Pressure sensitive adhesive composition

Abstract

Provided are a pressure-sensitive adhesive composition, a protection film, an optical laminate, a polarizing plate, and a display device. Provided is the pressure-sensitive adhesive composition which is excellent in various physical properties, such as endurance reliability, has excellent antistatic characteristics that change little over time. The pressure-sensitive adhesive composition can be used for a protection film, or can be used for an optical film, such as a polarizing plate, for example.

Claims

1. A pressure-sensitive adhesive composition comprising: a block copolymer including a first block having a glass transition temperature of 50° C. or higher, and a second block having a glass transition temperature of −10° C. or lower, the second block including a copolymer which is derived from (meth)acrylic acid ester monomer, a copolymeric monomer having a cross-linkable functional group, and a compound containing a nitrogen atom; and an antistatic agent, wherein the first block consists of a homopolymer which is derived from (meth)acrylic acid ester monomer, the block copolymer is a diblock copolymer having the first block and the second block, and the diblock copolymer is the only block copolymer in the pressure-sensitive adhesive composition.

2. The pressure-sensitive adhesive composition of claim 1, wherein the compound containing a nitrogen atom is an amide group-containing compound, an amino group-containing compound, an imide group-containing compound, or a cyano group-containing compound.

3. The pressure-sensitive adhesive composition of claim 2, wherein the amide group-containing compound is (meth)acrylamide, N,N-dialkyl (meth)acrylamide, N-alkylrol (meth)acrylamide, diacetone (meth)acrylamide, N-vinylacetamide, N,N-alkylene bisacrylamide, N-hydroxyalkyl (meth)acrylamide, N-hydroxy alkylaminoalkyl (meth)acrylamide, N-(2-aminoethyl)acrylamide hydrochloride, N-(3-aminopropyl)methacrylamide hydrochloride, N-(t-butoxycarbonyl-aminopropyl)methacrylamide, N,N-dialkylaminoalkyl (meth)acrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, or (meth)acryloylmorpholine; the amino group-containing compound is aminoalkyl (meth)acrylate, N-alkylaminoalkyl (meth)acrylate, or N,N-dialkylaminoalkyl (meth)acrylate; the imide group-containing compound is N-alkyl maleimide or itaconimide; and the cyano group-containing compound is (meth)acrylonitrile.

4. The pressure-sensitive adhesive composition of claim 1, wherein the compound containing a nitrogen atom is aminoalkyl (meth)acrylate, alkylaminoalkyl (meth)acrylate, dialkylaminoalkyl (meth)acrylate, or hydroxyalkyl (meth)acrylamide.

5. The pressure-sensitive adhesive composition of claim 1, wherein the block copolymer includes 5 parts by weight to 50 parts by weight of the first block and 50 parts by weight to 95 parts by weight of the second block.

6. The pressure-sensitive adhesive composition of claim 1, wherein the (meth)acrylic acid ester monomer is alkyl methacrylate.

7. The pressure-sensitive adhesive composition of claim 1, wherein the (meth)acrylic acid ester monomer is methyl methacrylate.

8. The pressure-sensitive adhesive composition of claim 1, wherein the second block includes a copolymer which is derived from 60 parts by weight to 99.8 parts by weight of the (meth)acrylic acid ester monomer, 0.1 parts by weight to 10 parts by weight of the copolymeric monomer having a cross-linkable functional group, and 0.1 parts by weight to 30 parts by weight of the compound containing a nitrogen atom.

9. The pressure-sensitive adhesive composition of claim 1, wherein the (meth)acrylic acid ester monomer is alkyl acrylate, and the second block includes a copolymer which is derived from 60 parts by weight to 99.8 parts by weight of the alkyl acrylate, 0.1 parts by weight to 10 parts by weight of the copolymeric monomer having a cross-linkable functional group, and 0.1 parts by weight to 30 parts by weight of the compound containing a nitrogen atom.

10. The pressure-sensitive adhesive composition of claim 1, further comprising a multifunctional cross-linking agent having two or more functional groups capable of reacting with the cross-linkable functional group.

11. The pressure-sensitive adhesive composition of claim 10, wherein the cross-linking agent is included in an amount of 0.01 parts by weight to 10 parts by weight with respect to 100 parts by weight of the block copolymer.

12. The pressure-sensitive adhesive composition of claim 1, wherein the antistatic agent is an organic salt or a metal salt.

13. The pressure-sensitive adhesive composition of claim 1, wherein the antistatic agent is included in an amount of 0.1 parts by weight to 20 parts by weight with respect to 100 parts by weight of the block copolymer.

14. A protection film comprising: a protection base layer; and the pressure-sensitive adhesive composition of claim 1, which is present at one side or both sides of the protection base layer.

15. A pressure-sensitive adhesive optical laminate comprising: an optical film; and a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition of claim 1, which is present at one side or both sides of the optical film.

16. A pressure-sensitive adhesive polarizing plate comprising: a polarizer; and a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition of claim 1, which is present at one side or both sides of the polarizer.

17. A display device comprising: the pressure-sensitive adhesive optical laminate of claim 15.

18. A display device comprising: the pressure-sensitive adhesive polarizing plate of claim 16.

Description

DETAILED DESCRIPTION

(1) The pressure-sensitive adhesive composition will be described below in detail with reference to the accompanying Examples and Comparative Examples. The range of the pressure-sensitive adhesive composition is not limited to the following Examples.

(2) 1. Molecular Weight Evaluation

(3) A number average molecular weight (Mn) and molecular weight distribution (PDI) were measured using a gel permeation chromatograph under the following conditions, and the measured results were converted using standard polystyrene of Aglient system to prepare a calibration curve.

(4) <Measuring Conditions>

(5) Measuring instrument: Agilent GPC (Agilent 1200 series, U.S.)

(6) Column: two PL Mixed B-connected

(7) Column temperature: 40° C.

(8) Eluant: tetrahydrofuran (THF)

(9) Flow rate: 1.0 mL/min

(10) Concentration: about 1 mg/mL (100 μL injection)

(11) 2. Surface Resistance Evaluation (Initial, Heat-Resisting, and Moisture and Heat-Resisting Surface Resistance)

(12) The polarizing plate prepared in Examples or Comparative Examples was cut to have a width length of 5 cm and a height length of 5 cm to prepare a specimen. For the prepared specimens (a laminating structure of TAC/PVA/TAC/PSA/PET: TAC=triacetyl cellulose, PVA=polyvinyl alcohol-based polarizing film, PSA=pressure-sensitive adhesive layer, PET=releasing film), the initial surface resistance (surface resistance before evaluating endurance reliability) of the pressure-sensitive adhesive layer was measured after peeling the releasing film off. After that, the specimen after measuring the initial surface resistance was left at 80° C. for 7 days, and the, the appearance thereof was evaluated. In addition, the specimen after measuring the initial surface resistance was left under the conditions of 60° C. and 90% relative humidity for 7 days, and then the surface resistance thereof (surface resistance after evaluating endurance reliability) was measured in the same way as described above. The surface resistance was measured according to the manual of a manufacturer using a measuring instrument (Hiresta-UP (MCP-HT 450, Mitsubishi chemical)).

(13) <Measuring Conditions>

(14) Measuring instrument: Hiresta-UP (MCP-HT 450, Mitsubishi chemical)

(15) Probe: URS

(16) Voltage: 500 V

(17) 3. Durability Evaluation (Heat-Resisting and Moisture and Heat-Resisting Durability)

(18) The polarizing plate prepared in Examples or Comparative Examples was cut to have a width of about 180 mm and a length of about 320 mm to prepare a specimen. And then, the specimen was attached to an available 19-inch panel. Since then, the panel was stored in an autoclave (50° C., 5 atmospheres) for about 20 minutes to prepare a sample. For the prepared sample, (1) heat-resisting durability was evaluated under the following criteria by observing the generations of bubbles and peeling after maintaining the sample at 80° C. for 500 hours, and (2) moisture and heat-resisting durability was evaluated under the following criteria by also observing the generations of the bubbles and peeling on the adhesion interface after putting the sample at the conditions of 60° C. and 90% relative humidity for 500 hours.

(19) <Evaluating Criteria>

(20) A: No generation of bubbles and peeling

(21) B: Slightly generation of bubbles and peeling

(22) C: Generation of bubbles and peeling in large quantities

(23) 4. Calculation of Glass Transition Temperature

(24) The glass transition temperature (Tg) of each of the blocks of the block copolymer was calculated according to the following Equation.
1/Tg=ΣWn/Tn  <Equation>

(25) In Equation, Wn represents a weight fraction of the monomer used in each of the blocks, and Tn represents a glass transition temperature that is exhibited when the monomers used forms a homopolymer.

(26) In other words, the right side of Equation is the result obtained by summing up the values calculated after calculating the values (Wn/Tn) obtained by dividing the weight fraction of the monomers used by the glass transition temperatures that are exhibited when the monomers form homopolymers for the respective monomers.

Preparation Example 1. Preparation of Block Copolymer (A1)

(27) 0.29 g of ethyl 2-bromoisobutyrate (EBiB) and 44.3 g of methylmethacrylate (MMA) were mixed with 17 g of ethyl acetate (EAc). After that, 0.008 g of CuBr.sub.2, 0.002 g of tris(2-pyridylmethyl)amine (TPMA), and 0.06 g of V-65 (2,2′-azobis(2,4-dimethyl valeronitrile)) were further added to the mixture thus obtained, and then were mixed. A flask containing the mixture thus obtained was sealed, and then stirred under a nitrogen atmosphere at about 25° C. for about 30 minutes. After that, by bubbling, the dissolved oxygen was removed. The mixture without oxygen was dipped in a reactor at about 67° C. to initiate the reaction (polymerization of first block). When the conversion rate of methylmethacrylate became about 75%, the bubbling was performed with nitrogen in advance, and then the mixture of 30.8 g of 2-dimethylamino ethyl acrylate (DMAEA), 123 g of butyl acrylate (BA), 3.8 g of hydroxybutyl arylate (HBA), and 202 g of ethyl acetate (EAc) was added under nitrogen. After that, 0.002 g of CuBr.sub.2, 0.006 g of TPMA, and 0.05 g of V-65 were put into the reaction flask to perform a chain extension reaction (polymerization of second block). When the conversion rate of the monomer (BA) became 80% or more, the reaction mixture was exposed with oxygen and then diluted with a proper solvent to stop the reaction to prepare the block copolymer (in the process, V-65 was properly divided and then added until the reaction end time in consideration of the half-life thereof).

Preparation Examples 2 to 5. Preparations of Block Copolymers (A2, A3, B1, and B2)

(28) The types of the raw materials (monomers) that were used when polymerizing the block copolymers were controlled to have the compositions as listed in the following Table 1, thereby preparing each of the block copolymer.

(29) TABLE-US-00001 TABLE 1 Block copolymer A1 A2 A3 B1 B2 First MMA ratio 26 26 26 26 21.1 block BMA ratio — — — — 4.2 HPMA ratio — — — — 0.8 Tg (° C.) 110 110 110 110 90 Mn (×10000) 1.9 1.9 1.9 1.9 2.3 PDI 1.27 1.27 1.27 1.27 1.36 Second BA ratio 58 68 68 72 58 block HBA ratio 2 2 2 2 2 DMAEA ratio 14 4 — 14 HEAA ratio — — 4 — Tg (° C.) −41 −45 −42 −46 −41 Block Mn (×10000) 10.6 10.1 10.2 10.8 12.2 copol- PDI 1.7 1.6 1.7 1.5 1.8 ymer Ratio unit: part by weight Tg: glass transition temperature Mn: number average molecular weight PDI molecular weight distribution BA: butyl acrylate HBA: 4-hydroxybutyl acylate MMA: methyl methacrylate BMA: butyl methacrylate HPMA: 2-hydroxypropyl methacylate DMAEA: dimethylaminoethyl acrylate HEAA: hydroxyethyl acrylamide

Preparation Example 6. Preparation of Random Copolymer (B3)

(30) The monomer mixture of 46 g of butyl acrylate (BA) and 1.3 g of hydroxyethyl acrylate (2-HEA) was put into a 1 L reactor having a cooling device for refluxing nitrogen gas and being easy to control a temperature control, and then as a solvent, 32 g of ethyl acetate (EAc) was put thereinto. After that, in order to remove oxygen, the nitrogen gas purging was performed for 1 hour, and then the reactor was maintained at 62° C. After uniformly being the mixture thus obtained, as a reaction initiator, 1 g of azobisisobutyronitrile (AIBN), which was diluted with ethyl acetate to have a concentration of 50%, was put into the reactor, and then the reaction was performed for 8 hours to prepare an acrylic-based copolymer without involving N.

Example 1

(31) Preparation of Coating Solution (Pressure-Sensitive Adhesive Composition)

(32) 0.5 parts by weight of a cross-linking agent (Coronate L, manufactured by Japan NPU), 0.1 parts by weight of dibutyltin dilaurate (DBTDL), and 0.2 parts by weight of the silane coupling agent having a beta cyanoacetyl group and an inorganic salt (LiTFSi, lithium trifluorosulfonylimide), an antistatic agent, were mixed with respect to 100 parts by weight of the block copolymer (A1) prepared in Preparation Example 1, and then, as a solvent, ethyl acetate was blended to control the coating solid content to be about 30 wt % to prepare a coating solution (pressure-sensitive adhesive composition).

(33) Preparation of Pressure-Sensitive Adhesion Polarizing Plate

(34) The release treating side of a releasing PET (poly(ethylene terephthalate) (MRF-38, manufactured by Mitsubishi) that was subjected to a releasing treatment and had a thickness of 38 μm was coated with the prepared coating solution to have the thickness of about 23 μm after drying, and then maintained in an oven of 110° C. for about 3 minutes. The coating layer formed on the releasing PET was laminated on a WV liquid crystal layer of the polarizing plate (laminated structure of TAC/PVA/TAC: TAC=triacetyl cellulose, PVA=polyvinyl alcohol-based polarizing film) coated with the WV (wide view) liquid crystal layer after drying to prepare a pressure-sensitive adhesion polarizing plate.

Example 2

(35) A pressure-sensitive adhesive composition (coating solution) and pressure-sensitive adhesion polarizing plate were prepared in the same method as Example 1, except that the copolymer (A2) prepared in Preparation Example 2 was used as a block copolymer when preparing the pressure-sensitive adhesive composition (coating solution).

Example 3

(36) A pressure-sensitive adhesive composition (coating solution) and pressure-sensitive adhesion polarizing plate were prepared in the same method as Example 1, except that the copolymer (A2) prepared in Preparation Example 2 was used as a block copolymer and an organic salt (tributylmethyl Ammonium Bis(trifluoromethanesulfone)imide) was used as an antistatic agent instead of an inorganic salt, when preparing the pressure-sensitive adhesive composition (coating solution).

Example 4

(37) A pressure-sensitive adhesive composition (coating solution) and pressure-sensitive adhesion polarizing plate were prepared in the same method as Example 1, except that the copolymer (A3) prepared in Preparation Example 3 was used as a block copolymer when preparing the pressure-sensitive adhesive composition (coating solution).

Comparative Example 1

(38) A pressure-sensitive adhesive composition (coating solution) and pressure-sensitive adhesion polarizing plate were prepared in the same method as Example 1, except that the copolymer (B1) prepared in Preparation Example 4 was used as a block copolymer when preparing the pressure-sensitive adhesive composition (coating solution).

Comparative Example 2

(39) A pressure-sensitive adhesive composition (coating solution) and pressure-sensitive adhesion polarizing plate were prepared in the same method as Example 1, except that the block copolymer (B2) prepared in Preparation Example 5 was used instead of the block copolymer of Preparation Example 1 when preparing the pressure-sensitive adhesive composition (coating solution).

Comparative Example 3

(40) A pressure-sensitive adhesive composition (coating solution) and pressure-sensitive adhesion polarizing plate were prepared in the same method as Example 1, except that the block copolymer (B3) prepared in Preparation Example 6 was used instead of the block copolymer of Preparation Example 1 when preparing the pressure-sensitive adhesive composition (coating solution).

(41) The results evaluated for the following Examples and Comparative Examples are listed in the following Table 2.

(42) TABLE-US-00002 TABLE 2 Comparative Example Example 1 2 3 4 1 2 2 Surface Before 2.2 3.1 3.7 2.8 2.4 2.3 590 resistance evaluating (×10.sup.10 endurance Ω/□) reliability After 2.5 3.7 3.9 3.1 78 2.7 3700 evaluating endurance reliability Change of surface Small Small Small Small big Small big resistance Endurance reliability A A A A A C B (heat-resisting) Endurance reliability A A A A A C C (moisture and heat- resisting)