JPH0321902A - Phase difference plate and production thereof - Google Patents

Abstract

PURPOSE:To improve optical uniformity and to eliminate the optical unequalness appearing as if clouds by consisting the phase difference plate of a biaxially oriented film-like material of a propylene-alpha-olefin copolymer contg. alpha-olefin exclusive of propylene at 0.5 to 5.0wt.% as a copolymn. component and specifying the phase difference value by a polarization microscope to a specific range. CONSTITUTION:This phase difference plate consists of the biaxially oriented film-like material of the propylene-alpha-olefin copolymer cont. the alpha-olefin exclusive of the propylene at 0.5 to 5.0wt.% as the copolymn. component. The plate is so formed that the phase difference value by the polarization microscope is in the 50 to 900nm range and the difference between the max. value and min. value of the phase difference values at arbitrary >=2 points on the film-like material is <=30nm. the unequalness like clouds generated by the fluctuation in the phase difference value is entirely eliminated in this way and the optical uniformity is obtd. This phase difference plate is usable as a compensation plate for preventing the coloration of a liquid crystal display element or as a ray reflection preventive material for various display devices when a circular polarizing plate is formed by combining this plate with a polarizing plate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optically uniform retardation plate and a method for manufacturing the same.

[Conventional technique wI1j. 111 which the invention seeks to solve
1) Retardation plates are used as anti-reflection materials for various display devices and as compensation plates for preventing coloring of liquid crystal display elements. In the past, crystals of inorganic compounds were used as retardation plates, but in recent years, thermoplastic resin films have come into widespread use because they are inexpensive and can be easily obtained with large areas. . For example, Tokuko Sho 53-1122
No. 8 discloses a retardation plate made of biaxially oriented polypropylene.

However, films made of such mature plastic resins are optically uneven, and good results cannot always be obtained when used in the above-mentioned applications. For example, when a retardation plate made of biaxially stretched polypropylene was observed while being held between two polarizing plates with parallel optical axes, optical irregularities that looked like clouds were observed.

[Means to solve the problem]

The inventors of the present invention have conducted extensive research to solve the L-optical non-uniformity of about 8 m in a retardation plate made of the above-mentioned mono- and biaxially drawn polypropylene, and have succeeded in solving the problem and proposed the present invention. It has come to this point.

That is, the present invention is based on a biaxially stretched agricultural product of a propylene-α-ole 7-yne copolymer body containing α-ole 7-yne other than propylene in an amount of 5 to 5% by copolymerization. Therefore, the phase difference value measured using a polarizing microscope is 5')"-90
Any Z in the range of 0 nm and on the material
The maximum value of the phase difference value at the above points, the minimum value of L and σ
) is a retardation plate that features a difference of 3 Q nm or less.

The retardation plate of the present invention contains α-11-fin other than prepylene as a copolymer component and has 0. 5 ” 5. Consists of a combination of globin 1/n and ~α-olefin including 0-benzene. Examples of α-olefins other than ethylene include ethylene, pudene-11bentene-1, etc. The temperature of these α-olepens must be 0.5 to 5.0 degrees Celsius. Considering the optical uniformity of the resulting retardation plate, the temperature should be within the range of 10 tons. (A) (Which is preferable?) If the α-4 refining content is outside the above range, it is not possible to obtain a retardation plate with optical uniformity (C). Unless other α-olefins are included as copolymerization components, a mere mixture of polypropylene and an α-olefin aggregate other than 1(but)pyrene will not achieve the object of the present invention. I can't.

The above e(1)':l robylene-α-olefin co-i combination has a melt flow index (m below, abbreviated as M) of 0. 1~30,! i'/10 minutes, even 05-20
．． 9/lo min °C, uniform k stretching is possible,
This is preferable because a retardation plate with less optical unevenness can be obtained.

The retardation plate of the present invention is a biaxially stretched film made of the above propylene-α-ole7 copolymer. The base stretching ratio for biaxial stretching is 4, 5 to 4 in the uniaxial direction, as described later.
7.0 times, and 7.0 in two axes perpendicular to the l-axis direction.
~110 times. Also, the thickness of the biaxially stretched film is . Although the retardation film of the obtained retardation plate may be selected depending on the selection, in order to obtain a retardation plate whose retardation m by the polarizing GUI mirror is 50 to 9OOnm under the above-mentioned biaxial stretching conditions, Generally selected from 10 to 100 μm.

As mentioned above, the retardation plate of the present invention has a retardation value of 50"900 nm as measured by a polarizing microscope. The retardation plate in which the retardation cage is within the range of 900 nm can be used in the specific two types described below. Although it can be obtained by biaxial stretching under conditions other than the axial direction, it is not preferable because it results in optical non-uniformity.

Furthermore, the retardation plate of the present invention has excellent optical uniformity. The University of Tokyo value of the retardation value measured by polarizing microscope wA measurement at arbitrary points of 02 or more on the retardation plate of the present invention. The difference in minimum feed L is 30 nm or less.Furthermore, the difference in retardation plate is 20 nm or less. In general, the maximum and minimum values of temperature are determined by the following method: 25 points on the retardation plate that are connected by 5 lines in the vertical and horizontal directions centering on the arbitrary 0) boin 1. This method uses the maximum and minimum values of the 25 phase difference values obtained by determining the phase difference sensitivity at point D using a polarizing microscope.

There are thousands of retardation plates of the present invention that eliminate optical irregularities that look like clouds, but in some cases, small irregularities the size of sesame seeds may occur. Since such small irregularities impair optical uniformity, it is preferable to mix a crystal nucleating agent in order to prevent this.The amount of crystal nucleating agent used is
It is preferable to select from the range of 0.01 to 8 parts by weight based on 100 parts by weight of the in copolymer. Examples of crystal nucleating agents include sodium benzoate, aluminum benzoate, aluminum tertiary benzoate, sodium adibate, aluminum adibate, dibenzylidene sorbitol, and derivatives thereof.

The retardation plate of the present invention can generally be manufactured by the following method. That is, α5-s. A propylene-α-olefin copolymer with an ox content st is uniaxially heated by ▲5 to 7.0 times in a temperature range of 50 to 5°C lower than the melting point of the propylene-α-olefin copolymer. It is a method of stretching 7.0 to 120 times in the biaxial direction at a temperature higher than the coherence in the uniaxial stretching and 5° C. lower than the melting point of the propylene-α-olefin copolymer. . The propylene-α-olefin copolymer can be prepared by a known method, for example,
After being shaped into a sheet by extrusion using a T-die, biaxial stretching is performed. In biaxial stretching, first, the melting point of the brobylene-α-ole7yne combination was
~5°C lower temperature range, preferably 40~7°C lower temperature, uniaxially 45~7.0 times, preferably 448~6
．． Stretching is performed 5 times. Next, in the above uniaxial direction Q stretching, the temperature is within a range of 5° C. or higher and 5° C. lower than the melting point of the propylene-α-olefin copolymer, preferably lower than the temperature in the uniaxial direction stretching. 7.0 to 12 in the biaxial direction within a temperature range of 5°C or higher and 7°C lower than the melting point of the brobylene-α-olefin copolymer.
Stretching tx is carried out by 0 times, preferably 7.5 to 115 times.

If the above-mentioned biaxial stretching ratio and stretching temperature are out of the above-mentioned ranges, it is preferable because an optically uniform retardation plate cannot be obtained or cannot be formed.

The retardation value of the retardation plate obtained by stretching may change over time. In order to prevent this, it is preferable to perform heat treatment at a temperature higher than the stretching temperature and lower than the melting point of the propylene-α-ole7yne copolymer for 10 to 120 seconds under tension or under limited shrinkage of 201 or less.

Furthermore, corona discharge treatment can also be performed for the purpose of improving surface properties such as adhesion.

〔effect〕

The retardation value of the present invention is in the range of 50 to 900 nm, and the variation in the retardation value at any point is extremely small. Therefore, the retardation plate of the present invention is optically uniform without any cloud-like unevenness caused by variations in retardation values. Therefore, the retardation plate of the present invention can be used as a compensating plate for preventing coloring of liquid crystal display elements, or as a light reflection prevention material for various display devices by combining with a polarizing plate to form a circularly polarizing plate. be able to.

〔Example〕

Examples and comparative examples are listed below to specifically explain the present invention, but the present invention is not limited to these examples. In the Examples and Comparative Examples, the retardation values were measured using a polarizing microscope manufactured by Olympus Optical Industries, Inc., and were determined from the difference in phase difference using a Pelleck type compensator using 550 nm white light as a light source.

Examples 1 to 3 and Comparative Examples 1 to 2 A mixture of propylene and ethylene with an ethylene content of 22% by weight, melting point = 142°C. MI=1. 'li/10 minutes)
0.08 parts by weight of dibenzylidene sorbitol was added to 100 parts by weight, extruded at 290°C using an extruder equipped with a T die, and brought into contact with a cooling roll at 35°C! ．． An unstretched film with a thickness of 3 m was obtained.

The obtained 7l2 stretched film-like material was subjected to l-axis firing and biaxial firing in a furnace and paper stretching as shown in Table '4f.

Measure the phase difference at 25 points at 55 intervals "c' in the vertical direction and left stone direction centering on any point of the obtained retardation plate 1
-, its average value and the difference between its maximum value and minimum value fl+1
Shown in the table. Furthermore, by holding the retardation plate between the polarizing plates with the optical axis flat, the result of optical unevenness can be detected as follows.
Also listed in the table. Note that the drawing in the l-axis direction was performed by changing the speed difference between a pair of heating rolls and a pair of cooling rolls, and the drawing in the biaxial direction was performed using a tenter. Then 1l of 8%
1! ! Heat treatment was performed at 140° C. under the limit shrinkage.

Example 4 Propylene-butene-l containing location & 0 wt% propylene-butene-l
Copolymer melting point = 140'' C.MI = 2, 1.!i'/
10 min) Add 0605 parts by weight of dibenzylidene sorbitol to 1 part by weight L,, Example-1, ? A L3 thick V-shaped stretched film was obtained in the same manner. The obtained unstretched film-like material was stretched 5.6 times in the l-axis direction at 118°C by the same method as in Example-1, and then stretched at 133°C in the biaxial direction.
It was stretched 9.0 times. Then, under 8% restricted contraction, 13
Heat treatment was performed at 8°C. The average value of the retardation values of the obtained retardation plate was 305 nm, and the difference between the maximum value and the minimum value was 14 nm. The optical properties were very good.

Example 5 Polyethylene copolymer containing 1.0% ethylene (melting point: 153°C, MI = 21.9/10 min) 1
0.0% of dibenzylidene sorbitol to 0.00% of Yabe.
Single translation part addition I-, Example-1k ZO by the same method
An unstretched film with a thickness of w was obtained.

The resulting unrolled paper-shaped pieces were rolled in the same manner in the same manner at 130°C 5 to 4 times, and then rolled in the biaxial direction at 145°C by 5 times. After that, heat treatment was performed at 148° C. under a limited shrinkage of 8%.

The average value of the retardation value of the obtained retardation plate was 633 nm.
The difference between the maximum value ε and the minimum value was 2 3 nm.

In addition, the optical characteristics were good.

Comparative Example 3 Propylene homopolymer (melting point 164°C, M1 = 1, 7
．． Example 1.
An unstretched film with a thickness of 3 m was obtained.

The obtained unstretched film was stretched 5.4 times at 151°C in the same manner as in Example 1,', and then stretched 1 times in two axial directions.
Stretched 9.2 times at 58°C. , 7σ) and then subjected to thermal IA treatment at 60°C under limited shrinkage of 8 degrees.

The retardation value of the obtained retardation plate was 4 6 8 nm, and the difference between the maximum value and the minimum value was 3 9 11 m.

In addition, cloud-like unevenness and sesame-like unevenness were observed when observing the polarizing plate.

Example 6 Ethylene content & 3% by weight Q propylene-ethylene co-l
Coalescence (melting point = 135°C, MI = 16 19/1 0 min)
0 parts of dibenzylidene sorbitol per 100 parts by weight
．． 05 parts by weight was added, and a thick unstretched ZOm film was obtained by the same method as in Example-1.

The obtained unstretched film-like material was stretched 54 times in the l-axis direction at 115° C. and then 9.2 times in the biaxial direction at 127° C. in the same manner as in Example-1. Thereafter, heat treatment was performed at 130° C. under a limited yield of 8%.

The average value of the retardation values of the obtained retardation plate was 318 nm, and the difference between the maximum value and the minimum value was l l nm. Further, the optical unevenness was very good.

Claims (2)

[Claims] (1) Consists of a biaxially stretched film of a propylene-α-olefin copolymer containing 0.5 to 5.0% by weight of α-olefin other than propylene as a copolymerization component, and has a retardation value measured using a polarizing microscope. is in the range of 50 to 900 nm,
A retardation plate characterized in that the difference between the maximum value and the minimum value of retardation values at any two or more points on the film-like material is 30 nm or less. (2) A propylene-α-olefin copolymer containing 0.5 to 5.0% by weight of an α-olefin other than propylene as a copolymerization component is added to 4.5 to 7.0 times in the uniaxial direction at a low temperature, and then at a temperature above the uniaxial stretching temperature and below 5°C below the melting point of the propylene-α-olefin copolymer. 7. Biaxially.
A method for producing a retardation plate according to claim (1), characterized in that the film is stretched by 0 to 12.0 times.