JP2002131540A - Thermoplastic film, phase contrast plate, circular polarizing plate and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic film uniform in the width direction, having optical characteristics less liable to deterioration even with age at high tempera ture and excellent in planeness. SOLUTION: The thermoplastic film is a stretched thermoplastic film whose retardation values Re (450), Re (550) and Re (650) measured at 450 nm, 550 nm and 650 nm wavelength satisfy the expressions: 0.60<Re (450)/Re (550)<0.97, 1.01<Re (650)/Re (550)<1.35, and the heat shrinkage starting temperature of the stretched thermoplastic film is 110-180 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic film, and a retardation plate, a circularly polarizing plate and a liquid crystal display using the same. In particular, the present invention relates to a thermoplastic film and a retardation plate effective as a λ / 4 plate in a reflection type liquid crystal display device including a guest-host type.

[0002]

2. Description of the Related Art A λ / 4 plate has many uses related to an antireflection film and a liquid crystal display device, and has already been actually used. However, even if it is referred to as a λ / 4 plate, most achieve λ / 4 at a specific wavelength. λ
If the wavelength region where / 4 can be achieved is narrow, there is a problem that the contrast of the displayed image is reduced. JP-A-5-27
Nos. 118 and 5-27119 disclose a retardation plate in which a birefringent film having a large retardation and a birefringent film having a small retardation are laminated so that their optical axes are orthogonal to each other. Is disclosed.
If the retardation difference between the two birefringent films is λ / 4 over the entire visible light wavelength range, the retardation plate theoretically functions as a λ / 4 plate over the entire visible light wavelength range. .

Japanese Patent Laid-Open Publication No. Hei 10-68816 discloses that a polymer film having a wavelength of λ / 4 at a specific wavelength and a polymer film of the same material and having a wavelength of λ / 2 at the same wavelength are laminated. A retardation plate that can obtain λ / 4 in the wavelength region is disclosed. JP 1
Japanese Patent Application Publication No. 0-90521 also discloses a retardation plate capable of achieving λ / 4 in a wide wavelength region by laminating two polymer films. Since all of these films are of a laminated type, two films are required and a laminating step is required, so that it has been difficult to reduce the cost. As a technique for solving this problem, Japanese Patent Application Laid-Open No. 2000-137116 discloses a single-type retardation plate using a stretched cellulose acetate film.

[0004]

The use of this retardation plate causes the following problems, so that improvements have been desired. (1) Non-uniformity of optical characteristics (retardation) occurs in the width direction when a film is formed with a width of 0.6 m or more, and color unevenness occurs when the film is incorporated in a liquid crystal display device. (2) When left at a high temperature for a long time, the developed optical characteristics are attenuated. (3) The flatness is poor, and streaks (corrugated sheets) and wrinkles are likely to occur. An object of the present invention is to provide a thermoplastic film which is uniform in the width direction, has optical characteristics that are hardly attenuated even at high temperatures, and has excellent flatness. Another object of the present invention is to provide a liquid crystal display device which is excellent in display quality and has no color spots by using the above-mentioned thermoplastic film or a retardation plate or a polarizing plate using the same.

[0005]

An object of the present invention is to provide a thermoplastic film of the following (1) to (13), a retardation plate of the following (14), a circularly polarizing plate of the following (15), and This has been achieved by the liquid crystal display device of (16). (1) Retardation values measured at wavelengths of 450 nm, 550 nm and 650 nm, Re (450), Re (55)
0), Re (650) is a stretched thermoplastic film satisfying the following formulas (1) and (2), wherein the stretched thermoplastic film has a heat shrinkage onset temperature of 110 ° C. or more and 180 ° C. or less. Characteristic thermoplastic film. 0.60 <Re (450) / Re (550) <0.97: Equation (1) 1.01 <Re (650) / Re (550) <1.35: Equation (2) (2) The above Re (550) is from 120 nm to 160
nm. or less, the thermoplastic film according to (1). (3) The heat according to (1) or (2), wherein the stretched thermoplastic film has an average value of an angle between a slow axis and a stretch axis in the film plane of ± 5 ° or less. Plastic film.

(4) DR0, DR20 and DR40 defined by the following equations (A) to (C) are | DR20 (λ) −DR0 at a wavelength of 450 nm and a wavelength of 750 nm.
(Λ) | ≦ 0.02, | DR40 (λ) −DR0 (λ)
| ≦ 0.02 is satisfied (1)
The thermoplastic film according to any one of (1) to (3). (A) DR0 (λ) = Re (λ) / Re (550) (B) DR20 (λ) = Re20 (λ) / Re20 (5)
50) (C) DR40 (λ) = Re40 (λ) / Re40 (5
50) wherein λ is the measurement wavelength; Re (λ) is the retardation value measured in the direction normal to the film surface;
Re20 (λ) is the retardation value measured at an angle of 20 ° from the normal direction of the film surface;
e40 (λ) is a retardation value measured at an angle of 40 ° from the normal direction of the film surface. (5) The in-plane refractive index nx of the stretched thermoplastic film in the in-plane slow axis direction, and the refractive index n in the direction perpendicular to the in-plane slow axis.
y and the refractive index nz in the thickness direction are 1 ≦ NZ = (nx−
The thermoplastic film according to any one of (1) to (4), which satisfies a relationship of (nz) / (nx−ny) ≦ 2.

(6) The above-mentioned stretched thermoplastic film has an IR two-color ratio of 1.5 or more of the CO stretch on the high stretch ratio side.
The thermoplastic film according to any one of (1) to (5), wherein the IR2 color ratio of CＣO expansion and contraction is 0.6 or more and 1.2 or less. (7) The above-mentioned stretched thermoplastic film has an IR two-color ratio of 1.4 or more and 1.8 or less of C—O expansion / contraction on the low stretch ratio side, and C =
The thermoplastic film according to any one of (1) to (6), wherein an IR two-color ratio of O expansion and contraction is 1.1 or more and 1.5 or less. (8) The thermoplastic film according to any one of (1) to (7), wherein the stretched thermoplastic film is made of acetylated cellulose having a degree of substitution of 2.4 to 2.9. . (9) The thermoplastic film according to any one of (1) to (8), wherein the stretched thermoplastic film is formed of a cellulose acetate film having two or more and ten or less layers laminated.

(10) The stretched thermoplastic film is
The thermoplastic film according to any one of (1) to (9), which is a film obtained by stretching at least uniaxially using at least one pair of nip rolls installed in a thermostat. . (11) The stretched thermoplastic film is a film obtained by being preheated while gradually heating at a temperature of 0.3 ° C./min or more and 50 ° C./min or less, and then stretched to obtain a film (1) to (10). The thermoplastic film according to any one of the above. (12) After stretching, the stretched thermoplastic film has a thickness of 0.
Installed at a distance of at least 05m and at most 0.7m2
The thermoplastic film according to any one of (1) to (11), which is a film obtained by passing at least 30 or more rolls at 50 ° C or more and 160 ° C or less.

(13) The stretched thermoplastic film is
(1) to (12), characterized in that the film is obtained by slow cooling at −0.3 ° C./min to −50 ° C./min after stretching.
The thermoplastic film according to any one of the above. (14) A retardation plate using the thermoplastic film according to any one of (1) to (13). (15) The retardation film and the polarizing film according to (14) are laminated such that the angle between the in-plane slow axis of the retardation film and the polarization axis of the polarizing film is substantially 45 °. A circularly polarizing plate, comprising: (16) A liquid crystal display device comprising at least one of the retardation plate according to (14) and the circularly polarizing plate according to (15).

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Retardation values, Re (450), Re (550), R, of the thermoplastic film of the present invention measured at wavelengths of 450 nm, 550 nm, and 650 nm.
e (650) satisfies the following equations (1) and (2). 0.60 <Re (450) / Re (550) <0.97: Formula (1) 1.01 <Re (650) / Re (550) <1.35: Formula (2) It is more preferable to satisfy the expressions (3) and (4). 0.65 <Re (450) / Re (550) <0.92: Formula (3) 1.04 <Re (650) / Re (550) <1.30: Formula (4) It is more preferable to satisfy the expressions (5) and (6). 0.70 <Re (450) / Re (550) <0.87: Equation (5) 1.07 <Re (650) / Re (550) <1.25: Equation (6) It is preferably from 120 nm to 160 nm, more preferably from 125 nm to 155 nm, further preferably from 130 nm to 150 nm.

In the present invention, DR0, DR20 and DR40 defined by the following (A) to (C) are | DR20 (λ) −DR0 at a wavelength of 450 nm and a wavelength of 750 nm.
(Λ) | ≦ 0.02, | DR40 (λ) −DR0 (λ)
| ≦ 0.02 is preferably satisfied, and | DR
20 (λ) −DR0 (λ) | ≦ 0.015, | DR40
It is more preferable to satisfy the relationship of (λ) −DR0 (λ) | ≦ 0.015, and | DR20 (λ) −DR0 (λ)
| ≦ 0.01, | DR40 (λ) −DR0 (λ) | ≦
It is desirable to satisfy the relationship of 0.01. (A) DR0 (λ) = Re (λ) / Re (550) (B) DR20 (λ) = Re20 (λ) / Re20 (5)
50) (C) DR40 (λ) = Re40 (λ) / Re40 (5
50) In the formulas (A) to (C), λ is a measurement wavelength;
(Λ) is the retardation value measured in the normal direction of the film surface; Re20 (λ) is the retardation value measured at an angle of 20 ° from the normal direction of the film surface; Re40 (λ) Indicates a retardation value measured at an angle of 40 ° from the normal direction of the film surface. Further, the average value of the angle between the slow axis and the stretching direction in the film plane is preferably within ± 5 °, more preferably within ± 4 °, and further preferably within ± 3 °. Further, the in-plane refractive index n in the slow axis direction
x, the refractive index ny in the direction perpendicular to the in-plane slow axis and the refractive index nz in the thickness direction are 1 ≦ NZ = (nx−nz) / (n
x−ny) ≦ 2, more preferably 1.2 ≦ (nx−n)
z) / (nx−ny) ≦ 1.9, more preferably 1.
3 ≦ (nx−nz) / (nx−ny) ≦ 1.8.

The thermal shrinkage initiation temperature of the thermoplastic film of the present invention on the high stretching ratio side is preferably from 110 ° C. to 180 ° C., more preferably from 120 ° C. to 170 ° C., and more preferably from 125 ° C. More preferably, the temperature is 160 ° C. or lower. As a result, it is possible to achieve optical characteristics that are not easily attenuated even at high temperatures and excellent flatness. In the present invention, the film is stretched in the vertical or horizontal direction or in both directions. In the case of uniaxial stretching, the stretching direction is referred to as the high stretching ratio side, and in the case of multiaxial stretching, the direction in which the stretching ratio is high is referred to as the high stretching ratio side.
When the film was stretched in multiple stages, the larger product of the respective draw ratios was taken as the higher draw ratio side.

The IR two-color ratio of C—O expansion and contraction on the high stretching ratio side is preferably 1.5 or more and 2.5 or less, more preferably 1.6 or more and 2.5 or less, and even more preferably 1.7 or more and 2.5 or less. preferable. The IR2 color ratio of C = O expansion and contraction is preferably 0.6 or more and 1.2 or less, more preferably 0.6 or more and 1.1 or less,
0.6 or more and 1.0 or less are more preferable. The IR2 color ratio of C—O expansion and contraction on the low stretch ratio side is preferably 1.4 or more and 1.8 or less, more preferably 1.5 or more and 1.8 or less.
It is more preferably at least 1.8 and at most 1.8. C = O stretching IR2
The color ratio is preferably from 1.1 to 1.5, more preferably from 1.2 to 1.5, even more preferably from 1.2 to 1.4. By using a film having such characteristics, a film having excellent heat resistance and optical characteristics can be obtained.

Such a thermoplastic film has achieved the above object by improving the material (additive) and the stretching method. The details are described below. [Polymer] The thermoplastic film of the present invention is formed from a thermoplastic polymer. The type of the polymer is not particularly limited, and a known thermoplastic polymer can be used.
It is preferable to use cellulose acetate as the thermoplastic polymer. Cellulose acetate is obtained by esterifying (substituting) a part or all of three OH groups of cellulose with an acetate group, and has a preferable substitution degree (acetylation degree) of 2.4 or more and 2.9 or less. Preferably it is 2.5 or more and 2.85 or less, more preferably 2.6 or more and 2.8 or less. These cellulose acetates may be used by blending those having different degrees of substitution. In this case, the average degree of substitution multiplied by the mixing ratio of the degree of acetylation may be within this range. The polymerization degree (viscosity average) of cellulose acetate is preferably from 200 to 700, more preferably from 250 to 550, even more preferably from 250 to 350. The viscosity average degree of polymerization can be measured by an Ostwald viscometer, and is determined by the following equation from the measured intrinsic viscosity [η] of cellulose acylate. DP = [η] / Km In the formula, DP is a viscosity average degree of polymerization, and Km is a constant 6 × 10 ⁻⁴ . Further, as the cellulose acetate, only unused (virgin) flakes may be used. More preferably, the formed cellulose acetate film waste is 3 wt% to 95 wt%, more preferably 6 wt% to 80 w.
t% or less, more preferably 10 wt% or more and 70 wt%
It is preferable to use a mixture of the following.

[Additives] In order to adjust the retardation value at each wavelength, it is preferable to add a retardation increasing agent to a thermoplastic film (particularly preferably, a cellulose acetate film). The retardation enhancer is used in an amount of 0.05 to 20 with respect to 100 parts by mass of the polymer.
It is preferable to use in the range of parts by mass, and 0.1 to 10
More preferably used in the range of parts by mass, 0.5 to
More preferably used in the range of 10 parts by mass,
Most preferably, it is used in the range of 0.5 to 3 parts by mass. Two or more retardation increasing agents may be used in combination. The retardation enhancer is 230 to 360 nm
It is preferable to have the maximum absorption wavelength in the wavelength region of. Further, it is preferable that the retardation increasing agent has substantially no absorption in the visible region. It is preferable to use a compound having at least two “aromatic rings” as the retardation increasing agent. This “aromatic ring” includes an aromatic hetero ring in addition to an aromatic hydrocarbon ring. The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). The aromatic hetero ring is generally an unsaturated hetero ring, preferably a 5-, 6- or 7-membered ring, more preferably a 5- or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of the aromatic hetero ring include a furan ring, a thiophene ring, a pyrrole ring, an oxazole ring, an isoxazole ring, a thiazole ring, an isothiazole ring, an imidazole ring, a pyrazole ring, a furazane ring, a triazole ring, a pyran ring, and a pyridine ring. , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring. Specific examples of the aromatic ring include a benzene ring, a furan ring, a thiophene ring, a pyrrole ring, an oxazole ring, a thiazole ring, an imidazole ring, a triazole ring, a pyridine ring, a pyrimidine ring, a pyrazine ring, and a 1,3,5-triazine ring. preferable.
The number of these aromatic rings is preferably 2 to 20, more preferably 2 to 12, and most preferably 2 to 6, and at least one is a 1,3,5-triazine ring. Are preferred. The bonding relationship between two aromatic rings can be classified into (a) a case where a condensed ring is formed, (b) a case where they are directly connected by a single bond, and (c) a case where they are bonded via a linking group. , Spiro bond cannot be formed), but the bond relationship may be any of (a) to (c).

Examples of the condensed ring of (a) (condensed ring of two or more aromatic rings) include an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a biphenylene ring, Naphthacene ring, pyrene ring, indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline Ring, isoquinoline ring,
A quinolidine ring, a quinazoline ring, a cinnoline ring, a quinoxaline ring, a phthalazine ring, a pteridine ring, a carbazole ring, an acridine ring, a phenanthridine ring, a xanthene ring, a phenazine ring, a phenothiazine ring, a phenoxatiin ring, a phenoxazine ring and a thianthrene ring; included. Preferred are a naphthalene ring, an azulene ring, an indole ring, a benzoxazole ring, a benzothiazole ring, a benzimidazole ring, a benzotriazole ring and a quinoline ring. The single bond in (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be linked by two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings. The connecting group (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, alkenylene group, alkynylene group, -CO-, -O-, -NH-, -S-, or a combination thereof. Examples of the linking group consisting of a combination are shown below. Note that the left and right relationships in the following examples of the linking group may be reversed.

C1: -CO-O-c2: -CO-NH-c3: -alkylene-O-c4: -NH-CO-NH-c5: -NH-CO-O-c6: -O-CO-O -C7: -O-alkylene-O-c8: -CO-alkenylene- c9: -CO-alkenylene-NH-c10: -CO-alkenylene-O-c11: -alkylene-CO-O-alkylene-O-CO
-Alkylene-c12: -O-alkylene-CO-O-alkylene-O-
CO-alkylene-O-c13: -O-CO-alkylene-CO-O-c14: -NH-CO-alkenylene- c15: -O-CO-alkenylene-

The aromatic ring and the linking group may have a substituent. Examples of the substituent include a halogen atom (F, C
l, Br, I), hydroxyl, carboxyl, cyano, amino, nitro, sulfo, carbamoyl, sulfamoyl, ureido, alkyl, alkenyl, alkynyl, aliphatic acyl, aliphatic acyloxy, alkoxy, alkoxycarbonyl , Alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamide group, aliphatic substituted amino group, aliphatic substituted carbamoyl group, aliphatic substituted sulfamoyl group, aliphatic substituted ureido group and non-aromatic Group heterocyclic groups.

The alkyl group preferably has 1 to 8 carbon atoms. A chain alkyl group is preferable to a cyclic alkyl group, and a linear alkyl group is particularly preferable.
The alkyl group may further have a substituent (eg, hydroxy, carboxy, alkoxy group, alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl,
-Hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl and 2-diethylaminoethyl. The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a linear alkenyl group is particularly preferable.
The alkenyl group may further have a substituent. Examples of the alkenyl group include vinyl, allyl and 1-hexenyl. The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a linear alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of the alkynyl group include ethynyl, 1-butynyl and 1-hexynyl.

The number of carbon atoms of the aliphatic acyl group is 1 to 1
It is preferably 0. Examples of the aliphatic acyl group include acetyl, propanoyl and butanoyl. The aliphatic acyloxy group preferably has 1 to 10 carbon atoms. Examples of the aliphatic acyloxy group include acetoxy. The alkoxy group preferably has 1 to 8 carbon atoms. The alkoxy group may further have a substituent (eg, an alkoxy group). Examples of alkoxy groups (including substituted alkoxy groups) include methoxy, ethoxy, butoxy and methoxyethoxy. The alkoxycarbonyl group preferably has 2 to 10 carbon atoms. Examples of the alkoxycarbonyl group include methoxycarbonyl and ethoxycarbonyl. The alkoxycarbonylamino group preferably has 2 to 10 carbon atoms. Examples of the alkoxycarbonylamino group include methoxycarbonylamino and ethoxycarbonylamino.

The number of carbon atoms of the alkylthio group is 1 to 1
It is preferably 2. Examples of the alkylthio group include methylthio, ethylthio and octylthio.
The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of the alkylsulfonyl group include methanesulfonyl and ethanesulfonyl. The aliphatic amide group preferably has 1 to 10 carbon atoms. Examples of the aliphatic amide group include acetamide. The aliphatic sulfonamide group preferably has 1 to 8 carbon atoms. Examples of the aliphatic sulfonamide group include methanesulfonamide, butanesulfonamide and n-octanesulfonamide. The aliphatic substituted amino group preferably has 1 to 10 carbon atoms. Examples of the aliphatic substituted amino group include dimethylamino, diethylamino and 2-carboxyethylamino. The aliphatic substituted carbamoyl group preferably has 2 to 10 carbon atoms. Examples of the aliphatic substituted carbamoyl group include methylcarbamoyl and diethylcarbamoyl. The aliphatic substituted sulfamoyl group preferably has 1 to 8 carbon atoms. Examples of the aliphatic substituted sulfamoyl group include methylsulfamoyl and diethylsulfamoyl. The aliphatic substituted ureido group preferably has 2 to 10 carbon atoms. Examples of the aliphatic substituted ureido group include methyl ureide. Examples of the non-aromatic heterocyclic group include piperidino and morpholino. The molecular weight of the retardation increasing agent is preferably from 300 to 800. Specific examples of the retardation increasing agent include JP-A-2000-111914 and JP-A-2000-275434.
And the compounds described in each of the specifications.

[Plasticizer] To the thermoplastic film (particularly preferably cellulose acetate film), a plasticizer can be added in order to improve the mechanical properties or to increase the drying speed. As the plasticizer, a phosphoric acid ester or a carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (T
PP) and tricresyl phosphate (TCP). Representative carboxylic esters include phthalic esters and citric esters. Examples of phthalate esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DB
P), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). Examples of citrate esters include:
Includes O-acetyl triethyl citrate (OACTE) and O-acetyl tributyl citrate (OACTB). Examples of other carboxylic esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic esters. Phthalate ester plasticizers (DMP, DEP, DBP, D
OP, DPP, DEHP) are preferably used. DE
P and DPP are particularly preferred. Since the amount of the plasticizer added may affect the wavelength dispersion, it needs to be adjusted together with the amount of the retarder. The amount of the plasticizer added is preferably 0.1 to 25% by mass, more preferably 1 to 20% by mass, and more preferably 3 to 15% by mass of the amount of the thermoplastic polymer (particularly preferably cellulose acetate). Is most preferred.

[Deterioration Inhibitors] Thermoplastic films (particularly preferably cellulose acetate films) include degradation inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid traps). Agents, amines). Regarding the deterioration inhibitor, see JP-A-3-199201.
No., 5-1907073, 5-194789,
These are described in JP-A-5-271471 and JP-A-6-107854. The amount of the deterioration inhibitor added is preferably 0.01 to 1% by mass, more preferably 0.01 to 0.2% by mass of the solution (dope) to be prepared. When the amount is less than 0.01% by mass, the effect of the deterioration inhibitor is hardly recognized. If the amount exceeds 1% by mass, bleed out (bleeding out) of the deterioration inhibitor on the film surface may be observed. Particularly preferred examples of the deterioration inhibitor include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

[Preparation of Cellulose Acetate Dope] It is preferable to produce a thermoplastic film (particularly preferably a cellulose acetate film) by a solvent casting method. In the solvent casting method, a film is manufactured using a solution (dope) in which a polymer is dissolved in an organic solvent. Organic solvents include ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and 3 carbon atoms.
It preferably contains a solvent selected from the group consisting of an ester having from 12 to 12 and a halogenated hydrocarbon having from 1 to 6 carbon atoms. Ethers, ketones and esters may have a cyclic structure. Ether, ketone and ester functional groups (i.e. -O-, -CO- and -COO-)
Compounds having two or more of any of the above can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any one of the functional groups.

Examples of the ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolan, tetrahydrofuran, anisole and phenetole. Examples of the ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone. Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of the organic solvent having two or more types of functional groups include
Includes 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol. The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogen atoms substituted by halogen atoms in halogenated hydrocarbons is preferably 25 to 75 mol%, and preferably 3 to 75 mol%.
The content is more preferably 0 to 70 mol%, still more preferably 35 to 65 mol%, and 40 to 60 mol%.
Most preferably, it is mol%. Methylene chloride is a typical halogenated hydrocarbon. Two or more organic solvents may be used as a mixture.

The polymer solution can be prepared by a general method. The general method means that the treatment is performed at a temperature of 0 ° C. or higher (normal temperature or high temperature). The solution can be prepared using a dope preparation method and apparatus in a usual solvent casting method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly, methylene chloride) as the organic solvent. The amount of the polymer is adjusted so that the obtained solution contains 10 to 40% by mass. More preferably, the amount of polymer is from 10 to 30% by weight. In the organic solvent (main solvent), any additives described below may be added.
The solution can be prepared by stirring the polymer and the organic solvent at room temperature (0 to 40 ° C.). The highly concentrated solution may be stirred under pressure and heating conditions. Specifically, the polymer and the organic solvent are placed in a pressurized container and hermetically sealed, and the mixture is stirred while being heated under pressure to a temperature not lower than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil. The heating temperature is usually 40 ° C. or higher, preferably 60 to 2
It is 00 ° C, more preferably 80 to 110 ° C.

The components may be roughly mixed in advance and then placed in a container. Moreover, you may put in a container sequentially. The container must be configured to be able to stir. The container can be pressurized by injecting an inert gas such as nitrogen gas. Further, an increase in the vapor pressure of the solvent due to heating may be used.
Alternatively, each component may be added under pressure after the container is sealed. When heating, it is preferable to heat from outside the container. For example, a jacket-type heating device can be used. Alternatively, a plate heater may be provided outside the container, and the entire container may be heated by circulating the liquid through piping. It is preferable to provide a stirring blade inside the container and stir using the stirring blade. The stirring blade preferably has a length reaching the vicinity of the container wall. At the end of the stirring blade, a scraping blade is preferably provided to renew the liquid film on the container wall. Instruments such as a pressure gauge and a thermometer may be installed in the container. Dissolve each component in the solvent in the container.
The prepared dope is taken out of the vessel after cooling, or is taken out and then cooled using a heat exchanger or the like.

The solution can be prepared by a cooling dissolution method. In the cooling dissolution method, the polymer can be dissolved even in an organic solvent that is difficult to dissolve by a normal dissolution method. In addition, even if it is a solvent which can dissolve a polymer by a usual dissolution method, the cooling dissolution method has an effect that a uniform solution can be obtained quickly. In the cooling dissolution method, first, a polymer is gradually added to an organic solvent with stirring at room temperature. The amount of polymer is between 10 and 4 in this mixture.
It is preferable to adjust so as to contain 0% by mass. More preferably, the amount of polymer is from 10 to 30% by weight. Further, an optional additive described below may be added to the mixture. Next, the mixture was -100 to-
10 ° C. (preferably −80 to −10 ° C., more preferably −50 to −20 ° C., and most preferably −50 to −20 ° C.)
(30 ° C.). Cooling, for example, dry ice
It can be carried out in a methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). Upon such cooling, the mixture of polymer and organic solvent solidifies. The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and 12 ° C./min.
/ Min or more is most preferable. A higher cooling rate is preferred, but 10,000 ° C./sec is the theoretical upper limit, 1000 ° C./sec is the technical upper limit, and
0 ° C./sec is a practical upper limit. The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling to the final cooling temperature.

Further, the temperature is raised to 0 to 200 ° C (preferably 0 to 150 ° C, more preferably 0 to 120 ° C,
Upon heating to (most preferably 0 to 50 ° C.), the polymer dissolves in the organic solvent. The temperature may be raised only at room temperature or may be heated in a warm bath. Heating rate is 4
C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The heating rate is preferably as fast as possible.
00 ° C / sec is the theoretical upper limit, 1000 ° C / sec is the technical upper limit, and 100 ° C / sec is the practical upper limit. The heating rate is a value obtained by dividing the difference between the temperature at which heating is started and the final heating temperature by the time from when heating is started to when the final heating temperature is reached. is there. As described above, a uniform solution is obtained. If the dissolution is insufficient, the operation of cooling and heating may be repeated. Whether or not the dissolution is sufficient can be determined only by visually observing the appearance of the solution. In the cooling dissolution method, it is desirable to use a closed container in order to avoid water contamination due to condensation during cooling. In addition, in the cooling and heating operation, when pressure is applied during cooling and pressure is reduced during heating,
The dissolution time can be reduced. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container.

[Formation of Cellulose Acetate Film]
The film formation of the thermoplastic film of the present invention will be described with reference to a cellulose acetate film which is particularly preferable as the thermoplastic film. From the prepared cellulose acetate solution (dope), a cellulose acetate film is produced by a solvent casting method. As a method and equipment for producing a cellulose acetate film, a solution casting film forming method and a solution casting film forming apparatus conventionally used for producing a cellulose triacetate film are used. The dope (cellulose acetate solution) prepared from the dissolving machine (pot) is temporarily stored in a storage pot, and the foam contained in the dope is defoamed or final prepared. The dope is fed from the dope discharge port to the pressurized die through a pressurized metering gear pump capable of, for example, high-precision quantitative liquid feeding according to the number of rotations, and the dope of the casting section running endlessly from the die (slit) of the pressurized die. At the peeling point where the support is evenly cast on the support and the support substantially makes a round, the freshly dried dope film (also referred to as a web) is peeled from the support. Both ends of the obtained web are sandwiched by clips, transported by a tenter while maintaining the width, and dried. Subsequently, the web is transported by a group of rolls of a drying device, dried, and wound up to a predetermined length by a winder. The combination of the tenter and the roll group drying device varies depending on the purpose. In a solution casting film forming method used for a silver halide photographic material or a functional protective film for an electronic display, in addition to a solution casting film forming apparatus, an undercoat layer, an antistatic layer, an antihalation layer, a protective layer, etc. In order to process the surface of the support, a coating device is often added. The following briefly describes each of the manufacturing steps, but is not limited thereto.

First, when the cellulose acetate solution (dope) prepared is prepared into a cellulose acetate film by a solvent casting method, the dope is cast on a drum or a band, and the solvent is evaporated to form a film. . The dope before casting has a solid content of 10 to 40%
It is preferable to adjust the concentration so that It is preferable that the surface of the drum or the band is finished in a mirror state. The casting and drying methods in the solvent casting method are described in US Pat.
No. 7603, No. 2492078, No. 2492977
No. 2492978, No. 2607704, No. 27
No. 39069, No. 2739070, British Patent 6407
Nos. 31, 736,892, JP-B-45-4
554, 49-5614, JP-A-60-1768
No. 34, No. 60-203430, No. 62-11503
There is a description in each gazette of No. 5. The dope has a surface temperature of 10
Casting on a drum or band at a temperature of not more than ° C is preferably used.

In the present invention, the obtained cellulose acetate solution may be cast as a single layer solution on a smooth band or drum as a support, or a plurality of cellulose acetate solutions of two or more layers may be cast. May be. When casting a plurality of cellulose acetate solutions, a film may be produced while casting and laminating a solution containing cellulose acetate from a plurality of casting ports provided at intervals in the traveling direction of the support. For example, JP-A-61-158
No. 414, JP-A-1-122419, and JP-A-1
The method described in each specification such as 1-198285 can be used. Alternatively, the film may be formed by casting a cellulose acetate solution from two casting ports, for example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245,
JP-A-61-104814, JP-A-61-15841
3 and JP-A-6-134933. Also, Japanese Patent Application Laid-Open No. 56-1
A method of casting a cellulose acetate film in which a flow of a high-viscosity cellulose acetate solution described in Japanese Patent No. 62617 is wrapped with a low-viscosity cellulose acetate solution and the high- and low-viscosity cellulose acetate solutions are simultaneously extruded may be used. Alternatively, by using two casting ports, peeling off the film formed on the support by the first casting port, and performing the second casting on the side in contact with the support surface,
It is also possible to make a film, for example,
The method described in Japanese Patent Publication No. 20235 can be used. The cellulose acetate solution to be cast may be the same solution or different cellulose acetate solutions, and is not particularly limited. In order to give a function to a plurality of cellulose acetate layers, a cellulose acetate solution according to the function may be extruded from each casting port.
In order to achieve the optical suitability and mechanical suitability of the present invention, a laminate is more preferable. The number of stacked layers is 2 or more and 10
The number of layers is preferably 2 or less, more preferably 2 or more and 6 or less, still more preferably 2 or more and 4 or less. Furthermore, the cellulose acetate solution of the present invention can be simultaneously cast with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, an ultraviolet absorbing layer, and a polarizing layer).

In a conventional single-layer liquid (single-layer casting method), it is necessary to extrude a high-concentration and high-viscosity cellulose acetate solution in order to obtain a required film thickness. The solids were generated due to poor stability and often caused problems such as lumps and poor flatness. By casting a plurality of cellulose acetate solutions from the casting port, a high-viscosity solution can be simultaneously extruded onto the support, and not only can the flatness be improved and an excellent planar film can be produced, By using a concentrated cellulose acetate solution, a reduction in the drying load can be achieved, and the production speed of the film can be increased. The thickness of the film after casting is 80-22
0 μm, more preferably 90 to 2 μm.
00 μm, and more preferably 100 to 180 μm. The cellulose acetate film may be provided with a matting layer containing a matting agent and a polymer on one or both sides to improve the handleability during production. As the matting agent and the polymer, the materials described in JP-A-10-44327 can be suitably used. Further, if necessary, both ends may be subjected to a thickness setting process.

[Stretching of Cellulose Acetate Film]
The optical film (retardation etc.) and the mechanical properties (elongation at break, breaking strength, bending strength) of the present invention can be achieved by stretching a thermoplastic film (particularly preferably cellulose acetate film). The invention is characterized in that this stretching method has been improved. Stretching is
The operation may be performed in any of the vertical and horizontal directions, or a combination thereof. Of these, preferred is longitudinal or horizontal uniaxial stretching, and more preferred is longitudinal uniaxial stretching.

The present invention is characterized in that stretching is performed in the following steps. (1) Preheating in a constant temperature bath Usually, preheating and longitudinal stretching are generally performed using a heat roll and / or a radiant heat source (such as an IR heater), but in the present invention, these are placed in a constant temperature bath. It is characterized by being carried out in. In these methods, since the temperature rises rapidly, wrinkles and streaking tend to occur when the film width after stretching is as wide as 60 cm or more. It is presumed that this is caused by a rapid thermal expansion of the base, but the expansion cannot be performed due to friction with the roll. Further, it is presumed that the heat roll or the radiant heat source easily causes temperature unevenness in the width direction, and that the temperature difference between the heated surface and the opposite surface of the film promotes the generation of wrinkles. On the other hand, when preheating is performed in a constant temperature bath, the temperature can be slowly increased, and the heating can be uniformly performed in the width direction and the front and back surfaces, so that these non-uniformities hardly occur. A preferred heating rate is 0.3 ° C / min or more and 50 ° C / min or less, more preferably 0.6 ° C / min or more and 30 ° C / min or less,
More preferably, it is 1.0 ° C./min or more and 10 ° C./min or less.

(2) Stretching in a constant temperature bath Following preheating, it is preferable to perform roll stretching in a constant temperature bath. In order to reduce a change in the temperature of the film, it is preferable to carry out the preheating in the same constant temperature bath. The preferred temperature is 115 ° C or more and 160 ° C or less, more preferably 120 ° C or less.
155 ° C or lower, more preferably 125 ° C or higher and 150
It is below ° C. The temperature difference between the film passages in the thermostat is 0
C. to 5 ° C., more preferably 0 ° C. to 4 ° C., still more preferably 0 ° C. to 3 ° C. The stretching is performed by installing a plurality of nip rolls in a thermostat and increasing the peripheral speed from the inlet side to the outlet side. As a result, the uniformity of the stretching temperature in the width direction is improved, the optical characteristics in the width direction can be made uniform, and the difference between the slow axis and the stretching axis can be reduced. The nip roll is preferably a combination of a metal roll and a roll lined with rubber. The diameter of the metal roll is preferably 5 cm or more and 50 cm or less, more preferably 10 cm or more and 30 cm or less, and the surface is preferably hardened with hard chrome or the like. In the case of wide stretching with a fill width of 0.6 m or more, a large stretching roll exceeding 50 cm is usually used, but the present invention is characterized in that a thin stretching roll of 50 cm or less is used. The diameter of the rubber-lined roll is preferably smaller than the metal roll, and the diameter is preferably 2 cm or more and 30 cm or less, more preferably 4 cm or more and 20 cm or less. The thickness of the lined rubber is 1m
m or more and 50 mm or less, more preferably 2 mm
Not less than 20 mm. The distance between these nip rolls is 0.1 m or more and 2 m or less, more preferably 0.2 m or more and 1.5 m or less, and still more preferably 0.3 m or more.
Not less than 1 m. In the case of wide stretching in which the fill width is 0.6 m or more, it is common to use a large roll exceeding 30 cm in accordance with a large stretched metal roll. In the present invention, a roll having such a small diameter is used. I have. The stretching is preferably performed by wrapping on the metal roll side, and the wrap angle is 60 degrees or more and 270 degrees or less, more preferably 70 degrees or more and 230 degrees or less, and further preferably 8 degrees or less.
0 degrees or more and 210 degrees or less.

Further, it is preferable to use a crown roll whose center portion is 0.05% or more and 2% or less, more preferably 0.1% or more and 1% or less as compared with the both ends of the rubber lining roll. "). When a normal roll is used, the stretching stress is easily concentrated on both ends of the film, and optical unevenness in the width direction is easily generated.However, the stretching stress applied to the film at the center portion using such a roll can be increased, so that both ends to the center can be used. Uniform optical characteristics can be achieved over the entire region in the width direction of the portion. Stretching may be performed in one step, but by performing it in multiple steps, the stability of optical characteristics at higher temperatures is increased. The preferred number of stages is 2 or more and 10 or less, more preferably 3 or more and 8 or less. It is preferable that the stretching ratio in the former stage is smaller than that in the latter stage. The preferred stretching ratio is 1.2 times or more and 1.8 times.
Times or less, more preferably 1.25 times or more and 1.75 times or less, further preferably 1.3 times or more and 1.7 times or less. Stretching may be performed in one step, or may be performed in multiple steps.
In the case of performing in multiple stages, the product of each stretching ratio may be set within this range. Stretching speed is 50% / min or more and 1000
% / Min or less, more preferably 80% / min or more and 800% / min.
Min / min, more preferably 100% / min to 700% / min.
Minutes or less. The preferred stretching temperature is 115 ° C. or higher and 160
° C or lower, more preferably 120 ° C or higher and 155 ° C or lower, still more preferably 125 ° C or higher and 150 ° C or lower.

(3) Post-rolling heat treatment between dense rolls After drawing, continuous passing between rolls densely arranged in a thermostatic oven during stretching can improve flatness (reducing wrinkles) and optical properties due to heat. This is preferable because a decrease in the water content can be prevented. The preferable distance between the rolls is 0.05 m or more and 0.7 m between the cores.
It is more preferably 0.1 m or more and 0.6 m or less, and still more preferably 0.1 m or more and 0.5 m or less. The preferred number of rolls is 2 or more and 30 or less, more preferably 3 or more and 25 or less, and still more preferably 4 or more and 20 or less. The diameter of these rolls is 4cm or more and 50c
m or less, more preferably 7 cm or more and 40 cm
Or less, more preferably 9 cm or more and 40 cm or less. At this time, it is preferable that the film is passed at a film temperature of 50 ° C. to 160 ° C., more preferably 60 ° C. to 150 ° C., and still more preferably 80 ° C. to 140 ° C.

(4) Control of Cooling Rate The film is cooled after stretching and post-heat treatment between dense rolls.
At this time, it is preferable to gradually lower the film temperature.
This is preferable because the optical characteristics can be prevented from deteriorating due to heat and the optical characteristics can be made uniform in the width direction. Preferred cooling rates are from -0.3 ° C / min to -50 ° C / min, more preferably-
0.6 ° C./min to −30 ° C./min, more preferably −
From 1.0 ° C / min to -10 ° C / min. Such cooling may be performed by passing through a plurality of thermostats whose temperature is gradually lowered, or through a plurality of heat rolls whose temperature is gradually lowered. It is most preferable that such cooling can be carried out continuously, but it is preferable to perform cooling in at least two or more stages, more preferably in three or more stages.

(5) Winding After cooling, the base is provided with slits at both ends and, if necessary, a knurling process, and then wound around a core. The thickness of the stretched film thus obtained is preferably 70 μm or more and 150 μm or less, more preferably 75 μm
Or more and 140 μm or less, more preferably 80 μm or more and 1
It is 30 μm or less. The film width after the stretching and before the slit is preferably 0.6 m or more and 3 m or less, more preferably 0.1 m or more.
It is 7 m or more and 2.5 m or less, more preferably 0.8 m or more and 2.2 m or less.

The thermoplastic film obtained as described above can be preferably used as a retardation plate used in a display device such as a liquid crystal display device and an optical apparatus.

[Circularly Polarizing Plate] The thermoplastic film (retardation plate) thus obtained acts as a λ / 4 plate. A circularly polarizing plate is obtained by bonding the polarizing plate and the polarizing plate such that the angle between the slow axis in the plane of the λ / 4 plate and the polarizing axis of the polarizing plate is substantially 45 °. A polarizing plate refers to a polarizing plate in which a polarizing film is sandwiched between transparent protective films. Substantially 45 ° means 40 to 50 °. The angle between the average direction of the slow axis in the plane of the λ / 4 plate and the polarization axis of the polarizing film is preferably 41 to 49 °, and 42 to 4 °.
The angle is more preferably 8 °, even more preferably 43 to 47 °, and most preferably 44 to 46 °. A circularly polarizing plate can also be obtained by laminating a λ / 4 plate and a polarizing film such that the angle between the in-plane slow axis of the λ / 4 plate and the polarizing axis of the polarizing film is substantially 45 °. Can be
The polarizing film includes an iodine-based polarizing film, a dye-based polarizing film using a dichroic dye, and a polyene-based polarizing film. The iodine-based polarizing film and the dye-based polarizing film are generally manufactured using a polyvinyl alcohol-based film. The polarization axis of the polarizing film corresponds to a direction perpendicular to the stretching direction of the film. It is preferable to provide a transparent protective film on the surface of the polarizing film opposite to the λ / 4 plate.

[Reflective Liquid Crystal Display Element] FIG. 1 is a schematic diagram showing a basic configuration of a reflective liquid crystal display device. The reflective liquid crystal display device shown in FIG. 1 includes a lower substrate (1),
Reflective electrode (2), lower alignment film (3), liquid crystal layer (4), upper alignment film (5), transparent electrode (6), upper substrate (7), λ / 4 plate (8), and polarizing film ( 9). The lower substrate (1) and the reflection electrode (2) constitute a reflection plate. Lower alignment film (3)-
The upper alignment film (5) forms a liquid crystal cell. λ / 4 plate (8)
Can be arranged at any position between the reflection plate and the polarizing film (9). In the case of color display, a color filter layer is further provided. The color filter layer is preferably provided between the reflective electrode (2) and the lower alignment film (3) or between the upper alignment film (5) and the transparent electrode (6). A reflective plate may be separately attached using a transparent electrode instead of the reflective electrode (2) shown in FIG. A metal plate is preferable as the reflector used in combination with the transparent electrode. If the surface of the reflector is smooth, only the specular reflection component may be reflected and the viewing angle may be narrowed. Therefore, it is preferable to introduce an uneven structure (described in Japanese Patent No. 2756206) on the surface of the reflection plate. When the surface of the reflection plate is flat (instead of introducing an uneven structure on the surface), a light diffusion film may be attached to one side (cell side or outside) of the polarizing film.

The liquid crystal cell is a TN (twisted nematic)
Type, STN (Supper Twisted Nematic) type or HAN
(Hybrid Aligned Nematic) type is preferred.
The twist angle of the TN type liquid crystal cell is preferably from 40 to 100 °, more preferably from 50 to 90 °, and most preferably from 60 to 80 °.
The value of the product (Δnd) of the refractive index anisotropy (Δn) of the liquid crystal layer and the thickness (d) of the liquid crystal layer is preferably 0.1 to 0.5 μm, and 0.2 to 0.4 μm. It is more preferred that there be. The twist angle of the STN type liquid crystal cell is 180
To 360 °, preferably 220 to 270 °
゜ is more preferable. The value of the product (Δnd) of the refractive index anisotropy (Δn) of the liquid crystal layer and the thickness (d) of the liquid crystal layer is preferably 0.3 to 1.2 μm.
More preferably, it is 5 to 1.0 μm. HAN
In the type liquid crystal cell, the liquid crystal is substantially vertically aligned on one substrate and the pretilt angle on the other substrate is 0 to 4
It is preferably 5 °. The refractive index anisotropy of the liquid crystal layer (Δ
The value of the product (Δnd) of (n) and the thickness (d) of the liquid crystal layer is
The thickness is preferably from 0.1 to 1.0 μm, and more preferably from 0.3 to 0.8 μm. The substrate on which the liquid crystal is vertically aligned may be a substrate on the reflection plate side or a substrate on the transparent electrode side. The polarizing film includes an iodine-based polarizing film, a dye-based polarizing film using a dichroic dye, and a polyene-based polarizing film. The iodine-based polarizing film and the dye-based polarizing film are generally manufactured using a polyvinyl alcohol-based film. The polarization axis of the polarizing film corresponds to a direction perpendicular to the stretching direction of the film. The reflection type liquid crystal display device can be used in a normally white mode in which the display is bright when the applied voltage is low and a dark display when the applied voltage is high, or in a normally black mode in which the display is dark when the applied voltage is low and the display is bright when the applied voltage is high. . Normally white mode is preferred.

[Guest-host reflective liquid crystal display device] FIG.
FIG. 1 is a schematic cross-sectional view showing a typical mode of a guest-host reflection type liquid crystal display element. The guest-host reflection type liquid crystal display device shown in FIG. 2 includes a lower substrate (11), an organic interlayer insulating film (1).
2), metal reflector (13), λ / 4 plate (14), lower transparent electrode (15), lower alignment film (16), liquid crystal layer (17), upper alignment film (18), upper transparent electrode (19) ), Light diffusion plate (2
0), an upper substrate (21) and an antireflection layer (22) are laminated in this order. The lower substrate (11) and the upper substrate (21) are made of a glass plate or a plastic film. Lower substrate (11) and organic interlayer insulating film (12)
A TFT (23) is attached between the two. The liquid crystal layer (17) is composed of a mixture of a liquid crystal and a dichroic dye. The liquid crystal layer is obtained by injecting a mixture of liquid crystal and a dichroic dye into the cell gap formed by the spacer (24). Instead of providing the light diffusing plate (20), the metal reflecting plate (13) may have a light diffusing function by making the surface of the metal reflecting plate (13) uneven. The antireflection layer (22) preferably has an antiglare function in addition to the antireflection function.

FIG. 3 is a schematic sectional view showing another typical embodiment of the guest-host reflection type liquid crystal display device. The guest-host reflection type liquid crystal display device shown in FIG.
1), organic interlayer insulating film (32), cholesteric color reflector (33), λ / 4 plate (34), lower transparent electrode (3)
5) A structure in which a lower alignment film (36), a liquid crystal layer (37), an upper alignment film (38), an upper transparent electrode (39), an upper substrate (41), and an antireflection layer (42) are laminated in this order. Having. The lower substrate (31) and the upper substrate (41) are made of a glass plate or a plastic film. Lower substrate (31)
A TFT (43) is provided between the TFT and the organic interlayer insulating film (32).
Is attached. The λ / 4 plate (34) may also function as a light diffusion plate. The liquid crystal layer (37) is composed of a mixture of a liquid crystal and a dichroic dye. The liquid crystal layer is obtained by injecting a mixture of liquid crystal and a dichroic dye into the cell gap formed by the spacer (44). A black matrix (45) is attached between the upper transparent electrode (39) and the upper substrate (41). Anti-reflection layer (4
2) preferably has an antiglare function in addition to the antireflection function.

The λ / 4 plate (thermoplastic film) according to the present invention includes the λ / 4 plate (8) of the reflection type liquid crystal display device described with reference to FIG. 1, and the guest-host reflection type described with reference to FIG. 2 and FIG. Λ / 4 plates (24) and (3) of liquid crystal display elements
4) Can be used. For a guest-host reflection type liquid crystal display device having a λ / 4 plate, see JP-A-6-22235.
No. 0, No. 8-36174, No. 10-268300,
Nos. 10-292175, 10-293301, 10-311976, 10-319442, 1
Nos. 0-3255953, 10-333138, 11
It is described in each publication of -38410. Λ according to the invention
The / 4 plate can also be used for the guest-host reflection type liquid crystal display device described in each of the above publications.

The method for measuring the optical characteristics and other characteristics of the thermoplastic film of the present invention will be described below. (1) Measurement of Retardation and Refractive Index Retardation values of the produced thermoplastic film (retardation plate) at wavelengths of 450 nm, 550 nm and 650 nm using an ellipsometer (M-150, manufactured by JASCO Corporation). Was measured. In addition, the refractive index nx in the in-plane slow axis direction at a wavelength of 550 nm and the refractive index in the direction perpendicular to the in-plane slow axis were measured from the refractive index measurement by Abbe refractometer and the measurement of the angle dependence of the retardation. n
y and the refractive index nz in the thickness direction are obtained, and NZ = (nx−
The value of (nz) / (nx-ny) was calculated. (2) Heat shrinkage starting temperature The sheet is cut into a length of 35 mm along the direction of the high draw ratio and a width of 3 mm along the direction of the low draw ratio. 25m at both ends in the longitudinal direction
Chuck at m intervals. This is measured with a TMA measuring instrument (TMA2940
(Thermomechanical Analyzer, manufactured by TA Instruments Co., Ltd.) and applying a force of 0.04 N while measuring the dimensional change while increasing the temperature from 30 ° C. to 200 ° C. at 3 ° C./min. The size at 30 ° C. is defined as the base length, and the temperature at which the resin shrinks by 500 μm from this is defined as the shrinkage starting temperature. (2) Measurement of difference (axis deviation) between the slow axis and the stretching axis The angle between the direction of the slow axis and the stretching direction of the cellulose acetate film is determined by an automatic birefringence meter (KOBRA-21AD).
H, Oji Scientific Instruments). The measurement was performed at the edge and the center in the film, and the difference between this and the stretching axis was determined. (3) Degree of acetyl substitution Measured from 13 C-NMR spectrum by the method described in the literature (Polymer Journal 17.1065-1069 (1985)). (4) IR two-color ratio (a) High stretching magnification side 5 cm long along low stretching magnification side, 1c along high stretching magnification side
Two sample films are cut to a width of m. This is 5cm
KRS-5 ATR crystal plate of length x 1 cm width (incident angle 60
90 ° polarized light and 0 ° polarized light are incident along the long side direction and integrated 100 times for IR measurement (710-type FT-IR, Nico
let company). The peak showing the maximum value between 1700 cm ^-1 and 1800 cm ^-1 is defined as C = O expansion and contraction,
A line connecting the average value of 1720 cm ^{-1 and} the average value of 1780 to 1800 cm ^{-1 was taken as} a baseline, and the absorbance at the difference between this and the peak maximum was measured at 0 degree polarization and 90 degree polarization, respectively (0 degree The absorbance of polarized light / (the absorbance of 90-degree polarized light) is defined as an IR two-color ratio of C = O stretching. 1200 cm ^-1
The peaks indicating the maximum value of between 1000 cm ^-1 from C-O
With expansion and contraction, the minimum value of 1200 to 1100 cm ^-1 and 950
The line connecting the minimum values of ８850 cm ⁻¹ is used as a baseline, and the absorbance of the difference between this and the peak maximum value is measured at 0 ° polarization and 90 ° polarization, respectively (absorbance of 0 ° polarization) /
(Absorbance of 90-degree polarized light) is defined as an IR two-color ratio of CO stretching. (B) Low stretch ratio side 5cm length along high stretch ratio side, 1c along low stretch ratio side
Two sample films are cut to a width of m. Thereafter, the IR two-color ratio is obtained in the same manner as in the above method.

【Example】

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto. 1. Preparation of Retardation Plate (Stretched Cellulose Acetate Film) (1) Composition As shown in Table 1, a cellulose acetate dope (high concentration solution) was prepared by selecting from the following two compositions. The retardation increasing agent was selected from the following two compounds and used, and is shown in Table 1. The amount added is 1.20 parts by mass for each level.

[0050]

Embedded image

(A) Methylene chloride (MC) -doped cellulose acetate (the degree of substitution is described in Table 1) 120 parts by mass 9.36 parts by mass of triphenyl phosphate 4.68 parts by mass of biphenyldiphenyl phosphate 704 parts by mass of methylene chloride methanol 61 .2 parts by mass

(B) Methyl acetate (MA) -doped cellulose acetate (substitution degree is described in Table 1) 118 parts by mass triphenyl phosphate 9.19 parts by mass biphenyl diphenyl phosphate 4.60 parts by mass tribenzylamine 2.36 parts by mass Parts Methyl acetate 530 parts by weight Ethanol 99.4 parts by weight Butanol 33.1 parts by weight

[0053]

[Table 1]

(2) Dissolution These were selected from the following three dissolution methods and carried out according to the methods shown in Table 1. (A) Dissolution at normal temperature (described as "normal temperature" in the column of dissolution method in Table 1) The compound shown in Table 1 is gradually added to a solvent with good stirring, and left at room temperature (25 ° C) for 3 hours. Swelled. The resulting swollen mixture was dissolved with stirring at 50 ° C. in a mixing tank with a reflux condenser. (B) Dissolution by cooling (described as "cooling" in the column of dissolution method in Table 1) The compound shown in Table 1 was gradually added to the solvent while stirring well, and left at room temperature (25 ° C) for 3 hours. Swelled. The resulting swelled mixture was cooled to −30 ° C. at −8 ° C./min with slow stirring, then cooled to the temperature shown in Table 1, and after 6 hours, the temperature was raised at + 8 ° C./min to increase the sol content. At a stage where the conversion to a certain extent proceeded, stirring of the contents was started. 5
The mixture was heated to 0 ° C. to obtain a dope. (C) High-pressure and high-temperature dissolution (described as "high temperature" in the column of dissolution method in Table 1) The cellulose acylate shown in Table 1 was gradually added to the solvent with good stirring, and the solution was added at room temperature (25 ° C). Leave to swell for a period of time. The obtained swollen mixture was placed in a double-walled stainless steel closed container. By passing high-pressure steam through the outer jacket of the vessel, it is heated at + 8 ° C / min.
It was kept at the temperature shown in Table 1 for 5 minutes. Thereafter, 50 ° C. water was passed through the outer jacket and cooled to −50 ° C. at −8 ° C./min to obtain a dope.

(3) Film formation A film was formed by selecting from the following two methods and described in Table 1. (A) Single-layer film formation The solution (dope) obtained by the above method is filtered with filter paper (N
o. 244, manufactured by Azumi Filter Paper Co., Ltd.) and flannel filter cloth, and then sent to a pressure die using a fixed-quantity gear pump, and dried and stretched using a band casting machine with an effective length of 6 m. The casting was performed so that the thickness was as shown in Table 2. The band temperature was 0 ° C. The film was exposed to air for 2 seconds for drying, and when the volatile content in the film became 50% by mass, the film was peeled off from the band, and further subjected to 3 minutes at 100 ° C., 5 minutes at 130 ° C., and 5 minutes at 160 ° C. The film was shrunk freely without fixing and dried stepwise, and the remaining solvent was evaporated to 1% or less. (B) Multilayer film formation Using a three-layer co-casting die, the dope having the above composition was filtered from the inner layer with a filter paper (No. 244, manufactured by Azumi Filter Paper Co., Ltd.) and a flannel filter cloth, and then 10% on both sides. After the dope diluted by increasing the amount of solvent is simultaneously discharged onto a metal support and layered and cast, using a band casting machine having an effective length of 6 m, drying is performed.
The film was cast so that the final film thickness after stretching became the thickness shown in Table 2. The band temperature was 0 ° C. The film was exposed to air for 2 seconds for drying, and when the volatile content in the film became 50% by mass, the film was peeled off from the band, and further subjected to 3 minutes at 100 ° C., 5 minutes at 130 ° C., and 5 minutes at 160 ° C. Then, the film is shrunk freely without fixing, dried in a stepwise manner, and the remaining solvent is evaporated to 1% or less. Thereafter, both ends are trimmed by 15 cm, and both ends are 50 μm high and 1 μm wide.
m knurling (thickness processing), length 3000
m of unstretched cellulose acetate film was obtained. The cellulose acetate film waste trimmed here is pulverized, mixed with unused cellulose acetate, and reused (30% by mass in the total cellulose acetate).
This was mixed).

(4) Stretching The unstretched sheet was selected from the following methods and stretched longitudinally by the method shown in Table 2. (A) Thermostatic chamber stretching method An unstretched cellulose acetate film is unwound from a delivery placed outside the thermostatic chamber and fed into the thermostatic chamber. Under the conditions shown in Table 2, this was preheated, stretched in a thermostat, heat-treated between dense rolls, and cooled. (B) Hot Roll Stretching Method After the unstretched cellulose acetate film was preheated on a hot roll under the conditions shown in Table 2, it was stretched under the conditions shown in Table 2 using the hot roll shown in Table 2 installed at room temperature. After doing
It was rapidly cooled using a cooling roll and wound up.

[0057]

[Table 2]

(5) Evaluation The evaluation results of the optical and mechanical properties are shown in Table 3. These evaluations were performed according to the above method. The flatness was evaluated by cutting the center and both ends into squares each measuring 30 cm on a side, placing this on a horizontal table, and measuring the height of the wavy wrinkles due to poor flatness using four calipers. And the maximum value is shown in Table 3. The permissible value is 3 mm or less. In any of the present invention, the wavy height is as low as this or less, and the flatness is good.

[0059]

[Table 3]

2. Preparation of Circularly Polarizing Plate The transparent protective film, the polarizing film, and the retardation plate produced by the above method were cut at a diagonal of 15 inches and laminated in this order to obtain a circularly polarizing plate. The angle between the slow axis of the retardation plate and the polarization axis of the polarizing film was adjusted to 45 °. This was mounted on a reflective liquid crystal panel, and the viewing angle characteristics were measured using a measuring device (EZ Contrast 160D, manufactured by ELDIM) (described as “fresh” in Table 3). This was further thermostated at 80 ° C. for 100 hours in a thermostat, and the results are shown in Table 3. In the present invention, the viewing angle at which the contrast ratio becomes 3 was 100 ° or more in all directions after fresh and thermo. On the other hand, in the comparative example, irrespective of the presence or absence of the retarder,
The angle was as low as 0 ° or less, and the reduction in the viewing angle after the thermostat was 50 ° or less. When the circularly polarizing plate produced according to the present invention is used, a wide viewing angle can be obtained.

3. Production of Reflective Liquid Crystal Display Element A glass substrate provided with an ITO transparent electrode and a glass substrate provided with an aluminum reflective electrode having fine irregularities were prepared. A polyimide alignment film (SE-7992, manufactured by Nissan Chemical Industries, Ltd.) was formed on each of the two glass substrates on the electrode side, and rubbing treatment was performed. Two substrates were stacked via a 2.5 μm spacer so that the alignment films faced each other. The directions of the substrates were adjusted so that the rubbing directions of the two alignment films intersect at an angle of 117 °. Liquid crystal (MLC-6252, manufactured by Merck) is injected into the gap between the substrates,
A liquid crystal layer was formed. Thus, the twist angle is 63
A TN type liquid crystal cell having ゜ and Δnd values of 198 nm was produced. The circularly polarizing plate produced by the above method was attached to the side of the glass substrate provided with the ITO transparent electrode via an adhesive. On top of that, a protective film whose surface was subjected to AR (anti-reflection) treatment was further adhered. 1k for the reflection type liquid crystal display device
Hz rectangular wave voltage was applied. Visual evaluation was performed with a white display of 1.5 V and a black display of 4.5 V. In the present invention, it was confirmed that neutral gray was displayed without coloration in both white display and black display. .
Next, when the contrast ratio of the reflection luminance was measured using a measuring instrument (EZcontrast160D, manufactured by Eldim), the contrast ratio from the front was 23, and the viewing angle at which the contrast ratio was 3 was determined according to the present invention. After that, it was more than 100 ° in all directions. On the other hand, in the comparative example, the freshness was as low as 100 ° or less regardless of the presence or absence of the retardation developing agent, and the viewing angle reduction after the thermostat was 50 ° or less.

4. Preparation of Guest Host Reflective Liquid Crystal Display Element A solution of a polymer for forming a vertical alignment film (LQ-1800, manufactured by Hitachi Chemical DuPont Microsystems) is applied on a glass substrate provided with an ITO transparent electrode, dried, and then rubbed. Processing was performed. The λ / 4 plate (retardation plate) manufactured in Example 3 was adhered on a glass substrate on which aluminum was deposited as a reflection plate with an adhesive. On a λ / 4 plate,
An SIO layer is provided by sputtering, and ITO is
A transparent electrode was provided. A solution of a polymer for forming a vertical alignment film (LQ-1800, manufactured by Hitachi Chemical DuPont Microsystems) is applied on the transparent electrode, dried, and then rubbed in a direction of 45 ° from the slow axis direction of the λ / 4 plate. Was done.
Two glass substrates were stacked via a 7.6 μm spacer such that the alignment films faced each other. The orientation of the substrate was adjusted so that the rubbing direction of the alignment film was antiparallel.
In a gap between the substrates, 2.0% by mass of a dichroic dye (NKX-1366, manufactured by Nippon Kogaku Dyeing Co., Ltd.) and liquid crystal (ZLI-2806,
A mixture with 98.0% by mass (Merck) was injected by a vacuum injection method to form a liquid crystal layer. A rectangular wave voltage of 1 kHz was applied between the ITO electrodes of the manufactured guest-host reflection type liquid crystal display device. In the present invention, white display 1V, black display 10
The transmittance at V is 65% and 6%, respectively, and the transmittance ratio (contrast ratio) between white display and black display is 11: 1.
The viewing angle at which a contrast ratio of 2: 1 can be obtained in the upper, lower, left, and right directions is 10 in both the fresh, thermo and vertical directions.
All were good at 0 ° or more. The transmittance was measured while increasing and decreasing the voltage, but no hysteresis was observed in the transmittance-voltage curve.

[0063]

According to the present invention, a wavelength of 450 nm, 550 n
m, the retardation value Re (4 measured at 650 nm)
50), Re (550), and Re (650) in a stretched thermoplastic film satisfying the following formulas (1) and (2), wherein a heat shrinkage initiation temperature is 110 ° C. or more and 180 ° C. or less. By using a thermoplastic film, a thermoplastic film having uniformity in the width direction, optical characteristics that are hardly attenuated even at high temperatures, and excellent in flatness is provided. Also, by using this film (or a circularly polarizing plate using a film), a liquid crystal display device having excellent display quality can be provided. 0.60 <Re (450) / Re (550) <0.97: Equation (1) 1.01 <Re (650) / Re (550) <1.35: Equation (2)

[0064]

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a basic configuration of a reflection type liquid crystal display device.

FIG. 2 is a schematic cross-sectional view showing a typical mode of a guest-host reflection type liquid crystal display device.

FIG. 3 is a schematic sectional view showing another typical embodiment of a guest-host reflection type liquid crystal display device.

[Explanation of symbols]

 Reference Signs List 1 lower substrate 2 reflective electrode 3 lower alignment film 4 liquid crystal layer 5 upper alignment film 6 transparent electrode 7 upper substrate 8 λ / 4 plate 9 polarizing film 11 lower substrate 12 organic interlayer insulating film 13 metal reflector 14 λ / 4 plate 15 lower Transparent electrode 16 Lower alignment film 17 Liquid crystal layer 18 Upper alignment film 19 Upper transparent electrode 20 Light diffusing plate 21 Upper substrate 22 Antireflection layer 23 TFT 24 Spacer 31 Lower substrate 32 Organic interlayer insulating film 33 Cholesteric color reflector 34 λ / 4 plate 35 lower transparent electrode 36 lower alignment film 37 liquid crystal layer 38 upper alignment film 39 upper transparent electrode 41 upper substrate 42 antireflection layer 44 spacer 45 black matrix

Continued on front page F-term (reference) 2H049 BA03 BA06 BA07 BA42 BB03 BB11 BB49 BB63 BC03 BC22 2H091 FA08X FA08Z FA11X FA11Z FA14Z FA35Y GA08 GA13 HA07 HA08 HA10 LA30 4F071 AA02 AA09 AF29Y AF31 AF61 AG28 AG29 AH19

Claims (16)

[Claims] 1. Wavelength 450 nm, 550 nm, 650 n
retardation value measured in m, Re (450), R
e (550) and Re (650) are stretched thermoplastic films satisfying the following formulas (1) and (2), and the heat shrinkage onset temperature of the stretched thermoplastic film is 110 ° C. or higher and 1
A thermoplastic film characterized by being at most 80 ° C .: 0.60 <Re (450) / Re (550) <0.97: Formula (1) 1.01 <Re (650) / Re (550) < 1.35: Equation (2). 2. The thermoplastic film according to claim 1, wherein Re (550) is 120 nm or more and 160 nm or less. 3. The heat according to claim 1, wherein the stretched thermoplastic film has an average value of an angle formed by a slow axis and a stretch axis in the film plane of ± 5 ° or less. Plastic film. 4. The DR defined by the following formulas (A) to (C):
0, DR20, DR40 are 450 nm wavelength and 75 wavelength
0 nm, | DR20 (λ) −DR0 (λ) |
≦ 0.02, | DR40 (λ) −DR0 (λ) | ≦ 0.
4. The lens system according to claim 1, wherein the relation of (2) is satisfied.
(A) DR0 (λ) = Re (λ) / Re (550) (B) DR20 (λ) = Re20 (λ) / Re20 (5)
50) (C) DR40 (λ) = Re40 (λ) / Re40 (5
50) [where, λ is a measurement wavelength; Re (λ) is a retardation value measured in a normal direction of the film surface; Re20 (λ) is 2 mm from a normal direction of the film surface.
Retardation value measured at an angle of 0 °; and Re40 (λ) is 40 ° from the direction normal to the film surface.
It is the retardation value measured at the angle of ゜]. 5. The stretched thermoplastic film has a refractive index nx in the in-plane slow axis direction, a refractive index ny in a direction perpendicular to the in-plane slow axis, and a refractive index nz in the thickness direction of 1 ≦ 1. NZ =
The thermoplastic film according to any one of claims 1 to 4, wherein a relationship of (nx-nz) / (nx-ny) ≤2 is satisfied. 6. The stretched thermoplastic film has an IR2 color ratio of 1.5 to 2.5 for C—O expansion and contraction on a high stretch ratio side and an IR2 color ratio of 0.6 to 1 for C ＝ O expansion. The thermoplastic film according to any one of claims 1 to 5, wherein the thickness is not more than 0.2. 7. The stretched thermoplastic film has an IR2 color ratio of 1.4 or more and 1.8 or less for C—O expansion and contraction on a low stretch ratio side, and an IR2 color ratio of 1.1 or more for C ＝ O expansion and contraction. 7. The thermoplastic film according to any one of claims 1 to 6, wherein the thickness is not more than 0.5. 8. The heat according to claim 1, wherein the stretched thermoplastic film is made of acetylated cellulose having a degree of substitution of 2.4 or more and 2.9 or less. Plastic film. 9. The thermoplastic film according to claim 1, wherein the stretched thermoplastic film is formed of a cellulose acetate film laminated in two or more layers and ten or less layers. . 10. The stretched thermoplastic film according to claim 1, wherein the stretched thermoplastic film is at least uniaxially stretched using at least one pair of nip rolls installed in a thermostat. The thermoplastic film according to any one of the above. 11. The stretched thermoplastic film according to claim 1, wherein
The thermoplastic film according to any one of claims 1 to 10, wherein the film is obtained by being preheated while gradually heating at a temperature of 3 ° C / min or more and 50 ° C / min or less and then stretched. 12. A roll of at least 2 rolls and at least 30 rolls of the stretched thermoplastic film set at a distance of from 0.05 m to 0.7 m after stretching.
The thermoplastic film according to any one of claims 1 to 11, wherein the film is obtained by passing the film at a temperature of not more than ℃. 13. The stretched thermoplastic film according to claim 1, wherein the stretched thermoplastic film is a film obtained by gradually cooling at −0.3 ° C./min to −50 ° C./min after stretching. The thermoplastic film according to any one of the above items. 14. A retardation plate using the thermoplastic film according to claim 1. Description: 15. The phase difference plate and the polarizing film according to claim 14 are laminated such that the angle between the in-plane slow axis of the phase difference plate and the polarization axis of the polarizing film is substantially 45 °. A circularly polarizing plate characterized by being made. 16. A liquid crystal display device using at least one of the phase difference plate according to claim 14 and the circularly polarizing plate according to claim 15.