Adhesive composition, and polarizing plate and display device manufactured using same

Abstract

The present invention relates to an acrylic adhesive composition, and a polarizing plate and a display device manufactured using the same, wherein the acrylic adhesive composition includes an acrylic copolymer formed by polymerizing a monomer mixture including a (meth)acrylic monomer and a (meth)acrylic monomer containing a hydroxy group, an isocyanate-based multi-functional curing agent, a curing retarder including a first curing retarder having a deblocking temperature of 110 C. or lower and a second curing retarder having a deblocking temperature of 130 C. or higher, and a silane coupling agent.

Claims

1. An acrylic adhesive composition comprising: an acrylic copolymer formed by polymerizing a monomer mixture including a (meth)acrylic monomer and a (meth)acrylic monomer containing a hydroxy group; an isocyanate-based multi-functional curing agent; a curing retarder comprising at least two kinds of curing retarders having different deblocking temperatures; and a silane coupling agent, wherein the curing retarder comprises a first curing retarder having a deblocking temperature of 110 C. or lower and a second curing retarder having a deblocking temperature of 130 C. or higher, and the first curing retarder and the second curing retarder are included in a weight ratio of 1:1 to 5:1, and wherein the acrylic adhesive composition does not comprise a peroxide.

2. The acrylic adhesive composition of claim 1, wherein the first curing retarder has a deblocking temperature of 70 C. to 110 C., and the second curing retarder has a deblocking temperature of 130 C. to 160 C.

3. The acrylic adhesive composition of claim 1, wherein the first curing retarder is one or more selected from the group consisting of acetylacetone, diethylmalonate, and methylethylketoxime.

4. The acrylic adhesive composition of claim 1, wherein the second curing retarder is one or more selected from the group consisting of acetone oxime, caprolactam and an alkylmercaptan-based compound.

5. The acrylic adhesive composition of claim 1, wherein the second curing retarder is acetone oxime.

6. The acrylic adhesive composition of claim 1, wherein the silane coupling agent is an alkoxy silane-based coupling agent.

7. The acrylic adhesive composition of claim 1, wherein the acrylic copolymer has a weight average molecular weight of 1,000,000 to 2,500,000 g/mol.

8. The acrylic adhesive composition of claim 1, wherein the isocyanate-based multi-functional curing agent is included in an amount of 0.01 to 5 parts by weight, the curing retarder is included in an amount of 1 to 5 parts by weight, and the silane coupling agent is included in an amount of 0.01 to 1 part by weight, based on 100 parts by weight of the acrylic copolymer.

9. The acrylic adhesive composition of claim 1, wherein the (meth)acrylic monomer is included in an amount of 80 parts by weight to 99 parts by weight, based on 100 parts by weight of the monomer mixture.

10. The acrylic adhesive composition of claim 1, wherein the (meth)acrylic monomer including a hydroxy group is included in 1 to 10 parts by weight, based on 100 parts by weight of the monomer mixture.

11. The acrylic adhesive composition of claim 1, wherein the curing retarder is included in an amount of 1 part by weight to 5 parts by weight, based on 100 parts by weight of the acrylic copolymer.

12. A polarizing plate comprising: a polarizing film; and an adhesive layer formed on one surface or both surfaces of the polarizing film and including a cured product of the acrylic adhesive composition of claim 1.

13. A display device comprising the polarizing plate of claim 12.

Description

MODE FOR CARRYING OUT THE INVENTION

(1) Hereinafter, Examples of the present invention will be described in detail so that those skilled in the art may easily carry out the present invention. However, the present invention may be embodied in many different forms, and is not limited to Examples set forth herein.

Preparation Example 1: Acrylic Copolymer (A)

(2) To a 3 L reactor in which nitrogen gas is refluxed and a cooling device is installed to facilitate temperature control, a monomer mixture containing 93 parts by weight of butyl acrylate (BA), 5 parts by weight of methyl methacrylate (MMA), and 2 parts by weight of hydroxybutyl acrylate (HBA) were introduced. Thereafter, 120 parts by weight of ethyl acetate (EAc) was introduced thereto as a solvent. Thereafter, nitrogen gas was purged for 30 minutes to remove oxygen, and then the temperature was maintained at 60 C. Thereafter, the mixture was reacted for 12 hours while further introducing 0.025 parts by weight of n-dodecylmercaptan (n-DDM) as a molecular weight control agent and 0.03 parts by weight of azobis(2,4-dimethylvaleronitrile) (V-65, Manufacturer: Wako) as a polymerization initiator thereto to prepare an acrylic copolymer (A).

Preparation Example 2: Acrylic Copolymer (B)

(3) To a 3 L reactor in which nitrogen gas is refluxed and a cooling device is installed to facilitate temperature control, a monomer mixture containing 96.5 parts by weight of butyl acrylate (BA), 3 parts by weight of hydroxyethyl acrylate (HEA), and 0.5 parts by weight of hydroxybutyl acrylate (HBA) were introduced. Thereafter, 120 parts by weight of ethyl acetate (EAc) was introduced thereto as a solvent. Thereafter, nitrogen gas was purged for 30 minutes to remove oxygen, and then the temperature was maintained at 60 C. Thereafter, the mixture was reacted for 12 hours while further introducing 0.01 parts by weight of n-dodecylmercaptan (n-DDM) as a molecular weight control agent and 0.03 parts by weight of azobis(2,4-dimethylvaleronitrile) (V-65, Manufacturer: Wako) as a polymerization initiator thereto to prepare an acrylic copolymer (B).

Preparation Example 3: Acrylic Copolymer (C)

(4) To a 3 L reactor in which nitrogen gas is refluxed an acrylic a cooling device is installed to facilitate temperature control, a monomer mixture containing 94 parts by weight of butyl acrylate (BA) and 6 parts by weight of acrylic acid (AA) were introduced. Thereafter, 120 parts by weight of ethyl acetate (EAc) was added thereto as a solvent. Thereafter, nitrogen gas was purged for 30 minutes to remove oxygen, and then the temperature was maintained at 62 C. Thereafter, the mixture was reacted for 10 hours while further introducing 0.01 parts by weight of n-dodecylmercaptan (n-DDM) as a molecular weight control agent and 0.03 parts by weight of azobis(2-4-dimethylvaleronitrile) (V-65, Manufacturer: Wako) as a polymerization initiator thereto to prepare an acrylic copolymer (C).

(5) The weight average molecular weight of the acrylic copolymer prepared in each of Preparation Examples 1 to 3 was measured under the following conditions using GPC. In making a calibration curve, the measurement results were converted using standard polystyrene of the Agilent system.

(6) <Measurement Conditions>

(7) Measurement device: Agilent GPC (Agulent 1200 series, USA)

(8) Column: Two PL Mixed B connections

(9) Column temperature: 40 C.

(10) Eluent: tetrahydrofuran

(11) Flow rate: 1.0 mL/min

(12) Concentration: 1 mg/mL (100 L injection)

(13) TABLE-US-00001 TABLE 1 Preparation Preparation Preparation Example 1 Example 2 Example 3 Acrylic copolymer A B C Monomer BA 93.0 96.5 94.0 mixture MMA 5 HEA 3 HBA 2 0.5 AA 6 Weight average 160 million 180 million 160 million molecular weight (Mw)

Example 1

(14) 100 parts by weight of the acrylic copolymer (A) prepared as described above, 0.10 parts by weight an isocyanate-based curing agent (Coronate L, manufactured by NPU Co., Ltd.), 0.9 parts by weight of acetylacetone as the first curing retarder, 0.6 parts by weight of acetone oxime as the second curing retarder, 0.35 parts by weight of a silane coupling agent (AD-M812, LG Chem), 1.5 parts by weight of an anti-static agent (HQ-115A, 3M Co., Ltd.), and 0.01 parts by weight of a crosslinking catalyst (Sigma-Aldrich, Dibutyltindilaurate) were mixed to prepare an adhesive composition.

(15) The prepared adhesive composition was applied on a release-treated surface of a release-treated polyethylene terephthalate (release PET) film having a thickness of 38 m such that the thickness thereof after being dried would be 23 m, and then dried for 3 minutes at 110 C. to form an adhesive layer. Thereafter, the adhesive layer was laminated on a polarizing plate to manufacture a polarizing plate including an adhesive layer.

Examples 2 to 8 and Comparative Examples 1 to 7

(16) An adhesive composition and a polarizing plate were prepared in the same manner as in Example 1 except that the types and contents of each component were changed as described in [Table 2] and [Table 3].

(17) TABLE-US-00002 TABLE 2 Example Example Example Example Example Example Example Example 1 2 3 4 5 6 7 8 Acrylic copolymer A A A A B B B B 100 100 100 100 100 100 100 100 Isocyanate-based 0.10 0.15 0.15 0.20 0.10 0.10 0.90 0.10 curing agent First curing Acetylacetone 0.9 2.0 0.5 2.5 retarder Diethylmalonate 1.5 3.2 4.0 Methylethylketoxime 0.4 Second curing Acetoneoxime 0.6 0.5 0.6 1 0.5 0.6 1.5 1.5 retarder Silane coupling agent 0.35 0.45 0.35 0.50 0.45 0.50 0.15 0.50 Anti-static agent 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Crosslinking catalyst 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01

(18) TABLE-US-00003 TABLE 3 Comparative Comparative Comparative Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Acrylic copolymer A A A B A B C 100 100 100 100 100 100 100 Isocyanate-based 0.09 0.20 0.15 0.90 0.20 0.10 2.50 curing agent First curing Acetylacetone 2.5 2.0 retarder Diethylmalonate 4 Methylethylketoxime 1 Second curing Acetoneoxime 1.5 0.5 retarder Silane coupling agent 0.50 0.45 0.15 0.50 0.50 0.35 Anti-static agent 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Crosslinking catalyst 0.01 0.01 0.01 0.01 0.01 0.01

(19) The physical properties of the adhesive layer and the polarizing plate prepared in each of Examples 1 to 8 and Comparative Examples 1 to 7 were measured by the following method, and the measurement results are shown in Table 4 to Table 5 below.

(20) Method for Measuring Physical Properties

(21) (1) Gel Fraction (%)

(22) Samples were collected from the adhesive layers formed in Examples and Comparative Examples, and the weight W.sub.0 of the samples was measured. Thereafter, ethyl acetate was added to the collected adhesive layer samples and dissolved for 72 hours, filtered through a 400 mesh stainless steel mesh of W.sub.3 (g), and then dried at 150 C. for 30 minutes. Thereafter, the total weight W.sub.2 (g) of the stainless steel mesh and residues was measured. A value obtained by subtracting the weight W.sub.3 of the stainless steel mesh from the total weight W.sub.2 was referred to as W.sub.1, and W.sub.0 and W.sub.1 were substituted in Equation (1) below to obtain a gel fraction.
Gel fraction (%)=(W.sub.1/W.sub.0)100Equation (1):
(2) Evaluation of Adhesion Force

(23) The polarizing plate manufactured in each of Examples and Comparative Examples was stored for 4 days under the constant temperature/humidity conditions (23 C., 50% R. H.), and then was cut to a size of 25 mm in width and 100 mm in length to prepare a specimen. Thereafter, the release PET film attached to the adhesive layer was peeled off, and the polarizing plate was attached to an alkali-free glass using a 2 kg roller in accordance with JIS Z 0237 regulation to prepare a specimen for measurement.

(24) The specimen for measurement was stored for 4 hours under the constant temperature/humidity conditions (23 C., 50% R. H.). Thereafter, using a texture analyzer (TA, manufactured by Stable Micro Systems, UK), a force required to completely separate a polarizing plate f from a glass substrate by pulling the polarizing plate at a peeling rate of 300 mm/min and a peeling angle of 180 was measured to evaluate adhesion force (unit: gf/25 mm).

(25) (3) Evaluation of Reworkability

(26) The polarizing plate manufactured in each of Examples and Comparative Examples was stored for 1 days under the constant temperature/humidity conditions (23 C., 50% R. H.), and then was cut to a size of 25 mm in width and 100 mm in length to prepare a specimen. Thereafter, the release PET film attached to the adhesive layer was peeled off, and the polarizing plate was attached to an alkali-free glass using a 2 kg roller in accordance with JIS Z 0237 regulation to prepare a specimen for measurement.

(27) Thereafter, the specimen for measurement was stored for 1 hour at 80 C., and then was stored for 1 hour under the constant temperature/humidity conditions (23 C., 50% R. H.). Thereafter, using a texture analyzer (TA, manufactured by Stable Micro Systems, UK), a force required to completely separate a polarizing plate from a glass substrate by pulling the polarizing plate at a peeling rate of 300 mm/min and a peeling angle of 180 was measured to measure rework force (unit: gf/25 mm), and reworkability was evaluated based on the following criteria.

(28) <Evaluation Criteria>

(29) : When rework force is less than 1,500 gf/25 mm

(30) : When rework force is 1,500 gf/25 mm to less than 2,500 gf/25 mm X: When rework force is 2, 500 gf/25 mm or greater
(4) Durability Evaluation

(31) The polarizing plate manufactured in each of Examples and Comparative Examples was attached on an alkali-free glass substrate and then stored in an autoclave (50 C. and 5 atmospheric pressure) for about 20 minutes to produce a specimen for measurement.

(32) The produced specimens for measurement were left to stand for 500 hours at a temperature of 80 C. and 95 C., respectively, and then the occurrence of bubbles or peeling was observed with the naked eye to evaluate heat resistance durability.

(33) In addition, the produced specimens for measurement were left to stand for 500 hours at a temperature of 60 C. and a relative humidity of 90%, and at a temperature of 65 C. and a relative humidity of 95%, respectively, and then the occurrence of bubbles or peeling was observed with the naked eye to evaluate moisture and heat resistance durability.

(34) <Evaluation Criteria>

(35) : No bubbles and peeling observed

(36) X: Bubbles and/or peeling observed

(37) TABLE-US-00004 TABLE 4 Example Example Example Example Example Example Example Example 1 2 3 4 5 6 7 8 Gel (%) 68 75 72 77 67 65 82 65 Adhesion force (gf/in) 380 240 310 240 360 380 350 380 Reworkability Heat resistant 80 C. durability 95 C. Moisture and 60 C., heat resistance 90% RH durability 65 C., 95% RH

(38) TABLE-US-00005 TABLE 5 Comparative Comparative Comparative Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Gel (%) 45 79 73 85 79 70 81 Adhesion force (gf/in) 720 230 240 290 230 340 960 Reworkability x x Heat resistant 80 C. x durability 95 C. x x x x x Moisture and 60 C., x heat resistance 90% RH durability 65 C., x x 95% RH

(39) As shown in Table 4 above, the polarizing plate manufactured by using the adhesive composition of each of Examples 1 to 8 had sufficient adhesion force, and also had excellent reworkability, heat resistant durability, and moisture and heat resistant durability. On the contrary, as shown in Table 5 above, the polarizing plate manufactured by using the adhesive composition of Comparative Example 1 in which only the second curing retarder was used and the first curing retarder was not included had adhesion force too high, making it difficult to rework, and had poor durability under high-temperature and high-temperature/high-humidity conditions.

(40) Meanwhile, the polarizing plate manufactured by using the adhesive composition of each of Comparative Examples 2, 5, and 6 in which only the first curing retarder was used and the second curing retarder was not included had good adhesion force and reworkability, but had poor heat resistance durability at 95 C.

(41) Meanwhile, the polarizing plate manufactured by using the adhesive composition of Comparative Example 3 in which the silane coupling agent was not used had good adhesion force and reworkability, but had poor moisture and heat resistance durability.

(42) In addition, the polarizing plate manufactured by using the adhesive composition of Comparative Example 4 in which the curing retarder was not used had good adhesion force and reworkability, but had poor heat resistance durability at 95 C. The polarizing plate manufactured by using the adhesive composition of Comparative Example 7 in which an acid-based copolymer was used as the acrylic copolymer had adhesion force too high, so that the reworkability thereof was significantly reduced.