OPTICAL MEMBER, PRESSURE-SENSITIVE ADHESIVE COMPOSITION AND LIQUID CRYSTAL DISPLAY

Abstract

Provided are an optical member, a pressure-sensitive adhesive composition, and an LCD. The optical member may have excellent endurance reliability even when a pressure-sensitive adhesive layer is formed to have a thickness of 20 m or less.

Claims

1. An optical member, comprising: a base layer; and a pressure-sensitive adhesive layer, which has a dynamic storage modulus of 0.0511 to 0.0772 MPa at 30 C. and a frequency of 500 Hz, including: an acryl polymer which is a polymerized product of monomers consisting essentially of: a first (meth)acrylic acid ester monomer capable of forming a homopolymer having a glass transition temperature of less than 0 C., a crosslinkable monomer including a crosslinkable functional group except an acid functional group, and a second (meth)acrylic acid ester monomer capable of forming a homopolymer having a glass transition temperature of 10 C. to 45 C., which is formed on one or both surfaces of the base layer, and which has a thickness of 20 m or less, wherein the acryl polymer has a weight average molecular weight of 1,650,000 to 1,900,000 and has a polymerization unit derived from 125 to 900 parts by weight of the first (meth)acrylic acid ester monomer with respect to 100 parts by weight of the second (meth)acrylic acid ester monomer.

2. The optical member according to claim 1, wherein the base layer is a polarizer, a polarizing plate, a retardation plate, a viewing angle retardation film or a brightness-enhancing film.

3. The optical member according to claim 1, wherein the acryl polymer has an acid value of 10 or less.

4. The optical member according to claim 1, wherein the first (meth)acrylic acid ester monomer is an alkyl (meth)acrylate capable of forming a homopolymer having a glass transition temperature of 70 C. to 30 C.

5. The optical member according to claim 1, wherein the second (meth)acrylic acid ester monomer is an alkyl (meth)acrylate.

6. The optical member according to claim 1, wherein the second (meth)acrylic acid ester monomer is an alkyl (meth)acrylate having a linear or branched alkyl group having 1 to 6 carbon atoms.

7. The optical member according to claim 1, wherein the second (meth)acrylic acid ester monomer is methyl acrylate or t-butyl acrylate.

8. The optical member according to claim 1, wherein the crosslinkable functional group except an acid functional group is at least one selected from the group consisting of a hydroxyl group, a glycidyl group, an isocyanate group and a nitrogen-containing functional group.

9. The optical member according to claim 1, wherein the pressure-sensitive adhesive layer has a glass transition temperature of 50 C. to 0 C.

10. The optical member according to claim 1, wherein the pressure-sensitive adhesive layer has a thickness of 15 m or less.

11. A pressure-sensitive adhesive composition, comprising: an acryl polymer having a dynamic storage modulus of 0.0511 to 0.0772 MPa at 30 C. and a frequency of 500 Hz, and having a polymerization unit derived from which is a polymerized product of monomers consisting essentially of: a first (meth)acrylic acid ester monomer capable of forming a homopolymer having a glass transition temperature of less than 0 C., a crosslinkable monomer including a crosslinkable functional group except an acid functional group, and a second (meth)acrylic acid ester monomer capable of forming a homopolymer having a glass transition temperature of 10 C. to 45 C., wherein the acryl polymer has a weight average molecular weight of 1,650,000 to 1,900,000 and has a polymerization unit derived from 125 to 900 parts by weight of the first (meth)acrylic acid ester monomer with respect to 100 parts by weight of the second (meth)acrylic acid ester monomer.

12. The composition according to claim 11, which is used to form a pressure-sensitive adhesive layer included in an optical member.

13. The composition according to claim 11, wherein the acryl polymer has an acid value of 10 or less.

14. A liquid crystal display, in which the optical member of claim 1 is attached to a liquid crystal panel by a pressure-sensitive adhesive layer of the optical member.

Description

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0059] Hereinafter, a pressure-sensitive adhesive composition will be described in further detail with reference to Examples and Comparative Examples, but the scope of the composition is not limited to the following Examples.

Preparation Example 1. Preparation of Acryl Polymer (A1)

[0060] A monomer mixture composed of 89 g of n-butyl acrylate, 10 g of methyl acrylate (MA) and 1 g of hydroxybutyl acrylate (HBA) was put into a 1000 cc reaction vessel equipped with a cooling apparatus to facilitate temperature control and reflux a nitrogen gas, and 100 g of ethyl acetate (EAc) was put into a solvent. Afterward, to remove oxygen, the mixture was purged with a nitrogen gas for 20 minutes, and maintained at 60 C. After the mixture was uniformly blended, and 0.03 g of azobisisobutyronitrile (AIBN) diluted with a reaction initiator in ethyl acetate at a concentration of 50% was added. The mixture was reacted for 8 hours, thereby preparing an acryl polymer having a weight average molecular weight of 1,790,000.

Preparation Example 2. Preparation of Acryl Polymer (A2)

[0061] An acryl polymer having a weight average molecular weight of 1,670,000 was prepared by the same method as described in Preparation Example 1, except that a monomer mixture in which 79 g of n-butyl acrylate (n-BA), 20 g of methyl acrylate (MA) and 1 g of hydroxybutyl acrylate (HBA) were mixed was used instead of the monomer mixture prepared in Preparation Example 1.

Preparation Example 3. Preparation of Acryl Polymer (A3)

[0062] An acryl polymer having a weight average molecular weight of 1,890,000 was prepared by the same method as described in Preparation Example 1, except that a monomer mixture in which 59 g of n-butyl acrylate (n-BA), 40 g of methyl acrylate (MA) and 1 g of hydroxybutyl acrylate (HBA) were mixed was used instead of the monomer mixture prepared in Preparation Example 1.

Preparation Example 4. Preparation of Acryl Polymer (A4)

[0063] An acryl polymer having a weight average molecular weight of 1,760,000 was prepared by the same method as described in Preparation Example 1, except that a monomer mixture in which 89 g of n-butyl acrylate (n-BA), 10 g of t-butyl acrylate (t-BA) and 1 g of hydroxybutyl acrylate (HBA) were mixed was used instead of the monomer mixture prepared in Preparation Example 1.

Preparation Example 5. Preparation of Acryl Polymer (A5)

[0064] An acryl polymer having a weight average molecular weight of 1,770,000 was prepared by the same method as described in Preparation Example 1, except that a monomer mixture in which 69 g of n-butyl acrylate (n-BA), 30 g of t-butyl acrylate (t-BA) and 1 g of hydroxybutyl acrylate (HBA) were mixed was used instead of the monomer mixture prepared in Preparation Example 1.

Example 1

[0065] Preparation of Pressure-Sensitive Adhesive Composition

[0066] 0.03 parts by weight of N,N,N,N-tetraglycidyl-1,3-dimethylbenzene as an epoxy-based crosslinking agent and 0.2 parts by weight of adducts of tolylene diisocyanate with trimethylolpropane as a multifunctional isocyanate-based crosslinking agent with respect to 100 parts by weight of the acryl polymer (A1) prepared above were respectively diluted in an ethylacetate solution at 10 wt %, and uniformly mixed to a suitable concentration in consideration of coatability.

[0067] Formation of Pressure-Sensitive Adhesive Film

[0068] The pressure-sensitive adhesive composition was coated and dried on one surface of a biaxially-oriented poly(ethylene terephthalate) (PET) film (thickness: 15 m), thereby forming a coating layer having a uniform thickness of 13 m. Subsequently, a releasing film was laminated on the coating solution and aged for 3 days under a constant temperature (25 C.) and constant humidity condition, thereby forming a pressure-sensitive adhesive film.

Example 2

[0069] A pressure-sensitive adhesive composition and a pressure-sensitive adhesive film having a coating layer having a uniform thickness of 13 m were formed by the same method as described in Example 1, except that the acryl polymer (A2) prepared in Example 2 was used.

Example 3

[0070] A pressure-sensitive adhesive composition and a pressure-sensitive adhesive film having a coating layer having a uniform thickness of 13 m were formed by the same method as described in Example 1, except that the acryl polymer (A3) prepared in Example 3 was used.

Example 4

[0071] A pressure-sensitive adhesive composition and a pressure-sensitive adhesive film having a coating layer having a uniform thickness of 13 m were formed by the same method as described in Example 1, except that the acryl polymer (A4) prepared in Example 4 was used.

Example 5

[0072] A pressure-sensitive adhesive composition and a pressure-sensitive adhesive film having a coating layer having a uniform thickness of 13 m were formed by the same method as described in Example 1, except that the acryl polymer (A5) prepared in Example 5 was used.

Comparative Example 1

[0073] An acryl polymer (B1) having a weight average molecular weight of 1,800,000 was prepared by the same method as described in Preparation Example 1, and a pressure-sensitive adhesive composition and a pressure-sensitive adhesive film having a coating layer having a uniform thickness of 13 m were formed, except that a monomer mixture in which 79 g of n-butyl acrylate (n-BA), 20 g of phenol acrylate (PHEA) and 1 g of hydroxybutyl acrylate (HBA) were mixed was used instead of the monomer mixture used in Preparation Example 1.

Comparative Example 2

[0074] An acryl polymer (B2) having a weight average molecular weight of 1,820,000 was prepared by the same method as described in Preparation Example 1, and a pressure-sensitive adhesive composition and a pressure-sensitive adhesive film having a coating layer having a uniform thickness of 13 m were formed, except that a monomer mixture in which 79 g of n-butyl acrylate (n-BA), 20 g of isobornyl acrylate (IBOA) and 1 g of hydroxybutyl acrylate (HBA) were mixed was used instead of the monomer mixture used in Preparation Example 1.

Comparative Example 3

[0075] An acryl polymer (B3) having a weight average molecular weight of 1,760,000 was prepared by the same method as described in Preparation Example 1, and a pressure-sensitive adhesive composition and a pressure-sensitive adhesive film having a coating layer having a uniform thickness of 13 m were formed, except that a monomer mixture in which 79 g of n-butyl acrylate (n-BA), 20 g of N-vinyl caprolactam (NVC) and 1 g of methyl acrylate (MA) were mixed was used instead of the monomer mixture used in Preparation Example 1.

Comparative Example 4

[0076] An acryl polymer (B4) having a weight average molecular weight of 1,800,000 was prepared by the same method as described in Preparation Example 1, and a pressure-sensitive adhesive composition and a pressure-sensitive adhesive film having a coating layer having a uniform thickness of 13 m were formed, except that a monomer mixture in which 99 g of n-butyl acrylate (n-BA) and 1 g of hydroxybutyl acrylate (HBA) were mixed was used instead of the monomer mixture used in Preparation Example 1.

Comparative Example 5

[0077] An acryl polymer (B5) having a weight average molecular weight of 1,800,000 was prepared by the same method as described in Preparation Example 1, and a pressure-sensitive adhesive composition and a pressure-sensitive adhesive film having a coating layer having a uniform thickness of 13 m were formed, except that a monomer mixture in which 95 g of n-butyl acrylate (n-BA) and 5 g of acrylic acid (AA) were mixed was used instead of the monomer mixture used in Preparation Example 1.

Comparative Example 6

[0078] An acryl polymer (B1) having a weight average molecular weight of 1,800,000 was prepared by the same method as described in Preparation Example 1, except that the monomer mixture in which 99 g of n-butyl acrylate (n-BA) and 1 g of hydroxybutyl acrylate (HBA) were mixed was used as the monomer mixture in Preparation Example 1, and a pressure-sensitive adhesive composition and a pressure-sensitive adhesive film having a coating layer having a uniform thickness of 13 m were formed by the same method as described in Example 1, except that 12 parts by weight of tris 2-hydroxy ethyl isocyanurate triacrylate (M370) was added with respect to 100 parts by weight of a solid content of a pressure-sensitive adhesive.

[0079] Example of Test

[0080] Physical properties were evaluated by the following methods with respect to the pressure-sensitive adhesive compositions or films formed in Examples and Comparative Examples.

[0081] Measurement Method 1. Measurement of Weight Average Molecular Weight

[0082] A weight average molecular weight of the pressure-sensitive adhesive composition was measured using GPC under the following conditions. To draw a calibration curve, standard polystyrene of an Agilent system was used, and measurement results were converted.

[0083] <Conditions for Measuring Weight Average Molecular Weight>

[0084] Measuring Tool: Agilent GPC (Agilent 1200 series, USA)

[0085] Column: two connected PL mixed B

[0086] Column Temperature: 40 C.

[0087] Eluent: Tetrahydrofuran

[0088] Flow Rate: 1.0 mL/min

[0089] Concentration: 2 mg/mL (100 L injection)

[0090] Measurement Method 1. Measurement of Dynamic Storage Modulus

[0091] A dynamic storage modulus of the pressure-sensitive adhesive composition was measured using ARES manufactured by TA corp. Dynamic storage moduli of the pressure-sensitive adhesive compositions in Examples 1 to 5 and pressure-sensitive adhesive compositions in Comparative Examples 1 to 6 were measured at a temperature of 30 C. and a frequency of 500 Hz by frequency sweep with respect to a pressure-sensitive adhesive under conditions of a sample thickness of 1 mm and a deformation ratio of 10% using a parallel plate fixture having a diameter of 8 mm

[0092] Measurement Method 3. Evaluation of Endurance Reliability

[0093] To evaluate durability with respect to humidity and thermal resistance of a pressure-sensitive adhesive film attached to a glass for an LCD, the film was left for 500 hours under the condition of a temperature of 60 C. and a relative humidity of 90% and a condition of a temperature of 70 C. and a relative humidity of 90%, and bubbling and peeling were observed.

[0094] Evaluation criteria for reliability were as follows:

[0095] : no bubbling or peeling was observed

[0096] : a little bubbling or peeling was observed

[0097] x: a large amount of bubbling or peeling was observed

[0098] Measurement Method 4. Measurement of Acid Value

[0099] An acid value was measured using an automatic titration device (COM-550, Hiranuma Sankyo), and calculated by the following Equation:

A={(YX)f5.611}/M[Equation 1]

[0100] In Equation 1, A is an acid value, Y is a titration amount (ml) of a sample solution, X is a titration amount (ml) of a solution containing 50 g of a mixed solvent, f is a factor of a titration solution, and M is a weight (g) of a polymer sample, and measurement conditions were as follows:

[0101] Sample solution: prepared by dissolving approximately 0.5 g of an acryl polymer sample in 50 g of a mixed solvent (toluene/2-propanol/distilled water=50/49.5/0.5, weight ratio)

[0102] Titration solution: 0.1N, 2-propanol-type potassium hydroxide solution (Wako Junyaku Kogyo, for test neutralization value of petroleum products)

[0103] Electrode: glass electrode, GE-101, Comparative electrode: RE-201

[0104] Measurement mode: for test neutralization value of petroleum products

[0105] Components and physical properties of the pressure-sensitive adhesive compositions in Examples 1 to 5 and Comparative Examples 1 to 6 according to the above methods are listed in the following Tables 1 and 2.

TABLE-US-00001 TABLE 1 Dynamic storage modulus Molec- at 30 C., ular Thick- 500 Hz weight ness Weight ratio (Mpa) (10,000) (m) Example 1 NBA:MA:HBA = 0.0543 179 13 acryl polymer 89:10:1 (A1) Example 2 NBA:MA:HBA = 0.0511 167 13 acryl polymer 79:20:1 (A2) Example 3 NBA:MA:HBA = 0.0772 189 13 acryl polymer 59:40:1 (A3) Example 4 NBA:t-BA:HBA = 0.0638 176 13 acryl polymer 89:10:1 (A4) Example 5 NBA:t-BA:HBA = 0.0541 177 13 acryl polymer 69:30:1 (A5) C. Example 1 NBA:PHEA:HBA = 0.0441 180 13 acryl polymer 79:20:1 (B1) C. Example 2 NBA:IBOA:HBA = 0.049 182 13 acryl polymer 79:20:1 (B2) C. Example 3 NBA:NVC:HBA = 0.0626 176 13 acryl polymer 79:20:1 (B3) C. Example 4 NBA:HBA = 0.047 180 13 acryl polymer 99:1 (B4) C. Example 5 NBA:AA = 0.078 180 13 acryl polymer 95:5 (B5) C. Example 6 NBA:HBA = 0.12 180 13 acryl polymer 99:1 + M 370 (B6) NBA: n-butyl acrylate MA: methyl acrylate t-BA: t-butyl acrylate HBA: hydroxybutyl acrylate PHEA: phenol acrylate IBOA: isobornylacrylate NVC: n-vinyl caprolactam AA: acrylic acid M 370: tris 2-hydroxy ethyl isocyanurate Triacrylate *C. Example: Comparative Example

TABLE-US-00002 TABLE 2 Endurance Endurance reliability reliability at 60 at 70 C., relative C., relative humidity of humidity of 90% for 90% for Acid 500 hours 500 hours value Comments Example 1 0 acryl polymer (A1) Example 2 0 acryl polymer (A2) Example 3 0 acryl polymer (A3) Example 4 0 acryl polymer (A4) Example 5 0 acryl polymer (A5) C. Example 1 0 acryl polymer (B1) C. Example 2 0 acryl polymer (B2) C. Example 3 0 acryl polymer (B3) C. Example 4 0 acryl polymer (B4) C. Example 5 20 Corrosion acryl polymer of ITO (B5) C. Example 6 0 Bending acryl polymer of cell (B6) * C. Example: Comparative Example

[0106] As shown in Tables 1 and 2, Examples 1 to 5 including the acryl polymer (A1) to the acryl polymer (A5) exhibited excellent endurance reliability despite being formed to a very small thickness of 13 m.

[0107] However, it was shown that the pressure-sensitive adhesive compositions of Comparative Examples 1 to 3 including the acryl polymer (B1) to the acryl polymer (B3), each of which had a monomer having a ring-type terminal end copolymerized in, had poor endurance reliability, and the pressure-sensitive adhesive composition including the acryl polymer (B4) in which a third acrylate-based monomer was not copolymerized according to the present application had slightly better endurance reliability than that in Comparative Examples 1 to 3, but showed insignificant results, compared with those in Examples 1 to 5 according to the present application

[0108] Meanwhile, the pressure-sensitive adhesive composition including the acryl polymer (B5) prepared by copolymerizing an acrylic acid monomer in Comparative Example 5 had fair endurance reliability. However, the composition had an acid value of 20 due to an acrylic acid showing acidity, and the ITO layer was corroded.

[0109] In addition, when tris 2-hydroxy ethyl isocyanurate triacrylate (M 370) was added to the pressure-sensitive adhesive composition including an acryl polymer in Comparative Example 4, the endurance reliability of the composition was improved but a cell was bent. This is because a dynamic storage modulus was increased too much by adding M370, which had a very high glass transition temperature. This could also be confirmed from Table 1.