Laminate

Abstract

Provided are a base film, a laminate, and a method of forming a polarizing film. Particularly, a base film which may effectively form a polarizing film having a thickness of approximately 10, 8, 7, 6, or 5 m or less and exhibiting excellent functions such as polarizing performance, a laminate, and a method of forming the same are provided. Therefore, a polarizing film may be formed by preventing tearing or curling during an elongation process, and easily elongating a polarizing material such as a polyvinylalcohol-based resin.

Claims

1. A polarizing film, comprising: an elongated laminate, wherein the elongated laminate comprises: a base film; an adhesive layer; and a polarizing material layer disposed on one or both surfaces of the base film via the adhesive layer, wherein the elongated laminate is prepared by assembling the base film, the adhesive layer and the polarizing material layer into a laminate, and then elongating the assembled laminate at a draw ratio of 5.6 to 15 fold to form the elongated laminate, wherein the base film includes thermoplastic polyurethane, wherein the thermoplastic polyurethane is a reaction product of a mixture including a polyol component, 1 to 50 parts by weight of a polyvalent isocyanate compound with respect to 100 parts by weight of the polyol component, and 0.1 to 30 parts by weight of a chain extender with respect to 100 parts by weight of the polyol component, wherein an absolute value of a difference in an elongation at break between the base film and the polarizing material layer ranges from 15 to 141.8%, and wherein an absolute value of a difference in elastic limit between the base film and the polarizing material layer is 1,000 MPa or less.

2. The polarizing film according to claim 1, wherein an absolute value of a difference in a tensile curve integral between the base film and the polarizing material layer ranges from 1,500 to 10,000 Nmm.

3. The polarizing film according to claim 1, wherein an absolute value of a difference in tensile strength between the base film and the polarizing material layer ranges from 0.5 to 40 MPa.

4. The polarizing film according to claim 1, wherein an absolute value of a difference in yield point between the base film and the polarizing material layer ranges from 1 to 50 MPa.

5. The polarizing film according to claim 1, wherein the base film has a recovery rate of 30% or less.

6. The polarizing film according to claim 1, wherein the polarizing material layer includes a polyvinylalcohol-based resin.

7. The polarizing film according to claim 1, wherein the polarizing material layer has a thickness of 15 to 100 m prior to elongation of the laminate.

8. A method of forming a polarizing film, comprising: assembling a laminate, the laminate comprising a base film, an adhesive layer, and a polarizing material layer disposed on one or both surfaces of the base film via the adhesive layer; and elongating the assembled laminate at a draw ratio of 5.6 to 15 fold, wherein the base film includes thermoplastic polyurethane, wherein the thermoplastic polyurethane is a reaction product of a mixture including a polyol component, 1 to 50 parts by weight of a polyvalent isocyanate compound with respect to 100 parts by weight of the polyol component, and 0.1 to 30 parts by weight of a chain extender with respect to 100 parts by weight of the polyol component, wherein an absolute value of a difference in an elongation at break between the base film and the polarizing material layer ranges from 15 to 141.8%, and wherein an absolute value of a difference in elastic limit between the base film and the polarizing material layer is 1,000 MPa or less.

9. The method according to claim 8, further comprising adsorbing a dichroic material to the polarizing material layer before the assembled laminate is elongated.

10. The method according to claim 8, wherein the polarizing material layer has a thickness of 10 m or less after the assembled laminate is elongated.

11. The method according to claim 8, further comprising: removing the elongated base film and adhesive layer from the elongated polarizing material layer.

12. The method according to claim 8, wherein the assembled laminate is elongated in an aqueous solution at a temperature ranging from 20 to 80 C.

13. The method according to claim 12, wherein the aqueous solution is a boric acid aqueous solution.

14. An elongated polarizing layer prepared by a method comprising: assembling a laminate, the laminate comprising a base film, an adhesive layer, and a polarizing material layer disposed on one or both surfaces of the base film via the adhesive layer; elongating the assembled laminate; and removing the elongated base film and the adhesive layer from the elongated polarizing material layer, wherein the base film includes thermoplastic polyurethane, wherein the thermoplastic polyurethane is a reaction product of a mixture including a polyol component, 1 to 50 parts by weight of a polyvalent isocyanate compound with respect to 100 parts by weight of the polyol component, and 0.1 to 30 parts by weight of a chain extender with respect to 100 parts by weight of the polyol component, wherein an absolute value of a difference in an elongation at break between the base film and the polarizing material layer ranges from 15 to 500%, and wherein an absolute value of a difference in elastic limit between the base film and the polarizing material layer is 1,000 MPa or less.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

ILLUSTRATIVE EMBODIMENTS

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

(3) The properties in the examples and comparative examples are measured as below.

(4) 1. Evaluation of Tensile Characteristic

(5) A tensile characteristic of a base film or a polarizing material layer (a PVA resin film in Example or Comparative Example) was evaluated by the following method. A sample was prepared by cutting the base film or polarizing material layer of Example or Comparative Example to have a size of 15 mm90 mm (widthlength). Subsequently, upper and lower parts of the sample were taped by 10 mm each, and fixed to a measuring device (XP plus, TA). Subsequently, a graph (X axis: distance, Y axis: force) of a force measured according to a distance until the sample was broken by being elongated in a vertical direction at an elongation speed of 300 mm/min and room temperature was illustrated, and converted into a graph (X axis: elongation, Y axis: tensile strength) of elongation and tensile strength by applying the area and thickness of the sample to evaluate tensile characteristics. A method of evaluating tensile characteristics such as a tensile modulus, a modulus of elasticity, an elongation, etc. from the tensile curve is known in the art.

(6) 2. Evaluation of Recovery Rate

(7) A recovery rate was evaluated by the following method. First, a base film of Example or Comparative Example was cut to have a size of 50 mm100 mm (widthlength). Afterward, a PVA film having the same size as the base film and a thickness of 30 m was adhered to one surface of the base film, thereby forming a laminate. Here, the adhesion between the PVA film and the base film was performed using a general water-based PVA-based adhesive. Afterward, the laminate was dipped in water (temperature: 60 C.) and elongated fivefold the original length in a vertical direction. Then, the resulting sample was taken out of water to peel the PVA film, and maintained at room temperature for 1 hour, and then a vertical length (T) of the base film was measured. Subsequently, the measured length (T) was assigned to Equation 100(TA)/A, thereby obtaining a recovery rate. In the Equation, A is a vertical length of the base film before elongation.

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

(9) A melt index was measured with a weight of a sample passing through an orifice having a diameter of 2.095 mm with a load of 500 g at 215 C. for 10 minutes according to ASTM D1238 (unit: g/10 min)

(10) 4. Evaluation of Hardness

(11) A hardness of a sample having a thickness of 2 mm was measured using a shore D hardness tester (ASKER, Japan) at room temperature.

PREPARATION EXAMPLE 1

Preparation of Base Film (TPU Film (A))

(12) A TPU film was formed using a mixture of polyester polyol prepared by known esterification between adipic acid and 1,4-butanediol and having a weight average molecular weight (Mw) of approximately 2,000, methylenediphenyl diisocyanate (MDI), and 1,4-butanediol (chain extender) by a known method. Particularly, an isocyanate-terminated prepolymer was prepared by adding the polyester-based polyol and the methylenediphenyl diisocyanate to a reaction vessel in a weight ratio of 1:1.46 (polyester-based polyol:MDI), and adding nitrogen at 80 C. to react while stifling at a speed of 200 rpm. Subsequently, TPU was synthesized by further adding 14 parts by weight of a chain extender (1,4-butanediol) with respect to 100 parts by weight of the prepolymer, and adding nitrogen at 80 C. while stirring at a speed of 200 rpm to react until a content of isocyanate (NCO) in the reaction vessel approached 0. The synthesized TPU was casted, thereby forming a TPU film having a thickness of approximately 50 m.

PREPARATION EXAMPLE 2

Formation of Base Film (TPU Film (B))

(13) A TPU film having a thickness of approximately 50 m was formed as described in Preparation Example 1, except that a mixture of 1,4-butanediol (BD) and neopentane glycol (NPG) in a weight ratio of 1:0.5 (BD:NPG) was used as a chain extender.

PREPARATION EXAMPLE 3

Formation of Base Film (TPU Film (C))

(14) A TPU film having a thickness of approximately 50 m was formed as described in Preparation Example 1, except that a mixture of 1,4-butanediol (BD) and neopentane glycol (NPG) in a weight ratio of 1:1.5 (BD:NPG) was used as a chain extender.

(15) Characteristics of each film formed above are summarized and listed in Table 1.

(16) TABLE-US-00001 TABLE 1 TPU film PVA resin Amorphous A B C film PET film Tensile curve 4343 7317 5404 1566 728 integral 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 Recovery rate 19 18.8 11.3 MI 30 30 30 Hardness 80D 75D 75D Tensile curve integral unit: Nmm Tensile strength unit: MPa Elongation unit: % Yield point unit: MPa Elastic limit unit: MPa Recovery rate unit: % MI (215 C. and 5 Kg base) unit: g/10 min PVA resin film: film formed using known PVA resin in preparation of polarizing film (thickness: approximately 30 m) Amorphous PET film (manufacturer: LG Hausys)

EXAMPLE 1

(17) A laminate was formed by stacking the PVA resin film shown in Table 1 on one surface of the TPU film (A) formed in Preparation Example 1 using a water-based PVA-based adhesive. Subsequently, the laminate was dipped in a dying solution (solvent: water) including iodine and potassium iodide at approximately 30 C. for a suitable period of time to adsorb iodine to the PVA resin film. A content of iodine in the dying solution was approximately 0.1 part by weight with respect to 100 parts by weight of water, and a content of potassium iodide was approximately 0.7 parts by weight with respect to 100 parts by weight of water. Subsequently, the laminate was dipped in a boric acid aqueous solution including boric acid and potassium iodide at approximately 60 C., and elongated until the final thickness of the PVA resin film approached approximately 5.8 m (draw ratio: approximately 5.6 folds). As the result of measurement after the PVA resin film was peeled off from the elongated laminator, it was confirmed that a polarizing film having a transmissivity of approximately 40% or more and a polarization degree of 99% or more was formed.

EXAMPLE 2

(18) A polarizing film was formed by the same method as described in Example 1, except that the TPU film (B) formed in Preparation Example 2 was used. The formed polarizing film had a transmissivity of approximately 40% or more, and a polarization degree of approximately 99% or more.

EXAMPLE 3

(19) A polarizing film was formed by the same method as described in Example 1, except that the TPU film (C) formed in Preparation Example 3 was used. The formed polarizing film had a transmissivity of approximately 40% or more, and a polarization degree of approximately 99% or more.

COMPARATIVE EXAMPLE 1

(20) A polarizing film was formed by the same method as described in Example 1, except that an amorphous PET film shown in Table 1 was used instead of a TPU film. However, in this case, a polarizing film exhibiting a suitable performance could not be formed since the PVA resin film was broken or curling occurred poorly as a draw ratio increased.

EXPLANATION OF THE MARKS

(21) 100: the laminate

(22) 101: the base film

(23) 102: the polarizing material layer or polarizing layer