JP3313407B2 - Phase difference plate and liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retardation plate capable of providing a liquid crystal display device having improved display coloring and contrast ratio, and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art As an STN type liquid crystal display device, the first type is known.
An STN liquid crystal display device having a configuration of a polarizing plate / driving liquid crystal cell / hue compensating liquid crystal cell / second polarizing plate has been developed. ("Nikkei Microdevices, August 1987, 3
6-38 "and" Nikkei Microdevice, 1987 "
October 2004, pp. 84-88 ")

[0003] The incident light becomes linearly polarized light via the first polarizing plate side, and becomes a elliptically polarized light due to a phase difference while passing through the driving liquid crystal cell. At this time, the ellipticity and azimuth angle depend on each wavelength. different. However, the transmitted light passing through the driving liquid crystal cell is twisted in the opposite direction while passing through the hue compensation liquid crystal cell, and the elliptically polarized light becomes linearly polarized light again (that is, the phase difference is canceled), and passes through the second polarizing plate. Taken out. As a result, the wavelength dependence of the transmitted light is eliminated, and the display becomes substantially black and white. Therefore, if necessary, a full color can be obtained by adding a color filter.

An STN liquid crystal display device using the above-mentioned driving liquid crystal cell and hue compensating liquid crystal cell is disadvantageous in that it is thick, heavy, and high in cost. There is also the problem of too much.

In order to solve this disadvantage, instead of using a liquid crystal cell for hue compensation, a retardation plate is used in which an optically isotropic film is laminated on both sides of a retardation film composed of a uniaxially stretched polymer film. (Hereinafter, referred to as FTN mode) has attracted attention. The basic configuration of this FTN mode liquid crystal display device is a polarizing plate / liquid crystal cell / a retardation plate / a polarizing plate.

Japanese Patent Application Laid-Open No. 64-519, filed by one of the present applicants, discloses that polyvinyl alcohol, polyester, polyetheramide, polyethylene and the like can be used as the uniaxially stretched film for the above purpose. ing.

Japanese Patent Application Laid-Open No. 1-118805 discloses that a film made of polyvinyl alcohol or a derivative thereof is uniaxially stretched and then treated with an aqueous solution containing boric acid on both sides or one side thereof to form an optically non-oriented high-density film. A retardation plate having a molecular film bonded thereto is shown. Here, the derivative of polyvinyl alcohol is a polyvinyl acetal such as polyvinyl butyral and polyvinyl formal.

[0008] JP-A-1-118819 and JP-A-1-124821 disclose an optical retardation film consisting of an oriented synthetic resin film or a photo-isotropic amorphous film laminated on at least one surface thereof. It is disclosed that an optical retardation substrate is used as one of the transparent electrode supporting substrates constituting a liquid crystal cell. JP-A-1-127329 discloses a laminate having an optical phase function in which the same optical retardation substrate as above is laminated on a release sheet via an adhesive layer. And, in these publications, as the polymer for the above retardation film, polycarbonate, phenoxy resin, polyparabanic acid resin, fumaric acid resin, polyamino acid resin, polystyrene, polysulfone, polyethersulfone, polyarylene ester, polyvinyl It is described that alcohol, ethylene-vinyl alcohol copolymer, polyvinyl chloride, polymethyl methacrylate, polyester, cellulosic polymer and the like are used. All of these applications and the application described in Japanese Patent Application Laid-Open No. 2-158701 described below are related to another application of the present applicant.

Japanese Patent Application Laid-Open No. 2-158701 discloses a retardation value of 30 of a cast film having a low orientation.
A composite phase plate composed of a birefringent multilayer film in which a plurality of layers of a birefringent unit film having a thickness of ~ 1000 nm are laminated and integrated with their optical axis directions aligned in the same direction is shown. Phenoxyether type crosslinkable resin, epoxy resin, acrylic resin, crosslinkable resin such as urethane resin, polycarbonate, polyarylene ester, polyether sulfone, polysulfone, polyethylene terephthalate, polybutylene terephthalate,
Polyvinyl chloride, polystyrene, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, amorphous polyolefin, fumaric acid resin, polyamino acid resin,
It is described that an ABS resin or the like is used.

Japanese Patent Application Laid-Open No. 2-256003 discloses a film formed by stretching a thermoplastic polymer film having no thickness variation uniaxially or biaxially in a direction perpendicular to the extrusion direction. Value is 1200
nm or less, and the deflection width of the retardation value is 10
% Or less, mainly an optical film for a retardation plate. As the thermoplastic polymer, a polycarbonate resin, a poly (meth) acrylate resin, a polystyrene resin, an acrylonitrile resin, a polyester resin ( Polyethylene terephthalate, polyester copolymer, etc.), polyamide resin, polyvinyl chloride resin,
It is described that polyolefin resin, polysulfone, polyethersulfone, fluorine resin and the like are used.

Japanese Patent Application Laid-Open No. 2-256023 discloses a liquid crystal cell comprising a film in which molecules having a negative intrinsic birefringence are plane-oriented and a uniaxially stretched film formed from a polymer having a positive intrinsic birefringence. And a liquid crystal display device inserted between a polarizing plate and a polystyrene-based polymer or an acrylate-based polymer as an example of the former polymer, and a polycarbonate as an example of the latter polymer. , Polyarylate, polyethylene terephthalate, polyether sulfone, polyphenylene sulfide, polyphenylene oxide, polyallyl sulfone, polyamide imide, polyolefin, polyacrylonitrile, cellulose, polyester and the like.

JP-A-2-257103 discloses that a polyvinyl alcohol film is stretched in a uniaxial direction and a retardation film having a retardation value of 300 to 800 nm is laminated with a polysulfone or polyarylate film. A retarder is shown.

[0013]

However, a retardation film composed of a uniaxially stretched film prepared from polymers described in the above-listed documents or a retardation film obtained by laminating an optically isotropic film on both or one surface thereof. Depending on the plate, regardless of whether a uniaxially stretched film is used as a single layer or a multilayer as a retardation film, the retardation generated by the STN cell cannot be compensated over all its wavelengths,
The problems of coloring and lowering of the contrast ratio could not be solved sufficiently.

Therefore, while solving the problems of the thickness and weight which are the problems of the STN liquid crystal display device using the driving liquid crystal cell and the hue compensating liquid crystal cell, the hue compensating liquid crystal cell is still required for coloring and contrast ratio. This method is inferior to the method used, and this point is a serious problem to be solved in the FTN mode using a retardation plate made of a polymer film.

The present invention relates to an FTN mode using a retardation film or a retardation plate in a liquid crystal display device for hue compensation.
The purpose of the present invention is to fundamentally solve the problems of coloring and contrast ratio, which have been pending.

[0016]

The retardation film of the present invention comprises a polymer film having a refractive index n _D of 1.60 or more, an Abbe number ν _D of 30.0 or less, and a glass transition point Tg of 60 to 160 ° C. in at least one direction. And a second stretched film (2) obtained by stretching a polymer film having a refractive index n _D of less than 1.60 in at least one axis direction. Further, the liquid crystal display device of the present invention is characterized in that at least one phase difference plate is formed between a pair of polarizing plates sandwiching a liquid crystal cell.

In this case, the retardation value R of the laminated film is 60 to 1000 nm, and the formula of the first stretched film (1) in the laminated film: ν _RF = △ nd (450 nm) / △ nd ( It is particularly desirable that the chromatic dispersion value ν _RF defined by (590 nm) is 1.10 or more.

Hereinafter, the present invention will be described in detail.

First stretched film (1) As described above, the first stretched film (1) has a refractive index n _D of 1.60 or more, an Abbe number ν _D of 30.0 or less, and a glass transition point Tg of It is composed of a stretched film obtained by stretching a polymer film satisfying all the properties at 60 to 160 ° C. in at least one direction.

The refractive index n _D refers to the refractive index with respect to the D line (589 nm) measured according to ASTM D-542. When the refractive index n _D is less than 1.60, even if other conditions are satisfied. The problem of coloring and contrast ratio cannot be solved.

The Abbe number ν _D is ν _D = (n _D −1) /
(N _F -n _C) is an index represented by, n _D, n _F,
n _C is D line (589 nm), F line (486 nm),
This is the refractive index for the C line (656 nm). When the Abbe number ν _D exceeds 30.0, the problems of coloring and contrast ratio cannot be solved even if other conditions are satisfied.

And a glass transition point Tg of 60 to 160 ° C.
When the glass transition point Tg is less than 60 ° C, the heat resistance is insufficient, while the glass transition point Tg is 160 ° C.
If it exceeds, the stretchability is impaired.

Examples of the polymer for the polymer film satisfying the above three conditions include brominated or chlorinated phenoxy ether polymers, polyethylene naphthalate, bisphenol-aromatic dicarboxylic acid polycondensate, polyvinyl naphthalene, Polyvinyl carbazole, polypentabromophenyl methacrylate, polypentachlorophenyl methacrylate, poly α-naphthyl methacrylate,
Examples thereof include poly p-divinylbenzene. The film finally has a refractive index n _D and Abbe number ν defined above.
_It suffices to satisfy _D and the glass transition point Tg. Films such as copolymers (including graft copolymers), coexisting polymers, post-modified products, and blends of two or more polymers having different characteristic values Or a laminated film of a plurality of polymer films.

Among these polymers, brominated or chlorinated phenoxy ether-based crosslinkable resins and polyethylene naphthalate are particularly important. The characteristic values of these polymer films are also influenced by the molecular weight, the film forming method, the degree of halogenation, and the like, but typical characteristic values are as follows.

N _D ν _D Tg Brominated phenoxy ether polymer 1.64 24 149 Chlorinated phenoxy ether polymer 1.63 25 140 Polyethylene naphthalate 1.65 19 113 Polyvinyl naphthalene 1.68 21 158 Polyvinyl carbazole 1.68 19 84 Poly p-divinyl benzene 1.62 28 106

Incidentally, the polymer film conventionally proposed as a retardation film has a refractive index n _D , Abbe number ν _D or glass transition point Tg out of the above range as described below. It cannot fulfill its purpose.

[0027] Polycarbonate: n _D is 1.58 to 1.59 polymethylmethacrylate: n _D is 1.49, [nu _D 57 polyvinyl alcohol: n _D is 1.49 to 1.53 Polyethylene terephthalate: n _D 1.53 Polyethylene: n _D 1.51 Polypropylene: n _D There 1.49 polyvinyl chloride: n _D is 1.54 to 1.55 polysulfone: Tg higher polyethersulfone than the 160 ° C.: Tg higher polyarylate than 160 ° C.: n _D is 1.61, [nu _D is 26, Tg is 215 ° C. polystyrene: n _D is 1.59, ν _D is 31 Polyphenylene oxide: Tg is 209 ° C. Polyacrylonitrile: n _D is 1.52, ν _D is 52 Cellulosic polymer: n _D is 1.49 to 1.51 Amorphous polyolefin: n _D is 1.52 Nylon 66: n _D Is 1.52 to 1.53, ν _D is 40 ABS resin: n _D is 1.54 Polyester copolymer: n _D is 1.52 to 1.57 Phenoxyether-based weight which is not brominated or chlorinated Coalescing: n _D is slightly less than 1.60 Polytetrafluoroethylene: n _D is 1.35

It is particularly desirable that the first stretched film (1) has a wavelength dispersion value ν _RF of 1.10 or more. Here, the chromatic dispersion value ν _RF is an index defined by the equation ν _RF = △ nd · (450 nm) / △ nd · (590 nm). If this value is less than 1.10, the dispersibility is insufficient. Cannot solve the problems of coloring and contrast ratio. The chromatic dispersion value ν _RF is 1.10 to 1.18
Thus, it is preferable to have the same value as that of the liquid crystal. However, depending on the compensation condition of the liquid crystal cell, a remarkable hue compensation effect may appear at a large value of 1.2 or more.

According to the study of the present inventors, the refractive index n _D is
1.60 or more, Abbe number ν _D is 30.0 or less, glass transition point Tg
It has been found that a stretched film obtained by stretching a polymer film having a temperature of 60 to 160 ° C. in at least one direction has a large wavelength dispersion value ν _RF . Therefore, the thickness and stretching conditions of the polymer film should be selected so that the wavelength dispersion ν _{RF of} the first stretched film (1) should be 1.10 or more.

The polymer film having the above characteristic values can be obtained by a casting method or a melt molding method. The stretching of the polymer film is performed at a temperature of 5 to 40 ° C., particularly 10 to 40 ° C., higher than the glass transition point Tg.
Usually, it is performed at a temperature about 30 ° C. higher or at a temperature before or after that, and it is preferable to perform aging after stretching. The stretching ratio is generally 1.1 to 6 times in one direction, especially 1.2 times.
It is often stretched up to 4 times. It is also possible to stretch in one direction while limiting the stretching ratio in the perpendicular direction or suppressing shrinkage in the perpendicular direction. In this case, biaxial stretching is performed.

Second stretched film (2) The second stretched film (2) is a stretched film obtained by stretching a polymer film having a refractive index n _D of less than 1.60 in at least one direction. However, if the refractive index n _D is extremely small, irregular reflection is likely to occur at the interface with the first stretched film (1). Therefore, the refractive index n _D is desirably 1.50 or more.

The polymer film of the second oriented film (2) for the production is not particularly limited for the first oriented film (1) Unlike the polymer film for the production Abbe number [nu _D, Abbe number [nu _D Although it may be 30.0 or less, it may exceed 30.0, but since it is rarely 30.0 or less, it usually exceeds 30.0 in many cases. The glass transition point Tg is not particularly limited, but is preferably 160 ° C. or lower from the viewpoint of easy stretching. Since the heat resistance is compensated by the first stretched film (1), the glass transition point Tg may be lower than 60 ° C.

Examples of the polymer for the polymer film for this purpose include polycarbonate, phenoxy ether polymer, polystyrene, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, cellulose triacetate, epoxy resin, ABS resin and the like. .

Laminated Film The retardation film of the present invention comprises a laminated film of the first stretched film (1) and the second stretched film (2). The lamination structure is (1) / (2), (1) / (2) / (1), (1) / (1) / (2), (2) / (1)
/ (2), (2) / (1) / (2) / (2), etc.

The retardation value R of the laminated film is 6
It is particularly desirable that the thickness be 0 to 1000 nm. When the retardation value R of the laminated film is less than 60 nm, the retardation function is insufficient, while when it exceeds 1000 nm, the film thickness must be extremely thick, and optical uniformity is impaired when such a thickness is increased. The hue compensation effect decreases.

Here, the retardation value R is represented by the formula: R = d · | n ₁ −n ₂ | = △ _nd (where d is the thickness of the film, and n ₁ is the refraction in the optical axis direction or in the direction perpendicular thereto). The index, n _2, is an index indicated by a refractive index orthogonal to the n ₁ direction, where the refractive index is for the sodium D line.

Although the retardation plate may be constituted only by the laminated film having such a layer constitution, it is also possible to further protect the optically isotropic film (3) by laminating at least one surface thereof.

Examples of the photoisotropic film (3) for this purpose include cellulose polymers (for example, cellulose triacetate), polycarbonates, polyparabanic acid resins,
Polystyrene, polyether sulfone, polyarylene ester, polysulfone, polyvinyl chloride, poly-4-
Examples thereof include methylpentene, polyphenylene oxide, an air-permeable resin, and a crosslinked resin cured product. Here, the air-permeable resin is polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyacrylonitrile, polyvinylidene chloride, and the like.The crosslinked resin cured product is a phenoxy ether type crosslinkable resin, an epoxy resin, an acrylic resin, an acrylic epoxy resin. And urethane resin, and not only a single-layer film but also a multi-layer film such as an ethylene-vinyl alcohol copolymer / phenoxy ether type crosslinkable resin can be used. The retardation value of the isotropic film is preferably 30 nm or less, more preferably 10 nm or less.

When a release sheet (5) is laminated on at least one surface of the retardation plate of the present invention via a pressure-sensitive adhesive layer (4),
It is advantageous in handling until it is used for manufacturing a liquid crystal display device.

The retardation plate of the present invention may be formed by laminating and integrating a polarizing plate into a phase plate with a polarizing plate, or as a substrate of a liquid crystal cell or by laminating and integrating with a substrate before manufacturing a liquid crystal cell. It can also be a substrate.

The phase difference plate of the present invention is an STN (Super
It is particularly useful as a hue compensation used in a liquid crystal display device of a (twisted nematic) type, that is, a retardation plate used in an FTN mode. In addition, it can be used for applications such as a transparent body for goggles, a transparent body for anti-glare, and an optical filter.

[0042]

As described above, the refractive index n _D is 1.60 or more,
Abbe number ν _D is 30.0 or less, glass transition point Tg is 60 to 1
A film that has been stretched at least uniaxially from a polymer film at 60 ° C. has a “substrate” in which the wavelength dispersion value ν _RF increases.
Has been found. Therefore, when a polymer film having such characteristic values is selected and stretched, a first stretched film (1) having a wavelength dispersion value ν _RF of 1.10 or more can be obtained. Since the first stretched film (1) has a large wavelength dispersion value ν _RF , when this is used as a retardation film,
The coloring and contrast ratio can be significantly improved.

However, when only the first stretched film (1) is used, unless the film thickness is considerably increased, the retardation value R is 60 to 1000 nm, particularly 500 to the optimum value.
The one with 700 nm cannot be obtained. However, since the first stretched film (1) is generally expensive,
Increasing the thickness of (1) is disadvantageous in terms of cost, and increasing the thickness tends to make it difficult to obtain optical uniformity, and obtaining a thick first stretched film (1) requires film-forming. And it is not always easy in a stretching technique. Therefore, utilizing the fact that the retardation value R has additivity, the lack of the retardation value R is compensated for by lamination of the second stretched film (2), and the polymer film for the second stretched film (2) is used. Paying attention to the refractive index n _D , care should be taken not to cause irregular reflection between the first stretched film (1) and the second stretched film (2). In addition, two or more retardation plates of the present invention can be incorporated in one liquid crystal display device.

[0044]

The present invention will be further described with reference to the following examples. Hereinafter, "parts" refers to parts by weight.

Embodiment 1 FIG. 1 is a sectional view showing an example of the retardation plate of the present invention.

First stretched film (1) On a polyester film as a support,
A brominated phenoxy ether resin having a bromine content of 52.9% by weight (YPB-43C manufactured by Toto Kasei Co., Ltd.) 25
Part by weight ratio of cyclohexanone and dioxane to 60:
After casting a solution dissolved in 75 parts of a mixed solvent of 40, the mixture was incompletely dried until the residual solvent amount was 5% by weight.
The film was peeled off from the polyester film and then dried until the residual solvent disappeared. The thickness of the obtained film is 70μ.
m, refractive index n _D is 1.64, Abbe number ν _D is 24, glass transition point Tg measured by DSC is 149 ° C., retardation value R is 2 nm, and heat distortion temperature (JIS K6911) is 1
It was 11 ° C.

[0047]

Embedded image

Next, the film was stretched three times in one direction at a temperature of 155 ° C., aged at the same temperature for 2 seconds, and the ends of both ears were cut. Thereby, the thickness is 42 μm.
m, retardation value R is 480 nm, wavelength dispersion value ν _RF
Of 1.14 was obtained.

The second stretched film (2) obtained a polycarbonate film by a casting method. The thickness is 80 μm, the refractive index n _D is 1.59, the Abbe number ν _D is 30.3, the glass transition point Tg is 135 ° C., and the retardation value R is 4
nm.

Next, the film was stretched 1.5 times in one direction at a temperature of 168 ° C., aged at the same temperature for 10 seconds, and the ends of both ears were cut. The thickness was 64 μm and the retardation value R was 98 nm. , The second wavelength dispersion value ν _RF is 1.09
A stretched film (2) was obtained.

Retardation plate The above-mentioned first stretched film (1) and second stretched film
After laminating and adhering with an acrylic adhesive so that the respective stretching directions of (2) become parallel, an optically isotropic film (3), comprising a 50 μm thick cellulose triacetate film on both sides of the laminated film (3), ( 3) was laminated and bonded with a urethane-based adhesive to prepare a retardation plate having a layer configuration of (3) / (1) / (2) / (3). This retardation plate had a retardation value R of 578 nm and a wavelength dispersion value ν _RF of 1.13.

Retardation plate with release sheet Release sheet made of polyester film having a thickness of 40 μm in advance
A release sheet (5) with a pressure-sensitive adhesive layer (4) having a 30 μm-thick acrylic pressure-sensitive adhesive layer (4) formed on the release-treated surface of (5) was prepared, and the retardation plate obtained above was prepared. On both sides. When the retardation plate is used, only the release sheet (5) is adhered to the object while being removed.

Using this retardation plate, a liquid crystal display device having the structure of polarizing plate / liquid crystal cell / retardation plate / polarizing plate was produced. FIG. 2 is a schematic diagram of a liquid crystal display device using the retardation plate of the present embodiment. The liquid crystal cell (102) has a substrate (10) on which a transparent electrode (104) and a rubbed alignment film (105) are formed.
3) are opposed via a spacer (106), and the liquid crystal (107) is filled. A phase difference plate (1) is placed below the liquid crystal cell (102).
09), which are combined with the upper polarizer (101) and the lower polarizer (10).
8) FIG. 5 shows the relationship among the axes when the liquid crystal display device of FIG. 1 is viewed from above. (401) is the magnitude of the twist angle of the liquid crystal, (403) is the angle from the horizontal direction to the rubbing direction (402) of the upper substrate of the liquid crystal cell, and (404) is the liquid crystal cell (10
2) Rubbing direction of the lower substrate. (406) is the angle from the horizontal direction to the polarization axis direction of the upper polarizer (405), (408) is the angle from the horizontal direction to the polarization axis direction of the lower polarizer (407),
(410) is the angle from the horizontal direction to the stretching axis direction (409) of the retardation plate. The direction of the angle is positive clockwise. The product Δnd of the refractive index anisotropy Δn of the liquid crystal and the cell thickness d is 0.86 μm
And At this time, the twist angle (401) of the liquid crystal is 240 degrees clockwise from bottom to top, the angle (403) is 30 degrees, and the angle (4
06) is 65 degrees, angle (408) is 95 degrees, angle (410) is 50
Degree. As the polarizing plate, a polarizing plate having a visible light transmittance of 42% and a degree of polarization of 99%, in which a cellulose triacetate film is adhered to both surfaces of a polyvinyl alcohol-iodine polarizing element film, is used. A nematic liquid crystal having a value ν _LC of 1.14 was used. This liquid crystal is composed of the following chemical composition.

[0054]

Embedded image

This liquid crystal display device has significantly improved coloring and contrast ratios, and also has slightly improved brightness, which is substantially comparable to a liquid crystal display device using a hue compensation liquid crystal cell. Was something.

Example 2 First stretched film (1) A polyethylene naphthalate film obtained by a melt extrusion molding method was prepared. The thickness of this film is 80 μm
The refractive index n _D was 1.65, the Abbe number ν _D was 18, and the glass transition point Tg measured by DSC was 113 ° C.

Next, the film was stretched 1.9 times in one direction at a temperature of 130 ° C., aged at the same temperature for 4 seconds, and the ends of both ears were cut.

As a result, a first stretched film (1) having a thickness of 60 μm, a retardation value R of 420 nm, and a wavelength dispersion value ν _RF of 1.18 was obtained.

A second stretched film (2) was used to obtain a polycarbonate film by a casting method. The thickness is 80 μm, the refractive index n _D is 1.58, the Abbe number ν _D is 30.3, the glass transition point Tg is 135 ° C., and the retardation value R is 1
It was 50 nm.

Next, this film was stretched 1.6 times in one direction at a temperature of 170 ° C., aged at the same temperature for 8 seconds, and the ends of both ears were cut. The thickness was 62 μm and the retardation value R was 150 nm. , The second wavelength dispersion value ν _RF is 1.09
A stretched film (2) was obtained.

Retardation plate The above-mentioned first stretched film (1) and second stretched film
After laminating and adhering with an acrylic adhesive so that the respective stretching directions of (2) become parallel, an optically isotropic film (3), comprising a 50 μm thick cellulose triacetate film on both sides of the laminated film (3), ( 3) was laminated and bonded with a urethane-based adhesive to prepare a retardation plate having a layer configuration of (3) / (1) / (2) / (3). This retardation plate had a retardation value R of 555 nm and a wavelength dispersion value ν _RF of 1.16.

Using this retardation plate, a liquid crystal display device was manufactured in the same manner as in Example 1. This liquid crystal display device has greatly improved coloring and contrast ratio, and is substantially comparable to a liquid crystal display device using a hue compensating liquid crystal cell.

Example 3 Example 1 was repeated except that a chlorinated phenoxy ether resin was used in place of the brominated phenoxy ether resin, and favorable results were obtained in accordance with Example 1.

Comparative Example 1 A polycarbonate film was obtained by a casting method. The thickness is 170 μm, the refractive index n _D is 1.58, the Abbe number ν _D is 30.3,
The glass transition point Tg was 140 ° C., and the retardation value R was 7 nm.

Next, after stretching this film twice in one direction at a temperature of 170 ° C., aging was carried out at a temperature of 165 ° C. for 6 seconds, and the ends of both ears were cut off. The thickness was 110 μm and the retardation value R was 570 nm. Thus, a stretched film having a wavelength dispersion value ν _RF of 1.09 was obtained.

Then, a thickness of 50 was applied to both sides of the stretched film.
An optically isotropic film composed of a cellulose triacetate film having a thickness of μm was adhered with a urethane-based adhesive to produce a retardation plate.

Using this retardation plate, a liquid crystal display device was manufactured in the same manner as in Example 1. In this liquid crystal display, the display was strongly colored blue and the contrast ratio was low.

Comparative Example 2 Polymethyl methacrylate, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyethylene terephthalate, polybutylene terephthalate, polyethylene, polypropylene, polyvinyl chloride, polystyrene, phenoxy ether Stretch ratio of 1.5 to 4 for polymers and polyacrylonitrile
A uniaxially stretched film was prepared, and an optically isotropic film made of a cellulose triacetate film was adhered to both sides of the film to form a retardation plate, which was then incorporated into a liquid crystal display.
It was colored as in Comparative Example 1 and had a low contrast ratio.

Example 4 A polyethylene naphthalate film having a refractive index n _D of 1.65, an Abbe number ν _D of 18, and a glass transition point Tg of 113 ° C. measured by DSC was stretched in one direction and then aged to obtain a wavelength. A first stretched film (1a) having a dispersion value ν _RF of 1.18,
(1b).

The refractive index n _D is 1.58 and the Abbe number ν _D is
30.3, After stretching a polycarbonate film having a glass transition point Tg of 135 ° C. measured by DSC in one direction,
After aging, second stretched films (2a) and (2b) having a wavelength dispersion value ν _RF of 1.09 were obtained.

The retardation value R of the first stretched film (1a) was set to 320 nm, and the retardation value R of the second stretched film (2a) was set to 100 nm. After laminating and bonding with an adhesive, a photoisotropic film (3) made of a cellulose triacetate film having a thickness of 50 μm is laminated and bonded with a urethane-based adhesive on both sides of the laminated film, and (3) /
A retardation plate having a layer configuration of (1a) / (2a) / (3) was produced.
This retardation plate had a retardation value R of 420 nm and a wavelength dispersion value ν _RF of 1.16. Using two of the retardation films, a liquid crystal display device having a structure of a polarizing plate / a liquid crystal cell / a retardation plate / a retardation plate / a polarizing plate was produced. FIG. 3 shows a schematic diagram of this liquid crystal display device. Transparent electrode on liquid crystal cell (202)
(204) and a substrate (203) on which a rubbed alignment film (205) is formed oppose via a spacer (206) and a liquid crystal (20) is formed.
7) is filled. Below the liquid crystal cell (202), there are retarders (209) and (210), which are connected to an upper polarizer (201).
And the lower polarizing plate (208). FIG. 6 shows the relationship between the axes when the liquid crystal display device of FIG. 3 is viewed from above. (501) is the magnitude of the twist angle of the liquid crystal, (503) is the angle from the horizontal direction to the rubbing direction (502) of the upper substrate of the liquid crystal cell (202),
(504) is the rubbing direction of the lower substrate of the liquid crystal cell (202). (Five
06) is the angle from the horizontal direction to the polarization axis direction of the upper polarizer (505), and (508) is the angle from the horizontal direction to the polarization axis direction of the lower polarizer.
The angle from (507), (510) is the angle from the horizontal direction to the stretching axis direction (509) of the upper retarder, and (512) is the angle from the horizontal direction to the stretching axis direction (511) of the lower retarder. Angle. The direction of the angle is positive clockwise. Liquid crystal refractive index anisotropy Δ
The product Δnd of n and the cell thickness d was set to 0.86 μm. At this time, the twist angle (501) of the liquid crystal is clockwise
04 degrees, angle (503) is 30 degrees, angle (506) is 0 degrees, angle
(508) 90 degrees, angle (510) 70 degrees, angle (512) 3
0 degrees. In this liquid crystal display device, the coloring and the contrast ratio are further improved as compared with Example 2, and
This was comparable to a liquid crystal display device using a liquid crystal cell for hue compensation. In addition, the first stretched film (1)
The retardation value R of a) is 300 nm, the retardation value R of the second stretched film (2a) is 100 nm, and the respective stretch directions are parallel to each other. A photoisotropic film (3) consisting of a 50 μm-thick cellulose triacetate film was laminated and bonded on both sides of the film with a urethane-based adhesive to form a layer structure of (3) / (1a) / (2a) / (3). Was produced. The retardation value of this retardation plate was 400 nm, and the wavelength dispersion value ν _RF was 1.16. Using two of the retardation plates, a liquid crystal display device having a configuration of a polarizing plate / a retardation plate / a liquid crystal cell / a retardation plate / a polarizing plate was produced. FIG. 4 shows a schematic diagram of this liquid crystal display device. Liquid crystal cell (302)
There is a transparent electrode (304) and a rubbed alignment film (305)
The substrate (303) on which is formed opposes via a spacer (306), and is filled with liquid crystal (307). This liquid crystal cell (302)
There are retardation plates (309) and (310) on both sides of this, which are sandwiched between an upper polarizing plate (301) and a lower polarizing plate (308). When the liquid crystal display device of FIG. 4 is viewed from above, the relationship between the axes can be shown in the same manner as in FIG. Also in this case, the direction of the angle is positive in the clockwise direction. The product Δnd of the refractive index anisotropy Δn of the liquid crystal and the cell thickness d was set to 0.86 μm. At this time, the twist angle of the liquid crystal (50
1) from bottom to top clockwise 240 degrees, angle (503)
30 degrees, angle (506) 80 degrees, angle (508) 10
The degree and angle (510) were set to 110 degrees, and the angle (512) was set to 70 degrees. This liquid crystal display device was much more improved in coloring and contrast ratio than Example 2, and was comparable to a liquid crystal display device using a hue compensation liquid crystal cell. Further, a liquid crystal display device having the following configuration was manufactured using the liquid crystal cell of Example 1.

1. Polarizing plate / (1a) / (2a) / (1b) / liquid crystal cell / polarizing plate 2. Polarizing plate / (1a) / (2a) / (1b) / (2b) / liquid crystal cell / polarized light Plate 3. Polarizer / (1a) / (1b) / (2a) / (2b) / liquid crystal cell / polarizer 4. Polarizer / (1a) / (2a) / liquid crystal cell / (1b) / polarizer 5 Polarizer / (1a) / (2a) / liquid crystal cell / (1b) / (2b) / polarizer 6. Polarizer / (1a) / (2a) / liquid crystal cell / (2b) / (1b) / polarization Plate 7. Polarizing plate / (1a) / (2a) / (1b) / Liquid crystal cell / (1a) / (2b)
/ (1b) / polarizer 8. Polarizer / (1a) / (2a) / (1b) / (2b) / liquid crystal cell / (1a)
/ (2a) / (1b) / (2b) / Polarizing plate

In the structures 1 to 8, the retardation values R of the first stretched films (1a) and (1b) and the second stretched films (2a) and (2b) are determined according to the respective structures. Set. The liquid crystal display device having the above-described configuration has significantly improved coloring and contrast ratio as compared with the second embodiment, and is comparable to a liquid crystal display device using a hue compensating liquid crystal cell.

[0074]

According to the present invention, the retardation film is a first stretched film.
(1) and the second stretched film (2) have a required retardation value R and a required wavelength dispersion value ν _RF by a skillful combination thereof. The device takes advantage of the advantages of FTN mode, such as lightness, thinness, and brightness, while significantly improving display coloring and a low contrast ratio, which were disadvantages of the device.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a retardation plate of the present invention.

FIG. 2 is a schematic view showing a structure of a liquid crystal display device using the retardation plate of the present invention.

FIG. 3 is a schematic diagram showing a structure of a liquid crystal display device using the retardation plate of the present invention.

FIG. 4 is a schematic diagram showing a structure of a liquid crystal display device using the retardation plate of the present invention.

FIG. 5 is a diagram showing a relationship between axes of a liquid crystal display device used in an example of the present invention.

FIG. 6 is a diagram illustrating a relationship between axes of a liquid crystal display device used in an example of the present invention.

[Explanation of symbols]

(1) ... first stretched film, (2) ... second stretched film, (3) ... optically isotropic film, (4) ... pressure sensitive adhesive layer, (5) ... release sheet, (101) ... upper side (102)… liquid crystal cell, (103)… substrate, (104)… transparent electrode, (105)… alignment film, (106)… spacer, (107)… liquid crystal, (108)… lower polarizing plate (109) ... retardation plate, (201) ... upper polarizing plate, (202) ... liquid crystal cell, (203) ... substrate, (204) ... transparent electrode, (205) ... alignment film, (206) ... spacer, (207)… liquid crystal, (208)… lower polarizer, (209)… retarder, (210)… retarder, (301)… upper polarizer, (302)… liquid crystal cell, (303)… Substrate, (304): Transparent electrode, (305): Alignment film, (306): Spacer, (307): Liquid crystal, (308): Lower polarizing plate, (309): Retardation plate, (310): Position Phase difference plate, (401) ... size of twist angle of liquid crystal, (402) ... rubbing direction of upper substrate, (403) ... upper substrate from horizontal direction (404)… rubbing direction of lower substrate, (405)… polarization axis direction of upper polarizer, (406)… angle from horizontal direction to polarization axis direction of upper polarizer, (407) … The polarization axis direction of the lower polarizing plate, (408)… the angle from the horizontal direction to the polarization axis direction of the lower polarizing plate, (409)… the stretching axis direction of the retardation plate, (410)… phase difference from the horizontal direction (501)… the magnitude of the twist angle of the liquid crystal, (502)… the rubbing direction of the upper substrate, (503)… the angle from the horizontal direction to the rubbing direction of the upper substrate, (504) The rubbing direction of the lower substrate, (505) the polarization axis direction of the upper polarizer, (506) the angle from the horizontal direction to the polarization axis direction of the upper polarizer, (507) the polarization axis direction of the lower polarizer , (508)… the angle from the horizontal direction to the polarization axis direction of the lower polarizer, (509)… the extension axis direction of the upper retardation plate, (510)… upward from the horizontal direction Angle to the stretching axis direction of the phase difference plate, (511) ... stretching axis direction of the lower phase difference plate, (512) ... angle from the horizontal direction to the stretching axis direction of the lower retardation plate

Continued on the front page (72) Inventor Osamu Okumura 3-3-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation (72) Inventor Rinjiro Ichikawa 1-4-6 Nihonbashi Bakurocho, Chuo-ku, Tokyo Fujimori Kogyo Co., Ltd. Inside the company (72) Inventor Kenji Hashimoto 1-4-6 Nihonbashi Bakurocho, Chuo-ku, Tokyo Fujimori Industries Co., Ltd. (72) Inventor Takashi Yamada 1-4-6 Nihonbashi Bakurocho, Chuo-ku, Tokyo Fujimori Kogyo Co., Ltd. (56) References JP-A-2-158701 (JP, A) JP-A-1-127329 (JP, A) JP-A-3-122602 (JP, A) JP-A-1-201607 (JP, A) JP-A-1-270004 (JP, A) JP-A-2-42406 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 5/30 G02F 1/1335 G02F 1/13363

Claims (3)

(57) [Claims] 1. A refractive index n _D of 1.60 or more and an Abbe number ν _D of 3
0.0 or less, a first stretched film (1) in which a polymer film having a glass transition point Tg of 60 to 160 ° C. is stretched in at least one direction, and a polymer film having a refractive index n _D of less than 1.60 is stretched in at least one direction. A retardation plate comprising a laminated film with the second stretched film (2). 2. A laminated film having a retardation value R of 6
0 to 1000 nm, and a wavelength dispersion value ν _RF defined by the formula ν _RF = △ nd · (450 nm) / △ nd · (590 nm) of the first stretched film (1) in the laminated film is 1.10 or more. Claim 1
The retardation plate as described. 3. A liquid crystal display device according to claim 1, wherein at least one phase difference plate according to claim 1 is formed between a pair of polarizing plates sandwiching a liquid crystal cell.