Polyester film and image display devices using the same

Abstract

A polyester film is provided, which has high in-plane hysteresis, excellent thickness uniformity, and good manufacturability, workability, and planarity. The polyester film disclosed has an in-plane hysteresis of 3000 nm to 30000 nm, an area alignment degree of 0.128 to 0.155, and a thickness non-uniformity of 8% or less in the film flow direction (furthermore, the thickness non-uniformity is a value calculated as (maximum thickness - minimum thickness) / average thickness × 100 (%)).

Claims

1. A polyester film having an in-plane retardation of 3000 nm to 30000 nm, an NZ coefficient of 1.65 to 3, and a thickness non-uniformity of 8% or less in the film flow direction. When Fourier transforming the thickness measurement data in the film flow direction and replacing the frequency with the period of the film length, the ratio A / B of the following A to the following B is 5 or less; (Furthermore, the thickness non-uniformity is a value obtained by (maximum thickness - minimum thickness) / average thickness × 100 (%)); A: the average amplitude of the top 5 points of the amplitude value with a period of 10 cm or more; B: the average amplitude of the top 5 points of the amplitude value with a period of 10 cm or less.

2. For the polyester film of claim 1, when the thickness measurement data of the film flow direction is Fourier transformed and the frequency is replaced by the period of the film length, the ratio of Amax to B, Amax / B, is 7 or less; Amax: the maximum value of the amplitude when the period is 10cm or more.

3. The polyester film of claim 1 or 2 has a thickness of 25 μm or more and 150 μm or less.

4. For polyester films as requested in item 1 or 2, the elongation at break in the film-forming flow direction is 4% or more.

5. The polyester film of claim 1 or 2 has a tensile strength of 50 MPa or more in the film-forming flow direction.

6. A polarizing filter protective film comprising a polyester film as claimed in any one of claims 1 to 5.

7. A polarizing plate having a polarizing protective film and a polarizing mirror as described in claim 6.

8. An image display device, wherein a polarizing plate as described in claim 7 is provided on the visual recognition side of the image display unit.

9. A transparent electrode substrate film comprising a polyester film as claimed in any one of claims 1 to 5.

10. A scattering prevention film comprising a polyester film as claimed in any one of claims 1 to 5.

11. A protective film for a screen surface, comprising a polyester film as claimed in any one of claims 1 to 5.

12. An image display device comprising any one of the transparent electrode substrate film of claim 9, the scattering prevention film of claim 10, and the screen surface protective film of claim 11.

13. The image display device of claim 12 is a flexible image display device.

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