Pressure sensitive adhesive composition

Abstract

The present invention relates to a pressure-sensitive adhesive composition, an optical member, a polarizing plate, and a display device. The pressure-sensitive adhesive composition according to an embodiment of the present invention may form a pressure-sensitive adhesive which has excellent general physical properties such as coating properties, endurance reliability, or the like, and which may stably maintain the physical properties for the long term. Further, the pressure-sensitive adhesive composition may be particularly applied to various optical films, thereby forming the pressure-sensitive adhesive layer which exhibits excellent adhesion with the optical film, and when the pressure-sensitive adhesive composition is applied to the polarizing plate, bending properties may be effectively prevented.

Claims

1. A pressure-sensitive adhesive composition, comprising: a block copolymer which has a first block having a glass transition temperature of 50 C. or more, and a second block having a crosslinkable functional group and a glass transition temperature of 10 C. or less; a multifunctional aziridine compound, in an amount of 0.01 to 10 parts by weight with respect to 100 parts by weight of the block copolymer; and a multifunctional isocyanate compound, in an amount of 0.01 to 10 parts by weight with respect to 100 parts by weight of the block copolymer, wherein the block copolymer comprises a range of 5 to 45 parts by weight of the first block and a range of 55 to 95 parts by weight of the second block, wherein the crosslinkable functional group is not included in the first block, and only included in the second block, wherein the first block consists of a homopolymer derived from a methacrylic acid ester monomer, wherein the block copolymer is a diblock copolymer having the first block and the second block, and wherein the block copolymer has a molecular weight distribution in a range of 1.7 to 2.5.

2. The pressure-sensitive adhesive composition of claim 1, wherein the crosslinkable functional group is a hydroxy group or a carboxyl group.

3. The pressure-sensitive adhesive composition of claim 1, wherein the second block comprises a range of 90 to 99.9 parts by weight of a polymerization unit of an alkyl (meth)acrylate, and a range of 0.1 to 10 parts by weight of a polymerization unit of a copolymerizable monomer having the crosslinkable functional group.

4. The pressure-sensitive adhesive composition of claim 1, wherein the first block has a number average molecular weight in a range of 2,500 to 100,000.

5. The pressure-sensitive adhesive composition of claim 1, wherein the block copolymer has a number average molecular weight in a range of 50,000 to 300,000.

6. A pressure-sensitive adhesive optical member comprising: an optical film; and a pressure-sensitive adhesive layer which is formed on one side of the optical film, and includes the pressure-sensitive adhesive composition of claim 1.

7. The pressure-sensitive adhesive optical member of claim 6, wherein a carboxyl group is present on a surface of the optical film, and the pressure-sensitive adhesive layer is adhered to the surface on which the carboxyl group is present.

8. The pressure-sensitive adhesive optical member of claim 6, wherein a corona-treated layer is present between the optical film and the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is adhered to the corona-treated layer.

9. A pressure-sensitive adhesive polarizing plate comprising: a polarizer; and a pressure-sensitive adhesive layer which is formed on one side of the polarizer, and includes the pressure-sensitive adhesive composition of claim 1.

10. The pressure-sensitive adhesive polarizing plate of claim 9, wherein a polarizer protective film in which a carboxyl group is present on a surface is present between the polarizer and the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is adhered to the surface of the protective film on which the carboxyl group is present.

11. The pressure-sensitive adhesive polarizing plate of claim 9, wherein a polarizer protective film in which a corona-treated layer is present on a surface is present between the polarizer and the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is adhered to the corona-treated layer.

12. A display device comprising the pressure-sensitive adhesive optical member of claim 6.

13. A display device comprising the pressure-sensitive adhesive polarizing plate of claim 9.

Description

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(1) Exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings. While the present invention is shown and described in connection with exemplary embodiments thereof, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.

(2) Hereinafter, the pressure-sensitive adhesive composition will be described in detail in conjunction with examples and comparative examples, but the scope of the pressure-sensitive adhesive composition is not limited to the following examples.

(3) 1. Molecular Weight Evaluation

(4) A number average molecular weight (Mn) and molecular weight distribution (PDI) were measured using GPC under the following conditions, a calibration curve was formed using standard polystyrene of an Agilent system, and then a measurement result was conversed.

(5) [Measurement conditions]

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

(7) Column: 2-PL Mixed B connected

(8) Column temperature: 40 C.

(9) Eluant: THF (tetrahydrofuran)

(10) Flow Velocity: 1.0 mL/min

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

(12) 2. Coating Properties Evaluation

(13) In the process of coating the pressure-sensitive adhesive composition prepared in examples and comparative examples on a release-treated surface of a PET (poly(ethylene terephthalate)) film (MRF-38; manufactured by Mitsubishi Chemical Corporation), coating properties were evaluated based on the following standard after observing a state of the coating layer by visual inspection.

(14) [Evaluation Standard] A: Air bubbles and stripes or the like on the coating layer were not determined by visual inspection B: Air bubbles and stripes or the like on the coating layer were slightly determined by visual inspection. C: Air bubbles and stripes or the like on the coating layer were clearly determined by visual inspection.

(15) 3. Interface Adhesive Force Evaluation

(16) An evaluation of an interface adhesive force was performed in the following order.

(17) [Measurement Order of Interface Adhesive Force]

(18) 1) A polarizing plate coated with the pressure-sensitive adhesive prepared in the examples and comparative examples was cut to a size of 7 cm12 cm (widthlength).

(19) 2) A release film was stripped from a pressure-sensitive adhesive surface of the cut polarizing plate, and then a tape with a size of 5 cm10 cm (widthlength) for measuring peel strength of the pressure-sensitive adhesive was laminated to the surface from which the release film was stripped.

(20) 3) After a lamination state was maintained for 5 minutes, the laminated tape was detached, and then an amount of the pressure-sensitive adhesive that remained on the pressure-sensitive adhesive surface of the polarizing plate from which the tape was peeled was observed by visual inspection to evaluate.

(21) [Evaluation Standard]

(22) A: The remaining pressure-sensitive adhesive accounted for 90% or more of the entire pressure-sensitive adhesive

(23) B: The remaining pressure-sensitive adhesive accounted for 50% or more to less than 90% of the entire pressure-sensitive adhesive

(24) C: The remaining pressure-sensitive adhesive accounted for less than 50% of the entire pressure-sensitive adhesive

(25) 4. Bending Properties Evaluation

(26) Bending properties of the polarizing plate were measured in the following order.

(27) [Measurement Order of Bending Properties]

(28) 1) STN soda lime glass having a width of about 40 mm, a length of about 410 mm, and a thickness of 0.7 mm was prepared, was cleaned using a solvent of ethyl acetate or isopropyl acetate such that no foreign substance remained, and then dried.

(29) 2) A polarizing plate coated with a coating solution (pressure-sensitive adhesive composition) prepared in the examples and comparative examples was cut to a size of 35 mm400 mm (widthlength) by lengthening a machine direction (MD) to prepare a specimen.

(30) 3) Specimens prepared in step 2) were adhered to a center of STN soda lime glasses prepared in 1) using a laminator to prepare samples.

(31) 4) After one side of each sample was fixed using a magnet in a heat-resistance condition at 25 C., a level of bending in an opposite direction to the fixed side was measured as a distance (S.sub.0) spaced from a reference point.

(32) 5) After an initial level of bending was measured, the samples were stored in a heat-resistance condition at 60 C. for 72 hours.

(33) 6) Then, while maintaining a heat-resistance condition at 60 C., a level of bending of the samples was measured as in the same method as in step 4), that is, a method of fixing one side of each sample, and then measuring a level of bending in an opposite direction to the fixed side as a distance (S.sub.0) spaced from a reference point.

(34) The level of bending (W) as measured above was represented by the following expression, and evaluated based on the following standard.
W=S.sub.1S.sub.0[Expression]

(35) [Evaluation Standard]

(36) A: W9 mm

(37) B: W11 mm

(38) C: W>11 mm 5. Calculation of Glass Transition Temperature

(39) 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

(40) 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.

(41) 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.

(42) 6. Measurement of Conversion Factor and Composition Ratio of Monomer

(43) 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.

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

(45) 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.

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

(47) 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 of BA and the peak of OCH.sub.2 of the polymer.

(48) [Calculation of Composition Ratio]

(49) 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]

(50) 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 a .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).

(51) 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 A1

(52) 0.1 g of ethyl 2-bromoisobutyrate (EBiB) and 14.2 g of methylmethacrylate (MMA) were mixed in 6.2 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 reached about 75%, a mixture of 155 g of butyl acrylate (BA), 0.8 g of hydroxybutyl acrylate (HBA), and 250 g of ethyl acetate (EAc) which were bubbled with nitrogen in advance were put therein under 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 about 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 introduced until the end of the reaction in the process in consideration of the half-life thereof).

PREPARATION EXAMPLES 2 to 5

Preparation of Block Copolymers A2 to A3, and B1 to B2

(53) The block copolymers were prepared in the same manner as in Preparation Example 1 except that types of raw materials, additives, or the like used upon polymerization of the first block were adjusted as shown in the following Table 1, and types of raw materials, additives, or the like used upon polymerization of the second block were adjusted as shown in the following Table 2.

(54) TABLE-US-00001 TABLE 1 Raw material Classification MMA BMA HPMA EBiB EA CuBr.sub.2 TPMA V-65 Block A1 14.2 0.1 6.2 0.002 0.005 0.017 copolymer A2 11.2 2.8 0.08 6.1 0.002 0.005 0.016 A3 9.4 6.3 0.07 6.8 0.002 0.005 0.016 B1 11.6 2.4 0.4 0.08 6.2 0.002 0.005 0.016 B2 5.8 0.1 2.5 0.001 0.002 0.007 Content unit: g 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.) EBiB: ethyl 2-bromoisobutyrate EA: Ethyl acetate TPMA: tris(2-pyridylmethyl)amine V-65: 2,2-azobis(2,4-dimethyl valeronitrile)

(55) TABLE-US-00002 TABLE 2 Raw material Classification BA HBA EA CuBr.sub.2 TPMA V-65 Block A1 115 0.8 250 0.006 0.01 0.05 copolymer A2 151 4.7 250 0.006 0.01 0.05 A3 146 9.3 250 0.006 0.01 0.05 B1 156 250 0.006 0.01 0.05 B2 163 0.8 250 0.006 0.01 0.05 Content unit: g BA: butyl acrylate (homopolymer Tg: about 45 C.) HBA: 4-hydroxybutyl acrylate (homopolymer Tg: about 80 C.) EA: Ethyl acetate TPMA: tris(2-pyridylmethyl)amine V-65: 2,2-azobis(2,4-dimethyl valeronitrile)

(56) Properties of the block copolymers prepared in the above-described method were as shown in the following Table 3.

(57) TABLE-US-00003 TABLE 3 Block copolymer Classification A1 A2 A3 B1 B2 First MMA ratio 100 80 60 81 100 block BMA 0 20 40 16 0 HPMA ratio 0 0 0 3 0 Tg( C.) 110 90 72 90 110 Mn(10000) 1.9 2.3 2.9 2.3 0.8 PDI 1.27 1.34 1.38 1.36 1.18 Second BA ratio 99.5 97.0 94.0 100.0 99.5 block HBA ratio 0.5 3.0 6.0 0.0 0.5 Tg( C.) 47 46.2 47.5 45 47.0 Block Mn (10000) 10.6 12.3 14.1 12.4 10.1 copolymer PDI 1.7 1.8 2.1 1.8 1.6 First 10.5:89.5 10.1:89.9 11.2:88.8 10.1:89.9 4.2:95.8 block:Second block (weight ratio) Unit of monomer ratio: parts by weight 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.) BA: butyl acrylate (homopolymer Tg: about 45 C.) HBA: 4-hydroxybutyl acrylate (homopolymer Tg: about 80 C.) Tg: glass transition temperature Mn: number average molecular weight PDI: molecular weight distribution

PREPARATION EXAMPLE 6

Preparation of Random Copolymer C1

(58) 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 1L-reactor refluxing nitrogen gas and equipped with a cooling device to facilitate control of the temperature, 200 ppm of n-dodecyl mercaptan was further added as a molecular weight controlling agent, 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, and thereby a random copolymer was prepared. The prepared random copolymer C1 has a number average molecular weight (Mn) of about 132,000, and a molecular weight distribution (PDI) of about 4.6.

EXAMPLE 1

(59) Preparation of Coating Solution (Pressure-sensitive Adhesive Composition)

(60) 0.1 parts by weight of the crosslinking agent (Coronate L; manufactured by Nippon Polyurethane Industry Co. Ltd), 0.05 parts by weight of the epoxy compound (T-746L; manufactured by Soken Chemical & Engineering 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 added and mixed, the mixture was adjusted such that solid fractions of a coating solution became about 25 wt %, and thereby a coating solution (pressure-sensitive adhesive composition) was prepared.

(61) Preparation of Pressure-sensitive Adhesive Polarizing Plate

(62) 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 AND COMPARATIVE EXAMPLES 1 to 5

(63) 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 4 upon a preparation of the pressure-sensitive adhesive composition (coating solution).

(64) TABLE-US-00004 TABLE 4 Example Comparative Example Classification 1 2 3 4 1 2 3 4 5 Block Type of A1 A1 A2 A3 A2 A3 B1 B2 C1 copolymer Content 100 100 100 100 100 100 100 100 100 Content of crosslinking 0.1 0.1 0.1 0.1 0.1 0.3 0.2 0.1 0.2 agent Content of epoxy 0.05 0.2 0.5 compound Content of aziridine 0.05 2.0 compound Content of DBTDL 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 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. ) Epoxy compound: T-746L (manufactured by Soken Chemical & Engineering Co., Ltd.) Aziridine compound: XAMA7 (manufactured by Bayer AG)

(65) The evaluation result of physical properties of each example and comparative example is shown in the following Table 5.

(66) TABLE-US-00005 TABLE 5 Example Comparative Example Classification 1 2 3 4 1 2 3 4 5 Coating A A A A A A B A A properties Interface A A A A C B B C B adhesive force Bending A A A A A C C C C properties

(67) The pressure-sensitive adhesive composition according to the embodiment of the present invention can form the pressure-sensitive adhesive which has excellent general physical properties such as coating properties, endurance reliability, or the like, and which can stably maintain the physical properties for the long term. Further, the pressure-sensitive adhesive composition can be particularly applied to various optical films, thereby forming the pressure-sensitive adhesive layer which exhibits excellent adhesion with the optical film, and when the pressure-sensitive adhesive composition is applied to the polarizing plate, bending properties can be effectively prevented.

(68) It will be apparent to those skilled in the art that various modifications can be made to the above-described exemplary embodiments of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention covers all such modifications provided they come within the scope of the appended claims and their equivalents.