TW201821575A - 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 rubber-based (meth)acryl monomer, 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 isocyanato-group-containing (meth)acrylate monomer, the hydroxyl-group-containing acrylic copolymer and the isocyanato-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

 Optical transparent adhesive composition, optical transparent adhesive film containing the same, and flat panel display device  

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

Examples of the flat panel display device include a liquid crystal display (LCD), a plasma display panel (PDP), an organic electroluminescent 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. When the optical films are stacked on each other or the optical film is attached to the display panel, an optically clear adhesive (OCA) is used. Therefore, an optically clear adhesive (OCA) must exhibit not only typical optical properties but also excellent heat and humidity resistance, heat resistance and adhesion.

In particular, there has recently been intense competition for developing flexible display devices. Since the flexible display device is bendable, curlable or foldable, the display panel and the optical film contained in the device are subjected to bending stress. Therefore, various properties of an optically transparent adhesive (OCA) for a flexible display device require further improvement.

For example, optically clear adhesives (OCAs) used in flexible display devices must have very high foldability properties to enable the device to be freely folded. Moreover, in view of the case where the flexible display device is used outdoors for a long time at a low temperature, the foldability at a low temperature should be excellent.

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

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

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

[reference list]

[Patent Literature]

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

Accordingly, the problems encountered in the related art are borne in mind when making the present invention, and the present invention is directed to providing an optically clear adhesive (OCA) composition capable of sufficiently satisfying a flexible display. The foldability, heat and humidity resistance, heat resistance and adhesion required of the device.

Further, the present invention is directed to an optically transparent adhesive film comprising the 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, a rubber-based (meth) acrylate monomer (rubber-based ( Meth) acryl monomer) and a photopolymerization initiator, wherein the photocurable (meth) acrylate copolymer comprises from 95% by weight to 99.9% by weight of the hydroxyl group-containing acrylic acid based on the total weight of the components of the copolymer Copolymer and 0.1% by weight to 5% by weight of an isocyanate group-containing (meth) acrylate monomer, the hydroxyl group-containing acrylic copolymer and the isocyanate group-containing (meth) acrylate monomer Forming a urethane bond, and the hydroxyl group-containing acrylic copolymer comprises 50% by weight to 98% by weight of a C ₁ -C ₁₂ linear chain of (meth)acrylic acid, based on the total weight of the monomers of the copolymer A branched alkyl ester monomer and 2% by weight to 50% by weight of a hydroxyl group-containing polymerizable monomer, and having a weight average molecular weight of 200,000 to 1,000,000.

Further, 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.

Further, the present invention provides a flat panel display device comprising an adhesive layer formed of the optically transparent adhesive of the present invention.

According to the present invention, an optically clear adhesive (OCA) composition and an optically transparent adhesive film can exhibit sufficiently high foldability, heat and humidity resistance, heat resistance and adhesion required for a flat panel display device and a flexible display device, and Therefore, the flat panel display device and the flexible display device can be made to have excellent durability.

According to the present invention, the flat panel display device is formed using the above-described binder composition, thereby exhibiting excellent foldability, heat and humidity resistance, heat resistance and adhesion, and high durability.

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

Here, the photocurable (meth) acrylate copolymer comprises 95% by weight to 99.9% by weight of the hydroxyl group-containing acrylic copolymer and 0.1% by weight to 5% by weight based on the total weight of the components of the copolymer. An isocyanate group-containing (meth) acrylate monomer, the hydroxyl group-containing acrylic copolymer forming a urethane bond with the isocyanate group-containing (meth) acrylate monomer, and the The hydroxyl group-containing acrylic copolymer comprises 50% by weight to 98% by weight of a (meth)acrylic C ₁ -C ₁₂ linear or branched alkyl ester monomer and 2 parts by weight based on the total weight of the monomers of the copolymer. % to 50% by weight of a hydroxyl group-containing polymerizable monomer and having a weight average molecular weight of 200,000 to 1,000,000.

In the present invention, the optically clear adhesive composition simultaneously includes a polar photocurable acrylate copolymer having a low glass transition temperature (Tg) and a rubber-based (meth)acrylic monomer, and thus can be expressed Excellent foldability, heat and moisture resistance and adhesion. An optically transparent adhesive composition having high heat resistance and durability can be obtained by photocrosslinking between a photocurable acrylate copolymer and a non-polar rubber-based (meth)acrylic monomer.

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

The photocurable (meth) acrylate copolymer can be prepared by copolymerizing a C ₁ -C ₁₂ linear or branched alkyl ester monomer of (meth) acrylate with a hydroxyl group-containing polymerizable monomer to obtain a hydroxyl-based acrylic copolymer backbone having a structure in which a thermosetting functional group (hydroxyl group) is introduced into its branch or terminal, and then the main chain is made to contain an isocyanate group under appropriate conditions ( The methyl acrylate monomer is reacted to replace at least some of the thermosetting functional groups (hydroxyl groups) of the backbone with an isocyanate-containing (meth) acrylate monomer.

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

In Chemical Formula A, R ₁ is C ₁ -C ₁₂ straight or branched chain alkyl group, R ₂ is C ₁ -C ₁₀ straight or branched alkylene, R ₃ is independently hydrogen or methyl, o and p is independently a natural number of 2 to 6, and l, m, and n each have a value determined by looking at the numerical range of the above monomers.

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

The rubber-based (meth)acrylic monomer may include, for example, at least one selected from the group consisting of compounds represented by the following Chemical Formula 1 and Chemical Formula 2:

In Chemical Formula 1 and Chemical Formula 2, R _{1 is} independently hydrogen or methyl, R _{2 is} independently a C ₂ -C ₆ linear or branched alkylene group, and R _{3 is} independently a group derived from a diisocyanate compound. And -N(H)-C(O)- is attached to both sides thereof, R _{4 is} independently a C ₂ -C ₁₂ linear or branched alkyl group, and the rubber-based polymer is a rubber monomer And a polymer having a weight average molecular weight of only 500 to 10,000 consisting only of carbon and hydrogen.

Examples of the rubber monomer may include butadiene, isobutylene, isoprene, and the like.

The rubber-based polymer is not particularly limited as long as it has rubber properties.

The diisocyanate compound may include, but is not limited to, HDI (extended hexyl diisocyanate), IPDI (isophorone diisocyanate), TDI (toluene diisocyanate), and XDI (Xylylene Diisocyanate).

The compound represented by Chemical Formula 1 and Chemical Formula 2 can be produced by the following Scheme 1.

[plan 1]

The (meth)acrylic C ₁ -C ₁₂ linear or branched alkyl ester monomer which is included in the hydroxyl group-containing acrylic copolymer in a polymerized form preferably has a glass transition temperature (Tg) of -70 ° C. Acetic acid C ₁ -C ₁₂ linear or branched alkyl ester monomer to -50 ° C, and more preferably C ₄ -C ₁₂ linear chain having a glass transition temperature (Tg) of -70 ° C to -50 ° C Or a branched alkyl ester monomer.

Examples of the C ₄ -C ₁₂ linear or branched alkyl ester monomer having a glass transition temperature (Tg) of from -70 ° C to -50 ° C may include: n-butyl acrylate, tributyl acrylate, acrylic acid Dibutyl ester, amyl acrylate, 2-ethyl butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate and isodecyl acrylate, either alone or in combination or more A combination of many. Among them, n-butyl acrylate or 2-ethylhexyl acrylate is preferably used.

If the glass transition temperature (Tg) of a C ₁ -C ₁₂ linear or branched alkyl ester monomer of acrylic acid 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.

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

The glass transition temperature (Tg) of -60 ℃ to -40 ℃ hydroxyl-containing acrylate monomer is preferably acrylate, hydroxypropyl -C ₄ -C ₆ straight chain or branched chain alkyl acrylate monomer.

Examples of the hydroxy-C ₄ -C ₆ linear or branched alkyl ester monomer may include 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate, and 6-hydroxyhexyl acrylate, which may be used alone or in A combination of two or more of them is used. Among them, 4-hydroxybutyl acrylate is preferably used.

If the glass transition temperature (Tg) of the hydroxyl group-containing 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, the content of the C ₁ -C ₁₂ linear or branched alkyl ester monomer (meth)acrylate may be from 50% by weight to 98% by weight, and the hydroxyl group-containing polymerizable monomer The content may be from 2% by weight to 50% by weight.

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

In addition, if the amount of the hydroxyl group-containing polymerizable monomer is less than 11% by weight, the amount of the hydroxyl group which is a hydrophilic group in the binder may be reduced, so moisture may not be trapped by the adhesive layer but may be discharged to the interface. Adhesiveness is disadvantageously deteriorated under heat and humidity resistance, and interface delamination may be disadvantageously caused. On the other hand, if the amount exceeds 50% by weight, moisture may be excessively absorbed by the binder, so the volume of the binder may increase and the cohesive force may be lowered, disadvantageously causing delamination and foaming of the interface.

Among the hydroxyl group-containing acrylic copolymers, other copolymerizable monomers known in the art may be included in the form of being polymerized. The kind of other copolymerizable monomers is not particularly limited, and examples thereof may include, but are not limited to, nitrogen-containing monomers such as (meth)acrylonitrile, (meth)acrylamide, and N-methyl (methyl). a acrylamide or N-butoxymethyl (meth) acrylamide; a styrene-based monomer such as styrene or methyl styrene; glycidyl (meth) acrylate; and a carboxylic acid Vinyl esters such as vinyl acetate.

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

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

The isocyanate-containing (meth) acrylate monomer included in the photocurable (meth) acrylate copolymer may be a linear chain of (meth)acrylic acid isocyanato (C ₁ -C ₁₀ ) Or a branched alkyl ester is exemplified. Here, the (C ₁ -C ₁₀ ) linear or branched alkyl group may include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, t-butyl, pentyl Base, hexyl, heptyl, octyl, 2-ethylhexyl, anthracenyl and fluorenyl. 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 from 0.1% by weight to 5.0% by weight based on the total of the components of the photocurable (meth) acrylate copolymer. If the amount of the (meth) acrylate monomer containing an isocyanate group is less than 0.1% by weight, the adhesive strength and heat resistance of the binder composition may be lowered. On the other hand, if the amount exceeds 5.0% by weight, the cohesive force of the binder may become too strong, disadvantageously deteriorating the foldability.

In the optically clear adhesive composition of the present invention, the content of polybutadiene/isoprene/isobutylene (meth)acrylic acid monomer is 100 parts by weight of the photocurable (meth) acrylate copolymer. It is 10 parts by weight to 40 parts by weight, and preferably 15 parts by weight to 30 parts by weight. If the amount of the rubber-based (meth)acrylic monomer is less than 10 parts by weight, it is difficult to ensure low-temperature foldability. On the other hand, when the amount exceeds 40 parts by weight, it is difficult to obtain adhesiveness, and the heat resistance is disadvantageously deteriorated.

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, and is also contained in the optically clear binder composition together with the photocurable (meth)acrylate copolymer.

The photopolymerization initiator is not particularly limited, and any photopolymerization initiator may 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 ultraviolet irradiation to initiate photopolymerization, such as a benzoin-based initiator, a hydroxyketone-based initiator, an amine. A ketone based starter and a phosphine oxide based starter.

If the amount of the photopolymerization initiator is too low, the effect of addition may become inconspicuous. On the other hand, if the amount is too high, properties such as durability or transparency may be maintained to deteriorate. Therefore, the amount can be determined in an appropriate manner.

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

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 from 0.02 part by weight 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 kind of the coupling agent is not particularly limited, and any coupling agent conventionally known in the art can be used in the preparation of the binder. Examples of the decane coupling agent may include: γ-glycidoxypropyltriethoxydecane, γ-glycidoxypropyltrimethoxydecane, γ-glycidoxypropylmethyldiethoxydecane , γ-glycidoxypropyltriethoxydecane, 3-mercaptopropyltrimethoxydecane, vinyltrimethoxydecane, vinyltriethoxydecane, γ-methylpropenyloxypropyl Trimethoxydecane, γ-methylpropenyloxypropyltriethoxydecane, 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 properties.

In addition, at least one additive selected from the group consisting of an epoxy resin, a curing agent, a UV stabilizer, an antioxidant, a colorant, a reinforcing agent, a filler, an antifoaming agent, a surfactant, and a plasticizer may be further included.

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 it can dissolve the monomers and copolymers used in the optically clear adhesive composition.

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

The solvent may be included in an amount of from 40 parts by weight to 85 parts by weight based on 100% by weight of the solid content of the optically clear adhesive composition.

In the optically clear adhesive composition of the present invention, a rubber-based (meth)acrylic monomer can be provided with a blend of a photocurable (meth)acrylate copolymer.

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

The optically transparent adhesive composition of the present invention can ensure collapsibility using a rubber-based (meth)acrylic monomer and a monomer having a low glass transition temperature, and is also suitably employed by radical polymerization. The curing system and the curing system using a crosslinking agent and a thermosetting functional group (hydroxyl group) can achieve moist heat resistance, heat resistance, and durability.

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

The coating process using the optically transparent adhesive composition of the present invention is not particularly limited, and examples thereof may include a typical process such as bar coating, spin coating, comma coating, and gravure coating. ). In the coating process, it is necessary to control the crosslinking reaction of the functional groups of the polyfunctional crosslinking agent contained in the binder composition so that the crosslinking reaction does not progress to achieve uniform coating. Thereby, the crosslinking agent can form a crosslinked structure during the curing and aging process after the coating process, thereby increasing the adhesion property, the cuttability and the cohesive force of the adhesive.

Moreover, it is preferred to carry out a coating process after sufficiently removing volatile components or foaming components (e.g., reaction residues) from the binder composition. Thereby, it is possible to prevent the elastic modulus from being lowered due to the crosslinking density or the molecular weight of the binder being too low, and also preventing the internal scatterer from being formed at a high temperature due to an increase in the size of the bubble between the glass plate and the adhesive layer.

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

Before or after the irradiation of light, an appropriate aging process may be performed to induce a reaction between the functional group of the crosslinking agent of the composition and the thermosetting functional group of the polymer, and the conditions are not particularly limited as long as the crosslinking reaction is carried out. It can be done as appropriate.

The adhesive composition for an optical film according to the present invention can be used for laminating 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, or 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 in a flexible display device.

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

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

Further, the present invention proposes a flat panel display device comprising an adhesive layer formed of 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 by the following examples and comparative examples, which are merely intended to illustrate the invention, but the invention is not limited to the examples, but 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 equipped with a condenser to facilitate the temperature while refluxing nitrogen gas. control. 120 parts by weight of ethyl acetate (EAc) solvent was added thereto, and the resulting reaction mixture was purged with nitrogen for 60 minutes to remove oxygen therefrom. Thereafter, the temperature was maintained at 70 ° C, 0.1 part by weight of a reaction initiator AIBN (azobisisobutyronitrile) was added thereto, and the reaction was allowed to proceed for 12 hours, thereby preparing an acrylic polymer having a weight average molecular weight of 450,000. A1.

Preparation Example 1-2: Preparation of Acrylic Polymer A2

An acrylic polymer A2 having a weight average molecular weight of 470,000 was prepared using 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 acrylic acid were used. 4-hydroxybutyl ester (4-HBA).

Preparation Example 1-3: Preparation of Acrylic Polymer A3

An acrylic polymer A3 having a weight average molecular weight of 450,000 was prepared using 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 were used. 2-Hydroxyethyl ester (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

An acrylic polymer A4 having a weight average molecular weight of 390,000 was prepared using the same polymerization technique as in Preparation Example 1-1, except that 90 parts by weight of n-butyl acrylate (n-BA) and 10 parts by weight of acrylic acid were used. 4-hydroxybutyl ester (4-HBA) 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 DBTDL (dibutyltin dilaurate) were placed in a condenser In the liter reactor, it is convenient to control its temperature while refluxing with nitrogen. The reaction was then carried out at 40 ° C under atmospheric pressure for 4 hours or more to obtain a photocurable (meth) acrylate copolymer B1.

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

A 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

A 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

A 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 a hard coat film for evaluation of flexibility

<Preparation of epoxy oxirane resin>

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

<Preparation of hard coating composition>

The oxime sol was mixed with diglycidyl ether 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, whereby a hard coat composition was obtained.

<Forming a hard coat film>

A hard coating composition was applied to a film of COP (cycloolefin polymer ZF-16, available from Zeon) having a thickness of 40 μm to a thickness of 50 μm, and subjected to corona surface treatment. membrane. The film was exposed to a mercury ultraviolet lamp (20 mW/cm ² ) for 5 minutes, and the reaction was initiated using triaryl sulfonium hexafluoroantimonate, followed by hydrothermal treatment at 50 ° C and 50% RH (relative humidity) for 60 minutes to form Hard coating film.

Example 1: Preparation of an optically clear adhesive composition

The optically clear adhesive composition was prepared by mixing the following: 100 parts by weight of the photocurable acrylate copolymer B1 of Preparation Example 2-1, 20 parts by weight of the rubber-based (meth)acrylic acid of the following Chemical Formula 3 , 0.07 parts by weight of a multifunctional crosslinking agent (Coronate L, available from NPU, Japan), 0.2 parts by weight of a photopolymerization initiator (hydroxycyclohexyl phenyl ketone, Irgacure 184, available from Ciba Specialty Chemicals, Switzerland) (Ciba Specialty Chemicals) obtained and 0.2 parts by weight of 3-glycidoxypropyltrimethoxydecane (KBM-403, available from Shin-Etsu).

In Chemical Formula 3, n is 15 to 25.

The compound of Chemical Formula 3 is TE-2000 available from Nippon Soda.

Example 2: Preparation of an optically clear adhesive composition

An optically clear adhesive composition was prepared in the same manner as in Example 1, except that the rubber-based (meth)acrylic monomer of the following Chemical Formula 4 was used instead of the rubber-based one of Chemical Formula 3 (A) Base) acrylic monomer.

In Chemical Formula 4, n is 15 to 25.

The compound of Chemical Formula 4 is TEAI-1000 available from Nippon Soda Corporation.

Comparative Example 1: Preparation of an optically clear adhesive composition

An optically clear adhesive composition was prepared by mixing the following: 100 parts by weight of the photocurable acrylate copolymer B3 of Preparation Example 2-3, 0.07 part by weight of a polyfunctional crosslinking agent (Coronate L, available from NPU Corporation of Japan) 0.2 parts by weight of a photopolymerization initiator (hydroxycyclohexyl phenyl ketone, Irgacure 184, available from Ciba Specialty Chemicals, Switzerland) and 0.2 parts by weight of 3-glycidoxypropyltrimethoxy decane ( KBM-403, can be confidently obtained by the company).

Comparative Example 2: Preparation of an optically clear adhesive composition

An optically clear adhesive composition was prepared by mixing the following: 100 parts by weight of the photocurable acrylate copolymer B4 of Preparation Example 2-4, 0.07 part by weight of a polyfunctional crosslinking agent (Coronate L, available from NPU Corporation of Japan) 0.2 parts by weight of a photopolymerization initiator (hydroxycyclohexyl phenyl ketone, Irgacure 184, available from Ciba Specialty Chemicals, Switzerland) and 0.2 parts by weight of 3-glycidoxypropyltrimethoxy decane ( KBM-403, can be confidently obtained by the company).

Example 3: Formation of an optically transparent adhesive film

The optically transparent adhesive compositions of Examples 1 and 2 and Comparative Example 1 and Comparative Example 2 were coated on a PET film having a thickness of 50 μm, and coated with an organic germanium release agent to obtain 100 μm after curing. The thickness, and then dried at 100 ° C for 5 minutes, thereby preparing Example 3-1 (using the optically clear adhesive composition of Example 1), Example 3-2 (using the optically clear adhesive composition of Example 2) Comparative 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) were each an optically transparent adhesive film.

Example 4: Forming a laminate with an adhesive layer

Using the optically transparent adhesive film of each of Example 3-1, Example 3-2, Comparative Example 3-1, and Comparative Example 3-2, an adhesive layer was formed on a 100 μm thick PET film (obtained from Mitsubishi). And UV light (obtained from Fusion) was irradiated with light of 1000 mJ/cm ² in the direction in which the film was formed, thereby preparing Example 4-1, Example 4-2, Comparative Example 4-1, and comparison. Each of Examples 4-2 had a laminate with an adhesive layer.

Example 5: Formation of a hard coat film/adhesive layer/PET laminate for evaluation of flexibility

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 × 100 mm. Next, the detached PET film was peeled off from the adhesive layer of the dicing laminate, and the resulting laminate was attached to a hard coating film for evaluation of flexibility prepared in Preparation Example 3 having a size of 50 mm × 100 mm, in an autoclave (50). It was pressed in °C, 5 atmospheres for about 20 minutes, and then aged under constant temperature and humidity conditions (23 ° C and 50% relative humidity) for 24 hours, thereby producing Example 5-1, Example 5-2, and Comparative Example 5-1. And Comparative Example 5-2, each of the bendability evaluation hard coat layer/adhesive layer/PET (100 μm) laminate.

Test Example: Evaluating the Properties of Optically Clear Binder Compositions

1. Assess foldability

<Evaluation method>

Evaluation criteria: IEC 62715

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

Device manufacturer: YUASA SYSTEM (Japan)

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

The hard coat film/adhesive layer/PET laminate for the evaluation of flexibility of each of Example 5-1, Example 5-2, Comparative Example 5-1, and Comparative Example 5-2 prepared in Example 5 was measured by the above evaluation method. To determine its foldability. The results are shown in Table 1 below.

<Evaluation criteria>

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

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

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

2. Assess durability

(1) Evaluation of heat resistance

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

<Evaluation criteria>

◎: no foaming or 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 heat and humidity resistance

The hard coat film/adhesive layer/PET laminate for the evaluation of the flexibility of each of Example 5-1, Example 5-2, Comparative Example 5-1, and Comparative Example 5-2 produced in Example 5 was compared with 90% at 60 ° C. The mixture was allowed to stand for 1,000 hours under humidity, and then it was observed whether foaming or peeling occurred. The sample was allowed to stand at room temperature for 24 hours immediately before sample evaluation, and then observed to evaluate its heat and humidity resistance. The results are shown in Table 1 below.

<Evaluation criteria>

◎: no foaming or peeling occurred

○: Number of foaming or peeling defects <5

△: 5 Number of foaming defects or peeling defects <10

×:10 Number of foaming or peeling defects

3. Assess 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 × 100 mm. Subsequently, the release PET film was peeled off from the adhesive layer of the cut laminate, and then the laminate having the adhesive layer was attached to the alkali-free glass using a 2 kg roller according to JIS Z 0237. The alkali-free glass to which the laminate was attached was pressed in an autoclave (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. Thereafter, the laminate was peeled off from the alkali-free glass using a TA (Texture Analyzer, available from Stable Micro Systems UK) at a peel rate of 300 mm/min and a peel angle of 180°. , measuring adhesion. The results are shown in Table 2 below.

As is apparent from the test results of Tables 1 and 2, the optically clear adhesive composition of the example of the present invention is excellent in foldability, heat and humidity resistance, heat resistance and adhesion. In particular, the foldability was remarkably high as compared with the optically clear adhesive composition of the comparative example. Since a rubber-based (meth)acrylic monomer is used in the present invention, the adhesion is low as compared with the comparative example.

Claims (12)

An optically transparent adhesive composition comprising a photocurable (meth) acrylate copolymer, a rubber-based (meth) acryl monomer, and a photopolymerization initiator. Wherein the photocurable (meth) acrylate copolymer comprises from 95% by weight to 99.9% by weight of the hydroxyl group-containing acrylic copolymer and from 0.1% by weight to 5% by weight based on the total weight of the components of the copolymer. Isocyanate-based (meth) acrylate monomer, the hydroxyl group-containing acrylic copolymer forms a urethane bond with the isocyanate group-containing (meth) acrylate monomer, and the hydroxyl group-containing The acrylic copolymer comprises 50% by weight to 98% by weight of a C ₁ -C ₁₂ linear or branched alkyl ester (meth) acrylate monomer and 2% by weight to the total weight of the monomer of the copolymer 50% by weight of a hydroxyl group-containing polymerizable monomer and having a weight average molecular weight of 200,000 to 1,000,000.  The optically transparent adhesive composition according to claim 1, wherein the hydroxyl group-containing polymerizable monomer is a monomer having a hydroxyl group and at least one ethylenically unsaturated bond.   The optically transparent adhesive composition according to claim 2, wherein the (meth)acrylic C ₁ -C ₁₂ linear or branched alkyl ester monomer has a glass transition temperature (Tg) of -70 ° C to - a 50 ° C acrylic C ₁ -C ₁₂ linear or branched alkyl ester monomer, and the monomer having a hydroxyl group and at least one ethylenically unsaturated bond has a glass transition temperature (Tg) of -60 ° C to -40 a hydroxyl group-containing acrylate monomer of °C. The optically transparent adhesive composition according to claim 1, wherein the rubber-based (meth)acrylic monomer comprises at least one selected from the group consisting of compounds represented by the following Chemical Formula 1 and Chemical Formula 2: In Chemical Formula 1 and Chemical Formula 2, R _{1 is} independently hydrogen or methyl, R _{2 is} independently a C ₂ -C ₆ linear or branched alkylene group, and R _{3 is} independently a group derived from a diisocyanate compound. And -N(H)-C(O)- is attached to both sides thereof, R _{4 is} independently a C ₂ -C ₁₂ linear or branched alkyl group, and the rubber-based polymer is a rubber monomer And a polymer having a weight average molecular weight of only 500 to 10,000 consisting only of carbon and hydrogen.  The optically transparent adhesive composition according to claim 1, wherein the optically transparent adhesive composition comprises 10 parts by weight to 40 parts by weight based on 100 parts by weight of the photocurable (meth) acrylate copolymer. The rubber-based (meth)acrylic monomer and 0.1 part by weight to 5 parts by weight of the photopolymerization initiator.    The optically clear adhesive composition according to claim 5, further comprising from 0.02 part by weight to 5 parts by weight of the polyfunctional crosslinking agent, based on 100 parts by weight of the photocurable (meth) acrylate copolymer.    The optically clear adhesive composition of claim 6, wherein the multifunctional crosslinking agent is a thermosetting polyfunctional isocyanate crosslinking agent or a polyfunctional (meth) acrylate crosslinking agent.    The optically clear adhesive composition according to claim 5 or 6, further comprising 40 parts by weight to 85 parts by weight of the solvent based on 100 parts by weight of the solid content of the optically clear adhesive composition.   The optically transparent adhesive composition according to claim 1, wherein the isocyanate group-containing (meth) acrylate monomer is an isocyanato(C ₁ -C ₁₀ )alkyl acrylate (isocyanato (C) ₁ -C ₁₀ )alkyl acrylate).  An optically clear adhesive film produced by coating a transfer film with the optically clear adhesive composition as claimed in claim 1.    A flat panel display device comprising an adhesive layer formed of the optically transparent adhesive as claimed in claim 1.    The flat panel display device of claim 11, wherein the flat panel display device is a flexible display device.