KR20210010168A - Adhesive coposition, protective film comprising same, foldable display device comprising same and manufacturing method of protective film - Google Patents

Abstract

The present application relates to an adhesive composition, a protective film comprising the same, a foldable display device comprising the same, and a method for manufacturing the protective film. In the case of the protective film including an adhesive sheet of the present invention, the protective film has excellent adhesion on a surface having a low surface energy (AF-treated surface).

Description

Adhesive composition, a protective film containing the same, a method for manufacturing a foldable display device and a protective film containing the same {ADHESIVE COPOSITION, PROTECTIVE FILM COMPRISING SAME, FOLDABLE DISPLAY DEVICE COMPRISING SAME AND MANUFACTURING METHOD OF PROTECTIVE FILM}

The present application relates to an adhesive composition, a protective film including the same, a foldable display device including the same, and a method of manufacturing a protective film.

With the recent development of display-related technologies, research and development of display devices capable of being deformable at the stage of use, such as folding, rolling in a roll shape, or stretching like a rubber band, are being developed. Since these displays can be deformed into various forms, it is possible to satisfy both the demand for an increase in size of the display in the use stage and the demand for miniaturization of the display for portability.

In addition, portable terminals such as wireless terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), and electronic notebooks have recently been miniaturized for portability.

However, since the user wants to receive information from various contents such as text information, video, and games through the screen of the portable terminal, the size of the display screen is required to be enlarged or widened. However, since miniaturization of the portable terminal leads to a reduction in the size of the display screen, there is a limit to satisfying both requirements.

Conventional display devices have used an unbreakable display, but in order to overcome the above limitations, a deformable display, that is, a display having a curved surface, a curved display, and a foldable display. A display (foldable display) and a rollable display (rollable display) and the like have been developed.

The deformable display device may not only be transformed into a pre-set form, but may be transformed into various forms in response to a user's request or a situation in which the display device is used. Accordingly, it is necessary to recognize a deformed shape of the display and control the display device according to the recognized shape.

On the other hand, when using a tablet PC or smartphone to which a deformable display is applied, a protective film is attached to the cover window of the product to prevent scratches on the product surface.

However, when folding/unfolding is repeated several times, such as a foldable display, the conventional transparent PI protective film has a problem that a fold mark occurs on the protective film itself. Accordingly, development is being made to prevent surface contamination by applying H/C treatment and AF coating to the cover window itself.

Surface contamination can be prevented by applying H/C treatment and AF coating to the cover window itself, but the cover window itself is made of glass, which may cause a problem of breaking, so the need for a film to protect it is also increasing. Due to the low surface energy due to the AF treatment of the cover window, it is difficult to attach the protective film through an adhesive with high adhesive strength, and if the protective film is attached through an adhesive with low adhesive strength, the protective film is repeated several times when folding/unfolding. A falling problem is occurring.

Accordingly, in attaching a protective film to protect a cover window of a foldable display device in order to solve such a problem, it is necessary to develop a novel adhesive composition, an adhesive sheet including the same, and a protective film including the same.

Japanese Patent Publication No. 2006-299283

The present application is to provide a pressure-sensitive adhesive composition, a protective film including the same, a foldable display device including the same, and a method of manufacturing a protective film.

An exemplary embodiment of the present application is a (meth) acrylate-based resin; A first monomer containing an amine group; And a second monomer including a hydroxy group, wherein the content of the first monomer is 1 to 30 parts by weight based on 100 parts by weight of the adhesive composition, and the content of the second monomer is 2 to 30 parts by weight based on 100 parts by weight of the adhesive composition. It is intended to provide a pressure-sensitive adhesive composition that is 20 parts by weight.

Another exemplary embodiment is a transparent base film; And it is to provide a protective film including a pressure-sensitive adhesive sheet including the pressure-sensitive adhesive composition according to the present application provided on one side of the transparent base film.

Another exemplary embodiment is a protective film according to the present application; A cover window provided on the pressure-sensitive adhesive sheet side of the protective film; And it is intended to provide a foldable display device including a plastic substrate provided on a surface of the cover window opposite to the surface in contact with the adhesive sheet.

Finally, an exemplary embodiment of the present application is preparing a transparent base film; And

A method for manufacturing a protective film comprising the step of forming a pressure-sensitive adhesive sheet by applying the pressure-sensitive adhesive composition according to the present application to one surface of the transparent base film,

After bonding the opposite side of the pressure-sensitive adhesive sheet to a substrate having a surface energy of 15mN/m or less, the adhesive strength measured by a 180° peel test at a speed of 5mm/s within 10 minutes at 23°C is 10gf/ Inch or more, to provide a method of manufacturing a protective film that is less than or equal to 300 gf/inch.

In the case of the pressure-sensitive adhesive composition according to an exemplary embodiment of the present application, since the first monomer containing an amine group and the second monomer containing a hydroxy group are contained in a specific amount, in the case of a protective film including a pressure-sensitive adhesive sheet containing the same, a lower surface It is characterized by having excellent adhesion on the energy-bearing surface (AF treatment surface).

In addition, in the case of the protective film according to the exemplary embodiment of the present application, the cover of the foldable display satisfies a specific adhesive strength range even when folding and unfolding are repeated when applied to a foldable display later. The foldable display has a feature that can prevent damage to the display as the window does not have lift or fold marks.

Lastly, in the case of the protective film according to the exemplary embodiment of the present application, when applied to a foldable display later, the adhesion to the cover window is excellent, so that even if folding and unfolding are repeated, a lifting phenomenon occurs. It has features that do not occur.

1 is a view showing a side view of a protective film according to an exemplary embodiment of the present application.

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

In the present specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless specifically stated to the contrary.

Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

An exemplary embodiment of the present application is a (meth) acrylate-based resin; A first monomer containing an amine group; And a second monomer including a hydroxy group, wherein the content of the first monomer is 1 to 30 parts by weight based on 100 parts by weight of the adhesive composition, and the content of the second monomer is 2 to 30 parts by weight based on 100 parts by weight of the adhesive composition. It is intended to provide a pressure-sensitive adhesive composition that is 20 parts by weight.

In the case of the pressure-sensitive adhesive composition according to an exemplary embodiment of the present application, as the content of the first monomer containing an amine group and the second monomer containing a hydroxy group are contained, in the case of a protective film including a pressure-sensitive adhesive sheet containing the same, a lower surface It has the characteristics of having excellent adhesion on the energy-bearing surface (AF treatment surface).

In the exemplary embodiment of the present application, the content of the first monomer may include 1 to 30 parts by weight based on 100 parts by weight of the pressure-sensitive adhesive composition.

In another exemplary embodiment, the content of the first monomer may include 1 to 30 parts by weight, preferably 1 to 28 parts by weight, and more preferably 1 to 25 parts by weight based on 100 parts by weight of the pressure-sensitive adhesive composition.

In the exemplary embodiment of the present application, the content of the second monomer may include 2 to 20 parts by weight based on 100 parts by weight of the pressure-sensitive adhesive composition.

In another exemplary embodiment, the content of the second monomer may include 2 to 20 parts by weight, preferably 5 to 17 parts by weight, and more preferably 7 to 17 parts by weight based on 100 parts by weight of the pressure-sensitive adhesive composition.

As the pressure-sensitive adhesive composition according to the present application contains the first monomer and the second monomer in the above content range, in the case of a pressure-sensitive adhesive sheet including the same, the adhesion to the surface having low surface energy satisfies a specific range, so that the adhesive strength is excellent. Have a characteristic.

In particular, in the case of the second monomer, when the glass transition temperature is high and exceeds the content range, the glass transition temperature of the entire pressure-sensitive adhesive composition is increased, and accordingly, the folding characteristics of the pressure-sensitive adhesive sheet may be lowered later, In the case of the second monomer, a reactive monomer may cause problems in terms of change over time, reliability, and stability. In the case of the pressure-sensitive adhesive composition according to an exemplary embodiment of the present application, the content of the second monomer is within a specific range. As satisfied, the folding characteristics are excellent, and reliability and stability are excellent.

In an exemplary embodiment of the present application, the (meth)acrylate-based resin provides a pressure-sensitive adhesive composition that is 60 to 95 parts by weight based on 100 parts by weight of the pressure-sensitive adhesive composition.

In another exemplary embodiment, the (meth)acrylate-based resin may be 60 to 95 parts by weight, preferably 65 to 95 parts by weight based on 100 parts by weight of the pressure-sensitive adhesive composition.

In the exemplary embodiment of the present application, the (meth)acrylate-based resin may have a weight average molecular weight of 100,000 g/mol to 3 million g/mol.

The weight average molecular weight is one of average molecular weights whose molecular weight is not uniform and the molecular weight of a certain polymer material is used as a reference, and is a value obtained by averaging the molecular weights of component molecular species of a polymer compound having a molecular weight distribution by weight fraction.

The weight average molecular weight can be measured through Gel Permeation Chromatography (GPC) analysis.

In this specification, (meth)acrylate is meant to include both acrylate and methacrylate. The (meth)acrylate-based resin may be, for example, a copolymer of a (meth)acrylic acid ester-based monomer and a crosslinkable functional group-containing monomer.

The (meth)acrylic acid ester monomer is not particularly limited, but examples thereof include alkyl (meth)acrylate, and more specifically, as a monomer having an alkyl group having 1 to 12 carbon atoms, pentyl (meth)acrylate, n-butyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethyl Hexyl (meth) acrylate, dodecyl (meth) acrylate, and may include one or more types of decyl (meth) acrylate.

The crosslinkable functional group-containing monomer is not particularly limited, but may include, for example, one or more of a hydroxy group-containing monomer, a carboxyl group-containing monomer, and a nitrogen-containing monomer.

Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylic Rate, 8-hydroxyoctyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, or 2-hydroxypropylene glycol (meth)acrylate.

Examples of the carboxyl group-containing monomer include (meth)acrylic acid, 2-(meth)acryloyloxyacetic acid, 3-(meth)acryloyloxypropyl acid, 4-(meth)acryloyloxybutyric acid, and acrylic acid. Duplex, itaconic acid, maleic acid, or maleic anhydride.

Examples of the nitrogen-containing monomer include (meth)acrylonitrile, N-vinyl pyrrolidone or N-vinyl caprolactam.

At least one of vinyl acetate, styrene, and acrylonitrile may be further copolymerized with the (meth)acrylate-based resin from the viewpoint of improving other functionalities such as compatibility.

In the exemplary embodiment of the present application, the (meth)acrylate-based resin is 2-ethylhexyl acrylate (2-EHA), butyl acrylate (BA), isooctyl acrylate (IOAA), and n-octyl acrylic It may be one or more selected from the group consisting of rate (NOAA).

In the exemplary embodiment of the present application, the (meth)acrylate-based resin may be 2-ethylhexyl acrylate (2-EHA).

In the exemplary embodiment of the present application, when the (meth)acrylate-based resin is 2-ethylhexylacrylate (2-EHA), it is combined with the first monomer and the second monomer of the pressure-sensitive adhesive composition to specify the glass transition temperature. Since it can be formed in a range, there is a characteristic of forming an adhesive sheet having particularly excellent folding characteristics when applied to a foldable display later.

In the exemplary embodiment of the present application, the glass transition temperature value of the (meth)acrylate-based resin may be 0°C or less.

In another exemplary embodiment, the glass transition temperature value of the (meth)acrylate-based resin is -110°C or more and 0°C or less, preferably -100°C or more and 0°C or less, more preferably -90°C or more and 0 It may be below ℃.

In an exemplary embodiment of the present application, a pressure-sensitive adhesive composition is provided in which the value of the glass transition temperature (Tg) of the pressure-sensitive adhesive composition is -50°C or less.

The glass transition temperature of the pressure-sensitive adhesive composition refers to a glass transition temperature value of the entire pressure-sensitive adhesive composition including all of the (meth)acrylate-based resin, the first monomer, and the second monomer included in the pressure-sensitive adhesive composition.

In the exemplary embodiment of the present application, the value of the glass transition temperature (Tg) of the pressure-sensitive adhesive composition may be -50°C or less, and may be -120°C or more, and preferably -110°C or more.

As the glass transition temperature value of the pressure-sensitive adhesive composition according to the present application satisfies the above range, the folding characteristics are particularly excellent. That is, in the case of the pressure-sensitive adhesive composition according to the present application, the glass transition temperature of the entire pressure-sensitive adhesive composition can be adjusted to a range of -50°C or less by adjusting the content of the first monomer and the second monomer included in the pressure-sensitive adhesive composition to a specific range. Accordingly, there is a feature that can form an adhesive sheet having particularly excellent folding characteristics.

In addition, when the glass transition temperature value of the (meth)acrylate-based resin is within the above range, the adhesive sheet containing the (meth)acrylate-based resin has excellent adhesive strength and excellent flow characteristics, so that when applied to a foldable display, the adhesive strength is excellent. Have a characteristic.

In the present specification, the glass transition temperature is a differential scanning calorimeter (DSC, Mettler, Inc.), and when a sample of about 10 mg is sealed in a dedicated pen and heated to a constant temperature environment, the endothermic heat of the material occurs. And a value measured by drawing the calorific value according to the temperature.

Specifically, the glass transition temperature is a nominal value described in literature, catalog or the like, or a value calculated based on the following general formula (1) (Fox formula).

[General Formula (1)]

1/Tg=W1/Tg1+W2/Tg2+… +Wn/Tgn

In the general formula (1), Tg is the glass transition temperature (unit: K) of the polymer A, and Tgi (i = 1, 2, ... n) is the glass transition temperature when the monomer i forms a homopolymer (unit : K), Wi (i = 1, 2, ... n) represents the mass fraction of all monomer components of the monomer i.

In the general formula (1), polymer A is monomer 1, monomer 2, ... , It means a calculation formula in the case of including n types of monomer components of monomer n.

In the exemplary embodiment of the present application, the glass transition temperature of the pressure-sensitive adhesive composition may be estimated through component analysis to estimate the content of each monomer, and accordingly, the glass transition temperature may be calculated based on the fox equation.

In the exemplary embodiment of the present application, the first monomer including the amine group is N-vinylpyrrolidone (NVP, N-vinyl-2-pyrrolidone); And it provides a pressure-sensitive adhesive composition that is at least one selected from the group consisting of acryloylmorpholine.

In the exemplary embodiment of the present application, the second monomer including the hydroxy group is 4-hydroxybutyl acrylate (4-HBA, 4-Hydroxybutyl acrylate); And N- (2-hydroxyethyl) acrylamide (HEAA, N- (2-Hydroxyethyl) acrylamide) provides a pressure-sensitive adhesive composition that is one or more selected from the group consisting of.

In particular, when the second monomer includes 4-hydroxybutyl acrylate (4-HBA, 4-Hydroxybutyl acrylate), the glass transition temperature of the entire pressure-sensitive adhesive composition can be designed in the range of -50°C, and accordingly The adhesive sheet has excellent folding characteristics.

In addition, when the second monomer contains N-(2-hydroxyethyl)acrylamide (HEAA, N-(2-Hydroxyethyl)acrylamide), the glass transition temperature is higher, but satisfies the above range. In this case, it has a characteristic that can exhibit a very excellent effect in adhesive properties.

In the exemplary embodiment of the present application, the pressure-sensitive adhesive composition provides a pressure-sensitive adhesive composition further comprising at least one selected from the group consisting of a solvent, a curing agent, a dispersant, a photoinitiator, a thermal initiator, a silane coupling agent, a plasticizer, and a tackifier. do.

In the exemplary embodiment of the present application, the crosslinking agent may include a crosslinkable compound, and the crosslinking agent may use an isocyanate-based crosslinking agent, and those known in the art may be used.

According to an exemplary embodiment of the present specification, the crosslinkable compound is hexanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate having 2 to 14 ethylene groups, trimethyl Allpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, 2-trisacryloyloxymethylethylphthalic acid, propylene group Propylene glycol di(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate with the number of 2 to 14 Compounds obtained by esterifying polyhydric alcohols such as a mixture of pentaerythritol hexa(meth)acrylate (to-2348, TO-2349, manufactured by Dong-A Synthetic Japan as a brand name) with α,β-unsaturated carboxylic acid; Compounds obtained by adding (meth)acrylic acid to a compound containing a glycidyl group, such as trimethylolpropane triglycidyl ether acrylic acid adduct and bisphenol A diglycidyl ether acrylic acid adduct; An ester compound of a compound having a hydroxyl group or ethylenically unsaturated bond, such as a phthalic acid diester of β-hydroxyethyl (meth)acrylate and a toluene diisocyanate adduct of β-hydroxyethyl (meth)acrylate, and a polyhydric carboxylic acid , Or adducts with polyisocyanates; (Meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; And 9,9'-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, and is not limited thereto, and known in the art. You can use common ones.

According to an exemplary embodiment of the present specification, the photoinitiator is a triazine-based compound, a biimidazole compound, an acetophenone-based compound, an O-acyloxime-based compound, a thioxanthone-based compound, a phosphine oxide-based compound, a coumarin-based compound, and benzope. It may be substituted with one or two or more substituents selected from the group consisting of non-based compounds.

Specifically, according to the exemplary embodiment of the present specification, the photoinitiator is 2,4-trichloromethyl-(4'-methoxyphenyl)-6-triazine, 2,4-trichloromethyl-(4'-me Toxoxystyryl)-6-triazine, 2,4-trichloromethyl-(pipelonyl)-6-triazine, 2,4-trichloromethyl-(3',4'-dimethoxyphenyl)-6 -Triazine, 3-{4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}propanoic acid, 2,4-trichloromethyl-(4'-ethyl ratio Triazine compounds such as phenyl)-6-triazine or 2,4-trichloromethyl-(4'-methylbiphenyl)-6-triazine; 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl biimidazole or 2,2'-bis(2,3-dichlorophenyl)-4,4',5 Biimidazole-based compounds such as ,5'-tetraphenylbiimidazole; 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxye Oxy)-phenyl (2-hydroxy) propyl ketone, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenyl acetophenone, 2-methyl-(4-methylthiophenyl)-2-mol Acetopes such as polyno-1-propan-1-one (Irgacure-907) or 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one (Irgacure-369) Non-based compounds; O-acyloxime compounds such as Irgacure OXE 01 and Irgacure OXE 02 of Ciba Geigy; Benzophenone compounds such as 4,4'-bis(dimethylamino)benzophenone or 4,4'-bis(diethylamino)benzophenone; Thioxanthone compounds such as 2,4-diethyl thioxanthone, 2-chloro thioxanthone, isopropyl thioxanthone, or diisopropyl thioxanthone; 2,4,6-trimethylbenzoyl diphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl phosphine oxide or bis(2,6-dichlorobenzoyl) propyl phosphine oxide Phosphine oxide compounds such as; 3,3'-carbonylvinyl-7-(diethylamino)coumarin, 3-(2-benzothiazolyl)-7-(diethylamino)coumarin, 3-benzoyl-7-(diethylamino)coumarin, 3-benzoyl-7-methoxy-coumarin or 10,10'-carbonylbis[1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-Cl] Coumarin-based compounds such as -benzopyrano[6,7,8-ij]-quinolizin-11-one, etc. may be used alone or in combination of two or more, but are not limited thereto.

In addition, the thermal initiator may use those known in the art.

Toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), ethyl acetate (EAc, Ethyl Acetate) may be used as the solvent, but to dissolve a specific substance. If possible, it is not limited thereto, and accordingly a general organic solvent may be used.

In the exemplary embodiment of the present application, the transparent base film; And it provides a protective film including a pressure-sensitive adhesive sheet including the pressure-sensitive adhesive composition according to the present application provided on one side of the transparent base film.

In the present application, the meaning of the pressure-sensitive adhesive sheet including the pressure-sensitive adhesive composition may include including the pressure-sensitive adhesive composition as it is.

In the present application, the meaning of the pressure-sensitive adhesive sheet including the pressure-sensitive adhesive composition may include drying and including the pressure-sensitive adhesive composition.

In the present application, the meaning of the pressure-sensitive adhesive sheet including the pressure-sensitive adhesive composition may include curing and including the pressure-sensitive adhesive composition.

In an exemplary embodiment of the present application, after bonding the opposite surface of the pressure-sensitive adhesive sheet to a substrate having a surface energy of 15 mN/m or less, at a speed of 5 mm/s, 180° at a speed of 5 mm/s after bonding the opposite surface of the adhesive sheet to a substrate having a surface energy of 15 mN/m or less. It provides a protective film that has an adhesive force measured by a peel test of 10 gf/inch or more and 300 gf/inch or less.

In another exemplary embodiment, after bonding the opposite surface of the pressure-sensitive adhesive sheet to a substrate having a surface energy of 15 mN/m or less, a 180° peel at a speed of 5 mm/s, within 10 minutes at 23°C. The adhesive force measured by the test may be 10 gf/inch or more, 300 gf/inch or less, preferably 20 gf/inch or more, 250 gf/inch or less, more preferably 20 gf/inch or more, and 200 gf/inch or less.

In another exemplary embodiment, after bonding the opposite surface of the pressure-sensitive adhesive sheet to a substrate having a surface energy of 15 mN/m or less, a 180° peel at a speed of 5 mm/s, within 10 minutes at 23°C. The adhesive strength measured by the test may be 10 gf/inch or more, 300 gf/inch or less, 10.5 gf/inch or more, 100 gf/inch or less, 10.5 gf/inch or more, and 50 gf/inch or less.

In an exemplary embodiment of the present application, after bonding the opposite surface of the pressure-sensitive adhesive sheet to the substrate having a surface water contact angle of 90° or more, within 10 minutes at 23°C and 180° at a speed of 5mm/s, It is intended to provide a protective film that has an adhesive force measured by a peel test of 10 gf/inch or more and 300 gf/inch or less.

In another exemplary embodiment, after bonding the opposite surface of the pressure-sensitive adhesive sheet to a substrate having a surface water contact angle of 90° or more, a 180° peel at a speed of 5mm/s within 10 minutes at 23°C. The adhesive force measured by the test may be 10 gf/inch or more, 300 gf/inch or less, preferably 20 gf/inch or more, 250 gf/inch or less, more preferably 20 gf/inch or more, and 200 gf/inch or less.

In another exemplary embodiment, after bonding the opposite surface of the pressure-sensitive adhesive sheet to a substrate having a surface water contact angle of 90° or more, a 180° peel at a speed of 5mm/s within 10 minutes at 23°C. The adhesive strength measured by the test may be 10 gf/inch or more, 300 gf/inch or less, 10.5 gf/inch or more, 100 gf/inch or less, 10.5 gf/inch or more, and 50 gf/inch or less.

As the adhesive strength of the pressure-sensitive adhesive sheet according to the present application satisfies the above range, the AF treatment of the foldable display has excellent characteristics of adhesion to one side, and accordingly, even if the foldable display is repeatedly folded/unfolded several times. The adhesive strength of the pressure-sensitive adhesive is excellent, so that lifting does not occur, and thus, the protective properties of the cover window of the foldable display are excellent.

The AF treatment is one of the surface treatment methods to lower the surface energy of a specific substrate, and is mainly treated with a fluorine component, and the resulting surface energy drops to a level of about 15 mN/m or less, and in the case of a water contact angle, a level of 100° or more. This means being.

That is, the cover window of the foldable display is a part where the touch is made due to its characteristics, and when the human body touches it, the AF treatment is performed as above to prevent the formation of fingerprints or sebum, and accordingly, the adhesive containing the adhesive composition of the present application In the case of the sheet, it is characterized by having high adhesion to a surface having low surface energy subjected to AF treatment.

In the present application, the adhesive force was measured using a texture analyzer (Stable Micro Systems) at a 180° angle and a peel rate of 300 mm/min, and the adhesive sheet according to the present invention was measured by 1 inch. After cutting into width, it was measured after attaching to a substrate having a surface energy of 15 mN/m or less or a substrate having a surface water contact angle of 90° or more by reciprocating once with a 2 kg rubber roller.

That is, the adhesive strength is attached to a substrate having a surface energy of 15 mN/m or less or a substrate having a surface contact angle of 90° or more by cutting the pressure-sensitive adhesive sheet according to the present invention to a width of 1 inch, and then reciprocating once with a 2 kg rubber roller. It refers to a value measured using a texture analyzer (Stable Micro Systems) after leaving at 23° C. for 10 minutes, peeling at a 180° angle and a peeling rate of 300 mm/min.

The substrate with a surface energy of 15 mN/m or less or a substrate with a surface water contact angle of 90° or more may be a glass substrate, a PI substrate, a stainless steel substrate, etc., and a substrate with a surface energy of 15 mN/m or less or a surface water contact angle of 90° or more If it is satisfied, it is not limited thereto.

In the exemplary embodiment of the present application, the substrate may have a surface energy of 15 mN/m or less, a surface energy of 14 mN/m or less, a surface energy of 12 mN/m or less, and a surface energy of 5 mN/m or more. .

In the exemplary embodiment of the present application, the substrate may have a surface water contact angle of 90° or more, a surface water contact angle of 100° or more, a surface water contact angle of 110° or more, and a surface water contact angle of 180° or less. have.

In the exemplary embodiment of the present application, the transparent base film is PET (polyethylene terephthalate), polyester, PC (polycarbonate), PI (polyimide), PEN (polyethylene naphthalate), PEEK (polyether ether ketone), PAR (polyarylate), PCO (polycylicolefin), polynorbornene (polynorbornene), PES (polyethersulphone), and may be selected from the group consisting of COP (cycloolefin polymer).

In another exemplary embodiment, the transparent base film may be PET (polyethylene terephthalate).

In the exemplary embodiment of the present application, the thickness of the transparent base film is 25 μm or more and 150 μm Hereinafter, preferably 38 µm or more and 130 µm or less, more preferably 50 µm or more and 125 µm or less.

The meaning that the base film is transparent here indicates that the light transmittance of visible light (400 to 700 nm) is 80% or more.

When the base film has the above range, the laminated protective film has a characteristic capable of thinning, and when applied to a foldable display, folding marks do not occur, and the cover window of the foldable display is sufficiently protected from external impact. You will have the characteristics that you can do.

In the exemplary embodiment of the present application, the thickness of the pressure-sensitive adhesive sheet is 10 μm or more and 100 μm It can be below.

In another embodiment, the thickness of the pressure-sensitive adhesive sheet is 10 μm or more and 100 μm Below, preferably 12 µm or more and 75 µm Or less, more preferably 15 µm or more and 50 µm It can be below.

When the thickness of the pressure-sensitive adhesive sheet is within the above range, the rate of occurrence of air bubbles in the pressure-sensitive adhesive sheet may be lowered, and accordingly, when bonding with the cover window later, the adhesive strength is excellent and the lifting phenomenon does not occur, and the dent It has a feature that does not cause any problems.

In the exemplary embodiment of the present application, the thickness of the protective film is 35 μm or more and 250 μm It provides the following protective film.

In another exemplary embodiment, the thickness of the protective film is 35 μm or more and 250 μm Below, preferably 50 μm or more and 200 μm Below, more preferably 60 µm or more and 150 µm It can be below.

Since the protective film has the above range, the thickness is appropriate when applied to a foldable display in the future, and adhesion does not decrease when applied to a display, and a protective film with excellent reliability is provided even if folding/unfolding is repeated several times. You will have the characteristics you can do.

In the exemplary embodiment of the present application, the pressure-sensitive adhesive sheet may be laminated in plural.

In an exemplary embodiment of the present application, a protective film is provided that further includes a release film on a surface opposite to a surface of the adhesive sheet in contact with the transparent base film.

Including a release film on one side of the pressure-sensitive adhesive sheet means that the release film is provided on the opposite side of the side of the pressure-sensitive adhesive sheet in contact with the base film.

In the exemplary embodiment of the present application, a hydrophobic film may be used as the release film, and as a layer for protecting an adhesive sheet having a very thin thickness, it refers to a transparent layer attached to one side of the adhesive sheet, and mechanical strength and thermal stability , A film having excellent moisture shielding properties, isotropic properties, etc. can be used. For example, acetate-based, polyester-based, polyethersulfone-based, polycarbonate-based, polyamide-based, polyimide-based, polyolefin-based, cycloolefin-based, polyurethane-based and acrylic resin films such as triacetylcellulose (TAC), etc. Can be used, but is not limited to this if it is a commercially available silicone-treated release film.

When the release film is applied to a display, all can be removed.

In an exemplary embodiment of the present application, the protective film according to the present application; A cover window provided on the pressure-sensitive adhesive sheet side of the protective film; And it is intended to provide a foldable display device including a plastic substrate provided on a surface of the cover window opposite to the surface in contact with the adhesive sheet.

That is, the cover window relates to the outermost display of the foldable display device, and the foldable display device refers to a display capable of folding and unfolding, and the foldable display device is a tablet PC including the same. , Mobile terminal, TV, etc. may all be included.

Specifically, the foldable display device includes a cover window; Adhesive layer; Polarizer; Adhesive layer; OLED panel; The back plate may have a sequentially stacked structure, and the protective film according to an exemplary embodiment of the present application serves to protect the surface of the cover window.

An exemplary embodiment of the present application is preparing a transparent base film; And forming a pressure-sensitive adhesive sheet by applying the pressure-sensitive adhesive composition according to the present application to one surface of the transparent base film,

After bonding the opposite side of the pressure-sensitive adhesive sheet to a substrate having a surface energy of 15mN/m or less, the adhesive strength measured by a 180° peel test at a speed of 5mm/s within 10 minutes at 23°C is 10gf/ Inch or more, to provide a method of manufacturing a protective film that is less than or equal to 300 gf/inch.

In the present application, the step of forming a pressure-sensitive adhesive sheet by applying the pressure-sensitive adhesive composition comprises: applying the pressure-sensitive adhesive composition to one surface of the transparent base film; Drying the pressure-sensitive adhesive composition; And it is intended to provide a method of manufacturing a protective film comprising the step of curing the pressure-sensitive adhesive composition.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

< Manufacturing example >

<Production of protective film>

After applying the pressure-sensitive adhesive composition, curing agent, and additives having the composition of Table 1 on the PET film, which is a transparent base film having a thickness of 50 μm, drying and curing were carried out by standing in an oven at 120° C. for 3 minutes. After that, a silicone release film was laminated on the filmed adhesive sheet surface.

Resin composition Mw (only) Tg (℃) AF Glass adhesion
(gf/inch) Example 1 2-EHA/NVP/4-HBA=80/15/5 52 -65 10.7 Example 2 2-EHA/NVP/4-HBA=75/15/10 57 -62 13.4 Example 3 2-EHA/NVP/4-HBA=75/20/5 58 -58 11.9 Example 4 2-EHA/NVP/4-HBA=70/25/5 48 -50 12.8 Example 5 2-EHA/NVP/4-HBA=90/5/5 44 -77 14.3 Example 6 2-EHA/NVP/4-HBA=94/1/5 45 -82 10.5 Example 7 2-EHA/NVP/4-HBA=85/10/5 48 -71 16.5 Example 8 2-EHA/NVP/4-HBA=70/15/15 46 -60 27 Example 9 2-EHA/NVP/4-HBA=65/15/20 47 -57 31 Example 10 BA/NVP/4-HBA=80/15/5 58 -35 10.2 Example 11 IOAA/NVP/4-HBA=80/15/5 51 -39 10.9 Example 12 NOAA/NVP/4-HBA=80/15/5 62 -45 17.2 Example 13 2-EHA/NVP/HEAA/4-HBA=75/15/5/5 46 -59 11.6 Example 14 2-EHA/ACMO/HEAA=80/15/5 47 -63 10.7 Example 15 2-EHA/NVP/HEAA=80/15/5 35 -62 43 Example 16 BA/IOAA/NVP/HBA=70/10/15/5 140 -35 15.4 Example 17 BA/IOAA/NVP/HBA=65/10/20/5 63 -28 33.3 Comparative Example 1 2-EHA/NVP/4-HBA=84/15/1 36 -67 6.6 Comparative Example 2 2-EHA/2-HEA=90/10 46 -80 8.2 Comparative Example 3 2-EHA/MA/2-HEA=80/10/10 42 -73 9.8 Comparative Example 4 EHA/AA=90/10 95 -75 7.4 Comparative Example 5 EHA/HBA=90/10 180 -83 4.4

Measurement of adhesion: After cutting the pressure-sensitive adhesive sheet into 1 inch in width, the opposite side of the surface in contact with the transparent base film is placed on a glass substrate (or a glass substrate having a water contact angle of 90° or more) treated with 11 mN/m of surface energy. After bonding with a roller, the adhesive strength was measured by a 180° peel test at a speed of 5mm/s within 10 minutes at 23°C.

In Table 1, 2-EHA is 2-ethylhexyl acrylate, NVP is N-vinyl-2-pyrrolidone, 4-HBA is 4-hydroxybutyl Acrylate (4-Hydroxybutyl acrylate), ACMO is Acryloylmorpholine, HEAA is N-(2-hydroxyethyl) acrylamide (N-(2-Hydroxyethyl)acrylamide), BA is butyl acrylate (Butyl) acrylate), IOAA is isoctyl acrylate, NOAA is n-octyl acrylate, MA is methyl acrylate, AA is acrylic acid, and 2-HEA Means 2-hydroxyethyl acrylate, respectively.

As can be seen from Table 1 above, in the case of the pressure-sensitive adhesive composition according to an exemplary embodiment of the present application, as the first monomer including an amine group and the second monomer including a hydroxy group are contained in a specific amount, a pressure-sensitive adhesive sheet including the same is included later. In the case of the protective film, it was confirmed that it had excellent adhesion (10 gf/inch or more) on the surface with low surface energy (AF treatment surface).

The AF treatment is one of the surface treatment methods to lower the surface energy of a specific substrate, and is mainly treated with a fluorine component, and the resulting surface energy drops to a level of about 15 mN/m or less, and in the case of a water contact angle, a level of 100° or more. This means that the cover window of the foldable display is a part of the foldable display where touch is made due to its characteristics, and when the human body touches it, AF processing is performed as above to prevent the formation of fingerprints or sebum, and accordingly, the adhesive of the present application In the case of the pressure-sensitive adhesive sheet including the composition, it was confirmed that it has high adhesion to the surface having low surface energy subjected to AF treatment.

In particular, as can be seen in Examples 1 to 9 and 13 to 15 of Table 1, when the glass transition temperature value of the pressure-sensitive adhesive composition satisfies the range of -50°C or less, in this case, folding characteristics when applied to a foldable display This has particularly excellent characteristics. That is, in Examples 1 to 9 and 13 to 15 of Table 1, the glass transition temperature of the entire pressure-sensitive adhesive composition could be adjusted to a range of -50° C. or less according to the specific content of a specific monomer, and accordingly, the folding characteristics were particularly It was confirmed that an excellent pressure-sensitive adhesive sheet could be formed.

10: adhesive sheet
20: transparent base film
40: protective film

Claims (17)

(Meth)acrylate resin; A first monomer containing an amine group; And a pressure-sensitive adhesive composition comprising a second monomer containing a hydroxy group,
The content of the first monomer is 1 to 30 parts by weight based on 100 parts by weight of the pressure-sensitive adhesive composition,
The content of the second monomer is 2 to 20 parts by weight based on 100 parts by weight of the pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition of claim 1, wherein the (meth)acrylate-based resin is 60 to 95 parts by weight based on 100 parts by weight of the pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition of claim 1, wherein the (meth)acrylate-based resin has a glass transition temperature (Tg) of 0°C or less. The pressure-sensitive adhesive composition of claim 1, wherein the pressure-sensitive adhesive composition has a glass transition temperature (Tg) of -50°C or less. The method according to claim 1, wherein the first monomer containing the amine group is N-vinylpyrrolidone (NVP, N-vinyl-2-pyrrolidone); And one or more selected from the group consisting of acryloylmorpholine. The method according to claim 1, wherein the second monomer containing a hydroxy group is 4-hydroxybutyl acrylate (4-HBA, 4-Hydroxybutyl acrylate); And N-(2-hydroxyethyl)acrylamide (HEAA, N-(2-Hydroxyethyl)acrylamide) of one or more selected from the group consisting of. The pressure-sensitive adhesive composition of claim 1, wherein the pressure-sensitive adhesive composition further comprises one or more selected from the group consisting of a solvent, a curing agent, a dispersant, a photoinitiator, a thermal initiator, a silane coupling agent, a plasticizer, and a tackifier. Transparent base film; And
A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive composition of any one of claims 1 to 7 provided on one side of the transparent base film;
Protective film comprising a. The method of claim 8,
After bonding the opposite side of the pressure-sensitive adhesive sheet to a substrate having a surface energy of 15mN/m or less, the adhesive strength measured by a 180° peel test at a speed of 5mm/s within 10 minutes at 23°C is 10gf/ inch or more, 300 gf/inch or less, which is a protective film. The method of claim 8,
After bonding the opposite surface of the pressure-sensitive adhesive sheet to a substrate having a surface water contact angle of 90° or more, the adhesive strength measured by a 180° peel test at a speed of 5mm/s within 10 minutes at 23°C is 10gf/ inch or more, 300 gf/inch or less, which is a protective film. The method according to claim 8, wherein the thickness of the transparent base film is 25 ㎛ or more 150 ㎛ The protective film which is the following. The method according to claim 8, wherein the thickness of the pressure-sensitive adhesive sheet is 10 ㎛ or more 100 ㎛ The protective film which is the following. The method of claim 8,
The protective film further comprises a release film on the opposite side of the surface of the pressure-sensitive adhesive sheet in contact with the transparent base film. The method of claim 8, wherein the transparent substrate film is PET (polyethylene terephthalate), polyester, PC (polycarbonate), PI (polyimide), PEN (polyethylene naphthalate), PEEK (polyether ether ketone), PAR (polyarylate), PCO (polycylicolefin), polynorbornene (polynorbornene), PES (polyethersulphone) and COP (cycloolefin polymer) that is selected from the group consisting of a protective film. The protective film according to any one of claims 8 to 14;
A cover window provided on the pressure-sensitive adhesive sheet side of the protective film; And
A plastic substrate provided on a surface of the cover window opposite to a surface in contact with the adhesive sheet;
Foldable display device comprising a. Preparing a transparent base film; And
Forming a pressure-sensitive adhesive sheet by applying the pressure-sensitive adhesive composition according to any one of claims 1 to 7 on one surface of the transparent base film;
As a method for producing a protective film comprising a,
After bonding the opposite side of the pressure-sensitive adhesive sheet to a substrate having a surface energy of 15mN/m or less, the adhesive strength measured by a 180° peel test at a speed of 5mm/s within 10 minutes at 23°C is 10gf/ Inch or more, 300 gf / inch or less to the manufacturing method of the protective film. The method of claim 16,
The step of forming an adhesive sheet by applying the adhesive composition
Applying the pressure-sensitive adhesive composition to one surface of the transparent base film;
Drying the pressure-sensitive adhesive composition; And
Curing the pressure-sensitive adhesive composition;
A method for producing a protective film comprising a.

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