KR102143606B1 - Optically Clear Adhesive Composition, and Optically Clear Adhesive Film comprising the Same, and Flat Panel Display - Google Patents

Abstract

The present invention is an optically transparent pressure-sensitive adhesive composition comprising a photocurable (meth)acrylate copolymer and a photopolymerization initiator, wherein the photocurable (meth)acrylate copolymer is an acrylic-containing hydroxy group based on the total weight of the structural units contained in the copolymer. It contains 95 to 99.9% by weight of the copolymer and 0.1 to 5% by weight of an isocyanate group-containing (meth)acrylate monomer, and the hydroxy group-containing acrylic copolymer and an isocyanate group-containing (meth)acrylate-based monomer form a urethane bond. Will,
The hydroxy group-containing acrylic copolymer has a glass transition temperature (Tg) of -45 to -60°C with respect to the total weight of the monomers contained in the copolymer, 50 to 95% by weight of an acrylate monomer having a caprolactone structure and an alkyl acrylate containing a hydroxyl group It includes 5 to 50% by weight of a monomer, and has a weight average molecular weight of 200,000 to 1 million, and provides an optically transparent adhesive composition, an optically transparent adhesive film and a flat panel display including the same.

Description

Optically Clear Adhesive Composition, Optically Clear Adhesive Film Comprising the Same, and Flat Panel Display

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

Flat panel displays include 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, and a luminance enhancing film are used. When these optical films are laminated to each other or the optical film is attached to a display panel, an optically transparent adhesive (OCA) is used. Therefore, an optically transparent adhesive (OCA) should have excellent moist heat resistance, heat resistance, and adhesion as well as optical properties.

In particular, in recent years, flexible display devices are being developed competitively. In the flexible display device, since the device itself is bent, rolled, or folded, the display panel and optical films included in the device are also subjected to bending stress. Therefore, more reinforced and diversified physical properties are required for the optically transparent adhesive (OCA) used in flexible displays.

For example, an optically transparent pressure-sensitive adhesive (OCA) used in a flexible display device should have excellent folding characteristics that enable flexible folding of the device. In particular, when considering the case of using the flexible display device for a long time outside in a low temperature state, the folding characteristic at low temperature should be excellent.

In addition, the optically transparent pressure-sensitive adhesive (OCA) used in a flexible display device is required to have more enhanced moisture and heat resistance. This is because the flexible display device repeats the process of folding and unfolding countless times during use, so that the possibility of moisture penetration through the folded and unfolded portion increases as much.

Further, as the flexible display device is bent, rolled, or folded, the display panel and optical films included in the device are also subjected to bending stress. Therefore, since it is easy to separate the stacked display panels and optical films, better adhesion is required, and more excellent durability is also required.

However, optically transparent pressure-sensitive adhesives (OCA) known to date have not sufficiently provided the above physical properties required by a flexible display device.

Republic of Korea Patent Publication No. 10-2016-0085759

The present invention has been devised to solve the above problems of the prior art, and provides an optically transparent adhesive (OCA) composition capable of sufficiently satisfying the folding characteristics, moist heat resistance, heat resistance, and adhesion required in a flexible display device. The purpose.

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

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

The photocurable (meth)acrylate copolymer contains 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-based monomer based on the total weight of the constituent units contained in the copolymer. The hydroxy group-containing acrylic copolymer and the isocyanate group-containing (meth)acrylate-based monomer form a urethane bond,

The hydroxy group-containing acrylic copolymer has a glass transition temperature (Tg) of -45 to -60°C with respect to the total weight of the monomers contained in the copolymer, 50 to 95% by weight of an acrylate monomer having a caprolactone structure and an alkyl acrylate containing a hydroxyl group It includes 5 to 50% by weight of a monomer, and provides a weight average molecular weight of 200,000 to 1 million, an optically transparent pressure-sensitive adhesive composition.

In addition, the present invention provides an optically transparent adhesive film, characterized in that produced by coating the optically transparent adhesive composition of the present invention on a transfer film.

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

The optically transparent adhesive (OCA) composition and optically transparent adhesive film of the present invention provide sufficient folding properties, heat-and-moisture resistance, heat resistance, and adhesion, which can be used in not only flat display devices, but also flexible display devices, and thus excellent durability. to provide.

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

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

The photocurable (meth)acrylate copolymer contains 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-based monomer based on the total weight of the constituent units contained in the copolymer. The hydroxy group-containing acrylic copolymer and the isocyanate group-containing (meth)acrylate-based monomer form a urethane bond,

The hydroxy group-containing acrylic copolymer has a glass transition temperature (Tg) of -45 to -60°C with respect to the total weight of the monomers contained in the copolymer, 50 to 95% by weight of an acrylate monomer having a caprolactone structure and an alkyl acrylate containing a hydroxyl group It includes 5 to 50% by weight of a monomer, and provides a weight average molecular weight of 200,000 to 1 million, an optically transparent pressure-sensitive adhesive composition.

The optically transparent pressure-sensitive adhesive composition of the present invention contains acrylate monomers having a caprolactone-based structure having a glass transition temperature (Tg) of -45 to -60°C, and thus has excellent folding properties and a glass transition temperature (Tg) of -45 to By including a large amount of acrylate and hydroxy group-containing alkyl acrylate monomers having a caprolactone-based structure of -60°C, it is excellent in moist heat resistance and adhesion, and by increasing the crosslinking density, it is to provide an optically transparent adhesive composition having excellent heat resistance and durability. It features.

In the present invention, the acrylate monomer having a caprolactone-based structure with a glass transition temperature (Tg) of -45 to -60°C has advantages such as low volatility, low toxicity, low acidity, low skin irritation, and ease of handling compared to other monomers. In addition, there is an advantage in that adhesion with the substrate is improved due to the large polarity.

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

The photocurable acrylate copolymer is copolymerized with an acrylate monomer having a caprolactone-based structure having a glass transition temperature (Tg) of -45 to -60°C and an alkyl acrylate monomer containing a hydroxy group, and a thermosetting functional group at the branch chain or terminal A hydroxy group-containing acrylic copolymer main chain into which (OH group) has been introduced is prepared, and then the isocyanate group-containing (meth)acrylate-based monomer is reacted with the main chain under appropriate conditions, so that at least the thermosetting functional group (OH group) of the main chain is It can be prepared by substituting some of the isocyanate group-containing (meth)acrylate-based monomers.

An acrylate monomer having a caprolactone-based structure having a glass transition temperature (Tg) of -45 to -60°C contained in the form of polymerization in the hydroxy group-containing acrylic copolymer may be represented by the following formula.

[Formula 1]

[Formula 2]

In the above formula, n and m are assumed to be constants 1 to 5.

Formula 1 may preferably have the structure of Formula 3, and Formula 2 may preferably have the structure of Formula 4 below.

[Formula 3]

[Formula 4]

The main chain is, for example, through a conventional polymerization method such as solution polymerization, photo polymerization, bulk polymerization, suspension polymerization, or emulsion polymerization. Can be manufactured.

The hydroxy group-containing alkyl acrylate monomer contained in a polymerized form in the hydroxy group-containing acrylic copolymer is specifically, for example, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate, 6-hydroxyhexyl acrylate, 8-hydroxyoctyl acrylate, 2-hydroxyethylene glycol acrylate, 2-hydroxypropylene glycol acrylate, and the like.

Among these, in particular, the hydroxy group-containing alkyl acrylate monomer may be a straight or branched chain alkyl acrylate monomer of hydroxy C ₄ ~ C ₆ , and specifically, for example, 4-hydroxybutyl acrylate, 5-hydroxypentyl Monomers such as acrylate and 6-hydroxyhexyl acrylate may be preferably used, and more preferably 4-hydroxybutyl acrylate may be used.

In the hydroxy group-containing acrylic copolymer, the acrylate monomer having a caprolactone-based structure having a glass transition temperature (Tg) of -45 to -60°C is contained in an amount of 50 to 95% by weight, and the hydroxy group-containing alkyl acrylate monomer is 5 It is preferably contained in to 50% by weight.

In addition, when the hydroxy group-containing alkyl acrylate monomer is contained in an amount of less than 5% by weight, OH groups, which are hydrophilic, are insufficient in the pressure-sensitive adhesive layer, so moisture cannot be held in the pressure-sensitive adhesive layer and moisture is discharged to the interface, resulting in reduced adhesion under moist heat resistance conditions. Peeling defect occurs, and when it is contained in an amount exceeding 50% by weight, the adhesive absorbs moisture in excess, expands the volume, and lowers the cohesive force, thereby causing interfacial peeling and bubbles.

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

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

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

As the isocyanate group-containing (meth)acrylate-based monomer included in the photocurable (meth)acrylate copolymer, isocyanato C ₁ ~C ₁₀ linear or branched alkyl (meth)acrylate may be used. In the above, the C ₁ ~C ₁₀ linear or branched alkyl group is methyl, ethyl, propyl, isopropyl, butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, Nonyl, decanyl, and the like, and among them, ethyl and propyl may be preferably used.

The isocyanate group-containing (meth)acrylate-based monomer may be included in an amount of 0.1 to 5.0% by weight based on the total weight of the constituent units included in the photocurable (meth)acrylate copolymer. When the crosslinking agent is included 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, and if it exceeds 5.0% by weight, the cohesive strength of the pressure-sensitive adhesive becomes too strong, and thus folding characteristics may be deteriorated.

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

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

If the content of the photopolymerization initiator is too small, the effect due to the addition may be insignificant, and if it is too large, it may adversely affect physical properties such as durability or transparency, so an appropriate content range can be selected in consideration of these points. .

The photopolymerization initiator may be included 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 optically transparent pressure-sensitive adhesive composition of the present invention may further include a multifunctional crosslinking agent. Such a multifunctional crosslinking agent is not particularly limited, and those known in the art may be used. Specifically, examples include a thermosetting polyfunctional isocyanate crosslinking agent, a polyfunctional (meth)acrylate crosslinking agent, and the like.

The multifunctional crosslinking agent may be further included in an amount of 0.02 to 5 parts by weight based on 100 parts by weight of the photocurable (meth)acrylate copolymer.

The optically transparent pressure-sensitive adhesive composition of the present invention may further include a silane coupling agent. The type of the coupling agent is not particularly limited, and a coupling agent commonly known in the field of manufacturing an adhesive may be used. For example, as a silane coupling agent, gamma-glycidoxypropyl triethoxy silane, gamma-glycidoxypropyl trimethoxy silane, gamma-glycidoxypropyl methyldiethoxy silane, gamma-glycidoxypropyl triethoxy Silane, 3-mercaptopropyl trimethoxy silane, vinyl trimethoxy silane, vinyl triethoxy silane, gamma-methacryloxypropyl trimethoxy silane, gamma-methacryloxy propyl triethoxy silane, gamma-aminopropyl Trimethoxy silane, gamma-aminopropyl triethoxy silane, 3-isocyanatopropyl triethoxy silane, and the like.

The silane coupling agent may be included in an amount of 0.01 parts by weight to 5 parts by weight, preferably 0.01 parts by weight to 1 part by weight, based on 100 parts by weight of the photocurable (meth)acrylate copolymer.

The optically transparent pressure-sensitive adhesive composition of the present invention may further include a tackifier for controlling adhesive performance.

In addition, it may further include one or more additives selected from the group consisting of an epoxy resin, a curing agent, an ultraviolet stabilizer, an antioxidant, a toning agent, a reinforcing agent, a filler, a defoaming agent, a surfactant, and a plasticizer.

The optically transparent pressure-sensitive adhesive composition of the present invention may further contain a solvent. As the solvent, any solvent known in the art may be used without limitation as long as it can dissolve the monomers and copolymers used in the optically transparent pressure-sensitive adhesive composition.

Representative examples of the solvent include ethyl acetate, methyl ethyl ketone, toluene, and acetonitrile. 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 optically transparent pressure-sensitive adhesive composition of the present invention may preferably be used in the range of 23 to 500cP to 2,500Cp.

The optically transparent pressure-sensitive adhesive composition of the present invention uses monomers having a low glass transition temperature to secure low-temperature folding characteristics, while appropriately employing a curing system by radical polymerization and a curing system by a crosslinking agent and a thermosetting functional group (OH group), It has the characteristics of securing moist heat resistance, heat resistance and durability.

The method for preparing the optically transparent pressure-sensitive adhesive composition of the present invention may be carried out by a method commonly used in this field, except for those described above. At this time, molecular weight modifiers and catalysts used in this field may be used without limitation.

The optically transparent pressure-sensitive adhesive composition of the present invention may further include an adhesion promoter, and by further including an adhesion promoter having a high polarity, heat resistance and adhesion may be more excellent.

The method of applying the optically transparent pressure-sensitive adhesive composition of the present invention is not particularly limited, and for example, bar coating, spin coating, comma coating or gravure coating, etc. It can be done in a universal way. In the coating process, it is preferable from the viewpoint of performing a uniform coating process to control the crosslinking reaction of the functional groups of the multifunctional crosslinking agent included in the pressure-sensitive adhesive composition to not proceed. Through this, the crosslinking agent may form a crosslinked structure in the curing and aging process after the coating operation, thereby improving cohesion, adhesive properties, and cuttability of the adhesive.

In addition, the coating process is preferably performed after sufficiently removing the bubble-causing component such as a volatile component or a reaction residue inside the pressure-sensitive adhesive composition. Accordingly, the crosslinking density or molecular weight of the pressure-sensitive adhesive is too low, so that the elastic modulus decreases, and bubbles existing between the glass plate and the pressure-sensitive adhesive layer are increased in a high temperature state, thereby preventing a phenomenon of forming a scattering body inside.

After forming the coating layer of the optically transparent pressure-sensitive adhesive composition, it is cured through light irradiation. In the present application, for example, when the ultraviolet irradiation method is applied, the ultraviolet irradiation may be performed using a means such as a high-pressure mercury lamp, an electrodeless lamp, or a xenon lamp.

In addition, before or after the light irradiation process, an appropriate aging process for inducing a reaction between the functional group of the crosslinking agent in the composition and the thermosetting functional group of the polymer may be performed, and the conditions in the process are not particularly limited as long as an appropriate crosslinking reaction can occur. .

The pressure-sensitive adhesive composition for an optical film of the present invention is, for example, a polarizing film, a retardation film, an anti-glare film, a wide viewing angle compensation film, or an optical film such as a luminance enhancing film are laminated to each other, or the optical film or a laminate thereof is displayed. It can be used for attaching to an adherend such as a panel.

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

In addition, the present invention provides an optically transparent adhesive film, characterized in that produced by coating the optically transparent adhesive composition on a transfer film.

As a transfer film used for the optically transparent pressure-sensitive adhesive film, a film known in this field may be used without limitation. In addition, the method of manufacturing the optically transparent pressure-sensitive adhesive film may be used without limitation, any method known in the art.

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

In the above, 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 using 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 and may be variously modified and changed.

Manufacturing example 1-1. Glass transition temperature ( Tg ) Is -45~-60℃ Caprolactone Structured Acrylate Monomer and Preparation of hydroxy group-containing monomer polymer (A1)

50 parts by weight of acrylate and 50 parts by weight of 4-hydroxybutyl acrylate (4-HBA) having a caprolactone-based structure represented by the following formula (3) in a 1L reactor equipped with a cooling device so that nitrogen gas is refluxed and temperature control is easy Then, after adding 120 parts by weight of ethyl acetate (EAc) as a solvent, nitrogen gas was purged for 60 minutes to remove oxygen. Thereafter, the temperature was maintained at 70° C., 0.1 parts by weight of AIBN (azobisisobutyronitrile) as a reaction initiator was added and reacted for 12 hours to prepare an acrylic polymer (A1) having a weight average molecular weight of 560,000.

[Formula 3]

Manufacturing example 1-2. Preparation of acrylic polymer (A2)

The polymerization reaction was carried out in the same manner as in Preparation Example 1-1, except that 95 parts by weight of acrylate having a caprolactone structure of Formula 3 and 5 parts by weight of 4-hydroxybutyl acrylate (4-HBA) were used. Was carried out to prepare an acrylic polymer (A2) having a weight average molecular weight of 620,000.

Manufacturing example 1-3. Preparation of acrylic polymer (A3)

The same method as in Preparation Example 1-1, except that 50 parts by weight of acrylate having a caprolactone-based structure of Formula 4 and 50 parts by weight of 4-hydroxybutyl acrylate (4-HBA) were used instead of Formula 3 By carrying out the polymerization reaction, an acrylic polymer (A3) having a weight average molecular weight of 590,000 was prepared.

[Formula 4]

Manufacturing example 1-4. Preparation of acrylic polymer (A4)

In Preparation Example 1-3, 95 parts by weight of acrylate having a caprolactone-based structure of Formula 4 and 5 parts by weight of 4-hydroxybutyl acrylate (4-HBA) The polymerization reaction was carried out in the same manner as that except that used to prepare an acrylic polymer (A4) having a weight average molecular weight of 630,000.

Manufacturing example 1-5. Preparation of acrylic polymer (A5)

In Preparation Example 1-1, instead of 50 parts by weight of acrylate having a caprolactone-based structure of Formula 3 and 50 parts by weight of 4-hydroxybutyl acrylate (4-HBA), acrylate 98 having a caprolactone-based structure of Formula 3 A polymerization reaction was performed in the same manner as the same except that parts by weight and 2 parts by weight of 4-hydroxybutyl acrylate (4-HBA)) were used to prepare an acrylic polymer (A5) having a weight average molecular weight of 550,000.

Manufacturing example 1-6. Preparation of acrylic polymer (A6)

In Preparation Example 1-2, the polymerization reaction was carried out in the same manner as that except that n-butyl acrylate (n-BA), which is a non-caprolactone-based compound, was used instead of the acrylate having a caprolactone-based structure of Formula 3 above. Was carried out to prepare an acrylic polymer (A6) having a weight average molecular weight of 350,000.

Manufacturing example 2-1. Photocurable Acrylate Preparation of copolymer (B1)

In a 1L reactor in which nitrogen gas is refluxed and a cooling device is installed to facilitate temperature control, 100 parts by weight of acrylic polymer (A1) solid content and 1 part by weight of 2-isocyanatoethyl methacrylate And 0.1 parts by weight of dibutyl tindilaulate (DBTDL). Subsequently, it was reacted at a temperature of 40° C. and atmospheric pressure for 4 hours or more, thereby preparing a photocurable (meth)acrylate copolymer (B1).

Manufacturing example 2-2. Photocurable Acrylate Preparation of 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.

Manufacturing example 2-3. Photocurable Acrylate Preparation of 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.

Manufacturing example 2-4. Photocurable Acrylate Preparation of 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.

Manufacturing example 2-5. Photocurable Acrylate Preparation of copolymer (B5)

A photocurable (meth)acrylate copolymer (B5) was prepared in the same manner as in Preparation Example 2-1, except that the acrylic polymer (A5) was used.

Manufacturing example 2-6 Photocurable Acrylate Preparation of copolymer (B6)

A photocurable (meth)acrylate copolymer (B6) was prepared in the same manner as in Preparation Example 2-1, except that an acrylic polymer (A5 was used).

Manufacturing example 3: Flexibility For evaluation Hard coating Production of film

<Preparation of epoxy siloxane resin>

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

<Preparation of hard coating composition>

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

<Manufacture of hard coating film>

The hard coating composition was coated with a thickness of 50 μm on a 40 μm thick COP (cycloolefin polymer, ZF-16, Zeon company) film surface-treated by corona 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 by the triarylsulfonium hexafluoroantimonate salt, and 50°C and 50% relative humidity Water heat treatment was performed for 60 minutes under conditions to form a hard coating film.

Example 1: Preparation of optically transparent pressure-sensitive adhesive composition

With respect to 100 parts by weight of the photocurable (meth)acrylate copolymer (B1) prepared in Preparation Example 2-1, 0.5 parts by weight of a polyfunctional isocyanate crosslinking agent (Coronate L, manufactured by NPU Japan), a photopolymerization initiator (hydroxycyclohexyl A pressure-sensitive adhesive composition was prepared by mixing 0.2 parts by weight of phenyl ketone, irgacure 184, and Swiss Civas Specialty Chemical (manufactured by).

Example 2: Preparation of optically transparent pressure-sensitive adhesive composition

The same as in Example 1, except that the photocurable (meth)acrylate copolymer (B2) prepared in Preparation Example 2-2 was used instead of the photocurable (meth)acrylate copolymer (B1) in Example 1 A pressure-sensitive adhesive composition was prepared by the method.

Example 3: Preparation of optically transparent pressure-sensitive adhesive composition

The same as in Example 1, except that the photocurable (meth)acrylate copolymer (B3) prepared in Preparation Example 2-3 was used instead of the photocurable (meth)acrylate copolymer (B1) in Example 1 A pressure-sensitive adhesive composition was prepared by the method.

Example 4: Preparation of optically transparent pressure-sensitive adhesive composition

The same as in Example 1 except for using the photocurable (meth)acrylate copolymer (B4) prepared in Preparation Example 2-4 instead of the photocurable (meth)acrylate copolymer (B1) in Example 1 A pressure-sensitive adhesive composition was prepared by the method.

Comparative example One: Preparation of optically transparent adhesive composition

A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that the photocurable acrylate copolymer (B5) prepared in Preparation Example 2-5 was used instead of the photocurable acrylate copolymer (B1) in Example 1 I did.

Comparative example 2: Preparation of optically transparent adhesive composition

A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that the photocurable acrylate copolymer (B6) prepared in Preparation Example 2-6 was used instead of the photocurable acrylate copolymer (B1) in Example 1 I did.

Example 5: Preparation of optically transparent adhesive film

Each of the optically transparent pressure-sensitive adhesive compositions prepared in Examples 1, 2, 3, and 4, Comparative Examples 1 and 2 was cured on a 50 μm-thick PET film coated with a silicone release agent. 100 µm, and dried at 100° C. for 5 minutes in Example 3-1 (using the optically transparent pressure-sensitive adhesive composition of Example 1), Example 3-2 (using the optically transparent pressure-sensitive adhesive composition of Example 2), Example 3-3 (using the optically transparent pressure-sensitive adhesive composition of Example 3), Example 3-4 (using the optically transparent pressure-sensitive adhesive composition of Example 4), Comparative Example 3-1 (using the optically transparent pressure-sensitive adhesive composition of Comparative Example 1) and An optically transparent adhesive film of Comparative Example 3-2 (using the optically transparent adhesive composition of Comparative Example 2) was prepared.

Example 6: Adhesive layer Formed Laminated Produce

Using the optically transparent adhesive films prepared in Example 3-1, Example 3-2, Example 3-3, Example 3-4, Comparative Example 3-1, and Comparative Example 3-2, the thickness of 100 μm A pressure-sensitive adhesive layer was laminated on a PET film (100um PET manufactured by Mitsubishi Corporation), and an amount of light of 1000 mJ/cm ² was irradiated using a UV lamp (Fusion Corporation) in the direction of the release film, respectively, in Example 4-1 and Example 4-2, The laminates in which the pressure-sensitive adhesive layers of Example 4-3, Example 4-4, Comparative Example 4-1, and Comparative Example 4-2 were formed were prepared.

Example 7: Flexibility For evaluation Hard coating film/ Adhesive layer /PET Laminated Produce

The laminates of Example 4-1, Example 4-2, Example 4-3, Example 4-4, Comparative Example 4-1, and Comparative Example 4-2 were cut to a size of 50 mm × 100 mm I did. Subsequently, the release PET film attached to the pressure-sensitive adhesive layer of the cut laminate was peeled off, and attached on the hard coating film for evaluation of flexibility prepared in Preparation Example 3 having a size of 50 mm × 100 mm, and an autoclave (50° C. , 5 atm) for about 20 minutes, followed by curing for 24 hours in constant temperature and humidity conditions (23° C., 50% relative humidity), respectively, in Example 5-1, Example 5-2, and Example 5-3, A hard coating film/adhesive layer/PET (100 μm) laminate for evaluating the flexibility of Example 5-4, Comparative Example 5-1, and Comparative Example 5-2 was prepared.

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

One. Folding characteristics evaluation

<Evaluation method>

Evaluation standard: 　IEC 62715

Evaluation equipment: No-load U-fold tester (DLDMLH-FS)

Equipment maker: YUASA SYSTEM (Japan)

Evaluation conditions: -20℃ / 10,000 times (Bent the hard coating side to fold inward)

Hard coating films for evaluating flexural properties of Examples 5-1, 5-2, 5-3, 5-4, Comparative Example 5-1, and Comparative Example 5-2 prepared in Example 5 The /adhesive layer/PET laminate was evaluated for folding characteristics according to the above evaluation method, and is shown in Table 1 below.

<Evaluation criteria>

○: No defect modes such as bubbles, peeling, cracks, etc. were observed in the laminate

?: A fine defect mode in the layered product was slightly visually recognized.

X: A defect mode, which is clearly visible with the naked eye, is visually recognized in the folding portion of the laminate.

2. Durability evaluation

(1) Heat resistance evaluation

Flexibility of Example 5-1, Example 5-2, Example 5-3, Example 5-4, Comparative Example 5-1, and Comparative Example 5-2 prepared in Example 5 prepared in Example 5 After the evaluation hard coating film/adhesive layer/PET laminate was left at a temperature of 80° C. for 1,000 hours, the occurrence of bubbles or peeling was observed to evaluate the heat resistance, and the results are shown in Table 1 below.

<Evaluation criteria>

◎: no air bubbles or peeling

○: Bubbles or peeling <5

△: 5 ≤ bubbles or peeling <10

×: 10 ≤ bubbles or peeling

(2) Moisture and heat resistance evaluation

Flexibility of Example 5-1, Example 5-2, Example 5-3, Example 5-4, Comparative Example 5-1, and Comparative Example 5-2 prepared in Example 5 prepared in Example 5 The evaluation hard coating film/adhesive layer/PET laminate was left at a temperature of 60° C. and 90%RH for 1,000 hours, and then bubbles or peeling were observed. At this time, immediately before evaluating the state of the specimen, it was left at room temperature for 24 hours and then observed to evaluate the heat and humidity resistance, and the results are shown in Table 1 below.

<Evaluation criteria>

◎: no air bubbles or peeling

○: Bubbles or peeling <5

△: 5 ≤ bubbles or peeling <10

×: 10 ≤ bubbles or peeling

3. Adhesion evaluation

The adhesive-forming laminates prepared in Examples 4-1, 4-2, 4-3, 4-4, Comparative Example 4-1, and Comparative Example 4-2 were 25 mm × 100 mm in size. The specimen was prepared by cutting to be. Subsequently, the release PET film adhered to the pressure-sensitive adhesive layer was peeled off, and the laminate with the pressure-sensitive adhesive layer formed was adhered to the alkali-free glass using a 2 kg roller according to JIS Z 0237. A sample was prepared by compressing the alkali-free glass to which the laminating agent was attached for about 20 minutes in an autoclave (50° C., 5 atm), and storing it in a constant temperature and humidity condition (23° C., 50% relative humidity) for 24 hours. Thereafter, using a TA equipment (Texture Analyzer, manufactured by Stable Micro Systems Co., Ltd.), the laminate was peeled from the alkali-free glass at a peeling rate of 300 mm/min and a peeling angle of 180 degrees, and the adhesion was measured, and the result was displayed. It is shown in 1.

As can be seen from the test results in Tables 1 and 2, the optically transparent pressure-sensitive adhesive compositions of the examples of the present invention were found to have excellent folding properties, moist heat resistance, heat resistance, and adhesion. In particular, it was confirmed that the folding characteristics were remarkably excellent compared to the optically transparent pressure-sensitive adhesive compositions of Comparative Example.

Claims (13)

As an optically transparent adhesive composition comprising a photocurable (meth)acrylate copolymer and a photoinitiator,
The photocurable (meth)acrylate copolymer contains 95 to 99.9% by weight of a hydroxy group-containing acrylic copolymer and 0.1 to 5.0% by weight of an isocyanate group-containing (meth)acrylate monomer based on the total weight of the constituent units contained in the copolymer. The hydroxy group-containing acrylic copolymer and the isocyanate group-containing (meth)acrylate-based monomer form a urethane bond,
The hydroxy group-containing acrylic copolymer is 50 to 95% by weight of an acrylate monomer having a caprolactone-based structure with a glass transition temperature (Tg) of -45 to -60°C based on the total weight of the monomer contained in the copolymer and an alkyl acrylic containing a hydroxyl group. It contains 5 to 50% by weight of the rate monomer, and the weight average molecular weight is 200,000 to 1 million,
The acrylate monomer having a caprolactone-based structure having a glass transition temperature (Tg) of -45 to -60°C has at least one monomer selected from the group consisting of the following Chemical Formulas 1 to 2, an optically transparent adhesive composition .
[Formula 1]

[Formula 2]

(In Formulas 1 and 2, m and n are each an integer of 1 to 5.) delete The method according to claim 1,
Formula 1 has the structure of the following formula 3, wherein the formula 2 is characterized in that it has a structure of the following formula 4, optically transparent pressure-sensitive adhesive composition.

[Chemical Formula 3]

[Formula 4]

The optically transparent pressure-sensitive adhesive composition of claim 1, wherein the hydroxy group-containing alkyl acrylate monomer is a hydroxy C ₄ to C ₆ linear or branched alkyl acrylate monomer. The method according to claim 1,
The optically transparent pressure-sensitive adhesive composition is an optically transparent pressure-sensitive adhesive composition comprising 0.1 to 5 parts by weight of a photopolymerization initiator based on 100 parts by weight of a photocurable (meth)acrylate copolymer. The method according to claim 5,
The optically 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 photocurable (meth)acrylate copolymer. The method according to claim 5 or 6,
The optically transparent adhesive composition further comprises 40 to 85 parts by weight of a solvent based on 100 parts by weight of a photocurable (meth)acrylate copolymer. The method according to claim 6,
The multifunctional crosslinking agent is a thermosetting polyfunctional isocyanate crosslinking agent or a polyfunctional (meth) acrylate crosslinking agent. The method according to claim 1,
An optically transparent pressure-sensitive adhesive composition further comprising an adhesion promoter. The method according to claim 1,
The isocyanate group-containing (meth)acrylate-based monomer is an optically transparent pressure-sensitive adhesive composition, characterized in that the isocyanate C ₁ ~ C ₁₀ alkyl acrylate. An optically transparent adhesive film, characterized in that produced by coating the optically transparent adhesive composition of claim 1 on a transfer film. A flat panel display device comprising an adhesive layer formed of the optically transparent adhesive composition of claim 1. The method of claim 12,
The flat panel display device, wherein the flat panel display device is a flexible display device.