KR20170120982A - Adhesive film, optical member comprising the same and optical display apparatus comprising the same - Google Patents

Abstract

Provided are an adhesive film, an optical member including the same, and an optical display device including the same. When tan is measured at -30-80C, the least value of the tan exists between 0C and 20C, and the least value of the tan is 0.2-0.4. The present invention provides an adhesive film capable of minimizing a difference in stability and the stability reduction ratio between high and room temperatures. The present invention provides an adhesive film capable of achieving excellent splitting resistance and stability at a high temperature and improving reliability by suppressing bubbles.

Description

TECHNICAL FIELD [0001] The present invention relates to an adhesive film, an optical member including the adhesive member, and an optical display device including the adhesive member. [0002]

The present invention relates to an adhesive film, an optical member including the same, and an optical display device including the same.

The optical display device includes a display element including a window film, a conductive film, and an organic light emitting element. A touch pad has a structure in which a transparent clear adhesive (OCA) is laminated between a window film and a conductive film. However, the transparent adhesive film may be laminated between two kinds of window films, conductive films, polarizing plates, and organic light emitting devices.

The pressure-sensitive adhesive film is excellent in peel strength and restoring force at room temperature, and can exhibit its function sufficiently in an optical display device by having an appropriate modulus. However, when the pressure-sensitive adhesive film is exposed to a high temperature, the pressure-sensitive adhesive film may have a remarkable decrease in restitution force as the crosslinking structure in the pressure-sensitive adhesive film is released, and the modulus may also be lowered. Further, at high temperature, the pressure-sensitive adhesive film may have poor reliability due to the generation of bubbles due to the occurrence of cracks in the crosslinked structure as the crosslinked structure is loosened. An adhesive film having a high degree of crosslinking can be produced even at a high temperature by using a large amount of a crosslinking agent. Accordingly, there is no such problem, and an adhesive film having excellent peel strength, restoring force, and reliability is required even when exposed to high temperature for a long time.

On the other hand, in recent years, a flexible display device having flexibility that can be folded and unfolded in an optical display device has been developed. The flexible display device can be folded and unfolded to make various shapes, thin, light and strong to impact. Flexible display devices require that the various optical elements included in the apparatus have flexibility. Since the transparent pressure-sensitive adhesive film is formed between the window film and the conductive film, the adhesive force of both sides must be excellent. Further, in order to be used in a flexible display device, the folding property should be good.

The background art of the present invention is disclosed in Korean Patent Publication No. 2007-0055363.

It is an object of the present invention to provide a pressure-sensitive adhesive film which can minimize the difference between the restoring force and the restoring force.

Another object of the present invention is to provide a pressure-sensitive adhesive film which is excellent in peel strength and restoring force at a high temperature and can suppress bubble generation and enhance reliability.

Another object of the present invention is to provide an adhesive film which is stably viscoelastic even at a high temperature, has good foldability, and is excellent in optical transparency.

It is still another object of the present invention to provide an optical member and an optical display device including the adhesive film of the present invention.

In the pressure-sensitive adhesive film of the present invention, when tan delta is measured in a temperature range of -30 DEG C to 80 DEG C, the minimum value of tan delta is 0 DEG C to 20 DEG C, and the minimum value of tan DELTA is 0.2 to 0.4 .

The adhesive film of the present invention can have a peel strength at 60 DEG C of 700 gf / in or more and a reduction in restitution force in the following 3: 50% or less:

<Formula 3>

Strength reduction ratio = (Strength 1 - Strength 2) / (Strength 1) x 100

(In the formula 3, the restoring force 1 and the restoring force 2 are as defined in the detailed description of the present invention).

The optical member of the present invention may include an optical film and an adhesive film of the present invention formed on at least one side of the optical film.

The optical display device of the present invention may include the pressure-sensitive adhesive film of the present invention.

The present invention provides a pressure-sensitive adhesive film capable of minimizing a reduction ratio of a restoration force and a difference in restoration force at a high temperature relative to a normal temperature.

The present invention provides a pressure-sensitive adhesive film which is excellent in peel strength and restoring force at a high temperature and can suppress bubble formation and enhance reliability.

The present invention provides an adhesive film having stably viscoelasticity at a high temperature, good foldability, and excellent optical transparency.

The present invention provides an optical member and an optical display device including the pressure-sensitive adhesive film of the present invention.

1 is a cross-sectional view of an optical display device according to an embodiment of the present invention.
2 is a cross-sectional view and a plan view of a specimen for measuring elongation and restoring force.
3 is a graph for calculating the elongation and restitution force.
4 is a conceptual diagram of a specimen for peel strength measurement.
5 is a graph of tan delta according to the measurement temperature of Example 1 and Comparative Example 1. Fig.

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

The terms "upper" and "lower" in this specification are defined with reference to the drawings, wherein "upper" may be changed to "lower", "lower" What is referred to as "on" may include not only superposition, but also intervening other structures in the middle. On the other hand, what is referred to as "directly on" or "directly above"

As used herein, "(meth) acrylic" may mean acrylic and / or methacrylic.

As used herein, "copolymer" may include oligomers, polymers or resins.

2 (a) and 2 (b), the terms "elongation" and "restoring force" refer to the case where both end portions of a PET (polyethylene terephthalate) film (thickness: 75 μm) The end portions of the two PET films were adhered to each other by a pressure-sensitive adhesive film having a length and a length (20 mm x 20 mm), respectively, at the first end portion and the second end portion, And the second end, and the contact area between the PET film and the pressure-sensitive adhesive film is measured as a specimen having a width and a length (20 mm x 20 mm). 2 (a), at the elongation and restoring force measuring temperatures, a jig is fixed to both end portions of the PET film that is not adhered to the specimen, one jig is fixed, and the other jig is fixed at 300 mm / at a rate of min thickness of the adhesive film (10 times the initial thickness of the adhesive film, X ₃₎ 1000% length of the (initial thickness:: X _0, unit ㎛) maintained for 10 seconds and pulled as much, and the adhesive film (300 mm / min) at the same speed as the pulling speed of the adhesive film, and the stretched length of the adhesive film when a force of 0 kPa is applied to the adhesive film is defined as X ₂ (unit: 탆). Referring to FIG. 3, a graph is obtained with the stretched length of the adhesive film as the X-axis and the force applied to the adhesive film as the Y-axis. When the length of the adhesive film stretched when a force of 90 kPa is applied to the adhesive film is X ₁ (unit: 탆), the elongation is a value calculated by the following formula 1 and the restoring force is a value calculated by the following formula 2:

<Formula 1>

Elongation = (X ₁ ) / (X ₀ ) x 100

<Formula 2>

Restoring force = (1 - (X ₂ ) / (X ₃ )) x 100

At this time, the initial thickness (X ₀ , unit: 탆) of the adhesive film may be 20 탆 to 300 탆. Elongation and resilience can be measured with TA.XT_Plus Texture Analyzer (Stable Micro System). The elongation and restoring force measurement temperatures can be 25 ° C and 60 ° C.

In the present specification, "folding condition" means that the adhesive film is placed between a corona-treated polyethylene terephthalate (PET) film (thickness: 125 μm) and a corona-treated PET film (thickness: 50 μm) Aged at room temperature and cut into pieces of length x length (100 mm x 160 mm), and PET film / adhesive film / PET film specimens were used. The specimen was fixed to a flexural evaluation equipment (CFT-200, Covotech) using an adhesive (4965, Tesa), and the length (length: 160 mm) of the specimen was measured at a folding measurement temperature at 30 cycles per minute and a cycle of 100,000 cycles was repeated by bending the adhesive film at a speed of 180 deg. (bending the adhesive film once in half and setting it as one cycle). In the present specification, "good folding" means that no streaking or the like occurs at the folding site when the folding condition is applied, and there is no breakage, lifting, peeling, bubbles or the like of the adhesive film.

The "average particle diameter" of the organic nanoparticles in the present specification is the particle diameter of the organic nanoparticles expressed by the Z-average value measured by a Zetasizer nano-ZS instrument using Malvern's water or organic solvent and confirmed by SEM / TEM.

As used herein, modulus refers to the storage modulus, unless otherwise specified for the type of modulus.

Hereinafter, an adhesive film according to an embodiment of the present invention will be described.

In the pressure-sensitive adhesive film according to an embodiment of the present invention, when tan delta is measured at -30 DEG C to 80 DEG C, the minimum value of tan delta is 0 DEG C to 20 DEG C, and the minimum value of tan DELTA is 0.2 to 0.4 . In the above range, even when the pressure-sensitive adhesive film is exposed to high temperature (e.g., 60 to 80 ° C), reduction in restitution force at room temperature can be minimized, peeling strength and restoring force are excellent even at high temperatures, The reliability of the apparatus can be improved. As known to those skilled in the art, tan delta means the ratio of loss modulus to storage modulus.

5 shows tan δ at -30 ° C to 80 ° C of the pressure-sensitive adhesive film of Example 1 of the present invention. 5, when the temperature of the adhesive film having the minimum value of tan delta at -30 DEG C to 80 DEG C and having the minimum value of tan delta is the inflection point, the tan δ decreases to a negative slope, and tan δ of the adhesive film increases gently with a positive slope from the inflection point to 80 ° C. The presence of the minimum value of tan δ at the inflection point when measured at -30 ° C. to 80 ° C. means that the adhesive film does not dissolve the crosslinking structure of the adhesive film even at high temperatures and thus retains the crosslinking structure at high temperatures. The minimum value of tan δ of from 0.2 to 0.4 at -30 캜 to 80 캜 means that the adhesive film can minimize the reduction of the restoring force when exposed to high temperature and can exert excellent peeling strength and restoring force even at high temperature. The minimum value of tan delta at 30 DEG C to 80 DEG C may preferably be 0.2 to 0.3.

Therefore, the pressure-sensitive adhesive film of this embodiment can have a restoring force reduction ratio of 50% or less, specifically 20% or less, more specifically 1% to 20% in the following 3. In the above range, the adhesive film may have viscoelastic recovery even when exposed to high temperature and excellent folding property:

<Formula 3>

Strength reduction ratio = (Strength 1 - Strength 2) / (Strength 1) x 100

(In the above formula 3, the restoring force 1 is the restoring force (unit:%) of the pressure-sensitive adhesive film at 25 캜,

Restorative force 2 is the restoring force (unit:%) of the adhesive film at 60 ° C)

The adhesive film of the present embodiment can have a difference in restitution force of the following formula (4) of not more than 40%, specifically 0.1 to 40%, more specifically 0.1 to 10%: In the above range, It has viscoelastic recovery properties and may have an excellent folding effect:

<Formula 4>

Resilience Difference = Resilience 1 - Resilience 2

(In the formula (4), the restoring force 1 is the restoring force (unit:%) of the pressure-sensitive adhesive film at 25 캜,

Restorative force 2 is the restoring force (unit:%) of the adhesive film at 60 ° C)

The restoring force 1 and restoring force 2 may be 40% or more, specifically 40% to 98%. In the above range, it has a viscoelastic recovery property and may have an excellent effect of folding.

Therefore, the peel strength at 60 DEG C of the pressure-sensitive adhesive film of this embodiment of the corona-pretreated PET film can be 700 gf / in or more, specifically 700 gf / in to 1000 gf / in. In this range, the pressure-sensitive adhesive film can provide good adhesion between the adherends and good stress relaxation force, thereby providing good folding and being used in a flexible display device. Also, in the above range, the pressure-sensitive adhesive film can stably exhibit viscoelasticity at a high temperature (e.g., 80 DEG C).

The pressure-sensitive adhesive film of this embodiment can have an elongation at 25 ° C of 900% or more and a peel strength at 25 ° C of 1000 gf / in or more for a corona-pretreated PET film. In this range, the pressure-sensitive adhesive film can provide good adhesion between the adherends and good stress relaxation force, thereby providing good folding and being used in a flexible display device. Further, in the above range, the pressure-sensitive adhesive film can stably exhibit viscoelasticity at a high temperature (e.g., 80 DEG C) and a low temperature (e.g., -20 DEG C). Specifically, the pressure-sensitive adhesive film may have a elongation of 900% to 1300% at 25 ° C.

The adhesive film may have a haze of 2% or less, specifically 0.1% to 0.9% and a total light transmittance of 90% or more, specifically 95% to 99% in a visible light region (e.g., a wavelength of 380 nm to 780 nm). Within this range, transparency is good and can be used in optical display devices. The thickness of the adhesive film may be 20 占 퐉 to 300 占 퐉, specifically 30 占 퐉 to 150 占 퐉. In the above range, it can be used in an optical display device.

The adhesive film can be realized by a pressure-sensitive adhesive composition comprising the organic nanoparticles described below. The pressure-sensitive adhesive composition will be described in detail below.

The pressure-sensitive adhesive film is formed of a pressure-sensitive adhesive composition comprising organic nanoparticles as described below, whereby the ratio of modulus at a modulus of -20 DEG C at 80 DEG C is 1: 1 to 1:10, specifically 1: 1 to 1: 8 , More specifically from 1: 1 to 1: 6. Within this range, the pressure-sensitive adhesive film has good durability and reliability with a low modulus ratio at a low temperature to a high temperature, and does not deteriorate the adhesive force between the adherend in a wide temperature range (-20 캜 to 80 캜) and can be used for a flexible optical member. The pressure-sensitive adhesive film may have a modulus of 10 kPa to 500 kPa at 80 ° C, specifically 10 kPa to 300 kPa, and a modulus of 10 kPa to 1000 kPa, specifically 50 kPa to 500 kPa at -20 ° C. Within this range, it is possible to have an excellent folding property at a low temperature and a high temperature and to prevent the adhesive film from being broken.

Hereinafter, the pressure-sensitive adhesive composition of the present invention will be described.

The adhesive film may be formed of a pressure-sensitive adhesive composition comprising a monomer mixture comprising an hydroxyl group-containing (meth) acrylate and an alkyl group-containing (meth) acrylate, an organic nanoparticle and an initiator, and the monomer mixture may contain a comonomer, A monomer, and a macromonomer. The adhesive film can be produced by a conventional method. For example, the pressure-sensitive adhesive composition may be coated on a release film and cured. Curing may include irradiation of the irradiation dose 400mJ / cm ² to 3000mJ / cm ² at a wavelength of 300nm to 400nm into a low-pressure lamp in an oxygen-free state.

The monomer mixture containing a hydroxyl group-containing (meth) acrylate and an alkyl group-containing (meth) acrylate can form a hydroxyl group (-OH) and an alkyl group-containing (meth) acrylic copolymer forming a matrix of an adhesive film. The glass transition temperature (Tg) of the hydroxyl group and the alkyl group-containing (meth) acryl-based copolymer may be -150 ° C to -13 ° C, specifically -100 ° C to -20 ° C. In the above range, the pressure-sensitive adhesive film has the above elongation and peel strength, and may have an excellent effect of folding. The (meth) acrylate containing a hydroxyl group and the (meth) acrylate containing an alkyl group are different from each other.

The hydroxyl group-containing (meth) acrylate can form a matrix of a pressure-sensitive adhesive film by cross-linking the copolymer, and can achieve an excellent adhesion and an excellent folding effect. The hydroxyl group-containing (meth) acrylate may be a (meth) acrylate containing at least one hydroxyl group. For example, the hydroxyl group-containing (meth) acrylate (a1) may be at least one selected from the group consisting of 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2- Cyclohexanedimethanol mono (meth) acrylate, 1-chloro-2-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (Meth) acrylate, 1,6-hexanediol mono (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, neopentyl glycol mono Acrylate, trimethylolethane di (meth) acrylate, 2-hydroxy-3-phenyloxypropyl (meth) acrylate, 4-hydroxycyclopentyl (meth) 4-hydroxycyclohexyl (meth) acrylate, ) It can be more than one kinds of acrylate and cyclohexanedimethanol mono (meth) acrylate. These may be used alone or in combination of two or more. In this case, the productivity of the adhesive film is improved, and the adhesive force of the adhesive film can be further improved. The hydroxyl group-containing (meth) acrylate may be included in the monomer mixture in an amount of 4 wt% to 45 wt%, for example 5 wt% to 40 wt%, 10 wt% to 30 wt%, and 15 wt% to 25 wt%. The adhesive strength and endurance reliability of the adhesive film can be further improved in the above range. In particular, 15 wt% to 25 wt% can improve the above-mentioned effects.

The alkyl group-containing (meth) acrylate can form a matrix of an adhesive film. Specifically, the alkyl group-containing (meth) acrylate may include unsubstituted linear or branched alkyl group-containing (meth) acrylic acid esters or alicyclic or aromatic (meth) acrylic acid esters having 1 to 20 carbon atoms. For example, the alkyl group-containing (meth) acrylate may be at least one selected from the group consisting of methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, (meth) acrylate, isooctyl (meth) acrylate, isooctyl (meth) acrylate, pentyl (meth) acrylate, (Meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentanyl (meth) acrylate, tricyclohexyl (meth) acrylate, And cyclodecane dimethanol di (meth) acrylate. More specifically, the alkyl group-containing (meth) acrylate may be a (meth) acrylate ester having an alkyl group having 4 to 8 carbon atoms, and may further increase the initial adhesion of the pressure-sensitive adhesive film. Specifically, the use of a (meth) acrylate having a branched alkyl group may further enhance the initial adhesion. The alkyl group-containing (meth) acrylate may be present in the monomer mixture in an amount ranging from 55% to 96%, such as 55% to 90%, 60% to 95%, 60% to 80% To 85% by weight. The adhesive strength and endurance reliability of the adhesive film can be further improved in the above range.

In one embodiment, the monomer mixture comprising a hydroxyl group-containing (meth) acrylate and an alkyl group-containing (meth) acrylate contains 4 wt% to 45 wt%, specifically 15 wt% to 25 wt% And from 55 wt% to 96 wt%, and specifically from 75 wt% to 85 wt%, of an alkyl group-containing (meth) acrylate. In the above range, folding according to a high elongation may have an excellent effect.

The monomer mixture may further contain comonomers depending on the required physical properties. More preferably, the comonomer having a glass transition temperature of -150 ° C to 0 ° C is preferred. In this case, the glass transition temperature of the (meth) acrylic copolymer formed from the monomer mixture can be lowered, and excellent adhesion can be maintained even at a low temperature (-20 캜), and a similar storage at a high temperature (80 캜) Modulus value.

The comonomer may be selected from the group consisting of a monomer having an amine group, a monomer having an amide group, a monomer having an alkoxy group, a monomer having a phosphoric acid group, a monomer having a sulfonic acid group, a monomer having a phenyl group, a monomer having a silane group, &Lt; / RTI &gt;

Monomers having an amine group include monomethylaminoethyl (meth) acrylate, monoethylaminoethyl (meth) acrylate, monomethylaminopropyl (meth) acrylate, monoethylaminopropyl (meth) acrylate, dimethylaminoethyl Acrylic acid-containing (meth) acrylate such as diethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, N-tert- butylaminoethyl (meth) acrylate, and methacryloxyethyltrimethylammonium chloride But are not necessarily limited to, monomers. In particular, the monomer having an amine group can further increase the peel strength.

The amide group-containing monomer may be at least one monomer selected from the group consisting of (meth) acrylamide, N-methyl acrylamide, N-methylmethacrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (Meth) acrylic monomers having an amide group such as bis (meth) acrylamide, 2-hydroxyethyl (meth) acrylamide, dimethyl (meth) acrylamide and diethyl (meth) acrylamide. It is not.

Examples of the monomer having an alkoxy group include 2-methoxyethyl (meth) acrylate, 2-methoxypropyl (meth) acrylate, 2-ethoxypropyl (meth) (Meth) acrylate, methoxypentyl (meth) acrylate, 3-ethoxypentyl (meth) acrylate, 2-ethoxypentyl ) Acrylate, 3-butoxyhexyl (meth) acrylate, and the like.

The monomer having a phosphoric acid group is preferably selected from the group consisting of 2- (meth) acryloyloxyethyldiphenyl phosphate (meth) acrylate, tri (meth) acryloyloxyethyl phosphate (meth) acrylate, tri (meth) acryloyloxyethyl phosphate (Meth) acrylate, and the like, but is not limited thereto.

The monomer having a sulfonic acid group may be an acrylic monomer having a sulfonic acid group such as sodium sulfopropyl (meth) acrylate, sodium 2-sulfoethyl (meth) acrylate, and sodium 2-acrylamido-2-methylpropane sulfonate But is not necessarily limited thereto.

The monomer having a phenyl group can be an acrylic vinyl monomer having a phenyl group such as p-tert-butylphenyl (meth) acrylate, o-biphenyl (meth) acrylate and phenoxyethyl (meth) acrylate, It is not.

The monomer having a silane group is preferably selected from the group consisting of 2-acetoacetoxyethyl (meth) acrylate, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (beta -methoxyethyl) silane, vinyltriacetoxysilane, Butoxypropyltrimethoxysilane, and the like, but is not limited thereto.

The (meth) acrylate containing an alkylene glycol unit can increase the elongation of the pressure-sensitive adhesive film and provide good folding, thereby making it possible to use the pressure-sensitive adhesive film in a flexible display device. The (meth) acrylate containing an alkylene glycol unit contains a plurality of alkylene glycol units, so that the (meth) acrylic copolymer can be made flexible and the elongation of the adhesive film can be further increased. The "plurality of alkylene glycol units" includes not only a plurality of alkylene glycol units of the same kind but also a plurality of different alkylene glycol units, as well as a case of containing a plurality of different alkylene glycol units. The above-mentioned "alkylene glycol unit" is an alkylene glycol unit having 2 to 5 carbon atoms such as an ethylene glycol group (-CH ₂ CH ₂ O-), a propylene glycol group (-CH ₂ CH ₂ CH ₂ O-, -CH ₂ CH (CH ₃₎ O- or _{-CH (CH 3) CH 2 O-} ), or butylene glycol group _{(-CH 2 CH 2 CH 2 CH} 2 O-, -CH 2 CH 2 CH (CH 3) O - or -CH (CH ₃₎ may represent a CH ₂ CH ₂ O-). Specifically, the alkylene glycol unit-containing (meth) acrylate may include at least one of (meth) acrylate containing at least one of an ethylene glycol unit and a propylene glycol unit. The (meth) acrylate containing ethylene glycol units may be selected from the group consisting of polyethylene oxide monomethyl ether (meth) acrylate, polyethylene oxide monoethyl ether (meth) acrylate, polyethylene oxide monopropyl ether (meth) acrylate, polyethylene oxide monoisopropyl ether (Meth) acrylate, polyethylene oxide monobutyl ether (meth) acrylate, polyethylene oxide monoisobutyl ether (meth) acrylate, polyethylene oxide mono butyl ether (meth) acrylate, polyethylene oxide monopentyl ether But are not limited to, polyethylene oxide alkylether (meth) acrylates such as polyethylene oxide dimethylether (meth) acrylate, polyethylene oxide diethylether (meth) acrylate and the like. The propylene glycol unit-containing (meth) acrylate may be at least one selected from the group consisting of polypropylene oxide monomethyl ether (meth) acrylate, polypropylene oxide monoethyl ether (meth) acrylate, polypropylene oxide monopropyl ether (meth) acrylate, polypropylene oxide mono (Meth) acrylate, polypropylene oxide monobutyl ether (meth) acrylate, polypropylene oxide monoisobutyl ether (meth) acrylate, polypropylene oxide mono butyl ether (meth) acrylate, polypropylene oxide (Meth) acrylate such as polypropylene oxide alkylether (meth) acrylate, polypropylene oxide dimethylether (meth) acrylate, polypropylene oxide diethylether (meth) , But is not limited to . These may be used alone or in combination of two or more.

The monomer having a glass transition temperature of -150 DEG C to 0 DEG C in the comonomer, particularly the homopolymer, is contained in the monomer mixture in an amount of 30 wt% or less, specifically 0 wt% to 30 wt%, more specifically 0.1 wt% to 20 wt% 0.1% by weight to 10% by weight. Within this range, an effect of excellent viscoelasticity at low temperature may be obtained.

The monomer mixture may further comprise a monomer having a carboxylic acid group. The monomer having a carboxylic acid group may be at least one monomer selected from the group consisting of (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, 3-carboxypropyl (meth) acrylate, 4-carboxybutyl (meth) acrylate, itaconic acid, Maleic anhydride, and the like, but are not necessarily limited thereto. The monomer having a carboxylic acid group may be contained in the monomer mixture in an amount of 5% by weight or less, specifically 3% by weight or less, more specifically 1% by weight or less. In the above range, the pressure-sensitive adhesive composition can further improve the adhesive strength and durability of the pressure-sensitive adhesive film.

In another embodiment, the monomer mixture comprising a hydroxyl group-containing (meth) acrylate, an alkyl group-containing (meth) acrylate, and a comonomer may comprise from 5% to 40% (Meth) acrylate containing 30% by weight alkyl group, from 55% by weight to 90% by weight, specifically from 60% by weight to 80% by weight, and from 0.1% by weight to 30% by weight, have. Within this range, there can be an excellent effect of folding along a high elongation.

The monomer mixture may further comprise a macromonomer. The macromonomer can further exert an excellent effect of adhesion on the adhesive film as the cohesive force improves. Macromonomers have functional groups curable by an active energy beam and can be polymerized with one or more of the abovementioned monomers. The macromonomer may be represented by the following formula:

&Lt; Formula 1 >

(In Formula 1, R ¹ is hydrogen or a methyl group, X is a divalent coupler, Y is methyl (meth) acrylate, ethyl (meth) acrylate, n- butyl (meth) acrylate, iso- butyl (meth) (Meth) acrylate, t-butyl (meth) acrylate, styrene, and (meth) acrylonitrile.

2 the coupler is an arylene group, -NR a C1 to C10 alkyl groups, C7 to C13 aryl alkyl group, C6 to C12 ² - (wherein, R ² is an alkyl group of hydrogen, or a C1 to C5), COO-, - _{O-, -S-, -SO 2 NH-,} -NHSO 2 -, may be a group derived from -NHCOO-, -OCONH, or heterocyclic. The divalent linking group may be represented by the following general formulas (1a) to (1d):

<Formula 1a>

&Lt; EMI ID =

&Lt; Formula 1c >

<Formula 1d>

(In the above Chemical Formulas (1a) to (1d), * denotes the connecting site of the element)

The macromonomer may have a number average molecular weight of 2,000 to 20,000, specifically 2,000 to 10,000, more specifically 4,000 to 8,000. Within the above range, sufficient adhesive strength can be obtained, heat resistance is excellent, and deterioration of workability due to an increase in viscosity of the pressure-sensitive adhesive composition can be suppressed. The macromonomer may have a glass transition temperature of from 40 캜 to 150 캜, specifically from 60 캜 to 140 캜, more specifically from 80 캜 to 130 캜. In the above range, the pressure-sensitive adhesive film can exhibit sufficient cohesive strength, and the degree of stickiness and deterioration of the adhesive force can be suppressed.

Commercial macromonomers may be used. For example, the terminal is a methacryloyl group; And a macromonomer having a Y segment of methyl methacrylate, a macromonomer having a Y segment of styrene, a macromonomer having a Y segment of styrene / acrylonitrile, and a macromonomer having a Y segment of butyl acrylate. The macromonomer may be contained in an amount of 20 wt% or less, specifically 0.1 wt% to 20 wt%, or 0.5 wt% to 10 wt% in the adhesive film. Within the above range, the viscoelasticity of the pressure-sensitive adhesive film can be balanced with the modulus and the restoring force, and the peeling force is increased.

In one embodiment, from 4% by weight to 40% by weight, specifically from 5% by weight to 20% by weight, of a hydroxyl group-containing (meth) acrylate in the total of the hydroxyl group-containing (meth) acrylate, the alkyl group- From 55% by weight to 95% by weight, specifically from 75% by weight to 90% by weight of the alkyl group-containing (meth) acrylate, from 0.1% by weight to 20% by weight, specifically from 0.5% by weight to 10% by weight of the macromonomer. In the above range, the folding performance at the high temperature 60 may be excellent.

The organic nanoparticles are incorporated in the pressure-sensitive adhesive composition so that the difference in the restoring force and the restoring force at high temperature compared with the room temperature can be minimized, the peeling strength and the restoring force can be increased at high temperature, and the reliability can be improved. The organic nanoparticles may have an average particle diameter of 10 nm to 400 nm, specifically 10 nm to 300 nm, more specifically 10 nm to 200 nm, more specifically 50 nm to 150 nm. Within this range, aggregation of the organic nanoparticles can be prevented, the folding of the adhesive film is not affected, and the transparency of the adhesive film can be good. The organic nanoparticles have a refractive index difference of 0.05 or less, specifically 0 or more and 0.03 or less, specifically 0 or more and 0.02 or less, with respect to the (meth) acrylic copolymer, for example, a hydroxyl group and an alkyl group- . In the above range, the transparency of the adhesive film can be excellent. The refractive index of the organic nanoparticles may be 1.40 to 1.70, specifically 1.45 to 1.60. Within the above range, the transparency of the adhesive film may be excellent.

The organic nanoparticles may include, but are not limited to, core-shell type and simple nanoparticles such as a bead type. In the case of the core-shell structure, the core and the shell can satisfy the following formula 5: When the above-mentioned particle form is used, the folding property of the pressure-sensitive adhesive film is good and it may be effective in balance and physical properties of elasticity and flexibility.

&Lt; EMI ID =

Tg (c) < Tg (s)

(Unit: 占 폚), and Tg (s) is the glass transition temperature (unit: 占 폚) of the shell.

As used herein, the term "shell" means the outermost layer of the organic nanoparticles. The core may be a single spherical particle. However, the core may further comprise additional layers surrounding the spherical particles if they have the above glass transition temperature.

Specifically, the glass transition temperature of the core may be -150 ° C to 10 ° C, specifically -150 ° C to -5 ° C, more specifically -150 ° C to -20 ° C. Within this range, there may be a low temperature and / or room temperature viscoelastic effect of the adhesive film. The core may include at least one of polyalkyl (meth) acrylate, polysiloxane, and polybutadiene having the above glass transition temperature.

The polyalkyl (meth) acrylate may be at least one selected from the group consisting of polymethyl acrylate, polyethylacrylate, polypropyl acrylate, polybutyl acrylate, polyisopropyl acrylate, polyhexyl acrylate, polyhexyl methacrylate, polyethylhexyl acrylate And polyethylhexyl methacrylate, polysiloxane, and is not necessarily limited thereto.

The polysiloxane can be, for example, an organosiloxane (co) polymer. The organosiloxane (co) polymer may be one which is not cross-linked, or a cross-linked (co) polymer may be used. In order to impart impact resistance and colorability, an organosiloxane (co) polymer in a crosslinked state can be used. It is a crosslinked form of organosiloxane, specifically crosslinked dimethylsiloxane, methylphenylsiloxane, diphenylsiloxane or a mixture of two or more thereof. By using a copolymerized form of two or more organosiloxanes, the refractive index can be adjusted from 1.41 to 1.50.

The crosslinking state of the organosiloxane (co) polymer can be determined by the degree of dissolution by various organic solvents. As the crosslinking state deepens, the degree of dissolution by the solvent becomes smaller. As the solvent for determining the crosslinking state, acetone, toluene and the like can be used. Specifically, the organosiloxane (co) polymer may have a portion which is not dissolved by acetone or toluene. The insoluble matter to the toluene of the organosiloxane copolymer may be 30% or more.

Additionally, the organosiloxane (co) polymer may further comprise an alkyl acrylate crosspolymer. The alkyl acrylate crosslinked polymer may be selected from the group consisting of methyl acrylate, ethyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate. For example, n-butyl acrylate or 2-ethylhexyl acrylate having a low glass transition temperature may be used.

Specifically, the glass transition temperature of the shell may be from 15 캜 to 150 캜, specifically from 35 캜 to 150 캜, more specifically from 50 캜 to 140 캜. In the above range, the dispersibility of the organic nanoparticles in the (meth) acrylic copolymer may be excellent. The shell may comprise a polyalkyl methacrylate having said glass transition temperature. For example, it is possible to use polymethylmethacrylate (PMMA), polyethylmethacrylate, polypropylmethacrylate, polybutylmethacrylate, polyisopropylmethacrylate, polyisobutylmethacrylate and polycyclohexylmethacrylate Rate, &lt; / RTI &gt; but is not necessarily limited thereto.

The core may comprise from 30 wt% to 99 wt%, specifically from 40 wt% to 95 wt%, and more specifically from 50 wt% to 90 wt%, of the organic nanoparticles. Within the above range, the folding property of the pressure-sensitive adhesive film may be good in a wide temperature range. The shell may comprise from 1 wt% to 70 wt%, specifically from 5 wt% to 60 wt%, more specifically from 10 wt% to 50 wt%, of the organic nanoparticles. Within the above range, the folding property of the pressure-sensitive adhesive film may be good in a wide temperature range.

The organic nanoparticles are contained in an amount of 0.1 to 20 parts by weight, specifically 0.1 to 10 parts by weight, more specifically 1 to 10 parts by weight, per 100 parts by weight of the monomer mixture for forming the (meth) acrylic copolymer . Within this range, there is an excellent effect of folding at a high temperature (60 DEG C), and a balance between the viscoelasticity, the modulus and the recovery force of the pressure-sensitive adhesive film can be achieved.

Organic nanoparticles can be prepared by emulsion polymerization, suspension polymerization, or solution polymerization.

The initiator may cure the (meth) acrylic copolymer formed from the monomer mixture. As the initiator, a photopolymerization initiator or a thermal polymerization initiator can be used. The initiator may be the same as or different from the initiator used in preparing the partially polymerized prepolymer. As the photopolymerization initiator, any photopolymerization initiator may be used as long as it can induce the polymerization reaction of the radical polymerizable compound described above during the curing process by light irradiation or the like. For example, benzoin, acetophenone, hydroxy ketone, amino ketone or phosphine oxide photoinitiators can be used. Specific examples thereof include benzoin, benzoin methyl ether, benzoin ethyl ether, benzo Benzoin isobutyl ether, acetophenone, dimethyl anino acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenyl Methyl-1- [4- (methylthio) phenyl] -2-morpholino-acetamide, acetophenone, 2-hydroxy- Propane) ketone, benzophenone, p-phenylbenzophenone, 4,4-non-cydiethylaminobenzophenone, dichloro (2-hydroxypropyl) Benzoquinone, 2-methyl anthraquinone, 2-ethyl anthraquinone, 2-t-butyl anthraquinone, 2-amino anthraquinone, thioxanthone, 2-ethyl thioxanthone, 2- , 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoic acid ester, oligo [2-hydroxy- (1-methylvinyl) phenyl] propanone] and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide. In the present application, one kind or more kinds of the above can be used, but the present invention is not limited thereto. The type of the thermal polymerization initiator is not particularly limited as long as it can induce polymerization reaction of the polymerizable compound. For example, a conventional initiator such as an azo-based compound, a peroxide compound or a redox- Can be used. Examples of the azo compound include 2,2-azobis (2-methylbutyronitrile), 2,2-triyl azo bis (isobutyronitrile), 2,2-triazabis 2-methyl azo bis (2-methylpropionate) and 2,2-phylazobis (4- (4-methoxyphenyl) Methoxy-2,4-dimethylvaleronitrile), and the like, and examples of the peroxide compound include inorganic peroxides such as potassium persulfate, ammonium persulfate or hydrogen peroxide; Or peroxydicarbonate, peroxydicarbonate, peroxy ester, tetramethyl butyl peroxyneodecanoate, bis (4-butylcyclohexyl) peroxydicarbonate, di (2-ethylhexyl) peroxycarbonate, Hexyl peroxy dicarbonate, dimethoxy butyl peroxy dicarbonate, hexyl peroxy dicarbonate, hexyl peroxy dicarbonate, diisopropyl peroxy dicarbonate, diethoxy ethyl peroxy dicarbonate, diethoxyhexyl peroxy dicarbonate, , Bis (3-methoxy-3-methoxybutyl) peroxy dicarbonate, dibutyl peroxy dicarbonate, dicetyl peroxy dicarbonate, dimyristyl peroxy dicarbonate, 1,1 , 3,3-tetramethylbutyl peroxypivalate, hexyl peroxypivalate, butyl peroxypivalate, trimethylhexanoyl peroxide, dimethylhydroxybutyl peroxy Amyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, amyl peroxy pivalate, t-butyl peroxy pivalate, t-amyl peroxide, Organic peroxides such as peroxy-2-ethylhexanoate, lauryl peroxide, dilauroyl peroxide, didecanoyl peroxide, benzoyl peroxide or dibenzoyl peroxide, Examples of the system compound include, but are not limited to, a mixture of a peroxide compound and a reducing agent in combination. In the present application, one kind or a mixture of two or more kinds of azo type, peroxide type or redox type compound as described above can be used. The initiator may be included in an amount of 0.0001 to 5 parts by weight, specifically 0.001 to 3 parts by weight, more specifically 0.001 to 1 part by weight, based on 100 parts by weight of the monomer mixture for forming the (meth) acrylic copolymer In the above range, the curing reaction can be completely proceeded, the remaining amount of the initiator remains, the permeability can be prevented from being lowered, the bubble generation can be lowered, and the reactivity can be improved.

The pressure-sensitive adhesive composition may further include a crosslinking agent. The cross-linking agent can increase the degree of crosslinking of the pressure-sensitive adhesive composition and increase the mechanical strength of the pressure-sensitive adhesive film. The crosslinking agent may comprise a multifunctional (meth) acrylate capable of curing with an active energy beam. In an embodiment, the crosslinking agent is selected from the group consisting of 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di Neopentylglycol adipate di (meth) acrylate, dicyclopentanyl di (meth) acrylate, caprolactone modified dicyclopentenyl di (meth) acrylate, ethylene oxide modified di Acrylate, di (meth) acryloxyethyl isocyanurate, allyl cyclohexyl di (meth) acrylate, tricyclodecane dimethanol (meth) acrylate, dimethylol dicyclopentanedi (meth) Ethylene oxide modified hexahydrophthalic acid di (meth) acrylate, tricyclodecane dimethanol (meth) acrylate, neopentyl glycol modified trimethylpropane di (meth) acrylate, Bifunctional acrylates such as adamantane di (meth) acrylate or 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene; (Meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide Trifunctional acrylates such as modified trimethylolpropane tri (meth) acrylate, trifunctional urethane (meth) acrylate or tris (meth) acryloxyethylisocyanurate; Tetrafunctional acrylates such as diglycerin tetra (meth) acrylate or pentaerythritol tetra (meth) acrylate; Pentafunctional acrylates such as dipentaerythritol penta (meth) acrylate; (Meth) acrylate, dipentaerythritol hexa (meth) acrylate, caprolactone modified dipentaerythritol hexa (meth) acrylate or urethane (meth) acrylate (ex. Isocyanate monomer and trimethylol propane tri (Meth) acrylates of polyhydric alcohols can be used as the crosslinking agent. The polyfunctional (meth) acrylates of polyhydric alcohols may be used alone or in combination of two or more. The crosslinking agent may be included in an amount of 0.001 to 5 parts by weight, specifically 0.003 to 3 parts by weight, specifically 0.005 to 1 part by weight, based on 100 parts by weight of the monomer mixture for forming the (meth) acrylic copolymer There is an effect of excellent adhesion and reliability in the above range.

The pressure-sensitive adhesive composition may further include a silane coupling agent. The silane coupling agent is free from bubbles or peeling even if the adhesive film is allowed to stand at a high temperature and a high humidity for a predetermined time in a frame having a predetermined radius of curvature, so that reliability can be improved. As the silane coupling agent, those conventionally known to those skilled in the art can be used. For example, there can be mentioned 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyl tri A silicon compound having an epoxy structure such as methoxysilane; A polymerizable unsaturated group-containing silicon compound such as vinyltrimethoxysilane, vinyltriethoxysilane and (meth) acryloxypropyltrimethoxysilane; Containing silicon compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane. ; And 3-chloropropyltrimethoxysilane, and the like, but are not limited thereto. Preferably, a silane coupling agent having an epoxy structure can be used. The silane coupling agent may be contained in an amount of 0.01 to 3 parts by weight, specifically 0.01 to 1 part by weight, based on 100 parts by weight of the sum of the hydroxyl group-containing (meth) acrylate and alkyl group-containing (meth) acrylate. In the above range, reliability can be secured in the bending state at the high temperature and high humidity described above, and the difference in peeling force between low temperature, normal temperature and high temperature can be low. The pressure-sensitive adhesive composition may optionally contain a curing accelerator, an ionic liquid, a lithium salt, an inorganic filler, a softener, a molecular weight modifier, an antioxidant, an antioxidant, a stabilizer, a tackifier resin, a modifying resin (polyol resin, phenol resin, (Coloring pigments, extender pigments, etc.), treating agents, ultraviolet light blocking agents, fluorescent whitening agents, dispersing agents, heat stabilizers, antioxidants, antioxidants, A light stabilizer, an ultraviolet absorber, an antistatic agent, a coagulant, a lubricant and a solvent. The pressure-sensitive adhesive composition may have a viscosity at 25 ° C ranging from 300 cPs to 50,000 cPs, and may have an effect of obtaining excellent coating and thickness uniformity in the above range.

Hereinafter, a method for producing a pressure-sensitive adhesive composition according to an embodiment of the present invention will be described.

The pressure-sensitive adhesive composition is produced by partially polymerizing the above-mentioned monomer mixture to prepare a viscous liquid containing a hydroxyl group and an alkyl group-containing (meth) acrylic copolymer (prepolymer) and an un polymerized monomer mixture and then adding an initiator and / Compositions may be prepared. A crosslinking agent, a silane coupling agent, an additive, and the like may be further included. In another embodiment, the pressure-sensitive adhesive composition is prepared by partially polymerizing a mixture containing the monomer mixture and the organic nanoparticles to prepare a viscous liquid containing a hydroxyl group and an alkyl group-containing (meth) acrylic copolymer (prepolymer) The pressure-sensitive adhesive composition may be prepared by incorporating an initiator. A crosslinking agent, a silane coupling agent, an additive, and the like may be further included. Partial polymerization may include solution polymerization, suspension polymerization, photopolymerization, bulk polymerization, or emulsion polymerization. Specifically, the solution polymerization can be carried out at 50 DEG C to 100 DEG C by adding an initiator to the monomer mixture. The initiator may be an acetophenone radical photopolymerization initiator including 2,2-dimethoxy-2-phenylacetophenone and the like. The partial polymerization can be polymerized at 25 DEG C with a viscosity of 1,000 to 10,000 cPs, specifically a viscosity of 2,000 to 9,000 cPs.

The optical member according to an embodiment of the present invention includes an optical film and an adhesive film formed on at least one side of the optical film, and the adhesive film may include an adhesive film according to embodiments of the present invention. Thus, the optical member has good bending and / or good folding properties and can be used in a flexible display device. However, the optical member can also be used in non-flexible display devices.

The optical film may be at least one selected from the group consisting of a window film, a window, a polarizing plate, a color filter, a retardation film, an elliptically polarizing film, a reflective polarizing film, an antireflection film, OLED device barrier layers, plastic LCD substrates, indium tin oxide (ITO), fluorinated tin oxide (FTO), aluminum doped zinc oxide (AZO), carbon nanotubes (CNT), nanowires such as Ag nanowires and graphene , And the like. The method for producing an optical film can be easily manufactured by a person having ordinary skill in the art to which the present invention belongs. For example, the touch panel can be formed by attaching the touch pad to a window or an optical film using an adhesive film. Or may be applied to an ordinary polarizing film as an adhesive film as in the prior art.

The optical display device of the present invention may include the pressure-sensitive adhesive film of the present invention. The optical display device may include an organic light emitting diode display, a liquid crystal display, and the like. The optical display device may include a flexible display device. However, the optical display device may include a non-flexible display device.

Hereinafter, a flexible display device according to an embodiment of the present invention will be described with reference to FIG. 1 is a cross-sectional view of a flexible display device according to an embodiment of the present invention.

1, a flexible display device 100 according to an exemplary embodiment of the present invention includes a display unit 110, an adhesive layer 120, a polarizer 130, a touch screen panel 140, and a flexible window film 150, and the adhesive layer 120 may include an adhesive film according to an embodiment of the present invention.

The display unit 110 is for driving the flexible display device 100 and may include an optical element including an OLED, an LED, a quantum dot light emitting diode (QLED) formed on a substrate and a substrate, or an LCD device. Although not shown in FIG. 3, the display unit 110 may include a lower substrate, a thin film transistor, an organic light emitting diode, a planarization layer, a protection layer, and an insulation layer.

The polarizing plate 130 may implement polarizing of the inner light or prevent reflection of the external light to realize the display or increase the contrast ratio of the display. The polarizing plate may be composed of a polarizer alone. Or the polarizing plate may include a polarizing film and a protective film formed on one or both sides of the polarizing film. Or the polarizing plate may include a polarizer and a protective coating layer formed on one or both sides of the polarizer. The polarizer, the protective film, and the protective coating layer may be conventional ones known to those skilled in the art.

The touch screen panel 140 senses a change in capacitance caused when a conductor such as a human body or a stylus touches, and generates an electrical signal. The display unit 110 can be driven by this signal. The touch screen panel 140 may include a first sensor electrode and a second sensor electrode formed between the first sensor electrode and the first sensor electrode, which are formed by patterning a conductive conductive material. have. The conductors for the touch screen panel 340 may include, but are not limited to, metal nanowires, conductive polymers, carbon nanotubes, and the like.

The flexible window film 150 may be formed at the outermost portion of the flexible display device 300 to protect the display device.

1, an adhesive layer is further formed between the polarizer 130 and the touch screen panel 140 and / or between the touch screen panel 140 and the flexible window film 150, thereby forming a polarizing plate, a touch screen panel, It is possible to strengthen the bonding between the window films. In one embodiment, the adhesive layer may be formed of a pressure sensitive adhesive composition comprising a (meth) acrylate based resin, a curing agent, an initiator, and a silane coupling agent. In other embodiments, the adhesive layer may comprise an adhesive film according to one embodiment of the present invention. Further, although not shown in FIG. 1, a polarizing plate is further provided under the display unit 110, so that polarized light can be realized.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It should be understood, however, that the same is by way of illustration and example only and is not to be construed in any way as limiting the invention.

Manufacturing example  One

Organic nanoparticles of core-shell structure were prepared by emulsion polymerization. The core is polybutyl acrylate, the shell is polymethyl methacrylate, the shell is 30 wt% of the organic nanoparticles, the core is 70 wt% of the organic nanoparticles, the average particle diameter is 130 nm, and the refractive index is 1.48 .

Manufacturing example  2

Organic nanoparticles of core-shell structure were prepared by emulsion polymerization. Wherein the core is polyethyl hexyl acrylate and the shell is polymethyl methacrylate and the shell is 30 wt% of the organic nanoparticles, the core is 70 wt% of the organic nanoparticles, the average particle diameter is 140 nm, the refractive index is 1.48, Particles were prepared.

Example  One

100 parts by weight of a monomer mixture comprising 80 parts by weight of 2-ethylhexyl acrylate (2-EHA) and 20 parts by weight of 4-hydroxybutyl acrylate (4-HBA), 3 parts by weight of the organic nanoparticles of Preparation Example 1, 0.005 parts by weight of Irgacure 651 (BASF) as an initiator were mixed well in the reactor. After the dissolved oxygen in the reactor was replaced with a nitrogen gas, the mixture was partially polymerized by irradiation with ultraviolet light for a few minutes using a low-pressure mercury lamp (BL lamp, manufactured by Sankyo) to obtain a hydroxyl group-containing (meth) acrylic copolymer (prepolymer) A viscous liquid (viscosity: 2130 cps) consisting of an un polymerized monomer mixture was prepared. 0.3 part by weight of initiator Irgacure 184 (BASF) was added to the viscous liquid and mixed to prepare a pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition was coated on a PET (polyethylene terephthalate) film (thickness: 50 탆) as a release film and covered with a 75 탆 thick release film on the upper side. Then, a low pressure lamp (50 mW / cm ² , Wavelength: 350 nm, BL Lamp manufactured by Sankyo Company) to obtain a transparent pressure-sensitive adhesive sheet having an adhesive film thickness of 50 탆.

Example  2 and Example  6

A transparent pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that the content of the monomers was changed as shown in Table 1 below.

Example  3 to Example  5

The content of each of 2-EHA, 4-HBA and 2- (diethylamino) ethyl acrylate (DEAA) in Example 1 was changed as shown in Table 1 below, and the types of the organic nanoparticles were changed to the following Table 1 A transparent pressure-sensitive adhesive sheet was obtained in the same manner.

Comparative Example  One

In Example 1, the content of 2-EHA, 2-HEA, and organic nanoparticles was changed as shown in Table 1 by changing 2-HEA (hydroxyethyl acrylate) instead of 4-HBA as shown in Table 1 The pressure-sensitive adhesive sheet was prepared in the same manner as described above.

The properties of the pressure-sensitive adhesive sheet prepared in Examples and Comparative Examples were evaluated in the following Table 1, and the results are shown in Table 1 and FIG.

(1) tan δ: The pressure-sensitive adhesive composition The release film was coated (for example, polyethylene terephthalate, PET film) and covering the release film of 75 ㎛ thickness on top, a low-pressure lamp for 6 minutes in the two-sided (50mw / cm ^2, (BL Lamp manufactured by Sankyo Co., Ltd.) to produce an adhesive film (thickness: 50 탆). The viscoelasticity was measured under a condition of auto strain at a shear rate of 1 rad / sec and a strain of 1% using a rheometer (Anton Paar MCR-501), which is a dynamic viscoelasticity measuring device. After removing the release film, the adhesive film was laminated to a thickness of 500 탆, and the laminate was punched with a perforator having a diameter of 8 mm and used as a specimen. The measurement was carried out with a jig of 8 mm while raising the temperature at a temperature rising rate of 5 / min at -30 캜 to 80 캜 under a load of 300 gf for the specimen. The measurement value of the minimum value of tan delta and the minimum value of tan delta and the minimum value of tan delta at -30 deg. C to 80 deg.

(2) Restoring force: The releasing film was released on the pressure-sensitive adhesive sheet of Examples and Comparative Examples to obtain a pressure-sensitive adhesive film. Resilience was evaluated by TA.XT_Plus Texture Analyzer (Stable Micro System).

2 (a) and 2 (b), when both end portions of a PET (polyethylene terephthalate) film (thickness: 75 μm) of width × length (50 mm × 20 mm) are respectively referred to as a first end portion and a second end portion (20 mm x 20 mm) in the order of the first end portion of the PET film / the second end portion of the PET film and the second end portion of the PET film, and the PET film (20 mm x 20 mm) between the adhesive film and the adhesive film. 2 (a), a jig is fixed to both end portions of the unprinted PET film of the specimen at 25 ° C, one of the jigs is fixed, and the other jig is fixed at 300 mm / min the thickness of the adhesive film at a rate (10 times the initial thickness of the adhesive film, X ₃₎ 1000% length of the (initial thickness:: X _0, unit ㎛) maintained for 10 seconds and pulled by the speed, pull the adhesive film (300 mm / min), and the stretched length of the pressure-sensitive adhesive film when a pressure of 0 kPa is applied to the pressure-sensitive adhesive film is defined as X ₂ (unit: μm). X ₂ and X ₃ are obtained at 60 ° C in the same manner as described above. Referring to FIG. 3, a graph is obtained with the stretched length of the adhesive film as the X-axis and the force applied to the adhesive film as the Y-axis. The restoring force is a value calculated by the following formula 2:

<Formula 2>

Restoring force = (1 - (X ₂ ) / (X ₃ )) x 100

(3) Difference in restoration force and difference in restoration force: Calculated using Equation 3 and Equation 4 using the restoring force of (2).

(4) Peel strength: The corona was treated twice (total dose: 156 dose) on a PET film of width x length x thickness (150 mm x 25 mm x 75 m) while discharging the plasma at a dose of 78 dose using a corona processor (NOW PLASMA). An adhesive film was obtained in the size of the width x length x thickness (100 mm x 25 mm x 50 m) in the transparent pressure sensitive adhesive sheet of Examples and Comparative Examples. The corona-treated PET film was laminated on both sides of the adhesive film and passed through a 2KG roller to prepare the specimen shown in Fig. 4 (a). The specimen was autoclaved at a pressure of 3.5 bar at 50 ° C for 1000 seconds and the peel strength was measured by fixing the specimen to a TA.XT_Plus Texture Analyzer (Stable Micro System). Referring to FIG. 4 (b), one PET film was fixed and another PET film was pulled at a rate of 50 mm / min at 25 ° C in a TA.XT_Plus Texture Analyzer, and 90 ° T-Peel peeling at 25 ° C The strength was measured. The sample was aged at 25 DEG C for 24 hours, and then peel strength at 90 DEG C was measured at 60 DEG C in a TA.XT_Plus Texture Analyzer at 60 DEG C by the same method.

(5) Bubble generation: An adhesive film having a thickness of 50 占 퐉 on one side of an adhesive film (13 cm 占 3 cm in length, 100 占 퐉 in thickness) and PET having a thickness of 100 占 퐉 on the back surface of the above- The PET film was bent in the direction of the PET with a thickness of 50 mu m so that the transverse length of the adhesive film was 1/2 between the parallel frames, aged at 70 DEG C and 93% relative humidity for 24 hours and irradiated with an optical microscope (Olympus EX-51 , 30 magnification) to evaluate the occurrence of bubbles.

(6) Modulus: The pressure-sensitive adhesive composition was coated on a release film (for example, polyethylene terephthalate or PET film), and a 75 μm thick release film was coated on the upper side. Then, a low pressure lamp (50 mw / cm ² , Sankyo (BL Lamp manufactured by Nihon Univ.) To produce an adhesive film. The viscoelasticity was measured at a shear rate of 1 rad / sec and strain 1% under an auto strain condition using a rheometer (Anton Paar MCR-501), a dynamic viscoelasticity measuring device. After removing the releasing film, the pressure-sensitive adhesive film was laminated to a thickness of 1 mm, and the laminate was perforated with a perforator having a diameter of 8 mm and used as a specimen. Using a 8 mm jig, a load of 300 gf was applied to the specimen, and the measurement was carried out at a temperature rising rate of 5 DEG C / min at -60 DEG C to 90 DEG C, and the modulus was recorded at -20 DEG C and 80 DEG C.

(7) Haze: Haze meter (model Nippon Denshoku Model NDH 5000) was used. The haze was measured for an adhesive film having a thickness of 50 탆 according to ASTM D 1003-95 5 ("Standard Test for Haze and Luminous Transmittance of Transparent Plastic").

Example Comparative Example One 2 3 4 5 6 One Monomer mixture
(Parts by weight) 2-EHA 80 78 79 82 80 82 65 4-HBA 20 22 20 17 19 18 0 DEAA 0 0 One One One 0 0 2-HEA 0 0 0 0 0 0 35 Organic nanoparticles
(Parts by weight) Production Example 1 3 3 3 3 0 3 0 Production Example 2 0 0 0 0 3 0 0 Initiator
(Parts by weight) Irgacure651 0.005 0.005 0.005 0.005 0.005 0.005 0.005 Irgacure184 0.3 0.3 0.3 0.3 0.3 0.3 0.3 tanδ Minimum value has exist has exist has exist has exist has exist has exist none Minimum value Measuring temperature (℃) 11.69 10.18 15.48 14.82 14.26 13.18 - Minimum value 0.253 0.239 0.227 0.212 0.233 0.264 - dynamic stability
(%) @ 25 ℃ 92 88 88 89 83 94 74 @ 60 ℃ 90 79 86 86 78 92 33 % Reduction of resilience 2.17 10.23 2.27 3.37 6.02 2.13 55.41 Resilience Difference (%) 2 9 2 3 5 2 41 Peel strength
(gf / in) @ 25 ℃ 1139 1428 1600 1816 1633 1320 646 @ 60 ℃ 814 839 896 869 845 767 572 Peel strength reduction ratio (%) 28.5 41.2 44 52.15 48.25 41.90 11.46 Peel strength difference (gf / in) 325 589 704 947 788 553 74 Bubble generation none none none none none none has exist Modulus
(kPa) @ -20 ℃ 72.3 54.1 79.3 79.9 74.8 79.7 695 @ 80 ℃ 20.3 15.8 23.9 24.0 19.0 17.5 29 Modulus at 80 &lt; 0 &
: Modulus at -20 &lt; 0 &gt; C 1: 3.56 1: 3.42 1: 3.32 1: 3.33 1: 3.94 1: 4.55 1: 23.97 Haze (%) 0.98 0.81 0.79 0.91 0.84 0.78 0.57

The adhesive film of the present invention has a minimum tan δ of 0 ° C. to 20 ° C. when the tan δ is measured at -30 ° C. to 80 ° C. as shown in Table 1 and FIG. 5, and the minimum value of tan δ is 0.2 To 0.4. As shown in Table 1, the adhesive film of the present invention can minimize the difference in restitution force between high temperature and normal temperature, has excellent peel strength even at high temperature, and has high reliability due to suppression of bubble formation at high temperature. In addition, the pressure-sensitive adhesive film of the present invention has a high modulus at high temperature, has excellent foldability at high temperatures, has an effect of preventing the adhesive film from being broken, and is optically transparent because of low haze.

On the other hand, as shown in Table 1 and FIG. 5, the adhesive film of the comparative example did not have a minimum tan δ value, and tan δ was continuously decreased with increasing the measuring temperature, and the reduction ratio and the restoring force difference The film was large compared to the film, the peel strength was low at high temperature, and bubbles were generated at high temperature.

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.

Claims (15)

When tan? Is measured at -30 占 폚 to 80 占 폚,
Lt; RTI ID = 0.0 &gt; 0 C &lt; / RTI &gt; to 20 C,
Wherein the minimum value of the tan delta is 0.2 to 0.4.
The peel strength at 60 占 폚 is 700 gf / in or more,
Wherein the restoring force reduction ratio in the following 3 is 50% or less,
<Formula 3>
Strength reduction ratio = (Strength 1 - Strength 2) / (Strength 1) x 100
(In the above formula 3, the restoring force 1 is the restoring force (unit:%) of the pressure-sensitive adhesive film at 25 캜,
The restoring force 2 is the restoring force (unit:%) of the pressure-sensitive adhesive film at 60 DEG C)
The adhesive film according to any one of claims 1 to 3, wherein the difference in restitution force of the following formula (4) is 40% or less:
<Formula 4>
Resilience Difference = Resilience 1 - Resilience 2
(In the formula (4), the restoring force 1 is the restoring force (unit:%) of the pressure-sensitive adhesive film at 25 캜,
Restorative force 2 is the restoring force (unit:%) of the adhesive film at 60 ° C)
The adhesive film according to any one of claims 1 to 3, wherein the restoring force of the following formula (2) is not less than 40% at 60 캜:
<Formula 2>
Restoring force = (1 - (X ₂ ) / (X ₃ )) x 100
(20 mm x 20 mm) when the both ends of a PET (polyethylene terephthalate) film (thickness: 75 m) of width x length (50 mm x 20 mm) are referred to as a first end portion and a second end portion, 20 mm), and the PET film was adhered in the order of the first end portion / the adhesive film of the PET film / the second end portion of the PET film, and the contact area between the PET film and the adhesive film was For a specimen having a width × length (20 mm × 20 mm), a jig was fixed to both end portions of the PET film at 60 ° C., one jig was fixed at 10 MPa and the other jig was pulled at a rate of 300 mm / min After reaching a length of 1000% (10 times the thickness, X ₃ ) of the thickness (unit: 탆) of the pressure-sensitive adhesive film, it was maintained for 10 seconds to remove stress, and the stretched length of the pressure-sensitive adhesive film was applied to the X- When a graph is obtained with the lagging force as the Y-axis, the adhesive film has a thickness of 100 Then it increased to 0%, pull rate and length equal to restore the speed (300mm / min) to increase the length of the adhesive film when the adhesive film is applied to the force of 0kPa X ₂ (unit: ㎛) a).
The adhesive film according to claim 1 or 2, wherein the pressure-sensitive adhesive film has a modulus of 10 kPa to 500 kPa at 80 캜.
The adhesive film according to claim 1 or 2, wherein the adhesive film has a haze of 2% or less at a wavelength of 380 nm to 780 nm.
The pressure-sensitive adhesive film of claim 1 or 2, wherein the pressure-sensitive adhesive film comprises a pressure-sensitive adhesive composition comprising a monomer mixture comprising a hydroxyl group-containing (meth) acrylate and an alkyl group-containing (meth) acrylate and organic nanoparticles.
The adhesive film according to claim 7, wherein the organic nanoparticles have an average particle diameter of 10 nm to 400 nm.
8. The method of claim 7, wherein the organic nanoparticles are core-
Wherein the core and the shell satisfy the following formula 5:
&Lt; EMI ID =
Tg (c) &lt; Tg (s)
(Unit: 占 폚), and Tg (s) is the glass transition temperature (unit: 占 폚) of the shell.
The adhesive film according to claim 7, wherein the organic nanoparticles are contained in an amount of 0.1 to 20 parts by weight per 100 parts by weight of the monomer mixture.
The adhesive film according to claim 1 or 2, wherein the monomer mixture further comprises a (meth) acrylic monomer having a glass transition temperature of the homopolymer of -150 ° C to 0 ° C.
12. The adhesive film according to claim 11, wherein the (meth) acrylic monomer having a glass transition temperature of -150 DEG C to 0 DEG C is a monomer having an amine group.
The pressure-sensitive adhesive film according to claim 7, wherein the pressure-sensitive adhesive composition further comprises at least one of an initiator, a silane coupling agent and a crosslinking agent.
An optical film, and an adhesive film formed on at least one surface of the optical film, wherein the adhesive film comprises the adhesive film of claim 1 or 2. [
An optical display device comprising the pressure-sensitive adhesive film of claim 1 or claim 2.

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