TW201819579A - 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, including a photocurable (meth)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, and the hydroxyl-group-containing acrylic copolymer includes, based on the total weight of monomers of the copolymer, 50~89 wt% of a C4-C12 linear or branched alkyl acrylate monomer having a glass transition temperature (Tg) of -70~-50 DEG C and 11~50 wt% of a hydroxy-C4-C6 linear or branched alkyl acrylate monomer having a glass transition temperature (Tg) of -60~-40 DEG C, and has a weight average molecular weight of 200,000 to 1,000,000.

Description

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

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

Examples of the flat panel display device include a liquid crystal display (LCD), a plasma display panel (PDP), an organic electroluminescence display (OLED), and the like.

Such a flat panel display device 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 one on top of the other or the optical film is attached to the display panel. Accordingly, optically clear adhesives (OCAs) must not only have typical optical properties, but also have excellent resistance to moist heat, heat, and adhesion.

In particular, the development of flexible display devices is currently in fierce competition. Since the flexible display device is bendable, rollable or foldable, the display panel and the optical film contained in the device are subjected to bending stress. Therefore, it is required to further improve various properties of an optically clear adhesive (OCA) used in a flexible display device.

For example, an optically clear adhesive (OCA) used in a flexible display device must have extremely foldable properties to enable flexible folding of the device. Furthermore, in consideration of the fact that the flexible display device is used outdoors for a long time, its low-temperature foldability must be excellent.

Further, an optically clear adhesive (OCA) used for a flexible display device must have a more improved moist heat resistance. The reason is that the flexible display device repeatedly accepts multiple folding and unfolding processes during its use, which may increase the possibility of moisture permeation through the folded and unfolded portions.

Further, when the flexible display device is bent, rolled or folded, the display panel and the optical film contained in the device are subjected to bending stress. Thus, since the stacked display panel and the optical film are easily separated from each other, high adhesion and high durability are required.

However, optically clear adhesives (OCAs) known today do not adequately provide the properties required for flexible display devices as described above.

 [reference list]    [Patent Literature]  

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

Accordingly, the present invention contemplates the problems encountered in the related art, and the present invention is intended to provide an optically clear adhesive (OCA) composition capable of sufficiently satisfying the foldability, moist heat resistance, heat resistance, and the like required for a flexible display device. And adhesion.

Further, the present invention is intended to provide an optically transparent adhesive film comprising an optically clear adhesive (OCA) composition and a flat panel display device.

Accordingly, the present invention provides an optically clear adhesive composition comprising a photocurable (meth) acrylate copolymer and a photopolymerization initiator, wherein the illuminant is based on the total weight of the composition of the copolymer. The cured (meth) acrylate copolymer comprises 95 to 99.9% by weight of a hydroxyl group-containing acrylic copolymer and 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 forms a urethane bond; and the hydroxyl group-containing acrylic copolymer includes 50 to 89% by weight based on the total weight of the monomers of the copolymer -70 to -50 ° C glass transition temperature (Tg) of C ₄ -C ₁₂ linear or branched alkyl acrylate monomer and 11 to 50 wt% with a glass transition temperature (Tg) of -60 to -40 ° C A hydroxy-C ₄ -C ₆ linear or branched alkyl acrylate monomer having a weight average molecular weight of from 200,000 to 1,000,000.

Further, the present invention provides an optically clear adhesive film which is produced by coating a transfer film using the optically transparent adhesive composition of the present invention.

Further, the present invention provides a flat panel display device comprising an adhesive layer made of the optically clear adhesive composition of the present invention.

According to the present invention, the optically clear adhesive (OCA) composition and the optically transparent adhesive film can have sufficient foldability, moist heat resistance, heat resistance, and adhesion to the flat display device and the flexible display device. It is endowed with excellent durability.

According to the present invention, the flat panel display device is manufactured using the above-described adhesive composition, and thus has excellent foldability, moist heat resistance, heat resistance and adhesion, and high durability.

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

As used herein, the photocurable (meth) acrylate copolymer comprises from 95 to 99.9% by weight of the hydroxyl group-containing acrylic copolymer and from 0.1 to 5% by weight based on the total weight of the copolymer component. The 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 acid The copolymer comprises from 50 to 89% by weight, based on the total weight of the monomers of the copolymer, of a C ₄ -C ₁₂ linear or branched alkyl acrylate having a glass transition temperature (Tg) of from -70 to -50 °C. a base ester monomer and 11 to 50% by weight of a hydroxy-C ₄ -C ₆ linear or branched alkyl acrylate monomer having a glass transition temperature (Tg) of from -60 to -40 ° C, and having from 200,000 to 1,000,000 Weight average molecular weight.

In the present invention, the optically clear adhesive composition includes a monomer having a low glass transition temperature (Tg), and thus it is possible to improve low-temperature foldability. The use of a large amount of OH group-containing monomers provides moisture heat resistance and adhesion, and increases the crosslinking density, resulting in an optically transparent adhesive composition having high heat resistance and durability.

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

The photocurable (meth) acrylate copolymer can be prepared by passing a C ₄ -C ₁₂ linear or branched alkyl acrylate monomer having a glass transition temperature (Tg) of -70 to -50 ° C. Copolymerization with a hydroxy-C ₄ -C ₆ linear or branched alkyl acrylate monomer having a glass transition temperature (Tg) of -60 to -40 ° C to obtain a hydroxyl group-containing acrylic copolymer backbone group Formulated such that a thermosetting functional group (OH group) is introduced into its branched chain or its terminal, after which the main chain is reacted with an isocyanate group-containing (meth) acrylate monomer under appropriate conditions, thereby containing an isocyanate group. The (meth) acrylate monomer replaces at least a portion of the thermoset functional group (OH group) of the backbone.

The structural formula of the photocurable (meth) acrylate copolymer can be represented by the following Chemical Formula 1.

In Chemical Formula 1, R ₁ is a C ₄ -C ₁₂ linear or branched alkyl group, R ₂ is a C ₁ -C ₁₀ linear or branched alkyl group, R ₃ is hydrogen or methyl, and o is The natural numbers from 1 to 3, and l, m, and n each have a value depending on the numerical range of the aforementioned monomers.

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

a C ₄ -C ₁₂ linear or branched alkyl acrylate monomer which is included in the polymerized form of the hydroxyl group-containing acrylic copolymer and has a glass transition temperature (Tg) of -70 to -50 ° C Examples may include n-butyl acrylate, tert-butyl acrylate, second butyl acrylate, amyl acrylate, 2-ethyl butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate The esters, and isodecyl acrylates, may be used singly or in combination of two or more thereof. Among them, it is preferred to use n-butyl acrylate or 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 foldability may be deteriorated.

a hydroxy-C ₄ -C ₆ linear or branched alkyl acrylate having a glass transition temperature (Tg) of from -60 to -40 ° C in a hydroxyl-containing acrylic copolymer. Examples of the monomer may include 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate, and 6-hydroxyhexyl acrylate, which may be used singly or in combination of two or more thereof. Among them, 4-hydroxybutyl acrylate is preferably used.

If the glass transition temperature (Tg) of the hydroxy-C ₄ -C ₆ linear or branched alkyl acrylate monomer is lower than -60 ° C, it is difficult to ensure its existence. On the other hand, if the glass transition temperature exceeds -40 ° C, the low-temperature foldability may be deteriorated.

In the hydroxyl group-containing acrylic copolymer, a C ₄ -C ₁₂ linear or branched alkyl acrylate monomer having a glass transition temperature (Tg) of -70 to -50 ° C is preferably contained in an amount of 50 to 89% by weight. And a hydroxy-C ₄ -C ₆ linear or branched alkyl acrylate monomer having a glass transition temperature (Tg) of -60 to -40 ° C is preferably contained in an amount of 11 to 50% by weight. Therefore, if the content of the hydroxy-C ₄ -C ₆ linear or branched alkyl acrylate monomer having a glass transition temperature (Tg) of -60 to -40 ° C is less than 11% by weight, it is used as an adhesive in the adhesive. The content of the hydrophilic group's OH group may be reduced, and thus the moisture may not be captured by the adhesive layer, but may be discharged to the interface, undesirably degrading the adhesion under wet heat resistance conditions, and the interface separation may occur undesirably. On the other hand, if the content exceeds 50% by weight, moisture may be excessively absorbed by the adhesive, and thus the volume of the adhesive increases, and the cohesive force may be lowered, undesirably causing the interface to be separated and foamed.

Among the hydroxyl group-containing acrylic copolymers, additional copolymerizable monomers known in the art can be further included in the polymerized form. The kind of the additionally copolymerizable monomer is not particularly limited, and examples thereof may include, but are not limited to, nitrogen-containing monomers such as (meth)acrylonitrile, (meth)acrylamide, N-methyl (A) Acrylamide, or N-butoxymethyl(meth)acrylamide; styrene-based monomers such as styrene or methylstyrene; glycidyl (meth)acrylate; and carboxy Acid vinyl esters such as vinyl acetate.

In view of flexibility and tear strength, when an additional copolymerizable monomer is included, the content thereof is preferably adjusted to 20 parts by weight or less based on a total of 100 parts by weight of the above monomers.

The weight average molecular weight of the hydroxyl group-containing acrylic copolymer refers to a value measured by gel permeation chromatography (GPC) using a polystyrene standard.

An isocyanate group-containing (meth) acrylate monomer encompassed in a photocurable (meth) acrylate copolymer, which may be an isocyanato-C ₁ -C ₁₀ linear or branched chain (methyl) An alkyl acrylate is exemplified. Wherein, the C ₁ -C ₁₀ linear or branched alkyl group may include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, second butyl, tert-butyl, pentyl, Hexyl, heptyl, octyl, 2-ethylhexyl, anthracenyl, and anthracenyl. Among them, an ethyl group or a propyl group is preferably used.

The isocyanate group-containing (meth) acrylate monomer may be used in an amount of 0.1% by weight to 5.0% by weight based on the total mass of the component of the photocurable (meth) acrylate copolymer. 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, undesirably degrading the foldability.

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

The photopolymerization initiator is not particularly limited, and any photopolymerization initiator can be used as long as it is known in the art. Examples of the initiator may include a typical initiator capable of generating a radical by UV irradiation, thereby initiating photopolymerization, such as a benzoin-based initiator, a hydroxyketone-based initiator, and an aminoketone-based initiator. Initiator, and initiator based on phosphine oxide.

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

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

The optically clear adhesive composition of the present invention may further comprise a multifunctional crosslinking agent. The polyfunctional crosslinking agent is not particularly limited and may include those 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 photocurable (meth) acrylate copolymer.

The optically clear adhesive composition of the present invention may further comprise a decane coupling agent. The type of the decane coupling agent is not particularly limited, and any coupling agent typically known in the field of the adhesive preparation can be used. Examples of the decane coupling agent may include γ-cyclopropoxypropyltriethoxydecane, γ-cyclopropoxypropyltrimethoxydecane, γ-cyclopropoxypropylmethyldiethoxydecane, γ-Cyclopropoxypropyltriethoxydecane, 3-mercaptopropyltrimethoxydecane, vinyltrimethoxydecane, vinyltriethoxydecane, γ-methacryloxypropyltrimethyl Oxydecane, γ-methacryloxypropyltriethoxydecane, γ-aminopropyltrimethoxydecane, γ-aminopropyltriethoxydecane, and 3-isocyanate Propyltriethoxydecane.

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

The optically clear adhesive composition of the present invention may further comprise a tackifier to adjust the adhesion efficiency.

Furthermore, it may further comprise at least one additive selected from the group consisting of epoxy resins, curing agents, UV stabilizers, antioxidants, colorants, reinforcing agents, fillers, defoamers , surfactants, and plasticizers.

The optically clear adhesive composition of the present invention may further comprise a solvent. Any solvent known in the art can be used without limitation as long as the solvent 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 content of the solvent may be 40 to 85 parts by weight based on 100 parts by weight of the photocurable (meth) acrylate copolymer.

The optically clear adhesive composition of the present invention preferably has a viscosity in the range of 500 cP to 2,500 cP at 23 °C.

The optically transparent adhesive composition of the present invention can ensure low-temperature foldability by using a monomer having a low glass transition temperature, and a suitable curing system by radical polymerization, and a crosslinking agent and a thermosetting functional group ( The OH-based curing system can also achieve moisture resistance, heat resistance, and durability.

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, except as described above. Herein, an industry-wide molecular weight controlling agent, a catalyst, or the like 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 a bar coating method, a spin coating method, a knife coating method, and a gravure coating method. During the coating process, the crosslinking reaction of the functional groups of the polyfunctional crosslinking agent included in the adhesive composition is controlled so as not to proceed in order to achieve uniform coating. Therefore, after the coating process, the crosslinking agent can form a crosslinked structure during curing and aging, thus improving the adhesive properties and cuttability of the adhesive, as well as cohesion.

Further, it is preferred that the coating process be performed after the volatile component or the foaming component, such as the reaction residue, is sufficiently removed from the adhesive composition. Thereby, it is possible to prevent the elastic modulus from being lowered due to the low crosslink density of the adhesive or the molecular weight being too low, and it is also possible to prevent the internal scatterer due to an increase in the bubble size between the glass plate and the adhesive layer at a high temperature. generate.

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

Before or after the illuminating, an appropriate aging treatment may be performed to induce a reaction between the functional group of the cross-linking agent of the composition and the thermosetting functional group of the polymer, and the conditions of the aging treatment are not particularly limited as long as it can be properly handled. The reaction can be done.

The adhesive composition for an optical film according to the present invention can be used to stack 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, to each other, or to an optical film Or a laminate thereof 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 device.

Further, the present invention relates to an optically clear adhesive film produced by coating a transfer film with the optically transparent adhesive composition of the present invention.

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

Further, the present invention relates to a flat panel display device comprising an adhesive layer made of the optically transparent adhesive composition of the present invention.

Herein, the flat panel display device is preferably a flexible display device.

The invention is exemplified by the following examples and comparative examples, and the examples and comparative examples are merely intended to illustrate the invention, but the invention is not limited by the examples, but may be modified and changed in various ways.

Preparation Example 1-1: Preparation of Acrylic Polymer A1

60 parts by weight of n-butyl acrylate (n-BA) and 40 parts by weight of 4-hydroxybutyl acrylate (4-HBA) were placed in a 1 liter reactor equipped with a condenser, thereby facilitating temperature control when nitrogen was refluxed. 120 parts by weight of ethyl acetate (EAc) was added thereto, and the resulting reaction mixture was purged with nitrogen for 60 minutes to remove oxygen therefrom. Thereafter, the temperature was maintained at 70 ° C, 0.1 part by weight of a reaction initiator azobisisobutyronitrile (AIBN) was added thereto, and the reaction was carried out for 12 hours, thereby preparing an acrylic polymer A1 having an average molecular weight of 450,000.

Preparation Example 1-2: Preparation of Acrylic Polymer A2

The acrylic polymer A2 having a weight average molecular weight of 470,000 was prepared by the same polymerization technique as in Preparation Example 1-1, except that 89 parts by weight of n-butyl acrylate (n-BA) and 11 parts by weight of 4-hydroxybutyl acrylate were used ( 4-HBA).

Preparation Example 1-3: Preparation of Acrylic Polymer A3

The acrylic polymer A3 having a weight average molecular weight of 450,000 was prepared by the same polymerization technique as in Preparation Example 1-1, except that 80 parts by weight of n-butyl acrylate (n-BA) and 20 parts by weight of 2-hydroxyethyl acrylate (20 parts by weight) were used. 2-HEA) was substituted for 60 parts by weight of n-butyl acrylate (n-BA) and 40 parts by weight of 4-hydroxybutyl acrylate (4-HBA).

Preparation Example 1-4: Preparation of Acrylic Polymer A4

The acrylic polymer A4 having a weight average molecular weight of 390,000 was prepared by 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 of 2-hydroxyethyl acrylate were used ( 2-HEA) was substituted for 60 parts by weight of n-butyl acrylate (n-BA) and 40 parts by weight of 4-hydroxybutyl acrylate (4-HBA).

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

100 parts by weight of the solid content of the acrylic polymer A1, 1 part by weight of 2-isocyanatoethyl methacrylate, and 0.1 part by weight of dibutyltin dilaurate (DBTDL) placed in a 1 liter reaction equipped with a condenser Inside the device, it is convenient to control the temperature when nitrogen is refluxed. Subsequently, the reaction was carried out at 40 ° C under atmospheric pressure for 4 hours or more, thus obtaining 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 Preparation Example 2-1 except that the acrylic polymer 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 Preparation Example 2-1 except that the acrylic polymer A3 was used.

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

The photocurable (meth) acrylate copolymer B4 was prepared in the same manner as in Production Example 2-1 except that the acrylic polymer A4 was used.

Preparation Example 3: Formation of a hard coating film for bendability evaluation

<Preparation of epoxy oxirane resin>

3-cyclopropoxypropyltrimethoxydecane (GPTS, available from Gillest) mixed with water in a ratio of 23.63 grams: 2.70 grams (0.1 mole: 0.15 moles), and then placed 100 ml two-necked bottle. Thereafter, 0.05 ml of ammonia was added as a catalyst to the mixture, and the mixture was stirred at 60 ° C for 6 hours, thereby preparing a decane sol.

<Preparation of hard coating composition>

The oxirane sol and dicyclopropyl ether were mixed in a weight ratio of 100:10, and 100 parts by weight of the resulting mixture was mixed with 2 parts by weight of triaryl sulfonium hexafluoroantimonate, thereby obtaining a hard coating composition.

<Generation of Hard Coating Film>

The hard coating composition was applied to a film of a cycloolefin polymer (COP, ZF-16, available from Zeon) having a thickness of 40 μm at a thickness of 50 μm, and subjected to a corona surface treatment, thereby preparing a film. The film was exposed to a mercury UV lamp (20 mW/cm 2 ) for 5 minutes and induced by triaryl hexafluoroantimonate, followed by hydrothermal treatment at 50 ° C and 50% relative humidity (RH). 60 minutes, thus producing a hard coating film.

Example 1: Preparation of optically clear adhesive composition

The optically clear adhesive composition was prepared in the following manner by mixing 100 parts by weight of the photocurable (meth) acrylate copolymer B1 of Preparation Example 2-1, 0.5 part by weight of a polyfunctional isocyanate crosslinking agent (Clonay ( Coronate) L, available from NPU Japan, and 0.2 parts by weight of a photopolymerization initiator (hydroxycyclohexyl phenyl ketone, Irgacure 184, available from Ciba Specialty Chemicals) , Switzerland) and prepared.

Example 2: Preparation of optically clear adhesive composition

The optically clear adhesive composition was prepared in the same manner as in Example 1 except that the photocurable (meth) acrylate copolymer B2 of Preparation Example 2-2 was used instead of the photocurable (meth) acrylate copolymer. B1.

Comparative Example 1: Preparation of optically clear adhesive composition

The optically clear adhesive composition was prepared in the same manner as in Example 1 except that the photocurable (meth) acrylate copolymer B3 of Preparation Example 2-3 was used instead of the photocurable (meth) acrylate copolymer. B1.

Comparative Example 2: Preparation of optically clear adhesive composition

The optically clear adhesive composition was prepared in the same manner as in Example 1, except that the photocurable (meth) acrylate copolymer B4 of Preparation Example 2-4 was used instead of the photocurable (meth) acrylate copolymer. B1.

Example 3: Formation of an optically transparent adhesive film

The optically clear adhesive compositions of Examples 1 and 2 and Comparative Examples 1 and 2 were applied to a PET film having a thickness of 50 μm, and coated with a polyfluorinated release agent, and after curing to a thickness of 100 μm, And then dried at 100 ° C for 5 minutes, thus producing Example 3-1 (using the optically clear adhesive composition of Example 1), Example 3-2 (using the optically clear adhesive composition of Example 2), and comparing Each of the optically clear adhesive films of Example 3-1 (using the optically clear adhesive composition of Comparative Example 1) and Comparative Example 3-2 (using the optically transparent adhesive composition of Comparative Example 2).

Example 4: Formation of a laminate with an adhesive layer

The optically transparent adhesive film of each of Example 3-1, Example 3-2, Comparative Example 3-1, and Comparative Example 3-2 was used to form a 100 μm thick PET film (from Mitsubishi). The agent layer, and the UV lamp (from Fusion) was used to form light at 1000 mJ/cm 2 in the direction in which the release film was formed, thus having Example 4-1, Example 4-2, and Comparative Example 4 The laminate of each of the adhesive layers of 1 and Comparative Example 4-2.

Example 5: Formation of hard coating film/adhesive layer/PET laminate for bendability evaluation

The laminate of each of Example 4-1, Example 4-2, Comparative Example 4-1, and Comparative Example 4-2 was cut into a size of 50 mm x 100 mm. Subsequently, the release PET film was peeled off from the adhesive layer of the cut laminate, and thereafter, the resultant laminate was attached to the hard coating film for the bendability evaluation manufactured in Preparation Example 3 (the size of which was 50) MM x 100 mm), pressurized in a high pressure steam cooker (50 ° C, 5 atm) for about 20 minutes, and then aged under constant temperature and constant humidity conditions (23 ° C and 50% relative humidity) for 24 hours, thus manufacturing examples 5-1. Each of Example 5-2, Comparative Example 5-1, and Comparative Example 5-2, a hard coat film/adhesive layer/PET (100 μm) laminate for evaluation of bendability.

Test case: Evaluation of the properties of optically transparent adhesive composition estimate

1. Evaluation of foldability

<Evaluation method>

Evaluation criteria: IEC 62715

Evaluation device: tension-free U-shaped folding test machine (DLDMLH-FS)

Device symbol: YUASA SYSTEM (Japan)

Evaluation conditions: -20 ° C / 10,000 times (bending so that the hard coating layer is facing inward)

Hard coating film/adhesive layer/PET laminate system for bendability evaluation of each of Example 5-1, Example 5-2, Comparative Example 5-1 and Comparative Example 5-2 produced in Example 5 It was measured to determine its foldability by the above evaluation method. The results are shown in Table 1 below.

<Evaluation criteria>

○: defects such as foaming, peeling, and cracking were not observed on the laminate.

△: Small defects were observed by naked eyes on the laminate

×: The defect is clearly observed by the naked eye on the folded portion of the laminate

2. Evaluation of durability

(1) Evaluation of heat resistance

Hard coating film/adhesive layer/PET laminate system for bendability evaluation of each of Example 5-1, Example 5-2, Comparative Example 5-1 and Comparative Example 5-2 produced in Example 5 It was allowed to stand at 80 ° C for 1,000 hours, after which whether foaming or peeling occurred was observed in order to evaluate heat resistance. The results are shown in Table 1 below.

<Evaluation criteria>

◎: neither foaming nor peeling occurred

○: number of foaming or peeling defects <5

△: 5 Number of foaming or peeling defects <10

×:10 Number of defects such as foaming or peeling

(2) Evaluation of resistance to moist heat

Hard coating film/adhesive layer/PET laminate system for bendability evaluation of each of Example 5-1, Example 5-2, Comparative Example 5-1 and Comparative Example 5-2 produced in Example 5 It was allowed to stand at 60 ° C and 90% relative humidity for 1,000 hours, after which it was observed whether foaming or peeling occurred. Just before the evaluation of the sample, the sample was allowed to stand at room temperature for 24 hours and then observed to evaluate its resistance to moist heat. The results are shown in Table 1 below.

<Evaluation criteria>

◎: neither foaming nor peeling occurred

○: number of foaming or peeling defects <5

△: 5 Number of foaming or peeling defects <10

×:10 Number of foaming or peeling defects

3. Evaluation of adhesion

The laminate having the adhesive layers of each of Example 4-1, Example 4-2, Comparative Example 4-1, and Comparative Example 4-2 was cut into a size of 25 mm x 100 mm. Subsequently, the release PET film was peeled off from the adhesive layer of the cut laminate, and thereafter, the laminate having the adhesive layer was attached to the alkali-free glass using a 2 kg roller according to JIS Z 0237. The alkali-free glass with the laminate attached thereto is pressurized in a high pressure steam pot (50 ° C, 5 atm) for about 20 minutes, and stored under constant temperature and constant humidity conditions (23 ° C and 50% relative humidity) for 24 hours. hour. Thereafter, when using a Texture Analyzer (TA) from Stable Micro Systems UK, a tear rate of 300 mm/min and a tear angle of 180 degrees from the alkali-free glass Adhesion was measured when the laminate was torn off. The results are shown in Table 2 below.

As 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 terms of foldability, moist heat resistance, heat resistance and adhesion. In particular, the foldability of the optically clear adhesive composition was significantly higher than that of the comparative example.

Although the preferred embodiment of the present invention has been disclosed for the purposes of illustration, it will be understood by those skilled in the art that various modifications and additions may be made without departing from the scope and spirit of the invention as disclosed in the appended claims. Replace.

Claims (10)

An optically transparent adhesive composition comprising a photocurable (meth) acrylate copolymer and a photopolymerization initiator, wherein the photocurable (based on the total weight of the composition of the copolymer) The acrylate copolymer comprises 95 to 99.9% by weight of a hydroxyl group-containing acrylic copolymer and 0.1 to 5% by weight of an isocyanate group-containing (meth) acrylate monomer, the hydroxyl group-containing acrylic copolymer and the isocyanate group-containing The (meth) acrylate monomer forms a urethane bond, and the hydroxyl group-containing acrylic copolymer comprises 50 to 89% by weight, based on the total weight of the monomer of the copolymer, having -70 to - C ₄ -C ₁₂ linear or branched alkyl acrylate monomer at 50 ° C glass transition temperature (Tg) and 11 to 50 wt % hydroxy-C having a glass transition temperature (Tg) of -60 to -40 ° C _4- C ₆ linear or branched alkyl acrylate monomer having a weight average molecular weight of from 200,000 to 1,000,000. The optically clear adhesive composition according to claim 1, wherein the C ₄ -C ₁₂ linear or branched alkyl acrylate having a glass transition temperature (Tg) of -70 to -50 ° C The body is at least one monomer selected from the group consisting of n-butyl acrylate, tert-butyl acrylate, second butyl acrylate, amyl acrylate, 2-ethyl butyl acrylate, acrylic acid 2 -ethylhexyl ester, n-octyl acrylate, isooctyl acrylate, and isodecyl acrylate, and the hydroxy-C ₄ -C ₆ straight chain or branch having a glass transition temperature (Tg) of -60 to -40 ° C The chain alkyl acrylate monomer is at least one monomer selected from the group consisting of 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate, and 6-hydroxyhexyl acrylate.  The optically clear adhesive composition according to claim 1, wherein the optically transparent adhesive composition comprises 0.1 to 5 based on 100 parts by weight of the photocurable (meth) acrylate copolymer. Parts by weight of photopolymerization initiator.    The optically clear adhesive composition according to claim 3, which further comprises 0.02 to 5 parts by weight of polyfunctional crosslinking based on 100 parts by weight of the photocurable (meth) acrylate copolymer. Agent.    The optically clear adhesive composition according to claim 3 or 4, which further comprises 40 to 85 parts by weight of the solvent based on 100 parts by weight of the photocurable (meth) acrylate copolymer.    The optically clear adhesive composition of claim 4, wherein the polyfunctional crosslinking agent is a thermosetting polyfunctional isocyanate crosslinking agent or a polyfunctional (meth) acrylate crosslinking agent.   The optically transparent adhesive composition according to claim 1, wherein the isocyanate group-containing (meth) acrylate monomer is an isocyanato-C ₁ -C ₁₀ linear or branched chain (A) Alkyl acrylate.  An optically clear adhesive film produced by coating a transfer film with an optically clear adhesive composition as described in claim 1 of the patent application.    A flat panel display device comprising an adhesive layer made of an optically transparent adhesive composition as described in claim 1.    The flat panel display device of claim 9, wherein the flat panel display device is a flexible display device.