JP3313406B2 - Retardation film, retardation 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 film, a retardation plate, and a liquid crystal display using the same, which can provide a liquid crystal display with improved display coloring and contrast ratio.

[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 board, ST
The phase difference generated by the N cell cannot be compensated for all wavelengths of light, and the problems of coloring and lowering the contrast ratio cannot be sufficiently solved.

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]

Means for Solving the Problems The retardation film of the present invention comprises:
It is made of a stretched film obtained by stretching 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. Further, the retardation plate of the present invention is obtained by laminating an optically isotropic film on at least one side of the retardation film. Further, the liquid crystal display device of the present invention is characterized in that at least one of the above-described retardation films or retardation plates is formed between a pair of polarizing plates sandwiching a liquid crystal cell.

In this case, when the retardation value R of the stretched film is 60 to 1000 nm and the wavelength dispersion value ν _RF defined by ν _RF = △ nd · (450 nm) / △ nd · (590 nm) is 1.10 or more. It is particularly desirable.

Hereinafter, the present invention will be described in detail.

As described above, the retardation film of the present invention has the following properties: 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. It is composed of a stretched film obtained by stretching a polymer film satisfying all requirements at least in a uniaxial direction.

The refractive index n _D refers to the refractive index with respect to the D line (589 nm) measured in accordance with ASTM D542. When the refractive index n _D is less than 1.60, coloring or coloring may occur even if other conditions are satisfied. The problem of the 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 film satisfying the above three conditions include brominated or chlorinated phenoxy ether polymers, polyethylene naphthalate, bisphenol-aromatic dicarboxylic acid polycondensates (bisphenol A,
Tetrabromobisphenol A, 1,1-bis- (4-
(Hydroxyphenyl) -cyclohexane, 4,4′-dihydroxytetraphenylmethane, bisphenol such as bisphenol S, terephthalic acid, isophthalic acid,
Naphthalene-2,6-dicarboxylic acid, pyridine-2,5
Polycondensates with dicarboxylic acids such as dicarboxylic acid and diphenyl-4,4-dicarboxylic acid or derivatives thereof), polyvinyl naphthalene, polyvinyl carbazole, polypentabromophenyl methacrylate, polypentachlorophenyl methacrylate, poly α-naphthyl methacrylate, poly A polymer film such as p-divinylbenzene is exemplified. The film only needs to finally satisfy the refractive index n _D , Abbe number ν _D and glass transition point Tg defined above, and may be a copolymer (including a graft copolymer), a coexisting polymer, It may be a film of a modified product, a film of a blend of two or more polymers having different characteristic values such as a refractive index, 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 6: n _D but 1.52 to 1.53, [nu _D is 40 ABS resin: n _D 1.54 polyester copolymer: n _D is phenoxyether polymer that 1.52 to 1.57 without brominated or chlorinated Body: n _D is slightly less than 1.60 Polytetrafluoroethylene: n _D is 1.35

The retardation film of the present invention comprising the above stretched film has a retardation value R of 60 to 1000 nm.
It is particularly desirable that the wavelength dispersion value ν _RF is 1.10 or more.

Here, the retardation value R is expressed by the following formula: R = d · | n ₁ −n ₂ | = △ _nd (where d is the thickness of the film, and n ₂ is the refractive index in the optical axis direction or in the direction perpendicular thereto). , n ₂ is a refractive index perpendicular to n ₁ direction, Note refractive index is an index represented by ones) to sodium D line. This retardation value R is 60 nm
If it is less than 1,000 nm, the retardation function is insufficient. On the other hand, if it exceeds 1000 nm, the thickness of the film must be extremely large. If the thickness is too large, the optical uniformity is impaired and the hue compensation effect is reduced.

The chromatic dispersion value ν _RF is an index defined by ν _RF = △ nd · (450 nm) / △ nd · (590 nm). If this value is less than 1.10, the dispersibility is insufficient, and The problem of coloring and contrast ratio cannot be solved. 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 retardation value R of the stretched film is 60 to 1000 nm and the wavelength dispersion value ν _RF is 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.

The retardation film made of the stretched film obtained as described above can be used as a retardation plate as it is, but is protected by laminating an optically isotropic film on at least one surface thereof. It can also be.

Examples of the optically isotropic film for this purpose include cellulose polymers (for example, cellulose triacetate), polycarbonate, polyparabanic acid resins, polystyrene, polyether sulfone, polyarylene esters, polysulfone, polyvinyl chloride, and poly-4. -Methylpentene, polyphenylene oxide, air-permeable resin, crosslinked resin cured product, and the like. 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 is laminated on at least one surface of the retardation film or the retardation plate via a pressure-sensitive adhesive layer,
It is advantageous in handling until it is used for manufacturing a liquid crystal display device.

The retardation film or the retardation plate may be laminated and integrated with a polarizing plate to form a retardation plate with a polarizing plate, or may be laminated and integrated with a substrate of a liquid crystal cell or a substrate before manufacturing the liquid crystal cell. A liquid crystal cell substrate with a plate can also be used.

The retardation film or retardation plate of the present invention is
It is particularly useful as a hue compensation used for a TN (super twisted nematic) type liquid crystal display device, that is, a retardation film or a retardation plate used for 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.

[0038]

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 in consideration of the thickness, the retardation value R is 60 to 1000 nm.
And a stretched film having a wavelength dispersion value ν _RF of 1.10 or more can be obtained. Since this stretched film has a large wavelength dispersion value, if this is used as a retardation film or as a retardation plate in which an optically isotropic film is laminated on at least one side, the coloring and contrast ratio can be significantly improved. it can. It should be noted that two or more such retardation films or retardation plates can be incorporated in one liquid crystal display device.

[0039]

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

Example 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.) 30
Parts by weight of cyclohexanone and dioxane are 50:
After casting a solution dissolved in 70 parts of a mixed solvent of 50, 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 98μ.
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 3 nm, and heat distortion temperature (JIS K6911) is 1.
It was 11 ° C.

[0041]

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. As a result, the thickness becomes 58μ.
m, retardation value R is 570 nm, wavelength dispersion value ν _RF
Was obtained from a stretched film having a thickness of 1.14, and a photo-isotropic film made of a cellulose triacetate film having a thickness of 50 μm was laminated and bonded on both sides of the retardation film with a urethane-based adhesive. A retardation plate was produced.

A release sheet with a pressure-sensitive adhesive layer having a 30 μm-thick acrylic pressure-sensitive adhesive layer formed on the release-treated surface of a release sheet made of a polyester film having a thickness of 40 μm was prepared. Laminated on both sides. When the retardation plate is used, it is attached to the target object while removing and removing only the release sheet.

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. 1 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. 4 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.

[0045]

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. In addition,
A phase difference element film may be used instead of the phase difference plate.

Example 2 A polyethylene naphthalate film obtained by a melt extrusion molding method was prepared. The thickness of this film is 150μ
m, 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, this film was stretched 1.9 times in one direction at a temperature of 130 ° C., aged at the same temperature for 3 seconds, and the ends of both ears were cut.

As a result, a retardation film composed of a stretched film having a thickness of 97 μm, a retardation value R of 570 nm, and a wavelength dispersion value ν _RF of 1.18 was obtained.

Using this retardation film, 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 produced by a casting method. The thickness is 170 μm, the refractive index n _D is 1.58, and the Abbe number ν _D is 3.
0.3, the glass transition point Tg was 140 ° C., and the retardation value R was 7 nm.

Next, the film was stretched twice in one direction at a temperature of 170 ° C., aged at a temperature of 165 ° C. for 6 seconds, and the ends of both ears were cut. The thickness was 110 μm and the retardation value R was 570 nm. As a result, a retardation film consisting of a stretched film having a wavelength dispersion value ν _RF of 1.09 was obtained.

Next, a thickness of 50 μm was formed on both sides of the retardation film.
An optically isotropic film made of a cellulose triacetate film having a thickness of m was bonded and laminated 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 In the same manner as in Comparative Example 1, polymethyl methacrylate, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyethylene terephthalate, polybutylene terephthalate, polyethylene, polypropylene, polyvinyl chloride, polystyrene, phenoxy ether-based polymer Coalescing,
As for polyacrylonitrile, a uniaxially stretched film having a draw ratio of 1.5 to 4 was prepared, and an optically isotropic film composed of a cellulose triacetate film was adhered to both sides of the film to form a retardation plate, and then incorporated in a liquid crystal display device. The display was colored in the same manner as in Example 1 and the contrast ratio was low.

Example 4 A polyethylene naphthalate film having a thickness of 110 μm obtained by a melt extrusion molding method was prepared. This film had 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.

This film is unidirectional at a temperature of 130 ° C.
After stretching 1.9 times, aging was performed at the same temperature for 3 seconds to give a thickness of 75 μm and a retardation value R of 4
A retardation film composed of a stretched film having a wavelength dispersion value of 20 nm and a wavelength dispersion ν _RF of 1.18 was obtained.

Using the two retardation films, a liquid crystal display device having a structure composed of a polarizing plate / liquid crystal cell / a retardation film / a retardation film / a polarizing plate was produced. FIG. 2 is a schematic diagram of a liquid crystal display device using the retardation film of the present embodiment. Liquid crystal cell (20
2) has a transparent electrode (204) and a rubbed alignment film (20
The substrate (203) on which (5) is formed is opposed via a spacer (206), and is filled with a liquid crystal (207). This liquid crystal cell (2
On the lower side of 02), there are retardation films (209) and (210), which are sandwiched between an upper polarizing plate (201) and a lower polarizing plate (208). FIG. 5 shows the relationship between each axis when the liquid crystal display device of FIG. 2 is viewed from above.
Shown in (501) is the magnitude of the twist angle of the liquid crystal, and (503) is the rubbing direction (5) of the upper substrate of the liquid crystal cell (202) from the horizontal direction.
The angle up to 02), (504) is the rubbing direction of the lower substrate of the liquid crystal cell (202). (506) is the angle from the horizontal direction to the polarization axis direction of the upper polarizer (505), (508) is the angle from the horizontal direction to the polarization axis direction of the lower polarizer (507), and (510) is the angle from the horizontal direction. Angle to the stretching axis direction (509) of the upper retardation film, (5
12) is from the horizontal direction to the stretching axis direction of the lower retardation film (511).
Up to the angle. 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. At this time, the twist angle (501) of the liquid crystal is 204 degrees clockwise from bottom to top, the angle (503) is 30 degrees, the angle (506) is 0 degrees, the angle (508) is 90 degrees, and the angle (510). 7
0 degree and the angle (512) were 30 degrees. This liquid crystal display device was further improved in coloring and contrast ratio as compared with Example 2, and was comparable to a liquid crystal display device using a hue compensation liquid crystal cell. Note that the same applies to the case where three or more retardation films having a retardation value R different from the retardation film are used between the polarizing plate and the liquid crystal cell instead of the two retardation films. In addition, the coloring and the contrast ratio can be further improved.
Note that a retardation plate may be used instead of the retardation film.

Example 5 A polyethylene naphthalate film having a thickness of 105 μm obtained by a melt extrusion molding method was prepared. This film had 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.

This film is unidirectional at a temperature of 130 ° C.
After stretching 1.9 times, aging was performed at the same temperature for 2 seconds to obtain a thickness of 72 μm and a retardation value R of 4
A retardation film consisting of a stretched film having a wavelength dispersion value of 00 nm and a wavelength dispersion value ν _RF of 1.17 was obtained.

Using the two retardation films, a liquid crystal display device having a structure of a polarizing plate / a retardation film / a liquid crystal cell / a retardation film / a polarizing plate was produced. FIG. 3 is a schematic view of a liquid crystal display device using the retardation film of the present embodiment. Liquid crystal cell (30
2) has a transparent electrode (304) and a rubbed alignment film (30
The substrate (303) on which (5) is formed opposes via a spacer (306) and is filled with liquid crystal (307). This liquid crystal cell (3
02), there are retardation films (309) and (310) on both sides, which are sandwiched between an upper polarizing plate (301) and a lower polarizing plate (308). When the liquid crystal display device of FIG. 3 is viewed from above, the relationship between the respective axes is as shown in FIG.
Can be shown in the same way as Also in this case, the direction of the angle is positive in the clockwise direction. Liquid crystal refractive index anisotropy Δn and cell thickness d
Was set to 0.86 μm. At this time, the liquid crystal twist angle (501) is clockwise clockwise 240 degrees from bottom to top.
(503) is 30 degrees, angle (506) is 80 degrees, angle (508) is 1
The angle (510) was set to 110 degrees and the angle (512) was set to 70 degrees. This liquid crystal display device was significantly improved in coloring and contrast ratio as compared with Example 2, and was comparable to a liquid crystal display device using a hue compensation liquid crystal cell. Note that two or more retardation films having a retardation value R different from that of the retardation film are used instead of the two retardation films on one or both of the retardation films disposed on both sides of the liquid crystal cell. This can further improve the coloring and the contrast ratio in the same manner as described above. Further, a retardation plate may be used instead of the retardation film.

Example 6 On a polyester film as a support, a polymer concentration of 80 parts of the brominated phenoxy ether resin of Example 1 and 20 parts of polyarylate dissolved in cyclohexanone was used.
After casting the solution of 0% by weight, it was incompletely dried until the amount of the residual solvent became 5% by weight, then peeled off from the polyester film, and then dried until the residual solvent disappeared.
The thickness of the obtained film is 98 μm, and the refractive index n _D is 1.6.
3, Abbe number ν _D was 27, glass transition point Tg measured by DSC was 156 ° C., and retardation value R was 4 nm.

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. As a result, the thickness is 57 μm.
m, retardation value R is 565 nm, wavelength dispersion value ν _RF
Was obtained, and an optically isotropic film made of a cellulose triacetate film having a thickness of 50 μm was laminated and bonded on both sides of the retardation film with a urethane-based adhesive. A retardation plate was produced.

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.

[0066]

Since the retardation film or retarder of the present invention has the necessary retardation value R and wavelength dispersion value ν _RF , a liquid crystal display incorporating the retardation film or retardation plate is used. In the device, while the lightness, thinness, and brightness, which are the advantages of the FTN mode, are secured, the coloring of the display and the low contrast ratio, which were the disadvantages, are significantly improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a structure of a liquid crystal display device using a retardation plate of the present invention.

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

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

FIG. 4 is a diagram showing a relationship between axes of a liquid crystal display device used in an example 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.

[Explanation of symbols]

(101) ... upper polarizer, (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 film, (210)… retarder film, (301)… upper polarizer, (302)… Liquid crystal cell, (303)… substrate, (304)… transparent electrode, (305)… alignment film, (306)… spacer, (307)… liquid crystal, (308)… lower polarizer, (309)… phase difference Base film, (310) ... phase difference base film, (401) ... magnitude of twist angle of liquid crystal, (402) ... rubbing direction of upper substrate, (403) ... angle from horizontal direction to rubbing direction of upper substrate, (404)… rubbing direction of lower substrate, (405)… polarization axis direction of upper polarizer, (406)… horizontal (407) ... the direction of the polarization axis of the lower polarizer, (408) ... the angle from the horizontal direction to the direction of the polarization axis of the lower polarizer, (409) ... (410) ... angle from horizontal direction to retardation film stretching axis direction, (501) ... magnitude of liquid crystal twist angle, (502) ... rubbing direction of 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 polarization axis direction of the upper polarizer from the horizontal direction (507) ... the direction of the polarizing axis of the lower polarizing plate, (508) ... the angle from the horizontal direction to the polarizing axis of the lower polarizing plate, (509) ... the stretching axis direction of the upper retardation film, (510)… the angle from the horizontal direction to the stretching axis direction of the upper retardation film, (511)… the stretching axis direction of the lower retardation film, (512)… from the horizontal direction to the lower phase Angle to extension axis direction of differential film

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Osamu Okumura 3-3-5 Yamato, Suwa City, Nagano Prefecture Seiko Epson Corporation (72) Inventor Rinjiro Ichikawa 1-4-6 Nihonbashi Bakurocho, Chuo-ku, Tokyo Inside Fujimori Kogyo Co., Ltd. (72) Inventor Kenji Hashimoto 1-4-6 Nihonbashi Bakurocho, Chuo-ku, Tokyo Inside Fujimori Kogyo Co., Ltd. (72) Takashi Yamada 1-4-6 Nihonbashi Bakurocho, Chuo-ku, Tokyo Fujimori Kogyo (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 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 (5)

(57) [Claims] 1. A refractive index n _D of 1.60 or more and an Abbe number ν _D of 3
A retardation film comprising a stretched film obtained by stretching a polymer film having a glass transition point Tg of 60 to 160 ° C. at least in a uniaxial direction at 0.0 or less. 2. A stretched film having a retardation value R of 6
The chromatic dispersion value ν _RF defined by 0 to 1000 nm and ν _RF = △ nd · (450 nm) / △ nd · (590 nm) is 1.10 or more.
The retardation film according to the above. 3. A retardation plate obtained by laminating an optically isotropic film on at least one surface of the retardation film according to claim 1. 4. A liquid crystal display device comprising at least one phase difference element film according to claim 1 formed between a pair of polarizing plates sandwiching a liquid crystal cell. 5. A liquid crystal display device according to claim 3, wherein at least one phase difference plate according to claim 3 is formed between a pair of polarizing plates sandwiching a liquid crystal cell.