KR20080097440A - Retarder, Polarizer, and Liquid Crystal Display - Google Patents

Abstract

Provide a novel retarder. The retardation plate of the present invention includes a first retardation layer and a second retardation layer, and the first retardation layer has in-plane retardation Re of 20 nm to 150 nm, and Nz using in-plane retardation Re and thickness direction retardation Rth. The Nz value defined as = Rth / Re + 0.5 is -6.5 to 0.5, and the second retardation layer has Re satisfying | Re | <30 nm, and Rth is in the range of 80 nm to 400 nm.

Description

Retardation Plates, Polarizers, and Liquid Crystal Displays {RETARDATION PLATE, POLARIZER PLATE, AND LIQUID CRYSTAL DISPLAY}

The present invention relates to liquid crystal displays, and more particularly to an in-plane switching (IPS) mode liquid crystal display driven by a transverse electric field applied to horizontally oriented liquid crystal molecules. The invention also relates to a retardation plate which contributes to an improvement in viewing angle characteristics of liquid crystal displays, in particular IPS-mode liquid crystal displays, and polarizing plates comprising the same.

Liquid crystal displays adopting the so-called TN mode have been widely used. The TN-mode liquid crystal display includes two crossed polarizers and a nematic liquid crystal layer oriented in a twisted manner between the polarizers and is driven by an electric field applied to the liquid crystal layer in a direction perpendicular to the substrate. In this mode, the birefringence of the liquid crystal layer in the oblique direction is poor, and as a result, light leakage occurs in the black state because the liquid crystal molecules stand up from the substrate in the black state. In order to overcome this problem, a film formed of a liquid crystal composition fixed in a hybrid orientation has been used for optical compensation of a liquid crystal cell and prevention of light leakage in a black state; And TN-mode liquid crystal displays employing such films have already been put to practical use. However, even with a film formed of a fixed liquid crystal, it is very difficult to achieve complete optical compensation of the liquid crystal cell without any problem, and the problem of incomplete suppression of gray level inversion at the lower side of the screen has not been solved.

In order to overcome this problem, a liquid crystal display (LCD) employing an in-plane switching (IPS) mode driven by a transverse electric field applied to the liquid crystal layer, and liquid crystal molecules having negative dielectric anisotropy are formed into protrusions or slits in the liquid crystal cell. Vertical alignment (VA) modes that are vertically arranged in the formed multi-domain structure have been proposed and put to practical use. Employing IPS or VA mode, these panels have been developed with the intention of being used not only as monitors but also as high brightness TVs. For this reason, weak light leakage in the oblique direction in the black state, which was not previously recognized as a problem, is regarded as one of the factors that degrade the display quality.

In order to improve the viewing angle characteristic of the IPS-mode LCD in the black state, a birefringent optical compensation material disposed between the liquid crystal layer and the polarizing plate has been proposed.

For example, transverse field type liquid crystal displays have been proposed that include a dual refraction medium having a phase difference to compensate for the retardation rise and fall upon tilting the liquid crystal layer between the substrate and the polarizer (hereinafter, often referred to as "JPA"). See Japanese Laid-Open Patent Publication No. H9-80424).

Films formed of various materials such as styrene-based polymers and discotic liquid crystalline compounds having negative intrinsic birefringence have also been proposed as optical compensation films for IPS-mode LCDs (JPA Nos. H10-54982, H11-202323 and H9). -292522).

For the compensation of IPS-mode LCDs, the use of a compensation layer with positive uniaxial optical anisotropy and an optical axis perpendicular to the substrate plane (see JPA No. H11-133408); Use of biaxial optical compensation sheets exhibiting half-wave retardation (see JPA No. H11-305217); And a combination use of a film showing negative retardation and an optical compensation layer showing positive retardation provided thereon as a protective film of the polarizing plate (see JPA No. H10-307291) has also been proposed.

However, the above-described film or the like is used to offset the birefringence anisotropy of the liquid crystal cell, whereby the viewing angle dependency is improved, and most LCDs including such a film are off-axis from crossed linear polarizers. ) Light leakage still occurs. Even if the film has been proposed as a film capable of reducing off-axis light leakage, it is very difficult to completely optically compensate the liquid crystal cell without causing any problem. In addition, optical compensation sheets capable of compensating IPS-mode liquid crystal cells require a plurality of stretched birefringent polymer films, and the thickness of such sheets consequently increases, which is disadvantageous in terms of thinning of the display device. On the other hand, the adhesive layer used for laminating the stretched film may shrink due to the influence of temperature and humidity changes, and as a result, defects such as peeling and warping of the film may occur.

Summary of the Invention

One object of the present invention is to provide a liquid crystal display, in particular an IPS-type liquid crystal display, in which not only the display quality but also the viewing angle characteristics are improved with a simple structure.

It is still another object of the present invention to provide a novel retardation plate and a polarizing plate using the same, which contribute to the improvement of the viewing angle characteristic of a liquid crystal display, in particular an IPS-type liquid crystal display.

In one aspect, the present invention provides a retardation plate comprising a first retardation layer and a second retardation layer, wherein the first retardation layer has an in-plane retardation Re of 20 nm to 150 nm, and an in-plane retardation Re and thickness direction rita The Nz value defined by Nz = Rth / Re + 0.5 using the date Rth is -6.5 to 0.5, and the second retardation layer has Re satisfying | Re | <30 nm and Rth ranging from 80 nm to 400 nm. to be.

As an embodiment of the present invention, a retardation plate is provided in which the first retardation layer is a cellulose-derivative film.

The cellulose derivative film may include at least one cellulose acylate derivative that satisfies the following conditions (a) and (b); The film is prepared by casting a dope comprising a cellulose acylate derivative that satisfies the following conditions (a) and (b) according to a solvent casting method to form a film and stretching the film:

(a) The cellulose acylate derivative has, instead of at least one of the three hydroxyl groups in the glucose unit of cellulose, at least one substituent having a polarization anisotropy Δα defined by the following formula (1) of 2.5 × 10 ⁻²⁴ or more:

(1): Δα = α _x- (α _y + α _z ) / 2

Where α _x is the largest component of the eigenvalues obtained by diagonalizing the polarization tensor; α _y is the second largest component of the eigenvalues obtained by diagonalizing the polarization tensor; and α _z is the polarization tensor Is the smallest component of the eigenvalues obtained by diagonalizing; And

(b) Substitution degree of substituent having ^Δα of 2.5 × 10 ^-24 cm ³ or more and Δα of 2.5 × 10 ^-24 cm ³ Substitution degree P _A and P _B which respectively show substitution degree of the less than substituent Satisfies Equations (3) and (4) below.

(3): 2P _A + P _B > 3.0

(4): P _A > 0.2

In one preferred embodiment, the substituent having ^Δα of 2.5 × 10 ⁻²⁴ cm ³ or more is an aromatic acyl group, and the substituent having Δα of less than 2.5 × 10 ⁻²⁴ cm ³ is an aliphatic acyl group.

The dope may comprise at least one phase difference regulator, such as a compound represented by the following formula (I):

Formula (I)

In the formula, Ar ¹ , Ar ² and Ar ³ each represent an aryl group or an aromatic heterocyclic group; L ¹ and L ² each represent a single bond or a divalent linking group; n is an integer of at least 3; And Ar ² and L ² may be the same or different, respectively.

As an embodiment, the second retardation layer is formed of a composition comprising a discotic liquid crystal compound; And a retarder in which the average director of molecules of the discotic liquid crystal compound is perpendicular to the layer plane of the second retardation layer.

In this embodiment, the second retardation layer may comprise at least one compound having at least one triazine ring group and / or at least one fluoro-aliphatic polymer, wherein the fluoro-aliphatic polymer is a fluoro-aliphatic group The branch may be a copolymer (polymer "A") comprising at least one repeat unit derived from a compound, and at least one repeat unit represented by the following formula (5):

Equation (5)

In the formula, R ¹ , R ² and R ³ each represent a hydrogen atom or a substituent; L represents a divalent connector selected from the group of connectors shown below or a divalent linker consisting of two or more selected from the group of connectors shown below:

(Coupler group)

Single bond, -O-, -CO-, -NR ^4- (R ⁴ represents a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group), -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; And

Q represents a carboxyl group (-COOH) or a salt thereof, a sulfo group (-SO ₃ H) or a salt thereof, or a phosphoxy group {-OP (= 0) (OH) ₂ } or a salt thereof.

In another aspect, the present invention provides a polarizing plate comprising at least the retardation plate and the polarizing film of the present invention.

In one embodiment of the polarizing plate, the polarizing film, the first retardation layer, and the second retardation layer are arranged in this order, and the direction of the slow axis of the first retardation layer and the direction of the absorption axis of the polarizing film are substantially orthogonal to each other.

In still another embodiment of the polarizing plate, the polarizing film, the first retardation layer, and the second retardation layer are arranged in this order, and the direction of the slow axis of the first retardation layer and the direction of the absorption axis of the polarizing film are substantially parallel to each other.

In another aspect, the present invention provides a liquid crystal display comprising at least a liquid crystal cell and a polarizing plate of the present invention.

The liquid crystal display may further include a second polarizing film. In this embodiment, the liquid crystal cell is disposed between the first polarizing film and the second polarizing film; Absorption axes of the first polarizing film and the second polarizing film are perpendicular to each other. Only a substantially isotropic adhesive layer and / or a substantially isotropic transparent protective film may be disposed between the second polarizing film and one of the pair of substrates disposed closer to the second polarizing film. The transparent protective film may be a cellulose acetate film satisfying the following relations (I) and (II):

(I): 0 ≦ Re (630) ≦ 10, and Rth (630) | ≤ 25

(II): | Re (400) -Re (700) | ≤ 10, and | Rth (400) -Rth (700) | ≤ 35

In formula, Re ((lambda)) is the in-plane retardation value (unit: nm) in wavelength (lambda) nm, and Rth ((lambda)) is the thickness direction retardation value (unit: nm) in wavelength (lambda) nm.

In one embodiment of the liquid crystal display, when viewed from the liquid crystal cell side, the second retardation layer, the first retardation layer, and the first polarizing film are arranged in this order;

The liquid crystal molecules of the liquid crystal layer are oriented horizontally with respect to the pair of substrates in a black state, and the average direction of the major axes thereof is parallel to the slow axis of the first retardation layer; And

The absorption axis of the first polarizing film and the slow axis of the first retardation layer are perpendicular to each other.

In another embodiment of the liquid crystal display, when visually recognized from the liquid crystal cell side, the second retardation layer, the first retardation layer, and the first polarizing film are arranged in this order,

The liquid crystal molecules of the liquid crystal layer are horizontal with respect to the pair of substrates in the black state, and the average direction of the major axes thereof is orthogonal to the slow axis of the first retardation layer; And

The absorption axis of the first polarizing film and the slow axis of the first retardation layer are parallel to each other.

1 is a schematic view showing an example of a liquid crystal display according to the present invention.

2 is a schematic view showing an example of another liquid crystal display according to the present invention.

3 is a schematic view showing an example of a pixel region of a liquid crystal display according to the present invention.

In these figures, reference numerals mean:

1 pixel region of the liquid crystal element;

Two pixel electrodes;

Three display electrodes;

4 rubbing direction;

5a, 5b average director of liquid crystal molecules in a black state;

Average directors of the liquid crystal molecules in the 6a, 6b back state;

7a, 7b, 19a, 19b protective film for polarizing films;

8, 20 polarizing film;

9, 21 polarization absorption axis of the polarizing film;

10 first retardation layer;

11 slow axis of the first retardation layer;

12 second retardation layer;

13, 17 cell substrates;

The rubbing direction of the 14 and 18 cell substrates;

15 liquid crystal layer; And

16 Slow axis direction of liquid crystal layer.

Preferred Embodiments of the Invention

The present invention will be described in detail.

Note that in this description, the expressions "... to ..." are used to mean a range including the lower limit and the upper limit described before and after.

In the description, Re (λ) and Rth (λ) mean in-plane retardation and thickness direction retardation at wavelength λ, respectively. Re (λ) is measured using KOBRA-21ADH (manufactured by Oji Scientific Instruments) for incident light having a wavelength of λ nm in a direction perpendicular to the film plane. Rth (λ) is calculated using KOBRA-21ADH based on the three retardation values, the assumption of the average refractive index and the input thickness value of the film, the first of the three retardation values being the Re (λ obtained above The second is the retardation measured for incident light of wavelength λnm in the direction rotated + 40 ° with respect to the film normal direction around the in-plane slow axis determined by KOBRA 21ADH as the tilt axis (rotation axis), and the third is It is the retardation measured with respect to incident light of wavelength (lambda) nm in the direction which rotated -40 degrees with respect to the film normal line direction about an in-plane slow axis as a tilt axis (rotation axis). Average refractive indices of various materials are described in published documents such as "Polymer Handbook" (JOHN WILEY & SONS, INC) and catalogs. If the value is not known, the value can be measured using an Abbe refractometer or the like. The average refractive index of the main optical film is illustrated below:

Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49) and polystyrene (1.59).

When the hypothesis value and thickness value of the average refractive index are input to KOBRA 21ADH, nx, ny and nz are calculated. The Nz value is calculated by substituting the values of Re and Rth calculated in accordance with the above-described method into Nz = Rth / Re + 0.5, which is a defining expression.

In the description, the term “parallel” or “orthogonal” means within a range of less than ± 10 ° with respect to the exact angle. The error from the correct angle is preferably less than ± 5 °, more preferably less than ± 2 °. The term "orthogonal" means within a range of less than ± 20 ° with respect to the exact angle. The error from the correct angle is preferably less than ± 15 °, more preferably less than ± 10 °. In addition, the term "ground axis" means the direction in which the refractive index becomes the maximum value. Incidentally, the refractive index is a value measured at λ = 550 nm in the visible light region unless otherwise specified.

In the description, the term "polarizing plate" is used for both a continuous web form of polarizing plate and a polarizing plate cut to size for bonding to a liquid crystal device, unless otherwise specified (in the description of the present invention, "foundation" "Punching", "cutout", etc.). In addition, in the description, the terms “polarizing film” and “polarizing plate” are used in different meanings, and “polarizing plate” means a laminate member having a transparent protective film for protecting a polarizing film on at least one side of the “polarizing film”.

The following paragraphs describe embodiments of the present invention with reference to the accompanying drawings. 1 and 2 are schematic diagrams showing embodiments of the liquid crystal display of the present invention. 3 is a schematic view showing an example of a pixel region of a liquid crystal display of the present invention.

[Liquid Crystal Display]

The liquid crystal display shown in FIG. 1 includes a polarizing film 8, 20, a first retardation layer 10, a second retardation layer 12, a pair of substrates 13, 17, and a pair of substrates. Arranged liquid crystal layer 15 is included. The polarizing films 8, 20 respectively include protective films 7a, 7b, and 19a, 19b thereon.

In the liquid crystal display shown in FIG. 1, the liquid crystal cell includes the substrates 13 and 17 and the liquid crystal layer 15 disposed therebetween. The product Δn · d of the refractive index anisotropy Δn and the thickness d (μm) of the liquid crystal layer in the transmission mode may have an optimum value within the range of 0.2 to 0.4 μm for the IPS-type cell without a twist structure. This range can ensure high luminance in the white state and small luminance in the black state, thereby making the display device excellent in brightness and contrast. The substrates 13 and 17 are each liquid crystal layer 15 such that the liquid crystal molecules are oriented almost horizontally with respect to the substrate surface along the rubbing direction (rubbing directions 14 and 18 in FIG. 1) provided to the alignment film when no voltage is applied or low voltage is applied, respectively. ) And an alignment film (not shown in FIG. 1) formed on the surface thereof. On the inner surface of the substrate 13 or 17, an electrode (not shown in FIG. 2) capable of applying a voltage to the liquid crystal molecules is formed.

3 schematically shows the alignment state of liquid crystal molecules in a single pixel region of the liquid crystal layer 15. 3 shows the alignment of liquid crystal molecules in a region having a very small area corresponding to a single pixel of the liquid crystal layer 15 together with the rubbing direction 4 of the alignment film formed on the inner surfaces of the substrates 13 and 17. And electrodes 2 and 3 formed on the inner surfaces of the substrates 13 and 17 and capable of applying a voltage to the liquid crystal molecules. Under active operation using a nematic liquid crystal having positive dielectric anisotropy as the field effect liquid crystal, the liquid crystal molecules are oriented along the directors 5a and 5b when no voltage is applied or when low voltage is applied, whereby a black state is obtained. . When a voltage is applied between the electrodes 2 and 3, the liquid crystal molecules change their orientation direction as indicated by the directors 6a and 6b depending on the voltage, so that a back state is obtained.

Referring again to FIG. 1, the polarizing films 8 and 20 are arranged such that the respective absorption axes 9, 21 cross each other. In the black state, the slow axis 11 of the first retardation layer 10 is orthogonal to the absorption axis 9 of the polarizing film 8, and is parallel to the average slow axis 16 of the liquid crystal molecules of the liquid crystal layer 15. . In the structure shown in FIG. 1, the same effect can be obtained if the slow axis 11 of the first retardation layer 10 is parallel to the absorption axis 9 of the polarizing film 8.

The first retardation layer 10 and the second retardation layer 12 may be introduced into the liquid crystal display as a retardation plate comprising two layers, or laminated polarizing film 8, protective film 7b, first It can be introduced into the liquid crystal display as a polarizing plate including the retardation layer 10 and the second retardation layer 12.

In the liquid crystal display shown in Fig. 1, the polarizing film 8 has two protective films 7a and 7b thereon, but the protective film 7b can be omitted. In addition, the polarizing film 20 includes two protective films 19a and 19b thereon, but may also omit the protective film 19a disposed closer to the liquid crystal layer 15. According to the present invention, based on the position of the liquid crystal cell, in the embodiment shown in FIG. 2, the first retardation layer and the second retardation layer may be disposed between the liquid crystal cell and the polarizing film on the observer side, or the back side It may be disposed between the liquid crystal cell and the polarizing film. In either of these configurations, in this embodiment, it is preferable that the second retardation layer is arranged closer to the liquid crystal cell.

Another embodiment of the invention is shown in FIG. 2. 2 is an embodiment in which the positions of the second retardation layer 12 and the first retardation layer 10 are exchanged, and the first retardation layer is disposed closer to the liquid crystal cell. In the liquid crystal display shown in FIG. 2, the protective film 7b or the protective film 19a can be omitted. In the embodiment shown in FIG. 2, the first retardation layer 10 has a slow axis 11 parallel to the absorption axis 9 of the polarizing film 8 in the black state, and the liquid crystal molecules of the liquid crystal layer 15 It is arranged to be orthogonal to the slow axis 16 direction. In the configuration shown in FIG. 3, the same effect can be obtained if the slow axis 11 of the first retardation layer 10 is orthogonal to the absorption axis 9 of the polarizing film.

In the embodiment shown in FIG. 2, the first retardation layer and the second retardation layer may be disposed between the liquid crystal cell and the polarizing film on the observer side based on the position of the liquid crystal cell, or the liquid crystal cell and It may be disposed between the polarizing film.

Although FIGS. 1 and 2 show an embodiment of a transmissive display device having an upper polarizer and a lower polarizer, the present invention may relate to an embodiment of a reflective display device having only one polarizer, in which case a liquid crystal Since the length of the optical path in the cell is halved, the optimum value of Δn · d is also roughly halved.

The liquid crystal display of the present invention is not limited to the configuration shown in Figs. 1 to 3 and may include other components. For example, a color filter may be disposed between the liquid crystal layer and the polarizing film. The surface of the protective film of the polarizing film may be anti-reflection finish or hard coating treatment. Any member having conductivity can be employed. A display device intended for use as a transmissive type may have, on its back, a backlight using a cold cathode or hot cathode fluorescent tube, a light emitting diode, an electroluminescent element, or an electro-luminescent element. . In this case, the backlight may be disposed above or below in FIGS. 1 and 2. A reflective polarizer, a diffuser plate, a prism sheet, or a light guide plate may be disposed between the liquid crystal layer and the backlight. As described above, the liquid crystal display of the present invention may be reflective, and only one polarizer is disposed on the observer side, and the reflective film is disposed on the rear surface of the liquid crystal cell or on the inner surface of the lower substrate of the liquid crystal cell. Of course, the front light using the above-described light source may be disposed on the observer side of the liquid crystal cell.

However, in the liquid crystal display shown in Figs. 1 and 2, it is preferable that there is no retardation region between the liquid crystal cell and the polarizing film 21, and instead an isotropic adhesive layer and / or substantially isotropic transparent therebetween. It is preferable that only a protective film is arrange | positioned. In the configuration shown in Figs. 1 and 2, the protective film 19a is preferably a substantially isotropic film. The substantially isotropic transparent protective film (protective film of polarizing film) is specifically a film whose in-plane retardation is 0-10 nm, and thickness direction retardation is -20-20 nm. Preference is given to films comprising cellulose acylate or cyclic polyolefins. Furthermore, the low-re (low-Re) cellulose acylate film mentioned later is preferable. Examples of the adhesive capable of forming an isotropic adhesive layer include a polyvinyl alcohol adhesive and an adhesive composed of a polyester polyurethane and an isocyanate crosslinking agent.

The liquid crystal display of the present invention includes those of an image direct view type, an image projection type, and a light modulation type. In the present invention, the embodiment in the form applied to an active matrix liquid crystal display using three or two terminals such as TFT and MIM is particularly preferable. Of course, embodiments in the form applied to passive matrix liquid crystal displays, also called based on time division driving, are also effective.

Preferred optical properties, materials and methods of the various components applicable to the liquid crystal display of the present invention are employed in the production of these components.

[First Phase Retardation Layer]

In the present invention, the first retardation layer has an in-plane retardation Re of 20 nm to 150 nm, and an Nz value of -6.5 to 0.5 defined by Nz = Rth / Re + 0.5 by Re and the thickness direction retardation Rth. In order to effectively reduce light leakage in the oblique direction, the first retardation layer more preferably has Re of 40 nm to 115 nm, even more preferably 50 nm to 85 nm. Similarly, in order to effectively reduce light leakage in the oblique direction, the first retardation layer more preferably has a Nz value of -5.5 to -0.5, even more preferably -4.5 to -2.5.

Basically, the material and configuration of the first retardation layer are not particularly limited as long as the above-described optical characteristics are maintained. For example, the first retardation layer may be coated with a retardation film composed of a birefringent polymer film, a retardation film formed by coating and continuously heating a polymer solution or a polymer-melting fluid, and a composition comprising a low molecular weight or high molecular weight liquid crystalline compound. It may be a retardation film including the formed retardation layer. These films can be used in a lamination manner.

It is preferable that a birefringent polymer film is excellent in control of birefringence, transparency, and heat resistance. The polymer material applicable here is not particularly limited as long as it can be a uniform biaxial film. Among them, a polymer material which may be a film by a solvent casting method or an extrusion method is preferable; Preferred examples of the polymer material include norbornene-based polymers, polycarbonate-based polymers, polyallylate-based polymers, polyester-based polymers, aromatic polymers such as polysulfone-based polymers, cellulose acylates, and two or three or more of these polymers. It includes a mixed polymer comprising a. Among them, the use of cellulose acylate is preferable.

The following paragraphs describe in detail the cellulose derivative film which is preferably applicable as the first retardation layer.

(Cellulose derivative film)

The cellulose derivative film having the above-described optical properties required for the first retardation layer can be produced by appropriately selecting the kind of the cellulose derivative used as the raw material, the kind and amount of the additive, the method of forming the film, and the film forming conditions. Cellulose derivative films having optical properties can be conventionally obtained by a solvent cast process and subsequent stretching using a cellulose derivative-containing dope that satisfies the following conditions (a) and (b):

(a) the cellulose derivative has, instead of at least one of the three hydroxyl groups in the glucose unit of cellulose, at least one substituent having a polarization anisotropy Δα defined by the following formula (1) of 2.5 × 10 ⁻²⁴ or more;

(1): Δα = α _x- (α _y + α _z ) / 2

In the formula, α _x is the largest component among the eigenvalues obtained by diagonalizing the polarization tensor; α _y is the second largest component of the eigenvalues obtained by diagonalizing the polarization tensor; And α _z is the minimum component among the eigenvalues obtained by diagonalizing the polarization tensor; And

(b) Substitution degree of substituent having ^Δα of 2.5 × 10 ^-24 cm ³ or more and Δα of 2.5 × 10 ^-24 cm ³ Substitution degree P _A and P _B which respectively show substitution degree of the less than substituent Satisfies Equations (3) and (4) below.

(3): 2P _A + P _B > 3.0

(4): P _A > 0.2

The number of hydroxyl groups in the glucose unit of cellulose is three, and any cellulose derivative naturally satisfies P _A + P _B ≦ 3.

(Cellulose derivative)

The cellulose derivative film is preferably manufactured using a cellulose derivative having a substituent having a large polarization anisotropy as a substituent which is preferably bonded to three hydroxyl groups on the β-glucose ring. The substituent having large polarization anisotropy on the β-glucose ring is oriented in the direction perpendicular to the main chain of the β-glucose ring during stretching to maximize the polarization anisotropy in the film thickness direction. The use of this kind of cellulose derivative enables the stable production of a film having the above-described optical properties.

In particular, by introducing a substituent having a large polarization anisotropy and adjusting the degree of substitution within a range satisfying Formulas (3) and (4), a film formed of such a cellulose derivative lowers other various properties such as softening temperature of the film. It does not have a desired optical properties.

Below with the above-described P _A and P _B which satisfies the formula (3 ') and (4') is more preferred to use a cellulose derivative.

(3 '): 2P _A + P _B > 3.0

(4 '): 0.2 <P _A <2.0

It is even more preferable to use cellulose derivatives having P _A and P _B described above that satisfy the following formulas (3 ") and (4").

(3 "): 2P _A + P _B > 3.0

(4 "): 0.2 <P _A <1.0

(Polarization anisotropy)

 The polarization anisotropy of the substituents can usually be calculated using Gaussian03 (Revision B.03, Gaussian, Inc., USA). More specifically, the structure of the substituents is optimized by calculation based on the B3LYP / 6-31G * level, and then the polarization rate is calculated using the structure thus obtained on the B3LYP / 6-311 + G ** level. If the obtained polarization tensor is then diagonalized, the polarization anisotropy can be calculated using the diagonal component thus obtained based on Equation (1).

It is preferable that the substituent which has large polarization anisotropy is orientated so that (alpha) _x and (alpha) _y may orthogonally cross and (alpha) _z may be parallel to the main chain of a cellulose derivative. Among them, having α _x oriented in the thickness direction of the film and having α _y oriented in the in-plane direction of the film tend to provide a negative value of the thickness direction retardation Rth. The orientation of α _x and α _y can be largely attributed to the substituent position on the glucopyranose ring of cellulose.

Substituents having ^Δα of 2.5 × 10 ⁻²⁴ cm ³ or more are preferably selected from aromatic acyl groups. Substituents having ^{Δα of} less than 2.5 × 10 ⁻²⁴ cm ³ are preferably selected from aliphatic acyl groups.

Examples of the arylacyl group include a group represented by formula (A).

Formula (A)

In formula (A), X represents a substituent. Examples of substituents include halogen atoms, cyano, alkyl, alkoxy, aryl, aryloxy, acyl, carbonamide, sulfonamide, ureido, aralkyl, nitro, alkoxy carbonyl, aryloxy carbonyl, aralkyloxy carbonyl, Carbamoyl, sulfamoyl, acyloxy, alkenyl, alkynyl, alkylsulfonyl, arylsulfonyl, alkyloxysulfonyl, aryloxysulfonyl, alkylsulfonyloxy, aryloxysulfonyl, -SR, -NH- CO-OR, -PH-R, -P (-R) ₂ , -PH-OR, -P (-R) (-OR), -P (-OR) ₂ , -PH (= O) -RP ( = O) (-R) ₂ , -PH (= O) -OR, -P (= O) (-R) (-OR), -P (= O) (-OR) ₂ , -O-PH ( = O) -R, -OP (= O) (-R) ₂ -O-PH (= O) -OR, -0-P (= 0) (-R) (-OR), -0-P ( (= 0) (-0-R) ₂ , -NH-PH (= O) -R, -NH-P (= O) (-R) (-OR), -NH-P (= O) (-OR ) ₂ , -SiH ₂ -R, -SiH (-R) ₂ , -Si (-R) ₃ , -O-SiH ₂ -R, -O-SiH (-R) ₂ and -O-Si (-R ) ₃ . In the formula, R represents an aliphatic, aromatic or heterocyclic group. In the formulas, X preferably represents halogen, cyano, alkyl, alkoxy, aryl, aryloxy, acyl, carbonamide, sulfonamide or ureido; And more preferably an aliphatic, aromatic or heterocyclic group; More preferably halogen, cyano, alkyl, alkoxy, aryloxy, acyl or carbonamide; Even more preferably halogen, cyano, alkyl, alkoxy or aryloxy; And even more preferably halogen, alkyl or alkoxy.

Examples of halogens include fluorine, chlorine, bromine and iodine atoms. The alkyl group may have a cyclic structure or a branched chain structure. It is preferable that carbon number of an alkyl group is 1-20, It is more preferable that it is 1-12, It is still more preferable that it is 1-6, It is still more preferable that it is 1-4. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, t-butyl, hexyl, cyclohexyl, octyl and 2-ethylhexyl. The alkoxy group may have a cyclic structure or a branched chain structure. It is preferable that carbon number of an alkoxy group is 1-20, It is more preferable that it is 1-12, It is still more preferable that it is 1-6, It is still more preferable that it is 1-4. The alkoxy group may have at least one substituent. Examples of alkoxy groups include methoxy, ethoxy, 2-methoxyethoxy, 2-methoxy-2-ethoxy ethoxy, butyloxy, hexyloxy and octyloxy.

It is preferable that it is 6-20, and, as for the carbon atom number of an aryl group, it is more preferable that it is 6-12. Examples of aryl groups include phenyl and naphthyl. It is preferable that it is 6-20, and, as for the carbon atom number of an aryloxy group, it is more preferable that it is 6-12. Examples of aryloxy groups include phenoxy and naphthoxy. It is preferable that it is 1-20, and, as for the carbon atom number of an acyl group, it is more preferable that it is 1-12. Examples of acyl groups include formyl, acetyl and benzoyl. It is preferable that it is 1-20, and, as for the carbon atom number of the said carbonamide, it is more preferable that it is 1-12. Examples of carbonamides include acetamide and benzamide. It is preferable that it is 1-20, and, as for the carbon atom number of sulfonamide, it is more preferable that it is 1-12. Examples of sulfonamides include methane sulfonamide, benzene sulfonamide and p-toluene sulfonamide. It is preferable that it is 1-20, and, as for the number of carbon atoms of a ureido group, it is more preferable that it is 1-12. Examples of ureido groups include unsubstituted ureidos.

It is preferable that it is 7-20, and, as for the carbon atom number of an aralkyl group, it is more preferable that it is 7-12. Examples of aralkyl groups include benzyl, phenethyl and naphthyl. It is preferable that it is 1-220, and, as for carbon number of alkoxycarbonyl, it is more preferable that it is 2-12. Examples of alkoxycarbonyl groups include methoxy carbonyl. It is preferable that it is 7-20, and, as for the carbon atom number of aryloxycarbonyl, it is more preferable that it is 7-12. Examples of aryloxycarbonyl groups include phenoxy carbonyl. It is preferable that it is 8-20, and, as for the carbon number of an aralkyloxy carbonyl group, it is more preferable that it is 8-12. Examples of aralkyloxy carbonyl include benzoyloxy carbonyl. It is preferable that it is 1-20, and, as for the carbon atom number of a carbamoyl group, it is more preferable that it is 1-12. Examples of carbamoyl groups include unsubstituted carbamoyl and N-methyl carbamoyl. It is preferable that it is 20 or less, and, as for the carbon atom number of a sulfamoyl group, it is more preferable that it is 12 or less. Examples of sulfamoyl groups include unsubstituted sulfamoyl and N-methyl sulfamoyl. It is preferable that it is 1-20, and, as for the carbon atom number of an acyloxy group, it is more preferable that it is 2-12. Examples of acyloxy groups include acetoxy and benzoyloxy.

It is preferable that it is 2-20, and, as for the carbon number of an alkenyl group, it is more preferable that it is 2-12. Examples of alkenyl groups include vinyl, allyl and isopropenyl. It is preferable that it is 2-20, and, as for the carbon atom number of an alkynyl group, it is more preferable that it is 2-12. Examples of alkynyl groups include thienyl. It is preferable that it is 1-20, and, as for the carbon atom number of an alkylsulfonyl group, it is more preferable that it is 1-12. It is preferable that it is 6-20, and, as for the carbon atom number of an arylsulfonyl group, it is more preferable that it is 6-12. It is preferable that it is 1-20, and, as for the carbon atom number of an alkyloxysulfonyl group, it is more preferable that it is 1-12. It is preferable that it is 6-20, and, as for the carbon atom number of an aryloxysulfonyl group, it is more preferable that it is 6-12.

In formula (A), the number "n" of the substituent X, which is attached to the aromatic ring, is in the range of 0 to 5, preferably 1 to 3, more preferably 1 or 2.

When n is 2 or more, they may be the same or different from each other, and may be combined with each other to be naphthalene, indene, indane, phenanthrene, quinoline, isoquinoline, chroman, chromman, phthalazine, acridine, indole and indole Condensation multi-rings such as lean can be formed. Substituent is preferably halogen, cyano, C _{1 -20} alkyl, C _{1 -20} alkoxy, C _{6 -20} aryl, C _{6 -20} aryloxy, C _{1 -20} acyl, C _{1 -20} carbon amides, C _{1 - 20} is selected from sulfonamides, and C _{1 -20} the group consisting of urea ear canal.

Examples of the group represented by formula (A) include, but are not limited to, those shown below. Preferred examples are Nos. 1, 3, 5, 6, 8, 13, 18 and 28 groups; More preferred examples are Nos. Groups 1, 3, 6 and 13;

As mentioned above, substituents having Δα of less than 2.5 × 10 ⁻²⁴ cm ³ are preferably selected from aliphatic acyl groups, more preferably aliphatic acyl groups having 2 to 20 carbon atoms, more specifically acetyl, propy Oryl, butyryl, isobutyryl, vareryl, pivaloyl, hexanoyl, octanoyl, lauroyl, stearoyl and the like. Of these, acetyl, propionyl and butyryl are more preferred, and acetyl is even more preferred. In the present invention, the above-mentioned aliphatic acyl group is meant to include those having additional substituents, and such substituents include those exemplified by X in the formula (A) shown above.

Cellulose derivatives can be synthesized using acid anhydrides or acid chlorides as acylating agents. The raw cellulose of the cellulose derivative applicable to the present invention includes cotton linter, and wood pulp (softwood, softwood), and cellulose derivatives obtained from any of the raw celluloses of both can be used, and in some cases, can be mixed. Do. Details of these raw celluloses are described, for example, unless otherwise specified, for example, "Lecture Course of Plastic Materials (17), Fiber-Forming Resins" (Marusawa and Uda). Published by the Daily Newspaper, 1970) and JIII Journal of Technical Disclosure 2001-1745 (p. 7-8).

Applicable reaction solvents when the acylating agent is an acid anhydride include organic solvents (eg acetic acid) and methylene chloride. As the catalyst, a protic catalyst such as sulfuric acid can be used. Where the acylating agent is an acid chloride, applicable catalysts include basic compounds. One of the most common synthetic methods industrially comprises mixed organic acid components, including any organic acid (acetic acid, propionic acid, butyric acid) or their acid anhydride (acetic anhydride, propionic anhydride, butyric anhydride) corresponding to acetyl and other acyl groups It is esterifying cellulose using and synthesize | combining a cellulose ester by it.

Cellulose, such as cotton linter and wood pulp, is activated using an organic acid such as acetic acid and then generally esterified using a mixed solution of the above described organic acid components in the presence of a sulfuric acid catalyst. The organic acid anhydride component is generally used in excess of the amount of hydroxyl groups present in the cellulose. In such esterification, not only esterification but also hydrolysis (depolymerization reaction) of the cellulose main chain (β1 → 4-glycosidic bond) proceeds. Progression of the hydrolysis reaction of the main chain lowers the degree of polymerization of the cellulose derivative, thereby lowering the physical properties of the cellulose derivative film formed thereby. Therefore, reaction conditions, such as reaction temperature, can be determined taking into account the preferable range of the degree of polymerization or the molecular weight of the formed cellulose derivative.

In order to obtain a cellulose ester having a high degree of polymerization (high molecular weight), it is important to adjust the maximum temperature to 50 ° C or lower in the esterification reaction. The maximum temperature is preferably adjusted to 35 to 50 ° C, more preferably 37 to 47 ° C. Reaction temperature of 35 degreeC or more is preferable at the point which can make progress of esterification smoothly. The reaction temperature of 50 degrees C or less is preferable at the point which avoids incompatible matters, such as the fall of the polymerization degree of a cellulose ester.

In particular, the substitution of the cellulose hydroxyl group with the aromatic acyl group can generally be carried out according to a method employing aromatic carboxylic acid chlorides or symmetric acid anhydrides derived from aromatic carboxylic acids, and mixed acid anhydrides. Particular preference is given to methods using acid anhydrides derived from aromatic carboxylic acids (Journal of Applied Polymer Science, Vol. 29, 3981-3990 (1984)). Examples of the method for substituting a hydroxyl group with an aromatic acyl group usually include (1) preparing a cellulose fatty acid monoester or diester, and then introducing the aromatic acyl group represented by the formula (A) described above into the remaining hydroxyl group; And (2) directly reacting a mixed acid anhydride of an aliphatic carboxylic acid and an aromatic carboxylic acid with cellulose. In the former method (1), the process for producing the cellulose fatty acid ester or the diester itself may be carried out according to known conditions, but the continuous reaction process for introducing an aromatic acyl group may be carried out under conditions determined according to the type of aromatic acyl group. Can be carried out according to the present invention, generally preferably at a reaction temperature of 0 to 100 ° C, more preferably 20 to 50 ° C, and preferably for a reaction time of at least 30 minutes, more preferably 30 to 300 minutes. Can be. In the latter method (2), the conditions in the reaction step of the mixed acid anhydride can be determined according to the type of mixed acid anhydride, and in general, the reaction temperature is preferably 0 to 100 ° C, more preferably 20 to 50 ° C, The reaction time is preferably 30 to 300 minutes, more preferably 60 to 200 minutes. Either reaction can be carried out in a solventless method or in a solvent, preferably in a solvent. Solvents applicable here may be dichloromethane, chloroform, dioxane and the like.

After the esterification, stopping the reaction while suppressing the rise in temperature can further suppress a decrease in the degree of polymerization, and it becomes possible to synthesize a cellulose ester having a large degree of polymerization. More specifically, after the reaction termination, by adding a reaction terminator (for example, water, acetic acid), excess acid anhydride that has not been used for esterification hydrolysis produces a corresponding organic acid. The hydrolysis reaction involves vigorous heat generation and raises the temperature inside the reaction apparatus. If the rate of addition of the reaction terminator is not too large, the reaction system rapidly generates heat beyond the cooling capacity of the reaction apparatus, causing the hydrolysis reaction of the cellulose main chain to proceed rapidly, thereby undesirably lowering the degree of polymerization of the cellulose produced thereby. There is no fear of such a problem. During the esterification reaction, some of the catalyst is combined with cellulose, but most of the catalyst is dissociated from the cellulose in the addition of the reaction terminator. Here, if the rate of addition of the reaction terminator is not too large, a sufficient dissociation time for dissociation of the catalyst can be ensured, so that a problem that a part of the catalyst can remain remaining bound to cellulose rarely occurs. The cellulose ester partially bonded to the strong acid catalyst is very low in stability, and can be easily decomposed by heat generated during drying to lower the degree of polymerization. For this reason, it is preferable to stop the reaction by adding a reaction terminator after the esterification reaction, preferably over a time of 4 minutes or more, more preferably over 4 to 30 minutes. The addition time of 30 minutes or less is preferable at the point which prevents the problem of the fall of industrial productivity.

 As the reaction terminator, water and alcohols capable of decomposing acid anhydrides are generally used. However, it is preferable to use a mixture of water and an organic acid in order to prevent precipitation of triester which shows only low solubility in various organic solvents. By carrying out the esterification reaction under the conditions described above, a high molecular weight cellulose ester having a mass average degree of polymerization of 500 or more can be easily synthesized.

The cellulose derivative preferably has a mass average degree of polymerization of 10 to 800, more preferably 370 to 600. The cellulose derivative preferably has a number average molecular weight of 1,000 to 230,000, more preferably 75,000 to 230,000, even more preferably 78,000 to 120,000. Cellulose derivatives having a small mass average molecular weight may also be used as additives in the form of a polymer mixed with cellulose triacetate, which is expected to control wavelength dispersion in the phase difference of the retardation film.

The cellulose derivative film preferably has a refractive index maximized in the thickness direction of the film such that the thickness direction retardation has a negative value as a result. More specifically, the preferred range of in-plane retardation of the cellulose derivative film may be expressed as 20 nm ≦ | Re (630) | ≦ 150 nm, and the preferred range of Nz values defined as Nz = Rth / Re + 0.5 is − 6.5≤Nz≤0.5, more preferably 30nm≤ | Re (630) | ≤120 nm and -4.5≤Nz≤-0.5, even more preferably 40nm≤ | Re (630) ≤ 90 nm and -4.0 ≤ Nz ≤ -1.0.

 To adjust the phase difference within a desired range, a phase difference regulator may be added to the cellulose derivative film. Here, the term "phase difference regulator" is used for any reagent that can raise, lower and express phase difference. When the cellulose derivative film is produced by a solvent cast process, a phase difference regulator may be added to the dope. Retardation modifiers employable in the present invention are preferably such as compounds having a high intrinsic birefringence and easily oriented in a film, that is, a compound having a strong retardation expression ability. Compounds having this class of properties can be exemplified by rod-like compounds and discotic compounds. When the film is stretched after being added to these compounds, rod-like or discotic molecules are oriented, making it possible to extensively control the retardation. In particular, when these compounds have liquid crystalline properties, the orientation of the rod-like liquid crystal compounds may increase the refractive index in the stretching direction, while the orientation of the discotic liquid crystalline compounds parallel to the film surface increases the refractive index in the in-plane direction of the film. You can. In the case where the cellulose derivative film does not contain such a phase difference regulator, especially when cellulose acylate having a large degree of substitution of aromatic ring acyl groups and large polarization anisotropy is used, birefringence is in the stretching direction (including the in-plane direction and the thickness direction). Increase in the vertical direction. If it is necessary to increase the negative phase difference in the thickness direction without increasing the in-plane retardation, such a liquid crystalline compound is preferably added to the film to increase the birefringence in the stretching direction and to reduce the in-plane retardation.

(Phase difference regulator)

The retardation modulator is preferably selected from compounds having a maximum end-to-end distance of the molecule of at least 20 mm 3 and a ratio of long axis to short axis of at least 2.0. It is possible to perform molecular orbital calculations using molecular orbital calculation software (eg MOPAC and WinMOPAC) to find the ratio of the long axis to the maximum end-to-end distance and short axis of the molecule. Preferred examples of the phase difference regulator include a compound represented by the formula (1).

Formula (1)

In formula (1), Ar ¹ , Ar ² and Ar ³ each represent an aryl group (aromatic hydrocarbon group) or an aromatic heterocyclic group; L ¹ and L ² each represent a single bond or a divalent linking group; n is an integer of at least 3; The plurality of Ar ² or L ² may be the same or different from each other.

The aryl represented by Ar ^1, Ar ² or Ar ³ groups are preferably selected from C _{6 -30} aryl group. The aryl group may have a monocyclic structure or a multi condensed ring structure. The aryl group may also have at least one substituent if possible. The substituent may be selected from the substituent group T described below. The aryl group and more preferably C _{6 -20} aryl group is selected from is selected more preferably from C _{6 -12} aryl groups such as phenyl, p- methylphenyl, and naphthyl.

The aromatic heterocyclic group represented by Ar ¹ , Ar ² or Ar ³ is preferably selected from aromatic heterocyclic groups containing at least one atom selected from nitrogen, oxy and sulfur atoms; More preferably a 5 or 6 membered aromatic heterocycle containing at least one atom selected from nitrogen, oxygen or sulfur atoms. The aromatic heterocyclic group may have at least one substituent if possible. The substituent may be selected from the substituent group T described below.

Examples of aromatic heterocyclic groups include furan, thiophene, pyrrole, imidazole, pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole, indazole, purine, thiazolin, thiazole, thiadiazole, oxa Sleepy, oxazole, oxadiazole, quinoline, isoquinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, acridine, phenanthrene, phenazine, tetrazole, benzimi Residues of dozol, benzoxazole, benzthiazole, benzotriazole, tetrazaindene, pyrrolotriazole, and pyrazolotriazole. Preferred examples of the aromatic heterocycle include residues of benzimidazole, benzoxazole, benzthiazole, benzotriazole.

In formula (1), each of L ¹ and L ² represents a single bond or a divalent linking group. Examples of divalent linking groups include -NR ^7- (R ⁷ represents a hydrogen atom or a substituted or unsubstituted alkyl or aryl group), -SO _2- , -CO-, alkylene, substituted alkylene, alkenylene, substituted alkenylene , Alkynylene, -O-, -S-, -SO- and any combination thereof; Among them, -O-, -CO-, -SO ₂ NR ^7- , -NR ⁷ SO _2- , -CONR ^7- , -NR ⁷ CO-, -COO- and -OCO- and alkynylene are preferable; And -CONR ^7- , -NR ⁷ CO-, -COO-, -OCO- and alkynylene are more preferred.

In the compound represented by formula (1), L ¹ and L ² When Ar ² which binds to both is phenylene, it is preferable that the relationship between the positions of L ¹ -Ar ² -L ² and L ² -Ar ² -L ² is para-position, 1,4-position.

Wherein n is preferably an integer of at least 3, more preferably in the range of 3 to 7; Even more preferably in the range of 3-5.

Among the compounds represented by the formula (1), the compound represented by the formula (2) is preferable as the phase difference regulator.

Formula (2)

In formula (2), R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ²¹ , R ²² , R ²³ and R ²⁴ each represent a hydrogen atom or a substituent; Ar ² represents an aryl group or an aromatic heterocyclic group; L ² and L ³ each represent a single bond or a divalent linking group; n is an integer of 3 or more; And Ar ² and L ² may be the same or different from each other.

In formula (2), the definitions of Ar ² , L ² , and n are the same as those in formula (1), respectively; The preferable range is the same as that of Formula (1), respectively. L ³ represents a single bond or a divalent linking group. The divalent linking group is preferably selected from -NR ^7- (R ⁷ represents a hydrogen atom or a substituted or unsubstituted alkyl or aryl group), alkylene, substituted alkylene, -O- and any combination thereof; Among them, -O-, -NR ^7- , -NR ⁷ SO ₂ -and -NR ⁷ CO- are more preferable.

R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ each represent a hydrogen atom or a substituent; Preferably a hydrogen atom, an alkyl group or an aryl group; More preferably hydrogen, methyl, ethyl, propyl, and isopropyl and C _{1 -4} alkyl group, or phenyl, or represents a C _{6 -12} aryl such as naphthyl; And more preferably represents a C _{1 -4} alkyl group;

R ²² , R ²³ and R ²⁴ each represent a hydrogen atom or a substituent; More preferably a hydrogen atom, an alkyl group, an alkoxy group or a hydroxy; And it shows an (even more preferably C _{1 -4} alkyl group and most preferably methyl), and more preferably, a hydrogen atom or an alkyl group;

Hereinafter, the substituent group T described above will be described.

Substituent group T is a halogen atom such as a fluorine, chlorine, boron and iodine atom; Alkyl (preferably C _{1 -30),} for example, methyl, ethyl, n- propyl, isopropyl, tert- butyl, n- octyl, and 2-ethylhexyl; Cycloalkyl (preferably C _{3 - 30} substituted or unsubstituted cycloalkyl), e.g., cyclohexyl, cyclopentyl and carrying out close-hexyl 4-n- dodecyl; Bicyclo-alkyl (preferably C _{5 - 30} is substituted or unsubstituted hwanbi cycloalkyl, i.e., C _{5 - 30} of bicyclo a monovalent moiety obtained by removing one hydrogen atom from an alkane), for example, bicyclo [l , 2,2] heptan-2-yl, bicyclo [2,2,2] octan-3-yl; Alkenyl (preferably C _{2 -30),} for example, vinyl, allyl; Cycloalkenyl (preferably C _{3 - 30} substituted or unsubstituted cycloalkenyl, i.e., C _{3 -} a monovalent moiety obtained by removing one hydrogen atom from a cycloalkene _30), for example, 2-cyclopenten- 1-yl, 2-cyclohexen-l-yl; Bicycloalkenylcarboxylic (preferably a substituted or unsubstituted non-cycloalkenyl, i.e., C _{5 - 30} of the monovalent moiety obtained by removing one hydrogen atom from bicyclo alkenes), for example, bicyclo [2,2, l] hepto-2-en-l-yl, bicyclo [2,2,2] octo-2-en-4-yl; Alkynyl (preferably C _{2 - 30} alkynyl a), for example, ethynyl, propargyl; _Aryl-, for example, phenyl, p- tolyl, naphthyl (preferably a C _{6 30} aryl group); Heterocycle (preferably the (more preferably C _{3 - 30} is a 5 or 6-membered, substituted or unsubstituted, aromatic or heterocyclic residue of a monovalent non-aromatic), for example, 2-furyl, 2-thienyl, 2 -Pyrimidinyl, 2-benzothiazolyl); Cyano, hydroxyl, nitro, carboxyl, alkoxy (preferably substituted or unsubstituted alkoxy which is C _1-30 ) such as methoxy, ethoxy, isopropoxy, t-butoxy, n-octyloxy, 2 Methoxyethoxy; Aryloxy (preferably C _{6 - 30} substituted or unsubstituted aryloxy group), for example, phenyloxy, 2-methylphenoxy, 4-t- butylphenoxy, 4-t- butylphenoxy, 3-nitrophenoxy , 2-tetradecanoyl phenoxy; Silyloxy (preferably C _{3 - 20} a silyloxy), for example, trimethylsilyloxy, t- butyldimethylsilyloxy; Heterocyclic oxy (preferably C _{2 - 30} is substituted or unsubstituted heterocyclic oxy), for example, 1-phenyl tetrazol-5-oxy, 2-tetrahydro-pyrenyl oxy; Acyloxy (preferably C _{2 - 30} is substituted or unsubstituted alkylcarbonyloxy, and C _{6 - 30} is substituted or unsubstituted arylcarbonyloxy), for example, formyloxy, acetyloxy, blood immediately yloxy, stearate Royloxy, benzoyloxy, p-methoxyphenylcarbonyloxy; Carbamoyl oxy (preferably C _{1 - 30} is substituted or unsubstituted carbamoyl oxy), for example, N, N- dimethylcarbamoyl-oxy, N, N- diethyl-carbamoyl-oxy, morpholinyl carbonyl noka Viterbo Oxyl, N, N-di-n-octylaminocarbonyloxy, Nn-octylcarbamoyloxy; Alkoxycarbonyloxy (preferably C _{2 - 30} is substituted or unsubstituted alkoxycarbonyloxy), for example, methoxy-carbonyloxy, ethoxycarbonyloxy, t- butoxycarbonyloxy, n- octyloxy-carbonyl Oxy; Aryloxy carbonyloxy (preferably C _{7 - 30} substituted or unsubstituted aryloxy carbonyloxy), such as phenoxy carbonyloxy, p- methoxyphenoxy carbonyloxy, pn- hexadecyl aryloxy phenoxy carboxylic Carbonyloxy; Amino (preferably from _{0 C-30} substituted or unsubstituted alkyl, and C _{6 - 30} is substituted or unsubstituted arylamino), for example, amino, methylamino, dimethylamino, anilino, N- methyl-anilino, Diphenylamino; Acylamino (preferably C _{1 - 30} is substituted or unsubstituted alkylcarbonylamino, and C _{6 - 30} is substituted or unsubstituted aryl carbonyl amino), for example, formylamino, acetylamino, pivaloyl amino, Lau Loylamino, benzoylamino; Aminocarbonylamino (preferably C _{1 - 30} is substituted or unsubstituted amino carbonyl amino), for example, carbamoyl-amino, N, N- dimethyl-amino-carbonyl-amino, N, N- diethylamino-carbonylamino, Morpholino carbonylamino; Alkoxycarbonylamino (preferably C _{2 - 30} is substituted or unsubstituted alkoxy carbonyl amino), for example, methoxycarbonyl-amino, ethoxy-carbonyl-amino, t- butoxycarbonylamino, n- octadecyl -1,3 Brassica Viterbo carbonyl-amino, N- methyl-methoxy carbonyl amino), an aryloxy carbonyl amino (preferably C _{7 - 30} substituted or unsubstituted aryloxy carbonyl amino), for example, phenoxycarbonylamino, p- chloro Phenoxycarbonylamino, mn-octyloxy phenoxy carbonylamino; Sulfamoyl amino (preferably C _{0 - 30} is substituted or unsubstituted sulfamoyl amino), for example, amino-sulfamoyl, N, N- dimethylamino-sulfonyl-amino, Nn- octylamino alkylsulfonylamino; Alkyl- or aryl-sulfonyl amino (preferably C _{1 - 30} is substituted or unsubstituted alkyl-sulfonyl-amino, and C _{6 - 30} is substituted or unsubstituted aryl-sulfonyl amino), for example, methyl-sulfonyl-amino , Butyl-sulfonylamino, phenyl-sulfonylamino, 2,3,5-trichlorophenylsulfonylamino, p-methylphenyl-sulfonylamino; Mercapto; Alkylthio (preferably substituted or unsubstituted alkylthio) such as methylthio, ethylthio, n-hexadecylthio; Arylthio (preferably C _{6 - 30} is substituted or unsubstituted aryl thio), for example, a phenylthio group, p- chlorophenylthio, m- methoxyphenyl thio; Heterocyclic thio (preferably C _{2 - 30} is substituted or unsubstituted heterocyclic thio), for example, a 2-benzothiazolyl thio and 1-phenyl tetrazol-5-ylthio; Sulfamoyl (preferably, C _{0 - 30} is substituted or unsubstituted sulfamoyl), e.g., N- ethyl sulfamoyl, N- (3- dodecyl-oxy-propyl) sulfamoyl, N, N- dimethylsulfamoyl, N- acetyl Sulfamoyl, N-benzoylsulfamoyl, N- (N'-phenylcarbamoyl) sulfamoyl; Sulfo; Alkyl- or aryl-sulfinyl (preferably C _{1 - 30} is substituted or unsubstituted alkyl-, or C _{6 - 30} is substituted or unsubstituted aryl-sulfinyl), for example, methylsulfinyl, ethyl sulfinyl, phenylsulfonyl Finyl, p-methylphenylsulfinyl; Alkyl- and aryl-sulfonyl (preferably C _{1 - 30} is substituted or unsubstituted alkyl-sulfonyl, and C _6-30 substituted or unsubstituted arylsulfonyl), for example, methylsulfonyl, ethylsulfonyl, phenyl Sulfonyl, p-methylphenylsulfonyl; Acyl (preferably formyl, C _{2 - 30} is substituted or unsubstituted alkylcarbonyl, and a C _{7 - 30} is substituted or unsubstituted aryl-carbonyl), for example, formyl, acetyl, pivaloyl benzoyl; Aryloxycarbonyl (preferably C _{7 - 30} substituted or unsubstituted aryloxy carbonyl), for example, phenoxycarbonyl, o- chloro-phenoxycarbonyl, m- nitro-phenoxycarbonyl, pt- butylphenoxy Brassica Levonyl; Alkoxycarbonyl (preferably C _{2 - 30} is substituted or unsubstituted alkoxycarbonyl), for example, methoxycarbonyl, ethoxycarbonyl, t- butoxycarbonyl, n- octadecyl -1,3 Brassica Viterbo group; Carbamoyl (preferably C _{1 - 30} is substituted or unsubstituted carbamoyl), for example, carbamoyl, N- methylcarbamoyl, N, N- dimethylcarbamoyl, N, N- di -n- Octylcarbamoyl, N- (methylsulfonyl) carbamoyl; Aryl- or heterocyclic-azo (preferably C _{6 - 30} is substituted or unsubstituted aryl azo and C _{3 - 30} substituted or unsubstituted heterocyclic azo), for example, phenylazo, p- chlorophenyl azo, 5 -Ethylthio-1,3,4-thiadiazol-2-yl azo; Imides such as N-succinimide, N-phthalimide); Phosphino (preferably substituted or unsubstituted phosphino with C _2-30 ) such as dimethyl phosphino, diphenyl phosphino, methylphenoxy phosphino; Phosphinylmethyl (preferably C _{2 - 30} is substituted or unsubstituted phosphinylmethyl), for example, phosphinylmethyl, di-octyloxy phosphinylmethyl, diethoxy phosphinylmethyl; Phosphinylmethyl aryloxy (preferably C _{2 - 30} is substituted or unsubstituted aryloxy phosphinylmethyl), for example, diphenoquinone rust Seaport RY carbonyl-oxy, di-octyloxy phosphinylmethyl oxy; Phosphinylmethyl amino (preferably C _{2 - 30} is substituted or unsubstituted phosphinylmethyl amino), for example, dimethoxyethane phosphinylmethyl, dimethylamino phosphinylmethyl amino; And _{silyl-comprises} (preferably ₃ C ₃₀ substituted or unsubstituted silyl group), for example, trimethylsilyl, t- butyl trimethylsilyl, phenyl dimethylsilyl.

Substituents may be substituted by at least one substituent selected from them. Examples of such substituents include alkylcarbonylaminosulfo, arylcarbonylaminosulfo, alkylsulfonylaminocarbonyl, and arylsulfonylaminocarbonyl. More specifically, methylsulfonylaminocarbonyl, p-methylphenylsulfonylaminocarbonyl, acetylaminosulfonyl, and benzoylaminosulfonyl are illustrated.

The plurality of substituents may be the same or different from each other. If possible, a plurality of substituents may combine with each other to form a ring.

Examples of the compound represented by formula (2) include, but are not limited to, those shown below.

Compounds represented by formula (3) are also preferred as phase difference modifiers.

Formula (3)

In the formula, R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁵ and R ³⁶ each represent a substituent; L ³¹ and L ³² each represent a single bond or a divalent linking group; n and m each represent an integer of 0 to 4; And p and q represent the integer of 0-3, respectively.

R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁵ and R ³⁶ may be the same or different from each other. R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁵ or The substituent represented by R ³⁶ is preferably selected from substituent group T. Among them, alkyl, alkoxy, alkoxycarbonyl, acyl, alkoxycarbonyloxy, cycloalkyl, acylamino, cyano and halogen atoms are more preferred. The plurality of substituents may be the same or different from each other, and if possible, may combine with each other to form a ring.

In formula (3), L ³¹ and L ³² each represent a single bond or a divalent linking group. L ³¹ And L ³² may be the same or may be different from each other. Preferred examples of the divalent linking group are -NR ^7- (R ⁷ represents a hydrogen atom or a substituted or unsubstituted alkyl or aryl group), -SO _2- , -CO-, alkylene, substituted alkylene, alkenylene, substituted alkenylene , Alkynylene, -O-, -S-, -SO- and any combination thereof; Among them, -O-, -CO-, -SO ₂ NR ^7- , -NR ⁷ SO _2- , -CONR ^7- , -NR ⁷ CO-, -COO-, -OCO- and alkynylene are more preferable. ; And -CONR ^7- , -NR ⁷ CO-, -COO-, -OCO- and alkynylene are even more preferred. Examples of substituents include those exemplified above as substituents for R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁵ and R ³⁶ .

In formula (3), n and m respectively represent the integer of 0-4; And when n or m is 2 or more, a plurality of R ³¹ or R ³² may be the same or different, respectively. In the formula, p and q each represent an integer of 0 to 3; And when p or q is 2 or more, a plurality of R ³³ or R ³⁴ may be the same or different, respectively. In which R ³³ and R ³⁵ or R ³⁴ and R ³⁶ may combine with each other to form a ring. In view of the phase difference control effect, the phase difference modifier is preferably selected from a symmetric compound (for example, a compound represented by formula (3) wherein the 1,4-substituents of the intermediate cyclohexane ring have the same structure).

Examples of the compound represented by formula (3) include, but are not limited to, those shown below.

Compounds represented by formula (4) are also preferred as retardation regulators.

Formula (4)

In formula (4), R ⁴¹ , R ⁴² , R ⁴³ and R ⁴⁴ each represent a substituent; E ¹ , E ² , E ³ and E ⁴ each represent an oxygen atom or a sulfur atom. In the formula, L ⁴¹ and L ⁴² each represent a divalent linking group; n and m each represent an integer of 0 to 4; And p and q each represent an integer of 1 to 10.

In formula (4), R ⁴¹ or The substituent represented by R ⁴² is preferably selected from substituent group T.

In formula (4), R ⁴³ or Preferred examples of the substituent represented by R ⁴⁴ are R ^41. or Same as exemplified as a preferred example of R ⁴² ; Among them, an alkyl group, cycloalkyl group, bicycloalkyl group, alkenyl group, cycloalkenyl group, bicycloalkenyl group, alkynyl group, aryl group, heterocyclic group, sulfamoyl group, alkyl- or aryl-sulfonyl group, acyl group, aryloxycarbonyl group , Alkoxycarbonyl group and carbamoyl group are preferable; And alkyl, cycloalkyl, alkenyl, aryl, acyl, aryloxycarbonyl, alkoxycarbonyl and carbamoyl groups are more preferred.

In formula (4), L ⁴¹ and L ⁴² each represent a divalent linking group, which may be the same or different from each other. The divalent linking group is preferably selected from groups other than arylene; More preferably alkylene, substituted alkylene, alkenylene, substituted alkenylene, alkynylene and any combination thereof. The combination may include other divalent linkers connecting them. Examples of such other linking groups are -NR ^7- (R ⁷ represents a hydrogen atom or a substituted or unsubstituted alkyl or aryl group), -O-, -S-, -SO-, -SO _2- , -CO-,- SO ₂ NR ^7- , -NR ⁷ SO _2- , -CONR ^7- , -NR ⁷ CO-, -COO- and -OCO-. Examples of the substituents include those exemplified above as examples of R ⁴¹ , R ⁴² , R ⁴³ and R ⁴⁴ .

In formula (4), n and m respectively represent the integer of 0-4; n and m each represent an integer of 2 or more; Multiple R ⁴¹ or R ⁴² may be the same or different, respectively. In the formula, p and q each represent an integer of 1 to 10; And when p or q is 2 or more, a plurality of E ³ , E ⁴ , L ⁴¹ or L ⁴² may be the same or different, respectively. In terms of retardation control effect, the retarder is preferably represented by the formula (4), in which the symmetric or pseudo-symmetric compound (e.g., the 1,4-substituents of the intermediate cyclohexane ring have the same or similar structure) Compound).

Examples of the compound represented by formula (4) include, but are not limited to, those shown below.

The amount of the phase difference regulator added is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, even more preferably 1 to 10 parts by mass, per 100 parts by mass of the cellulose derivative. The phase difference regulator may be added to the dope of the cellulose derivative used in the manufacture of the film, and in order to ensure stable mixing of the dope, it is preferable that the phase difference regulator is completely compatible with the cellulose derivative and less aggregated. To this end, a solvent solution and a phase difference regulator are mixed and stirred to prepare a control solution in advance, and the control solution is added to a small amount of the separately prepared cellulose derivative solution, and then stirred to further mix the mixture and the main cellulose derivative dope solution. The way is possible.

The phase difference regulators may be used independently or may be used as a mixture of two or more compounds based on any mixing ratio. These phase difference regulators may be added at any time during the dope preparation process or may be added at the final stage of the dope preparation process.

Second Retardation Layer

In the present invention, the second retardation layer has an in-plane retardation Re of | Re | <30 nm and Rth of 80 nm to 400 nm. The more preferred range of Rth of the second retardation layer depends on the optical properties of the other optical components, and in particular on the Rth of the protective film of the polarizing film (e.g., triacetyl cellulose film) arranged closer to the liquid crystal display. It usually depends. In order to effectively reduce the light leakage in the oblique direction, the second retardation layer preferably has Rth of 100 nm to 340 nm, more preferably 180 nm to 300 nm. On the other hand, Re of the second retardation layer is more preferably in the range of | Re | <10 nm.

The material and configuration of the second retardation layer are not particularly limited as long as they have the above-described optical characteristics. Among the retardation films comprising a retardation film composed of a birefringent polymer film, a retardation film formed by coating and continuously heating a polymer solution or a polymer-melting fluid, and a retardation layer formed by coating a composition containing a low molecular weight or high molecular weight liquid crystalline compound. It may be anything. These films can be used in a lamination manner.

The second retardation layer is preferably formed using a composition comprising at least one discotic liquid crystal compound, the discotic liquid crystal molecules being oriented with their directors directed in the normal direction on the layer plane, ie the discotic liquid crystal The molecules are oriented horizontally.

(Discotic liquid crystal)

Examples of discotic liquid crystalline compounds employable in the preparation of the second retardation layer include C. Destrade.et al. Benzene derivative described in the research report by (Mol. Cryst., 71, p. 111 (1981)), C. Destrade (Mol. Cryst., 122, p.141 (1985), Physics Lett. A, 78, p .82 (1990)) Torxene derivatives described in the research report by B. Kohneet al. Cyclohexane derivatives described in the study report by Angew. Chem., 96, p. 70 (1984), and J. M. Lehnet al. (J. Chem. Commun., P. 1794 (1985)) and J. Zhanget al. Azacrown-based and phenylacetylene-based macrocycles described in the research report by J. Am. Chem. Soc., 116, p. 2655 (1994).

Examples of discotic liquid crystalline compounds also include compounds having a core in the center of the molecule and having a linear alkyl group, an alkoxy group, and a substituted benzoyloxy group radially substituted as a side chain on the core. The compound is preferably such that the molecule or aggregate of molecules can exhibit rotational symmetry, thereby ensuring a particular orientation. In an optically anisotropic layer composed of a discotic liquid crystalline compound, the compound finally included in the optically anisotropic layer does not always have to be a discotic liquid crystalline compound, but from a low molecular weight discotic liquid crystalline molecule having a thermally reactive group or a photoreactive group Although initially initiated, it may be a compound whose liquid crystallinity is finally lost due to heat- or photo-assisted polymerization, crosslinking or polymerization. Preferred examples of the discotic liquid crystalline compound are JPA No. H8-50206. Polymerization of the discotic liquid crystalline compound is described in JPA No. H8-27284.

The composition used in the preparation of the second retardation layer may comprise a polymerization initiator. Among them, a photopolymerization initiator is preferable. The usage-amount of a photoinitiator is preferably 0.01-20 mass%, More preferably, it is 0.5-5 mass% of a composition (meaning a solid component with respect to what was prepared as a coating solution). Light irradiation for the polymerization of the discotic liquid crystalline molecules may be made by ultraviolet rays. The irradiation energy is preferably 20 mJ / cm ² to 50 J / cm ² More preferably 100 to 800 mJ / cm ² to be. Light irradiation can be carried out under heating conditions to promote the photopolymerization reaction.

The thickness of the second retardation layer formed using the composition containing the liquid crystal compound described above is preferably 0.1 to 10 µm, more preferably 0.5 to 5 µm, even more preferably 1 to 5 µm.

The second retardation layer may be prepared using a triazine ring containing compound that promotes horizontal alignment of the discotic liquid crystal molecules, and / or a polymer containing a fluoro-aliphatic group.

(Triazine ring-containing compound)

The second retardation layer preferably contains at least one kind of compound having a 1,3,5-triazine ring group. This compound contributes to the reduction of the inclination angle of the liquid crystalline compound, especially the discotic liquid crystalline compound, i.e., to the promotion of the horizontal orientation. Compounds having a 1,3,5-triazine ring group can be included in the composition used to form the second retardation layer. As a compound having a 1,3,5-triazine ring group applicable to the present invention, JPA No. Paragraphs [0060] to [0078] of 2005-134884, and JPA No. Preference is given to using the compounds described in paragraphs [0057] to [0081] of 2005-99248. In particular, it is preferable that the above-mentioned compound having a 1,3,5-triazine ring group contain fluorine atom (s).

(Fluoro-aliphatic group-containing polymer)

The second retardation layer preferably comprises at least one fluoro-aliphatic group containing polymer. The fluoro-aliphatic group containing polymer, when included in the above-mentioned composition, contributes to the improvement of coating performance of this composition prepared as a coating solution. It also has the function of promoting horizontal alignment of discotic liquid crystalline molecules. Preferred examples of fluoro-aliphatic polymers are JPA No. Paragraphs [0018] to [0056] of 2005-134884, JPA No. Paragraphs [0046] to [0054] of 2004-331812, JPA No. Paragraphs [0057] to [0066] of 2004-333861, JPA No. Paragraphs [0084] to [0096] of 2005-189285, JPA No. Paragraphs [0076] to [0095] of 2005-189286, JPA No. Paragraphs [0064] to [0077] of 2005-206638, and JPA No. Fluoro-aliphatic polymers described in paragraphs [0099] to [0117] of 2005-215398.

Polymers having a fluoride-aliphatic group are sometimes referred to hereinafter as "polymer A" and include at least one repeating unit derived from a compound having a fluoride-aliphatic group and at least one repeating unit represented by the formula (5). Is preferably selected from copolymers.

Equation (5)

In formula (II), R ¹ , R ² and R ³ each represent a hydrogen atom or a substituent; L represents a divalent linker selected from the group of connectors shown below or a divalent linker consisting of two or more selected from the group of connectors shown below:

(Coupler group)

Single bond, -O-, -CO-, -NR ^4- , where R ⁴ represents a hydrogen atom, an alkyl group, an aryl group or an aralkyl group, -S-, -SO _2- , -P (= O) ( OR ⁵ )-(wherein R ⁵ represents an alkyl group, an aryl group or an aralkyl group), an alkylene group and an arylene group.

Q represents a carboxyl group (-COOH) or a salt thereof, a sulfo group (-SO ₃ H) or a salt thereof, or a phosphonoxy group {-OP (= 0) (OH) ₂ } or a salt thereof.

In formula (5), preferably, R ¹ , R ² and R ³ are each represented by a hydrogen atom, an alkyl group, a halogen atom such as a fluorine, chlorine, bromine or iodine atom, or -LQ described below; And more preferably is represented by hydrogen, C _{1 -6} alkyl group, a chlorine atom or -LQ; Still more preferably a hydrogen atom or a C _{1 -4} alkyl group; Still more preferably a hydrogen atom or C _{1 -2} alkyl; Most preferably R ² And R ³ is hydrogen and R ¹ is hydrogen or methyl. Examples of alkyl groups include methyl, ethyl, n-propyl, n-butyl and sec-butyl. The alkyl group may have at least one substituent. Examples of substituents are halogen atom, aryl, heterocyclic group, alkoxyl, aryloxy, alkylthio, arylthio, acyl, hydroxy, acyloxy, amino, alkoxycarbonyl, acylamino, oxycarbonyl, carbamoyl , Sulfonyl, sulfamoyl, sulfonamide, sulfonyl and carboxyl. Note that when the alkyl group has any substituents, the number of carbon atoms in the alkyl group described above is the number of carbon atoms contained only in the alkyl group, and the carbon atoms included in the substituents are not counted. The number of carbon atoms included in other groups described below is defined to be the same as the number of carbon atoms in the alkyl group.

Wherein L is a divalent linking group selected from a group defined above or any combination of two or more selected from groups defined above. R ⁴ at -NR ⁴ -described above Represents a hydrogen atom, an alkyl group, an aryl group or an aralkyl group, preferably a hydrogen atom or an alkyl group. And R ⁵ at -PO (OR ⁵ )- Represents an alkyl group, an aryl group or an aralkyl group, preferably an alkyl group. R ⁴ or R ⁵ When is an alkyl group, an aryl group or an aralkyl group, its desired carbon number is the same as that described in substituent group T. L preferably comprises a single bond, -O-, -CO-, -NR ^4- , -S-, -SO _2- , an alkylene group or an arylene group, more preferably a single bond, -CO-, -O -, -NR ^4- , an alkylene group or an arylene group, and even more preferably a single bond. When L contains an alkylene group, the number of carbon atoms of an alkylene group becomes like this. Preferably it is 1-10, More preferably, it is 1-8, More preferably, it is 1-6. Preferred examples of the alkylene group include methylene, ethylene, trimethylene, tetrabutylene and hexamethylene. When L contains an arylene group, the number of carbon atoms of an arylene group becomes like this. Preferably it is 6-24, More preferably, it is 6-18, More preferably, it is 6-12. Preferred examples of the arylene group include phenylene and naphthalene. When L comprises a combination of an alkylene group and an arylene group, that is, a divalent linking group consisting of an aralkyl group, the number of carbon atoms of the aralkyl group is preferably 7 to 36, more preferably 7 to 26, and even more preferably 7 to 16. Preferred examples of the aralkyl group include phenylene methylene, phenylene ethylene and methylene phenylene. L may have any substituent. Examples of substituents are the same as those exemplified for the substituent of R ¹ , R ² or R ³ .

Examples of L include but are not limited to those shown below.

In formula (5), Q is a carboxyl group or carboxylate, for example lithium carboxylate, sodium carboxylate, potassium carboxylate, ammonium carboxylate (e.g. unsubstituted ammonium carboxylate, tetra Methylammonium carboxylate, trimethyl-2-hydroxyethylammonium carboxylate, tetrabutylammonium carboxylate, trimethylbenzylammonium carboxylate or dimethylphenylammonium carboxylate) or pyridinium carboxylate; Sulfo groups or sulfates (examples of counter cations are the same as those exemplified for the carboxylates above); Or phosphonoxy groups or phosphonoxylates (examples of relative cations are the same as those exemplified for the above carboxylates). Carboxyl, sulfo and phosphino groups are preferred, carboxyl and sulfo groups are more preferred, and carboxyl is most preferred.

Polymer A may comprise a single or a plurality of repeating units represented by formula (5). In addition, Polymer A may comprise a single or a plurality of repeat units derived from a compound having a fluoride-aliphatic group. In addition, the polymer A may include a single or a plurality of repeating units in addition to the repeating units described above. The other repeating unit is not limited to a specific type, and any repeating unit derived from a general purpose monomer capable of radical polymerization is preferably used.

Polymer A is preferably JPA No. Repeating units derived from the compound represented by formula [2] described in 2004-333861.

The amount of the monomer containing a fluoride-aliphatic group is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 30% by mass or more, based on the total amount of all monomers constituting the polymer A. The amount of the repeating unit represented by the formula (5) is preferably 0.5% by mass or more and more preferably 5 to 50% by mass with respect to the total amount of all monomers constituting the polymer A.

The weight-average molecular weight (Mw) of the polymer A used in the present invention is preferably 1,000,000 or less, more preferably 500,000 or less, even more preferably in the range of 5,000 to 50,000. Mw can be measured as molecular weight in terms of polystyrene (PS) using gel permeation chromatography (GPC).

Polymer A may have a polymerizable group as a substituent for fixing the alignment state of the discotic liquid crystal molecules.

Examples of polymer A include but are not limited to those shown below. In the formulas shown below, the numerical values refer to the mass% of each monomer, and Mw in the formulas shown below is assigned to a GPC with columns such as TSK Gel GMHxL, TSK Gel G4000 HxL, and TSK Gel G2000 HxL (manufactured by TOSOH). The PS-converted weight average molecular weight measured using THF as a solvent and a differential refractometer as a detector. In the formula, "a", "b", "c", "d", etc. mean a weight ratio.

The range of content of the fluoro-aliphatic group-containing polymer (polymer "A") in the second retardation layer described above is preferably 0.005 to 8% by mass in the composition (excluding the solvent when the composition is a coating solution), and 0.01 ~ 5 mass% is more preferable, and 0.01-1 mass% is more preferable. The addition amount of polymer "A" of less than 0.005% by mass may only cause a bad effect, while more than 8% by mass may cause insufficient drying of the coated film, or may adversely affect the performance as a retardation layer. (E.g., phase difference unevenness).

(Oriented film)

The second retardation layer containing the discotic liquid crystalline compound can be prepared using an alignment film. The alignment film not only improves the alignment characteristics of the discotic liquid crystalline molecules, but also contributes to the improvement of adhesion between the first retardation layer and the second retardation layer, which are sometimes composed of a cellulose derivative film or the like.

If the alignment film is formed using a polymer having a side chain having a crosslinking functional group bonded to the main chain, or a polymer having a crosslinking functional group in the side chain having a function of orienting the liquid crystalline molecules, the retardation film is formed of a polyfunctional monomer. If formed thereon using the comprising composition, it becomes possible to copolymerize the polymer in the orientation film and the polyfunctional monomer in the retardation film formed thereon. As a result, covalent bonds can be formed not only between the polyfunctional monomers, but also between the oriented film polymers and between the polyfunctional monomer and the oriented film polymer, whereby the oriented film and the retardation film can be firmly bonded. Therefore, by forming the oriented film using a polymer having a crosslinking functional group, the strength of the optical compensation sheet can be improved to a considerable extent. The crosslinking functional group in the oriented film polymer preferably includes a polymerizable group, like the polyfunctional monomer. More specifically, JPA No. Examples described in paragraphs [0080] to [0100] of 2000-155216 can be exemplified.

The oriented film polymer may be crosslinked using a crosslinking agent in addition to the crosslinking functional groups described above. Examples of crosslinking agents include aldehydes, N-methylol compounds, deoxyan derivative compounds, compounds which act by activating carboxyl groups, active vinyl compounds, active halogen compounds, isoxazoles and dialdehyde starches. Two or more crosslinking agents can be mixed. More specifically, JPA No. The compounds commonly described in paragraphs [0023] to [0024] of 2002-62426 can be exemplified. Highly active aldehydes, in particular glutaraldehyde, are preferred.

The amount of the crosslinking agent added is preferably in the range of 0.1 to 20% by mass of the polymer, more preferably in the range of 0.5 to 15% by mass. The amount of the unreacted crosslinking agent remaining in the alignment film is preferably 1.0 mass% or less, more preferably 0.5 mass% or less. This adjustment enables achieving a sufficient level of durability of the alignment film without causing reticulation even after long term use of the liquid crystal display or after being left under a high temperature, high humidity atmosphere.

An oriented film can be basically formed by coating the composition containing the polymer mentioned above as an oriented film formation material, and a crosslinking agent on a transparent support body, and then drying (crosslinking) and rubbing with heating. The crosslinking reaction can proceed at any time after coating on the transparent support. When a water-soluble polymer such as polyvinyl alcohol is used as a raw material for forming an oriented film, the coating solution preferably uses a mixed solution of an organic solvent (for example, methanol) and water having a defoaming function. The mass mixing ratio of water: methanol is preferably 0: 100 to 99: 1, more preferably 0: 100 to 91: 9. This adjustment can suppress foaming and can significantly reduce defects on the surface of the orientation film, and consequently the retardation layer.

Examples of coating methods that can be employed in forming the oriented film include spin coating processes, dip coating processes, curtain coating processes, extrusion coating processes, rod coating processes and roll coating processes. Rod coating processes are particularly preferred. The thickness of the oriented film after drying is preferably 0.1 to 10 mu m. Drying under heating may proceed at 20 ° C to 110 ° C. From the viewpoint of forming a sufficient degree of crosslinking, the temperature is preferably 60 ° C to 100 ° C, more preferably 80 ° C to 100 ° C. The drying time may be 1 minute to 36 hours, preferably 1 minute to 30 minutes. In addition, the pH is preferably set to an optimum value for the crosslinking agent to be used. When glutaraldehyde is used, the pH is preferably in the range of 3.5 to 9.5, more preferably in the range of 3.5 to 5.5.

The oriented film is preferably provided on a transparent support. The alignment film is preferably formed by crosslinking the polymer layer described above, for example. It is preferable not to provide rubbing for the horizontal orientation of the discotic liquid crystalline compound. It is also possible to align the liquid crystalline compound using the alignment film, fix the liquid crystalline compound while maintaining the alignment state to form a retardation layer, and then transfer only the retardation layer onto the polymer film (or transparent support). .

[Phase plate]

The present invention relates to a retardation plate comprising first and second retardation layers. The retardation plate of the present invention having the first and second retardation layers contributes to the improvement of viewing angle characteristics of liquid crystal displays, in particular IPS-type liquid crystal displays. The retardation plate of the present invention may be arranged as a single optical component (preferably between the polarizer and the liquid crystal cell) in a liquid crystal display. In addition, the retardation plate may be bonded to the polarizing film, and may be coupled to the liquid crystal display as a polarizing plate. The following paragraphs describe the polarizing plate of the present invention having a retardation plate and a polarizing film.

[Polarizing Plate]

The polarizing plate of this invention contains the retardation plate and polarizing film of this invention.

According to this invention, well-known polarizing films, such as a iodine containing polarizing film, a dye containing polarizing film using a dichroic dye, and a polyene type polarizing film, can be employ | adopted as a polarizing film. Iodine-containing polarizing films and dye-containing polarizing films are generally produced using polyvinyl alcohol-based films. The absorption axis of a polarizing film corresponds to the extending direction of a film. As a result, the polarizing film stretched in the longitudinal direction (transportation direction) has an absorption axis parallel to the longitudinal direction, while the polarizing film stretched in the transverse direction (direction perpendicular to the transport direction) has an absorption axis perpendicular to the longitudinal direction.

Preferred examples of the method for producing the polarizing plate of the present invention include a method comprising the step of continuously laminating the polarizing film and the retardation plate into its web shape. The web-shaped polarizing plate is cut to fit the screen size of the liquid crystal display.

The polarizing film is generally equipped with a protective film. The retardation plate of the present invention can function as a protective film for a polarizing film, in which case it is not necessary to bond an additional protective film to the polarizing film on the surface bonded to the surface of the retardation plate. In the polarizing plate of the present invention, it is preferable that only the isotropic adhesive layer and / or the substantially isotropic transparent protective film are disposed between the polarizing film and the retardation plate of the present invention. The substantially isotropic transparent protective film (protective film for polarizing film) is specifically a film whose in-plane retardation is 0-10 nm and thickness direction retardation is -20-20 nm. Preference is given to films comprising cellulose acylate or cyclic polyolefins. Examples of the adhesive capable of forming the isotropic adhesive layer include a polyvinyl alcohol adhesive and an adhesive composed of a polyester urethane and an isocyanate crosslinking agent.

The substantially isotropic low-Re cellulose acylate film that can be used as a transparent protective film preferably has an in-plane retardation Re (630) of 10 nm or less (0 ≦ Re (630) ≦ 10) at 630 nm and a thickness direction rita The absolute value of the datum Rth 630 is 25 nm or less (| Rth | ≤25 nm), more preferably 0≤Re (630) ≤5 and | Rth | ≤20 nm, even more preferably 0≤Re ( 630) ≦ 2 and | Rth | ≦ 15 nm. Low-Re cellulose acylate film is preferably | Re (400) -Re (700) | ≤10 and | Rth (400) -Rth (700) | ≤35, more preferably | Re (400) -Re (700 ) | ≤5 and | Rth (400) -Rth (700) | ≤25, and particularly preferably | Re (400) -Re (700) | ≤3 and | Rth (400) -Rth (700) | ≤15 Satisfies.

1st Embodiment of the polarizing plate of this invention relates to a polarizing plate, A 2nd phase difference layer, a 1st phase difference layer, and a polarizing film are arrange | positioned in this order, and the slow axis of a 1st phase difference layer and the absorption axis of a polarizing film are substantially Perpendicular to each other. In the second embodiment of the polarizing plate of the present invention, the second retardation layer, the first retardation layer, and the polarizing film are arranged in this order, and the slow axis of the first retardation layer and the absorption axis of the polarizing film are substantially parallel to each other. do. In the case where the first retardation layer is composed of the stretched polymer film, the slow axis direction of the first retardation layer is usually adjustable by the stretching direction. Similar effects can be obtained even if the positions of the first retardation layer and the second retardation layer are exchanged, but when the first retardation layer is composed of a polymer film (preferably a cellulose acylate film), it is possible to enable stability and a simple process. It is preferable that a 1st phase difference layer is arrange | positioned at the point in a polarizing film side.

The following paragraphs describe the features of the present invention more specifically with reference to Examples and Comparative Examples. Any material, amount of use, ratio, details of processing, procedures of processing, etc. may be appropriately modified without departing from the spirit of the invention. Accordingly, the present invention should not be construed as limited by the specific embodiments described below.

<Production of IPS-Mode Liquid Crystal Cell 1>

As shown in FIG. 3, on the pair of glass substrates, electrodes (references 2 and 3 in FIG. 3) are provided such that the distance between adjacent electrodes is 20 μm, on which a polyimide film is used as an oriented film. Provide and rub. The rubbing process is performed along the direction 4 shown in FIG. On one surface of another glass substrate, a polyimide film is provided and rubbed to obtain an orientation film. Laying and bonding the two glass substrates while facing each other, keeping the 3.9-μm distance (gap; d) therebetween, and aligning the rubbing direction of the two glass substrates in parallel with each other Then, the nematic liquid crystal composition having a refractive index anisotropy (Δn) of 0.0769 and a dielectric constant anisotropy (Δε) of 4.5 is filled in the space between the substrates. It was found that the liquid crystal layer had a d · Δn value of 300 nm.

<Production of First Retardation Layer>

<1-1> Preparation of Cellulose Acylate Solution

Substitution degree of a hydroxyl group is 1.2, acetyl group substitution degree is 0.2, and the specific example No. of the aromatic acyl group mentioned above. The cellulose derivative having a degree of substitution of 1 and 1.6 and the following composition were added to a mixing tank, and stirred for 6 hours to dissolve each component to prepare a cellulose derivative solution.

Cellulose derivative solution

100.0 parts by mass of cellulose derivative

Methylene chloride 403.0 parts by mass

60.2 parts by mass of methanol

7.8 parts by mass of triphenylphosphate

3.9 parts by mass of biphenyl diphenyl phosphate

<1-2> Preparation of Matte Dispersion

The following composition containing the cellulose derivative solution prepared by the above-mentioned method is put into a dispersion equipment, and the mat dispersion is prepared.

Mat  Dispersion

Silica Particles with Average Particle Size 16nm

2.0 parts by mass (manufactured by Aerosil R972, Nippon Aerosil Co., Ltd.)

Methylene chloride 72.4 parts by mass

10.8 parts by mass of methanol

10.3 parts by mass of the cellulose derivative solution described above

<1-3> Preparation of the retardation (Re) regulator

The following composition containing the cellulose derivative solution prepared by the above-mentioned method is put into a mixing tank, dissolved by stirring under heating to prepare a Re regulator solution.

Re  Regulator solution

20.0 parts by mass of Re regulator (described in Table 1)

58.3 parts by mass of methylene chloride

8.7 parts by mass of methanol

12.8 parts by mass of cellulose acylate solution

Per 100 parts by mass of cellulose acylate, the above-mentioned solution was mixed to adjust the Mat agent to 0.15 parts by mass and the Re regulator to 15 parts by mass, and the noodles were mixed while stirring so that the mass concentration of the noodles was adjusted to 19% by mass. It adds to methane / methanol (87/13 mass part), and also, stirring, heating, prepares dope for film forming.

The dope thus prepared is cast on a metal support using band casting equipment, and the formed self-supporting dope cast film is separated from the band. The separated dope film was held at its end with a tenter, stretched 1.3 times as the film width, and then dried while holding with the tenter, having a thickness of 80 μm, a length of 100 m in the longitudinal direction (casting direction), and a width direction To prepare a cellulose acylate film having a width of 1.3 m. Through the measurement of the incident angle dependence of Re using an automatic birefringence meter (KOBRA-21ADH manufactured by Oji Scientific Instuments), the cellulose acylate film No. 1 prepared as described above had Re of 67 nm and Rth of -200 nm. Nz was found to be -2.5. The film thus obtained is used as the first retardation layer.

Cellulose acylate film Nos. 2 to 5, and Nos. H1 and H2 are produced similarly to the production method of cellulose acylate film No. 1, except that the materials shown in Table 1 are each used and the stretching step is performed at the draw ratios shown in Table 1, respectively. Re, Rth and Nz values are calculated and summarized in Table 1.

<Production of Second Retardation Layer>

A coating solution for preparing an alignment layer having the following formulation is prepared and adjusted to pH 3.5 using potassium hydroxide. The surface of the cellulose acylate film No. 1 prepared as described above was saponified, and the coating solution was applied to the surface of the saponified film in the amount of 20 ml / m ² using a wire bar coater, followed by 60 seconds with 60 ° C. hot air. Dry for further 120 seconds with 100 ° C. hot air to obtain an oriented film.

(Formation of Coating Liquid for Orientation Layer)

20 parts by mass of the modified polyvinyl alcohol shown below

0.05 parts by mass of potassium hydroxide

Glutaraldehyde 0.5 parts by mass

360 parts by mass of water

120 parts by mass of methanol

0.35 parts by mass of ethyl citrate

(Manufacture of 2nd phase difference layer)

The component shown below is dissolved in 102 mass parts of methyl ethyl ketone, and the coating liquid for 2nd phase difference layer manufacture is prepared.

41.01 parts by mass of a discotic liquid crystalline compound shown below

Ethylene Oxide-Modified Trimethylolpropane Triacrylate

(V # 360, manufactured by Osaka Organic Chemical Industry, Ltd.) 4.06 parts by mass

0.04 parts by mass of a compound T-1 containing a triazine ring shown below

0.18 parts by mass of fluoro-aliphatic polymer P-100 shown below

1.35 parts by mass of a photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy)

Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 0.45 parts by mass

Discotic Liquid Crystal Compound

Triazine Ring Containing Compound T-1

Fluoro-aliphatic Polymer P-100

The coating solution is applied to the surface of the alignment film prepared as described above using a # 3.6 wire bar continuously and heated at 130 ° C. for 1 minute to orient the molecules of the discotic liquid crystal compound. The coating layer is then irradiated with UV at 100 ° C. for 1 minute using a high pressure mercury lamp to polymerize the discotic liquid crystal compound. The film is then cooled to room temperature to obtain a retardation layer. The thickness of the retardation plate thus prepared was found to be 2.5 μm thick. In this way, a retardation film No. 101 containing a cellulose acylate film and a retardation layer is obtained.

Thus prepared film No. The angle of incidence dependence of Re of 101 is measured using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instuments), and based on subtracting the previously measured contribution of cellulose acylate film No. 1 By calculating the properties, it was found that Re was 0.1 nm and Rth was 275 nm, and it was confirmed that the retardation layer thus prepared satisfies the optical properties required for the second retardation layer. It was also confirmed that the discotic liquid crystal molecules were oriented almost horizontally in the retardation layer.

In addition, retardation film Nos. 102-107, and Nos. H101 to H103 do not use the triazine ring compound T-1 and / or fluoro-aliphatic polymer P-100 used in the previous preparation of the retardation layer, except that they are replaced with the materials shown in Table 2, or Cellulose acylate film No. It is also prepared in the same manner as described above, except that 1 is replaced with the cellulose acylate film shown in Table 2, respectively.

As can be seen from the data shown in Table 1 and Table 2, in each of the retardation film Nos. 102 to 107, the cellulose acylate film satisfies the optical properties required for the first retardation layer, and the retardation layer formed thereon It has been found that the optical properties required for the two retardation layers are satisfied.

<Preparation of Low-Re Cellulose Acetate Film>

The component shown below is thrown into a mixing tank, and it is stirred, heating so that each component may melt | dissolve, and the cellulose acetate solution "A" is prepared.

(Composition of cellulose acetate solution "A")

100 parts by mass of cellulose acetate having a degree of substitution of 2.86

Triphenyl phosphate (plasticizer) 7.8 parts by mass

Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by mass

Methylene chloride (first solvent) 300 parts by mass

54 parts by mass of methanol (second solvent)

11 parts by mass of 1-butanol

The component shown below is thrown into another mixing tank, and it is stirred, heating so that each component may melt | dissolve, and the additive solution B-1 is prepared.

(Composition of Additive Solution B-1)

80 parts by mass of methylene chloride

20 parts by mass of methanol

40 parts by mass of optically anisotropic reducing agent

477 parts by mass of cellulose acetate solution "A" and 40 parts by mass of additive solution B-1 are added and thoroughly stirred to prepare a dope. The dope is cast on a drum cooled to 0 ° C. from the cast pot. While maintaining the solvent content at 70 mass%, the obtained film was peeled off, and the widthwise positive edge of the film was held with a pin tenter (pin tenter shown in FIG. 3 of JPA No. H4-1009), 3 to 5 mass The tenter is dried while maintaining the 3% elongation factor in the transverse direction (direction perpendicular to the machine direction) under a solvent content of%. The film is then further dried while transporting between the rolls of the annealing apparatus to produce a 80 μm thick low Re cellulose acetate film.

From the measurement of the angle of incidence dependence of Re and the calculation of the optical properties using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments), Re was confirmed to be 1 nm and Rth to 2.5 nm.

<Production of Polarizing Plate "A">

Next, the stretched polyvinyl alcohol film is adsorbed with iodine to prepare a polarizing film. On the other hand, a commercially available cellulose acetate film (Fujitack TD80UF, manufactured by FUJIFILM Corporation, Re = 3 nm, Rth = 45 nm) is saponified, and a polarizing plate "A" is bonded by bonding to one surface of the polarizing film using a polyvinyl alcohol-based adhesive. Manufacture.

<Production of Polarizing Plate B>

The stretched polyvinyl alcohol film is adsorbed with iodine to prepare a polarizing film. On the other hand, a commercially available cellulose acetate film (Fujitack TD80UF, manufactured by FUJIFILM Corporation) is saponified and bonded to both surfaces of the polarizing film using a polyvinyl alcohol-based adhesive to prepare polarizing plate B.

<Production of Polarizing Plate C>

A polarizing film is similarly produced, a commercially available cellulose acetate film (Fujitack TD80UF, manufactured by FUJIFILM Corporation) is saponified, and bonded to one surface of the polarizing film using a polyvinyl alcohol-based adhesive. The low-re cellulose acetate film prepared above was bonded to the other surface of the polarizing film in the same manner to prepare a polarizing plate C.

<Production of Polarizing Plate No. 1>

By using a polyvinyl alcohol-based adhesive, the retardation film No. 101 is used so that the surface of the first retardation layer is disposed on the polarizing film side, and the absorption axis of the polarizing film and the slow axis of the first retardation layer are perpendicular to each other. A polarizing plate No. 1 was produced by bonding to the surface of A ″ (the surface having no commercially available cellulose acetate film bonded here).

Thereafter, the slow axis of the first retardation layer is parallel to the rubbing direction of the liquid crystal cell (that is, the slow axis of the first retardation layer is parallel to the average slow axis of the liquid crystal molecules of the liquid crystal cell in a black state), and the second retardation Polarizing plate No. so that the surface of a layer is arrange | positioned at the liquid crystal cell side. 1 is bonded to one surface of the IPS-mode liquid crystal cell 1 prepared above. Next, the polarizing plate C is bonded to the other side of the IPS-mode liquid crystal cell so that the low-Re cellulose acetate film is disposed on the liquid crystal cell side, and the polarizing plate 1 and the polarizing plate C are cross-nicole aligned in terms of absorption axis, thereby Manufacture display No.201. The display characteristics of the liquid crystal display thus manufactured are evaluated as follows. The results are shown in Table 2.

(Evaluation of display characteristic)

The viewing angle dependence of the light transmittance of the produced liquid crystal display is measured. The measurement is performed while changing the ascending angle in the oblique direction from the front to 80 ° at 10 ° intervals, and changing the azimuth angle starting from the right horizontal direction (0 °) at 10 ° intervals to 360 °. The viewing angle dependency display characteristic difference (hereinafter, the viewing angle dependency difference in color tone and contrast may be referred to as "viewing angle dependency characteristic difference") is evaluated by observing the color tone and transmittance at each viewing angle.

Evaluation of display characteristics:

(Double-circle): excellent, very small viewing angle dependency characteristic difference;

○: good, showing only slight viewing angle dependency characteristic difference;

Δ: almost no difference in viewing angle dependency;

X: The viewing angle dependency characteristic difference is large.

Other liquid crystal displays are manufactured by the same method as described above, except that retardation films No. 101 are replaced with retardation films Nos. 102 to 107 and Nos. H101 to H103 in the manufacture of liquid crystal display No. 201, respectively. Properties are measured similarly. The evaluation results are shown in Table 2.

[Liquid Crystal Display Nos.202 ~ 207]

Using retardation film No. 101, according to the arrangement | positioning shown in Table 3, liquid crystal display Nos.202-208 are manufactured by the same method as liquid crystal display No.201, and display characteristics are evaluated by the same method as mentioned above.

[Liquid Crystal Display No.H201 (Comparative Example)]

On both sides of the IPS-mode liquid crystal cell 1 prepared above, a liquid crystal display is manufactured by bonding the polarizing plate C according to the cross-nicole arrangement. In the same manner as in the manufacture of Liquid Crystal Display No. 201, the polarizing plate is bonded so that the absorption axis of the first polarizing film is perpendicular to the rubbing direction of the liquid crystal cell. Light leakage is measured from the liquid crystal display thus manufactured. Display characteristics were evaluated as "x".

[Liquid Crystal Display No.H202 (Comparative Example)]

Using the polyvinyl alcohol adhesive, the above-mentioned cellulose acylate film No. 1 was bonded to the polarizing plate "A" on the side where the cellulose acetate film as the polarizing film was not bonded, and the film was the liquid crystal cell side. And a transmission axis of the polarizing film and a slow axis of the film so as to be perpendicular to each other to prepare a polarizing plate. In summary, a polarizing plate 5 including only the first retardation layer and no second retardation layer is produced.

The polarizing plate 5 has an average of the liquid crystal molecules of the liquid crystal cell in a state where the slow axis of the first retardation layer (cellulose acylate film No. 1) is perpendicular to the rubbing direction of the liquid crystal cell (that is, the slow axis of the first retardation layer is black). Perpendicular to the slow axis), and bonded to one surface of the IPS-mode liquid crystal cell 1 prepared above. Then, the polarizing plate "A" is bonded on the other surface of the IPS-mode liquid crystal cell 1 so that the polarizing plate protective film is disposed on the liquid crystal cell 1 side, and the polarizing plate "A" and the polarizing plate 5 are in the cross-nico arrangement, and thus the liquid crystal is bonded. Manufacture the display. Light leakage is measured from the liquid crystal display thus manufactured. Display characteristics were evaluated as "Δ".

Table 3-1

LDP No. 201 202 203 204 Absorption axis of the first polarizing film level level level level Slow axis of the first retardation layer Perpendicular level Perpendicular level Slow axis of the second retardation layer option option option option Slow axis of liquid crystal layer Perpendicular Perpendicular level level Low-Re Cellulose Acetate Film option option option option Absorption axis of the second polarizing film Perpendicular Perpendicular Perpendicular Perpendicular Light source Display Characteristics of IPS-LCD ◎ ◎ ◎ ◎

* "Horizontal" and "vertical" correspond to the left and right and up and down directions of the display, respectively.

* "Any" means "horizontal" or "vertical" direction.

* "None" means no phase difference plate is introduced.

Table 3-2

Example No. 205 206 207 208 Absorption axis of the first polarizing film level level level level Low-Re Cellulose Acetate Film option option option option Slow axis of liquid crystal layer Perpendicular Perpendicular level level Slow axis of the second retardation layer option option option option Slow axis of the first retardation layer Perpendicular level Perpendicular level Absorption axis of the second polarizing film Perpendicular Perpendicular Perpendicular Perpendicular Light source Display Characteristics of IPS-LCD ◎ ◎ ◎ ◎

* "Horizontal" and "vertical" correspond to the left and right and up and down directions of the display, respectively.

* "Any" means "horizontal" or "vertical" direction.

* "None" means no phase difference plate is introduced.

Table 3-3

Comparative Example No. H201 H202 Absorption axis of the first polarizing film Perpendicular level Slow axis of the first retardation layer none Perpendicular Slow axis of the second retardation layer none none Slow axis of liquid crystal layer Perpendicular Perpendicular Low-Re Cellulose Acetate Film option none Absorption axis of the second polarizing film Perpendicular Perpendicular Light source Display Characteristics of IPS-LCD × △

* "Horizontal" and "vertical" correspond to the left and right and up and down directions of the display, respectively.

* "Any" means "horizontal" or "vertical" direction.

* "None" means no phase difference plate is introduced.

According to the present invention, it is possible to improve the off axis, particularly the off axis in the 45 ° inclination direction, and the contrast, without degrading the display quality in the normal direction. That is, according to the present invention, it is possible to provide a liquid crystal display, in particular an IPS-type liquid crystal display, in which not only the display quality but also the viewing angle characteristic is improved with a simple structure. It is also possible to provide novel retardation plates which contribute to the improvement of viewing angle characteristics of liquid crystal displays, in particular IPS-type liquid crystal displays, and polarizing plates using the retardation plates.

Cross Reference to Related Application

This application is Japanese patent application No. 1, filed Jan. 24, 2006 under 35 USC 119. Claim priority interests for 2006-014832.

Claims (20)

A retardation plate comprising a first retardation layer and a second retardation layer, The first retardation layer has an in-plane retardation Re of 20 nm to 150 nm, an Nz value of -6.5 to 0.5 defined by Nz = Rth / Re + 0.5 using in-plane retardation Re and thickness direction retardation Rth. And The second retardation layer is a retardation plate, wherein Re satisfies | Re | <30 nm and Rth is in a range of 80 nm to 400 nm. The method of claim 1, And the first retardation layer is a cellulose-derivative film. The method of claim 2, The cellulose derivative film is a film obtained by casting a dope containing a cellulose derivative that satisfies the following conditions (a) and (b) according to a solvent casting method to form a film and stretching the film, (a) The cellulose acylate derivative is represented by the following formula (1), in place of at least one hydrogen of three hydroxyl groups in the glucose unit of cellulose: (1): Δα = α _x- (α _y + α _z ) / 2 Where α _x is the largest component of the eigenvalues obtained by diagonalizing the polarization tensor; α _y is the second largest component of the eigenvalues obtained by diagonalizing the polarization tensor; and α _z is the polarization tensor Is the smallest component of the eigenvalues obtained by diagonalizing), and the polarization anisotropy Δα is 2.5 × 10 ^-24 cm ³ Having at least one substituent that is greater than or equal to; And (b) Substitution degree of substituent having ^Δα of 2.5 × 10 ^-24 cm ³ or more and Δα of 2.5 × 10 ^-24 cm ³ Substitution degree P _A and P _B which respectively show substitution degree of the less than substituent Go below formulas (3) and (4), (3): 2P _A + P _B > 3.0 (4): P _A > 0.2 To satisfy the phase difference plate. The method of claim 3, wherein Said substituent whose said (triangle | delta) (alpha) is 2.5 * 10 <^-2> cm <^3> or more is an aromatic acyl group, The substituent whose said (triangle | delta) (alpha) is less than 2.5 * 10 <^24> -cm ³ is an aliphatic acyl group. The method of claim 3, wherein The dope comprises at least one phase difference regulator. The method of claim 5, wherein The phase difference regulator is a compound represented by the following formula (I), Formula (I)

In the formula, Ar ¹ , Ar ² and Ar ³ each represent an aryl group or an aromatic heterocyclic group; L ¹ and L ² each represent a single bond or a divalent linking group; n is an integer of at least 3; And Ar ² and L ² may each be the same or different. The method of claim 1, And the second retardation layer is formed of a composition comprising a discotic liquid crystal compound, and the average director of molecules of the discotic liquid crystal compound is perpendicular to the layer plane of the second retardation layer. The method of claim 1, And the second retardation layer comprises at least one compound having at least one triazine ring group. The method of claim 1, And the second retardation layer comprises at least one fluoro-aliphatic polymer. The method of claim 9, The fluoro-aliphatic polymer is a copolymer (polymer "A") comprising at least one repeating unit derived from a compound having a fluoro-aliphatic group, and at least one repeating unit represented by the following formula (5), Equation (5)

In the formula, R ¹ , R ² and R ³ each represent a hydrogen atom or a substituent; L represents a divalent linker selected from the group of connectors shown below or a divalent linker consisting of two or more selected from the group of connectors shown below, The linking group is a single bond, -O-, -CO-, -NR ^4- (R ⁴ represents a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group), -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; And Q represents a carboxyl group (-COOH) or a salt thereof, a sulfo group (-SO ₃ H) or a salt thereof, or a phosphoxy group {-OP (= O) (OH) ₂ } or a salt thereof. Polarizing film, and A polarizing plate comprising at least a retardation plate comprising a first retardation layer and a second retardation layer, The first retardation layer has an in-plane retardation Re of 20 nm to 150 nm, an Nz value of -6.5 to 0.5 defined by Nz = Rth / Re + 0.5 using in-plane retardation Re and thickness direction retardation Rth. And The second retardation layer is a polarizing plate, wherein Re satisfies | Re | <30 nm, and Rth is in the range of 80 nm to 400 nm. The method of claim 11, The polarizing plate wherein the polarizing film, the first retardation layer and the second retardation layer are arranged in this order, and the direction of the slow axis of the first retardation layer and the direction of the absorption axis of the polarizing film are substantially orthogonal to each other. The method of claim 11, The polarizing plate wherein the polarizing film, the first retardation layer and the second retardation layer are arranged in this order, and the direction of the slow axis of the first retardation layer and the direction of the absorption axis of the polarizing film are substantially parallel to each other. A liquid crystal display comprising at least a liquid crystal cell and the polarizing plate of claim 11. First polarizing film, The first retardation layer, A second retardation layer, and A liquid crystal display comprising at least a liquid crystal cell comprising a pair of substrates and a liquid crystal layer disposed between the pair of substrates, The first retardation layer has an in-plane retardation Re of 20 nm to 150 nm, an Nz value of -6.5 to 0.5 defined by Nz = Rth / Re + 0.5 using in-plane retardation Re and thickness direction retardation Rth. And Wherein the second retardation layer has Re satisfying | Re | <30 nm and Rth ranging from 80 nm to 400 nm. The method of claim 15, Further comprising a second polarizing film, Wherein the liquid crystal cell is disposed between the first polarizing film and the second polarizing film, and the absorption axes of the first polarizing film and the second polarizing film are perpendicular to each other. The method of claim 16, A liquid crystal in which only a substantially isotropic adhesive layer and / or a substantially isotropic transparent protective film are disposed between the second polarizing film and one of the pair of substrates disposed closer to the second polarizing film. display. The method of claim 17, The transparent protective film is a cellulose acetate film satisfying the following relations (I) and (II), (I): 0 ≦ Re (630) ≦ 10, and Rth (630) | ≤ 25 (II): | Re (400) -Re (700) | ≤ 10, and | Rth (400) -Rth (700) | ≤ 35 In the formula, Re (λ) is an in-plane retardation value (unit: nm) at the wavelength λ nm, and Rth (λ) is a thickness direction retardation value (unit: nm) at the wavelength λ nm. The method of claim 15, The second retardation layer, the first retardation layer, and the first polarizing film are arranged in this order when viewed from the liquid crystal cell side; The liquid crystal molecules of the liquid crystal layer are oriented horizontally with respect to the pair of substrates in a black state, and the average direction of the major axes thereof is parallel to the slow axis of the first retardation layer; And An absorption axis of the first polarizing film and a slow axis of the first retardation layer are perpendicular to each other. The method of claim 15, When viewed from the liquid crystal cell side, the second retardation layer, the first retardation layer, and the first polarizing film are arranged in this order, The liquid crystal molecules of the liquid crystal layer are horizontal with respect to the pair of substrates in a black state, and the average direction of their major axes is orthogonal to the slow axis of the first retardation layer; And An absorption axis of the first polarizing film and a slow axis of the first retardation layer are parallel to each other.

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