KR102141159B1 - Optically Clear Adhesive Composition, and Optically Clear Adhesive Film comprising the Same, and Flat Panel Display - Google Patents

Abstract

The present invention A) a photocurable (meth) acrylate copolymer; B) acrylate copolymers; And C) a photopolymerization initiator composition, wherein A) the photocurable (meth)acrylate copolymer is 95 to 99.9% by weight of an acrylic copolymer containing hydroxy groups and isocyanate based on the total weight of the structural units included in the copolymer. The group-containing (meth)acrylate monomer contains 0.1 to 5% by weight, and the hydroxy group-containing acrylic copolymer and the isocyanate group-containing (meth)acrylate monomer form a urethane bond, and the hydroxy group-containing acrylic copolymer 80 to 98% by weight of a straight or branched chain alkyl acrylate monomer of C ₄ to C _{12 having} a glass transition temperature of -70 to -50°C relative to the total weight of the monomers contained in the copolymer, and hydroxy C ₂ to C ₆ straight chain or Branched chain alkyl acrylate monomer containing 2 to 20% by weight, a weight average molecular weight of 500,000 to 2 million is a photocurable (meth) acrylate copolymer, the acrylate copolymer of the B) is a monomer included in the copolymer Contains 80 to 95% by weight of C ₄ to C ₁₂ linear or branched chain alkyl acrylate monomers and 5 to 20% by weight of polymerizable monomers containing an adhesion promoter, and does not contain a photocrosslinkable functional group, and a weight average molecular weight relative to the total weight. This is a 100,000 to 100,000 acrylate copolymer, wherein the photocurable (meth)acrylate copolymer of A) and the acrylate copolymer of B) are included in a weight ratio of 95:5 to 70:30, Provided is an optically transparent adhesive composition, an optically transparent adhesive film comprising the same, and a flat panel display device.

Description

An optically clear adhesive composition, and an optically clear adhesive film comprising the same, and a flat panel display

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

The 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 enhancing film, and the like are used. When these optical films are laminated to each other or when the optical film is attached to a display panel, an optically clear adhesive (OCA) is used. Therefore, the optical transparent adhesive (OCA) should basically have excellent moisture resistance, heat resistance, and adhesion with optical properties.

In particular, recently, flexible display devices have been developed competitively. Since the flexible display device itself is bent, rolled, or folded, the display panel and optical films included in the device are also subjected to bending stress. Therefore, the optical transparent adhesive (OCA) used in the flexible display requires more enhanced and diversified physical properties.

For example, an optically transparent 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, folding characteristics at a low temperature should be excellent.

In addition, the optical transparent pressure-sensitive adhesive (OCA) used in the flexible display device is required to further strengthen the heat and moisture resistance. This is because the flexible display device repeats the process of folding and unfolding numerous times during use, so that the possibility of moisture penetration through the folded and unfolded part increases as much.

In addition, the flexible display device is bent (bending), (rolling), folding (folding), the display panel and the optical films included in the device are also subjected to bending stress. Therefore, since it is easy to separate between the laminated display panel and the optical films, better adhesion is required, and more excellent durability is also required.

However, optical transparent adhesives (OCAs) known to date have not sufficiently provided the above-described physical properties required by the 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 to provide an optically transparent adhesive (OCA) composition capable of satisfactorily satisfying the folding properties, moisture 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 including the optically transparent adhesive (OCA) composition.

The present invention,

A) photocurable (meth)acrylate copolymer; B) acrylate copolymers; And C) an optically transparent adhesive composition comprising a photopolymerization initiator,

The A) photocurable (meth)acrylate copolymer is 95 to 99.9% by weight of an acrylic copolymer containing a hydroxy group and 0.1 to 5% by weight of an (meth)acrylate monomer containing an isocyanate group based on the total weight of the constituent units included in the copolymer. It includes, the hydroxy group-containing acrylic copolymer and the isocyanate group-containing (meth) acrylate-based monomer is to form a urethane bond,

The hydroxy group-containing acrylic copolymer is 80 to 98% by weight of a linear or branched chain alkyl acrylate monomer of C ₄ to C _{12 having} a glass transition temperature of -70 to -50°C relative to the total weight of the monomers contained in the copolymer, and hydroxy C ₂ ~ C _{6 It} is a photo-curable (meth)acrylate copolymer containing 2 to 20% by weight of a straight chain or branched chain alkyl acrylate monomer, and having a weight average molecular weight of 500,000 to 2 million,

The acrylate copolymer of B) is a polymerizable monomer containing 80 to 95% by weight of a straight or branched chain alkyl acrylate monomer of C ₄ to C ₁₂ and an adhesion promoter based on the total weight of the monomers contained in the copolymer 5 It contains ~20% by weight, does not contain a photocrosslinkable functional group, is an acrylate copolymer having a weight average molecular weight of 10,000 to 100,000,

The photocurable (meth)acrylate copolymer of A) and the acrylate copolymer of B) are included in a weight ratio of 95:5 to 70:30 to provide an optically transparent adhesive composition.

In addition, the present invention,

It provides an optical transparent pressure-sensitive adhesive film characterized in that it is prepared by coating the optical transparent pressure-sensitive adhesive composition of the present invention on a transfer film.

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.

The optically transparent adhesive (OCA) composition and optically transparent adhesive film of the present invention provide sufficient folding properties, moisture heat resistance, heat resistance, and adhesion to be used in a flexible display device as well as a flat panel display device, thereby providing excellent durability. to provide.

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

The present invention, A) photocurable (meth) acrylate copolymer; B) acrylate copolymers; And C) an optically transparent adhesive composition comprising a photopolymerization initiator,

The A) photocurable (meth)acrylate copolymer is 95 to 99.9% by weight of an acrylic copolymer containing a hydroxy group and 0.1 to 5% by weight of an (meth)acrylate monomer containing an isocyanate group based on the total weight of the constituent units included in the copolymer. It includes, the hydroxy group-containing acrylic copolymer and the isocyanate group-containing (meth) acrylate-based monomer is to form a urethane bond,

The hydroxy group-containing acrylic copolymer is 80 to 98% by weight of a linear or branched chain alkyl acrylate monomer of C ₄ to C _{12 having} a glass transition temperature of -70 to -50°C relative to the total weight of the monomers contained in the copolymer, and hydroxy C ₂ ~ C _{6 It} is a photo-curable (meth)acrylate copolymer containing 2 to 20% by weight of a straight chain or branched chain alkyl acrylate monomer, and having a weight average molecular weight of 500,000 to 2 million,

The acrylate copolymer of B) is 80 to 95% by weight of a straight or branched chain alkyl acrylate monomer of C4 to C12 and 5 to 20 of a polymerizable monomer containing an adhesion promoter, based on the total weight of the monomers contained in the copolymer. It contains a weight%, does not contain a photocrosslinkable functional group, is an acrylate copolymer having a weight average molecular weight of 10,000 to 100,000,

The photocurable (meth)acrylate copolymer of A) and the acrylate copolymer of B) are included in a weight ratio of 95:5 to 70:30 to provide an optically transparent adhesive composition.

A scene of A) from the optical transparent pressure-sensitive adhesive composition of the present invention, chemical conversion (meth) acrylate copolymer is foldable, including straight or branched chain alkyl acrylate monomers of C ₄ ~ C ₁₂ with a glass transition temperature of -70 ~ -50 ℃ It has excellent properties, high molecular weight, high crosslinking density through radical crosslinking between linked acrylic functional groups by urethane bonds, resulting in excellent heat resistance and durability, and adding hydroxy C ₂ to C ₆ linear or branched alkyl acrylate monomers. Including a large amount, it becomes excellent in moisture heat resistance and adhesion.

In addition, in the optically transparent pressure-sensitive adhesive composition of the present invention, the acrylate copolymer of B) has a low molecular weight and does not contain a photocrosslinkable functional group, and thus does not form crosslinking even after a photocrosslinking reaction, resulting in excellent folding properties, but low molecular weight acrylate When a large amount of a copolymer is included, a low-molecular-weight acrylate copolymer is bleed-out at the interface after formation of the adhesive layer, thereby improving durability and improving adhesion, resulting in a high polarity adhesion promoter. ) By containing a large amount of the containing polymerizable monomer, it becomes excellent in heat resistance and adhesion.

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

The photocurable (meth)acrylate copolymer of A) is 80 to 98 parts by weight of C ₄ to C ₁₂ linear or branched chain alkyl (meth)acrylate monomers having a glass transition temperature of -70 to -50°C and hydroxy. By copolymerizing 2 to 20 parts by weight of a hydroxy C ₂ to C ₆ straight chain or branched chain alkyl acrylate monomer, an acrylate copolymer main chain in which a thermosetting functional group (hydroxy group) is introduced into a branched chain or a terminal is prepared, followed by containing an isocyanate group ( It can be produced by replacing at least a part of the thermosetting functional group (hydroxy group) of the main chain with an isocyanate group-containing (meth)acrylate-based monomer by reacting the metha)acrylate monomer with the main chain under appropriate conditions.

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

Examples of the straight or branched chain alkyl (meth)acrylate monomer of C ₄ to C ₁₂ having a glass transition temperature of -70 to -50°C included in the polymerized form of the photocurable (meth)acrylate copolymer of A) n-butyl acrylate, t-butyl acrylate, sec-butyl acrylate, pentyl acrylate, 2-ethylbutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, isononyl acrylic Rate, etc., these may be used alone or in combination of two or more, and one or more monomers selected from n-butyl acrylate and 2-ethylhexyl acrylate may be preferably used.

When the glass transition temperature (Tg) of the C ₄ ~ C ₁₂ straight-chain or branched-chain alkyl acrylate monomer is less than -70°C, it is difficult to use for economic reasons, and when it exceeds -50°C, folding properties at low temperature A problem that deteriorates occurs.

Examples of the hydroxy C ₂ ~C ₆ straight chain or branched chain alkyl acrylate monomer contained in the polymerized form of the photocurable (meth)acrylate copolymer of A) are 2-hydroxyethyl acrylate, 3-hydroxy Propyl acrylate, 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate and 6-hydroxyhexyl acrylate, and the like. These may be used alone or in combination of two or more. The hydroxy C ₂ to C ₆ straight chain or branched chain alkyl acrylate monomers included in polymerized form in the photocurable (meth)acrylate copolymer of A) are preferably 2-hydroxybutylacrylate and 4-hydroxy It may be one or more monomers selected from hydroxybutyl acrylate.

The structure of the photocurable (meth)acrylate copolymer can be exemplified by Formula A:

[Formula A]

In the above formula

R ₁ is a C ₄ ~ C ₁₂ straight or branched chain alkyl group,

R ₂ is a C ₁ ~ C ₁₀ linear or branched alkylene group,

R ₃ is hydrogen or methyl,

O is a natural number from 2 to 6,

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

In the above hydroxyl group-containing acrylic copolymer, straight or branched chain alkyl acrylate monomers of C ₄ ~ C ₁₂ The glass transition temperature (Tg) of -70 ~ -50 ℃ is contained 80 to 98% by weight, hydroxy-C It is preferable that ₂ to C ₆ straight chain or branched chain alkyl acrylate monomers are included in 2 to 20% by weight. In the case where the hydroxy C ₂ ~C ₆ straight chain or branched chain alkyl acrylate monomer is contained in less than 2 parts by weight, the pressure-sensitive adhesive layer lacks hydroxy groups due to lack of hydrophilic groups due to the lack of hydrophilic groups, and moisture is discharged to the interface and moisture is released. Under the conditions of thermal conditions, (adhesiveness) decreases and interfacial peeling defects occur, and when it is included in excess of 20 parts by weight, the adhesive absorbs excess moisture to expand the volume and cohesion decreases, resulting in interfacial peeling and bubbles. do.

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

When the other copolymerizable monomer is included, it is preferable to adjust the content to 20 parts by weight or less based on 100 parts by weight of the monomers described above in consideration of flexibility or peeling force.

In the photocurable (meth)acrylate copolymer of A), the weight average molecular weight means the converted value for standard polystyrene measured by GPC (Gel permeation chromatograph).

As the isocyanate group-containing (meth)acrylate-based monomer, isocyanato C ₁ to C ₁₀ straight chain or branched chain alkyl (meth)acrylate may be used. In the above, 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, among which ethyl, propyl And the like can be preferably used.

For example, the isocyanate group-containing (meth)acrylate-based monomer may be a compound of Formula B below.

<Formula B>

In Chemical Formula A, R is -H or -CH ₃ and is an integer of n=1 to 10.

The isocyanate group-containing (meth)acrylate-based monomer in Formula 1, R is -CH ₃ , n=2 is an integer compound, that is, 2-isocyanatoethyl methacrylate (2-Isocyanatoethyl methacrylate) have.

The isocyanate group-containing (meth)acrylate-based monomer may be included in 0.1 parts by weight to 5.0% by weight based on the total weight of the constituent units included in the photocurable (meth)acrylate copolymer. When the isocyanate 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 lowered, and when it exceeds 5.0% by weight, the cohesive strength of the pressure-sensitive adhesive becomes too strong, so folding characteristics This can degrade.

The adhesion promoter-containing polymerizable monomer is a polar group-containing or reactive functional group-containing polymerizable monomer.

The adhesion-promoting agent (adhesion promotor)-containing polymerizable monomer is a compound of Formula 1; Compound of formula 2; Compound of formula 3; Chemical Formula 4; Compound of formula 5; Compound of formula 6; Compounds of formula 7; And it may be one or more selected from the group consisting of compounds of formula (8).

<Formula 1>

<Formula 2>

<Formula 3>

<Formula 4>

<Formula 5>

<Formula 6>

<Formula 7>

<Formula 8>

In the formula (7), X is a conjugate base of a strong acid having pKa <-3, and X is, for example, PF5, SbF6, mesylate (OMs), tosylate (OTs), triflate (OTf), Bis(fluorosulfonyl)imide (FSI), and bis(trifluoromethylsulfonyl)imide (TFSI).

Examples of C ₄ to C ₁₂ linear or branched chain alkyl (meth)acrylate monomers included in the polymerized form of the acrylate copolymer of B) are n-butyl acrylate, t-butyl (meth)acrylate, sec -Butyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, 2-ethylhexylacrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, iso Nonyl (meth)acrylate, and the like, and these may be used alone or in combination of two or more, and one or more monomers selected from n-butylacrylate and 2-ethylhexylacrylate are preferably used. Can.

In the acrylate copolymer of B), C ₄ to C ₁₂ linear or branched chain alkyl acrylate monomers are included in an amount of 80 to 95% by weight, and polymerizable monomers containing an adhesion promoter (5 to 20% by weight) It is preferred to include. When the polymerizable monomer containing an adhesion promoter (adhesion promotor) is included in an amount of less than 5% by weight, the low molecular weight acrylate copolymer migrates at the interface and bleeds out, thereby improving durability and improving adhesion. It is difficult to do the following, and if it exceeds 20% by weight, there is a fear that the flexibility of the adhesive layer is insufficient and the folding characteristics are deteriorated.

If the weight average molecular weight of the acrylate copolymer of B) is less than 10,000, there is a fear that the bleedout is severe and durability may be deteriorated, and if it exceeds 100,000, there may be a problem that the adhesion improving effect may be insufficient due to less bleedout. have.

In the optically transparent adhesive composition, it is preferable that the photocurable (meth)acrylate copolymer of A) and the acrylate copolymer of B) are contained in a weight ratio of 95:5 to 70:30. When the total content of the photocurable (meth)acrylate copolymer of A) and the acrylate copolymer of B) is less than 5 parts by weight based on 100 parts by weight, the effect of improving adhesion may be insufficient, When the total content of the photocurable (meth)acrylate copolymer of A) and the acrylate copolymer of B) is based on 100 parts by weight, the foldability of the fold decreases when the acrylate copolymer of B) exceeds 30 parts by weight Problems may arise.

The optically transparent pressure-sensitive adhesive composition of the present invention includes a photopolymerization initiator C) to efficiently induce a reaction of a radically polymerizable group. The C) photopolymerization initiator may be used in polymerization of a hydroxy group-containing acrylic copolymer, and finally, an optically transparent adhesive composition is also included in the photocurable (meth)acrylate copolymer.

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

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

The C) photopolymerization initiator is 0.1 to 5 parts by weight, more preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the total content of the photocurable (meth)acrylate copolymer of A) and the acrylate copolymer of B). Can be included.

The optically transparent adhesive composition of the present invention may further include a multifunctional crosslinking agent. The multifunctional crosslinking agent is not particularly limited, and those known in the art can be used. Specifically, a thermosetting polyfunctional isocyanate crosslinking agent, a polyfunctional (meth)acrylate crosslinking agent, etc. are mentioned.

The multifunctional crosslinking agent may further include 0.02 to 5 parts by weight based on 100 parts by weight of the total content of the photocurable (meth)acrylate copolymer of A) and the acrylate copolymer of B).

The optically transparent 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 adhesive manufacturing field can be used. For example, gamma-glycidoxypropyl triethoxy silane, gamma-glycidoxypropyl trimethoxy silane, gamma-glycidoxypropyl methyldiethoxy silane, gamma-glycidoxypropyl triethoxy as silane coupling agent Silane, 3-mercaptopropyl trimethoxy silane, vinyltrimethoxysilane, vinyltriethoxy silane, gamma-methacryloxypropyl trimethoxy silane, gamma-methacryloxypropyl triethoxy silane, gamma-aminopropyl And trimethoxy silane, gamma-aminopropyl triethoxy silane or 3-isocyanatopropyl triethoxy silane.

The silane coupling agent is an initiator of the total content of the photocurable (meth) acrylate copolymer of A) and the acrylate copolymer of B) 0.01 parts by weight to 5 parts by weight based on 100 parts by weight, preferably 0.01 parts by weight To 1 part by weight.

The optically transparent pressure-sensitive adhesive composition of the present invention may further include a tackifier to control adhesion performance.

In addition, it may further include one or more additives selected from the group consisting of epoxy resins, curing agents, ultraviolet stabilizers, antioxidants, colorants, reinforcing agents, fillers, antifoaming agents, surfactants and plasticizers.

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

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

The solvent may include 40 to 85 parts by weight based on 100 parts by weight of the total content of the photocurable (meth)acrylate copolymer of A) and the acrylate copolymer of B).

The viscosity of the optically transparent pressure-sensitive adhesive composition of the present invention may be preferably used in a range of 500 cP to 2,500 Cp at 23°C.

The method for preparing the optically 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 and catalysts used in this field may also be used without limitation.

The method for applying the optically transparent adhesive composition of the present invention is not particularly limited, for example, bar coating, spin coating, comma coating, or gravure coating. It can be done in a general purpose 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 not to proceed. Through this, the crosslinking agent can form a crosslinked structure in the curing and aging process after the coating operation, thereby improving the cohesive force, adhesive properties and cuttability of the adhesive.

In addition, the coating process is preferably performed after sufficiently removing the bubble-causing components such as volatile components or reaction residues inside the pressure-sensitive adhesive composition. Accordingly, the crosslinking density or molecular weight of the pressure-sensitive adhesive is too low, so the elastic modulus is lowered, and bubbles present between the glass plate and the pressure-sensitive adhesive layer in a high temperature state become large, thereby preventing the phenomenon of forming a scattering body therein.

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

In addition, an appropriate aging process that induces a reaction between the functional group of the crosslinking agent in the composition and the thermosetting functional group of the polymer may be performed before or after the light irradiation process, and 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, for example, polarizing film, retardation film, anti-glare film, a wide viewing angle compensation film or an optical film such as a brightness enhancing film, or laminated to each other, or display the optical film or a laminate thereof It may 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 optical transparent pressure-sensitive adhesive film characterized in that it is prepared by coating the optical transparent pressure-sensitive adhesive composition on a transfer film.

As the transfer film used for the optically transparent adhesive film, a film known in this field can be used without limitation. In addition, the method of manufacturing the optically transparent adhesive film can be used without limitation a 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, the flat panel display device is more preferably 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. Acrylate Preparation of copolymer (A1)

Nitrogen gas was refluxed, and 80 parts by weight of n-butyl acrylate (n-BA) and 20 parts by weight of 4-hydroxybutyl acrylate (4-HBA) were added to a 1 L 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° C., 0.5 parts by weight of a reaction initiator AIBN (azobisisobutyronitrile) was added, and reacted for 12 hours to prepare an acrylate polymer (A1) having a weight average molecular weight of 1.2 million.

Manufacturing example 1-2. Acrylate Preparation of copolymer (A2)

In Production Example 1, a weight average was performed by performing a polymerization reaction in the same manner, except that 90 parts by weight of n-butyl acrylate (n-BA) and 10 parts by weight of 4-hydroxybutyl acrylate (4-HBA) were used. An acrylate polymer (A2) having a molecular weight of 128 million was prepared.

Manufacturing example 1-3. Acrylate Preparation of copolymer (A3)

In Production Example 1, except that 98 parts by weight of n-butyl acrylate (n-BA) and 2 parts by weight of 4-hydroxybutyl acrylate (4-HBA) were used, the polymerization reaction was carried out in the same manner as the weight average. An acrylate polymer (A3) having a molecular weight of 1.39 million was prepared.

Manufacturing example 1-4. Acrylate Preparation of copolymer (A4)

In Preparation Example 1, except that 99.5 parts by weight of n-butyl acrylate (n-BA) and 0.5 parts by weight of 2-hydroxyethyl acrylate (2-HBA) were used, the polymerization reaction was carried out in the same manner as the weight average. An acrylate polymer (A4) having a molecular weight of 1.45 million was prepared.

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

Nitrogen gas is refluxed, and in a 1L reactor equipped with a cooling device to facilitate temperature control, 100 parts by weight of acrylate copolymer (A1) solids and 2-isocyanatoethyl methacrylate 1 0.1 parts by weight of DBTDL (dibutyl tindilaulate) was added. Subsequently, the mixture was reacted at a temperature of 40° C. and normal pressure for 4 hours or more 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 Production Example 2-1, except that the acrylate copolymer (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 Production Example 2-1, except that the acrylate copolymer (A3) was used.

Manufacturing example 2-4: Photocurable ( Meta ) Acrylate Preparation of copolymer (B4)

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 acrylate copolymer (A4) solid content and 2-isocyanatoethyl methacrylate 0.1 0.1 parts by weight of DBTDL (dibutyl tindilaulate) was added. Subsequently, the mixture was reacted at a temperature of 40° C. and normal pressure for 4 hours or more to prepare a photocurable (meth)acrylate copolymer (B4).

Manufacturing example 3-1. Acrylate Preparation of copolymer (C1)

Nitrogen gas was refluxed, and 90.9 parts by weight of n-butyl acrylate (n-BA) and 9.1 parts by weight of the monomer of Formula 2 were added to a 1 L 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° C., 0.5 parts by weight of a reaction initiator AIBN (azobisisobutyronitrile) was added, and reacted for 12 hours to prepare an acrylate polymer (C1) having a weight average molecular weight of 50,000.

<Formula 2>

Manufacturing example 3-2. Acrylate Preparation of copolymer (C2)

An acrylate polymer (C2) having a weight average molecular weight of 6.9 million was prepared in the same manner as in Production Example 3-1, except that the monomer of Formula 3 was used instead of the monomer of Formula 2.

<Formula 3>

Manufacturing example 3-3. Acrylate Preparation of copolymer (C3)

An acrylate polymer (C3) having a weight average molecular weight of 5.1 million was prepared in the same manner as in Preparation Example 3-1, except that the monomer of Formula 4 was used instead of the monomer of Formula 2.

<Formula 4>

Manufacturing example 3-4. Acrylate Preparation of copolymer (C4)

An acrylate polymer (C4) having a weight average molecular weight of 5.1 million was prepared in the same manner as in Preparation Example 3-1, except that the monomer of Formula 6 was used instead of the monomer of Formula 2.

<Formula 6>

Manufacturing example 3-5. Acrylate Preparation of copolymer (C5)

An acrylate polymer (C5) having a weight average molecular weight of 780,000 was prepared in the same manner as in Preparation Example 3-1, except that the monomer of Formula 6 was used instead of the monomer of Formula 2.

<Formula 7>

, 여기서 X는 = 트리플레이트(Triflate; OTf)임.

, Where X = triflate (OTf).

Manufacturing example 4: Flexibility For evaluation Hard coating Film production

<Epoxy siloxane resin production>

3-glycidoxypropyltrimethoxysilane (GPTS, Gelest Co.) 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. Then, 0.05 mL of ammonia was added to the mixture as a catalyst and stirred at 60° C. for 6 hours to prepare a ceylon acid sol.

<Preparation of hard coating composition>

The cilanic acid 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 respect to 100 parts by weight of the mixture to prepare a hard coating composition. It was prepared.

<Hard coating film production>

The hard coating composition was coated with a thickness of 50 μm on a 40 μm thick COP (cycloolefin polymer, ZF-16, Zeon) film surface-treated with corona. The film was exposed to a mercury UV (Ultra Violet) lamp (20 mW/cm ² ) for 5 minutes to initiate the triarylsulfonium hexafluoroantimonate salt to generate an acid, 50° C. and 50% of A heat treatment was performed for 60 minutes under a relative humidity condition to form a hard coating film.

Example 1: Preparation of optically transparent adhesive composition

80 parts by weight of the photocurable (meth)acrylate copolymer (B1) prepared in Preparation Example 2-1 and 20 parts by weight of (meth)acrylate copolymer (C1) prepared in Preparation Example 3-1, that is, Based on 100 parts by weight of the total content of the photocurable (meth)acrylate copolymer (B1) and acrylate copolymer (C1), 0.5 parts by weight of a polyfunctional isocyanate crosslinking agent (Coronate L, manufactured by NPU, Japan), photopolymerization initiator (hydroxycyclo Hexylphenyl ketone, irgacure 184, Swiss Chivas Specialty Chemical (manufactured) 0.2 parts by weight of the pressure-sensitive adhesive composition was prepared.

Example 2: Preparation of optically transparent adhesive composition

Except that 70 parts by weight of the photocurable (meth)acrylate copolymer (B2) prepared in Preparation Example 2-1 and 30 parts by weight of (meth)acrylate copolymer (C2) prepared in Preparation Example 3-2 were used. And the pressure-sensitive adhesive composition was prepared in the same manner as in Example 1.

Example 3: Preparation of optically transparent adhesive composition

Except that 75 parts by weight of the photocurable (meth)acrylate copolymer (B2) prepared in Preparation Example 2-1 and 25 parts by weight of (meth)acrylate copolymer (C3) prepared in Preparation Example 3-3 were used. And the pressure-sensitive adhesive composition was prepared in the same manner as in Example 1.

Example 4: Preparation of optically transparent adhesive composition

Except that 85 parts by weight of the photocurable (meth)acrylate copolymer (B2) prepared in Preparation Example 2-1 and 15 parts by weight of (meth)acrylate copolymer (C4) prepared in Preparation Example 3-3 were used. And the pressure-sensitive adhesive composition was prepared in the same manner as in Example 1.

Example 5: Preparation of optically transparent adhesive composition

Except that 95 parts by weight of the photocurable (meth)acrylate copolymer (B2) prepared in Preparation Example 2-1 and 5 parts by weight of (meth)acrylate copolymer (C5) prepared in Preparation Example 3-3 were used. And the pressure-sensitive adhesive composition was prepared in the same manner as in Example 1.

Comparative example One: Preparation of optically transparent adhesive composition

With respect to 100 parts by weight of the photocurable (meth)acrylate copolymer (B4) prepared in Preparation Example 2-4, 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 Chivas Specialty Chemical (product).

Comparative example 2. Preparation of optically transparent adhesive composition

An adhesive composition was prepared by mixing 0.5 parts by weight of a polyfunctional isocyanate crosslinking agent (Coronate L, manufactured by NPU, Japan) based on parts by weight of the acrylate copolymer (C1) prepared in 3-1.]

Example 6: Preparation of optically transparent adhesive film

Each of the optical transparent pressure-sensitive adhesive compositions prepared in Examples 1 to 5 and Comparative Examples 1 to 2 was coated on a 50 μm thick PET film coated with a silicone release agent so that the thickness after curing was 100 μm, and 5 minutes at 100° C. Drying for Example 6-1 (using the optically transparent adhesive composition of Example 1), Example 6-2 (using the optically transparent adhesive composition of Example 2), and Example 6-3 (the optically transparent adhesive of Example 3) Composition use), Example 6-4 (using the optically transparent adhesive composition of Example 5), Example 6-5 (using the optically transparent adhesive composition of Example 5), Comparative Example 3-1 (optical transparency of Comparative Example 1) Using the pressure-sensitive adhesive composition) and the optical transparent pressure-sensitive adhesive film of Comparative Example 3-2 (using the optically transparent pressure-sensitive adhesive composition of Comparative Example 2) was prepared.

Example 7: Adhesive layer Formed Laminate Produce

The optical transparent pressure-sensitive adhesive film prepared in Example 6-1, Example 6-2, Example 6-3, Example 6-4, Example 6-5, Comparative Example 3-1, and Comparative Example 3-2 Using a laminate of a pressure-sensitive adhesive layer on a PET film (100um PET manufactured by Mitsubishi Corporation) having a thickness of 100 µm, and irradiated with a UV lamp (Fusion) in the direction of the release film, irradiated with a light amount of 1000 mJ/cm ² , respectively, Example 7-1. , Example 7-2, Example 7-3, Example 7-4, Example 7-5, Comparative Example 4-1, and a laminate having the pressure-sensitive adhesive layer of Comparative Example 4-2 was prepared.

Example 8: Flexibility For evaluation Hard coating film/ Adhesive layer /PET Laminate Produce

The laminate of Example 7-1, Example 7-2, Example 7-3, Example 7-4, Example 7-5, Comparative Example 4-1, and Comparative Example 4-2 was 50 mm × It was cut to a size of 100 mm. Subsequently, the release PET film attached to the pressure-sensitive adhesive layer of the cut laminate was peeled off, and adhered onto a hard coating film for evaluation of flexibility, prepared in Preparation Example 3 having a size of 50 mm×100 mm, and autoclave (50° C. , 5 atmospheres) for about 20 minutes, and cured for 24 hours in constant temperature and humidity conditions (23°C, 50% relative humidity) for Example 8-1, Example 8-2, Example 8-3, A hard coating film/adhesive layer/PET (100 µm) laminate for evaluation of flexibility of Examples 8-4, 8-5, Comparative 5-1, and 5-5 was prepared.

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

One. Folding characteristics evaluation

<Evaluation method>

Evaluation standard: 　IEC 62715

Evaluation equipment: planar no-load U-shaped folding tester (DLDMLH-FS)

Equipment maker: YUASA SYSTEM (Japan)

Evaluation conditions: -20°C / 10,000 times (bending the hard coating side to be folded inward)

Example 8-1, Example 8-2, Example 8-3, Example 8-4, Example 8-5, Comparative Example 5-1, and Comparative Example 5-2 prepared in Example 8 above The folding properties of the hard coating film/adhesive layer/PET laminate for evaluating flexibility were evaluated according to the above evaluation method, and are shown in Table 1 below.

<Evaluation criteria>

○: Poor modes such as bubbles, peeling, and cracks were not observed in the laminate.

(Triangle|delta): Fine defect mode was visually visually recognized in the laminated body.

X: The defective mode obviously visually observed in the folding portion of the laminate.

2. Durability evaluation

(1) Heat resistance evaluation

Example 8-1, Example 8-2, Example 8-3, Example 8-4, Example 8-5, Comparative Example 5-1, and Comparative Example 5-2 prepared in Example 8 above After the hard coating film/adhesive layer/PET laminate for evaluating flexibility was left at a temperature of 80° C. for 1,000 hours, the presence or absence of bubbles or peeling was observed to evaluate the heat resistance and the results are shown in Table 1 below.

<Evaluation criteria>

◎: No bubbles or peeling

○: bubbles or peeling <5

△: 5 ≤ bubble or peeling <10

×: 10 ≤ bubbles or peeling

(2) Moisture resistance evaluation

Example 8-1, Example 8-2, Example 8-3, Example 8-4, Example 8-5, Comparative Example 5-1, and Comparative Example 5-2 prepared in Example 8 above After the hard coating film/adhesive layer/PET laminate for evaluating flexibility was left for 1,000 hours under a temperature of 60° C. and 90% RH, it was observed whether bubbles or peeling occurred. At this time, immediately after evaluating the state of the specimen, it was left standing at room temperature for 24 hours, and then observed and evaluated for heat and moisture resistance, and the results are shown in Table 1 below.

<Evaluation criteria>

◎: No bubbles or peeling

○: bubbles or peeling <5

△: 5 ≤ bubble or peeling <10

×: 10 ≤ bubbles or peeling

3. Evaluation of adhesion

Example 7-1, Example 7-2, Example 7-3, Example 7-4, Example 7-5, Comparative Example 4-1, and Comparative Example 4-2 prepared in Example 7 above Example 5-1, Example 5-2, Example 5-3, Comparative Example 5-1, and the laminate prepared with the pressure-sensitive adhesive layer prepared in Comparative Example 5-2 is cut to a size of 25 mm × 100 mm to cut the specimen It was prepared. Subsequently, the release PET film attached to the pressure-sensitive adhesive layer was peeled off, and a laminate formed with the pressure-sensitive adhesive layer was adhered to an alkali-free glass using a 2 kg roller according to the provisions of JIS Z 0237. The alkali-free glass to which the laminating agent was attached was compressed in an autoclave (50° C., 5 atmospheres) for about 20 minutes, and stored at constant temperature and humidity conditions (23° C., 50% relative humidity) for 24 hours to prepare a sample. Then, using the TA equipment (Texture Analyzer, manufactured by Stable Micro Systems, UK), the adhesive was measured while peeling the laminate from the alkali-free glass at a peeling speed of 300 mm/min and a peeling angle of 180 degrees, and the results are displayed. It is shown in 2.

[Table 1]

[Table 2]

As can be seen from the test results of Table 1 and Table 2, it was confirmed that the optical transparent pressure-sensitive adhesive compositions of the Examples of the present invention have excellent folding characteristics, heat resistance to moisture, heat resistance and adhesion. In particular, it was confirmed that the folding properties were remarkably excellent compared to the optically transparent adhesive compositions of the comparative example.

Claims (13)

A) photocurable (meth)acrylate copolymer; B) acrylate copolymers; And C) an optically transparent adhesive composition comprising a photopolymerization initiator,
The A) photocurable (meth)acrylate copolymer is 95 to 99.9% by weight of an acrylic copolymer containing a hydroxy group and 0.1 to 5% by weight of an (meth)acrylate monomer containing an isocyanate group based on the total weight of the constituent units included in the copolymer. It includes, the hydroxy group-containing acrylic copolymer and an isocyanate group-containing (meth) acrylate-based monomer is to form a urethane bond,
The hydroxy group-containing acrylic copolymer is 80 to 98% by weight of a linear or branched chain alkyl acrylate monomer of C ₄ to C _{12 having} a glass transition temperature of -70 to -50°C relative to the total weight of the monomers contained in the copolymer, and hydroxy C ₂ ~ C _{6 It} is a photo-curable (meth)acrylate copolymer containing 2 to 20% by weight of a straight chain or branched chain alkyl acrylate monomer, and having a weight average molecular weight of 500,000 to 2 million,
Straight or branched chain alkyl acrylate monomers of the glass transition of C ₄ ~ C ₁₂ temperature is -70 ~ -50 ℃ is n- butyl acrylate, t- butyl acrylate, sec- butyl acrylate, pentyl acrylate, 2 -Ethylbutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate and isononyl acrylate is at least one monomer selected from the group consisting of,
The acrylate copolymer of B) is 80 to 95% by weight of a straight or branched chain alkyl acrylate monomer of C ₄ to C ₁₂ and 5 to 20% by weight of a polymerizable monomer containing an adhesion promoter relative to the total weight of the monomers contained in the copolymer. It does not contain a photocrosslinkable functional group, and is an acrylate copolymer having a weight average molecular weight of 10,000 to 100,000,
The photocurable (meth)acrylate copolymer of A) and the acrylate copolymer of B) are included in a weight ratio of 95:5 to 70:30, optically transparent adhesive composition. The method according to claim 1,
The hydroxy C ₂ ~ C ₆ straight chain or branched chain alkyl acrylate monomer used to prepare the photocurable (meth)acrylate copolymer of A) is 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate , 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate and 6-hydroxyhexyl acrylate is one or more monomers selected from the group consisting of optically transparent adhesive composition. The method according to claim 1,
The straight or branched chain alkyl acrylate monomer of C ₄ to C ₁₂ having a glass transition temperature of -70 to -50°C used to prepare the photocurable (meth)acrylate copolymer of A) is n-butylacrylate And 2-ethylhexyl acrylate.
The hydroxy C ₂ ~ C ₆ straight chain or branched chain alkyl acrylate monomer is an optically transparent pressure-sensitive adhesive composition is at least one monomer selected from 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate. The method according to claim 1, wherein the isocyanate group-containing (meth) acrylate monomer is an isocyanato C ₁ ~ C ₁₀ alkyl (meth) acrylate optically transparent pressure-sensitive adhesive composition. The optically transparent pressure-sensitive adhesive composition of claim 4, wherein the isocyanate group-containing (meth)acrylate-based monomer is 2-isocyanatoethyl methacrylate. The method according to claim 1, The adhesion promoter-containing polymerizable monomer is a compound of Formula 1; Compound of formula 2; Compound of formula 3; Chemical Formula 4; Compounds of formula 5; Compound of formula 6; Compounds of formula 7; And one or more optical transparent pressure-sensitive adhesive composition selected from the group consisting of compounds of formula 8:
<Formula 1>

<Formula 2>

<Formula 3>

<Formula 4>

<Formula 5>

<Formula 6>

<Formula 7>

<Formula 8>

In Chemical Formula 7, X is PF5, SbF6, mesylate (OMs), tosylate (OTs), triflate (OTf), bis(fluorosulfonyl)imide; FSI), and bis(trifluoromethylsulfonyl)imide (TFSI). The method according to claim 1, wherein the straight chain or branched chain alkyl (meth)acrylate monomer of C ₄ ~ C ₁₂ used to prepare the acrylate copolymer of B) is n-butyl acrylate, t-butyl acrylate, sec One or more monomers selected from the group consisting of -butyl acrylate, pentyl acrylate, 2-ethylbutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate and isononyl acrylate The method according to claim 1, wherein C) the photopolymerization initiator is an optically transparent adhesive comprising 0.1 to 5 parts by weight based on 100 parts by weight of the total content of the photocurable (meth)acrylate copolymer of A) and the acrylate copolymer of B). Composition. The method according to claim 1, wherein the optically transparent adhesive composition further comprises 40 to 85 parts by weight of a solvent based on 100 parts by weight of the total content of the photocurable (meth)acrylate copolymer of A) and the acrylate copolymer of B). Optical transparent pressure-sensitive adhesive composition, characterized in that. The method according to claim 1, wherein the optically transparent adhesive composition further comprises 0.02 to 5 parts by weight of a multifunctional crosslinking agent based on 100 parts by weight of the total content of the photocurable (meth)acrylate copolymer of A) and the acrylate copolymer of B). Optical transparent pressure-sensitive adhesive composition comprising. An optical transparent pressure-sensitive adhesive film prepared by coating the optical transparent pressure-sensitive adhesive composition of claim 1 on a transfer film. A flat panel display comprising an adhesive layer formed of the optically transparent adhesive composition of claim 1. The method according to claim 12,
In the above, the flat panel display device is a flexible display device, characterized in that the flat panel display device.