TWI751199B - Optically clear adhesive composition, optically clear adhesive film comprising the same, and flat panel display device - 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, a polydimethylsiloxane-based (meth)acrylate compound, 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 ~ 98 wt% of a C₁-C₁₂ linear or branched alkyl (meth)acrylate monomer and 2 ~ 50 wt% of a hydroxyl-group-containing polymerizable monomer, and has a weight average molecular weight of 200,000 to 1,000,000.

Description

Optically clear adhesive composition, optically clear adhesive film comprising the same, and flat panel display device

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

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

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

In particular, the development of flexible display devices is currently facing fierce competition. Since a flexible display device is bendable, rollable, or foldable, the display panels and optical films included in the device are subject to bending stress. Therefore, various properties of optically clear adhesives (OCAs) for flexible display devices need to be further improved.

For example, an optically clear adhesive (OCA) for a flexible display device must have good foldability to ensure that the device can be freely folded. In addition, considering that when the flexible display device is used outdoors at low temperature for a long time, the foldability at low temperature must be excellent.

Also, an optically clear adhesive (OCA) used in a flexible display device must have enhanced resistance to heat and humidity. This is because the flexible display device is repeatedly folded and unfolded many times during use, so the possibility of moisture penetrating the folded and unfolded portion increases.

Also, when the flexible display device is bent, curled, or folded, the display panel and optical films included in the device are affected by bending stress. Therefore, since the stacked display panel and optical film are easily separated from each other, higher adhesion and higher durability are required.

However, currently known optically clear adhesives (OCAs) cannot sufficiently provide the above-mentioned properties required for flexible display devices.

〔Citation〕

[Patent Documents]

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

Therefore, the present invention keeps in mind the problems encountered in the prior art, and aims to provide an optically clear adhesive (OCA) composition, which can fully satisfy the foldability, damp-heat resistance, Heat resistance, and adhesion standards.

Furthermore, the present invention aims to provide an optically clear adhesive film comprising an optically clear adhesive (OCA) composition and a flat panel display device.

Accordingly, the present invention provides an optically transparent adhesive composition comprising a photocurable (meth)acrylate copolymer, a polydimethylsiloxane-based (meth)acrylate compound, and a photopolymerizable polymer A starter, wherein the photocurable (meth)acrylate copolymer comprises, based on the total weight of the copolymer components, 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 (isocyanate-group-containing (meth)acrylate) monomer, the hydroxyl-containing acrylic copolymer and the isocyanate group-containing (meth)acrylate monomer form a urethane bond, And the hydroxyl-containing acrylic copolymer comprises, based on the total monomer weight of the copolymer, 50 to 98% by weight of (meth)acrylic acid C ₁ to C ₁₂ straight or branched chain alkyl ester monomers and 2 to 50 % by weight of a hydroxyl group-containing polymerizable monomer having a weight average molecular weight of 200,000 to 1,000,000.

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

In addition, the present invention provides a flat panel display device comprising an adhesive layer formed by the optically transparent adhesive composition of the present invention.

According to the present invention, the optically clear adhesive (OCA) composition and the optically clear adhesive film can fully express the foldability, damp heat resistance, heat resistance and adhesiveness required for flat panel display devices and flexible display devices, and thus can provide Excellent durability.

According to the present invention, the flat panel display device made using the aforementioned adhesive composition thus exhibits excellent foldability, damp heat resistance, heat resistance, and adhesiveness and high durability.

The present invention relates to an optically transparent adhesive composition comprising a photocurable (meth)acrylate copolymer, a polydimethylsiloxane-based (meth)acrylate compound, and a photopolymerization initiator agent.

Here, the photocurable (meth)acrylate copolymer comprises, based on the total weight of the copolymer components, 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) base) acrylate monomer, the hydroxyl-containing acrylic copolymer and the isocyanate group-containing (meth)acrylate monomer form a urethane bond, and the hydroxyl-containing acrylic copolymer comprises, based on the of the total weight of monomer copolymer, 50-98% by weight of (meth) acrylate, a C ₁ to C ₁₂ linear or branched alkyl ester monomer and 2-50 wt% of hydroxyl group-containing polymerizable monomer and having Weight average molecular weight 200,000 to 1,000,000.

In the present invention, the optically clear adhesive composition comprises a polar photocurable acrylate copolymer having a low glass transition temperature (Tg) and a polydimethylsiloxane-based (meth)acrylate compound , thus exhibiting excellent foldability, heat and humidity resistance, and adhesion. By photocrosslinking reaction between photocurable acrylate copolymers with low Tg and polydimethylsiloxane-based (meth)acrylate compounds, a product with high heat resistance and durability can be obtained. optically clear adhesive composition.

The term "(meth)acrylate" as used herein means "acrylate" or "methacrylate".

Photocurable (meth)acrylate copolymers can be produced by copolymerizing (meth)acrylate C ₁ to C ₁₂ linear or branched alkyl ester monomers and hydroxyl-containing copolymerizable monomers to produce a hydroxyl-containing The main chain of the acrylic copolymer is configured such that a thermosetting functional group (hydroxyl group) is introduced into its branch or terminal, and then the main chain is reacted with an isocyanate group-containing (meth)acrylate monomer under suitable conditions, so that at least Some of the main chain's thermosetting functional groups (hydroxyl groups) are substituted with isocyanate group-containing (meth)acrylate monomers.

The structure of the photocurable (meth)acrylate copolymer is shown in the following chemical formula A:

In Chemical Formula A, R ₁ is C ₁ to C ₁₂ straight or branched chain alkyl, R ₂ is C ₁ to C ₁₀ straight or branched chain alkyl, R _{3 is} independently hydrogen or methyl, o and p is each independently a natural number of 2 to 6, and the numerical values of l, m, and n are each dependent on the numerical range of the above-mentioned monomers.

The backbone can be prepared by typical polymerization processes, such as solution polymerization, photopolymerization, bulk polymerization, suspension polymerization, or emulsion polymerization.

The polydimethylsiloxane-based (meth)acrylate compound may include, for example, at least one compound selected from the group consisting of compounds represented by the following chemical formulas 1 to 3:

In Chemical Formulas 1 to 3, R _{1 is} independently hydrogen or methyl, R ₂ is C ₁ to C ₅ linear or branched alkylene, and R _{3 is} independently derived from a diisocyanate compound and -N(H) -C(O)- is attached to the groups on both sides thereof, R ₄ is a C ₁ to C ₅ straight or branched chain alkylene, and P, Q and R are each independently a natural number of 3 to 100.

The diisocyanate compound may include, but is not limited to, Hexamethylene Diisocyanate (HDI), Isophorone Diisocyanate (IPDI), and Toluene Diisocyanate (TDI).

(Meth)acrylic acid C ₁ to C ₁₂ linear or branched alkyl ester monomer system is contained in the hydroxy-containing acrylic copolymer in polymerized form, which preferably has a glass transition temperature (Tg) -70 to (meth) acrylate, a C ₁ to C ₁₂ linear or branched alkyl ester monomer of -50 ℃, more preferably having a glass transition temperature (Tg) -70 to -50 ℃ acrylate of a C ₄ to C ₁₂ linear Chain or branched alkyl ester monomers.

Having a glass transition temperature (Tg) C -70 to -50 ℃ acrylate Examples of straight-chain or branched alkyl esters of ₄ to C ₁₂ may include: n-butyl acrylate, butyl acrylate, three, two, butyl acrylate, Amyl acrylate, 2-ethylbutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, and isononyl acrylate, the foregoing may be used alone or in combination of two or more. Of course, it is better to use n-butyl acrylate or 2-ethylhexyl acrylate.

If _{the glass transition temperature (Tg) of the C 1} -C ₁₂ linear or branched alkyl acrylate monomer is less than -70°C, its use is not economically feasible. On the other hand, when the glass transition temperature thereof exceeds -50°C, the low-temperature foldability deteriorates.

The hydroxyl-containing polymerizable monomer system is contained in the hydroxyl-containing acrylic copolymer in a polymerized form, preferably a monomer containing one hydroxyl group and one ethylenically unsaturated bond in one molecule, more preferably A hydroxyl-containing acrylate monomer having a glass transition temperature (Tg) of -60 to -40°C.

The hydroxy-containing acrylate monomer having a glass transition temperature (Tg) of -60 to -40°C is preferably a hydroxy-C ₄ -C ₆ linear or branched alkyl acrylate monomer.

Examples of hydroxy-C ₄ -C ₆ linear or branched alkyl acrylate monomers may include 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate, and 6-hydroxyhexyl acrylate, either alone or in combination Two or more are used in combination. Of course, it is preferred to use 4-hydroxybutyl acrylate.

If the glass transition temperature (Tg) of the hydroxyl group-containing acrylate monomer is less than -60°C, it is difficult to ensure the presence of the monomer. On the other hand, when the glass transition temperature thereof exceeds -40°C, the low-temperature foldability deteriorates.

In the hydroxyl group-containing acrylic copolymer, the content of (meth)acrylic acid C ₁ to C ₁₂ linear or branched chain alkyl ester may be 50 to 98% by weight, and the content of the hydroxyl group-containing polymerizable monomer may be 2 to 50% by weight.

_{More preferably, the content of C 1} to C ₁₂ linear or branched alkyl (meth)acrylate is 50 to 89% by weight, and the content of the hydroxyl group-containing polymerizable monomer is 11 to 50% by weight.

Also, if the content of the hydroxyl group-containing polymerizable monomer is less than 11% by weight, the amount of hydroxyl groups that are hydrophilic groups in the adhesive decreases, so that moisture may not be trapped by the adhesive layer and discharged to the interface. Adhesive conditions disadvantageously deteriorate adhesion and produce undesirable interfacial delamination. On the other hand, if its content exceeds 50% by weight, moisture is excessively absorbed by the adhesive, and thus the volume of the adhesive may increase and cohesion may decrease, thereby disadvantageously causing surface delamination and foaming.

In the hydroxyl-containing acrylic copolymer, further copolymerizable monomers known in the art may be included, and the copolymerizable monomer system exists in a polymerized form. Additional copolymerizable monomers of this type are not particularly limited, and examples thereof may include, but are not limited to: nitrogen-containing monomers, such as (meth)acrylonitrile, (meth)acrylamide, N-methyl N-butoxy methyl (meth)acrylamide; styrenic monomers such as styrene or methylstyrene ; glycidyl (meth)acrylate; and vinyl carboxylates, such as vinyl acetate.

In consideration of flexibility and peel strength, when another copolymerizable monomer is included, its content is preferably adjusted to 20 parts by weight or less, based on 100 parts by weight of the aforementioned monomer.

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

The isocyanate group-containing (meth)acrylate monomer system is included in the photocurable (meth)acrylate copolymer, an example of which can be (meth)acrylate isocyanato-C ₁ -C ₁₀ linear chain Or branched alkyl esters (isocyanato-C ₁ -C ₁₀ linear or branched alkyl (meth)acrylate). Here, the C ₁ -C ₁₀ straight or branched chain alkyl group may comprise: methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tertiary butyl, tertiary butyl, pentyl , hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, and decyl. Of course, ethyl or propyl is preferred.

The content of the isocyanate group-containing (meth)acrylate monomer is 0.1 to 5.0 wt % based on the total weight of the photocurable (meth)acrylate copolymer component. If the content of the isocyanate group-containing (meth)acrylate monomer is less than 0.1% by weight, the cohesion and heat resistance of the adhesive composition may decrease. On the other hand, if the content thereof exceeds 5.0% by weight, the cohesive force of the adhesive may become too strong, thereby disadvantageously deteriorating flexibility.

In the optically transparent adhesive composition of the present invention, the content of the polydimethylsiloxane-based (meth)acrylate compound is based on 100 parts by weight of the photocurable (meth)acrylate copolymer system 10 to 50 parts by weight, preferably 15 to 30 parts by weight. If the polydimethylsiloxane-based (meth)acrylate compound is used in an amount of less than 10 parts by weight, it is difficult to ensure low-temperature flexibility. On the other hand, if it is used in an amount exceeding 50 parts by weight, it is difficult to achieve good adhesion, and heat resistance is disadvantageously deteriorated.

The optically transparent adhesive composition of the present invention contains a photopolymerization initiator to effectively induce the reaction of polymerizable radicals. The photopolymerization initiator may be used during the polymerization reaction of the hydroxyl group-containing acrylic copolymer, and may also be included in the optically transparent adhesive composition together with the photocurable (meth)acrylate copolymer.

The photopolymerization initiator is not particularly limited, and any photopolymerization initiator known so far in the art can be used. Examples of the initiator may include typical initiators capable of generating radicals through ultraviolet light irradiation to thereby stimulate photopolymerization, such as benzoin-based initiators, alcohol-ketone-based initiators, amine ketone-based initiators, and phosphine oxidation System starter.

If the content of the photopolymerization initiator is too low, the effect produced may be so small that it becomes meaningless. On the other hand, if the content thereof is too high, stability such as durability or transparency may be deteriorated. Therefore, its appropriate content can be freely determined.

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

The optically transparent adhesive composition of the present invention may further comprise a multifunctional crosslinking agent. The polyfunctional crosslinking agent is not particularly limited, and may include polyfunctional crosslinking agents 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 multifunctional crosslinking agent is 0.02 to 5 parts by weight based on 100 parts by weight of the photocurable (meth)acrylate copolymer.

The optically transparent adhesive composition of the present invention may further comprise a silane coupling agent. The kind of the coupling agent is not particularly limited, and any typical coupling agent known in the field of adhesive preparation can be used. Examples of the silane coupling agent may include: γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxy Silane, gamma-glycidoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, gamma-methacryloyloxypropyl Trimethoxysilane, gamma-methacryloyloxypropyltriethoxysilane, gamma-aminopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, and 3-isocyanatopropyl Triethoxysilane (3-isocyanatopropyl triethoxysilane).

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

The optically transparent adhesive composition of the present invention further comprises a tackifier to adjust the adhesiveness.

And further comprises at least one additive selected from the group consisting of epoxy resins, curing agents, UV stabilizers, antioxidants, colorants, strengthening agents, fillers, defoaming agents, surfactants and plasticizers agent.

The optically transparent 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 monomers and copolymers can be dissolved in the optically clear adhesive composition.

Typical examples of solvents may include: ethyl acetate, methyl ethyl ketone, toluene, and acetonitrile.

The content of the solvent is 40 to 85 parts by weight based on 100 parts by weight of solids of the optically transparent adhesive composition.

In the optically clear adhesive composition of the present invention, the polydimethylsiloxane-based (meth)propionate compound is blended with the photocurable (meth)acrylate copolymer and is supply.

The optically clear adhesive composition of the present invention has a viscosity ranging from 500 centipoise (cP) to 2500 centipoise at 23°C.

The optically transparent adhesive composition of the present invention can ensure foldability by using a polydimethylsiloxane-based (meth)acrylate compound and a monomer having a low glass transition temperature, and by properly employing Moisture and heat resistance, heat resistance and durability can also be achieved through a curing system of radical polymerization and a curing system using a cross-linking agent and a thermosetting functional group (hydroxyl group).

In addition to the above description, the preparation method of the optically transparent adhesive composition of the present invention can be completed through any typical process in the art. Here, molecular weight controllers, catalysts and the like typical in the art can be used without limitation.

The coating method using the optically transparent adhesive composition of the present invention is not particularly limited, and examples thereof may include typical coating methods such as bar coating, spin coating, comma coating, and gravure coating. During the coating process, the cross-linking reaction of the functional groups of the polyfunctional cross-linking agent contained in the adhesive composition must be controlled to achieve a uniform coating. Therefore, the cross-linking agent can form a cross-linked structure during curing and aging after the coating process, thereby increasing the adhesion and cuttability as well as the cohesion of the adhesive.

And the coating process is preferably performed after the adhesive composition has sufficiently removed volatile components or foaming components (such as reaction residues). Therefore, the reduction of the elastic modulus due to excessively low crosslinking density or the molecular weight of the adhesive can be avoided, and the formation of internal scatterers caused by the increase in the size of the bubbles between the glass plate and the adhesive layer at high temperature can also be avoided.

After the coating of the optically transparent 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.

Appropriate aging procedures can be performed before or after light exposure for inducing reactions between the functional groups of the crosslinker and the thermosetting functional groups of the polymer in the composition. The conditions used for this aging procedure are not particularly limited, so long as the intended crosslinking reaction occurs.

The adhesive composition for optical films according to the present invention can be used to form optical films (such as polarizing films, phase difference films, anti-glare films, optical viewing angle compensation films or brightness enhancement films) stacked on each other, or to attach optical films or it is laminated to an object (eg, a display panel).

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

In addition, the present invention relates to an optically transparent adhesive film formed by coating a transfer film with the optically transparent adhesive composition of the present invention.

When the transfer film is used for the optically clear adhesive film, any known film in the art can be used without limitation. In addition, in the method of manufacturing the chemically transparent adhesive film, any method known in the art may be used without limitation.

Furthermore, the present invention relates to a flat panel display device comprising an adhesive layer formed from the optically transparent adhesive composition of the present invention,

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

The present invention will be specifically described through the following examples and comparative examples, which are only for illustrating the present invention, but the present invention is not limited to these examples, and various modifications and changes can be made.

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 with a condenser to facilitate temperature control with nitrogen reflux therebetween. 120 parts by weight of ethyl acetate (EAc) solvent was added thereto, and the resulting reaction mixture was flushed with nitrogen for 60 minutes to remove oxygen. After that, the temperature was maintained at 70° C., 0.1 part by weight of the reaction initiator azobisisobutyronitrile (AIBN) was added thereto, and the reaction was performed for 12 hours, thus preparing an acrylic polymer A1 having a weight average molecular weight of 450,000.

Preparation Example 1-2: Preparation of Acrylic Polymer A2

Acrylic polymer A2 with 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 n-butyl acrylate (n-BA) were used in this preparation example. 4-Hydroxybutyl acrylate (4-HBA).

Preparation Example 1-3: Preparation of Acrylic Polymer A3

Acrylic polymer A3 with 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 acrylic acid 2- Hydroxyethyl ester (2-HEA) replaced 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

Acrylic polymer A4 with 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 acrylic acid 4- Hydroxybutyl acrylate (4-HBA) replaced 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 acrylic polymer A1 (solid content), 1 part by weight of 2-isocyanatoethyl methacrylate (2-isocyanatoethyl methacrylate) and 0.1 part by weight of dibutyltin dilaurate (DBTDL) were placed in a 1 liter reactor with a condenser to facilitate temperature control with nitrogen reflux in between. Subsequently, the reaction was carried out at atmospheric pressure at 40° C. for 4 hours or more, thus producing 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 in this preparation example.

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 in this preparation example.

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 Preparation Example 2-1, except that acrylic polymer A4 was used in this preparation example.

Preparation Example 3: Formation of Hard Coat Film for Bendability Evaluation

<Preparation of epoxysiloxane resin>

3-Glycidoxypropyltrimethoxysilane (GPTS, available from Gelest) was mixed with water in a ratio of 23.63 g: 2.7 g (0.1 mol: 0.15 mol) and placed in a 100 mL two-neck flask. Then, 0.05 ml of ammonia as a catalyst was added to the mixture, and the mixture was stirred at 60° C. for 6 hours, thereby preparing a siloxane sol.

<Preparation of hard coat composition>

The siloxane sol and diglycidol were mixed at a weight ratio of 100:10, and 100 parts by weight of the resulting mixture was mixed with 2 parts by weight triarylsulfonium hexafluoroantimonate, thus preparing a hard coat composition thing.

<Formation of hard coat film>

The hard coating composition was coated with a thickness of 50 microns on a COP film (cycloolefin polymer, ZF-16, available from Zeon) having a thickness of 40 microns and subjected to a corona surface treatment, thus producing a film . The films were exposed to a mercury UV lamp (20 milliwatts per square centimeter (mW/cm ² )) for 5 minutes, and the reaction was excited with triarylsulfonium hexafluoroantimonate, and then heated at 50°C and 50% RH (relative humidity). ) was subjected to hydrothermal treatment for 60 minutes, thereby forming a hard coat film.

Example 1: Preparation of Optically Clear Adhesive Composition

By mixing 100 parts by weight of the photocurable acrylate copolymer B1 of Preparation Example 2-1, 20 parts by weight of the monomer of the following Chemical Formula 1, 0.07 parts by weight of a multifunctional crosslinking agent (Coronate L, purchased from Japan NPU), 0.2 Parts by weight of a photopolymerization initiator (hydroxycyclohexyl phenyl ketone, Irgacure 184, purchased from Chemicals for Cibart, Switzerland), and 0.2 parts by weight of 3-glycidoxypropyltrimethoxysilane (KBM-403, Purchased from Xinyue Silica Light) to prepare optically clear adhesive compositions.

In Chemical Formula 1, R ₁ is hydrogen, and P is 50.

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 the monomer of the following Chemical Formula 2 was used in this Example instead of the monomer of Chemical Formula 1.

In Chemical Formula 2, R ₁ is a methyl group, R ₂ is an ethylidene group, and Q is 50.

Example 3: Preparation of Optically Clear Adhesive Composition

By mixing 100 parts by weight of the photocurable (meth)acrylate copolymer B2 of Preparation Example 2-2, 30 parts by weight of the monomer of the following Chemical Formula 3, and 0.5 parts by weight of a polyfunctional isocyanate crosslinking agent (Coronate L , purchased from Japan NPU), and 0.2 parts by weight of a photopolymerization initiator (hydroxycyclohexyl phenyl ketone, Irgacure 184, purchased from Chemicals for Ciba, Switzerland), to prepare an optically transparent adhesive composition.

In Chemical Formula 3, R ₁ is hydrogen, R ₃ is a hexamethylene group, R ₄ is an ethylene group, and R is 50.

Comparative Example 1: Preparation of Optically Clear Adhesive Composition

By mixing 100 parts by weight of the photocurable acrylate copolymer B3 of Preparation Example 2-3, 0.07 parts by weight of a multifunctional crosslinking agent (Coronate L, purchased from NPU Japan), and 0.2 parts by weight of a photopolymerization initiator (Hydroxycyclohexyl phenyl ketone, Irgacure 184, purchased from Ciba Chemicals, Switzerland), and 0.2 parts by weight of 3-glycidoxypropyltrimethoxysilane (KBM-403, purchased from Silicon Light) , the preparation of optical adhesive compositions.

Comparative Example 2: Preparation of Optically Clear Adhesive Composition

By mixing 100 parts by weight of the photocurable acrylate copolymer B4 of Preparation Example 2-4, 0.07 parts by weight of a multifunctional crosslinking agent (Coronate L, purchased from Japan NPU), and 0.2 parts by weight of a photopolymerization initiator (Hydroxycyclohexyl phenyl ketone, Irgacure 184, purchased from Ciba Chemicals, Switzerland), and 0.2 parts by weight of 3-glycidoxypropyltrimethoxysilane (KBM-403, purchased from Silicon Light) , the preparation of optical adhesive compositions.

Example 4: Formation of Optically Transparent Adhesive Film

Each of the optically clear adhesive compositions of Examples 1 to 3 and Comparative Examples 1 to 2 was coated on a PET film having a thickness of 50 μm and coated with a siloxane release agent to achieve a thickness of 100 μm after curing. After drying at 100°C for 5 minutes, the optically transparent adhesive film of Example 4-1 (using the optically transparent adhesive composition of Example 1) and the optically transparent adhesive film of Example 4-2 (using the optically transparent adhesive composition of Example 1) were obtained. The optically transparent adhesive composition of Example 2), the optically transparent adhesive film of Example 4-3 (using the optically transparent adhesive composition of Example 3), the optically transparent adhesive film of Comparative Example 4-1 (using the comparative example) The optically transparent adhesive composition of 1) and the optically transparent adhesive film of Comparative Example 4-2 (using the optically transparent adhesive composition of Comparative Example 2).

Example 5: Formation of Laminate with Adhesive Layer

The optically transparent adhesive films of Example 4-1, Example 4-2, Example 4-3, Comparative Example 4-1, and Comparative Example 4-2 were each formed as an adhesive layer on a 100-micron-thick PET film (purchased from Mitsubishi). ^{), and irradiated with light of 1000 millijoules/square centimeter (mJ/cm 2} ) in the direction of forming the release film using a UV lamp (purchased from Fusion), so that each of Example 5-1, implementation of Lamination of the adhesive layers of Example 5-2, Example 5-3, Comparative Example 5-1 and Comparative Example 5-2.

Example 6: Formation of Hardcoat Film for Flexibility Evaluation/Adhesion Layer/PET Lamination

The laminates of Example 5-1, Example 5-2, Example 5-3, Comparative Example 5-1 and Comparative Example 5-2 were each cut to a size of 50 mm x 100 mm. The PET film was then peeled off from the adhesive layer of the cut laminate, after which the resulting laminate was attached to the hard coat film for bendability evaluation prepared in Preparation Example 3, 50 mm x 100 mm in size, in an autoclave ( 50° C., 5 atmospheres) and pressurized for 20 minutes, and then aged for 24 hours under constant temperature and constant humidity (23° C., 50% RH) conditions, so that Example 6-1 and Example 6-2 were obtained. Each of Example 6-3, Comparative Example 6-1, and Comparative Example 6-2 was used for bendability evaluation/adhesive layer/PET (100 micron) laminate hard coat.

Test Example: Evaluation of Properties of Optically Clear Adhesive Compositions

1. Foldability evaluation

<assessment method>

Evaluation standard: IEC 62715

Evaluation device: Tension-free U-shape folding test machine (DLDMLH-FS)

Device manufacturer: Yuasa Systems (Japan)

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

Each of Example 6-1, Example 6-2, Example 6-3, Comparative Example 6-1, and Comparative Example 6-2 produced in Example 6 was used for bendability evaluation/adhesive layer/PET stack The hardcoat of the layer was measured and determined for its foldability by the evaluation method described above. The results are shown in Table 1 below.

<Evaluation Criteria>

○: Defects such as blistering, peeling, and cracks are not observed on the laminate

△: There are microscopic defects on the laminate that can be observed with the naked eye

x: The folded portion of the laminate has a defect that can be clearly observed with the naked eye

2. Durability evaluation

(1) Evaluation of heat resistance

Each of Example 6-1, Example 6-2, Example 6-3, Comparative Example 6-1, and Comparative Example 6-2 manufactured in Example 6 was used for bendability evaluation/adhesion layer/PET stack The hard coat film of the layer was left to stand at 80° C. for 1,000 hours, after which it was observed whether blistering or peeling occurred to evaluate heat resistance. The results are shown in Table 1 below.

<Evaluation Criteria>

◎: Neither foaming nor peeling

○: Number of blistering or peeling defects <5

起泡或剝離缺陷數<10 △: 5

Number of blistering or peeling defects <10

起泡或剝離缺陷數 x: 10

Number of blistering or peeling defects

(2) Evaluation of damp heat resistance

Each of Example 6-1, Example 6-2, Example 6-3, Comparative Example 6-1, and Comparative Example 6-2 manufactured in Example 6 was used for bendability evaluation/adhesion layer/PET stack The hard coat film of the layer was left to stand at 60° C. and 90% RH for 1,000 hours, after which it was observed whether foaming or peeling occurred. Immediately before evaluating the samples, the samples were allowed to stand at room temperature for 24 hours and then observed to evaluate their resistance to damp heat. The results are shown in Table 1 below.

<Evaluation Criteria>

◎: Neither foaming nor peeling

○: Number of blistering or peeling defects <5

起泡或剝離缺陷數<10 △: 5

Number of blistering or peeling defects <10

起泡或剝離缺陷數 x: 10

Number of blistering or peeling defects

3. Adhesion assessment

The laminates each having the adhesive layers of Example 5-1, Example 5-2, Example 5-3, Comparative Example 5-1 and Comparative Example 5-2 were cut to a size of 25 mm x 100 mm. The PET film was then peeled off from the adhesive layer of the cut laminate, after which the laminate with the adhesive layer was attached to the alkali-free glass using a 2 kg roller according to JIS Z 0237. The alkali-free glass on which the laminate was attached was pressed in an autoclave (50°C, 5 atmospheres) for 20 minutes, and stored at a constant temperature and humidity (23°C, 50% RH) for 24 hours. After that, when the laminate was peeled off from the alkali-free glass at a peeling speed of 300 mm/min and a peeling angle of 180°, the adhesion was measured using a TA (texture analyzer, available from Stable Micro Systems, UK). The results are shown in Table 2 below

From the test results in Tables 1 and 2, the optically transparent adhesive compositions of the embodiments of the present invention are excellent in foldability, damp heat resistance, heat resistance and adhesiveness. In particular, the foldability was significantly higher than that of the optically clear adhesive composition of the comparative example. Since the polydimethylsiloxane-based (meth)acrylate compound was used in the present invention, the adhesiveness was lower than that of the comparative example.

Claims (9)

An optically transparent adhesive composition comprising a photocurable (meth)acrylate copolymer, a polydimethylsiloxane-based (meth)acrylate compound, and a photopolymerization initiator, wherein the curable (meth)acrylate The photocurable (meth)acrylate copolymer comprises, based on the total weight of the copolymer components, 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 (isocyanate-group-containing (meth)acrylate) monomer, the hydroxyl-containing acrylic copolymer and the isocyanate group-containing (meth)acrylate monomer form a urethane bond; and the hydroxyl-containing acrylic acid The series copolymer comprises, based on the total monomer weight of the copolymer, 50 to 98% by weight of (meth)acrylic acid C ₁ to C ₁₂ linear or branched alkyl ester monomers and 2 to 50% by weight of hydroxyl-containing A polymerized monomer having a weight average molecular weight of 200,000 to 1,000,000, wherein the hydroxyl-containing polymerizable monomer system has a hydroxyl group and an ethylenically unsaturated bond in one molecule of the monomer, wherein the (meth)acrylic acid C ₁ to C ₁₂ linear or branched chain alkyl ester monomer system has a glass transition temperature of -70 to -50 ° C (meth)acrylic acid C ₁ to C ₁₂ linear or branched chain alkyl ester monomer; and the The monomer system with one hydroxyl group and one ethylenically unsaturated bond in one molecule has a glass transition temperature of -60 to -40 ℃ of hydroxyl-containing acrylate monomers, wherein the polydimethylsiloxane-based The (meth)acrylate compound includes at least one compound selected from the group consisting of compounds represented by the following Chemical Formulas 1 to 3: [Chemical Formula 1]

In Chemical Formulas 1 to 3; R ₁ is independently hydrogen or methyl; R ₂ is C ₁ to C ₅ straight-chain or branched alkylene group; R ₃ is independently one derived from diisocyanate The compound and -N(H)-C(O)- are linked to the groups on both sides thereof; R ₄ is a C ₁ to C ₅ straight or branched chain alkylene; and P, Q and R are each independently 3 Natural numbers up to 100. The optically transparent adhesive composition of claim 1, wherein the optically transparent adhesive composition comprises, based on 100 parts by weight of the photocurable (meth)acrylate copolymer, 10 to 50 parts by weight of polydimethyl methacrylate Siloxane-based (meth)acrylate compound and 0.1 to 5 parts by weight of a photopolymerization initiator. The optically transparent adhesive composition according to claim 2, further comprising 0.02 to 5 parts by weight of a multifunctional crosslinking agent, based on 100 parts by weight of the photocurable (meth)acrylate copolymer. The optically transparent adhesive composition according to claim 3, wherein the multifunctional crosslinking agent is a thermal curing polyfunctional isocyanate crosslinking agent or a multifunctional (meth)acrylate crosslinking agent. The optically transparent adhesive composition according to claim 2 or 3, further comprising 40 to 85 parts by weight of a solvent, based on 100 parts by weight of the optically transparent adhesive composition. The optically transparent adhesive composition according to claim 1, wherein the isocyanate group-containing (meth)acrylate monomer system (meth)acrylate isocyanato-C ₁ -C ₁₀ linear or branched alkane base ester (isocyanato-C ₁ -C ₁₀ linear or branched alkyl(meth)acrylate). An optically transparent adhesive film, which is made by coating a transfer film with the optically transparent adhesive composition of claim 1. A flat panel display device comprising an adhesive layer formed of the optically transparent adhesive composition of claim 1. The flat panel display device according to claim 8, wherein the flat panel display device is a flexible display device.