KR20180029410A - Optically Clear Adhesive Composition, and Optically Clear Adhesive Film comprising the Same, and Flat Panel Display - Google Patents

Abstract

The present invention relates to an optically clear adhesive composition, an optically clear adhesive film comprising the optically clear adhesive composition, and a flat panel display device. An objective of the present invention is to provide the optically clear adhesive composition which is capable of sufficiently satisfying folding properties, moisture heat resistance, heat resistance and adhesion required in a flexible display device. The optically clear adhesive composition of the present invention comprises a photocurable (meth)acrylate copolymer and a photopolymerization initiator, wherein the photocurable (meth)acrylate copolymer includes 95 to 99.9 wt% of an acrylic copolymer containing a hydroxyl group and 0.1 to 5 wt% of a (meth)acrylate-based monomer containing an isocyanate group with respect to the total weight of constituent units included in the copolymer, the acrylic copolymer containing the hydroxyl group and the (meth)acrylate-based monomer containing the isocyanate group form a urethane bond, and the acrylic copolymer containing the hydroxyl group includes a (meth)acrylate monomer having a glass transition temperature (Tg) of -120 to -60°C and an alkyl acrylate monomer containing the hydroxyl group with respect to the total weight of the monomer included in the copolymer and has a weight average molecular weight of 200,000 to 1,000,000.

Description

TECHNICAL FIELD [0001] The present invention relates to an optical transparent pressure sensitive adhesive composition, an optical transparent pressure sensitive adhesive film containing the same, and a flat panel display device,

The present invention relates to an optical transparent pressure-sensitive adhesive composition, an optical transparent pressure-sensitive adhesive film containing the same, and a flat panel display.

A flat panel display device includes a liquid crystal display (LCD), a plasma display panel (PDP), and an organic electroluminescence display (OLED).

Such a flat panel display device includes a display panel and an optical film. As the optical film, a polarizing film, a retardation film, an anti-glare film, a wide viewing angle compensation film, a brightness enhancement film, and the like are used. When these optical films are stacked on each other or an optical film is attached to a display panel, an optically clear adhesive (OCA) is used. Therefore, optical transparent pressure sensitive adhesive (OCA) should have good heat resistance, heat resistance and adhesion with basic optical characteristics.

Particularly, in recent years, flexible display devices are being developed in a competitive manner. Flexible display devices are subject to bending stresses because the device itself is bending, rolling, and folding, so that the display panels and optical films included in the device are also subjected to bending stress. Therefore, the optical transparent pressure sensitive adhesive (OCA) used in flexible displays is required to be further strengthened and diversified in properties.

For example, the optical transparent tackifier (OCA) used in flexible display devices should have excellent folding properties to allow flexible folding of the device. Particularly, considering the case where the flexible display device is used for a long period of time at a low temperature, the folding property at low temperature should be excellent.

Further, the optical transparency adhesive (OCA) used in the flexible display device is required to have enhanced moisture resistance and heat resistance. This is because the flexible display device repeats the folding and unfolding process during use, so that the possibility of penetration of moisture through the folded and expanded portions is increased.

Also, display panels and optical films included in the device are subject to bending stresses as well, such as bending, rolling, folding, and the like. Therefore, since the laminated display panel and the optical films are easily separated from each other, better adhesion is required, and more excellent durability is also required.

However, optical transparent adhesives (OCA) known to date do not sufficiently provide the above-mentioned properties required for a flexible display device.

Korean Patent Publication No. 10-2016-0085759

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems of the prior art,

An object of the present invention is to provide an optical transparent pressure-sensitive adhesive (OCA) composition capable of sufficiently satisfying folding characteristics, wet heat resistance, heat resistance and adhesion required in a flexible display device.

It is another object of the present invention to provide an optical transparent adhesive film and a flat panel display device including the above optical transparent adhesive (OCA) composition.

In order to achieve the above object,

The present invention relates to an optical transparent pressure-sensitive adhesive composition comprising a photocurable (meth) acrylate copolymer and a photopolymerization initiator,

The photocurable (meth) acrylate copolymer is a copolymer of

, 95 to 99.9% by weight of a hydroxy group-containing acrylic copolymer and 0.1 to 5% by weight of an isocyanate group-containing (meth) acrylate monomer based on the total weight of the constituent units contained in the copolymer,

Wherein the hydroxy group-containing acrylic copolymer and the isocyanate group-containing (meth) acrylate monomer form a urethane bond,

The hydroxy group-containing acrylic copolymer includes a (meth) acrylate monomer having a glass transition temperature (Tg) of -120 to -60 ° C and a hydroxy group-containing alkyl acrylate monomer,

And has a weight average molecular weight of 200,000 to 1,000,000.

The present invention also provides an optical transparent pressure-sensitive adhesive film which is prepared by coating the above-mentioned optical transparent pressure-sensitive adhesive composition of the present invention onto a transfer film.

The present invention also provides a flat panel display comprising the pressure-sensitive adhesive layer formed from the optical transparent pressure-sensitive adhesive composition of the present invention.

The optical transparent pressure sensitive adhesive (OCA) composition and the optical transparent pressure sensitive adhesive film of the present invention provide not only a flat panel display but also a folding property, a wet heat resistance, a heat resistance and an adhesion property sufficient for use in a flexible display device, to provide.

Since the flat panel display of the present invention is manufactured using the pressure-sensitive adhesive composition as described above, it can provide excellent folding characteristics, moist heat resistance, heat resistance, adhesiveness, and excellent durability.

Hereinafter, the present invention will be described in more detail.

The present invention relates to an optical transparent pressure-sensitive adhesive composition comprising a photocurable (meth) acrylate copolymer and a photopolymerization initiator,

The photocurable (meth) acrylate copolymer is a copolymer of

, 95 to 99.9% by weight of a hydroxy group-containing acrylic copolymer and 0.1 to 5% by weight of an isocyanate group-containing (meth) acrylate monomer based on the total weight of the constituent units contained in the copolymer,

Wherein the hydroxy group-containing acrylic copolymer and the isocyanate group-containing (meth) acrylate monomer form a urethane bond,

The hydroxy group-containing acrylic copolymer includes a (meth) acrylate monomer having a glass transition temperature (Tg) of -120 to -60 ° C and a hydroxy group-containing alkyl acrylate monomer,

And has a weight average molecular weight of 200,000 to 1,000,000.

The optical transparent pressure sensitive adhesive composition of the present invention can improve the folding property at a low temperature by including a (meth) acrylate monomer having a low glass transition temperature (Tg). By containing a hydroxy group-containing alkyl acrylate monomer in a large amount, And by increasing the crosslinking density through the urethane bonds of the hydroxyl group and the isocyanate group, an optical transparent pressure-sensitive adhesive composition having excellent heat resistance and durability can be provided.

In the present invention, the term "(meth) acrylate" means "acrylate" or "methacrylate".

The photo-curable (meth) acrylate copolymer is obtained by copolymerizing a (meth) acrylate monomer having a glass transition temperature (Tg) of -120 to -60 ° C and an alkyl acrylate monomer having a hydroxy group to form a thermosetting functional group (Meth) acrylate monomer having an isocyanate group is reacted with the main chain under proper conditions to prepare a thermosetting functional group (OH) of the main chain, (Meth) acrylate containing at least one isocyanate group.

The main chain may be produced by a conventional polymerization method such as solution polymerization, photo polymerization, bulk polymerization, suspension polymerization or emulsion polymerization. .

The (meth) acrylate monomer having a glass transition temperature (Tg) of -120 to -60 ° C. contained in the form of being polymerized with the hydroxy group-containing acrylic copolymer may be a linear or branched (meth) acrylate monomer having 8 to 30 carbon atoms And more preferably at least one selected from the group consisting of the following formulas (1) to (5).

[Chemical Formula 1]

Isodecylacrylate < / RTI >

Glass transition temperature (Tg): -60 ° C

(2)

Isodecylmethacrylate < / RTI >

Glass transition temperature (Tg): -70 캜

(3)

2-propylheptylacrylate (2-propylheptylacrylate)

Glass transition temperature (Tg): -68 캜

[Chemical Formula 4]

Stearylmethacrylate,

Glass transition temperature (Tg): -100 ° C

[Chemical Formula 5]

Dodecyl (lauryl) methacrylate)

Glass transition temperature (Tg): -65 캜

If the glass transition temperature (Tg) of the (meth) acrylate monomer is less than -120 ° C., it is difficult to use due to economical efficiency and the durability of the optical transparent pressure sensitive adhesive composition is lowered. When the temperature is higher than -60 ° C., there arises a problem that the folding property is deteriorated.

Specific examples of the hydroxy group-containing alkyl acrylate monomer contained in the form of a polymer in the hydroxy group-containing acrylic copolymer include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate, 6-hydroxyhexyl acrylate, 8-hydroxyoctyl acrylate, 2-hydroxyethylene glycol acrylate and 2-hydroxypropylene glycol acrylate.

Of these, monomers such as 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate and 6-hydroxyhexyl acrylate can be preferably used, and more preferably 4-hydroxybutyl acrylate is used .

When the hydroxyl group-containing alkyl acrylate monomer exemplified above is used, the structure of the photocurable acrylate copolymer of the present invention can be represented by the following formula (6).

[Chemical Formula 6]

Wherein R < ₁ > is a linear or branched alkyl group having 8 to 30 carbon atoms,

R < ₂ > is hydrogen or a methyl group,

R < ₃ > is hydrogen or a methyl group,

R ₄ is a linear or branched alkylene group having 1 to 10 carbon atoms and a branched chain alkylene group having 4 to 10 carbon atoms,

Wherein R < ₅ > is hydrogen or a methyl group,

O is a natural number of 2 to 6,

Each of l, m and n has a value formed according to the usage amount range of the monomers described above.

In the hydroxy group-containing acrylic copolymer, the (meth) acrylic monomer having a glass transition temperature (Tg) of -120 to -60 ° C is contained in an amount of 50 to 95% by weight based on the total weight of the monomers contained in the copolymer, Containing alkyl acrylate monomer is preferably contained in an amount of 5 to 50% by weight.

When the hydroxy group-containing alkyl acrylate monomer is contained in an amount of less than 5% by weight, the hydroxy group, which is a hydrophilic group, is insufficient in the pressure-sensitive adhesive, so moisture can not be caught in the pressure-sensitive adhesive layer and moisture is discharged at the interface, If it is contained in an amount exceeding 50% by weight, the pressure-sensitive adhesive absorbs excess moisture and expands in volume, resulting in deterioration of cohesion, resulting in interfacial peeling and bubbling.

The hydroxy group-containing acrylic copolymer may further contain other copolymerizable monomers known in the art in a polymerized form. The kind of the other copolymerizable monomer is not particularly limited and includes, for example, (meth) acrylonitrile, (meth) acrylamide, N-methyl (meth) acrylamide or N-butoxymethyl The same nitrogen containing monomers; Styrene-based monomers such as styrene or methylstyrene; Glycidyl (meth) acrylate; Or vinyl esters of carboxy acid such as vinyl acetate, but are not limited thereto.

When the other copolymerizable monomers are included, the content thereof is preferably adjusted to 20 parts by weight or less based on 100 parts by weight of the total amount of monomers described above in consideration of flexibility and peel strength.

In the hydroxy group-containing acrylic copolymer, the weight average molecular weight means a value converted to a standard polystyrene measured by GPC (Gel Permeation Chromatograph).

The weight average molecular weight of the hydroxy group-containing acrylic copolymer is 200,000 to 1,000,000.

As the isocyanate group-containing (meth) acrylate monomer contained in the photocurable (meth) acrylate copolymer, an isocyanate C ₁ -C ₁₀ alkyl acrylate monomer may be used. Specifically, isocyanate C ₁ to ₁₀ linear or branched C ₄ to C ₁₀ branched alkyl acrylates may be used. Examples of the C ₁ -C ₁₀ linear or branched C ₄ -C ₁₀ branched alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert- butyl, pentyl, hexyl, heptyl, 2-ethylhexyl, nonyl, decanyl and the like, of which ethyl, propyl and the like can be preferably used.

The isocyanate group-containing (meth) acrylate monomer may be contained in an amount of 0.1% by weight to 5% by weight based on the total weight of the constituent units contained in the photocurable (meth) acrylate copolymer. When the isocyanate group-containing (meth) acrylate monomer is contained in an amount of less than 0.1% by weight, the cohesive strength and heat resistance of the pressure-sensitive adhesive composition may be deteriorated. When the content is more than 5% by weight, Can be lowered.

The optical transparent pressure sensitive adhesive composition of the present invention comprises a photopolymerization initiator in order to efficiently induce the reaction of the radical polymerizable group. The photopolymerization initiator can be used in polymerization of the hydroxy group-containing acrylic copolymer, and finally, the optical transparent pressure-sensitive adhesive composition is included together with the photopolymerizable (meth) acrylate copolymer.

The photopolymerization initiator is not particularly limited, and a photopolymerization initiator known in the art may be used. Specifically, typical initiators that can initiate photopolymerization by generating radicals by irradiation with ultraviolet rays or the like, such as benzoin-based initiators, hydroxyketone-based initiators, amino ketone-based initiators, or phosphine oxide-based initiators.

When the content of the photopolymerization initiator is too small, the effect due to the addition may be insignificant. When the content is too large, the physical properties such as durability and transparency may be adversely affected. Therefore, .

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

The optical transparent pressure sensitive adhesive composition of the present invention may further comprise a multifunctional crosslinking agent. Such a polyfunctional crosslinking agent is not particularly limited, and those known in the art can be used. Specific examples thereof include a thermosetting polyfunctional isocyanate crosslinking agent and a polyfunctional (meth) acrylate crosslinking agent.

The polyfunctional crosslinking agent may further comprise 0.02 to 5 parts by weight based on 100 parts by weight of the photocurable (meth) acrylate copolymer.

The optical transparent pressure sensitive adhesive composition of the present invention may further comprise a silane coupling agent. The kind of the coupling agent is not particularly limited, and coupling agents conventionally known in the art of pressure-sensitive adhesive production can be used. Examples of the silane coupling agent include gamma-glycidoxypropyltriethoxysilane, gamma-glycidoxypropyltrimethoxysilane, gamma-glycidoxypropylmethyldiethoxysilane, gamma-glycidoxypropyltriethoxy Silane, 3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, gamma-methacryloxypropyltrimethoxysilane, gamma-methacryloxypropyltriethoxysilane, gamma -aminopropyl Trimethoxysilane, gamma-aminopropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, and the like.

The silane coupling agent may be contained in an amount of 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 optical transparent pressure sensitive adhesive composition of the present invention may further comprise a tackifier for adjusting the tack performance.

In addition, it may further include 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, a defoamer, a surfactant and a plasticizer.

The optical transparent pressure sensitive adhesive composition of the present invention may further contain a solvent. As the 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 optical transparent pressure-sensitive adhesive composition.

Representative examples of the solvent include ethyl acetate, methyl ethyl ketone, toluene, acetonitrile and the like.

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

The viscosity of the optical transparent pressure-sensitive adhesive composition of the present invention is preferably in the range of 500 cP to 2,500 cP at 23 캜.

INDUSTRIAL APPLICABILITY The optical transparent pressure-sensitive adhesive composition of the present invention can be produced by appropriately combining a curing system by radical polymerization, a curing system by a crosslinking agent and a thermosetting functional group (-OH group) while ensuring folding properties by using monomers having a low glass transition temperature (Tg) Thereby ensuring durability.

The method for producing the optical transparent pressure-sensitive adhesive composition of the present invention can be carried out by a method commonly used in this field, except as described above. At this time, molecular weight regulators, catalysts and the like used in this field can be used without limitation.

The method of applying the optical transparency pressure-sensitive adhesive composition of the present invention is not particularly limited, and examples thereof include a bar coating method, a spin coating method, a comma coating method, and a gravure coating method. Can be performed in a general-purpose manner. From the viewpoint of performing a uniform coating process, it is preferable to control the crosslinking reaction of functional groups of the polyfunctional crosslinking agent contained in the pressure-sensitive adhesive composition in the coating process. Through this, the crosslinking agent forms a crosslinked structure during the curing and aging process after the coating operation, so that the cohesive force, the adhesive property and the cuttability of the pressure-sensitive adhesive can be improved.

Further, the application process is preferably performed after sufficiently removing the bubble-inducing component such as volatile components or reaction residues in the pressure-sensitive adhesive composition. Accordingly, the crosslinking density or the molecular weight of the pressure-sensitive adhesive is too low to lower the elastic modulus, and bubbles existing between the glass plate and the pressure-sensitive adhesive layer at a high temperature are increased to form a scattering body therein.

After forming a coating layer of the optical transparent pressure-sensitive adhesive composition, it is cured by light irradiation. In the present application, for example, in the case of applying the ultraviolet ray irradiation method, the ultraviolet ray irradiation can be performed by means of a high-pressure mercury lamp, an electrodeless lamp, or a xenon lamp.

In addition, a suitable aging step may be carried out before or after the light irradiation step to induce the reaction of the functional group of the crosslinking agent in the composition with the thermosetting functional group of the polymer, and the conditions in the process are not particularly limited as long as a proper crosslinking reaction can take place .

The pressure-sensitive adhesive composition for an optical film of the present invention can be obtained by, for example, laminating optical films such as a polarizing film, a retardation film, an anti-glare film, a wide viewing angle compensation film or a brightness enhancement film, And may be used for adhering to an adherend such as a panel or the like.

In particular, the pressure-sensitive adhesive composition for an optical film of the present invention can be preferably used for a flexible display device.

In addition,

Wherein the optical transparent pressure-sensitive adhesive composition is prepared by coating the above-mentioned optical transparent pressure-sensitive adhesive composition onto a transfer film.

As the transfer film used in the optical transparent pressure-sensitive adhesive film, films known in this field can be used without limitation. In addition, a method for producing an optical transparent pressure-sensitive adhesive film can be used without limitation in a method known in the art.

In addition,

And a pressure-sensitive adhesive layer formed from the optical transparent pressure-sensitive adhesive composition of the present invention.

It is more preferable that the flat panel display device is a flexible display device.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the following examples are intended to illustrate the present invention, and the present invention is not limited by the following examples, but may be variously modified and changed.

Manufacturing example  One. Photocurable Acrylate  Preparation of Copolymer (A1)

60 parts by weight of a compound of the following formula (1) having a glass transition temperature of -60 DEG C and 40 parts by weight of 4-hydroxybutyl acrylate (4-HBA) were added to a 1 L reactor equipped with a cooling device, . 120 parts by weight of ethyl acetate (EAc) was added as a solvent, and then nitrogen gas was purged for oxygen removal for 60 minutes. Thereafter, the temperature was maintained at 70 占 폚, 0.1 part by weight of AIBN (azobisisobutyronitrile) as a reaction initiator was added, and the reaction was carried out for 12 hours to prepare an acrylic copolymer having a weight average molecular weight of 450,000.

[Chemical Formula 1]

100 parts by weight of the acrylic copolymer, 0.5 part by weight of a polymerization inhibitor (BHT), 1 part by weight of 2-isocyanatoethyl methacrylate and 0.1 part by weight of dibutyl tin dilaurate (DBTDL) And the resulting mixture was charged into a 1 L reactor equipped with a cooling device for easy temperature control.

Subsequently, the reaction was carried out at a temperature of 40 ° C and at normal pressure for 4 hours or more to prepare a photocurable (meth) acrylate copolymer (A1).

Manufacturing example  2. Photocurable Acrylate  Preparation of Copolymer (A2)

A photocurable acrylate copolymer (A2) was prepared in the same manner as in Preparation Example 1, except that the compound of Chemical Formula 2 having a glass transition temperature of -70 ° C was used instead of the compound of Chemical Formula 1 Weight average molecular weight: 47,000).

(2)

Manufacturing example  3. Photocurable Acrylate  Preparation of Copolymer (A3)

The photocurable acrylate copolymer (A3) was prepared in the same manner as in Preparation Example 1, except that the compound of the following formula (3) was used instead of the compound of the formula (1) having a glass transition temperature of -68 캜 Weight average molecular weight: 530,000).

(3)

Manufacturing example  4. Photocurable Acrylate  Preparation of Copolymer (A4)

A photocurable acrylate copolymer (A4) was prepared in the same manner as in Preparation Example 1, except that the compound of the following formula (4) was used instead of the compound of the formula (1) having a glass transition temperature of -100 ° C Weight average molecular weight: 62,000).

[Chemical Formula 4]

Manufacturing example  5. Photocurable Acrylate  Preparation of Copolymer (A5)

A photopolymerizable acrylate copolymer (A5) was prepared in the same manner as in Preparation Example 1, except that the compound of Chemical Formula (5) having a glass transition temperature of -65 캜 was used instead of the compound of Chemical Formula (1) Weight average molecular weight: 580,000).

[Chemical Formula 5]

Manufacturing example  6. Photocurable Acrylate  Preparation of Copolymer (A6)

A photocurable acrylate copolymer (A6) was prepared in the same manner as in Preparation Example 1 except that hexyl acrylate (HA) having a glass transition temperature of -58 ° C was used in place of the compound of the formula (1) Weight average molecular weight: 37,000).

Manufacturing example  7. Flexibility  For evaluation Hard coating  Production of film

<Epoxy Siloxane  Resin Manufacturing>

3-glycidoxypropyltrimethoxysilane (GPTS, Gelest) and water were mixed at a ratio of 23.63 g: 2.70 g (0.1 mol: 0.15 mol) and placed in a 100 mL 2 neck flask. Then, 0.05 mL of ammonia was added as a catalyst to the mixture, and the mixture was stirred at 60 ° C for 6 hours to prepare a silanol acid sol.

< Hard coating  Composition Preparation>

The silylated sol and diglycidyl ether were mixed in a weight ratio of 100: 10, and 2 parts by weight of triarylsulfonium hexafluoroantimonate salt was mixed with 100 parts by weight of the mixture to prepare a hard coating composition. .

< Hard coating  Film Manufacturing>

The hard coating composition was coated on a COP (cycloolefin polymer, ZF-16, Zeon Co.) film having a thickness of 40 탆, which had been surface treated with corona, to a thickness of 50 탆 to prepare a film. The film was exposed to a mercury UV (Ultra Violet) lamp (20 mW / cm ² ) for 5 minutes to initiate the reaction with the triarylsulfonium hexafluoroantimonate salt and the reaction was allowed to proceed at 50 ° C and 50% And then subjected to a heat treatment for 60 minutes to form a hard coating film.

&Lt; Preparation of optical transparent pressure-sensitive adhesive composition >

Example  One.

0.5 part by weight of a multifunctional isocyanate crosslinking agent (Coronate L, manufactured by NPU, Japan) was added to 100 parts by weight of the photocurable (meth) acrylate copolymer (A1) prepared in Preparation Example 1, 0.5 part by weight of a photopolymerization initiator (hydroxycyclohexyl phenyl ketone , irgacure 184, manufactured by Ciba Specialty Chemicals, Inc.) were mixed to prepare an optical transparent pressure-sensitive adhesive composition of Example 1.

Example  2.

Except that the photocurable (meth) acrylate copolymer (A2) prepared in Preparation Example 2 was used instead of the photocurable (meth) acrylate copolymer (A1) prepared in Production Example 1 An optical transparent pressure-sensitive adhesive composition was prepared in the same manner as in Example 1.

Example  3.

Except that the photocurable (meth) acrylate copolymer (A3) prepared in Preparation Example 3 was used instead of the photocurable (meth) acrylate copolymer (A1) prepared in Preparation Example 1 An optical transparent pressure-sensitive adhesive composition was prepared in the same manner as in Example 1.

Example  4.

Except that the photocurable (meth) acrylate copolymer (A4) prepared in Production Example 4 was used instead of the photocurable (meth) acrylate copolymer (A1) prepared in Production Example 1 An optical transparent pressure-sensitive adhesive composition was prepared in the same manner as in Example 1.

Example  5.

Except that the photocurable (meth) acrylate copolymer (A5) prepared in Preparation Example 5 was used in place of the photocurable (meth) acrylate copolymer (A1) prepared in Preparation Example 1 An optical transparent pressure-sensitive adhesive composition was prepared in the same manner as in Example 1.

Comparative Example  One.

Except that the photocurable (meth) acrylate copolymer (A6) prepared in Production Example 6 was used instead of the photocurable (meth) acrylate copolymer (A1) prepared in Production Example 1 An optical transparent pressure-sensitive adhesive composition was prepared in the same manner as in Example 1.

Example  6. Preparation of optical transparent pressure-sensitive adhesive film

Each of the optical transparent pressure sensitive adhesive compositions prepared in Examples 1 to 5 and Comparative Example 1 was coated on a 50 탆 thick PET film coated with a silicone release agent to a thickness of 100 탆 after curing and dried at 100 for 5 minutes Example 6-2 (using the optical transparent pressure-sensitive adhesive composition of Example 2), Example 6-2 (using the optical transparent pressure-sensitive adhesive composition of Example 3), Example 6-2 (using the optical transparent pressure- , Example 6-5 (using the optical transparent pressure-sensitive adhesive composition of Example 4), Example 6-5 (using the optical transparent pressure-sensitive adhesive composition of Example 5) and Comparative Example 2-1 (using the optical transparent pressure- ) Of an optical transparent pressure-sensitive adhesive film.

Example  7. The pressure-  Formed Of the laminate  Produce

Using the optical transparent pressure-sensitive adhesive films prepared in Examples 6-1, 6-2, 6-3, 6-4, and 6-2 and Comparative Example 2-1, exemplary PET film by laminating an adhesive layer on (Mitsubishi Co. 100um PET), and by using a UV lamp (Fusion Co.) in the direction of the release film irradiated with the light amount of 1000mJ / cm ² each of example 7-1, example 7-2, A laminate having the pressure-sensitive adhesive layers of Example 7-3, Example 7-4, Example 7-5, and Comparative Example 3-1 was produced.

Example  8. Flexibility  For evaluation Hard coating  film/ Adhesive layer / PET Of the laminate  Produce

The laminate of Example 7-1, Example 7-2, Example 7-3, Example 7-4, Example 7-5, and Comparative Example 3-1 was cut into a size of 50 mm x 100 mm . Then, the release PET film adhered to the pressure-sensitive adhesive layer of the cut laminate was peeled off, adhered onto the 50 mm x 100 mm size hard coating film for flexural evaluation prepared in Production Example 7, and the autoclave 50, 5 atmospheric pressure) for about 20 minutes and cured for 24 hours under constant temperature and humidity conditions (23 DEG C, 50% relative humidity) to obtain Examples 8-1, 8-2, 8-3 and Hard coat film / pressure-sensitive adhesive layer / PET (100 占 퐉) laminate for flexural evaluation of Example 8-4, Example 8-5 and Comparative Example 4-1 were prepared.

Experimental Example  1. Measurement of physical properties of optical transparent pressure-sensitive adhesive composition

One. Folding (folding) characteristic evaluation

<Evaluation method>

Evaluation standard: IEC 62715

Evaluation equipment: Face-to-face unloaded U-folding tester (DLDMLH-FS)

Equipment maker: YUASA SYSTEM (Japan)

Evaluation conditions: -20 占 폚 / 10,000 times (bending such that the hard coating side is folded inward)

The hard coating film for flexural evaluation of Example 8-1, Example 8-2, Example 8-3, Example 8-4, Example 8-5 and Comparative Example 4-1 prepared in Example 8, The pressure-sensitive adhesive layer / PET laminate was evaluated for folding properties according to the above-mentioned evaluation method, and is shown in Table 1 below.

<Evaluation Criteria>

○: No defective modes such as bubbles, peeling, cracks were observed in the laminate

DELTA: A minute defective mode was visually visually observed in the laminate.

X: Bad mode clearly visible in the folded part of the laminate.

2. Evaluation of durability

2-1. Heat resistance evaluation

The hard coating film for flexural evaluation of Example 8-1, Example 8-2, Example 8-3, Example 8-4, Example 8-5 and Comparative Example 4-1 prepared in Example 8, The pressure-sensitive adhesive layer / PET laminate was allowed to stand at a temperature of 80 캜 for 1,000 hours, and the occurrence of bubbles or peeling was observed to evaluate heat resistance. The results are shown in Table 1 below.

<Evaluation Criteria>

◎: No bubble or peeling

○: Bubbles or peeling <5

?: 5 pieces? Bubbles or peeling <10 pieces

X: 10 pieces &lt; bubble &

2-2. Humidity Durability  evaluation

The hard coating film for flexural evaluation of Example 8-1, Example 8-2, Example 8-3, Example 8-4, Example 8-5 and Comparative Example 4-1 prepared in Example 8, The pressure-sensitive adhesive layer / PET laminate was allowed to stand at a temperature of 60 DEG C and a temperature of 90% RH for 1,000 hours, and then the occurrence of bubbles or peeling was observed. At this time, the sample was allowed to stand at room temperature for 24 hours immediately before the evaluation of the state of the specimen, and then the heat and humidity resistance was evaluated. The results are shown in Table 1 below.

<Evaluation Criteria>

◎: No bubble or peeling

○: Bubbles or peeling <5

?: 5 pieces? Bubbles or peeling <10 pieces

X: 10 pieces &lt; bubble &

3. Adhesion evaluation

The pressure-sensitive adhesive laminate prepared in Example 7-1, Example 7-2, Example 7-3, Example 7-4, Example 7-5 and Comparative Example 3-1 prepared in Example 7 The specimens were cut to a size of 25 mm x 100 mm. Then, the releasing PET film adhered to the pressure-sensitive adhesive layer was peeled off, and the laminate having the pressure-sensitive adhesive layer formed thereon was adhered to the alkali-free glass using a roller of 2 kg in accordance with JIS Z 0237. The alkali-free glass with the laminate was subjected to compression treatment for 20 minutes in an autoclave (50 ° C, 5 atmospheric pressure) and stored at room temperature and humidity (23 ° C, 50% relative humidity) for 24 hours to prepare samples. Thereafter, the adhesive agent was peeled from the alkali-free glass at a peeling speed of 300 mm / min and a peeling angle of 180 degrees using a TA instrument (Texture Analyzer, manufactured by Stable Micro Systems, UK) Respectively.

As can be seen from the test results of Tables 1 and 2, the optical transparent pressure-sensitive adhesive compositions of Examples of the present invention were found to have excellent folding properties, heat resistance, heat resistance and adhesion. Particularly, the folding properties were confirmed to be remarkably excellent as compared with the optical transparent pressure-sensitive adhesive compositions of the comparative examples.

On the other hand, the optical transparent pressure-sensitive adhesive composition of the comparative example did not contain a (meth) acrylate monomer having a glass transition temperature (Tg) of -120 to -60 ° C, resulting in a very poor folding property.

Claims (13)

1. An optical transparent pressure-sensitive adhesive composition comprising a photocurable (meth) acrylate copolymer and a photopolymerization initiator,
The photocurable (meth) acrylate copolymer is a copolymer of
, 95 to 99.9% by weight of a hydroxy group-containing acrylic copolymer and 0.1 to 5% by weight of an isocyanate group-containing (meth) acrylate monomer based on the total weight of the constituent units contained in the copolymer,
Wherein the hydroxy group-containing acrylic copolymer and the isocyanate group-containing (meth) acrylate monomer form a urethane bond,
The hydroxy group-containing acrylic copolymer includes a (meth) acrylate monomer having a glass transition temperature of -120 to -60 ° C and a hydroxy group-containing alkyl acrylate monomer,
And has a weight average molecular weight of 200,000 to 1,000,000. The optical transparent pressure-sensitive adhesive composition according to claim 1, wherein the (meth) acrylate monomer having a glass transition temperature of -120 to -60 ° C comprises a linear or branched alkyl group having 8 to 30 carbon atoms. The optical transparent pressure-sensitive adhesive composition according to claim 2, wherein the (meth) acrylate monomer having a glass transition temperature of -120 to -60 ° C. comprises at least one selected from the group consisting of the following formulas (1) to (5)
[Chemical Formula 1]

(2)

(3)

[Chemical Formula 4]

[Chemical Formula 5]

The optical transparent pressure-sensitive adhesive composition according to claim 1, wherein the hydroxyl group-containing alkyl acrylate monomer is a linear or branched alkyl acrylate monomer having hydroxy C ₄ to C ₆ . The acrylic copolymer according to claim 1, wherein the hydroxy group-containing acrylic copolymer comprises 50 to 95% by weight of a (meth) acrylate monomer having a glass transition temperature of -120 to -60 캜 based on the total weight of the monomers contained in the copolymer, And 5 to 50% by weight of a monomer. The optical transparent pressure-sensitive adhesive composition according to claim 1, wherein the optical transparent pressure-sensitive adhesive composition comprises 0.1 to 5 parts by weight of a photopolymerization initiator based on 100 parts by weight of a photocurable (meth) acrylate copolymer. [6] The optical transparent pressure sensitive adhesive composition of claim 6, wherein the optical transparent pressure sensitive adhesive composition further comprises 0.02 to 5 parts by weight of a multifunctional crosslinking agent based on 100 parts by weight of the photopolymerizable (meth) acrylate copolymer. The optical transparency pressure-sensitive adhesive composition according to claim 6 or 7, wherein the optical transparent pressure-sensitive adhesive composition further comprises 40 to 85 parts by weight of a solvent based on 100 parts by weight of the photocurable (meth) acrylate copolymer. The optical transparent pressure-sensitive adhesive composition according to claim 7, wherein the polyfunctional crosslinking agent is a thermosetting polyfunctional isocyanate crosslinking agent or a polyfunctional (meth) acrylate crosslinking agent. The optical transparent pressure-sensitive adhesive composition according to claim 1, wherein the isocyanate group-containing (meth) acrylate monomer is an isocyanate C ₁ -C ₁₀ alkyl acrylate monomer. An optical transparent pressure-sensitive adhesive film produced by coating the transfer film with the optical transparent pressure-sensitive adhesive composition of claim 1. And a pressure-sensitive adhesive layer formed from the optical transparent pressure-sensitive adhesive composition of claim 1. The flat panel display according to claim 12, wherein the flat panel display device is a flexible display device.