PROTECTIVE FILM

Abstract

[Summary] The present invention relates to a protective film and a polarizing plate comprising the same, and provides a protective film capable of minimizing the amount of static electricity that can be generated upon peeling the protective film.

Claims

1. A protective film having a pressure-sensitive adhesive layer comprising a polyorganosiloxane satisfying Formula 1 below and a metal salt: ##STR00002## wherein, n is any one number in a range of 0 to 1500, R.sub.1 to R.sub.8 are the same or different from each other and each independently hydrogen, an alkyl group, an alkoxy group, an alkenyl group, an alkynyl group or an alkylene oxide, and at least one of R.sub.1 to R.sub.8 is an alkylene oxide.

2. The protective film according to claim 1, wherein the metal salt forms a chelate with the polyorganosiloxane.

3. The protective film according to claim 1, wherein the metal salt comprises an alkali metal or an alkaline earth metal.

4. The protective film according to claim 1, wherein the metal salt comprises LiBr, LiI, LiBF.sub.4, LiPF.sub.6, LiSCN, LiClO.sub.4, LiCF.sub.3SO.sub.3, Li(CF.sub.3SO.sub.2).sub.2N, Li(C.sub.2F.sub.5SO.sub.2).sub.2N, Li(CF.sub.3SO.sub.2).sub.3C, K(CF.sub.3SO.sub.2).sub.2N).sub.2, or Mg((CF.sub.3SO.sub.2).sub.2N).sub.2.

5. The protective film according to claim 1, wherein the metal salt is comprised in an amount of 50 to 150 parts by weight, relative to 100 parts by weight of the polyorganosiloxane.

6. The protective film according to claim 1, wherein the polyorganosiloxane has a weight average molecular weight of 300 to 100,000.

7. The protective film according to claim 1, wherein the pressure-sensitive adhesive layer further comprises a pressure-sensitive adhesive base resin comprising a (meth) acrylic acid ester monomer as a polymerized unit.

8. The protective film according to claim 7, wherein the pressure-sensitive adhesive base resin and the polyorganosiloxane are comprised in an amount of 80 to 99.8 parts by weight and 0.01 to 10 parts by weight, respectively.

9. The protective film according to claim 7, wherein the pressure-sensitive adhesive base resin further comprises a polymerized unit derived from a copolymerizable monomer having a cross-linkable functional group.

10. The protective film according to claim 9, wherein the copolymerizable monomer having a cross-linkable functional group is at least one selected from the group consisting of a hydroxy group-containing comonomer, a carboxyl group-containing comonomer and a nitrogen-containing comonomer.

11. The protective film according to claim 9, wherein the copolymerizable monomer having a cross-linkable functional group is comprised in an amount of 0.01 to 14 parts by weight, relative to 100 parts by weight of the pressure-sensitive adhesive base resin.

12. The protective film according to claim 7, wherein the pressure-sensitive adhesive layer further comprises a multifunctional cross-linking agent for cross-linking the pressure-sensitive adhesive base resin.

13. The protective film according to claim 12, wherein the multifunctional cross-linking agent is at least one selected from the group consisting of an isocyanate compound, an epoxy compound, an aziridine compound and a metal chelate compound.

14. The protective film of claim 12, wherein the multifunctional cross-linking agent is a mixture of an aliphatic linear polyvalent NCO and an aliphatic cyclic polyvalent NCO.

15. The protective film according to claim 12, wherein the multifunctional cross-linking agent is comprised in the pressure-sensitive adhesive layer in an amount of 0.01 to 20 parts by weight, relative to 100 parts by weight of the pressure-sensitive adhesive base resin.

16. The protective film according to claim 1, wherein the pressure-sensitive adhesive layer further comprises a curing retardant.

17. The protective film according to claim 1, further comprising a base material layer, wherein the pressure-sensitive adhesive layer is formed on one surface of said base material layer.

18. The protective film according to claim 1, which is applied to an adherend having a surface energy of 15 mN/m to 40 mN/m.

19. A polarizing plate comprising a polarizer and the protective film according to claim 1 formed on one surface of said polarizer.

20. The polarizing plate according to claim 19, further comprising a coating layer formed on one surface of said polarizer and having a surface energy of 15 mN/m to 40 mN/m, wherein the protective film is formed on said coating layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, the present application will be described in more detail by way of examples according to the present application and comparative examples not complying with the present application, but the scope of the present application is not limited by the following examples.

EXAMPLE 1

[0032] <Preparation of Pressure-Sensitive Adhesive Layer>

[0033] 2-Ethylhexyl acrylate (2-EHA) and 2-hydroxyethyl acrylate (2-HEA) were copolymerized in ethyl acetate at a weight ratio of 98: 2 (2-EHA:2-HEA) to obtain a solution of an acrylic copolymer.

[0034] Then, 5 parts by weight of HMDI/IPDI (hexamethylene diisocyanate/isophorone diisocyanate) (=8/2 weight ratio (NCO %: 16 wt %)) as an isocyanate cross-linking agent, 7 parts by weight of acetyl acetone as a curing retardant, 0.5 part by weight of polydimethylsiloxane (weight average molecular weight: 20,000) having ethylene oxide bonded at the R.sub.5 position as a polyorganosiloxane of Formula 1 and 0.5 part by weight of Li(CF.sub.3SO.sub.2).sub.2N as a metal salt, relative to 100 parts by weight (solid content) of the acrylic copolymer, were mixed to obtain a pressure-sensitive adhesive composition.

[0035] <Preparation of Protective Film>

[0036] The pressure-sensitive adhesive composition was coated on one side of A4300 PET (Toyobo Co., Ltd.) (thickness: 100 m), and a transparent pressure-sensitive adhesive layer having a thickness of 15 m was formed after drying Immediately after drying, the release film is covered and aged at 40 C. for 4 days.

EXAMPLE 2

[0037] A protective film was prepared in the same manner as in Example 1, except that K(CF.sub.3SO.sub.2).sub.2N was used as the metal salt.

EXAMPLE 3

[0038] A protective film was prepared in the same manner as in Example 1, except that Mg((CF.sub.3SO.sub.2).sub.2N).sub.2 was used as the metal salt.

EXAMPLE 4

[0039] A protective film was prepared in the same manner as in Example 1, except that 1 part by weight of the polyorganosiloxane of Formula 1 was introduced.

COMPARATIVE EXAMPLE 1

[0040] A protective film was prepared in the same manner as in Example 1, except that the polyorganosiloxane of Formula 1 was not added.

COMPARATIVE EXAMPLE 2

[0041] A protective film was prepared in the same manner as in Example 1, except that polydimethylsiloxane was used instead of the polyorganosiloxane of Formula 1.

COMPARATIVE EXAMPLE 3

[0042] A protective film was prepared in the same manner as in Example 1, except that an ammonium salt ((n-C.sub.4H.sub.9).sub.3(CH.sub.3)N.sup.+ N(SO.sub.2CF.sub.3).sub.2) was used as an antistatic agent instead of the metal salt.

EXPERIMENTAL EXAMPLE 1

ESD (Electrostatic Discharge, kV) Measurement

[0043] A pressure-sensitive adhesive layer of a protective film prepared in Examples and Comparative Examples was laminated to an anti-glare layer of an anti-glare polarizing plate (TAC (tri-acetyl-cellulose film) film layer/PVA (polyvinyl alchol) layer/TAC film layer) having a surface energy in the range of 15 mN/m to 40 mN/m, and then a sample was prepared by tailoring the polarizing plate into A4 size and fixing the opposite side of the polarizing plate laminated with the protective film to the bottom surface through a double-faced tape. The measurement was performed using a STATIRON DZ-4 model from SHISHIDO Co. as an electrostatic instrument, where the measurement distance from the sample was fixed at 3 cm. While peeling the protective film at the peeling speed of 30 m/min and the peeling angle of 180, the static electricity to be generated was measured. In the measurement, it may be determined for the case of 0.5 kV or more to be poor and for the case of less than 0.5 kV to be good.

EXPERIMENTAL EXAMPLE 2

Staining Properties

[0044] A protective film prepared in Examples and Comparative Examples was laminated to an anti-glare polarizing plate in the same manner as in Experimental Example 1, and then left at 50 C. for at least one day, and a black tape was laminated to the opposite side of the polarizing plate laminated with the protective film to ensure the visibility of the staining property evaluation. Then, by repeatedly peeling the protective film from the polarizing plate and attaching it thereto, bubbles were artificially entrained and then allowed to stand at room temperature for at least one day. The protective film containing the bubbles was subjected to heat treatment at 50 C. for 3 hours, and then visually observed for staining. They were classified by representing O if bubble marks were not observed with the naked eye and X if bubble marks were observed with the naked eye.

TABLE-US-00001 TABLE 1 ESD(kV) Staining Example 1 0.15 Example 2 0.20 Example 3 0.22 Example 4 0.10 X Comparative Example 1 0.87 Comparative Example 2 0.72 Comparative Example 3 0.54

[0045] In Comparative Example 1, no polyorganosiloxane was added and in Comparative Example 2, polydimethylsiloxane was added, without any alkylene oxide functional group, and thus as a result of measuring static electricity in Comparative Examples 1 and 2, the static electricity was generated three times or more as compared with Examples. Also, as a result of measuring static electricity in the case of Comparative Example 3 in which the organic salt was included instead of the metal salt, the static electricity was generated twice or more as compared with Examples.