KR102302203B1 - Adhesive composition, and laminated film and display device including the same - Google Patents

Abstract

A pressure-sensitive adhesive composition, a laminated film, and a display device are disclosed. The disclosed pressure-sensitive adhesive composition includes a photo-curable pressure-sensitive adhesive resin, a photo-curable oligomer, a photo initiator, and a light absorber, and the light transmittance of the photo initiator in the light absorption wavelength region is 20% or less.

Description

Adhesive composition, adhesive film and display device {Adhesive composition, and laminated film and display device including the same}

A pressure-sensitive adhesive composition, a laminated film, and a display device are disclosed. More specifically, a pressure-sensitive adhesive composition, a laminated film, and a display device having a light transmittance of 20% or less in a light absorption wavelength region of a photoinitiator are disclosed.

In modern society, the rapid development of electric and electronic products, including computers, mobile phones, TVs, monitors, etc., the trend of miniaturization, thinning, and portability are intensifying, and the demand for smartphones and tablet PCs is rapidly increasing in recent years. In the case of a display used in these electronic devices, a flexible display having excellent design, thin and light, low energy consumption, and thin like paper has recently been developed from a conventional conventional flat-type display.

In general, in order to construct such a display panel, a process of forming a structure in which a functional substrate having a respective function or a substrate in the form of a film is laminated in multiple layers is performed. For example, Glass for protecting the display, a protective film or a shock-absorbing film; light emitting device; a metal substrate on which lines are deposited; optical films such as a polarizing plate, a retardation plate, and a luminance improving film; outermost metal case; and/or a flexible film substrate used in future flexible displays may be used. In order to laminate the substrates of numerous materials, a double-sided adhesive film material having high adhesion to each substrate is used to bond the substrates to each other.

On the other hand, in the case of a flexible display other than a conventional flat panel display, additional properties are required as well as optical properties, durability and adhesion required in a conventional flat panel display for a structure laminated with a functional substrate or an adhesive film used. Specifically, in the case of an adhesive film used for a flat panel display, there is little deformation due to an external force, but in the case of an adhesive film applied to a flexible display, stress is generated due to external bending or bending during use. In this case, it is difficult to deform into a curved shape due to the viscoelasticity of the pressure-sensitive adhesive itself, and problems such as stress transmission to the display or delamination within the structure occur, thereby causing a problem in the normal operation of the flexible display.

Korean Patent Application Laid-Open No. 10-2017-0097856 (hereinafter referred to as "Patent Document 1") discloses a loss modulus of elastic modulus in a wide temperature range by introducing two or more different crosslinking agents together with an acrylic polymer in order to solve this problem. An acrylic pressure-sensitive adhesive composition having little change and excellent bending reliability was presented. However, as in Patent Document 1, when an adhesive film having a constant surface state is used as an interlayer adhesive material of a flexible display, the adhesive force at the interface where the shape is deformed and the interface where the shape is not deformed are the same, so that the shape is deformed. After a large amount of stress is selectively applied to the Therefore, in this case, the stress generated intensively in the selected area is accumulated, which causes physical deformation in the entire structure.

On the other hand, US Patent Publication No. 8804324 (hereinafter referred to as "Patent Document 2") proposes a method of assembling a flexible display by enumerating the structures of various types of flexible displays, in particular, various types of foldable displays. Patent Document 2 also suggests a method of dispersing stress in terms of structural design with respect to a stress relaxation method in the part in which the flexible display flows, that is, in the folded part, but when the stress is accumulated in the bonding member used inside, the There is a problem that permanent deformation cannot be avoided. Therefore, the bonding member inside the display device also needs to be designed in a form capable of dispersing stress along the deformation pattern of the substrate.

[Prior art literature]

[Patent Literature]

(Patent Document 1) Korean Patent Publication No. 10-2017-0097856

(Patent Document 2) US Patent Publication No. 8804324

One embodiment of the present invention provides a pressure-sensitive adhesive composition having a light transmittance of 20% or less in the light absorption wavelength region of the photoinitiator.

Another embodiment of the present invention provides a laminated film comprising the pressure-sensitive adhesive composition.

Another embodiment of the present invention provides a display device including the pressure-sensitive adhesive composition or the laminated film.

One aspect of the present invention is

A photocurable adhesive resin, a photocurable oligomer, a photoinitiator and a light absorber,

The light transmittance in the light absorption wavelength region of the photoinitiator provides a pressure-sensitive adhesive composition of 20% or less.

The light absorption wavelength region of the photoinitiator may be 200 nm to 450 nm.

The content of the photocurable oligomer, the content of the photoinitiator, and the content of the light absorber are 10 parts by weight or more and 50 parts by weight or less, 0.1 parts by weight or more and 5 parts by weight or less, and 0.1 parts by weight, respectively, based on 100 parts by weight of the photocurable adhesive resin. It may be more than 20 parts by weight or less.

The light absorber may include a UV absorber, a free radical scavenger, an inorganic pigment, or a combination thereof.

Another aspect of the present invention is

It is prepared by coating and drying the pressure-sensitive adhesive composition on a substrate, and provides an adhesive film having a light transmittance of 20% or less in the light absorption wavelength region of the photoinitiator.

Another aspect of the present invention is

It provides an adhesive film prepared by irradiating a portion of one surface of the adhesive film with energy rays, and including both a photocured region and a non-photocured region on one surface.

The adhesive film has a surface in which 1% or more and 50% or less of the total surface area is a photocured region and the remaining surface area is a non-photocured region, and the photocured region may be divided into two or more sub-regions. .

The difference between the surface energy of the photocured region and the surface energy of the non-photocured region may satisfy Equation 1 below:

[Equation 1]

5mN/m < E2 - E1

E1: surface energy of photocured area

E2: The surface energy of the non-photocured area.

The difference between the adhesive force of the photocured region and the non-photocured region to the same substrate may satisfy Equation 2 below:

[Equation 2]

300gf/inch < A2 - A1

A1: Adhesion to the substrate of the photocured area

A2: Adhesion to the substrate of the non-photocured area.

The adhesion (A1) of the photocured region to the substrate may be 50 gf/in or less.

In the photocured area, the surface located opposite to the surface irradiated with the energy ray may have an adhesive force of 300 gf/inch or more to the substrate.

The adhesive film may have a storage modulus of 10 ³ Pa or more and 10 ⁵ Pa or less at 25° C., and the photocured region may include two or more sections having different storage modulus along a thickness direction.

Another aspect of the present invention is

It provides a display device including the adhesive film.

The display device may be a flexible display device.

According to one embodiment of the present invention, by selectively changing the surface energy and storage modulus of a specific region according to the partial irradiation with energy rays, it is possible to selectively reduce the adhesion and wettability of the driving part whose shape is deformed in the flexible display, This can prevent physical deformation due to concentration of stress on the display panel by inducing intentional dynamic interfacial peeling.

In addition, when an energy ray is irradiated to one surface of the adhesive film by including a light absorbing agent capable of absorbing light in the light absorption wavelength region of the photoinitiator together with the photoinitiator, the energy ray is intentionally prevented from penetrating to the opposite direction of the adhesive film It is possible to increase the storage modulus of only a portion of the surface in the thickness direction. Through this, since the adhesive film does not sharply increase the storage modulus of the entire adhesive film while reducing the adhesion to the substrate of a specific surface, the stress generated by the flow of the flexible display can be effectively alleviated.

However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1 is a schematic diagram of a pressure-sensitive adhesive composition according to an embodiment of the present invention.
2 is a cross-sectional view of an adhesive film according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to embodiments and drawings of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control.

Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

Unless otherwise stated, all percentages, parts, ratios, etc. are by weight. Also, when an amount, concentration, or other value or parameter is given as any one of a range, a preferred range, or a list of upper and preferred upper limits and lower preferred limits, this means any upper range limit or preferred value and any lower limit, whether or not the range is separately disclosed. It is to be understood that all ranges formed from any pair of range limits or preferred values are specifically disclosed. When a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoint and all integers and fractions within the range. It is intended that the scope of the invention not be limited to the particular values recited when defining the ranges.

Hereinafter, the pressure-sensitive adhesive composition, the pressure-sensitive adhesive film, and the display device according to embodiments of the present invention will be described in detail.

1. Adhesive composition

The pressure-sensitive adhesive composition according to an embodiment of the present invention includes a photo-curable pressure-sensitive adhesive resin, a photo-curable oligomer, a photo initiator, and a light absorber.

In the present specification, "photocurable adhesive resin" and "photocurable oligomer" may be distinguished from each other by a weight average molecular weight. Specifically, "photocurable adhesive resin" refers to a compound having a weight average molecular weight of 50,000 to 5,000,000, and "photocurable oligomer" refers to a compound having a weight average molecular weight of 500 to 40,000.

In the pressure-sensitive adhesive composition, the light transmittance in the light absorption wavelength region of the photoinitiator is 20% or less. In the pressure-sensitive adhesive composition, if the light transmittance in the light absorption wavelength region of the photoinitiator is 20% or more, the transmittance of energy rays in the thickness direction of the pressure-sensitive adhesive film increases. There is a problem in that it is difficult to implement a surface-curable adhesive film.

The light absorption wavelength region of the photoinitiator may be 200 nm to 450 nm. However, the present invention is not limited thereto, and other various compounds having a light absorption wavelength region may be used as the photoinitiator.

The pressure-sensitive adhesive composition includes a curing accelerator, an ionic liquid, a lithium salt, an inorganic filler, a softener, a molecular weight regulator, an antioxidant, an anti-aging agent, a stabilizer, a tackifying resin, a modified resin (polyol resin, phenol resin, acrylic resin, polyester resin, polyolefin resin, epoxy resin, epoxidized polybutadiene resin, etc.), leveling agent, defoaming agent, plasticizer, dye, pigment (color pigment, extender pigment, etc.), treatment agent, sunscreen agent, optical brightener, dispersant, heat stabilizer, light eye It may further include conventional additives such as tablets, antistatic agents, coagulants, lubricants and solvents (eg, ethyl acetate).

1.1. Photo-curable adhesive resin

The photo-curable pressure-sensitive adhesive resin, which is one component of the pressure-sensitive adhesive composition, has an unsaturated bond in the main skeleton structure of the polymer or in a terminal functional group. The unsaturated bond reacts with radicals generated from the photoinitiator by irradiation with energy rays to cause an addition reaction, thereby forming crosslinks with the photocurable adhesive resins or the photocurable oligomer.

The photocurable adhesive resin may include an acrylic adhesive resin, a rubber adhesive resin, or a combination thereof.

The acrylic adhesive resin may include an acrylic copolymer.

The acrylic copolymer, based on the total weight of the monomers constituting the acrylic copolymer, 85 to 99% by weight of a monomer having no crosslinkable functional group and 1 to 15% by weight of a monomer having a crosslinkable functional group may be synthetic. When the amount of the monomer having no crosslinkable functional group in the acrylic adhesive resin is less than 85% by weight, the number of crosslinkable functional groups is relatively large, so that the problem of storage stability of the adhesive composition and the lowering of the cohesive force of the adhesive composition due to the small molecular weight castability And, there may be a problem in the flexibility of the sheet, and when it exceeds 99% by weight, the number of crosslinkable functional groups is reduced and the reactivity is significantly lowered, so the reaction may not be performed well. this will fall

The acrylic copolymer may have a weight average molecular weight of 50,000 to 1,000,000. When the weight average molecular weight is less than 50,000, cohesive failure may occur and the sheet flexibility may be deteriorated.

The monomer having no crosslinkable functional group may include a (meth)acrylic acid ester monomer, but the present invention is not limited thereto. For example, the monomer having no crosslinkable functional group may be a (meth)acrylic acid ester having 1 to 20 carbon atoms in the alkyl group of the ester moiety. Here, the (meth)acrylic acid ester having 1 to 20 carbon atoms in the alkyl group of the ester moiety is methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) ) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylic rate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, or a combination thereof.

The monomer including the crosslinkable functional group may include at least one of a hydroxyl group, a carboxyl group, an amino group, and an amide group as a functional group. Specific examples of such monomers are 2-hydroxyethyl (meth)acrylic acid, 2-hydroxypropyl (meth)acrylic acid, 3-hydroxypropyl (meth)acrylic acid, 2-hydroxybutyl (meth)acrylic acid, 3-hydroxy (meth)acrylic acid hydroxyalkyl esters such as butyl (meth)acrylic acid and 4-hydroxybutyl (meth)acrylic acid; acrylamides such as (meth)acrylamide, N-methyl(meth)acrylamide, and N-methylol(meth)acrylamide; (meth)acrylic acid monomethyl amino ethyl, (meth)acrylic acid monoalkyl amino ester; ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid; or a combination thereof.

In addition, the rubber-based adhesive resin is styrene-butadiene-styrene rubber (SBSR), styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber (SISR), styrene-ethylene-butylene_styrene rubber (SEBSR) ), natural rubber (NR), ethylene-propylene-diene rubber (EPDM), ethylene-propylene rubber (EPM), polyacrylate rubber (ACM), butadiene rubber (BR), nitrile-butadiene rubber ( NBR), hydrogen substituted nitrile rubber (HNBR), chloroprene rubber (CR), chlorosulfonated polyethylene rubber (CSM), fluorocarbon rubber (FPM), ethylene-acrylic rubber (AEM), epichlorohydrin rubber (ECO), isoprene-based rubber (IR), polyisobutylene-based rubber (PIB), isoprene-isobutylene-based rubber (IIR), or a combination thereof.

The rubber-based adhesive resin may have a weight average molecular weight of 30,000 to 2 million. When the weight average molecular weight is 30,000 or less, cohesive failure may occur and the sheet flexibility may be deteriorated.

In a specific embodiment, the rubber-based adhesive resin improves adhesive function, heat resistance, heat aging, ozone resistance, chemical resistance, etc. by appropriately mixing a rubber-based adhesive resin with a small molecular weight and a rubber-based adhesive resin with a high molecular weight, and is added to other rubber-based adhesive resins. weather resistance can be improved. The preferred blending ratio can be changed according to the user's selection, but the rubber-based adhesive resin having a molecular weight of about 50,000 and the rubber-based adhesive resin having a molecular weight of about 1.2 million are 1:9 to 9:1, preferably 7:3 to 3:7. By blending in a weight ratio, desired physical properties can be obtained.

In order to achieve the required physical properties of the adhesive film according to an embodiment of the present invention, an antistatic agent, a tackifier, an inorganic filler, an organic filler, an antioxidant, a softener, a plasticizer, a light stabilizer, a leveling agent, a corrosion inhibitor to the rubber-based adhesive resin and/or other additives may be further added.

As the tackifier, any tackifier commonly used in the art may be used, for example, aliphatic petroleum resin, rosin-modified resin, rosin, or a mixture thereof may be used, but the present invention The present invention is not limited thereto.

1.2. photocurable oligomer

The photo-curable oligomer, which is one component of the pressure-sensitive adhesive composition, has two or more unsaturated functional groups, and if it is a material that causes a curing reaction by irradiating an energy ray, the type thereof is not particularly limited.

As with the photocurable adhesive resin, the unsaturated bond of the photocurable oligomer reacts with radicals generated from the photoinitiator by irradiation with energy rays to cause an addition reaction to form a crosslink between the photocurable adhesive resin or the photocurable oligomer. can

The photocurable oligomer may include a polyfunctional acrylate compound, an epoxy resin, a urethane resin, a silicone resin, or a combination thereof.

The polyfunctional acrylate compound is an epoxy (meth) acrylate oligomer, urethane (meth) acrylate oligomer, polyether (meth) acrylate oligomer, polyester (meth) acrylate oligomer, trimethylolpropane tri (meth) acrylate Oligomer, polyethylene glycol di(meth)acrylate oligomer, polyalkylene glycol di(meth)acrylate oligomer, dicyclopentenyl (meth)acrylate oligomer, dicyclopentenyloxyethyl (meth)acrylate oligomer, neopentyl Glycol di (meth) acrylate oligomer, dipentaerythritol hexa (meth) acrylate oligomer, isocyanuric acid-modified bifunctional (meth) acrylate oligomer, isocyanuric acid-modified trifunctional (meth) acrylate oligomer, non Phenoxyethanolfluorene acrylate oligomer, epoxy (meth)acrylate oligomer obtained by adding (meth)acrylic acid to the glycidyl group of bisphenolfluorene diglycidyl ether, bisphenoxyethanolfluorene acrylate oligomer, bisphenol Epoxy (meth)acrylate oligomers obtained by adding (meth)acrylic acid to the glycidyl group of fluorenediglycidyl ether, and compounds obtained by adding ethylene glycol or propylene glycol to the glycidyl group of bisphenol fluorenediglycidyl ether. It may include an oligomer introduced with a (meth)acryloyloxy group, or a combination thereof.

In addition, in the pressure-sensitive adhesive composition, the content of the photo-curable oligomer may be 10 parts by weight or more and 50 parts by weight or less based on 100 parts by weight of the photo-curable pressure-sensitive adhesive resin. If the content of the photo-curable oligomer is less than 10 parts by weight based on 100 parts by weight of the photo-curable adhesive resin, even if the photo-curing reaction is carried out by energy rays, the cross-linking density is lowered, so that the surface energy is not sufficiently lowered and the storage modulus is sufficiently high Since it does not rise, the adhesion and wettability to the substrate are not sufficiently deteriorated, so there is a possibility that the intentional dynamic interfacial peeling may not sufficiently occur in the portion of the adhesive film in contact with the flowing part of the flexible display. In addition, when the content of the photo-curable oligomer exceeds 50 parts by weight based on 100 parts by weight of the photo-curable adhesive resin, the photo-curing reaction by the energy ray excessively proceeds, and the storage modulus of the adhesive film is excessively increased and brittle. Therefore, there is a possibility that the adhesive film may be destroyed by the flow of the flexible display or the adhesive film may be physically permanently deformed because the stress cannot be sufficiently relieved.

1.3. photoinitiator

The type of the photoinitiator, which is one component of the pressure-sensitive adhesive composition, is not particularly limited as long as it is a substance capable of generating radicals by converting molecules to an excited state by irradiation with energy rays.

Radicals generated from the photoinitiator through the energy ray irradiation attack the unsaturated bonds included in the photocurable adhesive resin and the photocurable oligomer to induce an addition reaction, thereby forming a crosslink.

The photoinitiator may include a benzyldimethyl ketal-based initiator, a benzoin-based initiator, a hydroxy-based initiator, an amino ketone-based initiator, a caprolactam-based initiator, or a combination thereof. Specifically, the photoinitiator is benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2 -dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenylketone; 2-Methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl) Ketone, benzophenone, p-phenylbenzophenone, 4,4'-bis(diethylamino)benzophenone (EAB-F), dichlorobenzophenone, 2-methyl anthraquinone, 2-ethyl anthraquinone, 2-t- Butyl anthraquinone, 2-amino anthraquinone, 2-methyl thioxanthone, 2-ethyl thioxanthone, 2-chloro thioxanthone, 2,4-dimethyl thioxanthone, 2,4-diethyl thioxanthone ( DETX), 4-isopropylthioxanthone (ITX), benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylamino benzoic acid ester, oligo[2-hydroxy-2-methyl-1[4-(1-methylvinyl) )phenyl]propane], 2,4,6-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'-bis(2-methoxy Phenyl)-4,4',5,5'-tetraphenylbiimidazole (HABI-107), 2,2',4-tris(2-chlorophenyl)-5-(3,4-dimethoxyphenyl) -4',5'-diphenylbiimidazole (TCDM), or a combination thereof.

The photoinitiator may absorb light of different wavelengths depending on the type and structure thereof. Typically, the photoinitiator absorbs light of a wavelength of 200 to 450 nm and converts it to an excited state to generate radicals, thereby generating a photocurable adhesive resin and/or photoresist. It can induce a crosslinking reaction of the fire-type oligomer.

In the present specification, the term "light absorption wavelength region of photoinitiator" refers to the absorbance of a solution in which a photoinitiator is dissolved in acetonitrile or 1-methyl-2-pyrrolidone (NMP) at a concentration of 0.1% by weight with a UV Spectrum device. When , it means a region whose absorbance is 0.1 or more. When the light transmittance (%T) of the pressure-sensitive adhesive composition is measured by a UV Spectrum device, the light transmittance is 20% or less.

In addition, in the pressure-sensitive adhesive composition, the content of the photoinitiator may be 0.1 parts by weight or more and 5 parts by weight or less based on 100 parts by weight of the photocurable adhesive resin. If the content of the photoinitiator is less than 0.1 parts by weight based on 100 parts by weight of the photocurable adhesive resin, photocuring by energy ray irradiation is not sufficiently performed, so that the surface energy of the adhesive film is not sufficiently lowered and the storage modulus is not sufficiently increased. There is a possibility that the intentional dynamic interfacial peeling may not sufficiently occur in the portion of the adhesive film in contact with the flowing part of the flexible display because the adhesion and wettability to the substrate are not sufficiently deteriorated. In addition, when the content of the photoinitiator exceeds 5 parts by weight based on 100 parts by weight of the photocurable adhesive resin, when the photoinitiator is converted into an excited state to generate radicals, an excessive concentration of radicals is generated in a unit volume, so that radicals are terminated. The reaction (termination reaction) is accelerated, so that the photocuring of the adhesive film is not sufficiently performed, the content of the photoinitiator may be less than 0.1 parts by weight based on 100 parts by weight of the photocurable adhesive resin.

1.4. light absorber

The light absorber, which is one component of the pressure-sensitive adhesive composition, serves to reduce the generation of radicals of the photoinitiator by absorbing light in the light absorption wavelength region of the photoinitiator, thereby reducing the crosslinking reaction induction efficiency.

After preparing an adhesive film by applying and drying the adhesive composition according to an embodiment of the present invention to a substrate, when irradiating an energy beam to a specific surface (ie, smooth surface) of the adhesive film, the photoinitiator is The efficiency is lowered, and only the surface layer of a predetermined thickness among the surfaces irradiated with the energy ray causes a crosslinking reaction, and the crosslinking reaction is not performed properly in the lower part. For this reason, only the surface layer of a predetermined thickness is cured, so that the surface energy is lowered and the storage modulus is increased, so that the adhesion and wettability to the substrate are reduced. is beneficial for alleviating

The light absorber may include a UV absorber, a free radical scavenger, an inorganic pigment, or a combination thereof.

The UV absorber basically absorbs energy rays (specifically, ultraviolet rays) and performs a function of emitting it as thermal energy.

The UV absorber is 2-hydroxybenzophenone, 2-hydroxyphenyl benzotriazole, salicylate, cinnamate derivative, resorcinol monobenzoate, allyl ester, oxanilide, p-hydroxybenzoate or these may include a combination of

The free radical scavenger serves to remove and stop free radicals generated by decomposition of the photoinitiator by energy ray irradiation.

The free radical scavenger may include aryl esters, benzoates, phenolic primary antioxidants, amine primary antioxidants, hindered amine light stabilizers (HALS), or a combination thereof.

The inorganic pigment absorbs energy rays to prevent energy from being transmitted to the photoinitiator, and when the inorganic pigment is an electrically conductive material, removes radicals generated from the photoinitiator, that is, serves as a UV absorber and a free radical scavenger can perform both roles at the same time.

The inorganic pigment may include black pigments such as carbon black, graphite, and iron oxide; white pigments such as titanium oxide, calcium carbonate, clay, barium sulfate, and silica; colored pigments using other metals or metal oxides; or a combination thereof.

In addition, in the pressure-sensitive adhesive composition, the content of the light absorber may be 0.1 parts by weight or more and 20 parts by weight or less based on 100 parts by weight of the photocurable adhesive resin. When the content of the light absorber is less than 0.1 parts by weight based on 100 parts by weight of the photocurable adhesive resin, the light transmittance in the light absorption wavelength region of the photoinitiator of the adhesive film prepared by coating and drying the adhesive composition exceeds 20% Therefore, it is not possible to implement selective photocuring of only the surface portion of the adhesive film to be achieved in the present invention. In addition, when the content of the light absorber exceeds 20 parts by weight based on 100 parts by weight of the photo-curable adhesive resin, the light absorber serves to reduce the adhesive strength in the pressure-sensitive adhesive composition and the pressure-sensitive adhesive film, so that sufficient adhesion to the substrate cannot be obtained. is likely to be

1 is a schematic diagram of a pressure-sensitive adhesive composition 110 according to an embodiment of the present invention.

Referring to FIG. 1 , the pressure-sensitive adhesive composition 110 according to an embodiment of the present invention includes a photocurable pressure sensitive adhesive resin 111 , a photocurable oligomer 112 , a photoinitiator 113 and a light absorber 114 .

In the pressure-sensitive adhesive composition 110 , the photo-curable pressure-sensitive adhesive resin 111 , the photo-curable oligomer 112 , the photo initiator 113 , and the light absorber 114 may exist in a uniformly mixed state with each other.

2. Adhesive film

The pressure-sensitive adhesive film according to an embodiment of the present invention may be prepared by coating and drying the pressure-sensitive adhesive composition by a known method.

When the light transmittance (%T) of the adhesive film is measured using UV Spectrum equipment, the light transmittance (%T) in the light absorption wavelength region of the photoinitiator is 20% or less.

The pressure-sensitive adhesive film is formed by casting the pressure-sensitive adhesive composition on a silicone release-treated PET film (polyethylene tetrafluoroethylene film), and then gravure coating method, comma coating method, slot die coating method, doctor blade coating method, screen printing coating method, etc. After applying using a known coating method of, it can be prepared by volatilizing the volatile content of the pressure-sensitive adhesive composition by putting it in a drying oven heated to a predetermined temperature (eg, 120 ℃). A final product can be obtained by laminating a silicone release-treated PET film on the adhesive film prepared in this way.

2 is a cross-sectional view of an adhesive film 100 according to an embodiment of the present invention.

Referring to FIG. 2 , the adhesive film 100 according to an embodiment of the present invention includes a substrate 101 , an adhesive layer 110 ′, and a release film 120 in this order.

The substrate 101 may be a release film.

The pressure-sensitive adhesive layer 110 ′ may be prepared by applying and drying the pressure-sensitive adhesive composition 110 of FIG. 1 to the substrate 101 .

The adhesive film 100 may not include at least one of the substrate 101 and the release film 120 .

3. Surface-curing adhesive film

A surface-curable adhesive film according to an embodiment of the present invention includes a region photocured through energy ray irradiation on a portion of one surface of the adhesive film.

In order to photo-curing only a part of the adhesive film through energy rays, a photomask made of a material such as metal, ceramic, or paper that does not transmit energy rays is made to expose only a part of the adhesive film and the rest of the adhesive film is not exposed to the energy rays. Only a desired specific portion can be selectively photocured.

In addition, the type of energy ray used to form the photocured region is not particularly limited as long as it generates radicals by applying energy to the photoinitiator included in the pressure-sensitive adhesive composition, mercury lamp, Fe-doped mercury lamp, Ga- Ultraviolet (UV) light generated by applying voltage to a doped mercury lamp, electron beam (EB), infrared, X-ray, visible light, argon, CO ₂ or excimer laser laser beam, or LED lamp beam can be used.

The surface-curable adhesive film may have a surface in which 1% or more and 50% or less of the total surface area is a photocured region, and the remaining surface area is a non-photocured region.

In addition, the photocured region may include two or more sub-regions, which can be controlled according to a method of designing and manufacturing the photomask. According to the area and/or design of the flow part of the flexible display, the photocured area of the surface-curable adhesive film may be manufactured to match the flow part of the flexible display, so that the stress can be effectively relieved according to the flow of the flexible display.

If the surface area of the photocured region on one side of the surface-curable adhesive film (that is, the side located on the side to which the energy ray is irradiated) is less than 1% of the total surface area, the adhesion interface between the substrate and the photocured region (that is, of the substrate) The surface area of the substrate in contact with the photocured region among the total surface area) is small, so that stress due to shape deformation of the substrate cannot be sufficiently dispersed.

In addition, when the surface area of the photocured region of one surface (that is, the surface located on the side irradiated with energy rays) of the surface-curable adhesive film exceeds 50% of the total surface area, photocuring exhibiting high adhesion with the substrate interface Since the surface area of the non-removed area becomes excessively small, the overall adhesion to the substrate is lowered, so there is a possibility that a lifting phenomenon occurs inside the structure.

In the surface-curable pressure-sensitive adhesive film, the difference between the surface energy of the photocured region and the surface energy of the non-photocured region satisfies Equation 1 below.

[Equation 1]

5mN/m < E2 - E1

E1: surface energy of photocured area

E2: The surface energy of the non-photocured area.

If the difference (E2-E1) between the surface energy (E1) of the photocured region and the surface energy (E2) of the non-photocured region is 5 mN/m or less, the present invention aims to achieve It becomes impossible to realize the difference in selective adhesion and wettability.

As an example, the difference between the surface energy (E1) of the photocured region and the surface energy (E2) of the non-photocured region is 5 mN/m or less, and the surface energy (E1) of the photocured region and the light When all of the surface energy (E2) of the non-cured region is high, it is possible to implement high adhesion and wettability with the substrate in the non-photocured region, but the photo-cured region is attached to the portion where the shape of the substrate is deformed. Similarly, the adhesion and wettability to the deformable portion of the substrate are increased, and the stress caused by the deformation of the substrate cannot be efficiently dispersed. Therefore, there is a possibility that the substrate and the structure as a whole are affected by stress accumulation, thereby causing physical permanent deformation.

As another example, the difference between the surface energy E1 of the photocured region and the surface energy E2 of the non-photocured region is 5 mN/m or less, and the surface energy E1 of the photocured region and the When all of the surface energy (E2) of the non-photocured region is low, the photocured region that is attached to the portion where the shape of the substrate is deformed does not adhere to the deformable portion of the substrate, so the stress caused by the deformation of the substrate is effectively reduced. However, the adhesion and wettability of the interface of the substrate attached to the non-photocured region is poor, and there is a possibility that a lifting phenomenon may occur inside the structure.

In the surface-curable pressure-sensitive adhesive film, the difference between the adhesion force of the photocured region and the adhesion force of the non-photocured region to the same substrate satisfies Equation 2 below.

[Equation 2]

300 gf/inch (gram-force per inch) < A2 - A1

A1: Adhesion to the substrate of the photocured area

A2: Adhesion to the substrate of the non-photocured area.

If the difference (A2-A1) between the adhesion force (A1) of the photocured region and the adhesion force (A2) of the non-photocured region to the same substrate in the surface-curable adhesive film is within the above range, (i) the present invention It is possible to realize the difference in wettability and selective adhesion to the substrate within the single adhesive layer to be achieved in (ii) because of the low adhesion to the substrate in the photocured region to sufficiently relieve the stress caused by the deformation of the substrate. and (iii) the non-photocured region has a high adhesion to the substrate, so that the interlayers can be well fixed without delamination at the interface.

In the surface-curable adhesive film, regardless of the type of substrate, the adhesion (A1) of the photocured region to the substrate is 50 gf/in or less, 1 gf/in or more and 50 gf/in or less, 1 gf/in or more 20 gf/in or less, or 1 gf It can be greater than /in and less than or equal to 10 gf/in. To this end, any one of a plurality of substrates having different surface properties is selected, and then the adhesion properties of the photocured region are adjusted so that the adhesion (A1) of the photocured region to the substrate is 50 gf in the surface-curable adhesive film. /in or less, 1gf/in or more and 50gf/in or less, 1gf/in or more and 20gf/in or less, or 1gf/in or more and 10gf/in or less.

In the surface-curable pressure-sensitive adhesive film, the adhesive force of the side opposite to the side irradiated with energy rays among the photocured area to the substrate may be 300 gf/inch or more. As described above, the pressure-sensitive adhesive composition for producing the surface-curable pressure-sensitive adhesive film includes a light absorber that absorbs light in the light absorption wavelength region of the photoinitiator together with the photoinitiator. Therefore, when irradiating an energy ray to one surface of the adhesive film, the energy ray in the wavelength band that the photoinitiator can absorb is gradually reduced according to the depth from the surface of the adhesive film. Specifically, when the portion close to the surface portion irradiated with energy ray of the adhesive film is the upper layer of the adhesive film, and the portion close to the opposite side irradiated with energy ray is the lower layer of the adhesive film, the upper layer of the adhesive film is transmitted through the adhesive film Since the amount of incoming energy rays is large, radicals are generated as the photoinitiator is converted to an excited state, thereby efficiently forming a crosslinking structure between the phototypeable adhesive resin and/or the phototypeable oligomer. Since the amount of energy rays reached by the absorption of energy rays by the absorber is reduced, the efficiency of generating radicals by converting the photoinitiator into an excited state is lowered, so that a crosslinking structure cannot be formed between the photocurable adhesive resin and/or the photocurable oligomer. It is formed with a low degree of crosslinking. Therefore, in the case of the opposite side of the side irradiated with energy rays, since the adhesion to the substrate is maintained in a high state like the region not irradiated with energy rays, that is, the region not irradiated with energy rays, that is, the region not irradiated with the energy ray will be well fixed without causing delamination with other substrates. can

The adhesive film may have a storage modulus of 10 ³ Pa or more and 10 ⁵ Pa or less at 25° C., and the photocured region may include two or more sections having different storage modulus along a thickness direction.

If the storage modulus at 25° C. of the surface-curable adhesive film is ^{less than 10 3} Pa, there is a possibility that the thickness of the adhesive film is unevenly formed when the adhesive film is formed because the fluidity of the adhesive layer itself is high, and the adhesion according to the use process after attachment There is a possibility that the layer flows and flows out of the structure, which may cause a problem that a constant adhesion to the substrate cannot be implemented. In addition, when the storage modulus at 25° C. of the surface-curable adhesive film ^{exceeds 10 5} Pa, high adhesion to the substrate and wettability cannot be ensured, which may cause delamination.

In addition, since the amount of energy rays transmitted through the inside of the film gradually decreases according to the depth from the surface irradiated with the energy rays as described above, the region close to the surface in the thickness direction (ie, the upper layer of the adhesive film) and the surface A difference occurs in the degree of crosslinking of the photo-curable adhesive resin and/or the photo-curable oligomer between regions far away from the (ie, the lower layer of the adhesive film). As a result, in the case of the upper layer of the adhesive film, the crosslinking reaction proceeds a lot to increase the storage modulus, and in the case of the lower layer of the adhesive film, the crosslinking reaction hardly proceeds, thereby lowering the storage modulus. This is because when the storage modulus of the entire adhesive film is increased by photocuring through energy ray irradiation, it is impossible to efficiently disperse and relieve the stress generated by the flow of the flexible display throughout the substrate. It is designed in order not to excessively increase the storage modulus of the adhesive film itself while reducing the adhesion and wettability to the substrate by making the film.

4. Display device

The display device according to an embodiment of the present invention may include the adhesive film.

The display device may be a flexible display device.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Example 1>

50 parts by weight of ethyl acetate (EA) was added to 100 parts by weight of a photocurable adhesive resin (Aekyung Chemical, UV PSA 1800-6, weight average molecular weight: 600,000), and a photocurable oligomer (Nippon Chemicals, KAYARAD DPCA-20, Weight average molecular weight: 807) 20 parts by weight was added, followed by stirring for 30 minutes. Then, 1 part by weight of a photoinitiator (Ciba 製, IRGACURE 184) and 2 parts by weight of carbon black (Lion Chemical 製, EC300J) were added and stirred for an additional 30 minutes. The pressure-sensitive adhesive composition prepared as above was applied on a silicone release-treated PET film (Toray Advanced Materials, ROH751, 75㎛), dried to prepare an adhesive layer with a thickness of 20㎛, and then a silicone release-treated PET film (Toray Advanced Materials) , ROT101, 75 μm) was laminated so that the release-treated side was in contact with the adhesive layer. As a result, an adhesive film was obtained.

After cutting the prepared adhesive film to a size of 100mm x 100mm, on the upper surface of the adhesive film, a hole of 10mm x 90mm is drilled in the center of 100mm x 100mm and 2mm thick SUS (Steel Special Use Stainless) ^{) Material Photomask was placed on it, and it was irradiated with a light quantity of 300mJ/cm 2} using a UV irradiator (Litgen 製, high-pressure mercury lamp) to form a photocured area in the center of one side of the adhesive film. As a result, a surface-curable adhesive film was obtained.

<Example 2>

Except for using 100 parts by weight of photocurable adhesive resin (Aekyung Chemical, UVPSA5016, weight average molecular weight: 550,000) instead of 100 parts by weight of photocurable adhesive resin (Aekyung Chemical, UV PSA 1800-6, weight average molecular weight: 600,000) was prepared in the same manner as in Example 1, an adhesive layer, an adhesive film, and a surface-curable adhesive film.

<Example 3>

An adhesive layer, an adhesive film and a surface-curing adhesive film were prepared in the same manner as in Example 1, except that 5 parts by weight of graphite (3M 製, Cond5) was used instead of 2 parts by weight of carbon black (Lion Chemical 製, EC300J) did.

<Example 4>

An adhesive layer, an adhesive film and a surface-curing adhesive film were prepared in the same manner as in Example 1, except that 1 part by weight of a photoinitiator (Ciba 製, IRGACURE 907) was used instead of 1 part by weight of the photoinitiator (Ciba 製, IRGACURE 184). did.

<Example 5>

An adhesive layer, an adhesive film and a surface-curing adhesive film were prepared in the same manner as in Example 1, except that 1 part by weight of a photoinitiator (Ciba 製, DAROCUR TPO) was used instead of 1 part by weight of the photoinitiator (Ciba 製, IRGACURE 184) did.

<Example 6>

An adhesive layer, an adhesive film, and a surface-curing adhesive film in the same manner as in Example 1, except that 0.1 parts by weight of carbon black (Lion Chemical 製, EC300J) was used instead of 2 parts by weight of carbon black (Lion Chemical 製, EC300J) was prepared.

<Example 7>

An adhesive layer, an adhesive film, and a surface-curing adhesive film in the same manner as in Example 1, except that 20 parts by weight of carbon black (Lion Chemical 製, EC300J) was used instead of 2 parts by weight of carbon black (Lion Chemical 製, EC300J) was prepared.

<Example 8>

First, an adhesive layer and an adhesive film were prepared in the same manner as in Example 1. Then, instead of a 100mm x 100mm and 2mm thick SUS material Photomask with a 10mm x 90mm hole in the center, a 100mm x 100mm and 2mm thick SUS material Photomask with a 10mm x 10mm hole in the center. A surface-curable adhesive film was prepared in the same manner as in Example 1, except that

<Example 9>

First, an adhesive layer and an adhesive film were prepared in the same manner as in Example 1. Then, instead of a 100mm x 100mm and 2mm thick SUS material Photomask with a 10mm x 90mm hole drilled in the center, a 100mm x 100mm and 2mm thick SUS material Photomask with a 100mm x 50mm hole drilled in the center. A surface-curable adhesive film was prepared in the same manner as in Example 1, except that

<Example 10>

20 parts by weight of a photocurable oligomer (Nippon Kayaku 製, KAYARAD DPCA-20, weight average molecular weight: 807) and 1 part by weight of a photoinitiator (Ciba 製, IRGACURE 184) a photocurable oligomer (Nippon Kayaku 製, KAYARAD DPCA-20, weight Average molecular weight: 807), except that 10 parts by weight and 5 parts by weight of a photoinitiator (Ciba 製, IRGACURE 184) were used, an adhesive layer, an adhesive film, and a surface-curing adhesive film were prepared in the same manner as in Example 1.

<Example 11>

20 parts by weight of a photocurable oligomer (Nippon Kayaku 製, KAYARAD DPCA-20, weight average molecular weight: 807) and 1 part by weight of a photoinitiator (Ciba 製, IRGACURE 184) a photocurable oligomer (Nippon Kayaku 製, KAYARAD DPCA-20, weight Average molecular weight: 807), except that 50 parts by weight and 0.1 parts by weight of a photoinitiator (Ciba 製, IRGACURE 184) were used, an adhesive layer, an adhesive film, and a surface-curing adhesive film were prepared in the same manner as in Example 1.

<Comparative Example 1>

An adhesive layer, an adhesive film, and a surface-curable adhesive film were prepared in the same manner as in Example 1, except that carbon black (Lion Chemical 製, EC300J) was not used at all.

<Comparative Example 2>

An adhesive layer, an adhesive film and a surface-curing adhesive film in the same manner as in Example 1, except that 0.05 parts by weight of carbon black (Lion Chemical 製, EC300J) was used instead of 2 parts by weight of carbon black (Lion Chemical 製, EC300J) was prepared.

<Comparative Example 3>

An adhesive layer, an adhesive film, and a surface-curing adhesive film in the same manner as in Example 1, except that 25 parts by weight of carbon black (Lion Chemical 製, EC300J) was used instead of 2 parts by weight of carbon black (Lion Chemical 製, EC300J) was prepared.

<Comparative Example 4>

First, an adhesive layer and an adhesive film were prepared in the same manner as in Example 1. Then, instead of a 100mm x 100mm and 2mm thick SUS material Photomask with a 10mm x 90mm hole drilled in the center, a 100mm x 100mm and 2mm thick SUS material Photomask with a 1mm x 90mm hole drilled in the center. A surface-curable adhesive film was prepared in the same manner as in Example 1, except that

<Comparative Example 5>

First, an adhesive layer and an adhesive film were prepared in the same manner as in Example 1. Then, instead of 100mm x 100mm and 2mm thick SUS material Photomask with a 10mm x 90mm hole drilled in the center, a 100mm x 100mm and 2mm thick SUS material Photomask with a 60mm x 90mm hole drilled in the center. A surface-curable adhesive film was prepared in the same manner as in Example 1, except that

<Comparative Example 6>

Except for using 5 parts by weight of a photocurable oligomer (Nippon Kayaku 製, KAYARAD DPCA-20, weight average molecular weight: 807) instead of 20 parts by weight of a photocurable oligomer (Nippon Kayaku 製, KAYARAD DPCA-20, weight average molecular weight: 807) was prepared in the same manner as in Example 1, an adhesive layer, an adhesive film, and a surface-curable adhesive film.

<Comparative Example 7>

Except for using 55 parts by weight of a photocurable oligomer (Nippon Kayaku 製, KAYARAD DPCA-20, weight average molecular weight: 807) instead of 20 parts by weight of the photocurable oligomer (Nippon Kayaku 製, KAYARAD DPCA-20, weight average molecular weight: 807) was prepared in the same manner as in Example 1, an adhesive layer, an adhesive film, and a surface-curable adhesive film.

<Comparative Example 8>

An adhesive layer, an adhesive film and a surface-curing adhesive film were prepared in the same manner as in Example 1, except that 0.05 parts by weight of a photoinitiator (Ciba 製, IRGACURE 184) was used instead of 1 part by weight of the photoinitiator (Ciba 製, IRGACURE 184) did.

<Comparative Example 9>

An adhesive layer, an adhesive film, and a surface-curing adhesive film were prepared in the same manner as in Example 1, except that 10 parts by weight of a photoinitiator (Ciba 製, IRGACURE 184) was used instead of 1 part by weight of the photoinitiator (Ciba 製, IRGACURE 184) did.

In Examples 1 to 11 and Comparative Examples 1 to 9, the types and contents of the components used for manufacturing the pressure-sensitive adhesive composition, conditions for forming the pressure-sensitive adhesive layer and the photocured area thereon, and the area ratio of the photocured area are summarized. It is shown in Table 1 and Table 2 below. In Tables 1 and 2 below, the content of the components is based on parts by weight.

Example One 2 3 4 5 6 7 8 9 10 11 UVPSA1800-6 100 - 100 100 100 100 100 100 100 100 100 UVPSA5016 - 100 - - - - - - - - - EA 50 50 50 50 50 50 50 50 50 50 50 DPCA-20 20 20 20 20 20 20 20 20 20 10 50 IRGACURE 184 One One One - - One One One One 5 0.1 IRGACURE 907 - - - One - - - - - - - DAROCUR TPO - - - - One - - - - - - EC300J 2 2 - 2 2 0.1 20 2 2 2 2 Cond5 - - 5 - - - - - - - - UV light intensity (mJ/cm ² ) 300 300 300 300 300 300 300 300 300 300 300 Surface area ratio of photocured area (%) 9 9 9 9 9 9 9 One 50 9 9

comparative example One 2 3 4 5 6 7 8 9 UVPSA1800-6 100 100 100 100 100 100 100 100 100 UVPSA5016 - - - - - - - - - EA 50 50 50 50 50 50 50 50 50 DPCA-20 20 20 20 20 20 5 55 20 20 IRGACURE 184 One One One One One One One 0.05 10 IRGACURE 907 - - - - - - - - - DAROCUR TPO - - - - - - - - - EC300J - 0.05 25 2 2 2 2 2 2 Cond5 - - - - - - - - - UV light intensity (mJ/cm ² ) 300 300 300 300 300 300 300 300 300 Surface area ratio of photocured area (%) 9 9 9 0.9 54 9 9 9 9

evaluation example

Using each of the pressure-sensitive adhesive compositions and surface-curable pressure-sensitive adhesive films prepared in Examples 1 to 11 and Comparative Examples 1 to 9, physical properties were measured through the following evaluation examples, and the results are shown in Table 3 below.

<Evaluation Example 1: Absorbance and light transmittance evaluation>

<Evaluation Example 1.1: Evaluation of the light absorption wavelength region of the photoinitiator [Abs]>

A solution obtained by dissolving a photoinitiator, which is one component of the pressure-sensitive adhesive composition, in acetonitrile at a concentration of 0.1% by weight was placed in a 10mm x 10mm x 50mm quartz cell, and the absorbance (Abs) of the solution was measured with a UV Spectrum device (SHIMADZU 製, MPC-3100). After measuring, a wavelength region having an absorbance (Abs) of 0.1 or more was recorded as a light absorption wavelength region of the photoinitiator.

<Evaluation Example 1.2: Evaluation of light transmittance of the pressure-sensitive adhesive composition in the photoinitiator light absorption wavelength region [%T]>

After placing the pressure-sensitive adhesive composition in a 10mm x 10mm x 50mm quartz cell and measuring the light transmittance of the pressure-sensitive adhesive composition with a UV Spectrum device (SHIMADZU 製, MPC-3100), the average value of the light transmittance in the light absorption wavelength region of the photoinitiator is The transmittance was recorded.

<Evaluation Example 1.3: Evaluation of light transmittance of the adhesive film in the light absorption wavelength region of the photoinitiator [%T]>

After cutting the surface-curing adhesive film to a size of 10mm x 50mm and peeling the release film from both sides, attach the sample so that the exposure slot of the device is in the center of the sample, and use the UV Spectrum device (SHIMADZU 製, MPC-3100) to apply the adhesive film After measuring the light transmittance, the average value of the light transmittance in the light absorption wavelength region of the photoinitiator was recorded as the light transmittance.

<Evaluation Example 2: Surface energy evaluation [mN/m]>

_{Each solvent of water (H 2} O) as a hydrophilic solvent and diiodomethane (CH ₂ I ₂ ) as a hydrophobic solvent by using the Sessile Drop Technique on the surface of the photocured and non-photocured areas of the surface-curable adhesive film After measuring the contact angle of the surface with respect to a contact angle meter (Hucom System, Theta auto), the surface energy was calculated through Young-Dupre Equation (ASTM D5946).

<Evaluation Example 3: Evaluation of storage modulus [Pa]>

Viscoelasticity of the photocured region and the non-photocured region of the adhesive layer was measured in shear mode (1 Hz) using ARES (TA instruments 製), a dynamic viscoelasticity measuring device (Frequency: 1 rad/sec). Specifically, after separating the photocured area and the non-photocured area of the surface-curable adhesive film, and removing the release film (ie, the release-treated PET film), the photocured area is the photocured area between the photocured areas. The non-photocured area was laminated with each other to prepare a sample to have a thickness of 1 mm. The prepared laminated sample was used as a measurement specimen by piercing the sample with a drilling machine having a diameter of 8 mm. Measurement was performed at a temperature increase rate of 10 °C/min in a temperature range of -70 °C to 150 °C, and the storage modulus of each sample at 25 °C was recorded.

In addition, after etching the upper layer of the photocured region separated from the surface-curable adhesive film, that is, 15 μm thick from the upper surface using plasma etching equipment (SENTECH 製, SI500), only the lower layer of the photocured region was obtained. Then, they were laminated, and the storage modulus was measured according to the storage modulus measurement method.

In addition, after etching the lower layer of the photocured region separated from the surface-curable adhesive film, that is, 15 μm thick from the lower surface using plasma etching equipment (SENTECH 製, SI500), only the upper layer of the photocured region was obtained. Then, they were laminated, and the storage modulus was measured according to the storage modulus measurement method.

<Evaluation Example 4: Adhesion to the substrate [gf]>

After separating the photocured area and the non-photocured area of the adhesive layer, each was cut into 1-inch-thick strips. The adhesive side of the strip prepared by the above method was attached to a PET film (Toray Advanced Materials, XD500P, 50 μm) using a 2 kg rubber roller, and then left for 30 minutes. After that, the release film on the other side (ie, release-treated PET film) was peeled off, and the peeled side was laminated on the SUS (Steel Special Use Stainless) side using a rubber roller of 2 kg, and then left for 30 minutes. The 180 degree peeling force was measured for the specimen prepared by the above method at a speed of 300 mm/min using UTM equipment (Korinstech 製, LF Plus) at room temperature.

<Evaluation Example 5: Check whether physical deformation occurs>

A surface-hardened adhesive film (ie, the release film attached to both sides removed) is attached between two PI films (SKC Kolon 製, IF70, 50㎛) to form a PI film/adhesive film/PI film structure. Specimens for checking whether physical deformation occurred were prepared. Using the dynamic flexibility evaluation equipment (Science Town Co., Ltd., 5Axis Bending Test Machine, STS-5RT-100) for the specimen produced as described above, set the folding axis of the equipment to be located in the middle of the photocured area of the specimen, and , with a radius of curvature of 2.5 mm, repeated 3,600 times per hour to evaluate the dynamic flexibility for a total of 100,000 times, and then to evaluate whether physical deformation occurred in the folding part of the specimen.

Whether or not physical deformation occurred was evaluated by measuring the waviness in the vertical direction with respect to the folding direction of the specimen in close contact with the stage using a contact roughness meter (Linear Technology 製, Surfcom 1500SD2). Waviness was defined as the difference between the highest and lowest heights of the specimen relative to the horizontal. When the waviness of the specimen was 30 μm or more, it was determined that the PI film laminate had physical deformation by dynamic flexural evaluation.

In addition, if the intentional dynamic interfacial delamination does not sufficiently occur, physical deformation occurs. Here, “intentional dynamic interfacial peeling” means making a low surface energy region (ie, a portion with low adhesion) through photocuring so that it does not adhere to the substrate when evaluating flexibility in the laminate structure, thereby selectively creating interfacial peeling and deformation of the folding part means to prevent

Example One 2 3 4 5 6 7 8 9 10 11 Light absorption wavelength region of photoinitiator (nm) 200
~380 200
~380 200
~380 200
~400 200
~420 200
~380 200
~380 200
~380 200
~380 200
~380 200
~380 of the pressure-sensitive adhesive composition in the photoinitiator light absorption wavelength region
Light transmittance (%T) 10.3 11.1 14.4 9.9 10.3 19.2 3.0 10.3 10.4 10.8 10.1 Light transmittance (%T) of the adhesive film in the light absorption wavelength region of the photoinitiator 0.9 0.9 3.3 0.9 0.9 10.5 0.1 0.9 0.9 1.0 0.9 Surface energy of photocured area (E1, mN/m) 22.6 21.8 22.2 22.9 23.2 21.5 21.0 22.6 22.5 23.0 20.5 Surface energy of non-photocured area (E2, mN/m) 27.7 29.1 27.8 28.2 28.3 26.6 26.1 27.7 27.7 28.9 28.5 Difference in surface energy between regions (E2-E1, mN/m) 5.1 7.3 5.6 5.3 5.1 5.1 5.1 5.1 5.1 5.1 8.0 Adhesion to the substrate in the photocured area (A1, gf/inch) 11 9 13 8 11 9 8 11 11 18 5 Adhesion to the substrate in the non-photocured area (A2, gf/inch) 1140 740 860 1120 1200 1250 600 1140 1140 1190 1200 Difference in adhesion between areas (A2-A1, gf/inch) 1129 731 847 1112 1189 1241 512 1129 1129 1172 1195 Adhesion to the substrate opposite to the energy ray irradiation (gf/inch) 890 460 610 840 880 690 580 890 890 800 910 25℃ storage modulus of surface-curing adhesive film (kPa) 86 78 104 59 61 80 120 86 86 82 83 25℃ storage modulus of surface curing adhesive film upper layer (kPa) 182 306 211 164 143 210 450 182 182 170 420 25℃ storage modulus of surface curing adhesive film lower layer (kPa) 52 45 76 23 26 75 90 52 52 50 50 Whether physical deformation occurs X X X X X X X X X X X

comparative example One 2 3 4 5 6 7 8 9 Light absorption wavelength region of photoinitiator (nm) 200
~380 200
~380 200
~380 200
~380 200
~380 200
~380 200
~380 200
~380 200
~380 of the pressure-sensitive adhesive composition in the photoinitiator light absorption wavelength region
Light transmittance (%T) 61 42 4.1 10.3 10.3 11.2 10.0 10.1 12.5 Light transmittance (%T) of the adhesive film in the light absorption wavelength region of the photoinitiator 52 29 0.1 0.9 0.9 1.3 0.9 0.9 4.0 Surface energy of photocured area (E1, mN/m) 22.5 22.9 21.8 22.7 21.9 25.2 18.3 26.1 25.8 Surface energy of non-photocured area (E2, mN/m) 28.0 27.9 27.6 28.2 27.7 29.2 29.0 27.7 27.5 Difference in surface energy between regions (E2-E1, mN/m) 5.5 5.0 5.8 5.5 5.8 4.0 10.7 1.6 1.7 Adhesion to the substrate in the photocured area (A1, gf/inch) 10 9 16 10 10 120 3 650 420 Adhesion to the substrate in the non-photocured area (A2, gf/inch) 1750 1520 230 1160 1170 1190 1210 1140 1170 Difference in adhesion between areas (A2-A1, gf/inch) 1740 1511 214 1150 1160 1070 1207 490 750 Adhesion to the substrate opposite to the energy ray irradiation (gf/inch) 16 14 220 850 790 790 920 890 880 25℃ storage modulus of surface-curing adhesive film (kPa) 126 119 98 84 80 80 82 85 83 25℃ storage modulus of surface curing adhesive film upper layer (kPa) 118 122 111 176 169 120 750 100 95 25℃ storage modulus of surface curing adhesive film lower layer (kPa) 121 106 86 49 44 48 52 55 53 Whether physical deformation occurs ○ ○ X ○ ○ ○ ○ ○ ○

Referring to Tables 3 and 4, the surface-curable pressure-sensitive adhesive film prepared in Examples 1 to 11 includes a photocured region occupying 1% to 50% of the total surface area of the surface irradiated with energy rays and the rest. Since the difference in surface energy of the non-photocured region occupying the area exceeds 5 mN/m, it is possible to generate a difference in adhesion to the same substrate, ultimately inducing intentional dynamic interfacial peeling and physical deformation on the laminated substrate even after dynamic bending evaluation. It was found that no delamination occurred.

In addition, the surface-curable adhesive film prepared in Examples 1 to 11 has a light transmittance of 20% or less of the adhesive film in the light absorption wavelength region of the photoinitiator, so that photocuring by energy rays occurs only in the upper layer close to the surface of the adhesive film, Since it does not occur in the lower layer of the adhesive film, it was found that sufficient adhesion to the substrate could be realized on the opposite side irradiated with energy rays. At this time, even if a photoinitiator having a different structure or type is used or a different type of light absorber is used, if the light transmittance of the adhesive film in the light absorption wavelength region of the photoinitiator is 20% or less, the physical properties aimed at the present invention can be achieved. confirmed that there is.

In the case of Comparative Examples 1 and 2, if the light absorber is not used or the content thereof is very low, the energy ray is transmitted in the thickness direction of the adhesive film, so that it is impossible to photocur only the surface part targeted in the present invention. After the dynamic bending evaluation, the stress caused by the flow of the flexible display cannot be sufficiently alleviated because delamination occurs due to insufficient adhesion to the substrate on the opposite side to which the line is irradiated, and the storage modulus of elasticity of the side irradiated with energy rays rises rapidly. It was confirmed that physical deformation occurred.

In addition, in the case of Comparative Example 3, when the content of the light absorber is excessively contained in excess of 20 parts by weight based on 100 parts by weight of the photocurable adhesive resin of the adhesive composition, the light transmittance shows a very low value, but in the substrate of the adhesive film itself. Adhesion to the substrate (ie, adhesion to the substrate in the non-photocured area) is greatly reduced. As a result, when used as an interlayer adhesive material of a flexible display, it is not preferable because it may cause delamination between the substrates to be attached.

In the case of Comparative Example 4, since the surface area of the photocured region is less than 1% of the total surface area of the surface irradiated with energy rays, the region where the dynamic interface peeling occurs is small, and the stress caused by the change in the shape of the substrate is not sufficiently dispersed. As a result, it was possible to confirm the result that the shape of the substrate was physically deformed after the dynamic flexibility evaluation.

In addition, in the case of Comparative Example 5, the surface area of the photocured region occupied more than 50% of the total surface area of the surface irradiated with energy rays, so that the area of the non-photocured region responsible for high adhesion to the substrate was relatively It was small. As a result, a phenomenon occurred in which the folded portion of the substrate, ie, the photocured region, was lifted from the substrate after the dynamic flexural evaluation was performed, resulting in a problem in that the physical deformation of the substrate was recognized from the exterior due to delamination.

In addition, in the case of Comparative Example 6, the content of the photocurable oligomer is less than 10 parts by weight based on 100 parts by weight of the photocurable adhesive resin, so even if the photocuring reaction is carried out by energy rays, the crosslinking density is lowered and the surface energy is not sufficiently lowered. Intentional dynamic interfacial peeling did not occur sufficiently in the portion of the adhesive film in contact with the flowing part of the flexible display because the storage modulus was not sufficiently increased, and it was found that physical deformation occurred after the dynamic bending evaluation.

In addition, in the case of Comparative Example 7, the content of the photocurable oligomer exceeds 50 parts by weight with respect to 100 parts by weight of the photocurable adhesive resin, the photocuring reaction by the energy beam proceeds excessively, and the storage modulus of the adhesive film is excessively increased, It has been shown that the adhesive film is physically permanently deformed because it has brittleness and the adhesive film is destroyed by the flow of the flexible display or does not sufficiently relieve stress.

In addition, in the case of Comparative Example 8, the content of the photoinitiator was less than 0.1 parts by weight based on 100 parts by weight of the photocurable adhesive resin, and photocuring by energy ray irradiation was not sufficiently performed, so that the surface energy of the adhesive film was not sufficiently lowered and the storage modulus was low. Because it did not rise sufficiently, intentional dynamic interface peeling did not occur sufficiently in the portion of the adhesive film in contact with the flowing part of the flexible display, and it was found that physical deformation occurred after dynamic bending evaluation.

In addition, in the case of Comparative Example 9, when the content of the photoinitiator exceeds 5 parts by weight based on 100 parts by weight of the photocurable adhesive resin, when the photoinitiator is converted to an excited state to generate radicals, an excessive concentration of radicals is generated in a unit volume. The terminating reaction between each other was accelerated and the photocuring of the adhesive film was not sufficiently performed, so intentional dynamic interfacial peeling did not occur sufficiently in the part of the adhesive film in contact with the moving part of the flexible display, and physical deformation occurred after dynamic bending evaluation. .

Although the present invention has been described with reference to the drawings and embodiments, it will be understood that these are merely exemplary, and that those skilled in the art can make various modifications and equivalent other embodiments therefrom. Accordingly, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

100: adhesive film 101: substrate
110: adhesive composition 110': adhesive layer
111: photo-curable adhesive resin 112: photo-curable oligomer
113: photoinitiator 114: light absorber
120: release film

Claims (17)

delete delete delete delete As an adhesive film comprising an adhesive layer,
The pressure-sensitive adhesive layer is prepared by coating and drying a pressure-sensitive adhesive composition including a photo-curable pressure-sensitive adhesive resin, a photo-curable oligomer, a photo initiator and a light absorber on a substrate, and when the thickness is 20 μm, the light in the light absorption wavelength region of the photo initiator The transmittance is 20% or less,
Manufactured by irradiating energy rays to a portion of one surface of the adhesive film, including both a photocured area and a non-photocured area on one surface,
The difference between the adhesion force of the photocured region and the adhesion force of the non-photocured region to the same substrate satisfies Equation 2 below,
Adhesive film having an adhesive force of 300 gf/inch or more to the substrate of the side opposite to the side irradiated with energy rays in the photocured area:
[Equation 2]
300gf/inch < A2 - A1
A1: Adhesion to the substrate of the photocured area
A2: Adhesion to the substrate of the non-photocured area. delete 6. The method of claim 5,
The adhesive film has a surface in which 1% or more and 50% or less of the total surface area is a photocured region and the remaining surface area is a non-photocured region, wherein the photocured region is divided into two or more subregions. . 6. The method of claim 5
The difference between the surface energy of the photocured region and the surface energy of the non-photocured region is an adhesive film satisfying Equation 1 below:
[Equation 1]
5mN/m < E2 - E1
E1: surface energy of photocured area
E2: The surface energy of the non-photocured area. delete 6. The method of claim 5,
The adhesion (A1) of the photocured region to the substrate is 50 gf/in or less. delete 6. The method of claim 5
The adhesive film has a storage modulus at 25° C. of 10 ³ Pa or more and 10 ⁵ Pa or less, and the photocured region includes two or more sections having different storage modulus along a thickness direction. A display device comprising the adhesive film according to claim 5. 14. The method of claim 13,
The display device is a flexible display device.
6. The method of claim 5,
The light absorption wavelength region of the photoinitiator is 200nm to 450nm pressure-sensitive adhesive film. 6. The method of claim 5,
The content of the photocurable oligomer, the content of the photoinitiator, and the content of the light absorber are 10 parts by weight or more and 50 parts by weight or less, 0.1 parts by weight or more and 5 parts by weight or less, and 0.1 parts by weight, respectively, based on 100 parts by weight of the photocurable adhesive resin. An adhesive film of 20 parts by weight or more. 6. The method of claim 5
The light absorber is an adhesive film comprising a UV absorber, a free radical scavenger, an inorganic pigment, or a combination thereof.

Images