TW201819577A - Optically clear adhesive composition, and optically clear adhesive film comprising the same, and flat panel display - Google Patents

Abstract

This invention relates to an optically clear adhesive composition, an optically clear adhesive film including the same, and a flat panel display device, the optically clear adhesive composition including a photocurable (meth)acrylate copolymer, an acrylate copolymer, and a photopolymerization initiator, wherein the photocurable (meth)acrylate copolymer includes, based on the total weight of constituents of the copolymer, 95~99.9 wt% of a hydroxyl-group-containing acrylic copolymer and 0.1~5 wt% of an isocyanate-group-containing (meth)acrylate monomer, the hydroxyl-group-containing acrylic copolymer and the isocyanate-group-containing (meth)acrylate monomer form a urethane bond, the hydroxyl-group-containing acrylic copolymer includes, based on the total weight of monomers of the copolymer, 80~98 wt% of a C4-C12 linear or branched alkyl acrylate monomer having a glass transition temperature of -70~-50 DEG C and 2~20 wt% of a hydroxy-C2-C6 linear or branched alkyl acrylate monomer, and the photocurable (meth)acrylate copolymer has a weight average molecular weight of 500,000 to 2,000,000, and the acrylate copolymer includes, based on the total weight of monomers of the copolymer, 80~95 wt% of a C4-C12 linear or branched alkyl acrylate monomer and 5~20 wt% of an adhesion-promoter-containing polymerizable monomer, does not include a photo-crosslinkable functional group, and has a weight average molecular weight of 10,000 to 100,000, the photocurable (meth)acrylate copolymer and the acrylate copolymer being included at a weight ratio ranging from 95:5 to 70:30.

Description

 Optically transparent adhesive composition, optically transparent adhesive film including the same, and flat panel display  

The present invention relates to an optically clear adhesive composition, an optically transparent adhesive film comprising the composition, and a flat panel display.

Examples of the flat panel display include a liquid crystal display (LCD), a plasma display (PDP), an organic electric field light emitting display (OLED), and the like.

This flat panel display includes a display panel and an optical film. Examples of the optical film include a polarizing film, a retardation film, an anti-glare film, an optical viewing angle compensation film, a brightness enhancement film, and the like. An optically clear adhesive (OCA) is used when the optical films are stacked on each other or the optical film is attached to the display panel. Thus, optically clear adhesives (OCAs) must not only exhibit typical optical properties, but also have excellent resistance to moist heat, heat and adhesion.

In particular, the recent fierce competition for developing flexible displays is underway. Since the flexible display is bendable, crimpable or foldable, the display panel and the optical film contained in the device are subject to bending stress. Therefore, there is a need to further improve various properties of optically clear adhesives (OCAs) for flexible displays.

For example, optically clear adhesives (OCAs) for flexible displays must have very foldable properties to enable the device to be freely folded. Further, in consideration of the case where the flexible display is used for a long period of time at an outdoor low temperature, the folding property at a low temperature should be superior.

Moreover, optically clear adhesives (OCAs) for flexible displays must have further enhanced resistance to moist heat. This is because the flexible display is repeatedly subjected to a large number of folding and unfolding processes during its use, so the possibility of moisture passing through the folded and unfolded portions may increase.

Moreover, when the flexible display is bent, curled, or folded, the display panel and the optical film contained in the device are subjected to bending stress. Therefore, since it is easy to separate the stacked display panel and the optical film from each other, higher adhesion and higher durability are required.

However, conventional optically clear adhesives (OCAs) have hitherto not adequately provide the above-described properties required for flexible displays.

 [citation list]    [Patent Literature]  

(Patent Document 1) Korean Patent Application No. 10-2016-0085759

Accordingly, in view of the problems encountered in the prior art, the present invention is directed to an optical transparent adhesive (OCA) composition capable of sufficiently satisfying the foldability, moist heat resistance, heat resistance, and the like required for a flexible display. And adhesion.

Additionally, the present invention is directed to an optically clear adhesive film and flat panel display comprising an optically clear adhesive (OCA) composition.

Accordingly, the present invention provides an optically clear adhesive composition comprising a photocurable (meth) acrylate copolymer, an acrylate copolymer, and a photopolymerization initiator, wherein the photocurable (methyl) The acrylate copolymer comprises 95 to 99.9% by weight of the hydroxyl group-containing acrylic copolymer and 0.1 to 5% by weight of the isocyanate group-containing (meth) acrylate, based on the total weight of the copolymer component. a monomer, the hydroxyl group-containing acrylic copolymer and the isocyanate group-containing (meth) acrylate monomer form a urethane bond, and the hydroxyl group-containing acrylic copolymer is a copolymer monomer The C ₄ -C ₁₂ linear or branched alkyl acrylate monomer having a glass transition temperature of from -70 to -50 ° C and from 2 to 20 wt%, based on the total weight, is from 80 to 98 wt% a hydroxy-C ₂ -C ₆ linear or branched alkyl acrylate monomer, and the photocurable (meth) acrylate copolymer has a weight average molecular weight of 500,000 to 2,000,000; and, the acrylate copolymer Containing 80% based on the total weight of the monomer of the copolymer 95wt% of C ₄ -C ₁₂ alkyl acrylate monomer straight or branched chains and containing 5 to 20wt% of the adhesion promoting agent (adhesion-promoter) of the polymerizable monomer containing a photo-crosslinkable functional group And the weight average molecular weight is 10,000 to 100,000, and the photocurable (meth) acrylate copolymer and the acrylate copolymer are included in a weight ratio range of 95:5 to 70:30.

Further, the present invention provides an optically transparent adhesive film formed by coating a transfer film with the optically clear adhesive composition of the present invention.

Additionally, the present invention provides a flat panel display comprising an adhesive layer formed from the optically clear adhesive composition of the present invention.

According to the present invention, an optically clear adhesive (OCA) composition and an optically transparent adhesive film can exhibit sufficient foldability, moist heat resistance, heat resistance and adhesion required for a flat panel display and a flexible display, and thus can be imparted Excellent durability.

According to the present invention, a flat panel display manufactured using the above adhesive composition exhibits excellent foldability, moist heat resistance, heat resistance, adhesion, and durability.

The present invention relates to an optically clear adhesive composition comprising a photocurable (meth) acrylate copolymer, an acrylate copolymer, and a photopolymerization initiator.

Here, the photocurable (meth) acrylate copolymer comprises 95 to 99.9% by weight of the hydroxyl group-containing acrylic copolymer and 0.1 to 5% by weight based on the total weight of the copolymer component. a (meth) acrylate monomer containing an isocyanate group, the hydroxyl group-containing acrylic copolymer and the isocyanate group-containing (meth) acrylate monomer forming a urethane bond, the hydroxyl group-containing group The acrylic copolymer has a C ₄ -C ₁₂ linear or branched chain having a glass transition temperature of -70 to -50 ° C of 80 to 98 wt% based on the total weight of the copolymer monomers. An alkyl acrylate monomer and 2 to 20% by weight of a hydroxy-C ₂ -C ₆ linear or branched alkyl acrylate monomer, and the weight average molecular weight of the photocurable (meth) acrylate copolymer It is 500,000 to 2,000,000. Further, the acrylate copolymer comprises 80 to 95% by weight, based on the total weight of the monomers of the copolymer, of C ₄ -C ₁₂ linear or branched alkyl acrylate monomer and 5 to 20% by weight. The polymerizable monomer of the adhesion promoter, which does not contain a photocrosslinkable functional group, and has a weight average molecular weight of 10,000 to 100,000. Moreover, the photocurable (meth) acrylate copolymer and the acrylate copolymer are included in a weight ratio range of 95:5 to 70:30.

In the optically clear adhesive composition of the present invention, the photocurable (meth) acrylate copolymer has a C ₄ - C ₁₂ linear or branched alkyl acrylate having a glass transition temperature of -70 to -50 ° C. The ester monomer, thus exhibiting excellent foldability, has high molecular weight and high crosslink density due to free radical crosslinking with the acryloyl functional group linked through the urethane bond, and thus can be expressed High heat resistance and durability. Further, a large amount of a hydroxy-C ₂ -C ₆ linear or branched alkyl acrylate monomer is contained, thereby obtaining high moist heat resistance and adhesion.

In the optically clear adhesive composition of the present invention, the acrylate copolymer has a low molecular weight and does not contain a photocrosslinkable functional group, and thus does not form crosslink even after a photocrosslinking reaction, thereby exhibiting Excellent foldability. However, in the case where a large amount of the low molecular weight acrylate copolymer is contained, the low molecular weight acrylate copolymer may bleed out from the interface after the formation of the adhesive layer, thereby deteriorating durability and adhesion. In order to solve these problems, a large amount of a highly polar polymerizable monomer containing an adhesion promoter is contained, thereby improving moist heat resistance and adhesion.

As used herein, the term "(meth)acrylate" means "acrylate" or "methacrylate."

The photocurable (meth) acrylate copolymer can be copolymerized by 80 to 98 parts by weight of a C ₄ -C ₁₂ linear or branched (meth)acrylic acid having a glass transition temperature of -70 to -50 ° C. An alkyl ester monomer and 2 to 20 parts by weight of a hydroxy-C ₂ -C ₆ linear or branched alkyl acrylate monomer to obtain an acrylate copolymer backbone to introduce a thermosetting functional group (hydroxyl group) Branching or terminating, then subjecting the main chain to a (meth) acrylate monomer containing an isocyanate group, and substituting the isocyanate group-containing (meth) acrylate monomer for thermal curing of the main chain under appropriate conditions At least a portion of a functional group (hydroxyl group).

The main chain can be prepared by a typical polymerization method such as solution polymerization, photopolymerization, bulk polymerization, suspension polymerization, or emulsion polymerization.

C ₄ -C ₁₂ linear or branched alkyl (meth)acrylate having a glass transition temperature of -70 to -50 ° C contained in a photopolymerizable (meth) acrylate copolymer in a polymerized form Examples of the monomer may include n-butyl acrylate, tert-butyl acrylate, second butyl acrylate, amyl acrylate, 2-ethyl butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, acrylic acid The octyl ester, and isodecyl acrylate, which may be used singly or in combination of two or more, is preferably at least one selected from the group consisting of n-butyl acrylate and 2-ethylhexyl acrylate.

If the glass transition temperature (Tg) of a C ₄ -C ₁₂ linear or branched alkyl acrylate monomer is lower than -70 ° C, its use is not economically feasible. On the other hand, if the glass transition temperature exceeds -50 ° C, the low-temperature folding property may be deteriorated.

Examples of the hydroxy-C ₂ -C ₆ linear or branched alkyl acrylate monomer contained in the photocurable (meth) acrylate copolymer in a polymerized form may comprise 2-hydroxyethyl acrylate, acrylic acid. 3-hydroxypropyl ester, 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate, and 6-hydroxyhexyl acrylate, etc., which may be used singly or in combination of two or more. The hydroxy-C ₂ -C ₆ linear or branched alkyl acrylate monomer contained in a polymerizable form in the photocurable (meth) acrylate copolymer is preferably selected from the group consisting of 2-hydroxyethyl acrylate and At least one monomer in 4-hydroxybutyl acrylate.

The structure of the photocurable (meth) acrylate copolymer can be represented by the following chemical formula A.

In Chemical Formula A, R ₁ is a C ₄ -C ₁₂ linear or branched alkyl group, R ₂ is a C ₁ -C ₁₀ linear or branched alkylene group, R ₃ is a hydrogen or a methyl group, and o is 2 to 2 A natural number of 6, and each of l, m, and n has a value determined depending on the numerical range of the above monomer.

The hydroxyl group-containing acrylic copolymer preferably has 80 to 98% by weight of a C ₄ -C ₁₂ linear or branched alkyl acrylate monomer having a glass transition temperature (Tg) of -70 to -50 ° C and 2 to 20 wt% % hydroxy-C ₂ -C ₆ linear or branched alkyl acrylate monomer. If the amount of the hydroxy-C ₂ -C ₆ linear or branched alkyl acrylate monomer is less than 2 parts by weight, the amount of the hydroxyl group as a hydrophilic group in the adhesive may be reduced, and thus the adhesive layer may not The moisture is captured, but may be discharged to the interface, undesirably deteriorating the adhesion under moist heat and humidity conditions, and interface delamination may undesirably occur. On the other hand, if the amount exceeds 20 parts by weight, the adhesive may excessively absorb moisture, so the volume of the adhesive may increase, and the adhesion may be lowered, undesirably causing interfacial delamination and foaming.

The photocurable (meth) acrylate copolymer may further comprise additional copolymerizable monomers and are capable of being polymerized in the art. The kind of the other copolymerizable monomer is not particularly limited, and for example, may include a nitrogen-containing monomer such as (meth)acrylonitrile, (meth)acrylamide, N-methyl(meth)acrylamide, or N. - Butoxymethyl (meth) acrylamide; styrenic monomers such as styrene or methyl styrene; glycidyl (meth)acrylate; and vinyl carboxylates such as vinyl acetate.

When another copolymerizable monomer is contained, the amount thereof is preferably adjusted to 20 parts by weight or less based on 100 parts by weight based on the total of the above monomers in consideration of flexibility and peel strength.

The weight average molecular weight of the photocurable (meth) acrylate copolymer refers to a value measured by GPC (Gel Permeation Chromatography) using a polystyrene standard.

The isocyanate group-containing (meth) acrylate monomer may, for example, be an isocyanate group-C ₁ -C ₁₀ linear or branched alkyl (meth) acrylate. Here, the C ₁ -C ₁₀ linear or branched alkyl group may include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, t-butyl, pentyl. , hexyl, heptyl, octyl, 2-ethylhexyl, and fluorenyl. Among the above, ethyl or propyl is preferably used.

For example, the isocyanate group-containing (meth) acrylate monomer may be a compound of the following chemical formula B.

In Chemical Formula B, R is hydrogen or methyl, and n is an integer of 1 to 10.

The isocyanate group-containing (meth) acrylate monomer may be a compound of the formula B wherein R is a methyl group and n is 2, that is, 2-isocyanatoethyl methacrylate.

The isocyanate group-containing (meth) acrylate monomer may be used in an amount of from 0.1 to 5.0% by weight based on the total mass of the photocurable (meth) acrylate copolymer component. If the amount of the isocyanate group-containing (meth) acrylate monomer is less than 0.1% by weight, the cohesive force and heat resistance of the adhesive composition may be lowered. On the other hand, if the amount thereof exceeds 5.0% by weight, the cohesive force of the adhesive may become too strong, and the foldability is undesirably deteriorated.

The polymerizable monomer containing an adhesion promoter contains a polymerizable monomer having a polar group or a reactive functional group.

The polymerizable single system containing an adhesion promoter is selected from the compound of the following Chemical Formula 1, the compound of the following Chemical Formula 2, the compound of the following Chemical Formula 3, the compound of the following Chemical Formula 4, the compound of the following Chemical Formula 5, the compound of the following Chemical Formula 6, and the following chemical formula. At least one of the group consisting of the compound of 7 and the compound of the following chemical formula 8:

In Chemical Formula 7, X is a conjugate base having a strong acid having a pKa of less than -3, and X may be selected from PF5, SbF6, methanesulfonate (OMs), tosylate (OTs), trifluoromethanesulfonic acid. One of a group consisting of salt (OTf), bis(fluorosulfonyl) quinone imine (FSI), and bis(trifluoromethylsulfonyl) quinone imine (TFSI).

Examples of the C ₄ -C ₁₂ linear or branched alkyl (meth) acrylate monomer contained in the acrylate copolymer in a polymerized form may include n-butyl acrylate and tert-butyl (meth) acrylate. , (butyl) (meth) acrylate, amyl (meth) acrylate, 2-ethyl butyl (meth) acrylate, 2-ethylhexyl acrylate, n-octyl (meth) acrylate, (A) Isooctyl acrylate, isodecyl (meth) acrylate or the like, which may be used singly or in combination of two or more, and is preferably selected from n-butyl acrylate and 2-ethyl acrylate At least one monomer in the ester.

The acrylate copolymer preferably comprises 80 to 95% by weight of a C ₄ -C ₁₂ linear or branched alkyl acrylate monomer and 5 to 20% by weight of an adhesion promoter-containing polymerizable monomer. If the amount of the adhesion-promoting polymerizable monomer is less than 5% by weight, it is difficult to solve the problem of low durability and low adhesion due to bleed out of the acrylate copolymer having a low molecular weight at the interface. On the other hand, if the amount exceeds 20% by weight, the adhesive layer has poor flexibility, and thus the foldability may be deteriorated.

If the weight average molecular weight of the acrylate copolymer is less than 10,000, bleed out may become severe, and thus durability may be deteriorated. On the other hand, if the weight average molecular weight exceeds 100,000, the degree of improvement in adhesion may become insufficient due to low bleeding.

In the optically clear adhesive composition, the photocurable (meth) acrylate copolymer and the acrylate copolymer are preferably included in a weight ratio range of from 95:5 to 70:30. Based on the total of 100 parts by weight of the photocurable (meth) acrylate copolymer and the acrylate copolymer, if the amount of the acrylate copolymer is less than 5 parts by weight, the degree of improvement in adhesion may be Become insufficient. On the other hand, based on the total amount of the photocurable (meth) acrylate copolymer and the acrylate copolymer of 100 parts by weight, if the amount of the acrylate copolymer exceeds 30 parts by weight, it may cause folding Poor sex.

The optically clear adhesive composition of the present invention contains a photopolymerization initiator to effectively induce a reaction of a polymerizable radical group. The photopolymerization initiator may be used in the polymerization of the hydroxyl group-containing acrylic copolymer or may be contained in the optically clear adhesive composition together with the photocurable (meth)acrylate copolymer.

The photopolymerization initiator is not particularly limited as long as it is conventional in the art, any photopolymerization initiator can be used. Examples of the initiator may include, for example, a benzoin-based initiator, a hydroxyketone-based initiator, an aminoketone-based initiator, and a phosphine oxide-based initiator, which are capable of generating a radical by UV irradiation to initiate photopolymerization. Typical starter.

If the amount of the photopolymerization initiator is too low, the effect of addition may become insignificant. On the other hand, if the amount thereof is too high, properties such as durability or uniformity of transparency may deteriorate. Therefore, the amount thereof can be appropriately determined.

The photopolymerization initiator is preferably contained in an amount of from 0.1 to 5 parts by weight, more preferably from 0.5 to 2, based on 100 parts by weight based on the total of the photocurable (meth) acrylate copolymer and the acrylate copolymer. Parts by weight.

The optically clear adhesive composition of the present invention may further comprise a multifunctional crosslinking agent. The multifunctional crosslinking agent is not particularly limited and may include those well known in the art. Specific examples thereof may include a thermosetting polyfunctional isocyanate crosslinking agent, a polyfunctional (meth) acrylate crosslinking agent, and the like.

The content of the polyfunctional crosslinking agent may be 0.02 to 5 parts by weight based on 100 parts by weight of the total of the photocurable (meth) acrylate copolymer and the acrylate copolymer.

The optically clear adhesive composition of the present invention may further comprise a decane coupling agent. The kind of the coupling agent is not particularly limited, and any coupling agent known in the field of preparing an adhesive can be used. Examples of the decane coupling agent include γ-cyclopropoxypropyltriethoxydecane, γ-cyclopropoxypropyltrimethoxydecane, γ-cyclopropoxypropylmethyldiethoxydecane, γ. - cyclopropoxypropyltriethoxydecane, 3-mercaptopropyltrimethoxydecane, vinyltrimethoxydecane, vinyltriethoxydecane, gamma-methacryloxypropyltrimethoxy Baseline, γ-methacryloxypropyltriethoxydecane, γ-aminopropyltrimethoxydecane, γ-aminopropyltriethoxydecane, and 3-isocyanatopropyl Triethoxy decane.

The content of the decane coupling agent is from 0.01 part by weight to 5 parts by weight, based on 100 parts by weight of the total of the photocurable (meth) acrylate copolymer and the acrylate copolymer, preferably from 0.01 part by weight to 1 Parts by weight.

The optically clear adhesive composition of the present invention may further include a tackifier to adjust the adhesive properties.

Furthermore, it may further comprise at least one additive selected from the group consisting of an epoxy resin, a curing agent, a UV stabilizer, an antioxidant, a colorant, a reinforcing agent, a filler, an antifoaming agent, a surfactant, and a plasticizer. One of the groups.

The optically clear adhesive composition of the present invention may further comprise a solvent. Any solvent conventionally known in the art can be used without limitation as long as it can dissolve the monomers and copolymers used in the optically clear adhesive composition.

Typical examples of the solvent may include ethyl acetate, methyl ethyl ketone, toluene, and acetonitrile.

The solvent may be contained in an amount of from 40 to 85 parts by weight based on 100 parts by weight of the total of the photocurable (meth) acrylate copolymer and the acrylate copolymer.

The optically clear adhesive composition of the present invention preferably has a viscosity of from 500 centipoise (cP) to 2,500 centipoise at 23 °C.

In addition to the above, the method of preparing the optically clear adhesive composition of the present invention can be carried out by any method generally known in the art. Here, a molecular weight controlling agent, a catalyst, or the like which is typical in the art can be used without limitation.

The coating method using the optically clear adhesive composition of the present invention is not particularly limited, and examples thereof may include typical methods such as bar coating, spin coating, comma coating, and gravure coating. During the coating process, it is necessary to control the functional groups involved in the adhesive composition involving the polyfunctional crosslinking agent, thereby preventing the crosslinking reaction from occurring to achieve uniform coating. Thereby, the crosslinking agent can form a crosslinked structure in the curing and aging process after the coating process, thereby increasing the adhesion property and the cuttability and the cohesive force of the adhesive.

Further, it is preferred to carry out a coating process after sufficiently removing volatile components or foaming components, such as reaction residues, from the adhesive composition. Thereby, it is possible to prevent the elastic modulus from being lowered due to the crosslinking density or the molecular weight of the adhesive being too low, and to prevent the internal scatter body from being formed at a high temperature due to an increase in the size of the bubble between the glass plate and the adhesive layer.

After the coating of the optically clear adhesive composition is formed, it is cured by light irradiation. Here, when UV irradiation is performed, a high pressure mercury lamp, an electrodeless lamp, or a xenon lamp can be used.

Before or after the irradiation, the reaction between the functional group of the crosslinking agent in the composition and the thermosetting functional group of the polymer may be induced, and an appropriate aging process may be carried out, and the conditions are not particularly limited as long as the crosslinking reaction is appropriate. Occurs.

The adhesive composition for an optical film according to the present invention can be used for stacking optical films such as a polarizing film, a retardation film, an anti-glare film, an optical viewing angle compensation film, or a brightness enhancement film, which can be stacked on each other, or an optical film or The laminate is attached to a target such as a display panel.

In particular, the adhesive composition for an optical film according to the present invention is preferably used for a flexible display.

Further, the present invention proposes an optically transparent adhesive film formed by coating a transfer film with the optically clear adhesive composition of the present invention.

As the transfer film for the optically transparent adhesive film, any film known in the art can be used without limitation. Further, in the method of producing an optically transparent adhesive film, any method known in the art can be carried out without limitation.

Further, the present invention proposes a flat panel display comprising an adhesive layer formed of the optically clear adhesive composition of the present invention.

Here, the flat panel display is preferably a flexible display.

The invention is illustrated by the following examples and comparative examples, which are merely intended to illustrate the invention, but the invention is not limited thereto, and various modifications and changes can be made.

Preparation Example 1-1: Preparation of Acrylate Copolymer A1

80 parts by weight of n-butyl acrylate (n-BA) and 20 parts by weight of 4-hydroxybutyl acrylate (4-HBA) were placed in a 1 liter reactor equipped with a condenser to promote nitrogen reflux Its temperature control. 120 parts by weight of ethyl acetate (EAc) solvent was added thereto, and the resulting reaction mixture was purged with nitrogen for 60 minutes to remove oxygen. Thereafter, the temperature was maintained at 70 ° C, and 0.5 part by weight of a reaction initiator AIBN (azobisisobutyronitrile) was added thereto, and reacted for 12 hours, thereby preparing an acrylate copolymer A1 having a weight average molecular weight of 1,200,000.

Preparation Example 1-2: Preparation of Acrylate Copolymer A2

An acrylate copolymer A2 having a weight average molecular weight of 1,280,000 was prepared using the same polymerization technique as in Preparation Example 1-1, except that 90 parts by weight of n-butyl acrylate (n-BA) and 10 parts by weight were used. 4-hydroxybutyl acrylate (4-HBA).

Preparation Example 1-3: Preparation of Acrylate Copolymer A3

An acrylate copolymer A3 having a weight average molecular weight of 1,390,000 was prepared using the same polymerization technique as in Preparation Example 1-1, except that 98 parts by weight of n-butyl acrylate (n-BA) and 2 parts by weight of acrylic acid were used. 4-hydroxybutyl ester (4-HBA).

Preparation Examples 1-4: Preparation of Acrylate Copolymer A4

An acrylate copolymer A4 having a weight average molecular weight of 1,450,000 was prepared using the same polymerization technique as in Preparation Example 1-1, except that 99.5 parts by weight of n-butyl acrylate (n-BA) and 0.5 part by weight of acrylic acid were used. 2-Hydroxyethyl ester (2-HEA).

Preparation Example 2-1: Preparation of photocurable (meth) acrylate copolymer B1

100 parts by weight of acrylate copolymer A1 solid content, 1 part by weight of 2-isocyanatoethyl methacrylate, and 0.1 part by weight of DBTDL (dibutyltin dilaurate) were placed in 1 liter equipped with a condenser In the reactor, to promote temperature control while refluxing with nitrogen. Subsequently, the reaction was carried out at 40 ° C under atmospheric pressure for 4 hours or more to obtain a photocurable (meth) acrylate copolymer B1.

Preparation Example 2-2: Preparation of photocurable (meth) acrylate copolymer B2

The photocurable (meth) acrylate copolymer B2 was prepared in the same manner as in the preparation of Example 2-1, except that the acrylate copolymer A2 was used.

Preparation Example 2-3: Preparation of photocurable (meth) acrylate copolymer B3

The photocurable (meth) acrylate copolymer B3 was prepared in the same manner as in the preparation of Example 2-1 except that the acrylate copolymer A3 was used.

Preparation Example 2-4: Preparation of photocurable (meth) acrylate copolymer B4

100 parts by weight of acrylate copolymer A4 solid content, 0.1 part by weight of 2-isocyanatoethyl methacrylate, and 0.1 part by weight of DBTDL (dibutyltin dilaurate) were placed in 1 liter equipped with a condenser In the reactor, to promote temperature control while refluxing with nitrogen. Subsequently, the reaction was carried out at 40 ° C under atmospheric pressure for 4 hours or more to obtain a photocurable (meth) acrylate copolymer B4.

Preparation Example 3-1: Preparation of Acrylate Copolymer C1

90.9 parts by weight of n-butyl acrylate (n-BA) and 9.1 parts by weight of the following Chemical Formula 2 monomer were placed in a 1 liter reactor equipped with a condenser to promote temperature control while refluxing with nitrogen. 120 parts by weight of ethyl acetate (EAc) solvent was added thereto, and the resulting reaction mixture was purged with nitrogen for 60 minutes to remove oxygen. Thereafter, the temperature was maintained at 70 ° C, and 0.5 part by weight of a reaction initiator AIBN (azobisisobutyronitrile) was added thereto, and reacted for 12 hours, thereby preparing an acrylate copolymer C1 having a weight average molecular weight of 55,000.

Preparation Example 3-2: Preparation of Acrylate Copolymer C2

An acrylate copolymer C2 having a weight average molecular weight of 69,000 was prepared in the same manner as in the production of Example 3-1, except that the monomer of the following Chemical Formula 3 was used instead of the monomer of Chemical Formula 2.

Preparation Example 3-3: Preparation of Acrylate Copolymer C3

An acrylate copolymer C3 having a weight average molecular weight of 51,000 was prepared in the same manner as in the production of Example 3-1, except that the monomer of the following Chemical Formula 4 was used instead of the monomer of Chemical Formula 2.

Preparation Example 3-4: Preparation of Acrylate Copolymer C4

An acrylate copolymer C4 having a weight average molecular weight of 51,000 was prepared in the same manner as in the preparation of Example 3-1, except that the monomer of the following Chemical Formula 6 was used instead of the monomer of Chemical Formula 2.

Preparation Example 3-5: Preparation of Acrylate Copolymer C5

An acrylate copolymer C5 having a weight average molecular weight of 78,000 was prepared in the same manner as in the preparation of Example 3-1, except that the monomer of the following Chemical Formula 7 was used instead of the monomer of Chemical Formula 2.

<Chemical Formula 7>

In Chemical Formula 7, X-based triflate (OTf).

Preparation Example 4: Formation of a hard coat film for flexibility evaluation

<Preparation of epoxy oxirane resin>

3-Cyclopropoxypropyltrimethoxydecane (GPTS, taken from Gelest) and water were mixed at a ratio of 23.63 grams to 2.70 grams (0.1 mole: 0.15 mole) and then placed in a 100 ml two-necked flask in. Thereafter, 0.05 ml of ammonia as a catalyst was added to the mixture, and stirred at 60 ° C for 6 hours, thereby preparing a oxime sol.

<Preparation of hard coating composition>

The oxirane sol and the diglycidyl ether are mixed in a weight ratio of 100 to 10, and 100 parts by weight of the obtained mixture is mixed with 2 parts by weight of triarylsulfonium hexafluoroantimonate, thereby obtaining a hard Apply the composition.

<Formation of hard coat film>

A hard coat composition having a thickness of 50 μm was applied to a film having a thickness of 40 μm (cycloolefin polymer, ZF-16, available from Zeon Corporation), and subjected to surface corona treatment, thereby producing a film. The film was exposed to a mercury UV lamp (20 mW/cm 2 ) for 5 minutes, and the reaction was initiated using triarylsulfonium hexafluoroantimonate to produce an acid, which was then water at 50 ° C and 50% RH (relative humidity). The heat treatment was performed for 60 minutes to form a hard coat film.

Example 1: Preparation of optically clear adhesive composition

By mixing 80 parts by weight of Preparation Example 2-1 photocurable (meth) acrylate copolymer B1 and 20 parts by weight of Preparation Example 3-1 (meth) acrylate copolymer C1, that is, 100 parts by weight of the photocurable (meth) acrylate copolymer B1 and the acrylate copolymer C1, 0.5 parts by weight of a polyfunctional isocyanate crosslinking agent (Coronate L, available from NPU, Japan), and 0.2 parts by weight of a photopolymerization initiator (hydroxycyclohexyl phenyl ketone, Irgacure 184, obtained from Ciba Specialty Chemicals, Switzerland) was used to prepare an optically clear adhesive composition.

Example 2: Preparation of optically clear adhesive composition

An optically clear adhesive composition was prepared in the same manner as in Example 1, except that 70 parts by weight of the photocurable (meth) acrylate copolymer B2 and 30 parts by weight of Preparation Example 2-1 were used. Preparation Example 3-2 (meth) acrylate copolymer C2.

Example 3: Preparation of optically clear adhesive composition

An optically clear adhesive composition was prepared in the same manner as in Example 1, except that 75 parts by weight of the photocurable (meth) acrylate copolymer B2 and 25 parts by weight of Preparation Example 2-1 were used. Preparation Example 3-3 (meth) acrylate copolymer C3.

Example 4: Preparation of optically clear adhesive composition

An optically clear adhesive composition was prepared in the same manner as in Example 1, except that 85 parts by weight of the photocurable (meth) acrylate copolymer B2 and 15 parts by weight of Preparation Example 2-1 were used. Preparation Example 3-4 (meth) acrylate copolymer C4.

Example 5: Preparation of optically clear adhesive composition

An optically clear adhesive composition was prepared in the same manner as in Example 1, except that 95 parts by weight of the photocurable (meth) acrylate copolymer B2 and 5 parts by weight of Preparation Example 2-1 were used. Preparation Example 3-5 (meth) acrylate copolymer C5.

Comparative Example 1: Preparation of optically clear adhesive composition

By mixing 100 parts by weight of Preparation Example 2-4 photocurable (meth) acrylate copolymer B4, 0.5 part by weight of a polyfunctional isocyanate crosslinking agent (Coronate L, available from NPU, Japan), and 0.2 weight A photopolymerization initiator (hydroxycyclohexyl phenyl ketone, Irgacure 184, obtained from Ciba Specialty Chemicals, Switzerland) was used to prepare an optically clear adhesive composition.

Comparative Example 2: Preparation of optically clear adhesive composition

An optically clear adhesive composition was prepared by mixing 100 parts by weight of Preparation Example 3-1 acrylate copolymer C1 and 0.5 part by weight of a polyfunctional isocyanate crosslinking agent (Coronate L, available from NPU, Japan).

Example 6: Formation of an optically transparent adhesive film

Each of the optically clear adhesive compositions of Examples 1 to 5 and Comparative Examples 1 and 2 was coated on a PET film having a thickness of 50 μm, and an organic tantalum release agent was applied so as to have a thickness of 100 μm after curing. Then, it was dried at 100 ° C for 5 minutes, thereby producing Example 6-1 (using the optically clear adhesive composition of Example 1), and Example 6-2 (using the optically clear adhesive composition of Example 2) Example 6-3 (using the optically clear adhesive composition of Example 3), Example 6-4 (using the optically clear adhesive composition of Example 4), and Examples 6-5 (using the use of Example 5) Optically clear adhesive composition), Comparative Example 3-1 (using the optically clear adhesive composition of Comparative Example 1), and Comparative Example 3-2 (using the optically clear adhesive composition of Comparative Example 2).

Example 7: Formation of a laminate with an adhesive layer

The optical transparency of each of Example 6-1, Example 6-2, Example 6-3, Example 6-4, Example 6-5, Comparative Example 3-1, and Comparative Example 3-2 was used. Film, an adhesive layer was formed on a 100 μm thick PET film (taken from Mitsubishi Corporation), and a UV lamp (taken from Fusion Corporation) was used to irradiate light of 1000 mJ/cm 2 to form a release film, thereby manufacturing The adhesive layer of each of Example 7-1, Example 7-2, Example 7-3, Example 7-4, Example 7-5, Comparative Example 4-1, and Comparative Example 4-2 Laminate.

Example 8: Formation of a hard coat film/adhesive layer/PET laminate for evaluation of flexibility

Each of the laminates of Example 7-1, Example 7-2, Example 7-3, Example 7-4, Example 7-5, Comparative Example 4-1, and Comparative Example 4-2 was cut into 50 mm x 100 mm size. Subsequently, the PET film was peeled off from the adhesive layer of the cut laminate, and then the resulting laminate was adhered to a hard coating film for bending evaluation manufactured in Preparation Example 3 having a size of 50 mm × 100 mm. The pressure cooker was pressurized (50 ° C, 5 atm) for about 20 minutes, and then aged under constant temperature and humidity conditions (23 ° C and 50% RH) for 24 hours, thereby producing Example 8-1, Example 8-2, and carrying out Each of Example 8-3, Example 8-4, Example 8-5, Comparative Example 5-1, and Comparative Example 5-2, Hard Coating Film/Adhesive Layer/PET (100 μm for Flexibility Evaluation) ) Laminate.

Test Example: Evaluation of the Properties of Optically Clear Adhesive Compositions

1. Evaluation of foldability

<Evaluation method>

Evaluation criteria: IEC 62715

Evaluation device: tension-free U-fold tester (DLDMLH-FS)

Device manufacturer: YUASA SYSTEM (Japan)

Evaluation conditions: -20 ° C / 10,000 times (bending so that the hard coat is on the inside)

In Example 8-1, Example 8-2, Example 8-3, Example 8-4, Example 8-5, Comparative Example 5-1, and Comparative Example 5-2 produced in Example 8, Each of the hard coat film/adhesive layer/PET laminate for bending evaluation was measured by the above evaluation method to determine its foldability. The results are shown in Table 1 below.

<Evaluation criteria>

○: No defects such as foaming, peeling, and cracking were observed on the laminate.

△: Small defects were observed on the laminate with the naked eye.

×: The defect was clearly observed on the folded portion of the laminate with the naked eye.

2. Evaluation of durability

(1) Evaluation of heat resistance

In Example 8-1, Example 8-2, Example 8-3, Example 8-4, Example 8-5, Comparative Example 5-1, and Comparative Example 5-2 produced in Example 8, Each of the hard coat film/adhesive layer/PET laminate for bending evaluation was allowed to stand at 80 ° C for 1,000 hours, and then it was observed whether foaming or peeling occurred to evaluate the heat resistance. The results are shown in Table 1 below.

<Evaluation criteria>

◎: no foaming or peeling occurs

○: Number of foaming or peeling defects <5

△: 5 Number of foaming or peeling defects <10

×:10 Number of foaming or peeling defects

(2) Evaluation of resistance to heat and humidity

In Example 8-1, Example 8-2, Example 8-3, Example 8-4, Example 8-5, Comparative Example 5-1, and Comparative Example 5-2 produced in Example 8, Each of the hard coat film/adhesive layer/PET laminate for bending evaluation was allowed to stand at 60 ° C and 90% RH for 1,000 hours, and then it was observed whether foaming or peeling occurred. The sample was allowed to stand at room temperature for 24 hours immediately before sample evaluation, and then observed to evaluate its resistance to moist heat. The results are shown in Table 1 below.

<Evaluation criteria>

◎: no foaming or peeling occurs

○: Number of foaming or peeling defects <5

△: 5 Number of foaming or peeling defects <10

×:10 Number of foaming or peeling defects

3. Adhesion assessment

The production of Example 7 was carried out in the same manner as in Example 7-1, Example 7-2, Example 7-3, Example 7-4, Example 7-5, Comparative Example 4-1, and Comparative Example 4-2. The laminate of each adhesive layer was cut into a size of 25 mm x 100 mm. Subsequently, the PET film was peeled off from the adhesive layer of the cut laminate, and then the laminate having the adhesive layer was attached to the alkali-free glass using a 2 kg roller according to JIS Z 0237. The laminate-attached alkali-free glass was pressurized in a pressure cooker (50 ° C, 5 atm) for about 20 minutes, and stored under constant temperature and humidity conditions (23 ° C and 50% RH) for 24 hours. Thereafter, the laminate was peeled off from the alkali-free glass using TA (Texture Analyzer, available from Stable Micro Systems, UK) at a peel rate of 300 mm/min and a peel angle of 180° to measure adhesion. The results are shown in Table 2 below.

As is apparent from the test results of Tables 1 and 2, the optically clear adhesive composition of the examples of the present invention is excellent in foldability, moisture resistance, heat resistance, and adhesion. In particular, the foldability was remarkably high as compared with the optically clear adhesive composition of the comparative example.

While the preferred embodiment of the present invention has been disclosed for the purposes of illustration, it will be understood that Add and replace.

Claims (13)

An optically transparent adhesive composition comprising a photocurable (meth) acrylate copolymer, an acrylate copolymer, and a photopolymerization initiator, wherein the photocurable (meth) acrylate copolymer is The hydroxyl group-containing acrylic copolymer and 0.1 to 5% by weight of an isocyanate group-containing (meth) acrylate monomer, based on the total weight of the copolymer component, comprising 0.1 to 5 wt% of an isocyanate group-containing (meth) acrylate monomer. The hydroxyl group-containing acrylic copolymer and the isocyanate group-containing (meth) acrylate monomer form a urethane bond, and the hydroxyl group-containing acrylic copolymer is based on the total weight of the copolymer monomer a C ₄ -C ₁₂ linear or branched alkyl acrylate monomer having a glass transition temperature of from -70 to -50 ° C and from 2 to 20 wt % of a hydroxy-C ₂ -C ₆ linear chain having from 80 to 98 wt% Or a branched alkyl acrylate monomer, and the photocurable (meth) acrylate copolymer has a weight average molecular weight of 500,000 to 2,000,000; and the acrylate copolymer has a total monomer weight of the copolymer basis, comprising 80 to 95wt% of C ₄ -C ₁₂ straight-chain or branched-chain alkyl ester of acrylate And 5 to 20% by weight of an adhesion promoter-containing polymerizable monomer, which does not contain a photocrosslinkable functional group, and has a weight average molecular weight of 10,000 to 100,000, the photocurable (meth) acrylate copolymer and The acrylate copolymer is included in a weight ratio range of 95:5 to 70:30. The optically clear adhesive composition according to claim 1, wherein the glass having a glass transition temperature of -70 to -50 ° C for preparing the photocurable (meth) acrylate copolymer ₄ -C ₁₂ linear or branched chain of an alkyl acrylate monomer system selected from the group consisting of n-butyl acrylate, butyl acrylate, third, second, butyl acrylate, amyl acrylate, ethyl acrylate, butyl acrylate, 2 At least one monomer selected from the group consisting of ethylhexyl ester, n-octyl acrylate, isooctyl acrylate, and isodecyl acrylate; and the same for preparing the photocurable (meth) acrylate copolymer The hydroxy-C ₂ -C ₆ linear or branched alkyl acrylate monoester is selected from the group consisting of 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate, And at least one monomer consisting of a group consisting of 6-hydroxyhexyl acrylate. The optically clear adhesive composition according to claim 2, wherein the glass having a glass transition temperature of -70 to -50 ° C for preparing the photocurable (meth) acrylate copolymer ₄ -C ₁₂ linear or branched chain of an alkyl acrylate monomer system selected from the group consisting of n-butyl acrylate and acrylic acid is at least one monomer consisting of 2-ethylhexyl acrylate groups; and for the preparation of the photocurable The hydroxy-C ₂ -C ₆ linear or branched alkyl acrylate monoester of the (meth) acrylate copolymer is selected from the group consisting of 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate. At least one monomer. The optically clear adhesive composition according to claim 1, wherein the isocyanate group-containing (meth) acrylate single system (meth)acrylic acid isocyanato-C ₁ -C ₁₀ alkane Base ester.  The optically clear adhesive composition according to claim 4, wherein the isocyanate group-containing (meth) acrylate single system 2-isocyanatoethyl methacrylate.   The optically transparent adhesive composition according to claim 1, wherein the adhesion-promoting polymerizable single system is selected from the group consisting of a compound of the following Chemical Formula 1, a compound of the following Chemical Formula 2, a compound of the following Chemical Formula 3, At least one of the group consisting of the compound of the following Chemical Formula 4, the compound of the following Chemical Formula 5, the compound of the following Chemical Formula 6, the compound of the following Chemical Formula 7, and the compound of the following Chemical Formula 8: <Chemical Formula 5> In Chemical Formula 7, X is selected from the group consisting of PF5, SbF6, methanesulfonate (OMs), tosylate (OTs), triflate (OTf), bis(fluorosulfonyl) ruthenium ( FSI), and a group consisting of bis(trifluoromethylsulfonyl) quinone imine (TFSI). The optically transparent adhesive composition according to claim 1, wherein the C ₄ -C ₁₂ linear or branched alkyl (meth) acrylate monomer used for preparing the acrylate copolymer It is selected from n-butyl acrylate, tert-butyl acrylate, dibutyl acrylate, amyl acrylate, 2-ethyl butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, And at least one monomer of the group consisting of isodecyl acrylate.  The optically transparent adhesive composition according to claim 1, wherein the photocurable (meth) acrylate copolymer and the acrylate copolymer are based on 100 parts by weight in total, including The photopolymerization initiator is contained in an amount of from 0.1 to 5 parts by weight.    The optically transparent adhesive composition according to claim 1, wherein the photocurable (meth) acrylate copolymer and the acrylate copolymer are further based on 100 parts by weight, further comprising 40 Up to 85 parts by weight of solvent.    The optically clear adhesive composition according to claim 1, wherein the photocurable (meth) acrylate copolymer and the acrylate copolymer are based on a total of 100 parts by weight, further including 0.02. Up to 5 parts by weight of a polyfunctional crosslinking agent.    An optically transparent adhesive film produced by coating a transfer film with an optically transparent adhesive composition as described in claim 1 of the patent application.    A flat panel display comprising an adhesive layer formed of the optically clear adhesive composition of claim 1 of the patent application.    The flat panel display of claim 12, wherein the flat panel display is a flexible display.