Adhesive composition for polarizing plate, polarizing plate, and optical display device

Abstract

To provide an adhesive composition for a polarizing plate which yields an adhesive layer having superior adhesion between a COP-based film and a polarizer and also having superior adhesion after exposure to high temperature and high humidity.SOLUTION: An adhesive composition for a polarizing plate includes a curable compound and a photoinitiator. The curable compound includes an epoxy compound and a (meth)acrylate compound. The epoxy compound includes a mixture of a bifunctional alicyclic epoxy compound and a bifunctional aliphatic epoxy compound. The (meth)acrylate compound includes a mixture of a hydrophilic bifunctional (meth)acrylate compound, a hydrophobic bifunctional (meth)acrylate compound, and a vinyl group-containing (meth)acrylate compound. The hydrophobic bifunctional (meth)acrylate compound is a bifunctional (meth)acrylate compound having a linear alkylene chain with 9 or more carbon atoms. The vinyl group-containing (meth)acrylate compound is included in an amount of 10 to 15 pts.wt. relative to 100 pts.wt. of the curable compound.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an adhesive composition for a polarizing plate, a polarizing plate, and an optical display device.

Background Art

[0002] A polarizing plate includes a polarizer and polarizer protection films provided on both surfaces of the polarizer. The polarizer protection film may be a transparent protection film such as triacetyl cellulose (TAC), polyethylene terephthalate (PET), acrylic, polycarbonate, cyclic olefin polymer (COP), or a curable resin protection layer such as epoxy or acrylate. The TAC film is a high moisture permeability protection film, which has the advantages of being permeable to moisture and being easily adherable using an aqueous adhesive. The TAC film has limitations in improving the reliability of the polarizing plate. In polarizer protection films other than TAC, since the moisture in the adhesive cannot be completely dried, a solvent-free photocurable adhesive must be used.

[0003] Typical PET, COP, or acrylic films are low moisture permeability protection films, and photocurable adhesives must be used for these. Among these, COP-based films (e.g., manufactured by Konica in Japan) produced by solution casting and high stretching are preferred as polarizer protection films in that they are easy to adjust the retardation required for LCD panels using the VA method, but they are difficult-to-adhere films with conventional photocurable adhesives.

[0004] The background art of the present invention is described in Japanese Patent Application Laid-Open No. 2014-032270.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide an adhesive composition for a polarizing plate that provides an adhesive layer excellent in all of the adhesive force between a COP-based film produced by solution casting and high stretching and a polarizer and the adhesive force after high temperature and high humidity.

[0007] Another object of the present invention is to provide an adhesive composition for a polarizing plate that prevents decolorization of a polarizer after being exposed to high temperature and high humidity and provides an adhesive layer excellent in reliability.

Means for Solving the Problems

[0008] One embodiment of the present invention is an adhesive composition for a polarizing plate.

[0009] The adhesive composition for a polarizing plate contains a curable compound and a photoinitiator. The curable compound contains an epoxy-based compound and a (meth)acrylate-based compound. The epoxy-based compound contains a mixture of a bifunctional alicyclic epoxy-based compound and a bifunctional aliphatic epoxy-based compound. The (meth)acrylate-based compound contains a mixture of a hydrophilic bifunctional (meth)acrylate-based compound, a hydrophobic bifunctional (meth)acrylate-based compound, and a vinyl group-containing (meth)acrylate-based compound. The hydrophobic bifunctional (meth)acrylate-based compound is a bifunctional (meth)acrylate-based compound having 9 or more carbon atoms in the linear alkylene chain. The vinyl group-containing (meth)acrylate-based compound is contained in an amount of 10 to 15 parts by weight per 100 parts by weight of the curable compound.

[0010] Another embodiment of the present invention is a polarizing plate.

[0011] The polarizing plate includes a polarizer and a protective film laminated on the lower surface of the polarizer. The polarizer and the protective film are bonded to each other by an adhesive layer, and the adhesive layer contains a cured product of the adhesive composition for a polarizing plate of the present invention.

[0012] Still another embodiment of the present invention is an optical display device.

[0013] The optical display device includes the polarizing plate of the present invention.

Advantages of the Invention

[0014] The present invention can provide an adhesive composition for a polarizing plate that provides an adhesive layer excellent in adhesion between a COP-based film produced by solution casting and high stretching and a polarizer and adhesion after being exposed to high temperature and high humidity.

[0015] The present invention can provide an adhesive composition for a polarizing plate that prevents discoloration of a polarizer after being exposed to high temperature and high humidity and provides an adhesive layer excellent in reliability.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0017] With reference to the accompanying drawings, embodiments will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement them. The present invention can be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, parts not related to the description are omitted in order to clearly explain the present invention, and the same reference numerals are given to the same or similar components throughout the specification. In the drawings, the lengths, thicknesses, etc. of the respective components are shown for the purpose of explaining the present invention, and the present invention is not limited to the lengths, thicknesses, etc. described in the drawings.

[0018] In this specification, “upper” and “lower” are based on the drawings and are not necessarily fixed to the upper and lower parts. Depending on the viewing angle, “upper” may be changed to “lower” and “lower” may be changed to “upper”.

[0019] The terms used herein are merely for describing exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0020] The adhesive composition for a polarizing plate is used when adhering a polarizer and a polarizer protection film.

[0021] The adhesive composition for a polarizing plate has excellent adhesive strength between a polarizer and a polarizer protection film. As a result, even after being left for a long time under high temperature and high humidity conditions, it has excellent adhesive strength and realizes an adhesive layer that prevents discoloration of the polarizer even when left for a long time under high temperature and high humidity conditions. In particular, the adhesive composition for a polarizing plate has excellent adhesive strength (initial adhesive strength) between a COP-based film produced by solution casting and high stretching and a polarizer, and adhesive strength after being left for a long time under high temperature and high humidity conditions, and provides an adhesive layer that prevents discoloration of the polarizer even when left for a long time under high temperature and high humidity conditions and has excellent reliability.

[0022] In one specific example, in a polarizer - adhesive layer - polarizer protection film (for example, a COP-based film produced by solution casting and high stretching) laminate, the adhesive strength (initial adhesive strength) between the polarizer and the polarizer protection film is 130 gf / 25 mm or more, and for example, it may be from 130 gf / 25 mm to 500 gf / 25 mm. With the above range, excellent reliability and durability of the polarizing plate can be realized.

[0023] In one specific example, after leaving a polarizer - adhesive layer - polarizer protection film (for example, a COP-based film produced by solution casting and high stretching) laminate at a temperature of 60°C and a relative humidity of 95% for 2 days, the adhesive strength between the polarizer and the polarizer protection film is 150 gf / 25 mm or more, and for example, it may be from 150 gf / 25 mm to 500 gf / 25 mm. With the above range, excellent reliability and durability of the polarizing plate can be realized.

[0024] In one specific example, after leaving a polarizer - adhesive layer - polarizer protection film (for example, a COP - based film manufactured by solution casting and high stretching) laminate at a temperature of 60°C and a relative humidity of 95% for 500 hours, the length of iodine decolorization is less than 1 mm, for example, it may be 0 mm or more and less than 1 mm. With the above range, excellent reliability and durability of the polarizing plate can be realized.

[0025] In one specific example, when measuring the peel strength, the polarizer protection film may be a COP - based film manufactured by solution casting and high stretching.

[0026] The adhesive composition for a polarizing plate contains a curable compound and a photoinitiator. The curable compound contains (A) an epoxy - based compound and (B) a (meth)acrylate - based compound. (A) The epoxy - based compound contains a mixture of a bifunctional alicyclic epoxy - based compound and a bifunctional aliphatic epoxy - based compound. (B) The (meth)acrylate - based compound contains a mixture of a hydrophilic bifunctional (meth)acrylate - based compound, a hydrophobic bifunctional (meth)acrylate - based compound, and a vinyl - group - containing (meth)acrylate - based compound. The hydrophobic bifunctional (meth)acrylate - based compound is a bifunctional (meth)acrylate - based compound having 9 or more carbon atoms in the linear alkylene chain. The vinyl - group - containing (meth)acrylate - based compound is contained in an amount of 10 to 15 parts by weight per 100 parts by weight of the curable compound.

[0027] In the adhesive composition containing the above-described curable compound according to the present invention, that is, a bifunctional alicyclic epoxy compound, a hydrophilic bifunctional (meth)acrylate compound, and a vinyl group-containing (meth)acrylate compound, a bifunctional aliphatic epoxy compound and a hydrophobic bifunctional (meth)acrylate compound having 9 or more carbon atoms in the linear alkylene chain are further contained, and the content of the vinyl group-containing (meth)acrylate compound is within a specific content range of the present invention, which is 10 parts by weight to 15 parts by weight. Thereby, the polarizer protection film of the present invention enhances both the adhesive strength between the COP film produced by solution casting and high stretching and the polarizer and the adhesive strength after being exposed to high temperature and high humidity, suppresses the discoloration of the polarizer under high temperature and high humidity, and provides the effect of improving the reliability.

[0028] The curable compound is a photocurable compound, and the adhesive composition is a photocurable adhesive composition for a polarizing plate.

[0029] In one specific example, the curable compound may be contained in the adhesive composition for a polarizing plate in an amount of 90% by weight or more, for example, 90% by weight, 91% by weight, 92% by weight, 93% by weight, 94% by weight, 95% by weight, 96% by weight, 97% by weight, 98% by weight, 99% by weight, 100% by weight, for example, 90% by weight to 100% by weight, 93% by weight to 100% by weight, based on the solid content.

[0030] In one specific example, the total of the (A) epoxy compound and the (B) (meth)acrylate compound may be contained in 95 parts by weight or more, for example, 95 parts by weight, 96 parts by weight, 97 parts by weight, 98 parts by weight, 99 parts by weight, 100 parts by weight, preferably 99 parts by weight to 100 parts by weight, more preferably 100 parts by weight, out of 100 parts by weight of the curable compound. By adopting the above range, the effects of the present invention can be easily exhibited.

[0031] Epoxy compound

[0032] (A) The epoxy compound may be contained in an amount of 30 to 70 parts by weight out of 100 parts by weight of the curable compound. By adopting the above range, the binding force with the hydroxyl group of the polarizer increases, the problem of insufficient adhesive force is eliminated, and the problem of poor decolorization under high temperature and high humidity due to insufficient binding force with the polarizer caused by the decrease in the overall glass transition temperature of the adhesive layer can be solved. Preferably, (A) the epoxy compound may be contained in an amount of 40 to 60 parts by weight out of 100 parts by weight of the curable compound.

[0033] (A) The epoxy compound includes a bifunctional alicyclic epoxy compound and a bifunctional aliphatic epoxy compound.

[0034] In one specific example, the sum of the bifunctional alicyclic epoxy compound and the bifunctional aliphatic epoxy compound may be 95 parts by weight or more, for example, 95 parts by weight, 96 parts by weight, 97 parts by weight, 98 parts by weight, 99 parts by weight, 100 parts by weight, preferably 99 to 100 parts by weight, and more preferably 100 parts by weight, out of 100 parts by weight of the (A) epoxy compound. By adopting the above range, the effects of the present invention can be easily exhibited.

[0035] Since the bifunctional alicyclic epoxy compound has a relatively low initial reaction rate, it can advantageously affect the dimensional stability of the polarizing plate due to the property of high glass transition temperature. Since the bifunctional alicyclic epoxy compound binds to the hydroxyl group of the polarizer, it may be advantageous for increasing the peeling force between the polarizer and the protective film.

[0036] The difunctional alicyclic epoxy compound may mean a compound having two epoxidized alicyclic groups. For example, the difunctional alicyclic epoxy compound may include, but is not limited to, one or more of 3,4-epoxycyclohexylmethyl-3’,4’-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-3’,4’-epoxy-6’-methylcyclohexanecarboxylate, bis(3,4-epoxy-6-methylcyclohexyl) adipate, bicyclohexyl diepoxide (3,4,3’,4’-diepoxy-bicyclohexane), and 3,4-epoxycyclohexylmethyl-3’,4’-epoxycyclohexanecarboxylate modified epsilon-caprolactone.

[0037] The difunctional alicyclic epoxy compound may be included in an amount of 10 to 40 parts by weight, for example, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, 26 parts by weight, 27 parts by weight, 28 parts by weight, 29 parts by weight, 30 parts by weight, 31 parts by weight, 32 parts by weight, 33 parts by weight, 34 parts by weight, 35 parts by weight, 36 parts by weight, 37 parts by weight, 38 parts by weight, 39 parts by weight, 40 parts by weight, preferably 15 to 30 parts by weight, 20 to 30 parts by weight, per 100 parts by weight of the curable compound. By adopting the above range, the reaction can be stabilized by the structural stabilizing effect due to the relatively high polymerization rate of the alicyclic epoxy, and the problem of peeling between films can be eliminated.

[0038] The bifunctional alicyclic epoxy compound may be contained in an amount of 20 to 60 parts by weight, for example, 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, 26 parts by weight, 27 parts by weight, 28 parts by weight, 29 parts by weight, 30 parts by weight, 31 parts by weight, 32 parts by weight, 33 parts by weight, 34 parts by weight, 35 parts by weight, 36 parts by weight, 37 parts by weight, 38 parts by weight, 39 parts by weight, 40 parts by weight, 41 parts by weight, 42 parts by weight, 43 parts by weight, 44 parts by weight, 45 parts by weight, 46 parts by weight, 47 parts by weight, 48 parts by weight, 49 parts by weight, 50 parts by weight, 51 parts by weight, 52 parts by weight, 53 parts by weight, 54 parts by weight, 55 parts by weight, 56 parts by weight, 57 parts by weight, 58 parts by weight, 60 parts by weight, preferably 40 to 60 parts by weight, out of 100 parts by weight of the epoxy compound. By adopting this range, the effects of the present invention can be easily exhibited.

[0039] The bifunctional aliphatic epoxy compound has a relatively low reaction rate compared to the bifunctional alicyclic epoxy compound. The bifunctional alicyclic epoxy compound does not reduce the growth reaction rate of the epoxy compound during cationic polymerization. However, the bifunctional aliphatic epoxy compound causes a decrease in the growth reaction rate of the epoxy compound due to the property that a proton is captured by the epoxy compound during cationic polymerization. In the present invention, based on the growth rate reduction effect of the bifunctional aliphatic epoxy compound, in the difficult-to-adhere polarizer protection film, before the fluidity of the hydrophobic bifunctional (meth)acrylate disappears, the hydrophobic bifunctional (meth)acrylate is sufficiently permeated into the COP-based film so that the hydrophobic bifunctional (meth)acrylate is co-cured with the COP-based film produced by solution casting and high stretching, as described below. After that, good adhesion and reliability are imparted by post-curing.

[0040] In one specific example, the hydrophobic difunctional (meth)acrylate-based compound is present in an amount of 50 to 300 parts by weight, for example, 50 parts by weight, 55 parts by weight, 60 parts by weight, 65 parts by weight, 70 parts by weight, 75 parts by weight, 80 parts by weight, 85 parts by weight, 90 parts by weight, 95 parts by weight, 100 parts by weight, 105 parts by weight, 110 parts by weight, 115 parts by weight, 120 parts by weight, 125 parts by weight, 130 parts by weight, 135 parts by weight, 140 parts by weight, 145 parts by weight, 150 parts by weight, 155 parts by weight, 160 parts by weight, 165 parts by weight, 170 parts by weight, 175 parts by weight, 180 parts by weight, 185 parts by weight, 190 parts by weight, 195 parts by weight, 200 parts by weight, 205 parts by weight, 210 parts by weight, 215 parts by weight, 220 parts by weight, 225 parts by weight, 230 parts by weight, 235 parts by weight, 240 parts by weight, 245 parts by weight, 250 parts by weight, 255 parts by weight, 260 parts by weight, 265 parts by weight, 270 parts by weight, 275 parts by weight, 280 parts by weight, 285 parts by weight, 290 parts by weight, 295 parts by weight, 300 parts by weight, preferably 50 to 200 parts by weight, or 60 to 150 parts by weight, based on 100 parts by weight of the difunctional aliphatic epoxy-based compound. By adopting the above ranges, excellent adhesion to the COP-based film produced by solution casting and high stretching can be obtained due to the interaction between the above-described difunctional aliphatic epoxy-based compound and the hydrophobic difunctional (meth)acrylate-based compound.

[0041] In addition, for the difunctional aliphatic epoxy-based compound, the epoxy ring of the difunctional alicyclic epoxy-based compound can provide structural stability by being structurally confined by the lone pair of electrons of the ether group in the epoxy chain after protonation of the cation, which restricts polymerization.

[0042] Instead of the difunctional aliphatic epoxy-based compound, an adhesive composition containing an aromatic epoxy-based compound has a short carbon chain in which cations are difficult to be confined within the adhesive composition, so it is not easy to provide an effect of improving the peel strength.

[0043] The bifunctional aliphatic epoxy compound can contain at least one of a diglycidyl ether compound having a linear alkylene chain with 4 or more carbon atoms and a diglycidyl ether compound having 2 or more ethylene oxides or propylene oxides in the molecule. These bifunctional aliphatic epoxy compounds can easily exhibit the effects of the present invention in the adhesive composition of the present invention.

[0044] The diglycidyl ether compound having a linear alkylene chain with 4 or more carbon atoms can easily exhibit the effects of the present invention by the linear alkylene chain with 4 or more carbon atoms exhibiting the above-described reaction rate reduction effect.

[0045] The diglycidyl ether compound having a linear alkylene chain with 4 or more carbon atoms can have a straight-chain or branched-chain alkylene chain having 4 or more carbon atoms, preferably 4 to 10 carbon atoms, more preferably 4 to 6 carbon atoms. For example, the diglycidyl ether compound may be at least one of 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, and neopentyl glycol diglycidyl ether. Preferably, the diglycidyl ether compound is an unsubstituted diglycidyl ether compound having a linear alkylene chain with 4 to 6 carbon atoms, and may be at least one of 1,4-butanediol diglycidyl ether and 1,6-hexanediol diglycidyl ether.

[0046] The diglycidyl ether compound having 2 or more ethylene oxides or propylene oxides in the molecule can easily achieve the effects of the present invention by the 2 or more ethylene oxides or propylene oxides in the molecule providing the reaction rate reduction effect.

[0047] The diglycidyl ether-based compound having two or more ethylene oxides or propylene oxides in the molecule may be a diglycidyl ether-based compound having preferably 2 to 10 ethylene oxides or propylene oxides in the molecule. For example, the diglycidyl ether-based compound may be one or more of polyethylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether.

[0048] The bifunctional aliphatic epoxy-based compound may be contained in an amount of 10 to 40 parts by weight, for example, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, 26 parts by weight, 27 parts by weight, 28 parts by weight, 29 parts by weight, 30 parts by weight, 31 parts by weight, 32 parts by weight, 33 parts by weight, 34 parts by weight, 35 parts by weight, 36 parts by weight, 37 parts by weight, 38 parts by weight, 39 parts by weight, 40 parts by weight, preferably 15 to 30 parts by weight, 20 to 30 parts by weight, per 100 parts by weight of the curable compound. By adopting the above range, the time for the hydrophobic bifunctional (meth)acrylate to sufficiently penetrate into the COP-based film is provided, the bonding force with the hydroxyl group of the polarizer is strengthened, and the problem of insufficient peeling force is eliminated. Also, by having the role of the final curing that connects intermediate-sized polymer molecules to grow into a huge size with a relatively slower curing rate than alicyclic epoxy, problems related to the durability of the product can be solved.

[0049] The bifunctional aliphatic epoxy compound may be contained in an amount of 40 to 80 parts by weight, for example, 40 parts by weight, 41 parts by weight, 42 parts by weight, 43 parts by weight, 44 parts by weight, 45 parts by weight, 46 parts by weight, 47 parts by weight, 48 parts by weight, 49 parts by weight, 50 parts by weight, 51 parts by weight, 52 parts by weight, 53 parts by weight, 54 parts by weight, 55 parts by weight, 56 parts by weight, 57 parts by weight, 58 parts by weight, 59 parts by weight, 60 parts by weight, 61 parts by weight, 62 parts by weight, 63 parts by weight, 64 parts by weight, 65 parts by weight, 66 parts by weight, 67 parts by weight, 68 parts by weight, 69 parts by weight, 70 parts by weight, 71 parts by weight, 72 parts by weight, 73 parts by weight, 74 parts by weight, 75 parts by weight, 76 parts by weight, 77 parts by weight, 78 parts by weight, 79 parts by weight, 80 parts by weight, preferably 40 to 60 parts by weight, out of 100 parts by weight of the epoxy compound. By adopting the above range, the effects of the present invention can be easily exhibited.

[0050] In one specific example, in the above composition, the content of one or more of the epoxy compound having an aromatic group and the epoxy compound having a hydrogenated aromatic group may be less than 5 parts by weight, for example, 0 parts by weight or more and less than 5 parts by weight, or may be 0 parts by weight, out of 100 parts by weight of the curable compound.

[0051] (Meth)acrylate compound (B) The (meth)acrylate compound may be contained in an amount of 30 to 70 parts by weight, for example, 40 to 60 parts by weight, out of 100 parts by weight of the curable compound. By adopting the above range, the effects of the present invention can be easily exhibited.

[0052] (B) The (meth)acrylate compound includes a mixture of a hydrophilic bifunctional (meth)acrylate compound, a hydrophobic bifunctional (meth)acrylate compound, and a vinyl group-containing (meth)acrylate compound.

[0053] In one specific example, among 100 parts by weight of the (meth)acrylate-based compound (B), the total of the vinyl group-containing (meth)acrylate-based compound, the hydrophilic difunctional (meth)acrylate-based compound, and the hydrophobic difunctional (meth)acrylate-based compound is 95 parts by weight or more, for example, 95 parts by weight, 96 parts by weight, 97 parts by weight, 98 parts by weight, 99 parts by weight, 100 parts by weight, preferably 99 to 100 parts by weight, and more preferably 100 parts by weight. By adopting the above range, the effects of the present invention can be easily exhibited.

[0054] The hydrophilic difunctional (meth)acrylate-based compound may be a difunctional (meth)acrylate-based compound having two (meth)acrylate groups and an alkylene oxide group between the (meth)acrylate groups. Such a compound has a hydroxyl group such as a polarizer and exhibits advantageous adhesion performance to a hydrophilic adherend, and also has a high affinity for a polyester film treated with a primer, so it can contribute to an increase in adhesive strength. Preferably, the alkylene oxide group may be ethylene oxide or propylene oxide.

[0055] The alkylene oxide group may be contained in the above compound in two or more, for example, from 2 to 5. By adopting the above range, the effects of the present invention can be easily exhibited. For example, the hydrophilic difunctional (meth)acrylate-based compound may be one or more of diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate.

[0056] The hydrophilic difunctional (meth)acrylate compound may be contained in an amount of 5 to 20 parts by weight, for example, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, preferably 10 to 20 parts by weight, out of 100 parts by weight of the curable compound. By adopting the above range, the composition can have a stable liquid phase layer due to the affinity with the epoxy compound, and since the (meth)acrylate compound does not penetrate the COP-based film, a wide cured region of the adhesive can be formed through the polymerization reaction with the hydrophobic difunctional (meth)acrylate that has penetrated the COP-based film, and the effects of the present invention can be easily exhibited.

[0057] The hydrophilic difunctional (meth)acrylate compound is preferably contained in an amount of 10 to 60 parts by weight, for example, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, 26 parts by weight, 27 parts by weight, 28 parts by weight, 29 parts by weight, 30 parts by weight, 31 parts by weight, 32 parts by weight, 33 parts by weight, 34 parts by weight, 35 parts by weight, 36 parts by weight, 37 parts by weight, 38 parts by weight, 39 parts by weight, 40 parts by weight, 41 parts by weight, 42 parts by weight, 43 parts by weight, 44 parts by weight, 45 parts by weight, 46 parts by weight, 47 parts by weight, 48 parts by weight, 49 parts by weight, 50 parts by weight, 51 parts by weight, 52 parts by weight, 53 parts by weight, 54 parts by weight, 55 parts by weight, 56 parts by weight, 57 parts by weight, 58 parts by weight, 59 parts by weight, 60 parts by weight, preferably 10 to 50 parts by weight, 10 to 30 parts by weight, or 20 to 30 parts by weight, out of a total of 100 parts by weight of the (meth)acrylate compounds (B), preferably the total of the hydrophilic difunctional (meth)acrylate compound, the hydrophobic difunctional (meth)acrylate compound, and the vinyl group-containing (meth)acrylate compound. By adopting the above range, the hydrophilic difunctional (meth)acrylate compound remaining inside the adhesive without penetrating into the COP film and the (meth)acrylate compound penetrating into the COP film are appropriately distributed in ratio, the adhesive force is sufficiently exhibited, and the effects of the present invention can be easily exhibited.

[0058] Since the hydrophobic difunctional (meth)acrylate compound has low polarity, it has very excellent penetration characteristics with respect to a polarizer protection film having low polarity, particularly a COP film produced by solution casting and high stretching, and thus can contribute to enhancing the adhesive force to the protection film. However, in the present invention, not only the adhesive force to the COP film but also the adhesive force after being exposed to high temperature and high humidity is ensured, and in order to enhance the reliability, the above-described difunctional aliphatic epoxy compound and the following vinyl group-containing (meth)acrylate compound are contained within a specific content range.

[0059] The hydrophobic difunctional (meth)acrylate-based compound has two (meth)acrylate groups. The hydrophobic monofunctional (meth)acrylate-based compound having one (meth)acrylate group has smooth penetration into a polarizer protection film, particularly a COP-based film, but the increase in the degree of crosslinking is also limited, and it may be difficult to easily exhibit the effect of improving the peel strength.

[0060] The hydrophobic difunctional (meth)acrylate-based compound has an unsubstituted alkylene group having 9 or more carbon atoms in the alkylene chain between the (meth)acrylate groups. The (meth)acrylate-based compound having an alkylene group with less than 9 carbon atoms in the linear alkylene group has an increased polarity and smooth penetration into a polarizer protection film, particularly a COP-based film is not achieved, so it may be difficult to easily exhibit the effect of improving the adhesive strength.

[0061] The hydrophobic difunctional (meth)acrylate-based compound may not have an ether functional group (alkylene oxide group) such as ethylene oxide or propylene oxide.

[0062] In one specific example, the hydrophobic difunctional (meth)acrylate-based compound has an unsubstituted linear or branched alkylene group having 9 or more carbon atoms in the linear alkylene chain, for example, 9, 10, 11, 12, 13, 14, 15, preferably 9 to 15 or less, and may be, for example, one or more of 1,9-nonanediol di(meth)acrylate and 1,10-decanediol di(meth)acrylate. Preferably, the hydrophobic difunctional (meth)acrylate-based compound may be 1,9-nonanediol di(meth)acrylate.

[0063] The hydrophobic difunctional (meth)acrylate compound may be contained in an amount of 10 to 40 parts by weight, for example, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, 26 parts by weight, 27 parts by weight, 28 parts by weight, 29 parts by weight, 30 parts by weight, 31 parts by weight, 32 parts by weight, 33 parts by weight, 34 parts by weight, 35 parts by weight, 36 parts by weight, 37 parts by weight, 38 parts by weight, 39 parts by weight, 40 parts by weight, preferably 20 to 30 parts by weight, per 100 parts by weight of the curable compound. By adopting the above range, the penetration performance with respect to the COP-based film becomes sufficient, and the bonding with the hydrophilic difunctional (meth)acrylate compound inside the adhesive also becomes sufficient, so that the adhesive strength can be easily exhibited as a whole.

[0064] The hydrophobic difunctional (meth)acrylate compound is preferably contained in an amount of 30 to 80 parts by weight, for example, 30 parts by weight, 31 parts by weight, 32 parts by weight, 33 parts by weight, 34 parts by weight, 35 parts by weight, 36 parts by weight, 37 parts by weight, 38 parts by weight, 39 parts by weight, 40 parts by weight, 41 parts by weight, 42 parts by weight, 43 parts by weight, 44 parts by weight, 45 parts by weight, 46 parts by weight, 47 parts by weight, 48 parts by weight, 49 parts by weight, 50 parts by weight, 51 parts by weight, 52 parts by weight, 53 parts by weight, 54 parts by weight, 55 parts by weight, 56 parts by weight, 57 parts by weight, 58 parts by weight, 59 parts by weight, 60 parts by weight, 61 parts by weight, 62 parts by weight, 63 parts by weight, 64 parts by weight, 65 parts by weight, 66 parts by weight, 67 parts by weight, 68 parts by weight, 69 parts by weight, 70 parts by weight, 71 parts by weight, 72 parts by weight, 73 parts by weight, 74 parts by weight, 75 parts by weight, 76 parts by weight, 77 parts by weight, 78 parts by weight, 79 parts by weight, 80 parts by weight, preferably 30 to 60 parts by weight, 40 to 60 parts by weight, out of the total 100 parts by weight of the (B) (meth)acrylate compounds, preferably the total of the hydrophilic difunctional (meth)acrylate compound, the hydrophobic difunctional (meth)acrylate compound, and the vinyl group-containing (meth)acrylate compound. By adopting the above range, the ratio between the (meth)acrylate compound that penetrates into the COP film and the hydrophilic difunctional (meth)acrylate compound remaining inside the adhesive becomes appropriate, the peel force is sufficiently exhibited, and the effects of the present invention can be easily exhibited.

[0065] The vinyl group-containing (meth)acrylate compound has both a (meth)acrylate group and a vinyl group at the same time. This means that in addition to the physical entanglement between the epoxy compound and the (meth)acrylate compound, it has a chemical covalent bond between the epoxy compound and the (meth)acrylate compound, and by suppressing the movement between molecules even at high temperature and high humidity, it improves the adhesive strength after being exposed to high temperature and high humidity, and enhances the reliability by suppressing the decoloration of the polarizer after being exposed to high temperature and high humidity.

[0066] The vinyl group-containing (meth)acrylate compound is contained in an amount of 10 to 15 parts by weight per 100 parts by weight of the curable compound. When the amount of the vinyl group-containing (meth)acrylate compound is less than 10 parts by weight, the effect of improving the adhesive strength of the present invention and suppressing the decolorization of the polarizer may be reduced. When the amount of the vinyl group-containing (meth)acrylate compound exceeds 15 parts by weight, the interfacial peeling contribution effect with other components in the adhesive composition may decrease, and the hydrophobicity of the adhesive composition may increase, resulting in a decrease in the binding force with the polarizer, which is a hydrophilic substrate.

[0067] The vinyl group-containing (meth)acrylate compound has both a (meth)acrylate group and a vinyl group in the molecule. Therefore, the (meth)acrylate group binds to the hydrophilic difunctional (meth)acrylate compound and the hydrophobic difunctional (meth)acrylate compound, and the vinyl group binds to a mixture of a difunctional alicyclic epoxy compound and a difunctional aliphatic epoxy compound, whereby the effects of the present invention can be easily exhibited.

[0068] In one specific example, the vinyl group-containing (meth)acrylate compound may be a monofunctional (meth)acrylate and may be monofunctional vinyl. The vinyl group-containing (meth)acrylate compound is different from the hydrophilic difunctional (meth)acrylate compound and the hydrophobic difunctional (meth)acrylate compound.

[0069] In one specific example, the vinyl group-containing (meth)acrylate compound can have an alkylene oxide group. The alkylene oxide group is contained between the (meth)acrylate group and the vinyl group in the (meth)acrylate compound, and can also exhibit the effect of enhancing the compatibility with the above-described difunctional aliphatic epoxy ether compound and hydrophobic difunctional (meth)acrylate compound. For example, the alkylene oxide group may be an ethylene oxide group or a propylene oxide group, preferably an ethylene oxide group.

[0070] In one specific example, the vinyl group-containing (meth)acrylate compound may be a compound represented by the following Chemical Formula 1:

[0071] [Chemical Formula 1] CH2=CH-(-O-CH2CH2-)n-O-(C=O)-CHR=CH2 In Chemical Formula 1, R is hydrogen or a methyl group, and n is an integer from 1 to 5.

[0072] For example, the vinyl group-containing (meth)acrylate compound may be 2-(2-vinyloxyethoxy)ethyl (meth)acrylate or the like.

[0073] The vinyl group-containing (meth)acrylate compound may be contained in an amount of 10 to 40 parts by weight, for example, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, 26 parts by weight, 27 parts by weight, 28 parts by weight, 29 parts by weight, 30 parts by weight, 31 parts by weight, 32 parts by weight, 33 parts by weight, 34 parts by weight, 35 parts by weight, 36 parts by weight, 37 parts by weight, 38 parts by weight, 39 parts by weight, 40 parts by weight, preferably 20 to 30 parts by weight, out of a total of 100 parts by weight of the sum of the (B) (meth)acrylate compounds, preferably the sum of the hydrophilic difunctional (meth)acrylate compounds, the hydrophobic difunctional (meth)acrylate compounds, and the vinyl group-containing (meth)acrylate compounds. By adopting the above range, due to the copolymerization characteristics of the vinyl group-containing (meth)acrylate compound, the epoxy cured part and the acrylate cured part are connected to each other, thereby ensuring sufficient peel strength and improved durability of the adhesive layer.

[0074] The photoinitiator includes a mixture of a photo radical initiator and a photo cationic initiator.

[0075] The photoinitiator may be contained in an amount of 1 to 15 parts by weight, preferably 1 to 10 parts by weight, per 100 parts by weight of the curable compound. By adopting the above range, the problem that the adhesive composition is not cured is eliminated, and the problem that the light transmittance of the adhesive layer is reduced due to residues caused by excessive use can be solved.

[0076] The photo radical initiator may be a cyclohexyl phenyl ketone type, a thioxanthone type, or the like.

[0077] The photo radical initiator may be contained in an amount of 0.5 to 10 parts by weight, for example, 1 to 6 parts by weight, per 100 parts by weight of the curable compound. By adopting the above range, the adhesive composition can be sufficiently cured, and problems such as a decrease in adhesive strength and bleed-out of the photo radical initiator can be solved.

[0078] The photo cation initiator can include an onium salt of a cation and an anion that is an onium ion. Specific examples of the onium ion include diaryliodonium such as diphenyliodonium, 4-methoxydiphenyliodonium, bis(4-methylphenyl)iodonium, bis(4-tert-butylphenyl)iodonium, bis(dodecylphenyl)iodonium, (4-methylphenyl)[(4-(2-methylpropyl)phenyl)iodonium, triarylsulfonium such as triphenylsulfonium, diphenyl-4-thiophenoxyphenylsulfonium, diphenyl-4-(phenylthio)phenylsulfonium, bis[4-(diphenylsulfonio)-phenyl]sulfide, bis[4-(di(4-(2-hydroxyethyl)phenyl)sulfonio)-phenyl]sulfide, 5-2,4-(cyclopentadienyl)[1,2,3,4,5,6-η]-(methylethyl)-benzene]-iron(1+), etc. Specific examples of the anion include tetrafluoroborate (BF4 - ), hexafluorophosphate (PF6 - ), hexafluoroantimonate (SbF6 - ), hexafluoroarsenate (AsF6- ) Hexachloroantimonate (SbCl6 - ) and the like can be mentioned.

[0079] The photo cationic initiator may be contained in an amount of 0.5 to 10 parts by weight, for example, 1 to 6 parts by weight, based on 100 parts by weight of the curable compound. By adopting the above range, the adhesive composition can be sufficiently cured, and problems such as a decrease in adhesive strength and bleed-out of the photo cationic initiator can be solved.

[0080] The adhesive composition may be produced by mixing a curable compound and a photoinitiator. The adhesive composition may be a solvent-free type without a solvent, or may further contain a solvent to enhance coatability (coating property).

[0081] The adhesive composition may further contain an antioxidant, an ultraviolet absorber, an ionic conductive agent, a conductivity-imparting additive such as conductive metal oxide fine particles, a light diffusion-imparting additive, a viscosity modifier, etc., as long as the effects of the present invention are not impaired.

[0082] The polarizing plate of the present invention includes an adhesive layer formed of the adhesive composition for a polarizing plate of the present invention. The polarizing plate includes a polarizer and a protective film laminated on one surface of the polarizer, and the polarizer and the protective film are bonded together by an adhesive layer, and the adhesive layer includes a cured product of the adhesive composition of the present invention.

[0083] Referring to FIG. 1, the polarizing plate may include a polarizer 10, an adhesive layer 20 and a lower polarizer protective film 30 sequentially formed on one surface of the polarizer 10, and an upper polarizer protective layer 40 laminated on the other surface of the polarizer 10.

[0084] Polarizer The polarizer 10 can polarize external light or internal light.

[0085] The polarizer 10 can include a polyvinyl alcohol-based polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine or the like. For example, the polyvinyl alcohol-based polarizer is manufactured by dyeing a polyvinyl alcohol film with iodine or a dichroic dye and stretching it in a certain direction. Specifically, it is manufactured through a swelling process, a dyeing stage, and a stretching stage. The methods for performing each stage are commonly known to those skilled in the art. The polarizer 10 may have a thickness of 1 μm to 50 μm. By adopting the above range, the polarizer 10 can be used in an optical display device.

[0086] Adhesive layer The adhesive layer 20 is formed directly on the polarizer and the lower polarizer protection film, and can bond the polarizer and the lower polarizer protection film.

[0087] The adhesive layer 20 may be formed of the above-described composition for the adhesive layer. Specifically, it can be formed by applying the composition for the adhesive layer to one surface of the polarizer or the lower polarizer protection film with a predetermined thickness and then photocuring it. Photocuring is to cure the composition by UV irradiation, and can be performed by adjusting the light amount, wavelength, etc. according to the thickness to which the composition for the adhesive is applied. The adhesive layer 20 may have a thickness of 0.01 μm to 10 μm, preferably 1 μm to 5 μm. By adopting the above range, the adhesive force between the polarizer and the polarizer protection film can be ensured.

[0088] Lower polarizer protection film The lower polarizer protection film is laminated on the lower surface of the polarizer (the light incident surface of the internal light of the polarizer), and can provide an additional effect to the polarizing plate.

[0089] As the lower polarizer protection film, a normal polarizer protection film known to those skilled in the art, for example, the polarizer protection film described in the upper polarizer protection layer below, may be applied. In one specific example, in the present invention, as the anti-adhesive protection film, a COP-based film manufactured by solution casting and high stretching may be used as the lower polarizer protection film.

[0090] The COP-based film manufactured by solution casting and high stretching is excellent in that it is easy to adjust the retardation required for an LCD panel using the VA mode when applied to a polarizing plate.

[0091] Upper polarizer protection layer

[0092] The upper polarizer protection layer 40 is formed on the upper surface of the polarizer (the light emitting surface of the internal light of the polarizer) and can support the polarizer. The upper polarizer protection layer can include one or more of an optically transparent protective film and a protective coating layer.

[0093] When the upper polarizer protection layer is of the protective film type, it can include a protective film formed of an optically transparent resin. The protective film can be formed by melting and extruding the resin. If necessary, a stretching process can be further added. The resin can include one or more of cellulose ester resins including triacetyl cellulose, cyclic polyolefin resins including cyclic olefin polymer (COP), polycarbonate resins, polyester resins including polyethylene terephthalate (PET), polyether sulfone resins, polysulfone resins, polyamide resins, polyimide resins, acyclic polyolefin resins, polyacrylate resins including polymethyl methacrylate resins, polyvinyl alcohol resins, polyvinyl chloride resins, and polyvinylidene chloride resins. Preferably, the protective film may be a film formed of a cyclic polyolefin resin including cyclic polyolefin or the like.

[0094] When the upper polarizer protective layer is of the protective coating layer type, it can exhibit good adhesion, transparency, mechanical strength, thermal stability, moisture barrier property, and durability to the polarizer. In one specific example, the protective coating layer for the protective layer may be formed of an active energy ray curable resin composition containing an active energy ray curable compound and a polymerization initiator.

[0095] The active energy ray curable compound can include one or more of a cationic polymerizable curable compound, a radical polymerizable curable compound, a urethane resin, and a silicone resin. The cationic polymerizable curable compound may be an epoxy compound having at least one epoxy group in the molecule or an oxetane compound having at least one oxetane ring in the molecule. The radical polymerizable curable compound may be a (meth)acrylic compound having at least one (meth)acryloyloxy group in the molecule.

[0096] The thickness of the upper polarizer protective layer 40 is from 5 μm to 200 μm, specifically from 30 μm to 120 μm. In the case of the protective film type, it may be from 50 μm to 100 μm, and in the case of the protective coating layer type, it may be from 5 μm to 50 μm. By adopting the above range, the upper polarizer protective layer 40 can be used in the light emitting display device.

[0097] Although not shown in FIG. 1, a functional coating layer, for example, a hard coating layer, an anti-fingerprint layer, an anti-reflection layer, etc. may be further formed on the upper surface of the upper polarizer protective layer 40.

[0098] Although not shown in FIG. 1, when the upper polarizer protective layer 40 is of the protective film type, an adhesive layer can be further formed between the protective layer and the polarizer. The adhesive layer may be formed of a normal polarizing plate adhesive, for example, an aqueous adhesive, a photocurable adhesive, and a vacuum adhesive.

[0099] Although not shown in FIG. 1, the polarizing plate may further include a polarizer protection film, an antireflection film, a retardation film (liquid crystal layer or non-liquid crystal layer), etc., which are commonly used in polarizing plates.

[0100] The optical display device according to an embodiment of the present invention includes the polarizing plate of the present invention. For example, the optical display device may be a light-emitting element display device including a light-emitting element or a liquid crystal display device.

Example

[0101] Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred examples of the present invention. However, this is presented as a preferred example of the present invention, and in no way should it be construed that the present invention is limited thereby.

[0102] Example 1 (1) Preparation of an adhesive composition for a photocurable polarizing plate As the epoxy compound, 20 parts by weight of a bifunctional alicyclic epoxy compound (2021P, manufactured by Daicel Corporation) and 20 parts by weight of a bifunctional aliphatic epoxy compound (1,4-butanediol diglycidyl ether, manufactured by Kokoku Chemical Co., Ltd.) were used. As the (meth)acrylate compound, 15 parts by weight of dipropylene glycol diacrylate (M222, manufactured by Ajinomoto Chemical Co., Ltd.), 30 parts by weight of 1,9-nonanediol diacrylate (NDDA, manufactured by Kyoeisha Chemical Co., Ltd.), and 15 parts by weight of 2-(2-vinyloxyethoxy)ethyl acrylate (VEEA, manufactured by Nippon Shokubai Co., Ltd.) were used.

[0103] The epoxy compound and the (meth)acrylate compound were mixed, and 1 part by weight of a photo cationic initiator (Irgacure 184, 1-hydroxycyclohexyl phenyl ketone, manufactured by BASF) and 6 parts by weight of a photoacid generator (CPI-100P, manufactured by San-Apro Ltd.) were added to the mixture and mixed to prepare a solvent-free photocurable adhesive composition for a polarizing plate.

[0104] (2) Production of a polarizing plate

[0105] A polyvinyl alcohol film (PS#60, manufactured by Kuraray Co., Ltd., saponification degree: 99.5%, thickness: 60 μm) was immersed in a 0.3% iodine aqueous solution for dyeing, and then stretched in the machine direction (MD) at an MD uniaxial draw ratio of 6 times. The stretched polyvinyl alcohol film was subjected to hue correction by immersing it in a 3% boric acid solution and a 2% potassium iodide aqueous solution, and dried at 50°C for 4 minutes to produce a polarizer (light transmittance: 45%, thickness: 7 μm).

[0106] As the upper polarizer protective film, a polyethylene terephthalate (PET) film (thickness: 80 μm, stretched in the TD1 axis, manufactured by Toyobo Co., Ltd.) was used, and the surface to which the adhesive composition was applied was treated with a primer layer. As the lower polarizer protective film, a cyclic olefin polymer (COP) film (manufactured by Konica Corporation, produced by solution casting and high stretching, thickness: 37 μm) was used, and the surface to which the adhesive composition was applied was treated with corona treatment at 100 dose.

[0107] A photocurable adhesive composition prepared was applied to the surface treated with the primer layer of the upper polarizer protective film to a predetermined thickness, and a photocurable adhesive composition prepared was applied to the surface treated with corona treatment of the lower polarizer protective film to a predetermined thickness. After laminating the produced polarizers respectively, ultraviolet rays were irradiated from the lower polarizer protective film side to cure the adhesive composition, thereby producing a polarizing plate laminated in the order of upper polarizer protective film - adhesive layer - polarizer - adhesive layer - lower polarizer protective film. The production of the polarizing plate was carried out at a temperature of 22°C to 25°C and a relative humidity of 20% to 60%.

[0108] Examples 2 to 9

[0109] In the preparation of the solvent-free photocurable adhesive composition for a polarizing plate of Example 1, except that the content and / or type of each component were changed as shown in Table 1 below, the composition and the polarizing plate were prepared and produced in the same manner as in Example 1. In Table 1 below, "-" means that the component is not included.

[0110] Comparative Examples 1 to 8

[0111] In the production of the solvent-free photocurable adhesive composition for a polarizing plate of Example 1, except that the content and / or type of each component were changed as shown in Table 1 below, the composition and the polarizing plate were prepared in the same manner as in Example 1.

[0112] The physical properties shown in Table 2 below were evaluated for the polarizing plates prepared in the examples and comparative examples, and the results are shown in Table 2 below.

[0113] (1) Adhesive strength at room temperature (initial adhesive strength) (unit: gf / 25 mm)) A double-sided foam adhesive tape (VHS, manufactured by 3M) was attached to the lower polarizer protection film side of the polarizing plates prepared in the examples and comparative examples. The polarizer was cut to a length of MD×TD (25 mm×150 mm). After removing the release film of the double-sided foam adhesive tape, it was laminated on the surface of non-alkali glass (thickness: 0.5t) and left at room temperature for 30 minutes to prepare a test piece.

[0114] For the prepared test piece, a cutter blade was obliquely inserted between the polarizer and the lower polarizer protection film to slightly separate the space between the polarizer and the lower polarizer protection film. Then, the test piece was mounted on a Texture Analyzer (manufactured by TA). One side of the 90° both-side jig was clamped with the polarizer side, and the other side was clamped with the lower polarizer protection film side and mounted on the upper load cell. The peeling force obtained when peeling from the lower polarizer protection film side to the polarizer side at a peeling angle of 90°, a peeling speed of 300 mm / min, and a peeling temperature of 25°C was measured three times, and then the average peeling force was calculated.

[0115] (2) Adhesive strength after high temperature and high humidity A test piece was prepared in the same manner as in (1). Then, the test piece was left in a chamber at a temperature of 60°C and a relative humidity of 95% for 2 days, and after taking out the test piece, it was left at room temperature for 30 minutes. Then, the peeling force was measured three times in the same manner as in (1), and the average peeling force was calculated.

[0116] (3) Discoloration after high temperature and high humidity The polarizing plates produced in the examples and comparative examples were cut into squares with a size of 50 mm in width and 50 mm in length so that the absorption axis direction of the polarizer was at an angle of 45°, and test pieces were prepared by attaching them to a glass plate through an acrylic adhesive layer. After putting this test piece into a chamber at a temperature of 60°C and a relative humidity of 95%, it was left for 500 hours and then taken out. Then, as shown in Figure 2, the length 5 at which decolorization of iodine occurred in test piece 1 was measured in the diagonal direction from the four corners of the test piece, and the levels were classified as follows. ◎: Less than 1 mm, ○: 1 mm or more and less than 2 mm △: 2 mm or more and less than 3 mm ×: 3 mm or more

[0117]

Table 1

[0118] A) 2021P: Cycloaliphatic Epoxy, manufactured by Daicel Corporation B) DE200: 1,4-Butanediol Diglycidyl Ether, manufactured by Kukdo Chemical Co., Ltd. C) DE202: 1,6-Hexanediol Diglycidyl Ether, manufactured by Kukdo Chemical Co., Ltd. D) EX821: Polyethyleneglycol Diglycidyl ether, manufactured by Nagase ChemteX Corporation E) EX920: Polypropyleneglycol Diglycidyl Ether, manufactured by Nagase ChemteX Corporation F) YD128: Bisphenol-A Diglycidyl Ether, manufactured by Kukdo Chemical Co., Ltd. G) M222: Dipropylene Glycol Diacrylate, manufactured by Miwon Chemical Co., Ltd. H) NDDA: 1,9-Nonanediol Diacrylate, manufactured by Kyoeisha Chemical Co., Ltd. I) VEEA: 2-(2-Vinyloxyethoxy)ethyl Acrylate, manufactured by Nippon Shokubai Co., Ltd. J) M232: Triethylene Glycol Diacrylate, manufactured by Ajinomoto Chemical Co., Ltd. K) M200: 1,6-Hexanediol Diacrylate, manufactured by Ajinomoto Chemical Co., Ltd. L) M120: Lauryl Acryltae, manufactured by Ajinomoto Chemical Co., Ltd.

[0119]

Table 2

[0120] As shown in Table 2, the adhesive composition for a polarizing plate of the present invention is excellent in the adhesive strength between a COP-based film produced by solution casting and high stretching and a polarizer and the adhesive strength after a high-temperature and high-humidity test, prevents discoloration of the polarizer after the high-temperature and high-humidity test, and provides an adhesive layer with excellent reliability.

[0121] However, the adhesive composition for a polarizing plate of a comparative example that deviates from the configuration of the present invention could not fully exhibit the effects of the present invention.

[0122] Simple modifications and changes of the present invention can be easily implemented by those having ordinary knowledge in this field, and all such modified and changed aspects can be regarded as being included in the scope of the present invention.

Explanation of Reference Numerals

[0123] 10 Polarizer 20 Adhesive layer 30 Lower polarizer protection film 40 Upper polarizer protection layer

Claims

1. A composition containing a curable compound and a photoinitiator, wherein the curable compound contains an epoxy compound and a (meth)acrylate compound, the epoxy compound contains a mixture of a bifunctional alicyclic epoxy compound and a bifunctional aliphatic epoxy compound, the (meth)acrylate compound contains a mixture of a hydrophilic bifunctional (meth)acrylate compound, a hydrophobic bifunctional (meth)acrylate compound, and a vinyl group-containing (meth)acrylate compound, the hydrophobic bifunctional (meth)acrylate compound is a bifunctional (meth)acrylate compound having a linear alkylene chain with 9 or more carbon atoms, and the vinyl group-containing (meth)acrylate compound is contained in an amount of 10 to 15 parts by weight per 100 parts by weight of the curable compound, which is an adhesive composition for a polarizing plate.

2. The hydrophobic bifunctional (meth)acrylate compound is contained in an amount of 50 to 300 parts by weight per 100 parts by weight of the bifunctional aliphatic epoxy compound, which is the adhesive composition for a polarizing plate according to Claim 1.

3. The bifunctional aliphatic epoxy compound contains at least one of a diglycidyl ether compound having a linear alkylene chain with 4 or more carbon atoms and a diglycidyl ether compound having two or more ethylene oxides or propylene oxides in the molecule, which is the adhesive composition for a polarizing plate according to Claim 1.

4. The bifunctional aliphatic epoxy compound is contained in an amount of 10 to 40 parts by weight per 100 parts by weight of the curable compound, which is the adhesive composition for a polarizing plate according to Claim 1.

5. The hydrophobic bifunctional (meth)acrylate compound is contained in an amount of 10 to 40 parts by weight per 100 parts by weight of the curable compound, which is the adhesive composition for a polarizing plate according to Claim 1.

6. The vinyl group-containing (meth)acrylate compound is a compound represented by the following Chemical Formula 1, Chemical Formula 1 CH ２ =CH-( -O-CH ２ CH ２ - )n - O-(C=O)-CHR=CH ２ in Chemical Formula 1, R is hydrogen or a methyl group, and n is an integer from 1 to 5, which is the adhesive composition for a polarizing plate according to Claim 1.

7. The hydrophilic bifunctional (meth)acrylate compound is a bifunctional (meth)acrylate compound having an alkylene oxide group between two (meth)acrylate groups, which is the adhesive composition for a polarizing plate according to Claim 1.

8. The hydrophilic difunctional (meth)acrylate compound is contained in an amount of 5 to 20 parts by weight based on 100 parts by weight of the curable compound, and the adhesive composition for a polarizing plate according to claim 1.

9. The epoxy compound is contained in an amount of 30 to 70 parts by weight based on 100 parts by weight of the curable compound, and the adhesive composition for a polarizing plate according to claim 1.

10. The sum of the difunctional alicyclic epoxy compound and the difunctional aliphatic epoxy compound is contained in an amount of 95 parts by weight or more based on 100 parts by weight of the epoxy compound, and the adhesive composition for a polarizing plate according to claim 1.

11. The sum of the vinyl group-containing (meth)acrylate compound, the hydrophilic difunctional (meth)acrylate compound, and the hydrophobic difunctional (meth)acrylate compound is contained in an amount of 95 parts by weight or more based on 100 parts by weight of the (meth)acrylate compound, and the adhesive composition for a polarizing plate according to claim 1.

12. The sum of the epoxy compound and the (meth)acrylate compound is contained in an amount of 95 parts by weight or more based on 100 parts by weight of the curable compound, and the adhesive composition for a polarizing plate according to claim 1.

13. The curable compound is contained in an amount of 90% by weight or more based on the solid content in the adhesive composition for a polarizing plate, and the adhesive composition for a polarizing plate according to claim 1.

14. Including a polarizer and a protective film laminated on the lower surface of the polarizer, The polarizer and the protective film are bonded together by an adhesive layer, and the adhesive layer includes a cured product of the adhesive composition for a polarizing plate according to any one of claims 1 to 13, and a polarizing plate.

15. An optical display device including the polarizing plate according to claim 14.

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