JP4738280B2 - Optical compensation film, polarizing plate, and liquid crystal display device - Google Patents

Description

  The present invention relates to an optical compensation film, a polarizing plate, and a liquid crystal display device, and in particular, an optical compensation film having characteristics suitable for manufacturing a vertical alignment type liquid crystal display device having excellent viewing angle characteristics and a small film thickness, and The present invention relates to a polarizing plate and a liquid crystal display device having the optical compensation film.

  The liquid crystal display device includes a liquid crystal cell and a polarizing plate. The polarizing plate has a protective film and a polarizing film. The polarizing plate is obtained, for example, by dyeing a polarizing film made of a polyvinyl alcohol film with iodine, stretching, and laminating protective films on both surfaces thereof. In the transmissive liquid crystal display element, the polarizing plate is attached to both sides of the liquid crystal cell, and one or more optical compensation films may be disposed. In a reflective liquid crystal display device, a reflector, a liquid crystal cell, one or more optical compensation films, and a polarizing plate are arranged in this order. The liquid crystal cell includes a liquid crystal molecule, two substrates for encapsulating the liquid crystal molecule, and an electrode layer for applying a voltage to the liquid crystal molecule. The liquid crystal cell performs ON / OFF display depending on the alignment state of liquid crystal molecules, and can be applied to both transmission and reflection types. TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensatory Bend) ), Display modes such as VA (Vertically Aligned) and ECB (Electrically Controlled Birefringence) have been proposed.

  Among such LCDs, for applications that require high display quality, 90-degree twisted nematic liquid crystal display elements (hereinafter referred to as TN mode) driven by a thin film transistor using nematic liquid crystal molecules having positive dielectric anisotropy. Is mainly used. However, although the TN mode has excellent display characteristics when viewed from the front, the contrast decreases when viewed from an oblique direction, or gradation inversion that reverses brightness in gradation display occurs. There is a viewing angle characteristic that deteriorates, and there is a strong demand for this improvement.

  In recent years, as an LCD method for improving the viewing angle characteristics, nematic liquid crystal molecules having negative dielectric anisotropy are used, and the major axis of the liquid crystal molecules is set in a direction substantially perpendicular to the substrate without applying a voltage. A vertical alignment nematic liquid crystal display element (hereinafter referred to as VA mode) in which alignment is performed and this is driven by a thin film transistor has been proposed (see Patent Document 1). This VA mode not only has excellent display characteristics when viewed from the front, but also exhibits a wide viewing angle characteristic by applying a viewing angle compensation phase difference plate. In the VA mode, a wider viewing angle characteristic can be obtained by using two negative uniaxial retardation plates having an optical axis in a direction perpendicular to the film surface, above and below the liquid crystal cell. It is also known that a wider viewing angle characteristic can be realized by using a uniaxially oriented retardation plate having a positive refractive index anisotropy with a retardation value of 50 nm (see Non-Patent Document 1). .

  However, increasing the number of retardation plates increases the production cost, and tends to cause a reduction in yield because a large number of films are bonded together. Furthermore, since a plurality of films are used, the thickness increases, which may be disadvantageous for thinning the display device. Moreover, since an adhesive layer is used for lamination | stacking of a stretched film, an adhesive layer shrink | contracts by a temperature / humidity change, and defects, such as peeling and a curvature between films, may generate | occur | produce.

  As a method for improving these, a method of reducing the number of retardation plates (see Patent Document 2) and a method using a cholesteric liquid crystal layer (see Patent Document 3) are disclosed. However, even in these methods, it is necessary to bond at least a plurality of films, which is insufficient in terms of thinning and production cost reduction.

  Therefore, for the purpose of improving the above problems, Patent Document 4 discloses a method of continuously forming an optically anisotropic layer on a long support using a discotic liquid crystal. However, even in this case, in order to obtain necessary optical characteristics (particularly, Rth value), the coating film thickness becomes thick, and thus problems such as coating unevenness have occurred.

Japanese Patent Laid-Open No. 2-176625 JP-A-11-95208 JP 2000-304931 A JP 2001-128050 A SID 97 DIGEST Pages 845-848

  An object of the present invention is to provide an optical compensation film that is free of unevenness and that can be optically compensated accurately by a liquid crystal cell. A polarizing plate and a liquid crystal display device using the optical compensation film, particularly, VA mode A liquid crystal display device is provided.

  In order to solve this problem, the inventors of the present invention can obtain a high Rth value in a film provided with an optically anisotropic layer on a support, even if the optically anisotropic layer has a smaller thickness than the conventional film. I studied hard. If such a method is used, it is not necessary to increase the film thickness in order to obtain a high Rth value, so that coating unevenness can be prevented. As a result, it was found that the Rth value, which is the retardation in the thickness direction, can be increased by reducing the amount of ultraviolet light used for the polymerization of the optically anisotropic layer and relaxing the exothermic reaction between the liquid crystal molecules. Based on this finding, the present invention has been completed.

That is, the means for solving the above problems are as follows.
[1] An optical compensation film having an optically anisotropic layer on a polymer film substrate, having an in-plane retardation (Re) of 0 to 10 nm and a thickness direction retardation (Rth) of 100 to 300 nm. And Rth / d of the optically anisotropic layer (a value obtained by dividing retardation in the thickness direction by the film thickness) is 0.065 to 0.16.
[2] The optical compensation film according to [1], wherein Rth / d of the optically anisotropic layer is 0.085 to 0.16.

[3] The optical compensation film according to [1] or [2], which satisfies the following formula (1).
General formula (1)
1.03 ≦ Rth (450) / Rth (550) ≦ 1.30
[4] The optical compensation film according to any one of [1] to [3], wherein the optically anisotropic layer satisfies the following formula (2).
General formula (2)
1.06 ≦ Rth (450) / Rth (550) ≦ 1.30

[5] The optical compensation film according to any one of [1] to [4], wherein the optically anisotropic layer is formed from a polymerizable composition.
[6] The polymerizable composition contains a photopolymerization initiator, the photosensitivity range of the photopolymerization initiator is in the range of 330 nm to 450 nm, and the photopolymerization initiator contains atoms other than halogen radicals or hydrogen atoms. The optical compensation film according to [5], wherein a hydrocarbon radical having a number of 8 or less is generated.

[7] The optical compensation film according to [5] or [6], wherein the polymerizable composition contains a polyfunctional monomer having four or more double bonds.
[8] The polymerizable composition is a composition containing a discotic liquid crystalline compound having a polymerizable group, and the discotic structural unit of the discotic liquid crystalline compound is a polymer film substrate in the optically anisotropic layer. The optical compensation film according to any one of [5] to [7], which is horizontally oriented with respect to the surface.
[9] The optical compensation film according to [8], wherein the discotic liquid crystalline compound is a compound represented by the following formula (I).

[Wherein, A ¹ and A ² each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms; Atoms, halogen atoms, alkyl groups having 1 to 12 carbon atoms, alkoxy groups having 1 to 12 carbon atoms, acyl groups having 2 to 13 carbon atoms, alkylamino groups having 1 to 12 carbon atoms, Or an acyloxy group having 2 to 13 carbon atoms; or A ² and Y may combine to form a 5-membered ring or a 6-membered ring; Z is a halogen atom or the number of carbon atoms Is an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an acyl group having 2 to 13 carbon atoms, an alkylamino group having 1 to 12 carbon atoms, or 2 to 13 carbon atoms. Represents an acyloxy group; L represents —O— or —C; -, -S-, -NH-, an alkylene group, an alkenylene group, an alkynylene group, an arylene group and a divalent linking group selected from the group consisting of combinations thereof; Q represents a polymerizable group; , Represents an integer of 1 to 4; b represents an integer of 0 to (4-a)]

[10] The optical compensation film according to any one of [5] to [7], wherein the polymerizable composition contains a chiral nematic (cholesteric) liquid crystal compound.
[11] The optical compensation film according to any one of [5] to [10], wherein the optically anisotropic layer contains a fluoroaliphatic-containing polymer.
[12] The optically anisotropic layer according to any one of [1] to [5], comprising a polymer material having negative refractive index anisotropy when coated and having an optical axis in the normal direction of the surface. The optical compensation film according to any one of the above.
[13] The optical compensation film according to any one of [1] to [12], wherein a retardation in a thickness direction of the polymer film substrate is −25 to 25 nm.

[14] The optical compensation film according to any one of [1] to [13], wherein the polymer film is a cellulose acylate film.
[15] A polarizing plate having the optical compensation film according to any one of [1] to [14].
[16] A liquid crystal display device having the optical compensation film according to any one of [1] to [14].

[17] A liquid crystal layer including a pair of polarizing films whose absorption axes are orthogonal to each other, a pair of substrates disposed between the polarizing films, and a liquid crystal layer sandwiched between the substrates, The liquid crystal display device according to [16], wherein the sex molecules are aligned in a direction substantially perpendicular to the substrate in a non-driven state where no external electric field is applied.
[18] A second optical compensation film is further provided, and the second optical compensation film comprises a polymer stretched film, and the front retardation and the retardation in the thickness direction are represented by the following formulas (3) and (4): The liquid crystal display device according to [16] or [17].
General formula (3)
70 ≦ Re (550) ≦ 180
General formula (4)
30 ≦ Rth (550) ≦ 140

[19] The liquid crystal display device according to [18], wherein the second optical compensation film satisfies the following formula (5).
General formula (5)
0.7 ≦ Re (450) / Re (550) ≦ 1.0
[20] The liquid crystal display device according to [18] or [19], wherein the second optical compensation film is any of a cellulose acylate film, a norbornene film, a polycarbonate film, a polyester film, or a polysulfone film. .
[21] The second optical compensation film is directly laminated on one of the pair of polarizing films such that an in-plane retardation axis of the optical compensation film and an absorption axis of the polarizing film are orthogonal to each other. [20] The liquid crystal display device according to any one of [20].

  According to the present invention, it is possible to provide an optical compensation film in which a liquid crystal cell can be accurately optically compensated with a thin film without unevenness. A liquid crystal display device, particularly a VA mode liquid crystal display device, which has the optical compensation film of the present invention or a polarizing plate having the film, has excellent viewing angle characteristics.

  Hereinafter, an embodiment of the liquid crystal display device of the present invention and its constituent members will be described in order. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  In the present specification, “parallel” and “orthogonal” mean that the angle is within a range of strictly less than ± 10 °. In this range, an error from a strict angle is preferably less than ± 5 °, and more preferably less than ± 2 °. “Substantially parallel”, “substantially orthogonal”, and “substantially vertical” have the same meaning. Further, the “slow axis” means a direction in which the refractive index is maximized. Further, the measurement wavelength of the refractive index and the phase difference is a value at λ = 590 nm in the visible light region unless otherwise specified.

In this specification, “polarizing plate” is cut into a size to be incorporated into a long polarizing plate and a liquid crystal device unless otherwise specified (in this specification, “cutting” includes “punching” and “cutting out”. It is used in the meaning including both of the polarizing plates. In this specification, “polarizing film” and “polarizing plate” are distinguished from each other. “Polarizing plate” means a laminate having a transparent protective film for protecting the polarizing film on at least one side of the “polarizing film”. It shall be.
In the present specification, the description “(meth) acrylate” means “at least one of acrylate and methacrylate”. The same applies to “(meth) acrylic acid” and the like.

  In this specification, Re (λ) and Rth (λ) respectively represent in-plane retardation and retardation in the thickness direction at a wavelength λ. The measurement wavelength λ nm may be any wavelength as long as it is in the visible light range, specifically 400 to 800 nm, but is preferably in the range of 400 to 750 nm, preferably in the range of 400 nm to 700 nm. More preferably it is. In this specification, unless otherwise specified, Re and Rth mean values measured at 530 to 600 nm (or values calculated based on these values). In-plane retardation (Re) is a value measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments). When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth is calculated by the following method.

Rth is defined as Re, with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotation axis) (in the absence of the slow axis, any direction in the film plane is the rotation axis). )) At a step of 10 degrees from the normal direction to 50 degrees on one side with respect to the film normal direction, light of wavelength λ nm is incident from each inclined direction, and a total of 6 points are measured, and the measured retardation value KOBRA 21ADH or WR is calculated based on the assumed average refractive index and the input film thickness value.
In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing its sign to negative.
In addition, the retardation value is measured from the two inclined directions, with the slow axis as the tilt axis (rotation axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotation axis), Based on the value, the assumed value of the average refractive index, and the input film thickness value (d), Rth can also be calculated from the following equations (1) and (2).

The above Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction.
In formula (1), nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction perpendicular to nx in the plane, and nz represents the refractive index in the direction perpendicular to nx and ny. .
Formula (2) Rth = ((nx + ny) / 2−nz) × d
In the case where the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film having no so-called optic axis, Rth is calculated by the following method. Rth is the Re in 10 degree steps from −50 degrees to +50 degrees with respect to the normal direction of the film, with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotation axis). 11 points of light having a wavelength of λ nm are incident from an inclined direction, and KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed average refractive index, and the input film thickness value. Nz = (nx-nz) / (nx-ny) is further calculated from the calculated nx, ny, and nz. In this specification, unless otherwise specified, the measurement wavelength is 590 nm, and the measurement value is 25 ° C. and 60% RH.

  Hereinafter, the optical compensation film of the present invention will be described in detail. In the present invention, the optical compensation film eliminates image coloring of the liquid crystal display device and contributes to an increase in viewing angle. Further, when the support of the optical compensation film also serves as the protective film for the polarizing plate, or the optically anisotropic layer also serves as the protective film for the polarizing plate, the constituent members of the liquid crystal display device can be reduced. In other words, this aspect contributes to the thinning of the liquid crystal display device.

[Optical compensation film]
The optical compensation film of the present invention has substantially no in-plane retardation, negative refractive index anisotropy, and an optical axis in the normal direction. The in-plane retardation of the optical compensation film of the present invention is 0 to 10 nm, preferably 0 to 5 nm, and particularly preferably 0 to 3 nm. The retardation in the thickness direction is 100 to 300 nm, more preferably 120 to 270 nm, and particularly preferably 150 to 240 nm.
In addition, the wavelength dispersion Rth (450) / Rth (550) of the optical compensation film is preferably 1.03 or more, more preferably 1.06 or more, still more preferably 1.09 or more, and 1.12 or more. Is particularly preferred. (Here, Rth (450) represents the Re value at 450 nm, and Re (550) represents the Re value at 550 nm.) If these conditions are satisfied, the liquid crystal display element can be compensated over the entire visible light range. Become.

[Optically anisotropic layer]
The retardation Rth in the thickness direction of the optically anisotropic layer in the optical compensation film of the present invention divided by the film thickness d of the optically anisotropic layer, Rth / d is 0.065 to 0.160, Preferably, it is 0.075 or more, more preferably 0.085 or more. Moreover, Preferably it is 0.15 or less, More preferably, it is 0.14 or less. The in-plane retardation Re is 0 to 10 nm, preferably 0 to 5 nm. Such an optically anisotropic layer has an advantage that unevenness hardly occurs when continuously applied to a long support.

  In addition, the wavelength dispersibility Rth (450) / Rth (550) of the optically anisotropic layer is preferably 1.06 or more, more preferably 1.09 or more, still more preferably 1.12 or more. 15 or more is particularly preferable. (Here, Rth (450) represents the Re value at 450 nm, and Re (550) represents the Re value at 550 nm.) When these conditions are satisfied, the above wavelength is used as an optical compensation film when laminated on a polymer film. Dispersion characteristics can be exhibited, and the liquid crystal display element can be compensated over the entire visible light range.

[Optically anisotropic layer made of liquid crystalline compound]
The optical compensation film of the present invention is formed by laminating an optically anisotropic layer on a polymer film substrate. The optically anisotropic layer is preferably formed from a polymerizable composition, and in particular, from an optically negative refractive index anisotropy and a composition containing a liquid crystalline compound having a polymerizable group. Is preferred. As such an optically anisotropic layer, a layer formed from a polymerizable composition containing a chiral nematic (cholesteric) liquid crystalline compound, a composition containing a discotic liquid crystalline compound, and derived from the discotic liquid crystalline compound A layer in which the discotic structural unit is horizontally oriented with respect to the polymer film substrate surface.

The chiral nematic (cholesteric) liquid crystal compound means a compound that forms a chiral nematic (cholesteric) liquid crystal phase when a composition containing the compound is applied onto a polymer substrate. Compound or high-molecular liquid crystal compound.
In order to align the rod-like liquid crystalline compound with chiral nematic (cholesteric) orientation, an optically active rod-like liquid crystalline compound is used, or a mixture of the rod-like liquid crystalline compound and the optically active compound is used. The rod-like liquid crystalline compounds are azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano substituted phenyl pyrimidines, alkoxy substituted phenyl pyrimidines, Phenyl dioxanes, tolanes and alkenyl cyclohexyl benzonitriles are preferred.
A composition containing the compound can be applied on a polymer film substrate, and can be immobilized while maintaining the alignment state in the same manner as in the method for producing an optically anisotropic layer comprising a discotic liquid crystalline compound described later.

  The optically anisotropic layer can also be formed using a polymer material having negative refractive index anisotropy when coated and having an optical axis in the normal direction of the film surface. As such a polymer material, a film-forming material having at least one kind of aromatic ring (polyamide, polyimide, polyamic acid, polyester, polyesteramide, etc.) as proposed in JP-A-2000-190385 Or a low molecular weight compound capable of giving these polymers) has a negative refractive index anisotropy when coated, an optical axis in the normal direction of the surface, and is usually positive. Has retardation of wavelength dispersion.

[Optically anisotropic layer made of discotic liquid crystalline compound]
In the present invention, the optically anisotropic layer is preferably formed from a composition containing a discotic liquid crystalline compound.
Discotic liquid crystalline compounds are disclosed in various literatures (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); edited by the Chemical Society of Japan, Quarterly Chemical Review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10, Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 (1985); J. Zhang et al., J Am. Chem. Soc., Vol. 116, page 2655 (1994)) can be widely used. For the polymerization of the discotic liquid crystalline compound, for example, the method described in JP-A-8-27284 can be employed.

The discotic liquid crystalline compound preferably has a polymerizable group so that it can be fixed by polymerization. For example, a structure in which a polymerizable group is bonded as a substituent to a discotic core of a discotic liquid crystalline compound can be considered. A structure having a linking group between the discotic core and the polymerizable group is more preferable. When a structure having a linking group is employed, it becomes easier to maintain the alignment state in the polymerization reaction. The discotic liquid crystalline compound having a polymerizable group is preferably a compound represented by the following general formula (VI).
General formula (VI)
D (-LP) _n (In the general formula (VI), D is a discotic core, L is a divalent linking group, P is a polymerizable group, and n is an integer of 4 to 12) is there.)

  The discotic core (D), divalent linking group (L) and polymerizable group (P) in the formula (VI) are, for example, (D1) to (D15) described in JP-A No. 2001-4837. , (L1) to (L25) and (P1) to (P18) can be used.

  In the case of a discotic liquid crystalline compound having a polymerizable group, it is substantially horizontally aligned as described above. Preferable examples of the discotic liquid crystalline compound in this case also include those described in International Publication WO 01 / 88574A1, page 58, line 6 to page 65, line 8.

  In the optical compensation film of the present invention, the optically anisotropic layer preferably has a high refractive index anisotropy, and a discotic liquid crystalline compound that imparts a high refractive index anisotropy is disclosed in JP-A No. 2001-166147. To [0142] can be preferably used. Among these, the compound represented by the general formula [Chemical Formula 10] of [0050] is preferable, and the compound represented by the discotic compound (II) in [Examples] described later is particularly preferable.

[Horizontal alignment agent]
The composition for forming the optically anisotropic layer preferably contains at least one “horizontal alignment agent” in addition to the discotic liquid crystalline compound. By including at least one “horizontal alignment agent” in the composition, the discotic structural unit in the formed optically anisotropic layer can be aligned substantially horizontally with respect to the polymer film surface. In the present specification, “horizontal alignment” means the horizontal direction of the liquid crystal layer (for example, the surface of the support when the liquid crystal layer is formed on the support) in the major axis direction of the discotic liquid crystalline compound ( That is, it means that the disk surface of the core is parallel, but is not required to be strictly parallel. In this specification, the inclination angle between the disk surface of the core and the horizontal plane is less than 10 degrees. It shall mean orientation. The inclination angle is preferably 5 degrees or less, more preferably 3 degrees or less, further preferably 2 degrees or less, and most preferably 1 degree or less. The inclination angle may be 0 degree.

  As the horizontal alignment agent, compounds exemplified in JP-A-2005-128050 [0049] to [0082] or fluoroaliphatic-containing polymers can be preferably used, but in the present invention, fluoroaliphatic-containing polymers are more preferred. Among the fluoroaliphatic-containing polymers, a fluoroaliphatic-containing monomer and a copolymer of the following general formula (I) are particularly preferable.

[Copolymer of fluoroaliphatic-containing monomer and general formula (1)]
The composition for forming the optically anisotropic layer is used to make the director direction of the rod-like liquid crystal compound substantially parallel to the substrate (Re is substantially 0 nm) or to horizontally align the discotic liquid crystal compound. In order to make the direction of the director substantially perpendicular to the substrate (Re is substantially 0 nm), a fluoroaliphatic-containing polymer (hereinafter referred to as “polymer”) containing a repeating unit represented by the following general formula (1): A ”in some cases).

In the general formula (1), R ¹ , R ² and R ³ each independently represent a hydrogen atom or a substituent. Q is a carboxyl group containing at least one phenyl group (—COOH) or a salt thereof, a sulfo group (—SO ₃ H) or a salt thereof, a phosphonoxy group {—OP (═O) (OH) ₂ } or a salt thereof, It has a hydrophilic group (—OH) or acrylamide (—NR ⁴ — (R ⁴ represents a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group)). L represents an arbitrary group selected from the following linking group group, or a divalent linking group formed by combining two or more thereof.
(Linked group group)
Single bond, —O—, —CO—, —S—, —SO ₂ —, —P (═O) (OR ⁵ ) — (R ⁵ represents an alkyl group, an aryl group, or an aralkyl group), an alkylene group And an arylene group.

In general formula (1), R ¹ , R ² and R ³ each independently represent a hydrogen atom or a substituent exemplified in JP-A-2004-333852.

L represents a divalent linking group selected from the above linking group group, or a divalent linking group formed by combining two or more thereof. In the linking group group, R ^{4 in} —NR ⁴ — represents a hydrogen atom, an alkyl group, an aryl group or an aralkyl group, preferably a hydrogen atom or an alkyl group. R ⁵ in —PO (OR ⁵ ) — represents an alkyl group, an aryl group or an aralkyl group, and preferably an alkyl group. The carbon number when R ⁴ and R ⁵ represent an alkyl group, an aryl group or an aralkyl group is the same as that described in the “substituent group”. L preferably contains a single bond, —O—, —CO—, —NR ⁴ —, —S—, —SO ₂ —, an alkylene group or an arylene group, and is a single bond, —CO—, —O—. , —NR ⁴ —, an alkylene group or an arylene group is particularly preferable, and a single bond is most preferable. When L contains an alkylene group, the alkylene group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and particularly preferably 1 to 6 carbon atoms. Specific examples of particularly preferred alkylene groups include methylene, ethylene, trimethylene, tetrabutylene, hexamethylene groups and the like. When L contains an arylene group, the carbon number of the arylene group is preferably 6 to 24, more preferably 6 to 18, and particularly preferably 6 to 12. Specific examples of particularly preferred arylene groups include phenylene and naphthalene groups. When L contains a divalent linking group (that is, an aralkylene group) obtained by combining an alkylene group and an arylene group, the carbon number of the aralkylene group is preferably 7 to 34, more preferably 7 to 26, and particularly preferably. 7-16. Specific examples of particularly preferred aralkylene groups include a phenylenemethylene group, a phenyleneethylene group, and a methylenephenylene group. The group listed as L may have a suitable substituent. Examples of such a substituent include those similar to the substituents exemplified above as the substituents for R ^{1 to} R ³ .

  In the formula (1), Q is a carboxyl group, a salt of a carboxyl group (for example, lithium salt, sodium salt, potassium salt, ammonium salt (for example, ammonium, tetramethylammonium, trimethyl-2-hydroxyethylammonium, tetrabutylammonium, trimethyl). Benzylammonium, dimethylphenylammonium, etc.), pyridinium salts, etc.), sulfo groups, salts of sulfo groups (examples of cations forming salts are the same as those described above for carboxyl groups), phosphonoxy groups, salts of phosphonoxy groups (salts) Examples of the cation that forms are the same as those described above for the carboxyl group) and a hydrophilic group (hydroxyl group). A carboxyl group, a sulfo group, a phospho group, and a hydrophilic group are more preferable, and a carboxyl group or a hydrophilic group is particularly preferable.

  The polymer A may contain one type of repeating unit represented by the general formula (1), or may contain two or more types. The polymer A may have one or more repeating units derived from the fluoroaliphatic group-containing monomer. It is preferable to contain a fluoroaliphatic group-containing monomer described in the general formula [1] of JP-A No. 2004-333852. Furthermore, the polymer A may contain other repeating units. The other repeating units are not particularly limited, and preferred examples thereof include repeating units derived from ordinary radical polymerizable monomers. The polymer A may contain one or more repeating units derived from monomers selected from the monomer group described in JP-A-2004-46038 [0026] to [0033]. May be.

  Further, the polymer A may contain a repeating unit derived from a monomer represented by the general formula [2] described in JP-A-2004-333852.

  The mass average molecular weight of the polymer A used in the present invention is preferably 1,000,000 or less, more preferably 500,000 or less, and further preferably 5,000 or more and 50,000 or less. The mass average molecular weight can be measured as a value in terms of polystyrene (PS) using gel permeation chromatography (GPC).

  The polymerization method employed when producing the polymer A is not particularly limited, but the method described in [0035] to [0041] of JP-A No. 2004-46038 is preferably used.

  The polymer A may have a polymerizable group as a substituent in order to fix the alignment state of the liquid crystal compound.

  The polymer A used in the present invention can be produced by a known and commonly used method as described above. For example, it can be produced by adding a general-purpose radical polymerization initiator to an organic solvent containing the above-mentioned monomer having a fluoroaliphatic group, a monomer having a hydrogen bonding group, and the like, and polymerizing the mixture. Further, in some cases, other addition-polymerizable unsaturated compounds can be further added and produced by the same method as described above. Depending on the polymerizability of each monomer, a dropping polymerization method in which a monomer and an initiator are added dropwise to a reaction vessel is also effective for obtaining a polymer having a uniform composition.

  In the present invention, the addition amount of the “horizontal alignment agent” is preferably 0.01 to 20% by mass, more preferably 0.05 to 10% by mass, more preferably 0.1 to 10% by mass of the mass of the discotic liquid crystalline compound. 5% by mass is particularly preferred. In addition, said "horizontal alignment agent" may be used independently and may use 2 or more types together.

[Fixation of alignment state of liquid crystalline compounds]
When the optically anisotropic layer is formed from a composition containing a liquid crystal compound, it is preferable to fix the aligned liquid crystal compound while maintaining the alignment state. The immobilization is preferably carried out by a polymerization reaction of a polymerizable group introduced into the liquid crystal compound. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator, and a photopolymerization reaction is more preferable.

[Photopolymerization initiator]
Examples of the photopolymerization initiator include α-carbonyl compounds (described in the specifications of U.S. Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (as described in U.S. Pat. No. 2,448,828), α, A hydrocarbon-substituted aromatic acyloin compound (described in US Pat. No. 2,722,512), a polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a triarylimidazole dimer and p- Combinations with aminophenyl ketones (described in US Pat. No. 3,549,367), acridine and phenazine compounds (described in JP-A-60-105667, US Pat. No. 4,239,850) and oxadiazole compounds ( (Described in US Pat. No. 4,221,970) Can be adopted.

It is preferable that the optical compensation sheet of the present invention is produced by slightly reducing the amount of ultraviolet light. In this case, a portion where the light does not reach in the thickness direction of the optically anisotropic layer is generated, and the optically anisotropic layer is formed. May not be uniformly polymerized. Therefore, in order to maintain uniform polymerization in the thickness direction, a photopolymerization initiator that absorbs light in the long wave region and has high diffusibility of the generated radicals is preferable. More specifically, the photosensitive region is in the range of 330 nm to 450 nm. Therefore, it is preferable to use a radical that generates a hydrocarbon radical having 8 or less atoms excluding a halogen radical or a hydrogen atom as a polymerization initiating radical. Examples of the halogen radical include fluorine, chlorine, bromine, or iodine radicals, and a chloro radical is particularly preferable. The hydrocarbon radical having 8 or less atoms excluding a hydrogen atom may be a hydrocarbon radical having a substituent such as a halogenated hydrocarbon radical, and examples thereof include a methyl radical, an ethyl radical, a propyl radical, and a butyl radical. , Phenyl radical, tolyl radical, chlorophenyl radical, bromophenyl radical, benzoyl radical and the like. Matching the photosensitive wavelength with the light source is a necessary requirement for high sensitivity. Photopolymerization initiators with a photosensitive range of 330 nm to 450 nm have good matching with UV light sources such as metal halide lamps and high-pressure mercury lamps, and not only enable the polymerization reaction with low-power UV light but also optical compensation. This has the advantage that the sheet is less colored. Further, as described above, when the radical bulk of the photopolymerization initiator is small, the adhesion between the optically anisotropic layer and the alignment film is improved. This is because, as a result of the polymerizable radicals in the optically anisotropic layer having a small volume diffusing up to the alignment film, chemical bonds are formed on the surface of the alignment film, and the vicinity of the surface of the alignment film is cured, improving adhesion. It is estimated that
Furthermore, the photopolymerization initiator is preferably one that decomposes 30% or more with an energy amount of 100 mJ / cm ² . Although the example of a photoinitiator is described below, this invention is not limited to these.

The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution. Light irradiation for the polymerization of the liquid crystalline compound is preferably performed using ultraviolet rays. Irradiation energy is preferably ^{50mJ / cm 2 ~800mJ / cm 2} , further preferably 100 to 500 mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. The thickness of the optically anisotropic layer is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm.

[Polyfunctional monomer]
The composition containing a liquid crystal compound for forming the optically anisotropic layer preferably contains a polyfunctional monomer for the purpose of improving the adhesion to the alignment film described later. When forming an optically anisotropic layer with a lower UV light intensity than usual, the adhesiveness between the support and the optically anisotropic layer under the optically anisotropic layer is reduced. By incorporating a polyfunctional monomer having two or more functional groups into the adhesive, it is possible to improve the adhesiveness that tends to deteriorate.

  Two or more polyfunctional monomers include esters of polyhydric alcohol and (meth) acrylic acid [for example, ethylene glycol di (meth) acrylate, butanediol di (meth) acrylate, hexanediol di (meth) acrylate, 1, 4-cyclohexanediacrylate, pentaerythritol tetra (meth) acrylate], pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, Dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, pentaerythritol hexa (meth) acrylate, 1,2,3-cyclohexanetetra Tacrylate, polyurethane polyacrylate, polyester polyacrylate], modified ethylene oxide, vinylbenzene and derivatives thereof (for example, 1,4-divinylbenzene, 4-vinylbenzoic acid-2-acryloylethyl ester, 1,4-divinylcyclohexanone) ), Vinyl sulfone (eg divinyl sulfone), acrylamide (eg methylene bisacrylamide) and methacrylamide. Two or more of these monomers may be used in combination.

[Polyfunctional monomer having 4 or more double bonds]
As the polyfunctional monomer, it is particularly preferable to use a polyfunctional monomer having 4 or more double bonds in the molecule. The double bond is preferably an ethylenic (aliphatic) unsaturated double bond. The number of double bonds in the molecule is preferably 4-20, more preferably 5-15, and most preferably 6-10. The polyfunctional monomer is preferably an ester of an unsaturated fatty acid with a polyol having 4 or more hydroxyl groups in the molecule. Examples of unsaturated fatty acids include acrylic acid, methacrylic acid, maleic acid and itaconic acid. Acrylic acid and methacrylic acid are preferred. The polyol having 4 or more hydroxyl groups in the molecule is preferably a tetrahydric or higher alcohol or a trihydric or higher alcohol oligomer. The oligomer has a molecular structure in which polyhydric alcohols are linked by an ether bond, an ester bond or a urethane bond. Oligomers having a molecular structure in which polyhydric alcohols are linked by ether bonds are preferred.

  Esters of polyol and (meth) acrylic acid include pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, polyether polyol poly (meth) acrylate, Poly (meth) acrylates of polyester polyols and poly (meth) acrylates of polyurethane polyols are included. A commercial product of a polyfunctional monomer may be used. Monomers composed of an ester of polyol and acrylic acid are Mitsubishi Rayon Co., Ltd. (trade name: Diabeam UK-4154), Toa Gosei Co., Ltd. (trade name: Aronix M450) and Nippon Kayaku Co., Ltd. (trade name). : KYARAD · DPHA, SR355). Two or more polyfunctional monomers having four or more double bonds may be used in combination.

  You may use together the polyfunctional monomer which has a 4 or more double bond in a molecule | numerator, and the monomer which has 1-3 double bonds in a molecule | numerator. The combined use of monomers is effective for adjusting the viscosity and strength. That is, as the number of double bonds in the monomer increases, the intermolecular interaction increases and the viscosity increases. When the viscosity increases, it takes time to align the liquid crystal compound. On the other hand, the greater the number of double bonds, the stronger the strength of the optical compensation sheet. Appropriate viscosity and appropriate strength can be easily achieved by using two or more types of monomers in combination. The polyfunctional monomer having 4 or more double bonds in the molecule is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, based on the total amount of monomers. The polyfunctional monomer is added to the optically anisotropic layer together with the liquid crystalline molecules. The addition amount of the polyfunctional monomer is preferably 0.1 to 50% by mass, and more preferably 1 to 20% by mass with respect to the liquid crystal molecules.

  When forming an optically anisotropic layer from a composition containing a liquid crystalline compound, it is preferable to form the composition by applying the composition as a coating liquid on an alignment film. As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of the organic solvent include amide (for example, N, N-dimethylformamide), sulfoxide (for example, dimethyl sulfoxide), heterocyclic compound (for example, pyridine), hydrocarbon (for example, benzene, hexane), alkyl halide (for example, , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane) can be employed. Of these, alkyl halides and ketones are preferred. Further, two or more organic solvents may be used in combination. For the application of the coating solution, known methods (for example, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method) can be widely adopted.

[Alignment film]
In order to align the liquid crystalline compound, it is preferable to use an alignment film. Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known. The type of polymer used for the alignment film can be determined according to the alignment (particularly the average tilt angle) of the liquid crystal compound. For example, in order to align the liquid crystalline compound horizontally, a polymer (ordinary alignment polymer) that does not decrease the surface energy of the alignment film is used. Regarding specific types of polymers, matters described in known literatures on liquid crystal cells or optical compensation sheets can be widely adopted. In particular, when the liquid crystalline compound is aligned in a direction orthogonal to the rubbing treatment direction, for example, modified polyvinyl alcohol described in JP-A No. 2002-62427 and acrylic resin described in JP-A No. 2002-98836 are disclosed. An acid copolymer, a polyimide described in JP-A No. 2002-268068, and a polyamic acid can be preferably used. Any of the alignment films preferably has a polymerizable group for the purpose of improving the adhesion between the liquid crystalline compound and the polymer film substrate. The polymerizable group can be introduced by introducing a repeating unit having a polymerizable group in the side chain or as a substituent of a cyclic group. It is more preferable to use an alignment film that forms a chemical bond with the liquid crystal compound at the interface. As such an alignment film, for example, those described in JP-A-9-152509 can be employed.

  The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm. In addition, after aligning a liquid crystalline compound using an alignment film, the liquid crystalline compound is fixed in the aligned state to form an optically anisotropic layer, and only the optically anisotropic layer is formed on the polymer film substrate. You may transcribe.

[Polymer film substrate]
Examples of the polymer film substrate in the optical compensation film of the present invention include norbornene polymer films, polycarbonate polymer films, polyester polymer films, aromatic polymer films such as polysulfone, and cellulose acylate films. However, when a cellulose acylate film is used as a substrate, it becomes easy to use the optical compensation film as a polarizing plate protective film, which is particularly preferable. Such a polymer film can be produced by an appropriate method such as an extrusion method or a casting film forming method.
A stretched film such as a biaxially stretched film can also be used as the polymer film substrate of the present invention. A stretched film can be formed by subjecting an unstretched film produced as described above to stretching treatment by, for example, a longitudinal stretching method using a roll, a transverse stretching method using a tenter, a biaxial stretching method, or the like. The stretching temperature is preferably in the vicinity of the glass transition temperature (Tg) of the film to be treated, especially from Tg to less than the melting point.

As described above, in order to obtain good display characteristics, it is preferable that the wavelength dispersion Rth (450) / Rth (550) of retardation in the thickness direction of the optical compensation film of the present invention is high. On the other hand, in general, the wavelength dispersion of a polymer film is lower than that of an optically anisotropic layer formed from a liquid crystalline compound. In an optical compensation film having a certain Rth, an optical film in which a polymer film and an optically anisotropic layer are laminated. The wavelength dispersion of the compensation film as a whole decreases as the Rth of the polymer film increases. Accordingly, the Rth of the polymer film is preferably small.
Rth of the polymer film substrate used in the present invention is preferably −40 to 100 nm, more preferably −30 to 50 nm, still more preferably −25 to 25 nm, and particularly preferably −10 to 10 nm.

  Although the thickness of a polymer film base material can be suitably determined by retardation etc., generally 10-200 micrometers is preferable from the point of thickness reduction, 20-150 micrometers is more preferable, and 30-100 micrometers is especially preferable.

[Polarizing film]
Next, the polarizing film used in the polarizing plate and the liquid crystal display device of the present invention will be described in detail.
A polarizing film in particular is not restrict | limited, A well-known thing can be employ | adopted widely. For example, films made of hydrophilic polymers such as polyvinyl alcohol, partially formalized polyvinyl alcohol, partially saponified ethylene / vinyl acetate copolymer, dichroic dyes such as iodine and / or azo, anthraquinone and tetrazine A material obtained by adsorbing a dichroic material composed of the above material and subjecting it to stretching and orientation can be used. In the present invention, it is preferable to use the stretching method described in JP-A No. 2002-131548, and in particular, a width direction uniaxial stretching type tenter stretching machine in which the absorption axis of the polarizing film is substantially perpendicular to the longitudinal direction. It is preferable to use it.

  The polarizing film is usually used as a polarizing plate having at least one surface protected by a transparent protective film (also referred to as a protective film). The kind of transparent protective film is not particularly limited, and cellulose esters such as cellulose acetate, cellulose acetate butyrate, and cellulose propionate, polycarbonate, polyolefin, polystyrene, polyester, and the like can be used. The transparent protective film is usually supplied in a roll form, and it is preferable that the transparent protective film is continuously bonded to the long polarizing film so that the longitudinal directions thereof coincide. Here, the orientation axis (slow axis) of the transparent protective film may be any direction, but the orientation axis of the transparent protective film is preferably parallel to the longitudinal direction for ease of operation. Further, the angle between the slow axis (orientation axis) of the transparent protective film and the absorption axis (stretching axis) of the polarizing film is not particularly limited, and can be appropriately set according to the purpose of the polarizing plate.

  In addition, when producing a polarizing film using the width direction uniaxial stretching type tenter stretching machine preferably used in the present invention, the slow axis (alignment axis) of the transparent protective film and the absorption axis (stretching) of the polarizing film are used. Axis) will be substantially orthogonal.

  The Re value of the transparent protective film is preferably 10 nm or less, and more preferably 5 nm or less. From the viewpoint of such low retardation, polyolefins such as cellulose triacetate, ZEONEX, ZEONOR (both manufactured by Nippon Zeon Co., Ltd.), and ARTON (manufactured by JSR Co., Ltd.) are preferably used as the transparent protective film. It is done. Other examples include non-birefringent optical resin materials as described in JP-A-8-110402 or JP-A-11-293116. When cellulose acetate is used for the transparent protective film, Re and Rth are preferably less than 10 nm, and more preferably 2 nm or less, for the purpose of reducing the change in retardation due to environmental temperature and humidity.

  In the present invention, for the purpose of reducing the thickness or the like, one of the protective films of the polarizing film may also serve as the polymer film substrate in the above optical compensation film, or the above optical compensation film itself. Good. The optical compensation film and the polarizing film are preferably subjected to a fixing treatment from the viewpoint of preventing the optical axis from shifting and preventing foreign matters such as dust from entering. An appropriate method such as an adhesive method through a transparent adhesive layer can be applied to the fixed lamination. There is no particular limitation on the type of the adhesive and the like, and from the viewpoint of preventing changes in the optical properties of the constituent members, those that do not require a high-temperature process during curing or drying are preferable, and a long-time curing And those that do not require drying time. From such a viewpoint, a hydrophilic polymer adhesive or a pressure-sensitive adhesive layer is preferably used.

  For the formation of the pressure-sensitive adhesive layer, for example, a transparent pressure-sensitive adhesive using an appropriate polymer such as an acrylic polymer, a silicone-based polymer, polyester, polyurethane, polyether, or synthetic rubber can be used. Among these, acrylic pressure-sensitive adhesives are preferred from the viewpoints of optical transparency, adhesive properties, weather resistance, and the like. In addition, an adhesion layer can also be provided as needed on one side or both sides of a polarizing plate for the purpose of adhesion to an adherend such as a liquid crystal cell. In that case, when the pressure-sensitive adhesive layer is exposed on the surface, it is preferable to temporarily attach a separator or the like to prevent contamination of the pressure-sensitive adhesive layer surface until it is put to practical use.

  Appropriate functions such as a protective film for various purposes such as water resistance in accordance with the above-mentioned transparent protective film, an antireflection layer and / or an antiglare treatment layer for the purpose of preventing surface reflection, etc. on one or both sides of the polarizing film A layer may be formed. The antireflection layer can be suitably formed, for example, as a light interference film such as a fluorine polymer coating layer or a multilayer metal vapor deposition film. The antiglare layer is also formed by an appropriate method that diffuses the surface reflected light, for example, by providing a fine uneven structure on the surface by an appropriate method such as a resin coating layer containing fine particles, embossing, sandblasting or etching. can do.

  Examples of the fine particles include inorganic materials having an average particle diameter of 0.5 to 20 μm, such as silica, calcium oxide, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony oxide. One kind or two or more kinds of fine particles, such as crosslinked or uncrosslinked organic fine particles made of a suitable polymer such as polymethyl methacrylate and polyureta can be used. The above-mentioned adhesive layer or pressure-sensitive adhesive layer may contain such fine particles and exhibit light diffusibility.

[Optical performance of polarizing plate]
The optical properties and durability (short-term and long-term storage stability) of a polarizing plate comprising a transparent protective film, a polarizing film and a transparent support related to the present invention are commercially available super high contrast products (for example, Sanritz Corporation). It is preferable to have a performance equivalent to or higher than that of HLC2-5618, manufactured by HLC. Specifically, the visible light transmittance is 42.5% or more, and the degree of polarization ({(Tp−Tc) / (Tp + Tc)} 1/2 ≧ 0.9995 (where Tp is parallel transmittance and Tc is orthogonal) The change rate of the light transmittance before and after leaving for 500 hours in a 60 ° C., 90% humidity RH atmosphere and 500 ° C. in a dry atmosphere for 500 hours is 3% based on the absolute value. In the following, it is further preferable that the change rate of the polarization degree is 1% or less, further 0.1% or less based on the absolute value.

[Liquid Crystal Display]
An embodiment of the liquid crystal display element of the present invention will be described with reference to FIGS. FIG. 1 is a schematic view of an example of the configuration of a liquid crystal display element of the present invention, and FIG. FIG. 1 shows an example in which active driving is performed using a nematic liquid crystal having negative dielectric anisotropy as a field effect liquid crystal element.
In FIG. 1, a liquid crystal display element has a liquid crystal cell (5-8) and a pair of polarizing plates 1 and 14 arranged on both sides of the liquid crystal cell. An optically anisotropic layer 3 is disposed between the polarizing plate 1 and the liquid crystal cells 5 to 8, and an optically anisotropic layer 10 is disposed between the polarizing plate 14 and the liquid crystal cells 5 to 8. The liquid crystal cell includes an upper electrode substrate 5, a lower electrode substrate 8, and liquid crystal molecules 7 sandwiched between them. The liquid crystal molecules 7 are aligned in a direction perpendicular to the substrate in a non-driven state where no external electric field is applied, by rubbing treatment directions 6 and 9 applied to the opposing surfaces of the electrode substrates 5 and 8. So that it is controlled. The upper polarizing plate 1 and the lower polarizing plate 14 are laminated so that the absorption axis 2 and the absorption axis 15 are orthogonal to each other.

  As shown in FIG. 2, the polarizing plates 1 and 14 include a polarizing film 103 sandwiched between protective films 101 and 105. The polarizing plates 1 and 14 can be prepared by, for example, dyeing a polarizing film made of a polyvinyl alcohol film with iodine and performing stretching to obtain the polarizing film 104 and laminating the protective films 101 and 106 on both sides thereof. it can. In the case of lamination, it is preferable in terms of productivity when a total of three films of a pair of protective film and polarizing film are bonded together by a roll-to-roll process. Also, in the roll-to-roll lamination, as shown in FIG. 2, the slow axes 102 and 106 of the protective films 101 and 105 and the absorption axis 104 of the polarizing film can be easily laminated, It is preferable because the dimensional change and curling of the polarizing plate hardly occur and the polarizing plate has high mechanical stability. The same effect can be obtained if at least two axes of three films, for example, the slow axis of one protective film and the absorption axis of the polarizing film, or the slow axes of two protective films are substantially parallel. Is obtained.

In FIG. 1, the optically anisotropic layer 3 is preferably made of a polymer stretched film. Further, the front retardation and the retardation in the thickness direction preferably satisfy the following formula (3) and the following formula (4):
General formula (3)
70 ≦ Re (550) ≦ 180
General formula (4)
30 ≦ Rth (550) ≦ 140
Further, the film has the following formula (5)
General formula (5)
0.7 ≦ Re (450) / Re (550) ≦ 1.0
It is preferable to satisfy.

  The type of polymer in the polymer stretched film is not particularly limited, but norbornene polymer, polycarbonate polymer, polyarylate polymer, polyester polymer or polysulfone, or two of these polymers or Examples thereof include a polymer in which three or more kinds are mixed. Among them, those excellent in controllability of birefringence characteristics, transparency and heat resistance are preferable. The optically anisotropic layer 3 is preferably biaxial because the thickness of the optically anisotropic layer 10 can be reduced.

  The optically anisotropic layer 10 is preferably an optically anisotropic layer in the optical compensation film of the present invention described above, has an optically negative refractive index anisotropy, and an absolute value of the refractive index anisotropy is It is 0.060 or more and 0.085 or less, and Re is 0-10 nm. These optically anisotropic layers 3 and 10 eliminate the image coloring of the liquid crystal cell and contribute to the expansion of the viewing angle. The optically anisotropic layer 10 is particularly preferably formed from a composition containing a discotic liquid crystalline compound.

  In the liquid crystal display element of FIG. 1, an example in which only one optical anisotropic layer 10 is used is shown, but the optical anisotropic layer 10 may be two or more layers.

  In FIG. 1, when the upper side is the observer side, in FIG. 1, the optically anisotropic layer 3 has an optical anisotropy between the observer-side polarizing plate 1 and the observer-side liquid crystal cell substrate 5. The layer 10 is configured to be disposed between the back-side polarizing plate 14 and the back-side liquid crystal cell substrate 8, but the optically anisotropic layer 3 and the optically anisotropic layer 10 are interchanged. Alternatively, both of the optically anisotropic layers 3 and 10 may be disposed between the observer-side polarizing plate 1 and the observer-side liquid crystal cell substrate 5, or on the back side. You may arrange | position between the polarizing plate 14 and the board | substrate 8 for back side liquid crystal cells. In such an embodiment, the optically anisotropic layer 10 may also serve as a support for the optically anisotropic layer 3.

  The optically anisotropic layer 3 may be integrated with the polarizing plate 1 and can be incorporated in the liquid crystal display element in an integrated state with the polarizing plate 1. For example, the support of the first optically anisotropic layer may function as a protective film on one side of the polarizing film, such as a transparent protective film, a polarizing film, a transparent protective film (also used as a transparent support) and optical. It is preferable to form an integrated polarizing plate laminated in the order of anisotropic layers. When the integrated polarizing plate is incorporated in a liquid crystal display element, a transparent protective film, a polarizing film, a transparent protective film (also a transparent support), and an optically anisotropic layer 3 are formed from the outside of the device (the side far from the liquid crystal cell). It is preferable to incorporate them in this order.

  The optically anisotropic layer 10 is formed using the optical compensation film of the present invention. The optically anisotropic layer using the optical compensation film of the present invention can be incorporated in the liquid crystal display element as an integrated polarizing plate integrated with the polarizing plate 14, similarly to the optically anisotropic layer 3. In an embodiment in which the optically anisotropic layer 10 is formed from a composition containing a liquid crystalline compound, one protective film of the polarizing plate 14 may also serve as the transparent support of the optically anisotropic layer 10. In this embodiment, the integrated polarizing plate is laminated in the order of the transparent protective film, the polarizing film, the transparent protective film (also used as the transparent support) and the optically anisotropic layer 10, and the integrated polarizing plate is formed on the outer side (liquid crystal cell). It is preferable that the transparent protective film, the polarizing film, the transparent protective film (also as a transparent support), and the optically anisotropic layer 10 are incorporated in the liquid crystal display element from the far side.

  The liquid crystal display device of the present invention is not limited to the above configuration, and may include other members. For example, a color filter may be disposed between the liquid crystal cell and the polarizing film. In the transmissive liquid crystal display device, a backlight using a cold or hot cathode fluorescent tube, a light emitting diode, or an electroluminescent element as a light source can be disposed on the back surface. On the other hand, in the aspect of the reflective liquid crystal display device, only one polarizing plate needs to be disposed on the observation side, and a reflective film is provided on the back surface of the liquid crystal cell or the inner surface of the lower substrate of the liquid crystal cell. Of course, it is also possible to provide a front light using the light source on the liquid crystal cell observation side. Further, a transflective type in which a transmissive portion and a reflective portion are provided in one pixel of the display device is also possible.

  The type of the liquid crystal display device of the present invention is not particularly limited, and includes any of liquid crystal display elements of image direct view type, image projection type, and light modulation type. An active matrix liquid crystal display device using a three-terminal or two-terminal semiconductor element such as TFT or MIM is particularly effective in the present invention. Of course, the present invention is also effective in a passive matrix liquid crystal display device represented by a super-twisted nematic type (STN type) called time-division driving.

[VA mode liquid crystal cell]
In the present invention, the liquid crystal cell is preferably in a vertically aligned mode (VA mode). The VA mode liquid crystal cell is formed by sealing liquid crystal molecules having negative dielectric anisotropy between upper and lower substrates whose opposite surfaces are rubbed. For example, by using liquid crystal molecules having Δn = 0.0813 and Δε = −4.6, a director indicating the alignment direction of the liquid crystal molecules, that is, a liquid crystal cell having a so-called tilt angle of about 89 ° can be manufactured. At this time, the thickness d of the liquid crystal layer can be about 3.5 μm. The brightness at the time of white display changes depending on the magnitude of the product Δn · d of the thickness d (nm) of the liquid crystal layer and the refractive index anisotropy Δn. In order to obtain the maximum brightness, the thickness d of the liquid crystal layer is preferably in the range of 2 to 5 μm (2000 to 5000 nm), and Δn is in the range of 0.060 to 0.085.

Here, the refractive index anisotropy Δn is
Δn = Rth / film thickness (nm)
It is represented by

  A transparent electrode (not shown) is formed inside the substrate 5 and the substrate 8, but in a non-driving state in which a driving voltage is not applied to the electrodes, the liquid crystal molecules 7 in the liquid crystal layer are substantially separated from the substrate surface. As a result, the polarization state of the light passing through the liquid crystal panel is hardly changed. As described above, since the absorption axis 2 of the upper polarizing plate 1 of the liquid crystal cell and the absorption axis 15 of the lower polarizing plate 14 are substantially orthogonal, light does not pass through the polarizing plate. That is, the liquid crystal display element of FIG. 1 realizes an ideal black display in the non-driven state. On the other hand, in the driving state, the liquid crystal molecules are inclined in a direction parallel to the substrate surface, and the light passing through the liquid crystal panel changes the polarization state by the inclined liquid crystal molecules and passes through the polarizing plate.

  In FIG. 1, since an electric field is applied between the upper and lower substrates, an example in which a liquid crystal material having a negative dielectric anisotropy in which liquid crystal molecules respond perpendicularly to the electric field direction is shown. In the case where an electrode is disposed on one substrate and an electric field is applied in a lateral direction parallel to the substrate surface, a liquid crystal material having a positive dielectric anisotropy can be used. In a VA mode liquid crystal display element, the addition of a chiral material generally used in a twisted nematic mode (TN mode) liquid crystal display element is rarely used in order to deteriorate the dynamic response characteristics. Sometimes added to reduce defects.

  The characteristics of the VA mode are high-speed response and high contrast. However, there is a problem that the contrast is high in the front but decreases in the oblique direction. During black display, the liquid crystal molecules are aligned perpendicular to the substrate surface. When observed from the front, the liquid crystal molecules have almost no birefringence, so the transmittance is low and a high contrast can be obtained. However, when observed obliquely, birefringence occurs in the liquid crystalline molecules. Further, the crossing angle of the upper and lower polarizing plate absorption axes is 90 ° perpendicular to the front, but is larger than 90 ° when viewed from an oblique direction. Due to these two factors, leakage light tends to occur in the oblique direction, and the contrast tends to decrease. In the present invention, in order to solve this, the optically anisotropic layers 3 and 10 can be arranged at least one layer at a time.

  In the VA mode, liquid crystal molecules are tilted during white display, but the birefringence of the liquid crystal molecules when viewed from an oblique direction is different between the tilt direction and the opposite direction, resulting in differences in luminance and color tone. . In order to solve this, the liquid crystal cell is preferably multi-domain. Multi-domain refers to a structure in which a plurality of regions having different alignment states are formed in one pixel. For example, in a multi-domain VA mode liquid crystal cell, a plurality of regions in which tilt angles of liquid crystal molecules are different from each other when an electric field is applied exist in one pixel. In a multi-domain VA mode liquid crystal cell, the tilt angle of liquid crystal molecules due to application of an electric field can be averaged for each pixel, whereby the viewing angle characteristics can be averaged. In order to divide the orientation within one pixel, the electrode is provided with slits or protrusions, and the electric field direction is changed or the electric field density is biased. In order to obtain a uniform viewing angle in all directions, the number of divisions may be increased.

  Also, the liquid crystal molecules are difficult to respond at the alignment division region boundary. For this reason, in normally black display, since black display is maintained, a reduction in luminance becomes a problem. Adding a chiral agent to the liquid crystal material contributes to reducing the boundary region.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[Example 1]
Optical anisotropy formed by using cellulose acylate film as a polymer film substrate, applying a composition containing a polymerizable discotic liquid crystalline compound on it, horizontally aligning the discotic structural units, and then immobilizing by polymerization The present invention will be described by taking an optical compensation film having a conductive layer as an example.

<Production of cellulose acetate film (T1)>
(Preparation of cellulose acetate solution)
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a cellulose acetate solution A.
Composition of cellulose acetate solution A ――――――――――――――――――――――――――――――――――――
Cellulose acetate with an acetyl substitution degree of 2.94 100.0 parts by mass Methylene chloride (first solvent) 402.0 parts by mass Methanol (second solvent) 60.0 parts by mass ――――――――――――― ――――――――――――――――――――――

(Preparation of matting agent solution)
20 parts by mass of silica particles having an average particle diameter of 16 nm (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) and 80 parts by mass of methanol were mixed well for 30 minutes to obtain a silica particle dispersion. This dispersion was put into a disperser together with the following composition, and further stirred for 30 minutes or more to dissolve each component to prepare a matting agent solution.
Matting agent solution composition ――――――――――――――――――――――――――――――――――
Silica particle dispersion liquid having an average particle diameter of 16 nm 10.0 parts by mass Methylene chloride (first solvent) 76.3 parts by mass Methanol (second solvent) 3.4 parts by mass Cellulose acetate solution A 10.3 parts by mass ―――――――――――――――――――――――――――――

(Preparation of additive solution)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution.
Additive solution composition ――――――――――――――――――――――――――――――
The following optical anisotropy reducing agent 49.3 parts by mass The following wavelength dispersion adjusting agent 4.9 parts by mass Methylene chloride (first solvent) 58.4 parts by mass Methanol (second solvent) 8.7 parts by mass Cellulose acetate Solution A 12.8 parts by mass ――――――――――――――――――――――――――――――

(Production of cellulose acetate film)
94.6 parts by mass of the cellulose acetate solution A, 1.3 parts by mass of the matting agent solution, and 4.1 parts by mass of the additive solution were mixed after filtration, and cast using a band casting machine. The mass ratio of the compound that reduces optical anisotropy and the wavelength dispersion adjusting agent to cellulose acetate in the above composition was 12% and 1.2%, respectively. The film was peeled from the band with a residual solvent amount of 30% and dried at 140 ° C. for 40 minutes to produce a long cellulose acetate film T1 having a thickness of 80 μm. The in-plane retardation (Re) of the obtained film was 1 nm (the slow axis was a direction perpendicular to the film longitudinal direction), and the thickness direction retardation (Rth) was −1 nm.

The produced film was passed through a dielectric heating roll having a temperature of 60 ° C., and the film surface temperature was raised to 40 ° C., and then an alkaline solution A having the following composition was applied by a bar coater to 14 ml / m ² and heated to 110 ° C. After retaining for 10 seconds under a heated steam far infrared heater (manufactured by Noritake Co., Ltd.), 3 ml / m ^{2 of} pure water was applied using the same bar coater. The film temperature at this time was 40 degreeC. Next, washing with a fountain coater and draining with an air knife were repeated three times, and then the film was retained in a drying zone at 70 ° C. for 2 seconds and dried.

――――――――――――――――――――――――――――――――――
<Alkaline solution A composition>
――――――――――――――――――――――――――――――――――
Potassium hydroxide 4.7 parts by weight Water 15.7 parts by weight Isopropanol 64.8 parts by weight Propylene glycol 14.9 parts by weight C ₁₆ H ₃₃ O (CH ₂ CH ₂ O) ₁₀ H (surfactant) 1.0 part by weight Department ――――――――――――――――――――――――――――――――――

<Preparation of optical compensation film F11>
(Preparation of optically anisotropic layer)
On the surface of the long cellulose acylate film (T1) produced as described above, an alignment film coating solution having the following composition was continuously applied with a # 14 wire bar. The alignment film was formed by drying with warm air of 60 ° C. for 60 seconds and further with warm air of 100 ° C. for 120 seconds.
――――――――――――――――――――――――――
Composition of alignment film coating solution ――――――――――――――――――――――――――
The following modified polyvinyl alcohol 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde 0.5 parts by weight ――――――――――――――――――――――――――――

A coating liquid (S1) containing a discotic liquid crystalline compound having the following composition was continuously applied to the prepared alignment film with a # 6.0 wire bar. The conveyance speed of the film was 20 m / min. The solvent was dried in a step of continuously heating from room temperature to 80 ° C., and then heated in a drying zone at 120 ° C. for 90 seconds to align the discotic liquid crystalline compound. Subsequently, the temperature of the film is maintained at 90 ° C., UV light is irradiated at 500 mJ / cm ² using a high pressure mercury lamp, the orientation of the liquid crystal compound is fixed, the optically anisotropic layer B1 is formed, and the optical compensation film F11-200 was produced.

An optical birefringence meter (KOBRA-21ADH, Oji Scientific Instruments Co., Ltd.) obtained by removing only the optically anisotropic layer containing a discotic liquid crystalline compound from the produced optical compensation film F11-200 and the optical compensation film F11-200 The optical properties were measured using a). Re measured at a wavelength of 590 nm was 2 nm, and Rth was 200 nm. Re of only the optically anisotropic layer of the optical compensation film F1 was 0 nm, and Rth was 200 nm. It was also confirmed that an optically anisotropic layer in which the discotic liquid crystal structural unit was aligned substantially horizontally with respect to the film surface was confirmed.
The film thickness of the optically anisotropic layer was 2.65 μm, and the refractive index anisotropy was 0.075.

――――――――――――――――――――――――――――――――――――
Composition of coating liquid (S1) containing discotic liquid crystal compound ――――――――――――――――――――――――――――――――――――
The following discotic liquid crystalline compound (I) 91 parts by mass Ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 9 parts by mass Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) 3 parts by mass Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 1 part by mass The following fluoropolymer 0.4 part by mass Methyl ethyl ketone 212 parts by mass ――――――――――――――― ―――――――――――――――――――――

  For the optical compensation film F11-200 produced above, the coating film thickness was changed so that Rth was 180 nm, 160 nm, and 140 nm, and F11-180, F11-160, and F11-140 were produced.

<Preparation of optical compensation film F12>
For the F11-200 produced above, the cellulose acylate film (T1) is replaced with a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd., Re: 3 nm, Rth: 45 nm), and Rth is 200 nm. The film thickness of the optically anisotropic layer was adjusted so that F12-200 was produced.

  Furthermore, with respect to the optical compensation film F12-200 produced above, the coating film thickness was changed so that Rth was 180 nm, 160 nm, and 140 nm, and F12-180, F12-160, and F12-140 were produced.

<Preparation of optical compensation film F21>
The alignment film was formed on the cellulose acylate film (T1) in the same manner as the optical compensation film F11-200, and the coating liquid (S2) containing the discotic liquid crystalline compound having the following composition was prepared on the alignment film. The alignment film was continuously applied with a # 6.0 wire bar. The conveyance speed of the film was 20 m / min. The solvent was dried in a process of continuously heating from room temperature to 90 ° C., and then heated in a drying zone at 120 ° C. for 90 seconds to align the discotic liquid crystalline compound. Subsequently, the temperature of the film is maintained at 90 ° C., UV light is irradiated at 500 mJ / cm ² using a high-pressure mercury lamp, the orientation of the liquid crystal compound is fixed, the optically anisotropic layer B2 is formed, and the optical compensation film F21-200 was produced.

――――――――――――――――――――――――――――――――――――
Composition of coating liquid (S2) containing discotic liquid crystal compound ――――――――――――――――――――――――――――――――――――
91 parts by mass of the following discotic liquid crystalline compound (II): Mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate [KAYARAD DPHA: manufactured by Nippon Kayaku Co., Ltd.]
9 parts by mass The following photopolymerization initiator A 2 parts by mass The above fluoropolymer A 0.4 parts by mass Methyl ethyl ketone 254 parts by mass ――――――――――――――――――――――― ―――――――――――――

An optical birefringence meter (KOBRA-21ADH, Oji Scientific Instruments Co., Ltd.) obtained by removing only the optically anisotropic layer containing a discotic liquid crystalline compound from the produced optical compensation film F21-200 and optical compensation film F21-200. The optical properties were measured using a). Re measured at a wavelength of 590 nm was 2 nm, and Rth was 200 nm. Re of only the optically anisotropic layer of the optical compensation film F1 was 0 nm, and Rth was 200 nm. It was also confirmed that an optically anisotropic layer was formed in which the discotic liquid crystal molecules were aligned substantially horizontally with respect to the film surface.
The film thickness of the optically anisotropic layer was 2.2 μm and the refractive index anisotropy was 0.091.

  For the optical compensation film F21-200 produced above, the coating film thickness was changed so that Rth was 180 nm, 160 nm, and 140 nm, and F21-180, F21-160, and F21-140 were produced.

<Preparation of optical compensation film F22>
For the F21-200 produced above, the cellulose acylate film (T1) was replaced with a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd., Re: 3 nm, Rth: 45 nm), and Rth was changed to 200 nm. The film thickness of the optically anisotropic layer was adjusted so that F21-200 was produced.

  Furthermore, with respect to the optical compensation film F22-200 produced above, the coating film thickness was changed so that Rth was 180 nm, 160 nm, and 140 nm, and F22-180, F22-160, and F22-140 were produced.

<Preparation of optical compensation film F31>
The alignment film was formed on the cellulose acylate film (T1) in the same manner as the optical compensation film F11-200, and the coating liquid (S3) containing the discotic liquid crystalline compound having the following composition was prepared on the alignment film. It apply | coated continuously with the wire bar on the alignment film. The conveyance speed of the film was 20 m / min. The solvent was dried in a process of continuously heating from room temperature to 90 ° C., and then heated in a drying zone at 120 ° C. for 90 seconds to align the discotic liquid crystalline compound. Subsequently, the temperature of the film is maintained at 90 ° C., UV light is irradiated at 500 mJ / cm ² using a high-pressure mercury lamp, the orientation of the liquid crystal compound is fixed, the optically anisotropic layer B3 is formed, and optical compensation is performed. Film F31-200 was produced.

――――――――――――――――――――――――――――――――――――
Composition of coating liquid (S3) containing discotic liquid crystalline compound ――――――――――――――――――――――――――――――――――――
Discotic liquid crystalline compound (I) 82 parts by mass Ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 18 parts by mass Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) 3 parts by mass Part Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 1 part by weight The following fluoropolymer 0.4 part by weight Methyl ethyl ketone 212 parts by weight ――――――――――――――――― ―――――――――――――――――――

  For the optical compensation film F31-200 produced above, the coating film thickness was changed so that Rth was 180 nm, 160 nm, and 140 nm, and F31-180, F31-160, and F31-140 were produced.

<Preparation of optical compensation film F32>
For the F31-200 produced above, the cellulose acylate film (T1) was replaced with a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd., Re: 3 nm, Rth: 45 nm), and Rth was 200 nm. The film thickness of the optically anisotropic layer was adjusted so that F31-200 was produced.

  Furthermore, with respect to the optical compensation film F32-200 produced above, the coating film thickness was changed so that Rth was 180 nm, 160 nm, and 140 nm to produce F32-180, F32-160, and F32-140, respectively.

  The results of the optical compensation film prepared above are shown in Table 1.

From the above results, it can be seen that Rth / d can be significantly increased by using the discotic compound represented by the general formula (1).
[Example 2]

<Preparation of lower polarizing plate>
The above optical compensation film (F11-200) and Fujitac TD80UF were saponified and attached to both surfaces of the polarizing film with a roll-to-roll using a polyvinyl alcohol adhesive to produce an integrated polarizing plate (P11-200). . At this time, the optical compensation layer of the optical compensation film faced the outside of the polarizing plate.

  Regarding the other optical compensation films shown in Table 1, polarizing plates were prepared in the same manner as in P11-200.

[Example 3]
<Production of liquid crystal display device>
(Preparation of vertical alignment liquid crystal cell)
1% by weight of octadecyldimethylammonium chloride (coupling agent) was added to a 3% by weight aqueous solution of polyvinyl alcohol. This was spin-coated on a glass substrate with an ITO electrode, heat-treated at 160 ° C., and then rubbed to form a vertical alignment film. The rubbing treatment was performed so that the two glass substrates were in opposite directions. Two glass substrates were faced to each other so that the cell gap (d) was about 5.0 μm. A vertical alignment liquid crystal cell A was produced by injecting a liquid crystal compound (Δn: 0.06) mainly composed of ester and ethane into the cell gap. The product of Δn and d was 300 nm.

(Preparation of upper polarizing plate)
A polycarbonate film “Pure Ace WR” manufactured by Teijin Chemicals Limited was thermally relaxed near Tg to obtain a second optical compensation film A having Re of 120 nm and Rth of 78 nm.

  A roll-shaped polyvinyl alcohol film having a thickness of 80 μm continuously dyed in an aqueous iodine solution was stretched 5 times in the transport direction and dried to obtain a long polarizing film. Using a polyvinyl alcohol-based adhesive on one surface of the polarizing film, the second optical compensation film A is bonded so that the transmission axis of the polarizing film and the slow axis of the second optical compensation film A are parallel. A commercially available cellulose acetate film (Fujitac TD80UL, manufactured by Fuji Photo Film Co., Ltd.) saponified on the other surface was continuously bonded using a polyvinyl alcohol adhesive to produce a polarizing plate (P1).

(Incorporation of polarizing plate)
As shown in FIG. 2, the lamination angle of each film is 90 degrees when the horizontal direction when the display device is viewed from above is a reference (0 °), as shown in FIG. The angle of the protective film slow axis 102 and 106 was set to 90 °. The lower polarizing plate produced above was incorporated in a liquid crystal display device so that the optically anisotropic layer (10 in FIG. 1) was in contact with the upper liquid crystal cell substrate (8 in FIG. 1).
In addition, the upper polarizing plate was disposed between the upper polarizing plate (1 in FIG. 1) and the upper liquid crystal cell substrate (5 in FIG. 1) so that the second optical film would come. At this time, the slow axis of the second optical compensation film was configured to coincide with the transmission axis of the upper polarizing plate.

  As shown in Table 2, a liquid crystal display device incorporating the optical compensation film of the present invention produced above was produced.

  The liquid crystal display device produced above was evaluated for front and oblique light leakage, color and unevenness when viewed from the front and oblique directions, and summarized in Table 2.

(1) Light leakage (front)
A liquid crystal cell is placed on a Schaukasten set in a dark room without attaching a polarizing plate, and a luminance meter (spectral radiance meter CS-1000: Minolta Co., Ltd.) placed 1 m away in the normal direction. The luminance 1 was measured in ().
Subsequently, each liquid crystal display device having a polarizing plate bonded on the same Schaukasten as described above was placed, and the luminance 2 was measured in the same manner as described above.

(2) Leakage light (oblique)
A liquid crystal cell is placed on a Schaukasten set in a dark room with no polarizing plate attached, and is oriented 45 degrees to the left with respect to the rubbing direction of the liquid crystal cell and 60 degrees from the normal direction of the liquid crystal cell. The luminance 1 was measured with a luminance meter (spectral radiance meter CS-1000: manufactured by Minolta Co., Ltd.) installed at a distance of 1 m in the direction of.
Then, each liquid crystal display device having a polarizing plate bonded on the same Schaukasten as described above was placed, and the luminance 2 was measured in the same manner as described above.

(3) Color shift during black display (front)
Place the liquid crystal cell with the polarizing plate pasted on the Schaukasten set in the dark room, and observe the liquid crystal cell from the place 1m away in the normal direction. It was evaluated as follows. The intensity of the color shift was in accordance with the following criteria.
○: Specific color is not visible ○ △: Specific color is slightly visible
Δ: A specific color can be seen a little.
X: A specific color can be clearly seen.

(4) Color shift during black display (diagonal)
A liquid crystal cell is placed on a Schaukasten set in a dark room with a polarizing plate attached, and is oriented 45 degrees leftward with respect to the rubbing direction of the liquid crystal cell and 60 degrees from the normal direction of the liquid crystal cell. The color shift at the time of black display was evaluated based on the same criteria as the above (3) from a distance of 1 m in the direction of.

(5) Unevenness Place the liquid crystal cell 1 on the Schaukasten set in the dark room without placing the polarizing plate so that the substrate on which the electrode is disposed is on the Schaukasten side, and the left with respect to the rubbing direction of the liquid crystal cell. The unevenness was evaluated according to the following criteria when viewed from a direction of 45 degrees in the direction and 1 m away from the normal line direction of the liquid crystal cell at 60 degrees.
○: Unevenness is not observed.
○ △: Slightly uneven.
Δ: Unevenness is visible in part.
X: Unevenness is visible on the entire surface.

From the results in Table 2, the following is clear.
In the liquid crystal display device using the liquid crystal cell A, in various optical compensation films, when the retardation Rth in the thickness direction is 180 nm, the leakage light in the front and oblique directions is the least, and the color when viewed from the front and oblique directions is also small. Show the best optical properties.
The optical properties of various optical compensation films using T1 with Rth of 0 nm are better than those using TD80UF with Rth of 45 nm of the polymer film substrate.
In general, the higher the Rth of the optically anisotropic layer, the thicker the film and the more easily unevenness occurs. By increasing the Rth / film thickness, the film thickness can be reduced with the same Rth, and unevenness can be improved. By setting the Rth / film thickness of the optically anisotropic layer to 0.065 or more, even when the Rth of the optically anisotropic layer is 150 nm or more, a good surface shape without unevenness can be obtained.

[Example 4]
Here, a method for increasing Rth / d by decreasing the UV irradiation amount will be described.
The coating liquid (S1) containing the discotic liquid crystal compound in the form of an alignment film used for F11-200 was continuously applied onto the prepared alignment film with a # 6.0 wire bar. The conveyance speed of the film was 20 m / min. The solvent was dried in a step of continuously heating from room temperature to 80 ° C., and then heated in a drying zone at 120 ° C. for 90 seconds to align the discotic liquid crystalline compound. Subsequently, the temperature of the film is maintained at 80 ° C., UV light is irradiated at 500 mJ / cm ² using a high-pressure mercury lamp, the orientation of the liquid crystal compound is fixed, an optically anisotropic layer is formed, and the optical compensation film F51 Was made.

  F52 to F54 were produced by changing the irradiation amount of UV light as shown in Table 3 to the optical compensation film F51 produced above.

The coating liquid (S4) containing the discotic liquid crystalline compound in the form of the alignment film used in F11-200 was continuously applied onto the prepared alignment film with a # 6.0 wire bar. The conveyance speed of the film was 20 m / min. The solvent was dried in a step of continuously heating from room temperature to 80 ° C., and then heated in a drying zone at 120 ° C. for 90 seconds to align the discotic liquid crystalline compound. Subsequently, while maintaining the temperature of the film at 80 ° C., an optical anisotropic layer is formed by fixing the orientation of the liquid crystal compound by irradiating UV light with 500 mJ / cm ² using a high-pressure mercury lamp, and optical compensation Film F61 was produced.

  With respect to the optical compensation film F61 produced above, the irradiation amount of UV light was changed as shown in Table 3 to produce F62 to F64.

――――――――――――――――――――――――――――――――――――
Composition of coating liquid (S4) containing discotic liquid crystalline compound ――――――――――――――――――――――――――――――――――――
The following discotic liquid crystalline compound (I) 91 parts by mass Ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 9 parts by mass Photopolymerization initiator A 2 parts by mass The following fluoropolymer 0.4 parts by mass Methyl ethyl ketone 214 parts by mass ――――――――――――――――――――――――――――――――――――

  Furthermore, the coating liquid used for the optical compensation films F51 to F54 was changed from the discotic liquid crystalline compound (S1) to (S2) to produce films F71 to F74.

  Furthermore, the coating liquid used for the optical compensation films F51 to F54 was changed from the discotic liquid crystalline compound (S1) to (S5) to produce films F81 to F84.

――――――――――――――――――――――――――――――――――――
Composition of coating liquid (S5) containing discotic liquid crystalline compound ――――――――――――――――――――――――――――――――――――
Discotic liquid crystalline compound (II) 91 parts by mass Ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 9 parts by mass The following photopolymerization initiator A 2 parts by mass The above fluoropolymer A 0.4 parts by mass Methyl ethyl ketone 254 parts by mass ――――――――――――――――――――――――――――――――――――

  Produced above. Optical compensation films F51 to F54, F61 to F64, F71 to F74, and F81 to F84 were evaluated in the same manner as in Table 1, and the results are shown in Table 3.

The adhesion test was conducted by the following method.
(6) Adhesion evaluation The surface on the side having the low refractive index layer of each antireflection film sample was cut into 11 vertical and 11 horizontal cuts with a cutter knife in a total of 100 square squares. The polyester adhesive tape “No. 31B” manufactured by Nitto Denko Co., Ltd. was pressed and subjected to an adhesion test. The presence or absence of peeling was visually observed, and the following four-stage evaluation was performed.
◎: No peeling was observed in 100 squares ○: No peeling was observed in 100 squares within 2 squares △: peeling was observed in 100 squares 3 to 10 mm ×: The one in which peeling was observed in 100 cells exceeded 10 mm

From the results in Table 3, the following is clear.
Rth / d can be increased by decreasing the UV irradiation amount. At this time, the adhesiveness tends to deteriorate with a decrease in the UV irradiation amount, but the photosensitive area is 330 nm to 450 nm, and when the polymerization initiator A that generates a halogen radical is used, the adhesiveness is hardly deteriorated. Therefore, in order to increase Rth / d, it is a preferable embodiment to use a polymerization initiator A having a photosensitive region of 330 nm to 450 nm and generating a halogen radical.

  Further, from the comparison between F71 to F74 and F81 to F84, Rth / d can be increased by decreasing the UV irradiation amount. At this time, the adhesiveness tends to deteriorate as the UV irradiation amount decreases, but those using a polyfunctional monomer having a tetrafunctional or higher functional group as the polyfunctional monomer (F71 to F74) are trifunctional. Compared with (F81-F74) using a polyfunctional monomer, adhesion deterioration hardly occurs. Therefore, it is a preferable embodiment to use a polyfunctional monomer having a tetrafunctional or higher functional group in order to increase Rth / d.

Next, the amounts of the discotic liquid crystalline compound (II) and the polyfunctional monomer DPHA in the coating liquid (S2) containing the discotic liquid crystalline compound with respect to the optical compensation film F71 are changed as shown in Table 4, and F75 to F77 are changed. Was made.
Further, the amount of the discotic liquid crystalline compound (II) and the polyfunctional monomer V # 360 in the coating liquid (S5) containing the discotic liquid crystalline compound with respect to the optical compensation film F81 is changed as shown in Table 4, and F85 to F87 was produced.
These evaluation results are shown in Table 4.

From the results of Table 4, the following is clear.
Rth / d can be increased by decreasing the amount of polyfunctional monomer contained. At this time, when the amount of the monomer is decreased, the adhesion tends to be deteriorated. However, a polyfunctional monomer having a tetrafunctional or higher functional group as the polyfunctional monomer (F71 and F75 to F77) is 3 In contrast to the use of functional polyfunctional monomers (F81 and F85 to F87), adhesion deterioration is unlikely to occur. Therefore, it is a preferable embodiment to use a polyfunctional monomer having a tetrafunctional or higher functional group in order to increase Rth / d.

It is the schematic which shows an example of the liquid crystal display element of this invention. It is the schematic which shows an example of the polarizing plate which can be used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper polarizing plate 2 Upper polarizing plate Absorption axis 3 Optical anisotropic layer 4 Optical anisotropic layer slow axis direction 5 Liquid crystal cell upper electrode substrate 6 Upper substrate orientation control direction 7 Liquid crystalline molecule 8 Liquid crystal cell lower electrode substrate 9 Lower substrate orientation control direction 10 Optical anisotropic layer 14 Lower polarizing plate 15 Lower polarizing plate absorption axis direction 101 Polarizing plate protective film 102 Polarizing plate protective film slow axis direction 103 Polarizing plate polarizing film 104 Polarizing film absorption axis Direction 105 Polarizing plate protective film 106 Polarizing plate protective film Slow axis direction

Claims (19)

An optical compensation film having an optically anisotropic layer on a polymer film substrate, the in-plane retardation (Re) is 0 to 10 nm, and the thickness direction retardation (Rth) is 100 to 300 nm. And an optical compensation film having Rth / d (a value obtained by dividing retardation in the thickness direction by the film thickness) of 0.085 to 0.16 , wherein the optical anisotropic layer is , A discotic liquid crystalline compound having a polymerizable group, a polyfunctional monomer having four or more double bonds, which is an ester of a polyol having at least four hydroxyl groups and an unsaturated fatty acid, and a photopolymerization initiator An optical compensation film, which is a layer formed from a polymerizable composition, wherein the content of the polyfunctional monomer is 1 to 20% by mass with respect to the liquid crystal compound. The optical compensation film further comprises an alignment film between the polymer film substrate and the optically anisotropic layer, and the alignment film contains a modified polyvinyl alcohol having a polymerizable group. The optical compensation film described. The polyfunctional monomer having four or more double bonds is selected from the group consisting of pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, and dipentaerythritol hexa (meth) acrylate. It is the above, The optical compensation film of Claim 1 or Claim 2 characterized by the above-mentioned. The optical compensation film as described in any one of Claims 1-3 which satisfy | fills following formula (1).
General formula (1)
1.03 ≦ Rth (450) / Rth (550) ≦ 1.30 The optical compensation film according to any one of claims 1 to 4, wherein the optically anisotropic layer satisfies the following formula (2).
General formula (2)
1.06 ≦ Rth (450) / Rth (550) ≦ 1.30 The photosensitive region of the photopolymerization initiator is in the range of 330 nm to 450 nm, and the photopolymerization initiator generates a hydrocarbon radical having a number of atoms other than halogen radicals or hydrogen atoms of 8 or less . The optical compensation film according to any one of the above. The optical compensation film according to any one of claims 1 to 5, wherein the photopolymerization initiator is selected from the following compounds.

In the optically anisotropic layer, the optical compensation film of any one of claims 1 to 7, discotic structural unit of the discotic liquid crystal compound is aligned horizontally with respect to the polymer film substrate surface. The optical compensation film according to claim 1, wherein the discotic liquid crystalline compound is a compound represented by the following formula (I).

[Wherein, A ¹ and A ² each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms; Atoms, halogen atoms, alkyl groups having 1 to 12 carbon atoms, alkoxy groups having 1 to 12 carbon atoms, acyl groups having 2 to 13 carbon atoms, alkylamino groups having 1 to 12 carbon atoms, Or an acyloxy group having 2 to 13 carbon atoms; or A ² and Y may combine to form a 5-membered ring or a 6-membered ring; Z is a halogen atom or the number of carbon atoms Is an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an acyl group having 2 to 13 carbon atoms, an alkylamino group having 1 to 12 carbon atoms, or 2 to 13 carbon atoms. Represents an acyloxy group; L represents —O— or —C; -, -S-, -NH-, an alkylene group, an alkenylene group, an alkynylene group, an arylene group and a divalent linking group selected from the group consisting of these; Q is a polymerizable group; , Represents an integer of 1 to 4; b represents an integer of 0 to (4-a)] The optical compensation film according to claim 1 , wherein the optically anisotropic layer contains a fluoroaliphatic-containing polymer. 11. The optical compensation film according to claim 1 , wherein the retardation in the thickness direction of the polymer film substrate is −25 to 25 nm. The optical compensation film according to claim 1, wherein the polymer film is a cellulose acylate film. The polarizing plate which has an optical compensation film as described in any one of Claims 1-12 . The liquid crystal display device which has an optical compensation film as described in any one of Claims 1-12 . A pair of polarizing films whose absorption axes are orthogonal to each other, a pair of substrates disposed between the polarizing films, and a liquid crystal layer composed of liquid crystalline molecules sandwiched between the substrates, The liquid crystal display device according to claim 14 , wherein the liquid crystal display device is aligned in a direction substantially perpendicular to the substrate in a non-driven state in which no external electric field is applied. Furthermore, it has a 2nd optical compensation film, Said 2nd optical compensation film consists of a polymer stretched film, and front retardation and retardation of thickness direction satisfy | fill following formula (3) and following formula (4). The liquid crystal display device according to claim 14 or 15 .
General formula (3)
70 ≦ Re (550) ≦ 180
General formula (4)
30 ≦ Rth (550) ≦ 140 The liquid crystal display device according to claim 16 , wherein the second optical compensation film satisfies the following formula (5).
General formula (5)
0.7 ≦ Re (450) / Re (550) ≦ 1.0 The second optical compensation film, a cellulose acylate film, a norbornene-based film, a polycarbonate-based film, liquid crystal display device according to claim 16 or 17 Ru der either polyester film or polysulfone film. The second optical compensation film, in an arrangement the absorption axis of the polarizing film and the optical compensation film plane slow axis is orthogonal, any claim 16 to 18 are stacked directly on one of the pair of polarizing film 2. A liquid crystal display device according to item 1 .

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