Substrate film

Abstract

There are provided a substrate film, a laminate, and method of manufacturing a polarizing film. The present application provides a substrate film capable of effectively manufacturing a polarizing film having a thickness of about 10 m or less, about 8 m or less, about 7 m or less, about 6 m or less, or about 5 m or less and having an excellent function such as polarization performance, a laminate, and a method of manufacturing the same. According to the invention, it is possible to prevent tearing, curling, or the like from occurring in the elongation process and manufacture a polarizing film by easily elongating a polarization material such as a PVA-based resin.

Claims

1. A laminate, comprising: an elongatable substrate film satisfying the following Formula 1; and a polarizable material layer formed on either or both surfaces of the substrate film, wherein an absolute value of a difference (AB) between an integral value (A) of an elongation curve of the substrate film and an integral value (B) of an elongation curve of the polarizable material layer is in a range from 1,500 to 10,000 Nmm:
E/R5,[Formula 1] where, in Formula 1, E denotes an elongation having an unit of % of the elongatable substrate film measured at room temperature, R denotes a restoration ratio having an unit of %, the restoration ratio is measured such that a laminate manufactured by adhering a polyvinyl alcohol film having the same horizontal and vertical lengths as the substrate film and a thickness of 30 m to a surface of the substrate film cut to a horizontal length of 50 mm and a vertical length of 100 mm is elongated 5 times in a vertical direction in water having a temperature of 60 C., is taken out of the water, the polyvinyl alcohol film is released, the laminate is maintained for 1 hour at room temperature, a length (T) of the substrate film in a vertical direction is measured, and the measured value is assigned to Formula 100(TA)/A, where A in the Formula is a vertical length of the substrate film before the elongation, wherein the elongation of the substrate film is in a range of 200% to 1500%, and the substrate film comprises a thermoplastic polyurethane.

2. The laminate of claim 1, wherein the tensile strength of the substrate film is in a range of 20 MPa to 200 MPa.

3. The laminate of claim 1, wherein an integral value of the elongation curve of the substrate film is in a range of 2000 Nmm to 10,000 Nmm.

4. The laminate of claim 1, wherein a yield point of the substrate film is in a range of 10 MPa to 150 MPa.

5. The laminate of claim 1, wherein an elastic limit of the substrate film is in a range of 200 MPa to 1,000 MPa.

6. The laminate of claim 1, wherein the thermoplastic polyurethane is a reaction product of a mixture including a polyol, a polyisocyanate compound, and a chain extender.

7. The laminate of claim 6, wherein the polyol has a weight-average molecular weight in a range of 500 to 5,000.

8. The laminate of claim 6, wherein the total weight of the polyisocyanate compound and the chain extender in the mixture is in a range of about 1 part by weight to 90 parts by weight with respect to 100 parts by weight of the polyol.

9. The laminate of claim 6, wherein the mixture includes the polyisocyanate compound of 1 part by weight to 50 parts by weight with respect to 100 parts by weight of the polyol.

10. The laminate of claim 6, wherein the mixture includes the chain extender at 0.1 part by weight to 30 parts by weight with respect to 100 parts by weight of the polyol.

11. The laminate of claim 1, wherein the polarizable material layer is a polyvinyl alcohol-based resin-containing film or coating layer.

12. The laminate of claim 1, wherein the polarizable material layer has a thickness in a range of 15 m to 100 m.

13. A method of manufacturing a polarizing film comprising elongating the laminate of claim 1.

14. The method of claim 13, wherein the elongating the laminate is performed at a draw ratio in a range of 2 times to 15 times an original length.

15. The method of claim 13, wherein the elongating the laminate is performed in an aqueous solution in a range of 20 C. to 80 C.

16. The method of claim 15, wherein the aqueous solution is a boric acid solution.

17. The method of claim 13, wherein the polarizable material layer has a thickness of 10 m or less after the elongation.

18. A laminate, comprising: an elongatable substrate film satisfying the following Formula 1; and a polarizable material layer formed on either or both surfaces of the substrate film:
E/R5,[Formula 1] where, in Formula 1, E denotes an elongation having an unit of % of the elongatable substrate film measured at room temperature, R denotes a restoration ratio having an unit of %, the restoration ratio is measured such that a laminate manufactured by adhering a polyvinyl alcohol film having the same horizontal and vertical lengths as the substrate film and a thickness of 30 m to a surface of the substrate film cut to a horizontal length of 50 mm and a vertical length of 100 mm is elongated 5 times in a vertical direction in water having a temperature of 60 C., is taken out of the water, the polyvinyl alcohol film is released, the laminate is maintained for 1 hour at room temperature, a length (T) of the substrate film in a vertical direction is measured, and the measured value is assigned to Formula 100(TA)/A, where A in the Formula is a vertical length of the substrate film before the elongation, and wherein the substrate film is not amorphous and comprises a thermoplastic polyurethane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross sectional view of an illustrative laminate.

ILLUSTRATIVE EMBODIMENTS

(2) Hereinafter, the above will be described in detail with reference to the examples and comparative examples, but the scope of the application is not limited to the following Examples.

(3) Physical properties in examples and comparative examples were evaluated by the following methods.

(4) 1. Evaluation of Tensile Properties

(5) Tensile properties of a substrate film or a polarizable material layer (a PVA-based resin film in the examples and comparative examples) were evaluated by the following methods. A sample was prepared by cutting a substrate film or a polarizable material layer in Example or Comparative Example to a horizontal length of 15 mm and a vertical length of 90 mm. Then, 10 mm of a top and 10 mm of a bottom in a vertical direction were taped and wrapped and then the taped part was fixed in a measurement device (XP plus, commercially available from TA). Then, while the sample was stretched in a vertical direction at mom temperature and a tensile speed of 300 mm/min, a graph (X-axis: distance and Y-axis: force) of a force measured according to a distance until the sample is cut was illustrated. An area and a thickness of the sample were applied so that the graph was shown as a graph (X-axis: elongation and Y-axis: tensile strength) of an elongation and a tensile strength, and then each of the tensile properties was evaluated based on the graph. A method of evaluating tensile properties such as a tensile elastic modulus, a tensile elastic coefficient, and an elongation from an elongation curve is known.

(6) 2. Evaluation of Restoration Ratio

(7) A restoration ratio was evaluated by the following method. First, a substrate film of the examples or comparative examples was cut to a horizontal length of 50 mm and a vertical length of 100 mm. Then, a polyvinyl alcohol film having the same horizontal and vertical lengths as the substrate film and a thickness of 30 m was adhered to a surface of the substrate film to manufacture a laminate. In the above description, a typical water-based polyvinyl alcohol-based adhesive was used to adhere the polyvinyl alcohol film to the substrate film. Then, the laminate was immersed in water (temperature: 60 C.) and then was elongated 5 times in a vertical direction. Then, the laminate was taken out of the water and the polyvinyl alcohol film was released. The laminate was maintained at room temperature for 1 hour, and a length (T) of the substrate film in a vertical direction was measured. Then, the measured length (T) was assigned to Formula 100(TA)/A to calculate a restoration ratio. In the Formula, A denotes a vertical length of the substrate film before elongation.

(8) 3. Evaluation of Melt Index (MI)

(9) According to the ASTM D1238 standard, a melt index was measured by a weight of a specimen passing through an orifice having a diameter of 2.095 mm at a temperature of 215 C. during 10 minutes using 500 g of load (unit: g/10 min).

(10) 4. Evaluation of Hardness

(11) Hardness was measured using a sample having a thickness of 2 mm at room temperature by a Shore D durometer (ASKER Co., Ltd., Japan).

Manufacturing Example 1

Manufacture of Base Film (TPU Film (A))

(12) A TPU film was manufactured using a mixture which includes a polyester polyol prepared by known esterification of adipic acid and 1,4-butane diol and having a weight-average molecular weight (Mw) of about 2,000, methylene diphenyl diisocyanate (MDI) and 1,4-butanediol (chain extender) by a known-method. Specifically, the polyester-based polyol and the MDI were added at a weight ratio (polyester-based polyol:MDI) of 1:1.46 to a reactor. A reaction of the resulting mixture while stirring and adding nitrogen at 80 C. at a speed of 200 rpm was used to prepare an isocyanate terminated prepolymer. Then, the chain extender (1,4-butanediol) was additionally added at 14 parts by weight with respect to 100 parts by weight of the prepolymer and reacted while stirring and adding nitrogen at 80 C. and a speed of 200 rpm until a content of an isocyanate (NCO) in the reactor became 0 to synthesize TPU. The synthesized TPU was casted to manufacture a TPU film having a thickness of about 50 m.

Manufacturing Example 2

Manufacture of Base Film (TPU Film (B))

(13) A TPU film having a thickness of about 50 m was manufactured in the same manner as in Manufacturing Example 1 except that 1,4-butanediol (BD) and neopentane glycol (NPG) mixed at a weight ratio of 1:0.5 (BD:NPG) were used as a chain extender.

Manufacturing Example 3

Manufacture of Base Film (TPU Film (C))

(14) A TPU film having a thickness of about 50 m was manufactured in the same manner as in Manufacturing Example 1 except that 1,4-butanediol (BD) and neopentane glycol (NPG) mixed at a weight ratio of 1:1.5 (BD:NPG) were used as a chain extender.

(15) Properties of each manufactured film were summarized and shown in the following Table 1.

(16) TABLE-US-00001 TABLE 1 PVA- based TPU film resin Amorphous A B C film PET film Elongation curve 4343 7317 5404 1566 728 integral value Tensile strength 51 83 53 53 66 Elongation 378 491 413 519.8 6.8 Yield point 22 83 46 53 66 Elastic limit 545 390 754 120 1404 Restoration ratio 19 18.8 11.3 MI 30 30 30 Hardness 80D 75D 75D Elongation curve integral value unit: Nmm Tensile strength: MPa Elongation unit: % Elongation unit: MPa Elastic limit unit: MPa Restoration ratio unit: % MI (based on 215 C. and 5 Kg) unit: g/10 min PVA-based resin film: film formed by film-formation using known PVA-based resin used in manufacture of polarizing film (thickness: about 30 m) Amorphous PET film (manufacturer: LG Hausys, Ltd.)

Example 1

(17) The PVA-based resin film shown in Table 1 was laminated on a surface of the TPU film (A) manufactured in Manufacturing Example 1 using a water-based PVA-based adhesive to manufacture a laminate. Then, the laminate was immersed in a dye solution (solvent: water) including iodine and potassium iodide at a temperature of about 30 C. for an appropriate time and iodine was adsorbed into the PVA-based resin film. A content of the iodine in the dye solution was about 0.1 part by weight with respect to 100 parts by weight of water and a content of the potassium iodide was at about 0.7 parts by weight with respect to 100 parts by weight of water. Then, the laminate was immersed in a boric acid solution including boric acid and potassium iodide at a temperature of about 60 C., and elongated until a thickness of a final PVA-based resin film became about 5.8 m (draw ratio: about 5.6 times an original length). The PVA-based resin film was released from the elongated laminate for measurement. The result showed that a polarizing film having a transmittance of about 40% or more and a degree of polarization of 99% or more was manufactured.

Example 2

(18) A polarizing film was manufactured in the same manner as in Example 1 except that the TPU film (B) manufactured in Manufacturing Example 2 was used. A transmittance of the manufactured polarizing film was about 40% or more and a degree of polarization thereof was about 99% or more.

Example 3

(19) A polarizing film was manufactured in the same manner as in Example 1 except that the TPU film (C) manufactured in Manufacturing Example 3 was used. A transmittance of the manufactured polarizing film was about 40% or more and a degree of polarization thereof was about 99% or more.

Comparative Example 1

(20) A polarizing film was manufactured in the same manner as in Example 1 except that the amorphous PET film shown in Table 1 was used instead of the TPU film. However, in this case, as a draw ratio increases, the PVA-based resin film was broken or severely curled, and thereby it was unable to manufacture a polarizing film having an appropriate performance.

EXPLANATION OF MARKS

(21) 100: laminate 101: substrate film 102: polarizable material layer or polarizing film