Pressure sensitive adhesive composition

Abstract

The present applicant relates to a pressure-sensitive adhesive composition, and optical laminate, a polarizing plate, and a display device. In an embodiment of the present applicant, the pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive which has an excellent cohesive force or stress relaxation property, and thus has superior endurance reliability and light leakage suppression performance or the like may be provided. The pressure-sensitive adhesive composition according to an embodiment of the present applicant may be used, for example, for an optical film such as a polarizing plate or the like.

Claims

1. A pressure-sensitive adhesive laminate, comprising: a film selected from the group consisting of an optical film and a polarizing film; and a pressure-sensitive adhesive layer which is present on one side or both sides of the film, and includes a pressure-sensitive adhesive composition in which a crosslinked structure is formed, where the pressure-sensitive adhesive composition comprises: a diblock copolymer having a first block having a glass transition temperature of 50 C. or more, wherein the first block comprises a polymerization unit derived from a methacrylic acid ester monomer; and a second block having a crosslinkable functional group and a glass transition temperature of 10 C. or less, wherein the second block comprises a polymerization unit derived from acrylic acid ester monomer and copolymerizable monomer having the crosslinkable functional group, wherein the diblock copolymer has a number average molecular weight in a range of 200,000 to 374,000 and has a molecular weight distribution ranging from greater than 2.5 to 5.0.

2. The pressure-sensitive adhesive laminate of claim 1, wherein the first block has a number average molecular weight in a range of 10,000 to 250,000.

3. The pressure-sensitive adhesive laminate of claim 1, wherein the diblock copolymer has a room temperature viscosity of 3,000 cP or more in a state in which the diblock copolymer is diluted with ethyl acetate such that contents of solid fractions of the block copolymer are 30 wt %.

4. The pressure-sensitive adhesive laminate of claim 1, wherein a crosslinkable functional group is not included in the first block, and only included in the second block.

5. The pressure-sensitive adhesive laminate of claim 1, wherein the crosslinkable functional group is a hydroxy group.

6. The pressure-sensitive adhesive laminate of claim 1, wherein the second block comprises a polymerization unit derived from 90 to 99.9 parts by weight of the acrylic acid ester monomer, and 0.1 to 10 parts by weight of the copolymerizable monomer having the crosslinkable functional group.

7. The pressure-sensitive adhesive laminate of claim 1, further comprising a crosslinking agent which has two or more functional groups capable of reacting with the crosslinkable functional group.

8. The pressure-sensitive adhesive laminate of claim 7, wherein the crosslinking agent is included at a range of 0.01 parts by weight to 10 parts by weight with respect to 100 parts by weight of the block copolymer.

9. A display device comprising the pressure-sensitive adhesive laminate of claim 1, wherein the film is the optical film.

10. A display device comprising the pressure-sensitive adhesive plate of claim 1, wherein the film is the polarizing film.

Description

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(1) Hereinafter, the pressure-sensitive adhesive composition will be described in detail in conjunction with examples and comparative examples, but a scope 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) are measured using GPC under the following conditions, a calibration curve was formed using standard polystyrene of an Agilent system and a measurement result was converted.

(4) [Measurement Conditions]

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

(6) Column: 2PL Mixed B connected

(7) Column temperature: 40 C.

(8) Eluent: THF (tetrahydrofuran)

(9) Flow velocity: 1.0 mL/min

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

(11) 2. Solid Fractions of Coating Material

(12) Solid fractions of the coating material were evaluated using the following method.

(13) [Measurement Order of Solid Fractions of Coating Material]

(14) 1) A weight A of an aluminum dish was measured.

(15) 2) About 0.3 to 0.5 g (specimen before drying) of the pressure-sensitive adhesive composition prepared in examples or comparative examples is collected and put into the aluminum dish.

(16) 3) A thimbleful of a polymerization inhibitor (hydroquinone) solution dissolved in ethyl acetate (concentration: 0.5 wt %) was added to the pressure-sensitive adhesive composition using a pipette.

(17) 4) The pressure-sensitive adhesive composition was dried in an oven at 150 C. for 30 minutes to remove a solvent, etc.

(18) 5) The pressure-sensitive adhesive composition was cooled down at room temperature for 15 to 30 minutes, and a weight of residual components thereof (weight of the specimen after drying) was measured.

(19) 6) The solid fractions of the coating material were evaluated using the following expression according to the measurement result.
Solid fractions of coating material(unit: %)=100(DSA)/(S+E)[Expression]

(20) DS: weight of aluminum dish A+weight of specimen after drying (unit: g)

(21) A: weight of aluminum dish (unit: g)

(22) S: weight of specimen before drying (unit: g)

(23) E: weight of removed components (solvent, etc.) (unit: g)

(24) 3. Viscosity Evaluation

(25) A viscosity of the pressure-sensitive adhesive composition was evaluated using the measuring device (Brookfield digital viscometer (DV-I+, DV-II+Pro)) according to the following method.

(26) [Measurement Order of Viscosity]

(27) 1) 180 mL of the pressure-sensitive adhesive composition (sample) was put into a beaker, and then allowed to stand under conditions of a constant temperature and constant humidity (23 C./relative humidity of 50%) for about 1 hour to remove air bubbles.

(28) 2) A spindle was obliquely put into the pressure-sensitive adhesive composition (sample) such that a liquid surface of the sample was not deeper than a groove of the spindle, and air bubbles were not generated.

(29) 3) The spindle was connected to a viscometer, and the liquid surface of the sample was adjusted to match with the groove of the spindle.

(30) 4) A set speed key was pressed to select an rpm of the spindle.

(31) 5) A motor on/off key was pressed to operate the viscometer. The viscosity value was obtained after the viscosity value shown on the screen was stabilized. The rpm having about 10% or more of a confidence interval was searched for and fixed to measure the viscosity.

(32) 4. Coating Properties Evaluation

(33) The pressure-sensitive adhesive compositions prepared in the examples and comparative examples were coated, and a coating layer was observed by visual inspection to evaluate according to the following standard.

(34) [Evaluation Standard]

(35) A: Air bubbles and stripes or the like on the coating layer are not determined by visual inspection

(36) B: Air bubbles and stripes or the like on the coating layer are slightly determined by visual inspection.

(37) C: Air bubbles and stripes or the like on the coating layer are clearly determined by visual inspection.

(38) 5. Durability Evaluation

(39) The polarizing plates prepared in the examples and comparative examples were cut to have a width of about 180 mm and a length of about 320 mm to prepare specimens, and the specimens were adhered to commercial 19-inch panels. Then, the panels were stored in an autoclave (50 C., 5 atm) for about 20 minutes to prepared samples. Heat and humidity resistance durability of the prepared samples was evaluated based on the following standard after the samples were allowed to stand under conditions of 60 C. and relative humidity of 90% for 500 hours and observed for a generation of air bubbles and peeling. Heat resistance durability was also evaluated based on the following standard after the samples were maintained at 80 C. for 500 hours and then observed for a generation of air bubbles and peeling.

(40) Further, room temperature low humidity durability after heat and humidity resistance was evaluated based on the following standard after the samples which passed through an evaluation of heat and humidity resistance durability were maintained under conditions of 25 C. and relative humidity of 25% for 30 days and then observed for a generation of air bubbles and peeling.

(41) [Evaluation Standard]

(42) A: No air bubbles and peeling were generated

(43) B: Air bubbles and/or peeling were slightly generated

(44) C: Air bubbles and/or peeling were largely generated

(45) 6. Calculation of Glass Transition Temperature

(46) A glass transition temperature (Tg) of each block or the like of the block copolymer was calculated according to the following expression.
1/Tg=Wn/Tn[Expression]

(47) where Wn is a weight fraction of a monomer used in each block or the like, and Tn denotes a glass transition temperature shown when the used monomer forms a homopolymer.

(48) That is, in the expression, the right side shows a result of a sum of values calculated after calculating a value (Wn/Tn) of dividing the weight fraction of the used monomer by the glass transition temperature shown when the used monomer forms a homopolymer for every monomer.

(49) 7. Measurement of Conversion Factor and Composition Ratio of Monomer

(50) A conversion factor in the polymerization process of methyl methacrylate (MMA) which is a main monomer forming a first block in the block copolymer of the examples and comparative examples and butyl acrylate (BA) which is a main monomer forming a second block in the block copolymer of the examples and comparative examples, and composition contents in the block copolymer were calculated with the following expression according to the result of .sup.1H-NMR.

(51) [Conversion Factor of MMA]
MMA conversion factor (%)=100B/(A+B)

(52) where A is an area of a peak (near 3.4 ppm to 3.7 ppm) derived from a methyl group induced by MMA included in the polymer in .sup.1H-NMR spectra, and B is an area of a peak (near 3.7 ppm) derived from a methyl group of MMA which is not polymerized. That is, in consideration of the movement position of the peak of the methyl group in the structure of MMA, the conversion factor of the monomer was calculated.

(53) [Conversion Factor of BA]
BA conversion factor (%)=100C/(C+D)

(54) where D is an area of a peak (near 5.7 ppm to 6.4 ppm) derived from CH.sub.2 of a double bond end of BA in .sup.1H-NMR spectra, C is an area of a peak (near 3.8 ppm to 4.2 ppm) derived from OCH.sub.2 present in the polymer formed by polymerization of BA. That is, the conversion factor was measured by calculating the relative value of the peak of CH.sub.2 by a double bonded of BA and the peak of OCH.sub.2 of the polymer.

(55) [Calculation of Composition Ratio]

(56) The ratio of the first and second block of the block copolymer were calculated based on the following expression according to the ratio of methyl methacrylate (MMA) and butyl acrylate (BA) which are the main monomers used to form the first block and second block.
MMA contents in block copolymer (%)=100MMA peak area/BA peak area[Expression]

(57) In the above description, the MMA peak area is the value of an area per a .sup.1H proton of the peak near 3.4 to 3.7 ppm in the .sup.1H-NMR (peak observed for CH.sub.3 derived from MMA), and the BA peak area is the value of an area per .sup.1H proton of the peak near 3.8 to 4.2 ppm in the .sup.1H-NMR (peak observed for OCH.sub.2 present in the polymer formed by BA).

(58) That is, the weight ratio of the first and second block was computed by calculating the relative value of the CH.sub.3 peak of the MMA structure and the OCH.sub.2 peak of the polymer formed from BA

Preparation Example 1. Preparation of Block Copolymer A

(59) 0.1 g of ethyl 2-bromoisobutyrate (EBiB) and 28.4 g of methylmethacrylate (MMA) were mixed in 12.4 g of ethyl acetate (EAc). A flask containing the mixture was sealed with a rubber stopper, purged with nitrogen at about 25 C. for about 30 minutes with stirring, and dissolved oxygen was removed by bubbling. Then, 0.002 g of CuBr.sub.2, 0.005 g of tris(2-pyridylmethyl)amine (TPMA), and 0.017 g of 2,2-azobis(2,4-dimethyl valeronitrile) (V-65) were put into the mixture in which the oxygen was removed, immersed in a reactor of about 67 C. to perform a reaction (polymerization of the first block). When a conversion factor of methylmethacrylate became about 75%, a mixture of 310 g of butyl acrylate (BA), 1.6 g of hydroxybutyl acrylate (HBA) and 500 g of ethyl acetate (EAc) which were bubbled with nitrogen in advance was put therein in the presence of nitrogen. Thereafter, 0.006 g of CuBr.sub.2, 0.012 g of TPMA, and 0.05 g of V-65 were put into the reaction flask, a chain extension reaction was performed (polymerization of the second block). When a conversion factor of the monomer (BA) reached 80% or more, the reaction mixture was exposed to oxygen, and the reaction was brought to an end by diluting with a suitable solvent to prepare the block copolymer (V-65 was suitably divided and put until the end of the reaction in the process in consideration of the half-life thereof).

Preparation Examples 2 to 7. Preparation of Block Copolymers A2 to A4, and B1 to B3

(60) Each block copolymer as shown in the following Table 1 was prepared in the same manner as in Preparation Example 1 except that types of raw materials (monomer) and polymerization conditions were adjusted upon polymerization of the block copolymer.

(61) TABLE-US-00001 TABLE 1 Preparation Example 1 2 3 4 5 6 7 A1 A2 A3 A4 B1 B2 B3 First MMA ratio 100 80 60 70 80 60 81 block BMA ratio 0 20 40 30 20 40 16 HPMA ratio 0 0 0 0 0 0 3 Tg ( C.) 110 90 72 80 90 72 90 Mn 2.9 3.2 4.1 4.3 0.4 1.7 2.3 (10000) PDI 1.37 1.44 1.38 1.41 1.21 1.32 1.36 Second BA ratio 99.5 97.0 94.0 95.0 97.0 95.0 100 block HBA ratio 0.5 3.0 6.0 5.0 3.0 5.0 0 Tg ( C.) 47 46.2 47.5 47.0 46.2 47.0 45 Block Mn 23.7 27.3 33.5 37.4 2.3 10.4 12.2 copolymer (10000) PDI 2.8 3.1 3.3 4.1 1.4 2.2 1.8 Ratio unit: parts by weight Tg: glass transition temperature Mn: number average molecular weight PDI: molecular weight distribution BA: butyl acrylate (homopolymer Tg: about 45 C.) HBA: 4-hydroxybutyl acrylate (homopolymer Tg: about 80 C.) MMA: methyl methacrylate (homopolymer Tg: about 110 C.) BMA: butyl methacrylate (homopolymer Tg: about 27 C.) HPMA: 2-hydroxypropyl methacrylate (homopolymer Tg: about 26 C.)

Preparation Example 8. Preparation of Random Copolymer C1

(62) 10 parts by weight of methyl methacrylate (MMA), 87.3 parts by weight of n-butyl acrylate, and 2.7 parts by weight of 4-hydroxybutyl acrylate were put into a 1 L-reactor refluxing nitrogen gas and equipped with a cooling device to facilitate control of the temperature, and then 120 parts by weight of ethyl acetate as a solvent was put therein. Subsequently, the reactor was purged with a nitrogen gas to remove oxygen for about 60 minutes, 0.05 parts by weight of azobisisobutyronitrile (AIBN) which is a reaction initiator was put into the reactor while a temperature was maintained at 60 C., the reaction was performed for about 8 hours with adjusting polymerization conditions to ensure the molecular weight and molecular weight distribution as described below, and thereby a random copolymer was prepared. The prepared random copolymer C1 has a number average molecular weight (Mn) of about 232,000, and a molecular weight distribution (PDI) of about 4.9.

Example 1

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

(64) 0.05 parts by weight of the crosslinking agent (Coronate L; manufactured by Nippon Polyurethane Industry Co. Ltd.), 0.1 parts by weight of dibutyltin dilaurate (DBTDL), and 0.2 parts by weight of a silane coupling agent having a beta-cyanoacetyl group were mixed with respect to 100 parts by weight of the block copolymer A1 prepared in Preparation Example 1, ethyl acetate as a solvent was also mixed, the mixture was adjusted such that solid fractions of a coating solution became about 30 wt %, and thereby a coating solution (pressure-sensitive adhesive composition) was prepared.

(65) Preparation of Pressure-Sensitive Adhesive Polarizing Plate

(66) The prepared coating solution was coated on a release-treated surface of the release polyethylene terephthalate (PET) film with a thickness of 38 m (MRF-38, manufactured by Mitsubishi Chemical Corporation), and then maintained in an oven at 110 C. for about 3 minutes such that a coating layer having a thickness of about 23 m was formed after drying. After drying, the pressure-sensitive adhesive layer formed on the release PET film was laminated on a wide view (WV) liquid crystal layer of a polarizing plate (laminated structure: TAC/PVA/TAC, TAC=triacetyl cellulose film, PVA=polyvinyl alcohol-based polarizer film), one side of which was coated with the WV liquid crystal layer, and thereby a pressure-sensitive adhesive polarizing plate was prepared.

Examples 2 and 4, Comparative Examples 1 to 5

(67) The pressure-sensitive adhesive composition (coating solution) and pressure-sensitive adhesive polarizing plate were prepared in the same manner as in Example 1 except that each component and ratio were adjusted as shown in the following Table 2 upon a preparation of the pressure-sensitive adhesive composition (coating solution).

(68) TABLE-US-00002 TABLE 2 Example Comparative Example 1 2 3 4 1 2 3 4 5 Block Type A1 A2 A3 A4 B1 B2 B2 C1 B3 copolymer Content 100 100 100 100 100 100 100 100 100 Content of 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.2 0.1 crosslinking agent Content of DBTDL 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.2 0.1 Content of SCA 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Content unit: parts by weight Crosslinking agent: Coronate L (manufactured by Nippon Polyurethane Industry Co. Ltd.) DBTDL: Dibutyltin dilaurate SCA: silane coupling agent having -cyanoacetyl group (M812, manufactured by LG Chem, Ltd)

(69) The evaluation result of physical properties of each example and comparative example is shown in the following Table 3.

(70) TABLE-US-00003 TABLE 3 Example Comparative Example 1 2 3 4 1 2 3 4 5 Coating A A A A A A A A A properties Heat resistance A A A A C B A A C durability Heat and A A A A B A A B C humidity resistance durability Room A A A A C C C C C temperature low humidity durability