KR102143801B1 - 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; Polydimethylsiloxane-based (meth)acrylate compounds; And a photopolymerization initiator, wherein the photocurable (meth)acrylate copolymer contains 95 to 99.9% by weight of a hydroxy group-containing acrylic copolymer and an isocyanate group based on the total weight of the structural units contained in the copolymer (meta ) It contains 0.1 to 5% by weight of an acrylate monomer, and the hydroxy group-containing acrylic copolymer and an isocyanate group-containing (meth)acrylate-based monomer form a urethane bond,
The hydroxy group-containing acrylic copolymer is 50 to 98% by weight of a straight or branched chain alkyl (meth)acrylate monomer of C ₁ to C ₁₂ and 2 to 50% by weight of a polymerizable monomer containing a hydroxyl group based on the total weight of the monomers contained in the copolymer. It includes, and 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 device 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; Polydimethylsiloxane-based (meth)acrylate compounds; And as an optically transparent pressure-sensitive adhesive composition comprising a photopolymerization initiator,

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

The hydroxy group-containing acrylic copolymer is 50 to 98% by weight of a C ₁ to C ₁₂ straight or branched chain alkyl (meth)acrylate monomer and 2 to 50% by weight of a polymerizable monomer containing a hydroxyl group based on the total weight of the monomers contained in the copolymer. It includes, and 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; Polydimethylsiloxane-based (meth)acrylate compounds; And as an optically transparent pressure-sensitive adhesive composition comprising a photopolymerization initiator,

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

The hydroxy group-containing acrylic copolymer is 50 to 98% by weight of a C ₁ to C ₁₂ straight or branched chain alkyl (meth)acrylate monomer and 2 to 50% by weight of a polymerizable monomer containing a hydroxyl group based on the total weight of the monomers contained in the copolymer. It includes, and 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 polydimethylsiloxane (meth)acrylate compound, so that it has excellent folding properties, moist heat resistance, and adhesion, and photocurability It is characterized by providing an optically transparent pressure-sensitive adhesive composition having excellent heat resistance and durability by photo-crosslinking between an acrylate copolymer and a low Tg polydimethylsiloxane (meth)acrylate compound.

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

The photocurable (meth)acrylate copolymer is copolymerized with a C ₁ to C ₁₂ linear or branched alkyl (meth) acrylate monomer and a hydroxy group-containing polymerizable monomer, and a thermosetting functional group (hydroxy group) is added to the branched chain or terminal. At least a part of the thermosetting functional group (hydroxy group) of the main chain is isocyanate group-containing by preparing the introduced hydroxy group-containing acrylic copolymer main chain, and then reacting an isocyanate group-containing (meth)acrylate monomer with the main chain under appropriate conditions ( It can be prepared by substituting a 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 C ₁ ~ C ₁₂ linear or branched alkyl group,

R2 is a C ₁ ~ C ₁₀ 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 polydimethylsiloxane-based (meth)acrylate compound, for example, one or more selected from compounds represented by the following formulas 1 to 3 may be used:

[Formula 1]

[Formula 2]

[Chemical Formula 3]

In Formulas 1 to 3,

Each R1 is independently hydrogen or methyl

R2 is a C ₁ to C ₅ 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,

R4 is a C ₁ to C ₅ linear or branched alkylene group,

P, Q, and R are each independently a natural number of 3 to 100.

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

A C ₁ ~ C ₁₂ straight-chain or a branched-chain alkyl (meth) acrylate monomer contained in the polymerization to form the hydroxyl group-containing acrylic copolymer is a C ₁ ~ C ₁₂ The glass transition temperature (Tg) of -70 to -50 A straight or branched chain alkyl (meth)acrylate monomer may be preferably used, and more preferably a C4 to C12 straight or branched chain alkyl acrylate monomer having a glass transition temperature (Tg) of -70 to -50°C Can be used.

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 having one hydroxy group and one ethylenically unsaturated bond in the molecule 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 C ₁ to C ₁₂ straight or branched chain alkyl (meth) acrylate monomer is included in an amount of 50 to 98 wt%, and a hydroxy group-containing polymerizable monomer may be included in an amount of 2 to 50 wt%. have.

More preferably, the C ₁ ~ C ₁₂ 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).

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

The isocyanate group-containing (meth)acrylate-based monomer may be included in an amount of 0.1 to 5.0 wt% 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 decrease, and if it exceeds 5.0% by weight, the cohesive strength of the pressure-sensitive adhesive becomes too strong, so folding characteristics This can be degraded.

The polydimethylsiloxane-based (meth)acrylate compound contained in the optically transparent pressure-sensitive adhesive composition of the present invention is 10 to 50 parts by weight, more preferably 15 to 30 parts by weight based on 100 parts by weight of the photocurable (meth)acrylate copolymer. May be included as a wealth. If the polydimethylsiloxane-based (meth)acrylate compound is contained in less than 10 parts by weight, it is difficult to secure low-temperature folding characteristics, and if it contains more than 50 parts by weight, it is difficult to secure adhesive force, resulting in a problem of lowering heat resistance. I can.

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 polydimethylsiloxane-based (meth)acrylate compound 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 polydimethylsiloxane-based (meth)acrylate compound to secure folding properties, while a curing system by radical polymerization, a crosslinking agent, and a thermosetting functional group (hydroxy group) By appropriately employing a curing system together, it has 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

Based on 100 parts by weight of the photocurable acrylate copolymer (B1) prepared in Preparation Example 2-1, 20 parts by weight of a monomer represented by the following formula (1), a polyfunctional crosslinking agent (Coronate L, made in Japan NPU) 0.07 parts by weight, A pressure-sensitive adhesive composition by mixing 0.2 parts by weight of a photoinitiator (hydroxycyclohexylphenyl ketone, irgacure 184, Swiss Civas Specialty Chemical (manufactured by)) and 0.2 parts by weight of 3-glycidoxypropyltrimethoxyl silane (KBM-403 from Shin-Etsu) Was prepared.

[Formula 1]

In the above formula

R1 is hydrogen,

P is 50.

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 the monomer represented by Formula 2 was used instead of the monomer represented by Formula 1 in Example 1.

[Formula 2]

In the above formula

R1 is a methyl group,

R2 is an ethylene group,

Q is 50.

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

With respect to 100 parts by weight of the photocurable (meth)acrylate copolymer (B2) prepared in Preparation Example 2-2, 30 parts by weight of a monomer represented by the following formula (3), a polyfunctional isocyanate crosslinking agent (Coronate L, manufactured by NPU Japan) A pressure-sensitive adhesive composition was prepared by mixing 0.5 parts by weight and 0.2 parts by weight of a photopolymerization initiator (hydroxycyclohexylphenyl ketone, irgacure 184, Swiss Civas Specialty Chemical (manufactured)).

[Chemical Formula 3]

In Chemical Formula 3,

R1 is hydrogen,

R3 is a hexamethylene group,

R4 is an ethylene group,

R is 50

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 4: Preparation of optically transparent adhesive film

Each of the optically transparent pressure-sensitive adhesive compositions prepared in Examples 1, 2, 3, Comparative Examples 1 and 2 was cured on a 50 μm-thick PET film coated with a silicone release agent so that the thickness after curing was 100 μm. After coating and drying for 5 minutes at 100, Example 4-1 (using the optically transparent pressure-sensitive adhesive composition of Example 1), Example 4-2 (using the optically transparent pressure-sensitive adhesive composition of Example 2), Example 4-3 ( The optically transparent adhesive films of Example 3 using the optically transparent adhesive composition), Comparative Example 4-1 (using the optically transparent adhesive composition of Comparative Example 1) and Comparative Example 4-2 (using the optically transparent adhesive composition of Comparative Example 2) Was prepared.

Example 5: Adhesive layer Formed Laminated Produce

Using the optically transparent adhesive films prepared in Example 4-1, Example 4-2, Example 4-3, Comparative Example 4-1 and Comparative Example 4-2, a PET film having a thickness of 100 µm (100 µm manufactured by Mitsubishi Corporation) PET) was laminated on the pressure-sensitive adhesive layer, and in the direction of the release film, a UV lamp (fusion company) was used to irradiate a light amount of 1000 mJ/cm ² , respectively, in Example 5-1, Example 5-2, and Example 5-3, A laminate having the pressure-sensitive adhesive layers of Comparative Example 5-1 and Comparative Example 5-2 was prepared.

Example 6: Flexibility For evaluation Hard coating film/ Adhesive layer /PET Laminated Produce

The laminates of Example 5-1, Example 5-2, Example 5-3, Comparative Example 5-1, and Comparative Example 5-2 were cut into 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 curing for 24 hours under constant temperature and humidity conditions (23, 50% relative humidity), respectively, in Example 6-1, Example 6-2, Example 6-3, and Comparative Example A hard coating film/adhesive layer/PET (100 μm) laminate for evaluation of flexural properties of 6-1 and Comparative Example 6-2 was prepared.

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

One. Folding characteristics evaluation

<Evaluation method>

Evaluation standard: 　IEC 62715

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

Equipment maker: YUASA SYSTEM (Japan)

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

Hard coating film/adhesive layer/PET laminate for evaluating the flexibility of Example 6-1, Example 6-2, Example 6-3, Comparative Example 6-1 and Comparative Example 6-2 prepared in Example 6 The folding characteristics were evaluated according to the above evaluation method and are 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 6-1, Example 6-2, Example 6-3, Comparative Example 6-1 and Comparative Example 6-2 prepared in Example 6 for evaluating the bending hard coating film / adhesive layer / PET laminate After leaving for 1,000 hours at a temperature of 80, 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

Example 6-1, Example 6-2, Example 6-3, Comparative Example 6-1 and Comparative Example 6-2 prepared in Example 6 for evaluating the bending hard coating film / adhesive layer / PET laminate After leaving for 1,000 hours under the conditions of a temperature of 60 and 90%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 Examples 5-1, 5-2, 5-3, Comparative Example 5-1 and Comparative Example 5-2 to a size of 25 mm × 100 mm. I did. 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 6-1 Example 1 Preparation ○ ○ ○ Example 6-2 Example 2 Preparation ○ ○ ○ Example 6-3 Example 3 Preparation ○ ○ ○ Comparative Example 6-1 Comparative Example 1 Preparation × ○ ○ Comparative Example 6-2 Comparative Example 2 Preparation × ○ ○

Laminate with adhesive layer Adhesive composition used Adhesion Example 5-1 Example 1 Preparation 15N Example 5-2 Example 2 Preparation 12N Example 5-3 Example 3 Preparation 14N Comparative Example 5-1 Comparative Example 1 Preparation 23N Comparative Example 5-2 Comparative Example 2 Preparation 18N

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 compared to the comparative example because it contained a polydimethylsiloxane-based (meth)acrylate compound.

Claims (12)

Photocurable (meth)acrylate copolymer; Polydimethylsiloxane-based (meth)acrylate compounds; And as an optically transparent pressure-sensitive adhesive composition comprising a photopolymerization initiator,
The photocurable (meth)acrylate copolymer contains 95 to 99.9% by weight of a hydroxy group-containing acrylic copolymer and 0.1 to 5% by weight of an isocyanate group-containing (meth)acrylate monomer based on the total weight of the constituent units contained in the copolymer. The hydroxy group-containing acrylic copolymer and the isocyanate group-containing (meth)acrylate-based monomer form a urethane bond,
The hydroxy group-containing acrylic copolymer is 50 to 98% by weight of a C ₁ to C ₁₂ straight or branched chain alkyl (meth)acrylate monomer and 2 to 50% by weight of a polymerizable monomer containing a hydroxyl group based on the total weight of the monomers contained in the copolymer. Including, the weight average molecular weight is 200,000 to 1 million,
The glass transition temperature of the straight chain or branched chain alkyl (meth)acrylate monomer of C ₁ to C ₁₂ is -70 to -50 °C, and the glass transition temperature of the hydroxy group-containing polymerizable monomer is -60 to -40 °C,
The polydimethylsiloxane-based (meth)acrylate compound is an optically transparent pressure-sensitive adhesive composition, characterized in that at least one selected from compounds represented by the following formulas 1 to 3:
[Formula 1]

[Formula 2]

[Chemical Formula 3]

In Formulas 1 to 3,
Each R1 is independently hydrogen or methyl
R2 is a C ₁ to C ₅ linear or branched alkylene group,
R 3 is each independently a group derived from a diisocyanate compound with a -N(H)-C(O)- group bonded to both sides thereof,
R4 is a C ₁ to C ₅ linear or branched alkylene group,
P, Q, and R are each independently a natural number of 3 to 100. The method according to claim 1,
The hydroxy group-containing polymerizable monomer is a monomer having one hydroxyl group and one ethylenically unsaturated bond in the molecule. delete delete The method according to claim 1,
The optically transparent pressure-sensitive adhesive composition includes 10 to 50 parts by weight of a polydimethylsiloxane-based (meth)acrylate compound and 0.1 to 5 parts by weight of a photopolymerization initiator based on 100 parts by weight of a photocurable (meth)acrylate copolymer. An optically transparent pressure-sensitive adhesive composition comprising parts by weight. 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 isocyanate group-containing (meth)acrylate-based monomer is an isocyanato C ₁ ~ C ₁₀ straight or branched chain alkyl (meth) acrylate, characterized in that the optically transparent pressure-sensitive adhesive composition. 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.