JP3925877B2 - Manufacturing method of polarizing plate - Google Patents

Description

【００２５】
以上の実施例・比較例から明らかな如く、本発明の粘着フィルムを設けた後にケン化処理を行った場合には、塗膜の物性（接触角）を変化させずに偏光膜との貼合面のみをケン化させることが出来るので、偏光板としての表面撥水特性を容易に実現することができる。また、これらの結果は、本発明によって製造された偏光板の耐久性が良好であることを容易に予測させるものである。[0001]
[Technical field to which the invention belongs]
The present invention relates to a polarizing plate widely used for liquid crystal displays and the like, and more particularly to a method for producing a PVA polarizing plate.
[0002]
[Prior art]
In a PVA-iodine polarizing plate, conventionally, iodine having high optical anisotropy is adsorbed on a thin film of PVA (polyvinyl alcohol) in a potassium iodide aqueous solution, and then unidirectionally in a boric acid aqueous solution. A polarizing film stretched about 4 times is used. That is, a polarizing plate is obtained by laminating a highly optically transparent triacetylcellulose film on both surfaces of the polarizing film obtained as described above (application of polarizing film; 1986 (stock) ) CMC).
[0003]
In this case, in order to improve the adhesion between the triacetyl cellulose film and the polarizing film, the triacetyl cellulose film is usually subjected to a saponification treatment by immersing it in an inorganic alkaline aqueous solution before bonding. At this time, since the non-adhesive surface is saponified at the same time, the surface of the polarizing plate produced by bonding it to both surfaces of the polarizing film becomes hydrophilic.
As described above, when the surface of the polarizing plate (non-bonding surface with the polarizing film) becomes hydrophilic, when it is bonded to a glass plate or the like via an adhesive, troubles such as foaming due to moisture occur over time. Arise.
In addition, when a triacetyl cellulose film having a coating such as a hard coat is used, the properties of the coating may be impaired because the alkali contacts the coating without the saponification.
[0004]
Therefore, the present inventors have conducted saponification treatment only on the bonding surface of the triacetyl cellulose film with the polarizing film without changing the conventional polarizing plate production equipment and process, and as a result, before saponification treatment. In addition, it has been found that by providing a layer resistant to alkali on a surface where no change in characteristics is desired, the disadvantage of saponification treatment can be eliminated with almost no change in the manufacturing process of the conventional polarizing plate, The present invention has been reached.
[0005]
[Problems to be solved by the invention]
Therefore, the objective of this invention is providing the manufacturing method of the polarizing plate excellent in durability at the time of bonding on a glass plate etc.
[0006]
[Means for Solving the Problems]
The above object of the present invention is a method for producing a polarizing plate in which at least both surfaces of a polarizing film are bonded with a triacetyl cellulose film as a protective film, respectively, and a hard coat layer is formed on one surface of the triacetyl cellulose film. And / or after forming the antireflection layer, a protective layer resistant to alkali is further provided on the hard coat layer and / or antireflection layer , and then a saponification treatment is performed, so that only one side is provided. give the triacetyl cellulose film is saponified, and then achieved the triacetyl cellulose film on both surfaces of the polarizing film, by the manufacturing method of the polarizing plate, characterized in that the bonding in contact is saponified surface of its It was done.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The triacetyl cellulose film used in the present invention is a triacetyl cellulose film conventionally used as a protective film for a polarizing film, and the thickness thereof is not particularly limited.
Further, the protective layer provided on one surface of the triacetyl cellulose film may be peelable or substantially non-peelable. Here, “substantially non-peelable” means that the film cannot be peeled without breaking the triacetyl cellulose film and / or the protective layer.
[0008]
The protective layer that can be peeled off is coated with a film-forming resin that dissolves in a solution that does not swell the triacetylcellulose film, and then dried, or when a curable resin solution is applied and cured, an adhesive film with an adhesive layer is applied. In addition to the above, it may be provided by any method such as laminating a triacetyl cellulose film and an incompatible resin by coextrusion, but at least a layer that can withstand saponification in the subsequent process. It is necessary to be.
[0009]
Examples of the protective layer material that can be used in the present invention include polyethylene, polypropylene, polyvinyl chloride, polyester, polymethylpentene, polyphenylene sulfide, and fluorine resin. Further, when a curable resin is applied, it is sufficient that the cured resin layer is alkali-resistant. In particular, an antireflection film is advantageous because it does not need to be peeled off. Further, an antireflection film may be provided on one surface of the triacetylcellulose film surface, and a protective layer may be further provided on the antireflection film.
[0010]
When an adhesive film is used, it may be peeled off immediately after the saponification treatment, or may be peeled off after completing the final form (adhesive-coated product, reflector-bonded product, etc.) through the subsequent steps. . As the adhesive film, any film can be used as long as the surface of the triacetyl cellulose film is resistant to alkali to the extent that it is not affected by the saponification treatment and can be peeled off after the saponification treatment. However, when high heat is required in the process after saponification, it is necessary to have the required heat resistance except when peeling off before heat treatment.
As the pressure-sensitive adhesive, a rubber-based, acrylic-based, or silicone-based pressure-sensitive adhesive can be used.
[0011]
By using various triacetylcellulose films saponified only on one side obtained as described above, the saponified side is bonded to both sides of the polarizing film by a known method, so that the saponification can be easily performed. A polarizing plate having no surface can be obtained.
[0012]
Specifically, after a hard coat layer and / or an antireflection layer is formed on the side of the triacetylcellulose film where it is desired to avoid denaturation by alkali, the film is resistant to alkali on the hard coat layer and / or antireflection layer. A protective layer is provided, and saponification is performed to the extent necessary for bonding with the polarizing film (immersion time in alkali, alkali solution temperature, same concentration). Thereafter, a polarizing film is bonded to the treated surface of the triacetyl cellulose film by a known method to obtain a polarizing plate.
[0013]
【The invention's effect】
According to the present invention, since the surface of the polarizing plate is not made hydrophilic, durability is sufficient even if it is bonded to a glass surface or the like via an adhesive.
[0014]
【Example】
The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the examples.
[0015]
Example 1.
On one side of an 80 μm triacetyl cellulose film (Fujitack; trade name manufactured by Fuji Photo Film Co., Ltd.), a coating layer having the same composition as in Table 1 below was applied using a wire bar # 5 to obtain a coating layer. After drying by heating, the coating layer was irradiated with a 120 W / cm ultraviolet lamp from a distance of 10 cm for 1 second to produce a triacetyl cellulose film having a 5 μm hard coat layer. Subsequently, a PET-based adhesive film (manufactured by Fujimori Kogyo; TFB-4-367AS) was bonded to the hard coat surface.
[0016]
[Table 1]
───────────────────────────────────
Polyester acrylate: 95.5 parts by weight (beam set 710; trade name of Arakawa Chemical Co., Ltd.)
Photoinitiator: 4.5 parts by weight (Irgacure 184; trade name manufactured by Ciba-Gaykey)
Isopropyl alcohol; for viscosity adjustment (appropriate amount as diluent)
──────────────────────────────────
[0017]
Comparative Example 1
A coating solution having the same composition as that used in Example 1 was applied to one surface of an 80 μm triacetylcellulose film (Fujitack; trade name of Fuji Photo Film Co., Ltd.) using wire bar # 5. After a layer was obtained and dried by heating, the coating layer was irradiated with a 120 W / cm ultraviolet lamp for 1 second from a distance of 10 cm to produce a hard coat film having a 5 μm hard coat layer.
[0018]
Example 2
After using the coating solution shown in the following Table 2 instead of the coating solution used in Example 1, triacetyl cellulose having a hard coat layer and a protective layer on one side in exactly the same manner as in Example 1. A film was prepared.
[Table 2]
───────────────────────────────────
Polyester acrylate: 85.5 parts by weight (beam set 710; trade name of Arakawa Chemical Co., Ltd.)
Amorphous silica: 10.0 parts by weight (Silicia 350; manufactured by Fuji Silysia Chemical Ltd.)
Photoinitiator: 4.5 parts by weight (Irgacure 184; trade name manufactured by Ciba-Gaykey)
Isopropyl alcohol; for viscosity adjustment (appropriate amount as diluent)
──────────────────────────────────
[0019]
Comparative Example 2
A hard coat film having a 5 μm hard coat layer on one side of an 80 μm triacetyl cellulose film was prepared in exactly the same manner as in Example 2 except that the PET base adhesive film was not bonded.
Various physical properties of the obtained sample were measured and evaluated by the following measuring methods.
[0020]
Made by chemical resistance; after the films prepared in the above comparative examples and examples were immersed in a 2.0N (N) caustic soda solution (55 ° C.) for 3 minutes, the wettability (contact surface) and transparency of the surface to distilled water The property (haze degree) was measured.
In addition, about the hard coat film with an adhesive film, after processing, the adhesive film was peeled off and it measured.
In addition, an automatic contact angle meter CA-Z type manufactured by Kyowa Interface Science Co., Ltd. is used for measuring the contact angle, and a reflection / transmittance meter HR-100 type manufactured by Murakami Color Co., Ltd. is used for measuring the haze degree. It was used.
[0021]
Example 3
The coating liquid shown in Table 3 below was applied to the hard coat surface of the hard coat film produced in the same manner as in Comparative Example 1, and after heating and drying, the coating layer was irradiated with ultraviolet rays from a distance of 10 cm with a 120 W / cm ultraviolet lamp. Was irradiated for 1 second to prepare a triacetylcellulose film having a 3 μm hard coat protective layer.
[0022]
[Table 3]
───────────────────────────────────
Polyurethane acrylate: 95.5 parts by weight (beam set 550B; trade name of Arakawa Chemical Co., Ltd.)
Photoinitiator: 4.5 parts by weight (Irgacure 184; trade name manufactured by Ciba-Gaykey)
Isopropyl alcohol; for viscosity adjustment (appropriate amount as diluent)
───────────────────────────────────
[0023]
Example 4
After providing an antireflection layer by vapor deposition of a known antireflection material on the hard coat surface of the hard coat film produced in the same manner as in Comparative Example 1, the PET base material was coated on the antireflection layer surface in the same manner as in Example 1. An adhesive film was bonded.
The results of measuring and evaluating various physical properties of the obtained samples in the same manner as in Example 1 are as shown in Table 4.
[0024]
[Table 4]

[0025]
As is clear from the above examples and comparative examples, when the saponification treatment was performed after the adhesive film of the present invention was provided, the film was bonded to the polarizing film without changing the physical properties (contact angle) of the coating film. Since only the surface can be saponified, the surface water-repellent property as a polarizing plate can be easily realized. Further, these results easily predict that the durability of the polarizing plate produced according to the present invention is good.

Claims (6)

  At least a method for producing a polarizing plate in which a triacetyl cellulose film is bonded as a protective film on both sides of a polarizing film, and a hard coat layer and / or an antireflection layer is formed on one side of the triacetyl cellulose film After that, a triacetyl cellulose film in which only one side is saponified by providing a protective layer resistant to alkali on the hard coat layer and / or the antireflection layer and then performing a saponification treatment. Then, the triacetyl cellulose film is bonded to both surfaces of the polarizing film so that the saponified surfaces are in contact with each other.   The manufacturing method of the polarizing plate of Claim 1 which has the process of peeling the said protective layer after a saponification process.   The method for producing a polarizing plate according to claim 1, wherein the protective layer is an adhesive film obtained by applying an adhesive to a PET film.   The method for producing a polarizing plate according to claim 1, wherein the protective layer is a hard coat film. The method for producing a polarizing plate according to claim 1, wherein the surface layer before providing the protective layer is a hard coat layer, and the protective layer is an antireflection film.   The method for producing a polarizing plate according to claim 1, wherein the protective layer is made of polyurethane acrylate.