KR102027570B1 - Flexible display apparatus - Google Patents

Abstract

A display unit, a first adhesive film formed on the display unit, an optical film formed on the first adhesive film, a second adhesive film formed on the optical film, and a window film formed on the second adhesive film, The modulus of the second adhesive film at -20 ℃ to 25 ℃ is larger than the modulus of the first adhesive film, there is provided a flexible display device.

Description

Flexible display device {FLEXIBLE DISPLAY APPARATUS}

The present invention relates to a flexible display device.

Recently, optical display devices such as liquid crystal display devices and organic light emitting diode display devices have replaced glass substrates or high hardness substrates with films. Accordingly, a flexible display device having flexibility to be folded and unfolded has been developed. The flexible display device is not only thin and light as a film is used as a substrate, but also resistant to impact, and can be folded and unfolded so that it can be manufactured in various forms.

The flexible display device may include a display unit, an optical film, a window film, and the like. The flexible display device has a structure in which various optical films and window films are stacked on a display unit. In particular, the display unit may be manufactured in the form of a film such as an optical film and a window film. The display unit, the optical film, and the window film may each be adhered to an optical clear adhesive (OCA) film. Therefore, the OCA film should combine the display unit, the optical film, and the window film, and allow the flexible display device to be fully folded and have good reliability and / or durability.

Background art of the present invention is disclosed in Japanese Patent Laid-Open No. 2007-176542.

An object of the present invention is to provide a flexible display device having excellent folding properties even at low temperature, high temperature and / or high humidity.

Another object of the present invention is to provide a flexible display device which is free of bubbles, cracks and / or floats at high temperature and / or high humidity, and has good adhesion between the display unit, the optical film, and the window film, and which has excellent reliability and durability.

Still another object of the present invention is to provide a flexible display device capable of relieving stress by repeated folding.

The flexible display device of the present invention includes a display unit, a first adhesive film formed on the display unit, an optical film formed on the first adhesive film, a second adhesive film formed on the optical film, and the second adhesive film image Including a window film formed on, the modulus of the second adhesive film at -20 ℃ to 25 ℃ may be greater than the modulus of the first adhesive film.

The present invention provides a flexible display device having excellent folding properties even at low temperature, high temperature, and / or high humidity.

The present invention provides a flexible display device excellent in reliability and durability without bubble generation, cracking and / or lifting at high temperature and / or high humidity, and good adhesion between the display unit, the optical film, and the window film.

The present invention provides a flexible display device capable of relieving stress by repeated folding.

1 is a cross-sectional view of a flexible display device according to an embodiment of the present invention.
Figure 2 is a schematic diagram of a specimen for measuring the peel strength in the present specification.
3 is a cross-sectional view of a specimen for folding test herein.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. In addition, the same reference numerals are attached to the same or similar components throughout the specification.

In the present specification, "upper" and "lower" are defined based on the drawings. Depending on the viewpoint, "upper" may be changed to "lower" and "lower" to "upper". In addition, what is referred to as "on" or "on" may include a case in which another structure is interposed not only directly above but also in the middle. On the other hand, what is referred to as "directly on" or "directly on" means that there is no intervening structure in between.

As used herein, "(meth) acryl" refers to acrylic and / or methacryl.

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

In the present specification, the "bubble area ratio" for the display device is measured on a specimen that simulates the display device. The display unit includes a polyethylene terephthalate (PET) film (thickness: 100 µm) and a first adhesive film (thickness: 50). Μm), a PET film (thickness: 50 μm) with an optical film, a second adhesive film (thickness: 50 μm), and a specimen laminated sequentially with a PET film (thickness: 125 μm) with a window film. Cut into lengthwise (160 mm × 100 mm), bent in the direction of the window film between parallel molds at 1 cm intervals, and after aging (leave) for 24 hours at 60 ° C. and 93% relative humidity, bubbles were generated. Value obtained by analyzing the image taken by an optical microscope (Olympus, EX-51, 30x magnification) with Mountech's Mac-view software to calculate the area ratio of the total bubble area to the area of the specimen. to be.

In the present specification, the "modulus" of the adhesive film is elastic modulus, and viscoelasticity was measured under auto strain conditions at a shear rate of 1 rad / sec and strain of 1% using ARES (Anton Paar, Inc. MCR-501). A pressure-sensitive adhesive film (thickness: 50 μm) was laminated to a thickness of 500 μm, and the laminate was punched out using a puncher having a diameter of 8 mm to use a specimen. The measurement was performed at a temperature rise rate of 5 ° C./min at −60 ° C. to 90 ° C., and the modulus was measured at −20 ° C., 25 ° C., and 80 ° C.

In the present specification, the "peel strength" of the adhesive film was corona treated twice (total dose: 156 dose) in a PET (polyethylene terephthalate) film having a width x length x thickness (150 mm x 25 mm x 75 μm) at a dose of 78 dose using a corona treatment machine. Corona-treated surfaces of the PET film were laminated on both sides of an adhesive film (width x length x thickness, 100mmx25mmx50㎛), respectively, to prepare a specimen shown in FIG. The specimens were autoclaved at pressure of 3.5 bar at 50 ° C. for 1000 seconds and the specimens were fixed in a TA.XT_Plus Texture Analyzer (Stable Micro System). Referring to FIG. 2 (b), one PET film is fixed at 25 ° C. in TA.XT_Plus Texture Analyzer and the other PET film is pulled at a rate of 50 mm / min to measure T-peel peel strength.

In the present specification, "average particle diameter of organic nanoparticles" is expressed as Z-average value measured in an aqueous or organic solvent with a Maltas Zetasizer nano ZS device.

As used herein, "core-shell structure" may mean a conventional core-shell structure. In addition, the core or the shell may be single layer or multilayer, respectively, and “outer layer” means the outermost layer of the various layers.

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

Referring to FIG. 1, the flexible display apparatus 100 according to the present exemplary embodiment may include a display 91, a first adhesive film 92 formed on the display 91, and an optical film formed on the first adhesive film 92. 93, a second adhesive film 94 formed on the optical film 93, and a window film 95 formed on the second adhesive film 94.

Hereinafter, the first adhesive film 92 and the second adhesive film 94 will be described in detail.

The first adhesive film 92 may be formed between the display unit 91 and the optical film 93 to adhere the display unit 91 and the optical film 93 to each other. The second adhesive film 94 may be formed between the optical film 93 and the window film 95 to adhere the optical film 93 and the window film 95.

The second adhesive film 94 may have a larger modulus than the first adhesive film 92. The second adhesive film 94 should have a high modulus so as not to contain moisture or air coming from the external environment, and should have excellent storage and restoring force due to external strength. On the other hand, if the first adhesive film 92 has the same modulus as the second adhesive film 94, the folding property is not good and may cause a defect of the display unit 91 when folding. Therefore, the first adhesive film 92 has a modulus lower than that of the second adhesive film 94 and should be excellent in reliability and durability at high temperature and / or high humidity. Therefore, the flexible display device 100 according to the present embodiment may exhibit excellent folding property at room temperature as well as at low temperature, and there is no bubble, crack and / or lifting at high temperature and / or high humidity, and thus reliability and durability at high temperature and / or high humidity. This can be excellent. Specifically, at −20 ° C. to 25 ° C., the ratio of modulus (modulus of modulus / first adhesive film 92 of second adhesive film 94) is greater than 1.0 but less than or equal to 10, specifically 1.1 to 10, more specifically May be from 1.1 to 5. Within this range, good foldability, reliability and durability at high temperatures and high humidity are good, and even if the window film and / or the display portion are in the form of a film, the organic connection between them may be good and repeated folding may be possible. At 80 ° C., the ratio of modulus (modulus of the second adhesive film 94 / modulus of the first adhesive film 92) may be 1.0 or more, specifically 1.1 to 5. When the temperature described when referring to "modulus" or "ratio of modulus" herein is X ° C, X ° C may mean not only X ° C but also (X-5) ° C to (X + 5) ° C. .

The first adhesive film 92 may have a modulus of 150 kPa or less, specifically, 60 kPa to 100 kPa at -20 ° C. In the above range, regardless of the second adhesive film, the flexible display device can be folded well even at a low temperature, and even if the window film and / or the display unit is in the form of a film, the organic connection therebetween can be excellent and repeated folding can be possible. The second adhesive film 94 may have a modulus of 25 kPa or more, specifically 25 kPa to 50 kPa, and more specifically 28 kPa to 40 kPa at 80 ° C. In the above range, there is no bubble generation, cracks and / or lifting at high temperature, high humidity irrespective of the first adhesive film may be excellent in reliability and durability at high temperature, high humidity, and excellent resilience. In addition, even if the window film and / or the display portion is in the form of a film, the organic connection therebetween may be excellent and repeated folding may be possible.

In the flexible display device of the present embodiment, the bubble generation area ratio may be 5% or less, specifically 0% to 3%, and more specifically 0% to 1%. Within this range, reliability and durability can be ensured.

The first adhesive film 92 and the second adhesive film 94 may each have a peel strength of 800 gf / in or more, specifically 1100 gf / in to 2500 gf / in at 25 ° C. In the above range, the display unit, the optical film, and the window film may be organically connected to each other to increase the reliability of the flexible display device. The first adhesive film 92 and the second adhesive film 94 each have a thickness of 50 μm and a haze of 5% or less, specifically 3% or less, more specifically, in a visible light region (for example, a wavelength of 300 nmn to 800 nm). May be less than 1.5%. In the above range, the adhesive film can increase the transparency of the display device when used in the display.

Each of the first adhesive film 92 and the second adhesive film 94 may have a thickness of 1 μm to 2 mm, specifically 20 μm to 1 mm, and more specifically 50 μm to 100 μm. In the above range, the adhesive film can be used in the optical display device.

The first adhesive film 92 and the second adhesive film 94 may each include a cured product of the pressure-sensitive adhesive composition. Hereinafter, the pressure-sensitive adhesive composition (hereinafter, "adhesive composition") of one embodiment of the present invention for the first adhesive film, the second adhesive film will be described.

The pressure-sensitive adhesive composition may include monomer mixture and organic nanoparticles for a (meth) acrylic copolymer having a hydroxyl group.

The monomer mixture may form a (meth) acrylic copolymer having a hydroxyl group. The (meth) acrylic copolymer having a hydroxyl group may form a matrix of the adhesive film and provide the adhesive force of the adhesive film. The glass transition temperature of the (meth) acrylic copolymer having a hydroxyl group may be -150 ° C to -13 ° C, specifically -100 ° C to -20 ° C. While the pressure-sensitive adhesive film is excellent in the above range, there is an effect having excellent adhesion and reliability in a wide temperature range.

The monomer mixture may comprise (meth) acrylates and comonomers having hydroxyl groups. The "comonomer" is different from (meth) acrylate having a hydroxyl group.

(Meth) acrylate having a hydroxyl group is a (meth) acrylic acid ester having an alkyl group having 1 to 20 carbon atoms having at least one hydroxyl group, a (meth) acrylic acid ester having a cycloalkyl group having 5 to 20 carbon atoms having at least one hydroxyl group, Or a (meth) acrylic acid ester having an aryl group having 6 to 20 carbon atoms having at least one hydroxyl group. Specifically, the (meth) acrylate having a hydroxyl group is 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl It may be one or more of (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, but is not necessarily limited thereto. In particular, by using an alkyl group-containing (meth) acrylic monomer having 1 to 5 carbon atoms having a hydroxyl group, there may be an effect of increasing the adhesive strength of the pressure-sensitive adhesive film. The (meth) acrylic monomer having a hydroxyl group may be included in 5 to 40% by weight, for example 10 to 35% by weight of the monomer mixture. In the above range, the adhesive film has a low haze and may have an excellent adhesive force.

The comonomer is a (meth) acrylate having an alkyl group, a monomer having an ethylene oxide, a monomer having a propylene oxide, a monomer having an amine group, a monomer having an amide group, a monomer having an alkoxy group, a monomer having a phosphoric acid group, a monomer having a sulfonic acid group, One or more of a monomer having a phenyl group and a monomer having a silane group may be included, but is not necessarily limited thereto.

The (meth) acrylate having an alkyl group may include an unsubstituted linear or branched alkyl (meth) acrylic acid ester having 1 to 20 carbon atoms. For example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, iso-butyl (meth) acrylic Latex, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) One or more of acrylate, decyl (meth) acrylate, lauryl (meth) acrylate. Specifically, the initial adhesion of the pressure-sensitive adhesive film can be increased by using a branched alkyl (meth) acrylic acid ester having 4 to 8 carbon atoms.

The monomer having ethylene oxide is a (meth) acrylate monomer containing an ethylene oxide group (-CH ₂ CH ₂ O-), and polyethylene oxide monomethyl ether (meth) acrylate and polyethylene oxide monoethyl ether (meth) acryl Latex, polyethylene oxide monopropyl ether (meth) acrylate, polyethylene oxide monobutyl ether (meth) acrylate, polyethylene oxide monopentyl ether (meth) acrylate, polyethylene oxide dimethyl ether (meth) acrylate, polyethylene oxide diethyl ether Polyethylene oxide alkyl ether (meth) such as (meth) acrylate, polyethylene oxide monoisopropyl ether (meth) acrylate, polyethylene oxide monoisobutyl ether (meth) acrylate, polyethylene oxide monotertbutyl ether (meth) acrylate Acrylic ray It can be, but is not necessarily limited thereto.

The monomer having propylene oxide is a (meth) acrylate-based monomer containing a propylene oxide group (-CH ₂ CH ₂ CH ₂ O- or (-CH ₂ CHCH ₃ O-), and polypropylene oxide monomethyl ether (meth) Acrylate, polypropylene oxide monoethyl ether (meth) acrylate, polypropylene oxide monopropyl ether (meth) acrylate, polypropylene oxide monobutyl ether (meth) acrylate, polypropylene oxide monopentyl ether (meth) acrylate , Polypropylene oxide dimethyl ether (meth) acrylate, polypropylene oxide diethyl ether (meth) acrylate, polypropylene oxide monoisopropyl ether (meth) acrylate, polypropylene oxide monoisobutyl ether (meth) acrylate, Such as polypropylene oxide monotertbutyl ether (meth) acrylate Li be a vector (meth) acrylate, propylene oxide-alkyl, but is not necessarily limited thereto.

The monomer having an amine group is a (meth) acrylic monomer having an amine group, which is monomethylaminoethyl (meth) acrylate, monoethylaminoethyl (meth) acrylate, monomethylaminopropyl (meth) acrylate, monoethylaminopropyl ( Meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, N-tert-butylaminoethyl (meth) acrylate, methacryloxyethyltrimethylammonium chloride (meth) acrylic It may be an amine group-containing (meth) acrylic monomer, such as a rate, but is not necessarily limited thereto.

The monomer having an amide group is a (meth) acrylic monomer having an amide group, and includes (meth) acrylamide, N-methyl (meth) acrylamide, N-methylol (meth) acrylamide, and N-methoxymethyl (meth) acrylamide , N, N-methylene bis (meth) acrylamide, N-2-hydroxyethyl (meth) acrylamide, and the like, but is not necessarily limited thereto.

The monomer having an alkoxy group is a (meth) acrylic monomer having an alkoxy group, and 2-methoxyethyl (meth) acrylate, 2-methoxypropyl (meth) acrylate, 2-ethoxypropyl (meth) acrylate, and 2- Butoxypropyl (meth) acrylate, 2-methoxypentyl (meth) acrylate, 2-ethoxypentyl (meth) acrylate, 2-butoxyhexyl (meth) acrylate, 3-methoxypentyl (meth) Acrylate, 3-ethoxypentyl (meth) acrylate, 3-butoxyhexyl (meth) acrylate, but are not necessarily limited thereto.

As a monomer which has a phosphoric acid group, it is a (meth) acrylic-type monomer which has a phosphoric acid group, and 2- (meth) acryloyloxyethyl diphenyl phosphate (meth) acrylate and tri (meth) acryloyloxyethyl phosphate (meth) acrylate , Triacryloyloxyethyl phosphate (meth) acrylate, and the like, but is not necessarily limited thereto.

The monomer having a sulfonic acid group is a (meth) acrylic monomer having a sulfonic acid group and includes sulfopropyl (meth) acrylate sodium, 2-sulfoethyl (meth) acrylate sodium and 2-acrylamido-2-methylpropanesulfonic acid. Sodium, and the like, but is not necessarily limited thereto.

The monomer having a phenyl group is a (meth) acrylic monomer having a phenyl group, and may be p-tert-butylphenyl (meth) acrylate, o-biphenyl (meth) acrylate, or the like, but is not necessarily limited thereto.

The monomer having a silane group is a (meth) acrylic monomer having a silane group, 2-acetoacetoxyethyl (meth) acrylate, vinyltrimethoxysilane, vinyltriethoxysilane, vinyl tris (β-methoxyethyl) silane, It may be a vinyl monomer having a silane group such as vinyltriacetylsilane, methacryloyloxypropyltrimethoxysilane, but is not necessarily limited thereto.

Comonomers may be included in the monomer mixture from 60% to 95% by weight, specifically from 65% to 90% by weight. The adhesive film in the above range has an excellent adhesive strength and excellent reliability effect.

In one embodiment, the monomer mixture may comprise a (meth) acrylate having hydroxyl groups and a comonomer having a glass transition temperature of homopolymer in the comonomer of -150 ° C to 0 ° C. The "glass transition temperature" can be measured using TA Instrument's DSC Q20 for the homopolymer of each target monomer. Specifically, the homopolymer of each monomer was raised to 160 ° C. at a rate of 20 ° C./min, and then cooled slowly to maintain an equilibrium at 50 ° C., and to 160 ° C. at a rate of 10 ° C./min. After obtaining the endothermic transition curve at the time, the inflection point of the endothermic transition curve is determined as the glass transition temperature. The comonomer having a glass transition temperature of -150 ° C to 0 ° C of the homopolymer may be a comonomer having a glass transition temperature of -150 ° C to -20 ° C, more specifically -150 ° C to -40 ° C. Within this range, the folding property at low temperatures is excellent. Such comonomers are, for example, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, iso-butyl acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethyl Alkyl (meth) acrylate monomers including hexyl acrylate, dodecyl (meth) acrylate, and the like; Polyethylene oxide monomethyl ether (meth) acrylate, polyethylene oxide monoethyl ether (meth) acrylate, polyethylene oxide monopropyl ether (meth) acrylate, polyethylene oxide monobutyl ether (meth) acrylate, polyethylene oxide monopentyl ether ( Contains alkylene oxide groups including meth) acrylate, polypropylene oxide monomethyl ether (meth) acrylate, polypropylene oxide monoethyl ether (meth) acrylate, polypropylene oxide monopropyl ether (meth) acrylate, and the like ( Meth) acrylate monomers; (Meth) acryl which has the amino group containing monomethylaminoethyl (meth) acrylate, monoethylaminoethyl (meth) acrylate, monomethylaminopropyl (meth) acrylate, monoethylaminopropyl (meth) acrylate, etc. Acrylate monomers; (Meth) acrylate monomers having an alkoxy group including 2-methoxy ethyl (meth) acrylate, 2-methoxypropyl (meth) acrylate, 2-ethoxypropyl (meth) acrylate, and the like; It may be one or more of (meth) acrylate monomers having a silane group including 2-acetoacetoxyethyl (meth) acrylate, vinyltrimethoxysilane, vinyltriethoxysilane, and the like.

The monomer mixture may further include a monomer having a carboxylic acid group. Monomers having a carboxylic acid group include (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, 3-carboxypropyl (meth) acrylate, 4-carboxybutyl (meth) acrylate, itaconic acid, crotonic acid, maleic acid, and fumaric acid. And maleic anhydride, and the like, but are not necessarily limited thereto. The monomer having a carboxyl group may be further included in 10% by weight or less of the total monomer mixture, in particular 7% by weight or less, specifically 5% by weight or less. In the above range, the adhesive film has high adhesive strength and excellent reliability.

The monomer mixture may further comprise an alicyclic containing (meth) acrylate. The cycloaliphatic-containing (meth) acrylate is a (meth) acrylate containing a cycloalkyl group having 5 to 20 carbon atoms, such as isobornyl (meth) acrylate, bonyl (meth) acrylate, cyclohexyl (meth) acrylate, and the like. This is not necessarily the case. These can be applied individually or in mixture of 2 or more types. The cycloaliphatic-containing (meth) acrylate may be included in 0.01% to 5% by weight, for example 0.5% to 3% by weight, preferably 1% to 3% by weight of the total monomer mixture. In the above range, no bubbles or floating occurs under heat and moisture resistance, and have excellent durability.

The organic nanoparticles are excellent in low temperature and / or room temperature viscoelasticity, have a crosslinked structure, and stably exhibit high temperature and high humidity viscoelasticity. In an embodiment, the organic nanoparticles may form a chemical bond with the (meth) acrylic copolymer having a hydroxyl group.

Although the pressure-sensitive adhesive composition or the pressure-sensitive adhesive film includes organic nanoparticles, the pressure-sensitive adhesive composition or the pressure-sensitive adhesive film may have excellent transparency by having a specific refractive index difference with the (meth) acrylic copolymer having a specific average particle size of the organic nanoparticles and hydroxyl groups described below. . The organic nanoparticles may have an average particle diameter of 10 nm to 400 nm, specifically 10 nm to 300 nm, and more specifically 10 nm to 200 nm. In the above range, the aggregation of the organic nanoparticles can be prevented, and the transparency of the pressure-sensitive adhesive film may be excellent. The organic nanoparticles may have a refractive index difference of 0.05 or less, specifically 0 or more and 0.03 or less, specifically 0 or more and 0.02 or less, with a (meth) acrylic copolymer having a hydroxyl group. In the above range, the transparency of the pressure-sensitive adhesive film is excellent.

The organic nanoparticles have a core-shell structure, and the glass transition temperature of the core and the shell may satisfy the following Equation 1.

<Equation 1>

Tg (c) <Tg (s)

(In Formula 1, Tg (c) is the glass transition temperature (° C.) of the core, and Tg (s) is the glass transition temperature (° C.) of the shell).

Specifically, the glass transition temperature of the core may be -150 ℃ to 10 ℃, specifically -150 ℃ to -5 ℃, more specifically -150 ℃ to -20 ℃. It is possible to implement the modulus value required at a low temperature (-20 ℃) in the above range, excellent low temperature and / or room temperature viscoelastic properties. The core may include at least one polyalkyl (meth) acrylate having the glass transition temperature. For example, the core may be polymethyl acrylate, polyethyl acrylate, polypropyl acrylate, polybutyl acrylate, polyisopropyl acrylate, polyhexyl acrylate, polyhexyl methacrylate, polyethylhexyl acrylate and poly And may include, but are not necessarily limited to, one or more of ethylhexyl methacrylates. Preferably at least one of polybutyl acrylate and polyethylhexyl acrylate.

Specifically, the glass transition temperature of the shell may be 15 ℃ to 150 ℃, specifically 35 ℃ to 150 ℃, more specifically 50 ℃ to 140 ℃. Dispersibility of the organic nanoparticles may be excellent in the (meth) acrylic copolymer having a hydroxyl group in the above range. The shell may comprise a polyalkyl (meth) acrylate having the above glass transition temperature. For example, polymethyl methacrylate (PMMA), polyethyl methacrylate, polypropyl methacrylate, polybutyl methacrylate, polyisopropyl methacrylate, polyisobutyl methacrylate and polycyclohexyl methacrylate It may include one or more of the rate, but is not necessarily limited thereto. Preferably polymethyl methacrylate.

The core and the shell may include two or more layers, and the outermost layer of the organic nanoparticles may include one sheet of polyalkyl (meth) acrylate having a glass transition temperature of 15 ° C to 150 ° C. Specifically, the core may include at least one polyalkyl (meth) acrylate having a glass transition temperature of -150 ° C to 10 ° C, and at least one polyalkyl (meth) acrylate without limiting the glass transition temperature. The glass transition temperature of the entire core may satisfy -150 ° C to 10 ° C, but is not necessarily limited thereto. In addition, the shell may also include at least one polyalkyl (meth) acrylate having a glass transition temperature of 15 ° C to 150 ° C, and includes at least one polyalkyl (meth) acrylate without limiting the glass transition temperature. The glass transition temperature of may satisfy 15 ℃ to 150 ℃ is not necessarily limited thereto.

The shell may comprise 1% to 70% by weight, specifically 5% to 60% by weight, more specifically 10% to 50% by weight of the organic nanoparticles. The core may comprise 30% to 99% by weight, specifically 40% to 95% by weight, more specifically 50% to 90% by weight of the organic nanoparticles. In the content range of the shell and the core, viscoelastic properties are maintained over a wide temperature range, and the recovery force of the adhesive film is excellent.

The organic nanoparticles may be included in an amount of 0.5 parts by weight to 15 parts by weight, specifically 0.5 parts by weight to 10 parts by weight, and more specifically 0.5 parts by weight to 8 parts by weight, based on 100 parts by weight of the monomer mixture. In the above range, the viscoelasticity and modulus and recovery force can be balanced.

In one embodiment, the organic nanoparticles may be included in a polymerized state with the monomer mixture when preparing the (meth) acrylic copolymer having a hydroxyl group. In this case, the organic nanoparticles may be used in a state contained in the (meth) acrylic copolymer having a hydroxyl group. In another embodiment, the pressure-sensitive adhesive composition may include organic nanoparticles together with a (meth) acrylic copolymer having a hydroxyl group in an already prepared state. In this case, the organic nanoparticles may be included in the pressure-sensitive adhesive composition in a state separate from the (meth) acrylic copolymer having a hydroxyl group.

The pressure-sensitive adhesive composition may further include an initiator. The initiator may be a radical photopolymerization initiator or a thermal polymerization initiator, and may use the same or different initiator as the initiator used in preparing the (meth) acrylic copolymer having a hydroxyl group. As said photoinitiator, as long as it can induce the polymerization reaction of the radically polymerizable compound mentioned above in the hardening process by light irradiation etc., and can implement | achieve a 2nd crosslinked structure, any can be used. For example, benzoin type, acetophenone type, hydroxy ketone type, amino ketone type, or phosphine oxide type photoinitiator can be used, and specifically, benzoin, benzoin methyl ether, benzoin ethyl ether, benzo Phosphorus isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylanino acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenyl Acetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1one, 1-hydroxycyclohexylphenylketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino- Propane-1-one, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4-nonsidiethylaminobenzophenone, dichloro Benzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxane , 2,4-dimethyl thioxanthone, 2,4-diethyl thioxanthone, benzyldimethyl ketal, acetophenone dimethyl ketal, p-dimethylamino benzoic acid ester, oligo [2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone], 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, etc. are mentioned. In the present application, one or more of the above may be used, but is not limited thereto. The type of the thermal polymerization initiator is not particularly limited as long as it can induce a polymerization reaction of the polymerizable compound to implement the second crosslinked structure. For example, an azo compound, a peroxide compound, or a redox system is used. Conventional initiators such as compounds can be used. Examples of the azo compound in the above are 2,2-azobis (2-methylbutyronitrile), 2,2-triazobis (isobutyronitrile), 2,2-triazobis (2,4-dimethyl Valeronitrile), 2,2-nitazobis-2-hydroxymethylpropionitrile, dimethyl-2,2-methylazobis (2-methylpropionate) and 2,2-piazobis (4- Methoxy-2,4-dimethylvaleronitrile) and the like, and examples of the peroxide-based compound include inorganic peroxides such as potassium peroxide, ammonium persulfate or hydrogen peroxide; Or diacyl peroxide, peroxy dicarbonate, peroxy ester, tetramethylbutylperoxy neodecanoate, bis (4-butylcyclohexyl) peroxydicarbonate, di (2-ethylhexyl) peroxy carbonate, butylper Oxy neodecanoate, dipropyl peroxy dicarbonate, diisopropyl peroxy dicarbonate, diethoxyethyl peroxy dicarbonate, diethoxyhexyl peroxy dicarbonate, hexyl peroxy dicarbonate, dimethoxybutyl peroxy dicarbonate , Bis (3-methoxy-3-methoxybutyl) peroxy dicarbonate, dibutyl peroxy dicarbonate, dicetyl peroxy dicarbonate, dimyristyl peroxy dicarbonate, 1,1,3, 3-tetramethylbutyl peroxypivalate, hexyl peroxy pivalate, butyl peroxy pivalate, trimethyl hexanoyl peroxide, dimethyl hydroxybutyl peroxy neodeca Eight, amyl peroxy neodecanoate, butyl peroxy neodecanoate, t-butyl peroxy neoheptanoate, amyl peroxy pivalate, t-butyl peroxy pivalate, t- amyl peroxy-2- Organic peroxides such as ethylhexanoate, lauryl peroxide, dilauroyl peroxide, didecanoyl peroxide, benzoyl peroxide, or dibenzoyl peroxide, and the like, and examples of the redox-based compound And a mixture using a reducing agent and the like, but are not limited thereto. The initiator may be included in an amount of 0.01 to 5 parts by weight, specifically 0.05 to 3 parts by weight, more specifically 0.1 to 1 part by weight, based on 100 parts by weight of the monomer mixture. In the above range, the pressure-sensitive adhesive composition may fully proceed with the curing reaction, and the residual amount of initiator may remain to prevent the transmittance from decreasing.

The pressure-sensitive adhesive composition may further include a crosslinking agent. Crosslinkers are polyfunctional (meth) acrylates, for example 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentylglycol di (meth) acrylate, polyethylene Glycol di (meth) acrylate, neopentylglycol adipate di (meth) acrylate, dicyclopentanyl di (meth) acrylate, caprolactone modified dicyclopentenyl di (meth) acrylate , Ethylene oxide modified di (meth) acrylate, di (meth) acryloxyethyl isocyanurate, allylated cyclohexyl di (meth) acrylate, tricyclodecanedimethanol (meth) acrylate, dimethylol dicyclo Pentane di (meth) acrylate, ethylene oxide modified hexahydrophthalic acid di (meth) acrylate, tricyclodecane dimethanol (meth) acrylate, neopentylglycol modified trimethyl Difunctional acrylates such as propane di (meth) acrylate, adamantane di (meth) acrylate or 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 monomers and trimethylolpropane tri (meth) acrylate 6 functional acrylates, such as a reactant, etc., but are not limited thereto.They can be used alone or in mixture of two or more. Preferably, the crosslinking agent is a polyfunctional polyhydric alcohol having 2-20 hydroxyl groups. There is an effect of having excellent durability reliability by using (meth) acrylate The crosslinking agent is 0 to 10 parts by weight, specifically 0.01 to 7 parts by weight, specifically 0.01 parts by weight, based on 100 parts by weight of the monomer mixture. It may be included in an amount of 5 to 5. The pressure-sensitive adhesive film in the above range has the effect of excellent adhesion and increased reliability.

The pressure-sensitive adhesive composition may further include a silane coupling agent. The silane coupling agent may further include a siloxane-based or epoxy-based silane coupling agent, but is not limited thereto. The silane coupling agent may be included in an amount of 0.01 to 0.1 parts by weight, specifically 0.05 to about 0.1 parts by weight, based on 100 parts by weight of the monomer mixture. There is an effect of increasing the reliability in the above range.

The pressure-sensitive adhesive composition may optionally include a curing accelerator, an ionic liquid, a lithium salt, an inorganic filler, a softener, a molecular weight regulator, an antioxidant, an antioxidant, a stabilizer, a tackifying resin, a modified resin (polyol resin, a phenol resin, an acrylic resin, a polyester resin). , Polyolefin resins, epoxy resins, epoxidized polybutadiene resins, etc.), leveling agents, antifoaming agents, plasticizers, dyes, pigments (colored pigments, sieving pigments, etc.), treatment agents, sunscreen agents, fluorescent brighteners, dispersants, thermal stabilizers, Conventional additives such as light stabilizers, ultraviolet absorbers, antistatic agents, flocculants, lubricants and solvents may be further included.

The pressure-sensitive adhesive composition may have a viscosity of 25 ° C. to 300 cPs to 50,000 cPs. The pressure-sensitive adhesive composition in the above range may have an effect of obtaining excellent coating properties and thickness uniformity.

The first adhesive film and the second adhesive film may be each formed of an adhesive composition including the (meth) acrylic copolymer having the hydroxyl group and the organic nanoparticles. In order that the second adhesive film has a modulus larger than that of the first adhesive film at -20 ° C to 25 ° C, the pressure-sensitive adhesive composition for the second pressure-sensitive adhesive film has a (meth) acryl having a hydroxyl group in the monomer mixture compared to the pressure-sensitive adhesive composition for the first pressure-sensitive adhesive film. The rate of rate may be greater. Alternatively, since the second adhesive film has a larger modulus than the first adhesive film, the pressure-sensitive adhesive composition for the second adhesive film may further include a crosslinking agent or more crosslinking agent than the pressure-sensitive adhesive composition for the first adhesive film.

Hereinafter, the manufacturing method of an adhesive composition is demonstrated.

The pressure-sensitive adhesive composition may be prepared by mixing an initiator with a monomer mixture for a (meth) acrylic polymer having a hydroxyl group, polymerizing it, and then adding an organic nanoparticle and optionally an initiator, a crosslinking agent, a silane coupling agent, and various additives. However, the pressure-sensitive adhesive composition may be prepared by partially polymerizing a monomer mixture for a (meth) acrylic polymer having a hydroxyl group to prepare a prepolymer, and then introducing organic nanoparticles into the prepolymer. Alternatively, the pressure-sensitive adhesive composition may be prepared by adding organic nanoparticles to a monomer mixture for a (meth) acrylic polymer having a hydroxyl group, followed by partial polymerization or complete polymerization. The polymerization may include solution polymerization, suspension polymerization, photopolymerization, bulk polymerization, dispersion polymerization or emulsion polymerization. Specifically, the emulsion polymerization may be performed at 50 ° C. to 100 ° C. by adding an initiator to the monomer mixture and the organic nanoparticles in an aqueous solution. The initiator may include a radical photopolymerization initiator, and specifically, radical polymerization initiators including one or more of Azobisisobutyronitrile, Potassium persulfate, tert-butylhydroperoxide, and diisopropylbenzene hydroperoxide may be used, but are not limited thereto. Partial polymerization may comprise polymerizing at 25 ° C. after polymerization to a viscosity of at least 100 cPs, specifically from 1000 cPs to 20,000 cPs.

Hereinafter, the manufacturing method of an adhesive film is demonstrated.

Each of the first adhesive film and the second adhesive film may be prepared by applying a pressure-sensitive adhesive composition to a release film, for example, a PET (polyethylene terephthalate) film, drying and curing the film. At this time, the pressure-sensitive adhesive composition may be applied to the surface-treated PET film. For example, the PET film may be surface treated by corona pretreatment of 250 mJ / cm ² or more, thereby further increasing the peel strength of the first adhesive film and the second adhesive film, particularly at 25 ° C. and 60 ° C. The corona pretreatment may be, for example, a method of treating the PET film twice using a corona treatment (Now plasma) while discharging the plasma at a dose of 78 dose, but is not necessarily limited thereto.

Hereinafter, the display unit 91 will be described.

The display unit 91 is for driving the flexible display apparatus 100 and includes a substrate and a display including an organic light emitting diode (OLED), a light emitting diode (LED), or a liquid crystal display (LCD) element formed on the substrate. It may include an optical element for.

In one embodiment, the display unit may include a lower substrate, a thin film transistor, an organic light emitting diode, a planarization layer, a protective film, an insulating film. The lower substrate supports the display unit, and the lower substrate may include a thin film transistor and an organic light emitting diode. A flexible printed circuit board (FPCB) for driving the touch screen panel may be formed on the lower substrate. The flexible printed circuit board may further include a timing controller, a power supply, and the like for driving the organic light emitting diode array.

The lower substrate may include a substrate formed of a flexible resin. Specifically, the lower substrate may include a flexible substrate such as a silicon substrate, a polyimide substrate, a polycarbonate substrate, a polyacrylate substrate, but is not limited thereto.

In the display area of the lower substrate, a plurality of pixel areas are defined by crossing a plurality of driving wires (not shown) and sensor wires (not shown), and each pixel area includes a thin film transistor and an organic light emitting diode connected to the thin film transistor. An organic light emitting diode array may be formed. In the non-display area of the lower substrate, a gate driver for applying an electrical signal to the driving line may be formed in the form of a gate in panel. The gate-in panel circuit unit may be formed on one side or both sides of the display area.

The thin film transistor may control the current flowing through the semiconductor by applying an electric field perpendicular thereto, and may be formed on the lower substrate. The thin film transistor may include a gate electrode, a gate insulating film, a semiconductor layer, a source electrode, and a drain electrode. The thin film transistor may be an oxide thin film transistor using an oxide of indium gallium zinc oxide (IGZO), ZnO, or TiO as a semiconductor layer, an organic thin film transistor using an organic material as a semiconductor layer, an amorphous silicon thin film transistor using amorphous silicon as a semiconductor layer, Or a polycrystalline silicon thin film transistor using polycrystalline silicon as the semiconductor layer.

The planarization layer may cover the thin film transistor and the circuit part to planarize the top surface of the thin film transistor and the circuit part so that the organic light emitting diode is formed. The planarization layer may be formed of a spin-on-glass (SOG) film, a polyimide polymer, a polyacrylic polymer, or the like, but is not limited thereto.

The organic light emitting diode implements a display by emitting light by itself, and may include a first electrode, an organic light emitting layer, and a second electrode which are sequentially stacked. Adjacent organic light emitting diodes may be distinguished through an insulating film. The organic light emitting diode may include a bottom light emitting structure in which light generated in the organic light emitting layer is emitted through the lower substrate, or a top light emitting structure in which light generated in the organic light emitting layer is emitted through the upper substrate.

The protective film may cover the organic light emitting diode to protect the organic light emitting diode. The protective film may be formed of inorganic materials such as SiOx, SiNx, SiC, SiON, SiONC, and amorphous carbon (aC), (meth) acrylate, epoxy polymer, and imide polymer. It may be formed of an organic material such as. Specifically, the passivation layer may include an encapsulation layer in which a layer formed of an inorganic material and a layer formed of an organic material are sequentially stacked one or more times.

Hereinafter, the optical film 93 will be described.

The optical film 93 may be an optical device formed between the first adhesive film 92 and the second adhesive film 94 to provide a predetermined function to the flexible display apparatus 100.

1 illustrates a case in which the optical film is formed as one layer, the optical film may be formed by stacking a plurality of optical elements having the same function or a plurality of optical elements having different functions. . When the plurality of optical elements are stacked, the first adhesive film, the second adhesive film, or a conventional optical clear adhesive (OCA) may be used. In one embodiment, the optical film 93 may include one or more of a polarizer and a touch screen panel. The polarizer may implement polarization of internal light or prevent reflection of external light to implement a display or increase a contrast ratio of the display. The polarizing plate may be composed of a polarizer alone. Alternatively, the polarizer may include a polarizer and a protective film formed on one or both sides of the polarizer. Alternatively, the polarizing plate may include a polarizer and a protective coating layer formed on one or both surfaces of the polarizer. The polarizer, the protective film, and the protective coating layer may use a conventional one known to those skilled in the art. In addition, a polarizing plate may add a retardation film, an λ / 2 film or an λ / 4 film, which is an optical compensation film, and may include a retardation liquid crystal coating layer. The touch screen panel generates an electrical signal by detecting a change in capacitance generated when a human body or a conductor such as a stylus touches the touch screen panel, and the display unit may be driven by the signal. The touch screen panel is formed by patterning a flexible and conductive conductor, and may include a second sensor electrode formed between the first sensor electrode and the first sensor electrode to cross the first sensor electrode. The conductor for the touch screen panel may include, but is not limited to, metal nanowires, conductive polymers, carbon nanotubes, and the like. The touch screen panel may include a base layer and the patterned conductor, and the base layer may include an insulating conventional synthetic resin such as polyethylene terephthalate, polyimide, polycarbonate, polyacrylate, and the like. It may be formed of an insulating synthetic resin, or may be a polarizer or a polarizer protective film for thinning. In the present invention, the optical film may include a polarizing plate and a touch screen panel formed on the polarizing plate. However, when the optical film is a polarizing plate, the touch screen panel may be formed directly on the display unit 91.

Hereinafter, the window film 95 is demonstrated.

The window film 95 may be formed on the outermost side of the flexible display device 100 to protect the flexible display device. The window film 95 may include a flexible window film.

In one embodiment, the window film may include a base layer and a window coating layer.

The base layer supports the window film, and may be an optically transparent optical film. The optical film has a total light transmittance of 90% or more in the visible region, a cellulose resin including triacetyl cellulose, a polyethylene resin such as polyethylene terephthalate polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, And a flexible film formed of any one or more of a poly (meth) acrylate resin, a cycloolefin polymer resin, and an acrylic resin including a polycarbonate resin, a polyimide resin, a polyamide resin, a polystyrene resin, a polymethyl methacrylate, and the like. Can be. The optical film may have a thickness of 10 μm to 100 μm, specifically 20 μm to 75 μm, and more specifically 30 μm to 50 μm. It can be used as the base layer of the window film in the above range.

The base material layer may be a film laminate including the optical film. Specifically, the film laminate may include two or more of the optical films, and at least two or more of the optical films may be three or more film laminates laminated by an adhesive film. The adhesive film may be formed of a monomer mixture for the (meth) acrylic copolymer having the hydroxyl group, and an adhesive composition including the organic nanoparticles. The pressure-sensitive adhesive composition may further include one or more of the initiator, crosslinking agent, silane coupling agent, and additives. The adhesive film may be the same as or different from the first adhesive film and the second adhesive film.

In one embodiment, the film laminate may be a first optical film, a second optical film, and a three-layer film laminate in which the first optical film and the second optical film are laminated by the adhesive film. The first optical film and the second optical film are each one or more of polyethylene terephthalate resin, polycarbonate resin, polyimide resin, poly (meth) acrylate resin, cyclic olefin polymer resin, acrylic resin and polyamide resin. It may be a film formed by. Each of the first optical film and the second optical film has a thickness of 10 μm to 100 μm, specifically 20 μm to 75 μm, more specifically 30 μm to 50 μm, and the adhesive film has a thickness of 10 μm to 100 μm. This can be In the above range, it can be effective to maximize the impact resistance while maintaining good folding properties. The first optical film and the second optical film may be the same or different in thickness and material, respectively. The adhesive film may be the same as or different from the first adhesive film and the second adhesive film.

The window coating layer is formed on the base layer and is formed on the outermost side of the flexible display device, and may be a flexible coating layer. For example, the window coating layer may include a coating layer formed of siloxane resin.

In another embodiment, the window film may include a base layer, a window coating layer formed on one side of the base layer, and a hardness improving coating layer formed on the other side of the base layer. The window film 95 may have a pencil hardness of 6H or more, specifically 6H to 9H.

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. However, this is presented as a preferred example of the present invention and in no sense can be construed as limiting the present invention.

Preparation of Adhesive Film

Specific components used to prepare the adhesive film are as follows.

(A) Monomer to form a (meth) acrylic copolymer having a hydroxyl group

(a1) 2-ethylhexyl acrylate (EHA)

(a2) 4-hydroxybutyl acrylate (HBA)

(a3) 2-hydroxyethyl acrylate (HEA)

(B) Organic Nanoparticles

The core consists of polybutyl acrylate (PBA), the shell consists of polymethyl methacrylate (PMMA), the shell is 30% by weight of the organic nanoparticles, the core is 70% by weight of the organic nanoparticles, and the average particle diameter is 130 nm, refractive index is 1.48, organic nanoparticles prepared by emulsion polymerization

(C) initiator

(c1) Photoinitiator: Igacure 651 (2,2-dimethoxy-2-phenylacetophenone, BASF Corporation)

(c2) Photoinitiator: Igacure 184 (1-hydroxycyclohexyl phenyl ketone, BASF Corporation)

(D) Crosslinking agent: 1, 6-hexanediol diacrylate

Production Example  One

65 parts by weight of 2-ethylhexyl acrylate (a1), 100 parts by weight of the monomer mixture (A) comprising 35 parts by weight of 4-hydroxybutyl acrylate (a2), 4 parts by weight of organic nanoparticles (B) and a photopolymerization initiator (c1) 0.005 parts by weight of the mixture was mixed well in a glass vessel to prepare a mixture. The dissolved oxygen in the glass vessel was replaced with nitrogen gas and the mixture was partially polymerized by irradiating with ultraviolet light using a low pressure lamp (BL Lamp manufactured by Sankyo Co., Ltd.) for several minutes to have a hydroxyl group having a viscosity of about 2000 CPS ( A mixture comprising a meth) acrylic copolymer (prepolymer), the monomer, and the organic nanoparticles was obtained. The pressure-sensitive adhesive composition was prepared by adding 0.3 parts by weight of an additional photopolymerization initiator (c2) to 100 parts by weight of the monomer mixture (A).

The resulting pressure-sensitive adhesive composition was coated on a polyester film (release film, polyethylene terephthalate film, thickness 75 μm) to form an adhesive film having a thickness of 50 μm. After covering the release film having a thickness of 75㎛ on the top, and irradiated with a low pressure lamp (BL Lamp manufactured by Sankyo) for about 6 minutes on both sides to obtain a transparent adhesive sheet.

Production Example  2 to Production Example  6

A transparent adhesive sheet was prepared in the same manner as in Preparation Example 1, except that the content of each component in Preparation Example 1 was changed as shown in Table 1 below.

Physical properties of the adhesive films prepared in Preparation Examples 1 to 6 were evaluated according to the following physical property evaluation method, and the results are shown in Table 1 below.

Property evaluation method

(1) Modulus: Viscoelasticity was measured under auto strain conditions at a shear rate of 1 rad / sec and strain of 1% using ARES (Anton Paar, MCR-501), a dynamic viscoelasticity measuring device. After removing the release film, an adhesive film having a thickness of 50 μm was laminated to a thickness of 500 μm, and the laminate was punched out using a perforator having a diameter of 8 mm to be used as a specimen. Modulus was measured at a rate of temperature rise of 5 ° C./min from −60 ° C. to 90 ° C., and modulus was recorded at −20 ° C., 25 ° C., and 80 ° C.

(2) Peeling strength: A corona treatment was performed on a PET (polyethylene terephthalate) film having a width x length x thickness (150 mm x 25 mm x 75 μm) using a corona treatment (Two doses of corona at 78 doses). Corona-treated surfaces of the PET film were laminated on both sides of an adhesive film (width x length x thickness, 100mmx25mmx50㎛), respectively, to prepare a specimen shown in FIG. The specimens were autoclaved at pressure of 3.5 bar at 50 ° C. for 1000 seconds and the specimens were fixed in a TA.XT_Plus Texture Analyzer (Stable Micro System). Referring to (b) of FIG. 2, T-Peel peel strength was measured when one PET film was fixed at 25 ° C. and the other PET film was pulled at a speed of 50 mm / min in a TA.XT_Plus Texture Analyzer. .

(3) Haze: Haze meter (Nippon Denshoku company model NDH 5000) equipment was used. 50 μm adhesive film according to ASTM (American Society for Testing and Measurement) test method D 1003-95 5 (“Standard Test for Haze and Luminous Transmittance of Transparent Plastic”) Haze in the thickness was measured.

Production Example One 2 3 4 5 6 EHA (% by weight) 65 83 83 83 65 83 HBA (% by weight) 35 17 17 17 - - HEA (% by weight) - - - - 35 17 Initiator (c1) (part by weight) 0.005 0.005 0.005 0.005 0.005 0.005 Initiator (c2) (parts by weight) 0.3 0.3 0.3 0.3 0.3 0.3 Organic nanoparticles
(Parts by weight) 4 4 4 4 4 4 Crosslinking agent
(Parts by weight) 0 0 0.1 0.01 0 0 Modulus
(kPa); ＠ -20 ℃ 122 66.2 83 74 695 474 Modulus
(kPa); ＠ 25 ℃ 40.1 25.6 36 29 38.2 40 Modulus
(kPa); ＠ 80 ℃ 28.8 15.2 29 20 29 30 Peel strength
(gf / in); ＠ 25 ℃ 1601 1547 1633 1136 1700 1901 Haze (%) 0.9 0.8 0.9 0.9 0.9 0.8

Example  One

As shown in FIG. 3, the following display unit, a first adhesive film, an optical film, a second adhesive film, and a window film were sequentially stacked to prepare a specimen that simulates a flexible display device.

-Display unit: Replaced with the first PET film (thickness: 100㎛, Cosmoshine TA015, Toyobo)

-First adhesive film: pressure-sensitive adhesive film formed by the pressure-sensitive adhesive composition of Preparation Example 2 (thickness: 50㎛)

-Optical film (polarizing plate, touch screen panel): replaced by second PET film (thickness: 50㎛)

-Second adhesive film: pressure-sensitive adhesive film (thickness: 50㎛) formed from the pressure-sensitive adhesive composition of Preparation Example 1

-Window film: replaced by the third PET film (thickness: 125㎛)

Example  2, Comparative example  1 to Comparative example  3

In Example 1, except that the type of the first adhesive film and the second adhesive film is changed as shown in Table 2, a specimen that simulates a flexible display device was prepared in the same manner.

In Examples 1 to 2 and Comparative Examples 1 to 3, the following physical properties were evaluated and shown in Table 2 below.

(1) Bubble generation area ratio: The specimens prepared in Examples and Comparative Examples were cut horizontally x vertically (160 mm x 100 mm), bent in the direction of the window film between parallel frames at 1 cm intervals, and were subjected to 60 ° C and relative humidity. After aging for 24 hours at 93%, the bubble-produced part was analyzed with an optical microscope (Olympus, EX-51, 30x magnification) and analyzed by Mountech's Mac-view software. It is the value which calculated the ratio of area of (%).

(2) Folding test (-20 ° C.): The specimens prepared in Examples and Comparative Examples were cut into dimensions of width x length (70 cm x 140 cm) to prepare specimens for folding test, and the prepared specimens were autoclaved. Treatment at 50 ° C. and 3.6 bar pressure at 1000 sec. As shown in Fig. 3, the specimen is fixed to the folding test measuring instrument (COVOTEC Co., CFT series) to be folded in the direction of the window film so that the half point of the horizontal length of the specimen is folded, and the radius of curvature is 3 mm. 100,000 cycles were performed by repeatedly bending at −20 ° C. at a speed of 30 cycles (one cycle of bending the adhesive film in half and then releasing it). When peeling or foaming generate | occur | produced after 100,000 cycles, it marked with (circle) when no peeling and foaming generate | occur | produced.

division Properties Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 2nd adhesive film Adhesive film Preparation Example 1 Preparation Example 3 Preparation Example 2 Preparation Example 2 Preparation Example 6 Modulus (kPa, G ') -20 ℃ 122 83 66.2 66.2 474 25 ℃ 40.1 36 25.6 25.6 40 80 ℃ 28.8 29 15.2 15.2 30 Peel Strength (gf / in) 1601 1633 1547 1547 1901 First adhesive film Adhesive film Preparation Example 2 Preparation Example 4 Preparation Example 2 Preparation Example 5 Preparation Example 6 Modulus
(kPa, G ') -20 ℃ 66.2 74 66.2 695 474 25 ℃ 25.6 29 25.6 38.2 40 80 ℃ 15.2 20 15.2 29 30 Peel Strength (gf / in) 1547 1136 1547 1700 1901 Modulus comparison of the first and second adhesive films at -20 ° C to 25 ° C 2nd Adhesive Film>
1st adhesive film 2nd Adhesive Film>
1st adhesive film 2nd adhesive film =
1st adhesive film 2nd adhesive film
1st adhesive film 2nd adhesive film =
1st adhesive film Bubble generation area ratio (%) 0 0 8 50 0 Folding test ○ ○ ○ × ×

As shown in Table 2, the flexible display device according to the embodiment of the present invention was highly reliable with a ratio of bubble generation area of 0%, and no bubbles were generated, lifted, peeled, etc. even in the folding test even after folding 100,000 times. Folding was shown. In addition, as in Example 2, the specimens formed of the de-play part and the window film which are actually used may exhibit high temperature, high humidity reliability, and good folding properties.

On the other hand, the comparative example of the second adhesive film having the same or lower modulus than the first adhesive film has a high bubble generation area ratio, resulting in poor reliability or poor folding test results.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be manufactured in various forms, and a person of ordinary skill in the art to which the present invention pertains has the technical spirit of the present invention. However, it will be understood that other specific forms may be practiced without changing the essential features. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Claims (26)

A display unit, a first adhesive film formed on the display unit, an optical film formed on the first adhesive film, a second adhesive film formed on the optical film, and a window film formed on the second adhesive film,
As a flexible display device, the modulus of the second adhesive film at -20 ℃ to 25 ℃ is larger than the modulus of the first adhesive film,
The first adhesive film, the second adhesive film each comprises a cured product of the pressure-sensitive adhesive composition,
The pressure-sensitive adhesive composition is a flexible display device comprising a monomer mixture and organic nanoparticles to form a (meth) acrylic copolymer having a hydroxyl group.
The flexible display device of claim 1, wherein a ratio of the modulus of the second adhesive film to the modulus of the first adhesive film at −20 ° C. to 25 ° C. is greater than 1.0 and 10 or less.
The flexible display device of claim 1, wherein a ratio of the modulus of the second adhesive film to the modulus of the first adhesive film at 80 ° C. is 1.0 or more.
The flexible display device of claim 1, wherein the optical film comprises at least one of a polarizer and a touch screen panel.
The flexible display device of claim 4, wherein the touch screen panel includes a base layer and a patterned conductor.
The flexible display device of claim 5, wherein the base layer is a polarizer.
The flexible display apparatus of claim 1, wherein the optical film is a polarizing plate, and a touch screen panel is further formed directly on the display unit.
The flexible display apparatus of claim 1, wherein the display unit is an OLED, an LED, or an LCD.
The flexible display device of claim 1, wherein the first adhesive film has a modulus of 150 kPa or less at −20 ° C. 3.
The flexible display device of claim 1, wherein the second adhesive film has a modulus of 25 kPa or more at 80 ° C. 3.
The flexible display apparatus of claim 1, wherein the first adhesive film and the second adhesive film have peel strengths of 800 gf / in or more at 25 ° C., respectively.
The flexible display device of claim 1, wherein the flexible display device has a bubble generation area ratio of 5% or less.
delete The flexible display device of claim 1, wherein the organic nanoparticles have an average particle diameter of 10 nm to 400 nm.
The flexible display device of claim 1, wherein the organic nanoparticles have a core-shell structure, and glass transition temperatures of the core and the shell satisfy the following Equation 1.
<Equation 1>
Tg (c) <Tg (s)
(In Formula 1, Tg (c) is the glass transition temperature (° C.) of the core, and Tg (s) is the glass transition temperature (° C.) of the shell).
The flexible display device of claim 15, wherein a glass transition temperature of the core is -150 ° C. to 10 ° C., and a glass transition temperature of the shell is 15 ° C. to 150 ° C. 16.
The flexible display device of claim 1, wherein the organic nanoparticles are included in an amount of 0.5 parts by weight to 15 parts by weight based on 100 parts by weight of the monomer mixture forming the (meth) acrylic copolymer having the hydroxyl group.
The flexible display device of claim 1, wherein the organic nanoparticles have a refractive index difference of 0.05 or less from the (meth) acrylic copolymer having the hydroxyl group.
The flexible display apparatus of claim 1, wherein the monomer mixture comprises 60 wt% to 95 wt% comonomer and 5 wt% to 40 wt% (meth) acrylate having a hydroxyl group.
The method of claim 19, wherein the comonomer is an alkyl (meth) acrylate monomer, a monomer having an ethylene oxide, a monomer having a propylene oxide, a monomer having an amine group, a monomer having an amide group, a monomer having an alkoxy group, a monomer having a phosphoric acid group, At least one of a monomer having a sulfonic acid group, a monomer having a phenyl group, and a monomer having a silane group,
The comonomer is a flexible display device, the glass transition temperature (Tg) of the homopolymer is -150 ℃ to 0 ℃.
The flexible display device of claim 1, wherein the pressure-sensitive adhesive composition further comprises one or more of an initiator and a crosslinking agent.
The method according to claim 1, wherein the window film comprises a first optical film, a second optical film, and a three-layer film laminate in which the first optical film and the second optical film are laminated by an adhesive film, Flexible display device.
The method of claim 22, wherein the first optical film and the second optical film is one of polyethylene terephthalate resin, polycarbonate resin, polyimide resin, poly (meth) acrylate resin, cyclic olefin polymer resin, acrylic resin, respectively It is a film formed from the above resin, Flexible display apparatus.
The flexible display device of claim 22, wherein each of the first optical film and the second optical film has a thickness of 10 μm to 100 μm, and the adhesive film has a thickness of 10 μm to 100 μm.
The method of claim 22, wherein the pressure-sensitive adhesive film formed between the first optical film and the second optical film is formed of a pressure-sensitive adhesive composition containing a monomer mixture and organic nanoparticles for the (meth) acrylic copolymer having a hydroxyl group. , Flexible display device.
The flexible display device of claim 22, wherein the adhesive film is the first adhesive film or the second adhesive film.

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