JPS61204234A - Optically isotropic polysulfone film and production thereof - Google Patents

Abstract

PURPOSE:To provide the titled film composed of a polysulfone and having optical isotropy and excellent mechanical and chemical properties. CONSTITUTION:The objective optically isotropic film can be produced by dissolving a polysulfone in methylene chloride, casting the solution on a substrate, drying the cast film (preferably at 50-100 deg.C for 1-15min) to a residual volatile content of preferably <=20wt%, especially <=3%, and peeling off the film from the substrate. The concentration of the polysulfone in the methylene chloride solution is preferably 10-25%.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a polysulfone film and a method for producing the same;
In particular, the present invention relates to a polysulfone film having optical isotropy and a method for producing the same.

(Prior art) Polysulfone is a general term for polymers that have sulfone groups in the polymer chain, and has excellent thermal and mechanical properties.
Since it is a polymer with excellent chemical properties such as acid resistance and alkali resistance, it is used in various sensors, insulating tapes, xerographic films, etc.

For example, polysulfone is a product called polysulfone or Yucardel from Union Carbide, a product called Arilon from Unroyal, a product called Astrel 360 from 3M, and a product from I.C.I. It is commercially available under the name polyether sulfone from 1,C,1,) and is easily available.

A film made of polysulfone is commercially available from Toshiki Co., Ltd. under the trade name Trethron-PS.

On the other hand, as polymer films used as supports for optical filters, especially polarizing filters, cellulose ester films such as cellulose triacetate are widely used due to their excellent optical properties (although cellulose ester films are widely used due to their moisture resistance). Due to poor heat resistance,
Its use is subject to its own limitations.

Therefore, it is strongly desired to develop a polymer film that is mechanically and chemically excellent and has optical isotropy.

Conventional polysulfone films do not necessarily have sufficient optical properties, and none have optical isotropy.

Here, optical isotropy is defined by placing two polarizing plates with their planes of polarization at right angles, cutting off the passage of polarized light, and placing the film to be tested between the two polarizing plates. This refers to the property that there is no change in the transmitted light when it is rotated.

On the other hand, if a film without optical isotropy (a film with optical anisotropy) is placed between two polarizing plates and the transmitted light is observed, even if there is no change in the transmitted light when it is left still, it will change in the plane. When it is rotated to OoC, transmitted light can be seen as it rotates.

(Objective of the Invention) Therefore, an object of the present invention is to provide a film having excellent mechanical properties and chemical properties and optical isotropy, and a method for producing the same.

(Means for Solving the Problems) The object of the present invention is to cast a polysulfone film characterized by having optical isotropy and a methylene chloride solution containing polysulfone onto a support, and then remove residual volatile matter from the polysulfone film. This was achieved by a method for producing a polysulfone film characterized by peeling off the polysulfone film formed by drying the polysulfone film until it has a content of 20% by weight or less from the support.

As the polysulfone in the present invention, polymers having the following silicone unit price are preferably used.

In the present invention, polysulfo/ is used as a methylene chloride solution, and the concentration of polysulfo/ in the solution is z, yt.
o Weight staff, especially! It is preferable that θ to λj be the weight ratio.

Examples of solvents that can be used in addition to methylene chloride include benzene, acetone, cyclohexanone, N-methylpyrrolidone, dimethylformamide, and dimethylacetamide. It is preferable that If is 20% by weight or less.

The feature of the present invention is that a methylene chloride solution of polysulfone is polished through a casting die, cast onto a support such as a round metal band or drum, and dried for 9 hours, so that the residual volatile content is 202% or less, preferably 10%.
After reducing the amount by weight to less than 3%, particularly preferably to less than 3% by weight, the point is to peel off the formed film from the support. The drying conditions are 0~100°C1/-1! Preferably, it is for minutes.

After drying until the volatile content is reduced to 20% by weight or less, the film is peeled off from the support, so that shrinkage of the film due to subsequent volatilization can be suppressed, and there is no need to use a tenter to hold the film.

On the other hand, if the residual volatile content is 20 or more, it will not have self-retention properties and will need to be held with a tenter, etc., and the drying shrinkage will increase after peeling off, causing the film to be pulled in one direction by the tenter. , resulting in a film having optical anisotropy.

In the methylene chloride solution of polysulfone used in the present invention, a dye or an ultraviolet absorber may be present, if necessary.

Since the polysulfone film of the present invention has optical isotropy, it is useful as an optical filter, and particularly useful as a support for a polarizing quilter. Regarding the polarizing filter, reference may be made to the description in JP-A-76-70301.

The present invention will be further explained by showing examples below.

Example 7 100 parts (parts by weight) of polysulfone (UCC p-3!00) was dissolved in 4 parts of methylene chloride at 3r'C to form a completely homogeneous solution. The solution was heated to 300 CK and cast onto a stainless steel band support using a casting die with a liquid film thickness of 1 to 2 0 C, and was heated to 70 CK with a dry air of too 0 C.
It was dried for several minutes and peeled off from the support. Residual Methichrome is /
It was 2%.

The obtained film has a thickness of 0. /! It's Otm.

Even when tested with a polarizing film, it did not show any optical anisotropy.

Example-λ Too part of polyether sulfone (manufactured by ICI) was mixed with 200 parts of methylene chloride and 200 parts of chloroform.
C to completely dissolve the mixture and prepare a casting solution. Thereafter, a polyether sulfone membrane was created by the same operations as in Example 1. The residual solvent was λ.

The nine films obtained were optically isotropic films.

Comparative Example A polysulfone film having the composition of Example 1 was prepared with residual volatile content λj, 4
'l (drying for about 3 minutes), peeled off from the support, put it in a tenter and dried it with 1000C drying air for 5 minutes to remove the remaining volatile matter.
I made it to Chi.

When this film was examined in a polarizing film test, it was found to be a film that exhibited optical anisotropy in the direction in which it was stretched between tenters and contracted.

Claims (1)

[Scope of Claims] 1) A polysulfone film having optical isotropy, which is a film made of polysulfone and has optical isotropy. 2) Optical isotropy characterized by peeling off a polysulfone film formed by casting a methylene chloride solution containing polysulfone onto a support and drying until the residual volatile content becomes 20% by weight or less from the support. A method for producing a polysulfone film having