JPS61275704A - Production of polarizing film of dye base - Google Patents

Abstract

PURPOSE:To obtain a polarizing film having a high degree of polarization and high durability by adding a surface active agent or surface active agent and inorg. salt. into a dye dyeing liquid and boric acid treating liquid for treating a uniaxially stretched and oriented hydrophilic high-polymer film. CONSTITUTION:A film consisting of PVA or the deriv. thereof is used for the hydrophilic high-polymer film and after the film is preliminarily and uniaxially stretched and oriented prior to dyeing, the film is dyed with the aq. soln. contg. 1 or >=2 kinds of dyes as well as the inorg. salt and surface active agent. The film is thereafter subjected to the boric acid treatment to improve the polarizing performance and to provide durability to the film. The boric acid treatment is executed by immersing the film into the aq. soln. added with the boric acid and surface active agent or the boric acid, surface active agent and inorg. salt. The high-polymer film subjected to the dyeing and boric acid treatment stages is subjected to stages for rinsing, drying and if necessary heat treatment, by which the polarizing film is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves dyeing a uniaxially stretched and oriented hydrophilic polymer film with an aqueous solution containing a 1 m or more dye, an inorganic salt, and a surfactant, and then dyeing the film with boric acid and a surfactant. Alternatively, it relates to a method Cζ for producing a dye-based polarizing film obtained by post-treatment with an aqueous solution containing boric acid, a surfactant, and an inorganic salt, followed by washing with water and drying. The objective is to obtain a dye-based polarizing film that is highly transparent and has a high degree of polarization.

Currently, polarizing films are made by using stretch-oriented polyvinyl alcohol or its derivatives, or oriented polyene films produced by dehydrochlorinating polyvinyl chloride films or dehydrating polyvinyl alcohol films, and adding iodine or iodine as a polarizing element. It is generally manufactured by adsorbing a dichroic dye.

Among these, polarizing films that use iodine as a polarizing element have excellent initial polarization performance, but are weak against water and heat, and have problems with their durability when used for long periods in high temperature and high humidity conditions. There is.

In order to improve durability, methods such as strengthening the treatment with an aqueous solution containing formalin or boric acid, and using a polymer film with low moisture permeability as a retaining membrane have been considered, but Durability is insufficient in this condition.

In addition, a polarizing film using dichroic dye as a polarizing element is more durable against water and heat than a polarizing film using iodine, but the degree of polarization is lower than that of a polarizing film using iodine. It has the disadvantage of being inferior. To improve the degree of polarization, for example 'N? No. 1119-76171 discloses that after dyeing a polyvinyl alcohol film with an aqueous solution containing a dye and a nonionic surfactant, borate,
It is also stated that the degree of polarization can be improved by treatment with an aqueous solution containing a nonionic surfactant and stretching. According to this method, the degree of polarization is improved compared to the case where no surfactant or the like is added. (2) Durability at high temperature and high humidity is still not perfect.

There are other problems.

In view of this situation, the inventors of the present invention have made extensive studies and found that, in a method of obtaining a polarizing film by uniaxially stretching and orienting a hydrophilic polymer in advance, dye staining and high-temperature boric acid treatment, the present inventors have developed a method for obtaining a polarizing film by dye staining and high-temperature boric acid treatment. We discovered that a highly durable polarizing film with a high degree of polarization can be obtained by adding a surfactant or a surfactant and an inorganic salt to the processing solution.
This led to the present invention.

That is, in the present invention, a hydrophilic polymer film that has been uniaxially stretched and oriented in advance is dyed with an aqueous solution containing a 181 or more polar dye, an inorganic salt, and a surfactant, and then dyed with boric acid and a surfactant or boric acid and a surfactant. The present invention relates to a method for producing a dye-based polarizing film obtained by post-treatment with an aqueous solution containing an inorganic salt, followed by washing with water and drying.

The hydrophilic polymer film used in the present invention includes polyvinyl alcohol and its derivatives, those modified with olefins such as ethylene and propylene, crotonic acid, acrylic acid, methacrylic acid, maleic acid, etc.;
It is made of V-mu resin (ethylene-vinyl acetate resin), saponified EVA resin, etc. Among these, films made of polyvinyl alcohol and its derivatives are particularly useful polymer films for the present invention because they easily adsorb dyes and are highly oriented.

In the present invention, a method of uniaxially stretching and orienting a hydrophilic polymer film before dyeing is a wet method.
There are two methods, such as a dry method for tension stretching and a dry method for compression and stretching. Either method can be used, but it is important to achieve high transparency and high degree of polarization of the polarizing film and durability under high temperature and high humidity conditions. When considering properties, dyeing at high temperatures, boric acid treatment, etc. are useful, and for this purpose, a dry method of stretching at a temperature of 80° C. or higher is preferable. Furthermore, in order to obtain a uniform uniaxially stretched film with no stretching unevenness, compression stretching is more preferable. In addition, when wet stretching is performed, it becomes more useful if it is heat-treated in advance at a temperature of 80° C. or higher.

The dichroic dye used in the present invention may generally be any organic direct dye as long as it has a high dichroic ratio, but it is usually selected from azo dyes.

Organic direct dyes used in the present invention include, but are not limited to, Color Index Generic Ne-A
((3,1,Generia Name)
Direot Blaok l7), Cee Directieo-12(0,1,Direct
Yollov12), C, 1, Direct Orange 26
), C.I.R.4L/Kutb A/ -1 (0,I,
Direot Blue l).

C.I. Direct Red 81 (C, I.

Direct Red 91), C, X, Direot
Violet 9), C.I. Direct Orange T 07 ((3,I.

Direct Orange I Q 'I), Sea * Fuiken Directb/l/-71 (C, I, D
ireot Blue 71), C.I. Direct Blue 8 (C,I.

Direct Blue 7g), Sea*74
m direct fan 5f) 106 (0, 1, Dire
ot Brown 106), C.I. Direct Black 112 (0,I.

DireotBlaokl 12), Sea*74 m
F select 5 y ri 118 (0, I, Dire
ct Blaok l i8), C.I. Direct Blue 202 (0,I.

Direot Blue 202), Sea @ Eye Direct Red 2 (0, 1, Direat Rad
g), C* Eye Direct Violet 51
(0, I, Dir-eot Violet 51
), C.I. Direct Rate g l (0
,I, Direct Red 81)
Blaok 51), C.I. Direct Blackl 9 (0,I, Direot Black
l 9) ,', t −* I di left toy so
-28(0,I, DireotYellow 28
), CI Direct Red 79 (Ci, I
, Direat Bed 79) , Sea * Eye *
l”4 Rect L/7 Do 247 (0, I, Dire
ot 1led g 47), C.I. Direct Blue 168 (C, I.

Pireat Blue 5g),! ／ −@
Feed Direction Tag 9-:/85 (0, I, Di
reot Green 85), C.I. Direct Brown 22B (0, I.

Direct Brown 228), Sea *
74 e Direct 5-1 51 (C, 1, Di
rect Black 51), C.I. Direct Black 154 (C,I.

Direec Black l 54)
Yellow 44), C.I. Direct Black 82 (C, I.

Direot Black B2), Sea Direct A-142 (0, L
Direoc Yellow 142) I can raise my throat.

When carrying out the present invention, one or more of the above-mentioned various dyes may be appropriately selected. lfi
A single color polarizing film can be made using similar dyes, but this only has polarizing properties in the wavelength range specific to the dye,
In order to obtain a polarizing film having polarization properties over the entire wavelength range of visible light from 0 to 700 nm, it is necessary to
It is necessary to mix two or more types of dyes that have absorption properties and polarization properties in different wavelength ranges. By properly mixing and using dyes, it is possible to obtain a polarizing film that is neutral in color and has polarizing properties over the entire wavelength range of visible light. Specifically, the combination of dyes to create a neutral color is as follows: C.I. Direct Black 17, C.I. Direct Yellow 12, and C.I. Direct Blue 202. It is a mixture of dyes.

Furthermore, as a combination of dyes to make a neutral color, a mixture of eight types of dyes consisting of C-I Direct Black 17, C-I Direct Yellow 12, and C-I Direct Black 19, or C-I - Direct Black 17, C.I. Direct Yellow 12, C.I. Direct Blue 202,
and C.I.Direct Black 19 4
It is a mixture of different types of dyes.

As an even more preferable combination of dyes, the above-mentioned 8WI
Jlii or a combination of four types of organic direct dyes, C-I Direct Red 81. C.I. Direct Violet 9, C.I. Direct Red 2, C.I. Direct Red 81 and C.I. Direct Violet 51. When one or more types of organic direct dyes are mixed, the difference between the maximum light transmittance and the minimum light transmittance and the difference between the maximum degree of polarization and the minimum degree of polarization become smaller than when they are not mixed.
This is preferable because it provides a more neutral color and a higher degree of polarization.

In order to bring the color closer to cello and more completely neutral, it is also possible to appropriately mix dyes that have absorption ability in areas with high light transmittance and are not dichroic.

In the present invention, a general method for adsorbing an organic direct dye onto a polymer film is to dissolve the organic direct dye, an inorganic salt, and a surfactant in water, and then dye the polymer film. . At this time, when considering polarization performance, durability performance, etc., it is preferable that ξζ be dyed at as high a temperature as possible. Generally 40°C or higher, preferably 50°C
Dyeing is carried out at a temperature of 80° C. or lower. Generally, anhydrous and sulfur are used as inorganic salts for dyeing.
In addition, ξ using sodium and potassium sulfates, hydrochlorides, and nitrates can also be used. The strength of the inorganic salt to be added varies depending on the dye used, the temperature of the dyeing solution, etc., but is 0.8 to 10.
The range is wt%. When dyeing at a high temperature of 60°C or higher using polyvinyl alcohol film, 8 to 7
It is preferable to use it in the range of %.

As the surfactant used in dyeing I, nonionic, cationic or anionic surfactants can be used, but nonionic surfactants are more preferred. Nonionic surfactants include those obtained by addition polymerization of ethylene oxide to higher alcohols, those obtained by addition polymerization of ethylene oxide to nonylphenol, and any type thereof may be used. The amount of surfactant to be added is 0.005~Q,! There is sufficient effect within the range of 5 vt%.

After the dye is adsorbed onto the uniaxially stretched director film, boric acid treatment is performed to improve polarization performance and impart durability. The boric acid treatment is carried out by immersion in an aqueous solution containing boric acid and a surfactant or boric acid, a surfactant, and an inorganic salt.

The conditions for boric acid treatment vary depending on the type of polymer film used, the type of dye, etc., but generally boric acid 1
1JI is 1-15%, preferably 5-10%, the concentration of the surfactant added is 0.005-0.5%,
Preferably 0.02-0.2% of the inorganic salt added! 3
If the degree is outside the above-mentioned range of 0.1 degree, the treatment effect will be small and undesirable. The surfactant or inorganic salt used during the boric acid treatment can be the same as or different from the one used in the dyeing process, but it is preferable to use the same one. Furthermore, if necessary, fixing treatment may be performed in combination with an aqueous solution containing a cationic polymer compound.

The polymer film that has undergone the dyeing process and the boric acid treatment process is washed with water, dried, and if necessary, subjected to a heat treatment process to become a polarizing film.

In addition, the dye-based polarizing film obtained in this way has a protective layer with excellent optical transparency and mechanical strength on one or both sides.
It is used as a polarizing plate by laminating a film.

Safe! Materials for forming the membrane include conventionally used cellulose acetate films and acrylic films, as well as other fluorocarbon films such as tetrafluoroethylene-67propylene copolymers, polyester resins, and polyolefin resins. Alternatively, a film made of polyamide resin that is uniaxially stretched and oriented may be used.

Among them, a film obtained by uniaxially stretching or oriented high-density polyethylene or polypropylene film has a high degree of water vapor barrier property, and is therefore suitable as a film for maintaining a polarizing film.

The dye-based polarizing plate obtained in this way is as follows.

Compared to conventional dye-based polarizing plates, the polarizing performance and durability are improved. It has excellent polarizing performance comparable to iodine polarizing film using iodine as a polarizing element, and has improved durability under high temperature and high humidity conditions, making it particularly suitable for automotive applications and displays for various industrial instruments. It is suitable for applications that require high durability.

The present invention will be explained in more detail with reference to Examples below.
These are examples and are not limited to these.

In addition, the degree of polarization in the present invention refers to preparing two polarizing films or polarizing plates and measuring the light transmittance curve with the two polarizing plates superimposed. Measuring device: Takashi Seisakusho UV-2) 0
spectrophotometer), and is the value determined by the following formula.

Here, "I+" is a value (called parallel transmittance) measured when two samples are superimposed so that the polarizing films are aligned in the same direction, and H
The upper graph shows a value (referred to as orthogonal transmittance) measured when two samples are stacked so that the orientation directions of the polarizing films are orthogonal to each other.

Example 1 A polyvinyl alcohol film (Kuraray Vinylon ■ 7500) with a thickness of 75 μm was subjected to 4 times compression stretching in a longitudinal direction at 105° C. and used as a polarizing film base material. While this PV film was kept in a tensioned state, l1til) (Japanol・
First Black D...C.I. Direct Black from Sumitomo Chemical ■17) 0.08W1%
Anhydrous mirabilite 5. Qvt%, and surfactant (emul j
Boric acid 70s was immersed for 10 minutes in a 60°C aqueous solution containing 0.04 vt% of boric acid.
5 mat%, surfactant (Emulmin 70) 0, Q4vt
% in an aqueous solution at 65°C for 5 minutes, washed with water at 20°C, and dried to obtain a polarizing film. The single transmittance of this polarizing film at the maximum absorption wavelength (590 nm) is 42%.
The degree of polarization was 97%.

Comparative Example 1 No surfactant was added to the dye aqueous solution and boric acid aqueous solution,
A polarizing film was obtained in the same manner as in Example 1 except that the dyeing time with the aqueous dye solution was changed to 8 minutes. The single transmittance of this polarizing film at the maximum absorption wavelength (590 nm) is 4
2%, and the degree of polarization was 96%.

Comparative Example 2 A polyvinyl alcohol film (Kuraray Vinylon ■ 750G) with a thickness of 75μ was immersed in water at 80°C for 8 minutes, and after immersed in an aqueous dye solution at 85°C with the same composition as in Example 1 for 4 minutes, 4wt% boric acid, and Surfactant (Emulmin 7
0) It was treated for 2 minutes with an aqueous solution at 80°C containing wt% o, o a. Further, wet stretching was carried out 4 times in an aqueous solution at 80° C. containing 2 vt % of boric acid and 0.04 wt % of a surfactant (emulmin γ0), followed by washing with water and drying to obtain a polarizing film. The single transmittance of this polarizing film at the maximum absorption wavelength (590 nm) was 42%, and the degree of polarization was 96%.

Example 2 The same polarizing film base material as in Example 1 was kept under tension,
Dye (chrysophenin...C-I Direct Yellow 12 from Sumitomo Chemical Industries) 0.08Wj%, anhydrous sodium sulfate 6-OW, and surfactant (Emulmin 7)
G, manufactured by Sanyo Chemical Industries, Ltd.) consisting of 0.04 wt%
It was immersed in an aqueous solution of for 8 minutes. Furthermore, boric acid 7.5 wt%,
It was immersed for 5 minutes in an aqueous solution at 65° C. containing 0.04 wt% of a surfactant (Emulmin 70) and 0.04 wt% of anhydrous sodium sulfate, washed with water at 20° C., and dried to obtain a polarizing film. The single transmittance of this polarizing film at the maximum absorption wavelength (420 nm) was 42%, and the degree of polarization was 99%.

Comparative Example 8 Completely the same as Example 2, except that no surfactant was added to the aqueous dye solution, neither surfactant nor anhydrous sodium sulfate were added to the aqueous boric acid solution, and the dyeing time with the aqueous dye solution was 6 minutes. A polarizing film was obtained. The single transmittance of this polarizing film at the maximum absorption wavelength (420 nm) was 42%, and the degree of polarization was 97%.

Comparative Example 4 A polyvinyl alcohol film (Kuraray Vinylon ■ 7500) with a thickness of 76 μm was immersed in water at 80°C for 8 minutes, and after immersed in an aqueous solution at 85°C with the same composition as in Example 2 for 8 minutes, 4vt% boric acid and an interfacial Activator (Emulmin 70) 0.04w
The film was wet-stretched 4 times in an aqueous solution at 80° C. containing 0.08 wt % of anhydrous sodium sulfate, washed with water and dried to obtain a polarizing film. The single transmittance of this polarizing film at the maximum absorption wavelength (420 nm) was 42%, and the degree of polarization was 97%.

Example 8 The same polarized M base material as in Example 1 was kept under tension,
6fJ4 class dye (Japanol Fast Black D
...Above mentioned, Chrysophenine ... Aforementioned, Sumilite Sburable-80S ... C.I. Lu Direct Blue 202 of Sumitomo Chemical ■, Nirapon Fast Red B
B...Sumitomo Chemical's Sea Fist Eye Direct Red 81. Chive Brilliant Violet BK...
Sumitomo Chemical ■ C.I. Direct Violet 9, benzoperpyulin, 4B...Sumitomo Chemical T&C.I. Direct Red 2) 0.08 each
vt%, 0.06vt%, Otsu0mat%, 0.04wt
%, 0.04wt%, o, oswt%, anhydrous mirabilite s, o
It was immersed for 20 minutes in a 60°C aqueous solution consisting of vt9b and a surfactant (Emulmin 70 manufactured by Sanbe Kasei Kogyo Co., Ltd.) 0.04Wt96. Furthermore, it was immersed for 5 minutes in an aqueous solution at 65°C consisting of 7.5vt% boric acid, 0.04wt% surfactant (Emulmin 70), and 0.08ft% anhydrous sodium sulfate, washed with water at 20°C, and then dried. A polarizing film was obtained. This polarizing film has a visible light wavelength range (400 to 700
The average single transmittance in (nm) was 42%, and the degree of polarization was 96%.

Comparative Example 5 Completely the same as Example 8, except that no surfactant was added to the aqueous dye solution, neither surfactant nor anhydrous sodium sulfate were added to the aqueous boric acid solution, and the dyeing time with the aqueous dye solution was 16 minutes. The polarization family was obtained. The average single transmittance of this polarizing film in the visible light wavelength range (400 to 700 nm) was 42%, and the degree of polarization was 94%.

Comparative Example 6 A polyvinyl alcohol film (Kuraray Vinylon 7500) with a thickness of 75μ was immersed in water at 80°C for 8 minutes,
After 6 minutes of immersion in an aqueous dye solution at 85°C with the same composition as in Example 8, 4vt% boric acid and 0.0% surfactant (Emulmin 70) were added.
A polarizing film was obtained by wet stretching 4 times in an aqueous solution at 30°C consisting of 0.04 vt% and anhydrous mirabilite 0.08 wt%, washed with water, and dried to obtain a polarizing film.
~700 am), the average single transmittance is 4251
! P, and the degree of polarization was 94%.

Example 4, Comparative Example 7.8 A commercially available cellulose triacetate film (80μ, manufactured by Fuji Photo Film Co., Ltd.) was attached to both sides of the polarizing film obtained in Example 8 and Comparative Example 5.6 using a urethane adhesive. did. After measuring the initial performance of the polarizing plate obtained in this way, 85
It was left in a constant temperature and humidity chamber at 90% Rtl for 600 hours. Table 1 shows the polarization performance after the test.

Example 6 A ceremonial light board identical to that of Example 4 was prepared. After measuring the initial performance of this polarizing plate, it was left in a dryer at 100°C for 200 hours. The polarization performance after the test was measured, and it was exactly the same as the initial performance, with no change.

Claims (2)

[Claims] (1) After dyeing a uniaxially stretched and oriented hydrophilic polymer film with an aqueous solution containing one or more dyes, an inorganic salt, and a surfactant, A method for producing a dye-based polarizing film obtained by post-treatment with an aqueous solution containing salt, followed by washing with water and drying. (2) The method for producing a dye-based polarizing film according to claim 1, wherein the hydrophilic polymer film is a film made of polyvinyl alcohol or a derivative thereof.