloses a liquid crystal display device that can be visually recognized even when wearing polarized glasses by removing linearly polarized light using a depolarizing plate. However, the depolarizing plate is very expensive and is not suitable for a liquid crystal display device that is required to reduce the cost due to rapid market expansion, and the light used for display is dispersed in all directions. For this reason, there is a problem that an image that can be observed with the polarized glasses is darkened.

Japanese Patent Laid-Open No. 10-10522 Japanese Patent Laid-Open No. 10-10523

  The present invention has been made in view of such a situation, and a main object of the present invention is to provide a liquid crystal display device that can be viewed brightly even when polarized glasses are worn.

  In order to solve the above problems, the present invention provides a liquid crystal cell, a polarizer disposed on the display side of the liquid crystal cell, and linearly polarized light that is disposed closer to the display side than the polarizer and transmits the polarizer. A liquid crystal display device having an optical conversion layer having a function of converting into polarized light is provided.

According to the present invention, since the optical conversion layer is used, the polarizer has a function of converting the transmitted linearly polarized light into elliptically polarized light. Therefore, the polarizer is visible in a specific direction corresponding to the major axis direction of the elliptically polarized light. The image to be displayed can be brighter than the other directions. For this reason, according to the present invention, for example, by aligning the major axis of elliptically polarized light in the vertical direction, it is possible to obtain a liquid crystal display device that can be viewed brightly in a normal state with polarized glasses.
Therefore, according to the present invention, it is possible to obtain a liquid crystal display device that can be viewed brightly even when wearing polarized glasses.

  In the present invention, the optical conversion layer has a function of converting linearly polarized light transmitted through the polarizer into elliptically polarized light whose major axis direction is different from the polarization transmission axis of the polarizer. In particular, it is preferable to have a function of converting into elliptically polarized light whose major axis direction is a substantially vertical direction. This is because it becomes possible to visually recognize brighter in a state where the polarized glasses are worn.

Moreover, in this invention, it is preferable that the said optical converting layer contains the rod-shaped compound which formed the cholesteric structure. Since such an optical conversion layer is arranged in combination with the polarizer, it is not necessary to control the arrangement direction of each other and can be arranged in an arbitrary direction. This is because the liquid crystal display device of the present invention can be manufactured by a simple process by using the conversion layer.
Furthermore, it is easy to arbitrarily control the major axis direction of the elliptically polarized light after the linearly polarized light transmitted through the polarizer by the optical functional layer is converted into elliptically polarized light.
Thereby, the effect | action which makes the linearly polarized light of the said optical conversion layer elliptical polarized light, and the effect | action which rotates a polarization transmission axis can be adjusted easily.

  In the present invention, it is preferable that the optical conversion layer is formed by fixing chiral nematic liquid crystal.

  Furthermore, in the present invention, the selective reflection wavelength of the optical conversion layer is preferably 750 nm or more. As a result, the efficiency of converting linearly polarized light transmitted through the polarizer into elliptically polarized light in the optical conversion layer can be increased, and the liquid crystal display device of the present invention can be observed more brightly with polarized glasses attached. Because. In addition, since the selective reflection wavelength is outside the visible light region, it is possible to prevent a decrease in contrast due to coloring due to external light or reflection of display light.

  In the present invention, the polarization transmission axis of the polarizer is tilted to the left from the vertical direction when viewed from the display side, and the turning direction of the cholesteric structure is right rotation, or the polarization transmission axis of the polarizer is It is preferable that the display device is inclined from the vertical direction to the right side as viewed from the display side, and the turning direction of the cholesteric structure is a left rotation. This is because the thickness of the optical conversion layer in the present invention can be further reduced.

  In the present invention, the optical conversion layer is preferably capable of converting the linearly polarized light into elliptically polarized light having an ellipticity in the range of 0.006 to 0.8. Since the ellipticity after conversion by the optical conversion layer is in the range of 0.006 to 0.8, it is possible to obtain a liquid crystal display device that can be viewed brightly even in a normal state with polarized glasses. It is.

  The liquid crystal display device of the present invention has an effect that it can be viewed brightly even when the polarized glasses are worn.

  Hereinafter, the liquid crystal display device of the present invention will be described in detail.

  As described above, the liquid crystal display device according to the present invention includes a liquid crystal cell, a polarizer disposed on the display side of the liquid crystal cell, and linearly polarized light that is disposed on the display side of the polarizer and transmits the polarizer. And an optical conversion layer having a function of converting the light into elliptically polarized light.

Such a liquid crystal display device of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of the liquid crystal display device of the present invention. As illustrated in FIG. 1, a liquid crystal display device 10 of the present invention includes a liquid crystal cell 1 and a polarizer 2 disposed on the display side of the liquid crystal cell, and further on the display side of the polarizer. The optical conversion layer 3 is included.
In such an example, in the liquid crystal display device 10 of the present invention, the optical conversion layer 3 transmits light that has been linearly polarized by passing through the liquid crystal cell 1 and further through the polarizer 2, and converts it into elliptically polarized light. It has a function.
As illustrated in FIG. 1, in the liquid crystal display device 10 of the present invention, the polarizer 2 may be used as a polarizing plate P having a configuration in which both sides are sandwiched between polarizing plate protective films 2 ′. A polarizing plate P ′ including a polarizer may be disposed on the backlight side of the cell 1.
In FIG. 1, the X direction represents the display side, and the Y direction represents the backlight side (the same applies to the following drawings).

  Here, in the present invention, the “display side” means a side on which an observer of the liquid crystal display device observes an image displayed on the screen of the liquid crystal display device.

According to the present invention, since the optical conversion layer is used, the linearly polarized light that has passed through the polarizer can be converted into elliptically polarized light, so that it is visually recognized in a specific direction corresponding to the major axis direction of the elliptically polarized light. The image can be brighter than other directions. For this reason, according to the present invention, for example, by aligning the major axis of elliptically polarized light in the vertical direction, it is possible to obtain a liquid crystal display device that can be viewed brightly in a normal state with polarized glasses.
Therefore, according to the present invention, it is possible to obtain a liquid crystal display device that can be viewed brightly even when wearing polarized glasses.

The liquid crystal display device of the present invention has at least a liquid crystal cell, a polarizer, and an optical conversion layer, and may have any other configuration as necessary.
Hereafter, each structure used for this invention is demonstrated in order.

1. Optical Conversion Layer First, the optical conversion layer used in the present invention will be described. The optical conversion layer used in the present invention is disposed on the display side of a polarizer described later, and has a function of converting linearly polarized light transmitted through the polarizer into elliptically polarized light. In the liquid crystal display device of the present invention, the optical conversion layer converts light transmitted through the polarizer into elliptically polarized light instead of perfect circularly polarized light.
Hereinafter, the optical conversion layer used in the present invention will be described in detail.

(1) Optical Conversion Function As described above, the optical conversion layer used in the present invention has a function of converting linearly polarized light transmitted through a polarizer described later to elliptically polarized light (hereinafter, simply referred to as “optical conversion function”). .) The optical conversion function of the optical conversion layer in the present invention is not particularly limited as long as it can convert linearly polarized light into elliptically polarized light.

  The optical conversion function of the optical conversion layer in the present invention includes an aspect in which the major axis direction of the elliptically polarized light after the conversion is the same direction as the polarization transmission axis of the linearly polarized light before the conversion, and the major axis of the elliptically polarized light after the conversion An aspect in which the direction is a direction different from the polarization transmission axis of the linearly polarized light before conversion can be given. FIG. 2 is a schematic diagram for explaining such an aspect of the optical conversion function. As shown in FIG. 2, as an aspect of the optical conversion function provided in the optical conversion layer used in the present invention, the major axis direction of the elliptically polarized light after conversion is the same direction as the polarization transmission axis of the linearly polarized light before conversion. An aspect (FIG. 2 (a)), an aspect in which the major axis direction of the elliptically polarized light after conversion is different from the polarization transmission axis of the linearly polarized light before the conversion, and (FIG. 2 (b)) are mentioned. it can.

The optical conversion layer used in the present invention can be suitably used even if it has the optical conversion function of any of the above-described aspects, and in particular, the major axis direction of the elliptically polarized light after conversion is before conversion. It is preferable to have an optical conversion function in a direction different from the polarization transmission axis of linearly polarized light. This is based on the following reason.
That is, when the liquid crystal display device is observed with the polarized glasses attached, only linearly polarized light having a vibration plane in the direction parallel to the polarization transmission axis of the polarized glasses is observed. Here, since the polarizing glasses normally transmit only light having a vibration surface in the vertical direction, the polarizing glasses are mounted when the polarization transmission axis of the polarizer disposed on the display side of the liquid crystal display device is in the horizontal direction. In this state, the image cannot be observed. Further, if the polarization transmission axis of the polarizer is inclined from the vertical direction, an image that can be observed with the polarizing glasses attached will become dark.

  When the optical conversion layer having an optical conversion function has the major axis direction of the elliptically polarized light after the conversion different from the polarization transmission axis of the linearly polarized light before the conversion, the major axis direction of the elliptically polarized light after the conversion and The angle formed by the polarization transmission axis of the linearly polarized light can be appropriately determined according to the direction of the polarization transmission axis of the polarizer described later, and is not particularly limited.

  Moreover, it is preferable that the direction of the major axis of the elliptically polarized light after being converted by the optical conversion layer is a substantially vertical direction. Since the polarizing lens used in the polarizing glasses is generally arranged so that the polarization transmission axis is in the vertical direction, the major axis direction of the elliptically polarized light after being converted by the optical conversion layer is in the substantially vertical direction. This is because the liquid crystal display device of the present invention can be observed more brightly even when the polarized glasses are attached. This point will be described with reference to the drawings. FIG. 3 is a schematic diagram for explaining the reason why the direction of the major axis of the elliptically polarized light after being converted by the optical conversion layer is preferably a substantially vertical direction. As illustrated in FIG. 3, the polarizing lens used in the polarizing glasses G is arranged so that the polarization transmission axis is substantially in the vertical direction (direction indicated by g in the drawing) with the polarizing glasses attached. Accordingly, since the major axis direction (direction indicated by h in the figure) of the elliptically polarized light after being converted by the optical conversion layer 3 is a substantially vertical direction, the liquid crystal display device of the present invention can be installed even when the polarizing glasses are mounted. It is possible to observe brighter.

  Moreover, it is preferable that the optical conversion layer in the present invention can convert linearly polarized light into elliptically polarized light having an ellipticity in the range of 0.006 to 0.8. Since the ellipticity after conversion by the optical conversion layer is in the range of 0.006 to 0.8, it is possible to obtain a liquid crystal display device that can be viewed brightly even in a normal state with polarized glasses. It is.

(2) Configuration of Optical Conversion Layer The configuration of the optical conversion layer used in the present invention is not particularly limited as long as it exhibits the optical conversion function as described above. Therefore, as the optical conversion layer used in the present invention, any layer showing a birefringence capable of converting linearly polarized light into elliptically polarized light can be used. Examples of such an optical conversion layer include those containing a compound having refractive index anisotropy in a predetermined manner.

  Examples of the compound having refractive index anisotropy include a rod-shaped compound, a nematic liquid crystal compound, a discotic liquid crystal compound, and a polymer material having refractive index anisotropy. Accordingly, the optical conversion layer includes a rod-shaped compound, a nematic liquid crystal compound, a discotic liquid crystal compound, or the like having a compound having a refractive index anisotropy arranged in a predetermined state, or a refractive index anisotropy. What consists of a polymeric material which has can be used.

  In particular, in the present invention, it is preferable that the optical conversion layer includes a rod-like compound having refractive index anisotropy in a state of forming a cholesteric orientation. Such an optical conversion layer does not need to control the arrangement direction of each other when arranged in combination with the polarizer, and can be arranged in an arbitrary direction. Therefore, by using such an optical conversion layer, the liquid crystal display device of the present invention can be manufactured by a simple process.

The rod-like compound used in the present invention has a refractive index anisotropy, and is particularly limited as long as it can provide a desired optical conversion function to the optical conversion layer by arranging in the optical conversion layer. Is not to be done. Among them, as the rod-like compound used in the present invention, those having a polymerizable functional group in the molecule are preferably used, and among them, those having a polymerizable functional group capable of three-dimensional crosslinking are more preferably used. Since the rod-shaped compound has a polymerizable functional group, the rod-shaped compound can be polymerized and fixed, and therefore the optical conversion layer used in the present invention is less likely to change with time in the optical conversion function. Because it can be done.
In the present invention, the rod-shaped compound having the polymerizable functional group may be mixed with the rod-shaped compound having no polymerizable functional group.
The “three-dimensional cross-linking” means that liquid crystal molecules are polymerized three-dimensionally to form a network (network) structure.

  Examples of the polymerizable functional group include polymerizable functional groups that are polymerized by the action of ionizing radiation such as ultraviolet rays and electron beams, or heat. Representative examples of these polymerizable functional groups include radically polymerizable functional groups or cationic polymerizable functional groups. Further, representative examples of radically polymerizable functional groups include functional groups having at least one addition-polymerizable ethylenically unsaturated double bond, and specific examples include vinyl groups having or not having substituents, An acrylate group (generic name including an acryloyl group, a methacryloyl group, an acryloyloxy group, and a methacryloyloxy group) and the like can be given. Moreover, an epoxy group etc. are mentioned as a specific example of the said cation polymerizable functional group. In addition, examples of the polymerizable functional group include an isocyanate group and an unsaturated triple bond. Among these, from the viewpoint of the process, a functional group having an ethylenically unsaturated double bond is preferably used.

  Moreover, it is preferable that the rod-shaped compound in this invention is a liquid crystalline material which shows liquid crystallinity. This is because the liquid crystalline material has a large refractive index anisotropy, so that it becomes easy to impart a desired optical conversion function to the optical conversion layer.

  Specific examples of the rod-like compound used in the present invention include compounds represented by the following formulas (1) to (6).

  Here, the liquid crystalline materials represented by the chemical formulas (1), (2), (5) and (6) are disclosed in DJ Broer et al., Makromol. Chem. 190,3201-3215 (1989), or DJ Broer et al., Makromol. Chem. 190,2255-2268 (1989), or can be prepared similarly. The preparation of liquid crystalline materials represented by the chemical formulas (3) and (4) is disclosed in DE 195,04,224.

Specific examples of the nematic liquid crystalline material having an acrylate group at the terminal include those represented by the following chemical formulas (7) to (17).

  Furthermore, as a rod-shaped compound used for this invention, the compound represented by following formula (18) disclosed by SID06 DIGEST 1673-1676) can be illustrated.

  In the present invention, the rod-shaped compound may be used alone or in combination of two or more. For example, when the rod-shaped compound is used by mixing a liquid crystalline material having one or more polymerizable functional groups at both ends and a liquid crystalline material having one or more polymerizable functional groups at one end, The polymerization density (crosslink density) and the optical characteristics can be arbitrarily adjusted by adjusting the ratio, which is preferable.

  In the present invention, any optical conversion layer using any of the above rod-like compounds can be suitably used, but among these rod-like compounds exhibiting nematic liquid crystal properties, the rod-like compound is used in combination with a chiral agent. It is preferable to use an optical conversion layer. Since such an optical conversion layer is formed by fixing a chiral nematic liquid crystal, the long axis direction of the elliptically polarized light after the linearly polarized light transmitted through the polarizer is converted into elliptically polarized light by the optical conversion layer. This is because it becomes easy to arbitrarily control.

  The chiral agent is not particularly limited as long as the rod-shaped compound can be arranged in a predetermined cholesteric arrangement. As the chiral agent used in the present invention, for example, it is preferable to use a low molecular compound having axial asymmetry in the molecule as represented by the following general formula (19), (20) or (21).

In the general formula (19) or (20), R ¹ represents hydrogen or a methyl group. Y is any one of formulas (i) to (xxiv) shown above, and among them, any one of formulas (i), (ii), (iii), (v), and (vii) Preferably there is. Moreover, although c and d which show the chain length of an alkylene group can each take arbitrary integers in the range of 2-12, it is preferable that it is the range of 4-10, and is the range of 6-9. Is more preferable.

  When the optical conversion layer containing a rod-like compound having a cholesteric arrangement is used, the optical conversion layer used in the present invention has a selective reflection wavelength due to the cholesteric arrangement. Those having a selective reflection wavelength have a twist angle of 360 ° or more, which is a well-known fact in theory. The range of the selective reflection wavelength in the present invention is not particularly limited. However, by being outside the visible light region, it is possible to prevent a decrease in contrast due to coloring due to external light or reflection of display light.

  Moreover, when the thing containing the rod-shaped compound which formed the cholesteric arrangement | sequence is used as said optical conversion layer, the turning direction of the said cholesteric arrangement | sequence is not specifically limited. Among them, in the present invention, when the polarization transmission axis of the polarizer used in the present invention is inclined from the vertical direction to the left side when viewed from the display side, the turning direction of the cholesteric structure is preferably clockwise, When the polarization transmission axis of the polarizer is inclined from the vertical direction to the right side when viewed from the display side, it is preferable that the turning direction of the cholesteric structure is counterclockwise.

  These aspects will be described with reference to the drawings. FIG. 4 is a schematic view showing another example of the liquid crystal display device of the present invention. As illustrated in FIG. 4, the liquid crystal display device of the present invention has a cholesteric structure in the optical conversion layer 3 when the polarization transmission axis direction h of the polarizer 2 is inclined from the vertical direction to the left side as viewed from the display side. It is preferable that the swiveling direction is right-turned (FIG. 4A). On the other hand, when the polarization transmission axis direction h of the polarizer 2 is inclined from the vertical direction to the right side as viewed from the display side, the optical function It is preferable that the turning direction of the cholesteric structure in the layer 3 is counterclockwise (FIG. 4B).

  The axis of linearly polarized light passing through the cholesteric structure rotates due to the optical rotation associated with the cholesteric structure, and the rotation angle increases as the thickness of the cholesteric structure increases. By determining according to the inclination of the polarization transmission axis of the polarizer, it is possible to reduce the rotation angle of the elliptical polarization transmission axis until it coincides with the polarization transmission axis in the vertical direction of the sunglasses. For this reason, the thickness of the optical conversion layer on which the cholesteric structure is formed can be further reduced, and the thickness of the entire liquid crystal display device can be further reduced particularly in applications where thinness is required. Further, it is possible to reduce the cost by increasing productivity by simplifying the manufacturing process and reducing the amount of cholesteric liquid crystal material that is a relatively expensive material.

  The thickness of the optical conversion layer is not particularly limited as long as it is within a range in which a desired birefringence can be provided, depending on the type of compound having refractive index anisotropy contained. . In particular, in the present invention, the thickness of the optical conversion layer is preferably in the range of 0.1 μm to 100 μm, more preferably in the range of 0.5 μm to 20 μm, and in the range of 1 μm to 10 μm. More preferably it is.

The optical conversion layer may be composed only of the optical conversion layer, or may have a configuration in which the optical conversion layer is formed on an arbitrary substrate.
In addition, when the said optical conversion layer is formed integrally with a polarizing plate so that it may mention later, what consists of the said optical conversion layer single-piece | unit normally is used.

  When the optical conversion layer formed on an arbitrary substrate is used, the substrate used in the present invention is not limited to the birefringence of the optical conversion layer and has transparency. It is not particularly limited. Among them, the substrate used in the present invention usually preferably has a transmittance in the visible light region of 80% or more, and more preferably 90% or more. Here, the transmittance | permeability of a base material can be measured by JISK7361-1 (the test method of the total light transmittance of a plastic transparent material).

  As long as the base material used for this invention has the said transparency, even if it is a flexible material which has flexibility, it can also be used by the rigid material which does not have flexibility. In particular, in the present invention, it is preferable to use a flexible material.

  Examples of the flexible material include cellulose derivatives, cycloolefin-based polymers, acrylic resins such as polymethyl methacrylate, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polypropylene naphthalate, polyarylate, etc. polyester, polyvinyl alcohol, polyimide Examples of the base material include polysulfone, polyethersulfone, amorphous polyolefin, modified acrylic polymer, polystyrene, epoxy resin, and polycarbonate. In particular, in the present invention, it is preferable to use a substrate derived from cellulose or a cycloolefin polymer.

  As the cellulose derivative used in the present invention, a cellulose ester is preferably used, and among the cellulose esters, cellulose acylates are preferably used. This is because cellulose acylates are advantageous in terms of availability because they are widely used industrially.

  As the cellulose acylates, C 2-4 lower fatty acid esters are preferably used. Such a lower fatty acid ester may contain only a single lower fatty acid ester, for example, cellulose acetate, and a plurality of fatty acid esters such as cellulose acetate butyrate and cellulose acetate propionate may be used. It may be included.

  In the present invention, cellulose acetate can be particularly preferably used among the above lower fatty acid esters. Among cellulose acetates, it is most preferable to use triacetyl cellulose having an average acetylation degree of 57.5 to 62.5% (substitution degree: 2.6 to 3.0). Here, the degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation can be determined by measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like). In addition, the acetylation degree of the triacetyl cellulose which comprises a triacetyl cellulose film can be calculated | required by said method, after removing impurities, such as a plasticizer contained in a film.

  On the other hand, the cycloolefin polymer used in the present invention is not particularly limited as long as it is a resin having a monomer unit composed of a cyclic olefin (cycloolefin). Examples of such a monomer comprising a cyclic olefin include norbornene and polycyclic norbornene monomers.

  In addition, as a cycloolefin type polymer used for this invention, any of a cycloolefin polymer (COP) or a cycloolefin copolymer (COC) can be used conveniently.

  The cycloolefin-based polymer used in the present invention may be a homopolymer of a monomer composed of the above cyclic olefin or a copolymer.

  Specific examples of the substrate made of cycloolefin-based polymer used in the present invention include, for example, Ticona Topas, JSR Arton, Nippon Zeon Corporation ZEONOR, Nippon Zeon Corporation ZEONEX, Mitsui Chemicals, Inc. Examples include those obtained by subjecting these base materials to stretching treatment.

2. Next, the liquid crystal cell used in the present invention will be described. As the liquid crystal cell used in the present invention, a known liquid crystal cell generally used in a liquid crystal display device can be used. As a liquid crystal cell for a liquid crystal display device, all types of liquid crystal cells such as IPS, VA, OCB, ECB, STN, and TN are known depending on the arrangement of liquid crystal molecules in the cell. Any type of liquid crystal cell can be suitably used.

3. Polarizers As the polarizers used in the present invention, those generally known as polarizers used in liquid crystal display devices can be used, and detailed description thereof is omitted here.
A general liquid crystal display device includes a liquid crystal cell and polarizing plates disposed on both sides of the liquid crystal cell. The polarizing plate further includes a polarizer and polarizing plates disposed on both sides of the polarizer. Although it is generally composed of a protective film, the polarizer used in the present invention does not indicate the above polarizing plate, but means a polarizer obtained by removing the polarizing plate protective film from the polarizing plate.

4). Liquid Crystal Display Device As described above, the liquid crystal display device of the present invention uses at least a liquid crystal cell, a polarizer, and an optical conversion layer. The aspect in which these configurations are arranged in the liquid crystal display device of the present invention is not particularly limited as long as the optical conversion layer is arranged on the display side of the polarizer, and the liquid crystal display device is not limited. Any configuration can be adopted as appropriate according to the manufacturing method.

  Here, as described above, a polarizing plate generally used for a liquid crystal display device is composed of a polarizer and a polarizing plate protective film disposed on both sides of the polarizer. The polarizer used in the present invention may be used as such a polarizing plate, or may be used as a polarizer alone, but may be used as a polarizing plate in consideration of the temporal stability of polarization performance. preferable. And when a polarizer is used as a polarizing plate in this way, the said optical conversion layer may be used as an independent thing from the said polarizing plate, or is used by being formed integrally with a polarizing plate. May be. In the present invention, the optical conversion layer may be used in any of these modes, but is preferably used by being integrally formed with the polarizing plate. By using such an aspect optical conversion layer, the configuration of the liquid crystal display device of the present invention can be simplified, and the liquid crystal display device of the present invention can be made more efficient. .

  In the liquid crystal display device of the present invention, as an aspect in which the polarizing plate and the optical conversion layer are integrally formed, a polarizer, a first polarizing plate protective film disposed on the display side of the polarizer, and a polarizer In the polarizing plate having the second polarizing plate protective film disposed on the liquid crystal cell side, the optical conversion layer is formed on the display side surface of the first polarizing plate protective film, and the optical conversion layer is the polarizer and the first polarizing plate. The aspect formed between 1 polarizing plate protective films can be mentioned.

  These aspects will be described with reference to the drawings. FIG. 5 is a schematic cross-sectional view illustrating the case where the optical conversion layer is formed integrally with the polarizing plate in the liquid crystal display device of the present invention. As illustrated in FIG. 5, the liquid crystal display device 10 of the present invention includes a liquid crystal cell 1 and a polarizing plate P disposed on the display side of the liquid crystal cell 1, and the polarizing plate P is a polarizer 2. And a first polarizing plate protective film 2′a disposed on the display side of the polarizer 2 and a second polarizing plate protective film 2′b disposed on the liquid crystal cell side of the polarizer. The conversion layer 3 may be formed on the display-side surface of the first polarizing plate protective film (FIG. 5A). Alternatively, the optical conversion layer 3 may be formed between the polarizer 2 and the first polarizing plate protective film 2'a (FIG. 5B).

  In the present invention, any of the above-described two modes can be suitably used, but the mode illustrated in FIG. 5A is particularly preferable. This is because various functions such as AG (anti-glare), LR (low reflection), antifouling property and antistatic property required for the surface film can be imparted.

  The liquid crystal display device of the present invention has at least the liquid crystal cell, a polarizer, and an optical conversion layer, and any other configuration may be used as necessary. The arbitrary configuration used in the present invention can be appropriately determined according to the application, display method, etc. of the liquid crystal display device of the present invention, and is not particularly limited. Examples of such an arbitrary configuration include a polarizer or polarizing plate disposed on the backlight side of the liquid crystal cell, a retardation film (viewing angle compensation film) disposed on the backlight side of the polarizer, and the like. Can be mentioned.

  The liquid crystal display device of the present invention may be a transmissive liquid crystal display device, a reflective liquid crystal display device, or a transflective liquid crystal display device.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

[Example 1]
98 parts of liquid crystal monomer molecules (Paliocolor (registered trademark) LC1057 (manufactured by BASF)) having a polymerizable acrylate at both ends and a spacer between the mesogen at the center and the acrylate, and at both ends A cyclohexanone solution in which 2 parts of a chiral agent molecule having a polymerizable acrylate (Pariocolor (registered trademark) LC756 (manufactured by BASF)) was dissolved was prepared. The cyclohexanone solution was added with 2.5% by weight of a photopolymerization initiator (Irgacure 184) based on the liquid crystal monomer molecules (solid content: 40% by weight).

  On the other hand, on a transparent 0.7 mm thick glass substrate, a polyimide dissolved in a solvent (Optomer AL1254 manufactured by JSR) is coated by a spin coating method, dried, and formed at 200 ° C. (film thickness 0.1 μm). An alignment film was formed by rubbing in the direction. Then, such a glass substrate with an alignment film was set on a spin coater, and the cyclohexanone solution was applied on the alignment film.

Next, cyclohexanone in the cyclohexanone solution was evaporated at 80 ° C. and held at 100 ° C. for 2 minutes to align liquid crystalline monomer molecules. Then, the coating film is irradiated with ultraviolet rays of 500 mJ / cm ² , and the acrylate of the liquid crystalline monomer molecules and the acrylate of the chiral agent molecules aligned by radicals generated from the photoinitiator in the coating film are three-dimensionally crosslinked to be polymerized, An optical conversion layer was obtained by fixing the cholesteric structure on the alignment film. At this time, the film thickness of the optical conversion layer was 5.2 μm. Further, when measured with a spectrophotometer (UV-3100PC manufactured by Shimadzu Corporation), the selective reflection wavelength band was 1670 nm.

[Example 2]
99 parts of liquid crystalline monomer molecules (Paliocolor (registered trademark) LC1057 (manufactured by BASF)) having a polymerizable acrylate at both ends and a spacer between the mesogen in the center and the acrylate, and at both ends An optical conversion layer was formed in the same manner as in Example 1 except that a cyclohexanone solution in which 1 part of a chiral agent molecule having a polymerizable acrylate (Pariocolor (registered trademark) LC756 (manufactured by BASF)) was dissolved was used. Produced. At this time, the film thickness of the optical conversion layer was 5.4 μm. Further, when measured with the spectrophotometer, the selective reflection wavelength band was 1940 nm.

[Example 3]
98 parts of a liquid crystalline monomer molecule (Paliocolor (registered trademark) LC242 (manufactured by BASF)) having a polymerizable acrylate at both ends and a spacer between the mesogen in the center and the acrylate, and at both ends An optical conversion layer was formed in the same manner as in Example 1 except that a cyclohexanone solution in which 2 parts of a chiral agent molecule having a polymerizable acrylate (Pariocolor (registered trademark) LC756 (manufactured by BASF)) was dissolved was used. (However, the only difference was that after the cyclohexanone was evaporated at 80 ° C., the liquid crystalline monomer was oriented at 80 ° C.). At this time, the film thickness of the optical conversion layer was 4.0 μm. Further, when measured with the spectrophotometer, the selective reflection wavelength band was 1228 nm.

[Comparative Example 1]
A commercially available polycarbonate film (Gulliver 300 series manufactured by Sumitomo Dow Co., Ltd.) was heated and stretched with a stretching apparatus to obtain an in-plane retardation of 140 nm to obtain a λ / 4 sheet.

[Reference Example 1]
95 parts of a liquid crystalline monomer molecule (Paliocolor (registered trademark) LC242 (manufactured by BASF)) having a polymerizable acrylate at both ends and a spacer between the mesogen at the center and the acrylate, and at both ends The optical conversion layer was formed in the same manner as in Example 1 except that a cyclohexanone solution in which 5 parts of a chiral agent molecule having a polymerizable acrylate (Pariocolor (registered trademark) LC756 (manufactured by BASF)) was dissolved was used. It was produced (only the orientation temperature was 80 ° C.). At this time, the film thickness of the optical conversion layer was 5.0 μm. Further, when measured with the spectrophotometer, the selective reflection wavelength band was 530 nm.

[Evaluation]
(Luminance measurement with luminance meter)
In order to verify the effects of using the optical conversion layers prepared in the above Examples, Reference Examples, and Comparative Examples, evaluation was performed by the following methods. A schematic diagram of the evaluation method is shown in FIG. 6 (where FIG. 6B is a front view from the Z direction in FIG. 6A).
(1) Place the optical conversion layer on a liquid crystal monitor (PLE-E1902WS manufactured by Iiyama).
(2) A polarizing lens of polarizing glasses is installed on it.
(3) A luminance meter (BM-5A manufactured by Topcon) is installed at a position 600 mm away from the optical conversion layer.
(4) The luminance is measured while rotating the polarizing lens of the polarized glasses. At this time, the relationship between the rotation direction and rotation angle of the polarizing lens of the polarizing glasses and the polarization transmission axis of the liquid crystal is as shown in FIG.

  The obtained evaluation results are shown in Table 1 below. Here, 0.005 or less is defined as linearly polarized light and 0.9 or more and circularly polarized light.

It is a schematic sectional drawing which shows an example of the liquid crystal display device of this invention. It is the schematic explaining the optical conversion function of the optical converting layer used for this invention. It is the schematic which illustrates an example of the effect of the liquid crystal display device of this invention. It is the schematic which shows the other example of the liquid crystal display device of this invention. It is a schematic sectional drawing which shows the other example of the liquid crystal display device of this invention. It is the schematic explaining the luminance measuring method by a luminance meter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal cell 2 ... Polarizer 2 '... Polarizing plate protective film 2'a ... 1st polarizing plate protective film 2'b ... 2nd polarizing plate protective film 3 ... Optical conversion layer 10 ... Liquid crystal display device P, P' ... Polarizing plate G… Polarized glasses X… Display side Y… Backlight side

Claims (6)

A liquid crystal cell; a polarizer disposed on a display side of the liquid crystal cell; and an optical conversion layer disposed on the display side of the polarizer and having a function of converting linearly polarized light transmitted through the polarizer into elliptically polarized light. Have
The optical conversion layer state, and are not a function of converting linearly polarized light transmitted through the polarizer, the elliptically polarized light the major axis direction is the substantially vertical direction,
The optical conversion layer contains a rod-shaped compound having a cholesteric structure,
The liquid crystal display device, wherein the optical conversion layer has a selective reflection wavelength of 750 nm or more . The optical conversion layer has a function of converting linearly polarized light transmitted through the polarizer into elliptically polarized light whose major axis direction is different from the polarization transmission axis of the polarizer. 2. A liquid crystal display device according to 1. The liquid crystal display device according to claim 1 , wherein the optical conversion layer is formed by fixing a chiral nematic liquid crystal. The polarization transmission axis of the polarizer, characterized in that are inclined to the left side from the vertical direction as viewed from the display side, and the turning direction of the cholesteric structure is the right rotation, either of the preceding claims 3 A liquid crystal display device according to any one of the claims. The polarization transmission axis of the polarizer, characterized in that are inclined to the right from the vertical direction as viewed from the display side, and the turning direction of the cholesteric structure is left rotation, either of the preceding claims 3 A liquid crystal display device according to any one of the claims. The optical conversion layer, characterized in that the ellipticity of the linearly polarized light as it can be converted into elliptically polarized light in the range of 0.006 to 0.8, any of claims 1 to 5 A liquid crystal display device according to claim 1.

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