JP2003226763A - Method for producing negative birefringent polymer film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a negative birefringent film which is easy to control double refractive indices and, simultaneously, simple. <P>SOLUTION: In the polymer film having negative birefringence, the negative double refractive indices are controlled by varying the amount of the residual solvent present in the film. As the polymer, a polyimide or a polyetherketone is suitably used. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a negative birefringent polymer film whose negative birefringence can be controlled by a simple method.

[0002]

2. Description of the Related Art A film having negative birefringence (also called negative uniaxiality) is used for visual compensation of liquid crystal displays. Such a film may be formed of discotic liquid crystal (Japanese Patent Laid-Open No. 9-10465).
6, JP-A-9-194429, JP-A-9-
194430) or produced from a stretched polymer film (US Pat. No. 5,138,4).
74) or an unstretched polyimide film (US Pat. No. 5,344,916, US Pat. No. 5,480,964, US Pat. No. 5,580,950).
No. 6,238,753).

In obtaining these negative birefringent films, it is not easy to control the negative birefringence. For example, a discotic liquid crystal has a complicated chemical structure and is complicated to synthesize, resulting in an increase in cost.

In the case of a stretched film, it is controlled by changing the stretching ratio and the stretching direction. However, this method has the drawback that the film becomes extremely thin when the stretch ratio is increased, resulting in poor strength and difficulty in handling. Also,
There is also a method of producing a thick film and stretching the film to obtain a finished thickness, but it is technically extremely difficult to produce a thick film because uneven thickness is likely to occur.
Even if a thick film could be obtained,
A high degree of technology is required to precisely draw this. Also,
In the first place, the drawing method has a drawback that the yield is low.

Further, in the case of a polyimide negative birefringence film, it is shown in the above literature that it can be controlled by appropriately changing the structure of the polyimide. In particular,
Although the negative birefringence value can be increased by increasing the linearity and rigidity of the polyimide main chain, the availability of raw material monomers (diamine, dianhydride) necessary to change the structure of the polyimide is limited. There is a case.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a negative birefringent film, which is easy to control the birefringence and is simple.

[0007]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that a negative birefringence film, particularly a negative birefringence obtained by casting a polymer having an intrinsic negative birefringence value. With regard to the flexible film, it was found that the negative birefringence value can be controlled by a simple method, and the present invention has been completed.

That is, according to the present invention, in a polymer film having negative birefringence, the negative birefringence polymer is controlled by changing the amount of residual solvent contained in the film. A method for manufacturing a film is provided. Polyimide or polyetherketone is suitable as the polymer.

[0009]

The manufacturing method of the present invention is useful when a polymer having a negative birefringence value is cast to obtain a film. The polymer having a negative birefringence value can be used without limitation known ones, for example, polyimide,
Examples thereof include polyether ketone, polyether nitrile, polysulfone, and polycarbonate. Among them, polyimide or polyether ketone is preferable because a relatively high negative birefringence value can be obtained. The weight average molecular weight (Mw) of the polymer used is 2,000 to 1,000,
000, preferably 3,000 to 900,000, and more preferably 4,000 to 800,000. If the mass average molecular weight (Mw) is less than 2,000, the strength may be poor when a film is formed, while if it exceeds 1,000,000, the solubility in a solvent may be poor or the solution Storage stability may deteriorate.

Specifically, in the case of polyimide, those using the following as the diamine component and aromatic acid dianhydride can be mentioned. Examples of the diamine component include o
-Phenylenediamine, m-phenylenediamine, p-
Phenylenediamine, 2,4-diaminotoluene, 1,
4-diamino-2-methoxybenzene, 1,4-diamino-2-phenylbenzene, 1,3-diamino-4-chlorobenzene, 4,4-diaminobiphenyl, 4,4 '
-Diaminodiphenylmethane, 2,2-bis (4-aminophenyl) propane, 2,2-bis (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 4,4'- Diaminodiphenyl ether, 3,4
′ -Diaminodiphenyl ether, 1,3-bis (3-
Aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'- Bis (3-aminophenoxy) biphenyl, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4-
(4-Aminophenoxy) phenyl] -1,1,1,
3,3,3-hexafluoropropane, 4,4-diaminodiphenylthioether, 4,4'-diaminodiphenylsulfone, 2,2'-diaminobenzophenone,
3,3'-diaminobenzophenone, 1,8-diaminonaphthalene, 1,5-diaminonaphthalene, 2,6-diaminopyridine, 2,4-diaminopyrimidine, 2,4
-Diamino-s-triazine, 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl, 2,
2'-dibromo-4,4'-diaminobiphenyl, 2,
2'-dicyano-4,4'-diaminobiphenyl, 2,
2'-dichloro-6,6'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dicarboalkoxy-4,
4'-diaminobiphenyl and 2,2'-dicarboalkoxy-6,6'-dimethyl-4,4'-diaminobiphenyl are mentioned.

As the aromatic dianhydride, 3,3 ',
4,4'-benzophenone tetracarboxylic dianhydride,
2,3,3 ′, 4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic acid Dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (2,5,6-trifluoro-3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3 , 4-dicarboxyphenyl)
Propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, bis (3,4-dicarboxyphenyl) ether Dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 4,4 '-[4,4'-
Isopropylidene-di (p-phenyleneoxy)] bis (phthalic anhydride), N, N- (3,4-dicarboxyphenyl) N-methylamine dianhydride, bis (3,4-)
Dicarboxyphenyl) diethylsilane dianhydride, 2,
3,6,7-naphthalenetetracarboxylic dianhydride,
1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, thiophene-2,3,4,5
-Tetracarboxylic dianhydride, pyrazine-2,3,5
6-tetracarboxylic dianhydride, pyridine-2,3
5,6-Tetracarboxylic dianhydride, 2,2'-dibromo-4,4 ', 5,5'-biphenyltetracarboxylic dianhydride, 2,2'-diiodo-4,4', 5 5'-
Biphenyltetracarboxylic dianhydride, 2,2'-difluoro-4,4 ', 5,5'-biphenyltetracarboxylic dianhydride, 2,2'-bis (trifluoromethyl)
-4,4 ', 5,5'-biphenyltetracarboxylic dianhydride, 2,2'-bis (trichloromethyl) -4,4
′, 5,5′-biphenyltetracarboxylic dianhydride,
2,2'-bis (tribromomethyl) -4,4 ', 5
5'-biphenyltetracarboxylic dianhydride, 2,2 '
-Bis (triiodomethyl) -4,4 ', 5,5'-biphenyltetracarboxylic dianhydride, 3,6-diphenylpyromellitic dianhydride, 3,6-bis (trifluoromethyl) pyromellitic Acid dianhydride, 3,6-bis (methyl) pyromellitic dianhydride, 3,6-diiodopyromellitic dianhydride, 3,6-dibromopyromellitic dianhydride and 3,6-dichloro Examples include pyromellitic dianhydride.

In the case of polyetherketone, polyaryletherketone is particularly preferable, and among them, one having at least one fluorine atom in the repeating unit of the main chain is preferable. The polyaryl ether ketone referred to in the present invention is one having an ether group (-O-) and a ketone group (-C (= O)-) in a repeating unit, and these are linked by an aryl group. , Represented by the general formula (1).

[0013]

[Chemical 1] (In the formula, F is a fluorine atom, A is a halogen atom, a lower alkyl group or a lower alkoxy group, and x and y
Is an integer of 0 to 4, and m is 0 or 1. Also, n
Represents the degree of polymerization, and R ¹ is a group represented by the general formula (2). )

[Chemical 2] (In the formula, F is a fluorine atom, A ′ is a halogen atom,
A lower alkyl group or a lower alkoxy group, z and x ′ are integers of 0 to 4, p is 0 or 1, and R ²
Is a divalent aromatic group. )

Among them, in the general formula (1), y = 0 is preferable, and y = 0 and x'is more preferable.
= 0. These polyaryl ether ketones have a repeating structural unit represented by the following general formula (3), and R ¹
Is preferably a group represented by the following general formula (4).

[0015]

[Chemical 3] (In the formula, F is a fluorine atom, x is an integer of 0 to 4, m is 0 or 1, and n represents the degree of polymerization, and R
¹ is the same as the above formula (1). )

[0016]

[Chemical 4] (In the formula, F is a fluorine atom, z is an integer of 0 to 4, p is 0 or 1. R ² is a divalent aromatic group.)

Further, the above general formula (2) and the general formula
In (4), a divalent aromatic group (R ²) Is the following formula
At least one group selected from the group consisting of (5)
Preferably.

[0018]

[Chemical 5]

Specific examples of such preferable polyaryl ether ketones include those represented by the following general formula (6), general formula (7), general formula (8) or general formula (9). Can be mentioned. In these formulas, n represents the degree of polymerization.

[0020]

[Chemical 6]

[Chemical 7]

[Chemical 8]

[Chemical 9]

Among the polyether nitriles, polyaryl ether nitriles are particularly preferable, and among them, those having at least one fluorine atom in the repeating unit of the main chain are preferable. The polyaryl ether nitrile referred to in the present invention is
The repeating unit has an ether group (-O-) and a nitrile group (-CN), and these are linked by an aryl group, and is represented by the general formula (10).

[0022]

[Chemical 10] (However, R ³ represents a divalent organic group, and n represents the degree of polymerization.)

Of these, preferred are those in which R ³ in the general formula (10) is a divalent aromatic group.
Preferred specific examples include at least one group selected from the group consisting of the following formula (11).

[0024]

[Chemical 11]

Among them, the polyaryl ether nitrile represented by the general formula (12) is preferable because of its excellent solubility and transparency.

[0026]

[Chemical 12]

In the production method of the present invention, the amount of residual solvent in the film is adjusted by changing the coating conditions such as the film thickness, the solvent used for preparing the varnish, and the drying temperature.
Thereby, films having different negative birefringence values are obtained. In the present invention, the varnish can be prepared by dissolving the polymer in a solvent.
Generally preferred polymer solution concentrations are 1-80 wt%, more preferably 2-60 wt%, particularly preferably 3-5.
0 wt%, but the solvent used and the molecular weight of the polymer,
It depends on the structure, coating method and target film thickness.

In the present invention, any solvent can be used without particular limitation as long as it can dissolve the polymer. For example,
Halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, orthodichlorobenzene; phenol, parachlorophenol, o-chlorophenol, m-chlorophenol, o-cresol, m -Phenols such as cresol; aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, and 1,2-dimethoxybenzene; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, N- Ketone-based solvents such as methyl-2-pyrrolidone; ester-based solvents such as ethyl acetate and butyl acetate; t-butyl alcohol, glycerin, ethylene glycol, tris Alcoholic solvents such as ethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentanediol; amide solvents such as dimethylformamide, dimethylacetamide; acetonitrile, butyronitrile, etc. Nitrile solvents; ether solvents such as diethyl ether, dibutyl ether, tetrahydrofuran; carbon disulfide, ethyl cellosolve,
Butyl cellosolve and the like can be used alone or in combination.

The drying temperature for obtaining the polymer film of the present invention is appropriately selected according to the type of polymer or solvent, the required birefringence value and the like, and cannot be specified unconditionally, but is usually 40 ° C. or higher. 400 ° C or lower, preferably 5
0 ° C to 300 ° C, more preferably 60 ° C to 2
It is not higher than 00 ° C. By drying at 40 ° C. or higher, the film can be dried in a short time, and by drying at 400 ° C. or lower, oxidation and thermal decomposition of the film are less likely to occur. The coating film may be dried at a constant temperature or may be heated stepwise. The drying time is also appropriately selected, but is usually 10 seconds or more and 30 minutes or less, preferably 30 seconds or more and 25 minutes or less, and more preferably 1 minute or more and 20 minutes or less. 10 seconds or more 3
By drying for 0 minutes or less, a good film can be obtained without degrading the polymer.

The substrate to which the polymer solution is applied is not particularly limited as long as the finally obtained optical film is a film that exhibits optically negative uniaxiality. A glass substrate, a plastic substrate such as a plastic film, a stainless belt or a stainless drum, a metal substrate such as a copper foil, or the like can be used. Above all, it is preferable to use a plastic substrate, a stainless belt or a stainless drum in consideration of bonding with a polarizing plate described later.
If possible, it may be applied directly to the polarizing plate.

As the plastic film, polyethylene, polypropylene, poly (4-methylpentene-) is used.
1) Polyolefin, polyimide, polyamideimide, polyamide, polyetherimide, polyetheretherketone, polyketone sulfide, polyethersulfone, polysulfone, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacetal, Examples thereof include films formed from polycarbonate, polyarylate, acrylic resin, polyvinyl alcohol, polypropylene, cellulosic plastics, epoxy resin, phenol resin and the like. These plastic films may be optically isotropic or anisotropic.

Among the plastic films used for the substrate, polypropylene and polypropylene are preferred from the viewpoint of solvent resistance and heat resistance.
Polyethylene terephthalate and polyethylene naphthalate films are preferable. The thickness of the plastic film used as the substrate is usually 10 μm or more, preferably 20 μm.
m or more, and more preferably 30 μm or more. 10 μm
If the thickness is thinner, the strength of the substrate is weak, which may cause problems such as breakage during manufacturing.

As a coating method for obtaining the film of the present invention, any known method can be used. For example, a spin coating method, a roll coating method, a printing method, a dipping and pulling method, a curtain coating method, a Meyer bar coating method. The doctor blade method, knife coating method, tie coating method, gravure coating method, microgravure coating method, offset gravure coating method, lip coating method, spray coating method and the like can be used.

According to the method of the present invention, an optical film having a negative birefringence value which differs depending on the type of polymer can be obtained. By using this method, the thickness is 0.1 ~ 500μ
m, preferably 0.3 to 200 μm, more preferably 0.5 to 100 μm, and a negative birefringence value of 0.001 to 0.
A negative birefringent film in the range of 6, preferably 0.002 to 0.6, and more preferably 0.004 to 0.6 can be easily obtained.

The polymer film produced by the method of the present invention can be used as various optical films. The optical film may be a film alone or, if necessary, other optical members such as a retardation film having another refractive index structure, a liquid crystal film, a light scattering film, a diffractive film, a polarizing film (polarizing plate), a polarizer and the like. The combined laminate can be used for various optical applications, specifically, as an optical compensation member for various liquid crystal display elements. For example, by combining an industrially produced iodine-based or dye-based polarizer with the optical film of the present invention, and laminating the optical film on one side or both sides of the polarizer, the birefringence of the liquid crystal display device is improved. Can be a polarizing plate having a function of compensating and adjusting. When laminating the optical film of the present invention on one surface of the polarizer, a usual protective film can be laminated on the other surface of the polarizer.

The liquid crystal display element referred to here is, for example, ST
N (Super Twisted Nematic) cell, TN (Twisted Nem)
atic) cell, IPS (In-Plane Switching) cell, VA
(Vertical Alighned) cell, OCB (Optically Alig)
hned birefringence) cell, HAN (Hybrid Alighned)
Nematic) cell, ASM (Axially Symmetric Alighned)
Microcell), ferroelectric and antiferroelectric cells, and various types of cells such as those having regular orientation division and those having random orientation division. The liquid crystal display element in which the optical film is incorporated is a simple matrix type, TFT (Thin Film Transistor) electrode, TFD (Thin Film Transistor).
In-film diode) Any driving method such as an active matrix method using an electrode or the like, a plasma address method or the like may be used.

Further, the optical film can be used in a transmissive / semi-transmissive liquid crystal display element having a backlight system, a reflective liquid crystal display element having a reflector, and a projection type liquid crystal display element. Can be incorporated. The location of the optical film in the liquid crystal display element is not particularly limited, but is usually between the polarizing plate and the drive cell, and one or more sheets are provided above and / or below the drive cell. It is common to place an optical film. In this case, the optical film is a retardation film having a different refractive index structure, a liquid crystal film, a diffraction film, a light scattering film,
It can be installed in combination with a lens sheet or the like.

[0038]

The present invention will be described below with reference to examples.
The present invention is not limited to these examples. Further, "%" means "% by mass" unless otherwise specified.

(Refractive Index Measurement) Using an automatic birefringence meter (KOBRA 21ADH) manufactured by Oji Scientific Instruments, 590 nm
The refractive index at was measured. (Film thickness measurement) Anritsu digital micrometer K-
It was measured using Model 351C. (Amount of residual solvent) T manufactured by Seiko Instruments Inc.
Using GA100, 10 ℃ / from 30 ℃ to 500 ℃
The measurement was performed while raising the temperature at min, and the amount of mass reduction from 100 ° C. to 300 ° C. was taken as the residual solvent amount.

Example 1 A polyimide (Mw = 211,000) represented by the following structural formula (Formula 13) was dissolved in cyclohexanone to prepare a 15 wt% varnish. This varnish was spin-coated on a glass plate at different rotation speeds and dried at 150 ° C. for 15 minutes to obtain three types of films having different film thicknesses. The residual solvent amount and the negative birefringence (Δn) of the film are as shown in Table 1, and it was found that a film having a different Δn value depending on the residual solvent amount was obtained.

[0041]

[Chemical 13]

[0042]

[Table 1] Film thickness (μm) Δn of the film Amount of residual solvent (wt%) 1.9 0.044 3.4 5.6 0.036 5.4 10.7 0.031 6.5

A polyetherketone (Mw = 539,000) represented by the following structural formula (Formula 14) was dissolved in toluene to prepare a 10 wt% varnish. This varnish was spin-coated on a glass plate and dried at 100 ° C. for 10 minutes to obtain films with three different film thicknesses. The residual solvent amount and the negative birefringence (Δn) of the film are shown in Table 2, and it was found that a film having a different Δn value depending on the residual solvent amount was obtained.

[0044]

[Chemical 14]

[0045]

[Table 2] Film thickness (μm) Δn of the film Residual solvent amount (wt%) 11.10 0.0218 2.9 7.00 0.0273 2.1 2.70 0.0294 1.6

A polyether ketone (Mw = 208,000) represented by the following structural formula (Formula 15) was dissolved in toluene to prepare a 10 wt% varnish. This varnish was spin-coated on a glass plate and dried at 100 ° C. for 10 minutes to obtain films with three different film thicknesses. The residual solvent amount and the negative birefringence (Δn) of the film are as shown in Table 3, and it was found that a film having a different Δn value depending on the residual solvent amount was obtained.

[0047]

[Chemical 15]

[0048]

[Table 3] Film thickness (μm) Δn of the film Residual solvent amount (wt%) 16.93 0.0146 4.1 9.50 0.0169 3.7 4.43 0.0186 3.3

[0049]

As described above, according to the present invention, when a film is produced from a polymer having a negative birefringence value by a casting method, the negative birefringence value can be controlled very easily. Therefore, it is not necessary to synthesize a polymer having a complicated structure to obtain a desired negative birefringence value, and it can be applied to various polymers. Further, since a thin film can be obtained very easily without requiring a high-level technique such as precision stretching for thinning the film, it is industrially very useful.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 79:08 C08L 79:08 Z (72) Inventor Shusaku Nakano 1-2-1, Shimohozumi, Ibaraki-shi, Osaka No. Nitto Denko Corporation (72) Inventor Sadahiro Nakanishi 1-2, Shimohozumi, Ibaraki City, Osaka Prefecture F-term within Nitto Denko Corporation (reference) 2H049 BA06 BA42 BB42 BC01 BC22 4F071 AA51 AA60 AF31 BA02 BC01 4F205 AA32 AA40 AE10 AG01 AH73 GB01 GC01 GN22 GN24

Claims (2)

[Claims] 1. A method for producing a negative birefringent polymer film, which comprises controlling the negative birefringence index of a polymer film having negative birefringence by changing the amount of residual solvent contained in the film. . 2. The method for producing a negative birefringent polymer film according to claim 1, wherein the polymer having negative birefringence is polyimide or polyetherketone.