KR20210069306A - Foldable Adhesive film And Manufacturing Method Therefor - Google Patents

Abstract

The present invention relates to a foldable adhesive film and a manufacturing method thereof. More specifically, the present invention relates to: a foldable adhesive film which minimizes deformation at high temperatures and maintains constant creep strain and recovery from low to high temperatures to improve folding performance; and a manufacturing method thereof.

Description

Foldable Adhesive Film And Manufacturing Method Therefor

The present invention relates to a foldable adhesive film and a method for manufacturing the same, and specifically, to a foldable adhesive film having improved folding performance by minimizing deformation at high temperatures and maintaining constant creep strain and recoverability from low to high temperatures, and a foldable adhesive film and the same It relates to a manufacturing method.

A pressure-sensitive adhesive used in a foldable display requires sufficient deformation to relieve stress between layers generated during folding, and requires excellent recovery in order to recover to its original state.

Furthermore, since portable devices to which the foldable display is applied are used in various places from cryogenic to extremely high temperatures, they must have excellent folding performance in a wide temperature range. When the external force is removed while having strain, it is required to have excellent recoverability to recover to the original state.

In general, the pressure-sensitive adhesive is easily deformed in the high temperature region than in the low temperature region, but there is a problem in that the recovery ability to return to the original state after the external force is removed is deteriorated.

In order to solve this problem, when the deformation rate of the pressure-sensitive adhesive is designed to be low in consideration of the folding performance in the high temperature region, the deformation rate at room temperature and low temperature is further reduced, so that another problem occurred in that the folding performance at room temperature and low temperature is reduced.

Therefore, there was an urgent need to develop a technology for an adhesive film applied to a foldable display that improves strain and recoverability at room temperature and high temperature, and has a constant folding performance from a high temperature region to a low temperature region.

An object of the present invention is to provide a foldable adhesive film having improved strain and recovery at room temperature and high temperature by including a free volumizing agent including a chemical formula having a specific structure, and a method for manufacturing the same.

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

An exemplary embodiment of the present invention is a copolymer of a mixture containing (meth)acrylate containing at least one alkyl group having 2 to 10 carbon atoms, (meth)acrylate containing a polar group, and a free volumizing agent; and a crosslinking agent; A pressure-sensitive adhesive layer comprising a cured product of the pressure-sensitive adhesive composition comprising; and a substrate provided on one surface of the adhesiveness; including, a creep strain measured by applying a pressure of 10,000 Pa at 25° C. for 600 seconds is 100% or more, and 600 seconds after removing the pressure A foldable adhesive film having a strain after recovery of 15% or less is provided.

Another exemplary embodiment of the present invention is a copolymer of a mixture containing (meth)acrylate containing at least one alkyl group having 2 to 10 carbon atoms, (meth)acrylate containing a polar group, and a free volumizing agent; and a crosslinking agent; Providing a pressure-sensitive adhesive composition comprising; applying the adhesive composition on a substrate; The step of providing an adhesive layer by curing the adhesive composition is included, and the creep strain measured by applying a pressure of 10,000 Pa at 25° C. for 600 seconds is 100% or more, and the pressure is removed and 600 Provided is a method for manufacturing a foldable adhesive film having a strain after recovery of 15% or less after the lapse of seconds.

The foldable adhesive film according to an exemplary embodiment of the present invention can improve the folding performance by improving the creep strain and minimizing the strain after recovery after the external force is removed.

The method of manufacturing a foldable adhesive film according to another exemplary embodiment of the present invention can maintain a constant folding performance from a low temperature region to a high temperature region by controlling the strain realized in the foldable adhesive film and the strain after recovery by including a free volumetric agent. have.

1 is a schematic diagram of a sample for a dynamic folding test.
2 is a schematic diagram of a dynamic folding test.

Throughout this specification, when a part "includes" a certain element, it means that other elements may be further included, rather than excluding other elements, unless otherwise stated.

Throughout this specification, when a member is said to be “on” another member, this includes not only a case in which a member is in contact with another member but also a case in which another member is present between the two members.

Throughout this specification, the unit “part by weight” may mean a ratio of weight between each component.

Throughout this specification, "(meth)acrylate" is used in the collective sense of acrylate and methacrylate.

Throughout this specification, "A and/or B" means "A and B, or A or B."

Throughout this specification, the term "monomer unit" may refer to a form in which a monomer is reacted in a polymer, and specifically, the monomer undergoes a polymerization reaction to form a backbone of the polymer, for example, a main chain or a side chain. It can mean the shape forming the .

Throughout this specification, the "weight average molecular weight" and "number average molecular weight" of a compound may be calculated using the molecular weight and molecular weight distribution of the compound. Specifically, a sample sample having a concentration of 1 wt% of the compound is prepared by putting tetrahydrofuran (THF) and a compound in a 1 ml glass bottle, and a standard sample (polystyrene, polystryere) and a sample sample are filtered (pore size). After filtration through 0.45 μm), it is injected into a GPC injector, and the molecular weight and molecular weight distribution of the compound can be obtained by comparing the elution time of the sample sample with the calibration curve of the standard sample. In this case, an Infinity II 1260 (Agilient Corporation) may be used as a measuring device, the flow rate may be set to 1.00 mL/min, and the column temperature may be set to 40.0 °C.

Throughout this specification, “Glass Temperature (Tg)” refers to a sample in a temperature range of -60 ℃ to 100 ℃, heated at a heating rate of 5 ℃/min, and the elastic modulus at a frequency of 1 Hz is measured by a rheometer (Rheometer, TA). Company, ARES-G2) It can be obtained by measuring the temperature at the maximum value of tan δ, which is a result derived while measuring.

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

An exemplary embodiment of the present invention is a copolymer of a mixture containing (meth)acrylate containing at least one alkyl group having 2 to 10 carbon atoms, (meth)acrylate containing a polar group, and a free volumizing agent; and a crosslinking agent; A pressure-sensitive adhesive layer comprising a cured product of the pressure-sensitive adhesive composition comprising; and a substrate provided on one surface of the adhesiveness; including, a creep strain measured by applying a pressure of 10,000 Pa at 25° C. for 600 seconds is 100% or more, and 600 seconds after removing the pressure A foldable adhesive film having a strain after recovery of 15% or less is provided.

The foldable adhesive film according to an exemplary embodiment of the present invention can improve the folding performance by improving the creep strain and minimizing the strain after recovery after the external force is removed.

According to an exemplary embodiment of the present invention, the mixture may include (meth)acrylate including at least one alkyl group having 2 to 10 carbon atoms. Specifically, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, sec-butyl (meth) Acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-ethylbutyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) ) may include one or more selected from acrylates. More specifically, it is preferred that the mixture comprises 2-ethylhexyl (meth)acrylate. By selecting the above-mentioned monomer, the physical properties of the foldable adhesive film can be secured, and the glass transition temperature of the curing agent of the adhesive composition can be adjusted.

According to an exemplary embodiment of the present invention, the mixture may include (meth)acrylate including a polar group. Specifically, as the (meth)acrylate compound having a polar group, a (meth)acrylate compound in which a substituent containing atoms other than carbon and hydrogen is ester-bonded may be mentioned, and the substituent includes a hydroxyl group, an epoxy group, and a glycidyl ether. It may be a group, a tetrahydrofurfuryl group, an isocyanate group, a carboxyl group, an alkoxysilyl group, a phosphoric acid ester group, a lactone group, an oxetane group, a tetrahydropyranyl group, or an amino group.

According to an exemplary embodiment of the present invention, (meth)acrylate including a polar group is acrylic acid, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth) ) acrylate, 4-hydroxybutyl (meth) acrylate, cyclohexanedimethanol mono (meth) acrylate, glycidyl (meth) acrylate, 4-hydroxybutyl acrylate glycidyl ether, tetrahydrofur Furyl (meth) acrylate, 2-isocyanatoethyl (meth) acrylate, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 3- (meth) Acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 2-( Meth) acryloyloxyethyl phosphate, γ-butyllactone (meth) acrylate, (meth) acrylic acid (3-methyl-3-oxetanyl), (meth) acrylic acid (3-ethyl-3-oxetanyl) , tetrahydrofurfuryl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate. More specifically, the (meth)acrylate including a polar group may be acrylic acid. By selecting the (meth)acrylate containing a polar group from the above, the mechanical properties of the foldable adhesive film can be secured, and the degree of curing of the adhesive layer can be adjusted.

According to an exemplary embodiment of the present invention, (meth) acrylate containing at least one alkyl group having 2 to 10 carbon atoms, (meth) acrylate containing a polar group, and a copolymer obtained by polymerizing a mixture containing a free volumizing agent can By polymerizing the monomers and the free volumizing agent as described above, the glass transition temperature of the cured product of the pressure-sensitive adhesive composition including the polymer can be controlled, and the folding performance can be improved.

According to an exemplary embodiment of the present invention, the pressure-sensitive adhesive composition may include a crosslinking agent. Specifically, the crosslinking agent is 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neo Pentyl glycol adipate (neopentylglycol adipate) di (meth) acrylate, dicyclopentanyl (dicyclopentanyl) di (meth) acrylate, caprolactone modified dicyclopentenyl di (meth) acrylate, ethylene oxide modified di (meth) Acrylate, di(meth)acryloxy ethyl isocyanurate, allylated cyclohexyl di(meth)acrylate, tricyclodecanedimethanol (meth)acrylate, dimethylol dicyclopentanedi(meth)acrylate, ethylene Oxide modified hexahydrophthalic acid di (meth) acrylate, tricyclodecane dimethanol (meth) acrylate, neopentyl glycol modified trimethyl propane di (meth) acrylate, adamantane (adamantane) di (meth) acrylate or bifunctional acrylates such as 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene; Trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide trifunctional acrylates such as modified trimethylolpropane tri(meth)acrylate, trifunctional urethane (meth)acrylate, or tris(meth)acryloxyethyl isocyanurate; tetrafunctional acrylates such as diglycerin tetra(meth)acrylate or pentaerythritol tetra(meth)acrylate; 5-functional acrylates, such as dipentaerythritol penta (meth)acrylate; And dipentaerythritol hexa (meth) acrylate, caprolactone-modified dipentaerythritol hexa (meth) acrylate or urethane (meth) acrylate (ex. isocyanate monomer and trimethylolpropane tri (meth) acrylate 6-functional acrylates such as reactants, etc., but are not limited thereto. These can be used alone or in combination of two or more types. By selecting a crosslinking agent from the above, the crosslinking density of the adhesive layer, that is, the degree of curing can be adjusted, and the physical properties of the adhesive layer of the foldable adhesive film can be adjusted.

According to an exemplary embodiment of the present invention, the glass transition temperature of the (meth)acrylate including the alkyl group may be -80 ℃ to -30 ℃. Specifically, the glass transition temperature of the (meth)acrylate containing the alkyl group may be -75 °C to -35 °C, -70 °C to -40 °C, -68 °C to -45 °C or -65 °C to -50 °C. have. By adjusting the glass transition temperature of the (meth)acrylate containing the alkyl group within the above-described range, it is possible to improve the recoverability in a high temperature region, thereby improving the folding performance of the foldable adhesive film.

According to an exemplary embodiment of the present invention, the glass transition temperature of the (meth)acrylate including the polar group may be 50 °C to 150 °C. Specifically, the glass transition temperature of the (meth)acrylate containing the polar group is 55 °C to 145 °C, 60 °C to 140 °C, 65 °C to 135 °C, 70 °C to 130 °C, 75 °C to 125 °C, 80 °C to 120 °C, 85 °C to 115 °C, 90 °C to 110 °C or 95 °C to 105 °C. By adjusting the glass transition temperature of the (meth)acrylate including the polar group within the above-described range, it is possible to improve the recoverability in a high temperature region, thereby improving the folding performance of the foldable adhesive film.

According to an exemplary embodiment of the present invention, the mixture may include a free volumizing agent. As described above, since the mixture contains a free volumizing agent, it is possible to improve creep strain at room temperature and high temperature and improve recovery.

According to an exemplary embodiment of the present invention, the free volumizing agent may include one or more selected from the following Chemical Formulas 1 to 3.

[Formula 1]

R ₁ is a hydrogen atom; hydroxyl group; or an ester group having 2 to 6 carbon atoms, and R ₂ , R ₃ , and R ₄ are each independently a substituted or unsubstituted, linear or branched alkyl group having 1 to 10 carbon atoms.

[Formula 2]

R ₁ is a hydrogen atom; hydroxyl group; or an ester group having 2 to 6 carbon atoms, and R ₅ , R ₆ and R ₇ are each independently a substituted or unsubstituted, linear or branched alkyl group having 1 to 10 carbon atoms.

[Formula 3]

R ₁ is a hydrogen atom; hydroxyl group; or an ester group having 2 to 6 carbon atoms, R ₈ is an alkylene group having 1 to 4 carbon atoms, R ₉ and R ₁₀ are each independently a substituted or unsubstituted, linear or branched alkyl group having 1 to 10 carbon atoms, n is an integer from 1 to 10.

More specifically, the free volumizing agent preferably includes at least one selected from the following Chemical Formulas 4 to 9.

[Formula 4]

[Formula 5]

[Formula 6]

[Formula 7]

[Formula 8]

[Formula 9]

By selecting the free volumizing agent from the above formula, it is possible to improve the creep deformation rate at room temperature and high temperature, improve recovery, and improve the folding performance of the foldable adhesive film.

According to an exemplary embodiment of the present invention, the glass transition temperature of the cured product may be -80 ℃ to -20 ℃. Specifically, the glass transition temperature of the cured product may be -75 °C to -25 °C, -70 °C to -30 °C, -65 °C to -35 °C or -60 °C to -40 °C. More specifically, the glass transition temperature of the cured product is preferably -40 ℃. By controlling the glass transition temperature of the cured product within the above-described range, it is possible to improve the creep strain at room temperature and high temperature and improve recovery.

According to an exemplary embodiment of the present invention, the content of the (meth)acrylate including the alkyl group in the mixture may be 80.0% by weight to 99.9% by weight. Specifically, the content of the (meth)acrylate including the alkyl group is 81.0 wt% to 99.5 wt%, 82.0 wt% to 99.0 wt%, 83.0 wt% to 98.5 wt%, 84.0 wt% to 98.0 wt%, 85.0 wt% % to 97.5% by weight or 86.0% to 97.0% by weight. More specifically, the content of the (meth)acrylate including the alkyl group is preferably 98.0 wt%. By adjusting the content of the (meth)acrylate containing the alkyl group within the above range, the physical properties of the adhesive layer are satisfied, and the glass transition temperature of the cured product of the adhesive composition is adjusted to effectively remove the stress caused by folding during folding. can do.

According to an exemplary embodiment of the present invention, the content of the (meth)acrylate including the polar group in the mixture may be 0.1 wt% to 20.0 wt%. Specifically, the content of the (meth)acrylate including the polar group is 0.2 wt% to 19.0 wt%, 0.3 wt% to 18.0 wt%, 0.4 wt% to 17.0 wt%, 0.5 wt% to 16.0 wt% or 0.6 wt% to 15.0% by weight. More specifically, the content of the (meth)acrylate including the polar group is preferably 0.1% by weight. By controlling the content of the (meth)acrylate containing the polar group within the above-described range, it is possible to control the glass transition temperature of the cured product of the pressure-sensitive adhesive composition.

According to an exemplary embodiment of the present invention, the content of the free volumizing agent is 5 to 20 parts by weight relative to 100 parts by weight of a mixture of (meth)acrylate including the alkyl group and (meth)acrylate including the polar group it could be Specifically, the content of the free volumizing agent is 6 parts by weight to 17 parts by weight, 7 parts by weight to 15 parts by weight, based on 100 parts by weight of a mixture of (meth)acrylate including the alkyl group and (meth)acrylate including the polar group parts, 8 parts by weight to 13 parts by weight, or 9 parts by weight to 10 parts by weight. More specifically, the content of the free volumizing agent is preferably 7 parts by weight to 10 parts by weight based on 100 parts by weight of a mixture of (meth)acrylate including the alkyl group and (meth)acrylate including the polar group. By controlling the content of the free volumizing agent within the above-described range, it is possible to improve the creep deformation rate at room temperature and high temperature, improve recovery, and improve the folding performance of the foldable adhesive film.

According to an exemplary embodiment of the present invention, the content of the crosslinking agent may be 0.1 to 1.0 equivalents based on the copolymer. Specifically, the content of the crosslinking agent may be 0.1 to 1.0 equivalents, 0.2 to 0.9 equivalents, 0.3 to 0.8 equivalents, or 0.3 to 0.7 equivalents based on the mixture. By controlling the content of the crosslinking agent within the above-described range, the crosslinking density of the adhesive layer, that is, the degree of curing, can be adjusted, and the physical properties of the adhesive layer of the foldable adhesive film can be adjusted.

According to an exemplary embodiment of the present invention, a substrate provided on one surface of the adhesive layer may be included. Specifically, by including the substrate, the basic physical properties of the foldable adhesive film can be secured, and the screen of a foldable display device to which the foldable adhesive film is applied can be protected.

According to an exemplary embodiment of the present invention, the substrate is a polyethylene terephthalate film, a polytetrafluoroethylene film, a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a vinyl chloride copolymer film, a polyurethane film, ethylene - A vinyl acetate film, an ethylene-propylene copolymer film, an ethylene-ethyl acrylate copolymer film, an ethylene-methyl acrylate copolymer film, or a polyimide film may be used, but the present invention is not limited thereto.

According to an exemplary embodiment of the present invention, the thickness of the substrate may be 10 μm or more and 150 μm or less, 50 μm or more and 125 μm or less, or 50 μm or more and 100 μm or less. By adjusting the thickness of the substrate within the above-described range, stress generated when the foldable adhesive film is folded can be effectively removed, and the recovery properties of the foldable adhesive film can be improved.

According to an exemplary embodiment of the present invention, the foldable adhesive film may further include a release film. Specifically, the foldable adhesive film can be realized by being laminated in the order of the substrate, the adhesive layer, and the release film.

According to an exemplary embodiment of the present invention, the foldable adhesive film has a creep strain measured by applying a pressure of 10,000 Pa at 25° C. for 600 seconds to 100% or more. Specifically, the foldable adhesive film has a creep strain measured by applying a pressure of 10,000 Pa at 25° C. for 600 seconds from 100% to 200%, 110% to 190%, 120% to 180%, 130% to 170% or 140% to 160%. By controlling the creep strain of 25 ℃ implemented within the above-described range, it is possible to improve the folding performance of the foldable adhesive film.

In the present specification, creep strain means the ratio of the length stretched by applying a constant pressure for a certain time, that is, the strain, and in the present invention, the ratio of the length increased by applying a pressure of 10,000 Pa for 600 seconds is measured. it means.

According to an exemplary embodiment of the present invention, the foldable adhesive film may have a strain rate of 15% or less after recovery after 600 seconds of removing the pressure at 25°C. Specifically, the foldable adhesive film has a strain rate greater than 0% and less than 15%, 1% to 14%, 2% to 13%, 3% to 13%, 4% to 12%, 5% to 11%, 6% to 10%. By controlling the strain after recovery implemented in the foldable adhesive film within the above-described range, it is possible to improve the folding performance of the foldable adhesive film.

In the present specification, the strain after recovery (Strain After Recovery) means measuring the ratio of the length that is not recovered even after removing the pressure and stretching after a certain pressure and time has elapsed, that is, the strain, in the present invention A pressure of 10,000 Pa was applied for 600 seconds, and the ratio of the length that did not return after 600 seconds had elapsed was measured by removing the pressure.

According to an exemplary embodiment of the present invention, the foldable adhesive film has a creep strain measured by applying a pressure of 10,000 Pa at 60° C. for 600 seconds to 100% or more. Specifically, the foldable adhesive film has a creep strain measured by applying a pressure of 10,000 Pa at 60° C. for 600 seconds from 100% to 200%, 110% to 190%, 120% to 180%, 130% to 170% or 140% to 160%. By controlling the creep strain of 60 ℃ implemented within the above range, it is possible to improve the folding performance of the foldable adhesive film.

According to an exemplary embodiment of the present invention, the foldable adhesive film may have a strain rate of 15% or less after recovery after 600 seconds of removing the pressure at 60°C. Specifically, the foldable adhesive film has a strain rate greater than 0% and less than or equal to 15%, 1% to 14%, 2% to 13%, 3% to 13%, 4% to 12%, 5% to 11%, 6% to 10%. By controlling the strain after recovery implemented in the foldable adhesive film within the above-described range, it is possible to improve the folding performance of the foldable adhesive film.

As described above, by adjusting the creep strain realized at 25°C and 60°C and the strain after recovery, the folding performance at room temperature and high temperature can be improved.

Another exemplary embodiment of the present invention is a copolymer of a mixture containing (meth)acrylate containing at least one alkyl group having 2 to 10 carbon atoms, (meth)acrylate containing a polar group, and a free volumizing agent; and a crosslinking agent; Providing a pressure-sensitive adhesive composition comprising; applying the adhesive composition on a substrate; and curing the pressure-sensitive adhesive composition to provide an adhesive layer; and the creep strain measured by applying a pressure of 10,000 Pa at 25° C. for 600 seconds is 100% or more, and after 600 seconds have elapsed after removing the pressure Provided is a method for manufacturing a foldable adhesive film having a strain rate of 15% or less after recovery.

The method of manufacturing a foldable adhesive film according to another exemplary embodiment of the present invention can maintain a constant folding performance from a low temperature region to a high temperature region by controlling the strain and recovery properties implemented in the foldable adhesive film by including a free volumizing agent. .

As described in the foldable adhesive film according to an exemplary embodiment of the present invention, the same content as the manufacturing method of the foldable adhesive film will be omitted.

According to an exemplary embodiment of the present invention, it includes the step of applying the pressure-sensitive adhesive composition on a substrate. The coating method is not particularly limited. Specifically, the method for applying the adhesive composition on the substrate may be an applicator coating, a bar coater, a comma coater, or the like.

According to an exemplary embodiment of the present invention, the thickness of the adhesive layer may be 10 μm or more and 100 μm or less. Specifically, the thickness of the adhesive layer may be 15 μm or more and 80 μm or less, 20 μm or more and 60 μm or less, or 25 μm or more and 40 μm or less. By adjusting the thickness of the pressure-sensitive adhesive layer within the above-described range, it is possible to adjust the step embedding property and the adhesive force of the foldable pressure-sensitive adhesive film.

According to an exemplary embodiment of the present invention, the step of curing the pressure-sensitive adhesive composition to provide a pressure-sensitive adhesive layer. Specifically, the curing method is not particularly limited. Specifically, the curing method may be thermal curing, photocuring through ultraviolet irradiation, or photocuring through E-beam irradiation. By selecting the curing method described above, it is possible to form an adhesive layer included in the foldable adhesive film and secure physical properties required for the adhesive layer.

Hereinafter, examples will be given to describe the present invention in detail. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention is not to be construed as being limited to the embodiments described below. The embodiments of the present specification are provided to more completely explain the present invention to those of ordinary skill in the art.

Example One

(1) Preparation of copolymer

A mixture comprising 98% by weight of 2-ethylhexylacrylate (2-EHA) and 2% by weight of acrylic acid (AA) in a 1 L reactor; and 10 parts by weight of the mixture based on 100 parts by weight of a free volumizing agent represented by the following Chemical Formula 4; and then ethyl acetate (Ethyl Acetate, EAc) was added as a solvent. Then, after nitrogen gas was purged for about 1 hour to remove oxygen, the reactor temperature was maintained at 62 °C. After homogenizing the monomer mixture, 400 ppm of azobisisobutyronitrate (AIBN) as a reaction initiator and 400 ppm of n-dodecylmercaptan (n-DDM) as a chain transfer agent were added, and the monomer mixture was added. reacted. After the reaction, ethyl acetate was diluted to prepare a copolymer having a weight average molecular weight of 2 million.

[Formula 4]

(2) Preparation of adhesive composition

BXX-5240, an epoxy-based crosslinking agent, and BXX-5627, an isocyanate-based crosslinking agent were added to 100 g of the prepared copolymer, diluted to 18% by weight in an ethyl acetate solution, and then mixed with 0.4 equivalents of the crosslinking agent. After dilution with a solvent to control the solid content so as to have a suitable viscosity (500cp to 1500cp) for the coating, the mixture was stirred using a mechanical stirrer for 15 minutes or more, and then sealed to remove bubbles generated during mixing and left at room temperature for 1 hour.

(3) Preparation of adhesive film

A coating film of the adhesive composition was formed on the release film by using a comma coater, and then dried at a maximum temperature of 130° C. for 3 minutes to prepare an adhesive film with a thickness of 25 μm.

Example 2

An adhesive film was prepared in the same manner as in Example 1, except that in Example 1, 7 parts by weight of the free volumizing agent was used.

Example 3

An adhesive film was prepared in the same manner as in Example 1, except that in Example 1, 7 parts by weight of the free volumizing agent and 0.3 equivalent of the crosslinking agent were used.

Example 4

An adhesive film was prepared in the same manner as in Example 1, except that the free volumizing agent was used in Example 1 by the following Chemical Formula 5.

[Formula 5]

Example 5

An adhesive film was prepared in the same manner as in Example 1, except that in Example 1, the free volumizing agent was used in the following formula (8).

[Formula 8]

Example 6

An adhesive film was prepared in the same manner as in Example 1, except that in Example 1, the free volumizing agent was used in the following formula (9).

[Formula 9]

comparative example One

An adhesive film was prepared in the same manner as in Example 1, except that in Example 1, no free volumizing agent was included and 0.2 equivalent of a crosslinking agent was used.

comparative example 2

An adhesive film was prepared in the same manner as in Example 1, except that in Example 1, no free volumizing agent was included.

comparative example 3

Example 1 did not contain a free-volume agent, used butyl acrylate (BA) instead of 2-ethylhexyl acrylate (2-EHA), the glass transition temperature of the cured product was adjusted to -35 ° C, and An adhesive film was prepared in the same manner as in Example 1, except that 0.2 equivalent of the crosslinking agent was used.

comparative example 4

In Example 1, no free volumizing agent was used, butyl acrylate (BA) was used at 94 wt % instead of 2-ethylhexyl acrylate (2-EHA) and acrylic acid was used at 6 wt %, the cured product An adhesive film was prepared in the same manner as in Example 1, except that the glass transition temperature was adjusted to −25° C. and 0.2 equivalent of a crosslinking agent was used.

comparative example 5

Example 1 did not contain a free-volume agent, used carbitol acrylate (ethoxyethoxyethyl acrylate) instead of 2-ethylhexyl acrylate (2-EHA), the glass transition temperature of the cured product was - An adhesive film was prepared in the same manner as in Example 1, except that the temperature was adjusted to 42° C. and 1 equivalent of a crosslinking agent was used.

comparative example 6

Except that in Example 1, no free volumizing agent was included, beta-carboxyethyl acrylate was used instead of acrylic acid, the glass transition temperature of the cured product was adjusted to -41 ° C., and 0.2 equivalent of a crosslinking agent was used. An adhesive film was prepared in the same manner as in Example 1.

Experimental example 1 (creep strain measurement)

The adhesive films of Examples 1 to 6 and Comparative Examples 1 to 6 were prepared, and creep strain rates of 25°C and 60°C were measured.

The creep strain is a measure of the length ratio of the adhesive film, that is, the strain rate, immediately after applying a stress of 10,000 Pa to the adhesive film for 600 seconds.

Experimental example 2 (Measurement of strain after recovery)

The adhesive films of Examples 1 to 6 and Comparative Examples 1 to 6 were prepared, and the strains after recovery of Examples 1 to 6 and Comparative Examples 1 to 5 were measured.

The strain after recovery is measured by applying a pressure of 10,000 Pa to the pressure-sensitive adhesive film for 600 seconds, removing the pressure, and increasing the length ratio, ie, strain, after elapsed for 600 seconds.

Experimental example 3( dynamic folding exam)

1 is a schematic diagram of a sample for a dynamic folding test. Specifically, a hard coating layer, a polyimide film having a thickness of 50 μm, a hard coating layer, an adhesive layer prepared in the manufacturing process of Examples 1 to 6 and Comparative Examples 1 to 6, a polarizing plate, Examples 1 to 6 and Comparative Examples 1 to The adhesive layer prepared in the manufacturing process of step 6 and the layer simulating the display panel were sequentially laminated, and a sample of 7.8 X 14 cm was prepared.

2 is a schematic diagram of a dynamic folding test. Referring to FIG. 2 , after the sample was fabricated, a dynamic folding test of folding and unfolding the sample was performed 200,000 times at 25° C. by inserting it into a parallel plate having an interval of 5 mm. After the test was completed, the samples were collected, and the occurrence of bubbles, floating, and cracks in the hard coating layer were visually observed. If there is no bubble generation or lifting and no cracks in the hard coating layer, OK, and if bubbles or lifting or cracks in the hard coating layer occur, it is indicated as N.G.

Table 1 below summarizes the results of the Experimental Examples according to Experimental Examples 1 to 3 and the results of visually observing whether there are any folds in the folding part after the experiment according to Experimental Example 3.

division at 25 °C
Strain (%) at 60 °C
Strain (%) dynamic folding
exam dynamic folding
after the exam
Whether or not there are folds in the folding part creep strain after recovery
strain creep strain after recovery
strain 25 ℃ 60 ℃ 25 ℃ 60 ℃ Example 1 121.4 8.4 120.5 5.1 OK OK OK OK Example 2 105.7 8.2 104.5 3.6 OK OK OK OK Example 3 139.2 13.5 163.6 9.0 OK OK OK OK Example 4 124.2 8.7 124.2 5.6 OK OK OK OK Example 5 125.2 8.1 124.9 5.4 OK OK OK OK Example 6 123.1 7.3 122.8 5.2 OK OK OK OK Comparative Example 1 132 21.5 225.8 28.2 OK OK NG NG Comparative Example 2 85 6.4 95 3.6 NG NG - - Comparative Example 3 80 14.2 183 17.2 NG OK - NG Comparative Example 4 17 1.6 24.2 2.1 NG NG - - Comparative Example 5 243 34.4 564 201 OK OK NG NG Comparative Example 6 162 25 352 43.2 OK OK NG NG

Referring to Table 1, Examples 1 to 6 include the free volumizing agent of Chemical Formulas 1 to 3, thereby improving creep strain in the high temperature region and room temperature region, and reducing the strain after recovery. In other words, it was confirmed that the folding performance was improved by implementing both the opposite physical properties of deformation and recovery, and there were no bubbles and no lifting, no cracks in the hard coating layer, and no fold marks in the folding part (folding position) even when the dynamic folding test was performed. It was confirmed that this did not occur.

In contrast, Comparative Examples 1 to 6 did not include the free volumizing agent, and thus it was confirmed that neither the creep strain at room temperature nor the strain after recovery were satisfied. Comparative Examples 3 and 4 did not satisfy the glass transition temperature, so did not satisfy the dynamic folding test at room temperature, and it was confirmed that fold marks remain even if satisfied at high temperature.

In addition, in Comparative Examples 5 and 6, even if the glass transition temperature is adjusted in a range similar to that of Examples 1 to 6 by combining the (meth)acrylate monomer, the strain rate after recovery of the room temperature region and the high temperature region when the free volumizing agent is not included It was not satisfied, and it was confirmed that fold marks were generated in the folding part (folding position).

Therefore, according to the foldable adhesive film and method for manufacturing the same of the present invention, by including a free-volume agent, the foldable adhesive film increases the creep strain rate of the foldable adhesive film at high temperature and room temperature and reduces the strain rate after recovery, so that the foldable adhesive film It is possible to prevent the folding of the folding part and improve the folding performance.

Claims (11)

A cured product of an adhesive composition comprising a (meth)acrylate containing at least one alkyl group having 2 to 10 carbon atoms, a (meth)acrylate containing a polar group, and a mixture containing a free volumizing agent; and a crosslinking agent; Adhesive layer comprising; and
Including; a substrate provided on one surface of the adhesive layer;
Creep strain measured by applying a pressure of 10,000 Pa for 600 seconds at 25 ℃ is more than 100%,
A foldable adhesive film having a strain after recovery of 15% or less after the pressure is removed and 600 seconds have elapsed. The method according to claim 1,
Creep strain measured by applying a pressure of 10,000 Pa at 60 °C for 600 seconds is 100% or more,
A foldable adhesive film having a strain after recovery of 15% or less after 600 seconds of removing the pressure. The method according to claim 1,
The free volumizing agent comprising at least one selected from the following Chemical Formulas 1 to 3
Foldable adhesive film:
[Formula 1]

[Formula 2]

[Formula 3]

R ₁ is a hydrogen atom; hydroxyl group; Or an ester group having 2 to 6 carbon atoms,
R ₂ , R ₃ , R ₄ , R ₅ , R ₆ R ₇ , R ₉ and R ₁₀ are each independently a substituted or unsubstituted, linear or branched alkyl group having 1 to 10 carbon atoms,
R ₈ is an alkylene group having 1 to 4 carbon atoms,
n is an integer from 1 to 10; The method according to claim 1,
The glass transition temperature of the cured product is -80 ℃ to -20 ℃
Foldable adhesive film. The method according to claim 1,
The content of the (meth)acrylate containing the alkyl group is 80.0 wt% to 99.9 wt%
Foldable adhesive film. The method according to claim 1,
The content of the (meth)acrylate including the polar group is 0.1 wt% to 20.0 wt%
Foldable adhesive film. The method according to claim 1,
The content of the free volumizing agent is
5 to 20 parts by weight based on 100 parts by weight of a mixture of (meth)acrylate containing the alkyl group and (meth)acrylate containing the polar group
Foldable adhesive film. The method according to claim 1,
The content of the crosslinking agent is 0.1 to 1.0 equivalents based on the copolymer
Foldable adhesive film. A copolymer of a mixture containing (meth)acrylate containing at least one alkyl group having 2 to 10 carbon atoms, (meth)acrylate containing a polar group, and a free volumizing agent; and a crosslinking agent; step;
applying the adhesive composition on a substrate;
It includes; curing the pressure-sensitive adhesive composition to provide a pressure-sensitive adhesive layer;
Creep strain measured by applying a pressure of 10,000 Pa for 600 seconds at 25 ℃ is 100% or more,
A method of manufacturing a foldable adhesive film having a strain after recovery of 15% or less after the pressure is removed and 600 seconds have elapsed. 10. The method of claim 9,
The creep strain measured by applying a pressure of 10,000 Pa for 600 seconds at 60 ℃ is 100% or more,
A method of manufacturing a foldable adhesive film having a strain after recovery of 15% or less after the pressure is removed and 600 seconds have elapsed. 10. The method of claim 9,
The free volumizing agent comprising at least one selected from the following Chemical Formulas 1 to 3
Manufacturing method of foldable adhesive film:
[Formula 1]

[Formula 2]

[Formula 3]

R ₁ is a hydrogen atom; hydroxyl group; Or an ester group having 2 to 6 carbon atoms,
R ₂ , R ₃ , R ₄ , R ₅ , R ₆ R ₇ , R ₉ and R ₁₀ are each independently a substituted or unsubstituted, linear or branched alkyl group having 1 to 10 carbon atoms.
R ₈ is an alkylene group having 1 to 4 carbon atoms,
n is an integer from 1 to 10;

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