WO2021220196A1 - Adhesive composition, adhesive film, preparation method thereof and adhesive tape comprising same - Google Patents

Adhesive composition, adhesive film, preparation method thereof and adhesive tape comprising same Download PDF

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Publication number
WO2021220196A1
WO2021220196A1 PCT/IB2021/053537 IB2021053537W WO2021220196A1 WO 2021220196 A1 WO2021220196 A1 WO 2021220196A1 IB 2021053537 W IB2021053537 W IB 2021053537W WO 2021220196 A1 WO2021220196 A1 WO 2021220196A1
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Prior art keywords
adhesive
group
film
oligomer
adhesive composition
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PCT/IB2021/053537
Other languages
French (fr)
Inventor
Yeon Ung Bae
Yong Seok Seo
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3M Innovative Properties Company
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Publication of WO2021220196A1 publication Critical patent/WO2021220196A1/en

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/10—Adhesives in the form of films or foils without carriers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J4/00—Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16
    • C09J4/06—Organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond in combination with a macromolecular compound other than an unsaturated polymer of groups C09J159/00 - C09J187/00
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
    • C09J133/04—Homopolymers or copolymers of esters
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J163/00—Adhesives based on epoxy resins; Adhesives based on derivatives of epoxy resins
    • C09J163/10—Epoxy resins modified by unsaturated compounds
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/20—Adhesives in the form of films or foils characterised by their carriers
    • C09J7/22—Plastics; Metallised plastics
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/40—Adhesives in the form of films or foils characterised by release liners
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
    • C08K5/0025—Crosslinking or vulcanising agents; including accelerators
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2203/00—Applications of adhesives in processes or use of adhesives in the form of films or foils
    • C09J2203/326—Applications of adhesives in processes or use of adhesives in the form of films or foils for bonding electronic components such as wafers, chips or semiconductors
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00—Additional features of adhesives in the form of films or foils
    • C09J2301/30—Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier
    • C09J2301/312—Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier parameters being the characterizing feature
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00—Additional features of adhesives in the form of films or foils
    • C09J2301/40—Additional features of adhesives in the form of films or foils characterized by the presence of essential components
    • C09J2301/408—Additional features of adhesives in the form of films or foils characterized by the presence of essential components additives as essential feature of the adhesive layer
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00—Additional features of adhesives in the form of films or foils
    • C09J2301/40—Additional features of adhesives in the form of films or foils characterized by the presence of essential components
    • C09J2301/416—Additional features of adhesives in the form of films or foils characterized by the presence of essential components use of irradiation
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2433/00—Presence of (meth)acrylic polymer
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2463/00—Presence of epoxy resin

Definitions

  • the present invention relates to an adhesive composition with adhesive strength variability, an adhesive film, a preparation method thereof, and an adhesive tape, a laminate, and an apparatus comprising the same.
  • An adhesive tape with adhesive strength variability is a tape with adhesive strength changed by curing of an adhesive layer or the like as needed, and is useful in a field requiring temporary adhesion, such as a manufacturing process of an electronic device.
  • Korean Patent Registration No. 0476798 there is disclosed an adhesive tape that is cured in a short time by heating while easily temporarily adhering to an adherend due to its adherence at room temperature to exhibit strong adhesive strength.
  • a waterproof adhesive tape with a thickness of 350 pm has been used to attach internal components to a rear cover of a smartphone, but some sensors of a printed circuit board (PCB) are in contact with an adhesive surface of the tape, thereby causing a risk of damage to internal sensors or chip boards.
  • a general single-sided adhesive tape having a thickness of 10 pm is applied as a masking tape and is easily removed in a process of repairing a breakdown of a smartphone, thereby minimizing damage to the internal sensors or chip boards.
  • the adhesive surface of such a masking tape is also in direct contact with sensors or chips to damage the sensor or the chap. Therefore, there is a need for an adhesive composition that is applied to these masking tapes and does not cause the above problems.
  • MLCCs multilayer ceramic capacitors
  • a process of precisely cutting a raw material sheet is performed, and during such cutting, the raw material sheet needs to be firmly fixed and the cut chips need to be easily separated. Accordingly, even in such a process, a tape with adhesive strength variability may be applied, and such a tape is required to have thermal stability and high shear adhesive strength during cutting, and to change the adhesive strength to a very low level after cutting.
  • Adhesive compositions that implement adhesive strength variability by mixing various additives with existing adhesives have been developed, but these conventional adhesive compositions with adhesive strength variability have problems that the compatibility between existing adhesives and additives is not good, or a change in adhesive strength is not large.
  • an object of the present invention is to provide an adhesive composition with adhesive strength variability, an adhesive film, a preparation method thereof, a using method thereof, and an adhesive tape, a laminate and an apparatus including the same, which can exhibit high performance by solving the conventional problems.
  • an adhesive composition including a base polymer; a crosslinking agent reacting with the base polymer; a curable resin to be UV-cured after the reaction of the base polymer and the crosslinking agent; and an initiator curing the curable resin.
  • the curable resin includes a first oligomer, a second oligomer, and an organic acid, and the adhesive composition has first adhesive strength before UV curing and second adhesive strength after UV curing after the reaction of the base polymer and the crosslinking agent, wherein the second adhesive strength is lower than the first adhesive strength.
  • an adhesive film including a reaction product of a base polymer and a crosslinking agent, wherein the adhesive film contains a curable resin to be UV-cured and an initiator, the curable resin includes a first oligomer, a second oligomer, and an organic acid, and the adhesive film has first adhesive strength before UV curing and second adhesive strength after UV curing, and the second adhesive strength is lower than the first adhesive strength.
  • a preparation method of an adhesive film including the steps of: preparing a curable resin containing a first oligomer, a second oligomer and an organic acid; mixing a base polymer, the curable resin, an initiator, and a crosslinking agent; reacting the crosslinking agent with the base polymer to form a film-like polymer; and obtaining an adhesive film by preserving the curable resin and the initiator in the film-like polymer.
  • an adhesive tape including a base film; and the adhesive film disposed on one side of the base film.
  • a laminate including a first substrate; a second substrate; and the adhesive film disposed between the first substrate and the second substrate.
  • an apparatus including the adhesive tape or the laminate.
  • the adhesive composition and the adhesive film exhibit excellent adhesive strength at the beginning and then have adhesive strength almost close to 0 after UV curing, and as a result, a difference in adhesive strength is very large and color is clearly changed after UV curing, thereby easily checking a change in adhesive strength visually.
  • changes in properties may be minimized during transport/storage before use.
  • the adhesive film of the present invention and the adhesive tape including the same can be variously applied in fields requiring adhesive strength variability, such as adhering and manufacturing of electric devices.
  • FIG. 1 schematically illustrates structures of an adhesive composition according to the present invention before and after UV curing.
  • FIG. 2 is a graph showing changes in adhesive strength and storage modulus of the adhesive composition according to the present invention.
  • FIG. 3 illustrates an example of a cross-sectional view of an adhesive tape according to the present invention.
  • FIGS. 4 and 5 illustrate a preparation method of a curable resin added to the adhesive composition of the present invention and results of NMR analysis, respectively.
  • FIG. 6 illustrates a mechanism in which the adhesive composition and the adhesive film according to the present invention exhibit yellowing.
  • FIG. 7 illustrates an example in which a tape with adhesive strength variability is applied as a masking tape in a smartphone.
  • FIG. 8 illustrates an example in which a tape with adhesive strength variability is applied in a process of cutting a substrate for manufacturing an MLCC or the like.
  • an adhesive composition including a base polymer, a crosslinking agent, a curable resin, and an initiator.
  • the curable resin includes a first oligomer, a second oligomer and an organic acid, and may be UV-cured upon irradiation with UV light.
  • the base polymer may react with the crosslinking agent before the curable resin is cured by the initiator.
  • the base polymer may react with the crosslinking agent while the curable resin and the initiator are preserved, and the adhesive strength of the adhesive composition after the reaction may be rapidly lowered after UV curing.
  • An adhesive composition may include a base polymer; a crosslinking agent reacting with the base polymer; a curable resin to be UV- cured after the reaction of the base polymer and the crosslinking agent; and an initiator curing the curable resin.
  • the adhesive composition has first adhesive strength before UV curing and second adhesive strength after UV curing after the reaction of the base polymer and the crosslinking agent, wherein the second adhesive strength is lower than the first adhesive strength.
  • the adhesive composition according to the embodiment has different structures and properties before and after UV curing.
  • the base polymer reacts (that is, is crosslinked) with the crosslinking agent to form a film and the like, and the film formed above has properties different from the prior art in terms of physical properties such as adhesive strength.
  • FIG. 2 is a graph showing changes in storage modulus and adhesive strength of the adhesive composition according to an embodiment by UV irradiation.
  • the adhesive composition has a low storage modulus before UV curing, while the storage modulus increases rapidly after UV curing. Accordingly, the adhesive composition has excellent adhesive strength before UV curing, whereas after UV curing, the adhesive strength is rapidly lowered.
  • the adhesive composition has first adhesive strength before UV curing (i.e., while the curable resin and the initiator are preserved).
  • the first adhesive strength may be 200 gf/in or more, 250 gf/in or more, 300 gf/in or more, 350 gf/in or more, 400 gf/in or more, or 500 gf/in or more.
  • the first adhesive strength may be in the range of 200 gf/in to 10,000 gf/in, or 300 gf/in to 5,000 gf/in.
  • the adhesive strength (the first adhesive strength, the second adhesive strength, etc.) may be measured by ASTM D3330 which is a general measuring method in the art, and for example, may be adhesive strength measured for polyimide or stainless steel. A more detailed example of the measuring method has been specifically described in the following embodiment.
  • the adhesive composition has second adhesive strength after UV curing.
  • the second adhesive strength may be 100 gf/in or less, 50 gf/in or less, 30 gf/in or less, 20 gf/in or less, or 10 gf/in or less.
  • the second adhesive strength may be in the range of 0 gf/in to 100 gf/in, 0 gf/in to 50 gf/in, or 0 gf/in to 20 gf/in.
  • the first adhesive strength may be 200 gf/in or more and the second adhesive strength may be 100 gf/in or less.
  • the first adhesive strength may be 250 gf/in or more and the second adhesive strength may be 50 gf/in or less.
  • the first adhesive strength may be in the range of 200 gf/in to 3,000 gf/in, and the second adhesive strength may be in the range of 0 gf/in to 20 gf/in.
  • the second adhesive strength is lower than the first adhesive strength.
  • the second adhesive strength may be lower than the first adhesive strength by 100 gf/in or more, 150 gf/in or more, 200 gf/in or more, or 500 gf/in or more.
  • the first adhesive strength and the second adhesive strength may have a difference of 200 gf/in or more from each other.
  • a ratio of the first adhesive strength to the second adhesive strength may be 10 or more, 20 or more, 30 or more, 50 or more, 70 or more, or 100 or more.
  • a ratio of the second adhesive strength to the first adhesive strength may be 0.1 or less, 0.06 or less, 0.03 or less, 0.02 or less, or 0.01 or less.
  • the adhesive composition of the present invention includes a first oligomer as a curable resin, a second oligomer, and an organic acid, wherein a difference between the first adhesive strength and the second adhesive strength may be greater than that of a composition containing only one type of oligomer or organic acid and the difference in adhesive strength may be controlled by adjusting the ratio of the first oligomer, the second oligomer, and the organic acid.
  • the adhesive composition may satisfy a requirement as an optically transparent adhesive after the reaction of the base polymer and the crosslinking agent and before UV curing.
  • the adhesive composition may have a haze before UV curing of 5% or less, 2% or less, or 1% or less.
  • the adhesive composition may have a light transmittance before UV curing of 80% or more, 90% or more, or 95% or more.
  • the adhesive composition may satisfy the requirement as an optically transparent adhesive even after UV curing.
  • the adhesive composition may have a haze after UV curing of 5% or less, 2% or less, or 1% or less.
  • the adhesive composition may have a light transmittance after UV curing of 80% or more,
  • the adhesive composition may be discolored during UV curing in a state exposed to oxygen. That is, the adhesive composition may have a first color before UV curing and a second color after UV curing in the state exposed to oxygen.
  • the discoloration may be yellowing, and more specifically, the first color may be a colorless or white-based color, and the second color may be a yellow-based color. Accordingly, the second color may have a higher yellowness (YI) than the first color.
  • the adhesive composition may have excellent hardness after UV curing.
  • the adhesive composition may have a surface hardness of 1H or more or 2H or more after UV curing.
  • the adhesive composition according to the embodiment includes a base polymer, a crosslinking agent, a curable resin, and an initiator.
  • the adhesive composition according to the embodiment may further include a solvent and other additives.
  • each component of the adhesive composition will be described in detail.
  • the adhesive composition according to the embodiment includes a base polymer.
  • the base polymer exhibits an adhesive property as a main component of the adhesive composition.
  • the base polymer reacts (that is, is crosslinked) with a crosslinking agent to form a film and the like.
  • the base polymer may be included in the range of 35 wt% to 95 wt% based on the weight of the adhesive composition. Specifically, the base polymer may be included in the range of 40 wt% to 90 wt%, 45 wt% to 85 wt%, or 50 wt% to 80 wt% based on the weight of the adhesive composition. At this time, the content of the base polymer and the weight of the adhesive composition may be based on the solid content.
  • the base polymer may contain functional groups which are reactive with the crosslinking agent.
  • the base polymer may have at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, an acryl group, a methacryl group, an acetate group, and a vinyl group.
  • the base polymer may have an acrylate-based functional group. Accordingly, the base polymer may implement high modulus and hardness and lower second adhesive strength by causing crosslinking even between the acrylate-based functional groups by a radical reaction during UV curing to form an interpenetrated network structure with the cured chain of the first oligomer.
  • the content of the acrylate- based functional groups in the base polymer may be 1 wt% to 15 wt%.
  • a type of the acrylate-based functional group may be an acrylate functional group or a methacrylate functional group.
  • the base polymer may be an acrylic resin.
  • the base polymer may be an acrylic resin having an acrylate-based functional group.
  • the base polymer may be an acrylic copolymer resin.
  • the acrylic copolymer resin may be a resin copolymerized with at least two monomers selected from the group consisting of 2-ethylhexyl acrylate (2-EHA), butyl acrylate (BA), methyl acrylate (MA), vinyl acetate (VAc), acrylic acid (AA), and 2-hydroxyethyl acrylate (2- HEA).
  • the combination of at least two monomers constituting the acrylic copolymer resin may include 2-EHA/MA, BA/MA, AA/2-HEA, MA/2-HEA, BA/2-HEA, MA/AA/2-HEA, and the like.
  • the base polymer may be a thermocurable resin.
  • the base polymer may be a pressure sensitive adhesive (PSA) resin.
  • the weight average molecular weight (Mw) of the base polymer may be 1,000 to 200,000, and 10,000 to 200,000. Within the above range, transparency before UV curing of the adhesive composition may be more improved.
  • the curable resin included in the adhesive composition is to be UV-cured after the reaction between the base polymer and the crosslinking agent. That is, the curable resin may exist in an uncured state even after the reaction of the base polymer and the crosslinking agent.
  • the content of the curable resin in the composition may be 20 parts by weight to 100 parts by weight based on 100 parts by weight of the base polymer. Specifically, the content of the curable resin in the composition may be 20 parts by weight to 90 parts by weight, 20 parts by weight to 80 parts by weight, or 25 parts by weight to 70 parts by weight based on 100 parts by weight of the base polymer. At this time, the content range may be based on the solid content.
  • the curable resin includes a first oligomer, a second oligomer, and an organic acid.
  • the first oligomer is to be UV-cured after the reaction of the base polymer and the crosslinking agent. That is, the first oligomer may exist in an uncured state even after the reaction of the base polymer and the crosslinking agent. As such, the first oligomer in the uncured state may not be involved in the adhesive strength of the reaction product of the base polymer and the crosslinking agent. However, after the reaction of the base polymer and the crosslinking agent, the first oligomer is UV-cured as necessary, so that the adhesive strength of the reaction product may be rapidly lowered.
  • the first oligomer may be cured by an initiator (i.e., photoinitiator).
  • an initiator i.e., photoinitiator
  • FIG. 1 schematically illustrates structures of the adhesive composition according to the present invention before and after UV curing.
  • the adhesive composition before UV curing includes an oligomer 102 such as a first oligomer and an additive 103 such as an initiator together with a chain of a crosslinked base polymer 101, high adhesive strength and bonding strength may be exhibited by functional groups present in the base polymer and the oligomer.
  • a chain of a cured oligomer 102’ is generated by a radical reaction to form an interpenetrated network structure together with the chain of the crosslinked base polymer 101, so that the adhesive composition may exhibit high modulus and hardness, and low adhesive strength.
  • the first oligomer may have compatibility with the base polymer.
  • the first oligomer may be an epoxy -based oligomer.
  • the first oligomer may have acrylate-based functional groups at both ends.
  • the first oligomer may include repeating units derived from an epoxy acrylate-based compound.
  • the first oligomer may be at least one compound represented by the following Chemical Formula 1.
  • Xi is each independently a linear or branched Ci-io alkylene group
  • Li is each independently a Ci-io alkylene group, a C3-20 cycloalkylene group, or a Ci-10 alkyleneoxy group
  • Ro is each independently H or a C1-3 alkyl group
  • Ri is each independently H, a Ci-10 alkyl group, a Ci-10 alkoxy group, a C2-10 alkenyl group, or a C6-14 aryl group
  • m is an integer of 0 to 10, or 1 to 10.
  • Ci-10 alkylene group may include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, a sec-butylene group, a t-butylene group, a pentylene group, an isopentylene group, a t-pentylene group, a hexylene group, a heptylene group, an octylene group, an isooctylene group, a t-octylene group, a 2-ethylhexylene group, a nonylene group, an isononylene group, a decylene group, an isodecylene group, and the like.
  • C3-20 cycloalkylene group examples include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group, a decalinylene group, an adamantylene group, and the like.
  • Ci-io alkyleneoxy group may include a methyleneoxy group, an ethyleneoxy group, a propyleneoxy group, a butyleneoxy group, a sec-butyleneoxy group, a t-butyleneoxy group, a pentyleneoxy group, a hexyleneoxy group, a heptyleneoxy group, an octyleneoxy group, a 2-ethyl-hexyleneoxy group, etc.
  • Ci-io alkyl group examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, a pentyl group, an isopentyl group, a t-pentyl group, a hexyl group, a heptyl group, an octyl group, an isooctyl group, a t-octyl group, a 2-ethylhexyl group, a nonyl group, an isononyl group, a decyl group, an isodecyl group, and the like.
  • C1-3 alkyl group examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, etc.
  • Ci-10 alkoxy group examples include a methoxy group, an ethoxy group, a propoxy group, a butyloxy group, a sec-butoxy group, a t-butoxy group, a pentoxy group, a hexyloxy group, a heptoxy group, an octyloxy group, a 2-ethyl-hexyloxy group, etc.
  • Specific examples of the C2-10 alkenyl group include a vinyl group, an allyl group, a butenyl group, a propenyl group, etc.
  • C6-14 aryl group examples include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, etc.
  • the epoxy acrylate-based compound may have a bisphenol A skeleton.
  • the first oligomer may include repeating units derived from an epoxy acrylate-based compound having the bisphenol A skeleton.
  • the weight average molecular weight of the first oligomer may be in the range of 300 to 30,000, or 500 to 10,000.
  • the content of the first oligomer in the composition may be 10 parts by weight to 100 parts by weight based on 100 parts by weight of the base polymer. Specifically, the content of the first oligomer in the composition may be 10 parts by weight to 90 parts by weight, 10 parts by weight to 80 parts by weight, or 15 parts by weight to 70 parts by weight based on 100 parts by weight of the base polymer. At this time, the contents of the base polymer and the first oligomer may be based on the solid content.
  • the curable resin further includes a second oligomer different from the first oligomer.
  • the second oligomer reacts with an organic acid and the like in the adhesive composition to generate a plurality of functional groups (hydroxyl group, etc.), thereby improving initial adhesive strength of the adhesive composition.
  • the second oligomer is UV-cured with the first oligomer if necessary, so that the adhesive strength of the reaction product may be rapidly lowered.
  • the second oligomer may be an epoxy -based oligomer.
  • the second oligomer may have epoxide functional groups at both ends.
  • the second oligomer may be at least one compound represented by the following Chemical Formula 2.
  • X2 is each independently a linear or branched Ci-10 alkylene group
  • L2 is each independently a Ci-10 alkylene group, a C3-20 cycloalkylene group, or a Ci-10 alkyleneoxy group
  • R2 is each independently H, a Ci-10 alkyl group, a Ci-10 alkoxy group, a C2-10 alkenyl group, or a C6-14 aryl group
  • n is an integer of 0 to 10, or 1 to 10.
  • Ci-10 alkylene group may include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, a sec-butylene group, a t-butylene group, a pentylene group, an isopentylene group, a t-pentylene group, a hexylene group, a heptylene group, an octylene group, an isooctylene group, a t-octylene group, a 2-ethylhexylene group, a nonylene group, an isononylene group, a decylene group, an isodecylene group, and the like.
  • C3-20 cycloalkylene group examples include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group, a decalinylene group, an adamantylene group, and the like.
  • Ci-10 alkyleneoxy group may include a methyleneoxy group, an ethyleneoxy group, a propyleneoxy group, a butyleneoxy group, a sec-butyleneoxy group, a t-butyleneoxy group, a pentyleneoxy group, a hexyleneoxy group, a heptyleneoxy group, an octyleneoxy group, a 2-ethyl-hexyleneoxy group, etc.
  • Ci-10 alkyl group examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, a pentyl group, an isopentyl group, a t-pentyl group, a hexyl group, a heptyl group, an octyl group, an isooctyl group, a t-octyl group, a 2-ethylhexyl group, a nonyl group, an isononyl group, a decyl group, an isodecyl group, and the like.
  • Ci-io alkoxy group examples include a methoxy group, an ethoxy group, a propoxy group, a butyloxy group, a sec-butoxy group, a t-butoxy group, a pentoxy group, a hexyloxy group, a heptoxy group, an octyloxy group, a 2-ethyl- hexyloxy group, etc.
  • Specific examples of the C2-10 alkenyl group include a vinyl group, an allyl group, a butenyl group, a propenyl group, etc.
  • Specific examples of the C6-14 aryl group include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, etc.
  • the second oligomer may be an epoxy resin having a bisphenol A skeleton.
  • a bisphenol A skeleton changes the color of the adhesive composition to yellow under oxygen exposure conditions after UV curing, so that the curing may be easily checked with the naked eye.
  • FIG. 6 shows a mechanism for indicating the yellowing of the adhesive film according to the present invention, wherein an unreacted bisphenol A epoxy resin in the adhesive composition may cause photo oxidation by UV irradiation, resulting in rapid yellowing. More specifically, in a bisphenol group in the unreacted epoxy resin, a methyl (-CH3) group between the two phenyl groups may be formed into a quinone structure by oxidation upon UV irradiation to cause discoloration.
  • the weight average molecular weight of the second oligomer may be in the range of 300 to 30,000, or 500 to 10,000.
  • the content of the second oligomer in the adhesive composition may be 0.1 part by weight to 20 parts by weight based on 100 parts by weight of the base polymer. Specifically, the content of the second oligomer in the adhesive composition may be 0.1 part by weight to 10 parts by weight or 0.1 part by weight to 5 parts by weight based on 100 parts by weight of the base polymer. At this time, the contents of the second oligomer and the base polymer may be based on the solid content.
  • the organic acid may improve first adhesive strength (adhesive strength before UV curing) of the adhesive composition, due to a functional group (carboxyl group, hydroxyl group, etc.) contained therein or due to a functional group (e.g., a hydroxyl group by reaction with an epoxy group, etc.) generated by reaction with an oligomer present in the adhesive composition.
  • a functional group carboxyl group, hydroxyl group, etc.
  • a functional group e.g., a hydroxyl group by reaction with an epoxy group, etc.
  • the organic acid may have 1 to 5, or 1 to 3 functional groups.
  • the organic acid may have at least one functional group selected from the group consisting of a hydroxyl group, an acryl group, a methacryl group, an acetate group, and a vinyl group in addition to a carboxyl group.
  • the organic acid may contain a carbon double bond at an end.
  • the carbon double bond may cause a radical reaction with the functional groups of the base polymer and/or the oligomer during UV curing to increase the crosslinking density of the adhesive composition, thereby further lowering the second adhesive strength.
  • the organic acid may have a group containing a double bond between carbons.
  • the group containing the double bond between carbons may include an acrylic group, a methacrylic group, a vinyl group, etc.
  • the organic acid may be at least one compound represented by Chemical Formula 3 below.
  • R3 is H or a C1-3 alkyl group
  • L3 is a single bond, a Ci-10 alkylene group, a C3-20 cycloalkylene group, or a Ci-10 alkyleneoxy group.
  • C1-3 alkyl group examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, etc.
  • Specific examples of the Ci-10 alkylene group may include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, a sec-butylene group, a t-butylene group, a pentylene group, an isopentylene group, a t-pentylene group, a hexylene group, a heptylene group, an octylene group, an isooctylene group, a t-octylene group, a 2- ethylhexylene group, a nonylene group, an isononylene group, a decylene group, an isodecylene group, and the like.
  • C3-20 cycloalkylene group examples include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group, a decalinylene group, an adamantylene group, and the like.
  • Ci-10 alkyleneoxy group may include a methyleneoxy group, an ethyleneoxy group, a propyleneoxy group, a butyleneoxy group, a sec-butyleneoxy group, a t-butyleneoxy group, a pentyleneoxy group, a hexyleneoxy group, a heptyleneoxy group, an octyleneoxy group, a 2-ethyl-hexyleneoxy group, etc.
  • the organic acid may be an acrylic acid, and specifically, may include at least one of methacrylic acid and acrylic acid.
  • the molecular weight of the organic acid may be in the range of 50 to 1000, or 50 to 500.
  • the content of the organic acid in the composition may be 0.1 to 10 parts by weight, 0.1 to 5 parts by weight, or 0.1 to 3 parts by weight based on 100 parts by weight of the base polymer. At this time, the contents of the organic acid and the base polymer may be based on the solid content.
  • the adhesive composition according to the embodiment includes an initiator.
  • the adhesive composition may include a photoinitiator to UV-cure the curable composition.
  • a general photoinitiator specifically, at least one selected from the group consisting of ketones (benzophenone, acetophenone, etc.), benzoins, benzoin ethers, benzyls, and benzyl ketals may be used.
  • the photoinitiator may be benzoin ethers (e.g., benzoin methyl ether or benzoin isopropyl ether) or substituted benzoin ethers.
  • benzoin ethers e.g., benzoin methyl ether or benzoin isopropyl ether
  • substituted benzoin ethers e.g., benzoin methyl ether or benzoin isopropyl ether
  • the photoinitiator may be substituted acetophenone, for example, 2,2-diethoxyacetophenone or 2,2-dimethoxy-2-phenylacetophenone.
  • the photoinitiator may be substituted alpha-ketones (e.g., 2-methyl-2-hydroxypropiophenone), aromatic sulfonyl chlorides (e.g., 2- naphthalenesulfonyl chloride), or photoactive oximes (e.g., 1 -phenyl- 1,2-propanedi one-2- (O-ethoxy carbonyl) oxime).
  • alpha-ketones e.g., 2-methyl-2-hydroxypropiophenone
  • aromatic sulfonyl chlorides e.g., 2- naphthalenesulfonyl chloride
  • photoactive oximes e.g., 1 -phenyl- 1,2-propanedi one-2- (O-ethoxy carbonyl) oxime
  • the photoinitiator may be 1 -hydroxy cyclohexyl phenyl ketone, bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide, l-4-(2- hy droxy ethoxy )phenyl-2-hydroxy-2-m ethyl- 1 -propane- 1 -one, 2-benzyl-2-dimethylamino- l-4-morpholinophenyl)butanone, 2-dimethylamino-2-(4-methylbenzyl)-l-(4-morpholin-4- yl-phenyl)butan- 1 -one, 2-methyl- 1 -4-(methylthio)phenyl-2-morpholinopropane- 1 -one, 2- hydroxy-2-methyl-l-phenylpropan-l-one, and the like.
  • the photoinitiator may be 2-(2-oxo-2- phenylacetoxyethoxy)ethyl oxyphenylacetate, 2-(2-hydroxyethoxy)ethyl oxyphenylacetate, and the like.
  • Examples of commercially available photoinitiators may include Omnirad series from IGM Resin Co., Ltd., Ciba IRGACURE series from Ciba Specialty Chemicals Co., Ltd., Esacure KIP series from IGM Resins Co., Ltd., and the like.
  • the initiator may be used alone or in combination of two or more.
  • the initiator may be used by mixing two or more types of photoinitiators having different operating wavelengths.
  • the initiator may have a first initiator that acts in light having a wavelength of 365 nm to 390 nm; and a second initiator that acts in light having a wavelength of 320 nm or less.
  • the adhesive composition may further include a thermal initiator.
  • a water-soluble or water-insoluble (i.e., oil-soluble) thermal initiator may be selectively used.
  • persulfates such as potassium persulfate, ammonium persulfate, sodium persulfate, and mixtures thereof
  • oxidation-reduction initiators such as a reaction product of a reducing agent such as metabisulfite (e.g., sodium metabi sulfite) or bisulfate (e.g., sodium bisulfate) and persulfate
  • 4,4'-azobis (4-cyanopentanoic acid) and its soluble salts e.g., sodium salt, potassium salt
  • azos such as 2,2’-azobis (2-methylbutanenitrile), 2,2’-azobis (isobutyronitrile), and 2,2’-azobis (2,4-dimethylpentanenitrile); or peroxides such as benzoyl peroxide, cyclohexane peroxide, and lauroyl peroxide may be used.
  • the content of the initiator in the composition may be 0.1 part by weight to 20 parts by weight based on 100 parts by weight of the base polymer. Specifically, the content of the initiator in the composition may be 0.1 part by weight to 10 parts by weight or 0.1 part by weight to 5 parts by weight based on 100 parts by weight of the base polymer. In this case, the content of the base polymer and the content of the initiator may be based on an amount of the solid content or an amount other than a solvent.
  • the adhesive composition according to the embodiment includes a crosslinking agent.
  • the crosslinking agent reacts with the base polymer to form a film and the like.
  • the content of the crosslinking agent in the composition may be 0.1 part by weight to 20 parts by weight based on 100 parts by weight of the base polymer.
  • the content of the crosslinking agent in the composition may be 0.1 part by weight to 10 parts by weight or 0.1 part by weight to 5 parts by weight based on 100 parts by weight of the base polymer.
  • the contents of the crosslinking agent and the base polymer may be based on the solid content.
  • the crosslinking agent may contain a functional group which is reactive with the functional group of the base polymer.
  • the crosslinking agent may have one or at least two functional groups selected from the group consisting of an epoxy group, an isocyanate group, a carboxyl group, a hydroxyl group, an acryl group, a methacryl group, an acetate group, and a vinyl group.
  • the crosslinking agent may have an epoxy group or an isocyanate group.
  • the crosslinking agent may be a photo-crosslinking agent, a thermal crosslinking agent, or a combination thereof.
  • the photo-crosslinking agent may use a general multifunctional acrylic compound.
  • the photo-crosslinking agent may be at least one selected from the group consisting of diacrylate and triacrylate.
  • Specific examples of the photo-crosslinking agent may include 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate (HDD A), 1,9-nonanediol diacrylate, tripropylene glycol diacrylate, tetraethylene glycol diacrylate, trimethylolpropane triacrylate, and pentaerythritol triacrylate.
  • the thermal crosslinking agent may be an isocyanate-based, epoxy-based, or metal chelate-based compound.
  • the isocyanate-based compound may be a multifunctional aromatic or aliphatic isocyanate compound.
  • the isocyanate-based compound may be trimerized isocyanate such as a toluene diisocyanate-trimethylol propane (TDI- TMP) adduct.
  • the epoxy -based compound may have one or at least two epoxy groups, and may have a functional group reactive with the base polymer.
  • the metal chelate-based compound may be a chelate-based compound having a metal such as Zn, Ni, Mn, Fe, Co, Cr, Al, Ti or Zr.
  • An example of a commercially available thermal crosslinking agent may include GK series of TTT Korea Co., Ltd., and Saivinol hardener series from Saiden Chemical Industry Co., Ltd.
  • the adhesive composition according to the embodiment may further include a solvent.
  • the solvent may serve to adjust the viscosity of the adhesive composition.
  • the type of the solvent is not particularly limited, and may be, for example, at least one selected from the group consisting of toluene, a mixture of hexane/methyl ethyl ketone, xylene, and isopropyl acetate.
  • the mixing amount of the solvent is not particularly limited, but for example, the solvent may be mixed to have the solid content of the adhesive composition in the range of 30 wt% to 90 wt%, or 50 wt% to 80 wt%.
  • the adhesive composition according to the embodiment may further include other additives if necessary.
  • additives include tackifiers (e.g., rosin ester, terpene, phenol, and aliphatic synthetic hydrocarbon resin, aromatic synthetic hydrocarbon resin, or a mixture of aliphatic synthetic hydrocarbon resin and aromatic synthetic hydrocarbon resin), surfactants, plasticizers (other than a physical foaming agent), nucleating agents (e.g., talc, silica, or TiCk), fillers (e.g., inorganic fillers and organic fillers), fiber, aging inhibitors, antioxidants, UV-absorbers, antistatic agents, lubricants, pigments, dyes, reinforcing agents, hydrophobic or hydrophilic silica, calcium carbonate, toughening agents, flame retardants, finely grinded polymeric particles (e.g., polyester, nylon, or polypropylene), stabilizers (e.g., UV stabilizer), and combinations thereof.
  • tackifiers e.g., rosin ester, terpene, phenol, and
  • the content of the additives is not particularly limited as an appropriate amount to obtain desired properties of the composition, but may be, for example, 0.1 wt% to 10 wt% or 0.1 wt% to 5 w% based on the weight of the adhesive composition.
  • the adhesive composition according to the embodiment may be configured so that various components exemplified above have specific contents.
  • the adhesive composition may include 100 parts by weight of the base polymer, 0.1 to 20 parts by weight of the crosslinking agent, 20 to 100 parts by weight of the curable resin, and 0.1 to 10 parts by weight of the initiator.
  • the adhesive composition may include 100 parts by weight of the base polymer, 0.1 to 20 parts by weight of the crosslinking agent, 10 to 90 parts by weight of the first oligomer, 0.1 to 20 parts by weight of the second oligomer, and 0.1 to 10 parts by weight of the initiator.
  • the adhesive composition may include 100 parts by weight of the base polymer, 0.1 to 20 parts by weight of the crosslinking agent, 10 to 90 parts by weight of the first oligomer, 0.1 to 20 parts by weight of the second oligomer, 0.1 to 10 parts by weight of the organic acid, and 0.1 to 10 parts by weight of the initiator.
  • the adhesive composition may include 100 parts by weight of the first oligomer, 5 to 35 parts by weight of the second oligomer, and 1 to 6 parts by weight of the organic acid.
  • the contents of the components in the adhesive composition may be based on the amount of the solid content or the amount other than the solvent.
  • the adhesive composition according to the embodiment may be prepared by mixing a base polymer, a curable resin, a crosslinking agent, and an initiator and further mixing a solvent and other additives as necessary.
  • the base polymer may be prepared by a general method such as solution polymerization.
  • first oligomer, the second oligomer, and the organic acid may be purchased commercially or may be prepared, respectively.
  • the first oligomer, the second oligomer, and the organic acid may be prepared by reaction of any two of these compounds.
  • the first oligomer may be prepared by reaction of the second oligomer and the organic acid. Accordingly, the second oligomer and the organic acid are mixed and the reaction is partially performed to obtain a curable resin as a mixture of the first oligomer as the reaction product and the remaining unreacted second oligomer and organic acid.
  • FIG. 4 illustrates an example of a preparation method of the curable resin.
  • a bisphenol A epoxy acrylate-based compound when reacting a bisphenol A epoxy resin with an acrylic acid, a bisphenol A epoxy acrylate-based compound is generated, and an unreacted bisphenol A epoxy resin and an acrylic acid exist, so that the bisphenol A epoxy acrylate-based compound, the bisphenol A epoxy resin, and the methacrylic acid may be provided as a first oligomer, a second oligomer, and an organic acid, respectively.
  • a reaction molar ratio of the second oligomer and the organic acid may be 1 : 1 to 3, or 1 : 1.5 to 2.0, and in the range, it is advantageous to implement high adhesive strength before UV curing and high modulus after UV curing.
  • a catalyst may be used for a smooth reaction, and for example, a catalyst such as 4-methoxyphenol, 2,6-di-t-butyl-4-methoxyphenol, and 2-t-butyl-4- methoxyphenol may be used in an amount of 1 mol to 3 mol, or 1.3 mol to 1.9 mol with respect to 1 mol of the second oligomer.
  • the reaction temperature between the second oligomer and the organic acid may be 60°C or higher, for example, 60°C to 150°C, specifically 70°C to 110°C.
  • the reaction time between the second oligomer and the organic acid may be 30 minutes or more, for example, 30 minutes to 100 minutes, specifically 40 minutes to 80 minutes.
  • the content of the first oligomer in the mixture obtained through the reaction may be 60 wt% or more, 70 wt% or more, or 80 wt% or more, and also 95 wt% or less, 90 wt% or less, or 85 wt% or less.
  • the content of the first oligomer in the curable resin may be 60 wt% to 95 wt%, or 70 wt% to 90 wt%.
  • the weight ratio of the first oligomer, the second oligomer, and the organic acid may be 70 to 90:10 to 20:1 to 5.
  • the order and conditions for mixing the base polymer, the curable resin, the crosslinking agent, and the initiator in the preparation of the adhesive composition are not particularly limited, and the process may be suitably modified if necessary.
  • the viscosity may be adjusted by using a solvent in each mixing step.
  • the preparation method of the adhesive composition is not particularly limited, and the process conditions may be appropriately modified if necessary.
  • the adhesive composition according to the embodiment is used to form an adhesive film with variable adhesive strength, and thus, can be usefully applied in processes requiring adhesive strength variability, such as adhering and manufacturing of electric devices.
  • the adhesive composition may be applied to a masking tape inside an electronic device.
  • the adhesive composition may be applied to a masking tape that protects sensors or chips of an internal substrate of a mobile electronic device such as a smartphone from coming in direct contact with others.
  • the adhesive strength of the adhesive composition may rapidly decrease by UV curing, it is possible to prevent damage to the sensors or chips of the internal substrate when the masking tape is removed later if necessary.
  • the adhesive composition may be applied to the manufacture of a multilayer ceramic capacitor (MLCC).
  • the adhesive composition may be applied as an adhesive for attaching and fixing a raw material sheet to the substrate in a process of precisely cutting the raw material sheet of the MLCC to a predetermined dimension.
  • the adhesive composition strongly adheres the raw material sheet with high shear adhesive strength at the beginning of the process, and then significantly lowers the adhesive strength by UV curing, so that the cut chips can be easily detached.
  • a rate at which the detached chips re-adhere to the adhesive surface exposed to the outside is very low, so that the yield can be improved.
  • an adhesive film formed from the adhesive composition there is provided an adhesive film formed from the adhesive composition.
  • the adhesive film has lower adhesive strength after UV curing than before UV curing.
  • An adhesive film according to an embodiment is an adhesive film including a reaction product of a base polymer and a crosslinking agent.
  • the adhesive film contains a curable resin to be UV-cured and an initiator, the curable resin is curable by the initiator, the adhesive film has first adhesive strength before UV curing and second adhesive strength after UV curing, and the second adhesive strength is lower than the first adhesive strength.
  • the adhesive film according to the embodiment includes a reaction product of a base polymer and a crosslinking agent. That is, the adhesive film includes a crosslinked base polymer.
  • the adhesive film including the reaction product of the base polymer and the crosslinking agent contains a curable resin and an initiator
  • the curable resin includes a first oligomer, a second oligomer, and an organic acid.
  • the first oligomer and the initiator are dispersed in the reaction product of the base polymer and the crosslinking agent.
  • the first oligomer may have compatibility with the reaction product of the base polymer and the crosslinking agent.
  • the first oligomer may start curing by the action of the initiator as needed, thereby lowering the adhesive strength of the adhesive film.
  • the second oligomer and the organic acid may form an additional bond in the reaction product of the base polymer and the crosslinking agent.
  • the specific types and contents of the base polymer, the crosslinking agent, the first oligomer, the second oligomer, the organic acid, and the initiator included in the adhesive film are the same as those described in the adhesive composition.
  • the adhesive film according to the embodiment may further include other additives, and the specific types and contents thereof are the same as those described in the additives included in the adhesive composition.
  • the adhesive film according to the embodiment has first adhesive strength before UV curing and second adhesive force after UV curing.
  • the first adhesive strength is preferably higher than or equal to a certain level in order to initially attach the adhesive film to the substrate, and the second adhesive strength is preferably lower than or equal to a certain level in order to easily remove the adhesive film as necessary.
  • the specific ranges and measurement methods of the first adhesive strength and the second adhesive strength are the same as the range and measurement method of the first adhesive strength exemplified in the adhesive composition according to the embodiment.
  • the adhesive film may satisfy a requirement as an optically transparent adhesive film before UV curing.
  • the adhesive film may have a haze before UV curing of 5% or less, 2% or less, or 1% or less.
  • the adhesive film may have a light transmittance before UV curing of 80% or more, 90% or more, or 95% or more.
  • the adhesive film may satisfy a requirement as an optically transparent adhesive film even after UV curing.
  • the adhesive film may have a haze after UV curing of 5% or less, 2% or less, or 1% or less.
  • the adhesive film may have a light transmittance after UV curing of 80% or more, 90% or more, or 95% or more.
  • the adhesive film may be discolored during UV curing in a state exposed to oxygen. That is, the adhesive film may have a first color before UV curing and a second color after UV curing in the state exposed to oxygen.
  • the discoloration may be yellowing, and more specifically, the first color may be a colorless or white-based color, and the second color may be a yellow-based color. Accordingly, the second color may have a higher yellowness (YI) than the first color.
  • the adhesive film may have an excellent hardness after UV curing.
  • the adhesive film may have a surface hardness of 1H or more or 2H or more after UV curing.
  • the thickness of the adhesive film may be in the range of 0.2 pm to 1000 pm, 5 pm to 1000 pm, 5 pm to 200 pm, 10 pm to 100 pm, or 0.2 pm to 1 pm when prepared as a thin film.
  • the thickness of the adhesive film may be in the range of 0.1 mm to 5 mm or 1 mm to 3 mm when prepared as a thick film.
  • the adhesive film may be prepared by preparing an adhesive composition to be formed as a film.
  • a preparation method of an adhesive film includes the steps of: preparing a curable resin containing a first oligomer, a second oligomer and an organic acid; mixing a base polymer, the curable resin, an initiator, and a crosslinking agent; reacting the crosslinking agent with the base polymer to form a film-like polymer; and obtaining an adhesive film by preserving the curable resin and the initiator in the film- like polymer.
  • the preparing of the adhesive composition may be performed according to the conditions and procedures described above.
  • the reaction of the crosslinking agent and the base polymer may be performed by a general thermal curing process.
  • the thermal curing temperature may be in the range of 40°C to 150°C, 60°C to 150°C, 60°C to 120°C, or 100°C to 120°C
  • the thermal curing time may be 1 minute to 10 minutes, or 2 minutes to 5 minutes, but these thermal curing conditions may be adjusted according to the length and number of curing ovens.
  • aging e.g., aging at about 50°C for 3 days
  • aging may be further performed after the thermal curing.
  • the thermal curing process may be performed when the adhesive composition is coated on a base film.
  • the adhesive composition may be coated on the base film with an appropriate thickness, and the thermal curing may be performed in this process.
  • the coating may be performed by a method such as notch bar, comma, gravure, or die coating.
  • a coating rate may be in the range of about 1 m/min to 40 m/min or 5 m/min to 30 m/min, but the conditions may be adjusted according to the length of the curing oven.
  • the preserving of the curable resin and the initiator in the film-like polymer may be performed by suppressing an environment in which the initiator may act in the coated (and thermally cured) film-like polymer (for example, preventing UV light exposure).
  • the adhesive film according to the embodiment may be applied as an adhesive tape.
  • the adhesive film according to the embodiment may be formed on one side of the base film to provide a base type adhesive tape.
  • a single-sided adhesive tape including the adhesive film according to the embodiment as an adhesive layer may be used as a masking tape requiring very low adhesive strength.
  • this single-sided adhesive tape protects sensors or chips of an internal substrate of a mobile electronic device such as a smartphone from being in direct contact with others, while may prevent damage to the sensors or chips of the internal substrate from occurring when the masking tape is removed later.
  • a single-sided or double-sided adhesive tape provided with the adhesive film according to the embodiment as an adhesive layer may be used in a process requiring adhesive strength variability when manufacturing an organic light emitting diode (OLED) display panel and a liquid crystal display (LCD) panel.
  • OLED organic light emitting diode
  • LCD liquid crystal display
  • the adhesive film according to the embodiment may be used in the cutting process of the substrate.
  • FIG. 8 schematically shows a using method of an adhesive film according to an embodiment.
  • the using method of an adhesive film 100 may include attaching a first substrate 30 to the adhesive film 100; cutting the first substrate 30 into two or more units 31; reducing adhesive strength by irradiating UV light 60 to the adhesive film 100; and detaching the units 31 from the adhesive film 100.
  • Such a method may be applied to the manufacture of a multilayer ceramic capacitor (MLCC).
  • MLCC multilayer ceramic capacitor
  • a ceramic slurry is obtained from ceramic powder and a ceramic sheet is formed by tape casting, etc., and then a conductive material is coated by screen printing, etc., and a plurality of substrates obtained above are laminated to prepare a laminate sheet for manufacturing the MLCC.
  • Such a laminate sheet is subjected to a step of precisely cutting to a predetermined dimension, in which the adhesive film according to the embodiment may be used.
  • the adhesive film according to the embodiment is formed on a transparent base film, and the laminate sheet is attached to the surface of the adhesive film.
  • the adhesive film to which the laminate sheet is attached is placed on a hot plate of about 60°C to 70°C and cut precisely with a blade to divide the film into a plurality of chips.
  • UV light is irradiated to the adhesive film through the transparent base film to significantly lower adhesive strength, and then the cut chips by mechanical vibration or the like are detached from the adhesive film.
  • the adhesive film strongly attaches the laminate sheet with high shear adhesive strength before UV curing, while significantly lowers the adhesive strength by UV curing, so that the cut chips can be easily detached.
  • a rate at which the cut chips re adhere to an area exposed to the outside in the adhesive film is very low, so that the yield can be improved.
  • the area exposed to the outside in the adhesive film reacts with oxygen in the atmosphere and exhibits a yellow color during UV curing, so that the curing can be easily checked with the naked eye.
  • an adhesive tape including a base film; and an adhesive film disposed on one side of the base film.
  • the adhesive film included in the adhesive tape according to the embodiment has the same composition and properties as the adhesive film of the embodiment as described above.
  • the adhesive tape may be provided as a single-sided adhesive tape having only the one adhesive film as an adhesive layer, or a double-sided adhesive tape in which an additional adhesive layer is further disposed on the other side of the base film.
  • the adhesive layer added in the double-sided adhesive tape may include a general pressure- sensitive adhesive (PSA) or an adhesive having adhesive strength variability.
  • PSA general pressure- sensitive adhesive
  • the adhesive layer added in the double-sided adhesive tape may include the adhesive composition of one embodiment as described above.
  • FIG. 3 illustrates an example of a cross-sectional view of an adhesive tape according to the present invention. Referring to FIG. 3, the adhesive film 100 of the present invention is disposed on one side of the base film 200, and a release film 300 may be laminated on the other side thereof.
  • the base film may be a transparent polymer film, and for example, may be a transparent film including at least one resin selected from the group consisting of a polyester resin, a polyurethane resin, and a polyolefin (polyethylene, etc.) resin.
  • the base film may be constituted by paper, a plastic film, cloth, or metal foil.
  • materials suitable for the base film may include, for example, paper including both flat or smooth paper and textured paper such as crepe paper, natural or synthetic polymer films, natural and/or synthetic fibers and nonwoven fabric made from combinations thereof, fiber reinforced polymer films, fiber or yam reinforced polymer films or nonwoven fabric, and a multi-layer laminated structure.
  • the type of the release film used for the adhesive tape is not particularly limited, but may be, for example, at least one selected from the group consisting of a polyester (PET) film, a polyethylene (PE) film, a polypropylene (PP) film, and paper. Further, the release film may include a silicone coating layer on a surface in contact with the adhesive film. The thickness of the release film may be 5 pm to 100 pm, but may be thinner or thicker as necessary.
  • the release film may be transparent or may have light-shielding properties.
  • the adhesive tape may further include a light-shielding release film laminated on the surface of the adhesive film.
  • the light-shielding release film prevents the surface of the adhesive film from being unnecessarily exposed to UV light, thereby maintaining adhesive strength variability.
  • the adhesive film may be applied to a masking tape inside an electronic device.
  • FIG. 7 illustrates an example in which a tape with adhesive strength variability is applied as a masking tape in a smartphone.
  • a waterproof adhesive tape 20 having a thickness of 350 pm is used to attach internal components to a rear cover of a smartphone, and some sensors or chips (illustrated in a dotted circle in FIG. 7B) of a printed circuit board (PCB) are in contact with the adhesive surface of the tape 20 to damage the sensors or chips.
  • the adhesive tape 10 of the present invention of which the adhesive strength may be rapidly lowered by UV curing, is applied as a masking tape, and damage to the sensors or chips of the internal substrate may be prevented when the masking tape is removed later if necessary.
  • a laminate including a first substrate; a second substrate; and the adhesive film according to the embodiment disposed between the first substrate and the second substrate.
  • Each of the first substrate and the second substrate in the laminate may be made of a material such as metal, glass, ceramic, or polymer.
  • the materials of the first substrate and the second substrate may be stainless steel, glass, ceramic, polyolefin, polyimide, or the like, respectively.
  • the adhesive film may be attached on the entire surface of the substrate. Unlike this, the adhesive film may be partially attached to the surface of the substrate, so that the laminate may have an adhesive film application area and an adhesive film non-application area.
  • the adhesive film in the laminate may be the adhesive film according to the embodiment described above. Accordingly, the laminate structure may include the adhesive film having the above-described composition and properties.
  • an apparatus including the adhesive film or the laminate.
  • a specific type of the apparatus is not particularly limited, but may be, for example, a display device.
  • a display device according to an embodiment includes a display panel; and the adhesive film according to the embodiment attached onto the display panel.
  • a display device according to another embodiment includes a display panel; and the laminate according to the embodiment attached onto the display panel.
  • the display device may be an organic light emitting diode (OLED) display device or a liquid crystal display (LCD) device, and may be, for example, a mobile display device such as a smartphone.
  • OLED organic light emitting diode
  • LCD liquid crystal display
  • a base polymer (resins A1 to A2) was mixed with a UV curable resin (resins Bl to B3), an epoxy resin (resins Cl to C2), an organic acid, and the like, added an initiator, and finally mixed with a crosslinking agent to obtain an adhesive composition.
  • a UV curable resin (resins Bl to B3)
  • an epoxy resin (resins Cl to C2)
  • an organic acid and the like
  • Resin A1 TTT-6400 from TTT Korea Co., Ltd., acrylic resin substituted with about 6 wt% of an acrylate group having a double bond, Chemical Name: 2-propenoic acid, 2-methyl-, 2-hydroxyethyl ester, polymer with ethenyl acetate and 2-ethylhexyl 2-propenoate, 33.2 wt% of solid content
  • Resin A2 AT-422NT from Saiden Chemical Industry Co., Ltd. general acrylic resin without an acrylate group in a molecule, 30 wt% of solid content
  • Resin B1 UV curable resin obtained in Preparation Example 1, 100 wt% of solid content
  • Resin B2 Miramer SC-6400 from Miwon Specialty Chemical Co., Ltd., epoxy acrylate- based oligomer, 100 wt% of solid content
  • Resin B3 Miramer PU640 from Miwon Specialty Chemical Co., Ltd., aromatic urethane acrylate-based oligomer, 100 wt% of solid content
  • Resin Cl KER-828 from Kumho P&B Co., Ltd., bisphenol A epoxy resin, 100 wt% of solid content
  • Resin C2 KDCP-130EK80 from Kukdo Chemical Co., Ltd., phenol novolac type epoxy resin, 80 wt% of solid content
  • 379EG Omnirad 379EG from IGM Resin Co., Ltd., initial wavelength of 365 to 390 nm
  • Omnirad 754 from IGM Resin Co., Ltd., initial wavelength of 320 nm or less
  • GK-100 GK-100 from TTT Korea Co., Ltd., isocyanate-based crosslinking agent, 52 wt% of solid content
  • An adhesive composition was coated on a white polyethylene terephthalate (PET) film with a thickness of 7 pm at a rate of about 2 m/min.
  • the coated film was dried in a total 6 m of oven having three drying zones (at temperatures of 60°C, 100°C, and 140°C, respectively) having lengths of 2 m.
  • a tape having a 5 pm-thick adhesive layer formed on the PET film was obtained, and a 50 pm-thick black PET film was laminated on the surface of the adhesive layer to prevent unnecessary UV curing before the test UV curing
  • UV curing of the adhesive layer of the adhesive tape was performed by UV irradiation using UV equipment (energy 1000 mJ/cm 2 ) having a metal halide lamp (wavelength range of 250 to 420 nm, dominant wavelength of 365 nm).
  • An adhesive tape was attached to a stainless steel (SUS304) plate, and the adhesive strength (unit: gf/in) was measured while 180°-peeling the adhesive tape at a peeling rate of 305 mm/min according to ASTM D3330. After storing the adhesive tape at 22°C and 50%RH for 20 minutes, the adhesive strength (adhesive strength before UV curing) was measured, and then the adhesive layer was UV-cured and the adhesive strength (adhesive strength after UV curing) was measured within 20 minutes. A sample was cut to a width of 1 inch, and the adhesion test was repeated three times to obtain an average value.
  • a black PET release paper was removed from the adhesive tape, and UV was irradiated on the surface of the adhesive layer while exposed to oxygen. Thereafter, it was confirmed that the color of the adhesive layer was discolored.
  • the adhesive tape was attached to a stainless steel (SUS304) plate, and a static shear adhesive test was performed according to ASTM D3654. The time (unit: hr) to maintain the adhesion to a load of 1000 g under the condition of blocking light with a black film and at room temperature was measured.
  • the adhesive compositions A and J were compositions mixed with the UV-curable resin of Preparation Example 1, and included the remaining epoxy resin (second oligomer) and methacrylic acid (organic acid) together with the synthesized bisphenol A-based epoxy acrylate-based oligomer (first oligomer), and it was determined that excellent properties were exhibited by these components.
  • the surface hardness was the highest and the adhesive strength after UV curing was the lowest.
  • tapes prepared with different compositions were poor in terms of at least one property of adhesive strength, the color change, and the hardness.
  • tapes E and G could not be prepared as adhesive tapes due to gelation occurred during mixing by using only acrylic acid having high reactivity in the raw materials of the adhesive composition.

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Abstract

The present invention relates to an adhesive composition with adhesive strength variability and an adhesive film, which can be variously applied to fields requiring adhesive strength variability such as adhering and manufacturing of electric devices, by adding a UV curable oligomer resin to existing adhesives to exhibit excellent adhesive strength at the beginning and significantly reduce the adhesive strength after UV curing. The adhesive composition comprises a base Polymer; a crosslinking agent reacting with the base polymer; a curable resin to be UV-cured after the reaction between the base polymer and the crosslinking agent; and an initiator to cure the curable resin, wherein the curable resin includes a first oligomer, a second oligomer, and an organic acid.

Description

ADHESIVE COMPOSITION, ADHESIVE FILM, PREPARATION METHOD THEREOF AND ADHESIVE TAPE COMPRSING SAME
Background
The present invention relates to an adhesive composition with adhesive strength variability, an adhesive film, a preparation method thereof, and an adhesive tape, a laminate, and an apparatus comprising the same.
Summary
An adhesive tape with adhesive strength variability is a tape with adhesive strength changed by curing of an adhesive layer or the like as needed, and is useful in a field requiring temporary adhesion, such as a manufacturing process of an electronic device.
For example, in Korean Patent Registration No. 0476798, there is disclosed an adhesive tape that is cured in a short time by heating while easily temporarily adhering to an adherend due to its adherence at room temperature to exhibit strong adhesive strength.
In addition, recently, a waterproof adhesive tape with a thickness of 350 pm has been used to attach internal components to a rear cover of a smartphone, but some sensors of a printed circuit board (PCB) are in contact with an adhesive surface of the tape, thereby causing a risk of damage to internal sensors or chip boards. Accordingly, a general single-sided adhesive tape having a thickness of 10 pm is applied as a masking tape and is easily removed in a process of repairing a breakdown of a smartphone, thereby minimizing damage to the internal sensors or chip boards. However, there is still a problem in that the adhesive surface of such a masking tape is also in direct contact with sensors or chips to damage the sensor or the chap. Therefore, there is a need for an adhesive composition that is applied to these masking tapes and does not cause the above problems.
In addition, recently, a large number of multilayer ceramic capacitors (MLCCs) with very small sizes are used to control the flow of current in electronic communication devices, televisions, electric components of automobiles, etc. In order to manufacture the MLCCs, a process of precisely cutting a raw material sheet is performed, and during such cutting, the raw material sheet needs to be firmly fixed and the cut chips need to be easily separated. Accordingly, even in such a process, a tape with adhesive strength variability may be applied, and such a tape is required to have thermal stability and high shear adhesive strength during cutting, and to change the adhesive strength to a very low level after cutting.
Adhesive compositions that implement adhesive strength variability by mixing various additives with existing adhesives have been developed, but these conventional adhesive compositions with adhesive strength variability have problems that the compatibility between existing adhesives and additives is not good, or a change in adhesive strength is not large.
Therefore, an object of the present invention is to provide an adhesive composition with adhesive strength variability, an adhesive film, a preparation method thereof, a using method thereof, and an adhesive tape, a laminate and an apparatus including the same, which can exhibit high performance by solving the conventional problems.
According to an aspect of the present invention, there is provided an adhesive composition including a base polymer; a crosslinking agent reacting with the base polymer; a curable resin to be UV-cured after the reaction of the base polymer and the crosslinking agent; and an initiator curing the curable resin. The curable resin includes a first oligomer, a second oligomer, and an organic acid, and the adhesive composition has first adhesive strength before UV curing and second adhesive strength after UV curing after the reaction of the base polymer and the crosslinking agent, wherein the second adhesive strength is lower than the first adhesive strength.
According to another aspect of the present invention, there is provided an adhesive film including a reaction product of a base polymer and a crosslinking agent, wherein the adhesive film contains a curable resin to be UV-cured and an initiator, the curable resin includes a first oligomer, a second oligomer, and an organic acid, and the adhesive film has first adhesive strength before UV curing and second adhesive strength after UV curing, and the second adhesive strength is lower than the first adhesive strength.
According to yet another aspect of the present invention, there is provided a preparation method of an adhesive film including the steps of: preparing a curable resin containing a first oligomer, a second oligomer and an organic acid; mixing a base polymer, the curable resin, an initiator, and a crosslinking agent; reacting the crosslinking agent with the base polymer to form a film-like polymer; and obtaining an adhesive film by preserving the curable resin and the initiator in the film-like polymer. According to still another aspect of the present invention, there is provided an adhesive tape including a base film; and the adhesive film disposed on one side of the base film.
According to still yet another aspect of the present invention, there is provided a laminate including a first substrate; a second substrate; and the adhesive film disposed between the first substrate and the second substrate.
According to still yet another aspect of the present invention, there is provided an apparatus including the adhesive tape or the laminate.
According to the present invention, the adhesive composition and the adhesive film exhibit excellent adhesive strength at the beginning and then have adhesive strength almost close to 0 after UV curing, and as a result, a difference in adhesive strength is very large and color is clearly changed after UV curing, thereby easily checking a change in adhesive strength visually. In addition, due to excellent compatibility and thermal stability between the constituents of the adhesive composition, changes in properties may be minimized during transport/storage before use.
Accordingly, the adhesive film of the present invention and the adhesive tape including the same can be variously applied in fields requiring adhesive strength variability, such as adhering and manufacturing of electric devices.
Brief Description of the Drawings
FIG. 1 schematically illustrates structures of an adhesive composition according to the present invention before and after UV curing.
FIG. 2 is a graph showing changes in adhesive strength and storage modulus of the adhesive composition according to the present invention.
FIG. 3 illustrates an example of a cross-sectional view of an adhesive tape according to the present invention.
FIGS. 4 and 5 illustrate a preparation method of a curable resin added to the adhesive composition of the present invention and results of NMR analysis, respectively.
FIG. 6 illustrates a mechanism in which the adhesive composition and the adhesive film according to the present invention exhibit yellowing.
FIG. 7 illustrates an example in which a tape with adhesive strength variability is applied as a masking tape in a smartphone. FIG. 8 illustrates an example in which a tape with adhesive strength variability is applied in a process of cutting a substrate for manufacturing an MLCC or the like.
Detailed Description
Advantages and features of the present invention, and methods for accomplishing the same will be more clearly understood from embodiments described in detail below with reference to the accompanying drawings. However, the present invention is not limited to embodiments disclosed below, but may be embodied in various different forms. Thus, these embodiments are provided to make the disclosure of the present invention be complete and completely announce the scope of the present invention to those skilled in the art to which the present invention belongs, and the present invention is just defined by the scope of the appended claims.
The shapes, sizes, ratios, angles, numbers, and the like illustrated in the drawings for describing the present invention are merely illustrative, and the present invention is not limited to those illustrated in the drawings. Throughout this specification, like reference numerals denote like components. Further, in describing the present invention, a detailed explanation of known related technologies may be omitted to avoid unnecessarily obscuring the subject matter of the present invention.
The terms such as “including,” “having,” and “comprising” used herein are generally intended to allow components other than the details described to be added unless the terms are used with “only”. When a component is expressed as a singular form, any references to the singular form may include a plural form unless expressly stated otherwise.
Components are interpreted to include an ordinary error range unless otherwise expressly stated.
When a position relation between two parts is described using the terms such as “on”, “above”, “below”, and “next”, one or more other parts may be positioned between the two parts unless used with the expression “immediately” or “directly”.
Respective features of embodiments of the present invention can be partially or entirely connected or combined with each other, and can be technically interlocked or driven variously. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments to be described below are provided as examples so that the spirit of the present invention can be fully transferred to those skilled in the art. Therefore, the present invention is not limited to embodiments to be described below and may also be embodied in different forms.
Adhesive Composition
According to an aspect of the present invention, there is provided an adhesive composition including a base polymer, a crosslinking agent, a curable resin, and an initiator. The curable resin includes a first oligomer, a second oligomer and an organic acid, and may be UV-cured upon irradiation with UV light. The base polymer may react with the crosslinking agent before the curable resin is cured by the initiator. For example, the base polymer may react with the crosslinking agent while the curable resin and the initiator are preserved, and the adhesive strength of the adhesive composition after the reaction may be rapidly lowered after UV curing.
An adhesive composition according to one embodiment may include a base polymer; a crosslinking agent reacting with the base polymer; a curable resin to be UV- cured after the reaction of the base polymer and the crosslinking agent; and an initiator curing the curable resin. The adhesive composition has first adhesive strength before UV curing and second adhesive strength after UV curing after the reaction of the base polymer and the crosslinking agent, wherein the second adhesive strength is lower than the first adhesive strength.
Properties of Adhesive Composition
The adhesive composition according to the embodiment has different structures and properties before and after UV curing.
Change in adhesive strength
In the adhesive composition, the base polymer reacts (that is, is crosslinked) with the crosslinking agent to form a film and the like, and the film formed above has properties different from the prior art in terms of physical properties such as adhesive strength.
Accordingly, hereinafter, the properties of the adhesive composition while the curable resin and the initiator are preserved after the crosslinking agent reacts with the base polymer will be mainly described. FIG. 2 is a graph showing changes in storage modulus and adhesive strength of the adhesive composition according to an embodiment by UV irradiation. As shown in FIG. 2, the adhesive composition has a low storage modulus before UV curing, while the storage modulus increases rapidly after UV curing. Accordingly, the adhesive composition has excellent adhesive strength before UV curing, whereas after UV curing, the adhesive strength is rapidly lowered.
The adhesive composition has first adhesive strength before UV curing (i.e., while the curable resin and the initiator are preserved). The first adhesive strength may be 200 gf/in or more, 250 gf/in or more, 300 gf/in or more, 350 gf/in or more, 400 gf/in or more, or 500 gf/in or more. Specifically, the first adhesive strength may be in the range of 200 gf/in to 10,000 gf/in, or 300 gf/in to 5,000 gf/in.
In this specification, the adhesive strength (the first adhesive strength, the second adhesive strength, etc.) may be measured by ASTM D3330 which is a general measuring method in the art, and for example, may be adhesive strength measured for polyimide or stainless steel. A more detailed example of the measuring method has been specifically described in the following embodiment.
In addition, the adhesive composition has second adhesive strength after UV curing. The second adhesive strength may be 100 gf/in or less, 50 gf/in or less, 30 gf/in or less, 20 gf/in or less, or 10 gf/in or less. Specifically, the second adhesive strength may be in the range of 0 gf/in to 100 gf/in, 0 gf/in to 50 gf/in, or 0 gf/in to 20 gf/in.
As an example, the first adhesive strength may be 200 gf/in or more and the second adhesive strength may be 100 gf/in or less. As another example, the first adhesive strength may be 250 gf/in or more and the second adhesive strength may be 50 gf/in or less. As yet another example, the first adhesive strength may be in the range of 200 gf/in to 3,000 gf/in, and the second adhesive strength may be in the range of 0 gf/in to 20 gf/in.
The second adhesive strength is lower than the first adhesive strength. For example, the second adhesive strength may be lower than the first adhesive strength by 100 gf/in or more, 150 gf/in or more, 200 gf/in or more, or 500 gf/in or more. Specifically, the first adhesive strength and the second adhesive strength may have a difference of 200 gf/in or more from each other.
In addition, a ratio of the first adhesive strength to the second adhesive strength (the first adhesive strength/the second adhesive strength) may be 10 or more, 20 or more, 30 or more, 50 or more, 70 or more, or 100 or more. In addition, a ratio of the second adhesive strength to the first adhesive strength (the second adhesive strength/the first adhesive strength) may be 0.1 or less, 0.06 or less, 0.03 or less, 0.02 or less, or 0.01 or less.
The adhesive composition of the present invention includes a first oligomer as a curable resin, a second oligomer, and an organic acid, wherein a difference between the first adhesive strength and the second adhesive strength may be greater than that of a composition containing only one type of oligomer or organic acid and the difference in adhesive strength may be controlled by adjusting the ratio of the first oligomer, the second oligomer, and the organic acid.
Figure imgf000009_0001
The adhesive composition may satisfy a requirement as an optically transparent adhesive after the reaction of the base polymer and the crosslinking agent and before UV curing. For example, the adhesive composition may have a haze before UV curing of 5% or less, 2% or less, or 1% or less. In addition, the adhesive composition may have a light transmittance before UV curing of 80% or more, 90% or more, or 95% or more.
In addition, the adhesive composition may satisfy the requirement as an optically transparent adhesive even after UV curing. For example, the adhesive composition may have a haze after UV curing of 5% or less, 2% or less, or 1% or less. In addition, the adhesive composition may have a light transmittance after UV curing of 80% or more,
90% or more, or 95% or more.
Meanwhile, the adhesive composition may be discolored during UV curing in a state exposed to oxygen. That is, the adhesive composition may have a first color before UV curing and a second color after UV curing in the state exposed to oxygen. Specifically, the discoloration may be yellowing, and more specifically, the first color may be a colorless or white-based color, and the second color may be a yellow-based color. Accordingly, the second color may have a higher yellowness (YI) than the first color.
In addition, the adhesive composition may have excellent hardness after UV curing. Specifically, the adhesive composition may have a surface hardness of 1H or more or 2H or more after UV curing.
Components of Adhesive Composition The adhesive composition according to the embodiment includes a base polymer, a crosslinking agent, a curable resin, and an initiator. In addition, the adhesive composition according to the embodiment may further include a solvent and other additives. Hereinafter, each component of the adhesive composition will be described in detail.
Base Polymer
The adhesive composition according to the embodiment includes a base polymer.
The base polymer exhibits an adhesive property as a main component of the adhesive composition. In addition, the base polymer reacts (that is, is crosslinked) with a crosslinking agent to form a film and the like.
The base polymer may be included in the range of 35 wt% to 95 wt% based on the weight of the adhesive composition. Specifically, the base polymer may be included in the range of 40 wt% to 90 wt%, 45 wt% to 85 wt%, or 50 wt% to 80 wt% based on the weight of the adhesive composition. At this time, the content of the base polymer and the weight of the adhesive composition may be based on the solid content.
The base polymer may contain functional groups which are reactive with the crosslinking agent. For example, the base polymer may have at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, an acryl group, a methacryl group, an acetate group, and a vinyl group.
In addition, the base polymer may have an acrylate-based functional group. Accordingly, the base polymer may implement high modulus and hardness and lower second adhesive strength by causing crosslinking even between the acrylate-based functional groups by a radical reaction during UV curing to form an interpenetrated network structure with the cured chain of the first oligomer. The content of the acrylate- based functional groups in the base polymer may be 1 wt% to 15 wt%. In addition, a type of the acrylate-based functional group may be an acrylate functional group or a methacrylate functional group.
As an example, the base polymer may be an acrylic resin. Specifically, the base polymer may be an acrylic resin having an acrylate-based functional group.
The base polymer may be an acrylic copolymer resin. For example, the acrylic copolymer resin may be a resin copolymerized with at least two monomers selected from the group consisting of 2-ethylhexyl acrylate (2-EHA), butyl acrylate (BA), methyl acrylate (MA), vinyl acetate (VAc), acrylic acid (AA), and 2-hydroxyethyl acrylate (2- HEA). As a specific example, the combination of at least two monomers constituting the acrylic copolymer resin may include 2-EHA/MA, BA/MA, AA/2-HEA, MA/2-HEA, BA/2-HEA, MA/AA/2-HEA, and the like.
The base polymer may be a thermocurable resin. In addition, the base polymer may be a pressure sensitive adhesive (PSA) resin.
The weight average molecular weight (Mw) of the base polymer may be 1,000 to 200,000, and 10,000 to 200,000. Within the above range, transparency before UV curing of the adhesive composition may be more improved.
Curable resin
The curable resin included in the adhesive composition is to be UV-cured after the reaction between the base polymer and the crosslinking agent. That is, the curable resin may exist in an uncured state even after the reaction of the base polymer and the crosslinking agent.
The content of the curable resin in the composition may be 20 parts by weight to 100 parts by weight based on 100 parts by weight of the base polymer. Specifically, the content of the curable resin in the composition may be 20 parts by weight to 90 parts by weight, 20 parts by weight to 80 parts by weight, or 25 parts by weight to 70 parts by weight based on 100 parts by weight of the base polymer. At this time, the content range may be based on the solid content.
The curable resin includes a first oligomer, a second oligomer, and an organic acid. (1) First Oligomer
The first oligomer is to be UV-cured after the reaction of the base polymer and the crosslinking agent. That is, the first oligomer may exist in an uncured state even after the reaction of the base polymer and the crosslinking agent. As such, the first oligomer in the uncured state may not be involved in the adhesive strength of the reaction product of the base polymer and the crosslinking agent. However, after the reaction of the base polymer and the crosslinking agent, the first oligomer is UV-cured as necessary, so that the adhesive strength of the reaction product may be rapidly lowered.
The first oligomer may be cured by an initiator (i.e., photoinitiator).
FIG. 1 schematically illustrates structures of the adhesive composition according to the present invention before and after UV curing. Referring to FIG. 1 A, since the adhesive composition before UV curing includes an oligomer 102 such as a first oligomer and an additive 103 such as an initiator together with a chain of a crosslinked base polymer 101, high adhesive strength and bonding strength may be exhibited by functional groups present in the base polymer and the oligomer.
Referring to FIG. IB, after UV curing, a chain of a cured oligomer 102’ is generated by a radical reaction to form an interpenetrated network structure together with the chain of the crosslinked base polymer 101, so that the adhesive composition may exhibit high modulus and hardness, and low adhesive strength.
In addition, the first oligomer may have compatibility with the base polymer. The first oligomer may be an epoxy -based oligomer. In addition, the first oligomer may have acrylate-based functional groups at both ends. Specifically, the first oligomer may include repeating units derived from an epoxy acrylate-based compound.
As an example, the first oligomer may be at least one compound represented by the following Chemical Formula 1.
Chemical Formula 1
Figure imgf000012_0001
Wherein, Xi is each independently a linear or branched Ci-io alkylene group; Li is each independently a Ci-io alkylene group, a C3-20 cycloalkylene group, or a Ci-10 alkyleneoxy group; Ro is each independently H or a C1-3 alkyl group; Ri is each independently H, a Ci-10 alkyl group, a Ci-10 alkoxy group, a C2-10 alkenyl group, or a C6-14 aryl group; and m is an integer of 0 to 10, or 1 to 10.
Specific examples of the Ci-10 alkylene group may include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, a sec-butylene group, a t-butylene group, a pentylene group, an isopentylene group, a t-pentylene group, a hexylene group, a heptylene group, an octylene group, an isooctylene group, a t-octylene group, a 2-ethylhexylene group, a nonylene group, an isononylene group, a decylene group, an isodecylene group, and the like. Specific examples of the C3-20 cycloalkylene group include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group, a decalinylene group, an adamantylene group, and the like. Specific examples of the Ci-io alkyleneoxy group may include a methyleneoxy group, an ethyleneoxy group, a propyleneoxy group, a butyleneoxy group, a sec-butyleneoxy group, a t-butyleneoxy group, a pentyleneoxy group, a hexyleneoxy group, a heptyleneoxy group, an octyleneoxy group, a 2-ethyl-hexyleneoxy group, etc. Specific examples of the Ci-io alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, a pentyl group, an isopentyl group, a t-pentyl group, a hexyl group, a heptyl group, an octyl group, an isooctyl group, a t-octyl group, a 2-ethylhexyl group, a nonyl group, an isononyl group, a decyl group, an isodecyl group, and the like. Specific examples of the C1-3 alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, etc. Specific examples of the Ci-10 alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butyloxy group, a sec-butoxy group, a t-butoxy group, a pentoxy group, a hexyloxy group, a heptoxy group, an octyloxy group, a 2-ethyl-hexyloxy group, etc. Specific examples of the C2-10 alkenyl group include a vinyl group, an allyl group, a butenyl group, a propenyl group, etc. Specific examples of the C6-14 aryl group include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, etc.
In addition, the epoxy acrylate-based compound may have a bisphenol A skeleton. Specifically, the first oligomer may include repeating units derived from an epoxy acrylate-based compound having the bisphenol A skeleton.
The weight average molecular weight of the first oligomer may be in the range of 300 to 30,000, or 500 to 10,000.
The content of the first oligomer in the composition may be 10 parts by weight to 100 parts by weight based on 100 parts by weight of the base polymer. Specifically, the content of the first oligomer in the composition may be 10 parts by weight to 90 parts by weight, 10 parts by weight to 80 parts by weight, or 15 parts by weight to 70 parts by weight based on 100 parts by weight of the base polymer. At this time, the contents of the base polymer and the first oligomer may be based on the solid content.
(2) Second Oligomer
The curable resin further includes a second oligomer different from the first oligomer. The second oligomer reacts with an organic acid and the like in the adhesive composition to generate a plurality of functional groups (hydroxyl group, etc.), thereby improving initial adhesive strength of the adhesive composition. In addition, after the reaction of the base polymer and the crosslinking agent, the second oligomer is UV-cured with the first oligomer if necessary, so that the adhesive strength of the reaction product may be rapidly lowered.
The second oligomer may be an epoxy -based oligomer. In addition, the second oligomer may have epoxide functional groups at both ends.
As an example, the second oligomer may be at least one compound represented by the following Chemical Formula 2.
Chemical Formula 2
Figure imgf000014_0001
Wherein, X2 is each independently a linear or branched Ci-10 alkylene group; L2 is each independently a Ci-10 alkylene group, a C3-20 cycloalkylene group, or a Ci-10 alkyleneoxy group; R2 is each independently H, a Ci-10 alkyl group, a Ci-10 alkoxy group, a C2-10 alkenyl group, or a C6-14 aryl group; and n is an integer of 0 to 10, or 1 to 10.
Specific examples of the Ci-10 alkylene group may include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, a sec-butylene group, a t-butylene group, a pentylene group, an isopentylene group, a t-pentylene group, a hexylene group, a heptylene group, an octylene group, an isooctylene group, a t-octylene group, a 2-ethylhexylene group, a nonylene group, an isononylene group, a decylene group, an isodecylene group, and the like.
Specific examples of the C3-20 cycloalkylene group include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group, a decalinylene group, an adamantylene group, and the like. Specific examples of the Ci-10 alkyleneoxy group may include a methyleneoxy group, an ethyleneoxy group, a propyleneoxy group, a butyleneoxy group, a sec-butyleneoxy group, a t-butyleneoxy group, a pentyleneoxy group, a hexyleneoxy group, a heptyleneoxy group, an octyleneoxy group, a 2-ethyl-hexyleneoxy group, etc. Specific examples of the Ci-10 alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, a pentyl group, an isopentyl group, a t-pentyl group, a hexyl group, a heptyl group, an octyl group, an isooctyl group, a t-octyl group, a 2-ethylhexyl group, a nonyl group, an isononyl group, a decyl group, an isodecyl group, and the like. Specific examples of the Ci-io alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butyloxy group, a sec-butoxy group, a t-butoxy group, a pentoxy group, a hexyloxy group, a heptoxy group, an octyloxy group, a 2-ethyl- hexyloxy group, etc. Specific examples of the C2-10 alkenyl group include a vinyl group, an allyl group, a butenyl group, a propenyl group, etc. Specific examples of the C6-14 aryl group include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, etc.
Specifically, the second oligomer may be an epoxy resin having a bisphenol A skeleton. Such a bisphenol A skeleton changes the color of the adhesive composition to yellow under oxygen exposure conditions after UV curing, so that the curing may be easily checked with the naked eye.
FIG. 6 shows a mechanism for indicating the yellowing of the adhesive film according to the present invention, wherein an unreacted bisphenol A epoxy resin in the adhesive composition may cause photo oxidation by UV irradiation, resulting in rapid yellowing. More specifically, in a bisphenol group in the unreacted epoxy resin, a methyl (-CH3) group between the two phenyl groups may be formed into a quinone structure by oxidation upon UV irradiation to cause discoloration.
The weight average molecular weight of the second oligomer may be in the range of 300 to 30,000, or 500 to 10,000.
The content of the second oligomer in the adhesive composition may be 0.1 part by weight to 20 parts by weight based on 100 parts by weight of the base polymer. Specifically, the content of the second oligomer in the adhesive composition may be 0.1 part by weight to 10 parts by weight or 0.1 part by weight to 5 parts by weight based on 100 parts by weight of the base polymer. At this time, the contents of the second oligomer and the base polymer may be based on the solid content.
(3) Organic Acid
The organic acid may improve first adhesive strength (adhesive strength before UV curing) of the adhesive composition, due to a functional group (carboxyl group, hydroxyl group, etc.) contained therein or due to a functional group (e.g., a hydroxyl group by reaction with an epoxy group, etc.) generated by reaction with an oligomer present in the adhesive composition.
The organic acid may have 1 to 5, or 1 to 3 functional groups. For example, the organic acid may have at least one functional group selected from the group consisting of a hydroxyl group, an acryl group, a methacryl group, an acetate group, and a vinyl group in addition to a carboxyl group.
The organic acid may contain a carbon double bond at an end. The carbon double bond may cause a radical reaction with the functional groups of the base polymer and/or the oligomer during UV curing to increase the crosslinking density of the adhesive composition, thereby further lowering the second adhesive strength.
Specifically, the organic acid may have a group containing a double bond between carbons. Examples of the group containing the double bond between carbons may include an acrylic group, a methacrylic group, a vinyl group, etc.
As an example, the organic acid may be at least one compound represented by Chemical Formula 3 below.
Chemical Formula 3
Figure imgf000016_0001
Wherein, R3 is H or a C1-3 alkyl group; and L3 is a single bond, a Ci-10 alkylene group, a C3-20 cycloalkylene group, or a Ci-10 alkyleneoxy group.
Specific examples of the C1-3 alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, etc. Specific examples of the Ci-10 alkylene group may include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, a sec-butylene group, a t-butylene group, a pentylene group, an isopentylene group, a t-pentylene group, a hexylene group, a heptylene group, an octylene group, an isooctylene group, a t-octylene group, a 2- ethylhexylene group, a nonylene group, an isononylene group, a decylene group, an isodecylene group, and the like. Specific examples of the C3-20 cycloalkylene group include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group, a decalinylene group, an adamantylene group, and the like. Specific examples of the Ci-10 alkyleneoxy group may include a methyleneoxy group, an ethyleneoxy group, a propyleneoxy group, a butyleneoxy group, a sec-butyleneoxy group, a t-butyleneoxy group, a pentyleneoxy group, a hexyleneoxy group, a heptyleneoxy group, an octyleneoxy group, a 2-ethyl-hexyleneoxy group, etc.
For example, the organic acid may be an acrylic acid, and specifically, may include at least one of methacrylic acid and acrylic acid.
The molecular weight of the organic acid may be in the range of 50 to 1000, or 50 to 500.
The content of the organic acid in the composition may be 0.1 to 10 parts by weight, 0.1 to 5 parts by weight, or 0.1 to 3 parts by weight based on 100 parts by weight of the base polymer. At this time, the contents of the organic acid and the base polymer may be based on the solid content.
Initiator
The adhesive composition according to the embodiment includes an initiator.
For example, the adhesive composition may include a photoinitiator to UV-cure the curable composition.
As the photoinitiator, a general photoinitiator, specifically, at least one selected from the group consisting of ketones (benzophenone, acetophenone, etc.), benzoins, benzoin ethers, benzyls, and benzyl ketals may be used.
As an example, the photoinitiator may be benzoin ethers (e.g., benzoin methyl ether or benzoin isopropyl ether) or substituted benzoin ethers.
As another example, the photoinitiator may be substituted acetophenone, for example, 2,2-diethoxyacetophenone or 2,2-dimethoxy-2-phenylacetophenone.
As yet another example, the photoinitiator may be substituted alpha-ketones (e.g., 2-methyl-2-hydroxypropiophenone), aromatic sulfonyl chlorides (e.g., 2- naphthalenesulfonyl chloride), or photoactive oximes (e.g., 1 -phenyl- 1,2-propanedi one-2- (O-ethoxy carbonyl) oxime).
As still another example, the photoinitiator may be 1 -hydroxy cyclohexyl phenyl ketone, bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide, l-4-(2- hy droxy ethoxy )phenyl-2-hydroxy-2-m ethyl- 1 -propane- 1 -one, 2-benzyl-2-dimethylamino- l-4-morpholinophenyl)butanone, 2-dimethylamino-2-(4-methylbenzyl)-l-(4-morpholin-4- yl-phenyl)butan- 1 -one, 2-methyl- 1 -4-(methylthio)phenyl-2-morpholinopropane- 1 -one, 2- hydroxy-2-methyl-l-phenylpropan-l-one, and the like. As still another example, the photoinitiator may be 2-(2-oxo-2- phenylacetoxyethoxy)ethyl oxyphenylacetate, 2-(2-hydroxyethoxy)ethyl oxyphenylacetate, and the like.
Examples of commercially available photoinitiators may include Omnirad series from IGM Resin Co., Ltd., Ciba IRGACURE series from Ciba Specialty Chemicals Co., Ltd., Esacure KIP series from IGM Resins Co., Ltd., and the like.
The initiator may be used alone or in combination of two or more. For example, the initiator may be used by mixing two or more types of photoinitiators having different operating wavelengths. As a specific example, the initiator may have a first initiator that acts in light having a wavelength of 365 nm to 390 nm; and a second initiator that acts in light having a wavelength of 320 nm or less.
The adhesive composition may further include a thermal initiator.
As the thermal initiator, according to a curing method to be used, a water-soluble or water-insoluble (i.e., oil-soluble) thermal initiator may be selectively used. As the water-soluble initiator, persulfates such as potassium persulfate, ammonium persulfate, sodium persulfate, and mixtures thereof; oxidation-reduction initiators such as a reaction product of a reducing agent such as metabisulfite (e.g., sodium metabi sulfite) or bisulfate (e.g., sodium bisulfate) and persulfate; or 4,4'-azobis (4-cyanopentanoic acid) and its soluble salts (e.g., sodium salt, potassium salt), or the like may be used. As the oil-soluble initiator, azos such as 2,2’-azobis (2-methylbutanenitrile), 2,2’-azobis (isobutyronitrile), and 2,2’-azobis (2,4-dimethylpentanenitrile); or peroxides such as benzoyl peroxide, cyclohexane peroxide, and lauroyl peroxide may be used.
The content of the initiator in the composition may be 0.1 part by weight to 20 parts by weight based on 100 parts by weight of the base polymer. Specifically, the content of the initiator in the composition may be 0.1 part by weight to 10 parts by weight or 0.1 part by weight to 5 parts by weight based on 100 parts by weight of the base polymer. In this case, the content of the base polymer and the content of the initiator may be based on an amount of the solid content or an amount other than a solvent.
Crosslinking agent
The adhesive composition according to the embodiment includes a crosslinking agent.
The crosslinking agent reacts with the base polymer to form a film and the like. The content of the crosslinking agent in the composition may be 0.1 part by weight to 20 parts by weight based on 100 parts by weight of the base polymer. Specifically, the content of the crosslinking agent in the composition may be 0.1 part by weight to 10 parts by weight or 0.1 part by weight to 5 parts by weight based on 100 parts by weight of the base polymer. At this time, the contents of the crosslinking agent and the base polymer may be based on the solid content.
The crosslinking agent may contain a functional group which is reactive with the functional group of the base polymer. For example, the crosslinking agent may have one or at least two functional groups selected from the group consisting of an epoxy group, an isocyanate group, a carboxyl group, a hydroxyl group, an acryl group, a methacryl group, an acetate group, and a vinyl group. As a specific example, the crosslinking agent may have an epoxy group or an isocyanate group.
The crosslinking agent may be a photo-crosslinking agent, a thermal crosslinking agent, or a combination thereof.
The photo-crosslinking agent may use a general multifunctional acrylic compound. For example, the photo-crosslinking agent may be at least one selected from the group consisting of diacrylate and triacrylate. Specific examples of the photo-crosslinking agent may include 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate (HDD A), 1,9-nonanediol diacrylate, tripropylene glycol diacrylate, tetraethylene glycol diacrylate, trimethylolpropane triacrylate, and pentaerythritol triacrylate.
The thermal crosslinking agent may be an isocyanate-based, epoxy-based, or metal chelate-based compound. The isocyanate-based compound may be a multifunctional aromatic or aliphatic isocyanate compound. For example, the isocyanate-based compound may be trimerized isocyanate such as a toluene diisocyanate-trimethylol propane (TDI- TMP) adduct. The epoxy -based compound may have one or at least two epoxy groups, and may have a functional group reactive with the base polymer. The metal chelate-based compound may be a chelate-based compound having a metal such as Zn, Ni, Mn, Fe, Co, Cr, Al, Ti or Zr. An example of a commercially available thermal crosslinking agent may include GK series of TTT Korea Co., Ltd., and Saivinol hardener series from Saiden Chemical Industry Co., Ltd.
Solvent The adhesive composition according to the embodiment may further include a solvent.
The solvent may serve to adjust the viscosity of the adhesive composition.
The type of the solvent is not particularly limited, and may be, for example, at least one selected from the group consisting of toluene, a mixture of hexane/methyl ethyl ketone, xylene, and isopropyl acetate.
The mixing amount of the solvent is not particularly limited, but for example, the solvent may be mixed to have the solid content of the adhesive composition in the range of 30 wt% to 90 wt%, or 50 wt% to 80 wt%.
Additives
The adhesive composition according to the embodiment may further include other additives if necessary.
Specific examples of the additives include tackifiers (e.g., rosin ester, terpene, phenol, and aliphatic synthetic hydrocarbon resin, aromatic synthetic hydrocarbon resin, or a mixture of aliphatic synthetic hydrocarbon resin and aromatic synthetic hydrocarbon resin), surfactants, plasticizers (other than a physical foaming agent), nucleating agents (e.g., talc, silica, or TiCk), fillers (e.g., inorganic fillers and organic fillers), fiber, aging inhibitors, antioxidants, UV-absorbers, antistatic agents, lubricants, pigments, dyes, reinforcing agents, hydrophobic or hydrophilic silica, calcium carbonate, toughening agents, flame retardants, finely grinded polymeric particles (e.g., polyester, nylon, or polypropylene), stabilizers (e.g., UV stabilizer), and combinations thereof.
The content of the additives is not particularly limited as an appropriate amount to obtain desired properties of the composition, but may be, for example, 0.1 wt% to 10 wt% or 0.1 wt% to 5 w% based on the weight of the adhesive composition.
Specific Composition Example
The adhesive composition according to the embodiment may be configured so that various components exemplified above have specific contents.
According to the embodiment, the adhesive composition may include 100 parts by weight of the base polymer, 0.1 to 20 parts by weight of the crosslinking agent, 20 to 100 parts by weight of the curable resin, and 0.1 to 10 parts by weight of the initiator.
According to another embodiment, the adhesive composition may include 100 parts by weight of the base polymer, 0.1 to 20 parts by weight of the crosslinking agent, 10 to 90 parts by weight of the first oligomer, 0.1 to 20 parts by weight of the second oligomer, and 0.1 to 10 parts by weight of the initiator.
According to another embodiment, the adhesive composition may include 100 parts by weight of the base polymer, 0.1 to 20 parts by weight of the crosslinking agent, 10 to 90 parts by weight of the first oligomer, 0.1 to 20 parts by weight of the second oligomer, 0.1 to 10 parts by weight of the organic acid, and 0.1 to 10 parts by weight of the initiator.
In addition, the adhesive composition may include 100 parts by weight of the first oligomer, 5 to 35 parts by weight of the second oligomer, and 1 to 6 parts by weight of the organic acid.
The contents of the components in the adhesive composition may be based on the amount of the solid content or the amount other than the solvent.
Preparation Method of Adhesive Composition
The adhesive composition according to the embodiment may be prepared by mixing a base polymer, a curable resin, a crosslinking agent, and an initiator and further mixing a solvent and other additives as necessary.
The base polymer may be prepared by a general method such as solution polymerization.
In addition, the first oligomer, the second oligomer, and the organic acid may be purchased commercially or may be prepared, respectively. For example, the first oligomer, the second oligomer, and the organic acid may be prepared by reaction of any two of these compounds.
Specifically, the first oligomer may be prepared by reaction of the second oligomer and the organic acid. Accordingly, the second oligomer and the organic acid are mixed and the reaction is partially performed to obtain a curable resin as a mixture of the first oligomer as the reaction product and the remaining unreacted second oligomer and organic acid.
FIG. 4 illustrates an example of a preparation method of the curable resin.
Referring to FIG. 4, when reacting a bisphenol A epoxy resin with an acrylic acid, a bisphenol A epoxy acrylate-based compound is generated, and an unreacted bisphenol A epoxy resin and an acrylic acid exist, so that the bisphenol A epoxy acrylate-based compound, the bisphenol A epoxy resin, and the methacrylic acid may be provided as a first oligomer, a second oligomer, and an organic acid, respectively.
A reaction molar ratio of the second oligomer and the organic acid may be 1 : 1 to 3, or 1 : 1.5 to 2.0, and in the range, it is advantageous to implement high adhesive strength before UV curing and high modulus after UV curing.
In the reaction, a catalyst may be used for a smooth reaction, and for example, a catalyst such as 4-methoxyphenol, 2,6-di-t-butyl-4-methoxyphenol, and 2-t-butyl-4- methoxyphenol may be used in an amount of 1 mol to 3 mol, or 1.3 mol to 1.9 mol with respect to 1 mol of the second oligomer.
The reaction temperature between the second oligomer and the organic acid may be 60°C or higher, for example, 60°C to 150°C, specifically 70°C to 110°C. In addition, the reaction time between the second oligomer and the organic acid may be 30 minutes or more, for example, 30 minutes to 100 minutes, specifically 40 minutes to 80 minutes.
The content of the first oligomer in the mixture obtained through the reaction, that is, the curable resin may be 60 wt% or more, 70 wt% or more, or 80 wt% or more, and also 95 wt% or less, 90 wt% or less, or 85 wt% or less. Specifically, the content of the first oligomer in the curable resin may be 60 wt% to 95 wt%, or 70 wt% to 90 wt%. In addition, the weight ratio of the first oligomer, the second oligomer, and the organic acid may be 70 to 90:10 to 20:1 to 5.
The order and conditions for mixing the base polymer, the curable resin, the crosslinking agent, and the initiator in the preparation of the adhesive composition are not particularly limited, and the process may be suitably modified if necessary. In addition, the viscosity may be adjusted by using a solvent in each mixing step.
However, the preparation method of the adhesive composition is not particularly limited, and the process conditions may be appropriately modified if necessary.
Use of Adhesive Composition
The adhesive composition according to the embodiment is used to form an adhesive film with variable adhesive strength, and thus, can be usefully applied in processes requiring adhesive strength variability, such as adhering and manufacturing of electric devices.
As an example, the adhesive composition may be applied to a masking tape inside an electronic device. Specifically, the adhesive composition may be applied to a masking tape that protects sensors or chips of an internal substrate of a mobile electronic device such as a smartphone from coming in direct contact with others. In particular, since the adhesive strength of the adhesive composition may rapidly decrease by UV curing, it is possible to prevent damage to the sensors or chips of the internal substrate when the masking tape is removed later if necessary.
As another example, the adhesive composition may be applied to the manufacture of a multilayer ceramic capacitor (MLCC). Specifically, the adhesive composition may be applied as an adhesive for attaching and fixing a raw material sheet to the substrate in a process of precisely cutting the raw material sheet of the MLCC to a predetermined dimension. In particular, the adhesive composition strongly adheres the raw material sheet with high shear adhesive strength at the beginning of the process, and then significantly lowers the adhesive strength by UV curing, so that the cut chips can be easily detached. In addition, a rate at which the detached chips re-adhere to the adhesive surface exposed to the outside is very low, so that the yield can be improved.
Adhesive Film
According to another aspect of the present invention, there is provided an adhesive film formed from the adhesive composition.
The adhesive film has lower adhesive strength after UV curing than before UV curing.
An adhesive film according to an embodiment is an adhesive film including a reaction product of a base polymer and a crosslinking agent. The adhesive film contains a curable resin to be UV-cured and an initiator, the curable resin is curable by the initiator, the adhesive film has first adhesive strength before UV curing and second adhesive strength after UV curing, and the second adhesive strength is lower than the first adhesive strength.
Components of Adhesive Film
The adhesive film according to the embodiment includes a reaction product of a base polymer and a crosslinking agent. That is, the adhesive film includes a crosslinked base polymer.
In addition, the adhesive film including the reaction product of the base polymer and the crosslinking agent contains a curable resin and an initiator, and the curable resin includes a first oligomer, a second oligomer, and an organic acid. For example, the first oligomer and the initiator are dispersed in the reaction product of the base polymer and the crosslinking agent. The first oligomer may have compatibility with the reaction product of the base polymer and the crosslinking agent.
The first oligomer may start curing by the action of the initiator as needed, thereby lowering the adhesive strength of the adhesive film.
In addition, the second oligomer and the organic acid may form an additional bond in the reaction product of the base polymer and the crosslinking agent.
The specific types and contents of the base polymer, the crosslinking agent, the first oligomer, the second oligomer, the organic acid, and the initiator included in the adhesive film are the same as those described in the adhesive composition.
Further, the adhesive film according to the embodiment may further include other additives, and the specific types and contents thereof are the same as those described in the additives included in the adhesive composition.
Adhesive strength and other properties
The adhesive film according to the embodiment has first adhesive strength before UV curing and second adhesive force after UV curing. The first adhesive strength is preferably higher than or equal to a certain level in order to initially attach the adhesive film to the substrate, and the second adhesive strength is preferably lower than or equal to a certain level in order to easily remove the adhesive film as necessary. The specific ranges and measurement methods of the first adhesive strength and the second adhesive strength are the same as the range and measurement method of the first adhesive strength exemplified in the adhesive composition according to the embodiment.
The adhesive film may satisfy a requirement as an optically transparent adhesive film before UV curing. For example, the adhesive film may have a haze before UV curing of 5% or less, 2% or less, or 1% or less. In addition, the adhesive film may have a light transmittance before UV curing of 80% or more, 90% or more, or 95% or more.
The adhesive film may satisfy a requirement as an optically transparent adhesive film even after UV curing. For example, the adhesive film may have a haze after UV curing of 5% or less, 2% or less, or 1% or less. In addition, the adhesive film may have a light transmittance after UV curing of 80% or more, 90% or more, or 95% or more.
Meanwhile, the adhesive film may be discolored during UV curing in a state exposed to oxygen. That is, the adhesive film may have a first color before UV curing and a second color after UV curing in the state exposed to oxygen. Specifically, the discoloration may be yellowing, and more specifically, the first color may be a colorless or white-based color, and the second color may be a yellow-based color. Accordingly, the second color may have a higher yellowness (YI) than the first color.
In addition, the adhesive film may have an excellent hardness after UV curing. Specifically, the adhesive film may have a surface hardness of 1H or more or 2H or more after UV curing.
The thickness of the adhesive film may be in the range of 0.2 pm to 1000 pm, 5 pm to 1000 pm, 5 pm to 200 pm, 10 pm to 100 pm, or 0.2 pm to 1 pm when prepared as a thin film. Alternatively, the thickness of the adhesive film may be in the range of 0.1 mm to 5 mm or 1 mm to 3 mm when prepared as a thick film.
Preparation Method of Adhesive Film
The adhesive film may be prepared by preparing an adhesive composition to be formed as a film.
A preparation method of an adhesive film according to an embodiment includes the steps of: preparing a curable resin containing a first oligomer, a second oligomer and an organic acid; mixing a base polymer, the curable resin, an initiator, and a crosslinking agent; reacting the crosslinking agent with the base polymer to form a film-like polymer; and obtaining an adhesive film by preserving the curable resin and the initiator in the film- like polymer.
The preparing of the adhesive composition may be performed according to the conditions and procedures described above. The reaction of the crosslinking agent and the base polymer may be performed by a general thermal curing process. For example, the thermal curing temperature may be in the range of 40°C to 150°C, 60°C to 150°C, 60°C to 120°C, or 100°C to 120°C, and the thermal curing time may be 1 minute to 10 minutes, or 2 minutes to 5 minutes, but these thermal curing conditions may be adjusted according to the length and number of curing ovens. Further, after the thermal curing, aging (e.g., aging at about 50°C for 3 days) may be further performed.
The thermal curing process may be performed when the adhesive composition is coated on a base film. Specifically, the adhesive composition may be coated on the base film with an appropriate thickness, and the thermal curing may be performed in this process. The coating may be performed by a method such as notch bar, comma, gravure, or die coating. In addition, a coating rate may be in the range of about 1 m/min to 40 m/min or 5 m/min to 30 m/min, but the conditions may be adjusted according to the length of the curing oven.
In addition, the preserving of the curable resin and the initiator in the film-like polymer may be performed by suppressing an environment in which the initiator may act in the coated (and thermally cured) film-like polymer (for example, preventing UV light exposure).
Use of Adhesive Film
The adhesive film according to the embodiment may be applied as an adhesive tape. For example, the adhesive film according to the embodiment may be formed on one side of the base film to provide a base type adhesive tape.
As an example, a single-sided adhesive tape including the adhesive film according to the embodiment as an adhesive layer may be used as a masking tape requiring very low adhesive strength. Specifically, this single-sided adhesive tape protects sensors or chips of an internal substrate of a mobile electronic device such as a smartphone from being in direct contact with others, while may prevent damage to the sensors or chips of the internal substrate from occurring when the masking tape is removed later.
As another example, a single-sided or double-sided adhesive tape provided with the adhesive film according to the embodiment as an adhesive layer may be used in a process requiring adhesive strength variability when manufacturing an organic light emitting diode (OLED) display panel and a liquid crystal display (LCD) panel.
As yet another example, the adhesive film according to the embodiment may be used in the cutting process of the substrate. FIG. 8 schematically shows a using method of an adhesive film according to an embodiment. Referring to FIG. 8, the using method of an adhesive film 100 may include attaching a first substrate 30 to the adhesive film 100; cutting the first substrate 30 into two or more units 31; reducing adhesive strength by irradiating UV light 60 to the adhesive film 100; and detaching the units 31 from the adhesive film 100.
Such a method may be applied to the manufacture of a multilayer ceramic capacitor (MLCC). In order to manufacture the MLCC, a ceramic slurry is obtained from ceramic powder and a ceramic sheet is formed by tape casting, etc., and then a conductive material is coated by screen printing, etc., and a plurality of substrates obtained above are laminated to prepare a laminate sheet for manufacturing the MLCC. Such a laminate sheet is subjected to a step of precisely cutting to a predetermined dimension, in which the adhesive film according to the embodiment may be used. First, the adhesive film according to the embodiment is formed on a transparent base film, and the laminate sheet is attached to the surface of the adhesive film. Next, the adhesive film to which the laminate sheet is attached is placed on a hot plate of about 60°C to 70°C and cut precisely with a blade to divide the film into a plurality of chips. Finally, UV light is irradiated to the adhesive film through the transparent base film to significantly lower adhesive strength, and then the cut chips by mechanical vibration or the like are detached from the adhesive film.
The adhesive film strongly attaches the laminate sheet with high shear adhesive strength before UV curing, while significantly lowers the adhesive strength by UV curing, so that the cut chips can be easily detached. In addition, a rate at which the cut chips re adhere to an area exposed to the outside in the adhesive film is very low, so that the yield can be improved. In addition, the area exposed to the outside in the adhesive film reacts with oxygen in the atmosphere and exhibits a yellow color during UV curing, so that the curing can be easily checked with the naked eye.
Adhesive Tape
According to still another aspect of the present invention, there is provided an adhesive tape including a base film; and an adhesive film disposed on one side of the base film.
The adhesive film included in the adhesive tape according to the embodiment has the same composition and properties as the adhesive film of the embodiment as described above.
The adhesive tape may be provided as a single-sided adhesive tape having only the one adhesive film as an adhesive layer, or a double-sided adhesive tape in which an additional adhesive layer is further disposed on the other side of the base film. The adhesive layer added in the double-sided adhesive tape may include a general pressure- sensitive adhesive (PSA) or an adhesive having adhesive strength variability. For example, the adhesive layer added in the double-sided adhesive tape may include the adhesive composition of one embodiment as described above. FIG. 3 illustrates an example of a cross-sectional view of an adhesive tape according to the present invention. Referring to FIG. 3, the adhesive film 100 of the present invention is disposed on one side of the base film 200, and a release film 300 may be laminated on the other side thereof.
The base film may be a transparent polymer film, and for example, may be a transparent film including at least one resin selected from the group consisting of a polyester resin, a polyurethane resin, and a polyolefin (polyethylene, etc.) resin. Alternatively, the base film may be constituted by paper, a plastic film, cloth, or metal foil. In some embodiments, materials suitable for the base film may include, for example, paper including both flat or smooth paper and textured paper such as crepe paper, natural or synthetic polymer films, natural and/or synthetic fibers and nonwoven fabric made from combinations thereof, fiber reinforced polymer films, fiber or yam reinforced polymer films or nonwoven fabric, and a multi-layer laminated structure.
The type of the release film used for the adhesive tape is not particularly limited, but may be, for example, at least one selected from the group consisting of a polyester (PET) film, a polyethylene (PE) film, a polypropylene (PP) film, and paper. Further, the release film may include a silicone coating layer on a surface in contact with the adhesive film. The thickness of the release film may be 5 pm to 100 pm, but may be thinner or thicker as necessary.
The release film may be transparent or may have light-shielding properties. Specifically, the adhesive tape may further include a light-shielding release film laminated on the surface of the adhesive film. The light-shielding release film prevents the surface of the adhesive film from being unnecessarily exposed to UV light, thereby maintaining adhesive strength variability.
The adhesive film may be applied to a masking tape inside an electronic device. FIG. 7 illustrates an example in which a tape with adhesive strength variability is applied as a masking tape in a smartphone. Referring to FIG. 7A, recently, a waterproof adhesive tape 20 having a thickness of 350 pm is used to attach internal components to a rear cover of a smartphone, and some sensors or chips (illustrated in a dotted circle in FIG. 7B) of a printed circuit board (PCB) are in contact with the adhesive surface of the tape 20 to damage the sensors or chips. Accordingly, the adhesive tape 10 of the present invention, of which the adhesive strength may be rapidly lowered by UV curing, is applied as a masking tape, and damage to the sensors or chips of the internal substrate may be prevented when the masking tape is removed later if necessary.
Laminate
According to still another aspect of the present invention, there is provided a laminate including a first substrate; a second substrate; and the adhesive film according to the embodiment disposed between the first substrate and the second substrate.
Each of the first substrate and the second substrate in the laminate may be made of a material such as metal, glass, ceramic, or polymer. Specifically, the materials of the first substrate and the second substrate may be stainless steel, glass, ceramic, polyolefin, polyimide, or the like, respectively.
The adhesive film may be attached on the entire surface of the substrate. Unlike this, the adhesive film may be partially attached to the surface of the substrate, so that the laminate may have an adhesive film application area and an adhesive film non-application area.
The adhesive film in the laminate may be the adhesive film according to the embodiment described above. Accordingly, the laminate structure may include the adhesive film having the above-described composition and properties.
Apparatus
According to still another aspect of the present invention, there is provided an apparatus including the adhesive film or the laminate.
A specific type of the apparatus is not particularly limited, but may be, for example, a display device. A display device according to an embodiment includes a display panel; and the adhesive film according to the embodiment attached onto the display panel. A display device according to another embodiment includes a display panel; and the laminate according to the embodiment attached onto the display panel.
The display device may be an organic light emitting diode (OLED) display device or a liquid crystal display (LCD) device, and may be, for example, a mobile display device such as a smartphone.
Examples
Hereinafter, the present invention will be described in more detail with reference to Examples. However, these Examples are just to exemplify the present invention and the present invention is not limited thereto. Preparation Example 1: Preparation of UV curable resin (Resin Bl)
For the synthesis of a bisphenol A epoxy acrylate-based oligomer, a commercial bisphenol A type epoxy resin (manufacturer: Kumho P&B, product name: KER-828) reacted with methacrylic acid at 90°C for about 1 hour in a molar ratio of 1 : 1.8. In the reaction, as a catalyst, 4-methoxyphenol was used in an amount of 1.6 mol per 1 mol of the epoxy resin. As a result, as shown in FIG. 4, a reaction mixture (resin Bl) containing bisphenol A epoxy acrylate-based oligomer: bisphenol A epoxy resin: methacrylic acid in a weight ratio of 82: 15:3 was obtained. The results of 1H-NMR analysis of the synthesized UV-curable resin were shown in FIG. 5. Examples and Comparative Examples: Preparation of Adhesive Composition
A base polymer (resins A1 to A2) was mixed with a UV curable resin (resins Bl to B3), an epoxy resin (resins Cl to C2), an organic acid, and the like, added an initiator, and finally mixed with a crosslinking agent to obtain an adhesive composition. At this time, the component and content of each material in the final composition were as follows (values in parentheses in Table below were parts by weight of the solid content of each component converted based on 100 parts by weight of the solid content of the base polymer).
Examples
Table 1
Figure imgf000031_0001
Table 2
Figure imgf000032_0001
Resin A1 : TTT-6400 from TTT Korea Co., Ltd., acrylic resin substituted with about 6 wt% of an acrylate group having a double bond, Chemical Name: 2-propenoic acid, 2-methyl-, 2-hydroxyethyl ester, polymer with ethenyl acetate and 2-ethylhexyl 2-propenoate, 33.2 wt% of solid content
Resin A2 AT-422NT from Saiden Chemical Industry Co., Ltd., general acrylic resin without an acrylate group in a molecule, 30 wt% of solid content
Resin B1 : UV curable resin obtained in Preparation Example 1, 100 wt% of solid content
Resin B2: Miramer SC-6400 from Miwon Specialty Chemical Co., Ltd., epoxy acrylate- based oligomer, 100 wt% of solid content
Resin B3 : Miramer PU640 from Miwon Specialty Chemical Co., Ltd., aromatic urethane acrylate-based oligomer, 100 wt% of solid content
Resin Cl : KER-828 from Kumho P&B Co., Ltd., bisphenol A epoxy resin, 100 wt% of solid content
Resin C2: KDCP-130EK80 from Kukdo Chemical Co., Ltd., phenol novolac type epoxy resin, 80 wt% of solid content
379EG: Omnirad 379EG from IGM Resin Co., Ltd., initial wavelength of 365 to 390 nm
754: Omnirad 754 from IGM Resin Co., Ltd., initial wavelength of 320 nm or less
GK-100: GK-100 from TTT Korea Co., Ltd., isocyanate-based crosslinking agent, 52 wt% of solid content
AL: Saivinol hardener AL from Saiden Chemical Industry Co., Ltd., isocyanate-based crosslinking agent, 45 wt% of solid content
Test Example
The adhesive compositions of the Examples and Comparative Examples were tested as follows.
Preparation of Adhesive Tape
An adhesive composition was coated on a white polyethylene terephthalate (PET) film with a thickness of 7 pm at a rate of about 2 m/min. The coated film was dried in a total 6 m of oven having three drying zones (at temperatures of 60°C, 100°C, and 140°C, respectively) having lengths of 2 m. As a result, a tape having a 5 pm-thick adhesive layer formed on the PET film was obtained, and a 50 pm-thick black PET film was laminated on the surface of the adhesive layer to prevent unnecessary UV curing before the test UV curing
UV curing of the adhesive layer of the adhesive tape was performed by UV irradiation using UV equipment (energy 1000 mJ/cm2) having a metal halide lamp (wavelength range of 250 to 420 nm, dominant wavelength of 365 nm).
Test Example 1: Adhesion test (180° peeling adhesive strength)
An adhesive tape was attached to a stainless steel (SUS304) plate, and the adhesive strength (unit: gf/in) was measured while 180°-peeling the adhesive tape at a peeling rate of 305 mm/min according to ASTM D3330. After storing the adhesive tape at 22°C and 50%RH for 20 minutes, the adhesive strength (adhesive strength before UV curing) was measured, and then the adhesive layer was UV-cured and the adhesive strength (adhesive strength after UV curing) was measured within 20 minutes. A sample was cut to a width of 1 inch, and the adhesion test was repeated three times to obtain an average value.
Test Example 2: Color after UV curing
A black PET release paper was removed from the adhesive tape, and UV was irradiated on the surface of the adhesive layer while exposed to oxygen. Thereafter, it was confirmed that the color of the adhesive layer was discolored.
Test Example 3: Shear adhesion test
The adhesive tape was attached to a stainless steel (SUS304) plate, and a static shear adhesive test was performed according to ASTM D3654. The time (unit: hr) to maintain the adhesion to a load of 1000 g under the condition of blocking light with a black film and at room temperature was measured.
Test Example 4: Hardness
After irradiating the adhesive layer of the adhesive tape with UV, a pencil hardness test (load of 500 g) using graphite pencils of various hardnesses was performed. The hardness of the adhesive layer was determined by the hardness of the softest pencil among graphite pencils that left scratches on the surface.
Table 3
Figure imgf000035_0001
Table 4
Figure imgf000035_0002
As shown in Tables above, the adhesive strength, color change, and hardness of tapes A and J prepared using adhesive compositions A and J, respectively, were the best. The adhesive compositions A and J were compositions mixed with the UV-curable resin of Preparation Example 1, and included the remaining epoxy resin (second oligomer) and methacrylic acid (organic acid) together with the synthesized bisphenol A-based epoxy acrylate-based oligomer (first oligomer), and it was determined that excellent properties were exhibited by these components.
In particular, in the case of tape A containing all of these components and the base polymer having an acrylate functional group, the surface hardness was the highest and the adhesive strength after UV curing was the lowest.
On the other hand, tapes prepared with different compositions, such as containing only some of these components, were poor in terms of at least one property of adhesive strength, the color change, and the hardness.
On the other hand, tapes E and G could not be prepared as adhesive tapes due to gelation occurred during mixing by using only acrylic acid having high reactivity in the raw materials of the adhesive composition.

Claims

What is claimed is:
1. An adhesive composition comprising: a base Polymer; a crosslinking agent reacting with the base polymer; a curable resin to be UV-cured after the reaction between the base polymer and the crosslinking agent; and an initiator to cure the curable resin, wherein the curable resin includes a first oligomer, a second oligomer, and an organic acid, and the adhesive composition has first adhesive strength before UV curing and second adhesive strength after UV curing after the reaction of the base polymer and the crosslinking agent, wherein the second adhesive strength is lower than the first adhesive strength.
2. The adhesive composition of claim 1, wherein the first adhesive strength and the second adhesive strength have a difference of 200 gf/in or more from each other.
3. The adhesive composition of claim 1, wherein the adhesive composition has a surface hardness of 1 H or more after UV curing.
4. The adhesive composition of claim 1, wherein the adhesive composition is applied to a masking tape in an electric device.
5. The adhesive composition of claim 1, wherein the adhesive composition is applied to the manufacture of a multilayer ceramic capacitor (MLCC).
6. The adhesive composition of claim 1, wherein the first oligomer includes repeating units derived from an epoxy acrylate-based compound having a bisphenol A skeleton.
7. The adhesive composition of claim 1, wherein the second oligomer is an epoxy resin having a bisphenol A skeleton.
8. The adhesive composition of claim 1, wherein the organic acid contains a carbon double bond at an end.
9. The adhesive composition of claim 1, wherein the curable resin includes 100 parts by weight of the first oligomer, 5 to 35 parts by weight of the second oligomer, and 1 to 6 parts by weight of the organic acid.
10. The adhesive composition of claim 1, wherein the base polymer has acrylate-based functional groups, and the content of the acrylate-based functional groups in the base polymer is 1 wt% to 15 wt%.
11. The adhesive composition of claim 1, wherein the initiator includes a first initiator that acts in light having a wavelength of 365 nm to 390 nm; and a second initiator that acts in light having a wavelength of 320 nm or less.
12. An adhesive film comprising a reaction product of a base polymer and a crosslinking agent, wherein the adhesive film contains a curable resin to be UV-cured and an initiator, the curable resin includes a first oligomer, a second oligomer, and an organic acid, and the adhesive film has first adhesive strength before UV curing and second adhesive strength after UV curing, wherein the second adhesive strength is lower than the first adhesive strength.
13. A preparation method of the adhesive film of claim 12, comprising the steps of: preparing a curable resin containing a first oligomer, a second oligomer, and an organic acid; mixing a base polymer, the curable resin, an initiator, and a crosslinking agent; reacting the crosslinking agent with the base polymer to form a film-like polymer; and preserving the curable resin and the initiator in the film-like polymer to obtain an adhesive film.
14. A method of using an adhesive film comprising the steps of: attaching a first substrate to the adhesive film of claim 12; cutting the first substrate into two or more units; reducing adhesive strength by irradiating UV light to the adhesive film; and detaching the units from the adhesive film.
15. An adhesive tape comprising a base film; and the adhesive film of claim 12 disposed on one side of the base film.
16. The adhesive tape of claim 15, further comprising: a light-shielding release film laminated on the surface of the adhesive film.
17. A laminate comprising: a first substrate; a second substrate; and the adhesive film of claim 12 disposed between the first substrate and the second substrate.
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Citations (3)

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Publication number Priority date Publication date Assignee Title
EP2871219A1 (en) * 2012-07-04 2015-05-13 Dainippon Printing Co., Ltd. Adhesive layer and adhesive sheet
WO2021019359A1 (en) * 2019-07-31 2021-02-04 3M Innovative Properties Company Adhesive composition, adhesive film, laminate and preparation method thereof
WO2021019358A1 (en) * 2019-07-31 2021-02-04 3M Innovative Properties Company Double coated adhesive tape and method of using same

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KR100476798B1 (en) 1996-05-30 2006-01-27 닛토덴코 가부시키가이샤 Thermosetting Pressure Sensitive Adhesive and Adhesive Sheets

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2871219A1 (en) * 2012-07-04 2015-05-13 Dainippon Printing Co., Ltd. Adhesive layer and adhesive sheet
WO2021019359A1 (en) * 2019-07-31 2021-02-04 3M Innovative Properties Company Adhesive composition, adhesive film, laminate and preparation method thereof
WO2021019358A1 (en) * 2019-07-31 2021-02-04 3M Innovative Properties Company Double coated adhesive tape and method of using same

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