Optical Laminate

Abstract

The present application relates to an optical laminate. The present application can provide an optical laminate which can have stable durability even at a high temperature, particularly an ultra-high temperature of about 100 C. or higher, and that base material adhesiveness is excellent, other physical properties required for the optical laminate are also excellent, and even in the case of being disposed adjacent to the electrode, corrosion of the relevant electrode or the like is not induced.

Claims

1. An optical laminate comprising an optical film; and a pressure-sensitive adhesive layer formed on a side of the optical film, wherein the pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive polymer including a first alkyl (meth)acrylate unit having an alkyl group with 4 or more carbon atoms, a second alkyl (meth)acrylate unit having an alkyl group with 3 or less carbon atoms, an aromatic group-containing monomer unit and a hydroxyl group-containing monomer unit, and wherein the pressure-sensitive adhesive polymer includes the first alkyl (meth)acrylate unit in an amount of 45 wt % to 70 wt %, and 30 to 65 parts by weight of the second alkyl (meth)acrylate unit, 20 to 45 parts by weight of the aromatic group-containing monomer unit, and 4 to 8 parts by weight of the hydroxyl group-containing monomer unit, relative to 100 parts by weight of the first alkyl (meth) acrylate unit.

2. The optical laminate according to claim 1, wherein the pressure-sensitive adhesive layer has a storage modulus at room temperature of 0.07 MPa or more.

3. The optical laminate according to claim 1, wherein the pressure-sensitive adhesive layer has a gel fraction of 80 wt % or more according to Equation 1 below:
Gel fraction=B/A100 [Equation 1] wherein, A is a mass (unit: g) of the pressure-sensitive adhesive layer before immersing the pressure-sensitive adhesive layer in ethyl acetate, and B represents the dry mass (unit: g) of an insoluble fraction recovered after immersing the pressure-sensitive adhesive layer in ethyl acetate at room temperature for 24 hours.

4. The optical laminate according to claim 1, wherein the optical film is a polarizer.

5. The optical laminate according to claim 4, wherein the polarizer is a polyvinyl alcohol polarizer containing a potassium component and a zinc component.

6. The optical laminate according to claim 5, wherein the polyvinyl alcohol polarizer comprises the potassium component (K) and the zinc component (Zn) in a weight ratio (K/Zn) of 0.2 to 6.

7. The optical laminate according to claim 5, wherein the polyvinyl alcohol polarizer comprises the potassium component in an amount of 0.1 to 2 wt %.

8. The optical laminate according to claim 5, wherein the polyvinyl alcohol polarizer comprises the zinc component in an amount of 0.1 to 0.5 wt %.

9. The optical laminate according to claim 1, wherein the second alkyl (meth)acrylate unit is a methyl acrylate unit.

10. The optical laminate according to claim 1, wherein the aromatic group-containing monomer forming the aromatic group-containing monomer unit is represented by Formula 1 below: ##STR00003## wherein, R.sub.1 is hydrogen or an alkyl group, A is an alkylene group, n is an integer in a range of 0 to 3, Q is a single bond, O, S or an alkylene group, and P is an aromatic substituent.

11. The optical laminate according to claim 1, wherein the hydroxyl group-containing monomer unit is a hydroxyalkyl (meth)acrylate unit having a hydroxyalkyl group having a carbon number in a range of 3 to 6.

12. The optical laminate according to claim 1, wherein the pressure-sensitive adhesive polymer further comprises carboxyl group-containing monomer units and an amount of carboxyl group-containing monomer units in the pressure-sensitive adhesive polymer is 1 wt % or less.

13. The optical laminate according to claim 1, wherein the pressure-sensitive adhesive layer further comprises a crosslinking agent for crosslinking the pressure-sensitive adhesive polymer.

14. A display device comprising a display panel to which the optical laminate of claim 1 is attached via the pressure-sensitive adhesive layer of the optical laminate.

15. The optical laminate according to claim 1, wherein the pressure-sensitive adhesive layer has a storage modulus at room temperature of 0.07 MPa to 0.2 MPa.

16. The optical laminate according to claim 1, wherein the pressure-sensitive adhesive layer has a gel fraction of 80 wt % to 95 wt % according to Equation 1 below:
Gel fraction=B/A100 [Equation 1] wherein, A is a mass (unit: g) of the pressure-sensitive adhesive layer before immersing the pressure-sensitive adhesive layer in ethyl acetate, and B represents the dry mass (unit: g) of an insoluble fraction recovered after immersing the pressure-sensitive adhesive layer in ethyl acetate at room temperature for 24 hours.

Description

MODE FOR INVENTION

[0098] Hereinafter, the present application will be specifically described by way of examples, but the scope of the present application is not limited by the following examples.

[0099] 1. Method of Measuring Peel Force

[0100] The pressure-sensitive adhesive polarizing plates prepared in Examples or Comparative Examples were each cut to a width of 25 mm and a height of 200 mm to prepare a specimen, which was attached to a glass plate via the pressure-sensitive adhesive layer of the specimen. The peel force was measured while peeling off the pressure-sensitive adhesive polarizing plate at a peel angle of 90 degrees and a peel rate of 300 mm/min at an elapsed time of 1 hour after attachment of the specimen.

[0101] 2. Method of Measuring Gel Fraction

[0102] After holding each of the pressure-sensitive adhesive layers prepared in Examples or Comparative Examples at a constant temperature and humidity room (temperature: 23 C., relative humidity: 50%) for 7 days, 0.2 g (=A in gel fraction measurement equation) was collected. The collected pressure-sensitive adhesive layer was completely immersed in 50 mL of ethyl acetate, and then stored in a dark room at room temperature for 1 day. Subsequently, a portion (insoluble fraction) not dissolved in ethyl acetate was collected by filtering it through a 200 mesh (#200) stainless steel wire net and dried at a temperature of 150 C. for a period of 30 minutes to measure the dry mass of the insoluble fraction (B in gel fraction measurement equation). Subsequently, the gel fraction (unit: %) was measured by substituting the measurement result into the following equation.

[0103] <Gel Fraction Measurement Equation>

Gel fraction=B/A100

[0104] A: mass of the pressure-sensitive adhesive (0.2 g)

[0105] B: dry mass of insoluble fraction (unit: g)

[0106] 3. Method of Measuring Elastic Modulus

[0107] The pressure-sensitive adhesive compositions prepared in Examples or Comparative Examples were each coated between two release films and aged for 7 days under a constant temperature and humidity condition (temperature: 23 C., relative humidity: 50%) to prepare a pressure-sensitive adhesive layer having a thickness of about 22 m. Subsequently, the pressure-sensitive adhesive between the release films was cut to prepare a circumferential specimen of 8 mm1 mm (=diameterthickness), and then using a dynamic rheometer (ARES, RDA, TA Instruments Inc.), the storage modulus at 23 C. was measured while applying shear stress between parallel plates at a frequency of 1 Hz.

[0108] 4. ITO Corrosion Test

[0109] The pressure-sensitive adhesive compositions prepared in Examples or Comparative Examples were each laminated on a TAC (triacetyl cellulose) film having a thickness of 40 m and aged for 7 days under a constant temperature and humidity condition (temperature: 23 C., relative humidity: 50%) to prepare a pressure-sensitive adhesive layer specimen. Then, a typical ITO (indium tin oxide) film was cut to have a width of about 50 mm or so and a height of about 30 mm or so to prepare an ITO film specimen. Subsequently, on the ITO film specimen, a silver paste was applied to both ends in the transverse direction at a width of 10 mm or so, respectively. Subsequently, the pressure-sensitive adhesive layer specimen was cut to have a width of about 40 mm or so and a height of about 30 mm or so, and the pressure-sensitive adhesive layer specimen was attached to the ends on the silver paste at an interval of 5 mm or so to prepare a sample. The prepared sample was stored for about 250 hours under a high temperature and humidity condition (temperature: 85 C., relative humidity: 85%), and the change rate of resistance was evaluated with a linear resistance meter (Hioki, 3244-60 card hitester) as compared with before initial introduction to determine whether or not the ITO was corroded.

[0110] 5. High Temperature Durability (Lifting, Peeling and Foaming Evaluation)

[0111] The pressure-sensitive adhesive polarizing plates of Examples or Comparative Examples were each cut to have a width of about 140 mm or so and a height of about 90 mm or so to prepare a specimen, which was attached to a glass substrate at a pressure of 5 kg/cm.sup.2. The attachment was performed in a clean room so that bubbles or foreign materials were not generated. Subsequently, the prepared sample was kept in an autoclave for 15 minutes under conditions of 50 C. and 5 kg/cm.sup.2.

[0112] The sample was held at a temperature of about 100 C. for about 500 hours, and then durability was evaluated according to the following criteria.

[0113] <Evaluation Criteria>

[0114] O: no bubbling and peeling occurred

[0115] : bubbling and/or peeling occurred

[0116] X: severe bubbling and/or peeling occurred

[0117] 6. Keying Force Evaluation

[0118] Keying force means a physical quantity reflecting adhesiveness between a pressure-sensitive adhesive layer and a base material.

[0119] For each sample after the pressure-sensitive adhesive layers prepared in Examples or Comparative Examples were each laminated on a polarizing plate and aged for 7 days under a constant temperature and humidity condition (temperature: 23 C., relative humidity: 50%), keying force was evaluated. After removing the release film of the pressure-sensitive adhesive layer from the sample, it was visually confirmed how much the pressure-sensitive adhesive layer was left on the polarizing plate and evaluated, when a pressure-sensitive adhesive tape with a width of about 50 mm from American Tape Co., Ltd. was attached to the pressure-sensitive adhesive layer of the sample and the pressure-sensitive adhesive tape was separated from the pressure-sensitive adhesive layer. The weaker the keying force, the more the pressure-sensitive adhesive layer is separated from the polarizing plate and transferred to the pressure-sensitive adhesive tape during the evaluation, whereby a large amount of vacancies are confirmed, which are parts of the pressure-sensitive adhesive layer where the pressure-sensitive adhesive does not remain on the polarizing plate. It can be seen that the keying force is weak when there are many vacancy parts as above.

[0120] <Evaluation Criteria>

[0121] : vacancy having a diameter of 1 mm or more was not observed in the pressure-sensitive adhesive layer laminated on the polarizing plate as an adherend upon evaluation

[0122] O: 1 to 5 vacancies having a diameter of 1 mm or more were observed in the pressure-sensitive adhesive layer laminated on the polarizing plate as an adherend upon evaluation

[0123] : more than 5 vacancies having a diameter of 1 mm or more were observed in the pressure-sensitive adhesive layer laminated on the polarizing plate as the adherend upon evaluation

[0124] X: the vacancy area in the pressure-sensitive adhesive layer laminated on the polarizing plate as an adherend upon evaluation was larger than the area of the remaining pressure-sensitive adhesive layer

[0125] Preparation Example 1. Preparation of Pressure-Sensitive Adhesive Polymer (A)

[0126] n-Butyl acrylate (n-BA), benzyl acrylate (BzA), methyl acrylate (MA) and hydroxybutyl acrylate (4-HBA) were introduced into an 1 L reactor equipped with a cooling device for nitrogen gas refluxing and easy temperature control in a weight ratio of 62:15:20:3 (n-BA: BzA: MA: 4-HBA) and 100 parts by weight of ethyl acetate (EAc) was introduced as a solvent. Subsequently, nitrogen gas was purged for 1 hour to remove oxygen, and then, 0.03 parts by weight of azobisisobutyronitrile (AIBN) diluted to a concentration of 50 wt % in ethyl acetate was introduced as a reaction initiator and reacted for 8 hours to prepare a copolymer (A) having a molecular weight (Mw) of about 1,800,000 g/mol or so.

[0127] Preparation Example 2 to 7. Preparation of pressure-sensitive adhesive polymers B to G

[0128] Copolymers were prepared in the same manner as in Preparation Example 1, except that the compositions shown in Table 1 below were adopted.

TABLE-US-00001 TABLE 1 Preparation Example 1 2 3 4 5 6 7 A B C D E F G n-BA 62 84 64 63 84 64 81 BzA 15 15 15 15 15 15 15 MA 20 20 20 20 4-HBA 3 1 1 2 AA 1 1 4 Mw 1,800,000 1,500,000 1,800,000 1,800,000 1,650,000 1,800,000 1,300,000 Content unit: part by weight, n-BA: n-butyl acrylate, BzA: benzyl acrylate, MA: methyl acrylate, 4-HBA: 4-hydroxybutyl acrylate, AA: acrylic acid, Mw: weight average molecular weight

EXAMPLE 1

[0129] Preparation of Pressure-Sensitive Adhesive Composition

[0130] To the copolymer (A) of Preparation Example 1, about 0.12 parts by weight of an isocyanate crosslinking agent (T-39M, Japan Soken Co., Ltd.), about 1.0 part by weight of an ionic liquid (FC-4400, 3M Co.) and about 0.23 parts by weight of a silane coupling agent (T-789J, Japan Soken Co., Ltd.) were combined, relative to 100 parts by weight of the solid content of the copolymer (A).

[0131] Subsequently, a di-n-butyltin dilaurate catalyst (C-700, Hannong Chemicals Inc.) diluted with ethyl acetate at a concentration of about 0.5 wt % or so was combined thereto in an amount of about 0.001 parts by weight relative to 100 parts by weight of the solid content of copolymer (A). Then, after acetyl acetone as a crosslinking retarder was further combined thereto in an amount of about 1 part by weight relative to 100 parts by weight of the solid content of the copolymer (A), the mixture was diluted to an appropriate concentration and uniformly mixed, and then coated on a release paper and dried to produce a uniform pressure-sensitive adhesive layer having a thickness of 22 m.

[0132] Production of Polarizing Plate

[0133] A polyvinyl alcohol (PVA) film (Japan Synthetic Co., M2004) having a thickness of about 30 m was immersed in a dyeing solution at 30 C. containing 0.05 wt % of iodine and 1.5 wt % of potassium iodide for 60 seconds to be subjected to dyeing. Subsequently, the dyed polyvinyl alcohol film was immersed in a crosslinking solution at 30 C. containing 0.5 wt % of boron and 3.0 wt % of potassium iodide for 60 seconds to be subjected to crosslinking. Thereafter, the crosslinked polyvinyl alcohol film was stretched at a draw ratio of 5.5 times using a roll-to-roll stretching method. The stretched polyvinyl alcohol film was washed with water by immersing it in ion-exchanged water at 30 C. for about 20 seconds and immersed in a solution at 30 C. containing 1.5 wt % of zinc nitrate and 4.0 wt % of potassium iodide for about 10 seconds. Thereafter, the polyvinyl alcohol film was dried at a temperature of 80 C. for 200 seconds to produce a polarizer having a thickness of about 13 m. The potassium content in the produced polarizer was about 0.47 wt %, and the zinc content was about 0.17 wt %. Subsequently, a polarizing plate was produced by attaching a protective film of TAC (triacetyl cellulose) having a thickness of about 40 m on both sides of the polarizer.

[0134] Production of Optical Laminate (Pressure-Sensitive Adhesive Polarizing Plate)

[0135] The polarizing plate was stuck and processed to one side of the prepared pressure-sensitive adhesive layer to produce a pressure-sensitive polarizing plate (optical laminate).

COMPARATIVE EXAMPLE 1

[0136] To the copolymer (B) of Preparation Example 2, about 0.08 parts by weight of an isocyanate crosslinking agent (T-39M, Japan Soken Co., Ltd.), about 1.0 part by weight of an ionic liquid (FC-4400, 3M Co.) and about 0.23 parts by weight of a silane coupling agent (T-789J, Japan Soken Co., Ltd.) were combined, relative to 100 parts by weight of the solid content of the copolymer (B).

[0137] Subsequently, a pressure-sensitive adhesive polarizing plate was produced in the same manner as in Example 1, except that after a di-n-butyltin dilaurate catalyst (C-700, Hannong Chemicals Inc.) diluted with ethyl acetate at a concentration of about 0.5 wt % or so was combined thereto in an amount of about 0.006 parts by weight relative to 100 parts by weight of the solid content of copolymer (B), the mixture was diluted to an appropriate concentration and uniformly mixed, and then coated on a release paper and dried to produce a uniform pressure-sensitive adhesive layer having a thickness of 22 m.

COMPARATIVE EXAMPLE 2

[0138] To the copolymer (C) of Preparation Example 3, about 0.08 parts by weight of an isocyanate crosslinking agent (T-39M, Japan Soken Co., Ltd.), about 1.0 part by weight of an ionic liquid (FC-4400, 3M Co.) and about 0.23 parts by weight of a silane coupling agent (T-789J, Japan Soken Co., Ltd.) were combined, relative to 100 parts by weight of the solid content of the copolymer (C).

[0139] Subsequently, a pressure-sensitive adhesive polarizing plate was produced in the same manner as in Example 1, except that after a di-n-butyltin dilaurate catalyst (C-700, Hannong Chemicals Inc.) diluted with ethyl acetate at a concentration of about 0.5 wt % or so was combined thereto in an amount of about 0.006 parts by weight relative to 100 parts by weight of the solid content of copolymer (C), the mixture was diluted to an appropriate concentration and uniformly mixed, and then coated on a release paper and dried to produce a uniform pressure-sensitive adhesive layer having a thickness of 22 m.

COMPARATIVE EXAMPLE 3

[0140] A pressure-sensitive adhesive layer and a pressure-sensitive polarizing plate were produced in the same manner as in Comparative Example 2, except that the content of the isocyanate crosslinking agent (T-39M, Soken, Japan Soken Co., Ltd.) was changed to about 0.12 relative to 100 parts by weight of the solid content of the copolymer (C).

COMPARATIVE EXAMPLE 4

[0141] To the copolymer (D) of Preparation Example 4, about 0.12 parts by weight of an isocyanate crosslinking agent (T-39M, Japan Soken Co., Ltd.), about 1.0 part by weight of an ionic liquid (FC-4400, 3M Co.) and about 0.23 parts by weight of a silane coupling agent (T-789J, Japan Soken Co., Ltd.) were combined, relative to 100 parts by weight of the solid content of the copolymer (D).

[0142] Subsequently, a di-n-butyltin dilaurate catalyst (C-700, Hannong Chemicals Inc.) diluted with ethyl acetate at a concentration of about 0.5 wt % or so was combined thereto in an amount of about 0.001 parts by weight relative to 100 parts by weight of the solid content of copolymer (D). Then, a pressure-sensitive adhesive polarizing plate was produced in the same manner as in Example 1, except that after acetyl acetone as a crosslinking retarder was further combined thereto in an amount of about 1 part by weight relative to 100 parts by weight of the solid content of the copolymer (D), the mixture was diluted to an appropriate concentration and uniformly mixed, and then coated on a release paper and dried to produce a uniform pressure-sensitive adhesive layer having a thickness of 22 m.

COMPARATIVE EXAMPLE 5

[0143] A pressure-sensitive adhesive polarizing plate was produced in the same manner as in Example 1, except that after about 1 part by weight of a toluene isocyanate crosslinking agent (T-706BB, Japan Soken Co., Ltd.), about 0.005 parts by weight of an epoxy crosslinking agent (T-743L, Japan Soken Co., Ltd.), about 1.5 parts by weight of an ionic liquid (FC-4400, 3M Co.) and about 0.1 parts by weight of a silane coupling agent (T-789J, Japan Soken Co., Ltd.) were combined to the copolymer (E) of Preparation Example 5, relative to 100 parts by weight of the solid content of the copolymer (E), the mixture was diluted to an appropriate concentration and uniformly mixed, and then coated on a release paper and dried to produce a uniform pressure-sensitive adhesive layer having a thickness of 22 m.

COMPARATIVE EXAMPLE 6

[0144] A pressure-sensitive adhesive polarizing plate was produced in the same manner as in Example 1, except that after about 1 part by weight of a toluene isocyanate crosslinking agent (T-706BB, Japan Soken Co., Ltd.), about 0.005 parts by weight of an epoxy crosslinking agent (T-743L, Japan Soken Co., Ltd.), about 1.5 parts by weight of an ionic liquid (FC-4400, 3M Co.) and about 0.1 parts by weight of a silane coupling agent (T-789J, Japan Soken Co., Ltd.) were combined to the copolymer (F) of Preparation Example 6, relative to 100 parts by weight of the solid content of the copolymer (F), the mixture was diluted to an appropriate concentration and uniformly mixed, and then coated on a release paper and dried to produce a uniform pressure-sensitive adhesive layer having a thickness of 22 m.

COMPARATIVE EXAMPLE 7

[0145] A pressure-sensitive adhesive polarizing plate was produced in the same manner as in Example 1, except that after about 1.7 parts by weight of a toluene isocyanate crosslinking agent (T-706BB, Japan Soken Co., Ltd.), about 0.005 parts by weight of an epoxy crosslinking agent (T-743L, Japan Soken Co., Ltd.), about 0.7 parts by weight of an ionic liquid (HQ-115A, 3M Co.) and about 0.1 parts by weight of a silane coupling agent (T-789J, Japan Soken Co., Ltd.) were combined to the copolymer (G) of Preparation Example 7, relative to 100 parts by weight of the solid content of the copolymer (G), the mixture was diluted to an appropriate concentration and uniformly mixed, and then coated on a release paper and dried to produce a uniform pressure-sensitive adhesive layer having a thickness of 22 m.

[0146] The evaluation results of Examples and Comparative Examples above were summarized and described in Table 2 below.

TABLE-US-00002 TABLE 2 Example Comparative Example 1 1 2 3 4 5 6 7 Peel force (gf/25 mm) 750 500 900 850 750 700 1000 900 Gel fraction(wt %) 83 72 76 82 83 76 80 80 Elastic modulus (MPa) 0.091 0.044 0.063 0.072 0.091 0.08 0.105 0.088 High temperature durability X X ITO corrosion (%) 13 20 18 20 15 85 85 350 Keying test X