JP2003050316A - High wavelength dispersion optical retardation plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical retardation plate with large wavelength dispersion characteristics of birefringence and being obtainable as a whole cloth film with excellent solubility in a solvent and with high homogeneity by means of a solvent cast method. SOLUTION: The optical retardation plate composed of a copolymer obtained by polymerizing an acyclic olefin monomer (A) selected from ethylene and a 3-20C α-olefin compounds, a cyclic olefin monomer (B) selected from cyclic olefin compounds such as norbornene and an aromatic vinyl monomer (C) selected from vinyl compounds with an aromatic hydrocarbon unit such as styrene with a copolymerization ratio of 5-40 mol% aromatic vinyl monomer (C) and 60-95 mol% sum total of the acyclic olefin monomer (A) and the cyclic olefin monomer (B) and having >=1.1 wavelength dispersion coefficient α=R450 /R590 expressed by the ratio of retardation at 450 nm wavelength R450 to retardation at 590 nm wavelength R590 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retardation plate used in a liquid crystal display device or the like.

[0002]

2. Description of the Related Art A retardation plate is a super twisted nematic (ST
It is generally used as an optical compensation layer for N) type liquid crystal display devices, but various applications as an optical compensation layer have been studied,
As a result, there is a need for a retardation plate having various optical characteristics. In particular, a liquid crystal display device that requires a high-speed response uses a liquid crystal having a large wavelength dispersion characteristic of birefringence. Therefore, the retardation plate in the optical compensation layer also has Larger things are desired.

The wavelength dispersion characteristic of birefringence can be expressed by a ratio R ₄₅₀ / R ₅₉₀ of a retardation R ₄₅₀ at a wavelength of ₄₅₀ nm and a retardation R ₅₉₀ at a wavelength of 590 nm, and this ratio is generally called a wavelength dispersion coefficient α. I'm out.
A retardation plate having a large wavelength dispersion characteristic of birefringence, for example, a retardation plate having a wavelength dispersion coefficient α of 1.10 or more is made of aromatic polyarylate, polysulfone, polyether sulfone, or the like. There is a phase plate,
Since polysulfone and polyether sulfone have poor solubility in chlorinated hydrocarbons such as methylene chloride, it is not possible to obtain a solvent cast film that is a raw material for obtaining a retardation plate with high homogeneity. There is a problem.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a retardation plate made of a polymer different from known retardation plates and having a large wavelength dispersion characteristic of birefringence. Another object of the present invention is to provide a retardation plate which has good solubility in a solvent and can be made into a highly uniform original film by a solvent casting method.
As a result of earnest studies, the inventors of the present invention have found that a retardation plate capable of solving the above problems can be obtained by subjecting a polymer obtained by copolymerizing three specific types of monomers at a composition ratio within a certain range to a stretching process. Heading out, the present invention was reached.

[0005]

That is, the present invention provides the following components (A), (B) and (C): (A) at least one selected from ethylene and an α-olefin compound having 3 to 20 carbon atoms. At least 1 selected from (B) cyclic olefin compounds
A cyclic olefin monomer; and a copolymer of at least one aromatic vinyl monomer selected from (C) a vinyl compound having a cyclic unit composed of an aromatic hydrocarbon, wherein the aromatic vinyl monomer (C) is 5
.About.40 mol%, composed of a copolymer obtained by polymerizing at a copolymerization ratio such that the total amount of the acyclic olefin monomer (A) and the cyclic olefin monomer (B) is 60 to 95 mol%, and the wavelength is 45.
A retardation plate having a wavelength dispersion coefficient α (= R ₄₅₀ / R ₅₉₀ ) represented by a ratio of a retardation R _{450 at} 0 nm and a retardation R _{590 at} a wavelength of 590 nm of 1.1 or more.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The retardation plate in which a copolymer having a repeating unit composed of a monomer having a positive polarizability and a repeating unit composed of a monomer having a negative polarizability is stretched and oriented, the retardations derived from the respective repeating units cancel each other out. Therefore, the retardation of the copolymer is the difference in retardation of the components derived from the respective repeating units. Therefore, the wavelength dispersion property of such a copolymer is determined by the wavelength dispersion property of each repeating unit and the retardation of the component derived from each repeating unit. That is, chromatic dispersion can be controlled by introducing repeating units having different polarizability and chromatic dispersion into the polymer.

The role of the repeating unit derived from each of the non-cyclic olefin monomer (A), the cyclic olefin monomer (B) and the aromatic vinyl monomer (C) constituting the polymer which becomes the retardation film of the present invention is specifically described. Specifically, the repeating unit derived from the acyclic olefin monomer (A) has a role of imparting flexibility to the polymer, the polarizability is positive in the main chain direction of the polymer, and its wavelength dispersion is It is considered that the coefficient α _A ≈1.00. Further, the repeating unit derived from the cyclic olefin monomer (B) has a role of improving the heat resistance of the polymer, and the polarizability is considered to be substantially positive in the main chain direction of the polymer, and its wavelength dispersion coefficient α _It is considered that _B ≈ 1.00. Further, the repeating unit derived from the aromatic vinyl monomer (C) has a role mainly to improve the transparency of the polymer, the polarizability is negative in the direction of the main chain of the polymer, and its wavelength dispersion coefficient α _C It is considered that ≧ 1.00. By appropriately controlling the copolymerization ratio of these non-cyclic olefin monomer (A), cyclic olefin monomer (B) and aromatic vinyl monomer (C), flexibility and transparency,
It is possible to design a copolymer having an excellent balance of heat resistance and wavelength dispersion characteristics.

The composition ratio of the repeating unit derived from the acyclic olefin monomer (A), the repeating unit derived from the cyclic olefin monomer (B), and the repeating unit derived from the aromatic vinyl monomer (C) in the copolymer is , The repeating unit derived from the aromatic vinyl monomer (C) is 5 to
40 mol%, and the total of the repeating units derived from each of the non-cyclic olefin monomer (A) and the cyclic olefin monomer (B) is 60 to 95 mol%. The repeating unit derived from the cyclic olefin monomer (B) is 20 mol%
It is preferably at least 40 mol%, more preferably at least 40 mol% in consideration of flexibility and heat resistance. The repeating unit derived from the acyclic olefin monomer (A) is appropriately present in an amount of 1 mol% or more. The retardation due to the repeating unit derived from the aromatic vinyl monomer (C) is larger than the retardation due to the repeating unit derived from each of the non-cyclic olefin monomer (A) and the cyclic olefin monomer (B), and the smaller the difference is, The wavelength dispersion characteristic of birefringence when used as a retardation plate becomes large.

Further, the aromatic vinyl monomer (C) is
The retardation plate of the present invention has a function of controlling wavelength dispersion characteristics. In order to enhance the wavelength dispersion characteristics when the retardation plate is used, it is preferable that the aromatic vinyl monomer (C) is present in an amount of 9 mol% or more. Then, in order to obtain a copolymer having a wavelength dispersion coefficient α of 1.1 or more, a polymer composed of only the non-cyclic olefin monomer (A), a polymer composed of only the cyclic olefin monomer (B), and an aromatic vinyl monomer The wavelength dispersion coefficients of the polymer consisting only of (C) are α _A , α _B, and α _C, and they are derived from the acyclic olefin monomer (A), the cyclic olefin monomer (B), and the aromatic vinyl monomer (C), respectively. Retardation of the repeating unit at a wavelength of 590 nm is defined as x, y and z, and the retardation plate made of this copolymer has a wavelength of 5
Letting the retardation at 90 nm be R, a combination of x, y and z that satisfies the following formulas (I) and (II) may be used.

[0010] _{α C z- (α A x +} α B y) ≧ 1.1R (I) z- (x + y) = R (II)

The acyclic olefin monomer (A) and the cyclic olefin monomer (B) employed in the present invention have homodispersion wavelength dispersion coefficients α _A and α _{B of about} 1.0, respectively.
Since it is 0, an appropriate copolymerization ratio is determined by the wavelength dispersion coefficient α _{C of the} homopolymer of the aromatic vinyl monomer (C). For example, to obtain a retardation plate having a wavelength dispersion coefficient α of 1.20 and a retardation of 300 nm at a wavelength of 590 nm, if α _C = 1.10, then z: (x + y) = 2: 1. Such a copolymerization ratio is good, and x + y = 300 nm and z = 600 nm. Further, for example, when α _C = 1.07, the copolymerization ratio such that z: (x + y) = 2.86: 1.86 is good, and x + y = 558 nm and z = 858 nm. As can be seen from these examples, it is preferable that the difference between α _A and α _C and the difference between α _B and α _C are large, because x, y and z can be small respectively, and thus the retardation plate can be easily processed.

The retardation plate of the present invention is preferably a polymer having a glass transition temperature (Tg) of usually 100 ° C. or higher and heat resistance in consideration of the use environment. The glass transition temperature is more preferably 140 ° C. or higher.

Next, each monomer component constituting the copolymer will be described. Acyclic olefin monomer (A)
Is ethylene and / or an α-olefin compound having 3 to 20 carbon atoms. Here, as the α-olefin compound having 3 to 20 carbon atoms, for example, propylene, 1-butene,
1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, straight chain α- having 3 to 20 carbon atoms. Olefin and 4-methyl-
Branched α-containing 4 to 20 carbon atoms such as 1-pentene, 3-methyl-1-pentene and 3-methyl-1-butene
Examples include olefins. Among these, ethylene having 2 carbon atoms and propylene or 1-butene, which is a linear α-olefin having 3 or 4 carbon atoms, is used when the polymer of the present invention is formed into a film. It is preferable in terms of flexibility, and ethylene is particularly preferable for the same reason. The above-mentioned ethylene and α-olefin may be used alone or in combination of two or more kinds.

The cyclic olefin monomer (B) is a compound having a polymerizable carbon-carbon double bond in the carbon ring, and when copolymerized, a cyclobutane ring, a cyclopentane ring, or a cyclobutane ring is contained in the main chain of the copolymer. Cyclohexane ring, they are 2
It is a monomer capable of introducing an alicyclic ring such as one or more bonded rings. Specifically, bicyclo [2,2,1] hept-2-ene, which is usually called norbornene, 6-alkylbicyclo [2,2,1] hept-2-ene, 5,
6-dialkylbicyclo [2,2,1] hept-2-ene, 1-alkylbicyclo [2,2,1] hept-2-
Ene, 7-alkylbicyclo [2,2,1] hept-2
Norbornene derivatives in which an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, and a butyl group is introduced, and tetracyclo [4,4,0] also called dimethanooctahydronaphthalene , 1 ^2,5 , 1 ^7,10 ]
-3-dodecene and 8-alkyltetracyclo [4,4
4,0,1 ^2,5, 1 ^7,10] -3-dodecene, 8,9-dialkyl tetracyclo [4,4,0,1 ^2,5, 1 ^7,10]
A dimethanooctahydronaphthalene derivative in which an alkyl group having 3 or more carbon atoms is introduced at the 8-position and / or the 9-position of dimethanooctahydronaphthalene, such as -3-dodecene;
Furthermore, a norbornene derivative in which one or more halogens are introduced in one molecule, a dimethanooctahydronaphthalene derivative in which halogens are introduced at the 8- and / or 9-positions, and the like can be mentioned. These cyclic olefins are
They may be used alone or in combination of two or more.

The aromatic vinyl compound as the component (C) is one in which an aromatic group is bonded to a vinyl group forming a main chain by copolymerization with the acyclic olefin monomer (A) and the cyclic olefin monomer (B). Is. Specific aromatic groups include aromatic hydrocarbon groups having about 6 to 14 carbon atoms.

Vinyl compounds having an aromatic hydrocarbon group include styrene and its derivatives. The styrene derivative is a compound in which another group is bonded to styrene, and examples thereof include o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene,
alkyl styrenes such as o-ethyl styrene and p-ethyl styrene, hydroxy styrene, t-butoxy styrene, vinyl benzoic acid, vinyl benzyl acetate,
Substituted styrenes such as o-chlorostyrene and p-chlorostyrene in which a hydroxyl group, an alkoxy group, a carboxyl group, an acyloxy group, a halogen and the like are introduced into the benzene nucleus of styrene, 4-vinylbiphenyl, 4-hydroxy-4'- Examples thereof include vinyl biphenyl compounds such as vinyl biphenyl.

Among these aromatic vinyl monomers (C), from the viewpoint of wavelength dispersion characteristics, monomers having a benzene ring unit are preferable, for example, styrene and its derivatives are preferable. The above vinyl compounds having an aromatic group may be used alone or in combination of two or more.

The retardation plate copolymer of the present invention comprises a repeating unit derived from the acyclic olefin monomer (A), a repeating unit derived from the cyclic olefin monomer (B) and an aromatic vinyl monomer (C). And a repeating unit derived from each, specifically, ethylene / norbornene / styrene copolymer, ethylene / dimethanooctahydronaphthalene / styrene copolymer, propylene / norbornene / styrene copolymer, propylene / Dimethanooctahydronaphthalene / styrene copolymer, ethylene / norbornene / t-butoxystyrene copolymer and the like.

The copolymerization form of the copolymer may be either a random form or a block form as long as the effect of the present invention is not impaired, but the block form is such that three types of constituent monomers each form a domain. It is better to avoid such things as those that show sex may deteriorate transparency.

The copolymer used in the retardation plate of the present invention comprises, for example, a non-cyclic olefin monomer (A), a cyclic olefin monomer (B) and an aromatic vinyl monomer (C) in the presence of a metallocene catalyst. By copolymerizing
Can be manufactured. At that time, the copolymerization composition and the molecular weight can be changed by appropriately changing the polymerization conditions such as the amount of the non-cyclic olefin monomer (A), the cyclic olefin monomer (B) and the aromatic vinyl monomer (C), the polymerization temperature and the polymerization time. Etc. different copolymers can be obtained. This copolymer is an ultraviolet absorber within a range that does not impair the effects of the present invention,
It may contain various additives such as an antioxidant, a lubricant, an antistatic agent, an antibacterial agent, an antifogging agent and a plasticizer.

The retardation plate of the present invention is usually produced by using the above-described copolymer as a film and further stretching it. The method for forming the film is not particularly limited, but for example, a method such as a solvent casting method or a melt extrusion method can be adopted. The stretching method is not particularly limited, and examples thereof include transverse stretching by a tenter method and longitudinal stretching by roll-to-roll stretching.

[0022]

EXAMPLES Examples will be shown below, but the present invention is not limited to these examples.

Example 1 Ethylene, styrene and norbornene were mixed at 29:22:49.
The copolymer copolymerized at a molar ratio of
The film was 0 μm thick. The obtained film was longitudinally uniaxially stretched 1.5 times at 160 ° C. using an autograph. As a result, with negative polarization, R ₅₉₀ = 12.3 nm and R ₄₅₀ = 14.4.
A retardation plate with 1 nm and α = 1.15 was obtained.

Example 2 Ethylene, styrene and norbornene were mixed at 46:27:27.
The copolymer copolymerized at a molar ratio of
The film was 0 μm thick. The obtained film was longitudinally uniaxially stretched 1.6 times at 80 ° C. using an autograph. As a result, with negative polarization, R ₅₉₀ = 126.0 nm, R ₄₅₀ = 14
A retardation plate having a thickness of 2.7 nm and α = 1.13 was obtained.

Example 3 Ethylene, styrene and norbornene were added at 37:13:50.
The copolymer copolymerized in a molar ratio of
A film with a thickness of μm was used. The obtained film was longitudinally uniaxially stretched 1.8 times at 160 ° C. using an autograph. As a result, with negative polarization, R ₅₉₀ = 38.1 nm and R ₄₅₀ = 47.
A retardation plate with 0 nm and α = 1.23 was obtained.

Example 4 A copolymer obtained by copolymerizing ethylene, styrene and norbornene in a molar ratio of 41: 9: 50 was press-molded to 90 μm.
It was made a m-thick film. The obtained film was longitudinally uniaxially stretched 1.7 times at 160 ° C. using an autograph. As a result, with negative polarization, R ₅₉₀ = 2.7 nm, R ₄₅₀ = 7.1 nm,
A retardation plate with α = 2.63 was obtained.

[0027]

The retardation plate according to the present invention has a large wavelength dispersion characteristic of birefringence and is effectively used as an optical compensation layer of a liquid crystal display device using a liquid crystal having a large wavelength dispersion characteristic of birefringence. be able to. In addition, since the terpolymer of non-cyclic olefin monomer / cyclic olefin monomer / aromatic vinyl monomer that constitutes this retardation plate has high solubility in a solvent such as methylene chloride, The raw film for forming can be easily manufactured by the solvent casting method.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Nobuo Oi             Sumitomo Chemical Co., Ltd. 1-5 Anezaki Kaigan, Ichihara City, Chiba Prefecture             Business F term (reference) 2H049 BA06 BA25 BB47 BB48 BC03                       BC22                 2H091 FA11X FA11Z FB02 HA10                       KA02 LA16                 4J100 AA02P AA03Q AA07Q AB02R                       CA05 JA32 JA43

Claims (4)

[Claims] 1. At least one acyclic olefin monomer selected from ethylene and an α-olefin compound having 3 to 20 carbon atoms, at least one cyclic olefin monomer selected from a cyclic olefin compound, and an aromatic hydrocarbon. At least one aromatic vinyl monomer selected from vinyl compounds having a cyclic unit, the aromatic vinyl monomer is 5 to 40 mol%, and the total amount of the non-cyclic olefin monomer and the cyclic olefin monomer is 60 to 9
The wavelength dispersion coefficient α (= R ₄₅₀ / R ₅₉₀₎ is represented by the ratio of the retardation R ₄₅₀ at a wavelength of ₄₅₀ nm and the retardation R ₅₉₀ at a wavelength of 450 nm and is composed of a copolymer polymerized at a copolymerization ratio of 5 mol%. ) Is 1.1 or more, a retardation plate. 2. The retardation plate according to claim 1, wherein the cyclic olefin monomer is 20 mol% or more. 3. The retardation plate according to claim 1, wherein the non-cyclic olefin monomer is ethylene, propylene or 1-butene. 4. The retardation plate according to claim 1, wherein the aromatic vinyl monomer is styrene or its derivative.