JP3322406B2 - Polarizing film protective film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing film protective film, and more particularly to a polarizing film protective film having excellent moisture resistance.

[0002]

2. Description of the Related Art Conventionally, triacetate films have been used as protective films for polarizing films used in displays such as computers, small televisions, watches, calculators, and the like. However, the triacetate film is characterized by having a small optical anisotropy, but is inferior in moisture resistance and has a problem that the polarizing film is deteriorated by moisture absorption.

On the other hand, for example, Japanese Patent Application Laid-Open No. 60-138514 proposes a device using polyethersulfone as a base resin. However, although moisture resistance is good, birefringence is not always sufficient. It involves the problem of high cost.

[0004]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a polarizing film protective film which is inexpensive, has good birefringence, and is particularly excellent in moisture resistance.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a film composed of a specific composition can achieve the above object, and have completed the present invention. That is,
The present invention relates to an acrylic resin (A) comprising 50 to 70 parts by weight of methyl methacrylate, 10 to 20 parts by weight of maleic anhydride and 20 to 35 parts by weight of styrene, and a molecular weight of 30,000.
Butyl-modified acetylcellulose (B) having a weight ratio of the acrylic resin (A) / butyl-modified acetylcellulose (B) of 60 to 90/40.
A film for protecting a polarizing film, comprising a composition having a composition of from 10 to 10.

Acrylic resin (A) used in the present invention
Consists of 50 to 70 parts by weight of methyl methacrylate, 10 to 20 parts by weight of maleic anhydride and 20 to 35 parts by weight of styrene. If the methyl methacrylate is less than 50 parts by weight, the heat resistance is reduced, and if it exceeds 70 parts by weight, it becomes brittle,
When the amount of maleic anhydride is less than 10 parts by weight, the heat resistance decreases, and when it exceeds 20 parts by weight, the processability decreases. If the amount of styrene is less than 20 parts by weight, the processability deteriorates, and if it exceeds 35 parts by weight, it becomes brittle.

The molecular weight used in the present invention is 30,000-7.
The butyl-modified acetyl cellulose (B) of 0000 imparts and improves toughness without lowering the transparency, birefringence and moisture resistance of the film.

[0008] As butyl-modified acetyl cellulose,
Those having an acetyl group of 10 to 30%, a butyryl group of 30 to 50%, and a hydroxyl group of 1 to 5% are preferred. When the acetyl group is out of the above range, the miscibility with the acrylic resin (A) deteriorates. When the butyryl group is less than 30%, the miscibility with the acrylic resin (A) also deteriorates. Heat resistance decreases. Further, if the molecular weight is less than 30,000, it becomes brittle, and if it exceeds 70,000, the processability deteriorates, and for example, in the case of a solution casting method, the viscosity increases.

The composition used in the present invention has a weight ratio of acrylic resin (A) / butyl-modified acetylcellulose (B) in the range of 60 to 90/40 to 10. When the component (A) is less than the above ratio, the heat resistance is reduced, and when it is more than the above ratio, the toughness and the workability are reduced. In addition to the above main components, additives such as a leveling agent, an ultraviolet absorber, and a stabilizer may be added.

The above composition is formed into a film by extrusion molding or solution casting. Solvents used in the case of solution casting include methyl ethyl ketone, toluene, ethyl acetate and the like, and these may be used alone or in combination of two or more.

[0011]

The present invention will be described below in more detail with reference to Examples and Comparative Examples, which do not limit the scope of the present invention. In the following description, "part"
And "%" mean "parts by weight" and "% by weight" unless otherwise specified.

Example 1 70 parts of an acrylic resin comprising 70 parts of methyl methacrylate, 10 parts of maleic anhydride and 20 parts of styrene, and a cellulose acetate butyol having a molecular weight of 40,000 containing 36% of butyryl groups, 14% of acetyl groups and 2% of hydroxyl groups. Rate 3
A composition containing 0 parts, 0.5 parts of an ultraviolet absorber (trade name: Tinuvin 327, manufactured by Ciba Geigy), and 0.2 parts of a silicon-based leveling agent was dissolved in a mixture of a solvent, methyl ethyl ketone and toluene (solid content: 30%). A film having a thickness of 80 μm was prepared by a solution casting method. Table 1 shows the properties of the obtained film.

[0013]

[Table 1]

This film was adhered to both surfaces of a polarizing film to form a polarizing plate, which was incorporated into an LCD, and the protective performance was evaluated. A clear image was obtained over 10,000 hours, and no abnormality was observed.

Example 2, Comparative Examples 1-2 A film was prepared in the same manner as in Example 1 except that the composition of the acrylic resin was changed, and its performance was evaluated. Table 2 shows the results.

[0016]

[Table 2]

Example 2 showed good results, but Comparative Example 1 had a low softening temperature, so that film shrinkage, curl,
Wrinkles and the like occurred and could not be used for protecting the polarizing film. Further, Comparative Example 2 was laminated on a polarizing film, incorporated in an LCD, and evaluated for performance. However, a change in color tone and contrast could not be obtained, and a high-quality image could not be obtained.

[0018]

As described above, the polarizing film protective film of the present invention is inexpensive, has good birefringence, and is particularly excellent in moisture resistance, so that the performance of the polarizing film is prevented from deteriorating due to moisture absorption. can do.

Continuation of the front page (56) References JP-A-61-241703 (JP, A) JP-A-62-164745 (JP, A) JP-A-4-254803 (JP, A) JP-A-4-171403 (JP) (A) JP-A-61-231502 (JP, A) JP-A-61-151502 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 5/30 G02F 1/335

Claims (1)

(57) [Claims] 1. 50 to 70 parts by weight of methyl methacrylate, 10 to 20 parts by weight of maleic anhydride and styrene 20
Acrylic resin (A) comprising up to 35 parts by weight and a molecular weight of 3
Butyl-modified acetylcellulose (B) having a weight ratio of the acrylic resin (A) / butyl-modified acetylcellulose (B) of from 60 to 90000.
A film for protecting a polarizing film, comprising a composition of 0/40 to 10.