KR20180036223A - Adhesive Composition and Adhesive Sheet Using the Same - Google Patents

Abstract

The present invention provides an adhesive composition comprising an acrylic copolymer which includes a thermosetting functional group having a weight average molecular weight of 300,000 to 1,000,000 and a radically polymerizable functional group, a photoinitiator, and a thermosetting agent, wherein a stress relaxation ratio at 70°C after thermal curing is 0.04 to 0.1 and a stress relaxation ratio at 70°C after photo curing is 0.35 to 0.6. The adhesive composition according to the present invention is excellent in durability and adhesion to various substrates.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a pressure-sensitive adhesive composition,

The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition, and more particularly to a pressure-sensitive adhesive composition having excellent durability and excellent adhesion to various substrates.

Among the pressure-sensitive adhesives, optically clear adhesives (OCA) having high transparency are used for interlayer adhesion for laminating components in a display device. Such optical transparent pressure-sensitive adhesives are required to have high transmittance and low haze and satisfy properties such as adhesiveness to various substrates, heat resistance and anti-wet heat resistance.

In recent years, a flexible display device capable of maintaining the display performance even if bent like paper by using a flexible material such as plastic instead of a conventional glass substrate with a non-flexibility is rapidly emerging as a next generation display device, Development of an optical transparent pressure-sensitive adhesive excellent in adhesion and durability is required.

Korean Patent Laid-Open Publication No. 10-2014-0044269 discloses a (meth) acrylic copolymer comprising an alkyl group-containing (meth) acrylate having a carbon number of 12 or more, an alkyl group-containing (meth) acrylate having an alkyl group of 1 to 8 carbon atoms and a hydroxyl group- Sensitive adhesive composition. However, the pressure-sensitive adhesive composition has a problem that it is difficult to secure good adhesion and durability when applied to a flexible display device.

Korean Patent Publication No. 10-2014-0044269

An object of the present invention is to provide a pressure-sensitive adhesive composition which is excellent in durability and excellent in adhesion to various substrates.

Another object of the present invention is to provide a pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition.

On the other hand, the present invention provides a pressure-sensitive adhesive composition comprising a thermosetting functional group having a weight average molecular weight of 300,000 to 1,000,000 and an acrylic copolymer containing a radical polymerizable functional group, a photoinitiator and a thermosetting agent, wherein a stress relaxation ratio 0.04 to 0.1, and a stress relaxation ratio at 70 DEG C after photo-curing is from 0.35 to 0.6.

In one embodiment of the present invention, the thermosetting functional group and the radically polymerizable functional group-containing acrylic copolymer are obtained by reacting an acrylic copolymer containing 5 to 20% by weight of a hydroxyl group-containing monomer with a compound containing a radical polymerizable functional group in an amount of 100 moles To 5% by mole to 50% by mole based on the total mass of the composition.

In one embodiment of the present invention, the radically polymerizable functional group-containing compound may be an isocyanate group or an epoxy group-containing acrylate compound.

In one embodiment of the present invention, the thermosetting agent may be an isocyanate crosslinking agent.

In one embodiment of the present invention, the photoinitiator is contained in an amount of 0.01 to 1.0 part by weight based on 100 parts by weight of the thermosetting functional group and the radical polymerizable functional group-containing acrylic copolymer, and the thermosetting agent may be included in an amount of 0.04 to 0.1 part by weight .

On the other hand, the present invention provides a pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition according to the present invention has a stress relaxation ratio of 0.04 to 0.1 at 70 ° C after thermosetting and a stress relaxation ratio of 0.35 to 0.6 at 70 ° C after photo-curing, so that the durability is excellent and the adhesiveness to various substrates great. In particular, the pressure-sensitive adhesive composition according to the present invention is characterized in that monomers remaining in the acrylic copolymer are cured by radically polymerizable functional groups of the radical polymerizable functional group-containing compound to inhibit outgassing of bubbles, It is possible to suppress the flow-out problem, and to improve the step-difference landing property and step difference overcome.

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

An embodiment of the present invention is a pressure-sensitive adhesive composition comprising a thermosetting functional group and a radically polymerizable functional group-containing acrylic copolymer having a weight average molecular weight of 300,000 to 1,000,000, a photoinitiator and a thermosetting agent, wherein a stress relaxation ratio Is 0.04 to 0.1, and a stress relaxation ratio at 70 DEG C after photo-curing is 0.35 to 0.6.

After the thermosetting, the stress relaxation ratio (S / R ratio) at 70 ° C was measured by thermosetting (curing) the pressure-sensitive adhesive composition, measuring the modulus of elasticity after 1 second with a rheometer at 70 ° C and the modulus of elasticity after 300 seconds, Can be obtained by Equation (1).

[Equation 1]

Stress relaxation ratio = elasticity rate after 300 seconds / elasticity rate after 1 second

After the photo-curing, the stress relaxation ratio at 70 ° C was obtained by photocuring the thermosetting pressure-sensitive adhesive composition, measuring the modulus of elasticity after 1 second and modulus of elasticity after 300 seconds at 70 ° C with a rheometer, .

The stress relaxation ratio at 70 캜 after the heat curing may be 0.04 to 0.1. If the stress relaxation ratio at 70 ° C after the thermosetting is less than 0.04, bubbles may be generated during the autoclave processing after the sample lamination. If the stress relaxation ratio is more than 0.1, the tacky property may be insufficient during sample lamination.

The stress relaxation ratio at 70 캜 after the photo-curing may be 0.35 to 0.6. If the stress relaxation ratio at 70 캜 after the photo-curing is less than 0.35, the durability may be deteriorated. If the stress relaxation ratio is more than 0.6, the adhesion may be insufficient.

The thermosetting functional group and the radical polymerizable functional group-containing acrylic copolymer have a weight average molecular weight (in terms of polystyrene) measured by Gel Permeation Chromatography (GPC) of 300,000 to 1,000,000. When the weight average molecular weight of the thermosetting functional group and the radical polymerizable functional group-containing acrylic copolymer is less than 300,000, the cohesive force may be lowered. If the weight average molecular weight is more than 1,000,000, the coating property may be deteriorated.

In one embodiment of the present invention, the thermosetting functional group and the radically polymerizable functional group-containing acrylic copolymer are obtained by reacting an acrylic copolymer containing 5 to 20% by weight of a hydroxyl group-containing monomer with 100 parts by weight of the total of the hydroxyl group-containing monomer To 5% by mole to 50% by mole based on the total mass of the composition.

The hydroxyl group-containing monomer partially introduces a radically polymerizable functional group into the acrylic copolymer by chemical bond with the radically polymerizable functional group-containing compound, and the remainder is used for thermosetting to reinforce the cohesive force or adhesive strength of the pressure- And is a component for imparting cutability.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl Hydroxypropyleneglycol (meth) acrylate, hydroxyalkylene glycol having 2 to 4 carbon atoms in the alkylene group (e.g., methoxyethyl (meth) acrylate, Hydroxybutyl vinyl ether, 8-hydroxyoctyl vinyl ether, 9-hydroxynonyl (meth) acrylate, 4-hydroxybutyl vinyl ether, Vinyl ether, and 10-hydroxydecyl vinyl ether. Of these, 2-hydroxyethyl (meth) acrylate is preferable.

The hydroxyl group-containing monomer is preferably contained in an amount of 5 to 20% by weight based on 100% by weight of the total monomer used in the production of the acrylic copolymer. When the content is less than 5% by weight, cohesive failure tends to occur at the time of heating, and when it is more than 20% by weight, flow properties at the time of temperature rise may be lowered.

The thermosetting functional group and the radical polymerizable functional group-containing acrylic copolymer may contain, in addition to the hydroxyl group-containing monomer, a high-Tg monomer having a glass transition temperature (Tg) of 10 ° C to 100 ° C and a (meth) acrylate monomer .

For example, the thermosetting functional group and the radical polymerizable functional group-containing acrylic copolymer may contain 30 to 50% by weight of a high Tg monomer having a glass transition temperature (Tg) of 10 to 100 캜, 5 to 20% by weight of a hydroxyl group- And 40 to 60% by weight of (meth) acrylate monomer containing -12.

The high Tg monomer having a glass transition temperature (Tg) of 10 ° C to 100 ° C is a component for imparting elasticity to an acrylic copolymer to improve adhesion to various substrates, and includes t-butyl (meth) acrylate, methyl methacrylate (Meth) acrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, stearyl methacrylate, phenyl methacrylate, cyclohexyl methacrylate, isobonyl Benzyl methacrylate, 3,3,5-trimethylcyclohexyl acrylate, cyclohexyl acrylate, N-octylacrylamide, etc. These may be used alone or in combination of two or more. The (meth) acrylate means acrylate and methacrylate.

The high Tg monomer is preferably contained in an amount of 30 to 50% by weight based on 100% by weight of the total monomer used in the production of the acrylic copolymer. When the content is less than 30% by weight, it may be difficult to secure durability. When the content is more than 50% by weight, it may be difficult to secure adhesion.

The (meth) acrylate monomer having an alkyl group of 1 to 12 carbon atoms is a monomer having a glass transition temperature (Tg) lower than -10 ° C. Specific examples thereof include n-butyl acrylate, 2-ethylhexyl acrylate, Methyl acrylate, n-propyl acrylate, isopropyl acrylate, pentyl acrylate, n-octyl acrylate, nonyl acrylate, decyl acrylate and dodecyl acrylate. Of these, 2-ethylhexyl Acrylate, dodecyl acrylate, or mixtures thereof. These may be used alone or in combination of two or more.

The (meth) acrylate monomer having an alkyl group of 1 to 12 carbon atoms is preferably contained in an amount of 40 to 60% by weight based on 100% by weight of the total monomers used in the production of the acrylic copolymer. When the content is less than 40% by weight, the adhesive strength is not sufficient. When the content is more than 60% by weight, the cohesive strength may be lowered.

The acrylic copolymer may further contain other polymerizable monomers other than the monomers in an amount not lowering the physical properties such as adhesion, durability and adhesion, for example, 10% by weight or less based on the total amount.

The method for producing the acrylic copolymer is not particularly limited, and can be produced by methods such as bulk polymerization, solution polymerization, emulsion polymerization or suspension polymerization, which are commonly used in the art, and solution polymerization is preferred. In addition, a solvent, a polymerization initiator, a chain transfer agent for molecular weight control and the like which are usually used in polymerization can be used.

The radically polymerizable functional group-containing compound may be an isocyanate group or an epoxy group-containing acrylate compound.

For example, the radically polymerizable functional group-containing compound may be a compound represented by the following Formula 1:

[Chemical Formula 1]

Wherein R ¹ is hydrogen or a C ₁ -C ₁₀ alkyl group, R ² is a C ₂ -C ₁₀ alkylene group, and R ³ is an isocyanate group or an epoxy group.

As used herein, a C ₁ -C ₁₀ alkyl group means a linear or branched monovalent hydrocarbon group having 1 to 10 carbon atoms, and examples thereof include methyl, ethyl, n-propyl, i-propyl, n-butyl butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl and the like.

As used herein, a C ₂ -C ₁₀ alkylene group means a linear or branched divalent hydrocarbon having 2 to 10 carbon atoms, and includes, for example, ethylene, propylene, butylene, pentylene, hexylene, Tylene, octylene, nonylene, and the like, but are not limited thereto.

In one embodiment of the present invention, R ¹ is hydrogen, R ² is ethylene, and R ³ is an isocyanate group.

The radically polymerizable functional group-containing compound may be introduced in an amount of 5 to 50 mol% based on 100 mol% of the total of the hydroxyl group-containing monomer. If the addition amount of the radically polymerizable functional group-containing compound is less than 5 mol%, it may be difficult to secure the S / R ratio after photo-curing. If the addition amount is more than 50 mol%, the adhesion may deteriorate due to over-

DBTDL (dibutyltin dilaurate) may be used as a catalyst for introducing the radically polymerizable functional group-containing compound. The DBTDL may be added in an amount of 0.5 to 3 parts by weight based on 100 parts by weight of the entire radical polymerizable functional group-containing compound.

In one embodiment of the present invention, the photoinitiator includes, for example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, Phenylacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1- , 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino- (Diethylamino) benzophenone (EAB-F), dichlorobenzophenone, 2-methyl anthraquinone, 2-hydroxybenzophenone, Ethyl anthraquinone, 2-t-butyl anthraquinone, 2-amino anthraquinone, 2-methyl thioxanthone, 2-ethyl thioxanthone, 2-chlorothioxanthone, 2,4- 2,4-diethylthioxanthone (DETX), 4-isopropylthioxane (ITX), benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoic acid ester, oligo [2-hydroxy-2-methyl- 6-trimethylbenzoyl-diphenyl-phosphine oxide, 2- (3,4-methylenedioxyphenyl) -4,6-bis (trichloromethyl) -1,3,5-triazine, 2,2'- Bis (2-chlorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole (HABI-101), 2,2'- 5'-tetraphenylbiimidazole (HABI-107), 2,2 ', 4-tris (2-chlorophenyl) -5- (3,4-dimethoxyphenyl) -4' Imidazole (TCDM), and the like. These may be used alone or in combination of two or more.

The photoinitiator may be included in an amount of 0.01 to 1.0 part by weight based on 100 parts by weight of the total of the thermosetting functional group and the radical polymerizable functional group-containing acrylic copolymer. When the amount is less than 0.01 part by weight, the acrylic copolymer does not sufficiently cure, resulting in difficulty in realizing the mechanical properties and adhesiveness of the resulting pressure-sensitive adhesive sheet. When the amount exceeds 1.0 part by weight, discoloration and the like may occur due to residual initiator.

In one embodiment of the present invention, the thermosetting agent may be an isocyanate crosslinking agent.

Examples of the isocyanate crosslinking agent include tolylene diisocyanate, xylene diisocyanate, 2,4-diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tetramethyl xylene diisocyanate, Diisocyanate compounds such as naphthalene diisocyanate; An adduct obtained by reacting 3 moles of a diisocyanate compound with 1 mole of a polyhydric alcohol compound such as trimethylolpropane, an isocyanurate compound in which 3 moles of a diisocyanate compound is self-condensed, a diisocyanate obtained from 2 moles of 3 moles of a diisocyanate compound And multifunctional isocyanate compounds containing three functional groups such as burette, triphenylmethane triisocyanate and methylene bistriisocyanate in which the remaining one mole of diisocyanate is condensed in urea.

The thermosetting agent may be included in an amount of 0.04 to 0.1 part by weight based on 100 parts by weight of the thermosetting functional group and the radical polymerizable functional group-containing acrylic copolymer. If the amount is less than 0.04 parts by weight, the cohesive force becomes small due to insufficient thermal curing, and durability such as lifting may be lowered. If the amount is more than 0.1 parts by weight, stress relaxation may occur due to excessive crosslinking reaction.

The pressure-sensitive adhesive composition according to one embodiment of the present invention may contain, in addition to the above components, a silane coupling agent, a tackifier resin, a tackifier resin, a tackifier resin or the like to control the adhesion, cohesion, viscosity, elastic modulus, glass transition temperature, , An antioxidant, a corrosion inhibitor, a leveling agent, a surface lubricant, a dye, a pigment, a defoaming agent, a filler, a light stabilizer, and an antistatic agent.

The pressure-sensitive adhesive composition according to an embodiment of the present invention can be applied not only to a conventional flat panel display but also to a flexible display, and specifically to a display panel, a polarizer, a touch panel, a cover glass, a bezel, have.

One embodiment of the present invention relates to a pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive sheet according to an embodiment of the present invention may be one in which a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to the present invention is interposed between two base films.

Examples of the base film include a polyolefin film, a polyester film, an acrylic film, a styrene film, an amide film, a polyvinyl chloride film, a polyvinylidene chloride film and a polycarbonate film. Powder or the like.

The pressure-sensitive adhesive layer can be formed by coating a pressure-sensitive adhesive composition on one base film. The coating method is not particularly limited as long as it is a method known in the art. For example, a bar coater, an air knife, a gravure, a reverse roll, a kiss roll, a spray, a blade, a die coater, a casting, . Specifically, the pressure-sensitive adhesive composition is coated on one base film and dried at 30 to 150 ° C for 1 second to 2 hours, preferably for 5 seconds to 1 hour, and then dried at about 100 to 2000 mJ / cm 2, preferably 200 To 1500 mJ / cm < 2 > for curing.

Alternatively, the pressure-sensitive adhesive layer may be provided by applying a pressure-sensitive adhesive composition on one base film and thermosetting by drying at 30 to 150 DEG C for 1 second to 2 hours, preferably 5 seconds to 1 hour, It may be cured by bonding to an adherend and irradiating ultraviolet rays.

The thickness of the pressure-sensitive adhesive layer may be 30 to 2,000 mu m, preferably 50 to 1,500 mu m. If the thickness of the pressure-sensitive adhesive layer is less than 30 mu m, it may be difficult to cushion the impact generated from the outside. If the thickness is more than 2,000 mu m, the optical performance may be deteriorated.

The pressure-sensitive adhesive sheet according to an embodiment of the present invention may be subjected to surface treatment of the pressure-sensitive adhesive layer before bonding to improve adhesion.

The surface treatment method is not particularly limited, and the surface of the pressure-sensitive adhesive layer can be activated by a method such as corona discharge treatment, plasma treatment, ultraviolet irradiation, electron beam irradiation, or an anchoring agent application.

Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples and Experimental Examples. It should be apparent to those skilled in the art that these examples, comparative examples and experimental examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Manufacturing example : Preparation of Acrylic Copolymer

Manufacturing example  1: Thermosetting Functional group  And Radical Polymerizable Functional group  contain Preparation of acrylic copolymer (A1)

50 parts by weight of 2-ethylhexyl acrylate (2-EHA), 40 parts by weight of isobornyl acrylate (IBOA) and 2 parts by weight of 2-hydroxypropyl methacrylate were added to a 1 L reactor equipped with a cooling device, And 10 parts by weight of ethyl acrylate (2-HEA) were put in a reactor, and 100 parts by weight of ethyl acetate (EAc) was added as a solvent. Nitrogen gas was then purged for 1 hour to remove oxygen and then maintained at 80 ° C. After the mixture was homogeneously mixed, 0.1 part by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator, and the mixture was reacted for 8 hours. To the acrylic copolymer (A4), 2-isocyanatoethyl acrylate (AOI; 2-isocyanatoethyl acrylate) and DBTDL (dibutyltin dilaurate). The amount of 2-isocyanatoethyl acrylate to be added was controlled so as to be added in an amount of 10 mol% based on 100 mol% of all the hydroxyl group-containing monomers (2-HEA) contained in the acrylic copolymer (A4) Was controlled to be 1.0 part by weight based on 100 parts by weight of 2-isocyanatoethyl acrylate. Subsequently, the reaction was carried out at a temperature of 40 ° C. and at normal pressure for 4 hours or more to prepare an acrylic copolymer (A1) containing a thermosetting functional group and a radical polymerizable functional group (weight average molecular weight: 54,000, PDI 5.1).

The weight average molecular weight and molecular weight distribution of the acrylic copolymer were measured using GPC under the following conditions. For the preparation of the calibration curve, standard polystyrene of the Agilent system was used and the measurement results were converted.

<Conditions for measuring weight average molecular weight>

Meter: Agilent GPC (Agilent 1200 series, USA)

Column: Two PL Mixed B connections

Column temperature: 40 ° C

Eluent: tetrahydrofuran

Flow rate: 1.0 mL / min

Concentration: 1 mg / mL (100 μL injection)

Manufacturing example  2-5: Thermosetting Functional group  And Radical Polymerizable Functional group  contain Preparation of acrylic copolymers (A2, A3 and A5)

Acrylic copolymer (A2, A3 and A5) containing a thermosetting functional group and a radical polymerizable functional group was prepared in the same manner as in Preparation Example 1,

division
(Parts by weight) Copolymer composition Amount of AOI injected Weight average molecular weight (unit: million) EHA DA IBOA CA 2-HEA Production Example 1 (A1) 50 40 10 10 mol% 54 Production Example 2 (A2) 50 40 10 10 mol% 57 Production Example 3 (A3) 40 50 10 10 mol% 65 Production Example 4 (A4) 50 40 10 54 Production Example 5 (A5) 50 40 10 10 mol% 132

EHA: 2-ethylhexyl acrylate

DA: Dodecyl acrylate

IBOA: isobornyl acrylate

CA: cyclohexyl acrylate

2-HEA: 2-hydroxyethyl acrylate

Example  1 to 4 and Comparative Example  1 to 3: Preparation of pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet

A pressure-sensitive adhesive composition was prepared by mixing the thermosetting functional group and radically polymerizable functional group-containing acrylic copolymer, the photoinitiator and the thermosetting agent of the above Production Example in the composition shown in Table 2 below.

Example Comparative Example One 2 3 4 One 2 3 acryl
Copolymer Kinds A1 A1 A2 A3 A4 A1 A5 Content (parts by weight) 100 100 100 100 100 100 100 Photoinitiator Content (parts by weight) 0.1 0.1 0.1 0.1 - 0.1 0.1 Content of thermosetting agent (parts by weight) 0.06 0.08 0.06 0.06 0.06 - 0.06 Coating solids (wt%) 35% 35% 35% 35% 35% 35% 25% The coating liquid viscosity (cP) 1750 1780 1770 1440 1750 1770 2170

Photoinitiator: 1-hydroxycyclohexyl phenyl ketone (Irg 184, Ciba Specialty Chemicals, Switzerland)

Thermal curing agent: Coronate-L (Nippon Urethane)

The pressure-sensitive adhesive composition prepared above was coated on a releasing film coated with a silicone release agent to a thickness of 100 탆 and dried at 130 캜 for 5 minutes to form a pressure-sensitive adhesive layer, and a releasing film was bonded thereon. And UV-treated in the same manner to produce a pressure-sensitive adhesive sheet.

&Lt; UV treatment condition >

Ultraviolet irradiator: High pressure mercury lamp

Irradiation conditions: Light quantity (UVA) = 1500 mJ / cm ²

Experimental Example  One:

The physical properties of the pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet prepared in Examples and Comparative Examples were measured by the following methods, and the results are shown in Table 3 below.

(One) Coating property

The coating properties in the course of coating the pressure-sensitive adhesive composition prepared in Examples and Comparative Examples were evaluated by visual observation of the state of the coating layer according to the following criteria.

 <Evaluation Criteria>

?: No visible bubbles and / or stripe marks on the coating layer

B: Fine bubbles and / or stripe patterns were visually confirmed in the coating layer

X: Bubbles and / or stripe pattern was visually confirmed in the coating layer

(2) Adhesion

The release film on one side of the pressure-sensitive adhesive sheet prepared in Examples and Comparative Examples was peeled off, corona-treated on the pressure-sensitive adhesive side, and bonded to a PET film having a thickness of 38 탆, cut to a width of 25 mm and a length of 100 mm, . Then, the release film on the other surface was peeled off, and the pressure-sensitive adhesive sheet was attached to the alkali glass using a roller of 2 kg in accordance with JIS Z 0237. The alkali glass with the adhesive sheet was pressed for about 20 minutes in an autoclave (50 캜, 5 atmospheric pressure) and stored for 1 hour under constant temperature and humidity conditions (23 캜, 50% relative humidity) The adhesive sheet was peeled from the alkali glass at a peeling speed of 300 mm / min and a peeling angle of 180 degrees using an analyzer (Stable Microsystems, UK) to measure the adhesion.

Adhesive strength of PET (polyethylene terephthalate) and COP (cyclic olefin copolymer) was measured by the same method, except that PET and COP film were adhered on both sides of an alkali glass with an adhesive.

(3) Stress relaxation ratio (S / R Ratio )

The stress relieving ratios of the pressure-sensitive adhesive sheets prepared in the examples and the comparative examples were determined by the following equation (1) by confirming the elastic modulus after 1 sec and the elastic modulus after 300 sec, under the following conditions. The stress relaxation ratios were measured before and after UV curing, respectively.

[Equation 1]

S / R Ratio = elastic modulus after 300 seconds / elastic modulus after 1 second

Measuring instrument: Rheometer MCR-302, PP25 (25mmΦ)

Measurement conditions: Strain 25%, Axial force 1N

Thickness 500 탆 (5 sheets of 100 탆 overlap)

Temperature: 70 占 폚 (stabilization 10 min)

(4) Durability (heat resistance, Wet heat )

The release film on one side of the pressure-sensitive adhesive sheet prepared in Example or Comparative Example was peeled off, the pressure-sensitive adhesive sheet prepared by corona treatment on the pressure-sensitive adhesive side and the 40 占 퐉 COP film was cut into a size of 90 mm × 170 mm, After peeling, it was attached to a glass substrate (110 mm x 190 mm x 0.7 mm) to prepare a specimen. At this time, the applied pressure was 5 kg / cm &lt; 2 &gt;, and the clean room operation was performed so that bubbles or foreign matter would not occur. The heat resistance characteristics were observed for 500 hours at a temperature of 100 ° C. and then observed for occurrence of bubbles or peeling. The resistance to moisture and heat was measured at 85 ° C. and 85% RH for 500 hours, Respectively.

<Evaluation Criteria>

Ⓞ: No bubbles or peeling.

○: Bubbles or peeling <5

?: 5 pieces? Bubbles or peeling <10 pieces

X: 10 pieces &lt; bubble &

division Coating property Adhesion after UV curing (N / 25 mm) S / R Ratio durability Alkali glass PET COP Before UV curing After UV curing 100 ℃ 85 ° C, 85% RH Example 1 ○ 32 21 30 0.06 0.45 ○ Ⓞ Example 2 ○ 30 19 27 0.09 0.42 Ⓞ Ⓞ Example 3 ○ 34 23 30 0.07 0.51 ○ Ⓞ Example 4 ○ 38 22 33 0.05 0.53 ○ Ⓞ Comparative Example 1 ○ 33 22 22 0.06 0.07 X X Comparative Example 2 ○ 25 11 19 0.01 0.58 ○ ○ Comparative Example 3 X 29 13 25 0.11 0.45 ○ ○

As can be seen from Table 3, the pressure-sensitive adhesive compositions of Examples 1 to 4 were excellent in durability and excellent in adhesion to various substrates. However, it was confirmed that the pressure-sensitive adhesive compositions of Comparative Examples 1 and 2 had poor durability and adhesion. Further, it was confirmed that the pressure-sensitive adhesive composition of Comparative Example 3 using an acrylic copolymer having a weight average molecular weight of more than 1,000,000 had a decreased coating property.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Do. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Accordingly, the actual scope of the invention is defined by the appended claims and their equivalents.

Claims (7)

A pressure-sensitive adhesive composition comprising a thermosetting functional group and a radical polymerizable functional group-containing acrylic copolymer having a weight average molecular weight of 300,000 to 1,000,000, a photoinitiator and a thermosetting agent, wherein a stress relaxation ratio at 70 ° C after thermosetting is 0.04 to 0.1, And a stress relaxation ratio at 70 캜 after the drying is 0.35 to 0.6. The acrylic copolymer as claimed in claim 1, wherein the thermosetting functional group and the radically polymerizable functional group-containing acrylic copolymer have a radically polymerizable functional group-containing compound in an amount of 5 to 20% by weight of the hydroxyl group- To 5 to 50 mol% relative to the total amount of the pressure-sensitive adhesive composition. The positive resist composition of claim 2, wherein the hydroxyl group-containing monomer is at least one selected from the group consisting of 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, Hydroxypropyleneglycol (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyleneglycol (meth) acrylate, 2- Hydroxybutyl vinyl ether, 5-hydroxybutyl vinyl ether, 6-hydroxyhexyl vinyl ether, 7-hydroxyheptyl vinyl ether, 8-hydroxyoctyl vinyl ether, 9-hydroxynonyl vinyl ether, and 10-hydroxydecyl vinyl ether. The pressure-sensitive adhesive composition according to claim 2, wherein the radically polymerizable functional group-containing compound is an isocyanate group or an epoxy group-containing acrylate compound. The pressure-sensitive adhesive composition according to claim 1, wherein the thermosetting agent is an isocyanate-based crosslinking agent. The pressure-sensitive adhesive composition according to claim 1, wherein the photoinitiator is contained in an amount of 0.01 to 1.0 part by weight based on 100 parts by weight of the thermosetting functional group and the radical polymerizable functional group-containing acrylic copolymer, and the thermosetting agent is included in an amount of 0.04 to 0.1 part by weight. A pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition according to any one of claims 1 to 6.