JP2010039222A - Liquid crystal panel and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal panel which can be applied to a large-sized liquid crystal display device, and to provide the liquid crystal display device using the liquid crystal panel. <P>SOLUTION: The liquid crystal panel provided with a liquid crystal cell having a liquid crystal layer including liquid crystal molecules aligned in a homeotropic arrangement or a homogeneous arrangement when no electric field exists, a first polarizing plate disposed on one side of the liquid crystal cell, a second polarizing plate disposed on the other side of the liquid crystal cell and an optical rotation element converting linearly polarized light into linearly polarized light orthogonal thereto between the liquid crystal cell and the first polarizing plate or between the liquid crystal cell and the second polarizing plate. Absorption axes of the first and second polarizing plates are disposed to be parallel to each other in the liquid crystal panel. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal panel and a liquid crystal display device excellent in productivity.

  The liquid crystal display device has a structure in which a liquid crystal cell is sandwiched between two polarizing plates (a light source side polarizing plate and a viewing side polarizing plate). In general, the two polarizing plates have their absorption axes orthogonal to each other. Has been placed. Since a polarizing plate is generally produced continuously in a long shape, the film width is limited and is limited to a few meters at most, and is generally about 1 to 1.5 m in width. On the other hand, in recent years, there has been an increasing demand for a large screen for a liquid crystal display device. For example, a polarizing plate applicable to a size exceeding 65 inches (about 1640 mm) diagonal is required. As a large-screen TV, a wide type with a vertical: horizontal ratio of 9:16 is the mainstream, but since a polarizing plate has anisotropy, a liquid crystal display device in which the vertical and horizontal lengths of the screen are different is 2 In order to arrange the polarizing plates so that the absorption axes of the polarizing plates are orthogonal to each other, it is necessary that one of the polarizing plates sandwiching the liquid crystal cell and the other polarizing plate have different film widths. Therefore, for example, as shown in FIG. 1 (a), both the light source side polarizing plate 21 and the viewing side polarizing plate 22 have long axes having absorption axes 3 and 4 in the longitudinal direction (conveying direction during film production). In the case of using one cut out from the polarizing plate P, in order to obtain two polarizing plates whose absorption axes are orthogonal and equal in size, the width direction of the long polarizing plate P is set to the long side. It is necessary to cut out the other polarizing plate 22 so that the width direction of the long polarizing plate P is a short side. That is, since the length of the long side of the liquid crystal display device is limited within the width of the polarizing plate, for example, a polarizing plate having a width of 1400 mm or more is required to support a 65-inch TV.

  For such a problem of application to a large-screen liquid crystal display device, a method of achieving a large area by using a combined optical film in which end surfaces of a plurality of optical films are brought into contact with each other has been proposed (for example, patents). Reference 1). However, such a method of joining films is poor in mass productivity and may cause an increase in cost.

  In addition, a method of using a wide width polyvinyl alcohol (PVA) film as a base film of a polarizing plate (for example, Patent Document 2), a method of stretching in the width direction when manufacturing a polarizing plate (for example, Patent Document 3), etc. A method for increasing the width of the plate is known. However, wide films tend to be inferior in uniformity and handling properties, and the equipment cost for obtaining such a wide and long film increases.

  In addition, a polarizing plate used for a liquid crystal panel of a twisted nematic (TN) system or the like is obtained by using a retardation film stretched in an oblique direction or a circular polarizing plate in which a liquid crystal alignment film having an orientation direction in an oblique direction is laminated with a polarizing plate. A method for increasing the rate and productivity has been proposed (see, for example, Patent Document 4). However, those obtained by orienting the retardation plate in the oblique direction lacked uniformity in the orientation direction, and in some cases, sufficient display characteristics could not be obtained. Furthermore, since the phase difference plate has a so-called “wavelength dependency” in which the phase difference varies depending on the wavelength, sufficient characteristics cannot be obtained for all wavelengths of visible light, and the screen is colored. There was a case.

JP 2002-28939 A Japanese Patent Laid-Open No. 11-183726 JP-T 9-507308 JP 2004-151573 A

  In view of the above, an object of the present invention is to provide a liquid crystal panel applicable to a large liquid crystal display device and a liquid crystal display device using the liquid crystal panel.

  The above problem can be solved by a liquid crystal panel having an optical rotatory element that converts linearly polarized light into linearly polarized light orthogonal to the polarizing plate between one of the pair of polarizing plates that sandwich the liquid crystal cell and the liquid crystal cell.

That is, the present invention includes a liquid crystal cell having a liquid crystal layer including liquid crystal molecules aligned in a homeotropic alignment or a homogeneous alignment in the absence of an electric field;
A first polarizing plate disposed on one side of the liquid crystal cell;
A second polarizing plate disposed on the other side of the liquid crystal cell;
An optical rotatory element that converts linearly polarized light into linearly polarized light orthogonal to it either between the liquid crystal cell and the first polarizing plate or between the liquid crystal cell and the second polarizing plate;
And a liquid crystal panel in which absorption axes of the first polarizing plate and the second polarizing plate are arranged in parallel.

  In the liquid crystal panel of the present invention, the liquid crystal cell is preferably in a VA mode or an IPS mode.

  In the liquid crystal panel of the present invention, the optical rotatory element is preferably a liquid crystal layer in which the alignment direction of liquid crystal molecules gradually changes along the thickness direction of the layer. A chiral nematic liquid crystal layer twisted by 90 ° is more preferable.

In particular, from the viewpoint of improving display characteristics in a liquid crystal panel, the liquid crystal layer preferably has a predetermined thickness. In one embodiment, the product of the birefringence Δn _{545 at} a wavelength of 545 nm of the nematic liquid crystal material forming the chiral nematic liquid crystal layer and the thickness d of the liquid crystal layer is preferably 1400 nm or more.

  In one embodiment of the liquid crystal panel of the present invention, the liquid crystal cell is a VA mode liquid crystal cell, and further includes an optical compensation layer satisfying nx> ny ≧ nz. Here, nx represents the refractive index in the slow axis direction in the film plane, ny represents the refractive index in the fast axis direction in the film plane, and nz represents the refractive index in the thickness direction.

  Furthermore, the present invention relates to a liquid crystal display device having the liquid crystal panel.

  Since the liquid crystal panel of the present invention has an optical rotator that converts linearly polarized light into linearly polarized light orthogonal thereto, the two polarizing plates sandwiching the liquid crystal cell can be arranged so that their absorption axes are parallel, It is easy to handle a large liquid crystal display device without increasing the width of the polarizing plate, and the yield can be improved.

[Overview of the entire LCD panel]
FIG. 2 is a schematic cross-sectional view of a liquid crystal panel according to an embodiment of the present invention. The liquid crystal panel 100 of the present invention includes a liquid crystal cell 10, a first polarizing plate 21 disposed on one side of the liquid crystal cell 10, and a second polarizing plate 22 disposed on the other side of the liquid crystal cell 10. Between the liquid crystal cell 10 and the first polarizing plate 21 (corresponding to FIG. 2A), or between the liquid crystal cell 10 and the second polarizing plate 22 (corresponding to FIG. 2B). Either one has an optical rotatory element 30 for converting a certain linearly polarized light into a linearly polarized light orthogonal thereto.

  FIG. 3 is a schematic perspective view of the liquid crystal panel of the present invention. 3A corresponds to the configuration of FIG. 2A, and FIG. 3B corresponds to the configuration of FIG. For the sake of simplicity, the aspect ratio and thickness ratio of each component in these drawings are different from the actual ones.

  In the liquid crystal panel of the present invention, the absorption axis direction 3 of the first polarizing plate 21 and the absorption axis direction 4 of the second polarizing plate 22 are parallel. In the present specification and claims, “parallel” includes not only completely parallel but also substantially parallel, and the angle is generally within ± 3 °. , Preferably within ± 2 °, more preferably within ± 1 °, and even more preferably within ± 0.5 °. The term “orthogonal” includes not only completely orthogonal but also substantially orthogonal, and the angle is generally in the range of 90 ± 3 °, preferably 90 ± 2 °, more preferably The range is 90 ± 1 °, more preferably 90 ± 0.5 °. Similarly, the case where it is described as approximately 45 °, approximately 90 °, etc. includes a range of ± 3 ° from the angle, preferably ± 2 °, more preferably ± 1 °, still more preferably ± The range of 0.5 ° is included.

[Principle of the composition of this application]
Hereinafter, the liquid crystal panel of the present invention will be described with reference to each component drawing. In FIG. 5 and FIG. 6, reference numeral (r) is as shown in FIG. (C) represents linearly polarized light in the normal direction of the paper surface, and (b) and (c) linearly polarized light are orthogonal to each other. Further, (d) represents a dark state (black display) where light is not transmitted.

FIG. 5 is a conceptual diagram schematically showing the principle of black display in a conventional liquid crystal display device.
Naturally polarized light (r 1) emitted from the light source 81 is incident on the first polarizing plate 21.
Since the first polarizing plate 21 has the absorption axis 3 in the normal direction of the paper surface, the first polarizing plate 21 absorbs light in the normal direction of the paper surface and emits linearly polarized light (r2) in the horizontal direction of the paper surface as transmitted light.
The linearly polarized light transmitted through the first polarizing plate 21 enters the liquid crystal cell 10 (r5). In a liquid crystal display device including a liquid crystal cell (for example, a normally black VA mode or IPS mode liquid crystal cell) in which the polarization state is not converted and the liquid crystal cell is in a voltage-off state, the incident light (r5) is The polarization state is emitted to the viewing side without being converted (r6).
The linearly polarized light (r6) emitted from the liquid crystal cell 10 enters the second polarizing plate 22 (r7). Since the second polarizing plate 22 has the absorption axis 4 in the horizontal direction of the paper, the linearly polarized light (r7) is absorbed by the second polarizing plate 22 and a black display is obtained (r8).

  As described above, the conventional liquid crystal display device obtains a black display when the voltage is off by making the absorption axis direction 3 of the first polarizing plate 21 and the absorption axis direction 4 of the second polarizing plate 22 orthogonal to each other. Designed to be For this reason, in a liquid crystal display device in which the vertical and horizontal lengths of the screens are different, in order to arrange the two polarizing plates so that the absorption axes of the two polarizing plates are orthogonal to each other, as shown in FIG. Therefore, it is necessary to use one having different film widths between the other polarizing plate and the application to a large screen size.

FIG. 6 is a conceptual diagram schematically showing the principle of black display in a liquid crystal display device using the liquid crystal panel of the present invention.
Naturally polarized light (r11) emitted from the light source 81 is incident on the first polarizing plate 21.
Since the first polarizing plate 21 has the absorption axis 3 in the normal direction of the paper surface, the first polarizing plate 21 absorbs light in the normal direction of the paper surface and emits linearly polarized light (r12) in the horizontal direction of the paper surface as transmitted light.
The linearly polarized light that has passed through the first polarizing plate 21 enters the optical rotatory element 30 that converts the linearly polarized light into linearly polarized light that is orthogonal thereto (r13). Since the polarization direction is rotated by the optical rotatory element, the light emitted from the optical rotatory element 30 is linearly polarized light in the normal direction of the paper surface (r14).
This linearly polarized light enters the liquid crystal cell 10 (r15). In a liquid crystal display device including a liquid crystal cell (for example, a VA mode or IPS mode liquid crystal cell) in which the polarization state is not converted when the liquid crystal cell is in a voltage-off state, the polarization state of incident light (r15) is converted. It is injected to the viewer side without being done (r16).
The linearly polarized light (r16) emitted from the liquid crystal cell 10 enters the second polarizing plate 22 (r17). Since the second polarizing plate 22 has the absorption axis 4 in the normal direction of the paper surface, the linearly polarized light (r17) is absorbed by the second polarizing plate 22 and a black display is obtained (r18).

  6 illustrates the case where the optical rotator 30 is disposed between the liquid crystal cell 10 and the first polarizing plate 21 (light source side polarizing plate), FIG. 2B and FIG. In the case where the optical rotator 30 is disposed between the liquid crystal cell 10 and the second polarizing plate 22 (viewing-side polarizing plate) as shown in FIG. And the second polarizing plate 22 are arranged so that the absorption axis directions 3 and 4 are parallel to each other.

[Advantages of this application configuration]
(Application to large screen size and improvement of polarizing plate removal rate)
In general, a liquid crystal display device such as a television or a monitor for a personal computer has a different aspect ratio of the screen, so the screen is rectangular, and the polarizing plate used therefor is also rectangular. In the configuration of the present application, since the absorption axis directions of the first polarizing plate and the second polarizing plate are parallel, when cutting from a long polarizing plate, as shown in FIG. Both the polarizing plate 21 and the second polarizing plate 22 can be cut out so that the longitudinal direction of the long polarizing plate P is the long side of the first polarizing plate 21 and the second polarizing plate 22. Therefore, it is possible to cope with a large-screen liquid crystal display device as compared with the case of FIG.

  Tables 1 and 2 show the size of the polarizing plate corresponding to each screen size (horizontal: vertical = 16: 9) and the width direction when the polarizing plate corresponding to each size is cut out from the long polarizing plate. An example of the width efficiency (take rate) that can be used as a product based on the number of pieces that can be cut out (take number) is shown. Table 1 shows the case where the effective width of the long polarizing plate (the width excluding the end portion that cannot be used as a product out of the total width of the film) is 1000 mm, and Table 2 shows the case where the effective width is 1500 mm. Yes. Moreover, in Table 1 and Table 2, the light source side polarizing plate describes the case where the polarizing plate is cut out so that the film width direction is the long side of the rectangle, and the viewing side polarizing plate is the short side of the film width direction. However, the reverse is also true for the number and yield.

  When the effective width of the polarizing plate is 1000 mm (Table 1), the long side of the polarizing plate corresponding to a screen size of 46 inches or more exceeds the width of the film, so that the absorption axes of the two polarizing plates are perpendicular to each other. The configuration of the liquid crystal panel cannot cope with such a large-screen liquid crystal display device. On the other hand, by arranging an optical rotation element that converts linearly polarized light into linearly polarized light orthogonal to the polarizing plate and the liquid crystal cell, both the viewing side polarizing plate and the light source side polarizing plate are in the width direction of the long polarizing plate. Since the polarizing plate can be cut out so as to have a rectangular short side, it can be applied to a large-screen liquid crystal display device without increasing the width of the polarizing plate.

  In the case of 42 inches, in the conventional liquid crystal panel configuration in which the absorption axes of the two polarizing plates are orthogonal to each other, the removal rate of the light source side polarizing plate is 95%, whereas the removal rate of the viewing side polarizing plate is high. It is as low as 54%. In such a case, a polarizing element that converts linearly polarized light into linearly polarized light orthogonal to the polarizing plate is arranged between the viewing side polarizing plate and the liquid crystal cell, so that both the viewing side polarizing plate and the light source side polarizing plate are long polarizing plates. By cutting out the polarizing plate so that the width direction of the two becomes the short side of the rectangle, the removal rate in the width direction of both can be 95%.

  On the other hand, when the effective width of the polarizing plate is 1500 mm (Table 2), the conventional liquid crystal panel configuration adopting a configuration in which the absorption axes of the two polarizing plates are orthogonal is compatible with a liquid crystal display device having a screen size of 65 inches. However, the viewing rate of the viewing side polarizing plate is lower than that of the light source side polarizing plate. In such a case, as in the case of 42 inches with an effective width of 1000 mm, a polarizing element for converting linearly polarized light into linearly polarized light orthogonal to the polarizing plate is disposed between the viewing side polarizing plate and the liquid crystal cell. The removal rate can be increased.

  As described above, according to the configuration of the liquid crystal panel of the present invention, in addition to being able to cope with a large-screen liquid crystal display device, the direction in which the polarizing plate is cut out can be designed so as to be optimal for the screen size of the liquid crystal display device. Therefore, it is possible to increase the yield of the polarizing plate. Therefore, the configuration of the liquid crystal panel of the present application is advantageous in terms of productivity, cost, and reduction in the amount of waste, even when a wider polarizing plate is used.

(Resolution of LCD panel warpage)
In addition, according to the configuration of the present application, the problem of warping of a liquid crystal panel having a large screen size can be solved. In the conventional liquid crystal panel in which the absorption axes of the two polarizing plates are orthogonal to each other, the liquid crystal panel may be warped due to a difference in the heating dimension change direction of the polarizing plates arranged on the front and back of the liquid crystal cell. That is, as described above, the polarizing plate has anisotropy, but a commonly used polarizing plate is anisotropic by stretching a film adsorbing a dichroic substance such as iodine or a dichroic dye. Is expressed. The liquid crystal panel is combined with a light source such as a backlight to form a liquid crystal display device. However, the polarizing plate tends to contract or expand in the stretching direction due to heat from the light source or the external environment. Therefore, in the liquid crystal panel arranged so that the absorption axes of the two polarizing plates are orthogonal to the front and back of the liquid crystal cell, deformation stress is generated in different directions on the front and back of the liquid crystal cell, so that the peripheral portion of the liquid crystal panel is distorted. There are cases. Such distortion causes the panel to warp, and there is a problem that display defects such as light leakage are likely to occur in the peripheral portion of the panel. In particular, in a large-sized liquid crystal panel, the stress caused by such shrinkage or expansion becomes large, and thus the problem of such warpage and display defect tends to become remarkable.

  On the other hand, in the liquid crystal panel of the present invention, since the absorption axis directions of the polarizing plates arranged on the front and back of the liquid crystal cell are parallel, even when the polarizing plate contracts or expands due to heating, etc. Since the direction of the stress applied to the liquid crystal cell is the same on the front and back of the liquid crystal cell, the occurrence of distortion of the liquid crystal panel can be suppressed, and the warpage of the panel and display defects can be suppressed.

  Hereinafter, the liquid crystal cell, the polarizing plate, and the optical rotator constituting the liquid crystal panel of the present invention will be sequentially described.

[Liquid Crystal Cell]
2 and 3, the liquid crystal cell 10 used in the liquid crystal panel of the present invention has a pair of substrates 11 and 12 and a liquid crystal layer 13 as a display medium sandwiched between the substrates. In a general configuration, a color filter and a black matrix are provided on one substrate, a switching element that controls the electro-optical characteristics of the liquid crystal on the other substrate, and a scanning line that supplies a gate signal to the switching element. In addition, a signal line for supplying a source signal, a pixel electrode, and a counter electrode are provided. The distance (cell gap) between the substrates 11 and 12 can be controlled by a spacer or the like. For example, an alignment film made of polyimide or the like can be provided on the side of the substrates 11 and 12 in contact with the liquid crystal layer 13.

  The liquid crystal layer 13 includes liquid crystal molecules aligned in a homeotropic alignment or a homogeneous alignment in the absence of an electric field.

  “Homeotropic alignment” refers to a state in which the alignment vector of liquid crystal molecules is aligned perpendicularly (in the normal direction) to the substrate plane as a result of the interaction between the aligned substrate and the liquid crystal molecules. The homeotropic alignment includes a case where the alignment vector of the liquid crystal molecules is slightly inclined with respect to the normal direction of the substrate, that is, the case where the liquid crystal molecules have a pretilt. When the liquid crystal molecules have a pretilt, the pretilt angle (angle from the substrate normal) is preferably 5 ° or less. By setting the pretilt angle in the above range, a liquid crystal display device with high contrast can be obtained.

  In the liquid crystal cell, the refractive index ellipsoid preferably exhibits a relationship of nz> nx = ny. As a liquid crystal cell in which the refractive index ellipsoid shows a relationship of nz> nx = ny, according to the drive mode classification, for example, a vertical alignment (VA) mode is exemplified. In the present invention, when the liquid crystal cell includes liquid crystal molecules aligned in a homeotropic alignment in the absence of an electric field, the drive mode is particularly preferably a vertical alignment (VA) mode.

  The VA mode liquid crystal cell utilizes a voltage-controlled birefringence effect, and makes liquid crystal molecules aligned in a homeotropic alignment respond to the substrate with an electric field in a normal direction in the absence of an electric field. Specifically, as described in, for example, Japanese Patent Application Laid-Open No. Sho 62-210423 and Japanese Patent Application Laid-Open No. Hei 4-153621, in the case of a normally black method, liquid crystal molecules are formed on a substrate in the absence of an electric field. Therefore, when the upper and lower polarizing plates are arranged orthogonally, a black display can be obtained. On the other hand, in the presence of an electric field, the liquid crystal molecules operate so as to tilt in a 45 ° azimuth direction with respect to the absorption axis of the polarizing plate, whereby the transmittance increases and white display is obtained. In the present invention, the upper and lower polarizing plates (corresponding to the polarizing plates 21 and 22) are arranged in parallel. However, since it has 30 for converting linearly polarized light into linearly polarized light orthogonal thereto, it is a normally black method. Can be adopted.

The VA mode liquid crystal cell can be multi-domained by using a substrate having slits formed on electrodes or a substrate having projections formed on the surface as described in JP-A-11-258605, for example. It may be what you did. Rth _LC [590] of the liquid crystal cell in the absence of an electric field is preferably −500 nm to −200 nm, more preferably −400 nm to −200 nm. The Rth _LC [590] is appropriately set according to the birefringence of the liquid crystal molecules and the cell gap. The cell gap (substrate interval) of the liquid crystal cell is usually 1.0 μm to 7.0 μm.

  On the other hand, “homogeneous alignment” refers to a state in which the alignment vectors of the liquid crystal molecules are aligned in parallel and uniformly with respect to the substrate plane as a result of the interaction between the aligned substrate and the liquid crystal molecules. In the present specification, the homogeneous alignment includes the case where the liquid crystal molecules are slightly inclined with respect to the substrate plane, that is, the case where the liquid crystal molecules have a pretilt angle. The pretilt angle is usually 10 ° or less.

   In a liquid crystal cell including a liquid crystal layer including liquid crystal molecules aligned in a homogeneous arrangement in the absence of an electric field, a refractive index ellipsoid typically has a relationship of nx> ny = nz. Here, ny = nz includes not only the case where ny and nz are completely the same, but also the case where ny and nz are substantially the same.

  Representative examples of the liquid crystal cell include an in-plane switching (IPS) mode, a fringe field switching (FFS) mode, a ferroelectric liquid crystal (FLC) mode, and the like according to the classification according to the driving mode. Specific examples of the liquid crystal used in such a drive mode include nematic liquid crystal and smectic liquid crystal. In general, a nematic liquid crystal is used for the IPS mode and the FFS mode, and a smectic liquid crystal is used for the FLC mode. In the present invention, when the liquid crystal cell includes liquid crystal molecules that are aligned in a homogeneous alignment in the absence of an electric field, the driving mode is particularly preferably the plane switching (IPS) mode.

  The IPS mode uses a voltage-controlled birefringence (ECB) effect to generate liquid crystal molecules that are homogeneously aligned in the absence of an electric field, for example, between a counter electrode and a pixel electrode formed of metal. The substrate is made to respond with an electric field (also referred to as a transverse electric field) parallel to the substrate. More specifically, for example, Techno Times Publishing “Monthly Display July” p. 83-p. 88 (1997 edition) and “Liquid Crystal vol.2 No. 4” published by Japanese Liquid Crystal Society. 303-p. 316 (1998 edition), in the normally black mode, the alignment direction when no electric field is applied to the liquid crystal cell coincides with the absorption axis of the polarizing plate on one side, and the upper and lower polarizing plates are If they are arranged orthogonally, the display is completely black without an electric field. When an electric field is present, the transmittance according to the rotation angle can be obtained by rotating the liquid crystal molecules while keeping them parallel to the substrate. The IPS mode includes a super-in-plane switching (S-IPS) mode and an advanced super-in-plane switching (AS-IPS) mode using a V-shaped electrode or a zigzag electrode.

  The homogeneously aligned liquid crystal molecule refers to a liquid crystal molecule in which the alignment vector of the liquid crystal molecule is aligned in parallel and uniformly with respect to the substrate plane as a result of the interaction between the aligned substrate and the liquid crystal molecule. In the specification and claims of the present application, the case where the alignment vector is slightly inclined with respect to the substrate plane, that is, the case where the liquid crystal molecules have a pretilt is also included in the homogeneous alignment. When the liquid crystal molecules have a pretilt, the pretilt angle is preferably 20 ° or less from the viewpoint of maintaining high contrast and obtaining good display characteristics.

As the nematic liquid crystal, any appropriate nematic liquid crystal can be adopted depending on the purpose. For example, the nematic liquid crystal may have a positive or negative dielectric anisotropy. Difference in the ordinary refractive index of the nematic liquid crystal (n _o) and extraordinary refractive index as the (n _e), i.e. birefringence (.DELTA.nLC) can be properly selected by the response speed, transmittance, and the like of the liquid crystal, usually It is preferable that it is 0.05-0.30.

  Any appropriate smectic liquid crystal may be employed as the smectic liquid crystal depending on the purpose. Preferably, a smectic liquid crystal having an asymmetric carbon atom in a part of its molecular structure and exhibiting ferroelectricity (also referred to as a ferroelectric liquid crystal) is used. Specific examples of smectic liquid crystal exhibiting ferroelectricity include p-decyloxybenzylidene-p′-amino-2-methylbutylcinnamate, p-hexyloxybenzylidene-p′-amino-2-chloropropylcinnamate, 4 -O- (2-methyl) butyl resorcylidene-4'-octylaniline is mentioned.

  Any appropriate cell gap may be employed as the cell gap (substrate interval) of the liquid crystal cell depending on the purpose. The cell gap is preferably 1.0 to 7.0 μm. Within such a range, the response time can be shortened and good display characteristics can be obtained.

  Such a liquid crystal layer (as a result, a liquid crystal cell) typically has a refractive index of nx, ny, nz in the slow axis direction, the fast axis direction, and the thickness direction of the liquid crystal layer, respectively. The refractive index distribution of nx> ny = nz is shown. In this specification, ny = nz includes not only the case where ny and nz are completely the same, but also the case where ny and nz are substantially the same. Further, the “initial alignment direction of the liquid crystal cell” refers to a direction in which the in-plane refractive index of the liquid crystal layer that is generated as a result of alignment of liquid crystal molecules contained in the liquid crystal layer is maximized in the absence of an electric field. When the liquid crystal panel of the present invention includes liquid crystal molecules aligned in a homogeneous arrangement in the absence of an electric field as the liquid crystal cell, the initial alignment direction of the liquid crystal cell and the absorption axis directions of the first and second polarizing plates are parallel or It is preferable that they are orthogonal.

  In the present invention, the liquid crystal cell mounted on a commercially available liquid crystal display device may be used as it is.

[Polarizer]
In the present specification and claims, the term “polarizing plate” refers to an element that can convert natural light or polarized light into arbitrary polarized light. The polarizing plate used in the liquid crystal panel of the present invention is not particularly limited, but preferably converts natural light or various kinds of polarized light into linearly polarized light. Such a polarizing plate has a function of transmitting one of the polarized components when incident light is divided into two orthogonal polarized components, and absorbing, reflecting, and scattering the other polarized component. At least one function selected from the functions to be performed.

  The transmittance at a wavelength of 440 nm (also referred to as single transmittance) of the polarizing plate used in the present invention is preferably 41.0% or more, and more preferably 42.0% or more. Although the theoretical upper limit of the single transmittance is 50%, in practice, reflection due to the difference between the refractive index of air and the polarizing plate occurs, so the single transmittance does not become 50%. When a triacetyl cellulose film is used as a polarizer protective film described later, 43.2% is the upper limit.

  Further, the degree of polarization is preferably 99.8 to 100%, and more preferably 99.9 to 100%. If it is said range, the contrast of a front direction can be made still higher when it uses for a liquid crystal display device.

The single transmittance and the degree of polarization can be measured using a spectrophotometer. As a specific method for measuring the degree of polarization, the parallel transmittance (H ₀ ) and orthogonal transmittance (H ₉₀ ) of the polarizing plate are measured, and the formula: degree of polarization (%) = {(H ₀ -H ₉₀ ) / (H ₀ + H ₉₀₎ } ^1/2 × 100. The parallel transmittance (H ₀ ) is a transmittance value of a parallel laminated polarizing plate produced by superposing two identical polarizing plates so that their absorption axes are parallel to each other. The orthogonal transmittance (H ₉₀ ) is a value of the transmittance of an orthogonal laminated polarizing plate produced by superposing two identical polarizing plates so that their absorption axes are orthogonal to each other.

(Polarizer)
The function of converting natural light or polarized light of the polarizing plate into linearly polarized light is achieved by a polarizer. A polarizing plate is obtained by laminating a transparent film as a polarizer protective film on one or both sides of a polarizer as required.

  Any appropriate polarizer may be adopted as the polarizer depending on the purpose. For example, dichroic substances such as iodine and dichroic dyes are adsorbed on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. And a polyene-based oriented film such as a uniaxially stretched product, a polyvinyl alcohol dehydrated product or a polyvinyl chloride dehydrochlorinated product. In addition, a guest / host type polarizer in which a liquid crystalline composition containing a dichroic substance and a liquid crystalline compound disclosed in US Pat. No. 5,523,863 is aligned in a certain direction may be used. it can.

  Among such polarizers, from the viewpoint of having a high degree of polarization, a polarizer made of a polyvinyl alcohol film containing iodine (hereinafter sometimes simply referred to as “iodine polarizer”) is preferably used. Polyvinyl alcohol or a derivative thereof is used as a material for the polyvinyl alcohol film applied to the polarizer. Derivatives of polyvinyl alcohol include polyvinyl formal, polyvinyl acetal, and the like, olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, and their alkyl esters and acrylamide. Things. Polyvinyl alcohol having a polymerization degree of about 1000 to 10000 and a saponification degree of about 80 to 100 mol% is generally used.

  The polyvinyl alcohol film may contain an additive such as a plasticizer. Examples of the plasticizer include polyols and condensates thereof, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the plasticizer used is not particularly limited, but is preferably 20% by weight or less in the polyvinyl alcohol film.

  The polyvinyl alcohol film (unstretched film) is at least subjected to uniaxial stretching treatment and iodine dyeing treatment according to a conventional method. Furthermore, boric acid treatment and iodine ion treatment can be performed. Moreover, the polyvinyl alcohol film (stretched film) subjected to the treatment is dried according to a conventional method to form a polarizer.

  The iodine-based polarizer has the property of absorbing polarized light in the stretching direction (absorption axis) and transmitting light in the direction orthogonal to the stretching direction (transmission axis). When the polarizer is continuously produced in a long form (roll form), from the viewpoint of increasing productivity and the degree of polarization, a longitudinal stretching method in which the film is uniaxially stretched in the longitudinal direction, that is, the transport direction is generally used. Thus, the polarizer obtained by longitudinal stretching has an absorption axis in the film transport direction and a transmission axis in the width direction.

(Protective film)
The protective film for the polarizer is appropriately used for the purpose of preventing the polarizer from being damaged or deteriorated. In particular, an iodine-based polarizer or a polarizer using a liquid crystal material preferably has a protective film on both sides from the viewpoint of preventing sublimation of the dichroic substance and ensuring film strength.

  As a material constituting the protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, and the like is used. Specific examples of such thermoplastic resins include polycarbonate resins, polyvinyl alcohol resins, cellulose resins, polyester resins, polyarylate resins, polyimide resins, cyclic polyolefin resins, polysulfone resins, polyether sulfones. Resin, polyolefin resin, polystyrene resin, polyvinyl alcohol resin, and mixtures thereof. Further, a thermosetting resin such as urethane, acrylic urethane, epoxy, or silicone, or an ultraviolet curable resin can also be used. The protective film may contain one or more arbitrary appropriate additives. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a mold release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent. The content of the thermoplastic resin in the protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. When content of the said thermoplastic resin in a protective film is 50 weight% or less, the high transparency etc. which a thermoplastic resin originally has may not fully be expressed.

  Moreover, as a protective film arrange | positioned at the liquid crystal cell side of a polarizer, it is preferable to use a thing with high optical uniformity. If the protective film disposed between the polarizer and the liquid crystal cell has birefringence, the birefringence may affect the display characteristics of the liquid crystal panel. From such a viewpoint, as the protective film, a film having a small birefringence, that is, having optical isotropy is preferably used, and among these, a cellulose resin is generally used. As the cellulose resin, an ester of cellulose and a fatty acid is preferable. Specific examples of the cellulose ester resin include triacetyl cellulose, diacetyl cellulose, tripropionyl cellulose, dipropionyl cellulose, and the like. Among these, triacetyl cellulose is particularly preferable. Many products of triacetylcellulose are commercially available, which is advantageous in terms of availability and cost.

  As the cellulose film, for example, a method of annealing the cellulose resin by heating or solvent treatment, addition of an additive such as a retardation adjusting agent, a method of controlling the degree of substitution of the fatty acid cellulose resin with a fatty acid, etc. What controlled the thickness direction phase difference small can also be used.

  As the protective film, a film having a phase difference can be used instead of the optically isotropic film as described above. That is, by using the birefringence of the protective film disposed between the polarizer and the liquid crystal cell for optical compensation of the liquid crystal cell, the functions of the protective film of the polarizer and the optical compensation film (retardation plate) This can be achieved with a film, and can contribute to reducing the thickness, weight, and cost of the liquid crystal panel. Furthermore, in the present invention, it is also a preferable configuration that the substrate film as a support for a liquid crystal layer as a polarizing element described later, or the function of an alignment film is also used as a protective film for a polarizer.

  Although the thickness of a protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and a handleability, and thin-layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable. If the thickness of the protective film is excessively small, the polarizer may be inferior in durability in a high-temperature and high-humidity environment, or may cause problems such as local unevenness defects (knic defects).

  The same protective film may be used on both sides of the polarizer, or different ones may be used. In addition, a laminate of two or more layers can be used on one surface.

(Lamination of polarizer and protective film)
The method for laminating the polarizer and the protective film is not particularly limited, but from the viewpoint of workability and light utilization efficiency, it is desirable to laminate the layers without using an air gap. In the case of using an adhesive or a pressure-sensitive adhesive, the type thereof is not particularly limited, and various types can be used, but an adhesive is suitably used for laminating the polarizer and the protective film.

  Examples of the adhesive include acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyvinyl ether, vinyl acetate / vinyl chloride copolymer, modified polyolefin, epoxy-based, fluorine-based, natural rubber-based, and synthetic rubber. Those using a rubber-based polymer as a base polymer can be appropriately selected and used. In particular, a water-based adhesive is preferably used for laminating the polarizer and the optically isotropic film. Among them, those mainly composed of polyvinyl alcohol resin are used.

  Examples of the polyvinyl alcohol resin used for the adhesive include a polyvinyl alcohol resin and a polyvinyl alcohol resin having an acetoacetyl group. A polyvinyl alcohol resin having an acetoacetyl group is a polyvinyl alcohol-based adhesive having a highly reactive functional group, and is preferable because durability of the polarizing plate is improved.

  Polyvinyl alcohol resin is polyvinyl alcohol obtained by saponifying polyvinyl acetate; a derivative thereof; a saponified product of a copolymer of vinyl acetate and a monomer having copolymerizability; Examples thereof include modified polyvinyl alcohols that have been converted into ethers, ethers, grafts, or phosphoric esters. Examples of the monomer include unsaturated carboxylic acids such as (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, (meth) acrylic acid, and esters thereof; α-olefins such as ethylene and propylene, (meth) Examples include allyl sulfonic acid (soda), sulfonic acid soda (monoalkyl malate), disulfonic acid soda alkyl maleate, N-methylol acrylamide, acrylamide alkyl sulfonic acid alkali salt, N-vinyl pyrrolidone, N-vinyl pyrrolidone derivatives, and the like. . These polyvinyl alcohol resins can be used alone or in combination of two or more.

  Moreover, it is preferable that an adhesive agent contains a crosslinking agent. Examples of the crosslinking agent include alkylenediamines having two alkylene groups and two amino groups, such as ethylenediamine, triethylenediamine, and hexamethylenediamine; tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane tolylene diisocyanate adduct, triphenyl Isocyanates such as methane triisocyanate, methylene bis (4-phenylmethane triisocyanate, isophorone diisocyanate and their ketoxime block product or phenol block product; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di or triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether Epoxies such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde; glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, maleidialdehyde, phthaldialdehyde Dialdehydes such as: methylol urea, methylol melamine, alkylated methylol urea, alkylated methylolated melamine, acetoguanamine, condensates of benzoguanamine and formaldehyde, and the like; further sodium, potassium, magnesium, calcium, Examples thereof include salts of divalent metals such as aluminum, iron, nickel, or trivalent metals and oxides thereof, among which amino-formaldehyde Fats and dialdehydes are preferred, amino-formaldehyde resins are preferably compounds having a methylol group, and dialdehydes are preferably glyoxal, particularly methylol melamine, which is a compound having a methylol group. .

  Furthermore, from the viewpoint of suppressing the occurrence of uneven defects (knics), it is also preferable to include a metal colloid in the adhesive. Examples of such metal colloids include alumina colloid, silica colloid, zirconia colloid, titania colloid and tin oxide colloid. Specifically, those described in JP-A-2008-15383 can be suitably used.

  It is preferable to apply the adhesive so that the thickness of the adhesive layer after drying is about 10 to 300 nm. The thickness of the adhesive layer is more preferably from 10 to 200 nm, and even more preferably from 20 to 150 nm, from the viewpoint of obtaining a uniform in-plane thickness and sufficient adhesive strength. Attaching the pressure-sensitive adhesive layer or adhesive layer to the film can be performed by an appropriate method.

  The pressure-sensitive adhesive layer and the adhesive layer can also be provided on one side or both sides of the film as an overlapping layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as adhesive layers, such as a different composition, a kind, and thickness, in the front and back of a film.

  Further, the protective film may be subjected to a surface modification treatment such as hydrophilization for the purpose of improving the adhesiveness before attaching the adhesive or the pressure-sensitive adhesive. Specific examples of the treatment include corona treatment, plasma treatment, primer treatment, and saponification treatment.

(Surface treatment layer)
Furthermore, a surface of the protective film on which the polarizer is not adhered may be provided with a hard coat layer, antireflection treatment, antisticking, or a surface treatment layer for the purpose of diffusion or antiglare.

  The hard coat layer is provided for the purpose of preventing scratches on the surface of the polarizing plate. For example, a hard film with an appropriate UV curable resin such as acrylic or silicone is applied to the surface of the protective film. It can be formed by a method added to the above. The antireflection layer is provided for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the prior art. The anti-sticking layer is provided for the purpose of preventing adhesion with an adjacent layer (for example, a diffusion plate).

  The anti-glare layer is provided for the purpose of preventing external light from being reflected on the surface of the polarizing plate and hindering the viewing of the light transmitted through the polarizing plate. For example, a roughening method using a sandblasting method or an embossing method, It can be formed by imparting a fine concavo-convex structure to the surface of the protective film by an appropriate method such as a blending method of transparent fine particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle diameter of 0.5 to 20 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming the surface fine uneven structure, the amount of fine particles used is generally about 2 to 70 parts by weight, preferably 5 to 50 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure.

  The antireflection layer, anti-sticking layer, surface treatment layer such as a diffusion layer and an antiglare layer can be provided on the protective film itself, and can also be provided as a separate optical layer from the protective film. .

[Optical Rotator]
The optical rotatory element used in the liquid crystal panel of the present invention converts linearly polarized light into linearly polarized light orthogonal thereto. As long as the light is converted into orthogonal linearly polarized light, the light may be rotated by approximately 270 ° or approximately 450 ° in addition to rotating the polarized light by approximately 90 °. Further, the direction of rotation is not particularly limited. “Optical rotation” refers to a phenomenon in which the plane of polarized light rotates as linearly polarized light travels through a medium.

  Examples of the optically rotatory substance include inorganic crystals such as garnet single crystals, quartz, saccharides represented by glucose, chiral (optically active) organic molecules such as polylactic acid, and helicene. In addition, a liquid crystal layer in which the alignment direction of the liquid crystal molecules gradually and continuously changes along the thickness direction of the layer also exhibits optical activity.

  As an optical rotatory element used in the liquid crystal panel of the present invention, any material can be used without particular limitation as long as it is a material exhibiting optical rotatory properties as described above. From the viewpoint of productivity and handling properties, the orientation direction of liquid crystal molecules is A liquid crystal layer that changes gradually and continuously along the thickness direction of the layer can be preferably used. Examples of such a liquid crystal layer include those in which nematic liquid crystal molecules are twisted and aligned (sometimes referred to as “chiral nematic liquid crystal” or “cholesteric liquid crystal”). As such a liquid crystal layer, a nematic liquid crystal material (liquid crystal material in which the liquid crystal phase is a nematic phase) with a chiral agent added thereto and the alignment state fixed is preferably used. In particular, in the present invention, a chiral nematic liquid crystal layer in which the liquid crystal is twisted by approximately 90 ° can be preferably used from the viewpoint of productivity and handling properties.

  When a chiral nematic liquid crystal layer in which a chiral agent is added to a nematic liquid crystalline material is used as the optical rotatory element, the twist angle of the liquid crystal in the liquid crystal layer, that is, the rotation angle of the polarization of the optical rotatory element depends on the added amount of the chiral agent and the liquid crystal It can be adjusted by the thickness of the layer. In other words, the twisting pitch of the liquid crystal layer (sometimes referred to as “cholesteric pitch”) is adjusted by the amount of the chiral agent added, but the thickness of the liquid crystal layer is adjusted to the cholesteric pitch (the thickness at which the liquid crystal is twisted 360 °). The chiral nematic liquid crystal layer in which the liquid crystal is twisted by 90 ° can be formed by adjusting so that it becomes 1/4 of (equal).

In particular, in the present invention, the product (Δn ₅₄₅ × d) of birefringence Δn _{545 at} a wavelength of 545 nm and the thickness d of the optical rotatory element of the nematic liquid crystalline material used for the liquid crystal layer as the optical rotatory element is preferably 1400 nm or more. . In the case of optical rotation using chiral nematic liquid crystal, due to the birefringence of the liquid crystal layer, a phenomenon of light leakage may occur even when the chiral nematic liquid crystal layer has a twist angle of 90 °. On the other hand, in a liquid crystal layer in which the liquid crystal layer is twisted by 90 °, light leakage due to such birefringence can be reduced by increasing the thickness. This point will be described below.

In a configuration in which an optical rotatory element using a chiral nematic liquid crystal layer is present between two polarizing plates arranged in parallel in the absorption axis as in the liquid crystal panel of the present invention, the thickness d satisfies the following formula (1) In addition, the transmittance of monochromatic light of wavelength λ is theoretically zero.

However, in said formula (1), m is an integer greater than or equal to 1, and (DELTA) n ( _lambda) is birefringence in wavelength (lambda).

  The above equation (1) shows the condition that T (λ) = 0 in the following equation (2) representing the transmittance at the wavelength λ. The equation (2) is obtained when the thickness (cell gap) of a liquid crystal cell in a twisted nematic (TN) mode liquid crystal display device or the like is determined. H. Gooch and H.C. A. Tally, Appl. Phys., Vol. 8, 1575-1584 (1975)], θ = π / 2 (90 °) is substituted.

In a normal TN mode liquid crystal cell or optical rotatory element, a thickness d (sometimes referred to as “first minimum”) such that m = 1 is employed in the above formula (1). For example, when light leakage at a wavelength of 545 nm is minimized, the thickness of the optical rotation element is designed so that the value of (Δn ₅₄₅ × d) is about 470 nm. On the other hand, since the refractive index has a so-called “wavelength dependency” that varies depending on the wavelength, the birefringence Δn _λ also has a wavelength dependency. Therefore, the thickness d satisfying the above equation (1) varies depending on the wavelength λ. Therefore, even if the thickness of the optical rotation element is set so that the transmittance at a predetermined wavelength in the visible light region is theoretically zero, the transmittance at other wavelengths does not become zero, resulting in light leakage. Will occur. In addition, when the light leakage of a specific wavelength increases, the display may be colored.

  A preferred embodiment of the present invention is based on the new finding that good display characteristics can be obtained by increasing the thickness d of the optical rotation layer in consideration of the influence of the wavelength dependence of the birefringence. In other words, the amount of transmitted light (transmittance T) at a specific wavelength λ is as expressed by the above formula (2), and the Y value considering this over the entire wavelength range of the visible light region is the optical rotation element. This is based on the knowledge that it depends on the thickness d. The Y value is a tristimulus value Y of the XYZ color system corresponding to “brightness” in human vision, and can be expressed as the following equation (3).

The relationship between the Y value and the thickness d of the optical rotatory element will be described based on an example in a later embodiment, but the thickness at which the transmittance is minimum at a predetermined wavelength is different from the thickness at which the Y value is minimum. ing. Therefore, even if the thickness d is selected so that m in Formula (1) is an integer in order to minimize the transmittance at a predetermined wavelength (λ), the Y value is not necessarily minimized. On the other hand, when the product of the optical rotatory element and the birefringence (Δn ₅₄₅ × d) increases, the Y value tends to decrease as the thickness increases, and the thickness at which m = 1 in formula (1) (first) -Y value is smaller than in the case of minimum). Such a decrease in the Y value by adjusting the thickness is conceptually explained by the locus of polarization state conversion on the Poincare sphere. Hereinafter, with respect to the principle of the present invention and the fact that light leakage is reduced by increasing the thickness as described above, a retardation plate (1) having a retardation of ½ of the wavelength when using an optical rotator. A description will be given based on the trajectory conversion on the Poincare sphere while comparing with the case of using a / 2 wavelength plate.

The Poincare sphere is a method of expressing the polarization state of light rays by points on the sphere. When this sphere is viewed as the Earth, the North and South Pole points indicate circularly polarized light, and the equator points indicate linearly polarized light. The north or south pole and the equator point show elliptically polarized light, and the greater the latitude, the smaller the ellipticity, that is, the elliptically polarized light close to a perfect circle. The longitude on the equator corresponds to twice the angle of linearly polarized light. That is, two points having longitudes of 180 ° on the equator correspond to two orthogonal linearly polarized lights. Each point on the Poincare sphere is represented by _three Stokes parameters (S ₁ , S ₂ , S ₃ ). The Stokes parameter S ₀ = (S ₁ ² + S ₂ ² + S ₃ ² ) ^1/2 relates to the light intensity, but here, S ₀ = 1 is constant, that is, the Poincare sphere is represented as a sphere having a radius of 1.

  Even when a half-wave plate (or a 3/2 wavelength plate, a 5/2 wavelength plate, etc.) is arranged so that the optical axis (slow axis) direction is 45 ° with respect to the polarization direction of linearly polarized light, As in the case of using an optical rotatory element as in the present application, linearly polarized light is converted into linearly polarized light orthogonal thereto. However, when such a half-wave plate or the like is used, the above-described Y value tends to increase as compared to the case where an optical rotatory element as in the present application is used.

FIG. 7 shows a point A: (S ₁ , S ₂ , S ₃ ) on a Poincare sphere by a half-wave plate having a half retardation for monochromatic light of a predetermined wavelength (for example, 545 nm). = ( _-1 , 0, 0) shows a locus when linearly polarized light is converted into linearly polarized light at point B: (S ₁ , S ₂ , S ₃ ) = (1, 0, 0). 7A is a sketch, FIG. 7B is a projection onto the S ₂ -S ₃ plane, FIG. 7C is a projection onto the S ₃ -S ₁ plane, and FIG. 7D is a view onto the S ₁ -S ₂ plane. (The same applies to FIGS. 8 and 9 below).

The light transmitted through the incident side polarizing plate (incident linearly polarized light) is represented by a point A: (S ₁ , S ₂ , S ₃ ) = (− 1, 0, 0). The incident linearly polarized light moves (south-down) on the meridian while increasing the latitude while keeping the longitude as it advances in the thickness direction of the half-wave plate. This represents a state in which linearly polarized light is converted into elliptically polarized light as the thickness direction is advanced, and the ellipticity approaches one. Then, at the intermediate point in the thickness direction of the half-wave plate (corresponding to a quarter-wave retardation), the South Pole, that is, the point M: (S ₁ , S ₂ , S ₃ ) = (0, 0, −1) ) Is circularly polarized light. Further on in the thickness direction of the half-wave plate, this time while reducing the latitude Stokes parameter S ₁ is in the positive region, it moves on the meridian (north). This represents a state in which the circularly polarized light is converted into elliptically polarized light whose major axis direction is orthogonal to the previous one, and the ellipticity approaches 0 as it progresses in the thickness direction of the half-wave plate. Finally, the light is emitted from the half-wave plate as a linearly polarized light of point B: (S ₁ , S ₂ , S ₃ ) = (1, 0, 0). This point B exists on the equator like the point A representing the linearly polarized light incident on the half-wave plate, and since the longitude differs from the point A by 180 °, the linearly polarized light orthogonal to the incident linearly polarized light. It corresponds to. The linearly polarized light represented by this point B reaches the exit-side polarizing plate, but light is absorbed when the incident-side polarizing plate and the exit-side polarizing plate are parallel to each other. Therefore, it becomes dark display.

On the other hand, in FIG. 8, in the above formula (1), when the thickness d of the optical rotatory element satisfies the condition of m = 1, the linearly polarized light at point A is linearly polarized at point B orthogonal to the Poincare sphere. The trajectory in the case of being converted into is shown. When an optical rotatory element having an optical rotation angle of 90 ° as in the present invention is used, the linearly polarized light at point A: (S ₁ , S ₂ , S ₃ ) = (− 1, 0, 0) causes the optical rotatory element to move in the thickness direction. As the process proceeds to (2), the latitude on the Poincare sphere is smaller than that in the case of the half-wave plate, that is, through a state close to linear polarization, the longitude is converted, that is, the polarization direction is rotated. Then, at an intermediate point in the thickness direction of the optical rotatory element, it is converted into orthogonal linearly polarized light B: (S ₁ , S ₂ , S ₃ ) = (1, 0, 0) via the intermediate point M, and the optical rotation. Ejected from the element. Since this light is absorbed by the exit-side polarizing plate as in the case of the half-wave plate, a dark display is obtained.

Further, FIG. 8 shows a case where the linearly polarized light at the point A is converted into the linearly polarized light at the point B orthogonal to the Poincare sphere when the thickness of the optical rotatory element satisfies the condition of m = 4 in the above formula (1). Shows the trajectory. In this case, the longitude is converted on the Poincare sphere while the latitude is kept smaller than in the case of m = 1. Then, at 1/4 of the thickness of the optical rotatory element, it once reaches the point M ₁ on the equator, that is, becomes linearly polarized light, and further at an intermediate point M _{2 having} a thickness of 1/2 and a point M _{3 having a} thickness of 3/4. Is also linearly polarized light, and finally converted into orthogonal linearly polarized light B: (S ₁ , S ₂ , S ₃ ) = (1, 0, 0) and emitted from the optical rotation element. Since this light is absorbed by the polarizing plate on the emission side, a dark display is obtained.

The case of m = 4 has been described above. In the case of m = 2 and 3, the linearly polarized light B is orthogonal when the latitude is smaller than that of m = 1 and the latitude is larger than that of m = 4. It is converted into (S ₁ , S ₂ , S ₃ ) = (1, 0, 0) and emitted from the optical rotator. In addition, when m = 5 or more, the latitude is further reduced, that is, it is converted into orthogonal linearly polarized light B through a path closer to the equator. In theory, when m = ∞, the Poincare sphere The upper trajectory will move 180 ° on the equator. Thus, it can be seen that as m is larger, that is, the thickness of the optical rotation element is larger, the polarization state is converted in a state closer to linearly polarized light.

  Next, when the wavelength dependence of birefringence is taken into consideration, it will be described below that the Y value can be reduced by using an optical rotatory element. As described above, the birefringence of the polymer or the liquid crystal molecule has wavelength dependency, and the birefringence generally increases as the wavelength becomes shorter. Therefore, for example, when green light near a wavelength of 545 nm is designed to minimize light leakage, for blue light near a wavelength of 440 nm, birefringence is a value suitable for minimizing light leakage. Tend to be larger. On the other hand, for red light near the wavelength of 650 nm, birefringence tends to be smaller than a value suitable for minimizing light leakage.

The influence of this wavelength dependence will be described first based on the locus of light on the Poincare sphere when a phase difference plate is used. FIG. 10 shows that when the retardation is larger than ½ of the wavelength, the linearly polarized light at point A: (S ₁ , S ₂ , S ₃ ) = (− 1, 0, 0) on the Poincare sphere is point B. The locus | trajectory in the case of converting into ₁ elliptically polarized light is shown. For example, when a retardation plate (1/2 wavelength plate) having 1/2 retardation is used for monochromatic light having a predetermined wavelength (for example, 545 nm) as described above, other wavelengths ( For example, in the case of 440 nm, the retardation is larger than ½ of the wavelength.

Like the case of the half-wave plate shown in FIG. 7, the linearly polarized light incident on the phase difference plate temporarily moves southward on the meridian while increasing the latitude on the Poincare sphere as it travels in the thickness direction. After that, it goes north, and becomes a linearly polarized light of (S ₁ , S ₂ , S ₃ ) = B (1, 0, 0) with a retardation of ½ of the wavelength. However, since the retardation of the retardation plate is larger than ½ of the wavelength, it goes further north over the equator on the Poincare sphere and reaches the point B ₁ on the meridian. This indicates that the light emitted from the wave plate is elliptically polarized light. The latitude of the point B ₁ , in other words, the distance between the point B and the point B ₁ corresponds to the elliptical polarization ellipticity. The distance between the point B and the point B ₁ increases as the retardation deviates from ½ of the wavelength. Elliptically polarized light represented by the point B ₁ represents, not completely absorbed by the exit side polarizing plate, the transmitted light is to be observed as light leakage. As the distance between the points B and B ₁ is increased this light leakage increases.

Next, the influence of wavelength dependency when an optical rotatory element is used will be described. First, the case where the thickness d of the optical rotatory element satisfies the condition of m = 1 in the formula (1) at the predetermined wavelength λ has been described with reference to FIG. Is generally larger than 1 (not necessarily an integer) due to the wavelength dependence of birefringence. FIG. 11 shows that the linearly polarized light at point A: (S ₁ , S ₂ , S ₃ ) = (− 1, 0, 0) on the Poincare sphere when m is greater than 1 and not an integer. It shows the trace when being converted into elliptically polarized light at the point B _2. As the linearly polarized light at point A travels through the optical rotatory element in the thickness direction, it follows a trajectory similar to the case of m = 1 in FIG. 8 and reaches a point M ′ on the equator with a thickness corresponding to m = 1. When the thickness direction is further advanced, it proceeds in the southern hemisphere while changing the latitude with the same trajectory shape as before, and reaches the point B ₂ where the latitude on the same meridian is different from the point B. As in the previous Figure 10, the light leakage increases as the distance between the points B and B ₂ becomes large.

On the other hand, the case where the thickness d of the optical rotatory element satisfies the condition of m = 4 in the equation (1) at the predetermined wavelength λ has been described above with reference to FIG. 9, but due to the influence of the wavelength dependence of birefringence. In addition, on the shorter wavelength side than λ, m is generally larger than 4 (not necessarily an integer). FIG. 12 shows that when m is larger than 4 and is not an integer, the linearly polarized light of point A: (S ₁ , S ₂ , S ₃ ) = (− 1, 0, 0) on the Poincare sphere is It shows the trace when being converted into elliptically polarized light of B _3. As the linearly polarized light at point A travels through the optical rotatory element in the thickness direction, it follows a similar trajectory as in the case of m = 4 in FIG. 3, and at the thickness corresponding to m = 1, 2, 3, 4, respectively on the equator. via points, latitude on the same meridian and the point B to reach the different B _3. Then, the light leakage increases as the distance between the point B and B ₃ is increased. Here, it can be seen that the distance between the points B and B ₃ is smaller than the distance between the points B and B ₁ or the points B and B _{2 described above} .

  As described above, this is related to the fact that as the value of m increases, the polarization state is converted while maintaining a locus closer to the equator on the Poincare sphere, in other words, a state close to linear polarization. The greater the value of m in Equation (1), that is, the greater the thickness of the optical rotator, the smaller the deviation from linearly polarized light even when m deviates from the integer value. Therefore, even if the birefringence has wavelength dependence, the light leakage, that is, the Y value for the entire visible light region is reduced.

Conventionally, as the optical rotatory element, the thickness d is generally set so as to satisfy m = 1 (first minimum) in the formula (1), but as shown conceptually using a Poincare sphere. In addition, when m = 1, the difference from the case where the retardation plate is used is small, that is, the distance between the points B and B ₁ and the distance between the points B and B ₂ are substantially the same. On the other hand, by increasing the thickness, light leakage can be reduced at other wavelengths, and as a result, the Y value is reduced. The thickness at which the Y value is smaller than in the case of the first minimum varies depending on the wavelength dispersion of the liquid crystal compound forming the liquid crystal layer, but as will be shown later in the examples, the product of birefringence and thickness of the optical rotation element (Δn ₅₄₅ When xd) is 1400 nm or more, the Y value tends to be small. The product of birefringence and thickness (Δn ₅₄₅ × d) of the optical rotatory element is more preferably 1500 nm or more, further preferably 1600 nm or more, and particularly preferably 1700 nm or more. In such a range, the Y value tends to show a monotonous decrease as the thickness of the optical rotatory element increases.

In addition, although it was mentioned that (Δn ₅₄₅ × d) is preferably 1400 nm or more, the present invention increases the thickness d of the optical rotation layer to increase the visible light region due to the wavelength dependence of birefringence. This is based on a new finding that the influence of light leakage occurring at each wavelength can be reduced and the Y value can be reduced as a result.

  In addition, when λ satisfying the above formula (1) is included in the visible light region, the transmittance T at the time of black display at the wavelength λ can be reduced, so that good display characteristics are obtained. In general, in a liquid crystal panel, color display is possible by using three color filters of red (R), green (G), and blue (B), but the design is based on the transmission wavelength of the color filter. From the viewpoint, it is preferable that λ satisfying the above formula (1) exists in the range of 450 to 650 nm. Further, from the viewpoint of optimally designing green light having the highest visibility among the above three colors, it is preferable that λ satisfying the above formula (1) exists in the range of 530 to 570 nm. Since light with a green wavelength (near 545 nm) has high visibility in human vision, it is possible to obtain a display with excellent visibility by reducing light leakage in the green wavelength region (resulting in a Y value). Tends to be smaller).

The present invention is not limited to the case where (Δn ₅₄₅ × d) of the optical rotatory element satisfies 1400 nm or more, but when the (Δn ₅₄₅ × d) of the optical rotatory element is less than 1400 nm, the visible light region ( 380 to 780 nm), preferably in the range of 450 to 650 nm, more preferably in the range of 500 to 600 nm, still more preferably in the range of 530 to 570 nm, and preferably has a wavelength λ that satisfies m = 2 in the above formula (1). . In such a case, the Y value can be made smaller than in the case of the first minimum with m = 1. However, the Y value tends to be higher than when (Δn ₅₄₅ × d) is 1400 nm or more.

  Further, by increasing the thickness, light leakage in black display can be suppressed and the Y value can be reduced. In addition, it is also possible to suppress the influence of the characteristic change due to the thickness variation of the optical rotation element. That is, when a liquid crystal layer is used as an optical rotatory element, the thickness is generally in the range of 0.1 to several tens of micrometers as will be described in detail later, but when the liquid crystal layer is produced in a large area, It is difficult to make the thickness completely uniform, and variations in thickness occur in the same liquid crystal layer or between products with separately manufactured liquid crystal layers. The variation in thickness causes the twist angle of the liquid crystal layer in the optical rotation layer, that is, the variation in the optical rotation angle and the deviation from the thickness d that satisfies the condition of the above formula (1). May be uneven. Such variation in thickness within a product or between products can be suppressed by adopting an optical rotatory element composed of a liquid crystal layer having a large thickness.

  As described above, it is preferable that the thickness d of the optical rotator is larger from the viewpoint of obtaining good display characteristics by reducing the Y value. However, the thickness d is 10 μm or less from the viewpoint of productivity of the optical rotator. Is preferable, and it is more preferable that it is 7 micrometers or less.

(Optical rotation element placement angle)
When using an optical rotatory element that includes a liquid crystal layer in which the orientation direction of liquid crystal molecules gradually changes along the thickness direction of the layer, the orientation direction of liquid crystal molecules on one side and the other side of the optical rotatory element However, in the liquid crystal panel of the present invention, the absorption axis direction of the polarizing plate closer to the optical rotator is parallel to the alignment direction of the liquid crystal molecules on the surface of the optical rotator facing the polarizer. Or it is preferable that it is orthogonal. For example, in FIG. 3A, the orientation direction of the liquid crystal molecules on the direction of the absorption axis 3 of the first polarizing plate 21 adjacent to the optical rotator 30 and the surface of the optical rotator 30 facing the first polarizing plate 21. The form in which 5a is orthogonal is schematically illustrated. In FIG. 3B, the orientation of the liquid crystal molecules on the absorption axis 4 direction of the second polarizing plate 22 adjacent to the optical rotator 30 and the surface of the optical rotator 30 on the side facing the second polarizing plate 22. A form in which the directions 5a are parallel is schematically illustrated. By adopting such an angle arrangement, the contrast of the liquid crystal display device of the present invention can be set to a level comparable to that of a conventional liquid crystal display device in which two polarizing plates are arranged so as to be orthogonal to each other. .

(Optical rotator manufacturing method)
Although the material and manufacturing method of the liquid crystal layer as the optical rotatory element are not particularly limited, as described above, a liquid crystal material (nematic liquid crystal material) having a nematic liquid crystal phase is preferably used. As such a liquid crystalline material, for example, a liquid crystalline polymer or a liquid crystalline monomer can be used. The liquid crystal material may have a liquid crystallinity manifestation mechanism that may be either lyotropic or thermotropic.

  The liquid crystalline material is preferably a liquid crystalline monomer (for example, a polymerizable monomer and a crosslinkable monomer). This is because the alignment state of the liquid crystalline monomer can be fixed by polymerizing or crosslinking the liquid crystalline monomer, as will be described later. After aligning the liquid crystalline monomers, for example, if the liquid crystalline monomers are polymerized or crosslinked, the alignment state can be fixed thereby. Here, a polymer is formed by polymerization and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystalline. Therefore, in the formed liquid crystal layer, for example, a transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change specific to the liquid crystal compound does not occur. As a result, the liquid crystal layer is an optical compensation layer that is not affected by temperature changes and has excellent stability.

  The liquid crystalline monomer is not particularly limited, and any appropriate liquid crystalline monomer can be adopted. For example, Japanese translations of PCT publication No. 2002-533742 (International Publication No. 00/37585), European Patent No. 358208 (US Pat. No. 5,211,877), European Patent No. 66137 (US Pat. No. 4,388,453), International Publication No. 93/22397, European Patent No. 0261712. Polymerizable mesogenic compounds described in German Patent No. 19504224, German Patent No. 4408171, British Patent No. 2280445, and the like can be used. Specific examples of such a polymerizable mesogenic compound include, for example, trade name Paliocolor LC242 from BASF, trade name E7 from Merck, and trade name LC-Silicon-CC3767 from Wacker-Chem. Moreover, the following materials can also be used suitably as a monofunctional or bifunctional reactive mesogenic compound.

  For the purpose of aligning the nematic liquid crystal with chiral nematic alignment, it is preferable to use a chiral agent. The content of the chiral agent can be appropriately selected depending on the kind of the chiral agent and nematic liquid crystal to be used, the thickness of the optical rotator (liquid crystal layer), etc., but forms a cholesteric pitch suitable for twisting the liquid crystal layer by 90 °. From the viewpoint, the addition amount of the chiral agent is preferably 0.005 to 0.5 parts by weight and more preferably 0.01 to 0.3 parts by weight with respect to 100 parts by weight of the nematic liquid crystalline material. If the addition amount of the chiral agent is excessively low, the twist of the liquid crystal becomes small. For example, it is necessary to excessively increase the thickness for obtaining a liquid crystal layer twisted by 90 °. May be inferior. In addition, if the amount of the chiral agent added is excessively high, the liquid crystalline material becomes difficult to exhibit a liquid crystal state (the temperature range showing the liquid crystal phase becomes narrow), and thus it is necessary to perform temperature control at the time of manufacturing with extremely high precision. There is a case. Further, since the thickness for forming the liquid crystal layer twisted by 90 ° is reduced, the Y value of the liquid crystal display device is increased, and a good black display may not be obtained. In addition, a chiral agent can be used individually or in combination of 2 or more types.

  As the chiral agent, any appropriate material capable of aligning the liquid crystalline material in a desired chiral nematic orientation can be adopted. As the chiral agent to be added, those having an optically active group and not disturbing the orientation when mixed with a liquid crystal compound can be suitably used. The chiral agent may or may not have liquid crystallinity. Any chiral agent having a reactive group can be used, but those having a reactive group can be suitably used from the viewpoint of heat resistance and solvent resistance of the optical rotatory element (liquid crystal layer). Examples of the reactive group include a (meth) acryloyloxy group, an azide group, and an epoxy group, and the same (meth) acryloyloxy group as the polymerizable reactive group of the polymerizable liquid crystal compound is preferable. From the viewpoint of heat resistance and solvent resistance, those having two or more polymerization reactive groups are preferable.

Examples of the chiral agent having two or more polymerizable functional groups include the following materials.

  Further, as the chiral agent, a commercially available product such as a trade name “Pariocolor LC756” manufactured by BASF Corporation may be used.

The torsional force of such a chiral agent is preferably 1 × 10 ⁻⁸ nm ⁻¹ · (wt%) ⁻¹ or more, and more preferably 1 × 10 ⁻⁷ nm ⁻¹ · (wt%) ⁻¹ to 1 × 10 ⁻² nm ⁻¹ · (wt%) ⁻¹ , most preferably 1 × 10 ⁻⁶ nm ⁻¹ · (wt%) ⁻¹ to 1 × 10 ⁻³ nm ⁻¹ · (wt%) ^-1 . By using a chiral agent having such a twisting force, the cholesteric pitch of the liquid crystal layer can be controlled within a desired range.

  In forming the liquid crystal layer, a method of applying a liquid obtained by dissolving or dispersing a liquid crystal composition containing the above liquid crystalline compound, chiral agent and other additives in a solvent onto a substrate is suitably used. Such a liquid crystal composition preferably contains a polymerization initiator, a crosslinking agent (curing agent) and the like. By using a polymerization initiator or a crosslinking agent, a liquid crystal layer formed of a liquid crystal material in a liquid crystal state can be fixed. As such a polymerization initiator or crosslinking agent, any appropriate substance can be adopted as long as the effects of the present invention can be obtained. Examples of the polymerization initiator include benzoyl peroxide (BPO) and azobisisobutyronitrile (AIBN). Commercially available polymerization initiators such as trade names Irgacure 184, Irgacure 907, Irgacure 369, and Irgacure 651 manufactured by Ciba Japan can also be suitably used. Examples of the crosslinking agent (curing agent) include an ultraviolet curing agent, a photocuring agent, and a thermosetting agent. More specifically, an isocyanate type crosslinking agent, an epoxy type crosslinking agent, a metal chelate crosslinking agent, etc. are mentioned. These may be used alone or in combination of two or more.

  The content of the polymerization initiator or the crosslinking agent is preferably 0.01 to 15% by weight, more preferably 0.1 to 10% by weight, and still more preferably based on 100 parts by weight of the nematic liquid crystal compound. 1 to 7% by weight. If the content of the polymerization initiator or the crosslinking agent is too small, the liquid crystal layer may not be sufficiently fixed. In addition, when the content of the polymerization initiator or the crosslinking agent is excessively large, the temperature range in which the liquid crystalline material exhibits a liquid crystal phase is narrowed, and it may be difficult to control the temperature when forming the liquid crystal layer.

  The liquid crystal composition may further contain any appropriate additive as required. Examples of the additive include a deterioration inhibitor, a modifier, a surfactant, a dye, a pigment, a discoloration inhibitor, and an ultraviolet absorber. These additives may be used alone or in combination of two or more. More specifically, examples of the deterioration inhibitor include phenol compounds, amine compounds, organic sulfur compounds, and phosphine compounds. Examples of the modifier include glycols, silicones, and alcohols. The surfactant is added for the purpose of smoothing the surface of the optical compensation layer. For example, silicone-based, acrylic-based, and fluorine-based surfactants can be used.

  As a method for forming the liquid crystal layer, any appropriate method can be adopted as long as the effects of the present invention are not impaired. A typical forming method includes a step of spreading a solution obtained by dissolving the liquid crystal composition in a solvent on a substrate to form a spread layer, and a liquid crystalline material in the liquid crystal composition exhibiting a chiral nematic liquid crystal phase. And a step of heating the spreading layer. Such heating may also serve as drying of the solvent. Furthermore, the step of arbitrarily subjecting the spreading layer to at least one of a polymerization treatment and a crosslinking treatment to fix the orientation of the liquid crystalline material, the step of transferring the liquid crystal layer formed on the substrate to another substrate, It is preferable to contain. Hereinafter, a specific procedure of the forming method will be described.

  First, a liquid crystal coating liquid is prepared by dissolving or dispersing a liquid crystal material, a chiral agent, and, if necessary, a polymerization initiator or a crosslinking agent and various additives in a solvent. The liquid crystal material, the chiral agent, the polymerization initiator, the crosslinking agent, and the additive are as described above. The solvent used for the liquid crystal coating liquid is not particularly limited. Specific examples include halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, methylene chloride, trichloroethylene, tetrachloroethylene, chlorobenzene, orthodichlorobenzene, phenol, p-chlorophenol, o-chlorophenol, m. -Phenols such as cresol, o-cresol, p-cresol, aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, 1,2-dimethoxybenzene, acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, cyclohexanone Ketone solvents such as cyclopentanone, 2-pyrrolidone and N-methyl-2-pyrrolidone, ester solvents such as ethyl acetate and butyl acetate, t-butyl alcohol, glycerin , Alcohols such as ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentanediol, amides such as dimethylformamide and dimethylacetamide Examples thereof include solvents, nitrile solvents such as acetonitrile and butyronitrile, ether solvents such as diethyl ether, dibutyl ether, tetrahydrofuran and dioxane, carbon disulfide, ethyl cellosolve, and butyl cellosolve. Among these, toluene, xylene, mesitylene, MEK, methyl isobutyl ketone, cyclohexanone, cyclopentanone, ethyl cellosolve, butyl cellosolve, ethyl acetate, butyl acetate, propyl acetate, and ethyl cellosolve are preferable. These solvents may be used alone or in combination of two or more.

  Next, the liquid crystal coating solution is coated on the substrate to form a spread layer. As a method for forming the spreading layer, any appropriate method (typically, a method in which a coating solution is fluidly developed) can be employed. Specific examples include a roll coating method, a die coating method, a spin coating method, a wire bar coating method, a dip coating method, an extrusion method, a curtain coating method, and a spray coating method.

Any appropriate substrate capable of aligning the liquid crystalline material can be adopted as the substrate. Typically, various plastic films are mentioned. Although it does not restrict | limit especially as a plastic, For example, polyolefin, such as a triacetyl cellulose (TAC), polyethylene, a polypropylene, poly (4-methyl pentene-1), a polyimide, a polyimide amide, polyether imide, polyamide, polyether ether ketone , Polyether ketone, polyketone sulfide, polyether sulfone, polysulfone, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacetal, polycarbonate, polyarylate, acrylic resin, polyvinyl alcohol, polypropylene, cellulose resin, An epoxy resin, a phenol resin, etc. are mentioned. Moreover, what arrange | positioned the above plastic films and sheet | seats on the surfaces, such as metal substrates, such as aluminum, copper, and iron, a ceramic substrate, and a glass substrate, can also be used. Can also be used that form a SiO ₂ oblique deposition film on the substrate or the plastic film or the surface of the sheet. The thickness of the substrate is preferably 5 μm to 500 μm, more preferably 10 μm to 200 μm, and most preferably 15 μm to 150 μm. If it is such thickness, since it has sufficient intensity | strength as a board | substrate, generation | occurrence | production of problems, such as a fracture | rupture at the time of manufacture, can be prevented, for example.

  Moreover, it is preferable that the said board | substrate is equipped with a liquid crystal aligning film. Various conventionally known alignment films can be used. For example, a film formed by rubbing a thin film made of polyimide, polyvinyl alcohol or the like on a substrate, a stretched film, a cinnamate skeleton In addition, a polymer having an azobenzene skeleton or a polyimide irradiated with polarized ultraviolet rays can be used.

  In the case where the liquid crystal layer is produced in the form of a long roll, the alignment film preferably has an alignment direction in the film longitudinal direction, that is, the transport direction, from the viewpoint of productivity. Moreover, if it has an orientation direction in a film conveyance direction, it can laminate | stack with a long polarizing plate and roll tow roll which have an absorption axis in a longitudinal direction, and can be made into a long laminated polarizing plate provided with an optical rotation element. This is also preferable in terms of points. As the alignment film, a stretched film can be used as described above. Furthermore, for example, since an iodine-based polarizer is stretched in the longitudinal direction of the film, it is possible to replace the polarizer with a liquid crystal alignment film and apply a liquid crystal coating liquid on the polarizer. In addition, the number of liquid crystal panel production steps and the number of laminated films can be reduced by using, as alignment films, components used in liquid crystal panels such as polarizer protective films and optical compensation layers (optical compensation films) described later. can do.

  The coating amount of the liquid crystal coating liquid can be appropriately set according to the concentration of the coating liquid, the thickness of the target layer, and the like, but from the viewpoint of making the thickness of the liquid crystal layer uniform, the coating thickness (wet thickness) is 1. It is preferably ˜100 μm, and more preferably 2 to 50 μm. In the present invention, as described above, it may be necessary to increase the thickness from the viewpoint of preventing coloring of black display. In such a case, when the coating thickness exceeds the above range, it is preferable to employ a method of performing coating with the thickness within the above range a plurality of times from the viewpoint of making the thickness uniform. For example, a method of applying twice with a thickness of 45 ° or a method of applying three times with a thickness of 30 ° can be employed. For example, in the case of a method of applying three times with a thickness that gives a twist angle of 30 °, the first layer is 0 to 30 °, the second layer is 30 to 60 °, the third layer is 60 to 90 °, and each layer is 30 °. A twist angle of 90 ° can be achieved by rotating the arrangements one by one.

  In this case, the second layer and the third layer can be applied in a wet state before the first layer is dried. From the viewpoint of uniformity of thickness, the first layer is once dried and necessary. And then applying the second layer after fixing the orientation of the liquid crystal layer and then applying the third layer after fixing the orientation of the second liquid crystal layer. It is preferable to sequentially perform fixing. In the case of sequential application in this way, an alignment film may be formed before application of each layer. However, if the alignment of the liquid crystal is fixed, the liquid crystal alignment layer is the same as the alignment film. Therefore, the target twist angle (90 °) can be achieved without forming an alignment film. For example, when three layers of 30 ° liquid crystal layers are applied, the liquid crystal molecules are oriented in the direction of 30 ° on the surface layer of the first layer, and therefore on the surface adjacent to the first layer in the second development layer. Has a twist angle of 30 to 60 ° when the liquid crystal molecules are aligned at 30 ° and the spread layer is solidified. Similarly, the second surface layer in which liquid crystal molecules are aligned in the direction of 60 ° serves as an alignment film, and the third layer can be a liquid crystal layer having a twist angle of 60 to 90 °. Although the case where three liquid crystal layers having a twist angle of 30 ° are applied has been described as an example, the same can be applied to the case where a liquid crystal layer having another twist angle is applied a plurality of times.

  In addition, when a plurality of liquid crystal layers are prepared in advance and three liquid crystal layers having a predetermined angle, for example, a twist angle of 30 °, are laminated, each layer is rotated by 30 ° and disposed. , A liquid crystal layer having a twist angle of 90 °.

  By applying heat treatment to the development layer developed on the base material (alignment film), the liquid crystalline material can be aligned in a state showing a liquid crystal phase. Since the spread layer contains a chiral agent together with the liquid crystalline material, the liquid crystalline material is twisted and aligned in a state showing a liquid crystal phase. As a result, the spread layer (liquid crystal material constituting the layer) exhibits chiral nematic alignment (helical alignment).

  The temperature condition for the heat treatment can be appropriately set according to the type of the liquid crystalline material. Specifically, it is preferable to heat the liquid crystalline material to a temperature exhibiting liquid crystallinity. For example, in the case of the liquid crystalline material described above as “Chemical Formula 1”, the temperature range exhibiting liquid crystallinity is generally in the range of 90 to 185 ° C. It is preferable to heat within this range, and from the viewpoint of imparting sufficient orientation to the liquid crystalline material, the heating temperature is more preferably 120 ° C. or higher, considering the heat resistance of the substrate, From the viewpoint of expanding the selection range, the heating temperature is preferably 160 ° C. or lower. The heating time is preferably 30 seconds or longer, and more preferably 1 minute or longer. If the treatment time is excessively short, the liquid crystal material may not take a sufficient liquid crystal state. On the other hand, the heating time is preferably 10 minutes or less, more preferably 8 minutes or less, and most preferably 7 minutes or less. If the heating time is excessively long, problems such as sublimation of the additive may occur.

  Next, in a state where the liquid crystalline material exhibits chiral nematic alignment, the development layer is subjected to polymerization treatment or crosslinking treatment to fix the alignment of the liquid crystalline material. More specifically, by performing the polymerization treatment, the liquid crystalline material (polymerizable monomer) and / or the chiral agent (polymerizable chiral agent) is polymerized, and the polymerizable monomer and / or polymerizable chiral agent becomes a polymer molecule. Fixed as a repeating unit. In addition, by performing a crosslinking treatment, the liquid crystalline material (crosslinkable monomer) and / or the chiral agent forms a three-dimensional network structure, and the crosslinking monomer and / or the chiral agent is fixed as a part of the crosslinked structure. Is done. As a result, the alignment state of the liquid crystal material is fixed. Note that a polymer or a three-dimensional network structure formed by polymerizing or cross-linking a liquid crystalline material does not cause a phase state transition and is strictly “non-liquid crystalline”. Therefore, in the formed liquid crystal layer, for example, transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change peculiar to liquid crystal molecules does not occur, and an orientation change due to temperature does not occur. As a result, the formed liquid crystal layer is not affected by temperature and can exhibit stable optical rotation.

  The specific procedure of the above-mentioned polymerization treatment or crosslinking treatment can be appropriately selected depending on the kind of polymerization initiator and crosslinking agent to be used. For example, when a photopolymerization initiator or a photocrosslinking agent is used, light irradiation may be performed, and when an ultraviolet polymerization initiator or an ultraviolet crosslinking agent is used, ultraviolet irradiation may be performed. When a cross-linking agent is used, heating may be performed. The irradiation time of light or ultraviolet rays, irradiation intensity, total irradiation amount, and the like can be appropriately set according to the type of liquid crystalline material, the type of substrate, the characteristics desired for the liquid crystal layer, and the like. Similarly, the heating temperature, the heating time, and the like can be appropriately set according to the purpose.

  The liquid crystal layer formed on the substrate (alignment film) in this way may be used as it is, or may be peeled off from the substrate. Furthermore, it can be transferred to another film such as a polarizing plate, a liquid crystal cell, or other film. Further, the transfer can be performed a plurality of times to adjust the orientation angle of the liquid crystal layer and the front and back of the surface. The transfer is preferably performed via an adhesive, and when the transfer is performed a plurality of times, for example, a method of using an adhesive having a high adhesive force in sequence can be suitably employed.

[Formation of liquid crystal panel]
The liquid crystal panel of the present invention can be formed by any appropriate method using the liquid crystal cell 10, the first polarizing plate 21, the second polarizing plate 22, and the optical rotator 30. In addition, the liquid crystal panel of the present invention can include an optical layer other than the above and other members. Examples thereof include the above-described antireflection layer, antisticking layer, surface treatment layer such as a diffusion layer and an antiglare layer, and a brightness enhancement film. Moreover, an optically isotropic film, an optical compensation layer (optical compensation film), etc. can also be included.

(Brightness enhancement film)
The brightness enhancement film is not particularly limited, and transmits linearly polarized light having a predetermined polarization axis such as a dielectric multilayer thin film or a multilayer laminate of thin film films having different refractive index anisotropy. Other materials that reflect light can be used. As such a brightness enhancement film, for example, trade name “D-BEF” manufactured by 3M Co., Ltd. may be mentioned. Further, a cholesteric liquid crystal layer, particularly an oriented film of a cholesteric liquid crystalline polymer, or a film in which the oriented layer is supported on a film substrate can be used. These reflect the right and left circularly polarized light and transmit the other light. For example, the product name “PCF350” manufactured by Nitto Denko Corporation, the product name “Transmax” manufactured by Merck, etc. Can be mentioned.

(Optical compensation layer)
The optical compensation layer is used for the purpose of coloring the liquid crystal cell due to birefringence, preventing light leakage in an oblique direction, and widening the viewing angle. The optical compensation layer can be disposed between the liquid crystal cell 10 and the first polarizing plate 21 or the second polarizing plate 22. Further, it may be disposed between the first polarizing plate 21 or the second polarizing plate 22 and the optical rotator 30, or may be disposed between the optical rotator 30 and the liquid crystal cell 10. Moreover, it can also arrange | position to both.

  Examples of the optical compensation layer include various retardation plates and viewing angle compensation films. Examples of the retardation plate include a birefringent film obtained by uniaxially or biaxially stretching a polymer material, a liquid crystal polymer alignment film, and a liquid crystal polymer alignment layer supported by a film. The stretching treatment can be performed by, for example, a roll stretching method, a long gap stretching method, a tenter stretching method, a tubular stretching method, or the like. In the case of uniaxial stretching, the stretching ratio is generally about 1.1 to 3 times. The thickness of the optical compensation layer is not particularly limited, but when a stretched film is employed as the retardation plate, the thickness is generally 10 to 200 μm, preferably 20 to 100 μm.

  Examples of the polymer material used for the retardation plate include polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polycarbonate, polyarylate, polysulfone, polyethylene terephthalate, and polyethylene. Naphthalate, polyethersulfone, polyphenylene sulfide, polyphenylene oxide, polyallylsulfone, polyvinyl alcohol, polyamide, polyimide, polyolefin, polyvinyl chloride, cellulosic resin, or any of these binary and ternary copolymers, Examples include graft copolymers and blends. These polymer materials become oriented products (stretched films) by stretching or the like.

  Examples of the liquid crystalline polymer include various main chain types and side chain types in which a conjugated linear atomic group (mesogen) imparting liquid crystal alignment is introduced into the main chain or side chain of the polymer. Can be mentioned. Specific examples of the main chain type liquid crystalline polymer include, for example, a nematic alignment polyester liquid crystalline polymer, a discotic liquid crystalline polymer, and a cholesteric liquid crystalline polymer having a structure in which a mesogen group is bonded at a spacer portion that imparts flexibility. Etc. Specific examples of the side chain type liquid crystalline polymer include polysiloxane, polyacrylate, polymethacrylate, or polymalonate as a main chain skeleton, and a nematic alignment imparting paraffin through a spacer portion composed of a conjugated atomic group as a side chain. Examples thereof include those having a mesogen moiety composed of a substituted cyclic compound unit. These liquid crystalline polymers are, for example, solutions of liquid crystalline polymers on alignment treatment surfaces such as those obtained by rubbing the surface of a thin film such as polyimide or polyvinyl alcohol formed on a glass substrate, or those obtained by obliquely depositing silicon oxide. It is performed by developing and heat-treating.

  The retardation plate may have an appropriate retardation according to the purpose of use, such as those for the purpose of compensating for various wavelength plates or birefringence of liquid crystal layers, compensation of viewing angle, and the like. What laminated | stacked a phase difference plate and controlled optical characteristics, such as phase difference, etc. may be used.

  For example, in a retardation plate (negative biaxial plate) satisfying nx> ny> nz, the front phase difference is 40 to 100 nm, the thickness direction phase difference is 100 to 320 nm, and the Nz coefficient is 1.1 to 4.5. It is preferable to use a satisfactory one. For example, in a phase difference plate (positive A plate) that satisfies nx> ny = nz, it is preferable to use a plate that satisfies a front phase difference of 20 to 500 nm. For example, in a retardation plate (negative A plate) that satisfies nz = nx> ny, it is preferable to use a retardation plate that satisfies a front retardation of 20 to 500 nm. For example, in a (Z) retardation plate that satisfies nx> nz> ny, it is preferable to use a retardation plate that has a front phase difference of 20 to 500 nm, an Nz coefficient exceeding 0, and 0.9 or less. In addition, for example, a material satisfying nx = ny> nz, nz> nx> ny, or nz> nx = ny can be used.

  Note that nx represents the refractive index in the slow axis direction in the film plane, ny represents the direction perpendicular to the slow axis in the film plane, that is, the refractive index in the fast axis direction, and nz represents the refractive index in the thickness direction. Further, the front phase difference Re is expressed by Re = (nx−ny) × d, and the thickness direction phase difference Rth is expressed by Rth = (nx−nz) × d. Where d is the thickness of the film. The Nz coefficient is represented by Nz = (nx−nz) / (nx−ny).

  Such a retardation plate can be appropriately selected according to the applied liquid crystal display device. For example, in the case of a VA mode liquid crystal panel, in terms of a three-dimensional refractive index, nx> ny = nz, nx> ny> nz, nx> nz> ny, nx = ny> nz (uniaxial, biaxial, Z conversion) In this case, Re = 0 to 240 nm and Rth = 0 to 500 nm are preferably used. In the case of an IPS mode liquid crystal panel, in terms of the three-dimensional refractive index, nx> ny = nz, nx> nz> ny, nz> nx = ny, nz> nx> ny (uniaxial, Z conversion, positive C plate, positive It is preferable to use a retardation plate of (A plate).

  In addition, as a phase difference plate, not only a film but the polymer coating layer etc. which are described in Unexamined-Japanese-Patent No. 2004-0708203 etc. can also be used, for example. Further, as described above, the transparent film as the polarizer protective film may have the function of a retardation plate.

  The viewing angle compensation film is a kind of retardation plate, and is used to widen the viewing angle so that the image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen. It is a film. Such a viewing angle compensation film is composed of an alignment film such as a liquid crystalline polymer or a film in which an alignment layer such as a liquid crystalline polymer is supported on a transparent substrate. A normal retardation plate uses a birefringent polymer film uniaxially stretched in the plane direction, whereas a retardation plate used as a viewing angle compensation film stretches biaxially in the plane direction. A polymer film having birefringence, a polymer having birefringence with a controlled refractive index in the thickness direction that is uniaxially stretched in the plane direction and also stretched in the thickness direction, and a bi-directionally stretched film such as a tilted orientation film are suitable. Used. Examples of the inclined alignment film include a film obtained by bonding a heat-shrink film to a polymer film and stretching or / and contracting the polymer film under the action of the contraction force by heating, or a film obtained by obliquely aligning a liquid crystalline polymer. Is mentioned. The raw material polymer of the phase difference plate is the same as the polymer described in the previous phase difference plate, preventing coloration due to a change in the viewing angle based on the phase difference by the liquid crystal cell and expanding the viewing angle for good viewing. An appropriate one for the purpose can be used.

  Optical compensation in which an alignment layer of a liquid crystalline polymer, particularly an optically anisotropic layer composed of a tilted alignment layer of a discotic liquid crystalline polymer, is supported by a triacetyl cellulose film in order to achieve a wide viewing angle with good visibility. A layer can be suitably used.

(Lamination of each member)
Each member is preferably laminated via an adhesive layer, a pressure-sensitive adhesive layer, or the like. In that case, the adhesive or pressure-sensitive adhesive is transparent, has no absorption in the visible light region, and the refractive index is desirably as close as possible to the refractive index of each layer from the viewpoint of suppressing surface reflection. As the adhesive, those described above in the lamination of the polarizer and the protective film can be suitably used. As the pressure-sensitive adhesive, an acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer can be appropriately selected and used. In particular, those having excellent optical transparency, such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and having excellent weather resistance, heat resistance and the like can be preferably used.

  In addition to the above, from the viewpoints of prevention of foaming and peeling phenomenon due to moisture absorption, deterioration of optical characteristics due to thermal expansion difference and the like, prevention of warpage of liquid crystal cells, and formation of liquid crystal display devices with high quality and excellent durability. An adhesive layer having a low moisture absorption rate and excellent heat resistance is preferred.

  The pressure-sensitive adhesive layer is, for example, a natural or synthetic resin, in particular, a tackifier resin, a filler, a pigment, a colorant, an antioxidant made of glass fiber, glass beads, metal powder, or other inorganic powders. An additive to be added to the pressure-sensitive adhesive layer may be contained. Moreover, the adhesive layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient. Although the thickness of an adhesive layer can be suitably determined according to a use purpose, adhesive force, etc., generally it is 1-500 micrometers, 2-200 micrometers is preferable, 3-100 micrometers is more preferable, and 4-50 micrometers is more preferable.

(Liquid crystal panel formation order)
In the present invention, the order in which the liquid crystal panels are formed is not particularly limited, and the liquid crystal panels may be formed by a method of sequentially laminating each member separately, or a material obtained by laminating several members in advance may be used. In addition, although the lamination order is not particularly limited, in the present invention, a polarizing plate and an optical rotatory element, and a laminated polarizing plate in which a surface treatment layer, a brightness enhancement film, an optical compensation layer, etc. are laminated in advance, are prepared in advance. By laminating this with a liquid crystal cell, it is possible to achieve excellent quality stability and assembly workability.

  In addition, it is preferable to laminate | stack the said polarizing plate or a laminated polarizing plate, and a liquid crystal cell through an adhesive and especially an acrylic adhesive layer as mentioned above. In particular, from the viewpoint of productivity and workability, it is preferable to prepare in advance as a pressure-sensitive adhesive layer on the side of the polarizing plate to be bonded to the liquid crystal cell, and to laminate this with the liquid crystal cell.

  Further, in the present invention, a laminated polarizing plate in which a polarizing plate and an optical rotatory element and, if necessary, other optical layers are laminated, is laminated in a roll-to-roll manner from the viewpoint of productivity. Thus, it is preferably used as a long laminated polarizing plate. Further, as described above, a protective film for a polarizer and an optical compensation layer (retardation plate) are used as a support (alignment film), and a liquid crystal coating liquid for forming a liquid crystal layer as an optical rotation element is continuously applied thereto. Thus, a long laminated polarizing plate having an optical rotatory element can be obtained.

  The (laminate) polarizing plate thus obtained is preferably bonded to a liquid crystal cell after being processed to a predetermined size. In the present invention, as described above, by adopting a configuration in which the first polarizing plate and the second polarizing plate are bonded to the liquid crystal cell so that the absorption axes of the first polarizing plate and the second polarizing plate are parallel to each other, It is possible to improve the yield of the polarizing plate.

  When a pressure-sensitive adhesive layer for laminating a liquid crystal cell is provided on the (laminate) polarizing plate, the pressure-sensitive adhesive can be attached either before or after the polarizing plate is cut out from the long laminated polarizing plate. From the viewpoint of property, it is preferable to attach an adhesive layer before cutting out the polarizing plate. By forming a long (laminated) polarizing plate provided with an adhesive layer and cutting it into a predetermined size, the productivity and workability of the liquid crystal panel can be improved.

  The exposed surface of the pressure-sensitive adhesive layer is preferably covered with a separator for the purpose of preventing contamination until it is practically used. Thereby, it can prevent contacting an adhesive layer in the usual handling state. As the separator, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, nonwoven fabric, net, foamed sheet, metal foil, laminate thereof, or the like, silicone-based or long-chain alkyl-based, fluorine-based An appropriate material according to the prior art, such as those coated with an appropriate release agent such as molybdenum sulfide or molybdenum sulfide, can be used.

[Liquid Crystal Display]
The liquid crystal display device of the present invention includes the liquid crystal panel and means for supplying light to the liquid crystal panel such as a light source or a reflector. As an example of the liquid crystal display device of the present invention, a transmissive liquid crystal display device including a light source will be described. FIG. 13 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. The liquid crystal display device 300 includes at least a liquid crystal panel 100 and a backlight unit 200 disposed on one side of the liquid crystal panel 100. In the illustrated example, the case where the direct type is adopted as the backlight unit is shown, but this may be a side light type, for example.

  When the direct method is employed, the backlight unit 200 preferably includes a light source 81, a reflective film 82, and a prism sheet 84. Although not shown, it is also preferable to have a diffusion plate or a brightness enhancement film. When the side light system is adopted, preferably, in addition to the above-described configuration, a light guide plate and a light reflector are further provided. In addition, as long as the effect of this invention is acquired, the optical member illustrated in FIG. 13 may be partly omitted depending on the design of the illumination method of the liquid crystal display device, or may be replaced with another optical member. Can be done.

  The liquid crystal display device of the present invention can be used for any appropriate application, for example, OA equipment such as a personal computer monitor, a notebook personal computer, a copy machine, a mobile phone, a clock, a digital camera, and a personal digital assistant (PDA). , Portable devices such as portable game machines, household electrical equipment such as video cameras, televisions, microwave ovens, back monitors, car navigation system monitors, car audio and other in-vehicle devices, and information displays for commercial stores Security equipment such as monitoring monitors, nursing care and medical equipment such as nursing monitors and medical monitors. In particular, the liquid crystal display device of the present invention can be suitably used for large liquid crystal display devices such as televisions and information monitors.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the examples shown below. In addition, the measured value etc. which were used in the Example were obtained by the following methods.

[Measuring method]
(Optical rotation angle)
The optical rotation angle of the optical rotatory element was measured by the trade name “OPTIPRO” manufactured by Shintech.

(Thickness)
The thickness of the optical rotatory element was measured with a film thickness meter (trade name “MCPD2000” manufactured by Otsuka Electronics Co., Ltd.).

(Transmittance and Y value)
One hour after the backlight was turned on with the power of the liquid crystal display device turned on, the liquid crystal panel was displayed in black, and the transmittance and Y value at each viewing angle were measured using a trade name “EZ-contrast” manufactured by ELDIM. Note that the transmittance and the Y value are based on the luminance (100%) of the backlight unit of the liquid crystal display device (when the liquid crystal panel is not interposed).

[Production of optical rotatory element]
[Production Example 1]
(Preparation of liquid crystal coating liquid)
99.902 parts by weight of a nematic liquid crystalline material [trade name “Pariocolor LC242” (Δn ₅₄₅ = 0.1) manufactured by BASF], 0.0981 parts by weight of a chiral agent [trade name “Pariocolor LC756 manufactured by BASF” 270 parts by weight of 5 parts by weight of a UV polymerization initiator [trade name “Irgacure 907” manufactured by Ciba Japan], 0.5 parts by weight of a leveling agent [trade name “BYK370” manufactured by Big Chemie] A liquid crystal coating solution A having a concentration of 27% by weight was prepared.

(Formation of liquid crystal layer)
The obtained liquid crystal coating solution was applied onto an alignment film of polyvinyl alcohol using a # 15 wire bar. The liquid crystal layer was aligned while being dried in an oven at 90 ° C. for 3 minutes, and cured by irradiating 300 mJ / cm ² of UV light to obtain an optical rotatory element. The obtained optical rotatory element is referred to as an optical rotatory element A.

[Production Example 2]
(Preparation of liquid crystal coating liquid and formation of liquid crystal layer)
A liquid crystal coating solution B was prepared in the same manner as in Production Example 2 except that the composition of the coating solution was changed as shown in Table 3. The obtained liquid crystal coating liquid B was applied onto an alignment film of polyvinyl alcohol using a # 30 wire bar. The liquid crystal layer was oriented while being dried in an oven at 90 ° C. for 5 minutes, and cured by irradiating 300 mJ / cm ² of UV light to obtain an optical rotatory element. The obtained optical rotatory element is referred to as an optical rotatory element B.

[Production Example 3]
(Preparation of liquid crystal coating liquid and formation of liquid crystal layer)
A liquid crystal coating solution C was prepared in the same manner as in Production Example 1 except that the composition of the coating solution was changed as shown in Table 3.
(Formation of liquid crystal layer)
The obtained liquid crystal coating liquid C was applied onto a polyvinyl alcohol alignment film using a # 20 wire bar. This was dried in an oven at 90 ° C. for 5 minutes to orient the liquid crystal layer and cured by irradiating 300 mJ / cm ² of UV light to obtain a liquid crystal solidified layer (liquid crystal layer having a liquid crystal twist angle of 45 °). The liquid crystal coating liquid C is further applied onto the obtained liquid crystal solidified layer using a # 20 wire bar, then dried again in an oven at 90 ° C. for 5 minutes, and irradiated with 300 mJ / cm ² of UV light. To obtain a liquid crystal layer having a twist angle of 90 ° for the liquid crystal. This is an optical rotation element C.

[Production Example 4]
(Preparation of liquid crystal coating liquid and formation of liquid crystal layer)
A liquid crystal coating solution D was prepared in the same manner as in Production Example 1 except that the composition of the coating solution was changed as shown in Table 3. The obtained liquid crystal coating layer D was coated, dried and cured twice using a # 28 wire bar in the same manner as in Production Example 3 to prepare a liquid crystal layer having a liquid crystal twist angle of 90 °. . This is an optical rotation element D.

[Production Example 5]
(Preparation of liquid crystal coating liquid and formation of liquid crystal layer)
A liquid crystal coating solution E was prepared in the same manner as in Production Example 1 except that the composition of the coating solution was changed as shown in Table 3.
(Formation of liquid crystal layer)
The obtained liquid crystal coating solution E was applied onto a polyvinyl alcohol alignment film using a # 24 wire bar. This was dried in an oven at 90 ° C. for 5 minutes to orient the liquid crystal layer, and cured by irradiating 300 mJ / cm ² of UV light to obtain a liquid crystal solidified layer (liquid crystal layer having a liquid crystal twist angle of 30 °). The liquid crystal coating liquid E is further applied onto the obtained liquid crystal solidified layer using a # 24 wire bar and then dried again in an oven at 90 ° C. for 5 minutes to apply, dry and cure the liquid crystal layer. Repeated twice, a liquid crystal layer having a liquid crystal twist angle of 90 ° was produced. This is the optical rotation element E

[Production Example 6]
(Preparation of liquid crystal coating liquid and formation of liquid crystal layer)
A liquid crystal coating solution F was prepared in the same manner as in Production Example 1 except that the composition of the coating solution was changed as shown in Table 3. Using the # 30 wire bar, the obtained liquid crystal coating layer F was coated, dried and cured three times in the same manner as in Production Example 5 to produce a liquid crystal layer having a liquid crystal twist angle of 90 °. . This is an optical rotation element F.

  The thicknesses of the optical rotators A to F obtained in Production Examples 1 to 6 are m = 1, 2, 3, 4, 5, 6 when the wavelength λ = 545 nm in the formula (1), respectively. It corresponds to the thickness.

[Production Examples 7 to 12]
In the production example 1, the following compound (Δn ₅₄₅ = 0.3) was used as the nematic liquid crystalline material instead of “Pariocolor LC242”, the composition ratio of the liquid crystal coating liquids G to L, and the wire bar used for coating Optical rotatory elements G to L were obtained in the same manner as in Production Example 1 except that the counts were as shown in Table 4.

[Production Examples 13 to 14]
In Production Example 3, instead of “Pariocolor LC242” as the nematic liquid crystalline material, the following compound (Δn ₅₄₅ = 0.3) was used, the composition ratio of the liquid crystal coating liquids M and N, and the wire bar used for coating A liquid crystal layer having a twist angle of 90 ° was prepared by repeating application, drying and curing of the liquid crystal layer twice in the same manner as in Production Example 3 except that the counts were as shown in Table 4. These are optical rotation elements M and N, respectively.

The thicknesses of the optical rotatory elements G to L obtained in the above Production Examples 7 to 12 are m = 1, 2, 3, 4, 5, 6 when the wavelength λ = 545 nm in the formula (1), respectively. It corresponds to the thickness. The optical rotatory element N obtained in Production Example 14 corresponds to a thickness of m = 11. On the other hand, in the thickness of the optical rotatory element M obtained in Production Example 13, m is not an integer when the wavelength λ = 545 nm in the formula (1), and the optical rotatory element M has a thickness of m = 8.27. It corresponds to.

[Production of laminated polarizing plate]
[Production Example 15]
(Transfer of optical rotation element)
The optical rotatory element C obtained in Production Example 3 is substantially optically isotropic (front phase difference is 0.5 nm or less, thickness direction retardation is 1.0 nm or less) as protective films on both sides of the polarizer. The polarizing plate has an absorption axis direction and optical rotation on a commercially available polarizing plate [trade name “NPF SIG1423DU” manufactured by Nitto Denko, single transmittance: 42.6%, polarization degree: 99.99%, manufactured by Nitto Denko]. An optical rotation element was formed by transferring the film by removing the alignment film after laminating via an acrylic adhesive so that the alignment direction of the liquid crystal molecules on the surface facing the polarizing plate of the element was orthogonal. A laminated polarizing plate C was produced.

[Production Example 16]
A laminated polarizing plate E in which an optical rotation layer was laminated was produced in the same manner as in Production Example 15 except that the optical rotatory element E was used in place of the optical rotatory element C in Production Example 15.

[Production Example 17]
A laminated polarizing plate I in which optical rotation layers were laminated was produced in the same manner as in Production Example 15 except that the optical rotatory element I was used in place of the optical rotatory element C in Production Example 15.

[Production Example 18]
A laminated polarizing plate J in which an optical rotatory layer was laminated was produced in the same manner as in Production Example 15 except that the optical rotatory element J was used in place of the optical rotatory element C in Production Example 15.

[Reference Example 1]
(Backlight)
A liquid crystal panel was removed from Sharp's liquid crystal television product name “AQUAS LC46RX1W” and used as a single backlight.
(Measurement of polarizing plate characteristics)
The laminated polarizing plate C obtained in Production Example 15 and a commercially available polarizing plate [trade name “NPF SIG1423DU” manufactured by Nitto Denko] were disposed so that both absorption axes were parallel. However, the laminated polarizing plate C was disposed so that the surface having the optical rotatory element faces the other polarizing plate. This was placed on the backlight taken out from the above liquid crystal television, and the transmittance and Y value were measured.

[Reference Examples 2 to 4]
In the above Reference Example 1, in place of the laminated polarizing plate C, the polarizing plate was parallel to the backlight in the same manner as in Reference Example 1 except that the laminated polarizing plates E, I and J obtained in Production Examples 16 to 18 were used. The transmittance and Y value were measured.
[Comparative Production Example 1]
Uniaxially stretched polycarbonate film having a phase difference at 545 nm of 273 nm and an Nz coefficient of 1 (trade name “Elmec R film” manufactured by Kaneka) and the polarizing plate (trade name “NPF SIG1423DU” manufactured by Nitto Denko) A laminated polarizing plate in which a retardation layer was formed was laminated by using an acrylic pressure-sensitive adhesive so that the angle formed by the slow axis direction of the polycarbonate film and the absorption axis direction of the polarizing plate was 45 °. .

[Comparative Production Example 2]
A norbornene-based resin film [trade name “ZEONOR FILM” manufactured by Nippon Zeon Co., Ltd.] having a retardation at 545 nm and an Nz coefficient of 1 formed by uniaxial stretching, and the polarizing plate [trade name “NPF SIG1423DU manufactured by NITTO DENKO”] ]] Is laminated using an acrylic pressure-sensitive adhesive so that the angle formed by the slow axis direction of the norbornene-based resin film and the absorption axis direction of the polarizing plate is 45 °, and a retardation layer is formed. A polarizing plate was produced.

[Comparative Reference Example 1]
In the above Reference Example 1, instead of the laminated polarizing plate C, the polarizing plate was placed on the backlight in the same manner as in Reference Example 1 except that the laminated polarizing plate obtained by laminating the polycarbonate film obtained in Comparative Production Example 1 was used. Arranged in parallel, the transmittance and Y value were measured.

[Comparative Reference Example 2]
In the above Reference Example 1, the polarizing plate was placed on the backlight in the same manner as in Reference Example 1, except that the laminated polarizing plate C obtained by laminating the norbornene-based film obtained in Comparative Production Example 2 was used instead of the laminated polarizing plate C. The transmittance and Y value were measured.

[Comparative Reference Example 3]
Two commercially available polarizing plates [trade name “NPF SIG1423DU” manufactured by Nitto Denko] were placed on the backlight so that the absorption axes thereof were orthogonal to each other, and the transmittance and Y value were measured.

  Table 5 shows the types of optical rotatory elements (or retardation plates) used in Reference Examples 1 to 4 and Comparative Reference Examples 1 to 3, and the measurement results of Y value (%) on the backlight. Moreover, the viewing angle distribution (cone figure) of the measurement result of Y value is shown in FIGS. In Table 5 and FIGS. 14 to 20, the absorption axis direction of the polarizing plate disposed on the upper side (side away from the backlight) is the azimuth angle reference (0 °), and the normal direction of the screen (front view). It is expressed as a polar angle reference (0 °).

  In Comparative Reference Example 1 (FIG. 18) using a polycarbonate retardation plate, light leakage occurs in the front direction due to the influence of the wavelength dependence of the retardation of the polycarbonate retardation film. Moreover, in the diagonal direction, it turns out that a light leak is large compared with the comparative reference example 3 (FIG. 20) which has arrange | positioned the polarizing plate orthogonally (cross Nicol). On the other hand, in Comparative Production Example 2 (FIG. 19) using a norbornene-based film, since the wavelength dependence of the retardation is small compared to the polycarbonate film, light leakage at the front is small, but Comparative Reference Example 3 Compared to the above, there was no change in light leakage. Further, the amount of light leakage in the oblique direction was substantially the same as in Comparative Reference Example 2.

  On the other hand, in Reference Examples 1 to 4 (FIGS. 14 to 17) using an optical rotatory element, although slightly inferior to Comparative Reference Example 3, compared to Comparative Reference Examples 1 and 2, the front and oblique directions It can be seen that the light leakage is remarkably improved. In particular, in Reference Examples 2 and 4 where the thickness is large, it can be seen that light leakage is improved in both the front and diagonal directions.

[Reference Example 5]
When the optical rotation element having a twist angle (optical rotation angle) of 90 ° for the liquid crystal layer is manufactured by the nematic liquid crystalline material used in the manufacture of the optical rotation elements of Production Examples 1 to 6, the thickness d of the optical rotation element is variously changed. In this case, the transmittance T (%) and the Y value (%) at a wavelength of 545 nm were calculated based on the equations (2) and (3). FIG. 21 shows the calculation results represented in a graph of horizontal axis: thickness, vertical axis: transmittance T or Y value. 21A and 21B are obtained by changing the scale of the horizontal axis (thickness) of the same graph.

[Reference Example 6]
When the optical rotation element whose twist angle (optical rotation angle) of the liquid crystal layer is 90 ° is manufactured by the nematic liquid crystalline material used in the manufacture of the optical rotation elements of the manufacturing examples 7 to 14, the thickness d of the optical rotation element is variously changed. In this case, the transmittance T (%) and the Y value (%) at a wavelength of 545 nm were calculated based on the equations (2) and (3). FIG. 22 shows the calculation results represented in a graph of horizontal axis: thickness, vertical axis: transmittance T or Y value. 22A and 22B are obtained by changing the scale of the horizontal axis (thickness) of the same graph.

As understood from FIGS. 21 and 22, the transmittance T has a minimum value in the thickness where m is an integer in the equation (1), whereas the Y value is in a region where the thickness is small. Although it shows a tendency to increase or decrease similar to the transmittance T, the behavior differs from the transmittance T as the thickness increases. As the thickness increases, a monotonic decrease appears. The change point appears in a region where Δn ₅₄₅ × d = 1400 nm.

[Evaluation of the effect of axial misalignment]
[Reference Example 7]
In the production example 14, instead of the alignment direction of the liquid crystal molecules on the surface facing the polarizing plate of the optical rotatory element E being orthogonal to the absorption axis direction of the polarizing plate, the angle between the two is changed from 90 ° to 0.5 °, respectively. Laminated polarizing plates arranged at an angle of 1 °, 2 ° were prepared, and were arranged so that the absorption axes of the polarizing plates were parallel as in Reference Example 1, and the transmittance and Y value were measured.

[Reference Example 8]
In Production Example 16, instead of the orientation direction of the liquid crystal molecules on the surface facing the polarizing plate of the optical rotatory element J being orthogonal to the absorption axis direction of the polarizing plate, the angle between the two is changed from 90 ° to 0.5 °, respectively. A laminated polarizing plate arranged with a shift of 1 °, 2 ° was prepared, and placed on the backlight so that the absorption axis of the polarizing plate was parallel, as in Reference Example 1, and the transmittance and Y value were measured. did.

  Table 6 shows the measurement result of the Y value on the backlight of Reference Example 7, and FIG. 23 shows the viewing angle distribution (cone diagram) of the measurement result of the Y value. Further, Table 7 shows the Y value measurement results on the backlight of Reference Example 8, and FIG. 24 shows the viewing angle distribution (cone diagram) of the Y value measurement results. Note that FIGS. 23 and 24 (a), (b), and (c) represent cases where the angle of the axis deviation is 0.5 °, 1 °, and 2 °, respectively. The reference of the angle is the same as in the case of the reference examples 1 to 4.

[Production of liquid crystal panel and liquid crystal display device including cellulose-based retardation film]
[Example 1]
(Liquid crystal cell)
Take out the liquid crystal panel from a commercially available liquid crystal display device equipped with a VA mode liquid crystal panel [Sharp's liquid crystal television product name “AQUIS LC46RX1W”], remove all the optical films placed above and below the liquid crystal cell, and A liquid crystal cell having a cleaned glass surface (front and back) was used.

(Production of light source side polarizing plate)
A laminated polarizing plate A in which optical rotation layers were laminated was produced in the same manner as in Production Example 15 except that the optical rotator A was used in place of the optical rotator C in Production Example 15. On the side of the laminated polarizing plate A provided with the optical rotation layer, a cellulose-based retardation film having a retardation at 545 nm of 50 nm, a retardation in the thickness direction of 150 nm, and an Nz coefficient of 3 [trade name “N- manufactured by Konica Minolta” TAC KC4HR-1 "] was laminated via an acrylic pressure-sensitive adhesive so that the slow axis of the retardation film and the absorption axis of the polarizing plate were parallel to each other.
(Preparation of viewing side polarizing plate)
On one side of a commercially available polarizing plate [trade name “NPF SIG1423DU” manufactured by Nitto Denko], a cellulose-based retardation film similar to the above is acrylic based so that the slow axis of the retardation film and the absorption axis of the polarizing plate are orthogonal to each other. It laminated | stacked through the adhesive of this.
(Production of liquid crystal display device)
The light source side polarizing plate and the visual recognition side polarizing plate prepared above were bonded to the front and back of the liquid crystal cell using an acrylic adhesive to prepare a liquid crystal panel. At the time of bonding, the viewing side polarizing plate having no optical rotatory element is arranged so that the absorption axis direction is the same as the light source side polarizing plate arranged in the original liquid crystal panel, and the viewing side polarizing plate having the optical rotatory element is arranged. The plate was arranged so that the absorption axis direction was orthogonal to the light source side polarizing plate arranged in the original liquid crystal panel, and the absorption axes of the two polarizing plates were made parallel.
The liquid crystal panel thus obtained was reassembled with the backlight unit of the original liquid crystal display device as the backlight of the original liquid crystal display device to produce a liquid crystal display device.

[Examples 2 to 12]
In the production of the light source side polarizing plate of Example 1, two sheets were obtained in the same manner as in Example 1 except that the optical rotators B to E and the optical rotators G to K, M, and N were used instead of the optical rotator A. A liquid crystal display device having a liquid crystal panel in which the absorption axes of the polarizing plates were arranged in parallel was produced.

[Comparative Example 1]
In the production of the light source side polarizing plate of Example 1 above, instead of the laminated polarizing plate A, the laminated polarizing plate on which the polycarbonate retardation layer obtained in Comparative Production Example 1 was formed was used. On the side provided with the retardation layer, the same cellulose-based retardation film as described above was laminated via an acrylic pressure-sensitive adhesive so that the slow axis of the retardation film and the absorption axis of the polarizing plate were parallel. A liquid crystal display device including a liquid crystal panel in which the absorption axes of two polarizing plates were arranged in parallel was prepared in the same manner as in Example 1 except that this light source side polarizing plate was used.

[Comparative Example 2]
In Comparative Example 1, the same procedure as in Comparative Example 1 was used except that the laminated polarizing plate formed with the norbornene-based retardation layer obtained in Comparative Production Example 2 was used instead of the laminated polarizing plate of Comparative Production Example 1. A liquid crystal display device including a liquid crystal panel in which absorption axes of two polarizing plates are arranged in parallel was produced.

[Comparative Example 3]
In Example 1 above, as the light source side polarizing plate, similarly to the viewing side polarizing plate of Example 9, a cellulose-based retardation film is placed on one side of a polarizing plate [trade name “NPF SIG1423DU” manufactured by Nitto Denko]. Using a laminate with an acrylic adhesive so that the slow axis of the retardation film and the absorption axis of the polarizing plate are orthogonal to each other, both the light source side polarizing plate and the viewing side polarizing plate are arranged in the original liquid crystal panel. It was laminated on the liquid crystal cell via an acrylic pressure-sensitive adhesive so that the absorption axis direction was the same, that is, the absorption axis directions of the viewing side polarizing plate and the light source side polarizing plate were orthogonal. This was reassembled with the backlight unit of the original liquid crystal display device to produce a liquid crystal display device in which the absorption axes of the two polarizing plates were arranged orthogonally.

  The transmittance and Y value were measured when the liquid crystal display devices of Examples 1 to 12 and Comparative Examples 1 to 3 were set to black display. The Y value is shown in Table 7, and the viewing angle distribution (cone diagram) of the Y value measurement results is shown in FIGS. Furthermore, the transmission spectrum at the time of carrying out black display of the liquid crystal display device of Examples 3-5, 8-10 and Comparative Examples 1-3 is shown to FIGS. 40 to 48, (a) shows an azimuth angle of 0 ° direction (absorption axis direction of the viewing side polarizing plate), and (b) shows a polar angle change (0 °, 30 °, 60 °) in an azimuth angle of 45 ° direction. The transmission spectrum is shown. The angle is determined by setting the long side direction (right side) of the screen of the liquid crystal display device as an azimuth reference (0 °).

When comparing FIGS. 25 to 36 according to the examples and FIGS. 37 and 38 according to comparative examples 1 and 2, the present invention using the optical rotator element used the retardation film even when incorporated in a liquid crystal display device. As compared with the case, it can be seen that the transmittance is low in a wide region of visible light, and as a result, the Y value is also small, and a black display with little color is obtained. In particular, in Examples 3 to 5 and 8 to 12 in which Δn ₅₄₅ × d is 1400 nm or more, light leakage in the azimuth angle 45 ° direction is suppressed in addition to the front direction, and the thickness of the optical rotation element is adjusted. Thus, it can be seen that a black display that is less colored and that is comparable to Comparative Example 3 (FIG. 39) in which the polarizing plate is arranged in crossed Nicols can be obtained.

Thus, it is clear from the transmittance spectra of FIGS. 40 to 48 that the Y value can be reduced by using the optical rotation element. That is, in Comparative Examples 1 and 2 (FIGS. 46 and 47) using a retardation film, the transmittance is small near 545 nm where the retardation is ¼ of the wavelength, but the transmittance at other wavelengths is low. Since the screen is colored and the Y value is large due to the large size, in the embodiment, the difference in transmittance due to such a wavelength is small, which is more neutral than when a retardation plate is used. Can be obtained. It can be seen that this tendency becomes more prominent as Δn ₅₄₅ × d of the optical rotation element increases. Furthermore, it can be seen that in a liquid crystal panel using an optical rotator as in the present invention, optical compensation can be performed using an optical compensation layer similar to that of a conventional liquid crystal panel.

  Furthermore, in Example 11 (FIG. 35) using the optical rotator M, when the thickness of the optical rotator M is near the wavelength of 545 nm, m is not an integer, but as compared with Examples 6 to 10 where m is an integer. Therefore, good display characteristics with little light leakage are obtained. This confirms that the Y value is not necessarily minimized when m is an integer in the equation (1), as previously shown in Reference Examples 5 and 6 (FIGS. 23 and 24). It can be said.

[Evaluation of influence of thickness shift of optical rotation element]
[Reference Example 9]
In Example 6, instead of the optical rotator G, the liquid crystal layer thickness of the optical rotator G is 0.1 μm, 0.2 μm, 0.3 μm, 0.4, and 0.5 μm thick, respectively. A liquid crystal panel was prepared in the same manner as in Example 6 except that it was equipped with a cellulosic phase difference film, and the absorption axes of two polarizing plates were arranged in parallel, and this was reassembled with a backlight unit. A display device was produced.

  Table 9 shows the Y value at the time of black display of each liquid crystal display device in which the thickness of the liquid crystal layer of the optical rotatory element was changed in this way, and FIG. 49 shows the viewing angle distribution (cone diagram) of the measurement result of the Y value. 49, (a) is the same as Example 6 (FIG. 30), and (b), (c), (d), (e), and (f) each have a liquid crystal layer thickness of 0.1 μm. , 0.2 μm, 0.3 μm, 0.4 μm, and 0.5 μm thick optical rotatory elements are used.

[Reference Example 10]
In Example 7, instead of the optical rotator H, liquid crystal layer thicknesses of the optical rotator H were respectively made 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, and 0.5 μm thick, A liquid crystal panel having a cellulose phase difference film and having two polarizing plates arranged in parallel was prepared in the same manner as in Example 2 except that it was used, and the liquid crystal panel was reassembled with the backlight unit. A display device was produced.

  Table 10 shows the Y value at the time of black display of each liquid crystal display device in which the thickness of the liquid crystal layer of the optical rotator is changed in this way, and FIG. 50 shows the viewing angle distribution (cone diagram) of the measurement result of the Y value. In FIG. 50, (a) is the same as Example 7 (FIG. 31), and (b), (c), (d), (e), and (f) each have a liquid crystal layer thickness of 0.1 μm. , 0.2 μm, 0.3 μm, 0.4 μm, and 0.5 μm thick optical rotatory elements are used.

  In Example 8, in place of the optical rotator I, liquid crystal layer thicknesses of the optical rotator I were respectively made 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, and 0.5 μm thick, A liquid crystal panel having a cellulose-based phase difference film and having two polarizing plates arranged in parallel was prepared in the same manner as in Example 8 except that it was used, and the liquid crystal panel was reassembled with the backlight unit. A display device was produced.

  The Y value at the time of black display of each liquid crystal display device in which the thickness of the liquid crystal layer of the optical rotator is changed is shown in Table 11, and the viewing angle distribution (cone diagram) of the measurement result of the Y value is shown in FIG. 51, (a) is the same as Example 8 (FIG. 32), and (b), (c), (d), (e), and (f) each have a liquid crystal layer thickness of 0.1 μm. , 0.2 μm, 0.3 μm, 0.4 μm, and 0.5 μm thick optical rotatory elements are used.

  In Table 9 above, when the thickness of the optical rotatory element is exactly m = 1 in the formula (1), the Y value at each viewing angle is minimized, and the Y value increases as the thickness increases by 0.1 μm. Tend. On the other hand, in Table 10, when the thickness of the optical rotatory element is 0.1 μm or 0.2 μm larger than when m = 2 in the formula (1), the Y value at each viewing angle is small. In Table 11, when the thickness is 0.4 μm larger than when m = 3, the Y value in the front and diagonal directions is the smallest. Thus, it can be seen that the thickness at which the transmittance T at a wavelength of 545 nm is minimized and the thickness at which the Y value is minimized. Thus, in carrying out the present invention, in order to minimize the transmittance T at a specific wavelength, chromatic dispersion is considered rather than designing the thickness so that m in Equation (1) is just an integer. Thus, it is understood that it is preferable to design the thickness so that the Y value is minimized.

  Further, comparing Tables 9 to 11 and FIGS. 49 to 51, in Reference Example 9 in which the thickness of the optical rotatory element is small, the change in display characteristics due to the change in thickness is large, whereas the thickness increases as the thickness of the optical rotatory element is increased. A change in display characteristics due to the change is suppressed. In this way, by designing the thickness of the optical rotatory element, it is possible to reduce the effect of thickness variations due to production conditions etc. on the liquid crystal display characteristics, so the manufacturing condition width (process window) should be widened. It is possible and is excellent in mass productivity.

[Effect of optical axis misalignment]
[Reference Example 12]
In Example 8 above, instead of the orientation direction of the liquid crystal molecules on the surface facing the polarizing plate of the optical rotatory element I being orthogonal to the absorption axis direction of the polarizing plate, the angle formed by both is changed from 90 ° to 1 °, respectively. A liquid crystal panel in which the absorption axes of two polarizing plates are arranged in parallel is provided in the same manner as in Example 8 except that a laminated polarizing plate arranged by shifting by 2 °, 3 °, 4 °, and 5 ° is prepared. A liquid crystal display device was produced.

  Table 12 shows the Y value at the time of black display of each liquid crystal display device in which the arrangement angle of the optical rotatory element is shifted from the orthogonal direction, and FIG. 52 shows the viewing angle distribution (cone diagram) of the measurement result of the Y value. In FIG. 52, (a) is the same as that of the eighth embodiment (FIG. 32), and (b), (c), (d), (e), and (f) each indicate the arrangement angle of the optical rotator I by 1. Corresponding to the case of shifting by 2 °, 3 °, 4 °, 5 °.

[Reference Example 13]
In Example 9, instead of the orientation direction of the liquid crystal molecules on the surface facing the polarizing plate of the optical rotatory element J being orthogonal to the absorption axis direction of the polarizing plate, the angle between the two is changed from 90 ° to 1 °, respectively. A liquid crystal panel in which the absorption axes of two polarizing plates are arranged in parallel is provided in the same manner as in Example 9 except that a laminated polarizing plate arranged by shifting by 2 °, 3 °, 4 °, and 5 ° is prepared. A liquid crystal display device was produced.

  Table 12 shows the Y value at the time of black display of each liquid crystal display device in which the arrangement angle of the optical rotatory element is shifted from the orthogonal direction, and FIG. 52 shows the viewing angle distribution (cone diagram) of the measurement result of the Y value. In FIG. 52, (a) is the same as that of the eighth embodiment (FIG. 32), and (b), (c), (d), (e), and (f) each indicate the arrangement angle of the optical rotator I by 1. Corresponding to the case of shifting by 2 °, 3 °, 4 °, 5 °.

[Production of liquid crystal panel and liquid crystal display device including norbornene-based retardation film]
[Example 13]
(Production of light source side polarizing plate)
The optical rotatory element G is used as the optical rotatory element, and instead of the cellulose-based retardation film in Example 1, biaxially stretched, the retardation at 545 nm is 50 nm, the thickness direction retardation is 150 nm, and the Nz coefficient is 3. Is a norbornene-based retardation film [trade name “ZEONOR FILM” made by ZEON Corporation] and a polarizing plate [trade name “NPF SIG1423DU” made by NITTO DENKO], and the retardation axis of the retardation film and the absorption axis of the polarizer are parallel. It laminated | stacked through the acrylic adhesive so that it might become.

(Preparation of viewing side polarizing plate)
A norbornene-based retardation film similar to the above is applied to one side of a commercially available polarizing plate [trade name “NPF SIG1423DU” manufactured by Nitto Denko], and acrylic so that the slow axis of the retardation film and the absorption axis of the polarizing plate are orthogonal to each other. It laminated | stacked through the adhesive of this.

(Production of liquid crystal display device)
In the production of the liquid crystal panel of Example 1, a liquid crystal in which the absorption axes of the two polarizing plates are arranged in parallel in the same manner except that the light source side polarizing plate and the viewing side polarizing plate are prepared as described above. A liquid crystal display device having a panel was produced.

[Examples 14 to 19]
Two polarizing plates were produced in the same manner as in Example 13 except that optical rotation elements H, I, J, K, M, and N were used in place of the optical rotation element G in the production of the light source side polarizing plate of Example 13. A liquid crystal display device comprising a liquid crystal panel in which the absorption axes of these were arranged in parallel was produced.

[Comparative Example 5]
In the above Example 13, as the light source side polarizing plate, similarly to the viewing side polarizing plate in Example 13, a norbornene-based retardation film is placed on one side of a polarizing plate [trade name “NPF SIG1423DU” manufactured by Nitto Denko]. Using a laminate with an acrylic adhesive so that the slow axis of the retardation film and the absorption axis of the polarizing plate are orthogonal to each other, both the light source side polarizing plate and the viewing side polarizing plate are arranged in the original liquid crystal panel. It was laminated on the liquid crystal cell via an acrylic pressure-sensitive adhesive so that the absorption axis direction was the same, that is, the absorption axis directions of the viewing side polarizing plate and the light source side polarizing plate were orthogonal. This was reassembled with the backlight unit of the original liquid crystal display device to produce a liquid crystal display device in which the absorption axes of the two polarizing plates were arranged orthogonally.

  The transmittance and Y value were measured when the liquid crystal display devices of Examples 13 to 19 and Comparative Example 4 were set to black display. The Y value is shown in Table 14, and the viewing angle distribution (cone diagram) of the measurement result of the Y value is shown in FIGS. The angle is determined by setting the long side direction (right side) of the screen of the liquid crystal display device as an azimuth reference (0 °).

[Production of liquid crystal panel and liquid crystal display device with polyimide coating layer]
[Example 20]
(Optical compensation layer)
In the same manner as in Example 1 of JP-A-2004-78203, 2,2′bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride and 2,2′-bis (trifluoromethyl)- A phase difference plate in which a polyimide optical compensation layer was formed on a triacetyl cellulose (TAC) film substrate was produced by applying and processing a polyimide synthesized from 4,4′-diaminobiphenyl on a substrate. The optical compensation layer had a phase difference at 545 nm of 55 nm and a thickness direction retardation of 200 nm (Nz coefficient was 3.6).

(Production of light source side polarizing plate)
In Example 1 using the optical rotator G as the optical rotator, a retardation film having a polyimide optical compensation layer formed on the TAC film substrate was used instead of the cellulose-based retardation film. Lamination was performed with an acrylic adhesive so that the axis and the absorption axis of the polarizing plate were parallel. In addition, at the time of lamination | stacking, it laminated | stacked so that the TAC film side of retardation film might oppose an optical rotatory element.

(Preparation of viewing side polarizing plate)
A commercially available polarizing plate [trade name “NPF SIG1423DU” manufactured by Nitto Denko] was used as it was.

(Production of liquid crystal display device)
In the production of the liquid crystal panel of Example 1, a liquid crystal in which the absorption axes of the two polarizing plates are arranged in parallel in the same manner except that the light source side polarizing plate and the viewing side polarizing plate are prepared as described above. A liquid crystal display device having a panel was produced.

[Examples 21 to 26]
In the production of the light source side polarizing plate of Example 20, two optical sheets were used in the same manner as in Example 20 except that optical rotators H, I, J, K, L, M, and N were used instead of the optical rotator G. A liquid crystal display device including a liquid crystal panel in which the absorption axes of the polarizing plates are arranged in parallel was produced.

[Comparative Example 5]
In Example 20, a retardation film in which a polyimide optical compensation layer is formed on the same TAC film substrate as in Example 27 without using the optical rotator G as a light source side polarizing plate is used as a retardation film. A layer laminated with an acrylic pressure-sensitive adhesive so that the phase axis and the absorption axis of the polarizing plate were parallel to each other was used. The viewing side polarizing plate is the same as that in Example 20, and both the light source side polarizing plate and the viewing side polarizing plate have the same absorption axis direction as that of the original liquid crystal panel, that is, the viewing side polarizing plate. Were laminated on the liquid crystal cell with an acrylic adhesive so that the absorption axis directions of the light source side polarizing plate were orthogonal to each other. This was reassembled with the backlight unit of the original liquid crystal display device to produce a liquid crystal display device in which the absorption axes of the two polarizing plates were arranged orthogonally.

  The transmittance and the Y value were measured when the liquid crystal display devices of Examples 20 to 26 and Comparative Example 5 were set to black display. The Y value is shown in Table 15, and the viewing angle distribution (cone diagram) of the measurement result of the Y value is shown in FIGS. The angle is determined by setting the long side direction (right side) of the screen of the liquid crystal display device as an azimuth reference (0 °).

  As can be seen from Examples 13 to 19 and Examples 20 to 26, the liquid crystal panel of the present invention using an optical rotator can obtain a black display with a small Y value even in various optical compensation modes. . In particular, by controlling the thickness of the optical rotatory element, it can be seen that display characteristics comparable to those of a conventional liquid crystal display device in which polarizing plates are arranged in crossed Nicols can be obtained.

  In each of the above examples, comparative examples, etc., in order to facilitate the comparison of differences depending on the configuration, the protective film of the polarizer and the optical compensation layer were provided separately in all examples. As described above, a single film can be provided with a plurality of functions such as a polarizer protective film, an optical compensation layer, and an alignment substrate for a liquid crystal layer forming an optical rotatory element.

  As described above, as shown in the respective embodiments, the liquid crystal panel using the optical rotatory element of the present invention can obtain a black display with little color loss even when the polarizing plates are arranged in parallel. In particular, by adjusting the thickness of the liquid crystal layer, it is possible to obtain a good black display with little color and no inferiority compared to the case where conventional polarizing plates are arranged orthogonally. In the liquid crystal panel of the present invention, the viewing angle characteristics can be improved by an optical compensation layer such as a retardation film, as in the conventional liquid crystal panel in which two polarizing plates are arranged orthogonally.

  Moreover, since it arrange | positions so that the absorption axis of two polarizing plates may become parallel in the front and back of a liquid crystal cell, it can contribute to the enlargement and the improvement of the removal rate of a polarizing plate.

It is a conceptual diagram showing a mode that two polarizing plates are cut out from a elongate polarizing plate. (A) shows a case where two polarizing plates whose absorption axes are orthogonal are cut out (conventional technology), and (b) shows a case where two polarizing plates whose absorption axes are parallel are cut out (present invention). 1 is a schematic cross-sectional view of a liquid crystal panel according to an embodiment of the present invention. The schematic perspective view of the liquid crystal panel of this invention is represented. It is a figure for demonstrating the natural light, the linearly polarized light, and the dark state in the figure showing the principle of the liquid crystal panel of this invention. It is a conceptual diagram which represents typically the principle of the black display in the conventional liquid crystal display device. It is a conceptual diagram which represents typically the principle of the black display in the liquid crystal display device using the liquid crystal panel of this invention. It is a conceptual diagram showing the conversion of the polarization state on Poincare when a phase difference plate is used. (A) is a sketch, (b) is a projection onto the S ₂ -S ₃ plane, (c) is a projection onto the S ₃ -S ₁ plane, and (d) is a projection onto the S ₁ -S ₂ plane. Represents It is a conceptual diagram showing conversion of the polarization state on Poincare at the time of using an optical rotatory element. (A) is a sketch, (b) is a projection onto the S ₂ -S ₃ plane, (c) is a projection onto the S ₃ -S ₁ plane, and (d) is a projection onto the S ₁ -S ₂ plane. Represents It is a conceptual diagram showing conversion of the polarization state on Poincare at the time of using an optical rotatory element. (A) is a sketch, (b) is a projection onto the S ₂ -S ₃ plane, (c) is a projection onto the S ₃ -S ₁ plane, and (d) is a projection onto the S ₁ -S ₂ plane. Represents It is a conceptual diagram showing the conversion of the polarization state on Poincare when a phase difference plate is used. It is a conceptual diagram showing conversion of the polarization state on Poincare at the time of using an optical rotatory element. It is a conceptual diagram showing conversion of the polarization state on Poincare at the time of using an optical rotatory element. It is a schematic sectional drawing showing an example of the liquid crystal display device by embodiment of this invention. It is a figure showing the measurement result of Y value in reference example 1. It is a figure showing the measurement result of Y value in reference example 2. It is a figure showing the measurement result of Y value in reference example 3. It is a figure showing the measurement result of Y value in reference example 4. It is a figure showing the measurement result of Y value in comparative reference example 1. It is a figure showing the measurement result of Y value in comparative reference example 2. It is a figure showing the measurement result of Y value in comparative reference example 2. Calculation of transmittance T (%) and Y value (%) at a wavelength of 545 nm in the case where an optical rotatory element having a twist angle of 90 ° for the liquid crystal layer is manufactured by changing the thickness d of the optical rotatory element by using a nematic liquid crystalline material. It is a graph showing a result. (A) And (b) changes the scale of the horizontal axis (thickness) of the same graph. Calculation results of transmittance T (%) and Y value (%) at a wavelength of 545 nm in a case where an optical rotatory element having a twist angle of 90 ° in a liquid crystal layer is manufactured by changing the thickness of the optical rotatory element by using a nematic liquid crystalline material. It is a graph showing. (A) And (b) changes the scale of the horizontal axis (thickness) of the same graph. It is a figure showing the influence on the Y value of the arrangement | positioning axis shift of the optical rotation element in the reference example 5. FIG. (A), (b), and (c) show the cases where the angle of the axis deviation is 0.5 °, 1 °, and 2 °, respectively. It is a figure showing the influence on the Y value of the arrangement | positioning axis | shaft deviation of the optical rotation element in the reference example 6. FIG. (A), (b), and (c) show the cases where the angle of the axis deviation is 0.5 °, 1 °, and 2 °, respectively. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 1. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 2. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 3. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 4. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 5. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 6. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 7. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 8. It is a figure showing the measurement result of Y value in the liquid crystal display of Example 9. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 10. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 11. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 12. It is a figure showing the measurement result of Y value in the liquid crystal display of comparative example 1. It is a figure showing the measurement result of Y value in the liquid crystal display of comparative example 2. It is a figure showing the measurement result of Y value in the liquid crystal display of comparative example 3. It is a figure showing the Y value spectrum in the liquid crystal display device of Example 3. (A) shows the azimuth angle 0 ° method, and (b) shows the transmission spectrum when the polar angle is changed in the azimuth angle 45 ° direction. It is a figure showing the transmittance | permeability spectrum in the liquid crystal display device of Example 4. (A) shows the azimuth angle 0 ° method, and (b) shows the transmission spectrum when the polar angle is changed in the azimuth angle 45 ° direction. It is a figure showing the transmittance | permeability spectrum in the liquid crystal display device of Example 5. (A) shows the azimuth angle 0 ° method, and (b) shows the transmission spectrum when the polar angle is changed in the azimuth angle 45 ° direction. It is a figure showing the transmittance | permeability spectrum in the liquid crystal display device of Example 8. (A) shows the azimuth angle 0 ° method, and (b) shows the transmission spectrum when the polar angle is changed in the azimuth angle 45 ° direction. It is a figure showing the transmittance | permeability spectrum in the liquid crystal display device of Example 9. (A) represents the azimuth angle 0 ° method, and (b) represents the transmission spectrum when the polar angle is changed in the azimuth angle 45 ° direction. It is a figure showing the transmittance | permeability spectrum in the liquid crystal display device of Example 10. (A) shows the azimuth angle 0 ° method, and (b) shows the transmission spectrum when the polar angle is changed in the azimuth angle 45 ° direction. It is a figure showing the transmittance | permeability spectrum in the liquid crystal display device of the comparative example 1. (A) shows the azimuth angle 0 ° method, and (b) shows the transmission spectrum when the polar angle is changed in the azimuth angle 45 ° direction. It is a figure showing the transmittance | permeability spectrum in the liquid crystal display device of the comparative example 2. (A) shows the azimuth angle 0 ° method, and (b) shows the transmission spectrum when the polar angle is changed in the azimuth angle 45 ° direction. It is a figure showing the transmittance | permeability spectrum in the liquid crystal display device of the comparative example 3. (A) shows the azimuth angle 0 ° method, and (b) shows the transmission spectrum when the polar angle is changed in the azimuth angle 45 ° direction. It is a figure showing the measurement result of Y value in the liquid crystal display of reference example 9. (A) is the same as Example 6, and (b), (c), (d), (e), and (f) are the thicknesses of the liquid crystal layers of 0.1 μm, 0.2 μm, and 0.3 μm, respectively. The measurement result of the Y value of the liquid crystal display device using the optical rotatory element having a thickness of 0.4 μm and 0.5 μm is shown. It is a figure showing the measurement result of Y value in the liquid crystal display of reference example 10. (A) is the same as Example 7, and (b), (c), (d), (e), and (f) are the thicknesses of the liquid crystal layers of 0.1 μm, 0.2 μm, and 0.3 μm, respectively. The measurement result of the Y value of the liquid crystal display device using the optical rotatory element having a thickness of 0.4 μm and 0.5 μm is shown. It is a figure showing the measurement result of Y value in the liquid crystal display of reference example 11. (A) is the same as that of Example 8, and (b), (c), (d), (e), and (f) respectively have a liquid crystal layer thickness of 0.1 μm, 0.2 μm, and 0.3 μm. The measurement result of the Y value of the liquid crystal display device using the optical rotatory element having a thickness of 0.4 μm and 0.5 μm is shown. It is a figure showing the measurement result of Y value in each liquid crystal display of reference example 12. (A) is the same as that of Example 86, (b), (c), (d), (e), and (f) respectively indicate the arrangement angles of the optical rotatory elements at 1 °, 2 °, 3 °, and 4 °. The measurement result of Y value of a liquid crystal display device provided with the liquid crystal panel using the laminated polarizing plate which shifted and arrange | positioned 5 degrees is represented. It is a figure showing the measurement result of Y value in each liquid crystal display of reference example 13. (A) is the same as in Example 9, and (b), (c), (d), (e), and (f) respectively indicate the arrangement angles of the optical rotatory elements at 1 °, 2 °, 3 °, and 4 °. The measurement result of Y value of a liquid crystal display device provided with the liquid crystal panel using the laminated polarizing plate which shifted and arrange | positioned 5 degrees is represented. It is a figure showing the measurement result of Y value in the liquid crystal display of Example 13. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 14. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 15. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 16. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 17. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 18. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 19. It is a figure showing the measurement result of Y value in the liquid crystal display of comparative example 4. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 20. It is a figure showing the measurement result of Y value in the liquid crystal display of Example 21. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 22. It is a figure showing the measurement result of Y value in the liquid crystal display of Example 23. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 24. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 25. It is a figure showing the measurement result of Y value in the liquid crystal display device of Example 26. It is a figure showing the measurement result of Y value in the liquid crystal display of comparative example 5.

Explanation of symbols

3 Absorption axis (direction)
4 Absorption axis (direction)
5a, 5b Orientation direction of liquid crystal molecules 10 Liquid crystal cell 11 Substrate 12 Substrate 13 Liquid crystal layer 21, 22 Polarizing plate 30 Optical rotator 81 Light source 82 Reflective film 84 Prism sheet 100 Liquid crystal panel 200 Backlight unit 300 Liquid crystal display device

Claims (7)

A liquid crystal cell having a liquid crystal layer containing liquid crystal molecules aligned in a homeotropic alignment or a homogeneous alignment in the absence of an electric field;
A first polarizing plate disposed on one side of the liquid crystal cell;
A second polarizing plate disposed on the other side of the liquid crystal cell;
An optical rotatory element that converts linearly polarized light into linearly polarized light orthogonal to it either between the liquid crystal cell and the first polarizing plate or between the liquid crystal cell and the second polarizing plate;
A liquid crystal panel in which absorption axes of the first polarizing plate and the second polarizing plate are arranged in parallel.   2. The liquid crystal panel according to claim 1, wherein the liquid crystal cell is in a VA mode or an IPS mode.   3. The liquid crystal panel according to claim 1, wherein the optical rotator is a liquid crystal layer in which the alignment direction of liquid crystal molecules gradually changes along the thickness direction of the layer.   The liquid crystal panel according to claim 3, wherein the liquid crystal layer is a chiral nematic liquid crystal layer in which the liquid crystal is twisted by approximately 90 °. The liquid crystal panel according to claim 4, wherein a product of birefringence Δn _{545 at} a wavelength of 545 nm and a thickness d of the liquid crystal layer of the nematic liquid crystalline material forming the chiral nematic liquid crystal layer is 1400 nm or more.   The liquid crystal panel according to claim 2, wherein the liquid crystal cell is a VA mode liquid crystal cell, and further includes an optical compensation layer satisfying nx> ny ≧ nz. (Nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, and nz is the refractive index in the thickness direction) A liquid crystal display device comprising the liquid crystal panel according to claim 1.