JPH1195208A - Liquid crystal display device and film for visual field angle compensation used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to obtain a TFT-VAN-LCD having an excellent visual field angle characteristic by paralleling or orthogonally intersecting the delay phase axis within the film plane of specific phase difference films with the absorption axis of adjacent polarizing films. SOLUTION: The phase difference film for visual field angle compensation comprising one or two sheets of the phase difference films is disposed between a liquid crystal cell and at least one the polarizing films. The retardation (R) value within the film plane expressed by the equation I; R=(nx -ny )×d of the phase difference film of this liquid crystal display device exceeds 0 nm and below 100 nm and the retardation (R') value of the film thickness direction expressed by equation II; R'=[(nx +ny )/2-nz ]×d is >=100 nm and the delay phase axis within the film parallels or intersects orthogonally with the absorption axis of the adjacent polarizing films. In the equations I, II, nx is the refractive index in the delay phase axis direction within the film plane, ny is the refractive index in the direction perpendicular to the delay phase axis direction within the film plane, nz is the refractive index in the thickness direction of the film, and d is the thickness of the film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly to a vertically aligned nematic liquid crystal display having excellent viewing angle characteristics.

[0002]

2. Description of the Related Art Liquid crystal display devices (hereinafter, referred to as "LCD") are used in watches and calculators, and are used in laptop word processors that require a large display capacity. Even those used in personal computers and the like have come to be widely used as flat display devices. Among such LCDs, for applications requiring high display quality, a nematic liquid crystal molecule having a positive dielectric anisotropy is used, and a 90-degree twisted nematic liquid crystal display device (hereinafter, referred to as “TFT”) driven by a thin film transistor is used. -T
N-LCD ". ) Is mainly used. However, although the TFT-TN-LCD has excellent display characteristics when viewed from the front, contrast decreases when viewed from an oblique direction, and grayscale inversion where brightness is reversed in grayscale display. It has a viewing angle characteristic that the display characteristic deteriorates when it occurs, and this improvement is strongly demanded.

In recent years, as a method of LCD for improving the viewing angle characteristics, a nematic liquid crystal molecule having a negative dielectric anisotropy is used, and the major axis of the liquid crystal molecule is set in a direction substantially perpendicular to the substrate without applying a voltage. A vertically aligned nematic liquid crystal display device (hereinafter, referred to as "TFT-VAN-LCD") in which alignment is performed and driven by a thin film transistor has been proposed (JP-A-2-176625). This TF
The T-VAN-LCD has not only excellent display characteristics when viewed from the front as well as the TFT-TN-LCD,
A wide viewing angle characteristic is exhibited by applying the viewing angle compensating retardation film. TFT-VAN-LCD has SID
97 DIGEST, pages 845 to 848, a wider viewing angle characteristic can be obtained by using two negative uniaxial retardation films having an optical axis in a direction perpendicular to the film surface above and below the liquid crystal cell. You can get this L
It is also known that a wider viewing angle can be achieved by using a uniaxially oriented retardation film having a positive refractive index anisotropy with a 50 nm in-plane retardation value for a CD.

However, SID 97 DIGES
Use of three retardation films as described on pages 845 to 848 does not only increase the production cost but also causes a problem such as lowering the yield due to laminating a large number of films. is there.

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have been able to use a viewing angle compensating retardation film comprising one or two retardation films and satisfying required optical characteristics. TFT-VA with excellent viewing angle characteristics
The present inventors have found that an N-LCD can be obtained and the characteristics of these viewing angle compensating retardation films, and have completed the present invention.

[0006]

That is, the present invention is directed to a pair of transparent substrates in which a transparent electrode is formed on a transparent substrate and a vertical alignment film is provided on the transparent electrode so that the transparent electrodes face each other. Nematic liquid crystal having negative dielectric anisotropy is sandwiched in this gap at a fixed distance, and the long axis of the liquid crystal molecule is oriented in a direction substantially perpendicular to the transparent substrate without applying voltage. A liquid crystal cell having a structure, a pair of polarizing films disposed above and below the liquid crystal cell so that their absorption axes are orthogonal to each other, and one or two sheets between at least one of the liquid crystal cell and the polarizing film. A vertically aligned nematic liquid crystal display device comprising a viewing angle compensating retardation film composed of the above retardation film, wherein the viewing angle compensating retardation film has an in-plane film represented by the formula (1): of Tha retardation (R) value is equal to or less than 100nm exceed 0 nm, and a film thickness direction retardation (R ') value of the formula (2) is 100
A liquid crystal display device comprising a retardation film having a thickness of at least nm and a slow axis in a film plane being parallel or orthogonal to an absorption axis of an adjacent polarizing film. _{R = (n X -n Y)} × d (1) R '= [(n X + n Y) / 2-n Z] × d (2) n X: refractive index in a slow axis direction of the film plane n _Y: the refractive index of the n _X and the vertical direction within the film plane n _Z: refractive index in the film thickness direction d: film thickness

[0007] TFT-VAN-LC used in the present invention
In the liquid crystal cell for D, a transparent electrode is formed on a transparent substrate,
A pair of transparent substrates provided with a vertical alignment film on the transparent electrode are arranged at a fixed distance so that the transparent electrodes face each other, and a nematic liquid crystal having a negative dielectric anisotropy is provided in the gap. It has a structure in which the long axes of liquid crystal molecules are oriented in a direction substantially perpendicular to the transparent substrate in a state of being sandwiched and no voltage is applied.

In the liquid crystal cell, the product of the refractive index anisotropy of the nematic liquid crystal (hereinafter, referred to as “Δn _LC ”) and the distance between the glass substrates (hereinafter, referred to as “d _LC ”) (Δn _LC・).
d _LC) is set to be usually about 0.2Myuemu～0.4Myuemu. As such a liquid crystal cell, a liquid crystal cell in which a driving element composed of a thin film transistor for driving each pixel is formed on one of the transparent electrodes (Japanese Patent Laid-Open No. 17662/1990).
No. 5), and a structure in which a partition made of a polymer is provided around each pixel (SID 96 DIgest 630 pages)
633), a liquid crystal cell sandwiching a vertically aligned nematic liquid crystal, and an electric field control method for an enclosure electrode as a driving method [Preprints of the 19th Liquid Crystal Symposium, pp. 308-309 (1993)]
Or plasma address method (Nikkei Microdevice 199
A liquid crystal cell of a type in which a vertically aligned nematic liquid crystal is driven using August, 5th, pp. 163 to 166 is also exemplified.

The vertical alignment film is not particularly limited as long as the liquid crystal can be tilted and aligned so that light is efficiently transmitted by birefringence of the liquid crystal when a voltage is applied, and is made of polyimide. The alignment film is rubbed so that the liquid crystal molecules are aligned and tilted in one direction when a voltage is applied, or a photoreactive polymer such as polyvinyl cinnamate is irradiated with polarized ultraviolet rays so that the liquid crystal molecules are unidirectional when a voltage is applied. Or a plurality of controlled directions. A pair of polarizing films above and below such a liquid crystal cell are arranged such that their absorption axes are orthogonal to each other, and the direction of the absorption axis with respect to the liquid crystal cell is such that light is efficiently transmitted when voltage is applied. Are located. For example, when the alignment film is a rubbed polyimide film in which the liquid crystal molecules are inclined in one direction when a voltage is applied, the absorption axis of the polarizing film is set to be normally 45 degrees with respect to the inclination direction of the liquid crystal molecules. Is done.

Further, a viewing angle compensating retardation film is disposed on at least one of the liquid crystal cell and the polarizing film. The R value of the viewing angle compensating retardation film is 0 nm.
Over 100 nm, preferably 30 nm to 8
0 nm. Further, the R ′ value is 100 nm or more,
Preferably, the value is approximately the same as the Δn _LC · d _LC of the liquid crystal cell used. However, in an actual TFT-VAN-LCD, 100 nm to 30 nm which is approximately 100 nm smaller than Δn _LC · d _{LC of the} liquid crystal cell
It is preferably set to 0 nm, more preferably 15 nm.
0 nm to 250 nm. Actual TFT-VAN-L
In a CD, the most commonly used polarizing film as a pair of polarizing films disposed above and below is a protective film of triacetyl cellulose (hereinafter referred to as "TAC"), which is slightly in-plane oriented. , A single TAC film has an R ′ value of about 50 nm, and a total of R ′ values of two polarizing films used above and below the liquid crystal cell is about 100 nm.
This is because it has characteristics equivalent to nm. The balance between the R value and the R ′ value of the retardation film is as follows:
R ′ / R is preferably 2 or more and 6 or less. Such a retardation film particularly effectively improves the visual characteristics of a TFT-VAN-LCD,
It is most suitable as a film for visual compensation for LCD, and by using this, the TFT-VAN-LC of the present invention can be used.
D can have excellent visual properties.

Such a viewing angle compensating retardation film is
For example, it can be obtained by biaxially orienting a film made of a thermoplastic polymer by a method such as uniaxial stretching. The raw film for obtaining biaxial orientation is obtained by dissolving a thermoplastic polymer in an appropriate solvent, casting this solution on a stainless steel belt, drum or release PET, and drying the belt or drum. Alternatively, it is preferable to form a film by a solvent casting method in which the film is separated from the release PET because a film having excellent uniformity can be obtained.

The polymer to be used is not particularly limited as long as it can achieve uniform biaxial orientation and has a positive refractive index anisotropy, but it is easy to obtain the R ′ value specified in the present invention. And aromatic polymers such as polycarbonate polymers, polyarylate polymers, polyester polymers, and polysulfone. Because these aromatic polymers easily develop refractive index anisotropy, the polymer chains are oriented parallel to the film surface and randomly oriented within the film surface during film formation by the solvent casting method, R is approximately 0 nm
In contrast, R ′ can be easily set to 100 nm or more.

When such a solvent cast film is uniaxially stretched to cancel the plane orientation to make it uniaxial, R ′ becomes approximately R / 2, and the desired optical characteristics cannot be obtained. In order to obtain a specific R value by stretching while maintaining R ′ at 100 nm or more, it is necessary to uniaxially stretch while maintaining this plane orientation to obtain biaxial orientation. As a method of obtaining biaxial orientation by uniaxial stretching, a transverse stretching method using a tenter is known. However, since these polymers easily develop an R value by stretching, R is set to 100 nm by a tenter transverse stretching method. In order to achieve the following, stretching at a lower magnification or stretching at a higher temperature than the optimal conditions for obtaining uniformity is required. However, under such stretching conditions, it is difficult to ensure the uniformity of the R value and R 'value and the uniformity in the direction of the slow axis in the film plane. For this reason, a method of uniaxially stretching in the film flow direction by applying a slight stress when peeling from the belt, drum or release PET during film formation in the solvent casting method is preferably used.

Aromatic polymers such as polycarbonate polymers, polyarylate polymers, polyester polymers, and polysulfone are preferable as described above because they easily exhibit refractive index anisotropy. Large change in retardation value due to stress due to large photoelastic coefficient, caused by heat when exposed to high temperature in the state of being stuck between liquid crystal cell and polarizing film using adhesive In the case of a transmissive liquid crystal display device, the retardation value is deviated due to the unevenness of the stress generated due to the heat of the backlight. It may cause unevenness.

When used under such use conditions in which such a stress is applied, a polymer having a small absolute value of the photoelastic coefficient can be used so that the uniformity of the retardation value does not decrease. Specifically, a polymer having an absolute value of the photoelastic coefficient of 10 × 10 ⁻¹³ cm ² / dyne or less is preferable. Incidentally, the polycarbonate from bisphenol A has an absolute value of the photoelastic coefficient of about 100 × 10 ⁻¹³ cm ² / d.
yne. Such a polymer having a small absolute value of the photoelastic coefficient includes, for example, an acrylic polymer and a cyclic olefin polymer, and has a positive refractive anisotropy and is excellent in heat resistance. A cyclic olefin polymer is preferably used. As the cyclic olefin polymer, a norbornene polymer is preferably used because of its excellent heat resistance.

Examples of the norbornene-based polymer are represented by the general formula (I) (In the formula, a represents 0 or a positive integer, b and c each represent a positive integer, and R ¹ , R ² , R ³ , and R ⁴ each independently represent a hydrogen atom, a hydrocarbon residue, or a phenyl group. Or a polar group.). Here, a nitrile group etc. are illustrated as a polar group.

Application of a norbornene-based polymer to a retardation film is described in JP-A-6-59121. Japanese Patent Application Laid-Open No. 6-59121 discloses a polymer structure suitable for a retardation film for a super-twisted nematic liquid crystal display device. However, when a is increased, a negative refractive index anisotropy is developed. Therefore, the TFT-VA
As the polymer used for the viewing angle improving retardation film for N-LCD, it is preferable that a in the general formula (I) is 0 or 1 so as to exhibit a positive refractive index anisotropy.

Further, since the cyclic olefin-based polymer has smaller refractive index anisotropy than the aromatic polymer, the R value defined in the present invention is more than 0 nm and 100 nm or less; It may be difficult to obtain a retardation film having an R ′ value of 100 nm or more by uniaxial stretching during film formation by a solvent casting method. In this case, the target retardation film can be obtained by uniaxially stretching the film formed by the solvent casting method by a tenter transverse stretching method or the like. In the case of the cyclic olefin polymer, unlike the aromatic polymer, the R value is hardly developed, and therefore, the film is stretched under conditions that can ensure uniform optical characteristics without reducing the stretching ratio or increasing the stretching temperature. be able to.

However, in the range of conditions for obtaining uniform optical properties in the tenter transverse uniaxial stretching method, the R ′ value is small, the R value is more than 0 nm and 100 nm or less, the R ′ value is 100 nm or more, and R ′ / In some cases, a retardation film having R of 2 to 6 cannot be obtained. When the R ′ value is small and the biaxial orientation is insufficient, or when a normal uniaxially oriented retardation film is used, it is necessary to increase the R ′ value without substantially changing the R value. In order to obtain a characteristic range, one negative uniaxial retardation film having an R value of 10 nm or less and an optical axis having a specific value of R ′ substantially in the normal direction of the film, and having a slow axis parallel to the film. Alternatively, they are laminated so as to be orthogonal. This makes it possible to realize optical characteristics in which the R value is more than 0 nm and not more than 100 nm, the R ′ value is not less than 100 nm, and R ′ / R is 2 to 6 in the stacked state. Here, the R value in the laminated state is the sum of the respective R values when the slow axes of the two films are parallel, and is the difference between the respective R values when the slow axes are orthogonal. . The R 'value is the sum of the respective R' values in both the parallel and orthogonal cases.

When the R value is 10 nm or less and the R 'value is 1
As a negative uniaxial retardation film having an optical axis of not less than 00 nm substantially in the normal direction of the film, a polyimide plane orientation film (POLYMER Vol. 7, No. 23, 532)
1) and a retardation film using an inorganic layered compound (JP-A-5-196819).

As the retardation film using the inorganic layered compound, from the viewpoint of productivity and durability, for example, a retardation film using a swellable viscosity mineral, specifically, an organic clay composite and a hydrophobic resin are used. It is also possible to use a retardation film having at least one layer having the following structure. As the organic clay complex, for example, a compound obtained by compounding a clay mineral having a layered structure with an organic compound can be used.

Examples of the clay mineral having a layered structure include smectites and swelling mica. Examples of those belonging to the smectite group include hectorite, montmorillonite, bentonite, and the like, substituted substances, derivatives and mixtures thereof. Among these,
A chemically synthesized smectite group is preferably used for a retardation film because it has few impurities and is excellent in transparency. In particular, synthetic hectorite having a controlled particle size can be used.

As the organic compound, for example, a compound capable of reacting with an oxygen atom or a hydroxyl group of a clay mineral, an exchangeable cation contained in a clay mineral, for example, an alkali metal ion such as Na ⁺ and K ⁺ , Ca ²⁺ , Mg ²⁺ For example, an ionic compound which can be exchanged with an alkaline earth metal ion such as Al ³⁺ and a metal ion such as Al ³⁺ is used, and examples thereof include an amine compound. Examples of the amine compound include a quaternary ammonium compound, urea, hydrazine, doditerpyridinium and the like, but a quaternary ammonium compound is preferably used because of easy exchange with exchangeable cations. The quaternary ammonium compound is usually introduced as a cation. Examples of the cation include an alkyl group such as dimethyl dioctadecyl ammonium ion, dimethyl benzyl octadecyl ammonium ion, and trioctyl methyl ammonium ion. And those having a long-chain substituent such as methyl / diethyl / polyoxypropylene (degree of polymerization: 25) / ammonium ion. These organic compounds are desirably used in an equivalent amount to the cation exchange capacity of the clay mineral, but may be added in the range of 0.5 to 1.5 times the cation exchange capacity during production. Absent.

Such an organoclay composite can be prepared by appropriately selecting an organic compound to be used, such as low-polarity aromatic hydrocarbons such as benzene, toluene and xylene; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; It can be easily dispersed in various organic solvents such as high-polarity solvents such as lower alcohols such as ethanol and propanol, and halogenated hydrocarbons such as carbon tetrachloride, chloroform, dichloromethane, and dichloroethane. The organic clay complex dispersible in the organic solvent thus obtained is usually hydrophobic, and when dispersed in the organic solvent, the unit crystal layer can be swollen until it becomes colloidal. Mixed with a suitable hydrophobic resin, coated on a suitable substrate, dried and formed into a film, so that the unit crystal layer of the organoclay composite can be oriented and used as a retardation film. Become.

Examples of the hydrophobic resin include polyvinyl acetal resins such as polyvinyl butyral polyvinyl formal, and cellulose resins such as cellulose acetate butyrate.

The concentration of the organoclay composite in the dispersion when the layer comprising the organoclay composite and the hydrophobic resin is formed on the substrate is preferably as high as possible because the thickness of the layer can be increased. If the concentration is too high, gelation or the like occurs and the film-forming property deteriorates. Therefore, the composition ratio of the organoclay composite and the hydrophobic resin is usually 1: 2 to 10: 1 by weight, and the total The solid content is used in the range of 3 to 15% by weight. Further, a plurality of these organic clay composites may be used in combination. The retardation film can be used as a single film after being peeled from the formed substrate, but can also be used as it is formed on the transparent substrate using a transparent substrate. When the substrate to be formed is flat,
The unit crystal layer of the organoclay composite has its layered structure oriented parallel to the flat plate surface and randomly in-plane. Accordingly, a refractive index structure in which the refractive index in the film plane is larger than the refractive index in the film thickness direction is exhibited. Due to the refractive index anisotropy, the film can be used as a negative uniaxial retardation film having an R value of 10 nm or less and an R 'value of 100 nm or more, whose optical axis is substantially in the normal direction of the film.

The two retardation films as described above are placed in TF
When used in a T-VAN-LCD, two sheets may be stacked and placed between the upper and lower polarizing films and the liquid crystal cell, or two sheets may be placed between the upper and lower polarizing films and the liquid crystal cell, respectively. It may be arranged.

[0028]

The TFT-VAN-LCD of the present invention has excellent viewing angle characteristics.

[0029]

The present invention will be described below in detail with reference to examples.
However, the present invention is not limited to this. In addition,
The value was determined by the following method. (1) In-plane retardation (R) value Measurement device: Polarizing microscope [Nikon Corporation, Optiphoto-
Pol] monochromatic light having a wavelength of 546 nm was measured by an ordinary method. (2) Retardation (R ') value in the film thickness direction R, R₄₀(Measured at a 40 degree angle with the slow axis as the tilt axis.
Retardation value), d (thickness of retardation film)
And the average refractive index of the retardation film (n₀)Using,
From the following equations (3) to (6),
R_X, N_Y, N _Z, And R ′ is calculated according to equation (4).
Calculated. R = (n_X-N_Y) × d (3) R₄₀= (N_X-N_Y′) × d / cos (φ) (4) (n_X+ N_Y+ N_Z) / 3 = n₀ (5) R '= [(n_X+ N_Y) / 2-n_Z] × d (6) where φ and n_Y’Is the following equation (7),
This is indicated by (8). φ = sin^-1[Sin (40 °) / n₀] (7) n_Y’= N_Y× n_Z/ [N_Y ^Two× sin^Two(Φ) + n_Z ^Two× cos^Two(Φ)]^1/2(8)

Example 1 A 23% methylene chloride solution of a polycarbonate composed of bisphenol A (average refractive index n ₀ = 1.59, number average molecular weight in terms of polystyrene of about 70,000) was dissolved in 800 m.
It is cast on a stainless steel belt of about 24 m length by about 24 m length and dried, and the residual solvent is about 20%, the peeling stress from the belt is reduced, and the film is peeled off while being uniaxially stretched in the film flow direction. To reduce the residual solvent, 700mm wide T
A viewing angle compensating retardation film (140 μm thick) for FT-VAN-LCD was obtained. The optical characteristics of this film are represented by an average of three points taken at intervals of 200 mm in the width direction.
55.5 nm, and R ₄₀ = 90.2 nm. R ′ = 193 nm as a calculated value from these values,
R ′ / R = 3.5.

Example 2 A viewing angle compensation for a TFT-VAN-LCD was performed in the same manner as in Example 1 except that the peeling stress from the stainless steel belt was made smaller than that in Example 1 and the film was uniaxially stretched in the film flow direction. Retardation film was obtained. The optical characteristics of this film were R = 42.9 nm and R ₄₀ = 71.2 nm on average at three points sampled at 200 mm intervals in the width direction. R ′ = 158 nm as a calculated value from these values
And R ′ / R = 3.7.

Example 3 Average refractive index n₀= 1.51 and a thickness of 100 μm
The absolute value of the photoelastic modulus is 4.1 × 10^-13cm^Two/ Dyn
Solvent cast film of norbornene polymer as e
[ARTON film manufactured by Nippon Synthetic Rubber Co., Ltd.]
= 6.3 nm and R₄₀= 13.6 nm. This
R ′ = 36 nm as a calculated value from these values.
This film is uniaxially stretched 1.2 times at 200 ° C.
A difference film was obtained. This film has a thickness of 95 μm.
R = 51.5 nm, and R ₄₀= 56.4 nm
Was. As a calculated value from these values, R '= 23 nm
there were. Hydrophobic resin (trade name Denka Butyral # 30)
1.75% by weight of 00-K Denki Kagaku Kogyo Co., Ltd.)
Organic clay composite 1 [Product name Lucentite STN
3.94% by weight of organic chemicals
Soil complex 2 [trade name Lucentite SPN Coupke
Manufactured by Mical Co., Ltd.] and toluene at 65.
1% by weight, 18.6% by weight of methylene chloride, acetone
An organic solvent dispersion containing 9.3% by weight was
Reacetylcellulose film [Trade name: Fujitack SH
-80 Fuji Photo Film Co., Ltd.]
And then dried at 85 ° C and then at 105 ° C.
A film was obtained. The thickness of this film is 3.7 μm,
The working width was 400 mm. This film is
Negative uniaxial retardation film with axis approximately in the film normal direction
Was This retardation film has R = 6.4 nm.
Yes, R₄₀= 24.8 nm. Average refractive index n₀=
Assuming 1.50, a value calculated from these values is R '=
It was 90 nm. These two retardation films are retarded
Laminated using an adhesive so that the axes are orthogonal, and R = 4
5.1 nm, the total R '= 113 nm,
View for TFT-VAN-LCD where R '/ R = 2.5
A retardation film for field angle compensation was obtained.

Example 4 A solvent cast film (ARTON film) of the same norbornene polymer as used in Example 3 was used at 190 ° C.
The retardation film uniaxially stretched 1.2 times with a thickness of 93
μm, R = 80.0 nm, R ₄₀ = 89.7
nm. R ′ = 4 as a calculated value from these values
7 nm. In the same manner as in Example 3, the thickness of the coating layer composed of the organic clay composite and the hydrophobic resin was 14.6 μm.
m to obtain a negative uniaxial retardation film having an effective width of about 400 mm and an optical axis substantially in the normal direction of the film. This retardation film had R = 5.5 nm and R ₄₀ = 49 nm. Average refractive index n ₀ = 1.5
As 0, R ′ = 213 as a calculated value from these values
nm. By laminating these two retardation films using an adhesive such that the slow axes are orthogonal to each other, R = 7
4.5 nm, the total R ′ = 260 nm,
A viewing angle compensating retardation film for TFT-VAN-LCD with R '/ R = 3.5 was obtained.

Embodiment 5 In a TFT-VAN-LCD, the product of the refractive index anisotropy (Δn _LC ) of the liquid crystal having negative dielectric anisotropy and the distance (d _LC ) between the glass substrates is Δn _LC TFT in which one viewing angle compensating retardation film for TFT-VAN-LCD of Examples 1 to 4 is arranged between at least one of a liquid crystal cell having d _LC of about 0.3 μm and the linear polarizing film. -VA
N-LCDs exhibit wider viewing angle characteristics.

Claims (15)

[Claims] A transparent electrode is formed on a transparent substrate, and a pair of transparent substrates provided with a vertical alignment film on the transparent electrode are arranged at a fixed distance so that the transparent electrodes face each other. A liquid crystal cell having a structure in which a nematic liquid crystal having a negative dielectric anisotropy is sandwiched in a gap, and a long axis of liquid crystal molecules is aligned in a direction substantially perpendicular to a transparent substrate in a state where no voltage is applied; and A viewing angle composed of a pair of polarizing films disposed so that their absorption axes are perpendicular to each other above and below, and one or two retardation films between at least one of the liquid crystal cell and the polarizing film. A vertically aligned nematic liquid crystal display device comprising a compensation retardation film, wherein the viewing angle compensation retardation film has an in-plane retardation (R) value of 0 nm represented by the formula (1). Yue A retardation film having a retardation (R ') value of 100 nm or less and a retardation (R') in the film thickness direction represented by the formula (2) of 100 nm or more, wherein the absorption of a polarizing film having an adjacent in-plane slow axis is A liquid crystal display device characterized by being parallel or orthogonal to an axis. _{R = (n X -n Y)} × d (1) R '= [(n X + n Y) / 2-n Z] × d (2) n X: refractive index in a slow axis direction of the film plane n _Y: the refractive index of the n _X and the vertical direction within the film plane n _Z: refractive index in the film thickness direction d: film thickness 2. A retardation film for viewing angle compensation, wherein the in-plane retardation (R) value is 30 nm to 80 nm.
The liquid crystal display device according to claim 1, wherein a retardation (R ') value in a film thickness direction is from 150 nm to 250 nm. 3. The film according to claim 1, wherein the ratio R ′ / R of the in-plane retardation (R) value to the retardation (R ′) value in the film thickness direction is 2 to 6. Item 3. A liquid crystal display device according to item 2. 4. A retardation film for compensating a viewing angle, wherein at least one retardation film made of a polymer having a positive refractive index anisotropy is used.
3. The liquid crystal display device according to 1. 5. A retardation film comprising at least one retardation film obtained by forming a polymer having a positive refractive index anisotropy by a solvent casting method and then stretching the film in a uniaxial direction. The liquid crystal display device according to claim 4, wherein: 6. The polymer according to claim 4, wherein the polymer having a positive refractive index anisotropy is any one of a polycarbonate polymer, a polyarylate polymer, a polyester polymer and polysulfone. Liquid crystal display device. 7. The polymer according to claim 4, wherein the polymer having a positive refractive index anisotropy is a polymer having an absolute value of a photoelastic coefficient of 10 × 10 ⁻¹³ cm ² / dyne or less. Liquid crystal display device. 8. absolute value of photoelastic coefficient of 10 × 10 ^-13 cm ²
The liquid crystal display device according to claim 7, wherein the polymer having a ratio of / dyne or less is a cyclic olefin polymer. 9. The viewing angle compensating retardation film is made of a cyclic olefin polymer and has an R value exceeding 0 nm and 100 nm.
A single uniaxially stretched film and a single negative uniaxial retardation film having an R value of 10 nm or less and an optical axis substantially in the normal direction of the film are laminated. The liquid crystal display device according to claim 8, wherein the R value is 30 nm to 80 nm, the total R 'value is 150 nm to 250 nm, and R' / R is 2 to 6. 10. A viewing angle compensating retardation film having a vertical alignment nematic liquid crystal display device having an R value of more than 0 nm and not more than 100 nm and an R ′ value of not less than 100 nm. 11. The retardation film for compensating viewing angle of a vertically aligned nematic liquid crystal display device according to claim 10, comprising one retardation film. 12. The vertical alignment nematic liquid crystal display device according to claim 10, which is obtained by uniaxially stretching a polymer film made of a polycarbonate polymer, a polyarylate polymer, a polyester polymer or polysulfone. A retardation film for viewing angle compensation. 13. The retardation film according to claim 10, wherein R ′ / R is 2 to 6. 14. A uniaxially stretched film composed of a cyclic olefin polymer film and having an R value of 100 nm or less, and a negative uniaxial retardation having an R value of 10 nm or less and an optical axis substantially in the normal direction of the film. One film is laminated, and the R value in the laminated state is 30 nm to 80.
nm, the total R ′ value is 150 nm to 250 nm, and R ′ / R is 2 to 6. A retardation film for viewing angle compensation of a vertically aligned nematic liquid crystal display device. 15. A negative uniaxial retardation film having an R value of 10 nm or less and an optical axis substantially in the normal direction of the film is a retardation film using a swelling clay mineral. 4. The retardation film for viewing angle compensation of a vertically aligned nematic liquid crystal display device according to item 1.