JPH0713023A - Phase difference film and method for regulating wavelength dependence of phase difference film - Google Patents

Abstract

PURPOSE:To obtain an inexpensive phase difference film in which wavelength dependence is easily regulated without requiring a complicated process by incorporating a plasticizer into a thermoplastic resin. CONSTITUTION:This phase difference film consists of 100 pts.wt. thermoplastic resin and 2-20 pts.wt. plasticizer. The plasticizer, to be used is, for example, phthalic acid-base plasticizer such as dimethylphthalate and diethylphthalate, aliphatic dibasic acid-base plasticizer such as adipic acid-2-ethylhexyl and adipic acid-di-n-decyl, phosphate-base plasticizer such as tributhylphosphate and tri-2- ethylhexylphosphate, and epoxy plasticizer such as epoxidized soybean oil and epoxydized talleol fatty acid 2-ethylhexyl. It is preferable to use a polymer plasticizer such as polyester-base or polyether-base one at the standpoint that the polymer has small transfer property.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical film, and more particularly to a retardation film in which the wavelength dependence can be adjusted by adding a plasticizer and a method for adjusting the wavelength dependence of the retardation film.

[0002]

2. Description of the Related Art In recent years, various retardation films have been studied as optical films used in the field of liquid crystal display devices, particularly for improving the display quality of STN liquid crystal display devices.

Recently, studies have been made to improve the responsiveness of STN liquid crystal display devices, but for high speed response, the wavelength dependence (R =
In 1.15), the display quality is insufficient, and the one having a larger R value is desired. The R value is the most preferable value depending on the structure of the liquid crystal cell, and it is desired that the R value can be controlled by the retardation film. However, R
Since the value is determined by the structure of the polymer, a method in which two films having different kinds of structures are stacked and used (Japanese Patent Laid-Open No. Hei 3)
-13917, JP-A-3-13916, etc.) have been proposed. However, there are many disadvantages in the process such as cost increase and adjustment of the angle of superposition and adhesion.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a retardation film which is inexpensive, and whose wavelength dependence is easily adjusted without requiring complicated steps, and a method of adjusting the wavelength dependence of the retardation film. It is provided.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above circumstances, and have found that the above problems can be solved by incorporating a plasticizer, and have completed the present invention.
That is, the first of the present invention is a retardation film containing 2 to 20 parts by weight of a plasticizer with respect to 100 parts by weight of a thermoplastic resin, and the second of the present invention is based on 100 parts by weight of a thermoplastic resin. 2 to 20 parts by weight of a plasticizer is added to each of the methods to adjust the wavelength dependence of the retardation film.

The retardation film is obtained by stretching the film to generate birefringence (Δn) and having Re (retardation) represented by Re = Δn · d (d is the thickness of the film). Color unevenness when sandwiched between polarizing plates is important in the quality of the retardation film, but the film thickness accuracy of the original film is closely related to the color unevenness. As a method for producing the raw fabric, there are extrusion molding and casting from a solution in which a polymer is dissolved, but from the viewpoint of film thickness accuracy and surface property, casting to form a film is preferable. The Re of the retardation film is selected from the range of 10 to 2000 nm according to the liquid crystal device used.

Examples of the thermoplastic resin used in the present invention include polyarylate and polycarbonate. Polyarylate is preferable in terms of heat resistance and transparency.

[0008] The plasticizer is generally added for the purpose of improving the processability of the resin in the melt molding of the thermoplastic polymer, but in the present invention, it is added for the purpose of adjusting the wavelength dependence. The type of plasticizer that can be used is that it dissolves in a solvent together with the polymer, and the solution is cast onto glass or a belt to form a film, peeled and dried at a high temperature to remove the solvent, and then stretched to give a predetermined Re. Any material that does not impair the appearance of the film such as transparency can be used in the step of obtaining the retardation film.

Examples of such plasticizers include phthalic acid type plasticizers such as dimethyl phthalate, diethyl phthalate,
Di-n-butyl phthalate, di-n-octyl phthalate,
Di-2-ethylhexyl phthalate, diisooctyl phthalate, n-octyl phthalate, di-n-decyl phthalate, diisodecyl phthalate, di-n-dodecyl phthalate, diisotridecyl phthalate, dicyclohexyl phthalate, butylbenzyl phthalate , Di-2-ethylhexyl isophthalate; Aliphatic dibasic acid plasticizers include 2-ethylhexyl adipate, di-n-decyl adipate, diisodecyl adipate, di-2-ethylhexyl azelate, dibutyl sebacate, sebacine. Acid di-2
-Ethylhexyl; as a phosphoric acid ester-based plasticizer,
Tributyl phosphate, tri-2-ethylhexyl phosphate,
2-ethylhexyl phosphate, tricresyl phosphate; epoxidized soybean oil, epoxidized tall oil fatty acid 2-ethylhexyl as epoxy plasticizer; butyl stearate, butyl oleate as fatty acid ester plasticizer; chlorine-containing plasticizer , Chlorinated paraffin, chlorinated fatty acid methyl; as the polymer plasticizer, a polymer plasticizer containing an ester group (dibasic acid such as adipic acid, sebacic acid, phthalic acid and 1,2-propylene glycol, 1; , 3
A polycondensate with a glycol such as butylene glycol),
Examples thereof include ether group-containing polymer plasticizers (polyethylene glycol dimethyl ether, polyethylene glycol benzoate), and these may be used alone or in combination of two or more. In addition, among these plasticizers, polyester-based,
Polymer type plasticizers such as polyether type are preferable.

The plasticizer is added in an amount of 2 to 20 parts by weight based on 100 parts by weight of the thermoplastic resin. If it is less than 2 parts by weight, a sufficient effect cannot be obtained, and if it exceeds 20 parts by weight, problems such as deterioration of heat resistance and bleeding of the plasticizer occur. The film of the present invention may have an ordinary transparent hard coat layer on one side or both sides thereof for the purpose of surface protection, or may have a gas barrier layer. According to the present invention, it is possible to increase the wavelength dependence R represented by the following formula (I) by 0.02 or more. R = Re (400) / Re (550) (I) where Re (400) is the retardation at a wavelength of 400 nm and Re (550) is the retardation at a wavelength of 550 nm.

[0011]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Example 1A: Synthesis of amorphous aromatic polyester (PAR1) 2,2-bis (4-hydroxyphenyl) propane 2
0.11 g, bis (3,5-dimethyl-4-hydroxyphenyl) methane 15.06 g, para-t-butylphenol 0.95 g, sodium hydrosulfite 0.26 g, 5N-NaOH aqueous solution 78.2 ml, water 17
6.8 ml was mixed in a 300 ml eggplant type flask in a nitrogen atmosphere and cooled to 5 ° C. to prepare an alkaline aqueous solution of dihydric phenol. On the other hand, terephthalic acid chloride 21.
32 g and 9.14 g of isophthalic acid chloride were dissolved in 255 ml of methylene chloride in another 300 ml eggplant-shaped flask under a nitrogen atmosphere and cooled to 5 ° C. In a 1 liter separable flask, 137 ml of water and 0.16 g of benzyltributylammonium chloride as a catalyst were charged in a nitrogen atmosphere and cooled in the same manner. While vigorously stirring, the above two liquids were continuously added simultaneously by pumping over 10 minutes. After 2 hours from the completion of the addition, 0.42 g of benzoyl chloride was dissolved in 5 ml of methylene chloride, and the solution was added thereto. After 20 minutes, stirring was stopped. After decanting the aqueous layer, the same amount of water was added and the mixture was neutralized with a small amount of hydrochloric acid while stirring. After repeating desalting by decanting and washing with water, 300 ml of methylene chloride was added to dilute, the solution was heated to 40 to 50 ° C, and water in the polymer methylene chloride was removed by azeotropic dehydration with methylene chloride. 1
Methylene chloride was distilled to 5% by weight. The molecular weight of this polymer was ηsp / c = 0.90 (32 ° C., 0.32 g / dl in chloroform).

B: Preparation of Retardation Film The polymer obtained in A above was added to a methylene chloride solution, and Table 1 was added.
The plasticizer shown in 1 was added and mixed. SU these solutions
Cast on S plate, leave at room temperature for 60 minutes, peel off the film, 4
It is sandwiched between one-sided fixing jigs and dried under the conditions shown in Table 1, and about 100
A μm thick film was obtained. 11cm x 1 from this film
A 1 cm sample is cut and stretched using a stretching tester (X4HD-HT, Toyo Seiki Seisakusho), and a microscopic polarization spectrophotometer (TFM-120AF) manufactured by Oak Seisakusho Co., Ltd.
T) was used to measure the wavelength dependence [drawing speed: 10 cm
/ Min (100% / min), draw ratio: 1.2 times]. The results are shown in Table 1.

Example 2A: Synthesis of amorphous aromatic polyester (PAR2) 20.79 g of bis (3,5-dimethyl-4hydroxyphenyl) sulfone, 2,2-bis (4-hydroxyphenyl) propane 15. 49 g (molar ratio 5/5), para
0.62 g of t-butylphenol, 0.48 g of sodium hydrosulfite, 13.44 g of NaOH and 224.4 ml of water were mixed in a 300 ml eggplant-shaped flask under a nitrogen atmosphere and cooled to 5 ° C. to obtain an alkali of dihydric phenol. An aqueous solution was prepared. On the other hand, terephthalic acid chloride 1
3.99 g and 13.99 g of isophthalic acid chloride were dissolved in 233 ml of methylene chloride in another 300 ml eggplant-shaped flask under a nitrogen atmosphere and cooled to 5 ° C. In a 1 liter separable flask, 130 ml of water and 0.14 g of tetrabutylphosphonium bromide as a catalyst were charged in a nitrogen atmosphere and cooled in the same manner. While vigorously stirring, the above two liquids were continuously added simultaneously by pumping over 10 minutes. After 2 hours from the completion of the addition, 0.42 g of benzoyl chloride was dissolved in 5 ml of methylene chloride, and the solution was added thereto. After 20 minutes, stirring was stopped. After decanting the aqueous layer, the same amount of water was added and the mixture was neutralized with a small amount of hydrochloric acid while stirring. After repeating desalting by decanting and washing with water, 300 ml of methylene chloride was added to dilute, the solution was heated to 40 to 50 ° C, and water in the polymer methylene chloride was removed by azeotropic dehydration with methylene chloride. 1
Methylene chloride was distilled to 8% by weight. The molecular weight of this polymer was ηsp / c = 0.85 (32 ° C., 0.32 g / dl in chloroform), and the Tg determined by the TMA method was 240 ° C.

B: Preparation of Retardation Film In the methylene chloride solution of the polymer obtained in the above A, Table 1
The plasticizer shown in 1 was added and mixed. SU these solutions
Cast on S plate, leave at room temperature for 60 minutes, peel off the film, 4
It is sandwiched between one-sided fixing jigs and dried under the conditions shown in Table 1, and about 100
A μm thick film was obtained. 11cm x 1 from this film
A 1 cm sample is cut and stretched using a stretching tester (X4HD-HT, Toyo Seiki Seisakusho), and a microscopic polarization spectrophotometer (TFM-120AF) manufactured by Oak Seisakusho Co., Ltd.
T) was used to measure the wavelength dependence [drawing speed: 10 cm
/ Min (100% / min), draw ratio: 1.2 times]. The results are shown in Table 1.

[0016]

[Table 1] * 1 Number of parts by weight relative to 100 parts by weight of resin * 2 Wavelength dependence R = Re (400) / Re (55
0) However, Re (400) is a retardation at a wavelength of 400 nm Re (550) is a retardation at a wavelength of 550 nm * 3 W-1000 Dainippon Ink and Chemicals, Inc. polyester polymer plasticizer * 4 DEP diethyl phthalate

[0017]

As described above, according to the present invention, it is possible to obtain a retardation film whose wavelength dependence is adjusted by adding a plasticizer.

Claims (5)

[Claims] 1. A retardation film containing 2 to 20 parts by weight of a plasticizer with respect to 100 parts by weight of a thermoplastic resin. 2. The retardation film according to claim 1, wherein the thermoplastic resin is polyarylate. 3. The retardation film according to claim 1, wherein the wavelength dependence R represented by the following formula (I) is increased by 0.02 or more. R = Re (400) / Re (550) (I) where Re (400) is the retardation at a wavelength of 400 nm and Re (550) is the retardation at a wavelength of 550 nm. 4. The plasticizer is phthalic acid type, polyester type,
4. At least one selected from the group consisting of a polyether type, an aliphatic dibasic acid type, a phosphoric acid ester type, an epoxy type, a fatty acid ester type, and a chlorine-containing type.
The retardation film described. 5. A method for adjusting the wavelength dependence of a retardation film, which comprises adding 2 to 20 parts by weight of a plasticizer to 100 parts by weight of a thermoplastic resin.