Multilayer sheet and multilayer electronic device comprising the same

Abstract

The multilayer sheet according to the embodiment of the present application includes: a transparent film having a total light transmittance of 85% or more according to ISO 13468; a coating layer disposed on one surface of the transparent film; and an elastic film disposed under the other surface of the transparent film; the multilayer sheet having a Martens hardness (HM) of 180 N / mm2or more measured on the surface of the coating layer 2 The multilayer sheet according to the embodiment of the present application does not substantially delaminate from the substrate even if repeatedly folded or wound, and has excellent surface hardness, and thus is excellent in scratch resistance, dent resistance, and the like.

Description

Technical Field

[0001] This embodiment relates to a multilayer sheet that can be applied to protect displays and the like, and a multilayer electronic device including the same. Background Technology

[0002] With the diversification of mobile devices such as mobile phones, smartphones, and tablets, and information processing terminals such as ATMs and kiosks, the applications of surface protective sheets are becoming increasingly widespread. Furthermore, the emergence of various types of display devices, such as foldable, flexible, and rollable displays, demands are placed on surface hardness capable of suppressing scratches and sufficient durability for repeated folding and rolling. In addition, optical properties are also required when applied to displays.

[0003] As related prior art, there are Korean Patent No. 10-1798759 and Korean Patent No. 10-1810422, etc. Summary of the Invention

[0004] The problem the invention aims to solve

[0005] The purpose of this embodiment relates to a multilayer chip and a multilayer electronic device including the same. The multilayer chip has excellent applications in areas such as display protection.

[0006] means for solving problems

[0007] As one embodiment for achieving the above-mentioned objectives, the multilayer sheet comprises: a transparent film having a total light transmittance of 85% or more according to ISO 13468; a coating disposed on one surface of the transparent film; and an elastic film disposed under the other surface of the transparent film, wherein the multilayer sheet has a Martens hardness (HM) of 180 N / mm. 2 The martensitic hardness mentioned above is measured on the surface of the coating of the multilayer sheet.

[0008] The elastic modulus (ηIT) of the multilayer sheet can be 62% or more, and the elastic modulus is measured on the surface of the coating of the multilayer sheet.

[0009] The ratio of the thickness of the transparent film to the thickness of the elastic film can be from 0.5 to 3.

[0010] The strain-restoration index (TR index) is a value determined on the surface of the coating of the multilayer sheet according to the following formula 1. The TR index (unit: / μm) can be greater than 0.8 and less than 2.

[0011] [Formula 1]

[0012]

[0013] In Equation 1 above, HMd is the Martens hardness value per unit thickness (1 μm) of the multilayer sheet measured on the surface of the coating (unit: N / (mm)). 2 ×μm), CITd is the indentation creep value per unit thickness (1μm) of the multilayer sheet measured on the surface of the coating (unit: % / μm), Rcd is the recovery rate value per unit thickness (1μm) of the multilayer sheet measured on the surface of the coating (unit: % / μm), H IT The indentation hardness (unit: N / mm) of the multilayer sheet is measured on the surface of the coating. 2 ).

[0014] As another embodiment for achieving the aforementioned objective, a multilayer sheet includes: a transparent film; a coating disposed on one surface of the transparent film; an adhesive layer disposed under the other surface of the transparent film; and an elastic film disposed under the adhesive layer; the martensitic hardness (HM) of the multilayer sheet, measured on the surface of the coating, is 180 N / mm. 2 above.

[0015] The indentation creep value per unit thickness (1 μm) of the multilayer sheet, measured on the surface of the coating, can be from 0.02% / μm to 0.05% / μm.

[0016] The recovery rate of the multilayer sheet per unit thickness (1 μm) measured on the surface of the coating can be from 0.4% / μm to 1.2% / μm.

[0017] The ratio of the thickness of the elastic membrane to that of the adhesive layer can be from 1:0.02 to 1:1.

[0018] The recovery rate of the multilayer film can be above 66%.

[0019] As another embodiment for achieving the stated purpose, a multilayer electronic device includes: a multilayer sheet as described above; and a light-emitting functional layer disposed on the lower part of the multilayer sheet.

[0020] Invention Effects

[0021] The multilayer sheet and multilayer electronic device according to this embodiment do not substantially delamination from the substrate even with repeated folding or rolling, and have excellent surface hardness, thus exhibiting excellent scratch resistance and dent resistance. The multilayer sheet can be used as a protective sheet for displays and has excellent applicability in multilayer electronic devices. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the structure of a multilayer sheet according to one embodiment.

[0023] Figure 2 A conceptual diagram illustrating the structure of a multilayer sheet according to another embodiment.

[0024] Figure 3 A conceptual diagram illustrating the structure of a multilayer electronic device according to another embodiment.

[0025] Explanation of reference numerals in the attached figures

[0026] 100: Multilayer film

[0027] 10: Coating

[0028] 20: Transparent film

[0029] 30: Adhesive layer

[0030] 42: Elastic membrane

[0031] 150: Light-emitting functional layer

[0032] 200: Multilayer electronic device

[0033] t1: Measurement point on the coating surface Detailed Implementation

[0034] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings to enable those skilled in the art to readily implement the present invention. However, the present invention can be implemented through various different methods and is not limited to the embodiments described in this specification. Throughout the specification, the same reference numerals are used to refer to the same or similar components.

[0035] In this specification, when a component is described as "including" another component, it means, unless otherwise stated, that other components are also included, not excluded.

[0036] In this specification, when describing a component as "connected" to another component, it includes not only the case of "direct connection" but also the case of "connection with other components in between".

[0037] In this specification, "B is located on A" means that B is located on A in direct contact with A or in the presence of other layers in between, and should not be interpreted as B being located on the surface of A in contact with A.

[0038] In this specification, the upper and lower positions of each layer will be described based on the accompanying drawings. However, the positions of each layer are not limited to those shown in the drawings, and the distinction between upper and lower layers should be understood as an explanation of the relative concepts of the positions of each layer.

[0039] In this specification, the term "combination of..." included in the Markush-type description refers to a mixture or combination of one or more elements selected from the group of elements constituted by the Markush-type description, thereby implying that the invention includes one or more elements selected from the group of said elements.

[0040] Throughout this specification, references in the form of "A and / or B" mean "A, B, or A and B".

[0041] Throughout this specification, unless otherwise specified, terms such as “first,” “second,” or “A,” “B,” etc., are used to distinguish them from each other.

[0042] Unless otherwise specified, the use of the singular in this specification is to be interpreted as including the meaning of singular or plural as the context suggests.

[0043] In this specification, the storage modulus is measured according to ASTM D4065 in a Hitachi DMA7100 model over a temperature range of -50°C to 100°C. The heating rate is 5°C / minute.

[0044] In this instruction manual, room temperature is based on approximately 20°C, and normal temperature is based on approximately 25°C.

[0045] In this specification, in-plane retardation (Ro) is a parameter defined by the product of the anisotropy of the refractive index of two mutually perpendicular axes on the plane of the object being measured (Δnxy = |nx - ny|) and the thickness (d) (Δnxy × d). It is a measure of the degree of optical isotropy and anisotropy. Furthermore, the minimum in-plane retardation (Romin) refers to the lowest measured value when the in-plane retardation (Ro) is measured at multiple points within the plane of the film.

[0046] In this specification, the thickness direction retardation (Rth) is defined as the average of the phase differences obtained by multiplying the two birefringences, Δnxz (=|nx-nz|) and Δnyz (=|ny-nz|), when viewed from a cross-section along the thickness direction of the film by the film thickness (d). Furthermore, the maximum thickness direction retardation (Rthmax) refers to the highest measured value when the thickness direction retardation (Rth) is measured at multiple points within the film plane.

[0047] In this specification, the text and / or numbers listed together with the compound name refer to the abbreviation of the compound name.

[0048] In this specification, for ease of explanation, the relative dimensions, thicknesses, etc. of the components shown in the accompanying drawings may be exaggerated.

[0049] The multilayer sheet used in this embodiment will now be described in more detail.

[0050] Figure 1 This is a schematic diagram illustrating the structure of a multilayer sheet according to one embodiment. Figure 2 This is a conceptual diagram illustrating the structure of a multilayer sheet according to another embodiment. (Refer to...) Figure 1 and Figure 2 The multilayer sheet of this embodiment will be described in more detail.

[0051] To achieve the above objectives, a multilayer sheet 100 according to one embodiment of this invention includes a transparent film 20; a coating 10 disposed on one surface of the transparent film; and an elastic film 42 disposed under the other surface of the transparent film.

[0052] To achieve the above objectives, a multilayer sheet 100 according to an embodiment of this invention includes a transparent film 20; a coating 10 disposed on one surface of the transparent film; an adhesive layer 30 disposed under the other surface of the transparent film; and an elastic film 42 disposed under the adhesive layer.

[0053] Transparent film 20

[0054] The transparent film 20 serves as a support for the multilayer sheet and can be used as a base layer for coatings and adhesive layers.

[0055] The transparent film 20 is a thin film with a total light transmittance (transmittance) of 85% or more according to ISO 13468. The transmittance of the transparent film 20 can be 85% or more. For example, the transmittance can be 88% or more, 89% or more, or less than 99%. However, the transmittance is not limited to this, as long as it is applicable to the support layer of a display cover film.

[0056] The haze of the transparent film 20 can be less than 3%. For example, the haze can be less than 2%, less than 1.5%, or less than 1%. The haze can also be greater than 0%. In this case, the multilayer film can be made more transparent.

[0057] The yellow index (YI) of the transparent film 20 can be 3 or less. For example, the yellow index can be 3 or less, 2.8 or less, 2.2 or less, 1.0 or less, 0.8 or less, or 0.5 or less. Furthermore, the yellow index can be greater than 0.

[0058] The transparent film 20 can have excellent retardation characteristics.

[0059] The in-plane phase difference (Ro) of the transparent film 20 can be less than 600 nm, less than 500 nm, less than 400 nm, less than 300 nm, or less than 200 nm. When within these ranges, the possibility of iris patterns appearing depending on the viewing angle can be minimized when the multilayer film is applied to the front of the display.

[0060] The minimum in-plane phase difference (Romin) of the transparent film 20 can be less than 200 nm or less than 150 nm. Specifically, the minimum in-plane phase difference can be less than 120 nm, less than 100 nm, less than 85 nm, less than 75 nm, or less than 65 nm.

[0061] The lower limit of the in-plane phase difference of the transparent film 20 can be 0 nm, or, in order to achieve a balance between optical properties and mechanical properties, the lower limit of the in-plane phase difference (Ro) can be 10 nm or more, 30 nm or more, or 50 nm or more.

[0062] The thickness direction phase difference (Rth) of the transparent film 20 can be above 4,000 nm, above 5,000 nm, or above 5,500 nm.

[0063] The maximum thickness direction phase difference (Rthmax) of the transparent film 20 can be above 6,000 nm, for example, above 6,500 nm, above 7,500 nm, above 8,000 nm, or above 8,500 nm.

[0064] The ratio (Rth / Ro) of the thickness direction phase difference (Rth) of the transparent film 20 relative to the in-plane phase difference (Ro) can be 10 or more, 15 or more, or 20 or more. The smaller the in-plane phase difference (Ro), the larger the thickness direction phase difference (Rth), which is more conducive to preventing the generation of iris spots. Therefore, the ratio of the two values ​​(Rth / Ro) is preferably large.

[0065] The ratio (Rthmax / Romin) of the maximum thickness direction phase difference (Rthmax) of the transparent film 20 relative to the minimum in-plane phase difference (Romin) can be 30 or more, 40 or more, 50 or more, or 60 or more.

[0066] The transparent film possessing the properties described above has a high degree of molecular orientation, thereby promoting crystallization and thus exhibiting mechanical properties above a suitable level. Furthermore, in this case, the occurrence of iris spots can be effectively suppressed. The phase difference is based on values ​​measured on a transparent film 20 with a thickness of 40 μm to 50 μm.

[0067] The tensile strength of transparent film 20 can be 15 kgf / mm. 2 That's all. Specifically, the tensile strength can be 18 kgf / mm. 2 Above, 20kgf / mm 2 Above, 21 kgf / mm 2 Above or 22 kgf / mm 2 above.

[0068] The elongation of the transparent film 20 can be 15% or more. Specifically, the elongation can be 16% or more, 17% or more, or 17.5% or more.

[0069] The modulus of the transparent film 20 can be 2.5 GPa or higher. For example, the modulus can be 3 GPa or higher, 3.5 GPa or higher, 3.8 GPa or higher, or 4.0 GPa or higher. The modulus can be 10 GPa or lower, or 8 GPa.

[0070] The compressive strength of the transparent film 20 can be 0.4 kgf / μm or higher. Specifically, the compressive strength can be 0.45 kgf / μm or higher, or 0.46 kgf / μm or higher.

[0071] Polyester films can be used as the transparent film 20.

[0072] As the transparent film 20, polyimide films can be used.

[0073] Polyamide films can be used as transparent film 20.

[0074] As the transparent film 20, polyimide-amide films can be used.

[0075] For example, the transparent film 20 may be a transparent polyester film.

[0076] The polyester film may include polyester resin.

[0077] The polyester resin may be a homopolymer resin or a copolymer resin obtained by the polycondensation of dicarboxylic acid and diol. Alternatively, the polyester resin may be a blend resin containing the homopolymer resin or copolymer resin.

[0078] Examples of the dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethylene dicarboxylic acid, diphenylsulfone carboxylic acid, anthracene dicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyl adipic acid, trimethyl adipic acid, pimelic acid, azelaic acid, sebacic acid, octanoic acid, dodecanedicarboxylic acid, etc.

[0079] Furthermore, examples of the diols include ethylene glycol, propylene glycol, hexanediol, neopentyl glycol, 1,2-cyclohexanediethanol, 1,4-cyclohexanediethanol, decanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, etc.

[0080] Preferably, the polyester resin can be an aromatic polyester resin with excellent crystallinity. For example, the polyester resin may include polyethylene terephthalate (PET) resin as a main component.

[0081] When the transparent film 20 is a polyester film, the polyester film may include about 85% by weight or more of a polyester resin, specifically PET resin, and more specifically, its content may be 90% by weight or more, 95% by weight or more, or 99% by weight or more. As another example, in addition to PET resin, the polyester film may also include other polyester resins. Specifically, the polyester film may also include about 15% by weight or less of polyethylene naphthalate (PEN) resin. More specifically, the polyester film may also include about 0.1% by weight to 10% by weight or about 0.1% by weight to 5% by weight of PEN resin.

[0082] Polyester films containing the aforementioned components exhibit increased crystallinity and improved mechanical properties such as tensile strength during the preparation process involving heating and stretching.

[0083] In addition to polyester resins, the transparent film 20 may also contain fillers.

[0084] The filler can be at least one selected from the group consisting of barium sulfate, silicon dioxide, and calcium carbonate. By including the filler, the transparent film 20 can improve roughness and rollability, and can also improve the run-through and scratch-reduction effects during film preparation.

[0085] The particle size of the filler can be greater than 0.01 μm and less than 1.0 μm. For example, the particle size of the filler can be from 0.05 μm to 0.9 μm or from 0.1 μm to 0.8 μm, but is not limited thereto.

[0086] Based on the total weight of the transparent film 20, the content of the filler can be from 0.01 wt% to 3 wt%. For example, based on the total weight of the transparent film 20, the content of the filler can be from 0.05 wt% to 2.5 wt%, 0.1 wt% to 2 wt%, or 0.2 wt% to 1.7 wt%, but is not limited thereto.

[0087] The thickness of the transparent film 20 can be 15 μm or more, 20 μm or more, 30 μm or more, 40 μm or more, 55 μm or more, 65 μm or more, 75 μm or more, or 100 μm or more, and can be less than 500 μm, less than 400 μm, less than 300 μm, less than 200 μm, less than 120 μm, less than 95 μm, or less than 85 μm. As a specific example, the thickness of the transparent film 20 can be from 15 μm to 120 μm, more specifically, from 20 μm to 95 μm, or from 25 μm to 85 μm. Within this thickness range, the transparent film can obtain sufficient mechanical properties and excellent optical properties.

[0088] The transparent film can be any of the following products sold by SKC: SH33 / 34, SH37 / 38, TF110, V7610, V5400, V7611, TU94, TU63A, TOF50, etc., but is not limited to these.

[0089] The transparent film is prepared according to the usual method for preparing transparent films.

[0090] For example, in the case of polyester film, it is prepared by a preparation method including the following steps: (1) extruding (pressing out) a composition containing polyester resin to obtain an unstretched film; (2) stretching the unstretched film in the length and width directions; and (3) heat-setting the stretched film.

[0091] In the preparation method described above, the unstretched film is prepared by extruding a raw resin and then subjecting it to preheating, stretching, and heat setting. Furthermore, the extrusion can be performed at temperatures ranging from 230°C to 300°C or from 250°C to 280°C.

[0092] The unstretched film is preheated at a certain temperature before stretching. The preheating temperature range is determined based on the glass transition temperature (Tg) of the polyester resin, satisfying a range of Tg+5°C to Tg+50°C, and simultaneously satisfying a range of 70°C to 90°C. If the preheating temperature is within this range, the unstretched film can ensure easy stretching flexibility and effectively prevent breakage during stretching.

[0093] The stretching is performed by biaxial stretching, and can be performed in both the transverse (stretching direction, TD) and longitudinal (machine direction, MD) directions, for example, by simultaneous biaxial stretching or successive biaxial stretching. Preferably, a successive biaxial stretching method can be used, in which stretching is performed first in one direction and then in a direction perpendicular to that direction.

[0094] The longitudinal stretch ratio can be in the range of 2.0 to 5.0, more specifically, in the range of 2.8 to 3.5. Additionally, the transverse stretch ratio can be in the range of 2.0 to 5.0, more specifically, in the range of 2.9 to 3.7. Preferably, the longitudinal stretch ratio d2 and the transverse stretch ratio d1 are similar; specifically, the ratio of the longitudinal stretch ratio d2 to the transverse stretch ratio d1 (d2 / d1) can be 0.5 to 1.0, 0.7 to 1.0, or 0.9 to 1.0. When the length before stretching is set to 1.0, the stretch ratios d1 and d2 represent the length after stretching. Furthermore, the stretching speed can be from 6.5 m / min to 8.5 m / min, but is not particularly limited.

[0095] The stretched sheet can be heat-set at 150°C to 250°C, more specifically, at 160°C to 230°C. The heat setting can be performed for 5 seconds to 1 minute, more specifically, for 10 seconds to 45 seconds.

[0096] After the heat setting begins, the film can be relaxed in the longitudinal and / or transverse directions at a temperature range of 150°C to 250°C.

[0097] Coating 10

[0098] The coating 10 is disposed on one surface of the transparent film 20.

[0099] The lower surface of coating 10 faces the transparent film 20, while its upper surface can be the outermost surface exposed to the outside.

[0100] The lower surface of coating 10 can be in direct contact with transparent film 20, or bonded to transparent film 20 through an additional layer.

[0101] The coating 10 can be in direct contact with one surface of the transparent film 20.

[0102] The coating 10 can improve the mechanical and / or optical properties of the transparent film 20.

[0103] The coating 10 may include at least one coating material selected from organic components, inorganic components, and organic / inorganic composite components.

[0104] The coating material may include an organic resin. Specifically, the organic resin may be a curable resin or an adhesive resin.

[0105] Coating 10 can be a curable coating.

[0106] The coating 10 may contain at least one selected from the group consisting of urethane acrylate compounds, acrylate compounds, acrylic compounds and epoxy acrylate compounds, or a cured product thereof.

[0107] The coating 10 may contain urethane acrylate compounds, acrylate compounds or their cured products.

[0108] The coating 10 may contain urethane acrylate compounds, acrylate compounds, acrylic compounds or their cured products.

[0109] The carbamate acrylate compounds may contain carbamate bonds as repeating units and may have multiple functional groups.

[0110] The urethane acrylate compound can be a compound formed by reacting a diisocyanate compound with a polyol, in which the end of the urethane compound is replaced by an acrylate group.

[0111] For example, the diisocyanate compound may include at least one of a straight-chain, branched, or cyclic aliphatic diisocyanate compound having 4 to 12 carbon atoms and an aromatic diisocyanate compound having 6 to 20 carbon atoms. The polyol comprises 2 to 4 hydroxyl groups (-OH) and may be a straight-chain, branched, or cyclic aliphatic polyol compound having 4 to 12 carbon atoms or an aromatic polyol compound having 6 to 20 carbon atoms. Terminal substitution of the acrylate group can be achieved using acrylic compounds having functional groups capable of reacting with isocyanate groups (-NCO). For example, acrylic compounds having hydroxyl and amino groups can be used, and hydroxyalkyl acrylates or aminoalkyl acrylates having 2 to 10 carbon atoms can be used.

[0112] The carbamate acrylate compounds may include 2 to 15 functional groups.

[0113] Examples of the urethane acrylate compounds include, but are not limited to, difunctional urethane acrylate oligomers with a weight-average molecular weight of 1,400 to 25,000, trifunctional urethane acrylate oligomers with a weight-average molecular weight of 1,700 to 16,000, tetrafunctional urethane acrylate oligomers with a weight-average molecular weight of 500 to 2,000, hexafunctional urethane acrylate oligomers with a weight-average molecular weight of 818 to 2,600, nonfunctional urethane acrylate oligomers with a weight-average molecular weight of 2,500 to 5,500, decafunctional urethane acrylate oligomers with a weight-average molecular weight of 3,200 to 3,900, and decafunctional urethane acrylate oligomers with a weight-average molecular weight of 2,300 to 20,000.

[0114] The glass transition temperature (Tg) of the urethane acrylate compounds is -80°C to 100°C, -80°C to 90°C, -80°C to 80°C, -80°C to 70°C, -80°C to 60°C, -70°C to 100°C, -70°C to 90°C, -70°C to 80°C, -70°C to 70°C, -70°C to 60°C, -60°C to 100°C, -60°C to 90°C, -60°C to 80°C, -60°C to 70°C, -60°C to 60°C, -50°C to 100°C, -50°C to 90°C, -50°C to 80°C, -50°C to 70°C, or -50°C to 60°C.

[0115] The acrylate compound may be at least one selected from the group consisting of substituted or unsubstituted acrylic acid and substituted or unsubstituted methacrylate. The acrylate compound may include 1 to 10 functional groups.

[0116] Examples of the acrylate compounds include, but are not limited to, trimethylolpropane triacrylate (TMPT A), ethoxylated trimethylolpropane triacrylate (TMPEOTA), propoxylated glycerol triacrylate (GPTA), pentaerythritol tetraacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), etc.

[0117] The weight-average molecular weight of the acrylate compounds can be 500 to 6,000, 500 to 5,000, 500 to 4,000, 1,000 to 6,000, 1,000 to 5,000, 1,000 to 4,000, 1,500 to 6,000, 1,500 to 5,000, or 1,500 to 4,000. The acrylate equivalent of the acrylate compounds can be 50 g / eq to 300 g / eq, 50 g / eq to 200 g / eq, or 50 g / eq to 150 g / eq.

[0118] The acrylic compounds may include 1 to 10 functional groups. Examples of the acrylic compounds include monofunctional epoxy acrylate oligomers with a weight-average molecular weight of 100 to 300, difunctional epoxy acrylate oligomers with a weight-average molecular weight of 250 to 2000, or epoxy acrylate oligomers with a weight-average molecular weight of 1000 to 3000.

[0119] The epoxy acrylate compounds may include 1 to 10 functional groups. Examples of such epoxy acrylate compounds include, but are not limited to, monofunctional epoxy acrylate oligomers with a weight-average molecular weight of 100 to 300, difunctional epoxy acrylate oligomers with a weight-average molecular weight of 250 to 2000, or tetrafunctional epoxy acrylate oligomers with a weight-average molecular weight of 1000 to 3000. The epoxy equivalent of the epoxy acrylate compounds may be 50 g / eq to 300 g / eq, 50 g / eq to 200 g / eq, or 50 g / eq to 150 g / eq.

[0120] Based on the total weight of coating 10, the content of the organic resin can be from 30% to 100% by weight, 40% to 90% by weight, or 50% to 80% by weight.

[0121] Coating 10 may optionally further include filler.

[0122] For example, the filler can be inorganic particles. Examples of fillers include silica, barium sulfate, zinc oxide, or aluminum oxide. The particle size of the filler can be from 1 nm to 100 nm. Specifically, the particle size of the filler can be from 5 nm to 50 nm or from 10 nm to 30 nm. The filler may include inorganic fillers with different particle size distributions. For example, the filler may include a first inorganic filler with a D50 of 20 nm to 35 nm and a second inorganic filler with a D50 of 40 nm to 130 nm. Based on the total weight of the coating, the filler content can be 25% by weight or more, 30% by weight or more, or 35% by weight or more. Furthermore, based on the total weight of the coating 10, the filler content can be less than 50% by weight, less than 45% by weight, or less than 40% by weight. Preferably, the coating 10 may not include inorganic fillers such as silica. In this case, for example, the adhesion between the transparent film 20 and the coating 10 having the composition can be improved.

[0123] The coating 10 may further include a photoinitiator or a reactant thereof. The photoinitiator may participate in the process of curing the resin, etc., into a coating.

[0124] Examples of the photoinitiators include, but are not limited to, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, methyl benzoylcarbamate, α,α-dimethoxy-α-phenylacetophenone, 2-benzoyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, or bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. In addition, examples of commercial products include Irgacure 184, Irgacure 500, Irgacure 651, Irgacure 369, Irgacure 907, Darocur 1173, Darocur MBF, Irgacure 819, Darocur TPO, Irgacure 907, Esacure KIP 100F, etc. The photoinitiators can be used alone or in combination of two or more different types.

[0125] Coating 10 can also have functions such as anti-glare, anti-fouling, and anti-static.

[0126] Coating 10 may further include an antifouling agent. For example, coating 10 may include a fluorinated compound. The fluorinated compound may have antifouling properties. Specifically, the fluorinated compound may be an acrylate compound having a perfluoroalkyl group, such as perfluorohexylethyl acrylate, but is not limited thereto.

[0127] The coating 10 may further include an antistatic agent. The antistatic agent may include an ionic surfactant. For example, the ionic surfactant may comprise an ammonium salt or a quaternary alkylammonium salt, and the ammonium salt and quaternary alkylammonium salt may comprise halides such as chlorides or bromides.

[0128] The coating 10 may also contain additives such as surfactants, ultraviolet absorbers, ultraviolet stabilizers, anti-yellowing agents, leveling agents, or dyes for improving color values. For example, the surfactant may be a mono- or difunctional fluoroacrylate, a fluorinated surfactant, or a silicone surfactant. The surfactant may be included in the coating 10 in a dispersed or crosslinked form. Furthermore, examples of ultraviolet absorbers may include benzophenone compounds, benzotriazole compounds, or triazine compounds, and examples of ultraviolet stabilizers may include tetramethylpiperidine. The content of these additives can be adjusted in various ways without reducing the physical properties of the coating. For example, based on the total weight of the coating, the content of the additives may be from 0.01% by weight to 10% by weight, but is not limited thereto.

[0129] The coating 10 may consist of a single layer or two or more layers.

[0130] Coating 10 can be formed as a single layer and can increase the surface durability of multilayer sheets while also providing anti-fingerprint or anti-fouling effects.

[0131] The thickness of coating 10 can be 2 μm or more, 3 μm or more, 5 μm or more, or 7 μm or more, and can be less than 50 μm, 30 μm or less, 20 μm or less, or 10 μm or less. With the above-mentioned thickness, it is possible to impart an appropriate level of durability, such as surface hardness, to the multilayer sheet while making the thickness relatively thin, and also to maintain the overall flexibility of the multilayer sheet.

[0132] Coating 10 can be formed by coating preparation methods.

[0133] The method for preparing the coating may include a curing step after applying the composition used to prepare the coating.

[0134] The composition used to prepare the coating may include at least one of an organic resin composition, an inorganic resin composition, and an organic / inorganic composite composition.

[0135] The composition used to prepare the coating may include at least one of an acrylic compound, a siloxane compound, or a silsesquioxane compound. Furthermore, the composition used to prepare the coating may also contain inorganic particles.

[0136] As a specific example, the composition used to prepare the coating may contain urethane acrylate compounds, acrylate compounds, and fluorinated compounds.

[0137] In addition, the composition used to prepare the coating may, as needed, include a photoinitiator, antifouling additive, antistatic agent, other additives and / or organic solvent.

[0138] As organic solvents, they can be used alone or in combination with other alcohol solvents such as methanol, ethanol, isopropanol, and butanol; alkoxy alcohol solvents such as 2-methoxyethanol, 2-ethoxyethanol, and 1-methoxy-2-propanol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, and cyclohexanone; ether solvents such as propylene glycol monopropyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, and diethylene glycol-2-ethylhexyl ether; and aromatic solvents such as benzene, toluene, and xylene.

[0139] Since the content of the organic solvent can be adjusted in various ways without reducing the physical properties of the coating, the content of the organic solvent is not particularly limited. However, based on the solids in the composition for preparing the coating, the composition for preparing the coating may contain the organic solvent such that the weight ratio of solids to organic solvent is about 1:1 to 1:250. When the content of the organic solvent is within this range, suitable flowability and coatability can be obtained.

[0140] The composition for preparing the coating may contain 10% to 30% by weight of an organic resin, 0.1% to 5% by weight of a photoinitiator, 0.01% to 2% by weight of an antifouling additive, 0.1% to 10% by weight of an antistatic agent, and a residual amount of an organic solvent.

[0141] Based on the above composition, the mechanical properties of the coating, as well as its antifouling and antistatic properties, can be improved simultaneously.

[0142] The composition used to prepare the coating can be applied to a transparent film using conventional coating methods, and then cured. Coating methods can include rod coating, blade coating, roller coating, doctor blade coating, mold coating, microgravure coating, comma blade coating, slot die coating, lip coating, or solution casting, etc.

[0143] The composition used to prepare the coating after coating can be subjected to drying and curing processes sequentially or simultaneously.

[0144] The drying process is the removal of organic solvents from the composition used to prepare the coating after application. The drying can be carried out at temperatures of 40°C to 100°C, preferably 40°C to 80°C, 50°C to 10°C, or 50°C to 80°C, and the drying time can be about 1 minute to 20 minutes, preferably about 1 minute to 10 minutes or 1 minute to 5 minutes.

[0145] The curing process is the process of initiating a chemical reaction in the composition used to prepare the coating to form a film. Depending on the resin or the like used in the composition used to prepare the coating, appropriate photocuring and / or thermocuring methods can be applied.

[0146] Elastic membrane 42

[0147] The elastic membrane 42 preferably has stable elasticity over a wide temperature range.

[0148] The energy storage modulus of the elastic membrane 42 at room temperature or ambient temperature can be below 3 GPa. The energy storage modulus of the elastic membrane 42 at room temperature or ambient temperature can be below 2 GPa.

[0149] Compared to PET films, the elastic film 42 has a relatively low storage modulus value at room temperature or ambient temperature. These properties impart more stable bending characteristics to the elastic film or multilayer sheets including it, and further mitigate the transmission of externally applied impacts to the article disposed on its back.

[0150] The storage modulus of the elastic membrane 42 at -40℃ can be below 2300MPa or below 2000MPa. The storage modulus of the elastic membrane 42 at -40℃ can be above 200MPa, above 400MPa, or above 500MPa.

[0151] The storage modulus of the elastic membrane 42 at 0°C can be less than 2500 MPa, or less than 2000 MPa. The storage modulus of the elastic membrane 42 at 0°C can be greater than 20 MPa, or greater than 150 MPa. The storage modulus of the elastic membrane 42 at 0°C can be between 180 MPa and 1200 MPa.

[0152] The storage modulus of the elastic membrane 42 at 40°C can be 10 MPa or more, or 90 MPa or more. The storage modulus of the elastic membrane 42 at 40°C can be 3000 MPa or less, or 2000 MPa or less. The storage modulus of the elastic membrane 42 at 40°C can be between 100 MPa and 1200 MPa.

[0153] The storage modulus of the elastic membrane 42 at 80°C can be 4 MPa or more, or 20 MPa or more. The storage modulus of the elastic membrane 42 at 80°C can be less than 2000 MPa, or less than 1000 MPa. The storage modulus of the elastic membrane 42 at 80°C can be from 40 MPa to 950 MPa, or from 60 MPa to 350 MPa.

[0154] The difference between the energy storage modulus of the elastic membrane 42 at 80°C and at -40°C can be from -1000 MPa to 1000 MPa. For convenience, the absolute value of this difference can be expressed by subtracting the smaller value from the larger value, in which case the difference can be 1000 MPa. The elastic membrane with this characteristic exhibits a small difference in energy storage modulus over a wide temperature range from high to low, thus demonstrating stable energy storage modulus characteristics over a considerably wide temperature range.

[0155] The energy storage modulus index of the elastic membrane 42, as expressed by Equation 2 below, can be from 20 MPa to 350 MPa.

[0156] [Equation 2]

[0157]

[0158] In Equation 2 above, KSM is the storage modulus index of the elastic membrane, and SM n The storage modulus (MPa) of the elastic membrane was measured at a temperature of n °C.

[0159] For example, SM -40 SM represents the storage modulus (MPa) of the elastic membrane measured at -40°C. 20 SM represents the storage modulus (MPa) of the elastic membrane measured at 20°C. 80 It is the storage modulus (MPa) of the elastic membrane measured at 80℃.

[0160] When an elastic membrane has the energy storage modulus index value as described above, it can have a relatively stable degree of energy storage modulus change over a wide temperature range, thereby exhibiting stable elastic properties over a wide temperature range.

[0161] The elastic membrane 42 can have a strength of 2500 kJ / m 2The above impact strength, 3500 kJ / m 2 The above impact strength and 4500kJ / m 2 The above impact strength. The elastic membrane 42 can have 5000 kJ / m. 2 The above impact strength, and can have 10000 kJ / m 2 The following impact strengths. Elastic membranes with these properties can effectively absorb external impacts and are not easily broken or damaged, thus making them excellent for use as covering membranes.

[0162] The elastic membrane 42 can absorb energy of 1.4J or more, and can also absorb energy of 1.5J or more. Furthermore, the elastic membrane 42 can absorb energy of 1.6J or more, and can also absorb energy of less than 2.0J. With these characteristics, the elastic membrane 42 can effectively absorb external impacts, thus the membrane itself is less prone to damage. It also reduces the impact transmitted to the protected object, making it an excellent choice for a covering membrane.

[0163] The impact strength and the absorbed energy are based on the results of evaluating the tensile-impact strength of the elastic membrane according to the JIS K 7160 standard. The specific measurement conditions will be based on the experimental examples provided below.

[0164] The thickness of the elastic membrane 42 can be less than 2000 μm. The thickness of the elastic membrane can be less than 1500 μm, less than 1000 μm, less than 500 μm, less than 300 μm, less than 200 μm, or less than 100 μm. The thickness of the elastic membrane can be greater than 1 μm. The thickness of the elastic membrane can be greater than 10 μm, greater than 20 μm, or greater than 30 μm.

[0165] The elastic film 42 has excellent optical properties.

[0166] The haze of the elastic film 42 can be less than 3% or less than 2%. The haze of the elastic film 42 can be less than 1.5% or less than 1.2%. The haze of the elastic film 42 can be greater than 0.01% or greater than 0.1%. When the elastic film has the above-mentioned haze, it is advantageous to apply it to the display area of ​​a display device.

[0167] The visible light transmittance of the elastic film 42 can be 85% or more, or 88% or more, or 90% or more. The visible light transmittance of the elastic film can be 99.99% or less. The elastic film 42, or the multilayer sheet 100 including it, having such characteristics is advantageous for use as a protective layer (or cover window) for electronic devices.

[0168] The yellow index (YI) of the elastic membrane 42 can be less than 1. The yellow index can be a value measured using a Color meterultra scanpro manufactured by Hunter Associates Laboratory, Inc. in YI E313 (D65 / 10) mode.

[0169] For the elastic film 42, the difference between the yellow index before exposure and the yellow index after 72 hours of exposure to ultraviolet light at a power of 3.0W with wavelengths from 280nm to 360nm can be less than 2. For the elastic film, the difference between the yellow index before exposure and the yellow index after 72 hours of exposure to ultraviolet light at a power of 3.0W with wavelengths from 280nm to 360nm can be less than 1. For the elastic film, the difference between the yellow index before exposure and the yellow index after 72 hours of exposure to ultraviolet light at a power of 3.0W with wavelengths from 280nm to 360nm can be greater than 0.1. Elastic films with these characteristics exhibit minimal or almost no yellowing of the coating even after exposure to ultraviolet light, i.e., they possess excellent ultraviolet durability.

[0170] The elastic membrane 42 can be a membrane in which no cloudiness is observed. The area of ​​the elastic membrane where cloudiness is observed can be less than 1% of the total area. In this case, the total area is based on the total film area applied to the product. The cloudiness can be objectified by measuring haze; a haze measurement value greater than 1% is considered to indicate a perceptible cloudiness. The degree of cloudiness can be adjusted by controlling the gelation degree, molecular weight distribution, etc., of the resin used to prepare the elastic membrane.

[0171] The elastic membrane 42 can exhibit excellent durability. This excellent durability can be determined by dynamic bending evaluation results.

[0172] The dynamic bending evaluation was conducted according to the IEC 62715-6-1 standard. The elastic membrane was subjected to 200,000 dynamic bending tests at -40°C with a curvature radius of 2 mm and a bending degree of 2 seconds / cycle to confirm whether there were cracks in the elastic membrane.

[0173] The elastic membrane 42 exhibits excellent durability, showing no substantial cracking after 200,000 dynamic bending tests at -40°C with a curvature radius of 2 mm and a bending intensity of 2 seconds per cycle, in accordance with IEC 62715-6-1 standard.

[0174] This refers to the fact that the elasticity at low temperatures is relatively lower than that at normal or high temperatures, and the elastic membrane also exhibits excellent elasticity in tests involving repeated bending over a wide temperature range.

[0175] The elastic membrane 42 may contain a polymer with amide residues as repeating units.

[0176] The elastic membrane 42 may be a plastic film comprising a polymer having amide residues as repeating units.

[0177] The elastic membrane 42 may be an elastomeric film comprising a polymer having amide residues as repeating units.

[0178] Based on the total amount of polymer contained in the elastic membrane, the content of amide residues can be 50% by weight or more, or 60% by weight or more. Based on the total amount of polymer contained in the elastic membrane, the content of amide residues can be 80% by weight or less, or 70% by weight or less. When a polymer having these properties is applied to the elastic membrane, an elastic membrane with superior mechanical properties can be provided.

[0179] The elastic membrane 42 may contain elastic polyamide (long-chain polyamide). For example, the elastic polyamide may be from Arkema. wait.

[0180] The elastic membrane 42 may comprise a polyether block amide (PEBA). The polyether block amide may comprise two phases: a polyamide region as a rigid region and a polyether region as a flexible region. The polyamide region has a melting point above approximately 80°C, specifically approximately 130°C to 180°C, and can substantially constitute a rigid region as a crystalline phase. The polyether region has a glass transition temperature below approximately -40°C, specifically -80°C to -40°C, existing in a low-temperature region, and can substantially constitute an amorphous soft region. For example, the polyether block amide may be from Arkema Corporation. Evonik E, etc.

[0181] The elastic film 42 may contain thermoplastic polyurethane (TPU), that is, a copolymer of polyurethane block (PU) and polyether block (PE), also known as polyether urethane.

[0182] The elastic membrane 42 may contain a polyether ester copolymer (COPE).

[0183] As an elastic membrane, a thin film prepared by the method disclosed in Korean Patent No. 10-2286935 can be used.

[0184] Adhesive layer 30

[0185] The adhesive layer 30 may be disposed beneath the other surface of the transparent film 20.

[0186] The upper surface of the adhesive layer 30 may face the transparent film 20, or may be in direct contact with the transparent film 20, or may be bonded to the transparent film 20 by an additional layer.

[0187] The upper surface of the adhesive layer 30 can be in contact with the other side of the direct transparent film 20.

[0188] The lower surface of the adhesive layer 30 can be in direct contact with the elastic membrane 42, or it can be bonded to the elastic membrane 42 through an additional layer.

[0189] The lower surface of the adhesive layer 30 can be directly bonded to the light-emitting functional layer via an elastic film, or it can be bonded to the light-emitting functional layer by intervening an additional intermediate layer therebetween, thus serving as part of a multilayer electronic device.

[0190] An optically transparent adhesive layer can be used as adhesive layer 30.

[0191] The adhesive layer 30 can be an acrylic adhesive layer, a urethane adhesive layer, or a silicone adhesive layer; specifically, it can be a silicone adhesive layer. When a silicone adhesive layer is used, it provides an adhesive layer with high light transmittance, heat resistance, weather resistance, etc. In particular, the adhesive layer according to this embodiment, described later, has high adhesion even when its thickness is relatively thin, thus further improving the physical properties of the multilayer sheet compared to existing optically clear adhesives (OCA) such as acrylic adhesive layers.

[0192] As adhesive layer 30, an adhesive layer with high adhesion can be applied.

[0193] In order to maintain the physical properties of multilayer sheets even after repeated bending or folding, the performance of not only the transparent film or coating, but also the adhesive layer used to fix the transparent film or coating and inhibit delamination should be improved. The inventors of this invention have been able to achieve this improved performance by applying a silicone-based adhesive layer.

[0194] Silicone adhesive layers can be obtained by drying and / or curing after applying the silicone adhesive composition.

[0195] The silicone adhesive composition may include a silicone adhesive, a catalyst, and a solvent.

[0196] In this embodiment, an organosilicon MQ resin may be further included to improve the adhesion of the organosilicon adhesive layer. Here, the organosilicon MQ resin is a polymer having at least two methyl groups in the siloxane backbone of cage-like oligosiloxanes represented by the general formula RnSiXmOy. In the general formula, R can be an alkyl group having 1 to 5 carbon atoms, including at least two methyl groups. In the general formula, X is hydrogen, hydroxyl, chloro, or an alkoxy group having 1 to 5 carbon atoms. In the general formula, n, m, and y are integers from 2 to 200. Specifically, it may include a polymer composed of R1R2X3SiOy. 1 / 2 The M-unit (mono-terminated siloxane unit) and the unit composed of SiO2 4 / 2 The Q unit represents a tetra-terminated siloxane unit. The weight-average molecular weight can range from 2000 g / mol to 8000 g / mol. When organosilicon MQ resin is applied to adhesive layers, it can improve adhesion, especially initial adhesion.

[0197] As silicone adhesives, commercially available silicone adhesives suitable for optical purposes can be used. Specifically, peroxide-curing silicone adhesives and addition-reaction silicone adhesives can be used.

[0198] For example, peroxide-curable silicone adhesives may be Shin-Etsu Chemical's KR-100, KR-101-10, KR-130, Dow Chemical's DOWSIL SH 4280, Momentip Performance Materials' SilGrip PSA 510, or equivalent products.

[0199] For example, addition-reactive silicone adhesives may be Shin-Etsu Chemical Co., Ltd.'s KR-3700, KR-3701, X-40-3237, X-40-3240 and X-40-3291-1; Dow Chemical Co., Ltd.'s DOWS IL SD4580, DOWSIL 4584, DOWSIL 4585 and DOWSIL 4587L; Momentive Advanced Materials Co., Ltd.'s SilGrip TSR1512, TSR1516; and other equivalent products.

[0200] As for silicone adhesives, the application of addition-reaction silicone adhesives may be advantageous in terms of process convenience.

[0201] For the purpose of enhancing adhesion, silicone MQ resin can be used in conjunction with silicone adhesives. Examples of silicone MQ resins include Shin-Etsu Chemical's X-92-128 and X-41-3003; Momentive Advanced Materials' SilGrip SR545 and SilGrip SR1000; and equivalent products.

[0202] As a catalyst, a platinum catalyst can be used; for example, Shin-Etsu Chemical's CAT-PL-50T or equivalent products can be used. This catalyst shortens the curing time, thereby enabling the effective formation of an adhesive layer even when using relatively heat-sensitive transparent films or substrates, without substantially damaging the substrate.

[0203] For example, the solvent may be toluene or the like, but it may be used without limitation to the extent that it does not reduce the performance of the silicone adhesive layer.

[0204] Based on 100 parts by weight of the silicone adhesive, the silicone adhesive composition may contain 5 or more parts by weight, 8 or more parts by weight, 10 or more parts by weight, 20 or more parts by weight, 30 or more parts by weight, or 40 or more parts by weight of silicone MQ resin. Based on 100 parts by weight of the silicone adhesive, the silicone adhesive composition may contain 90 or less parts by weight, 80 or less parts by weight, 70 or less parts by weight, or 60 or less parts by weight of silicone MQ resin. When the silicone adhesive and the silicone MQ resin are applied together in the above proportions, excellent adhesion is obtained even with a relatively thin thickness.

[0205] Based on 100 parts by weight of silicone adhesive, the silicone adhesive composition may contain 0.5 to 2 parts by weight or 0.8 to 1.5 parts by weight of a catalyst. The catalyst promotes curing, thereby enabling the silicone adhesive composition to effectively form an adhesive layer.

[0206] The silicone adhesive composition may also contain a solvent, which dilutes the silicone adhesive composition or imparts flowability to the silicone adhesive composition, thereby improving workability such as coating and contributing to the formation of a relatively thin adhesive layer with excellent overall physical properties. For example, the solvent may be toluene or the like, but it can be used without limitation without reducing the performance of the silicone adhesive layer.

[0207] For example, the silicone adhesive composition may contain 20% to 30% by weight of silicone adhesive, 2% to 25% by weight of silicone MQ resin, 0.2% to 0.5% by weight of catalyst, and 50% to 70% by weight of solvent.

[0208] The silicone adhesive composition can be coated onto another surface of the transparent film 20, thereby forming a silicone-based curable adhesive layer. Alternatively, the silicone adhesive composition can be coated onto one surface of a separate base film (not shown) and then laminated onto the other surface of the transparent film 20. However, depending on the process sequence, drying and curing can be performed immediately after coating or as separate processes. The silicone adhesive composition can be coated to form a thin layer, which is then dried so that it can be contained within the adhesive layer in a state prior to complete curing by heat or light. The dried layer of the silicone adhesive composition prior to such curing is referred to as the precursor layer of the silicone-based curable adhesive layer.

[0209] The precursor layer can be cured by heat or light, thereby forming the adhesive layer 30. Exemplarily, the adhesive layer can be formed by configuring the precursor layer and the surface to be bonded in direct contact and heat-curing at 90°C to 130°C for 1 to 5 minutes.

[0210] The adhesive layer 30 may include repeating units derived from a silicone adhesive and repeating units derived from a silicone MQ resin. Based on 100 parts by weight of repeating units derived from the silicone adhesive, the adhesive layer 30 may contain 5 or more, 8 or more, 10 or more, 20 or more, 30 or more, or 40 or more parts by weight of repeating units derived from the silicone MQ resin. Based on 100 parts by weight of repeating units derived from the silicone adhesive, the adhesive layer 30 may contain 90 or less, 80 or less, 70 or less, or 60 or less parts by weight of repeating units derived from the silicone MQ resin. In this case, even with a thinner thickness, excellent optical properties and a sufficiently high level of adhesion can be obtained.

[0211] To ensure stable bending and curling properties, the energy storage modulus of the adhesive layer 30 is preferably within a specified range. In particular, considering the potential for heat generation due to various environments and devices used in applications such as display devices, the adhesive layer preferably possesses a modulus and adhesive force capable of performing stable functions within the temperature variation range on the surface side of the device.

[0212] The energy storage modulus of the adhesive layer 30 can be below 100 MPa, below 90 MPa, or below 80 MPa at -40℃. The energy storage modulus of the adhesive layer 30 can be above 0.1 MPa at -40℃.

[0213] The energy storage modulus of the adhesive layer 30 can be below 100 MPa, below 90 MPa, or below 80 MPa at -20℃. The energy storage modulus of the adhesive layer 30 can be above 0.1 MPa at -20℃.

[0214] The energy storage modulus of the adhesive layer 30 can be below 70 MPa, below 55 MPa, or below 45 MPa at 0°C. The energy storage modulus of the adhesive layer 30 can be above 0.1 MPa at 0°C.

[0215] The energy storage modulus of the adhesive layer 30 can be below 50 MPa, below 35 MPa, or below 25 MPa at 20°C. The energy storage modulus of the adhesive layer 30 can be above 0.1 MPa at 20°C.

[0216] The energy storage modulus of the adhesive layer 30 can be below 20 MPa, below 15 MPa, or below 5 MPa at 40°C. The energy storage modulus of the adhesive layer 30 can be above 0.1 MPa at 40°C.

[0217] The energy storage modulus of the adhesive layer 30 can be less than 10 MPa, less than 5 MPa, or less than 3 MPa at 60°C. The energy storage modulus of the adhesive layer 30 can be greater than 0.1 MPa at 60°C.

[0218] The adhesive force of adhesive layer 30 can be above 200 gf / inch. The adhesive force refers to the adhesive force after the adhesive layer has cured; specific evaluation methods are shown in the experimental examples described later.

[0219] The adhesive strength of adhesive layer 30 can be above 200 gf / inch, above 250 gf / inch, above 300 gf / inch, above 350 gf / inch, above 400 gf / inch, above 450 gf / inch, above 500 gf / inch, or above 550 gf / inch. The adhesive strength of adhesive layer 30 can be below 2200 gf / inch. The adhesive strength of adhesive layer 30 can be below 2000 gf / inch, below 1800 gf / inch, below 1500 gf / inch, below 1200 gf / inch, or below 1000 gf / inch.

[0220] The adhesive force per unit thickness (1 μm) of the adhesive layer 30 can be 80 gf / inch or more, 100 gf / inch or more, 110 gf / inch or more, 140 gf / inch or more, 150 gf / inch or more, or 160 gf / inch or more. The adhesive force per unit thickness (1 μm) of the adhesive layer 30 can be less than 300 gf / inch or less than 250 gf / inch. Forming an adhesive layer with high adhesive force per 1 μm unit thickness is beneficial for obtaining sufficient adhesive layer thickness with a relatively thin layer. The adhesive force per 1 μm unit thickness can vary depending on the type and thickness of the applied adhesive layer and is based on the cured thickness.

[0221] The thickness of the adhesive layer 30 can be greater than 1 μm.

[0222] The thickness of the adhesive layer 30 can be greater than 1 μm, 1.5 μm or more, 1.8 μm or more, 2 μm or more, 2.5 μm or more, 3 μm or more, or 3.5 μm or more. Alternatively, the thickness of the adhesive layer 30 can be less than 20 μm, 10 μm or less, 8 μm or less, or 7 μm or less. In these cases, excellent adhesion can be achieved.

[0223] The adhesive layer 30 has excellent optical properties.

[0224] The adhesive layer 30 is a film with a total light transmittance (transmittance) of 85% or more according to ISO 13468. The transmittance of the transparent film 20 can be 85% or more. For example, the transmittance can be 88% or more, 89% or more, or less than 99%.

[0225] The haze of the adhesive layer 30 can be less than 3%. For example, the haze can be less than 2%, less than 1.5%, or less than 1%. The haze can also be greater than 0%.

[0226] The yellow index (YI) of the adhesive layer 30 can be 3 or less. For example, the yellow index can be 3 or less, 2.8 or less, 2.2 or less, 1.0 or less, 0.8 or less, or 0.5 or less. Furthermore, the yellow index can be greater than 0.

[0227] The adhesive layer 30 has excellent optical properties and high adhesion, so it is not easy to delaminate even under repeated bending or winding conditions.

[0228] Multilayer film 100

[0229] Multilayer sheets 100 can be used to stably protect internal devices in environments where repeated bending and folding occur. Therefore, multilayer sheets with bending resistance, absorption of externally applied impacts, and high scratch and dent resistance on exposed surfaces are required.

[0230] The inventors of this invention propose a multilayer sheet with a relatively thin laminate structure, wherein the multilayer sheet exhibits excellent properties such as hardness and recovery rate as measured on the surface by nanoindentation tests, etc.

[0231] The inventors of this invention discovered that, regarding hardness and other properties measured by nanoindentation testing, which is considered a surface feature, even if the maximum indentation depth is only a portion of the coating, these values ​​may vary not only due to the coating itself but also due to the influence of other layers located beneath it. The inventors formed a laminate of an elastic film with high bending and curl resistance over a relatively wide temperature range and a coating with excellent surface properties, and placed a transparent film with excellent transparency that provides support between the elastic film and the coating, thereby proposing a multilayer sheet with excellent surface properties such as recovery characteristics and hardness.

[0232] Nanoindentation testing is an analytical technique that interprets the force-displacement curve obtained by applying a small force (load) on the order of μN to mN to an indenter with a specified geometry to the surface of a material and then removing it. This curve is used to determine various mechanical properties such as hardness, elastic modulus, tensile properties, and residual stress.

[0233] The indenter tip can have a variety of geometries, such as conical, pyramidal, triangular pyramid (Berkovich or Vickers pyramid), or cylindrical flatpunch.

[0234] Because polymer materials are typically viscoelastic, when pressed in by the tip of the indenter, they reach the maximum depth (h) under maximum force. max When the indenter is removed and the pressure through the tip of the indenter is released, part of the deformation recovers due to the elasticity of the polymer, but the rest does not recover permanently and leaves a dent with a fixed depth (hp).

[0235] Stiffness (S), projected contact area (Ap), test force (F), and maximum indentation depth (hmax) under maximum force were determined by nanoindentation tests to obtain force-displacement curves. Based on these results, the indentation modulus (EIT) and indentation hardness (H) can be calculated. ITNanoindentation tests can be performed according to ISO 14577-1:2002(E) standards, including Vickers hardness (HV), Martens hardness (HM), indentation creep (CIT), and recovery relation (ηIT). For example, the nanoindentation test can be performed according to ISO 14577-1:2002(E) standards.

[0236] Martens hardness (HM), also known as composite hardness, is calculated from test force, indentation depth, etc., and provides ductile and elastic material properties different from indentation hardness. In the following text, HMd is the Martens hardness value (N / (mm)) of the multilayer sheet measured per unit thickness on the surface of the coating. 2 The value of HMd (×μm) can be obtained by dividing the HMd value by the thickness of the multilayer film.

[0237] Indentation creep (CIT) describes the additional deformation of a material under constant force. To determine indentation creep (CIT), an indenter is pressed into a sample with a constant force for a relatively long period of time (minutes to hours), and the indentation depth is calculated by measuring the indentation depth with continuous pressure increases. In the following, CITd is the indentation creep value (% / μm) of the multilayer sheet measured per unit thickness of the coating surface, which can be obtained by dividing the CIT value by the thickness of the multilayer sheet.

[0238] Recovery can be calculated based on the value measured by nanoindentation testing using the following formula.

[0239] Recovery rate (%) = [(h max(@30mN) -h p ) / h max(@30mN) ]×100

[0240] Among them, h max(@30mN) The maximum indentation depth (μm) is determined by pressing the coated surface downwards with a force of 30 mN for 15 seconds and holding it (creep) for 5 seconds. p It is the depth (μm) of the indentation left after the force is removed and the indentation fails to recover.

[0241] Rcd is the recovery rate (% / μm) of the multilayer sheet measured per unit thickness on the surface of the coating, which can be obtained by dividing the recovery rate value by the thickness value of the multilayer sheet.

[0242] Indentation hardness (H) ITIndentation hardness (H), also known as plastic hardness, measures a material's resistance to permanent (plastic) deformation under maximum force, thus determining its ductility, malleability, and impact resistance. IT The maximum test force (Fmax) is calculated by dividing the maximum test force (Fmax) by the value of the contact projected area (Ap) at the penetration depth (Fmax / Ap).

[0243] Unless otherwise stated, all measurements are based on values ​​determined on the coated surface by nanoindentation testing in accordance with ISO 14577-1:2002(E).

[0244] Multilayer sheets preferably possess surface durability and impact resistance exceeding specified levels, along with excellent recovery rate or resilience to external forces, minimal permanent deformation, and a thin thickness. The strain-restoration index (TR index) can be used as an index to comprehensively evaluate these characteristics. The unit of the TR index is [μm], and it is represented by Equation 1 below.

[0245] [Formula 1]

[0246]

[0247] In Equation 1 above, HMd is the martensitic hardness value (N / (mm) of the multilayer sheet per unit thickness (1 μm) measured on the surface of the coating. 2 ×μm), CITd is the indentation creep value (% / μm) per unit thickness (1μm) of the multilayer sheet measured on the surface of the coating, Rcd is the recovery rate value (% / μm) per unit thickness (1μm) of the multilayer sheet measured on the surface of the coating, H IT The indentation hardness (N / mm) of the multilayer sheet measured on the surface of the coating. 2 ).

[0248] The TR index (unit: / μm) measured on the surface of the coating of the multilayer sheet 100 can be 0.8 or higher and 2 or lower. The TR index can be 2 or lower, or 1.8 or lower, or 1.6 or lower. The TR index can be 0.9 or higher, 1 or higher, 1.1 or higher, or 1.2 or higher. Multilayer sheets with TR index values ​​within the above ranges form thinner thicknesses, and the coating surface is robust, exhibiting excellent resistance to permanent deformation and a superior recovery rate.

[0249] The martensitic hardness HM of the multilayer sheet 100 measured on the surface of the coating can be 180 N / mm. 2 The above could be 187 N / mm. 2The above could be 190 N / mm. 2 The above could be 192 N / mm. 2 The above could be 194 N / mm. 2 The above could be 196 N / mm. 2 The above could be 197 N / mm. 2 The martensitic hardness HM of the multilayer sheet 100 measured on the surface of the coating is 200 N / mm. 2 the following.

[0250] The martensitic hardness value per unit thickness measured on the surface of the coating is HMd (unit: N / (mm)). 2 (×μm)) represents.

[0251] The HMd value of the multilayer sheet 100 can be 1.3 N / (mm). 2 (×μm) or higher, or can be 1.4N / (mm) 2 (×μm) or higher, or can be 1.5N / (mm) 2 (×μm) or higher, or can be 1.6N / (mm) 2 (×μm) or higher, or can be 1.7N / (mm) 2 (×μm) or higher, or can be 1.9N / (mm) 2 (×μm) or higher, or can be 2.0 N / (mm) 2 The HMd value of the multilayer sheet 100 can be 3 N / (mm²) or higher. 2 Below (×μm), or can be 2.5N / (mm). 2 Below (×μm). Multilayer sheets with this HMd value can be formed into thinner sheets and have excellent surface hardness properties.

[0252] The indentation creep CIT of the multilayer sheet 100 measured on the surface of the coating can be less than 4.3%, less than 4.2%, or less than 4.1%. The indentation creep CIT of the multilayer sheet 100 measured on the surface of the coating can be more than 3.5%.

[0253] The indentation creep value per unit thickness measured on the surface of the coating is expressed as CITd (unit: % / μm).

[0254] The CITd value of the multilayer sheet 100 can be less than 0.05% / μm or less than 0.045% / μm. Alternatively, the CITd value of the multilayer sheet 100 can be greater than 0.02% / μm or greater than 0.025% / μm. Multilayer sheets with such CITd values ​​can be formed into thinner sheets and exhibit excellent resistance to deformation under external forces.

[0255] The indentation hardness H of the multilayer sheet 100 measured on the surface of the coating. IT (Unit: N / mm) 2 It can be 370 N / mm 2 The following may be 360 ​​N / mm 2 The following is an example of the indentation hardness H measured on the surface of the coating of the multilayer sheet 100. IT (Unit: N / mm) 2 ) can be 330N / mm 2 The above could be 335 N / mm. 2 The above could be 340 N / mm. 2 The above applies. Within this range, multilayer sheets can have a plasticity and hardness suitable for use as protective films.

[0256] The elastic modulus ηIT of the multilayer sheet 100, measured on the surface of the coating, can be 62% or more. The elastic modulus ηIT can be 65% or less.

[0257] The recovery rate (%) of the multilayer sheet 100 measured on the surface of the coating can be 66% or more. The recovery rate can be 75% or less, or 73% or less.

[0258] The recovery rate per unit thickness (1 μm) of the multilayer sheet 100 measured on the surface of the coating is expressed as Rcd (% / μm).

[0259] The Rcd value of the multilayer sheet 100 can be 0.4% / μm or higher, or 0.5% / μm or higher, or 0.55% / μm or higher. Alternatively, the Rcd value of the multilayer sheet 100 can be 1.2% / μm or lower, or 1% / μm or lower, or 0.8% / μm or lower. In this case, the multilayer sheet can have a relatively excellent recovery rate compared to its thickness and can possess properties suitable for use as a protective film.

[0260] In the multilayer sheet 100, the length from the upper surface of the coating 10 to the lower surface of the elastic film 42 can be less than 500 μm, less than 300 μm, or less than 200 μm. The length can be more than 70 μm.

[0261] The thickness ratio of the elastic film to the transparent film can be from 1:0.5 to 1:3, or from 1:1 to 1:2.8. When the two films are applied together within the aforementioned thickness range, it is advantageous to simultaneously impart sufficient support properties, bending and elastic recovery properties, etc.

[0262] The thickness ratio of the elastic film to the adhesive layer can be from 1:0.02 to 1:1, or from 1:0.02 to 1:0.6, or from 1:0.02 to 1:0.4, or from 1:0.02 to 1:0.25. When the elastic film and the adhesive layer are applied with the above thickness ratios, delamination will not occur even when subjected to external forces such as repeated bending and folding.

[0263] Multilayer film 100 can have excellent optical properties.

[0264] The haze of the multilayer film 100 can be less than 3%, less than 2%, or less than 1%. The haze can be greater than 0%, or greater than 0.5%.

[0265] The transmittance of the multilayer film 100 can be 88% or more, or 90% or more. The transmittance can be 99% or less, or 95% or less. The transmittance is based on the total light transmittance according to ISO 13468.

[0266] The yellow transmittance index of the multilayer film 100 can be less than 1, less than 0.8, less than 0.65, or less than 0.6. The yellow transmittance index can be greater than 0 or greater than 0.3.

[0267] Multilayer electronic devices 200

[0268] Figure 3 A conceptual diagram illustrating the structure of a multilayer electronic device according to another embodiment. (Reference) Figure 3 The multilayer electronic device 200 will be described in detail.

[0269] The multilayer electronic device 200 includes: a multilayer sheet 100; and a light-emitting functional layer 150 disposed beneath the multilayer sheet 100.

[0270] The multilayer film 100 can be used as a cover layer for the multilayer electronic device 200.

[0271] The multilayer electronic device 200 may be, for example, a display device, and exemplaryly, a large-area display device, a foldable display device, a bendable display device, or a flexible display device. Furthermore, the multilayer electronic device 200 may be a bendable mobile communication device (e.g., a mobile phone) or a bendable laptop computer.

[0272] The light-emitting functional layer 150 includes a light-emitting layer (not shown).

[0273] The light-emitting layer includes a device that emits light according to a signal in a display device. Exemplarily, the light-emitting layer includes: a signal transmission layer that transmits an external electrical signal to a color-producing layer; a color-producing layer disposed on the signal transmission layer and displaying color according to a given signal; and an encapsulation layer that protects the color-producing layer. The signal transmission layer may include thin-film transistors (TFTs), such as LTPS, a-Si TFTs, or oxide TFTs, but is not limited thereto. As an encapsulation layer, thin-film encapsulation (TFE) may be used, but is not limited thereto.

[0274] The light-emitting layer can be disposed on a support layer (not shown). As the support layer, a layer with insulating and heat-resistant properties can be applied; for example, a polyimide film, a glass layer, a PET film, etc., can be applied.

[0275] The light-emitting functional layer may also include a sensor layer (not shown). As a sensor layer, touch sensors, etc., can be applied.

[0276] The light-emitting functional layer may also include a polarizing layer (not shown). The polarizing layer may be disposed on the light-emitting layer or on the sensor layer.

[0277] The following will provide a more detailed description through specific embodiments. These embodiments are merely examples to aid in understanding the invention, and the scope of the invention is not limited thereto.

[0278] 1. Preparation of adhesive composition

[0279] The following materials were prepared: KR-3700 from Shin-Etsu Chemical Industry Co., Ltd. as a silicone adhesive; X-92-128 from Shin-Etsu Chemical Industry Co., Ltd. as a silicone MQ resin; CAT-PL-50T, a platinum-based catalyst from Shin-Etsu Chemical Industry Co., Ltd. as a catalyst; and toluene as a solvent. The adhesive layer composition was mixed in the amounts shown in Table 1 below and then applied.

[0280] 2. Formation and curing of the adhesive layer; evaluation of the physical properties of the cured adhesive layer.

[0281] After curing, a precursor layer was obtained by die-coating onto a PET film (NRF grade manufactured by SKC) at the thickness shown in Table 1 below and then drying. Drying and curing were carried out at 90°C for 5 minutes.

[0282] As an adhesive force test, the adhesive force was measured in the form of a T-peel using the QC-M1F UTM model from COMETECH Inc., at a peeling speed of 300 mm / min.

[0283] Table 1

[0284]

[0285] * is based on the content of silicone adhesive per 100 parts by weight.

[0286] **This refers to the adhesive force measured at the corresponding adhesive layer thickness.

[0287] *** is a value obtained by dividing the adhesive force measured at the corresponding adhesive layer thickness by the thickness, and is expressed as adhesive force per 1 μm unit thickness or gf / (inch·μm).

[0288] Referring to Table 1 above, the adhesive force generally tends to increase with increasing adhesive layer thickness. Furthermore, when comparing at the same thickness, except for 1 μm, the adhesive force of Preparation Example 2, which uses the adhesive layer constituting Preparation Example 2, is generally the best. However, Preparation Examples 1 and 3 also exhibit excellent adhesive force with changes in thickness.

[0289] When observing the adhesive force per unit thickness, which confirms the adhesive force relative to the thickness, generally, the adhesive force increases with increasing thickness, but the increase in width tends to decrease even when the same composition is applied.

[0290] Therefore, it can be seen that a relatively thin adhesive layer can be obtained with sufficient adhesion.

[0291] 3. Preparation of multilayer wafers

[0292] SKC prepared new delayed-retardation film (NRF) grade PET films of various thicknesses and used them as transparent films.

[0293] As a coating, a coating preparation composition having the composition shown in Table 2 below was applied to a surface of a transparent film by a mold coating method. Subsequently, it was heat-treated at 60°C for 3 minutes to dry the solvent, and then cured by irradiation with 1J UV light, thereby forming a coating with a thickness of approximately 5μm.

[0294] Table 2

[0295]

[0296] In the sample with the adhesive layer, the adhesive composition was applied to the other surface of the transparent film of the laminate (i.e., a laminate with a coating formed on one surface of the transparent film) in the same manner as described above, and was dried to form a precursor layer, which was then cured to form the adhesive layer. The composition used was the same as that in Composition Preparation Example 2.

[0297] As the elastic membrane, an elastic membrane manufactured by SKC using PEBA resin from Arkema, France, was employed. The elastic membrane was prepared using the method described in Korean Patent No. 10-2286935, but the thickness of the elastic membrane was as shown in the table below. In short, the polyether block amide resin (Arkema Pebax) was used... TM Rnew TM 72R53 or 55R53 (Arkema) is placed in an extruder and melt-blended at about 220°C, and then extruded into a single layer to prepare a PEBA film with a thickness of about 35 μm or about 50 μm.

[0298] One surface of the elastic membrane is bonded to the other surface of the adhesive layer and then cured, thereby preparing a sample in which a coating layer, a transparent membrane, an adhesive layer, and an elastic membrane are stacked in sequence.

[0299] The specific layer structure and the thickness of each layer are shown in Table 3 below.

[0300] Table 3

[0301]

[0302] 4. Evaluation of the physical properties of multilayer wafers

[0303] (1) Optical properties and color

[0304] Optical properties and color were measured. The average visible light transmittance of the film samples was measured according to ISO 13468 using a haze meter (NDH-5000W, Nippon Denshoku Kogyo Co., Ltd.), and the haze was measured according to ISO 14782. The yellow index (YI) of the samples was measured according to ASTM-E313 using a spectrophotometer (UltraScan PRO, Hunter Laboratories) at 10° using a D65 light source. The results are shown in Table 4 below.

[0305] (2) Thickness measurement

[0306] The thickness of each layer was measured using a Filmetrics F-20 instrument, following the manufacturer's manual. Measurements at 3 to 5 points in the sample were verified, and the average value was taken as the thickness.

[0307] (3) Evaluation of bending resistance

[0308] The multilayer film of the example was bonded to a 35 μm thick elastic layer (SKC manufactured a single-layer extruded film using PEBA72R grade resin from Arkema, France), and then subjected to a dynamic folding test to determine its bending resistance. After 200,000 cycles of dynamic folding tests at room temperature (approximately 20°C) with a curvature radius of 2 mm and a bending speed of 2 seconds per cycle, the presence of cracks was confirmed. Cracks were visually inspected for presence. No cracks were observed in any of the multilayer films of the examples upon visual inspection, and therefore were rated as good.

[0309] (4) Nanoindentation test

[0310] Nanoindentation tests were performed on the prepared samples. Multilayer sheets were cut into A4 size and stored at 25±5℃ and 50±5%RH until the test, without any separate pretreatment. The samples were then evaluated using a nanoindentation surface analyzer (FISCHERSCOPE HM2000, FISCHER). Specifically, the samples were positioned on a glass test plate (GLA SS TEST PLATE, Fischerscope Part no. 600-028) with the coated surface (or, in the case of no coating, the surface of the transparent film) on top (i.e., the indentation surface) as the sample holder. The samples were then pressed down with a force of 30 mN for 5 seconds at room temperature using a diamond tip, held for 5 seconds (creep), and then lifted upwards while performing nanoindentation tests. This determined the martensitic hardness (HM), indentation modulus (EIT), elastic modulus (ηIT), indentation creep (CIT), and maximum deformation (h) under a force of 30 mN. max(@30mN) The recovery rate was determined according to ISO 14577-1:2015 and 14577-2:2015. The recovery rate was calculated using the following formula.

[0311] Recovery rate (%) = [(h max(@30mN) -h p ) / h max(@30mN) ]×100

[0312] Among them, h max(@30mN) The maximum indentation depth (μm) is achieved when the coating surface is pressed down with a force of 30 mN for 15 seconds and held for 5 seconds (creep). p It is the depth of the indentation (μm) left after the force has been removed and the indentation has not recovered.

[0313] The evaluation results are shown in Table 4 below.

[0314] Table 4

[0315]

[0316] *ND indicates that it was not detected.

[0317] **HMd is HM (N / mm) 2 The value is obtained by dividing the total thickness (μm).

[0318] **CITd is the value obtained by dividing CIT (%) by the total thickness (μm).

[0319] **Rcd is the value obtained by dividing the recovery rate (Recovery, %) by the total thickness (μm).

[0320] The unit of the TR index is [ / μm], and it is represented by Equation 1 below.

[0321] [Formula 1]

[0322]

[0323] In Equation 1 above, HMd is the martensitic hardness value (N / (mm)) of the multilayer sheet per unit thickness (1 μm) measured on the surface of the coating. 2 ×μm), CITd is the indentation creep value (% / μm) per unit thickness (1μm) of the multilayer sheet measured on the surface of the coating, Rcd is the recovery rate value (% / μm) per unit thickness (1μm) of the multilayer sheet measured on the surface of the coating, H IT The indentation hardness (N / mm) of the multilayer sheet measured on the surface of the coating. 2 ).

[0324] Referring to Tables 2 and 3 above, it can be confirmed that surface properties such as hardness vary depending on the stacking method of the multilayer sheet. To ensure excellent utilization of the multilayer sheet as a cover sheet for display devices, it must possess excellent optical properties, be resistant to scratches, and exhibit high resistance to permanent deformation even under strong force. It also needs to have impact resistance. Therefore, it is preferable to use a portion of the layer that is elastic, and it needs to have good resilience to prevent indentation. In the cases of samples 8 to 19 above, although the values ​​vary depending on the thickness of the applied film, they all exhibit appropriate levels of hardness, indentation creep, and recovery rate. Therefore, it can be concluded that the multilayer sheet of this embodiment possesses excellent physical properties suitable for application as a display protective sheet, etc.

[0325] The preferred embodiments of the present invention have been described in detail above, but the scope of the present invention is not limited thereto. Various modifications and improvements made by those skilled in the art based on the basic concepts of the present invention as defined in the appended claims are also within the scope of the present invention.

Claims

1. A multilayer sheet, characterized in that, include: The transparent film has a total light transmittance of over 85% according to ISO 13468. A coating is disposed on one surface of the transparent film, and An elastic membrane is disposed beneath the other surface of the transparent membrane; The storage modulus index of the elastic membrane, as expressed by Equation 2 below, ranges from 20 MPa to 350 MPa. [Equation 2] In Equation 2 above, KSM is the storage modulus index of the elastic membrane, and SM n The storage modulus of the elastic membrane, measured at n℃, is expressed in MPa. Among them, SM -40 Storage modulus of the elastic membrane measured at -40℃, in MPa (saturation point). 20 Storage modulus of the elastic membrane measured at 20°C, in MPa (sq m). 80 This is the storage modulus of the elastic membrane measured at 80℃, with units of MPa. The martensitic hardness of the multilayer sheet, measured on the surface of the coating, is 180 N / mm. 2 above, The thickness ratio of the elastic membrane to the transparent membrane is from 1:0.5 to 1:

1.

2. The multilayer sheet according to claim 1, characterized in that, The elastic modulus of the multilayer sheet, measured on the surface of the coating, is greater than 62%.

3. The multilayer sheet according to claim 1, characterized in that, The deformation recovery index is based on the value of Equation 1 below. The deformation recovery index measured on the surface of the coating is greater than 0.8 and less than 2, and the unit of the deformation recovery index is / μm; [Formula 1] In Equation 1 above, HMd is the martensitic hardness value per unit thickness (1 μm) of the multilayer sheet measured on the surface of the coating, with the unit of the martensitic hardness value being N / (mm). 2 (×μm) CITd is the indentation creep value per unit thickness of 1 μm of the multilayer sheet, measured on the surface of the coating, and the unit of the indentation creep value is % / μm. Rcd is the rate of recovery of the multilayer sheet per unit thickness of 1 μm, measured on the surface of the coating, and the unit of the rate of recovery is % / μm. H IT The indentation hardness is measured on the surface of the coating of the multilayer sheet, and the unit of the indentation hardness is N / mm. 2 .

4. A multilayer sheet, characterized in that, include: The transparent film has a total light transmittance of over 85% according to ISO 13468. A coating is applied to one surface of the transparent film. An adhesive layer is disposed beneath the other surface of the transparent film, and An elastic membrane is disposed beneath the adhesive layer; The storage modulus index of the elastic membrane, as expressed by Equation 2 below, ranges from 20 MPa to 350 MPa. [Equation 2] In Equation 2 above, KSM is the storage modulus index of the elastic membrane, and SM n The storage modulus of the elastic membrane, measured at n℃, is expressed in MPa. Among them, SM -40 Storage modulus of the elastic membrane measured at -40℃, in MPa (saturation point). 20 Storage modulus of the elastic membrane measured at 20°C, in MPa (sq m). 80 This is the storage modulus of the elastic membrane measured at 80℃, with units of MPa. The martensitic hardness of the multilayer sheet, measured on the surface of the coating, is 180 N / mm. 2 above, The thickness ratio of the elastic membrane to the transparent membrane is from 1:0.5 to 1:

1.

5. The multilayer sheet according to claim 4, characterized in that, The indentation creep value of the multilayer sheet, measured on the surface of the coating, is 0.02% / μm to 0.05% / μm per 1μm of unit thickness.

6. The multilayer sheet according to claim 4, characterized in that, The recovery rate of the multilayer sheet per unit thickness of 1 μm, measured on the surface of the coating, is 0.4% / μm to 1.2% / μm.

7. The multilayer sheet according to claim 4, characterized in that, The thickness ratio of the elastic membrane to the adhesive layer is from 1:0.02 to 1:

1.

8. The multilayer sheet according to claim 4, characterized in that, The recovery rate of the multilayer film is over 66%.

9. A multilayer electronic device, characterized in that, include: Multilayer sheet according to any one of claims 1-8; as well as A light-emitting functional layer is disposed on the lower part of the multilayer sheet.

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