TWI727092B - 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℃ and 11 ~ 50 wt% of a hydroxy-C4-C6 linear or branched alkyl acrylate monomer having a glass transition temperature (Tg) of -60 ~ -40℃, 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 composition, and flat panel display

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

Examples of flat panel display devices include liquid crystal displays (LCD), plasma display panels (PDP), organic electroluminescence displays (OLED), and the like.

Such flat panel display devices include display panels and optical films. Examples of optical films include polarizing films, retardation films, anti-glare films, optical viewing angle compensation films, brightness enhancement films, and the like. When the optical films are stacked on top of each other or the optical films are attached to the display panel, an optically transparent adhesive (OCA) is used. Accordingly, the optically transparent adhesive (OCA) must not only have typical optical properties, but also must have excellent moisture and heat resistance, heat resistance, 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 bear bending stress. Therefore, it is required to further improve various properties of optically transparent adhesives (OCA) used in flexible display devices.

For example, an optically transparent adhesive (OCA) used in a flexible display device must have extremely foldable properties, so that the device can be flexibly folded. Furthermore, considering that the flexible display device is used outdoors for a long time, its low-temperature foldability must be excellent.

In addition, the optically transparent adhesive (OCA) used in the flexible display device must have more improved moisture and heat resistance. The reason is that the flexible display device is repeatedly subjected to multiple folding and unfolding processes during its use, which may increase the possibility of moisture permeating through the folded and unfolded parts.

In addition, 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. As such, since the stacked display panel and the optical film are easily separated from each other, higher adhesion and higher durability are required.

However, optically transparent adhesives (OCA) known today cannot sufficiently provide the properties required for flexible display devices.

[Reference List] [Patent Literature]

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

Accordingly, the present invention keeps in mind the problems encountered by related technologies, and the present invention intends to provide an optically transparent adhesive (OCA) composition that can fully meet the foldability, moisture and heat resistance, heat resistance, and heat resistance required for flexible display devices. And adhesiveness.

In addition, the present invention intends to provide an optically transparent adhesive film and a flat panel display device including an optically transparent adhesive (OCA) composition.

Therefore, the present invention proposes an optically transparent adhesive composition comprising a photocurable (meth)acrylate copolymer and a photopolymerization initiator, wherein the photocurable adhesive composition is based on the total weight of the copolymer's components. The cured (meth)acrylate copolymer includes 95 to 99.9wt% hydroxyl-containing acrylic copolymer and 0.1 to 5wt% isocyanate group-containing (meth)acrylate monomer, the hydroxyl-containing acrylic copolymer and The isocyanate group-containing (meth)acrylate monomer forms a urethane bond; and based on the total weight of the monomers of the copolymer, the hydroxyl-containing acrylic copolymer includes 50 to 89 wt% -70 to -50°C glass transition temperature (Tg) C ₄ -C ₁₂ linear or branched chain alkyl acrylate monomer and 11 to 50wt% with -60 to -40°C glass transition temperature (Tg) The hydroxy-C ₄ -C ₆ linear or branched alkyl acrylate monomer, and has a weight average molecular weight of 200,000 to 1,000,000.

In addition, the present invention provides an optically transparent adhesive film, which is made 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, which includes an adhesive layer made of the optically transparent adhesive composition of the present invention.

According to the present invention, the optically transparent adhesive (OCA) composition and the optically transparent adhesive film can have sufficient foldability, moisture and heat resistance, heat resistance, and adhesion required for flat panel display devices and flexible display devices. It can be endowed with excellent durability.

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

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

As used herein, the photocurable (meth)acrylate copolymer includes, based on the total weight of the composition of the copolymer, 95 to 99.9% by weight of acrylic copolymer containing hydroxyl groups and 0.1 to 5% by weight An 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 The copolymer includes, based on the total weight of the monomers of the copolymer, 50 to 89 wt% C ₄ -C ₁₂ linear or branched alkyl acrylate with a glass transition temperature (Tg) of -70 to -50°C _{Base ester monomer and 11 to 50wt% hydroxyl-C 4} -C ₆ linear or branched alkyl acrylate monomer with glass transition temperature (Tg) of -60 to -40°C, and 200,000 to 1,000,000 Weight average molecular weight.

In the present invention, the optically transparent adhesive composition includes a monomer having a low glass transition temperature (Tg), and thus may improve low-temperature foldability. Due to the use of a large number of monomers containing OH groups, it can provide moisture and heat resistance and adhesion, and can increase the crosslinking density, resulting in an optically transparent adhesive composition with high heat resistance and durability.

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

The preparation method of the photocurable (meth)acrylate copolymer can be through the C ₄ -C ₁₂ linear or branched alkyl acrylate monomer with a glass transition temperature (Tg) of -70 to -50°C _{Copolymerized with hydroxyl-C 4} -C ₆ linear or branched alkyl acrylate monomers with a glass transition temperature (Tg) of -60 to -40°C to obtain a hydroxyl-containing acrylic copolymer main chain structure It is formulated so that the thermosetting functional group (OH group) is introduced into its branched chain or its terminal, and then the main chain is reacted with the isocyanate group-containing (meth)acrylate monomer under appropriate conditions to thereby contain the isocyanate group The (meth)acrylate monomer replaces at least part of the thermosetting functional group (OH group) of the main chain.

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 alkylene 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 monomer.

The backbone 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 with a glass transition temperature (Tg) of -70 to -50°C included in the form of being polymerized in a hydroxyl-containing acrylic copolymer Examples include n-butyl acrylate, t-butyl acrylate, second butyl acrylate, pentyl acrylate, 2-ethylbutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate Ester, and isononyl acrylate, which can be used alone or in combination of two or more of them. Among them, it is preferable to use n-butyl acrylate or 2-ethylhexyl acrylate.

If _{the glass transition temperature (Tg) of the 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 its glass transition temperature exceeds -50°C, the low-temperature foldability may be deteriorated.

_{Hydroxy-C 4} -C ₆ linear or branched alkyl acrylate contained in the form of being polymerized in a hydroxyl-containing acrylic copolymer and having a glass transition temperature (Tg) of -60 to -40°C Examples of monomers may include 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate, and 6-hydroxyhexyl acrylate, which may be used alone or in combination of two or more of them. Among them, it is preferable to use 4-hydroxybutyl acrylate.

If the glass transition temperature (Tg) of the hydroxyl-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 its glass transition temperature exceeds -40°C, the low-temperature foldability may deteriorate.

_{In the hydroxyl-containing acrylic copolymer, the preferred content of C 4} -C ₁₂ linear or branched alkyl acrylate monomer with a glass transition temperature (Tg) of -70 to -50°C is 50 to 89 wt% _{, And the hydroxyl-C 4} -C ₆ linear or branched alkyl acrylate monomer with a glass transition temperature (Tg) of -60 to -40°C is preferably 11 to 50wt%. _{Therefore, if the content of the hydroxyl-C 4} -C ₆ linear or branched alkyl acrylate monomer with a glass transition temperature (Tg) of -60 to -40°C is less than 11wt%, it can be used in the adhesive as The content of the OH group of the hydrophilic group may be reduced, and therefore the moisture cannot be captured by the adhesive layer, but may be discharged to the interface. Under the condition of damp heat resistance, the adhesion is undesirably deteriorated, and interfacial delamination may occur undesirably. On the other hand, if its content exceeds 50wt%, water may be excessively absorbed by the adhesive, and therefore the volume of the adhesive may increase, and cohesion may be reduced, undesirably causing interfacial delamination and blistering.

In the hydroxyl-containing acrylic copolymer, the additional copolymerizable monomers known in the industry can be further included in the polymerized form. The types of additional copolymerizable monomers are not particularly limited, and examples thereof may include, but are not limited, nitrogen-containing monomers such as (meth)acrylonitrile, (meth)acrylamide, N-methyl(formaldehyde) Yl)acrylamide, or N-butoxymethyl(meth)acrylamide; styrene-based monomers such as styrene or methylstyrene; glycidyl (meth)acrylate; and carboxylate Acid vinyl esters such as vinyl acetate.

In consideration of flexibility and tear strength, when additional copolymerizable monomers are included, the content is preferably adjusted to 20 parts by weight or less based on a total of 100 parts by weight of the aforementioned monomers.

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

The (meth)acrylate monomers containing isocyanate groups included in the photocurable (meth)acrylate copolymers can be isocyanate-C ₁ -C ₁₀ linear or branched (methyl) ) Take alkyl acrylate as an example. Wherein, C ₁ -C ₁₀ linear or branched alkyl groups may include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, second butyl, tertiary butyl, pentyl, Hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, and decyl. Among them, it is preferable to use an ethyl group or a propyl group.

Based on the total weight of the components of the photocurable (meth)acrylate copolymer, the isocyanate group-containing (meth)acrylate monomer can be used in an amount of 0.1wt% to 5.0wt%. If the amount 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 amount exceeds 5.0 wt%, the cohesive force of the adhesive may become too strong, undesirably deteriorating foldability.

The optically transparent adhesive composition of the present invention contains a photopolymerization initiator to effectively induce the reaction of polymerizable free radicals. The photopolymerization initiator can be used in the polymerization of the hydroxyl-containing acrylic copolymer, and can 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 can be used as long as it is known in the industry. Examples of initiators can include typical initiators that can generate free radicals through UV irradiation and thus initiate photopolymerization, such as benzoin-based initiators, hydroxyketone-based initiators, and aminoketone-based initiators. Initiators and initiators based on phosphine oxides.

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

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

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

Based on 100 parts by weight of the photocurable (meth)acrylate copolymer, the content of the multifunctional crosslinking agent may be 0.02 to 5 parts by weight.

The optically transparent adhesive composition of the present invention may further include a silane coupling agent. The type of silane coupling agent is not particularly limited, and any coupling agent typically known in the field of adhesive preparation can be used. Examples of silane coupling agents may include γ-cyclopropoxypropyltriethoxysilane, γ-cyclopropoxypropyltrimethoxysilane, γ-cyclopropoxypropylmethyldiethoxysilane, γ-Cyclopropoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethyl Oxysilane, γ-methacryloxypropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and 3-isocyanate Propyl triethoxysilane.

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

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

In addition, it may further include at least one additive selected from the group consisting of: epoxy resin, curing agent, UV stabilizer, antioxidant, colorant, strengthening agent, filler, defoamer , Surfactant, and plasticizer.

The optically transparent adhesive composition of the present invention may further include a solvent. Any solvent known in the industry can be used without limitation, as long as the solvent can dissolve the monomers and copolymers used in the optically transparent adhesive composition.

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

Based on 100 parts by weight of the photocurable (meth)acrylate copolymer, the content of the solvent may be 40 to 85 parts by weight.

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

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

In addition to the foregoing description, the preparation method of the optically transparent adhesive composition of the present invention can be carried out by any method typically known in the industry. In this article, typical molecular weight control agents and catalysts in the industry 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 methods such as bar coating, spin coating, doctor blade coating, and gravure coating. During the coating process, the crosslinking reaction of the functional groups of the multifunctional crosslinking agent included in the adhesive composition must be controlled so that it does not proceed in order to achieve uniform coating. Therefore, after the coating process, during the curing and aging process, the cross-linking agent can generate a cross-linked structure, which improves the adhesive properties, cutability, and cohesion of the adhesive.

Furthermore, it is preferable that the coating process is performed after sufficiently removing volatile components or foaming components, such as reaction residues, from the adhesive composition. Thereby, it is possible to prevent the decrease of the elastic modulus caused by the crosslink density of the adhesive or the molecular weight is too low, and it is also possible to prevent the internal scatter caused by the increase of the bubble size between the glass plate and the adhesive layer at high temperature generate.

After the coating layer of the optically transparent adhesive composition is formed, it is cured by light. In this article, when UV irradiation is performed, a high-pressure mercury lamp, an electrodeless lamp, or a xenon lamp can be used.

Before or after exposure, appropriate aging treatment can be carried out to induce the reaction between the functional group of the crosslinking agent of the composition and the thermosetting functional group of the polymer. The conditions of the aging treatment are not particularly limited, as long as the crosslinking can occur properly. The joint reaction is sufficient.

The adhesive composition for optical films according to the present invention can be used to stack optical films (such as polarizing films, retardation films, anti-glare films, optical viewing angle compensation films, or brightness enhancement films) on top of each other, or to stack optical films Or its laminate is attached to a target, such as a display panel.

In particular, the adhesive composition for optical films according to the present invention is preferably used for flexible display devices.

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

As for the transfer film used in the optically transparent adhesive film, any film known in the industry can be used without limitation. Furthermore, in the manufacturing method of the optically transparent adhesive film, any method known in the industry can be used without limitation.

In addition, the present invention relates to a flat panel display device, which includes 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 present invention is clearly illustrated by the following examples and comparative examples. The examples and comparative examples are only used to illustrate the present invention, but the present invention is not limited by these examples, but can be modified and changed variously.

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) are placed in a 1 liter reactor equipped with a condenser, thus facilitating temperature control when nitrogen is 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 parts by weight of the reaction initiator azobisisobutyronitrile (AIBN) was added thereto, and the reaction proceeded 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

The acrylic polymer A2 with a weight average molecular weight of 470,000 was prepared using the same polymerization technique as 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 ( 4-HBA).

Preparation Example 1-3: Preparation of Acrylic Polymer A3

The acrylic polymer A3 with a weight average molecular weight of 450,000 was prepared using the same polymerization technique as 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 ( 2-HEA) instead of 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 with a weight average molecular weight of 390,000 was prepared using the same polymerization technique as 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 ( 2-HEA) instead of 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 light-curable (meth)acrylate copolymer B1

100 parts by weight of the solid content of acrylic polymer A1, 1 part by weight of 2-isocyanatoethyl methacrylate, and 0.1 part by weight of dibutyltin dilaurate (DBTDL) are placed in a 1 liter reaction equipped with a condenser Inside the vessel, it is convenient to control the temperature when the 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 light-curable (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 light-curable (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 light-curable (meth)acrylate copolymer B4

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

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

<Preparation of epoxy silicone resin>

3-cyclopropoxypropyltrimethoxysilane (GPTS, obtained from Gelest) was mixed with water in a ratio of 23.63 g: 2.70 g (0.1 mol: 0.15 mol), and then placed 100ml two-necked bottle. Thereafter, 0.05 ml of ammonia was added to the mixture as a catalyst, and the mixture was stirred at 60°C for 6 hours, thereby preparing a silicone sol.

<Preparation of Hard Coating Composition>

The silicone sol and the 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 hexafluoroantimonate, thereby obtaining a hard coating composition.

<Formation of Hard Coating Film>

The hard coating composition was applied to a cycloolefin polymer (COP, ZF-16, from Zeon) film having a thickness of 40 microns in a thickness of 50 microns, and subjected to corona surface treatment, thereby preparing a film. The film was exposed to a mercury UV lamp (20 mW/cm²) for 5 minutes, and the reaction was induced by triaryl hexafluoroantimonate, followed by hydrothermal treatment at 50°C and 50% relative humidity (RH). For 60 minutes, a hard coating film was formed.

Example 1: Preparation of optically transparent adhesive composition

The preparation method of the optically transparent adhesive composition is as follows: by mixing 100 parts by weight of the photocurable (meth)acrylate copolymer B1 of Preparation Example 2-1, 0.5 parts by weight of the multifunctional isocyanate crosslinking agent (Clonil ( Coronate) L, available from NPU Japan Corporation), and 0.2 parts by weight of a photopolymerization initiator (hydroxycyclohexyl phenyl ketone, Irgacure 184, available from Ciba Specialty Chemicals) , Switzerland) and to be prepared.

Example 2: Preparation of optically transparent adhesive composition

The optically transparent 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物B1.

Comparative example 1: Preparation of optically transparent adhesive composition

The optically transparent 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物B1.

Comparative Example 2: Preparation of optically transparent adhesive composition

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

Example 3: Formation of optically transparent adhesive film

The optically transparent adhesive composition of each of Examples 1 and 2 and Comparative Examples 1 and 2 was applied to a PET film having a thickness of 50 microns, and coated with a silicone release agent, which reached a thickness of 100 microns after curing. And then dried at 100°C for 5 minutes, thus manufacturing Example 3-1 (using the optically transparent adhesive composition of Example 1), Example 3-2 (using the optically transparent adhesive composition of Example 2), and comparing Example 3-1 (using the optically transparent adhesive composition of Comparative Example 1) and Comparative Example 3-2 (using the optically transparent adhesive composition of Comparative Example 2) each optically transparent adhesive film.

Example 4: Generation of laminate with 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 make an adhesive on a 100-micron-thick PET film (from Mitsubishi). The agent layer and the release film were formed in the direction of using a UV lamp (from Fusion) to irradiate light at 1000 millijoules/cm². Therefore, the production has Example 4-1, Example 4-2, and Comparative Example 4- 1 and Comparative Example 4-2 Each of the laminates of the adhesive layer.

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

Each laminate 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 torn off from the adhesive layer of the cut laminate, and thereafter, the resulting laminate was attached to the hard coating film for bendability evaluation (with a size of 50) manufactured in Preparation Example 3. Mm x 100 mm), pressurized in a high-pressure steam cooker (50°C, 5 atmospheres) for about 20 minutes, and then aged for 24 hours under constant temperature and humidity conditions (23°C and 50% relative humidity), thus manufacturing the embodiment 5-1, Example 5-2, Comparative Example 5-1, and Comparative Example 5-2 Each of the hard coating film/adhesive layer/PET (100 microns) laminate for bendability evaluation.

Test example: Evaluation of properties of optically transparent adhesive composition estimate

1. Foldability evaluation

<Assessment method>

Evaluation standard: IEC 62715

Evaluation device: Tension-free U-shaped folding tester (DLDMLH-FS)

Device symbol: YUASA SYSTEM (Japan)

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

Example 5-1, Example 5-2, Comparative Example 5-1, and Comparative Example 5-2 manufactured in Example 5 Hard coating film/adhesive layer/PET laminate system for bendability evaluation After measurement, the foldability is determined by the above evaluation method. The results are shown in Table 1 below.

<Evaluation Criteria>

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

△: Minor defects observed by naked eyes on the laminate

×: Defects clearly observed by naked eyes on the folded part of the laminate

2. Evaluation of durability

(1) Evaluation of heat resistance

Example 5-1, Example 5-2, Comparative Example 5-1, and Comparative Example 5-2 manufactured in Example 5 Hard coating film/adhesive layer/PET laminate system for bendability evaluation Let it stand at 80°C for 1,000 hours, and then observe whether foaming or peeling occurs in order to evaluate the heat resistance. The results are shown in Table 1 below.

<Evaluation Criteria>

◎: Neither foaming nor peeling occurs

○: Number of foaming or peeling defects<5

發泡或剝離缺陷之數目<10 △: 5

Number of foaming or peeling defects<10

諸如發泡或剝離缺陷之數目 ×: 10

Number of defects such as foaming or peeling

(2) Evaluation of resistance to humidity and heat

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

<Evaluation Criteria>

◎: Neither foaming nor peeling occurs

○: Number of foaming or peeling defects<5

發泡或剝離缺陷之數目<10 △: 5

Number of foaming or peeling defects<10

發泡或剝離缺陷之數目 ×: 10

Number of foaming or peeling defects

3. Evaluation of Adhesion

The laminate having the adhesive layer 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 torn off from the adhesive layer of the cut laminate, and then, in accordance with JIS Z 0237, the laminate with the adhesive layer was attached to the alkali-free glass using a 2kg roller. The alkali-free glass with the laminate attached to it is pressurized in a high-pressure steam boiler (50°C, 5 atmospheres) for about 20 minutes, and stored under constant temperature and humidity conditions (23°C and 50% relative humidity) for 24 minutes hour. Afterwards, when using a Texture Analyzer (TA), obtained from Stable Micro Systems UK (Stable Micro Systems UK), with a tearing rate of 300 mm/min and a tearing angle of 180 degrees, the glass was removed from the alkali-free glass. The adhesion is measured when the laminate is torn off. The results are shown in Table 2 below.

As is obvious from the test results in Table 1 and Table 2, the optically transparent adhesive composition of the embodiment of the present invention is excellent in terms of foldability, heat resistance, heat resistance, and adhesion. In particular, the foldability of the optically transparent adhesive composition is significantly higher than that of the comparative example.

Although preferred specific examples of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various modifications, additions, and additions may be made without departing from the scope and essence of the present invention as disclosed in the scope of the attached patent application. replace.

Claims (10)

An optically transparent adhesive composition comprising a photocurable (meth)acrylate copolymer and a photopolymerization initiator, wherein the photocurable (A) (Base) acrylate copolymers include 95 to 99.9% by weight of hydroxyl-containing acrylic copolymers and 0.1 to 5% by weight of isocyanate group-containing (meth)acrylate monomers, the hydroxyl-containing acrylic copolymers and the isocyanate group-containing (meth)acrylate monomers The (meth)acrylate monomer forms a urethane bond, and based on the total weight of the monomers of the copolymer, the hydroxyl-containing acrylic copolymer includes 50 to 89 wt% with -70 to- C ₄ -C ₁₂ linear or branched alkyl acrylate monomer with glass transition temperature (Tg) of 50°C and 11 to 50wt% hydroxyl group with glass transition temperature (Tg) of -60 to -40°C _{4- C6} linear or branched alkyl acrylate monomer, and has a weight average molecular weight of 200,000 to 1,000,000. The optically transparent adhesive composition described in item 1 of the scope of patent application, wherein the C ₄ -C ₁₂ linear or branched alkyl acrylate monomer 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, third butyl acrylate, second butyl acrylate, pentyl acrylate, 2-ethylbutyl acrylate, 2 -Ethylhexyl, n-octyl acrylate, isooctyl acrylate, and isononyl acrylate, and the hydroxyl group having a glass transition temperature (Tg) of -60 to -40°C-C ₄ -C ₆ linear or branched 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 transparent adhesive composition as described in item 1 of the scope of patent application, wherein based on 100 parts by weight of the photocurable (meth)acrylate copolymer, the optically transparent adhesive composition contains 0.1 to 5 Parts by weight of photopolymerization initiator. The optically transparent adhesive composition described in item 3 of the scope of the patent application, based on 100 parts by weight of the photocurable (meth)acrylate copolymer, further contains 0.02 to 5 parts by weight of multifunctional crosslinking Agent. The optically transparent adhesive composition as described in item 3 or 4 of the scope of patent application, based on 100 parts by weight of the photocurable (meth)acrylate copolymer, further contains 40 to 85 parts by weight of solvent. The optically transparent adhesive composition according to item 4 of the scope of patent application, wherein the multifunctional crosslinking agent is a thermosetting multifunctional isocyanate crosslinking agent or a multifunctional (meth)acrylate crosslinking agent. The optically transparent adhesive composition described in item 1 of the scope of the patent application, wherein the isocyanate group-containing (meth)acrylate monomer is an isocyanate group-C ₁ -C ₁₀ linear or branched (former) Base) Alkyl acrylate. An optically transparent adhesive film, which is manufactured by coating a transfer film with an optically transparent adhesive composition as described in item 1 of the scope of the patent application. A flat panel display device, which comprises an adhesive layer made of the optically transparent adhesive composition as described in item 1 of the scope of patent application. The flat panel display device described in item 9 of the scope of patent application, wherein the flat panel display device is a flexible display device.