JPS6136204B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polarizing film with good water resistance. Conventional polarizing film substrates are primarily polyvinyl alcohol (PVA). This type of polarizing film is made by impregnating a PVA film with iodine or a dichroic dye and then stretching it several times.
It has the feature that setting the color tone is relatively easy. However, since PVA, the film base material, is a hydrophilic polymer, there are problems with water resistance as a polarizing film, and even moisture in the air can cause deterioration of physical properties and polarization properties. Therefore, polyethylene terephthalate, polyvinyl chloride, and the like have attracted attention as polymers with good water resistance, and various polarizing films have been experimentally produced. However, there is no known material that completely satisfies the requirements for water resistance, polarization, heat resistance, film strength, film formability, etc. The present invention has been made in view of these circumstances, and aims to provide a polarizing film that inherits as much of the advantages of conventional PVA-based polarizing films as possible and improves only the drawbacks of water resistance as much as possible. That is. That is, the film base material in the polarizing film provided by the present invention has the general formula (In the formula, R ¹ is hydrogen or lower alkyl, R ² is hydroxy or hydroxy (lower) alkyl, n is a natural number, provided that the number of carbon atoms in brackets is at least 3), containing 50 mol% or more of repeating units. It is an alcohol-based polymer. Because this polymer has more carbon atoms than the repeating units in traditional PVA, it is more hydrophobic and has improved water resistance once formed into a film. In addition to homopolymers formed from exactly the same monomers, the above alcoholic polymers include copolymers obtained from monomers in which R ¹ and R ² in formula () are changed, and other monomers (for example, acrylic esters). It also includes copolymers obtained in combination with other polymers (such as the following), and also refers to those in which a crosslinking reaction is performed using free hydroxy contained in the polymer. These configurations will be explained in more detail below. The lower alkyl represented by R ¹ in the general formula () includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tertiary butyl,
Saturated lower alkyls such as pentyl and hexyl have high versatility, and hydroxy (lower) alkyls represented by R ² include hydroxymethyl,
2-hydroxyethyl, 1-hydroxyethyl,
3-hydroxypropyl, 2-hydroxypropyl, 2-(hydroxymethyl)ethyl, 2-methyl-2-hydroxyethyl, 4-hydroxybutyl, 2-methyl-3-hydroxypropyl, 2-
Hydroxy saturated (lower) alkyls such as methyl-2-hydroxypropyl, 1-hydroxy-2-methylpropyl, 5-hydroxypentyl, 6-hydroxyhexyl have long been utilized. Like this
The repeating unit () having R ¹ and R ² has 3 or more carbon atoms, and the homopolymer or copolymer consisting essentially of such alcohol has extremely high hydrophobicity and is insoluble in water. However, it has good affinity for organic solvents, and although it varies depending on R ¹ and R ² , dimethylformamide,
dimethyl sulfoxide, pyridine, dioxane,
Soluble in methanol, tetrahydrofuran, etc. Monomers that can be copolymerized with the vinyl alcohol monomer forming the repeating unit of general formula () include (meth)acrylic esters such as methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate; vinyl such as vinyl acetate; Examples include esters; styrenes such as styrene, methylstyrene, and nitrostyrene; vinyl halides such as vinyl chloride and vinyl bromide; however, vinyl monomers other than those exemplified may be used. However, the repeating unit represented by the general formula () must not be less than 50 mol%, and 50
When the amount is less than mol%, a polarizing film having sufficient polarizing ability cannot be obtained. In addition, the film base polymer shown above has a large number of hydroxy groups in its molecules, so when cross-linking takes advantage of its reactivity, it forms a network-like molecular structure and improves its mechanical strength. do. Such crosslinking agents include polyepoxy compounds (for example, trimethylolpropane triglycidyl ether,
propylene glycol diglycidyl ether, terephthalic acid glycidyl ester, etc.), polyisocyanate compounds (e.g. tolylene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, etc., and their Bunte salts), polyalkoxymethyl compounds ( Examples include bifunctional reactive compounds such as hexamethoxymethylmelamine, tributoxymethylmelamine, etc.) and aldehyde compounds (glyoxal, formaldehyde, etc.). It goes without saying that polyfunctional compounds other than those exemplified may also be used. When the crosslinking reaction using the crosslinking agent is carried out in this manner, the polymer itself becomes insoluble and infusible, and its mechanical strength is also greatly improved, so that the scope of its application as a polarizing film is greatly expanded. Next, a general method for manufacturing such a polarizing film will be described. The present invention is not limited to the method for producing the polymer that serves as the film base material, and all known polymerization methods or those that will be developed in the future can be applied. However, as is obvious from the characteristics of the polarizing film, the above-mentioned crosslinking reaction must be carried out after film formation and stretching. The obtained polymer is mixed with other polymers or polarizing elements, and if necessary, with pigments, etc., and subjected to a film forming process. The film forming method is not limited to the present invention and any known or future-developed methods can be used, but a solution casting method is preferred in terms of uniformity of film thickness. In carrying out this method, the polymer or polymer mixture is dissolved in the above-mentioned organic solvent (the preferred concentration is 0.5 to 30%), and casting is performed at a temperature lower than the boiling point of the solvent to obtain a uniform thickness. make a film. To explain the other polymers for the above-mentioned formulation, they should be selected taking into consideration the performance desired for the finished film, and they should be selected based on the performance desired for the finished film. Typical polymers include (meth)acrylate polymers or copolymers (e.g., polymethyl methacrylate, polyethyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethyl Acrylate, methyl methacrylate/ethyl methacrylate copolymer, methyl methacrylate/2-hydroxyethyl methacrylate copolymer, etc.); Acrylonitrile polymers (e.g. polyacrylonitrile, methyl acrylate/acrylonitrile copolymer,
Ethyl acrylate/acrylonitrile copolymer, vinyl acetate/acrylonitrile copolymer, etc.); vinyl halide polymers (e.g. polyvinyl chloride, vinyl chloride/vinyl acetate copolymer, etc.)
is exemplified. When blending these polymers, repeating units () in all polymers should be
It is desirable to take care to ensure that the amount of Further, in the film of the present invention, the iodine and the dichroic dye, which serve as polarizing elements, may be added to the polymer solution before film formation as described above. It may also be a method of immersing it in a solution of iodine or dichroic dye and adsorbing it to the film molecules. In the case of iodine, it is also possible to adsorb it by placing a film in a heated sublimation stream of iodine. In this way, adsorption after film formation may be performed before or after stretching, which is a common method in manufacturing polarizing films. Moreover, it does not matter before or after crosslinking. Furthermore, the stretching is
This is carried out by uniaxially stretching approximately 2.5 to 6 times at room temperature or under heating. Of course, the type of dichroic dye does not limit the present invention, but typical examples include chrysophenin (CI No. 24895), Eisen Primula,
Yellow 5GLH (CINo.25300), Kayaras Capro Yellow GRL (CINo.29020), Aisin
Soga Corning RN (CINo.24910), Eisen Direct Green BH (CINo.30295),
Sirius Supra Olive GL (CI
No.31985), Phenamine Diazo Olive G
(CINo.30220), Direct Sky Blue 6B
(CINo.24410), Sumilight Splat Blue G
(CINo.34200), Kayaras Supra Blue
FF2GL (CINo.51300), DURAZOL Brilliant Blue B BP (CINo.51310), Remazol Yellow RTN (CINo.22010), Garuda Soga Yellow 2G (CINo.24850), Garuda Soga Yellow GN ( CINo.25130), Chlorazole Green G (CINo.30315), Direct Brilliant Green 3B (CI
No.30200), Benzo Blue Black BH (C.
I.No.22590), Polyphenyl Blur G (CI
No.30350), Nitsupon Dark Green B (C.
I.No.30280), Animal Chrome Navy Blue B (CINo.31930), Diazole Dark
Violet N (CINo.22565), Dianyl Blue R (CINo.22540), Direct First Blue CR (CINo.31910), Solius Blue Light BR (CINo.34210), Chloramine First Blue RL (CINo. .34146), Sirius Blue 6G (CINo.34230), Sirius Violet 3B (CINo.27980), Diazo Blue BR
(CINo.34085), Diazophenyl Blue RR
(CINo.34010), Diazo Navy Blue BP
(CINo.35085), Solantine Red 8BL (CI
No.28160), Solantine Pink 4BL (CI
No.25380), etc. are shown. The amount of iodine or dichroic dye added should be determined depending on the hue required of the polarizing film and the wavelength range in which the highest polarizing ability should be exhibited, and should not be uniformly regulated. Since the polarizing film obtained by the above method is based on a special polymer containing 50 mol% or more of repeating units as shown by the general formula (),
Water resistance is extremely good. In addition, conventional hydrophobic polymers with added iodine or dichroic dyes, which are provided with a top priority on improving water resistance, generally tend to sacrifice polarization performance, but the film obtained with the present invention The polarization performance of is extremely excellent.
There is also the advantage that mechanical strength can be significantly improved by utilizing a crosslinking reaction. Taking advantage of these features, the polarizing film of the present invention can be used in various optical devices, panel photo filters, sunglasses,
It can be used in various fields such as liquid crystal display devices, windows of houses or buildings, etc. The present invention will be explained below with reference to Examples. In the examples, "parts" means parts by weight. Also, what is shown as "average contrast" is (light transmittance when two polarizing films are stacked so that their respective polarizing elements are in parallel)/(light transmittance when two polarizing films are stacked with each polarizing element in parallel) It is the average value of the ratio given by (light transmittance) when the elements are stacked in a perpendicular position, and is further calculated by "C50".
indicates the time required until the average contrast decreases by 50% when the polarizing film is placed under 90% RH. Example 1 Commercially available reagent grade isopropenyl acetate (100 parts)
2% benzoyl peroxide (3 parts) was added thereto, and bulk polymerization was carried out at 90°C for 70 hours. After the reaction was completed, the solution was poured into petroleum benzene to precipitate and separate the produced polymer. This was purified by reprecipitation method, Polyisopropenyl acetate (degree of polymerization: 500, yield: about 50%) having the repeating unit shown was obtained. This was added to an acetone-water mixture (volume ratio 3:1) to give a concentration of 1%, and after adding 2.5 equivalents of sodium hydroxide, it was saponified at 40°C for 2 hours. The reaction solution was poured into a large amount of acidic water, and the resulting precipitate was separated and purified. The obtained polymer did not show carbonyl absorption in IR, but strong alcohol absorption was observed at 3300 and 1200 cm ^-1 . It was determined to be polyisopropenyl alcohol having the repeating unit shown in This polymer (50 parts) was dissolved in dimethylformamide (800 parts) and cast onto a glass plate at 80°C.
A dry film was formed in 4 hours. This film was mixed with a solution of iodine in ethyl ether (iodine: 7 parts, potassium iodide:
saturation amount, ethyl ether: 1000 parts) at room temperature.
Immersed for a minute. Then dry at room temperature and remove the film.
A transparent polarizing film was obtained by stretching about 5 times at 70°C. The parallel color was very light brown, and the average contrast was 3.0. When this film was then immersed in water for 7 days at room temperature, it showed an average contrast of 2.8 and extremely good water resistance. Example 2 Polyisopropenyl alcohol (25
Part) and polymethyl methacrylate (25 parts) were dissolved in dimethylformamide (1000 parts), (1) Direct Sky Blue 6B (0.5 parts) was added, and after casting on a glass plate, it was heated at 85℃ for 3 hours. (2) A film was formed in the same manner with the addition of Congo Red (0.4 part). (3) A film was formed in the same manner with the addition of Eisen Direct (0.6 part). As a comparative example, PVA (50 parts) was dissolved in water and a film was formed according to (1) to (3) above. The film of the present invention was stretched 6 times at 95°C, and the comparative film was
It was stretched 6 times under humid heat at 40°C and dried. The performance of the polarizing film thus obtained was as shown in Table 1.

[Table] Example 3 Methyl vinyl ketone (45
) and styrene (5 parts) were dissolved in benzene, benzoyl peroxide was added at a concentration of 1%, and then 50
Polymerization was carried out at ℃ for 60 hours. When petroleum benzene was poured to precipitate and separate the polymer, and it was purified using the reprecipitation method, Copolymer of methyl vinyl ketone and styrene having the repeating unit shown (degree of polymerization 350, yield 30%)
was gotten. This product 1.5%, lithium aluminum hydride 3%
A tetrahydrofuran solution (1) was prepared and refluxed for 24 hours with stirring. The reaction solution is made hydrochloric acidic,
The polymer was poured into ice water to precipitate it and purified by reprecipitation method. The obtained polymer showed no carbonyl absorption in IR, but strong alcohol absorption was observed at 3300 and 1100 cm ^-1 . It was determined to be a copolymer of secondary butenyl alcohol and styrene having the repeating unit shown below. Also, almost the same as above A copolymer of isobutenyl alcohol and styrene having the repeating unit shown was obtained. Each copolymer (5 parts) was dissolved in dimethylformamide (100 parts) together with benzo blue black (0.03 parts), and dry films were formed by a conventional method.
Each film was stretched 5 times at 70°C to obtain a pale blue polarizing film (10μ). A thin aqueous solution of trimethylolmelamine (10%) and zinc borofluoride (5%) was applied to each of these films, and the film was heated at room temperature.
It was subjected to a crosslinking reaction for 24 hours. The obtained polarizing films were left in an atmosphere of 70° C., 95% RH and 90° C., 5% RH for 300 hours. The average contrast before and after treatment remained completely unchanged.

Claims (1)

[Claims] 1. General formula (In the formula, R ¹ is hydrogen or lower alkyl, R ² is hydroxy or hydroxy(lower) alkyl, n is a natural number, provided that the number of carbon atoms in brackets is at least 3) at 50 mol% or more A water-resistant polarizing film whose base material is an alcohol-based polymer. 2 In claim 1, iodine or 2
A water-resistant polarizing film that uses colored dye as a polarizing element. 3. A water-resistant polarizing film according to claim 1 or 2, which is obtained by crosslinking hydroxyl in the film obtained by film formation and stretching with a crosslinking agent.