JP2008009389A - Liquid crystal panel and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal panel which is advantageous in that the view angle is wide, the level of coloration of letter and image is low even when the screen is viewed from any direction and the color shift is small and to provide a liquid crystal display device. <P>SOLUTION: In the liquid crystal panel comprising at least a liquid crystal cell, a first polarizer disposed on one side of the liquid crystal cell, a second polarizer disposed on the other side of the liquid crystal cell, and a phase difference film disposed between the liquid crystal cell and the first polarizer, the phase difference film comprises a thermoplastic polymer containing at least a substituent represented by the following general formula (I) and, in the phase difference film, the in-plane phase difference value at a wavelength of 750 nm is larger than the in-plane phase difference value at a wavelength of 550 nm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal panel having a high contrast ratio in an oblique direction, and a liquid crystal display device.

A liquid crystal display device (hereinafter sometimes referred to as LCD) is an element that displays characters and images by utilizing the electro-optical characteristics of liquid crystal molecules. One of the driving modes of the LCD is a vertical alignment (VA) mode. Conventionally, VA mode LCDs have the drawback of a narrow viewing angle. Further, the LCD has a problem that characters and images are colored when the screen is viewed from an oblique direction. Further, the LCD has a problem that the color greatly changes depending on the direction (also referred to as color shift). In order to solve this problem, for example, a retardation film having a characteristic in which a retardation value measured with long-wavelength light is larger than a retardation value measured with short-wavelength light (also referred to as reverse wavelength dispersion characteristic) A liquid crystal panel using this is disclosed (for example, see Patent Document 1). However, in a liquid crystal display device having a conventional liquid crystal panel, the drawbacks of a narrow viewing angle and screen coloration and color change have not been sufficiently improved. Therefore, improvement of this subject is desired.
Japanese Patent No. 3648240

  An object of the present invention is to provide a liquid crystal panel and a liquid crystal display device which have a wide viewing angle and which are small in coloration of characters and images and small in color shift no matter which direction the screen is viewed from 360 °.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the following liquid crystal panel, and have completed the present invention.

  The liquid crystal panel of the present invention includes a liquid crystal cell, a first polarizer disposed on one side of the liquid crystal cell, a second polarizer disposed on the other side of the liquid crystal cell, and the liquid crystal cell. And a retardation film (A) disposed between the first polarizer and the retardation film (A), the substituent (a) represented by the following general formula (I): The in-plane retardation value (Re [750]) at a wavelength of 750 nm is larger than the in-plane retardation value (Re [550]) at a wavelength of 550 nm.

In formula (I), R ^{1 to} R ⁷ are each independently a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or a linear or branched group having 1 to 4 carbon atoms. A halogenated alkyl group, a linear or branched alkoxy group having 1 to 4 carbon atoms, a linear or branched thioalkoxy group having 1 to 4 carbon atoms, a linear or branched alkoxycarbonyl group, an acyloxy group, amino Represents a group, an azide group, a nitro group, a cyano group, a hydroxyl group, or a thiol group (where R ¹ is not a hydrogen atom).

  In a liquid crystal panel according to a preferred embodiment, the liquid crystal cell includes liquid crystal molecules aligned in a homeotropic alignment.

  In the liquid crystal panel of a preferred embodiment, the slow axis direction of the retardation film (A) is substantially perpendicular to the absorption axis direction of the first polarizer.

  In the liquid crystal panel of a preferred embodiment, the thermoplastic polymer is a vinyl acetal polymer, an olefin polymer, or a carbonate polymer.

The liquid crystal panel of a preferred embodiment includes an in-plane retardation value (Re [750]) at a wavelength of 750 nm of the retardation film (A) and an in-plane retardation value (Re [550]) at a wavelength of 550 nm. The difference (ΔRe _750−550 = Re [750] −Re [550]) is 5 nm or more.

In the liquid crystal panel of the preferred embodiment, the in-plane birefringence (Δn _xy [590]) of the retardation film (A) at a wavelength of 590 nm is 0.001 or more.

In the liquid crystal panel of a preferred embodiment, the absolute value of the photoelastic coefficient of the retardation film (A) is 50 × 10 ⁻¹² (m ² / N) or less.

  In the liquid crystal panel of a preferred embodiment, the refractive index ellipsoid of the retardation film (A) exhibits a relationship of nx> ny = nz or nx> ny> nz.

  The liquid crystal panel of a preferred embodiment further includes a retardation film (B) in which a refractive index ellipsoid shows a relationship of nx = ny> nz between the retardation film (A) and the second polarizer. ing.

  In the liquid crystal panel of a preferred embodiment, the retardation film (B) is selected from the group consisting of a cellulose polymer, an amide imide polymer, an imide polymer, an amide polymer, an ether ether ketone polymer, and a cycloolefin polymer. At least one polymer.

In the liquid crystal panel of a preferred embodiment, the difference (D _A −D _B ) between the chromatic dispersion value (D _A ) of the retardation film ( _A ) and the chromatic dispersion value (D _B ) of the retardation film (B). It is 0.05 or more.
However, the chromatic dispersion value (D _A ) is a value calculated from the equation: Re [750] / Re [550]. Re [750] and Re [550] are in-plane retardation values at wavelengths of 750 nm and 550 nm, respectively. The chromatic dispersion value (D _B ) is a value calculated from the formula: R40 [750] / R40 [550]. R40 [750] and R40 [550] are phase difference values measured by tilting 40 degrees from the normal direction at wavelengths of 750 nm and 550 nm, respectively.

  According to another aspect of the present invention, a liquid crystal display device is provided. This liquid crystal display device includes any one of the above liquid crystal panels.

  According to the present invention, by using a specific retardation film, there is provided a liquid crystal panel having a wide viewing angle, small coloration of characters and images, and small color shift regardless of the direction of 360 ° viewing the screen. it can. A liquid crystal display device including such a liquid crystal panel has a wide viewing angle, a small color shift, etc., and excellent display characteristics.

〔Definition of terms〕
The definitions of terms and symbols in this specification are as follows.
(1) Refractive index (nx, ny, nz):
“Nx” is the refractive index in the direction in which the in-plane refractive index is maximum (that is, the slow axis direction). “Ny” is a refractive index in a direction orthogonal to the slow axis in the plane (that is, in the fast axis direction). “Nz” is the refractive index in the thickness direction.
(2) In-plane retardation value:
The in-plane retardation value (Re [λ]) refers to the in-plane retardation value of the film at a wavelength λ (nm) at 23 ° C. Re [λ] is a value calculated by Re [λ] = (nx−ny) × d, where d (nm) is the thickness of the film.
(3) Phase difference value of 40 degree inclination:
R40 [λ] refers to a retardation value measured by tilting 40 degrees from the normal direction of the film at a wavelength λ (nm) at 23 ° C.
(4) In-plane birefringence:
The in-plane birefringence (Δn _xy [λ]) is a value calculated by the equation: Re [λ] / d.
(5) Thickness direction retardation value:
The retardation value in the thickness direction (Rth [λ]) refers to the retardation value in the thickness direction of the film at 23 ° C. and the wavelength λ (nm). Rth [λ] is a value calculated by Rth [λ] = (nx−nz) × d, where d (nm) is the thickness of the film.
(6) Birefringence index in the thickness direction:
The birefringence (Δn _xz [λ]) in the thickness direction is a value calculated by the formula: Rth [λ] / d.
(7) Nz coefficient:
The Nz coefficient is a value calculated by the formula: Rth [590] / Re [590].
(8) Chromatic dispersion value:
The chromatic dispersion value (D _A ) is a value calculated from the formula: Re [750] / Re [550]. The chromatic dispersion value (D _B ) is a value calculated from the formula: R40 [750] / R40 [550].
(9) In this specification, the description “nx = ny” or “ny = nz” includes not only the case where they are completely the same, but also the case where they are substantially the same. Therefore, for example, even when nx = ny, the case where Re [590] is less than 10 nm is included.
(10) In this specification, “substantially orthogonal” includes a case where an angle formed by two optical axes is 90 ° ± 2 °, and preferably 90 ° ± 1 °. “Substantially parallel” includes a case where an angle formed by two optical axes is 0 ° ± 2 °, and preferably 0 ° ± 1 °.

[A. Overview of LCD panel
The liquid crystal panel of the present invention includes a liquid crystal cell, a first polarizer disposed on one side of the liquid crystal cell, a second polarizer disposed on the other side of the liquid crystal cell, and the liquid crystal cell. And a retardation film (A) disposed between the first polarizer and the first polarizer.

  The retardation film (A) includes a thermoplastic polymer having at least a substituent (a) represented by the following general formula (I), and has an in-plane retardation value (Re [750]) at a wavelength of 750 nm. It is larger than the in-plane retardation value (Re [550]) at a wavelength of 550 nm.

In formula (I), R ^{1 to} R ⁷ are each independently a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or a linear or branched group having 1 to 4 carbon atoms. A halogenated alkyl group, a linear or branched alkoxy group having 1 to 4 carbon atoms, a linear or branched thioalkoxy group having 1 to 4 carbon atoms, a linear or branched alkoxycarbonyl group, an acyloxy group, amino Represents a group, an azide group, a nitro group, a cyano group, a hydroxyl group, or a thiol group (where R ¹ is not a hydrogen atom).

  A preferred embodiment of the liquid crystal panel of the present invention will be described with reference to FIGS. FIG. 1 is a schematic cross-sectional view of a liquid crystal panel according to a first embodiment of the present invention. The liquid crystal panel 101 includes a first polarizer 21, a retardation film (A) 31, a liquid crystal cell 10, and a second polarizer 22 at least in this order. The retardation film (A) 31 is disposed between the liquid crystal cell 10 and the first polarizer 21.

  FIG. 2 is a schematic cross-sectional view of a liquid crystal panel according to the second embodiment of the present invention. The liquid crystal panel 102 includes a first polarizer 21, a retardation film (A) 31, a liquid crystal cell 10, a retardation film (B) 32, and a second polarizer 22 in at least this order. The retardation film (A) 31 is disposed between the liquid crystal cell 10 and the first polarizer 21. The retardation film (B) 32 is disposed between the liquid crystal cell 10 and the second polarizer 22. According to such a form, since a retardation film is arrange | positioned at the both sides of a liquid crystal cell, even when expansion | swelling and shrinkage | contraction arise in a retardation film, a distortion is hard to produce in a liquid crystal cell. As a result, it is possible to obtain a liquid crystal panel that hardly causes optical unevenness.

  FIG. 3 is a schematic cross-sectional view of a liquid crystal panel according to the third embodiment of the present invention. The liquid crystal panel 103 includes a first polarizer 21, a retardation film (A) 31, a retardation film (B) 32, a liquid crystal cell 10, and a second polarizer 22 in this order. The retardation film (A) 31 is disposed between the retardation film (B) 32 and the first polarizer 21. The retardation film (B) 32 is disposed between the liquid crystal cell 10 and the retardation film (A) 31.

  FIG. 4 is a schematic sectional view of a liquid crystal panel according to the fourth embodiment of the present invention. The liquid crystal panel 104 includes a first polarizer 21, a protective layer (A) 23, a retardation film (A) 31, a liquid crystal cell 10, a retardation film (B) 32, and a protective layer (B). 24 and the second polarizer 22 are provided at least in this order. The protective layer (A) 23 is disposed between the first polarizer 21 and the retardation film (A) 31. The protective layer (B) 24 is disposed between the second polarizer 22 and the retardation film (B) 32. The retardation film (A) 31 is disposed between the liquid crystal cell 10 and the protective layer (A) 23. The retardation film (B) 32 is disposed between the liquid crystal cell 10 and the protective layer (B) 24. According to such a form, since the retardation films (A) and (B) are not directly attached to the adjacent polarizer, the contraction stress of the polarizer hardly affects the retardation film. As a result, it is possible to obtain a liquid crystal panel that hardly causes optical unevenness.

  In practice, an optional protective layer or surface treatment layer may be disposed on the side of the first and / or second polarizer opposite to the side having the liquid crystal cell. Further, an arbitrary adhesive layer may be provided between the constituent members of the liquid crystal panel. The “adhesive layer” refers to a layer that joins surfaces of adjacent members and integrates them with practically sufficient adhesive force and adhesion time. Examples of the material for forming the adhesive layer include an adhesive, a pressure-sensitive adhesive, and an anchor coating agent. The adhesive layer may have a multilayer structure in which an anchor coating agent is formed on the surface of an adherend and an adhesive layer or a pressure-sensitive adhesive layer is formed thereon. Further, the adhesive layer may be a thin layer (also referred to as a hairline) that cannot be recognized with the naked eye. Hereinafter, although the detail of the structural member of this invention is demonstrated, this invention is not limited only to the following specific embodiment.

[B. Liquid crystal cell)
Referring to FIG. 1, a liquid crystal cell 10 used in the present invention has a pair of substrates 11 and 11 ′ and a liquid crystal layer 12 as a display medium sandwiched between the substrates 11 and 11 ′. One substrate (active matrix substrate) 11 ′ includes a switching element (typically a TFT) for controlling the electro-optical characteristics of the liquid crystal, a scanning line for supplying a gate signal to the active element, and a signal line for supplying a source signal. Are provided (both not shown). The other substrate (color filter substrate) 11 is provided with a color filter. The color filter may be provided on the active matrix substrate 11 ′. Alternatively, for example, when an RGB three-color light source is used for the backlight of the liquid crystal display device as in the field sequential method, the color filter can be omitted. A distance (cell gap) between the substrate 11 and the substrate 11 ′ is controlled by a spacer (not shown). An alignment film (not shown) made of polyimide, for example, is provided on the side of the substrate 11 and the substrate 11 ′ in contact with the liquid crystal layer 12. Alternatively, for example, when the initial alignment of liquid crystal molecules is controlled using a fringe electric field formed by a patterned transparent electrode, the alignment film can be omitted.

  The liquid crystal cell preferably includes liquid crystal molecules aligned in a homeotropic alignment. In this specification, “homeotropic alignment” means a state in which the alignment vector of liquid crystal molecules is aligned perpendicularly (normally) to the substrate plane as a result of the interaction between the aligned substrate and the liquid crystal molecules. Means things. 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, when 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, and more preferably 3 ° or less. By setting the pretilt angle in the above range, a liquid crystal display device with a high contrast ratio can be obtained.

  In the liquid crystal cell, the refractive index ellipsoid preferably has a relationship of nz> nx = ny. Examples of the driving mode of the liquid crystal cell in which the refractive index ellipsoid has a relationship of nz> nx = ny include a vertical alignment (VA) mode and a vertical alignment ECB (Electrically Controlled Birefringence) mode. Preferably, the liquid crystal cell is in 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, VA mode liquid crystal cells are described in, for example, Japanese Patent Application Laid-Open Nos. 62-210423 and 4-153621. In the VA mode liquid crystal cell, in a normally black system, liquid crystal molecules are aligned in a normal direction with respect to the substrate in the absence of an electric field. For this reason, the liquid crystal cell can obtain a black display when the upper and lower polarizing plates are arranged orthogonally. On the other hand, in the VA mode liquid crystal cell, 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, thereby increasing the transmittance and obtaining white display. It is done.

  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. Such a liquid crystal cell includes, for example, an ASV (Advanced Super View) mode manufactured by Sharp Corporation, a CPA (Continuous Pinwheel Alignment) mode manufactured by the same company, and an MVA (Multi-domain Vertical Alignment) mode manufactured by Fujitsu Limited. PVA (Patterned Vertical Alignment) mode manufactured by Samsung Electronics Co., Ltd., EVA (Enhanced Vertical Alignment) mode manufactured by the same company, SURVIVAL (Super Ranged Viewing by VERY VALENTIVE VALENTIVE VALENTIVE VALENTIVE VALENTIVE VINTAGE VALENTIVE VALENTIVE VALENTIVE VALENTIVE VALENTIVE VALENTIVE VALENTIVE VALENTIVE VALENTIVE VALENTIVE VALENTIVE VENTIVE VALENTIVE VENTIVE VALENTIVE VENTIVE VALENTIVE VENTIVE VALENTIVE VENTIVE NETWORK

Rth _LC [590] of the above liquid crystal cell in the absence of an electric field is preferably −500 nm to −200 nm, more preferably −400 nm to −200 nm. Here, Rth _LC [590] is a retardation value in the thickness direction of the liquid crystal cell measured at a wavelength of 590 nm at 23 ° C. The value of Rth _LC [590] is appropriately set depending on 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.

  As the liquid crystal cell, the one mounted on a commercially available liquid crystal display device may be used as it is. As a commercially available liquid crystal display device including a VA mode liquid crystal cell, for example, a 37V type liquid crystal television (trade name “AQUIS LC-37AD5”) manufactured by Sharp Corporation, and a 32V type wide liquid crystal television manufactured by SUMSUNG (product) Name “LN32R51B”), a liquid crystal television manufactured by Nanao Co., Ltd. (trade name “FORIS SC26XD1”), a liquid crystal television manufactured by AU Optronics (trade name “T460HW01”), and the like.

[C. Polarizer]
In this specification, a “polarizer” refers to an element that can convert natural light or polarized light into arbitrary polarized light. The first and second polarizers used in the present invention are not particularly limited, but preferably convert natural light or polarized light into linearly polarized light. Such a polarizer preferably has a function of transmitting one of the polarized components when incident light is divided into two orthogonal polarized components, and absorbing and reflecting the other polarized component. And at least one function selected from the function of scattering. The thicknesses of the first and second polarizers are preferably 5 μm to 50 μm, respectively. The first and second polarizers are arranged so that the absorption axis direction of the first polarizer is preferably substantially orthogonal to the absorption axis direction of the second polarizer. The first and second polarizers may be the same or different.

  The first and second polarizers preferably have a single transmittance of 38% to 45% and a degree of polarization of 99% or more. The theoretical upper limit of the degree of polarization is 100%. A liquid crystal display device having a high contrast ratio in the front direction can be obtained by using a polarizer having the single transmittance and the degree of polarization as described above.

  Any appropriate one can be selected as the first and second polarizers used in the present invention. The first and second polarizers preferably contain iodine and a vinyl alcohol polymer. Such a polarizer can be usually obtained by dyeing a polymer film containing a vinyl alcohol-based polymer as a main component with an iodine aqueous solution and further stretching it. The iodine content of the polarizer is preferably 2% to 5% by weight. By setting the iodine content in the above range, a polarizer having excellent optical characteristics can be obtained.

  The vinyl alcohol polymer can be obtained by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer. The saponification degree of the vinyl alcohol polymer is preferably 95 mol% or more. The saponification degree can be determined according to JIS K 6726-1994. By using a vinyl alcohol polymer having a saponification degree in the above range, a polarizer having excellent durability can be obtained.

  The average degree of polymerization of the vinyl alcohol polymer can be appropriately selected depending on the purpose. The average degree of polymerization is preferably 1200 to 3600. The average degree of polymerization can be determined according to JIS K 6726-1994.

  Any appropriate molding method can be adopted as a method for obtaining the polymer film containing the vinyl alcohol polymer as a main component. Examples of the molding method include the method described in JP-A No. 2001-315144 [Example 1].

  The polymer film containing the vinyl alcohol polymer as a main component preferably contains a plasticizer and / or a surfactant. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. As said surfactant, a nonionic surfactant is mentioned, for example. The content of the plasticizer and the surfactant is preferably more than 1 and 10 parts by weight or less with respect to 100 parts by weight of the vinyl alcohol polymer. The plasticizer and surfactant are used for the purpose of further improving the dyeability and stretchability of the polarizer.

  A commercially available film can be used as it is for the polymer film containing the vinyl alcohol polymer as a main component. Examples of polymer films based on commercially available polyvinyl alcohol resins include, for example, the product name “Kuraray Vinylon Film” manufactured by Kuraray Co., Ltd., the product name “Tosero Vinylon Film” manufactured by Tosero Co., Ltd., and Nippon Gosei. A trade name “Nippon Vinylon Film” manufactured by Chemical Industry Co., Ltd. may be mentioned.

  An example of a method for manufacturing a polarizer will be described with reference to FIG. FIG. 5 is a schematic diagram showing the concept of a typical production process of a polarizer used in the present invention. In this manufacturing method, a polymer film 301 containing a vinyl alcohol-based polymer as a main component is fed out from a feeding unit 300 and is first immersed in an aqueous solution bath 310 containing iodine. At this time, the polymer film 301 is subjected to a swelling and dyeing process while tension is applied in the film longitudinal direction by rolls 311 and 312 having different speed ratios. Next, the polymer film is immersed in a bath 320 of an aqueous solution containing boric acid and potassium iodide, and subjected to a crosslinking treatment while tension is applied in the longitudinal direction of the film by rolls 321 and 322 having different speed ratios. Is done. The film subjected to crosslinking treatment is immersed in an aqueous solution bath 330 containing potassium iodide by rolls 331 and 332 and subjected to a water washing treatment. The polymer film that has been washed with water is dried by a drying means 340 and wound up by a winding unit 360. The draw ratio of the polarizer 350 is generally 5 to 7 times the original length.

[D. Retardation film (A)]
1 to 4, the retardation film (A) 31 used in the present invention is disposed between the liquid crystal cell 10 and the first polarizer 21. When the retardation film (A) is disposed, the positional relationship between the slow axis direction of the retardation film (A) and the absorption axis of the first polarizer can be appropriately selected according to the purpose. Preferably, the retardation film (A) is such that the slow axis direction of the retardation film (A) and the absorption axis direction of the first polarizer are substantially orthogonal or substantially parallel. And a first polarizer. More preferably, the retardation film (A) and the first retardation film (A) are arranged so that the slow axis direction of the retardation film (A) and the absorption axis direction of the first polarizer are substantially perpendicular to each other. A polarizer is arranged.

[D-1. Retardation Film (A) Material]
The retardation film (A) used in the present invention contains a thermoplastic polymer having at least a substituent (a) represented by the following general formula (I). The content of the thermoplastic polymer is preferably 50 to 100 (weight ratio) with respect to 100 of the total solid content of the retardation film (A). In the present specification, “thermoplastic” refers to a property of softening by heating to show plasticity and solidifying by cooling. In addition, the “polymer” includes a high polymer having a degree of polymerization (when the polymer includes a plurality of structural units, the total degree of polymerization of each structural unit) of 20 or more, and further, the degree of polymerization is 2 or more. Includes less than 20 low polymers (also referred to as oligomers).

In formula (I), R ^{1 to} R ⁷ are each independently a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or a linear or branched group having 1 to 4 carbon atoms. A halogenated alkyl group, a linear or branched alkoxy group having 1 to 4 carbon atoms, a linear or branched thioalkoxy group having 1 to 4 carbon atoms, a linear or branched alkoxycarbonyl group, an acyloxy group, amino Represents a group, an azide group, a nitro group, a cyano group, a hydroxyl group, or a thiol group (where R ¹ is not a hydrogen atom).
Hereinafter, “halogen atom, linear or branched alkyl group having 1 to 4 carbon atoms, linear or branched halogenated alkyl group having 1 to 4 carbon atoms, linear or branched alkyl group having 1 to 4 carbon atoms” An alkoxy group, a linear or branched thioalkoxy group having 1 to 4 carbon atoms, a linear or branched alkoxycarbonyl group, an acyloxy group, an amino group, an azide group, a nitro group, a cyano group, a hydroxyl group, or a thiol group " Collectively, it may be referred to as “substituent (a)”.

In the above formula, R ¹ is used to control the conformation of the thermoplastic polymer to which the substituent (a) is bonded. Specifically, since the R ¹ site adjacent to the bond (bonding site with the main chain) of formula (I) is the above substituent (a), the substituent (a) and the main chain have steric hindrance. It is considered that the planar structure of the naphthyl group of the above formula (I) is oriented in a direction substantially perpendicular to the orientation direction of the main chain of the thermoplastic polymer. By using the thermoplastic polymer having the formula (I) that is oriented in this way, the in-plane retardation value (Re [750]) at a wavelength of 750 nm becomes the in-plane retardation value (Re [550]) at a wavelength of 550 nm. ) (That is, exhibiting reverse wavelength dispersion characteristics), the retardation film (A) can be obtained.
Accordingly, if R ¹ in the formula (I) is sterically larger than the hydrogen atom, it may cause steric hindrance with the main chain, and therefore R ¹ can be appropriately selected from the substituent (a).
On the other hand, since R ^{2 to} R ^{7 in} the formula (I) are less likely to cause steric hindrance with the main chain than R ¹ to R ⁷ , R ^{2 to} R ⁷ may be a hydrogen atom, a) may be used. Preferably at least R ⁷ is a hydrogen atom, more preferably R ^{2 to} R ⁷ are hydrogen atoms.

  Arbitrary appropriate methods may be employ | adopted for the introduction method to the polymer of the said substituent (a). Examples of the introduction method include: (i) a method in which a polymer having a reactive site that can be substituted with the substituent is previously polymerized, and a compound having the substituent (a) is reacted with the reactive site of the polymer. (Ii) A method of copolymerizing the monomer having the substituent (a) with another monomer.

  The compound and monomer having the substituent (a) are 1-naphthalene derivatives, and those suitable for the introduction method into the polymer can be selected. The compound and monomer having the substituent (a) are, for example, 1-naphthaldehyde, 1-aminonaphthalene, 1-hydroxynaphthalene, 1-naphthone, and derivatives thereof.

  As the thermoplastic polymer, those having an arbitrary structure may be adopted as long as the thermoplastic polymer has the substituent (a). Examples of the bond of the main chain of the thermoplastic polymer include an acetal bond, a bond between carbon atoms, a carbonate bond, an ester bond, an amide bond, a urethane bond, an ether bond, and a siloxane bond. Bonds preferable as a material for forming the retardation film (A) are an acetal bond, a bond between carbon atoms, and a carbonate bond. That is, the thermoplastic polymer is preferably a vinyl acetal polymer, an olefin polymer, or a carbonate polymer. This is because, when the polymer is used, a retardation film (A) having reverse wavelength dispersion characteristics and a small absolute value of the photoelastic coefficient can be obtained. The olefin polymer includes a cyclic olefin polymer in addition to the chain olefin. Examples of the cyclic olefin-based polymer include ring-opening polymers such as norbornene and dicyclopentadiene, and hydrogenated products thereof.

  Particularly preferably, the thermoplastic polymer has at least a repeating unit represented by the following general formula (II). In the formula (II), the arrangement order of each basic unit of l, m, and n is not particularly limited, and may be any of alternating, random, or block. Such a thermoplastic polymer is excellent in solubility in a general-purpose solvent (for example, acetone, ethyl acetate, toluene, etc.) and exhibits a glass transition temperature excellent in operability such as stretching.

In the general formula (II), R ^{1 to} R ⁷ are each independently a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, a linear chain having 1 to 4 carbon atoms, or A branched alkoxy group, a linear or branched thioalkoxy group having 1 to 4 carbon atoms, a linear or branched alkoxycarbonyl group having 1 to 4 carbon atoms, an acyloxy group, an amino group, an azide group, a nitro group, Represents a cyano group, a hydroxyl group, or a thiol group (where R ¹ is not a hydrogen atom); A ¹ and A ² each independently represent a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or a substituted or unsubstituted phenyl group. A ³ is a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted cycloalkyl group having 5 to 10 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted group. It represents a naphthyl group or a substituted or unsubstituted heterocyclic group. A ⁴ represents a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, a benzyl group, a silyl group, a phosphoric acid group, an acyl group, a benzoyl group, or a sulfonyl group.

  The thermoplastic polymer (vinyl acetal polymer) having at least the repeating unit represented by the general formula (II) is, for example, at least two compounds selected from a vinyl alcohol polymer and an aldehyde compound and / or a ketone compound. Is dispersed or dissolved in a solvent and reacted in the presence of an acid catalyst. In the condensation reaction of the vinyl alcohol polymer, at least two kinds of compounds selected from aldehyde compounds and / or ketone compounds may be reacted at the same time or may be reacted one by one (sequential reaction). The degree of acetalization of the vinyl acetal polymer is preferably 40 mol% to 99 mol%. This reaction is a condensation reaction with a vinyl alcohol polymer, and is also referred to as acetalization when an aldehyde compound is used. In the present specification, “acetalization” includes ketalization using a ketone compound.

  In the general formula (II), the basic unit 1 is, for example, a unit formed by a condensation reaction between a vinyl alcohol polymer and 1-naphthaldehydes or 1-naphthones. Examples of the 1-naphthaldehydes include 2-methoxy-1-naphthaldehyde, 2-ethoxy-1-naphthaldehyde, 2-propoxy-1-naphthaldehyde, 2-methyl-1-naphthaldehyde, 2,6 -Dimethyl-1-naphthaldehyde, 2,4-dimethyl-1-naphthaldehyde, 2-hydroxy-1-naphthaldehyde, etc. are mentioned. Examples of the 1-naphthones include 2-hydroxy-1-acetonaphthone and 8'-hydroxy-1'-benzonaphthone.

  In the general formula (II), the basic unit m is a unit formed by a condensation reaction between a vinyl alcohol polymer and an arbitrary aldehyde compound or ketone compound. Examples of the aldehyde compound include formaldehyde, acetaldehyde, 1,1-diethoxyethane (acetal), propionaldehyde, n-butyraldehyde, cyclohexanecarboxaldehyde, 5-norbornene-2-carboxaldehyde, benzaldehyde, 3,4-dimethoxy. Benzaldehyde, 2-nitrobenzaldehyde, 4-cyanobenzaldehyde, 4-carboxybenzaldehyde, 4-phenylbenzaldehyde, 4-fluorobenzaldehyde, 1-naphthaldehyde, 2-naphthaldehyde, 6-methoxy-2-naphthaldehyde, 3-methyl- 2-thiophene carboxaldehyde, 2-pyridine carboxaldehyde, etc. are mentioned.

  Examples of the ketone compound include acetone, ethyl methyl ketone, diethyl ketone, t-butyl ketone, dipropyl ketone, allyl ethyl ketone, acetophenone, p-methylacetophenone, 4′-aminoacetophenone, 4′-methoxyacetophenone, 2′- Hydroxyacetophenone, 3′-nitroacetophenone, benzalacetophenone, propiophenone, benzophenone, 4-nitrobenzophenone, 2-methylbenzophenone, p-bromobenzophenone, cyclohexyl (phenyl) methanone, 2-butyronaphthone, 1-acetonaphthone, etc. It is done.

In the general formula (II), A ⁴ is used to adjust the water absorption rate to an appropriate value by protecting the remaining hydroxyl group (also referred to as end cap treatment). When the water absorption is reduced, a retardation film (A) having high transparency and excellent retardation stability can be obtained. However, depending on the application and purpose for which the retardation film of the present invention is used, the substituent may not be end-capped (that is, A ⁴ may be a hydrogen atom).

The above A ⁴ is, for example, after obtaining the polymer remaining hydroxyl groups react with hydroxyl groups to form a substituent (i.e., endcapped possible) (also referred to as a protecting group) any suitable group used It is done. Examples of the protective group include benzyl group, 4-methoxyphenylmethyl group, methoxymethyl group, trimethylsilyl group, triethylsilyl group, t-butyldimethylsilyl group, acetyl group, benzoyl group, methanesulfonyl group, bis-4-nitro. And phenyl phosphite. The reaction conditions for the end cap treatment include, for example, a polymer having a hydroxyl group remaining and a chloride of a target substituent in the presence of a catalyst such as 4 (N, N-dimethylamino) pyridine at 25 ° C. to 100 ° C. And stirring for 1 to 20 hours. By using the protective group, a retardation film (A) having high transparency and excellent retardation stability can be obtained even in a high temperature and humidity environment.

In the general formula (II), the ratio of l, m, and n can be appropriately set according to the purpose. The ratio of the basic unit 1 is preferably 2 mol% to 40 mol%, more preferably 2 mol% to 30 mol%. The ratio of the basic unit m is preferably 20 mol% to 80 mol%, more preferably 30 mol% to 75 mol%. The ratio of the basic unit n is preferably 1 mol% to 60 mol%, more preferably 5 mol% to 50 mol%. However, l + m + n = 100 mol%. By using a polymer having a ratio of each basic unit within the above range, excellent reverse wavelength dispersion characteristics are exhibited, excellent retardation is exhibited by stretching, and in-plane birefringence (Δn _xy ) is large. A phase difference film (A) can be obtained.

  The weight average molecular weight of the thermoplastic polymer is preferably 1,000 to 1,000,000, and more preferably 3,000 to 500,000. By setting the weight average molecular weight in the above range, a retardation film (A) excellent in mechanical strength can be obtained. The weight average molecular weight is a value determined by GPC method (polystyrene standard) using tetrahydrofuran as a developing solvent.

  The glass transition temperature of the thermoplastic polymer is preferably 100 ° C to 190 ° C, more preferably 110 ° C to 170 ° C. By setting the glass transition temperature in the above range, a retardation film (A) excellent in heat resistance and molding processability can be obtained. The glass transition temperature can be determined by the DSC method according to JIS K 7121-1987.

  The retardation film (A) may further contain any appropriate additive. Examples of the additive include a plasticizer, a heat stabilizer, a light stabilizer, a lubricant, an antioxidant, an ultraviolet absorber, a flame retardant, an antistatic agent, a compatibilizer, a crosslinking agent, and a thickener. It is done. The amount of the additive used is preferably more than 0 and 30 parts by weight or less with respect to 100 parts by weight of the thermoplastic polymer.

[D-2. Various properties of retardation film (A)]
In the retardation film (A) used in the present invention, the in-plane retardation value (Re [750]) at a wavelength of 750 nm is larger than the in-plane retardation value (Re [550]) at a wavelength of 550 nm. The retardation film (A) exhibits so-called reverse wavelength dispersion characteristics.

The difference (ΔRe _750−550 = Re) between the in-plane retardation value (Re [750]) at the wavelength 750 nm of the retardation film (A) and the in-plane retardation value (Re [550]) at the wavelength 550 nm. [750] -Re [550]) is preferably 3 nm or more, and more preferably 4 nm to 25 nm. By _using the retardation film (A) with ΔRe _750-550 in the above range, the viewing angle is wide, and the color of characters and images is small and the color shift is small no matter what direction the screen is viewed from 360 °. A liquid crystal display device can be obtained.

Conventionally, it has been difficult to produce a retardation film having a large ΔRe _750-550 . With the retardation film (A) of the present invention, ΔRe _750-550 can be increased, so that ideal wavelength dispersion characteristics can be obtained particularly in the red wavelength region. Therefore, the liquid crystal panel using the retardation film (A) can reduce the leakage of the backlight light to the viewer side when, for example, a black image is displayed. Therefore, the liquid crystal display device can be prevented from being colored red.

The wavelength dispersion value (D _A ) of the retardation film (A) is preferably more than 1, more preferably 1.02 to 1.30, and particularly preferably 1.04 to 1.15. Here, the chromatic dispersion value (D _A ) is a value calculated from the equation: Re [750] / Re [550]. The D _A by using a retardation film (A) falls within the above range, it is possible to obtain a liquid crystal display device having more excellent display characteristics.

  The transmittance (T [590]) at a wavelength of 590 nm of the retardation film (A) is preferably 85% or more, and more preferably 90% or more.

The in-plane birefringence (Δn _xy [590]) of the retardation film (A) at a wavelength of 590 nm is preferably 0.001 or more, and more preferably 0.0012 or more. As the retardation film having a large Δn _xy [590], a film having a desired retardation value can be made thin. In particular, when the retardation film (A) includes a thermoplastic polymer having at least the repeating unit represented by the general formula (II), Δn _xy [590] as compared with other polymers exhibiting reverse wavelength dispersion characteristics. Has a feature of large. The Δn _xy [590] is preferably 0.005 or less from the viewpoint of optical uniformity of the film.

The absolute value (C [590]) (m ² / N) of the photoelastic coefficient of the retardation film (A) is preferably 50 × 10 ⁻¹² or less, more preferably 30 × 10 ⁻¹² or less. . A retardation film having a small absolute value of the photoelastic coefficient in the above range is less likely to cause optical unevenness due to stress, for example. The C [590] is preferably 5 × 10 ⁻¹² or more from the viewpoint of obtaining a retardation film (A) having a large Δn _xy [590].

  The refractive index ellipsoid of the retardation film (A) preferably exhibits a relationship of nx> ny = nz (also referred to as positive uniaxiality) or a relationship of nx> ny> nz (both negative biaxiality). Say). When the refractive index ellipsoid of the retardation film (A) shows a relationship of nx> ny = nz, Re [590] and Rth [590] of the retardation film (A) are 10 nm or more, and | Rth [590] −Re [590] | is less than 10 nm. When the refractive index ellipsoid of the retardation film (A) shows a relationship of nx> ny> nz, Re [590] and Rth [590] of the retardation film (A) are 10 nm or more, and Rth [590] -Re [590] is 10 nm or more.

  When the refractive index ellipsoid of the retardation film (A) shows a relationship of nx> ny = nz, Re [590] of the retardation film (A) is preferably 60 nm to 180 nm, more preferably 70 nm to 170 nm. The Nz coefficient of the retardation film (A) is preferably more than 0.9 and less than 1.1.

  When the refractive index ellipsoid of the retardation film (A) shows a relationship of nx> ny> nz, Re [590] of the retardation film (A) is preferably 40 nm to 160 nm, more preferably 50 nm to 150 nm. Rth [590] of the retardation film (A) is preferably 60 nm to 180 nm, and more preferably 70 nm to 170 nm. The Nz coefficient of the retardation film (A) is preferably 1.1 to 6.0, and more preferably 1.1 to 4.0.

When the retardation film (A) is used in the configuration shown in FIG. 4, the retardation value of the retardation film (A) depends on the refractive index ellipsoid of the protective layer (A) and the retardation value. It can be set appropriately as appropriate. For example, when the refractive index ellipsoid of the protective layer (A) exhibits a relationship of nx = ny> nz (also referred to as negative uniaxiality), Re _A [590] of the retardation film (A) is the protective layer ( The sum of A) and Rth _H [590] (Re _A [590] + Rth _H [590]) is preferably set to be 100 nm to 180 nm. Specifically, for example, when Rth _H [590] is 60 nm, Re _A [590] of the retardation film (A) is preferably 40 nm to 120 nm. The details of the protective layer (A) will be described later.

  The thickness of the retardation film (A) can be appropriately set to an appropriate value depending on the purpose. The thickness is preferably 20 μm to 200 μm, and more preferably 30 μm to 100 μm. When the retardation film (A) is in the above thickness range, a practically sufficient mechanical strength and desired optical characteristics can be obtained.

The water absorption of the retardation film (A) is preferably 8% or less, more preferably 2% to 6%. Further, the moisture permeability of the retardation film (A) is preferably not 400 g / ^{m 2} or less, more preferably from ^{10g / m 2 ~200g / m 2} . In particular, when the retardation film (A) includes a thermoplastic polymer having at least the repeating unit represented by the general formula (II), the water absorption rate is higher than other general-purpose polymers, and the moisture permeability is high. It has the characteristic of being low. Such a retardation film (A) has excellent adhesion to the polarizer and can prevent deterioration of the polarizer due to water vapor.

[D-3. Method for producing retardation film (A)]
In one embodiment, the retardation film (A) used in the present invention is obtained by molding the thermoplastic polymer or the resin composition containing the thermoplastic polymer into a sheet shape to obtain a polymer film (A). Further, the polymer film (A) is further stretched to align the main chain and the side chain in the thermoplastic polymer.

  The polymer film (A) can be obtained by any appropriate forming method. Examples of the molding process include compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP molding, and solvent casting.

  As a method for stretching the polymer film (A), any suitable stretching method can be adopted depending on the purpose. Examples of the stretching method include a longitudinal uniaxial stretching method, a transverse uniaxial stretching method, a longitudinal and transverse simultaneous biaxial stretching method, and a longitudinal and transverse sequential biaxial stretching method. The stretching direction may be the longitudinal direction (MD direction) of the film or the width direction (TD direction). Moreover, you may extend | stretch in the diagonal direction (diagonal extending | stretching) using the extending | stretching method of FIG. 1 of Unexamined-Japanese-Patent No. 2003-262721.

  Conditions for stretching the polymer film (A) can be appropriately set. The stretching temperature is preferably Tg + 1 ° C. to Tg + 30 ° C. with respect to the glass transition temperature (Tg) of the polymer film (A). The draw ratio is preferably more than 1 and not more than 3 times. The feeding speed at the time of stretching is preferably 0.5 m / min to 30 m / min in view of mechanical accuracy, stability and the like. By selecting such conditions, it is possible to obtain a retardation film (A) having a highly transparent retardation value and high transparency.

[E. Retardation film (B)]
In the liquid crystal panel of the present invention, preferably, the refractive index ellipsoid has a relationship of nx = ny> nz (also referred to as negative uniaxiality) between the retardation film (A) and the second polarizer. The retardation film (B) shown is further provided. The retardation film (B) is preferably disposed adjacent to the liquid crystal cell in order to optically compensate for the birefringence (nz> nx = ny) of the liquid crystal cell. In one embodiment, as shown in FIGS. 2 and 4, the retardation film (B) is disposed between the liquid crystal cell and the second polarizer. In another embodiment, as shown in FIG. 3, the retardation film (B) is disposed between the liquid crystal cell and the retardation film (A). Such a liquid crystal panel can obtain a wider viewing angle.

[E-1. Retardation Film (B) Material]
As a material for forming the retardation film (B), any appropriate material can be adopted as long as the refractive index ellipsoid shows a relationship of nx = ny> nz. The retardation film (B) is preferably at least one selected from the group consisting of cellulose polymers, amideimide polymers, imide polymers, amide polymers, ether ether ketone polymers, and cycloolefin polymers. Contains polymer. When these polymers are formed into a sheet shape by the solvent casting method, the molecules are likely to spontaneously orientate during the evaporation process of the solvent, so that the refractive index ellipsoid shows a relationship of nx = ny> nz. Is easily obtained. These polymers can be obtained, for example, by the method described in US Pat. No. 5,344,916.

  The retardation film (B) may be one using a liquid crystal composition. When a liquid crystal composition is used, the retardation film (B) is a solidified layer or a cured layer of a liquid crystal composition containing a rod-like liquid crystal compound aligned in a planar alignment, or a discotic liquid crystal aligned in a columnar alignment. It includes a solidified layer or a cured layer of a liquid crystal composition containing a compound. If a liquid crystal compound is used, a thin retardation film can be obtained because the birefringence in the thickness direction is large.

  A retardation film comprising a solidified layer or a cured layer of a liquid crystalline composition containing a rod-like liquid crystal compound aligned in the planar arrangement can be obtained, for example, by the method described in JP-A No. 2003-287623. Further, a retardation film comprising a solidified layer or a cured layer of a liquid crystalline composition containing a discotic liquid crystal compound aligned in the columnar arrangement can be obtained by, for example, a method described in JP-A-9-117983. .

  Particularly preferably, the retardation film (B) contains an imide polymer. Preferably, the imide polymer has a hexafluoroisopropylidene group and / or a trifluoromethyl group. More preferably, the imide-based polymer has at least a repeating unit represented by the following general formula (III) or a repeating unit represented by the following general formula (IV). The imide-based polymer containing these repeating units is excellent in transparency and solubility in general-purpose solvents, and has a large birefringence index in the thickness direction. Furthermore, in order to show a steep positive wavelength dispersion characteristic, the relationship of the wavelength dispersion characteristic with the retardation film (A) described later; ΔD can be increased.

In the general formulas (III) and (IV), G and G ′ are a covalent bond, a CH ₂ group, a C (CH ₃ ) ₂ group, a C (CF ₃ ) ₂ group, a C (CX ₃ ) ₂ group (here X is a halogen.), Each independently from the group consisting of CO, O, S, SO ₂ , Si (CH ₂ CH ₃ ) ₂ and N (CH ₃ ) groups. Represents a group selected, and may be the same or different.

  In the general formula (III), L is a substituent, and e represents the number of substitutions. L is, for example, a halogen, an alkyl group having 1 to 3 carbon atoms, a halogenated alkyl group having 1 to 3 carbon atoms, a phenyl group, or a substituted phenyl group, and in a plurality of cases, they are the same or different. e is an integer from 0 to 3.

  In the above general formula (IV), Q is a substituent, and f represents the number of substitutions. Q is, for example, selected from the group consisting of hydrogen, halogen, alkyl group, substituted alkyl group, nitro group, cyano group, thioalkyl group, alkoxy group, aryl group, substituted aryl group, alkyl ester group, and substituted alkyl ester group And when Q is plural, they are the same or different. f is an integer from 0 to 4, and g and h are integers from 1 to 3, respectively.

  The imide-based polymer can be obtained, for example, by a reaction between tetracarboxylic dianhydride and diamine. The repeating unit of the general formula (III) is, for example, a tetracarboxylic acid having 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl as a diamine and at least two aromatic rings. It can be obtained by reaction with dianhydride. As the repeating unit of the general formula (IV), for example, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropanoic acid dianhydride is used as a tetracarboxylic dianhydride, and this is combined with an aromatic ring. It can be obtained by reacting with at least two diamines. The reaction may be, for example, chemical imidization that proceeds in two stages or thermal imidization that proceeds in one stage.

  Any appropriate tetracarboxylic dianhydride may be selected. Examples of the tetracarboxylic dianhydride include 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropanoic dianhydride and 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride. 2,3,3 ′, 4-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride, 2,2′-dibromo-4,4 ′, 5 , 5′-biphenyltetracarboxylic dianhydride, 2,2′-bis (trifluoromethyl) -4,4 ′, 5,5′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4 '-Biphenyltetracarboxylic dianhydride, 4,4'-bis (3,4-dicarboxyphenyl) ether dianhydride, 4,4'-oxydiphthalic dianhydride, 4,4'-bis (3 4-dicarboxyl Yl) sulfonic acid dianhydride, bis (2,3-carboxyphenyl) methane dianhydride, bis (3,4-carboxyphenyl) diethyl silane dianhydride, and the like.

  Any appropriate diamine may be selected. Examples of the diamine include 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl, 4,4′-diaminobiphenyl, 4,4′-diaminophenylmethane, 4,4 ′-( 9-fluorenylidene) -dianiline, 3,3′-dichloro-4,4′-diaminodiphenylmethane, 2,2′-dichloro-4,4′-diaminobiphenyl, 4,4′-diaminodiphenyl ether, 3,4′- Examples include diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenylthioether, and the like.

  The imide-based polymer is a polyethylene oxide standard weight average molecular weight (Mw) using a dimethylformamide solution (a solution obtained by adding 10 mM lithium bromide and 10 mM phosphoric acid to make a 1 L dimethylformamide solution) as a developing solvent. However, it is preferably 20,000 to 180,000. The imidation ratio of the polymer is preferably 95% or more. The imidation rate can be determined from an integral intensity ratio between a proton peak derived from polyamic acid, which is a polyimide precursor, and a proton peak derived from polyimide.

[E-2. Various properties of retardation film (B)]
In the retardation film (B), the refractive index ellipsoid shows a relationship of nx = ny> nz. In this case, Re [590] of the retardation film (B) is less than 10 nm, more preferably less than 5 nm. Rth [590] of the retardation film (B) is 10 nm or more, preferably 100 nm to 350 nm, and more preferably 120 nm to 310 nm.

When the retardation film (B) is used in the configuration shown in FIG. 4, the retardation value of the retardation film (B) is appropriately set in consideration of the optical characteristics of the protective layer (B). Can be done. For example, if the refractive index ellipsoid of the protective layer (B) shows the relation: nx = ny> nz, _Rth B of the retardation film (B) [590] is, _Rth H [590] of protective layer (B) (Rth _B [590] + Rth _H [590]) is preferably set to be 100 nm to 350 nm. Specifically, for example, when Rth _H [590] is 60 nm, Rth _B [590] of the retardation film (B) is preferably 40 nm to 290 nm. Details of the protective layer (B) will be described later.

  The transmittance (T [590]) at a wavelength of 590 nm of the retardation film (B) is preferably 85% or more, and more preferably 90% or more.

The birefringence (Δn _xz [590]) in the thickness direction at a wavelength of 590 nm of the retardation film (B) is preferably 0.005 or more, more preferably 0.01 or more, and particularly preferably 0.8. 03 or more. As the retardation film having a large Δn _xz [590], a film having a desired retardation value can be made thin. The Δn _xz [590] is preferably 0.08 or less and more preferably 0.06 or less from the viewpoint of the optical uniformity of the film.

  The retardation film (B) preferably has a 40 ° inclination retardation value (R40 [750]) at a wavelength of 750 nm smaller than a 40 degree inclination retardation value (R40 [550]) at a wavelength of 550 nm. The retardation film (B) exhibits a so-called positive wavelength dispersion characteristic.

The difference (ΔR40 _550-750 ) between the retardation value (R40 [550]) at a wavelength of 550 nm and the retardation value (R40 [750]) at a wavelength of 750 nm of the retardation film (B). = R40 [550] -R40 [750]) is preferably 5 nm or more, and more preferably 5 nm to 20 nm. By _using the retardation film (B) with ΔR40 _550-750 in the above range, the viewing angle is wide, and the color of characters and images is small and the color shift is small no matter what direction the screen is viewed from 360 °. A liquid crystal display device can be obtained.

_{D B} of the retardation film (B) is preferably less than 1.0, more preferably from 0.85 to 0.98, particularly preferably 0.90 to 0.96. Here, the chromatic dispersion value (D _B ) is a value calculated from the formula: R40 [750] / R40 [550]. The D _B by using a retardation film (B) within the above range, it is possible to obtain a liquid crystal display device having more excellent display characteristics.

The retardation wavelength dispersion value of the film (A) and _{(D A),} the difference of the retardation wavelength dispersion value of the film _{(B) (D B) (} ΔD = D A -D B) is preferably 0.05 It is above, More preferably, it is 0.07-0.17, Especially preferably, it is 0.09-0.15. By using the retardation film having ΔD in the above range, the optical compensation of the liquid crystal panel is more optimally performed. As a result, a liquid crystal display device having even better display characteristics can be obtained.

  The thickness of the retardation film (B) can be appropriately set to an appropriate value depending on the purpose. The thickness is preferably 0.5 μm to 100 μm. When an imide polymer is used as the retardation film (B), the thickness of the retardation film (B) is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 6 μm. If it is said range, the retardation film (B) which is thin and has the target optical characteristic can be obtained.

[E-3. Method for producing retardation film (B)]
The method for producing the retardation film (B) used in the present invention is not limited to the method using the spontaneous molecular orientation of the polymer molecules as described above, the method using the liquid crystalline composition, any molding processing method, A stretching method may be selected. Examples of the molding method and the stretching method include those described in the above section D-3.

[F. Protective layer (A) and (B)]
The protective layers (A) and (B) used in the present invention are used to reduce the shrinkage and expansion of adjacent polarizers and further increase the mechanical strength. The protective layers (A) and (B) may be the same or different. The thickness of the protective layers (A) and (B) is preferably 20 μm to 100 μm.

  The refractive index ellipsoids of the protective layers (A) and (B) preferably exhibit a relationship of nx = ny> nz or a relationship of nx = ny = nz (also referred to as optically isotropic). . When the refractive index ellipsoid of the protective layer shows a relationship of x = ny> nz, Re [590] of the protective layer is less than 10 nm, and Rth [590] is 10 nm to 80 nm. When the refractive index ellipsoid of the protective layer shows a relationship of nx = ny = nz, Re [590] and Rth [590] of the protective layer are both less than 10 nm.

  Any appropriate material can be adopted as the material for forming the protective layers (A) and (B). Preferably, the protective layer includes a polymer film including at least one polymer selected from the group consisting of a cellulose-based polymer, a cycloolefin-based polymer, and an acrylic polymer. The polymer film containing the cellulose polymer can be obtained by, for example, the method described in Example 1 of JP-A-7-112446. A polymer film containing the cycloolefin-based polymer can be obtained, for example, by the method described in JP-A-2001-350017. The polymer film containing the acrylic polymer can be obtained by the method described in Example 1 of JP-A-2004-198952, for example.

[G. Liquid crystal display device)
The liquid crystal display device of the present invention includes the liquid crystal panel. FIG. 6 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. It should be noted that the ratios of the vertical, horizontal, and thickness of each component shown in FIG. 6 are different from actual ones for easy viewing. The liquid crystal display device 200 includes at least a liquid crystal panel 100 and a backlight unit 80 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 type is adopted, the backlight unit 80 preferably includes at least a light source 81, a reflection film 82, a diffusion plate 83, a prism sheet 84, and a brightness enhancement film 85. When the sidelight method is adopted, preferably, the backlight unit further includes at least a light guide plate and a light reflector in addition to the above-described configuration. In addition, as long as the effect of the present invention is obtained, a part of the optical member illustrated in FIG. 6 can be omitted depending on the application, such as the illumination method of the liquid crystal display device and the driving mode of the liquid crystal cell, or Other optical members can be substituted.

  The liquid crystal display device may be a transmissive type that irradiates light from the back side of the liquid crystal panel to view the screen, or a reflective type that irradiates light from the viewing side of the liquid crystal panel to view the screen. good. Alternatively, the liquid crystal display device may be a transflective type having both transmissive and reflective properties.

  The liquid crystal display device of the present invention has a feature that, for example, the viewing angle is wide. The viewing angle (polar angle range with a contrast ratio of 10 or more) of the liquid crystal display device is preferably 160 ° or more in the vertical direction and 160 ° or more in the horizontal direction. The average value of the contrast ratio of the liquid crystal display device at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° is preferably 50 or more, and more preferably 80 to 200. Further, the minimum value of the contrast ratio of the liquid crystal display device at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° is preferably 20 or more, and more preferably 30 to 150.

The liquid crystal display device of the present invention has a feature that, for example, when a screen displaying a black image is viewed from an oblique direction, red coloring is small no matter which direction the screen is viewed from 360 °. The average value of a ^* at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° of the liquid crystal display device is preferably 6 or less, and more preferably 2 or less. The maximum value of a ^* at the polar angle of 60 ° and the azimuth angle of 0 ° to 360 ° of the liquid crystal display device is preferably 11 or less, and more preferably 7 or less. The above a ^* is the color coordinate of the CIE1976L ^* a ^* b ^* color space. The above a ^* represents the red size of the screen, and an ideal state where the screen is not colored is a ^* = 0.

The liquid crystal display device of the present invention has a feature that, for example, when a screen displaying a black image is viewed from an oblique direction, the color shift is small no matter which direction the screen is viewed from 360 °. The difference between the maximum value and the minimum value of Δa ^* b ^* [= {(a ^* ) ² + (b ^* ) ² } ^1/2 ] having a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° of the liquid crystal display device is , Preferably 9 or less, more preferably 5 or less. The maximum value of Δa ^* b ^* at the polar angle of 60 ° and the azimuth angle of 0 ° to 360 ° of the liquid crystal display device is preferably 11 or less, and more preferably 7 or less. The a ^* and b ^* are color coordinates a ^* and b ^* defined in the CIE 1976 L ^* a ^* b ^* color space. Δa ^* b ^* represents the magnitude of coloring of the screen, and Δa ^* b ^* = 0 in an ideal state where the screen is not colored.

[H. (Use)
The liquid crystal display device of the present invention is used for any appropriate application. Applications include, for example, OA equipment such as personal computer monitors, notebook computers, and copiers, mobile phones, watches, digital cameras, personal digital assistants (PDAs), portable devices such as portable game machines, video cameras, televisions, microwave ovens, etc. Home appliances, back monitors, car navigation system monitors, car audio and other in-vehicle equipment, exhibition equipment such as commercial store information monitors, security equipment such as surveillance monitors, nursing care monitors, medical monitors, etc. Nursing care / medical equipment.

  Preferably, the use of the liquid crystal display device of the present invention is a television. The screen size of the television is preferably a wide 17 type (373 mm × 224 mm) or more, more preferably a wide 23 type (499 mm × 300 mm) or more, and particularly preferably a wide 32 type (687 mm × 412 mm) or more. .

The present invention will be further described using the above examples and comparative examples. In addition, this invention is not limited only to these Examples. In addition, each analysis method used in the Example is as follows.
(1) Measurement of single transmittance of polarizer:
Using a spectrophotometer [product name “DOT-3” manufactured by Murakami Color Research Laboratory Co., Ltd.], the Y value after correcting the visibility was measured with a two-degree field of view (C light source) of JLS Z 8701-1982. did.
(2) Measurement of polarization degree of polarizer:
Using a spectrophotometer [product name “DOT-3” manufactured by Murakami Color Research Laboratory Co., Ltd.], the parallel transmittance (H ₀ ) and orthogonal transmittance (H ₉₀ ) of the polarizer are measured. Degree (%) = {(H ₀ −H ₉₀ ) / (H ₀ + H ₉₀ )} ^1/2 × 100. The parallel transmittance (H ₀ ) is a transmittance value of a parallel laminated polarizer prepared by superposing two polarizers of the same type so that their absorption axes are parallel to each other. The orthogonal transmittance (H ₉₀ ) is a value of the transmittance of an orthogonal stacked polarizer produced by superposing two polarizers of the same type so that their absorption axes are orthogonal to each other. In addition, these transmittance | permeability is Y value which performed visibility correction | amendment by the 2 degree visual field (C light source) of JlS Z 8701-1982.
(3) Measuring method of phase difference value (Re [λ], Rth [λ]), Nz coefficient, T [590]:
Measurement was performed at 23 ° C. using a trade name “KOBRA21-ADH” manufactured by Oji Scientific Instruments. In addition, the value measured using the Abbe refractometer [Atago Co., Ltd. product name "DR-M4"] was used for the average refractive index.
(4) Measuring method of thickness:
When the thickness was less than 10 μm, measurement was performed using a thin film spectrophotometer [manufactured by Otsuka Electronics Co., Ltd., “instant multiphotometry system MCPD-2000”]. When the thickness was 10 μm or more, measurement was performed using an Anritsu digital micrometer “KC-351C type”.
(5) Method for measuring molecular weight of polyimide:
Polyethylene oxide was calculated as a standard sample by a gel permeation chromatograph (GPC) method. The equipment, instruments and measurement conditions are as follows.
Sample: A sample was dissolved in an eluent to prepare a 0.1% by weight solution.
-Pretreatment: After standing for 8 hours, it was filtered through a 0.45 µm membrane filter.
・ Analyzer: “HLC-8020GPC” manufactured by Tosoh Corporation
-Column: Tosoh GMH _XL + GMH _XL + G2500H _XL
Column size: 7.8 mmφ x 30 cm each (total 90 cm)
Eluent: Dimethylformamide (added with 10 mM lithium bromide and 10 mM phosphoric acid to make up to 1 L dimethylformamide solution)
-Flow rate: 0.8 ml / min.
・ Detector: RI (differential refractometer)
-Column temperature: 40 ° C
・ Injection volume: 100 μl
(6) Measuring method of absolute value (C [590]) of photoelastic coefficient:
Using a spectroscopic ellipsometer [product name “M-220” manufactured by JASCO Corporation], the sample (size 2 cm × 10 cm) is sandwiched at both ends and stress (5 to 15 N) is applied to the phase difference at the center of the sample. The value (23 ° C./wavelength 590 nm) was measured and calculated from the slope of the function of stress and retardation value.
(7) Measuring method of water absorption:
Measured according to method A of JIS K 7209-1984 “Testing method for water absorption rate and boiling water absorption rate of plastics”, the mass (M ₁ ) after adjusting the condition of the test piece, and the mass increase before and after water absorption (M ₂ − M ₁ ) ratio [{(M ₂ −M ₁ ) / M ₁ } × 100]. M ₂ is the mass after water absorption of the specimen. A test piece having a size of 5 cm × 5 cm was used.
(8) Method of measuring moisture permeability:
Measured according to JIS Z 0208-1976 “Method of testing moisture permeability of moisture-proof packaging material”. As the sample, a circular film sheet having a thickness of 3 mm or less and a thickness of 70 to 80 mmφ was used. In the moisture permeation test, a constant temperature and humidity device under conditions of a temperature of 40 ± 0.5 ° C. and a relative humidity of 90 ± 2% was used.
(9) Measuring method of glass transition temperature (Tg):
Using a differential scanning calorimeter [Seiko Co., Ltd. product name “DSC-6200”], it was determined by a method according to JIS K 7121 (1987) (measurement method of plastic transition temperature). Specifically, a sample of 3 mg was heated twice (heating rate: 10 ° C./min) in a nitrogen atmosphere (gas flow rate: 80 ml / min), measured twice, and the second data was adopted. The calorimeter corrected the temperature using a standard material (indium).
(10) Measuring method of contrast ratio:
After 30 minutes have passed since the backlight was turned on in a dark room at 23 ° C., the Y value of the XYZ display system was measured when displaying a white image and a black image using the product name “EZ Contrast 160D” manufactured by ELDIM. did. The contrast ratio “YW / YB” in the oblique direction was calculated from the Y value (YW) in the white image and the Y value (YB) in the black image. The long side of the liquid crystal panel was set to an azimuth angle of 0 °, and the normal direction was set to a polar angle of 0 °.
(11) Measuring method of coloring (a ^* ) and color shift amount (Δa ^* b ^* ) of liquid crystal display device:
After 30 minutes have passed since the light was turned on in a dark room at 23 ° C., a polar name of 60 ° and an azimuth angle of 0 ° to 360 ° of a screen displaying a black image using a product name “EZ Contrast 160D” manufactured by ELDIM. The color coordinates a ^* and b ^* , defined in the CIE 1976 L ^* a ^* b ^* color space, were measured. The oblique color shift amount (Δa ^* b ^* ) was calculated from the equation: {(a ^* ) ² + (b ^* ) ² } ^1/2 .

Preparation of polarizer [Reference Example 1]
A commercially available polarizing plate [trade name “NPF SIG1423DU” manufactured by Nitto Denko Corporation] was used as the polarizing plate A as it was. The polarizing plate A includes a polarizer and protective layers disposed on both sides of the polarizer. The single transmittance of the polarizer was 43%, and the degree of polarization was 99%. In each of the two protective layers of the polarizing plate A, the refractive index ellipsoid shows a relationship of nx = ny = nz, Re [590] = 0.5 nm, and Rth [590] is 1 nm.

[Reference Example 2]
A commercially available polarizing plate [trade name “NPF SEG1423DU” manufactured by Nitto Denko Corporation] was used as the polarizing plate B as it was. The polarizing plate B includes a polarizer and protective layers disposed on both sides of the polarizer. The single transmittance of the polarizer was 43%, and the degree of polarization was 99%. In each of the two protective layers of the polarizing plate B, the refractive index ellipsoid shows a relationship of nx = ny> nz, Re [590] = 0.5 nm, and Rth [590] is 60 nm.

Preparation of liquid crystal cell [Reference Example 3]
The liquid crystal panel was taken out from a commercially available liquid crystal display device including a VA mode liquid crystal cell [a Sony 40-inch liquid crystal television product name “BRAVIA KDL-40X1000”]. All optical films such as polarizing plates disposed above and below the liquid crystal cell were removed. The front and back of the glass plate of the obtained liquid crystal cell were washed, and liquid crystal cell A was obtained.

Synthesis of polyvinyl acetal polymer [Reference Example 4]
8.8 g of a vinyl alcohol polymer [manufactured by Nippon Synthetic Chemical Co., Ltd., trade name “NH-18” (polymerization degree 1800, saponification degree 99.0%)] in an air circulation drying oven at 105 ° C. for 2 hours After drying, it was dissolved in 167.2 g of dimethyl sulfoxide. 11.8 g of 2-methoxy-1-naphthaldehyde, 10.6 g of benzaldehyde, and 0.80 g of p-toluenesulfonic acid monohydrate were added thereto, followed by stirring at 40 ° C. for 1 hour. To the reaction solution, 23.64 g of 1,1-diethoxyethane (acetal) was further added and stirred at 40 ° C. for 1 hour. Thereafter, 2.13 g of triethylamine was added to terminate the reaction. The obtained crude product was reprecipitated with 1 L of methanol. The filtered polymer was dissolved in tetrahydrofuran and reprecipitated again with methanol. This was filtered and dried to obtain 11.5 g of a white polymer. The polymer was a vinyl acetal polymer having a repeating unit represented by the following structural formula (V) as measured by ¹ H-NMR. The vinyl acetal polymer had a glass transition temperature of 131 ° C.

Synthesis of imide polymer [Reference Example 5]
2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropanoic acid dianhydride in a reaction vessel (500 mL) equipped with a mechanical stirrer, Dean-Stark device, nitrogen inlet tube, thermometer and condenser tube [Clariant Japan Co., Ltd.] 17.77 g (40 mmol) and 2,2-bis (trifluoromethyl) -4,4′-diaminobiphenyl [Wakayama Seika Kogyo Co., Ltd.] 12.81 g (40 mmol) added. Subsequently, a solution in which 2.58 g (20 mmol) of isoquinoline was dissolved in 275.21 g of m-cresol was added, and the mixture was stirred at 23 ° C. for 1 hour (600 rpm) to obtain a uniform solution. Next, the reaction vessel was heated using an oil bath so that the temperature in the reaction vessel became 180 ± 3 ° C., and stirred for 5 hours while maintaining the temperature to obtain a yellow solution. After further stirring for 3 hours, the heating and stirring were stopped, and the mixture was allowed to cool to room temperature.

  Acetone was added to the yellow solution in the reaction vessel to completely dissolve the gel to prepare a diluted solution (7% by weight). When this diluted solution was gradually added to 2 L of isopropyl alcohol while stirring, a white powder was precipitated. This powder was collected by filtration and poured into 1.5 L of isopropyl alcohol for washing. Further, the same operation was repeated once again for washing, and then the powder was collected again by filtration. This was dried in a 60 ° C. air circulation type constant temperature oven for 48 hours and then dried at 150 ° C. for 7 hours to obtain a polyimide powder of the following structural formula (VI) (yield 85%). The polyimide had a polymerization average molecular weight (Mw) of 124,000 and an imidation ratio of 99.9%.

Production of retardation film (A) [Reference Example 6]
The vinyl acetal polymer (25 parts by weight) prepared in Reference Example 4 was dissolved in methyl ethyl ketone (100 parts by weight) to prepare a 20% by weight solution. This solution is uniformly cast in the form of a sheet with a comma coater on the surface of a polyethylene terephthalate film [trade name “Lumirror S27-E” manufactured by Toray Industries, Inc.] having a thickness of 75 μm. In the oven (error ± 1 ° C.), the solvent was evaporated while gradually raising the temperature from low temperature to 80 ° C. for 20 minutes, 120 ° C. for 20 minutes, and 150 ° C. for 60 minutes. The polyethylene terephthalate film was peeled off to prepare a polymer film (A-1) having a thickness of 120 μm. The polymer film (A-1) had a transmittance of 90% and a residual volatile component amount of 5%. The polymer film (A-1) was stretched 1.7 times at 135 ° C. ± 1 ° C. by a fixed-end lateral uniaxial stretching method using a dry heat biaxial stretching apparatus. The retardation film (A-1) thus obtained is shown in Table 1.

[Reference Example 7]
The polymer film (A-1) produced by the same method as in Reference Example 6 is 1.7 times at 140 ° C. ± 1 ° C. by a fixed-end lateral uniaxial stretching method using a dry heat biaxial stretching device. Stretched. Thus, obtained retardation film (A-2) is shown in Table 1.

Production of retardation film (B) [Reference Example 8]
The polyimide powder produced in Reference Example 5 was dissolved in methyl isobutyl ketone to prepare a 15% by weight polyimide solution. This solution is uniformly cast in the form of a sheet with a comma coater on the surface of a polyethylene terephthalate film [trade name “Lumirror S27-E” manufactured by Toray Industries, Inc.] having a thickness of 75 μm. In the oven (error ± 1 ° C.), the solvent was evaporated while gradually raising the temperature from low temperature to 80 ° C. for 2 minutes, 135 ° C. for 5 minutes, and 150 ° C. for 10 minutes. The polyethylene terephthalate film was peeled off to prepare a polyimide layer (retardation film (B)) having a thickness of 3 μm. In the retardation film (B), the refractive index ellipsoid shows a relationship of nx = ny> nz, and T [590] = 91%, Re [590] = 1 nm, Rth [590] = 120 nm, D _B (R40 [750] / R40 [550]) = 0.936.

Production of liquid crystal panel and liquid crystal display device [Example 1]
The retardation film (A-1) obtained in Reference Example 6 is applied to the surface on the viewing side of the liquid crystal cell A prepared in Reference Example 3 through the acrylic pressure-sensitive adhesive layer (20 μm). The slow axis direction of A-1) was stuck so as to be substantially orthogonal to the long side direction of the liquid crystal cell A. Next, the polarizing plate A obtained in Reference Example 1 is applied to the surface on the viewing side of the retardation film (A-1) via an acrylic pressure-sensitive adhesive layer (20 μm). Adhering was performed so that the direction was substantially parallel to the long side direction of the liquid crystal cell A. At this time, the absorption axis direction of the polarizing plate A and the slow axis direction of the retardation film (A-1) are substantially orthogonal.

Subsequently, the retardation film (B) obtained in Reference Example 7 was attached to the backlight side surface of the liquid crystal cell A via an acrylic pressure-sensitive adhesive layer (20 μm). Next, the polarizing plate B obtained in Reference Example 2 is applied to the backlight side surface of the retardation film (B) via the acrylic pressure-sensitive adhesive layer (20 μm) in the absorption axis direction of the polarizing plate B. However, it was stuck so as to be substantially orthogonal to the long side direction of the liquid crystal cell A. At this time, the absorption axis direction of the polarizing plate A and the absorption axis direction of the polarizing plate B are substantially orthogonal. FIG. 7 shows the wavelength dispersion characteristics of the retardation film (A-1) and retardation film (B) used in the liquid crystal panel of Example 1. The vertical axis in FIG. 7 is Re / Re [550] for the plot of the retardation film (A-1), and R40 / R40 [550] for the plot of the retardation film (B). . In the liquid crystal panel A, ΔD (D _A −D _B ) = 0.12.

This liquid crystal panel A was combined with the backlight unit of the original liquid crystal display device to produce a liquid crystal display device A. FIG. 8 is a contrast contour map of the liquid crystal display device of Example 1. As shown in FIG. 8, in this liquid crystal display device A, a characteristic region having a contrast of 10 or less was not observed in all directions. Therefore, the viewing angles in the vertical direction and the horizontal direction of the liquid crystal display device A were both 160 ° or more.
The liquid crystal display device A includes
Mean value of contrast ratio of polar angle 60 °, azimuth angle 0 ° to 360 ° = 81.5,
Minimum value of contrast ratio of polar angle 60 °, azimuth angle 0 ° to 360 ° = 24.9,
Average value of a ^* of polar angle 60 °, azimuth angle 0 ° to 360 ° = 1.00,
Maximum value of a ^* of polar angle 60 °, azimuth angle 0 ° to 360 ° = 5.60,
Difference between maximum value and minimum value of Δa ^* b ^* of polar angle 60 ° and azimuth angle 0 ° to 360 ° = 3.77
Maximum value of Δa ^* b ^* at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° = 8.59,
Met.

[Example 2]
A liquid crystal panel B was prepared in the same manner as in Example 1 except that the retardation film (A-2) was used instead of the retardation film (A-1), and the polarizing plate B was used instead of the polarizing plate A. And the liquid crystal display device B was produced. In the liquid crystal panel B, ΔD (D _A −D _B ) = 0.116. Also in this liquid crystal display device B, no characteristic region having a contrast of 10 or less was observed in all directions. Therefore, the viewing angles in the vertical direction and the horizontal direction of the liquid crystal display device B were both 160 ° or more.
The liquid crystal display device B is
Mean value of contrast ratio of polar angle 60 °, azimuth angle 0 ° to 360 ° = 79.9,
Minimum value of contrast ratio of polar angle 60 °, azimuth angle 0 ° to 360 ° = 34.1,
Average value of a ^* of polar angle 60 ° and azimuth angle 0 ° to 360 ° = 5.38
The maximum value of a ^* at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° = 10.51.
Difference between maximum value and minimum value of Δa ^* b ^* at polar angle of 60 ° and azimuth angle of 0 ° to 360 ° = 7.03,
Maximum value of Δa ^* b ^* at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° = 10.59,
Met.

[Comparative Reference Example 1]
A commercially available liquid crystal display device (Sony 40-inch liquid crystal television product name “BRAVIA KDL-40X1000”) including a VA mode liquid crystal cell was used as the liquid crystal display device X as it was.
The liquid crystal display device X includes:
Average value of a ^* of polar angle 60 °, azimuth angle 0 ° to 360 ° = 6.67,
The maximum value of a ^* at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° = 11.84,
The difference between the maximum value and the minimum value of Δa ^* b ^* at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° = 9.31
Maximum value of Δa ^* b ^* at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° = 11.85,
Met.

[Evaluation]
FIG. 9 shows changes in coloration (a ^* ) of the liquid crystal display devices of Example 1 and Comparative Reference Example 1 at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° on a screen displaying a black image. FIG. 10 shows changes in the color shift amount (Δa ^* b ^* ) at the polar angle 60 ° and the azimuth angle 0 ° to 360 ° of the screen displaying the black image in the liquid crystal display devices of Example 1 and Comparative Reference Example 1. is there. As is clear from FIGS. 9 and 10, the liquid crystal display device of Example 1 has much more variation depending on the azimuth angle of a ^* and Δa ^* b ^* than the liquid crystal display device of Comparative Reference Example 1. It can be seen that the coloring and the color shift are remarkably small even if the screen is viewed from any 360 ° direction.

  As described above, since the liquid crystal panel of the present invention exhibits excellent display characteristics, it can be suitably used for liquid crystal televisions, mobile phones and the like.

It is a schematic sectional drawing of the liquid crystal panel by the 1st Embodiment of this invention. It is a schematic sectional drawing of the liquid crystal panel by the 2nd Embodiment of this invention. It is a schematic sectional drawing of the liquid crystal panel by the 3rd Embodiment of this invention. It is a schematic sectional drawing of the liquid crystal panel by the 4th Embodiment of this invention. It is a schematic diagram which shows the concept of the typical manufacturing process of the polarizer used for this invention. 1 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. It is a graph which shows the wavelength dispersion characteristic of the phase difference film (A-1) used for the liquid crystal panel of Example 1, and phase difference film (B). FIG. 3 is a contrast contour map of the liquid crystal display device of Example 1. It is a graph which shows the change of coloring (a ^* ) in the polar angle 60 degrees of the screen which displayed the black image of the liquid crystal display device of Example 1 and the comparative reference example 1, and azimuth | direction angles 0 degree-360 degrees. FIG. 6 is a graph showing changes in color shift amount (Δa ^* b ^* ) at a polar angle of 60 ° and an azimuth angle of 0 ° to 360 ° of a screen displaying a black image in the liquid crystal display devices of Example 1 and Comparative Reference Example 1. is there.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal cell 11, 11 'Board | substrate 12 Liquid crystal layer 21 1st polarizer 22 2nd polarizer 23 Protective layer (A)
24 Protective layer (B)
31 Retardation film (A)
32 retardation film (B)
80 Backlight unit 81 Light source 82 Reflective film 83 Diffuser plate 84 Prism sheet 85 Brightness enhancement films 101, 102, 103, 104 Liquid crystal panel 200 Liquid crystal display device 300 Feeding part 301 Polymer film 310 Aqueous solution bath containing iodine 320 Boric acid and iodine Aqueous solution bath 330 containing potassium iodide Aqueous solution baths 311, 312, 321, 322, 331, 332 roll 340 containing potassium iodide Drying means

Claims (12)

A liquid crystal cell, a first polarizer disposed on one side of the liquid crystal cell, a second polarizer disposed on the other side of the liquid crystal cell, the liquid crystal cell and the first polarizer A retardation film (A) disposed between and at least,
The retardation film (A) includes a thermoplastic polymer having at least a substituent (a) represented by the following general formula (I), and has an in-plane retardation value (Re [750]) at a wavelength of 750 nm. A liquid crystal panel larger than the in-plane retardation value (Re [550]) at a wavelength of 550 nm:
In the formula, each of R ^{1 to} R ⁷ independently represents a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or a linear or branched halogenated group having 1 to 4 carbon atoms. Alkyl group, linear or branched alkoxy group having 1 to 4 carbon atoms, linear or branched thioalkoxy group having 1 to 4 carbon atoms, linear or branched alkoxycarbonyl group, acyloxy group, amino group, azide Represents a group, a nitro group, a cyano group, a hydroxyl group, or a thiol group (where R ¹ is not a hydrogen atom).   The liquid crystal panel according to claim 1, wherein the liquid crystal cell includes liquid crystal molecules aligned in a homeotropic alignment.   The liquid crystal panel according to claim 1 or 2, wherein a slow axis direction of the retardation film (A) is substantially orthogonal to an absorption axis direction of the first polarizer.   The liquid crystal panel according to claim 1, wherein the thermoplastic polymer is a vinyl acetal polymer, an olefin polymer, or a carbonate polymer. The difference (ΔRe _750−550 = Re) between the in-plane retardation value (Re [750]) at the wavelength 750 nm of the retardation film (A) and the in-plane retardation value (Re [550]) at the wavelength 550 nm. The liquid crystal panel according to claim 1, wherein [750] −Re [550]) is 3 nm or more. The liquid crystal panel according to any one of claims 1 to 5, wherein an in-plane birefringence (Δn _xy [590]) of the retardation film (A) at a wavelength of 590 nm is 0.001 or more. The liquid crystal panel according to claim 1, wherein an absolute value of a photoelastic coefficient of the retardation film (A) is 50 × 10 ⁻¹² (m ² / N) or less.   The liquid crystal panel according to claim 1, wherein the refractive index ellipsoid of the retardation film (A) shows a relationship of nx> ny = nz or nx> ny> nz.   Any one of Claim 1 to 8 further equipped with the phase difference film (B) in which a refractive index ellipsoid shows the relationship of nx = ny> nz between the said phase difference film (A) and the said 2nd polarizer. Liquid crystal panel according to crab.   The retardation film (B) contains at least one polymer selected from the group consisting of cellulose polymers, amideimide polymers, imide polymers, amide polymers, ether ether ketone polymers, and cycloolefin polymers. The liquid crystal panel according to claim 9. The retardation wavelength dispersion value of the film (A) and _{(D A),} the difference _(D A -D _B) of the retardation wavelength dispersion value of the film _{(B) (D} B) is 0.05 or more, wherein Item 9 or 10 liquid crystal panel:
Here, the chromatic dispersion value (D _A ) is a value calculated from the formula; Re [750] / Re [550], and Re [750] and Re [550] are in-plane at wavelengths of 750 nm and 550 nm, respectively. The chromatic dispersion value (D _B ) is a value calculated from the equation: R40 [750] / R40 [550], and R40 [750] and R40 [550] have a wavelength of 750 nm and This is a phase difference value measured at an inclination of 40 degrees from the normal direction at 550 nm.   A liquid crystal display device comprising the liquid crystal panel according to claim 1.