JPH05196818A - Phase difference blank film, phase difference plate and liquid crystal display device formed by using the same - Google Patents

Abstract

PURPOSE:To provide the phase difference plate which can afford a liquid crystal display panel solving the problems of coloration and contrast ratio which are heretofore unsolved. CONSTITUTION:A high-polymer film formed a compsn. consisting of a high polymer (A) which yields a film having >=1.60 refractive index nD <=30.0 Abbe number nuD and 60 to 160 deg.C glass transition point Tg and a high polymer (B) which yields a film having <1.60 refractive index nD is at least uniaxially stretched to obtain a stretched film. The retardation value R of the stretched film is set at 60 to 1000nm and the wavelength dispersion value nuRF at >=1.10. The phase difference plate constituted by laminating an optically isotropic film on the phase difference blank film consisting of such stretched film or at least one surface thereof is used for hue compensation of the liquid crystal display panel.

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 device which can provide a liquid crystal display device with improved display coloring and contrast ratio.

[0002]

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

The incident light becomes linearly polarized light after passing through the first polarizing plate side, and becomes a elliptically polarized light due to a phase difference while passing through the driving liquid crystal cell. The ellipticity and the azimuth angle at that time 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 compensating 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 is substantially black and white. Therefore, if necessary, a color filter can be added to achieve full color.

The STN liquid crystal display device using the driving liquid crystal cell and the hue compensating liquid crystal cell described above has the disadvantages of being thick, heavy and costly, and when it is of a reflective type, it becomes dark. There is also the problem of too much.

Therefore, in order to eliminate this disadvantage, a method using a retardation plate in which optically isotropic films are laminated on both sides of a retardation element film made of a uniaxially stretched polymer film is used instead of the hue compensation liquid crystal cell. (Hereinafter, referred to as FTN mode) is drawing attention. The basic configuration of this FTN mode liquid crystal display device is a polarizing plate / liquid crystal cell / retarder / polarizing plate.

Japanese Unexamined Patent Publication (Kokai) No. 64-519, filed by one of the applicants, shows that polyvinyl alcohol, polyester, polyetheramide, polyethylene, etc. can be used as the uniaxially stretched film for the above purpose. ing.

In Japanese Patent Laid-Open No. 118805/1989, a film made of polyvinyl alcohol or a derivative thereof is stretched uniaxially and then treated with an aqueous solution containing boric acid to form an optically non-oriented film on both sides or one side. A retardation plate laminated with a molecular film is shown. Here, the derivative of polyvinyl alcohol is polyvinyl acetal such as polyvinyl butyral and polyvinyl formal.

In JP-A-1-118819 and JP-A-1-124821, an optical retardation element film formed of an oriented synthetic resin film or an optically isotropic amorphous film is laminated on at least one surface thereof. It has been shown that an optical retardation substrate is used as one transparent electrode supporting substrate that constitutes one of liquid crystal cells. Further, 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, polyether sulfone, polyarylene ester, polyvinyl. It is described that alcohol, ethylene-vinyl alcohol copolymer, polyvinyl chloride, polymethylmethacrylate, polyester, cellulosic polymer and the like are used. Note that both of these applications and the application of Japanese Patent Application Laid-Open No. 2-158701 described below are applications of another of the applicants.

Japanese Patent Laid-Open No. 2-158701 discloses a retardation value of 30 comprising 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 up to 1000 nm are laminated and integrated in a state in which the respective optical axis directions are 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 ABS resin or the like is used.

Japanese Unexamined Patent Publication (Kokai) No. 2-256003 discloses a film formed by uniaxially or biaxially stretching a thermoplastic polymer film having no variation in thickness in the direction perpendicular to the extrusion direction, and its retardation. Value is 1200
nm or less, and the fluctuation range of the retardation value is 10
% Or less is shown mainly for optical films for retardation plates, and as the thermoplastic polymer, a polycarbonate-based resin, a poly (meth) acrylate-based resin, a polystyrene-based resin, an acrylonitrile-based resin, a polyester-based resin ( Polyethylene terephthalate, polyester copolymer, etc.), polyamide resin, polyvinyl chloride resin,
It is said that polyolefin resin, polysulfone, polyether sulfone, fluorine resin and the like are used.

Japanese Unexamined Patent Publication (Kokai) No. 2-256023 discloses a liquid crystal cell in which a film in which molecules having a negative intrinsic birefringence value are plane-oriented and a uniaxially stretched film formed from a polymer having a positive intrinsic birefringence value are used. There is shown a liquid crystal display device which is inserted between a polarizing plate and a polarizing plate.A polystyrene polymer or an acrylate polymer is an example of the former polymer, and a polycarbonate is 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 retardation film having a retardation value of 300 to 800 nm obtained by uniaxially stretching a polyvinyl alcohol film is laminated with a polysulfone-based or polyarylate-based film. A retarder is shown.

[0013]

However, a retardation element film made of a uniaxially stretched film prepared from the polymers described in a large number of documents listed above or a retardation obtained by laminating an optically isotropic film on both sides or one side thereof. Depending on the board, ST
The phase difference caused by the N cell cannot be compensated for over all the wavelengths of light, and the problem that coloring occurs and the contrast ratio becomes low could not be sufficiently solved.

Therefore, although the problem of the thickness and weight of the STN liquid crystal display device using the driving liquid crystal cell and the hue compensating liquid crystal cell is solved, the hue compensating liquid crystal cell is still used for the coloring and the 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.

According to the present invention, in the FTN mode in which a retardation film or a retardation plate is used for hue compensation in a liquid crystal display device,
The purpose is to fundamentally solve the problems of coloring and control ratio, which have been a problem in the past.

[0016]

The retardation element film of the present invention comprises:
A polymer (A) which gives a 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. and a polymer (B) which gives a film having a refractive index n _D of less than 1.60. ) A polymer film formed from the composition (1) and a stretched film obtained by stretching at least uniaxially. Further, the liquid crystal display device of the present invention is characterized in that at least one layer of the retardation film is formed between a pair of polarizing plates sandwiching a liquid crystal cell.

In this case, the retardation value R of the stretched film is 60 to 1000 nm and the wavelength dispersion value ν _RF defined by the formula ν _RF = Δn · d (450 nm) / Δn · d (590 nm) is 1.10. The above is particularly desirable.

The retardation plate of the present invention is formed by laminating an optically isotropic film on at least one surface of the retardation element film. Further, another liquid crystal display device of the present invention is characterized in that at least one layer of the retardation plate is formed between a pair of polarizing plates sandwiching a liquid crystal cell.

The present invention will be described in detail below.

Polymer (A) As the polymer (A), the refractive index n _D is 1.60 or more, the Abbe number ν _D is 30.0 or less, and the glass transition point Tg is 60 to 160 ° C. A polymer that gives a film is used.

The refractive index n _D means the refractive index for the D line (589 nm) measured according to ASTM D-542. When the refractive index n _D is less than 1.60, other conditions are satisfied. Unable to solve the problem of coloring and contrast ratio.

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

The glass transition point Tg is 60 to 160 ° C.
It is also required that the glass transition point Tg is less than 60 ° C, the heat resistance is insufficient, while the glass transition point Tg is 160 ° C.
When it exceeds, the stretchability is impaired.

The polymer (A) satisfying the above three conditions is a brominated or chlorinated phenoxyether polymer, polyethylene naphthalate, bisphenol-
Aromatic dicarboxylic acid polycondensates (bisphenol A, tetrabromobisphenol A, 1,1-bis- (4-hydroxyphenyl) -cyclohexane, 4,4′-dihydroxytetraphenylmethane, bisphenol S and other bisphenols, and terephthalic acid , Isophthalic acid, naphthalene-2,6-dicarboxylic acid, pyridine-2,5-dicarboxylic acid, diphenyl-4,4-dicarboxylic acid and other dicarboxylic acids or their polycondensates with derivatives), polyvinylnaphthalene, polyvinylcarbazole, Examples include polypentabromophenyl methacrylate, polypentachlorophenyl methacrylate, poly α-naphthyl methacrylate, poly p-divinylbenzene and the like. The polymer (A) may be a copolymer (including a graft copolymer), a coexisting polymer, a post-modified product, a blended product and the like.

Of these polymers, brominated or chlorinated phenoxy ether type crosslinkable resins and polyethylene naphthalate are particularly important. The characteristic values of the films made of these polymers are also influenced by the molecular weight, the film forming method, the degree of halogenation, etc., but the 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 Polyvinylcarbazole 1.68 19 84 Poly p-divinylbenzene 1.62 28 106

The polymer film conventionally proposed as a retardation film has a refractive index n _D , an Abbe number ν _D or a glass transition point Tg which is out of the above range as described below. I cannot fulfill my purpose.

Polycarbonate: n _D is 1.58 to 1.59 Polymethylmethacrylate: n _D is 1.49, ν _D is 57 Polyvinyl alcohol: n _D is 1.49 to 1.53 Polyethylene terephthalate: n _D is 1.53 Polyethylene: n _D is 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 Cellulose 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 : N _D 1.60 Weak polytetrafluoroethylene: n _D 1.35

Polymer (B) As the polymer (B), a polymer that gives a film having a refractive index n _D of less than 1.60 is used. However, the refractive index n _D
When the value becomes smaller, the light scattering occurs when a film is formed by blending with the polymer (A). Therefore, the refractive index n _D is preferably 1.50 or more.

[0030] The polymer (B) is not particularly limited Abbe number [nu _D Unlike polymer (A), Abbe number [nu _D
May be 30.0 or less or may exceed 30.0, but 30.0
Since there are few things below, it usually exceeds 30.0 in many cases. Regarding the glass transition point Tg, the polymer (A)
Because heat resistance and stretchability are secured by blending with
It does not matter if the temperature is lower than 60 ° C or higher than 160 ° C.

As the polymer (B) for this purpose, polycarbonate, phenoxy ether polymer, polystyrene, nylon 6, polybutylene terephthalate, polyarylate, polysulfone, polyether sulfone, polyphenylene sulfide, polyphenylene oxide,
Examples include polyparabanic acid resin and the like.

A polymer film is obtained by forming a film of the composition of the polymer (A) and the polymer (B). A casting method or a melt molding method is adopted as a film forming method.

The stretching of the polymer film is usually carried out at a temperature which is 5 to 40 ° C., especially 10 to 30 ° C. higher than the glass transition point Tg thereof or a temperature around it, and aging is carried out after the stretching. Preferably. The stretching ratio is generally 1.1 to 6 times, particularly 1.2 to 4 times in one direction. It is also possible to stretch in one direction while limiting the stretching ratio in the orthogonal direction or suppressing contraction in the orthogonal direction. In this case, biaxial stretching is performed.

The retardation value R of the stretched film is 6
It is particularly desirable that the thickness is 0 to 1000 nm. When the retardation value R of the stretched film is less than 60 nm, the retardation function is insufficient. On the other hand, when it exceeds 1000 nm, the film thickness has to be extremely increased. The hue compensation effect is reduced.

[0035] Here, the retardation value R, wherein _{R = d · | n 1 -n} 2 | = △ n · d ( although, d is the thickness of the film, n ₁ is a refractive optical axis direction or perpendicular direction The refractive index, n ₂ is a refractive index orthogonal to the n ₁ direction, and the refractive index is for sodium D line).

It is particularly desirable that the stretched film 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 formula ν _RF = Δn · d (450 nm) / Δn · d (590 nm). If this value is less than 1.10, the dispersibility is insufficient and the display The problem of coloring and contrast ratio cannot be solved. Chromatic dispersion value ν _RF is 1.10 to 1.18
As described above, it is preferable to have the same value as that of the liquid crystal, but depending on the compensation condition of the liquid crystal cell, a large value of 1.2 or more may cause a remarkable hue compensation effect.

Therefore, in order to obtain such retardation value and wavelength dispersion value ν _RF , the blending ratio of the polymer (A) and the polymer (B), the thickness of the polymer film and the stretching conditions should be selected. Is. The weight ratio of the polymer (A) to the polymer (B) is 20:80 to 95: 5, preferably 3
It is often selected from the range of 0:70 to 90:10, but it is not necessarily limited to this range.

Retardation Element Film The retardation element film made of the above stretched film is usually formed by laminating and protecting an optically isotropic film on at least one surface thereof to form a retardation plate.

As the optically isotropic film for this purpose, a cellulosic polymer (for example, cellulose triacetate), polycarbonate, polyparabanic acid resin, polystyrene, polyether sulfone, polyarylene ester, polysulfone, polyvinyl chloride, poly-4 is used. -Methylpentene, polyphenylene oxide, air-permeable resin, cured crosslinkable resin and the like. Here, the air-permeable resin is polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyacrylonitrile, polyvinylidene chloride, etc., and the crosslinkable resin cured product is a phenoxyether type crosslinkable resin, epoxy resin, acrylic resin, acrylic epoxy resin. It is also possible to use not only a monolayer film but also a multi-layer film such as an ethylene-vinyl alcohol copolymer / phenoxy ether type crosslinkable resin. The retardation value of the optically isotropic film is preferably 30 nm or less, more preferably 10 nm or less.

Laminating a release sheet on at least one surface of the above retardation film or retardation plate with a pressure-sensitive adhesive layer interposed between them is advantageous in handling the liquid crystal display device.

The retardation element film or retardation plate of the present invention is laminated and integrated with a polarizing plate to form a retardation plate with a polarizing plate, or as a substrate of a liquid crystal cell or a substrate before manufacturing a liquid crystal cell. It is also possible to use a liquid crystal cell substrate with a retardation plate.

The retardation element film or retardation plate of the present invention is S
It is particularly useful as a retardation element film or retardation plate used in hue compensation used in a liquid crystal display device of TN (Super Twisted Nematic) system, that is, in FTN mode. In addition, it can also be used in applications such as transparent bodies for goggles, transparent bodies for antiglare, and optical filters.

[0043]

According to the research conducted by the present inventors, the refractive index n _D is 1.60.
Above, Abbe number ν _D is 30.0 or less, glass transition point Tg is 6
It has been found that a polymer film of 0 to 160 ° C. stretched in at least a uniaxial direction has a “quality” that the wavelength dispersion value ν _RF becomes large. Therefore, when a polymer film having such characteristic values is selected and stretched in consideration of the thickness, the retardation value is 60 to 100.
It is possible to obtain a stretched film having a wavelength dispersion value ν _{RF of} 0 nm of 1 nm or more. Since this stretched film has a large wavelength dispersion value ν _RF, when it is used as a retardation film (two or more films can be used), coloring and contrast ratio can be remarkably improved.

However, a polymer having the above-mentioned characteristic values is generally expensive, and the film-forming property and the stretchability are not always smooth, which is disadvantageous in terms of cost and also in the manufacturing process. It may require high technology. Therefore, in the present invention, while paying attention to the refractive index n _D of the polymer (B) so as not to cause light scattering, the polymer (B) is blended with the polymer (A) for balance and necessary. The retardation value R and the wavelength dispersion value ν _RF are secured.

[0045]

EXAMPLES The present invention will be further described with reference to examples. Hereinafter, “parts” means parts by weight.

Example 1 Refractive index n _D 1.64 and Abbe number ν _D 2 when cast film formation
4, a brominated phenoxyether resin having a bromine content of 52.9% by weight (YPB-manufactured by Tohto Kasei Co.
43C), a refractive index n _D 1.59, an Abbe number ν _D 30.3, and a glass transition point Tg 13 measured by DSC when a casting film is formed.
A polycarbonate that gives 5 ° C. was prepared.

[0047]

[Chemical 1]

A solution prepared by dissolving 20 parts of the above-mentioned brominated phenoxyether resin and 5 parts of polycarbonate in 75 parts of cyclohexanone was cast on a polyester film as a support, and the mixture was mixed until the residual solvent amount became 5% by weight. After being completely dried, it was peeled from the polyester film and then dried until the residual solvent disappeared. The obtained film had a thickness of 110 μm, a refractive index n _D of 1.63, an Abbe number ν _D of 25, and a glass transition point Tg measured by DSC.
Was 138 ° C. and the retardation value R was 2 nm.

Next, this film was stretched twice in one direction at a temperature of 162 ° C., and after aging at the same temperature for 8 seconds, both edges were cut. As a result, the thickness is 78μ
m, retardation value R is 575 nm, wavelength dispersion value ν _RF
Since a retardation element film composed of a stretched film of 1.13 was obtained, an optical isotropic film made of a cellulose triacetate film having a thickness of 60 μm was laminated and adhered on both sides of the retardation element film with a urethane adhesive. A retardation plate was produced.

A release sheet with a pressure-sensitive adhesive layer, in which a 30-μm-thick acrylic pressure-sensitive adhesive layer was previously formed on the release-treated surface of a 40-μm-thick polyester film release sheet, was prepared. Laminated on both sides of the plate. When the retardation plate is used, only the release sheet is peeled off and attached to the object.

Using this retardation plate, a liquid crystal display device having a constitution of polarizing plate / liquid crystal cell / retardation plate / polarizing plate was produced. FIG. 1 shows a schematic view of a liquid crystal display device using the retardation plate of this embodiment. The liquid crystal cell (102) has a substrate (10) on which a transparent electrode (104) and a rubbing-treated alignment film (105) are formed.
3) face each other with a spacer (106) in between and are filled with liquid crystal (107). Below the liquid crystal cell (102), a retarder (1
09), which is the upper polarizing plate (101) and the lower polarizing plate (10).
8) FIG. 4 shows the relationship of each axis when the liquid crystal display device of FIG. 1 is viewed from above. (401) is the size 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) The rubbing direction of the lower substrate. (406) is the angle from the horizontal direction to the polarization axis direction of the upper polarizing plate (405), (408) is the angle from the horizontal direction to the polarization axis direction of the lower polarizing plate (407),
(410) is the angle from the horizontal direction to the stretching axis direction (409) of the retardation plate. The angle direction is positive in the clockwise direction. 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) to 65 degrees, angle (408) to 95 degrees, angle (410) to 50 degrees
The degree As the polarizing plate, a polarizing plate having a visible light transmittance of 42% and a polarization degree of 99% obtained by sticking a cellulose triacetate film on 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 composition shown below.

[0052]

[Chemical 2]

This liquid crystal display device has not only a great improvement in coloring and contrast ratio but also a slight improvement in brightness, and is substantially comparable to the liquid crystal display device using the hue compensating liquid crystal cell. It was a thing. In addition,
A retardation element film may be used instead of the retardation plate.

Example 2 Refractive index n _D 1.65 and Abbe number ν _D 1 when melt-casting
8. Polyethylene naphthalate which gives a glass transition point Tg of 113 ° C. measured by DSC, and polyethylene which gives a refractive index n _D 1.56, an Abbe number ν _D 36 and a glass transition point Tg of 72 ° C. measured by DSC when melt-casting Prepared terephthalate.

A composition having a weight ratio of polyethylene naphthalate and polyethylene terephthalate of 70:30 was supplied to an extruder and melt-cast at a temperature of 290 ° C. to obtain a thickness of 9
A film having a thickness of 2 μm, a glass transition point Tg of 108 ° C. and a retardation value R of 18 nm was obtained.

Next, this film was stretched 1.9 times in one direction at a temperature of 125 ° C., and after aging at the same temperature for 4 seconds, both ears were cut. This makes the thickness 65
μm, retardation value R is 575 nm, wavelength dispersion value ν
_A retardation element film (retardation plate) composed of a stretched film having an _RF of 1.15 was obtained.

Using this retardation plate, a liquid crystal display device was manufactured in the same manner as in Example 1. This liquid crystal display device was significantly improved in coloring and contrast ratio, and was substantially comparable to the liquid crystal display device of the system using the 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 according to Example 1 were obtained.

Comparative Example 1 A polycarbonate film was produced by a casting method. Thickness is 170 μm, refractive index n _D is 1.59, 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, this film was stretched twice in one direction at a temperature of 170 ° C., and after aging at a temperature of 165 ° C. for 6 seconds, both ears were cut to have a thickness of 110 μm and a retardation value R of 570 nm. A retardation film made of a stretched film having a wavelength dispersion value ν _RF of 1.09 was obtained.

Then, a thickness of 50 μm is formed on both surfaces of this retardation film.
An optically isotropic film made of a cellulose triacetate film of m 2 was laminated and adhered with a urethane adhesive to prepare a retardation plate.

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

Comparative Example 2 In the same manner as in Comparative Example 1, polymethylmethacrylate, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyethylene terephthalate, polybutylene terephthalate, polyethylene, polypropylene, polyvinyl chloride, polystyrene, phenoxy ether-based polymer. Coalescing,
Regarding polyacrylonitrile, a uniaxially stretched film having a draw ratio of 1.5 to 4 was prepared, and an optically isotropic film made of a cellulose triacetate film was attached to both surfaces of the film to form a retardation plate, which was then incorporated into a liquid crystal display device. The display was colored similarly to the above and the contrast ratio was low.

Example 4 Refractive index n _D 1.65 and Abbe number ν _D 1 when melt-casting
8. Polyethylene naphthalate which gives a glass transition point Tg of 113 ° C. measured by DSC, and polyethylene which gives a refractive index n _D 1.56, an Abbe number ν _D 36 and a glass transition point Tg of 72 ° C. measured by DSC when melt-casting A composition having a weight ratio of terephthalate of 70:30 is supplied to an extruder to form a melt film, and then stretched in one direction to have a thickness of 78 μm, a retardation value R of 420 nm and a wavelength dispersion value ν _RF of 1.14.
To obtain a retardation film.

A liquid crystal display device having a constitution of polarizing plate / liquid crystal cell / retarding film / retarding film / polarizing plate was produced by using two sheets of this retardation film. FIG. 2 shows a schematic view of a liquid crystal display device using the retardation film of this embodiment. Liquid crystal cell (20
2) includes a transparent electrode (204) and an alignment film (20
The substrate (203) on which (5) is formed faces each other through the spacer (206) and is filled with the liquid crystal (207). This liquid crystal cell (2
The retardation element films (209) and (210) are located on the lower side of 02) and are sandwiched between the upper polarizing plate (201) and the lower polarizing plate (208). FIG. 5 shows the relationship between the axes when the liquid crystal display device of FIG. 2 is viewed from above.
Shown in. (501) is the size of the twist angle of the liquid crystal, (503) is from the horizontal direction to the rubbing direction of the upper substrate of the liquid crystal cell (202) (5
The angle up to 02), and (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 polarizing plate (505), (508) is the angle from the horizontal direction to the polarization axis direction of the lower polarizing plate (507), and (510) is the horizontal direction. The 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 angle direction is positive in the clockwise direction.
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
The angle (512) was 0 degree and 30 degrees. This liquid crystal display device was further improved in coloring and contrast ratio as compared with Example 2, and was comparable to the liquid crystal display device using the hue compensating liquid crystal cell. The same as above by using three or more retardation film having a retardation value R different from that of the retardation film instead of the two retardation films between the polarizing plate and the liquid crystal cell. Further, the coloring and the contrast ratio can be further improved.
A retardation plate may be used instead of the retardation film.

Example 5 Refractive index n _D 1.65 and Abbe number ν _D 1 when melt-casting
8. Polyethylene naphthalate which gives a glass transition point Tg of 113 ° C. measured by DSC, and polyethylene which gives a refractive index n _D 1.56, an Abbe number ν _D 36 and a glass transition point Tg of 72 ° C. measured by DSC when melt-casting A composition having a weight ratio of terephthalate of 75:25 was fed to an extruder to form a melt film, and then stretched in one direction to have a thickness of 85 μm, a retardation value R of 400 nm, and a wavelength dispersion value ν _RF of 1.06.
To obtain a retardation film.

A liquid crystal display device having a structure of polarizing plate / retarding film / liquid crystal cell / retarding film / polarizing plate was produced by using two sheets of this retardation film. FIG. 3 shows a schematic view of a liquid crystal display device using the retardation film of this embodiment. Liquid crystal cell (30
2) is a transparent electrode (304) and an alignment film (30
The substrate (303) on which (5) is formed faces each other through the spacer (306) and is filled with the liquid crystal (307). This liquid crystal cell (3
There are retarder films (309) and (310) on both sides of 02), which are sandwiched between the upper polarizing plate (301) and the lower polarizing plate (308). Even when the liquid crystal display device of FIG. 3 is viewed from above, the relationship between the axes is as shown in FIG.
Can be shown as well. Also in this case, the angle direction is positive in the clockwise direction. Liquid crystal refractive index anisotropy Δn and cell thickness d
The product .DELTA.nd of .DELTA. At this time, the twist angle (501) of the liquid crystal is 240 degrees clockwise from the bottom to the top.
(503) is 30 degrees, angle (506) is 80 degrees, angle (508) is 1
The angle (510) was 0 degrees, the angle (510) was 110 degrees, and the angle (512) was 70 degrees. This liquid crystal display device was further improved in coloring and contrast ratio as compared with Example 2, and was comparable to the liquid crystal display device using the hue compensating liquid crystal cell. By using two or more retardation element films having retardation values R different from those of the above retardation element films on one or both of the retardation element films arranged on both sides of the liquid crystal cell, coloring and The contrast ratio can be further improved. A retardation plate may be used instead of the retardation film.

[0068]

The retardation element film or retardation plate of the present invention is
Since the polymer (A) and the polymer (B) are skillfully combined to form a film, and then the film is stretched, a stretched film having the required retardation value R and wavelength dispersion value ν _RF is obtained. A liquid crystal display device incorporating a retardation film or a retardation plate remarkably improves the coloring and low contrast ratio of the display, which are the drawbacks, while utilizing the advantages of the FTN mode such as lightness, thinness and brightness. Has been done.

[Brief description of 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 view 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 of axes of a liquid crystal display device used in an example of the present invention.

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

[Explanation of symbols]

(101) ... upper polarizing plate, (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 polarizing plate, (209) ... retardation element film, (210) ... retardation element film, (301) ... upper polarizing plate, (302) ... Liquid crystal cell, (303) ... Substrate, (304) ... Transparent electrode, (305) ... Alignment film, (306) ... Spacer, (307) ... Liquid crystal, (308) ... Lower polarizing plate, (309) ... Phase difference Elementary film, (310) ... retardation elemental 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 direction of upper polarizing plate, (406) ... horizontal direction Angle from the direction to the polarization axis of the upper polarization plate, (407) ... the polarization axis direction of the lower polarization plate, (408) ... the angle from the horizontal direction to the polarization axis direction of the lower polarization plate, (409) ... position Stretching axis direction of retardation plate, (410) ... angle from horizontal direction to stretching axis direction of retardation plate, (501) ... size of twist angle of liquid crystal, (502) ... rubbing direction of upper substrate, (503) … Angle from horizontal direction to rubbing direction of upper substrate, (504)… Rubbing direction of lower substrate, (505)… Polarizing axis direction of upper polarizing plate, (506)… Polarizing axis direction of upper polarizing plate Angle of (507) ... polarization direction of lower polarizing plate, (508) ... angle from horizontal direction to polarization axis of lower polarizing plate, (509) ... stretching direction of upper retardation film, (510)… An 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 up to the stretch axis direction of the differential element film

 ─────────────────────────────────────────────────── ─── Continuation of 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 Industrial Co., Ltd. (72) Inventor Kenji Hashimoto 1-4-6 Nihonbashi Bakurocho, Chuo-ku, Tokyo Fujimori Kogyo Co., Ltd. (72) Takashi Yamada 1-4-6 Nihonbashi Bakuro-cho, Chuo-ku, Tokyo Fujimori Industrial Co., Ltd. In the company

Claims (5)

[Claims] 1. A refractive index n _D of 1.60 or more and an Abbe number ν _D of 3
A polymer film formed from a composition of a polymer (A) which gives a film having a glass transition point Tg of 60 to 160 ° C. of 0.0 or less and a polymer (B) which gives a film having a refractive index n _D of less than 1.60. A retardation element film comprising a stretched film obtained by stretching at least uniaxially. 2. A stretched film having a retardation value R of 6
The wavelength dispersion value ν _RF defined by the formula ν _RF = Δn · d (450 nm) / Δn · d (590 nm) is 0 to 1000 nm and is 1.10 or more.
The retardation plate described. 3. A retardation plate obtained by laminating an optically isotropic film on at least one surface of the retardation element film according to claim 1. 4. A liquid crystal display device, wherein at least one layer of the retardation film of claim 1 is formed between a pair of polarizing plates sandwiching a liquid crystal cell. 5. A liquid crystal display device, wherein at least one layer of the retardation film of claim 3 is formed between a pair of polarizing plates sandwiching a liquid crystal cell.