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

Abstract

To provide an adhesive composition for a polarizing plate that yields an adhesive layer having superior adhesive strength between a polarizer and a polarizer protective film.SOLUTION: An adhesive composition for a polarizing plate is provided that comprises a curable compound and a photoinitiator. The curable compound includes an epoxy compound and a (meth)acrylate compound. The epoxy compound comprises a mixture of a novolac epoxy compound and an aliphatic epoxy compound. The (meth)acrylate compound comprises a mixture of a hydrophilic (meth)acrylate compound, a hydrophobic (meth)acrylate compound, and a vinyl group-containing (meth)acrylate compound. The vinyl group-containing (meth)acrylate compound constitutes 10 to 40 pts.wt. of 100 pts.wt. of the curable compound. A polarizing plate comprising the adhesive composition for a polarizing plate, and an optical display device comprising the polarizing plate, are also provided.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] One embodiment of 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 on both sides of the polarizer. The polarizer protection film may be a transparent protection film such as triacetyl cellulose (TAC), polyethylene terephthalate (PET), acrylic, polycarbonate, cycloolefin polymer (COP), or a curable resin protection layer such as epoxy or acrylate. The TAC film is a high moisture permeability protection film, has the advantages of being permeable to moisture and being easily adhered using an aqueous adhesive. However, the TAC film has limitations in enhancing the reliability of the polarizing plate. Polarizer protection films other than TAC cannot dry the moisture of the adhesive and must use a solvent-free photocurable adhesive.

[0003] Typical PET, COP, or acrylic films are low moisture permeability protection films, and these must use a photocurable adhesive. Among these, COP-based films (Konica Corporation, Japan) manufactured by solution casting and high stretching are preferred as polarizer protection films in that they provide an effect of increasing the curability of the photocurable adhesive due to an increase in light transmittance, but 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] Japanese Patent Application Laid-Open No. 2014-032270

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 having excellent adhesion between a polarizer and a polarizer protection film.

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

[0008] Still another object of the present invention is to provide an adhesive composition for a polarizing plate that has excellent optical transparency in a crude liquid state and has no haze.

Means for Solving the Problems

[0009] One aspect of the present invention is an adhesive composition for a polarizing plate.

[0010] 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 novolak epoxy-based compound and an aliphatic epoxy-based compound. The (meth)acrylate-based compound contains a mixture of a hydrophilic (meth)acrylate-based compound, a hydrophobic (meth)acrylate-based compound, and a vinyl group-containing (meth)acrylate-based compound. The vinyl group-containing (meth)acrylate-based compound is contained in an amount of 10 to 40 parts by weight per 100 parts by weight of the curable compound.

[0011] Another aspect of the present invention is a polarizing plate.

[0012] 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 overlapped by an adhesive layer, and the adhesive layer contains a cured product of the adhesive composition.

[0013] Still another aspect of the present invention is an optical display device.

[0014] The optical display device includes the polarizing plate of the present invention.

Advantages of the Invention

[0015] The present invention provides an adhesive composition for a polarizing plate that provides an adhesive layer having excellent adhesion between a polarizer and a polarizer protection film.

[0016] The present invention provides an adhesive composition for a polarizing plate that prevents discoloration of a polarizer even after being exposed to high temperature and high humidity and provides an adhesive layer having excellent reliability.

[0017] The present invention provides an adhesive composition for a polarizing plate that is excellent in optical transparency in a crude liquid state and has no haze.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0019] With reference to the accompanying drawings, the 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 embodied in various different forms and is not limited to the embodiments described herein. In the drawings, in order to clearly explain the present invention, parts not related to the explanation are omitted, 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 set for the purpose of explaining the present invention, and the present invention is not limited to the lengths, thicknesses, etc. described in the drawings.

[0020] The terms used herein are used only for explaining exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0021] In this specification, "upper" and "lower" are based on the drawings, and are not necessarily fixed as upper and lower. Depending on the viewing perspective, "upper" may be changed to "lower" and "lower" may be changed to "upper".

[0022] The adhesive composition for a polarizing plate is used for adhering a polarizer and a polarizer protective film.

[0023] The adhesive composition for a polarizing plate has excellent adhesive strength between the polarizer and the polarizer protective film, and realizes an adhesive layer capable of preventing discoloration of the polarizer even after being left for a long time under high temperature and high humidity. In particular, the adhesive composition for a polarizing plate has excellent adhesive strength between a normal film used for the polarizer protective film, such as triacetyl cellulose (TAC), polyethylene terephthalate (PET), polycarbonate (PC), cycloolefin polymer (COP), acrylic film, and a COP-based film produced by solution casting and high stretching and the polarizer, and prevents discoloration of the polarizer even after being left for a long time under high temperature and high humidity, and provides an adhesive layer with excellent reliability. The adhesive composition for a polarizing plate has excellent optical transparency in a crude liquid state, has no haze, and provides an optically transparent adhesive layer during photocuring.

[0024] 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 novolac epoxy-based compound and an aliphatic epoxy-based compound. The (meth)acrylate-based compound contains a mixture of a hydrophilic (meth)acrylate-based compound, a hydrophobic (meth)acrylate-based compound, and a vinyl group-containing (meth)acrylate-based compound. The vinyl group-containing (meth)acrylate-based compound is contained in an amount of 10 to 40 parts by weight per 100 parts by weight of the curable compound.

[0025] In the present invention, among the epoxy compounds used in conventional adhesive compositions for polarizing plates, instead of using bifunctional alicyclic epoxy compounds, a mixture of novolac epoxy compounds and aliphatic epoxy compounds is used, and as the (meth)acrylate compound, a mixture of a hydrophilic (meth)acrylate compound, a hydrophobic (meth)acrylate compound, and a vinyl group-containing (meth)acrylate compound is used, and the vinyl group-containing (meth)acrylate compound is contained in an amount of 10 to 40 parts by weight per 100 parts by weight of the curable compound. Thereby, the present invention not only improves the adhesive strength between a normal polarizer protection film, a solution-cast and highly stretched COP-based film and a polarizer, suppresses the discoloration of the polarizer after being exposed to high temperature and high humidity, but also provides an optically transparent adhesive layer after curing with improved reliability and compatibility.

[0026] In one embodiment, the curable compound may be contained in an amount of 90% by weight or more, for example, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100% by weight, preferably 95 to 100% by weight, based on the solid content of the adhesive composition for polarizing plates.

[0027] In one specific example, the total amount of the epoxy compound and the (meth)acrylate compound may be contained in an amount of 95 parts by weight or more, for example, 95, 96, 97, 98, 99, 100 parts by weight, preferably 99 to 100 parts by weight, more preferably 100 parts by weight, per 100 parts by weight of the curable compound. By selecting the above range, excellent adhesive strength, reliability, and improvement effects of compatibility can be obtained.

[0028] The curable compound may be a photocurable compound.

[0029] Epoxy compound The epoxy compound may be contained in an amount of 30 to 70 parts by weight per 100 parts by weight of the curable compound. Within the above range, there is no problem of insufficient peel strength due to insufficient penetration of the (meth)acrylate compound into the polarizer protection film, and there is no problem of causing discoloration under high temperature and high humidity due to a decrease in the overall glass transition temperature of the adhesive layer and insufficient bonding force with the polarizer. Preferably, the epoxy compound may be contained in an amount of 40 to 60 parts by weight.

[0030] The epoxy compound includes a mixture of a novolak epoxy compound and an aliphatic epoxy compound.

[0031] In one embodiment, the sum of the novolak epoxy compound and the aliphatic epoxy compound may be contained in an amount of 95 parts by weight or more, for example, 95, 96, 97, 98, 99, 100 parts by weight, preferably 99 to 100 parts by weight, and more preferably 100 parts by weight per 100 parts by weight of the epoxy compound. With the above range, the effects of the present invention can be obtained more easily.

[0032] Since the novolak epoxy compound has a high glass transition temperature, it may be advantageous for enhancing the reliability of the polarizing plate. The novolak epoxy compound has a relatively low reaction rate compared to the bifunctional alicyclic epoxy compound commonly used in the adhesive composition, and thus can impart relatively high peel strength performance.

[0033] The novolak epoxy compound may include, as a polyfunctional epoxy compound, for example, a compound represented by the following Chemical Formula 1.

[0034]

Chemical formula

[0035] In Chemical Formula 1, R1, R2, and R3 are each hydrogen or an alkyl group having 1 to 10 carbon atoms, R4, R5, and R6 are each independently an alkyl group having 1 to 10 carbon atoms, m1 and m3 are each independently an integer from 0 to 3, m2 is an integer from 0 to 2, n is an integer from 1 to 1000.

[0036] For example, the novolak epoxy compound may contain one or more of cresol novolak epoxy compounds including O-cresol novolak epoxy, and phenolic novolak epoxy compounds.

[0037] The novolak epoxy compound may be contained in an amount of 10 to 40 parts by weight, for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 parts by weight, preferably 15 to 30 parts by weight, per 100 parts by weight of the curable compound. By the above range, the problem of haze generation in the adhesive composition is eliminated, and the problem of a decrease in peel strength due to suppression of penetration of other components in the adhesive composition into the adherend can be prevented.

[0038] The novolak epoxy compound may be contained in an amount of 20 to 60 parts by weight, for example, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60 parts by weight, preferably 40 to 60 parts by weight, per 100 parts by weight of the epoxy compound. By the above range, improvement of adhesive strength, reliability, and compatibility can be facilitated.

[0039] The aliphatic epoxy compound has the property of having a long induction period due to stabilization caused by hydrogen bonding with an adjacent oxygen atom after the epoxy ring is protonated. The aliphatic epoxy compound undergoes a post-reaction after a long induction period. Thereby, effects such as an increase in peel strength and improvement of reliability under high temperature and high humidity can be provided.

[0040] Aliphatic epoxy compounds delay the growth reaction of epoxy compounds due to the property that protons in the epoxy compounds are captured during cationic polymerization. In the present invention, based on the growth delay effect of aliphatic epoxy compounds, a COP film, which is a difficult-to-adhere polarizer protection film produced by solution casting and high stretching, cures with a hydrophobic difunctional (meth)acrylate described later. Therefore, before the fluidity of the hydrophobic difunctional (meth)acrylate disappears, sufficient time is provided for the hydrophobic difunctional (meth)acrylate to penetrate into the COP film, and then post-curing is performed to impart good adhesive strength and reliability.

[0041] In one embodiment, the hydrophobic (meth)acrylate compound may be contained in an amount of 50 to 200 parts by weight, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200 parts by weight, preferably 50 to 100 parts by weight, based on 100 parts by weight of the aliphatic epoxy compound. In the above range, excellent adhesive strength to the COP film produced by solution casting and high stretching can be achieved due to the interaction between the above-described aliphatic epoxy compound and the hydrophobic (meth)acrylate compound.

[0042] In addition, the aliphatic epoxy compound can increase the optical transparency of the adhesive composition for a polarizing plate containing a novolac epoxy compound and a (meth)acrylate compound described later, and can increase the compatibility of the adhesive composition. In one embodiment, the adhesive composition may have a haze (for example, measured in the visible light region) of 1% or less, for example, 0 to 1%.

[0043] The aliphatic epoxy compound may contain one or more of a monoglycidyl ether compound having a linear alkyl chain with 4 or more carbon atoms, 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. These aliphatic epoxy compounds can more easily achieve the effects of the present invention in the adhesive composition of the present invention.

[0044] The monoglycidyl ether compound having a linear alkyl chain with 4 or more carbon atoms can have a linear or branched alkyl chain with 4 or more carbon atoms, preferably 4 to 10, more preferably 4 to 6 carbon atoms. For example, the monoglycidyl ether compound may include butyl monoglycidyl ether including n-butyl monoglycidyl ether, 2-ethylhexyl monoglycidyl ether, and the like.

[0045] Since the diglycidyl ether compound having a linear alkylene chain with 4 or more carbon atoms provides a reaction delay effect, the effects of the present invention can be more easily realized.

[0046] The diglycidyl ether compound having a linear alkylene chain with 4 or more carbon atoms can have a linear or branched alkylene chain with 4 or more carbon atoms, preferably 4 to 10, more preferably 4 to 6 carbon atoms. For example, the diglycidyl ether compound may be one or more 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 4 to 6 carbon atoms, and may be one or more of 1,4-butanediol diglycidyl ether and 1,6-hexanediol diglycidyl ether.

[0047] A diglycidyl ether-based compound having two or more ethylene oxides or propylene oxides in the molecule can more easily achieve the effects of the present invention because two or more ethylene oxides or propylene oxides in the molecule have a reaction delay effect.

[0048] A diglycidyl ether-based compound having two or more ethylene oxides or propylene oxides in the molecule can preferably be a diglycidyl ether-based compound having 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.

[0049] Preferably, the aliphatic epoxy compound may include one or more of a monoglycidyl ether-based compound having a linear alkyl chain with 4 or more carbon atoms and a diglycidyl ether-based compound having a linear alkylene chain with 4 or more carbon atoms. In this case, the adhesive strength, reliability, and compatibility of the present invention can be further improved.

[0050] The aliphatic epoxy compound may be contained in an amount of 10 to 40 parts by weight, preferably 15 to 30 parts by weight, per 100 parts by weight of the curable compound. Within the above range, the above-described effects of the present invention are provided, the peeling force is increased by ensuring the initial reaction rate, and there is no problem of deterioration in the reliability of the polarizing plate due to a low glass transition temperature.

[0051] The aliphatic epoxy compound may be contained in an amount of 40 to 80 parts by weight, for example, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80 parts by weight, preferably 40 to 60 parts by weight, per 100 parts by weight of the epoxy compound. Within the above range, the adhesive strength, reliability, and compatibility can be easily improved.

[0052] In one embodiment, among 100 parts by weight of the epoxy compound, one or more of the alicyclic epoxy compound and the hydrogenated aromatic epoxy compound may be contained in an amount of 5 parts by weight or less, preferably 0 to 5 parts by weight, and may even be 0 part by weight.

[0053] (Meth)acrylate compound (Meth)acrylate compounds may be contained in an amount of 30 to 70 parts by weight per 100 parts by weight of the curable compound. In the above range, the adhesive strength, reliability, and compatibility can be easily improved. Preferably, the (meth)acrylate compounds may be contained in an amount of 40 to 60 parts by weight.

[0054] (Meth)acrylate compounds include a mixture of hydrophilic (meth)acrylate compounds, hydrophobic (meth)acrylate compounds, and vinyl group-containing (meth)acrylate compounds.

[0055] In one embodiment, the total of the vinyl group-containing (meth)acrylate compound, the hydrophilic (meth)acrylate compound, and the hydrophobic (meth)acrylate compound in 100 parts by weight of the (meth)acrylate compound is 95 parts by weight or more, for example, 95, 96, 97, 98, 99, 100 parts by weight, preferably 99 to 100 parts by weight, and more preferably 100 parts by weight. In this range, the improvement of the adhesive strength, reliability, and compatibility can be facilitated.

[0056] The hydrophilic (meth)acrylate compound exhibits advantageous performance for the adhesion between the polarizer and the polarizer protection film, particularly a hydrophilic base material such as a TAC film, and has a high affinity for the PET film treated with the primer, so it can provide an advantageous effect for adhesion.

[0057] In one embodiment, the hydrophilic (meth)acrylate compound may be a bifunctional (meth)acrylate having two (meth)acrylate groups as a bifunctional (meth)acrylate and having an alkylene oxide group between the (meth)acrylate groups. The above compound exhibits advantageous adhesion performance to a hydrophilic adherend having a hydroxyl group such as a polarizer, and also has a high affinity for a polyester film treated with a primer, and thus can contribute to an increase in adhesive strength. The alkylene oxide group may be ethylene oxide or propylene oxide.

[0058] One or more, preferably two or more, more preferably two to five alkylene oxide groups may be contained in the above compound. With the above range, the effects of the present invention can be more easily realized. For example, the hydrophilic (meth)acrylate 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.

[0059] The hydrophilic (meth)acrylate compound may be contained in an amount of 5 to 30 parts by weight, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 parts by weight, preferably 10 to 25 parts by weight, per 100 parts by weight of the curable compound. In the above range, there are no problems such as the reaction rate being too high and interfacial peeling due to high shrinkage force.

[0060] The hydrophilic (meth)acrylate compound may be contained in an amount of 10 to 80 parts by weight, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 parts by weight, preferably 10 to 60 parts by weight, 10 to 50 parts by weight, 20 to 40 parts by weight, per 100 parts by weight of the (meth)acrylate compound. In the above range, adhesion, reliability, and compatibility can be more easily improved.

[0061] Since the hydrophobic (meth)acrylate compound has a low polarity, it has very excellent penetration characteristics with respect to a polarizer protection film having a low polarity, particularly a COP-based film produced by solution casting and high stretching, and can contribute to the adhesion to the protection film and the increase in adhesion after exposure to high temperature and high humidity.

[0062] The hydrophobic (meth)acrylate compound can have two (meth)acrylate groups as a bifunctional (meth)acrylate compound. The hydrophobic monofunctional (meth)acrylate compound having one (meth)acrylate group has smooth penetration with respect to a polarizer protection film, particularly a COP-based film, but the increase in the degree of crosslinking is limited, and it is not easy to exhibit the effect of improving the peel strength.

[0063] The hydrophobic (meth)acrylate compound can have an unsubstituted linear alkylene group having 6 or more carbon atoms between the (meth)acrylate groups. A linear alkylene group having less than 6 carbon atoms increases the polarity of the compound, making it difficult to penetrate a polarizer protection film, particularly a COP-based film. As a result, it is not easy to exhibit the effect of improving the peel strength.

[0064] The hydrophobic (meth)acrylate compound may not have an ether functional group (alkylene oxide group) such as ethylene oxide or propylene oxide.

[0065] In one embodiment, the hydrophobic (meth)acrylate compound has an unsubstituted linear or branched alkylene group having 6 or more carbon atoms, for example, 6 to 15 carbon atoms, and includes, for example, hexanediol di(meth)acrylate such as 1,6 - hexanediol di(meth)acrylate, octanediol di(meth)acrylate such as 1,8 - octanediol di(meth)acrylate, nonanediol di(meth)acrylate such as 1,9 - nonanediol di(meth)acrylate, and decanediol di(meth)acrylate such as 1,10 - decanediol di(meth)acrylate, and may be one or more of them. Preferably, the hydrophobic (meth)acrylate compound may be one or more of 1,6 - hexanediol di(meth)acrylate and 1,9 - nonanediol di(meth)acrylate.

[0066] The hydrophobic (meth)acrylate compound may be contained in an amount of 10 to 40 parts by weight, for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 parts by weight, preferably 20 to 30 parts by weight, per 100 parts by weight of the curable compound. Within the above range, both the adhesion to a hydrophobic polarizer protection film such as a COP - based film and the adhesion to a hydrophilic polarizer and a hydrophilic polarizer protection film can be improved.

[0067] The hydrophobic (meth)acrylate compound may be contained in an amount of 10 to 80 parts by weight, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 parts by weight, preferably 10 to 60 parts by weight, 10 to 50 parts by weight, 20 to 40 parts by weight, per 100 parts by weight of the (meth)acrylate compound. Within the above range, the adhesion, reliability, and compatibility can be easily improved.

[0068] The vinyl group-containing (meth)acrylate compound has both a (meth)acrylate group and a vinyl group. Therefore, in addition to the physical twist between the epoxy compound and the (meth)acrylate compound, there is a chemical covalent bond between the epoxy compound and the (meth)acrylate compound. As a result, the movement between molecules is suppressed even under high temperature and high humidity, the adhesive strength after being exposed to high temperature and high humidity and the discoloration of the polarizer after being exposed to high temperature and high humidity are suppressed, and as a result, the effect of enhancing the reliability can be provided.

[0069] The vinyl group-containing (meth)acrylate compound is contained in an amount of 10 to 40 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 adhesive strength of the present invention as described above and the effect of suppressing the discoloration of the polarizer may be reduced. When the amount of the vinyl group-containing (meth)acrylate compound exceeds 40 parts by weight, the interfacial peeling contribution effect with other components in the adhesive composition may be reduced, the hydrophobicity of the adhesive composition may increase, and the binding force with the polarizer which is a hydrophilic base material may be reduced.

[0070] 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 combines with a hydrophilic (meth)acrylate compound and a hydrophobic (meth)acrylate compound, and the vinyl group combines with a mixture of a novolak epoxy compound and an aliphatic epoxy compound, whereby the effect of the present invention can be more easily provided.

[0071] In one embodiment, the vinyl group-containing (meth)acrylate compound is a monofunctional (meth)acrylate compound and may also be a monofunctional vinyl compound. The vinyl group-containing (meth)acrylate compound is different from the hydrophilic (meth)acrylate compound and the hydrophobic (meth)acrylate compound.

[0072] In one embodiment, the vinyl group-containing (meth)acrylate compound may 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 provide an effect of enhancing the compatibility between the above-described aliphatic epoxy ether compound and the (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.

[0073] In one embodiment, the vinyl group-containing (meth)acrylate compound may be a compound represented by the following Chemical Formula 2.

[0074] [Chemical Formula 2] CH2=CH-(-O-CH2-CH2-)n-O-(C=O)-CHR=CH2

[0075] In Chemical Formula 2, R is hydrogen or a methyl group, n is an integer from 1 to 5.

[0076] For example, the vinyl group-containing (meth)acrylate compound may be 2-(2-vinyloxyethoxy)ethyl (meth)acrylate or the like.

[0077] The vinyl group-containing (meth)acrylate compound may be contained in an amount of 10 to 80 parts by weight, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 parts by weight, preferably 10 to 60 parts by weight, 20 to 60 parts by weight, based on 100 parts by weight of the total of the (meth)acrylate compounds, preferably the total of the hydrophilic (meth)acrylate compounds, the hydrophobic (meth)acrylate compounds, and the vinyl group-containing (meth)acrylate compounds. Within the above range, the adhesive strength, reliability, and compatibility can be more easily improved.

[0078] The photoinitiator includes a mixture of a photo radical initiator and a photo cationic initiator.

[0079] The photoinitiator may be contained in an amount of 1 to 15 parts by weight, preferably 1 to 10 parts by weight, based on 100 parts by weight of the curable compound. Within the above range, there is no problem that the adhesive composition remains uncured, and there is no problem that the light transmittance of the adhesive layer decreases due to the remaining amount when an excessive amount is used.

[0080] The photo radical initiator may be a cyclohexyl phenyl ketone-based compound, a thioxanthone-based compound, or the like.

[0081] 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, based on 100 parts by weight of the curable compound. Within the above range, the adhesive composition can be sufficiently cured, and there are no problems such as a decrease in adhesive strength and bleed-out of the photo radical initiator.

[0082] The photo cation initiator may contain an onium salt of a cation that is an onium ion and an anion. Specific examples of the onium ion include diaryl iodonium 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+), and the like. Specific examples of the anion include tetrafluoroborate (BF4 - )), hexafluorophosphate (PF6 - )), hexafluoroantimonate (SbF6 - )), hexafluoro-arsenate (AsF6- ) hexa-chloro-antimonate (SbCl6 - ) and the like.

[0083] 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. In the above range, the adhesive composition can be sufficiently cured, and there are no problems such as a decrease in adhesive strength and bleed-out of the photo cationic initiator.

[0084] The adhesive composition can be produced by mixing a curable compound and a photo initiator. The adhesive composition may be a solvent-free type without a solvent, or may further contain a solvent to enhance coatability.

[0085] The adhesive composition may further contain an antioxidant, an ultraviolet absorber, an ionic conductive agent, a conductive additive such as conductive metal oxide fine particles, a light diffusion additive, a viscosity modifier, etc. within a range that does not impair the effects of the present invention.

[0086] The cured product of the adhesive composition may have a glass transition temperature of 30 to 150°C, preferably 50 to 120°C. In the above range, it can show the effect of preventing layer separation cracking during cutting and improving thermal shock reliability.

[0087] 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 overlapped by the adhesive layer, and the adhesive layer includes a cured product of the adhesive composition of the present invention.

[0088] Referring to FIG. 1, the polarizing plate may include a polarizer 10, an adhesive layer 20 sequentially formed on one surface of the polarizer 10, a lower polarizer protective film 30, and an upper polarizer protective layer 40 laminated on the other surface of the polarizer 10.

[0089] Polarizer The polarizer 10 can polarize external light or internal light.

[0090] The polarizer 10 may 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.

[0091] The polarizer 10 may have a thickness of 1 to 50 μm. By adopting the above range, the polarizer 10 can be used in an optical display device after being modified.

[0092] 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.

[0093] The adhesive layer 20 may be formed of the above-described composition for the adhesive layer. Specifically, after applying the composition for the adhesive layer to one surface of the polarizer or the lower polarizer protection film with a predetermined thickness, it may be formed by photocuring. Photocuring refers to curing the composition by UV irradiation, and it may be performed while adjusting the light amount, wavelength, etc. according to the coating thickness of the composition for the adhesive.

[0094] The adhesive layer 20 may have a thickness of 0.01 to 10 μm, preferably 1 to 5 μm. Within the above range, the adhesive force between the polarizer and the polarizer protection film can be ensured.

[0095] Lower polarizer protection film 30 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 further effects to the polarizing plate.

[0096] In one embodiment, the lower polarizer protection film can be an ordinary polarizer protection film known to those skilled in the art, for example, the polarizer protection film described in the upper polarizer protection layer below can be applied.

[0097] In other embodiments, in the present invention, a COP-based film manufactured by solution casting and high stretching can be used as the lower polarizer protection film as the difficult-to-adhere protection film.

[0098] The COP-based film manufactured by solution casting and high stretching is excellent in that it provides an effect of increasing the curability of the photocuring adhesive due to an increase in light transmittance when applied to a polarizing plate.

[0099] Upper polarizer protection layer The upper polarizer protection layer 40 is formed on the upper surface of the polarizer and can support the polarizer. The upper polarizer protection layer may include one or more of an optically transparent protective film and a protective coating layer.

[0100] When the upper polarizer protection layer is of the protective film type, it may 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 includes 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), polyethersulfone 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.

[0101] When the upper polarizer protective layer is of the protective coating layer type, good adhesion, transparency, mechanical strength, thermal stability, moisture barrier property, and durability to the polarizer can be enhanced. In one embodiment, 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.

[0102] The active energy ray curable compound may 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.

[0103] The thickness of the upper polarizer protective layer 40 may be 5 μm to 200 μm, specifically 30 μm to 120 μm, and may be 50 μm to 100 μm in the case of the protective film type, or may be 5 μm to 50 μm in the case of the protective coating layer type. By adopting the above range, the upper polarizer protective layer 40 can be used in the light-emitting display device.

[0104] 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. can be further formed on the upper surface of the upper polarizer protective layer 40.

[0105] 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, or a pressure-sensitive adhesive.

[0106] Although not shown in FIG. 1, the polarizing plate may further include a polarizer protective film, an anti-reflection film, a retardation film (liquid crystal layer or non-liquid crystal layer), etc. that are usually used in polarizing plates.

[0107] 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, a liquid crystal display device, or the like.

Example

[0108] Hereinafter, based on the preferred embodiments of the present invention, the configuration and operation of the present invention will be described in more detail. However, this is presented as a preferred example of the present invention, and in no sense should it be construed that the present invention is limited thereby.

[0109] Example 1 (1) Preparation of an adhesive composition for a photocurable polarizing plate As the epoxy compound, 25 parts by weight of a novolak epoxy compound (O-cresol novolak epoxy compound, KUKDO Chemical Co., Ltd.) and 25 parts by weight of an aliphatic epoxy compound (1,4-butanediol diglycidyl ether, KUKDO Chemical Co., Ltd.) were used. As the (meth)acrylate compound, 20 parts by weight of dipropylene glycol diacrylate (Miwon Co., Ltd.), 20 parts by weight of 1,9-nonanediol diacrylate (Keiei Co., Ltd.), and 10 parts by weight of 2-(2-vinyloxyethoxy)ethyl acrylate (Nippon Shokubai Co., Ltd.) were used.

[0110] 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, BASF Co., Ltd.) and 6 parts by weight of a photoacid generator (CPI-100P, San-Apro Co., Ltd.) were added to the mixture and mixed to prepare a solvent-free photocurable adhesive composition for a polarizing plate.

[0111] (2) Fabrication of a polarizing plate A polyvinyl alcohol film (PS#60, Kuraray, saponification degree: 99.5%, thickness before stretching: 60 μm) was immersed in a 0.3% iodine aqueous solution for dyeing, and then stretched in the machine direction (MD) with an MD uniaxial stretching ratio of 6 times. The stretched polyvinyl alcohol film was immersed in an aqueous solution of 3% boric acid and 2% potassium iodide for hue correction, and dried at 50 °C for 4 minutes to produce a polarizer (light transmittance: 45%, thickness: 7 μm).

[0112] As the upper polarizer protective film, a polyethylene terephthalate (PET) film (thickness: 80 μm, TD1-axis stretching, Toyobo) 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 cycloolefin polymer (COP) film (manufactured by solution casting and high stretching, thickness: 37 μm, Konica) or a triacetyl cellulose-based film (Zero TAC, thickness: 40 μm) was used, and the surface to which the adhesive composition was applied was treated with corona treatment at 100 dose.

[0113] The 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 the photocurable adhesive composition prepared was applied to the surface treated with corona treatment of the lower polarizer protective film to a predetermined thickness. After the produced polarizers were overlapped respectively, from the lower polarizer protective film side, ultraviolet irradiation was carried out under the conditions of 400 mW / cm 2 , 1000 mJ / cm 2 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 22 - 25 °C and a relative humidity of 20 - 60%.

[0114] Examples 2 to 6 In the preparation of the solvent-free photocurable adhesive composition for a polarizing plate of Example 1, the composition and the polarizing plate were prepared and produced in the same manner as in Example 1, except that the content and / or type of each component was changed as shown in Table 1 below. In Table 1 below, "-" means that the component is not contained.

[0115] Comparative Examples 1 to 7 In the preparation of the solvent-free photocurable adhesive composition for a polarizing plate of Example 1, the composition and the polarizing plate were produced in the same manner as in Example 1, except that the content and / or type of each component was changed as shown in Table 1 below.

[0116] The physical properties shown in Table 2 below were evaluated for the polarizing plates produced in the examples and comparative examples, and the results are shown in Table 2 below.

[0117] (1) Compatibility of the adhesive composition After preparing the adhesive compositions produced in the examples and comparative examples, visual observation was carried out and evaluation was made according to the following criteria. ○: The composition is transparent. X: There is layer separation or haze in the composition.

[0118] (2) Adhesive strength For the polarizing plates produced in the examples and comparative examples, a double-sided foam adhesive tape (VHS, 3M) was attached to the lower polarizer protection film side, and 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 overlaid on a non-alkali glass surface (thickness: 0.5t) and left at room temperature for 30 minutes to prepare a test piece.

[0119] In the prepared test piece, a cutter blade was obliquely inserted between the polarizer and the lower polarizer protection film to attempt to slightly separate the space between the polarizer and the lower polarizer protection film. The adhesiveness was evaluated according to the following criteria. ○: The lower protection film and the polarizer are not separated at all △: The lower protection film and the polarizer are intermittently separated. X: The lower protective film and the polarizer are easily separated.

[0120] (3) High-temperature and high-humidity reliability Polarizers were fabricated in the examples and comparative examples such that the absorption axis direction of the polarizer was at a 45° angle, cut into a size of a 50 mm x 50 mm square, and attached to a glass plate via an acrylic adhesive layer to prepare test pieces. After the test pieces were placed in a chamber at 60°C and 95% relative humidity and left for 500 hours, they were taken out. Then, as shown in Figure 2, the length 5 at which iodine color fading occurred in test piece 1 was measured in the diagonal direction from the four corners of the test piece, and the level was 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

[0121]

Table 1

[0122] A) o-Cresol novolac epoxy-based compound (KUKDO Chemical Co., Ltd.) B) Phenol novolac epoxy-based compound (KUKDO Chemical Co., Ltd.) C) 1,4-Butanediol diglycidyl ether (KUKDO Chemical Co., Ltd.) D) Butyl monoglycidyl ether (Daicel Corporation) E) Dipropylene glycol diacrylate (Miwon Co., Ltd.) F) Triethylene glycol diacrylate (Miwon Co., Ltd.) G) 1,9-Nonanediol diacrylate (Keiei Co., Ltd.) H) 1,6-Hexanediol diacrylate (Miwon Co., Ltd.) I) 2-(2-Vinyloxyethoxy)ethyl acrylate (Nippon Shokubai Co., Ltd.)

[0123]

Table 2

[0124] As shown in Table 2, the adhesive composition for a polarizing plate of the present invention is excellent in optical transparency in a crude liquid state, has no haze, is excellent in adhesive strength between a polarizer and a polarizer protection film, prevents decolorization of the polarizer after high temperature and high humidity, and provides an adhesive layer with excellent reliability.

[0125] On the other hand, the adhesive composition of the comparative example that does not satisfy the configuration of the adhesive composition of the present invention could not provide any of the effects of the present invention.

[0126] Simple modifications and changes of the present invention can be easily implemented by those having ordinary knowledge in this field, and all such modifications and changes are considered to be included in the scope of the present invention.

Explanation of Reference Numerals

[0127] 10: Polarizer, 20: Adhesive layer, 30: Lower polarizer protection film, 40: Upper polarizer protection layer

Claims

1. comprising a curable compound and a photoinitiator, The curable compound includes an epoxy compound and a (meth)acrylate compound, The epoxy-based compound includes a mixture of a novolac epoxy-based compound and an aliphatic epoxy-based compound, The (meth)acrylate compound includes a mixture of a hydrophilic (meth)acrylate compound, a hydrophobic (meth)acrylate compound, and a vinyl group-containing (meth)acrylate compound; The vinyl group-containing (meth)acrylate compound is contained in an amount of 10 to 40 parts by weight based on 100 parts by weight of the curable compound.

2. The adhesive composition for polarizing plates according to claim 1 , wherein the total content of the novolac epoxy compound and the aliphatic epoxy compound is 95 parts by weight or more based on 100 parts by weight of the epoxy compound.

3. 2. The adhesive composition for polarizing plates according to claim 1, wherein the novolac epoxy compound is contained in an amount of 10 to 40 parts by weight based on 100 parts by weight of the curable compound.

4. 2. The adhesive composition for polarizing plates according to claim 1, wherein the aliphatic epoxy compound comprises at least one of a monoglycidyl ether compound having a linear alkyl chain having 4 or more carbon atoms, a diglycidyl ether compound having a linear alkylene chain having 4 or more carbon atoms, and a diglycidyl ether compound having two or more ethylene oxides or propylene oxides in the molecule.

5. 2. The adhesive composition for polarizing plates according to claim 1, wherein the aliphatic epoxy compound is contained in an amount of 10 to 40 parts by weight based on 100 parts by weight of the curable compound.

6. The adhesive composition for polarizing plates according to claim 1 , wherein the hydrophobic (meth)acrylate compound comprises a bifunctional (meth)acrylate compound having an unsubstituted linear alkylene group having 6 or more carbon atoms.

7. 2. The adhesive composition for polarizing plates according to claim 1, wherein the hydrophobic (meth)acrylate compound is contained in an amount of 10 to 40 parts by weight based on 100 parts by weight of the curable compound.

8. 2. The adhesive composition for polarizing plates according to claim 1, wherein the hydrophobic (meth)acrylate compound is contained in an amount of 50 to 200 parts by weight based on 100 parts by weight of the aliphatic epoxy compound.

9. The adhesive composition for polarizing plates according to claim 1 , wherein the hydrophilic (meth)acrylate compound comprises a bifunctional (meth)acrylate compound having an alkylene oxide group between (meth)acrylate groups.

10. The vinyl group-containing (meth)acrylate compound is a compound represented by the following chemical formula 2: [Chemical formula 2] CH ２ =CH-(-O-CH ２ -CH ２ -)n-O-(C=O)-CHR=CH ２ In the above Chemical Formula 2, R is hydrogen or a methyl group; 2. The adhesive composition for polarizing plates according to claim 1, wherein n is an integer of 1 to 5.

11. 2. The adhesive composition for polarizing plates according to claim 1, wherein a total amount of the vinyl group-containing (meth)acrylate compound, the hydrophilic (meth)acrylate compound, and the hydrophobic (meth)acrylate compound is 95 parts by weight or more per 100 parts by weight of the (meth)acrylate compound.

12. 2 . The adhesive composition for polarizing plates according to claim 1 , wherein the total amount of the epoxy compound and the (meth)acrylate compound is 95 parts by weight or more based on 100 parts by weight of the curable compound.

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

14. The polarizer includes a protective film laminated on a lower surface of the polarizer, A polarizing plate, comprising: the polarizer and the protective film laminated together with an adhesive layer; and the adhesive layer comprising a cured product of the adhesive composition for polarizing plates according to claim 1 .

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

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