Polyvinyl alcohol-based film, polarizing film and polarizing plate, and method for manufacturing polyvinyl alcohol-based film

Abstract

To provide: a polyvinyl alcohol-based film which is capable of obtaining a polarizing film which has excellent balance between swellability and extensibility during producing a polarizing film, causes no breakage during producing a thin polarizing film, exhibits high polarizing performance and has less color unevenness; and a polarizing film and a polarizing plate using the polyvinyl alcohol-based film.SOLUTION: There is provided a long polyvinyl alcohol-based film having a thickness of 40 μm or less in which the degree of swelling (SA) and the degree of swelling in the width direction (SX) when immersed in water at 30°C for five minutes, the degree of swelling in the length direction (SY) and the degree of swelling (SB) when uniaxially stretched at a stretching speed of 0.12 m / min in water at 30°C so that the stretching ratio is 3 times satisfy the following expressions (1) to (3): 190%≤SA≤230% (1), 220%≤SB≤310% (2) and 1.01≤SY / SX≤1.20 (3).SELECTED DRAWING: None

Claims

1. A polyvinyl alcohol-based film with a thickness of 40 μm or less, characterized in that it satisfies the following formulas (1) to (3), and is used as a raw material film for manufacturing polarizing films. 190%≦S A ≦230%・・・(1) 220%≦S B ≦310%・・・(2) 1.03≦S Y / S X ≦1.20・・・(3) In the above formula (1), S A This represents the degree of swelling by mass when a rectangular film-like sample measuring 10 cm in the width direction (TD) and 20 cm in the flow direction (MD) is cut from the center of the above polyvinyl alcohol-based film in the width direction, and this film-like sample is further cut into strips 3 mm wide and 20 cm long, and these strip samples are immersed in 30°C water for 5 minutes. In the above formula (2), S B This represents the degree of swelling by mass when a rectangular film-like sample measuring 5 cm in the width direction (TD) and 15 cm in the flow direction (MD) is cut from the center of the above polyvinyl alcohol-based film in the width direction, and this sample is uniaxially stretched in water at 30°C at a stretching speed of 0.12 m / min to a stretching ratio of 3 times. In the above formula (3), S X This represents the degree of swelling based on the width dimension when a square film-like sample measuring 10 cm in the width direction (TD) and 10 cm in the flow direction (MD) is cut from the center of the above polyvinyl alcohol-based film in the width direction, and this sample is immersed in 30°C water for 5 minutes. Y This value represents the degree of swelling based on the length dimension when a square film-like sample measuring 10 cm in the width direction (TD) and 10 cm in the flow direction (MD) is cut from the center of the above polyvinyl alcohol-based film in the width direction, and this sample is immersed in 30°C water for 5 minutes.

2. The polyvinyl alcohol-based film used as a raw material film for manufacturing a polarizing film according to claim 1, characterized in that the width of the polyvinyl alcohol-based film is 2 m or more.

3. A polyvinyl alcohol-based film used as a raw material film for manufacturing a polarizing film according to claim 1 or 2, characterized in that the length of the polyvinyl alcohol-based film is 2 km or more.

4. A polarizing film characterized in that it uses a polyvinyl alcohol-based film used as a raw material film for manufacturing a polarizing film according to any one of claims 1 to 3.

5. The polarizing film according to claim 4, characterized in that the degree of polarization is 99.5% or higher.

6. The polarizing film according to claim 4 or 5, characterized in that its single-layer transmittance is 42% or more.

7. A polarizing plate comprising a polarizing film according to any one of claims 4 to 6, and a protective film provided on at least one side of the polarizing film.

Images