JPS6285203A - Production of polarizing film - Google Patents

Abstract

PURPOSE:To improve the moisture and heat resistances and the polarizing property by uniaxially stretching a polyvinyl alcohol film contg. iodine, treating the stretched film with the acidic soln. of glutaraldehyde and drying it. CONSTITUTION:A PVA film is immersed in an aqueous soln. contg. iodine and potassium iodide and is uniaxially stretched 2-6 times in a wet state The stretched film is treated with the acidic soln. of 4-3pH contg. 20-1% glutaraldehyde under the tension and is dried at 75-130 deg.C. Since the film is treated with the soln. contg. glutaraldehyde, the moisture and heat resistances are improved and the degree of polarization of light at about 750nm can be increased.

Description

[Detailed description of the invention] [Field of invention] The present invention relates to a method for manufacturing a polarizing film.

Polarizing films are widely used in combination with sunglasses, antireflection plates, and liquid crystals, such as calculators, watches, office automation equipment, and automobile display equipment, and will continue to be used in even wider fields. As the fields of use have expanded in this way, the performance requirements for polarizing films have become stricter, and there has been a need for polarizing films that are resistant to moisture and heat and have a high degree of polarization.

The present invention relates to a method for producing a polarizing film with excellent moisture and heat resistance and high polarization properties.

[Prior art]

Polarizing films commonly used at present are made by impregnating a polyvinyl alcohol (hereinafter abbreviated as PVA) film with a dichroic dye or iodine and stretching it uniaxially, or by impregnating a dichroic dye or iodine after stretching the PVA film uniaxially. It is made by crosslinking with boric acid.

However, if the thus obtained polarized light pattern is placed in a high temperature and high humidity atmosphere such as a relative humidity of 10%, the degree of polarization deteriorates within a few days, making it unsuitable for immersion.

For the purpose of completely improving this, polyester or nylon is used instead of PVA (JP-A Show II-/2100, JP-A Show 5r-a+ri-O, JP-A-Sho to-/!tμO/), PV
Consideration is being given to using At-dehydrated polyvinylene (Tokuko Sho tO-/Ari 03, Tokko Sho 60-/λ3t7), and using partially polyenized polyvinyl chloride (Tokuko Sho! Tar ≠ 2t Colo). However, although these films have improved moisture resistance, they do not have a sufficient degree of polarization when compared with current PVA-iodine polarizing films.

[Purpose of the invention]

The present invention improves these points and relates to a method for producing a polarizing film that has moisture and heat resistance and has a polarizing property equivalent to or higher than that of current polarizing films.

[Structure of the invention]

According to the present invention, after impregnating PVA with gold iodide, -Ni
It has been found that the object can be achieved by stretching the film to a length of 7 liters, treating it with an acidic solution containing at least glutaraldehyde, and drying. Even among aldehydes, formalin, acetaldehyde, and glyoxal were found to be less effective, while glutaraldehyde was found to be extremely effective.

PVA can be impregnated with iodine by dipping the PVA in an aqueous solution of iodine and potassium iodide. After immersion, the film is stretched in a wet state/axially by a factor of 2 to 2 times. After stretching, the film is treated under tension with a solution containing at least glutaraldehyde. The mystery of glutaraldehyde in glutaraldehyde solution, the degree depends on the processing time of the PVA20
% to 7% is good. The pH of the glutaraldehyde bath solution should be less than μ, preferably less than 3, and there is no problem even if potassium iodide is added to this solution.

Examples of acids that can be used include inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid, and organic acids such as citrus acid and acetic acid.

After treatment with an acidic solution of glutaraldehyde, washing with water may be performed to remove excess glutaraldehyde.

The drying temperature after treatment is preferably 7 to 0 c or more and i3 to 0 c or less. There is no problem in drying in the initial stage, drying at low temperature, and post-drying to separate parts.

Treatment with @solution containing glutaraldehyde not only improves moisture and heat resistance, but also surprisingly improves resistance to long wavelengths, especially 7. It was found that the degree of polarization of light near rOnm was improved.

The polarizing film treated with glutaraldehyde and dried is a film of cellulose triacetate, cellulose acetate butyrate, -axially oriented polyethylene terephthalate, polyether sulfone, etc. There is no problem in laminating and using it for protection.

Examples will be described below, and measurements and evaluations in the examples will be performed using the following methods.

[Degree of polarization] Using a two-spectrum photometer, measure two polarizing films stacked in the same orientation direction, and measure the transmittance Ii at the maximum absorption wavelength at a given time! i, kTo, the orientation directions were set at right angles to each other, and the transmittance at the maximum absorption wavelength was calculated using the following formula as T2O.

Furthermore, the degree of polarization at f [f total 7j Onm was calculated in the same manner from the respective transmittances when the wavelength was set to fz7j Onm.

[Humidity and heat resistance]: @degrees RO 0C, relative humidity? Hiro in the atmosphere of O%! Leave it for a while and then the degree of polarization? Measure and see the decrease in the initial degree of polarization! Money within 1 A1!
A case where the temperature decreased by more than a factor of 0 with gold B1 up to 20% was classified as C.

Example/ A PVA film (optical film made by Kuraray ■) with a thickness of 75μ was prepared by adding iodine/% (wt) and potassium iodide 2% (wt).
) After soaking in an aqueous solution for 7 minutes, the sample was stretched to 3 times its width in a wet state and then pressed. Glutaraldehyde for catatonic deafness! %(wt)
, hydrochloric acid 0.3j% (wt) water gQ (pI-(/,
3o) for 7 minutes and dried at 700°C for 70 minutes to obtain a polarizing film. A 10 μm cellulose triacetate film was laminated as a protective film on both sides of this polarizing film to obtain a sample (1).

A PVA film similar to Comparative Example/Example/was prepared with iodine/% (w t
), immersed in an aqueous solution of 2% (w t ) potassium iodide for 7 minutes, then wet-boiled and stretched to 3@. Glyoxal 2.2 t (wt), hydrochloric acid 0.3 while in a nervous state
% (wt) aqueous solution for 7 minutes, and
The film was dried at c for 70 minutes to obtain a polarizing film. Example (1)
A similar protective film was laminated to prepare sample (2).

Comparative Example A PVA film similar to that of Example 1 was heated to 100°C, stretched 3 times in one direction, and heat treated at 200°C for 70 minutes. This film was kept under tension with 3% iodine (wt)
, potassium iodide (wt), glutarartebide 7% (wt), hydrochloric acid (0%), jJ-chi (wt) for 2 minutes immersed in an aqueous solution (pH=/, 4!j) of 100
It was dried at 0C to form a polarizing film.

A protective film similar to that of Example il+ was laminated and a sample (
3).

Comparative Example 3 Same as Example (1) fZPVkt Yaw )”/% (
wt ), 1 in an aqueous solution of 2% (wt ) potassium iodide.
After immersion for 1 minute, it was stretched 3 times, immersed for 1 minute in an aqueous solution of boric acid≠thi(wt) under tension, and then heated at 1000C for i.
Dry for o minutes to form a polarizing film.

A protective film similar to that in Example (1) was laminated and the sample (
4) Reminder.

The degree of polarization and moisture resistance and heat resistance of the above samples were examined. The results are shown in Table 1. It can be seen that the method of the present invention is also superior.

Table 7

Claims (1)

[Claims] In a method for producing a polarizing film in which an iodine-containing polyvinyl alcohol film is uniaxially stretched, after the iodine-containing polyvinyl alcohol film is uniaxially stretched,
A method for producing a polarizing film, which comprises treating with an acidic solution of glutaraldehyde and drying.