Protective film

Abstract

The present invention relates to a protective film, a conductive laminate including the protective film, and a polarizing plate including the protective film, and provides the protective film which has peel strength controlled to be low, thus allowing for an easy removal of the protective film, which has an excellent polymerization stability and pot life, and may prevent a problem of an additive transfer to an adherend due to the additive.

Claims

1. A protective film, comprising a pressure-sensitive adhesive layer which contains: a pressure-sensitive adhesive base resin having polyorganosiloxane as a polymerization unit, wherein the polymerization unit of polyorganosiloxane is derived from a compound of Formula 1: ##STR00002## wherein: n is an integer in the range of 0 to 1,500; R represents identical or different components, and represents hydrogen, an alkyl group, an alkoxy group, or an alkynyl group, respectively, and P is a polymerizable functional group; and the polyorganosiloxane has a functional group equivalent of 3,000 to 20,000 g/mol; a multifunctional crosslinking agent which crosslinks the pressure-sensitive adhesive base resin, wherein the multifunctional crosslinking agent is a mixture of an aliphatic linear polyvalent NCO and an aliphatic ring-shaped polyvalent NCO, the aliphatic linear polyvalent NCO and aliphatic ring-shaped polyvalent NCO present in a ratio in the range of 6:4 to 9:1 to form the mixture; and a curing retarder.

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

3. The protective film of claim 1, wherein the polymerizable functional group comprises an alkenyl group, an epoxy group, a cyano group, a carboxyl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group.

4. The protective film of claim 1, wherein the pressure-sensitive adhesive base resin further comprises a (meth)acrylic acid ester monomer as a polymerization unit.

5. The protective film of claim 4, wherein the pressure-sensitive adhesive base resin comprises polymerization units derived from 80 to 99.8 parts by weight of the (meth)acrylic acid ester monomer and 0.1 to 10 parts by weight of polyorganosiloxane.

6. The protective film of claim 4, wherein the pressure-sensitive adhesive base resin further comprises a polymerization unit derived from a copolymerizable monomer having a crosslinkable functional group.

7. The protective film of claim 6, wherein the copolymerizable monomer having a crosslinkable functional group is one or more selected from the group consisting of a hydroxy group-containing comonomer, a carboxyl group-containing comonomer, and a nitrogen containing-comonomer.

8. The protective film of claim 6, wherein the copolymerizable monomer having a crosslinkable functional group is included at 0.01 to 14 parts by weight with respect to 100 parts by weight of the pressure-sensitive adhesive base resin.

9. The protective film of claim 1, wherein the multifunctional crosslinking agent is included at 0.01 to 20 parts by weight with respect to 100 parts by weight of the pressure-sensitive adhesive base resin in the pressure-sensitive adhesive layer.

10. The protective film of claim 1, wherein the curing retarder is one or more selected from the group consisting of methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, stearyl acetoacetate, acetyl acetone, 2,4-hexanedione, or benzoyl acetone.

11. The protective film of claim 1, further comprising a base layer, wherein the pressure-sensitive adhesive layer is formed on one side of the base layer.

12. The protective film of claim 11, wherein the base layer comprises a one-component polymer such as a polycarbonate, a polyether sulfone, a polyacrylate, a polyester-based polymer, a polyolefin-based polymer or a norbornene-based polymer, a copolymerized polymer, or an epoxy-based polymer.

13. The protective film of claim 1, wherein the pressure-sensitive adhesive base resin is a resin which requires 5 hours or more until a viscosity of the resin is increased to twice or more than the initial viscosity of the resin which has just been prepared, immediately after the resin is mixed with a crosslinking agent.

14. The protective film of claim 1, wherein the polymerizable functional group comprises an alkenyl group, an epoxy group, a cyano group, or a carboxyl group.

15. The protective film of claim 1, wherein the curing retarder comprises a -keto ester selected from the group consisting of methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate.

16. A conductive laminate comprising: a conductive film having at least one conductive layer; and the protective film of claim 1 adhered to one side of the conductive film.

17. A polarizing plate comprising: at least one polarizer; and the protective film of claim 1 adhered to one side of the polarizer.

Description

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(1) Hereinafter, the present invention will be described in detail in conjunction with examples according to an embodiment of the present invention and comparative examples not according to an embodiment of the present invention, but is not limited to the following examples.

Example 1

(2) Preparation of Pressure-sensitive Adhesive Layer

(3) In ethyl acetate, 2-ethylhexyl acrylate (2-EHA), X-22-2426 (Shin-Etsu Chemical Co., Ltd.) as reactive polyorganosiloxane, and 2-hydroxyethyl acrylate (2-HEA) were copolymerized in the weight ratio of 89:1:10 (2-EHA:X-22-2426:2-HEA), and thereby an acryl-based copolymer solution was obtained.

(4) Then, 7.5 parts by weight of HMDI/IPDI (=8/2 weight ratio (NCO %:16 wt %)) which is an isocyanate-based crosslinking agent, 7 parts by weight of acetyl acetone as a curing retarder, and 0.01 parts by weight of dibutyltin dilaurate as a catalyst with respect to 100 parts by weight of the acryl-based copolymer (solid fraction) were mixed, and thereby a pressure-sensitive adhesive composition was obtained.

(5) Preparation of Protective Film

(6) The pressure-sensitive adhesive composition was coated on one side of A4300 PET (Toyobo Co., Ltd.) (thickness: 100 m), dried, and thereby a transparent pressure-sensitive adhesive layer which has a thickness of 20 m was formed. The transparent pressure-sensitive adhesive layer which was coated on one side of A4300 PET was aged at 40 C. for 4 days immediately after drying and covering a release film.

(7) Preparation of Conductive Laminate

(8) The prepared protective film was adhered to one side of L2CC5 (LG Chem, Ltd.) as an ITO film. The protective film was laminated such that a pressure-sensitive adhesive layer of the protective film contacts a hard coating layer of the ITO film.

Example 2

(9) The protect film and conductive laminate were prepared in a same manner as in Example 1 except that X-22-174DX (Shin-Etsu Chemical Co., Ltd.) was used as polyorganosiloxane instead of X-22-2426 (Shin-Etsu Chemical Co., Ltd.).

Example 3

(10) The protect film and conductive laminate were prepared in a same manner as in Example 1 except that 2-ethylhexyl acrylate, X-22-2426 (Shin-Etsu Chemical Co., Ltd.) as polyorganosiloxane, and 2-hydroxyethyl acrylate were used in the weight ratio of 94:1:5 (2-EHA:X-22-2426:2-HEA) to prepare a copolymer, and 3.8 parts by weight of HMDI/IPD (=8/2 weight ratio (NCO %:16 wt %)) which is an isocyanate-based crosslinking agent was used with respect to 100 parts by weight of the copolymer.

Example 4

(11) The protect film and conductive laminate were prepared in a same manner as in Example 1 except that 2-ethylhexyl acrylate, X-22-2426 (Shin-Etsu Chemical Co., Ltd.) as polyorganosiloxane, and 2-hydroxyethyl acrylate were used in the ratio of 94.5:0.5:5 (2-EHA:X-22-2426:2-HEA) to prepare the copolymer, and 3.8 parts by weight of HMDI/IPDI (=8/2 weight ratio (NCO %:16 wt %)) which is the isocyanate-based crosslinking agent was used with respect to 100 parts by weight of the copolymer.

COMPARATIVE EXAMPLE 1

(12) The protective film and conductive laminate were prepared in a same manner as in Example 1 except that 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate was used in the ratio of 85:15 (2-EHA:2-HEA) to prepare the copolymer without adding polyorganosiloxane, and 11.7 parts by weight of HMDI/IPDI (=8/2 weight ratio (NCO %:16 wt %)) which is the isocyanate-based crosslinking agent was used with respect to 100 parts by weight of the copolymer.

COMPARATIVE EXAMPLE 2

(13) The protective film and conductive laminate were prepared in a same manner as in Example 1 except that 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate was used in the ratio of 95:5 (2-EHA:2-HEA) to prepare the copolymer without adding polyorganosiloxane, and 3.8 parts by weight of HMDI/IPDI (=8/2 weight ratio (NCO %:16 wt %)) which is the isocyanate-based crosslinking agent was used with respect to 100 parts by weight of the copolymer.

COMPARATIVE EXAMPLE 3

(14) The protective film and conductive laminate were prepared in a same manner as in Example 1 except that 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate as a resin were used in the ratio of 90:10 (2-EHA:2-HEA) to prepare the copolymer, 0.1 parts by weight of BYK-377 not having a polymerizable functional group was added with respect to 100 parts by weight of the copolymer as polyorganosiloxane, and 7.5 parts by weight of HMDI/IPDI (=8/2 weight ratio (NCO %:16 wt %)) which is the isocyanate-based crosslinking agent was used with respect to 100 parts by weight of the copolymer.

EXPERIMENTAL EXAMPLE 1

Peel Strength

(15) The pressure-sensitive adhesive layers of the protective films which are aged (cured) in the examples and comparative examples were adhered to the hard coating layer of the ITO film, a heat treatment was performed thereon at 150 C. for 1 hour, and then a peel strength (width: 1 inch) was measured using a high speed peel tester (CBT-4720; manufactured by Chung-buk Tech) at a peeling angle of 180 and a peeling speed of 20 m/min under conditions of room temperature.

EXPERIMENTAL EXAMPLE 2

Pot Life

(16) A viscosity of the pressure-sensitive adhesive composition prepared in the examples and comparative examples was measured under conditions of a spindle #63, a temperature of 25 C., and at a rate of 50 rpm using a rotation viscometer (LVDV-II pro; manufactured by Brookfield Engineering Laboratories, Inc.). The viscosity of the composition in which the copolymer and the crosslinking agent were just mixed was assumed as an initial viscosity, and a change of the time required until the viscosity increased twice or more than the initial viscosity was measured, and defined as a pot life.

EXPERIMENTAL EXAMPLE 3

Haze

(17) The protective film was peeled off from the conductive laminate prepared in the examples and comparative examples, and then haze of the conductive laminate was measured using a hazemeter (HM-150).

(18) TABLE-US-00001 TABLE 1 Pot life (hr) Peel strength (gf/in) Haze (%) Example 1 12 19 0.82 Example 2 11 21 0.89 Example 3 75 86 0.84 Example 4 74 91 0.81 Comparative 2 25 0.89 Example 1 Comparative 74 154 0.88 Example 2 Comparative 10 25 2.1 Example 3

(19) In Comparative Examples 1 and 2, a polyorganosiloxane chain was not introduced into the pressure-sensitive adhesive layer, and thus an insufficient pot life was obtained or high peel strength was measured. In Comparative Example 3, as a result of including polyorganosiloxane as an additive, it was determined that the additive was transferred to the ITO after peeling off the protective film, thereby decreasing optical physical properties.