KR102143802B1 - Optically Clear Adhesive Composition, and Optically Clear Adhesive Film comprising the Same, and Flat Panel Display - Google Patents

Abstract

The present invention is a photocurable (meth) acrylate copolymer; Rubber-based (meth)acrylic monomers; And as an optically transparent pressure-sensitive adhesive composition comprising a photopolymerization initiator,
The photocurable (meth)acrylate copolymer is 95 to 99.9% by weight of an acrylic copolymer containing a hydroxyl group and 0.1 to 5% by weight of an isocyanato group-containing (meth)acrylate monomer based on the total weight of the constituent units contained in the copolymer. Including, wherein the hydroxy group-containing acrylic copolymer and the isocyanato group-containing (meth) acrylate-based monomer formed a urethane bond,
The hydroxy group-containing acrylic copolymer includes 50 to 98% by weight of a C1 to C12 straight or branched chain alkyl (meth)acrylate monomer and 2 to 50% by weight of a hydroxy group-containing polymerizable monomer based on the total weight of the monomers contained in the copolymer. And, it provides an optically transparent adhesive composition, characterized in that the weight average molecular weight of 200,000 to 1 million, 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

Photocurable (meth)acrylate copolymer; Rubber-based (meth)acrylic monomers; And as an optically transparent pressure-sensitive adhesive composition comprising a photopolymerization initiator,

The photocurable (meth)acrylate copolymer is 95 to 99.9% by weight of a hydroxy group-containing acrylic copolymer and 0.1 to 5% by weight of an isocyanato group-containing (meth)acrylate-based monomer based on the total weight of the constituent units contained in the copolymer. Including, wherein the hydroxy group-containing acrylic copolymer and the isocyanato group-containing (meth) acrylate-based monomer formed a urethane bond,

The hydroxy group-containing acrylic copolymer contains 50 to 98% by weight of a C1 to C12 straight or branched chain alkyl (meth)acrylate monomer and 2 to 50% by weight of a hydroxy group-containing polymerizable monomer based on the total weight of the monomers contained in the copolymer. And, it provides an optically transparent pressure-sensitive adhesive composition, characterized in that the weight average molecular weight of 200,000 to 1 million.

In addition, the present invention

It 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

It provides a flat panel display device comprising the 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, photocurable (meth) acrylate copolymer; Rubber-based (meth)acrylic monomers; And as an optically transparent pressure-sensitive adhesive composition comprising a photopolymerization initiator,

The photocurable (meth)acrylate copolymer is 95 to 99.9% by weight of a hydroxy group-containing acrylic copolymer and 0.1 to 5% by weight of an isocyanato group-containing (meth)acrylate-based monomer based on the total weight of the constituent units contained in the copolymer. Including, wherein the hydroxy group-containing acrylic copolymer and the isocyanato group-containing (meth) acrylate-based monomer formed a urethane bond,

The hydroxy group-containing acrylic copolymer contains 50 to 98% by weight of a C1 to C12 straight or branched chain alkyl (meth)acrylate monomer and 2 to 50% by weight of a hydroxy group-containing polymerizable monomer based on the total weight of the monomers contained in the copolymer. And, it relates to an optically transparent pressure-sensitive adhesive composition, characterized in that the weight average molecular weight of 200,000 to 1 million.

The optically transparent pressure-sensitive adhesive composition of the present invention includes a polar photocurable acrylate copolymer and a low-Tg rubber-based (meth)acrylic monomer together to provide excellent folding properties, moist heat resistance, and adhesion, and photocurable acrylate copolymer It is characterized by providing an optically transparent pressure-sensitive adhesive composition having excellent heat resistance and durability by photo-crosslinking between and non-polar rubber-based (meth)acrylic monomers.

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

The photocurable (meth)acrylate copolymer is copolymerized with a C1 to C12 linear or branched alkyl (meth)acrylate monomer and a hydroxy group-containing polymerizable monomer, and a thermosetting functional group (hydroxy group) is introduced at the branched chain or terminal. At least a part of the thermosetting functional group (hydroxy group) of the main chain is converted into an isocyanato group by preparing a hydroxy group-containing acrylic copolymer main chain, and then reacting an isocyanato group-containing (meth)acrylate monomer with the main chain under appropriate conditions. It can be prepared by replacing it with a containing (meth)acrylate-based monomer.

The structure of the photocurable (meth)acrylate copolymer may be illustrated by the following Formula 1:

[Formula 1]

In the above formula

R1 is a C1-C12 linear or branched alkyl group,

R2 is a C1-C10 linear or branched alkylene group,

Each R3 is independently hydrogen or methyl,

o and p are each independently a natural number of 2-6,

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

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.

As the rubber-based (meth)acrylic monomer, for example, one or more selected from compounds represented by the following formulas 1 to 2 may be used:

[Formula 1]

[Formula 2]

In Formulas 1 to 2,

Each R1 is independently hydrogen or methyl

R2 is each independently a C ₂ ~ C ₆ linear or branched alkylene group,

R3 is a group derived from a diisocyanate compound, each independently with a -N(H)-C(O)- group bonded to both sides thereof,

Each R4 is independently a C ₂ to C ₁₂ linear or branched alkylene group,

The rubber-based polymer refers to a polymer containing a rubber monomer and having a weight average molecular weight of 5 to 10,000 consisting of only carbon and hydrogen.

Examples of the rubber monomer in the above include butadiene, isobutene, isoprene, and the like.

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

In the above, examples of the diisocyanate compound include Hexamethylene Diisocyanate (HDI), Isophorone Diisocyanate (IPDI), Toluene Diisocyanate (TDI), and Xylylene Diisocyanate (XDI), but are not limited thereto.

The compounds represented by Formulas 1 to 2 may be prepared, for example, by the following Scheme 1.

[Scheme 1]

The C1 to C12 straight or branched chain alkyl (meth)acrylate monomers contained in the form of polymerization in the hydroxy group-containing acrylic copolymer include C ₁ to C ₁₂ having a glass transition temperature (Tg) of -70 to -50°C. A straight or branched chain alkyl acrylate monomer may be preferably used, and more preferably a C ₄ to C ₁₂ straight or branched chain alkyl acrylate monomer having a glass transition temperature (Tg) of -70 to -50°C may be used. have.

Examples of C ₄ to C ₁₂ straight or branched chain alkyl acrylate monomers having a glass transition temperature (Tg) of -70 to -50°C include n-butyl acrylate, t-butyl acrylate, sec-butyl acrylate, Pentyl acrylate, 2-ethylbutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, isononyl acrylate, and the like, and these may be used alone or in combination of two or more. Can be used. Among these, n-butyl acrylate and 2-ethylhexyl acrylate can be preferably used.

In the above, when the glass transition temperature (Tg) of the straight-chain or branched-chain alkyl acrylate monomer of C ₁ ~ C ₁₂ is -70°C, it is difficult to use due to economic efficiency, and when it exceeds -50°C, the folding characteristics at low temperature A problem of deterioration occurs.

As the hydroxy group-containing polymerizable monomer contained in the form of polymerization in the hydroxy group-containing acrylic copolymer, a monomer containing a hydroxy group and having one or more ethylenically unsaturated bonds may be preferably used. Further, more preferably, a hydroxy group-containing acrylate-based monomer having a glass transition temperature (Tg) of -60 to -40°C may be used.

The glass transition temperature (Tg) is -60 ~ As the hydroxy group-containing acrylate-based monomer at -40°C, a hydroxy C ₄ ~C ₆ straight or branched chain alkyl acrylate monomer may be preferably used.

Examples of the hydroxy C ₄ ~C ₆ straight chain or branched chain alkyl acrylate monomers include 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate, 6-hydroxyhexyl acrylate, etc. It may be used alone or in combination of two or more. Among these, 4-hydroxybutyl acrylate can be preferably used.

In the above, a monomer having a glass transition temperature (Tg) of less than -60°C of the hydroxy group-containing acrylate monomer is difficult to exist, and when it exceeds -40°C, a problem of deteriorating the folding characteristics at low temperature may occur.

In the hydroxy group-containing acrylic copolymer, a C1 to C12 linear or branched chain alkyl (meth)acrylate monomer is included in an amount of 50 to 98% by weight, and a hydroxy group-containing polymerizable monomer may be included in an amount of 2 to 50% by weight.

More preferably, the C1-C12 linear or branched chain alkyl (meth)acrylate monomer may be included in an amount of 50 to 89% by weight, and a hydroxy group-containing polymerizable monomer may be included in an amount of 11 to 50% by weight.

If the hydroxy group-containing polymerizable monomer is contained in an amount of less than 11% by weight, the hydroxy group, which is a hydrophilic group, is insufficient in the pressure-sensitive adhesive, so that moisture cannot be held in the pressure-sensitive adhesive layer, and moisture is discharged to the interface. This may occur, and if it is contained in an amount exceeding 50% by weight, the pressure-sensitive adhesive absorbs an excessive amount of moisture, expands the volume, and lowers the cohesive force, which may cause interfacial peeling and air 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).

Isocyanato group-containing (meth)acrylate-based monomers included in the photocurable (meth)acrylate copolymer may include isocyanato (C1 ~ C10) linear or branched alkyl (meth)acrylate. . In the above (C1 ~ C10) linear or branched chain 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 isocyanato 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 isocyanato group-containing (meth)acrylate-based 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 reduced, and if it exceeds 5.0% by weight, the cohesive strength of the pressure-sensitive adhesive becomes too strong. Folding characteristics may deteriorate.

The polybutadiene/isoprene/isobutene (meth)acrylic monomer contained in the optically transparent pressure-sensitive adhesive composition of the present invention is 10 to 40 parts by weight, more preferably 15 parts by weight based on 100 parts by weight of the photocurable (meth)acrylate copolymer. It may be included in to 30 parts by weight. When the rubber-based (meth)acrylic monomer is included in an amount of less than 10 parts by weight, it is difficult to secure low-temperature folding characteristics, and when it is included in an amount exceeding 40 parts by weight, it is difficult to secure adhesive force, and heat resistance 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 solid content included in the optically transparent pressure-sensitive adhesive composition.

In the optically transparent pressure-sensitive adhesive composition of the present invention, the rubber-based (meth)acrylic monomer may be present in a blended state with a 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 a monomer having a low glass transition temperature and a rubber-based (meth)acrylic monomer to secure folding characteristics, while a curing system by radical polymerization and a curing system by a crosslinking agent and a thermosetting functional group (hydroxy group) are appropriate. Adopted together, it has the features of securing heat and humidity 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 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

It 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

It 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: Preparation of acrylic polymer (A1)

Nitrogen gas was refluxed, and 60 parts by weight of n-butyl acrylate (n-BA) and 40 parts by weight of 4-hydroxybutyl acrylate (4-HBA) were added to a 1L reactor equipped with a cooling device to facilitate temperature control. . 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, 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 450,000.

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

In Preparation Example 1, except that 89 parts by weight of n-butyl acrylate (n-BA) and 11 parts by weight of 4-hydroxybutyl acrylate (4-HBA) were used, the polymerization was carried out in the same manner as the weight average. An acrylic polymer (A2) having a molecular weight of 470,000 was prepared.

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

In Preparation Example 1, instead of 60 parts by weight of n-butyl acrylate (n-BA) and 40 parts by weight of 4-hydroxybutyl acrylate (4-HBA), 80 parts by weight of n-butyl acrylate (n-BA) and 2- Except that 20 parts by weight of hydroxyethyl acrylate (2-HEA) was used, the polymerization was carried out in the same manner to prepare an acrylic polymer (A3) having a weight average molecular weight of 450,000.

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

In Preparation Example 1, instead of 80 parts by weight of n-butyl acrylate (n-BA) and 20 parts by weight of 4-hydroxybutyl acrylate (4-HBA), 90 parts by weight of n-butyl acrylate (n-BA) and 4- Except for using 10 parts by weight of hydroxybutyl acrylate (4-HBA), the polymerization was carried out in the same manner as that to prepare an acrylic polymer (A4) having a weight average molecular weight of 390,000.

Manufacturing example 2-1: Photocurable ( Meta ) 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 for 4 hours or more at a temperature of 40 and atmospheric pressure to prepare a photocurable (meth)acrylate copolymer (B1).

Manufacturing example 2-2: Photocurable ( Meta ) 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 ( Meta ) 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 ( Meta ) 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 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 acrylate copolymer (B1) prepared in Preparation Example 2-1, 20 parts by weight of a rubber-based (meth)acrylic monomer represented by the following formula (3), a multifunctional crosslinking agent (Coronate L, made in Japan NPU) ) 0.07 parts by weight, photoinitiator (hydroxycyclohexylphenyl ketone, irgacure 184, Swiss Civas Specialty Chemical (manufactured)) 0.2 parts by weight and 3-glycidoxypropyltrimethoxyl silane (Shin-Etsu Corporation KBM-403) 0.2 parts The parts were mixed to prepare a pressure-sensitive adhesive composition.

[Chemical Formula 3]

In the above formula, n is 15-25.

As the compound of Formula 3, TE-2000 from "Nihon Soda" was used.

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

A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that a rubber-based (meth)acrylic monomer represented by Formula 4 was used instead of using the rubber-based (meth)acrylic monomer represented by Formula 3 in Example 1. .

[Formula 4]

In the above formula, n is 15-25.

As the compound of Formula 3, TEAI-1000 from "Japan Soda" was used.

Comparative example One: Preparation of optically transparent adhesive composition

Based on 100 parts by weight of the photocurable acrylate copolymer (B3) prepared in Preparation Example 2-3, 0.07 parts by weight of a multifunctional crosslinking agent (Coronate L, manufactured by NPU in Japan), a photopolymerization initiator (hydroxycyclohexylphenyl ketone, irgacure 184) , Swiss Chivas Specialty Chemical (manufactured) 0.2 parts by weight and 3-glycidoxypropyltrimethoxy silane (Shin-Etsu Corporation KBM-403) 0.2 parts by weight were mixed to prepare a pressure-sensitive adhesive composition.

Comparative Example 2: Preparation of optically transparent adhesive composition

Based on 100 parts by weight of the photocurable acrylate copolymer (B4) prepared in Preparation Example 2-4, 0.07 parts by weight of a multifunctional crosslinking agent (Coronate L, manufactured by NPU Japan), a photoinitiator (hydroxycyclohexylphenyl ketone, irgacure 184) , Swiss Chivas Specialty Chemical (manufactured) 0.2 parts by weight and 3-glycidoxypropyltrimethoxy silane (Shin-Etsu Corporation KBM-403) 0.2 parts by weight were mixed to prepare a pressure-sensitive adhesive composition.

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

Each of the optically transparent pressure-sensitive adhesive compositions prepared in Examples 1, 2, Comparative Example 1 and Comparative Example 2 was coated on a 50 μm-thick PET film coated with a silicone release agent so that the thickness after curing became 100 μm, and 100 And dried 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), and Comparative Example 3-1 (Comparative Example 1) The optically transparent adhesive films of the optically transparent adhesive composition) and the comparative example 3-2 (the optically transparent adhesive composition of comparative example 2 were used) were manufactured.

Example 4: Preparation of a laminate with an adhesive layer formed

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

Example 5: Preparation of hard coating film/adhesive layer/PET laminate for flexural evaluation

The laminates of Example 4-1, Example 4-2, Comparative Example 4-1, and Comparative Example 4-2 were cut to a size of 50 mm × 100 mm. 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 evaluating the flexibility prepared in Preparation Example 3 having a size of 50 mm × 100 mm, and an autoclave 50, 5 atm) for about 20 minutes, and cured for 24 hours under constant temperature and humidity conditions (23, 50% relative humidity), respectively, in Example 5-1, Example 5-2, Comparative Example 5-1 and Comparative Example A hard coating film/adhesive layer/PET (100 μm) laminate for evaluating the flexibility of 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)

The hard coating films/adhesive layers/PET laminates for evaluating the flexibility of Examples 5-1, 5-2, Comparative Example 5-1 and Comparative Example 5-2 prepared in Example 5 were used in the above evaluation method. Therefore, the folding characteristics were evaluated and 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

Example 5-1, Example 5-2, Comparative Example 5-1 and Comparative Example 5-2 prepared in Example 5, the hard coating film/adhesive layer/PET laminate for evaluation of flexural properties at a temperature of 80 for 1,000 hours After leaving for a while, the heat resistance was evaluated by observing whether bubbles or peeling occurred, 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

The hard coating film/adhesive layer/PET laminate prepared in Example 5-1, Example 5-2, Comparative Example 5-1, and Comparative Example 5-2 for flexural evaluation at a temperature of 60 and 90% After leaving for 1,000 hours under the condition of RH, it was observed whether bubbles or peeling occurred. 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

A specimen was prepared by cutting the adhesive-forming laminate prepared in Example 4-1, Example 4-2, Comparative Example 4-1, and Comparative Example 4-2 to have a size of 25 mm × 100 mm. 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, 5 atm), and storing it in a constant temperature and humidity condition (23, 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.

Hard coating film/adhesive layer/PET laminate for flexural evaluation Adhesive composition used Folding characteristics durability Moisture and heat resistance Heat resistance Example 5-1 Example 1 Preparation ○ ○ ○ Example 5-2 Example 2 Preparation ○ ○ ○ Comparative Example 5-1 Comparative Example 1 Preparation × ○ ○ Comparative Example 5-2 Comparative Example 2 Preparation × ○ ○

Adhesive-forming laminate Adhesive composition used Adhesion Example 4-1 Example 1 Preparation 14N Example 4-2 Example 2 Preparation 12N Comparative Example 4-1 Comparative Example 1 Preparation 23N Comparative Example 4-2 Comparative Example 2 Preparation 21N

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. In the case of adhesion, it was confirmed that it was insufficient than the comparative example because it contained a rubber-based (meth)acrylic monomer.

Claims (12)

Photocurable (meth)acrylate copolymer; Rubber-based (meth)acrylic monomers; And as an optically transparent pressure-sensitive adhesive composition comprising a photopolymerization initiator,
The photocurable (meth)acrylate copolymer is 95 to 99.9% by weight of an acrylic copolymer containing a hydroxyl group and 0.1 to 5% by weight of an isocyanato group-containing (meth)acrylate monomer based on the total weight of the constituent units contained in the copolymer. Including, wherein the hydroxy group-containing acrylic copolymer and the isocyanato group-containing (meth) acrylate-based monomer formed a urethane bond,
The hydroxy group-containing acrylic copolymer has a glass transition temperature (Tg) of -70 to -50 ℃ C1 to C12 linear or branched chain alkyl (meth) acrylate monomer 50 to 98 weight based on the total weight of the monomer contained in the copolymer % And 2 to 50% by weight of a hydroxy group-containing polymerizable monomer having a glass transition temperature (Tg) of -60 to -40 °C, and a weight average molecular weight of 200,000 to 1 million,
The rubber-based (meth)acrylic monomer is an optically transparent pressure-sensitive adhesive composition, characterized in that at least one selected from compounds represented by the following Formulas 1 to 2:
[Formula 1]

[Formula 2]

In Formulas 1 to 2,
Each R1 is independently hydrogen or methyl
R2 is each independently a C ₂ ~ C ₆ linear or branched alkylene group,
R3 is a group derived from a diisocyanate compound, each independently with a -N(H)-C(O)- group bonded to both sides thereof,
Each R4 is independently a C ₂ to C ₁₂ linear or branched alkylene group,
The rubber-based polymer refers to a polymer containing a rubber monomer and having a weight average molecular weight of 5 to 10,000 consisting of only carbon and hydrogen.
The method according to claim 1,
The hydroxy group-containing polymerizable monomer is a monomer containing a hydroxy group and having at least one ethylenically unsaturated bond. delete delete The method according to claim 1,
The optically transparent pressure-sensitive adhesive composition comprises 10 to 40 parts by weight of a rubber-based (meth)acrylic monomer and 0.1 to 5 parts by weight of a photopolymerization initiator based on 100 parts by weight of the photocurable acrylate copolymer. The method of 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 of 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 5 or 6,
The optically transparent pressure-sensitive adhesive composition further comprises 40 to 85 parts by weight of a solvent based on 100 parts by weight of solid content contained in the optically transparent pressure-sensitive adhesive composition. The method according to claim 1,
The isocyanato group-containing (meth)acrylate-based monomer is an isocyanato (C1 ~ C10) optically transparent pressure-sensitive adhesive composition, characterized in that the 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 11,
The flat panel display device, wherein the flat panel display device is a flexible display device.